WO2012106443A1 - Compositions for wet air scrubbers and methods for operating and cleaning wet air scrubbers using the same - Google Patents

Abstract

Provided are compositions for use in air scrubbers and methods for cleaning air scrubbers using the same. Compositions include at least one of components A, B, C, D, and E. Component A includes at least one surfactant and at least one enzyme. Component B includes at least one surfactant. Component C includes at least one pH control agent. Component D includes at least one defoamer. Component E includes at least one enzyme. Further provided are methods of operating an air scrubber, including adding a composition comprising a surfactant to a fluid stream in the air scrubber; maintaining a first temperature of the fluid stream for a first period of time; and maintaining a second temperature of the fluid stream for a second period of time, the first temperature being greater than the cloud point of the surfactant, and the second temperature being less than the cloud point of the surfactant.

Description

COMPOSITIONS FOR WET AIR SCRUBBERS AND METHODS FOR OPERATING AND CLEANING WET AIR SCRUBBERS USING THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 61/438,317, which was filed on February 1 , 201 1 , and is incorporated herein by reference in its entirety

FIELD OF INVENTION

[0002] The present disclosure relates to compositions for cleaning and operating wet air scrubbers.

INTRODUCTION

[0003] Wet air scrubbers may be used with rendering plants. Rendering plants process unwanted and unused animal parts and tissue, for example, from meat-processing houses and slaughter houses, and convert them into useful finished goods including animal feed, fuel oil, and Pharma Cos ingredients. The air surrounding rendering plant equipment may have a bad odor and may contain volatile organic compounds (VOCs).

[0004] Air scrubbers may be used to reduce or eliminate malodor at rendering plants, for example, by removing volatile organic compounds from the air. A wet air scrubber operates on the principle that VOCs in the air diffuse into water and consequently are prevented from entering the atmosphere. Air scrubbers may, for example, comprise a tower with water flowing from the top of the tower to the bottom of the tower, with water then recycled to the top of the tower again. As air from a rendering plant is flowed through the air scrubber, VOCs may be removed from the air. While some air scrubbers rely on sprayed water to create an air/water interface for purification, some air scrubbers use plastic or stainless steel media to increase air/water surface area and to decrease water flow as the air flows upwards through the scrubber. If the water in the air scrubber is being treated with an oxidizer or other conventional treatment solution including acidified bleach, chlorine dioxide, ozone and/or permanganates, this media is often fouled with insoluble high molecular weight proteins, oils, greases, and other organic debris. This fouling may cause several problems. First, as the media is fouled, the cross section available for air flow decreases, and the removal efficiency of volatile organic compounds is diminished. Second, the organic debris may act as a source of odor, especially after downtime when the water is not recirculating, if the recirculating water temperature temporarily increases during operation due to process temperature changes, and/or when treatment chemical is not being fed. The air scrubber at rest may allow hydrogen sulfide generating anaerobic bacteria under the deposits to flourish.

[0005] Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

SUMMARY

[0006] In certain embodiments, provided are methods of operating a wet air scrubber, the method comprising adding a composition comprising a surfactant to a fluid stream in the wet air scrubber, maintaining a first temperature of the fluid stream for a first period of time, and maintaining a second temperature of the fluid stream for a second period of time, wherein the first temperature is greater than the cloud point of the surfactant, and the second temperature is less than the cloud point of the surfactant. The composition may further comprise an enzyme.

[0007] In other embodiments, provided are methods of operating a wet air scrubber, the method comprising adding to a fluid stream in the wet air scrubber a composition comprising component E and at least one of component A and component B, wherein component A comprises (1 ) a surfactant and (2) an enzyme, component B comprises at least one of (1 ) a detersive surfactant and a defoamer, (2) at least one low-foam surfactant, and (3) a combination thereof, and component E comprises (1 ) an enzyme. The methods may further comprise maintaining a first temperature of the fluid stream for a first period of time, and maintaining a second temperature of the fluid stream for a second period of time.

[0008] In other embodiments, provided are methods of enhancing the efficacy of an enzyme in a composition used to clean a wet air scrubber, the method comprising adding to the composition an amount of at least one of component A or B such that the efficacy of the enzyme for cleaning the wet air scrubber is not substantially impeded, wherein component A comprises (1 ) an amphoteric surfactant and (2) an enzyme, and component B comprises at least one of (1 ) a detersive surfactant and a defoamer, (2) at least one low-foam surfactant, and (3) a combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS [0009] Figure 1 is a schematic diagram of a wet air scrubber. DETAILED DESCRIPTION

[0010] The present disclosure is not limited in its disclosure to the specific details of construction, arrangement of components, or method steps set forth herein. The compositions and methods disclosed herein are capable of being made, practiced, used, carried out and/or formed in various ways. The phraseology and terminology used herein is for the purpose of description only and should not be regarded as limiting. Ordinal indicators, such as first, second, and third, as used in the description and the claims to refer to various structures or method steps, are not meant to be construed to indicate any specific structures or steps, or any particular order or configuration to such structures or steps. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification, and no structures shown in the drawings, should be construed as indicating that any non-claimed element is essential to the practice of the invention. The use herein of the terms "including," "comprising," or "having," and variations thereof, is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items. Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings.

[0011] Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. For example, if a concentration range is stated as 1 % to 50%, it is intended that values such as 2% to 40%, 10% to 30%, or 1 % to 3%, etc., are expressly enumerated in this specification. These are only examples of what is specifically intended, and all possible combinations of numerical values between and including the lowest value and the highest value enumerated are to be considered to be expressly stated in this disclosure. Use of the word "about" to describe a particular recited amount or range of amounts is meant to indicate that values very near to the recited amount are included in that amount, such as values that could or naturally would be accounted for due to manufacturing tolerances, instrument and human error in forming measurements, and the like. [0012] No admission is made that any reference, including any non-patent or patent document cited in this specification, constitutes prior art. In particular, it will be understood that, unless otherwise stated, reference to any document herein does not constitute an admission that any of these documents forms part of the common general knowledge in the art in the United States or in any other country. Any discussion of the references states what their authors assert, and the applicant reserves the right to challenge the accuracy and pertinency of any of the documents cited herein. All references cited herein are fully incorporated by reference, unless explicitly indicated otherwise. The present disclosure shall control in the event there are any disparities.

[0013] In certain embodiments, provided are compositions for use in a wet air scrubber, for example, an air scrubber at a rendering plant as depicted schematically in Figure 1. Wet air scrubbers may include, for example, a packed tower scrubber, a spray tower scrubber, an orifice scrubber, a venturi scrubber, a fiber-bed scrubber, an impingement-plate scrubber, a spray nozzle scrubber, a fluidized-bed scrubber, a packed-bed scrubber, multiple-stage scrubbers, baffle spray scrubber, a counter-flow scrubber, a crossflow scrubber, and combinations thereof. Wet air scrubbers can be custom designed by, for example, an independent designer, or competent staff at a rendering facility. Wet air scrubbers are commercially available, for example, from Verantis, AC Corporation, Sep Control Inc., and Millpoint Industries Inc. Compositions according to the disclosure may also be used with packed media wet air scrubbers at factories or plants including, but not limited to, municipal wastewater plants, pet food plants, flavor and fragrance plants, breweries, and grain operations such as corn processing. The compositions according to the disclosure may remediate odors and provide air scrubbers with more effective pollution control without foam. Air scrubbers can be contaminated with entrained fat, oil, or grease (FOG) carried over from the cooker. FOG includes, but it not limited to, at least one of fat, oil, grease, tallow, suet, lard, animal parts, and yellow grease, and combinations thereof. Compositions according to the disclosure may emulsify and remove FOG deposited on the scrubber media and/or prevent FOG accumulation. The compositions may comprise at least one of component A, component B, component C, component D, and component E.

