BTX: Problem and solution - 1: Activated carbon eliminates Claus deactivation problem

In order to remove aromatic contaminants before they reach the converter beds, Saudi Aramco has installed regenerable activated-carbon beds upstream of the sulfur-recovery units (SRUS) and finally deal with chronic Claus catalyst deactivation, low sulfur recovery, frequent shutdowns to replace catalyst and problems associated with benzene, toluene and xylene (BTX). The SRU's were not operating as designed and a study was conducted to establish resolve the BTX issue. After numerous year of contemplating for the solution and the elimination of various potential solutions, the carbon units were designed for a specification involving acid-gas flow 65 MMscfd, feed pressure 13 psig, feed temperature 100°F and total BTX content a little more than 500 ppm. The new process involved fitting of a bypass on the carbon-bed unit so that it can be taken offline and the SRU left in service; in order to heat the acid gas before going to the carbon-bed vessels, the shell and U-tube exchanger uses low-pressure steam; BTX removal was possible by adsorption which takes place with acid gas in upward flow; the bed is decommissioned when the bed becomes fully loaded with hydrocarbons; steam is introduced under flow control to the top of the bed through a distributor during regeneration and water is sent to a new waste water stripper made to treat produced regeneration steam condensate to boiler-feed-water quality while BTX from the three-phase separator is injected into crude oil.