Survey of influence of biomass mineral matter in thermochemical conversion of short rotation willow coppice

Abstract

Short rotation willow coppice (SRC) has been investigated for the influence of K, Ca, Mg, Fe and P on is pyrolysis and combustion behaviours. These metals are the typical components that appear in biomass. The willow sample was pre-treated to remove salts and metals by hydrochloric acid, and this demineralised sample was impregnated with each individual metal at the same mol/g biomass (2.4x10 -4 mol g -1 demineralised willow). Characterisation was performed using thermogravimetric analysis, and differential thermal analysis (DTA) for combustion. In pyrolysis, volatile fingerprints were measured by means of pyrolysis -gas chromatography -mass spectrometry (PY-GC-MS). The yields and distribution of pyrolysis products have been influenced by the presence of the catalysts. Most notably, both potassium and phosphorous strongly catalysed the pyrolysis, modifying both the yield and distribution of reaction products. Temperature programmed combustion TGA indicates that combustion of biomass char is catalysed by all the metals, while phosphorus strongly inhibits the char combustion. In this case, combustion rates follow the order for volatile release/combustion: P>K>Fe>Raw>HCl>Mg>Ca, and for char combustionK>Fe>raw>Ca~Mg>HCl>P. The samples impregnated with phosphorus and potassium were also studied for combustion under flame conditions, and the same trend was observed, i.e. both potassium and phosphorus catalyse the volatile release/combustion, while, in char combustion, potassium is a catalyst and phosphorus a strong inhibitor, i.e. Kimpregnated > (faster than) raw > demineralised >> P-impregnated. IntroductionBiomass and energy crops are being considered as serious options for reducing carbon dioxide emissions from electricity production. Biomass includes a vast range of materials including agricultural and forestry residues, lignocellulosic components of wastes, as well as energy crops. In the UK there are financial incentives for using biomass grown specifically for electricity production, i.e. energy crops, and this has started to develop the supply chain for, in particular, short rotation willow coppice and Miscanthus. A number of studies have examined the agronomy and the variability of these and other energy crops, in terms of "fuel quality" attributes, particularly the inorganic content. 1,2 The mix of inorganics affects the ash behaviour during combustion and this has been the subject of a number of reviews.The main plant nutrients needed for energy crop production are nitrogen, phosphorus, and potassium. Other typical metals present in the fuel are Al, Ca, Fe, Mg, Na and Si. Similarly the main inorganic components in SRC bark clonal varieties have been reported to vary in the range 0.09-0.12 wt % P, 0.2-0.5 wt% K, 0.9-1.5 wt% Ca and 0.05-0.16 wt% Mg, while for the stems the ranges reported are lower: 0.04-0.07 wt% P, 0.1-0.2 wt% K, 0.5-0.9 wt% Ca and 0.02-0.05 wt% Mg. 5Pyrolysis temperature, heating rate, and biomass type are important factors influencing the volatilisation of alkali species in the biomass. 6...

Effects of four types of dilute acid washing on moso bamboo pyrolysis using Py–GC/MS

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Pyrolysis of pine and gasification of pine chars – Influence of organically bound metals

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TGA‐FTIR study of the pyrolysis of sodium citrate and its effect on the pyrolysis of tobacco and tobacco/SBA‐15 mixtures under N2 and air atmospheres

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