CO2 recovery/generation

[Potties]

Hi, I’m currently working as an intern at a bottling company and have been asked to do a feasibility study on a 1000 kg/h CO2 (beverage grade) plant.

The most attractive options have been identified as follow:

1) Recovering the CO2 from flue gas from either of the two boilers currently at the plant (one coal and one natural gas) of which only one is used at a time. Both produce an excess of steam, so there is enough energy available for the later amine/CO2 desorption process. Flue gas analysis is not available at the moment, but has been requested and should be available in the next few days.

2) Constructing a new natural gas boiler/burner used solely for the generation of CO2. Preliminary calculations have shown that at least 525 Nm/h (ref 0°C) will be required to achieve a final product stream as stated.

Now, can anyone tell me what the potential problems that I should look for? Obviously the recovery option would be the cheapest, but I’m weary of unforeseen problems.

I would also like to know which amine solution (MEA, DEA etc.) would be the best to use. Furthermore what concentrations/temperatures of solvent would be most favourable; apparently there are many problems when using higher conc. of MEA. Lastly, I would like to know what the energy requirement is for the absorption/ desorption process (Kj/kg CO2).

Thanks for any help provided

 

[PersonalProfile]

No idea, though suspect 1. would be scuttled on (or potential for) contaminates alone, let alone (I assume) cost of plant etc.

Again, no idea, though I understood industrial CO2 was generally yielded via chemical reaction.

http://en.wikipedia.org/wiki/Carbon_dioxide#Industrial_production

Regards,
Lyle

 

[Montemayor]

Potties:

Yours is an assignment I have done many times in the past. I even have developed an Excel workbook in Spanish/English regarding the subject of generating food-grade CO2 from a combustion process in a fire tube boiler. I designed, built, and operated this type of plant in several countries when I was a young engineer.

It would take a very long time to write out ALL the potential problems that you should look for and I don’t believe that is a just query to post on this Forum. This is not a Forum dedicated to teach Chemical Engineering; it is intended to help out Chemical Engineers who have specific, well-defined problems in an engineering assignment or application. It is far more expedient and efficient for you to specify in a detailed list the specific issues you are having problems with or don’t understand. That way, the issues can be addressed in an orderly manner. For example:

1) I recommend you employ a 10%-15% MEA solution in your design. This will impose a steam load on your boiler and you should confirm this with a complete process heat and mass balance.
2) Your energy requirements (MEA reboiler duty) will be determined by your heat and mass balance.

Do not fail to create a detailed Scope of Work for your process design. This means that you should consider how you must not only generate the pure, low-pressure CO2, but also compress, dry, treat, and store the resultant product. This will lead you to the realization that you must employ a 2-stage process compressor, an adsorption dryer, and a refrigeration unit to liquefy and store the product.

If interested, you can elaborate your specific needs in this thread and I can help you. But I can only help you to the extent that you furnish as much basic data and scope as you can possibly furnish.

 

[dcasto]

to assist you some more, primary amines like mea require very little pressure to react, whereas secondary amines like DEA require more pressure. This means you need only compress the flue gas to say 50 psig before going to the amine contactor in MEA, but you'd need at least 150 psig on the dea (200 psig to get maximum loading and recovery).

This are discussed in the GPSA data Book I believe.

At the GPA a couple of years ago, there were papers presented on CO2 sequestration from a coal power plant. The results showed that about 30% of the power plants energy would be consumed just to remove the CO2 from the stack. And that is just removal and not compressed to pipeline and injection pressures.

 

[Potties]

A mass/heat balance found that MEA soultions with concentrations above 18% will be required due to the amount of steam available.
-Thanks for your help in highlighting potential problems there Montemayor

Reasearch showed that it would there are many problems (most notibly dust) when purifying CO2 from coal burner flue gas. This will raise the capital rquired for the project to such a degree that will not be feasible for the quantities of CO2 that we wish to produce.

Now for further quesions:

1) How long does startup usually take for a CO2 generation plant? i.e. the time required to reach steady state

2)What lifespan can one expect from the MEA and how will this lifespan be affected by the MEA concentration chosen?

 

[case3452]

am just new but will help you the next time i log in.

 

[TD2K]

What is the company expecting you to produce? Enough design development to allow estimate of capital and operating/maintenance costs so you can screen your options? How much time do you have? What type of support do you have access to in order to accomplish the above?

This seems to be a pretty ambitious task.