Ranchhodwadi Main Road, Near Kuvadava Road, Rajkot No. 3, Shreyas Anand Complex, 1st Floor, Opposite Parul Garden, Ranchhodwadi Main Road, Near Kuvadava Road, Rajkot - 360003, Dist. Rajkot, Gujarat
When making comparisons of the efficiencies of different grinding and crushing machines it is desirable to be able to estimate the work actually done in crushing the ore from a given size of feed to a given size of product, the screen analysis of both feed and product being determined. Messrs. Klug and Taylor, in a paper on this subject, published in the monthly journal of the Chamber of Mines, have described a method adopted by them in calculations made in connection with a series of trials of grinding pans. Their method is based upon the assumption that if a quantity Q of material consisting of particles of average diameter x be crushed down until the average diameter of the particles is y then the work done in grinding is proportional to Q x/y. Thereis no theoretical basis for this assumption that the writer is aware of, and it does not appear to satisfy the fundamental conditions necessary. If the material be further crushed until the diameter become z, the additional work done is measured by Q y/z. Now the work done in crushing from diameter x to diameter z in one operation is proportional to Q x/z, and therefore we ought to have:
But these expressions are not in general equal to one another. In other words, according to the theory underlying this method, if we crush from diameter x to diameter y, and then from diameter y to diameter z, the total work done will be different to what it will be if we crush direct from diameter x to diameter z. This cannot be right. Further, if we make y = x, the expression for the work done still has the value Q, although in reality no work is done at all.
The method proposed in this paper enables such calculations to be made more simply, and rests upon the principle that if a quantity Q of material that will just pass through a screen of m meshes to the lineal inch be crushed until it will just pass through a screen of m meshes to the inch, then the work done in crushing is proportional to Q (n-m). This is founded upon the reasons following, and is also in agreement with the results of practical experiment.
Suppose that we have a quantity Q of material made up of particles of average diameter x, then the number of particles is proportional to the quantity divided by the volume of each particles i.e. to Q/x.Now, let these be crushed to some smallerdiameter y. If we suppose one of the original particles is a cube, whose side is x, and that this is divided up into cubes each of side y, the division may be affected by shearing along three sets of parallel planes at right angles as shown in Fig. 1. The number of such shearing planes parallel to one side is x/y 1 and these are each of area x. In order to divide up the original cube, then, along one set of these parallel planes the work required to be done is proportional to (x/y 1)x, and since the shearing has to be effected along three such sets of planes, the total work done is measured by 3(x/y 1)x. But these are Q/xparticles, and therefore the total work done in reducing a quantity Q from average diameter x to diameter y is measured byQ/x3(x/y 1)x, or leaving out the constant, Q (1/y 1/x). According to this, if we now further crush down to diameter z the additional work done is Q (1/z 1/y),and the total work done in crushing from diameter x to diameter z = Q(1/y 1/x) + Q(1/z 1/y), which = Q(1/z 1/x), thesame as if the crushing were all done in one operation.
To make the computation, then, it is necessary to determine the reciprocal of the diameter of the particle. But this is very nearly double the number of meshes per lineal inch of the screen through which the particle will just pass, as is seen from the following table for the I.M.M. standard laboratory screens:
It consequently follows that the crushing of a quantity Q of ore, consisting of particles of uniform size that will just pass through a screen of m meshes per lineal inch down to another uniform size, such that they will just pass through a screen of n meshes per lineal inch, requires an amount of work proportional to Q (n m).
