PRO/II Process Engineering

TM

Sulfuric Acid Alkylation Casebook

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 PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

Contents
Contact Information.................................................................................................................. 3
Case 4: Sulfuric Acid Alkylation ............................................................................................. 7
Abstract.................................................................................................................................... 7
Market Position ......................................................................................................................... 7
Comparison to HF Alkylation...................................................................................................... 8
Chemistry ........................................................................................................................... 9
Simulation Scope and Objectives ............................................................................................. 11
Reactor Modelling ................................................................................................................... 12
Sulfuric Acid Alkylation Flowsheet ............................................................................................ 13
RUN #1 Aut o-Refrigeration and Iso-Stripper Operation .............................................................. 15
Runs #2 and #3 Deisobutanizer with Auto -thermal Refrigeration and Deisobutanizer wit h effluent
Refrigeration .......................................................................................................................... 18
Conclusions ............................................................................................................................ 20

References .............................................................................................................................. 21
Appendix A Keyword Input ................................................................................................. 23
Appendix B Input Changes for Run 2 and 3 .................................................................... 31
Appendix C Wet Sulfuric Acid Process ............................................................................ 33

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 PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

Case 4: Sulfuric Acid Alkylation

Abstract
Computer flowsheet simulation of plant processes has become a widely accepted design and
optimization tool in today's refinery. Because most refinery processes have a high degree of thermal
integration and mat erial recycle, process simulation is oft en the only way to quantify how different unit
operations interrelate in the overall flowsheet environment.
The H2SO4 alkylation plant is used in this paper as a vehicle to demonstrat e how a modern flowsheet
simulator, PRO/ II, may be used to evaluate process alternatives, which include parametric studies of
flowsheet variables and changes in flowsheet configuration. Three flows heet variables are perturbed to
study the effect on economically sensitive flowsheet paramet ers. Two key flowsheet configuration design
decisions are explored:
 Effluent refrigeration vs. aut o refrigeration
 De-is obut anizer vs. iso-stripper operation
This work does not make definitive judgments on the merits of these options, but rather demonstrates
how these design choices may be evaluated by the process engineer using modern simulation
technology.

Market Position
Alkylate is a high octane component in gasoline blends. It is composed primarily of iso -octanes and
iso-heptanes which mak e a very small contribution to the overall vapor pressure, and no contribution to
the aromatic or olefin content. These have become key issues in refinery planning since implementation
of the Clean Air Act Amendments of 1990. See References on page 21 (points 1 and 2. Inc reasing
alkylate production can partially offset the need to reduce reforming severities to meet aromatic targets.
Alkylation can also be used to reduce olefin content in gasoline.
The following table shows the octane and vapor pressure characteristics of the principal reactants and
products of an alkylation plant. This demonstrates that, although the octane numbers of alkylation feeds
are suitable for gasoline production, the vapor pressures are excessive.

Table: Octane and Vapor Pressure Characteristics of Alkylate Reactants and Products.

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PRO/II Process Engineering Sulfuric Acid Alkylation Casebook Case 4: Sulfuric Acid Alkylation

See References on page 21 point 3.

Reactor products have excellent octane as well as vapor pressure characteristics. Sulfuric acid alkylation
is a highly complementary process for refineries that are c onsidering on-site MTBE production. See
Referenc es on page 21 point 4. The MTBE process selectively reacts isobutylene
from the olefin stream, permitting 1- and 2-butylene to pass through for alkylation. Isobutylene produces
lower quality alkylate, while 1- and 2-butylene produce superior alkylate.

Comparison to HF Alkylation
The relative advantages of hydrofluoric acid (HF) to H2SO4 alkylation have been vigorously debated in
the open literature and in the marketplace for years. See References on page 21 point 5. From about
1960 through the 1980s, HF alkylation was preferred to H2SO4 alkylation in new plants. The advantages
of HF include superior product when the olefin content is high in propylene and isobutylene, and reduced
catalyst cost. Also, HF alkylation does not require refrigeration or acid regeneration so it is marginally
better in that respect.
More recently, preferences have shifted toward H2SO4 alkylation. This is due in part to the high
corrosive nature of the HF acid, which requires exotic materials of construction. The process is also
much more hazardous due to the HF acid, and is not readily acceptable environmentally. Safety and
liability considerations, together wit h a reduction in isobutylene content in the olefin feed (due to the
MTBE plant), are additional factors. Also, the more recent development of the "wet sulphuric acid
process" (described briefly in Wet Sulfuric Acid Process on page 33) ameliorates may of the
disadvant ages previously incurred by H2S O4 alkylation. Together, all these factors are changing the
economics to favor H2SO4 alkylation. Several refiners, particularly those near major population centers,
are considering revamping their HF alkylation facilities to H2S O4 alkylation.

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Case 4: Sulfuric Acid Alkylation PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

Chemistry
The primary purpose of the alkylation reactor is to join isobutane and a light olefin to form branched
alkylates. See References on page 21 point 6.

Disproportionation reactions contribute to a distribution of alkylate products from iC5 to C12+; for
example:

Olefin polymerization is undesirable and is usually minimized by proper mixing, low reaction
temperatures and high isobutane concentrations.

The polymers form acid-soluble oils that foul the sulfuric acid catalyst, resulting in excessive purge and
makeup requirements. As the acid strength weakens, an "acid runaway", characterized by low octane
and increased acid consumption, may occur.

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 PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

Simulation Scope and Objectives

The objective is to model the overall basic sulfuric acid alkylation process in a manner that permits the
process engineer to analyze virtually all flowsheeting issues. The flowsheet models presented here allow
the following questions to be answered with few or no changes to the input description:
 How is the process affected if more propane is circulated in the depropanizer-refrigeration recycle?
 How is the process affected if more isobutane is recycled from the de-isobutanizer?
 What are the optimum feed tray locations for each of the four distillation columns?
 How do the utility requirements change for changes in feed-stock?
o What are the total reboiler steam requirements for all four distillation columns?
o What is the total refrigeration duty?
 If supplemental isobutane is available, where is the optimum place in the flowsheet to introduce this
feed?
 For a given reactor volume, what is the space velocity?
 What are the differences if the deisobutanizer is operated as an isostripper instead of a conventional
tower?
 How is the refrigeration duty affected if effluent refrigeration rather than autorefrigeration is chosen?
 How much reboiler duty is saved if the debutanizer is eliminated by drawing a normal butane rich
side stream off of the deisobutanizer? How is the isobutane recycle affected?
The simulation makes the following simplifying assumptions:
 Feed pretreatment is not included. When the amine towers are working correctly, their operation has
no effect on the flowsheet.
 Caustic treatment is not considered. The reactor products generally run through a caustic wash to
neutralize acid carry-over and ester formation. When the acid settler is working correctly, the caustic
wash has little effect on the heat or hydrocarbon balance, so it may be safely deleted from the
simulation.
 The stoichiometry is fixed for each isobutane-olefin reaction pair, and each olefin reacts to extinction.
The REA CTOR MODEL section clarifies this further.
 Sulfuric acid is assumed to be 100% pure and totally immiscible with t he process hydrocarbon. In
reality, circulating sulfuric acid is generally maintained at 85 to 96 weight percent.
 The trace amount of hydroc arbon absorbed by the acid is disposed of by the acid purge and may
usually be ignored in the hydrocarbon balance. Acid entrained or absorbed in the reactor
hydrocarbon effluent is neutraliz ed by caustic wash, and does not normally have a significant effect
on the hydrocarbon balance. For flowsheet simulation purpos es, the only effect of having a sulfuric
acid circulation is to correctly account for the flowing heat capacity.

