Gypsum mining

China's gypsum deposits are large in scale and good in quality. In 1996, the total output of gypsum in the country reached 28 million tons. There are more than 500 mines distributed in 20 provinces (districts), but only 30 large and medium-sized mines with an annual output of more than 100,000 tons, including 6 with an annual output of 500,000 tons: Yingcheng Gypsum Mine and Shaodong Gypsum Mine, Zhangzhou Gypsum Mine, Pingyi Gypsum Mine, Hualu Gypsum Group (Cangshan), Taiyuan Gypsum Mine. With an annual output of 400,000 tons, there is Nanjing Gypsum Mine. The general situation of gypsum mining in China: First, the reserves are abundant, but the resources are unevenly distributed. The three provinces of Northeast China, Zhejiang, Fujian, Henan, Hainan and other provinces lack gypsum. The transportation problem of supply and marketing has always been a difficult point affecting the development of gypsum industry in many areas; There are many poor ore, rich ore, alabaster and ordinary gypsum, and less fiber gypsum, which affects the development of the construction gypsum products industry to some extent. Third, the level of technical equipment for mining, although the mining level of large and medium-sized mines and other domestic minerals Similar, but many small mines are relatively backward; fourth is the influence of mineral characteristics on mining, fiber gypsum soft and easy to wear, mining and shipping should try not to make it into powder ore and loss, avoid smashing, avoid using strontium ore Equipment, avoiding the use of funnels for ore mining. Alabaster also has problems of wear and tear, such as Taiyuan gypsum mine. The mining face has been transported with ore by electric raft. Because the ore is soft, it often becomes very fine dust and is fascinated by the working surface. After the water was sprinkled, the working surface was muddy due to the muddy nature of the ore, and the machine was later changed. Alabaster is cheaper and slightly harder than fiber gypsum. In terms of wear, there is no requirement for fiber gypsum. The mining of alabaster and ordinary gypsum can be used for trackless mining, using the room-column method and comprehensive method mining, such as Taiyuan gypsum mine, Lingshi gypsum mine; fiber gypsum has been filled with long-walled mining method.

(1) Mining methods and division of mining scale

The mining methods of China's gypsum mines include open pit mining and underground mining, but mainly underground mining. Open-pit mining mines include Ningxia Gantang Gypsum Mine, Gansu Jingtai Gypsum Mine, Qinghai Xining Gypsum Mine, and Sichuan Dawei Gypsum Mine.

(2) Developing transportation

The underground mine transportation method of gypsum mine is determined according to the specific conditions. Yingcheng gypsum mine, four-point mine, Pingyi gypsum mine, Shaodong gypsum mine, etc. are used for shaft development; Yingcheng gypsum mine three-point mine, Tonghua gypsum mine, etc. Pioneering; Nanjing gypsum mine and other joints using vertical shafts and inclined shafts; Taiyuan gypsum mine, Lingshi gypsum mine, etc.

The Lingshi gypsum mine used to develop the Pingshuo well, but it was unsuccessful. Because alabaster and ordinary gypsum are easy to be dusted during the process of ore discharge, and the mud is pinched, it often causes the plugging accident of the chute under the action of water, and the production is not normal; the funnel is discharged and the dust is faint when there is no water. General ventilation measures are also difficult to solve, and the technical and economic effects are not good.

Taiyuan gypsum mine has been developed with flat track and no track, and full trackless mining has been successful. The trackless development, also known as the ramp development, is very popular in foreign countries, and the development of the flat track is a special case. The use of non-track equipment for mining, full trackless mining, Taiyuan gypsum mine is the second example of the Chinese mining industry, both typical and advanced. The favorable conditions for the mine to adopt the trackless mining are as follows: 1 The ore body is buried higher than the ground, which is a gently inclined layer, and the inclination angle is generally 5° to 10°, which is suitable for the transportation of flat rafts and the stratified mining of automobiles in the ore body. 2 The general panel roadway and the mining and cutting roadway are basically built in the mine body. Although the car is transported and the roadway section is large, the amount of ore recovered during the infrastructure construction is also large, which reduces the infrastructure cost of the roadway. 3 Alabaster, ordinary gypsum and its surrounding rock have good stability. The goaf is up to 10m, and the span of the mine is 12~15m. It is long-lasting and allows large-scale trackless equipment. Although the section of the roadway is large (average cross-sectional area is 14m2), the actual statistical support rate is only 8%, and the roadway support rate is small. It is one of the main reasons for the success of the mine using trackless mining. 4 Adopting trackless mining, it can be produced on the edge of the foundation. It can be put into production locally and put into production easily. 5 The production scale is not large, there are not many transportation vehicles in the pit, and the ventilation problem is better solved. Due to the use of trackless mining, the Yuquan mining area has an annual production capacity of 400,000 tons. It was completed in 1993 with a total investment of only 17.5 million yuan. The unit investment per ton of ore is only 43.75 yuan, and the same scale of mines during this period At 100 yuan or more. Although there are still some imperfections, this method of development is applicable to such gypsum deposits.

