Hello,
I'm Francois Delannoy,
Head of Sales for Evaporation and Crystallization Technologies.
Hello, I'm Aniss Zenati,
Business Development Manager in the
team of Evaporation and Crystallization.
Today,
we will present you the technology of mechanical
vapor recompression for alumina refineries.
Let's first make an introduction to MVR technology.
So,
in alumina refineries,
there are operational units where the energy demand
is high and the evaporation unit is one of them.
The MVR technology enables to electrify your
production and electrify the evaporation process.
It consists
in being able to reuse low-grade heat energy into
high-grade heat energy by compressing vapors.
GEA has led many MVR projects back in the years
in alumina refineries as well as in
other fields of the mining industry.
As an example,
we can give the example of Martinsberg,
Berg in the 20th century.
It was in 1957,
already in those years,
for an evaporation capacity of 150 tons an hour with MVR technology.
Also,
in the years 2000,
we have implemented 30 tons per hour evaporation units in China.
And recently, at this moment,
while we speak,
we are executing one project in Europe.
And there are many others that we conduct other projects in parallel.
So,
MVR is a technology that is proven,
that is known within GEA,
and that is also used in the chemical plants in general?
That's very important.
That's right.
It's a proven technology.
You're right.
It's very important to say because the
alumina industry is quite conservative.
But,
I mean,
MVR applied to evaporation units is proven.
We are also using this technology in other fields,
in other mining applications,
such as lithium refining,
or salt plants,
or any other hydro-metallurgic plants.
So, technical principles and thermodynamics.
So,
the fundamental of an MVR system is to recompress
vapors that are at a low pressure or a low temperature.
And by compressing it,
you increase the pressure,
you increase the temperature of condensation.
And by this means,
you can use this vapor,
this low-grade heat vapor,
on a heat exchanger,
and you can condense this heat.
So,
at the end,
you recover this heat that is in this low-grade vapor.
Compressor power depends on the temperature rise,
the pressure rise,
the pressure differential.
So, it depends on the heat exchange area that
you allocate for your heat exchanger,
and it depends also on your boiling point elevation of your product.
MVR technology recovers heat, like I said,
and it can be applied either to a falling film
type or forced circulation type of evaporators.
So,
MVR uses electrical energy only,
even for startup,
or do we need a little bit of steam?
So, that's right.
We need a little bit of live steam for the startup,
like for a time frame of eight hours.
But once you have heat up your system,
you start your MVR machines,
you can stop immediately your live steam,
and you can run only with your compressors,
and there's absolutely no live steam required.
So, during normal operation, I would say.
That is one.
And the other advantage,
as well,
that we should say,
is that you don't need cooling water.
Everything is,
all your vapor that you are using is
entirely compressed and entirely recovered and condensed.
So,
that you don't need
any cooling water system to condense some vapors.
This is a schematic to explain this,
what we set.
So,
on this falling film evaporator,
you can see the process vapor here of an example of 10 tons per hour.
So,
we recompress those vapors.
And by raising up the pressure and the temperature of condensation,
we can use
this vapor,
this process vapor,
back on the shelf side,
back on the service side of your heat exchanger.
So,
that's really great.
Because there's no loss of enthalpy.
So,
the compressor enables to raise up the vapor enthalpy,
the vapor pressure,
and the vapor saturated temperature.
This is what enables you to use it and to be able to
condense it on the shelf side of your main heat exchanger.
Capacity of such units can be up to
100 tons an hour on a single body.
So, up to 100 tons per hour on a single body.
Do we have a limit for refinery and overall limit or not at all?
Well,
we don't have really a limit because
you can set such units side by side.
So, you can set three,
four, five units side by side,
enabling you to have
an evaporation capacity of 200 tons,
300 tons,
400 tons per hour.
So, basically, there's no real limit.
Performance and implementation.
So,
you have here the specific conception
of the classical steam-driven system.
So,
six-effect falling film and here multi-flash trains.
You can see that for MBR,
in the middle of the table,
there is no steam consumption
and there is no cooling water consumption.
But you need to allocate for this significant electrical power.
That is what needs to be scheduled.
Single-stage fan is limited to 8,
10 degrees temperature rates.
There are other technologies, but less robust.
The technology we use are centrifugal
fans that can sustain some droplets.
So, it's very robust.
