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Merox - Mercaptan Removal (pH/ORP & Oxygen)

Merox Mercaptan Removal

Mercaptans (RSH) are organosulfur compounds that are often present in unrefined or partially refined hydrocarbon feedstocks. These chemicals have several undesirable attributes including strong odor (garlic smell), corrosivity, and degradation of downstream additives as well as the hydrocarbon end products. For these reasons mercaptans must be removed through a catalytic process. In this paper we will examine the Merox process and the Barben Analytical products used at different points throughout the treatment stages.

Oxygen Measurment Challenges
Oxygen measurement applications can be difficult due to the moisture and contaminant gases in the stream. The presence of hydrocarbons eliminates zirconia-based oxygen sensors as due to high internal heat required to perform the measurement. Paramagnetic oxygen technology may be affected by residual water vapor which can condense and corrode small moving parts within the analyzer. Tunable Diode Laser (TDLAS) technology is a suitable yet costly solution. Frequently the end user turns to electrochemical cells for these applications due to their low cost; however they have multiple issues as well.

pH Measurement Challenges
Both extraction and sweetening Merox processes present challenges for pH measurement. Excess caustic combined with mercaptans, disulfides, and other contaminants can quickly poison the electrolyte and AgCl element used in most pH sensors. Once the sensor is poisoned the pH measurement becomes unreliable resulting in more frequent calibration. Residual oil passing by the sensor can plug the porous reference junction used in most conventional sensor designs leading to constant cleaning of the sensor tip and eventual lost measurement. Entrained catalyst fines can abrade the sensor causing premature failure of the measurement electrode.