plaquette INCA 2005
25/08/05
9:54
Page 1
ADVANCED TECHNOLOGIES
VOXALTM - VOC Abatement
SCHERING-PLOUGH
Choose VOXALTM environmental solution
www.airliquide.com
plaquette INCA 2005
25/08/05
9:54
Page 2
VOC trapping for Schering-Plough in Singapore
Although solvents play an essential role in several
processes, they turn out to be undesirable when they are
released to the atmosphere. More and more stringent
regulations force manufacturers to limit the release of
Volatile Organic Compounds (VOC) including solvents.
In addition to the environmental
aspect, there is the aim of making
profit from a product which would
otherwise evaporate.
Schering-Plough
requirement
The condensation technologies
(mechanical or cryogenic
The VOC recovery unit has been designed for treatment of gaseous emissions
refrigeration) provide the best
from an expansion to a steroid production facility. The unit is located
solution to this double challenge.
downstream of a general scrubber and is designed to remove at least 98% of
Based on its long experience in
VOCS. Being a batch plant, gaseous discharges fluctuate rapidly within a wide
cryogenics, the Advanced
range of flow and concentration. Typical sources of emissions are Nitrogen
Technologies (DTA) of Air Liquide
purging of vessels and lines, operation of dryers, and gaseous by-products
have designed the VOXALTM range
from reactions.
of standard cryogenic heat
Typical gas flowrate to be treated is 50 Nm3/h, but the unit is designed for
exchangers.
200 Nm3/h to account for instantaneous peak flowrates during purging
The VOXALTM technology was
operation. Typical VOCS emissions are Acetone, Isopropyl Alcohol, Methanol,
chosen in 2003 by Schering-
Methylene Chloride, with a total concentration around 50 g/Nm3. The batch
Plough Ltd in Singapore, Tuas
process takes 80-90 hours to complete, and typically 1 to 2 batches per week
West Drive site.
are produced throughout the year.
1
:
1-2 :
2
:
2-3 :
3
:
Gaseous mixture at condenser inlet
Cooling of the gaseous mixture
Dew Point
Active phase of condensation
Final Concentration
Figure 1 - Phase diagram
2
Figure 2 – VOXALTM
heat exchanger design
plaquette INCA 2005
25/08/05
9:54
Page 3
VOXALTM Technology
The cryo-trapping process takes place in a liquid Nitrogen cooled enclosure in which
pollutant gases pass through. Solvents condense or crystallize while the purified gas
(inert gas) is released. Then, these liquid or solid solvents can be recovered to be
re-used or stored in a safe area. Nevertheless, solvents are never cooled at –196°C
(temperature of liquid Nitrogen) since they would instantaneously crystallize and clog
the heat exchanger. The perfect temperature is adjusted for each operation, according
to the thermodynamic properties of the VOC.
Principle
Cryo-condensation allows the
recovery of solvents or
hydrocarbons in their liquid form.
This is a reliable and particularly
flexible technology which can be
adapted to all types of process.
This simple and efficient principle
may be illustrated by the phase
diagram (Figure 1 below). When
cooling down a gas containing
one condensable compound, the
first liquid droplet appears when
the partial pressure reaches its
saturation level (point 2 at
Figure 1) : the point is called the
dew point of the compound. Then
starts the condensation phase
(from point 2 to 3 on figure 1) :
vapour pressure decreases
according to temperature
following Antoine's equation,
Ln (P) = A -
B
T+C
where A, B and C are figures
experimentally defined for each
compound, P is partial pressure
and T is temperature.
The expected compound
concentration inside the vector
VOC emissions to very low levels
by rapidly trapping the VOCS at a
Advantage of the cryocondensation process
very low temperature. Boiling
• Modularity: AIR LIQUIDE's know-how
point of liquid Nitrogen at
leads to original solutions resulting from
atmospheric pressure is -196°C.
engineering studies and the
Evaporating one kilogram of liquid
development of specific equipment, thus
Nitrogen (around 1.24 litres)
enabling AIR LIQUIDE to provide "tailor
absorbs around 200 kJ. Heated
to ambient temperature, gaseous
Nitrogen absorbs about the same
made" equipment (picture 1).
