WO1980001997A1 - Coating method with emissions abatement ii - Google Patents

Abstract

A process of coating using a sprayable coating composition in a spraybooth that communicates with a water wash, the water wash permitting contact between airborne components of the sprayable coating composition that enters the water wash and scrubbing water of a high volume, low energy wet scrubber operating at an inlet and outlet pressure difference of less than about 10 inches of water. More particularly, this invention relates to an improvement in the coating process which comprises (A) spraying in the spraybooth a scrubbable coating composition comprising a volatile organic compound that boils above about 98 C at atmospheric pressure, is water soluble above about 0.6% by weight at 20 C and is transitory in the scrubbing water; (B) capturing in the scrubbing water a volatile portion of said scrubbable coating composition wherein the volatile portion comprises an amount of the volatile organic compound and wherein an ingredient of the scrubbing water reacts with a portion of the amount; and (C) maintaining a concentration of the volatile organic compound and reaction products of the volatile organic compound in the scrubbing water below that at which efficiency falls below about 10% (preferably higher, e.g. at least 30%) of a maximum efficiency.

Description

COATING METHOD WITH EMISSIONS ABATEMENT II BACKGROUND OF THE INVENTION

This invention relates to a process of coating a workpiece in a spraybooth using a sprayable coating composition; the sprayable coating composition comprises volatile organic compound; the spraybooth communicates with a water wash.

More particularly, the invention relates to contact in the water wash between scrubbing water of a conventional high volume, low energy, wet scrubber and airborne components of the sprayable coating composition that exit the spraybooth through the water wash.

Still more particularly, this invention relates to an improvement in such a coating process in which there is abatement of emissions comprising volatile organic compound(s). "Volatile organic compound(s)", as used herein refers to a compound (s) in a coating composition, (normally as part of its liquid carrier) which is emitted as vapor or otherwise during industrial coating operations.

In industrial spraybooths, workpieces receive coating from manual, automatic or manual and automatic spray application of sprayable coating composition. Not all the coating composition, however, associates with the workpieces. Rather, airborne components of the coating composition subsist in the booth. Large volumes of air draw these airborne components to low energy, wet scrubbers. These scrubbers "knock down" or otherwise take particulates from the air. The problem of still other of these airborne components remains.

It has been suggested by some that reduction of emissions comprising volatile organic compounds from industrial spraybooths requires extensive hardware modification. Others suggest employment of water base, powder or significantly higher solids coating formulations.

In accordance with this invention, however, it has been discovered that high volume, low energy, wet scrubbers, now commonly associated with industrial spraybooths, may be operated in a manner that captures certain volatile organic compounds from airborne components that enter the water wash.

It is an object of this invention to provide abatement of volatile organic compounds that emit during industrial spraybooth operations wherein the abatement requires neither extensive hardware modification nor extensive coating composition reformulation.

This application is related to a concurrently filed and commonly assigned application of Scheutzle and Traicoff entitled "Coating Method With Emissions Abetment I". The

Scheutzle and Traicoff application is herein incorporated by reference.

SUMMARY OF THE INVENTION

This invention relates to a process of coating using a sprayable coating composition in a spraybooth that communicates with a water wash, the water wash permitting contact between airborne components of the sprayable coating composition that enters the water wash and scrubbing water of a high volume, low energy wet scrubber operating at an inlet and outlet pressure difference of less than about 10 inches of water. More particularly, this invention relates to an improvement in the coating process which comprises (A) spraying in the spraybooth a scrubable coating composition comprising a volatile organic compound that boils above about 98°C at atmospheric pressure, is water soluble above about 0.6% by weight at 20°C and is transitory in the scrubbing water; (B) capturing in the scrubbing water a volatile portion of said scrubbable coating composition wherein the volatile portion comprises an amount of the volatile organic compound and wherein an ingredient of the scrubbing water reacts with a portion of the amount; and (C) maintaining a concentration of the volatile organic compound and reaction products of the volatile organic compound in the scrubbing water below that at which efficiency falls below about 10% (preferably higher, e.g. at least 30%) of a maximum efficiency. Preferably, the scrubbing water comprises base; also, preferably, the reaction between the volatile organic compound and the ingredient is a hydrolysis reaction,

A preferred embodiment comprises (a) spraying in the spraybooth a scrubbable coating composition comprising a volatile organic compound that boils above about 120ºC at atmospheric pressure, is water soluble above 0.6% by weight, preferably above about 6% by weight at 20ºC and is hydrolyzable; (b) capturing in the scrubbing water a portion of the scrubbable coating composition wherein the portion comprises an amount of the volatile organic compound and the scrubbing water has a ph that enhances hydrolysis; and (c) maintaining a concentration of the volatile organic compound and hydrolysis products of the volatile organic compound in the scrubbing water below that at which efficiency falls below about 10% of a maximum efficiency. In its embodiment, the pH is preferably basic, desirably above about 9 and more preferably between about 9.5 and 11.5. The amount captured may be up to about 90% or more by weight of the weight of the volatile organic compound of aforementioned characteristics sprayed in the spraybooth.

Spraying may be electrostatically or otherwise; electrostatic has the advantage of higher transfer efficiency than conventional application that further results in reduced emissions from the process of coating in accordance with the invention.

In still another enobodiment, this invention comprises (a) spraying in the spraybooth a scrubbable coating composition comprising a volatile organic compound that boils above about 98ºC at atmospheric pressure and is soluble above about 6% by weight at 20ºC and a hydrolyzable volatile organic compound that boils above about 98ºC and is water soluble above about 0.6% by weight at 20ºC; (b) capturing in the scrubbing water a volatile portion of the scrubbable coating composition wherein the portion comprises an amount of the compound and the scrubbing water has a pH that enhancss hydrolysis of the hydrolyzable scrubbable compound; and (c) maintaining a concentration of the volatile organic compounds and any hydrolysis product thereof below that at which efficiency falls below about 10% of a maximum efficiency. In still more preferred embodiments, this invention comprises biologically, physicochemical or biologically and physicochemically removing one or more products of the preferred hydrolysis reaction so as to maintain a concentration of the volatile organic compound and any hydrolysis products thereof in the scrubbing water below chat at which efficiency falls below about 10% of a maximum efficiency.

Capture by the scrubbing water of a volatile organic compound of the aforementioned characteristics may or may not result in a lasting increase in the amount of the volatile organic compound in the scrubbing water. Since it is, however, transitory in the scrubbing water, then it does not, of course, accumulate as rapidly in the scrubbing water as comparable volatile organic compounds that are not transitory; it also, therefore, does not retard as readily capture of further amounts of it by the scrubbing water.

Uptake of the volatile organic compound of the aforementioned characteristics by the scrubbing water continues when the weight rate of capture exceeds the weight rate of loss of the volatile organic compound and any products therefrom, from the scrubbing water to the atmosphere. Advantageously, it has been discovered that by this invention the scrubbing water can take up relatively large amounts of certain volatile organic compounds for extended period at high efficiency, e.g., up to 90%. Thus, within the ambit of conventional water wash and wet scrubber operation, paint spraybooths may operate, in accordance with this invention, in a manner that transfers volatile emissions therefrom into water. Physicochemical, biological or physicochemical and biological process may then treat and remove volatile organic compounds and their products from the water. This invention accordingly further includes maintaining uptake by the scrubbing water of volatile organic compound of the aforementioned characteristics. The uptake by the scrubbing water is maintained when the amount of volatile organic compound or product therefrom does not exceed certain levels, i.e., below about 50 grams/liter in one embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates in schematic form one type of paint spraybooth with associated (in this case integral) water back sections that may be operated in accordance with this invention. Associated hardware such as pumps, valves, filters, scrubbing devices, et. have been omitted for simplicity and greater clarity.

