Understanding refractory api 936 reading vi

Understanding REFRACTORY For API936 Personnel Certification ExaminationReading 6My Pre-exam Self Study Notes2nd October 2015

Charlie Chong/ Fion Zhang

Iron Treatment Station in Basic O

xygen Furnace

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hong/ Fion Zhang

h t t p : / / w w w . p o i n t f o u r l t d . c o m / d o c u m e n t s / i n d u s t r i a l p h o t o g _ n e w . h t m l

Iron Treatment Station in Basic Oxygen Furnace

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BOF Tapping

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hong/ Fion Zhang

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BOF Tapping

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BODY OF KNOWLEDGE FORAPI936 REFRACTORY PERSONNELCERTIFICATION EXAMINATIONAPI certified 936 refractory personnel must have knowledge of installation, inspection, testing and repair of refractory linings. The API 936 Personnel Certification Examination is designed to identify applicants possessing the required knowledge. The examination consists of 75 multiple-choice questions; and runs for 4 hours; no reference information is permitted on the exam. The examination focuses on the content of API STD 936 and other referenced publications.


REFERENCE PUBLICATIONS:A. API Publications: API Standard 936; 3rd Edition, Nov 2008 - Refractory Installation Quality Control

Guidelines - Inspection and Testing Monolithic Refractory Linings and Materials.

B. ACI (American Concrete Institute) Publications: 547R87 - State of the art report: Refractory Concrete 547.1R89 - State of the art report: Refractory plastic and Ramming Mixes

C. ASTM Publications: C113-02 - Standard Test Method for Reheat Change of Refractory Brick C133-97 - Standard Test Methods for Cold Crushing Strength and Modulus of

Rupture of Refractories C181-09 - Standard Test Method for Workability Index of Fireclay and High

Alumina Plastic Refractories C704-01 - Standard Test Method for Abrasion Resistance of Refractory Materials

at Room Temperatures


Charlie Chong/ Fion Zhang http://www.gentside.com/star-wars/wallpaper/page_2.html

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http://greekhouseoffonts.com/Charlie Chong/ Fion Zhang


The Magical Book of Refractory

Fion Zhang at Shanghai2nd October 2015


Reading VIContent: Reading 1 : Introduction to the Characteristics of Refractories and

Refractory materials Reading 2 : Refractory manufacturing Refractory testing and Refractory

properties Reading 3 : AP 42, Fifth Edition, Volume I Chapter 11: Mineral Products

Industry Refractory Manufacturing Reading 4 : The Fundamentals of Refractory Inspection with Infrared

Thermography


Reading 1: Introduction to the Characteristics of Refractories and Refractory materials

Charlie Chong/ Fion Zhang http://ispatguru.com/introduction-to-the-characteristics-of-refractories-and-refractory-materials/

Reading 1: Introduction to the Characteristics of Refractories and Refractory materials

A suitable selection of the refractory lining material for a furnace can only be made with an accurate knowledge of the chemical (mineralogical) and physical properties of the refractories and refractory materials, and of the stresses of the materials during service. There are four types of stresseswhich refractories face during their period of service. These are given below:

Thermal (effects) The important properties for thermal stresses are pyrometric cone equivalent (PCE), refractoriness under load (RUL), Thermal expansion under load (creep), hot modulus of rupture, thermal expansion, reheat change (after-shrinkage and after-expansion) and thermal shock resistance.

Thermo-technical The important properties for thermo-technical stresses are thermal conductivity, specific heat, bulk density, melting point, thermal capacity and temperature conductivity. (physical properties?)


Mechanical The important properties for mechanical stresses are cold modulus of rupture and deformation modulus, crushing strength, abrasion resistance, porosity and density. (physical properties and forms)

Chemical The important properties for chemical stresses are chemical composition, mineralogical composition and crystal formation, pore size distribution and types of pores, gas permeability and resistance to slag, glass melts, gases and vapours.


Some of the important physical and chemical properties are given below:

1. Melting point Melting point (melting temperatures) specify the ability of materials to withstand high temperatures without chemical change and physical destruction. The melting points of major elements that constitute refractory composition in pure state vary from 1700 deg C to 3480 deg C. The melting point serves as a sufficient basis for considering the thermal stability of refractory mixtures and is an important characteristic indicating the maximum temperature of use.

2. Size and dimensional stability The size and shape of the refractories is an important feature in design since it affects the stability of any structure. Dimensional accuracy and size is extremely important to enable proper fitting of the refractory shape and to minimize the thickness and joints in construction.


3. Porosity Porosity is a measure of the effective open pore space in the refractory and is expressed as the average percentage of open pore space in the overall refractory volume. The mechanical strength of a refractory material is largely determined by the true porosity which is composed of closed pores and open pores, the latter being either permeable or impermeable. For higher mechanical strength, low porosity of the refractory bricks is aimed. The important properties with respect to porosity is its behaviour during chemical attack by molten metal, slag, fluxes and vapour which can penetrate and thereby contribute to degradation of the refractory structure. High porosity materials tend to be highly insulating as a result of high volume of air they trap. The content of open pores of a brick is calculated from the water absorption. By using the water air displacement method, the open pores are classified either as permeable or effective or as impermeable pores.


4. Bulk density The bulk density (BD) is generally considered in conjunction with apparent porosity. It is a measure of the weight of a given volume including the pore space of the refractory. It is one of the important characteristic and provides a general indication of the product quality. An increase in bulk density increases the volume stability, the heat capacity, the resistance to abrasion and slag penetration. The bulk density is determined by means of a (1) hydrostatic scale, according to the (2) mercury displacement method or (3) by measurement.


