ACKNOWLEDGEMENT I have completed my six weeks Training at IOCL Panipat successfully in PX-PTA Plant (Petrochemical Division). It was a great learning experience although its not possible to cover all the aspects of refining processes. By the way I am satisfied that I have a fair Idea about functioning of units and process involved. I would like to thanks Mr. L.D Batra ( Manger,T & D) for his gentle concern. I would also like to thank Mr. P.K Das , Mr. Manish Tewari Mr Sujeet, Mr Neeraj Singhal and all those who contributed to make this training successful.

-AMIT KUMR SINGH (Vocational Trainee at IOCl Panipat)

INDIAN OIL PETROCHEMICAL PROJECT PX ( Para- Xylene ): Product of Heart Cut Naptha having boiling point 138.4 DegC Process Involved: 1Destillation 2Absorption 3Desulphurization 4Reforming 5PX-Separation(Adsorption) 6Isomerisation 7Trans-alkylation 8Disproportion 9Solvent Extraction 10Fractionation etc. PTA- Two steps from PX 1.Catalytic Oxidation of PX to make CTA (Crude Terepthallic Acid) 2.Purification of CTA to PTA Hydrogenation Crystallization Solvent Recovery Centrifuging Drying Conveying etc Licensors PX Units -----UOP Design PTA Units-----DuPont Design

PX PACKAGE UNITS: 1NHT 2CCRU 3SULPHOLANE 4BTF 5TATORAY 6XFU 7PAREX 8ISOMAR PTA PACKAGE UNITS: 1OXIDATION PLANT 2PURIFICATION PLANT USES: PX IS USED TO FORM: 1DMT 2PTA 3PET PTA IS USED TO MAKE: 1PSF(Polyester Staple Fiber) 2PFY(Polyester Filamone Yarn) 3Polyester Resins BENZENE IS USED IN FOLLOWING: 1Caprolactum(Nylon) 2LAB(Detergent) 3Phenol 4Styrene 5Nitro Benzene 6Chlorobenzene 7Solvent Pesticides

UNIT NHTU CCRU XFU

CAPACITY 50,0000 50,0000 452700

MAX. Pr(Kg/cm2) & Temp.(Deg C) 40 6 20 345 545 285

PURPOSE Naptha Treatment Catalytic Reforming enrich aromatic precursors Separate C6,C7 from C8+ streams to generate mixed Xylenes High Purity Benzene 7 Toluene(secondary feed to PX production) Re-establishing equilibrium mixture of isomers in Parex unit Raffinate to increase yield of PX. Recover PX from mixed Xylenes Disproportion & Transalkylation of Toluene along with C9 aromatics to maximize PX. PTA by catalytic oxidation

BTF

308500 115500

ISOMAR

1654600

23

429

PAREX TATORAY

2017300 349600 35 500

PTA Plant

5530000

85

350

NAPTHA HYDROTREATE R

INTRODUCTIONNaptha Hydrotreating process is a catalytic refining process employing a slect catalyst and a hydrogen rich gas stream to decompose organic sulphur ,oxygen and nitrogen compounds contained in hydrocarbon fractions. Additionaly removes organo-metallic compounds and saturated olefinic compounds. AIM-To remove Platforming poisons from naptha . CATALYST-Alumina base impregnated with compounds of cobalts ,nickel and molybedenum in oxidized state.