Figure 2 illustrates a pilot scale spraybooth with integral water wash back section. This pilot scale spraybooth was used in Pilot Trials I, II, and III in the examples,

Figure 3 is a schematic of the total hydrocarbon content (THC) and gas chromatography (GC) sampling systems of the Pilot Spraybooth of Figure 2.

Figure 4 is a schematic of east water pit system, air sampling lines and analyzers monitored in the assembly plant (AP) trial of the examples.

Figures 5, 6 and 7 are graphs showing solvent uptake in scrubbing water in Pilot Trials I, II and III respectively.

Figures 8 and 9 are graphs showing uptake by scrubbing water during the AP trial using 119B and 120C coating compositions, respectively.

Figure 10 is a graph showing the effects of scrubbing during the AP trial using coating composition 120C.

Figure 11 shows schematically the AP stock sampling port and flow measurement port locations.

Figure 12 shows the AP prime spraybooth stack sampling system.

Figure 13 shows the AP stack sample manifold flow regulation system. Figure 14 shows the AP east main enamel spraybooth stack sampling system.

DETAILED DESCRIPTION OF THE INVENTION Scrubbable compound" as used hereinafter shall refer to a volatile organic compound which (1) boils above about 98ºC at atmospheric pressure and (2) is (are) water soluble above about 0.6% by weight at 20°C. "Transitory scrubbable compound" shall refer to a scrubbable compound that reacts with an ingredient in the scrubbing water preferably at a rate at least about 5% of its rate of uptake by the scrubbing water. An example of such ingredient is a base. Another example is acid. Still another ing.edient is potassium permanganate. Reactions include hydrolysis, oxidation, chelation, etc.

For example, Figure 1 shows schematically one type of spraybooth with associated water wash. Workpieces, e.g. autobodies, as in Figure 1, enter and exit the spraybooth along a line perpendicular to the spray of a sprayable coating composition and along a grate opening to the water wash. Relatively clean air enters the booth downwardly and perpendicular to the workpieces and grate. The relatively clean air draws subsisting airborne components of the coating composition through the grate into the water wash. The water wash comprises a wet scrubber that takes particulate, and in the case of this invention, an amount of volatile organic compound from the air. The air enters the water wash at a rate of between about 250-3000 cubic feet per minute per linear foot (cfm/ft) of the booth, and mote usually between about 500-1500 cfm/ft.

This invention particularly concerns use of high volume, low energy wet scrubbers that operate at inlet and outlet pressure differences below about 10 inches of water and even as low as below 6 inches of water, e.g. about 1-5 inches of water pressure difference. The pressure drop may be determined by pressure measurements at convenient locations

^'BURE within the water wash. For example, measurements may be made at locations of just before first water contact and just after last water contact in the water wash; the difference of these measurements is a measurement of the pressure difference. Another way to characterize conventional spraybooth wet scrubbers is by what is referred to as amount of particulate that emits after wet scrubbing. "Grain" refers to the amount of particulate per unit volume of air, e.g., 1 grain equals 0.0648 g/scfm. Water flow in the water wash may vary. Normally, it will be between about 5-100 gallons per minute per linear foot of the spraybooth. Countercurrent air and water flows in the water wash are preferred in accordance with the invention; water washes with concurrent air and water flows should, however, also be suitable.

In the process of this invention, there is selection with respect to the type of sprayable coating composition sprayed. More particularly, the sprayable coating composition is selected to be a scrubbable coating composition. A scrubbable coating composition comprises a transitory scrubbable compound.

Preferred scrubbable compounds comprise oxygenated compounds. More preferred scrubbable compounds are selected from the group consisting of esters, ethers and alcohols. Examples of the esters are mono and di esters such as acetates, adipates, glutarates, succinates and the like. More specifically, examples are cellosolve acetate (i.e. ethylene glycol monoethyl ether acetate), methyl cellosolve acetate (i.e. ethylene glycol monomethyl ether acetate), butyl cellosolve acetate (i..e. ethylene glycol monobutyl ether acetate), butyl acetate ethyl carbitol acetate (i.e. diethylene glycol monoethyl ether acetate), butyl carbitol acetate (i.e. diethylene glycol monobutyl ether acetate). Examples of the alcohols are amino alcohols such as alkanol amines, ester alcohols, and ether alcohols. More specific examples of alcohols are triethanol amine, butyl carbitol

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WiPO (i.e. diethylene glycol monobutyl ether), cellosolve (i.e. ethylene glycol monoethyl ether), methyl cellosolve (i.e. ethylene glycol monorcethyl ether), butanol and ethylene glycol. An example of an ether diethyl carbitol (diethylere glycol diethyl ether), (For convenience hereinafter, anycompound, however, comprising an ester group shall be considered an ester; any compound not comprising an ester but having an ether group shall be considered an ether.) Any of these compounds may also be transitory scrubbable compounds if the scrubbing water has an ingredient that reacts with it.

A preferred transitory scrubbable compound is an ester and especially an ether ially linked ester such as cellosolve acetate. A preferred transitory compound also preferably boils above about 120°C. Advantageously, scrubbable, as well as transitory scrubbable compounds, alone or together are suitable for use in aqueous and non-aqueous coating compositons at desired levels. A desired level is as high a percentage as possible of the volatile organic compound in the coating composition, taking into account other factors in coating composition formulation. Examples of. aqueous and non-aqueous coating comnositions are those including thermoplastics, and/cr theromosets which, in turn, may be topcoats, sealers, primers. etc. The process of this invention further includes capture of transitory scrubbable compounds by the scrubbing water in the water wash. "Scrubbing water" as used herein means water in the water wash and any additives therein that com^s into scrubbable contact with airborne components of a sprayable coating composition. This contact is, for example, between water of a venturi spray or water curtain or other high volume, low energy scrubber air water interface and the airborne components.

As is well known, scrubbing water typically contains water treatment compounds. The process of this invention has not been found to detract from function or employment of typical water treatment compounds.

~ OMPI yλ The usual function of water treatment compounds is to enhance and maintain the ability of scrubbing water to "knock down" or otherwise take particulate from air passing through the water wash. This function includes water treatment compounds that act to "kill" paint overspray. It includes water treatment compounds that may act to detachify, coagulate, precipatate, float or otherwise treat paint overspray. It still even further includes water treatment compounds that are surfactants, anti corrosion agents, bacteriocides, fungicides, etc. Examples of water treatment compound formulations include those in U.S. Patents 3,985,922; 4,002,490; 4,090,001; 4,125,476; 4,130,674 and Canadian Patent 589,360.

