Hazardous waste (hereinafter referred to as hazardous waste) has a wide variety, complex composition and serious regional differentiation, and improper treatment will bring a series of livelihood and social problems. Practice has proved that high temperature incineration is an effective way of safe disposal and capacity reduction of hazardous waste, and the rotary kiln incineration process is one of the effective disposal processes in hazardous waste treatment, which has the advantages of treating many types of hazardous waste and large capacity.
Since the 1990s, China has gradually begun to use rotary kiln incineration system to treat hazardous waste. In recent years, kiln shutdown accidents caused by refractory material damage have occurred frequently, which seriously affect the stable operation rate of hazardous waste incineration production line, and put forward an urgent need for the refractory lining design optimization and efficient operation of hazardous waste incineration furnace in rotary kiln.
At present, the collaborative treatment of hazardous waste in cement kilns mainly includes solid hazardous waste, waste liquid and RDF alternative fuel, which are mainly processed from preheater, decomposing furnace, rear kiln mouth and kiln head cover, etc. Typical feeding methods are shown in Figure 1.
Rotary kiln incinerator is a professional hazardous waste incineration device, as shown in Figure 2. The main equipment consists of rotary kiln, secondary combustion chamber, waste heat boiler, quench tower, deacidification and dust removal system. All kinds of hazardous waste after pretreatment enter the combustion system through different feeding methods. Under the action of its own gravity and continuous rotation of rotary kiln, the material and the combustion air are fully in contact, completing the process of drying, gasification and combustion, and finally the residual part is quenched into ash and slag.
According to the direction of gas and solid flow, or the position of the burner in the rotary kiln, the rotary kiln incinerator can be divided into two forms: countercurrent and concurrent flow. Among them, the heat source of the burner is in the feed end of the rotary kiln, and the solid and flue gas go towards the same direction, becoming the downstream type; On the contrary, the heat source of the burner is at the discharge end, and the solid and flue gas are opposite, which is called countercurrent type. At present, the dangerous waste incineration system is mainly based on the design of the downstream rotary kiln, and the countercurrent rotary kiln is more suitable for the dangerous waste with high moisture content or low calorific value. The rotary kiln incinerator has the characteristics of wide applicability and can simultaneously treat hazardous wastes of solid, liquid and gas. Under the situation of increasingly strict environmental protection requirements, professional rotary kiln hazardous waste incinerator has obvious advantages. According to statistics, China's rotary kiln hazardous waste incineration system has about 800 processing lines, with processing capacity ranging from 20t/d to 120t/d. In 2018, China's hazardous waste incineration disposal capacity reached 6.16 million tons/year, of which professional rotary kiln incineration accounted for 53%, mainly distributed in Zhejiang, Jiangsu, Shandong, Hebei, Fujian and other places