Industrial gas humidification
Gas-fired humidification is a growing market in North America as companies realize the importance of humidification for the health of their employees and of their equipment. Gas humidification is being chosen over other technologies because of its simplicity and the cost-effectiveness of natural gas. Gas humidification is being used in printing facilities, high-tech manufacturing plants, schools, hospitals, and office buildings.
Humidification in industrial environments
In general, between 30% and 60% relative humidity (RH) is optimal, according to Phil Lilja, product manager at DriSteem. "The recommended RH level can vary by application so we encourage those responsible to reference the DriSteem humidification handbook with RH levels recommended for processes and ASHRAE 55-2017: Thermal Environmental Conditions for Human Occupancy for more detail on acceptable ranges for humidity," Lilja said.
Chris Habets, business development manager for energy and sustainability at Nortec Humidity says that humidity levels strongly depend on the process and suggests that a 40% to 60% RH is required for many industrial processes. This level is ideal for preventing electrostatic discharge and for employee health without risking condensation forming on equipment.
Humidification systems are installed in industrial facilities to eliminate electrostatic discharge (ESD), hygroscopic material protection, health, and human comfort. "Fluctuating and low relative humidity levels contribute to a number of problems in commercial applications including production line disruptions or failures, loss or degradation of materials, inconsistent environmental conditions in labs and other critical applications, and negative effects on occupant health," said Lilja.
Habets added, "Companies humidify their industrial environments to meet air-quality standards for their processes and for their employees. Many production environments require that the RH around the equipment and products be maintained to prevent damage from electrostatic discharge, to ensure material maintains the correct properties for processing, or to ensure paints adhere properly. Additionally, proper humidification can prevent infection spreading among employees."
Eliminating ESD is important not only for worker comfort and safety, but also to protect settings and calibration on electronic devices including process controls. Hygroscopic materials including wood, paper and leather require higher ambient humidity levels to assure dimensional stability and product quality. Printing operations and paper storage require especially tight controls on humidity to prevent paper from shrinking, curling or jamming in processing equipment.
Gas versus electric humidifiers
Although there are other approaches to adding humidity to a building, such as direct steam injection into the air stream, which would require the facility to have a steam boiler, only natural gas and electric humidifiers are consider for this comparison.
The choice of humidification system depends on many factors including the energy source available, capacity required, supply water, available space, and maintenance requirements. Lilja explains the different types and their advantages:
- Gas-fired humidifiers have the lowest operating cost for a steam-generating humidifier, and a broad capacity range
- Electric resistive humidifiers have a broad capacity range and very accurate control capabilities
- Electrode humidifiers are easy to maintain—simply replace the cylinder—and the lowest first cost
- Adiabatic humidifiers provide humidification and evaporative cooling at the same time.
According to Lilja, if natural (or LP) gas is available as an energy source and there is the ability to vent flue gases to the outside, gas-fired humidifies, such as the recently introduced GTS humidifier LX series, are an excellent choice for museums, libraries, government/military facilities, and industrial facilities (manufacturing, pharmaceutical, biotech, etc.).
Operational cost is the main advantage of gas humidifiers over electrical units. "The operational cost of efficient gas fired humidification typically provides a very fast payback over electric humidification," Habets said. "Additionally, natural gas humidifiers can provide much higher loads out of a single unit than an electric unit, which reduces installation time and controls complexity."
Both electric and gas humidifiers are efficient. "While electric humidifiers are nearly 100% efficient in operation, the cost of electricity per energy unit is two to three times higher than that of natural gas," said Lilja. "DriSteem’s GTS LX series gas-fired humidifiers operate at up to 93% efficiency, making the cost of operation much less than that of an electric steam humidifier."
Gas humidifier industry offers help
When looking for any humidification system, Habets says to take into account the actual humidification design load of the system, which is often during peak airside economizer season.
"Ensure that the building design allows for proper venting—either vertically or horizontally—per the manufacturer. Don’t forget to consider efficiency of different gas-fired humidifiers, and don’t be afraid to reach out to a manufacturer or their representative for more information," he said.
Lilja says that DriSteem’s EnergyCalc calculator allows users to compare gas and electric humidification costs in their area. In many locations, the savings from switching to gas are so significant that they can replace old electric units with new GTS gas humidifiers from DriSteem and let the energy savings pay for the cost and installation.
Case study: Gas humidification keeps museum artifacts safe
The Glenn H. Curtiss museum in Hammondsport, N.Y. is dedicated to preserving the history of flight. Rooms are filled with artifacts dating back to the first flight of Glenn H. Curtiss in 1908, which was the first official, pre-announced public flight in the U.S.
Visitors can take a trip back in time to the early days of flight, viewing actual aircraft, replicas, and objects that are a part of early aviation history. But what the observer of these historical objects won’t see is that the preservation of artifacts in this institution was once in danger because of a lack of proper humidification.
The importance of maintaining proper humidification
The Curtiss museum is filled with hundreds of objects containing a variety of materials, such as wood, canvas, fabric, and paint that are subject to cracking, chipping, peeling, and distortion without proper humidity levels—ideally 40% to 60% relative humidity (RH). When the Curtiss Museum opened, a humidification system was not installed, and the RH level hovered between 3% and 10%. Jim White, the museum’s engineer, knew that he needed to maintain humidification at an RH level of at least 40% with minimal fluctuation (±3%), or jeopardize the preservation of the museum’s contents.
Meeting the museum’s specifications and budget
White had specific objectives in choosing a humidification system. "My first consideration was to find a system that could handle a large area yet fit in the limited floor space I had available," said White. The local DriSteem representative, Brian Willemsen of R.L. Kistler, suggested a steam-to-steam humidification system. This system provides chemical-free steam to the space and, because it uses boiler steam as the heat source, it has very low energy costs.
There was just one problem: The museum does not have a boiler. "We knew the steam-to-steam product would work for the museum, but to operate the system, the facility would have to invest in a boiler," Willemsen said, "and we just didn’t want them to have to make that extra investment."
Because the museum has natural gas as an energy source, Willemsen told White about the DriSteem GTS gas-to-steam humidifier, which can provide chemical-free, low-cost humidification with the control the museum required and fit in the allotted space, without adding additional equipment. "What excited me most about the GTS humidifier was the fact that it was a direct-fired, stand-alone unit that could be provided with an area-type steam distribution system designed to distribute steam in large spaces without ductwork," said White. "And, I was certainly excited about the lower energy costs we would incur by using natural gas instead of electricity."
Meeting humidification demands
"The GTS humidifier from DriSteem has met all of my expectations," White said. "I thought we may need to add one more unit to humidify the 2,000 cfm continuous outdoor air supplied by our rooftop air conditioners. But we’re up and running at ideal RH levels and the single GTS humidifier is performing beautifully."
Now White can claim with confidence that the artifacts in the Glenn H. Curtiss museum are being preserved for future flight history enthusiasts. Visitors can continue to explore their fascination with man’s ability to fly and see firsthand the history of aircraft at the Glenn H. Curtiss museum.
This article originally appeared in the Gas Technology Spring 2018 issue.