Technology

Our Electrostatic Separation Technology

A proven process for dry, chemical-free particle separation

Operating Principle

The STET electrostatic separator utilizes electrical charge differences between materials, produced by surface contact known as triboelectric charging. When two materials are in contact, the material with the highest affinity for electrons becomes negatively charged, while the other becomes positively charged. Electron affinity depends on the surface properties and will result in substantial differential charging of materials in a mixture of discrete particles.

How the STET Process Works

The entirely dry process, which requires no additional materials and produces zero wastes, works as follows:

  • Material is fed into a thin gap between two parallel planar electrodes.
  • The materials acquire opposite charges through interparticle contact.
  • Charged particles are attracted to the electrode plate of opposite charge.
  • A high-speed open-mesh belt moves differently charged particles toward opposite ends of the separator.

The continuous-loop high-speed belt creates counter-current flow of the separating particles, and triboelectric separation charging and recharging within the separator. This feature is unique to the STET separator.

Benefits of the STET Separator

The STET separator offers benefits to a wide range of industries and applications, including:

  • It is entirely dry, requiring no water, chemicals, or wastewater treatment.
  • It operates continuously.
  • It consumes only a small amount of electrical energy —1-4 kWhr per ton of feed processed, depending on the density of the material processed — which is used to operate the belt motors.
  • It is easily permitted, as the only emissions control device required is a dust collector for nuisance dust.
  • Often, there is little or no pre-processing required for feed material to the separator other than size reduction to the appropriate particle size.
  • Unlike other electrostatic processing equipment, it does not require high-temperature thermal pre-treatment.
  • The separator design is relatively simple and compact. A machine designed to process up to 40 tons per hour (density-dependent) is approximately 30 ft (9 m) long, 5 ft (1.5 m) wide, and 9 ft (2.8 m) tall.
  • The belt and associated rollers are the only moving parts, making maintenance both simple and infrequent.
  • It is easy to operate, with rapid start-up and shut-down; rapid response to feed variability; automation of many functions; and requiring limited operator qualification.
  • The electrodes are stationary and are composed of a highly durable material.

More Details on the STET Equipment Technology

The STET separator is a parallel-plate electrostatic separator, with the electrode plates oriented horizontally rather than vertically, as is the case in most parallel-plate separators. Additionally, the STET separator performs particle tribo-charging and conveying simultaneously via a high-speed open mesh conveyor belt. This feature allows for both a very high specific processing rate as well as the ability to process powders much finer than conventional electrostatic devices.

Our separator machinery has been in commercial operation since 1995, separating unburned carbon from fly ash minerals (typical D50 approximately 20 µm) produced in coal-fired power plants. Our electrostatic separation machine has also succeeded in beneficiating other inorganic materials, including minerals such as calcium carbonate, talc, barite, and others. The STET separator has also been successfully applied to processing agricultural materials such as oilseed meals and pulses, animal meals, and rendering products.

The particles are charged by the triboelectric effect through particle-to-particle collisions within the gap between the electrodes. The applied voltage between the electrodes is between ±4 and ±10 kV relative to ground, giving a total voltage difference of 8 – 20 kV across a very narrow electrode gap of nominally 1.5 cm (0.6 inch).

Particles are introduced to the STET separator at one of three locations (Feed Ports). The STET separator produces only two products: a negatively charged particle stream collected on the positively charged electrode, and a positively charged particle stream collected on the negatively charged electrode.

The products are conveyed to the respective hoppers at each end of the STET separator by the separator belt, and they fall out of the separator by gravity. The STET separator does not produce a middlings or recycle stream, although multiple pass configurations to improve product purity and/or recovery are possible.

In addition, the belt generates a high-sheer, high-turbulence zone between the two electrodes, promoting tribo-charging. The counter-current travel of the separator belt allows for continuous charging and re-charging of particles within the separator, eliminating the need for a pre-charging system upstream of the STET separator.

