The world produces 490 million tons of garbage every year, and China alone produces nearly 150 million tons of municipal waste every year. The cumulative stock of domestic waste in China's cities has reached 7 billion tons. According to the forecast of the State Environmental Protection Administration, my country's annual urban waste output will be 152 million tons in 2010 and will reach 210 million tons in 2015 and 2020.
my country's urban waste incineration power generation was first put into operation in 1987. After that, with the launch of a large number of environmental protection industrialization and environmental protection high-tech industrialization projects, waste incineration power generation technology has developed rapidly, realizing the localization of large-scale waste incineration power generation technology, and the waste incineration processing capacity has increased in the past five years. It has increased by 5 times. For details, please see the "Analysis Report on Market Prospects and Investment Strategic Planning of China's Waste-to-Energy Power Industry".
The principles of garbage disposal are harmlessness, reduction and resource utilization. Waste incineration power generation can save a lot of land resources by greatly reducing landfills. It also reduces the air pollution of groundwater and the surrounding environment of the landfill.
According to my country's current policies, urban domestic waste incineration power generation technology will be dominated by mechanical grate furnaces, supplemented by coal-waste mixed combustion fluidized bed waste incineration technology and other technologies. Based on the calculation of a two-stage reciprocating waste incineration equipment with a daily processing capacity of 1,800 tons, the annual power generation can reach 160 million kilowatt hours, which can save 48,000 tons of standard coal, and reduce annual nitrogen oxide emissions by 480 tons and sulfur dioxide emissions by 768 tons.
“Coalbed methane, domestic waste landfill gas, nitrogen oxides, etc. are important sources of global warming.” Han Yeju, President of China and Asia Pacific of the British Syndic Carbon Fund, believes that waste power generation is mainly affected by some The constraints of technical or process issues, such as the highly toxic waste gas generated by combustion during power generation, have not been effectively solved for a long time, so the key to effective emission reduction is the use of advanced technology.
In developed countries, waste treatment and resource utilization have become mature industries, and waste incineration power generation technology is developing towards large-scale and high-efficiency. For example, European countries have formulated strict waste incineration standards and strictly implemented them; the United Kingdom has stipulated in its non-fossil fuel convention and Germany in its new energy law that the power generated by direct waste incineration is mandatory to be connected to the Internet, and electricity price subsidies or green electricity prices are implemented. .
It is understood that my country’s annual urban domestic waste production is about 150 million tons, of which landfill accounts for 70%, incineration and composting account for 10%, and the remaining 20% ??is difficult to recycle. Among them, the waste-to-energy rate is less than 10%, which is equivalent to wasting 2,800 megawatts of electricity every year. The value of discarded "renewable waste" is as high as 25 billion yuan.
According to the "National Urban Environmental Sanitation "Eleventh Five-Year Plan"", the national urban domestic waste removal volume will reach 180 million tons in 2010, and harmless waste treatment will reach more than 60%. Experts pointed out that if by 2010, the amount of waste incineration accounts for 10% of the total waste production, and the incineration heat is used for power generation and heating, then by 2010, new waste incineration equipment with a daily processing capacity of 32,000 tons will be needed.
With the continuous development of technologies in various aspects such as garbage recycling, processing, transportation, and comprehensive utilization, waste-to-energy generation is likely to become one of the most economical power generation technologies. From the perspective of long-term benefits and comprehensive indicators, it will be optimal. for traditional electricity production. After the resource-based waste is incinerated, the heat is used to generate electricity to achieve comprehensive utilization of waste. According to relevant statistics, my country's current urban garbage removal volume has reached 1 trillion t/a, which is equivalent to 14 million tons of standard coal if the average low calorific value is 2900kJ/kg. If 1/4 of it is used for incineration power generation, the annual power generation can reach 6 billion kilowatt-hours, which is equivalent to the power generation of an installed 1,200MW thermal power unit. Harmless waste incineration power generation can achieve harmless waste, because waste is incinerated at high temperatures (around 1000°C), which can be sterile and decompose harmful substances, and the exhaust gas is discharged after being purified and treated to meet standards, making it more completely harmless.
The residue after reduction of waste incineration is only 10% to 30% of the original volume, thus extending the service life of the landfill and easing the shortage of land resources.
Therefore, the construction of waste power plants is very conducive to urban environmental protection, especially the protection of land resources and water resources, and the realization of sustainable development. Is waste-to-energy really so magical? The key to the problem is that the above algorithm uses the calorific value of foreign waste and foreign waste-to-energy plants that do not exist in China to calculate the benefits of Chinese waste-to-energy plants. For example, foreign garbage has a high calorific value, with each kilogram of garbage burning can produce 3,000 kcal of heat, while Chinese garbage has a water content of as high as 60%. After certain treatment, the calorific value generated by combustion per kilogram can only reach 900-1000 kcal. That is to say, the calorific value of processed garbage is less than 1/3 of that in foreign countries. However, when calculating the coal saving amount of garbage, foreign garbage is used Calculated based on the caloric content, the so-called 2 tons of garbage are equivalent to 1 ton of coal. China's major cities produce 100 to 150 million tons of garbage annually, so 50 to 60 million tons of coal can be saved. In fact, it takes 6 tons of garbage in China to support 1 ton of coal. Even if there are 100 million tons of garbage, if all of it is used to generate electricity, it can only support 16 to 17 million tons of coal. Since Chinese garbage contains 60% water, a reduction of about 70% can be achieved. But this reduction can be achieved even without burning.
The environmental benefits of waste incineration power plants are still uncertain. Whether the SO2, CO and dioxins produced by waste combustion can be removed and whether they can meet national environmental protection standards is still a question. If dioxin cannot be effectively removed, the harm to the environment cannot be underestimated.
The economics of a waste incineration power plant is closely related to the calorific value of the waste. Foreign countries generally stipulate that the calorific value of garbage does not reach 1,500 kilocalories per kilogram, and it is not suitable to build waste incineration power plants. So why can China use garbage that can only reach 900 to 1,000 kilocalories after certain treatment for power generation? Due to the small amount of combustible materials in garbage, garbage power plants have to use fuel and coal to support combustion, causing garbage incineration power plants to become small fuel and coal-fired power plants in disguise. Various preferential conditions granted by the state to waste-to-energy plants and high electricity prices have helped small oil-fired power plants and small coal-fired power plants that should be shut down.
Why does foreign garbage have a high calorific value but Chinese garbage has a low calorific value? This is because China has the virtue of frugality and a good waste recycling system. Newspapers, books, notebooks, cartons, furniture, etc. are all recycled at recycling stations. Even if a small amount of combustible materials are thrown into the trash can, there is still a lot of waste. Scavengers pick up, and even after the trash reaches the landfill, there are still people there picking it up. Therefore, many municipal wastes in China contain very few combustible materials and are mostly kitchen waste, which is not suitable for incineration for power generation. In order to prevent the construction of power plants in places that do not have waste incineration power generation, firstly, government departments must strictly control the construction of waste incineration power plants. Only places with the capacity to build waste incineration power plants will approve the construction of plants and provide various preferential policies; secondly, for the power generation purchased from waste power plants on-grid The amount must be calculated based on the amount of garbage entering the factory and the calorific value of the garbage. If the amount of electricity generated by the garbage exceeds it, it will not be purchased, and the electricity price will not be discounted.