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Flotation is a complex beneficiation process, which involves a variety of process factors and operational factors. How to ensure the stable and efficient operation of flotation stage is one of the important topics of flotation concentrators. Fodamon engineer concluded that the flotation production operation mainly includes the control of middling circulation, the judgment of the change of flotation foam properties, and the adjustment of flotation machine inflation and pulp level. In this article, we will teach you to master the flotation production operation from these three aspects.

a. Control of ore circulation in flotation

The circulating quantity of middling is an important factor in the flotation stage, which is directly related to the smoothness and stability of the flotation process. The circulating amount of medium ore should be determined according to the nature of ore. Generally speaking, ores with serious oxidation and alteration are easy to produce slime in the grinding stage. At this time, the minerals or conjoined bodies that have been separated from monomers in the middling are covered by slime, which will pollute the surface of mineral particles that have just entered the flotation operation. This kind of ore should choose open circuit flotation or reduce the circulation of middling during flotation.

The circulating amount of ore in flotation should generally be controlled within the range of 25% – 40%. Under the requirement of high recovery rate, the circulation volume can be appropriately increased. Under the requirement of higher concentrate grade, it is necessary to appropriately reduce the circulating amount of middling.

b. Judgement of the property change of flotation foam

The properties of flotation foam include the color of foam, the thickness of foam layer, the size of foam, the virtual and solid surface of foam, the annexation, stability, fluidity of foam, and the sound of foam scraping. From these properties, we can judge whether the ore washability is good or bad and whether other process conditions are suitable. Among them, the thickness of the foam layer is closely related to factors such as the amount of aeration and the dosage of reagents. Excessive thickness of the foam layer will reduce the recovery rate and improve the concentrate grade.

The observation of flotation foam state is to observe the changes of foam color, size and other states in the operation area of a stage of roughing, cleaning and scavenging. Take the foam layer in the first stage of roughing as an example. The foam layer in the first stage of roughing is generally thick, dark in color, uniform in size, and can flow smoothly. Foam is stable and non sticky. The color and thickness of foam in the operation area change significantly from the first tank to the last tank, and foam makes a swish when it scrapes into foam tank. At this time, the thickness of foam layer is generally between 100~300mm, and the thickness of foam layer in cleaning operation is between 300~500mm.

c. Adjustment of flotation machine inflation and pulp level

Air is one of the important media in flotation process. After sufficient aeration and reagent mineralization, the minerals in the pulp can form a stable flotation carrier foam. If the gas is inflated excessively, the oxidation degree of minerals will increase, which will reduce the floatability of minerals. Proper inflation can keep the foam layer in the flotation machine stable without turning over. The specific situation needs to be determined in combination with the operation performance of the flotation machine. Generally, medium or low inflation can effectively improve the flotation recovery.

For the self-priming flotation machine, except for the first cell feeding flotation machine, the air inlet pipes of other flotation machines operating in the same row cannot be closed. For large flotation machines, the adjustment of flotation machine inflation and pulp level should be mainly fine-tuning, so that a relatively thick foam layer and a stable foam area can be formed in the flotation machine. The thickness control of flotation foam layer in the first cell of roughing should be adjusted first, and other cells should be determined according to the actual production situation.

The above are the three major flotation production operations. The flotation operation is practical. Before the flotation operation, it is necessary to understand the performance and characteristics of the equipment in the flotation operation in detail, give full play to the advantages of the equipment, and achieve fast collection, early collection, fast collection and more collection, so as to improve the flotation separation index. In actual production, flotation operators need to observe repeatedly and analyze constantly to improve their identification ability.

The utilization rate of aluminum slag after grinding by ball mill is very high. With the continuous processing of aluminum slag in the market, the application of aluminum slag ball mill is also increasing, and then there are many types of aluminum slag ball mill equipment in the market. The output, price and performance of different equipment are very different. Fodamon engineers in this paper take aluminum slag ball mill as an example.

Aluminum slag ball mill is mainly composed of bearings, rotating parts, transmission parts, lining plates and other parts. However, due to the fact that the installation of ball mill components is not as simple as other equipment, abnormal faults often occur during the operation of the machine due to improper installation, which affects the production capacity of the machine. Therefore, pay more attention when installing components.

a. Installation of lining plate of aluminum slag ball mill

When installing the lining plate of the ball mill, pay attention to remove the internal oil dirt. During installation, ensure that the clearance of the lining plate is not greater than 16mm, and then fix the screw of the lining plate. And pay attention to carefully pad the sealing packing and gasket to prevent the leakage of mineral powder.

b. Installation of bearing part of aluminum slag ball mill

When installing the bearing part of the ball mill, no matter what kind of installation method is adopted, it must be ensured that the machined surface on the bearing chassis should be on the same horizontal plane, and its levelness should be checked with a level gauge or level gauge. The main bearing of the feed end cover must be slightly moved outward from the nominal size of the installation to meet the needs of cylinder elongation due to heat (refers to dry), and the anchor screw holes should not be filled with cement, It should be 300 mm above the upper end of the spiral. Finally, when installing the oil supply device, it is necessary to adjust the gap between the oil scraper and the oil ring to avoid jamming and make the oil supply work smoothly.

