METHOD OF ELIMINATING MALODOURS FROM GASES

Abstract: Disclosed is a method of eliminating the odour from a malodourous gas, where the odour is due to the presence of a C10 to C18 fatty acid in the gas. An aqueous solution containing at least a stoichiometric amount of a base that reacts with said C10 to C18 fatty acid to produce a salt is sprayed into the gas.

Description: METHOD OF ELIMINATING MALODOURS FROM GASES This invention relates to a method of eliminating foul-smelling odours from gases. 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 odour and its release may generate complaints from people in the vicinity. Companies making PVC are often 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. According to one aspect of this invention there is provided a method of making poly(vinylchloride) using a C 10 to Cj 8 fatty acid salt, where said poly(vinylchloride) is dried in air, and said air is released to the atmosphere, and said air is malodorous, the method of including the step of reducing the malodorousness of the air, where said malodour is due to the presence of Cio to Cis fatty acid in said air, by spraying into said air an aqueous solution containing at least a stoichiometric amount of a base that reacts with said o to C 18 fatty acid to produce a salt. In one embodiment said odour is due to the presence of a C 10 to C 14 saturated aliphatic fatty acid in said air. In a specific embodiment said odour is due to the presence of lauric acid in said air. Preferably said base is selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide and mixtures thereof. Conveniently said base is sodium carbonate. Advantageously the concentration of said base in said aqueous solution s about 0.05 wt% to about saturation. Conveniently the concentration of said base in said aqueous solution is about 0.02 to about 1.0 wt%. Preferably the amount of said base is about 2 to about 4 times stoichiometric. Advantageously said aqueous solution is atomized. Conveniently the concentration of said fatty acid in said air is less than 100 ppm. Preferably the volume of said air is at least 283m7min (10,000 SCFM). According to another aspect of this invention there is provided a process for making poly(vinylchloride) wherein an ammonium salt of lauric acid, palmitic acid, or stearic acid is used as a surfactant in manufacturing a poly(vinylchloride) aqueous emulsion and said aqueous emulsion is sprayed into warm air to dry said polyvinyl(chloride), the process including the step of rendering said air less malodourous by spraying into said air an aqueous solution containing about 2 to about 4 times the amount of a base that is needed to react with any lauric acid, palmitic acid, or stearic acid in said air. Conveniently said ammonium salt is ammonium laurate. Preferably said base is sodium carbonate. Conveniently the concentration of said base in said aqueous solution is about 0.2 to about 1.0 wt%. Advantageously said aqueous solution is atomized. Preferably said base is selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide and mixtures thereof. Conveniently the concentration of said lauric acid, palmitic acid, or stearic acid in said air is less than 100 ppm. Preferably the volume of said warm air is at least 283m /min (10,000 SCFM). The invention also relates to a method of making poly(vinylchloride) comprising (A) polymerising vinyl chloride monomer in an emulsion micro- suspension polymerisation process to produce an emulsion containing particles of poly(vinylchloride); (B) adding ammonium laurate to said emulsion; (C) spraying said emulsion into warm air, whereby lauric acid is formed; (D) passing said warm air through a poly(vinyl chloride) drying system; and (E) spraying into said warm air from said drying system an aqueous solution of about 0.05 to about 1.0 wt% sodium carbonate containing about 2 to about 4 times the amount of sodium carbonate needed to stoichiometrically react with said lauric acid. The source of the objectionable odour in drying gases from certain PVC polymers is fatty acid. Fatty acid is formed from an ammomum fatty acid salt, which is used in the PVC polymerisation 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. 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. The invention will now be described, by way of example. 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 Cι 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 283m (10,000 SCFM) as other methods are too expensive to handle so much gas. Into the gas to be de-odorized 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: Example 1 The stack gas emanating from a commercial PVC manufacturing plant in which an ammonium laurate surfactant was used in a vinyl chloride emulsion micro-suspension polymerisation process was found to contain 5.6 to 7.3 mg/m 3 of lauric acid, 0.6 to 2.3 mg/m 3 of cetyl alcohol, and 0.02 to 0.2 mg/m 3 of stearyl alcohol. By smelling pure lauric acid, the odour of the stack gas was determined to be primarily due to lauric acid. Example 2 A laboratory scale lauric acid emitting stack was constructed to test the effectiveness of various substances in eliminating the odour of lauric acid. The stack was placed in a closed laboratory room and aqueous solutions of various materials were sprayed into the exhaust gas from the stack. After 10 minutes, 5 members of a