Design And Research On Heating Supply Of Circulating Water With High Back Pressure In Regulating Extraction Unit

China is vigorously promoting energy saving and emission reduction of energy industry and the “developing large units and suppressing small ones” policy,a large number of small-scale decentralized heating boilers have been limited and shut down,because of their high energy consumption,serious loss of heat source,pollutant emissions are not qualified.However,with the increasing scale of urban construction,urban residents heating load also is increasing year by year,more and more heat and power plants participate in the heating market,and became the main heat source of central heating.At present,co-generation unit in the case of guaranteed power generation,due to the limitation of medium pressure cylinder extraction,the unit is basically in full load operation state,therefore,the city’s central heating market will appear larger heating gap the next few years.The need for large pure condensing steam turbine unit or adjusting the extraction unit to implement heating transformation,in order to meet heating requirements of urban heating.The main reason for the low thermal efficiency of the thermal power plant equipped with the adjustment of the steam extraction heating unit is its greater cold source loss.At present,aspect of waste heat recovery in the heat and power unit,high back pressure circulating water heating technology is a feasible development direction to improve the heating capacity and energy saving and consumption reduction.High back pressure circulating water heating technology is to improve the exhaust steam pressure of the steam turbine,to recover the waste heat of exhaust steam,to reduce the loss of the cold source to zero,to improve the thermal efficiency of the unit,and to solve the problem of urban heat supply shortage and environmental pollution.This paper takes a 300 MW unit with high back pressure circulating water heating project of Baoding as an example.On the basis of the thermal system modeling of the high back pressure unit,the economy and security of the high back pressure heat supply reformation is calculated by the simulation.Firstly,through the example analysis,they are obtained on reasonable heating mode,the main and auxiliary equipment,the system design of the high back pressure circulating water heating system.Secondly,the variable working condition of the condenser is calculated,determining the scope of steam turbine exhaust pressure;according to different power load and heating load,which is determine the economic back pressure by the comprehensive cost coal consumption method;calculation and analysis of effect of circulation water flow and water temperature on the economy of the thermal system.Thirdly,simulation and calculation characteristics of the thermodynamic system about several typical operating conditions,and the economy index of thermal system under typical operating conditions are calculated by heat method.Finally,the thermal economy and the safe of the unit before and after the high back pressure transformation are analyzed and compared thought the actual heating data,and the static payback period of high back pressure heat recovery is calculated.The simulation results show that the unit has achieved remarkable economic benefit and good energy-saving and emission-reduction effect after high pressure circulating water heat supply,which provides a reference for the economic analysis of the same type of heat supply unit.