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

Transcription

1 8 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 Manager tel , hugo.kittel@crc.cz Czech Refining Co. (CRC), O.Wichterleho 809, 78 Kralupy n.vlt.. 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 (CS) unit implemented as an important part of 0 ppm S Mogas solution in Česká rafinérská a.s. (CRC). This unit is based entirely on distillation 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 linear ming (LP) to find an optimal solution of development projects in refineries.. Analysis of problem - Three-Cut Splitter Genesis Clean Mogas solution in CRC has been already reported [SVÁTA, KITTEL, 007], therefore only 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 00. Original scheme of gasoline production in the unit was relatively simple, see exhibit. Exhibit : Original FCC gasoline scheme APROCHEM 009 Odpadové fórum Milovy

2 Two gasoline fractions (light and heavy cut) were withdrawn from the main FCC fractionator.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 0 ppm S and it was planned to blend all FCC gasoline into Mogas. Exhibit : CS unit in the Kralupy refinery CS unit was implemented in CRC as a fast-track investment solution for 0 ppm S Mogas. It is based on a Shell Global Solutions, Inc. technology. The idea was to split of full range FCC gasoline into three fractions (light-, heart-, and heavycuts) 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. CS and reconstructed NHT were commissioned and operated successfully in the Kralupy refinery since Jan. 00, see exhibit. Having CS unit in operation, it was considered also as a part of 0 ppm S Mogas solution. In order to minimize CAPEX necessary to achieve a 0 ppm S in Mogas, technological scheme of FCC gasoline desulfurization was improved adding a new Selective Hydrodesulfurization (SHDS) unit downstream of CS (PRIME G+ technology, commissioned in Oct. 007). Corresponding technological scheme see exhibit. Exhibit : New FCC gasoline scheme APROCHEM 009 Odpadové fórum Milovy

3 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 0 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 and, 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.. Results - Three-Cut Splitter Opportunities Exhibit : CS yields Yield (%wt) Density (kg/m) S (ppm wt) MON E 70 E00 E0 E0 Light cut 7 9 8,0 Heart cut , 9,0 9,0 Heavy cut 88 8, 9 Standard yields and base properties of CS cuts as per current Databook of the Kralupy refinery are in exhibit. Being separately treated, the cuts are again repooled 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 Diesel c) 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 a reforming feed. These options have been studied exploiting CRC s Development Model based on LP. Six scenarios have been defined, differing from each other in way of processing of FCC cuts:. scenario, implemented in the CRC s Strategic Plan. It is corresponding to optimized FCC heavy cut blending into Diesel and maximized Diesel production, as forecasted for the future.. 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.. FCC heart cut partially unselectively treated using max available capacity on NHT. Heavy cut to Diesel optimized. FCC heart cut partially unselectively treated using max available capacity on NHT, heavy cut to Diesel closed. This resembles the original CRC s 0 ppm S Mogas solution, but having still part of heart cut selectively treated in the new SHDS unit.. 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. APROCHEM 009 Odpadové fórum Milovy

4 . 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 ) Individual scenarios listed above and focusing on alternative processing of FCC heart and heavy cuts can be characterized as follows: Exhibit : Studied scenarios Heart cut to NHT Heavy cut to diesel 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 NHT unit, 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 - : Exhibit : Distribution of FCC gasoline (kt/yr, % of FCC input) CS Feed FCC gasoline to Mogas MEROX light cut SHDS heart cut Heart cut untreated UNIONFINER heavy cut NHT heavy naphtha NHT medium naphtha Heavy cut to Diesel 8, 0,8,9,,,,, 7,,,7 7,,9 77, 8,, 9,8,8 97, 7,, 78, 8, 7,8 9,8,8 7,, 77, 8, 9,8,8 8,9 8, 0,,8 97,7,,0,0 Gasoline (% off FCC input) To Mogas (% off FCC input) To SC (% off FCC input) To Diesel (% off FCC input) To Diesel & LCO (% off ) 0,0, 0 9, 9,07 0,8 0, , 0,,8,0 7, 7,0 0,8 8,7,07 0 9, 0,0 7,,0, 0,8 0,9,7 0 9, 9, 7,, 90,7 79,8 8,, 9, 8,7,0 78,,0 9,8 80,8 9,, 7,7,0 0,80 9.8, 89,9 79,0,8 7, 8,, 77, 7, 89,7 79,,9, 9, 7,9 0,98 Exhibit 7: Quality of FCC gasoline for Mogas Density (kg/m) S (ppm wt) RON MON E 70 E00 E0 E0 Aromatics (%vol) Benzene (%vol) 77,, 89,7 79,,7, 9,0 8,0 0,98 APROCHEM 009 Odpadové fórum 009 7,, 9,0 80, 0, 0, 79, 0, Milovy

