Schematic Design For Low Temperature Waste Heat Utilization Of Blast Furnace Slag Water

There is a great amount of waste heat generated during the product process of iron and steel industry.High and medium grade heat recovery reduces energy intensity of crude steel significantly.However,large amount of low grade waste heat still needs to be developed and utilized.This research has investigated the low grade waste heat discharge from blast furnace slag in ironmaking process.Based on thermal analysis theory,the availability of low grade waste heat was analyzed;then the corresponding heat recovery technologies are discussed;finally,economic and environmental benefits of low grade waste utilization are evaluated.The benefits of capturing and utilising low grade waste heat are highly dependent on the qualities and properties of the heat in the waste streams.The temperature of the low grade heat stream is the most important parameter.This research make use of the key parameter to determine the definition and identification method.Selecting 3200 m~3 blast furnace as the research object,molten blast furnace slag,blast furnace slag water and hot air from dry granulation equipment generate different types of waste heat.Based on practical engineering data and experimental data in references,the heat quantites,exergy and energy level of these waste heat are calculated.Distinct heating technique utilizing blast furnace slag water is mature and used widely in northern steel plants.A practical case for recovering waste heat from two3200 m~3 blast furnace is studied in this work.Basic information,technical scheme,investment cost,benefit index and environment revenue are analyzed to prove the technical and economic feasibility of this project.In the end,taking the big steel plant as the research object,blast furnace slag cooling water,furnace flue gas,compressed air,and recirculating cooling water are considered to carry avaiable heat.Cogeneration technology,district heating and refrigeration cycle are used to recover the waste heat.Economic and environmental benefits of low grade waste utilization are evaluated to make better choice of low grade heat utilization.Meanwhile,blast furnace slag water heat utilization project is analyzed in detail on technical proposal,economic benefit and environmental effects.The results shows that the low temperature wast heat recovery is effective and deserves to spread.Organic rankine cycle is a promising wast heat recovery technique for blast furnace slag water.This equipment can produce electiriciy that is high quality energy,and can operate continuously in the whole year.A mathematical model is formulate to simulate organic rankine cycle system operation and is solved by Matlab.Selecting 3200 m~3 blast furnace as the research object,system structure,initial temperature of blast furnace slag water,organic working fluid,evaporating temperature and pinch temperature difference are analyzed to evaluate the thermal performance and find optimal desigh scheme.