Andritz develops energy saving Spunlace Technology
After three years in development, Andritz Nonwoven is representing the next generation in spunlace dewatering and drying technology in commercial operation: neXecodry, nonwoven drying and dewatering technology. The results have been dramatic in terms of energy savings and drying efficiency
The neXecodry drying and dewatering system was developed by Andritz Nonwoven to significantly reduce energy costs in both new and existing nonwovens spunlace production lines.
The development of neXecodry technology followed Andritz Nonwoven’s path of the company’s proven “innovation process” for bringing new ideas to market, according to Frederic Noelle, research & development manager for Andritz’s nonwovens business.
“We use a systematic approach to move from idea stage to commercial-scale production,” says Noelle. “This ensures that our technologies are ‘proven’ before ever finding their way into a customer’s plant. We are optimizing the equipment and processes that are already in place in the spunlace production line. The risk is virtually zero, and the opportunity for savings is large.”
The “idea stage” began in 2012, as Andritz Nonwoven began looking at ways to address rising energy costs – one of the key cost items in any spunlace nonwovens line. “Customers tell us that their energy cost for dewatering and drying the nonwovens web is roughly 40% of their total energy operating cost,” Noelle says. “This is a significant number, and improving on this has a direct effect on our customer’s bottom line. Clearly, that is something we wanted to focus on.”
Andritz started with a clean sheet of paper to explore various “what if” scenarios for dewatering and drying. Engineers did an analysis of the processing line to determine which factors, in terms of energy consumption, were the main cost drivers. Three particular factors came to the forefront: initial dewatering of the web after the bonding process, dryer/exhaust heat circulation and recovery, and the design of the dryer itself. All of these factors are addressed in unique ways by the neXecodry technology.
Once the fact gathering and analysis was complete, the “creative innovation” process began. “We set aside the conventional thinking that might limit our solutions and tried to brainstorm some not-so-conventional thinking within our R&D staff. For example, Andritz engineers knew that a good first step would be to improve the mechanical dewatering of the web, since lower initial moisture into the dryer leads to lower energy consumption in the dryer itself. “Dewatering is typically accomplished through high-volume vacuum extraction,” Noelle explains. “The bonding process and the water removal processes in spunlace nonwoven production relies on pumps – equipment which generates heat.” The “Aha” moment for Andritz R&D experts came when questioned was posed, “What if we close our energy loop in the process by capturing the heat from the pumps – and use that heat in the water extraction process?”
Combining the right pumps with the optimum vacuum levels and air temperatures led Andritz Nonwoven to a significant result – a 15% reduction in the volume of water entering the dryers with the spunlace web – without any additional electricity consumption. This reduction was documented on a line that previously had state-of-the-art dewatering and drying equipment. So, the first contribution of patent pending neXecodry technology to energy savings is achieving a 15% reduction in the amount of water that has to be evaporated in the dryer.
The classic technique for recovering heat from dryer exhaust air involves a heat exchanger in a process called “indirect” energy recovery. While conventional heat exchangers usually loses approximately 40% of heat energy, the technique developed for Andritz’s neXecodry technology system uses “direct” energy recovery, with virtually no thermal energy loss. This new direct energy technique is also patent pending. When accompanied by Andritz’s with web temperature and automated moisture control, the web drying is optimized on a continual basis in real-time. With these elements in place, neXecodry technology has been shown to increase drying capacity by 15%, allowing higher production or a significant reduction in specific energy consumption for the same production.
The neXecodry technology development project also included a completely new construction for the drum in through-air dryers. The drum design (called U-Drum) has an extraordinarily high open area – 96% – permitting high airflow at a low pressure drop for extremely efficient drying. The U-Drum (patent pending) is fabricated of 100% stainless steel. Its structural rigidity and integrity are such that it can be offered on lines with working widths up to six meters and at speeds of up to 1200 meters per minute.
The U-Drum design is Andritz Nonwoven’s cornerstone development in a new generation of dryers with high evaporation capacity and low electrical ventilation power consumption. While these next-generation dryers have enhanced capabilities, they maintain the existing advantages of previous generations—two-temperature zones, wet and dry ends, drum out design, and easy access for cleaning and maintenance.
While neXecodry technology is available for new production lines, it was designed to be easily transported to and installed in existing lines to improve the economics of virtually any spunlace nonwovens plant. In fact, most of the neXecodry technology installations operating today have all been installed on existing lines. The upgrades were completed in less than three days.
In addition to the economics, in some cases the quality of the spunlace nonwoven products improves due to optimized drying and production stability. It is important to know that the neXecodry technology does not contact the web, it does not alter the product properties, it does not degrade the web pattern even for sensitive fibers, and it will not overheat or overdry. The reduction in residual water content entering the dryer, and the large evaporation area in the U-Drum design, enables plants to operate at lower drying temperatures and air pressures. This maintains perfect conditions for premium quality nonwovens in terms of bulk and softness.
When nonwovens producers want to save operating costs, they must consider measures to lower a line’s specific energy consumption. However, these measures cannot detract from production stability and the quality of the final product. The neXecodry technology from Andritz Nonwoven is an innovative approach that meets customers requirements—ease of installation, a sound economic payback and
the best quality of nonwovens products.
Andritz Nonwoven has produced a line of spunlace nonwoven equipment that is efficient, according to Noelle. “We have been part of improvements in capacity, speed, and fabric quality in terms of uniformity and excellent MD/CD ratios,” he says. “And now, we are at a new level.”
Recently, nonwoven producers are facing challenges over and above energy and quality issue. The neXecodry dewatering and drying technology solution contributes to a plant’s ability to reduce its carbon footprint by reducing energy consumption and supports the producers in meeting their sustainability goals.