Waste heat is the sensible heat and latent heat which is not used properly in energy dissipation devices of industrial enterprises. It includes waste heat from high temperature exhaust gas, cooling medium, waste steam, waste water, high temperature products, slag, chemical reaction, combustible waste gas waste liquid and waste heat, etc. Waste heat resources can be divided into three categories according to the temperature: high temperature waste heat (heat resources temperature higher than 500℃ ;Medium temperature waste heat (heat resources temperature from 200 to 500℃ ); Low temperature waste heat (flue gas of temperature below 200 ℃ and liquid of temperature below 100 ℃).Waste heat recovery methods are various and mainly divided into two categories: heat recovery (direct use of heat energy) and power recovery (conversion into power or electricity reuse).
Waste heat recovery - medium to high temperature waste heat
The waste heat boiler utilizes medium and high temperature flue gas to convert the water in the boiler into steam. The steam accumulates to a certain temperature and pressure and starts to be discharged into the water supply system. The cold water in the water supply system is heated into hot water and supplied to the production department or residents.
Hot air heat exchanger utilizes the heat of high temperature flue gas to heat the cold air into hot air and discharge it, which is used in the production process. The high temperature flue gas is recycled through waste heat utilization, and finally becomes low-temperature flue gas and discharged into the air, which can not only save the steam or coal that the energy-using unit needs, but also reduce the thermal pollution of flue gas.
Waste heat recovery –low temperature waste heat
The main technology used for the recovery of low temperature waste heat is heat pump technology, and typical equipment is lithium bromide absorption heat pump. Absorption heat pumps can be divided into two types according to the different heat sources required: One type is the heat pump, which utilizes high grade heat energy (such as steam, gas, etc.) as the power, recovery of low temperature heat source (such as waste heat water), produce hot water at a higher temperature for heating or process requirements of equipment; Another type is the heating type heat pump, which is a kind of equipment usually uses lower temperature waste heat (or waste heat) as the power, through the special function "absorption heat" of the lithium bromide absorption heat pump,to produce hot water with higher temperature than waste heat.