Especially preferred water treatment compound formulations include amines, aluminates, silicates and the like at a variety of basic pH levels. Modifiers of pH may be added on a continous basis to circulating scrubbing water.

Examples of commercially available water treatment compounds are those of Nalco 8724 containing polyelectrolyte; Nalco 8723 containing polyelectrolyte; Nalco 2 containing sodium aluminate, and Nalco 8735.

Having served a function of treatment of paint overspray, water treatment compounds may be removed along with treated overspray by conventional means. The process of this invention preferably includes such a removal and an addition of make up water treatment compounds.

In order that capture by the scrubbing water of scrubbable compound continue in the process of this inventior, the scrubbing water has a concentration of a transitory scrubbable compound and products therefrom below that at which efficiency falls below about 10% of a maximum efficiency. Normally, such is an amount below 50 grams/liter of scrubbable compound, e.g., between about 0.1-20 grams/liter. Maximum efficiency, however, is when the scrubbing water is essentially free of the transitory scrubbable compound and any product therefrom. Preferred scrubbable coating compositions comprise a hydrolyzable scrubbable compound that boils above about 120ºC. Uptake by the scrubbing water of such preferred hydrolyzable scrubbable compound continues with desirable efficiency even when the scrubbing water contains higher levels of hydrolyzable scrubbable compounds and products therefrom within the above ranges.

Removal of transitory scrubbable compounds (are any products therefrom) from scrubbing water may be by biological, physicochemical or biological and physicochemical processes; alternatively, the scrubbing water may be simply replaced with fresh (e.g., municipal) water. Examples of physicocheraical processes include coagulation, precipitation, filtration, absorption, ion exchange, membrane separation, and chemical oxidation.

In preferred applications of principles of the invention, several factors play a role in coating composition selection. As mentioned, the sprayable coating composition is selected to be a scrubbable coating composition, i.e., comprise a transitory scrubbable compound. Of course, the higher the level of transitory scrubbable compounds, the more emissions that may be abated.

The pressure drop of the water wash affects efficiency. Higher pressure drops cause more efficient capture of transitory scrubbable compounds. Further, lower levels of transitory scrubbable compounds in the scrubbing water allows higher efficiencies.

Still other factors that may be considered include boiling temperature of the transitory scrubbable compound. The scrubbing water generally retains higher boiling scrubbable compounds longer than lower boiling scrubbable compounds, assuming equal solubilities. Similarly, the scrubbing water generally retains more water soluble transitory scrubbable compounds longer than less water soluble transitory scrubbable compounds, assuming equal boiling points. Furthermore, the pH, for example, can affect efficiency at which the scrubbing water takes up hydrolyzable compound.

In the preferred applications, other factors, of course, affect emissions from the water wash. The amount of emissions abated in accordance with this invention may be generally added to the amount of abatement achieved by these other factors. Examples of these other factors include (1) solids content of the coating composition, (2) transfer efficiency of spray application, e.g., mode of spraying and (3) manner of handling emissions from bake ovens, e.g., incineration by catalyst.

EXAMPLES

A. Pilot Plant Trials

1. Facility and Parameters of Operation There were three pilot plant (AP-PP) trials. The spraybooth in each trial was a five-foot, side-draft spraybooth manufactured by Sinks Manufacturing Company; it had a H.R. Black Company Model PDSB paint sludge filter system. Schematic representation of the spraybooth test assembly appears in Figure 2; operating parameters for each trial appear in Table 1. Operation in accordance with manufacturer's specifications suggested that the back section had a 3 grain efficiency during the first two trials and a 5 grain efficiency during the last trial.

Table 2 shows solvent composition and physical properties of sprayable coating compositions used in the three trials. Trial 1 examined high solids enampl 3760; Trial 2 examined non-aqueous dispersion enamel 5180; Trial 3 examined high solids enamel 3742.

A Binks Model 61 automatic spraygun equipped with a 63C fluid nozzle and 53PR air cap sprayed paint at a rate in each trial of 0.002 gallons of solids per minute per linear foot of back section. The spraygun, actuated automatically on a 15 second cycle, operated with open gun times ranging between 2 and 4 seconds in each cycle. The spraygun nozzle was diagonally five feet from the air inlet of the back section. The spray from the nozzle was in a vertical fan shape and at approximately -45° from

horizontal. Mounting the pressure pot of the spraygun on a scale enabled the spray rate to be monitored and controlled.

A Nalco Model V-6 mini-pump metered Nalco 8724 water treatment compound continuously into the spraybooth water; metering was proportional to paint spray rate. A Great Lakes Instruments, Inc. (GLI) Model A605421A pH monitor/controller used with a GLI Model P60L-4-1 submergible pH probe and a Nalco Model V6 mini-pump controlled booth water pH automatically by addition of Nalco 2 or Nalco 8735 water treatment compounds. Addition of Nalco 71-D6 defoaming compounds as required and in 80 ml. aliquots controlled foam in the first two trials; a FMI Model RP-6400 pump continuously metered the 71-D6 into the booth water in the last trial. Other spraying conditions and chemical addition fates appear in Table 3.

2. Sampl ing and Analysis

(a) Air Emissions - Total Hydrocarbon Analysis

A Beckman Model 402 Total Hydrocarbon (THC) Analyzer continuously monitored stack emissions . An Omniscr ibe Model B5217-5 two-channel recorder simultaneously displayed instantaneous and electronically integrated (over ten , 15 second spray per iods) output from the analyzer .

The THC analyzer was zeroed with Ultra Zero Air (Air Monitor ing , Inc . ) and spanned with 80 and 204 ppm propane-in-air standards ( ± 1% accuracy, Accublend , Scott Research Company) approximately every five hours . Samples of stack emissions passed anisokinetically through a twelve foot stainless steel line to the analyzer during the first trial . Heat tracing occurred over all but a two-foot , in-stack section of this sample line . In the other trials, the system shown in Figure 3 isokinetically sampled stack emissions .

(b) Air Emissions - Gas Chromatographic (GC) Analysis

GC analyses determined emission rates of specif ic solvents . Dupont Model 4000 constant flow, personnel sampl ing pumps collected known volumes of air emissions directly from the spraybooth exhaust stack onto traps containing Tenax GC polymer. Selection of sampling times averaged rapid temporal changes in stack emission levels. The inlet of a Hewlett Packard Model 5711A Gas Chromatograph equipped with a flame ionization detector (FID) received heat desorbed samples from the traps.

In other trials, samples came from the sample bypacs stream of the Beckman 402 THC Analyzer. Sampling occurred approximately every two hours in these trials. (A Hewlett

Packard 3385A integration system reduced the 5711A data in ail trials.

(c) Spraybooth Water - GC Analysis

A Perkin Elmer Sigma 1 GC system equipped with a flame ionization detector (FID) measured uptake of specific solvents into the spraybooth water. Collection of booth water grab samples occurred every ninety minutes in 25 ml. headspace-free vials fitted with teflon lined caps. After centifugation to remove suspended solids, there was direct aqueous injection into the Sigma GC.

(d) Paint Sludge - GC Analysis A Hewlett Packard 5720 Gas Chromatograph equipped with a Unacon Model 780 sample introduction system and a

Hewlett Packard Model 3380S integrator analyzed sludge samples. Airtight containers stored frozen grab samples of floating and sunken sludge.

