First, the choice of grinding equipment
The choice of grinding equipment, mainly according to the nature of the ore processed, production scale, product size requirements and other conditions, at the same time should consider the enterprise's requirements for equipment level and automation, investment limits and other factors, and finally through program comparison to determine.
In general, small beneficiation plant design in the conventional rod mill or ball mill; to be considered for large-scale concentrator autogenous grinding, SAG, what is preferably a conventional device.
(I) Principles of Selection of Mills The following principles are generally considered for mill selection:
(1) Guarantee production capacity. The selected grinding equipment is used to achieve the required output under the conditions of ensuring the required fineness of grinding.
(2) The ability is appropriate to leave a surplus. The design should consider the change of hardness and fineness of the ore. Generally, the deep ore of the ore deposit will become hard or thin, and the selected grinding machine should be able to adapt, and ensure the initial smooth operation.
(3) Grinding tests must be done. When there is no actual data in the design, the grinding test must be required. Especially for large-scale concentrators, the grinding machine selection calculation and proportional enlargement should be carried out from the basic data obtained.
(4) Appropriate consideration of equipment size. The large size of equipment is a recent design trend. Due to the large-scale equipment, the total equipment is light in weight, small in area, less in production system, less in operators and auxiliary systems, and correspondingly low in investment and production costs. However, the operation and management level of large equipment is high, and if the operating rate is slightly reduced, the production of the concentrator is greatly reduced.
(5) Select equipment with high operating rate. There are also good and bad points in the same type of equipment. Rod mills and self-grinding machines sometimes have lower operating rates, but are still suitable under certain conditions. In principle, equipment with high operating rate should be selected to reduce maintenance and parking time.
(II) Selection of mill type At present, the grinding equipment commonly used in the concentrator is a rod mill, a lattice ball mill , an overflow ball mill, a self-grinding mill and a gravel mill.
A rod mill This machine is characterized in that the grinding medium is in line contact with the ore in the grinding machine. The grinding medium has a “sieving actionâ€, so it has the advantage of selective crushing, so it is not easy to be crushed and the product size is even. Therefore, it is especially suitable for grinding brittle materials. China's tungsten, tin ore re-election plant used a lot. The unit production capacity of the rod mill during rough grinding is greater than that of the ball mill; when the product size is less than 0.5 mm, the capacity is reduced. The most suitable product size is 3~1 mm. The ore size is generally 15~25 mm, and the large diameter rod grinding can reach 40~50 mm. It simplifies the crushing process by giving it a three-stage open-break process. The rod mill product is fed to the lower ball mill for re-grinding, which can improve the ball mill production capacity. For example, Baotou Concentrator in China used a 3200×4000 mm rod mill for four-stage crushing. There are many examples of using a rod mill in a foreign concentrator and a ball mill in the second stage, especially in Canada and the former Soviet Union. [next]
The disadvantage of the rod mill is that the operating rate is relatively low.
B Grid type ball mill Grid type ball mill is divided into two types: short tube type and long tube type. The short tube type is used for rough grinding, the fineness of the grinding product is about 45~50%-200 mesh; the long tube type is suitable for fine grinding, and the general grinding product fineness is used when it is above 65%-200 mesh.
The characteristics of the equipment are: there is a grid plate at the end of the discharge, the slurry surface is low, and the ore discharge is accelerated, so that the qualified ore particles can be discharged in time to avoid over-grinding; because the liquid level is low, the impact of the ball is small, It is beneficial to the broken ore; in addition, it can hold large balls and small balls, and the ball loading is also large, which is easy to realize the reasonable addition of the ball; its production capacity is 10~15% larger than that of the overflow ball mill. The disadvantage is that the structure is more complicated and the equipment maintenance is more troublesome.
C Overflow Ball Mill This equipment is characterized by simple construction, easy maintenance, and fine grinding products, generally below 0.2 mm. Commonly used in the second section of grinding and coarse concentrate and medium mine re-grinding. Due to the high surface level of the ore in the mill, the slurry has a long residence time in the machine, and the production capacity is lower than that of the lattice type ball mill, which is easy to produce excessive pulverization.
