Study On Utilization Of Low Grade Waste Heat Potential In Steel Plant For Heating

With the continuous advancement of urbanization in China,the demand for building heating is increasing day by day.Under the background of carbon neutral era,the heating energy structure is in urgent need of transformation,and it is necessary to find suitable clean heating energy.Using low grade waste heat for heating is an important direction to solve the shortage of heating energy and energy saving and emission reduction of steel mills.It can also achieve better environmental and economic benefits.Using low grade waste heat for heating is an important direction to solve the shortage of heating energy and energy saving and emission reduction of steel mills.It can also achieve better environmental and economic benefitsThis paper analyzes and excavates the low-grade waste heat resources of steel mills,combined with the actual production process of a steel mill,determines the low-grade waste heat sources of the main technological processes su ch as sintering process,coking process,iron making process,steel making process,steel rolling process and so on.Through on-site investigations and field tests,the basic parameters of low-grade waste heat sources in steel mills were obtained,and the stability,grade,quantity and other waste heat characteristics were analyzed.Due to the wide variety of low-grade waste heat in steel mills,the low-grade waste heat of steel mills is integrated with the T-Q diagram and the pinch method,which visually reveals the distribution characteristics of steel mill waste heat,which is convenient for guiding the design and optimization of the heat extraction process in the pl ant.Aiming at the configuration mode of the low-grade waste heat heating system in the steel plant,the analysis was carried out from two aspects: the configuration of the heating power station and the configuration of the heat extraction in the plant.Clarified the importance of reducing the return water temperature of the primary grid to the waste heat heating system.The two methods of absorption heat exchange unit+ electric heat pump and plate heat exchanger + electric heat pump cooling of the thermal power station are analyzed and compared,and the optimal configuration method of the thermal power station is obtained;the heat extraction process in the plant is analyzed,and The optimal heat extraction configuration method based on all direct heat exchange and partial direct heat exchange + heat pump is proposed;the complete process of the waste heat heating system is finally determined,and the operation mode of the waste heat heating system is analyzed.Take Shandong Laiwu Steel Plant A and Steel Plant B as waste heat recovery heating cases for analysis.For steel plant A,15? primary grid return water,based on the in-plant heat extraction process of all direct heat exchange,the primary grid water supply temperature can be obtained at 54.7?,combined with the configuration of the plant and heating power station,and the economic efficienc y of the waste heat heating system The model can calculate that the static payback period of Steel Plant A is 6 years.For Steel Plant B,due to the need to transport heat over long distances,it is necessary to consider the impact of primary grid parameters on the waste heat heating system.Based on the further expansion of the economic model of the waste heat heating system of the steel mill,the effects of different primary grid supply and return water temperature are analyzed.The influence law of the a nnual cost of the waste heat heating system shows that the annual cost of the waste heat heating system is the smallest when the water supply temperature of the pri mary network is 75°C and the temperature of the return water of the primary network is 20°C.Under this condition,the static payback period of Steel Plant B is 9 years.With different waste heat heating system processes,the waste heat heating systems of Steel Plant A and Steel Plant B are more economical.