Petroleum processing
- 3. PRESENTED BY: MADAN LAL KHATRI K16PG55(3rd year student) Petroleum and Natural Gas Dept: Muet SZAB Campus Khairpur mir’s
- 4. CONTENTS: • 1. Introduction • 2. Physical Processes • 3. Thermal Processes • 4. Catalytic Processes • 5. Conversion of Heavy Residues
- 5. 1.0) INTRODUCTION: • Petroleum refining processes are the chemical engineering processes and other facilities used in petroleum refineries (also referred to as oil refineries) to transform crude oil into useful products such as • liquefied petroleum gas (LPG), • gasoline or petrol, • kerosene, • jet fuel, • diesel oil • fuel oils.
- 6. • Over 600 refineries worldwide have a total annual capacity of more than 3500 x 106 tones. • Goal of oil refining is twofold: • i. production of fuels for transportation, power generation and heating; and • ii. production of raw materials for the CPI(Consumer Price Index (CPI) • Some modern petroleum refineries process as much as 800,000 to 900,000 barrels (127,000 to 143,000 cubic meters) per day of crude oil 1.0) INTRODUCTION:
- 7. 2.0) REFINING PROCESSES 2.1)Physical Separation Process Distillation Solvent extraction Propane deasphalting Solvent dewaxing Blending 2.2)Chemical Catalytic Conversion Processes Hydro treating Catalytic reforming Catalytic cracking Hydrocracking Catalytic dewaxing Alkylation Polymerization Isomerization 2.3)Thermal Chemical Conversion Processes Visbreaking Delayed coking Flexi coking
- 9. • Desalting/dehydration • How does distillation work? • Crude distillation • Propane deasphalting • Solvent extraction and dewaxing • Blending 2.1)PHYSICAL SEPARATION PROCESS:
- 10. • Crude oil often contains water, inorganic salts, suspended solids, and water-soluble trace metals. • Step 0 in the refining process is to remove these contaminants so as to reduce corrosion, plugging, and fouling of equipment and to prevent poisoning catalysts in processing units. • The two most typical methods of crude-oil desalting are chemical and electrostatic separation, and both use hot water as the extraction agent. • In chemical desalting, water and chemical surfactant (demulsifiers) are added to the crude, which is heated so that salts and other impurities dissolve or attach to the water, then held in a tank to settle out. • Electrical desalting is the application of high-voltage electrostatic charges to concentrate suspended water globules in the bottom of the settling tank. Surfactants are added only when the crude has a large amount of suspended solids. 2.1.0)DESALTING/DEHYDRATION
- 11. • The crude oil feedstock is heated to 65-180°C to reduce viscosity and surface tension for easier mixing and separation of the water. The temperature is limited by the vapor pressure of the crude-oil feedstock. • In both methods other chemicals may be added. Ammonia is often used to reduce corrosion. Caustic or acid may be added to adjust the pH of the water wash. 2.1.0)DESALTING/DEHYDRATION CONT….
- 13. • Distillation is defined as: • – a process in which a liquid or vapour mixture of two or more substances is separated into its component fractions of desired purity, by the application and removal of heat. 2.1.1)DISTILLATON:
- 14. • Distillation is based on the fact that the vapour of a boiling mixture will be richer in the components that have lower boiling points. • Thus, when this vapour is cooled and condensed, the condensate will contain the more volatile components. At the same time, the original mixture will contain more of the less volatile components. • • Distillation is the most common separation technique and it consumes enormous amounts of energy, both in terms of cooling and heating requirements. • Distillation can contribute to more than 50% of plant operating costs. 2.1.1)DISTILLATON CONT….
- 15. • Process Objective: • To distill and separate valuable distillates (naphtha, kerosene, diesel) and atmospheric gas oil (AGO) from the crude feedstock. • Primary Process Technique: • – Complex distillation • Process steps: • – Preheat the crude feed utilizing recovered heat from the product streams • – Desalt and dehydrate the crude using electrostatic enhanced • liquid/liquid separation (Desalter) • – Heat the crude to the desired temperature using fired heaters 2.1.1)CDU PROCESS
- 16. • – Flash the crude in the atmospheric distillation column • – Utilize pumparound cooling loops to create internal liquid reflux • – Product draws are on the top, sides, and bottom 2.1.1)CDU PROCESS CONT….
