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Design Of Water Gas Shift Converter


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#1 Guest_ChE801_*

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Posted 03 December 2005 - 08:30 AM

hi
I am a student of final year chemical engg .. I have my final year project about the design of WATER GAS SHIFT REACTOR (CO + H2 = CO2 + H2) and I am using iron oxide as catalyst.. Since its a fixed bed catalytic reactor so I have to use the PLUG FLOW EQUATION to solve for the volume of the catalyst ..
Now i want to know what things should I focus on for a good desiging of the reactor .. since it is a reversible reaction should i work out its equilibrium conversion or use about 80-90% as given in literature...
please guide me how should I design this reactor ... I want to design it well .. what factors are important in the design of rector ...
please reply

#2 Guest_ChE801_*

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Posted 03 December 2005 - 08:41 AM

I forgot to enter the data given to me ... the composition of gas is
CO 55%
CO2 10%
H2 33%
rest is N2 , H2S
the gas pressure is 500 psi, temperature is raised by heat exchange with steam from 30F to 650F (reaction temp for this catalyst) .. I also have a question that steam to be used in the reaction should also be at 500 psi?
also what are basic difference between fixed bed , moving bed and fluidized bed reactors
please help me so that I can be able to design it well

#3 Ankur Shah

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Posted 23 December 2005 - 04:12 AM

hey! you have a lot of questions!!!

comments:

1) correct me if i am wrong, but i have designed a fixed bed reactor using the weight of catalyst equation, (from fogler). Once the weight of the catlayst is obtained, u need to find out catalyst properties like void volume porosity density etc and hence find out the volume of the catlayst. the volume of a fixed bed ractor is mainly defined by the volume of the catalyst bed. hence, u will have to check what sort of supports are used in the reactor. (most reactor design books give u info abt this, but i would say there is one on fixed bed design also...).. for approx volume of the reactor check perry... they have a list of common industrial processes, and volumes for certain capacities..

2) reg the conversions, i would say if u can calculate the equilibrium conversion from ur data and show that typical reported values of conversion that would be great. if u cant find the 80% mark, then assume 80% and design ahead...

3) for 'good' designing of the reactor study the misc openings that will be needed on the reactor, the reactor thickness, try to do a hazop analysis etc etc...

4) Steam used neednt be at 500 psi. Heat is what u are exchanging and hence, the temperature is what matters. rem!! ensure a delta T of 10 C. btw... are u sure u would be using steam here? because for this u will require Very very high pressure steam and that is gen diff to generate. Maybe u use direct fired heaters or something of the sort... (but if u are using this in the NH3 process, then it wont be a problem...)

5) Fixed Bed: Here there a two methods. either u have an entire mesh of the support of the catalyst and u have the catalyst sprayed onto the support (supports are gen activated carbn, silica etc etc...). or u simply throw into the reactor the catalyst made on rashig rings etc...
Moving Beds: these are gen used in the petroleum(/chemical) industry. here there is a continuous circulation of the catalyst from the reactor to the regenrator.
Fluidised bed: here the bed is suspended due to the velocity of the particles (mainly gases.)

Ankur

P>S:were u still waiting for this reply?

#4

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Posted 23 December 2005 - 08:41 AM

Hi Ankur Shah
Thanks for your reply. I have some corrections to make in your reply

1) First of all it was quite difficult for me to understand the english you wrote, you have used so many sort terms like reg, u,i etc etc. I hope next time when you reply you use proper english so that it is easy for me to understand.

2) Secondly, I have to use steam in the steam because the reaction is between the gas and steam.

3) Finally question about the steam pressure, the pressure of the reactor vessel is about 500 psig, now if I use steam at a pressure less than 500psig then how the steam is going to enter the vessel because flow always takes place from higher pressure to lower pressure.

Now in the end I would like to ask you if you did the hazop study of the reactor you designed, if yes than it is possible that you can send it to me by attaching it in your reply.