PROCESS PRINCIPLESSix basic types of reactions occurs in NHT. 1.Organic Sulphar to sulphide C-C-C-C-SH + H2 = C-C-C-C + H2S Operating Range-(315-340oc) At High Temprature C-C-C=C + H2S= C-CS-C-C(mercaptan) A specified level of sulphar is required to optimize slectivity and stability of catalyst. 2.Nitrogen Compounds to Ammonia Ammonium Chloride formed casues product to slop.Denitrification is favoured more by pressure than temperature so design pressure for unit is crucial. 3.Organic Oxygen to water By hydrogenation of Carban-Hydroxyl Bond. Any Oxygenator in the product will quantatively to water in the Platforming unit.Units normally not designed for oxygen removal may find difficulty to get adequate product quality. 4.Olefins saturation Hydrogenation of olefins necessary to prevent fouling or coke deposits in downstream units.Reactions are exothermic in nature ,these should be

handle with care. Straight Naptha- Low Olefins Cracked Naptha-High Olefins. 5.Chloride to Halide conversion Halide removal is much less at operating conditions mainly nitrogen & sulphar removal governed. Periodic checks of sample required for chlorine content as HIGH CHLORIDE CONTENT CAUSES CORROSION TO DOWNSTREAM OF THE REACTOR. 6.Metal Removal Mainly arsenic, iron, magnesium,phosporus, lead removal.These reactions are temperature dependent . REACTIONS Desulpharification Olefin Saturation Denitification RATE OF RX 100 80 20 RELATIVE HEAT OF RX 1 5 0.1

PROCESS FLOW SCHEME Naphta Hydrotreating Unit mainly divided in three sections1.REACTOR SECTION WITH RECYCLE GAS Naphta feed pas through combined feed exchanger to heat up feed then it will pass through the charge heater to reach desired reaction temperature.Feed goes to reactor added with hydrogen gas and reaction will take place in reactor. 2.STRIPPING SECTION Stripper Section will strip off hydrogen sulphide,water, light hydrocarbons and dissolved hydrogen. 3.SPLITTER SECTION Stripper bottoms may contain C5 and minus compounds and it will be necessary to fractionate the hydrotreated before sending to platforminf

feed. Splitter will split stream in two partsLess than C5 in overhead(light naptha) Above C5 in Bottoms (as heavy naptha) ALTERNATE USES OF NHT 1.Stabilizing naptha from storage using stripper section - Removing light ends 2.Stripping Sweet Naptha Operate stripper section at total reflux thus removing all water .

CCRPLATFORMER

INTRODUCTION As name suggest this unit employed of continuous catalyst generation one of the greatest achievement in Refining Technology processes. CCRU produces high octane reformats or aromatics raw material for further processing downstream. 1By products are Hydrogen and LPG 2Accomplished in Hydrogen atmosphere at elevated temperature and pressure across a Platinum containing catalyst . FEED SPECIFICATIONS Completely Hydrogenated ,product specificationsTotal Sulphar Aromatic Hydrocracking

DEL H(k cal/mol H2) 10.5(endothermic) 16.9(exothermic) -13.5

Catalyst Chemistry The Platforming Catalyst should have proper balance between the metallic and acid function.This is important to minimize the hydrocracking while maximize the dehydrogenation and dehydrocyclization reaction. This balance is maintained by proper balance H2O/Cl control. In the vapor phase the HCl and H2O are in equilibirium with the hydroxyl groups and chloride groups on the surface.Too much water on the vapor phase will force chlorides from the surface leading to an under chloride catalyst. While too much chloride in vapor phase has the reverse effect. Therfore

Proper control of water/ chlorides is crucial in maintaining an active acid site.

CATALYST REGENARATOR

INTRODUCTION For any Catalyzed reaction or operation its necessary to have a optimally working catalyst as deactivation of catalyst will lead to decline in production as well as purity of the product. In platformer catalyst regeneration is must because reforming catalyst is different from traditional catalyst in which SOR and EOR temp play a vital role. In platformer catalyst should have a proper balance between the Acid and metal function. As due to coke deposition on the catalyst surface active surface area of the catalyst decreases and consumption or disbalance of chlorine concentration in the catalyst acid site weaken the fuctioning of the catalyst decline in the Dehydrogenation as well Dehydrocyclization reaction. SO IN PLATFORMER REGENRATION OF CATALYST IS MUST. Regeneration also necessary to avoid : 1.Increase in Recator Pressure Drop 2.Exchanger Fouling Catalyst Chemistry Base- Alumina Acid Sites-Chloride Metal Sites- Platinum Each step must be done well for optimal catalyst performance and catalyst life. REGENRATION Regenration involves the following steps 1.Coke Burning 2.Oxychlorination 3.Drying 4.Reduction

