DE-BOTTLENECKING A De-Iso-BUTANIZER WITH … three streams are accumulated in a feed drum. The...
Transcript of DE-BOTTLENECKING A De-Iso-BUTANIZER WITH … three streams are accumulated in a feed drum. The...
Total Refinery Antwerp 1 AIChE Meeting, 10-14 April 05 Sulzer Chemtech Debottlenecking a DIB with VGPlus
DE-BOTTLENECKING A De-Iso-BUTANIZER
WITH “VGPlus” HIGH PERFORMCE TRAYS
By
Giuseppe Mosca, Gitta Van Hemel, Roberto Tocco, Sulzer Chemtech.
And
Bruno Lestrade, Total Refinery Antwerp, Belgium.
Presented in the Distillation Symposium of the 2005 Spring AIChE Meeting
Atlanta, Georgia, 10 – 14 April 2005
Unpublished
Copyright 2005: Total Refinery Antwerp, and Sulzer Chemtech Winterthur.
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Abstract
Increasing throughput in major existing equipment, such as distillation columns, is a key
factor to economically meet production targets.
To successfully maximize plant’s performances, a deep knowledge of the process and its
characteristics is a must, but certainly not enough.
It is also crucial to fully comprehend the equipment being used, their mechanisms of
operation, limitations and capabilities. This includes, among others, furnaces, exchangers,
pumps, and mass transfer devices for distillation columns: fractionation trays, random
and structured packing and associated liquid and vapor distributors.
The purpose of this paper is to provide an overview of the key factors to successfully
implement revamping projects with the goal to maximize capacity without compromising
efficiency.
A commercial experience will be discussed in detail, where the use of one of the most
advanced mass transfer components, i.e. VGPlus tray, yields to the best cost effective
solution of revamping for a De-IsoButanizer at Total Refinery Antwerp, Belgium.
The paper will cover the description of the unit, the scope of the revamping, its
implementation, and the achieved performances.
Process simulation details will be also presented for a better understanding of column
capacity versus mass transfer separation efficiency, and their optimization while dealing
with existing columns.
1) De-IsoButanizer Plant: Process description
The Unit (see figure 1.1) may receive feed from three different sources; the compositions
of the streams differ substantially from each other, one being the richest in Iso-C4,
another one the poorest, and the third in the middle. The richest stream is not fed in a
continuous mode, actually is used only in case of high demand of Iso-butane for the
downstream Alkylation plant. The three streams are accumulated in a feed drum.
The homogenized feed is pumped, preheated by mean of a stream coming from the Iso-
Stripper, and finally enters the distillation column above tray 29. The feed flow rate is in
cascade with level of the accumulator, while its temperature is not automatically
controlled. The fractionator separates Iso-Butane from Normal-Butane and heavier.
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Figure 1.1: De-IsoButanizer Plant
The De-IsoButanizer overhead vapor is cooled, condensed by mean of water coolers, and
accumulated at the top receiver. The reflux flow rate set point is in cascade with the
temperature control of the top pilot tray. The flow rate of the Iso-Butane product is
cascaded with the top receiver ‘s level control. A common pump serves both the Iso-
Butane product and the top reflux. The overhead product is one of the feedstocks for the
Alkylation Unit. The duty at the kettle reboiler is provided with a hot fluid coming from
another Unit with which it’s integrated.
The bottom product is pumped and sent to stock after cooling at ambient temperature, its
flow rate is in remote set point with the level control of the kettle reboiler.
Before the revamping, the Unit was able to produce at most 150 tons/day of Iso-Butane.
2) Scope of the Revamping
A feasibility study was commissioned with the scope of identifying the maximum
achievable production of Iso-Butane. The results of the study showed that the Iso-Butane
throughput could have been doubled versus the current production, after modifying and
or adding a certain number of equipment; while keeping unchanged the existing vessel of
the distillation tower, the feed accumulator and the top receiver.
56
1
28
n-C4
29
From Iso-Stripper
Reboiling Fluid
FC
FC
FCLC
PC
LCFC
10FC
TC
Fuel Gas
Iso-C4Feed-1
Feed-2
Feed-3
LC
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The study included the evaluation of all the equipment based on two cases with different
compositions: “Design Feed” and “Alternate Feed”, being the first one the main case (see
Table 2.1). The ultimate capacity of the “Alternate Feed” was determined by fully
utilizing the reboiler and condenser duties of the first case; only the bottom product pump
and cooler were designed based on the controlling Alternate Feed case.
