Abstract:
A process is disclosed for manufacturing a concentrated residue from a photopolymer fluid which includes photopolymer and photopolymer solvent. The photopolymer fluid may be derived by chemically etching a photopolymer layer of a printing plate with a solvent. The process includes distilling the photopolymer fluid to recover the solvent and concentrate the photopolymer fluid to form a concentrated photopolymer residue, and mixing a flash-point-increasing agent with the concentrated photopolymer residue in an amount sufficient to raise the flash point temperature of the concentrated photopolymer residue to a pre-selected temperature to form the concentrated residue. The flash-point-increasing agent may be mixed with the waste photopolymer fluid prior, during, or after distillation. Also, the flash-point-increasing agent includes oils, such as paraffinic and naphthenic oils and a blend thereof.

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to the field of solvent recovery devices. More particularly, the present invention relates to a device and method for recovering a solvent utilized in photopolymer plate processing operations. 
     II. Description of the Related Art 
     It is known in the prior art to produce printing plates from acrylic elastomer resins and synthetic rubbers utilizing photoengraving and chemical milling techniques. Generally, a layer of such resins or rubbers are placed onto a surface of a flexible plate and then exposed to light through a photographic film or stencil having a desired pattern to be formed onto the printing plate. Exposure of the resins and rubbers to light cures the resins and rubbers, altering the susceptibility of the resins and rubbers to removal by a photopolymer solvent. By applying the photopolymer solvent to the light exposed layer of resins or rubbers on the printing plate, the uncured photopolymer resin or rubber is chemically etched away by the photopolymer solvent in a pattern reverse to that of the film or stencil. The resin or rubber etched from the plate is removed with the waste photopolymer fluid. 
     Typically, the solvents utilized for the photopolymer solvent are relatively costly and generally have flash point temperatures above 140° F., defining the photopolymer solvent as a Class III liquid in accordance with 29 CFR 1910.106(a)(18)(ii). Further, disposal of the waste photopolymer fluid is likewise relatively expensive and presents environmental problems and concerns. Therefore, to more efficiently produce the aforementioned printing plates, devices were developed to recover the photopolymer solvent from the waste photopolymer fluid. 
     Prior art photopolymer solvent recovery devices utilize vacuum assisted distillation to separate the photopolymer solvent from the photopolymer resins or rubbers. Upon separation and removal of the photopolymer solvent, the residue resins or rubbers remain in the device as a concentrated residue. Typically, the residue is removed from the device by gravity flow through a drain. One problem with this device is that recovery of the photopolymer solvent is limited. To maintain fluidity of the concentrated residue, a certain amount of photopolymer washout fluid must remain in the residue, otherwise the resins or rubbers will coalesce into an amorphous solid within the device. Once the solid is formed, the device can not be operated until the operator enters and manually removes the solid from the device. This is undesirable because it is both time-consuming and exposes the operator to the chemicals comprising the waste photopolymer fluid. Further, it has been discovered that the concentrated residue has a flash point temperature between 100 and 140° F., defining the residue as Class II liquid in accordance with 29 CFR 1910.106(a)(18)(i). Not only is the residue a potential fire hazard, particularly as the residue is drained from the device at an elevated temperature, its disposal is subject to special handling requirements which increase disposal expenses, as compared to a Class III liquid. 
     In the photopolymer solvent recovery industry, efforts to date are directed to maintaining residue fluidity while maximizing solvent recovery. These efforts resulted in the development of a device utilizing a surrogate solvent to maintain residue fluidity. The surrogate solvent is added to the device during vacuum assisted distillation to replace the photopolymer solvent being separated and removed from the waste photopolymer fluid. The surrogate solvent maintains the photopolymer resins and rubbers in concentrated solution by coating the acrylic elastomer particles to prevent cross linking and vulcanization, thereby preventing coalescence of the residue as the photopolymer solvent fluid is removed. Even after the residue cools, the residue remains a liquid. Also, by utilizing a low cost surrogate solvent, the economic efficiency of the device is increased due to higher photopolymer solvent recovery. An example of such a device is described in U.S. Pat. No. 5,308,452. 
     Once the distillation process is completed, it is desirable to remove the concentrated residue from the device as soon as possible. However, a fire hazard exists if the flash point temperature of the concentrated residue is below 140° F. As hot concentrated residue is drained from the device, the residue presents a fire hazard due to tribal chain electrical reaction with some prior art devices, particularly when the device is operating at a relatively high distillation temperature. Due to the heat of the residue, the air and vapors proximate to the draining, hot residue expands rapidly and generates static electricity as the gaseous molecules move past one another. Although the device may be grounded, electrical discharge can occur across the gaseous molecules themselves, generating a spark to ignite the vapors and the residue. As a safety precaution, some prior art devices permit the concentrated residue to cool within the device prior to draining. Again, this is undesirable due to the risk of the concentrated residue solidifying in the device, and the device can not renew distillation operations until the device is drained of the concentrated residue. 
