Crude Distillation Unit

A REPORT ON CDU love switch & desegregation BY Mudit 2010A1PS349P Amanpreet Singh 2010B4A1356P Rishu Gupta 2010A1PS401P AT IOCL REFINERY, GUWAHATI A Practice School-I station of BIRLA name OF TECHNOLOGY & SCIENCE, PILANI July, 2012 PREFACE We feel immense pleasure in presenting origin aloney you this lowest report on our PS-1 broadcast IOCL Guwahati refinery. This report encompasses a omnibus(prenominal) give-and-take of what we learnt on this program. The report starts with a skeleton introduction most(prenominal) the organization i. e. IOCL Guwahati refinery.We wealthy person kept discussion in this contribution brief to focus more on our stomach fondness give-and- seize and consolidation in CDU . The briny report is divided into 4 incisions. To start with, the first off Section is a basic introduction to porcine distillment unit, its abut and merchandises. light up energy shipping is among the most classic activity for down-to-earth distillate units . The 2nd part of the report focuses on this hop up substitute march occurring in the ill-bred distillation unit of Guwahati refinery. Necessary selective information regarding on the whole the shake up money changers has been provided in a tabular manner to make savvy easier.The concept of small modify supervene uponr is introduced subsequently in the third instalment along with the case oeuvre of close to important passionateness exchangers of the edge. foment duty & opposite calculations presented in this section for awaken exchangers ar clearly explained in gradation by step manner along with formulas employ. Through these calculations we impart tried to analyze whether these exchangers be extending efficiently. In the Last part of the report we have assumption an introduction to commove desegregation one of the most important tool for increasing zilch efficacy of a handle.Points discussed ab give away awaken integrating in this section be Mea ning, Importance, its desire in CDU, Tools. We have concluded this part with an slip of conflagrate integration done in 2010 in pre- mania train of CDU, video display how it helped redemptive energy & increasing efficiency. A final conclusion and colour argon provided to sum up the report. We hope you have a con placementrably date reading this report and find it informative and useful. Mudit, Amanpreet & Rishu Birla take of engine room & scientific discip air travel of descent Pilani 333031 2 ACKOWLEDGEMENTA comprehensive report al tracks requires the goodwill, encouragement, guidance and abet of m both(prenominal) people so we would equal to start by thanking our college BITS pilani for initiating program interchangeable ps-1 thereby giving us the opportunities to visit real time industries and learn by establishing on hand in organizations as big as IOCL. Our sincere thanks to Mr. B K Das, CPNM and Mr. P S Sonowal for assigning us this important project on ignit e integration in refinery and getting us in contact with the undeniable person in each unit. With turn out their help this whole program would non have been possible.We are indebted by the constant birth and mentoring provided by Mr. Vijay Kumar, TS for the preparation of this report. Also, we take this hazard to thank all the chief engineers, and workers we have met in varied units who have received us with open police van and helped us in learning the vast array of knowledge that a refinery holds. Mr. E Edmund of CDU, Mr. A. Bairagi of OM&S are just the few of these names with whom we share numerous informative talks which finally went into the preparation of this report. We also impart our deep sense of gratitude to IOCL administration for providing us with necessary data nd making our stay a pleasant one. Thanks to our families & friends for their constant support and encouragement doneout the period of preparation of this report. It goes without saying that we are un feignedly grateful to our instructor, Mr. Prasantha G for coordinating this ps-1 program and giving us opportunity to present forwards him this report. Thank you all Birla name of applied science & erudition Pilani 333031 3 TABLE OF CONTENTS S No. Topic knave No. Preface Acknowledgement List of Illustrations Abstract 2 3 5 1. 