Известия Томского политехнического университета: Инжиниринг георесурсов (Feb 2020)
EFFICIENCY ANALYSIS OF STEAM REHEATING IN HEAT RECOVERY STEAM GENERATOR OF HEAT-EXTRACTION ENERGY UNIT GT-TOPPING
Abstract
Relevance. Redeveloping of the existing heat-power equipments is one of the priority areas of power generation development. Adoption of gas turbine unit to the thermal scheme of steam-power energy unit with the preservation of power plant infrastructure is a less costly variant comparing with the construction of new combined cycle power plants energy units. One of the low-cost variant for the integration of gas turbine units into the thermal scheme of steam-turbine energy units is to use the heat recovery steam generator thermal capacity for reheating the working fluid spent in the steam turbine with utilization of the remaining heat for feed water and main condensate heating. Compared with the most common schemes with displacement of regenerative heating to heat recovery steam generator, the proposed alternative variant allows increasing the thermal efficiency of the steam-turbine circuit. The analysis of gas turbine units energy characteristics showed the need to research the scheme and parameters of the steam reheating for heat-extraction energy units taking into account the operating modes of steam turbine. Object: steam-turbine energy unit T–165/210–130 with gas turbine topping (GT-topping) for reheating of the working fluid spent in the steam turbine with utilization of the remaining heat for feed water and main condensate heating. The aim of the research is to select scheme and calculate the optimal parameters of steam reheating as applied to the steam-turbine energy unit T–165/210–130 with GT-topping, analyze its main performances during the work on the heat schedule when steam reheating temperature changes in heat recovery steam generator. Methods: system analysis and mathematical modeling. Results. The authors have developed the mathematical model and program for calculating the proposed scheme and performed the features analysis associated with the organization of steam reheating in GT-topping heat recovery steam generator. Furthermore, we showed that the efficiency of heat-extraction energy unit with steam reheating can be increased by organizing steam reheating in GT-topping heat recovery steam generator. In addition, we determined that in this case, the highest efficiency of a steam-turbine energy unit with GT-topping during operation in the design heat-extraction mode is achieved, when steam reheating temperature is below the nominal value.
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