     Thus, there remains a need for a device for separating photopolymer solvent from waste photopolymer fluid which maximizes solvent recovery while producing a coalescable concentrated residue having a flash point temperature in excess of 140° F. Accordingly, it is to the provision of such that the present invention is primarily directed. 
     SUMMARY OF THE INVENTION 
     This invention overcomes the disadvantages of the prior art by providing a modular solvent recovery device that is simple in design and construction, relatively inexpensive to fabricate and easy to use. The modular solvent recovery device is readily transportable and connectable to a conventional plate processor without any modifications to the plate processor. The device includes an enclosure which provides access to the device interior. A frame supports a tank having a solvent section and a waste fluid section. The waste fluid section receives waste photopolymer fluid directly from the plate processor, and because the device is automated, the device is capable of receiving the waste photopolymer fluid on a continuous basis. Recovered solvent is transported directly to the plate processor from the solvent section. A still receives waste photopolymer fluid from the waste fluid section of the tank and distills the waste photopolymer fluid by application of heat and vacuum pressure thereto to separate and recover a desired solvent from the waste photopolymer fluid and reduce the waste photopolymer fluid to a concentrated residue. The device employs a novel flash-point-increasing agent delivery system to supply a flash-point-increasing agent to the concentrated residue in an amount sufficient to raise the flash point temperature of the concentrated residue to a predetermined temperature. This novel process enables the flash point temperature of the concentrated residue to be raised to a temperature that qualifies the concentrated residue, if maintained as a liquid through reduced solvent recovery, to be classified as a Class III residue. Importantly, this novel process permits almost complete recovery of the solvent while maintaining flowability of the coalescing concentrated residue. Further, the concentrated residue can be drained immediately after distillation operations cease without risk of fire due to tribal chain electrical reaction. 
     The still has a novel manhole device to removably seal a manhole of the still. The manhole device comprises a pivotally and telescopically mounted closure having wheels rotatably mounted thereto. Tracks are mounted to the still to engage the wheels and raise the closure vertically above a manhole of the still upon pivotal movement of the closure. 
     The modular solvent recovery device utilizes an ultrasonic sensor to detect fluid levels in the tank and residue level in a residue container. A housing is provided to enclose ultrasonic fluid level sensors. 
     It is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     Other advantages and capabilities of the invention will become apparent from the following description taken in conjunction with the accompanying drawings showing preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and the above objects as well as objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein: 
     FIG. 1 is a perspective view of a modular solvent recovery device made in accordance with the present invention in fluid communication with a plate processor; 
     FIG. 2 is one side elevation view of the device of FIG. 1 illustrating a condenser in fluid communication with a tank; 
     FIG. 3 is another side elevation view of the device of FIG. 1 illustrating a drum cavity; 
     FIG. 4 is a front elevation view of the device of FIG. 1 illustrating heaters and a still; 
     FIG. 5 is a schematic representation of the component parts that make up the embodiment of the device of FIG.  1  and their interconnections with each other; 
     FIG. 6 is a schematic representation of a container of a flash-point-increasing agent in fluid communication with the still; 
     FIG. 7 is a schematic representation of the container of the flash-point-increasing agent operatively disposed and in fluid communication between the still and a waste fluid section of the tank; 
     FIG. 8 is a schematic representation of the container of the flash-point-increasing agent in fluid communication with the waste fluid section of the tank; 
     FIG. 9 is a schematic representation of the container of the flash-point-increasing agent operatively disposed to provide the flash-point-increasing agent to a residue drum; 
     FIG. 10 is a perspective view of the drum cavity and a retaining door; 
     FIG. 11 is a partial perspective view of another embodiment of the present invention; 
     FIG. 12 is a rear elevation view of the device of FIG. 11 illustrating the condenser in fluid communication with a reservoir; 
     FIG. 13 is a partial perspective view of the reservoir; 
     FIG. 14 is a schematic representation of the component parts that make up the embodiment of the device of FIG.  11  and their interconnections with each other; 
     FIG. 15 is a partial perspective view of a manhole device made in accordance with the present invention with a closure pivoted away from a manhole; 
     FIG. 16 is a partial perspective view of the closure sealably engaging the flange; 
     FIG. 17 is a partial perspective view of a clamp engaging the closure; 
     FIG. 18 is a partial perspective view of the clamp pivoted away from the closure; 
     FIG. 19 is a perspective view of a ultrasonic sensor housing made in accordance with the present invention; and 
     FIG. 20 is a side elevation, section view of the housing of FIG. 19 taken along line  19 — 19 . 
