Soil repair technology cement kiln co-disposal technology
Technical principle
Utilizing the features of high temperature in cement rotary kiln, long gas stay, large heat capacity, good thermal stability, alkaline environment and no waste discharge, cement clinker is produced while incinerating and curing contaminated soil. Organic contaminated soil enters the cement rotary kiln from the kiln flue gas chamber. The maximum temperature of the gas phase in the kiln is up to 1800 ℃ and the material temperature is about 1450 ℃. Under the high temperature of the cement kiln, the organic pollutants in the contaminated soil are transformed into inorganic compounds , The high-temperature gas stream is in full contact with alkaline materials (CaO, CaCO3, etc.) of high fineness, high concentration, high adsorption and high homogeneity distribution, effectively inhibiting the emission of acidic substances and converting sulfur and chlorine into inorganic salts Fixed; heavy metal contaminated soil from raw meal ingredients into the cement kiln system, so that heavy metals fixed in the cement clinker.
2. Conditions of use
For contaminated soil, can handle organic pollutants and heavy metals.
It should not be used in soils contaminated by heavy metals such as mercury, arsenic and lead. Due to the limited requirements for the content of chlorine and sulfur in the feedstock, the dosage of contaminated soil should be carefully determined when using this technology.
3. Technology route
(1) technical route
(2) the key technical parameters
The key technical parameters that affect the co-treatment effect of cement kiln include: cement rotary kiln system configuration, alkaline content of contaminated soil, initial concentration of heavy metal pollutants, chlorine and fluorine, sulfur and contaminated soil.
1) Cement rotary kiln system configuration: The new dry-process rotary kiln equipped with perfect flue gas treatment system and flue gas on-line monitoring equipment should not be less than 2,000 tons / day for single-line design clinker production.
2) Content of Alkaline Substances in Contaminated Soils: Polluted soils provide siliceous materials. However, due to the high content of K2O and Na2O in the contaminated soils, the alkali equivalent of the intermediate products and the final products in the process of cement production is high, which affects the quality of the cement Before starting cement kiln co-processing, the amount of contaminated soil should be determined based on the K2O and Na2O contents in the contaminated soil.
3) Initial Concentration of Heavy Metal Pollutants: The concentration of heavy metal pollutants in the kiln ingredients shall meet the requirements of "Technical Specification for Environmental Protection of Solid Waste Wasted in Cement Kilns" (HJ622).
4) Content of chlorine and fluorine in contaminated soil: The dosage of chlorine and fluorine added into the kiln should be controlled according to the technological characteristics of cement rotary kiln to ensure the normal production and product quality of cement rotary kiln to meet the national standard. The content of fluorine in the kiln material should not exceed 0.5%, and the content of chlorine should not exceed 0.04%.
5) Sulfur content in contaminated soil: During the co-processing of cement kiln, the content of sulfur in contaminated soil should be controlled. The total content of sulfide and organosulfur in the material should not exceed 0.014%. From the kiln, kiln tail high temperature dosing of the total sulfur and the dosing system, the total dosage of sulfate sulfur should not exceed 3000mg / kg.
6) Amount of contaminated soil: The dosage of contaminated soil should be comprehensively determined according to the content of alkaline substances, heavy metals, chlorine, fluorine and sulfur in contaminated soil and the moisture content of contaminated soil.
(3) configuration of equipment and pharmaceuticals
Cement kiln co-processing mainly by the soil pretreatment system, feeding system, cement rotary kiln and supporting systems, monitoring system.
Soil pretreatment system in a closed environment, including closed storage facilities (such as inflatable greenhouses), screening facilities (screening machine), exhaust gas treatment system (such as activated carbon adsorption system, etc.), pre-treatment system exhaust through the exhaust treatment system After the discharge standards.
The material feeding system mainly includes a hopper, a plate feeder, a belt weighing scale and a hoisting machine. The entire feeding process is in an airtight environment to prevent pollutants and dust from being emitted into the air during the feeding process, resulting in secondary pollution.
Cement rotary kiln and supporting systems include preheater, rotary cement kiln, kiln high temperature fan, tertiary air duct, rotary kiln burner, grate cooler, kiln bag dust collector, screw conveyor, trough conveyor machine.
The monitoring system mainly includes on-line monitoring of oxygen, dust, nitrogen oxides, carbon dioxide, moisture and temperature as well as regular monitoring of cement kiln exhaust gas and cement clinker to ensure the effect of contaminated soil treatment and production safety.
4. Technology costs
The treatment cycle is related to the production capacity of cement production line and the amount of contaminated soil added. The amount of contaminated soil added is related to the characteristics of pollutants in the soil, the degree of pollution and the soil characteristics. The amount of contaminated soil and the treatment cycle are generally determined by calculation. Add less than 4% of the amount of cement clinker. The domestic application costs 800-1000 yuan / m3.
5 repair effect
More mature abroad, widely used in hazardous waste treatment, but applied to contaminated soil treatment is relatively small. Domestic engineering applications.