The metallurgical sludge of the steel plant mainly includes: blast furnace gas mud, converter dust and dust and ash.

During the steel making process, about 2% of the raw materials added to the converter will be converted into dust, and the amount of converter dust generated is about 20 kg/ton. Steelmaking dust is mainly composed of iron oxide, accounting for 70% to 95%, and other oxide impurities (such as CaO, ZnO, etc.) account for 5% to 30%. Converter steelmaking dust is generally used as a raw material for sintering, but zinc is a harmful element in the iron making process. Because it is easy to form a furnace in the process of blast furnace smelting, it affects the flow of charge and gas, so the converter dust is in the recycling process. In the middle, the fine ore and the C and Zn-rich tail mud can be recovered by the beneficiation method. Adding OG mud suspension to the sintering mixture is beneficial to the granulation of the mixture. With the increase of the OG mud dosage, the 1mm particle size ratio of the mixture is rapidly reduced, which is beneficial to improve the gas permeability of the mixture, increase the yield, reduce the cost and protect the mixture. surroundings.

The composition of the blast furnace gas mud is mainly about 20% of iron oxide, 23% of carbon, 1% to 5% of zinc, and more oxides such as CaO, SiO2 and Al2O3. The amount of blast furnace dust generated is about 25 kg/t. The blast furnace gas mud particles are finer, and less than 200 mesh accounts for more than 90%. The blast furnace gas mud is characterized by high content of zinc, iron, carbon, moisture, fine particles, and zinc is mainly present in smaller particles. The blast furnace gas and gas ash can be extracted by using hydraulic separation and beneficiation method to extract Zn-rich and C-rich tail mud as resources.

At present, the recycling rate of metallurgical dust in large enterprises in China can reach 100%. The process and technology of converter mud, dust removal ash and gas mud are at a relatively advanced level, which can bring good economic benefits to enterprises.

The process of comprehensive utilization of metallurgical sludge is as follows:

(1) Dry process of converter mud and dust removal ash
Converter mud, dust removal ash → sintering return mine → mixed material processing plant.

(2) Converter mud wet process
Converter mud → mixing tank → pipeline → sintering batching belt → converter mud drying + iron oxide scale + chemical binder → stirring and mixing → pressurizing into balls → drying in the furnace → pellets.

(3) Gas mud utilization process

Gas mud → re-election → iron fine powder → sintering plant → zinc-containing mud → fire method to extract zinc.

Steelmaking sludge is a by-product of dust removal from oxygen top-blown converters, and this resource is very precious. The chemical composition fluctuates greatly, the iron content is high, the basic oxide content is high, and the particle size is fine. The sludge can be used as a raw material for sintering and pelletizing, and can exchange part of the iron-containing raw material, and combines a small amount of binder and solvent. Reduce costs and reduce the role of steel plant sewage.

Sludge is a good iron raw material, the following methods of use:

1. As the ingredients directly return to the sintering and utilization, it has a great impact on the environment, easy to form a group alone, mixing is not easy, affecting the effectiveness of comprehensive utilization.
2. Pipeline transportation to the sinter plant for shotcrete utilization, the steelmaking sludge can be concentrated to a certain solid concentration at a short distance, and the pipeline is sent to the sintering as a substitute for the sintering make-up water.
3. The steel slag powder pellets are mixed and then extruded into a sludge pellet by a molding agent to be used as a steelmaking slag coolant, and a good effect is obtained. The state attaches great importance to environmental protection, and attaches importance to the treatment of converter sludge generated by steel enterprises. The growth of energy shortage price affects the development of the steel industry, and it is inevitable to find new ways and means.

Among the metallurgical slags, there are mainly blast furnace water quenching slag, steel slag, blast furnace heavy slag, etc., in which blast furnace water quenching slag and blast furnace heavy slag utilization rate is higher, while steel slag utilization rate is lower, only about 20%. The long-term stacking of unused metallurgical slag is not comprehensively utilized in time. On the one hand, the metallurgical slag will gradually lose its activity and it will be difficult to reuse. On the other hand, the metallurgical slag will occupy a large amount of land and will seriously pollute the environment. How to make heavy use of metallurgical slag has become a top priority for all steel companies.

