PHENOL ACETONE PLANT. 40,000 metric tons Phenol 23,000 metric tons Acetone 2,500 metric tons Alpha Methyl Styrene (AMS)

Transcription

1 PHENOL ACETONE PLANT 40,000 metric tons Phenol 23,000 metric tons Acetone 2,500 metric tons Alpha Methyl Styrene (AMS)

2 Phenol Acetone

3 Phenol/Acetone Plant Originally licensed by British Petrol eum Company, the reaction section has been upgraded to a state of the art process in 1999, which also improves the operation of the Oxidation section and includes the purification of Alfa Mehtyl Styrene (AMS). Facilities are formed of 8 sections: 1.OXIDATION/CONCENTRATION. 2.REACTION. 3.WASHING OF CLEAVAGE. 4.DISTILLATION OF ACETONE. 5.DISTILLATION OF PHENOL. 6.PURIFICATION OF AMS / RECOVERY OF CUMENE. 7.RECOVERY OF PHENOL. 8.DEFENOLATION.

4 1. OXIDATION / CONCENTRATION The raw material for this section is Cumene which is oxidized using compressed air. Cumene is previously washed with a caustic solution to remove impurities that can affect the oxidation. Air may be eventually washed to mainly neutralize SO2 traces coming out of the Sulfuric Acid Plant stack. S02 free dry air is fed through the bottom to each one of three reactors (Oxidizers) interconnected in series under pressure and temperature conditions. Cumene is fed to the first of said reactors to form Cumene hydroperoxide (CHP) in concentrations of up to 12%, the mixture of Cumene and CHP overflows to the 2 nd and then to 3 rd oxidizer to reach 17 and 21% as CHP respectively. This reaction is exothermic so that vapors with traces of cumene are carried in the spent gasses stream. The Cumene is recovered in a condensation/separation system (Off Gas Section) and after washing (to remove organic acids and traces of phenol) reintegrated to the oxidation i process. Cumene free exhausted gases are sent to the atmosphere. The so oxidized process stream is sent into a pressure relief vessel and thereafter to a couple of columns where cumene in excess evaporates under conditions of vacuum and temperature to concentrate the CHP up to 80%; vapor of cumene is then condensed and sent to the caustic washing system to later be reincorporated to the oxidation process.

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6 REACTION The reaction system is to cleavage the CHP to produce Phenol and Acetone with the lowest delivering of high boiling point by products and the highest output of one market demand by product: Alpha Methyl Styrene (AMS). The system is formed of 2 reactors and uses Sulfuric Acid to catalyze the reaction. In the 1 st reactor take place the following reactions: Partial Cleavage of CHP. Dehydration of Carbinol to deliver AMS. Reaction of Carbinol with CHP to produce Di Cumyl Peroxide (DCP). Such reactions develop under conditions of: 1.Temperatures between 50 a 53 Celsius degrees 2. Low concentration of catalyzer 3.Concentration of Cumene in CHP ranging between 10 to15%. 4.Recycling flux of Acetone in excess with respect to CHP. 5.Less than 1.0% of Water content in produce of reaction In the 2 nd reactor following reactions are carried into effect: Total cleavage of CHP to Phenol and Acetone Conversion of DCP to AMS, Phenol and Acetone Conversion of Carbinol to AMS.

7 REACTION Above reactions take place under below conditions: 1.High temperature ( ºC). 2.Low acidity on account of addition of a co-catalyzer (Aqueous Ammonia solution) which reacts with the Sulfuric Acid stream to form up to 70-85% of Ammonia Bisulphate 3.Smooth Sulfuric Acid activity due to water being injected at 2º reactor inlet 4.Minimal residence time in the system. 5.Addition of Acetone in excess to reach higher selectivity by lowing Phenol And Sulfuric Acid concentrations. Mentioned conditions support the lowest output of by products and the highest production of AMS. The 1 st reactor system consist of one 3 heat exchangers/two recycling pumps loop. CHP is pumped to the recycling loop through one static mixer where is mixed with other products of reaction before going into heat exchangers. Sulfuric Acid is pumped to the recycling pumps inlet where Acetone and water are added too. Thereafter goes to an intermediate vessel where more Acetone, Water and Aqueous Ammonia Solution is added to promote high selectivity of conversion to DCP. Produce of reaction is pumped to the 2 nd reactor system which consist of one heat exchanger, one heater and accessories for conversion to DCP.