    
    
     The reference numbers in the drawings relate to the following: 
       22 =plate processor 
       24 =solvent feed conduit 
       26 =waste photopolymer fluid conduit 
       30 =modular solvent recovery device 
       32 =frame 
       34 =enclosure 
       36 =exhaust fan 
       38 =suction hole 
       39 =exhaust hose 
       40 =still 
       41 =still interior 
       42 =manhole 
       43 =flange 
       44 =inner periphery of flange 
       45 =rim of flange 
       46 =manhole device 
       47 =closure 
       48 =arm of closure 
       49 =mounting cylinder of closure 
       50 =rod 
       51 =wheel 
       52 =track 
       53 =proximal end of track 
       54 =shoulder of track 
       55 =stop 
       56 =handle 
       57 =clamp 
       58 =receiver 
       59 =slot of receiver 
       60 =bolt 
       61 =nut 
       62 =dump opening 
       63 =dump valve 
       64 =residue container 
       65 =heating assembly 
       66 =jacket of heating assembly 
       67 =heater 
       70 =tank 
       71 =partition 
       72 =solvent section of tank 
       73 =waste fluid section of tank 
       74 =liquid level sight glass 
       75 =drain valve 
       75   a =sample port valve 
       76 =waste fluid feed conduit 
       77 =control valve 
       78 =solvent delivery pump 
       79 =tank pump assembly 
       80 =tank pump 
       80   a =discharge port of tank pump 
       80   b =suction port of tank pump 
       81 =tank pump discharge conduit 
       82 =three-way valve 
       83 =solvent section conduit 
       84 =waste fluid section conduit 
       85 =wand 
       86 =condenser 
       87 =inlet water conduit 
       88 =water pressure sensor 
       89 =water return conduit 
       90 =vacuum pump 
       91 =solvent discharge conduit 
       92 =solvent check valve 
       93 =solvent delivery conduit 
       94 =solvent priming conduit 
       95 =flash-point-increasing agent delivery system 
       96 =agent container 
       97 =agent conduit 
       98 =agent port 
       99 =agent control valve 
       100 =pressure conduit 
       101 =controller 
       102 =switch panel 
       103 =drum cavity 
       104 =first wall of drum cavity 
       105 =second wall of drum cavity 
       106 =rear wall of drum cavity 
       107 =bottom wall of drum cavity 
       108 =cavity door 
       109 =gasket 
       110 =light sensor 
       111 =ultrasonic sensor 
       112 =housing 
       113 =upper wall of housing 
       114 =support wall of housing 
       115 =back wall of housing 
       116 =front wall of housing 
       117 =aperture of front wall 
       118 =housing cavity 
       119 =platform 
       120 =sensor opening 
       121 =solvent section pump assembly 
       122 =suction conduit 
       124 =reservoir 
       125 =reservoir top wall 
       126 =reservoir side wall 
       127 =reservoir interior 
       128 =sample cube 
       129 =baffle section 
       130 =cube conduit 
       131 =baffle wall 
       132 =reservoir conduit 
       133 =waste fluid meter 
       134 =solvent meter 
       135 =solvent sight glass 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For a fuller understanding of the nature and desired objects of this invention, reference should be made to the following detailed description taken in connection with the accompanying drawings. Referring to the drawings wherein like reference numerals designate corresponding parts throughout the several figures, reference is made first to FIG.  1 . FIG. 1 of the drawings illustrates a modular solvent recovery device  30  made in accordance with the present invention operably connected in fluid communication with a conventional plate processor  22 . The various component parts of the device  30  are mounted onto a frame  32  and enclosed within an enclosure  34  mounted to the frame  32 . Enclosure doors (not shown) are strategically placed on the enclosure  34  to permit access therein to the component parts. The component parts of the device  30  are connected in operative fluid communication with the plate processor  22  through a solvent feed conduit  24  and a waste photopolymer fluid conduit  26 . The solvent feed conduit  24  transports solvent from the device  30  to the plate processor  22 , and the waste photopolymer fluid conduit  26  transports waste photopolymer fluid generated during plate making operations of the plate processor  22  to the device  30 . 
     Solvents are employed in the plate processor  22  to dissolve portions of a synthetic polymeric resin plate exposed to light in a photopolymer plate making process. The plate making process that takes place in the plate processor  22  is conventional, is not a part of the present invention, and therefore is not described in detail. The waste photopolymer fluid received by the device  30  of the invention from the plate processor contains a mixture of the selected solvent and photopolymer solids consisting of acrylic elastomer resins and synthetic rubber. The photopolymer solids are soluble in the selected solvent. 
     With continued reference to FIG.  1  and referring additionally to FIGS. 2 through 5, the general arrangement of the device  30  is shown. The device  30  comprises a still  40 , a heating assembly  65 , a tank  70 , a solvent delivery pump  78 , a tank pump assembly  79 , a condenser  86 , a vacuum pump  90 , a flash-point-increasing agent delivery system  95 , a programmable controller  101 , a switch cabinet  102 , and a drum cavity  103 . 
