Low-NOx flue gas heat recycling system and method for thermal desorption of soil

Abstract

The invention discloses a low-NOx flue gas heat recycling system and method for thermal desorption of soil. The low-NOx flue gas heat recycling system comprises a secondary combustion chamber heatingunit, a flue gas distribution device, an induced draft fan set, a soil pre-drying kiln and a tail gas treatment device. Part of flue gas is distributed through a secondary combustion chamber, one partof the flue gas directly enters the tail gas treatment device, and the other part of the flue gas is output to the soil pre-drying kiln to pre-dry the crushed and screened contaminated soil through heat exchange; and water in the pre-dried soil is separated out and flows to the flue gas distribution device together with the low-temperature flue gas subjected to heat exchange. One part of the fluegas is discharged into the tail gas treatment device, and the other part of the flue gas serving as circulating flue gas enters a secondary combustion chamber combustor for combustion supporting so that flue gas recirculation is realized, and the overall stability and the heat efficiency of the thermal desorption system can be improved. The system can be installed according to actual conditions,the investment cost is low, the structure is simple, and the system is suitable for promotion and application. According to the system and the method, the problems that a continuous organic contaminated soil thermal desorption system is high in energy consumption and large in NOx emission can be improved.

Description

technical field [0001] The invention relates to the field of contaminated soil remediation devices, in particular to a low NO x Flue gas heat recovery system and method. Background technique [0002] After the implementation of the policy of "retreating cities and entering parks" and "retreating two and entering three" in China, the land left by polluting enterprises pollutes the atmosphere and endangers the health of the surrounding people. The polluted land urgently needs to be repaired. Direct ex-situ thermal desorption technology is widely used in the remediation of the above-mentioned contaminated soils. Direct thermal desorption technology has developed rapidly in my country in recent years. Soil thermal desorption projects have been carried out in various places to deal with the land pollution problems left by the relocation of polluting enterprises. The method of heating organic polluted soil to above the boiling point of organic matter is adopted to make organic po...

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Problems solved by technology

The temperature of the flue gas in the flue gas channel at the tail of the second combustion chamber is nearly 1000°C, and the flue gas carries a lot of heat. It will cause a lot of energy waste if it is directly cooled by the quench tower and then sent to the exhaust gas treatment device to remove the system.

The commonly used waste heat utilization system transfers heat energy to other places through heat exchangers, the system is complex, the heat loss is large, the system stability is poor, and the cost is high

[0004] At present, the development direction of direct thermal desorption technology is focused on improving the soil remediation rate and treating more types of pollutants. There are few related studies on the energy saving and consumption reduction performance of soil direct thermal desorption devices and the reduction of secondary pollution.

Moreover, the second combustion chamber belongs to the adiabatic furnace, and there is no heat exchange surface inside the furnace, so the heat is easily accumulated in the local area, causing the increase of nitrogen oxide generation

Low NOx combustion in an adiabatic furnace needs to achieve an excellent flame dispersion effect. Low NOx combustion is to reduce the concentration of NOx in the combustion tail gas by improving combustion equipment or controlling combustion conditions. Ordinary low NOx combustion The burner cannot achieve the expected NOx emissions due to insufficient flame dispersion, requiring a special design of the burner

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