How to choose a centrifuge?

Centrifuges are widely used in various laboratories such as hospital laboratories, scientific research institution laboratories, food and drug testing laboratories, and food hygiene laboratories. Centrifuge selection should pay attention to the following aspects.

Rotating speed

Centrifuges can be divided into low-speed centrifuges (≤6000r/min), high-speed centrifuges (≤25000r/min) and ultra-high-speed centrifuges (≥30000r/min) according to the rotating speed.

When the particle size of the material is between 1 micron and 50 microns, it can be separated by a low-speed centrifuge. The rotation speed is about 4000 to 7000 rpm, and the relative centrifugal force is about 2000 grams to 9420 grams. Generally, a desktop low-speed centrifuge or a floor-standing low-speed large-capacity centrifuge is used.

When separating viruses and other substances in animal and plant tissues with a diameter of about 0.1-1 micron, it is recommended to use a high-speed refrigerated centrifuge with a rotation speed of 10,000-20,000 rpm and a centrifugal force of about 10,000 rpm. grams to 100,000 grams.

When separating various proteins, DNA, RNA and other components with a diameter of about 0.002 to 0.1 microns, an ultracentrifuge is required, with a speed of more than 40,000 rpm and a centrifugal force of 100,000 to 400,000 g.

separation performance

Separation performance is the most basic function, including separation effect, washing effect, processing capacity, degree of automation, etc. Due to the different properties of materials, including material viscosity, density, slurry solid-liquid ratio, etc., it is difficult to accurately determine the final separation effect. When the solid phase material is a crystalline product, and the degree of damage to the crystallization is required to be low during separation, the selection of the centrifuge needs to be based on the size and concentration of the solid particles in the suspension (or emulsion), and the density difference between the solid and the liquid (or two liquids). , liquid viscosity, filter residue (or sediment) characteristics.

Generally speaking, the separation coefficient is an important factor affecting the separation effect of the centrifuge. The separation coefficient is related to the rotational speed of the drum and the diameter of the drum, and is proportional to the square of the angular velocity of the drum.

Washing refers to the washing of the filter cake. Some materials need to wash the filter cake with washing liquid, and some even need multiple washings to meet the requirements, which requires a washing tube. The washing effect and washing time have a great relationship with the pore size, arrangement position and structure of the washing tube. The processing capacity of the centrifuge is related to the physical and chemical properties of the material and the separation requirements, and is generally estimated by the number of cycles per hour and the quality of the filter cake in a single operation.

When separating some organic active substances such as enzymes, a refrigerated centrifuge is selected when a constant temperature needs to be maintained during the separation process. There are low-speed refrigerated centrifuges and high-speed refrigerated centrifuges. Then select the appropriate centrifuge according to the required speed and rotor capacity.

Corrosion resistance

The materials separated by the centrifuge are generally corrosive to a certain extent, and the material of the parts in contact with the materials must meet the requirements of corrosion resistance in order to ensure safe use. When selecting the type, the structural material, gasket material, surface treatment measures, and filter cloth material should be determined. When selecting the type, you can inform our company of the properties of the material (chemical properties, temperature during separation, etc.), so that our company can make suggestions for the selection of centrifuge materials according to the characteristics of the separation medium, and indicate to ensure that the centrifuge meets the anti-corrosion requirements.

Explosion-proof performance

If the materials processed by the centrifuge contain flammable and explosive substances such as organic solvents, the centrifuge should have explosion-proof performance. When the material contains benzene, toluene, petroleum ether, cyclopentane and other flammable and explosive substances; dichloroethane, carbon tetrachloride, methanol, ethanol, ether, methyl ethyl ether, acetone, cyclohexanone, ethylene glycol ether , ethylene glycol butyl ether, formaldehyde, acetaldehyde, pyridine, explosion-proof centrifuges should be used. The explosion-proof performance depends on the explosion-proof requirement level of the process.

In previous explosion-proof occasions, only the preparation of explosion-proof motors was proposed. In the past two years, for the occasions where the processed materials contain organic solvents, most of them have put forward protection requirements for harmful gases. In fact, to achieve true explosion-proof, various measures can be taken in the preparation of electromechanical accessories, such as the use of explosion-proof motors, explosion-proof lighting, anti-static belts, anti-collision and so on. Measures, safety interlock, hydrogen protection device, non-contact dynamic braking, static grounding, automatic explosion-proof control, etc. Therefore, the customer needs to specify the characteristics of the separated medium and the explosion-proof requirements and grades when ordering. .