     The device  30  is provided with slits (not shown) through a portion of the enclosure walls  34  to permit air flow through the enclosure walls  34  and into the enclosure interior as gasses collected in the enclosure interior are exhausted from the enclosure  34  and the plate making room by an exhaust fan  36 . A vacuum inlet of the exhaust fan  36  is operably connected to a suction hole  38  located beneath the still  40 , and an exhaust hose  39  connected to an outlet of the fan  36 . The exhaust hose  39  extends to a safe area outside the enclosure  34  and the plate making room in which the device  30  is located. Any gases that may collect inside the enclosure  34  are drawn through the suction hole  38  by the exhaust fan  36  and exhausted through the exhaust hose  38  to the safe area exterior to the enclosure  34 . By providing the exhaust fan  36  and the exhaust hose  39  within the enclosure  34 , the enclosure  34  qualifies as a Class 1, Division 2 enclosure, and no special rooms or areas are needed to be constructed or modified to house the device  30 . This enables the device  30  to be housed in the plate making room itself with no changes being required of the plate making room. 
     Now, referring to FIGS. 1-4,  6 - 9  and  15 - 18 , the still  40  comprises a sealable vessel having a still interior  41  accessible through a manhole  42  located at the top of the still  40 . Extending outwardly from the still  40  at the manhole  42  is a annular flange  43 . The flange  43  has an inner periphery  44  which is contiguous with the manhole  42  and a rim  45 . During operation, the manhole  42  is sealed by a manhole device  46 . The manhole device  46  has a closure  47  pivotally and telescopically mounted to the still adjacent the flange  43 . Extending outwardly from the closure  47  is an arm  48  having a mounting cylinder  49  which pivotally and slidably engages a rod  50  extending outwardly from the still  40 . Oppositely and rotatably mounted to the closure  47  are two spaced-apart wheels  51 . Two spaced-apart tracks  52  extend upwardly from the still  40  proximate the flange  43  along the respective paths of the wheels  51  to engage the wheels  51  as the closure  47  pivots away from the manhole  42 . At a proximal end  53  of the tracks  52  are rounded shoulders  54  positioned to engage the wheels  51  upon pivotal movement of the closure  47 . As the closure  47  pivots, the wheels  51  engage the respective shoulders  54  and cause the closure  47  to vertically rise above the flange  43  and roll along the tracks  52  to clear the closure  46  from obstructing the manhole  42 . Because the wheels  51  are oppositely disposed on the closure  47 , the mounting cylinder  49  slides upwardly along the rod  50  with minimal binding. A stop  55  is mounted to one of the tracks  52  to engage the respective wheel  51  and prevent the closure  47  from pivoting beyond the still track  52 . A handle  56  extends outwardly from the closure  47  to assist an operator in pivoting and raising the closure  47 . The handle  56  is foamed covered for improved gripping capability by the operator. A gasket (not shown) is disposed between the closure  47  and the rim  45  to assist in sealing the closure  47  to the flange  43 . A plurality of clamps  57  are pivotally mounted to the still  40  adjacent the flange  43  to releasably engage the closure  47  and contract the closure  47  into sealable engagement with the flange  43 . Receivers  58  having U-shaped slots  59  are mounted to the closure  47 . Pivotally mounted to the still  40  are threaded bolts  60  which are placeable into the slots  59 . Matingly threaded wing nuts  61  are adjustably disposed on the bolts  60 . Upon rotation of the nuts  61  in one direction, the nuts  61  respectively engage the receivers  58  and exert pressure against the receivers  58  to seal the closure  47  to the flange  43 . Rotating the nuts  61  in the opposite direction releases the pressure and enables the bolts  60  to be pivoted and removed from the slots  59  so that the closure  47  may be unseated from the flange  43 . Pivoting the closure  47  in the opposite direction from the stop  55 , the wheels  51  rollingly engage the respective tracks  52  and disengage the tracks  52  at the shoulders  54 , permitting the closure  47  to seat on the rim  45  of the flange  43  and seal the manhole  42 . 
     The bottom of the still  40  is tapered toward a dump opening  62  at the center of the still  40  bottom. Mounted to the still  40  at the dump opening  62  is an actuatable dump valve  63  to control the release of any contents of the still  40 . The dump valve  63  communicates with a residue container  64  positioned below the still  40 , as illustrated in FIG.  9 . By supporting the still  40  above the residue container  64 , residue can be drained from the still  40  to the residue container  64  solely by gravitation, eliminating the need for a pump. 
     A heating assembly  65  heats the still  40  and the contents of the still interior  41 . The heating assembly  65  includes an oil filled jacket  66  that substantially surrounds the exterior of the still  40 . Electric heaters  67  are mounted to the exterior of the oil filled jacket  66  and heats the oil contained in the jacket  66 . As the temperature of the oil contained in the jacket  66  is increased by the heater  67 , the still  40  and the material contained in the still interior  41  are heated by conduction. Other equivalent heating assemblies may be employed with the present invention other than the heating assembly  65  shown. 
