Biomass gasification thermodynamic model including tar and char

V. Kirsanovs*, A. Žandeckis and C. Rochas

Institute of Energy Systems and Environment, Riga Technical University, Azenes iela 12/1, LV-1048 Riga, Latvia
*Correspondence: vladimirs.kirsanovs@rtu.lv

Abstract:

Biomass gasification is a thermochemical process in which feedstock is heated to high temperatures in a condition of absence of oxygen. As a result, biomass is converted into the combustible syngas, which typically consists of carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), methane (CH4), nitrogen (N2) and water vapour (H2O). Biomass gasification process simulation plays an important role in gasification process comprehension and optimization. Typically, gasification models have only one output flow in the process mass balance, which represents the amount of the produced syngas. Tar and char also are significant products of gasification process. This study presents a thermodynamic biomass gasification model. The fundamental distinction of the proposed model, comparing to other available models, is that tar and char also are taken into account in developed model. Gasification process is affected by many factors. Similarly, the amount of produced tar and char can significantly vary depending on gasifier operation conditions. Literature review on the previous studies is done to determinate the most critical factors which affect tar and char formation. Results show that temperature in the gasifier, equivalence ratio and fuel properties have dominant effect on the products yield. Two regression models are elaborated to present the amount of the produced tar and char depending on independent variables. The achieved mathematical equations are added to the developed thermodynamic model of the gasification process. Biomass gasification process is simulated with different values of fuel moisture and equivalence ratio. The results show that produced syngas amount, calorific value and biomass energy conversion efficiency are more realistic after tar and char including in the model.

Key words:

biomass gasification, char, mathematical model, syngas., tar

Investigation of fuel effect on biomass gasification process using equilibrium model

V. Kirsanovs* and A. Žandeckis

¹Riga Technical University, Faculty of Power and Electrical Engineering, Institute of Energy Systems and Environment, Azenes street 12/1, LV1048 Riga, Latvia; *Correspondence: vladimirs.kirsanovs@rtu.lv

Abstract:

Gasification is one of the most promising technologies of converting biomass into energy. Different type of biomass can be used for gasification process since there are no strict limitations for parameters of used fuel. Various types of biomass are used in Latvia for production of energy. Wood fuels make up the main part of used biomass in Latvia. However, many non-wood biomass types are available as well. This study presents the comparison of wood and non-wood biomass use in gasification process. Biomass gasification model based on thermodynamic equilibrium was used to simulate gasification process with various biomass types. All input parameters were constant in model except fuel properties. In general gasification process was simulated with seven types of biomass – draff from beer production, common reed, middling from oats and wheat sieving, straw from grain cultivation, buckwheat hulls, rapeseed by-product from biofuel production, as well as wood. These non-wood biomass types are available in Latvia. Produced syngas calorific value and gasification process efficiency are taken as the indicators to examine the gasification performances using various biomass types. The regression model was proposed to describe relation between fuel properties and efficiency of the gasification process. Results show that non-wood biomass can be successfully used for gasification process. Ash content growth in the fuel promotes temperature decrease in the reactor. Fuel chemical composition has effect on the produced syngas composition and heating value.

Key words: