the role of a new fcc gasoline three-cut splitter in ... · pdf fileaprochem 2009 •...

1309APROCHEM 2009 • OdpadOvé fórum 2009 20.–22. 4. 2009 Milovy1309

The Role of a New FCC Gasoline Three-Cut Splitter in Transformation of Crude Oil Hydrocarbons in CRC

Hugo Kittel, Ph.D., Strategy and Long –Term Technical Development Managertel. +420 315 71 8603, e-mail [email protected]

Czech Refining Co. (CRC), O.Wichterleho 809, 278 52 Kralupy n.Vlt.

1. Introduction

Despite of very fast development of new technologies to process crude oil hydrocarbons,distillation remains as a base technological process how to produce hydrocarbon fractions of specific properties. It means that responding to current challenges of crude oil processing also fractionation technology can contribute positively.

This paper deals with a new Three-Cut Splitter (3CS) unit implemented as an important part of 10 ppm S Mogas solution in Česká rafinérská a.s. (CRC). This unit is based entirely ondistillation technology. New opportunities related to the commissioning of this unit are discussed here.

In addition, this paper aims in parallel to demonstrate advantage of application of linearprogramming (LP) to find an optimal solution of development projects in refineries.

2. Analysis of problem - Three-Cut Splitter Genesis

Clean Mogas solution in CRC has been already reported [SVÁTA, KITTEL, 2007], thereforeonly central facts will be recapitulated in this paper. All efforts were focused on FCC unit.

FCC unit in the Kralupy refinery was commissioned in April 2001. Original scheme of gasoline production in the unit was relatively simple, see exhibit 1.

Exhibit 1: Original FCC gasoline scheme

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1310APROCHEM 2009 • OdpadOvé fórum 2009 20.–22. 4. 2009 Milovy

Two gasoline fractions (light and heavy cut) were withdrawn from the main FCC fractionator.Heavy Mogas was unselectively treated on UNIONFINER (UOP, unit without stabilizer), and then again pooled, MEROXED (UOP), and blended into Mogas. Original scheme was designed for Mogas with 350 ppm S and it was planned to blend all FCC gasoline into Mogas.

3CS unit was implemented in CRC as afast-track investment solution for 50 ppm S Mogas. It is based on a Shell Global Solutions, Inc. technology. The idea wasto split of full range FCC gasoline into three fractions (light-, heart-, and heavy-cuts) and to treat each cut separately in already available technologies. To treat heart-cut, an existing Naphtha Hydrotreating unit (NHT) in Kralupy was modified adding new liquid quench into reactor, to control exothermic effects of treating of olefinic feed. 3CS and reconstructed NHT were commissionedand operated successfully in the Kralupy refinery since Jan. 2005, see exhibit 2.

Having 3CS unit in operation, it was considered also as a part of 10 ppm SMogas solution. In order to minimizeCAPEX necessary to achieve a 10 ppm S in Mogas, technological scheme of FCC gasoline desulfurization was improved

adding a new Selective Hydrodesulfurization (SHDS) unit downstream of 3CS (PRIME G+ technology, commissioned in Oct. 2007). Corresponding technological scheme see exhibit 3.

Exhibit 3: New FCC gasoline scheme

Exhibit 2: 3CS unit in the Kralupy refinery

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Original possibility to treat FCC heart cut also unselectively in NHT has been kept also as part the new solution.

On the one hand, the final technological scheme for 10 ppm S Mogas operates number of facilities and therefore is related to relatively high variable and maintenance costs. On the other hand, comparing both exhibits 1 and 3, the new scheme gives number of alternatives how to route FCC gasoline cuts characterized by different distillation and composition. That is why these alternatives have been researched exploiting CRC´s LP Development Model.

3. Results - Three-Cut Splitter Opportunities

Standard yields and base properties of 3CS cuts as per current Databook of the Kralupy refinery are in exhibit 4.

Being separately treated, the cuts are again re-pooled into one FCC gasoline blending component. Part of pooled volume is than transferred from Kralupy to Litvínov refinery, to be blended in Mogas there.

Having three fully different FCC gasoline cuts, next alternative approach can be considered:

a) Generally, do not finally pool treated FCC fractions, however use them separately and selectively.

b) Specifically, route heavy cut into Dieselc) Specifically, route heart cut into NHT and than again re-distilled semi-product put

partially into Steam cracker (SC) feed pool or partially use heavy fraction as areforming feed.

