roll crushers coal advantages

7 things youd better know about coal double roll crusher machine - hongxing machinery

Roll crusher has a simple structure with a less excessive crushing phenomenon. The tooth shape, size, and arrangement of roll surface can be changed with the properties of the material, and the medium-hard and soft ore can be crushed in medium and fine. And, whats more, the roll crusher equipment is mainly composed of a roller wheel, roller bearing, pressing and regulating device and driving device. Generally, a double roll crusher often crushes aggregate materials by two rolls, it is suitable for medium and soft stone materials, especially for coal materials.

The driving mechanism is driven mainly by two motors, which is dragged to the slot wheel through a triangular belt and rotates according to the relative direction. When the material is broken, the material passes through the roller through the feeding port, which is crushed and broken, and the finished product is discharged under the chassis. In order to be safe, the transmission part should install the safety cover according to the actual situation. Outstanding advantages of coal double roller crushers: Excellent and efficient crushing TEMP effect:The output of Hongxing double roll crusher is 1.5 times of that of conventional crushers, and the particle size of the finished stone is uniform, the size is reasonable, and the dust content is low. Production cost: There is a broken tooth ring on the double roll crusher, and the wear of the double roll crusher sleeve can be replaced to a certain extent, so as to reduce the downtime and the production cost. Safe and stable operation: The limit rectangular hydraulic coupler not only absorbs the impact force at the time of crushing, but also ensures the smooth operation of the machine, and also has the function of safety protection for the machine. Reduce over crushing and wear parts: The dual function of crushing and screening reduces the over-crushing and energy consumption of the material, prolongs the service life, and has the TEMP effect of shearing and stretching crushing. The material is not easy to be blocked : non-equal round, non-meshing, and non-constant speed operation of two rollers and the phenomenon of material blockage of the roller crusher will be reduced.

Roll crusher is also called double roll crusher, which is mainly used for fine crushing operation with ore particle size less than 80mm. The utility model has the advantages of small volume, large crushing ratio, low noise, simple structure, and convenient maintenance. The particle size of the broken material is uniform, the over-crushing rate is low, and the particle size of the finished product is 0.5 40 mm.

The tooth roll crusher is mainlymade upof transmission device, frame part, crushing roller, mechanical spring device, linkage mechanism and so on. It is suitable for coal, metallurgy, mining, chemical industry, building materials, and other industries, and toothed roll crusher is more suitable for the crushing of raw coal (including gangue) in large coal mines or coal preparation plants. The crushing capacity of a toothed roll crusher is large, and the limited distance between motor and reducer to prevent power overload and sensor overload protection, which is safe and reliable.

One of the most simple and intuitive differences between the double roll crusher and the toothedroll crusher is the tooth, in other words, the toothedroll crusher has the tooth, double roll crusher doesnt have the tooth. On the other hand, it is possible to distinguish from the mode operation of the apparatus, the drive mechanism of the roller crusherisdriven by two motors, by means of a triangular belt drive to the sheave, and rotating in a relativedirection. When the material is crushed, the material passes through the roller wheel from the feeding port, is crushed by the rolling, and the broken finished product is discharged from the bottom of the bottom frame.

Hongxing tooth roller crusher adopts special wear-resistant tooth roller to rotate at high speed, and the material is split and broken (the traditional tooth-roller crusher is crushed by low-speed extrusion), and the mechanism of high productivity is formed. The pitch of the toothedroller machine is adjusted hydraulically, and the bearing of the HXJQtoothedroller shaft is lubricated. Generally, the toothed roll crusher has the designof optimization, the tensile shear selection, high-efficiency, low-consumption anduniform discharginggranularity.

Recently, an Indian customer named Jim has come to HXJQ corporation for purchasing double roll crushers, at first, HXJQ coal roll crusher price has surprised him a lot, cause the roll crushers not only has excellent quality but also great advantages (comparing to other roll crushers). After a conversation with our salesman, Jim has adopted the advice raised by the salesman. Additionally, Jim has also seen the worksite of our crushers on HXJQ website.