(e) Air, Water, Sludge - GC - Mass Spectometric Analysis (GM-MS)

A Hewlett Packard 5992B GC-MS system provided qualitative confirmation of solvent identity of spraybooth water, sludge and air emissions. Sampling techniques were identical to those in GC analysis.

-^UREA OMPI (f) Flow Measurements

Spraybooth exhaust flow measurements were in accordance with Ford Manufacturing Standards BAX-2 procedures.

3. Results Pilot Trials (a) Booth Water Capture

Figures 5, 6 and 7 illustrate an increase in the amount of solvent compounds in booth water as a function of paint spraying time for pilot trials I, II and III, respectively. Non-polar compounds like xylene and esposol 260 did not appear appreciably in the booth water.

Figures 5, 6 and 7 express cellosolve acetate by combining cellosolve acetate and its hydrolysis product cellosolve.

(b) Air Emissions Tables 8, 9 and 10 show solvent concentration (corrected to 760 mm Hg , 20 ºC) at selected times during each of the three pilot trials. In these tόbles, the weight per unit volume solvent concentrations are also recalculated as their equivalent total hydrocarbon concentration in terms of propane. These totals are compared to actual THC concentrations measured by the 3eckman 402 Analyzer. The calculations used carbon number response factors derived from the literature or from empirical results.

(c) Sludge Characteristics and Solvent Composition Tables 11, 12 and 13 show results of analysis of bottom and floating sludges taken during Trials I, II and III, respectively.

(d) Solvent Material Balance

Tables 14, 15 and 16 present material balances for several sampling periods during Pilot Trials I, II and III, respectively. For each sampling period, solvent spray rate versus solvent emission and capture rate is presented. The materials balances range between 81 and 102 percent. An assumption for. the calculations in Tables 14, 15 and 16 is that the sludge had a composition as presented in Tables il , 12 and 13, respectively. The sludge production rate was estimated from weight solids of each original paint since all the paint solids sprayed during the pilot tr ials entered the back sec tion .

(e) Efficiency - Pilot Trials

At operation of the back section at 4.9 inches pressure drop (3-grain particulate scrubbing efficiency), there was removal by cellosolve acetate at 80% efficiency. At operation of the back section at 2.6 inches pressure drop (5-grain efficiency), there was removal of cellosolve acetate at 55% efficiency. Table 7 shows cumulative scrubbing efficiencies for cellosolve acetate and butyl carbitol over selected spray periods.

B. Production Trials

1. Facility and Trial Description

The production trials were under conditions of commercial spray painting of automobiles in an automotive assembly plant (AP). During the production trials, approximately 62 vehicles per hour received prime and top coats. Figure 4 shows schematically pertinent portions of spraybooth, water line and stack arrangement of the AP painting process. In the AP coating operation, electrσcoated vehicle bodies passed sequentially through a Prime Spraybooth, a Prime Bake Oven, a West Main Enamel Booth, an East Main Enamel Booth, a Main Enamel 3ake Oven, and, if required, a Tutone-Repair Spray Booth and Bake Oven. In a west end of the Pr ime Spraybooth , mod if ied Behr-Ransbury equipment electrostatically sprayed approximately 50% of a taupe primer. Stacks 9 and 10 (Figure 4) exhaust the west end.

OM yOλv, WI Manual spray equipment thereafter sprayed gray primer around vehicle door jambs and rocker panel areas. The manual spray equipment sprayed the remaining amount of taupe primer. A total of 10 stacks and fans exhausted the Prime Spraybooth.

The vehicles then exited the Prime Spraybooth and entered the Prime Bake Oven. The residence time in the Prime Bake Oven was about 21 minutes. A single stack exhausted the Prime Bake Oven. Vehicles next entered the West Main Enamel Booth.

Behr-Este equipment and four spraypersons sprayed, respectively, electrostatically and manually, topcoat in the West Main Enamel Booth.

Vehicles then entered the adjoining East Main Enamel Booth. Ten to twelve spraypersons sprayed remaining exterior and interior topcoats in the East Main Enamel Booth. Fourteen stacks and fans exhausted the East Main Enamel Booth.

Stack exhaust flows for the Prime Spraybooth, the Prime Bake Oven, and the East Main Enamel Booth appear in Table 4.

Although the East and West Enamel Booths adjoined one another, their back sections received water from different storage pits. A west water pit supplied scrubbing water to the West Main Enamel and Tutone and Repair Booth back sections; an east water pit supplied scrubbing water to the Prime Spraybooth and East Main Enamel Booth back sections.

The production trials concerned particularly taupe primer 119C and primer 120C sprayed in the Prime Spraybooth. As can be seen from the above, noted arrangement of the AP, however, the Prime Spraybooth back section could not be isolated from activity in the East Main Enamel Booth because their back sections shared water of the east water pit. To obtain a material balance, therefore, with respect to specific solvents, it was necessary to determine the amount of each solvent sprayed in the East Main Enamel and Prime Spraybooths and to analyze simultaneously the exhaust air from the Prime

_.OMPI Spraybooth and Prime Oven Stacks, the East Main Enamel Booth stacks and water of the east water pit.

(It is recognized, however, that the material balance as above noted, omits certain other factors that were not adequately quantified. For example, vehicles entering the East Main Enamel Eooth from the adjoinging West Main Enamel Booth offgassed into the back section, of the East Main Enamel Booth. Thus, solvent sprayed in the West Main Enamel Booth contaminated water of the east water pit. Contamination would be expected to be less significant in the 120C trial because relatively less cellosolve acetate was sprayed in the West Main Enamel Booth during the 120C trial. Secondly, a phenomenum which may be referred to as "crosstalk" occurred between spraybooths, back sections and pits. The Prime Spraybooth stacks, for example, exhausted n-butyl acetate and butyl cellosolve even though these solvents arose from spraying in the East Main Enamel Booth. Other exogeneous factors that affected efficiency in material balances included: apparent malfunction of scrubbing equipment in certain back sections; cleaning/purge compositions containing solvent and utilized in the booths during the trials.)

The east water pit held 170,000 ± 5000 gallons during the two production trials. At the beginning of each trial, the water showed essential freedom of solvent. The retention time of water in the east water pit was about 10 minutes. Metering of Nalco 8724 to the water was at a rate of about 1.5 gallons per hour. The water had a basic pH which was in a range between 10-10.5 through most of the trials. A combination of manual and constant metered additions of caustic (50%) maintained the pH. The first trial examined emission from taupe primer 119B; the trial lasted two days. The second trial examined primer 120C; it lasted four days.

In the first trial, several one-hour volume delivery measurements at the paint mixing pots in the paint kitchen determined primer usage. Hourly production data on vehicle color and enamel use per vehicle information developed empir ical l y dur ing the second tr ial de term ined enamel usage in the East Main Enamel Booth. Volume measurements made at the paint mixing pots in the paint kitchen provided paint usage in the second trial after subtraction of enamel usage in the West Main Enamel and Tutone-Repair Booths. Industrial engineering open-gun time, fluid delivery rate, and spray gun information provided proportions delivered to each Booth. This analysis suggested 65 ± 10% of the enamel from the paint kitchen went to the West Main Enamel Booth, 10 ± 1.5% went to the Tutone-Repair Booth, and 25 ± 4% went to the East Main Enamel Booth.