These options have been studied exploiting CRC´s Development Model based on LP. Sixscenarios have been defined, differing from each other in way of processing of FCC cuts:

1. Base scenario, implemented in the CRC´s Strategic Plan. It is corresponding tooptimized FCC heavy cut blending into Diesel and maximized Diesel production, as forecasted for the future.

2. FCC heavy cut to Diesel closed. It corresponds to max FCC gasoline production,correspond to the scheme considered in the original FCC project, and reflects more and less current CRC´s operation.

3. FCC heart cut partially unselectively treated using max available capacity on NHT.Heavy cut to Diesel optimized

4. FCC heart cut partially unselectively treated using max available capacity on NHT, heavy cut to Diesel closed. This resembles the original CRC´s 50 ppm S Mogas solution, but having still part of heart cut selectively treated in the new SHDSunit.

5. FCC heart cut unselectively treated using max available capacity on NHT, heavy cut blended fully into Diesel. It is corresponding to minimal FCC gasoline production.

Exhibit 4: 3CS yieldsLight cut Heart cut Heavy cut

Yield (%wt) 27 51 22Density (kg/m3) 649 755 848S (ppm wt) 15 10 15MON 82,0 79,5 84,5E 70 100,0 0,0 0,0E100 100,0 49,0 0,0E150 100,0 95,0 0,0E210 100,0 100,0 90,0

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6. “Liberalized” scenario, all alternatives available to process FCC gasoline opened and optimized. This scenario goes with is ideas even over what was considered in the CRC´s SP (scenario 1)

Individual scenarios listed above and focusing on alternative processing of FCC heart and heavy cuts can be characterized as follows:

Exhibit 5: Studied scenariosScenario 1 2 3 4 5 6Heart cut to NHT Closed Closed Fixed max Fixed max Fixed max OptimizedHeavy cut to diesel Optimized Closed Optimized Closed Fixed max Optimized

As concerns premises of the Development model, Mogas production and delivery of SC feed have been limited to certain max in studied scenarios, however Diesel production has been considered as open. Current available capacities have been respected, with exception of NHTunit, which has been opened for this simulation to be able to process FCC heart cut there.

Important results of modeling, e.g. distribution of FCC gasoline, quality of pooled FCC gasoline cuts, utilization of important capacities, impact of scenarios on transfer of components between two CRC´s refineries and on production, and economic impact of scenarios are as per next exhibits 6 - 11:

Exhibit 6: Distribution of FCC gasoline (kt/yr, % of FCC input)Scenario 1 2 3 4 5 63CS Feed 618,2 653,2 671,1 672,2 671,6 618,1FCC gasoline to Mogas 503,8 653,2 413,9 512,4 363,1 503,1

MEROX light cut 166,9 173,1 177,4 178,1 177,6 166,8SHDS heart cut 315,3 336,4 185,3 186,5 185,5 297,7Heart cut untreated 0,0 0,0 0,0 0,0 0,0 16,6UNIONFINER heavy cut 21,6 143,7 51,2 147,8 0,0 21,0

NHT heavy naphtha 0,0 0,0 95,8 95,8 95,8 0,0NHT medium naphtha 0,0 0,0 63,8 63,8 63,8 0,0Heavy cut to Diesel 114,4 0,0 97,6 0,0 148,9 115,0

Gasoline (% off FCC input) 50,60 50,82 50,56 50,83 50,60 50,59To Mogas (% off FCC input) 41,23 50,82 31,18 38,76 27,36 41,17To SC (% off FCC input) 0,00 0,00 12,03 12,07 12,03 0,00To Diesel (% off FCC input) 9,36 0,00 7,35 0,00 11,22 9,41To Diesel & LCO (% off …) 19,07 9,65 17,02 9,65 20,86 19,11

Exhibit 7: Quality of FCC gasoline for MogasScenario 1 2 3 4 5 6Density (kg/m3) 717,5 742,5 712,4 738,1 692.8 717,5S (ppm wt) 13,1 11,5 12,4 11,0 13,5 27,4RON 89,7 91,0 90,7 91,8 89,9 89,7MON 79,1 80,1 79,8 80,8 79,0 79,1E 70 36,7 30,2 48,1 39,1 54,8 36,9E100 61,4 50,2 63,4 51,6 72,3 61,4E150 96,0 79,3 91,3 74,7 100,0 96,1E210 100,0 100,0 100,0 100,0 100,0 100,0Aromatics (%vol) 18,0 31 18,7 32,0 8,5 17,9Benzene (%vol) 0,98 0,76 1,02 0,80 1,16 0,98