a, per cent. of material just passing through p meshes to the inch b, per cent. of material just passing through q meshes to the inch c, per cent. of material just passing through r meshes to the inch and this be ground down to a product consisting of d, per cent. of material just passing through s meshes to the inch e,per cent. of material just passing through t meshes to the inch
the work done in grinding may be found by first of all computing the work required to reduce the feed down to some very small uniform size of, say, m meshes to the inch, next computing the work required to reduce the product of the machine down to the same size of m mesh, and then substracting the two. That is to say, the total work done in the machine is proportional to:
This gives us, then, a very simple rule for finding the work done in a grinding machine, which we may best describe by a numerical example. Suppose that we wish to compare the efficiencies of the grinding effected by two machines, the feed and resultant products of which grade as follows :
We have then to multiply each percentage by the number of meshes to which it corresponds. Thus, the material passing through 20 mesh, and caught on 40, will be considered to correspond to an average size of 30 mesh, and the percentage of this class of material is accordingly multiplied by 30. Regarding the material that passes through 160 mesh as equivalent to an average size of 180 mesh, we may arrange the computation as follows:
Thus the total work done in crushing by machine A is proportional to 5,808 x 20 = 116,160, and that by machine B to 6,103 x 17 = 103,751, and the crushing efficiencies of the two machines are in the proportion of 116 : 104 nearly.
The energy required to liberate a mineral of economic interest from its gangue constituents in the host rock is described in this chapter. The design of equipment use for the purpose is indicated in some details. Standard laboratory tests for determining this energy are described for ball and rod mills systems of grinding. The methods of calculating this energy is illustrated with worked examples.
Mineral processing, art of treating crude ores and mineral products in order to separate the valuable minerals from the waste rock, or gangue. It is the first process that most ores undergo after mining in order to provide a more concentrated material for the procedures of extractive metallurgy. The primary operations are comminution and concentration, but there are other important operations in a modern mineral processing plant, including sampling and analysis and dewatering. All these operations are discussed in this article.
Routine sampling and analysis of the raw material being processed are undertaken in order to acquire information necessary for the economic appraisal of ores and concentrates. In addition, modern plants have fully automatic control systems that conduct in-stream analysis of the material as it is being processed and make adjustments at any stage in order to produce the richest possible concentrate at the lowest possible operating cost.
Sampling is the removal from a given lot of material a portion that is representative of the whole yet of convenient size for analysis. It is done either by hand or by machine. Hand sampling is usually expensive, slow, and inaccurate, so that it is generally applied only where the material is not suitable for machine sampling (slimy ore, for example) or where machinery is either not available or too expensive to install.
Many different sampling devices are available, including shovels, pipe samplers, and automatic machine samplers. For these sampling machines to provide an accurate representation of the whole lot, the quantity of a single sample, the total number of samples, and the kind of samples taken are of decisive importance. A number of mathematical sampling models have been devised in order to arrive at the appropriate criteria for sampling.
After one or more samples are taken from an amount of ore passing through a material stream such as a conveyor belt, the samples are reduced to quantities suitable for further analysis. Analytical methods include chemical, mineralogical, and particle size.
Even before the 16th century, comprehensive schemes of assaying (measuring the value of) ores were known, using procedures that do not differ materially from those employed in modern times. Although conventional methods of chemical analysis are used today to detect and estimate quantities of elements in ores and minerals, they are slow and not sufficiently accurate, particularly at low concentrations, to be entirely suitable for process control. As a consequence, to achieve greater efficiency, sophisticated analytical instrumentation is being used to an increasing extent.
In emission spectroscopy, an electric discharge is established between a pair of electrodes, one of which is made of the material being analyzed. The electric discharge vaporizes a portion of the sample and excites the elements in the sample to emit characteristic spectra. Detection and measurement of the wavelengths and intensities of the emission spectra reveal the identities and concentrations of the elements in the sample.
In X-ray fluorescence spectroscopy, a sample bombarded with X rays gives off fluorescent X-radiation of wavelengths characteristic of its elements. The amount of emitted X-radiation is related to the concentration of individual elements in the sample. The sensitivity and precision of this method are poor for elements of low atomic number (i.e., few protons in the nucleus, such as boron and beryllium), but for slags, ores, sinters, and pellets where the majority of the elements are in the higher atomic number range, as in the case of gold and lead, the method has been generally suitable.
