Gillian Chew

Turbine Speed Control Hydrogen Recycle Compressor

Uncategorized /

Success Story: Turbine Speed Control Hydrogen Recycle Compressor The turbomachinery operating within a refinery hydroprocessing unit requires some of the most capable actuation in the world. These compressors and pumps must be controlled accurately and reliably for a refinery to meet its operational goals. Typically, this machinery is driven by a steam turbine which converts thermal energy to rotational energy. A poor controlling or unreliable actuator can lead to inefficiency which erodes the bottom line and/or unplanned shutdowns which interrupt throughput. The inlet steam control actuator is arguably one of the most critical and valuable components within hydroprocessing unit. REXA recently upgraded a series of steam turbines driving hydrogen recycle compressors at a refinery in Mississippi. These steam turbines were operated by OEM style hydraulic actuators utilizing pilot valves and power pistons requiring an external oil supply. External oil supply circuits are common in many older OEM actuators systems but come with significant drawbacks. The biggest being oil contamination and a need for frequent and costly maintenance. In addition, the internal varnishing within the system can cause static friction (stiction) resulting in poor control. The original actuator exhibited a position hunting effect which ultimately led to poor control of the steam turbine with large RPM swings – disrupting the downstream process. Refinery personnel consulted REXA’s industrial rotating equipment specialists, who developed a user-specific solution. After reviewing the issues, REXA proposed it’s, “Rotating Equipment Total Integrated Solution.” This specialized package includes an on-site evaluation and training, custom engineered actuator mounting hardware, 3D installation drawings, TAR supervision and support, and actuators/calibration.     Literature Read the full Success Story by downloading here!  Download

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Mill Feedwater Pressure Control

Wastewater Treatment, Water and Wastewater, Water Treatment /

Success Story: Mill Feedwater Pressure Control Copper is a valuable metal used in many residential, commercial, and industrial products. From wiring and consumer electronics to HVAC systems to electrical vehicles, copper is an essential element necessary to produce such products. Copper mining is a complex process and water is its’ lifeblood. It allows for the separation and recovery of salable copper. Throughout the milling and flotation cell processed, over double the amount of water is required throughout the crush-grind-flotation-concentrate circuit. Poor control of the mine’s water supply can negatively impact process run-time, leading to constrained production levels and hurting the bottom line. Additionally, as a mine ages, copper ore grade generally decline. To maintain target recovery rates, mines must process more material called ore tons. As time passes this adds to the mine’s overall water consumption.  Around the world mining companies are working to develop a more sustainable production method to address environmental concerns and maintain stable operations. Chile is home to the world’s largest copper mine and it is the country’s largest water consumer. In 2018, the mine underwent an expansion project to implement a desalination plant and added a necessary pipeline to feed the operation. The goal was to operate entirely on desalinated water by the year 2030. In 2020, 10 years ahead of the planned schedule, that goal was achieved. The mine’s water source is pumped over 3,100 meters above sea level to a reservoir near the mine. From there, the water is then delivered through a 36-inch discharge line and is controlled with an 18-inch globe valve. The pond is the sole water supply to the mill andconcentrator.  Greater process control is the hallmark of REXA’s Electraulic™ Actuators. Our actuators are more precise and accurate in performance than pneumatics and more reliable than traditional hydraulic technologies. This mine’s location is remote, arid, and the ambient temperature can drop below 0°C in the winter. For this project, themine had considered pneumatic actuators. The decision was made to not use the pneumatics because of their marginal positioning accuracy and reliability. To keep the concentrator process running, it is crucial that there is water present. Mine operators chose to rely on REXA Electaulic™ Actuators as the final control element to control water flow rate and emergency shutoff. Upon an unexpected loss of power, the linear actuators, equipped with accumulator bottles, produce up to 20,000 lb (89,000 N) of thrust that can safely close the valves using pressurized nitrogen.  In 2021, desalinated water is now used to supply all the copper mine’s water requirements. REXA actuators played a vital role in this successful four-year transition. Our self-contained Electraulic™ system locks the cylinder in place, when no movement is required, minimizing wear and tear on moving components and eliminating unnecessary power consumptions. REXA Electraulic™ Actuators have been engineered for use for constant modulating duty cycle and precise positioning independent of load variation. REXA’s actuation package supports various control system protocols including HART (Highway Addressable Remote Transducer) and Ethernet IP. Pipeline flow control is an excellent example where reliable positioning performance is necessary to prevent and minimize unscheduled downtime! Copper is a valuable metal used in many residential, commercial, and industrial products. From wiring and consumer electronics to HVAC systems to electrical vehicles, copper is an essential element necessary to produce such products. Copper mining is a complex process and water is its’ lifeblood. It allows for the separation and recovery of salable copper. Throughout the milling and flotation cell processed, over double the amount of water is required throughout the crush-grind-flotation-concentrate circuit. Poor control of the mine’s water supply can negatively impact process run-time, leading to constrained production levels and hurting the bottom line. Additionally, as a mine ages, copper ore grade generally decline. To maintain target recovery rates, mines must process more material called ore tons. As time passes this adds to the mine’s overall water consumption. Around the world mining companies are working to develop a more sustainable production method to address environmental concerns and maintain stable operations. Chile is home to the world’s largest copper mine and it is the country’s largest water consumer. In 2018, the mine underwent an expansion project to implement a desalination plant and added a necessary pipeline to feed the operation. The goal was to operate entirely on desalinated water by the year 2030. In 2020, 10 years ahead of the planned schedule, that goal was achieved. The mine’s water source is pumped over 3,100 meters above sea level to a reservoir near the mine. From there, the water is then delivered trhough a 36-inch discharge line and is controlled with an 18-inch globe valve. The pond is the sole water supply to the mill and concentrator.     Literature Download the entire Success Story here to learn more!  Download