Table 2.1: Feed compositions for the Design and Alternate case
Component / Case Design Feed (%wt) Alternate Feed (%wt)
Propane
Iso-Butane
Normal-Butane
Unsaturated C4s
C5s
2.70
31.20
65.72
0.35
0.03
2.78
23.70
73.18
0.21
0.13
Total 100 100
Since the De-IsoButanizer is integrated with another Unit, which provides the reboiling
duty, the study was performed setting a maximum available duty of 13.5 MMKcal/h.
The condenser duty and the reflux ratio were calculated from the required Iso-Butane
recovery and purity, as well as from the achievable mass transfer efficiency at the
existing tower.
A process simulation study was performed to identify the optimum feed inlet location,
reflux ratio and number of trays with the goal of maximizing the capacity of the column.
For a given existing column, only reducing the tray spacing can increase the number of
theoretical stages, provided that the fractionation trays are properly designed.
For a required separation target, the reflux decreases by increasing the theoretical stages,
until a minimum value is approached. At reduced reflux, the vapor & liquid traffic
through the column decreases, thus the hydraulic capacity of the tower should increase.
However while decreasing the tray spacing to achieve more separation stages, the
hydraulic capacity of the column decreases, approximately with the square root of the
tray spacing. Therefore, for a given column (internal diameter and height), and separation
goals, there is an optimum working point, that can be determined from a proper analysis
of the number of stages, reflux ratio and tray spacing. (See Figure 2.1, 2.2, 2.3)
Total Refinery Antwerp 5 AIChE Meeting, 10-14 April 05 Sulzer Chemtech Debottlenecking a DIB with VGPlus
Figure 2.1: Reflux Ratio VS Theoretical Stages
Figure 2.2: Reb. & Cond. Duty VS Theoretical Stages
Figure 2.3: Capacity of the existing Column VS Theoretical Stages
9
11
13
15
17
19
21
35 40 45 50 55 60 65 70 75
N° of Theoretical Stages
Du
ty (M
MK
cal/h
)
Reboiler
Condenser
Duty available
9
11
13
15
17
19
35 40 45 50 55 60 65 70 75
N° of Theorethical Stages
Ref
lux
Rat
io
75
80
85
90
95
100
105
35 40 45 50 55 60 65 70 75
N° of Theoretical Stages
Flo
od
ing
(%)
Optimum Point
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For this De-IsoButanizer, the minimum flooding factor (maximum capacity) was found
for a number of actual trays, very close to the existing one, providing with approximately
48 theoretical stages i.e. 86 % tray efficiency, for a total of 50 stages (assuming 1 stage
each for reboiler & condenser). Therefore it was decided to retrofit the tower with a one
by one tray replacement. The hydraulic results of the VGPlus trays are here after shown
in Table 2.2.
Table 2.2: Hydraulic Performances at Revamp conditions
Tray Type: VGPlus
The selected option allowed a big saving for the project implementation; since additional
actual trays were not needed, the job could have been done without adding new tower
attachments, nor welding to the vessel, resulting in a very fast and cost effective solution
of revamping.
However, there are several other revamp projects where a higher number of actual trays
could be required, therefore new support rings are a must. Even for such cases, Sulzer
Chemtech has tailored mechanical solutions to minimize the site work activities, which
will not be discussed since they are out of the scope of this paper.
