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In the chemical heat pipe concept, energy is transported long distances by using a high temperature heat source (e.g., a nuclear reactor) at the sender end to convert a mixture of gases (e.g., CO2 and CH4, or H2O and CH4) into an energy-rich combination (CO and H2), and then transporting the mixture by pipeline at close to room temperature to the receiver end. At the receiver end, the stored energy is released by the reverse reaction to generate steam or produce heat for process purposes. Candidate reactions for this system include the Hy-Co reaction (CO2 + CH4 = 2CO + 2H2) and the Eva-Adam reaction (CH4 + H2O = CO + 3H2). As written, these reactions are endothermic in the forward direction and exothermic in the reverse direction. In the Eva-Adam reaction, the forward conversion (steam or methane reforming) is favored by high temperatures and low pressures. For example, at a temperature of 1100 K and a pressure of 1 atmosphere, the degree of advancement in the forward direction is about 93%. The reverse conversion (methanation) is favored by low temperatures and high pressures. For example, at 800 K and 25 atmospheres, the degree of advancement in the reverse direction is about 95%. Thus, heat representing most of the heat of reaction can be made available at the sender end at a relatively high temperature. Since the system requires two pressure levels, compressors (and turbines to drive them) are necessary, as well as strategically placed heat exchangers. Thus results a closed cycle gas turbine system with a dissociating gas as the working fluid. This paper analyzes the Eva-Adam system and evaluates the energy-delivered to energy-supplied ratio. The efficiency is improved if the return pipeline is insulated.Copyright © 1988 by ASME |
