Wood Gas Generator or Nl

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SECORITY CLASSIF!CATIOM OF THIS PAG-E

ORNL-6404

3 4456 0299433 3

Construction o f a Simplified Wood Gas Generator for Fueling11 TITLE (Include Security Clarv'ficafion)Internal Combustion Engines in a Petroleum Emergency12 PERSONAL AUTHOR(S)

16 SUPPLEMENTARY NOTATION

19 ABSTRACT (Continue on reverse if necessary ~ n didentify by block number)'his report i s one in a ser ies o f emergency technology assessments sponsored by the Federahergency Management Agency ( F E M A ) .l lus t ra ted ins t ruct ions for the fabr ica t ion, ins ta l la t ion , a n d operation o f a biomassiasif ier unit ( t h a t i s , a "producer gas " generator, a l s o called a "wood gas" generator) whs capable o f providing emergency fuel f o r vehicles, such as tr ac to rs a n d trucks, in thevent t h a t normal petroleum sources were severely disrupted for an extended period o f time.'hese instructions are prepared i n t h e format o f a manual f a r use by any mechanic who i saeasonably proficient i n metal fabrication o r engine repair.

The purpose of th i s report i s t o develop det ailed ,

his report attempts t o preserve the knowledge about wood gasification a s p u t into practicase during Norld War 11. Detailed, step-by-step fab ric ati on procedures ar e presented f o riniplified version of the World War 11, hibert wood gas generator, T h i s simple, s t r a t i f i e(cont d )

22 a N A M E OF RESPONSIBLE INDIVIDUAL

SECURlTY CLASSIFICATION OF THIS PAGE83 APR edition may be used until exhausted.All other editions are obsolete.


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19. ABSTRACT (contd)downdraft gasifier unit can be constructed from materials which would be widelyavailable in the United Sta tes in a prolonged petroleum crisis, Fo r example,the body o f the unit consists o f a galvanized metal garbage can a t o p a smallmetal drum; common plumbing fittings are used t h r o u g h o u t ; a n d a large, s ta in lesssteel mixing bowl i s used f o r the grate,, The en t i re compact un it was mounted o n t othe front o f a farm tractor a n d successfully f i e l d tested, using wood chips a sthe only fuel.a s well a s i ts operation i s included.Photographic documentation o f t h e actual assembly of the unit

SECURITY C L A S S I F I C A T I O N O F T H I S PAGE


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0Dist. Category UC-41

Energy Division

1-1. LaFontaineG. P. Zimmerrnan

Biomass Energy Foundation, Inc.Miami, Florida

Date Published: March 1989

Prcparcd for th eF E D E R A L E M E R G E N C Y MANAGEMENT AGENCYWashington, DC 20472Interagcncy Agreement; FEMA No. EMW-84-51737(Work Unit 3521 D) and DOE No. 1457-1457-A1

Prepared by theOAK KlDGE NATI ONAL LABORATORY

Oak Ridge, Tcnncssec 37831-6285operatcd byM A R T I N M A R I E I T A EN ERGY SYSTEMS, Inc.for the

US. D E P A R T M E N T OF ENERGYu n d c r contract DE-AC115-84QR214


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CONTENTSPage

EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VS.1. PRINCIPLES OF SOLID FUEL GASIFICATION . . . . . . . . . . . . . . . viS.2. THE STRATIFIED, DOW NDM FT GASIFIER . . . . . . . . . . . . . . . . vi

CONVERSION FACTORS FOR SI UNITS .......................... xmLIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvLIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviiABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11. WHAT IS A WOOD GAS GENERATOR AND HOW DOES IT WORK? 31.1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2. PRINCIPLES OF SOLID FUEL GASIFICATION . . . . . . . . . . . . . . . . 41.3. BACKGROUND INFORMATiON . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.3.1. The World War 11, Imbert Gasifier . . . . . . . . . . . . . . . . . . . . . . 41.3.2. The Stratified, Downdraft Gasifier . . . . . . . . . . . . . . . . . . . . . . 7

...

. . .

2. BUILDING YOUR OWN WOOD GAS GENERATOR . . . . . . . . . . . . . . . .FUEL HOPPER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .THROTTLE CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1. BUILDING THE GAS GENERATOR UNIT AND THE2.2. BUILDING THE P R I M Y FILTER UNIT2.3. BUILDING THE CARBUREXNG UNIT WITE-1 H E AIR AND

3. OPERATING AND MAINTAINING YOUR WOOD GAS GENERATOR . .3.1. USING WOOD AS A FUEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.2. SPECIAL CONSIDERATIONS AND ENGINE MODIFICATIONS ~ . .3.3. INITIAL START-UP PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . .3.4. ROUTINE START-UP PROQ=EDUI%E. . . . . . . . . . . . . . . . . . . . . . .3.5. DRIVING .4N D NORMAL OPERATION . . . . . . . . . . . . . . . . . . . .3.6. SHU7TING-DQWN THE GASTFIER UNIT3.7. ROUTINE MA'1NTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.7.1 Daily Mainterlance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.7.2 Weekly Maintenance (or every 15 hours of operation) . . . . . . .

3.7.3 Biweekly Maintenance (or every 30 hours of operation) . . . . . .3.8. OPERATING PROBLEMS AND TROUBLE-SHOOTING . . . . . . . . .3.9. HALARDS ASSOCIATED WITH GASIFIER OPERATION3.9.1. Toxic Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.9.2. Technical Aspects of "Gcncrator Gas Poisoning" . . . . . . . . . . . .3.9.3. Fire Hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

. . . . . . .

131417195555555656575757585858585858595947BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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This report is one in a series of ernergcncy technology assessments sponsored by theFederal Emergency Managcment Agency (FEMA). The pu rpose of this report is to developdetailed, illustrated instructions for th e fabrication, installation, and o peration of a biomassgasificr unit @e.,a "producer gas" generato r, also called a "wood gas" generator) which iscapable of providing emergency fuel for vehiclcs, such as lractors and trucks, should normalpetrolcurn sources be severely disrupted for an extend ed period of t ime. T hes e instructionshave been prepared as a manual for use by any mechanic who is reasonably proficient inmetal fabrication o r enginc repair.Fuel gas, produced by t he reduction of coal and p eat, was used for heating as early as1840 in Europe and by 1884 had been adapted to fuel engines in England. Prior to 1948,gas gener ator units were a familiar, but not extensively utilized, technology. However, petrol-eum shortagcs during World War I1 led to widespread gas generator applications in thetransportation industries of Western Europe. (Charcoal-burning taxis, a related application,were still common in Korca as late as 1978.) The United States, never faced with suchprolonged or sevcrc oil shortages, has lagged far behind E ur op e an d t he O rient in familiaritywith and application of this technology. However, a catastrophic event could disrupt thesupply of petroleum in this country so severely that this technology might be critical inmeeting the energy needs of some essential economic activities, such as the production anddistribution of food.In occupied Denmark during World War 11, 95% of all mobile farm machinery,tractors, trucks, stationary engines, and fishing and ferry boats were powered by wood gasgenerator units. Even in neutral Sweden, 40 % of all motor traffic operated on gas derivedfrom wood o r charcoal. All over Europe, Asia, and Australia, millions of gas generators werein operat ion hctween 1940 and 1946. Because of the wood gasifier's somcwhat low effici-cncy, th e inconvenience of opera tion, and th e potential hea lth risks from toxic fumes, m ostof such units were abandoned when oil again became available in 1945. Except for thetechnology of producing alternate fuels, such as methane or alcohol, the only solution foroperating existing internal combustion engines, when oil and pc t rokum products a re no tavailable, has been these simple, inexpensiv e gasifier units.This report attempts t o preserve the knowlcdge about wood gasification that was putinto pmcaical use during World War 11. In this report, detailed step-by-step procedures arepresented for constructing a simplified vcrsion of the World W ar II wood gas generator; thissimple, stratified, downdraft gasifier unit (shown schematically in Fig. S-1) can be constructedfrom materials which would be widely available in the United Slates in a prolongedpetroleum crisis. For example, the body of the unit consists of a galvanized metal garbagecan atop a srnail metal drum; common plumbing fittings are used throughout; and a large,stainless steel mixing bowl is used for the grate. A prototypc gasifier unit was fabricatedfrom these instructions (sec Fig- S-2); this unit was then mountcd onto the front of a farmtractor and successfully field tested, using wood chips as the only fuel (see Fig. S-3) . Photo-graphic docum entation of thc actual assembly of the uni t, as well as its opera tional ficld tcst,is includcd in the body of this report.The use of wood gas generators nccd not bc limited to transportation applications.Stationary engines can also be fucled by wood gasifiers to run clectric generators, pumps,and industrial equipment. In Fact, the use of wood gas as a fuel is not even restricted to

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gasoline engines; if a small amount of diesel fuel is used for ignition, a propcrly adjusteddiesel engine ca n be operated primarily on wood gas introduced through the inta ke manifold.

