CONSIDER ON-DEMAND NITROGEN
Both membrane and PSA units produce nitrogen at precise purities, flow rates and pressures. A single nitrogen generator can meet your needs for shifts ranging from 8 to 24 hours.
Generating your own nitrogen frees you from reliance on a third party and its terms and conditions. Moreover, compared to other options, on-demand generators provide added safety and significant cost savings as well as a sustainable approach to the supply of nitrogen.
PROPERLY SIZE THE GENERATOR
When determining the required amount of blanketing gas, you must consider both liquid loss during pump-out and condensation of tank vapors during atmospheric thermal cooling. The maximum flow rate and desired purity determines the size of the nitrogen generator required. Here are the steps for sizing a blanketing generator:
1. Determine the gas flow rate due to pump-out (Table 1).
2. Find the gas flow rate due to atmospheric cooling (Table 2).
3. Add the requirements of 1 and 2 to get the size of the nitrogen generator needed.
Note that in a pressurized system the makeup nitrogen demand might be fairly low if a user rarely dumps the tank. However, it's important to provide sufficient capacity to maintain the blanket during tank pump-out and changes in height due to temperature. In this case, size the generator to accommodate the pump-out speed. For example, a blanket provided by pressure affects the chemical in a different way than a blanket provided by continuous purge. In addition, a non-pressurized system also must accommodate the contraction and pump-out speed and maintain a blanket to keep up with leakage.
DAVID J. CONNAUGHTON is product marketing manager, industrial gas generators, global development, for the Filtration and Separation Division of Parker Hannifin Corporation, Haverill, Mass. E-mail him at email@example.com.