D from the mill since the mill grinding process and the conventional process of Comparative disadvantages E pebble mill main advantage of this device is: the use of gravel for the grinding media to reduce the consumption of steel, for the noble metals, uranium ore quality can reduce iron Pollution, in addition, is not easy to smash and mud, so it is good for sorting. The equipment grinding products can reach -320 mesh, accounting for 90%. The finer the grinding product, the lower the cost, the lower the production capacity compared with the ball mill, which increases the weight of the equipment or increases the specification and increases the investment. The gravel mill is generally used for the second section of the two-stage grinding. Our Phoenix Mountain copper mine for secondary grinding, the better. Gravel mills are compared to other mill applications. A ball mill can be used as a gravel mill.
Second, the determination of the appropriate grinding fineness
In the design of the concentrator, the appropriate grinding fineness is generally determined according to the recommendations of the “Selection Test Reportâ€. When the ore dressing index is not much different and the fineness changes greatly, it is economical to choose coarse grinding. Sometimes it is difficult to judge the most economical grinding fineness based on the relationship between grinding fineness and recovery rate, especially when designing large-scale concentrating plants, so it is necessary to make program comparison and economic analysis.
According to product price, electricity cost, recovery rate, investment and other factors to find out the relationship between grinding fineness and net present value, the net present value is used to determine the best grinding fineness.
The program comparison and economic analysis are as follows:
(1) Relationship between fineness of grinding products and recovery rate;
(2) the relationship between the fineness of the grinding product and the required power; [next]
(3) The relationship between required power and recovery rate;
(4) Calculate the investment according to the fineness selection equipment;
(5) Calculate the investment required to consume one kilowatt hour;
(6) Calculate the cost according to power consumption, ball consumption and lining consumption;
(7) Calculate the output value of the product according to the metal recovery rate;
(8) Relationship between fineness of grinding products and net present value.
Under the conditions of different product prices and electricity prices, the annual working capital of the enterprise within the production period is determined by investment, production cost and product output value; the net present value at different discount rates is calculated by using liquidity; measured by net present value income. The finest grind product has the highest net present value.
Several basic conditions for calculation:
(1) The annual working day of the concentrator;
(2) The ore dressing plant handles the annual amount of minerals;
(3) The annual mining volume and ore grade of mining, as well as the change of ore grindability:
(4) A graph showing the relationship between the change of the grinding power and the recovery rate;
(5) Mining costs:
(6) Beneficiation cost (except for grinding power consumption, ball consumption and liner consumption):
(7) smelting and concentrate transportation costs;
(8) Variable production costs:
Power cost yuan / kW • hour;
Liner consumption kg / kW • hour;
Liner cost yuan / ton;
Media consumption kg / kW • hour;
The cost of the medium yuan / ton;
(9) Investment in grinding operations.
Third, rod mill, ball mill production capacity calculation method
The calculation methods of rod mill and ball mill production capacity are basically the same; the commonly used methods are: (1) volumetric method; (2) Bond work index method; (3) Thompson specific surface area method; (4) energy efficiency method . [next]
Recently, a simulation algorithm was used to carry out the scale-up of the mill and the calculation of the grinding process.
(1) Volumetric volumetric method is to calculate the grinding machine production capacity according to the new ore amount processed per unit volume of the grinding machine per hour or according to a newly formed certain level of ore volume; generally -0.074 mm (-200 mesh) A calculation level benchmark.
In the design, the production capacity of the grinding machine is based on the ore grindability of the test and refers to the production index of the enterprise dealing with similar ore, as well as the type, size, ore and product size and other operating conditions of the selected grinding machine. Corrected differently.
The designed grinding machine is expressed in q- 74 according to the newly formed unit production capacity of -0.074 mm, and q in terms of raw ore.
A Calculation of a section mill Mill unit production capacity (utilization coefficient) q X can be calculated as follows:
The choice of grinding equipment, mainly according to the nature of the ore processed, production scale, product size requirements and other conditions, at the same time should consider the enterprise's requirements for equipment level and automation, investment limits and other factors, and finally through program comparison to determine.
