WO2009018299A1 - Dry cleaning apparatus using brominated solvents - Google Patents

Abstract

Apparatus utilizing a brominated solvent as a cleaning fluid in a dry cleaning process is disclosed. The dry cleaning process includes a washing stage using the brominated solvent to remove soil from soiled articles, a solvent recovery stage purifying and recycling the brominated solvent used in the washing ' stage, and a drying stage using a heated drying gas to remove and recover residual brominated solvent from the articles cleaned in the washing stage. When used in a dry cleaning process, the brominated solvent results in substantial energy savings and lower capital costs, for example based on the elimination of filters and adsorbers from the various process stages.

Description

DRY CLEANING APPARATUS USING BROMINATED SOLVENTS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The benefit under 35 USC § 119(e) of U.S. provisional patent application Serial No. 60/953,628 filed August 2, 2007, the disclosure of which is incorporated herein by reference, is claimed.

BACKGROUND OF THE INVENTION Field of the Disclosure

[0002] The disclosure generally relates to the dry cleaning of articles such as clothes, rugs, and other fabrics and, more particularly, to the use of a brominated solvent as a cleaning fluid in a dry cleaning process, and a dry cleaning apparatus capable of emissions-free operation without the necessity of carbon adsorbers and other emission control equipment.

Brief Description of Related Technology

[0003] The process of dry cleaning purportedly began in France in the 1840's. Various fluids have been historically used as dry cleaning solvents. Initially, these included hazardous solvents such as kerosene, gasoline, and benzene. Later solvents included perchloroethylene (PCE), hydrocarbons (e.g., petroleum distillate Stoddard solvents, synthetic paraffins), silicon-based solvents (e.g., cyclic siloxanes), and pressurized liquid carbon dioxide.

[0004] These dry cleaning solvents have disadvantages that render their use unfavorable. Hydrocarbons are flammable and potentially toxic, silicon-based solvents are flammable and do not clean as well as the other solvents, and carbon dioxide requires high-pressure equipment much different from other conventional dry cleaning processes.

[0005] As the predominant conventional dry cleaning solvent, PCE has significant drawbacks related to environmental, health, and energy concerns. US EPA NESHAP (National Emission Standards for Hazardous Air Pollutants) regulations limit PCE emissions, for example while transferring articles from the washer to the dryer in a transfer system or when venting to the atmosphere while the dry cleaning vessel is rotating. PCE is listed as a Group 2A carcinogen. PCE's high boiling point of 250 ⁰F (121 ⁰C) requires a substantial energy input to purify and recover PCE from a cleaning rinseate containing the solvent.

[0006] Processes using the above dry cleaning solvents have the additional disadvantage that they often require the use of expensive adsorbers (e.g., to remove residual solvent from recycled drying gas and prevent its release to the environment) and/or filters (e.g., to remove solvent contaminants that are removed from dry cleaned articles and then co-distilled with the solvent in a solvent recovery process).

[0007] Dry cleaning machines can be classified into two types: transfer and dry-to- dry. Similar to residential washing machines and dryers, transfer machines have a washing/extracting unit and a separate drying unit. Following the wash cycle, articles are manually transferred from the washer/extractor to the dryer. The transfer of wet fabrics is the predominant source of emissions in these systems. Dry-to-dry machines wash, extract, and dry the articles in a single vessel of a washing machine, so articles enter and exit the machine dry. Because the transfer step is eliminated, a dry-to-dry machine has a much lower emission of volatile cleaning fluid than transfer machines.

[0008] The presence of volatile cleaning fluid in these processes, however, has compelled the use of carbon adsorbers and other emission control equipment that can be costly, can be attendant with their own emissions hazards, and can complicate and reduce efficient operation of a dry cleaning apparatus.

SUMMARY OF THE INVENTION

[0009] Disclosed herein are processes and apparatus that utilize a brominated solvent as a cleaning fluid in a dry cleaning process. Brominated solvents are generally safer than other conventional dry cleaning solvents (e.g., with respect to toxicity, flammability, hazardousness), and they reduce operating and capital costs of the dry cleaning process. The disclosed apparatus is capable of emissions-free or emissions-light operation without the necessity of carbon adsorbers and other emissions control apparatus required by conventional dry cleaning apparatus. That operation is possible because of a unique arrangement and selection of heat exchange equipment within the apparatus and the dry cleaning solvent.

[0010] The disclosed dry cleaning apparatus includes a cleaning vessel having an inlet and an outlet, a fluid recycle line, a condenser having an inlet and a vapor effluent outlet, and a heater having an inlet and an outlet. The fluid recycle line is in fluid communication with both the cleaning vessel inlet and the cleaning vessel outlet. The condenser inlet is in fluid communication with the cleaning vessel outlet. The heater inlet is in fluid communication with the condenser vapor effluent outlet, and the heater outlet is in fluid communication with the cleaning vessel inlet. In the disclosed apparatus, the condenser is capable of reducing a concentration of dry cleaning solvent vapor in a cleaning vessel vapor effluent to a level of about 200 ppm or less. The fluid communication between the condenser vapor effluent outlet and the cleaning vessel inlet is free of adsorbers or other emission control apparatus, and the fluid recycle line is free of filters. Preferably, the fluid communication between the condenser vapor effluent outlet and the cleaning vessel inlet is also free of filters and the fluid recycle line is also free of adsorbers or other emission control apparatus. In various embodiments, the dry cleaning apparatus also includes a recirculating fan upstream of the heater, a solids trap in fluid communication with the cleaning vessel outlet, a solvent tank having an outlet in fluid communication with the cleaning vessel inlet, and/or a distillation apparatus having an inlet in fluid communication with the cleaning vessel outlet. Preferably, the heater includes both a a refrigeration energy reclamation coil and a still energy reclamation coil.

[0011] Various embodiments of a process for dry cleaning soiled articles are disclosed herein. One such embodiment includes charging a cleaning vessel with a cleaning fluid and at least one or more soiled articles. The cleaning fluid includes a brominated solvent and a cationic detergent. The articles contain soil to be removed. The process also includes agitating the cleaning vessel containing the cleaning fluid and the soiled articles to remove at least a portion of the soil present in the articles to form a cleaning rinseate. The cleaning rinseate includes the brominated solvent, the cationic detergent, and the removed soil, and cleaned articles. [0012] In another embodiment, a process for purifying a brominated dry cleaning solvent includes charging a distillation apparatus with a cleaning rinseate that includes a brominated solvent, a cationic detergent, and soil; and, heating the distillation apparatus to a temperature sufficient to release at least a portion of the brominated solvent from the cleaning rinseate and to form: an overhead vapor distillate and a bottoms residue. The overhead vapor distillate includes the released brominated solvent, and the bottoms residue includes the cationic detergent and the soil.

[0013] In yet another embodiment, a process for drying dry-cleaned articles includes feeding heated drying gas into a cleaning vessel containing cleaned articles. The cleaned articles have a brominated solvent present therein. The process also includes agitating the drying gas-fed cleaning vessel to form a cleaning vessel vapor effluent that includes the drying gas and released brominated solvent. The process further includes condensing the cleaning vessel vapor effluent to form a liquid condensate that includes the released brominated solvent, and a condenser effluent that includes cooled drying gas. The process also includes recycling the condenser effluent to a heater and heating the cooled drying gas to re-form the heated drying gas.