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Process Gas Compressor Flow Control – For Hot Briquetted Iron

Metals Processing, Mining and Metals /

Success Story: Process Gas Compressor Flow Control – For Hot Briquetted Iron In 2020, the largest North American producer of flat-rolled steel completed a new direct reduction plant. The plant produces Hot Briquetted Iron (HBI), a versatile iron source needed to produce steel in electric arc furnaces, basic oxygen furnaces, and blast furnaces. The plant has a closed loop gas circuit that dedusts, compresses, and reheats the gas. Natural gas is also added to the loop. To achieve the highest quality HBI product, optimum process control of product temperature and furnaceatmosphere is required.  In May 2021, the direct reduction plant’s HBI pellets were transferred to their sister company’s blast furnace. In the blast furnace, the HBI blends with coke and iron ore additions. Iron ore is rich in iron oxides, which are reduced by carbon monoxide to form elemental iron and carbon dioxide. Not only are carbon dioxide emissions reduced using HBI on blast furnaces, but also the blast furnaces run more efficiently. Four months into the HBI pellet production, the plant’s operations group had grown increasingly frustrated with their pneumatic actuators. The actuators’ were doing an inadequate job of positioning the compressor Inlet Guide Vanes (IGVs).  Accurate positioning of each compressor on the IGVs is necessary to precisely control the gas throughout, with two compressors in series. Doing this effectively ensures optimal gas flow through the compressor. The compressor IGVs used a pneumatic rotary actuator. During start-up, the pneumatic actuators had one-second delays before moving to position. The slow and inaccurate positioning led to terrible vibration, causing the compressor to shut down. In some cases, up to six manual attempts were tried before the process could restart.  In May 2022, both compressor IGV’s were upgraded with a REXA Electraulic™ Linear Actuator. REXA supported the upgrade by providing a site survey, engineering drawings, and onsite start up commissioning. Plant personnel immediately noticed improved repeatable accuracy to 0.1% of span, regardless of process conditions. The REXA actuators have the capability to open from 0-20%, in under two seconds, without overshoot. For this reason, the plant can now safely start up the compressors without vibration. The process gas stability has also improved, leading to better control of the HBI product chemistry. By utilizing REXA actuators, the steady state process gas flow oscillation was reduced from +/-2,000 m3/hour to +/- 50 m3/hour. Other benefits of improved process control are the reduction in natural gas consumption and less modulating of the 24 downstream control valves. In turn, the control valves’ maintenance intervals were extended. Producing and using HBI contributes to the steel company’s greenhouse gas reduction initiative. REXA actuators contributed to improving the HBI plant operations with improving process gas stability.  Literature Click download to further explore the ROI this plant had in this Success Story!  Download

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Geothermal Power Wellhead Valves

