MVR is the abbreviated form of the mechanical vapor re-compression.This is a technology that recovers the energy of the secondary vapor it generates and therefore reduces the demand for external energy.As early as in 1960s,this technology applied successfully to chemical,pharmaceutical,paper-making,waste-water treatment and desalination fields.
MVR technical principle
When mechanical vapor is re-compressed,the mechanically driven compressor will compress the secondary vapor generated by the evaporator to form a higher pressure.In this sense,the compressor acts as a heat pump to increase energy to the vapor.In another word,in this process,the low-temperature vapor is compressed by the compressor to improve its temperature and pressure and increase its enthalpy and then flow into the heat ex-changer for heat exchange and condensation so as to make use of the latent heat of the secondary vapor.Except machine start-up,no generation of additional vapor is required during the entire evaporation process.
Technical characteristics
1,Low energy consumption,low operation cost
2,Small space occupation
3,Require fewer public utilities and less total investment
4,Stable operation and high degree of automation
5,Require no primary steam
6,Short retention time due to frequently used single effect
7,Simple process,high practicability,and excellent service performance at some loads
8,Low operation costs
9,Capable of evaporating at and below 40celsius without any refrigerating plant and therefore particularly suitable for heat sensitive materials.
Design and function
Vapor compressor currently used for MVP technology has two forms:the positive displacement type and the centrifugal type
Among positive displacement compressors,the most commonly used compressor is the Roots compressor which compresses gas by bringing two or three lobed rotors to relative motions in the cylinder.This kind of compressor keeps two rotors engaged with each other by relying on synchronic mesh gears located on the rotor axle ends;the curved surface of each concave on the rotor,together with the inside wall of the cylinder,forms a working displacement,which carries away the gas from the gas suction port during rotor rotation,when the carried gas moves to the vicinity of the exhaust port,the pressure in the working displacement will abruptly pick up at the moment,It is to connect with the exhaust port due to the return of gas at higher pressure,and the gas then is delivered to the exhaust passage.This compressor has a large pressure ratio and a small sucking rate.
Centrifugal compressors provide gas energy by means of high-speed rotation of impeller blades.In these compressors,the gas is accelerated and then passes through the diffuser at downstream of the impeller to decelerate.In doing so,the kinetic energy is transformed into pressure energy.According to the direction of fluids passing through the impeller ,these compressors are named axial flow,mixed flow,or centrifugal compressors respectively.They are renowned for large pressure ratio,big flow rate,and good stability.
Whichever is the most suitable compressor depends on specific operating conditions and the economy of the entire system.Critical parameter s include the pressure rise to be achieved and volume flow of steam to be compressed.
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