Metal surface mining deposits in general to go through the following four manufacturing processes: drilling, blasting, loading shovel and transport, the above steps link interrelated and influence each other, mutual restraint, together constitute the basic production cycle of open-pit mining, this chapter will introduce The main problems in each of the above production processes.
First, the piercing operation
Perforation is the first production process for open-pit mining of mines. The operation is to use some kind of perforating equipment to pierce the blastholes in the planned step area to provide a charging space for the subsequent blasting work. The quality of the perforation work directly affects the production efficiency and blasting quality of the blasting process. In the entire open pit mining process, the cost of perforation operations accounts for about 10% to 15% of the total production cost of ore mining.
Up to now, there are two kinds of perforation methods widely used in open pit mine production: thermal crushing method and mechanical crushing method. The corresponding perforating equipments include fire drill, steel rope impact drill, down-the-hole drill, and roller drill. Drilling trolleys, in which the use of roller cones is the most widely used, followed by down-drilling, fire drills and rock drilling rigs are only used under certain conditions, and steel rope impact drills have been eliminated. In recent years, some experts at home and abroad are still exploring new perforation methods, such as frequency explosion rock drilling, laser rock drilling, ultrasonic rock drilling, chemical rock drilling and high pressure water jet rock drilling, but the corresponding rock drilling equipment is currently designed. It is still in the experimental development stage and has not been widely used in actual production.
The choice of piercing equipment for open pit mines depends mainly on the masonability of the mining rock, the mining scale requirements and the designed bore diameter.
Second, blasting operations
Blasting work is another important process in open-pit mining. The whole ore rock is broken and loosened by blasting operation to form a burst of a certain shape, which provides working conditions for subsequent mining operations. Therefore, the quality of the blasting work and the effect of the blasting directly affect the production efficiency of the subsequent loading operations and the cost of the loading operation. Among the total production costs of open pit mining, the cost of blasting operations accounts for approximately 15% to 20%.
The basic requirements for open mining for blasting work are:
(1) There is sufficient blasting reserve to meet the requirements of continuous operation of the excavator. Generally, the amount of ore blasting each time should meet the needs of the excavator for 5 to 10 days and nights;
(2) It is necessary to have a reasonable ore block to ensure the lowest total cost of the entire mining process. Specifically, the mass of rock after production blasting should be less than the maximum block allowed by the bucket of the excavating equipment and the maximum block allowed by the inlet of the coarse crusher;
(3) The piled pile has a good shape, the front impulse is small, there is no upturn, there is no root, the explosion pile is concentrated and there is a certain degree of looseness, in order to improve the efficiency of the shovel equipment. Do not destroy the horizon layer in complex ore bodies to facilitate the selection of mining;
(4) There is no blasting hazard. The earthquake, flying stone, noise and other hazards caused by blasting should be controlled within the allowable range. At the same time, the backlash, back crack and side cracking caused by blasting should be controlled as much as possible.
(5) The blasting design is reasonable, so that the comprehensive cost of perforation, blasting, shovel loading and crushing in the whole mining process is the lowest.
During the entire open-pit mining process of the deposit, different blasting methods are required according to different production requirements and different blasting scales in each production period. The blasting operations in the open-pit mining process can be divided into the following three types: large-scale blasting during the construction period, normal mining blasting during the production period, and step-by-step (or parallel) controlled blasting at the end of each level production.
Third, mining and transportation
The loading and unloading operations are inseparable, and the two influence each other and restrict each other. How to choose the mining equipment, whether the matching of the specifications and quantity of the mining equipment is reasonable, and whether the connection between the mining work and the transportation work is smooth will greatly affect the investment scale, production efficiency and production cost of the mining enterprise. At present, the development trend of the loading and transporting process is mainly reflected in the integration and continuity of the large-scale, mining and transportation of the mining equipment.
(1) Loading and loading equipment
The content of the loading operation is to use the loading machinery to excavate the ore from the weaker ore body or the explosive pile after the blasting, and put it into a certain transportation tool or directly to a certain unloading point. The loading and unloading work is the central link of the whole production process of the open pit mine. The process and production capacity largely determine the mining mode, technical appearance, mining strength of the open pit and the overall economic effects of mining.
The mechanical equipment used in the loading operation includes a mechanical single bucket excavator, a bucket shovel, a front loading machine, a bucket excavator, and a chain bucket excavator. For metal open pit mines, because the ore rock is generally hard, most of the world's metal open pit mines are mainly loaded with single bucket excavators and front loading machines. With the advancement of blasting technology and excavator manufacturing technology, the application of large wheeled excavators in metal mines is promising.
(2) Transportation operations and transportation equipment
Open pit mining transport operations is installed in a subsequent operation step, the basic task is loaded into the transport apparatus to transport ore mines reservoir, or beneficiation plant crushing station, where the delivered waste rock rock. In addition, it undertakes the auxiliary transportation task in open-air production, which transports the personnel, equipment and materials required in the production process to the workplace.
In the open pit mining process, transportation operations play an important role. According to statistics, the capital investment of the mine transportation system accounts for about 60% of the total infrastructure cost, the transportation operation cost accounts for 30% to 40% of the ore mining cost, and the labor of transportation operations accounts for more than half of the total labor of ore mining. Therefore, the mode of transportation operations and the rationality of the transportation system will directly affect the economic benefits of open pit production.
