J. Andries

Biomass pyrolysis/gasification for product gas production: the overall investigation of parametric effects

The conventional biomass pyrolysis/gasification process for production of medium heating value gas for industrial or civil applications faces two disadvantages, i.e. low gas productivity and the accompanying corrosion of downstream equipment caused by the high content of tar vapour contained in the gas phase. The objective of this paper is to overcome these disadvantages, and therefore, the effects of the operating parameters on biomass pyrolysis are investigated in a laboratory setup based on the principle of keeping the heating value of the gas almost unchanged. The studied parameters include reaction temperature, residence time of volatile phase in the reactor, physico-chemical pretreatment of biomass particles, heating rate. of the external heating furnace and improvement of the heat and mass transfer ability of the pyrolysis reactor. The running temperature of a separate cracking reactor and the geometrical configuration of the pyrolysis reactor are also studied. However, due to time limits, different types of catalysts are not used in this work to determine their positive influences on biomass pyrolysis behaviour. The results indicate that product gas production from biomass pyrolysis is sensitive to the operating parameters mentioned above, and the product gas heating value is high, up to 13-15 WJ/N m(3).

Catalytic pyrolysis of biomass for hydrogen rich fuel gas production

Hydrogen is a clean and efficient energy source and is expected to take an important role in future energy demand. A possibly good route to produce hydrogen is by using cheap biomass as a source through thermochemical conversion technology. The paper addresses this topic, and particular attention is paid to the application of catalysts. Several types of catalysts have been investigated in our test rig at wide ranges of operating temperatures, and the results show that the catalyst has a positive influence on the yield of hydrogen rich gas. The hydrogen concentration of pyrolytic gas is considerably improved by some types of catalysts. The results obtained here can be very useful for scale production of hydrogen based on the biomass resource.

Thermochemical conversion of brown coal and biomass in a pressurised fluidised bed gasifier with hot gas filtration using ceramic channel filters, measurements and gasifier modelling

Biomass (wood and Miscanthus pellets) and Rhenish brown-coal were gasified using a 1.5 MWth (max.) pressurised fluidised bed gasification (PFBG) installation. NOx precursor and tar emissions were studied by varying process parameters like the fuel type, pressure, temperature and air factor. Carbon conversions were well above 80%. Fuel-nitrogen conversion into NH3 was mostly above ca. 50%. Fuel-nitrogen conversion into HCN was significantly lower. Results were in-line with comparable investigations with bottom feeding. Measurements of the gas composition for Miscanthus gasification were compared with a steady-state model based on elementary reaction chemistry and heterogeneous gas-char reactions related to the emission of nitrogen species. A flash pyrolysis model (FG-DVC-biomass version) was applied to determine the initial yields. Measurements and model simulation results were in reasonably good agreement.

Biomass Gasification in a Circulating Fluidised Bed—Part I: Preliminary Experiments and Modelling Development

Due to the advantages of circulating fluidised bed application, circulating fluidised bed was used to gasify biomass in our laboratory and the preliminary results are presented here. Based on the preliminary results obtained, an improved gasification concept is proposed. In this concept, the riser is divided into several sections according to the sequences of reactions: i.e., devolatilisation (pyrolysis), gasification, cracking and combustion (oxidation). The focus of this concept is to isolate the devolatilisation and gasification processes from the combustion process. Based on this concept, the modelling has been developed inclusive of characteristic fluid-dynamics, kinetic chemical reactions, and mass and energy balance. The model can be expected to predict the overall performance of biomass-fuelled circulating fluidised-bed gasifier incorporating with the emissions release.

Biomass conversion into fuel gas using circulating fluidised bed technology: the concept improvement and modelling discussion

Abstract Fuel gas production from biomass using circulating fluidised bed technology is presented in our laboratory. This improved technical concept is aiming at producing high quality gas, in terms of low tar level and particulates carried out in the fuel gas, and overall emissions’ reduction associated with fuel gas combustion, as well as stable and reliable operation with the minimum fluctuations in the producer gas volume and composition. Based on this concept, a characteristic theoretical modelling approach involving hydrodynamics, chemical reaction kinetics, and energy balance is accordingly discussed. In addition, very preliminary experimental results from a laboratory-made test rig are also given.