     A tank  70  is mounted to the frame  32  to store both solvent and waste photopolymer fluid. Within the tank  70  is a partition  71  which divides the tank  70  and forms a solvent section  72  and a waste fluid section  73 . The solvent section  72  receives and holds the solvent, and the waste fluid section  73  receives and holds the waste photopolymer fluid. Significant space and fabrication cost savings are created by providing a tank  70  having such a configuration. Liquid level sight glasses  74  are operably mounted to the sections  72  and  73  to provide the operator with a visual indication of fluid levels within the respective sections  72  and  73 . Drain valves  75  are respectively mounted to the sections  72  and  73  to manually empty or sample fluid contained within the sections  72  and  73 . A waste fluid feed conduit  76  operably connects the waste fluid section  73  to the still  40  in fluid communication. An actuatable control valve  77  is disposed between the waste fluid section  73  and the still  40  within the waste fluid feed conduit  76  to control the volume of waste photopolymer fluid transferred from the waste fluid section  73  to the still  40 . Waste photopolymer fluid is operably transported from the plate processor  22  through the waste photopolymer fluid conduit  26  to the waste fluid section  73  of the tank  70 . The solvent feed conduit  26  is operably connected in fluid communication to the solvent section  72 . A solvent delivery pump  78  is operably disposed within the solvent feed conduit  26  to draw solvent from the interior of the solvent section  72  and supply the solvent to the plate processor  22 . 
     A tank pump assembly  79  is operably connected to the tank  70  to provide the operator with the ability to add solvent or waste photopolymer fluid to the device  30  from a source (not shown) independent of the plate processor  22 . The tank pump assembly  79  has a tank pump  80  mounted to the frame  32  and a tank pump discharge conduit  81  mounted to a tank pump discharge port  80   a  of the tank pump  80 . A three-way valve  82  is mounted to the tank pump discharge conduit  81  to provide fluid communication to the sections  72  and  73  of the tank  70 . A solvent section conduit  83  is mounted to the three-way valve  82  and is operably connected to the solvent section  72 , and a waste fluid section conduit  84  is mounted to the three-way valve  82  and operably connected to the waste fluid section  73 . A hollow wand  85  is operably connected in fluid communication to a suction port  80   b  of the tank pump  80 . The wand  85  is constructed of a flexible, solvent resistant material and is insertable into the source. Upon appropriate manipulation of the three-way valve  82  and by engaging the tank pump  80 , either solvent or waste photopolymer fluid is drawn from the source and respectively delivered to the solvent section  72  or the waste fluid section  73 , depending upon the contents of the source. 
     As shown in FIG. 2, a condenser  86  is operably mounted to the still  40  to condense solvent vapors produced in the still  40 . The condenser  86  is supplied with cooling water from a water source external to the device  30 . The cooling water is supplied by the water source through an inlet water conduit  87  extending between the water source and operably connected in fluid communication with the condenser  86 . The supply of water through the inlet water conduit  87  is monitored by a water pressure sensor  88  that is operably connected to the control logic of the device  30 . Additionally, the water temperature is monitored by a thermocouple probe (not shown) operably connected to the control logic of the device  30 . In the event that the water pressure or temperature exceeds respective predetermined set point pressures or temperatures, the control logic of the device  30  terminates operation of the device  30 . The cooling water passes through the condenser  86  to condense solvent vapor traveling through the condenser  86 , and is returned to a water return conduit  89  external to the device  30  operably connected in fluid communication with the condenser  86 . 
     Vacuum pressure is created in the still  40  by a vacuum pump  90  sufficient to draw waste photopolymer fluid from the waste fluid section  73  of the tank  70  through the waste fluid feed conduit  76  to the still  40 . A solvent discharge conduit  91  communicates with the still interior  41  and extends from the still interior  41  through a solvent check valve  92  and the condenser  86  to the vacuum pump  90 . The solvent check valve  92  provided in the solvent discharge conduit  91  ensures that fluid flow progresses in only one direction through the solvent discharge conduit  91 . The vacuum pump  90  provided in the solvent discharge conduit  91  creates a vacuum pressure in the solvent discharge conduit  91  and the still  40 . The vacuum pressure draws distilled solvent from the still interior  41 , through the solvent discharge conduit  91  and the condenser  86 , and the vacuum pump  90  supplies the distilled solvent through a solvent delivery conduit  93  to the interior of the solvent section  72  of the tank  70 . A solvent priming conduit  94  operably connected to the solvent discharge conduit  91  and the solvent section  72  to supply solvent to the vacuum pump  90  as a coolant until sufficient distilled solvent flow is generated from the still  40  to fully charge and cool the vacuum pump  90 . 
