SBR Archives - International Mining

One of the most-watched shaft sinking projects in the sector right now is located in the UK, with the Woodsmith project in north Yorkshire having been on the radar for a number of reasons.

First off, it is a project that has changed hands recently.

Originally guided by Sirius Minerals, the 10 Mt/y project was acquired by Anglo American in 2020, a transaction that came with a fresh look at the whole project execution phase.

The change in ownership and re-assessment of plans drawn up by Sirius – a much smaller company guided by different investor pressures and operating procedures – led to Anglo American relieving DMC Mining, the lead shaft sinking contractor, of its duties.

Another reason for watching the project is the planned use of Shaft Boring Roadheader (SBR) technology from Herrenknecht.

After debuting at the Jansen potash project in Saskatchewan, Canada, where it excavated two 8-11 m diameter blind shafts down to circa-1,000-m-depth with the help of DMC as the contractor, SBR 2.0 – the second generation of the technology – was put to the test in Belarus at the Slavkaliy-owned Nezhinsky potash project. It ended up breaking shaft sinking records under the guidance of contractor Redpath Deilmann on a project to sink two 8-m diameter shafts (one to 750-m depth and one to 697-m depth).

Herrenknecht, with its experience in mechanised tunnelling, developed the SBR for the mechanised sinking of blind shafts in soft-to-medium rock. Based on the proven technology of the Herrenknecht Vertical Shaft Sinking Machine, the SBR offers improved safety performance compared with conventional shaft sinking methods while also achieving higher advance rates, according to the company.

The SBR is a 60-m tall, suspended shaft sinking machine, with 12 work decks and two service platforms. A telescopic, boom-mounted cutting head is used to precisely excavate rock via a partial-face cutting method. The cutting head works in a cycle, starting each cut from shaft centre to shaft wall, repeating until a layer of material is removed. Excavation proceeds in 1-m increments, followed by SBR lowering sequences.

The SBR was chosen for Woodsmith by Sirius over the conventional drill and blasting method due to its advantages in improving safety and schedule. This methodology, Sirius said, would allow the company to satisfy several operational objectives, moving away from the use of explosives and providing a safer, more predictable work method. Instead of a linear process, the SBR allows work to be completed concurrently as the shaft is sunk, as well as minimising damage to exposed host rock, and further improving safety while minimising downtime. Work decks above the cutting head allow workers to install shaft lining and tubbing as excavation continues, while a pneumatic mucking system removes waste rock.

The third generation of technology – which builds on the first two deployments with, among other things, the addition of two retractable robotic probes to test and grout the ground ahead for safer excavation and an additional control cabin on surface for more remote operation – is due to sink production and service shafts with 6.75-m diameters to depths of 1,594 m and 1,565 m, respectively, at Woodsmith based on the Sirius plan.

These SBRs are being supported by four triple sheaved winches from SMS SIEMAG and conveyors from Herrenknecht-owned H + E Logistik GmbH, among other support equipment.

Work on the service shaft commenced in 2021 with former Anglo American Chief Executive, Mark Cutifani, confirming in July of that year that the “first cut” with the SBR had taken place in the service shaft.

This progress was made while the company was still completing a detailed technical review on Woodsmith to ensure the technical and commercial integrity of the full scope of its design. This review has a particular focus on the sinking of the two main shafts, the development of the underground mining area, and the changes required to accommodate both increased production capacity and the more efficient and scalable mining method of using only continuous miners, Anglo American said.

Since the first cut was made in July 2021, however, Anglo American and Redpath Deilmann – which is now leading the sinking project as shaft sinking contractor – have been reviewing the existing plans for sinking with the SBRs, carrying out minor hardware changes on the machines and ensuring all staff have the appropriate training to facilitate the completion of the shaft sinking process. The Redpath Group is also involved in the drill-and-blast-based sinking for the materials transport system (MTS) shaft.

Various shaft sinking rates have been mooted in the past at Woodsmith, and Anglo American is currently working to develop the optimal solution for the facility based on technical standards.

The sinking at Woodsmith represents a different challenge to the two previous SBR projects conducted to this point.

For starters, there is no ground freezing expected to take place at Woodsmith – unlike what happened in Canada and Belarus. This process, while time consuming and only used to freeze unstable water-bearing strata around the shaft, can create more rock uniformity to aide consistent cutting rates.

There is also the MTS level to consider at Woodsmith, with plans to carry out lateral development work around the 360-m-level to join up the production shaft with this level where polyhalite ore will be transported along a 37-km tunnel to Wilton near the port. This means vertical cutting and loading may be halted while the MTS level connection is established.

All these factors, along with the performance of previous SBR work, will be incorporated into the engineering work Anglo American is carrying out at Woodsmith, but, in terms of the SBR, signs are that work on the service shaft could recommence shortly, with plans to start sinking in the production shaft by the end of the year.

Anglo American has gone public with a bid to buy Sirius Minerals and its North Yorkshire polyhalite project in the UK.

The all-cash bid, which values Sirius at £386 million ($507 million), comes shortly after Sirius announced a strategic review for the project that included a broader process to seek a major strategic partner for the asset.

Anglo says it identified the project as being of potential interest some time ago, given the quality of the underlying asset in terms of scale, resource life, operating cost profile and the nature and quality of its product.

The North Yorkshire polyhalite project, which is spilit into two stages, will see product extracted via two mine shafts and transported to Teesside, in the northeast of England, on a conveyer belt system in an underground tunnel. It will then be granulated at a materials handling facility (MHF), with the majority being exported to overseas markets.

Infrastructure development on the project includes sinking the shafts at the Woodsmith mine to access the polyhalite deposit (using Herrenknecht’s Shaft Boring Roadheader); developing a 37 km-long underground mineral transport system using tunnel boring machines; constructing a MHF in Teesside for granulating or chipping the mined material into the final product; and harbour facilities comprising an approximately 3.5 km-long overland conveyor, a ship berth and a ship loader located adjacent to the harbour on the River Tees.

In its announcement this morning, Anglo said: “The project has the potential to fit well with Anglo American’s established strategy of focusing on world-class assets, particularly in the context of Anglo American’s portfolio trajectory towards later cycle products that support a fast-growing global population and a cleaner, greener, more sustainable world.”

Anglo is not new to the fertiliser market having, until 2016, a phosphates business in Brazil. It sold the mine, beneficiation plant, two chemical complexes and two further mineral deposits that made up this business that year to China Molybdenum in a $1.5 billion deal that also included its niobium assets.

Sirius announced its strategic review back in September 2019 after it had to terminate a $2.5 billion revolving credit facility stage 2 financing for the project (to get it to 20 Mt/y capacity) due to a worsening of market conditions for a required bond raising.

This led to the company slowing development across the project in order to preserve funding to allow more time to “develop alternatives and preserve the significant amount of inherent value in this world-class project”, Chris Fraser, Managing Director and CEO, said at the time.

This saw the company lay out a pathway that would still see first polyhalite production in the June quarter of 2022, but could see the ramp-up to stage one 10 Mt/y polyhalite capacity reached in the September quarters of 2025 or 2026, depending on if there was a 12 or 24 month deferral of the planned development scope.

Anglo said, during the first two years after an offer is successfully completed, development work on the project is expected to be broadly in line with Sirius’ revised development plan “although Anglo American intends to update the development timeline, optimise mine design and ensure appropriate integration with its own operating standards and practices”.

It added: “Anglo believes that the project has the potential to become a world-class, low-cost and long-life asset. Sirius has progressed the development of the project to an advanced stage, with construction now under way for over two years.

“Sirius has indicated that this is currently the world’s largest known high-grade polyhalite deposit with a JORC reserve of 290 Mt, with a grade of 88.8%, and a resource of 2,690 Mt. The resource indicated by Sirius has the scale, thickness and quality to be mined efficiently using bulk mining methods through a relatively simple, low-energy, non-chemical production process.”

In addition, Sirius has indicated the project could operate at an EBITDA margin potentially well in excess of 50%, according to Anglo, leaving the project well positioned for strong through-the-cycle profitability with a long anticipated asset life.

“At this stage, the project requires a significant amount of further financing to develop and commission the operation that has proven challenging for Sirius to procure on an economic basis,” the diversified miner said. “Anglo American, as one of the world’s leading mining companies, has the resources and capabilities to help build on the achievements of the Sirius team. Anglo American remains committed to its disciplined capital allocation framework.”

Anglo explained that there is potential long-term benefits in applying its technical expertise in both the development and operational phases, as well as utilising its recognised Operating Model to drive safety and productivity to “world-leading standards”.

“Integration into Anglo American’s global marketing network would provide full mine-to-market capabilities and build on Anglo American’s institutional experience in the world’s major fertiliser markets,” it added.

Sirius’ polyhalite product, POLY4, is a multi-nutrient fertiliser certified for organic use and has the potential to generate demand at a competitive cost that supports a strong margin, according to Anglo.

“POLY4 is an attractive low-chloride alternative to traditional potassium-bearing mineral products on a cost-effective basis. It includes four of the six key nutrients that plants need to grow – potassium, sulphur, magnesium and calcium,” it said. “The use of fertilisers is one of the most effective ways to improve agricultural yields and therefore help to address the anticipated future imbalance between food, feed and biofuel demand and supply caused by a fast-growing global population and limited additional land availability for agricultural use.”

Woodsmith Shaft Boring Roadheaders about to re-start cutting process

Anglo American eyes polyhalite potential with Sirius Minerals bid