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PRO/II Process Engineering Sulfuric Acid Alkylation Casebook SAL CustomProperty-Reusable DITA Topic (TEST)

Reactor Modelling
Reaction Stoichiometry
A fixed stoichiometry for each pair of reacting components is derived from the work of Cupit, et al. See
Referenc es on page 21 point 7. This reference provides reaction yields on a volumetric basis. PRO/II
was used to normalize the products to mass balanc e with t he feeds. Note that, although it is necessary to
adjust the stoichiometry to mass balance, it is not necessary to normalize the stoichiometry to integer
coefficients.
The table lists the coefficients used in this simulation. Heat of reaction data need not be supplied. PRO/ II
automatically accounts for reaction enthalpy via pure component heat of formation data adjusted for
temperature and pressure.
Table: Stoichiometric Coefficients for Alkylating Pairs of Components

Olefin Propylene Isobytylene 2-Butylenes 1-Butylene

Reactant
olefin 12.3008 8.5683 10.9924 11.5763
isobutane 12.3461 10.5445 11.3223 9.9587
Products
isopentene 0.5541 1.2706 0.6346 0.6877
2,3-dimethylbut ane 0.5553 0.5925 0.6261 0.5870
2,4-dimethylpentane 2.3756 0.3827 0.2832 0.3016
2,3-dimethylpentane 5.9539 0.2638 0.1703 0.1730
2,2,4-trimethylpentane 0.4574 2.5703 3.3018 3.1778
2,3-dimethylhex ane 0.1062 0.5101 0.5566 0.6466
2,4-dimethylhex ane 0.0731 0.3627 0.4360 0.5271
2,3,4-trimethyl pent ane 0.3969 2.1523 4.6514 4.2314
2,2,5-trimethylhexane 0.0821 0.3998 0.1852 0.1686
C9s (nbp=280, mw=128) 0.0594 0.2074 0.0782 0.0984

C10s (nbp= 325, mw=142) 0.6688 0.2754 0.0891 0.0720

C11s (nbp= 365, mw=156) 0.4325 0.2134 0.799 0.0761
C12s (nbp= 395, mw=170) 0.0468 0.5173 .02831 0.2674
C13+ (nbp= 425,mw=184) 0.0315 0.0239 0.0000 0.0079

Reactor Configurations

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SAL CustomProperty-Reusable DITA Topic (TEST) PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

In the auto-refrigeration flowsheets considered by this paper, the reaction vessel is divided int o four
reaction chambers. Flashing occurs in each chamber to balance the exothermic heat of reaction. In the
flowsheet where effluent refrigeration is considered, the reaction takes place in a single reaction
chamber under sufficient pressure to suppress vapor flashing. This work assumes the reaction is
maintained at 45 F. Temperatures significantly above 45 F result in excessive acid consumption and
lower octane. Temperatures significantly below 45 F increase the refrigeration load. Liquid hydrocarbon
and acid phases coexist in the reactor.
The reactor could be modeled with a reactor unit operation using conventional two phase equilibrium
models, followed by a three phase flash. This has one disadvantage in that the reactor is nested two
levels deep in controller and recycle loops, and rigorous three phase flashes add to the calculation
overhead. In this paper, a stream calculator unit operation replac es the three-phase flash. This allows
the user to mathematically manipulate stream separation.
One other solution for modeling a three phas e reactor is to declare the acid as a solid component. It thus
carries with it a fixed heat capacity, but no vapor pressure. This strategy is not used in the simulations
presented here, but has been proven in preliminary runs for t his work.
Thermodynamic Models
The Soave modification to the Redlich Kwong equation of state is used for all unit operations in the
flowsheet for the calculation of equilibrium, enthalpy and entropy. See Ref erences on page 21 point 8.

Sulfuric Acid Alkylation Flowsheet

The flowsheet for the sulfuric acid alkylation plant wit h auto- refrigeration and isostripper design is shown
in figure below.
Treat ed saturated feed is combined with recycle from the refrigeration circuit and depropanized in
column DE C3. The overhead enters the deethanizer DEC2 and leaves the flowsheet as fuel gas and
HD5 propane product. The bottoms are cooled to 100 F and enter the economizer toget her with
condensed propane rich
re-frigeration and supplemental isobutane feed. E vaporation in the economizer cools the stream to 55 F.
The pressure is then let down to 30 psia as it enters the first reaction chamber together with sulfuric acid
and recycle isobutane.
Acid and hydrocarbon are cascaded into each of four reaction chambers in sequence. Olefin feed enters
the tube side of the economizer where it is cooled to 65 F.
The stream is split into four equal parts, each of which enters a separate reaction chamber. Olefin react s
to extinction with isobutane in each chamber to form alkylate.

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PRO/II Process Engineering Sulfuric Acid Alkylation Casebook SAL CustomProperty-Reusable DITA Topic (TEST)

Figure: H2SO4 Alkylation Plant

Vaporization in each chamber approximat ely compensat es for the heat of reaction to maintain the
reactor at about 45 F throughout. All of the vapor is collected and recycled to the refrigeration circuit. Acid
is settled and decanted. Part of the acid is purged for onsite or offsite regeneration. The hydroc arbon
enters the isostripper DIC4 where normal butane and alkylate product is separated from the isobut ane
rich recycle. The alkylate is then stabilized to an RVP of 12 psi in the debu -taniz er DE C4. The
hydrocarbon feeds to the flowsheet are shown in the table.
Table: Feed Hydrocarbon Conditions

Component Rates, standard liq. vol, bbl/hr

Saturated Feed Olefin Feed Supplemental Isobutane

Stream ID 1 2 3

methane 2.0 - -
ethane 10.1 - -
propane 100.0 9.0 -
Isobutane 187.5 95.0 36.0
normal butane 100.0 50.0 9.0
propylene - 9.0 -

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SAL CustomProperty-Reusable DITA Topic (TEST) PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

isobutylene - 14.0 -
2-butylene - 175.0 -
2-butylene - 56.0 -
Isopentane - 5.0 -
Total 399.5 413.0 45.0
Temperat ure, F 100 100 100
Pressure, psia 400 215 400

The supplemental isobutane feed has been included here to demon-strate that alternate sources of
isobutane with varying compositions and thermal conditions may be processed.

Table: Acid Feed to Reactor

Stream Property Property Value

Feed Stream ID SA1

Stream ID SA1
Acid rate, 106 lb/ hr 1.00
Temperat ure, F 45
Pressure, psig 40

The optimum flowsheet feed location for this stream may or may not be the same as for the bulk of the
isobutane feed. The effects of alternate feed locations may be quickly tested via simulation

RUN #1 Auto-Refrigeration and Iso-Stripper Operation

Simulation Strategy
The success of the simulation convergence depends on which flow -sheet variables have assumed
values, and which are calculated by the program. Assumed values may be investigated through
sensitivity analyses and optimization techniques. Referring to the flowsheet in Figure H2S O4 Alkylation
Plant, convergence stability is enhanced by fixing flowrates at least once in each of the recycl e circuits.
Thus, the bottoms of depropanizer DEC3 is specified to contain a fixed value of 50 mole/hr of propane,
and the overhead rat e from deis obutanizer is fixed at 1000 bbl/hr.
The economizer H2 is operated in a manner that fixes the outlet temperatur e of both sides of the
exchanger. Normally, there are only enough degrees of freedom to specify one outlet temperature of a
heat exchanger; however, the upstream pressure on the saturates side is varied by controller C1 until
both temperature specifications are met. This control loop is embedded in anot her c ontrol loop as well as
a recycle loop. It is thus essential that the tolerance is tightened, enabling the external loops to see clean
derivatives. Since this is the innermost loop, a good practice is to set this tolerance just barely loose
enough to ensure convergence on each pass. An absolute tolerance of 0. 0001 F is used in this
demonstration.

