China’s Large Scale Coal Prepration Plant

 1. China’s Coal Preparation Industry:

China is the largest coal producer in the world. In 2011, the coal production in China is 3.5 billion ton, accounting for approximately 49 percent of global coal production. The increase in raw coal production also promotes technology and capacity in China’s coal preparation industry. At present, over 40 extra-large scale coal preparation plants ( each plant has capacity of more than 10.00Mtpa ) are in operation in China, the largest one is 32.50Mtpa. Heavy medium separation are widely used in new built coal preparation, the washing limit for thermal coal feed lower and lower, the equipment selection tends larger which brings the whole washing system simplified, the local equipment developed and manufactured are more and more used. By discussing designs of several typical thermal coal preparation plants and coking coal preparation plants in China, this thesis introduces the current design of China’s extra-large coal preparation plants, and sums up the prevailing design features and trends of extra-large coal preparation plants.

2.1 Pingshuo Anjialing Coal Preparation Plant

Pingshuo Anjialing Coal Preparation Plant was the first modern extra-large coal preparation plant designed by China. Design capacity reaches 15.00 Mtpa and practical capacity is 25.00 Mtpa, which was the largest capacity at that time. Major mechanical and electrical equipment was imported from technology-advanced countries.

Two process systems exist in the Anjialing Coal Preparation Plant; the export coal preparation system and the domestic coal preparation system.

-          The export coal system applies a process of classification and primary & secondary heavy medium separation: lump coal of 150-13 mm is fed to a heavy medium bath separator for primary and secondary separation, and fine coal of 13-0.15 mm is fed to a heavy medium cyclone for primary and secondary separation.

-          The domestic coal system applies a process of classification and heavy medium separation: lump coal of 150-13 mm is fed to a heavy medium bath separator for separation, and fine coal of 13-0.15 mm is fed to a heavy medium cyclone for separation.

-          Slurry from the two systems is recovered by hyperbaric filter.

Since the Anjialing Coal Preparation Plant was put into production, its performance has been superb with all products qualified in quality and quantity and sound technical and financial indicators. It was awarded both first class (Ministry level) and silver prizes (national level).

With the successful design of the Anjialing coal preparation plant, China’s engineering of coal preparation plants reached the world’s advanced level, along with the promotion of efficiency and size.

 

 

2.2 Pingshuo 1# Mine Coal Preparation Plant and 2# Mine Coal Preparation Plant

The design capacity of the Pingshuo 1# Mine Coal Preparation Plant and the 2# Mine Coal Preparation Plant is 10.00 Mtpa,and capacities of each of these plants achieve more than 17.00 Mtpa. Classification and heavy medium separation processes are applied as follows:

- Lump coal of 150-13 mm is fed to a heavy medium bath for separation, fine coal of 13-0.5 mm is fed to a heavy medium cyclone for separation; slurry is recovered by hyperbaric filter. Major mechanical and electrical equipment was imported from technology-advanced countries.

Considering that both CPPs have the same design capacity, raw coal property and product structure, all-purpose design was successfully applied to the main buildings of both the 1# Mine Coal Preparation Plant and the 2# Mine Coal Preparation Plant. This was the first application of all-purpose design in an extra-large coal preparation plant in China – another landmark in the wake of successful application of all-purpose design in coal preparation plants of 1.80 MtpaMt/a in capacity.

In recent years, performance indices of the two CPPs remain at world advanced levels:

- Average Ep value of heavy medium bath separator is 0.02.

- Average Ep value of heavy medium cyclone is 0.035.

- Medium consumption per ton raw coal is respectively 0.45 kg and 0.33 kg.

- Water consumption per ton raw coal is respectively 0.04m³and 0.03m³.

- Power consumption per ton raw coal is respectively 3.27 kW·h and 3.55 kW·h/t.

The Pingshuo 1# Mine Coal Preparation Plant and the 2# Mine Coal Preparation Plant were awarded first class prizes (Ministry level) and are now being considered for golden prizes (national level).

 

2.3 Pingshuo Muguajie Coal Preparation Plant

The first-stage project (8.00 Mtpa) of Pingshuo Muguajie Coal Preparation Plant was put into production in 2006with the second-stage project (17.00  Mtpa) currently under construction. Capacity of the first-stage project in practice reached 10.00 Mtpa, capacity of the second-stage project in practice will reach 22.50 Mtpa and total capacity in practice will reach 32.50 Mtpa, which will be the largest coal preparation plant in China.

