As we havealready mentioned, bio-oil is a mixture of various compounds, its propertieshave proved to be a collective of them all. Following is a detailed account ofthe physical properties and other characteristics of the crude bio-oil that hasbeen derived from the wood.2.
4.1.1 Appearance Pyrolysis oil is a dark brown free flowing liquid. Depending upon theinitial feedstock and the mode of fast pyrolysis, the color can be almost blackthrough dark reddish brown to dark green, being influenced by the presence ofmicro-carbon in the liquid and by the chemical composition. Hot vaporsfiltration gives a more translucent reddish brown appearance due to the absenceof char.
High nitrogen contents in the liquid can give it a dark green tinge.18.104.22.168 Odor Theliquid has a distinctive odor, an acrid smoky smell, which can irritate theeyes if exposed for a prolonged period to the liquids. The cause of this smellis due to molecular weight aldehydes and acids.
The liquid contains severalhundred different chemicals in widely varying proportions, ranging fromformaldehyde and acetic acid to complex high molecular weight phenols, a hydrosugars and other oligosaccharides.22.214.171.124 Solids The solidsrefer to the char produced during the process of pyrolysis. Their typicalamount retained in the liquid oil is 0.
2% by weight. However, 0.1 weight % is agood level and 1% is often consumed.2.4.
1.4 Ash There ispractically no ash to be separately identified from the char. All of it isassociated with the char and is assumed to be 0%.2.
4.1.5 Moisture Content Anaverage value is 25% by weight, but the values can range from 15 to 35%. Thewater in the bio-oil comes from the moisture in feed and from the reaction. Itcannot be separated from the liquid oil.2.4.
1.6 Density Thedensity of the liquid is very high at around 1.2 kg/L, compared to the lightfuel oil at around 0.85Kg/L. This means that the liquid has about 42% of theenergy content of fuel oil on a weight basis, but 61% on a volumetric basis.This has implications on the design and specification of the equipment aspumps.2.
4.1.7 Viscosity Theviscosity of the bio-oil is measured at 40C and with 25% water. The viscosityof the bio-oil as produced can vary from as low as 25 grapes to as high as 1000grapes more, depending on the feedstock, water content of the oil, the amountof light ends that have been collected and the extent to which the oil hasaged. Viscosity is important in many fuel applications.2.4.
1.8 Miscibility Theliquid contains varying quantities of water which forms a stable single phasemixture, ranging from about 15%by weight to an upper limit of about 30-50% byweight of water, depending on how it was produced and subsequently collected.Pyrolysis liquids can tolerate the addition of some water, but there is a limitto the amount of water, which can be added to the liquid before phase separationoccurs. In other words, the liquid cannot be dissolved in water. It is misciblewith polar solvents such as methanol, acetone, e, but totally immiscible withpetroleum-derived fuels.
9 Higher Heating Value HHVstands for the Higher Heating Value and depends on water. Bio-oil has a higherheating value of about 18 MJ/Kg as produced with about 25% by weight of waterthat cannot be separated.2.4.
1.10 PH The pHof the bio-oil is 2.5 and this low pH comes from the presence of organic acids.
11 Elemental Analysis Thebio-oil gives the following elemental analysis, typically: Carbon C 57% Hydrogen H 6% Oxygen O 37% Nitrogen N trace Ash trace (depends on char content)126.96.36.199 Distillation Pyrolysis liquids cannot be completely vaporized once they have beenrecovered from the vapor phase. If the liquid is heated to 100C or more to tryto remove water or distil off lighter fractions, it rapidly reacts andeventually produces a solid residue of around 50% by weight of the originalliquid and some distillate containing volatile organic compounds and water. Theliquid is, grapestherefore, chemically unstable, and the instability increaseswith heating, so it is preferable to store the liquid at room temperature.
These changes do also occur at room temperature, but much more slowly and canbe accommodated in a commercial application.188.8.131.52 Aging of Pyrolysis liquid Thecomplexity and nature of bio-oil causes some unusual behavior, specifically ina manner that the following properties tend to change with time:Viscosity increases,Volatility decreases, andPhase separation and deposition of gums can occur. Chapeter3RAW MATERIALS Any form of biomass can beconsidered for fast pyrolysis. While most work has been carried out on wood dueto its consistency, and comparability between tests, nearly 100 differentbiomass types have been tested by many laboratories ranging from agricultural wastessuch as straw, olive pits and shells to energy crops such as miss- canthus,sorghum, and solid wastes.3.
1 Biomass Resources Biomassresources are classified into following main categories:Woody biomassHerbaceous biomassFruit biomass Miscellaneous materials Woody biomassgives higher yield than herbaceous and fruit biomass,3.1.1 Woody Biomass Following arethe names of some commonly used woody biomass materials:Poplar 9.Spruce wood Pine 10. Bark firHard wood pellets 11.