A successful separation of a valuable mineral from its ore can be determined by heavy-liquid testing, in which a single-sized fraction of a ground ore is suspended in a liquid of high specific gravity. Particles of less density than the liquid remain afloat, while denser particles sink. Several different fractions of particles with the same density (and, hence, similar composition) can be produced, and the valuable mineral components can then be determined by chemical analysis or by microscopic analysis of polished sections.
Coarsely ground minerals can be classified according to size by running them through special sieves or screens, for which various national and international standards have been accepted. One old standard (now obsolete) was the Tyler Series, in which wire screens were identified by mesh size, as measured in wires or openings per inch. Modern standards now classify sieves according to the size of the aperture, as measured in millimetres or micrometres (10-6 metre).
In order to separate the valuable components of an ore from the waste rock, the minerals must be liberated from their interlocked state physically by comminution. As a rule, comminution begins by crushing the ore to below a certain size and finishes by grinding it into powder, the ultimate fineness of which depends on the fineness of dissemination of the desired mineral.
In primitive times, crushers were small, hand-operated pestles and mortars, and grinding was done by millstones turned by men, horses, or waterpower. Today, these processes are carried out in mechanized crushers and mills. Whereas crushing is done mostly under dry conditions, grinding mills can be operated both dry and wet, with wet grinding being predominant.
Some ores occur in nature as mixtures of discrete mineral particles, such as gold in gravel beds and streams and diamonds in mines. These mixtures require little or no crushing, since the valuables are recoverable using other techniques (breaking up placer material in log washers, for instance). Most ores, however, are made up of hard, tough rock masses that must be crushed before the valuable minerals can be released.
In order to produce a crushed material suitable for use as mill feed (100 percent of the pieces must be less than 10 to 14 millimetres, or 0.4 to 0.6 inch, in diameter), crushing is done in stages. In the primary stage, the devices used are mostly jaw crushers with openings as wide as two metres. These crush the ore to less than 150 millimetres, which is a suitable size to serve as feed for the secondary crushing stage. In this stage, the ore is crushed in cone crushers to less than 10 to 15 millimetres. This material is the feed for the grinding mill.
In this process stage, the crushed material can be further disintegrated in a cylinder mill, which is a cylindrical container built to varying length-to-diameter ratios, mounted with the axis substantially horizontal, and partially filled with grinding bodies (e.g., flint stones, iron or steel balls) that are caused to tumble, under the influence of gravity, by revolving the container.
A special development is the autogenous or semiautogenous mill. Autogenous mills operate without grinding bodies; instead, the coarser part of the ore simply grinds itself and the smaller fractions. To semiautogenous mills (which have become widespread), 5 to 10 percent grinding bodies (usually metal spheres) are added.
Yet another development, combining the processes of crushing and grinding, is the roll crusher. This consists essentially of two cylinders that are mounted on horizontal shafts and driven in opposite directions. The cylinders are pressed together under high pressure, so that comminution takes place in the material bed between them.
South Africa is the world's second largest vermiculite ore producer, only after the United States. South African vermiculite total reserve is about 73 million tons, accounting for 35.9 percent of the world's reserves. In addition, South Africa is the world's largest exporter of vermiculite. South African vermiculite annual export volume accounts for nearly 90% of world trade. In South Africa, among the domestic production of non-metallic minerals, vermiculite is a major foreign exchange mineral. The major producer of vermiculite is Palabora region, accounting for over 90% of vermiculite total reserve in South Africa.
According to different production requirements, product specifications of vermiculite are as follows:8-12MM ,4-8MM ,2-4MM ,1-2MM ,0.3-1MM ,40-60 mesh,60-80 mesh,80-100 mesh, 100 mesh, 150 mesh, 200 mesh, 325 mesh, etc.