The proprietary STET separator is a high feed rate, commercially proven processing system. The maximum processing capacity of the STET separator is mostly a function of the volumetric feed rate that can be conveyed through the electrode gap by the STET separator belt. Other variables — such as the speed of the belt, the distance between the electrodes, and the aerated density of the powder — affect the maximum feed rate typically to a lesser extent.

For relatively high-density materials such as fly ash, the maximum processing rate of a 42-inch (106 cm) electrode width commercial separation unit is roughly 40 – 45 tons per hour of feed. For less dense feed materials, the maximum feed rate is lower.

Simple Operation

The STET separator provides end users with adjustable control of product quality and can be integrated into existing process flowsheets. In addition, the STET separator offers multiple automation options:

  • On-board PLC Controls
  • Auto electrode gap adjustment
  • Auto belt tensioning
  • Auto belt tracking
  • HMI (Human Machine Interface) touch screen controls
  • Built-in alarm and fault functions that are dynamically generated for safe operation
  • One-button auto-start/auto-stop features
View our global patents list

Fly Ash

Minerals

Animal Feed

Human Food

Jose Rivera Ortiz

Production and Development Manager

Jose Rivera-Ortiz joined the company in 2004 as a Manufacturing Mechanical Technician. Over the years he took on many roles and responsibilities in the research and development and service and engineering departments. Jose is now the Manager of Production and Development as well as the Field Service Manager, and is responsible for manufacturing and production, field service, and product development. He holds many patents for STET belt development and equipment upgrades. Previous to joining STET Jose lived in Puerto Rico and worked as a chemical technician.

Lewis Baker

Service Manager

Lewis Baker provides engineering support to STET's fleet of processing plants throughout Europe and Asia and handles technical aspects of business development. He joined ST in 2004, initially as Plant Manager for STET's fly ash processing facility at Didcot Power Station in the UK, before moving to a broader role in technical support. After graduating from the University of Wales with a master’s degree in chemical engineering, Lewis held a number of roles in plant design and commissioning, process engineering, and plant management.

Kamal Ghazi

Senior Project Manager

Kamal Ghazi is a Project Manager with experience in mineral processing and industrial project implementation. He also collaborates closely with clients to ensure the successful integration of the STET Separator into their operations. Kamal joined STET in July 2015 as a Process Engineer and participated in designing and establishing the first-ever landfilled fly ash processing plant for Titan America in 2020. A mineral engineer by education, he earned a master’s degree from Tehran University and a bachelor’s degree from Kerman University.

Scott Mechler

Senior Mechanical Engineer

Scott Mechler is responsible for mechanical design work on STET’s electrostatic separator machines, focused primarily on research and development of new generations of separators. He joined the company in 2024 after a decade of experience in designing large high-tech industrial equipment in highly regulated design environments. Scott received a bachelor’s degree in mechanical engineering, with a minor in biomechanical engineering, from Northeastern University.

Traci Geer

Office Manager

Traci Geer is responsible for the daily operations of the STET office, facility management, marketing, special events, and safety. She also provides support to the leadership team, staff, and human resources. She joined the company in 2017 after having worked as an executive assistant to the Superintendent of a virtual public school. Earlier, she spent a decade as an IT system analyst. Traci earned a bachelor’s degree in computer information systems and an associate’s degree in management from Bentley University.

Tim Choi

Electrical and Controls Engineering Manager

Tim Choi is the Electrical and Controls Engineering Manager at STET. He joined the company in 2017 as a Senior Electrical and Controls Engineer. Since then, he has contributed to developing control systems for separators, commissioning various balance of plant systems, and working on equipment development at the Needham facility. Tim has been in a managerial role since 2021. He holds a bachelor’s degree in electrical engineering from Hanyang University in Korea and a master’s degree in electrical engineering from the University of Texas at Arlington.

Richard Lane

Pilot Plant and Laboratory Technician

Richard Lane, who has been with STET for more than 13 years, is responsible for analyzing daily pilot plant run samples in the lab. He also helps prepare, mill, condition, and organize samples to be run in the pilot plant. After so many years working with STET technology in the pilot plant, Rich has gained an intimate knowledge of the machines along with vast experience with the separation processes. He received an associate’s degree in applied science from Massasoit.

