Popular Science |Knowledge Of Waste Incineration Power Generation Projects

Waste incineration power generation means that the waste is fed into the incinerator through the feed port of the incinerator, and the waste is fully burned at a temperature of 800°C ~ 1000°C, and a large amount of heat generated during the incineration process is heated to superheated steam. Then it is led to the steam turbine, and the high-temperature and high-pressure steam passes through the steam turbine to convert the heat energy into electric energy, thereby realizing the process of generating electricity. The flue gas generated during the incineration of garbage in the incinerator is purified and discharged into the atmosphere through the chimney through the purification and dust removal equipment. The slag and fly ash produced after incineration are collected and comprehensively utilized or landfilled. After incineration, the volume of garbage is reduced by 80% to 90%, and the weight is reduced by 70%. Therefore, the use of incineration to treat garbage can achieve the effect of reducing weight and volume. Waste incineration also has the advantages of small footprint, waste heat power generation, complete and effective elimination of bacteria, and waste residue can be used as building materials. Based on the above advantages, vigorously promote waste incineration power generation to benefit the country and the people.

Main features of waste incineration technology:

Waste incineration power generation is to burn domestic waste at high temperature to convert combustible waste in domestic waste into carbon dioxide and water. Domestic waste incineration power generation has the advantages of "harmless, reduced, and recycled". Specifically, it has the following five advantages:

1. Project land use province. For the same amount of waste treatment, the land area required by a waste incineration plant is only 1/20-1/15 of that of a sanitary landfill.

2. The processing speed is fast. The decomposition time of garbage in sanitary landfills usually takes 7 to 30 years, and incineration treatment can be completed in about 2 hours as long as the melting point of garbage is lower than 850 °C.

3, the reduction effect is good. The same amount of waste can be reduced by about 30% by landfilling, 60% by composting, and 90% by incineration.

4. Low pollution discharge. According to the research and measurement of the German authoritative environmental research institute, if the same strict EU pollution control standards are adopted, the pollution generated by waste incineration is only about 1/50 of the sanitary landfill.

5. High energy utilization. Each ton of waste can be incinerated to generate electricity of more than 300 kWh. About every 5 people's household waste can be incinerated to generate electricity to meet the daily electricity demand of 1 person.

Generally speaking, for large and medium-sized cities with dense population, developed economy and scarce land resources, waste incineration should be preferred.

Main processes used in domestic waste incineration

Waste-to-energy is the collection of various wastes for sorting. High-temperature incineration is performed on those with higher combustion values, and the heat energy generated in the high-temperature incineration is converted into high-temperature steam, which drives the turbine to rotate and the generator generates electricity. Fermentation, anaerobic treatment of incombustible organic matter, and finally drying and desulfurization produce methane gas, that is, biogas. After combustion, the heat energy is converted into steam, which drives the turbine to rotate, and drives the generator to generate electricity.

The main technologies of the main device of waste incineration power generation include mechanical grate incinerators, fluidized bed incinerators, rotary incinerators, CAO incinerators, and pulse-throwing incinerators. At present, the main domestic waste incineration technologies are mechanical grate furnace technology and fluidized bed technology.

The working principle of the mechanical grate incinerator: the garbage enters the inclined downward grate through the feeding hopper. Due to the staggered movement between the grate, the garbage is pushed downward, so that the garbage passes through various areas on the grate in turn until it burns out. out of the furnace. Combustion air enters from the lower part of the grate and mixes with the garbage. The high-temperature flue gas passes through the heating surface of the boiler to generate hot steam, and the flue gas is also cooled. Finally, the flue gas is treated by the flue gas treatment device and discharged.

