Fault analysis and improvement of dry fog dust suppression system for Tipper

Chen Min

(The Second Port Branch of Qinhuangdao Port Co., LTD., Qinhuangdao 066000, China)

Abstract: This paper analyzes the reasons for the high failure rate of dry fog dust suppression device of first-stage coal dump in Qinhuangdao Port, and makes targeted improvement to reduce the failure rate.

Key words: Tipper; Dry fog dust suppression system; Fault analysis; improve

introduction

The dust phenomenon often occurs when dumper is unloading coal. The dust amount mainly depends on the particle size and water content of coal to be unloaded. Especially in winter, in order to prevent the occurrence of frozen coal, coal production enterprises generally reduce the water content of coal, which leads to the unloading operation of port enterprises, a large amount of dust is generated in the dump area, the concentration of high energy up to thousands of milligrams per cubic meter, the pollution is quite serious, seriously endangering the health of workers. To produce dust, it is necessary to install a set of effective dust removal device.

The first phase of Qinhuangdao Port coal dump was put into operation in 2004. The dust removal device was originally designed as water spray type dust removal, which not only wastes a lot of water resources, but also has very limited dust removal effect. In recent years, the state has paid more and more attention to environmental protection, and the effect of this traditional water spray type dust removal completely fails to meet the requirements of environmental protection. Therefore, in 2016, the dust removal device of the dumper was uniformly replaced with the micron dry fog dust suppression device with more obvious dust removal effect and more mature technology.

1. Tipper dry fog dust suppression device

The principle of dry fog dust suppression device is to atomize water to a high degree to form a large number of 1 μm water mist particles. The water mist particles are sprayed to the dust producing area through the sprinkler head in the form of mist. The water mist will be adsorbed with the dust particles in the air and fall down under gravity after combination, so as to achieve the purpose of dust generation. The smaller the water mist particles are, the greater the coalescence probability is, and the better the dust suppression effect will be.

Dry fog dust suppression device mainly includes ultrasonic nozzle, screw type air compressor, air storage tank, micron level dry fog dust suppression host, dry fog box controller, dry fog box assembly, electric heat tracing device and water and gas pipeline components, the dust work flow

See Figure 1.

Figure 1 Work flow of dry fog dust suppression device

2 Problems in the use of dry fog dust suppression device of tipper

The first phase dry fog dust suppression system of Qinhuangdao Port coal was installed in 2016, and the failure rate remained high after a period of use, which was mainly shown in three aspects.

(1) Water pipe insulation tracing heat in hopper area of dry fog dust removal system was damaged by large lump coal.

(2) The dry fog controller box in the hopper area is poorly sealed, and the water vapor enters the controller, resulting in short circuit and system shutdown.

(3) In the hopper area, the connection of the control line of the dry fog controller has poor contact or short connection to the ground, resulting in the dry fog protection air switch off and stop. Due to the high failure rate, dry fog dust suppression device is useless, so it is imperative to reform it.

3 Transformation Scheme

In view of the problems existing in the process of using the dry fog dust suppression system of tipper, two aspects of technical transformation of the dry fog dust suppression system are carried out.

(1) Install a protective cover on the insulation system of the waterway pipeline in the tipping of the tipper to prevent the collision and damage of the block coal to the insulation system during the tipping operation.

(2) Transform the control mode of the dry fog controller to the spray fog box, reduce the number and placement position of the dry fog controller, eliminate the control line layout in the hopper area, and reduce the electrical failure rate of the dry fog dust suppression system.

Due to the narrow foundation pit of the tipper, the dry fog dust suppression system is arranged on the tipping side of the dust retaining wall, the water pipeline position is limited, and the installation is low. During the tipping operation of the tipper, as the rotating speed of the tipper is 1.44r /min, a large chunk of coal is thrown out in a parabolic motion path and hit the thermal insulation tracing system located in the lower water pipeline. The water pipe insulation material falls, the hot line is broken, and the tap water in the pipeline freezes and expands.