COKE BURNING Coke + O2------> Co2 + H2O + Heat O2 concentration is controlled limit Heat 1Hydrothermal damage to Catalyst Base 2Agglomeration of platinum OXYCHLORINATION PERC + O2--------> 2Cl2 + 2H2 HCl + O2-----------> Cl2 + H2O Base-OH + HCl-----> Base-Cl + H2O Metal + O2-(Cl2)-------> oxidized/ dispersed metal Cl2 is necessary to redisperse agglomerated Pt. DRYING Base-H2O + Dry gas-----> Base + gas + H2O Advantages 1Improves Catalyst reduction 2Limit moisture Carry over to Reactor Section. REDUCTION Oxidised Metal + H2------> Reduced Metal + H2O Propertly Balanced Operation Increasing Oxygen Supply------> Coke Burning in Regeneration Zone Increasing Coke Supply----------> Cokes Breaks through into Chlorination Zone Desired Coke Oxygen Balance 1Moderate Burning Temperature 2Catalyst properly preserved 3Maximum Catalyst Life

SULPHOLANE UNIT

INTRODUCTION Liquid-liquid extraction from the reformate stream with solvent followed by extractive distillation process is the most effective means of purifying aromatics from reformate stream. Repulsion of one hydrocarbon relative to other measure the ability of solvent to discriminate between them and thus achieve separation.The relative repulsion is called slectivity of the solvent. Shell Sulpholane unit uses sulpholane as a solvent to recover benzene ,toluene , xylene and C9 aromatics of high purity from an aromatic rich deheptanised strem. The extraction take place by counter current contact of hydrocarbans with sulpholane solvent in liquid phase. SHELL PROCESS The process employs a raindeck extractor for extracting aromatics and a jet deck controller for washing the aromatic lean raffinate product to recover solvent,a water stripping column is provided to remove traces of dissolved non aromatics from the solvent- rich wash water. The non aromatics hydrocarbans remaining in the rich solvent are removed in the s stripper column and recycled to extractor . a recovery column is used to recover the solvent from the aromatic product (extract). Un desired material , including degradation products from the decomposition of solvent are removed in the solvent regenerator section .The aromatic extract is the clay treated to remove olefins and is fractionated in the benzene and the toluene columns. Solvent regeneration The sulpholane solvent undergoes minor oxidative degradation . A small slip stream of circulating solvent is directed to the solvent regenerator for

removal of oxidized solvent , polymers and salt formed by neutralization with MEA. The regenerator operates under vacuum and run intermittently in conjuction with recovery column. The heavy components (regenerator bottoms ) are rejected to drums.

OPERATING CONDITIONS Raindeck Extractor Pressure Kg/cm2 Temperature Deg C Solvent Flow Kg/hr Raffinate Water Wash Column Pressure Kg/cm2 Temperature Deg C Raffinate Flow Kg/hr Stripper Pressure Kg/cm2 Top Temperature Deg C Bottom Temperature Deg C Recovery Column Pressure Kg/cm2 Top Temperature Deg C Bottom Temperature Deg C 2.8 131 3291 9.8 88 79334

0.7 124 174 -0.6 72 173

Solvent Conditioning Degradation Mechanism Sulpholane undergoes oxidation degradation to acid at temperature

above 200 deg C. The oxygen attacks the sulpholane to form acid which is followed by ring opening and sulphur dioxide abstraction(release). The SO2 reversibly reacts with unsaturated aldehydes to from very strong corrosive acids . The thermostable acidic polymers are weaks acids partly soluble in sulpholane and at high concentrations appear as solids.