c. Installation of transmission part of aluminum slag ball mill

The transmission part is the key installation object of the ball mill. For example, when installing the big and small gears, pay attention to check the parallelism of the center lines of the big and small gears, and its imbalance shall not exceed the standard requirements, as well as the tooth side clearance of the gear, and its value shall be guaranteed to be within the range of 0.4-1.2mm. Finally, pay special attention to that when checking the contact condition of the tooth surface, it should be checked by coloring, and the contact length should not be less than 50% of the tooth length, and the angle height should not be less than 60% of the tooth height.

d. Installation of rotating part of aluminum slag ball mill

When installing the rotating part, the dirt on all connecting and fitting surfaces should be removed first. Secondly, it is not allowed to lift the whole rotating part with the lifting ring on the end cover, and it is not allowed to add any gasket on the contact surface between the barrel flange and the inlet and outlet cover flange (but a layer of lead should be painted before assembly).

During installation, pay attention not to scratch and bruise the working surface of the neck, and when installing the neck, use a level gauge to check, and the horizontal deviation of the center line of the journal at both ends shall not be greater than 5mm. Finally, after everything is installed correctly, proceed to the next step of installation.

With the increasing demand for nickel ore and the deepening development of nickel sulfide ore, the development of laterite nickel ore has gradually become a new trend of nickel ore development. The geological structure of laterite nickel ore is relatively complex, and the nickel content and mineral composition of different deposits are very different. It is difficult to enrich it through traditional beneficiation methods. At present, the beneficiation methods of laterite nickel ore include nickel sulfur process, rotary kiln submerged arc furnace process (RKEF), sintering blast furnace reduction process, direct reduction process, acid leaching process, etc.

The enrichment of laterite nickel ore by pyrometallurgical methods such as nickel sulfur process, rotary kiln submerged arc furnace process (RKEF), sintering blast furnace reduction process and direct reduction process is limited by power supply, and there are problems such as high investment and high pollution. The beneficiation of laterite nickel ore by chemical beneficiation processes such as acid leaching is the beneficiation direction of laterite nickel ore. Fodamon studied different types of laterite nickel ores. Good beneficiation results can be obtained by using atmospheric acid leaching, pressurized acid leaching, and atmospheric + high pressure combined acid leaching to treat laterite nickel ores.

a. Atmospheric pressure acid leaching of laterite nickel ore

Atmospheric acid leaching method is applicable to laterite nickel ore with high magnesium content. Sulfuric acid and hydrochloric acid are generally used as leaching agents. In the process of treatment, the laterite nickel ore is ground to a certain concentration of pulp, added with a certain concentration of acid, the temperature is controlled to leach the nickel, cobalt, iron, magnesium, aluminum and other elements in the ore, and then treated after separation and washing; Then neutralize the pulp with alkali to remove impurities such as magnesium, iron and aluminum. After liquid-solid separation and washing, the obtained liquid is re precipitated to obtain nickel cobalt hydroxide; The remaining liquid is then neutralized to remove calcium and magnesium, and then returned to production and discharge. Iron in laterite nickel ore leaching solution is converted into iron phosphate, and then further processed into lithium iron phosphate.

b. Pressure acid leaching process of laterite nickel ore

The pressurized acid leaching process is suitable for laterite nickel ore with high limonite content and low magnesium content. First, laterite nickel ore is ground and prepared into a pulp with a stable concentration, which is preheated and leached under a stable sulfuric acid concentration. During leaching, nickel, cobalt, iron, aluminum and other elements are dissolved together. After separation and washing, impurities such as iron and aluminum enter the slag, while nickel and cobalt remain in the solution. According to the requirements of the product scheme, different processes can be used to produce high-quality nickel cobalt hydroxide, nickel cobalt sulfide or nickel cobalt sulfate crystals.

c. Atmospheric pressure + high pressure combined acid leaching process of laterite nickel ore

Atmospheric pressure high pressure two-stage acid leaching of laterite nickel ore can be used for ores containing different contents of magnesium in an ore body. The acid leaching process will produce excess acid after treatment, and neutralization treatment is required in the later purification process of the leaching solution, which will have varying degrees of impact on the subsequent impurity removal operations. Therefore, Fodamon studied the two-stage leaching process based on the two processes of Atmospheric Acid Leaching and high-pressure acid leaching, and used the combined process of atmospheric pressure leaching and high-pressure acid leaching to treat laterite nickel ore. its main purpose is to neutralize the excess acid in the leaching solution, So as to remove part of ferric iron. The free acid can be neutralized by adding the atmospheric acid leaching solution of high magnesium laterite nickel ore to the low magnesium mineral for two-stage high-pressure acid leaching.

