Research on Active Dustproof of Coal handling system 1

： Coal handling system of Power plant(CHP) is easy to produce dust, which is the most 4 serious place of coal dust pollution in thermal power plant. With the gradual improvement of 5 national environmental protection requirements, the control of coal dust becomes more and more 6 important. The author believes that we should not wait for the pollution caused by coal dust to be 7 treated, but should take the initiative to attack, and should take the initiative to prevent dust, 8 starting from the source of coal transportation. In the process of designing coal conveying of 9 thermal power plant for many years, the author has carried out on-site investigation on many coal 10 handling systems, summarized experience and obtained relevant data. Through further analysis, 11 the main causes of coal dust are mastered, and the relevant measures of active dust control are put 12 forward from the technical point of view, in order to provide help for the comprehensive control of 13 coal dust in power industry. 14

Coal is a major source of India's energy supply having the lowest energy cost 2 among the different fossil fuels accounting for 45% of the total energy mix and 60% 3 of the installed electricity capacity. Future prediction indicates that coal is likely to 4 remain one of the primary energy sources for a long time in energy production. [1] 5 The coal handling system is prone to dust, which is the most serious place for coal 6 dust pollution in thermal power plant. In industries using bulk quantities of materials, 7 it is often necessary to store very large amounts of particulate materials. Any such 8 storage and the associated materials handling is likely to present dust problems.[2] 9 With the improvement of environmental protection requirements, the active dust 10 prevention is the highlight of CHP. 11 In the traditional design, the domestic and international coal dust control work is 12 mainly based on dust removal. When it comes to coal dust control, people's first 13 reaction is to set up a dust collector. This paper believes that the focus of coal dust 14 control work should be to prevent coal dust from dusting from the perspective of 15 process facilities. It should be based on active dust prevention, not dust removal after 16

dusting. 17
The author has summarized many years of work experience, conducted 18 After the building or equipment is sealed, a suction device can be arranged under 1 the hopper, a negative pressure is generated at the coal hopper, the rising air mass 2 generated during the discharge is effectively eliminated, and a water spray device is 3 arranged at the discharge port of the coal hopper. Seal the coal dust in the coal hopper. 4 Coal yard, as one of the most important links of coal storage in fossil fired power 5 plant, its economy effect, security and environmental friendliness has drawn 6 worldwide attention. [7] Compared to open air coal yard, the enclosed coal yard has 7 the advantage of higher land use rate as well as better outdoor air condition.
[8] 8 Ventilation, one of the crucial methods to improve indoor environment in coal yard, 9 helps to improve indoor thermal condition and decrease the combustible 10 concentration.
[9] The whole coal yard is sealed. The strip-shaped closed coal shed 11 and round closed coal shed are commonly used in the project to ensure that the 12 surrounding environment of the coal yard is not polluted by coal dust, and a dust 13 suppression device is installed inside the closed coal shed. 14 3.2.2 Water spray active dustproof 15 It has been recognized that such conventional approach provides an estimation 16 result with a substantial margin of error which could affect the effectiveness and 17 performance of the dust removal system.[10] In a more realistic viewpoint, foot-print 18 area of water spray, which can be estimated by the trajectory of the droplets on the 19 periphery of the water spray, would also affect the removal efficiency. [11] In addition, 20 the overall efficiency of spray nozzles should be estimated by taking into account the 21 11 / 36 ambient condition, such as wind velocity and concentration of fugitive dust in the 1 ambient air, as well as the generation of fugitive dust by the apparatus of interest.
[12] 2 A water spray device is arranged at the position of the dumper and the unloading 3 ditch, and is interlocked with the unloading device. The sprinkler is arranged 4 three-dimensionally in the dust-prone position in the coal unloading device, and the 5 nozzles are arranged in the unloading direction. The nozzle spacing can be arranged 6 according to the spacing of 300~500mm. The number of nozzles and the amount of 7 water spray can be adjusted according to the different coal quality. 8 A water spray device is arranged in the closed coal shed, arranged around the 9 coal yard and on both sides of the turbine track base, and the spacing should be 10 considered to be less than 30 meters. It is also possible to provide a spray dustproof 11 device at the wheel hopper on the bucket machine equipment, and to interlock with 12 the bucket turbine from the start and stop. 13 The water spray device uses industrial water, and generally sprays and 14 humidifies coal pile twice a day for half an hour. The water sprayed on the surface of 15 the coal pile is volatilized faster, especially in dry weather. It is considered to add the 16 dust suppressant to the spray water, a dust suppressant by applying a blend of mixed 17 polyethylene oxide (g-PEO) and sodium dodecyl sulfate (SDS), The g-PEO&SDS 18 solution, utilizing SDS converted the hydrophobic coal surface to a hydrophilic area 19 by the adsorption of the surfactant molecule exclusively at hydrophobic sites and 20 g-PEO linked closely with the coal dust to form a layer of gel film on the surface of 21 12 / 36 the coal dust after air-drying, possessed the optimal performance for coal dust control 1 and did not affect the use of the coal. [13] 2 4 Carrier equipment active dustproof 3 The carrier equipment of the CHP mainly includes belt Conveyor, coal chutes 4 and guide troughs. Normally, the belt is respectively supported by the idlers. During the operation, 13 under the action of the driving force, rolling friction is formed between the belt and 14 the idler idler, so that the belt runs forward along the length direction of the Conveyor. 15 Due to factors such as equipment manufacturing, construction, installation, etc., the 16 force of the belt during operation is uneven, and the upper belt surface may be 17 deflected. It is easy to spill coal from out the belt surface. The center line of the idler is not perpendicular to the running direction of the 20 belt, and is at an angle of 90 ° ± θ, as shown in Figure 2. Then, the belt will be shifted 21 13 / 36 to a direction larger than the right angle side. This is because the surface of the idler 1 and the belt are in contact with each other, and the circumferential rotation direction 2 of the idler is at an angle of θ with the linear running direction of the tape, and the 3 final running direction is met. In the vector synthesis relationship, the friction between 4 the idler and the belt pushes the belt to one side to form a deviation.  is not tight. When the coal is dropped inside the blanking chute, the initial velocity is large, 16 and a strong induced wind is generated, which causes dust to overflow in the above holes or 17 gaps. e. Arrange the coal chute vertically, when the height difference is more than 5 meters, 10 the coal will fall quickly, and the gravity will easily damage the guide trough and the 11 overflow apron at the lower tribe point, causing gaps between the equipment to cause coal 12 overflow. 13