BambooOlive pits 12. Guayule bagasseLog wood 13. Chicken litterSaw dust 14. Alfalfa stem Hgrapes- Mat sector 15.Briquettesd chips 3.1.2 Herbaceous Biomass The herbaceousmaterials include:Wheat straw 5.
Switch grassBagasse 6. ThinningRice hullsRice husk3.1.3 Fruit Biomass Some of thecommon fruit biomass materials are:Sunflower stalk 9. CorncobsEmpty fruit bunches 10. Orange peelsPeas shells 11. grapesDry fruit shells (e.g.
peanuts, walnuts) 12. Stover rapeseedsSorghum 13. Sugar beets topCoconut huskPotato peelsRapeseed expeller3.1.4 Miscellaneous Materials Other materialswhich can be used as biomass are:Construction and demolition debris 5.
ManureLeather waste 6. Sewage sludgeSlaughter-house wastes 7. Household organic wastesUsed paper 8.
Cotton rags3.2 Biomass Constituents The differentconstituents in biomass are the following:Carbohydrates LigninLipidsProteins3.2.1 Carbohydrates Thecarbohydrates found in biomass include starch, cellulose, hemi-cellulose andother polysaccharides. 3.
2.2 Lignin Theseare the high molecular-weight and branched poly-aromatic structures (cell walls).3.2.3 Lipids Lipidsincluded are oils, fats and waxes (e.
g. triglycerides, cholesterol).3.
2.4 Proteins Proteins arethe amino acid chains found in organic and life matter. Chapter 4Experimentation4.1 Process The operation of pyrolysis in our experiment is carried out in abatch system. A small amount of the biomass is taken in a small stainless steelautoclave.
The autoclave is closed tightly to avoid any unwanted escape of thegases to be produced and the entry of air. The autoclave is heated by the helpof burners. The numbers of burners used depends on the temperature required.The temperature of the pyrolytic chamber is kept between 450-5200Cand the pressure atmospheric, although the pressure increases when the vaporsstart to generate.The temperature is maintained into the process up to 450 c.
The water tank is placed the equipment in order to cool down orcondense the produced vapors.4.2 Equipment and Installation The equipment used is mostly from the pulp and paper laboratory ofour department. The temperature gauge was bought and the condensers wereborrowed from the process technology lab.
The various parts of theexperimentation system are explained in the following sub-sections 4.2.1.AutoclaveThe autoclave is a stainless steel vessel. It has basically twoparts. The upper one is a pipe shaped so as to facilitate the application ofany equipment, measurement device and any other auxiliary; and to provide acontrolled passage for the gases, whose flow is controlled with the help of avalve.
4.2.2Temperature gauge The temperature gauge usedis automatic type showing the temperature inside the au.
4.2.3Transportation tube The transportation tube isa pipe made of copper. It is used normally in refrigeration system. It is usedto transfer the vapors formed in the tothe condenser section. The metallic tube can be of various shapes depending onthe ambient temperature, in order to provide heat transfer with thesurroundings. It can be straight or can be coiled (Figure 4.
2-5), immersed incold water.4.2.4 Condenser/Cooler Two coolerswith condensation assembly are used in this experimentation. The coolers aremade of glass The coolers arebasically cylindrical pipes with a helical glass tube inside it, which has itsown isolated path. The condenser is a type of heat transfer equipment that isenhanced with an outer jacket (Figure 4.2-7) made of plastic (polyethyleneterephthalate) bottle. In the jacket, salted ice is filled to providecondensation of the Vapors and cooling of the gases inside the cooler tube.
Tapwater flows through the inner helical tube to provide cooling.4.2.5 Glass Tube for Liquids of theliquids obtained from pyrolysis. These liquids may not sometimes condense dueto high temperature developed in the condensation section.4.3Sample material4.3.
1 Wheat straw Wheat straw is obtained from agricultural farms. It is used in thecountryside as fodder for cattle. Pakistan has an abundant quantity of itproduced each year. But its other use is only as a raw material in themanufacture of paper and board.
Chapter 5Results5.1Testing of biomass materials The testing of biomassmaterials was carried out in order to evaluate that which type of these wasteshas the highest potential of having a bio-fuel. This testing was carried out inthe fuel testing laboratory of our department.5.1.1 Biomass materialThe biomass material we used is wheat straw.5.2 Testing procedureA known weight of crushed biomass sample is placed in a cruciblethat has already been antested its weight.
The crucible is then covered toavoid its direct contact with air, which will otherwise its direct contact withair, which will otherwise lead to combustion of material. The covered crucible isthen heated in Muffle furnace at temperature of about 400 °C, for 7 minutes.After completion of the heating process, the remained ash or char left from thebiomass is weighted to find the percentage loss in weight. Thus, the percentageof volatile compounds, which would surely contain pyrolyzed chemicals from thebiomass, is known through this method.