Cypress Development Corp reports positive results from a PEA of the its Clayton Valley lithium project in Nevada, USA. The PEA was prepared by Global Resource Engineering (GRE). Highlights:

• NPV of $1.45 billion at 8% discount rate and 32.7% IRR on after-tax cash flow
• Lithium carbonate price of $13,000/t based on Benchmark Research market study
• Average annual production rate of 24,042 t of lithium carbonate over 40-year life
• Capital cost estimate of $482 million, pre-production and operating cost estimate averaging $3,983/t of lithium carbonate
• Updated Resources from May 1, 2018 estimate: Indicated Resource of 831 Mt at 867 ppm Li, or 3.835 Mt lithium carbonate equivalent (LCE)
• Inferred Resource of 1,120 Mt at 860 ppm Li, or 5.126 Mt LCE.

Cypress CEO Dr. Bill Willoughby commented “This is another important milestone for the project and Cypress. The PEA outlines the steps necessary for a mine and mill at Clayton Valley, including a sulphuric acid plant which is the main driver in the costs. GRE uses a conventional approach in processing and developed a production schedule that utilizes only a small fraction of the total resources on the property. The end result is a project that has strong economics and the potential to generate significant cash flow.”

GRE evaluated four options for mine equipment and mill feed transportation and selected an in-pit feeder-breaker with slurry pumping for the base case. No drilling or blasting is required, and the only major piece of mobile equipment is a wheel loader to feed the in-pit feeder-breaker. Waste mining is minimal, amounting to a total of 6 Mt over the 40-year mine life.

The plant design by GRE includes agitated tank leaching, and a multi-stage thermal-mechanical evaporation system for concentrating leach solution. Slurried feed is transported to the mill where lithium extraction is achieved through leaching at elevated temperatures with dilute sulphuric acid. The sulphuric acid concentration is targeted at 5%, with the addition of concentrated acid delivered from the on-site acid plant.

The estimated acid plant capacity is 2,000 t/d of sulphuric acid, generated from the combustion of elemental sulphur trucked to the site in the molten state. The acid plant has the potential to produce up to 25 MW of electricity, but at additional capital expense. For this study, only enough electricity will be generated to run the acid plant. Steam from the plant will be used for heating in the leaching and evaporation stages of processing.

Leaching will take place in a primary leach vessel followed by a series of thickeners. Retention time in the leach circuit is estimated at four to six hours with acid consumption estimated at 125 kg/t of feed. Overflow from the final leach thickener is pumped to a primary impurity removal circuit where calcium hydroxide is added to precipitate iron and aluminium, and the thickened underflow filtered and conveyed to a dry-stack tailings facility. The purified solution is reduced in volume via a multi-stage thermal-mechanical evaporation system where evaporate is collected and recycled as process water, and the condensate is treated by stage-wise addition of sodium hydroxide and soda ash to precipitate calcium, manganese and magnesium before advancing to final product production. Precipitation of the final product occurs with the addition of soda ash, producing a lithium carbonate product targeted at 99.5% purity. Net recovery of lithium throughout processing is estimated at 81.5%.

Process water for the operation will be obtained by recycling barren leach solution after treating in a reverse osmosis plant, and by introducing fresh make-up water, estimated at 345 m3/h and delivered via pipeline from a well field located off-site.