And this is what we need for mining application.
We need robust machines.
We allocate also for reserve on the delta T for compensating
the scaling on the product side.
And the evaporation capacity can be adjusted thanks
to a VSD that is set on the motor of the fan.
So,
you can tune directly the RPM of the fan
that is directly tuning your delta T of ET.
COP improvement.
COP improvement.
COP stands for Coefficiency of Performance.
And here we can really see that
MVR systems are better performing compared to steam-driven systems.
We have taken the classical efficiency,
energy efficiency of a steam-driven system.
That is basically a steam economy of
4.0 ton per ton of steam.
So,
this is the specific efficiency for such a steam-driven system.
We speak in terms of steam economy and we compare the
evaporation to the consumption of the steam in ton per ton.
And let's compare that to an MVR system
that has a temperature rise of 20 degrees.
So, this is here the equation.
That ends up to a result of 3.06.
Which means that an MVR system is three times
more efficient than a classical six-effect system.
So,
it's clear here with this calculation
that MVR technology is more efficient.
Impressive.
Retrofitting and evaporator configurations.
So,
MVR system in an existing refinery can be
offered either as a pre-concentration stage
or directly retrofitting your existing multiple-effect unit.
And it can be applied either to falling
film or to forced circulation evaporators.
What we like to offer in order to be
efficient in terms of installation.
We like to offer a side evaporator
acting a little bit as a pre-concentrator.
It enables to continue your production.
So, you don't need to stop your production.
You continue to
produce while we are building this evaporator.
It's very important for a bioprocess and for an alumina
refineries to always have available its evaporation capacity.
Building such side units
enables to raise a part,
I mean,
to raise the caustic concentration for
a part of your available spent liquor.
And what can be done is to mix
this portion of your spent liquor together
with the other portion of spent liquor.
It's offering you a liquor that is pre-concentrated
and that can be sent to your existing evaporator.
Here on the side,
you have the table with the specific figures.
So,
by this means you can increase your overall
evaporation capacity by 100 tons per hour,
in this case,
in this example.
And you can see immediately because
for this additional 100 tons per hour,
you have no steam consumption.
Mechanically, it's improving your steam economy.
Of course,
you have to allocate for a little bit more
electrical power because you need this to
feed your machines, your compressor.
Economical and regional consideration.
Let's take a practical example for an evaporation line having
a capacity of 170 tons per hour of evaporation capacity.
So,
such a capacity can be achieved on a single line
of evaporation for a steam-driven system.
So,
it can be either a multi-flash drain or a
six-effect or a seven-effect evaporator,
a falling film evaporator.
Whereas for an MVR system,
it has to be two or three parallel units for this capacity,
170.
So,
it can be two times 85 tons an hour or three times 57 tons per hour.
The capex advantage for a steam-driven system is
that you don't have to pay for those machines.
However,
you have six bodies or seven bodies in the case of the falling film,
and you have even nine or 12 bodies
in the case of multi-flash drains.
What is nice with the MVR system is that
you have only two bodies or three bodies.
That is
offering immediately a saving of steel structure,
a saving in terms of piping cost,
and
a saving also in terms of cabling.
So,
many fields of scope of supply of substructure projects
is being decreased in case of an MVR project.
However,
you have to pay for the compressor machines.
So, the one is compensating the other.
What we see when we do the comparison is that the capex
for MVR system and for steam-driven system is comparable.
Even the MVR system,
we found that it's approximately 5% less.
But, okay, 5% is not a lot, but, okay,
it's slightly in the advantage of the MVR system.
So, capex is slightly lower for MVR system.
But what can you say about the OPEX?
So,
the OPEX,
that's where we can have a strong saving thanks to MVR technology.
We have taken
the same capacity, 170 tons an hour,
and we have taken this energy cost,
Europe-based cost.
So,
30 euro per ton for the steam and 0.1 euro
per kilowatt for the electrical power.
It ends up with
this cost for one-year OPEX.
So,
10 million approximately in the case of the live
steam-driven system and about 7 million euro
after a year of production with an MVR system.
So,
it's offering a saving
of 3 million euro in the case of MVR system in this case.
So, if we talk about return of investments,
which kind of ROI can we achieve?
