Saving money on its energy bills turned out to be a lot of hot air for flexible packaging innovator Shields Bag Printing.
As a custom blown film extruder, Shields Bag extrudes, prints and converts film for flexible packaging products used in a wide range of industries. The company produces more than 100 lines of products that are shipped to clients all over the world, from produce bags to high graphic shrink-wrap.
The company traces its roots back to 1935, when Frank Shields opened a print shop in Yakima. He and his sons built a successful commercial print shop, and in the mid-1950s branched out into flexible packaging.
In 2011, Derek LaFramboise, environmental affairs manager for Shields Bag Printing, learned that Cascade Natural Gas had government incentive money available for heat recovery projects. He began consulting with staff from the utility as well as nearby Washington State University about projects that might help Shields Bag capture waste heat and reduce its utility costs.
Eventually, an energy audit was conducted as part of an overall review of the company's operations.
In its final report back to the company, the utility noted Shields Bag was releasing heated air from its oxidizer units - heat that represented lost energy dollars essentially being vented into the atmosphere. The oxidizers treat the exhaust from the flexographic printing presses, using air heated to more than 300 degrees to break down VOCs (Volatile Organic Compounds) into carbon dioxide and water.
When the utility company delivered its final report to Shields Bag, three options were suggested for the company to improve its efficiency and reduce its energy waste from the oxidizers:
• Install a system that would capture the waste heat for other uses
• Install a new, more efficient oxidizer unit
• Replace the oxidizer with a biological system
A new system, whether it was a more efficient oxidizer or a biological system, was not seen as an effective solution for Shields Bag because of the capital costs. However, with the natural gas utility and the state of Washington offering financial incentives for a reduction in gas usage, the company began looking for a solution that would capture the waste heat from the oxidizers and re-use it for other purposes.
"When we started looking at our energy consumption, our natural gas usage was way up there," LaFramboise said. "It prompted us to explore options to reduce the volume, and heat recovery was the option that lead us to the oxidizer modification."
MEGTEC proposed installing a heat coil system filled with a water-glycol mix in the stacks of the oxidizer exhaust that would capture the waste heat and make it available for transfer to other applications, such as pre-heating the air inlets for the oxidizers themselves. By pre-heating the air using recovered heat, less gas would be needed to heat the oxidizers to their optimal temperatures.
But MEGTEC's solution did not stop there. While heating the intake inlets for the oxidizer would reduce the amount of gas needed to reach the right temperature, there would still be excess heat left in the recovery system that could be used for other applications.
Working with Shields Bag, MEGTEC engineers also proposed using the coil system to transfer surplus heat from the oxidizer exhaust to pre-heat the dryer oven intakes on the production side of the operation as well.
Again, by using the heat from the oxidizer exhaust to warm the air entering the oven intakes, less energy was required to achieve the optimal temperature for the operation of the dryer ovens. With the amount of heat in the system, the recovery system was also able to pre-heat the dryer intakes for six of Shields Bag's production lines.
Shields Bag opted for MEGTEC's proposed solution, and its staff performed much of the installation in a two-phase approach that minimized production downtime. Engineers for MEGTEC worked on-site during the installation, providing assistance at critical times and with the start-up of the new heat recovery system.
Shields Bag experienced immediate returns on two fronts once the heat recovery system was active.
The company experienced a reduction in its natural gas consumption that ranges from 8,500 to 10,000 therms a month without any loss in production levels. The variations are the result of different lines being shut down at various times. The estimated cost of a therm of natural gas for an industrial user is $1 per therm, resulting in an estimated savings for Shields Bag of roughly $10,000 per month in energy costs. Not only is a savings in fuel usage recognized, this also provides a substantial drop in carbon emissions and products of combustion.
Additionally, the company has reported lower maintenance costs associated with heat controls for the oxidizer and the drying ovens. With the intake air pre- heated by the recovery system, less energy is needed to heat it to optimal temperatures and operators are making fewer adjustments to the control settings. Additionally, the warmers in the intake vents don't need to operate as long. Supervisors on the line report the ovens better maintain consistent temperature and are more reliable since the installation was completed.
"It's a lot like when you have home furnace at 70 degrees. When it's warming the air in the house, it clicks on and off just enough keep the temperature constant," LaFramboise said. "It's when you open the doors and let in the cold outside air that the furnace has to work harder."
"While many companies are seeking to 'green' their process and reduce their carbon footprint, knowing where to start is often the challenge," said LaFramboise. Getting started is often as easy as asking for help. In the case of Shields Bag, asking about financial incentives resulted in the company looking for ways to reduce its energy use.
"Once you ask, it really gets the ball rolling," LaFramboise said. "You start to see all kinds of other areas you can dig into."
Additional benefits also become apparent. Since Shields Bag is now burning less natural gas, it has also reduced its emission of carbon dioxide and other compounds associated with burning natural gas.
For Shields Bag, saving money on its energy use is more than just a lot of hot air – saving money is a lot of hot air vented in the right direction.