Study On Supercritical CO₂ Generating Circle Basing On Medium And High Temperature Waste Heat Utilization Of Boilers And Industral Furnaces

The energy development and utilization has been one of the basic problems against the healthy development of our country's economy and society.As a great consumer of energy,China's enery consumption structure is focused on fossil energy.As our country's economy development entered a new normal and energy development stepped on a new stage,the structural over capacity of traditional energy is still prominent.The misson of clean energy replacing is tough and we are facing great pressure to save energy and to reduce consumption.It's a long way to go to transform our energy structure.Primary energy releases a mass of heat in combustion process,of which the heat that has not been utilized would be remained as the so-called waste heat resource after combusion.Waste heat resource comes mainly from flue gas of power plant boilers and industrial furnaces.Carrying out researches of flue gas waste heat and recoverying energy from that can not only increase efficiency of energy comprehensive utilization,but also make great sense in increasing environmental benefit and promoting energy-saving and emission-reduction.Supercritical CO2 circle has advantages of simple systems,compact equipments,environment-friendly,flexible,high efficiency and strong adaptability.It has a broad application prospect in power plant boilers and industrial furnaces.This paper constructs a supercritical CO2 circle aiming at utilization process of medium and high temperature waste heat.Then it analyses its system performance in theory and carries out optimization calculation to work out the optimized circle parameters and the specific net work and efficiency under different initial temperatures of flue gas.After that it constructs a supercritical CO2 circle with backheating system,finding it increases more than 10%in specific net work and at least 12%in efficiency comparing with that of simple supercritical CO2 circle.The reason might be that introducing the backheating system can effectively increase the average endothermic temperature an reduce the average exothermic temperatureThis paper also studies the effect laws that operational parameters have on the supercritical CO2 circle.It works out that increasing the inlet pressure of the compressor,increasing the inlet temperater of the tubine,increasing the insentropic efficiency of both the compressor and the tubine and increasing the waste heat initial temperature can all increase the specific net work and the circle heat efficiency.The inlet temperature of compressor should be valued above and near the supercritical temperature so that the density of CO2 whould be larger and then the compressor would waste less work to compress the CO2.In this way,it can increase the specific net work and the circle heat efficiency of the supercritical CO2 circle.This paper constructs a supercritical CO2 circle basing on a 1000MW power unit which saves 4.27g/(kW·h)of standard coal consumption rate of power generation,which is 1.7 times of that of traditional low-temperature economizer.At last,this paper studies the case of high temperature flue gas waste heat utilization.It constructs a supercritical CO2 circle with backheating system basing on an AOD furnace to utilize flue gas waste heat,outputting power of 4276kW,which is 1.9 times of that of regular waste heat boiler generation system.