All interna l combustion eng ines actually run o n vapor, no t liquid. he liquid fuels usedby gasoline engines are vaporized before they enter the combustion chamber above thepistons. In diesel engines, the fuel is sprayed in to the combustion cham ber as fine dropletswhich burn as they vaporize. Th e purpose of a gasifier, then, is to transform solid fuels intogascous oncs and to keep the gas free .of harmful constituents, A gas generator unit issimultaneously an energy coriverter and A filter. In these twin tasks lie its advantages and itsdifficulties.In a s ense, gasification i s a form of incom gletc combustion- -heat from the burning solidfuel creates gases which arc un able to burn completely because of the insufficient amountsof oxygen from the available supply of air. The same chemical laws which govern combus-tion processes also apply to gasification. There are many solid biomass fuels suitable forgasification-from woo d an d pa pe r to peat, lignite, and coal, including co ke derived from coal.All of these solid fuels arc composed primarily of carbon with varying amounts of hydrogen,oxygen, and impurities, such as sulphur, ash, and moisturc. Thus, the aim of gasification isthe almost comp lete transformation of these constituents in to gaseous form so that only theashes and inert materials remain. In creating wood gas for fueling intcrnal combustionengines, it is important that the gas not only be properly produced, but also preserved andnot consumed until it is introduced into the engine where it may be appropriately burned.Gasification is a physiochemical process in which chemical transformations occur alongwith th e conversion of energy. The chemical reactions an d thermochem ical convcrsions whichoccur inside a wood gas generator are too long and too complicated to be covered here;however, such knowledge is not necessary for constructing and o per atin g a woo d gasifies. Byweight, gas (wood gas) produced in a gasifier unit contains approximately 20% hydrogen(HJ, 20% carbon monoxide (CO), and sniall amounts of methane, all of which arecombustible, plus 50 to 60% nitrogen (NJ. T h e nitrogen is not combustible; however, it doe soccupy volume and dilutes the wood gas as it enters and burns in an engine, As the woodgas burns, the products of combustion are carbon dioxide (CO,) and watcr vapor (NQ).O n e of the by-products of wood gasification is carbon monoxide, a poisonous gas. Thetoxic hazards associated with breathing this gas should be avoided during refueling operationso r prolonged idling, particularly in inadequately ventilated areas. E xcept for t he obvious firehazard resulting from the combustion processes inside the unit, carbon monoxide poisoningis the major potential hazard during normal operation of these simplified gasifier units.

Until the early 1980s, wood gasifiers all over the world (including the World W ar I1designs) operated on the principle that both the fuel hopper and the combustion unit beabsolutely airtight; the hopper was sealed with a top or lid which had to bc opened everyt ime wood was added. Smoke and gas vented into the atmosphere while wood was beingloaded; the operato r had to be careful not to breath e th e unpleasant smokc and toxic fumes.

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Ove r th e last few years, a new gasifier design has b een developed through coopcrativeefforts among researchers at th e Solar Energy Research Institute in Colorado, the Universityof California in Davis, the O pe n University in London, t he Buck Ro gers Company in Kansas,and the Biomass Energy Foundation, Inc., in Florida. This simplified design employs abalanced, negative-pressure co ncept in which the old type of sealed fuel hopper is no longernecessary. A closure is only used to preserve the fuel when the engine is stopped. This newtechnology has several pop ular names, including "stratified, down draft gasification" and "opento p gasification." Several years of laboratory and fieId testing h;we indicated that su ch sirnpie,inexpensive gasifiers can be built from existing hardware and will perform very well asemergency units.

A schematic diagram of the stratified, downdraft gasifier is shown in Fig. S-1. Duringopcration of this gasifier, air passes uniformly downw ard throug h fou r zoncs, hen ce th e nam e"stratified:"1.

2.

3.

4.

T he uppermost zone contains unreacted fuel through which air and oxygen enter. Thisregion serves th e same funct ion as the fuel hopper in the older, W orld War I1 dcsigns.In the second zone, the wood fuel reacts with oxygen during pyrolysis. Most of thevolatile comp onents of the fuel are burned in this w n e and provide heat for continuedpyrolysis reactions. At the bottom of this zone, all of th e available oxygen from th e airshould be completely reacted. T he op en to p design ensures uniform access of air tothe pyrolysis region.The third zone is made up of charcoal from the second zone. Hot combustion gasesh m the pyrolysis region react with the charcoal to convert the carbon dioxide andwater vapor into carbon monoxide and hydrogen.The inert char and ash, which constitute the fourth zone, are normally to o cool tocause further reactions; however, because the fourth zone is available to absorb heator oxygcn as conditions change, it serves both as a buffer and as a charcoal storageregion. Below this zone is the grate. The presence of char and ash serves to protectthe grate from excessive temperatures.The stratified, downdraft dcsign has a numbcr of advantages over the World War TIgasifier designs. The ope n top permits fuel to be fed mo re easily and allows easy access.Thecylindrical shape is easy to fabricate and permits continuous flow of fuel. N o special fuelshapc or pretreatment is necessary; any blocky fuel can be used.T he foremost question abou t the operation of the stratified, downdraft gasifier concernschar and ash removal. As the charcoal reacts with the combustion gases, it eventually reachesa very low density and breaks up into a dust containing all of the ash as well as a percentageof the original carbon. This dust may be partially carried away by the gas an d might even-

tually begin to plug the gasificr. Hence, i t must be removed by shaking or agitation. Whenthe stratified gasifier unit is used to power vehicles, it is automatically shak en by the vehicle'smotion.An important issue in the design of th e stratiliied, dow ndraft gasifier is the preventionof fuel bridging and channeling. High-grade biomass fuels, such as wood blocks or chip s, willflow down through the gasifier because of gravity and downdraft air flow. However, otherfuels (such as shredded chips, sawdust, and bark) can form a bridge, which will obstructvii


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continuous flow and cause very high temperatures. Bridging can be prevented by stirring,shaking, or by agitating the grate or by having it agitated by the vehicles movement. Forprolonged idling, a hand-operated shakcr has been included in the design in this report.A prototype unit of thc stratified, downdraft gasificr design (s ee Figs. S-2 and S-3) hasbeen fabricated according to the instructions in this report; however, it has not b een widcly

tested at this time. The reader is urged to use his ingenuity and initiative in con structing hisown wood gas generator. As long as the principle of airtightness in the combustion regions,in the connecting piping, and in the filter units is followed, the form, shape, and method ofassembly is not important.The wood gasifier design presented in this report has as its origin the proventechnology used in World War TI during actual shosta cs of gasoline and diesel fuel, I tshould be acknowledged that ther e ar e alterriate technologies (such as methane productionor use of alcohol fuels) for keeping internal combustion engines in operation during aprolonged pet aoleuin crisis; the wood gasifier unit desacribcd in this report represents onlyon e solut ion to the problem.

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t ,

ORNL-DWG 8 7 - 1 4 5 5 3

< / vY -CARBURETOR CONNECTIONS FILTER UNIT GASIFIER UNITFig. S-1. Schematic View of th e stratified, downdraft gasifier.


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ORNL- Photo 5321-86

Eb =m

I

Fig. S-2The prototypewood gas generator unit mounted onto a tractor-X


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CONVEXSION FACTORS FOR SI UNITS

English units have been retained in th e body of this report. The report refers tocomnicrcially available materials and sizes which are commonly expressed in English units.The conversion factors for SI units are given below:

Lo convert from,

cubic fcct ( f t 3 )

foot (ft)cubic yards (yd3)Fahrenheit degrees (OF)gallon (gal)horsepower (hp)inch (in.)pound (Ih)q u a r l (qt.)

IT Ocubic meters (m3)Kelvin degsces (K)meter (m )cubic meters (m3)metcr (m)kilogram (kg)cubic mcters (m3)

cubic m eters (m3)

watt (W)

9.02530.7W(see Note 1)0.39483.785 x 10-30.02540.45369.464 x lo1

745.7

a

Note 1: To convcrt tcmperatures, use the following equation,K = 27 3 f 0.5556 X (F - 32)where

,

F i s the temperature in Fahrcnhcit degrees, andM is thc tcrnperaturc in Kelvin degrees.

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Fig. S.1 .Fig. S.2 .Fig. S.3 .Fig. 1.2 .Fig. 1.3 .Fig. 1.1 .Fig. 2.1 .Fig. 2.2.Fig. 2.3 .Fig. 2.4 .Fig. 2.5 .Fig. 2.6 .Fig. 2.7.Fig. 2.8 .Fig. 2.9.Fig. 2.10 .Fig. 2.11 .Fig. 2.12 .Fig. 2.13 .Fig. 2.14 .Fig. 2.15 .Fig. 2.16 .Fig. 2.17 .Fig. 2.18 .Fig. 2.19 .Fig. 2.20 .Fig. 2.21 .Fig. 2.22 .Fig. 2.23 .Fig. 2.24 .Fig. 2.25 .Fig. 2.26 .Fig. 2.27 .

Schematic view of the stratified. downdraft gasifier . . . . . . . . . . . . . ixThc prototype wood gas generator unit mountedonto a t rac tor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xWood gas generator unit in operation during field tcsting . . . . . . . xi'Wood gas generator unit in operation during field testing . . . . . . . . 9Schematic view of t h e World W ar TI. Imbeert gasifier . . . . . . . . . . . . 10Schematic view of th e stratiEied. d ~ ~ ~ ~ r a f tgasifier . . . . . . . . . . . . . 11The prototype wood gas generator unit mountedont o a t rac tor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Exploded. schematic diagram of the wood gas generator unitThe fire tube and circular top plate of the gasifier unit . . . . . . . . . . 24Drilling holes into the stainfess stcel mixing bowl to be usedfor the gra te . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Chains attached to the lip of the stainless steel mixing bowl . . . . . . . 26Connect the mixing bowl to the top plate with chains . . . . . . . . . . . 27Braze. do not weld. the plumbing fittings to the thinwallcd drums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Exploded. schematic diagram of the g ra teshaking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Parts for the shaker assembly ............................ 30The support frame can be brazed or bolted to the side of th egasifier unit . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . . .. 31Containers used in constructing the prototype gasifier unit . . . . . . . . 32Cover for the fuel hopper. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Operating configuration of the fuel hopper and its cover . . . . . . . . . 34Lock ring and welded tabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Exploded. schematic diagram of the filter unit . . . . . . . . . . . . . . . . 36Detail of the standoffs or the bottom plate ofth e fi l ter unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Divider plate (#l )an d bottom plate (#3). with standoffs (#4).for the filter unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Circular lid (#I) fo r the filter unit . . . . . . . . . . . . . . . . . . . . . . . . 39Assembled and installed blower ( # l ) . extension assembly (#4).and conduit connectors or gas inlet (#2) and outlet (#3) onlid of filter unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Filter container (#I) showing latches (#2) for lid and hose( # 3 ) around top . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Exploded. schematic diagram of the carbureting unit andcontrol valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4344Butterfly valve assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Assembled carburetion unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

and the fuel hoppcr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Blower (#1) with exhaust extension assembly . . . . . . . . . . . . . . . . 40

Schemalic diagram of a butterfly conlrol valve. . . . . . . . . . . . . . . . .Parts required fo r the butterfly valve . . . . . . . . . . . . . . . . . . . . . . 45Assembled buttcrfly valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47


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LIST OF ETGURES (continued)

Fig. 2-28. Carburetion unit attached to engines existingintake manifold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Ignite a single piece of newspaper to start the garifier unit;push the flaming newspaper through the ignition port andIgniting the exh aust gas will demo nstrate that the gasifier unitRefill the fuel hopper before it becomes two-thirds empty . . . . . . . .The lid m ust be used to cover the fuei hopper in w et weather

Fig. 3-1. Virtually all varieties of wood chips can be used for fuel . . . . . . . . 60directly into the grate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61is working properly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62or when shutting the unit down . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Fig. 3-2.

