ABSTRACT

Because of the cogeneration of heat and power within combined heat and power plants (CHPs), higher overall efficiencies are ensured that enable an efficient conversion of fossil fuels into usable energy. Owing to the increasing application of CHPs, the utilization of common power plants is reduced, leading to the minimization of exhaust gas emissions since electrical power and process heat are both utilizable where they are actually produced. In the process of a high-temperature combined heat and power plant, natural gas and water are converted into a hydrogen-rich synthesis gas by steam reforming. After a CO purification by a two-stage water-gas-shift reactor, the synthesis gas is added to the stack, where it is converted to electrical and thermal energy. Using the numerical pinch method, it is possible to obtain miscellaneous variants of internal heat transfers by determining the minimal heating and cooling demands, as well as the optimal temperatures of heating and cooling liquids. With the assistance of simulation software like ASPEN PLUS, these variants can be energetically compared by considering variable load categories. If the system is running in power-controlled mode, the accumulated heat of the stack cannot be dissipated usefully, and loss of heat takes place. Because of the temperature level of the HT-PEM (160−180°C) the application of the pinch method can demonstrate the possibility of the energetic use of this heat within the process leading to a remarkably increased electrical efficiency.