8 REACTION To prevent vaporization of Acetone the 2nd reactor operates pressurized at kg/cm 2. From there products of reaction are sent to an internal flashing stage to obtain in a separator tank under vacuum conditions Acetone which is cooled and condensed in 3 Condensers and then stored to feed both 1st and 2nd reactor Concentrated CHP in the bottom of the evaporator is cooled and stored before pass to the stage of washing produce of Cleavage. SAFETY IN SECTION OF REACTION The high recirculation rate of added product of reaction through the heat exchange reactors to CHP ratio is a key feature for safety operation of the section. Low concentration of Sulfuric Acid in the first reactor system contributes to smooth the reaction. Operation of one calorimeter on line behind reactor 1C based on proportionality of rise in temperature among the calorimeter inlet/outlet and the volume of CHP cleavage in it to assure the formation of DCP..

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10 WASHING OF CLEAVAGE Before distillate the produce of cleavage, the catalyzer (Sulfuric Acid) and organic acids should be neutralized to avoid by products and to prevent corrosion to equipment. Such neutralization is made by means of aqueous sodium sulfate solution and adding alkaline ph sodium phenate solution to neutralize the extracted acid and to free Phenol from the phenate to obtain more sodium sulfate. The aqueous phase is drained to the defenolation section. Washing of cleavage is made in two vessels; the first one is used as a mixer and the second as decanter. Washed produce of cleavage overflows to the first storage vessel from where is fed to one coalescer for sodium salts to be removed up to a highest concentration of 30ppm. The product so treated is stored in the 2nd vessel to be fed to distillation section.

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12 DISTILLATION OF ACETONE The Distillation section counts on 2 main Distillation trains for purifying Phenol And Acetone in separate starting with one column from which feeding streams are sent to each one. A) In the Crude Acetone column, product of Cleavage is pre heated and then fed as a mixture of liquid and vapor. The quality of finished products depend on the correct operation of this column. On the top crude Acetone is obtained and part of this stream is sent back as reflux. The balance is fed to the Lights Column. B) In the Lights Column low boiling point impurities are taken out on the top and phenol carried from the Crude Acetone column is neutralized. Lights free Acetone in the bottom of the column is fed to the Acetone Stripping column. Temperature of operation to this column is supplied by hot vapors coming on from the hydro extractive column in the Phenol Train that is used as heating fluid in the Lights Column re boiler.

13 DISTILLATION OF ACETONE The Distillation section counts on 2 main Distillation trains for purifying Phenol And Acetone in separate starting with one column from which feeding streams are sent to each one. A) In the Crude Acetone column, product of Cleavage is pre heated and then fed as a mixture of liquid and vapor. The quality of finished products depend on the correct operation of this column. On the top crude Acetone is obtained and part of this stream is sent back as reflux. The balance is fed to the Lights Column. B) In the Lights Column low boiling point impurities are taken out on the top and phenol carried from the Crude Acetone column is neutralized. Lights free Acetone in the bottom of the column is fed to the Acetone Stripping column. Temperature of operation to this column is supplied by hot vapors coming on from the hydro extractive column in the Phenol Train that is used as heating fluid in the Lights Column re boiler.

