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Cement kiln coordinated disposal of solid waste program

  Urban solid waste treatment is a major difficulty in urban environmental health management, and the new dry cement kiln coordinated disposal of solid waste technology in the disposal cost, pollution control has obvious advantages, is one of the effective means to realize garbage reduction, harmless, resource-based, energy.In this paper, several methods and development history of collaborative disposal of solid waste in cement kilns are introduced.

  The background,Since the reform and opening up, with the rapid development of China's economy, the rapid improvement of people's living standards, the continuous acceleration of urbanization process, the output of municipal solid waste has been increasing.In recent years, China's urban household waste emissions have increased by more than 10% every year. In addition, the domestic stock of garbage has exceeded 8 billion tons, which occupies land and pollutes the environment.In addition, due to insufficient attention paid to garbage classification and collection in China, garbage is basically mixed collection, with high water content, low calorific value and high organic composition. The composition of garbage varies greatly with regions and seasons.

  At present, harmless disposal methods of urban household garbage in China include sanitary landfill, high-temperature composting and incineration. Figure 1 shows the proportion of disposal methods of garbage in China in 2014, indicating that China is still dominated by landfill [2].However, due to the characteristics of the most obvious reduction effect, the most thorough harmless, and the effective utilization of incineration heat, the proportion of incineration has been rising rapidly in recent years. It can be predicted that incineration is gradually becoming the most important way to deal with urban waste.

  Compared with the traditional waste incineration, the construction and operation cost of power generation by incineration is higher, and the ash and slag generated need secondary treatment.Municipal solid waste (MSW) produced by separate incineration includes bottom ash and fly ash, and its main chemical composition is similar to that of cement raw materials, and it has certain gel activity

  2. Introduction of several schemes for collaborative disposal of domestic garbage by cement kilns and comparison 2.1 status quo of collaborative disposal of domestic garbage by cement kilns at home and abroad

  The collaborative waste disposal technology of cement kilns in the world started in the 1970s, and was first tested in Lawrence cement plant of Canada in 1974. Subsequently, more than ten cement plants including Peerless in the United States and Ruderdorf in Germany carried out tests successively.Up to now, it has more than 30 years of research and application history in Europe, North America, Japan and other developed countries, and has accumulated a lot of experience in alternative fuel research and ecological cement production.According to statistics, the fuel replacement rate of the Netherlands reached over 85% in 2007, and that of Japan, Belgium, Switzerland and Austria reached over 50% in 2013, and that of the United States reached about 30%.

  Cement kiln in our country for coordination living garbage technology popularization, only nanjing kaisheng, conch, sinoma, jinyu, huaxin, CRC, citic, the building materials such as several leading cement enterprise group, and in the cement kiln cement equipment group synergy disposal of household garbage, only a few provinces like guizhou organization promotes the cement kiln garbage disposal of life work together.At present, more than 30 production lines for coordinated disposal of household garbage in cement kilns have been put into operation nationwide, accounting for less than 2% of the total cement production lines.

  2.2 main schemes for cement kilns' collaborative disposal of household waste

  The core of coordinated disposal of household garbage in cement kilns is to make full use of combustible components and ash and slag materials in urban household garbage in the cement production process, combine the production characteristics of cement kilns and apply appropriate technical solutions, so as to make garbage reduction, harmless, resource-based and energy-oriented.The main processing schemes can be roughly classified as follows:

  2.2.1 solid waste is put into the kiln

  2.2.1.1 directly mix garbage into other materials to make derivative raw materials or low calorific value fuel for cement kiln treatment

  The technology is to make household waste into low-calorific value fuel or derivative raw materials, then use cement kiln disposal.After household garbage enters the site, lime is spread for disinfection and anticorrosion, part or all of construction garbage is sorted out, dehydration and crushing are carried out, then the lime saturation coefficient is adjusted, and modified burn AIDS and adhesives are added, finally forming.The adjustment of lime saturation coefficient is to add quicklime, hydrated lime, stone powder, calcium carbide slag and one or more other calcium-containing materials, so that appropriate silicate mineral, aluminate mineral and ferrite mineral can be generated in the ash slag and the cement clinker quality can be avoided to cause great fluctuation.

  If the target is low value fuel, then can add asphalt, tar, waste oil, dextrin, organic synthetic adhesive, etc.If the target is to generate raw materials, various industrial waste residues, tailings and carbon-containing raw materials can be added, such as the technology of hunan building materials institute.This technical route requires local use of waste materials that can be used in the preparation of household waste.

  2.2.1.2 microbial fermentation and drying were used to prepare waste RDF as alternative fuel for cement kilns

  RDF technology is the establishment of a specialized household waste pretreatment plant, mixed household waste for crushing and fermentation drying and other series of treatment, select the combustible part, its secondary crushing, adding additives, molding and screening, made RDF.RDF, with its low water content and high calorific value, can be used as an alternative fuel for the cement industry.The main flow is shown in figure 2.This technology strengthens the pretreatment of mixed household garbage, and the use of RDF products in the cement industry can reduce the consumption cost of enterprise resources and energy. In this process, it is not necessary to transform the original cement kiln system, which is conducive to the popularization of the technology.

  

典型的RDF水泥协同处置生活垃圾工艺流程图

 

  Figure 2 typical RDF cement collaborative disposal of household waste process flow chart

  2.2.2 refuse is incinerated and put into kilns in gaseous form

  2.2.1.1 collaborative disposal of domestic waste by grate furnace and cement kiln (nanjing kaisheng)

  

炉排炉与水泥窑协同处置生活垃圾工艺流程图

 

  FIG. 3 process flow chart of the cooperative disposal of domestic garbage by the grate furnace and cement kiln

  Landfill landfill waste by truck to the storage, structure of the closed negative pressure, negative pressure generated by garbage library induced draft fan, smelly air preheater, introduced the wind, from the use of the high temperature of waste incineration flue gas heated to 220 ℃ for combustion-supporting wind.

