Research On Waste Energy Utilization Of Extracted Heating Steam In Large-Scale Combined Heat And Power Units

As the country's energy-saving and emission-reduction efforts continue to increase,it was an important issue to in-depth tap the energy-saving potential of thermal power units and increase the energy efficiency of thermal power units.Due to the warming of the climate and the increase of building energy efficiency,the temperature of the supply-water and return-water was obviously lower than the design temperature,resulting the pressure of the extracted heating steam is much higher than the needed steam pressure,there was a huge loss in the heating process of the heating network,which limited the further energy efficiency of the cogeneration unit.To solve the problems,this paper focused on how to achieve efficient utilization of heating extraction steam energy.Based on the first and second laws of thermodynamics,this paper conducted related research on the heating system of large-scale cogeneration units and proposes three types of waste energy utilization of extraction steam,including the addition of extraction ejector,heating network circulation pump electric pump to change the steam pump and the addition of super low pressure steam turbine.Taking a 300 MW direct air cooled unit as the research object,the thermodynamic calculation model was established using EBSILON Professional software,and the accuracy of the model was verified.Based on the established EBSILON model,the energy-saving effects of the different extraction waste energy utilization measures of conventional heat supply steam extraction unit are calculated;The energy flow diagram and exergy flow diagram of the extraction steam power generation system applied to the conventional cogeneration unit was drawn.The influence of main parameters such as heating load,power generation load and water supply temperature on the new system is analyzed.At the same time,the feasibility of the application of extraction steam power generation system in conventional high back pressure heating unit is demonstrated,and its energy saving mechanism is studied.The results showed that all three types of energy utilization had certain energy-saving effects,and the measure of super-low pressure turbines was particularly significant.The standard coal consumption rate for power generation in conventional heat supply steam extraction unit with an super-low pressure generator can be reduced to 12.48 g/kW h and 7.03 g/kW h in the novel high back-pressure unit with super-low pressure turbine units.It can be seen that there was still huge potential for energy saving in the heating extraction section,which provides reference and theoretical guidance for the further optimization of energy-saving for heating units.