- 17. • To extract more distillates from the atmospheric residue, the bottom from the atmospheric CDU is sent to the vacuum distillation unit. • ◦ The vacuum unit distillates are classified as light vacuum gas oil (LVGO), medium vacuum gas oil (MVGO), and heavy vacuum gas oil (HVGO). In addition a vacuum residue is produced. If the distillates are feed to downstream conversion process, their sulphur, metal and asphaltene content should be reduced by hydrotreating or hydroprocessing. • ◦ In some refineries the whole atmospheric residue is hydroprocessed before vacuum distillation. The vacuum unit can also be used to produce lubrication oil grade feed stocks. This depends on the quality of the crude oil feed to the refinery as only special types of crude can produce lube grade feed stocks. 2.1.2) VACUUM DISTILLATION UNIT (VDU):
- 18. • – To recover valuable gas oils from reduced crude via vacuum distillation. • Primary Process Technique: • – Reduce the hydrocarbon partial pressure via vacuum and stripping steam. • Process steps: • – Heat the reduced crude to the desired temperature using fired heaters • – Flash the reduced crude in the vacuum distillation column • – Utilize pump around cooling loops to create internal liquid reflux • – Product draws are top, sides, and bottom 2.1.2) VACUUM DISTILLATION UNIT (VDU):
- 19. • In this process, lube oil stock is treated by a solvent, such as N-methyl pyrrolidone (NMP), which can dissolve the aromatic components in one phase (extract) and the rest of the oil in another phase (raffinate). The solvent is removed from both phases and the raffinate is dewaxed. 2.1.3)SOLVENT EXTRACTION
- 20. • This is the only physical process where carbon is rejected from heavy petroleum fraction such as vacuum residue. Propane in liquid form (at moderate pressure) is usually used to dissolve the whole oil, leaving asphaltene to precipitate. The deasphalted oil (DAO) has low sulphur and metal contents since these are removed with asphaltene. This oil is also called ‘‘Bright Stock’’ and is used as feedstock for lube oil plant. The DAO can also be sent to cracking units to increase light oil production. • ◦ When the crude oil enters the unit, it carries with it some brine in the form of very fine water droplets emulsified in the crude oil. The salt content of the crude measured in pounds per thousand barrels (PTB) can be as high as 2000. Desalting of crude oil is an essential part of the refinery operation. The salt content should be lowered to between 5.7 and 14.3 kg/1000 m3 (2 and 5 PTB). Poor desalting has the following effects: • ◦ Salts deposit inside the tubes of furnaces and on the tube bundles of heat exchangers creating fouling, thus reducing the heat transfer efficiency; • 1) Corrosion of overhead equipment; • 2)The salts carried with the products act as catalyst poisons in catalytic cracking units. 2.1.4) SOLVENT DE-ASPHALTING
- 21. • Process:To remove the salts from the crude oil, the water-in oil emulsion has to be broken, thus producing a continuous water phase that can be readily separated as a simple decanting process. The process is accomplished through the following steps • Water washing • Heating • Coalescence 2.1.4) SOLVENT DE-ASPHALTING
- 22. • The raffinate is dissolved in a solvent (methyl ethyl ketone, MEK) and the solution is gradually chilled, during which high molecular weight paraffin (wax) is crystallized, and the remaining solution is filtered. The extracted and dewaxed resulting oil is called ‘‘lube oil’’. In some modern refineries removal of aromatics and waxes is carried out by catalytic processes in ‘‘all hydrogenation process’’. 2.1.5)SOLVENT DEWAXING
- 23. • Blending is the physical mixture of a number of different liquid hydrocarbons to produce a finished product with certain desired characteristics. • • Products can be blended in-line through a manifold system, or batch blended in tanks and vessels. • • In-line blending of gasoline, distillates, jet fuel, and kerosene is accomplished by injecting proportionate amounts of each component into the main stream where turbulence promotes thorough mixing. • • Additives including octane enhancers, anti-oxidants, anti-knock agents, gum and rust inhibitors, detergents, etc. are added during and/or after blending to provide specific properties not inherent in hydrocarbons. 2.1.6)BLENDING
- 24. • Fluid catalytic cracking (FCC) is the main player for the production of gasoline. The catalyst in this case is a zeolite base for the cracking function. The main feed to FCC is VGO and the product is gasoline, but some gas oil and refinery gases are also produced. • Process Objective: • – To convert low value gas oils to valuable products (naphtha and diesel) and slurry oil. • • Primary Process Technique: • – Catalytic cracking increases H/C ratio by carbon rejection in a continuous process. 2.2.1) CATALYTIC CRACKING
- 25. • ◦ Process steps: • – Gas oil feed is dispersed into the bottom of the riser using steam • – Thermal cracking occurs on the surface of the catalyst • – Disengaging drum separates spent catalyst from product vapors • – Steam strips residue hydrocarbons from spent catalyst • – Air burns away the carbon film from the catalyst in either a “partial-burn” or “full- burn” mode of operation • – Regenerated catalyst enters bottom of riser-reactor 2.2) CATALYTIC CRACKING CONT….