In actual production, different lateritic nickel ores have different properties and mineral compositions, which cannot be blindly copied. It is suggested that the mine owners do a good job in Beneficiation tests, clarify the nature of the deposit, and formulate beneficiation schemes targeted to obtain ideal economic benefits.

Mining ball mill is an important part of the grinding system. Ensuring its stable and efficient operation plays a vital role in the whole concentrator. Among them, the big gear is one of the important components of the mining ball mill, and its service life will directly affect the service life of the mining ball mill.

Generally, the service life of the big gear of the mining ball mill can reach more than 12 years, but in practical application, the service life of the big gear of most mining ball mills is only about 5-8 years, and some of them are even less than 4 years, which not only hinders the normal production and operation, but also increases the maintenance and procurement costs. Next, Fodamon engineer will show you the main reasons for the wear of the big gear of the mining ball mill and the corresponding solutions.

a. Poor gear hardness and sealing of gear end face

National clear standards: the hardness of the big gear of the mining ball mill must be above hb300, and the hardness of the pinion tooth surface must be above hrc45. However, in the actual production process, some manufacturers cancel the internal stress elimination processing technology in order to shorten the maintenance time, which is easy to deform the gear.

In addition, most of the transmission gears of mining ball mills adopt end face pressure sealing, which has the disadvantage of insufficient gear sealing. After the mining ball mill operates for a period of time, the felt on the gear end face loses elasticity due to long-term extrusion, resulting in cracks at the felt. Once the mining ball mill is in a dusty operating environment, dust and impurities will enter the cracks, affecting the lubrication effect of the mining ball mill gear and causing gear wear.

Terms of settlement:

1. Improve gear processing accuracy and reduce tooth surface roughness

At present, the machining accuracy of mining ball mill gear is generally grade 9-9-8dc or grade 9-8-8dc, and the tooth surface roughness is generally 3.2um. The accuracy can be improved to grade 8-8-7dc or grade 8-7-7dc, and the roughness can be reduced to 1.6um. At the same time, the machining accuracy of the pinion can be improved and the roughness can be reduced. It can not only improve the meshing accuracy of the gear pair and reduce the unit load, but also improve the lubrication and double the film thickness ratio.

2. Adopt new materials and improve the hardness of tooth surface

Alloy steel material 42CrMo4 and other normalizing hardness hb210-240 can be used, and the material price difference is not large, so as to improve the contact strength and wear resistance of mining ball mill gear. In addition, the gear tooth surface can be hardened by cold work to improve the hardness and wear resistance.

3. Thoroughly solve the problem of mortar feeding into the big gear

In order to improve the service life of the big gear, the problem of feeding mortar into the big gear must be solved, such as improving the structure of the big gear cover and adding the sand (slurry) retaining function to make it have a reliable sealing effect; At the same time, improve the sealing structure of lining plate bolts to prevent slurry leakage from the source.

b. Improper installation and maintenance of mining ball mill

The low installation accuracy of the mining ball mill or the deformation under load will cause eccentric load, which will increase the contact stress on the tooth surface of the big gear and accelerate the wear of the big gear. In addition, the newly installed mining ball mill big gear has a great impact on the wear life of mining ball mill big gear in the initial wear stage of operation (i.e. running in period). If the running in period is not handled well, the gear of the mining ball mill will directly enter the stage of severe wear, thereby intensifying the wear of the gear.

Terms of settlement:

1. Install in strict accordance with the installation procedures

◆ fully ensure that the top clearance, runout, contact, etc. of the large and small gears meet the specified requirements, and ensure the meshing accuracy of the large and small gears at the same time;

◆ considering the influence of working deflection deformation under the load of the mining ball mill, calculate the elevation difference of the inlet and outlet ends, and ensure that the meshing accuracy is met during operation to avoid eccentric load;

◆ when assembling the pinion, the pressing method should be adopted to prevent premature wear due to the annealing of the pinion and the reduction of the hardness of the tooth surface due to hot assembly, which will reduce the meshing accuracy and affect the big gear. When the pinion is worn to the limit, it should be replaced in time to avoid impact load due to excessive meshing clearance;

◆ when changing the pinion, it can be manually polished or shot blasted to reduce the gear roughness;

◆ after the big gear is worn to the limit, it can be repaired and reused according to the wear condition, so as to prolong the service life of the gear and save material costs;

◆ ordinary gears can be repaired by large displacement method, and large pressure angle repair method can be adopted for large displacement gears.

2. Good running in should be carried out at the initial stage

Good running in can improve the surface condition of gear teeth, reduce the height of peak tip, increase the radius of peak spherical surface and reduce roughness. Only a small oil film thickness can ensure that the metal between the surface micro convex bodies does not contact directly, so that the gear will soon enter the elastohydrodynamic lubrication stage. In order to achieve satisfactory running in effect, the time of no-load test run should be appropriately extended. During the load test run, the load should be gradually loaded in stages from light to heavy, and the interval should be extended. After running in is qualified, replace with new oil, and thoroughly clean the pinion and oil sump of the mining ball mill.

