Mineral Recovery

Cement Kiln Feed Control Background Cement is pyroprocessed in long, cylindrical kilns that rotate axially at a rate 30 to 250 revolutions per hour. The axis of the kiln is slightly sloped, typically 1-4º, enabling the raw mix or meal that’s fed into the upper end of the tube to be properly processed at the prescribed rate. A burner  pipe located at the opposite end of the kiln produces charge temperatures of approximately 1450º C. Kilns are frequently as much as 12 feet in diameter, which is large enough to accommodate an automobile. In many instances, kilns are taller than the height of a 40-story building. The limestone and clay mixture gradually moves through the kiln. Certain elements are driven off in the form of gases. The remaining elements unite to form a substance called clinker. Clinker comes out of the kiln as red-hot gray balls, about the size of marbles. After cooling, clinker is grinded and mixed with small amounts of gypsum and limestone to make cement.  Literature Download the full Cement Kiln Feed Control Application Spotlight! Download

Heap Leaching Acid Feed Control Background Heap leaching is an industrial mining process that consists of the extraction of precious metals from ore through a series of acidic chemical reactions. During this process, the non-valuable earth materials or gangue go through a series of acidic chemical reactions which absorb specific minerals and re-separate them. The main difference between heap leach mining and in-situ mining is the use of a heap pad to separate the ore.  Producing high quality agglomerated ore requires minimal process variation of feed solutions entering the kiln. Tightly-controlled acid feed rates provide stable and predictable agglomerated spheres, therefore leading to less acid consumption and improved leaching. Relying on pneumatic actuators to reliably actuate the ball or globe valve controlling the acid feed flow to the mixer could spell disaster, though.  Achieving greater process control is a hallmark of REXA’s Electraulic™ Actuators. Our actuators solve problems with feed rate set-points and variation, resulting in a more efficient process with higher yield. Learn more about the many benefits our actuators provide for heap leaching applications in our full Application Spotlight below!  Literature Download the Heap Leaching Acid Feed Control Application Spotlight! Download

HPAL Autoclave Inlet Discharge Isolation Control High Pressure Acid Leaching (HPAL) autoclave leaching is an effective method to recover Nickel laterite ores.  HPAL is a demanding process with slurry temperatures above 250°C and pressures above 55 atm.  REXA  Linear  and  Rotary  Actuators are used to control slurry feed inlet and discharge isolation valves at the autoclave, preheaters, and acid stripper.  Large torque outputs in a small package and actuator reliability are important to HPAL operational safety and uptime.  Benefits: Reliable on/off control  Large torque output  Motor or accumulator driven  Withstands harsh, wet and humid atmospheric conditions  Literature Download the High Pressure Acid Leaching Application Spotlight! Download

Improve Copper Recovery Background on Copper Recovery Copper mining typically encompasses separating sulfide ore and recovery of purer metal particles from gangue minerals using froth flotation. The sulfide ore is then crushed, grinded and milled into fine particles. These fine particles then mix with water into a slurry, feeding into a flotation cell.  An agitator at the bottom of the cell stirs the slurry (also called pulp) and suspends the particles in the mix. Air supplied to the cell through the agitator creates bubbles, which rise to the top of the tank, creating the froth. The addition of chemicals to the tank enables the metal particles to attach themselves to the bubbles as they rise to the surface. The “tailings,” or residue, remaining in the slurry exit an outlet in the base of the tank and are generally discharged to a tailing pond. Why REXA? Most mines rely on pneumatic actuators to control the pulp height in flotation cells via modulating dart valves. Unfortunately, even with the use of smart positioners, these actuators cannot control or maintain the proper pulp level due to the compressibility of air.  Thanks to REXA’s unique Electraulic™ technology, our actuators improve flotation level control by precisely modulating the opening and closing of each tank’s dart valves. Literature Download the full Improve Copper Recovery Application Spotlight to read more! Download

POX Autoclave Slurry Flow Control Background Pressure oxidation (POX) autoclave leaching is an effective method to recover refractory gold.  POX is a demanding process with slurry temperatures above 200°C and pressures above 25 atm. REXA  Linear  and  Rotary  Actuators are used to control autoclave slurry level where reliability and positioning control are important for improving gold recovery.  Benefits: Precise Modulating Control  Reliability  Large thrust  Stiffness of Hydraulics  Seat loading cylinder to protect the ceramic trim  Literature Download the Slurry Feed Discharge & Isolation Control Application Spotlight! Download