Discussion on Comprehensive Utilization Technology of Coal Gangue

introduction

Coal gangue coal mining, washing and processing the solid waste generated in the process. According to incomplete statistics, there are currently about 4.5 billion tons of coal gangue stacked in the country over the years. There are more than 1,600 large-scale meteorites, occupying about 15,000 hectares of land, and the annual increase is 1.5-200 million tons. . The stacking of coal gangue not only occupies a large amount of land, but also spontaneous combustion or even explosion accidents under certain conditions, causing casualties and damage to the coal mine drainage system, affecting safe production. At the same time, harmful gases such as sulfur dioxide, nitrogen oxides, carbon oxides and soot emitted from coal gangue spontaneous combustion pollute the surrounding atmosphere and seriously affect the health of residents in the mining area.

I. Comprehensive utilization status of coal gangue in China

China has been using coal gangue for decades, but so far, the comprehensive utilization level of coal gangue in China is not high. The main performance is in the backwardness of technical equipment, small scale of enterprises, insufficient development stamina and weak competitiveness. At present, the proportion of China's coal gangue comprehensive utilization technology and equipment level reaching the international advanced level in the 1990s is still not high, and some coal gangue comprehensive utilization technologies with high technical content have not been widely used. According to reports, the overall utilization rate of coal gangue in the United States, Britain and Germany has reached more than 90%, while the country with coal as the main energy source has less than 50% utilization rate of coal gangue, which leads to At present, the accumulation of coal gangue in China is increasing at a rate of 1.5 to 200 million tons per year, and the damage of meteorites is becoming more and more serious.

Therefore, efforts should be made to comprehensively utilize coal gangue, strengthen the development and application of coal gangue comprehensive utilization technology, and finally realize the transformation of coal gangue into treasure, and promote the healthy development of the coal industry and the sustainable development of the national economy.

Second, the main ways of comprehensive utilization of coal gangue

(1) Coal gangue power generation

Coal gangue power generation is an important way to comprehensively utilize coal gangue. Coal gangue power plants mainly use washing and excavation meteorites with calorific value between 6.53 and 8.37 MJ/kg. At present, the coal system waste rock power generation mostly uses fluidized bed combustion technology, and the most mature and mature technology is a circulating fluidized bed boiler of 35t/h and 75t/h.

China's use of coal gangue power generation has formed a certain scale, the installed capacity of the national meteorite power plant has been developed to 5 million kW, the annual consumption of coal gangue using gangue power generation is about 45 million tons, accounting for about 60% of the comprehensive utilization of coal gangue. . It can be seen that coal gangue power generation not only consumes a large amount of coal gangue, but also turns waste into treasure, and can save a lot of coal resources and alleviate the increasingly tense situation of coal power, and its economic, social and environmental benefits are very significant.

(2) Using coal gangue to produce building materials

The building materials and products that can be produced by using coal gangue mainly include: coal gangue brick, coal gangue block, coal gangue general cement, coal gangue special cement, light aggregate, mosaic and glazed brick, and the like. This is another important direction for the comprehensive utilization of coal gangue, which can consume a large amount of coal gangue.

1. Coal gangue brick making technology. The use of coal gangue bricks similar to the clay composition can be used to burn bricks without soil, without coal or with less coal, saving land and energy. The main process of making bricks with coal gangue is: crushing→grinding→stirring→pressing→forming→drying (dehumidifying)→baking→finished products. Compared with traditional clay bricks, vermiculite bricks are superior in strength and corrosion resistance to clay bricks, and have fast drying and low shrinkage.

2. Coal gangue is used to make cement. The application of coal gangue to the cement industry has done a lot of work at home and abroad. Research and practice show that the use of coal gangue to produce cement clinker, ordinary Portland cement, non-clinker or less clinker cement and special cement (such as fast hard cement, double fast cement, jet cement, etc.) have broad application prospects. .

3. Coal gangue is used to make light aggregate. Coal gangue is an ideal raw material for the production of lightweight aggregates. The lightweight aggregate fired with coal gangue has good performance and can be used to prepare concrete of 200-300. It has the characteristics of light weight, low water absorption and high strength, and is suitable for making various building prefabricated parts.

(3) Coal gangue production fertilizer

The use of coal gangue as raw material for the production of agricultural fertilizer has been applied at home and abroad. Coal gangue contains about 15% to 20% of organic matter, and is rich in trace elements such as B, Zn, Cu, Co, Mn, and Mo, which are essential for plant growth. The content of N, P, K and trace elements in some coal gangue is several times that of ordinary soil, and it can be processed to produce organic fertilizer and microbial fertilizer.