Neutralization The acidic compounds formed by degradation of sulpholane these are to be neutralized by injecting MEA. PH is maintained in the range of 5.5~6.0. The salts formed by neutralization with MEA decompose at high temperature . Clay treating of Extract Clay treating is done to remove olefins as in particular di-olefins (from reformer) being polar are partly extracted along with aromatics. So its necessary to treat the extract from sulpholane extraction. Thiophenes and mercaptans are broken down to H2S which will concentrate in the benzene product. LHSV Normally kept 1 Clay Life 5000~7000 MT of aromatics /ton of clay. Clay Disposal When the bed is exhausted the removal of aromatics is easily effected by flashing followed by stream stripping .The after it can be dumped in a truck and used for landfill.

PAREX UNIT

INTRODUCTION Para-Xylene is the intermediate product used in the manufacture terepthalic acid(PTA) and di-methyl tere-phalate(DMT). The reformate from CCR is extracted for aromatics. The paraxylene is slectively adsorbed on fixed bed Zeolite crystals (adsorbant) from the mixed xylenes, the adsorbed para xylene is then displaced from the adsorbent bed by using a desorbent. The desorbent and para Xylene are separated by fractionation to get para Xylene. PAREX is just one of the family of UOP SORBEX processes that effect separations by means of simulated counter current adsorption. PX is produced by separating it from a mixture of C8 aromatics isomers and non aromatic hydrocarbans. It can be achieved by crystallization or by adsorption.Crystallization is commonly proven, but it requires refrigeration and recover about 60% of para Xylene per pass. The Parex Proces recovers >96% PX per pass while consuming less utilities. The by products of the Parex process are are the C8 or aromatics rejected as raffinate.Toulene is also rejected as another by product and is routed to TATORAY for trans alkylation to benzene and xylene. Para-Xylene forms the feed stock for manufacture of Terephthallic acid by oxidation process. C6H4-(CH3)2 + 2O2---------> C6H4-(COOH)2 + H2O Para-Xylene is also used for the production of dimethyl terephthalate (DMT), another raw material in production of polyester fibers and plastic.

C6H4-(CH3)2 + CH3-OH -------> CH3-COO-C6H4-COO-CH3

ADSORBENT The adsorbent consists of X-Type Zeolite ,an aluminosillicate held together by a clay binder . The particle size of the adsorbent ranges from 20 to 60 mesh. Alumina rich sieves have very high affinity to water and other polar molecules. Silica are essentially hydrophobic and adsorb n- paraffins in preference to water. All hydrocarbans in the feed can enter the selective pores of the adsorbent But paraxylenes is passed through the adsorbent more slowly than the other feed components. DESORBENT The desorbent is a liquid of different boiling from the feed components which is capable of displacing feed components from the adsorbent.Two types of adsorbents are used Heavy Adsorbent Light Adsorbent The light desorbent utilizes toluene desorbent and ADS-4 adsorbent .This is slected when cost of fuel is low & for once through operation. Hy desorbent has lower operating cost.It has design advantages when intergrated with isomerisation loop or non extracted feed stocks containing relatively high level of non aromatics .The heavy desorbent system utilizes D-1000 desorbent whose main component is para diethyl benzene)p-DEB) and adsorbent ADS-27 FEEDSTOCK

Several types of feed stock can be separated in PAREX unit. These includes extracted C8 aromatics , unextracted C8 aromatics from reformate heartcut,Deheptanized C8 isomerate & Pyrolysis gasoline.

