Molten salt oxidation of mixed waste: Preliminary bench-scale experiments without radioactivity

Abstract

Molten salt oxidation (MSO) is a process in which organic wastes are oxidized. by sparging them with air through a bed of molten sodium carbonate (bp = 851°C) at >_900°C. This process is readily applicable to the mixed waste because acidic products from CI, S, P, etc., in the waste, along with most metals and most radionuclides, are retained within the melt as oxides or salts. Rockwell International has studied the application of MSO to various wastes, _including some mixed waste. 5 A unit used by Rockwell to study the mixed waste treatment is presently in use at Oak Ridge National Laboratory (ORNL). ORNL's studies to date have concentrated on chemical flowsheet questions. Concerns that were studied included carbon monoxide (CO) emissions, NO x emissions, and metal retention under a variety of conditions. Initial experiments show that CO emissions increase with increasing NaCI content in the melt, increasing temperature, and increasing airflow. Carbon monoxide content is especially high (>2000ppm) with high chlorine content (> 10%). Thermal NO_ emissions are relatively low (<5 ppm) at temperatures < 1000°C. However, most (85-100%) of the nitrogen in the feed as organic nitrate or amine was released as NO x. The metal contents of the melt and of knockout pot samples of condensed salt show high volatilities of Cs as CsCl. Average condensed salt concentrations were 60% for barium and 100% for strontium and cobalt. The cerium disappeared-perhaps from deposition on the alumina reactor walls.

Cyanide Destruction in Molten Carbonate Bath: Melt and Gas Analyses

“…Unfortunately, COx data were not collected as a function of the gas flow rate. These reactions are in agreement with the findings of a previous study where it was pointed out that the melt accumulates nitrogen compounds when CO and CO2 levels are low and releases nitrogen oxides when CO and CO2 levels are high (10). Figures 3b and 4a indicate that the amount of NOx increases (rapidly at first and then slowly) and the amount of COx decreases (slowly), respectively, with increasing oxygen content of the input gas.…”

“…The salt of choice is Na 2 CO 3 because of its stability and nontoxicity at high temperatures, ability to retain acidic gaseous products, high thermal conductivity, availability, and cost. Mixtures of Na 2 CO 3 −Li 2 CO 3 −K 2 CO 3 , Na 2 CO 3 −NaCl, and Na 2 CO 3 −Na 2 SO 4 have also been used ( , ).…”

“…The exhaust gas streams contain moisture along with small quantities of CO, CO 2 , N 2 , N 2 O, NO, NO 2 , F 2 , Cl 2 , HF, HCl, SO 2 , SO 3 and phosphorus-bearing gases, which can be released into the atmosphere without secondary processing. So far, this technology has been used to process a wide variety of organic and mixed wastes ( − ), and the results suggest that it could be a viable alternative to incineration. No data, however, has been obtained regarding the oxidation of cyanides in molten carbonate baths.…”

Scientific and Engineering Literature Mini Review of Molten Salt Oxidation for Radioactive Waste Treatment and Organic Compound Gasification as well as Spent Salt Treatment

“…Many scientific papers report the MSO destruction of chemical and hazardous wastes as well as radioactive and mixed wastes [1,40,82,93]. There are a few papers on general types of waste that are spiked and used as surrogates for hazardous or radioactive wastes [13,18].…”

Molten salt oxidation of chloro-organic compounds: Experimental results for product gas compositions and final forms studies

“…The molten sodium carbonate has several important characteristics: (1) it is stable, nontoxic, and compatible with the CO2 and HjO products; (2) it reacts with acidic products such as HCl or CI2 from organic chlorine compounds (SO2, P2O5, etc.) to form sodium salts that remain in the melt; and (3) it is an excellent heat-transfer medium and heat sink.…”