According to the value of the separation factor, centrifuges can be divided into two groups: normal centrifuges(K r< 3500) и supercentrifuges(K p > 3500).

Normal centrifuges are mainly used for separating various suspensions, except for suspensions with a very low solids concentration, as well as for removing moisture from bulk materials. Super centrifuges are used to separate emulsions and fine suspensions.

Normal centrifuges can be settling and filtering. Super centrifuges are settling type devices and are divided into tubular ultracentrifuges used to separate fine suspensions, and liquid separators used to separate emulsions.

An essential feature of the type of centrifuges is the method of unloading sediment from them. Unloading is done manually, with the help of knives or scrapers, screws and pistons moving back and forth (pulsating), as well as under the action of gravity and centrifugal force.

According to the location of the axis of rotation, vertical, inclined and horizontal centrifuges are distinguished. The rotor shaft of a vertical centrifuge is supported at the bottom or suspended from above.

Depending on the organization of the process, centrifuges are divided into periodically and continuously operating.

Three-column centrifuges. Apparatuses of this type belong to normal settling or filtering centrifuges of periodic action with manual sludge unloading.

In a three-column filter centrifuge with a top discharge of sediment (Fig. V-14), the suspension to be separated is loaded into a perforated rotor 1, the inner surface of which is covered with a filter cloth or metal mesh. The rotor, by means of a cone 2, is mounted on a shaft 3, which is driven by an electric motor through a V-belt transmission. The liquid phase of the suspension passes through the fabric (or mesh) and holes in the wall of the rotor and is collected in the bottom of the bed 4, covered with a fixed casing 5, from where it is discharged for further processing. The sediment formed on the walls of the rotor is removed, for example, with a spatula, after opening the cover of the casing 6.

To mitigate the impact of vibrations on the foundation, the frame 7 with the rotor mounted on it, the drive and the casing are suspended by means of vertical rods 8 with ball heads on three columns 9 located at an angle of 120 °. This provides some freedom for the rotor to vibrate. The centrifuge is equipped with a brake that can only be activated after the motor has stopped.

Three-column centrifuges are also made with bottom discharge of sediment, which is more convenient in production conditions.

The centrifuges under consideration are characterized by low height and good stability and are widely used for long-term centrifugation.

Overhead centrifuges. These centrifuges are also among the normal settling or filtering centrifuges with a vertical rotor and manual discharge of the sediment.

On fig. V-15 shows a bottom discharge suspended sludge centrifuge. The feed slurry is fed through conduit 1 to a solid-walled rotor 2 mounted on the lower end of shaft 3. The upper end of the shaft has a conical or ball bearing (often fitted with a rubber gasket) and is driven directly by an electric motor connected to it. The solid phase of the suspension, since its density is greater than the density of the liquid phase, is thrown under the action of centrifugal force to the machines of the rotor and is deposited on them. The liquid phase is located in the form of an annular layer closer to the axis of the rotor and, as the newly arriving portions of the suspension are separated, it overflows over the upper edge of the rotor into the space between it and the fixed casing 4. The liquid is removed from the centrifuge through the fitting 5. To unload the sediment, the conical cover 6 is lifted onto the chains and push it manually between the ribs 7, which serve to connect the rotor to the shaft.

Suspended settling centrifuges are designed to separate fine suspensions of low concentration, which allows the suspension to be fed into a rotating rotor continuously until a sediment layer of sufficient thickness is obtained.

Hanging filter centrifuges facilitate the removal of sediment from the rotor and are therefore used for short centrifugation runs.

Modern overhead centrifuges are fully automated and have software control. The advantage of these centrifuges is the admissibility of some vibration of the rotor. In addition, they prevent aggressive liquids from entering the support and drive. At present, overhead centrifuges with manual sludge discharge are gradually being replaced by more advanced centrifuges.

In hanging self-unloading centrifuges, the lower part of the rotor has a conical shape, and the angle of inclination of its walls is greater than the angle of repose of the resulting sediment. With this arrangement of the rotor, the sediment slides off its walls when the centrifuge stops.

To prevent vibrations resulting from uneven loading of the rotor in overhead centrifuges, an annular valve is used through which the incoming suspension is distributed evenly around the entire perimeter of the rotor. To facilitate the unloading of sediment from overhead centrifuges, scrapers are sometimes used to cut off the sediment from the walls of the rotor at a reduced speed of rotation.

Horizontal centrifuges with blades for sediment removal. Centrifuges of this design are normal settling or filtering batch centrifuges with automated control.