With the development of vermiculites applications, South African abundant vermiculite resource has been extensively developed. And many vermiculite processing plants are built in recent years. In general, we need jaw crusher, impact crusher and vibrating feeder, vibrating screen as well as belt conveyor. After being transported from the mining site, the raw vermiculite mine needs store and select at first, to ensure the vermiculite continuous and stable quality fed into the follow process. In the primary crushing process, we usually choose jaw crusher to crush vermiculite ore into small size within 8 mm. Use vibrating screen to screen the crushed vermiculite into different sizes, and send suitable particles into the next step, while the other part returned for re-crushing. We recommend impact crusher as secondary crusher to crush vermiculite into small size less than 2 mm. At last, send crushed vermiculite to the mill for grinding.Customers can choose different kinds of grinding mill according to different requirements, such as vertical mill, trapezium mill, ball mill, and so on.
And you can choose the mobile vermiculite crusher, which gathers all the machines above together. Compared with traditional and fixed vermiculite processing line, mobile vermiculite crusher has many unmatchable features. It is designed with more reasonable and compact structure, which greatly reduces the occupying area. And compared with fixed crushing plant, mobile vermiculitecrusher can work without disassembly, transportation and installation, soit can greatly reduce the investment. The crusher can move to vermiculite mining area without any environment limit to reduce transportation cost and foundation building cost. It is more flexible and adaptable. And it is easy for installation and maintenance. Our efficient mobile vermiculite crusher adopts advanced manufacturing technique and high-end materials. So it has higher carrying capacity and more reliability. It is easy to adjust the size of the final products. And the crushed materials are in good particle shape. According to different production requirement, it can match with other equipment easily.
According to a series of processing, vermiculite has a wide application. Its main purpose is still to make building materials. In the U.S. consumption structure, vermiculite accounts for 52% used as mortar and cement mixing materials and lightweight concrete aggregate. In English, 40% of vermiculite is used asconcrete, plastering mud, and cement coagulant.It can also be used as adsorbents, fireproof insulation materials, machinery lubricants, soil improvers, and so on.
SBMis professional vermiculite processing equipment manufacturer. We have more than 20 years experience. Our products are welcomed by South African vermiculite miners. All of our products adopt the advanced technology from the world, and made by high quality materials. We can also design a complete vermiculite processing plant according to customers requirement. It is with the features of large capacity, low production cost, long service life and so on.
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Williams Patent Crusher is a leading industrial hammer mill manufacturer. Our industrial size reduction machines can handle any material size reduction job. Choose a Williams machine for high efficiency and economy. Using midair and impact crushing, grinding, and shredding, our machines can handle virtually any material.
A hammer mill is a particle size reduction machine. These machines grind and crush material using continual, high-speed hammer blows. This internal hammer shatters and disintegrates the material. Mills can be primary, secondary, or tertiary crushers, allowing for a wide variety of applications.
Williams hammer mills are a popular choice when it comes to particle size reduction. While many use these machines as rock crushers and stone crushers, they offer more versatility. Some of the industries and applications that benefit from this machine are:
Williams has been designing and manufacturing industry-leading hammer mills since 1871. We continue to innovate to exceed the evolving needs of our customers worldwide. Our vision is to recognize changes in the marketplace and provide a quality product. With Williams, you receive a quality product that always delivers the efficiency and ruggedness you expect.
Williams manufactures rugged hammer mills to handle high-tonnage size reduction jobs. This heavy-duty equipment reduces large materials, such as automobile bodies. More applications include rock and coal crushing, reducing limestone to sand and pulverizing metal turnings. They can also shred waste, wood, and paper for baling or burning.
The Williams Rocket Hammer Mill rapidly reduces non-abrasive materials to particle sized pieces. Applications include turning materials into fine granules. These materials include cereal, animal by-products, sawdust, expeller cake, rags, and wood pulp.
Meteor hammer mills use a high hammer-tip speed to produce a finer product. If your finished product needs to have specific characteristics, this is the ideal hammer mill. It is well suited for producing high-quality fluff for the absorbent and non-woven fiber markets.
The Type GP Hammer Mill is a simple, rugged machine for small and medium capacity particle size reduction jobs. It's used for a variety of applications from coal to limestone to salt cake, sawdust, and woodchips. It is a versatile machine that performs efficient particle size reduction. The Type GP also has customization options to meet your specific application needs.
