Compressed air quality is a serious matter. Depending on your end use or application, any particulates, vapors or aerosols present may damage your products or equipment. Because of this, operators install filters to remove particulates and aerosols and dryers to remove excess moisture. But sometimes operators can take air quality too far, surpassing necessary limits and sacrificing costly electricity.
How low does PDP really need to be?
Many operators dry instrument air to -40°F pressure dew point (PDP) to ensure that absolute no moisture remains in the air, but this is a common mistake. Attaining a -40°F PDP is overkill; it requires much more energy compared to the minimum level of acceptable PDP for instrument air quality, which is 18°F below the minimum ambient temperature. By adjusting this factor, operators can save energy, reduce their carbon footprint and keep money in their wallets.
Let’s take a look at an example using two drying technologies with different PDP requirements: a heatless desiccant dryer at -40°F and a heat of compression dryer at -3°F. You may be wondering why we’re choosing two different technologies, but don’t worry. We’ll explain soon. For now, let’s continue with our scenario.
Here are our site conditions and process requirements:
Oil-free compressor
Minimum ambient temperature = 15°F
Flow = 1,000 cfm
Pressure = 100 psig
Ambient temperature = 80°F
Relative humidity = 60%
Ambient pressure = 14.5 psi(a)
Heatless desiccant dryer with -40°F PDP
With a heatless desiccant dryer is there is always purge loss. Coupled with the low PDP of -40°F, this amounts to a total annual energy consumption of 387,000 KWh and annual CO2 production of 166,000 kg. At the price of $0.07/KWh, the annual electricity cost will be $27,000 for the compressor and dryer alone. Not only does this scenario harm the environment, it can seriously impact the bottom line.
Heat of compression dryer with -3°F PDP
Now, let’s change the required PDP to -3°F. (Remember that the minimum level of acceptable PDP is 18°F below the minimum ambient temperature. In this case, that is 15°F-18°F=-3°F.) Using a heat of compression dryer, the total annual energy consumption will be 5,610 KWh and the annual CO2 production will be 2,410 kg. At the price of $0.07/KWh, the annual electricity cost is considerably lower at $392.
Higher PDP means higher savings
As you can see, by making two small changes (technology and PDP), facilities can save approximately $26,708 annually and reduce their carbon footprint to a fraction of its original size.
Oh, and the reason two different technologies are compared is this: at a higher PDP, you do not need the same type of dryer. There may be even better solutions with different drying technologies. You should always check with compressed air experts and manufacturers before making a decision; they can help you with PDP requirements, calculations and offer recommendations on the best drying technology for your needs.
Want to find out if you could be saving money? Contact one of our compressed air experts today to get started.