3. The later maintenance of the mining ball mill is not in place

When the mining ball mill operates under bad conditions for a long time, the mining ball mill components will gradually age with time, especially in the working environment with more dust particles, the leakage of slurry from the cylinder or the lining plate bolt hole of the discharge end cover into the big gear without timely removal will cause the big gear to wear to a certain extent. In addition, if the mining ball mill is running in the state of lack of oil or no oil, it will cause dry friction, which will also aggravate the wear of big gears.

Terms of settlement:

1. Ensure proper selection and use of lubricating oil

Lubricating oil is an important guarantee for the normal operation of the large gear of the mining ball mill, which has the function of noise reduction and wear reduction. If the lubrication viscosity of the big gear of the mining ball mill is insufficient, it is difficult to form an oil film, which intensifies the wear degree of the big gear and affects the service life. Therefore, it is necessary to scientifically and reasonably select the lubricating oil type and lubrication mode of mining ball mill.

◆ lubricating oil type selection:

When choosing the lubricating oil for mining ball mill, we need to pay special attention to the viscosity and oiliness of the lubricating oil. The commonly used lubricating oil types of mining ball mills include lubricating oil, grease and solid lubricant. Most concentrators often use lubricating oil for the anti-wear of mining ball mill gears. The lubricating oil mentioned here can be subdivided into gear oil and mechanical oil. Among them, gear oil has high viscosity, good oiliness and contains more polar substances, which is easier to form oil film in the transmission process of mining ball mill gears, so the application range of gear oil is also more extensive.

◆ lubrication mode selection:

The lubrication methods of mining ball mill gear mainly include manual lubrication, oil pool lubrication, oil dripping lubrication and jet lubrication. Compared with other lubrication methods, the mining ball mill adopts the large and small gear ring spray lubrication system, which can ensure that the dry oil atomizer periodically sprays a certain amount of grease to the gear working surface, so as to realize lubrication and reduce gear wear. Its lubricant effect is far beyond the lubrication effect of ordinary lubrication methods, and it adopts visual PLC control, which can maintain basic parameters, control the amount of oil injected each time and display the working process, This lubrication method is more in line with the needs of modern concentrators and has gradually replaced other lubrication methods.

In the production process, the operator of the mining ball mill must strictly abide by the equipment use, maintenance procedures and lubrication system, and must regularly observe the oil level, regularly add oil, and regularly clean and change oil. The big gear shall be cleaned and oil changed at least once a year. If it is found that the big gear enters pulp, water or other impurities, it must be stopped immediately, and the big gear and oil pool must be thoroughly cleaned and replaced with new oil.

2. Strengthen daily maintenance and overhaul

Careful daily maintenance and overhaul work is an important link to ensure the normal operation and reduce wear of the large gear of the mining ball mill, such as regularly checking the stability of the injection system, the temperature of the gear meshing surface, etc. For big gears, the system can be completely cleaned with organic solvent every one to two years to ensure that the system is smooth and flexible, and the scale remaining on the tooth surface can be removed in time, so as to prolong the service life of big gears.

The above three points are the main reasons for the wear of the big gear of the mining ball mill and the solutions. Once problems are found, the operators of the mining ball mill must timely and accurately analyze and judge the cause of the failure, and find the corresponding treatment methods according to the cause of the failure, so as to ensure the normal operation and production efficiency of the mining ball mill and reduce economic losses.

Manganese ore is divided into manganese carbonate ore and manganese oxide ore. For different manganese ores, the beneficiation process is also different. Fodamon engineer analyze how to beneficiate according to different mineral properties as follows:

a. Beneficiation method and process flow of manganese carbonate ore

The main minerals in manganese carbonate ore are siderite, calcium siderite, manganese calcite and siderite; Gangue minerals include silicate and carbonate minerals, which are often accompanied by impurities such as sulfur and iron. The ore composition is relatively complex, and the embedded particle size of manganese minerals is fine to several microns, which is not easy to dissociate, and it is difficult to obtain a higher concentrate grade.

The beneficiation methods of manganese carbonate ore mostly adopt strong magnetic separation, heavy medium beneficiation and flotation. Sedimentary manganese sulfate ores generally adopt the sequential preferential flotation process of carbonaceous shale, pyrite and manganese minerals. Hydrothermal lead-zinc bearing carbon manganese ores generally adopt flotation strong magnetic separation process. In some sulfur-containing and manganese rich ores, manganese minerals are mainly sulfur manganese ores, which are generally removed by roasting. Some manganese carbonate rich ores are also roasted to remove volatile components to obtain finished ores.