Williams Ring Crushers are also known as turnings crushers. They reduce the size of metal turnings, bullshellings, or clips through impact crushing. Ring crushers produce their rated capacities with little down time and custom capabilities. This customization allows you to meet the exact specifications for your material reduction application.
This type of hammer mill is the ideal choice for applications requiring a large feed opening. It is suitable for continuous jobs with either hourly output or reduction ratio. These machines have rigid steel plate frames that resist shock and failure from fatigue. The adjustable breaker plates also compensate for wear.
The Traveling Breaker Plate Mill is a non-clog hammer mill. This engineering allows a Slugger Crusher to reduce rock, clay, shale and bauxite to or smaller. It can reduce wet, sticky materials to a size suitable for further refinement. Its self-cleaning breaker plates reduce maintenance and service costs.
These mills are overrunning machines, reducing material on breaker plates and then crushing on grates. Their design is for operations that need processed feed before reaching the discharge area. Both models have very rugged construction for considerable material reduction.
This machine's name comes from its ability to reverse the direction of the rotor. This rotor supports the hammers, bringing fresh grinding edges into action. The reversible capabilities lower the frequency of servicing. Our reversible hammer mills increase production, double the life of your hammers, and reduce maintenance costs. Learn more about Williams reversible hammer mills.
This machine's name comes from its ability to reverse the direction of the rotor. This rotor supports the hammers, bringing fresh grinding edges into action. The reversible capabilities lower the frequency of servicing. Our reversible hammer mills increase production, double the life of your hammers, and reduce maintenance costs.
This type of hammer mill has rigid hammers rather than swing mounted. This design makes the machine effective for the pulverization of soft, fibrous, or bulky materials into fine powders. It is also suitable for the reduction of friables like coal. Each ridged arm breaker has many edges that can be indexed and presented as wear occurs. Learn more about our rigid arm breaker machines.
This type of hammer mill has rigid hammers rather than swing mounted. This design makes the machine effective for the pulverization of soft, fibrous, or bulky materials into fine powders. It is also suitable for the reduction of friables like coal. Each ridged arm breaker has many edges that can be indexed and presented as wear occurs.
The general term gypsum refers to two minerals, raw gypsum and anhydrite. Raw gypsum is calcium dihydrate (Ca [SO4] 2H2O), also known as dihydrate gypsum or plaster. Anhydrite is anhydrous calcium sulfate.
It is a very important industrial raw material that is widely used in construction, building materials, industrial and artistic models, chemical industry (sulfuric acid production, paper filler, paint filler), agriculture, food processing, pharmaceutical, and many other industries and applications.
The plaster of Paris (also known as hemihydrate gypsum), divided into -type gypsum powder and -type gypsum powder, is formed from gypsum raw materials by heating at a high temperature of 105-200 .
The -type gypsum powder has good crystallinity and solidity, so it can be used in ceramic molds, sculptures, gypsum lines and high-end buildings. The -type gypsum powder is mainly used for mortar levelling, gypsum board production, painting, etc.
Gypsum powder can be used as Portland cement retarder in the concrete industry. In agriculture, because gypsum powder is alkaline, it is possible to sprinkle it into the acidic soil to integrate the ph value of the soil so as to make use of a lot of lands.
In the pharmaceutical industry, gypsum is the main medicine in the famous Chinese medicine " Baihu Tang ", which has a good effect in treating acute high fever and thirsty irritable. In addition, dentists use plaster to make models of gums, and surgeons also use plaster to repair the fractures.
Is gypsum harmful to humans? Is gypsum powder safe to eat? Will gypsum kill plants? Here is a video about how gypsum is used, including its uses in toiletries, food additive, fertilizer, chalks, etc. It also shows the process of gypsum.
In recent years, the gypsum industry has developed rapidly. Gypsum building materials are increasingly welcomed by the market and recognized by society with their applications becoming more and more widespread.