In order to solve the above problems, a protective cover is installed in the water heat preservation and tracing system of tipper tipping side. The insulation material of the initial design is rock wool tube, and the rock wool tube is protected by 1.5 mm thick iron drum. Due to the insufficient strength of the iron sheet, it is deformed and dropped under the impact of the large coal many times, which causes the rockwool tube to fall. In order to reduce the diameter of the protective cover and rationally distribute the pipeline space, consider re-selecting the insulation material first. On the premise of meeting the insulation characteristics, reduce the thickness of the insulation material around the pipeline as far as possible. After the selection of rubber and plastic sponge finally determined. Rubber and plastic pipe insulation material has low thermal conductivity, a detailed independent bubble structure, no air convection, completely closed cell structure, good thermal insulation effect, the material and water vapor completely isolated. It will not cause physical changes in the environment above 89 yi and below -60 Yi, and the rubber and plastic insulation pipe material is not absorbent, no condensation, long service life, easy to bend, convenient construction, very suitable for the use of this position.

The protective cover is cut in the middle of the pipe with a diameter of 200 mm and a wall thickness of 8 mm. The expansion bolt is effectively fixed on the dust retaining wall. The pipe is protected in the space formed by the protective cover on the wall after being insulated with rubber and plastic sponge.

Due to the narrow foundation pit of the tipper, the working environment of the dry fog controller, its control valve and control line arranged in the foundation pit is extremely harsh, which is not only polluted by water mist and dust, but also damaged by the vibration of the equipment and the impact of coal in the process of overturning. In order to reduce the failure rate of this location, the simple method is to reduce the number of zero parts of dry fog dust suppression equipment in the foundation pit, especially the electronic control system which is greatly affected by water fog, reduce the failure points and enhance the reliability of the equipment. After in-depth and detailed analysis, it is decided to change the control mode of the spray box. In the initial design, each spray box is equipped with a dry mist spray box assembly controller, but now all spray boxes in the foundation pit are controlled by a controller placed on the external wall of the foundation pit, as shown in Figure 2. After the renovation, all electrical control lines and valves are cancelled in the foundation pit internal medicine, greatly reducing the probability of failure. Studies have shown that the change of air pressure is significant among the factors affecting the dust suppression effect of dry fog dust suppression equipment. Under the condition that the water pressure remains unchanged, the atomized particle size becomes smaller with the increase of air pressure. When the air pressure reaches 0.6MPa, more than 50% atomized particle diameter will be less than 10 μm. After atomization, particles will collide with each other and condense together. At this time, a small part of particles will become larger in diameter, and the proportion of these larger particles will gradually decrease with the increase of air pressure. Once the pressure exceeds a certain value, the proportion of larger particles will increase with the increase of air pressure.

Figure 2 Process of dry fog system after transformation

According to the research results, the air pressure entering the spray box should be stable after changing the control mode of the spray box. The spray duration does not change, and the total amount of compressed air consumed by each spray cycle does not change. The designed air storage tank is sufficient to supply the compressed air needed for spray, and the pressure gauge of the system gas path indicates that the pressure of spray cycle does not fluctuate. After the transformation, the pipe path from the dry fog controller to the spray box becomes longer. It is necessary to check the time for the compressed air to reach the end fog box, so as to ensure that the compressed air in each spray box can arrive instantaneously and the spray effect at the beginning of the working cycle. The treatment point parameters of micron level dry fog dust suppression system are shown in Table 1.

The pressure loss along the road can be ignored, so the average pressure can be calculated in this checking calculation. When achieved with considerable accuracy. In the standard state or free state (0 ℃, 0.1MPa), the gas flow calculation formula is as follows.

According to Formula (1), the distance from the dry fog controller to the long position of the spray pipeline is 10m. It can be seen that the time required for the resume pressure of the gas pipeline after the transformation is 0.16s, and the rapid response can be ignored.

4 Effect

This transformation solves the problem of heat preservation and heat trace damage of the layout pipeline in the tipper dry fog dust suppression system in the tilting foundation pit, prevents the failure of the electrical control system in the foundation pit, simplifies the dry fog dust suppression control system in the foundation pit, reduces the downtime and maintenance time, and improves the reliability of the dry fog dust suppression system. At the same time, the labor intensity of maintenance personnel is reduced, the risk factors of falling from high altitude caused by the failure of the dry fog dust suppression system in the coal grate maintenance system is reduced, and the coefficient of maintenance personnel is improved.