Looking to make your material processing business greener, leaner and more efficient?
Adding fluid bed exhaust recycling (also known as air recirculation) to a new or older model drying system can be an effective way to achieve those goals and add revenue to your bottom line. In some cases, material processors stand to save as much as 50% on energy costs, in addition to improving environmental air quality.
Of course, several factors will determine the actual benefits you stand to gain from reusing previously heated air. With this in mind, here are five key questions you can ask to evaluate whether your application is a good fit for taking the next step.
What type of material are you drying?
While almost any material can benefit from a fluid bed equipped with an exhaust recycling system, there are a few material characteristics that may make your application more ideal than others.
Material with large particle sizes and bound moisture content (moisture that does not escape as easily as more porous substances) are good candidates for air recirculation. That is because they reduce drying efficiency and require more gas, electricity or steam to reach the desired dry state. A few examples where fluid bed exhaust recycling would have a significant impact on energy consumption include:
- Building materials
- Pharmaceutical formulations
- Hygroscopic substances
What temperature range do you use to dry the material?
In most circumstances, 150°F (66°C) is a good rule of thumb for deciding whether air recirculation makes sense.
At this temperature, there is usually enough heat energy available in the exhaust air to make recirculation viable for offsetting energy costs.
While this benchmark is a good starting point for consideration, the specific temperature range can vary depending on the material being processed, drying objectives and the design of the fluid bed system.
What other material processing goals do you expect to achieve?
While lowering energy costs is one obvious goal, exhaust air recycling systems can also improve environmental conditions. In one case in particular, we had a customer reach out to us for help resolving unwanted odors that resulted from the drying of insect larvae. By introducing the air exhaust recycling system into their process, we were able to alleviate the smell and lower energy costs.
In other cases, customers have benefited from exhaust recycling by lowering emissions of air pollutants. This includes complying with Environmental Protection Agency regulations and eliminating the need to pay and apply for air quality permits.
How quickly would the recycling system pay for itself?
In many cases, fluid bed air recirculation systems have the potential to offer relatively quick payback periods. Depending on the specific use case, material processors can anticipate achieving payback on their investment in 12-24 months.
To get a more accurate calculation, you should reach out to a knowledgeable material process expert to discuss your specific requirements and inquire about testing your application for a quality analysis. Some manufacturers, such as Kason, offer the ability to test your application for free prior to purchase.
How much heated air can or should be repurposed?
One other question that you may be thinking is how much heated air can be repurposed. To those unfamiliar with the science behind fluid bed drying systems, 100% may be preferred. However, in most cases, 50% is optimal.
While recirculating usable air is an energy-efficient approach, it can result in increased moisture content. By introducing fresh air into the system, which is the case for partial fluid bed exhaust recycling, it is easier to control the temperature within the fluid bed and remove excess moisture. By doing this, it helps prevent product quality issues.
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