Table 5 shows the cellosolve acetate concentration of the 119B and 120C coatings and enamels sprayed in the East Main Enamel. Booth along with the volume of each- coating sprayed daily.

2. Sampling and Analytical Techniques

(a) Air missions - Total Hydrocarbon Analysis (THC)

Three Beckπian THC Analyzer Systems monitored continuously (eight hours a day in the first trial, sixteen hours a day in the second trial) volatile stack emissions from the Prime Spraybooth, the Prime Bake Oven and the East Main

Enamel Spraybooth. A heat-traced manifold system provided an average sample from all 10 stacks on the Prime Spraybooth to a Beckman Model 402 THC Analyzer. A second, heat-traced manifold system provided an average sample from seven of the fourteen East Main Enamel Spraybooth stacks to a Beckman 400

THC Analyzer. Total hydrocarbon measurements made on all 14 enamel booth stacks determined that the emission rate from the seven stacks monitored during the trial was equivalent to the seven not monitored. In both of these stack systems, the fraction of the total THC analyzer flow taken from each particular stack was proportioned to each stacks contribution to the total booth exhaust flow. A second Beckman 402 THC Analyzer monitored exhaust emissions from the single stack on

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, y λ , WiPO - the Prime Bake Oven. Figure 11 illustrates sampling locations on the exhaust stacks of each system.

(b) Air Emissions - Gas Chromatographic Analysis

GC determined the emission rates of specific solvents in stack emissions from the Prime Spraybooth, the Prime Bake

Oven and the East Main Enamel Booth. Dupont Model 4000 constant flow personnel sampling pumps collected known volumes of hydrocarbon vapor onto traps containing Tenax GC polymer.

Samples came from the FID bypass streams on the three THC Analyzers used to monitor the Prime Booth, Prime Bake Oven, and East Main Enamel Stack Systems. Sampling frequency, flow, time and gas chromtographic system used for analyzing samples appear in Table 6.

The Hewlett Package Model 5711A gas chromatograph was the same instrument used in the pilot plant trials except that a Perkin Elmer Sigma 1 Data System reduced the data.

A Hewlett Packard Model 5720 gas chromatograph equipped with a Unacon Model 780 Sample Introduction System and a Hewlett Packard Model 33805 Integrator analyzed certain Prime Bake Oven and East Main Enamel Booth emissions.

(c) Air Emissions - Sampling Location and Technique at Prime, Enamel and 3ake Stacks

A heat-traced stainless steel manifold system provided an average emission sample from the - ten prime spraybooth stacks. Figure 11 illustrates sampling point on each stack. As illustrated in Figure 12, 1/4" i.d. sections of line (Technical Heaters, Inc. Model 500-1/4) linked each stack to a central 3/8" i.d. trunk line (Technical Heaters,

Inc. Model 500-3/8) leading to the Beckman 402 THC analayzer. A Technical Heaters, Inc. Model 10450 Temperature Controller maintained the 1/4" sample lines at approximately 300°F and the 3/8" lines at approximately 230°F. A Nupro SS-4MG metering valve protected by a Nupro SS-4F-T7 15 micron sintered-metal filter and located at the connecting point

IJUR between the 1/4" and 3/8" lines regulated the flow from each stack ( Figure 13 ) . Closure of an in-line toggle valve to bypass the flow through a Matheson Model 603 rotametεr accomplished flow monitoring . The same rotameter , equipped with Swagelok Quick-Connect Connectors , permitted balance of the flow from each stack on the system. Sample flow from each stack was between 0.5 and 1.0 1/min.

A Metal Bellows Model 302HT pump provided sample flow. An Associated Testing Laboratories, The Model BP-1102 oven maintained pump temperature at 285ºF to prevent sample condensation . The effluent from the pump was split . Approximately 1.9 1/min . of flow went to the THC analyzer and the remaining flow vented through a S-110 dry test, meter . The Beckman 402 THC Analyzer was modif ied so that flow from the glass fiber f ilter bypassed the internal metal bellows pump and went directly to the FID capillary-splitter .

The THC analyzer was zeroed with Ultra Zero Air (Air Monitor ing , Inc . ) and spanned with an 80 ppm propane-in-air standard approximately every four hours . An additional two-point calibration was performed daily with 80 and 204 pom propane-in-air standards (t 1% accuracy, Scott Research Co . ) . The output from the THC analyzer was recorded directly and was also electronically integrated over periods of 10 .0 minutes . An Omniscr ibe Model B5217-5 two-pen recorder recorded both outputs continuously.

A heat-traced stainless manifold system provided an average emission sample GC and THC analysis from seven of the fourteen East Main Enamel Spraybooth stacks ( Figure 14 ) . The sampling point on each stack is illustrated in Figure 11. The heat-traced sample lines and the associated temperature and flow control equipment used on the East 'Main Enamel Booth were identical to the equipment used on the Pr ime Spraybooth ( Figure 12, 13 ) . A Metal Bellows Model 158HT pump prov ided sample flow. Heat tracing of the pump head and the sample lines leading to the FID detector on the Beckman 400 THC Analyzer prevented sample condensation . Effluent from the pumps was split. Approximately 2.2 1/min. of flow went to the THC analyzer and the remaining flow vented through a Rockwell Model S-110 dry test meter (Figure 14).

The Beckman 400 THC Analyzer was zeroed with Ultra Zero Air (Air Monitoring, Inc.) and spanned with 204 ppm propane-in-air standard approximately every four hours (± 1% accuracy, Scott Research Co.). An Omniscribe Model B5118-4 strip chart recorder recorded continuously the output from the THC analyzer.

Prime Bake Oven

A Beckman 402 THC Analyzer monitored emissions from the single stack on the Prime Bake Oven. Samples of the emissions passed through an eleven foot heat- traced line supplied with the THC analyzer. The instrument was zeroed with Ultra Zero Air (Air Monitoring, Inc.) and spanned with 204 ppm propane-in-air standard (± 1% accuracy, Scott Research Co.) approximately every four hours. A Weather Measure Model EPR-200A strip chart recorder recorded continuously the output from the THC analyzer.

(d) Spraybooth Water - Gas Chromatographic Analysis

A Perkin Elmer Sigma 1 Gas Chromatographic System measured solvents in the water of the East Pit System. Booth water grab samples occured approximately every 2.5 hours in 25 ml headspace-free vials fitted with teflon-lined caps. The GC received the samples (after centifugation to remove suspended solids) by direct aqueous injection.

(e) Paint Sludge - Gas Chromatographic Analysis

Grab samples of floating and sunken paint sludge occurred during each AP trial from the East Water Pit System. The sludge was a mixture of taupe and gray primer and enamel overspray. Measurement and equipment was identical to that described in A 2.d. (f) Air and Water - GC - MS Analysis

A Hewlett Packard 5992B GC-MS System analyzed the

Prime Spraybooth, Prime Bake Oven, East Main Enamel Stack

Emissions, and East Pit System Water prior to the trials.