There are many double roll crusher manufacturersproducing this kind of crusher machine, one of the most popular mining crushers manufactures is China HXJQ. As we all know, Hongxing Machinery offers multiple types of double roll crushers, you can choose your ideal crushers according to double roll crushers catalog. There are many double roll crushers for sale.

roll crusher with stable performance | fote machinery

Applied materials: coal, pebble, limestone, dolomite, granite, construction waste, pebbles, glass, cement clinker, basalt, iron ore, quartz stone, coal gangue, etc. Its advantages: high capacity, ability to handle wet, sticky feeds.

Roll crusher, as one of the most economical and practical crushers, is designed to handle the first and second crushing of friable minerals and stones such as coal, clay, coal gangue, limestone, slag, cement clinkers, and shale, etc.

According to the number of rollers, the FTM roll crushers can be divided into three types: single roll crusher, double-roll crusher, and multi-roll crusher. And the most common one is double-roll crusher.

Roll crusher is applied more widely than other crushers because of its small volume and cheap price. With the adjustable discharging system, it can be used flexibly in coarse and fine crushing processes of the industries such as cement, chemical engineering, electricity, mining, metallurgy, building materials, and others.

Roll crushers can adjust the wedge device between rollers to control the feed and discharge size of the machine. Also, it is equipped with a spring device to protect the crushing machine and avoid shutdown caused by overload and iron passing.

When the adjustable bolt pulls the wedge upward, the wedge pushes the movable roller away from the fixed wheel, then the gap between the two rollers becomes larger, and the discharge port becomes larger, and vice versa.

The gasket device adjusts the size of the discharge by increasing or decreasing the thickness of the gasket. When the gasket is added, the gap between the two rollers becomes larger, and vice versa.

The unique structure of rollers makes selective crushing of the roll crushing equipment. Since minerals fed are crushed along its internal friable crack, the finished products are uniform with the cube shape.

The minerals are crushed under the force of rollers and machine body, and ores smaller than the gap between roller and machine frame (of single roll crusher) or roller (of multi-roll crusher) will pass directly without repeated crushing.

With the supporting CPU, operators can control roll crushing machines and monitor gaps between rollers, and clean up the crushing cavity through the central control room, which will help save energy of 30% to 50%.

The main working parts of the roller crusher is the cylindrical rollers. The rollers are supported by the fixed and movable bearings, and they are relatively rotating which are driven by the motor. The materials are crushed by the friction of the rotating rollers, and the finished products are discharged from the gap of the rollers.

The spring is used to balance the pressure generated between the rolls. If there are non-crushed materials falling between the two rollers, the compression spring of bearings can be pushed to make a large gap so that non-crushed materials can be discharged immediately.

The quality of the crushers has a great impact on its price. The high-quality equipment will cost more in terms of workmanship, technology, materials, etc. Meanwhile, it will have a long service life, low failure rate, and better performance, and bring more profit to investors.

In 2019, Fote has exported a total of 39 roll crushers to India, Indonesia, Zimbabwe, Vietnam, South Africa, the United States, Pakistan, the Philippines and other countries, mainly for coal, bentonite, rare earth ore, limestone, aluminum, manganese and others.

Exports of mining machinery have been booming in recent years and Fote has already opened markets in Africa, Southeast Asia, etc. Fote Heavy Machinery has supported foreign customers with low-price and high-quality roll crushing equipment, which has been popular among the majority of customers.

In recent years, the Indonesian government has taken actions to improve its infrastructure and promote economic development. As a result, Indonesia's demand for crushers has increased significantly.

The roll crusher produced by Fote has fine finished products and the best effect on sand making for river pebble. Due to its good finished product size, low powder content and low price, it is widely favored by Indonesian customers.

Firstly, Fote Heavy Machinery is a professional manufacturer of roller crushers. In order to improve the company's comprehensive strength, Fote has introduced international first-class production lines on the basis of original techniques.

Secondly, FTM produces various types of crushing equipment that is suitable for crushing, sand making and milling hundreds of minerals, and ensures excellent quality, good performance and low price.

Thirdly, Fote has provided patient and prudential after-sales service and all-round consideration for customers, and actively created high-tech crushing equipment to take the leading position in the international market.

