? x DE-FG36-92 ID 13138 Mem braneDistillation Hybrid Process

BP Chemicals

APPENDIX I

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or use- fulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spe- cific commercial product, proctss, or service by trade name, trademark, manufac- turer, or otherwise does not necessarily constitute or imply its endorsement, w m - mendation. or favoring by the United States Government or any agency thereof. The views and opinions of authors exptessed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

c

DISCLAIMER

Portions of this document may be illegible electronic image products. Images are produced from the best available original document.

, 1

BP Chemicals Selective Olefin Recovery

Evaluation of Absorption/Stripping for Second Phase Expansion

of KG G a s Cracker

December, 1995

STONE & WEBSTER ENGINEERING HOUSTON, TEXAS

BP CHEMICALS December, 1995 Selective Olefin Recovery

1.0 INTRODUCTION

This report addresses technology evaluation for a second phase expansion of BP Chemical Ltd.’s (BPCL) KG cracker. Its primary objective was to determine if the absorptiodstripping technology being developed by BPCL is competitive with cryogenic demethanization technology. The expansion basis for this evaluation is a :150,000 MTA ethylene increment. This increment represents an increase in KG’s capacity from 450,000MTA after the current expansion to an ultimate capacity of 600,000 MTA.

‘Two recovery systems for a 150,000MTA expansion are compared:

Case A - Absorptiodstripping Expansion

Case B - A R S Expansion

Another objective of this report was to confirm the magnitude of the economic advantages of the absorptiodstripping technology for grass roots applications. For that evaluation, absorptiodstripping was compared with the original 350,000 MTA IKG recovery system. The two additional 350,000MTA grass roots cases evaluated are:

Case C - AbsorptioxdStripping - Grass Roots Design

Case D - Conventional Cryogenic Recovery (Original KG 350,000MTA design)

-& Webster Engineering Corporation Houston, Texas

RP CHlEMICALS Selective Olefin Recovery

Rev.1 January, 1996

2.0 SUMMARY

2.1 EXECUTIVESUMMARY

A 150,000 MTA KG expansion was selected as a basis for evaluation of the economics of the absorptiodstripping process for plant retrofits. A new parallel cracked gas compressor was incorporated into each expansion design, rather than using other means such as a combination of rewheeling and increasing the suction pressure. Installed costs may, therefore, be higher than required. The intent was to make the design bases consistent so that the comparison between schemes would also be consistent.

KG is currently being expanded from its original nameplate of 350,000 MTA to 450,000 MTA ethylene. Alternate recovery system designs were prepared for an absorptiodstripping expansion (Case A) and an A R S expansion (Case B). This second expansion would bring the total ethylene capacity of KG to 600,000MTA.

The cracked gas feed basis for this study (primarily based on ethane feed) is the same feed basis as is being used for the current expansion. Debottlenecking of back end equipment was ignored to simplify the analysis.

Equipment factored estimates were prepared for the installed cost of each expansion alternate. Variable operating costs were also determined. The estimated installed cost of the absorptiodstripping expansion is lower than that of an A R S expansion. Capital cost savings of greater than 20% are indicated. However, its variable operating cost is 50% higher, due mainly to the impact of lower feed and product recoveries and the valuation of quench water at LP steam cost. Even so, the payout for the additional investment in A R S relative to an absorptiodstripping expansion js 3-4 years. Therefore, if the various assumptions made in this study hold up, absorptiodstripping is competitive with A R S for this expansion application.

,4 350,000MTA plant size was selected as a basis for evaluation of the economics of the absorptiodstripping process for grass roots applications. A grass roots absorptiodstripping recovery system design was prepared (Case C). The recovery system for the original KG design was used as a basis (Case D).

]Estimates were prepared for the installed cost and variable operating cost of each grass roots alternate. system as compared with a conventional recovery system are greater than 30%. Its

Capital cost savings of the grass roots absorptiodstripping

Stone & Webster’s ARS demethanization technology is generally competitive for expansions of 30 % :I

and greater, and so to evaluate absorptiodstripping fairly, a 33% increment was chosen.

