PROJECT: Ethylbenzene Production

As a process engineer you are hired to design a chemical plant to produce $80,000$ tons per annum $(t/$a$)$ of ethylbenzene from benzene and ethylene. Benzene $($assumed pure$)$ and Ethylene $($containing mole fraction of $0\mathrm{.}93$ ethylene, $0\mathrm{.}07$ ethane$)$ feed are available at $\frac{20}{b}ar$ and $298K.$ Ethane is inert.

It may be assumed that the only reactions occurring are:

$C_6{H}_6+C_2{H}_4{C}_6{H}_5{C}_2{H}_5$

$()+()+$

$\backslash$table$[[$H$-301,$R$-301,$E$-301,$V$-301,$T$-301,$E$-302,$E$-303,$T$-302,$E$-304,$E$-305],[$fired$,$ethylbenzene,reactor,flash,benzene,benzene,benzene,ethylbenzene,ethylbenzene,ethylbenzene$],[$heater$,$reactor,cooler,drum,tower,tower,tower,tower,tower,tower$]]$

Unit $300$: Ethylbenzene Process

The molar ratio of benzene to ethylene are approximated at $8$:$1,$ in order to minimize yielding tri$-$ and higher ethyl benzene. The plant should operate for $330$ days in a year, to allow for shutdown and maintenance.

Calculate flow rates and composition of Benzene, Ethylene, Ethylbenzene and Diethylbenzene in each stream. Show all calculations:

Process Description

Fresh benzene $($Stream $1)$ and ethylene $($Stream $2)$ are combined with a recycle stream containing unreacted benzene and a small amount of ethyl benzene. The combined stream is fed to a reactor where all of the ethylene in the feed reacts. The reactor effluent $($Stream $5)$ is cooled so that most of the benzene, ethyl benzene, and diethyl benzene condenses. An ethane impurity from the ethylene feed as well as some benzene and ethyl benzene vapor are purged from the process and used as fuel gas. The condensed liquid is fed to the first distillation column. A high purity benzene stream is removed from the top of the column and recycled. The bottoms from the first column are sent to a second distillation column. The second column produces high$-$purity ethyl benzene in the top stream and diethyl benzene in the bottom. Data on the composition of these streams are provided in a following section.

Additional Process Information

Stream $1-$ Assume that benzene is pure at $25C(298K)$ and $2000$kPa $(20$ bar$)$

Stream $2-$ The ethylene feed stream at $25C(298K)$ and $2000$kPa $(20$ bar$)$ containing mole fraction of $0\mathrm{.}93$ ethylene and $0\mathrm{.}07$ ethane. Ethane does not react but moves through the process as an inert gas until it is purged in Stream $7.$

Stream $3-$ Benzene$-$to$-$ethylene molar ratio is adjusted to control reaction selectivity. Use a $8$:$1$ ratio when making hand calculation.

Stream $4$: mixed feed heated to $400C.$

R$-301-$ The limiting reactant achieves $100\%$ conversion. Reaction selectivity is determined by B$3/$E$3$ ratio.

Stream $6$: vapor$/$liquid mixture, steam may be produced in E$-301,$ cooling water may also be used, the temperature and pressure of Stream $6$ are decision variables.

Stream $7$: $-$ Fuel gas composition.

Stream $8$: mostly benzene, ethylbenzene, and di$-$ethylbenzene, the sole purpose of V$301$ is to allow the vapor and liquid mixture in Stream $6$ to separate at the same temperature and pressure as Stream $6.$

Stream $9$: $-$ Benzene recycle.

Stream $10$: $-$ Ethylbenzene$/$di$-$ethylbenzene mixture.

Stream $11$: $-$ Product ethylbenzene.

Stream $12$: $-$ di$-$ethylbenzene to waste treatment.

You are required to assess the feasibility of such a process by producing the following:

A conceptual design of the process.

A detailed design of the REACTOR AND ONE other major piece of equipment $($such as a heat exchanger, separator, or other equipment$).$