Major research initiatives underway in the United States and European Union (EU) are striving to better understand industrial drying and to address the technical and economic issues posed by such operations.
Speaking in July 2016 at the opening of the Center for Advanced Research in Drying (CARD), based at Worcester Polytechnic Institute (WPI), Worcester, Mass., its director, WPI professor Jamal Yagoobi, pointed out that industrial drying processes waste about 2% of the 100 quadrillion BTUs (or quads) of energy used each year in the United States.
“If CARD achieves its aim of improving the energy efficiency of those processes by 10%, it could save 0.2 quads of energy each year. Also, since steam is the prime media used in industrial heating and drying, by making drying more efficient, the Center also aims to help reduce annual water usage in the U.S. by about 10 billion kilograms,” he added.
CARD received its initial funding though the National Science Foundation’s Industry/University Cooperative Research Centers program; it brings together researchers from WPI and the University of Illinois at Urbana-Champaign (UIUC) to tackle drying issues facing its industrial members.
“We have four main goals: to save member companies money by improving their energy efficiency; to help them meet sustainability goals; to improve their products and throughput; and to develop the skills of our students as their next generation workforce,” notes CARD program manager Mark Lippi.
The center (Figure 1) is targeting manufacturing sectors that rely on energy-intensive drying processes such as: chemicals, pharmaceuticals and textiles; food and agriculture products; and forestry products such as paper, tissue and wood. The membership already includes Flint Hills Resources, Hershey’s, Kimberly-Clark, Ingredion, Massachusetts Clean Energy Center, Mondelez International and PepsiCo, among others. Each pays $50,000/yr for membership.
“While the details are confidential, we basically have three buckets of projects: new/novel drying technologies, sensor technologies — because it’s very important to be able to follow material changes through the drying process — and understanding the structural fundamentals of difficult-to-process materials,” he explains.
The universities and industrial partners jointly set research priorities at two annual meetings.
“We really only got started in February 2017 and we decided on 11 projects in our first year,” says Lippi.
Six, deemed sufficiently important, were rolled over into the 2018 quota of 12 projects. These projects focus on sensor development, novel impinging jet nozzles, and basic understanding of structural mechanisms of products. For example, WPI is taking the lead on: enhancement of heat and mass transfer with innovative jet nozzles; fundamental understanding of rapid air drying of paper tissues; and enhancement of municipal wastewater biosolids drying by changing interfacial energy to promote uniform aggregation. UIUC is heading efforts on: a wireless passive micro-electromechanical sensor for in-situ measurements of trapped moisture and pressure; and ultrasonic non-thermal drying of wet biopolymeric materials.
“I’m a bit disappointed about the five that were dropped, but that’s a function of how this program works — our industry members decide which projects to fund,” notes Lippi.
He believes that the most exciting developments will come from CARD’s work on sensors and novel drying technologies.
Both universities have long experience in sensor development and are uniquely positioned to do this kind of work, he stresses.
One initiative to watch here is the development of optical non-destructive testing (ONDT) sensors with extremely fine resolutions. These can detect changes in surface shape and texture as well as volumetric changes to different media during and after the drying process. Such ONDT sensors promise extremely accurate real-time monitoring and control of drying processes.
Among efforts to improve the drying operation itself, CARD researchers are applying ultrasound to dewatering. “In some industries, for example tissue paper manufacturing, the moisture content of the final product can sometimes be below 1%. We believe ultrasound will help to unbind and transfer water out of the material, making the drying process more efficient. The program is essentially focused on fluid transfer issues in different materials, so anything that improves the transport of fluids out of a material is of interest to us,” he adds.
Lippi is excited about the progress made to date. However, he would like to get members from additional industry sectors. This would open up a broader palette of projects and provide more funding so that ideas currently on hold can proceed.
“We are targeting chemicals and pharmaceutical companies,” he notes. While the main priority for industrial members is to access the research and keep up with new developments in drying, he believes that having access to a pool of skilled students and possible future employees who understand their drying processes is a significant lure, too.