Gillian Chew

BF Steam Turbine RPM Control

Metals Processing /

BF Steam Turbine RPM Control What is a Blast Furnace? The mining industry uses blast furnaces for smelting to produce industrial metals, such as pig iron. It is top-charged with iron ore, coke and limestone while huge quantities of air blast enter the bottom of the furnace from the blower. Oxygen within this air first reacts with the coke to produce carbon monoxide, which then reacts with the iron ore in a reduction reaction. Molten slag and iron leave the bottom of the furnace, while carbon monoxide, carbon dioxide and nitrogen leave the top. This is a continuous process, which if interrupted by unscheduled downtime, leads to increased costs.  Steam Turbine Control Solution Steam turbine speed control is a critical application requiring superior reliability. REXA Electraulic™ Actuators enable a smooth and reliable supply of cold blast “wind” flow to your blast furnaces.  The consequences of an actuator fail are devastating to plant iron making operations.  Loss of “wind” causes the molten burden in the furnace to drop, therefore resulting in damage to the furnace and an interruption of production.  Our self-contained Electraulic™ actuators require zero oil maintenance, making them virtually maintenance-free.  Benefits: Reliable Operation in Tough and Demanding Environments  Accurate (0.1%) and Repeatable Positioning  Smart Communications for Reviewing Actuator Health/History  The BF Turbo Blower has many applications that REXA can provide an immediate solution for including:  Inlet Guide Vane Control  Anti-choke Control  Blower Anti-Surge Control 

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Blast Furnace Gas Pressure Control

Metals Processing /

Blast Furnace Gas Pressure Control Background Steel making is an energy-intensive process. At a tier one integrated steel mill in Jamshedpur, India, the mill energy consumption required for steel production meets with power generation produced at the power houses on site. As their primary fuel sources, this steel mill uses by-product gases from blast furnaces and coke ovens.  What is Blast Furnace Gas? Blast Furnace Gas (BFG) is the key fuel source used at the combustion boiler to generate steam. This steam is used in various plant processes, as well as the steam generator, to produce electrical power. There are three power houses in the plant, each with five to seven boilers. BFG feed has two issues: a variable incoming flow rate and a low, fluctuating calorific energy constant.  Problem The key in producing high quality steam is to have minimal process variation of incoming BFG entering the boiler. Furthermore, greater process control enables efficient combustion and boiler product steam pressure – leading to stable-pressured steam.  Unfortunately, even with the use of smart positioners, pneumatic actuators lack precision due to the compressibility of air. REXA Electraulic™ Actuators, however, are able to work through this and provide more precise and accurate performance than pneumatic and traditional hydraulic technologies.  Solution Check out the full Blast Furnace Gas Pressure Control Application Spotlight below! Be sure to also view our webinar showcasing how our actuation technology can enhance this application’s efficiency.  Literature Download our Steel Mill Blast Furnace Gas Pressure Control Application Spotlight! Download

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Gas Pressure Control – Baghouse

Metals Processing /

Gas Pressure Control – Baghouse A baghouse is an air pollution control device commonly used in steel mills. Baghouses remove particulates out of hot gases from various steelmaking processes.  The use of air dampers controls the gas pressure to optimize particulate recovery and process availability. Rexa actuators are used to precisely maintain vacuum pressure; even a slight positive pressure inside the bags can result in reduced cleaning efficiency.  Benefits: Precise modulating control  Reliability 

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Cement Kiln Feed Control

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

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Heap Leaching Acid Feed Control

Mineral Recovery /

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

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HPAL Autoclave Inlet & Discharge Isolation Control

Mineral Recovery /

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

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Improve Copper Recovery

Mineral Recovery /

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

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POX Autoclave Slurry Control

Mineral Recovery /

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

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Power Needle Operation

Hydroelectric Power /

Power Needle Operation Controlling the power needle is critical to any hydroelectric plant with an impulse turbine configuration. Operating head ranges are between 20-2000 meters where the water is converted to a high velocity jet stream when released from the nozzle’s orifice. As part of the nozzle for an impulse turbine, the power needle controls the water jet that impinges on a series of buckets rotating the runner.  There are two types of impulse turbines – Pelton and Turgo. A Pelton turbine power needle is in-line with the buckets of the runner that splits the water jet in half for maximum efficiency. The water impinges on the buckets from an incline, releasing it to the other side of the buckets with a Turgo turbine. Orientation can either be vertical or horizontal. Single and multi-jet power needles can also be utilized for a system. A deflector or other method of redirecting the water jet can be used both for more control and safety. The use of either turbines or configuration can vary depending on plant strategy.  Literature Download the Power Needle Application Spotlight to read more! Download

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Terminal Inlet Valve Bypass

Hydroelectric Power, Power, Webinar /

Terminal Inlet Valve Bypass Background Plant setup can vary depending on plant design, geography and size. A plant setup with a reaction turbine and penstock usually features two components:  Turbine Inlet Valve (TIV)  Turbine Inlet Valve Bypass  The TIV, also known as a guard or shutoff valve, prevents or allows water from entering the turbine. The Turbine Inlet Valve Bypass is installed on the downstream end of the penstock before the turbine. Although the TIV Bypass spends most of its time in the closed position as a low-duty cycle application, it still plays an important role in the startup sequence with the TIV. During startup, before the TIV can be opened, the TIV Bypass opens to equalize pressure upstream and downstream of the TIV.  The TIV Bypass employs different valve and actuator technologies and integrates within the TIV body itself in some configurations. Actuator types can differ between electro-mechanical, hydraulic, and even manual operation for smaller plants.  Problem An imbalance of pressure between both sides of the TIV can wreak havoc on any unit with turbines experiencing turbulence, cavitation and mechanical shock/fatigue. Consequently, this reduces the life of the equipment and can even completely disable it. The greater the pressure delta – the greater the risk, which makes the TIV Bypass a critical part of the startup sequence to equalize pressure.  Both electro-mechanical and electro-hydraulic actuators can cause problems when actuating a TIV Bypass. Electro-mechanical actuators cause sticking, which means the valve either intermittently gets stuck or is jammed in place. Gearing within these actuators can cause gradual wear, leading to slop and possible valve “floating”. Similarly, electro-hydraulic actuators are susceptible to different forms of contamination including entrained air, oxidation, water, and more.  Solution Therefore, plants should consider REXA Electraulic™ actuators for their TIV Bypass systems. Literature Download the Terminal Inlet Valve Bypass Application Spotlight!  Download

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