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DA NANG UNIVERSITY OF TECHNOLOGYCHEMICAL PETROLEUM----------SUBJECT: NGHI SN REFINERYCRUDE DISTILLATION UNITProfessor : NGUYN NH LMStudents : HONG TRNG TIN DNG TH ANH NG TN QUANGClass : 11H51CONTENT2INTRODUCTIONDESCRIPTION OF UNITINTRODUCTION3Unit processing objectivesThe objective of the CDU is to provide primary separation of crudes to produce straight run blendstocks of distillate products (after suitable downstream treatment processes) and feedstocks for other downstream process units.INTRODUCTION4Feed:100% Kuwait Export crudeThe CDU has been designed to process an average of 9.66 Million Tonnes perAnnum Products:OverheadKeroseneGasoilResidueDESCRIPTION OF UNIT5Cold Crude Preheat Section Crude Desalting SectionHot Crude Preheat and Preflash Section Crude Charge Heater Section Crude Distillation Column & Side Strippers Section Product Cooling & Rundown Section Crude Column Overheads Section
Cold crude oil feedstock from the offsite storage tanks is pumped by Offsite Crude Charge Pumps 010-P-001A/B/C to the CDU which the effluent desalter water makeup from 010-E-006A/B/C/D before the Crude is heated in the first exchanger by Top Pumparound in 010-E-001A/B/C/Dand then split into three parallel streams under flow control and the fallback on differential pressure control. The first split (30% of total crude flow rate) is heated first by Kero Product in the heat exchanger 010-E-002A/B and then by Kero Pumparound in 010-E-004A/B/C/D.The second split (45% of total crude flow rate) is heated by Atm. Residue Product in 010-E-005The fallback which is under differential pressure control is heated by AGO Product in 010-E-003All the three splits are then recombined and sent to the Desalting section. The temperature of the preheated crude is around 150C before entering the desalter section.Cold Crude Pre-heat Section6
Desalter water from the second stage desalter is injected in-line to the heated crude and is then intimately mixed across a mixing valve which provides a fixed pressure drop and enters the 1st stage desalter of the Desalting Section 010-A-001.Demulsifier is added into the dewatered crude from first stage desalter and mixed intimately with the fresh water (from Desalter Water Surge Drum 010-V-001) across the second stage mixing valve before entering the 2nd stage desalter.Effluent from 1st stage desalter is first cooled in exchanger 010-E-006A/B/C/D by desalter water feed. The effluent is then air cooled in 010-AC-002 and then passed through 010-E-007A/B under level control where it is cooled using cooling waterThe cooled effluent then flows to the effluent treatment plant (ETP).
Crude Desalting SectionCold Crude7
Stripped sour water from the Sour Water Stripping Unit (SWS) and oxygen scavenged service water (after dosage of bisulphite) under level control provide the wash water to the 2nd stage desalterThis water is first collected in the Desalter Water Surge Drum, 010-V-001, before being pumped into the second stage of the Desalter Package 010-A-001, as well as, into the crude stream upfront the Cold Crude/Top PA Exchanger, 010-E-001, by the Desalter Water Makeup Pumps, 010-P-003 A/B under ratio controlled flowBefore entering the second stage desalter, the wash water is preheated in the Desalter Water Feed/Effluent Exchanger, 010-E- 006Fresh water connection is provided for desludging of both the desalters. This water will also be used for washing tube bundles of Desalter Effluent Air Cooler,010-AC-002The Desalter Water Circulation Pumps, 010-P-004 A/B, take water from the Second Stage Desalter, and deliver it to the First Stage Desalter.8
The desalted crude from 2nd stage desalter is first split into three parallel streams for maximum heat recovery.A portion of the crude, under flow control (45% of total desalted crude flow rate), is heated first by Kero Pumparound and then by LAGO Pumparound.
Second split of the desalted crude under differential pressure control, is heated by Atm Residue.
The remaining portion (25% of total desalted crude flow rate) under flow control is heated by AGO Product.
The flashed crude streams at the outlet of control valves at each exchanger trains are recombined and sent to the Pre Flash Drum.
Hot Crude Preheat & Preflash Section9
The antifoaming chemical injection is provided upstream of the preflash drum to prevent foaming in the preflash drum.Light hydrocarbons flash off and are sent as flashed vapours to the flash zone of the Atmospheric Crude Distillation Column.The flashed crude leaving the pre-flash drum is pumped by Flashed Crude Pumps and is split into two streams for maximum heat recovery.One of the flashed crude streams, under flow control, is heated by LAGO PA & by HAGO PA.The remaining portion of the flashed crude which is heated under differential pressure control by Atm Residue then combine with the ealier stream.This combined stream is finally heated by exchanging heat with Atmospheric Residue.10
Preheated flashed crude enters the Crude Charge Heater at around 302C , where it is partially vaporized before entering the flash zone of the Crude Distillation Column . Its 8 passes parallel.
