includes an economizer feature that monitors the pressure in the reserve cylinders and switches to draw gas off those containers before they reach the relief-valve setting of 350 psig and are prevented from venting CO2
into
the surrounding area. As previously discussed, this venting can be as much as 2% per day of the contents of the container for a single-reserve liquid cylinder, which can be as much as 7–8 lb of CO2
per day. By employing a
system that includes an economizer program, this can be reduced or ef- fectively eliminated.
Figure 3 – Overhead view of a liquid cylinder.
a computer-controlled algorithm to monitor if an increase in the primary side’s pressure occurs once a changeover to the reserve side has taken place, which indicates residual contents that can be used. This in itself can improve your green rating by as much as 20–30%, and means that all but 2–3% of the CO2
purchased is being used.
The other most important thing to determine is that your facility justifi es using cryogenic liquid cylinders as the reserve and that the system also
Clearly, it is important that, when sizing your system using liquid cylinders, the total number of containers online both as primary and reserve supply is adequate to supply your facility for at least a week of usage, but that the total daily NER based on 2% of their total contents is less than your daily expected usage. Doing so as closely as possible ensures that your required daily demand is satisfi ed, and also that, with the use of an appropriate sys- tem, the amount of CO2
released by the container’s relief valves is minimized
or eliminated as much as possible. Your facility is then as green and safe as possible, given its requirement for CO2
.
Larry Gallagher is Specialty Gas Products Manager, CONCOA, 1501 Harpers Rd., Virginia Beach, VA 23454, U.S.A.; tel.: 800-225-0473; fax: 757-422-3125; e-mail:
lgallagher@concoa.com.
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