By Harvey Haugen
The development of new selective mining technology should revolutionize the industry. There is a realization, that while the new potash megaprojects are an attractive short-term economic “gold mine” for the province, the long-term viability of these projects will be challenged by improved technology, dramatically reducing energy costs, greenhouse gas emissions, and addressing potential impending water shortages.
The promise of the new technology will become a reality in the next couple years. The technology is well documented and close to being “proven”. Work continues to make it even better.
The progress of this technology has been impeded, as several companies, catering to investor expectations, have championed numerous projects across Saskatchewan that lack robust scientific backing. These companies saw the Beechy presentations on selective mining, starting in 2010 and they liked the idea of low-cost production. They then went to their friends and consultants and put together expensive projects, full of investor “candy” without taking the time to understand what was really involved.
Over the past 10 years, I have studied the publicly available data on each of these new potash proposals. We see complicated processes, some produce by-products, use cogeneration, use cooling ponds, use submerged combustion heaters, or do downhole heating and fracking. Now we have one company “using vapor recompression evaporation”, but no indication of how it fits into the process or what will happen to salt produced. While all these “good ideas” have application somewhere, none of these ideas are particularly relevant to a simple selective potash mine. The management, consultants, and former potash executives have been well served by these schemes, all at the expense of shareholders. But no product yet.
What, then, has to be done to make this technology a reality?
The first thing is to get a competent management team to build and run the mine. A mine manager is a team leader. He/she may not be an expert in corporate finance or marketing, or necessarily have 30 years in the industry. A successful new mine will need a unique manager who is a competent team leader and builder. The nature of a small mine requires a lot of management expertise in a small team, maybe even more than for a large mine. This will include technical, safety, human relations, and purchasing and accounting disciplines, as well as handling regulatory issues with environment and health and safety. It is critical that management standards, cost control, and operating procedures are set up at the outset. This is not simple. The management culture that is established now will determine the ultimate long-term success of the company. Today, there are large, well equipped potash mines that simply do not produce anywhere near capacity due to long-term management deficiencies.
A successful mine will need to develop technical and operating expertise. This cannot be outsourced. The consultants have proved to simply promote the same old ideas that have not worked. While carrying professional accreditation, my experience over the last 50 years is that they often have limited knowledge of the basics of potash technology. They have to be directed. Selective mining is a unique approach to potash mining. It is simple, but also draws on years of experience in process design, equipment selection, and corrosion control.
The advice of the retired CEOs and oilfield experts may not have much to offer either, especially on technical matters. In fact, in many cases they have been an obstruction. We need a good scientific approach based on a solid understanding of the technology, sound engineering, and computer modelling of the process.
The project depends on an ore reserve. A potential resource has to be identified, based on well core data and seismic information. A selective mine will require a critical reassessment of the ore body, since only selected high-grade ore layers will be mined. These high-grade layers need to be identified and quantified. Core samples need to be tested to determine ore liberation and cut-off grade. Mining sequence has to be determined. Selective mining proceeds primarily horizontally, with vertical development from the drilled hole, in “high grade”, up to “cutoff grade” or a salt formation. Ore reserves need to be recalculated to reflect selective mining of only the “high-grade” ore zones.
The site for the mine should be selected based on site access to utilities, to road and rail, but more importantly, on a careful evaluation of the best information on the ore deposit, considering the slope of the deposit and any identified anomalies. Site selection must match the mine plan. A long-term mine plan is required.
Mistakes have been made in the past. One proposed mine was located on the extreme corner of the lease between two rail lines and roads as far away from power lines and gas lines as was possible. One of the new mines appears to been poorly located on the south edge of a narrow, 10-metre-deep valley (in the red beds). Wells will have to cross the valley as they are drilled from the plant site making drilling very difficult, and a successful outcome unlikely. Another site was selected to access carnallite ore which is far more difficult to mine than sylvinite.
The Beechy patented plan uses curved flow patterns. Beechy can collaborate with new licensed operations on their plans and significant advances have been made in the last year to improve our understanding of these designs. In addition, an inexpensive system, using passive seismic, is being considered for continuous monitoring cavern development.
Design and drilling of caverns need careful attention. The design must be done based on the requirements of potash mining, not those of oil production. Most importantly, the drill must have a steering head with the gamma detector as close to the bit as possible. In Manitoba, the high-grade ore is thick, but with one-and-a-half degree offset directional control, the drill was out of the zone 10 to 20 per cent of the time. (A steering drill should have been used.) One of the consultants tell us that with the “Moab” plan, the expectation is that the drill will be out of the zone 50 per cent or more of the time. This won’t work for selective mining. There is no reason that with the right equipment, the drill will be in the zone from start to finish. Incidentally this should also greatly improve the likelihood of connecting horizontal wells, even without a ranging tool.
The gamma detector should be accurately calibrated. If the directional people simply adjust the calibration randomly, the results are always suspect. Real-time laboratory analyses should be done on the drilling mud, as well as on the chips as the holes are being drilled. (Simple, low-cost X-ray spectrometers are available that will handle this.) A careful analysis of the brine, and evaluation from a phase diagram, will dramatically reduce salt addition to the mud, and reduce disposal requirements. Chip analyses will verify gamma readings and ensure drilling is on target. No deviations will be allowed from the target zone, even if the drill has to be backed up and deflected.