• Flexibility of use: use of liquid
Nitrogen traps VOCS from effluents
with high variations of flowrate and/or
energy. In addition, low cost of
concentration. Because of its high
LN2 makes it the perfect
cooling power at low temperatures,
refrigeration fluid when required
liquid Nitrogen allows quick start-up,
temperatures are below -30°C.
copes with surges (flowrate or content)
of the effluent in the process and
Technology design
Air Liquide has developed this
specific VOC trapping technology
provides great flexibility for the solvent
recovery unit.
• Reliability/Low maintenance:
using liquid Nitrogen for more
simplicity of equipment and absence
than 30 years.
of rotating machines mean that
The VOXALTM cryogenic heat
exchanger is of tube and shell
type, where liquid Nitrogen flows
and vaporizes inside the tubes,
and process gas flows through a
minimum maintenance is required.
• Safety: use of liquid Nitrogen allows a
reliable answer to the constraints of
processes presenting particular risks
(flammability, explosion, toxicity).
• Compactness: the overall dimensions
baffle network inside the shell
are very small; the recovery unit
(see Figure 2).
supplied on a skid fits into a small
Condensates accumulate in the
lower part of the heat exchanger
around a bundle of small tubes.
footprint.
• Recovery of solvents: cryogenic
condensation enables the condensed
gas implies a minimal temperature
solvents to be re-used in the
to be reached (point 3). The
production circuits if necessary. This
minimal temperature depends on
technology does not produce pollution
compound properties,
environmental regulation, and
mixture with other compounds.
transfer.
• Optimisation: re-use of gaseous
Nitrogen is possible for other applications
on site (N2 blanketing, etc...)
The use of liquid Nitrogen reduces
3
plaquette INCA 2005
25/08/05
9:54
Page 4
Design of the unit for Schering-Plough
A customized solution for Schering-Plough is requested
to achieve 99% solvent recovery.
- two cryogenic traps working in
Thermodynamic calculations show
heat exchanger surface. A
that it is necessary to cool down
parallel alternatively cycling from
precondenser (HE01) operating
the process gas down to –130°C
purification to regeneration
with glycolated water at +3°C
to remove 98% of VOCS (mainly
(See Figure 3.)
(available at Schering-Plough’s
Methylene Chloride).
• Precondenser HE01
site) is used to remove 95% of the
(See Figure 4.)
Because of moisture in the
water. The precondenser also
The VOXAL
process gas, there would be a
covers almost 70% of the total
Schering-Plough cryotrapping unit
rapid clogging of the cryogenic
cooling energy, and thus reduces
consists of 2 main stages:
heat exchanger due to the
the Liquid Nitrogen consumption
- a precondenser
crystallisation of water on the cold
on the cryogenic stage.
TM
process in the
Main properties of VOCS:
Freezing point
Boiling point
Acetone (C3H6O)
-95°C
+50°C
Isopropyl Alcohol (C3H8O)
-88°C
+82°C
Methanol (CH4O)
-97°C
+65°C
Methylene Chloride (CH2Cl2)
-97°C
+40°C
0°C
+100°C
Water (H2O)
General process diagram:
Figure 3 – VOXALTM process for Schering-Plough
4
plaquette INCA 2005
25/08/05
9:54
Page 5
The VOXALTM solution relies on the utility of liquid nitrogen which brings the following
added value: on site availability, capacity to reach very low temperature, high cooling
power, safe operation, no cross contamination and possibility to recycle nitrogen in the
process.
• Cryogenic traps HE02A and
• De-icing of HE02A and
HE02B. The cryogenic trap
HE02B traps. The cryogenic
includes a two stages of
traps have to be defrosted from
purification. The first stage
time to time to operate
(HE02A) cools down the
continuously in trapping phase.
process gas to –90°C, and the
Defrosting is done by circulation
second stage (HE02B) to
of gaseous Nitrogen previously
–130°C. This dual stage design
heated by a N2 steam heater.
allows to first condense at
Hot N2 then flows through a
–90°C (below freezing point of
heat exchanger (tube side) to
Methylene Chloride), than at
gently reheat the heat
–130°C to complete the
exchanger surface above the
process gas purification. A
melting point of water (above
design with a single stage at
0°C). The de-icing phase takes
–130°C would have significantly
around 4 hours while the VOC
increased the clogging rate of
trapping phase lasts around 90
the heat exchanger.
hours (see Figure 5).
