The proposed processing plant is designed to produce 250,000 metric tons per year of standard-grade muriate of potash (MOP) using solution mining and crystallisation techniques.
Report context
The Preliminary Economic Assessment for the Vanguard Project, prepared for Gensource Potash Corporation, describes a proposed solution mining and processing operation to recover potassium chloride (KCl) from an underground Sylvinite ore deposit. The technical report includes process descriptions for the major processing areas from solution recovery through product load-out, together with process design criteria. The report date is indicated by the preliminary economic assessment status.
Processing route
Injection and Solution Recovery
Return brine from processing will be heated to 70 °C and pumped to the wellfield for re-injection into mine caverns. The return brine will have a concentration of approximately 8.6 wt. % KCl and 20.1 wt. % NaCl. Heating will be accomplished in a steam heated shell-and-tube heat exchanger from approximately 47 °C to 70 °C. Make-up water will be added to the brine prior to heating to account for additional water needed to fill the mine cavity as ore is mined and removed.
Production brine from the wellfield is expected to increase in KCl concentration to 12.6 wt. %. Prior to the Crystallizer Feed Tank, the brine will be pre-cooled in a heat exchanger with the mine return brine, which will also pre-heat the return brine as an energy saving step.
Cooling and Crystallization
From the feed tank, brine will be pumped to the Vacuum Crystallizer for initial recovery of KCl. In the Vacuum Crystallizer, brine will be cooled to 35 °C, causing some KCl to precipitate as crystalline solids. The crystallizer will have a slurry recirculation pump to promote crystal growth.
Cooling will be accomplished by a steam ejector pulling a vacuum in the crystallizer body, causing vaporization of water and cooling of the crystallizer contents. Water vapour will be condensed in a barometric condenser using cooled return brine as the condensing media.
From the Vacuum Crystallizer, KCl slurry will be pumped to the debrining process for recovery of KCl solids. Mother liquor (saturated KCl solution) will be pumped to the Surface Cooled Crystallizer for further recovery. In the Surface Cooled Crystallizer, mother liquor will be cooled to 10 °C, resulting in additional KCl solids precipitation. Four axial flow recirculation pumps will pump the crystallizer contents through shell-and-tube heat exchangers for cooling, then back to the crystallizer for crystal growth. The cooled media in the exchanger will be chilled water from the chiller installation.
KCl Debrining
Slurry containing KCl solids from the Vacuum Crystallizer and Surface Cooled Crystallizer will be pumped to hydroclones to pre-concentrate the solids from 20 wt. % to approximately 50 wt. % prior to being sent to the KCl Centrifuges. Overflow from the hydroclones will be sent to the Centrate Tank. The concentrated underflow will gravity feed through a launder to the KCl Centrifuges. The KCl centrifuges will be screen-bowl type and will produce a dryer feed cake with a solids weight fraction of approximately 95%.
KCl Drying
A fluidized bed dryer will be used to dry residual moisture from the KCl solids and produce a potash product with a maximum of 0.15 wt. % H₂O. Air for fluidizing and drying will be heated by natural gas firing. The exit temperature for the dried solids has been designed to be 150 °C.
Fluidizing air exiting the dryer will enter a gas cyclone for initial removal of entrained KCl dust. Overhead air from the cyclone will flow to a venturi scrubber where water contact will remove finer dust particles. Dust collected in the cyclone and scrubber water will flow to the Fines Dissolver Tank. A portion of the mother liquor from the Surface Cooled Crystallizer will be introduced into the tank to dissolve collected dust and return it to solution for the Vacuum Crystallizer Feed Tank.
Compaction
Due to the relatively cool temperatures experienced in cooling crystallizers, it is expected that up to 50% of KCl crystal solids produced will be below the size typical for standard potash product: 98% + 0.21 mm. A product screen will separate product-size KCl solids from the dryer. The underflow from the Product Screen will be sent to a compaction system to increase crystal size.
Product-size material from the screen will be conveyed to the Product Cooler where it will be cooled to 90 °C using a water-jacketed solids cooler. Heated water exiting the cooler at approximately 32 °C will be used for make-up water for the mine and recovery process.
Product Load-out
Anti-caking agent and de-dusting oil will be added to the cooled standard potash product. The product will then be conveyed to shipping containers for storage and shipment. A dual stage container tipping system will be used for loading, weighing and handling. For a standard 20-foot (6.1 m) shipping container, the loaded containers will contain approximately 35 metric tons of product assuming a 90% fill volume.
Plant Utilities
Major utilities systems for the plant include: steam boiler, turbine/generator cogeneration, chiller, cooling tower, water treatment, waste disposal, and disposal well system.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| Annual production rate | 250,000 | metric tons per year | Design |
| Product grade | Standard (SNG 83) | , | Design |
| Product purity (weighted average) | 96.0 | % | Design |
| Process design purity target | 99.9 | % | Design |
| Plant utilisation | 8,000 | hours per year | Design |
| Annual turnaround | 160 | hours (6.7 days) | Design |
| Scheduled downtime | 300 | hours (12.5 days) | Design |
| Unscheduled downtime | 300 | hours (12.5 days) | Design |
| Plant recovery | 97.3 | % | Design |
| Total process losses | 2.70 | % | Design |
| Mining required | 256,937 | metric tons per year KCl | Design |
| Injection stream temperature (leaving plant) | 75 | °C | Design |
| Injection stream temperature (at wellhead) | 72 | °C | Design |
| Production stream temperature (at wellhead) | 55 | °C | Design |
| Production stream temperature (at plant) | 52 | °C | Design |
| Return brine KCl concentration | 8.6 | wt. % | Design |
| Return brine NaCl concentration | 20.1 | wt. % | Design |
| Production brine KCl concentration | 12.6 | wt. % | Expected |
| Production stream KCl concentration | 155 | g/l | Design |
| Production stream NaCl concentration | 242 | g/l | Design |
| Vacuum crystallizer temperature | 35 | °C | Design |
| Surface cooled crystallizer temperature | 10 | °C | Design |
| Hydroclone feed solids concentration | 20 | wt. % | Design |
| Hydroclone underflow solids concentration | 50 | wt. % | Design |
| Centrifuge cake solids weight fraction | 95 | % | Design |
| Dried product moisture maximum | 0.15 | wt. % H₂O | Design |
| Dried solids exit temperature | 150 | °C | Design |
| Product cooler exit temperature | 90 | °C | Design |
| Product cooler water exit temperature | 32 | °C | Design |
| Anticaking agent addition rate | 102 | g/t | Design |
| Dedusting oil addition rate (18 wt%) | 1,411 | g/t | Design |
| Ore deposit specific gravity | 2.17 | , | Design |
| Container capacity (20-ft container, 90% fill) | 35 | metric tons | Design |
Project website: https://www.gensourcepotash.ca/vanguard-area-projects/
Technical qualifications
The process descriptions and design criteria presented in this preliminary economic assessment represent proposed design values and expected performance. The report states that a Design Criteria was developed at the onset of the project design and was used as the basis for detailed material and energy balance, equipment design, and utility consumption calculations. No historical operating data from this specific project are reported, and no testwork results are described in the recovery methods sections. The production stream composition at the wellhead and plant stream temperatures are design values. The ore deposit specific gravity, anticaking agent rate, and dedusting oil rate are process design criteria. The report is a Preliminary Economic Assessment and is not a feasibility study.
Source: Technical Report – Preliminary Economic Assessment, Vanguard Project, prepared for Gensource Potash Corporation, sections 17.1–17.9, including Table 17.1: Process Design Criteria.
