Section of 3 Meter Oxidation OvenHarper offers advanced oxidation ovens to complement its industry-leading furnaces for Carbon Fiber processing. Our state-of-the-art oven designs available for tow-bands from 300mm to greater than 4000mm. Harper’s most recent 3 meter wide production scale Oxidation Oven (section of Oven pictured right) demonstrates outstanding performance for key metrics including air velocity uniformity measuring at 2.2%, and temperature uniformity of +/-2.5°C throughout the entire heated length. This innovative oven design enables enhanced performance with higher and more efficient rates of production.

For the customer, our technology advancements equal faster oxidation through elimination of the chimney effect, improved velocity uniformity and range, assurance of temperature uniformity at a variety of flow rates, and optimal control of the reaction ultimately enhancing fiber quality. Some of these designs improvements include:

  • Superior atmospheric seals
  • Continuous monitoring of supply, recirculation, and exhaust flow rates
  • Improved, patent-pending nozzle design
  • Process based instrumentation array
  • Quadrant construction for improved installation

The most distinctive feature of Harper’s cutting-edge design, the innovative atmospheric end seal, reduces fugitive emissions, increases the active volume of the oven, and offers reduced energy consumption over alternatives.  The seals have independent adjustment of the top and bottom inside and outside slots.  Each pass has an independent vent with adjustable draw control and the exhaust plenum connects to a dedicated fan/VFD.  As a result of these innovative design features, there is no vertical mixing in the seal, less air ingress, and virtually no process gas escape.

Harper’s instrumentation improvements include a two-tier balancing methodology, responsive quench system and rapid cool down system, emissions monitoring, and inherently safer pressure relief system. Additionally, Harper’s modular construction design is another advancement that sets us apart from the competition.  Our oxidation ovens have shown a 90% reduction in labor versus similar field erection times into a full line pilot system (300mm).

Additionally, Harper’s proprietary multiflow Research Oven as a part of our Microline® system offers parallel, cross, and down airflow directions in a single oven, which allows for true evaluation of different flow techniques. The oven’s uniformity specifications meet or exceed best-in-class for each flow regime.

Innovations in Alternative Precursor Processing

Harper Oxidation OvensAlthough Carbon Fiber is predominantly produced from polyacrylonitrile (PAN) and pitch, there is an increasing necessity for alternative, low cost and renewable precursors as the industry grows to applications such automotive. Harper has the unique ability to adapt our technology to process nontraditional precursors throughout the entire thermal process, including within the oxidation ovens. By using nontraditional precursors such as lignin, rayon, polyethylene, and blends, customers can lower their operating costs and reduce the residence time in the oven. To custom engineer the equipment for the unique process needs, we take into consideration the chemistry of the precursor to determine the materials of production. Whether the precursor is unsupported by its weight requiring a belt furnace or is a tow, Harper provides solutions for these emerging precursors throughout the full process. We have designed our oxidation ovens to be able to produce these emerging precursors throughout all line sizes, from research to production scale, demonstrated in our complete line installed at Oak Ridge National Laboratory’s Carbon Fiber Technology Center.

Innovations in Gas Fired Heating

Harper is supporting the advancement of the Carbon Fiber market through designs for gas-fired production scale ovens, as well sizing dryers and air pollution abatement systems, to take advantage of natural gas benefits. Current energy markets and environmental regulations have produced significant advantages to thermal processing equipment that use natural gas for fuel, and Harper has unparalleled experience with producing reliable combustion heated processing equipment for a variety of industries and applications. Capital cost for gas-fired equipment comes at a slight premium and the return on investment (ROI) can vary with the location of the installation. However, we have seen an ROI of less than two years in North America when compared with electrically heated equipment. Additional options for heat recovery to increase efficiency can be implemented in regions of the world that command higher fuel gas prices.

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