Case
Section above-feed below-feed above-feed below-feedVaporFlow rate kg/h 208570 182290 201910 180800Density Kg/m3 19.563 19.670 19.497 19.586C-factor m/sec 0.086 0.074 0.083 0.074
LiquidFlow rate kg/h 195080 210030 190910 212010Density Kg/m3 509.4 511.8 509.9 512.3Surf.Tension mN/m 6.95 6.97 6.98 6.99Viscosity cp 0.1 0.1 0.1 0.1L-Loading m3/h/m2 55.50 59.48 54.26 59.98
HydraulicJet flood % 80 70 78 70DC flood % 73 78 72 80Weir loading gpm/inch 9.50 10.18 9.29 10.27Dry Drop mmH20 29.45 22.37 27.69 22.11Delta P mBar 6.15 5.70 5.99 5.69
Column ID: 2964 mm Tray Spacing: 610 mm
Tray Eff. 86 % Tray Eff. 86 %
System Factor: 1
Design Feed Alternate FeedCase
Section above-feed below-feed above-feed below-feedVaporFlow rate kg/h 208570 182290 201910 180800Density Kg/m3 19.563 19.670 19.497 19.586C-factor m/sec 0.086 0.074 0.083 0.074
LiquidFlow rate kg/h 195080 210030 190910 212010Density Kg/m3 509.4 511.8 509.9 512.3Surf.Tension mN/m 6.95 6.97 6.98 6.99Viscosity cp 0.1 0.1 0.1 0.1L-Loading m3/h/m2 55.50 59.48 54.26 59.98
HydraulicJet flood % 80 70 78 70DC flood % 73 78 72 80Weir loading gpm/inch 9.50 10.18 9.29 10.27Dry Drop mmH20 29.45 22.37 27.69 22.11Delta P mBar 6.15 5.70 5.99 5.69
Column ID: 2964 mm Tray Spacing: 610 mm
Tray Eff. 86 % Tray Eff. 86 %
System Factor: 1
Design Feed Alternate Feed
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3) Unit modifications
Since the production of the Iso-Butane was significantly increased, several other
equipments had to be modified and or replaced, with the exceptions of the distillation
tower, the feed accumulator and the top receiver (see Figure 3.1).
Figure 3.1: Unit Modifications
Required changes include installation of new condensers, reboiler, feed pumps, overhead
pumps, bottom product pumps, two additional preheat exchangers, and several control
valves. The fractionation trays of the distillation tower have been replaced with VGPlus
high performance trays to handle the big increasing of the vapor/liquid loadings without
compromising the mass transfer efficiency (see Figure 3.2). The VGPlus trays have been
tested at FRI providing excellent performances: very high capacity and efficiency, at
vapor & liquid loadings below the system limit (see Figure 3.4).
While retrofitting existing columns, direct welding to the tower wall should be
minimized, since it would require the post weld heat treatment, a very costly and time-
consuming site activity, which shall be avoided during the Plant turnaround. Tailored
designed adaptors were used to fit the new trays in the existing supports (see Figure 3.3).
A new liquid distributor was installed at the top reflux, as well as a new advanced
degassing box was needed for the flashing feed between tray 28 and tray 29.
56
1
28
n-C4
29
Feed-1
Feed-2
Feed-3
From Iso-Stripper
Reboiling Fluid
FC
FC
LC
FCLC
LCFC
10FC
TC
Fuel Gas
Iso-C4
Major Unit modifications- new feed pumps;- new top pumps;- new bottom pumps;- new feed pre-heater;- new reboiler;- new condensers.
PC
New VGPlusHPTraysNew VGPlusHPTrays
Total Refinery Antwerp 8 AIChE Meeting, 10-14 April 05 Sulzer Chemtech Debottlenecking a DIB with VGPlus
Figure 3.2: VGPlus High Performance Trays
Featuring Enhanced Downcomer, MVG valves, and Push Valves
Figure 3.3: Adaptor for Side & Central downcomer
MVG valve
Existing DC bolting bar
New DC bolting bar
Portion of Existing DC bolting bar to be removed
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Figure 3.4: VGPlus tray: FRI test I-C4 / N-C4, 11 Bara, total reflux
4) Unit performances after Revamping
The Unit is running for more than 4 years without any problems either at the equipment
being modified or at the distillation column. To check the actual Unit performances, in
particular the capacity & the efficiency of the fractionator, a test run was done on
November 2004.
4.1) Plant Data
Hourly averaged operating data have been recorded from the control room for more than
two days: flow rates, temperatures, pressures, level ‘s controls, on line analyzers,
openings of control valves. The Unit was running at a capacity lower than design, and
product purities much better than design, therefore the reflux ratio was higher than
design, and consequently the vapor & liquid loadings through the column were
consistently higher than the ones at design conditions.
The pressure profile was slightly lower than design: 6.4 versus 6.7 Barg at top of tower;
as well as the top temperature at the top receiver was approx. 10 °C lower than design.
A temperature survey was done to cross check some critical temperatures: feed inlet to
the tower, in & out of the reboiling fluid, top reflux, and bottom of the tower, by mean of
Effi
cien
cy (%
)
Cs (ft/s)
Competitor Tray VGPlusCs (m/sec)
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a laser pyrometer; the measured values were in line with the ones recorded at the
Distributed Control System (DCS).
A plant survey was done also for some critical pressures: the gathered data matched very
well with the DCS at the bottom of the tower; a discrepancy was observed for the top
tower pressure: 6.55 Barg versus 6.46, however this delta did not affect the recalculated
process performances such as duties at reboiler & condenser, reflux flow rate, or product
purities, because the bottom pressure was practically the same and the top receiver
temperature was 20 °C below the bubble point.