Catalytic Application to Biomass Pyrolysis in a Fixed Bed Reactor

Chinese rice straw and sawdust were pyrolyzed at an atmospheric pressure fixed bed reactor. The final product distribution of the pyrolysis process and gas composition are presented here. The particular attention of pyrolysis investigation is paid to the effect of catalysts on the pyrolytic gas yield. Several types of catalysts have been investigated in our test-rig, and moreover the influence of the catalyst load on the pyrolytic gas yield has also been investigated. The results show that catalysts, particularly chromium oxide, have a strong positive influence on the pyrolytic gas, while CuO even inhibits the pyrolytic gas yield.

Pressurized fluidized bed combustion and gasification of coal using flue gas recirculation and oxygen injection

A combined cycle incorporating pressurized fluidized bed combustion of coal with pure oxygen and recycled flue gas followed by pressurized combustion of the fuel gas using pure oxygen, is a process which produces electricity and heat with a high efficiency and a flue gas with a high CO2 concentration. CO2 recovery from this process can be done more easily than from conventional coal conversion processes. In this way a high efficiency coal conversion process can be realized with low CO2 emissions. The specific aim of the project is to assess the technical feasibility of this process. For this purpose a 1.6 MWth pressurized fluidized bed combustion test rig has been modified to study experimentally the gasification process and the pressurized combustion of the resulting low calorific value fuel gas. The objectives of the project, the modified test rig and the experimental results obtained from combustion experiments with coal, recirculated flue gas and pure oxygen are described. The conversion efficiencies and the emission of harmfull components measured during these experiments are analyzed and compared with values obtained during combustion and gasification using air.

Pressurised Combustion of Biomass-Derived, Low Calorific Value, Fuel Gas

During a 3 year (1996 – 1998) project, partly funded by the EU as part of their JOULE 3 programme, experimental and theoretical research will be done on the pressurised combustion of biomass-derived, LCV, fuel gas.

Pressurized fluidized bed gasification of coal using flue gas recirculation and oxygen injection

Abstract A combined cycle incorporating pressurized fluidized bed gasification of coal with pure oxygen and recycled flue gas followed by pressurized combustion of the fuel gas using pure oxygen, is a process which produces electricity and heat with a high efficiency and a flue gas with a high CO2 concentration. CO2 recovery from this process can be done more easily than from conventional coal conversion processes. In this way a high efficiency coal conversion process can be realized with low CO2 emissions. The specific aim of the project described in this paper is to to assess the technical feasibility of this process. For this purpose an existing 1.6 MWth pressurized fluidized bed combustion test rig is being modified to study experimentally the gasification process and the pressurized combustion of the resulting low calorific value fuel gas. The paper gives a description of the objectives of the project, the modified test rig and the experimental programme which is planned for the second half of 1995.

Nitrogenous emissions from the delft pressurized fluidized bed combustor

Experimental and theoretical work on Pressurized Fluidized Bed Combustion (PFBC) of coal are main topics at the Laboratory for Thermal Power Engineering of the Delft University of Technology, The Netherlands. A sub pilot scale test rig is used operating at pressures up to 10 bar and a maximal thermal capacity of 1.6 MW. At present, emphasis is laid on chemical reactions within the combustor which play a role in the formation and destruction of CO, CO2, NO, N20, NO 2 and SO 2. In the freeboard, downstream of the first cyclone and in the stack of the PFBC test rig gas concentrations have been measured using specially developed systems for flue gas sampling. Gas analysis has been performed using conventional gas analysis instruments and a Fourier Transform InfraRed (FT-IR) spectrometer. The effect of ammonia injection in the exhaust of the combustor (SNCR) and staged combustion on the emissions was determined.