|Application of gas chromatography-mass spectrometry (GC-MS) in the quantitative analysis of organic compounds generated in gasification/pyrolysis coupled Fischer-Tropsch (FT) reactor: syngas clean up and hydrocarbon production.
|Analysis of Complex Energy Products
|Mr Geraint Sullivan
Abstract Information :
Waste is a growing environmental problem with landfill sites having limited space and much of the waste taking decades to decompose. It is estimated that nearly 80% of mass sent to landfill has the potential to be recycled. Some recycling routes can utilize the carbon content of waste material, converting it to useful products, such as an energy source. Pyrolysis and gasification are two approaches used to recycle waste high in carbon; these methods use thermal energy in a controlled environment to produce a flammable gas (syngas) and bio-oil, with solid biochar also produced during pyrolysis. Syngas can be used in secondary routes to generate hydrocarbon fuels; carbon monoxide within syngas can be hydrogenated using a catalyst under high pressures and temperatures in the Fischer-Tropsch (FT) process. However, syngas can also contain undesirable, organic tars. These impurities often require removal for interfacing gasification/pyrolysis and other technologies as they can foul downstream processes (such as FT) and cause mechanical damage, resulting in increased operational costs and reduced process efficiency. The aim of this work was to develop and investigate a cheap method of syngas clean-up and the resulting hydrocarbon production for an improved hyphenated gasification/pyrolysis-FT process.
Initial studies showed that a series of connected acetone scrubbers were highly effective at removing tars (>90% efficiency) with acetone capable of removing troublesome, small volatile unsaturated compounds, such as acetylene. Other benefits of acetone was that it was easily recycled and compatible with the GC-MS analytical method offering the potential for online monitoring of unknown tar products from different waste streams. Other common scrubbers, such as methanol, water and other solvent based scrubbers, are less effective at trapping smaller volatile organics and have difficulty in recycling; once saturated require disposal. 'Clean' syngas from waste was converted into hydrocarbon compounds as a continuous process by combining the pyrolyser/gasifier and FT reactor. A cobalt oxide catalyst, termed CAT-1, was developed and synthesized in-house using impregnated cobalt chloride on aluminium oxide. Cobalt oxide formation typically involves a long calcination process (600°C in air for 12 hours); in this study the process was developed to remove this step, making the process more economically feasible. Initial data from the gasification/pyrolysis-FT system and catalyst development are promising showing syngas with minimal contamination and the desired hydrocarbon end product. However, further work is required to optimise the processes to generate higher efficiencies and yields.