Application: Fly Ash

Turning Grey Fly Ash into Green

Recycle your fly ash and give it new purpose

Coal Fly Ash Beneficiation Overview

As the energy industry moves from freshly generated ash to harvested ash, you need the best separation equipment to recover, harvest, and beneficiate fly ash to make it suitable for use in concrete.

Used commercially since 1995, our completely dry electrostatic separation process for pulverized coal (PC) fly ash beneficiation has generated over 25 million tons of high-quality fly ash for concrete production. Recycled fly ash is an environmentally friendly product used to create concrete with high strength, durability, workability, and reduced heat of hydration.

In use at 12 power stations throughout the United States, Canada, the United Kingdom, Poland, and the Republic of Korea, controlled low-LOI ProAsh® products generated with STET technology have been approved for use by more than 20 state highway authorities, as well as many other specification agencies.

How STET Beneficiates Coal Fly Ash

STET uses a proprietary, industrially proven dry, triboelectrostatic separation process to beneficiate fly ash. The system separates particles based on surface charge differences, allowing carbon to be reduced without adding water or chemical reagents. That matters because many conventional approaches utilize high-temperature thermal combustion, add process complexity, require wet handling, or create a product that then needs to be dried again before shipment or use.

The STET process is continuous and designed for fine particles, which makes it well-suited for fly ash. STET has 30 years of experience operating its separation equipment in industrial settings and has processed over 25 million tons of fly ash. Operating as a non-thermal, water-free system, it helps simplify plant layout, eliminate water-related constraints, minimize impacts to air emissions,  and produce a dry product stream ready for use. For coal fly ash applications, the result is a cleaner, more consistent ash product with improved reuse potential at competitive operating and investment costs.

Reasons to Believe

STET electrostatic separation achievements include:

  • 25M tons of fly ash has been processed in our history.
  • We have enabled the avoidance of >20M tons of CO2 emissions—equivalent to taking 4.3 million cars off the road for a year.
  • We have enabled our customers to save over 8.5 billion gallons of water, which is more than 11,000 Olympic-sized swimming pools.
  • ProAsh quality has been certified under the ASTM C618, CSA A3001-23 and EN 450.

  • ProAsh produced by our technology is used in some of the most demanding projects, including high rise buildings, bridges, tunnels, and other critical infrastructure.

Unlock Fly Ash Potential with STET

Fly ash beneficiation can improve product value while converting waste to a valuable construction material.

  • Improved product quality and consistency: Beneficiation reduces unburned carbon and variability, producing a cleaner, more reliable material for concrete, cement, and other industrial applications.
  • Greater beneficial reuse and reduced disposal: More ash can be diverted from landfill into higher-value use, improving sustainability and reducing waste volumes.
  • Combustion-free processing: Minimum air emissions make the STET process easier to permit.
  • No water. No chemicals: STET’s dry electrostatic process eliminates water usage, wastewater generation, and contamination from chemical reagents.
  • Simplified processing and handling: A dry process avoids wet handling and downstream drying, making the product easier to transport, store, and use.
  • Continuous, high-rate, single-step process: With processing capacities of up to 45 tons per hour, the STET separator integrates seamlessly into existing workflows with consistent output.
  • Reduced operating costs: Lower energy consumption, no landfill costs, and reduced environmental remediation contribute to improved economics.
  • Revenue growth opportunities: Turning a waste material into a viable, marketable product creates new revenue streams.
  • End-to-end solution: From initial concept to fully permitted and supported plant, STET provides the technology, equipment, services, and support needed to optimize fly ash processing and commercialization.
Unlock Fly Ash Potential with STET

The STET™ End-to-End Service Model

Putting our know-how to work for you

Evaluate

  • Assess customer needs
  • Sample testing
  • Bench-scale testing

Trial

  • Pilot plant trials (in-house at STET)
  • Full-service lab testing
  • Pilot plant of large sample
  • Optimization of prep steps (milling, drying, deagglomeration)
  • Market development

Design

  • Confirm plant design through pilot plant trials
  • Control system design
  • Finalize plant design
  • Estimate construction, production, and manufacturing costs

Build/Install

  • Develop detailed engineering (typically done by a third-party specialist)
  • Manufacturing of proprietary parts
  • Construction of the plant

Optimize

  • Rigorous statistics and design of experiments (DOE) based approach

Marketing and Ongoing Support

  • Co-marketing programs of fly ash products
  • Maintenance program
  • Technical support
  • Scale-up as needed
  • Warehousing & inventory

FAQs

What is fly ash beneficiation?

Fly ash beneficiation is the process of upgrading fly ash so it meets tighter quality targets and can be used in higher-value applications.

Is coal ash the same as fly ash?

Not exactly. Coal ash is a broader term that can include several ash types. Fly ash is one specific fraction and is the main focus in many beneficiation applications.

How does beneficiation improve ash value?

It improves consistency and removes limiting components, such as excess carbon, so the ash can be used in more demanding markets and applications, including ready-mix concrete.

What industries use beneficiated fly ash?

The most common uses are in concrete and cement, but other industrial applications can also use beneficiated fly ash, depending on the final product properties.

View the Fly Ash Resource Library

Learn More About the STET Electrostatic Particle Separators

Please tell us about your application and needs


Fly Ash

Minerals

Animal Feed

Human Food

Jose Rivera Ortiz

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Herve Guicherd

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

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

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

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

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.”