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PRO/II Process Engineering Sulfuric Acid Alkylation Casebook SAL CustomProperty-Reusable DITA Topic (TEST)

The reactor RX1A effluent temperat ure is controlled at 45 F by adjusting s plitter S1. This has the effect of
circulating more or less refrigerant through the auto -refrigeration circuit and thus cooling the reactor to a
greater or lesser extent. The number of control iterations is limited to 5 as it is not necessary to solve this
recycle to completion on each recycle pass. This permits the recycle and control loop to converge
simultaneously, reducing CP U time. An absolute tolerance of 0.0002 F is used.
Effluent processing includes t wo-stage compression followed by an after-cooler condenser. To speed up
recycle calculations, all these unit operations are replaced by single flash drum MCOM. Following the
successful convergence of all recycle loops, detailed effluent calculations are performed once by solving
two compressors and a heat exchanger (see figure below). Altho ugh the compressors do not require
excessive amounts of CPU, the number of passes through t his loop make it well worthwhile to reduce the
two P-S (constant pressure - constant entropy) compressors and one P-T (constant pressure - constant
temperature) heat exchanger to the single P-T flash unit MCOM.

Input De scription
Keyword Input on page 23 lists the PRO/II key word input file for the auto - refrigeration/isostripper batch
run. This is revision 2 that is compatible with PRO/II versions 8 and 9. An electronic copy of the file is
available in the %P2Install% \manual\casebook\inputs\ directory, where %P2Install% is the directory
where P RO/II is installed.
Results
Key operating conditions for the base case and case studies are summarized in the table, including total
reboiler duties, reactor effluent flowrat es and isobutane content, refrigeration l oads, and product flows.
These parameters form the basis for calculating operating expenses.

Table: Key Flowsheet Parameters

Run #1 - Auto-refrigeration and Isostripper Operation

Base Ca se More C3 More i C4 More n C4 in Feed

Recycle Recycle

Input Flow Parameters

C3 in de-propanizer 50 100 50 50
bottom s, mole s/hr
Recycle from i sostripper, 2525 2525 2600 2525
bbl/hr

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SAL CustomProperty-Reusable DITA Topic (TEST) PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

Additional normal butane

in saturate s feed, bbl/hr
0 0 0 50
6
Calculated Flow Parameters Reboiler duties, 10 Btu/hr

De-ethanizer DEC2 1.25 1.25 1.25 1.25

De-propanizer DEC3 28.08 28.76 29.74 29.80
Iso-stripper DIC4 80.75 80.75 87.35 84.45
De-butanizer DEC4 9.4 9.41 9.9 12.43
Total reboiler duties 119.48 120.17 128.24 127.93

HC liquid reactor effluent

Hot volume rate, gpm 2216.46 2216.46 2270 2253

isobutane content, liq vol 65.5 65.5 66.4 66.7
%

Compre ssor shaft power, hp

Stage 1 995 994 978 1045

Stage 2 2005 2005 2005 2069
Total compressor duty 3000 2999 2983 3114

Product flowrates at standard conditions Ga s products, m scfh

Fuel gas 19.33 19.34 19.32 19.34

Liquid products, bbl/hr
Liquid propane 109.6 109.7 110.1 109.8
Normal butane 121.7 121.4 122.3 169.5
12 RVP alkylate 519.9 519.9 520.3 520.6

Table: Significance of Simulation Results for Run #1

Case Observation Conclusion

More C3 in depropanizer Increases depropanizer reboiler Profit ability is improved when propane in
bottoms duty depropanizer bottoms is minimized.

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PRO/II Process Engineering Sulfuric Acid Alkylation Casebook SAL CustomProperty-Reusable DITA Topic (TEST)

Increases isobut ane Increase in octane and decreas e in acid

concentration in reactor. consumption due to iso- butane content,
Reduces reactor and settler together with reduced compressor loading,
More iC4 recycle more than compensates for inc reas e in
residence time due to increased
reboiler duty. If the iso-stripper hydraulics and
reactor throughput.
reactor residence time requirements are not
Increases isostripper reboiler limiting, profitability improves as iso- butane
duty. recycle increases.
Reduces first stage compressor
load.
Reactor iso-butane Although normal butane is an inert
concentration decreases. component in the reactor, it adversely affects
More nC4 in feed
plant profitability. In particular, the dec rease in
Reactor throughput increases.
reactor iso-butane concentration translates to
The debutanizer reboiler rate
a significant drop in octane and increase in
increases in proportion to
acid consumption.
increases in product butane.
The refrigeration load
requirement decreases.

Runs #2 and #3 Deisobutanizer with Auto-thermal

Refrigeration and Deisobutanizer with effluent Refrigeration
Keyword Input on page 23 provides listings of differences in key word files from run 1 to runs 2 and 3.
Figure below illustrat es the difference in configuration between the isostripper and the deis obut anizer in
the flowsheet.

The deis obutanizer overhead constitutes the isobutane rich recycle to the reactor. Based on the recycle
rate chosen, the reflux and feed tray location is optimized in a separat e run constrained by an 80 percent
of flood specification. The larger the recycle, the smaller the reflux with the limiting case being the
isostripper design demonstrated by Run #1.
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SAL CustomProperty-Reusable DITA Topic (TEST) PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

In the flowsheet for the effluent refrigeration process, the reactions occur under pressure with cooling
coils sufficient to keep all hydrocarbons in the liquid state.
After decanting the acid, the hydrocarbon reactor effluent is let down and passed through the tube side of
the reactor. A 10 F hot- out/cold-out approach is assumed to be sufficient to cool the reactor, thus the
tube side outlet is assumed to be at 35 F.
Input De scription
The changes required in the input file are shown in Input Changes for Run 2 and 3 on page 31.
Results
Key operating conditions for all three configurations studied are summarized in the table.

