Product Quality and Policy A steady evolution in product specifications caused by an endless wave of fresh environmental regulations plays a major role in the development of petroleum refining technologies India has also put in place Auto Fuel policy prepared by group of experts and accepted by the government of India for the implementation in the country. The policy provides a clear cut road map for changes in vehicular technology and corresponding fuel quality for the whole country. It is estimated that the existing domestic oil refineries in addition to the investment of Rs 10,000 crores already made to achieve Euro stage II / Bharat Stage II auto fuel specifications would need to incur an additional investment of around Rs.18,000 crores by the year 2005. Further investment of around Rs.12,000 crores will need to be made during the period 2005-2010.
Constraints Faced by Refiners 1.Spiraling crude cost 2.Current refinery configuration not able to meet clean fuels specifications for MS and HSD. 3.Lower distillate production (production of more bottoms) 4.Need to produce value added products 5.Older technologies (High energy consumption) 6.Environmental issues
Gasoline Specifications Characteristics Bharat II Bharat III (Equivalent to meet EURO III emission Norms) Bharat IV (Equivalent to meet EURO III emission Norms) Density @ 15 o C, Kg/m 3 710-770720-775720-775 Distillation a) Recovery up to 70 o C, % Vol. b) Recovery up to 100 o C, % Vol. c) FBP (max), o C 10-4540-7021510-4540-7021010-4540-70210 RON, Min. 88 (Reg.) 93 (Premium) 91 (Reg.) 95 (Premium) 91 (Reg.) 95 (Premium AKI, Min 84 (reg.) 88 (Premium) 81 (Reg., MON)) 85 (Premium, MON) 81 (Reg., MON)) 85 (Premium, MON) Sulphur, wt%, Max. 0.050.0150.0050 RVP, kPa, max 35-606060 Benzene Cointent, max (% vol) 3.0 (Metro) 5.0 (rest) 11 Olefin Content, max, % volume -21(Reg.) 18 (Premium) 21(Reg.) 18 (Premium Aromatics Contents, max, % volume -4235
Major Changes in specifications Sulphur Reduction Benzene Reduction Aromatics Reduction Octane Retention RVP Limitation Olefins Limitation
Sulphur Reduction In gasoline Pool Main Sulphur contributor in Gasoline pool is FCC Naphtha Generally reducing ‘ S ’ in FCC naphtha may enable refinery to meet pool Sulphur specifications
FCC Naphtha Treatment Strategies to reduce ‘ S ’ content of FCC Naphtha may include : Processing of low Sulphur crudes End Point reduction of FCC Naphtha FCC Feed hydrotreating FCC Naphtha hydro treatment
FCC Feed Hydrotreating A large variety of technologies are available for FCC Feed hydro treatment. The benefits of these technologies are: Reduction in FCC gasoline Sulphur Improvement in FCC yields with respect to gasoline & LPG LCGO Sulphur reduction Lower FCC emissions However, all the technologies require large capital investments, and Hydrogen requirements are also very high.
FCC Naphtha Hydrotreating A large variety of technologies are available for FCC Naphtha hydro treatment. However, the main challenge is to retain Octane No. Available technologies are: (A)Conventional Hydrotreating (B)Selective Hydrotreating (C)Non – Selective Hydrotreating combined with Octane Recovery (D)Developing technologies e.g. Adsorption & selective hydrotreating combined with Sorption
FCC Naphtha Hydrotreating (A)Conventional Hydrotreating Conventional Hydrotreating achieves desulphurization with almost complete olefins saturation. Therefore causes substantial octane loss. Hence, may not be preferable with existing configurations of most of Indian Refineries that rely on FCC naphtha heavily to meet octane specification of MS Pool.
FCC Naphtha Hydrotreating (B)Selective Hydrotreating Selective Hydrotreating achieves desulphurization with very little olefins saturation, hence loss of octane is very minimal. This technology may be suitable for most of Indian Refineries.
FCC Naphtha Hydrotreating (C)Non-Selective Hydrotreating with Octane recovery Non-Selective Hydrotreating with Octane recovery achieves desulphurization with partial or total olefins saturation and employs other reactions e.g. Isomerization to gain lost octane during desulfurization. This technology may be the best suited for Indian refineries as some amount of LPG is also generated but proven ness of technology remains a issue.
FCC Naphtha Hydrotreating (D)Developing technologies Although new developing technologies are very promising yet the reliability and proven ness of the technology is an issue while selecting the technology for FCC Naphtha treatment.
FCC Naphtha Hydrotreating (E)Other Options Other options to meet gasoline Sulphur may also be built in while deciding the configuration of refinery. This may include routing heart-cut of FCC Naphtha splitter to Reformer. However, such strategies require thorough study as it may give rise to problems like benzene increase in reformate and also would require additional capacity in reformer.
Benzene Reduction In gasoline Pool Main Benzene contributor in Gasoline pool is Reformer If the reformer already exists, the choices to reduce benzene content in reformate are limited to options like lower operating severity, lower operating pressure and changes in catalyst formulation. However, these changes have limited effect on benzene content of reformate.
Benzene Reduction In gasoline Pool 1.Avoid Benzene Production 2.Convert or destroy benzene 3.Recover Benzene for Petrochemical production Benzene reduction options :
Benzene Reduction In gasoline Pool 1.Avoid Benzene Production: Pre-fractionation process scheme to reduce benzene content in reformate includes distillation of benzene precursors from the feed to reformer through a naphtha splitter. The precursors for benzene are Cyclohexane (CH), Methylcyclopentane (MCP) and the benzene contained in the Naphtha. The light naphtha containing the benzene precursors can be routed to a C5/C6 Isomerization Unit. This is the least expensive solution but has limitation of C7 content in ISOM feed. Also, since some benzene still will be formed in Reformer due to dealkalization of heavier aromatics and the dehydrocyclization of paraffins, this configuration will still not eliminate total benzene production in Reformer.
Benzene Reduction In gasoline Pool 2.Convert/ destroy Benzene : Another option is to postfractionate / extract the reformate and then hydrogenate the benzene into Cyclohexane which can then be routed to an ISOM unit to regain the octane loss in hydrotreating. The benzene rich stream from Reformate splitter can also be used as petrochemicals feed stock
Aromatics Reduction In gasoline Pool It may be difficult to meet aromatics specifications along with octane specification if the MS Pool is only a mix of Reformate and light naphtha / isomerate. In such case, octane boosting additives may be required. FCC Naphtha may dilute the aromatics in total pool but it has its own limitations due to high Sulphur and olefins content. Another option can be to reduce severity of operation in reformer but this will decrease the octane of reformate and also the hydrogen production. Changing feed cut points may also have little effect on Aromatics from Reformer
Aromatics Reduction In gasoline Pool Other options for reduction in aromatics content of gasoline pool can be production of Petrochemicals after extraction / fractionation of reformate. However, most of the refineries will have to manage the aromatics by dilution effect either through isomerate or through FCC Naphtha and / or ethrification / alkylation.
Olefins Management In gasoline Pool FCC gasoline is the main contributor for the olefins in MS Pool. FCC Naphtha hydrotreating can reduce olefins but with octane loss. Etherification of C5 cut of FCC Naphtha can help in achieving olefins targets. However, oxygenates future is uncertain.
Octane Management In gasoline Pool Octane recovery may be achieved by : 1.Light Naphtha Isomerization 2.Etherification 3.Alkylation 4.Reforming
Octane Management In gasoline Pool 1.Light Naphtha Isomerization: Benefits of this process are that the Isomerate produced from ISOM Unit is a good diluent in terms of sulfur, aromatics and olefins and provides octane boost to the gasoline pool. However, requires large capital investment and have limitations of high RVP.
Octane Management In gasoline Pool 2.Etherification: Since, oxygenates future is uncertain, this process may not be considered as a good option. 3.Alkylation: Benefits of this process are that the Alkylate is a good diluent in terms of sulfur, aromatics and olefins and provides octane boost to the gasoline pool. However, HF acid usage in the process posses a safety issue.
Octane Management In gasoline Pool 4.Reforming: Reformate is the main constituent of today ’ s MS pool which contributes towards octane improvement. However, due to its high aromatic content, its use has to be limited in order to achieve total MS quality.