14 DISTILLATION OF ACETONE C) Bottoms of lights column are received in the Stripping Column where Acetone is removed from the feeding stream composed of Acetone, Cumene, AMS, and other components heavier than Acetone. Product in the bottom is sent to a decanter where the organic phase overflows to the feeding tank of AMS distillation/cumene recovery section and the remaining aqueous phase is sent to washing of Cleavage system. D) The Pure Acetone Column operates as a Rectifier Tower, it process the distillated product coming out from the top of the Stripping Column. Acetone of 99.65% Purity is obtained on the top, part of this Acetone is recycled as reflux to the column for the rectification and the balance is sent to the Pure Acetone Storage Tank. In the Pure Acetone Column bottom, heavy products with traces of Acetone are obtained. This stream is used as reflux in the Stripping Column to distillate all of the Acetone.

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16 This section counts on 4 columns: DISTILLATION OF PHENOL A) To the Column of Heavies are fed the bottoms of the Crude Acetone Column which are Phenol and heavy impurities. There under conditions of vacuum and temperature phenol and lights are obtained on the top while heavy impurities plus small volumes of non distillated t d phenol remain in the bottom. This product is sent to the Phenol Recovery Section. Product on top of the Column of Heavies goes through a heat exchanger to be condensed and to heat the stream coming out from the bottom of the Hydro Extractive/Dehydrator Column. The so condensed product is then cooled and stored in the Column of Heavies Reflux Tank. From this tank, part of the produce is sent back to the top of same column for rectifying phenol and the balance is sent to the Hydro Extractive/Dehydrator ti t column for lights to be separated.

17 DISTILLATION OF PHENOL B) In the Hydro Extractive/Dehydrator column products lighter than phenol (Cumene, Toluene, water, etc,) are eliminated. In the hydro extractive section (top of the column) light hydrocarbons and water being injected as reflux to form with them low boiling point azeotropes are separated while in the Dehydrator section (bottom of the column) traces of water in phenol overflowing through heat exchangers located in the top of it are fully eliminated. Heating of this section is made with High Pressure Steam from Steam Generators located in the Utilities Plant. C) Phenol from the bottom of the Dehydrator Section is fed to the Pure Phenol Column previously passing trough the Purification Resins Columns where content of impurities like Ketones, Mesitile Oxide and hydroxiacetone are reduced to meet sales specifications. Before being fed to the Pure Phenol Column, phenol coming out of the Purification Resins Columns is filtered, pre heated and passed through a heat exchanger.

18 DISTILLATION OF PHENOL D) In the Pure Phenol Column traces of heavies are separated in the bottom and traces of lights are eliminated in the top. Purity of phenol being obtained in the middle of the column is at least 99.97%. 97% Part of this product issent back to same column as reflux, other portion is sent to the first distillation column to eliminate lights and the balance is sent to be cooled to C and then stored in the day tanks. From these vessels, Pure Phenol is sent to storage in the finished product tank farm where Citric acid is added to prevent discoloration of the product.

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20 Resins of Purification CWR CWS Phenol Purification To Phenol Resins

21 PURIFICATION OF AMS/ RECOVERY OF CUMENE This section is made of 3 columns which operates under vacuum conditions to purify AMS A) In the Column of Lights the portion of Cumene/AMS is separated from mixed light hydrocarbons coming from the Storage tank: Before being fed, this stream is pre heated in a heat exchanger with Medium Pressure Steam. On the top of the column low boiling point components are obtained and condensed to be stored in the Column of Lights Reflux Tank. Part of stored material is sent back to the column and the balance is purged in batch as small fractions of light products to the stage of recovering of phenol. The portion with higher boiling point composed of Cumene/AMS is taken out of the bottom of the column to be condensed in 2 condensers and then stored in a Tank from which is fed to the Cumene Column

22 PURIFICATION OF AMS/ RECOVERY OF CUMENE B) The column of Cumene separates a stream of AMS free Cumene/light impurities on the top. This product is condensed and stored in a tank to partially being recycled to the column and the balance sent to the stage of washing of cumene as recovered product to be oxidized. In the bottom of the column lights free AMS/Heavies remain to be fed to the column of Purification of AMS. A good control of content of Cumene in the bottom of this column is key for the compliance of required finished product quality. To keep it one Chromatograph operates on line analyzing samples received from the column bottom line of recirculation each 13 minutes and reporting contents of impurities like Sec and Tert Butyl benzene as well as n- Propyl Benzene.