The first-stage project of Muguajie CPP applies a process of classification and heavy medium separation: lump coal of 150-13 mm is fed to a heavy-medium bath separator for separation, fine coal of 13-0.5 mm is fed to a heavy medium cyclone for separation; and the second-stage project applies a process of classification and primary & secondary heavy medium separation: lump coal of 150-13 mm is fed to a heavy-medium bath separator for primary & secondary separation, fine coal of 13-0.5 mm is fed to a heavy medium cyclone for primary & secondary separation. Slurry of the whole plant is recovered by hyperbaric filter. Major mechanical and electrical equipment was imported from technology-advanced countries.

The second-stage project of Muguajie CPP applies three separation systems with a primary heavy medium bath separator width of 7925 mm and a primary heavy medium cyclone diameter of 1400. The unit system has a capacity of 7.50-8.00 Mtpa; the largest unit capacity of coal preparation plants in the world.

 

3. TYPICAL EX-LARGE COKING COAL PREPARATION PLANTS IN THE HUAIBEI Mining AREA

3.1 Xinwen Longgu Coal Preparation Plant

Longgu Coal Preparation Plant, located in the Juye Coalfield, belongs to Xinwen Mining Group. It is an extra-large coking coal preparation plant (10 Mtpa in capacity) which has been awarded several national, provincial and ministry-level prizes in engineering excellence. It applies the following processes: Raw coal is classified at 50 mm, the classified raw coal of 300-50 mm is separated by a moving bed jig then the cleaned coal is crushed into -50 mm and fixed with the classified raw coal of -50 mm. The mixed coal of 50-0.5 mm is fed to two-product HM cyclone for primary and secondary separation, and the mixed coal of -0.5 mm is fed to a flotation cell for separation. The floated coal is dewatered by hyperbaric filter and the flotation tailings are recovered by filter press after thickening. All critical equipment is imported from reputable foreign suppliers.

 

3.2 Huaibei Linhuan Coal Preparation Plant

Huaibei Linhuan Coal Preparation Plant is one of the largest coking coal preparation plants in the world. The total design capacity is 12.50 Mtpa; the first-stage project 4.5 Mtpa and the second-stage project 8.00 Mtpa. Major mechanical and electrical equipment was imported from technology-advanced countries.

The raw coal feed of the Linhuan Coal Preparation Plant comes from 7 mines in the Huaibei mine area comprising fat coal, primary coking coal, 1/3 coking coal, gas coal and meager lean coal. The process applies heavy medium separation: lump coal of 50-0.5 mm is fed to a non-pressure 3-product heavy medium cyclone for separation, course slurry coal is recovered by heavy medium separation, and slurry is recovered by floatation separation after desliming and thickening. The floated coal is dewatered by hyperbaric filter and tailings are dewatered by filter press after thickening. The entire process is operated in a closed washing water cycle. Meanwhile, the cleaned coal product with an ash content of less than 11% and moisture less than 8.50% is used as raw material of the coking plant. The side product with Qnet,ar=12.54MJ/kg (3000kcal/kg) as low heat value fuel is used for power generation.

Currently, the practical capacity of Linhuan CPP reaches 15.0 Mtpa with excellent performance indicators, i.e. recovery efficiency ≥95%, medium loss for per tonne of raw coal ≤1.5 kg and water consumption for per tonne of raw coal ≤0.1m³per ton.

 

3.3 Huaibei Wobei Coal Preparation Plant

The Huaibei Wobei Coal Preparation Plant is located in Woyang mine area, Huaibei, China. The raw coal feed is mainly from the coal mines of Wobei, Liudian, Huagou, Huagouxi, Zhanglou, Xuguanglou and Yuaner etc. comprising primary coking coal, fat coal and 1/3 coking coal. Wobei Coal Preparation Plant applies processes the same as that of the Linhuan Coal Preparation Plant: lump coal of 50-0.5 mm is fed to non-pressure 3-product heavy medium cyclone for separation, course slurry coal is recovered by heavy medium separation, and slurry is recovered by floatation separation after desliming and thickening. The floated coal is dewatered by hyperbaric filter and tailings are dewatered by filter press after thickening. The entire process is operated in a closed washing water cycle. Meanwhile, the cleaned coal product with an ash content of less than 11% and moisture less than 10.00% is used as raw material of the coking plant, and the washed mix coal with an ash content of less than 35.00% and moisture less than 10.00% is used for power generation.

The design capacity of the Wobei Coal Preparation Plant is 12.00 Mtpa however the system configuration is designed on the basis of 15.00-16.00 Mtpa in capacity. Four independent washing system modules, The capacity of each m module is 3.75-4.00 Mtpa. The project is still under construction and near ready to be put into production. At that stage, Wobei Coal Preparation Plant will become the largest mine-locating coking coal preparation plant in the world.

