As a material, carbon fiber has fundamentally changed many of the products we use every day, making them lighter, stronger and more durable. The manufacturing process is typically unique to each supplier, and it can be as complex as the fiber molecules themselves. Equally as challenging are the air-pollution control systems used on the production equipment.

This year, two institutions on opposite sides of the world rolled out new carbon-fiber processing techniques that utilize different, yet highly effective, air-pollution abatement technologies that also drive down production costs.

When the first conversion plants came online, operating costs were not critical design parameters and neither were the environmental effects of production. Today, however, the manufacturing of carbon fiber is heavily regulated by the environmental community, and producers are continually looking to reduce the energy demands of this heat-intensive process.

Oxidation and carbonization furnaces and industrial ovens have the potential to emit hydrogen cyanide (HCN), ammonia (NH₃) and volatile organic compounds (VOCs). Some of these pollutants are immediately dangerous to human health, even in very small quantities. Other pollutants of concern for carbon-fiber producers include harmful gases such as carbon monoxide (CO) and nitrogen oxide (NOx). These emissions not only contribute to global warming but also have a direct correlation with the manufacturer’s consumption of energy. 

Recycling at the Forefront in the U.K.

The strength, durability and lightweight characteristics of carbon fiber make it perfect for manufactured products like airplanes and automobiles. Unfortunately, most waste ends up in landfills, where those same attributes do not allow the carbon fiber to break down like other organic material. To combat this problem, the University of Nottingham opened a new, state of-the-art facility dedicated to the reuse of this valuable resource.

In conjunction with industry partners, Nottingham University has developed a pilot-scale carbon-fiber recycling plant. The team set out to develop and commercialize recycled fiber that maintains the material strength at a cost savings to manufacturers using carbon fiber in their products. The result was a lightweight, low-cost material made from recycled carbon fiber that gives users a competitive advantage over virgin carbon fiber. 

The team at Nottingham knew that an air-pollution control device would be necessary to meet the local emission requirements for HCN and NH₃. They also realized that there was the potential to reuse some of the energy released during the combustion of these carbon-fiber processing emissions.  

Anguil Environmental Systems (Anguil) was selected to provide the air-pollution control system for the University of Nottingham. The company’s experience with similar applications and ability to make a custom-designed system to meet the unique needs of this pilot-scale recycling facility were the primary determining factors it was chosen for the project. Anguil manufactured, installed and recently brought online a Thermal Recuperative Oxidizer with dual heat recovery. 

A stainless steel heat exchanger within the oxidizer reduces the amount of supplemental fuel required to bring the process emissions up to combustion temperatures. In addition, a secondary heat recovery system downstream of the oxidizer captures most of the remaining heat. This is enough energy to preheat the air for the process equipment. When in operation, little external heat is required to fuel the oxidizer or carbon-fiber oven, making the entire system self-sustaining. The oxidizer has been achieving a 99% destruction-rate efficiency at the Nottingham facility.     

A Technology Transfer in the U.S.

Recognizing the need for this industry to develop a lower-cost carbon-fiber material, the U.S. Department of Energy built a custom-designed conversion process at Oak Ridge National Laboratory (ORNL). The process equipment, which was designed by Harper International, makes this one of the most sophisticated and capable facilities in the industry. The carbon-fiber technology line in Oak Ridge, Tenn., allows commercial partners to test the scalability of emerging carbon-composite materials before commercial production.   

To treat the exhaust streams coming from the carbon-fiber process, Anguil was commissioned to design, manufacture and install a multi-stage direct-fired thermal oxidizer (DFTO). The abatement system is capable of destroying nitrogen compounds without the formation of NOx, which is a typical byproduct in conventional oxidation processes. Gases move through zones within the DFTO under varying conditions where the total emission destruction efficiencies are over 99% with minimal NOx generation. Even though this application does not warrant additional NOx reduction, the DFTO has the capability of adding selective non-catalytic reduction to further reduce the environmental impact. 

About Anguil Environmental Systems

Anguil Environmental Systems is an air-pollution control and energy-recovery system provider headquartered in Milwaukee, Wis., with offices in the U.K. and Asia. The company is intimately familiar with the capture, control and compliance hurdles that processing plants face. For additional information about Anguil, please visit www.anguil.com or e-mail info@anguil.com.