Effective Air Separation Applied to Low Emission Energy System

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Improvement of a cryogenic air separation system combined with O_2/CO_2 combustion process are Studied. An improved air separation process for O_2/CO_2 combustion plant is proposed and simulated.A conventional cryogenic air separation plant loses much exergy in the air compression process. One of the methods to reduce energy consumption in the air compression process is to adopt a single rectification column instead of a double rectification column. The single column process is possible to operate at lower pressure. In result, the energy consumption for O_2 production is reduced by 14% compared with the double column process.One of the other methods to reduce the energy consumption for air separation is utilizing cold exergy of LNG for the air separation process in a LNG fired power plant. We proposed a novel process to utilize the LNG cold exergy for the air separation, and simulated. The low temperature compression of air is performed to reduce the energy consumption. The LNG cold exergy is utilized at low temperature to increase the efficiency of cold exergy. The energy consumption for O_2 production is reduced by 40.7% compared with the conventional one, and the efficiency of LNG cold exergy becomes 57.3%.Improvement of performance in a cryogenic heat exchanger is necessary to reduce the energy consumption. A fibrous media heat exchanger in proposed, which has large heat transfer area. Experiments and numerical simulations are performed to estimate the performance of the heat exchanger in cryogenic operation. The fibrous media heat exchanger has higher thermal efficiency than conventional packed beds regenerators, when the heat exchanger length is short. Effect of frost deposition caused by water vapor in the air is estimated for continuous operation. The frost deposition occurs where the temperature gradient is large, and the amount of frost increases linearly to the operating time.