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[Alawi]

Hello every one, once again I would like to bring up the subject of measuring H2S in LPG. The ASTM test method D 2420 is a very widely used test method for indicating the presence of H2S in LPG . The result of the test is “Negative” or “ positive”. A negative result means that the sample has “Passed “ the test and there is no H2S in the sample. In The scope of the D 2420 test method document it states that the test has a sensitivity of about 4 mg/m3 (2.8 ppm) , this means that a sample that passes the test can potentially have a 2.8 ppm H2S content. In some design codes the maximum H2S content is about 1.0 ppm. I am strongly urging you experts whom have actual experience in petroleum refining to follow up on this subject and reply to this message, it is of crucial importance that this matter (at least for one situation) is Clearfield till its roots.
1- If LPG when tested for H2S via D 2420 test method passes the test but still has the potential of having a lower or equal to 2.8 ppm H2S then all equipment including piping and storage tanks may need to take this into consideration during there design. Is this statement correct?
2- The presence of water (humidity ) in the LPG effects the allowable content of H2S allowed for in the LPG . If there is water than the H2S content must go down. To my understanding and from previous messages I have posted in this forum water in LPG is checked visually in most refineries.
I am hopping and very much interested in talking to engineers whom are in direct contact with such issues. It will be very helpful to share experience with one another and have an idea about methods used in refineries for testing H2S and water in LPG. There are others tests that can be used to measure H2S for example gas chromatography, certain potentiometric methods. There are also aspects related to the sampling of the LPG, on line or through steel cylinders for batch sampling. Water content can be measured through an electronic hygrometer. I don’t know how other refineries work, I can not travel to other refineries, the only way is by email or telephone.
Since we are on the subject, a college is facing some problems with design calculations for a sand coalescer that will be used to help remove any water from our LPG product downstream a soda caustic washer, any suggestions.

Kind regards

Alawi