PROCESS PRINCIPLES Equilibrium: No net change occurring in the process Ki= K(Phase A)/K(Phase B) Enrichment Factor: The relationship between the concentration of a component I two different phases. Yi,j=Ki/Kj As the Enrichement factor becomes larger the separation between the two components becomes easier. ADSORBENT SYSTEM In a system where the actual circulation of solid adsorbent ,the adsorbent moves continuously in a close d past the fixed circuit past the fixed points where the fed and desorbent are added and extract and raffinate are withdrawn. The same effect can be achieved by keeping the adsorbent bed stationary and periodically moving the points which the liquid stream are added and withdrawn from the chamber,this will simulate the motion. ZONE-I: Section Between the Feed and Raffinate points Primary function is to Adsorp ParaXylene. ZONE-II:Section between the Extract and Feed points. Primary function of ZONE II is to remove extract from the pores of the adsorbent. ZONE-III: Section between the Desorbent and the Extract point.

Primary function of this ZONE is to desorb A from the Pores. ZONE-IV: Section between the Raffinate and the Desorbent This act like buffer ,its purpose is to keep component B to avoid contamination. LINE FLUSH The line between the rotary valve and the bed is employed successively in carrying feed to bed and carrying extract from it. To avoid extract contamination with feed components it is necessary to flush the line Similarly if the line for extract is subsequently use for desorbent line flush and secondary flush are used.

XYLENE FRACTIONATOR

INTRODUCTION The Xylene Fractionator unit fractionates three streams into four product streams .The Separation is achieved by three Columns ,a reformate splitter column, a xylene column, and a Hy aromatics column. Feed Streams 1Reformate from CCR unit 2Toulene column bottoms from BT fractionation unit 3Recycle xylene stream from Isomerization unit. Product Streams 1C7 cut 2C8 Parex feed cut 3C9 aromatics for Tatoray 4C10 Heavy aromatic cut The C7 material is sent to sulpholane unit for aromatic extraction and separation of aromatics by extractive distillation. The reformate splitter bottom material is clay treated to remove olefins and then sent to xylene column, The C8 aromatics product is taken overhead from the xylene column to Parex. The C9+ Hy aromatics from the bottoms of the xylene column is sent to Hy aromatics column. The C9 material is routed to Tatoray for undergoing dis-proportionate trans alkylation reactions. The special feature of the xylene fractionation unit is the high pressure Xylene column Design. By this design we can use the column overhead

vapours as heating media to reboil the extract and the raffinate columns in the Parex unit. PROCESS DISCRIPTION Feed to the Xylene Fractionation is a combination of Debutanizer bottoms from CCR, Toluene column Bottoms and clay treated recycle xylenes from the Isomar deheptanizer bottoms. The overheads from the xylene column are condensed in the reboiler of reformate splitter ,Parex Raffinate reboiler and Parex extract column reboiler.The Xylene column bottoms are use to reboil the Parex extract column, Isomar deheptanizer column,Parex desorbent re-run column,Heavy aromatics column as well as clay treater feed.

ISOMAR UNIT

INTRODUCTION Isomerisation is a catalytic isomerisation process to efficiently convert a mixture of C8 aromatics to a near equilibrium mixture of PX and OX. It employs a dual function noble metal catalyst which operates in a pressure and temperature range that favours p-x and o-x from meta xylene (m-x) and ethyl benzene and to crack many of saturates from the fresh feed. FEED The feed to isomar unit is the rafinate from the Parex unit.The raffinate is p-x and o-x depleted. The fee dis combined with Hydrogen rich recycle gas , vaporized and sent to the fixed bed radial flow reactor. The effluent is condensed so that the hydrogen rich recycle gas can be seprated from the liquid. The liquid is sent o fractionator to remove light material from the products . The Bottoms is sent to clay treater and subsequently the xylene splitter column in xylene fractionation unit. General Discription The isomar unit consists of a reactor section and a fractionation section where C7 material is removed . The deheptanizer net bottoms stream is clay treated and sent to xylene fractionation unit . The raffinate stream from the Parex unit is recycled back to the Isomar unit where C8 aromatics are efficiently isomerised to desired p-X and o-X products. PROCESS PRINCIPLES Xylene Isomerisation Reactions The acidity of the Isomar catalyst is much stronger than reforming catalyst,

as this is required for isomerisation.Xylene equilibrium is a function of temperature . At 400 Deg C Equilibrium concentration are: 24 % each of o-X & p-X The balance being m-X, Ethylbenzene equilibrium concentration is 8% of C8 aromatics.