Regards and take care

#5 Ankur Shah

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Posted 23 December 2005 - 01:04 PM

hey!

smile.gif) okie okie!!! will be better with more accurate English. smile.gif)

1) Alright. A few more comments. I hope you haven't made the mistake that apears in the reaction in your first post.

2) I guess there some confusion regarding heating the stream. You had said that the stream entering the reactor is HEATED by steam in a heat exchanger. That's why I said any pressure is fine. Now, you tell me that you are using the same steam in your reactor itself. So now, you will need to ensure that the pressure of the steam is either equal to or more than 500 psig. There is a heuristic which says: When mixing two fluid streams, the pressure of the exit stream will be equal to the pressure of the stream with the lower pressure. {yes, it took me a few minutes to comprehend this... so expect the same for yourself...wink.gif) }

3) Please understand, not assume, that the pressure of the reactor is being maintained at the required pressure by the feed stream(s), and by no other means.

4) I am attaching the part of my report which had a short part of HAZOP analysis. It is better if you look over the net, or through some books for detailed HAZOP understanding. (the formatting is non-existent in my report...)

Ankur

Attached Files



#6 Ankur Shah

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Posted 24 December 2005 - 02:15 PM

hey!

found this to me a good link on ur hazop problem...

http://www.cheresour...p?showtopic=223

Ankur

#7

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Posted 21 January 2006 - 03:34 AM

Hi Mr. Art Montemayor
While searching on this site I found the following thread in which you have respond to the same design problem.

http://www.cheresour...x.php/t504.html <--- click here

Although I have designed the reactor, but I am very interested to get the designs you have with you, so that I can see what mistakes I have made and what other factors should I consider in the design of this reactor. I have searched a lot of literature from the Internet and libraries, which include books like Samuel Strelzoff's "Technology and Manufacture of Ammonia", journals from which I got the Kinetic data etc etc.
I would be very gratefull if you provide me with the design you have.

Hoping to get a good response.
Thanks in advance

#8 Dan

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Posted 13 February 2006 - 03:58 AM

Hi Ali thanks for your responses. I live in London how about you?
The problem with the books you listed was there were lots of them dealing with different topics I did not know which one.
Did you design exactly the same thing? the water gas shift for ammonia production? I have a big problem to be honest and that is I have a 3 month old baby therefore not enouph time for research and everything.
Now I'm trying to find the reaction rate and the equilib constant. Am I on the right track?

Please respond as soon as you can
Thanks

#9 aliadnan

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Posted 13 February 2006 - 07:51 AM

Hi Dan

Well the Water Gas Shift Reaction is as follows

CO + H2O --------> CO2 + H2


In this reaction what we are basically doing is to convert the undesired CO into H2 which is the basic component in production of ammonia. The reference of the journal I gave you in the last reply has the Reaction Rate Equation and Equilibrium constant relation. When you read that article from the journal you will come to know about many things about the reaction and what basically is happening, what are the reaction temperature and pressure and what catalyst is suitable for this reaction etc etc.
Now coming to the design, get a book Reaction Engineering book and study the design steps in the desiging of the Fixed Bed reactor, what are the factors which are involved in it, Design equation etc etc.
Try the book by Foggler, another book by Rase, there is a case study of Shift Reactor in the Rase's book Vol 2. (Sorry I don't remember the names of the books, so I have mentioned the name of authors).

I hope this helps

Regards
Ali

#10 Dan

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Posted 20 February 2006 - 08:47 AM

Hi Ali

thanks for ur reply. What I've done so far is: calculated K( equilib constant)= 12.86@T=650K but when I calculate conversion it comes to 99.7% meaning that almost all CO is converted but this seems wrong because if all CO is converted there's no need for low temp shift after the high temp one.

I'm stock I have so many books but I'm so confused. Please help me and reply as soon as possible!!!!!

