Former coal plant process analysis 1, the election
The Gushuyuan Coal Preparation Plant adopts the jigging coal preparation process, in which the lump coal workshop is divided into l3～120mm class lump coal. According to statistics, the average coal consumption rate of the pre-renovation lump coal workshop is 15%-20%, of which the final coal less than 13mm accounts for about 15%-18% of the total meteorite, while the lump coal larger than l3mm generally does not exceed 2. % one 5%.
If the raw coal has a higher moisture content, the proportion of coal with less than 13 mm in the coal brought by the meteorite can be as high as 30% or more. The reason for this situation is mainly because the grading and screening efficiency is low. After a large amount of the final coal enters the jig, it enters the bucket elevator through the sieve hole of the jig.
According to experience, the more wet the coal, the worse the screening effect of the raw coal grading sieve. The more coal is entered into the jig, the more serious the jigging machine is, and the higher the coal rate of the meteorite.
Therefore, the excessive coal entering the jig is the main reason for the over-standard of the washing stone. If the screening efficiency of the raw coal grading sieve can be improved, the amount of coal entering the jig can be reduced.
At present, the screening efficiency is improved by increasing the amplitude of the screening machine or extending the length of the screen surface. For a sieving machine that has been shaped, any increase in the amplitude of the sifter will affect the life of the sifter's exciter bearing, and even cause bearing damage, while the increase in amplitude will also create
It is impossible to extend the screen surface of the screening machine by forming problems such as cracking of the screen frame and the beam. Therefore, it is not feasible to improve the screening efficiency by modifying the screening machine, and switching to other types of screening machines is limited by the space of the factory.
If the size of the sieve mesh is increased, for example, the mesh hole is increased to 20mm or even 25mm, although the sieve amount of the sieve on the sieve can be increased, this will cause a small piece of coal larger than 13mm to enter the final coal, resulting in loss of lump coal. So this method is not feasible.
2, the transformation plan
Because the method of improving the screening efficiency of the screening machine can not solve the problem that the meteorite has exceeded the standard of coal, it is decided to rescreen the meteorite discharged from the jig, and the piece of vermiculite is separated from the end coal, and the coal is returned to the warehouse. This can reduce the coal rate of the meteorite.
The specific process setting is to install two linear vibrating screens under the head of the gangue bucket elevator and the medium coal bucket elevator. The meteorite discharged from the jig enters the bucket hoist and then enters the vibrating screen. , using wet screening, screening out the end coal of less than 13 mm in the vermiculite,
The piece of vermiculite larger than l3mm on the sieve is transported to the 602 stone silo by a belt conveyor.
After the bottom coal is collected by the water tray, it is transported by hydraulics to the fishing pit. After preliminary dewatering by the fine coal bucket elevator, it is further dehydrated by the centrifugal dewatering machine. The dehydrated product is transferred from the 324 tape conveyor to the 501 tape conveyor. Machine, the last person cylinder warehouse is recovered as sieve coal.
3, feasibility analysis
3.1 Feasibility of installing vibrating screen
Due to the limitation of space height, the screening machine can only be installed on the third floor of the main building, its height is only 4m, but the installation height of the 1.5m wide screening machine is generally about 2.5m, and there is still 1.5 for the sieve on the sieve. At the height of m, two reinforced concrete beams with a section of 600×300 are built under the floor of the screen. The two beams are calculated to withstand the dynamic loads generated by two 2t screens. The space under the screen does not interfere with the installation of the water tray. Therefore, the floor has the conditions for installing two vibrating screens.
3.2 Wet screening can recover 95% of the final coal in the washed vermiculite
Since the bucket hoist is generally 20% hydrated from the bottom of the jig, it is difficult to screen material, so the best way is to use wet screening. In the screening process, with a certain pressure of flushing, forced coal in the middle of the vermiculite sieve, because the production of vermiculite and medium coal is not large, about 60t / h, when the screening efficiency of the two screening machines reaches 95% or more Meet operational requirements.
3.3 The failure of the screening machine will not affect the operation of the system.
Install a movable gate in the original coal drum. When the gate is turned to one side, the meteorite can directly enter the 601 scraper conveyor; when the gate turns to the other side, the meteorite can enter the vibrating screen and sieve. Once the vibrating screen or under the screen has failed, the gate can be turned to the other side, allowing the meteorite to enter the scraper conveyor directly.