     Referring to FIGS. 4-9, a flash-point-increasing agent delivery system  95  is operably connected in fluid communication with the device  30  to provide a flash-point-increasing agent to a concentrated residue generated by distillation operation. As the still  40  distills the waste photopolymer fluid, solvent is removed from the still  40  and the waste photopolymer fluid is reduced to the concentrated residue. The desired solvent to be distilled may be any number of commercially available solvent blends, including the widely used prior art solvent blend of alcohol-perchloroethylene. Examples of some commercial solvents typically employed in plate making operations by plate processors  22  to dissolve portions of the photopolymer coated plate include solvents marketed under the trade names OPTISOL, distributed by DuPont Company; SOLVIT, distributed by Polyfibron Technologies, Inc.; and NUTRE CLEAN, distributed by NuPro Technologies. Although it is desirable to maximize solvent recovery from the waste photopolymer fluid, a portion of the solvent remains as a component of the concentrated residue. Due to the distillation operation, the mixture of the solvent, generally a Class III liquid, and the photopolymer remaining within the concentrated residue undergo chemical change, resulting in the concentrated residue having a flash point temperature between 100 and 140° F. Thus, the concentrated residue is a Class II residue. By mixing a flash-point-increasing agent with the concentrated residue, the flash point temperature can be raised to a predetermine temperature. 
     Under current regulatory definitions, it is desirable for the flash point temperature of the concentrated residue to be in excess of 140° F. Flash-point-increasing agents, such as heavy carrier oils, particularly paraffinic and naphthenic oils or a mixture thereof, bind the solvent and prevent solvent vapors from emitting from the concentrated residue, thereby raising the flash point temperature of the concentrated residue and curtailing a fire hazard created by tribal chain electrical reactions. By adding about 3 gallons of the flash-point-increasing agent to 100 gallons of waste photopolymer fluid, a concentrated residue is produced having a flash point temperature in excess of 140° F., which resultingly classifies the concentrated fluid residue as a Class III residue. The amount of flash-point-increasing agent needed to produce a concentrated residue having a predetermined or desired flash point temperature can vary, depending upon the solvent. As a result, distillation within the still  40  can be conducted at higher temperatures, if desired, to increase solvent recovery. Although the flash-point-increasing agent does not prevent the acrylic elastomer particles of the concentrated residue from coalescing, into a molten state, the agent lubricates the coalesced particles and prevents the particles from bonding and caking onto the still interior  41 . Further, the agent acts as a carrier oil and temporarily maintains the coalesced particles in suspension, which allows more solvent to be removed from the still  40 . Studies have shown that use of the agent have increased solvent recovery from approximately 97% to approximately 99% by volume of the solvent contained within the waste photopolymer fluid, while the concentrated residue maintains fluidity at elevated temperatures. However, once the concentrated residue cools, the residue becomes a solid, plastic mass. The concentrated residue is maintainable as a Class III liquid by reducing solvent recovery. 
     In the embodiment shown in FIG. 6, the flash-point-increasing agent is supplied from an agent container  96  operably connected to the still interior  41  through an agent conduit  97  connected in fluid communication to an agent port  98  on the still  41 . An actuatable agent control valve  99  controls the amount of flash-point-increasing agent delivered to the still  40 . Another wand  86  is utilized to operably connect the agent control valve  99  to the agent container  96 . In another embodiment, shown in FIG. 7, the agent conduit  97  is operably connected in fluid communication with the waste fluid feed conduit  76 , supplying the flash-point-increasing agent to the still  40 . Yet, in the embodiment shown in FIG. 8, the agent conduit  97  is operably connected in fluid communication with the waste fluid section  73  of the tank  70 , and the flash point increasing agent is supplied to the still  40  through the waste fluid section  73 . Still, in the embodiment shown in FIG. 9, the agent conduit  97  is disposed to deliver the flash point increasing agent to the residue container  64  as the concentrated residue is dropped from the still  40  through the dump valve  63 . Further, the flash-point-increasing agent can be added to the residue container  64  and mixed with the concentrated residue therein. In the event vacuum pressure is insufficient to draw the agent from the agent container  96  through the agent conduit  97  to the desired location, an agent pump (not shown) is placed in operable fluid communication with the agent conduit  97  may be utilized to deliver the agent. 
     Pneumatic pressure is supplied through a pressure conduit  100  to an auto pilot valve (not shown) and an pneumatically controlled valve (not shown) in response to a control command signal generated at the controller  101 , which is operably connected to a switch panel  102 , by control logic of the device  30 . The auto pilot valve, the pneumatically controlled valve and their operative connection to the switch panel  102  of the device  30  are conventional and are not described in detail for the purpose of simplifying the description of the invention. The controller  101 , preferably a programmable computer, is operably connected to all acutatable valves of the device  30  through the switch panel  102 . Alternatively, solenoid controlled valves may be operatively connected with the switch panel  102  and opened and closed in response to command signals generated by control logic of the device  30 . 