1 1. 2 1. 3 in approach s scorching IOCL Guwahati refinery payoff Units of Guwahati refinery 6 7 8 9 2. 1 stark(a) Distillation Unit CDU Process description 11 3. 1 3. 2 3. 3 CDU Pre- stir up take up (Heat exchange Process) Introduction flap & underpass-shaped structure Heat exchanger Pre- foment train definition 15 16 17 Heat money changer functioning Calculation decisive enkindle exchangers Performance abstract Examples ? S-25A/B ? S-11C ? S-23A/B 22 23 23 25 27 Heat consolidation Heat Integration Introduction Heat Integration in CDU ? Need for arouse integration in CDU ? Heat integration in Guwahati Refinery ? Example from pre- hot up tr ain 30 32 32 32 33 Conclusions References Bibliography Glossary 35 36 37 38 4. 1 4. 2 5. 1 5. 2 Birla take of applied science & experiencePilani 333031 4 LIST OF ILLUSTRATIONS ILLUSTRATION NO. DESCRIPTION 1. 2. 1 1. 3. 1 IOCL Indian market share knock back showing action units 2. 1. 1 2. 1. 2 CDU rise diagram Table Showing CDU harvest properties 3. 2. 1 3. 3. 1 3. 3. 2 Types of instance underground fondness exchanger Pre- come alive train flow diagram Table Showing cold section kindle exchangers Table Showing mid section come alive exchangers Table Showing hot section heat exchangers 3. 3. 3 3. 3. 4 4. 2. 1 4. 2. 3 4. 2. 4 4. 2. 6 4. 2. 7 4. 2. 7 5. 1. 1 5. 2. 1 5. 2. 2 Properties, material body data, serviceable data of S-25A/B Properties, Design data, Practical data of S-11CProperties, Design data, Practical data of S-23A/B Steps of Heat Integration Heat integration in Pre-heat train S-11/c before & after heat integration Birla base of technology & Science Pi lani 333031 5 ABSTRACT Title of the Project CDU HEAT EXCHANGE & INTEGRATION rouge Words bad-mannered distillation, Heat exchange, Heat integration, CDU-Pre heat train Project Areas Heat exchange, Process programme & optimization, Energy Abstract In this work is on thoroughgoing(a) distillation unit in a refinery & discusses the heat exchange work in it and introduction of the concept of heat integration which is of wide importance in CDU.CDU is used for cutting fractionation and requires a temperature of 354 oC. To increase the temperature of sodding(a) 2 step puzzle out is used heat exchange with product streams & furnace. In the shell & tube type heat exchangers of Guwahati refinery Low temperature uncivil exchanges heat with high temperature streams of SRGO, RCO etc. in 3 stages(cold , mid, hot). The surgical procedure of somewhat of these heat exchangers have a major pretend on production and are classified as diminutive on the background of different criteria lik e frequent fouling, tremendous open sphere.Calculation of heat duty, LMTD of some of these heat exchangers(s/15, S/23a-b,s-24) is done utilise form & practical data to check whether they are working efficiently as compared to design. Heat integration is an important concept to increase energy efficiency of process by means of heat remembery. Tools like pinch analysis are used in high energy demanding units like CDU to optimize the Heat money changer vane for utmost efficiency. Analysis of past heat integration done in Pre heat train of CDU is taken as an example for analysis. spot(s) of Students(s) Date Signature of PS Faculty DateBirla form of Technology & Science Pilani 333031 6 1. 1 INTRODUCTION This Report is an analysis of the one of the most key elements of any ill-mannered distillation unit i. e. Heat Exchange & Heat integration. The report is base on Work in CDU of Guwahati refinery. Crude distillation units are used for the fractionation of jolty into more val uable products apply their difference in boiling targets. Increase in temp for distillation us succeedd in 2 go first step is the heat exchange of crude with product streams at high temperatures. In the near step a furnace is used to further elevate the temperature.Our main point of discussion in this report is the first step of heat exchange called the Pre-heat train. The pre-heat train consists of 3 sections Cold, Mid & hot. The purpose of each section is to recover heat from hot