3.4 The under-sieving pipeline can operate normally
The submerged pipeline can introduce part (small amount) of circulating water, transport the final coal with water, and the slope of the pipeline is 20-35, so it is generally not blocked; a 50×50mm rafter is added at the inlet of the water tray to prevent it. Large vermiculite enters the vertical centrifuge due to damage to the sieve plate.
3.5 The recovered coal will not affect the commercial coal ash of the sieve coal.
Although the recovered end coal will also be mixed with the end vermiculite, the amount is very small, and the ash content is generally 20% to 25%. After mixing with a large amount of the final fine coal of the vertical centrifuge (the ash is generally less than 15%), the coal is mixed. The ash will not exceed 20%. The user requires that the final coal ash content of the commodity does not exceed 21%, so it can fully meet the commercial coal ash index.
3.6 Wet screening does not affect the washing system
The wet screening water is all from the circulating water system. The flow rate of the circulating pump is 2000m3/h, the water consumption of the normal coal washing is 1500m3/h, and the water consumption of the wet screening is less than l00m3/h. Moreover, the water used for the wet screening flows back to the circulating water system, which basically does not cause a decrease in the circulating water, so it does not affect the washing system.
4 transformation and implementation
(1) Selection of screening machine. After design and calculation, the screening machine below the gangue bucket elevator is (3.0×1.5) m type, the maximum processing capacity is 150t/h, and the normal feeding amount is generally lower than 120t/h. The screening machine below the medium coal bucket elevator adopts (1.2×2.4) m type, the maximum processing capacity is 100t/h, and the normal feeding amount is generally lower than 90t/h.
(2) Draw the installation contact map. Draw the installation contact diagram of the equipment on the screen, the submerged water tray and the submerged pipeline, flushing pipeline and other equipment.
(3) Design of components. The undersize coal tube is limited by space and the angle can only reach 20. The section can reach (400×600)mm. In order to ensure the normal transportation of the meteorite, the circulating water must be added into the cylinder and transported to the vibrating screen by hydraulic means. The bottom of the screen can be up to 42 degrees. ~60. Under the impact of the water flow on the screen, it can be ensured that all the final coal that has been screened enters the under-screen pipeline. The filial pipe is made of φ350mm pipe with an average slope of 15. , long l9m.
(4) Electrical design. In order to reduce costs, all electrical parts are designed and installed by the coal preparation plant. The two screens are all local control equipment, that is, they are turned on and off by the driver's site. Once a fault occurs, the upper equipment can be locked by the 601 scraper conveyor.
(5) Processing and production. In addition to the purchase of two vibrating screens, the rest of the equipment is produced by the coal preparation plant. For example, 4 coal slag cylinders are used for processing, 25m2 steel plate is used, total weight is 2t; 2 water trays are processed under the sieve, 20m2 steel plate is used, the total weight is 1.5t; 2 steel pipes with elbows of φ350mm and length 20m are processed; One steel pipe with a length of 100 mm and a length of 10 m is welded with one steel pipe of φ350 mm and length of 20 m.
(6) Equipment installation. The installation of the equipment is entirely the responsibility of the coal preparation plant. Due to space constraints, the electric lifting equipment cannot be used at the site, and only the chain hoist can be used for lifting. The installation sequence is as follows: open the hole with a diameter of 400mm on the upper floor, install the water tray under the sieve, install the screen, attach the scaffold, install the screen and the upper pipe, install the sieve on the coal, and finally pass through the floor. The pipe is made waterproof.
5 economic benefit analysis
(1) When the coal preparation plant is in normal production, it is calculated according to the daily production of 800t of vermiculite. The final coal containing vermiculite is generally between 15% and 20%, calculated at 15%, and the screening efficiency is 95%. 800t × 15% × 95% = l14t, that is, the daily value can be about 11,400 yuan. On the other hand, the daily transportation cost of meteorites can be reduced by nearly 400 yuan, saving nearly 140,000 yuan per year.
(2) Ratio of investment to output. Two vibrating screens were put in, and the outsourcing cost is estimated to be about 80,000 yuan. Pipes and coal pipes need about 10,000 yuan, a total investment of 90,000 yuan.
(3) Annual increase benefit: RMB 114,000 × 350d + 140,000 yuan - 90,000 yuan = 4.04 million yuan.
After the transformation of the washing and coal preparation equipment, the output value and economic benefits of the final coal in the washing stone were greatly improved. At the same time, the use of washing and coal preparation equipment to recover a large amount of coal resources, improve the output value, and obtain objective economic benefits, providing a successful case for other coal preparation plants to use the washing and coal preparation equipment to improve the output of old mines.
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