Thanks a lot
Dan

#11 abhi_agrawa

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Posted 21 February 2006 - 12:03 AM

Dan,
I have not seen the paper that gives the equilibrium constant, but I know that:
1) The conversion of CO in the HT Shift reactor is about 75-80%
2) The conversion of CO in LT shift is about 90-95%
3) The overall conversion is about 98-99%
4) Depending upon the feed, you may have to select a MT Shift also
5) H2S is a poison for the catalyst usually used in this reaction
6) After the Shift converters, a Methanator is used to convert unreacted CO to Methane
7) The CO concentration in the HT Shift reactor outlet is usually in the range 3-5%

The reason for lower temperature reaction is that it favor complete carbon monoxide conversion, the higher temperature reactions allow recovery of the heat of reaction at a sufficient temperature level to generate high pressure steam.

Usually the HT shift reactor employs Iron Oxide catalyst which is promoted by Chromium and the LT Shift. The HT Shift catalyst is usually Aluminium Oxide, Copper Oxide and Zinc Oxide.

Hope this will clarify few thing,
-abhishek

#12 aliadnan

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Posted 21 February 2006 - 09:43 AM

HI Dan

What Abhishek has said is 100% correct. If you have studied the lecture you should have known these things by now.
The conversion which you calculated is at what temperature and pressure?? Is it the temperature of the inlet? Well Shift Reactor is usually an Adiabatic reactor and the temperature rises with the length of reactor, since this reaction is Exothermic so the rate of reaction decreases with the temperature rise. I have read in the Journal, reference of which is Moe, M, James, CEP(Chemical Engineerng Progress),Vol 58,Pages 33-36 (1962), that if the the temperature rise along the length of reactor is about 100-110 F then you can use the outlet temperature to calaculate the equilibrium constant, this constant is then used in the rate equation to calculate the catalyst volume.

Now Remember the Equlibrium consversion just shows that it is the maximum possible conversion which is possible at the temperature and for this conversion to take place an infinitely long reactor may be required. And the conversion used in the reactor design is less then that, you can use the conversion given by Abhishek or check from the data you have about the reactor oulet condition that concentration of CO you require from the HTS ( You can use CO concentration which Abhishek has written, because it is usually the one in the industries). Now from this CO concentration you can calculate the conversion and then proceed further.
Calculate the Volume or weight of catayst using the design equation and Rate equation. Once you have the volume of the catalyst then you calcuate the diameter and height etc etc.

I hope this helps.
Please correct me if I am wrong in any of my statements.

Regards
Ali

#13 abhi_agrawa

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Posted 21 February 2006 - 09:52 PM

Hi Ali,
A word of caution about using the Equilibrium constant at the reactor oulet for your calculations of the reactor. This method was (probably) proposed as the computing power available in 1962 was very small. Thus precise calculations for the reactor may not be easy to make. However, this will lead to errors in your estimate. Therefore, in the current context it is important that rigorous equations be solved.

-abhishek

#14 Dan

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Posted 25 February 2006 - 08:17 AM

Ali & Abhishek,
Many many thanks for ur care and response.
I recalculated my conversion at the outlet temp= 85% which sounds better, (before I had calculated at the inlet temp and I was told by my teacher I had to use outlet temp). I am still waiting for the CEP magazine that I have requested to get the rate equation and other info to continue the design. At the moment I have calculated the equilib constant= 5.542 and conversion= 85%(all for HTS). If there is anything you guys think I should know please inform me as soon as possible. I need the equations to calculate the vol of reactor which I think should be in the magazine. Or if you know any eq I can use please tell me.

Thanks very very much
respond soon

Dan

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Posted 03 March 2007 - 09:18 PM

Hi!