Stone& Webster Engineering Corporation Houston, Texas

BP CHI3MICALS Selectivle Olefin Recovery

Rev.1 JaIiuary, 1996

variable operating cost is also lower by about 11 %, assuming that quench water has zero value for a grass roots plant. This operating cost benefit considers the impact of lower feed and product recoveries for the absorptiodstripping process. The design for that process is non-optimized. Optimization would increase the operating cost savings of the absorptiodstripping process to perhaps 20-30 % over conventional technology. The absorptiodstripping process therefore offers substantial economic incentives, and further development appears justified.

The following conclusions may be drawn from this study:

(1) Absorptiodstripping technology is competitive with ARS technology for further expansion of KG.

(2) Absorptiodstripping technology is expected to be competitive with cryogenic ciemethanization technologies such as ARS for other plant expansion applications. Specific advantages of absorptiodstripping will depend upon the extent and location of bottlenecks.

(3) Absorptiodstripping technology offers substantial economic advantages in both capital and operating costs for grass roots units.

Stone & Webster recommends that BPCL proceeds with additional development and engineering of the absorbedstripper process, based on the design presented in this report.

Additional R&D efforts that should be stressed are:

(1) Identification and testing of a suitable non-volatile ligand. (2) Confibmation of VLE data for ethylene,propylene, and butene-1 complexes. (3) Development of additional VLE data for cis- and trans-2-butene, isobutylene, lY3-butadiene, propadiene, and carbon monoxide complexes. (4) Pilot plant testing of the absorptiodstripping process. ( 5 ) Corrosion testing of alternate materials at various simulated process conditions.

Additional engineering efforts that should be considered are:

(1) Additional basic engineering for a selected case, including P&I D development. (2) Preparation of a more accurate cost estimate for that case, including quotes on major equipment and bulk material takeoffs.

Stone 8c Webster Engineering Corporation Houston, Texas

BP CHEMICALS Selective Olefin Recovery

December, 1995

2.2 CASE A - ABSORPTION/STRIPPING EXPANSION

Section 3.0 presents a design for the absorptiodstripping system. (Please refer to process flow diagrams in Section 3.2.)

For this system, cracked gas is taken off a new three-stage cracked gas compressor and treated in a new caustic scrubber and new front acetylene hydrogenation unit. The treated gas is then scrubbed with cuprous nitrate solution in an absorber, and the solution is stripped to produce a mixed olefins stream. The absorber offgas, which contains almost all of the paraffins and some unabsorbed olefins, is partially returned to the cracking furnaces as recycle feed. The amount of recycle will be based on the limit of the chilling traiddemethanizer system to reject additional hydrogen and methane, and the amount of additional furnace capacity installed. Excess absorber offgas is sent to fuel. Unhydrogenated acetylenes, dienes, and CO are recovered in a solution reclaiming operation, and are sent to the existing ciemethanization system to reject CO. The mixed olefins are compressed, dried, and fractionated in a two-column system. Polymer-grade ethylene is taken as the distillate product off the first (deethylenizer) column. Propylene is taken as the distillate off the second (depropylenizer) column, and sent to the existing C3 hydrogenation system and propylene tower for upgrading. C4+ olefins from the bottom of the depropylenizer are sent to the existing depropanizer.

