Killing two birds with one stone: Can fuel cells operate on a high energy density fuel derived from coal?

点击翻译按钮获取中文摘要

There are large quantities of coal available throughout the world, especially in a number of developing and emerging countries (e.g. China, India etc). However, the burning of coal produces a large amount of CO2, and produces significant amounts of pollution. Acetylene is easily made from calcium carbide which in turn is easily made from coal (coke) and calcium carbonate. Although acetylene does not burn cleanly, there is significant evidence in the literature that it is electochemically consumed in a very clean fashion in aqueous electrolytes and hence may be an ideal candidate for use as a fuel in a polymer electrolyte fuel cell. Acetylene would probably not be as good a fuel for solid oxide fuel cells, and the likelyhood of cracking, and subsequent deposition of solid carbon is high. This is not the case for polymer electrolyte fuel cells for which the presence of copious amoutns of water precludes the cracking reaction. Therefore, a viable approach to more cleanly use the coal reserves would be to convert that coal into calcium carbide (this can be done using renewable energy sources) and then transporting the calcium carbide to where the energy is required. The acetylene could then be liberated from the calcium carbide, and utilised in a fuel cell utilising acetylene as a fuel. Advantageously, calcium carbide is a very energy dense fuel (it stores 50% more energy than petrol) but is very safe - it does not burn easily at all, thus it is ideal for storage and transport.Because of the way in which calcium carbide is produced, it may be possible to prevent as much as 60% of the CO2 that would normally be produced from burning the coal entering the environment.The benefits of acetylene and calcium carbide may be summarised as follows: a) The calcium carbide fuel is made from coal (coke), and CaCO3 in a very simple process. There is the prospect for sequestration of 60% of the carbon dioxide produced within the complete cycle;b) Very high volumetric energy density / the energy content of the acetylene liberated from solid CaC2 is 50% greater than petrol, and three times greater than methanol;c) Calcium carbide is easy and safe to transport and use. Acetylene would only be produced as needed, so accidental discharge of gas is significantly reduced compared to e.g. hydrogen;d) Clean electrochemical oxidation to CO2 and very low crossover compared to other fuels considered for portable systems (c.f. methanol in the DMFC);e) Pure acetylene has very low toxicity, and in the past has been used as an anaesthetic gas;Hence, calcium carbide, and the acetylene fuel that it produces would be an ideal fuel for portable fuel cell systems / i.e. as a replacement for the DMFC in portable electronic equipment. Over the longer term, such fuel cells may also be considered for larger scale mobile applications (automobiles) and even stationary systems, e.g. Combined Heat and Power systems for houses.The goal of this project is to take the first step in this process and assess whether acetylene can be utilised in a fuel cell. This has not been looked at before