Particleboard plant emissions control
A North American wood products facility relies on steam to produce multiple grades, thicknesses and sizes of melamine panels. The facility has three wood waste boilers, each followed by cyclone dust collectors. Process gas from each set of cyclones feeds into an induced draft (ID) fan; where the streams are combined and then sent through a common duct connected to the stack.
The facility needed to reduce emissions from burning wood waste, but plant performance and environmental requirements also needed to be in balance in order to hit production targets. The customer had precise operational goals so it was critical that the design of the emissions control solution accommodate current and future production variability.
Dürr Megtec specified and installed a new dry electrostatic precipitator (DESP) to treat the process gas from the three wood-fired boilers. The equipment was installed downstream of the ID fans and included inlet ductwork, along with an outlet plenum-mounted stack.
The design of the Dürr Megtec DESP collecting plates offers more efficient cleaning and dust removal during rapping. To ensure optimized particulate and ash collection, the rigid discharge electrodes feature a specific geometry and special pin distribution configuration to accommodate the process conditions.
Dürr Megtec engineers had to accommodate site-specific system requirements, which included access and ease of maintenance, as well as working within the existing plant footprint. These were key factors in routing ductwork and equipment placement. The job site also required the team to design around existing elevated bark conveyors and other equipment.
It was critical the facility not experience any affiliated downtime. The dry ESP and related systems work as designed and achieved all of the stated goals. The system has easily surpassed the environmental test requirements and has been operating in accordance with local environmental legislation since commissioning.
A pioneering leader in the window-film industry was literally burning money to operate its coating lines. The company produces thin solar-control laminated films used to screen UV rays, block heat, reduce glare, increase occupant comfort, and enhance aesthetics. The company also produces multi-ply safety and security films that reduce hazards when glass shatters. The products are used in vehicles, homes, and buildings worldwide.
The company was using a decades-old recuperative thermal oxidizer to destroy solvents from the drying ovens on its three process lines. Thermal energy from the oxidizer exhaust was recovered by heat exchangers and used to operate the process ovens and other in-plant systems. Unfortunately, the operating efficiency and capacity limitations of the oxidizer created problems.
The plant was using more than 100,000 therms of gas monthly. The 20,000-scfm oxidizer used a single two-speed exhaust fan to serve three processes. The fan caused capacity and continuity conflicts between lines. This demanded continuous monitoring and adjustment by operators, and caused 25 percent lower line speeds at times.
In addition to productivity issues, air temperatures from the exchangers exceeded 800°F, which was much hotter than the dryers needed. The oxidizer yielded more heat than the plant could use and valuable energy had to be vented to the atmosphere.
Dürr Megtec proposed a 40,000-scfm CleanSwitch® regenerative thermal oxidizer (RTO). This unit has a proprietary switch valve that delivers high VOC destruction without a flush system. The Dürr Megtec engineering study determined the RTO exhaust could be safely used in the drying ovens. Also proposed was a new heat recovery system and operating sequence that would run more efficiently without wasting energy. Upgraded equipment was also supplied, including T-dampers, exhaust fans, and the hot and cold fans for the heat recovery system.
The customer agreed with the recommendations and based its decision on the benefits of the CleanSwitch® design, combined with the extensive process coating and drying knowledge of Dürr Megtec and its willingness to take on non-routine problems.
The CleanSwitch® RTO achieved VOC destruction efficiencies above 99 percent. The fan design enabled the three production lines to run independently with no operator involvement. And the RTO capacity eliminated the need to reduce line speeds, which helped the plant see higher production.
The RTO provides process air at a more useful 400°F. And when all processes are on line, the CleanSwitch® RTO spends approximately 40 percent of the time in self-sustain, which does not use any gas at all. The RTO and heat recovery system reduced typical monthly gas by 93 percent. The energy savings provided full return on investment in only 18 months.
Engineering a better way to coat battery electrodes
An electrode manufacturer was looking for a better method of electrode coating and requested a collaborative effort with Dürr Megtec in an effort to develop a simultaneous two-sided coating and drying process that did not require a vertical web path through the dryer. The potential customer approached Dürr Megtec because they were familiar with its patented air flotation drying equipment and R&D pilot line capabilities.
The traditional tandem coating process is characterized by coating and drying one side of the current collector, then re-running the foil through the entire coating and drying process for the second side of the foil. Tandem coating also requires a longer manufacturing line that takes up more factory space.
Technology previously developed for simultaneous two-sided battery electrode coating dictated the need for a vertical air flotation dryer. However, the customer did not want a vertical web-path dryer because of the substantial building height required and the increased difficulty in providing operator access for tending purposes compared to a dryer with a horizontal web path.
The engineering goal was to develop a simultaneous two-sided coating method that uses a horizontal air flotation dryer instead of a vertical dryer. Dürr Megtec engineering and R&D teams developed a new coating concept and refined it through extensive testing on the Dürr Megtec R&D pilot line.
The new Dürr Megtec process required just a single pass. There was only one coating station, one dryer, and all equipment was located on the same level of the facility, all within a small footprint compared to a traditional tandem coating line.
Potential benefits of the single-pass feature of the Dürr Megtec slot-die tension web coating line include:
- Reduced electrode manufacturing costs
- Effective doubling of production volume without changing line speed
- Reduced waste
- Lower capital and operating costs
- Improved overall production