In the horizontal blade centrifuge (fig. V-16), the operations of suspension loading, centrifugation, washing, mechanical drying of the sediment and its discharge are performed automatically. The centrifuge is controlled by an electro-hydraulic automatic machine, which allows controlling the degree of filling of the rotor by the thickness of the sludge layer.

The suspension enters the perforated rotor 1 through the pipe 2 and is evenly distributed in it. On the inner surface of the rotor there are lining sieves, a filter cloth and a grid, which ensures a tight fit of the sieves to the rotor in order to avoid their bulging, which is unacceptable when removing sediment with a knife. The rotor is in a cast casing 3, consisting of a lower stationary part and a removable cover. Centrifuge is removed from the centrifuge through nozzle 4. Sediment is cut off by knife 5 (which, when the rotor rotates, rises with the help of hydraulic cylinder 6), falls into the guide inclined chute 7 and is removed from the centrifuge through channel 8. The described centrifuge is designed to separate medium and coarse suspensions.

C pulsating piston centrifuges for sludge discharge. These devices are continuous filtering centrifuges with a horizontal rotor (fig. V-17). moves along the inner surface of the funnel and gradually acquires a speed almost equal to the speed of rotation of the rotor. Then the suspension is thrown through the holes in the funnel onto the inner surface of the sieve in the zone in front of the piston 5. Under the action of centrifugal force, the liquid phase passes through the sieve slots and is removed from the centrifuge casing through the fitting 6. The solid phase is retained on the sieve in the form of sediment, which periodically moves to edge of the rotor when the piston moves to the right by about 1/10 of the length of the rotor. Thus, for each stroke of the piston, the amount of sediment corresponding to the length of the piston stroke is removed from the rotor; while the piston makes 10-16 strokes in 1 min. The precipitate is removed from the casing through channel 7.

The piston is mounted on a rod 8 located inside the hollow shaft 9, which is connected to the electric motor and imparts rotational motion to the rotor. A hollow shaft with a rotor and a rod with a piston and a conical funnel rotate at the same speed. The direction of the reciprocating movement of the piston changes automatically. At the other end of the rod, a disk 10 is mounted perpendicular to its axis, on the opposite surfaces of which, in a special device, the oil pressure created by the gear pump alternately acts.

In centrifuges with a sediment washer, the casing is divided into two sections, through one of which the washing liquid is discharged.

The described centrifuge is used for processing coarse, easily separable suspensions, especially in cases where damage to the particles of the sludge during its unloading is undesirable.

Centrifuges with inertial sludge discharge. These centrifuges are normal continuous filter centrifuges with a vertical conical rotor.

WITH suspension containing coarse-grained material, such as coal, ore, sand, enters the centrifuge from above through funnel 1 (Fig. V-19). Under the action of centrifugal force, the suspension is thrown to the conical rotor 2 with perforated walls. In this case, the liquid phase of the suspension passes through the holes of the rotor and is removed from the centrifuge through channel 3, while solid particles, the size of which should be larger than the size of the holes, are retained inside the rotor. The layer of solid particles formed in this way, the friction angle of which is less than the angle of inclination of the walls of the rotor, moves to its lower edge and is removed from the centrifuge through channel 4. In order to increase the duration of the period during which the liquid is separated from the solid particles, their movement is inhibited by the screw 5, rotating slower than the rotor. The necessary difference between the speeds of rotation of the rotor and the screw is achieved using a gear reducer.

Centrifuges with inertial sludge discharge are used to separate suspensions, coarse-grained materials.

Centrifuges with vibratory sludge discharge. Centrifuges of this design are normal continuous filter centrifuges with a vertical or horizontal conical rotor.

The disadvantage of the above-described centrifuge with inertial sludge discharge is the inability to control the speed of sludge along the walls of the rotor. This drawback is eliminated in centrifuges with vibratory sludge discharge, the principle of operation of which is as follows.

The centrifuge has a conical rotor with a wall inclination angle smaller than the sediment friction angle along the wall. Therefore, the movement of sediment along the walls from the narrow to the wide end of the rotor under the action of centrifugal force is impossible. In this case, axial vibrations are used to move the sediment in the rotor, which are created by a mechanical, hydraulic or electromagnetic device. In this case, the vibration intensity determines the speed of sludge movement in the rotor, which makes it possible, in particular, to provide the necessary degree of sludge dehydration.

Liquid separators. These units are continuous supercentrifuges with a vertical rotor.

Such supercentrifuges include liquid separators having a rotor with a diameter of 150-300 mm, rotating at a speed of 5000-10000 rpm. They are intended for the separation of emulsions, as well as for the clarification of liquids.

