Due to the different nature of the material conveyed by the belt conveyor, the amount of material adhesion on the belt surface and the difficulty of cleaning are also very different, so the cleaning methods used are also different. If the sweeper is not designed and installed in combination with the characteristics of the material, it will not only fail to achieve the expected cleaning effect, but also easily cause damage to the belt surface and shorten the service life of the belt. My company since2019In view of the belt material problem of belt conveyor, it cooperated with many sweeper manufacturers to carry out on-the-spot trial effect evaluation, and at the same time carried out many discussions and adjustment tests in combination with the actual production, finally solving the problem of incomplete belt surface cleaning of belt conveyor.

1 belt conveyor belt surface material causes

Most of the materials transported by the belt conveyor in cement enterprises are clinker, cement, coal-fired slag powder, coal gangue, limestone, coal, clay, desulfurization gypsum and other raw materials. The reason why the surface materials cannot be completely separated is that the moisture content of coal-fired slag powder, clinker, cement and other materials is low (≤0.5%), the dust particles adsorbed on the surface of the belt are mainly fine powder, the dust particles are very small, the surface energy is very large, resulting in electrostatic adsorption; Second, the moisture content of coal, clay, desulfurization gypsum and other materials is in10%~17%Between, due to the surface tension of water, the particles have a cohesive force, so it is easier to adhere to the belt surface;1%~4%In addition to the adsorption of fine powder dust, a small amount of powdery materials are adhered to the belt surface due to moisture content. Fourth, because the belt surface of the belt conveyor is uneven, powdery materials and particles are mixed between the gaps of the belt surface.

2 The classification and working principle of the sweeper

The function of the sweeper is mainly to effectively clean the belt surface adhesion or materials of the belt conveyor, which can prevent the adhesion from the package corrosion of the roller, reduce the environmental pollution caused by the random shedding of the belt surface adhesion, and prevent accidents. Common sweeper mainly has the following several. Scraper sweeper:①Polyurethane sweeper, automatic tension alloy sweeper, scraper sweeper, etc;②Roller brush sweeper: electric roller brush sweeper, brush sweeper, rotary sweeper;③Air-swept sweeper: compressed air purging, blower purging, etc.

The working principle of the scraper sweeper is that the working surface of the scraper is close to the load surface of the conveyor belt to clean and unload the materials bonded on the conveyor belt. It has a good cleaning effect on the material adhered to the belt surface due to high moisture content.

The working principle of the roller brush sweeper is mainly that the brush tip is in slight contact with the belt surface, and the rotation direction of the nylon brush is opposite to the running direction of the return conveyor belt, so as to brush the fine particles of powdery materials stuck on the belt surface to achieve the purpose of cleaning. It has a good cleaning effect on powdery materials with small moisture content.

The working principle of the air-swept sweeper is mainly to rely on a certain wind pressure of the gas to purge the belt surface to achieve the purpose of cleaning the belt surface. It has a good cleaning effect on powdery materials or fine powders with serious surface damage and small moisture content.

3 Current status of cleaning effect in the operation of belt conveyor

The main materials conveyed by the belt conveyor of our company are: clinker, limestone, coal gangue, coal-fired slag powder, desulfurization gypsum, etc. The quality of each material is shown in the table.1The blanking area on the belt conveyor is shown in the figure.1The installation position of the cleaner is shown in the figure.2.

Table1Quality of each material (P·O 42.5Cement production batching)

From Figure1and figure2It can be seen that the desulfurization gypsum first falls into the belt, contacts with the belt surface, and then is limestone, coal gangue and coal slag mixture, clinker. In other words, materials with different moisture and particle sizes are in contact with the belt.

