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Characteristics and Analysis of Municipal Solid Waste Fluidized Bed Incineration Technology at Home and Abroad

来源: 作者: 岑宇虹,李晓东 阅读:30521 网友评论0 Updated: 2008-05-05 09:02 Source: Author: Cen Yuhong, Li Xiaodong reading: 30521 2010 0 comments

Abstract : Environmental pollution caused by urban garbage and its proper treatment is one of the urgent problems facing China. The fluidized bed incineration technology is considered to be a municipal waste incineration method with superior comprehensive performance, and is especially suitable for the national conditions of low heat value of waste in China. In the past 20 years, fluidized bed incineration (FBI) technology has gradually been applied in some developed countries and regions such as Japan, North America, and Europe (especially in Scandinavian countries). As of 1995, 16 thousand fluidized bed incinerators have been completed and put into operation all over the world, of which 151 are in Japan. The scale of operation is continuously expanding, and the capacity of single incinerator waste treatment has increased to 25 t / h. The main forms of fluidized bed are bubbling fluidized bed (BFB), circulating fluidized bed (CFB) and inner circulating fluidized bed (ICFB).

Keywords : United States, Europe, Japan, domestic, municipal waste, fluidized bed, incineration technology

Environmental pollution caused by urban garbage and its proper treatment is one of the urgent problems facing our country. The fluidized bed incineration technology is considered to be a municipal waste incineration method with superior comprehensive performance, and is especially suitable for the national conditions of low heat value of waste in China. In the past 20 years, fluidized bed incineration (FBI) technology has gradually been applied in some developed countries and regions such as Japan, North America, and Europe (especially in Scandinavian countries). As of 1995, 16 thousand fluidized bed incinerators have been completed and put into operation all over the world, of which 151 are in Japan. The scale of operation is continuously expanding, and the capacity of single incinerator waste treatment has increased to 25 t / h. The main forms of fluidized bed are bubbling fluidized bed (BFB), circulating fluidized bed (CFB) and inner circulating fluidized bed (ICFB).

At present, bubbling fluidized bed incineration technology is generally used in Japan, and the single unit incineration capacity is generally less than 4t / h, while the United States tends to build large circulating fluidized bed incinerators with a single unit processing capacity of 10-25t / h. In the 1960s, research and development and application of coal-fired fluidized bed technology were carried out in China. Since the 1980s, some scientific research units have successively carried out research on fluidized bed waste incineration technology. The technology of Zhejiang University was successfully applied to the 150t / d municipal solid waste incineration in 1998, and the technology of the Institute of Engineering Thermophysics of the Chinese Academy of Sciences was applied to a 100t / d stale garbage incinerator. Comprehensive analysis of the development and application of domestic fluidized bed technologies shows that these technologies are still based on small and medium capacity and have not yet been promoted and need to be further improved. Due to the development prospects of fluidized bed technology, some researchers have begun to carry out large-scale, industrialized work. For example, Zhejiang University has begun the development of a fluidized bed incinerator with a daily processing capacity of 300t. At the same time, the relevant state departments have paid considerable attention to fluidized bed technologies and provided some funding to encourage the development of these technologies.

introduction

Environmental pollution caused by urban garbage and its proper treatment is one of the urgent problems facing our country. From the perspective of sustainable development strategy, the goal of garbage treatment should be to achieve harmlessness, resource utilization and reduction, especially urban domestic garbage has been considered as a resource that can provide energy. At present, there is a relatively common view that incineration is the fastest and most effective technical method to reduce waste. The fluidized bed has the advantages of high combustion efficiency, wide load adjustment range, low pollutant emissions, high combustion intensity in the furnace, and suitable for burning low-calorific fuel, so it is considered to be an incineration method with excellent comprehensive performance, especially suitable for China's garbage. National conditions of low calorific value.