Geothermal, Power /

Success Story: Geothermal Power Wellhead Valves With the demand for renewable energy continuing to increase, geothermal power is quickly becoming a focal point in generation company portfolios. Producing about one-sixth of the carbon dioxide emitted by a clean natural gas fueled plant, geothermal energy production ensures a sharp reduction in greenhouse gas emissions. There are three types of geothermal power designs-dry steam, flash and binary cycles.  Regardless of plant design, everything begins at the wellhead. Often separated from the plant by significant distances, production wells include Emergency Shutoff Valves (ESVs) and flow control valves-both of which play key roles in the process. Therefore, they need to function reliably to ensure no interruption of the flow of steam or brine to the plant.  A geothermal power plant in New Zealand recently experienced unstable control of their production wellhead valves and sought out REXA for a solution. The previously-installed pneumatic actuators were not able to accurately control the valves during both start-up and normal operation. This caused large pressure swings in the process and immense water hammer down the line, which on two separate occasions led to bending pipework and broken pipe brackets.  Leaks within the valve’s stem packing required tightening, making it even more difficult for the pneumatics to overcome the additional packing friction. This negatively affected the pneumatic actuators positioning accuracy resulting in frequent overshoot and correction which lead to water hammer.  This plant needed a solution, and they needed it quickly. Luckily, they already had REXA Rotary Actuators installed on their emergency dump valves! These were used to overcome brine build-up on the disc of the butterfly valves, which helped assure them REXA could overcome any stiction problems on the production wellhead valves. For this reason, as well as the fact that the electro-hydraulic set up of REXA Actuators provide more accurate and reliable control than pneumatics, this plant successfully installed three REXA XPAC Linear Actuators!  Since the initial installation in March 2019, our customer has greatly improved their control of the production wellhead valves with no more large swings in the process. Water hammer down the line is now a thing of the past. Literature Read the full Success Story by downloading here!  Download

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Nickel Mine Oxygen Compressor Inlet Guide Vanes

Metals Processing /

Success Story: Nickel Mine Oxygen Compressor Inlet Guide Vanes A large nickel mine in Ontario, Canada produces nickel metal, which is used in the manufacturing of smartphones and rechargeable batteries that power electric cars. Sulfur dioxide (SO2) is a major air pollutant emitted in the roasting, smelting, and converting of sulfide ores. Fortunately, the SO2 is recovered and utilized to make sulfuric acid (H2SO4), an important coproduct that contributes to the mine’s operational revenue. This high-grade sulfuric acid is used to make recyclable fertilizers and paper products.  Oxygen gas is an important precursor compound required in the expanded process to make sulfuric acid. The gas is generated on site and supplied to the nickel smelter where it is used in flash furnaces that produce iron oxides, sulfur dioxide (SO2), and nickel matte. The sulfur dioxide produced by flash smelting is used to make sulfuric acid,removing the major environmental effect of smelting. Pressurized oxygen must be available to the nickel smelter, or the acid plant will need to halt operations – potentially costing up to $60,000USD per day in revenue. This very scenario worried the nickel mine’s acid plant operations management team since a legacy oxygen plant was beingdecommissioned. This meant there was no longer a backup supply.  The plant has two multistage centrifugal compressors, each powered by a large electric motor. Accurate positioning of the compressor inlet guide vanes (IGVs) is necessary to precisely control the gas throughout the compressor. Doing this effectively ensures the most efficient gas flow through the compressor. The plant operations group grew increasingly frustrated with the pneumatic actuators’ poor performance in positioning the IGVs. The mechanical position switches would drift—requiring recalibration every 6–8 weeks. Due to the compressibility of air, the compressor turndown increased to safely operate without surging, at the cost of compressor efficiency. In 2016, both compressor IGVs were upgraded with six REXA Electraulic™ Linear Actuators. Plant personnel immediately noticed improved accuracy—repeatable to 0.1% of span, regardless of process conditions.  The plant also noticed significant energy savings, since the Electraulic™ Actuators accurately controlled at a higher maximum capacity flow within turndown range. Each compressor had a 0.5 MW power reduction due to the improved air flow and higher compressor efficiency. The annual savings in electricity are calculated to be $1,092,000 USD per year. Literature Read the full Success Story by downloading here!  Download

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Steel Making Reheat Furnace Pressure

