Centrifuge is the use of centrifugal force, the separation of liquid and solid particles or liquid and liquid mixture of each component in the machinery.
Centrifuge is mainly used for the suspension of solid particles and liquid separation; Or emulsion in the two kinds of different density and mutual miscibility of the separated liquid (such as cream) was isolated from milk; It can also be used to eliminate wet solid in the liquid, such as use washing machines to jilt dry wet clothes; Special speed tubular separator can separate different density of the gas mixture; Using different density and particle size of solid particles in a liquid sedimentation velocity of different characteristics, some sedimentation centrifuge can also be of solid particles by density or size grading.
Centrifuge used in chemical, petroleum, food, pharmaceutical, mineral processing, coal, water treatment and shipping departments.
In ancient China, people use the rope tied at the end of the POTS, and the other end of the rope in hand, rotating shaking jar, squeezing out the honey in the jar, produces centrifugal force that is the early application of centrifugal separation principle.
Industrial centrifuges was born in Europe, the middle of the 19th century, for example, successively appeared textile dewatering centrifuge with three legs, separation of crystal sugar and sugar refinery on the hang type centrifuge. The earliest centrifuge are intermittent operation and artificial discharge.
Due to the improved slag discharging mechanism, the 1930 s saw the emergence of continuous operation of the centrifuge, intermittent operation of centrifuges for realized the automatic control also get development.
Industrial centrifuges, according to the structure and separation requirements can be divided into filtering centrifuge, sedimentation centrifuge and three types of separator.
Centrifuge has a high speed rotary cylinder around the axis of itself, known as the rotary drum, usually driven by electric motors. Suspension (or emulsion) join drum, after being driven and drum with rotate speed, separation of components under the action of centrifugal force, and discharge, respectively. Generally, the higher the drum rotating speed, separation effect is better.
The role of the centrifugal separator principle has two kinds of centrifugal filtration and centrifugal sedimentation. Centrifugal filtration is to make suspending liquid centrifugal pressure generated in a centrifugal force field, the effect on the filter medium, make the liquid through a filter medium, filtrate and solid particles trapped in the filter medium surface, so as to realize liquid - solid separation; Centrifugal sedimentation is the use of suspension (or emulsion) density of different components in the centrifugal field rapid subsidence of the principle of stratification, realize the liquid - solid (or liquid - liquid separation.
Kind of experimental analysis is the use of centrifuge for clarification and enrichment of solid particles, liquid or liquid-liquid separation, the separator have atmospheric pressure, vacuum, freezing conditions different structural type of the operation.
Measure centrifuge separation separation factor are the important indicators of performance. It said by separating the material inside the drum by the ratio of centrifugal force and gravity, the separation factor, the greater the separation is usually more rapid, separation effect is better. Centrifuge separation factor is commonly used in industry of 100 ~ 20000, speeding tubular separator separation factor can be as high as 62000, separator separation factor analysis with speeding up to 610000. Decision centrifuge processing power of the other factor is the work area of the drum, large work area capacity is big.
Choose centrifuge must be according to the size of the solid particles in a suspension (or emulsion) and concentration, solid and liquid (or two liquids) density difference, liquid viscosity, residue (or sediment), and to meet the requirements of separation and so on carries on the comprehensive analysis, meet the filter cake moisture content (sediment) and the filtrate separation (liquid) clarify the degree requirements, preliminary selection using which kind of centrifuge. Then press capacity and automation of operation requirements, determine the type and gauge of the centrifuge, finally verified by practical test.
In general, for suspending liquid containing particle size greater than 0.01 mm particles, can be used to filter centrifuge; For particles in the suspension or tiny to compression deformation, appropriate chooses sedimentation centrifuge; Low solid content, small particles for suspension and for liquid clarification degree requirements are high, should choose separator.
When suspending liquid containing small particles let stand don't move, because the role of the gravitational field of suspended particles sinking gradually. The heavier particles, the sinking faster, whereas density than the liquid of small particles will rise. Particles moving under the gravitational field is associated with the size, shape and density of particles, and is related to the strength of the gravitational field and the viscosity of the liquid. Like red blood particles, the size of a micron in diameter, in normally under the action of gravity to observe their settlement process.
In addition, the material in the medium in the sedimentation was accompanied by a diffusion phenomenon. Diffusion is unconditional absolute. Is inversely proportional to the diffusion and the quality of the material, the smaller the particle diffusion is more serious. And settlement is relative, conditional and subject to external forces to movement. Settlement is proportional to the mass, the bigger the particle sedimentation. In less than a few microns particles such as viruses or protein, they come colloid or half colloid state in solution, using only the force of gravity is impossible of sedimentation process was observed. The slower because the smaller the particle sedimentation, and diffusion phenomenon is more serious. So need to strong centrifugal force generated by the centrifuge to force these particles sedimentation movement overcome diffusion.
Centrifugal is strong centrifugal force generated from the centrifuge rotor high-speed rotation, speed up the settlement of particles in the liquid, the samples in different subsidence coefficient and buoyant density of the material.