I. Natural advantages
Similar to the principle of waste incineration for power generation, co-processing of solid waste in cement kilns also uses high temperature to treat waste. But unlike waste incineration, the co-processing method of cement kiln directly uses the high temperature of the kiln of the cement production line, and the temperature is much higher than that of the waste incineration plant.
For waste disposal, a sufficiently high temperature means a sufficiently large advantage. As far as co-processing of solid waste by a cement kiln is concerned, it can fully and stably burn solid waste, solid metal waste in the solid waste can be discharged without waste residue, and toxic and harmful organic substances such as dioxin will be completely decomposed or effectively controlled.
People in the industry also said that the temperature of the cement kiln is as high as 1450 ° C, which can absorb various wastes and decompose or solidify harmful substances including heavy metals in the crystal structure of cement.
In addition to the advantages of fuel, furnace temperature control, labor and marginal cost of production and construction, the co-processing of solid waste by cement kilns has almost become the mainstream way after waste incineration.
Since the 1970s, developed countries and regions such as Europe, the United States, and Japan have begun to promote the solid waste disposal in cement kilns on a large scale. So far, it has become one of the most popular mature technologies. Whether it is solid waste treatment or the development of the cement industry It has a double meaning.
2. Favorable policies
In view of the seriousness of solid waste pollution in China and the transformation and upgrading of the cement industry, China has begun to promote the technology and equipment for cooperating the treatment of various solid wastes in cement kilns from the 12th Five-Year Plan period. From the actions of the national policy level, we can clearly see the importance attached to the solid waste co-processing of mud kiln:
In January 2013, the "Circular Economy Development Strategy and Immediate Action Plan" issued by the State Council explicitly proposed to encourage cement kilns to co-resource the treatment of municipal solid waste, sewage plant sludge, hazardous waste, waste plastic and other wastes, replacing some raw materials, Fuel, and promote the cyclic link between the cement industry and related industries and social systems.
In May 2014, the NDRC, the Ministry of Environmental Protection and other seven ministries and commissions issued the Opinions on Promoting the Cooperative Resource Recycling of Urban and Industrial Wastes in the Production Process, and proposed the use of existing cement kilns for co-processing of domestic waste for pilot projects.
In February 2016, the Ministry of Environmental Protection began to solicit opinions on the “Technical Policies for the Collaborative Disposal of Waste Pollution in Cement Kilns” to provide clearer policy support for promoting this technology.
In June 2016, the National Catalogue of Hazardous Wastes (2016 Edition) revised and issued by the Ministry of Environmental Protection clearly stated that “the co-processing of cement kilns is not managed according to hazardous wastes”.
In December 2016, the “Technical Policy for the Pollution Prevention and Control of Cooperative Disposal of Cement Kilns” was officially launched, and the co-processing of solid waste by cement kilns ushered in a real “spring”.
In June 2017, the relevant person in charge of the Ministry of Environmental Protection answered reporters' questions on the "Guidelines for the Examination of the License for the Cooperative Disposal of Hazardous Waste in Cement Kilns".
In addition, the co-processing of cement kiln has been listed by the Ministry of Industry and Information Technology as an important credit project for industrial energy conservation and green development in 2017, and it has been paid much attention by both local provinces and cities and major cement companies.
Data show that five major cement kilns in the country, such as Conch, Sinoma, Jinyu, Huaxin and China Resources, have formed a “school” of co-processing technology for municipal waste.
At the same time, the voice of opposition to co-processing of cement kilns cannot be ignored, and more and more attention is being paid. China Environmental Protection Online summarizes the following key points:
First, co-processing of solid waste in cement kilns is a new thing. It started late in China and is not perfect in many aspects, such as technical design, operation management, and risk management.
Second, the co-processing of solid waste by cement kilns has a limited substitution effect on fuels and raw materials for cement production, and it limits the scale of solid waste treatment and the reliable and safe treatment.
Third, China's cement industry is still in surplus. Cement companies use cement kilns to co-process solid waste, which poses a double threat to the capacity reduction of the cement industry and the stability of the solid waste treatment market.
Fourth, China's domestic garbage has high moisture content, high ash content, low calorific value, and high chlorine element. It is difficult for the pretreatment system of co-processing solid waste in cement kilns to effectively reduce the chlorine content in the garbage, or even increase the chlorine content, thereby aggravating air pollution.
Fifth, from the trial practice at this stage, there are problems such as odor emissions from cement kiln co-processing solid waste projects, leachate not up to standard treatment, and RDF moisture content not meeting design requirements.
Because of many constraints, China's cement kiln co-processing of solid waste pilots for more than two years has accounted for less than 3% of the total domestic waste disposal.
It is true that compared with traditional landfill and incineration treatment methods, the advantages of co-processing solid waste in cement kilns are obvious. The state also supports in many aspects such as policies and funds. However, due to the late start, technical, operational, and regulatory aspects The construction of the system was careless and sound, so it also faced obstacles in the development process. There is still a long way to go to break the game, and we will explore it.