International therapy
Garbage disposal methods (using garbage (biomass) to produce charcoal, tar and gas) Municipal solid waste disposal methods widely used at home and abroad mainly include sanitary landfill, high-temperature composting and incineration. The proportion of these three main garbage disposal methods depends on the geographical environment; The composition of garbage and the level of economic development are different.
Due to the complex composition of municipal solid waste and the influence of economic development level, energy structure, natural conditions and traditional habits, the treatment of municipal solid waste abroad is generally different from that in China. Often different regions of a country adopt different treatment methods, and it is difficult to have a unified model, but in the end they all aim at harmlessness, resource utilization and reduction.
From the perspective of application technology, foreign countries mainly adopt landfill, incineration, composting and comprehensive utilization, which has a high degree of mechanization and forms a system and complete sets of equipment. Judging from the situation of various treatment methods abroad, there are the following trends:
(1) Due to the increasing shortage of energy and land resources in industrialized countries, the proportion of incineration treatment is gradually increasing; ⑵ Landfill method has always occupied a large proportion as the final treatment means of garbage; (3) Most agricultural developing countries mainly use compost; (4) Other new technologies, such as pyrolysis, sea reclamation, mountain piling and landscaping, are also making constant progress.
Incineration is a widely used municipal waste treatment technology in the world. Large-scale garbage incineration treatment system equipped with heat energy recovery device is gradually becoming the mainstream of incineration treatment because it meets the requirements of energy recovery.
Foreign industrialized countries, especially Japan and Western Europe, are generally committed to promoting the application of waste incineration technology. The extensive application of incineration technology abroad not only benefits from developed economy, large investment and high calorific value of garbage, but also lies in the maturity and advanced incineration technology and equipment.
Many famous companies in the world have invested in the development of incineration technology and equipment, and the main equipment and auxiliary equipment are matched. Foreign industrialized countries are mainly committed to improving the original incineration devices and developing new incinerators, making them develop in the direction of high efficiency, energy saving, low cost and low pollution, and the degree of automation is getting higher and higher.
China's urban garbage treatment started late. By the end of 1992, the national garbage and excrement removal capacity reached112,640,000 t, while the harmless garbage and excrement treatment plants only had 37 1 seat, with a total treatment capacity of 71501t/d. In recent years,
Hangzhou, Changzhou, Tianjin, Mianyang, Beijing, Wuhan and other cities have designed mechanical composting production lines with China characteristics on the basis of learning the technical experience of foreign cities. The success of building waste incineration plants in Shenzhen, Leshan and other cities also provides experience for the application of incineration technology in various cities;
Shenyang, Anshan and other cities have implemented unified management and centralized incineration of hospital waste, and also embarked on a new way of special waste treatment.
China processing method
The technical countermeasures of municipal solid waste treatment in China are sanitary landfill and high-temperature composting, which will promote the development of incineration technology in cities with conditions, especially in coastal economically developed areas.
In recent years, cities have begun to carry out basic and applied research on waste incineration, developed small rotary waste incinerators including NF series reverse combustion, RF series pyrolysis and HL series, and built a number of simple incineration plants (stations) in small and medium-sized cities.
1985, Shenzhen imported complete sets of incineration technology and equipment from Mitsubishi Corporation of Japan, and built the first large-scale (300t/d) modern waste incineration power generation comprehensive treatment plant in China, which laid the foundation for the localization of municipal waste incineration devices in China.
Discussion on the treatment methods of urban garbage
An objective analysis of the changes in the composition of municipal solid waste in China in recent years shows that with the development of China's economy and the improvement of people's living standards, the contents and calorific value of combustible materials in municipal solid waste have increased significantly. Generally, after pretreatment such as classification and sorting, the calorific value of municipal solid waste is close to that of municipal solid waste in developed countries.
Therefore, some cities in China, especially the economically developed coastal areas, have the foundation to develop incineration technology.
Relevant state departments and some experts and scholars have drawn up plans to implement garbage incineration in the center of China. A stone stirred up a thousand waves, which set off a debate about "incineration" and "anti-incineration" of municipal waste and caused a great sensation among the people.
