Chapter5

5.1 For ethylbenzene process in Figure B.2.1 Feeds: benzene, ethylene Products: ethylbenzene, fuel gas (by-product)

5.2 For styrene process in Figure B.3.1 Feeds: ethylbenzene, steam Products: styrene, benzene/toluene (by-products), hydrogen (by-product), wastewater

(waste stream)

5.3 For drying oil process in Figure B.4.1 Feeds: acetylated castor oil Products: acetic acid (by-product), drying oil, gum (waste stream)

5.4 For maleic anhydride process in Figure B.5.1 Feeds: benzene, air (note that dibutyl phthalate is not a feed stream) Products: raw maleic anhydride (Stream 13), off gas (waste stream)

5.5 For ethylene oxide process in Figure B.6.1 Feeds: ethylene, air, process water Products: fuel gas (by-product), light gases (waste stream), ethylene oxide, waste water

(waste stream)

5.6 For formalin process in Figure B.7.1 Feeds: methanol, air, deionized water Products: off-gas (waste - must be purified to use as a fuel gas), formalin

5.7 The main recycle streams for the styrene process in Figure B.3.1 are: ethylbenzene recycle (Stream 29) , reflux streams to T-401 and T-402

5.8 The main recycle streams for the drying oil process in Figure B.4.1 are: acetylated castor oil (Stream 14) , reflux streams to T-501 and T-502

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5.9 The main recycle streams for the maleic anhydride process in Figure B.5.1 are: Dibutyl phthalate (Stream 14), circulating molten salt loop (Steam 15 and 16), and reflux to T-601 and T-602

5.10 Process description for ethylbenzene process in Figure B.2.1

Raw benzene (Stream 1), containing approximately 2% toluene, is supplied to the Benzene Feed Drum, V-301, from storage. Raw benzene and recycled benzene mix in the feed drum and then are pumped by the benzene feed pump, P-301A/B, to the feed heater, H-301, where the benzene is vaporized and heated to 400C. The vaporized benzene is mixed with feed ethylene (containing 7 mol% ethane) to produce a stream at 383C that is fed to the first of three reactors in series, R-301. The effluent from this reactor, depleted of ethylene, is mixed with additional feed ethylene and cooled in Reactor Intercooler, E-301, that raises high pressure steam. The cooled stream at 380C is then fed to the second reactor, R-302, where further reaction takes place. The effluent from this reactor is mixed again with fresh ethylene feed and cooled to 380C in Reactor Intercooler, E-302, where more high pressure steam is generated. The cooled stream, Stream 11, is fed to the third reactor, R-303. The effluent from R-303, containing significant amounts of unreacted benzene, Steam 12, is mixed with a recycle stream, Stream 13, and then fed to three heat exchangers, E-303 – 305, where the stream is cooled. The energy extracted from the stream is used to generate high- and low-pressure steam in E-303 and E-304, respectively. The final heat exchanger, E-305, cools the stream to 80C using cooling water.

The cooled reactor effluent is then throttled down to a pressure of 110 kPa and sent to the Liquid Vapor Separator, V-302, where the vapor product is taken off and sent to the fuel gas header and the liquid stream is sent to column, T-301. The top product from T-301 consists of purified benzene that is recycled back to the benzene feed drum. The bottom product containing the ethylbenzene product plus diethylbenzene formed in an unwanted side reaction is fed to a second column, T-302. The top product from this column contains the 99.8 mol% ethylbenzene product. The bottom stream contains diethylbenzne and small amounts of ethylbenzene. This stream is recycled back through the feed heater, H-301, and is mixed with a small amount of recycled benzene to produce a stream at 500C that is fed to a fourth reactor, R-304. This reactor converts the diethylbenzene back into ethylbenzene. The effluent from this reactor, Stream 13, is mixed with the effluent from reactor R-303.

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5.11 Process description of drying oil process in Figure B.4.1

Acetylated castor oil (ACO) is fed to the Recycle Mixing Vessel, V-501, where it is mixed with recycled ACO. This mixture is then pumped via P-501A/B to the Feed Fired Heater, H-501, where the temperature is raised to 380C. The hot liquid stream, Stream 4, leaving the heater is then fed to the Drying Oil Reactor, R-501, that contains inert packing. The reactor provides residence time for the cracking reaction to take place. The two-phase mixture leaving the reactor is cooled in the Reactor Effluent Cooler, E-501, where low-pressure steam is generated. The liquid stream leaving the exchanger is at a temperature of 175C and is passed through one of two filter vessels, V-502A/B, that removes any gum produced in the reactor. The filtered liquid, Stream 7, then flows to the ACO Recycle Tower, T-501. The bottom product from this tower contains purified ACO that is cooled in the Recycle Cooler, E-506, that raises low-pressure steam. This stream is then pumped via P-504A/B back to V-501 where it is mixed with fresh ACO. The overhead stream, Stream 9, from T-501 contains the drying oil and acetic acid produced from the cracking of ACO. This stream is fed to the Drying Oil Tower, T-502, where the ACO is taken as the bottom product and the acetic acid is taken as the top product. Both the acetic acid, Stream 11, and the ACO, Stream 12, are cooled (not shown in Figure B.4.1) and sent to storage.

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5.12 Process description for ethylene oxide process in Figure B.6.1

Ethylene oxide (EO) is formed via the highly exothermic catalytic oxidation of ethylene using air. Feed air is compressed to a pressure of approximately 27 atm using a three stage centrifugal compressor, C-701-3, with intercoolers, E-701 and E-702. The compressed air stream is mixed with ethylene feed and the resulting stream, Stream 10, is further heated to a reaction temperature of 240C in the Reactor Preheater, E-703. The reactor feed stream is then fed to the first of two reactors, R-701. The feed passes through a bank of catalyst filled tubes submerged in boiler feed water. The resulting exothermic reaction causes the boiler feed water (bfw) to vaporize and the pressure is maintained in the shell of the reactor to enable the production of medium pressure steam. Combustion of the ethylene and ethylene oxide also occur in the reactor. The reactor effluent is cooled in E-704 and is then recompressed to 30.15 bar in C-704 prior to being sent to the EO Absorber, T-701. The EO in the feed stream to the absorber, Stream 14, is scrubbed using water and the bottom product is sent to the EO column, T-703, for purification. The overhead stream from the absorber is heated back to 240C prior to being fed to a second EO reactor, R-702 that performs the same function as R-701. The effluent from this reactor is cooled and compressed and sent to a second EO absorber, T- 702, where the EO is scrubbed using water. The bottom product from this absorber is combined with the bottom product from the first absorber and the combined stream, Stream 29, is further cooled and throttled prior to being fed to the EO column, T-703. The overhead product from the second absorber is split with a purge stream being sent to fuel gas/incineration and the remainder being recycled to recover unused ethylene. The EO column separates the EO as a top product with waste water as the bottom product. The latter stream is sent off-site to water treatment while the EO product is sent to product storage. A small amount of non-condensables are present as dissolved gases in the feed and these accumulate in the overhead reflux drum, V-701, from where they are vented as an off gas.

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