In the tray-type liquid separator (Fig. V-20), the mixture to be processed in the settling zone is divided into several layers, as is done in settling tanks to reduce the path traveled by the particle during settling. The emulsion is fed through the central pipe 1 to the lower part of the rotor, from where it is distributed through the holes in the plates 2 in thin layers between them. The heavier liquid, moving along the surface of the plates, is thrown by centrifugal force to the periphery of the rotor and discharged through the hole 3. The lighter liquid moves to the center of the rotor and is removed through the annular channel 4.

The holes in the trays are located approximately along the interface between the heavier and lighter liquids. In order for the liquid not to lag behind the rotating rotor, it is equipped with ribs 5. For the same purpose, the plates have protrusions that simultaneously fix the distance between them.

An example of plate-type separators are widely used milk separators.

This nondescript gray cylinder is the key link in the Russian nuclear industry.

Of course, it doesn’t look very presentable, but as soon as you understand its purpose and look at the technical characteristics, you begin to realize why the state guards the secret of its creation and structure like the apple of its eye.

Yes, I forgot to introduce: in front of you is a gas centrifuge for separating uranium isotopes VT-3F (n-th generation). The principle of operation is elementary, like that of a milk separator, heavy, under the influence of centrifugal force, is separated from the light. So what is the significance and uniqueness? To begin with, let's answer another question - but in general, why separate uranium? Natural uranium, which lies right in the ground, is a cocktail of two isotopes: uranium-238 and uranium-235 (and 0.0054% U-234). Uranium-238 is just a heavy, gray metal. You can make an artillery shell out of it, well, or ... a keychain. But what can be done from uranium-235? Well, firstly, an atomic bomb, and secondly, fuel for nuclear power plants. And here we come to the key question - how to separate these two, almost identical atoms, from each other? No, really, HOW?! By the way: The radius of the nucleus of the uranium atom is -1.5 10-8 cm. In order for uranium atoms to be driven into the technological chain, it (uranium) must be turned into a gaseous state. There is no point in boiling, it is enough to combine uranium with fluorine and get HFC uranium hexafluoride. The technology for its production is not very complicated and expensive, and therefore HFCs are obtained right where this uranium is mined. UF6 is the only highly volatile uranium compound (when heated to 53°C, hexafluoride (pictured) goes directly from solid to gaseous). Then it is pumped into special containers and sent for enrichment.

A bit of history At the very beginning of the nuclear race, the greatest scientific minds, both the USSR and the USA, mastered the idea of ​​diffusion separation - passing uranium through a sieve. The small 235th isotope will slip through, while the "thick" 238th one will get stuck. And to make a sieve with nano-holes for the Soviet industry in 1946 was not the most difficult task. From the report of Isaac Konstantinovich Kikoin at the Scientific and Technical Council under the Council of People's Commissars (given in the collection of declassified materials on the USSR atomic project (Ed. Ryabev)): At present, we have learned how to make grids with holes of about 5/1,000 mm, i.e. . 50 times the mean free path of molecules at atmospheric pressure. Therefore, the gas pressure at which isotope separation on such grids will occur must be less than 1/50 of atmospheric pressure. In practice, we expect to work at a pressure of about 0.01 atmospheres, i.e. under good vacuum conditions. The calculation shows that in order to obtain a product enriched to a concentration of 90% in a light isotope (such a concentration is sufficient to obtain an explosive), about 2,000 such stages must be connected in a cascade. In the machine designed and partially manufactured by us, it is expected to produce 75-100 g of uranium-235 per day. The installation will consist of approximately 80-100 "columns", each of which will contain 20-25 steps." Below is a document - Beria's report to Stalin on the preparation of the first nuclear explosion. Below is a small reference to the accumulated nuclear materials by the beginning of the summer of 1949.

And now imagine for yourself - 2000 hefty installations, for the sake of some 100 grams! Well, where to go, bombs are needed. And they began to build factories, and not just factories, but entire cities. And okay, only cities, these diffusion plants required so much electricity that they had to build separate power plants nearby. In the photo: the world's first K-25 uranium gaseous diffusion enrichment plant in Oak Ridge (USA). Construction cost $500 million. The length of the U-shaped building is about half a mile.

In the USSR, the first stage D-1 of plant No. 813 was designed for a total output of 140 grams of 92-93% uranium-235 per day in 2 cascades of 3100 separation stages identical in power. An unfinished aircraft plant in the village of Verkh-Neyvinsk, which is 60 km from Sverdlovsk, was allocated for production. Later it turned into Sverdlovsk-44, and the 813th plant (pictured) into the Ural Electrochemical Plant - the world's largest separating production.