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.

advantages of roll crusher

Description: With the continuous progress of China's economic development, people's awareness of environmental protection gradually progress. All walks of life try to the way of green development path with energy saving and environmental protection. advantages of roll crusher is applied in cement, chemical industry, electric power, metallurgy, building materials, refractories and other industrial departments. It is suitable for crushing medium hard materials, such as limestone, slag, coke, coal etc. Now, we will discuss the roll crusher.

In recent years, due to the continuous progress of the society, the economy of our country has made great progress. The progress and development of China's major industries are affected by the economic development and social progress, the advantages of roll crusher crusher industry is most obvious. People for the machinery and equipment requirements are constantly increasing. The progress of society and development of low carbon economy has great effect to the progress and development of crusher equipment. In order to adapt to the new market development, crusher enterprise develops the new road.

The new environment-friendly crusher equipment is great technology breakthrough in crusher industry. With the advantages of roll crusher technologies, crusher industry ushers in prosperity. In the crusher industry, the technology maturity is the roller crusher. Its market share is very high. The important development goal of crushing machine industry is the development of environmental protection crusher equipment. The performance of crusher and technology improved, allow it to develop good.

Facing the new change of energy saving and environmental protection, roll crusher companies accelerate the progress of technology research and development strength. Let roll crusher true carry out into the green products of energy-saving environmental protection.

Roll crusher improves its performance through technology development. It plays a promoting role in energy saving and emission reduction. For the diversification of products and energy saving and emission reduction breakthrough, it successfully open the market.

As an important equipment in mine stone sand, roll crusher is the most rapid development in our country. The development of science and technology is a very good development opportunity for the crusher industries. The roll crusher industry holds this opportunity and ushers in the new development.

how a roller crusher crush coal gangue | fote machinery

Coal gangue is an abandoned rock discharged during coal mining and processing. When mining coal, the rock layers or bottom plates from the roof of the coal seam, as well as the various types of rock excavated and blasted from around the coal seam during the excavation are all called coal gangue.

Coal gangue utilization is an important part of comprehensive utilization of resources. The utilization of coal gangue can increase the economic benefits of coal enterprises, improve coal mine production structure and environmental quality.

In China, the total installed capacity of generators of low calorific value fuel such as coal gangue reached 28 million kW, and the single unit capacity was from 6 to 300 MW. The annual utilization of coal gangue was 140 million tons, and the annual power generation was 160 billion kWh.

Since the 1970s, the US Bureau of Mines has sampled and analyzed all coal gangue hills and made comprehensive plans for coal gangue utilization. For example, the heat energy is directly recovered from the burning coal gangue mountain for both recovering the heat and controlling pollution.

Because coal gangue brick products have characteristics of lightweight, high strength, good load-bearing seismic performance, excellent thermal insulation, heat insulation and sound insulation, so it is a broad market.

Road construction and backfilling are also important ways for comprehensive utilization of coal gangue. The use of coal gangue as engineering packing materials do not require an increase in cost and need a large amount of use, which brings good economic efficiency to the coal mine.

There are three main types of coal gangue for chemical use: the first is to extract a rare element in coal gangue by various methods, such as Ga, Se, Ti, Co, etc. The second is to recover beneficial mineral products such as kaolin; the third is the production of silicon, aluminum, sulfur and other inorganic chemical products.

The use of coal gangue fertilizer is mainly based on the fact that coal gangue contains rich organic carbon, and the organic matter content in the soil can be greatly increased after being applied to the soil.

The roll crusher is mainly suitable for fine crushing operations with a feed size of less than 150 mm and a finished product size of 100 mesh to 2 mm. What are the advantages of the roll crusher in use?

Compared with the striking type crushing equipment, the biggest disadvantage of the roll crusher is that the "crushing ratio" is relatively small, the particle size of the product changes with the wear of the gap of the roller, and the crushing effect on the sheet-like material is poor.

Therefore, the most important thing about using the roll crusher is the method of stepwise crushing. When crushing coal gangue, it should go through three processes of "coarse-middle-fine crushing".

The surface of the roll crusher is easily worn to grooves and makes the gap between the rolls larger, thereby reducing the crushing effect. When the roller is new, the gap between the two rollers is the smallest, and the fineness of the crushing is the best.

Therefore, to obtain a good coal gangue crushing product, the work we have to do is to minimize the variation value from fine to coarse, and to control the crushing particle size within the allowable range to ensure the quality of the product.

