Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Organic component
Reexamination Certificate
1999-11-24
2001-01-09
Dunn, Tom (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Organic component
C423S210000, C526S344100, C526S344200, C095S237000
Reexamination Certificate
active
06171569
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of eliminating foul-smelling odors from gases. In particular, it relates to eliminating the odor of fatty acids from air by spraying a solution of a base into the air.
In manufacturing poly(vinylchloride) (PVC) by an emulsion process, an emulsion of PVC particles in water is sprayed into warm air to evaporate the water and dry the resulting PVC particles. A fan forces huge volumes of this air through a drying system, which trap the PVC particles, and the air is then released into the atmosphere. This air can have an objectionable odor and its release generates complaints from people in the vicinity. Companies making PVC are being required to de-odorize this air. Deodorizers tested have not been found to be effective and scrubbers, though probably effective, cost many millions of dollars to install and operate.
SUMMARY OF THE INVENTION
I have discovered that the source of the objectionable odor in drying gases from certain PVC polymers is fatty acid. Fatty acid is formed from an ammonium fatty acid salt, which is used in the PVC polymerization process as a surfactant. Although the fatty acid is present in only ppm (parts per million, by weight) concentrations, it can be detected by a human being having a nose of average sensitivity, at ppb (parts per billion, by weight) concentrations. I have further found that spraying the drying gas with an aqueous solution of a base forms a salt, which significantly reduces or eliminates the odor because these salts have little or no odor. Spraying with a basic solution costs very little to implement and operate, is safe to handle, and does not add harmful chemicals to the environment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
This invention is applicable to gases containing C
10
to C
18
fatty acids and it is particularly applicable to gases containing C
10
to C
14
saturated aliphatic fatty acids. Examples of such acids include lauric acid, palmitic acid, and stearic acid. The invention is most useful if the concentration of the fatty acid in the gas is less than about 100 ppm as other methods may not be suitable at those low concentrations. The invention is also most useful for treating very large volumes of gas, such as more than 10,000 SCFM (standard ft
3
/min, 283 m
3
/min) as other methods are too expensive to handle so much gas.
Into the gas to be deodorized is sprayed an aqueous solution of a base that will react with the fatty acid to form a salt. Examples of bases that can be used include sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide, and mixtures thereof. The preferred base is sodium carbonate because it has been found to be very effective and it is inexpensive and safe to use. The concentration of the solution should be about 0.05 wt % to saturation as lower concentrations may be less effective; preferably, the concentration is about 0.2 to about 1.0 wt %. At least a stoichiometric amount of base should be used, but more than about 7 times stoichiometric is usually unnecessary. To ensure that all or almost all of the fatty acid is reacted without using excess base, it is preferable to use about 2 to about 4 times the stoichiometric amount of base. The solution should be sprayed into the air to be treated in a finely-divided form, preferably atomized.
The following examples further illustrate this invention:
REFERENCES:
patent: 1716028 (1929-02-01), Canon
patent: 3054653 (1962-09-01), Barton
patent: 3864485 (1975-02-01), Horsley
patent: 4186259 (1980-01-01), Bush
patent: 986524 (1965-02-01), None
patent: 10140179 (1998-05-01), None
Abstract of article titled, “Degree of Fatty Acid Neutralization by Aqueous Sodium Hydrogen Carbonate Solutions” by A. N. Morgunov et al. in Maslo-Zhir. Prom-st. (10), 20-2 (1976).
Brookes Anne E.
Dunn Tom
Fuerle Richard D.
Occidental Chemical Corporation
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