2 replies to this topic

[du3z]

Hi all,

I'm new

Well,anyhow, these two weeks might be possibly be my last, since the dateline for my final year paper is due next friday.

So a little background info on my project:

My team (of 10 students), are designing an IGCC plant with carbon capturing option. The entire cohort is split to different problem statements, eg, 500 MW production, varying cost of coal, $carbon tax, %carbon capture required. The design project is split into 3 portions, namely, an preliminary design of the entire plant - interim report 1, interim report 2 -an operational and mechanical design of a specific unit operation (seperator/reactor/heat exchanger, of which my subgroup of 3 did the heat exchanger design), and lastly, interim report 3 - which includes everything else. This time around, I'm assigned to a 3 man team doing the economics of the plant.

Having read some of the posts here, and, textbooks, I can only conclude that it is impossible, given the timeframe, and manpower nor expertise, to decently get a reliable cost estimate. Nonetheless, we need to.

Now to get things started, I have tried to cost estimate one of the designs made in interim report 2, namely, an absorber column. From seider's and Peters/Timmerhaus, i understand that there are mainly 3 components to a tower column.

1)cost of shell, including skirt, nozzles, etc.
2)cost of packing, internals
3)cost of auxiliary components.

Specifications:
Column height: 43.4m
Two elliptical head: 2m
Skirt: ~ 4.6m
Column Di ~ 8.55m
Shell thickness: 0.1m (head thickness assumed to be 0.1m as well)
MOC: Stainless Steel 304
Random Packing (0.050m Metal Pall Ring): 31m

The report has no info on nozzle, etc. It has 6 manholes, but no specified size. Now i understand that this is a non-standard size, but i will use the figure provided by seader's nonetheless, to get some figures (which would safe to say, be an underestimate).

Without even proceeding to calculate the cost of component #2,

I calculated F.O.B of empty shell ~ $5066816.8
Then the bare-module cost would be (if i read the F_{BM = 4.16, vertical pressure vessel?)
That, would give me a CBM ~} $_{21077957.89 .} (21mil, am i reading this right?) Factoring cost index , base 500, project 2011 figures based on best fit from 5 yrs data ~ 571 (can't find any latest figures for 2011) That would give me $22.76mil.

Before even proceeding on to include packing costs:
Huh, are distillation columns supposed to be so expensive? Is it a mis-design problem, or a cost-estimation problem?

Well I hope to move past this manual calculations exercise soon, and proceed on to use Capcost to calculate the rest of the plant, given that only 3 unit operations were actually sized, I see no point in giving an extremely detailed cost estimate for the entire plant, and thus this would only serve as a sample calculation given in the report.
Thank you for your time, and responses once again!

Jon

Edited by du3z, 19 April 2011 - 02:33 PM.

[du3z]

I almost forgot to mention, the absorber in question is the CO₂ absorber column, running on selexol. Granted, I'm not well versed in this part in the project, but could this explain the reason for it's humongous size and so justify the costs?

[clarenceyue]

Dear Du3z,

I understand your pain because I also had to do my design project just about a year ago. But the point is, you are not making it clear which method you are going to use to estimate your TOTAL CAPITAL INVESTMENT.

I am now assuming that you are planning to use Guthrie's method since only this method uses a so called bare-module factor. The simplest one is to use the Lang factor method, which for your case, since it is an IGCC plant, it is a mix of solids/fluids plant, so a final lang factor of about ~4.5 would be a good guess (although you can work out the details).

In short, TOTAL CAPITAL INVESTMENT = LANG FACTOR * (TOTAL FOB COSTS OF MAJOR EQUIPMENT).

You may like to know that Peters & Timmerhaus have a spreadsheet that you can download and work on it at the following url:

http://highered.mcgr...readsheets.html

My advice to you is to forget about being accurate in this case, since you are only doing an order of magnitude analysis for your final year project, so an estimate of +/- 50% is definitely tolerable.
Another thing, if you want us to help you more, it would be very helpful to put all the relevant information in a spreadsheet so we can add comments and help you.

Best of luck in your design project.