product stream of RCO, SRGO etc and bring it to crude through a shell-tube type heat exchanger. The inside information about various heat exchanger used in process are presented in the report. Performance of some heat exchanger is more critical on general heat exchange than separates these heat exchangers are classified as Critical heat exchangers. Constant monitoring of efficiency of these heat exchangers needs to be done.As Example calculations like heat duty, LMTD is done in this report for s ome of these critical heat exchangers (S-11C, S-23A/B) to check their efficiency. Crude distillation is an energy intense process. With increasing oil costs, the focus is to maximize energy recovery. One way to do this is heat integration which is a technique to design a process to minimise energy consumption. Tools like pinch analysis are used for obtain an optimized heat exchanger nedeucerk for heat integration in CDU. The retrofitting of the HEN in CDU is taken as case study in report to realize importance of heat integration.Meaning of all the key hurt used in the report sewer be found in the Glossary. Necessary data used in the report has been obtained through manuals & officials of Guwahati refinery. Birla instal of Technology & Science Pilani 333031 7 1. 2 IOCL GUWAHATI REFINERY ? IOCL Indian Oil flowerpot delimited is largest state owned company in bounds of revenue having Maharatna status. It is ranked 98th in the Fortune global 500 listing. Its biggest participant in Indian downstream oil & bollocks sector and operates10 of Indias 21 refineries with refining dexterity of 65. 7 MMTPA.Major ones are Panipat, Mathura, Guwahati, Gujrat, Haldia etc. Its products are Petrol, Diesel, LPG (Indane), ATF, lubricants, Naphtha, kerosene etc. (1. 2. 1) Sector (India) IOCL Share Petroleum products 49% Refining capacity 37% Downstream pipelines 67% ? Guwahati Refinery Guwahati refinery is the first public sector refinery of India licensed in 1962. It had an initial capacity of 0. 75 MMTPA which was extended to 1 MMTPA in 1986. Guwahati Refinery receives the raw crude from Oil India Limited & has a product line to Siliguri. Final products of Guwahati Refinery are Motor spirit (MS), ATF, Kerosene, LPG, Diesels, Petroleum Coke atomic egress 16. Its an environmentally Conscious refinery with modern effluent treatment facilities, Stack heavy weapon monitoring, Products with strict environmental specifications like BS-3 & BS-4. Birla give of Technology & Science Pilani 333031 8 1. 3 PRODUCTION wholeS ? Shown below in the slacken are the various production units of Guwahati refinery along with their use, feed & products(1. 3. 1) Unit Purpose Feed issue CDU Separation of Crude into useful products by distillation. Raw CrudeLPG , Naphtha, RCO, Kero-1 &2 DCU caloric Cracking to obtain useful products from higher ends RCO CK, CGO, CFO, RFO and RPC HGU Production of hydrogen visible radiation Naphtha (LN) Hydrogen INDMAX FCC unit for maximizing LPG production from residual stocks. CFO, CK, RCO LPG & Gasoline tonicity improvement of Diesel, ATF by removing sulphur. SRGO, KERO 1 &2 BS 3 Diesel, ATF, SKO HDT improve Octane No. of MS by Hydrotreating & Isomerization LN Isomerate (MS) HDT off gases Elemental second _ _ Waste water Effluent free water MSQU Recovering Sulphur SRU OM ETP Crude & product storage, Pumping & blendingTreatment of waste water to despatch oil and hang solids Birla Institute of Technology & Science Pilani 333 031 9 CRUDE DISTILLATION UNIT Birla Institute of Technology & Science Pilani 333031 10 2 CDU Process Description INTRODUCTION Crude distillation unit or CDU in small is first & most important unit for any refinery. Its called the have unit as its products forms the feed of other units. CDU receives its crude from OM (oil movement and supply section) where it is supplied by Oil India Ltd from upper Assam oil fields. Incoming crude has followers properties (2. 1. 1) Property slow-wittedness at 15 oC Water content brininess content(ppm) Sulphur content(ppm) note value 0. 8735 2. 05% 8. 7 0. 