Fly ash is fine ash collected from the flue gas after coal combustion. Fly ash is the main solid waste discharged from coal-fired power plants.The main oxides of fly ash in thermal power plants in China are: SiO2, Al2O3, FeO, Fe2O3, CaO, TiO2, etc.With the development of the electric power industry, the fly ash emission from coal-fired power plants increases year by year, which has become one of the industrial waste residues with large displacement in China.A large amount of fly ash without treatment, will produce dust, pollution of the atmosphere;If discharged into the water system, the river will be silted up, and the toxic chemicals in it will also cause harm to human body and biology.However, fly ash can be used as a resource, such as concrete admixture.
China is a big coal producing country, which takes coal as the basic fuel for electric power production.Steady development of energy industry in China, power generation capacity annual growth rate of 7.3%, the rapid development of power industry, has brought the rapid increase of fly ash emissions, emissions from coal-fired power plant every year, the total amount of fly ash increases year by year, fly ash emissions of 125 million tons in 1995, about 150 million tons, 2000 by the year 2010 will reach 300 million tons, to our country's national economic construction and ecological environment caused great pressure., on the other hand, China is a country with a per capita possession of resources co., LTD., the comprehensive utilization of fly ash, waste, pollution for profit, has become China's economic development an important technical and economic policy, is to solve our country electric power production environmental pollution, resource of the contradiction between the lack of important means, is also faced to solve one of the tasks of electric power production.After development, fly ash has been widely used in construction, building materials, water conservancy and other departments.
Chemical composition of fly ash
The main oxides of fly ash in thermal power plants in China are: SiO2, Al2O3, FeO, Fe2O3, CaO, TiO2, MgO, K2O, Na2O, SO3, MnO2, etc., in addition to P2O5, etc.Silicon oxide and titanium oxide come from clay and shale.Iron oxide mainly comes from pyrite;Magnesium oxide and calcium oxide come from their corresponding carbonates and sulfates.
The element composition (mass fraction) of fly ash is: O47.83%, Si11.48% ~ 31.14%, Al6.40% ~ 22.91%, Fe1.90% ~ 18.51%, Ca0.30% ~ 25.10%, K0.22% ~ 3.10%, Mg0.05% ~ 1.92%, Ti0.40% ~ 1.80%, S0.03% ~ 4.75%, na0.00 % ~ 1.40%, P0.00% ~ 0.90%, Cl0.00% ~ 0.12%, other 0.50% ~ 29.12%.
Because the ash content of coal varies widely, and this change occurs not only in the coal from different coal seams around the world or in the same region, but also in different parts of the same coal mine.Therefore, the specific chemical composition of fly ash content, also due to the origin of coal, coal combustion mode and degree of different and different.Gq-3b fly ash analyzer mainly detects silicon dioxide, aluminum trioxide, iron dioxide trioxide, calcium oxide, iron oxide, titanium dioxide and other elements in fly ash.The main chemical composition of fly ash is shown in the table below.
In the 1970s, the world energy crisis, environmental pollution and exhaustion of mineral resources strongly stimulated the research and development of fly ash utilization. International fly ash conferences were held for many times, and the research work was getting deeper and deeper, and great progress was made in the application.Fly ash has become an attractive raw material of new building materials and chemical products in the international market, which is rich in resources, low in price and beneficial to the environment.Most of the researches on fly ash have turned from theoretical research to applied research, especially the important research and exploitation of resources.The product that USES fly ash to produce is increasing ceaselessly, technology is updating ceaselessly.Compared with the past, great changes have taken place in the comprehensive utilization of fly ash at home and abroad. The main changes are as follows: the guiding ideology of fly ash treatment has been transformed from the simple environmental perspective to comprehensive treatment and resource utilization.The comprehensive utilization way of fly ash is developed from the application of roadbed, filling, soil transformation and other aspects in the past to the advanced utilization way of cement raw materials, cement mixture, large scale water conservancy project, bulk concrete products, advanced filler and so on.
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