This Small Business Innovation Research Program (SBIR) Phase I project will focus on the design, construction, and verification of a terahertz (THz) hydration mapping system for use in paper manufacturing. THz radiation is defined as the submillimeter region of the electromagnetic spectrum, and is a relatively new and expanding area of research that promises unique imaging capabilities. THz imaging utilizes illumination from the 100 GHz to 10 THz band to generate contrast in targets unavailable to systems operating in the NIR, visible, and UV bands. THz illumination is ideally suited to nondestructive evaluation, security imaging, process control, and medical imaging for a number of reasons, including its nonionizing nature, its wavelength, its achievable broad instantaneous bandwidth, and the large real and imaginary parts of the dielectric constant of water at THz frequencies. Paper manufacturing currently lacks hydration metrology with sufficient spatial resolution and water concentration sensitivity to detect local distributions of water in drying paper products, and the current industry standard is costly and has safety concerns due to its associated ionizing radiation.
The broader impact/commercial potential of this project spans several fields that rely on careful moisture control, including wood manufacturing, plastics, agriculture, chemical processing, and concrete manufacturing. This proposal will initially focus on the papermaking process, which is a very expensive, capital-intensive process. Both downtime on a paper machine and scrap paper (unwanted paper) are highly valuable. As a result, process control is key, and the ability to remove water quickly and consistently is one of the most important process control variables. Out-of-spec moisture increases downtime, reduces efficiency, increases costs, increases scrap levels, and reduces quality to the consumer. Current process control techniques are insufficient and lead to added cost, increased energy use, and a large amount of wasted paper that must be recycled or land filled. The global paper manufacturing industry is enormous, with over $130 billion in sales and nearly 100 million metric tons of product annually in the U.S. alone. Therefore, improvements in process control can result in significant reductions in global energy use, global wood consumption, and paper costs.
Introduction: This Small Business Innovation Research (SBIR) Phase I focused on the exploration of terahertz hydration imaging technology for high speed accurate measurement of paper moisture during paper stock and paper products manufacturing. While this technology is applicable to any type of paper product, the work funded by this SBIR focused primarily on sanitary products such as paper towels and toilet paper, as these are the domestic paper product segments with the most reliable growth. The moisture level throughout the process as well as moisture uniformity across the sheet are critical. Current practice limits hydration monitoring to few locations, uses ionizing radiation, is slow, and has limited accuracy. This phase I SBIR focused on the development and experimental verification of a terahertz moisture monitoring system. An experimental terahertz system was constructed, numerous transmission and reflection mode mounting schemes were evaluated to assess the optimal mode, and scanning of moisture content of paper products was investigated. Broader Impacts: The papermaking process is a very expensive, capital-intensive process. Downtime on a paper machine is valued at over $50,000/hr, and scrap paper (unwanted paper) is valued at over $5000/10 min. As a result, process control is key, and the ability to remove water quickly and consistently is one of the most important process control variables. Out-of-spec moisture increases downtime, reduces efficiency, increases costs, increases scrap levels, and reduces quality to the consumer. Current papermaking operations run scrap levels of 5-8%, and the vast majority of scrap is due to uneven moisture profile. Clearly, current process control techniques are insufficient and lead to added cost, increased energy use, and a large amount of wasted paper that must be recycled or land filled. The global paper manufacturing industry is enormous, with over $130 billion in sales and nearly 100 million metric tons of product annually in the U.S. alone. Therefore, improvements in process control can result in significant reductions in global energy use, global wood consumption, and paper costs. THz technology is ideally suited to moisture monitoring during paper manufacturing, and if successful, may also have application to several additional NDE fields that rely on careful moisture control, including cork manufacturing, wood manufacturing, plastics, agriculture, paint processing, and concrete manufacturing.