Ethyl Benzene Conversion Ethyl benzene reacts at high severities and the products would be mostly benzene and Heavy aromatics..Conversion becomes more difficult approach to equilibrium..Products will be result of dealkylation rather than isomerisation. Basically Isomerisation occurs via collapse to a five member ring(Trimethyl cyclopentane and expansion back to six member ring with the methyl group moved to different location on the aromatic ring. The presence of Napthenes (mainly C8) makes conversion possible by rapid hydrogenation the aromatic system so that it will be additive to the Isomerisation path. The desired isomerisation required a catalyst having both metal(platinum) and strong acid function. In the course of the reaction some C8 aromatic ring loss by trans alkylation, dealkylation and cracking , these are unavoidable. Isomar Catalyst The I-20 catalyst is a bifunctional extrudate catalyst containg both acid sites(zeolite) and metal sites (Platinum).The acid function is quite stable so no halogen injection is required. The metal function provided by platinum is affected by coke build up to acertain extent. As a result gradual decline in EB conversion is experienced and regeneration of catalyst is necessary. OPERATING CONDITIONS

CFE Inlet temp deg C Outlet temp deg C Furnace Outlet temp deg C Reactor Feed Flow Kg/Hr Outlet temp deg C Pressure Kg/cm2

SOR 104 372 204409 375 8.1

EOR 104 385 417 204409 420 16.5

BENZENETOULENE FRACTIONATOR

INTRODUCTION There are three separate streams entering the BT Fractionation unit 1Overhead from sulpholane recovery column 2Overhead material from Parex finishing column 3Bottoms material of Tatoray stripper. The streams are fractionated to produce pure benzene and toluene. The bottom Xylene Rich stream is routed to Xylene Fractionation column for recovery of C8 stream. PROCESS DISCRIPTION The overhed material from the sulpholane recovery column is collected in the clay treater charge tank. From the Charge tank the material is pumped and preheated by charge heater and olefins are removed by using clay treater.Feed mixed with Parex unit overhead material from the finishing column. The combined stream then enters to the benzene column which separate pure benzene product stream from the water , toluene and heavier aromatics. NOW bottoms are sent to toluene column where toluene separated. Net column bottoms is pumped to Xylene fractionation unit.

TATORAY UNIT

INTRODUCTION The Tatoray process is a catalytic process for transalkylation and disproportionation of aromatics. That is a C7(toluene) and C9 aromatics are converted to benzene (C6) and mixed xylenes and C10 aromatics. Thus Tatoray unit increses the production of benzene and C8 aromatics from toluene and C9 fraction.Toulene from the BT fractionation and C9 aromatics from the Xylene column are fed to Tatoray reactor where reaction take place in presence of Hydrogen. The reaction products are stripped of lighter material and sent back to the BT fractionator for separation of Benzene and toluene recycle and C8+ aromatic stream which is charged to the Xylene stripper for further processing and separation of the C9 aromatics recycle. PROCESS PRINCIPLES Chemistry: The basic Chemical reaction is the transalkylation of methyl group in methyl substituted aromatic compounds so as to obtain more desirable species from les desirables one. Typically a mixture of toluene and heavy methyl benzene is converted to benzene and C8 aromatics . The feed also contain ethyl, propyl and butyl substituted aromatic compounds and saturates. The deactivation of the catalyst is due to Saturtates ,bicyclis and hetromolecules normally crack to lighter components on account of higher severity associated with their hydrocarcking.The optimum conversion taking into account fed stocks ,product values and utility costs is the fed having about 40% of the mixed feed (C9) and 43-47% for toluene fee d(C7).

