| Fossil fuel is used for heating in winter in China, the efficiency of thistechnology is low and a significant amount of greenhouse gases are discharged.Compared with the traditional heating, the bio-gas which derived from biomassgasification for heating is efficient and green. Meanwhile, the biomass is abundantand widely distributed. Using bio-gas for heating can save coal and protectenvironment.At the moment, bio-gas which derived from biomass gasification is mainly usedfor cooking and not often used for heating due to its low calorific value and high tarcontent. The biggest difference between bio-gas heating and traditional fossil fuelheating is the fuel of bio-gas heating is obtained from renewable biomass.In this study, the biomass gasification model was built by Aspen Plus software.The simulation about the major factors which influenced the gasification efficiency ofbiomass were investigated through this model in order to determine the optimalcondition of biomass gasification. The results show that the optimal gasificationcondition is: the reaction temperature interval800~850℃, atmospheric pressure,H2O/C ratio=0.8~1.0, Ca/C ratio=0.6~0.8. In addition, in order to improve thecalorific value of bio-gas and to better deal with the crude glycerin produced in theprocess of biodiesel production, the process of co-gasification of biomass and glycerinwere also simulated in this paper. The optimal condition is: reaction temperature800~850℃, G/B ratio=1.0~1.2, H2O/C ratio=0.8~1.0, pressure no more than0.1MPa.The substitutability between bio-gas and conventional gas was studied byanalyzing the gas alternative indexes such as gas density, gas caloric value, theoreticalair requirement, Wobbe index, burning velocity and combustion potential. Thedifference among bio-gas and natural gas, artificial gas, methane was discussed. Theresearch reveals that both the calorific value and combustible component content ofbio-gas is low which cause the non-substitutability between bio-gas and conventionalgas. Therefore, other gasification agent should be chosen to instead of air in the actualgasification process so as to reduce the N2content in bio-gas. A case was studiedwhich is bio-gas using winter heating in a scale of100households in Tianjin area. The study about economics and carbon emissions of bio-gas heating show that it achievedsa running cost saving of21,000RMB/a and a carbon emission reduction of920tons/a.At the end the Simulink software was used to simulate the combustion state ofbio-gas in gas-fired boiler. The furnace temperature was880~970℃and the thermalexposure was0.57~0.79MW. The key factor deciding the combustion performance iscaloric value which was concluded from the study of three different bio-gases burningin gas-fired boiler. |
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