Studies On Decrease Of Equipment Corrosion In Sulfolane Extraction System

Sulfolane is extensively employed in refinery and petrochemicalindustry as an ideal solvent for the extraction of aromatic hydrocarbons.However, sulfolane always deteriorates during the operation due to theformation of acidic substances such as SO42-,sulfonics and carbonxylacids. In addition,small amount of Cl-1 ion accumulates in the solvent.These substances and ions cause the serious corrosion , damage and evenunexpected stop of the extraction equipment, which result in thesignificant loss of sulfolane solvent.Based on the analysis of operating conditions of the existingeqiupment and the comparison of the purification methods for the removalof sulfur and chloride ion, anion-exchange resin was chozen in this paperto remove the corrosive ions in sulfolane. The macroporous weak baseanion-exchange resin was determined through the experiments and thesuiable conditions was set:space rates(w) 6.0h-1,temperature 40～45℃,pressure 1.5Mpa.The lean solvent sulfolane processing amount were larger than 300per mass of the anion-exchange resin. The pH value of purified solventwas above 6.0 and the acid value decreased,the Cl-content decreased from5.0mg/L to less than 1.0mg/L .The equipment corrosion was effectivelyinhabited,the anti-corrosion ratio was over 70%,sometimes could be over80%.The anion echange resin has good thermal stability and no pyrolysiscould be found in the range of selected operating temperature range.Theresin could be regerated using 3%NaOH aqueous solution and recycledafter water washing. The Na+ ion in sulfolane solvent was less than0.3mg/L when the water washing ratio was 40:1. No Na+ ion could bedetected in the aramatic hydrocarbons ater extraction. The deterioationcondition was almost same before and after purification, and no harmfulinfluence would be brought in this unit and subsequent units.The results of scale-up experiments were better than those ofsmall-scale(lab-scale) experiments under the same operating conditions. Itcould be predicted using the ion exchanger operation theory that the resultsof industrial-scale experiments would be better than those of pilot-scaleexperiments.Less wastes would be produced by employing the anion exchangeresin to purify sulfolane , the wastes could be treaed together with totherwastes and thus no additional investment was needed. The directeconomical benefit would be near 4 million per year. The benefit would beeven larger when considering the more stable running of the relatedequipments.