High-efficiency back-flushing decoking method for flue gas waste heat recovery system

Abstract

The invention relates to a high-efficiency back-flushing decoking method for a flue gas waste heat recovery system and aims to realize removal of tar adhered to the interior of a heat exchanger by the aid of high-temperature air generated by a hot air generator. The system comprises a back-flushing decoking unit, a cooling unit, an automatic control unit and the like. The automatic control unit is capable of recording pressure difference of a flue gas side in the heat exchanger, and the back-flushing decoking unit is started when the pressure difference is higher than a set peak value. During decoking, the tar in the heat exchanger is quickly removed by the high-temperature air generated by the hot air generator, and waste gas is fed into an adsorption chamber to realize tar adsorption; in a decoking process, overhigh internal temperature of the heat exchanger can be prevented by the aid of the cooling unit. The system with an online decoking function is environment friendly, and the high-efficiency back-flushing decoking method can be widely applicable to flue gas waste heat recovery systems of heating furnaces and the like to improve system efficiency.

Description

technical field [0001] The patent of the present invention relates to a high-efficiency backflushing and decoking method used in a flue gas waste heat recovery system, and the system involved in the method. Background technique [0002] In the 21st century, with the depletion of fossil fuels and the increasingly serious environmental pollution, energy conservation and emission reduction has undoubtedly become a hot topic. At present, in the production process of heating furnaces in the domestic steel and petroleum industries, in order to avoid problems such as dew point corrosion and coking, the flue gas (usually at about 300°C) after preheating the combustion air is often used to directly Discharge, resulting in waste heat waste. If the flue gas temperature is lowered below the dew point temperature, although more heat can be utilized, coking will occur in the heat exchanger, and coking is not conducive to heat exchange, and it will affect production in severe cases. In v...

AI Technical Summary

Problems solved by technology

At present, in the production process of heating furnaces in the domestic steel and petroleum industries, in order to avoid problems such as dew point corrosion and coking, the flue gas (usually at about 300°C) after preheating the combustion air is often used to directly discharge, resulting in waste of waste heat

If the flue gas temperature is lowered below the dew point temperature, although more heat can be utilized, coking will occur in the heat exchanger, and coking is not conducive to heat exchange, and it will affect production in severe cases.

In view of the coking phenomenon of the heat exchanger, it must be cleaned in time before it can continue to be used to meet the production conditions. Some refineries use high-pressure water cleaning method, which is time-consuming and labor-intensive, and has a low safety factor.

At present, domestic large oil refineries adopt the steam coking method, which is low in cost. Although the steam decoking method can greatly shorten the downtime, the steam method has its inherent disadvantages: the safety factor is lower than that of high-pressure water, and the labor intensity of workers is high. Poor temperature control will burn and bend the heat exchange tube

Now developed countries in foreign countries adopt mechanical decoking method, which is commonly called PIGGING, which is called through ball in China. Domestic through ball is basically used for pipe cleaning only after commissioning, not suitable for sharp bends or pipes. 90-degree cast elbow (plug), foreign mechanical decoking technology is far superior to domestic, high decoking efficiency, but the biggest disadvantage of mechanical decoking is that it cannot be decoked online, and disassembly is more troublesome

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