Pressure was taken at the feed inlet to the tower after the control valve and the preheat
exchanger; the location was practically the same of the temperature indicator of the DCS,
for the most reliable definition of the specific enthalpy of the feed entering the tower.
Pressure was also taken at the suction and discharge sections of the pumps, together with
the absorbed ampere, providing another alternate of crosschecking the material balance
and top reflux flow rate. Per each day of the test, a complete set of samples was taken and
sent to the lab for the gas chromatography analysis.
4.2) Selection of Plant Data
For a given plant, same size and hold up of the TRA De-IsoButanizer, 24 hours test run at
steady operating conditions should be enough for a reliable evaluation of the process
performances, of course the longer the time frame the better the reliability, provided that
the stability can be maintained. It is also well understood that a so big and complex
Refinery such as TRA is not a pilot plant, therefore as longer is the time frame of a test
run, as higher is the possible variation of the operating conditions. This is even more
valid for this DIB because the feed can come from three different sources, and the
reboiling duty is fully integrated with another Unit.
Among the gathered data, it was possible to select 24 hours in which the Unit was
running quite steady, here after called Test-1:
- Only two types of feed were on stream, the third was stopped since more than two
hours, enough to make sure that the feed accumulator was completely renewed
and the content representative of the two streams only.
Total Refinery Antwerp 11 AIChE Meeting, 10-14 April 05 Sulzer Chemtech Debottlenecking a DIB with VGPlus
- The top & bottom tower pressures were also constant, as well as the top & bottom
tower temperatures, resulting in quite uniform product purities.
- The feed flow rate was within a fluctuation of 4%.
- The level of the feed ‘s accumulator constant, as well as the level of the kettle
reboiler, some fluctuation was detected at the level of the top receiver.
- The top reflux and the reboiling fluid flow rates were also quite steady: variation
within 3.9 and 1.4 % respectively.
The averaged values of these 24 hours have been set as reference for building the
simulation model and for the evaluation of the Unit performances.
4.3) Material Balance Reconciliation
Compensation was done for all the flow meters, as per the actual density at standard and
running temperature versus the design values of the ring orifices. An overall - 3.7% delta
material balance was found (total out higher than total in). It is believed that the outlet
could be more reliable because the control valves of the two feed streams were fully
open: 105%, while the relevant flow meters were away from the full scale.
On the basis of the gas chromatography analysis of the combined feed and the
composition of the top & bottom products, a components material balance was done to
check the expected yields. Since more than 98% of the streams is constituted by Iso-C4
and Nor-C4, the balance has been limited only to these two components. It came out that
the yield of top product should have been a bit higher than measured: 1.3 %, well within
the acceptable deviation. The reconciliated material balance is shown in Table 4.3.1.
Table 4.3.1: Reconciliated Material Balance for Test-1
Component / Stream Feed Top Bottom
Propane
Iso-Butane
Nor-Butane
Unsaturated C4s
C5s
Total
% Wt
% Wt
% Wt
% Wt
% Wt
%Wt
0.38
31.42
67.79
0.27
0.14
100
1.21
97.65
0.82
0.32
100
0.78
98.77
0.25
0.20
100
Flow rate Kg/h 31550 9980 21570
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4.4) Process Simulation Model
This is a fundamental path while checking the performances of an existing distillation
column. Deep process know-how, and simulation skills are mandatory to build a true
reliable computer model. The following steps have been taken:
1) The feed composition was set as per the lab gas chromatography analysis of
the total stream coming from the feed ‘s accumulator.
2) The feed flow rate was set as per the reconciliated material balance.
3) The specific enthalpy of the feed at the tower inlet was set from the given
composition, the recorded temperature, and the pressure gathered at the field.
4) The pressure profile of the tower (top & btm) was set as per the data recorded
from the DCS, for the top receiver the data taken at plant was used.
5) The specific enthalpy of the top reflux was set as per the plant data by setting
its temperature as the data recorded from the DCS.
6) Product purities: Normal-Butane at the top and Iso-Butane at the bottom have
been set as per the plant data.
7) The number of theoretical stages in the tower has been changing till matching
the condenser duty (actually the top reflux flow rate) and / or the reboiler
duties (actually the reboiling fluid flow rate).