[0014] Component A may comprise at least one surfactant and at least one enzyme. The surfactant may include, but not be limited to, a non-ionic surfactant, a cationic surfactant, an anionic surfactant, an amphoteric surfactant, or combinations thereof. [0015] Examples of nonionic surfactants include, but are not limited to, amides, alkanolamides, amine oxides, block polymers, alkoxylated primary and secondary alcohols, alkoxylated alkylphenols, alkoxylated fatty esters, sorbitan derivatives, glycerol esters, propoxylated and alkoxylated fatty acids, alcohols, and alkyl phenols, glycol esters, polymeric polysaccharides,

[0016] Nonionic surfactants are conventionally produced by condensing ethylene oxide with a hydrocarbon having a reactive hydrogen atom, e.g., a hydroxyl, carboxylic acid group, primary and secondary amino, or primary or secondary amido group, in the presence of an acidic or basic catalyst. Nonionic surfactants may have the general formula RA(CH₂CH₂0)_nH wherein R represents the hydrophobic moiety, A represents the group carrying the reactive hydrogen atom and n represents the average number of ethylene oxide moieties. R may be a primary or a secondary, straight or slightly branched, aliphatic alcohol having from about 8 to about 24 carbon atoms. A more complete disclosure of nonionic surfactants can be found in U.S. Pat. No. 4,1 1 1 ,855, Barrat, et al., issued September 5, 1978, and U.S. Pat. No. 4,865,773, Kim et al., issued September 12, 1989, which are hereby fully incorporated by reference.

[0017] Other nonionic surfactants useful in the composition include ethoxylated alcohols or ethoxylated alkyl phenols of the formula R(OC₂H4)_nOH, wherein R is an aliphatic hydrocarbon radical containing from about 8 to about 18 carbon atoms or an alkyl phenyl radical in which the alkyl group contains from about 8 to about 15 carbon atoms, and n is from about 2 to about 14. Examples of such surfactants are listed in U.S. Pat. No. 3,717,630, Booth, issued Feb. 20, 1973, U.S. Pat. No. 3,332,880, Kessler et al., issued July 25, 1967, and U.S. Pat. No. 4,284,435, Fox, issued August 18, 1981 , which are hereby fully incorporated by reference.

[0018] Moreover, other nonionic surfactants include the condensation products of alkyl phenols having an alkyl group containing from about 8 to about 15 carbon atoms in either a straight chain or branched chain configuration with ethylene oxide, said ethylene oxide being present in an amount from about 2 to about 14 moles of ethylene oxide per mole of alkyl phenol. The alkyl substituent in such compounds can be derived, for example, from polymerized propylene, diisobutylene, and the like. Examples of compounds of this type include nonyl phenol condensed with about 9 moles of ethylene oxide per mole of nonyl phenol, dodecyl phenol condensed with about 8 moles of ethylene oxide per mole of phenol, and the commercially available T-DET® 9.5 marketed by Harcros Chemicals Incorporated. [0019] Other useful nonionic surfactants are the condensation products of aliphatic alcohols with from about 2 to about 14 moles of ethylene oxide. The alkyl chain of the aliphatic alcohol can either be straight or branched, primary or secondary, and may contain from about 8 to about 18 carbon atoms. Examples of such ethoxylated alcohols include secondary alcohol nonionic surfactants such as ENS-70, the condensation product of myristyl alcohol condensed with about 9 moles of ethylene oxide per mole of alcohol, and the condensation product of about 7 moles of ethylene oxide with coconut alcohol (a mixture of fatty alcohols with alkyl chains varying in length from 10 to 14 carbon atoms). Examples of commercially available nonionic surfactants in this type include: Tergitol™ 15-S-7 or 15-S-9 marketed by Union Carbide Corporation; Neodol™ 45-9, Neodol™ 23-6.5, Neodol™ 45-7 and Neodol™ 45-4 marketed by Shell Chemical Company; Kyro EOB marketed by The Procter & Gamble Company; and Berol® 260 and Berol® 266 marketed by Akzo Nobel. Other suitable non-ionic surfactants include Neodol™ ethoxylates, commercially available from Shell Chemicals (Houston, TX) and Tergitol™ surfactants, commercially available from Dow (Midland, Ml). A mixture of nonionic surfactants may also be used.

[0020] Examples of anionic surfactants include, but are not limited to, sulfosuccinates and derivatives, sulfates of ethoxylated alcohols, sulfates of alcohols, sulfonates and sulfonic acid derivatives, sulfates and sulfonates of alkoxylated alkylphenols, phosphate esters, and polymeric surfactants. Suitably, anionic surfactants may include, but are not limited to, alkyl sulfate, ether sulfate, alkyl benzene sulfonate, alpha olefin sulfonate, diphenyloxide disulfonate, alkyl naphthalene sulfonate, sulfosuccinate, sulfosuccinamate, naphthalene-formaldehyde condensate, isethionate, N-methyl taurate, phosphate ester, and ether carboxylate.

[0021] Amphoteric surfactants may include betaines and betaine derivatives. Amphoteric surfactants may also include, but are not limited to, amphoteric imadazoline derivatives and fatty amine and fatty amine ethoxylate derivatives. Amphoteric imadazoline derivatives may include, but are limited to, amphodiacetates, amphoacetates, amphocarboxylates, amphopropionate, amphodipropionate, and hydroxypropyl sulfonate. Fatty amine and fatty amine ethoxylate derivatives may include, but are not limited to, betaines, alkyl betaine, sultaine, dihydroxyethyl glycinate, alkyl amidopropyl betaine, and aminopropionate.

[0022] Cationic surfactants may include amine surfactants, those containing non-quaternary nitrogen, those containing quaternary nitrogen bases, those containing non-nitrogenous bases and combinations thereof. Such surfactants are disclosed in U.S. Pat. No. 3,457,109, Peist, issued July 22, 1969, U.S. Pat. No. 3,222,201 , Boyle, issued Dec. 7, 1965 and U.S. Pat. No. 3,222,213, Clark, issued December 7, 1965, which are hereby fully incorporated by reference.

[0023] One category of cationic surfactants may include quaternary ammonium compounds with the general formula RXYZ N⁺A , wherein R is an aliphatic or cycloaliphatic group having from 8 to 20 carbon atoms and X, Y and Z are members selected from the group consisting of alkyl, hydroxylated alkyl, phenyl and benzyl. A is a water soluble anion that may include, but is not limited to, a halogen, methosulfate, ethosulfate, sulfate and bisulfate. The R group may be bonded to the quaternary group through hetero atoms or atom groups such as -0-, -COO-, - CON-, -N-, and -S-. Examples of such compounds include, but are not limited to, trimethyl- hexadecyl-ammonium sulfate, diethyl-octadecyl-phenyl-ammonium sulfate, dimethyl-dodecyl- benzyl-ammonium chloride, octadecylamino-ethyl-trimethyl-ammonium bisulfate, stearylamido- ethyl-trimethyl-ammonium methosulfate, dodecyloxy-methyl-trimethyl-ammonium chloride, cocoalkylcarboxyethyl-di-(hydroxyethyl)-methyl-ammonium methosulfate, and combinations thereof.

[0024] Another category of cationic surfactants may be of the di-long chain quaternary ammonium type having the general formula XYRR-|N⁺A , wherein X and Y chains may contain an average of from about 12 to about 22 carbon atoms and R and Ri may be hydrogen or C1 to C4 alkyl or hydroxyalkyl groups. Although X and Y may contain long chain alkyl groups, X and Y may also contain hydroxy groups or may contain heteroatoms or other linkages, such as double or triple carbon-carbon bonds, and ester, amide, or ether linkages, as long as each chain falls within the above carbon atom ranges.

