Brief introduction of knowledge related to waste heat utilization and recovery

Brief introduction of knowledge related to waste heat utilization and recovery
In this article, the main knowledge related to the utilization of residual heat is summarized.Residual heat refers to the energy that cannot be used for energy utilization under certain economic and technological conditions, i.e. energy that is left over or abandoned. The utilization of residual heat is an important means of improving economic efficiency and energy conservation and reducing emissions.
Firstly, there are seven types of residual heat, including high-temperature waste gas residual heat, cooling medium residual heat, waste steam, waste water, high-temperature products, slag residual heat, chemical reaction residual heat, combustible waste gas, waste liquid, and high-pressure fluid residual pressure.
Secondly, there are various ways of utilizing residual heat. The main three ways are direct use of heat energy, residual heat power generation, and comprehensive utilization of residual heat.
Thirdly, there are three principles for utilizing residual heat. The commonly used utilization methods of waste gas residual heat are: ① installing heat exchangers; ② installing residual heat boilers behind the exchangers; ③ vaporizing the bottom tube of the furnace; ④ generating electricity (cogeneration); ⑤ producing refrigeration.
The recovered heat is mainly used for preheating air for combustion, preheating coal gas, and generating steam. For a furnace, the air, fuel, and workpiece are preheated and then returned to the furnace, which can stabilize the flame, improve fuel temperature, combustion efficiency, and furnace efficiency.
Fourthly, there are three types of utilization methods for residual heat. (1) sintering waste gas. After being discharged into the atmosphere, about 50% of the heat energy is discharged in the form of infrared radiation from the sintering machine smoke gas and cooling machine waste gas, which wastes energy and pollutes the environment.The temperature of the sintering machine smoke gas is not high, and people have not paid enough attention to the recovery and utilization of this part of the heat energy before. However, there is great development space because the sintering furnace exhaust gas not only has a large quantity, but also can recover a lot of heat.(2) coke oven flue gas. Compared with other waste gases, the recovery significance of coke oven flue gas is more significant because it involves important energy problems such as gas fuel balancing in metallurgy enterprises, reducing the use of oil, etc.Therefore, it is necessary to accelerate the process. Coke oven flue gas belongs to ultra-low calorific fuel, and its gas source pressure is unstable. It is not suitable for long-distance transportation or as domestic coal gas, and the difficulty of cyclical utilization is relatively large.Except for hot air furnace, boiler, it can only be used for reblending furnace and steel heating furnace, dual preheating furnace, etc. The commonly used method for converting the coke oven flue gas into electricity is combustion power generation. (3) converter coal gas.Due to the cyclical production of converters, the flue gas waste heat also has intermittent emission. The intermittent emission makes the residual heat boiler only produce steam intermittently. To transform intermittent supply of gas into continuous and stable gas source, steam accumulators can be set in the supply system to increase the overall efficiency of boiler by 3%-5%.One of the reasons that affects the recovery of converter coal gas is the unsafe factor in the converter coal gas recovery process. This situation is determined by the characteristics of converter coal gas recovery process and the characteristics of converter coal gas itself. However, it is possible to safely recover converter coal gas by understanding the characteristics of converter coal gas and the production rules, and taking corresponding measures.