What are centrifuges for? What is a centrifuge? Rating of similar devices.

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 vibration of the rotor. 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 rotor axis 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.

In hanging filter centrifuges, the removal of sediment from the rotor is facilitated and therefore they are used for short centrifugation processes.

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 precipitate 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 area 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 nozzle 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 disc 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 it is undesirable to damage the particles of the sludge during its unloading.

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 steps 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.

General at the meeting said:“The situation is critical. The defense of the country is under threat. If we do not rectify the situation quickly, 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 the State Corporation Rosatom, recalls:“Our experts 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.

Centrifuges are machines used in laboratories, medical facilities and factories to separate suspended material from media in which they are mixed.

This is done by rotating closed containers of mixture very rapidly around a fixed center point.

The centrifugal force created by this movement forces the denser material in suspension against the walls of the container, effectively separating it from the solution. These devices are used to separate solids from liquid suspension media; for example, they are an important medical tool for separating plasma from blood samples.

Article tags:

• centrifuge;
• centrifuge machine;
• medical centrifuge;
• centrifuge rotor;
• filter centrifuge;
• centrifuge for plasmolifting;
• centrifuge laboratory medical;
• centrifuge speed;

How do centrifuges work?

The basic principle of the centrifuge is centrifugal force. If a bucket half-full of water is rapidly rotated in a circle, overhead and back to the ground, the centrifugal force created by the rotation of the bucket causes the water to move towards the bottom. This is what keeps the water in the bucket even when it is upside down.

Most centrifuges use this force in a similar way and consist of a housing with a lid and a driven central rotor. The rotor has a series of holes around the circumference in which containers are placed, usually test tubes with a solution. When the machine lid is closed and the centrifuge is turned on, the rotor rotates at high speed. As with the bucket experiment, centrifugal force causes any substance in the solution that is denser than the liquid to be pressed against the outer walls of the tubes, separating it from the liquid in the process.

Once the centrifuge has completed its cycle, it gradually slows down and stops to prevent turbulence that could lead to re-mixing of the solution. This delay period also allows all separated material to fall towards the bottom of the tube. Once the rotor has stopped, the tube can be removed and the samples processed.

In some cases, the centrifuge may have a screen at one end to allow liquids to pass while solids remain trapped inside the tube. Others may hold the pipes at a fixed angle, or allow them to deflect as they rotate. The position of the tube and the speed of rotation of the centrifuge may vary depending on the type of solution being separated.

Density division

Thus, any amount of suspended materials can be separated from the suspension. Each different substance will separate in order of density, forming different layers at the bottom of the pipe when the machine is stopped. This is known as the principle of sedimentation. For example, a blood sample placed in a centrifuge for a suitable cycle length will completely break down with heavier blood cells collecting at the bottom and lighter blood plasma at the top. This is especially useful in identifying all components of unknown solutions.

Other uses

Centrifuge devices are not only used in laboratories; they see widespread use in wastewater management, in the oil industry and even in sugar and milk processing. As a rule, medical and scientific laboratory centrifuges are small table-top devices. On the other hand, the industrial machines used to separate the magnetite slurry from process water in a coal plant can be very large.

The gas centrifuges used in the uranium enrichment process are equipped with specially designed containers that include a strategically placed inner ladle. When rotated, this scoop collects the desired uranium-235 isotope while the heavier 238 isotope collects on the walls of the container. This, however, is a much longer process than liquid slurry separation, often requiring several thousand cycles.

Large centrifuges are also used to subject people to extreme forces in a controlled environment. The external force generated by such a large machine can be used to simulate the enormous gravitational forces (G-forces) that an astronaut or fighter pilot might experience while traveling at very high speeds. Geotechnical modeling is another area where centrifuges are used to simulate gravity stresses in prototypes.

How to buy a Laboratory Centrifuge?

The centrifuge is used in a wide variety of industries and the choice of various types is quite large, so buying can be very difficult. In order to choose the right device, buyers are encouraged to identify the specific uses in which they need a centrifuge to do what is usually dictated by the industry in which the person works. Once this has been determined, the user must explore the various models and features to determine the right centrifuge for a particular task. Centrifuges are most often required for medical and laboratory use. These devices are available from many medical and laboratory stores. Medical and lab stores are increasingly hard to find in physical form (not online), many of which already exist ONLY online. Unfortunately, the online store has its advantages and disadvantages. The advantage is the wide range of fixtures and functions available for viewing and comparison, but the disadvantage is that the user cannot see and know exactly what he or she is buying until the item arrives.

An overview of the different types of centrifuges will help you understand this issue.

Working principle of laboratory centrifuge

Centrifuges rotate objects around a central fixed axis, usually at high speed. This high speed turn imposes a force on objects in the form of increased gravity through centripetal acceleration. This causes the denser materials inside the containers at the outer edge to move further away from the axis of rotation, and the lighter materials move closer to the axis of rotation. Due to this action, centrifuges speed up sedimentation time.

