Experiments and modeling of fixed-bed debarking residue pyrolysis: The effect of fuel bed properties on product yields

This paper presents a study on the fixed-bed pyrolysis of debarking residue obtained from Norway spruce. Analysis is based on the dynamic model of packed bed pyrolysis which was calibrated by determining appropriate reaction rates and enthalpies to match the model predictions with the experimental data. The model comprises mass, energy and momentum equations coupled with a rate equation that describes both the primary and secondary pyrolysis reactions. The experiments used for the model calibration determined the yields of solid, liquid and gaseous pyrolysis products as well as their compositions at three distinct holding temperatures. Subsequently, the dynamic model was used to predict the product yields and to analyze the underlying phenomena controlling the overall pyrolysis reaction in a fixed-bed reactor.Peer reviewe

CO₂ gasification of bio-char derived from conventional and microwave pyrolysis

Thermal-chemical processing of biomass is expected to provide renewable and clean energy and fuels in the future. Due to the nature of endothermic reactions, microwave and conventional heating have been applied to this technology. However, more studies need to be carried out to clarify the difference between these two heating technologies. In this work, we investigated two bio-char samples produced from conventional pyrolysis of wood biomass (yield of bio-char: 38.48 and 59.70 wt.%, respectively) and one bio-char produced from microwave pyrolysis with a yield of 45.16 wt.% from the same biomass sample at different process conditions. Various methodologies have been used to characterise the bio-chars. CO₂ gasification of bio-char has also been studied using a thermogravimetric analyser (TGA) and a fixed-bed reaction system. The results show that volatile and carbon contents of the bio-char derived from microwave pyrolysis were between the two conventional bio-chars. However, the microwave bio-char is more reactive for CO₂ gasification, as more CO was released during TGA experiments, and the CO release peak was narrower compared with the CO₂ gasification of the conventional bio-chars. It is suggested that the conventional bio-char is less reactive due to the presence of more secondary chars which are produced from secondary reactions of volatiles during the conventional biomass pyrolysis. While the microwave pyrolysis generates more uniform bio-chars with less secondary char, and therefore, has advantages of producing bio-char for downstream char gasification

The sustainability of liquid biofuels

The report, commissioned by DfT, is a meta-analysis of some 900 reports on the CO2 impact of different biofuels and an analysis of the different life-cycle methods of undertaking the comparison

Development of a Liquid Metal Based Fuel Gas Scrubbing System

The objective of this research project is to perform studies on an analogous room temperature packed bed scrubber operating under non-wetting conditions, providing insight and understanding towards the development of a high temperature packed bed gas scrubber irrigated by molten tin

Experiments and modeling of fixed-bed debarking residue pyrolysis

This paper presents a study on the fixed-bed pyrolysis of debarking residue obtained from Norway spruce. Analysis is based on the dynamic model of packed bed pyrolysis which was calibrated by determining appropriate reaction rates and enthalpies to match the model predictions with the experimental data. The model comprises mass, energy and momentum equations coupled with a rate equation that describes both the primary and secondary pyrolysis reactions. The experiments used for the model calibration determined the yields of solid, liquid and gaseous pyrolysis products as well as their compositions at three distinct holding temperatures. Subsequently, the dynamic model was used to predict the product yields and to analyze the underlying phenomena controlling the overall pyrolysis reaction in a fixed-bed reactor. (C) 2015 Elsevier Ltd. All rights reserved.Peer reviewe

A study on the combustion dynamics of a biomass fuel bed in a BioGrate boiler

The main objective of this research was to study fuel bed combustion dynamics of a BioGrate boiler with a mechanistic model. First, the fuel specific pyrolysis reaction rates were experimentally determined for the model. Second, the model was validated and finally, it was used to investigate the effects of the primary air flows on drying, pyrolysis and char consumption rates occurring inside the fuel bed. The research results are presented and the role of the dynamic behaviour of the reactions on improving the efficiency of the biomass combustion process discussed.Peer reviewe

Destruction of Tar in a Novel Coandă Tar Cracking System

The main objective of this research program was to develop and test a small-scale system that used a novel Coandă burner for tar destruction through partial oxidation. An experimental rig consisting of a tar injector, in which wood pellets were pyrolyzed, and a Coandă tar cracking unit was designed, constructed, and operated to determine the effectiveness of the unit. The experimental program was divided into two phases, so that comparisons of the tar composition with and without treatment could be made. In the first phase, wood pellets were pyrolyzed at a range of temperatures between 500 and 800 °C and the pyrolysis products (gas, tar, and char) were analyzed. Increasing the temperature from 500 to 700 °C caused an increase in the production of hydrogen, methane, and carbon dioxide. As the pyrolysis temperature increased from 500 to 800 °C, there was a decrease in the yield of gravimetric tar in the sampled gas from 67.2 to 15.7 g/nm3. This reduction can be attributed to higher pyrolysis temperature, causing an increase in thermal cracking and depolymerization reactions, which, in turn, promotes production of permanent gas species. In the second phase, the gas produced in the first phase was treated in sub-stoichiometric conditions in the Coandă tar cracker. When the yield of tar species found in the treated and untreated gases is compared when the pyrolysis temperature of the tar injector was set at 800 °C, benzene was reduced by 95%, toluene was reduced by 96%, naphthalene was reduced by 97.7%, and the gravimetric tar yield was reduced by 86.7%. The Coandă tar cracker was shown to be effective at significantly reducing the tar content in the product gas. The reduction can be attributed to the high flame temperature (>1000 °C) and the addition of oxygen, which leads to the formation of free radicals, causing tar destruction