Based on sized ISBL equipment for this design, a factored estimate was prepared. Stainless steel was used as the primary material of construction for the absorption/ stripping section equipment. It was assumed that the only costs related to clebottlenecking existing ISBL equipment were for a new fourth 90 bar ethylene pump, rewheeling of the propylene refrigeration compressor and turbine, and a new fourth propylene refrigeration condenser. I

Among the assumptions made were that the ethylene product (deethylenizer overhead) would not require upgrading, and that there was sufficient surplus capacity aivailable in the existing C3 hydrogenation system and propylene tower. When recycling absorber offgas as furnace feed, hydrogen and methane will be rejected by the existing chilling traiddemethanizer system. Recycle of absorber offgas to the furnaces has not been studied since new furnace capacity will be required for any 150,000 MTA expansion. The chilling traiddemethanizer and furnace capacity will limit the amount of offgas which can be recycled. After the furnaces and c:hilling/train demethanizer are fully loaded, the balance of the absorber offgas will have to be sent to the fuel system.

For this study, it has been assumed that 50% of the absorber offgas can be recycled a.s furnace feed for the expansion case.

-8r Webster Engineering Corporation Houston, Texas

1

RP CHEMICALS Selective Olefin Recovery

December, 1995

The new cracked gas compressor has been designed as a three-stage system based on total recycle of the absorber offgas as feed. The installed cost and operating cost is, therefore, conservative.

On the above basis, the estimated installed cost for a recovery section using the absorptiodstripping process is $46,900,000 (U.S.G.C. basis). This estimate has an accuracy of -15/+30%, and is exclusive of any front end debottlenecking costs from the feed systems to the suction of the cracked gas compressor. Other exclusions to the estimate are itemized in Section 3.6.

The variable operating cost of the absorptiodstripping system is presented in Section 3.7. For the utility cost basis presented in that section, the variable operating cost to produce 150,000 MTA ethylene is $l0,240,000/year, or $0.068/kg ethylene.

2!.3 CASE B - ARS EXPANSION

Section 4.0presents a typical design for an A R S expansion.

A R S is generally attractive for expansions of 30-40% and greater. One of its prime aLdvantages is that refrigeration requirements are only slightly increased. (On a k;wh/MT ethylene basis, refrigeration power requirements are significantly decreased.) Therefore, existing refrigeration compressors can be reused with rnodifications. For this 150,000 MTA A R S expansion, the existing propylene refrigeration system can be reused by rewheeling the compressor and turbine, and a.dding additional condenser capacity. It has been assumed that no modifications are required for the ethylene refrigeration system.

For KG, an A R S expansion from 450,000 MTA To 600,000 MTA would typically involve the following new equipment and modifications to existing equipment:

0 0

0 0

A new five-stage cracked gas compressor (150,000 MTA) A new caustic system (150,000 MTA). Common equipment is shared with the existing caustic system, as in Case A. A new set of dehydrators (150,000 MTA) A new chilling train with two new dephlegmators, and new exchangers and separators (600,000 MTA) A new cold demethanizer with reboiler and condenser A new recontacting tower (no reboiler or condenser required) A new set of cold demethanizer feed pumps A new C2 hydrogenation system Retraying of the existing ethylene tower A new stripping tower to serve as an extension of the existing ethylene tower

-8: Webster Engineering Corporation Houston, Texas

I

BP CHIEMICALS Selective Olefin Recovery

Rev.1 J a ~ b r y , 1996

0

0

0

0 0

Repiping of the existing ethylene tower reboiler A set of new stripping tower feed pumps A new fourth 90 bar ethylene pump Rewheeling of the existing propylene refrigeration compressor and turbine. A new fourth propylene refrigeration condenser.

A factored estimate was prepared for the ISBL A R S expansion on the same basis as the absorbedstripper expansion. Equipment was prorated from a similar ARS expansion, and costed. On this basis, the estimated installed cost for a 150,000MTA ARS expansion is $60,000,000(U.S.G.C. basis). This estimate has the same accuracy as the absorbedstripper estimate, and is based on the same exclusions and inclusions.

The variable operating cost for 150,000MTA of incremental ethylene via an A R S expansion is presented in Section 4.7 for the same utility cost basis as the absorber/stripper expansion. On this basis, the variable operating cost is $7,943,000/year, or $O.O53/kg ethylene.