  Fresh rubbish into biological after drying after storage pit, can reduce the moisture, improve the calorific value, after drying the garbage after driving grab to drying, burning, burning in the grate furnace, incinerator combustion outlet flue gas temperature is 850 ~ 950 ℃, after high temperature flue gas preheater decomposition furnace is piped in, mix with the high temperature of decomposing furnace flue gas, and then, from the bottom after a cyclone tube heat exchange with uncooked materials and top-down.

  Decomposition furnace combustion flue gas temperature is greater than 850 ℃, the residence time in more than 7 seconds, the molecular structure of the toxic and harmful substances in the smoke was completely destroyed, thus reach the national discharge standard.

  After iron is removed from the furnace, the slag discharged from the furnace is sent to the cement raw material mill as the cement raw material to realize the recycling of resources. The heavy metal harmful elements are solids dissolved in the clinker after calcining at high temperature in the rotary kiln.

  The leachate generated in the process of garbage storage is high concentration organic sewage. After filtration treatment, it is sprayed into the calciner for high-temperature evaporation and oxidation treatment to completely decompose organic components and realize innocuous treatment.

  2.2.1.2 garbage incineration gasifier and cement kiln co-processing domestic garbage (conch)

  CKK technology is to establish a parallel waste incineration gasifier outside the cement kiln system, and then guide the flue gas and slag after incineration back to the kiln system for disposal.

  The main flow is shown in figure 4.

  The whole process of living garbage disposal in the closed negative pressure environment, free of dust and gas leaking problem, garbage incineration flue gas produced by pyrolysis of the kiln system and high efficient dust removal system incorporated after discharging standard, slag can be used as substitute raw material are fixed in cement clinker, or as a mixed material and the final was fixed in the cement concrete.

  

垃圾焚烧气化炉与水泥窑协同处置生活垃圾工艺流程图

 

  FIG. 4 process flow chart of garbage incineration gasifier and cement kiln co-disposing household garbage

  The use of cement kiln incineration of municipal solid waste, its ash and slag directly into the burning base raw materials, to participate in the solid phase reaction of clinker calcining, can not only avoid the discharge of harmful substances, but also reduce the consumption of mine resources, truly realize the "three" goal of garbage treatment;

  The cement kiln burning system is used to replace the exhaust gas purification system of waste incineration treatment process, which simplifies the treatment process and reduces the corresponding investment.

  Ease occupation, save construction investment;

  We will reduce overcapacity in the cement industry and promote green transformation and development.

  2.2.1.3 combined disposal of domestic waste by rotary incinerator and cement kiln (hefei institute)

  Garbage into the factory by the junk car transport after first by the criterion of weighing, transported to the discharging platform, the discharging door discharge to store waste storage pit, and the grab by the garbage and putting it into the factory time separate pile up inside the pool, and then by the garbage cranes and grab the rubbish to the rubbish bin, the garbage pusher, put the rubbish uniform feeding rotary incinerator;

  Sampling 887 ℃ hot air from the kiln head as incinerator combustion gas, garbage burning after the hot flue gas into the preheater system, garbage burned in incinerators at about 1200 ℃, the temperature control in the period of waste incineration gas temperature for 2 seconds, above the temperature above 850 ℃ for 5 seconds;

  After the gas enters the preheating decomposition system, it will conduct heat exchange with raw materials, and decompose some harmful substances at the same time, so as to realize the recycling, harmlessness and reduction of garbage treatment.

  The flow chart is shown in figure 5.

  

回转式焚烧炉与水泥窑协同处置生活垃圾工艺流程图

 

  FIG. 5 process flow chart of combined disposal of domestic waste by rotary incinerator and cement kiln

  2.2.1.4 combined treatment of domestic waste by hot plate furnace and cement kiln (Smith, Denmark)

  The technological process and structure of the hot plate furnace are shown in FIG. 6. The bottom of the hot plate is equipped with a circular plate (1 ~ 4 r/h) with adjustable rotating speed. The combustible waste (garbage) is measured and then fed into the furnace.

  Kiln three specific with combustible rubbish, partial high temperature into the hot plate in furnace, in the slow rotating disk to fully oxidation burning, from raw materials imported into slag and discharged, the mixture on the disk to run about 270 °.

  Residue discharged into down at fine fly ash and raw meal with the decomposition of around 1050 ℃ high temperature gas into the furnace.

  According to the nature of combustible garbage, the rotation speed of the disc can be adjusted so that it can have enough time in the furnace to achieve the purpose of full combustion.

  When unexpected failure occurs in the firing system, the cold raw material bin located above the hot pan furnace can directly put raw materials into the furnace, blocking the garbage combustion, so that the fire on the hot pan furnace will be extinguished quickly, to avoid excessive environmental protection emissions when the cement kiln system is abnormal.

  

热盘炉与水泥窑协同处置生活垃圾工艺流程图

 

  Fig.6 process flow chart of domestic waste disposal in cooperation between hot plate furnace and cement kiln

  Three, endnotes

  Cement kiln for coordination living garbage can make full use of waste heat and the ash after burning, and the organic combination of cement production process, greatly reducing the traditional waste incineration power generation environmental protection operation cost of the project, the realization of the maximum reduction, harmless and recycling of waste, energy, and make the garbage "into".The coordinated disposal of domestic garbage with the new dry method cement kiln can control the risk of the impact on the cement line, and the product will not cause harm to environmental safety, and has obvious environmental and social benefits, so it will certainly become one of the preferred methods of garbage treatment in the future.

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