According to the US mining forecast, the world's gypsum demand will increase at a rate of 2.5% in the next few years. It is estimated that the world's gypsum demand will reach 300 million tons in 2030. The total annual consumption of the gypsum board will reach 2.04 billion square meters.
With the increase in the market demand for gypsum powder, the requirements for its production technology are getting higher and higher, so the price has risen accordingly. The price of gypsum powder is generally calculated in tons.
Its price varies with its accuracy and use. The price of gypsum powder is between $ 28.8-$ 403.6 per ton according to its whiteness and fineness. The cooked gypsum powder is about $ 28.8-$ 158.6 per ton, the cooking gypsum is about $ 72.1-$ 317.2 per ton, and the refined gypsum powder is about $ 201.8-$ 720.8 per ton.
1. The ex-factory price of Australian recycled gypsum is $ 35.00 per ton, plus $ 25 per ton freight, which is $ 60.00 per ton at the farm gate, and $ 10.00 per ton to spread. Its purity is measured at 17% S wet weight. Total cost of gypsum supply and application per ton of pure CaSO4.2H20 = (35+25+10) 18.6 17 = $ 76.59 per ton.
2. The ex-factory price of gypsum mined in New South Wales is $ 15 per ton, plus $ 40.00 per ton freight, which is $ 60.00 per ton at the farm gate, and $ 11.00 per ton to spread. Its purity is measured at 15% S wet weight. Total cost of gypsum supply and application per ton of pure CaSO4.2H20 = (15+40+11) 18.6 15 = $ 81.84 per ton.
The world's major gypsum producing countries are the United States, Iran, China, Brazil, Canada, Mexico, Spain, Thailand, etc. The United States, Brazil, China, and Canada are rich in gypsum resources.
The largest consumption area of gypsum is the building decoration material industry, which is mainly used to manufacture gypsum boards for construction and decoration. In many countries, the manufacture of slabs accounts for more than 80% of gypsum consumption.
The mining technology of gypsum ore is divided into two categories: the mining of fibrous gypsum ore and the mining of alabaster, ordinary gypsum and anhydrite mines. Due to the difference in physical and mechanical properties of the ore and surrounding rock, the mining technology of these two kinds of gypsum mines is very different.
Fibrous gypsum has low hardness and its rock consolidating coefficient is 1.2 for parallel fibrous gypsum and 1.5 for vertical fibrous gypsum. Because it is brittle, it will easily become fine ore to be lost. Due to the high price of the ore, most fibrous gypsum mines adopt the longwall method, selective mining and filling method.
The mining techniques of alabaster mine, ordinary gypsum mine and anhydrite mine are similar. The room and pillar mining method (generally 8-12 m in width) and breasting method are adopted. The drilling of gypsum ore is easy, but the explosive consumption is large, generally 0.34 kg/t.
The roller drilling rig is modern new drilling equipment. It is suitable for drilling operations of various hardness of minerals and rocks with the characteristics of high perforation efficiency, low operating cost, high mechanization and automation. At present, it has become a widely used perforation equipment in open-pit mines all over the world.
The excavator is composed of the power plant, working device, swing mechanism, control mechanism, transmission system, moving mechanism, auxiliary equipment, etc. The excavator can also perform pouring, lifting, installation, piling, ramming, and pile pulling operations after changing its working device.
After sieving with the vibrating screen equipment, the finished material conforming to the size is sent to the finished product area, while the large material is returned to the crusher for being crushed again until it meets the required size.
The common gypsum crushing equipment is the jaw crusher with a crushing ratio of 4-6. The jaw crusher, which is often used as the primary gypsum crushing equipment, can crush large pieces of gypsum into 150 mm particle size.
If the gypsum crushed by the jaw crusher cannot meet the particle size requirements, secondary gypsum crushing equipment such as cone crushers, hammer crushers, and impact crushers can be equipped to carry out further medium and fine crushing of gypsum. Specific equipment should be configured depends on the actual needs of the customer.
