Comparison of practical application of pulse bag dust removal system VS vacuum vacuum cleaning system

Dust is one of the ten major hazards of China's key prevention and control. It is listed in the first category of the Classification of Occupational Disease Hazard Factors issued by the Ministry of Health. It is an important occupational hazard that pollutes the working environment and harms the health of workers. factor. All dust particles are harmful to the body, and different characteristics of productive dust may cause damage to different parts and degrees of the body. Workers work in dusty environments for a long time, and inhalation of dust in the lungs can cause a variety of occupational lung diseases, the most harmful of which is pneumoconiosis. An important measure to control the dust hazard is to adopt a ventilation and dust collection facility to control dust emission to reduce the concentration of dust in the workplace air. To this end, designing and installing an effective dust collection system is an important measure in controlling dust hazards and environmental management. This paper introduces the respective application characteristics of the two dust collection systems in environmental management, and discusses the system design of the two dust collection systems in combination with engineering examples.

1 pulse bag dust removal system

The dust removal system generally consists of a gas collection vacuum hood, an intake pipe and its accessories, a dust removal device , an ash discharge device, a fan, an exhaust stack, and an electric control device. The utility model utilizes the power generated by the fan to clean the dust-containing gas from the dust source into the dust removing device through the exhaust pipe, and the purified gas is discharged through the exhaust chimney, and the recovered dust is collectively discharged by the ash discharging device and returned to the process flow.

Table 1 common dust collector types, scope of application and performance

As a high-efficiency dust removal device, the bag filter is characterized in that the dust is collected from the dust-containing gas by using a porous bag-shaped filter element, and the dust removal efficiency of the fine dust can reach 99% or more. See Table 1 for details, and It is highly adaptable due to the properties of specific resistance and the like, and satisfactory working results can be obtained under conditions of high or low dust concentration. In addition, its various specifications, flexible application, easy to recover dry materials, no sludge treatment wastewater pollution and other issues.

The key point of the bag type dust collector is the cleaning. The cleaning effect determines the success or failure of the bag filter and the whole system to a large extent. The pulse blowing method has the strongest cleaning ability and the best effect, allowing high The pulsed bag filter featuring this cleaning method has become the mainstream of choice for dust removal equipment in recent years. The working principle of the pulse bag type dust removal system is: after the dust-containing gas enters the pulse bag type dust remover, the air flow speed decreases, the coarse particles in the dust directly precipitate to the ash hopper, the fine dust is filtered through the filter bag with the air flow, and the dust adheres to the filter bag. On the outside, as the accumulation of dust accumulates, the pressure difference between the inside and outside of the dust filter bag gradually increases. When the pressure difference reaches the set value, the pulse valve diaphragm automatically opens, the pulsed air is sprayed into the filter bag through the nozzle, and the filter bag expands. Therefore, the dust adhering to the filter bag is detached to achieve the effect of dust removal, and the purified gas satisfying the discharge requirement can be directly discharged into the atmosphere through the fan.

In the design of the dust removal system, three important steps must be grasped: 1) the sealing of the dust source point, 2) the reasonable determination of the design air volume of the system, and 3) the setting of the vacuum hood, which determines the size of the entire dust removal system. Important conditions for energy efficiency, investment size, operating costs, and dust collection. The following is an example of an engineering example to analyze the important role of these three links in the design of the dust removal system.

1.1 Project Introduction

After an item phosphate rock crushing transported by the belt conveyor to the next process and then finely sieved, since the transport belt there is a high drop inevitably caused by flying dust escape, thereby setting the pulse bag dust removal system The system diagram is shown in Figure 1.

1.2 Dust removal system analysis

It can be seen from Fig. 1 that the dust removal system is relatively simple, and the dust is collected into the pulse bag type dust collector by means of a closed dust cover at the transfer point of the belt conveyor, and filtered by the filter bag to satisfy the purification. The discharge standard gas is led to the conical hood directly into the atmosphere by the fan, and the dust attached to the filter bag is pulsed and then dropped into the ash bucket to the belt conveyor to the next process, and the mineral is recycled.

In the dust removal system, the first thing that needs to be the cooperation of the craftsmanship is to take closed measures against the dust escape points, and to close the dust generated by the dust source points in a small range, which is convenient for organized and effective dust collection. The ratio of the gas to the dust removal system is increased, and the scale of the dust removal system is reduced to some extent. The sealing of the dust source point is very important for the size of the entire dust removal system, dust removal effect and operational economy. The conventional sealing method is as shown in Fig. 2. By setting a certain length of the guide groove on the belt conveyor, the dust curtain is installed at the end to seal the dust in a partial range.