test panel entered the room to note any odours present. The substances tested and the results are as follows: 1. Proprietary blend of essential (natural) oils, sold by Odour Control Technology 2. Proprietary blend of essential (natural) oils, sold by Environmental Control 3. Proprietary material sold by Odour Management, Inc. 4. Proprietary material sold by Betz Dearborn 5. Proprietary material sold by Betz Dearborn Example 3 At a large PVC manufacturing plant where ammonium laurate was used as a surfactant, the stack air flow was about 1700 m /min (60,000 SCFM) and the lauric acid in the stack emissions ranged from 0.057 to 0.74 kg/hr 1.26 to 1.64 lb/hr. A nozzle was inserted into the exhaust stack before the fan and 0.068 kg/min (0.15 lb/min) of a 5 wt% aqueous solution of sodium carbonate was sprayed in atomized form into the stack gas through the nozzles. Over a three month period, complaints about odours from persons in the vicinity declined by 75%, compared to the same period the previous year. In the present specification "comprise" means "includes or consists of and "comprising" means "including or consisting of. The features disclosed in the foregoing description, or the following Claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims: WE CLAIM: 1. A method of making poly(vinylchloride) using a C 10 to Cι 8 fatty acid salt, where said poly(vinylchloride) is dried in air, and said air is released to the atmosphere, and said air is malodorous, the method of including the step of reducing the malodorousness of the air, where said malodour is due to the presence of o to C 18 fatty acid in said air, by spraying into said air an aqueous solution containing at least a stoichiometric amount of a base that reacts with said Cio to Cι 8 fatty acid to produce a salt. 2. A method according to Claim 1 wherein said odour is due to the presence of a Cio to Cι 4 saturated aliphatic fatty acid in said air. 3. A method according to Claim 2 wherein said odour is due to the presence of lauric acid in said air. 4. A method according to any one of the preceding Claims wherein said base is selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, and mixtures thereof. 5. A method according to Claim 4 wherein said base is sodium carbonate. 6. A method according to any one of the preceding Claims wherein the concentration of said base in said aqueous solution is about 0.05 wt% to about saturation. 7. A method according to Claim 6 wherein the concentration of said base in said aqueous solution is about 0.02 to about 1.0 wt%. 8. A method according to any one of the preceding Claims wherein the amount of said base is about 2 to about 4 times stoichiometric. 9. A method according to any one of the preceding Claims wherem said aqueous solution is atomized. 10. A method according to any one of the preceding Claims wherein the concentration of said fatty acid in said air is less than 100 ppm. 11. A method according to any one of the preceding Claims wherein the volume of said air is at least 283m 3 /min (10,000 SCFM). 12. A process for making poly(vinylchloride) wherein an ammomum salt of lauric acid, palmitic acid, or stearic acid is used as a surfactant in manufacturing a poly(vinylchloride) aqueous emulsion and said aqueous emulsion is sprayed into warm air to diy said polyvinyl(chloride), the process including the step of rendering said air less malodourous by spraying into said air an aqueous solution containing about 2 to about 4 times the amount of a base that is needed to react with any lauric acid, palmitic acid, or stearic acid in said air. 13. A method according to Claim 12 wherein said ammomum salt is ammonium laurate. 14. A method according to Claim 13 wherein said base is sodium carbonate. 15. A method according to Claim 12, 13 or 14 wherein the concentration of said base in said aqueous solution is about 0.2 to about 1.0 wt%. 16. A method according to any one of Claims 12 to 15 wherein said aqueous solution is atomized. 17. A method according to any one of Claims 12 to 16 wherein said base is selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium biocarbonate, sodium hydroxide, potassium hydroxide and mixtures thereof. 18. A method according to any one of Claims 12 to 17 wherein the concentration of said lauric acid, palmitic acid, or stearic acid in said air is less than 100 ppm. 19. A method according to any one of Claims 12 to 18 wherein the volume of said warm air is at least 283m 3 /min (10,000) SCFM). 20. A method of making poly(vinylchloride) comprising (A) polymerising vinyl chloride monomer in an emulsion micro- suspension polymerisation process to produce an emulsion containing particles of poly(vinylchloride); (B) adding ammonium laurate to said emulsion; (C) spraying said emulsion into warm air, whereby lauric acid is formed; (D) passing said warm air through a poly(vinyl chloride) drying system; and (E) spraying into said warm air from said drying system an aqueous solution of about 0.05 to about 1.0 wt% sodium carbonate containing about 2 to about 4 times the amount of sodium carbonate needed to stoichiometrically react with said lauric acid.

Inventors: BRANDT DANIEL J, BRANDT, DANIEL, J.
Applicants: OCCIDENTAL CHEM CO, STEPHENS DINAH, OCCIDENTAL CHEMICAL CORPORATION, STEPHENS, DINAH
Application year: 2000
Main classification: C08F6
IPC codes: B01D53, C08F6, C08F14