In the past 20 years, fluidized bed incineration (FBI) technology has gradually been applied in some developed countries and regions such as Japan, North America, and Europe (especially in Scandinavian countries). As of 1995, 164 fluidized bed incinerators worldwide have been completed and put into operation, of which 151 are in Japan. The scale of operation is continuously expanding, and the capacity of single incinerator waste treatment has increased to 25t / h. The main forms of fluidized bed are bubbling fluidized bed (BFB), circulating fluidized bed (CFB) and inner circulating fluidized bed (ICFB). The main difference between a bubbling fluidized bed and a circulating fluidized bed incinerator is that the bubbling fluidized bed tends to be small-scale, while the circulating fluidized bed tends to large-scale co-firing of waste and coal. In the treatment of municipal solid waste, these technologies use complex pre-treatment systems to pre-treat the waste and then incinerate [such as made into waste-derived fuel (RDF)], or directly use primary waste. At present, bubbling fluidized bed incineration technology is generally used in Japan, and the single unit incineration capacity is generally less than 4t / h, while the United States tends to build large circulating fluidized bed incinerators with a single unit processing capacity between 10-25t / h.

In the 1960s, the development and application of coal-fired fluidized bed technology was carried out in China. Since the 1980s, some scientific research units such as Zhejiang University, Institute of Engineering Thermophysics, Chinese Academy of Sciences, and Institute of Mechanics, Chinese Academy of Sciences have conducted fluidized bed waste incineration technology. Research. The technology of Zhejiang University was successfully applied to a 150t / d municipal solid waste incinerator in 1998, and the technology of the Institute of Engineering Thermophysics of the Chinese Academy of Sciences was applied to a 100t / d stale garbage incinerator.

1 Overview and analysis of fluidized bed incineration technology in developed countries

1.1 U.S. fluidized bed incineration technology and its application

Landfills in the United States are mainly landfills, but about 25% of the waste is currently processed through incineration. In the early stage of the application of fluidized bed technology, some advanced European bubbling fluidized bed incineration technologies were mainly introduced, such as the Fayetteville waste recycling power plant located in North Carolina. The bubbling fluidized bed incinerator was developed by British KraernerEnviroPowerAB. The company's incinerator has a thermal power of 60MWt and 100% incineration of municipal solid waste (MSW), generating 18MWe for heating and power generation. The application features of this technology are mainly reflected in the use of temperature to control NOx emissions, the use of limestone in the furnace to control SO 2 , spraying ca (OH) 2 in the flue to remove HCl, the tail uses an activated carbon adsorption device to control heavy metals and Emissions of trace amounts of toxic organic pollutants [such as dioxins and polycyclic aromatic hydrocarbons (PAHs)]. With the development of fluidized bed incineration technology, by 1995, there were three bubbling fluidized bed incineration facilities in the United States that co-fired RDF and other fuels.

Compared with bubbling fluidized bed technology, circulating fluidized bed technology has the advantages of high efficiency and low pollution. Some large companies in the United States, such as FW (FosterWheelerPowerCorporation) and B & W (Babcock & WilcoxPowerCorporation), have gradually developed circulating fluidized bed incineration technology. FW applied CFB incineration technology to build a comprehensive waste incineration plant in Robbins Village, Illinois. The plant was completed and put into operation in January 1997 with a processing capacity of 1000 tMSW / d. This is the first time that the CFB technology has been used in the United States. RDF. The plant has two RDF production lines, two RDF circulating fluidized bed combustion systems, two modern air pollution control systems and a steam turbine. The power generation is 55MW and the annual processing capacity is 500,000 tons. The parameters of a single CFB incinerator are as follows: the processing capacity is 600tRDF / d, the steam flow rate is 28.86kg / s, the superheated steam temperature is 443 C, and the pressure is 6.2MPa. The incinerator is characterized by the use of a water-cooled cloth air plate with a guide nozzle and a bed material cooler to return the bed material to the furnace. Combustion efficiency> 99%, boiler efficiency> 81%. The bed temperature was controlled at 829-913 C. SO 2 and HCl were removed by dry tail.

1.2 European fluidized bed incineration technology and its application

In Europe, the representative of fluidized bed technology is the successful incineration technology developed by the British company KraernerEnviroPowerAB. The company's first bubbling fluidized bed MSW incinerator was completed in Sweden in 1979 and the first circulating fluidized bed MSW incinerator was completed in 1984. As of 1995, the company had launched 13 fluidized bed MSW incinerators.

