Briefly describe the knowledge related to waste heat utilization and recovery

Briefly describe the knowledge related to waste heat utilization and recovery
Waste heat refers to the energy that cannot be used for energy utilization under certain economic and technological conditions, namely surplus and waste energy. Waste heat recovery and utilization is an important means to improve economic efficiency and energy conservation and emission reduction.
1、 Waste heat type.
The waste heat mainly includes seven types: high-temperature waste gas waste heat, cooling medium waste heat, waste steam and wastewater waste heat, high-temperature product and slag waste heat, chemical reaction waste heat, combustible waste gas waste heat and waste heat, and high-pressure fluid residual pressure.
2、 Waste heat recovery pathways.
There are various ways to recover and utilize waste heat, but there are mainly three ways: direct utilization of heat energy, waste heat power generation, and comprehensive utilization of waste heat.
3、 The principle of waste heat recovery.
The commonly used utilization methods for waste heat utilization include: ① installing heat exchangers; ② Install a waste heat boiler behind the heat exchanger; ③ Bottom tube vaporization cooling; ④ Power generation (cogeneration); ⑤ Refrigeration.
The recovered heat is mainly used for preheating combustion air, preheating coal gas, and generating steam. For a heating furnace, preheating the air, fuel, and workpiece before sending them back into the furnace can stabilize the flame, improve fuel temperature, combustion efficiency, and furnace thermal efficiency.
4、 Waste heat utilization method
(1) Sintering waste gas.
After firing, about 50% of the thermal energy is emitted into the atmosphere through sensible heat from sintering machine flue gas and cooling machine exhaust gas, which not only wastes heat but also pollutes the environment. The flue gas temperature of the sintering machine is not high. Previously, people did not pay enough attention to the recovery and utilization of this part of heat energy, but in reality, there is great development space because the sintering furnace exhaust gas not only has a large quantity, but also can recover a large amount of heat.
(2) Blast furnace gas.
Compared with other exhaust gases, the recovery of blast furnace gas has greater significance because it involves important energy issues such as gas fuel balance in metallurgical enterprises and reducing oil burning. Therefore, the process should be accelerated. Blast furnace gas belongs to ultra-low calorific value fuel, and its gas source pressure is unstable. It is not suitable for long-distance transportation or use as domestic gas, making it difficult to recycle. Except for hot blast furnaces and boilers, it can only be used for reheating coke ovens, steel rolling heating furnaces, and double preheating furnaces. The common method for converting and utilizing blast furnace coal gas is combustion for power generation.
(3) Converter gas.
Due to the periodicity of converter production, the exhaust waste heat is also intermittent and periodic, which means that the waste heat boiler can only generate steam intermittently. In order to transform intermittent gas supply into a continuous and stable gas source, a steam heat storage device can be installed in the gas supply system, which can generally improve the thermal efficiency of the boiler by 3% to 5%.
One of the reasons that affects the recovery of converter gas is the presence of unsafe factors during the process. This situation is determined by the recovery process of converter gas and the characteristics of converter gas itself, but it is necessary to master the characteristics and production rules of converter gas, take corresponding measures, and it is completely safe to recover.