Modelling of a downdraft biomass gasifier with finite rate kinetics in the reduction zone

Abstract

SUMMARYA model of a downdraft gasifier has been developed based on chemical equilibrium in the pyro-oxidation zone and finite rate kinetic-controlled chemical reactions in the reduction zone. The char reactivity factor (C RF ) in the reduction zone, representing the number of active sites on the char and its degree of burn out, has been optimized by comparing the model predictions against the experimental results from the literature. The model predictions agree well with the temperature distribution and exit gas composition obtained from the experiments at C RF 5 100. A detailed parametric study has been performed at different equivalence ratios (between 2 and 3.4) and moisture content (in the range of 0-40%) in the fuel to obtain the composition of the producer gas as well as its heating value. It is observed that the heating value of the producer gas increases with the increase in the equivalence ratio and decrease in the biomass moisture content. The effect of divergence angle of the reduction zone geometry (in the range of 30-1501) on the temperature and species concentration distributions in the gasifier has been studied. An optimum divergence angle, giving the best quality of the producer gas, has been identified for a particular height of the reduction zone.

Modeling of hydrogen production process from biomass using oxygen blown gasification

“…The reverse trend in CO concentration beyond a critical equivalence ratio occurs due to the shift in equilibrium condition with the change in temperature. This trend in variation beyond f ¼ 2 has been reported in the earlier gasifier literature, where the gasifier is modeled either by equilibrium consideration [30] or using kinetic rates of reaction [31]. The same trend had been reported from experiments [30,32] as well.…”

Modeling of fixed bed downdraft biomass gasification: Application on lab-scale and industrial reactors

“…, Babu and Sheth , and Roy et al . presented similar models focused on the catalytic effect of char on the heterogeneous reactions occurring in the reduction zone. Gao and Li modeled the process of downdraft gasification by considering a kinetic model of pyrolysis within an equilibrium setting for the reduction zone and taking into account pyrolysis temperature as a model input.…”

Clean Poultry Energy System Design Based on Biomass Gasification Technology: Thermodynamic and Economic Analysis

“…Thus, using a chemical equilibrium model to simulate the downdraft fixed bed gasification process will produce large errors [17]. To control the simulation errors, a combined model of the chemical equilibrium and the kinetics control reactions is widely used for the fixed bed gasification process simulation [3,27,28]. Although the combined model has been successfully used for wood and animal manure gasification simulation, no study has used it for poultry gasification simulation to date [15].…”

“…Because the fuel and air inputs to the gasifier are from the top, the gasifier can be separated into four zones of drying, pyrolysis, combustion, and reduction from the top to the bottom (shown in Figure 2b). , the combustion and reduction zones include the major reactions of gasification process [27,31]. Therefore, in the simulation process, the total gasifier was re-grouped into two reaction zones: a pyro-oxidation zone and a reduction zone.…”