1.1 Development direction of metallurgical slag resource treatment and comprehensive utilization

The metallurgical slag resource treatment and comprehensive utilization refers to magnetic separation and removal of iron from metallurgical slag and the use of tailings for the production of building materials. The waste steel recovered from the metallurgical slag can be returned to the steel plant for smelting and reuse; the magnetically recovered tailings can be used to produce cement mixed materials, road substrates, masonry cement, ready-mixed mortar, concrete bricks, perforated bricks, Metallurgical slag autoclaved aerated blocks and other building materials.

1.2 Metallurgical slag resource treatment and comprehensive utilization and energy saving and environmental protection

The method of producing energy-saving and environmentally-friendly building materials by using metallurgical slag is to use the renewable resources such as metallurgical slag, blast furnace gas and waste heat steam generated by the steel plant to produce a new process of energy-saving, environmentally-friendly and replaceable high-energy building materials. The steel slag after crushing magnetic separation and iron has more minerals such as free CaO, and these minerals are hydraulic. When steel slag is used together with blast furnace water-quenched slag, Ca(OH)2 precipitated by steel slag can promote alkaline slag, and slag can eliminate the adverse effect of free CaO in steel slag and improve product volume stability. . The heavy slag after crushing magnetic separation and iron removal has the characteristics of good density and good volume stability, and can replace gravel and yellow sand as the coarse and fine aggregate of building materials. In this paper, steel slag mixed materials, steel slag slag concrete bricks and metallurgical slag autoclaved aerated blocks are taken as examples to analyze the relationship between metallurgical slag comprehensive utilization and energy saving and environmental protection.

(1) Energy-saving and environmental protection analysis of steel slag mixed materials

Steel slag has been used in the cement industry for more than 30 years in China. According to incomplete statistics, domestically, 10 million tons of steel slag can be used annually. The steel slag mixture used for the production of cement must be dried. At present, the common drying method is to transport the steel slag mixture containing about 12% of water to the cement plant by car, and then use the combustion of coal to generate hot air for drying. This process increases the amount of car transport by 10% on the one hand and coal resources on the other. Nowadays, the economic way of using steel slag as cement admixture is to use the blast furnace gas, a by-product produced by the ironworks, to dry on the spot, which can greatly save the transportation volume of automobiles and oil, coal and other resources. Using the blast furnace gas produced by the ironworks, the blast furnace gas is dried on site. The first moisture per ton of steel slag is dried to 2% of the final moisture, and 150 cubic meters of blast furnace gas is required (the calorific value is 3500 kcal/m3). Each year, 10 million tons of steel slag mixed materials need 1.5 billion cubic meters of blast furnace gas, equivalent to 750,000 tons of standard coal (the calorific value of standard coal is about 7000 kcal / kg); 10 million tons of steel slag mixed materials per year (the distance is 30 kilometers) It can save 450,000 liters of oil for transportation of automobiles (the heavy-duty trucks consume 1.5 liters/100 kilometers per ton of steel slag oil) and the coal consumption is 750,000 tons.

(2) Energy-saving and environmental protection analysis of steel slag slag concrete brick

Steel slag slag concrete brick is mainly made of steel slag slag masonry cement as cementing material, steel slag, water quenching slag and blast furnace heavy slag as aggregate, and then a certain amount of additives are added, semi-dry pressing and forming, steel mill A metallurgical slag brick produced by the method of residual heat steam curing. The production process was implemented in the building materials production line of Xinyu Iron and Steel Co., Ltd. in 2006. It has been proved by theory and practice that the performance indexes of the steel slag slag concrete brick produced by the process are better than the national standard requirements, and the product cost is low. More than 90% of the production raw materials are metallurgical slag discarded by the steel plant, and the steel plant waste heat steam is used for maintenance. In line with national industrial policies for energy conservation and environmental protection. Taking Xinyu Iron and Steel Co., Ltd. as an example of a steel slag slag concrete brick production line with an annual output of 300,000 cubic meters, it can consume about 110,000 tons of steel slag, 110,000 tons of slag and 220,000 tons of heavy slag per year. It can use a large amount of metallurgical slag for steel mills. And produce good economic benefits.

