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Presentation On Removal Of Silica From

Wheat Straw And Sacchrum Munja

Presented By-Jyoti Blehria Gct/095730Ashok S. Mahara Gct/095701

Khim S. Tangania Gct/095711Harendra Ku. Singh Gct/095742

Project Guide-Mr. A.S.K. SinhaAP, Chemical Deptt.

S.L.I.E.T, Longowal

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CONTENTS

Introduction of sacchrum munja and wheat straw

S. munja and wheat straw as raw material for paper industry

Problems associated with silica in raw material

Chemical analysis of sample without impregnation

Impregnation of sample with NaOH and urea

Comparison of silica content of sample for different conditions.

Conclusions

References

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Saccharum munja, known as munja is a grassfound in arid areas and along river banks in India.

It grows up to 2 meters in height.

It is used as a raw material for thatching roofs,making baskets, as animal feed & it is also usedfor making ropes.

Additional uses like paper making, chemicalextraction and carbon production are alsoconsidered.

SACCHARUM MUNJA

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Sacchrum-munja

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The global agricultural sectorproduces billions of tonnes ofwheat straw.

Only a small fraction of this isused as animal feeds and for

energy production.

Most of the agricultural wastesare left unused, creating

environmental problems due toimproper waste managementsuch as on-site burning and land-dumping.

on-site burning

AGRICULTURAL WASTE-WHEAT STRAW

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WHEAT STRAW AND SACCHRUM MUNJA AS RAW

MATERIAL FOR PAPER INDUSTRY:-

Paper made from wheat straw and munja by mixing withconventional pulp are indistinguishable from regular wood-pulppaper.

As a renewable resource they can be replaced annually,compared to much longer growth cycle of wood.

As a source of paper fiber, these takes pressure off the forests.

pulp sources, like wheat straw and munja, are less energy,water, and chemical-intensive.

There are some technical challenges, one of which is the issueof silica content, higher in agricultural sources than wood pulp.

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Non-wood pulp production represents less than 10% of totalworlds pulp source

Wheat straw Sacchrum munja

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.

PROBLEMS ASSOCIATED WITH SILICA IN

THESE RAW MATERIAL:-

In the recovery furnaces it tends to form glass

which makes it very, very difficult to recover thecooking chemicals.

The reduction in heat transfer efficiencies.

If the black liquor is concentrated in a multiple-

effect evaporation system, some of the silicaprecipitates and deposits onto the evaporatorheating surfaces, rapidly decreasing their capacity.

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Cont.

The presence of silica in black liquor can alsocause high black liquor viscosity, which limits thesolids concentration that can be achieved duringevaporation. As a result, many mills do not

concentrate and burn the liquor. They simplydischarge it.

The presence of silica in the green liquor

causes "settling" problems within the causticizingplant.

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Scale formed due to silica

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PROCEDURE TO DETERMINE SILICACONTENT IN A SAMPLE:-

First of all take the known wt. of sample in a crucible.

Dry the sample in oven and get the moisture content.

Put the sample in muffle furnace for two hours at about600C, what we get is the total ash content.

Cool the ash and add 5ml HCl then evaporate HCl on steambath (any temp.), this procedure is repeated three times.

Finally dilute the mass and heat.

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Cont.

Filter on ashless filter paper, then wash the residue withhot water till free from chlorides

Dry the filter paper with residue and ignite in furnace at

575C.

Cool the ash and take the wt., the wt. obtained is the silicacontent of the sample.

Silica % = (wt. of silica in gram/wt. of test specimen ingram)

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Silica content of different materials-:

Followings data are obtained from literature review-

Wheat straw contains 3-10% silica

Rice straw contains 9-14% silica

Cereals(barley, oat & rye) straw have 1-6% silica

Wood on the other hand have less than 1% silica

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Methods to solve silica problem-

Black liquor desilication with CO2.

Two stage causticizing desilication method.

Green liquor desilication with lime.

And the use of ammonium or potassium based pulping with theliquor disposed as a fertilizer.

The appropriate pretreatment (dry cleaning) of straw is one ofthe solutions to minimize scaling problem in the recovery system.

The dry cleaning system is fairly simple; it has low specific

power consumption and its investment costs are rather low.

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Chemical analysis without impregnation-:

Before carrying out impregnation and desilication experiment,

chemical analysis of Wheat straw and sacchrum munja wasperformed.The results of the analysis are listed bellow-:

analysis wheat straw sacchrum munja

wt. of sample 10g 10g

moisture % 14% 22%

total ash % 5.30% 4.10%

silica % 3.50% 1.50%

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Impregnation of sample :Impregnation of wheat straw & munja was conducted in a 500ml beaker, with a provision of heating & liquor circulation. Theexperimental conditions were maintained as follows-:10 g of dried sample were soaked with 200g of solution of urea& sodium hydroxide of different concentration, the time ofimpregnation was also varied.

Experimental condition for straw impregnation-:

sample

temp.

(C) reaction time(hrs)

chemical charge

NaOH

(%) urea(%)sacchrum

munja 50 0.25 0.5 0.75 1 15 2 5 2 5 10

wheat

straw 50 0.25 0.5 0.75 1 15 2 5 2 5 10

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Cont.

After the impregnated samples were air dried, the total ash & acid insoluble ash(silica) were determined.

1

1.4

0.9

3

0

0.5

1

1.5

2

2.5

3

3.5

1 2 3 4

silica(%)

comparision in silica content for 2% conc. soln.

