Biomass Air-steam Gasification Research Articles

An experimental study on biomass air–steam gasification in a fluidized bed

The characteristics of biomass air–steam gasification in a fluidized bed are studied in this paper. A series of experiments have been performed to investigate the effects of reactor temperature, steam to biomass ratio (S/B), equivalence ratio (ER) and biomass particle size on gas composition, gas yield, steam decomposition, low heating value (LHV) and carbon conversion efficiency. Over the ranges of the experimental conditions used, the fuel gas yield varied between 1.43 and 2.57 N m 3/kg biomass and the LHV of the fuel gas was between 6741 and 9143 kJ/N m 3. The results showed that higher temperature contributed to more hydrogen production, but too high a temperature lowered gas heating value. The LHV of fuel gas decreased with ER. Compared with biomass air gasification, the introduction of steam improved gas quality. However, excessive steam would lower gasification temperature and so degrade fuel gas quality. It was also shown that a smaller particle was more favorable for higher gas LHV and yield.

Two phase biomass air-steam gasification model for fluidized bed reactors: Part I—model development

A two-phase model capable of predicting the performance of fluidized bed biomass air-steam gasification reactor during dynamic and steady state operations was developed based on the two phase theory of fluidization. Material and energy balances were taken into consideration and the minimization of free energy technique was used to calculate the gas mole fractions. The fluidized bed was divided into three zones (jetting, bubbling and slugging) and the mass and heat transfer coefficients were calculated for each zone in both bubble and emulsion phases. The model includes the hydrodynamics, transport and thermodynamic properties of fluidized bed. The finite element method was used to solve the partial differential equations. The input variables of the computer program included fluidization velocity, steam flow rate and biomass to steam ratio. The model is capable of predicting the bed temperature, gas mole fractions, higher heating value and production rate.

Two phase biomass air-steam gasification model for fluidized bed reactors: Part II—model sensitivity

A sensitivity analysis was performed on the two phase biomass gasification model developed by Sadaka et al. (Biomass Bioenergy) to test its response to variations in three operating parameters (fluidization velocity, steam flow rate and biomass to steam ratio). The model performance criteria included bed temperature, gas compositions, higher heating value and gas production rate. The results showed that the model was sensitive to changes in all operating parameters. The temperatures of the reactor were more influenced by changes in the steam flow rate than those of fluidization velocity and biomass to steam ratio. The steam flow rate has the most effect on the mole fractions of CH 4, and CO 2 followed by the biomass to steam ratio and then the fluidization velocity. In the case of H 2, and CO the biomass to steam ratio has the most effect on their mole fractions followed by the steam flow rate and then fluidization velocity. The fluidization velocity has the most effect on the mole fraction of N 2. The biomass to steam ratio has the most effect on the gas higher heating value and the gas production rate.

Two-phase biomass air-steam gasification model for fluidized bed reactors: Part III—model validation

The developed two-phase air-steam gasification model (Biomass Bioenergy, xxxxx) was validated using the experimental results obtained from a dual distributor fluidized bed reactor. The reactor was operated on wheat straw at various fluidization velocities, steam flow rates and biomass to steam ratios. A good agreement between the model predictions and experimental data was obtained under all operating conditions studied. The model predicted the temperatures of the bubble, emulsion and solid phases, the mole fractions of methane, hydrogen, carbon monoxide, carbon dioxide and nitrogen, and the higher heating value of the producer gas with high accuracy ( R 2=0.88–0.98). The correlation coefficient ( R 2) for the gas production was somewhat lower (0.75), which could be attributed to the assumption that the gases behaved ideally.