5. Cold crushing strength It is a measure of the mechanical strength of the refractory brick. In furnaces, cold crushing strength (CCS) is of importance, because of bricks with high crushing strength is more resistant to impact from rods or during removal of slag than a brick with a low CCS. It is a useful indicator to the adequacy of firing and abrasion resistance in consonance with other properties such as bulk density and porosity.

Comments:Typical CCS Values:Brick grade CCS (N /mm2)Silica 15 -20Fire clay 12 - 70Corundum 35 - 80Magnesia 50 - 110Magnesia chromite 30 - 70Magnesia spinel > 40Insulating Brick 3 - 20


6. Pyrometric cone equivalent It is the measurement of the refractoriness. Pyrometric cone eqquivalent (PCE) is the ability to withstand exposure to elevated temperature without undergoing appreciable deformation.

Refractories due to their chemical complexity melt progressively over a range of temperature. This softening behaviour of the refractories is determined by PCE which consists of comparing ceramic specimen of known softening behaviour (seger or orton cones) with the cone of the refractory.

Pyrometric cones are small triangular ceramic prisms that when set at a slight angle bend over in an arc so that the tip reaches the level of the base at a (1) particular temperature if heated (2) at a particular rate. The bending of the cones is caused by the formation of a viscous liquid within the cone body, so that the cone bends as a result of viscous flow.


PCE is measured by making a cone of the refractory and firing it until it bends and comparing it with standard cone. PCE is useful for the quality control purpose to detect variations in batch chemistry that changes or errors in the raw material formulation.

Refractoriness points to the resistance of the refractory to the extreme conditions of heat (> 1000 deg C) and corrosion when hot and molten materials are contained while being transported and/or processed. PCE cones before and after firing is shown at Fig. 1


Fig 1 PCE cones before and after firing


PCE cones after firing


The Wiki: Pyrometric cones EquivalentPyrometric cones are pyrometric devices that are used to gauge heatworkduring the firing of ceramic materials. The cones, often used in sets of three as shown in the illustration, are positioned in a kiln with the wares to be fired and provide a visual indication of when the wares have reached a required state of maturity, a combination of time and temperature. Thus, pyrometriccones give a temperature equivalent; they are not simple temperature-measuring devices.

DefinitionThe pyrometric cone is "A pyramid with a triangular base and of a defined shape and size; the "cone" is shaped from a carefully proportioned and uniformly mixed batch of ceramic materials so that when it is heated under stated conditions, it will bend due to softening, the tip of the cone becoming level with the base at a definitive temperature. Pyrometric cones are made in series, the temperature interval between the successive cones usually being 20 degrees Celsius. The best known series are Seger Cones (Germany), Orton Cones (USA) and Staffordshire Cones (UK).

Charlie Chong/ Fion Zhang https://en.wikipedia.org/wiki/Pyrometric_cone

Self-supporting cones prior to firing (top) and after (bottom)


Seger cones after use


HistoryIn 1782, Josiah Wedgwood created accurately scaled pyrometric beads, which led him to be elected a fellow of the Royal Society.

The modern form of the pyrometric cone was developed by Hermann Segerand first used to control the firing of porcelain wares at the KniglichePorzellanmanufaktur (Royal Porcelain Works) in Berlin, in 1886. Seger cones are to this day made by a small number of companies and the term is often used as a synonym for pyrometric cones. The Standard Pyrometric Cone Company was founded in Columbus, Ohio, by Edward J. Orton, Jr. in 1896 to manufacture pyrometric cones, and following his death a charitable trust was established to operate the company, now known as the Edward Orton Jr. Ceramic Foundation (also known as the Orton Ceramic Foundation or simply "Orton") in suburban Westerville, Ohio.


Glaze cones were made by evaporating water from a liquid glaze until the resulting mass reached the consistency of a plastic clay. The plastic mixture was then formed into cones that were dried and set in a soft pad of clay in a kiln. When observed through the viewing port of a kiln, the potter could see when a glaze cone had reached its melting point. The rings were removed from the kiln through special loopholes in the kiln walls using metal rods and examined for signs of melting in the glaze.


UsageFor some products, such as porcelain and lead-free glazes, it can be advantageous to fire within a two-cone range. The three-cone system can be used to determine temperature uniformity and to check the performance of an electronic controller. The three-cone system consists of three consecutively numbered cones: Guide cone one cone number cooler than firing cone. Firing cone the cone recommended by manufacturer of glaze, slip, etc. Guard cone one cone number hotter than firing cone.Additionally, most kilns have temperature differences from top to bottom. The amount of difference depends on the design of the kiln, the age of the heating elements, the load distribution in the kiln, and the cone number to which the kiln is fired. Usually, kilns have a greater temperature difference at cooler cone numbers. Cones should be used on the lower, middle and top shelves to determine how much difference exists during firing. This will aid in the way the kiln is loaded and fired to reduce the difference. Downdraft venting will also even out temperatures variance.


Both temperature and time and sometimes atmosphere affect the final bending position of a cone. Temperature is the predominant variable. The temperature is referred to as an equivalent temperature, since actual firing conditions may vary somewhat from those in which the cones were originally standardized. Observation of cone bending is used to determine when a kiln has reached a desired state. Additionally, small cones or bars can be arranged to mechanically trigger kiln controls when the temperature rises enough for them to deform. Precise, consistent placement of large and small cones must be followed to ensure the proper temperature equivalent is being reached. Every effort needs to be made to always have the cone inclined at 8 from the vertical. Large cones must be mounted 2 inches above the plaque and small cones mounted 15/16 inches. With the cones having their own base, "self-supporting cones" eliminate errors with their mounting.