Metals Processing /

Success Story: Steel Making Reheat Furnace Pressure Steel companies around the world continuously introduce and enhance processes that emphasize sustainable development. Key sustainable targets include minimizing the environmental footprint and increasing energy efficiency. These companies proactively develop actions to decrease fossil fuel consumption, thus reducinggreenhouse gas emissions. Through all these initiatives, companies proves it is possible to be socially responsible while reducing operational cost to produce quality steel. Modern continuous rolling mills produce large quantities of thin sheet metal but consume significant amounts of energy—particularly with reheat furnaces. These furnaces are gas fuel energy intensive, second only to blast furnaces.  The reheat furnace is located at the hot strip mill and is the process step before hot rolling. In this step, steel billets, plates, or blocks are usually heated from room temperature to ~1,200 C°. At this temperature, the billet can be hot rolled and achieve the desired metallurgical, mechanical and dimensional properties of hot rolled products. Optimal operations require the minimization of fuel consumption, while maintaining a controlled steel billet thermal soak.  From economic, production, and environmental standpoints, the operation of reheating furnaces is of great importance to the steel making process. Economically, the consumption of fuel needed for reheating can represent up to 15% of the operational cost of a rolling process. With respect to productivity, a reheat furnace capacity often dictates the production rate for the rollers, which means that reheating is usually the bottleneck in achieving the maximum production volume. The furnace operation must be reliable, as any downtime will cost the average sized mini mill nearly $45,000 per hour in lost product revenue.  Maintaining a controlled ramp up and holding soak temperature is not a straightforward task. Heat transfer to the steel billets is influenced by internal temperature setpoint of the furnace, flow rate of fuels and flow rate of air. Maintaining furnace pressure is very important. If the furnace pressure is too low, air will ingress in the furnace with oxygen, potentially causing scale formation, impacting quality and productivity. If the furnace operates too high, then the fuel consumption will increase operational cost.  Literature Download the full Success Story here!  Download

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Chemical Processing Turbine Governor

Uncategorized /

Success Story: Chemical Processing Turbine Governor Steam turbines are found in almost any processing plant or power generation facility. Used as the driver for other rotating equipment, steam turbines convert thermal energy to rotational energy — ultimately controlling the input speed or power of a driven device. Any turbine downtime negatively impacts the overall plant process. Therefore,reliable and repeatable control is imperative for efficient plant process and maximum profitability.  A chemical plant in Ohio recently experienced nuisance downtime from process inconsistencies and required improvements to their BDO (butanediol) compressor’s steam turbine governor control valve actuation system. Their system consisted of a simplistic hydraulic power piston actuator, which was challenging to retrofit with LVDT (Linear Variable Differential Transformer) position feedback. Modulating the power piston’s hydraulic relay required its’ driver to make thousands of tiny reversals every hour — adding up to tens of millions of reversals each year.  Thanks to REXA’s Electraulic Actuators, this plant’s concerns are a thing of the past! Our actuators require no oil filters or oil-based maintenance – making them highly reliable. Regular maintenance intervals for our actuators on steam turbine systems are not typically required until after 7-10 years of service, ensuring long-lasting repeatability. High performance allows for control at +/- 1 RPM, allowing fast synchronization and exceptional load control.  Once installed, our customer noticed immediate improvement on the turbine’s speed control and RPM swing. With REXA self-contained actuators, the customer was able to eliminate constant repair and replacement, the need for an external oil supply requiring scheduled maintenance, and many other peripherals within the governor control valve actuator loop such as the LVDT feedback, positioning modules, etc.  Literature Download the full Success Story here to read more!  Download

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Supercritical Power Plant Condenser Level Control