     The pneumatic pressure signals supplied through the pressure conduit  100  to operate the auto pilot valve are controlled in response to command signals generated by control logic of the device  30 . The pneumatic pressure control signals also selectively activate the solvent delivery pump  78  to pump solvent through the solvent feed conduit  24  to the plate processor  22 . Deactivating the solvent delivery pump  78  interrupts the supply of solvent through the solvent feed conduit  24 . 
     Now, referring to FIGS. 3 and 10, positioned beneath the still  40  is a drum cavity  103  to receive the residue container  64 . The drum cavity  103  comprises a first wall  104 , a second wall  105 , a rear wall  106  and a bottom wall  107 . The suction hole  38  is disposed through the rear wall  106 . Pivotally mounted to the frame  32  is a cavity door  108  which removably engages the first, second and bottom walls  104 ,  105  and  107 . A gasket  109  is removably mounted to the cavity door  108  to assist in creating a seal between the cavity door  108  and the first, second and bottom walls  104 ,  105  and  107 . The cavity door  108  has sufficient height to contain and hold the contents of the still  40  in the event of an undesired spill. Located on the first and second walls  104  and  105  are light sensors  110  operably connected to the controller  101  to detect the presence of the residue container  64 . By placing the residue container  64  within the drum cavity  103 , the residue container  64  interrupts the light beam emitting between the light sensors  110 , permitting the dump valve  63  to open and drain the contents of the still  40 . While the light sensors  110  detect the emitted light beam, the controller  101  prevents the dump valve  63  from actuating open. 
     Referring to FIGS. 1-4,  19  and  20 , ultrasonic sensors  111  operably connected to the controller  101  are utilized to detect fluid levels in the solvent section  72 , the waste fluid section  73  and the residue container  64 . Housings  112  are provided to enclose each ultrasonic sensor  111 . The housing  112  comprises a upper wall  113 , two support walls  114  extending downwardly from the upper wall  113 , a back wall  115  extending downwardly from the upper wall  113  and between the two support walls  114 , and a front wall  116  extending downwardly and outwardly from the upper wall  113  and between the two support walls  114 . The back wall  115  has an aperture  117  to receive the ultrasonic sensor  111 . In combination, the upper, support, back and front walls  113 ,  114 ,  115  and  116  define a housing cavity  118  to receive and enclose the ultrasonic sensor  111 . Disposed between the drum cavity  103  and the still  40  is a platform  119 . Extending through the top of the solvent and waste fluid sections  72  and  73  and the platform  119  are sensor openings  120 . The housings  112  are respectively mounted to the top of the solvent and waste fluid sections  72  and  73  and the platform  119  with the housing cavity  118  in conjunction with the sensor opening  120 . 
     In operation of the device  30 , waste photopolymer fluid containing a solvent desired to be distilled from the fluid and recovered is supplied from the plate processor  22  through the waste photopolymer fluid conduit  26  to the waste fluid section  73  of the tank  70 . 
     Upon reaching a predetermined level of waste photopolymer fluid in the waste fluid section  73 , the vacuum pump  90  is activated, creating a vacuum pressure in the still  40 . After sufficient vacuum pressure is developed, the control valve  77  opens to permit a predetermined amount of waste photopolymer fluid to travel through the waste fluid feed conduit  76  to the still interior  41 . After the predetermined amount of waste photopolymer fluid is received by the still  40 , control logic of the device  30  causes a signal to be sent to the control valve  77 , causing it to close and interrupt the supply of waste photopolymer fluid to the still interior  41 . While waste photopolymer fluid is being supplied to the still interior  41 , the controller  101  signals the agent control valve  99  to open to permit a supply of flash-point-increasing agent to travel through the agent conduit  97  to the waste fluid feed conduit  76  where the agent is commingled with the waste photopolymer fluid and supplied to the still interior  41 . After a predetermined amount of the flash-point-increasing agent is supplied to the still interior  41 , the control logic of the device  30  causes a signal to be sent to the agent control valve  99 , causing it to close and interrupt the supply of flash point increasing agent to the still interior  41 . 
