For a mineral processing plant, the quality of mineral processing design directly affects the final beneficiation index, investment and construction cost and production cost after putting into operation. Therefore, when designing the mineral processing process, we should choose a scheme with mature technology, advanced technology, reliable production and high economic benefit, and follow the following principles and methods.
1. The overall principle of mineral processing design
The mineral processing design shall be based on the process flow recommended in the reviewed or approved processing test report and on the practice experience of similar production plants. When determining the process flow of mineral processing, the selection and rejection of the associated minerals proposed in the mineral processing test report shall be determined after technical and economic comparison. When determining the program and technical indexes of mineral processing products, it should be based on the principle of improving economic benefits, through program comparison, the type, quality and recovery rate of recovered products should be determined as the main indexes. and the data of similar production plants should be used for reference and the average advanced indexes should be adopted. Mineral processing equipment should be large-scale. When the process flow is the same, large plants should have 2-3 series, process simple or mature ones can have 1 series, and medium-sized and small plants should have 1-2 series. Specific series can be determined after program comparison. When the main useful, harmful mineral contents in the selected raw ore change greatly, or the ore supply points are many, the ore types are complex, there should be ore distribution facilities. The conventional grinding process should reduce the particle size of the crushed products, more crushing and less grinding. The particle size of the final crushing product shall be determined according to the scale of the mining plant, the nature of the ore and the selected crushing equipment. In the design of backwater process, facilities that can ensure normal water supply when there is no water to be returned in the early stage of production shall be provided.
2. Crushing and screening
When the ore is not caking, not agglomerating or not blocking the crushing and screening equipment, the large and medium-sized mine plants should use three-stage or two -stage one closed-circuit process, small plants should use two-stage one closed-circuit process. When the crushing product is used as ball mill feed, the particle size of conventional crushing product should be less than or equal to 15mm, and that of ultra-fine crushing product should be less than 12mm; when it is used as rod mill feed, the particle size of final crushing product should be less than 25mm. When the ore contains more mud and powder, and in the arid area, the ore is not sticky, it is appropriate to use closed - circuit screening crushing process. In dry and rainy season area, when the ore is not sticky and not blocked in the dry season, it is advisable to use the crushing screen process that can be opened and closed. When ore containing mud and water more, but is not agglomerated and medium viscosity, can use open circuit crushing process. In ore feeding, if the particle size of ore less than ore discharge product accounts for more than 20% of ore, pre-screening should be set. Raw ore bin shall be set before coarse crushing. More than two (including two) medium and fine crushing screening equipment should be set up intermediate distribution bin. In the crushing machine of large-scale plants ore feeding, when the grain content of the final product is more than 15% or contains more powder ore, dry intensified screening shall be set before medium crushing, and the output part is the final product. When the feeding ore contains powder and mud and is wet, the ore washing process can be used, but it must be confirmed after demonstration.
3. Scrubbing
The scrubbing and grading method can make ore remove harmful components, improve product quality, grade, or improve the processing performance after the appropriate use of ore scrubbing process. Laboratory test can be used as design basis for a single ore scrubbing process. It is not suitable to set up the intermediate ore heap or the storage bin which is easy to be blocked in the scrubbing process.
4. Grinding and classification
The selection of grinding and classification processes for different product sizes should meet the following requirements: (1) when the grinding mineral product size is 0.5mm-3.0mm, primary rod grinding process can be used. (2) when the particle size of grinding products is less than 0.074mm and the content is less than or equal to 70%, primary ball grinding process can be used. (3) when the particle size of the grinding product is less than 0.074mm and the content is more than 70%, two-stage grinding process should be adopted. (4) when the particle size of grinding products in small plant is less than 0.074mm and the content is less than 80%, primary ball grinding process should be adopted. When open circuit crushing is adopted and the grinding particle size is greater than 25mm, the rod grinding process should be adopted in the first grinding stage of large and medium-sized plant. When the distribution of useful minerals is uneven and easy to be over-crushed, the rod grinding or stage grinding process should be used. When the ore contains a lot of mud, water, clay and malleable mud, and it is difficult to use conventional crushing and ore washing methods for treatment, the self-grinding and semi self-grinding processes should be used. When iron ions in grinding products affect the quality of separation products, the grinding process of gravel mill or special grinding medium should be used.
5. Gravity separation
The gravity separation process design should be based on the ore properties, mineral processing test reports, the construction scale of mine plant, and the production practice of similar chemical mine plant, so as to achieve "early tailings discarding and more tailings discarding, early collection and more collection". The selected particle size of gravity separation shall be determined according to the mineral processing test report and the selected equipment. When the difference of specific magnetization coefficient between useful minerals and gangue minerals is small and the density difference is large, gravity separation process can be used. Before the gravity separation operation, classifying, desliming and other operations can be set. For the selected ore of heavy medium processing, a screening and desilting operation shall be set up before separation operation. When the ore mud content is more than 5%, the ore washing operation should be set up. The medial products of gravity separation shall be milled and separated separately according to the material properties. The middling can adopt the process of first separating and then milling, or first milling and then separating. The middling which is difficult to separate due to its complex nature should be treated by other methods.
6. Magnetic separation
For the ore suitable for dry magnetic separation, it is advisable to use dry magnetic separation under the condition of coarser particle size to discard part of waste rock in advance. The waste particle size of the coarse-grained dry magnetic separation should be determined according to the test results. For the ore with uneven distribution of useful minerals, the stage grinding and stage separation process should be adopted. When grinding classifying, fine screening classifying or magnetic separation are carried out after the magnetic separation of strong magnetic minerals, the pulp shall be demagnetized first. Before the strong magnetic separation operation, the operation of removing strong magnetic minerals shall be set. Prior to the operation of strong magnetic separation, the coarse size screening shall be set. When fine screening operation can improve concentrate grade, fine screening operation should be set.
7. Flotation
For the easily slimy ore, it is advisable to set up desliming operation before the flotation operation. Pulping operation shall be set before floating operation. When concentrate grade is required to be high and useful minerals are inlaid finely, multi-stage grinding process of concentrate should be adopted. The concentration of slurry should be increased without affecting the separation index of flotation operation. The range of increasing concentration should be determined according to the ore processing test. In the multi-stage separation process, the return location of middling should be determined by the test results, and the design can be adjusted according to the concentrate quality requirements and the nature of medium ore.
8. Dewatering
When ceramic filter and filter press are used for dewatering, if can make the fine concentrate moisture less than or equal to 10%, it is appropriate to use two-stage dewatering. When the moisture content of fine concentrate is less than or equal to 8%, three-stage dehydration should be adopted. For the coarse concentrate in gravity and magnetic separation, sedimentation tank, dewatering screen and dewatering bin can be used for primary dewatering. When dry discharge of fine tailings is required, two-stage dewatering process after concentration and filtration should be adopted. The plant is located in the cold area, and the moisture content of concentrate powder is more than 10%, when the concentrate is transported outside, a three-stage dewatering process with drying or other methods should be used to solve the transportation freezing problem in winter. For bulk transportation of coarse concentrate, the moisture content shall not be less than 4% and that of fine concentrate shall not be less than 6%. When the coarse concentrate with less than 4% water and the fine concentrate with less than 6% water are transported outside, they should be transported in bags or special vehicles.
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