KraernerEnviroPowerAB launches first and third generation bubbling fluidized bed incinerators. The third generation incinerator uses a pulsating air feed injection port to ensure uniform fuel distribution in the bed. The reasonable geometry of the guide hood and the bottom of the furnace makes it extremely convenient to discharge ash and noncombustible materials. The ash and air sorting mechanism makes the bed material return to the furnace and returns the ash and slag to the furnace. A symmetrical secondary air system is arranged on the double arch structure of the furnace chamber to ensure that the air in the suspension section is balanced and stable, and the degree of turbulence is large, which is conducive to complete combustion. At the same time, three winds are set in the furnace combustion area and the top of the furnace, so that the top airflow has a plug-like flow pattern. As for the exhaust gas treatment system, the oxidizing atmosphere and uniform flue gas components maintained in the bottom area of the furnace can not only make the combustion more complete, but also prevent the water-cooled wall from being corroded.

In order to further increase the flow turbulence in the bed and reduce NOx emissions, the third-generation incinerator uses recirculation of flue gas into the bed and double arch structure. A radiation cooling flue is set at the end of the furnace, and a radiation cooling flue is set before the flue gas enters the convection heating surface at the tail, which can avoid superheater corrosion, local high temperature and scaling, and ensure that the flue gas is in a certain oxidizing atmosphere. Points are even.

1.3 Japanese fluidized bed incineration technology and its application

Japan is a world leader in waste fluidized bed incineration technology, and more than half of its waste is treated with fluidized bed incineration. In 1991, there were 113 municipal waste fluidized bed incinerators in Japan, and by 1995 it had increased to 131. There are many manufacturers of garbage fluidized bed incinerators in Japan, the main ones of which are: Ishikawa Shimano, Mitsui Shipbuilding, Kurimoto, Ebara Manufacturing, Japan Steel, Kobe Steel, etc.

2 Domestic fluidized bed incineration technology and its characteristics

The development and application of domestic fluidized bed combustion technology began as early as the 1960s, but mainly concentrated in the coal-fired field. Research on the incineration of fluidized-bed refuse was officially started in the 1980s. Due to the complex composition, high moisture content and low calorific value of domestic solid waste in China (the domestic calorific value of native urban solid waste is currently around 1000kcal / kg, compared with 2000-3000kca1 / kg in developed countries), the mobile waste is mixed and incinerated. The characteristics and secondary pollution characteristics are quite complicated, and some mature fluidized bed technologies abroad are not very suitable for treating urban garbage in China. Therefore, it is necessary to develop and apply a waste incineration fluidized bed technology suitable for China's national conditions, but the above characteristics of China's municipal waste have brought considerable difficulty to the development and application of the technology.

Zhejiang University has been devoted to the development of municipal solid waste incineration technology suitable for the national conditions since the 1980s, and through the comprehensive integration of related technologies such as waste pretreatment, flue gas treatment, slag separation and recovery, ignition under the bed, automatic control of incinerator thermal engineering, etc. , Formed a new system of municipal solid waste internal circulating fluidized bed incineration technology. The characteristics of this technology are mainly reflected in: ① Stable combustion of a fluid bed of different gravity. For incineration of garbage, the heterogeneous fluidized bed developed by the Institute of Thermal Engineering of Zhejiang University uses a fluidized bed system composed of different particles (in quartz sand and garbage) with large differences in gravity, which can prevent large pieces of garbage in the bed. Sedimentation and deflection of light-grained garbage components to ensure stable combustion. ② On the fluidized air distribution structure, the inclined air distribution combined with the fixed wind hood is used to form the internal circulation of the material bed. The special design of the air distribution device and combustion equipment can ensure that the easily crushed primary garbage is fully incinerated in the furnace. ③ In order to achieve the purpose of efficient and clean incineration, a segmented combustion method and a secondary air tangential arrangement method are adopted to fully mix the combustion air in the furnace, improve the combustion status, reduce the CO emission concentration and control the NOx emission; and adopt international The above-mentioned dioxin suppression method is used to effectively inhibit the generation of dioxins, that is, the temperature in the furnace is kept uniformly in the range of 850-950 C; the residence time of the flue gas in the high temperature section is greater than 3s; the combustion chamber is fully mixed; and the heating surface is strengthened Blow. In order to control the emission of SO 2 , HCl, HF, Cl 2 and heavy metals in the tail gas, a wet flue gas scrubbing device developed by Zhejiang University was used to scrub the tail gas.

