Simulation of a pilot‐scale dual‐fluidized‐bed gasifier for biomass

Abstract

A dual‐fluidized‐bed gasifier was constructed and operated at the Woodland Biomass Research Center in Woodland, CA. The pilot‐scale gasifier had a capacity of 5 tons/day of feedstock and was based on the Pyrox process developed by Kunii et al. In this system, the fluidized‐bed combustion process with air is separated from the biomass gasification process with steam and recycle gas. This decreases the nitrogen content in the producer gas. The heat released in the combustion of the char is transported by a ceramic bed material circulating between the combustor and gasifier. Commercial wood pellets were used as feedstock for the present study. Gas composition, temperatures, and pressures were measured to characterize the operation of the gasifier. A positive feature of the system was the high circulation rate and efficient energy transfer between the combustor and gasifier. Analysis of the system was performed using Aspen Plus™ software to calculate mass and energy‐balances. A restricted equilibrium model for the producer‐gas composition agreed reasonably well with the measured non‐equilibrium gas composition for most gases. The restricted equilibrium model over‐predicted the H2 concentrations. A more complex rate‐based kinetic model would be necessary to fully capture the details of the non‐equilibrium gas composition in this pilot‐scale gasifier. © 2014 American Institute of Chemical Engineers Environ Prog, 33: 732–736, 2014

Challenges and Opportunities of Modeling Biomass Gasification in Aspen Plus: A Review

“…Even though equilibrium models are less advanced than kinetic models, they are still capable of modeling gasification processes especially for fixed‐bed gasifiers (downdraft or updraft) operating nearly at equilibrium conditions. Still, there are also studies based on this approach to model other types of gasifiers like fluidized‐bed gasifiers , , , , , , , . However, neglecting tar modeling, duration and heterogeneity of the reaction within the gasifier and heat losses limit the modeling to fluidized‐bed gasifiers .…”

“…Even though each study handles the modeling process from a different technological perspective, the main goal is the development of a realistic process model with high efficiency and product quality. The number of studies dealing with biomass gasification has significantly increased, especially within the last decade , and there are many review studies based on a variety of aspects . However, as compiled in Tab.…”

Analysis of dual fluidized bed gasification integrated system with liquid fuel and electricity products

“…And the efficiency of this system is much higher than the traditional biomass system due to the high property syngas produced by DFB reactor. And there are also some simulation works [5,15,16] investigate the industrial performance of DFB technology, but most of which just combust this high property syngas to produce electricity. Considering that the syngas has a high hydrogen content and proper H 2 /CO ratio, it is a promising way to convert biomass into liquid oil by FischereTropsch technology [17,18].…”

Modelling of indirect steam gasification in circulating fluidized bed reactors

“…A commercial scale Pyrox unit with a capacity of 450 t/d MSW was built to Funabashi City in 1983 and operated for 8 years [1,5]. Recently, West Biofuels has commissioned a pilot-scale Pyrox unit in Woodland, California [6]. The pilot uses wood pellets with a capacity of 5 t/d, which equals thermal input of about 1 MWth.…”