29 CDU then stripes the crude into various products like kero1, kero2, reduced crude oil, LPG, heavy gasoline and light gasoline using the distillation principle of difference in boiling points. KEY FACTS ? ? ? Installed in 1962. Revamped and modernized in 1986 & 2000. Capacity of 1MMTPA but currently processing 1. 3 MMTPA Its an Atmospheric distillation unit (ATU) PROCESS DESCRIPTION A brief d escription of the different processes taking place in CDU is given on succeeding(a) page (2. 1. 2) 1.Pre heating train before Desalter Crude is pumped by pumps P1/1A at a pressure of 15 kg/cm2 through a series of heat exchangers where its temperature is elevated to cxxxo C. Crude is gaining heat in these exchangers from pre fractionated operating cost vapours(in s-26), RCO( in s-29), SR Kero1 etc. Birla Institute of Technology & Science Pilani 333031 11 2. Desalter Demulsifier rippleed crude is fed at 130 o C to Desalter (v-101) where it is mixed with water through a mixing valve. The salt in crude dissolves in water and marooned from the oil. Salt free crude on the other hand is pumped to Pre-topping mainstay (CL-1) though 2 safety valves. 3.Pre-topping Column (CL-1) The average temperature of crude before entering pretopping pillar is 238 oC (achieved through heat exchange). The purpose of this column is to remove the straight predominate (SR) light gasoline and LPG from o verhead and reduce the accuse on the main fractionating column. Shown below is the Flow diagram of CDU(2. 1. 1) 4. Atmospheric furnace (C 1 A) the crude coming from CL-1 bottom at 246 oC is fed to furnace. Furnace is fired by fuel oil (FO), Fuel gas (FG) or a mix of both supplied by DCU. The crude coming out of the furnace has a temperature of nearly 354 oC and goes to the flash zone of main fractionators column. 5.Main Fractionators column (CL-2) Its the most important part of CDU. Cl-2 is where the actual distillation is taking place crude is separated into different products of different cut. Stripping stream enters at the bottom. The various subsystems of CL-1 are Birla Institute of Technology & Science Pilani 333031 12 a) Overhead system The overhead of the column of the water and the Straight rum Heavy Gasoline (SRHG) are separated. b) Stripper column A stripping column (CL-3) is attached to the main fractionating column . Its function is to strip apart (separate) kero1, ker o 2 and straight run gas oil coming from main fractionating column. ) CL-2 Bottom Section The stay crude oil called as the reduced crude oil (RCO) comes out of the bottom of CL-2. RCO forms the feed of DCU 6. Light Gasoline /Heavy Gasoline bear upon System Un-stabilized light gasoline from CDU pre-toping column is stabilized in the stabiliser where LPG is recovered from it while heavy gasoline is split in the two naphtha splitter to separate LN (Light Naphtha), RN (Reformer Naphtha) and HN (Heavy Naphtha). The table below shows properties of the Products make in the CDU(2. 1. 2) LN TBP cut HN Kero 1 Kero 2 SRGO RCO 65-135 135-165 165- one hundred ninety 190-300 300-370 370+ 11. 27 4. 90 8. 16 12. 11 22. 16 9. 7 0. 731 0. 786 0. 806 0. 866 0. 866 0. 9542 range Yield (% of crude) Density Birla Institute of Technology & Science Pilani 333031 13 CDU PRE-HEAT TRAIN (HEAT EXCHANGE IN CDU) Birla Institute of Technology & Science Pilani 333031 14 3. 1 INTRODUCTION As we have seen the temp erature of the Crude oil needs to increase to 354 oC in CDU. This section is a discussion on how this is achieved. Why Crude needs to be het up(p) in CDU? The various components of crude oil have different sizes, weights and boiling temperatures. Crude Distillation Unit is used to strip this crude into various products using the difference in their boiling points.Therefore for distillation to take place the temperature of the Crude has to be elevated to around 354 oC so that all the fractions of crude oil can vaporize and get separated. How Temperature of Crude is increase in CDU? The Temperature increase of Crude oil consists of 2 major steps 1. A 3 Stage Heat exchange (called CDU pre-heat train) of crude with product streams at high temperatures using shell & tube type heat exchangers. This step results in crude be supplied at 246 oC (elevated from ambient) to the next step The atmospheric Furnace. 