2 replies to this topic

[jguido]

I was wondering what is the most affordable technology for removal of carbon dioxide from a syngas? As well, what is a good vendor for buying carbon dioxide scrubbers?

Thanks

[Art Montemayor]

Jguido:

Yours is a probing and interesting question for a student. However, it is deficient in that it does not identify the specific application you are referring to. This makes it difficult or nearly impossible to give an answer without first qualifying it or making several assumptions. You really should be specific in defining your application in order to generate a specific and useful answer.

As an example, consider that probably a majority of forum members knows that syngas (“synthesis gas”) is a gas usually produced from a non-gaseous feedstock (such as Naphtha) and used as feedstock to produce (or “synthesize”) a low-Btu fuel gas or a specific end-product (such as Ammonia). For those that lack an understanding of this definition, I suggest the following thread be read and used as a basis of understanding what I will explain:

http://www.cheresour...=1242&hl=syngas

The specifics you fail to identify are such important items such as:

1) the composition of the Syngas. The content of CO₂ is important in analyzing whether one process is better over another. Not all Sygases are necessarily the same in composition and this will affect the chosen process.
2) The pressure of the Syngas. This also will be a factor in selecting the chosen process;
3) The presence of contaminants such as H₂S, mercaptans, and other sulfur compounds;
4) The total flow rate of Syngas to be processed;
5) The quality of the product Syngas after CO₂ removal.

Basically and in general, amine solutions are used to remove the CO₂ by employing an absorber-stripper-exchangers closed system. Such systems are well explained and illustrated in the book “Gas Purification” (by Kohl & Riesenfeld; Gulf Publishing; 1979).

I don’t know what you mean by the term “affordable”. If you have intentions of investing money in the competitive gas processing/Syngas business, you should have “deep pockets”. A syngas plant is far removed from a “Ma & Pa” type of operation – in complexity and cost.

Identifying a designer/fabricator for a CO₂ “scrubber” requires you identify the above-mentioned basic data. Additionally, I would ask what you mean by a scrubber. The basic equipment in an amine solution process are:

1) An amine absorber. Also called a “contactor” tower.
2) An amine Stripper, complete with reboiler and overheads cooler-condenser.
3) “Lean” Amine solution exchanger(s) and cooler.
4) A “Lean” Amine solution pump.

There is no “scrubber” employed. The unit operations used are Absorption and Stripping. As you can appreciate it (by reading “Gas Purification”), the CO₂ process can become quite expensive if you are handling a low-pressure, high flow rate, contaminated syngas.

The amine processes available for removing the CO₂ are various: Monoethanolamine (MEA), Diethanolamine (DEA), Diglycolamine (DGA), Methyldiethanolamine (MDEA), etc. Each type of solution fits a certain “niche” or application. They don’t necessarily compete with each other. The amine process has been employed industrially since Mr. R. R. Bottoms patented the process for the Girdler Corporation in 1930. Many improvements have been made and many variations of the basic process exist.

There are other processes and methods available to remove CO₂ from a gas stream and you will find them all listed in Kohl & Riesenfeld.

Perhaps if you can give us detailed specifics on what you have in mind or have been assigned as a student, we might be able to add further helpful information or answers.

[djack77494]

Guys,
There are other commercially available processes useful for removing large quantities of CO2 from high pressure gases. One that I worked with in they early years of my career in coal gasification technology was the Benfield Process. It involved circulating an inorganic carbonate solution between Absorber and Stripper Columns. CO2 would be chemically absorbed in the lean solution, which would react carbonate ions to bicarbonate ions; in the Stripper, the reverse reaction would occur, with CO2 being liberated. BUT, like Art said, the choice of approach is absolutely dependent on the specifics of your application, Unfortunately (or fortunately) engineering is not a business that lends itself well to generalizations.
Doug