Keywords: municipal solid waste recycling technology pollution control
1, China municipal solid waste treatment status and resource utilization technology.
According to the idea of integrated management of municipal solid waste, the collection and transportation of municipal solid waste is also an important part of integrated management of municipal solid waste. At present, the collection and transportation methods of urban garbage in China are still in a relatively backward stage, and most of the domestic garbage is collected by mixing, not by classification. On the one hand, mixed collection increases the quantity of urban garbage collection and transportation, and consumes more manpower, material resources and financial resources; On the other hand, it increases the technical difficulty, engineering investment and operation cost of municipal solid waste treatment, which is not conducive to the reduction, resource utilization and harmless treatment of municipal solid waste. At present, there are three recycling technologies: landfill, composting and incineration. The following is an analysis of the current situation of the three technologies.
(1), Status of Municipal Solid Waste Landfill Treatment
For a long time, most cities in China have used open-air stacking, natural ditch filling and pit filling to absorb urban garbage, which not only encroached on valuable land resources, but also caused potential impact and harm to the environment. In particular, the leachate of municipal solid waste produced by landfill site has not been collected and treated, which leads to serious pollution of water resources and its environment. Since the end of 1980s, the technology of municipal solid waste landfill in China has developed to a certain extent, and a number of relatively perfect sanitary landfills (or quasi-sanitary landfills) have been built all over the country. In these sanitary landfills (or quasi-sanitary landfills), there are generally relatively perfect anti-seepage systems, leachate collection and treatment systems, landfill gas drainage systems, rain and sewage diversion systems, etc. Imported high-density polyethylene liners are also used in municipal solid waste sanitary landfills built in Shenzhen, Beihai, Beijing and Tianjin. However, at present, there are still many shortcomings in the bottom seepage control, landfill gas collection and utilization, leachate collection and treatment, layered compaction of landfill operation, daily coverage and final recovery of most municipal solid waste landfills in China.
(2) The present situation of municipal solid waste composting.
At present, the composting technology of municipal solid waste in China is in a relatively shrinking state. Practice has proved that the compost produced by mixed collection of municipal solid waste has low fertilizer efficiency, many impurities and high cost, which is not convenient for farmland production and affects its market development. The mechanized municipal waste composting plants built in Wuxi, Hangzhou, Beijing, Shanghai and other places during the Seventh Five-Year Plan period were closed down one after another due to technical and market reasons. At present, some municipal waste composting plants with low mechanization and mainly static aerobic fermentation technology are widely used in China. It is characterized by simple process, less mechanical equipment and low investment and operation cost, but there are also some problems, such as low composting quality, the odor and sewage generated in the composting process have not been effectively treated, and the urban garbage composting plant has a great impact on the surrounding environment. Reducing the cost of composting, improving the quality of composting products and opening up market channels are the key factors for the development of municipal solid waste composting technology, and the important condition affecting these factors is to realize the classified collection of organic waste.
(3) Present situation of municipal solid waste incineration treatment
Incineration is a new hotspot of municipal solid waste treatment technology in China. Compared with developed countries, China's municipal solid waste incineration technology has just started, and it can't meet the growing demand at present. The huge market potential has attracted many enterprises to invest in the development of municipal waste incineration technology and equipment. On the basis of introducing foreign advanced technology and equipment to build the first modern municipal waste incineration plant in China, Shenzhen completed the localization project of No.3 incinerator in combination with the national eighth five-year plan. The localization level of the equipment has reached more than 80%, and the technical performance has reached or exceeded the level of the original imported equipment, which has laid the foundation for the localization of urban waste incineration equipment in China. In the past three years, some economically developed cities in China, especially coastal cities such as Shanghai, Guangzhou, Beijing, Shenzhen, Zhuhai, Beihai, Ningbo, Xiamen, etc. , is actively preparing for the establishment of municipal waste incineration plant. At present, the total scale of municipal waste incineration plants under construction and planning is about 1 10,000 tons/day, and most of them are built by introducing technology and equipment. Most of the garbage incineration plants built in China have a low level of technology and equipment, which makes it difficult to operate normally and meet the pollution control standards.
2. Analysis of the present situation of urban garbage disposal.
At present, China's urban garbage disposal system is easy to discuss and analyze. Urban garbage disposal is only in its own way. Generally speaking, the composition of municipal waste is characterized by high moisture (because of the high proportion of kitchen waste), high ash (high ash in areas with low gas permeability) and low calorific value; The collection method is basically mixed collection. At present, the present situation of urban garbage disposal can be summarized as follows:
(1) In most cities, most municipal wastes are still piled up in the open air, simply buried, and littering is quite common.