2.4 COMPARATIVE EVALUATION- EXPANSION CASES

Evaluation of the two expansion cases must consider differences in installed cost, operating cost, and feed and product recoveries. Installed costs and operating costs have been discussed above.

The absorption/stripping process was assumed to have an ethylene recovery of 98 % . The ethylene recovery for conventional cryogenic technology is close to 100%. Propylene recovery for the absorptiodstripping process was assumed to be 90%, versus almost 100 % for conventional recovery technology. Butylene recovery was assumed to be 95% for the absorption/stripping process, versus almost 100% for conventional technology.

Operating cost impacts of lower ethylene, propylene, and C4 recoveries for the a'bsorptiodstripping process must be included in any comparison. Since the absorber offgas is only partially recycled as furnace feed, there will be costs associated with differences between product and fuel values for unrecovered ethylene, propylene, and mixed C4s. There will also be costs associated with differences between feed and fuel values for unrecovered ethane and propane in the offgas. These costs have all been considered, assuming that unrecovered ethane and propane can be used as fuel. A. summary of their impact is presented in Table 2.4.1 ,and the basis is presented in Table 2.4.2.

The estimated installed costs, operating costs, and cost impact of the differences in feed and product recoveries for the two expansion cases are summarized below. To

Webster Engineering Corporation Houston, Texas

, 1

BP CHEMICALS Selective Olefin Recovery

Rev.1 Ja~iuary, 1996 -

account for the different unconverted feed and product recoveries, the cracked gas feed has been held constant, resulting in a 1% higher ethylene product rate for Case 13.

Case

Recovery Process

13asis

1:ncremental Capacity (MTA ethylene)

13stimated Installed Cost

Difference in Installed Cost Relative to Base

Annual Operating Cost

Difference in Operating Cost

Cost Impact of Feedstock and Product Recovery

Difference in Operating Cost Adjusted for Differences In Feed and Product Recovery

Relative to Base

Payout, years

A

Absorption/Stripping

Plant expansion

150 , 000

$46,900,000

($13,100,000) (22 %)

$lO,239,000/yr

+$2,296,000/yr

+ $17695,000/yr

$3,99lY000/yr

+50%

Base

B

ARS

Plant expansion

151,500*

$60,000,000

Base -

$7,943,000/yr

Base

Base

Base

-

3.3

For this plant expansion application, the absorptioxdstripping process has a lower installed cost ( 22 % less), but a significantly higher operating cost ( 50 % greater). The payout of the A R S expansion as compared to an absorptiodstripping expansion is 3-4 years. Therefore, if the various assumptions made in this study hold up, the absorptiodstripping process is competitive with A R S for this particular application.

* Product ethylene capacity is 1% higher than Case A on an equivalent feed basis.

Stone &: Webster Engineering Corporation Houston, Texas

BP CHEMICALS Selective Olefin Recovery

Rev.1 January, 1996

Case Recovery Process

Recovered Ethylene, MTA Ethylene to Fuel, MTA Product Ethylene Value Fuel Ethylene Value Total Ethylene Value Difference in Ethylene Value

Recovered Propylene, MTA Propylene to Fuel, MTA Product Propylene Value Fuel Propylene Value T~otal Propylene Value Difference in Propylene Value

Recovered C ~ S , MTA C4s to Fuel, MTA Piroduct C4 Value Fuel C4 Value Total C4 Value Difference in C4 Value

Recycle Ethane to Feed, MTA Erhane to Fuel, MTA Recycle Ethane Value Fuel Ethane Value Total Ethane Value Difference in Ethane Value

Recycle Propane to Feed, MTA Propane to Fuel, MTA Recycle Propane Value Fuel Propane Value Total Propane Valuc Difference in Propane Value

