The rapid development of industrialization has highlighted the problem of environmental pollution on which human beings depend. The unreasonable disposal of various wastes harmful to the natural environment has resulted in the pollution of soil and groundwater. Soil pollution has the characteristics of concealment and irreversibility. It will not only directly or indirectly endanger human health, but also lead to many other environmental problems. At present, the pollutants harmful to the soil can be divided into four categories according to their nature: organic pollutants, heavy metal pollutants, radioactive pollutants and pathogenic microbial pollutants, among which organic pollutants and heavy metal pollution and their combined pollution sites are more common. According to the World Bank’s “Current Situation Analysis of Rehabilitation and Redevelopment of Polluted Sites in China” published in 2010, 3/5 of the sites left over by industrial enterprises in recent years have serious organic pollution, and their remediation work is facing serious challenges. Most of the sites vacated after relocation are in urgent need of functional transformation and secondary development. The contaminated soil of these sites has become a “chemical time bomb”, which seriously threatens human health and environmental safety, and has become an urgent soil environmental problem to be solved.
In order to solve this problem, Luoyang Building Materials Architectural Design and Research Institute has developed an organic contaminated soil remediation system, which uses direct heating to form soil preheating and exhaust gas cooling zones, high temperature thermal desorption zones, gas preheating and soil cooling zones in rotary kiln furnaces. The system has the characteristics of simple structure, low energy consumption, high desorption efficiency, and can be solid. Now, the organic contaminated soil is effectively remediated. Most of the separated gases containing organic pollutants are directly burned and decomposed in the kiln, and a small amount of them enter the tail gas treatment system with smoke and dust, and are discharged after the treatment reaches the standard. Advantages: thorough removal, more applicable, can deal with highly polluted soil, small occupation area.
Process Flow Chart of Rehabilitation of Contaminated Soil by Rotary Kiln
Technical scheme for remediation of contaminated soil by rotary kiln:
The rotary kiln-type thermal desorption and incineration integrated organic contaminated soil remediation system includes contaminated soil pretreatment system, feed system, rotary kiln-type thermal desorption system and tail gas treatment system. One end of the rotary kiln-type thermal desorption system is provided with a solid inlet and a gas outlet, and the other end is provided with a solid outlet and a burner connection port. The over-feeding system is connected with the solid inlet and outlet of the rotary kiln thermal desorption system; the gas outlet of the rotary kiln thermal desorption system is connected with the inlet of the tail gas treatment system through the pipeline; The features are as follows: the contaminated soil pretreatment system includes a crushing device and a screening device, which makes the contaminated soil air-dried, crushed and screened, and the moisture of the pretreated soil is less than 20% and the particle size is smaller than 20 The feeding system comprises a movable belt conveyor, a feeding hopper and an impeller feeder. One end of the movable belt conveyor is connected with the outlet of the contaminated soil pretreatment system, the other end is connected with the inlet of the feeding hopper, and the outlet of the feeding hopper is connected with the inlet of the impeller feeder; the outlet of the impeller feeder is connected with the inlet of the rotary kiln pyrolysis machine. The solid inlet and outlet of the suction system are connected; the contaminated soil entering the rotary kiln thermal desorption system can be desorbed in the rotary kiln equipped with gas burner, and the gasified matter is guided to the exhaust device by the induced draft fan after cyclone dust removal, bag dust removal and activated carbon adsorption treatment; after cooling, the treated soil particles are repaired and discharged from the rotary kiln after qualified detection. The whole process of thermal desorption treatment of contaminated soil.
Technical Characteristics of Rehabilitation of Contaminated Soil by Rotary Kiln
A rotary kiln thermal desorption and incineration integrated organic contaminated soil remediation system includes soil pretreatment system, feed system, thermal desorption system and tail gas treatment system. The contaminated soil pretreatment system is connected with solid feed port of rotary kiln thermal desorption system through feed system; the gas outlet of rotary kiln thermal desorption and desorption system is connected with tail gas treatment system through pipeline. The contaminated soil pretreatment system comprises a crushing device and a screening device, and the feeding system comprises a movable belt conveyor, a feeding hopper and an impeller feeder. The two ends of the movable belt conveyor are connected with the outlet of the contaminated soil pretreatment system and the inlet of the feeding hopper respectively, and the outlet of the feeding hopper is connected with the phase of the impeller feeder. The impeller feeder is connected with the solid inlet and outlet of the rotary kiln thermal desorption system; the contaminated soil is desorbed in the rotary kiln equipped with gas burner, and the gases are guided to the exhaust device after adsorption treatment; the treated and repaired soil particles after cooling are discharged from the rotary kiln after qualified detection.
Advantages of rotary kiln in remediation of contaminated soil:
1. The temperature of high temperature thermal desorption zone in rotary kiln is 150~550 degrees C. It can adjust the appropriate thermal desorption temperature according to the types of organic species in contaminated soil. The organic matter in contaminated soil can be completely removed with minimum energy consumption to achieve the purpose of soil remediation.
2. The contaminated soil enters the main body and is heated directly by the burning flame. Most of the organic pollutants released by thermal desorption are discharged with flue gas, and a small amount of them are burned directly in the flame.
3. The outlet gas temperature of the thermal desorption system is 105-150 degrees C, and the outlet solid temperature < 100 degrees C does not require additional gas and solid cooling devices, which reduces the heat loss of the outlet gas and solid, has high thermal efficiency and low energy consumption.
4. The device has good mobility and is convenient for transfer between and within the site.