[0014] Additional features of the invention may become apparent to those skilled in the art from a review of the following detailed description, taken in conjunction with the drawings, examples, and appended claims.

BMEF DESCRIPTION OF THE DRAWINGS

[0015] For a more complete understanding of the disclosure, reference should be made to the following detailed description and accompanying drawings wherein:

[0016] Figure 1 illustrates process diagram for a dry-cleaning process using a brominated solvent, the process including a washing stage, a solvent recovery stage, and a drying stage.

[0017] Figure 2 illustrates the washing stage of the dry-cleaning process of Figure 1.

[0018] Figure 3 illustrates the solvent recovery stage of the dry-cleaning process of Figure 1. [0019] Figure 4 illustrates the drying stage of the dry-cleaning process of Figure 1.

[0020] While the disclosed process and apparatus are susceptible of embodiments in various forms, specific embodiments of the invention are illustrated in the drawings (and will hereafter be described) with the understanding that the disclosure is intended to be illustrative, and is not intended to limit the invention to the specific embodiments described and illustrated herein.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Disclosed herein are apparatus and dry cleaning processes preferably using a brominated solvent. The dry cleaning process includes three different sub-processes that are performed during various stages of a complete dry cleaning circuit 10, as illustrated in Figures 1-4. First, a washing stage 12 uses the brominated solvent to remove soil from soiled articles. Second, a subsequent solvent recovery stage 14 purifies and recycles the brominated solvent used in the washing stage 12. Third, a drying stage 16 that is subsequent to the washing stage 12 and generally in parallel with the solvent recovery stage 14 uses a heated drying gas to remove and recover residual brominated solvent from the articles cleaned in the washing stage 12. Figure 1 illustrates the dry cleaning circuit 10 as a whole, while Figures 2-4 individually illustrate the washing stage 12, the solvent recovery stage 14, and the drying stage 16, respectively. The disclosed apparatus perform the various stages of the dry cleaning circuit 10.

Dry Cleaning Washing Process

[0022] The dry cleaning circuit 10 and the washing stage 12 utilize a cleaning vessel 20. The cleaning vessel 20 is generally capable of agitating its contents. For example, the cleaning vessel 20 can include a drive mechanism and an internal rotating drum (not shown) having a perforated outer surface, making it capable of agitation (i.e., when rotating at lower speeds) and capable of performing a rotary extraction (i.e., when rotating at higher speeds to extract liquids present in the cleaning vessel 20 contents. The cleaning vessel 20 also preferably includes a plurality of internal paddles (not shown) that lift and drop the contents during agitation, thereby providing additional mechanical action to dislodge soils and other particulates from the contents to be cleaned.

[0023] The cleaning vessel 20 can have any suitable capacity, but a capacity of at least about 25 gallons (gal) is desirable for use in commercial applications. Preferably, the capacity ranges from about 20 gal to about 75 gal, or about 25 gal to about 50 gal, for example about 25 gal, 35 gal, or 50 gal. Alternatively, the capacity can be expressed in terms of the weight of articles that can be conveniently contained in a wash load. Put this way, the capacity preferably ranges from about 40 Ib (18 kg) to about 150 Ib (68 kg), or about 50 Ib (23 kg) to about 100 Ib (45 kg), for example about 50 Ib (23 kg), 70 Ib (32 kg), or 100 Ib (45 kg). When a 25-gallon cleaning vessel 20 includes the internal rotating drum, a rotating drum drive motor (not shown) having a power of about 10 horsepower (hp) is generally sufficient to achieve desired agitation/rotation rates. Specifically, the internal rotating drum is capable of rotating at speeds of at least about 400 revolutions per minute (rpm), with speeds of about 40 rpm to about 50 rpm being suitable for agitation while cleaning/drying, and with speeds of about 400 rpm to about 500 rpm being suitable to extract liquids present in the cleaning vessel 20 contents.

[0024] The cleaning vessel 20 in general, and in particular its components that are exposed to the cleaning vessel 20 contents (e.g., articles to be cleaned, the dry cleaning solvent, washing detergent) during normal operation, is preferably constructed of stainless steel to prolong its lifetime and prevent corrosion. For similar reasons, the remaining (exposed) components of the dry cleaning circuit 10 equipment are also preferably constructed of stainless steel.

[0025] Before soiled articles are loaded into the cleaning vessel 20 and subjected to the dry cleaning process, they are spotted, weighed, and sorted. The soiled articles are not particularly limited, and include clothes, garments, and other fabrics capable of being cleaned in a conventional dry cleaning process. As used herein, the term "soil" is also not particularly limited and generally refers to any materials capable of being removed from the articles in a conventional dry cleaning process. For example, soils can include insoluble organic or inorganic material (e.g., dirt) on the articles that can be removed and rinsed away by the mechanical action of agitated solvent and articles contacting each other. Similarly, soils can also include stains (e.g., oil-based, water- based, protein-based, and combinations thereof) that can be removed by dissolution of the stain material in at least one of the cleaning solvent (i.e., the brominated solvent), water, and a cationic detergent added to the cleaning vessel 20. Examples of oil- based soils include oils, greases, fatty acids, oil-based paints, foodstuffs such as chocolate, etc. Examples water-based soils include wine, perspiration, urine, water- based (latex) paints, etc. Examples of protein-based soils include blood, urine, eggs, etc.

[0026] Spotting is the application of a small amount of solvent or other cleaning agent (i.e., a spotting agent) to a soiled article for stain removal. Spotting is performed manually, most often before the articles are loaded into the cleaning vessel 20. However, spotting can be performed after the entire dry cleaning cycle is completed and the cleaned articles are removed from the cleaning vessel 20. The amount of a spotting agent applied to a soiled article is usually less than one ounce. A wide variety of compounds are used in the spotting agents, for example depending on the type of stain and the solvent used in the dry cleaning machine. The spotting agents and dry cleaning solvent work in tandem, and many spotting agents are preferably used with a particular solvent. Two categories of spotting agents include dry-side (used on oil-based stains) and wet-side (used on water-based) agents. Some common chemicals contained in spotting agents include amyl acetate, acetic acid, hexylene glycol, butyl cellosolve, and xylene. The spotting agents can include the same brominated solvent used as the dry cleaning solvent to enhance their cleaning ability.

[0027] Sorting typically involves separating dark- and light-colored articles so that they can be cleaned separately to reduce the potential effect of dye transfer to light colored articles. Sometimes articles are sorted by fabric weight, for example separating thick wools from sheer silks to better optimize drying times. If clothes are not fully dry when they are removed from the machine, residual dry cleaning solvent in the garment is released to the surrounding environment.

[0028] The operator then loads the articles through a sealed access door (not shown) into the cleaning vessel 20. For the 25-gallon cleaning vessel 20 described above, up to about 55 lbs (25 kg) of articles can be loaded into the cleaning vessel 20. Smaller wash loads are possible, for example when a shorter cycle time is desired (e.g., by reducing the required drying time), or when certain articles are incompatible for cleaning with other articles. The operator then closes the access door and initiates the washing cycle. A pre-programmed programmable logic controller (PLC) automatically controls the duration and operating conditions of the washing cycle, including the washing, solvent recovery, and drying stages 12, 14, and 16, respectively. The washing program generally varies depending on the type of article being cleaned and the size of the wash load, for example varying the wash time, the time the solvent is in direct contact with the articles, and/or the degree of agitation/rotation used on the article. The PLC automatically and consistently controls all functions of the dry cleaning circuit 10.

