All welded SS304 plate type heat exchanger for MVR evaporator of
heating water, oil, juice
Non-foaming design
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.
Non-plugging design
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.
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.
Cleanest condensates
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
Operation
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 |
| Incoming concentration(%) | 10 | 10 | 20 |
| Out concentration(%) | 45 | 20 | 45 |
| Evaporator area(㎡) | 10000 | 8500 | 4000 |
| Condenser area(㎡) | 800 | / | 300 |
| Consumption | Steam (t/h) | 25 | / | 9 |
| Electricity(kWh/h) | 500 | 1600 | 180 |
| Water(t/h) | 900 | / | 350 |
| Running cost | RMB/hour | 4500 | 960 | 1633 |
| RMB/T water evaporation capacity | 45 | 25.93 |
| RMBx10000/Day | 10.8 | 6.2 |
| RMBx10000/Year(340days) | 3672 | 2115 |
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.
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