I have every book out mentioned above plus more.
I am design a fixed bed catalytic adiabatic reactor for a steam reforming of natural gas.
I have to design the water gas shift reactors HTS and LTS.
I have no data on the rate constant etc, just the space velocity.
the only other info I have is>
HTS
chromium promoted iron oxide catalyst
6x6 mm or 9.5x9.5 mm pellets
Space Velocity = 4000 h^-1
Tin = 266.7 C
T out = 369.1 C
P = 3558 kPa
mass flow/molar flow
compositions of entering feed

LTS
copper zinc oxide catalyst supported on alumina
Space Velocity = 4000 H^-1
Tin = 226.7 C
T out = 258.1 C
P = 3558 kPa
mass flow/molar flow
compositions of entering feed

Can some one help me!
Ive read every book and still cant figure out where to start and what steps to take.
and this is due on monday march 5!!!!

Thank you!!!
Jill
chillie_2@hotmail.com

#16 Aysh

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Posted 04 March 2008 - 12:26 PM

Hi,

I also have to design but only high temperature shift reaction. This is the data I've gathered so far:
The inlet gas composition is obtained from steam reformer which should contain 10-13% CO
the conversion will be 90%.
The reaction is run in an adiabatic fixed bed reactor at about 350 oC and 450 oC as the inlet and outlet temperature respectively.
the pressure is about 30atm.
The catalyst used is iron-chrome (ferrochrome), Fe3O4 with 10% of Cr2O3

Now, what do i do next?

Thank you!

#17 Aysh

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Posted 04 March 2008 - 12:43 PM

Hi, but how do we get the design and rate equation?

#18 mishra.anand72@gmail.com

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Posted 05 March 2008 - 03:46 AM

Use as given in literature and also state units in SI because I don't understand your units.

#19 Aysh

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Posted 05 March 2008 - 08:50 AM

Hi,

Sorry but may I know which article it is you are referring to please? Could you please post again the article if you dont mind, because I cant find your previous post.

thanks alot!

#20 sphoo1

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Posted 25 August 2008 - 08:18 PM

Hi,

I am also designing a water gas shift reaction. I had the book Rase and Fogler. However, i am not sure where to start. I have the all temperatures and flow rates of inlet and outlet. I am not adding steam to my system my synthesis gas from the gasification contains about 2:1 mol of water to CO, and i do not need a 100% conversion. I have the equilibrium constant as well. As for the catalyst, I have th following information.

CoO: 1.8-2.5%, MoO3: > 8% , MgAl2O3: 12%, Crystalline Phase MgAl2O4+Al2O3 Carrier balance.
Bulk Density: 55 lbs/cuft—881.02kg/m3
Optimum Operating Temperature: 400-800 F.—204.44 to 426.67oC
Typical Pressure: 400-600 psig-- 27.58 to 41.37barg
Shape: extrudate / Green Color.
Size: 3.5-4 mm
Surface area: >120 m2/g
Crush Strength: >27-30 lbsf/ particle
Inlet Sulfur Average: 500-5000 ppm
H2O/C: 2-8
CO conversion at 92% first passes at 662 F

But i am not sure how to use them. Can anyone please help me? I need to get the design going. What should i do after i found the equilibrium constant?

Thanks

#21 adeel99

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Posted 23 December 2011 - 11:06 AM

Hi....I m a student of chemical engg, I need data regarding water gas shift reactor....I am just at initial steps. kindly help me to calculate conversion of reaction and optimum temperature and pressure conditions. please suggest me books and websites. if u will mail something useful to me then I will be very thankful to you........adeelaslam99@gmail.com

#22 Dawood

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Posted 19 May 2012 - 10:11 AM

Hi
I am a Student of Chemical engineering and require to Design High Temperature Shift Converter and Low Temperature Shift Converter for an Ammonia Plant.
Can anyone help me with the designing steps i should follow and which book is worth following because i am really lost in finding a correct and Solid approach.
initially i have Mole% of the gas, Teperature and Pressure, and Mass Flowrate.

#23 kkala

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Posted 19 May 2012 - 02:24 PM

Searching the forum for this topic may give data that could be useful. For instance http://www.cheresour...roduction-plant '> http://www.cheresour...roduction-plant .




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