Quoted: Additionally, small cones or bars can be arranged to mechanically trigger kiln controls when the temperature rises enough for them to deform.


Control of variabilityPyrometric cones are sensitive measuring devices and it is important to users that they should remain consistent in the way that they react to heating. Cone manufacturers follow procedures to control variability (within batches and between batches) to ensure that cones of a given grade remain consistent in their properties over long periods. A number of national standards and an ISO standard have been published regarding pyrometric cones.

Even though cones from different manufacturers can have relatively similar numbering systems, they are not identical in their characteristics. If a change is made from one manufacturer to another, then allowances for the differences can sometimes be necessary.


7. Refractoriness under load Refractoriness under load (RUL) evaluates the softening behaviour of fired refractory bricks at rising temperature and constant load conditions. RUL gives an indication of the temperature at which the brick will collapse in service condition with similar load. However, under actual service conditions the bricks are heated only on one face and most of the load is carried by the relatively cooler rigid portion of the refractory bricks. Hence, the RUL test gives only an index of refractory quality, rather than a figure which can be used in a refractory design. Under service conditions, where the refractory used is heating from all sides such as checkers, partition walls etc. the RUL test data is quite significant. For RUL, samples in cylindrical shape of 50 mm height and 50 mm diameter are heated at a constant rate under a load of 0.2 N/mm2 (0.2Mpa) and the change in height includes the thermal expansion and also the expansion of test equipment. The test results are taken from the recording. The initial temperature is taken at 0.6 % compression while the final temperature is taken at 20 % compression or when the specimen has collapsed. RUL curves of different refractories are at Fig 2


Fig 2 RUL curves of different refractories


0.2 N/mm2

50 x 50 mm

RUL Testing Set-up


RUL


8. Thermal expansion under load (Creep) Thermal expansion under load (Creep) is a time dependent property which determines the deformation in a given time and at a given temperature by a refractory under stress. Refractory material must maintain dimensional stability under extreme temperatures (including repeated thermal cycling) and constant corrosion from hot liquid and gases. In the creep test, specimen of 50 mm diameter and 50 mm height with an internal bore for the measuring rod is heated at constant rate and under a given load (generally at 0.2 N/mm2). After the required temperature is reached, the samples is held for 10 -50 hours. The compression of the specimen, after maximum expansion has been attained, is given in relation to the test time as a measure of creep at a specified test temperature. Creep curves of refractories are at Fig 3


Fig 3 Creep curves of refractories


Creep curves of refractories


Softening under load


9. Volume stability, expansion and shrinkage at high temperaturePermanent change in the dimension of a refractory due to contraction and expansion during service can take place due to:

The changes in the allotropic forms which cause a change in specific gravity.

A chemical reaction which produces a new material of altered specific gravity.

The formation of a liquid phase Sintering reactions Due to fluxing by dust and slag or by the action of alkalis in case of fireclay

refractories.

After heating to high temperatures and subsequent cooling, a permanent change in dimensions often occurs. This can cause either loosening of bricks during service or the destruction of brickwork due to the pressure. Permanent linear change (PLC) on heating and cooling of the refractory bricks give an indication of volume stability of the brick as well as the adequacy of the processing parameters during manufacture. It is particularly significant as a measure of conversion achieved in the manufacture of silica refractories.


10. Reversible thermal expansion Refractories like any other materials expands when heated and contracts when cooled. The reversible thermal expansion is a reflection on the phase transformation (?) that occurs during heating and cooling. The PLC and the reversible expansion are followed in the design of refractory lining for provision of expansion joints. As a rule, those with a lower thermal expansion co-efficient are less susceptible to spalling.


Fig 4 Thermal expansion of different refractories


11. Thermal conductivity Thermal conductivity is defined as the quantity of heat that will flow through a unit area in direction normal to the surface area in a defined time with a known temperature gradient under steady state conditions. It indicates general heat flow characteristics of the refractory and depends upon the chemical and mineralogical composition as well as the application temperature. High thermal conductivity refractories are needed for some applications such as coke ovens, regenerators etc. On the other hand refractories with lower thermal conductivity are preferred in most application since they help in conserving heat energy. Porosity is an important factor in heat flow through refractories. The thermal conductivity of a refractory decreases on increasing its porosity. Although it is one of the least important properties as far as service performance is concerned, it evidently determines the thickness of the brickwork.


12. Thermal shock resistance It characterizes the behaviour of refractories to sudden temperature shocks. Temperature fluctuations can reduce the strength of the brick structure to a high degree and can lead to disintegrtaion or spalling in layers There are several methods of determining the thermal shock resistance each having its own advantages and disadvantages.

13. Specific heat The specific heat is a material and temperature related energy factor and is determined with the help of calorimeters. The factor indicates the amount of energy (calories) needed to raise the temperature of one gram of material by 1 deg C. Compared to water, the specific heats of refractory materials are very low. These values are less than one fourth () of value of specific heat of water.


14. Abrasion resistance The mechanical stress of refractory bricks is not caused by pressure alone, but also the abrasive attack of the solid raw materials as it slowly pass over the brickwork and by the impingement of the fast moving gases with fine dust particles. Therefore the cold crushing strength is not alone sufficient to characterize the wear of the refractories. There is no approved method for testing abrasion resistance but there are some methods available to give reference values such as Bohme grinding machine method and sand blast method etc.