[0025] An additional category of cationic surfactant may include the bis(ethoxylated) ammonium quaternary compounds having the general formula:

wherein R is methyl, ethyl or propyl group, R-i is an alkyl group having from 8 to 18 carbon atoms, an alkenyl group having 8 to 18 carbon atoms or mixtures thereof, x is a number from 1 to 40, y is a number from 1 to 40, wherein x + y is between 10 to 60, and A is a water soluble anion. Examples of such compounds include, but are not limited to, alkyl bis(ethoxy) methyl ammonium methyl sulfate (15 moles EO), stearyl methyl bis(ethoxy) ammonium chloride (12 moles EO), stearyl ethyl bis(ethoxy) ammonium ethyl sulfate (15 moles EO), tallow methyl bis(ethoxy) ammonium methyl sulfate (15 moles EO), tallow ethyl bis(ethoxy) ammonium ethyl sulfate (15 moles EO), hydrogenated tallow methyl bis(ethoxy) ammonium chloride (15 moles EO), coco methyl bis(ethoxy) ammonium methyl sulfate (20 moles EO), and combinations thereof.

[0026] Other cationic surfactants may include sulfonium, phosphonium, and mono- or tri- long chain quaternary ammonium materials and those described in U.S. Pat. No. 4,259,217, Murphy, issued March 31 , 1981 , U.S. Pat. No. 4,222,905, Cockrell, September, 16, 1980, U.S. Pat. No. 4,260,529, Letton, issued April 7, 1981 , U.S. Pat. No. 4,228,042, Letton, issued October 14, 1980, and U.S. Pat. No. 4,228,044, Cushman, issued October 14, 1980, each of which is fully incorporated herein by reference.

[0027] Additional cationic surfactants may include ditallowalkyldimethyl (or diethyl or dihydroxyethyl) ammonium chloride, ditallowalkyldimethylammonium methyl sulfate, dihexadecylalkyl (C16) dimethyl (or diethyl, or dihydroxyethyl) ammonium chloride, dioctodecylalkyl (C18) dimethylammonium chloride, dieicosylalkyl (C20) dimethylammonium chloride, methyl (1 ) tallowalkyl amido ethyl (2) tallowalkyl imidazolinium methyl sulfate (commercially available as Varisoft 475 from Ashland Chemical Company), or mixtures of those surfactants.

[0028] Additional surfactants that may be useful according to the disclosure may be found in U.S. Patent Nos. 6,054,139, 6,547,063, and 7,572,933, each of which is incorporated herein by reference in their entireties.

[0029] Suitably, the surfactant of component A may be amphoteric. The surfactant of component A may be a zwitterion. Component A may comprise two or more surfactants. Component A may comprise at least about 1 %, at least about 2%, at least about 5%, or at least about 7% of surfactant by weight. Component A may also comprise less than about 95%, less than about 15%, less than about 10%, or less than about 8% of surfactant by weight. Component A may comprise about 1 to about 95 wt%, about 2 to about 15 wt%, about 5 to about 15 wt%, about 5 to about 10 wt%, or about 7 to about 8 wt% of surfactant.

[0030] The enzyme of component A may be at least one of a protease, a lipase, a hydrolase, a cellulase, an amylase, and a combination thereof. Component A may comprise an amylase and a protease. Component A may comprise less than about 10 wt%, less than about 5 wt%, less than about 2 wt%, less than about 1 wt%, or less than about 0.5 wt% of enzyme. There are many materials derived from plant, animal, and microbial sources that have been known to those skilled in the art to be rich sources of enzymes. These source materials may be used with full, partial, or no purification of enzymes to obtain enzymes for use in the composition. For example, the enzyme may be exogenously produced from a recombinant or wild-type organism. The enzyme may be purified. The enzyme may be a fermentation product.

[0031] The balance of component A may or may not comprise preservatives, fragrances, and enzyme stabilizers such as propylene glycol and borates.

[0032] Suitably, component A is commercially available as ReNew A (Diversey, Sturtevant, Wl).

[0033] Component B may comprise at least one surfactant. The surfactant may include, but not be limited to, a non-ionic surfactant, a cationic surfactant, an anionic surfactant, a low-foam surfactant, or a combination thereof. The at least one surfactant of component B may be a detersive surfactant. Examples of surfactants are provided above with respect to component A.

[0034] In certain embodiments, component B may comprise a low-foam surfactant. Low- foam surfactants may include, but are not limited to, nonionic ethylene oxide (EO) containing surfactants, capped alkoxylates such as capped ethoxylates, capped alcohol alkoxylates such as capped alcohol ethoxylates, EO/PO (ethylene oxide group/propylene oxide group block copolymer, fatty alcohol alkoxylates, alkoxylated amines such as ethoxylated amines, amine surfactants, low cloud point nonionic surfactants (as detailed below), and those set forth above with respect component A. Suitably, low-foam surfactants may include, but are not limited to, Triton™ surfactants such as Triton™ DF-12, Triton™ CF-32 and Triton™ CF-10 (Dow, Midland, Ml); Pluronic® surfactants such as Pluronic® 25-R-2, Pluronic® N-3, Pluronic® SLF-18, Pluronic® L-61 , and Pluronic® L-62 (BASF, Florham Park, NJ); and Plurafac® surfactants such as Plurafac® LF-403, Plurafac® LF-101 , and Plurafac® LF-400 (BASF, Florham Park, NJ).

[0035] In certain embodiments, the surfactant of component B may be non-ionic. Suitably, the surfactant of component B may be selected from the group consisting of a primary alcohol ethoxylate and a secondary alcohol ethoxylate. The surfactant of component B may be an alkyl phenol, although alkyl phenol surfactants may degrade to non-environmentally-friendly compounds, which may not be desired in certain applications. The surfactant of component B may have a hydrophilic-lipophilic balance (HLB) of at least about 8, at least about 9.5, at least about 10, or at least about 1 1.2. The surfactant of component B may have a HLB of less than about 14, less than about 12.5, less than about 12, or less than about 1 1.8. The surfactant of component B may have a HLB of about 8 to about 14, about 9.5 to about 12.5, about 10 to about 12, and about 1 1.2 to about 1 1 .8. Component B may comprise any combination of two or more non-ionic surfactants combined in a ratio to achieve an HLB of at least about 8, at least about 9.5, at least about 10, or at least about 1 1 .2. Component B may comprise any combination of two or more non-ionic surfactants combined in a ratio to achieve an HLB of less than about 14, less than about 12.5, less than about 12, or less than about 1 1.8. Component B may comprise any combination of two or more non-ionic surfactants combined in a ratio to achieve an HLB of about 8 to about 14, about 9.5 to about 12.5, about 10 to about 12, and about 1 1 .2 to about 1 1.8. HLB of a surfactant is a measure of the degree to which it is hydrophilic or lipophilic, determined by calculating values for the different regions of the molecule. HLB values may be found, for example, in McCutcheon's Emulsifiers & Detergents (2009, MC Publishing Company, Glen Rock, NJ). For example, component B may include Tergitol™ 15-S-7, commercially available from Dow (Midland, Ml). Component B may include at least one of Neodol™ 91-6, Neodol™ 91-2.5, Neodol™ 23-6.5, Neodol™ 23-3, Neodol™ 45- 7, Neodol™ 45-4, Neodol™ 25-3, Neodol™ 25-12, Neodol™ 25-9, Neodol™ 91-8, Neodol™ 25-5, Neodol™ 25-7 (commercially available from Shell Chemicals, Houston, TX); Triton™ surfactants such as Triton™ DF-12, Triton™ CF-32, Triton™ CF-10 (Dow, Midland, Ml); Plurafac® LF-403 (BASF, Florham Park, NJ), Pluronic® surfactants such as Pluronic® 25-R-2, Pluronic® N-3, Pluronic® SLF-18, Pluronic® L-62 (BASF, Florham Park, NJ); or a combination thereof. Component B may comprise at least two surfactants combined in any ratio including, but not limited to, 1 :1 , 1 :2, 1 :3, 1 :4, 1 :5, 1 :6, 1 :7, 1 :8, 1 :9, 1 :10, 1 :15, 15:1 , 10:1 , 9:1 , 8:1 , 7:1 , 6:1 , 5:1 , 4:1 , 3:1 , or 2:1. One suitable component B is commercially available as ReNew B (Diversey, Sturtevant, Wl). Component B may comprise Triton™ DF-12, Plurafac® LF-403, or a combination thereof.

