Page 18 - Microsoft Word - Sulfo and Sulfa 1.doc

60°C to –80°C). The high dew point causes product quality problems in the sulfonation
process and accelerates corrosion of the process equipment. Third, the pressure of the
air/SO from the sulfuric acid plant is usually not sufficient to overcome the pressure
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drop of the sulfonation system. Compressing the air/SO from the converter is not trivial
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as it requires a high alloy compressor to withstand the corrosive environment created by
the wet air/SO stream. This problem can be overcome, but the solution is not
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inexpensive. Considering all the problems inherent in utilizing the converter gas stream
from a sulfuric acid plant, the conclusion is that it is technically feasible. However this
choice adds significant operational difficulties and does not result in a major cost savings
over installing a complete sulfur burning sulfonation plant.

Another possible source of SO for sulfonation is produced by boiling oleum to produce
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gaseous SO which is then blended with dry air. It is practically limited to locations
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where fresh oleum can be received, and depleted oleum returned by pipeline. Compared
to sulfur burning, this process somewhat reduces the equipment requirement. However,
it still requires an air supply system, an oleum boiler and an SO metering system.
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Unlike a sulfur burning plant which generates its own heat for air dryer regeneration, this
air supply system requires an external source of heat which adds extra utility expenses.
Also, significant safety hazards are associated with handling concentrated oleum. Such
an installation may be economical for a few site locations, and at least one is
commercially operating in North America.

Some of the first air/SO sulfonation plants installed were based on use of liquid SO .
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These plants require an air supply system identical to the system described below for a
sulfur burning plant except that it also requires an external heat source for air dryer
regeneration. In addition, a liquid SO plant requires an SO storage system. This
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storage system is usually a large 20,000 to 80,000 kg storage tank located in a heated
room and maintained at a temperature of about 40–43°C. Heating the SO storage room
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can be a significant cost in colder climates. In case of SO leaks, the room must be
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sealed and should have provision for scrubbing any SO that escapes into the room's
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atmosphere. In the sulfonation process, the liquid SO is metered from the storage tank
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into a steam heated vaporizer where it is evaporated and mixed into the dried air stream
from the air supply system. From this point on, the process is identical to a sulfur
burning air/SO sulfonation plant, described below. A liquid SO storage and metering
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system is shown in Figure 18. Because of the rigorous storage requirements imposed by
the hazardous nature of liquid SO , the installed cost for a liquid SO sulfonation facility
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is close to that for a sulfur burning installation.
There are significant safety advantages to a sulfur burning system. With sulfur burning
air/SO sulfonation processes, the only SO on site is the small quantity of dilute gaseous
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material in the process piping between the converter (SO to SO ) and the sulfonation
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