Table: Comparison of Key Flow sheet Parameters for Al ternate Configurations

Refrigeration circuit Auto- Refrigeration Auto- Refrigeration Effluent Refrigeration

Deisobutanizer Isostripper Deisobutanize r Deisobutnaize r

configuration

Calculated Flow Parameters

6
Reboiler duties, 10 Btu/hr

De-ethanizer DEC2 1.25 1.18 1.18

De-propanizer DEC3 28.08 27.12 27.20
Iso-stripper DIC4 80.75 80.09 80.77
De-butanizer DEC4 9.4 9.42 9.45
Total reboiler duties 119.48 117.81 119.49
HC liquid reactor effluent
Hot volume rate, gpm 2216.46 1131 1120
isobutane, liq vol % 64.0 50.7 50.3
Compressor shaft power, hp
Stage 1 995 1399 1527
Stage 2 2005 1986 2160
Total compressor duty 3000 3385 3687
Product flowrates at standard conditions Ga s products, m scfh

Fuel gas 19.33 19.37 19.36

Liquid products, bbl/hr
Liquid propane 109.6 109.3 109.2
Normal butane 121.7 122.9 123.2
12 RVP alkylate 522.3 522.2 522.3

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PRO/II Process Engineering Sulfuric Acid Alkylation Casebook SAL CustomProperty-Reusable DITA Topic (TEST)

Significance of Results for Runs #2 and #3

Compari son Observation Conclusion

Isostripper vs. Debutanizer operation decreases The isostripper operation requires a

deisobutanizer substantially the isobutane cont ent in substantially larger capit al investment for
the reactor. increased reactor and settler volumes.
The benefit to this is a substantially
The deisobut anizer operation
improved octane and lower acid
substantially decreases the reactor
consumption due to the higher reactor
volumetric throughput.
isobutane concentration.
The deisobut anizer operation
decreases the depropanizer duty, but
increases refrigeration load.
Auto vs. effluent Autorefrigeration requires less Based on the operating parameters
refrigeration refrigeration. considered here, autorefrigeration
operation is more economical.

Licensors of aut orefrigeration alkylation point out that the lower temperat ures
required on the tube side of effluent refrigeration reactors accounts for the higher
compression requirements.[References -9].
Note, however, that the two reactor designs are fundamentally different. Other
considerations, not included here, such as capital costs and mixing utilities, have
an important impact.

Conclusions
Steady state process simulation technology has matured to the point where large scale highly integrated
process plants are simulated routinely to ans wer " what if" questions ranging from small paramet ric
changes to changes in plant configuration. PRO/II has been used to demonstrat e this capability in
solving a sulfuric acid alkylation flowsheet which has a high degree of recycle and thermal integration.
Typical process questions regarding this flows heet have been posed and answered.

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 PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

References
1. Masters, K.R., "Alkylation's Role in Reformulated Gasoline" , presented at 1991 Spring National
Meeting A IChE.
2. Unzelman, G.H., "U.S. Clean Air Act Expands Role for Oxygen - ates", Oil & Gas Journal, April 15,
1991.
3. API, Tec hnical Data Book Petroleum Refining, Volume 1 (1987).
4. Chapin, L.E., Liolios, G.C. and Robertson, T.M., "Which Alkylation? HF or H2SO4?", Hydrocarbon
Processing, September 1985, pg. 6771.
5. Myer, D.W., Chapin, L.E. and Muir, R.F., "Cost Benefits of Sulfuric Acid Alkylation," Chem. Eng.
Progress, 79, 8, pg. 5965 (1983).
6. Lee, L. and Harriott, P., "The Kinetics of Isobutane Alkylation in Sulfuric Acid," I&EC Process Design
Dev., 16, 3 (1977).
7. Cupit, C. R., Gwyn, J.E. and Jernigan, E.C., "Special Report Catalytic Alkylation", Petroleum and
Chemical Engineering, 33, 47, 1961 and 34, 49, (1962).
8. Soave, G., "Equilibrium Constants from a Modified Redlich Kwong Equation of States," Chem. Eng.
Sci., 27, 11771203 (1972).
9. Lerner, H. and Citarella, V.A., "Exxon Researc h and Engineering Sulfuric Acid Alkylation
Technology", presented at 1991 NP RA Annual Meeting.

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 PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

A PPENDIX A
Keyword Input
Input File

$ Generated by PRO/II Keyword Generation System <version 10.2>

$ Generated on: Fri Aug 24 16:25:26 2018
TITLE PROJECT=H2SO4 ALKY, PROBLEM=ALKY12B, USER=SIMSCI
PRINT INPUT=ALL, STREAM=COMPONENT, RATE=M,LV, HISTORY=ON
TOLERANCE DEFAULT=V94 , DUTY=0.005, MISCELLANEOUS=0.01
DIMENSION ENGLISH, MDUTY=ON, BASIS=MOLE, LIQVOL=BBL, XDENSITY=SPGR
OUTDIMENSION ADD, SI
SEQUENCE DEFINED=FX,HT3,FB2,DEC3,FB2X,PC1,S1,V1,H2,C1,OLSP,RX1A, &
F1X,RX1B,F1Y,RX1C,F1Z,RX1D,F1ZZ,SETL,VAPR,C2,MCOM,P2,DIC4, &
FT1,P1,DEC4,FB4,CL4,P3,DEC2,FB1,CL1,SCTN,CMP1,CMP2,AFTR
CALCULATION TRIALS=40, RECYCLE=TEAR
COMPONENT DATA
CURRENT SEARCH = SIMSCI,PROCESS
LIBID 1,C1/2,C2/3,C3/4,IC4/5,NC4/6,PROPENE/7,ISOBUTENE/ &
8,T2BUTENE,,2BUTENE/9,1BUTENE/10,IC5/11,23DMB/12,24MP/ &
13,23MP/14,224MPN/15,24HX/16,23HX/17,234MP/ &
18,225MHX, BANK=CURRENT
LIBID 24,H2SO4, BANK=SIMSCI
PETRO 19,C9S,128.26,0.73,280
PETRO 20,C10S,142.28,0.74,325
PETRO 21,C11S,156.31,0.75,365
PETRO 22,C12S,170.34,0.76,395
PETRO 23,C13S,184.36,0.77,425
TC 24,1203.5
PC 24,928.24
ASSAY FIT=ALTERNATE, CONVERSION=API94, CURVEFIT=CURRENT, &
FORMATION=CURRENT, KVRECONCILE=TAILS
VISCOSITY(V) CORRELATION=1, DATA=24,,,1
CONDUCTIVITY(V) CORRELATION=1, DATA=24,,,1
THERMODYNAMIC DATA
TRESET CONSTANT = NOFLASH
METHOD SYSTEM=SRK, SET=SRK, DEFAULT
WATER PROPERTY=IF97, TRANSPORT=IF97
ENTHALPY(L) ALPHA=SIMSCI
SA06 24,1.81341,1.25196,0.566576
ENTHALPY(V) ALPHA=SIMSCI
SA06 24,1.81341,1.25196,0.566576
STREAM DATA
$ SATURATE FEED
PROPERTY STREAM=1, TEMPERATURE=100, PRESSURE=400, PHASE=M, &
COMPOSITION(LV,BBL/H)=1,2/2,10/3,100/4,187.5/5,100
$ OLEFIN FEED
PROPERTY STREAM=2, TEMPERATURE=100, PRESSURE=215, PHASE=M, &
COMPOSITION(LV,BBL/H)=3,9/4,95/5,50/6,9/7,14/8,175/9,56/ &
10,5
$ MAKE-UP
PROPERTY STREAM=3, TEMPERATURE=100, PRESSURE=400, PHASE=M, &