The working principle of the fluidized bed incinerator: the furnace body is composed of a porous distribution plate, a large amount of quartz sand is added into the furnace, the quartz sand is heated to above 600 ℃, and hot air above 200 ℃ is blown into the bottom of the furnace to make the hot sand Boil up and throw in the garbage. The rubbish boils with the hot sand, and the rubbish quickly dries, catches fire, and burns. The proportion of unburned garbage is relatively light, and it continues to boil and burn. The proportion of burned garbage is relatively large and falls to the bottom of the furnace. After water cooling, the coarse slag and fine slag are sent to the outside of the plant by sorting equipment. A small amount of medium slag and Quartz sand is sent back to the furnace through the lifting equipment for further use.

How to control exhaust emissions?

The waste gas emitted by waste incineration plants mainly comes from the flue gas generated by the incineration process, and its main pollutants are dust, hydrogen chloride, sulfur dioxide, nitrogen oxides, dioxins and heavy metals.

The computer control system can realize a high degree of automation of waste incineration, thermal energy utilization, flue gas treatment and other processes, and control the set combustion conditions (temperature higher than 850 °C, flue gas residence time greater than 2 seconds, etc.) The original emission concentration is reduced to a minimum, and the complete decomposition of organic substances such as dioxins is ensured.

Install various effective flue gas treatment equipment, such as bag dust removal, activated carbon adsorption of harmful substances, etc., and use flue gas online monitor to continuously monitor the flue gas emission indicators of each incineration line to ensure that the emission of flue gas pollutants from the waste incineration plant meets the regulations standard requirement.

How to control odor emissions?

1. Compression trucks with good airtightness and automatic loading and unloading structure should be used to transport garbage to minimize the overflow of odor.

2. Air curtains should be set up at the entrance and exit of the garbage unloading hall, and the electric unloading door should be closed before and after unloading the garbage truck to prevent the odor from escaping.

3. The garbage pond should adopt a closed design, and set up an air suction port above the garbage pond to lead the odorous gas as combustion air to the incinerator for high-temperature decomposition, and make the garbage pond and the discharge hall in a negative pressure state.

4. Standby activated carbon waste gas purification facilities should be set up. During the shutdown of the whole plant for maintenance, the odor in the garbage pool must be purified by activated carbon waste gas purification facilities before it can be discharged.

5. The leachate treatment system should be designed as a closed structure, and an air duct should be installed at the top, and the generated biogas and odor will be introduced into the incinerator for high-temperature decomposition through the air duct and exhaust fan.

How to control dioxin emissions?

Dioxins that people often say are actually the abbreviations of dioxin-like substances, which refer to two types of organic compounds containing many congeners or isomers with similar structures and properties. There are a total of 210 species, of which only Very few species are considered toxic.

Dioxin is not a nuisance peculiar to waste incineration plants. It is a compound produced when organic matter is heated with chlorine, which is a relatively common chemical phenomenon. Dioxins can be found in the air, soil, water, food and garbage. Studies have shown that food is the main source of dioxins, and about 90% of the dioxins exposed to human body come from the diet.

The waste incineration plant controls the emission of dioxins, keeps the temperature in the incineration furnace above 850 degrees, and controls the flue gas to stay in the furnace for more than 2 seconds, so that the dioxins can be completely decomposed; the second is that the flue gas passes through the advanced purification treatment system, The unit dioxin concentration is controlled within 0.1 nanograms, meeting the most stringent emission standards in the world.

How to dispose of slag and fly ash?

The slag is mainly the residue after the incineration of domestic waste, the amount of which depends on the composition of the waste, and its main components are manganese oxide, silicon dioxide, calcium oxide, aluminum oxide, iron oxide, scrap metal, and a small amount of untreated Burnt organic matter, etc. The slag produced by waste incineration is treated harmlessly at high temperature, and then the waste metal such as scrap iron and steel is separated by magnetic separation.