[0036] Component C may comprise a pH control agent. The pH control agent may comprise an acid, a base, or a combination thereof. Component C may comprise an acid such as mineral acids, organic acids, or any other acid effective to drive ammonia to ammonium in the air scrubber. Component C may comprise an alkaline metal salt. Suitably, component C may comprise citric acid. Suitably, component C is commercially available as ReNew Balance (Diversey, Sturtevant, Wl). Component C may be added to the air scrubber in an amount effective to maintain the pH of the solution in the air scrubber at a pH effective to eliminate malodor compounds such as H₂S as well as NH₃. With a pKa of 9.3 for the reaction NH₃ + H⁺□ NH₄ ⁺, a pH of about 7.3 may drive the reaction to about 99% NH₄ ⁺. As such, NH₃ may be one malodorous compound formed in a rendering plant that may be converted at low pH to NH₄ ⁺, thus converting malodor or noxious gas to a water soluble salt that may not evaporate or smell bad but may remain in the recirculating water. H₂S may be eliminated at high pH. H₂S may not be a factor for some air scrubbers, as H₂S is a metabolic by-product of anaerobic bacteria and many air scrubbers are fully aerated. As such, the pH of an air scrubber may be balanced between about 7.5 and lower for controlling NH₃ levels, and about 7.5 and higher for controlling H₂S levels. Controlling NH₃ levels includes controlling low molecular weight organic nitrogen- containing compounds like amines and amine oxides, and controlling H₂S levels also includes controlling low molecular weight sulfur-containing compounds like mercaptans and thiols. The pH of the air scrubber may be maintained at a pH of at least about 5.0, at least about 5.5, at least about 6.0, at least about 6.5, at least about 6.6, at least about 6.7, at least about 6.8, at least about 6.9, at least about 7.0, at least about 7.1 , at least about 7.2, at least about 7.3, at least about 7.4, or at least about 7.5. The pH of the air scrubber may be maintained at a pH of less than about 9.0, less than about 8.8, less than about 8.6, less than about 8.4, less than about 8.2, less than about 8.0, less than about 7.9, less than about 7.8, less than about 7.7, or less than about 7.6. Suitably, the pH of the air scrubber is maintained at a pH of about 5.0 to about 9.0, about 6.0 to about 9.0, about 6.8 to about 8.0, about 7.0 to about 7.9, about 7.3 to about 7.8, and about 7.5 to about 7.6. Suitably, component C is added to the air scrubber in amount effective to maintain the pH of the air scrubber at about 7.5-7.6.

[0037] Compositions may include component D. Component D may comprise a chemical defoamer. Examples of chemical defoamers include, but are not limited to, silicone-based defoamers; steric acids or fatty acids such as long chain fatty acids; fatty alcohols; oils such as paraffin, mineral oil, and vegetable oil; ethoxylated nonionic surfactants used above their cloud point, EO/PO (ethylene oxide group/propylene oxide group) block copolymers; and low-foaming surfactants such as capped ethoxylates. Suitably, the defoamer may be hydrophobic silica. In certain embodiments, component D may comprise at least one of Antifoam SE-21 (Dow Corning), Silfoam SD860, Silfoam SD168 (Wacker Corp), Tego 3062 (Goldschmidt), or a combination thereof. Many nonionic ethylene oxide derivative surfactants, as described above for component B, are water soluble and have cloud points below the intended use temperature of the composition (as described below), and therefore may be useful defoaming agents. As the temperature is increased, the cloud point may be reached, at which point the surfactant precipitates out of solution and may function as a defoamer. The surfactant may act as a defoamer when used at temperatures at or above this cloud point. The cloud point of nonionic surfactants is defined as the temperature at which a 1 wt % aqueous solution becomes insoluble in water. Suitably, a chemical defoamer of component D may comprise surfactants having cloud points that are below the intended use temperature of the air scrubber composition. Examples of ethylene oxide derivatives include, but are not limited to, polyoxyethylene-polyoxypropylene block copolymers, alcohol alkoxylates (e.g., Triton□ DF-12), low molecular weight EO containing surfactants, and derivatives thereof. Some examples of polyoxyethylene-polyoxypropylene block copolymers include, but are not limited to, the following:

_(EO)_x_(PO)_y_(EO)_x

_(PO)_y_(EO)_x_(PO)_y

_(PO)y_(EO)x_(PO)y_(EO)x_(PO)y

(EO)x (PO)y (PO)y(EO) x

\ /

N -N

/ \

(EO)x(PO)y (PO)y(EO) x

(PO)y(EO)x (EO) x(PO)y

\ /

N- N

/ \

(PO)y(EO)x (EO) x(PO)y wherein EO represents an ethylene oxide group, PO represents a propylene oxide group, and x and y reflect the average molecular proportion of each alkylene oxide monomer in the overall block copolymer composition. Some examples of block copolymer surfactants include, but are not limited to, commercial products such as Pluronic® surfactants such as Pluronic® 25-R-2 and TETRONIC® surfactants (BASF, Florham Park, NJ). It is believed that one skilled in the art would understand that a nonionic surfactant with an unacceptably high cloud point temperature or an unacceptably high molecular weight would either produce unacceptable foaming levels or fail to provide adequate defoaming capacity in a detersive or cleaning composition. Other examples of defoamers include Plurafac® alcohol alkoxylates such as Plurafac® LF-403 (BASF, Florham Park, NJ) and Triton™ surfactants such as Triton D DF-12 (Dow, Midland, Ml) Component D may be added to the other components in combination with or separately. Component D may be added to the air scrubber composition to a final concentration of at least about 0.1 %, at least about 0.5%, at least about 1 %, or at least about 3% (wt%). Component D may be added to the air scrubber composition to a final concentration of less than about 5%, less than about 3%, or less than about 1 %. The concentration of component D may be about 25 to about 400 ppm, and may be about 25-200 ppm.

[0038] A mechanical defoamer may be used in conjunction with the compositions or as an alternative to component D. Mechanical defoamers are known by those of skill in the art and may include, but are not limited to, circulating disks, ultra sound, pulsed lasers, fluidized beds, high pressure spray nozzles. Examples of mechanical defoamers are described in Takesono et al., Journal of Chemical Technology & Biotechnology (2002) 78: 48-55; Deshpande et al. Chemical Engineering and Processing (2000) 39: 207-217; and U.S. Patent Nos. 6,599,948; 6,962,618; and 5,299,175, each of which is fully incorporated by reference.