Total Debit to Absorption/Stripping

Table 2.4.1 Cost Impact of Differences in Feed

and Product Recoveries

A Absorption/Stripping

150,000 1,500

$76,500,000/yr $1 70,W/yr

($595,000/yr) $76,670,000/yr

38,500 2,000

$15,400,000/yr $230,00O/yr

$15,63O,W/yr ($570,00O/yr)

22,000 -

$3,300,000/yr

$3,300,000/yr ($30,00O/yr)

23,500 23,500

$2,940,000 $2,700,000/yr $5,640,000/yr

($230,00O/yr)

7,700 7,700

$1,15O,OOO/yr $890,000/yr

$2,040,0001yr ($270,00O/yr)

* Product ethylene capacity is 1% higher than Case A on an equivalent feed basis.

B Conventional

151,508

$77,265,000/yr -

- $77,265,000/yr

40,500

$l6,200,000/yr -

$16,200,000/yr -

22,000

$3,300,000/yr

$3,300,000/yr

47,000

$5,870,000/yr

$5,870,000/yr -

15,400

$2,3 10,000/yr -

$2,3 10,000/yr

Stone & Webster Engineering Corporation Houston, Texas

BP CHEMICALS December, 1995 Selective Olefin Recovery

Table 2.4.2

Basis for Calculated Differences in Feed and Product Recoveries

Products $/MT

Ethylene Propylene Mixed C4s

5 10 400 150

Feeds

Ethane Propane Butane

Fuel

Fuel Gas

125 150 160

115

Stone & Webster Engineering Corporation Houston, Texas

BP CHEMICALS Selectivle Olefin Recovery

December, 1995 ~

2:.5 CASE C - ABSORPTION/STRII'PING - GRASS ROOTS

To determine the attractiveness of the absorptiodstripping process for a grass roots application, process designs and installed cost estimates were prepared for the a bsorptiodstripping process and a conventional cryogenic recovery system. For this comparison, it was assumed that a new 350,000MTA recovery system would be built a t Grangemouth. The two cases are:

Case C - AbsorptiodStripping - Grass Roots Design

Case D - Conventional Cryogenic Recovery (Original KG 350,000 MTA design)

Case C differs somewhat from the absorber/stripper expansion case. Since there is no chilling train or demethanizer, hydrogen and methane are rejected by sending all of the absorber offgas to fuel, rather than recycling a portion of it as furnace feed. A two-stage cracked gas compressor is sufficient to supply absorber feed, rather than a three-stage compressor, since fuel header pressure requirements are lower than furnace feed pressure requirements. Since there is no existing C3 hydrogenation system to tie in to, a new system is included. Hydrogen for this system is obtained from a small PSA unit treating a very small portion of the absorber offgas. The expansion case shared some equipment with the existing caustic system. The grass roots case requires all new equipment for the caustic system.

A factored estimate was prepared for Case C. The estimated installed cost for a 350,000 MTA grass roots absorptiodstripping recovery system is $85,400,000 (U.S.G.C. basis). This estimate has the same accuracy (-15/+30%) as the other estimates, and is based on the same exclusions and inclusions.

The variable operating cost for a 350,000 MTA absorptiodstripping recovery system is presented in Section 5.7. Based on the assumptions presented, the variable operating cost is $l4,240,000/year, or $O.O407/kg ethylene.

2.6 CASED - CONVENTIONAL CRYOGENIC RECOVERY- GRASSROOTS

F:or this case, it was assumed that a new 350,000MTA cryogenic recovery system identical to the original recovery system, would be built at Grangemouth. For a description of this process, please refer to the Stone & Webster job books. Sized equipment included in the recovery system definition is summarized in Section 6.3

A factored estimate was prepared for Case D on the same basis as the other cases. Return equipment cost data from the original KG plant was used to confirm

Stone & Webster Engineering Corporation Houston, Texas

1

BP CHEMICALS Selective Olefin Recovery

Rev.1 J&uary, 1996

equipment costs for the other cases. The estimated installed cost for a 350,000MTA grass roots conventional cryogenic recovery system is $125,300,000 (U.S.G.C. basis). This estimate has the same accuracy as the other estimates (-15/+30%), and is based on the same exclusions and inclusions.

