1.Status of waste heat utilization
The use of waste heat has two main functions: first, to produce low-quality steam for production and living needs; second, to produce high-pressure steam for power generation. The production process of metallurgical enterprises from raw materials, coking, sintering to iron making, steel making, continuous casting and steel rolling produces a large amount of waste gas, waste water and slag containing available heat, and there are intermediate products and semi-finished products containing available energy between the processes, and the full recovery and utilization of these energies is one of the signs of the modernization of enterprises.
In the energy expenditure of various industrial furnaces, waste gas waste heat accounts for about 15% to 35%, which is a kind of high quality energy that is easy to convey and use after purification and treatment, and is not easy to cause environmental pollution after combustion without slagging and dust removal. If the process requirements to provide the appropriate calorific value of gas for energy, but also conducive to improving product quality.
2.the principle of recovery
Commonly used waste gas waste heat utilization methods are: ① installation of heat exchanger; ② installation of waste heat boiler after the heat exchanger; ③ vaporization and cooling of furnace bottom tube; ④ power generation (cogeneration); ⑤ refrigeration. The recovered heat is mainly used to preheat combustion air, preheat gas and produce steam. For the heating furnace, preheating air, fuel or workpiece and returning flue gas waste heat to the furnace can stabilize the flame, improve the fuel temperature and combustion efficiency as well as the thermal efficiency of the furnace.
Industrial furnace and kiln waste heat recovery poor reasons, in addition to high exhaust temperature and heat exchanger capacity is small, little attention is paid to the flue gas and hot air of the sensible heat failed to effectively save the flue gas from the furnace, inhalation of cold air, underground flue leakage, gas leakage, bypass flue short circuit and poor insulation of the pipeline, so that most of the furnace in the recovery device before the flue gas heat loss of up to 30% to 50%, back to the furnace hot air sensible heat loss of 20% to 33%. In response to this situation, a series of measures to reduce the furnace flue gas temperature and can fully preserve and recover the waste heat exhaust - supply air system, so that the above two heat losses are reduced to 5% and 3% or so, while developing a variety of efficient and economical heat exchanger and can use the full hot air combustion device, the recovery of the flue gas temperature can be reduced to 180 ~ 250 ℃, no longer need to install expensive and poor utilization of waste heat boiler It is in this situation that the new concept of "full self-recovery of waste heat" is proposed: firstly, we try to reduce the flue gas temperature and volume of smoke discharged from the furnace, and reduce the heat loss in the process of waste heat recovery, and then the waste heat is recovered to the maximum extent and sent to the furnace through a high-efficiency heat exchanger. Then the waste heat is recovered to the maximum extent and sent to the furnace through a high-efficiency heat exchanger.
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