Catalytic Reforming Catalytic reforming is used to improve the quality of naphtha from the crude distillation unit. The catalytic reforming unit uses a catalyst to allow the chemical reactions to take place under "reasonable" temperatures and pressure and "encourage" the desired hydrocarbons to be produced. This process provides higher octane material to the gasoline pool to help meet the octane specifications on the gasoline. The process also produces hydrogen which is used to remove sulfur from refinery streams in the hydrotreating processes. This process provides higher octane material to the gasoline pool to help meet the octane specifications on the gasoline. The process also produces hydrogen which is used to remove sulfur from refinery streams in the hydrotreating processes.
StreamAdvantagesLimitations Light Isomerate Low Density Nil Olefin /Sulfur /Benzene/Aromatics High RVP Reformate High RON Nil Sulfur/Low Olefins High Density/Aromatics Light FCC Gasoline High RON/Low Density High Sulfur/Olefins/ RVP Heavy FCC Gasoline Low Sulfur /Benzene olefins/RVP High Aromatics/ Low RON
LPG H2 ISOMERATE TREATED HEAVY FCC GASOLINE TREATED LIGHT FCC GASOLINE NAPHTHA SPLITTER UNIT NHT/CCR MSPOOLMSPOOL SELECTIVE HYDROGENATION & SPLITTER SECTION PRIME G+ UNIT NAPHTHA HYDROTRTEATER & ISOMERISATION MAKE UP H2 PURGE GAS H2 MAKE UP FROM CCR FG REFORMATE AXENS UNITS UOP UNITS SR FULL RANGE NAPHTHA FCC NAPHTHA GREEN FUELS & EMISSION CONTROL PROJECT, HPCL-MR MAKE UP H2
Product Blending Product blending is where the different petroleum fractions are combined together to make the final product. The fractions are mixed so they meet the specifications discussed earlier. Each product has a specific recipe that calls for the proper mix of petroleum fractions. For example, in order to make gasoline, the refiner would mix naphtha, reformate, catalytic gasoline, Isomerate, etc., so that the mixture had the required octane number, vapor pressure, sulfur level, aromatics content, etc. The process requires knowing these values for all of the components going into the blend. Product blending is where the different petroleum fractions are combined together to make the final product. The fractions are mixed so they meet the specifications discussed earlier. Each product has a specific recipe that calls for the proper mix of petroleum fractions. For example, in order to make gasoline, the refiner would mix naphtha, reformate, catalytic gasoline, Isomerate, etc., so that the mixture had the required octane number, vapor pressure, sulfur level, aromatics content, etc. The process requires knowing these values for all of the components going into the blend.
Conclusion There is no single best solution All the processes have advantages as well as drawbacks Optimum solution for technological option for meeting gasoline pool specifications is refinery specific For optimization of gasoline pool and selecting the best technology, a thorough study is called for taking into considerations specific to each refinery
Diesel Specifications Characteristics Bharat II Bharat III (Equivalent to meet EURO III emission Norms) Bharat IV (Equivalent to meet EURO IV emission Norms) Density @ 15 o C, Kg/m 3 820 - 860 820 - 845 820 – 845 Distillation a) Min. recovery at 350 o C, % Vol. b) Min. recovery at 370 o C, % Vol c) 95% Vol. recovery at o C, Max 8595--360--360 Cetane No., Min. 485151 Cetane Index, Min 464648 Sulphur, wt%, Max. 0.050.0350.005 Water Content, vol%, max 0.050.020.02 Flash Point, Abel Min, o C 353535 PAH, wt%, Max -1111
Major Changes in specifications Sulphur Reduction PAH Reduction Cetane Improvement Density Limitation Reduction of 95% distillation point
Sulphur Reduction in Diesel Options for Sulphur reduction in diesel are: 1.Choose crudes or condensate low in Sulphur levels This option has limitation and can not be sustained due to high price of low Sulphur crudes and also limited possibility of meeting EURO III / IV diesel specifications
Sulphur Reduction in Diesel 2.Purchase low sulfur diesel blend stock This option can be used if such a blend stock is readily available but only small quantities of low sulphur diesel can be produced from this option
Sulphur Reduction in Diesel 3.Install / revamp existing DHDS Unit Option to install a new DHDS / DHDT unit or to revamp the existing DHDS Unit is refinery specific as the hydraulic capacity requirements as well as design limitations / plot area availability factors vary with each refinery. Revamps of most of the existing units may require installation of additional reactor(s), catalyst change and / or improving recycle gas purity.