The crushed gypsum is sent to a ball mill for grinding until 90% of it is less than 149 m (100 mesh). The ground gypsum powder leaves the mill in the form of airflow and is collected in the cyclone separator.
The ball mill is mainly a machine for dry or wet grinding of the crushed gypsum. The machine is mainly used for repeated grinding of the raw materials in the barrel through the steel ball medium in the ball mill to complete the ball grinding operation.
The cyclone separator is suitable for purifying non-viscous, non-fibrous dry dust larger than 1-3 microns. It is purification equipment with simple structure, convenient operation, high-temperature resistance and low equipment cost.
Under the design pressure and air volume conditions, solid particles 10 m can be removed. At the operating point, the separation efficiency is 99%, and within 15% of the operating point, the separation efficiency is 97%. Under normal working conditions, the pressure drop of a single cyclone separator at the operating point is not greater than 0.05 MPa.
The gypsum material is lifted by an elevator and transported into the top silo of the rotary kiln preheater. Then, the gypsum material is evenly distributed into rooms of the preheater through the feeding pipe.
In the preheater, gypsum is heated to about 900 C by the flue gas of the roasting kiln at 1150 C, and about 30% of it is decomposed. Then, it is pushed into the rotary kiln by a hydraulic push rod, and -type hemihydrate gypsum (180240 ), anhydrous gypsum (350 ) and overfired gypsum (450700 ) can be produced.
The gypsum produced after calcining and decomposing in the rotary kiln is sent to the cooler to be cooled to below 100 C by the cold air blown in the cooler and discharged. The gypsum from the cooler is sent to the product warehouse via a vibrating feeder, bucket elevator, and belt conveyor.
Gypsum rotary kiln is a kind of thermal equipment for calcining gypsum. Its appearance and shape are similar to lime rotary kiln and cement rotary kiln. Its main structure includes kiln head, kiln tail sealing device, rotary cylinder, supporting device, back-up roll device, etc.
The finished gypsum clinker calcined in the gypsum rotary kiln produced by Fote has the characteristics of high taste, high purity, easy to control during the production process, high mixing degree of raw materials, uniform raw meal composition, high strength grade of the clinker, with less dust in the grinding process, less fly ash in the calcining process and reasonable price.
The large demand and wide application of gypsum powder have stimulated the prosperity of many industries and fields, so the production of high-quality gypsum powder is the general trend of the gypsum powder industry in the future.
Fote Heavy Machinery, as one of the three major mining machinery manufacturers in China, has 38 years of experience. We are always ready to provide you with high-quality milling equipment and the best service.
As a leading mining machinery manufacturer and exporter in China, we are always here to provide you with high quality products and better services. Welcome to contact us through one of the following ways or visit our company and factories.
Based on the high quality and complete after-sales service, our products have been exported to more than 120 countries and regions. Fote Machinery has been the choice of more than 200,000 customers.
Only where a group of mines operates in a single district are costs comparable and then only with reservations. In general, cost systems are fairly uniform, yet in studying costs of a number of plants it is noticeable that in some cases there is a tendency to omit certain operations which are proper charges against ore dressing and treatment. These should cover the first stage of coarse crushing, whether it be underground or on the surface, as well as the disposal of the residue, the recovery of bullion, and returns from products sold and must include the cost for labor, power, supplies, repairs, and compensation.
In 1936 when data were being compiled for Cyanidation and Concentration of Gold and Silver Ores, considerable published information was available on milling costs in various parts of the world. At the present time, however, it is extremely difficult to obtain reliable figures on the cost of ore treatment owing to the fact that during a period of rising prices and wages the mine managements do not consider current cost data typical of normal operation and are unwilling to release them for publication.
Another factor which applies particularly to the United States and Canada and which tends to make cost-per-ton figures unreliable is the disparity between the rated capacity of many of the mills and the actualtonnage being handled today. This is partly attributed to shortage ofunderground labor and partly to the fact that during the war period not only was maintenance heavier than normal but opportunities for improvements in technique were lacking.
