Green Museum: Glass Furnace Recuperators

The Corning Museum of Glass is committed to being a responsible steward–leaving not only our collection, but also our facilities and grounds, in the best, most sustainable, state possible for future generations to enjoy. We strive to incorporate green practices in our operations and we consistently look for ways to minimize the environmental footprint of our facilities and our activities.

Part of the Museum’s efforts to become more energy efficient is focused on glassmaking spaces.  The centerpiece of any hot glass shop is the glass melting furnace. These furnaces are not very energy efficient. To offset some energy use, we recuperate heat from the furnace, which incorporates the use of waste heat and reduces energy consumption.

Glass in furnace is melted to 2100 degrees F.

Glass in the furnace is melted to 2100 degrees F.

The stack of bricks is the flue, a channel in a chimney for carrying flame and smoke to the outer air. Typically, the flue gasses are cooled by mixing with room air and then vented to the outside. In this method, the heat is entirely wasted.

The flue, a channel in a chimney for carrying flame and smoke to the outer air, alongside the furnace.

The flue, a channel in a chimney for carrying flame and smoke to the outer air, alongside the furnace.

Air is 78% nitrogen, 21% oxygen and 1% other gasses. That means that 79% of the air does nothing but enter the furnace at room temperature and leave at 2000 degrees F. The furnace expends energy to heat these gasses up with little to show for it. It is a bit like a person blowing on soup to cool it off.

Lewis Olson, the Museum’s Hot Glass Show technical team leader, showed me one device the Museum uses which improves efficiency by about 15%.

A furnace with recouperator.

A furnace with recouperator.

Above is one of the Museum’s newer glass melting furnaces. Across the top is a recuperator. It is a device which looks like an automotive muffler. Cool combustion air enters from below behind the furnace. The combustion air travels through a pipe in the center of the recuperator. This pipe is jacketed by a larger pipe through which the exhaust gasses from the furnace travel. The flue gasses exit the furnace through a pipe on the top right of the furnace and exit the recuperator on the top left. The combustion air is mixed with fuel (either natural gas or propane) at the burner which is the green device on the right side of the furnace. The flue gas leaves the furnace around 2000 degrees F. The combustion air is heated from ambient temperature to about 550 degrees F using this waste heat. This reduces the amount the air has to be heated and decreases overall gas consumption.

A view of the recouperator on the glass furnace.

A view of the recuperator on the glass furnace.

As part of the Museum’s green initiatives, recuperators are being added to all new and rebuilt furnaces. Learn more about the Museum’s green initiatives:

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John Cowden works with special projects at The Corning Museum of Glass and supported the Hot Glass Show Innovation theater construction project in his retirement. Cowden was a supervisor and narrator at the Hot Glass Show from 1999 to 2011. Before joining the Museum, Cowden had more than 10 years of experience in the field of glassworking, primarily using cold working techniques, processes such as slumping, making molds, grinding, and polishing, where time is not a pressure.

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  1. Hello Mr. Cowen,

    I have heard people that I think are pretty smart discuss, pro and con, the efficiency of recuperators based on the following question; Doesn’t the heated combustion air have less oxygen by volume than air at a lower temperature making the heated combustion air actually less efficient? Why isn’t this true? Thanks and have a nice week.

    • Thanks for your patience, Steven. Our Hot Glass Show manager got in touch with a combustion engineer at Corning Inc. and here is his response:
      The short answer is that yes, hot air is less dense and carries less oxygen, but that deficit is easily compensated for by increasing the volume of combustion air. The biggest benefit comes from the reduction in energy required to raise the temperature of the combustion air. Our combustion air is preheated to about 600 degrees F and we have seen a 15-20% reduction in fuel used when compared to the same furnace when it was not recuperated. We were able to track this accurately with our ultralight furnace (in the photos) which operates on 100 lb. propane cylinders.

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