[0029] The washing stage 12 begins by charging the cleaning vessel 20 with soiled articles to be cleaned (as described above) and with a cleaning fluid. The cleaning fluid generally includes a brominated solvent and a cationic detergent. Preferably, the cationic detergents are those disclosed in U.S. Serial No. 60/927,118, filed May 1, 2007, and U.S. Serial No. 12/104,918 filed April 17, 2008, which are hereby incorporated herein by reference in their entirety and collectively referred to herein as the '118 and '918 applications. As illustrated in Figure 1, the brominated solvent is generally added to the cleaning vessel 20 by pumping the brominated solvent from a solvent tank 65 through a line 136 with a pump 45. In typical commercial applications, the solvent tank 65 preferably has a capacity of about 50 gal (e.g., a stainless steel 55-gal drum), and the pump 45 preferably is a 1.5-hp open impeller pump capable of passing small-diameter (e.g., up to about 0.375 inch-diameter (about 1 cm-diameter) particles and achieving flow rates of at least about 30 gpm. The brominated solvent is then pumped through a line 140, past a junction (e.g., a three- way valve 144 as illustrated), through a line 148, and then into the cleaning vessel 20 via an inlet orifice 22 (e.g., sealed with a solenoid valve). The brominated solvent is generally added in an amount of about 20 gal per 55 Ib of articles in the cleaning vessel 20. The brominated solvent preferably has a temperature slightly above room temperature (e.g., 85 ⁰F (29.4 ⁰C)), and this temperature is preferably maintained throughout the washing stage 12. The cationic detergent is preferably stored and added to the cleaning vessel 20 separately from the brominated solvent. For example, a solution containing the cationic detergent can be manually injected by the operator via the orifice 22 or a different orifice (not shown), preferably in an amount of about 0.5 oz to about 1 oz cationic detergent solution per 10 lbs (4.5 kg) of articles. Alternatively, a separate reservoir (not shown) for the cationic detergent solution can be separately maintained along with a means for injecting (e.g., an additional pump, a syringe, a pressurized reservoir) a pre-selected amount of the solution at the beginning of the washing stage 12.

[0030] The brominated solvent preferably is a non-hazardous, non-toxic organic solvent having at least one bromine atom per solvent molecule and having favorable physical properties for dry cleaning. Relevant physical properties include: boiling point, cleaning solvency, specific gravity, viscosity, surface tension, water solubility, polarity, and evaporation rate.

[0031] The boiling point of the brominated solvent affects the cost of recovering and ability to recycle clean brominated solvent from contaminated brominated solvent that has been used in a previous wash cycle. A lower boiling point requires less thermal energy to distill clean brominated solvent from contaminated brominated solvent and further results in fewer, if any, high-boiling point contaminants from being co-distilled and recovered with the clean brominated solvent. Preferably the boiling point is less than about 240 °F (115 ⁰C), for example in a range of about 100 ⁰F (37.7 °C) to about 215 ⁰F (102 ⁰C), about 135 ⁰F (57 ⁰C) to about 170 ⁰F (77 ⁰C), or about 155 ⁰F (68 ⁰C) to about 160 ⁰F (71 ⁰C).

[0032] The cleaning solvency of solvent is measured by a standard Kari-Butanol laboratory test ("KB" value; ASTM D 1133-04). A high KB value means the cleaning agent is more aggressive and active; mild cleaners have lower KB values whereas more powerful cleaners have higher KB values. A high KB value also reduces the time required for the washing stage 12. Preferably, the KB value is at least about 100, for example in a range of about 110 to about 150.

[0033] The specific gravity of a solvent is important for "solvent drop" processes using falling drops of solvent to impart mechanical action for cleaning. A higher weight resulting from a higher specific gravity can impart the mechanical action needed to remove insoluble soils. Preferably, the specific gravity is at least about 1.1, for example in a range of about 1.2 to about 1.5.

[0034] The viscosity of solvent represents its ability to flow. A lower viscosity allows the solvent to more easily flow within and penetrate the fibers of a fabric, thereby increasing the solvent's ability to remove soils. Preferably, the viscosity is less than about 0.7 cP at 25 ⁰C, for example in a range of about 0.2 cP to about 0.6 cP at 25 ⁰C.

[0035] Similarly, the surface tension of solvent represents its ability to wet a fabric. The lower the surface tension, the easier it is to wet a larger surface area of an article's fabric, thereby increasing the solvent's ability to remove soils. Preferably, the viscosity is less than about 30 dyn/cm at 20 ⁰C, for example in a range of about 15 dyn/cm to about 30 dyn/cm at 20 ⁰C.

[0036] A solvent's water solubility and polarity represent the solvent's ability to more easily dissolve and remove water-soluble stains and soils from an article. Preferably, a solvent is polar and has a water solubility of at least about 0.05 g/100 ml at 25 ⁰C, for example in a range of about 0.1 g/100 ml to about 0.5 g/100 ml at 25 ⁰C.

[0037] The evaporation rate of a solvent is measured relative to the evaporation rate of butyl acetate. A higher evaporation rate decreases the drying time required for dry cleaned articles during the drying stage 16. Preferably, the evaporation rate is at least about 2, for example in a range of about 3 to about 10.

[0038] Suitable brominated solvents having many of the desirable physical properties listed above include monobromoalkanes, in particular those having from two to four carbon atoms. Suitable monobromoalkanes include ethyl bromide, n- propyl bromide, iso-propyl bromide, n-butyl bromide, sec-butyl bromide, tert-butyl bromide, and combinations thereof. A preferred brominated solvent is n-propyl bromide.

[0039] In further embodiments, the cleaning fluid can include or exclude other components. Preferably, the cleaning fluid is free or substantially free of non- brominated solvents, for example PCE, hydrocarbons, silicon-based solvents, and carbon dioxide. In certain embodiments, the cleaning fluid may additionally include a small amount of water, for example acting as a diluent for the cationic detergent in the cationic detergent solution and assisting in the removal of water-soluble soils/stains during the cleaning stage 12. Preferably, the cleaning fluid also includes at least one solvent stabilizer to increase the useful lifetime of a batch of brominated solvent, for example, by preventing the brominated solvent from forming acidic compounds capable of corroding the equipment in the dry cleaning circuit 10. Suitable solvent stabilizers include nitromethane, nitroethane, nitropropane, nitrobutane, nitropentane, propylene oxide, 1 ,2-epoxy butane (i.e., butylene oxide), pentylene oxide, hexylene oxide, cyclohexene oxide, 1,3-dioxolane, 1,4-dioxane, and combinations thereof.

[0040] In a preferred embodiment, the cleaning fluid includes two independent cleaning fluids (i.e., a first cleaning fluid and a second cleaning fluid) that are independently charged to the cleaning vessel 20. The first cleaning fluid includes the brominated solvent and is essentially free of the cationic detergent. A preferred first cleaning fluid also includes the solvent stabilizers nitromethane, 1,2-epoxy butane, and 1,3-dioxolane, and is commercially available under the trade name DRYSOLV from Enviro Tech International, Inc. (Melrose Park, IL). The second cleaning fluid includes the brominated solvent, water, and the cationic detergent, for example including the detergent compositions disclosed in the '118 and '918 applications. A preferred second cleaning fluid according to the disclosure of the '118 and '918 applications is commercially available under the trade name DRYSOLV D from Enviro Tech International, Inc.).