And although the technology of diffusion separation, albeit with great technological difficulties, was debugged, the idea of ​​mastering a more economical centrifugal process did not leave the agenda. After all, if you manage to create a centrifuge, then energy consumption will be reduced from 20 to 50 times! How is a centrifuge set up? It is arranged more than elementarily and looks like an old washing machine operating in the “spin / dry” mode. In a sealed casing is a rotating rotor. This rotor is supplied with gas (UF6). Due to the centrifugal force, hundreds of thousands of times greater than the Earth's gravitational field, the gas begins to separate into "heavy" and "light" fractions. Light and heavy molecules begin to group in different zones of the rotor, but not in the center and along the perimeter, but at the top and bottom. This occurs due to convection currents - the rotor cover is heated and a backflow of gas occurs. At the top and bottom of the cylinder there are two small tubes - the intake. A depleted mixture enters the lower tube, and a mixture with a higher concentration of 235U atoms enters the upper tube. This mixture enters the next centrifuge, and so on, until the concentration of uranium 235 reaches the required value. A chain of centrifuges is called a cascade.

Technical features. Well, firstly, the rotation speed - in the modern generation of centrifuges, it reaches 2000 rpm (I don’t even know what to compare with ... 10 times faster than a turbine in an aircraft engine)! And it has been working non-stop for THREE DECADES of years! Those. now the centrifuges that were turned on under Brezhnev are spinning in cascades! The USSR no longer exists, but they keep spinning and spinning. It is not difficult to calculate that during its working cycle the rotor makes 2,000,000,000,000 (two trillion) revolutions. And what kind of bearing can handle it? Yes, none! There are no bearings. The rotor itself is an ordinary top, at the bottom it has a strong needle resting on a corundum thrust bearing, and the upper end hangs in a vacuum, held by an electromagnetic field. The needle is also not simple, made of ordinary wire for piano strings, it is hardened in a very tricky way (what - GT). It is not difficult to imagine that with such a frantic rotation speed, the centrifuge itself must be not just durable, but super-strong. Academician Iosif Fridlyander recalls: “Three times they could have been shot. Once, when we had already received the Lenin Prize, there was a major accident, the lid of the centrifuge flew off. Pieces scattered, destroyed other centrifuges. A radioactive cloud has risen. I had to stop the entire line - a kilometer of installations! In Sredmash centrifuges were commanded by General Zverev, before the atomic project he worked in the department of Beria. The general said at the meeting: "The situation is critical. The defense of the country is under threat. If we do not quickly rectify the situation, the 37th year will repeat for you." And immediately the meeting was closed. We then came up with a completely new technology with a completely isotropic uniform structure of the covers, but very complex installations were required. Since then, these covers have been produced. There were no more troubles. There are 3 enrichment plants in Russia, many hundreds of thousands of centrifuges.
In the photo: tests of the first generation of centrifuges

The rotor cases were also metal at first, until they were replaced by ... carbon fiber. Lightweight and extremely tear resistant, it is an ideal material for a rotating cylinder. UEIP General Director (2009-2012) Alexander Kurkin recalls: “It got ridiculous. When testing and testing a new, more "revolving" generation of centrifuges, one of the employees did not wait for the rotor to stop completely, disconnected it from the cascade and decided to transfer it to the stand in his arms. But instead of moving forward, no matter how hard he resisted, he embraced this cylinder and began to move backward. So we saw with our own eyes that the earth rotates, and the gyroscope is a great force.” Who invented? Oh, it's a mystery steeped in mystery and shrouded in obscurity.

Here you have German captured physicists, the CIA, SMERSH officers and even the downed spy pilot Powers. In general, the principle of a gas centrifuge was described at the end of the 19th century. Even at the dawn of the Atomic Project, Viktor Sergeev, engineer of the Special Design Bureau of the Kirov Plant, proposed a centrifugal separation method, but at first his colleagues did not approve of his idea. At the same time, scientists from defeated Germany fought over the creation of a separation centrifuge in a special NII-5 in Sukhumi: Dr. Max Steenbeck, who worked under Hitler as the chief engineer of Siemens, and Gernot Zippe, a former Luftwaffe mechanic, a graduate of the University of Vienna. In total, the group included about 300 "exported" physicists. Aleksey Kaliteevsky, General Director of CJSC Centrotech-SPb of Rosatom State Corporation, recalls: “Our specialists came to the conclusion that the German centrifuge is absolutely unsuitable for industrial production.