The cementitious material used in the production of steel slag slag concrete bricks is made of metallurgical slag self-contained M22.5 masonry cement, eliminating the need for high-energy PS32.5 or more finished cement. The aggregate of steel slag slag concrete bricks uses the metallurgical slag of the steel plant on site, which can reduce the mining excavation volume and vehicle transportation volume of 360,000 tons of sandstone every year. The maintenance of steel slag slag concrete bricks is maintained by steel mill waste heat steam, which saves coal resources. The production line integrates the comprehensive utilization of metallurgical slag, waste heat steam, blast furnace gas and other renewable resources. It can save sand and stone transportation (with a distance of 30 kilometers) and use 162,000 liters of oil per year (heavy load trucks consume 1.5 per ton of steel slag oil). l / 100 km); can save 90,000 tons of finished cement per year, equivalent to about 10,000 tons of standard coal (110 kg / ton of finished cement); at the same time reduce the production and use of 200 million clay bricks per year, equivalent The standard coal is 30,000 tons (the clay brick coal consumption is 100 kg/m3). If 100 large-scale steel plants nationwide build an annual production line of 300,000 cubic meters of steel slag slag concrete bricks, the annual utilization of metallurgical slag will be about 44 million tons, saving 16.2 million liters of oil for transportation and 4 million tons of coal. In this way, the metallurgical slag discarded by the steel plant is used in large quantities, and the market of clay bricks is replaced a lot, and the cultivated land is protected. At the same time, since the steel slag slag concrete is a burn-free brick, energy saving can be achieved.

(3)Energy-saving and environmental protection analysis of metallurgical slag autoclaved aerated block production

The metallurgical slag autoclaved aerated block is made by adding steel slag and slag to the slurry, adding powdery composite additive, appropriate amount of gypsum and gas generating agent, and adding by gas, pre-culture, cutting, autoclaving and other processes. Gas block products. The metallurgical slag produced by the process has good performance in steam-pressing and aerating blocks, meets the needs of industrial and civil construction, and can consume metallurgical slag in large quantities. More than 90% of the raw materials used in the process are metallurgical slag. The steam is produced by using the blast furnace gas, a by-product of the ironworks, and the product cost is low. The production line consumes about 75 million cubic meters of blast furnace gas per year (heat value is 3200 kcal / cubic meter), equivalent to about 34,000 tons of standard coal (the calorific value of standard coal is 7000 kcal / kg). Taking Xiangtan Iron and Steel Group Co., Ltd. as an example of an annual production of 300,000 cubic meters of metallurgical slag autoclaved aerated block production line, it can consume about 140,000 tons of steel slag and 140,000 tons of slag per year. It can use a large amount of metallurgical slag and produce a good economy. benefit. If 100 large-scale steel mills in the country build an average of 300,000 cubic meters of metallurgical slag autoclaved aerated block production line, they can use about 30 million tons of metallurgical slag, saving 3.4 million tons of coal per year.

In the process of producing refractory balls, a hydroforming method is usually used. The following is an introduction to the press forming method and some suggestions for equipment selection.

1. The press forming method is the most used forming method in the production of refractory balls. The method uses a ball press and a steel die to compress the formulated refractory ball material into a sphere. Since general machine forming refers to a semi-dry material forming method having a water content of 4% to 9%, it is also called semi-dry molding. The equipment commonly used in this method includes a friction brick press, a lever press, and a hydraulic press.

2. The press forming process is essentially a process in which the particles in the ball are densely packed and the air is discharged to form a dense sphere. The machine-formed refractory ball has the advantages of high density, high strength, small shrinkage and shrinkage, and easy control of the size of the refractory ball. Therefore, this method plays a major role in the production of refractory balls.

3. In order to obtain a dense sphere during press forming, sufficient pressure must be given to the pellet. The pressure should be such that it can overcome the internal friction between the pellets, overcome the external friction between the pellet and the mold wall, and overcome the pressure distribution caused by the moisture of the pellet, the particles and the uneven filling in the mold. Uniformity.

