Constant and consistent control of the humidity levels in all stages of the paper processing and printing industries is critical for optimum results. To maintain the moisture content of the paper and to ensure proper operation of the equipment, humidity levels between 40% and 55% are required.
By maintaining these humidity levels, the paper quality and the finished product are improved. Dimensional stability of the paper, optimum ink transfer, and improved reliability can all be achieved. The result is less paper jams or breaks, reduced paper curl and cracking while maintaining maximum equipment speed. Shrinkage and static electricity are also eliminated from the process.
So, if maintaining a specific humidity level is desired for improved operations and increased profitability, what is the best way to achieve the required humidity levels?
The two most common approaches for humidification in the paper processing and printing industries include adiabatic humidification (direct evaporation) and isothermal humidification (steam).
Adiabatic humidification involves pressurizing the water up to 1000 psi and distributing it through a specialized nozzle where it is atomized down to as low as 10 microns (10 millionths of a meter) and introduced into the air that requires conditioning. Due to the microscopic size of these droplets, they possess a huge surface area relative to their volume and provide a rapid evaporation rate and a very effective humidification process.
Adiabatic humidification differs from the isothermal process in several important aspects.
First, it does not introduce any thermal energy (heat) into the water supply or the surrounding air. In fact, due to the process of thermal dynamics, the evaporative process will reduce the ambient temperature throughout the area where the system is operating. This can be critical in facilities where increased temperatures are a result of the operation of the equipment.
Second, the adiabatic humidification process saves time and money compared to most isothermal methods of humidification. An adiabatic humidification system requires about 15 watts of electricity to provide 8 lbs. (1 gallon) of water capacity. A comparably sized steam system would require approximately 3000 watts for the same water capacity.
An adiabatic humidifi8cation system also provides lower start up and maintenance costs
Historically, the complications associated with the need for re-circulated water for an adiabatic humidification system presented significant challenges, increased the operational costs, and required additional maintenance. The need for re-circulated water was largely due to inferior products and the inability to obtain high absorption rates of the moisture. Improved design and technology within the high pressure fog industry has addressed this deficiency and eliminated the need for water recirculation.
By eliminating the need for re-circulated water; by incorporating improved technologies; and because the process does not introduce heat, has lower start-up, operational, and maintenance costs with a proven performance record, adiabatic humidification systems are now the preferred option for humidification needs in the paper processing and printing industries.