Abstract
For the purpose of establishing recycle technology to reduce environmental load, technical and practical development of supercritical water is required. An area of high impact on above purpose is in the recycling of sulfur-containing wastes that are produced in gas clean-up facilities of coal gasification processes. For this purpose, pseudo-first order rate constants were evaluated for thiosulfate ion and thiocyanic ion decomposi-tion in subcritical water and in supercritical water (SCW). Experiments were conducted to decompose so-dium thiosulfate and sodium thiocyanate at 340-400°C and at 25MPa. Thiosulfate ion could be decomposed 100% in 10s reaction time to sulfite, sulfate, and sulfide ions in SCW. Thiocyanic ion could be decomposed 20% in 30s in SCW. When thiosulfate ion was added to sodium thiocyanate solution, however, decomposition rate increased to about 30%. Main reaction pathways and kinetics were determined with a flow reactor. The results show that thiosulfate ion can be completely decomposed in SCW, but that decomposition of thiocyanic ion in SCW requires different conditions, additives, or oxidants.