When crushing coal gangue, to achieve the target particle size, three processes of "coarse-middle-fine crushing" are usually carried out. According to the previous configuration experience, we configure a detailed crushing production line for the 10t/h coal gangue:

Raw material warehouseGZD6502300 vibrating feederPE400600 jaw crusher2PG0640 roll crusher3YK1237 vibrating screenDMC64 dust collectorfinished silo (also several B500 conveyors of different lengths).

It can be seen from the above that when there are three specifications of the finished coal gangue, the jaw crusher can be used as the first crush, and the roll crusher is used for the medium and fine crushing.

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.

coal crushing: new-type toothed roll crusher vs traditional toothed roll crusher | hxjq

In the coal industry, the requirements for the particle size of the finished product are extremely strict. Generally, the particle sizes of the finished products are between 25 and 70 mm. If it is too large, the furnace will be blocked and further coal processing can't be performed.

Toothed roll crusher is the mature coal crushing equipment applied in the current coal industry, which satisfies all the demands of customers by its advantages of large capacity and low over-crushing rate.

Based on the original toothed roll crushers, HXJQ Mining Machinery has optimized the structure and materials of rollers according to the customers' requirements, so that to adapt the nature of hard gangue and special working conditions and ensure the normal production of coal enterprises.

Traditional toothed roll crusher is usually driven by double-motors. Two sets of motors, couplers and reducers are adopted to drive the independent rollers so that the rollers have the power to crush large coal materials.

The coupler is applied between reducer and rolls to transfer torque. And the toothed rollers and drive system are connected with the machine frame respectively to eliminate the vibrating of toothed roll crusher.

Traditional toothed roll crusher with ring structure has the advantages of stable and reliable performance, and the disadvantages of low wear resistance and hard to replace. Once the traditional toothed roll crusher is damaged, it must be returned to the factory for overhaul.

The traditional rollers are connected by the bolts and tooth-holders, which offers small bearing capacity. Therefore, the traditional toothed roll crushers are mainly applied in the clean-coal crushing process, because the raw coal will cause damage to roll crusher teeth.

In terms of tooth position, the roll crusher teeth are set in the peripheral direction, adopting the setting form of large tooth alternating with a small one. Under the premise of normal discharging size, the crushing force of roller can be improved efficiently, so that to increase the capacity, wear-resistance and service life.

As the picture shows, the new-type tooth-holder adopts the form of regular octagon. The toothed rollers and toothed holders are connected by the flat kay and socket head cap screws (the traditional ones are connected by bolts).

The contacted areas between tooth and toothed holders are processed and improved completely, and torque is transferred by flat key so that can prevent the socket head cap screws from the shearing force of coal materials. And the screws can be firmer and more reliable.

Meanwhile, the fastening bolt and the toothed roller holder are connected by the screw fastening blocks, which makes that the joint strength is ensured, and the interchangeability and the replaceability are also reliable.

The teeth are the main wearing parts of the toothed roll crusher, so it is very necessary to choose a suitable material. Therefore, it is required that the material should have enough hardness, toughness, impact resistance and wear resistance. Also, the following machinability and weldability should be considered.

When parts of high manganese steel are impacted repeatedly, the surface of parts gets changed, and the hardness increases rapidly, which can reach up to HRC54. It will improve the wear resistance significantly, but the inside of parts keeps flexibly. These are the main features of high manganese steel.

However, the toothed roll crushers crush coal materials by shearing and stretching, along with less impacting and squeezing, which makes high manganese steel can't play its advantages to enhance the hardness and strength. Therefore, high manganese steel is not suitable for making teeth.

To better improve the wear-resisting performance of teeth, traditional toothed roll crusher always adopts the low-alloy quenched and tempered steel as the material to make tooth of roll crushers. In general, 40 Cr is used to process the tooth. After processing, the compressive strength and the service life of tooth are improved.

However, since there are only a few millimeters thick wear-resisting layer in the surface of the tooth, it is required to be overlaid frequently in the process of use, which brings a large workload to workers.

The teeth of the new toothed roll crusher adopt the integral casting molding process, optimizes the proportion of the main elements such as C, Cr, Mn, Mo, Si, Ni. The medium carbon bainitic steel is selected finally to be the material of toothed roll.