8) Simulation program: Provision version 7.0 from SIMSCI, with SRK
thermodynamic package.
The model showed a good match for the temperature profile: only half degree C higher
temperature at the top of the tower: 52.5 VS 51.9 C; similar temperature at the top pilot
tray: 53.7 VS 53.8 C; and practically same temperature at the bottom of the tower: 68 VS
67.9 C. The top reflux flow rate was matched for 93 % tray efficiency: 309 m3/h from the
plant versus the simulated 315 m3/h. The only discrepancy was found at the reboiler
duty, being the plant data (measured from reboiling fluid flow rate and delta temperature)
consistently higher than simulated: 24.1 versus 16.1 MMKcal/h. The measured value
from the plant looked unrealistic as it was 79% higher than the reboiler design duty;
while a well designed Kettle may provide not more than 30 % of spare capacity.
Total Refinery Antwerp 13 AIChE Meeting, 10-14 April 05 Sulzer Chemtech Debottlenecking a DIB with VGPlus
To match a so high reboiler duty the efficiency of the trays should have been reduced
down to 84%; the top reflux flow rate would have been extremely high: 420 m3/h, even
higher than the full scale of the instrument; also this data looked unrealistic since the
opening of the relevant control valve never exceeded the 55%.
To crosscheck this data, the hydraulic rating of the tray was performed: at such high top
reflux flow rate, the trays would have been far above the flooding point: 120%, and the
column could not operate at all; while for the other set of data (matching the top reflux
flow rate), the trays were still very loaded, however within the flooding point: 89 %, see
here after table 4.4.1.
A further crosschecking was done with the power absorbed by the electrical motor of the
overhead pump versus the hydraulic one calculated from the flow rate, the head and the
efficiency. Also this method confirmed the validity of the measured top reflux flow rate.
In summary whichever parameter was used for the crosschecking of the condenser and
the reboiler duties, the measured top reflux flow rate was definitely the right one.
Table 4.4.1: Hydraulic Performances for the Test-1
Tray type: VGPlus
Case
Section above-feed below-feed above-feed below-feedVaporFlow rate kg/h 225200 215800 297000 284500Density Kg/m3 18.929 18.876 18.933 18.890C-factor m/sec 0.094 0.090 0.124 0.118
LiquidFlow rate kg/h 215300 237400 287000 306100Density Kg/m3 511.2 514.3 511.2 514.2Surf.Tension mN/m 7.08 7.15 7.08 7.15Viscosity cp 0.1 0.1 0.1 0.1L-Loading m3/h/m2 61.04 66.90 81.37 86.28
HydraulicJet flood % 89 86 121 117DC flood % 80 89 107 115Weir loading gpm/inch 10.45 11.46 13.94 14.78Dry Drop mmH20 35.48 32.67 61.71 56.74Delta P mBar 6.66 6.55 9.17 8.81
Column ID: 2964 mm Tray Spacing: 610 mm System Factor: 1
Matching Top Reflux Matching Reboiler DutyTray Eff. 93% Tray Eff. 84%
Case
Section above-feed below-feed above-feed below-feedVaporFlow rate kg/h 225200 215800 297000 284500Density Kg/m3 18.929 18.876 18.933 18.890C-factor m/sec 0.094 0.090 0.124 0.118
LiquidFlow rate kg/h 215300 237400 287000 306100Density Kg/m3 511.2 514.3 511.2 514.2Surf.Tension mN/m 7.08 7.15 7.08 7.15Viscosity cp 0.1 0.1 0.1 0.1L-Loading m3/h/m2 61.04 66.90 81.37 86.28
HydraulicJet flood % 89 86 121 117DC flood % 80 89 107 115Weir loading gpm/inch 10.45 11.46 13.94 14.78Dry Drop mmH20 35.48 32.67 61.71 56.74Delta P mBar 6.66 6.55 9.17 8.81
Column ID: 2964 mm Tray Spacing: 610 mm System Factor: 1
Matching Top Reflux Matching Reboiler DutyTray Eff. 93% Tray Eff. 84%
Total Refinery Antwerp 14 AIChE Meeting, 10-14 April 05 Sulzer Chemtech Debottlenecking a DIB with VGPlus
4.5) Additional sets of Plant data
In order to check the effect of the delta material balance as well as the fluctuation of the
top receiver level, two more sets of data were evaluated, at which the Unit was running
practically constant without any fluctuation, here after called Test-2 and Test-3.