Fig. 3-3.Fig. 3-4.Fig. 3-5. 63


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LIn OF TABLES

Table 2.1 .Table 2.2 . Fire tube dimensions ................................. 52

List of materials or the gasifier unit and the woodfuel hopper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Table 2.3 . List of materials for the primary filter unit . . . . . . . . . . . . . . . . . 53Table 2.4. List of materials for the carbureting unit . . . . . . . . . . . . . . . . . . . 54Table 3.1 . Trouble-shooting your wood gas generator . . . . . . . . . . . . . . . . . . 65Table 3.2 . Effects of breathing carbon monoxide ..................... 66


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1

6

N.EaFontaineG. P. Zirnmerman

This rcpor t is on e in a se ries of emcrgen cy technology assessmcnts spoilsoredby the Federal Emergency Management Agency (FEMA). The purpose of thisrcpor t is to develop detailed, illustratcd instructions for the fabrication,installation, and operation of a biomass gasifier unit (k,a producer gasgenerator , also called a wood gas generator) that is capable of providingcmergency fuel Lor vehicles, such as tractors and trucks, in th c e v e n t tha t normalpetroleum sources wcre S C V ~ J ~ I Ydisrupted for a n estendcd period of time. lneseinstructions have: bee n prepare d as a manual for use by an y mechanic who isrcasonably proficient in mctal fabrication or engine repair .his repor t a t tempts to preserve thc knowledge about wood gasification thatwas p ut in to practical usc during World W ar I T . Detailed, stcp-by-step fabricationprocedurcs a r e presented for a simplified version of the World War I T , lmberhwood gas generator. This simple, stratified, downdraft gasificr unit can heconstructcd from materials that would bc widely availalblc in the United Statesin a prolongcd petroleum crisis. For example, t he body of the unit consists of agalvanized nictal garbage ca n atop a small metal drum ; comm on plum bing fittingsthroughout ; and a large, stainless steel mixing bowl for thc grate, The en t i r ecompact unit was mountcd on to the f ron t o f a farm t rac tor and successfully fieldtested, using wood chips as the only fucl. Photographic documentation of th eactual assembly of the mi&as well as its operation is included.


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3

1. WHAT IS A WOOD GAS GENERATOR AND HOW DOES ITWORK?This report is one in a ser ies of emergency technology asscssmcnts spon sored by t heFederal Emergency Management Agency (FEMA). Th e purpose of this report is to developdetailed, illustrated instructions for the fabrication, installation, and operation OC a biomassgasif'icr unit (Le., a "producer gas'' generator, also called a "wood gas" generator) that iscapable of providing emergency fuel for vehiclcs, such as tractors and trucks, in Lhe eventthat normal petroleum sources WCK severely disrupted f o r an extende d period of t ime. Thes einstructions have bce n prep ared as a manual for use by any mechanic wh o is reasonably pro-ficient in metal fabrication o r enginc repair.

Y L ~gas, produccd by the reduction of coal and peat, was used for heating, as earlyas 1840 in Europe, and by 1854 i t had been adapted to fuel engines in England. Before1940, gas generator units were a farmiliar, but not extensively utilized, technology. However,petroleurn sh ortages during World W ar I1 led to widespread gas generator applications in thetransportation industries of Western Europe. (Charcoal-burning taxis, a related application,were still ccmimon in Korea as late as 1970.) T h e United States, never faced with such pro-longed or scvere oil shortages, has lagged far behind Europc and the Orient in familiaritywith and application of this tcchnology; howcver, a catastrophe could so severely disruptthc supply o f petrole um in this country th at this technology m ight bc critical in meeting theenergy needs of some essen tial economic activities, such as the production and distributionof food.This report attempts to preserve the knowledge about wood gasification as put intopractical use during, World W ar 11. Detailed, step-by-step procedures are presented in thisreport fo r constructing a simplified version of the World War 11, Imbert wood gas generator.This simple, stratified, downdraft gasifier unit can be constructed from materials that wouldbe widely available in the Unitcd States in a prolonged petroleum crisis. For example, thebody of the unit consists of a galvanize metal garbage can a top a small metal drum;common plumbing Gttings throughout; and a large, stainless stccl mking bowl for the grate .A prototype gasifier unit was fabricated from these instructions. This unit was then mountedonto the front of a gasolinc-engine Farm tractor and successfully field tested, using woodchips as t h e only fuel; see Fig. 1- 1 (all figures and tables are presented at the end of theirrespective sections). Photographic documentation of th e actual assembly of the unit, as wellas its operational field test, is included in this report.The use of wood gas generators need not be limited to transportation applications.Stationary eng ines can also be fucled by wood gasifiers to ru n electric generators, pum ps, andindustrial equipment. In fact, the use of wood gas as a fuel is not even restricted to gaso-l ine engines; if a small amount of diesel fuel is used for ignition, a properly adjusted dieselengine can be operated primarily on wood gas introduced through the intake manifold.However, this report is concerned with t he operat ion of four-cycle gasoline engines ratedfrom 10 t o 150 horsepower. If more information is need ed ab ou t c3perating gasifiers on other


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4fuels (such as coal, charcoal, peat, sawdust or seaweed), a list of relevant literature iscontained in the Bibliography at the end of (his report.The goal of this report is to furnish information for building a homemade wood gasgenerator made out of ordinary, available hardware, in o rde r to get tractors, trucks, andot he r vehicles opera ting without delay, if a se vcrc liquid fuel emergen cy should arise. Sec-tion 1 describes gasification principles and wood gas generators, in general, and gives somchistorical background about their operation and effectiveness. Section 2 contains detailedstep-by-step instructions for constructing your own w ood gas gen erat or unit; illustrations andphotographs arc included to prevent confusion. Section 3 contains information o n operating,maintaining, and trouble-shooting your wood gas generator; also included are some veryimportant guidclincs on safety when using your gasifier system.T h e wood gasifier design presented in this repor t has as its origin the proventechnology used in World War 11 during actual shortages of gasoline and diesel fuel. Itshould be acknowledged that th ere are alte rnate technologies (such as meth ane productionor use of alcohol fuels) for keeping internal combustion engines in operation during aprolonged petroleum crisis; the wood gasiEier unit described in this report represents onlyon e solut ion t o th e problem.

1.2 PRINCIPLES OF SOLID FUEL GASIFICATIONAll interna l combustion en gines actually run o n vapor, not liquid. The liquid fuels usedin gasoline engines ar e vaporized before they cn ter t he combustion chamber above thepistans. In diesel engines, the fuel is sprayed into the combustion chamber as fine dropletswhich burn as they vaporizc. The purpose of a gasifier, then, is to transform solid fuels intogaseous ones and to keep the gas f ree of harmful constituents. A gas generator unit is,simultaneously, an energy converter and a filter. In these twin tasks lie its advantages andits difficulties.The first question many p eop le ask abo ut gasifiers is, "W here does th e combustible gascome from?" Light a wooden match; hold i t in a horizontal position; and notice that whilethe wood becomes charcoal, it is not actually burning but is releasing a gas that begins toburn brightly a short distance away from the matchstick. Noticc the gap between thematchstick and the luminous flame; this gap contains th e wood gas which starts burning onlywhen properly mixed with air (which contains oxygen). By weight, this gas (wood gas) fromthe charring wood contains approximately 20% hydrogen (H2),20% carbon monoxide (CO),and small amounts of m ethane, all of which are combustible, plus 50 to 60% nitrogen (N2).The nitrogen is not combustible; however, it does occupy volume an d dilutes t he wood gasas i t enters and burns in an engine. As the wood gas burns, the products of cornbustion arecarbon dioxide (CO,) and water vapor ( H 2 0 ) .Thc sam e chemical laws which govern combustion processes also apply to gasification.Thc solid, biomass fuels suitable for gasification cover a wide range, from wood and paperto peat, lignite, and coal, including coke derived from coal. All of these solid fuels arecomposed primarily of carbon w ith varying am ounts of hydrogen, oxygen, and im purities, suchas sulphur, ash, and moisture. Thus, the aim of gasification is the almost completetransformation of these constituents into gaseous form SO that only the ashes and inertmaterials remain.In a sen se, gasification is a form of incomp lete cornbustion; heat from th e burning solid

fuel creates gases which are unable to burn completely, due to insufficient amounts of


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5oxygen from the available supply of air. In the matchstick example above, as thc wood wasburncd and pyrolyzed into charcoal, wood gas was created, but the gas was also consumedby combustion (since therc was an ~ n ~ ~ m ~ ~ ~ ssupply of ai r in thc room). In creating woodgas or fueling intcrnal combustion engines, it is imp~rtantthat the gas not only be properlyproduced, but also preserved and not consime until it is introduced into thc engine whereit may be appropriately burned.Gasification is a p ~ i ~ ~ o c ~ c ~ ~ ~ ~ ~process in which chemical transformations occur alongwith the canversion (sf enengy.Thc chemical reactions and thermoch eniical conversions whichoccur inside a wood gas generator are too long and too complicated to be covered here.Such knowledge is not necessary for constructing and operating a wood gasifier. Books withsuch inlormation are listed in the Refeerencc Sccdion (see, for example, Reed 1979, Vol. 11;or Reed and Das 1988).

