Chemistry: analytical and immunological testing – Sulfur containing
Patent
1984-10-26
1986-12-16
Bashore, S. Leon
Chemistry: analytical and immunological testing
Sulfur containing
436164, G01N 3300
Patent
active
046297049
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for assaying sulphur trioxide and to apparatus for carrying out the method.
The object of the present invention is to provide a method and apparatus for assaying sulphur trioxide which is capable of forming a mist, and particularly for monitoring industrial emission process gases containing sulphur trioxide, for controlling the recycling of such gases and/or the emission of said gases to the surroundings, with the view of protecting the environment.
BACKGROUND ART
When producing sulphur acid problems relating to the undersirable emission of sulphur trioxide constantly occur, such occurrence being particularly evident when process equipment becomes overloaded and/or break downs in operation occur and/or production is re-started after such break downs.
Such emission can be tolerated in itself, provided that it is on such a small scale as to have no chronic effect on the environment. The emission of such gases must not be continuous, however, and consequently it is necessary to monitor gases which derive from industrial processes and which are liable to create emission problems.
Although with respect to certain gases, it is possible to assay the gas in the actual chimney stack, using light-absorption assaying methods herefor, the gas has either already been discharged from the system to the surroundings, or is in the process of being discharged, thereby rendering it impossible to recycle the gas, should such prove desirable.
Thus, there is a demand for a method by which the sulphur trioxide content of a dry exhaust gas can be measured downstream of an absorption tower in a sulphuric acid plant, so that the gas can be checked and controlled in a rapid fashion.
DISCLOSURE OF THE INVENTION
It has now surprisingly been found possible, in accordance with the present invention, to assay gases containing sulphur trioxide which is able to form a mist, the invention being characterized by drawing the dry gas into a closed space by suction; contacting the gas with air comprising normal humidity which reacts therewith to form a mist; and measuring the light extinction properties of the gas.
By means of the present invention gases comprising sulphur trioxide in an amount down to 35 mg SO.sub.3 per m.sup.3 can be determined using ordinary air having a normal humidity, i.e. a water content of 15 to 20 g of H.sub.2 O per m.sup.3. It has been noted that the water content should not be less than about 15 g of H.sub.2 O per m.sup.3, although the amount of sulphur trioxide is low and that thereby not all water is needed.
Further characterizing features of the invention are set forth in the following claims.
The present invention will now be described with reference to the accompanying drawing, in which
FIG. 1 is a sectional view of a preferred first embodiment of an assaying apparatus according to the invention, placed in a residual gas conduit; and
FIG. 2 is a cross-sectional view of a second preferred embodiment of an assaying apparatus according to the invention.
Referring first to FIG. 1, there is illustrated a cylindrical tube 1, suitably made of an acid-proof material such as acid-proof steel or polypropylene. Arranged on one end 2 of the tube is a housing 3 which contains a mirror 4. Immediately in front of the housing 3 is a gas inlet pipe 5. Arranged in the vicinity of the mirror 4 is a second inlet pipe 6, said pipe being intended to conduct air and/or an inert gas. Arranged on the other end 7 of the tube 1 is a second housing 8 which contains a photodiode 9 and a receiver, photocell, 10. The receiver 10 is coupled to a transmitter 11, which transfers incoming signals to a writer and/or display instrument (not shown). Coupled to the housing 8 is a supply pipe 12, which is arranged to transfer said air and/or inert gas. The pipe 12 communicates with the pipe 6 and also with a connector 13 arranged around the photodiode 9 and receiver 10, for the introduction of said air/inert gas to the region around said diode and receiver. Also arranged at said other en
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Bashore S. Leon
Boliden Aktiebolag
Manoharan V.
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