7 replies to this topic

[Steve90]

Hi guys !!

 

I have a sour natural gas (containing only CO2) with the following conditions

 

Pressure 70 barg

Temperature 98.2°C

 

Is it essential to reduce the gas temperature before entering the DEA contactor to nearly 40°C for example?

 

Thanks

[Zauberberg]

There are a few key reasons why decrease in temperature is required:

 

1) Improve absorption efficiency. This is particularly important for CO2.

2) Reduce design temperature for the treated gas piping downstream. In case the treated gas is routed to a pipeline, the maximum temperature should not exceed the maximum temperature of pipeline coating material (usually around 50 degC).

3) If Amine unit is followed by dehydration unit, cooling the gas will significantly reduce water load on the dehydration unit.

[Steve90]

thanks Dejan u'r always helping me !

[RockDock]

An air cooler would probably do the trick. I wouldn't say you have to get down to 40C, but I would want to cool it to at least under 60C.

 

The temperature is not going to matter too much for the absorption of CO2 with DEA, but the reaction with DEA is exothermic. I would expect to see a Rich amine T of about 80-90C and sweet gas T of 65-70C.

[Satyajit]

Hi Steve,

                The feed gas temperature influences the kinetics of CO2 absorption reaction and equilibrium CO2 content in rich solution. This temperature is also guiding the heat requirement in your stripping section.  Re-boiler duty in stripping section will increase if you bring down the inlet temperature too much.  Therefore, an optimum temperature ( operating range) is normally selected to meet the product purity and specific energy requirement of CO2 removal process selected.

This temperature is normally fixed by licensor by taking care of many aspects including CO2 slip, height of the column, type of packing , rich solution loading, specific energy requirement, water balance etc.  As others have highlighted, the feed gas temperature for sure should not be at 90C but at a moderate temperature of 65-75C.  I would suggest you to contact your CO2 removal licensor for the best advice.

You can see the impact of  feed gas temperature by running aspen simulation model for DEA based CO2 removal process.   

Kind regards,

Satyajit

[RockDock]

Just to be clear, I would not consider 65-75 C to be a moderate temperature. It is certainly high for an inlet feed.

 

The temperature will not have a significant impact on CO2 slip, either. The main issue would be the rich amine temperature, and perhaps the temperature of the absorber. It will get warmer and effect the pH. You may limit yourself to stainless steel material by operating at such high temperatures. I would also avoid using the aspen simulation for amine sweetening. You want to use an ionic simulator, like ProMax. That way you can model the actual reactions taking place and get a good prediction of the temperature increase due to the heat of reaction.

[Philip le Grange]

Hi,

 

Is this H2S and CO2 removal or only CO2 removal? Several plants in the middle east operate with feed gas in the 60 to 70C range. Often they will use DGA as it works better at higher temperatures than other commonly used amine like DEA.

 

Kind Regards,

Philip le Grange

(www.AmineExperts.com)

[RockDock]

DGA is a good solvent to use, especially in hot environments. However, you will need to add another air cooler to cool one of the stages near the bottom of the absorber with DGA. If that is not done, you will likely see corrosion in the absorber, as it will get too hot.