Exhaust Gas Heat Recovery Industrial Gas-to-Gas Heat Exchangers

Exhaust Gas Heat Recovery Industrial Gas-to-Gas Heat Exchangers

In the industrial production process, a large amount of exhaust gases containing heat will be generated. The direct discharge of these exhaust gases not only causes energy waste, but also may cause thermal pollution to the environment. Industrial gas-to-gas heat exchanger is used to recover heat from the exhaust gas and transfer the heat to the gas that needs to be heated, thus improving the efficiency of energy use.

Advantages of exhaust gas heat recovery

(i) Energy saving

By recovering heat from exhaust gases, the energy consumption required to heat other gases can be reduced. For example, in the iron and steel industry, a large amount of high-temperature exhaust gas from the sintering process can be transferred to combustion air through a gas-to-gas heat exchanger. According to statistics, such a heat recovery system can increase energy utilisation by about 10% - 30% and reduce production costs.

(ii) Reduction of greenhouse gas emissions

When the heat of the exhaust gas is recovered and used to preheat the gas for combustion, the combustion efficiency can be improved and the amount of fuel used can be reduced. This means that the emission of carbon dioxide and other greenhouse gases will be reduced accordingly, which helps the enterprise to achieve the goal of energy saving and emission reduction, and has a positive significance for environmental protection.

(iii) Improvement of process efficiency

In some industrial processes, such as chemical reactions require the participation of gases at specific temperatures. The use of exhaust gas heat recovery system can quickly heat the gas to the required temperature, speeding up the reaction and improving the efficiency of the entire production process.

Design and application considerations

(i) Temperature and pressure

The temperature and pressure ranges of the exhaust gas and the gas being heated need to be considered. Different heat exchanger materials and structures have different capacities for temperature and pressure. For example, in high-temperature and high-pressure exhaust gas recovery scenarios, such as those generated by catalytic cracking units in refineries, heat exchangers that can withstand high temperatures and pressures need to be selected with reasonable strength calculations and design.

(ii) Gas composition and corrosivity

The composition of the exhaust gas may contain corrosive substances, such as sulfur dioxide, hydrogen chloride and so on. These components can cause corrosion of the heat exchanger. Therefore, when designing and selecting materials, it is necessary to consider using corrosion-resistant materials, such as stainless steel, titanium alloy or using anti-corrosion coatings. For example, in the chemical industry, special alloy materials may be required for heat exchangers for exhaust gases containing acidic gases.

(iii) Gas flow and flow rate

In order to ensure good heat transfer, the flow rate and flow velocity of the exhaust gas and the heated gas need to be reasonably controlled. A flow rate that is too slow will result in low heat transfer efficiency, while a flow rate that is too fast may cause excessive pressure drop and increase energy consumption. It is important to determine the optimum range of flow rates and flow velocities through hydrodynamic calculations and experiments.