[0039] The compositions may comprise component E. Component E comprises at least one enzyme, in addition to any enzyme present in any of the other components, e.g., component A. Enzymes include, but are not limited to, a protease, a lipase, a hydrolase, a cellulase, an amylase, a mannanase, and a decarboxylase. There are many materials derived from plant, animal, and microbial sources that have been known to those skilled in the art to be rich sources of enzymes. These source materials may be used with full, partial, or no purification of enzymes to obtain enzymes for use in the composition. For example, the enzyme may be exogenously produced from a recombinant or wild-type organism. The enzyme may be purified. In certain embodiments, the enzyme may comprise a lipase. The lipase may be, for example, LIPEX® 100 L from Novozymes (Bagsvaerd, Denmark). The enzyme may be a fermentation product. Component E may be added such that the final concentration of enzyme in the composition is at least about 1 ppm, at least about 2 ppm, at least about 3 ppm, at least about 4 ppm, at least about 5 ppm, at least about 6 ppm, at least about 7 ppm, at least about 8 ppm, at least about 9 ppm, at least about 10 ppm, at least about 1 1 ppm, at least about 12 ppm, at least about 13 ppm, at least about 14 ppm, or at least about 15 ppm. Component E may be added such that the final concentration of enzyme in the composition is less than about 40 ppm, less than about 35 ppm, less than about 30 ppm, less than about 25 ppm, or less than about 20 ppm. Component E may be added such that the final concentration of enzyme in the composition is about 2-40 ppm, about 5-40 ppm, 10-35 ppm, about 15-30 ppm, or about 5-15 ppm. [0040] As discussed above, the air scrubber composition may comprise at least one of components A, B, C, D, and E. The components may be pre-mixed or added individually or in any combination. The air scrubber composition may comprise component A. The air scrubber composition may comprise component B. Component B may comprise at least one of capped alkoxylate, an EO/PO (ethylene oxide group/propylene oxide group) block copolymer, a fatty alcohol alkoxylate, a nonionic ethylene oxide (EO) containing surfactant, an alkoxylated amine, an amine surfactant, a low cloud point nonionic surfactant, and a combination thereof. The air scrubber composition may comprise component A and component B comprising a low-foaming surfactant. The air scrubber composition may comprise components B and E. The air scrubber composition may comprise components A and E. The air scrubber composition may comprise components A, B, and E. The air scrubber composition may comprise components A, B, C, D, and E. The air scrubber composition may comprise component A, component B comprising a low-foaming surfactant, and component E. The air scrubber composition may comprise components B, C, and D. The air scrubber composition may comprise components A, C, and D. Additional variations and combinations are envisioned.

[0041] The air scrubber composition may optionally include additional ingredients. Additional ingredients may include, but are not limited to, chelating agents, dispersants, corrosion inhibitors, fragrance or odor counteractants, enzymes, bacteria, anti-microbial agents, acid, alkaline metal salts, tracing compounds, hydrotropes, solvents, viscosity modifiers, and appearance modifiers known to those skilled in the art. Examples of chelants include, but are not limited to, EDTA, NTA, and poly phosphates. Examples of dispersants include, but are not limited to, acrylic acid homopolymers, polymers of acrylic and maleic acids and hydrophobically modified versions of these polymers. Examples of corrosion inhibitors include, but are not limited to, nitrite salts, and silicate and polysilicate salts. Examples of odor counteractants include, but are not limited to, cyclodextrins. Examples of hydrotropes include, but are not limited to, sodium xylene sulfonate and sodium cumene sulfonate. Examples of solvents include, but are not limited to, high boiling gylcol ethers. Examples of viscosity modified include, but are not limited to, natural gums such as guar and synthetic polymeric resins such as carboxy methyl cellulose and Carbopol brand polymers.

[0042] The air scrubber composition may be used in the air scrubber at an operating temperature of at least about 10°C, at least about 1 1 °C, at least about 12°C, at least about 13°C, at least about 14°C, at least about 15°C, at least about 16°C, at least about 17°C, at least about 18°C, at least about 19°C, or at least about 20°C. The air scrubber composition may be used in the air scrubber at an operating temperature of less than about 80°C, less than about 75°C, less than about 70°C, less than about 65°C, less than about 60°C, less than about 55°C, less than about 50°C, less than about 45°C, less than about 40°C, or less than about 35°C. The air scrubber composition may be used in the air scrubber at an operating temperature of about 10°C to about 80°C, about 1 1 °C to about 75°C, about 12°C to about 70°C, about 13°C to about 60°C, about 14°C to about 50°C, and about 15°C to about 45°C. In certain embodiments, the operating temperature may be less than about 50°C. In certain embodiments, the operating temperature may be below about 40°C. The operating temperature may be on at which the malodor is minimized. Lower temperature increases solubility of volatile components.

[0043] As shown in the Examples, it was discovered that the concentration of hardness ions in the wet air scrubber may affect the efficiency of the composition in cleaning the wet air scrubber. Hardness ions may be present in water of the air scrubber fluid stream. Hardness ions may include, but are not limited to, calcium and magnesium. Soluble calcium may have a negative impact on the ability of component E to remove FOG in a wet air scrubber. Without being limited by theory, inclusion of component A and/or component B in the wet air scrubber composition may prevent hardness ions from impeding the activity of component E.

[0044] Surfactants may emulsify FOG on wet air scrubber media but may also have a tendency to foam. Foam may interfere with the operation of the wet air scrubber. The cloud point of a fluid is the temperature at which dissolved solids are no longer completely soluble and, as such, the dissolved solids precipitate as a second phase to give the fluid a cloudy appearance. At temperatures greater than the cloud point of a surfactant, the surfactant may not produce foam. At temperatures less than the cloud point of a surfactant, the surfactant may produce foam.

[0045] In certain embodiments, further provided are methods of operating a wet air scrubber comprising (a) adding a composition comprising a surfactant to a fluid stream in the wet air scrubber; (b) maintaining a first temperature of the fluid stream for a first period of time; and (c) maintaining a second temperature of the fluid stream for a second period of time. The first temperature may be greater than the cloud point of the surfactant, and the second temperature may be less than the cloud point of the surfactant. The composition may comprise at least one of components A, B, C, D and E. For example, an air scrubber may be operated for a first time period at a first temperature greater than the cloud point of a surfactant in the composition, for example, in component B, to prevent production of foam. An air scrubber may be maintained for a second time period at a second temperature less than the cloud point of the surfactant, to continue to assist in cleaning of the wet air scrubber. This may be accomplished, e.g., by turning off the air scrubber.

[0046] The first and second periods of time may independently be at least about 15 min, at least about 30 min, at least about 1 h, at least about 4 h, at least about 6 h, at least about 8 h, at least about 12 h, at least about 24 h, at least about 36 h, at least about 48 h, at least about 72 h, at least about 96 h, at least about 1 week, at least about 2 weeks, or at least about 3 weeks. The first and second periods of time may independently be less than about 6 weeks, less than about 5 weeks, less than about 4 weeks, or less than about 3 weeks. The first and second periods of time may independently be about 30 min to about 6 weeks, about 12 h to about 5 weeks, about 36 h to about 4 weeks, or about 72 h to about 3 weeks.

[0047] For example, the cloud point of Triton™ DF-12 is about 17°C (about 63°F). As such, an air scrubber may be operated for a first time period at a first temperature greater than about 17°C to prevent production of foam, and the air scrubber may be turned off and maintained for a second time period at a second temperature less than about 17°C to continue to assist in cleaning of the wet air scrubber. The temperature of the wet air scrubber composition may be alternated between temperatures greater than and less than the cloud point or between the first and second temperatures.

[0048] The air scrubber compositions may remove FOG, reduce the rate of FOG accumulation, prevent the accumulation of FOG, or combinations thereof. The air scrubber compositions may remove at least about 20%, at least about 30%, at least about 40% or at least about 50% of the FOG in an air scrubber. The air scrubber compositions may remove less than about 100%, less than about 95%, less than about 90%, or less than about 85% of the FOG in an air scrubber. The air scrubber compositions may remove about 20% to about 100%, about 30% to about 95%, about 40% to about 90%, or about 50% to about 85% of the FOG in an air scrubber.

[0049] In certain embodiments, the air scrubber compositions may be low-foam. In a Venturi Scrubber, for example, about 6 inches of foam or less at the bottom of the air scrubber may be low foam and suitable for normal operation, about 6 to about 18 inches of foam at the bottom of the air scrubber may be moderate foam for normal operation, and about 18 to about 72 inches of foam or more at the bottom of the air scrubber may be high foam for normal operation. Too much foam may interfere with operations of the air scrubber. For example, high foam may result in composition leaking out of outlet ducts, build-up of foam around the drain, and damage to equipment including electrical equipment.

[0050] In certain embodiments, the air scrubber compositions may have low turbidity. For example, turbidity of the air scrubber composition may be at least about 100, at least about 200, at least about 300, at least about 400, or at least about 500 FAU. Turbidity of the air scrubber composition may be less than about 5000, less than about 4500, less than about 4000, less than about 3500, or less than about 3000 FAU. Turbidity of the air scrubber composition may be about 100 to about 5000, about 200 to about 4500, about 300 to about 4000, about 500 to about 3500, or about 600 to about 3000 FAU.

[0051] Components A, B, C, D, and E may be added to the air scrubber individually or in combination. Components A, B, and E may be continually added to the recirculating water in the air scrubber to maintain the appropriate concentration. The target concentration for components A, B, C, D, and E may be determined based on the Chemical Oxygen Demand (COD, mg/L) of the recirculating water in the air scrubber. COD is a measure of how much organic material is entering the water, and is an indication of the VOC level. The COD of the recirculating water may be determined by on-site measurement or by sending a sample to an off-site laboratory. As described below, the COD levels may depend on the organic loading of the air coming into the air scrubber, and this loading may fluctuate over time based on what raw materials are running through the cooker and include VOCs and aerosolized organic materials such as fat, oil, grease, bone meal, and protein. Once a representative value is determined, the following equations may be used to calculate the target concentrations of components A and B for each air scrubber:

[Component A] = (0.075)(COD in mg/L) + 125 = mg/L of Component A

[Component B] = (0.070)(COD in mg/L) + 25 = mg/L of Component B

The concentration of COD in the recirculating water of a wet air scrubber is typically less than about 1 ,000 mg/L, but compositions according to the invention may be used with any COD concentration.

[0052] For example, components A and B may be added to a final combined concentration of at least about 1 ppm, at least about 10 ppm, or at least about 100 ppm. Components A and B may be added to a final combined concentration of less than about 750 ppm, less than about 400 ppm, or less than about 300 ppm. Components A and B may be added to a final combined concentration of about 1 ppm to about 750 ppm, about 1 to about 400 ppm, about 10 to about 300 ppm, or about 100 to about 300 ppm. Component A may be added to a final concentration of at least about 50 mg/L, at least about 100 mg/L, or at least about 125 mg/L. Component A may be added to a final concentration of less than about 400 mg/L, less than about 300 mg/L, or less than about 250 mg/L. Component A concentrations may range from about 50 to about 400 mg/L, about 100 to about or about 300 mg/L, or about 125 to about 250 mg/L. Component B may be added to a final concentration of at least about 10 mg/L, at least about 20 mg/L, or at least about 25 mg/L. Component B may be added to a final concentration of less than about 200 mg/L, less than about 95 mg/L, or less than about 75 mg/L. Component B concentrations may range from about 10 to about 200 mg/L, about 20 to about 95 mg/L, or about 25 to about 75 mg/L. The ratio of component A to component B may be at least about 1 :1 , at least about 1 :2, at least about 1 :3, at least about 1 :4, at least about 1 :5, at least about 1 :6, at least about 1 :7, or at least about 1 :8. The ratio of component A to component B may be less than about 1 :1 , less than about 1 :2, less than about 1 :3, less than about 1 :4, less than about 1 :5, less than about 1 :6, less than about 1 :7, or less than about 1 :8. The ratio of component A to component B may be about 1 :1 , about 1 :2, about 1 :3, about 1 :4, about 1 :5, about 1 :6, about 1 :7, or about 1 :8. In certain embodiments, the ratio of component A to component B may be about 1 :2 to about 1 :6. In certain embodiments, the ratio of component A to component B may be about 1 :4.

[0053] Component A and component B may be continually added to the recirculating water in the air scrubber to maintain the appropriate concentration, which is further detailed below. The volume of component A and component B to be delivered may be determined as follows:

Hourly Component A Dosage = (Target)(MU Rate)( 0.228) = mL/h Component A

Hourly Component B Dosage = (Target)(MU Rate)( 0.228) = mL/h Component B wherein Target = Target concentration of component in mg/L, and MU Rate = Fresh water supply (Make Up) in gallons per hour. The concentrations of components A and B may be monitored by taking measurements of the volume of composition delivered and the volume of make up water being supplied to the air scrubber, and then calculating the maintenance dose as follows: Component A Concentration = (Component A Volume)(4.39) = mg/L Component A

(Make Up Rate)

wherein Component A Volume = Milliliters of Component A delivered to the air scrubber in 1 hour, and Make up Rate = Volume of make up water to the air scrubber in gallons per minute. The concentration of component B may be calculated in the same way.

[0054] The compositions may be added to recirculating water in an air scrubber. The composition may be added continuously to the air scrubber to maintain a concentration of at least one of the components A, B, C, D, and E as described above. The compositions may be used in a much less amount than conventional air scrubber treatment solutions and still effectively remove malodor. The compositions may also keep the media of the air scrubbers cleaner than with conventional air scrubber treatment solutions, that is, compositions may be used in air scrubbers without the need for periodic off-line alkaline detergent cleaning to remove grease. Media in air scrubbers may be cleaned during operation (on-line) with compositions according to the disclosure while simultaneously removing odor from air of a rendering plant.

[0055] To determine how much of the composition to add to the air scrubber during operation, a variety of mechanisms known in the art may be used. For example, a pH detector may be used to monitor the pH of the solution in the air scrubber. The pH of the solution in the air scrubber may be maintained at suitably ranges as detailed above. For example, if the pH goes below about 7.5-7.6, less component C may be added to the air scrubber, and if the pH goes above about 7.5-7.6, more component C may be added to the air scrubber.

[0056] Alternatively or in combination with a pH monitoring system, another embodiment of the invention is to monitor the concentration of NH₃ in the air scrubber with an ion-selective electrode. The organic load in an air scrubber as indicated by the NH₄ ⁺ concentration may vary with time due to fluctuations in raw material composition (e.g. relative fat and protein content, percent moisture, presence of hair or feathers) and raw material availability in the rendering plant. As the raw material changes in the rendering plant from hour to hour, day to day, or season to season, the concentration and composition of gases entering the air scrubber may change. The primary organic compound entering the air scrubber may be ammonia (NH₃), and this gas may be used as a marker to determine the air scrubber water treatment requirements. Specifically, an ammonium ion selective electrode (ISE) may be used in the recirculating water (located in the sump or drain) to detect total NH₄ ⁺ in solution. A monitoring system and control loop may directly measure NH₄ ⁺ in solution and provide a millivolt signal back to a dual channel controller. The ISE may be connected to a controller (for example, Rosemount model 1056), which may supply a 4-20 mA signal to a pump controller. The pump controller may manage the pump frequency and duration for each component being fed into the air scrubber. This two channel controller may be configured to show ammonium concentration on one channel, and pH on the other, or may be connected to two independent ammonium ion ISE sensors. As such, components A and B may be fed into the air scrubber based on feedback from an ion selective electrode (ISE) monitoring and control feedback system. If the concentration of NH₃ high, then more of a composition comprising component A and B may be added to the air scrubber. If the concentration of NH₃ is low, then less of a composition comprising component A, B, and/or C may be added to the air scrubber. For example, about 250 mg/L of component A and about 75 mg/L of component B may be added to the air scrubber for ammonium levels of 1 ,000 mg/L in the recirculating water. If less ammonium is detected, for example, the amounts of components A and B may be reduced to at least about 125 and about 25 mg/L, respectively. The temperature of the inlet gas stream from the rendering plant may be less than 100°F, as hot gases may not dissolve into water and may therefore leave the scrubber as a malodor.