Temperature (°C)
Figure 4 – Condensation rate according to temperature
Picture 1 – VOXALTM unit on site
Figure 5 – trapping / defrosting
cycle simulation for a nominal
flowrate of 50 Nm3/h
5
plaquette INCA 2005
25/08/05
9:54
Page 6
Skid assembled and factory tested units allows a very short
commissioning time.
General assembly
of the unit
The VOXALTM unit has been fully
skid mounted at Air Liquide’s
workshop. The unit was
assembled and shiped in a
horizontal position and was
erected vertically on site by
Schering-Plough. The general
dimension of the unit is a footprint
of 3m x 3m and a total height of
8m.
Automatic control
of the unit
The VOXALTM unit is automatically
controlled through a PLC, located
in a remote electrical room.
Operation of the unit is monitored
through a PC screen in the
supervision room.
Telemonitoring
of the unit
Capability of telemonitoring is
included in the design of the
system. Upon customer request
real time supervision can be done
at any time from Air Liquide’s
office in France using a standard
phone line.
Figure 6 – General assembly drawing
6
plaquette INCA 2005
25/08/05
9:54
Page 7
Design of the unit for Schering-Plough
After completion of the performance test, Michael MINERVA said “The VOC system
went smoother than I expected, considering the problems we had with other suppliers.
You and the rest of the commissioning team did a great job in bringing this system on
line. Things seem to run much better with me staying 9,000 miles away!”
Qualification of the unit:
maximal flowrate, pressure drop
Motivation of Schering-
A Factory Acceptance Test (FAT)
at nominal and maximal flowrate,
Plough in the Air Liquide
had been performed in the
and finally Liquid Nitrogen
technology:
workshop two weeks before
consumption during a long
According to Michael MINERVA,
shipping the unit to Singapore. In
duration test. The following
based in Head Office New Jersey
addition to a mechanical and
characteristics were measured
– USA, Director of Environmental
control review, a cooling down
during SAT: pressure drop less
Projects for Schering-Plough, the
than 10mbar at maximal flowrate
Air Liquide solution was selected
of 200 Nm3/h, temperature
among several cryogenic
control within 10°C, and liquid
solutions. In addition to removal
Nitrogen consumption within 2%
efficiency, a major concern of
of the estimate.
Schering-Plough was to have a
Finally, a Performance Test was
unit with a very low pressure drop
done after SAT and the following
at any operating condition, even
performances were measured:
when the system is partly clogged
• 98,9% removal efficiency for
because of icing. Air Liquide
test was done to check the
temperature control in operational
conditions (without solvent).
A Site Acceptance Test (SAT) was
performed in Singapore after
completion of the mechanical and
electrical connections. The SAT
took approximately two weeks to
demonstrate the following
functionality: full loop check,
temperature control and stability
Methylene Chloride for the worst
guaranteed a pressure drop of
with flowrate rapidly fluctuating
measurement.
less than 30 mbar through the
between 10 to 200 Nm3/h,
• 99,8% removal efficiency for
system, which made the
autonomy of the system in
Methanol for the worst
difference versus the competitor’s
trapping phase at nominal and
measurement.
solution.
7
plaquette INCA 2005
25/08/05
9:54
Page 8
ADVANCED TECHNOLOGIES
Contacts
SCHERING-PLOUGH / USA
Michael MINERVA
Phone 00 1 908 629 3455
[email protected]
www.schering-plough.com
ADVANCED
TECHNOLOGIES
www.airliquide.com
Founded in 1902 and now present in 65 countries with 35 000 employees, AIR LIQUIDE is the world leader in industrial and medical gases and related services.
The Group offers innovative solutions based on constantly enhanced technologies to help manufacture many indispensable everyday products and preserve life.
Made in France - Vassel-Palisse.com - 07-05 - 100 UK
AIR LIQUIDE FRANCE
Phone 00 33 4 76 43 62 11
Fax. 00 33 4 76 43 62 71
E-mail: [email protected]
www.dta.airliquide.com