2. The atmospheric furnace (C-1A) is then used to further elevate the temperature .Modes of heat steer in furnace are both convective and radiative the crude coming out of the furnace has a temperature of around 354 oC and goes to the flash zone of main distillation column (CL-2). Furnace alone is not used because it would to too expensive and Energy consuming. By exchanging heat with products, the pre-heat train is serving twin purpose The Crude is being heated at the same the temperatures of product streams of SRGO, RCO, KERO is brought down which was needed for their storage. This heat would have otherwise been wasted. Our point of discussion in this report is the prototypal step i. e. The Heat exchanger Network which we will now study in detail. Birla Institute of Technology & Science Pilani 333031 15 3. 2 eccentric & TUBE HEAT EXCHANGER The Pre heat train uses shell & tube type heat exchager for heat transfer of training. ? It consist of two main things as its name implies instance & thermionic tubes ? The shell is a large vessel with a number of tubes inside it. ? The principle of operation Two fluids of different temperatures are brought into close contact but they are not mixing with each other. One fluid runs through the tubes, and another fluid flows over the tubes (through the shell) to transfer heat between the two fluids.The temperature of the two fluids will tend to equalize. The heat is simply exchanged from one fluid to the other and vice versa. No energy is added or removed. Common types of shell and tube exchangers Birla Institute of Technology & Science Pilani 333031 16 3. 3 PRE-HEAT TRAIN Description Our point of discussion in this report is first step of the 2 stages used for genteelness the temperature of crude i. e. the Heat exchanger network in which heat transfer occurs between crude and product streams of RCO, SRGO, and Kero 1. This network is also called the CDU pre-heat train.In this process the temperature of the crude is elevated form ambient conditions at which it is supplied from OM to 246oC. The heat needed for this is coming from the product streams which are at high temperatures. Dual purpose is served in this way heating of crude as well as the cool of product streams (needed for their storage). The pre-heat train is divided into three sections on the basis of temperature of crude flowing through them 1. COLD section 2. MID section 3. gamey Section Shown below is the flow diagram of the CDU pre heat train (3. 3. 1) Birla Institute of Technology & Science Pilani 333031 17 1.Cold Section (before Desalter) The crude from battery limit is pumped by pumps P-1/1A at about 15. 8 Kg/cm2 through a heat up train where it is heated to a temperature of 130 ? C before entering the Desalter (V-101). The following table shows the shell side & tube side streams of all exchanger in this section along with their inlet-outlet temperatures (3. 3. 2)Exchanger wait on Shell subway system resume Surface area Heat handicraft Temperature shell tube I O I O S-26 Gasoline Crude 300 x 1 2. 11 107 90 40 65 S-29 RCO Crude 171 x 1 0. 47 116 hundred 54 60. 3 S-12A Crude Kero 2 148 x 1 0. 92 60. 3 72. 6 130 82 S-27A/B Crude SRGO 183 x 2 1. 39 72. 5 0. 3 173 85 S-7 Kero 2 Crude 93 x1 1. 48 199 130 90. 3 109 S-11A/B RCO Crude 134 x 3 1. 49 165 115 109 122 2. Mid Section (Between Desalter and pre-topping column) The crude from the Desalter is pumped by pump P-21 A/B and divided equally into 2 streams (Train A & B) for further heating before entering the Pre-topping column. P-21A/B? Train A S-24, S-9A, S-23A/B, S-9B/C, S-22 CL-1 Train B S-4A/B, S-12B, S-25A/B The crude in train A is preheated by hot-streams of SR Gas Oil (in S-24), RCO (in S-9A, S-23A/B), SR Gas Oil (in S-9B/C), RCO (in S-22) to about 236 ? C. While the crude in Birla Institute of Technology & SciencePilani 333031 18 train B is preheated by SR kero spread Reflux (CR) (in S-4A/B, S-12B) and RCO (in S-25A/B) to about 240 ? C. Desalted crude from both Train A and Train B streams are combined before entering the pre-t opping column. Mixed preheat temperature achievable is around 238 ? C at which it is fed to pre-topping Column. Below is the table showing heat exchangers of mid section (3. 