Aluminum smelting is an important process to change alumina ore into aluminum, a lightweight metal. This process uses high heat for a period of time to separate the oxygen from the alumina. The temperature can reach over 1000oF (538oC) to cause this separation. As a reference, two pounds (0.9 Kg) of alumina ore is needed to make one pound (0.45 Kg) of aluminum. Inside the ovens and exhaust ducts, they are lined with a cement brick to contain the heat and fumes. Over time, the brick can get weak and have hot spots. Once the brick is compromised, the system has to be shut down for days to replace the brick. This is an expensive process and time-consuming. To help reduce the hot spots and extend the life of the brick, the smelting company was using ¼” copper tubes to blow compressed air to reduce the heat. This was costing the company a lot of money to operate; so, they contacted EXAIR for a better solution.
EXAIR has been manufacturing intelligent compressed air products since 1983. And one thing that we know how to do is to save money on compressed air blow-off applications. For this company above, they had 90 open pipes throughout their plant. I was able to do a quick calculation for this customer to compare the copper tube to a Super Air Nozzle. A ¼” copper tube will use roughly 33 SCFM (935 SLPM) of compressed air at 80 PSIG (5.5 bar). As a replacement nozzle in a hot area, EXAIR recommended a model 1100SS Super Air Nozzle which will use 14 SCFM (396 SLPM) at 80 PSIG (5.5 bar). With a simple connection, they could mount the ¼” NPT Super Air Nozzle at the end of each tube. With the cost to make compressed air at $0.25/1,000 ft3, we can calculate the air savings.
33 SCFM (copper tube) – 14 SCFM (Model 1100) = 19 SCFM savings
The operation for the smelting plant was 24 hours and 7 days a week. The amount of savings is as follows:
19 ft3/min * 60 min/hr * 24 hr/day * 7 days/week * $0.25/1,000 ft3 = $47.88 savings per week per nozzle.
Since they have 90 nozzles, this would save them $4,309.20 each week!
How can we do this? With cooling capacities, it is dependent on the mass of air that can be moved. With our Super Air Nozzles, we are near an amplification ratio of 25:1. This means that for every one part of compressed air, we can entrain 25 parts of ambient air. Also, with our Super Air Nozzles, we can generate a laminar air flow which has a velocity profile that has the air moving in the same direction. An open pipe has turbulent flow, which means that the velocity is traveling in different directions and not working together. And the amplification ratio is very low. I did a demonstration to illustrate this effect here: Video Blog: Laminar and Turbulent Flows. The large volume of air creates good cooling without using too much compressed air to reduce the hot spot temperatures. In keeping the temperature under control, they could continue operations and lessen the concern for untimely shut-downs and costly maintenance.
By using air to cool, you can do it safely and efficiently. As a benefit, the Super Air Nozzles reduced the noise level as well. Saving a lot of money; having an effective way to reduce stress on the cement bricks; and reducing the noise nuisance were great replacements for this company. If you would like to speak about cooling applications, you can contact an Application Engineer; even something as large as a smelting oven.
John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb
