Recent interest in carbon-free energy has revived molten salt research for use in concentrating solar plants (CSP) and molten salt nuclear reactors (MSR). Most chlorides used for coolant applications include magnesium chloride as a major constituent which occurs naturally with absorbed water that hydrolyzes upon dehydration. To reduce the corrosivity of the salts, this water must be removed prior to use. The current state of the art utilizes carbochlorination to remove trace magnesium oxide dissolved in the salt. Carbon tetrachloride (CCl4) and phosgene (COCl2) are effective at removing oxide but carry considerable risk due to toxicity. Chloroform (CHCl3) offers a less toxic, a less expensive, and a more effective alternative. Carbochlorination reagents, such as CCl4, CHCl3, and COCl2, were evaluated using thermodynamics and CHCl3 proved most favorable above the melting point of typical magnesium chloride-based mixtures. Mixtures of potassium and magnesium chloride (KCl:MgCl2 68:32 by mole) were sparged with CCl4 and CHCl3 for comparison. Chloroform treatment substantially reduced oxide content of the salt melt within 24 hours at temperatures as low as 550oC. It also reduces dissolved oxide when sparging with air, making it effective against oxygen or moisture infiltration to the gas supply. This talk presents new results demonstrating the effectiveness of CHCl3 treatment for dehydration of chloride salts.

Utilizing chloroform to purify molten chlorides

2019 Fall National Meeting

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