(g) Flow Measurements

Personnel made spraybooth and oven exhaust flow measurements in accordance to the Ford Motor Company Manufacturing BAX-2 procedure. Prime spraybooth and oven flows measurements occurred during five of the six trial days. East Enamel stack flows were cross-checked at the beginning of the first trial and assumed to be constant during the remainder of both AP experiements. Figure 11 illustrates the stack flow measuring points.

3. Results - Production Trial (a) Solvent Capture in Water

Figures 8 and 9 illustrate uptake of specific solvents into the water of the AP East Pit-System during the 119B and the 120C taupe primer trials as a function of paint spraying time. Figures 8 and 9 express results as increasing booth water concentration and as mass of solvent, captured. Least squares regression analysis gave cellosolve acetate accumulation in the booth water at a rate of 4.5 ± 0.3 kg/hr of spraytime during the 1198 trial and at 11.9 ± 0.2 kg/hr during the 120C trial. The solvent pentoxane accumulated in the booth water during both trials. It was a constituent of a cleaning/purge solvent blend and not contained in any primer or enamel solvent package.

(b) Solvent Air Emissions Table 17 and tables 18, 19 and 20 show daily average stack emission rate for specific solvents from the Prime Spraybooth, the Prime Bake Oven, and the East Main Enamel Spraybooth during the 119B and 120C trials, respectively. The tables express emission rates in terms of kilograms of solvent emitted per hour of paint spraying time (corrected to 20°C, 29.9" Hg . ) Calculations account for daily differences in stack flows (Table 4). The tables express average concentration of each solvent in milligrams per cubic meter (standard conditions: 29.9" Hg, 20ºC); and the total concentration is reexpressed in terms of propane (C₃H₈) and compared to the daily average THC concentrations measured at each source with either a Beckman 400 or 402 Analyzer. The difference between the measured and calculated THC concentrations for the Prime and Enamel Spraybooths seldom exceeded 10 percent. Fluctuations in the measured THC values through each day, however, frequently exceeded this level. Measurements in the Prime Spraybooth showed a highly variable methane background ranging from 9 to 90 ppm as C₃H₈. A comparison between the calculated and measured THC values for the bake oven (Table 19) is inappropriate because of such a variability.

(c). Sludge Solvent Composition

Essentially two solvents, cellosolve acetate and xylene, appeared in samples of bottom and floating sludge. The amount of xylene was between 2.5 and 12.5 weight percent of dry sludge; the amount of cellosolve acetate ranged between 0.8 and 2.0 weight percent.

(d) Scrubbing Efficiency - Material Balance Table 21 shows material balances on the cellosolve acetate sprayed in the East Pit Water System during the 119B and 120C trials. The material balance compares the sum of emission rates from the Prime Spraybooth, Prime Bake Oven and the East Main Enamel Spraybooth plus the rate of cellosolve acetate captured in the booth water (absent sludge) to the rate at which cellosolve acetate was sprayed in the Prime and East Main Enamel Spraybooth.

_OMPI

.A WiPQ The percentage of cellosolve acetate captured in the spraybooth water was 28 ± 5% and 29 t 5% of the total sprayed in the 1193 and 120C trials, respectively. Efficiency appears closer to 32 ± 6% when considering the amount of cellosolve acetate in the sludge and the minor amounts of solvent other than cellosolve acetate captured in the spraybooth water. This capture efficiency translates into a 5% reduction in VCC for the 119B coating and a 19% reduction in VOC for the 120C coating.

Table 22 compares Prime Spraybooth stack volatile organic compound emission rate to spray rate. An efficiency in the first trial can not be based on this data because the. emission rate exceeds the spray rate. An efficiency in the second trial (emitted over sprayed) is 13%. Error analysis, however, suggests the latter result neither proves nor disproves reduction of emissions because errors in the measurements involved in the material balance were i 22%. (e) Comparison to Water Base Coatings Figure 10 gives an example of how backsection scrubbing abatement might be used, in part, to reduce the equivalent emissions (VOC) of a 120C solvent based primer and assuming abatement by the various techniques is additive. This solvent based primer applied unabated using non-electrostatic spray equipment, has a VOC of 4.8 lb./gal. By applying this primer using electrostatic application, and assuming an increase in system transfer efficiency, say from 50 to 65%, could in effect lower the equivalent VOC of this material to approximately 3.7 lb./gal. Utilizing backsection scrubbing abatement of 19% could lower the equivalent VOC of this primer, applied electrostatically, even further, say down to about 3.0 lbs./gal. Furthermore, if the solvent had been scrubbed even more effectively, as i.e. 32%, as observed in pilot trials, the VOC emissions could possibly be reduced even as low as 2.5 lbs./gal.

S _. __0MPI__ C. Sparging

I. Circulation of solvent laden water (having approximately 3.5 grams/liter cellosolve and cellosolve acetate) through the back section of the Pilot Spraybooth at the conclusion of Pilot Trial III was for 48 hours. Booth exhaust air and back section water flows were 5000 CFM and 175 GPM, respectively. Butyl carbitol and cellosolve did not change significantly in amount at the end of 48 hours but cellosolve acetate had a reduction by 50%. Light alcohols and ketones left the water in about 6 hours.

D. Circulation of the East Water Pit water for 24 hours at the conclusion of the 120C production trial caused a 5% by weight reduction of cellosolve in the pit water. The Prime Spraybooth and East Main Enamel Booths ran continuously during the 24 hours. Because the pit water was at a pH between 10-10.5, cellosolve acetate hydrolyzed to cellosolve.

E. Following general procedures outlined in A (Pilot Trials) above, .except that there is spray of a different sprayable coating composition and a booth water pH of 10.5, resulted in an efficiency of 90% with respect to capture of cellosolve acetate in a 5 grain back section.

Water Treatment Compounds

Nalco 8735 and 8724 have the following characteristics:

8724 8735

Specific Gravity, (60/60F) 1 . 518 1.327

Organic Agents None None

Water Content, % by Weight 63 15

Pour Point, % -25 60 pH , ( as rece ived ) 13 .72 - - - -

Sol id Content , % by we ight 57 . 2 64.2

Spectrographic Analysis of Solids, %

Sodium as Ka Major Major Potassium as K Major 2.0 Silicon as SiO₂ 0.1 13.0 Aluminum as AI₂O₃ 0.02 3.3 Calc ium as CaO - - - - 0.2 Lead as Pb - - - - 0.02

Infrared Analysis:

Spectrograms of 18735 are characteristic of Sodium Carbonates.

