The 2022 preliminary economic assessment for the Piskanja borate project in Serbia, prepared for Erin Ventures and Temas Resources, raises the target concentrate grades to 40 to 45% B2O3. The report states that the metallurgical parameters are largely assumptions pending testwork.
The Technical Report and Preliminary Economic Assessment for the Piskanja Borate Project, Serbia, was prepared for Erin Ventures Inc. and Temas Resources Corp., with an effective date of June 24, 2022 and a signature date of August 1, 2022. The report says more testing is needed to find the best way to upgrade the Piskanja mineralization to a minimum marketable concentrate grade. Borate beneficiation is, however, established and widely used in Turkish boron mines. The PEA assumes a flowsheet like that of the Emet colemanite plant in Turkey. Per Burat (2008), Emet treats 600,000 t a year of 27% B2O3 ore to make 300,000 t a year of concentrate at 43% B2O3. The Piskanja plan produces about 250 ktpa of colemanite and ulexite concentrates, and later 25 ktpa of boric acid.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | June 24, 2022 | Not applicable | For Erin Ventures Inc. and Temas Resources Corp. |
| Average head grade (mine plan) | 34.99 | % B2O3 | Range of head grades in the mine plan |
| Colemanite concentrate | 40 | % B2O3 | Assumed |
| Ulexite concentrate | 45 | % B2O3 | Assumed |
| Mixed colemanite/ulexite concentrate | 40 | % B2O3 | Assumed |
| Tailings grade | 7.5 | % B2O3 | From the magnetite fraction in SGS HIMS testwork |
| Concentrate production | About 250 | ktpa | Colemanite and ulexite in total |
| Boric acid production | 25 | ktpa | Later in the mine life; 80% B2O3 recovery assumed |
| Beneficiation tailings | 18 to 200, average 47 | ktpa | Varies with ROM grade |
| Boric acid tailings | 42 | ktpa | Expected |
| Tailings to backfill | 95 | % | 5% to the TSF |
| TSF | About 150,000 m³ over about 6 ha | Not applicable | Double 2 mm HDPE liner |
Overview
The Emet reference flowsheet concentrates colemanite by disintegration, washing and size classification. Coarse sizes are upgraded by attrition tumbling and hand sorting, and fines below 6 mm by attrition scrubbing and size classification. For Piskanja, the PEA assumes a similar beneficiation route to colemanite, ulexite and mixed concentrates. A boric acid plant would follow later in the mine life. Mass yield and B2O3 recovery in beneficiation vary with run-of-mine grade, against fixed concentrate and tailings grades. About 95% of the beneficiation and boric acid tailings is used as underground backfill. The rest goes to a lined tailings storage facility (TSF) south of the plant.
Key Process Stages
Beneficiation (assumed). Disintegration, washing and classification are followed by attrition tumbling and sorting for coarse material and attrition scrubbing for fines. The process is modelled to give 40% B2O3 colemanite, 45% B2O3 ulexite, and 7.5% B2O3 tailings.
Boric acid. A 25 ktpa boric acid plant is assumed at a typical industry recovery of 80% of B2O3. The report recommends testing how feed grade affects sulphuric acid consumption.
Tailings storage. Of about 1.22 Mt of tailings produced over the project, about 61,000 t (55,000 m³ at a dry density of 1.1 t/m³) goes to the TSF. The site is a former Ibar Mine settling pond for coal washing, on already-degraded land. The conceptual dam is about 4.4 m high, with a 5 m crest, 1V:2.5H downstream and 1V:3H upstream slopes, and 1 m of freeboard. It uses downstream construction, as in the 2014 PEA. The design volume is about three times the need, to allow emergency spill catchment. Tailings are delivered as slurry by pipeline. A decant system returns water to the plant, and a leak detection system sits between and below the HDPE liners.
Additional Interesting Data and Summary
The report says only very limited metallurgical testwork supports the PEA. That work brought the iron content of the product close to target, but it did not upgrade the boron content to the assumed 40% B2O3. No specific process plant engineering was done, and plant costs are high-level estimates from generic databases and similar projects. Future testwork should cover the full range of grade and mineralogy, meaning the ratios of colemanite, ulexite and howlite. Dry stacking of tailings remains an option pending geophysical, rheological and geochemical testing.
In summary, the 2022 Piskanja PEA is a conceptual borate flowsheet modelled on Turkish colemanite practice. It assumes 40 to 45% B2O3 concentrates and a small boric acid plant, and its process basis remains unproven by testwork.
Key Processes
- Ore disintegration, washing and size classification (assumed)
- Attrition tumbling, hand sorting and attrition scrubbing (assumed)
- Colemanite and ulexite concentrate production
- Boric acid production with sulphuric acid
- Tailings backfill and lined slurry tailings storage
Source: Technical Report and Preliminary Economic Assessment for the Piskanja Borate Project, Serbia, prepared for Erin Ventures Inc. and Temas Resources Corp., effective date June 24, 2022.
Earlier report summaries
Earlier versions of this profile, based on older technical reports, are retained below for source traceability. Dates and figures reflect each report’s own effective date and are superseded by the current information above.
Piskanja Project — 2014 PEA
The 2014 PEA for the Piskanja project assumes a conceptual processing route to produce colemanite concentrate and boric acid, based on limited testwork and no demonstrated technically feasible process route.
Report context
The preliminary economic assessment (PEA) for the Piskanja project was prepared by SRK Consulting in September 2014. The report acknowledges that no technically feasible process route has yet been demonstrated that can upgrade the Piskanja ore to what is considered a minimum marketable colemanite concentrate grade. The processing assumptions and conceptual flowsheet presented in the PEA are based on a limited amount of non-definitive metallurgical data.
Processing route
Processing assumptions
For the purpose of the PEA, SRK assumed that a process can be developed to upgrade the ore to satisfactory levels of B₂O₃ and iron. The assumed criteria are a concentrate grade of 35% B₂O₃ for the range of head grades in the proposed mine plan (24.3-32.9% B₂O₃) and a tailings grade of 7.5% B₂O₃, the figure achieved for the magnetite fraction in the SGS HIMS testwork.
Production plan
The production plan calls for the production of both colemanite concentrate and boric acid, the latter at a rate of 25 ktpa and the former at a rate of approximately 200 ktpa. SRK modelled this production scenario according to a conceptual process route shown in block form as Figure 17-1 in the report.
The mass yield and B₂O₃ recovery across the beneficiation stage are variable, a function of the variable run-of-mine grade and the fixed concentrate and tailings grades. For the boric acid plant, a fixed B₂O₃ recovery of 80% has been assumed as representing a typical industry value.
Tailings management
The quantity of beneficiation plant tailings is projected to range from 22 ktpa to 123 ktpa over the life of the project, averaging 88 ktpa. The quantity of tailings from the boric acid plant is expected to be 49 ktpa.
A desktop study was undertaken to determine the possible location for the tailings storage facility (TSF) to store 5% of 1.8 million tonnes of colemanite tailings and 5% of 1.0 million tonnes of boric acid tailings material. The amount of tailings material to be stored within the TSF totals 0.135 Mt (0.122 Mm³) at a dry density of 1.1 t/m³. The remaining 95% of boric acid and colemanite tailings will be utilised for backfill.
Site selection
The site selection study was not carried out as the client’s preferred location was the site immediately south of the proposed plant. The client stated that this site was previously used by the Ibar Mine to clarify water for the coal washing plant and was therefore considered a perfect location for the TSF.
TSF design
A conceptual TSF design has been developed by SRK to store about 150,000 m³ of tailings material that occupies an area of about 6 ha including the dam footprint area. SRK considered a downstream construction method for the proposed facility, which will require the construction of full height dam walls using suitable material for construction acquired from local borrow areas. The dam wall will have slopes of 1V:2.5H on the downstream side and 1V:3H on the upstream side and a crest width of 5 m. The maximum dam height at the lowest ground is about 4.4 m, and the crest elevation at 381 metres above sea level. A freeboard of 1 m was added to the dam height.
Tailings waste will be disposed as slurry which will be delivered via a pipeline into the facilities. SRK did not consider dry stacking at this stage as there are many unknowns regarding the final tailings product. The conceptual design includes a double 2 mm HDPE liner system with a leakage detection system between the liners and below the bottom liner.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Concentrate grade (B₂O₃) | 35% | Assumed design criterion |
| Head grade range (B₂O₃) | 24.3-32.9% | Proposed mine plan |
| Tailings grade (B₂O₃) | 7.5% | Based on SGS HIMS testwork (magnetite fraction) |
| Colemanite concentrate production | ~200 ktpa | Production plan |
| Boric acid production | 25 ktpa | Production plan |
| Boric acid plant B₂O₃ recovery | 80% | Assumed typical industry value |
| Beneficiation plant tailings (life-of-project range) | 22-123 ktpa | Projected, variable |
| Beneficiation plant tailings (average) | 88 ktpa | Projected |
| Boric acid plant tailings | 49 ktpa | Projected |
| TSF storage capacity | 150,000 m³ | Conceptual design |
| TSF storage mass | 0.135 Mt | At dry density 1.1 t/m³ |
| TSF area | ~6 ha | Including dam footprint |
| Dam slopes (downstream:upstream) | 1V:2.5H : 1V:3H | Conceptual design |
| Dam crest width | 5 m | Conceptual design |
| Maximum dam height | 4.4 m | At lowest ground |
| Dam crest elevation | 381 masl | Conceptual design |
| Freeboard | 1 m | Conceptual design |
Project website: https://www.theglobeandmail.com/investing/markets/markets-news/ACCESS%20Newswire/1076360/boron-one-holdings-inc-advances-with-potential-partner/
Technical qualifications
The report states that only a very limited amount of metallurgical testwork has been undertaken in support of the production of this PEA. This work consisted of some upgrading testwork which, while resulting in a reduction in the iron content of the product to close to the assumed target level, did not result in any significant upgrading of the boron content, at least not to the assumed minimum figure of 35% B₂O₃ for a saleable colemanite concentrate.
The metallurgical parameters developed for the PEA are therefore largely assumptions based on a limited amount of non-definitive data. Virtually no specific engineering was conducted with regard to the process plant design, and the process plant capital and operating costs subsequently generated are high level estimates based on generic databases and parallel project data.
No technically feasible process route has yet been demonstrated that can upgrade the Piskanja ore to what is considered to represent a minimum marketable colemanite concentrate grade.
Geophysical, rheological and geochemical testing on tailings material is recommended to evaluate the preferred tailings deposition method.
*Source: Piskanja Project , 2014 PEA, U5932 Piskanja 43-101 PEA_Final.docx, September 2014, sections 17.1, 17.2, 17.3*
