¡VAMOS! mining concept for submerged inland mining on any continent

¡VAMOS! equipment on trial at Lee Moor, Devon, UK

Today, the WEDA Dredging Summit and Expo 2018 starts1. Tomorrow, Olivier Marcus is going to present a paper on the ¡VAMOS! project2, I assisted co-authoring. The message we wanted to convey is the applicability of the ¡VAMOS! system we’ve developed in a European Research and Development consortium3. By now we were well acquainted with the European Situation, but as this was going to be presented in the United States I had to do some research all over, for the American market situation. It turned out that ¡VAMOS! concept could be used their as anywhere else.

Schematic of typical vertical ore body in an opencast or submerged setting (Credit: ¡VAMOS!)

First of all, some explanation what the ¡VAMOS! project is about. We’ve noticed that here in Europe mineral resources are heavily depleted or located at locations that are not accessible due to their economic or environmental value. One solution would be to dig deeper, but in open cast mining, you’ll run into an enormous overburden removal and drainage problems. The other is to tunnel mining, but that is very expensive and dangerous. The ¡VAMOS! concept opens up a new approach: submerged mining.

Diagram of the original ¡VAMOS! concept (Credit:¡VAMOS!)

Instead of pumping the water out, we use it to transport the mineral to the plant. And this is very familiar for us in the dredging industry. So, we’ve found another location where we can discover dredging! Usually dredging involves transporting huge volumes of sediment, but the fraction of the ore, that is really paying for the operation tends to be very small. In mining terms it is the ore grade. Depending on the ore grade, the operation can be economically feasible or not. As this is a very fine line, mining economics have already done a lot of research on this and they call it the ‘Exergy Cost’. In short: an operation for low grade ore may be more expensive when the mineral is expensive. In fact, when one is mining sand, the ore grade is 100% and the price will be low, so the profit has to come from its volume.

Exergy cost (kWh) needed for producing a given mineral from bare rock to market. (Credit: Valero)

This model is basically applicable in both the European and the American market. Although the local business mentality will result in different underlying economic calculations. In Europe we were working with a report on the critical resources that are on the agenda of the European Commission4. It turns out, that now the United States has their own list of critical minerals5, just signed into executive order6. The list differs somewhat, but is certainly recognisable. This is a good indication, that the ¡VAMOS! mining concept can be evaluated equally to the other options for the American market.

Medium-Term (2015–2025) Criticality Matrix (Credit: US DOE)

So, who knows, maybe there is an innovative entrepreneur in Olivier’s audience at the WEDA and the first real production model might be put to work in an American mine. At least, when delivering a product like this, we would not have to worry about the Jones Act.

MV handling on LARV at Lee Moor test site in Devon, UK

References

  1. Dredging Summit and Expo 2018, WEDA
  2. WEDA Dredging Summit & Expo, Damen
  3. ¡VAMOS!
  4. EIP on Raw Materials, European Commission
  5. Interior Seeks Public Comment on Draft List of 35 Minerals Deemed Critical to U.S. National Security and the Economy, US Department of the Interior
  6. A Federal Strategy To Ensure Secure and Reliable Supplies of Critical Minerals, Executive Order 13817 of December 20, 2017

See also

Dual Stage Dredge Pump and Double Action Pump Drive for ¡VAMOS!

 

¡VAMOS! equipment on trial at Lee Moor, Devon, UK

These days I have been very busy drafting a manuscript about our ¡VAMOS! project results1 for a dredging conference paper. As every writing process, there is so much to tell and so little space available. At a certain moment there follows a phase called: ‘kill your darlings’. You have to scrap parts that contribute less to the main message of the article. Still some of those orphans are worth sharing. So here is a part from the paper that might be interesting for you.

For those unfamiliar with ¡VAMOS!, it is a Viable Alternative Mining Operating System2, where we are cooperating in a 17 partner consortium to develop equipment and procedures for exploiting mineral reserves in disused or currently unavailable mines in the EU3. Many mines are disused, but still contain some reserves, that are unrecoverable due to an uneconomic stripping ratio4.

Schematic of typical vertical ore body in an opencast or submerged setting (Credit: ¡VAMOS!)

We developed a prototype mining vehicle (MV) and an accompanying launch and recovery vessel (LARV)5. Although the requirement for the slurry circuit on the MV are deceivingly similar to a normal dredge system, there is one fundamental difference in character: vertical transport. At the system architecture phase we assumed a dredging depth of at least 100 m. For clean water, this poses not so much of a problem, once pumping mixture is where the geodetical height difference comes into play. At 100 m a 1500 kg/m³ mixture requires an additional 5 bar of static head.

Influence of vertical riser on the head requirements of a dredge pump

The dredge pump has to cope with the large variation in head requirements. For the prototype machine, the only option is to vary the dredge pump speed. Still at a normal operating condition, we expected a head requirement for 10 to 16 bar. This is why we developed a dual stage dredge pump, it delivers double the head of a normal dredge pump.

The variation of the pump speed has been accomplished by various controllers working together. The power is generated on the LARV by a diesel engine driving a generator. A frequency drive supplies a hydraulic power pack on the MV. The power pack has a variable displacement pump for controlling the flow. At the dredge pump side there is also a variable displacement motor.

¡VAMOS! prototype drive train arrangement

With this setup in place, the dredge pump can vary between a slurry circuit just filled up with clean water and a fully filled riser with heavy mixture at the operating point. On top of that, there will always be the possibility, that the density increases even more. The flow will reduce and so will the power consumption. This enables the drive to increase the speed for extra oompf of the dredge pump to clear the riser. Where normally the dredge pump speed is controlled by the pump swash plate, the motor swash plate is so to speak the turbo boost. This is similar to a constant power drive for normal dredges, but the vertical riser makes the problem more pronounced.

So, not only the starting up of a dredge pump should be considered in the design of the drive train, but also the variations in operating point. Regarding the comments I received on my last post, yes indeed a production model of the ¡VAMOS! system would have an all-electric drive. Just be sure to have enough copper in the motor to cover every possible operating point.

Dual stage dredge pump with constant power drive mounted on a crowded MV equipment bay

References

  1. Successful demonstration of ¡VAMOS! technology in UK
  2. ¡VAMOS!
  3. Strategic Implementation Plan for the European Innovation Partnership on Raw Materials
  4. Developments in Mining Equipment and Pumps for Subsea and Inland Submerged Deposits, Kapusniak et al. WODCON 2013
  5. ¡VAMOS! reaches Design Freeze Milestone

See also