Test-2 included 11 hours data, all the three feed sources were on stream, therefore the
composition of the combined feed was different from Test-1, material balance deviation
within 2.4 %.
Test-3 included 7 hours data, characterized by a sharper separation Iso-C4 / Nor-C4,
material balance deviation within 3.5%, two only feed sources were on stream, therefore
its composition was the same as per the Test-1. The relevant reconciliated material
balances are here after shown in Table 4.5.1 and 4.5.2.
Table 4.5.1: Reconciliated Material Balance for Test-2
Component / Stream Feed Top Bottom
Propane
Iso-Butane
Nor-Butane
Unsaturated C4s
C5s
Total
% Wt
% Wt
% Wt
% Wt
% Wt
% Wt
0.46
34.05
65.05
0.32
0.12
100
1.33
97.43
0.83
0.41
100
0.84
98.70
0.27
0.19
100
Flow rate Kg/h 29300 10070 19230
Table 4.5.2: Reconciliated Material Balance for Test-3
Component / Stream Feed Top Bottom
Propane
Iso-Butane
Nor-Butane
Unsaturated C4s
C5s
Total
% Wt
% Wt
% Wt
% Wt
% Wt
%Wt
0.38
31.42
67.79
0.27
0.14
100
1.20
97.57
0.87
0.36
100
0.68
98.89
0.23
0.20
100
Flow rate Kg/h 29470 9350 20120
Total Refinery Antwerp 15 AIChE Meeting, 10-14 April 05 Sulzer Chemtech Debottlenecking a DIB with VGPlus
The simulation results confirmed the conclusions highlighted for Test-1, basically a very
good match for all the operating data and product purities, except for the reboiler Duty,
which was still far away from the expected one.
Also these two additional cases showed very high tray efficiency: over 91%. The
hydraulic calculations of the trays, for these two tests, have been omitted since the vapor
and liquid traffic through the column were very close to the ones of Test-1, practically the
same for Test-3 and just 4.8% lower for Test-2.
4.6) Summary of the test run
The Unit was working very well, providing performances higher than expected, without
any significant plant ‘s limitations.
- Within the approximation of the reconciliated data, the duty at the condenser
system was quite high (10% over design), and no limitation was observed,
therefore a higher spare capacity is expected.
- Within the approximation of the reconciliated data, the duty at the reboiler was
also quite high (20% over design), and no limitation was observed, therefore a
higher spare capacity is expected.
- Even if the fractionation trays were highly loaded, the mass transfer efficiency
was very high: over 91 %; the tower was running very smoothly; and 10%
additional capacity is expected.
5) Conclusions
1) While maximizing existing plant’s capacity without compromising efficiency, one
of the most critical equipment to look at is the distillation tower and associated
mass transfer components.
2) The VGPlus High Performance Trays provide the petrochemical industry with a
very cost effective tool to push the towers up to their ultimate capacity set by
vessel diameter.
3) Determining the optimum working point while retrofitting a distillation tower is
not an easy task. A combination of process know-how and mass transfer
components design skill is crucial to successfully achieve challenging targets.
Total Refinery Antwerp 16 AIChE Meeting, 10-14 April 05 Sulzer Chemtech Debottlenecking a DIB with VGPlus
Acknowledgments
Sulzer Chemtech gratefully acknowledge Total Refinery Antwerp for the permission of
publishing this data.
References
1) G. Mosca, E. Tacchini, G. Scribano, “High Performance Trays for Distillation
Columns” presented at the 1st CHEM ARAB Conf., Beirut, Lebanon (January 2001).
2) Dale Nutter, David Perry “Sieve Upgrade 2.0 – The MVG™ Tray”, presented at the
AIChE Spring National Meeting, Houston, Texas, (March 1995).
3) Kister Z.H, Brown E., Sorensen K., “Sensitivity analysis is key to successful DC5
simulation”, Hydrocarbon Processing (October 1998).
4) J.L. Bravo, J. Sikkenk, G. Mosca, L. Tonon, M. Roza, “Design and revamp of modern
C2 Splitters with High Capacity MTC and fast installation techniques” presented at the
ARTC Petrochemical conference, Bangkok, Thailand (March, 2002).
5) Sloley, A.W., “High Capacity Distillation”, Hydrocarbon Processing (August 1998).
6) Kister, H. Z., “Distillation design”, McGraw-Hill, New York (1992).
7) Simulation Sciences Inc. “PRO/II process simulation program” Version 7.0.
8) Sulzer Chemtech “Sultray version 7.2”