EKC 111-Integrated Design Sem 2, May 2014

8/12/2019 EKC 111-Integrated Design Sem 2, May 2014

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Integrated Design1st Year

Semester II, Academic Session 2013-2014

EKC 111

Due date: 26 May 2014

(Group Project: 4 students in a group, you are requested to present your massbalance spreadsheet to the lecturer)

1. Project Topic: Production of Methanol through hydrogenation of CO/CO2.Methanol has been used as the feed for the production of acetic acid and

formaldehyde. The annual production of methanol grows by 4% per year. Generally,

the traditional methanol production technology features four main processes, which

is the purification of the feed stock materials (natural gas), reforming (to prepare

the synthesis gas), methanol synthesis and methanol purification. The three mainraw materials used are the natural gas comprised of 96% methane and trace amount

of hydrogen sulphide, stream as well as oxygen that used for oxygen blow auto-

thermal reforming in the reforming processes.

The existence of hydrogen sulphide in the methanol synthesis loop will greatly

reduce the catalytic activity in the steam reformer and reactor. Hence, the natural

gas contains low levels of sulphur compounds need to undergo a desulphurization

process to reduce the sulphur levels of less than one part per million. The

desulphurization process is operating at a temperature of 350C and pressure of 20

bar. The feed is channel through zinc oxide beds where hydrogen sulphide is

adsorbed:

Two steps of catalytic reforming process involved in order to prepare the synthesis

gas. Reforming is the process which transforms the methane (CH4) and the steam

(H2O) to intermediate reactants of hydrogen (H2), carbon dioxide (CO2) and carbon

monoxide (CO). In the first step, the natural gas and steam are supplied to the steam

reformer with catalyst bed of nickel at approximately 600C.

The reformed gas, which consists of gas mixture of hydrogen, carbon monoxide,

unreacted methane and un-decomposed steam leaves the steam reformer at 850C

and 25 bar and routed to oxygen blown auto-thermal reformer (ATR). The operation

in ATR is carried out under higher temperature (1000 C) and higher pressure (50bar). Oxygen also being supplied to the reactor such that it can react with hydrogen

in order to lower the H2to CO ratio:

In this process, the oxygen has also partially oxidizes methane to produce carbon

monoxide and hydrogen gas.

After removing excess heat from the reformed gas, the reformed gas will then enter

a flash column to remove the excess steam. The separation is occurred at 50C and

50 bar. The bottom product (water) will be removed and the top product (carbon

monoxide, carbon dioxide and hydrogen) will be then compressed to 80 bar before

entering at the top of the methanol production stage in the synthesis reactor.Reformed gas is then routed into the methanol reactor (CO/CO2hydrogenations) at


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approximately 230C such that hydrogen and carbon monoxide can react to

synthesis methanol in the presence of a highly selective copper based catalyst. Here

the reactants are converted to methanol-steam mixture product with composition of

68% methanol and 31% water, as shown below:

The product mixture (methanol, hydrogen, steam, carbon monoxide and carbondioxide) is then discharged at the bottom of the reactor. In fact, methanol conversion

is at a rate of 5%, the product mixtures are separated in the flash column (top

product: hydrogen, carbon monoxide and carbon dioxide; bottom product:

methanol, steam), operated at 10oC and 50 bar. There is a continual recycling

whereby the unreacted gases (hydrogen, carbon monoxide and carbon dioxide) are

recycled in the synthesis loop to increase the overall methanol conversion. The

methanol-water stream is then heated to 80C and sent to distillation column to

separate the water from the methanol. In this tower, a methanol-rich stream,

containing approximately 99.86% of methanol is taken as top product and sent to a

central methanol storage vessel. The water comes out as bottom product contains a

lot of impurities and need to be sent to wastewater treatment plant for further

treatment.


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1. Process Flow Diagram (PFD)

Figure 1: Block flow diagram for methanol process


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Figure 2: PFD for methanol process


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2. Problem StatementIn EKC 157 Chemical Engineering Drawing (Semester 1, 2013/2014) you were asked to

prepare a block diagram and PFD of a plant producing methanol through hydrogenation

of CO/CO2 based on the given proses description. The process description and the

sample block diagram as well as the PFD are attached. In this Integrated Design projectyou are requested to perform a mass balance on a unit operation with non-reactive

process and a unit operation with reactive process.

2.1Unit operation with reactive process, Autothermal Reformer (R-103 in PFD).Assume reaction taking place with alkane conversion of 100%, hydrogen yield of 90%

and 25 % excess oxygen for alkane oxidation. Take a basis of 100 kmol/h and give the

mass balance values up to 4 significant figures.

Table 1: Inlet composition of R-103

Component Mass fraction

CO2 0.1637

N2 0.0019

CH4 0.0658

C2H6 0.0178

C3H8 0.0066

C4H10 0.0013

H2O 0.5058

CO 0.1727

H2 0.0644

2.2Unit operation with non-reactive process, Flash Separator (V-101 in PFD).Assume 100 % water removal in Flash Separator.

2.2.1 Perform a mass balance on Autothermal Reformer and Flash Separator

individually based on the information given above using MS Excel.

2.2.2 Perform a mass balance integrating both the operation units.

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EKC 111-Integrated Design Sem 2, May 2014