1 3 BACKGROUND INFORMATIONT h e u se of wood to provide heat is as old as mankind; but by burning the wood we

only utilize about one-third of its energy. Two-thirds is lost into the environment with thesmoke. Gasification is a method of coliecting the smoke and its combustible components.Making a combustible gas from coal and wood began around 1790 in Europe. Such manu-factured gas was used for street lights and was piped into houses for heating, lighting, andcooking. Factories used it for steam boilers, and farmers opera ted the ir machinery on woodgas and coal gas. After the discovery of large petroleum reserves in Pennsylvania in 1859,the enti re world changed to oil-a chea per an d more convenient Fuel. Thousand s of gas worksall over the world were cventually dismantled.Wood gas generators are not technological marvels that can totally eliminate ourcurrent dependence on oil, reduce the impacts of an energy crunch, or produce long-termeconomic relief from high fossil fuel prices, but they are a proven em ergency solution whensuch fuels become unobtainable in case of war, civil upheaval, or natural disaster. In fact,many people can recall a widespread use of wood gas generators during World War 11,whenpetroleum products were not available for the civilian populations in many countries.Naturally, the people most affected by oil and petroleum scarcity made the greatestadvancements in wood gas generator technology.In occupied Denmark during World War 11, 95% of all mobile farm machinery,tractors, trucks, stationary engines, fishing and ferry boats were powered by wood gasgenerators. Even in neutral Sweden, 40% of al l motor traffic operatcd o n gas derived fromwood or charcoal (Reed and Jantzen 1979). All over Europe, Asia, and Australia, millionsof gas gencrators were in operation between 1940 an d 1946. Bccause of the wood gasiEierssomewhat low efficiency, thc inconvenience of operation, and the potential health risks Fromtoxic fumes, most ol such units were abandoned when oil again became available in 1945.Except for t he technology of producing alternate fuels, such as methane or alcohol, the onlysolution for ope rating existing interna l combustion eng ines, when oil and petroleurn productsare not available, has been these simple, inexpensive gasifier units.


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shaken at intervals. Ash buildup below th e grate can be removed during clcaning operations.Usually, wood contains less than 1% ash (by weight). However, as the charcoal i s consumed,it eventually collapses to form a powdery charcoal/ash mixture which may represen t 2 to 10%(by weight) of the total Cue1 mass.The cooling unit required fo r the Tmbert gasifier consists of a water-filled precipitatingtank and an autoniolive radiator-type gas cooler. The precipitating tank removes all unac-ceptable tars and most of the Gne ash Crom the gas flow, while the radiator further cools thegas, A second filter unit, containing a fine-mesh filtration material, is used to remove the lasttraces 01any ash or dust that may have survived passage through the cooling unit. Oncc outof the filter unit, the wood gas is mixed with air in the vehicle's carburetor and is thenintroduced directly in to t he engine's intake manifold.

The World War 11, Imbert gasifier requires wood with a low moisture content (lessthan 20% by weight) and a uniform, blocky fuel in order to allow easy gravity feed throughth e constricted hcarth. Twigs, sticks, and bark shreds cann ot be used. Th e constriction at thehearth and the protruding air nozzles present obstructions to th e passage of the fuel and maycreate bridging and channeling followed by poor quality gas out put , as unpyrolyzed fuel falisinto the reaction zone. The vehicle units of the World War I1 era had ample vibration tojar thc carefully sized wood blocks through the gasifier. In fact, an entire industry emergedfor preparing wood for use in vehicles at that time (Reed and Jantzern 1979). However, theconstricted hearth dcsign seriously limits the range of wood fuel shapes that can besucccssfully gasified without expensive cubing or pelletizing pretreatment. It is this limitationthat makes the Imbert gasifier less flexible for emergency use.In summary, the World War IT Imbert gasifier design has stood thc test of t ime andhas successfully bec n mass produced. It b relatively inexpensive, uses simple constructionmaterials, is easy to fabricate, and can be operated by motorists with a minimum amount oftraining.

1.3.2 The St r a t i f i d Downdr af t GasifierUntil the early 198Os, wood gasifiers all over the world (including the World War I1designs) operatcd on thc principle that both the fuel hopper and the combustion unit beairtight; the hopper was sealed with a top o r lid that had to be o pene d every time wood wasadded. Smoke and gas vented into the atmosphere while new wood was being loaded; theopctator had to be careful not to breathe the unpleasant smoke and toxic fumes.Over the last fcw years, a new gasifier design has been developed through cooperative

efforts among researchers at th e Solar Energy Research Institute in Colorado, the Universityof California in Davis, the O pe n University in London, the Buck Rogers Company in Kansas,and the Biomass Energy Foundation, Inc., in Florida (Reed and Das 1988). 'This simplifieddesign employs a balanced, negative-pressure con cept in which th e old type of sealed fuelhopper is no Iongcr nccessary, A closure is only used to preserve the fuel when thc engineis stopped. This new technology has several popular names, including "stratified, downdraftgasification'f and "ope n to p gasification." Two years of laboratory and field testing haveindicated tha t such simple, inexpensive gasifiers can b e built from existing hardware and willpcrform very well as emergency units.A schematic diagram of the stratified, downdraft gasifier is shown in Fig. 1-3. Duringoperation of this gasifier, air passes uniformly downward through four zones, hence th e name"stratified:"


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2.

3.

4.

The uppermost zone contains unreacted fucl through which air and oxygen enter. Thisregion serves the same function as the fuel hopper in the Imbert design.In the second zone, the wood fuel reacts with oxygen during pyrolysis. Most of thevolatile compo nents of the fue l are burned in this zone and provide heat for continuedpyrolysis reactions. At the bot tom of this zone, all of th e available oxygen from the airhas completely reacted. The open top design ensures uniform access oE air to thepyrolysis region.Th e th ird zone is made up of charcoal from the second zone. Hot combustion gasesfrom the pyrolysis region react with the charcoal to convert the carbon dioxide andwater vapor into carbon monoxide and hydrogen.The inert char and ash, which constitute the fourth zone, are normally too cool. tocause furth er reactions; howcvcr, since the fo urth zone i s available to absorb heat oroxygen as conditions change, it serves both as a buffer and as a charcoal storageregion. Below this zone is the grate . T he prcsence of char and ash serves to protectth e gr ate from excessive temperatures.The stratified, downdraft design has a number of advantages over the World War 11,Im ber t gasifier. llie ope n top permits fucl to be fed mo re easily and allows easy access. Thecylindrical shape is easy to fabricate and permits continuous flow of fuel, N o special furlshape: or pretreatment is necessary; any blwky fuel can be used.Th e foremost question abou t the operat ion of th e stratified, downdraft gasificr concernschar and ash removal. As th e charcoal reacts with th e combustion gases, it eventually reachesa very low density and breaks up into a dust containing all of the ash as well as a percentage

of th e original carbon. This dust may be partially carried away by the gas; however, it mighteventually begin to plug the gasifier, and so i t must be removed by shaking o r agitation. Boththe Irnbert gasificrs and the stratified concept have a provision f or shaking th e grate; whenthey arc used to power vehicles, they arc automatically shaken by the vehicles motion.An important issue in the design of th e stratified, down draft gasi5,ea is the preventionof fuel bridging and channeling. High-grade biomass fuels such as wood blocks or chips willflow down through the gasifier under the influence of gravity, and downdraft air flow.However, ot he r fuels (such as shrcdd ed wood, sawdust, and bark) ca n form a. bridge. tha t willthese widely available biomass residues. Bridging ca n be prevented by stirring, shaking, or byagitating th e gra te or by having it agitated by th e vehicles m ovement. For prolonged idling,a hand-operated shaker has been included in the design.

A proto type design of the stratified, downdraft gasifier design has been developed. Thedetailed but simple design is described and illustrated in Sect, 2; however, it has not bcenwidely tested at this time. The reader is urged to use his ingenuity and initiative in con-structing his own wood gas generator. As Iong as the principle of airtightness in thecombustion regions, in the connecting piping, and in the filter units is followed, the form,shape, and method of assembly is not important.

pievcnt continuous flow and cause very high temperatinres. Obviously, it is desirabl-CI to rase


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The fnZBowing fabric ation ins truc tion s, parts lists, an d illwst~atiionsdescribe: the prototypegasifier unit shown schc atically in Fig. 1-3,rl%sse ~ ~ s ~ ~ar e simple and easy to follow.The dimensions in th e ~ o ~ ~ ~ ~ ; ~ ~plans are given in inches rathcr than in millimeters to makeconstruction casier for those who might be ~~f~~~~~~~ with the metric system and to allowthe builder t o take advantage of available, alternatc construction matcrials. Th willbe obviousto th e expcrienccd engineer, mechanic, or builder that most of th e d ~ ~ e ~ s i o ~ s(for example,plate thicknesses and clennout diameters) arc no t critical to th e acccptable p erformance ofthe finished gasifier unit.The pro to type gasi fi er un it desc ribed in thc f o l ~ o ~ n gtext was actually constructed andfield tested on a gasoline-engine farm tractor (a 35-hp, John Deere 1010 Special); see Fig. 2-I. The unit operated very well, and on par wi th the European, World War 11 designs, butit has not had the test of t ime nor the millions of operating hours like the older Imbertdesign. This new stratified design was devclopcd for the Construction of simple, inexpensiveemergency wood gas generator units. The prototype dcsign below should be considered tobe the absolute minimum in regard to materials, piping and filter arrangement, andcarburetor system connections,The gasifier unit, as described below, is designed to maintain proper cooling, even atmoderate vehicle speeds. If this unit is to be used on stationary engines or on slow-movingvehicles, a gas coolcr and a secondary filter must be placed in the piping system between thegenerator unit and the carburetor. The ideal temperature fo r th e wood gas at the inlet tothe carburetor manifold would be 7PF, with acceptable peaks of 140 to 1WF. For every 10degrees above 7@F, an estimated 1% horsepower is lost. Cooler gas has higher density and,therefore, contains more combustible components per unit volume.