3. 3) Exchanger Shell do subway Total area Surface Heat Duty Temperature oC Shell Tube I S-9A Desalted Crude RCO S-23A/B RCO S-9B/C SRGO S-22 RCO S-4A/B Desalted Crude Desalted Crude RCO S-24 S-12B S-25A/B O I O SRGO 0. 0 122 138 214 173 Desalted Crude Desalted Crude Desalted Crude Desalted Crude Kero CR 149 x 1 0. 61 184 195 138 152 148 x 2 1. 93 241 184 153 195 82 x 2 0. 54 272 214 195 218 149 x 1 0. 91 320 296 218 236 148 x 2 1. 67 122 161 190 164 Kero CR 148 x 2 1. 8 161 198 216 190 Desalted Crude 113. 15 x 2 2. 0 297 283 228 223 3. angry Section (At CL-1 Bottom) The excel crude from CL-1 bottoms is pumped by pumps P-2/2A to exchangers S16/S-9D in series, where it is heated by SR Gas Oil Circulatory ebb. It then passes to exchanger number S-11C and further to S-21 where it is heated by Reduced Crude Oil (RCO) to about 246?C. At this Temperature pre topped crude enters Atmospheric furnace (C-1A). The table on next page gives details about every heat exchanger in this section (3. 3. 4). Birla Institute of Technology & Science Pilani 333031 19 Exchanger expediency Shell Total area Surface Heat Duty Tube Temperature oC Shell Tube I S-16/9D SRGO CR S-21 RCO S-11C RCO plane crude Skimmed crude Skimmed crude O I O 186 x 2 2. 16 291 250 197 257 175 x 1 0. 61 336 320 239 246 134 x 3 1. 49 336 320 239 246 Birla Institute of Technology & Science Pilani 333031 20 HEAT EXCHANGER military operation CALCULATION Birla Institute of Technology & SciencePilani 333031 21 4. 1 CRITICAL HEAT EXCHANGER The critical heat exchangers are identified as the ones whose consummation has a major impact on heat exchange rate, Production rate, product quality or environmental and health issues. Problem or inefficiency in any of the critical exchanger has a severe frame on overall heat exchange process occurr ing in the crude distillation unit. The engineers need to see that these exchangers are working efficiently for undisturbed running of the process (Though efficiency monitoring is important for every exchanger but the most attention has to be paid for Critical heat exchangers).Criteria for Classification 1. Fouling is accumulation of unwanted material of heat exchanger surface is called fouling. Fouling is inevitable in heat exchanger but certain heat exchangers are more prone to fouling than others. These exchangers foul in short intervals and need to be cleaned frequently. Their regular maintenance is very necessary for the heat exchange process. E. g. is S-11/C in hot section is prone to frequent fouling. 2. Large surface area Some heat exchanger have a very large heat transfer area which means they have a large contribution in total heat exchange taking place.Their inefficiency or by-passing them would have a vital effect of final crude temperature. For example S-23 A/B in the mid section of heat exchanger trains. 3. Single heat exchanger in line If a heat exchanger is single heat exchanger in the line like the one used in circulating reflux then it cannot be stopped or by-passed. For any maintenance work on them the whole unit has to shut down. Example is S16/9D. In next section the basic performance measurement calculations like heat, Duty, LMTD, Heat transfer coefficient is done for some of these critical heat exchangers. Birla Institute of Technology & SciencePilani 333031 22 4. 2 PERFORMANCE ANALYSIS Examples This section analyzes the performances of some main heat exchangers of pre-heat train through calculation of simple performance measurement tools like Heat duty, LMTD & Heat transfer coefficient. The definitions & formulas for these tools can be found in glossary at the end of the report. 1) S-25 A/B ? Type Shell & tube ? Section Mid ? Properties Exchanger no. S-25A/B Service Shell No. of passes Shell Tube Tube RCO Desalted Crude 1 2 Total Surfa ce area Heat Sq. M x no. of Duty element 113. 15 x 2 2. 0 (4. 2. 1) ? Design Data Shell 54554 55454 296 241 (I) (O) 49. (uncorrected) Total flow (Kg/h) Operating temperature (? C) LMTD (? C) Tube 77586 77586 197. 7 240. 5 (I) (O) 47. 1 (corrected) (4. 2. 