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Exhibit 8: Utilization of important CRC´s capacities (% of Databook capacity)Scenario 1 2 3 4 5 6NRL-CDU 100,0 100,0 100,0 100,0 100,0 100,0AVD-CDU 100,0 100,0 100,0 100,0 100,0 100,0NRK-CDU 100,0 91,0 100,0 93,6 100,0 100,0FCC 92,1 96,9 100,0 99,6 100,0 92,1FCC - 3CS 92,0 97,2 99,9 100,0 99,9 92,0FCC - SHDS 93,5 99,7 50,6 55,3 50,0 88,6FCC - UNIONFINER 67,2 71,0 73,5 73,0 73,6 67,2NRK - NHT 94,7 81,4 117,2 107,7 117,1 94,7NRK - SR 100,0 73,5 100,0 88,1 100,0 100,0

Exhibit 9: Changes in transfer of components between CRC´s refineries (delta kt/yr)Scenario 1 2 3 4 5 6Litvínov -> KralupySum; includes * Base 140,3 19,9 115,5 53,3 1,3

Reformate (pipeline) Base -22,5 -24,3 -59,6 -13,2 1,3Hydrotreated Kero Base 17,5 -20,6 16,9 -15,5 0,1Hydrocrackate Base 145,2 64,8 158,2 82,0 0,0

Kralupy -> Litvínov 0,0Sum; includes * Base 105,9 49,2 88,0 88,1 -0,5

Naphtha Base 59,1 156,0 138,3 156,8 -2,6MTBE Base -0,5 1,9 -0,2 5,8 0,0FCC Gasoline pool Base 54,8 -85,7 -43,9 -72,0 2,1LLCO Base -8,0 17,4 -6,7 20,6 0,0

Note: * Not all individual transfers reported here

Exhibit 10: Production of the main commodities in CRC (delta kt/yr)Scenario 1 2 3 4 5 6Mogas Base 0,0 -37,1 0,0 -113,4 0,0JET Base -27,1 0,0 -23,3 0,0 0,0Diesel Base -167,7 -17,5 -141,9 38,9 -1,1SC Feed Base 0,0 0,0 0,0 0,0 0,0

SC naphtha Base 145,2 90,8 158,2 97,0 0,0SC hydrocrackate Base -145,2 -90,8 -158,2 -97,0 0,0

Exhibit 11: Impact on refinery margin (%)Scenario 1 2 3 4 5 6Refinery Margin Base -3,18 -0,98 -3,03 -1,08 0,03

Results presented in the exhibits above can be summarized as follows:

• Studied scenarios have evidently huge impact on CRC´s capacities utilization of gasoline related units, transfers, production of the main commodities, and refinery margin. They have also impact on capacity utilization of the Kralupy refinery, however not Litvínov one.

• Up to 11 %wt of FCC feed can be re-routed from Mogas to Diesel pool, and 12 %wtto SC feed pool. FCC gasoline volume blended into Mogas can be reduced from 51 to 27 %wt. Diesel yield of the Kralupy FCC unit can be increased to almost 21 %wt,considering also LCO. These results are changing view of the FCC unit performance.

• As concerns pooled FCC gasoline: Density, distillation and aromatics are impacted in individual schemes significantly and vary in broad range (aromatics for example from

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8,5 to 32,0 % vol), on the other hand sulfur content, RON, MON, and benzene contentare not impacted so much.

• Routing FCC heavy cut exclusively to Mogas pool as per scenarios 2 and 4 has significant impact on properties of FCC pooled gasoline, reduces SR capacity utilization, and Diesel and JET production drops.

• Routing possible maximum of FCC hear cut to NHT has impact on capacity utilization of this unit (a revamp would be necessary). Almost all unselectively treated FCC heart cut is transferred as a feed for SC, because SR unit in Kralupy is fully utilized already in the base scenario. There is surplus of SR feed.

• Alternative routing of heart and heavy cuts shows interesting impact on SC and FCC diet, increasing volume of naphtha for SC unit on account of hydrocrackate and transferring surplus of hydrocrackate to feed FCC unit, see scenarios 2 to 5.

• In limited Mogas market, routing FCC gasoline out of Mogas pool increases capacity utilization of the Kralupy FCC unit.