Kristin Cappello

Operations Manager

Kristin Cappello joined the company in 2014 as a Purchasing and Accounting manager, added Materials Manager to her role, and became the Operations Manager in 2022. She is responsible for supply chain management, inventory and purchasing, customer relations, and operation planning. Previous to 2014, Kristin worked as an Office Manager and Executive Assistant in a corporate/family law firm and as a part-time Real Estate Agent. She received her bachelor’s degree in political science/pre-law from Northeastern University.

Kelsie Garretson

Lead Chemist

Kelsie Garretson is responsible for the daily operations of the STET lab, including testing, instrument maintenance and upkeep, and data collection. Some of the instruments she manages include protein analyzers, near-infrared (NIR) spectrometers, and X-ray fluorescent (XFR) analyzers.

She joined STET in 2021 after graduating from Boston University with a bachelor’s degree in earth and environmental science, with a minor in marine science. She is currently pursuing a master’s degree in natural resources and environmental science from the University of Illinois at Urbana-Champaign.

Tom Newman

Process Engineer

Tom Newman joined STET in 2022, handling the day-to-day operation of minerals testing. He designs experiments, analyzes data, optimizes results, and writes reports to provide insights to customers. Tom often travels with STET’s containerized unit to provide on-site support for mineral enrichment projects. He also works on research and development projects to find new ways to improve and understand the triboelectrostatic process. He received a bachelor’s degree in chemical engineering from the University of Pittsburgh. As part of his role at STET, he attends conferences to share his research findings with peers in the mineral processing industry.

Natsuki Barber

Senior Food Technologist

Natsuki Barber is responsible for human food and animal feed customer projects as well as R&D in those areas, especially managing research collaboration. Before joining STET in 2019, Natsuki worked as a food scientist with the Northern Crop Institute, where she developed deep understanding of crop physiology, functionality, application, processing, and nutrition. She worked especially closely with the development and application of plant protein ingredients.. She holds a bachelor’s degree in food science and a master’s degree in cereal science, both from North Dakota State University.

Abhishek Gupta

Director of Process Engineering

Abhishek Gupta leads bench and pilot-scale test programs to develop novel applications of STET electrostatic separation technology. He also manages auxiliary equipment selection, process design, separator installation, and optimization for commercialized applications. Abhishek joined STET in 2014 as a process engineer. Before that, he worked at QD Vision, a nanotechnology company working with semiconductor crystals called Quantum Dots, to develop display and lighting products. He is a chemical engineer by education with a bachelor’s degree in chemical engineering from the Indian Institute of Technology (IIT) and a master’s degree in chemical engineering from Penn State University.

Tomasz Wolak

Director, Business Development

 Tomasz Wolak is working to introduce STET technology for animal feed and human food industries outside the United States and for fly ash and minerals industries in Europe. Tomasz originally joined STET in 2019 as a Business Development Manager for Europe, focusing on human food and animal feed applications. He has worked in the food and feed industries in both engineering and operational roles, gaining insight on design, engineering, and manufacturing as well as operating and optimizing processing plants. Tomasz earned a master’s degree in mechanical engineering from the University of Science and Technology in Cracov and an executive MBA from Apsley Business School in London, and he participated in an advanced management and leadership program at Rotterdam School of Management.

Kyle Flynn

Director, Business Development
Kyle Flynn is responsible for STET business activities in North America, as well as providing technical support to business development activities worldwide. He joined STET in 2008 as a member of the process engineering group. He has worked closely with customers and the pilot plant to develop projects worldwide for the processing of food and feed materials, industrial minerals, and fly ash using the patented dry STET technology. Kyle has assisted in commissioning multiple industrial mineral and fly ash separators, as well as research and development, process design and process optimization. Beginning in 2018, Kyle joined the business development team. Kyle received a bachelor’s degree in chemical engineering from Worcester Polytechnic Institute (WPI) and a master’s degree in chemical engineering from North Carolina State University.

Hervé Guicherd

Vice President, Business Development

Since 2018, Hervé Guicherd has served as Vice President of Business Development for STET, responsible for building, animating, and supporting the business development team. He has assumed many roles during his more than quarter century with the company, including International Business Development Director in charge of introducing STET products in new applications (e.g., mining) and new territories outside the Americas (e.g., India, East Asia); European Business Development Manager (based in Greece); and positions in supply chain and marketing. After an early career as a Navy Officer, Hervé held several positions in marketing and sales during his long involvement with technology-related companies. He received a business degree from the University of Bordeaux; a master’s degree in electrical engineering from the Institute Polytechnique of Bordeaux; and an MBA from the Darden Graduate School of Business at the University of Virginia.

Lou Comis

Controller
Lou Comis has been responsible for all aspects of financial analysis for STET since joining the company in 2017. Previously, Lou held controller positions at Siemens Medical, for the PLM R&D division, and at Draeger Medical. Immediately before joining STET he was a consultant working with companies migrating from Oracle’s Enterprise to Hyperion Financial Management. He began his career as a financial analyst and finance manager for companies including WR Grace, Polaroid, and Siemens Healthcare. Lou earned an MBA with a concentration in finance from Bentley University’s Elkin B. McCallum Graduate School of Business.

David Schaefer

Vice President of Engineering and Manufacturing
David Schaefer is responsible for the manufacturing division and the design and build of STET’s patented electrostatic separation equipment. He works closely with the company’s commercial and processing teams to enhance STET’s customer experience and help drive innovation. David has more than 30 years of engineering and manufacturing leadership experience in technology and product development in everything from multifunction printers to self-driving vehicle technology. Additionally, he has consulted for several startup operations and founded an energy technology development company, eWindSolutions. Earlier in his career, he was director of mechanical engineering and chief new product architect at Xerox and a staff engineer in product development at IBM. His deep experience with innovation-driven technology and leading end-to-end engineering programs helps drive the entrepreneurial spirit of STET. David earned a bachelor’s degree in mechanical engineering from Rochester Institute of Technology. He holds multiple patents in the areas of product performance improvement, cost reductions, and usability improvements

Frank Hrach

Chief Technology Officer
As Chief Technology Officer for STET, Frank Hrach is responsible for STET process technology development for fly ash and industrial minerals, and design, construction, and commissioning of new processing facilities. He joined STET in 1995, bringing over 25 years of experience in research & development, design & construction, and operation of specialty chemical, material handling, and high temperature combustion processes. Before becoming CTO, he served as Director of Process Engineering. Frank received a bachelor’s degree in chemical engineering and a master’s degree in chemical engineering practice from the Massachusetts Institute of Technology.

Tom Cerullo

President
“Leading a unique mix of technology and business development individuals, my job is to help customers gain more value from their processes and products. Notably, our niche is to create value from waste and by-product streams. Sustainability is in our DNA, viewing near-zero waste as a reality within our reach. “While our separation technology is recognized for delivering products of high value in cement, minerals, and protein for humans and animals, entering new markets requires addressing the needs of many stakeholders and achieving buy-in from private and public organizations. This demands a comfort level with the big picture and opening minds to new endeavors. Projects take vision and commitment to bring to fruition, and that’s why our staying power, backed by Titan Cement, an international cement and technology leader, is necessary for continuous success.” Tom Cerullo’s leadership roles at STET began in operations, sales, and business development. At the start of his career, he managed STET’s early commercial installations, the first of which was commissioned in 1995. He has helped drive the growth and evolution of the business from startup to the viable commercial business it is today. Tom is a graduate of the Massachusetts Maritime Academy, which provides a unique education for professionals entering the merchant marine, the military services, and the global marketplace. Before joining STET, he spent more than 4 ½ years as a marine engineer with Military Sealift Command. Adds Tom, “A rigorous academic program, combined with a regimented lifestyle at a young age, gave me a foundation for taking responsibility, having the discipline to endure long-term challenges, and persevering  through complex challenges.”