 

4. CHARACTERISTICS OF EXTRA-LARGE COAL PREPARATION PLANT IN CHINA

4.1 Expansion of Capacity

Along with the continuous development of mining technology and the expanding production of coal mines, the design capacity of coal preparation plants is expanded with mature coal preparation technology and reliable equipment. In the near future, the raw coal treatment capacity for the largest coking coal preparation plant will exceed 15.0 Mtpa and 50.0 Mtpa for the largest steam coal preparation plant.

 

4.2 Wide Application of Heavy Medium Separation

With China’s economic boom, the quality of coal product needs to be improved. On the other hand, with long term mining, the quality of newly-mined raw coal is relatively inferior and to make things worse, raw coal produced in most parts of China is difficult to process. Therefore, as heavy medium technology has become mature and reliable, it has been widely applied. Meanwhile, the jigging process is applied to raw coal with better washability property, and the flotation process is mainly applied to separate slurry of coking coal and PCI coal, and other processes  rationally applied.

Over recent decades, heavy medium process has been unprecedentedly widely applied as it is advantageous in separation efficiency and automation. The newly-built extra-large coal preparation plants mainly apply heavy medium separation. Generally, coking coal preparation plants mainly apply primary & secondary separation by 3-product heavy medium cyclone or 2-product heavy medium cyclone and steam coal preparation plants mainly apply heavy medium bath separator for lump coal separation and heavy medium cyclone for fine coal separation.

 

4.3 Equipment Selection Tends to Larger Size

Upsizing of design capacity relies on upsizing of coal preparation equipment.

Large equipment is prevailing to equip coal preparation plants. Heavy medium cyclones of more than 1.3m in diameter, heavy medium baths of more than 7m in width, jig machines of more than 5m in width, flotation cells of more than 16m³in volume, screens of more than 3.6 min width, centrifuges of more than 1.4m in diameter, hyperbaric filters of 120m² in filtering area, filter presses of more than 450m² in filtering area, thickeners of more than 45m in diameter, magnetite separators of 1.2m in diameter are widely applied in coal preparation plants.

Currently, upsizing of equipment is a trend. The largest HM bath applied in China is 7925 mm in width, the largest screen is 4.9m in width, the largest HM cyclone is 1500 mm in diameter and the largest centrifuge is 1500 mm in diameter.

 

4.4 Unattended Operation with Highly Automatic System

The application of an on-line ash analyzer, a HM density control system, a computer control system accessory management system and an automatic loading system guarantees control of coal product quality and further improves production. The improvement of reliability of electrical components, mechanical parts, hydraulic components and pneumatic components guarantees the automatic level of the coal preparation plant to reduce labor, improve operation safety, reduce production cost, stabilize product quality and promote economic benefit.

The automation system of CPP is an assembly application system based on network and information management. Comprehensive automation systems is the trend for future coal preparation plants.

 

4.5 More Local made Equipment in Extra-large scale CPPs.

 

Presently, complete slurry treatment system is applied in all large and extra-large coal preparation plants in China so that the slurry recovery and process water close circuit can be realized. For slurry with good properties, thickening and press filtering (hyperbaric filtering) are applied. For slurry with inferior properties, two-staged thickening and recovery are applied and water-clarifying thickener and emergency thickener are allied to ensure water is circulated in a close circuit. The recovered slurry coal is mixed with product coal or fed to a thermal power plant as fuel.    

Bunker and closed stockpile are applied for storage of raw coal and product coal of large and extra-large coal preparation plants, and existing open-air coal stockpiles are modified into bunkers or covered, thus coal cannot be seen from outside.

In the recent years, density of dust in the workshop of coal preparation plants has been greatly reduced to improve the occupational environment by applying highly-efficient dedusting systems of negative pressure induction dedusting and atomization dedusting. 

A whole-area washing system has been established along with the construction of coal preparation plants to solve hygiene issues.  

Modularizing, steel structures, steel grating, color plates, daylighting bands and glass curtain walls have been widely applied in the design of coal preparation plants to adopt modern aesthetical features. Landscapes and afforesting also improve the environment.

Environment protection and aesthetical improvement is the trend of design and construction of coal preparation plants.

 

About BHEC:

BHEC is a large-scale consultancy , engineerring design and EPC contractor engaged in coal mine, coal processing, low calorific coal fired power station and coal water fuel plant. In China. BHEC has 1450 full time employees,including 3 design masters of state level, 167 engineers of professor level and nearly 470 for senior engineers and 320 engineers, and has completed 98 general planning of coal filed, 90 more coal preparation plants,coal water fuel plants built on EPC basis, engineering designs for more than 400 mines and more than 550 coal preparation plants,over 80 power plants range from 3MW to 200MW and more than 30 coal water fuel projects. Besides, the company has also made designs for hundreds of projects related to municipal construction, communication and building for civil and industrial uses.

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