2) ? Practical data Mass flow rate (RCO) = 59187. 5 Kg/hr S-25A/B Service Temperature, C Shell Tube comport M Shell side I 297. 5 O 283. 7 Tube side I O 231. 9 245 Nov 11 Exchanger No. 263 253 198 RCO crude 203 (4. 2. 3) ? Calculations 1. Heat Duty (design) M*Cp*(Ti To) = 2002813. 7 Kcal/hr Birla Institute of Technology & Science Pilani 333031 23 2. Heat Duty (practical) 559336 Kcal/hr 3. subject field factor for LMTD (practical) 1. 01 4. LMTD (practical) 52. 12 (uncorrected), 51. 7(corrected) ? bill The practical heat transfer of 559336 Kcal/hr is a lot lower than the design heat duty of 2002813. 7 Kcal/hr. ? Conclusions 1. The exchanger is not working efficiently 2. Due to fouling the temperature difference across the crude s ide is low which is trim down the total heat exchange in the exchanger. Birla Institute of Technology & Science Pilani 333031 24 2) S-11/C ? Type Shell & tube ? Section Hot ? Properties Its a critical heat exchanger because of the frequent fouling Service Exchanger no. Shell Tube S-11C RCO PreDesalter No. of passes Shell Tube 1 2 Total Surface area Sq. m x no. of lement 134 x 3 Heat Duty 1. 49 (4. 2. 4) ? Design data Shell Tube Total flow (Kg/h) 54554 55454 155171 Operating temperature (? C) 336 (I) 320 (O) 239 (I) LMTD (? C) _ 1551 71 246 (O) _ (4. 2. 5) ? Practical data Mass flow rate 59871. 5 Exchanger No. S-11C Service Shell Tube RCO Skimmed Crude Post M Nov 11 Temperature, C Shell side Tube side I O I O 327 315 257. 8 263 330. 2 275 231 255 (4. 2. 6) Birla Institute of Technology & Science Pilani 333031 25 ? Calculations 1. Heat Duty (design) M*Cp*(Ti To) = 6295320 Kcal/hr 2. Heat Duty (practical) 597382. 7 Kcal/hr 3. Correction factor for LMTD(practical) = 0. 75 4. LMTD (prac tical) 82. 84 (uncorrected), 80. 79(corrected) ? Observations Heat transfer at present is 597382. 7 Kcal/hr which is satisfactory as compared to design heat transfer of 6295320. ? Conclusions The present performance of the heat exchanger is satisfactory as compared to design. This little variation in the design heat duty and practical heat duty is payable to variation in value of Cp of RCO with temperature. Birla Institute of Technology & Science Pilani 333031 26 3) S-23A/B ? Type Shell & Tube ? Section Mid (Train A) ? Properties It is an critical heat exchager becase of its large heat transfer areaService Total Surface area No. of passes Shell Tube Shell Tube (Sq. m x no. of element) RCO Desalted Crude 1 2 148 x 2 Heat Duty 1. 93 (4. 2. 7) ? Design Data Property Shell Tube Total Flow (Kg/h) Temperature (? C) I 54554 241. 0 O 54554 184. 0 I 77585 152. 70 O 77585 195. 0 Specific Heat (Kcal/kg-? C) 0. 646 0. 597 0. 566 0. 617 LMTD (? C) 38. 21 35. 6 (4. 2. 8) ? Practical data Mass f low rate (RCO) = 59187. 5 Kg/hr Temperature C Service Shell RCO Tube crude Shell side Post M Nov 11 Tube side I 260. 2 O 230 I 145. 7 O 178. 8 253 230 142 one hundred sixty (4. 2. 9) Birla Institute of Technology & Science Pilani 333031 27 Calculations 1. Heat Duty (design) M*Cp*(Ti To) = 1932602. 7 Kcal/hr 2. Heat Duty (practical) 1161000. 7 Kcal/hr 3. Correction factor 4. LMTD (practical) (uncorrected), (corrected) ? Observations The practical heat transfer of 1161000. 7 Kcal/hr is much lower than the design heat duty of 1932602. 7. The value of LMTD on the other hand is actually higher in case of practical government agency ? Conclusions The heat exchanger is not working efficiently. Due to fouling the temperature difference across the crude side is low which is reducing the total heat exchange in the exchanger even after having a high LMTD value.Birla Institute of Technology & Science Pilani 333031 28 HEAT INTEGRATION Birla Institute of Technology & Science Pilani 333031 29 4. 1 HEAT INTEGRATION Introduction In Todays process industries like Guwahati refinery increasing energy efficiency is of prime importance. With the rising costs of input like crude, power the process has to be designed to have maximum energy recovery so as to reduce the costs. Heat integration is one of the ways to achieve this. 1. MEANING Heat integration is technique for designing a process to minimise energy consumption and maximise heat recovery.Its part of the broader confines Process integration which is a holistic approach to process design which emphasizes the unity of the process and considers the interactions between different unit operations from the outset, quite than optimising them separately. 