CHEC Annual Day, 2009 Effect of experimental conditions on biomass gasification in an entrained-flow reactor Ke Qin Supervisors: Prof. Anker Degn Jensen Assoc. Prof. Peter Arendt Jensen Assoc. Prof. Weigang Lin

2/12 Outline Introduction Experimental  Apparatus  Biomass fuels and applied operating condition Results and discussion  Effect of temperature  Effect of excess air coefficient  Effect of steam/carbon molar ratio  Effect of biomass type Conclusions

3/12 Gasification is one of the key technologies for biomass utilization, especially in the field of liquid fuels and chemicals production. In production of liquid fuels, it is important to control the syngas quality from gasification with respect to both the H 2 /CO ratio and harmful impurities, such as tar. Of several gasification methods, the entrained flow gasifier has the advantage to produce a gas with low tar content and possibility to run at high temperature and pressure. Introduction> Experimental> Results and discussion> Conclusions Background

4/12 In this work, biomass gasification was investigated in atmospheric pressure entrained flow reactor with respect to gas composition soot tar as a function of operating conditions, such as temperature (T) excess air coefficient (λ) steam/carbon molar ratio (H 2 O/C) biomass type Introduction> Experimental> Results and discussion> Conclusions Objective

5/12 Setup - Entrained flow reactor Introduction> Experimental> Results and discussion> Conclusions Fuel feeder Solid sampler Liquid sampler Gas sampler and analyzer Flue gas treatment Feeding gas (air) Main gas (air+steam) Vent Flue gas cooler

6/12 Fuels Wood (Beech saw dust) Straw (Pulverized wheat straw pellet) Proximate analysis Moisturewt. % Volatilewt. % Fixed carbonwt. % Ashwt. % Lower Caloric ValueMJ/kg Ultimate analysis Carbonwt. % Hydrogenwt. % Oxygenwt. % Nitrogenwt. % Sulphurwt. % Proximate and ultimate analysis (on a delivered basis) Introduction> Experimental> Results and discussion> Conclusions High alkali content

7/12 Introduction> Experimental> Results and discussion> Conclusions Gasification processes and reactions O 2 +N 2 Steam Biomass Pyrolysis Partial combustion Char and soot gasification Water gas shift reaction Soot formation - Unconverted char - Soot - Tar - Hydrocarbons - Main gas species H 2, CO, CO 2, and N 2 - Trace species COS, H 2 S,NH 3 and so on Reactor Reactor outlet compounds Inlet to reactor

8/12 High temperature favors soot formation, but at higher temperature soot also has a higher gasification reactivity. Introduction> Experimental> Results and discussion> Conclusions Effect of temperature on soot and tar Wood, λ=0.25, H 2 O/C=0.5 %T=1350°CT=1000°C Tar021.8 Soot There is a trade off between tar and soot formation because of soot formation from tar and hydrocarbons polymerization.

9/12 Introduction> Experimental> Results and discussion> Conclusions Effect of temperature on producer gas The yield of producer gas increases as the temperature increases. Gas formation is caused by the conversion of tar and larger hydrocarbons into lighter gaseous products. Producer gas = H 2, CO, CO 2 and C x H y

10/12 Introduction> Experimental> Results and discussion> Conclusions Effect of temperature on gas composition The yields of H 2 and CO increase and CO 2 decreases with increasing temperature. The yield of C x H y decreases because it is converted to soot and light gases at higher temperature.

11/12 Gasification of wood and straw has been investigated in a laboratory scale atmospheric pressure entrained flow reactor. The residence time of fuel in the entrained flow reactor was 1-2s. Char was completely converted. The amount of producer gas (H 2, CO, CO 2 and C x H y ) increases significantly when the temperature increases from 1000ºC to 1350ºC, which is caused by the conversion of tar and larger hydrocarbons into lighter gaseous products. There is a trade off between tar and soot formation. At 1350ºC, tar is minimized, but soot is present in the gas (35.26g/kg fuel). The soot yield can only be slightly reduced by addition of steam. Wood and straw gasification provides similar gas composition. Straw has a high alkali content, but it does not change the gas composition significantly. Introduction> Experimental> Results and discussion> Conclusions Conclusions

CHEC Annual Day, 2009 Thanks for the Attention !