Research On Performance Of High Back-pressure Heating Units Of Combined Heat And Power Generation

Combined heat and power generation is of great significance to projects of energy conservation and emission reduction in our country. Along with the development of science and technology, the capacity of combined heat and power generation unit has become bigger and bigger, and forms of heat supply has become many and varied. Among all the heat supply methods, extraction heating is of most popularity. With the development of heating technology, high back pressure heat supply gets public attention for its efficient recycling of cold source waste heat and simple heat supply system. Therefore, taking the high back pressure unit which is medicated from extraction heating unit as an object, deeply study the performance of high back pressure unit is necessary, which can provide theoretical guidance for follow-up modification and operation.In this paper, the software named Ebsilon is used to model a 350MW wet cooling unit from a thermal power plant. The unit is operated in the conditions of high back pressure, which supply heat by waste heat of exhaust steam. There are two forms of modification, single rotor form and double rotors form. Comparison has been made between these two forms from following aspects:power, efficiency and the operation cost. The result shows that double-rotor form is slight superior to single-rotor form. Generally speaking, single-rotor form is more economic than double-rotor form.Taking a 330MW as an example, Ebsilon is used to simulate the high back pressure operation mode, comparison on energy utilization rate is made between high back pressure heat supply mode and traditional extraction heating mode under conditions of different temperatures of water supply and return. Furthermore, the optimal operating back pressure is calculated under different outdoor temperature. The result indicates that to be compared with the extraction heating mode, the high back pressure heat supply mode is suitable for districts where the demanded temperature of heating supply is relatively low and the temperature of return water of primary network can be decreased to a lower value. By using the high back pressure unit, the exhaust steam heat is utilized, and the energy utilization rate of unit is increased, the area of heat-supply service is expanded, and the electric energy production can be increased to some degree. The lower the temperature of return water of primary network is and the bigger the area of heat-supply service is, the bigger the advantage of high back pressure unit will be.