In general, small beneficiation plant design in the conventional rod mill or ball mill; to be considered for large-scale concentrator autogenous grinding, SAG, what is preferably a conventional device.
(I) Principles of Selection of Mills The following principles are generally considered for mill selection:
(1) Guarantee production capacity. The selected grinding equipment is used to achieve the required output under the conditions of ensuring the required fineness of grinding.
(2) The ability is appropriate to leave a surplus. The design should consider the change of hardness and fineness of the ore. Generally, the deep ore of the ore deposit will become hard or thin, and the selected grinding machine should be able to adapt, and ensure the initial smooth operation.
(3) Grinding tests must be done. When there is no actual data in the design, the grinding test must be required. Especially for large-scale concentrators, the grinding machine selection calculation and proportional enlargement should be carried out from the basic data obtained.
(4) Appropriate consideration of equipment size. The large size of equipment is a recent design trend. Due to the large-scale equipment, the total equipment is light in weight, small in area, less in production system, less in operators and auxiliary systems, and correspondingly low in investment and production costs. However, the operation and management level of large equipment is high, and if the operating rate is slightly reduced, the production of the concentrator is greatly reduced.
(5) Select equipment with high operating rate. There are also good and bad points in the same type of equipment. Rod mills and self-grinding machines sometimes have lower operating rates, but are still suitable under certain conditions. In principle, equipment with high operating rate should be selected to reduce maintenance and parking time.
(II) Selection of mill type At present, the grinding equipment commonly used in the concentrator is a rod mill, a lattice ball mill , an overflow ball mill, a self-grinding mill and a gravel mill.
A rod mill This machine is characterized in that the grinding medium is in line contact with the ore in the grinding machine. The grinding medium has a “sieving actionâ€, so it has the advantage of selective crushing, so it is not easy to be crushed and the product size is even. Therefore, it is especially suitable for grinding brittle materials. China's tungsten, tin ore re-election plant used a lot. The unit production capacity of the rod mill during rough grinding is greater than that of the ball mill; when the product size is less than 0.5 mm, the capacity is reduced. The most suitable product size is 3~1 mm. The ore size is generally 15~25 mm, and the large diameter rod grinding can reach 40~50 mm. It simplifies the crushing process by giving it a three-stage open-break process. The rod mill product is fed to the lower ball mill for re-grinding, which can improve the ball mill production capacity. For example, Baotou Concentrator in China used a 3200×4000 mm rod mill for four-stage crushing. There are many examples of using a rod mill in a foreign concentrator and a ball mill in the second stage, especially in Canada and the former Soviet Union. [next]
The disadvantage of the rod mill is that the operating rate is relatively low.
B Grid type ball mill Grid type ball mill is divided into two types: short tube type and long tube type. The short tube type is used for rough grinding, the fineness of the grinding product is about 45~50%-200 mesh; the long tube type is suitable for fine grinding, and the general grinding product fineness is used when it is above 65%-200 mesh.
The characteristics of the equipment are: there is a grid plate at the end of the discharge, the slurry surface is low, and the ore discharge is accelerated, so that the qualified ore particles can be discharged in time to avoid over-grinding; because the liquid level is low, the impact of the ball is small, It is beneficial to the broken ore; in addition, it can hold large balls and small balls, and the ball loading is also large, which is easy to realize the reasonable addition of the ball; its production capacity is 10~15% larger than that of the overflow ball mill. The disadvantage is that the structure is more complicated and the equipment maintenance is more troublesome.
C Overflow Ball Mill This equipment is characterized by simple construction, easy maintenance, and fine grinding products, generally below 0.2 mm. Commonly used in the second section of grinding and coarse concentrate and medium mine re-grinding. Due to the high surface level of the ore in the mill, the slurry has a long residence time in the machine, and the production capacity is lower than that of the lattice type ball mill, which is easy to produce excessive pulverization.