23
PRO/II Process Engineering Sulfuric Acid Alkylation Casebook Keyword Input

RATE(LV)=45, COMPOSITION(LV)=4,80/5,20
$ MAKEUP N-BUTANE FOR CASE STUDY ANALYSIS
PROPERTY STREAM=1NB, TEMPERATURE=100, PRESSURE=400, PHASE=M, &
RATE(M)=1e-005, COMPOSITION(LV)=5,1
$ ACID FEED
PROPERTY STREAM=SA1, TEMPERATURE=45, PRESSURE=40, PHASE=M, &
COMPOSITION(WT,LB/H)=24,1000000
PROPERTY STREAM=27P, TEMPERATURE=102.7592019382, PRESSURE=400, &
PHASE=L, COMPOSITION(M,LBM/H)=13,0.0210278983241/ &
15,0.009436464716165/16,0.009032638265915/ &
18,0.002107546198187/1,1.364945278984e-013/ &
2,1.184359533373e-005/3,117.8864320203/4,393.4737021587/ &
5,106.5513626464/10,0.9727451406226/11,0.1469421937343/ &
12,0.03012494954658/14,0.1158322388953/17,0.08160671999939/ &
19,0.0004910220466326/20,0.0001749780068539/ &
21,4.454291028249e-005/22,5.037889621665e-005/ &
23,2.948079097789e-007
$ RECYCLE STREAM DATA ESTIMATES
PROPERTY STREAM=26, TEMPERATURE=100, PRESSURE=87.94039073763, &
PHASE=L, COMPOSITION(M,LBM/H)=13,0.1983324018463/ &
15,0.08900333323801/16,0.08520431062302/18,0.01987688527433/ &
1,1.316530722696e-012/2,0.0001123055797812/3,1088.785832391/ &
4,3745.610694635/5,987.64812945/10,9.164636285397/ &
11,1.385557822282/12,0.2840793906002/14,1.092352327662/ &
17,0.7697960459052/19,0.004632408762095/20,0.001650936334744/ &
21,0.000420300369349/22,0.0004753966652377/ &
23,2.782096519621e-006
PROPERTY STREAM=30R, TEMPERATURE=62, PRESSURE=85, PHASE=M, &
COMPOSITION(M,LBM/H)=13,1.905159650228/15,1.098785007364/ &
16,1.137983544617/18,0.2856550578301/2,2.165013105747e-006/ &
3,493.581376642/4,6090.641838164/5,2052.713786576/ &
10,37.78343818693/11,8.81323452861/12,2.449320736682/ &
14,11.33787970093/17,9.65259653528/19,0.08257728800491/ &
20,0.04130617484735/21,0.0143938059679/22,0.0206435139969/ &
23,0.0001544898722649
PROPERTY STREAM=27P_R1, TEMPERATURE=102.7592019382, PRESSURE=400, &
PHASE=M, COMPOSITION(M,LBM/H)=13,0.0210278983241/ &
15,0.009436464716165/16,0.009032638265915/ &
18,0.002107546198187/1,1.364945278984e-013/ &
2,1.184359533373e-005/3,117.8864320203/4,393.4737021587/ &
5,106.5513626464/10,0.9727451406226/11,0.1469421937343/ &
12,0.03012494954658/14,0.1158322388953/17,0.08160671999939/ &
19,0.0004910220466326/20,0.0001749780068539/ &
21,4.454291028249e-005/22,5.037889621665e-005/ &
23,2.948079097789e-007
$ DEIC4 FEED
PROPERTY STREAM=253X, TEMPERATURE=110, PRESSURE=115, REFSTREAM=251
$ DEC2 FEED
PROPERTY STREAM=11B, TEMPERATURE=135.52, REFSTREAM=11A
PROPERTY STREAM=1_R1, REFSTREAM=1
PROPERTY STREAM=1NB_R1, REFSTREAM=1NB
PROPERTY STREAM=24_R1, REFSTREAM=24
PROPERTY STREAM=29_R1, REFSTREAM=29
NAME 1,SATURATED FEED/2,OLEFIN FEED/3,MAKEUP IC4/27P,RCY_SAT/ &
26,COMP SURGE DRUM LIQ/30R,IC4 RCY/24,RXN VAPORS/ &
10,DEC3 FEED/11,PROPANE TO DEC2/12,DEC3 BOTTOMS
NAME 20,OLEFIN TO RXN/21,IC4 TO RXN/25,RXN LIQUIDS/27,RCY TO DEC3/ &
30,DEIC4 OVHD/32,BUTANE/332,ALKYLATE/40,FUEL GAS/ &

24
Keyword Input PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

41B,HD5 PROPANE
RXDATA
RXSET ID=RS1
REACTION ID=RX1
$ PROPENE - ISOBUTENE REACTION
STOICHIOMETRY 4,-12.346/6,-12.301/10,0.5541/11,0.5553/ &
12,2.3756/13,5.9539/14,0.4574/15,0.0731/16,0.1062/ &
17,0.3969/18,0.0821/19,0.0594/20,0.6688/21,0.4325/ &
22,0.0468/23,0.0315
REACTION ID=RX2
$ ISOBUTENE - ISOBUTANE REACTION
STOICHIOMETRY 4,-8.5683/7,-10.544/10,1.2706/11,0.5925/ &
12,0.3827/13,0.2638/14,2.5703/15,0.3627/16,0.5101/ &
17,2.1523/18,0.3998/19,0.2074/20,0.2754/21,0.2134/ &
22,0.5173/23,0.0239
REACTION ID=RX3
$ 2-BUTENE - ISOBUTANE REACTION
STOICHIOMETRY 4,-10.992/8,-11.323/10,0.6347/11,0.6261/ &
12,0.2832/13,0.1703/14,3.3018/15,0.436/16,0.5566/ &
17,4.6514/18,0.1852/19,0.0782/20,0.0891/21,0.0799/ &
22,0.2831
REACTION ID=RX4
$ 1-BUTENE - ISOBUTANE REACTION
STOICHIOMETRY 4,-11.576/9,-9.9587/10,0.6877/11,0.587/12,0.3016/ &
13,0.173/14,3.1778/15,0.5271/16,0.6466/17,4.2314/ &
18,0.1686/19,0.0984/20,0.072/21,0.0761/22,0.2674/ &
23,0.0079
UNIT OPERATIONS
FLASH UID=FX, NAME=OLEFIN FD
$ THIS SIMULATES THE OLEFIN FEED FROM THE BOTTOM OF THE
$ OLEFIN DEPROPANIZER (WHICH WILL BE ADDED AT A LATER DATE
FEED 2
PRODUCT L=2A
BUBBLE TEMPERATURE=200
FLASH UID=HT3, NAME=PRECHILLER
$ PRECOOLS OLEFIN FEED TO 100 F
FEED 2A
PRODUCT L=2B
ISO TEMPERATURE=100, DP=5
HX UID=FB2
COLD FEED=1,1NB,27P, L=10
OPER CTEMP=170
COLUMN UID=DEC3, NAME=SAT DEC3
PARAMETER TRAY=40,IO
FEED 10,20,TNOTSEPARATE, NOTSEPARATE
PRODUCT OVHD(M)=11,60, BTMS(M)=12, SUPERSEDE=ON
CONDENSER TYPE=BUBB, PRESSURE=310
DUTY 1,1,,CONDENSER
DUTY 2,40,,SIDEHC2
PSPEC PTOP=315, DPCOLUMN=10
PRINT PROPTABLE=BRIEF
ESTIMATE MODEL=CONVENTIONAL, RRATIO=9
SPEC ID=COL1SPEC1, REFLUX(LBM/H), VALUE=4000
SPEC ID=COL1SPEC2, STREAM=12, RATE(LBM/H), COMP=3,WET, &
VALUE=50
VARY DNAME=CONDENSER
VARY DNAME=SIDEHC2
TRATE SECTION(COLSECT-1)=2,39,SIEVE, PASSES=2, &

