The ABEL HM Pump Platform for Autoclave Feed
By David Donato
As an engineering student I became interested in fluid mechanics and the role that fluid transfer plays in our lives. From the HVAC systems in our homes that circulate conditioned air to keep us comfortable throughout the seasons to waste water treatment plants that make sure we are kept safe from harmful wastewater contaminants, we rely on the transfer of fluid to make our lives comfortable and safe. Often the processes that involve fluid transfer or conditioning goes unnoticed by us during our day to day activities. However, one thing is certain, there is a pump or pressure differential somewhere in the system that is transferring fluid for our benefit.
Now, as an Inside Sales Engineer for ABEL Pump Technology, a positive displacement pump and pump technology company that has been providing industry expertise for more than 70 years, I am exposed to many fascinating processes previously unknown to me. One of these processes, in mining, is the autoclave cycle used in mineral extraction from sulfide ore.
Within the autoclave cycle is the specialized piece of equipment known as an autoclave that must be fed at specific, constant and often times high pressures and flow rates, requiring a very specialized type of pump.
Extracting gold, copper or other minerals from sulfide ore is an extensive process. The autoclave cycle for mineral recovery is a component used in this process. Transferring the ore slurry through the autoclave circuit is not a job that can be left to just any pump. A positive displacement, hydraulic piston-diaphragm (or piston-membrane) pump is the best tool for the job.
The autoclave circuit starts after the sulfide ore has first been ground, classified by using hydro cyclones and then to a floatation process, and then thickened. The type of reagents used in the autoclave vary depending on the sulfide ore from which a mineral is being extracted. This can result in a slurry with a high solids concentration. The exact operating conditions of an autoclave will vary depending on the sulfide ore however, during some autoclave circuits, temperatures can reach more than 200°C and pressures can rise to more than 800 PSI (55 bar). The temperature and pressure of the slurry must be considered when choosing materials for the positive displacement piston diaphragm pump.
Many positive displacement pumps can easily handle the high flow rate and pressure required by the autoclave process. However, few pumps can also handle abrasive slurry like the ABEL model HM piston-diaphragm pump. As with temperature and pressure, flow rates for autoclaves vary, usually from 100 GPM up to 330 GPM (22 m3/h – 75 m3/h) or more. The flow rate and pressure fall well within normal operating capabilities of some of the larger positive displacement pumps.
Triplex Positive Displacement Pump, Top View
A triplex positive displacement, hydraulic piston diaphragm pump like the ABEL model HMT, is a three piston, single acting pump. The pistons are 120°out of phase from each other to maximize their natural dampening effect. During each stroke cycle of the crankshaft, each piston acts on a volume of hydraulic fluid, driving one of three diaphragms into a hermetically sealed pumping chamber. The decrease in volume of the pumping chamber discharges slurry through the discharge check valve.
Triplex Positive Displacement Pump, Side View
A quadraplex pump, or more accurately, a duplex double-acting pump like the ABEL model HMQ is another high flow rate, high pressure hydraulic piston diaphragm pump used in autoclave feed. Unlike a triplex pump a duplex-double acting pump uses only two pistons to actuate four diaphragm housings. The suction and discharge concept is the same as the triplex piston when acting on a single volume of hydraulic fluid. The difference with the duplex-double acting pump is that one piston acts on two diaphragm housings on the same side of the pump. Whether the piston acts in the forward stroke or aft stroke, hydraulic fluid is being acted on in both diaphragm housings causing both a suction and discharge action in the two diaphragm housings.