Note: ASTM C704-01Standard Test Method for AbrasionResistance of Refractory Materials atRoom Temperature


15. Modulus of Rupture or Modulus of deformation During thermal stress, generally combined with altered physical-chemical conditions because of infiltration, strain conditions occur in refractory brickwork which can lead to brick rupture or crack formation. In order to determine the magnitude of rupture stress, the resistance to deformation under bending stress (rupture strength) is measured. Determination of the modulus of deformation in the cold state is carried out, together with modulus of rupture, on a test bar resting on two bearing edges. In general, a high ductility is looked for in refractory bricks,i.e. a large deformation region without rupture, which means a high value of the ratio of modulus of rupture to modulus of deformation.The modulus of rupture is defined as the maximum stress of a rectangular test piece of specific dimensions which can withstand maximum load until it breaks, expressed in N/mm2. For hot modulus of rupture (HMOR) load is applied at a high temperature. The international standard test method is described in ISO 5013 with test piece dimensions of 150 mm x 25 mm x 25 mm.

Note: ASTM C133-97 Standard Test Methods for Cold Crushing Strength and Modulus of Rupture of Refractories


16. Mineralogical composition and crystal formation The behaviour of refractories of identical composition also depends on the type of raw materials used and on the reactions achieved during firing of the bricks. A glassy phase is more susceptible to attack by slag than a tightly interlocked crystal lattice structure. Two methods are used to identify mineralization composition. In the first method polarizing microscope or scanning electron microscope (SEM) is used. In the second method X-ray diffraction analysis is done.


EndofReading1.Charlie Chong/ Fion Zhang

Reading 2: Refractory manufacturing Refractory testingand Refractory properties


Refractory manufacturing Refractory testing and Refractory propertiesWhat is refractory ?Is it a material which should withstand high temperature only ?The right definition is that it should withstand high temperature,resistance tothermal and thermo chemical load, posses high volume stability, resistant toerosion and abrasion, be tough , and resistant to chemical corrosionetc. Or otherwise it should have high RUL, high PCE, low conductivity , highhot MOR, high creep resistance and optimum CCS etc.

There is no refractory material which posses all the above properties 100 %

Overall it is a compromise with all the above properties.Choice of refractories depend on the operating and mechanicalconditions of the kiln.



CCS testing machine


Cold crushing equipment and CCS values

Brick grade CCS ( N / mm2)Silica 15 -20Fire clay 12 - 70Corundum 35 - 80Magnesia 50 - 110Magnesia chromite 30 - 70Magnesia spinel > 40Insulating Brick 3 - 20


PCE


Creep test equipments


Refractoriness under load RULThis is a measure of the resistance of a refractory body to the combinedeffects of heats of load.This test helps to study the behavior of a refractoryproduct when subjected to a constant load under conditions of progressivelyrising temperature. The ground mass / matrix helps to bond the entire mass ofa refractory brick strongly together. The amount and the strength of the glassis fixed by the alumina - silica ratio, fluxing oxide content and the temperatureof firing. It is an important parameter to decide upon the safer limit of servicetemperature in a given situation. Contributing factors to the increasedresistance to the pressure are:

a) More thorough distribution of liquid throughout the brickb) The growth of crystals through the influence of heatc) Crystallization of a portion of the liquid during cooling.


High temperature creepIn a brick held at constant temperature and pressure, gradual solution of solidmaterial up to the limits of its solubility in the liquid may cause some increasein the viscosity of the liquid. This increase is dependent on the nature ofground mass, glass content. Higher glass content will result higherdeformation in this situation. This property of refractoriness is called hightemperature creep. Lower deformation will ensure rigidity under the servicecondition. The creep is the measurement of deformation of a refractoryproduct as a function of time when it is subjected to a constant load andheated at a specified temperature.


Creep Curve


Softening under load


Linear expansion (Permanent linear change)High temperature reheat test may be used to reveal1) if a brick has been fired long enough or at a high temperature2) whether a brick has adequate refractoriness and volume stability It is

expressed as a percentage , preferably by the ratio of the length of the test piece after heating and the original value of the length


Equipments used to determine Thermal expansion


Thermal expansion or refractory materials


Equipments for thermal shock resistance test


MOP- The resistance to bending stress of refractory products provideinformation on their deformation behavior at high temperature.


HMOP


Chemical compositionBy quantifying all the constituents present in refractory, it is possible toassess the chemical properties and melting behavior of a given refractory.Asit is important to know the % Al2O3 in high alumina brick, % MgO inmagnesite brick , and % SiO2 in silica brick etc.,the determination of minorconstituents has also been recognized as controlling factors in theperformance of many refractories. The chemical composition is of greatimportance with respect to attack by slag , glass melts , flue dusts and vapors.In general the principle applies that a brick is more resistant the lower the rateof chemical reaction gradient between the slag and brick is.

Therefore, where the acid slag is expected , acid bricks are preferably used , and basic bricks where basic slag is expected.


According to the behavior during contact reaction, the following groups ofbricks can be differentiated.

Acid group - fused (99% SiO2), Silicon carbide bricks, Zircon crystobalite . Zircon silicate

Basic group - dolomite, magnesia, magnesia chrome, chrome magnesia ,forsterite

Inert or neutral - carbon , high alumina chromite group


Cup corrosion test

Alkali test of a high alumina brickwith K2CO3

Alkali test of a sic containinghigh alumina brick with K2CO3


Mineralogical investigations by X-ray diffraction Determination of themineral phases composition of material X-ray diffraction diagram of a usedmagnesia spinel brick grade, salt infiltrated.