Secondly, in the design of the dust removal system, the design air volume of the system must be reasonably determined, so that the design of the entire dust removal system is economical and reasonable. Under the premise of ensuring effective control of the dust escape point, do not arbitrarily enlarge the dust removal air volume, otherwise it will cause dust removal. The system is huge, the pipeline size is large, the energy consumption is increased, the cost and operating cost are increased, and the burden of the dust collector is increased. The design of the dust removal system consists of two parts, one is the amount of air brought in by the material, and the other is the amount of air that is inhaled in a tightly closed vacuum hood. The design manual [4] gives detailed description of the sealing cover and exhaust air volume of common production equipment. The dust removal system can be designed and implemented. The dust removal design air volume of this project is based on the blanking height difference and the inclination angle of the chute in the actual process flow. It is calculated and determined in conjunction with the design manual, and then corrected according to the bandwidth of the belt conveyor. Generally, the minimum wind speed of the dust removal duct can be determined by the characteristics of the dust. After the air volume of the system is determined, the diameter of the air duct can be calculated according to the wind speed of the dust removal duct. Here, it should be noted that the selection of the wind speed in the duct should be considered comprehensively. The effect and economy, the small wind speed will cause the diameter of the air duct to be too large, the dust is easy to deposit and block the pipeline. The large wind speed will increase the resistance along the path and the local resistance, the energy consumption of the fan increases, and the dust wears on the pipe wall. Increased and shortened pipeline life. Generally for mineral dust, the wind speed in the pipe before the precipitator is preferably 16m/s to 18m/s, of course, it must be greater than the specified minimum wind speed, and the wind speed after the dust collector is 8m/s to 10m/s. Finally, calculate the system loss of the most unfavorable loop, adjust the pipe diameter of the branch pipe, control the unbalanced pressure difference between the branch pipes after 10%, and set the ventilation butterfly valve at the appropriate position of the branch pipe for the system balance adjustment, and then according to the system loss The fan is properly selected.

Finally, the design of the dust hood must be emphasized in the design of the dust removal system. If the design of the dust hood is reasonable, the use of a small amount of air can effectively control the escape of the dust. Conversely, a large amount of air is not necessarily achieved. The following basic principles must be followed for the installation of the dust hood: 1) The setting of the dust hood should be determined according to the principle of preventing the dust from escaping to the surrounding environment. The suction of the dust hood should utilize the movement of the polluted air flow as much as possible. 2) The dust hood should not be placed in the dusty or splash zone of the airflow to avoid inhaling a large amount of powder. 3) The dust hood needs a certain space to reduce the positive pressure by the buffer airflow, and the shrinkage angle should not be greater than 60° when connecting with the nozzle. 4) The dust hood should surround the dust source as much as possible to limit the diffusion of dust to a minimum range, which is convenient for collecting dust and reducing the amount of air to some extent. 5) The suction hood is designed to be simple in structure, easy to install, and does not affect process operation and maintenance management.

In the design of the pulse bag type dust removal system, it is necessary to point out that the dust removal effect is not to consider how much dust is collected, but to control the dust to escape, forming a certain negative pressure at the dust source point, which will inevitably dust. Unified collection of recycling, with the goal of protecting the working environment and controlling dust hazards. Therefore, in the design of the dust removal system, it is necessary to closely follow this principle, on the basis of the dust source point sealing, reasonably determine the design air volume of the system, follow the setting principle of the vacuum hood, and avoid the fan and pipeline caused by the excessive air volume. And the dust removal equipment is huge, it is also possible to take away the raw materials that should not be taken away, and increase the burden of the dust collector.

The following describes another dust collection system---vacuum vacuum suction system, which is different from the pulse bag type dust removal system, which is a dust collection system that collects dust or materials as much as possible and reduces the manual cleaning intensity.

2 vacuum vacuum cleaning system

Vacuum vacuum suction system is a facility that uses vacuum suction principle to collect dust and materials scattered on the ground, floor, equipment and pipelines, and then transfer and process. The system generally consists of a suction nozzle, a suction pipe system, a cyclone separator, a bag filter, a vacuum pump and its valve control equipment [5]. Workers only need to insert the suction hose into the vacuum inlet to start the system. The dust and impurities in the workshop will pass through the dust collection pipe and be sent to the vacuum cleaner away from the workshop. The vacuum system is equipped with a variety of suction ports, which can quickly clean the places where traditional cleaning methods such as deep platforms and deep trenches are difficult to clean. It is a new cleaning method that replaces hydraulic ash and manual cleaning.

The characteristics of the vacuum vacuum system are:

1) The main unit is separated from the cleaning area to eliminate the noise pollution of the conventional vacuum cleaner.

2) Dust or material of large and small particles can be sucked out in the factory building, and directly enter the dust collecting bin of the main machine through the dust suction pipe to prevent secondary pollution.

3) When using, just insert the vacuum hose into the vacuum socket, no need to drag the heavy host to the back and forth. The main machine adopts super vacuum suction to quickly absorb dust and materials, which is convenient, efficient and greatly reduces the labor intensity of workers. .