- 26. • Alkylation is the process in which isobutane reacts with olefins such as butylene (C ¼ 4 ) to produce a gasoline range alkylate. The catalyst in this case is either sulphuric acid or hydrofluoric acid. The hydrocarbons and acid react in liquid phase. Isobutane and olefins are collected mainly from FCC and delayed coker. • ◦ Process Objective: • – To combine light olefins (propylene and butylene) with isobutane to form a high octane gasoline (alkylate). • Primary Process Technique: • – Alkylation occurs in the presence of a highly acidic catalyst (hydroflouric acid or sulfuric acid). 2.2.2) ALKYLATION:
- 27. • • Process steps: • Olefins from FCC are combined with IsoButane and fed to the HF Reactor where alkylation occurs • Acid settler separates the free HF from the hydrocarbons and recycles the acid back to the reactor • A portion of the HF is regenerated to remove acid oils formed by feed contaminants or hydrocarbon polymerization • Hydrocarbons from settler go to the DeIsobutanizer for fractionating the propane and isobutane from the n-butane and alkylate • Propane is then fractionated from the isobutane; propane as a product and the isobutane to be recycled to the reactor • N-Butane and alkylate are deflourinated in a bed of solid adsorbent and fractionated as separate products. 2.2.2) ALKYLATION CONT…
- 28. • Isomerization of light naphtha is the process in which low octane number hydrocarbons (C4, C5, C6) are transformed to a branched product with the same carbon number. This process produces high octane number products. One main advantage of this process is to separate hexane (C6) before it. • Process Objective: • – To convert low-octane n-paraffins to high-octane iso-paraffins. 2.2.3) ISOMERIZATION:
- 29. • Process steps: • Desulfurized feed and hydrogen are dried in fixed beds of solid • dessicant prior to mixing together • – The mixed feed is heated and passes through a hydrogenation reactor to saturate olefins to paraffins and saturate benzene • The hydrogenation effluent is cooled and passes through a isomerization reactor • The final effluent is cooled and separated as hydrogen and LPGs which typically go to fuel gas, and isomerate product for gasoline blending. 2.2.3) ISOMERIZATION CONT…
- 30. • This is a mild thermal cracking process used to break the high viscosity and pour points of vacuum residue to the level which can be used in further downstream processes. In this case, the residue is either broken in the furnace coil (coil visbreaking) or soaked in a reactor for a few minutes (soaker visbreaker). The products are gases, gasoline, gas oil and the unconverted residue. • Feed Sources • The feed to visbreaker can be either • Atmospheric residue (AR) • Vacuum residue (VR) • Vacuum residue is the heaviest distillation product and it contains two fractions: heavy hydrocarbons and very heavy molecular weight molecules, such as asphaltene and resins. 2.3) VISBREAKING
- 31. • When a hydrocarbon is heated to a sufficiently high temperature thermal cracking occurs. This is sometimes referred to as pyrolysis (especially when coal is the feedstock). When steam is used it is called steam cracking. We will examine two thermal processes used in refineries. • • Visbreaking • • Delayed coking 2.3)THERMAL PROCESS:
- 32. • The main reaction in visbreaking is thermal cracking of heavy hydrocarbons, since resins are holding asphaltene and keep them attached to the oil. The cracking of resinwill result in precipitation of asphaltene forming deposits in the furnace and will aslo produce unstable fuel oil. The cracking severity or conversion is limited by the storage stability of the final residual fuel. • Visbreaking Severity • ◦ The severity of visbreaking can be defined according to the following • ◦ considerations: • Stability of residual fuel on storage • ◦ Material produced that boils below 160 0C (330 0F) (conversion) • ◦Percent reduction in product viscosity (25–75%) 2.3.1) VISBREAKING REACTIONS:
- 33. • These processes are considered as upgrading processes for vacuum residue. • ◦ Coking is the process of carbon rejection from the heavy residues producing lighter components lower in sulphur, since most of the sulphur is retained in the coke. • Coke can be formed from the condensation of polynuclear aromatics (such as nbutylnapthalene) • ◦ Two types of coking • 1. Delayed Coking • 2. Flexicoking 2.3.2)COKING:
- 34. • This process is based on the thermal cracking of vacuum residue by carbon rejection forming coke and lighter products such as gases, gasoline and gas oils. Three types of coke can be produced: sponge, shot and needle. The vacuum residue is heated in a furnace and flashed into large drums where coke is deposited on the walls of these drums, and the rest of the products are separated by distillation. • Process Objective: • ◦ To convert low value resid to valuable products (naphtha and diesel) and coker gas oil. 2.3.2) DELAYED COKING:
- 35. • ◦ Primary Process Technique: • Thermocracking increases H/C ratio by carbon rejection in a semi-batch process. • ◦ Process steps: • ◦ Preheat resid feed and provide primary condensing of coke drum vapors by introducing the feed to the bottom of the main fractionator • ◦ Heat the coke drum feed by fired heaters • ◦ Flash superheated feed in a large coke drum where the coke remains and vapors leave the top and goes back to the fractionator • ◦ Off-line coke drum is drilled and the petroleum coke is removed via hydrojetting. 2.3.2) DELAYED COKING CONT…
- 36. • In this thermal process, most of the coke is gasified into fuel gas using steam and air. The burning of coke by air will provide the heat required for thermal cracking. The products are gases, gasoline and gas oils with very little coke. 2.3.3) FLEXICOKING: