Technical and Economic Analysis of Production Pipeline Design in Coal Preparation Plant
Dong Shijun (Nanjing Coal Design and Research Institute, Nanjing 210031, China) unifies the problems that should be paid attention to in the aspects of pipeline calculation, production pipeline anti-wear and flange setting.
1 Introduction Analysis of the production pipeline design of the common domestic reinforced concrete structure coal preparation plant can be found, generally use the beam and column as the support and the parallel or vertical fixed pipeline laying method with the building shaft line, and rarely use the discharge point from the coal preparation equipment. The straight line arrangement to the end point, and the latter method is more suitable for the characteristics of easy wear and easy clogging of the coal preparation pipeline. The design of the production pipeline of the coal preparation plant also has problems such as the small diameter of the pipe calculated by the self-flow pipe and the excessive number of flanges. All kinds of problems make the production pipeline design unreasonable, high cost, frequent and complicated to maintain, and it is necessary to improve and perfect it.
2 Uniform reinforced concrete structure for production pipeline effectiveness and aesthetics Due to the large equipment load, the section design of the civil engineering design is often large, and sometimes it is not convenient to lay the production pipeline in a straight line (hereinafter referred to as “straight-modeâ€, others The pipeline is not beautiful, which means that sometimes the flat-mode is more reasonable. This requires that the design of the production pipeline of the reinforced concrete coal preparation plant should distinguish between different pipeline types and conditions to determine which method to use. Blocked production pipes must be arranged in a straight-line manner as much as possible. Pipes that are not easily worn and clogged can be arranged in a flat-to-mode manner to meet aesthetic requirements. Sometimes such pipes can also be arranged in a straight-line manner for convenience. The purpose of transportation and use is to achieve the purpose of unifying the effectiveness and aesthetics of the production pipeline. By using the straight-line arrangement as much as possible, the number and wear of the elbows can be reduced, the pipeline life can be prolonged, the pipeline blockage can be reduced, and production can be reduced. Pipeline investment and use costs.
According to the above, it can be concluded that the rational design principle of the pipeline is to first consider its effectiveness, and secondly to take into account the aesthetics. Of course, the production pipeline of the steel structure workshop can be calculated by simple calculation of the straight-line 3 production pipeline. There are some problems in the calculation. The main reason is that the diameter of the self-flow pipe is small, which makes the pipeline easy to block. The main reason is that the fullness of the pipeline does not fully consider the difference between the slime water and the general drainage. Frequent maintenance leads to excessive undue interference to the production and more clearing devices. Therefore, it is necessary to make necessary improvements and adjustments to the fullness index of the coal-separating pipeline.
The material conveyed by the self-flow production pipeline of the coal preparation plant is easy to precipitate, which makes the production pipelines more likely to deposit and block with the unit volume of materials. Therefore, the inner diameter of the production pipe should be adjusted according to the different conditions of the slime water (such as concentration, particle size, density, etc.). Although the flow rate of the self-flow exceeds the critical flow rate, the deposition of materials will be alleviated, but after all, unlike the pressure pipeline, the flow state of the coal slurry in the latter pipeline is uniform, that is, the speed is relatively uniform, and the slope and fullness of the gravity pipeline belong to the relationship. This self-flow production pipeline also has serious problems of fullness. When the slope of the pipeline is large, that is, when the flow rate of the slime water is large, the flow state is more unstable than the general drainage, and the ventilation effect is even worse, that is, the effective ventilation space is reduced, which will affect the self-flow transportation of the material, and the heavier transport of the mineral pipeline is likely to cause Deposition is blocked. In summary, the value of the fullness selected in the previous design is too small.
The fullness of the production pipeline must be less than the fullness of the general drainage pipeline, ie <0.7, and the coal slurry concentration should be used in the design to determine the different pipeline fullness. The recommended value range is 0.6 0.4. If the value is too small, the utilization of the pipeline will be greatly reduced. In addition, the remaining factors must be considered. After calculation, the diameter of the pipe is enlarged by 12, and sometimes it is necessary to increase the number of stages to ensure the use of the pipe.
4 production pipeline anti-wear and cancel most of the flanges of the coal preparation plant production pipeline wear is the most serious heavy medium pipeline, mainly because the heavy medium is magnetite powder with much higher density and hardness than coal, elbow, tee The speed of the grinding is also much larger than that of coal. Therefore, according to the technical and economic analysis and comparison, the appropriate anti-wear methods, such as the use of wear-resistant elbows and other fittings. However, sometimes the use of such pipe fittings is relatively small, which makes the ordering and maintenance of such pipe fittings more troublesome, which makes design and use less convenient. This paper only analyzes the principle of making easy-to-wear pipe fittings and the corresponding pipe installation problems when using ordinary material steel pipes.