Areas of use for centrifuges in the laboratory

Centrifuges have many applications and perform well in a wide range of applications that include the separation of liquids.

Laboratory centrifuge

Centrifuge laboratory is a device used in science to separate suspensions by density. The denser particles are released and migrate to the bottom of the tube, while the lighter particles move to the top. The machine is round in shape and has openings into which test tubes can be inserted. Before turning on, the cover covers the top of the machine, after which it can be rotated by its motor at a very high speed.

If someone wants to separate it into its components - red blood cells, white blood cells, platelets and plasma, they use a centrifuge. The plasma will float on top because it has the lowest density. Further, plasma can be used to separate organelles from cells and to isolate nucleic acids. Here are some examples of how a centrifuge can be used.

Most centrifuges in use today are for medical and laboratory use. As already mentioned, these devices separate materials suspended in liquid mixtures. In the medical field, separation of plasma from red blood cells is commonly used. Plasma is much lighter than erythrocytes, and as a result of centripetal acceleration, erythrocytes settle to the bottom of the tube, and the plasma rises to the top. The most common centrifuges in the field of medicine are ultracentrifuges and hematocrit centrifuges.

Ultracentrifuges are used in the fields of molecular biology, biochemistry and polymers and are designed to rotate the rotor at extremely high speeds. Hematocrit centrifuges are specialized centrifuges that allow the researcher to measure the number of red blood cells in whole blood.

Beauty parlor centrifuges

Other labs, such as cosmetics labs, use centrifuges to separate elements in constituent chemicals to create a variety of lotions, creams, and other beauty products.

Centrifuges for the mining industry

The mining industry uses large, heavy machines called horizontal centrifuges to separate gold and other heavy minerals suspended in water. Horizontal centrifuges are used in other industries to recover materials from water used to clean or cool machines.

Centrifuges in the aerospace industry

Some of the largest centrifuges are used in the aerospace industry. Most people know these as "G-Force Boosters" that test the astronaut and pilot for endurance for high g forces, for supersonic flight and spacewalk, and then, for recovery under the earth's atmosphere. However, the aerospace industry uses these large centrifuges for other purposes as well, including endurance testing of materials and equipment under the same conditions.

Centrifuges in the nuclear industry

The nuclear enrichment industry uses gas centrifuges. These centrifuges work on the same principle, but separate the isotopes from the host gas. The most common use for gas centrifuges is to enrich uranium for energy production and, to a much lesser extent, weapons enrichment.

Centrifuges for industrial use

Screen centrifuges are among the most common industrial centrifuges. These centrifuges contain a metal or plastic mesh screen with holes in it at the outermost edge. As the rotor rotates, the holes only allow particles of a given size, trapping large particles on the screen. Some screen centrifuges contain multiple screens, thereby separating particles into different thickness levels.

Centrifuges for household appliances

A familiar use of centrifuges in household appliances, washing machines are industrial centrifuges. When the load is on the spin cycle, the centripetal force pushes the water and clothes towards the edge of the outer screen. The clothes will be caught in the screen (drum walls), but water can pass through (through the holes). This allows the garment to reach a certain level of dryness before it is put into the dryer for final drying.

Comparison of centrifuges

Not all centrifuges are the same type and are equal. There are two main factors to consider: rotational speed and rotor design.

Rotational speed

Comparing centrifuges can be both easy and difficult. Once the type of centrifuge required has been determined, the customer can begin to compare the different specifications of the models. One of the most important considerations is determining what speeds are needed for the application in which the centrifuge will be used, as different speeds can produce different results with the same materials.

However, rotation per minute or RPM is not the only factor to consider when comparing similar centrifuges. This is because, depending on the rotation angle of the containers, different values ​​of centripetal force can be applied to content with different rotation speeds.

Rotor design

The angle of the rotor used in the centrifuge is also important. Many centrifuges for laboratory use have interchangeable rotors, allowing a single centrifuge to be used for a variety of applications. Some centrifuges come with a spare rotor, which is the most commonly used, and some come without a rotor at all, so the buyer should be careful to read product descriptions carefully when buying centrifuges.

For a customer, there is nothing more frustrating than losing time to buy a centrifuge that cannot be used due to the lack of a rotor. If the centrifuge you purchase does not come with a rotor, a rotor designed for a particular purpose must be purchased separately.

Rotor angles and perforations

The rotors contain holes evenly spaced around the central spindle for proper load distribution. Special plastic, glass or metal tubes designed for use in centrifuges are inserted into these holes. Rotors come in a variety of capacities and designs. The user must use consumables appropriate for the particular rotor for the proper application.