• Scenarios 1, 3, 5, and 6, allowing blending of FCC heavy cut to Diesel, are economically more profitable then other ones. Solution implemented into CRC´s SP(scenario 1) represents practically the best possible alternative.

• Evaluation of individual scenarios can change in relation to continuously developingproduction premises and priorities. However, for CRC is central the existence of flexibility to adapt on these changing premises.

As concerns individual scenarios, it is possible to add:

• Scenario 1: Majority of produced FCC heart cut is blended into Diesel. However, the FCC unit and the FCC downstream units are not utilized fully.

• Scenario 2: Max FCC gasoline volume is blended into Mogas. FCC gasoline has high density, aromatics content, and octane numbers. Crude processing in the Kralupyrefinery drops in relation to previous scenario. Low capacity utilization of SR unit could cause problem as concerns hydrogen balance in Kralupy on the end of SR catalyst circle. Transfers are increasing in both directions, e.g. also related costs. Diesel production drops significantly and correspondingly to volume of FCC heavy cut re-routed from Diesel to Mogas pool. As concerns refinery margin, for a Mogas limited and Diesel open market is this scenario the worst one.

• Scenario 3: About 45% of hear-cut is treated unselectively in NHT and delivered as a feed for SC. Volume of heavy cut blended into Diesel is lower in this scenario than in base scenario because heavy cut is substituting heart cut in the FCC gasoline pool. Utilization of SHDS unit is naturally very low in this scenario. Heart and heavy cuts could be therefore combined and treated on SHDS only and UNIONFINER can be shut-downed. Impact on transfers, production, and refinery margin are only moderate.

• Scenario 4: Closing of FCC heavy cut to Diesel here is more important than routing of heart cut to NHT, therefore this scenario is similar to scenario 2. Interesting is comparison of refinery margins, which signalizes that in current situation unselective treating certain portion of heart cut could be beneficial.

• Scenario 5: It corresponds to max SC feed and Diesel component yield from FCC in parallel, and consequently min FCC gasoline yield. The FCC gasoline is pooled lightcut and part of heart cut only. It is very light and it has very low content of aromatics.Reduced Mogas and increased Diesel production can be achieved in the same time!

• Scenario 6: Unselective treating of heart cut is not supported in LP model having opened all routes. Only change to the base scenario is bypassing of SHDS for certain

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small volume of heart cut, exploiting reserve in Mogas components sulfur balance andsaving variable costs of SHDS. However, results are very close to base scenario.

4. Conclusions

To achieve sustainable and reliable 10 ppm Mogas production, and deciding within investment and time limits, CRC developed an original and complex technological scheme ofFCC gasoline processing. The new 3CS unit, commissioned as a fast-track project and originally considered also as a “short period solution”, represents finally the central facility of scheme of selective treating and blending of FCC gasoline.

Results presented in this paper show possible huge impacts of a as concerns CAPEX relatively small and as concern purpose relatively specialized facility (3CS) on capacity utilization of gasoline related units, transfers, production of the main commodities, and CRC´s refinery margin.

CRC´s solution for 10 ppm S Mogas with 3CS allows to vary significantly volume (27 – 51% of the FCC input) and quality of FCC gasoline blended into Mogas, to increase yield of Diesel components from the FCC units up to 21% of the FCC input, and to produce about 12% of FCC feed as a SC feed. These results are changing view of Kralupy FCC technology performance.

Moreover, FCC light cut gasoline, which is not touched in this paper, represents further challenge for researching.

5. References

SVÁTA, Josef; KITTEL, Hugo: "Selection of the Best Technology for Selective Hydrogenation of FCC Gasoline for CRC and Impact on the Refinery Configuration". Proceedings of APROCHEM 2007conference, p.1357. Milovy, 16 – 18.4.2007.

6. Index of Abbreviations

3CS Three-Cut SplitterAVD Atmospheric Vacuum Distillation ComplexCAPEX Capital ExpendituresCDU Crude Distillation UnitCRC Czech Refining Company FCC Fluid Catalytic CrackingJET Aviation KeroseneLP Linear ProgrammingLPG Liquefied Petroleum GasesMON Motor Octane NumberNHT Naphtha HydrotreaterNRK New Refinery KralupyNRL New Refinery LitvínovRON Research Octane NumberSC Steam CrackingSHDS Selective HydrodesufurizationSP Strategic PlanSR Semiregenerative Reformer

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