The government's plan to establish municipal waste incineration treatment plants in major cities has met with fierce opposition from ordinary people, and the disadvantages of establishing waste incineration areas in the center and periphery of cities outweigh the advantages.
Regarding municipal waste, most countries adopt the methods of incineration and burial. However, the problem is not that simple. The problem of human waste disposal, which the world environmental protection organization is most concerned about, is a very difficult thing. The best way to treat human excreta is not the simplest way to burn and bury it before.
Nowadays, human beings have to rethink how to deal with the garbage they produce. Burying and burning are not the best solutions.
Urban landfill will cause serious geological water and soil pollution. Because human domestic garbage contains many toxic and harmful substances, germs, viruses and various heavy metal elements, it is very easy to endanger the normal survival and reproduction of human beings and organisms.
Radiation treatment is a harmless treatment method that uses gamma rays and electron beams to irradiate municipal solid waste to achieve sterilization and disinfection.
Sludge and other wastes discharged from sewage treatment plants contain a large number of germs, such as germs, viruses, parasitic eggs and so on. These bacteria are so energetic that it is difficult to kill them completely by common sterilization methods such as heating or adding lime. These solid wastes are applied to farmland as fertilizers, and some bacteria can survive in the soil for months, causing soil and water pollution and threatening human and animal health.
In the early 1970s, based on the application of radioactive technology in agriculture, a new technology of "waste radiation treatment" was formed. The European Association for Agricultural Nuclear Technology (ESNA) established the "Waste Radiation Treatment Group". 1977 the second international conference on waste radiation was held in Sweden.
Compared with chemical, biological and fermentation methods, waste radiation treatment method has many advantages. Its equipment is simple and easy to operate. Waste can be sent to radiation treatment equipment through pumps or other conveying tools, and the purpose of sterilization can be achieved after radiation irradiation. But also has strong radiation penetration and thorough sterilization.
After the sludge is irradiated, the particles will change from small to large, which makes the sludge have good dehydration and sedimentation performance.
Both the United States and Germany have such treatment plants. Kashima sludge radiation treatment plant in Boston, USA, with a daily treatment capacity of 375m? . Its equipment is shown in the figure. The sludge transfer drum is made of stainless steel with a length of 132 cm and a diameter of 45 cm. The minimum radiation dose is 400,000 rads, and the electron beam energy is 850 kiloelectron volts.
The German sludge radiation treatment plant in Wandell has an hourly treatment capacity of 6m? The workshop covers an area of 400㎡ and is 9 meters high. The minimum radiation dose used is also 400,000 rads.
Practical experience has proved that the higher the electron beam energy of sludge radiation treatment equipment, the greater the thickness of sludge layer passing through the electron beam radiation area. When the thickness of sludge layer is 1.5 ~ 5 mm, the electron beam energy is 750 kV ~1.5 MeV; The width of sludge layer should be 1.2m, and the velocity should be 2m/s. ..
The cost of sludge treatment by radiation method is not high. A treatment plant with a plant area of 1.50㎡ in the Federal Republic of Germany can treat the sludge discharged from municipal sewage treatment plants with a population of 200,000 to 1 10,000, and its treatment cost is 2.70 Deutsche Mark per ton of sludge.
Due to the different types and quantities of pathogens contained in the waste, the effective radiation dose is also different, and the general safe dose is below 6.5438+0 million rad. Commonly used radiation sources are 60 cobalt, 137 cesium, 90 strontium and 85 krypton. It is an economical and feasible method to use waste radioisotopes.
During radiotherapy, as long as the radioactive source is sealed, such as placed in concrete or other containers with a wall thickness of 1.5m, and the radiation dose does not exceed the above-mentioned safe value, there will be no radioactive pollution, and there will be no post-treatment problem to eliminate radioactive absorption.
In addition, rural garbage disposal is also an urgent problem to be solved.
General treatment method
The general methods of garbage disposal can be summarized as material utilization, energy utilization and landfill disposal.
Material utilization, also known as material recycling, refers to physical transformation, chemical transformation (including chemical modification and thermal transformation such as pyrolysis and gasification) and biological transformation (including microbial transformation, insect transformation and animal transformation). ).
