An important means of selecting the granularity. Investment in infrastructure and production costs in the beneficiation plant crushing and grinding plant accounted for most mineral processing costs, therefore, broken grinding operations is the key to job Concentrator. Choosing the right grinding process is one of the most important decisions in the design of the concentrator. However, in the general beneficiation test, the grinding process and the grinding machine are not suitable for the study of the ore size. Therefore, the designer should make the best design plan based on the production practice and the ore friability data.
At present, the commonly used grinding principle processes at home and abroad include: crushing-ball milling-ball milling process; crushing-rod grinding-ball milling process; crushing-rod grinding-gravel grinding process; crushing-ball milling process; single-stage self-grinding process; Semi-self-grinding) - ball milling process; self-grinding - gravel grinding process; single-stage semi-self-grinding process and self-grinding - ball milling - crushing process. The first four are conventional grinding processes. The ore is crushed to a size of 10 to 25 mm by two to three stages, and is continuously milled into a ball mill or a rod mill to the required particle size. Self-grinding machine feed size is 200 ~ 350mm. Production practices show that each process has its advantages and disadvantages. For a particular ore, a process with more advantages than disadvantages should be selected, and the process should be simplified in industrial production. The main factors affecting the selection of the grinding process are:
(1) The ore properties are mainly the physical properties of the ore hardness, blockiness, brittleness and primary slime content; the structure of the ore; the mineral composition and the content of clay minerals; the embedding characteristics of minerals. In general, conventional processes can be applied in addition to ore containing a lot of mud and water. The self-grinding is suitable for treating ore types with well-defined grain boundaries and stable rock composition. The self-grinding process is sensitive to the structure and structure of the ore and the grain size composition of the ore. Therefore, if self-grinding, especially for large plants, is required, semi-industrial or industrial tests must be carried out, and detailed technical and economic comparisons with conventional processes are required to provide a reliable basis for design. Sorting of ore [e.g. fragile tungsten, tin ore], the comminution process should avoid excessive pulverization, crushing the general - rod mill - rod mill (or ball) process. When dealing with clayey ore, the use of semi-self-grinding can eliminate problems that are difficult to solve in production such as crusher clogging and low screening efficiency in conventional processes.
(2) Equipment performance Each type of equipment has its own fixed characteristics. For example, the crushing ratio of the gyratory crusher is between 3 and 5; the crushing ratio of the short-head cone crusher is between 4 and 8. It can be seen that if the ore is to be broken into the grinding grain size, it is generally not completed by a piece of crushing. For example, the bar mill has a relatively uniform particle size and less pulverization, and the product size is 3 ~ 1mm; the overflow ball mill has a finer particle size, generally less than 0.2mm, but is prone to over-grinding; the self-grinding machine can make minerals It breaks along its interface, so that the same ore can be separated from the mineral in the case of coarser grinding. It can be seen that the grinding equipment is working within a certain particle size range, and the selected grinding process should be adapted to the product size that the grinding equipment can achieve. The crushing-ball milling process is selected. Although the particle size boundary between crushing and grinding is currently developing in the direction of multiple crushing and grinding, the short-head cone crusher commonly used now has a product size of less than 10 mm, which means crusher performance. Determine the limit value of the product's granularity. If the crushing-rod grinding process is selected, the particle size of the crusher can be controlled to about 25mm. In addition, if the rod mill product size is required to be less than 0.5 mm, the rod mill production capacity will be greatly reduced. Therefore, even if the tungsten tin ore is processed, the ball mill is selected when fine grinding is required, and the lattice type ball mill can be selected at this time.
(3) Energy consumption and steel consumption In any concentrating plant, both the normal process and the self-grinding process are the most energy-intensive operations. According to the production cost statistics of various domestic concentrators, electricity consumption and steel consumption account for 40% to 60% of the processing cost of mineral processing, which means that reducing energy consumption and steel consumption can improve the economic benefits of the concentrator. Therefore, energy consumption and steel consumption play an important role in evaluating the grinding process.
When choosing a grinding process in your design, you should consider how you can keep energy consumption and steel consumption to a minimum. Compared to conventional processes, the unit energy consumption of the full self-grinding and semi-self-grinding processes is about 25% higher, while the steel consumption is lower. For example, the US Cyprus-Pima Mine Company compares the average process with the semi-self-grinding process, and the average steel consumption is 13.50%, but the power consumption is 15.5% lower. This means that the cost of conventional steel processes consume just balance the cost of electricity from mill processes more than half consumed. In the mountains of copper ore concentrator slightly since the mill - milling process compared with conventional processes, and high power consumption 32.87 percent, the same steel consumption, easy to see, and high power consumption will increase production costs. The unit power consumption of the gravel mill is almost the same as that of the ball mill; the energy consumption of the lattice ball mill is about 15% higher than that of the overflow ball mill of the same efficiency. Therefore, for areas with higher electricity costs, it is advantageous to choose a conventional grinding process with lower energy consumption.
(4) Investment and production costs of the process plan In addition to the above factors, the total investment and production costs of each plan should be compared when determining the grinding process. The investment and production cost should be selected. The main factors affecting investment and production costs are: 1) Process structure: According to the data, the small-scale plant adopts three-stage closed-circuit crushing (broken to less than 10mm), which is about 25% higher than the two-stage closed-circuit crushing (broken to less than 13mm). After the scale is greater than 2.5 kt/d, the difference is reduced and stable. Compared with the two-stage grinding, when a mill has the same power, a section of grinding investment is greater than two sections of grinding, because the first section needs grinding. There are feeding system and storage system, but the production cost is low. 2) Grinding method; that is, self-grinding, semi-self-grinding, gravel grinding, rod grinding and ball milling, etc. Generally, under the same production capacity, semi-self Grinding investment is lower than full self-grinding; gravel mill has higher investment than ball mill of the same power, but the production cost is low. 3) Equipment specifications: Practices in recent years have shown that in order to reduce capital investment and production costs, crushing and grinding equipment Specifications growing, and industrial production proved that the maximum size of the mill installed a mechanical problem does not exist, but may not reach the best effect. in 1988, China's "black gold mine beneficiation design rule of a number of principles laid down" has been Provision, main plant
F Milton Lewis and JL Coburn of the United States conducted a three-stage crushing process for a copper ore dressing plant in Arizona with a semi-autogenous grinding-ball milling process to minimize investment and production costs. Large scale equipment is used in each scheme. The results are shown in Table 7-3-1.
The above comparison results show that the semi-self-grinding process is superior to the conventional grinding process, the estimated investment is about 30% lower, and the production cost is slightly lower than the conventional process.
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