2% NaOHtreateds.m.

2%NaOHtreatedw.s. 2% urea

treateds.m.

2% urea

treatedw.s.

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1.4

2.6

1

3.2

0

0.5

1

1.5

2

2.5

3

3.5

1

silica (%)

5% NaOHtreated(munja)

5% ureatreated(munja)

5% ureatreated

(w. straw)5% NaOHTreated(w. straw)

Comparison in silica content of wheat straw & munja when treated

with 5% NaOH & urea, at 50C for 15 min.

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0

0.5

1

1.5

2

2.5

3

3.5

4

untreated 2% NaOH 2% urea 5%NaOH 5%urea

Silica%

s.m.

w.s.

Comparison of silica content of sample after

impregnation with diff. conc. Soln.

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0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 min 15 min 30 min 45 min 60 min

Silica(%)

Time (min)

Change in silica content with increase inimpregnation time for urea treated

w.s.

s.m.

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Definition of lignin-:Lignin is called the incrusting material forming a part of the cellwall and middle lamella in wood. It is an aromatic, amorphous

substance containing phenolic methoxyl, hydroxyl, and otherconstituent groups; its chemical structure has not been fullyelucidated.In this method of determination, lignin (also known as klason

lignin) is defined as constituent insoluble in 72% sulfuric acid.

Acid-insoluble lignin determination-:Summary of method

The carbohydrates in wood and pulp are hydrolyzed andsolublized by sulfuric acid; the acid-insoluble lignin is filtered off,dried and weighed.

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Significance-:Different raw material such as wood, wheat straw, rice straw,sachhrum-munja etc. contains different amount of lignin.Removal of lignin is a main objective of pulping and bleaching

processes.

Determination of lignin content provides information forevaluation and application of processes.

Hardness, bleachability, and other pulp properties, such ascolor, are also associated with the lignin content.

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Experimental procedure to determine lignincontent-:

Add 15 ml 72% sulfuric acid to the beakers containing the testspecimens (10 to 15C).

After the specimen is dispersed, cover the beaker with a watchglass and keep it in a bath at 20 1C for 2 h. Stir the material

frequently during this time to ensure complete solution.

Add about 300 to 400 mL of water to a flask and transfer thematerial from the beaker to the flask. Rinse and dilute with water

to 3% concentration of sulfuric acid, to a total volume of 575 ml.

Boil the solution for 4 h, maintaining constant volume byfrequent addition of hot water.

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Cont.Allow the insoluble material (lignin) to settle. If the lignin is finelydispersed, it may require a longer period to settle.

Without stirring up the precipitate, decant the supernatantsolution.

Wash the lignin free of acid with hot water.

Dry the crucible with lignin in an oven at 105 3C to constant

weight. Cool in a descicator and weigh.

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CalculationFor each determination, calculate the lignin content in the test

specimen as follows:

Lignin, % = A 100 / W

where: A = weight of lignin, g. W = oven-dry weight of test specimen, g

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Procedure for estimation of holocellulose inraw material-:

20g of sample is extracted with a mixture of methanol-benzene(1:2) in a soxholet apparatus.

5g of OD extracted sample is put in 250ml flask and 150mlsolution containing 1.5g of Sodium chlorite and 10 drops of acetic

acid at 70 C is added to it. The flask is loosely covered andregulated at 70C

After 1hr add another 10 drops of acetic acid and a solution

containing 1.5 g of sodium chlorite. This operation is repeated thretimes every hour.

The contents of the flask are cooled in a water bath and filteredimmediately. It is finally washed with 50ml acetone and dried under

vacuum till constant weight is obtained.

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calculation:-

% moisture in sample= [(initial wt wt of OD sample)/ wt of OD sample] * 100

Holocellulose % = (wt of OD holocellulose/wt OD sample)* 100

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72.9%

20.5%

4.8% 1.8%

% composition of wheat strawwithout treated

holocellulose

klason lignin

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20.515.4

72.9 71.4

0

10

20

30

40

50

60

70

80

wheat straw withouttreated

wheat straw treatedwith 2%urea

(%)composition

Variation in klason lignin & holocellulose content

klason lignin holocellulose

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Urea can be better choice because-:

Urea is easy to handle and to use with no health risks.

It can be purchased everywhere and it is considerably cheaperthan both NaOH and NH3.

For sacchrum munja 2% urea gives best results.

For wheat straw silica content decreases with increase inimpregnation time in urea solution.

There is no appreciable change in hollocellulose content &

lignin content decreases almost 5% when treated with 2% urea.

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CONCLUSIONS-:

Up to 40% silica was removed from sacchrum munjawhen it was treated with 2% urea.

Up to 62% silica was removed from wheat straw whentreated with 2% NaOH solution, impregnated for 15 min.

Even low level of chemical charge causes leaching ofsilica significantly

When impregnation time is increased for wheat straw inurea solution then silica content decreases with time.

Urea can be beneficial in removing silica from wheatstraw & sacchrum munja.

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REFERENCES:

http://www.springerlink.com

http://www.sciencedirect.com

http://en.wikipedia.org

http://www.google.co.in

http://www.ineeltechnologies.com/

Pekarovic j., Joyee T.W.: desilication of agriculturalresidue

http://www.springerlink.com/http://www.sciencedirect.com/http://en.wikipedia.org/http://www.google.co.in/http://www.google.co.in/http://en.wikipedia.org/http://www.sciencedirect.com/http://www.springerlink.com/

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