Th e millions of wood gasifiers built during World W ar II proved that shape, form, an dconstruction material had little o r no effect o n the performance of the unit. Judicioussubstitution or the use of seavcnged parts is, therefore, quite acceptable. Wh at h impartantis that:1. the f i re tubc dimensions (inside diameter and length) must be correctly selected tomatch the rated horsepower of particular engine which i s to be fueled,2. airtightness of the gas generator unit and all connecting piping must he maintained atall times, and3. unnecessary friction should be eliminated in all of the air and gas passagcs by avoiding

sharp bends in the piping and by using piping siacs which are not too small .


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Figure 2-2 shows an exploded view of the gas generator unit and the fuel hopper; thelist o f materials is given in Table 2-1 (all figurcs and tables mentioned in Sect. 2 arepresented at the ciid of Sect. 2). Only th e dimensions of thc fire tubc: (Item 1A) must bereasonably closc; all othe r dimensions and materials can b e substituted as long as completeairtightness i s maintained. In the following instructions, all i tem numbers refer both to Fig.2-2 and to Table 2-1.The prototype unit described in this report was constructed for use with a 35-hpgasoline engine; the un i t has a fire tube diameter of 6 in. (as determine d from Table 2-2).A gas generator unit containing a fire tubc up to 9-in. diametcr (Le., a gasifier unit forfueling engines up to abou t 65 hp) can be constructed from the f o l l o ~h ginstructions. Ifyour engine rcquires a fire tu be diameter of 10 in. or more, us? a 5s-gal drum for the gasunit and another 55-gal drum for the fuel hoppcr.The following fabrication procedure is very general and can be applied to theconstruction of gas generator units of any size; however, the specific dimensions which aregiven in the parts list and in the instructions below arc for this particular prototype unit. Allaccompanying photographs were taken during the actual assembly of the prototype unit .

The fabrication procedure is as follows:Using th e displacement or horsepower rating of the eng ine to bc fueled by th e gasifierunit, determine the dimensions (inside diameter and length) of th e firc tube (Item 1A)f rom T able 2-2, Fabricate a cylindrical tube O B cu t a length of correctly sized pipe tomatch th c dimensions from T able 2-2. (For th e prototype gasifier un it illustrated in thisreport, a 6-in.-diam firetube wa s uscd; its length was 19 in.)The circular top plate (Item 2A) should be cut to a d iameter equal to the outsidediameter of th e gasifier housing drum (Item 3A) at its top. A circular hole should th enbe cut in the center of the top pla te ; the d iameter of this hole must he equal t o t h eoutside dianictcr of th e fire tube. Ifnefire tube (Item 1A) should then be welded ata right angle to the top pla te ( I tem 2A) as shown in Fig. 2-3.Th e g ra te ( I tem 4A) should bc mads from a stainless steel mixing bowl or colander.Approximately 125 holes with diameters of l l2 in. should be drilled in the bottom andup the s ides of the mixing bowl; scc Fig. 2-4. A U-bolt (Item SA) should be weldedhorizontally to the side of the gra te , 2 in. from its bottom. This 1J-bolt will beinterlocked with the shake r mechanism (Itcm 12A) in a later step.The support chains (Item 6A) are to be attached to t he gr ate in thre e evenly spacedholes drilled under the lip of the anking bowl or colander; s ee Fig. 2-5. Th e s c chainsa re to b c connected to the top plate (Item 2A) with eyebolts (Item 7A), as shown inFig. 2-6. Each eyebolt should have two nuts , on e o n each side of thc top plate, so tha tthe eyebolts can he adjusted to the pro per length. When assembled, the bottom of th efiretube should bc 1.25 in. above th e bottom of the mixing bowl.A hole equa l to the outside diameter of the ash cleanout port (Item 8A) should be c utin to the s ide of the gasifier housing drum (Item 3A); the bot tom cdge of this hole


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16about 5 in. up the inside walls near the bottom. All edges should be rounded T o r easyash removal.

14. The fuel hopper (Item 15A) is to be m a d e fmrm a sccond container with its hottornup as shown in Fig. 2-11. Remove the botlorn, leaving a U 4 - h lip a round thc cireunn-ference.

15. A garden hose ( I tem 14A)should be cut to a length q u a l to the circumference of thefucl hopper [Item 15A) and should then be slit along its entire length. It should beplaced over th c edge of th e fuel hopper from which the bottom was removed. T h i s willprevent injury to the operator whecr adding wood fuel to the unit. To insure close fi tof the garbage can lid (Item 16A), a piece ofweatlier stripping (Item 18A) should beattached under the lid where it makes contact with th e fuel hopper.16. Cut four support bars (Item 19A) to lengths 2.5 in. longer than the height of the fuelhopper (Item 15A). Drill a 3/8-in. hole in each end of all four support bars; theseholcs should be centered 3/4 in. from thc ends. Bend 2 in. of each end of these

support bars over at a right angle; then, mount them evenly spaced around the fuelhopper (I tem 15A) with U 4 - h bolts ( Item 20A). O n e of the bends on each suppor tbar should be as close to t he lower edge of the fuel hopper as possible,17. Cut four metal triangular standoffs (Item 21A) and braze, weld, or rivet them flatagainst the edge of the garbage can lid (Item 16A) as shown in Fig. 2-12; they must

be aligned with the fo ur suppo rt bars (Item 19A) attached to t h e fue l hopper. Duringoperation, the garbage can lid must have a minimum 3/4-in. opening for air passage;the standoffs should provide this clearance when they are engaged into the holes inthe top edges of the support bars (Item 19A); see Fig. 2-13.18. Two eye hooks (Item 22A) should be attached to opposite sides of the garbage can

lid (Itern 16A). Two screen door springs (Item 23A) should be a t tached to the garbagecan handles and used under tension to keep t he t op lid (Item 16A>e i ther open o rclosed.19. Cut the oil drum lock ring (Item 24A> to the exact circumference of the top plate(Item 2A) so that it will fit snugly around the gasifies unit housing drum (Item 3A).20. Cut four 2 by 2 by 1/4-in. tabs (Item 25A); then, braze these tabs to the lock ring(Item 24A), evenly spaced and in aligriinent with the support bars (Item 19A) on t hefuel hopper. Drill a 3/8-in. hole in each tab to align with the holes in the fuel hoppersupport bars (Item 19A). The lock ring i s shown in Fig. 2-14.21. The connecting pipe (Item 29A) between the gasifier unit and the filtcr unit shouldbe attached to the gasifier housing drum (Item 3A) a t a point 6 in. below the top ofthe drum. This pipe must be a minimuin of 2-in. in diameter and should be at least 6f t long for cooling purposes. At least o n e of the ends of this pipe must be removablefor cleaning and m aintenance. O n this prototype unit, a n airtight electrical conduitcon nec tor was used; this connection is visible in Fig. 2-1. Man y similar plumbing devices


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22.

23 .

are available and can be used if they are suitable for operation at 400F and above.The pipe can also be welded or brazed directly to the housing drum.When assembling the gasifier unit, th e upright bar (Item 2AA) o n th e shaker assemblymust be placed inside the U-bolt (Item SA) on the gra te .The lock ring will then clamp the gasifier unit housing drum (I tem 3A) and the topplate (Itcm 2A ) together. The fucl hopper sup ort bars (Item 1 9 4 must be attachedto the tabs (Item 25A) o n t h c lock ring with bolts (Ttcm 26A). High temperaturesilicone (Ite m 27A) should be applicd to all d g c s to make an airl ight connection. T helock ring connections are shown in the lower portion of Fig. 2-13.

Figurcs 2-15 and 2-16 show exploded Views of the primary fitter unit; the list ofmaterials is given in Tablc 2-3 (all figures and tablcs menlioncd in Sect, 2 are prcsentcd atthc end of Sect. 2). In the following instructions, all itcrn numbers refcr to e i ther Fig. 2-15or 2-16 and to Tablc 2-3.

The prototype primary filter unit was made from a 5-gal paint can. Tha t size seems tobe sufficient for gasifiers with fire tubes up to 10 in. in diametcr. If a fire tube diameter ofmore than 10 in. is required, then a 20-gal garbage can or a 30-gal oil drum should bc used,The filter unit could be fabricated in any shape or form as long as airtightness andunobstructed flow of gas are provided. If a 5-gal container is used, it must be clean and frecof any chcmical residue. l l ic top edge m ust bc straight and without any indentations. If analternate container can be found or fabricated, a larger diameter will pcrnit longer operationbetween clcanings.T he piping ( I tem 29A in Figs. 2-2 and 2-15) which connecls the gas generator unit tothe primary filter shoulld be considered to be a necessary part of the cooling system andshould never have ala inside diameter less than 2 in. A flexible automotivc cxhaust pipe wasused on the prototype filter unit described below; it was shapcd into a semicircular arc sothat increased length would achieve a greatcr cooling effect.Tne fabrication procedure fur the filter unit follow:1.

2.

3.