Care must be taken in designing curvature from the vertical into the horizontal potash zone. If the curvature is too short, problems can occur with stuck drills and difficult casing installation. There is no reason to limit the start of the curvature at 300 (or even 600) metres above zone.
The design of the processing plant should be developed from the simplicity of the phase chemistry. The mine operation must produce a saturated, equilibrated brine. That means the maximum amount of salt and potash dissolved for a given temperature. Brine temperature from the mine should be a few degrees above surrounding rock temperature to minimize heat loss to the formation.
This brine is cooled to produce pure potash crystal. Part of the heat removed from the crystallizers (up to 60 per cent) can be recovered to heat the brine returning to the mine. Though cooling ponds have been used in Saskatchewan solution mines, they are really not a continuous operation, with the best production at below -20 degrees C. There is no heat recovery. Vacuum crystallizers do not work very well at low temperatures, so the best option is some kind of contact-cooled crystallizer. The simplest and least expensive of these is the patented Beechy wiped surface crystallizers. Optimization of any crystallizer system requires careful study and control.
Cooling water is typically supplied by cooling towers or large cooling ponds. Either of these methods consume a lot of water and are difficult to manage in winter conditions. With the Beechy crystallizers, air-cooled fin fan units are recommended for all but the hottest days. This minimizes water consumption. The operating plan can be adjusted in warm weather, using higher mine temperatures on these days or accepting reduced production. A cooling tower could be used to supplement contact cooling in the hottest days.
Brine heating is done using a high-temperature water heater, about 15 to 20 PSI, 250 F (125 C.). This simplifies the heating with minimal water treatment required, no steam traps or condensate treatment or piping. The brine is heated with hot water in a titanium plate heat exchanger.
The application of heat pumps could supplement the boiler heat, while providing additional cooling for crystallization (additional cooling, especially in summer months). Heat pumps will increase capital cost but significantly reduce GHG (with hydro power) to near zero.
The simple mine design requires low pump pressures. The majority of the head is from flow resistance in the piping to the well, in the casing to the formation level, then in the return casing to surface and back to the plant. The brine returning from the mine is higher in density than the hot brine to the mine. This adds a small additional head based on mined depth, brine concentrations and temperature. At 1000- metre depth, pump pressure should be 250 to 400 psi (depending on line sizing and resistance).
Consideration should be given to optimum sizing of well casing and surface lines. The wells should be as close to the plant as possible. This should all be weighed against the additional cost for larger wells or additional pumping capacity. A higher head on the pump (smaller lines) results in heat being produced in the pipelines which could be a good thing in this application with heat-sensitive saturated brines. Corrosion control is important with cathodic protection recommended for the wells and corrosion inhibitors for casing and pipelines.
Basic utilities should be in place from the start. Commissioning a new plant is not easy. Having to operate with temporary utilities complicates the operation. While brackish water sounds like a good idea, a supply of fresh water is absolutely required anyway, whether from a separate source or by reverse osmosis. With proper process design, water use is minimal for the mining operation. In some locations the cost of bringing in natural gas is very high. With the Beechy method, the whole plant could be operated on electric power (possibly supplemented with some propane) with the extra capital cost offset in part by the cost of gas lines, and operating cost offset by low carbon emissions.
Product drying can be done in a conventional rotary or fluid bed dryer. Beechy is working on an alternate contact heated dryer with electric heating, which allows reuse of most of the energy input. More important, it eliminates the need for a stack and stack scrubber and associated GHG.
When granulation is required, wet granulation methods should be considered, especially in small plants. Product, direct from the centrifuge, can be granulated on a pan, or in a drum or pin granulator. Granules are then dried and sized. This provides a simple low-cost but very flexible granulation system producing a high-quality end product.
Most presentations on new projects emphasize arrangements for marketing of product. We believe that selective mining design supports our claims of dramatic reduction in operation costs, capital cost and GHG reduction. This makes the product extremely marketable on its merit. The emphasis should be placed on getting a consistent high-grade product from the technology, as soon as possible.
Harvey Haugen is 79 years old and has worked in potash and related processes since June 1969. He worked for the big mines until 1987, then primarily on smaller grassroots developments, including Big Quill Resources at Wynyard, the first ion exchange potassium sulphate plant. He has developed the Glasserite potassium sulphate expansion at Wynyard, a sodium sulphate mine, a magnesium sulphate mine, sodium carbonate production from pulp mill waste, and Biodiesel technology. Since 2009, he has worked primarily on selective solution mining.
Our approach to technology has been to develop the process, starting at basic chemistry and phase diagrams, production of detailed computer modelling of the process, supported by extensive laboratory and pilot studies to verify the models.
Our patented system has been in place now for 15 years. We have attempted to find application for the technology by presenting papers at SMRI, and have made presentations to government, engineering companies, and prospective potash mines.
The prevailing sentiment appears to lean towards a fascination with mega projects, while the notion of a $20 to $40 million endeavour is deemed unremarkable, despite its potential for equivalent production and lower costs compared to the billion-dollar ventures. Conversely, there’s an alternate perspective wherein some individuals find it effortless to adopt information and then claim it as their own idea. However, it’s important to note that while it may seem straightforward, it’s not quite as simple as it appears!