The mode of transport can be open pit dump trucks, railway transport, the transport belt conveyor, skip lifting ramp combined transport and shipping various ways into the composition, such as: dump truck ¾ intermodal rail, dump truck 3â„4 belt conveyor combined transport, dump truck (or railway locomotive) 3â„4 ramp bucket joint transport.
At present, the transportation forms adopted by domestic open pit mines are mainly automobile transportation and railway transportation. Practice has proved that railway transportation has low plane climbing capacity and large engineering volume of transportation lines. The plane size of the line is large, and it is suitable for open pit mines with small depth and large plane size. Some mines that used to be transported by a single railway in China have experienced a significant decrease in efficiency as the mining depth of the stope has increased. Even the lower part of the stope cannot continue to deploy the railway to develop the pit line. The upper stope still continues the joint transportation mode of railway transportation, such as Dagangshan Iron Mine of Anshan Iron and Steel and Gongchangling Iron Mine of Bengang. Because the car has the ability to climb steeply, the plane size of the transportation line is small, the transportation period is relatively short, the transportation is flexible, the transportation line is simple to build and maintain, and it is suitable for intensive mining, it has been widely used in modern open pit mines. However, compared with railway transportation, the freight rate per ton-km of automobile transportation is high, and the equipment maintenance is complicated. The number of skilled workers is large, the energy consumption of oil is large, and the exhaust gas and dust generated during operation pollute the atmosphere. In order to overcome the above shortcomings, future open-pit mine car transportation is developing in the following directions:
1. Increase the load capacity of the car. The tonnage of mining dump trucks has been developed from the original 3.5 tons, 8 tons, 10 tons, 15 tons, 20 tons to 32 tons, 68 tons, 100 tons, 150 tons. In large open-pit mines abroad, the largest tonnage of mining dump trucks in the 1970s and 1980s has reached 180 tons, generally ranging from 120 tons to 150 tons. The use of large-scale transportation equipment has increased the transportation production capacity of the equipment, reduced the transportation production cost, and accelerated the mining speed of the mine;
2. Improve the structure of the car and develop a dual-energy electric wheel car. The electric wheel vehicle adopts an external power source and a diesel engine in combination on the driving power, and applies an external power source when the heavy truck is going uphill, and uses the brake power generation to feed back to the grid when the load is downhill.
3. Improve road quality to reduce tire wear and damage to parts;
4. Strengthen the maintenance and overhaul of the car;
5. Improve the organization and scheduling of automobiles to improve the effective operation rate of automobiles;
6. In the deep open pit mine, in order to keep the automobile transportation within a reasonable range of transportation, and fully utilize the efficiency of automobile transportation, the transportation mode of the automobile and other transportation equipment is usually adopted. The latest development trend of joint transportation is automobile and The belt conveyor is united.
The application of the belt conveyor in the open pit mine is in the ascendant. The domestic Dagushan iron ore mine adopts the 3â„4 inclined well belt transportation system of the automobile 3â„4 semi-fixed crushing station. Due to the large climbing ability of the belt conveyor, continuous or semi-continuous operation, high automation level, large transportation capacity and low transportation cost, the application of deep open pit mines at home and abroad is more and more extensive.
Fourth, the rock drilling project
An important feature of open-pit mining of metal deposits is that the topsoil and rocks overlying the ore bodies must be first stripped, the ore bodies exposed, and the ore mined. Therefore, the exfoliation and abandonment of overlying rock and topsoil (collectively referred to as waste rock in the ore body) is an indispensable production link in open-pit mining of metal deposits. In order to ensure the safe and continuous mining of metal deposits, the amount of waste rock is usually several times larger than that of ore, and the waste rock after stripping must be transported to the designated site (usually called waste rock yard or dumping site). Stacking. Therefore, the waste disposal work of waste rock and the waste rock yard are quite large. According to statistics, the average floor space of China's metal open-pit mine waste rock yard is about 39% to 55% of the total mine area, and the rock-discharge workers account for about 10% to 15% of the total number of mines. It accounts for 6% of the unit cost of stripping. Therefore, how to improve the labor productivity and mechanization of rock drilling work is an important means to improve the economic benefits of open pit mining.
The waste rock that is transported and stripped to the waste rock yard for disposal is usually called a rock discharge project. The economic efficiency of the rock-discharging project mainly depends on the location of the waste rock field, the method of rock drainage and the reasonable selection of the rock-discharging process. The rock drainage project is a systematic project, which involves the waste rock disposal process, the establishment and development planning of the waste rock field, the stability of the waste rock field, the prevention and control of waste rock pollution, and the rehabilitation of the waste rock field. . The rock-discharging project must be linked to the production process of the mining site and comprehensively planned. Selecting the waste rock site according to local conditions, rationally planning the rock-discharging project, and scientifically managing the rock-discharging operation are not only related to the production capacity and economic benefits of the mine, but also The social environment and ecological balance are also of great significance.
At present, the development trend of open pit rock drainage technology and waste rock yard management is mainly reflected in three aspects:
1. Adopt high-efficiency rock-discharging technology and rock-discharging equipment to improve rock stratum strength;
2. Increase the stacking height, increase the rock discharge capacity per unit area of ​​the waste rock field, increase the utilization rate of the waste rock yard, and reduce the land area of ​​the waste rock farm;
3. Rehabilitation of waste rock sites in a timely manner to reduce the pollution of the waste rock field to the ecological environment.
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