Manganese carbonate ore contains some refractory ores. Manganese is closely associated with iron, phosphorus or gangue, and the embedded particle size is very fine, which is difficult to separate. Smelting methods can be considered. For example, manganese rich slag method for treating high phosphorus and high iron manganese ore, nitric acid leaching method for producing active manganese dioxide and electrolytic method for producing metallic manganese have been used in industrial production. In addition, there are calcium bisulfite method and bacterial leaching method.

b. Beneficiation method and process flow of manganese oxide ore

Manganese minerals in manganese oxide ores are mainly hard manganese, pyrolusite and hydromanganese, while gangue minerals are mainly silicate minerals and carbonate minerals, often accompanied by pig iron, phosphorus, nickel, cobalt and other components. The beneficiation method of manganese oxide ore is mainly gravity separation. Weathered manganese oxide ores often contain a large amount of slime and fine ore, and ore washing gravity separation method is used in production. The net ore obtained by washing the raw ore to remove the slime can be used as finished ore, and some need to be re selected with jigging and shaking table. Sometimes, ore washing overflow also needs to be further recovered by gravity separation or strong magnetic separation. Some sedimentary primary manganese oxide ores, due to mining dilution, adopt heavy medium and jigging to remove gangue in production to obtain massive concentrate.

Among iron bearing manganese oxide ores, iron minerals are mainly limonite. Iron and manganese are difficult to be separated by gravity separation, flotation or strong magnetic separation, so reduction roasting magnetic separation method is needed. The process of ore washing, reduction roasting, magnetic separation gravity separation has been adopted in industry.

Bauxite actually refers to the ores that can be used in industry and are composed of gibbsite, boehmite or diaspore as the main minerals. In this article, Fodamon engineer will briefly introduce the main beneficiation process of bauxite.

Bauxite, also known as bauxite, is generally a fine dispersed colloidal mixture composed of diaspore, boehmite and gibbsite in various proportions. Bauxite often coexists with iron oxides and hydroxides, anatase, kaolinite, chlorite and other clay minerals. Sometimes it also contains calcium, magnesium, sulfur and other minerals. Bauxite can be divided into high alkali bauxite, high titanium bauxite and high iron bauxite according to its impurities.

The process of separating bauxite concentrate from bauxite ore is actually a process of removing gangue minerals and harmful impurities, separating high aluminum minerals and low aluminum minerals, so as to obtain a concentrate with high aluminum silicon ratio.

The main beneficiation methods of bauxite include ore washing, flotation, magnetic separation, chemical beneficiation, etc. Ore washing is the simplest and effective method to improve the aluminum silicon ratio of bauxite. Generally, the aluminum silicon ratio of ore can be increased by about 2 times through ore washing, which is more effective for the separation of loose ores. Ore washing is often combined with other separation methods to form a ore washing (screening washing) – Classification – manual separation process.

Flotation method can be used to separate boehmite and kaolinite in alkaline medium with oxidized paraffin soap and tar oil as collectors. Magnetic separation is used to separate iron bearing minerals. Chemical beneficiation mainly includes roasting desilication, which is based on the fact that the main silicon bearing mineral in the ore is aqueous aluminosilicate. After roasting, part of Si () Z is transformed into amorphous silicon oxide particles that are easily soluble in alkali, which improves the aluminum silicon ratio of the material.

Generally speaking, the main beneficiation process of bauxite will adopt different beneficiation process according to different types of ore. For example, in the beneficiation process of gibbsite kaolinite bauxite, it is often used to separate mud and sand first, remove iron by magnetic separation after coarse grinding, and flotation after slime grinding. The flotation reagent is prepared with oleic acid, tar oil and engine oil in a ratio of 1:1:1.

The bauxite flotation concentrate contains 49.65% alumina and the recovery rate is 45.3%. A1203/sio2 is 12.3. The desilication and beneficiation process of high silicon bauxite is more effective by flotation method. Aluminum mineral collectors include fatty acids and sulfonates, and regulators include sodium hexametaphosphate, tannic acid, sodium pyrophosphate, soda and sodium carbonate. The beneficiation process of high iron bauxite will adopt different iron removal methods according to the content, type and distribution characteristics of iron minerals. The common ones are magnetic separation, roasting magnetic separation and carrier flotation iron removal.

In general, the beneficiation methods of bauxite are complex, and the corresponding beneficiation process should be selected according to the type and characteristics of the ore in the beneficiation process. At present, bauxite in China is mostly separated by flotation.

Vibrating feeder and vibrating screen are common auxiliary equipment in mine production. There will be some problems in the process of use. Fodamon engineers have summarized some problems and solutions based on years of experience.

The vibrating feeder can send block or granular materials to the receiving equipment uniformly and continuously in production. It is the first process of the whole production line. Afterwards, it is often broken with the jaw crusher. The working efficiency of the vibrating feeder has an important impact not only on the productivity of jaw crusher, but also on the production efficiency of the whole production line.