Figure1Blanking area of material on belt conveyor

Figure2Installation and arrangement of belt conveyor sweeper before reconstruction

In view of the problem that the desulfurization gypsum with high moisture content is the first to contact the belt, and it is also the most difficult to clean the surface attachments, the measures we have taken are: the first stage uses polyurethane sweeper and scraper sweeper to clean, and the cleaning effect can be achieved.40%~50%However, the desired goal was not achieved. In order to improve the cleaning effect, the contact surface between the sweeper and the belt is increased, the pressure of the sweeper on the belt surface is increased, and the sweeping force is improved. However, after adjustment, the wear of the sweeper is obviously accelerated, especially the groove is formed on the contact surface, and the cleaning effect is only maintained.4 dbegan to decline. Material skinning begins in the center area of the belt face. In the second stage, in view of the problems existing in the first stage, the contact pressure of polyurethane sweeper, scraper sweeper and belt surface is reduced, and a roller brush sweeper is added for cleaning, and the cleaning effect can be achieved.60%~70%. However, there is a common problem in the first stage and the second stage, that is, the angle of the receiving plate is too slow, which is lower than the repose angle of the material accumulation, and the material of the receiving plate is steel plate, the surface is rough, and the friction coefficient is large, resulting in the increase of the material cleaned by the sweeper.ADistrict andBThe area is silted up, in which the rolling brush sweeper runs about.8 hAfter that, the materials cleaned down are in.BAfter the area is silted up, it can contact the roller brush, causing the roller brush to clean the belt while taking up the silted materials, greatly reducing the cleaning effect.

4 Analysis of the causes of poor cleaning effect in the operation of belt conveyor

(12) The polyurethane cleaner can effectively remove the desulfurized gypsum adhered to the belt surface and the material particles mixed in the gap of the belt surface. The greater the contact pressure, the better the cleaning effect. However, the greater the pressure, the greater the damage to the belt joint. At the same time, the sliding friction resistance increases after the pressure increases, the sweeper wears faster, and the cleaning effect deteriorates as the wear degree of the sweeper increases. Secondly, the cleaning effect of polyurethane cleaner on fine powder dust particles is not obvious.

(22) The working principle and function of scraper sweeper and polyurethane sweeper are basically the same, and the cleaning effect on high moisture adhesion materials is good, but the cleaning effect on fine powder dust particles is not obvious. At the same time, due to the close distance between the scraper sweeper and the receiving plate, the cleaning materials are accumulated. If the sweeper is not cleaned in time, the sweeper will be buried by the materials, the belt surface will contact the materials twice, and the cleaning effect will be greatly reduced.

(32) The roller brush sweeper moves relative to the belt, and the roller brush rotates to clean the belt surface, and has a good cleaning effect on dust materials with low moisture adhered to the belt surface. Although the cleaning effect on fine powder dust particles and low moisture dust materials is better than that of the scraper sweeper, its cleaning effect still cannot achieve the expected purpose. At the same time, the distance between the roller brush cleaner and the receiving plate is relatively close. If the materials are not cleaned in time after being deposited during operation, the deposited materials will directly wrap the roller brush, causing the roller brush to fail and completely lose its cleaning effect.

5 Combination Selection of Belt Conveyor Sweeper and Transformation Ideas of Material Plate

In order to fully understand the cleaning effect of the sweeper, the following tests and data collection were carried out with the batching belt of our company as an example.800 mm, the effective contact width of the material is about700 mm, the belt speed of the belt conveyor is1.25 m/s. In the absence of sweeper cleaning, the bandwidth800 mmLength1 000mmThe band surface in the range (S=0.8 m22) Collect attached materials and dust, approx.27 g.

After using a single cleaner, the materials and dust attached to the belt surface are collected (S=0.8 m2) The total weight within the scope, compare the use effect of each cleaner, and the effect comparison is shown in the table.2.

Table2 Use effect data of each cleaner

by table2It can be seen that in view of the current situation of the belt conveyor of our company, if the above sweeper is used alone, the effect is difficult to achieve.60%Above, combined with the existing problems at this stage, it is decided after demonstration that the combination selection and application should be carried out in combination with the different characteristics of the materials, the different types of functions and advantages and disadvantages of the sweeper. At the same time, the connecting plate is reformed to make the inclination angle of the connecting plate greater than the repose angle of material accumulation, and then the surface of the connecting plate is treated to reduce the friction coefficient.

