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[gvdlans]

In an old topic: http://www.cheresour...cal-co2-system/

Art Montemayor wrote a.o.:

 

 If you analyze the thermodynamic state and phase that the CO2 finds itself in under both conditions of relief and exit pressures, you will discover that you are expanding a supercritical fluid into the region where only saturated vapor and Dry Ice can exist. This is because you are expanding a supercritical fluid directly to atmospheric pressure. You are going to have a LOT OF TROUBLE with your exhaust piping and system. As I stated previously, you will be producing Dry Ice snow and it will clog up and plug your exhaust piping to the point where it will not be functioning. This is a dangerous and hazardous situation that you could create for yourself.

 

In my company we have a project were the gas from the wells contains high% of CO2. This CO2 is separated (membrane units) and the resulting CO2 rich stream (up to~85% CO2) is compressed and re-injected into the wells (in order to maintain the well pressure). As an example, we can have a stream with 85 mole% CO2 (remainder mainly methane, no water), at 164 bara and 49 degC. When this system is depressurized or when a relief valve opens, the pressure is reduced to the relief header pressure (say 2 bar), and as stated by Art above, there will be solid CO2 (= dry ice) formation. A couple of studies were done into this phenomena, that are clear about the fact that dry ice will be formed downstream the (relief) valve. Less clear is whether this will result in blocked lines. Reasons why the lines would not be blocked is that the gas velocities are high and there is no water present (water would act as a kind of glue, without water you get a fine powder that is not expected to result in blockage with the high gas velocities).

 

Does anyone have actual experience with blocked tail-ends, flare lines as a result of dry ice formation?

 

Can anyone (including Art...  ) give advise on how to design/check the relief lines or any other measure to mitigate this potential blockage? What conditions are required to get blockage?

Edited by gvdlans, 09 February 2013 - 01:52 AM.