[0041] Once the cleaning vessel 20 has been charged with the cleaning fluid and the soiled articles, the cleaning vessel 20 and its contents are agitated (e.g., rotated in the case of an internal rotating drum) to remove at least a portion of the soil present in the articles. Preferably, the cleaning vessel 20 is agitated in one direction for a first pre-selected time, and then agitated in the reverse direction for a second pre-selected time. The total agitation time is preferably less than about 10 min, or less than about 6 min, for example about 4 min. The agitation direction is preferably reversed three times in a single cycle, for example including four 1 -minute sub-cycles, with the agitation direction of each sub-cycle being reversed relative to the preceding sub- cycle. The agitation/rotation results in cleaned articles and creates a cleaning rinseate including the brominated solvent, the cationic detergent, the removed soil, and other optional ingredients of the cleaning fluid (e.g., water, solvent stabilizers, etc.).

[0042] While the cleaning vessel 20 is agitated, a portion of the cleaning rinseate is preferably continuously recycled in a fluid recycle line. As illustrated in Figure 1 , at least a portion of the cleaning rinseate is withdrawn from the cleaning vessel 20 via an outlet orifice 23 through lines 100 and 104 by the pump 45. The cleaning rinseate is then recycled through the line 140, past the junction 144, through line 148, and then into the cleaning vessel 20 via the orifice 22. Thus, the fluid recycle line illustrated in Figure 1 includes lines 100, 104, 140, and 148. The continuous recycling and reintroduction of the cleaning rinseate provides additional mixing, splashing, and mechanical action to improve the rate of soil removal from the articles in the cleaning vessel 20. The cleaning rinseate is preferably recycled at a rate of about 30 gpm when the cleaning vessel is initially charge with about 20 gal of cleaning fluid, and the recycle rate can be adjusted accordingly based on wash load size and solvent charge volumes.

[0043] Preferably, the recycling of the cleaning rinseate also includes passing the removed portion of the cleaning rinseate through a conventional solids trap 25 along the fluid recycle line, prior to reintroducing the removed portion into the cleaning vessel 20. As illustrated in Figure 1, the line 100 is an inlet to the solids trap 25 and the line 104 is a bottom outlet from the solids trap 25. When liquid (e.g., the cleaning rinseate) is flowing through the solids trap, larger solid items (e.g., buttons, pens, lighters, coins, etc. that may have been added to the cleaning vessel 20 along with the articles but were subsequently removed by the cleaning action therein) can be captured and removed from the flow system, thereby preventing damage to and/or plugging of downstream unit operations.

[0044] Once the agitation of the cleaning vessel 20 is complete, the recycle of the cleaning rinseate (if any) is terminated as well. Much of the cleaning rinseate then collects at the bottom of the cleaning vessel 20 and is removed (e.g., by draining or pumping), while a residual portion of the cleaning rinseate remains in the cleaned articles. A rotary extraction can be performed prior to removing the cleaning rinseate from the cleaning vessel, thereby lowering the amount of residual cleaning rinseate remaining in the cleaned articles. Preferably, the residual cleaning rinseate is removed from the cleaned articles by first charging the cleaning vessel with additional, fresh (i.e., free from cleaning rinseate impurities) brominated solvent and then once again agitating the cleaning vessel 20 to remove at least a portion of the residual cleaning rinseate from the cleaned articles. The fresh brominated solvent is preferably supplied from the solvent tank 65 and recycled through the cleaning vessel 20 in the same manner as described above for the initial cleaning. Similar to the cleaning rinseate, the additional brominated solvent (which is no longer fresh due to the extraction of additional cleaning rinseate from the cleaned articles) is then removed from the cleaning vessel.

[0045] At this point, two subsequent process stages generally begin and are performed in parallel: the solvent recovery stage 14 and the drying stage 16.

Solvent Recovery Process Loop

[0046] The solvent recovery stage 14 utilizes a distillation apparatus 50. In one embodiment, the distillation apparatus 50 can be a conventional still or other apparatus for heating a liquid mixture and collecting the released vapor, for example those used in other dry cleaning processes using non-brominated solvents. Preferably, the distillation apparatus 50 is a still of stainless steel construction having a flat, slightly inclined base and heating mechanism integral with the outer surface of the flat base, opposite the interior volume of the distillation apparatus. The heating mechanism can be, for example, an integral boiler having a water sump with electrical immersion heaters of about 27 kilowatt (kW) power rating and dimpled steam platecoil, of which the heat transfer surface is the bottom plate of the still. The flat base and the heating mechanism facilitate the cleaning of the still for the plant operator. With no internal steam coils or electric heating elements obstructing access, the operator can quickly clean out the still bottoms and return the still to an operating status. The use of electric heating elements instead of steam may also reduce heat emissions from a dry cleaner plant and lower or eliminate the capital/operating costs associated with a separate steam boiler.

[0047] The solvent recovery stage 14 begins by charging the distillation apparatus 50 with the cleaning rinseate, for example including the brominated solvent, the cationic detergent, and the soil removed from the cleaned articles in the previous wash stage 12. As illustrated in Figure 1, the cleaning rinseate from the cleaning vessel 20 is drained and pumped through the lines 100 and 104 by the pump 45. The cleaning rinseate exits the pump 45 through the line 140 and then through a line 152 via the junction 144 into the distillation apparatus 50. If the additional, fresh brominated solvent was also added to the cleaning vessel in the previous wash stage 12 to remove additional residual cleaning rinseate, the additional brominated solvent can be pumped to the distillation apparatus 50 as well.

[0048] The distillation apparatus 50 preferably has a sufficient internal volume to accommodate at least two complete solvent charges of the cleaning vessel - an initial charge of the brominated solvent used for washing and a second charge of the brominated solvent for rinsing. Accordingly, the volume is preferably at least about 40 gal.

[0049] The distillation apparatus 50 is generally operated as a batch operation. Specifically, all of the cleaning rinseate to be purified is fed to the distillation apparatus 50, and then heat is applied to begin distillation. The distillation apparatus 50 is heated to a temperature sufficient to release at least a portion of the brominated solvent from the cleaning rinseate and to form: (i) an overhead vapor distillate including the released brominated solvent, and (ii) a bottoms residue. Preferably, the temperature is at or slightly above the boiling point of the brominated solvent. For example, when the brominated solvent is one of the monobromoalkanes listed above, the temperature is in a range of about 100 ⁰F (38 °C) to about 215 °F (101 ⁰C), about 135 ⁰F (57 ⁰C) to about 170 ⁰F (77 ⁰C), or about 155 ⁰F (68 ⁰C) to about 160 ⁰F (71 ⁰C). In a preferred embodiment, when the brominated solvent is n-propyl bromide, the temperature is preferably about 158 ⁰F (70 ⁰C) (i.e., the boiling point of n-propyl bromide).