Guide trough coal dust pollution 14
The guide trough is installed at the end of the conveyor, and its function is to prevent 15 the coal falling from the coal chute from being scattered, and the coal can be rapidly 16 accumulated in the center of the belt tape on the conveyor to form a stable shape. The guide 17 trough should have sufficient height and section. The design of the guide trough structure 18 mainly includes the section type, length, and sealing form. The traditional guide trough is a 19 type with a curved top, which increases the internal volume of the guide trough, which is 20 beneficial to reduce the induced wind pressure and is equipped with a dust-proof curtain at 21 17 / 36 the exit. The periphery of the guide trough should be able to automatically adjust the 1 corresponding sealing pressure with the change of internal airflow pressure to ensure good 2 air tightness, so that the inside of the guide trough is completely isolated from the outside, 3 and the effect of exhausting dust is ensured. 4 In actual use, the wear of the guide trough itself is very serious, resulting in serious 5 dusting and powder leakage and pollution. The main reason is that the traditional guide 6 trough and the belt are closed with a rubber skirt, and the sealing effect is poor. When the 7 conveyor is in operation, the coal piece flowing down from the coal chute will exert a large 8 impact force on the belt in the guiding trough under the action of gravity, causing elastic 9 vibration of the belt, resulting in rubber skirt and belt. There is a gap between them, and the 10 small coals are ejected from there. Since the entire length of the guide trough is about 10 11 meters, there are many gaps, so there are many powder leakage points in the lower part of 12 the guide trough. 13 The lack of tight sealing between the guide trough and the belt is the root cause of 14 powder spraying around the guide trough. The "large drop in the coal chute" and the "small   The direction of the synthetic external force received by the belt is inconsistent 10 with the running direction, which is the root cause of the deviation of the belt. 11 Therefore, it is necessary to improve the design, manufacture, installation, 12 commissioning, use and maintenance of the conveyor. The method of adjusting the 13 deviation of the belt can be summarized as the following.  To control the belt surface fluctuation, it is necessary to strictly control the 7 design, manufacture and installation. According to the use requirements, the running 8 speed of the conveyor should be reduced as much as possible, the spacing of the idlers 9 should be arranged reasonably, and the selection and delivery volume of the belt 10 should be strictly controlled. Adjust the idler with a large beating range.    The equipment seal mainly includes between the head funnel and the coal chute, 1 between the coal chute and other coal chute, between the coal chute and the buffer air 2 locker, between the buffer air locker and the guide trough, and between the guide 3 trough and the belt. 4 If flange connection is used between the above equipment, a reliable gasket 5 should be installed for sealing to avoid direct connection. 6 In the seal between the side of the guide trough and the belt, it is recommended 7 to provide a flexible double-layer sealing material with good elasticity, high strength 8 and wear resistance. The inner layer sealing material mainly controls a large amount 9 of coal flow on the belt surface, and the outer layer sealing material leaks the coal 10 powder from the gap of the inner layer sealing material to be controlled between the 11 double-side sealing materials. To avoid belt is in a subsidence and forming a gap 12 between the sealing materials, a pallet can be placed between the idlers to lift the belt. The basic parts of the head funnel are versatile and can be flexibly adapted to the 1 needs of use. It is necessary to make the basic selection parameters of the head funnel 2 as the comprehensive determination factor of the head funnel selection, such as the 3 bandwidth, belt speed, inclination angle and coal particle size. This can make the head 4 funnel suitable for the parabola requirements of all types of conveyor heads, so that 5 the coal flows smoothly and without impact into the head funnel and the lower tribe 6 coal chute, which can effectively eliminate the phenomenon of dust pollution impact 7 of coal flow and chute wall collision.  For the shortage of traditional coal chute, we often use streamlined chute to make 17 up for the shortage of traditional coal chute. The streamlined chute has the following 18