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The amount of moisture that collects in the container will depend upon the moisture content in the SO
2
and the rate
of SO
2
withdrawals. Therefore, each installation will require a special procedure of boil-off time and frequency of
boil-off. In most cases moisture will be visible in the sulfonator rotameter tube, and when this moisture disappears
the boil-off procedure can be terminated. This procedure requires redundancy in the SO
2
Vaporizer equipment to
allow intermittent Vaporizer shutdown periods.
Those installations not using Vaporizers will probably not experience corrosion as severe as those with Vaporizers.
This is directly related to the increased corrosive activity of the heated SO2 caused by the elevated temperature of
the moisture in the Vaporizers.
However, those systems not using Vaporizers suffer a problem of considerable importance. Owing to the low vapor
pressure of SO
2
it reliquefies readily in the supply system. This phenomenon interferes severely with the ability to
meter the SO
2
with any degree of accuracy.
The best system for handling SO
2
dechlorination procedures is to use a storage tank that can be pressurized to
75 - 100 psi and deliver the SO
2
to conventional vaporizing equipment. Boiling off the moisture described above
should reduce the corrosive maintenance problem to within the limits currently experienced by the usual
chlorination system.
The above moisture removal procedure eliminated corrosion failure of the Vaporizers at the plant where three Sulfur
Dioxide Vaporizers at this same plant have been in operation for at least twenty years. This illustrates the magnitude
of the problem and the vast difference between the packaging of Chlorine versus Sulfur Dioxide.
The above procedure was devised after a careful examination was made of the lower section of the SO
2
container
vessel in all three Vaporizers that failed. There were a series of pin-holes distributed around the circumference of the
vessel right at the SO
2
liquid-vapor interface.
Summary of Contents for Capital Controls 71V3B Series
Page 1: ... 1 115 6031 0 Instruction Manual Series 71V3B Electrically Heated Vaporizer CAPITAL CONTROLS ...
Page 9: ... 9 115 6031 0 Figure 1 Sectional Diagram ...
Page 17: ... 17 115 6031 0 Figure 4 Outline Mounting Dimensions 12 kW 15 kW Heaters ...
Page 18: ...115 6031 0 18 Figure 5 Outline Mounting Dimensions 18 kW Heater ...