The proportional relationship between the three depends on the dispersion of the pellets, the composition of the pellets, the moisture of the pellets, the size and shape of the spheres, and the like. Although there are several theoretical formulas for calculating the relationship between pressure and sphere densification, such as the change of the spherical pores with the logarithm of the pressure, the test method is usually used to determine the pressure per unit area of ​​the sphere, and the pressure is determined accordingly. The total pressure that the brick machine should have.

The requirements of the ball forming machine for the ball material should have a certain fluctuation range except for the moisture, and there are certain requirements for the particle size. For example, there should be a reasonable particle size ratio, and the bulk density should be as large as possible. Generally, the critical particle size is 3 to 5 mm, and the fine powder content of less than 0. 088 mm should be in the range of 35% to 45%.

The most common defects of machine-formed refractory balls are spallation and layer density. A spallation is a lamellar crack formed perpendicular to the direction of pressurization formed during pressurization. Excessive moisture in the ball, excessive fines, too little binder and excessive pressure can lead to spalling.

Therefore, these parameters must be controlled in production. The layer density phenomenon, that is, the density of the refractory balls after molding, is reversed in the direction of pressurization. The unidirectionally pressurized refractory ball from the top is generally dense and sparse, and the same horizontal plane is medium-density and sparse. This is due to the friction between the ball particles and the friction between the ball and the die wall. The method of reducing the external friction by double-sided pressing and lubricating the four walls of the mold can reduce the phenomenon and reduce the porosity of the sphere.

The selection of molding equipment should be considered comprehensively according to the quality requirements, size and production quantity of the refractory ball. Generally, the refractory ball for the heating furnace or the product with simple shape, large quantity and general quality requirements can be selected with the lever ball press with high production efficiency; the refractory ball with higher quality requirement can adopt the friction with the nominal pressure not lower than 2000K•N. Pressure ball machine.

The briquetting machine sleeve is an indispensable component in the briquetting machine. The briquetting sleeve determines the shape of the pressing machine. It is a layer of surface excavation included on the outside of the core of the briquetting machine. A cylindrical member having a ball socket. According to the different assembly methods, it is divided into one-piece and sub-package. With the development of briquette technology, the durability and molding rate of molding equipment have been widely concerned. The mainstream ball presses are generally cast with 9 chrome 2 molybdenum roll material, which has the strongest wear resistance and will greatly improve the use of briquetting equipment. life.

Since some of the press ball presses are relatively hard, generally 65Mn castings, 9 chrome 2 molybdenum or alloy can also be used. The specific situation should be selected according to the actual situation of the material. With the development of briquette technology, the durability and molding rate of molding equipment have been widely concerned. The mainstream ball press is generally made of 9 chrome 2 molybdenum roll material casting, which has the strongest wear resistance and will greatly improve the use of pressure ball machine equipment. life.

 

Briquetting machine roll set

 

First, the briquetting machine has no key assembly form:

1. Tightly fit with the hot-packing method, that is, the roller sleeve with the ball socket is heated and then mounted on the hub. This assembly form has high processing precision, strict processing temperature control, and must have special equipment when replacing, generally used for high-pressure ball press , for example: strong mineral powder ball press, powerful ball press, high pressure dry powder ball press

2, the cone set method, that is, the roller sleeve or the hub design has a taper, and the middle taper sleeve is tight. This form is beneficial to the disassembly and assembly of the roller sleeve, and is applied to a medium and low pressure ball press, such as a desulfurization gypsum ball press. Static pressure ball machine, etc.

3. Bolt fastening method, that is, the sleeve and the hub are designed with bolt holes, which are tightened with refined high-strength bolts. This method is beneficial to the on-site disassembly and assembly of the roller sleeve, and the wet medium and low pressure ball presses are more used.

Second, the briquetting machine key joint assembly method: that is, the shaft and the roller sleeve have key grooves, and the shaft and the sleeve are coupled by the key. Since the key groove and the thread are opened on the shaft, the diameter of the main shaft is slightly larger than the shaft diameter of the keyless assembly form. .

Third, the briquetting machine roller disassembly assembly form: that is, the roller sleeve is divided into several equal parts, and is fastened by the positioning pin and the bolt on the hub. In the manufacturing process of the roller tile, the heat treatment is adopted, and the roller tile is easily deformed, and cannot be smoothly replaced in the future, the heat treatment is omitted, and the roller tile is not durable. Due to the assembly method, the roller is small in size and light in weight, which is very advantageous for on-site replacement. Therefore, the ball press is very popular, but the durability of the ball press roller needs to be improved as soon as possible.

The field application of the roller mill is divided into three parts, and at the same time, as a precaution in the use of the high-pressure roller mill, I hope to help you.

First, feeding

(1) The high-pressure roller mill must be densely fed during use. If the feed is loose, the uneven force on the roll surface will reduce the life of the roll surface.
(2) The high-pressure roller mill must have proper powder in the feed, not only the material on the screen, otherwise the life of the roll surface will be greatly reduced.
(3) The high-pressure roller mill should be evenly fed, otherwise it will cause the squeeze roller to deflect and reduce the extrusion effect. In severe cases, the host will jump.

Second, iron treatment

If there is metal in the feed of the high-pressure roller mill, the life of the roll surface will be reduced. If the metal near or larger than the roll gap size is fed into the high-pressure roll mill, the partial roll surface load will be too large, resulting in damage to the stud or roll surface. If there is metal in the feed to the high pressure roller mill, the following measures can be taken to protect the roll surface.
(1) Install metal detectors and iron removers on the feed belt of the high pressure roller mill.
(2) If it is closed-circuit screening, the iron remover can be installed above the discharge end of the material on the sieve. At this time, the material on the sieve is in a loose state, which can effectively remove the magnetic metal minerals therein.
(3) In the self-grinding/semi-self-grinding machine process, if the cone crusher and the high-pressure roller mill are combined as a hard stone crushing device, a curved iron remover can be installed at the discharge end of the mill (only for non-magnetic and weak magnetic properties) Mineral), de-ironing the self-grinding/semi-self-grinding machine, and installing metal detectors and iron removers on the subsequent return belt to ensure that all metal materials in the return material are removed.
(4) In the iron removal system, the iron remover should be used in combination with the metal detector, because the iron remover can only remove the magnetic metal in the feedstock, and for the non-magnetic metal, it should be manually removed by the metal detector.

Third, the bypass system

At present, many conditional mines have set up a bypass system in the high-pressure roller mill system, which can not delay production when the high-pressure roller mill fails, periodically repairs and replaces the roller surface. The bypass system is suitable for three-stage closed-circuit crushing + high-pressure roller mill ultra-fine crushing process, in high-pressure roller mill parking or under certain special conditions (such as continuous rain, excessive air humidity, high-pressure roller mill running poorly), materials It can be directly fed into the subsequent ball mill to make the production continuous.

1. The necessity of the crushing process

In the self-grinding/semi-self-grinding process, critical size particles, called hard stones, are produced, which are the sieved portions of the self-grinding and semi-self-grinding discharges after sieving. The particle size range of the hard stone is generally 25 to 90 mm. These ores are too large in size and cannot be broken by other bulk materials in the self-grinding process. They cannot be broken by steel balls in semi-self-grinding, and the particle size as grinding media is too small. The existence of the stone causes the input power of the mill to be constant, and the cyclic load is increased, resulting in an increase in the unit energy consumption of the grinding. In addition, if there are too many critical dimensions in the mill, the grinding process will change from impact-based to grinding-based, resulting in over-grinding and making the product too fine. Therefore, self-grinding/semi-self-grinding machines are often stubborn. Stone crushing equipment combines applications.

2. Advantages of high pressure roller mill as a hard rock crusher

The particle size range of the hard stone is generally 25 ~ 90 mm. The traditional cone crusher is a hard rock crusher. The product size is still relatively large, and some of it may still be within the particle size range. The hard rock crushing effect is not good. The high-pressure roller mill is used as the stone crusher. The product has finer particle size and can effectively solve the problem of stone. After the stone is pressed by the high-pressure roller mill, if the fine powder content is high, it can be directly classified into the subsequent ball mill. mine.

3, high pressure roller grinding stone crushing process

As described above, the high-pressure roll mill is used as a hard stone crusher in that there is a problem that the yield of the hard stone is small and the grain size of the hard stone is large. Under normal circumstances, the stone is first crushed by a cone crusher and then into the high-pressure roller mill. Figure 2 shows two typical high-pressure roller mills.