A h o le q u a l t o t h e o u ts id e d ia me te r o f the drain tube (Item 13B in Fig. 2-15] shouldbe cut in to the side of t h e filter container (Item 1s);th e bot tom edge of this holeshould be about 1/2 in. lrom the inside bottom of thc container.Th e dra in tube ( I tem 13B) should be inserted into th e previously cut hole in the filtercontainer and should be positioned so that i ts nonlhreaded end is near the cen te r ofthe container and k about 1/2 in. off the bottom.. On cc this position has been ensured,braze (do not weld) the drain pipe into the side of t e filter conlainer. C ~ S Cth ethreaded, exterior end of the drain pipe with the pipe cap (Item 14Coat the bottom of the fi l ter container (Item IN) with a l d - i n . layer of hydrauliccement (Item 28A), taking care not to plug or obstruct th e en d of thc drain tube (Item13B) with cement (i.e., fi l l the drain tube with a paper, styrofoam, o r other easilyremov able, but rigid material). The cemcnt should also be applied for about 1.5 in. up


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4.

5.

6.

7.

8.

9.

10.

thc inside walls of the container near its bottom. R ou nd t he ed ges slightly; the cemcnl;is to provide a pathway for any liquid conde nsate to drain out through th e drain tube.The cement rrrlnst be allowcd to harden befcre procEeding with the fabrication stepsbelow. Rem ove the fil ler material from the drain tubc when thc cement has hardened.A circular bottom plate (Item 2B) should be cut to a diameter i/2 in. smaller than theinside diamete r of th e filter container (Item 1s).lhis will allow for hea t expansion andeasy removal for cleaning. This bottom plate should be drilled with as many 3/4-.-in.holes as are practical for the s ize of the plate. Three evenly spaced 3/8-in. holes shoulldalso be drilled around the edge of the bottom plate for the spacer bolts (Item 3 B ) .Fig. 2-16 shows the deta il of using three bolts (Item 3 8 ) as spacers for the bo t tomplate (Item 23). The length of th e bolts should be adjusted to provide a clearance ofabout 2-in. between th e layer of cemcnt in the bot tom of the container (I tem IS) an dthc bottom plate (Item 28).A rectangular divider plate (Item 4s) should be cut to a width 1/4 in. less than theinside diameter of the filter containcr (Item 1B) and to a height 2.5 in. less than theinside heigh t of the container . Thk divider plate should then be welded at a right angleto the centerline of the bottom plate (Item 2B ) as shown in Fig. 2-17.C u t a piece of high-temperature hydraulic hosc (Item 5B) to a length equal to thecircumference of the fi lter cotitainer. It should he slit along i ts entire length and thenplaccd over the top edge of the fi l ter container (Item 1B) to cnsurc airtightness.A circular lid (Item 6B) should be cut equal tQ the outs ide d iamcte r of the filtercontainer (Item 1B).Th ree holes should be cut in to this :id for the exhaust p ipe ( I tem29A) from the gasifier unit, the blower (Item 7B), and the filter exhaust pipe (ltcmlOI3) to the engine manifold. Note the arrangement of these holes: the pipe (Item29A) from the gasifier unit must enter the lid o n on e s ide of the divider plate (Item413); th e blower (Item 7B ) and the fi l ter exxhausl pipe (Item IOB) to the enginemanifold must b e located on t h e o t h e r side of th e divider plate. This arrangement canbe seen in Fig. 2-18.The connecting pipe (Item 29A) between the gasifier unit and the filter unit shouldbe attached to t he l id (Item 5R)of the fi l ter containcr. At least on c of the ends of theconnecting pipe (Item 29A) must be removable for cleaning and maintenance. On thisprot otyp e unit, an airtight elcctrical conduit conn ecto r was used. Many similar pllumbingdevices are available and can be used if they are suitable for operat ion a t 400F an dabos7e, The pipe can also be welded or brae& directly to the lid.Attach the blower (Item 7%) to the filter container lid ( I tem GBj. On the prototypegasifier illustrated in this report, a heater blower f rom a Volkswagen automobile: wasused. Connections for a vertical extcnsion tubc ( l tcm 8B) will have to be fabricatedas shown iil Fig. 2-19. *4closing cap (Item 9B) is rcquired fo r the blower exhaust tube.A plumbing cap of stecli or plastic with a close fit can be used or fabricated to fit. Thevcrtical extension 2nd the closing cap arc visiblc in Fig. 2-1.


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1911.

12.

13.

14.

15.

2.3.

The gas outlet (Item 1OB) to the carbureting uni t on the engine should be 1.25 in.minimum diameter. In fabricating this wnn ection , all abrupt bends should be avoidedto ensure fre c flow of gas. Using plum bing elbows is one solution. The gas outlet (Ilem1QB)can ei ther b e welded or brazed lo the lid (Item 6B) of the filter container or anairtight, electrical conduit connector can be used.Latching dcvices (Item IlB) should be welded or brazed to the lid (see Fig. 2-20) andto the sides (see Fig. 2-21) of the filter container. An air-tight connection between thelid and the filter container must bc maintained.C ut two lengths of h igh - t empe r a tu r e hy~ r au~ ichose (I tem 12B) equal to th e height ofthe divider plate (Itern 4B); cut a third length ofhose equal to the w idth of the dividerplate. Slit each hosc along its entire length. Place the first two hoses on each side ofth c divider plate, and place thr= third hosc along the top edge of the divider plate asshown in Fig. 2-17.Insert the diviclcr plate (Item 4B ) into the filter container (Item IB), making siirc thatthe spacer bolls (I tem 3B), adjust the height of the divider plate so that it is exactlyflush with the top of the filter container. Make sure that the lid (Item 5B)will scatflatly and tightly against the top edge of the divider plate.thc hoses (Ttcm 12 ) create an airtight seal along all sides. By changing the length of

Fill the filter container (Item 1B) o n both sides or lh e divider plate w ith wood chips,the same kind as would be uscd for fucl in the gasifier unit. After carefully packingand leveling these wood chips, place the lid (Item 6B) o n th e filter container, and closethe latches tightly.

Figures 2-22 and 2 -23 show explodcd views of th e carbureting unit; the list of materialsis giveti in Table 2-4 (all figures and tables mentioned in Sect. 2 are presented at the endof Scct. 2 ) . In the following instructions, all item numbers refer both to Figs. 2-22 and 2-23 and to Table 2 4. Thc f o i l o w ~ ~ gis a simple and easy way to assemble a carburctor toachieve both a i r mixture and throt t le ctmlaol. I t can be mounted to ei ther updraft ordow ndraft manifolds by simply turning t hc unit o ver. Most o f the fabrication procedure belowis dcvoted to the assembly of tw o butterfly valves: one for the throt t le valve and one for theair mixture valve. e remainder of thc carburetor unit can be assembled from ordinary,thrcaded plumbing parts.

Th c inside diameter of the piping used in th e carburetor uni t must be relatcd to thcs i a of the engine and should never be smaller than the intake opening on the enginemanifold. If in doubt o n thc inside diameter for the pipe and/or hose sizes, always go witha larger diameter. This. will rcduce friction losses and will give longer operating hoursbctween cleanings. iter un i t it should normally be below 180F.About 2f t f rom the f i lter ccmtaincr , an r ive water hose can be connectcd to the pipe on thecarbureting unit. This rubber hose will keep engine vibration from creating ais leaks in theWhcn the wood gas leave


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20filter un i t o r in the connccting piping. The hose must be a fairly new i tem; such hoses havca steel spring inside to keep them from collapsing when negative prssslnrc i s applied. TSiespring wil! soon rust if it has first beeii subjected to water and then io the bot wood ga senriched with hydrogen.l 'he fabrication procedure for the assembly of two butterfly valves follows:

I'he manifold adapter (Item I@ in Fig. 2-22) must be fitted with bolts and/or holes formounting onto the engine's existing intake manifold. Bccause gasoline engines areproduced with so many different types of intake manifolds, ingenuity and coinnmnsense must be used to modify the manifold adap ter (Item 1C) for each different engincto be opera ted on wood gas. A gasket (Item 7C) should he cut to match the shape ofthe engine intake fitting.'I'he butterfly valve (Item 3C) is shown in Figs. 2-24 and 2-25; two such valves arerequired. A 3/8-in. hole should be drilled through the diameter of each valve body(I tem 1CC) at the midpoint of its length.The valve plate (Item 2CC) must be oval in sha pe with th e dimensions given in ' Iable2-4. An oval valve plate must be used so that, in the closed position, t he valve will beabout 100 off center. This will ensure that the valve will come to a co mplete s top inthe closed position.Th e cdges of the valve plate (Item 2CC), around the longer diameter of the oval,should be bevcled to provide a positive, airtight closure. Two evernly spaced, 1/4-in.holes should be drilled along the shorter diameter of the oval plate.The valve supp ort rod (Item 3 C C ) should be filed o r ground flat on one side as shownin Fig. 2-24; the flat area must begin 1/4 in. from one en d and must continuc for adistance equal to the inside diameter of the valve body (Item 1CC).Two 3/16-in. holes should be drilled into th e flat area of the valve support rod (I tem3CC); these holes must align with the holes in the valve plate (Item 2CC). They mustalso be tapped (with threads) to accept the valve plate screws (Item 4CC).T h e butterfly valve (Item 3C) should be assembled by first placing the valve supportrod (Item 3CC) through the hole in th e valve M y (I tem ICC). Th e valve p late (I tem2CC) should be dropped in to one end of the valve body and t k i l inserted into thc flatarea of the valve support rod. Tlne two screws (Item 4C'G) should be used to at tachthe valve plate to the suppo rt rod. Check to see that the assembled valve pllatc rotatesfreely and seats completely in the closed position.A nut (Item 6CC) should be welded flat against on e side of thc throt t le arm (I temSCC) near i ts end. A 1/8-in. hole should be drilled into the s ide of the nu t and mustbe threaded to accept the sat screw (Itrm 7CC). At least one hole should be drilledinto the throt t le arm for attachment of the enginc throttle control or air controllinkages.