D from the mill since the mill grinding process and the conventional process of Comparative disadvantages E pebble mill main advantage of this device is: the use of gravel for the grinding media to reduce the consumption of steel, for the noble metals, uranium ore quality can reduce iron Pollution, in addition, is not easy to smash and mud, so it is good for sorting. The equipment grinding products can reach -320 mesh, accounting for 90%. The finer the grinding product, the lower the cost, the lower the production capacity compared with the ball mill, which increases the weight of the equipment or increases the specification and increases the investment. The gravel mill is generally used for the second section of the two-stage grinding. Our Phoenix Mountain copper mine for secondary grinding, the better. Gravel mills are compared to other mill applications. A ball mill can be used as a gravel mill.
Second, the determination of the appropriate grinding fineness
In the design of the concentrator, the appropriate grinding fineness is generally determined according to the recommendations of the “Selection Test Reportâ€. When the ore dressing index is not much different and the fineness changes greatly, it is economical to choose coarse grinding. Sometimes it is difficult to judge the most economical grinding fineness based on the relationship between grinding fineness and recovery rate, especially when designing large-scale concentrating plants, so it is necessary to make program comparison and economic analysis.
According to product price, electricity cost, recovery rate, investment and other factors to find out the relationship between grinding fineness and net present value, the net present value is used to determine the best grinding fineness.
The program comparison and economic analysis are as follows:
(1) Relationship between fineness of grinding products and recovery rate;
(2) the relationship between the fineness of the grinding product and the required power; [next]
(3) The relationship between required power and recovery rate;
(4) Calculate the investment according to the fineness selection equipment;
(5) Calculate the investment required to consume one kilowatt hour;
(6) Calculate the cost according to power consumption, ball consumption and lining consumption;
(7) Calculate the output value of the product according to the metal recovery rate;
(8) Relationship between fineness of grinding products and net present value.
Under the conditions of different product prices and electricity prices, the annual working capital of the enterprise within the production period is determined by investment, production cost and product output value; the net present value at different discount rates is calculated by using liquidity; measured by net present value income. The finest grind product has the highest net present value.
Several basic conditions for calculation:
(1) The annual working day of the concentrator;
(2) The ore dressing plant handles the annual amount of minerals;
(3) The annual mining volume and ore grade of mining, as well as the change of ore grindability:
(4) A graph showing the relationship between the change of the grinding power and the recovery rate;
(5) Mining costs:
(6) Beneficiation cost (except for grinding power consumption, ball consumption and liner consumption):
(7) smelting and concentrate transportation costs;
(8) Variable production costs:
Power cost yuan / kW • hour;
Liner consumption kg / kW • hour;
Liner cost yuan / ton;
Media consumption kg / kW • hour;
The cost of the medium yuan / ton;
(9) Investment in grinding operations.
Third, rod mill, ball mill production capacity calculation method
The calculation methods of rod mill and ball mill production capacity are basically the same; the commonly used methods are: (1) volumetric method; (2) Bond work index method; (3) Thompson specific surface area method; (4) energy efficiency method . [next]
Recently, a simulation algorithm was used to carry out the scale-up of the mill and the calculation of the grinding process.
(1) Volumetric volumetric method is to calculate the grinding machine production capacity according to the new ore amount processed per unit volume of the grinding machine per hour or according to a newly formed certain level of ore volume; generally -0.074 mm (-200 mesh) A calculation level benchmark.
In the design, the production capacity of the grinding machine is based on the ore grindability of the test and refers to the production index of the enterprise dealing with similar ore, as well as the type, size, ore and product size and other operating conditions of the selected grinding machine. Corrected differently.
The designed grinding machine is expressed in q- 74 according to the newly formed unit production capacity of -0.074 mm, and q in terms of raw ore.
A Calculation of a section mill Mill unit production capacity (utilization coefficient) q X can be calculated as follows:
[next]
The effect of the ore size on the mill, especially the ball mill output, is a complex problem that is not only related to the nature of the ore, but also to the mill's structural type and operating conditions. Therefore, although many people at home and abroad have done research and proposed many algorithms, the results are inconsistent, sometimes very different. It seems that the best way to solve this problem is through experimentation. Since the required grinding products have different particle sizes under the same conditions, the feeding size has different effects on them, so sometimes the two can be considered together to form a correction coefficient, expressed as K FP .
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