25
PRO/II Process Engineering Sulfuric Acid Alkylation Casebook Keyword Input

DIAMETER(TRAY)=120, DIAMETER(SIEVEHOLE,IN)=0.5, &

WEIR=2, DCC=1.5
HX UID=FB2X
HOT FEED=12, L=121, DP=5
COLD FEED=1_R1,1NB_R1,27P_R1, L=10X
CONFIGURE COUNTER, U=80, TPASS=1, SPASS=1
DEFINE DUTY(MMON,BTU/HR) AS HX=FB2, DUTY(MMON,BTU/HR)
HX UID=PC1, NAME=ECON PRECOOL
HOT FEED=121, L=122, DP=5
UTILITY WATER, TIN=70, TEMPERATURE=80
CONFIGURE COUNTER, U=100
OPER HTEMP=100
SPLITTER UID=S1
FEED 26
PRODUCT M=27, M=28
OPERATION OPTION=FILL
SPEC STREAM=27, RATE(LV,BBL/H),TOTAL,WET, VALUE=75
VALVE UID=V1
FEED 28
PRODUCT M=28V
OPERATION DP=30
HX UID=H2, NAME=ECONOMIZER, ZONES(OUTPUT)=5
HOT FEED=2B, L=20, DP=3
COLD FEED=122,3,28V, L=21, V=29, DP=1
CONFIGURE COUNTER, U=80
OPER HTEMP=65
CONTROLLER UID=C1
SPEC STREAM=21, TEMPERATURE(F), VALUE=55, ATOLER=0.0001
VARY VALVE=V1, DP(PSI), MAXI=70
CPARAMETER IPRINT, SOLVE
$ REACTOR SECTION
SPLITTER UID=OLSP, NAME=OLEFIN_SPLITTER
FEED 20
PRODUCT M=20A, M=20B, M=20C, M=20D
OPERATION OPTION=FILL
SPEC STREAM=20A, RATE(LBM/H),TOTAL,WET, DIVIDE, REFFEED, &
RATE(LBM/H),WET, VALUE=0.25
SPEC STREAM=20B, RATE(LBM/H),TOTAL,WET, DIVIDE, REFFEED, &
RATE(LBM/H),WET, VALUE=0.25
SPEC STREAM=20C, RATE(LBM/H),TOTAL,WET, DIVIDE, REFFEED, &
RATE(LBM/H),WET, VALUE=0.25
CONREACTOR UID=RX1A, NAME=1ST_STAGE
FEED 20A,21,30R,SA1
PRODUCT M=24X
OPERATION ADIABATIC, PRESSURE=30
RXCALCULATION MODEL=STOIC
RXSTOIC RXSET=RS1
REACTION RX1
BASE COMPONENT=6
CONVERSION 1
REACTION RX2
BASE COMPONENT=7
CONVERSION 1
REACTION RX3
BASE COMPONENT=8
CONVERSION 1
REACTION RX4
BASE COMPONENT=9

26
Keyword Input PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

CONVERSION 1
STCALCULATOR UID=F1X, NAME=3_PHASE
FEED 24X,1
OVHD L=25A, V=24A
BTMS M=25AX
FOVHD(M) 1,23,1
FOVHD(M) 24,24,0
OPERATION STOP=ZERO
CONREACTOR UID=RX1B, NAME=2ND_STAGE
FEED 20B,25A,25AX
PRODUCT M=24Y
OPERATION ADIABATIC, PRESSURE=29
RXCALCULATION MODEL=STOIC
RXSTOIC RXSET=RS1
REACTION RX1
BASE COMPONENT=6
CONVERSION 1
REACTION RX2
BASE COMPONENT=7
CONVERSION 1
REACTION RX3
BASE COMPONENT=8
CONVERSION 1
REACTION RX4
BASE COMPONENT=9
CONVERSION 1
STCALCULATOR UID=F1Y, NAME=3_PHASE
FEED 24Y,1
OVHD L=25B, V=24B
BTMS M=25BX
FOVHD(M) 1,23,1
FOVHD(M) 24,24,0
OPERATION STOP=ZERO
CONREACTOR UID=RX1C, NAME=3RD_STAGE
FEED 20C,25B,25BX
PRODUCT M=24Z
OPERATION ADIABATIC, PRESSURE=28
RXCALCULATION MODEL=STOIC
RXSTOIC RXSET=RS1
REACTION RX1
BASE COMPONENT=6
CONVERSION 1
REACTION RX2
BASE COMPONENT=7
CONVERSION 1
REACTION RX3
BASE COMPONENT=8
CONVERSION 1
REACTION RX4
BASE COMPONENT=9
CONVERSION 1
STCALCULATOR UID=F1Z, NAME=3_PHASE
FEED 24Z,1
OVHD L=25C, V=24C
BTMS M=25CX
FOVHD(M) 1,23,1
FOVHD(M) 24,24,0
OPERATION STOP=ZERO

27
PRO/II Process Engineering Sulfuric Acid Alkylation Casebook Keyword Input

CONREACTOR UID=RX1D, NAME=4TH_STAGE

FEED 20D,25C,25CX
PRODUCT M=24ZZ
OPERATION ADIABATIC, PRESSURE=27
RXCALCULATION MODEL=STOIC
RXSTOIC RXSET=RS1
REACTION RX1
BASE COMPONENT=6
CONVERSION 1
REACTION RX2
BASE COMPONENT=7
CONVERSION 1
REACTION RX3
BASE COMPONENT=8
CONVERSION 1
REACTION RX4
BASE COMPONENT=9
CONVERSION 1
STCALCULATOR UID=F1ZZ, NAME=3_PHASE
FEED 24ZZ,1
OVHD L=25D, V=24D
BTMS L=25DX
FOVHD(M) 1,23,1
FOVHD(M) 24,24,0
OPERATION STOP=ZERO
STCALCULATOR UID=SETL, NAME=ACID_SETTLER
FEED 25D,1/25DX,1
OVHD L=25, V=24E, PRESSURE=26
BTMS M=SA2, PRESSURE=26
FOVHD(M) 1,23,1
FOVHD(M) 24,24,0
OPERATION STOP=ZERO
MIXER UID=VAPR, NAME=RXN_VAPORS
FEED 24A,24B,24C,24D,24E
PRODUCT V=24
CONTROLLER UID=C2
SPEC STREAM=25, TEMPERATURE(F), VALUE=45, ATOLER=0.0002
VARY SPLITTER=S1, SPEC(1), MINI=1, MAXI=1000, STEPSIZE=20
CPARAMETER IPRINT, SOLVE, ITER=5
$ REFRIGERATION CIRCUIT
FLASH UID=MCOM
FEED 24,29_R1
PRODUCT L=26
BUBBLE TEMPERATURE=100
$ PRODUCT PURIFICATION CIRCUIT
PUMP UID=P2, NAME=EFFL_PUMP
FEED 25
PRODUCT L=251
OPERATION PRESSURE=120
$ After first run, substitute first insert in Appendix 4-B for Column DIC4
COLUMN UID=DIC4, NAME=ISO-STRIPPER
PARAMETER TRAY=42,IO=40
FEED 253X,1,TNOTSEPARATE, NOTSEPARATE
PRODUCT OVHD(M)=30, BTMS(M)=31,1300, SUPERSEDE=ON
DUTY 1,42,,SIDEHC1
PRINT PROPTABLE=BRIEF
ESTIMATE MODEL=CONVENTIONAL, RRATIO=3
PRESSURE 1,90/42,95