5 Exhibit 8: Utilization of important CRC s capacities (% of Databook capacity) NRL-CDU AVD-CDU NRK-CDU FCC FCC - CS FCC - SHDS FCC - UNIONFINER NRK - NHT NRK - SR 9, 9,0 9, 7, 9,7 9,0 9,9 97, 99,7 7,0 8, 7, 99,9 0, 7, 7, 9, 99,, 7,0 07,7 88, 99,9 7, 7, 9, 9,0 88, 7, 9,7 Exhibit 9: Changes in transfer of components between CRC s refineries (delta kt/yr) Litvínov -> Kralupy Sum; includes * Reformate (pipeline) Hydrotreated Kero Hydrocrackate Kralupy -> Litvínov Sum; includes * Naphtha MTBE FCC Gasoline pool LLCO Note: * Not all individual transfers reported here 0, -, 7,, 9,9 -, -0,,8, -9,,9 8,, -, -, 8,0 0,9 9, -0,,8-8,0 9,,0,9-8,7 7, 88,0 8, -0, -,9 -,7 88,,8,8-7,0 0, Exhibit 0: Production of the main commodities in CRC (delta kt/yr) Mogas JET Diesel SC Feed SC naphtha SC hydrocrackate -7, -7,7, -, Exhibit : Impact on refinery margin (%) Refinery Margin -,8-7, -7, 90,8-90,8 -, -,9 8, -8, -, 8,9 97,0-97,0-0,98,, 0, -0, -,, -,0 -,08 -, 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 %wt of FCC feed can be re-routed from Mogas to Diesel pool, and %wt to SC feed pool. FCC gasoline volume blended into Mogas can be reduced from to 7 %wt. Diesel yield of the Kralupy FCC unit can be increased to almost %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 APROCHEM 009 Odpadové fórum Milovy

6 8, to,0 % vol), on the other hand sulfur content, RON, MON, and benzene content are not impacted so much. Routing FCC heavy cut exclusively to Mogas pool as per scenarios and 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 to. In limited Mogas market, routing FCC gasoline out of Mogas pool increases capacity utilization of the Kralupy FCC unit. s,,, and, allowing blending of FCC heavy cut to Diesel, are economically more profitable then other ones. Solution implemented into CRC s SP (scenario ) represents practically the best possible alternative. Evaluation of individual scenarios can change in relation to continuously developing production 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: : Majority of produced FCC heart cut is blended into Diesel. However, the FCC unit and the FCC downstream units are not utilized fully. : Max FCC gasoline volume is blended into Mogas. FCC gasoline has high density, aromatics content, and octane numbers. Crude processing in the Kralupy refinery 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. : About % 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. : 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. Interesting is comparison of refinery margins, which signalizes that in current situation unselective treating certain portion of heart cut could be beneficial. : 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 light cut 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! : 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 APROCHEM 009 Odpadové fórum Milovy

7 small volume of heart cut, exploiting reserve in Mogas components sulfur balance and saving variable costs of SHDS. However, results are very close to base scenario.. Conclusions To achieve sustainable and reliable 0 ppm Mogas production, and deciding within investment and time limits, CRC developed an original and complex technological scheme of FCC gasoline processing. The new CS 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 (CS) on capacity utilization of gasoline related units, transfers, production of the main commodities, and CRC s refinery margin. CRC s solution for 0 ppm S Mogas with CS allows to vary significantly volume (7 % of the FCC input) and quality of FCC gasoline blended into Mogas, to increase yield of Diesel components from the FCC units up to % of the FCC input, and to produce about % 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.. 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 007 conference, p.7. Milovy, Index of Abbreviations CS AVD CAPEX CDU CRC FCC JET LP LPG MON NHT NRK NRL RON SC SHDS SP SR Three-Cut Splitter Atmospheric Vacuum Distillation Complex Capital Expenditures Crude Distillation Unit Czech Refining Company Fluid Catalytic Cracking Aviation Kerosene Linear Programming Liquefied Petroleum Gases Motor Octane Number Naphtha Hydrotreater New Refinery Kralupy New Refinery Litvínov Research Octane Number Steam Cracking Selective Hydrodesufurization Strategic Plan Semiregenerative Reformer APROCHEM 009 Odpadové fórum Milovy