B$\mathrm{.}2.$ ETHYLBENZENE PRODUCTION, UNIT $300$

The majority of ethylbenzene $($EB$)$ processes produce EB for internal consumption within a coupled process that produces styrene monomer. The facility described here produces $80,000$ tonne$/$y of $99\mathrm{.}8$mol$\%$ ethylbenzene that is totally consumed by an on$-$site styrene facility. As with most EB$/$styrene facilities, there is significant heat integration between the two plants. In order to decouple the operation of the two plants, the energy integration is achieved by the generation and consumption of steam within the two processes. The EB reaction is exothermic, so steam is produced, and the styrene reaction is endothermic, so energy is transferred in the form of steam.

B$\mathrm{.}2\mathrm{.}1.$ Process Description $[1,2]$

The PFD for the EB process is shown in Figure B$\mathrm{.}2\mathrm{.}1.$ A refinery cut of benzene is fed from storage to an on$-$site process vessel $($V$-301),$ where it is mixed with the recycled benzene. From V$-301,$ it is pumped to a reaction pressure of approximately $2000$kPa $(20$ atm$)$ and sent to a fired heater $(H-301)$ to bring it to reaction temperature $($approximately $400C).$ The preheated benzene is mixed with feed ethylene just prior to entering the first stage of a reactor system consisting of three adiabatic packed$-$bed reactors $($R$-301$ to $R-303),$ with interstage feed addition and cooling. Reaction occurs in the gas phase and is exothermic. The hot, partially converted reactor effluent leaves the first packed bed, is mixed with more feed ethylene, and is fed to E$-301,$ where the stream is cooled to $380C$ prior to passing to the second reactor $($R$-302),$ where further reaction takes place. High$-$pressure steam is produced in E$-301,$ and this steam is subsequently used in the styrene unit. The effluent stream from R$-302$ is similarly mixed with feed ethylene and is cooled in E$-302($with generation of high$-$pressure steam$)$ prior to entering the third and final packed$-$bed reactor, R$303.$ The effluent stream leaving the reactor contains products, by$-$products, unreacted benzene, and small amounts of unreacted ethylene and other noncondensable gases. The reactor effluent is cooled in two waste$-$heat boilers $($E$-303$ and E$-304),$ in which high$-$pressure and low$-$pressure steam, respectively, is generated. This steam is also consumed in the styrene unit. The two$-$phase

mixture leaving E$-304$ is sent to a trim cooler $($E$-305),$ where the stream is cooled to $80C,$ and then to a two$-$phase separator $($V$-302),$ where the light gases are separated and, because of the high ethylene conversion, are sent overhead as fuel gas to be consumed in the fired heater. The condensed liquid is then sent to the benzene tower, T$-3$o$1,$ where the unreacted benzene is separated as the overhead product and returned to the front end of the process. The bottoms product from the first column is sent to T$-302,$ where product EB $($at $99\mathrm{.}8$mol$\%$ and containing less than $2ppm$ diethylbenzene $[$DEB$])$ is taken as the top product and is sent directly to the styrene unit. The bottoms product from T$-302$ contains all the DEB and trace amounts of higher ethylbenzenes. This stream is mixed with recycle benzene and passes through the fired heater $(H-301)$ prior to being sent to a fourth packed$-$bed reactor $($R$-304),$ in which the excess benzene is reacted with the DEB to produce EB and unreacted benzene. The effluent from this reactor is mixed with the liquid stream entering the waste$-$heat boiler $($E$-303).$

Stream summary tables, utility summary tables, and major equipment specifications are shown in Tables B$\mathrm{.}2\mathrm{.}1-$B$\mathrm{.}2\mathrm{.}3.$

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Figure B$\mathrm{.}2\mathrm{.}1.$ Unit $3$oo: Ethylbenzene Process Flow Diagram

Table

a $$383359$

Table B$\mathrm{.}2\mathrm{.}2.$ Utility Summary Table for Unit $300$

$\backslash$table$[[$Stream Name,$\backslash$table$[[$bfw to$],[$E$-301]],\backslash$table$[[$bfw to$],[$E$-302]],\backslash$table$[[$bfw to$],[$E$-303]],\backslash$table$[[$bfw to$],[$E$-304]],\backslash$table$[[$cw to$],[$E$-305]]],[$Flowrate $(k\frac{g}{h}),851,1121,4341,5424,118,300],[$Stream Name,$\backslash$table$[[$Ips to$],[$E$-306]],\backslash$table$[[\backslash$table$[[$cw to$],[$tE$-307]]]],\backslash$table$[[$hps to$],[$E$-308*]],\backslash$table$[[cw$ to$],[$E$-309]],],[$Flowrate $(k\frac{g}{h}),4362,174,100,3124,125,900,]]$

Table B$\mathrm{.}2\mathrm{.}3.$ Major Equipment Summary for Unit $300$

$\backslash$table$[[$Heat Exchangers,$],[E-301,E-306$