| Popis: |
The most commonly used hydrogen sulfide (H2S) scavengers, hexahydrotriazines, are cost effective, efficient solutions to sour gas treatment. As the product consumes H2S and the by-product concentration increases, very often solid deposits occur, the most problematic of which is "amorphous dithiazine". It is produced from a solution of, for example, tris-(2-hyroxyethyl)-hexahydro-s-triazine. Recent findings have confirmed that this material is not a different physical form of the monomeric dithiazine but rather a polymeric structure which results from opening of the dithiazine ring. Evidence is presented here for the first step in this polymerization reaction. Thereafter, a ring opening of the dithiazine occurs to yield a polymeric, highly insoluble material. It has been observed that the critical chemical species in the initiation of this chain reaction is the bisulfide anion that is produced from the reaction of H2S with ethanolamine liberated in the sulfur insertion reaction undergone by tris-(2-hyroxyethyl)-hexahydro-s-triazine. This process has been artificially induced by the reaction of monomeric or crystalline 5-hydroxyethyl dithiazine and ethanolammonium hydrosulfide. It is hoped that a better understanding of the chemical process giving rise to this intractable solid will enable more efficient, environmentally favorable disposal of the waste fluids and, at best, total avoidance of this undesirable condition. A novel approach to address this issue of troublesome solids, the use of an alternative scavenger type, is presented in this paper. The disposal of the waste fluids was a key issue in our consideration since the disposal of spent triazine based scavenger fluids is becoming ever more challenging and costly. Scaling tendencies at high pH is another issue for any new scavenger and plays a key role in the method of waste fluid disposal. Recent field trial data are also presented to demonstrate the efficacy of the new scavenger. |