Reaction Methyl group: Toluene + H2-----> Benzene + mixed Xylenes + C9 + C10 Toluene + C9 + H2------> Mixed Xylenes +C9 +C10 Ethyl Group: Ethyl benzene + H2-------> Benzene + Ethane Ethyl benzene + H2------->Toluene + Methane Ethyl benzene + H2------->mixed Xylenes PROCESS DISCRIPTION The fresh feed from the Tatoray unit comes from the overheads of the Toluene column in the BT fractionation unit and the overheads of the Heavy aromatics column in the Xylene fractionation unit routed to Feed surge drum. Feed from the feed surge drum is pumped and is first combined with the Hydrogen rich recycle gas in the combined feed exchanger where it is preheated and vaporized with the Reactor effluent upto reaction temperature Which then fed to reactor where reaction takes place. Reactor effluent is then condensed to ambient temperature and then separated in a separator.

PTA (PURIFIED TEREPTHALIC ACID)

INTRODUCTION PTA is a white crystalline Compound, in powder form having a Median Particle size (MPS) in 90-120 Microns. This is primarily used for polyester, PET & Films manufacture Terepthallic acids is produced by liquor phase oxidation of Para-Xylene Oxidation Process is a series Reaction in the following four steps. Step 1: CH3-C6H4-CH3 + O2 = CHO-C6H4-CH3 + H2O Para-Xylene(PX) Methyl Benzaldehyde Step 2: CH3-C6H4-CH3 + O2 = COOH-C6H4-CH3 Methyl Bezaldehyde Para- Toluic Acid Step 3: COOH-C6H4-CH3 + O2 = COOH-C6H4-CHO + H2O Para- Toluic Acid 4-CBA (Carboxy Benzaldehyde Step 4: COOH-C6H4-CHO + O2 = Cooh-C6H4-COOH 4-CBA (Carboxy Benzaldehyde Terepthallic Acid Overall Reaction is as follows: CH3-C6H4-CH3 (PX) + 3O2 = COOH-C6H4-COOH(TA) + 2H2O

PTA plant is divided in two sections 1Oxidation 2Purification Primary Reaction of TA formation take place in oxidation plant .

However oxidation product is called CTA( Crude Terephallic Acid), as it contains about 2000-3000 ppm of 4-CBA and some coloured impurities. Purification Plant reduces 4-CBA to less than 25 ppm in finished product .This is done by Hydrogenation reaction af 4-cba TO P-Toluic Acid which can be removed with relative ease. COOH-C6H4-CHO + H2 = COOH-C6H4-CH3 + H2O 4-CBA (Carboxy Benzaldehyde Para- Toluic Acid

OXIDATION SECTION PAC(Process Air Compressor ) & Reactions Oxidation Reaction takes place in a cster (continuous Stirred Tank Reactors ).There are two parallel Reactors in which pX is reacted with air. Reaction take place at 15 Bar G and 200 Deg Celsius. Air supplied at 18 Bar G and 160 Deg C by Compression of Atmosphere air in 5 stage Centrifugal Compressor(called PAC). PAC is driven by motor , Steam turbine and Hot gas expander. PX along with Rotary Filter Mother Liquor( mainly acitic Acid and catalyst) is pumped to the Reactors through Static Mixer. Acetic acid keeps solid TA produced in suspension as slurry for ease of transfer of material. Catalyst is a combination of Cobalt acetate,Maganese Acetate , HBr (Hydrobromic acid Reaction slurry is depressurized in a series of three agitated Crystallizers operating at 11 Bar G & 185 Deg C/ 3 Bar G & 155 Deg C/-0.5 Bar G & 95 Deg c. Reaction is Highly exothermic. Vaporized Acetic Acid and PX are condensed in a series of Heat Exchangers in Reactor overheads.First majority of PX and acetic Acid are condenses because of higher Boiling Point 6 of Acetic Acid and these streams are returned back to Reactors as Reflux. Next water rich streams named Water Draw Off are condensed .Since water is a reaction product it has to be remove removed from the system. Water Draw off and Crystallizers Flash vapors are sent to Dehydration (DH) Column for Water separation from the acetic acid.