The Steenbeck apparatus did not have a system for transferring the partially enriched product to the next stage. It was proposed to cool the ends of the lid and freeze the gas, and then unfreeze it, collect it and put it into the next centrifuge. That is, the scheme is not working. However, the project had some very interesting and unusual technical solutions. These "interesting and unusual solutions" were combined with the results obtained by Soviet scientists, in particular with the proposals of Viktor Sergeev. Relatively speaking, our compact centrifuge is one-third the fruit of German thought, and two-thirds of Soviet thought.” By the way, when Sergeev came to Abkhazia and expressed to the same Steenbeck and Zippe his thoughts on the selection of uranium, Steenbeck and Zippe dismissed them as unrealizable. So what did Sergeyev come up with. And Sergeyev's proposal was to create gas sampling devices in the form of Pitot tubes.

But Dr. Steenbeck, who, as he believed, ate his teeth on this topic, was categorical: “They will slow down the flow, cause turbulence, and there will be no separation!” Years later, working on his memoirs, he will regret it: “An idea worthy of coming from us! But it didn’t cross my mind…” Later, when he was outside the USSR, Steenbeck no longer dealt with centrifuges. But Geront Zippe, before leaving for Germany, had the opportunity to get acquainted with the prototype of Sergeyev's centrifuge and the ingeniously simple principle of its operation. Once in the West, "cunning Zippe", as he was often called, patented the design of the centrifuge under his own name (patent No. 1071597 of 1957, pending in 13 countries). In 1957, having moved to the USA, Zippe built a working installation there, reproducing Sergeev's prototype from memory. And he called it, let's pay tribute, "Russian centrifuge" (pictured).

By the way, Russian engineering has shown itself in many other cases. An example is the elementary emergency shut-off valve. There are no sensors, detectors and electronic circuits. There is only a samovar faucet, which with its petal touches the frame of the cascade. If something goes wrong, and the centrifuge changes its position in space, it simply turns and closes the inlet line. It's like in a joke about an American pen and a Russian pencil in space.

Our Days This week the author of these lines attended a significant event - the closure of the Russian office of observers of the US Department of Energy under the HEU-LEU contract. This deal (high-enriched uranium-low-enriched uranium) was, and still is, the largest nuclear energy agreement between Russia and America. Under the terms of the contract, Russian nuclear scientists processed 500 tons of our weapons-grade (90%) uranium into fuel (4%) HFCs for American nuclear power plants. Revenues for 1993-2009 amounted to 8.8 billion US dollars. This was the logical outcome of the technological breakthrough of our nuclear scientists in the field of isotope separation, made in the postwar years. In the photo: cascades of gas centrifuges in one of the UEIP workshops. There are about 100,000 of them here.

Thanks to centrifuges, we have received thousands of tons of relatively cheap, both military and commercial product. The nuclear industry, one of the few remaining (military aviation, space), where Russia holds unquestioned superiority. With foreign orders alone for ten years ahead (from 2013 to 2022), Rosatom's portfolio, excluding the HEU-LEU contract, is $69.3 billion. In 2011, it exceeded 50 billion... In the photo, a warehouse of containers with HFCs at UEIP.

All research medical centers and good hospitals are equipped with laboratories. Here, the staff examines the analyzes of patients, comes up with something new in the field of pharmacology and studies certain diseases. Without laboratory research, it would be impossible to study new ailments and fight them.

Each laboratory has different equipment. And a laboratory centrifuge is a device that is impossible to do without.

What is a laboratory medical centrifuge?

Any laboratory can work fully only when it has an optimal set of tools and instruments that are ready for regular use. A laboratory centrifuge is a device that is used daily in medical and scientific practice. The main task of this device is to separate substances by density and consistency using centrifugal force. Thus, the substances with the maximum specific gravity are placed in the periphery, and the fractions with the minimum specific gravity become closer to the axis of rotation.

In scientific and medical practice, it is quite common to separate various liquids into fractions using laboratory medical centrifuges. The liquid is placed in a special container, and after turning on the device, the centrifuge begins to rotate around its axis very quickly. As a result, homogeneous elements are formed - components of the original liquid.

What is centrifugation?

Centrifugation is the operation of a centrifuge. It is based on the law of physics on centrifugal force and allows you to decompose liquids into components as quickly as possible, which is impossible, for example, when settling, filtering or squeezing. The higher the rotor speed and the higher the intensity of its revolutions, the more efficient the device works.

Laboratory centrifuges with or without refrigeration are classified:

• For low-speed devices in which the rotor frequency is 25,000 rpm.
• High-speed units with a rotation speed of 40,000 rpm.
• Ultra-high-speed centrifuges, in which the rotor speed exceeds 40,000 rpm.