Aromatics Reduction in Diesel Options for Aromatics reduction in diesel are: 1.Choose high paraffinic crudes Choosing this option will depend upon the availability and overall refinery configuration as well as the profitability of refinery while running such crude. This option may also pose limitations in other process units e.g. Reformer.
Aromatics Reduction in Diesel 2.Purchase low aromatics diesel blend stock This option can be used if such a blend stock is readily available but only small quantities of low aromatics diesel can be produced from this option. Also refiners may opt to route high aromatic diesel streams to alternate products e.g. Fuel oil but this will affect overall refinery profitability and reduce diesel volumes.
Aromatics Reduction in Diesel 3.Severe Hydrotreating Aromatics reduction can be achieved with change in catalyst from CoMo to NiMo but this may limit catalyst bed temperatures due to equilibrium shift at high temperatures or else the conventional catalyst systems can be used at high pressures and low LSHV. For significant reduction of aromatics noble metal catalyst systems may be required which require high capital investment. Thus option for aromatics saturation is also very specific for each refinery.
Cetane Number Improvement in Diesel Options for Cetane Number improvement in diesel are: 1.Use Cetane Improving additives This option will be mainly driven by the economics of this option in comparison to other options and will also depend upon availability of such additives.
Cetane Number Improvement in Diesel 2.Mild hydrocracking & Aromatics saturation This option may call for an additional stage and will depend upon the feed characteristics and therefore is also specific for each refinery.
Density Reduction in Diesel Density reduction is achieved during deep hydrodesulphurization and depends upon the feedstock properties as well as on the operating conditions. Around 10-20 Kg/M 3 reduction can be expected as a result of sulphur removal and saturation of di- and tri- aromatic compounds. This combined with reduction in 95% distillation temperature will enable refiners to meet density specifications.
Reduction of 95% distillation point The best way of reducing 95% distillation point of the diesel is to adjust the draws of the crude distillation tower. This may result in reduction of diesel volume but will also help in density reduction, reduction in heavy aromatic compounds, refractive sulfur compounds that are difficult to treat will be removed from the feed and cold flow properties will also improve. Other option will be to go for mild hydrocracking.
Conclusion There is no universal single solution Optimum solution for technological option for meeting Diesel pool specifications is refinery specific Detailed study will help for an integrated solution
Technological Options for Bottoms of Barrel Up gradation
Bottoms of Barrel Up gradation Technologies Two types of technologies are available 1.By removal of carbon 2.By addition of H2 Following are the Processes for achieving the above objectives: 1.Removal of carbon – Visbreaking, Delayed coker, Solvent Deasphalting, Resid fluid catalytic cracking. 2.Addition of H2 – Catalytic Hydrocracking process.
Details of the Technologies I. VISBREAKER MERITS Mild thermal cracking without catalyst Vacuum gas oil to Hydrocracker as feed to improve refinery distillate yield, if vacuum flasher is installed Low investment DEMERITS Leaves behind 70% to 75% weight - very heavy residue Production of very large quantities of furnace oil Stability problems in FO
Details of the Technologies II. DELAYED COKER MERITS Deep Thermal cracking process without catalyst. The conversion is high, the rest being Raw Petroleum Coke (RPC) Low Capital Investment. The ISBL capital investment foe 2.0 MMTPA capacity is Rs 400 to 450 crores. Low operating cost compared DEMERITS The Coker gas oil cetane number is 30 to 35. Needs high pressure DHDT to meet Euro-III & Euro IV specifications Coker Naphtha needs De-Sulphurisation Large space required for Coke yard Coke disposal may be a potential problem
Details of the Technologies I. SOLVENT DEASPHALTING MERITS Recovers paraffin components of the Short Residue. This recovered stream is feed to FCC or HCU units (Limited to MCR, asphaltenes and metals) Low investment cost DEMERITS DAO recovery will be limited to 40%-50% wt. The residue from SDA unit, Pitch, is very hard and has higher concentration of metals, Conradson carbon, etc. Thus the pitch is unsuitable to be sold as Bitumen. This need to be diluted
Details of the Technologies SHORT RESIDUE BASED OR PETROLEUM COKE BASED INTREGRATED GASIFICATION COMBINED CYCLE (IGCC) MERITS Partial oxidation of Short residue or petroleum coke to Syn Gas (CO+H2) in the presence of steam. No catalyst is needed Further, H2, Power and steam can be produced from the Syn Gas. Syn Gas itself can be sold to Down stream fertilizer industry or petrochemical Industry. Completely converts bottom of the barrel to valuable and clean products. DEMERITS Solid wastes like heavy metal sludge is produced. This may pose disposal problems. Investment is very high. The practical problem of recovering money for power sold to State Electricity board exists.
