Innovative Application of Roller Screening Technology at Zhao Gu Yi Coal Preparation Plant！

Abstract: This article outlines the importance of coal slurry reduction in coal preparation plants and introduces the working principle of the new roller screen. The practical application at the Zhao Gu?Yi Mine coal preparation?plant shows that after the application of the new roller screen, not only has the coal preparation process been improved, achieving the direct use of raw coal as a product and reducing coal slurry, relieving environmental pressure, but also maximizing the production efficiency of the coal preparation?plant.

Keywords: Coal preparation?plant, coal slurry reduction, roller screen, application effect

1. Overview of the Coal preparation?Plant

Zhao Gu Yi Mine coal preparation?plant is an important smokeless coal washing and processing base of Henan Energy and Chemical Group. It started construction in October 2007 and was put into operation on May 10, 2009, with a washing capacity of 3.00 Mt/a. The designed coal preparation?process includes shallow groove sorter for main repreparation?of lump coal, pressure three-product heavy medium cyclone sorter for repreparation?of fine coal with mud removal, spiral sorter and TBS sorter for coarse coal slurry, and concentration and pressure filtration for coal slurry water. The precision of the preparation?process is high, with high yield of clean coal, reliable and flexible system, and strong adaptability to changes in coal quality and product quality. The main products include special-washed medium chunks, No. 2 washed medium chunks, washed small chunks, washed granular coal, washed fine coal, and fine coal. Secondary products include medium coal, coal slurry, and washed small gangue. The chunked clean coal has advantages such as low ash content, low ash fusion temperature, and high calorific value, making it a high-quality raw material for the chemical industry. The ash content of washed fine coal is around 10.00%, mainly used in the metallurgical industry as blast furnace injection coal. The calorific value of fine coal is around 22.99 MJ/kg, making it a high-quality coal for power generation.

In recent years, due to changes in the working face conditions of the mine, the fine particle content and moisture content of the raw coal at Zhao Gu Yi Mine have increased, resulting in difficult screening. In addition, due to limitations in coal preparation process and production capacity, the coal preparation plant at Zhao Gu Yi Mine cannot directly use fine coal as a product after the raw coal is graded. The original coal is directly wet screened, and after the screened material is completely de-mudded through a three-product heavy medium cyclone sorter, the washed fine coal, medium coal, and gangue are mixed again to enter the product bin, resulting in a large amount of coal slurry and an increase in coal slurry production. Furthermore, due to environmental requirements, the coal slurry drying system has been shut down, increasing the difficulty of selling coal slurry and causing the coal slurry to accumulate, severely restricting normal coal preparation plant production. Therefore, while meeting customer needs, how to optimize the product structure and reduce coal slurry has become a key focus of the coal preparation plant's work.

2. Importance of Coal Slurry Reduction

2.1 Compliance with China's Energy and Environmental Protection Policies

Coal slurry reduction conforms to the national requirements of "accelerating the improvement of the technological level of the coal industry, increasing the safe and reliable coal supply capacity, promoting the sustained, healthy, stable, and coordinated development of the coal industry," "enhancing the clean utilization of coal," "energy conservation, emission reduction, environmental protection," and the requirements of sustainable development. It is also an effective means and way to improve the quality of coal products and extend the coal industry chain.

2.2 Product Structure Adjustment to Meet Market Demand

The original design of the coal preparation system cannot directly produce fine coal products. After coal grading, fine coal can only be selected as washed fine coal through a three-product heavy medium cyclone sorter. According to market demand and the company's requirements for product structure adjustment, it is necessary to add a set of fine coal screening system to achieve the goal of product structure adjustment and coal slurry reduction.

2.3 Requirements to Improve Enterprise Economic Benefits

Coal slurry reduction can reduce the amount of coal slurry water in the washing system, independently produce screened fine coal, improve the quality of coal products, increase product diversification, and enhance the economic benefits of enterprises.

