Material in kettle reboilers

[ahmela]

Hello,
I'm working with a project dealing with a C02 Capture Plant used in a CCPP (combined cycle power plant). In my work I will compare two configurations of kettle reboilers: One with condesing steam as heating medium in the tubes, and the other with hot pressurised water in the tubes.

The chemical solvent used in the shell side is 30% MEA with a temperature of 120C.

I wonder what material is usually used in kettle reboilers for this purpose when steam is condensing inside the tubes, and the pressure is around 1,6 bar(a). The tube diameter is 1 inch OD.

Can we use the same material when water at a pressure of 110 bar(a) is used in the tubes and just increase the tube thickness?

/Thank you

 

[TJOrlowski]

Are you looking to purchase equipment that can be used interchangeably: sometimes using steam in the tubes, and sometimes using water in the tubes? Or are you just doing a cost-benefit of two different designs?

As long as your system is closed-loop and properly treated, you should be able to use the same material for the tubes, and just increase increase thickness to accomodate the increased pressure. Material selection will most likely be controlled by the shell-side media in your case.

-TJ Orlowski

 

[ahmela]

Hello,
The idea is to use one kettle reboiler with two heating coils used at the same time, one with steam and one with pressurised water, but I don't know if this configuration is appliable yet. Otherwise two seperated reboilers have to be used.
I've find out that stainless steel is the best choise of material when using 30% MEA as in our case, due to the corrision risk. Is this a good choise, or can we use a cheaper material?

I have another question of how big kettle reboiler can be. I have calculated the needed heat transfer area to 5500 m^2 for the steam tubes, and 400 m^2 for the water tubes. When I compare these numbers in

http://www.mathce.com,

the largest reboiler there have an area of 30000 ft^2 (2787 m^2). Can kettle reboilers not be larger or do we have to use several reboilers, which will increase the costs dramatically??

Thank you.

 

[TJOrlowski]

300 series (304/L and 316/L) have become economical choices for tube materials.

As far as feasability, and required surface area, you should contact an actual designer/fabricator of reboilers, give them your performance requirements, and let them design it.

It sounds like you are looking for a single kettle, with tube bundles/heads on each end. The bundle on each end can either be TEMA type T straight tube with floating internal head, or TEMA type U u-tube bundle, or a combination of both.

The maximum size of the kettle will depend on the capabilities of the shop you work with.

-TJ Orlowski