In the work of the vibrating screen, the vibration of the screen body is used to make the materials loose, layered and thoroughly screened, so as to achieve the purpose of material separation. The screening effect of vibrating screen not only has a great impact on the product value, but also has a direct impact on the efficiency of the next operation.

The feeding speed of the vibrating feeder, the feeding and unloading speed of the vibrating screen have a direct impact on the efficiency of the whole production line. The reasons for the slow feeding of the vibrating feeder, the reasons for the non feeding and non feeding of the vibrating feeder and the solutions are shared below.

*Reasons for slow feeding of vibrating feeder

a. Insufficient chute inclination
Solution: adjust the installation angle. Select the fixed position at both ends of the feeder for raising / lowering according to the site conditions.

b. The included angle of eccentric blocks at both ends of vibration motor is inconsistent
Solution: adjust after checking whether the two vibrating motors are consistent.

c. Consistent vibration direction of vibration motor
Solution: it is necessary to adjust the wiring of any one of the vibrating motors to ensure that the two motors operate in reverse and that the vibration track of the vibrating feeder is straight.

d. Insufficient exciting force of vibration motor
Solution: it can be adjusted by adjusting the position of the eccentric block (the excitation force can be adjusted by adjusting the phase of the eccentric block. One of the two eccentric blocks is fixed and the other is movable. Loosen the bolts of the movable eccentric block. When the phases of the two eccentric blocks coincide, the excitation force is the largest and decreases in turn; during adjustment, ensure that the phase of the eccentric blocks of the same group of motors is consistent).

*No discharging of vibrating screen

Reasons:
a. The screen box of the vibrating screen shall be horizontally level with the water level during installation. If the horizontal level of the screen box is not balanced, the screen surface will shift to a certain extent, and the material cannot flow in a straight line;
b. When the support spring of the screen box is too rigid, it is easy to subject the material to excessive exciting force, resulting in severe vibration. If the support spring is damaged, it will also cause uneven force on the material and abnormal flow;
c. After the screen of vibrating screen is broken for a long time, the material can not flow normally on the screen surface;
d. When the vibrating screen is fed unevenly, the materials cannot be subjected to uniform exciting force, which will also lead to abnormal material flow on the screen surface of the linear vibrating screen.

Solutions:
a. Adjust the horizontal plane of the linear vibrating screen to keep the screen box horizontal;
b. Select the support spring with certain toughness as the support of the linear vibrating screen to avoid the damage of the support spring due to excessive rigidity. Adjust the support spring and replace the damaged spring structure and the damaged screen;
c. Keep the materials fed evenly and continuously, and do not feed too much or too little to cause unbalanced load of the screen box.

Customers often ask about the beneficiation costs in addition to the mechanical equipment used for beneficiation? Today, engineers from Fodamon summarized the costs related to the product design of the concentrator as follows:

(1) Raw material cost: raw ore mining cost plus transportation cost of raw ore from the mining site to the concentrator.

(2) Auxiliary material cost: the designed auxiliary material consumption quota is multiplied by the local material price, or according to the national material unit price (if the transportation distance is long, the transportation and miscellaneous expenses of materials shall be considered.) Multiplied by the design consumption quota.

(3) Water and electricity consumption for beneficiation: the designed water and electricity consumption index is multiplied by its unit price (the water and electricity index shall deduct the electricity and water consumption for repair and administrative welfare facilities).

(4) Wages of production workers: refers to the basic wages and auxiliary wages of direct production workers and auxiliary production workers engaged in Beneficiation Production (excluding the wages of machine repair, maintenance and non production personnel).

(5) Wage surcharges for production workers: 11% of total wages according to national regulations.

(6) Major repair expenses and maintenance expenses (including materials, wages, power, depreciation and other expenses for major repair and maintenance): it is calculated by multiplying the major repair rate and maintenance rate by the investment amount of fixed assets per unit product (deducting the expenses of machine repair, overhaul, administrative and Living welfare facilities).

The major repair rate is generally 2 ~ 2.5% of the original value of fixed assets, and the maintenance rate is generally 3 ~ 6% of the original value of fixed assets. The maintenance cost can also be calculated by multiplying the cost of equipment and buildings (structures) in the original value of fixed assets by their corresponding rates. The competent departments of all regions have regulations on the rates of enterprises, which can be implemented by reference.

(7) Basic depreciation expenses: generally, basic depreciation is withdrawn according to the service life of the enterprise or the service life of the equipment and buildings (structures) invested in fixed assets.

When the service life of an enterprise is very long, 20 years is generally taken as the economic calculation life of the enterprise for the calculation of basic depreciation.

The formation rate of fixed assets shall be calculated according to the design estimate, deducting the expenses of machine repair, maintenance, administrative and Living welfare facilities in the fixed assets. If there is no design estimate, it can be calculated as 0.85 ~ 0.9 of the total investment.

(8) Management fees (including workshop expenses and enterprise management fees): due to the large number of projects, it is complicated and difficult to calculate in detail during the design, which can be selected according to the actual indicators of similar enterprises.