Spectrograms of $8724 are characteristic of Carbonates,

Foam Characteristics No foam Extracable Oil, % by Wt. 19.5

Polyvalent Metal Salts, ml. 8724 % by weight 1 Specific Gravity, (60/60F) 9.0 Flash Point, (C.O.C.) 1 . 174 (None to boil ing )

%_. ^WiP0 .. TEST DATA: Continued

8724

Pour Point, F -27

Solubility in Water (50:50) Complete pH, (as received) 0.65

Water Content, % by Weight 70

Odor Not Objectionable

Solid Content, % by Weight 28.3

Surface Tension, dynes/cm. 44.4

Viscosity 3 74 F, cSt 8.31

Spectrographic Analysis, % Sodium as Na 0.40 Potassium as K less than 0.05 Silicon as SiO₂ 0.10 Aluminum as AI₂O₃ 31.0 Calcium as CaO 0.20 Lead as Pb - - - -

Also, 8724 compound is believed to be 10% by weight of polyaraine synthesized from the following materials:

1 . 0. 42% diethylene glycol

2. 0 .58% polyethylene oxide

3. 1 .08% ethylene oxide

4 . 0 .75% epichlorohydrin

5. 2.04% HMDA

6 . 0.02% 1.11 -dichlorobutane-2

TABLE 1. PILOT SPRAYBOOTH OPERATING PARAMETERS

Parameter Pilot Trial Number

I II III

Backsection particulate 3 3 3 scrubbing efficiency, grams/1050 SCFM

Stack exhaust flow, SCFM 4800±5% 4800±5% 4900±5%

Backsection water nozzle flow, gal/min ~150 ~150 ~150

Backsection water nozzle pressure, psi 4.0 4.0 4.0

Backsection water nozzle type, turns 3 3 5.

Backsection venturi diameter, inches 14 M 17

Backsection static pressure, inches H₂O 4.9 4.9 2.6

Backsection front water curtain flow, gal/min 50 ~ 50 ~ 50

Booth system volume 1800 1800 1800

TABLE 2. PAIMT SOLVENT COMPOSITION AND PΛIUT FilYSICΛL PROPERTIES

Physical Property Paint Svstem

%Wt Solids 65.5 45.2 63.4

Density (lb/gal) 10.2 9.0. 10.25

V.O.C. (calculated lb/gal) 3.52 4 .93 3.84

Viscosity (#4 F.C.) 34" 35" 32

Solvent Weight Percent of Total Solvent

Cellosolve Acetate 49.9 5.2 48.1

Butyl Carbitol 15..5 9.1 13.6

Isoproponol 17.9 14.6 16.3

Heptane 3.2 - 4.3

Naptha 1.4 8.0 -

N-butyl Acetate 0.7 - -

Isobutanol 10.6 11.1 9.7

Xylenes traces -

Methylamyketone 47.8 0.2 Methylethylketone 3.6 3.5 Esposol 260 F - 4.3 VM+P Naptha - - Toluene - - N-Butanol - - 2-ethylhcxanol - -

TRIAL I II III TABLE 3. PAINT SPRAYING CONDITIONS AND BOOTHWATER CHEMICAL ADDITIVES RATES

Parameter Pilot Trial I II III

1. Paint tested 3760 518 3722

2. Length of trial spraying time,hours 92 15 51

3. Spraying time/day,hours 5 5 20

4. Paint solids delivery rate, gal/min. linear foot of booth 0.002 0.002 0.002

5. Paint spray rate, gal/min 0.0176 0.0345 0.0183

6. Spraygun fluid delivery rate, f1.02./min 14 26 14

7. Open gun time en 15 sec. cycle, seconds 2.4 2.6 2.5

8. Spraygun atomizetion pressure, psi 70 70 70

9. Paint pot pressure approximate, psi 70 20 40

10. Nalco 8724 addition rate, % by volume of paint sprayrate 6 3.1 6

11. Nalco 2 addition rate

(approx.) ml/min 7 7 -

12. Nalco 8735 addition rate

(approx.) ml/rnin - - 2

13. Nalco 71-DS defoamer addition rate, ml/min -2 -2 1.0

TABLE 4 AP STACK EXHAUST FLOWS

Flow, SCFM

Prime Prime East Main Enamel Spraybooth

TRIAL I Spraybooth Bake Oven

171,900 16,240 204,300

DAY 1 DAY 2 171,900 16,240 "

TRIAL II

DAY 1 174,800 14,900 "

DAY 2 169,300 15,620 "

DAY 3 183,300 15,800 "

DAY 4 161,500 16,800 "

STACK EMISSIOM ANALYTICAL PARAMETERS

TABLE 6.

Sampling Sampling GC System

Sampling

Site Frequency Flow Time (per shift) (ral/min) (min)

Prime Spraybooth 3-4 21.4 20 HP 5711A

Prime Bake Oven 1 28.8 12 HP 5711A

Prime Bake Oven 2 28.8 12 HP 5720

East Main Enamel 1 21.3 30 HP 5711A

East Main Enaimel 2-3 21.3 30 HP 5720

TABLE 7. CUMULATIVE SPRAYBOOTH SCRUBBING EFFICIENCY FOR CELLOSOLVE ACETATE AND BUTYL CARBITOL - PILOT TRIALS I and III

Percent Cumulative Scrubbing Efficiency*

Spraying Time Pilot Trial I Pilot Trial III Hours Cellosolve Butyl Cellosolve Butyl

Acetate Carbitol Acetate Carbitol

10 97 81 57 67

30 94 80 57 82

50 82 78 54 92

70 72 73 - -

90 65 66 - -

*Cumulative Scrubbing Efficiency = mass of solvent captured in time, t mass of solvent sprayed in time, t

TABLE 11. SLUDGE SOLVENT ANALYSIS - PILOT TRIAL I

Spraying Time Solvent Composition - Weight Percent in Dry Sludge

Hours Methanol Isopropanol Isubutanol Cellosolve Cellosolve Butyl Water^Δ Acetate Carbitol

10 .56 0.27 0,57 0.01 0.07 0.19 25

50 i.7 0.93 2.2 0.15 0.10 0.83 20 75 1.4 0.96 1.6 0.20 0.24 1.2 27

80* 1.3 0.39 1.7 0.13 0.24 1.1 23

90 1.2 0.82 1.4 0.15 0.26 1.0 -

Average 1.23 0.77 1.50 0.13 0.18 0.86 24 ^ΔWeight percentage of wet sludge as sampled. *Bottom sludge sample, all other samples were floating sludge.

TABLE 12. SLUDGE SOLVENT ANALYSIS - PILOT TRIAL II

Solvent Composition-Wt. % of Dry Sludge

Spraying Time Water* N-Butanol Xylenes Espesol 260 Hours

3 3.9 6.7 2.8 18

8 4.1 7.1 3.3 17

12 3.4 7.8 2.4 16

Average 3.8 7.2 2.8 17

*Weight percent of wet sludge as sampled

14 . SOLVENT MATE RIAL BALANCE - PILOT TRIAL I

TABLE

Spraying Time mitted & Capture

Hours Sprayed Captured Captured Emitted E in Sludge in Water in Air Sprayed

10 1678 55 1144 325 0.91

20 1678 55 1022 543 0.97

40 1678 190 763 681 0.97

60 1678 190 586 731 0.90

TABLE 15 . SOLVENT MATERIAL BALANCE - PILOT TRIAL II

Grams of Solvent /Hour Spraying Time

Sprayed Captured Captured Emitted Emitted & Captured Hours in Sludae in water in Air Sprayed

1.1 4420 520 239 3440 0.95

3.9 4420 520 144 3550 0.95

6.7 4420 520 81 3550 0.99

11.3 4420 520 71 3770 0.99

12 4420 520 69 3860 1.01

TABLE 16. SOLVEMT MATERIAL BALANCE PILOT TRIAL III

Spraying Time Grams of Solvent/Hour

Hours Sprayed Captured Captured Emitted Emitted & Captured in Sludge in water in Air Spraved

