Performance of erythorbic acid as an oxygen scavenger in thermally aged lean MEG

Abstract

The objective of this work is to further evaluate the performance of the erythorbic acid oxygen scavenger designed by (Kundu and Seiersten, 2017) within 85% wt. Thermally Aged Lean Mono Ethylene Glycol (TAL-MEG). Experiments were performed at two levels of dissolved oxygen concentrations including 1000 ppb and >7500 ppb at pH values of 6, 9 and 11. Furthermore, the erythorbic acid oxygen scavenger was evaluated under conditions representative of an industrial MEG regeneration system in terms of salt and organic acid concentrations to replicate field usage. Strong performance of erythorbic acid in combination with manganese and diethylethanolamine (DEAE) was observed under field conditions suggesting that erythorbic acid may provide an attractive alternative oxygen scavenger for use in the oil and gas industry in place of traditional sulfite based scavengers. However, the results generated within TAL-MEG showed a reduction in the performance of erythorbic acid oxygen scavenger when compared to fresh MEG solution. Moreover, results confirmed that varying acetic acid concentration did not affect oxygen scavenger performance within TAL-MEG. It was observed that the pH of the solution was the primary factor in determining the performance of the erythorbic oxygen scavenger tested with insufficient oxygen removal achieved at a pH of 6. In contrast, strong performance was achieved at pH 9 and 11 successfully reaching below 20 ppb dissolved oxygen concentration within a reasonable timeframe with little to no impact due to the presence of mineral salt ions and organic acids.