In our DHDT unit stripper bottom doctor test result is positive while after taking sample test from vacuum drier bottom result is negative, what could be possible reasons. Stripper feed is heat exchanged with stripper bottom and then stripper bottom routed to drier. We are maintaining stripper inlet temperature around 260deg C. HP steam temperature at stripper inlet is 280 degC.Jun-2022
Roger Haglund, Eprom, firstname.lastname@example.org
You can have a feed-effluent heat exchanger leak, smaller amounts of feed is bypassing the stripper/dryer and this contaminates the product. Check the differential pressure, I expect your product pump pressure is higher than the stripper feed.
Nghia phu Pham, Haldor Topsoe, email@example.com
Removing H2S in the steam stripper could be close to passing doctor test. The remaining H2S is further reduced in the vacuum drier together with water. The H2S content in the bottom of the vacuum drier is then low enough to pass doctor test. Increasing the stripping steam could make the stripper product pass doctor test.