In view of the above analysis, we have re-selected, designed and assembled the sweeper, and modified the receiving plate, as shown in the figure.3shown. Makes the sweeping effect nearly95%Further clean production has been achieved. Among them, the independent design adds a high-pressure air curtain cleaner to clean the fine powder back, avoiding the use of compressed air to clean the belt surface by some companies, resulting in an increase in the load of the air compressor, an increase in power consumption and a certain impact on the stability of the grinding system.

Figure3Combined Installation of Sweeper of Belt Conveyor and Transformation Layout of Material Plate

(1) In view of the use effect and characteristics of polyurethane sweeper and scraper sweeper, we have reduced the contact pressure between polyurethane sweeper and scraper sweeper and belt surface on the original basis: first, to prolong the service life and maintenance time of the sweeper; The second is to reduce damage to belt joints and belt surfaces. In order to make up for the problem of poor cleaning effect caused by reducing the pressure, an automatic tension alloy sweeper is added between the two. The contact surface of the cleaner is made of alloy material, which effectively prolongs the use time, and maintains a certain pressure range and upper and lower elastic movable space between the contact surface and the belt surface through the pressure spring, which effectively avoids and reduces the damage to the belt joint. This3The scraper type cleaner can effectively remove the adhesion of the belt surface.65%~70%of material.

(23) Replace the original roller brush cleaner with an electric roller brush cleaner to increase the rotation speed of the electric roller brush and improve the cleaning force of the brush on the belt surface. The high-speed movement of the brush can be by the scraper pressure adhesion on the surface of the fine powder to clean and peel off and break loose, so that the fine powder material and the surface of the contact energy is reduced, and further improve the cleaning effect.80%~85%.

(32) After cleaning by the electric roller brush cleaner, the residual fine powder, a small amount of water-containing adhesive materials and the fine powder in the gap of the belt surface are not completely removed, so as to further remove these materials. Our company has independently designed a high-pressure air curtain cleaner to carry out comprehensive purging of the belt surface. After purging, the cleanliness of the belt surface increases greatly and the cleaning effect reaches95%Above.

(4) In order to solve the problem that the cleaned material deposition affects the use effect of the cleaner, the angle of the receiving plate is adjusted in combination with the space position on site. The angle of the receiving plate is determined28°Adjust40°~45°, make its angle close to the natural repose angle of the material, and at the same time, a polytetrafluoroethylene plate is laid on the surface of the receiving plate to reduce the friction coefficient of the plate surface, so that the cleaned material can directly slide down into the blanking port.

6 Effect of application

For the cleaning of the return belt surface of the belt conveyor, the cleaner should be selected according to the characteristics of the materials conveyed by the belt. In production, the most difficult thing to completely remove is the fine powder attachment containing moisture. After three scraper sweepers clean a large amount of attached materials and dust on the belt surface, the electric roller brush and high-pressure air curtain are used together to remove the remaining fine powder attachment on the belt surface, which can greatly improve the cleaning production effect and realize cleaning. At the same time, it is also very important to reduce the impact of the removal of materials and dust deposition on the cleaning, and should be considered in the process of installation and transformation. Through the above transformation, the staff cleaning operation time is reduced from once per shift to once per week.

7 Conclusion

This paper introduces a series of measures such as the selection and use of sweepers and the transformation of the feeding port in order to achieve clean production and solve the problem of belt conveyor return belt surface cleaning. It basically solves the environmental pollution caused by incomplete cleaning of the return belt surface, and also greatly reduces the labor intensity of employees. Later with the development of society, belt conveyor return with surface cleaning to achieve“Zero”Residue is an inevitable trend, and the diversification of cleaners and the application of new cleaning technologies will be new research directions.