DRUPA, May 29th 2008 – Web offset technologies from Goss International not only provide productivity and competitive advantages, they can reduce the environmental impact of printing as well. Breakthroughs ranging from gapless blankets, pinless folders and automated controls to DigiRail and Automatic Transfer technologies reduce waste considerably. The Goss Ecocool dryer typifies this connection between innovative technology and "greener" production.
Lowering energy consumption is an increasingly important objective in virtually every business. In the printing industry, companies that do so can reduce their impact on the environment and improve profitability. The Ecocool dryer, which was introduced at drupa 2000 as the first web offset dryer with an integrated chill roll section, helps printers achieve these all-important objectives. The latest Ecocool/T model features a new integrated afterburner and pollution control system that increases heat exchange efficiency and reduces energy usage – for both drying and afterburning – up to 40 percent over and above the energy savings already afforded by earlier models.
"With the latest Ecocool technology, we're maximizing the use of the evaporated ink solvents," explains Rob Bosman, product manager for Goss International. "Instead of releasing solvent-laden exhaust air to a separate pollution control device, we are burning it and using the energy to fuel the dryer in a closed-loop system. By using a controllable heat exchanger, the maximum use of the ink solvents and, by consequence, the minimum consumption of gas can be achieved."
While the concept of afterburning is not new, Bosman says advanced Goss technology has increased the efficiency in the heat exchange process, reducing the fossil fuels necessary to operate the dryer and also reducing the solvent emissions.
"By hitting the solvent hydrocarbons with high temperatures, they are broken down into CO2 and water," he explains. "Consequently, the air that is eventually emitted to the atmosphere is about 99.9 percent clean."
Ecocool dryers can be installed with new Goss press systems, with presses made by other suppliers, and as an enhancement for existing presses.
As the printed web enters the Ecocool dryer, it is typically heated to 140ºC (284ºF), via burner units on either side of the web. During this process, solvents evaporate out of the ink and are extracted along with the air just before the cooling section of the dryer. In the upper and lower burner units, the solvent-laden air passes through a heat exchanger which typically heats it up to 550ºC (1020ºF), creating combustion energy.
The air then passes into the primary burner chamber where it is heated to even higher temperatures of approximately 790ºC (1454ºF), the temperature needed to incinerate the solvents effectively. By the time the air reaches the end of the first burner chamber, the solvents have been incinerated. Some of this clean air – between 0 and 40 percent – is channeled back into the dryer through an automatically regulated hot-air valve that opens or closes depending on the energy needed for drying the web. The rest flows through the secondary burner chamber and is ultimately expelled from the dryer as CO2 via an exhaust outlet.
Integrated chill rolls – a defining feature of the Ecocool dryer and a breakthrough that improves print quality by preventing solvent condensate from developing between the chill rolls and the cooling web – also have a positive environmental impact. Since the chill rolls remain free of a boundary layer of condensate, cleaning requirements are not needed, along with the VOC waste and operator exposure associated with cleaning solvents. Any remaining ink solvents released in the chill section are also drawn back into the Ecocool dryer due to the immediate proximity of the chill rolls.
The Ecocool chill stand can also be equipped with an infrared camera to measure the exit temperature of the web after the chill section and to vary the chill power, accordingly reducing the energy required for cooling. In conventional systems, a fixed amount of chill power is used, causing light stock to be cooled down to a lower temperature than heavy stock.
"Improved print quality and web handling, a result of integrating the chill rolls and incorporating other technologies, remain key features of the Ecocool dryer," according to Bosman. "However, with rising fuel costs and the increased focus on environmental impact, our advanced pollution control and afterburner technology are emerging as equally important advantages for printers. We will continue to focus on more efficient and economical dryers for optimum runability."
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