23 PURIFICATION OF AMS/RECOVERY OF CUMENE C) The Column for Purification of AMS functions as a Rectifier Tower. It receives the stream coming on from the bottom of the Column of Cumene. On the top AMS is obtained and condensed to be stored in a vessel. Part of the stored material is sent back to the column for the rectification and the balance is sent to the storage Day tank with a purity of at least 99.51%. To avoid polymerization an stabilizer is added. From the bottom of the column a stream of heavy impurities mixed with small quantities of AMS is extracted and cooled to be placed together with product drained from the bottom of the column of Cumene and be sent as purge of heavies to the section for recovery of phenol

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25 RECOVERY OF PHENOL In this stage Phenol, Cumene and AMS contained in the stream coming on from trains of distillation is recovered. In one Cracking Drum the free phenol is distilled and heavy phenols are thermally fractioned. Heaviest products are drained in batch to be stored and disposed as alternative fuel oil. Products distilled in the Cracking Drum leave as vapors on the top directly to the Acetophenone Column where Phenol, Cumene and AMS are evaporated and thereafter cooled and condensed in a tank from which one portion is recycled back to the column for rectification and the balance is sent to the section of washing of cleavage. In the bottom, Acetophenone with traces of phenol is extracted, cooled and stored for being used as solvent to dilute heavy residues in the Cracking Drum. The energy for heating these 2 phases is provided to heaters by hot vapors of a thermic oil in turn evaporated in a direct flame heater that operates with natural gas.

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27 DEFENOLATION This section is to recover the phenol contained in all of different aqueous streams drained from process: Washing of Cleavage, Distillation of Acetone, vacuum ejectors hot wells and washing of equipment when carried out. Operation is made in 3 stages: Primary Decanter. Water stored in a ditch is fed to the 1rst stage where content of phenol in the aqueous phase is extracted using Cumene recycled from the Secondary decanter by mixing both streams. The turbulence generated makes the phenol pass to the Cumene before going into the decanter. The mixture is decanted and the separated aqueous phase with traces of phenol is sent to the Plant Waste water System. The cumene with phenol overflows to the mixer. Mixer. In this equipment is installed an internal diffuser to improve efficiency in extraction of phenol. Before entering to the mixer streams with fresh caustic soda and sodium phenate with caustic soda in excess are injected. It is in this stage when defenolation occurs. Secondary Decanter. In this stage phenol free cumene is decanted and then overflows to the tank of feeding to purification of AMS. Part of the aqueous phase is recycled to the Primary Decanter and the balance is sent to section of Washing of Cleavage as sodium phenate.

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29 PHENOL ACETONE NAMEPLATE CAPACITY, TPY: PHENOL 40,000 ACETONE 23,000 AMS 2,500 INSTANT VELOCITY; TPD: PHENOL 120 ACETONE 72 AMS 7 OST, % : 96.8 YIELDS OF RAW MATERIALS TO PHENOL, TON/TON CUMENE: CUMENE (WITH CUMENE CONVERTED TO AMS CREDITED) H2SO4: CAUSTIC SODA: AMMONIA: YIELDS OF BY PRODUCTS TO PHENOL, TON/TON ACETONE AMS TAR

30 PHENOL ACETONE CONSUMPTION OF UTILITIES VS PHENOL STEAM, TON/TON: 6.32 ELECTRICITY, KWH/TON: REFRIGERANT, M3/TON: COOLING WATER, M3/TON: COMPRESSED AIR, M3/TON: NATURAL GAS, M3/TON*: *Consumption on Thermal Oil Heating System.

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