The medium carbon bainitic steel has good hardenability. After quenching and tempering heat treatment, bainite with high hardness and wear resistance is processed. It has an excellent comprehensive performance of HRC50 hardness and compressive strength of 1500 MPa.

In addition, the material of the entire toothed roller structure, including the toothed roller, the toothed roller holder and the threaded fastening block, is reasonably matched, so that the strength and hardness of each component are more balanced and reasonable.

The raw coal is first crushed to below 300mm by the jaw crusher, and then crushed to below 70mm by a toothed roller crusher, and then transported to the coal storage bin by the belt conveyor. After screening, the final product of 25~70mm is sold to the chemical company.

The customer said it requires technical improvement urgently in their worksite urgently to reduce the operating cost of the enterprise and the labor intensity of the workers and to ensure the normal operation of the production system.

Since the new toothed roller crusher was put into use, the equipment has been running stably, the discharge size of the products is significantly improved, the over-crushing rate reduces, and the block-forming rate is highly increased (see the following table).

It can be seen from the above table that the difference between the qualified products before and after the replacement is 18.2%, which greatly improves the output of qualified products and creates great economic benefits for the enterprise.

In addition, the new toothed roller crusher has high wear resistance, and the fastening bolt is not easy to loosen, which reduces a large amount of maintenance time, the labor intensity of workers, and the maintenance cost of the coal crushing process.

With the transformation and upgrading of the coal industry, it is an inevitable trend to vigorously develop coal chemical industry. The coal chemical industry has strict requirements on the particle size of coal, which puts higher requirements on the crushing equipment.

The new toothed roller crusher can optimize the crushing operation of the raw coal by a series of optimizations on the structure and material of the toothed roller. It has a high block rate and a small maintenance amount. With the obvious technical advantages, the promotion prospects of new-type toothed roll crusher are broad.

dual roll crushers, how they function

Roll crushers have a theoretical MAXIMUM reduction ratio of 4:1. If a 2 inch particle is fed to the roll crusher the absolute smallest size one could expect from the crusher is 1/2 inch. Roll crushers will only crush material down to a minimum particle size of about 10 Mesh (2 mm). A roll crusher crushes using compression, with two rolls rotating about a shaft, towards the gap between the rolls. The gap between the rolls is set to the size of product desired, with the realization that the largest feed particle can only be 4 times the gap dimension. The particles are drawn into the gap between the rolls by their rotating motion and a friction angle formed between the rolls and the particle, called the nip angle. The two rolls force the particle between their rotating surface into the ever smaller gap area, and it fractures from the compressive forces presented by the rotating rolls. Some major advantages of roll crushers are they give a very fine product size distribution and they produce very little dust or fines. Rolls crushers are effectively used in minerals crushing where the ores are not too abrasive and they are also used in smaller scale production mining of more abrasive metal ores, such as gold. Coal is probably the largest user of roll crushers, currently, though. Coal plants will use roll crushers, either single roll or double roll, as primary crushers, reducing the ROM coal. Usually, these crushers will have teeth or raised forms on the face of the roll. (Roll crushers used for minerals and metal ores have smooth faced rolls.)

The particles are drawn into the gap between the rolls by their rotating motion and a friction angle formed between the rolls and the particle, called the nip angle. The two rolls force the particle between their rotating surface into the ever smaller gap area, and it fractures from the compressive forces presented by the rotating rolls. Some major advantages of roll crushers are they give a very fine product size distribution and they produce very little dust or fines. Rolls crushers are effectively used in minerals crushing where the ores are not too abrasive and they are also used in smaller scale production mining of more abrasive metal ores, such as gold. Coal is probably the largest user of roll crushers, currently, though. Coal plants will use roll crushers, either single roll or double roll, as primary crushers, reducing the ROM coal. Usually, these crushers will have teeth or raised forms on the face of the roll. (Roll crushers used for minerals and metal ores have smooth faced rolls.)

roll crushers | mclanahan

Roll Crushers are designed to handle the primary, secondary and tertiary stage crushing of friable materials such as coal, salt, clay, bauxite, limestone and other minerals of similar characteristics in the mining, power generation and numerous other industries. Roll Crushers are one of the most widely used crushers in the mining industry and have numerous advantages, such as high capacity, low headroom, low horsepower, the ability to handle wet, sticky feeds and the generation of minimum fines while producing a cubical product.

