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New System Installs Air Cannons Without Process Shutdown.

Martin Engineering recently announced a new technology that allows specially trained technicians to mount air cannons on furnaces, preheaters and in other high-temperature locations while production continues uninterrupted.

The company said it developed the patent-pending Martin Core Gate system to reduce expensive downtime associated with traditional installation methods, which require high-heat processes to be halted to allow core drilling and mounting of the cannons. Martin said it has proven the technology in dozens of installations to date, helping bulk handlers maintain effective material flow and minimize shutdowns, improving efficiency while reducing lost production time.

The new system has been paired with Martin's Smart Nozzle Series, a family of air cannon nozzle designs that can be serviced or replaced during production without removing the cannons themselves. With all installation and service performed from outside the vessel or process, the Core Gate system also contributes to a safer workplace by minimizing the difficulty and hazards of installation and maintenance, according to the company.

"Both of these innovations represent significant technical breakthroughs in the industry," said Global Flow Aids Manager Brad Pronschinske. "In the past, when material accumulation problems became an issue, processors would have to either limp along until the next scheduled shutdown or endure expensive downtime to install an air cannon network. That could cost a company hundreds of thousands of dollars per day in lost production," he said.

"Our initial advancement was engineering a nozzle design that could be safely replaced with no production stoppage," Pronschinske continued. "Now this new technology allows us to add air cannons and nozzles to an operation while it's in full swing, without disrupting the process."

To install air cannons in a running process, Martin technicians first conduct an assessment of the accumulation patterns and blockages to identify the proper air cannon locations, then drill through the outer wall and weld the Core Gate in place. The core drill is mounted, checked for alignment and started, with progress monitored as it works its way through the refractory. As soon as the drill cuts through the refractory, the drill is backed out and an isolation shield is slid into place to protect workers from the severe environment. The Smart Nozzle assembly is mounted next using an eight-bolt pattern, followed by the nozzle itself.

Replacing a conventional fan nozzle on existing equipment typically requires the removal of refractory material from around the nozzle opening, usually with a pneumatic hammer from inside the vessel. Martin said that process invariably weakens the surrounding refractory and renders it more susceptible to spider-webbing and subsequent cracking. In contrast, Martin said its replacement system leaves the refractory undisturbed during service, and one worker can safely perform installations or maintenance from outside the vessel. The design features a smaller footprint than typical fan jet nozzles, delivering a larger blast pattern than pipe nozzles or standard fan jet designs.

"Now, as soon as a material accumulation issue is identified, we can inspect the problem, design an air cannon layout and install the units quickly," Pronschinske said. "As long as the blockage isn't so severe that it completely obstructs the process flow, we can generally keep production moving while we mount the equipment for the solution."

Sustainable Solutions for Managing Brine From Tailings

Working with SRK Consulting colleagues in Vancouver, Canada, SRK Consulting's office in Cape Town, South Africa, has conducted preliminary groundwater modeling to assist a mining client in South America to find an environmentally sustainable solution for managing brine emanating from mine tailings.

According to Sheila Imrie, SRK principal hydrogeologist and specialist groundwater numerical modeler, the management of waste brines is a common challenge for mines worldwide, and the client is investigating the options for disposing of sodium chloride (NaCl) brine over a 23-year mine life and potentially after closure.

"A number of brine management options were evaluated for the project to consider at prefeasibility stage," said Imrie, "all of which had to take into account the relevant environmental regulations in conjunction with the geological setting and other conditions in the mining area."

These included brine evaporation in surface ponds or in a brine concentrator and discharging brine into surface water. Surface evaporation was considered unfeasible owing to the climatic water surplus of the region, while a brine concentrator would incur the excessive cost of a necessary lengthy high-voltage power transmission line. In any event, the subsequent disposal of concentrated brine would still need to be managed.

Discharging to surface water, while practiced in other jurisdictions, was not favorable for this project despite the high natural attenuation potential in the region's rivers.

"Brine injection to surface infiltration basins was also considered but did not appear feasible due to an increased potential for affecting shallow groundwater resources--and potentially surface water--in the vicinity of the infiltration ponds," she said.

The option deemed most practical--and evaluated further through reviewing available information, field testing and numerical groundwater modeling--was the injection of brine to a deep aquifer using injection wells.

The solids discharged from the horizontal belt filter will be conveyed to the tailings management area (TMA) developed over the life of the mine and through the post-closure period. Some of the tailings are sent underground and used as backfill in mined-out panel rooms while the rest of the tailings are stored in two tailings facilities on the surface. Upon settling of the solid material, the resultant brine needs to be removed and disposed from the tailings dam.

Situated on plastic and clay composite liners, the tailings would consist largely of waste sodium-chloride salt, with some impurities such as other salts, sand, silt and clay. Rainfall would progressively dissolve the salt, leaving a small residue of insoluble material. Brine generated through this process and from the recycling of brine from the process plant would collect in lined settling ponds at the base of each TMA.

"The potential options for managing waste brines depend very much on having the right geology and hydrogeology," Imrie said. "In this project area, these particular aquifer conditions--where there is sufficiently low permeability near the surface and higher permeability with depth--allowed us to identify an aquifer about 400 meters deep that has the potential to be a good injection site."

While unusual, these conditions presented a good opportunity for further study, to ensure that vertical movement of the brine would be limited. This would allow the brine to attenuate horizontally over time without finding its way to groundwater receptors.

A preliminary evaluation of brine injection feasibility--in line with the early-stage evaluation of the project as a whole--was undertaken through a combination of numerical groundwater and geochemical modeling. While the groundwater modeling evaluated the likely pressure increases and brine plume migration associated with injection, the geochemical modeling focused on the potential for chemical precipitation resulting from the interaction of oxygenated brine with anoxic brackish groundwater, as this could potentially clog the aquifer and injection wells.

"I was appointed to assist with the prefeasibility numerical groundwater modeling scenarios to simulate potential impact of multiple injection wellfield designs," said Imrie. "We developed a 2D, axisymmetric radial groundwater flow model to evaluate pressure effects and plume migration --as the hydrostratigraphy was relatively horizontal and homogeneous--and to model density-driven groundwater flow. We evaluated numerous brine injection scenarios, and a range of sensitivity analyses were undertaken to help address inherent uncertainty in the knowledge of hydrogeological conditions."

The next stage of investigation, she said, will include follow-up drilling, installation of test wells, piezometric monitoring, and hydraulic testing to confirm the injection horizon continuity and hydraulic characteristics.

The installation of deep, nested vibrating-wire piezometers to provide reliable piezometric head profiles will also be necessary, as will the optimization of the injection field design, including monitoring points and program details based on outcomes of the investigations.

"This will allow the remodeling of expected pressure response and brine migration on the basis of the updated information," she said. "Numerical groundwater models are essential tools for investigating the behavior of aquifer systems in time and space. By ensuring that each phase of model development is appropriately designed to meet current project objectives, we provide our clients with a cost-effective and defensible means to evaluate system responses and potential impacts of current and future groundwater-related management options under consideration."

Caption: The Core Gate system can be installed entirely from the outside of a vessel, allowing processes to continue and providing safer working conditions for the installers.

Caption: The system employs a core drill and isolation shield to preserve the integrity of the interior refractory material and protect workers from the severe interior environment.

Caption: Model results showing estimated brine TDS concentrations at 400 m below ground level, as well as alterations in the level of the local groundwater table, under the assumptions of brine injection at 16 wells at a rate of 1,295 [m.sup.3]/h and concentration of 300,000 mg/L, at the end of the life of the mine (23 years).
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Publication:E&MJ - Engineering & Mining Journal
Date:Oct 1, 2018
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