The process plant for the Tugaske Project is designed to produce 250,000 tonnes per year of saleable muriate of potash (MOP), available as pink or clear granular grade product. The operation uses solution mining to selectively dissolve potassium chloride (KCl) from an underground sylvinite ore deposit containing both KCl and sodium chloride (NaCl). Heated brine is injected into the mine caverns, and the resulting production brine is processed through a multi-stage crystallization circuit to recover KCl crystals. The recovered solids are dried in a fluid bed dryer and compacted to achieve a granular particle size distribution suitable for fertilizer markets. Final product handling involves glazing, storage, and loadout via rail or truck, with reagents added to ensure product quality and flowability.
The technical report, dated 2019, was prepared to summarize the recovery methods for the Tugaske Project. The original process design was completed by Engcomp and Innovare. In November 2019, Gensource engaged K-UTEC AG Salt Technologies, Koeppern GmbH & Co KG, and Ebner GmbH & Co KG (collectively, KKE) to take full design-supply-commission responsibility for the process plant. KKE provides a process guarantee with liquidated damages if the design fails to meet agreed performance requirements, including product quantity and quality. Engcomp remains responsible for the overall heat and mass balance and supply of utilities, and will integrate KKE’s efforts into the overall process design.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Nominal plant capacity | 250,000 | tonnes per year | Saleable MOP, pink or clear granular grade |
| Return brine injection temperature | 100 | °C | Heated in series of 3 steam heated shell-and-tube heat exchangers |
| Return brine concentration | 8.5 KCl, 20.5 NaCl | wt. % | Before heating |
| Production brine concentration | 12.7 | wt. % KCl | Expected increase across well field |
| Production brine temperature | 60 | °C | Pre-cooled in plate and frame heat exchanger |
| Crystallization stages | 6 | stages | 4 vacuum, 2 surface cooled |
| Final mother liquor temperature | 10 | °C | Achieved in SCC with chilled glycol/water |
| De-brining cake moisture | 5 | % | After cyclone and centrifuge |
| Dryer discharge temperature | 130 | °C | Fluid bed dryer outlet solids |
| Final product temperature | 60 | °C | Achieved in cooling side of glazing dryer/cooler |
| Product sizing | SGN 300 | dimensionless | Screen middling fraction |
| Reagents | Iron oxide, anti-caking amine, dedusting oil | Not applicable | Applied for colour, flow, and dust control |
Overview
The Tugaske Project is a proposed solution mining operation for potash in Saskatchewan, Canada. The process plant is nominally designed to produce 250,000 tonnes per year of saleable MOP, available as pink or clear granular grade product. Return brine from processing is heated to 100 °C and pumped to the wellfield for re-injection into the mine caverns, where it selectively dissolves KCl from the underground sylvinite ore deposit. The production brine, at approximately 60 °C, is pre-cooled in a heat exchanger against the mine return brine before feeding the crystallization circuit. The crystallization circuit progressively cools the brine to 10 °C, producing KCl crystals. The slurry is de-watered, dried, compacted, sized, glazed, and stored or loaded for shipment.
Key Process Stages
The process can be divided into four main areas: process brine and mine circulation, crystallization, de-brining and drying, and compaction, sizing, and glazing. Additional reagent addition and product storage and loadout complete the flowsheet.
Process brine, mine, circulation, and storage. Return brine from processing, at a concentration of approximately 8.5 wt. % KCl and 20.5 wt. % NaCl, is heated from approximately 50 °C to 100 °C in a series of 3 steam heated shell-and-tube heat exchangers. Make-up water is added prior to heating to replace the volume of ore removed by mining. The heated brine is injected into the mine caverns, where a near saturated NaCl brine (under saturated in KCl) selectively dissolves KCl from the sylvinite ore. The production brine, with KCl concentration expected to increase to approximately 12.7 wt. %, is collected at the surface in the Vacuum Crystallizer Feed Vessel. Prior to this, the approximately 60 °C brine is pre-cooled in a plate and frame heat exchanger against the mine return brine, providing an energy saving step.
Crystallization. The crystallization circuit comprises a 6-stage cooling crystallization process with four vacuum crystallizers followed by two surface cooled crystallizers (SCC). Each stage has two outlets (solution and slurry) allowing crystal growth to be adjusted during operations, and each stage can be by-passed for maintenance. In the vacuum crystallizers, cooling is accomplished by a steam ejector system creating a vacuum, causing water vaporization and cooling by flashing. The water vapour is condensed in barometric condensers using cooled brine as the condensing media. Brine flows from one crystallizer to the next by gravity. From the vacuum crystallizers, the brine is pumped to the two-effect SCC system, also arranged in series, where the mother liquor is further cooled to 10 °C. Recirculation pumps move crystallizer contents through shell-and-tube heat exchangers, with a mixture of ethylene glycol and water circulating through the tubes in series from the second to the first stage. Cooling flow temperature is maintained by mechanical chillers. The KCl slurry from the final SCC stage is pumped to the de-brining process.
De-brining, also called de-watering or separation. The KCl slurry from the crystallization circuit is pumped to the de-brining circuit. A cyclone operates as a clarifier, separating KCl crystals from the depleted brine. The cyclone underflow, containing the KCl crystals, flows by gravity to a centrifuge, while the overflow flows to a mixing vessel. The de-brined cake is expected to have 5% moisture and is sent to the drying circuit.
Drying. A screw conveyor pushes the wet cake into a static fluidized bed dryer, which uses natural gas to heat the air. The fluidizing air suspends the particles, and the exit temperature for the dried solids is expected to reach 130 °C. The dryer exhaust enters a gas cyclone for initial removal of entrained KCl dust, followed by a venturi scrubber where water collects finer dust particles before the air exits the scrubber stack. Collected fines are re-introduced to the system. Water is evaporated when hot air is injected to suspend particles, and a cool air stream is blown through the dryer bed to achieve the desired final product temperature of 60 °C. The very fine material will be re-introduced to the compactor.
Compaction, sizing, and glazing. Due to the relatively high nucleation rates in the surface cooled crystallizers, the particle size distribution of the KCl crystals is likely finer compared to mechanized mining and flotation processes. Therefore, all dryer discharge (100%) is compacted in a roller press, or compactor. The compactor operates in closed circuit with a flake breaker, impact crusher, and sizing screen. The screen middling fraction constitutes the final product, sized at SGN 300, typical for granular potash. The very fine material is re-introduced to the compactor, while collected fines are fed back from the dust collection system.
Glazing and reagent addition. After drying and sizing, raw water is sprayed on the hot product to harden its surface, a process referred to as glazing. Excess moisture is evaporated and the product is cooled to a maximum of 60 °C before conveying to product storage or directly to loadout. Iron oxide powder, naturally reddish in colour, is added to the KCl dryer discharge product before compaction to produce a pink coloured product. Anti-caking amine is applied to impede capture of ambient moisture and lumping, and de-dusting oil is applied as a dust suppression agent during handling. These reagents support the integrity of the final granular product and minimize degradation.
Product storage and loadout. Engcomp is responsible for the design of the product storage and loadout system. Cool granular product from the sizing processes is moved through material handling devices and stored in the final product storage building, or loaded directly into bulk railcars or bulk trucks. Product is reclaimed from storage using front-end loaders and dropped into hoppers. A small dust collection baghouse in the transfer tower collects dust generated from material handling equipment, the loadout screen, and the rolls crusher.
Additional Interesting Data and Summary
Potash produced from solution mining is pure and naturally white or clear. The addition of iron oxide before compaction allows for better impregnation into the KCl product, creating a more consistent colour throughout each granule. The design accounts for all dryer discharge to be compacted due to the finer particle size distribution from the crystallization circuit when compared to mechanized mining and flotation processes typical for other Saskatchewan producers.
The fine material from the sizing process is stockpiled in a covered bunker. The company may opt to sell the fine material as is or re-introduce it to the process.
KKE represent world-class services in potash and salt process design and equipment fabrication and supply, taking full design-supply-commission responsibility with a process guarantee. Engcomp is responsible for the overall heat and mass balance, supply of utilities, and design of the product storage and loadout system.
Key Processes
- Solution mining with heated brine injection for selective KCl dissolution
- Multi-stage cooling crystallization (4 vacuum, 2 surface cooled)
- De-brining via cyclone and centrifuge
- Fluid bed drying with gas cyclone and venturi scrubber for dust control
- Compaction in closed circuit with flake breaker, impact crusher, and sizing screen
- Glazing with raw water spray and cooling to 60 °C
- Reagent addition of iron oxide, anti-caking amine, and de-dusting oil
- Product storage and loadout via front-end loaders, hoppers, and bulk rail or truck loading
Source: Tugaske Project , 2019 Technical Report, 2019. Project website: Gensource Tugaske Project
Project website: Tugaske Project, 2019 Technical Report