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219. Place the nut (Itcm 6CC) on the throt t le arm over the eiad of th e vahc suppor t rod(Itcm 3CC) and use th e set screw (Item 7CG) to secure t he assemblyy.,Thc throttle ar mcan be placed in any convenient oricntation. Assembled butterfly valves a re s h o w inFig. 2-26.

10. The remaining parts of the carburetor assembly should he screwed together as shownin Fig. 2-27. Pipe thread compound should be used to make airtight connections. T heled carburetor unit ~ h o ~ l dbe attached to th e engine's intake ~a~~~~~~~as shownin Fig. 2-2811. This prototype gasificr was designed to opera te if gasoline wcrc unavailable; but, if dualoperation on wood and gasoline i s dcsired, the elbow ( i tem 2 C ) awPd b e replaced witha tee, allowing a gasoline carburetor to also be mounted.12. Th e arm o n t he but terf ly valve (I tem 3 C ) which is closest to the elbow (Item 2C) isto b e connec ted to the foot- (or, on tractors, hand-) operated accelerator. The otherbutterfly valve is to be used as the air mixture control valve and can be operated with

a manual choke cable. If the engine has an automatic choking device, then a hand-operated choke cable should be installed. Both buttcrfly valves and their connectingcontrol linkages must operate smoothly with th e ability to adjust t he valvc yet ke ep itstationary in th e selected position during operation. The linkages must close th e valvesairtight when the engine is off.13. The air inlet (Item 6C) should be connected by an extension hose or pipe, either iron

or plastic, to th e existing engine's air filter in order to prevent road dust or agriculturalresidue from entering the engine.14. The wood gas inlet (Item SC) is to be connected to the outlet piping (Item 1OB asshown in Fig. 2-15) from the wood gas filter unit. Part of this connection should be

a high-temperature rubber or neoprene hose to absorb engine vibration.


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22

1

ORNL-Photo 5321-86

* ' I

Fs 2-1-The prototype wood gas generator unit mounted onto a tractor.


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24

I

ORNL-Photo C533-87

P


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ORNL-Photo 4472-87

- 1

"L

I , -1

-I1t

m0

b

Fig. 24. Drilling holes into the stainless steel mixing bowl to beused for the grate. Note th e U-bolt in the foreground.


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i\

3YMi!M


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i

i32.9sln


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29

ORNL-DWG 87-14555

Fig- 2-8. Exploded, schem atic diagram of the grate shaking mechanism.


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I

3

O R N L - P h o t o 4496-87

w0


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32ORNL-Photo 4499-87

I

L

III

Fig- 2-11. Containers used in constructing the prototype gasser unit. At right, a 20-gal garbage can (the fuel hopper) is shown on top of a 30-gal metal drum (the gasifier unithousing). The 5-gal paint can, at left, is used as the filter container.


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,-.c


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34

ORNL-Photo 5342-86

Pi

I

Fig. 2-13-Operating configuration of the fuel hopper and its cover,


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I-IzQf0

1


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36ORNL-DWG 87-14556

Fig. 2-15. Exploded, schematic diagram of the milter unit.


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37

ORNL-DWG 87-14557

Fig-2-16. Detail of the standoffs for the bottom plate of the filter unit.


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r-I


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n

ORNL- Photo 4525-87

A

t i * I C 1Fig. 2-18. Circular lid (#1) for the filter unit Note the arrangement of the holes;divider plate would roughly run from 10 o'clock position to 4 o'clock position (assuming 12o'clock is t aken to be a t the rear of the photograph). Also shown are the conduit connectors(# 2 and #3) and accompanying nuts (#4 and #5) for inside the lid.


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e


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42

ORNL-Photo 451 7-87

c

Fig-2-21. Fdter container(#1) showing latches (#2) for lid and hose (#3) around top-


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ORNL-DWG 87-14558

f ig . 2-22. Exploded, schematic diagram of the carbureting unit and control valves.


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44

ORNL-DWG 87-14559

Fig 2-23. Schematic diagram of a butterfly control valve.


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J=I-1z&0 n

%,Y

1


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ORNL-Photo 4485-87

I

L

Fig. 2-25. Butterfly&e assembly. No te that the valve has been assembled outside ofthe valve body for clarity.

Y


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47

ORNL-Photo 4487-87

fig. 2-26. Assembled butterfly valves.


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rCLI--1ze0

A

LLA

...

L

P+

G9)Yi?

c


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O R N L - P h o t o 531 7-86IA

Fig. 2-28. Carburetion unit attached to engines existing intake manifold. Wood gasenters from the side of the tee; air enters from the right-hand end. The butterfly valve atthe right (partially obscured) is connected to the air control (choke) cable; the left valve isconnected to the throttle linkage.


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50Table 2-1.List of materials for the gasifier unit and the wood fuel hopper

Item Quan tity Description1 A

2 A

3 A

4 A

5 A6 A7 A8 A9 A

10A

11A12A1 A A2AA3A A4A A5A A6AA7A A

1

1

1

1

113112

2

1111121

Metal pipe, tube, o r other, open-ended metal cylinder; diameter andlength from Table 2-2; minimum wall thickness of 1/4 in.Circular metal plate with thickness of 1/8 in.; diameter equal tooutside diameter of Item lk30-gal metal oil drum o r metal container with approximate dimensionsof 18 in. (diameter) by 29 in. (height); container must have a bottom.10-quart stainless steel mixing bowl, colander, or other stainless steelbowl with approximately 14-in. diameter and 6-in. depth.2-in. metal U-bolt.3/16-in. metal chain with 1-in. links; 7 ft total length.1/4-in. eyebolts, 3 in. length with two nuts for each eyebolt.4-in. metal pipe nipple.Metal pipe cap for Item 8 k3-in. metal pipe nipple.

Metal pipe cap for Item 1 O kShak er assembly; see Fig. 2-8.Metal In- in. pipe; 6 in. length.Iron bar stock; square or round, 1/2 in.; 6 in. length.ln- in. bol t ; 8 in. long.Iron bar stock; rectangular, 1/4 by 1 in.; 10 in. length.In-in. flat washer.ln- in. nuts .Metal pipe cap or bushing for Item 1AA.


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51Table 2-1.(Continued)

Item Quantity Description13 A14A15A

16A17A

18A

19A20A21A22.423A2 4 h2SA24,A2'7A

28A

29A

125

1

11

1

1124221441

1

1

Iron bar stock; rectangular, 114 by 2 in.; 10 ft Icngth.1/4-in. bolts; 3/4 in. length; with nuts.20-gal metal garbage can or metal container with approximatedimensions of 18 in. (top diameter) by 24 in. (height); bottom is notrequired.Lid for 20-gal garbage can.Garden hose; 112 t o 5/8 in. diameter; lcngtli equal to circumfcrcnceof Item 1SA.Foam w c a th e r stripping with adhesivc backing; 1/4 by 1 in.; lengthequal to circumfcrencc of l t cm 15A.Iron bar stock; rectangular, 614 by 2 in.; 10 ft length.114-in. bolts; 3/4 in. length; with nuts.Metal triangles; 2 by 2.5 in., 118 to 114 in. thick.Metal eye hook.Screen door spring, 14 in. Icngth.Lock ring for 30-gal (or larger) oil drum.Metd sq iaar~s ;2 by 2 in., 1/4 in. thick.3 p in. bolts; 3 in. length.Tubs= I P ~high ternpcraturc silicone of: liquid high tcrnpcrature gasketaterial.60-lb. sack of hydraulic or o the r waterproof cement [such as SEC-PLUG (tm), which is maunfactured by the Atlas Chemical Company,Miami, IT].2-in. pipe, electrical conduit, flcxible automobile exhaust pipe, orother mctal tubing; 6-ft minimum length. Pipe must be able towithstand temperaturcs of 4WF.


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52

Inside diam eter Minimum Engine power Typical engine(inches) length (horsepow er) displacement(inches) (cubic inches)

24 a678910

11121314

1616161820222426283032

5153048506580100120

140160

10306080

100130160200240280320

-- A fire tube with an inside diameter of less than 6 in. wouldcreate bridging problems with wood chips and blocks. If the enginei s rated at or below 15 horsepower, use a 6-in. minimum fire tubediameter and create a throat rcstriction in the bottom of the tubecorresponding to the diameter entercd in the above table.

For engines with displacement rated in liters, theconversion lactor is 1 liter = 61.02 cubic inches.The horsepower listed above is t h e SAE net brakehorsepower as measured at the rear of the transmission withstandard accessories operating. Since the figures vary when agiven engin e is installed and used for different purposes, suchfigures are representative rather than exact. The abovchorsepower ratings are given at th e engincs highest opera tingspeed.


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53Table 2-3.List of materials for the primary filter unit

a

Item Quantity Description

1B

2%

3B4B

5B

hB

7B

8B

9B10 B

11B

12B

13B14B

1

1

31

1

1

1

1

11

3

1

11

5-gal meta l can o r o thc r m etal conta iner with minimum dimensionsof 11.5-in. diameter and 13 in. tall.Circular metal plate; diameter equal to 1/2 in. smaller than insidediameter of I tem 1B; thickness of 1/8 in.3/8-in. bolts; 3 in. length with two nuts for each bolt.Rectangular snclal platc; width equal t o 1/4 in. smaller than insidedlametcr of Itern 1B; h eig ht q u a l to 2.5 in. smaller than internalheight of I tem 1B ; 1/8 in. thick.High-teanperaturc hosc, 3 /8 t o $/8 in. diarnetcr; length equal tocircumference of I tem BB.Circular m ctal plate; ~ ~ a ~ g t ~ ~equal to outside diameter of Item IR;thickness of l/S in.12-volt blower (automotive heater type); case and fan must be allmctal.Metal cxtension pipe for blower outlct , including elbows an dconnections for vertical orientation; I k ~~~~~~~~ length.C ap fo r I tem 8R; plastic i s atxccptahle.1.25411. metal pipe, electrical mnduit, automotive exhaust pipe,other metal tubing; 2 ft minimurn length.Metal latch fo r securely connccting Items 1B and GB together. Suchdcvices as sui tcase o r luggage catches, bail-type latches, window sashcatches (with strike), or wing-nut latchcs are acceptable.High- temperature hose, 318 to 518 in. diameter; length eq ual to th reetimcs the height of Xtem 4B.Me t a l l/Z-in. pipe, threaded on one cnd; 8 in. length.Me t a l pipe cap fo r Item 13B.