(2) In some areas, especially in the economically developed eastern coastal areas, there is a shortage of suitable sites for municipal solid waste landfills, and there are fewer and fewer sites;
(3) Under the condition of mixed collection, municipal solid waste compost is difficult to develop, and some areas are still shrinking;
(4) Municipal solid waste incineration is still in its infancy. Domestic independent research and development of municipal waste incineration equipment is not mature, and the price of imported incineration equipment system is too high, which makes the economic strength of most cities unbearable. According to the requirements of Pollution Control Standard for Domestic Waste Incineration (GWKB3), it is suitable for municipal waste incineration facilities with high moisture content, high ash content and low calorific value. Whether domestic or independent research and development, its engineering investment and operating costs are relatively high, and it is generally difficult to popularize.
3. Problems existing in the recycling of urban garbage in China.
China's municipal solid waste is growing rapidly. By the end of 2000, the annual removal of municipal solid waste exceeded1.65,438+0.8 billion tons. With the economic growth and the improvement of people's living standards, especially the optimization of civil fuel structure, the output and composition of municipal solid waste in China have also undergone fundamental changes. Various indications show that the utilization potential of urban solid waste in China is huge.
After analysis, there are the following problems in urban garbage recycling in China: ① Mixed recycling of urban garbage increases the difficulty of garbage recycling. The municipal solid waste in China basically belongs to mixed recycling, which requires a lot of manpower, material resources and financial resources to separate useful substances from the recycled garbage, which is not conducive to the recycling of municipal solid waste. ② The technology of recycling municipal solid waste is backward. In China, there are more inorganic components than organic components, more combustible components than combustible components, and more compostable components than compostable components. There are differences among large, medium and small cities, so it is difficult to recycle and the economic benefits are poor. (3) Lack of funds for recycling municipal solid waste. The cost of municipal solid waste treatment in China mainly comes from the government, and the amount is limited, while the construction of large sanitary landfill plants or incineration power plants requires a lot of money, resulting in poor infrastructure for resource utilization of municipal solid waste. (4) Imperfect laws and regulations and poor management. At present, China focuses on the reduction of waste, but does not pay enough attention to the recycling of waste, and there is no corresponding recycling method, so the management is poor, and the current management system is not conducive to the recycling of waste. ⑤ Weak awareness of resource utilization. With the improvement of living standards, people's consumption concept has changed, and the concept of resource recycling is weak and difficult.
4. Countermeasures for recycling urban garbage in China
To sum up, relying solely on a certain technology is not the fundamental way to solve the garbage problem.
As far as the current situation is concerned, because China's policy on waste incineration power generation is not perfect, it is not mature to rely on waste incineration power generation, and the surplus electricity other than the factory's own electricity is sold online. Moreover, the calorific value of garbage is low, the installed capacity of incineration power generation is small, the power generation cost is high, and the electricity price is not competitive compared with conventional power generation. From the economic point of view, garbage incineration is not the best way to recycle garbage.
It has become a consensus that garbage is a resource. Therefore, it is unscientific to simply "treat" garbage, and it must be comprehensively utilized based on the diversity of components in garbage and the recovery of resources and energy. Comprehensive utilization should include the following aspects
1) Recycling of usable materials (waste paper, metal, glass, etc. );
2) Composting in Corruptible organics;
3) Energy utilization of non-perishable organic matter with high calorific value;
4) Solidification treatment of ash, realizing the materialization of ash.
At present, some units in China have begun to try this method, but due to technical problems, the utilization efficiency of resources and energy is low, and it is impossible to solve the problem of high energy consumption in the process by using the energy of garbage itself. The system has high operating cost and low technical content, which is not conducive to industrial promotion. The development of comprehensive waste treatment system should aim at self-sufficiency of system energy. On the one hand, it can greatly reduce the production cost; On the other hand, choosing a smaller installed power generation capacity can greatly reduce the construction cost of the system, which is more suitable for the national conditions and has a broad market prospect, resulting in considerable social and economic benefits.
References:
Zang Wenchao. Present situation and management problems of municipal solid waste in China. Environmental protection, 1998, (8): 4 1 ~ 43
[2] Zhou. Present situation and countermeasures of solid waste resource utilization in Beijing. Environmental protection, 1998, (9): 44 ~ 46
[3] Wu Yongbao. On the recycling and reduction of industrial solid waste. Shanghai Environmental Science, 1993,12 (2): 9 ~11.
[4] Fang Chuanglin. Direction of sustainable development and utilization of garbage resources in China. Environment, 1996, (9): 30 ~ 3 1.
[5] Deng Xiaolong. Discussion on comprehensive treatment and resource utilization technology of municipal solid waste. Environment, 1998, (5): 38 ~ 39.