Microscopically techniques ( micrologies) Light micoscopy ( transmitted light and reflected light microscopy Microprobe analysis ( WDS, EDS) Scanning electron microscopy Advantages of these micrlogies opposite

other investigation methods Diagnosis of mineral phases composition in raw materials , refractory

products etc and their configuration ( textural/ structural criterions, pore shape and size etc


Mineralogical investigations- Reflected light microscopy Pictures of magnesia- spinel brick grades with different raw material composition


Microprobe Analysis- Chemical mineralogical composition in mmBoundary between slag and corundum brick

Polished section image(reflected light microscope)

Back scattered electron image(microprobe)


Mineralogical investigations- Scanning electron microscopy (SEM)Hydration of Magnesia . crack formation ,caused by formation ofbrucite(Mg(OH)2


Minerological investigations

Reading 3: AP 42, Fifth Edition, Volume I Chapter 11: Mineral Products IndustryRefractory Manufacturing

Charlie Chong/ Fion Zhang http://www3.epa.gov/ttn/chief/ap42/ch11/


AP42.VI-11.5 Refractory Manufacturing11.5.1 Process DescriptionRefractories are materials that provide linings for high-temperature furnaces and other processing units. Refractories must be able to withstand physical wear, high temperatures (above 538C [1000F]), and corrosion by chemical agents. There are two general classifications of refractories, clay and nonclay. The six-digit source classification code (SCC) for refractory manufacturing is 3-05-005. Clay refractories are produced from fireclay (hydrous silicates of aluminum) and alumina (57 to 87.5 percent). Other clay minerals used in the production of refractories include kaolin, bentonite, ball clay, and common clay. Nonclay refractories are produced from a composition of alumina (


There are two general classifications of refractories: clay and nonclay. Clay refractories are produced from: fireclay (hydrous silicates of aluminum) and alumina (57 to 87.5%). kaolin, bentonite, ball clay, and common clay.

Nonclay refractories are produced from a composition of: alumina (


Refractories are produced in two basic forms:1. formed objects, and 2. unformed granulated or plastic compositions.

The preformed products are called bricks and shapes. These products are used to form the walls, arches, and floor tiles of various high-temperature process equipment.

The Unformed compositions include:1. mortars, 2. gunning mixes, 3. castables (refractory concretes), 4. ramming mixes, and5. plastics.

These products are cured in place to form a monolithic, internal structure after application.


Refractory manufacturing involves four processes: raw material processing, forming, firing, and final processing. Figure 11.5-1 illustrates the refractorymanufacturing process. Raw material processing consists of crushing andgrinding raw materials, followed if necessary by size classification and rawmaterials calcining and drying. The processed raw material then may be dry-mixed with other minerals and chemical compounds, packaged, and shipped as product. All of these processes are not required for some refractory products.

Forming consists of mixing the raw materials and forming them into the desired shapes. This process frequently occurs under wet or moist conditions.Firing involves heating the refractory material to high temperatures in aperiodic (batch) or continuous tunnel kiln to form the ceramic bond that givesthe product its refractory properties. The final processing stage involvesmilling, grinding, and sandblasting of the finished product. This step keeps theproduct in correct shape and size after thermal expansion has occurred. Forcertain products, final processing may also include product impregnation withtar and pitch, and final packaging.

12

FIRING(SCC 3-05-005-07, -09)

DRYING(SCC 3-05-005-01, -08)

FORMING

MIXING

STORAGE

12

1

SCREENING/CLASSIFYING

1

1

1

1

DRY-MIXING/BLENDING

PACKAGING

1 1

COOLING

2 1

MILLING/FINISHING SHIPPING

12

1

1

2

PM EMISSIONS

GASEOUS EMISSIONS

(OPTIONAL)

(OPTIONAL)CALCINING/

DRYING(SCC 3-05-005-02)

WEATHERINGSTORAGE

TRANSPORTING

CRUSHING/GRINDING(SCC 3-05-005-02)

11.5-2 EMISSION FACTORS 1/95

Figure 11.5-1. Refractory manufacturing process flow diagram.1(Source Classification Codes in parentheses.)


Fused Products & Ceramic Fibers.Two other types of refractory processes also warrant discussion. The first is production of fused products. This process involves using an

electric arc furnace to melt the refractory raw materials, then pouring the melted materials into sand-forming molds.

Another type of refractory process is ceramic fiber production. In this process, calcined kaolin is melted in an electric arc furnace. The molten clay is either fiberized in a blowchamber with a centrifuge device or is dropped into an air jet and immediately blown into fine strands. After theblowchamber, the ceramic fiber may then be conveyed to an oven for curing, which adds structural rigidity to the fibers. During the curingprocess, oils are used to lubricate both the fibers and the machinery used to handle and form the fibers. The production of ceramic fiber for refractory material is very similar to the production of mineral wool.


11.5.2 Emissions And ControlsThe primary pollutant of concern in refractory manufacturing is particulate matter (PM). Particulate matter emissions occur during the crushing, grinding,screening, calcining, and drying of the raw materials; the drying and firing ofthe unfired "green" refractory bricks, tar and pitch operations; and finishing ofthe refractories (grinding, milling, and sandblasting).

Emissions from crushing and grinding operations generally are controlled with fabric filters. Product recovery cyclones followed by wet scrubbers are used on calciners and dryers to control PM emissions from these sources. The primary sources of PM emissions are the refractory firing kilns and electric arc furnaces. Particulate matter emissions from kilns generally are not controlled. However, at least one refractory manufacturer currently uses a multiple-stage scrubber to control kiln emissions. Particulate matter emissions from electric arc furnaces generally are controlled by a baghouse. Particulate removal of 87 percent and fluoride removal of greater than 99 percent have been reported at one facility that uses an ionizing wet scrubber.