The heater outlet temperature around 358oCCrude Charge Heating Section11
The Pass Balancing Control has two objectives: To control the total flow of Crude to Charge Heater reset by Pre-Flash Drum level Controller. To equalise the individual pass outlet temperatures.12
The fuels use for the heater include : fuel oil and Fuel gas and spent air ( merox Unit)The heater outlet temperature is controlled through the Burners Control System, which sends a set point signal to either fuel oil or fuel gas control valve, depending on the type of fuel being fired. Also, the Burners Control System receives a signal from the O2 analyser to ensure that the desired heater efficiency is achieved by the control of excess air13
To ensure satisfactory thermal efficiency from the heater, the flue gases from this heater are used to preheat the combustion air.14
Partially vaporized crude from each pass of the crude charge heater 010-H-001 at around 347-359C is combined in the common transfer line before entering the flash zone of the CDU (010-C-001).In the CDU, 010-C-001, the crude is fractionated into 4 products: KER, LAGO, HAGO and ARReflux between the side streams is provided by 4 PA circuits: Top PA over trays 1 to 4, Kero PA over trays 14 to 16, LAGO PA over trays 23 to 25, and HAGO PA over trays 26 to 28Crude Distillation Column and Side Strippers Section15
The top PA is circulated by the Top PA pump, 010-P-006, and is heat integrated with the crude in heat exchanger 010-E-001The PA is further cooled in the Top PA Return Air Cooler 010-AC-001 before being refluxed in the column.Crude column top temperature is controlled by duty control taking input from the crude column top temperature control, the temperature differential and flow control of the top PA circuit.Corrosion inhibitor is injected in the PA pump suction to reduce corrosion int eh top PA circuit.16
The kerosene PA is circulated by the Kero PA Pump, 010-P-007, and is heat integrated with the crude in heat exchangers 010-E-008 and 010-E-004The temperature of this section of the crude column is controlled by a duty control between the temperature differential and flow control of the kerosene PA circuit.The LAGO PA is circulated by the LAGO PA Pump, 010-P-009, and is heat integrated with the crude in heat exchangers 010-E-012 & 010-E-010. The temperature of this section of the crude column is controlled by a duty control between the temperature differential and flow control of the LAGO PA circuit.The HAGO PA is circulated by HAGO PA Pump, 010-P-011 A/B, and is heat integrated with the crude by heat exchangers 010-E-013. After heat exchange, HAGO PA is returned to the the column. Provision is kept for the HAGO product draw-off to be taken to the AGO stripper, 010-C-003.Continuous pumpback to the column is provided for each of the above PA pumps. Pump back flow-rate is controlled by chimney tray level. There is also a provision of bypassing the heat exchanger trains in each of the PA circuits except the top PA one (which has a provision of a bypass only around 010- E-001).17
The naphtha overhead product, together with stripping steam, is condensed in the Crude Column Overhead Condenser, 010-AC-006, and run into the Crude Column Overhead Receiver, 010-V-005, where vapour, oil and water separate. Neutraliser (to neutralize acid gases) and Corrosion Inhibitor (to control corrosion) are injected into the Crude Column overhead line.There is also a provision of fuel gas in the overhead receiver for maintaining column pressure during start-up.Crude Column Overhead Section18
The vapour leaves the receiver under a split range pressure control to the Offgas Compressor Suction Drum in LPG recovery unit.The oil phase from the receiver is pumped by the CDU Overhead Liquids Pumps, 010-P-014 A/B, under level-flow cascade control, to the LPG recovery unit for further processing.A part of this overhead liquid can be used as cold reflux and added to 010-AC-001 outlet during startups and for additional temperature control flexibility in the CDU overheads.The water phase from the overhead receiver is pumped under level control by the Sour Water Pump, 010-P-015 A/B, to the Sour Water Stripping Unit (SWS).Deentrained liquid from LP compressor suction drum (011-V-001) and 1st stage spillback from LP compressor (011-A-001) of the LPGRU (Unit 011) is added to the overhead line from the crude distillation column at the upstream of the overhead condenser.19
Kerosene product is drawn from the main column tray under stripper level control to the downstream Kerosene Stripper, 010-C-002The stripper contains 6 valve trays over