Microbial fertilizer is a new product of ecological agriculture and green food in recent years. High organic gangue contained, carrying nitrogen fixation, phosphorus solution, the best solution of potassium microorganisms and a carrier matrix. Gangue microbial fertilizer production process is simple, low energy consumption, low investment, production process does not slagging, such as Nanpiao Mining Bureau in cooperation with the Chinese Academy of Agricultural Sciences developed the "Golden Feng card" 1 of microbial fertilizer, and Shandong Longkou Mining Bureau The “Tian Li Bao” microbial fertilizer developed and produced by Beijing Tianlibao Science and Technology Research Institute has achieved good social and economic benefits.

(4) Preparation of chemical raw materials from coal gangue

The main use of chemical extraction gangue is one element of a gangue or silicon aluminum production by various methods. For coal gangue with high aluminum content, the chemical products developed include crystalline aluminum chloride, polyaluminum chloride, aluminum sulfate, 4Ã… zeolite and so on.

1. Crystalline aluminum chloride. Hardener mainly used for precision casting (higher intensity ferric chloride), paper sizing precipitating agent, coagulant purified water, wood preservatives, producing Al (OH) _3, such as plastic.

2. Polyaluminium chloride. Also known as basic aluminum chloride, is an inorganic polymer compound, a new type of coagulation and precipitation agent, widely used in water purification and sewage treatment, as well as paper, leather, casting, medicine, light industry, machinery, etc. field. The production of polyaluminum chloride from coal gangue has small investment, low cost and simple process.

3, 4Ã… zeolite. 4Ã… zeolite is currently the best non-phosphorus detergent builder. Its decontamination effect is comparable to that of sodium tripolyphosphate (STPP), and it is harmless to the human body. It is non-destructive to fabrics, easy to biodegrade, beneficial to environmental protection, and has broad application prospects. . The traditional method for producing 4A zeolite is mainly hydrothermal synthesis using NaSiO ₃ and NaAIO ₃ as raw materials, and the raw material cost is high. The use of coal gangue to produce 4Ã… zeolite raw materials is sufficient, low cost and high efficiency.

In addition, since the main component of the residue left after the production of the aluminum salt from coal gangue is SiO2, in addition to the above high aluminum product, the residue can also be used to produce water glass, white carbon black and the like.

(5) Preparation of new materials from coal gangue

1. Coal gangue synthesis silicon carbide (SiC). Silicon carbide materials are widely used in industrial fields such as abrasives, refractories, high-temperature structural ceramics, metallurgy and high-power electronics with excellent high-temperature strength, high thermal conductivity, high wear resistance and corrosion resistance. Industrial production of silicon carbide is mainly based on quartz sand, petroleum coke or high-quality anthracite. It is a high-energy and high-pollution industry by high-temperature electrothermal reduction in the furnace to form silicon carbide. High silicon gangue and bituminous coal are used as raw materials to synthesize SiC. Compared with traditional raw materials, the reaction speed is fast and the reaction temperature is low. It can replace quartz sand and most expensive petroleum coke, and can reduce energy consumption. And production costs, with high application value and application prospects. This is a new way for the comprehensive development and utilization of coal gangue.

2. Preparation of 4Ã… molecular sieve by coal gangue. Traditional molecular sieve production, most of the domestic and international methods of synthesis of chemical raw materials such as sodium hydroxide, water glass and caustic soda. Due to the shortage of these raw materials, the high price, the complicated production process, and the high production cost, the application range of the molecular sieve is hindered. The use of kaolinite-rich coal gangue to produce molecular sieves is rich in raw materials, simple in process, low in cost, and has strong market competitiveness.

(6) Discussion on underground treatment technology of coal gangue

The traditional coal gangue treatment method is to raise the coal gangue out of the well for centralized storage or reprocessing, which not only greatly increases the mine transportation volume and increases the transportation cost, but also discharges the coal gangue on the surface and takes up a lot of valuable land resources. At the same time, coal gangue piled up in the mountains will spontaneously ignite, which will seriously affect the safe production of coal mines and the safety of workers, and cause pollution of the atmosphere and water sources in the mining area. Therefore, if the appropriate method can be adopted to make the coal gangue not out of the well or less, then the problems caused by the accumulation of surface coal gangue into the mountain can be fundamentally solved.

At present, coal mine workers at home and abroad have found in the long-term practice and research that in the process of underground coal mining, it is completely feasible to try not to produce cockroaches or less cockroaches. The main technical processes include the following:

1. Less open rock lanes, multiple coal roads or full coal lanes. In recent years, with the acceleration of mining speed and the increase of yield in mining face, the maintenance time of roadway has been shortened; the improvement of support technology has greatly reduced the difficulty of maintaining coal roadway; the improvement of transportation equipment and the application of new transportation equipment The restrictions on the curvature radius and slope of the roadway are getting smaller and smaller, and the improvement of the self-ignition and ignition technology of the coal seam prevention layer has laid a good foundation for the construction of the less open rock roadway, the multiple coal roadway or the whole coal roadway. In recent years, coal enterprises in Germany and the United Kingdom have gradually applied all-coal tunnel development technology. Some coal mines have cancelled the drainage system; China’s Chun’an Village Mine and Shenhua Group’s Dali Tower Mine have also achieved full coal lane layout. Dig the road meteorites.

2. Apply mechanical coal bunker underground. The traditional underground coal bunker is generally arranged in the rock formation. It is used for excavation, and it is used immediately after use, resulting in a great waste and a large amount of meteorites. In order to reduce the number of defects in the well or try not to go out, it is necessary to apply a mechanical coal bunker. The mechanical coal bunker in the mining area (or working surface) is a movable coal bunker, which can be moved to other locations for reuse after being used.

3. The underground diverticulum is moved to the ground. The underground blasting material library is excavated in a stable rock formation. “The underground blasting material library must have an independent ventilation system”, and it is often necessary to dig long ventilation tunnels. However, as the degree of mechanization of mining has increased, the use of downhole blasting equipment has become less and less. If the underground blasting material library is moved to the ground, this not only reduces the amount of excavation of the diverticulum itself and the resulting meteorites, but also reduces the amount of excavation work and the resulting meteorites for the ventilation tunnels dedicated to the diverticulum. .

4. Filling the goaf with underground meteorites is an important method to reduce the occurrence of meteorites. For the condition that the goaf (or working face) inclination angle is greater than 42o, the self-weight filling method is the easiest. The meteorite can be transported by the (tape) conveyor to the return air lane behind the working surface, and the meteorite can be directly unloaded into the goaf; or the shovel loading and automatic unloading vehicle can directly unload the meteorite transportation to the gob; or use the monorail Auxiliary vehicles such as cranes, rail cars, and rack cars directly unload the meteorites into the goaf.

5. Coal preparation in the underground. About 15% of the raw coal produced by the mining face is meteorite. If it is selected in the underground, it will not only make the meteorite not go out, but also reduce the mine's transportation capacity and increase transportation costs. Downhole selection is easy to achieve, such as picking at the work surface; setting a low speed (tape) conveyor in the downhole raw coal transportation lane or paralleling the low speed conveyor to mechanical or manual picking in order not to affect the conveying capacity.

Third, the recommendations for the comprehensive utilization of coal gangue

1. Research and development of a batch of coal gangue comprehensive utilization technology, focusing on the research and development of large-scale coal-fired gangue circulating fluidized bed boilers and complete power generation technology, simple and efficient flue gas desulfurization, ecological microbial reclamation technology, kaolin deep processing and other technologies. The development of the comprehensive disposal and utilization technology and technology of the waste rock mountain. Through the joint research and development of industry, academia and research, we will gradually establish a technological innovation mechanism for technology introduction, digestion and absorption, and independent development, track the development trend of international comprehensive utilization technology and equipment, and shorten the gap between China's coal gangue comprehensive utilization technology and equipment level and the world.

2. Accelerate the technical transformation of the comprehensive utilization of coal gangue in existing enterprises, and use advanced and practical technologies to transform backward, polluting technologies, processes and equipment, such as the use of circulating fluidized bed boilers to transform the boiling furnaces of old power plants, and fundamentally solve the coal gangue power plant. The problem of pollution; the use of hard plastic, semi-hard plastic molding technology to transform the backward soft plastic molding technology and equipment, so that the coal gangue bricks on the scale, the upper level.

3. Promote a batch of advanced and applicable comprehensive utilization technology of coal gangue, focus on promoting circulating fluidized bed boilers above 75t/h, and promote limestone desulfurization and electrostatic dust removal technology in the furnace.

4. Strengthen the role of technology guidance, accelerate the promotion and application of advanced and mature technologies, establish and improve the promotion and technology transfer network of coal gangue comprehensive utilization technology and products, effectively release technology and supply and demand information, and promote the effective transformation of scientific research results.

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