[0050] The bottoms residue includes the cationic detergent and the removed soil from the cleaning rinseate, and it can also include water if originally present in the cleaning fluid. The bottoms residue accumulates slowly in the distillation apparatus 50, and it need only be removed intermittently to avoid excessive build-up and the resulting undesirable insulation of the distillation apparatus 50. During normal operation, the bottoms residue can be removed via a drain 156 approximately every two days, for example after about 16 to about 20 wash cycles. When using the disclosed system of solvents, detergents, and operating conditions, the bottoms residue is generally a viscous, liquid mixture that can be easily removed from the distillation apparatus 50 without resorting to labor- and time-intensive scraping.

[0051] In additional embodiments, the overhead vapor distillate can include other components. The cleaning rinseate can further include water (e.g., if water is an initial component of the cleaning fluid), in which case the heating of the distillation apparatus 50 releases at least a portion of the water from the cleaning rinseate and the overhead vapor distillate further includes the released water. If solvent stabilizers are also added to the cleaning fluid, certain of the stabilizers can be recovered in the overhead vapor distillate and recycled. For example, two preferred stabilizers used in connection with n-propyl bromide, nitromethane and 1,3-dioxolane, can be recovered and recycled: nitromethane has a high boiling point (214 ⁰F (101 ⁰C)), but forms an azeotropic mixture with n-propyl bromide, and 1,3-dioxolane has a low boiling point (74 ⁰F (23 ⁰C)), so both can be at least partially recovered and recycled with n-propyl bromide. A third preferred stabilizer, 1,2-epoxy butane, is generally consumed during the operation of the normal wash circuit, and it cannot be appreciably recycled. A preferred method of replenishing a depleted stabilizer (e.g., 1,2-epoxy butane) includes fortifying the second cleaning fluid that contains the cationic detergent (described above) with the stabilizer.

[0052] The overhead vapor distillate exits the distillation apparatus 50 via a line 160 and can be passed via a line 161 to a first (water cooled) condenser 55 or to a still energy reclaim coil 44, which is discussed in more detail below in connection with the drying process loop. The first condenser 55 is a conventional unit, generally has a heat duty sufficient to handle the heat input of the distillation apparatus 50, and operates at cold temperature in a range of about 40 ⁰F (4 ⁰C) to about 85 ⁰F (29 ⁰C), for example about 60 ⁰F (16 ⁰C). Water used in the first condenser is controlled with a temperature-actuated modulating valve (not shown) placed on an inlet side of the heat exchanger 55. The valve includes a bypass line that ordinarily remains closed by a hand-operated valve, except in the case of modulating a valve failure. The temperature-actuated modulating valve includes a thermocouple (not shown) located in a liquid condensate line 122 (discussed below). Where the dry cleaning solvent is a brominated solvent, the temperature of the temperature- actuated modulating valve preferably is set at about 75 ⁰F (24 ⁰C) to about 135 ⁰F (57 ⁰C), for example at 105 ⁰F (41 ⁰C). The temperature-actuated modulating valve opens and closes to maintain this set temperature.

[0053] A liquid condensate formed in the first condenser 55 includes the released brominated solvent. The temperature of the liquid condensate is generally about 95 ⁰F (35 ⁰C), and it gradually reduces to a final storage temperature of about 85 ⁰F (29 ⁰C) in the storage tank 65. If the overhead vapor distillate includes water, then the liquid condensate is a multiphase liquid condensate further including the released water. Any recovered solvent stabilizers in the condensate are generally in the solvent phase of the condensate.

[0054] In the illustrated embodiment of Figure 1, the liquid condensate is the multiphase liquid condensate that is fed via a line 122, through a junction 120 (e.g., a three-way valve as illustrated), and then via a line 124 to a water separator 60. The water separator 60 separates the released water and the released brominated solvent into discrete continuous phases. The water separator 60 can be any conventional liquid-liquid separator, and is preferably a gravity separator, for example a settling tank. The water separator 60 preferably has an internal volume of about 11 gal, which provides a sufficient residence time based on a typical distillation rate of about 1 gpm to about 3 gpm condensate entering the water separator 60. The water separator 60 may include a cooling coil to accelerate the separation. A wastewater stream is withdrawn from the water separator 60 via a line 128 through a valve (not shown) to a secondary separator 61 of somewhat smaller capacity than water separator 60. The released water overflows into the secondary water separator 61 where further separation can occur. Any brominated solvent contained in the released water will settle to the bottom of the secondary water separator 61 and can be withdrawn via a line 132 and fed to the solvent tank 65 for storage until the next washing stage 12 begins. After the released brominated solvent is removed from the secondary water separator 61, the released water can be drained and disposed via an outlet line 129 to the secondary separator 61.

Drying Process Loop

[0055] The drying stage 16 also utilizes the cleaning vessel 20 and the overhead vapor distillate exiting the distillation apparatus 50. Once the washing stage 12 is completed, the drying stage 16 begins by feeding a heated drying gas (e.g., air) into the cleaning vessel 20. The cleaned articles present in the cleaning vessel 20 contain residual brorninated solvent remaining from the previous washing and/or rinsing steps of the washing stage 12. Relative to conventional processes, the heated drying gas has a low temperature, preferably having a temperature of about 100 ⁰F (38 °C) to about 150 ⁰F (66 ⁰C), for example about 140 ⁰F (60 ⁰C) to about 145 ⁰F (63 ⁰C). For typical commercial wash loads, the flow rate of the drying gas throughout the entire drying stage 16 circuit is a variable air volume flow rate between about 75 cfrm to about 750 cfm, preferably optimized in the drying stage 16 to both reduce the drying time and maximize the solvent recovery rate. For example, starting out at a higher flow rate and gradually decreasing over the course of the drying stage 16 to a lower flow rate based on optimized recovery parameters. These values can be suitably adjusted based on varying wash load sizes, desired drying times, etc. As illustrated in Figure 1, the heated drying gas is fed to the cleaning vessel 20 via a line 128 and through an inlet orifice 21.

[0056] The cleaning vessel 20 and its contents are agitated while the heated drying gas is being continuously fed into the vessel. The convective action resulting from the flowing heated drying gas and the agitated articles within the cleaning vessel 20 promotes the rapid evaporation and release of the brominated solvent from the articles, thus creating a cleaning vessel vapor effluent including the drying gas and the released brominated solvent. The cleaning vessel vapor effluent is then withdrawn from the cleaning vessel 20 via the outlet orifice 23 through the line 100. Preferably, the vapor effluent is also passed through the solids trap 25 to remove any small solids particulates (e.g., lint) that may have been dislodged from the articles and transported out of the cleaning vessel 20 by the flowing drying gas. [0057] In any event, the cleaning vessel vapor effluent then flows through a line 108 (either as a continuation of the line 100 or as the outlet of the solids trap 25) to a second condenser 30. The second condenser 30, described in more detail below, reduces (or eliminates) the amount of dry cleaning solvent present in the vapor effluent to provide a condenser vapor effluent (i.e., drying gas). The condenser vapor effluent preferably contains about 200 ppm or less of the dry cleaning solvent and is passed via a line 120 to a heater 40, described in more detail below) before being fed via line 128 into the cleaning vessel 20. More preferably, the condenser vapor effluent contains about 150 ppm or less of the dry cleaning solvent, even more preferably about 100 ppm or less of the dry cleaning solvent, and still even more preferably about 50 ppm or less of the dry cleaning solvent.

