Manufacturer of Laser Welding stainless steel Pillow Heat Exchanger Plate for Falling Film MVR evaporator
Mechanical Vapor Recompression (MVR) evaporator
Mechanical vapor Recompression reduces the energy used in the evaporation process by up to 90% compared with conventional systems.
It works by reusing the heat energy contained in the vapor.This energy would otherwise be wasted.In a typical falling film evaporation plant the feed liquid enters the top of a vertical chamber called a Calandria.The liquid is dispersed across a large number of vertical tubes as it flows downwards it tends to form a film on the inside of the tube.Between the top and the bottom sections of the Calandria there is a sealed are where the tubes pass through a jacket of high temperature vapor.This section acts as a heating exchanger. As the hot vapor condenses on the outside of the tubes,it releases latent heat which raises the temperature of the feed liquid in the tubes.By the time the feed liquid leaves the bottom of the tube,much of the water has been evaporated off leaving a concentrated viscous liquid.The water which has been evaporated off leaves the tube as vapor.In the bottom section of the Calandria,some of the concentrated liquid gathers and can be drawn off,the hot mixture passes into a cooler chamber called the Separator where more of the concentrated liquid falls to the bottom to be drawn off and the vapor rises to the top.This vapor now contains most of the energy that was initially fed into the system.
The turbo fan sucks the vapor from the Separator and re-compresses it,raising the pressure and so increasing the temperature to the point where the vapor can once again be used as a source of heat.The unit is extremely robust,gas tight turbo fan ideally suited to the pressure,temperatures and volumes of the MVC evaporation process.At its heart is an ultra high speed impeller with a tip velocity of over 1000 Km/h faster than the speed of a jet airliner.The rotor probably has the highest tip velocity of any welded impeller ever manufactured.The re-heated vapor can then be fed back into the Calandria to provide the heat energy required to evaporate more feed liquid as it passes down the tubes.The Mechanical Vapor Compression process is a high energy efficient and cost effective way of retaining and reusing the latent heat contained in the vapor.Energy that would otherwise be wasted.Once the process has been started and brought up th temperature the only energy input required is the electricity to drive the Turbo fan.
As energy costs increase, the use of Mechanical Vapor Recompression (MVR) evaporators has also increased. The energy savings possible by using MVR technology is significant. MVR evaporators are designed to operate with very low specific energy consumption while producing clean condensate to minimize fresh water consumption in the mill.
Best possible energy efficiency
Compared to multiple-effect evaporators, MVR evaporators consume considerably less energy.
Low vapor velocities inside the evaporator, low shear rates, and the free flow falling film construction are advantages of the design in minimizing foam creation. This is especially important in MVR evaporators, not only to maximize the production of clean condensate, but also for protection of the compressor or fan.
Uniform liquor distribution of the liquor over the lamellas, and the continuous redistribution of the liquor created by the dimpled shape of the lamella surface, ensure a completely wetted heating surface and eliminate local scaling or over-concentration of liquor. The lamella heating surface ensures that water-soluble scaling can be washed away by a simple dilution wash, eliminating the need for time-consuming and costly outages for cleaning.
Highly efficient condensate segregation in the evaporator ducts and lamellas, plus the integrated stripping of foul condensate fractions, produce clean and re-usable water.
MVR Technical Characteristics
MVR technology uses the generated vapor for heat instead of expensive heat sources
MVR technology does not require a cooling tower, greatly reducing the use of cooling water
MVR technology is more efficient than traditional multi-effect evaporation technology saving energy and reducing operating costs
MVR technology is truly energy-saving, water-saving, environmentally-sound, and helps with resource recycling
MVR technology achieves low-temperature evaporation, greatly reducing the impact on your material
MVR technology system structure is simple, fully-automated, with continuous operation
MVR systems consist of an evaporator, a vapor compressor, separators, pumps, piping, instrumentation, and electrical control components
MVR systems can be designed around simple evaporators or sophisticated falling film tube evaporators
MVR systems can use simple vapor compression or sophisticated roots pumps
MVR systems can have low liquid holdup, or be larger volume tank systems
MVR systems can achieve a variety of evaporation, process design and fluid composition will determine this
Working principle drawing
The operation of the two evaporation processes for the treatment of wheat straw pulp black liquor is shown in the table.
Operation of two evaporation processes for treating paper pulp black liquor
|item||5 effect station||combined evaporation process|
|MVR pre concentration||5-effect evaporation station|
|Evaporation water (t/h)||100||64.28||35.72|
|RMB/T water evaporation capacity||45||25.93|
Note:In operation cost estimation:steam 150rmb/t,electricity 0.6 rmb/kWh,water 0.5rmb/t.
The investment of combined evaporation process equipment increased: evaporator (2500 m2) 375x10000 RMB; MVR compressor 400x10000rmb, total 775x10000 RMB
Annual operating cost reduction of combined evaporation process: 3672-2115 = 1557 (10000RMB)
Investment increase payback period of combined evaporation process: 755 ÷ 1557=0.5year
It can be seen that taking the scale of 100t / h as an example, the combined evaporation process can recover the increased investment in half a year, and save 1557 (10000 RMB) every year in the future, with considerable economic benefits.