Realize the reuse, recycling and recycling of the material properties of garbage, including the recycling of traditional material resources and the transformation of perishable organic garbage into high-quality material resources.
Energy utilization, also known as energy recovery, refers to converting the internal energy of garbage into heat energy and electric energy, including incineration power generation, heating and cogeneration.
Landfill treatment refers to landfill treatment of useless garbage that cannot be recycled (including material utilization and energy utilization).
From the whole life cycle of garbage, garbage disposal should also include source reduction and emission control. Strictly speaking, reduction refers to source reduction. By changing product design habits, changing raw material purchasing habits, changing consumers' purchasing and consumption habits, and changing business models, we can reduce resource waste and waste generation in the process of production and life.
Generally speaking, garbage disposal should adhere to the concept of classification and step-by-step utilization of source emission reduction, material utilization, energy utilization and landfill disposal, develop all aspects of garbage disposal in a balanced way, and give full play to the role of various garbage disposal methods, especially to strengthen the material utilization of classified garbage, reduce the amount of garbage generated and reduce the amount of garbage discharged after each level of treatment.
Extended data:
development prospect
From 65438 to 0986, the modern urban garbage disposal industry in China began to develop gradually. Since 2000, the capacity of municipal solid waste treatment has been significantly improved, especially the advanced waste treatment technology has been gradually applied.
During the period of 1- 1 1 in 2007, the total industrial output value of waste resources and waste materials recycling and processing industries in China was 6 1, 149,109,000 yuan, a year-on-year increase of 58.75%. Accumulated product sales revenue was 59,540,739,000 yuan, a year-on-year increase of 53.58%; Accumulated profits were 1, 6 14,130,000 yuan, up 5 1. 17% year-on-year.
From June to August, 2008, the national waste resources and waste materials recycling and processing industry achieved a total industrial output value of 64,530.292 million yuan, a year-on-year increase of 57.42%; Accumulated product sales income was 62,446 yuan, 1 1000 yuan, up 54.54% year-on-year; The accumulated profit was 265,438+000,576 yuan, up by 865,438+0.14% year-on-year.
With the increasing attention to environmental problems, energy conservation and environmental protection have become the development theme of various countries, and have begun to provide opportunities for the industrial development of garbage disposal. The average annual growth rate of garbage in the world is 8.42%, while that in China exceeds 10%.
The world produces 490 million tons of garbage every year, and China alone produces nearly 65.438+500 million tons of urban garbage every year. The accumulated storage of municipal solid waste in China has reached 7 billion tons. Under such a huge pressure of garbage, there is reason to believe that the garbage disposal industry will become a star industry in China in the future.
Renewable resources have become a new starting point of resource circulation and an important part of circular economy. In addition, in the process of recycling waste resources and materials, it not only solves the problem of resource shortage, but also reduces the discharge of waste, which can be described as "killing two birds with one stone".
China has continuously introduced policies to support the development of the garbage disposal industry, and local government leaders have begun to attach great importance to the construction of garbage landfills and increase investment. It can be predicted that the prospects of the garbage disposal industry are very broad. [3]?
The treatment rate of domestic garbage in the county is low, and the harmless treatment rate of 20 10 is estimated to be only 25%.
China's garbage disposal industry started late, but through these years' development, China's garbage disposal industry has begun to take shape, the market capacity of garbage disposal has increased substantially, the market penetration rate has increased rapidly, and the number of enterprises entering the sanitation industry has also increased rapidly. The garbage disposal market in China has entered the growth period from the introduction period and is maturing.
In 20 15 years, the national urban domestic waste removal capacity was1920,000 tons, and the harmless treatment capacity of urban domestic waste was1800,000 tons. Among them, the sanitary landfill capacity is1.1.500 million tons, accounting for 63.9%; The amount of incineration was 665.438 million tons, accounting for 33.9%;
Other treatment methods accounted for 2.2%. The harmless treatment rate reached 93.7%, which was 1.9 percentage points higher than that of 20 14. The harmless treatment capacity of domestic waste incineration facilities in China is 210.6 million tons/day, accounting for 32.3% of the total treatment capacity.
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