[0058] Any condenser capable of reducing the concentration of a dry cleaning solvent vapor in the cleaning vessel vapor effluent to a level of 200 ppm or less is suitable for use as the second condenser 30. One such condenser is a finned tubular coil. The coil preferably has a face (or opening) area of about 1 square foot (0.09 square meters) to about 2 square feet (0.18 square meters), more preferably about 1.5 square feet (0.14 square meters). Generally, the face (or opening) area is that portion of the coil at the entrance point of the cleaning vessel vapor effluent. The coil also preferably has a heat exchanging capacity of up to about 50,000 BTU/hour. The finned tubular coil preferably is constructed of copper tubular coils with aluminum fins, and preferably is coated with a halogenated solvent-resistant material, such as polyamide or ElectroFin® polymeric e-coat. The coating serves to prevent degradation of the finned tubular coils, which degradation could adversely affect its heat transfer capabilities.

[0059] A refrigeration system (not shown) supplies liquid refrigerant to the second condenser 30. That system preferably is capable of delivering a heat exchange capacity of about 3,000 BTU/hour to about 47,000 BTU/hour at respective cold temperatures in a range of about -94 ⁰F (-70 ⁰C) to about -13 ⁰F (-25 ⁰C). Preferably, the refrigeration system is either a compound (dual-stage compressor) or cascade (dual compressor) system that uses R-404a as the primary liquid refrigerant or, alternatively, R-507a, -R410a, or refrigerants having similar properties. As described in more detail below, the refrigerant will evaporate in cooling the cleaning vessel vapor effluent in the condenser to provide a condenser effluent and a liquid condensate.

[0060] Multiple compression refrigeration systems, such as those preferred herein, are more energy efficient than conventional, single-stage systems because the energy necessary to achieve high compression ratios in single-stage compressions systems increases dramatically as the compression ratio increases. For example, to achieve a 9:1 compression ratio with a compound compressor or cascade system would require two separate 3:1 compression ratio cycles in series. The total energy required to achieve two separate 3:1 compression cycles is significantly less than that required to achieve a single 9:1 compression cycle; however, the net effect is the achievement of the 9:1 compression ratio.

[0061] A finned tubular coil is generally designed to either cool a gaseous vapor (transfer heat energy) or remove moisture (transfer mass energy). Coils designed to transfer heat energy are typically characterized by large surface areas, which can be accomplished by placing a large number of fins in close proximity to one another. In that design, a greater proportion of transferred energy in the coils is in the form of thermal energy versus mass energy. That design is conventional in the dry cleaning industry. Coils designed to transfer mass energy are not characterized by large surface areas; instead, the design is focused on creating concentration gradients at the coil surfaces and maximizing the surface area upon which contact between the vapor stream and this concentration gradient occurs. In this latter design, a greater proportion of transferred energy in the coils is in the form of mass energy versus thermal energy. This latter design is unconventional in the dry cleaning industry. It has been discovered that this design is vastly more energy efficient and faster at condensing dry cleaning solvent present in the cleaning vessel vapor effluent, hi combination with the compound or cascade compressor systems preferred herein, it is now possible to generate a much faster and much more efficient condensation of these vapors because the preferred compressor system is able to generate sufficiently-high differential concentration gradients because of the sufficiently low temperatures it is capable of achieving. [0062] Evaporation of refrigerant in the second condenser 30 is controlled by a metering device. The metering device could be an electronic expansion valve, mechanical expansion valve, fixed or variable orifice expansion device, or a fixed capillary tube. The second condenser 30 will cool the cleaning vessel vapor effluent to produce the condenser effluent exiting the second condenser 30 via line 120, and a liquid condensate exiting the second condenser 30 via a line 116. The liquid condensate includes the released brominated solvent recovered from the articles in the cleaning vessel 20. The condenser effluent includes the drying gas (e.g., cooled to about 75 ⁰F (24 ⁰C)).

[0063] Preferably, the low operating temperature of the second condenser 30 results in the liquid condensate containing essentially all of the dry cleaning solvent (e.g., the brominated solvent) contained in the cleaning vessel vapor effluent, and the condenser effluent is accordingly essentially free of the dry cleaning solvent (e.g., a concentration of brominated solvent vapor in the condenser effluent of less than 200 ppm brominated solvent). This helps maximize the recovery of the dry cleaning solvent, reducing both waste and potential operator exposure to residual dry cleaning solvent remaining in the dried articles and/or the cleaning vessel 20 at the end of the drying stage 16. For typical solvent volumes used during the wash stage 12, the amount of the recovered brominated solvent, for example, can be significant: about 5 gal per drying stage 16. Preferably, the recovered brominated solvent is recycled and returned to the solvent tank 65 for further use.

[0064] Heretofore, low dry cleaning solvent concentrations in the drying gas were possibly only with a combination of condensers and emission control apparatus (including carbon adsorbers, for example). In efficiently achieving low second condenser 30 operating temperatures, and thereby maximizing recovery of the dry cleaning solvent, the fluid communication between the condenser vapor effluent outlet and the cleaning vessel inlet is free of adsorbers or other emission control apparatus required by conventional dry cleaning apparatus and processes. Moreover, energy requirements and dry-to-dry cycle times and sources of potentially hazardous waste (e.g., carbon adsorption media) are reduced. [0065J In an embodiment, the cleaned articles can also contain water (e.g., if the cleaning fluid originally contained water), in which case the cleaning vessel vapor effluent will further include water vapor released from the cleaned articles. In this case, the liquid condensate of the second condenser 30 is a multiphase liquid condensate including both the released brominated solvent and the released water. As illustrated in Figure 1 , the multiphase liquid condensate is preferably transported via line 116 through the junction 120, and then via the line 124 to the water separator 60. The liquid condensate in line 116 need not, however, be combined with the liquid condensate in line 122 prior to introduction into the water separator 60. These liquid condensate lines may be separately and directly fed to the water separator. The brominated solvent present the multiphase liquid condensate can be recovered and returned to the solvent tank 65 as described above for the solvent recovery stage 14.

[0066] As illustrated, the condenser effluent is preferably forced through the second condenser 30 via a line 112 by a recirculating fan 35. The recirculating fan 35 can be either a constant speed, constant volume flow rate model or, preferably, a variable speed, variable volume flow rate model. Although it could be located elsewhere in the drying stage 16, the fan 35 preferably is located upstream of the second condenser 30 and upstream of the heater 40 (described below).

[0067] The condenser effluent (i.e., drying gas) exiting the second condenser 30 is then recycled to a heater 40 via line 120. The heater 40 re-heats the drying gas (e.g., to a temperature of about 130 ⁰F (54 ⁰C) to about 150 ⁰F (66 ⁰C)), and then the heated drying gas is reintroduced to the cleaning vessel 20 to continue the drying stage 16. Preferably, the heater 40 includes a refrigeration energy reclamation coil 42 and a still energy reclaim coil 44. In another embodiment, the still energy reclaim coil 44 could be replaced with or supplemented by a steam energy coil (not shown).