Pollutants emitted as a result of combustion in the calcining and kilning processes include sulfur dioxide (SO2), nitrogen oxides (NOx), carbonmonoxide (CO), carbon dioxide (CO2), and volatile organic compounds(VOC). The emission of SOx is also a function of the sulfur content of certainclays and the plaster added to refractory materials to induce brick setting.Fluoride emissions occur during the kilning process because of fluorides inthe raw materials. Emission factors for filterable PM, PM-10, SO2, NOx , andCO2 emissions from rotary dryers and calciners processing fire clay arepresented in Tables 11.5-1 and 11.5-2. Particle size distributions for filterableparticulate emissions from rotary dryers and calciners processing fire clay arepresented in Table 11.5-3.

Volatile organic compounds emitted from tar and pitch operations generally are controlled by incineration, when inorganic particulates are not significant. Based on the expected destruction of organic aerosols, a control efficiency in excess of 95 percent can be achieved using incinerators.


Table 11.5-1 (Metric Units). EMISSION FACTORS FOR REFRACTORYMANUFACTURING: FIRE CLAY, EMISSION FACTOR RATING: D

a Factors represent uncontrolled emissions, unless noted. All emission factors in kg/Mg of raw material feed. SCC = Source Classification Code. ND = no data.b Filterable PM is that PM collected on or before the filter of an EPA Method 5 (or equivalent) sampling train. PM-10 values are based on cascade impaction particle size distribution.


Table 11.5-2 (English Units). EMISSION FACTORS FOR REFRACTORY MANUFACTURING: FIRE CLAY, EMISSION FACTOR RATING: D


Table 11.5-3. PARTICLE SIZE DISTRIBUTIONS FOR REFRACTORYMANUFACTURING: FIRE CLAY, EMISSION FACTOR RATING: D


Chromium is used in several types of nonclay refractories, including chrome-magnesite, (chromite-magnesite), magnesia-chrome, and chrome-alumina.Chromium compounds are emitted from the ore crushing, grinding, materialdrying and storage, and brick firing and finishing processes used in producingthese types of refractories. Tables 11.5-4 and 11.5-5 present emission factorsfor emissions of filterable PM, filterable PM-10, hexavalent chromium, andtotal chromium from the drying and firing of chromite-magnesite ore. Theemission factors are presented in units of kilograms of pollutant emitted permegagram of chromite ore processed (kg/Mg CrO3) (pounds per ton ofchromite ore processed [lb/ton CrO3]). Particle size distributions for the dryingand firing of chromitemagnesite ore are summarized in Table 11.5-6. Anumber of elements in trace concentrations including aluminum, beryllium,calcium, chromium, iron, lead, mercury, magnesium, manganese, nickel,titanium, vanadium, and zinc also are emitted in trace amounts by the drying,calcining, and firing operations of all types of refractory materials. However,data are inadequate to develop emission factors for these elements.


Emissions of PM from electric arc furnaces producing fused cast refractory material are controlled with baghouses. The efficiency of the fabric filtersoften exceeds 99.5 percent. Emissions of PM from the ceramic fiber processalso are controlled with fabric filters, at an efficiency similar to that found inthe fused cast refractory process. To control blowchamber emissions, a fabricfilter is used to remove small pieces of fine threads formed in the fiberizationstage. The efficiency of fabric filters in similar control devices exceeds 99percent. Small particles of ceramic fiber are broken off or separated duringthe handling and forming of the fiber blankets in the curing oven. An oil isused in this process, and higher molecular weight organics may be emitted.However, these emissions generally are controlled with a fabric filter followedby incineration, at an expected overall efficiency in excess of 95 percent.


Table 11.5-4 (Metric Units). EMISSION FACTORS FOR REFRACTORY MANUFACTURING: CHROMITE-MAGNESITE ORE, EMISSION FACTOR RATING: D (except as noted)


Table 11.5-5 (English Units). EMISSION FACTORS FOR REFRACTORY MANUFACTURING: CHROMITE-MAGNESITE ORE, EMISSION FACTOR RATING: D (except as noted)


Table 11.5-6. PARTICLE SIZE DISTRIBUTIONS FOR REFRACTORY MANUFACTURING: CHROMITE-MAGNESITE ORE DRYING AND FIRING

Reading 4: The Fundamentals of Refractory Inspection with Infrared Thermography

Charlie Chong/ Fion Zhang http://www.irinfo.org/articleofmonth/pdf/article_2_2006_james.pdf


The Fundamentals of Refractory Inspection with Infrared ThermographyAbstractThermography has been used to inspect the condition of refractory lined vessels and piping for many years now. It is a proven and accepted methodfor locating damaged and missing refractory material. Most companieshowever, do not fully understand the full benefits of performing refractorysurveys. They mainly use thermography only before a plant turnaround todetermine the extent of refractory damage in order to estimate the materialsand labor needed for the repairs. This paper discusses the fundamentals ofrefractory inspection and how Thermal Diagnostics Limited has been usingInfrared thermography in Trinidad and Tobago as an effective means ofpredicting areas of future refractory problems in addition to pre-turnaroundsurveys.

