On the feasibility and possibility of heating water for district heating systems through the use of heat of the main condensate after cogeneration turbines

Abstract

The possibilities of increasing the efficiency of cogeneration turbines of CHP plants through the use of low-potential heat carriers for water heating in district heat supply systems and increasing the generation of CHP electricity are considered. The existing technologies of heating the makeup water of the district heating system upstream water treatment apparatuses do not always provide the required heating temperature and do not have the sufficient energy efficiency. The technologies of using the main condensate of the exhaust steam in the turbine to heat the feed water in additional heaters included in the system of regeneration of cogeneration turbines are developed. The use of these technologies contributes to increasing the flow rate and reducing the enthalpy of the steam of regenerative outlets of the turbine used to heat this condensate, and, therefore, increases the combined heat and power generation. In order to determine the industrial applicability of the proposed solutions, experimental studies of the regeneration systems of turbo-units under the conditions of Ulyanovsk СHPPs-1 have been carried out. Multiparameter data arrays on operation of turbine condensate-feed path have been collected, and regression equations have been obtained to calculate the main condensate flow temperatures depending on various factors. On the basis of experimental data there have been calculated the minimum and maximum flow rates of feed water that can be heated to the desired temperature in the surface heaters included in the regeneration system of the turbines, the flow graphs of the heated feed water are constructed depending on the temperature of the main condensate after the turbines. The fields of application of the proposed technological solutions in operating heat supply systems are defined. The evaluation of energy efficiency is carried out using the method of specific generation of CHP electricity and conventional fuel economy at the implementation of the proposed solutions is calculated.