Introduction Chapter-1
Figure 1.9: Types of gasifier a) Downdraft gasifier b) updraft gasifier c) cross draft gasifier (Source: www.soi.wide.ad.jp/class/20070041/slides/05/index_42.html)
The generation of these gasses is by response of water vapor and carbon dioxide through a shining layer of charcoal. Along these lines the way to gasifier outline is to make conditions such that a) biomass is lessened to charcoal and b) charcoal is converted to CO and H2. Since there is an association of air, oxygen and biomass in the gasifier, they are characterized by the way air and oxygen is presented in it.
Introduction Chapter-1 pyrolysis is often termed as bio-oil (or unprocessed bio-oil) but not bio-fuel. Bio oil obtained from biomass pyrolysis is dim tan in shade, free flowing with smoky smell. The properties of bio oil rely on upon different variables, for example, feedstocks, bio-oil preparation procedures, and other operating conditions. The physical properties of bi-oil demonstrate that bio-oils are a complex mixture of more than 300 compounds derived from the depolymerization and fragmentation reactions of cellulose, hemicellulose and lignin.
The organic compounds present in unprocessed bio-oil are acids, alcohol, ethers, ketones, aldehydes, phenols, esters, sugar, furans, and nitrogen mixes. The phenolic compositions are structured by the decomposition of lignin, while different oxygenates, for example, sugars, and furans are produced by the depolymerization of cellulose and hemicellulose of biomass. The esters, acids, alcohols, ketones and aldehydes are obtained by the decomposition of random little oxygenated compounds. As a consequence of exceedingly gooey/viscous, thermally precarious, and highly corrosive nature of unprocessed bio-oils renders these bio-oils less helpful as an option to routine fuels. The unprocessed bio-oils are less steady ascribed to the action of oxygenated chemicals, because of the negative chemical properties like presence of acids, ethers and esters, aldehydes, ketones, alcohols, and other high oxygen substances. Accordingly the viscosity of the bio-oil may be increased amid the storage and experiences several chemical reactions amid the aging of bio-oils. The viscosity of unprocessed bio-oil differs from 25 cSt to 1000 cSt relying upon feedstock, water substance of bio-oil, and pyrolysis procedure utilized. As the bio-oil has high thickness, it counts for higher pressure drop, hence increasing venture/investment (stock).
Low temperature heating is a transcendent answer to lessen viscosity. The viscosity can be likewise controlled by adding solvents like alcohols to unprocessed bio oil before
Introduction Chapter-1 upgradation. Besides, lignin obtained from the softwood biomass material has mostly three forerunners and to be specific they are pocumaryl alcohol, coniferyl alcohol, and sinapyl alcohol.
Lignin is the highest temperature resistant in the three noteworthy parts of biomass and regularly disintegrates at 208oC - 500oC. Because of this decay results char formation prompting the simple blockage of spouts. The presence of high oxygen and high moisture substance lessens the heating value, and serious corrosivity due to acid richness. These unprocessed bio-oils have low heating values when contrasted with petroleum fuels. The higher heating value of plant based bio-oils is larger than wood and farming based bio-oils. There are numerous different attributes of unprocessed bio oil are low H/C proportion, nitrogen and sulfur vicinity, stage division, poisonous quality, high temperature affectability, extreme ignition delay.
Disadvantages of unprocessed Bio-oils
Biofuels are not less expensive in terms of both financial aspects and ecology.
Researches contend that the energy needed to create the one gallon of bio fuel is equal to the vitality creation of a few gallons of the petroleum fuel.
Variation of bio fuel quality is an alternate critical issue to be explored. The nature of the bio fuel created differs for product to harvest plant to plant. Such a variety of unsaturated oils leave sticky deposits which needs further handling includes extra cost.
Biofuels doesn't toll much better. In light of the higher than petroleum gel purpose of numerous biodiesel-creating oils, a biodiesel motor can be troublesome if not difficult to begin in icy climate. The issue is far and away more terrible for the unadulterated vegetable oils. A percentage of the oils created from these plant and rural plants have higher thickness which lessens the fuel stream to the practically identical.
Introduction Chapter-1
Bio-oils possess higher viscosity leads to ageing problem while it is stored; maintaining high pressure drops in pipelines during transportation leads to higher maintenance of equipment.
Bio-oil is highly non-homogenous which leads to the layering or partial separation of phases also causing filtration problems.
Lower values of pH of bio-oil refers to higher acidic nature which leads to the corrosion problems.
Bio-oils contain higher alkali metals causing solid depositions in combustion chambers, boilers reduces the efficiency of the equipment
The higher water content of bio-oil makes severe complications in terms of increasing viscosity, reducing heating values, decreases the stability, and also leads to phase separation.