The high-pressure roller mill can be broken as the third stage after being crushed, or it can be used as the fourth-stage superfine operation after the fine crushing operation. The high-pressure roller grinding process can be divided into three types: open-circuit crushing, edge material return crushing and vibrating screen closed-circuit crushing.

1, open circuit crushing process
The high-pressure roller mill open-circuit crushing process refers to the high-pressure roller mill product directly entering the next working process, and no longer returns to the crushing process of the high-pressure roller mill. The open roll product can be directly fed into the ball mill for grinding, or it can be classified first, and the coarse product enters the ball mill for grinding. This process has obvious advantages when the fine powder content of the rolled product is high.
The advantage of the open circuit crushing process is that the process flow is simple and smooth, the system is stable, and the operation and management are convenient. However, due to the non-grading operation, the product granularity is uneven, and the rolled product will be mixed with a little large particle material, which is bad for subsequent grinding. Impact, the actual operation of the plant can be added to the appropriate amount of large balls to alleviate such problems.

2, the edge material return to the crushing process
The high-pressure roller mill edge material returning crushing process refers to the process in which the high-pressure roller grinding intermediate product directly enters the next working process, and the material is returned to the high-pressure roller mill to be broken again. After rolling, the intermediate product can directly enter the ball mill for grinding, or it can be classified first, and the coarse product enters the ball mill for grinding. This process has obvious advantages when the fine powder content of the rolled product is high.
The process also has the advantages of simple and smooth process, stable system and convenient operation and management. The proportion of edge material can be adjusted within the range of 0 to 50%, but it is not possible to return all the coarse minerals that have not been rolled by the high pressure roller mill. . Compared with the open circuit system configuration, the proportion of coarse-grained products has dropped sharply, but the crushing is still incomplete. There are also a lot of large-grain materials in the rolled products, which will have adverse effects on subsequent grinding.

3, closed circuit crushing process
The high-pressure roller grinding closed-circuit crushing process is divided into dry screening and wet screening according to the different classification methods.
The dry screening of the high-pressure roller mill requires a dispersing machine to disperse the cake of the roller press, otherwise the screening efficiency will be greatly reduced. In addition, since the whole process adopts dry grinding, dry screening and dry sorting, the moisture content of the material is required to be high, and it is not suitable to treat materials with high water content. At the same time, attention should be paid to dustproof work, and dust removal is required. Equipment, etc. The process is mainly applied to non-metallic minerals and ore containing less mud, as well as water-deficient and arid areas.

With the increasing application of powder metallurgy products, the size and shape of metal powder particles are increasingly demanding, and the properties and size of metal powders depend to a large extent on the production method of the powder and its preparation. Process, so the preparation technology of powder is constantly developing and innovating.

First, mechanical method

The mechanical method is a processing method for breaking a metal into a powder of a desired particle size by means of a mechanical external force, and the chemical composition of the material in the preparation process is substantially unchanged. The methods currently in common use are atomization and mechanical pulverization. The advantage is that the process is simple, the yield is large, and ultrafine powders of high melting point metals and alloys which are difficult to obtain by conventional methods can be prepared.

Mechanical pulverization method: The mechanical pulverization method is not only an independent milling method, but also often an indispensable supplementary process for other milling methods. The solid metal is broken down into powder mainly by crushing, crushing and grinding. There are two types of crushing equipment:

Crushed equipment mainly used for crushing: coarse crushing equipment such as crusher, rolling mill and jaw crusher;

Fine crushing equipment mainly used for crushing and grinding: hammer mill, rod mill, ball mill, vibrating ball mill, agitating ball mill, etc.
Preparation of metal powder by high energy ball milling

The mechanical pulverization method is mainly suitable for pulverizing brittle and easy-to-work harden metals and alloys such as tin, manganese, chromium, high carbon iron, iron alloys and the like. The method has low efficiency and high energy consumption, and is used as a supplement to other milling methods or for mixing powders of different properties.

