EXTRACTION IN PETROLEUM OIL REFINING

EXTRACTION IN PETROLEUM OIL REFININGA TERM PAPER PRESENTATIONWHAT IS EXTRACTION?Extraction, better known as Solvent Extraction is a process basically used to purify products in the refinery. It involves the use of a solvent to extract or remove the unwanted components present in the products.AIMS OF SOLVENT EXTRACTIONTo remove components present in the product that could lead to corrosion in subsequent processing stepsTo remove components present in the product that could lead to catalyst poisoning in subsequent processing stepsTo remove components that would otherwise reduce the quality of the product.

COMPONENTS OF CONCERN THAT NEED TO BE REMOVEDAromatics: These are Benzene, Toluene and Xylene collectively referred to as BTXDissolved metals: These include nickel, vanadium and copper.Organic compounds containing sulphur, nitrogen and oxygen.Inorganic saltsDouble salts that were present in the crude feedstockMECHANISMS OF SOLVENT EXTRACTIONDISSOLUTION: The impurities have a higher solubility in the solvent than they do in the feed so that when they come in contact with the solvent, they get drawn into it.

PRECIPITATION: The impurities are caused to precipitate out of the product.PRODUCTS THAT USUALLY REQUIRE SOLVENT EXTRACTIONNaphthaKeroseneGas oilsLubricating oil

BASIC PROCESS STEPSEXTRACTION: The extraction process takes place in an extractor which consists of a vertical column with numerous contactor plates.

EXTRACTORABCEDKEY:A = Aromatic-rich reformate feedB = SolventC = Non-aromatic raffinateD = Non-aromatic-heavy recycle stream E = Aromatic-rich solventFig. 1: A simplified diagram of extraction step in solvent extraction processBASIC PROCESS STEPS (Contd)SOLVENT STRIPPING: This is the step where the used solvent from the extractor is separated from the absorbed aromatics. It is carried out in the solvent stripper.

SOLVENT STRIPPERBADECKEY:A = Aromatic-rich solvent (from extractor)B = Condensed stripper overhead stream containing mainly solvent with trace hydrocarbons C = BTX product streamD = mixed raffinate/aromatic/solvent streamE = Nearly hydrocarbon-free solvent stream Fig. 2: A simplified diagram of stripping step in solvent extraction processBASIC PROCESS STEPS (Contd)EXTRACT WASHING: The extract (BTX) from the Solvent Stripper is washed with water to remove residual solvent before being sent for further processing.

BASIC PROCESS STEPS (Contd)RAFFINATE WASHING: Raffinate leaving the Extraction Tower is washed with water to remove residual solvent before being sent for further processing.

BASIC PROCESS STEPS (Contd)SOLVENT CONDITIONING: These are steps taken to maintain the solvent purity. The solvent degrades over time due to the accumulation of various high boiling and polar contaminants causing it to lose efficacy. Examples of such solvent conditioning processes include filtration, adsorption and batch distillation.SOME SOLVENT EXTRACTION METHODSS/NPROCESSSOLVENT USED1The Udex extraction processDiethylene glycol 2The Sulfolane processTetrahydrothiophene 1-1 dioxide (sulfolane) 3The Tetra processtetraethylene glycol4The Carom ProcessA proprietary glycol/glycol ether mix 5The Lurgi Arosolvan ProcessN-methyl-2-pyrrolidinone mixed with water or glycol 6The dimethyl sulfoxide processDimethyl sulfoxide (DMSO) and butane7The Formex processN-formylmorpholine8The Morphylex ProcessN-formylmorpholineTable 1: A summary of some solvent extraction processesSOME SOLVENT EXTRACTION METHODS (Contd)S/NPROCESSSOLVENT USED9The Redex process (Recycle Extract Dual Extraction)-10Mofex ProcessMonomehtylformamide solvent mixed with water11Arex ProcessN-Methyl -caprolactam12Dou-Sol ProcessSelecto or Selectox (which is a mixture of phenol and cresylic acids) and liquid Propane13CIS ProcessPropylene carbonate 14Carmex ProcessMethyl carbonate REFERENCESBriggs, Terry and Patel, Vijay P. (1978) Evaluation of Benzene-Related Petroleum Processing Operations. Retrieved September 21, 2014 from: http://nepis.epa.gov/Exe/ZyPDF.cgi/91009Y36.PDF?Dockey=91009Y36.PDFC&I Engineering, Inc. (2014) Aromatics Extraction Retrieved September 21, 2014 from: http://www.cieng.com/a-111-319-ISBL-Aromatics-Extraction.aspxComyns, Alan E. (Ed.) (2000) Encyclopedic Dictionary of Named Processes in Chemical Technology. Retrieved September 21, 2014 from: http://lib.lhu.edu.vn/ViewFile/11122Dyke, Kate Van (1997) Fundamentals of Petroleum 4th Ed. Austin, TX: Petroleum Extension Service, the University of Texas at Austin.How Products Are Made (2014) Kerosene Retrieved September 20, 2014 from: http://www.madehow.com/Volume-7/Kerosene.htmlREFERENCES (Contd)King Abdulaziz University, Jeddah (no date) Aromatic hydrocarbons [PowerPoint slides]. Retrieved September 21, 2014 from: www.kau.edu.sa/Files/0053956/Files/60695_Chap%202B%20petro.pptMohammed-Dabo, I. A. and Balarabe, Y. U. (2014). CHEN 807 Module Two Petroleum Refining: Lecture notes. Ahmadu Bello University, Nigeria.Oil refinery (2014). Wikipedia, the free encyclopaedia. Retrieved September 17, 2014 from: http://en.wikipedia.org/wiki/Oil_refineryRousseau, Ronald W. (1987) Handbook of Separation Process Technology. John Wiley & Sons. Google books . Available from: http://books.google.comRydberg, Jan (2004) Solvent Extraction Principles and Practice, Revised and Expanded. CRC Press. Google books. Available from: http://books.google.comTHANK YOU

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