Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture
Reexamination Certificate
1998-07-10
2001-02-06
Langel, Wayne (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Reexamination Certificate
active
06183708
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the use of peroxy acid compounds in odor reduction. The invention further relates to removing odor compounds from the atmosphere or from volumes of gas arising from the processing of organic materials. The processing can occur in large processing plants or in small loci such as kitchens or doctors offices. More specifically, the invention relates to an improved odor reduction process using a finely divided or atomized peroxygen compound containing spray to treat gaseous or other effluent containing odor compounds with increased efficacy. The odor can comprise organic and inorganic compounds including organic sulfur compounds, organic nitrogen compounds, organic oxo-compounds, ammonia, hydrogen sulfide, etc. and mixtures thereof. Odor is reduced by means of reacting the effluent containing the odor compounds with an aqueous odor reduction compound.
BACKGROUND OF THE INVENTION
Industrial plants, agricultural installations, hospitals, kitchens, etc. that handle large quantities of organic material such as hog farms, dairy farms, chicken farms, meat packing plants, animal rendering plants, composting plants, paper mills, sewage treatment plants and other similar installations can generate large quantities of odors that typically exit the facility in an odor contaminated atmospheric effluent flume or other effluents. Such an effluent can contain a large variety of odoriferous or odor causing inorganic and organic chemicals or molecules including organic sulfides or organic thiols (mercaptans), monoamines, diamines, triamines, ammonia, alcohols, formaldehyde, acetaldehyde, carboxylic acids, skatole, carbon disulfide and hydrogen sulfide and other odor forming oxidizable compounds. An atmospheric effluent having one or more of such compounds can have a strong odor and can be highly objectionable within the plant to plant personnel and outside the plant to plant neighbors.
An odor is a gas phase emission that produces an olfactory stimulus. The odor thresholds of many chemicals that act as odor compositions common throughout the chemical process industries include, for example, ethyl sulfide having an odor threshold in the atmosphere of 0.25 ppb, hydrogen sulfide with an odor threshold of 0.4 ppb, dimethyl sulfide with an odor threshold of 1.0 ppb, ethyl mercaptan with an odor threshold of 1.0 ppb, methyl mercaptan with an odor threshold of 1.1 ppb. With a low threshold a small amount of these and similar odors common in plant effluent are serious olfactory problems. Such odors result from processing large quantities of organic materials and are generated by the action of micro-organisms in any biologically active system on a source of organic material producing the odors.
There are many other odor producing chemicals possible, however, as shown in this representative, non-inclusive list:
1. Sulfur compounds
Hydrogen Sulfide
Thiophene
Carbonyl Sulfide
Isobutyl Mercaptan
Methyl Mercaptan
Diethyl Sulfide
Ethyl Mercaptan
n-Butyl Mercaptan
Dimethyl Sulfide
Dimethyl Disulfide
Carbon Disulfide
3-Methylthiophene
Isopropyl Mercaptan
Tetrahydrothiophene
tert-Butyl Mercaptan
2, 5-Dimethylthiophene
n-Propyl Mercaptan
2-Ethylthiophene
Ethyl Methyl Sulfide
Diethyl Disulfide
2. Organic nitrogen compounds
Primary amines
secondary amines
tertiary amines
pyridines
amides
ammonia
3. Organic oxygen compounds (oxo-hydrocarbon compounds)
primary alcohols
carboxylic acids
aldehydes
ketone compounds
phenolics
Attempts have been made to reduce the production of the odor compounds and to reduce the release of the odor compounds from plants. Robinson, “Develop a Nose for Odor Control”,
Chemical Engineering News,
October 1993 contains a generic disclosure of odor problems and conventional odor control using aqueous treatment compositions including H
2
O
2
, FeCl
3
, KMnO
4
, NaOH and others. Careful control over the organic materials within the plant and reduction of microbial populations within the plant have been attempted to reduce the generation of the odor compounds in the plant atmosphere. Attempts to scrub the odor compounds from the plant atmosphere have been made using a variety of simple absorptive and oxidizing scrubbing materials with standard particle size atomized or finely divided aqueous particulate. Fragrance chemicals that simply mask the offensive odors have been tried. Sodium hydroxide (NaOH), activated carbon are useful absorptives. Oxidizing materials such as ozone (O
3
), chlorine dioxide (ClO
2
), sodium hypochlorite (NaClO) and others have been attempted. Some degree of success has been achieved using these oxidative materials to remove organic odor molecules from atmospheric effluents. While chlorine dioxide has had some success, chlorine dioxide is highly toxic, difficult to handle and must be generated on site. Such difficulties lead to substantial resistance to its use. Further hydrogen peroxide is also known for odor control. Hydrogen peroxide by itself is not effective against a broad range of odor constituents without additional treatment materials. However, the application of oxidative technologies including ozone, hydrogen peroxide, chlorine dioxide and other oxidants have had some limited success.
The use of peroxyacid materials in microbiological methods are also known. For example, Grosse-Bowing et al., U.S. Pat. Nos. 4,051,058 and 4,051,059 disclose peroxyacetic containing antimicrobial compositions. Stas et al., U.S. Pat. Nos. 4,443,342 and 4,595,577 disclose the treatment of waste water and waste gases containing dialkyldisulfides by metal catalytic oxidation of these compounds by means of a peroxide compound in an aqueous medium. Lokkesmoe, U.S. Pat. No. 5,409,713 teaches peroxyacetic materials as microorganism sanitizers or growth inhibitors in aqueous transport systems typically containing produce and large amounts of challenged soil load.
Fraser, in “Peroxygens in environmental protection”,
Effluent and Water Treatment Journal,
June 1986 disclose that hydrogen peroxide (H
2
O
2
) can be used to reduce odor. Fraser only discusses microbial control with peroxyacetic acid and does not correlate odor control to peroxy acid treatment or concentration. Littlejohn et al., “Removal of NO
x
and SO
2
from Flue Gas by Peroxy acid Solutions”,
Ind. Eng. Chem. Res.
Vol. 29, No. 7, pp. 1420-1424 (1990) disclose peroxyacids in removing nitric oxides and sulfur dioxide from coal fire derived flue gas.
Peroxyacetic acid, neat and in aqueous solution, has a strong pungent oxidizing odor resembling but stronger than acetic acid. Such materials have not been seriously considered as odor reducing materials because of the nature of its odor. The concern being that in any treatment process using a significant amount of peroxyacetic acid, the resulting treated effluent would inherently obtain the pungent odor of the peroxyacetic acid. Further, peroxyacetic acid solution inherently contain large amounts of acetic acid (HOAc).
In adsorption technology, increasing surface area equates to an increase in contact surface, thereby improving adsorption performance. Because surface area is an important criteria, there have been attempts to use fogged or atomized aqueous solutions in odor control. For example, Murray et al., U.S. Pat. No. 4,994,245, discloses the use of atomized sulfuric acid and surfactant, followed by bleach and hydrogen peroxide treatments for odor reduction. Morrison, U.S. Pat. No. 4,708,855, uses a finely divided alkali mist to reduce airborne odors in a cement plant.
BRIEF DISCUSSION OF THE INVENTION
The invention involves an improved process for removing odor compounds from an atmospheric plant fluid effluent. In the process of the invention, the plant atmosphere or other effluent is contacted with an atomized, fogged or otherwise finely divided spray of aqueous treatment solution containing a controlled amount of a peroxyacid. Sufficient peroxy acid is used to control odor but not contribute a peroxy acid smell to the treated effluent. The process is typically conducted outside the venturi restriction zone or tower packin
Bennett Scott P.
Hei Robert D. P.
Lokkesmoe Keith D.
McLaren Jay H.
Wei Guang-jong Jason
Ecolab Inc.
Langel Wayne
Medina Maribel
Merchant & Gould P.C.
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