Atomization method: The method of directly crushing a liquid metal or alloy to obtain a powder is called atomization method, and is a widely used metal powder preparation method which is second only to the reduction method in production scale. The atomized powder has the advantages of high sphericity, controllable powder particle size, low oxygen content, low production cost and adaptability to the production of various metal powders. It has become the main development direction of high performance and special alloy powder preparation technology, but the production efficiency is low. The defect of ultra-fine powder is not high, and the energy consumption is relatively large, which limits the application of the atomization method.

Second, physical chemistry

The physico-chemical method refers to a method for producing an ultrafine powder by changing the chemical composition or the state of aggregation of the raw material during the preparation of the powder. According to different chemical principles, it can be divided into reduction method, electrolysis method, carbonyl method and chemical replacement method.

Reduction method: Reduction of metal oxides and metal salts to produce metal powder is one of the most widely used milling methods. In particular, the reduction method is most economical when directly using ore and metallurgical industrial waste such as rolled steel scales. The advantages of the reduction method are simple operation, easy control of process parameters, high production efficiency and low cost, and are suitable for industrial production. The disadvantage is that it is only suitable for metal materials which are easy to react with hydrogen and become brittle and easily broken after hydrogen absorption.

Electrolysis method: Electrolysis is a method in which a metal powder is deposited on a cathode by electrolytically melting an aqueous solution of a salt or a salt. It plays an important role in powder production. Its production scale is second only to the reduction method in physical and chemical methods, and it can control the milling particle size. The prepared powder has high purity and the elemental powder can reach more than 99.7%. However, the electrolysis method consumes more electricity, and the cost is higher than that of the reduced powder and the atomized powder. Therefore, in the total powder production, the proportion of electrolytic powder is relatively small.

Carbonyl method: Since the metal carbonyl is easily decomposed into a metal and a CO gas at a low temperature, a metal carbonyl metal powder can be obtained by a reverse reaction of a synthetic metal carbonyl. The carbonyl method can be used not only to obtain micron-sized powders, but also to obtain nano-sized powders; not only can a single pure metal and alloy powder be prepared, but also a coated powder can be obtained. The highly developed surface of the carbonyl powder itself is incomparable to the powders produced by other methods and is the best material for chemical power plates and catalysts.

Chemical substitution method: According to the activeness of the metal, the less active metal is replaced from the metal salt solution by a highly active metal, and the metal (metal powder) obtained by the replacement is further processed by other methods. The method of refining into a metal powder is called a chemical replacement method. The method is mainly applied to the preparation of inactive metal powders such as Cu, Ag, and Au.

With the advancement of technology, metal powder has shown good application prospects in metallurgy, chemical industry, electronics, magnetic materials, fine ceramics and sensors. However, due to the limitations of traditional preparation techniques, the application of metal powder is restricted. Although many new production processes and methods have been applied, the problems of smaller scale and higher cost are still not well solved. In order to promote the development of metal powder materials, it is necessary to intensify innovation, learn from each other’s strengths, and develop production processes with higher output and lower cost.

If not properly maintained, the conveyor may experience rapid belt wear and component failure, resulting in downtime and maintenance. This has a corresponding negative impact on productivity and profit. Therefore, we must improve the most common problems with conveyors and the understanding and prevention of problems in the future.

The transportation of mineral products accounts for a large proportion of the total mining cost. Therefore, conveyor systems have become a universal solution to improve operational efficiency. The challenge is that conveyors typically operate under extremely harsh conditions, such as dirty environments, high or low temperatures, and high humidity. If not properly maintained, the conveyor may experience rapid belt wear and component failure, resulting in downtime and repairs. This will have a corresponding negative impact on productivity and profit. Therefore, we must improve the most common problems with conveyors.

First, the belt runs off
Problem: When the belt deviates from its desired path, the belt runs off. This is a serious problem that can result in belt damage, equipment failure, and material spillage. There are many reasons for belt deviation, such as insufficient belt tension, eccentric load, incorrect splicing, component deflection, material accumulation on components and components, and so on.
Solution: The best solution is to find out the root cause of the belt deviation to prevent the same problem in the future. Conducting a belt check helps identify all potential problems that cause deviations in order to develop a suitable solution. If the belt has a slight deviation, use the self-aligning roller to correct the belt’s trajectory and ensure that it will always run straight ahead.