Heat of Exotherm is removed by first generating LP stream, then ELP stream then heating up to PAC turbine Condensate /DM water going to DEAERATOR and finally against cooling water LP and ELP stream are sent to the PAC steam turbine for power recovery . Gases after cooling goes to the HP (HIGH Pressure ) Absorber for removal of organics by scrubbing with first acetic acid and then by water. Online analyzers are mounted in reactor off gas for indicating O2,CO2,CO volume percentage. This helps in quality control.

Filtration and Drying Slurry from 3rd crystallizers is filtered in rotary vacuum filters. Cake is collected above filter clothes and then Conveyed by screws in to a Rotary Steam Tube Driers .Drying obtained by indirect contact .Steam passes through tubes.Acid vapors are carried along with Gas circulated by Blowers. Acid vapors are removed in a scrubber and then inerts are vented out to atmospheric absorber for final scrubbing before letting them to Atmosphere.CTA product is conveyed to CTA fee d Hooper by conveying gas . Rotary Filter separated Liquid is called mother liquor is sucked in through Filter cloth by Vacuum pumps. Mother Liquor is rich in catalyst and hence majority of it is recycled out.15-20% of mother Liquor is purge out for removal of Reaction impurities Expansive Cobalt is recovered from purged mother Liquor by addition of Oxalic Acid , which forms Cobalt Oxalate and then separated by using a high speed centrifuges. Purged Mother Liquor devoid of cobalt is sent to Solvent recovery section. Solvent Recovery Purge Mother Liquor is concentrated in a series of forced Circulation and a thin Film Evaporator to remote maximum possible acetic acid by vaporization using LP steam & HP steam. Vapors from evaporator goes to DH column. Cake is diluted with water and then burned in thermal oxidizer which is a down fired furnace.This breaks down to CO/CO2.

DH column is an azeotropic Column using n-PA (Normal propyl Acetate ) as Entrainer n-PA bring down the boiling point and hence reduced load on reboiler and condenser. DH Column bottom Product is called DH solvent (5-7% water) and it used as solvent for scrubbing.

PURIFICATION SECTION In this section Hydrogenation of 25-30% CTA is done at high pressure and Temperature(75-85 Bar G and 282-285 Deg C) Temperature is required to keep CTA in solution for the Reaction and Pressure is required to avoid boiling and provide Partial Pressure for Hydrogenation. First slurry is made in water in Agitated Feed Slurry Drum. Then Slurry is Pumped to high pressure by Sundyne pumps. Heating is done in Preheaters using process streams and then finally by Fired Heater using Therminol as Heat Transfer Media. Hydrogen is compressed from 19 Bar G to 85-90 Bar G in Reciprocating H2 Compressors. Hydrogenation take place on a 0.5 % Palladium Catalyst(Charcoal Base) Reactor is having fixed bed of 20 tons of catalyst and Heated CTA solution is sprayed through distributor over the Catalyst and then H2 reacts inside the Reactor. Reacted material is depressurized in aseries Five Agitated Crystallizers to 38 Bar G/22 bar G /14 Bar G/7.5 Bar G / 4 Bar G. First Three Crystallizers flash steam utilized for slurry preheating. Fifth Crystallizers Slurry is pumped in pressure centrifuges operating at 4 Bar G. High Pressure is required to maintain p-Toluic acid in solution. Pressure Centrifuge Liquor is the main plant effluent After cooling the effluent TA and p-TA are recovered and recycled back to

oxidation, filtrate to ETP. Pressure Centrifuge cake is reslurried with fresh DM water. Atmospheric centrifuge cake is dried in Rotary Steam Tube Drier. Dried product is stored in Batch Tanks and after Laboratory analysis sent to Marketing Silos.