(3) Mining process

The mining process of gypsum mine is divided into two categories: one is the mining of fiber gypsum mine; the other is the mining of alabaster, ordinary gypsum mine and anhydrite mine. Due to the differences in the physical and mechanical properties of ore and surrounding rock, the two types of gypsum mines have great differences in mining processes.

The hardness of fiber gypsum is small, and its rock solidity coefficient is f=1.2 for parallel fibers and f=1.5 for vertical fibers, and it is brittle and easily becomes powdery or lost. Due to the high price of ore, the main fiber gypsum mines in China use long-walled filling and mining methods. The blastholes of the mining ore mining shall not be placed on the fiber gypsum belt. The rock cutting machine shall not be grooved in the fiber gypsum belt. After the mine falls, the stone is manually selected on the working surface, the meteorite is filled in the goaf, and the ore is loaded into the mine car. Figure 1 shows the longwall selection filling mining method adopted by Yingcheng Gypsum Mine along the trend. In the six communities, the cutting machine grooving, eye blasting, filling, loading and transportation, and other processes are carried out in turn, and the work efficiency of the workers on the working surface is 1.08 t/(work • class). The production capacity of the ore block is 150-220t/d.

The alabaster mine, ordinary gypsum mine and anhydrite mine mining process are similar. Taking the Taiyuan gypsum mine as an example, the ore and surrounding rock are dense and stable. The toughness coefficient of the ore is f=3, and some exposed areas of the goaf are up to 1,500 m2. The multi-layered ore body has a total thickness of 4 to 13 m and is subjected to the room-pillar method (general room width of 8 to 12 m) and comprehensive mining. Gypsum mine rock drilling work is easy, the mine amount of a class of mining is only 2h rock drilling time, but the explosive consumption is large, generally 0.34kg / t. The goaf should be forced to ceiling. Both the Nanjing Gypsum Mine and the Dingyuan Gypsum Mine use the room-column method, but they have some characteristics in combination with the occurrence of the ore body. The Tonghua gypsum mine adopts a comprehensive method.

Trackless mining requires a high level of ventilation. In order to control the concentration of harmful gases in the pit, comprehensive measures are adopted: the exhaust gas of the diesel equipment should be purified; the ventilation should be diluted to dilute; when the output or output is large, the mining schedule should be increased to increase the mining time; the diesel front loading machine cannot enter the pit because It is always in an idle state and has a high concentration of harmful gases. Mine safety regulations in the Ministry of metallurgical industry equipment required pit diesel power unit required air volume index 4m3 / (kW • min). However, the domestic diesel dump truck engines are all direct-injected, and air volume is required to be increased according to US standards. The ventilation pit of Taiyuan Gypsum Mine uses two 4-72-11NO20B centrifugal fans to pump out in parallel to increase the air volume.

(4) Common technical equipment

The technical equipment for underground mining of gypsum mines is mainly for lifting, transportation, gas, ventilation, drainage and mining equipment, rock drilling equipment and so on. Large and medium-sized mine gas compressors have a displacement of 40m3/min and 20m3/min air compressors. The exhaust pressure is 0.8MPa, the former is 250kW, and the latter is 130kW. The gypsum deposit has a large displacement. The drainage equipment usually uses a diameter of Φ159~Φ299mm, and the second tube is used for one work. Domestic D-type pumps are usually used. Ventilation equipment uses 4-72 centrifugal fans, and the power of large and medium-sized mine ventilators is about 155-320kW. Rail transport equipment, gauge distance is 600mm, motor vehicle 7t and 10t wire type; trackless transport uses 10t pit dump trucks, also used 8.8kW and 11kW tractors for mining, mining with tractors is not ventilated required. Alabaster, ordinary gypsum and anhydrite mines are equipped with tire-type electric loaders, 2m3 buckets or electric scrapers with smaller buckets. In order to avoid contamination of underground air, diesel equipment is not used; High and its physical and mechanical properties, Yingcheng gypsum mine mining face is still using manual loading. Rock equipment is mostly light rock drills and electric drills.