http://www.tdlir.com/


IntroductionFirst, let me introduce myself to those who do not know me. I am Sonny James, born and raised in Montreal, Canada but now living and working inbeautiful Trinidad and Tobago. I have been doing thermography for the pastthirteen years. My first thermographic inspection was helping my father withan electrical survey of a plastic injection factory. He strapped the camera onmy shoulder and said, find me some hot spots! From that day on, I wasfascinated by this remarkable technology. So, I am here today to talk aboutrefractory inspections. Now, there may be some of you saying to yourselves,what can a person from Trinidad and Tobago know about inspectingrefractory? And my answer would be this:


The Island of Trinidad may well be considered the capital of refractory lined vessels. Trinidad is the largest producer and exporter of ammonia andmethanol in the entire world. To date, we have 10 ammonia plants producing5.7 million tons per year and 7 methanol plants producing 6.5 million tons peryear. Trinidad and Tobago has the two largest methanol plants in the world;ATLAS Methanol that produces 1.7 million tons per year and M5000 thatproduces 1.8 million tons per year. We also have the largest direct reducediron (DRI) steel plant in the world (1.4 million ton DRI MidrexTM Megamod)and much, much more. Most of these plants also surpass the technology thatis currently found in North America and Europe as they are new, state-of-the-art designs and much more efficient. The main reason Trinidad and Tobago isthe world leader in ammonia and methanol production is due to its abundanceof natural gas. In fact, the United States imports approximately 75% of itsLNG directly from Trinidad and Tobago.


What is just as amazing is that most of these plants are situated in an area only approximately 4 square miles called the Point Lisas Industrial Estate. Inan average year, I inspect over 20 steam reformers, secondary reformers,boilers, transfer li ne piping, furnaces, and other refractory lined vessels.Because Trinidad has so many chemical plants situated so close to eachother, it is imperative that high safety standards be put in place. One meansof preventing a catastrophic failure is by regularly inspecting equipment withinfrared thermography.


DiscussionWhy Inspect for Refractory Problems?What many people are unaware of is that the repair cost of refractory lined

equipment and the consequences that may occur due to refractory failuregreatly exceeds that of rotating machinery and electrical failures. This ismainly because:

1. Repairing refractory lined equipment usually requires a total plant shutdown. This equipment is essential for the process and backups are not available, unlike a motor, pump or MCC breaker that can easily be switched over to a backup with minimal or no production loss.

2. The repair cost of refractory lined equipment is usually hefty, as it requires a lot more manpower labor, heavy equipment, materials and time to effectively carry out repairs.

The main reason a vessel or piping is lined with internal refractory is because the internal temperature is so hot that it will destroy the actual steel shell ofthe vessel. So, refractory material is installed in order to minimize the heating of the external shell.


Internal Refractory Damage of Piping, Resulting in Critical Overheating of Steel


Refractory also ensures that valuable energy is not being wasted and that vessel efficiency is kept at optimum levels. Refractory comes in variousmaterials and application techniques such as brick, injectable, gunite, etcRefractory is also exposed to tremendous stresses during a vesselsoperation. There is a great deal of expansion, contraction, heat, cyclic andconvection (wind) stresses inside vessels such as reformers and boilers.There are even some refractory lined equipment that are under highpressures, such as transfer line piping. All of these stresses can causerefractory failure. When there is refractory failure, there is an inadequateinsulating barrier between the extreme internal heat and the weak steel shell.This can lead to a vessels shell overheating and burn-through, resulting indangerous gases, flames and heat exposure. Structural weakening can alsooccur, with the end result being a catastrophic failure.

When you have a vessel or piping that is under high pressure, you have the dangers of a massive and potentially deadly explosion. It should be noted thatwhen dealing with high-pressure equipment, the maximum allowabletemperature of the metal is drastically reduced because of this added stress.


Primary Reformer Wall Showing Multiple Refractory Problems


The Inspection: When to Inspect?Refractory inspection is both an art and a science. Almost all thermographicinspections of refractory are performed while the vessel is operating under normal or full rates. This is because many thermographers and engineers aretaught that IR should only be done when the equipment is under an adequateamount of load. This may be true for electrical and rotating equipment, butnothing can be further from the truth when it comes to refractory. The fact isthat during the start-up cycle of a vessel, it goes through a series of changesin process and temperature that affect the refractorys behavior. When an IRinspection is conducted during the initial start-up period, you may noticeseveral hot areas. This is usually due to cracks, gaps and voids in therefractory wall. These hot areas should be recorded for future reference, asthese are the areas most prone to failure.


With change of process, increased temperature and time during the start-up, you may notice these initial anomalies getting considerably hotter. Someareas may even reach close to critical temperature and even start to showvisible signs of overheating on the external shell. These hot spots should alsobe recorded at this stage. The critical hot spots should also be closelymonitored during the course of the start-up.

When the vessel is close to or has reached full rates and temperature, you may notice that most of the hot spots observed during the stages of start-uphave reduced in size and temperature. This is because the refractory hasproperly expanded and sealed off the cracks and gaps.


You may also notice that some hot spots have remained. This is because there is some problem with the refractory at that area such as cracks, voids,failure, damage, etc. These problems should be recorded at this particulartime, as these will be the majority of hot spots that will be observed duringroutine inspections while the vessel is under normal operation.


36-Hour Timeline of Refractory Hot Spot During a Plant Start-Up


By inspecting refractory during different start-up stages, you have recorded all current problems and you have also recorded potential areas that aresusceptible to future problems or failure. You are now on your way to asuccessful predictive maintenance program for your refractory lined vesselsby establishing your baseline data for future trending and monitoring.