Figure 97 shows the relationship between the tonnage capacity and total milling cost, per ton based on the 1939 figures for a number of typical Canadian plants. Saving in overhead and labor is the principal factor that enters into the decreasing cost per ton for the larger operations.
Considerable variation will be found in individual cases depending upon hardness of ore, fineness of grind, hours of treatment required, reagent consumption, and the situation of the property in its bearing on cost of supplies, etc.
The total cost of producing an ounce of gold in Canada increased from $22.35 in 1939 to $32.07 in 1945, according to the report of the director of the Ontario Mining Association for 1945. This represents a 43.5 per cent increase. From various other data which are available, however, it appears that milling and treatment costs (mining excluded) have probably not risen on the average over about 30 per cent. The broken line in Fig. 97 indicates estimated present (1948) average cost on the basis of this 30 per cent rise.
Kerr Addison, for instance, is milling 2800 tons per day for a total of 72 cents per ton. Hollinger in the 40 weeks ending Oct. 6, 1948, milled an average of 3627 tons per day at a total cost of 77.29 cents per ton, of which 37.90 cents was labor cost.
Where a combination of flotation and cyanidation is used, the combined cost approximates this same percentage. This includes such items as heating and lighting, sampling, assaying, experimental work, repairs, and various indirect costs, depending upon the system of cost distributions in use. It is partly because widely different methods of charging out such costs have been adopted that considerable divergence in overall cost distribution is to be found.
Consolidated Beattie gold mines is a good example of a large plant employing flotation, roasting, and the cyanidation of concentrates. Approximately 1300 tons per day of arsenical gold is treated for an overall cost of $1.05 per ton, distributed as shown in Table 98.
The roasting cost works out at approximately $1.22 per ton of concentrate, distributed as shown in Table 99. At MacLeod Cockshutt Gold Mines, Ltd., the cost of roasting in 1941- 1942 was 32 cents per ton milled or $1.25 per ton of ore roasted, while at Lake Shore mines for the same year the cost was about 80 cents per ton roasted.
The 700-ton mill operated by the Standard Cyanide Co. in Nevada between the years 1939 and 1942, when it was closed as a result of government order during the Second World War, succeeded in making a profit from ore carrying as little as 0.06 oz. gold per ton. Cheap, open-pit mining methods were used, and good extractions were obtained when grinding to only 3 mesh. These, among other factors, made for extremely low-cost operation. The 596,482 tons milled yielded $1.86 per ton at a total cost of $1.18 per ton of which $0.52 was milling cost.
The power required in cyanide plants varies with type of ore, fineness of grind, etc., but in general the range is 20 to 30 kw.-hr. per ton of daily capacity. The power distribution at Preston East Dome mines in Ontario, Canada, is shown in Table 102. The relative distribution of power between the crushing and grindingsections will vary according to the fineness of crushing and the type of plant, but on the average these departments will together consume 60 to 70 per cent of the total power.
Flotation. The power consumption for straight single-product flotation plants varies, according to A. M. Gaudin, from 12 to 20 kw.-hr. perton, depending on the fineness to which the ore is ground. The average percentage power costs for the various.departments of seven United States producers is given in Table 103.
The power consumption at Randfontein Estates, which is milling 13,000 tons per day by the older sand-slime process, is shown in Table 104. Distribution figures for the new 2100-ton-per-day Marievale plant are shown in Table 105.
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The Bond grindability test is currently used in the minerals industry to provide data fundamental to the design of commercial milling installations. In some instances it was found that the work index for the fine limiting sizes (such as 53 m) was abnormally high. Observations of the test procedure suggested that the dry screening procedure seemed likely to give rise to errors.
Other alternative modified Bond test procedures were discussed to solve this problem. Wet Bond milling and screening tests were carried out to avoid incomplete screening of the circulating load at fine sizes. Because the work index required for dry milling was greater than for wet milling, in order to calculate the standard Bond index, the Bond index obtained from wet milling had to be multiplied by 1.3. The results from the dry and wet tests correlated very well.