Document Type

Working Paper

Date of this Version

4-20-2018

Abstract

Sodium cyanide and specialty cyanide production are essential operations for various industrial processes, with primary applications in mining and mineral processing. Sodium cyanide, despite the high toxicity inherent in the material and its production process, is expected to grow 5% annually, with a projected global demand of 1.1 million tonnes in 2018. This report details a process design for producing sodium cyanide through the use of two intermediate reactions and successive downstream separations. The first major step is the production of hydrogen cyanide gas from ammonia and methane derived from natural gas, via the industry standard Andrussow reaction over a platinum-rhodium gauze catalyst. Aqueous sodium cyanide is produced via a neutralization reaction of absorbed hydrogen cyanide gas with aqueous sodium hydroxide. Downstream processes include the crystallization of solid sodium cyanide from the aqueous product, with the solid product being removed from slurry and brought to low-moisture content through a series of solid-liquid separations. The low-moisture solids are formed into the final briquette product, which is 97.7% sodium cyanide by mass at a capacity of 61.5M tonnes/year, and containing sodium carbonate as the principal impurity. Unconverted ammonia is recovered and recycled back to the feed of the HCN reactor, increasing the molar percent yield of hydrogen cyanide gas on the basis of fed ammonia from 60% to 70.9%. The project requires $35.6MM in Total Capital Investment and produces a Net Present Value of $72.5MM after 15 operating years and presents an Internal Rate of Return of 48.4%. The project will break even in its third operating year when it hits full production capacity. The design is recommended due to its strong return on investment and high resilience to market fluctuations.

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Date Posted:20 April 2018