The variable operating cost for a 350,000 MTA grass roots conventional cryogenic recovery system is presented in Section 6.5. Based on the assumptions presented, the variable operating cost is $25,740,000/year, or $O.O735/kg ethylene.

2.7 COMPARATIVE EVALUATION- GRASS ROOTS CASES

As in the expansion cases, evaluation of the grass roots cases must consider differences in installed cost, operating cost, and feed and product recoveries. Installed costs and operating costs have been discussed above.

The absorptiodstripping process was assumed to have an ethylene recovery of 98 % , propylene recovery of 90%, and butylene recovery of 95%. Olefin recovery is essentially 100 % for cryogenic recovery technology.

Although both grass roots cases are based on 350,000MTA of ethylene production, the absorptiodstripping case will require a slightly larger front end because of its lower ethylene recovery. The installed cost impact of the slightly larger front end has been neglected in this study. However, the operating cost impacts of lower ethylene, propylene, and C4 recoveries have been included. Since the absorber offgas is not recycled as furnace feed, there will be costs associated with the absorptionlstripping c,ase in terms of the differences between product and fuel values for unrecovered ethylene, propylene, and mixed C4s. There will also be costs associated with the differences between feed and fuel values for unrecovered ethane and propane in the offgas. As in the expansion comparison, these costs have all been considered, assuming that unrecovered ethane and propane can be used as fuel. A summary of these cost impacts is presented in Table 2.7.1. The basis is the same as that presented in Table 2.4.2.

The estimated installed costs, operating costs, and cost impact of the differences in feed and product recoveries for the two grass roots cases are summarized below. To a.ccount for the different unconverted feed and product recoveries, the cracked gas feed has been held constant, resulting in a 2% higher ethylene product rate for Case I>.

Stone 8: Webster Engineering Corporation Houston, Texas

BP CHEMICALS Selective Olefin Recovery

Rev.1 January, 1996

Case C D

Recovery Process Absorption/Stripping Conventional

Basis Grass Roots Grass Roots

Capacity, MTA ethylene 350,000 357,000*

Elstbated Installed Cost $85,400,000 $125,300,000

Difference in Installed Cost ($39,900,000) Relative to Base (32%)

Base -

A,nnual Operating Cost $14,240,000/yr $25,740,000/yr

Difference in Operating Cost ($1 1,5OO,OOO/yr) Base

Cost Impact of Feedstock and Product Recovery +$8,740,000/yr Base

Difference in Operating Cost Adjusted for Differences ($2,76O,OOO/yr) Base In Feed and Product Recovery

Relative to Base (11%) -

Payout, years NIA Base

For a grass roots application, the absorptiodstripping process has a considerably lower installed cost ( 32 % less) as well as a lower operating cost ( 11 % less) than a conventional cryogenic recovery process. As discussed above, the savings in operating cost reflects the lower feed and product recoveries of the absorptiodstripping process. Without the adjustment for lower recoveries, the operating cost savings would be 45 %. This higher figure represents a target for pirocess improvement.

Product recoveries for the absorptiodstripping process have been conservatively estimated. Higher recoveries are probable. In addition, an optimized absorptiodstripping flowsheet would utilize higher severity cracking with higher feed conversions, since unconverted feed is not recycled. These parameters have not been optimized for this study. Optimization would improve the operating cost savings of th.e absorptiodstripping process to a value most likely in the 20-30% range.

* Product ethylene capacity is 2% higher than Case C on an equivalent feed basis.