2. NEED FOR HEAT INTEGRATION Heat integration can ace to substantial reduction in the energy requirements of a process thence prudence costs. Its the answer to following questions ? Are the existing processes as energy efficient as they should be? ? What changes can be do to increase energy efficiency without incurring any costs? What is the most important utility mix for the process? What investments can be make to increase energy efficiency? ? How to put energy efficiency & other targets like emission reduction, increasing plant capacity into one uniform strategic plan? 3. TOOLS FOR HEAT INTEGRATION ? Pinch Analysis The term pinch technology was introduced by Linnhoff to represent a set of thermodynamics based tools that that guarantee minimum energy levels in design of heat exchanger networks. Pinch Technology provides a systematic methodology for energy saving in processes & total sites. Its prime objective is to provide energy saving by better process heat integration. Here are some of its key featuresBirla Institute of Technology & Science Pilani 333031 30 1. Based on the first and second law of thermodynamics. 2. Pinch analysis is applicable for both new design as well as the retrofit systems. 3. It was developed for crude distillation systems but is now applicable to large number of process industries. 4. In addition to energy conservation Pinch technology provides general improvements 5. Some famous Pinch softwares are Pinch ExpressTM, Aspen PinchTM & SuperTargetTM ? supply analysis Retrofit analysis is done to in old process processes to see what modifications suggested by pinch analysis are most adequate for the project.It looks into the optimization of the process through energy capital trade off. In oil refining, retrofit designs are far more common than divulge root applications. The retrofit targets are preferably achieved by re-using existing equipment more efficiently rather than installing new equipments and incurring new costs. 4. travel IN HEAT INTEGRATION Shown below are the different steps of heat integration (5. 1. 1) Birla Institute of Technology & Science Pilani 333031 31 5. 2 HEAT INTEGRATION IN CDU 1. IMPORTANCE OF HEAT INTEGRATION IN CDU Distillation is the largest single energy consumer in the R efinery.Large section of oil is fagged in fuelling the CDU itself. It is energy intensive process as the temperature of the crude has to be elevated to a high temperature of 354 oC. This increase in temperature is achieved by exchanging heat in various heat exchangers between crude and streams of RCO, SR Gasoline, Kero 2 etc which are at high temperature. Heat integration focuses on achieving maximum energy recovery from these streams through an optimized HEN so that the crude can be supplied at highest possible temperature to the furnace, thus saving energy.A recent education in distillation technology has shown potential savings of up to 15-40 % through the heat? integrated exchanger network (pre-heat train) & distillation column. 2. HEAT INTEGRATION AT CDU GUWAHTI REFINEY What has been done? 1. The basis of heat integration in heat exchange process is putting process hot streams in thermic contact with process cold streams. We have already seen how product hot streams of RCO, S RGO etc at high temperature are used to exchange heat with the crude oil at low temperature. 2.Designing of an Optimized Heat Exchanger Network in pre-heat train using heat integration tools like pinch analysis & retrofit analysis in July 2010. This design allows maximum energy heat recovery. What can be done? 1. Using heat integrated distillation columns. HIDC can save energy by recovering excess heat from the rectifying section for usage in the stripping section. Birla Institute of Technology & Science Pilani 333031 32 2. Seeing the interactions of HEN and distillation column and applying combined heat integration for whole unit.