What substances can be separated into particles using a centrifuge?

This device is designed to separate such biological fluids as blood, urine, lymph, mother's milk. These substances are heterogeneous, and when studying the analyzes of a sick person, one cannot avoid their easy separation using a laboratory centrifuge.

The most frequently examined, of course, is human blood. With the help of special centrifuges, you can prepare blood products, obtain blood serum suitable for transfusion, and much more.

In addition, this unit is designed not only for separating liquid substances into components, but also for separating solid fractions from liquids. Liquids, which include particles of varying severity, are easily distributed into components using a laboratory centrifuge. It can be not only blood or lymph, but also various suspensions.

Design features of the equipment

The above equipment is a drum equipped with holes of different diameters. It is in them that test tubes with test materials are installed at different angles. A fairly powerful centrifuge motor and a sealed lid ensure high-quality and full-fledged operation of the device.

The main difference between centrifuges is the design. It can be different and depends on the purpose for which this equipment will be used in the future.

Main elements of the device

Modern centrifuges used in laboratory and medical practice are equipped with many useful features, such as a timer, interchangeable nozzles, a device rotation speed controller, and others. But the basic elements are unchanged, and these are:

• Device body and sealed cover.
• A special working chamber in which test tubes are placed.
• Rotor.
• Engine.
• Remote Control.
• Power unit.

More expensive models may be equipped with a display, sensors, detector device, cooling system, automatic lid lock, etc.

Traditionally, manufacturers use stainless steel, polypropylene, aluminum, and various metal alloys in the manufacture of the case and hermetic cover. This ensures the durability of the equipment. Many of the materials used in the manufacture of this equipment are resistant to aggressive environments.

Aggregate classification

Centrifuges laboratory and medical have their own classification. Therefore, it is necessary to familiarize yourself with it before buying this device.

According to the type of unit, they are divided into general laboratory, hematocide and devices equipped with a cooling system. The first type of centrifuge is the most popular and widespread. The second is designed to conduct blood tests. Still others allow the test substance to be cooled during the analysis.

Devices are also classified according to the type and volume of working utensils. These can be: microcentrifuges (tabletop), small volume units, large volume centrifuges, floor options, universal centrifuges.

Do not forget about the functions of a laboratory centrifuge. There are machines with a low rotation speed, high-speed units, centrifuges that provide several functions, as well as ultracentrifuges.

How to choose a centrifuge?

When choosing a centrifuge for laboratory and medical research, there are several factors to consider.

First of all, it is necessary to decide what types of analyzes will be carried out using this equipment. In the field of biochemistry, hematology, immunochemistry, cytology, different devices with different technical characteristics and operating modes are used.

Next, you need to determine the scope of future research and what types of source materials you plan to use. It will be useful to take into account the safety requirements. If you plan to study small volumes of substances, then a microcentrifuge will be enough for these purposes.

For a small or mobile laboratory, there is no need to purchase bulky equipment, because in this case the amount of research will be small. As a rule, large centrifuges are equipped with a host of additional features that are likely not to be used. No need to overpay. A compact benchtop laboratory centrifuge is the ideal solution for this situation.

Since its size is small, it will not interfere with other research activities. It is very simple and easy for her to provide power (connects to a regular outlet).

What technical parameters to pay attention to when choosing a device?

If you decide to purchase a centrifuge for high-quality laboratory and scientific research, then first of all pay attention not to the speed of rotation of the rotor. Typically, the rotor speed in most laboratory-type devices, for example, in the laboratory centrifuge TsLMN R-10-02 and others, does not exceed 3000 rpm (if we are talking about desktop models). Practice has shown that centrifuges with a speed of 4000 revolutions are most in demand today, since this value is sufficient for laboratory conditions.

The type of rotor can be horizontal or angular.

Find out how many test tubes are placed per tab in the unit. Specify the allowable volume of test tubes.

Paying attention to the above specifications, you can choose the best device at a good price. The price of units usually varies from 18 to 270 thousand rubles.

Where else are these units used?

Manufacturers of laboratory centrifuges have tried to make them multifunctional and every year they release more and more advanced models. This unit is an indispensable assistant in medical, chemical, experimental and even industrial laboratories. It allows you to accurately investigate the various compositions of substances.

In the oil industry, such devices are used in the study of hydrocarbons, as well as in monitoring the quality of the road surface. Centrifuges are also used for ore dressing and in the production of washing machines.

In the agricultural sector, centrifuges are used to effectively clean grain, extract honey from honeycombs, and separate fat from milk.

