Wennan Zhang

Co-gasification of coal and biomass: Synergy, characterization and reactivity of the residual char.

The synergy effect between coal and biomass in their co-gasification was studied in a vertical fixed bed reactor, and the physic-chemical structural characteristics and gasification reactivity of the residual char obtained from co-gasification were also investigated. The results shows that, conversion of the residual char and tar into gas is enhanced due to the synergy effect between coal and biomass. The physical structure of residual char shows more pore on coal char when more biomass is added in the co-gasification. The migration of inorganic elements between coal and biomass was found, the formation and competitive role of K2SiO3, KAlSiO4, and Ca3Al2(SiO4)3 is a mechanism behind the synergy. The graphization degree is enhanced but size of graphite crystallite in the residual char decreases with biomass blending ratio increasing. TGA results strongly suggest the big difference in the reactivity of chars derived from coal and biomass in spite of influence from co-gasification.

Effects of potassium salts loading on calcium oxide on the hydrogen production from pyrolysis-gasification of biomass

The effects of potassium (K) salts loading on CaO on the H2 production from pyrolysis-gasification of wheat straw were investigated. The loading of 0.25 wt% KCl could significantly enhance the CO2 absorption capability of CaO. The CO2 concentration in the product gas decreased sharply from 20.83 to 11.70 vol%, and the H2 concentration increased from 48.2 to 55.5 vol%. While the loading of 0.25 wt% K2CO3/K2SO4 inhibited the enhancing effect of CaO. Further increasing the loading of KCl on CaO, the CO2 absorption of CaO declined, but the catalytic effect of KCl on the gasification process was promoted. The loading of 0.25 wt% KCl on CaO significantly improved the cyclic performance of CaO during the pyrolysis-gasification process. Higher H2 concentration and more CO2 absorbed by CaO were obtained with the loading of 0.25 wt% KCl even after 5 cycles compared with those of pure CaO in the first cycle.

A Study on the Pyrolysis Behaviour of Different Biomass Fuels Using Thermogravimetry and Online Gas Analysis

Fuel availability and flexibility are important issues for biomass-based heat/power and advanced biofuel plants. The physical and chemical properties of biomass feedstocks vary from one to others t ...

CATALYTIC REDUCTION OF TAR/CH4 BY AN INTERNAL REFORMER IN A DFB GASIFIER

An internal reformer is developed for in-situ catalytic reforming of tar and methane (CH4) in allothermal gasifiers. Reduction of tars and CH4 in the syngas is a challenge for commercialization of biomass fluidised-bed gasification technology towards advanced automotive fuel production. This paper presents an initial study on the internal reformer operated with and without Ni-catalytic pellets in the Mid Sweden University (MIUN) DFB (Dual Fluidised Bed) gasifier, by evaluation of the syngas composition and tar/CH4 content. The novelty with the application of Ni-catalyst in this paper is the selected location where intensive gas to catalytic-material and bed-material contacts improve the reforming reactions. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases down to 5 g/m3 and the CH4 content down below 6% in the syngas. The tar content will be decreased further to lower levels, with increased gas contact to the specific surface area of the catalyst and increased catalyst surface-to-volume ratio. The new design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas quality.

Internal Tar/CH4 Reforming using a Novel Design in a Biomass Dual Fluidised Bed Gasifier

Reforming of tars and methane (CH4) in syngas is a significant challenge for low-temperature biomass gasification. For a dual fluidised bed gasifier (DFBG), catalytic bed materials are usually used to promote the reforming reactions. Intensive contact between gas and catalytic bed material at high temperature enhances the internal tar/CH4 reforming. The MIUN gasifier, built for research into synthetic fuel production, is a dual fluidised bed gasifier (DFBG). The results with different bed materials (silica sand, olivine and Fe-impregnated olivine) give roughly equivalent amounts of methane and gravimetric tar in the raw untreated syngas, and need to be reduced to an acceptably low level. The gasification research group at MIUN investigates a novel design in the MIUN gasifier, to increase the gasification efficiency, suppress the tar generation and to upgrade the syngas quality. The first step is taken towards a novel design in the MIUN gasifier. The application is expected to significantly enhance the syngas quality.

A study on kinetic model for cellulose pyrolysis modeling

Publisher Summary This chapter explains a study on kinetic model for cellulose pyrolysis modeling. The chapter presents the study, which proposes an improved kinetic model for cellulose pyrolysis based on the Broido-Shafizadeh model and the recent advance in the field. The modified B-S model adopts a set of new kinetic data for the competitive reactions. This can help to eliminate the error caused by thermal lag in temperature measurement. The presence of the liquid “Active cellulose” is discussed and considered in the pyrolysis kinetics. Furthermore, a detailed secondary reaction scheme of volatile is suggested. The present kinetic model with the modifications is expected to give more accurate prediction in the cellulose pyrolysis modeling. New kinetic data for the competitive reaction is recommended. Including “active cellulose” in B-S model is discussed and suggested. The secondary reaction is also addressed in the proposed scheme. Finally, a mathematical model based on the presented kinetic scheme is expected to give more accurate prediction of cellulose pyrolysis.