In 1997, Zhejiang University applied this new fluidized bed incineration technology to transform a 35t / h chain furnace of Hangzhou Jinjiang Group Yuhang Thermal Power Plant into a municipal waste fluidized bed incinerator. The urban domestic waste in some areas of Hangzhou will be burned. After the transformation, each incinerator will treat 150t of waste per day. The renovation project was completed in mid-August 1998, and it has been running for more than one year. The average incineration of garbage is 6.98t per hour, which meets and exceeds the design requirements (150t per day is designed to be treated, that is, 6.25t per hour incineration), the largest garbage The amount of incineration can exceed 11t / h (corresponding to more than 250t of incinerated waste per day). The cost of processing waste per ton is about 25 yuan.

According to Fang Jianhua and others from the Institute of Engineering Thermophysics of the Chinese Academy of Sciences, the 100t / d circulating fluidized bed waste incinerator incineration system developed by the Institute of Engineering Thermophysics of the Chinese Academy of Sciences has a main technical indicator of 80-100t / d of municipal solid waste per day. . When the incineration heat value is greater than 4000kJ / kg and the moisture content is less than 50% of the garbage, no auxiliary fuel is required for operation, and the dust and harmful gases comply with national environmental protection regulations.

This technical feature is reflected in the simple sorting of extra large non-combustible materials (such as concrete blocks) before the garbage enters the furnace, and the rest of the garbage can be burned in the furnace. According to the author, the current incinerator does not have continuous long-term operating conditions. The furnace was put into trial operation in June 1997.

Sheng Hongzhi et al., Institute of Mechanics, Chinese Academy of Sciences, conducted cold and hot state experiments on the diffusion and segregation characteristics and heat transfer characteristics of heterogeneous fuels, and developed a high-moisture, low-calorific-value fuel with internal swirling fluidized bed combustion technology. The results of the study were designed for a 10t / d thermal test furnace. Its characteristics are reflected in the use of oblique air distribution to achieve internal swirling fluidization to achieve the purpose of improving incineration efficiency and reducing pollution. But the technology has not yet been commercialized.

Comprehensive analysis of the development and application of domestic fluidized bed technologies shows that these technologies are still based on small and medium capacity and have not yet been promoted (some technologies have not yet entered the application stage) and need to be further improved. Due to the development prospects of fluidized bed technology, some researchers have begun to carry out large-scale, industrialized work. For example, Zhejiang University has begun the development of a fluidized bed incinerator with a daily processing capacity of 300t. At the same time, the relevant state departments have paid considerable attention to fluidized bed technologies and provided some funding to encourage the development of these technologies.

3 conclusion

Looking at the development and application of fluidized bed waste incineration technology at home and abroad, foreign fluidized bed incineration technology has achieved commercialization and large scale, and has good development prospects. The treatment of municipal waste incineration in China is just beginning, but some researchers have developed fluidized bed incineration technology suitable for China's national conditions and successfully applied to the treatment of municipal solid waste.

However, for domestic R & D applications, much work remains to be done:

① Considering the current complex composition of domestic municipal waste and the low heating value, domestic development of new technologies for waste treatment and utilization should be targeted to national conditions, and do not blindly introduce technologies and equipment that are expensive at initial investment and operating costs and are not suitable for national conditions. In addition, since most of China's current technology development capabilities are concentrated in universities and research institutes, in order to transform technology into productivity as soon as possible, the combination of industry, university and research should be a good bridge.

② The treatment and utilization of urban garbage has a long-term impact and is related to the whole people. Therefore, the state should pay full attention to it when formulating policies. The current waste treatment and utilization in China is still a product of the planned economy era and belongs to public utilities. At present, enterprises can be explored to participate in and undertake waste treatment and utilization, and the state will provide policy support in terms of taxation, credit, and financial subsidy policies.

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