Without a centrifuge, it is simply impossible to do without isotope fission in physics.

There are two main types of centrifuges: settling and filtering. Settling centrifuges are used to separate emulsions and suspensions by settling dispersed particles under the influence of centrifugal forces. Filter centrifuges are also widely used in the chemical industry.

Centrifuge classification In general, it is possible for the following parameters:

• by type of process organization (continuous and periodic);
• according to the location of the shaft (inclined, horizontal, vertical);
• according to the method of sludge unloading (with centrifugal unloading, gravity, auger, manual, etc.)

Centrifuges according to the separation factor are divided into two groups and are called normal centrifuges (K p<300) и сверхцентрифугами (К р >3000).

Normal centrifuges are most commonly used to separate all suspensions except those with very low solids concentrations. Supercentrifuges, in turn, are used to separate fine suspensions and emulsions.

The principle of operation of the decanter centrifuge

If we divide centrifuges according to their purpose, then we can distinguish settling, filtering and separating (separating) centrifuges.

• Filtering centrifuges are equipped with perforated drums, which are covered from the inside, as a rule, with a cloth or other filtering partition. This type of centrifuge is used to separate suspensions having a granular or crystalline solid phase, as well as solid and piece materials.
• Settling centrifuges, having a solid drum without holes, are used to separate suspensions that are difficult to filter, as well as to clarify suspensions containing a small amount of solids.
• Separating centrifuges are also equipped with a solid drum. This type of centrifuge is most often used to separate concentrated suspensions and emulsions.

In addition to the above, centrifuges are divided according to the method of sludge discharge. The sludge can be discharged manually, with scrapers and knives that move back and forth, and with the help of gravity or centrifugal force.

Centrifuges can also be divided according to the arrangement of supports, on the basis of which they are suspended and standing, and according to the location of the axis - vertical, horizontal and inclined.

According to the process of organizing centrifugation, the devices are divided into continuous and periodic.

Centrifuges operated intermittently have three main periods of operation:

1. Starting the centrifuge and filling its drums.
2. Rotation of the drum at a constant speed, as well as the separation of an inhomogeneous mixture.
3. Drum braking and unloading.

The filling of the drum is done when the empty drum rotates at a certain speed, which is less than the working one, or when the full rotation speed is reached. In some cases, the drum must be loaded before the centrifuge starts. The sediment is removed after the centrifuge has stopped or when the drum is rotating at low speed.

Quite often, after the main centrifugation process has been carried out, it becomes necessary to wash the sediment. For this, washing water is squeezed out, which is carried out by additional start-up of the centrifuge drum. In some cases, it is also necessary to wash out certain components of the initial mixture.

In operating centrifuges, a solid drum or with holes is periodically used.

Operating principle of drum centrifuge

In this case, the drum is enclosed in a casing that serves as a collector of the filtrate or washing liquid, as well as a protective fence in case of failure or destruction of the drum. The drum is rotated by an electric motor.

Due to the centrifugal force, the liquid is pushed through the filter material and the holes in the drum. The liquid is collected in the casing and then removed through the pipeline.

If it is necessary to obtain a sediment containing a minimum amount of moisture, then perforated drums are used. With their help, it is possible to achieve a final moisture content of the sediment of about 1-5% (with a very finely divided solid phase - up to 40%). If solid drums are used for these purposes, then much more moisture will remain in the sediment (about 70% or more).

In order to increase the separation efficiency, special annular inserts are installed in solid drums, which reduce the velocity of the liquid near the walls. Thus, the sedimentation process of solid particles is greatly improved.

Batch centrifuges are usually produced with a vertical shaft. Discharge of material in such centrifuges can be lower or upper. Lower unloading is considered more convenient, but it requires a lot of physical labor. To facilitate unloading, the apparatuses are quite often supplied with an easily controlled mechanical shovel. Some centrifuges of this type are self-unloading.

If in standing centrifuges equipped with a vertical shaft and a rigid support, there is an uneven distribution of the processed material, then unsafe and rather strong oscillations of the drum occur. Because of this, modern centrifuges are equipped with elastic bearings, while the shaft bearing is installed in a spherical sleeve.

The most commonly used batch centrifuges are the three-column suspended centrifuges and the top-support centrifuges.