5 1910 110 851 589 0.81

15 1910 110 831 667 0.84

25 1910 110 818 1020 1.02

35 1910 110 770 952 0.96

46 1910 110 647 940 0.89

Claims

WHAT IS CLAIMED IS:

1. In a process of coating a workpiece using a sprayable coating composition in a spraybooth that communicates with a water wash, said water wash permitting contact between airborne components of said sprayable coating composition that enter said water wash and scrubbing water of a high volume, low energy wet scrubber operating at an inlet and outlet pressure difference in a range of less than about 10 inches of water, the improvement which comprises:

A. spraying in said spraybooth a scrubbable coating composition comprising a volatile organic compound that boils above about 98°C at atmospheric pressure and is water soluble above about 0.6% by weight at 20ºC and is transitory in said scrubbing water;

B. capturing in said scrubbing water a volatile portion of said scrubbable coating composition wherein said volatile portion comprises an amount of said volatile compound and wherein an ingredient of said scrubbing water reacts with a portion of said amount; and

C. maintaining a concentration of said volatile organic compound and reaction products of said volatile organic compound in said scrubbing water below that concentration at which efficiency falls below 10% of a maximum efficiency.

2. A process of coating in accordance with Claim 1, wherein said scrubbing water comprises base.

3. A process of coating in accordance with Claim 1, wherein the reaction between said portion of said amount and said ingredient is a hydrolysis reaction.

4. A process of coating in accordance with Claim 1, which comprises electrostatically spraying a portion of said scrubbable coating composition.

^UREΛTΓ

OMPI

-A^. ^WiP0 ,

5. A process of coating in accordance with Claims 1 or 2 or 3 or 4, wherein said scrubbable coating composition comprises a volatile organic compound that boils above about 120ºC and is water soluble above about 6% be weight.

6. A process of coating in accordance with Claim 5, wherein said scrubbable coating composition comprises an ester.

7. A process of coating in accordance with Claim 6, wherein said ester comprises an etherially linked ester.

8. A process of coating in accordance with Claim 7, wherein said ester comprises cellosolve acetate.

9. A process of coating in accordance with Claim 6, wherein said scrubbable coating composition comprises butyl carbitol.

10. A process of coating in accordance with Claims 1 or 2 or 3 or 4 or 6, wherein said scrubbing water contains cellosolve acetate and reaction products thereof in an amount below about 25 grams per liter.

11. In a process of coating a workpiece using a sprayable coating composition in a spraybooth that communicates with a water, wash, said water wash permitting contact between airborne components of said sprayable coating composition that enter said water wash and scrubbing water of a high volume, low energy wet scrubber operating at inlet and outlet perssure difference in a range of less than about 10 inches of water, the improvement which comprises:

A. spraying a scrubbable coating composition comprising a volatile organic compound that boils above about

98ºC at atmospheric pressure, is water soluble above about 0.6% by weight at 20ºC and is hydrolyzable;

B. capturing in said scrubbing water a portion of said scrubbable coating composition wherein said portion

OM comprises an amount of said volatile organic compound and said scrubbing water has a pH that enhances hydrolysis; and

C. maintaining the concentration of said volatile organic compound and hydrolysis products of said volatile organic compound in said scrubbing water below that concentration at which efficiency falls below 10% of a maximum efficiency.

12. A process of coating in accordance with Claim 11, wherein said volatile organic compound is water soluble above about 6% by weight at 20°C.

13. A process of coating in accordance with Claim 11, wherein said pH is basic.

14. A process of coating in accordance with Claim 11, which comprises electrostatically spraying a portion of said scrubbable coating composition.

15. A process of coating in accordance with Claim 11 or 12 or 13 or 14, wherein said hydrolyzable volatile organic compound boils above about 120ºC.

16. A process of coating in accordance with Claim

15, wherein said scrubbable coating composition comprises an ester.

17. A process of coating in accordance with Cla im

16, wherein said ester comprises cellosolve acetate.

18. A process of coating in accordance with Claim 15 or 16, wherein said pH is above about 9.

19. In a process of coating of workpiece using a sprayable coating composition in a spraybooth that communicates with a water wash, said water wash permitting contact between airborne components of said sprayable coating composition that enter said water wash and scrubbing water of a high volume, low energy wet scrubber operating at inlet and outlet pressure difference of less than about 10 inches, the improvement which comprises:

A. spraying in said spraybooth a scrubbing coating corapositon comprising a volatile organic compound that boils above about 98ºC at atmospheric pressure and is soluble above about 6% by weight at 20C and a volatile organic compound that boils above about 93ºC at atmospheric pressure, is water soluble above 0.6% by weight at 20°C and is hydrolyzable; B. capturing in said scrubbing water a portion of said scrubbable coating compositon wherein said portion comprises an amount of said compounds and said scrubbing water has a pH that enhances hydrolysis; and

C. maintaining the concentration of said volatile organic compounds and any hydrolysis products thereof below that concentration at which efficiency falls below about 10% of a maximum efficency.

20. A process of coating in accordance with Claim 19, wherein said pH is basic.

21. A process of coating in accordance with Claim 19, which comprises electrostatically spraying a portion of said scrubbable coating composition.

22. A process of coating in accordance with Claim 19 or 20 or 21, wherein said volatile organic compound that is hydrolyzable boils above about 120ºC.

23. A process of coating in accordance with Claim

22, wherein said scrubbable coating compostion comprises an ester.

24. A process of coating in accordance with Claim

23, wherein said ester comprises cellosolve acetate.

25. A process of coating in accordance with Claim 22 or 23, wherein said pH is above about 9.

26. In a process of coating a workpiece using a sprayable coating composition in a spray booth that communicates with a water wash permitting contact between airborne components of said sprayable coating composition that enters said water wash and scrubbing water of a high volume, low energy wet scrubber operating at inlet and outlet pressure difference in a range of less than about 6 inches of water, the improvement which comprises:

A. spraying in said spraybooth a scrubbable coating composition comprising a volatile organic compound that boils above about 120ºC at atmospheric pressure, is soluble in water above about 0.6% by weight at 20C and is hydrolyzable;

B. capturing in said scrubbing water a portion of said scrubbable coating composition herein said portion comprises between about 10-90% by weight of said volatile organic compound and said scrubbing water has a pH than enhances hydrolysis; and

C. biologically, physiocochemically or biologically and physiocochemically removing a product of said hydrolysis from said scrubbing water so as to maintain the concentration of said volatile organic compound and hydrolysis products therof in said scrubbing water below that concentration at which efficiency falls below about 10% of a maximum efficiency.

27. A process of coating in accordance with Claim 26 wherein said pH is basic.

28. A process of coating in accordance with Claim 26 which comprises electrostatically spraying a portion of said scrubbable coating composition.

29. A process of coating in accordance with Claim 26, or 27, or 28 wherein said volatile organic compound is water soluble above about 6% by weight.

30. A process of coating in accordance with Claim 29 wherein said scrubbable coating composition comprises an ester.

31. A process of coating in accordance with Claim 30 wherein said ester comprises an etherially linked ester.

32. A process of coating in accordance with Claim 31 wherein said ester comprises cellosolve acetate.