Hydroprocessing Reactors The Hydro processing technologies available today employs various types of reactors Fixed bed, Fluidized or Ebullating bed and slurry phase reactors are the commonly used types. Selective Hydrotreating Fixed Bed Reactors Expanded Bed Reactors Slurry Phase Reactors
Hydroprocessing Reactors 1] Fixed Bed Reactors Most early reactors designed were of fixed bed type. These reactors have been able to hydrocrack atmospheric residue successfully, but their ability to handle vacuum residue has not been convincingly proved yet The main disadvantage in this type of reactor is the difficulty in handling catalyst due to plugging and pressure drop problems
Hydroprocessing Reactors 2] Expanded Bed Reactors In expanded bed reactors the catalyst is in fluidized state. This results in good contact between catalyst, resid feed and hydrogen rich gas. These reactors have processed vacuum resid successfully.They are more flexible than fixed bed reactors, don ’ t get clogged or chocked, have lower pressure drop and can be operated at higher temperatures. Catalyst handling does not pose problems and hence there is better control over catalyst activity and product quality. Ammoco\Lumus crest and HRI (Hydrogen research Incorporation) Texaco use expanded bed reactors in their hydrocracking processes. Both the processes can use highly contaminated vacuum residue as feed giving high conversion.
Hydroprocessing Reactors 3] Slurry Phase Reactors Here the liquid feed,catalyst and gas are in a mixed state. This results in good dispersion of the catalyst and hence good contacting. Petro canada and the canadian centre for Mineral and energy Technology have developed a slurry process which uses a cheap iron containing additive to control coking and eliminate hot spots.The process has been tested on a 5000 bbls/day demonstration plant. An attractive feature of this process is that the operating pressure is significantly lower than in other hydrocracking processes. Hence investment and operating costs are expected to be lower. Unocal has integrated the CANMET process with its own UNIONFINING and UNICRAcKING Processes to form the U-CAN process.
Summary of the Salient features of the available technologies S. No Bottoms Up gradation Processes Plant cost comparison Advantages / Disadvantages 1Visbreaker Base cost (BC) Reduces FO make but not Substantially FO quality issue – Not addressed 2 Solvent De asphalting 85 % of BC Reduces FO make but not Substantially FO quality issue – Not addressed 3Delayed Coker200 % of BC Nil FO make Increases Light and middle Refinery Yield patterns Coke disposal / Utilization to be addressed 4 Hydro Processing 500 % of BC Reduces FO make Produces excellent quality of FO
Economic evaluation of various alternatives 1.Feed stock type 2.Plant size 3.Market demand for various products 4.Initial cost 5.Operating cost 6.Integrability of the process with existing units 7.Quality of the products 8.Flexibility of the process in respect of feed quality and/or product variation 9.Environmental factors 10.Finally the economic returns.
Concluding Remarks The capacity utilization of Indian refineries compares favorably with the utilization capacity of refineries in the developed world. The product pattern of refineries has undergone significant changes with addition and modernization of secondary processing facilities and availability of appropriate mix of crudes. India is becoming a major global market for petroleum products. Consumption of petroleum products increased from 57 MMTPA in 1991- 92 to 107 MMTPA in 2000 and forecasts for 2005 put market volume at around 164 MMTPA. The Hydrocarbon Vision 2025 report estimates future refining demand at 368 MMTPA by 2025. The auto fuel policy of government of India provides a clear cut road map for changes in vehicular technology and corresponding fuel quality for whole of the country. It further suggests taking into account security of supply and prevailing logistic perspective that liquid fuels should remain as main auto fuels in the whole country while encouraging CNG/LPG in areas affected by higher pollution levels.