[0057] U.S. Patent No. 4,206,074 issued June 3, 1980, U.S. Patent No. 4,780,237 issued October 25, 1988, EP 1 ,682,643 granted August 22, 2007, and International Patent Application No. PCT/US 10/47344 filed August 31 , 2010, each of which is hereby incorporated fully by reference, may each contain components that are useful in the methods and compositions for cleaning air scrubbers.

[0058] Embodiments of the disclosure are further detailed in the examples below.

EXAMPLES

[0059] In the examples, mg/L refers to an amount of component being added in mg to a volume (L) of make up water in the air scrubber.

[0060] Example 1 : Evaluation of Lipase to Remove Tallow from a Plastic Surface with Varying [Ca²⁺]

[0061] A 125 mL Erlenymeyer flask made of polymethylpentene (PMP) were cleaned by gently scrubbing with a 50°C solution of 5% DAWN® dish soap (Procter and Gamble, Cincinnati, OH) and rinsing at least 5 times in tap water. The washed flasks were dried for 1 h at 100°C. The flasks were then removed from the oven and allowed to cool for at least 30 min. Each flask was weighed to the nearest 0.1 mg.

[0062] Yellow grease (unrefined tallow) was melted at 100°C, and 0.25 mL of melted grease was distributed in a continuous band along the inside periphery of an Erienmeyer flask. The lard was allowed to solidify by remaining at room temperature for 30 min. Each flask was then weighed again to the nearest 0.1 mg.

[0063] An aliquot of 50 mL of various enzyme/surfactant compositions was added to each flask. The enzyme/surfactant compositions were as detailed in Table 1. When used, the lipase added was LIPEX® 100 L from Novozymes (Bagsvaerd, Denmark). The samples were placed on a rotary shaker for 13 h at 200 rpm and 30°C. Compositions were then removed from the flasks, and any loosely adhering yellow grease was removed by gently rinsing the flasks 4 times with cold tap water. The flasks were dried for 1 h at 100°C. The flasks were removed from the oven, allowed to cool for at least 30 min, and weighed to the nearest 0.1 mg.

Enzyme/Surfactant Compositions.

[0064] Results are shown in Table 2. As shown, a greater concentration of calcium reduced the performance of the composition in removing FOG.

Table 2. Weight of flasks.

[0065] Example 2: Evaluation of Lipase to Remove Tallow from a Plastic Surface with Varying pH

[0066] A 125 mL Erienymeyer flask made of polymethylpentene (PMP) were cleaned by gently scrubbing with a 50°C solution of 5% DAWN® dish soap (Procter and Gamble, Cincinnati, OH) and rinsing at least 5 times in tap water. The washed flasks were dried for 1 h at 100°C. The flasks were then removed from the oven and allowed to cool for at least 30 min. Each flask was weighed to the nearest 0.1 mg. [0067] Yellow grease (unrefined tallow) was melted at 100°C, and 0.25 mL of melted grease was distributed in a continuous band along the inside periphery of an Erienmeyer flask. The lard was allowed to solidify by remaining at room temperature for 30 min. Each flask was then weighed again to the nearest 0.1 mg.

[0068] An aliquot of 50 mL of various enzyme/surfactant compositions was added to each flask. The enzyme/surfactant compositions were as detailed in Table 3. When used, the lipase added was LIPEX® 100 L from Novozymes (Bagsvaerd, Denmark). The samples were placed on a rotary shaker for 14 h at 200 rpm and 30°C. Compositions were then removed from the flasks, and any loosely adhering yellow grease was removed by gently rinsing the flasks 4 times with cold tap water. The flasks were dried for 1 h at 100°C. The flasks were removed from the oven, allowed to cool for at least 30 min, and weighed to the nearest 0.1 mg.

Enzyme/Surfactant Compositions.

[0069] Results are shown in Table 4. As shown, pH affected the removal of grease. A pH of about 7.8 was optimal for FOG removal, perhaps due to optimal enzyme performance at this pH.

Table 4. Weight of flasks.

[0070] Example 3

[0071] A 125 mL Erienymeyer flask made of polymethylpentene (PMP) were cleaned by gently scrubbing with a 50°C solution of 5% DAWN® dish soap (Procter and Gamble, Cincinnati, OH) and rinsing at least 5 times in tap water. The washed flasks were dried for 1 h at 100°C. The flasks were then removed from the oven and allowed to cool for at least 30 min. Each flask was weighed to the nearest 0.1 mg. [0072] Yellow grease (unrefined tallow) was melted at 100°C, and 0.25 mL of melted grease was distributed in a continuous band along the inside periphery of an Erienmeyer flask. The lard was allowed to solidify by remaining at room temperature for 30 min. Each flask was then weighed again to the nearest 0.1 mg.

[0073] An aliquot of 50 mL of various enzyme/surfactant compositions was added to each flask. The enzyme/surfactant compositions were as detailed in Table 5. The samples were placed on a rotary shaker for 12-14 h at 200 rpm and 30°C. Compositions were then removed from the flasks, and any loosely adhering yellow grease was removed by gently rinsing the flasks 4 times with cold tap water. The flasks were dried for 1 h at 100°C. The flasks were removed from the oven, allowed to cool for at least 30 min, and weighed to the nearest 0.1 mg.

Table 5. Enzyme/Surfactant Compositions.

[0074] Results are shown in Table 6 and were compared with those from Example 2. As shown, pH affected the removal of FOG, and without lipase, a greater pH was needed to remove the FOG.

Table 6. Weight of flasks.

[0075] Example 4: Evaluation of Lipase to Remove Tallow from a Plastic Surface with Varying [Ca²⁺] and Surfactant Concentrations

[0076] A 125 mL Erienymeyer flask made of polymethylpentene (PMP) were cleaned by gently scrubbing with a 50°C solution of 5% DAWN® dish soap (Procter and Gamble, Cincinnati, OH) and rinsing at least 5 times in tap water. The washed flasks were dried for 1 h at 100°C. The flasks were then removed from the oven and allowed to cool for at least 30 min. Each flask was weighed to the nearest 0.1 mg. [0077] Yellow grease (unrefined tallow) was melted at 100°C, and 0.25 mL of melted grease was distributed in a continuous band along the inside periphery of an Erienmeyer flask. The lard was allowed to solidify by remaining at room temperature for 30 min. Each flask was then weighed again to the nearest 0.1 mg.

[0078] An aliquot of 50 mL of various enzyme/surfactant compositions was added to each flask. The enzyme/surfactant compositions were as detailed in Table 7. When used, the lipase added was LIPEX® 100 L from Novozymes (Bagsvaerd, Denmark). All compositions included 0.1 M Tris buffer. The samples were placed on a rotary shaker for 12-14 h at 200 rpm and 30°C. Compositions were then removed from the flasks, and any loosely adhering yellow grease was removed by gently rinsing the flasks 4 times with cold tap water. The flasks were dried for 1 h at 100°C. The flasks were removed from the oven, allowed to cool for at least 30 min, and weighed to the nearest 0.1 mg.

Enzyme/Surfactant Compositions.

[0079] Results are shown in Table 8. In the presence of surfactants, adding calcium to lipase had no effect on the removal of FOG. Without surfactants, adding calcium to lipase hindered the removal of FOG. In the presence of calcium, adding surfactant to lipase improved the removal of FOG. Without calcium, adding surfactants to lipase had no effect on the removal of FOG. Without calcium, adding lipase to surfactants improved the removal of FOG. In the presence of surfactants with or without calcium, adding lipase improved the removal of FOG.

[0080] In the absence of calcium, surfactant was not required for efficient removal of FOG, and increasing the surfactant concentration improved the removal of FOG. Optimal removal of FOG occurred with a lipase concentration of 10-25 ppm. In the presence of calcium, surfactants alone were inadequate for removing FOG, but surfactants with enzymes did improve removal of FOG.

Table 8. Weight of flasks.

[0081] Example 5

[0082] A composition comprising 200 ppm ReNew A (Diversey, Sturtevant, Wl), 100 ppm ReNew B (Diversey, Sturtevant, Wl), and an effective amount of ReNew C (Diversey, Sturtevant, Wl) to a pH of about 7.2 to about 8.0 is used in at least one commercially-available wet air scrubber. Lipase (LIPEX® 100 L from Novozymes, Bagsvaerd, Denmark) is added to the fluid stream of the air scrubber to a final concentration of about 5 ppm and increased continuously in increments of about 5 ppm to a final concentration of about 25 ppm. With lipase included in the fluid stream, the pH of the fluid stream is maintained at about pH 7.6 to 8.0. The temperature of the fluid stream is about 80-100°F (about 26-40°C) for 6 days during each week. For 1 day each week, the air scrubber is turned off, allowing the temperature of the air scrubber fluid stream to fall to ambient temperature, which may be about 34-40°F (1-5°C). The air scrubber is run with lipase for about 4 to 6 weeks. A satisfactory foam level of low to no foam is maintained, and the composition is expected to do at least one of reduce FOG accumulation, prevent FOG accumulation, and remove FOG.

[0083] Thus, the disclosure provides, among other things, a composition for cleaning and operating wet air scrubbers.

Claims

CLAIMS We claim:

1. A method of operating a wet air scrubber, the method comprising:

(a) adding a composition comprising a surfactant to a fluid stream in the wet air scrubber;

(b) maintaining a first temperature of the fluid stream for a first period of time;

(c) maintaining a second temperature of the fluid stream for a second period of time, wherein the first temperature is greater than the cloud point of the surfactant, and the second temperature is less than the cloud point of the surfactant.

2. The method of claim 1 , wherein the first temperature is at least about 20°C, and wherein the second temperature is less than about 20°C.

3. The method of claim 1 , wherein the first temperature is at least about 15°C, and wherein the second temperature is less than about 15°C.

4. The method of any one of the above claims, wherein the first period of time is about 72 h to about 3 weeks, and wherein the second period of time is about 72 h to about 3 weeks.

5. The method of any one of the above claims, wherein the composition further comprises at least one enzyme.

6. The method of any one of the above claims, wherein the composition comprises at least one of component A and component B, and

(ii) component A comprises:

(1 ) an amphoteric surfactant; and

(2) an enzyme; and

(ii) component B comprises at least one of:

(1 ) a detersive surfactant and a defoamer;

(2) at least one low-foam surfactant; and

(3) a combination thereof.

7. The method of claim 6, wherein the composition further comprises component C and component D, wherein component C comprises at least one acid and component D comprises at least one defoamer.

8. The method of claim 5, wherein the enzyme comprises a lipase.

9. A method of operating a wet air scrubber, the method comprising:

(a) adding to a fluid stream in the wet air scrubber a composition comprising component E and at least one of component A and component B, wherein

(i) component A comprises:

(1 ) a surfactant; and

(2) an enzyme;

(ii) component B comprises at least one of:

(1 ) a detersive surfactant and a defoamer;

(2) at least one low-foam surfactant; and

(3) a combination of (ii)(1 ) and (ii)(2); and

(iii) component E comprises:

(1 ) an enzyme.

10. The method of claim 9, wherein the composition further comprises component C and component D, wherein component C comprises at least one acid and component D comprises at least one defoamer.

1 1 . The method of claim 9 or 10, further comprising:

(b) maintaining a first temperature of the fluid stream for a first period of time; and

(c) maintaining a second temperature of the fluid stream for a second period of time.

12. The method of any one of claims 9-1 1 , wherein component A comprises an amphoteric surfactant.

13. The method of any one of claims 8-12, wherein the first temperature is greater than the cloud point of the surfactant of component A or B, and the second temperature is less than the cloud point of the surfactant of component A or B.

14. The method of any one of claims 9-13, wherein the low-foam surfactant of component B is selected from a capped alkoxylate, an EO/PO (ethylene oxide group/propylene oxide group) block copolymer, a fatty alcohol alkoxylate, a nonionic ethylene oxide (EO) containing surfactant, an alkoxylated amine, an amine surfactant, a low cloud point nonionic surfactant, and a combination thereof

15. The method of any one of claims 9-14, wherein the composition comprises at least one of a capped alkoxylate, an EO/PO (ethylene oxide group/propylene oxide group) block copolymer, and a fatty alcohol alkoxylate.

16. The method of any one of the above claims, wherein the composition comprises component A and the surfactant of component A comprises a zwitterion.

17. The method of any one of claims 6 and 9-15, wherein the composition comprises component A, and the surfactant of component A comprises two amphoteric surfactants at about 5 to 15% wt of component A.

18. The method of any one of claims 6 and 9-17, wherein the composition comprises component A, wherein the enzyme of component A comprises at least one of an amylase and a protease.

19. The method of any one of claims 6 and 9-18, wherein the composition comprises component B.

20. The method of any one of claims 6 and 9-19, wherein the composition comprises component A and component B.

21 . The method of claim 19 or 20, wherein component B comprises a surfactant having an HLB of about 8 to about 14.

22. The method of any one of claims 9-21 , wherein the composition comprises component E.

23. The method of claim 22, wherein the enzyme of component E comprises lipase.

24. The method of any one of the above claims, wherein FOG is reduced.

25. The method of claim 24, wherein FOG is reduced in the presence of at least one hardness ion.

26. The method of claim 25, wherein the hardness ion comprises calcium.

27. The method of any one of the above claims, further comprising defoaming the composition with a mechanical defoamer.

28. The method of any one of the above claims, wherein the composition comprises a detersive surfactant.

29. The method of any one of the above claims, wherein the composition comprises at least one of a capped ethoxylate; an EO/PO (ethylene oxide group/propylene oxide group) block copolymer; an ethylene oxide derivative; an alcohol ethoxylate; and a low-foam surfactant.

30. The method of any one of the above claims, wherein the composition comprises component B, and component B comprises a capped alkoxylate.

31 . The method of any one of the above claims, wherein the composition comprises component B, and component B comprises an EO/PO (ethylene oxide group/propylene oxide group) block copolymer.

32. The method of any one of the above claims, wherein the composition comprises component B, and component B comprises a fatty alcohol alkoxylate.

33. The method of any one of the above claims, wherein the composition comprises component B, and component B comprises an alcohol ethoxylate.

34. The method of any one of the above claims, wherein the composition comprises component B, and component B comprises a capped alcohol ethoxylate.

35. The method of any one of claims 5-33, wherein the composition comprises component A, component B, component C, and component E, wherein component C comprises at least one acid.

36. The method of claim 35, wherein component A comprises an amphoteric surfactant, component B comprises a low-foam surfactant, component C comprises citric acid, and component E comprises lipase.

37. A method of enhancing the efficacy of an enzyme in a composition used to clean a wet air scrubber, the method comprising adding to the composition an amount of at least one of component A or B such that the efficacy of the enzyme for cleaning the wet air scrubber is not substantially impeded, wherein

(i) component A comprises:

(1 ) an amphoteric surfactant; and

(2) an enzyme, and

(ii) component B comprises at least one of:

(1 ) a detersive surfactant and a defoamer;

(2) at least one low-foam surfactant; and

(3) a combination of (ii)(1 ) and (ii)(2).