Houston, We Have a Problem!In refractory inspection, as with pretty much almost every other type of equipment inspected, there always comes the dreaded question of How HotIs Too Hot? Now, when it comes to refractory, there is no one temperature oranswer to your overheating problems. Many factors come into play whenyoure dealing with a piece of equipment that usually results in total plantshutdown if repairs are to be done. Face it! Plants are in business to makemoney and the only way they make money is by production. So most of thetime, shutting down a vessel for refractory repairs as a result of an excessivehot spot is usually not an option.


Certain factors must be weighed first, such as: Safety of plant personnel (Id like to think that this is #1 on the list) Affects on the equipment and end product Business interruption costs Current market price of the product being produced at the plant And others

In most cases, overheating sections due to refractory problems can be temporarily overcome and controlled by certain methods. Remember that themain purpose of the refractory is to minimize the amount of heat exposed tothe steel shell of the vessel. Therefore, if you no longer have this ability in acertain area due to internal refractory problems, you may be able to controland minimize the overheating on the external surface with the use of steamlances, hoses and spargers and in some cases with a constant flow of water.


The process of external cooling will keep the shell of the vessel at that area from overheating and failure. The result: being able to keep the plantoperational and making money. It is important to understand that althoughyou now have a way of keeping the area cool via external means, you muststill monitor this area on a frequent basis in order to verify that the cooling iseffective and that the internal problem is not spreading or worsening. It shouldalso be noted that this approach does not always apply to all critical refractoryhot spots. There are some situations that you have no choice but to shut thevessel down to perform repairs. In some cases, you may be able to repairthese overheating areas online with injectable refractory and otherspecialized online refractory repair techniques. You should also try to inspectand record all repairs in order to maintain a proper trend and database.


Visible Example of Steam Cooling & Injectable Refractory Nipples


Based on my years of experience inspecting refractory lined equipment, I have established a user defined Delta-T repair criteria that has proven to be quite efficient in prioritizing the severity of most refractory hot spots:

# 1: 1C - 35C (2F - 63F): Indicates a possible minor problem &warrants periodic checks.

# 2: 35C - 70C (63F - 126F): Indicates problem & warrants periodic monitoring.

# 3: 70C - 100C (126F - 180F): Indicates concern & warrants frequent monitoring.

# 4: >100C (>180F): Indicates high concern & warrants monitoring & corrective measures.


This Delta-T repair criteria is very conservative and is only used as a guideline for plant engineers to determine what actions are warranted.Ultimately, the deciding factor as to exactly How Hot is Too Hot is unique forevery type of equipment. It is recommended that accurate Absolutetemperatures be documented in order to reference with the maximumallowable shell temperature for that particular piece of equipment. It is onlyfrom these Absolute temperatures that an effective course of action can betaken.


Identification of Refractory ProblemsWhen inspecting refractory lined piping such as a transfer line, locating and identifying problems due to refractory failure is fairly simple as there areusually no internal structures within the piping that may confuse thethermographer.


Refractory Problems on a Typical Transfer Line Piping


However, when inspecting vessels such as steam reformers, boilers, heaters, etc., it is important to know what the internal make-up of each vessel is.Internal supports and structures such as brackets, beams, trays, tubes andbolts that are attached to the shell of the vessel may actually be thermallyvisible during the inspection. This is because of heat conduction. So, knowingwhat is inside a vessel can help you in your analysis and diagnosis of yourinspection.


Top of Convection Box Showing Effects of Heat Conduction from Internal Anchors


There are also certain areas within every vessel that are prone to refractory failure. Vessels are mainly designed by their functional or operationalcharacteristics. Although the design of a vessel does accommodate refractoryinstallation, there is no costeffective way to design a vessel to be fullyrefractory failure-proof. Some areas on vessels that are prone to refractoryfailure are:

Welded joint sections Corners and seams Man-way sections Top 180 of piping Roofs Opening areas such as sight-ways and ports Burner areas


Although these are the most common places where refractory failure occurs, it is not uncommon to have problems and failures on the vertical wall sectionsand bottom flooring. It is important to inspect every accessible part of a vesseland piping in order to perform an effective refractory inspection.

That is why it is important to take your time and inspect in a systematic way, making sure everything is inspected because the area you missed will quite often be the area that fails. Its good practice to first perform a walkthrough of the entire vessel or piping system before turning on your imager.

By doing this before your survey you benefit from: Knowing how and where to start the inspection and what route to take Identifying potentially unsafe and hazardous conditions Identifying visibly noticeable problems and flagging them for your IR

inspection


ConclusionWith the highly competitive markets out there, it is important to keep your production costs down as well as try to prevent equipment failures. By usingInfrared Thermography actively and frequently on refractory lined equipment,you are in a better position to predict problems, keep your equipmentrunning during problem times and also properly schedule repairs andestimate the total materials needed for these repairs. The notions thatrefractory inspections should only be performed just before a scheduled plantturnaround in order to estimate repairs or be performed only when a visibleproblem is evident should be reviewed. Most refractory lined equipment iscritical to your plants operation and should therefore be monitored on aregular basis.


Point Lisas Industrial Estate Trinidad

http://www.tdlir.com/


Good Luck!


Good Luck!

Understanding REFRACTORY For API936 Personnel Certification Examination Reading 6Reading 1: Introduction to the Characteristics of Refractories and Refractory materialsReading 2: Refractory manufacturing Refractory testing and Refractory propertiesReading 3: AP 42, Fifth Edition, Volume I Chapter 11: Mineral Products IndustryRefractory ManufacturingReading 4: The Fundamentals of Refractory Inspection with Infrared ThermographyGood Luck!

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