Stone & Webster Engineering Corporation Houston, Texas

BP CHEMICALS Rev.1 Jahuary, 1996 Selective Olefin Recovery

Table 2.7.1 Cost Impact of Differences in Feed

and Product Recoveries

(Case :Recovery Process

:Recovered Ethylene, MTA ]Ethylene to Fuel, MTA Product Ethylene Value Fuel Ethylene Value ‘Total Ethylene Value ]Difference in Ethylene Value

Recovered Propylene, MTA I?ropylene to Fuel, MTA I?roduct Propylene Value l?uel Propylene Value Total Propylene Value Difference in Propylene Value

Recovered C ~ S , MTA (34s to Fuel, MTA Product C4 Value Fuel C4 Value Total C4 Value Difference in C4 Value

Recycle Ethane to Feed, MTA Ethane to Fuel, MTA Recycle Ethane Value Fuel Ethane Value Total Ethane Value Ilifference in Ethane Value

C AbsorptionlStripping

350,000 7,000

$178,500,000/yr $800,00O/yr

$179.300,000/yr ($2,770 ,OOO/yr)

86,000 9,500

$34,400,000/yr $1,090,000/yr

$35,490,0001yr ($2,7 lO,OOO/yr)

25,900 25,500

$3,880,000/yr $2,930,000/yr $6,8 10,00O/yr ($9OO,OOO/yr)

110,000

$12,650,000/yr $12,650,000/yr ($1,100,00O/yr)

Recycle Propane to Feed, MTA F’ropane to Fuel, MTA 36,000 R.ecycle Propane Value - Fuel Propane Value $4,140,000/yr Total Propane Value $4,140,000/yr Difference in Propane Value ($1,26O,OOO/yr)

Total Debit to AbsorptionBtripping ($8,74O,OOO/yr)

D Conventional

357,008

$182,070,000/yr

$l82,070,000/yr

-

-

95,500

$38,200,000/yr

$3 8,200,000/yr

-

-

5 1,400

$7,7 10,00O/yr

$7,710,000/yr

110,000

$13,750,000/yr

$l3,750,000/yr

36,000

$5,400,000/yr

$5,400,000/yr

* Product ethylene capacity is 2% higher than Case C on an equivalent feed basis.

Stone &: Webster Engineering Corporation Houston, Texas

. - L

1

BP CHEMICALS Rev.1 Jarkary, 1996 Selective Olefin Recovery

2.8 CONCLUSIONS

‘The following conclusions may be drawn from this study:

(11) Absorptiodstripping technology has the potential of being competitive with A R S technology for further expansion of KG. Savings of over 20% in capital cost are expected. However, its operating cost is 50% higher, due mainly to lower recovery of products and unconverted feed, and the valuation of quench water at LP steam cost. Even so, the payout of A R S as compared with absorptiodstripping is 3-4 years.

(2) Absorptiodstripping technology is expected to be competitive with cryogenic demethanization technologies such as A R S for other plant expansion applications. The degree of competitiveness will depend upon the extent and location of bottlenecks.

(3) Absorptiodstripping technology offers substantial economic advantages in both capital and operating costs for grass roots units. Savings of over 30% in capital cost and 20-30% in operating cost are expected.

1!.9 RECOMMENDATIONS I Stone & Webster recommends that BPCL proceeds with additional engineering and pilot plant testing of the absorberhtripper process, based on the design presented in this report.

Additional R&D efforts that should be stressed are:

(1) Identification and testing of a suitable non-volatile ligand. (2) Confirmation of VLE data for ethylene,propylene, and butene-1 complexes. (3) Development of additional VLE data for cis- and trans-2-butene, isobutylene, 1,3-butadiene, propadiene, and carbon monoxide complexes. (,4) Pilot plant testing of the absorptiodstripping process. (5) Corrosion testing of alternate materials at various simulated process conditions.

Additional engineering efforts that should be considered are:

(1) Additional basic engineering for a selected case, including P&I D development. (:2) Preparation of a more accurate cost estimate for that case, including quotes on major equipment and bulk material takeoffs.

Stone & Webster Engineering Corporation Houston, Texas