Common categories of rotors are fixed angle and swivel rotors. Fixed angle rotors have specific openings at the corners to separate targets. Swivel rotors allow containers to be placed vertically and rotated to horizontal positions due to centripetal force.

Consideration of Consumables

Another consideration when using and purchasing centrifuges is the required consumables. Once a centrifuge has been selected and the appropriate rotor has been identified and installed, the next consideration is the container used in the centrifuge. Until the last century, glass was the most common type of container used in centrifuges.

However, glass vials may crack or shatter under pressure if the surface integrity is compromised. Because of this, the use of plastic containers is on the rise, although glass is still in use. The disadvantage of plastic is that all plastic is slightly porous, so glass is still used in many medical applications.

How to buy a centrifuge?

Specialized online stores can be an excellent source for purchasing centrifuges. However, many products are types of centrifuges that do not apply to typical laboratory use. Because of this, a situation may arise where the buyer must look at the centrifuge specifically in the Business and Industry category for centrifuges.

Within this category are more specific sub-categories, with the healthcare sector being the best place to look for laboratory centrifuges. This section is divided, as a rule, even more for a more precise search. The first sub-category, laboratory equipment, has a section Centrifuges and parts with a specific area of ​​centrifuges. This last category is probably the best place to find centrifuges suitable for laboratory use.

Consumables have a similar categorical tree to search through. In the Business & Industry category, go to Healthcare, Laboratory & Life Science, and then Lab Supplies. This area has additional sub-categories dedicated to specific types of supplies, including disposables, plastics, laboratory glassware, pipettes, pipes, valves and fittings, and other supplies.

Summary of Laboratory Centrifuge

Centrifuges are relatively simple machines, but they are very difficult to buy online. Unfortunately, due to the dwindling number of physics lab stores, online centrifuge stores are becoming more and more necessary. Therefore, researching and compiling comparative information when purchasing centrifuges has become more important than ever.

The first step for the purchaser is to determine the type of centrifuge required, often determined by the industry in which the centrifuge will be used. The customer is then invited to explore and compare the various applications and features offered by these centrifuges and determine what is right for you. Finally, buying centrifuges online becomes easy in any type of online store and auction site.

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 about 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 Supply.

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 have 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 most 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.

Centrifuges can be with a vertical and horizontal arrangement of the shaft and drum, intermittent action (suspension supply and sediment discharge are carried out periodically), semi-continuous (suspension is supplied continuously, and sediment is discharged periodically) and continuous action (suspension supply and sediment discharge are carried out continuously).

A batch settling centrifuge with manual sludge discharge (Fig. 7.6) consists of a drum mounted on a rotating shaft and placed in a housing. Under the action of the centrifugal force that occurs during the rotation of the drum, solid particles are deposited in the form of a continuous layer of sediment on the wall of the drum, and the clarified liquid overflows into the casing and is removed through the nozzle located below. At the end of the process, the sediment is unloaded from the centrifuge.

The process in a settling centrifuge consists of separating (settling) the suspension and pressing or compacting the sludge.

Continuous settling horizontal centrifuges with screw sludge discharge (NOGSh) are used in the starch industry to obtain concentrated starch sediment and in other industries.

The centrifuge consists of a rotor and an internal screw device enclosed in a housing. The slurry is fed through the central tube into the hollow screw shaft. At the outlet of this pipe inside the screw, the suspension is distributed in the cavity of the rotor under the action of centrifugal force.

The rotor rotates in a casing in hollow pins. The auger rotates in trunnions located inside the trunnions of the rotor. Under the action of centrifugal force, solid particles are thrown to the walls of the rotor, and the liquid forms an inner ring, the thickness of which is determined by the position of the drain holes on the end of the rotor. The resulting sediment moves due to the lag of the screw rotation speed from the rotor rotation speed to the holes in the rotor, through which it is discharged into the chamber 6 and removed from the centrifuge.

When moving along the rotor, the sediment is compacted. If necessary, it can be washed.

Filter centrifuges periodic and continuous action are divided according to the location of the shaft into vertical and horizontal, according to the method of unloading sediment - into centrifuges with manual, gravitational, pulsating and centrifugal unloading of sediment. The main difference between filter centrifuges and settling centrifuges is that they have a perforated drum covered with a filter cloth.

In a batch filter centrifuge (Fig. 8.14), the suspension is loaded into the drum from above. After loading the suspension, the drum is set into rotation. The suspension under the action of centrifugal force is thrown to the inner wall of the drum. The liquid dispersed phase passes through the filter septum, and the precipitate falls on it. The filtrate through the drain pipe is sent to the collection. The sediment after the end of the filtration cycle is unloaded manually through the lid 3.

The design of the filter centrifuge with a perforated drum is similar to the design of an automatic settling centrifuge with continuous knife removal of sediment.