3. Analysis of Raw Coal Particle Size Composition

The results of the raw coal screening test at the coal preparation?plant are shown in Table 1. From ?Table 1, it can be seen that the ash content of the raw coal is 43.91%, belonging to high ash content coal. The yield of particle size greater than 50 mm is 20.95%, with an ash content of 68.32%, indicating a high gangue content coal. The yield of lump coal with particle size greater than 25 mm is 35.01%, and the yield of particle sizes 13-10 mm and 10-8 mm is 7.43% and 5.77%, respectively, with low yields in each particle size. The yield of particle size 8-0 mm is 40.69%, with a yield of 25.38% for particle size 3-0 mm, indicating a high yield of powdered coal. The yield of native coal slurry with a size less than 0.5 mm is 17.50%, with an ash content of 52.54%, indicating that the gangue is relatively soft and fragile.

?In the existing production process, due to the fact that all raw coal less than 13 mm enters the washing process, it causes difficulties in the treatment of coal slurry water, resulting in a large amount of coal slurry production, equipment losses, and increased washing costs. Therefore, the coal preparation?plant considers process transformation to add a process step where fine coal is directly used as a product, reducing the amount of native coal slurry entering the coal slurry water system, achieving a reduction in coal slurry production, alleviating environmental pressure, and increasing the economic benefits of the enterprise.

4. Working Principle of the New Roller Screen

The new roller screen consists of multiple sets of rotating screens, each screen shaft is equipped with several screen pieces, and the screen pieces on adjacent screen shafts intersect to form screen holes. Materials smaller than the screen holes pass through the screens during operation, while block-shaped materials larger than the screen holes roll on the screen pieces and are discharged from the outlet. The screening principle is shown in Figure 1. The new rolling screen has a screening mechanism of "dynamic screen holes, self-cleaning of materials," with the advantages of high screening efficiency, high reliability, high environmental protection, and large single-machine processing capacity.

In traditional grading equipment, such as vibrating screen equipment (loose screen, high-amplitude screen, banana screen), rolling screen, compound sinusoidal screen, etc., due to the screening mechanism and structure, there are common problems of low screening efficiency and high failure rate in grading fine powdered coal. The new rolling screen overturns the traditional screening concept, applicable to screening any type of coal, especially coal with high water content, high viscosity, and severe mud, with a high mud removal efficiency. It will become a new generation of efficient screening machine to replace traditional screening equipment.

5. On-Site Application Analysis of the Rolling Screen

5.1 Application

Zhao Gu Yi Mine coal preparation?plant uses a new rolling screen with a length of 8.4 m and a width of 2.2 m to grade and screen raw coal. The screen discs are arranged in a mutually intersecting manner, with the first section using a 8 mm grade and the second section using a 13 mm grade. After the application of the new rolling screen, Zhao Gu Yi Mine achieved direct production of screened fine coal products, solving the problem of the original design where raw coal could only be wet screened, and after the screened material was completely de-mudded through a three-product cyclone sorter, washed fine coal, medium coal, and gangue were mixed again to enter the fine coal bin. It reduces the amount of coal slurry and makes the production system more complete and flexible to meet market demand. The comparison of product yields before and after the application of the new rolling screen is shown in Table 2.

From Table 2, it can be seen that the coal slurry yield after the application of the rolling screen is 17.23%, a decrease of 1.48% compared to before the application; the fine coal yield is 19.90%, an increase of 1.92% compared to before the application; and the gangue yield is 14.71%, a decrease of 0.44% compared to before the application.

5.2 Economic Benefits Analysis

As shown in Table 3, the coal preparation?plant at Zhao Gu Yi Mine had an incoming washed raw coal volume of 1.7711 million tons from May to September, reducing the coal slurry volume by 26,200 tons. The operating income before coal slurry reduction was 977.5909 million yuan, and the operating income after coal slurry reduction was 984.7140 million yuan, resulting in an increased income of 7.1231 million yuan.

6. Conclusion

The application of the new rolling screen at Zhao Gu Yi Mine coal preparation?plant shows that the equipment has high screening efficiency, especially for coal types with high water content, high viscosity, and severe mud. After the application at Zhao Gu Yi Mine coal preparation?plant, it not only improves the washing process, reduces the coal slurry yield, and alleviates environmental pressure but also increases the economic benefits of the coal preparation?plant.

Contact for more: ?

Tiffany Chen

?? ：+86 182 8210 3350

?? ：[email protected]

?? : https://www.hotminingepc.com/