Application Research And Practice Of Waste Heat Of Iron And Steel Enterprises In Urban Heating System

The Iron and Steel industry is an important basic and pillar industry of China's national economy.It is a resource and energy-intensive industry.It is also a major energy consumer,and a major user of air pollution and water pollution.With the rapid development of China's national economy,the demand for the output,type and quality of steel is higher and higher,which brings more pressure on energy and environment.At the same time,China has a vast territory,rapid urbanization,and a relatively large increase in heating demand.In the context of national “industry-city integration”,this article aims to find a new way to resolve the two contradictions,that is,to integrate the waste heat of iron and steel companies and use it as a heat source in cities heating systems through simple,economical and feasible distribution methods.This paper introduces the distribution of waste heat resources in each process of the iron and steel industry.And it uses two methods of waste heat utilization analysis,enthalpy analysis and exergy analysis,to analyze the Iron and steel enterprise waste heat application modes which use blast furnace slag water and circulating water for low vacuum operation of generator set.The theoretical analysis proves that the waste heat resources of iron and steel enterprises are rich in theory and the quality of waste heat meets the demand for heat supply.In this paper,through the investigation and analysis of waste heat energy resources such as low-pressure steam and hot water in various production processes and heating units of a domestic iron and steel enterprise,this paper points out the existing and unused waste heat resources in the production process and finds the main problems: 1.Some production processes have the problems of high quality,low quality and low efficiency of steam,which increases the operating cost;2.The steam consumption of the living system is too large;3.The steam is transported over a long distance,and the process loss is large;4.The steam metering system Imperfect;5.There are still a lot of waste heat resources that have not been recycled.In view of the existing problems,put forward optimization and improvement plans to explore the potential of the use of waste heat in iron and steel enterprises in urban heating: 1.Optimization of steam system for production process 2.Optimization of low-quality waste heat system 3.Optimization of steam system for bathroom 4.Canteen and laundry Wait for the optimization of the system for small steam users.Through the optimizing and reforming plan,the steam recovery is 147 t / h,and the residual heat of hot water is 652.65 MW.Finally,this paper combined with the practical application of waste heat in urban heating of a iron and steel company in Shandong,made a comprehensive analysis from the aspects of project overview,heating planning,heat load,selection of heat source and heating temperature,and the configuration and construction of heating system.Conclusions are as follows:(1)In order to improve the utilization efficiency of waste heat in iron and steel enterprises2×25MW+1×50MW condensing generators were transformed into a low-vacuum operating mode during the heating period,and the slag washing water of no.1 ~ no.5 blast furnace was used as the water supplement of the whole system,these measures have been taken to realize the demand for central heating in the surrounding urban areas.This project greatly improves the comprehensive utilization efficiency of energy in iron and steel enterprises,saves coal consumption,and reduces the emission of air pollutants.The project has significant energy-saving benefits,environmental benefits,dual economic benefits in power generation and heating.(2)The softened water after the heat exchange of blast furnace slag water was used as the water replenishment of the whole heating system.The waste heat resources of blast furnace slag water in the blast furnace ironmaking section of iron and steel enterprises are further utilized to save waste heat resources and avoid heat pollution.(3)Steam water heat exchanger was used in the whole heating system.In cold period or failure of the unit,steam water heat exchanger ensures stable operation of the heating system.The heat source of steam water heat exchanger comes from the waste heat steam of converter,heating furnace and sintering section in the plant.(4)The coal-fired heating boilers in the original urban areas will be shut down after completion of the project.The project will reduce the coal consumption by 546,000 tons,the SO2 emissions by 17,300 tons,and the dust emissions by 32,700 tons every year.In this project,the original system was barely affected by the waste heat recovery methods except the generating capacity.The power output will be slightly affected by the low vacuum operation of the power generation system.For steel enterprises,residual heat is "waste heat"."Waste heat" is used for heating,it saves a great deal of heat source cost and has remarkable economic benefits.The extensive use of waste heat in urban heating systems has added a brand new "product" to iron and steel companies and provided a powerful impetus for development.