The design of vacuum vacuum suction system should pay attention to the following aspects: firstly determine the capacity of the vacuum cleaner, which can be determined according to the suction capacity required for the farthest point of the dust suction. Generally, it can work 2 to 5 nozzles at the same time. To design, the air volume of each nozzle is calculated according to 150~300m3/h [5]; secondly, the air flow rate in the pipeline is determined, and the speed is too high, which will cause defects such as material crushing, friction loss of pipe fittings and power consumption. However, if the flow rate is too low, it will easily cause material loss and pipeline blockage, which will affect the normal vacuuming work. Refer to Table 2 for the recommended flow rate of common materials. Finally, optimize the design of the suction pipe network to reduce the suction capacity. Pipe network resistance loss, saving energy and operating costs. The following is a detailed analysis in combination with an engineering example.

2.1 Project Introduction

During the transportation process, the ore is scattered and the materials are scattered. It falls on the floors, floors and equipment of the trestle, transfer station and belt gallery. In order to clean the scattered dust and materials, a vacuum vacuum system is installed. A suction port is provided at intervals along the belt corridor, and a branch interface is left on the pipeline for connecting various nozzles during cleaning. The system diagram is shown in Figure 3, and the pipeline connection details are shown in Figure 4.

2.2 Vacuum vacuum suction system analysis

In the design of vacuum vacuum cleaning system, the most important part is the optimization design of the suction pipe network. Due to the particularity of the flow of materials in the pipeline, the layout and connection of the piping system also has its own characteristics, and the pipe must be fully considered. The road is sealed, does not cause blockage, reduces wear, reduces drag, and is easy to replace. This is strictly different from the design of the pipeline of the pulse bag type dust removal system. The following points must be noted in the design [5]:

1) As can be seen from the system diagram, the vacuum suction pipe is composed of a vertical main pipe, a horizontal branch pipe and a suction pipe. When the branch pipe is taken from the main pipe, the branch pipe joint or the Y-shaped joint is used. It is necessary to ensure that the material flow in the branch pipe is at an angle of 15° with the flow direction of the material in the main pipe, and the Y-shaped fork is at an angle of 30°, and the material flow direction and the main pipe in the branch pipe The material flow direction is in the downstream direction.

2) It can be seen from the detailed connection diagram of the pipeline that the connection between the pipeline and the pipeline, the pipe fittings and the pipe fittings, and the pipe and the pipe fittings should be connected by pressing joints, which is not suitable for welding. The nozzle plane is 90° to the centerline of the pipe. After the butt joint is tight, tighten the compression joint. The end of the pipe is connected by a pipe joint and a quick joint, and the port is sealed with a dust plug.

3) In order to ensure that the suction point at the farthest point can be effectively sucked, the resistance loss of the pipe network should be reduced as much as possible. The suction pipe should be arranged as short and straight as possible, and the essential elbow should be 6 to 12 times. Radius of curvature. When the branch pipe is taken from the horizontal pipe, the branch pipe must be taken out from the side or top of the main pipe and not from the bottom.

4) The connection between the hose and the end of the pipe uses a quick joint, and the pipe at the suction end of the pipe is vertically downward so that the hose is attached vertically upwards, thereby ensuring that the material flow from the hose is vertically ascending into the pipe. .

5) When the pipeline system is connected for commissioning, all nodes should be inspected one by one and should not be leaked to ensure the negative pressure inside the pipeline.

3 conclusions

In industrial buildings, it is essential to design and install an effective dust collection system in order to protect the environment and control dust hazards. In this paper, the application characteristics of pulse bag dust removal system and vacuum vacuum cleaning system are introduced. Combined with engineering examples, the system design of two dust collection systems is discussed and the following conclusions are drawn:

1) Pulse bag type dust removal system and vacuum negative pressure vacuum system are two different dust collection systems. When design is selected, the concept should not be confused. The design task should be clearly defined according to the professional conditions of the process. The goal of the pulse bag type dust removal system is to control the dust to escape, form a certain negative pressure at the dust source point, and collect and recycle the unavoidable dust uniformly, not to collect as much dust or material as possible; vacuum negative pressure The goal of the vacuum system is to collect as much dust or material as possible and reduce the intensity of manual cleaning.

2) In the design of the pulse bag type dust removal system, three important steps must be grasped: the sealing of the dust source point, the reasonable design of the system design air volume and the dust cover setting, and the effective control of the dust escape point. Under the premise, it is imperative to increase the design air volume or increase the wind speed of the vacuum hood, so as to avoid inhaling materials and increase the burden of the dust collector, resulting in huge fan, pipeline and dust removal equipment and increased energy consumption.

3) In the vacuum vacuum cleaning system design, the dust suction pipe network should be optimized, tightly around the design points, minimize the pipe network resistance loss, and ensure that the suction point at the farthest point can effectively absorb.

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