Recently, we have noticed foaming and high pressure drop in our recycle gas amine absorber column in our Diesel HDS unit. DEA is being used in the system. The column was isolated , water washed and put back in service. However, the foaming problem still persists. The antifoam chemical (non silicone based) dosage rate also was increased. But, the foaming continues. The pressure drop of the column gradually increases from 0.12 to 0.22 Kg/cm2 after introduction of minimum gas through the column and foam is being observed in the bottom of the column. Due to this, liquid is getting carried over to the suction of Recycle gas and causing tripping of the compressor.
15 days prior to the observed problem, a new antifoam chemical trial supplied by alternate vendor has been started. After addition of this antifoam chemical, it has been noticed that the amine colur changed to milky white. During the initial 15 days, the column pressure drop was observed to be normal. After 15 days, while the unit restarted after trip, foaming and resultant high pressure drop in the column was noticed.
1. What could be the possible reasons for foaming in the column? 2. Does anyone have similar experience? If so, what was done to suppress the foaming?
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