Chlorine Solubility

Solving Problems

Conclusion

Modern Technology

Chlorine Vacuum Lines vs. Solution Lines (Chlorine Solubility in Water)

Even though the concept of the direct cylinder-mounted gas chlorinator
utilized with a remote ejector close-coupled to the application point
has over 33 years of proven history, there still exists a great deal of
confusion and misinformation regarding the desirability of avoiding
chlorine solution lines whenever possible.


Chlorine Solubility. Chlorine is only slightly soluble in water,
Theoretically, only about 0.7% chlorine can be dissolved in water at
68 F (20 C). Practical solubility, which requires considerable
mixing and time, is about half this value. In conventional solution-feed
chlorinators there is not sufficient time or mixing in the ejectors and
solution lines to get even this practical solubility. As temperature
increases, the solubility drops off very rapidly. The insolubility of
chlorine in water was a major reason for the development of a vacuum gas
chlorinator system which separated the ejector from the vacuum
regulating and chlorine flow metering components.
The REGAL System. In the REGAL system, the chlorine gas is conducted
from the chlorinator to the point of diffusion through a vacuum line. The
gas is never above atmospheric pressure in this line. At the ejector,
the chlorine gas is mixed with water (at vacuum conditions) and
immediately injected into the treated system through a diffuser. The
chlorine that has not been dissolved in the water is in the form of
thousands of almost microscopic bubbles which, when entering the much
larger flow of the main stream, are immediately dissolved.
Whenever possible, locate the booster pump and ejector in the same area
as the point of chlorine application, and just run chlorine vacuum
tubing to the ejector from the chlorinator. This eliminates friction
loss problems, eliminates dangerous chlorine solution lines, and reduces
the required booster pump size significantly. Comparing the examples
above, placing the ejector at the application point only requires the
booster pump to raise the suction pressure by 49 psig (3.44 kg/cm2). Of
course, in both examples, friction losses in the booster pump suction
piping would have to be added to the ``boost" requirements.

For practicality, economy and safety, place the gas chlorinator ejector
as close as possible to the chlorine application point.
Before 1960, when James Haskett, Chlorinators Inc.
founder, designed and patented the cylinder-mounted all-vacuum-operated
gas chlorinator, most chlorinators worked essentially the same way.
Pressure from the tanks forced the gas through one line to an ``ejector"
where it was mixed with water. Water pressure then forced the
chlorine/water solution through another line to the ``diffuser" that
injected it into the water or wastewater being treated. If either line
failed, gas would escape unimpeded. Failure of any of the many valves
these systems employed would also cause gas to escape.

Haskett's design -- mounting the chlorinator on the cylinder and
using a vacuum to pull the gas to the ejector -- eliminated the gas
pressure line.

This design makes it very difficult for chlorine to escape. If any part
of the equipment should fail, the flow of chlorine is immediately -- and
automatically -- shut off.

The problem of corrosion, which contributed to the difficulties of the
pressure systems, is also significantly reduced by Mr. Haskett's design,
and the pressure line, the most serious source of corrosion in gas
chlorination equipment, is eliminated.

In Mr. Haskett's design, chlorine gas bubbles immediately enter the main
stream, and are quickly dissolved. Further, beginning with the
regulator, the gas is never under pressure, and it is mixed with water
in the ejector under vacuum conditions.

Another important point: laws prohibiting the use of chlorine gas could
be costing you a lot of money, because chlorine gas is far more
economical than either sodium or calcium hypochlorite. The tank contains
100% chlorine, which can never lose strength. Calcium hypochlorite has
only 65-70% total weight chlorine available, and sodium hypochlorite
only 10% or less by the time it is used. You need 1.5 pounds of calcium
hypochlorite, or 1.2 gallons of sodium hypochlorite (average 10%) to
equal a pound of liquid (gas) chlorine. Both calcium and sodium
hypochlorite lose strength in storage.

Although the initial cost of gas chlorination equipment may be higher
than that required for calcium or sodium hypochlorite, the savings in
material costs quickly make up the difference.