28
Keyword Input PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

$ The next line sets the iC4 recycle rate

SPEC ID=COL2SPEC1, STREAM=30, RATE(LV,BBL/H),TOTAL,WET, &
VALUE=2525
VARY DNAME=SIDEHC1
TRATE SECTION(COLSECT-1)=2,41,SIEVE, PASSES=4, &
DIAMETER(TRAY)=156, DIAMETER(SIEVEHOLE,IN)=0.5, &
WEIR=2, DCC=1.5
HX UID=FT1, NAME=EFFL_RECL, ZONES(OUTPUT)=5
HOT FEED=30, L=30R, DP=5
COLD FEED=251, L=252, DP=5
CONFIGURE COUNTER, U=90, TPASS=1, SPASS=1
OPER HTEMP=62
PUMP UID=P1
FEED 27
PRODUCT L=27P
OPERATION PRESSURE=400
$ THE DEBUTANIZER CIRCUIT IS SOLVED OUTSIDE THE LOOP
COLUMN UID=DEC4, NAME=DEBUTANIZER
PARAMETER TRAY=30,IO ERRINC=1.05
FEED 31,15,TNOTSEPARATE, NOTSEPARATE
PRODUCT OVHD(M)=32,350, BTMS(M)=33, SUPERSEDE=ON
CONDENSER TYPE=TFIX, PRESSURE=80, TEMPERATURE=100
DUTY 1,1,,CONDENSER
DUTY 2,30,,SIDEHC2
PRINT PROPTABLE=BRIEF
ESTIMATE MODEL=CONVENTIONAL, RRATIO=3
PRESSURE 2,85/30,90
SPEC ID=COL3SPEC1, STREAM=33, RVP, VALUE=12
SPEC ID=COL3SPEC2, STREAM=32,PCT(LV), COMP=10,WET, VALUE=2
VARY DNAME=CONDENSER
VARY DNAME=SIDEHC2
TRATE SECTION(COLSECT-1)=2,29,SIEVE, PASSES=1, &
DIAMETER(TRAY)=60, DIAMETER(SIEVEHOLE,IN)=0.5, &
WEIR=2, DCC=1.5
HX UID=FB4, NAME=EFFL_ALKY, ZONES(OUTPUT)=5
HOT FEED=33, L=331, DP=5
COLD FEED=252, L=253, DP=5
CONFIGURE COUNTER
OPER CTEMP=110
HX UID=CL4, NAME=ALKY_CLR, ZONES(OUTPUT)=5
HOT FEED=331, L=332, DP=5
UTILITY WATER, TIN=70, TEMPERATURE=80
CONFIGURE COUNTER
OPER HTEMP=100
$ THE DEETHANIZER IS SOLVED OUTSIDE THE LOOP
PUMP UID=P3
FEED 11
PRODUCT L=11A
OPERATION PRESSURE=600
COLUMN UID=DEC2, NAME=DEETHANIZER
PARAMETER TRAY=20,IO
FEED 11B,5,TNOTSEPARATE, NOTSEPARATE
PRODUCT OVHD(M)=40,40, BTMS(M)=41, SUPERSEDE=ON
CONDENSER TYPE=PART, PRESSURE=420
DUTY 1,1,,CONDENSER
DUTY 2,20,,SIDEHC2
PSPEC PTOP=425, DPCOLUMN=10
PRINT PROPTABLE=BRIEF

29
PRO/II Process Engineering Sulfuric Acid Alkylation Casebook Keyword Input

ESTIMATE MODEL=CONVENTIONAL, RRATIO=2

SPEC ID=COL4SPEC1, TRAY=1, TEMPERATURE(F), VALUE=100
SPEC ID=COL4SPEC2, STREAM=41, TVP(PSIG), VALUE=203
VARY DNAME=CONDENSER
VARY DNAME=SIDEHC2
TSIZE SECTION(COLSECT-1)=2,19,SIEVE, SPACING(TRAY)=24, DMIN=15
HX UID=FB1
HOT FEED=41, L=41A, DP=5
COLD FEED=11A, L=11B, DP=5
CONFIGURE COUNTER
OPER HOCO=5
HX UID=CL1
HOT FEED=41A, L=41B, DP=5
UTILITY WATER, TIN=70, TEMPERATURE=80
CONFIGURE COUNTER
OPER HTEMP=100
$ THE COMPRESSOR REQUIREMENTS CAN BE CALCULATED AFTER
$ THE RECYCLE LOOPS ARE SOLVED
VALVE UID=SCTN, NAME=SUCTION
FEED 24_R1
PRODUCT V=240
OPERATION PRESSURE=23
COMPRESSOR UID=CMP1, NAME=1ST STAGE
FEED 240
PRODUCT V=241
OPERATION CALCULATION=GPSA, COPT=SING, EFF=80
DEFINE PRES(PSIA) AS STREAM=29, PRESSURE(PSIA), MINUS,1
COMPRESSOR UID=CMP2, NAME=2ND STAGE
FEED 241,29
PRODUCT V=260
OPERATION CALCULATION=GPSA, COPT=SING
DEFINE PRES(PSIA) AS STREAM=26, PRESSURE(PSIA), PLUS,5
FLASH UID=AFTR, NAME=AFT_COOL
FEED 260
PRODUCT L=261
BUBBLE DP=5
$ -----------------------------------------------------
RECYCLE DATA
LOOP NUMBER=1, START=FB2, END=P1, TOLE=0.0025
LOOP NUMBER=2, START=DEC2, END=FB1,WEGSTEIN, TOLE=0.0005
$ -----------------------------------------------------
CASESTUDY OLDCASE=BASECASE,NEWCASE=MORE_C3
CHANGE COLUMN=DEC3,SPEC(2),VALUE=100
DESC INCREASE C3 IN THE BOTTOMS OF THE
DESC SATURATE DEPROPANIZER.
CASESTUDY OLDCASE=BASECASE,NEWCASE=MORE_IC4
CHANGE COLUMN=DIC4,SPEC,VALUE=2600
DESC INCREASE IC4 RECYCLE
CASESTUDY OLDCASE=BASECASE,NEWCASE=MORE_NC4
CHANGE STREAM=1NB,RATE(LV),VALUE=50
DESC INCREASE NC4 IN SATURATE FEED
END

30
 PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

A PPENDIX B
Input Changes for Run 2 and 3
Keyword Input File Inserts
Run 2 (De-isobutanizer Configuration) and Run 3(E ffluent Refrigeration Configuration)
Substitute these file inserts for the corresponding sections if input listed in Appendix B
.
Insert 1: Debutanizer

Original input to discard:

COLUMN UID=DIC4, NAME=ISO-STRIPPER

PARAMETER TRAY=42,IO=40
FEED 253X,1,TNOTSEPARATE, NOTSEPARATE
PRODUCT OVHD(M)=30, BTMS(M)=31,1300, SUPERSEDE=ON
DUTY 1,42,,SIDEHC1
PRINT PROPTABLE=BRIEF
ESTIMATE MODEL=CONVENTIONAL, RRATIO=3
PRESSURE 1,90/42,95
$ The next line sets the iC4 recycle rate
SPEC ID=COL2SPEC1, STREAM=30, RATE(LV,BBL/H),TOTAL,WET, &
VALUE=2525
VARY DNAME=SIDEHC1
TRATE SECTION(COLSECT-1)=2,41,SIEVE, PASSES=4, &
DIAMETER(TRAY)=156, DIAMETER(SIEVEHOLE,IN)=0.5, &
WEIR=2, DCC=1.5

Changed input to insert:

COLUMN UID=DIC4, NAME=DEISOBUTANIZER

PARAMETER TRAY=43,IO
FEED 253X,20,TNOTSEPARATE, NOTSEPARATE
PRODUCT OVHD(M)=30, BTMS(M)=31,1300, SUPERSEDE=ON
DUTY 1,1,,SIDEHC1
DUTY 2,43,,SIDEHC2
PRINT PROPTABLE=BRIEF
ESTIMATE MODEL=CONVENTIONAL, RRATIO=3
PRESSURE 1,85/2,90/43,95
$ The next line sets the iC4 recycle rate
SPEC ID=COL2SPEC1, STREAM=30, RATE(LV,BBL/H),TOTAL,WET, &
VALUE=1000
SPEC ID=COL2SPEC2, REFLUX(BBL/H), VALUE=1600
VARY DNAME=SIDEHC1
VARY DNAME=SIDEHC2

31
PRO/II Process Engineering Sulfuric Acid Alkylation Casebook Input Changes for Run 2 and 3

TRATE SECTION(COLSECT-1)=2,42,SIEVE, PASSES=4, &

DIAMETER(TRAY)=156, DIAMETER(SIEVEHOLE,IN)=0.5, &
WEIR=2, DCC=1.5

Insert 2: Effluent Refrigeration

Changed input to be inserted.

Replace CONREACTOR RX1A with:

PUMP UID=P4, NAME=Sats Pump

FEED 21
PRODUCT L=21X
OPERATION PRESSURE=80
CONREACTOR UID=RX, NAME=1st_stage
FEED 20A,21X,30R,SA1
PRODUCT M=25X
OPERATION ISOTHERMAL, TEMPERATURE=45, PRESSURE=80
RXCALCULATION MODEL=STOIC
RXSTOIC RXSET=RS1
REACTION RX1
BASE COMPONENT=6
CONVERSION 1
REACTION RX2
BASE COMPONENT=7
CONVERSION 1
REACTION RX3
BASE COMPONENT=8
CONVERSION 1
REACTION RX4
BASE COMPONENT=9
CONVERSION 1
STCALCULATOR UID=ACST, NAME=Acid Settler
FEED 25X,1
OVHD L=25A, V=24A
BTMS M=25AX
FOVHD(M) 1,23,1
FOVHD(M) 24,24,0
OPERATION STOP=ZERO
FLASH UID=TUBE, NAME=Cooling Tubes
FEED 25A_R1
PRODUCT V=24AK, L=25AK
ADIABATIC TEMPERATURE=35, PESTIMATE=20
DEFINE DUTY(MMON,BTU/HR) AS CONREACTOR=RX, DUTY(MMON,BTU/HR), &
TIMES,-1

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 PRO/II Process Engineering Sulfuric Acid Alkylation Casebook

A PPENDIX C
Wet Sulfuric Acid Process
The availability of a suitable catalyst is also an important factor in deciding whether to building an
alkylation plant. When sulfuric acid is used, significant volumes are needed. Access to a suitable plant is
required for the supply of fresh acid and the disposition of spent acid. If a sulfuric acid plant must be
constructed specifically to support an alkylation unit, such construction will have a significant impact on
both the initial requirements for capital and ongoing costs of operation.
Alternatively it is possible to install a WSA Process unit to regenerate the spent acid. The WSA process
is the ideal choice for regeneration of spent sulphuric acid. No drying of the gas takes place. This means
that there will be no loss of acid, no acidic waste material and no heat is lost in process gas reheating.
The selective condensation in the WSA condenser ensures that the regenerated fresh acid will be 98%
w/w even with the humid process gas. It will
be possible to combine spent acid regeneration with disposal of hydrogen sulphide by using hydrogen
sulphide as fuel.[A-5].
The wet sulfuric acid process (WSA process) is one out of many gas desulfuriz ation processes on the
market today. Since its introduction in the 1980s, where it was patented by the Danish catalyst company
Haldor Tops øe A/S, it has been recognised as an efficient process for recovering sulfur from various
process gasses in the form of commercial quality sulfuric acid (H2SO4). The WSA process is applied in
all industries where removal of sulfur is an issue.
Wet catalysis processes differ from ot her contact sulfuric acid processes in that the feed gas still contains
moisture when it comes into contact with the catalyst. The sulfur trioxide formed by cataly tic oxidation of
the sulfur dioxide reacts instantly with the moisture to produce sulfuric acid in the vapour phase to an
extent determined by the temperature. Liquid acid is subs equently formed by condensation of the sulfuric
acid vapour and not by absorption of the sulfur trioxide in concentrat ed sulfuric acid, as is the case in
contact processes based on dry gases. The concentration of the product acid depends on the H2O/SO3
ratio in the catalytically converted gases and on the condensation temperature. [A-5] [A-6]
The wet catalysis process is especially suitable for processing the wet gasses obtained by the
combustion of hydrogen sulfide (H2S) cont aining off-gasses.[A-7] The combustion gasses are merely
cooled to the converter inlet temperature of about 420-440 °C. To process these wet gasses in a
conventional cold-gas contact process (DCDA ) plant would necessitate cooling the gas to an
economic ally unacceptable extent to remove the large excess of moisture.
Therefore in many cases Wet catalysis processes is a more cost- efficient way of treating hydrogen
sulfide containing off-gases.

Description of the wet sulfuric acid proce ss (WSA)

In the first step, sulfur is burned to produce sulfur dioxide.
S (s) + O2 (g) --> SO2 (g) (4-4)
or Hydrogen sulfide H2S gas is incinerated to SO2 gas.
H2S + 3/2O2 --> H2O + SO2 + 518KJ/mole (4-5)
This is then oxidized to sulfur trioxide using oxygen in the presence of a vanadium (V) oxide catalyst.
2 SO2 + O2 --> 2 SO3 + 99KJ/mole (in presence of V2O5) (4-6)
The sulfur trioxide is hydrat ed into sulfuric acid H2SO4.
SO3 + H2O --> H2SO4 (g) + 101 KJ/mole (4-7)
The last step is the condens ation of the sulfuric acid to liquid 97 - 98% H2SO4

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PRO/II Process Engineering Sulfuric Acid Alkylation Casebook Wet Sulfuric Acid Process

H2SO4 (g) + 0.17H2O (g) --> H2SO4(l) + 69 KJ/mole

References
 Sulphur recovery; (2007) The Process Principles, details advances in sulphur recovery by the WSA
process. Denmark: Jens Kristen Laurs en, Haldor Tops øe A/S. Reprinted from Hydrocarbon Engi -
neering August 2007
 U.H.F Sander, H. Fischer, U. Rothe, R. Kola (1984). Sulphur, Sul- phur Dioxide and Sulphuric Acid
(1st Edition ed.). The British Sul- phur Corporation Limited. ISBN 0902777645.
 Gary, J.H. and Handwerk, G.E. (1984). Petroleum Refining Technol - ogy and Economics (2nd
Edition ed.). Marcel Dekker, Inc. ISB N 0824771508.

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