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54Table 24. Lirt of materi

Item Quantity Dcscription1c 12c 13 c1cc 22 c c 2

3 c c 24cc 45 c c 26CC 17CC 14 c 15c 16C 17c 18C 1

1.25-in. closet flange-1.25-in. male-to-female 45 ' pipe elbow.Butterfly valve; see Fig. 2-23.1.25411. pipe nipple or thread ed length of pipe, %in. length.Oval metal plate; 1/16 in. thick; short dimension equal to insidediameter of I tem PCC; long dimension equal to 1.02 t imes the shortdimension.3/8-in. diameter rod; 2.5 in. length.3116411. screws; 3/16 in. length.Flat bar stock; rcctaragular, l/2 by 3 in.; 1/8 in. thick.7/16-in. nut.1/8-in. se t screw.1.25-in. t e c with all k m a l c threads.1.25-in. pipe nipple o r threaded length of pipe, 3 in. length.1.25-in. pipe o r hose.Gasket material; sized to cover I tem 1C.T u b e of pipe compound or Teflon tape for sealing threadcdassemblies.


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3, OPERATING AND M A I N T m G YOUR W O D GAS GENERATOR3.1 USING WOOD AS A FUEL

Because wood was used extensively as generator fuel during World War 11, and sinceit is plentiful in most parts of the populated U nited States, i t merits particular attention forus e as an emergency source of energy. When used in gas generators, about 20 Ib of woodhave the energy equivalence of on e gallon of gasoline.Wood consists of carbon, oxygen, hydrogen, and a small amount of nitrogen. As a ga sgenerator fucl, wood has several advantages. The ash content is quite low, only 0.5 to 2%(by weight), depending on thc: specks and upon the presence of bark. W d i s frce ofsulphur, a contaminant that easily forms sulfuric acid which can cause corrosion damage toboth the engine and the gas generator. Wood is easily ignited-a definite virtue for th e

operation o l any gas generator unit.The main disadvantages for wood as a fuel a re its bulkiness and its moisture content.As it is a relatively light material, one cubic yard of wood produces only 500 to 600 lb of gasgenerator fuel. Moisture content is notoriously high in wood fuels, and i t must be broughtbelow 20% (by weight) before it can be uscd in a gas generator unit. By weight, themoisture in grecn wood runs from 25 to 60%, in air-dried wood from 12 to 15%, and inkiln-dried wood about 8%. Moisture content can be measured quite easily by carefullyweighing a specimen of the wood, placing it in an oven at 220F for thirty minutes,reweighing the specimen, and reheating it until its weight decreases to a constant value. T heoriginal moisture content is cquivalent to the w eight lost ,T he prototype unit in this manual (with an 6-in.-diam firctube) operated well on b othwood chips (minimum size: 3/4 by 3/4 by 1/4 in.) and blocks (up t o 2-in. cubes); see Fig. 3-1 (all figures and tables mentioned in Sect. 3 arc presented a t the end of Sect. 3) . Largcrsizes could be used, if the firetube diameter is increased to prevent bridging of the individualpicces of wood; of course, a throat restriction would then have to be addcd to the bottomof th e f i re tube so as to satisfy the dimensions in Table 2-2 in Sect. 2.

3.2 SPE ENGINE NODElCATIONSTo s tar t the f ire in the gasifier, the blower must be used to create a suction airflowthrough the wood in the hopper and downward in the firetube. If an especially high horse-power engine is to be fueled by the gasifier unit, thcn it might be neccssary to install twosuch blowers and run them simultaneously during start-up.When the wood gas leaves the gasifier unit, all the oxygen pulled down with the airthrough the firctube has been chemically converted and is contained in carbon monoxidc(CO) and water (H,Q). Th e wood gas is unable to burn without being mixed with th e properamount of additional oxygen. If an air leak develops below the grate area, the hot gas willburn while consuming the available oxygen and will create heat; this will almost certainlydestroy the gasificr unit if it is not detected soon. If an air leak develops in th e fi l ter unitor in t he connecting piping, the gas will beconic saturated with improper amounts of oxygen


78/94

56and will become too dilute to power the engine. Therefore, airtightness from the gasifierunit to th e engirie is absolutely essential.Ideally, as the wood gas enten the engine manifold it should be mixed with air in aratio of 1:l or 1.1:l (air to gas) by volume, The carburetion system dcscribed in this reportwill provide this mixture with a minimum of friction losses in th e piping. Th e throt t le controlvalve and the air control valve must be opcrab lc rom the driver's seat of th e vehicle.T h e engine's spark plug gaps should be adjusted to between 0.012 atid 0.015 in.; theignition tinting should be adjustcd to "early."

Initially, you will need to add charcoal to the grate below the Gretube. Subsequentoperat ion will already have the grate full of charcoal which has been left over from theprevious operating period.Fill th e firetube with charcoal' to a levcl 4 in. above the grate. Fill th e hopper withair-dried wood; then, proceed with the routine start-up directions below.

3.4 ROUTINE nART-UP PROCEDURE1. Agitate the g ra te shaker handle for a t least twenty seconds to s hak e down th e charcoalfrom th e previous o perating period.2. Open the ash cleanout port and remove the ashes from the generator housing drum.Lubricate the threads of the cleanout port with high-temperature sil icone, and closethe cover of the cleanout port so that i t is airtight.3 . Fill th e hopper with wood fuel, and tamp the fuel down lightly. Either leave the lid

completely off the fuel hopper, or adjust the opening around the lid to a 3/4-in. (orlarger) clearance.4. Close th e carburetor's air control valve and remove th e cover from the blower exhausto n t o p oE the filter unit. Start the blower, and let it run for thirty seconds to avoidexplosion of residual gas in the system. 'T'hen, with the blower still operating, proceedwith the ncxt step.5. O pe n the ignition port , and ignite a 12- by 12-in. piece of newspaper; with a long sticko r wire, push the burning shee t of newspaper into the gratc; see Fig. 3-2. Close theignition port. If no smoke appears at the blower's exhaust port, repeat the s tar t -up

'Charcoal produced for outdoor barbecue grills is not well suited or gas generatoruse. To produce a bet ter grade of charcoal, place a rag soaked in alcohol on the gra te,or place 3 to 5 pages of newspaper on the gra te, then fill th e fire tube to a height of 18to 12 in. with well-dried wood. H avc all th e valves closed and le t th e f i re tube act as achimney until th e wood is converted to charcoal.


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57

,

sequence from Step (e).Tf repeated attempts fail, new charcoal should be added to theunit as described in Sect. 3.3, above, and the start-up ignition sequence should berepeated.6. Aftcr a few minutes of smoky exhaust, test the gas at the blower exhaust by safely andcarcfully attempting to ignite it ; see Fig. 3-3 . ell th e gas bWnS ConSkteIPtly We l l , Stop

the blower and replace thc covcr the blower exhaust.7. O p en ihc carhinrct:tolis air control valve, adjust the cngiwcs accelerator, and star t theengine in a normal manner. k t th b cngine warm up slowly ( two t o Gvc mirautcs). If

t h e engin c fails to start or dies rcpcatedliy, restart the DIOWCH and rcpcat the ignitionsequence f rom Step (4)

4.5 D NO

3.7 R 8 EPeriodically check all nuts o n the gasifier unit, thc fuel hopper, the filter unit, and thecarburetor for snugness; check all p n c t r a t i o n s and fittings for airbightness. In addition,perform the following maintcnance activities ais s c h e d u l d :


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583.7.1 Daily Maintenmcc

Opcn ;he ash cleanout port of the gasificr housing d i lm and remove th e ashes aftershaking t h e grate for at least thirty seconds. Replace the covci oE the p i t after coating thethreads with high-temperature silicom to ~ S I I T Cairtightness. Open the drain tube at th ebottom of th e flltei container and allow any liquid eondensate to drain out; remember toC~OSCth c drain 'Lube when finished

C k a n o u t th e gasifier housing d ru m , thc file1 hoppix; znd thc filter.. Xinsc out thepiping and conrrectioris to and from the f ick i . Replace th e :.i.card hip inside th e kiltci. (Theused wood chips fron th c filter can bc clumped into the f i d hopper a i d hrirned to producewood gas.) Use high-temperattirc siliconc 011a!l pipe corrnections and on th e filtei lid toens ure ai1tightness.

Make sure t l ra i al l pipe coniipsctions are secure and airtight. Check and tightcn al lmounting connections to th e vehic!c chassis. Ciicck for rust on the outside of the gasgenerator horrsing drum especiaiiy on the lower nrgiiin. C h a t with high-temperatureprotective paint as necessary.

A discwiioii of pob lem s and thc ii related causes and cures is corrtairned in the trouble-shooting guide of Table 3-1. Many operalional problems can be traced to failure to maintainth c airtightness of all piping connectio ns and fittings; t h e piping should be routinely checkedto prevcnt such problems.

Unfo r tunatcly, gas genera tor o peration involves cer

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Wood Gas Generator or Nl

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