[0068] Drying gas entering the heater 40 first passes through the refrigeration energy reclamation coil 42, which contains hot refrigerant recycled from the second condenser 30 that at least partially re-heats the drying gas. The still energy reclamation coil 44 further heats the drying gas to the desired drying temperature. As shown in Figure 1, the overhead vapor distillate exiting the distillation apparatus 50 in line 160 can be passed via line 161 and a normally open (N/O) valve 166 to the first condenser 55, or via line 162 and a normally closed valve 168 to the still energy reclaim coil 44. When passed to the still energy reclaim coil 44, heat is transferred from the vapor distillate to the drying gas. The drying gas heated to the desired drying temperature exits the still energy reclaim coil 44 in line 128 and is thereafter passed into the cleaning vessel 20. The vapor distillate cooled as a result of the heat transfer exits the still energy reclaim coil 44 via a line 164 and a normally closed valve 170, and is ultimately passed to the first condenser 55 for further cooling and condensing. The vapor pressure of the vapor distillate is sufficient to convey the vapor distillate from the distillation apparatus 50 through the still energy reclaim coil 44 and to the first condenser 55.

[0069] The use of the thermal energy present in the vapor distillate exiting the distillation apparatus 50 to heat the drying gas heretofore has not been found in the dry cleaning industry. Through a combination of controls and appropriate valves (e.g., the normally open valve 166, and the normally closed valves 168 and 170), it has been determined that the thermal energy can be efficiently exchanged in the manner described above, and minimize the amount of water used to condense the vapor distillate in the first condenser 55. The three valves — i.e., the normally open valve 166, and the normally closed valves 168 and 170 — can be tied to a common solenoid, such that during operation of the solvent recovery cycle, the vapor distillate flows to the first condenser 55, but during operation of the drying cycle, the vapor distillate flows to the heater 40. The normally open valve 166 includes a stroke limiter to prevent the valve from completely closing. The stroke limiter is helpful to prevent back pressure buildup and avoid over-pressurization and leaks in the system, or ruptures in the still energy reclaim coil 44 or distillation apparatus 50.

[0070] The drying stage 16 continues in this recycle/re-heat mode of operation for a pre-selected time controlled by and optimized by a feedback loop managed by a PLC system to maximize the removal and recovery of the brominated solvent from the cleaned articles and the resulting cleaning vessel vapor effluent. After the preselected time, the heater 40 is disabled while the drying gas cools as it continues to circulate through the agitated cleaning vessel 20 and the second condenser 30. This cooling cycle continues until the cleaning vessel 20 and the cleaned, dried articles reach a temperature of between about 70 ⁰F (21 ⁰C) to about 90 ⁰F (32 ⁰C), for example about 80 F (27 ⁰C). Preferably, there also exists an interlock on the front door that prevents the operator from opening it until the brominated solvent vapor concentration inside the cleaning vessel 20 is under 200 ppm. At this time the operator can access the cleaning vessel 20 and remove the articles for final finishing (e.g., pressing, packaging).

Brominated Dry Cleaning Solvent

[0071] The use of a brominated solvent in the disclosed processes and apparatus yields significant advantages compared to conventional dry cleaning processes (e.g., those that utilize PCE). Table 1 presents a comparison between the relevant physical properties of a preferred brominated solvent mixture (DRYSOLV) and a conventional dry cleaning solvent, PCE. The commercially available DRYSOLV mixture contains: n-propyl bromide (95.989 wt.%), nitromethane (0.5 wt.%), 1,2-epoxy butane (1 wt.%), 1,3-dioxolane (2.5 wt.%), and Neutroleum Alpha #288-575 (0.011 wt.%, as an odor mask).

Table 1 — Solvent Comparison Physical Property DRYSOLV™ PCE

Boiling Point A_n ° A ²⁵⁰ °^F (¹²¹ °^C)

Cleaning Solvency (KB value) 130 90

Specific Gravity 1.31 1.62

Viscosity (at 25 °C) 0.5 cP 0.75 cP

Surface Tension (at 20 ⁰C) 26.1 dyn/cm 32.3 dyn/cm

Water Solubility (at 25 ⁰C) 0.24 g/lOOml 0.01 g/lOOml

Polarity Polar Non-polar

Evaporation Rate (Butyl Acetate = 1) 4.7 1.5

[0072] Substantial energy savings result from the use of the brominated solvent, and energy savings of up to about 30% relative to a conventional PCE process are possible. The lower boiling point of the brominated solvent reduces the amount of heat radiation losses to the environment from the distillation apparatus 50, which in turn reduces a dry cleaner's plant air conditioning requirements. Even though the latent heats of vaporization of the DRYSOLV mixture and PCE are approximately equal, the lower boiling point of DRYSOLV means that less sensible heat is required to raise the temperature of the cleaning rinseate in the distillation apparatus 50 to the distillation temperature, thereby reducing the energy required for distillation. Distillation energy is also saved based on the higher evaporation rate of DRYSOLV, which accelerates the distillation process (e.g., up to about three times faster than a conventional PCE distillation) and shortens cycle times. The lower boiling point of the brominated solvent also means that a lower drying temperature is required to achieve a sufficient solvent vapor pressure for rapid drying (e.g., about 120 ⁰F (49 ⁰C) to about 125 ⁰F (52 ⁰C) for DRYSOLV compared to about 160 ⁰F (71 ⁰C) for PCE), which in turn lessens the energy input required for the drying stage and reduces heat- induced stress/damage to the dried articles.

[0073] The brominated solvents are generally able to clean articles at least as effectively as PCE, if not more effectively. As illustrated in Table 1, DRYSOLV has superior cleaning abilities in most relevant properties (e.g., higher cleaning solvency and water solubility, lower viscosity and surface tension) relative to PCE, and this results lower washing/cleaning times and also shortens cycle times.

[0074] Filtration and adsorption systems generally used in conventional dry cleaning processes can be eliminated when the brominated solvents are used. Filtration and adsorption systems require significant energy and create large amounts of waste in conventional machines. Some methods require steam to strip the solvent from the filters/adsorbers at the end of the cycle (i.e., an additional time and energy requirement), and the used filters/adsorbers themselves contribute to hazardous waste.

[0075] In conventional processes, a carbon filter adsorber is generally used in the drying loop, being generally placed just upstream of the cleaning vessel. With reference to Figure 1 , a conventional PCE process would typically use a carbon filter adsorber located along the line 128, between the heater 40 and the cleaning vessel 20. The carbon filter adsorber is needed in a conventional process to remove residual PCE from the recycled drying gas stream in order to both increase the rate of removal of additional residual PCE from articles in the cleaning vessel and to prevent the re- introduction of PCE into the cleaning vessel that would be released to the environment upon completion of the drying cycle. In contrast, the use of the brominated solvent in combination with the second condenser 30 allows a complete or nearly complete recovery of the brominated solvent, and no carbon filter adsorbers are required in the present process/apparatus. For example, the line 128 between the heater 40 and the cleaning vessel 20 is free of adsorbers and, preferably, also free of filters.

[0076] Similarly, a conventional process generally uses a collection of filters (e.g., spin disk filters, cartridge filters) in the liquid washing loop. With reference to Figure 1 , a conventional PCE process would typically use a spin disk filter and a cartridge filter located upstream of the cleaning vessel 20, for example along the dry cleaning solvent lines 100, 104, 136, 140, and/or 148. These filters are required in a conventional process to remove contaminants from the recycled PCE solvent that are co-distilled with PCE in the solvent recovery process. Because PCE has a high boiling point (250 ⁰F (121 ⁰C)), a significant amount of soils contained in the cleaning rinseate are distilled, condensed, and recovered along with PCE in the solvent recovery process. These additional soil contaminants reduce cleaning performance and will otherwise accumulate in the dry cleaning system if they are not removed. In contrast, the lower boiling point of the brominated solvent (e.g., 158 °F (70 ⁰C) for n- propyl bromide) results in virtually no soil contaminants being co-distilled with the brominated solvent, and no filters are required in the present process/apparatus. For example, the fluid recycle line for the cleaning vessel 20 is free of filters and, preferably, also free of adsorbers.