Well,
in this case, the ROI can be 3 to 5 years,
which is
really nice for such a mining project where,
in general,
producers are looking for 5 years ROI because
they invest for the long term.
In some other cases,
in some other mining applications,
it can be even a return on investment of a year only.
So,
it can be from 1 year to 5 years with this base of Europe-based cost.
However,
in some other regions of the world,
for captive power plants
fed with gas or with coal,
you can decrease your steam cost
a lot.
And it can even be down to 10 euro per ton.
So,
in the case of 10 euro per ton,
you will have here 10 million divided by 3.
So, it will give
a minus 3 million and not a plus 3 million of saving.
It will be a 3 million of saving for the steam-driven system.
So, it's completely the other way around.
So,
for those regions of the world where
the primary source of energy is coal,
MVR is still interesting
for CO2 emission reduction.
But in this case,
we should look for other source of electrical power.
We will speak about that in a minute.
Context and energy mix.
So,
like I said,
in some regions of the world,
aluminum refineries are fed with coal
and coal-fired captive power plants.
And in this case,
yes,
the live steam is very cheap and you have to consume it.
So,
evaporation units are nice for consuming this live steam.
If we still want to implement MVR system for CAPEX
reason and for CO2 emission reduction reason,
we should look to alternative sources of
electrical power such as solar panel fields
or wind turbines.
And those installations should be
supported by battery energy grid storage
in order to ensure a steady electrical power supply.
And in this case,
yes,
you can definitely support an MVR project,
an MVR evaporation project.
So,
again,
another slide that is giving some
insights of some aluminum refineries.
We have taken here public data for two refineries
in India where the primary source of energy is coal.
And we can see,
yes,
that the power generation is largely in favor of steam generation
and in a lesser extent for electrical power generation.
The other table is giving the comparison between coal-fired
captive power plant and gas-fired captive power plant.
We can see with gas,
we have much more electrical power generation compared to steam.
So,
for gas-fired captive power plant,
yes,
MVR units are interesting,
definitely,
because we can consume.
There is enough electrical power available for supplying
the electrical power to an MVR evaporation line.
For what concerns coal,
it's less positive.
So,
this is where we have to look for
alternative source of electrical power.
We have also made some calculations here
to explain what is the impact
if we installed an MVR
evaporation line where the primary source of energy is coal.
So,
such a refinery with coal is generating approximately
80 megawatts of electrical power and 400
tons of steam coming from the captive power plant.
That is also coming with a lower electrical power
generation that will turn down to be 72 megawatts generated.
That means an additional 8 megawatts needed for the electrical power.
So,
at the end,
you have two power consumption to consider.
Your power consumption of your MVR
units and also the compensation for the
decrease of power generation to your captive power plant.
So,
it's 8 megawatts for your captive power plant compensation.
It enables to save 10% of coal and 10% of your CO2 emission.
However,
that requires a proper electrical power,
like I have explained.
And that should be part of your CAPEX because a solar
panel filled with battery energy grid storage has a CAPEX.
So, it has to be scheduled as well.
What we can do for such units such as aluminum
refineries where the primary energy is coal
is to offer a 7-effect falling film.
So, in GEA, we can offer that.
We can offer even retrofitting of our
existing 6-effects into 7-effects.
And we are also offering that as a brand new project,
as brand new lines of evaporation.
And with a 7-effects falling film units,
we can offer steam economy of 5.0 or even higher.
This is also enabling to save consumption of coal.
And this is also enabling lowering of CO2 emission.
In a lower manner,
but still, it's better than a 6-effect.
Conclusion.
So,
as a conclusion,
we have seen that MVR technology
significantly improve energy efficiency.
And offering a COP three times better
compared to a classical steam-driven system.
Cost and operational benefits.
MVRs offer comparable
capital costs compared to a classical steam-driven system.
But it can offer clearly better operational
expenses depending on the region of the world.
But in many regions of the world,
yes,
you will have
a much lower operational expense.
Sustainability and decarbonization.
MVR supports your electrification
and your elimination of fossil fuel.
Helping refineries to meet their global sustainability goals.
implementation consideration.
There should be a careful assessment of
the power availability and energy sources.
Scrutinity is essential for a successful
MVR project and an MVR integration.
So, thank you very much.
We hope that you enjoyed this webinar.
And we remain at your disposition for any questions.
Thank you.
Thank you all.
