Thermochemical conversion of Brewers Spent Grain combined with catalytic reforming of pyrolysis vapours

Abstract

The brewing process is an energy intensive process that uses large quantities of heat and electricity. To produce this energy requires a high, mainly fossil fuel consumption and the cost of this is increasing each year due to rising fuel costs. One of the main by-products from the brewing process is Brewers Spent Grain (BSG), an organic residue with very high moisture content. It is widely available each year and is often given away as cattle feed or disposed of to landfill as waste. Currently these methods of disposal are also costly to the brewing process. The focus of this work was to investigate the energy potential of BSG via pyrolysis, gasification and catalytic steam reforming, in order to produce a tar-free useable fuel gas that can be combusted in a CHP plant to develop heat and electricity. The heat and electricity can either be used on site or exported. The first stage of this work was the drying and pre-treatment of BSG followed by characterisation to determine its basic composition and structure so it can be evaluated for its usefulness as a fuel. A thorough analysis of the characterisation results helps to better understand the thermal behaviour of BSG feedstock so it can be evaluated as a fuel when subjected to thermal conversion processes either by pyrolysis or gasification. The second stage was thermochemical conversion of the feedstock. Gasification of BSG was explored in a fixed bed downdraft gasifier unit. The study investigated whether BSG can be successfully converted by fixed bed downdraft gasification operation and whether it can produce a product gas that can potentially run an engine for heat and power. In addition the pyrolysis of BSG was explored using a novel “Pyroformer” intermediate pyrolysis reactor to investigate the behaviour of BSG under these processing conditions. The physicochemical properties and compositions of the pyrolysis fractions obtained (bio-oil, char and permanent gases) were investigated for their applicability in a combined heat power (CHP) application.