What are the fundamentals to separate hydrogen sulphide and ammonia from two stage sour water stripping unit?
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02/04/2011
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S Banik, Centre for High Technology, sbdr@rediffmail.com
Recent trend of SRU design involves use of oxygen-enriched air which creates higher temperature in the main combustion chamber. Presence of ammonia can easily be handled as temperature is higher. Oxy-enriched air gives higher capacity over conventional SRU and allows single stage stripper. Existing SRU can be easily converted for oxy-enriched air. This involves marginal cost.
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09/03/2011
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Egbert van Hoorn, Hocon B V, Egbertvh@hotmail.com
The first answer is in principle correct.
The main point of a two stage sour water stripper is to separate the H2S and NH3 in two streams.
Historically there were problems with the handling of NH3 in a SRU.
Today it is well known that the main points of processing NH3 in a SRU are temperature and residence time. In our opinion there are very limited cases which justify two stage stripping. It adds a lot of costs to the SWS unit. It does not always offer what is expected.
The purity of the products is not always as is being claimed.
Perhaps as illustration is that the pioneer of this process does not use it.
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19/02/2011
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
It is steam stripped as follows:
In a 2-column system, H2S is yielded overhead from the first column using steam stripping, usually using a reboiler with medium pressure steam to the reboiler. Column pressure is 120 psig. The sour water feed enters below a trayed or packed top section. First column bottoms feeds the second column, which has a reboiler using low pressure steam. Column pressure 20 psig. Some of the bottoms flow from the second column is recycled to the first column on the top tray. The rest is the stripped water product. NH3 is yielded overhead from the second column, which can use either an overhead condenser or top pumparound.
A 2-stage unit may contain 30 to 48 trays in the first column and 40 to 44 trays in the second column. One such process is the Chevron WWT™ process.
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