Example

[0077J The cleaning efficiency for a cleaning fluid according to the disclosure was tested in a dry cleaning apparatus. A series of standard fabric test swatches containing a controlled variety of different types and amounts of soil was added to a 40-lb wash load of a commercial dry cleaning cycle. The test swatches are available from the International Fabricare Institute (IFI; Laurel, MD). The test swatches were pinned to a garment of the wash load. The wash load of medium colored garments was added to the cleaning drum of a 40-lb capacity conventional dry cleaning machine (dry-to-dry configuration) available from Columbia/ILSA Machines Corp. (West Babylon, NY).

[0078] The cleaning drum was then charged with a cleaning fluid including 20 gal of DRYSOLV (i.e., a brominated solvent containing n-propyl bromide; see above) and 2 oz of DRYSOLV D (i.e., a cationic detergent; see above). No other moisture or solvents/detergents were added to the cleaning drum. The garments were then agitated in a 5 -minute wash cycle while the cleaning fluid was recirculated through the cleaning drum. The garments were then rinsed and the resulting cleaning rinseate was drained from the cleaning drum. The cleaned garments were dried with heated, recirculating air while agitating the cleaning drum and condensing the recirculating air to remove the brominated solvent. In contrast to conventional dry cleaning processes (e.g., those using PCE as a cleaning solvent), no filters or adsorbers were used in either of the washing circuit or the drying circuit of this dry cleaning process.

[0079] The cleaned test swatches were then removed from their garment and were analyzed by IFI according to IFFs standard cleaning performance test. The cleaned test swatches were evaluated in several categories, including: % graying, % yellowing, % whiteness, % water-soluble soil removal, and % rug soil removal. Graying, yellowing, and whiteness were also separately evaluated for both polyester- cotton (PC) blend fabrics and cotton (C) fabrics. The results of the cleaning performance test are shown in Table 2 (where the number in parentheses indicates a quartile distribution performance ranking evaluated against other conventional dry cleaning processes analyzed by IFI according to its standard cleaning performance test):

Table 2 - Cleaning Performance: DRYSOLV and DRYSOLV D Cleaning Fluid Cleaning Category Result

% Graying (PC) 2 % (1)

(C) 4 % (2)

% Yellowing (PC) 0 % (1)

(C) 0 % (l)

% Whiteness (PC) 97 % (1)

(C) 98 % (1)

% Water-Soluble Soil Removal 82 % (1)

% Rug Soil Removal 88 % (2) [0080J The results of Table 2 indicate that a cleaning fluid including a brominated solvent and a cationic detergent generally performs at least as well, if not better than, other conventional dry cleaning processes.

[0081J Because other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention.

[0082J Accordingly, the foregoing description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications within the scope of the invention may be apparent to those having ordinary skill in the art.

[0083] Throughout the specification, where the compositions, processes, or apparatus are described as including components, steps, or materials, it is contemplated that the compositions, processes, or apparatus can also comprise, consist essentially of, or consist of, any combination of the recited components or materials, unless described otherwise. Combinations of components are contemplated to include homogeneous and/or heterogeneous mixtures, as would be understood by a person of ordinary skill in the art in view of the foregoing disclosure.

Claims

What is claimed is:

1. A dry cleaning apparatus comprising: a cleaning vessel having an inlet and an outlet for a dry cleaning solvent; a fluid recycle line in fluid communication with the cleaning vessel inlet and the cleaning vessel outlet; a condenser capable of reducing a concentration of dry cleaning solvent vapor in a cleaning vessel vapor effluent to a level of about 200 ppm or less, the condenser having a vapor effluent outlet, and an inlet in fluid communication with the cleaning vessel outlet; and, a heater having an inlet in fluid communication with the condenser vapor effluent outlet, and an outlet in fluid communication with the cleaning vessel inlet; wherein: the fluid communication between the condenser vapor effluent outlet and the cleaning vessel inlet is free of adsorbers or other emission control apparatus; and, the fluid recycle line is free of filters.

2. The dry cleaning apparatus of claim 1, wherein the fluid communication between the condenser vapor effluent outlet and the cleaning vessel inlet is free of filters.

3. The dry cleaning apparatus of claim 1, wherein the fluid recycle line is free of adsorbers or other emission control apparatus.

4. The dry cleaning apparatus of claim 1 further comprising a recirculating fan having an inlet in fluid communication with the cleaning vessel outlet, and an outlet in fluid communication with the condenser inlet.

5. The dry cleaning apparatus of claim 1 further comprising a solids trap, the solids trap comprising an inlet in fluid communication with the cleaning vessel outlet via the fluid recycle line, a gas outlet in fluid communication with the condenser, and a liquid outlet in fluid communication with the cleaning vessel inlet via the fluid recycle line.

6. The dry cleaning apparatus of claim 1, wherein the heater further comprises a refrigeration energy reclamation coil and a still energy reclamation coil.

7. The dry cleaning apparatus of claim 1 further comprising a solvent tank having an outlet in fluid communication with the cleaning vessel inlet.

8. The dry cleaning apparatus of claim 1 further comprising a distillation apparatus having an inlet in fluid communication with the cleaning vessel outlet.

9. The dry cleaning apparatus of claim 1 , wherein the condenser comprises a finned tubular coil.

10. The dry cleaning apparatus of claim 9, wherein the coil has a face area of about 1 square foot (0.09 square meters) to about 2 square feet (0.18 square meters).

11. The dry cleaning apparatus of claim 9, wherein the coil has a heat exchanging capacity of up to about 50,000 BTU/hour.

12. The dry cleaning apparatus of claim 1, wherein the condenser comprises a refrigeration system capable of delivering a heat exchange capacity of about 3,000 BTU/hour to about 47,000 BTU/hour.

13. The dry cleaning apparatus of claim 12, wherein the refrigeration system is selected from the group consisting of a compound compressor system and cascade compressor system.

14. The dry cleaning apparatus of claim 1, wherein the dry cleaning solvent comprises a brominated solvent and a cationic detergent.

15. The dry cleaning apparatus of claim 14, wherein the brominated solvent comprises at least one monobromoalkane selected from the group of consisting of ethyl bromide, n-propyl bromide, iso-propyl bromide, n-butyl bromide, sec-butyl bromide, tert-butyl bromide, and combinations thereof.

16. The dry cleaning apparatus of claim 15, wherein the brominated solvent comprises n-propyl bromide.

17. The dry cleaining apparatus of claim 14, wherein the dry cleaning solvent is free of perchloroethylene.

18. The dry cleaning apparatus of claim 14, wherein the dry cleaning solvent further comprises a solvent stabilizer selected from the group consisting of nitromethane, nitroethane, nitropropane, nitrobutane, nitropentane, propylene oxide, 1,2-epoxy butane, pentylene oxide, hexylene oxide, cyclohexene oxide, 1,3- dioxolane, 1 ,4-dioxane, and combinations thereof.