Uncategorized /

Success Story: Supercritical Power Plant Condenser Level Control Supercritical and Ultra-Supercritical plants are a vital part of global power generation. They operate above the critical pressure and temperature of water (3206.2 psia at 705 °F), up to a maximum of 4350 psia and 1170 °F. Since feed water is turned into steam as it travels through the boiler tubes, the startup system requires a problem-free operation.  One of the most important parts of a power plant is the condenser. Drawn into the condenser, the steam is “condensed” back into water so it can be used repeatedly within the plant. Plants need reliable actuation to efficiently control the condenser application process and maintain maximum MW output.  A supercritical coal-fired power plant in South Africa experienced control issues with their condenser level control valve. The installed pneumatic piston-type actuator could not properly control the valve due to a combination of process parameters changes, compressibility of air and valve static friction. Erratic hunting for position and water hammer resulted in the breakage of downstream pipework hangers and welds of the pipework leading into the feedwater deaerator. Consequently, this meant the whole generating unit needed to come offline and be drained for the pipework to be welded — sometimes taking more than 12 hours to repair. This lengthy downtime, as well as a significant loss in revenue and availability of MW output, proved disastrous. To combat these continuous issues, plant operators worked with REXA to size and custom engineer an Electraulic™ actuator to fit on top of the existing control valve. Our actuator’s incompressibility of oil, solid-state electronics and superior control performance eliminated the poor control and associated water hammer. Upon installation, plant operators noticed an almost immediate improvement in the stability of the condenser level with additional improvements in other feedwater equipment (LP heaters, flashbox, etc.)    Literature Click here to download the full Success Story! Download

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Improved Air Control And Furnace Safety

Uncategorized /

Success Story: Improved Air Control and Furnace Safety REXA recently conducted a successful installation on a crude unit heater at a refinery in California. Furnaces help refineries and petrochemical plants break down and convert hydrocarbon fluids into fuels or chemicals such as gasoline, diesel, ethylene, and propylene. When making process improvements, these facilities tend to overlookimproving furnace draft control. There are many instruments to choose from when optimizing the draft in a process heater. The challenge is safely elevating process fluid temperature to a target level, maximizing thermal efficiency and throughput and reducing O2, CO and NOx emissions.  This refinery suffered from many damper-related issues. Having 3 furnaces on a single selective catalyst reduction (SCR) unit with all air supplied by one forced draft fan and all flue gas extracted by one induced draft fan, it’s imperative all dampers operate reliably. This complicated furnace/SCR arrangement include 3 stack dampers, 3 combustion dampers, a forced draft (FD) fan suction damper and two split induced draft (I/D) fan suction dampers.  The plant retrofitted this crude unit with balanced draft SCR equipment over 20 years ago and has experienced damper issues ever since. The dampers were replaced to fix the problem, but unfortunately the pressure drop across the dampers proved too much for the pneumatic actuators to control. This resulted in delayed damper response, causing poor draft pressure control. This led to fuel-rich operation or bogging conditions – a major safety concern.  The plant then consulted REXA to find the necessary solution. After installing the new dampers and directly mounting our actuator, plant operators almost immediately noticed a significant improvement in damper performance air control. For the first time in decades, the crude unit started up without issue and the dampers began and continue to control better than ever before! Literature Read the full Success Story by downloading here! Download

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Sootblower Steam Pressure Reduction Temperature Control

Uncategorized /

Success Story: Sootblower Steam Pressure Reduction Temperature Control Supercritical and Ultra-supercritical plants are a vital part of global power generation. They operate above the critical pressure and temperature of water (3206.2 psia at 705 °F ), up to a maximum of 4350 psia and 1170 °F. Since feed water is turned into steam as it travels through the boiler tubes, the startup system requires problem-free operation.  One of the most important parts of a power plant is the condenser. Drawn into the condenser, the steam is “condensed” back into water so it can be used repeatedly within the plant. Plants need reliable actuation to efficiently control the condenser application process and maintain maximum MW output.  A supercritical coal-fired power plant in South Africa experienced control issues with their condenser level control valve. The installed pneumatic piston-type actuator could not properly control the valve due to a combination of process parameters changes, compressibility of air and valve static friction. Its erratic hunting for position and the ensuing water hammer resulted in the breakage of downstream pipework hangers and welds of the pipework leading into the feedwater deaerator. Consequently, this meant the whole generating unit needed to come offline and be drained for the pipework to be welded—sometimes taking more than 12 hours to repair. This lengthy downtime results in a significant loss in revenue, and MW availability.  To combat these continuous issues, plant operators worked with REXA to size and custom engineer an actuator to fit on top of the existing control valve. Our actuator’s incompressibility of oil, solid-state electronics and superior control performance eliminated the poor control and associated water hammer. Upon installation, plan operators noticed an almost immediate improvement in the stability of the condenser level with additional improvements in other feedwater equipment (LP heaters, flashbox, etc). Literature Click here to read the full Success Story!  Download

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