Second, material return
Problem: When a small amount of material adheres to the belt, the transport opportunity is returned. This can cause the material to build up under the conveyor belt or accumulate on the rollers and rollers. Certain materials, such as cohesive soils and certain ores, adhere more easily to the belt than others. Although the amount of return shipments is negligible, the time is long, and there are tons of materials accumulated, which has to be cleaned up twice. Material return also poses safety and environmental hazards, increases cleaning costs, and is generally not conducive to optimal operation of the conveyor system.
Solution: A simple solution is to install a net belt that is designed to prevent backhaul. The benefits of the net belt are sufficient to offset the upfront investment costs. Reduce material spills, save on maintenance costs, and create a safer working environment. In addition, the clean belt prevents premature roll damage, extends belt life and keeps the system in optimum operating condition.

Third, the belt is damaged
Problem: There are several reasons for belt damage, such as excessive impact, deviation, improper use of the sealing system or belt cleaner, component jamming and insufficient drum traction. The belt is the most expensive part of the conveyor, so you must find the potential cause of the belt problem and take active measures to avoid irreparable damage.
Solution: There are many reasons for belt damage, so there are many different solutions. For example, installing a cushioning roller or bracket in the feed zone can dissipate the impact of the falling material, thereby reducing wear and tear on the belt. The use of a suitable sealing system prevents the belt from being damaged by stagnant materials. Use a suitable roller wrap to increase friction and prevent the belt from slipping without damaging it quickly. These solutions help minimize maintenance downtime, usually determined by a single belt check. Belt inspection can capture minor belt damage to avoid serious failures in the future.

The jaw crusher has the advantages of large crushing ratio, simple operation and convenient maintenance, and is widely used in construction, mining, cement and other industries. However, a large amount of dust is generated during the production process, causing a large pollution. With the step-by-step follow-up of environmental supervision, it is extremely urgent to thoroughly deal with dust. So what are the causes of dust, and what can we do to effectively reduce the impact of dust?

Causes of dust generation during machine operation

1. The principle of the fan is the same. When the crusher rotor breaks the material at high speed, the air in the upper chute of the crusher is continuously sucked to the tail to form a high-pressure airflow. The dust collector sucks away, and the portion that is not sucked away carries a large amount of pulverized coal and is flushed out from the gap of the lower chute.

2. The chute of the tail is linear, and the flow area is also large. The high-pressure airflow is easy to stay from here.

3. The dust collection point of the dust collector disposed outside the jaw crusher is scattered, because the suction pipe is long and has many elbows, so the resistance to vacuum is very large, and it absorbs some externally while vacuuming. Cleaner air.

4. The dust absorbed by the dust collector is filtered and sent back to the belt conveyor by the screw conveyor. The outlet position is just below the dust hood. The pulverized coal will be immediately blown away by the high pressure airflow and sucked away by the vacuum pipe. Secondary pollution.

Effectively reduce dust

After analyzing the causes of dust generation, we can use the following methods to solve the problem and effectively remove dust:

1. For the high-pressure wind generated by the high-speed rotation of the crusher, we can try our best to seal the chute behind the crusher and the belt conveyor. For high-pressure wind, we can use the dredging method to reduce the pressure wind.

When the rotor of the jaw crusher rotates at a high speed, a lower pressure zone is generated at the upper feed port. If the high pressure zone in the lower part of the rotor and the upper low pressure zone are connected, the air flow will be in the differential pressure. Next, the high pressure zone exiting the crusher is returned to the low pressure zone of the inlet, thereby forming a closed loop of the airflow inside the crusher system, removing the wind pressure of the chute after the crusher, and reducing the external discharge of the dust.

2. Remove the unnecessary points of the dust collector and close the remaining one of the dust suction points to the tail chute, thus increasing the vacuuming capacity of the vacuum cleaner.

3. For the dust of the dust collector absorber, shift the return port, move the discharge port inside the chute to the outside, and then use the cloth bag to put the coal powder into the trough, and then manually clean it. At this time, the air flow A closed loop is formed, which reduces the amount of coal powder sucked by the precipitator, and the labor intensity of the worker is not large.