What about the high content of stone powder in dry-type machine-made sand? After years of experience, Fodamon engineers have summarized six practical stone powder control methods.

There are four forms of stone powder in manufactured sand:

(1) Free powder: stone powder particles do not bond with each other and are not adsorbed on the sand surface, and can move freely under the action of wind and gravity.

(2) Agglomerate powder: the stone powder particles are tightly agglomerated to form stone powder agglomerates with large particle size, and the particles adhere to and polymerize with each other. This kind of stone powder polymer is difficult to remove by traditional powder separation equipment due to its large particle size and quality.

(3) Attached powder: there are stone powder particles attached to the surface of sand particles with larger particle size. When the surface of sand particles is smooth, stone powder particles are easy to be removed under mechanical force. When the surface of sand particles is uneven, stone powder particles and sand particles adhere to each other tightly, which is difficult to be separated by general mechanical methods.

(4) Crevice powder: there are often some natural or hundreds of micron wide crevices on the sand surface due to mechanical crushing. These crevices are often filled with a large number of stone powder particles. This is one of the most compact methods of stone powder adhesion.

6 kinds of stone powder control technologies and equipment are as follows:

1. Feeding vibrating grate screen

The increase of argillaceous content in manufactured sand will increase the water demand, affect the strength of concrete, and thus have a certain impact on its compressive capacity. Therefore, before the raw material enters the sand making process, it is necessary to remove the sludge screen waste and treat it as waste material, which can significantly reduce the moisture content of the raw material at the same time.

According to different material conditions, select the appropriate screen spacing to achieve different desilting effects; Under the condition that the mountain is thick, the vegetation is difficult to be removed, the mountain is seriously weathered, the clay content in the interlayer is large, and it is easy to mix with the soil, increasing the spacing between the sieve strips can effectively reduce the silt content.

2. Aggregate chute powder removing device

After screening, the aggregate of a certain specification of the screening machine enters the aggregate unloading chute. An overall removable diffusion air distribution chamber is arranged at a suitable place, and the blower is connected with it. In this way, when the free dust on the aggregate surface passes through the chute, it is blown up by the blower, and then collected into the dust collector under the suction of the dust collector.

In addition, the suction air volume of the dust collector can be controlled by adjusting the pipe regulating valve. Under the condition that the blower is in the form of frequency conversion, the ratio of blowing and suction can be adjusted through the frequency conversion control of the blower and the adjustment of the regulating valve, so as to realize the continuous control of the powder content of the finished sand and gravel aggregate within a certain range.

3. High frequency vibration screening pretreatment

Basic principle: the machine-made sand is pretreated by high-frequency vibration for powder dispersion, powder sand separation and coarse and fine classification, and then the stone powder is removed by wind.

Specific method: after the materials are crushed by the sand making machine, when entering the screening module, they can be dispersed through the disperser or the screw rod, which has a preliminary dispersion effect on the agglomerated and adhered stone powder and improves the uniformity of material distribution. At this time, the stone powder can be preliminarily selected through the air separation device. After the primary selection, the materials enter the high-frequency vibrating screen with vibration frequency of 60-80hz and amplitude of 0.15-2.4mm for screening. The vibration intensity of this equipment is 3.5-5 times that of ordinary equipment, which can produce large mechanical force, and has a good dispersion and separation effect on agglomerated stone powder and surface adhesive stone powder. At the same time, the coarse and fine classification of machine-made sand can be realized efficiently.

Compared with ordinary vibrating screen, the powder removal efficiency of machine-made sand after screening by high-frequency vibrating screen is significantly increased by about 40%, and the required air volume is reduced by 45%.

4. Centrifugal separator

A powder concentrator is used in the sand making process. Its main function is to separate the excess stone powder and useful particles and recycle them respectively.

Its working principle is: the gas and powder are mixed to form a gas-solid two-phase flow. The rotating distributor and high-speed air flow make the powder containing air flow obtain centrifugal force during rotation. The centrifugal force obtained by different particle sizes is different, so as to realize the separation of coarse and fine powder particles. At the same time, the coarse and fine powders were recovered by corresponding methods. The useful particles are the finished sand, and the useless fine powder is the waste material.

From the installation position of the powder concentrator in the building station, it can be divided into raw material powder concentrator and finished material powder concentrator process layout. The separator has strict requirements on moisture content. When the feed moisture content is higher than 5%, the powder removal efficiency of the separator will be seriously reduced. When the feed water content is 2%, the powder concentrator can give full play to its efficiency, and the sand formation rate is between 60%-70%.