Fly ash is a hazardous waste and must be collected separately and shall not be mixed with domestic waste, incineration residues, etc., nor with other hazardous wastes. The waste incineration fly ash shall not be stored for a long time in the factory area, shall not be easily disposed of, and shall not be transported and discharged at will. The waste incineration fly ash must first undergo necessary stabilization and solidification treatment in the factory area. After the stabilization and solidification treatment and the leaching toxicity test are passed, it can be sent to a safe landfill or a sanitary landfill using special closed transportation means. landfill. When conditions permit, other treatment and disposal methods that meet the requirements of the standard can also be used.

How to dispose of leachate?

Leachate belongs to high-concentration organic wastewater, which needs to be discharged through a special multi-channel purification process. The amount of landfill leachate is mainly affected by the composition, moisture and storage days of the incoming garbage. Leachate has the following characteristics: complex and changeable pollutant components, large changes in water quality, high organic pollutant concentration, high ammonia nitrogen concentration, high heavy metal ion and salt content.

At present, there are many processes for wastewater treatment, but due to the high concentration and complex composition of the leachate, special requirements are put forward for the treatment process. Generally speaking, the basic treatment process of landfill leachate can optimize the combination of several different treatment process units on the principle of making full use of the economic rationality of biochemical treatment. It is difficult to achieve strict effluent by only relying on a single treatment process. Require. At present, the most widely used treatment methods are: biological method + membrane technology treatment, which is "anaerobic + membrane bioreactor + nanofiltration + reverse osmosis + concentrate treatment system". The advantage of using membrane technology is that the quality of the effluent is better and can meet higher discharge requirements.

What is the development prospect and direction of waste incineration power generation project?

1. Stricter flue gas emission standards. With the full implementation of the "Standards for Pollution Control of Domestic Waste Incineration", the operation of domestic waste incineration facilities and the control of pollution emissions will be more stringent. The emission concentration limits of major pollutants in the new standard are basically equivalent to those of the European Union. The incineration plant has been built for technical transformation to meet higher emission requirements. The new incineration plant will be based on the commonly used denitrification, dry/semi-dry deacidification, activated carbon adsorption to remove dioxins and heavy metals, and bag filter to remove smoke and dust. In addition, the wet process with higher deacidification efficiency, advanced SCR low-temperature catalytic denitration and dioxin decomposition technology are adopted to greatly reduce the emission of major flue gas pollutants.

2. More significant energy efficiency. In order to greatly reduce the energy consumption of the waste incineration plant, the power generation efficiency is significantly improved. The incinerator uses flue gas recirculation technology, which saves energy and greatly reduces the production of nitrogen oxides. The low-temperature catalytic denitrification system is used to achieve simultaneous and efficient removal of nitrogen oxides and dioxins, while reducing the energy consumption of higher-temperature catalysts by 50%. above. At the same time, the intelligent combustion control system is adopted, the furnace and boiler design are optimized, the steam parameters are improved, the large-scale incineration power generation equipment is used, and the air cooling tower is used for cooling, which reduces the energy consumption of the forced ventilation cooling tower usually used in domestic incineration plants by more than 90%.

3. More effective comprehensive utilization of resources. The development trend of waste incineration is to have more advanced comprehensive utilization of resources to achieve near "zero discharge" of sewage and co-processing of solid waste. The sewage in the plant is recycled after being treated to achieve near "zero discharge" of sewage in the whole plant. Supports efficient co-processing of various solid wastes, such as co-processing of medical waste and sludge. The construction of incineration plants will give priority to the application of new energy-saving materials, environmental protection materials, and recycled materials, and the slag of the waste incineration plant will be used as building materials to realize comprehensive utilization of resources.

4. Development and application of more advanced incineration technology. In order to further reduce the pollutant emission in the waste treatment process, countries are competing to develop various cutting-edge technologies for waste treatment: waste pyrolysis and gasification technology, ash melting technology after incineration, plasma incineration technology and waste-derived fuel preparation technology. These technologies can further realize the harmlessness and reduction of waste, and are especially suitable for the disposal of waste after classification, and will also be the development direction of waste incineration in the future.

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