The simplified design gives these units excellent reliability and requires very little maintenance. Roll Crushers are designed with built-in tramp relief that allows for the passing of uncrushable materials while continuing operation and returning to the initial product setting.

Since patenting the first Single Roll Crusher in 1894, McLanahan has become an expert and leader in the industry in the design and manufacture of single and two stage Roll Crushers. The selection process for each application is based on extensive equipment knowledge and a wealth of test data developed in our research lab or through on-site testing.

McLanahan offers belt-driven Roll Crushers in four designs: Single Roll, Double Roll, Triple Roll and Quad Roll Crushers, which provide a substantial return on investment by operating at low cost and maximizing yield by generating minimal fines. The rugged design, which incorporates a fabricated steel base frame lined with replaceable abrasion-resistant steel liners, stands up to the toughest mineral processing applications while providing safe and simple operation, including an automatic tramp relief system to allow uncrushable objects to pass while the crusher remains in operation. These crushers are also versatile, allowing for adjustments in roll speeds and gap settings to meet most any application requirement.

Whether the application requires a single-stage or two-stage crusher, the forces necessary to perform the crushing remain the same: a combination of impact, shear and compression. The impact force occurs as the material enters the crusher and is impacted by the rotating roll. Shear and compression forces occur as the feed material is pulled between the crushing plate and/or crushing rolls.

Depending on the feed size, material is fed into the crushing chamber and encounters a single or a pair of rotating rolls. If a two-stage reduction is required, either a Triple or Quad Roll configuration can be used. In this scenario, the top stage of the crusher performs the primary reduction either by crushing the material between the roll and crushing plate or between a pair of rolls. The material is then fed directly between the two bottom-stage rolls for additional processing.

If a single-stage reduction is required, then depending on the feed-to-product-size ratio of reduction, either a Single or Double Roll Crusher can be selected. Regardless of the crusher type selected, Roll Crushers allow for the material to fracture along naturally occurring cleavage lines, which helps with minimizing fines generation.

Yes, it will. When a wet, sticky feed is fed to a two-stage crusher, you run the risk of plugging the crusher between the top and bottom stages. If a wet, sticky feed is anticipated and the ratio of reduction requires two stages of crushing, it is recommended that two separate single stages be used.

A good rule of thumb is: Single Roll Crushers have a 6:1 ratio of reduction, Double Roll Crushers have a 4:1, Triple Roll Crushers have a 6:1 on the top stage and a 4:1 on the bottom stage, and Quad Roll Crushers have a 4:1 on both the top and bottom stage.

Single Roll Crushers are typically used as primary crushers that provide a crushing ratio of up to 6:1. They crush materials such as ROM coal, mine refuse, shale, slate, gypsum, bauxite, salt, soft shale, etc., while producing minimal fines. Designed with intermeshing roll teeth and a curved crushing plate, they are extremely effective in reducing slabby feeds.

Double Roll Crushers provide a 4:1 reduction ratio. They are typically used as a secondary or tertiary crusher for materials such as ROM coal with refuse, limestone, gypsum, trona, shale, bauxite, oil shale, clean coal, coke, salt, quicklime, burnt lime, glass, kaolin, brick, shale and wet, sticky feeds. Each machine is custom engineered with roll elements and tooth patterns selected depending on theapplication requirements to produce a cubical product with minimal fines.

Triple Roll Crushers are ideal for producers who want to accomplish two stages of reduction in one pass. They can be used in coal, salt, coke, glass, and trona operations, among others. Triple Roll Crushers combine a Single Roll Crusher with a Double Roll Crusher to form a crusher that is capable of achieving a 6:1 reduction ratio in the primary stage and a 4:1 reduction in the secondary stage while producing a cubicle product at high capacity.

Quad Roll Crushers are ideal for producers, including those with preparation plants, who want to accomplish two stages of reduction in one pass. They can be used in coal, salt, lime, pet coke and potash operations, among others. Quad Roll Crushers are capable of achieving a 4:1 reduction ratio before feeding the crushed material to the secondary stage for an additional 4:1 reduction to make the final product.