5. V-type static Classifier + dynamic high-efficiency powder concentrator

The raw materials enter the sand making machine, after vibration screening, the coarse powder is returned to the sand making machine, and the fine powder is sent to the combined classifier of V-type static Classifier + dynamic high-efficiency powder concentrator. After homogenization by the material distributor, it enters the classification system. The coarse particles enter the finished product warehouse. The fine particles and powder enter the dynamic classifier with the air flow. The sand and stone classification is adjusted by adjusting the rotating speed of the dynamic classifier. The qualified products are discharged into the finished product warehouse through the coarse powder pipe. Adjust the particle grading of the finished product. The fine powder will be collected with the gas through the cyclone dust collector and enter the stone powder silo. The air flow will enter the V-shaped air inlet through the circulating fan.

6. Air screen

On the basis of vibrating screening, the air screen combines the wind separation technology to realize the three functions of particle size adjustment, classification and screening.

Its working principle: the materials are evenly spread under the action of the air screen dispersion device and blown to different positions in the air separation room by the blower. The lighter the materials (the smaller the particle size), the farther away the positions are blown, and the longer the screening distance is; The lightest stone powder will be blown to the powder outlet, absorbed by the induced draft fan of the dust collector, and finally concentrated in the powder tank. At the same time, the particle size adjustment board automatically adjusts the proportion of returned materials to fine tune the fineness modulus of finished sand, so as to ensure the stability of the fineness modulus of finished sand.

For the dry sand making system using air screen, the moisture content of raw materials shall be controlled below 1.6% (surface moisture content 0.6%), without mud, the feeding particle size shall be 0-25mm and the grading shall be continuous. If the raw materials are changed, the system capacity will change. If the raw materials contain too much mud or stone powder, the separation process such as powder concentrator or powder removal equipment shall be adopted in the front section.

Flotation is a complex beneficiation process. During the operation of the flotation plant, the operation of the flotation machine has an important impact on the flotation effect, which will directly affect the indicators of flotation products. It is very important to operate and adjust the flotation machine scientifically. The operating factors of the flotation machine mainly include the amount of aeration, the size of the circulating hole area, the gap of the mixing mechanism, the amount of foam scraping and the level of the liquid level, etc. In this paper, Fodamon engineer will discuss the influence of the above flotation machine operation factors on the flotation effect.

A. Adjustment of flotation machine inflation

Due to the particularity of flotation, the air charge of flotation machine is very important in the flotation process, and the appropriate air charge is the premise of good flotation index. Too much aeration will reduce the selectivity to useful minerals. When the aeration exceeds the limit, flotation bubbles will even merge to form air flow, resulting in liquid surface overturning, unable to form a stable foam layer, so that useful minerals will be lost in the tailings.

Generally, when the pulp concentration fed into the flotation machine is high and the floatability of useful minerals is good, the air charging capacity can be appropriately increased to ensure that the flotation machine has a high processing capacity. When the concentrate index is strictly required, the mineral floatability is poor or the flotation pulp concentration is low, the air charge can be appropriately reduced. According to the sequence of different flotation chambers, the air charging capacity of each flotation chamber is also different, so it should be ensured that each flotation chamber can form a stable foam layer.

B. Circulating hole area of flotation machine

In actual production, the area of circulating holes should be adjusted according to the quality of flotation products, the processing capacity and type of flotation machine to form an appropriate circulating capacity. At the same time, the sundries on the circulating holes should be treated regularly to avoid the blockage of the circulating holes.

C. Flotation machine mixing mechanism clearance

The radial and axial clearances between the impeller and stator of the mechanically agitated flotation machine have a significant impact on the performance of the flotation machine. The increase of the radial and axial clearances between the impeller and stator will lead to the decrease of the air charging capacity, pulp suction capacity and air charging uniformity coefficient of the flotation machine, and increase the power consumption of the flotation machine.

Generally, the radial clearance of the mixer mechanism of the flotation machine is not more than 8mm, and the axial clearance is not more than 10mm. When the flotation machine is discharged for maintenance, the clearance can be detected with a metal or plastic feeler gauge. During the detection, multiple points shall be measured along the circumference of the impeller and the average value shall be taken.

D. Froth scraping and liquid level adjustment of flotation machine

Foaming is an important process of the flotation machine, which is related to the flotation liquid level and has an important impact on the product quality and recovery rate of flotation concentrate. If the foam layer cannot be scraped out of the flotation machine in time, it will lead to the backlog of foam layer and the loss of useful minerals in the tailings, which will not only affect the recovery rate of concentrate, but also affect the processing capacity of the flotation machine. On the contrary, if the foam is scraped out with a part of pulp, the concentrate quality will be reduced. Therefore, it is very important to adjust the flotation liquid level. It should be noted that when the flotation liquid level is raised, the amount of foam scraping will increase, and the foam layer will become thinner. It should be judged according to the flotation machine structure and process links, and adjusted in time.

The above is the influence of flotation machine operation on flotation effect. In the actual production, the operation requirements of the flotation machine are different according to the different process stages. It should be comprehensively considered according to the actual situation and the process production conditions, and operate the flotation machine scientifically and reasonably to ensure the long-term stability of the process indicators and economic benefits.