The wear rate of the heavy medium pipe is related to the flow rate of the slurry. The high-to-low potential energy of the self-flow pipe makes the impact flow rate much higher than the economic flow rate or critical flow rate of the pressure pipe. Therefore, the wear of the elbow or the like is much more serious than that of the pressure tube. Since the density of the magnetite powder is relatively large, the hardness is high and it is not easy to be pulverized and the particle size is fine, so that it has a large specific surface area. The magnetite powder and the steel pipe are both hydrophilic, and the magnetite powder easily removes the air to form a knot by the attraction of water, resulting in the easy deposition of the anti-sludge water at the end (or the lower part) under the action of gravity and water flow. The dense layer of the deposited layer can replace the wear-resistant elbow. Therefore, the ordinary elbow of the self-flow tube should be replaced by the wear-resistant oblique tee type with the end portion blocked by heavy medium deposition. The method: in the wear-resistant oblique three-way low-end welding of the bulkhead steel plate, because the depth of the required deposition of the ore particles does not need to be large, as long as the formed wear layer can be satisfied, so the wear-resistant oblique tee end pipe should be as short as possible, As a result, the resistance of the gravity pipe is increased, which makes the site easy to block. Use the flat tube bottom, that is, the outer side of the steel pipe to weld the bulkhead steel plate, which is more beautiful and reasonable than the outer welded bulkhead steel plate, and it is easier to do it shorter. In some coal preparation plants, the bottom of the wear-resistant oblique tee pipe is left long, and a large number of flanges are arranged at the end for cleaning, resulting in the overfilling of the flange.
At the tee where the branch pipe and the main pipe are connected, since the coal slurry water acts as a guide buffer for the wear shock, the impact force on the steel pipe is reduced, that is, the wear is alleviated and the service life is prolonged, but the angle of the oblique tee should be as small as possible. The pipe connected to the riser should also be directly connected, and the 45* elbow for guiding should not be used to reduce the elbow wear. As a result, the flange can be eliminated, and the welding pipe can be inclined at the on-site dry pipe opening, which reduces the workload of the installation welding and reduces the pipe resistance. If several diagonal tees are successively welded in the riser, the amount of steel pipe worn here will be less, and it will also facilitate the compact arrangement of the production pipes. For other elbows, it is recommended to use stamping elbows or elbows, because the inner wall is relatively smooth, not easy to wear and block, and the appearance is also beautiful.
When the production pipeline needs to be repaired or replaced, the above position is treated by electric welding and gas cutting. Because it is not easy to produce explosive combustion, it is safer. In addition to the flanges that need to be connected at the inlet and outlet of the equipment, flanges are no longer provided in other places to reduce the investment and production cost of the pipeline.
5 production pipeline laying method to improve the flat-mode laying is relatively simple, as long as the pipeline is fixed on the beam and column, which is also the reason why the design is generally reluctant to adopt the straight-mode, and even some design manuals and other materials have similar requirements. Without first considering the intrinsic use requirements of the pipeline.
The straight-line pipe laying method can be directly fixed on the steel structure in the steel structure coal preparation workshop, and in the reinforced concrete structure coal preparation plant, since the pipes are mostly not close to the column, they can be pre-formed on the beam side or the beam bottom. The buried steel plate is used to fix the pipeline, and the hanger can be fixed under the floor. For example, when the soil construction beam at the fixed pipeline location is relatively high and it is not convenient to fix the pipeline, the pipeline below DN150 can be fixed by vertical method on the horizontal plane by using the hanger; for the steel pipe with a certain width above the DN150 pipeline, the bolts at both ends are used. Pulling through the floor to hold some steel bars and fixed brackets, the fixed brackets can be made in some standard drawings, which is more beautiful. This method is easy to install, is more suitable for the construction site, and reduces the number of embedded steel plates and the cumbersome calculations caused thereby. However, sometimes the fixed hanger needs to be placed close to the civil bearing beam to avoid affecting the floor structure when the bending moment of the floor is too large. In addition, the bolts on the floor should not be exposed to prevent corrosion from affecting the structure of the bracket. After the anti-rust treatment, the soil is leveled by the soil. On the contrary, it is required to set up a small load-bearing beam fixed pipe for civil engineering.
6 The setting of the valve of the slurry pump outlet pipe is due to the large amount of coal mud which is deposited by the slurry pump outlet pipe, which sometimes causes the valve to not open. Therefore, the valve should be installed at the pump outlet pipe tee or flat pipe or inclined pipe. Since the arrangement of the pump is sometimes at an angle or even a large angle, the suction pipe is not bent or facilitates the arrangement of the pump. At this time, according to the general flat tee design, the valve has to be placed at a higher position, which is inconvenient for operation and maintenance. At this time, the connection tee of the two pumps should be made into a space three-way type in the case where the space angle is allowed to be installed, so that the pipeline avoids the storage device. Obviously, the slurry pump should also be arranged to meet the installation dimensions of the space tee as much as possible in order to set the valve. Of course, space angle installation methods can also be used for other pipes.
7 Conclusion The design of the production pipeline should be uniform in terms of effectiveness and aesthetics, and the calculation index of the production pipeline should be adjusted to make the calculation of the pipeline conform to the actual situation and the use is reasonable. The production pipeline adopts the correct and reasonable wear-resisting method, and the number of flanges is greatly reduced, so as to reduce the various costs of the production pipeline and improve the use effect of the production pipeline. (: 2000-07-10 Editor: Yan Naiqiu)
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