Centrifuge classification:

	Type	Working mode	Sludge discharge method
Normal centrifuges (F<3500)	Filter centrifuges	periodic action	Manual
			Gravity
			knife
		continuous action	inertial
			Pulsating piston
			Screw
	Settling centrifuges	periodic action	Manual
			knife
			Centrifugal
		continuous action	Screw
Supercentrifuges (Ф>3500)	Tubular centrifuges	periodic action	Manual
	Separators	periodic action	Manual
		continuous action	hydraulic

The principle of operation of this centrifuge is that the suspension is fed through a pipe into the inner drum, and then through the windows it is discharged into the settling drum. At this stage, the separation of the suspension occurs. The clarified liquid enters the casing and is discharged through the branch pipe. The auger moves the sediment and removes it through the nozzle.

Many drivers and truck owners believe that oil centrifuges deprive motor oils of useful additives. However, this is really easy to believe, because. The principle of centrifugal separation is, by definition, capable of separating substances of different masses. However, does this apply to oil additives?

As already mentioned, centrifugation is filtration under the action of centrifugal forces. Centrifuges are widely used in the chemical industry, where they are used to purify liquids from solids with a higher density. It is not difficult to guess that heavy impurities can settle by themselves, but the centrifuge significantly speeds up this process.

In practice, the capabilities of the centrifuge are limited to screening out only sufficiently large particles. Therefore, with full confidence we can say that the centrifuge cannot stratify the engine oil, separating the additives from the base. The point is also that during the production of motor oils, the additive package is carefully designed at the molecular level and dissolved in a special mixture of base bases, after which an environment with a high degree of uniformity is formed.

If the process of mixing the components of the oil takes place in violation of technology, then it can exfoliate by itself under the influence of gravity alone. But this will be an extremely low-quality product, so manufacturers try to mix the components in such a way that the oil is in a stable state throughout the warranty period and the period of operation.

Stratifying high-quality oil with a centrifuge is almost impossible, no matter how hard you try. Neither centrifuge nor settling for liquids whose components are connected at the molecular level does not work here. But low-quality oils produced in violation of the technology can exfoliate already in the canister, long before they get into the centrifuge of the oil purification system in the engine.

The inevitable friction processes that occur during the operation of any engine or other mechanism generate wear products - metal particles. In addition, dust, sludge and other technological and mechanical impurities get into the oil. Most of all, oil in diesel engines of commercial vehicles is subject to such pollution. Absolutely all of the listed contaminants worsen the quality of the lubricant and contribute to the rapid wear of the motor.

Sludge, as a rule, is formed in low-temperature zones of the engine, where there is an intensive condensation of the steam released during the combustion of the fuel. In these places, sludge accumulates the most. Basically, this is the crankcase and the zones under the timing valve cover. When the oil loses a critical level of dispersing properties, the sludge particles are combined into arrays, forming a brown viscous substance. These deposits gradually thicken the oil, which in turn leads to a deterioration in its fluidity and difficult pumping through the channels. As a result, the oil does not reach all the parts that need lubrication, and so-called engine oil starvation occurs. Its symptoms are a drop in oil pressure in the system, scuffing of rubbing surfaces, and in the worst case, engine jamming.

Mechanical contaminants pose a danger as an abrasive that increases the wear of parts. Centrifuges mounted on the engine help to remove solid particles and sludge from the oil. But gradually this problem began to be solved not by eliminating the consequences of mechanical wear, but by eliminating its causes.

However, back to additives. Let us assume that foreign particles formed during the operation of the oil and prone to coarsening capture detergent and dispersant additives adsorbed on the surface of contaminants. Under the action of centrifugal forces, such particles, which have reached a certain size, can actually be screened out by a centrifuge. But do not forget that these additives are introduced into the oil so that pollutants do not settle on engine parts. The action of detergent-dispersant additives is complex. It manifests itself as the stabilization of insoluble products of hydrocarbon oxidation, keeping them in a finely dispersed state and counteracting their adhesion and increase in size. Thanks to these additives, the oil remains homogeneous and stable throughout its operation. But this is provided that the oil is of high quality. In case of violation of the production technology, the described scheme partially or completely does not work, as a result of which the period from replacement to replacement is reduced, or premature wear of engine parts occurs.

If clots still form in high-quality oil, then this may signal a malfunction of the engine itself, for example, malfunctions in the fuel system. By the way, fuel is a serious factor affecting the "margin of safety" of the oil. Diesel, which is sold by domestic filling stations, unfortunately, is not always suitable for engines of Euro-3 and higher classes.

On most modern diesel trucks and special equipment, equipment such as a centrifuge is no longer installed. However, not because it somehow affects the properties of the oil. With the serviceability of all engine systems that are regularly checked during maintenance, as well as when using high-quality oils and fuels, there are simply no large particles that could be captured by a centrifuge. And since there are no such contaminants in the oil, then the centrifuge becomes unnecessary.