DESIGN SOLUTIONS ON THE LOW TEMPERATURE CORROSION PROBLEM FOR HEATING SURFACES OF HEAT EXCHANGERS AT GAS TURBINE CHP

Abstract

The article is devoted to the problem of low temperature corrosion of heating surfaces occurring in the non-heating season in heat exchangers of gas turbine cogeneration power plant when working on 150/70 heating system temperature chart. An overview is presented of the existing methods of eliminating such corrosion, including the analysis of their drawbacks. A new approach to ensuring the required temperature level of water in the heat exchangers is proposed. Based on the proposed approach, design solutions are developed and proposed aimed at eliminating the problem of low temperature corrosion of the heating surfaces during the non-heating season. The developed solutions are based on the arrangement of loop pre-heating of the network water where the reverse network water is heated to the minimum allowable temperature at the inlet to the gas-water heat exchanger (GWHE). Two options of thermal circuits with a closed circuit coolant circulation are proposed. The circuits differ in the method of heating the heating medium flowing in WTO: the first one operates by burning fuels in boilers, and the second one by using the heat of the exhaust gas entering the dedicated heating surface of GWHE. The advantage of the first option is the ability to disable the loop pre-heating at low outdoor temperatures when the temperature of the water at the inlet to GWHE exceeds the allowed minimum which reduces the annual cost of electricity for own needs. The advantage of the second option of the thermal circuit is a reduction in energy costs of the circulation pump operation by reducing the flow of coolant circulating in a closed circuit. The calculations of the proposed thermal schemes allowed to conclude that the proposed methods of closed loop pre-heating of the network water provide acceptable water temperature in GWHE with consideration of CHP operation modes throughout the year and help to prevent low-temperature corrosion of heat exchangers heating surfaces.