Biomass gasifiers updraft gasifier

Pyrolysis of biomass is known to produce a complex mixture of phenolic compounds, which are derived primarily from the lignin fraction of the biomass (1-4) Elder and Soltes (5, 6) have investigated a phenolic fraction obtained from pyrolysis oils made in an updraft gasifier by TECH AIR as a source of phenolic adhesives a phenolics fraction was separated by solubility differences of oil fractions based on solubility of acids in aqueous bicarbonate solutions and... 

No company is presently developing pressurised systems for downdraft, updraft, cyclonic or entrained bed gasifiers for biomass feedstocks and it is difficult to imagine that such a technology could ever be developed into a commercial product due to the inherent problems of scale, tar removal and cost. 

When biomass is gasified, relatively large quantities of tar are produced, e.g., from 10 % of the fuel in an updraft gasifier to 2 to 4 % in a fluidized bed. The amount and composition of the tars are dependent on the fuel, the pyrolysis conditions and the secondary gas phase... 

While this characteristic is problematic for many applications, it is important to note that the uncracked compounds lead to an increase in heating value and carbon conversion in the product gas. In addition, the gradual heating that takes place as the biomass moves down the reactor also creates distinct reaction zones in the system. From the top to the bottom, the zones are the drying zone, the pyrolysis zone, the reduction zone, and the combustion zone. Ash removal takes place at the bottom. Figure 12 shows a schematic of a updraft gasifier. 

Gas composition and tar content in the product gas from different biomass gasification r under different conditions are reported in Tables 1.3 and 1.4. The produced gas must have a certain percentage of burnable gas (>20 % CO and >10 % H2), a minimum amount of tar content (<100 mg Nm ) and be completely free of dust and other poisonous gases (NH3, SO2, etc.). To satisfy the requirement of product gas, a comprehensive research has been done in the last decades. The entire reactor systems can be classified into two categories (1) updraft gasifier and (2) downdraft gasifier. 

Table 1.3 Gas composition and tar content in the product gas from different biomass gasification in updraft gasifier under different conditions [174]... 

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