     At this point in the operation of the device  30 , the control logic of the device  30  controls the electric heaters  67  to heat the oil contained in the oil filled jacket  66  surrounding the still  40  to a desired temperature. The heated oil surrounding the still  40  heats the volume of waste photopolymer fluid and volume of flash-point-increasing agent supplied to the still interior  41  to the waste photopolymer fluid boiling point. Because the flash-point-increasing agent has a higher boiling point temperature than the solvent, the solvent is distilled out from the mixture of waste photopolymer fluid and flash-point-increasing agent, and the flash point increasing agent remains with the waste photopolymer fluid. A thermocouple (not shown) is provided in the still interior  41  to monitor the waste photopolymer fluid vapor temperature in the still interior  41  and provide an indication of the temperature to the operator at the controller  101  and to the control logic of the device  30  for safety monitoring of the temperature by the control logic. An auto-fill probe (not shown) is provided in the still interior  41  to monitor the level of the waste photopolymer fluid within the still interior  41  and provide a signal to the control panel and to the control logic of the device  30 . The auto-fill probe detects the boiling action of the contents of the still interior  40 . As the solvent is separated from the waste photopolymer fluid and removed from the still  40 , the level of waste photopolymer fluid and the flash-point-increasing agent drops with in the still interior  41  and the boiling components fail to contact the auto-fill probe. A signal is sent to the controller  101  and the control logic of the device  30  from the auto-fill probe, and the control logic of the device signals the control valve  77  to open to permit additional waste photopolymer fluid to travel through the waste fluid feed conduit  76  to the still interior  41 . Once the auto-fill probe detects the boiling components, control logic of the device  30  causes a signal to be sent to the control valve  77 , causing it to close and interrupt the supply of waste photopolymer fluid to the still interior  41 . The sequence of supplemental waste photopolymer addition to the still interior  41  continues until a total predetermined amount of waste photopolymer fluid is received by the still  40 . Upon reaching the total predetermined amount of waste photopolymer fluid, the control logic of the device  30  prevents the control valve  77  from opening for the remainder of the device  30  distillation cycle. At this point in the operation of the device  30 , the control logic of the device  30  begins the final cycle and continues distillation for a predetermined amount of time. 
     Operation of the vacuum pump  90  supplies vacuum pressure through the solvent discharge conduit  91  to the still interior  41 . The increased temperature of the waste photopolymer fluid contained in the still interior  41  and the vacuum pressure supplied to the still interior  41  together cause the solvent contained in the waste photopolymer fluid to vaporize. However, the flash-point-increasing agent does not vaporize and remains with the waste photopolymer fluid in the still interior  41 . The solvent vapor distilled from the waste photopolymer fluid is drawn through the solvent discharge conduit  91  by the vacuum pressure created by the vacuum pump  90 . The solvent vapor is drawn through the condenser  86  where the vapor is condensed into a liquid. The liquid solvent is drawn from the condenser  86  through the solvent discharge conduit  91 , the solvent check valve  92 , and the vacuum pump  90  and is supplied by the vacuum pump  90  through the solvent delivery conduit  93  to the interior of the solvent section  72  of the tank  70  where the distilled solvent is collected and stored. 
     As the solvent is distilled from the waste photopolymer fluid contained in the still interior  41  becomes more concentrated and coalesces toward a soft, plastic, amorphous solid to form a concentrated residue. The flash-point-increasing agent prevents the concentrated residue from being completely reduced to an amorphous solid incapable of flowing out of the tank interior by suspending and lubricating the coalesced particles. Further, the flash-point-increasing agent lubricates the still interior  41  to prevent bonding and caking of the concentrated residue on the still  40  within the still interior  41 . 
     At the conclusion of the predetermined amount of time for the final cycle, the control logic of the device  30  controls the electric heaters  67  to terminate heating the oil contained in the oil filled jacket  66  surrounding the still  40 . At this point in the operation of the device  30 , a control command generated at the controller  101  by the control logic of the device  30  signals the actuatable dump valve  63  to open, permitting the concentrated residue, a Class III residue, to drain in a molten state from the still interior  41  into the residue container  64  disposed within the drum cavity  103 . Upon cooling, the concentrated residue, with the flash-point-increasing agent, becomes solid. 
     The solvent distilled from the waste photopolymer fluid and stored in the solvent section  72  of the tank  70  is drawn through the solvent feed conduit  24  out of the solvent section  72  by the solvent delivery pump  78  back to the plate processor  22  in response to a signal supplied to the controller  101 . 
     When the residue container  64  is filled with concentrated residue and flash-point-increasing agent drained from the still interior  41 , a signal is sent to the controller  101  by the ultrasonic sensor  111 , preventing the dump valve  63  from opening until the operator empties or replaces the filled residue container  64 . The contents of the filled residue container  64  are transportable and disposable as a Class III residue. Upon emptying and returning the residue container  64  to the drum cavity  103 , the device  30  is enabled to operate in the above described manner. 
     Now, referring to FIGS. 11-14, the general arrangement of another embodiment of the device  30  made in accordance with the present invention is shown. In addition to the still  40 , the heating assembly  65 , the tank  70 , the solvent delivery pump  78 , the condenser  86 , the vacuum pump  90 , the flash-point-increasing-agent delivery system  95 , the controller  101 , the switch cabinet  102 , and the drum cavity  103 , this embodiment further comprises a solvent section pump assembly  121 , a reservoir  124 , a waste fluid meter  133  and a solvent meter  134 . Except as described below, the components of the device  30  function and operate as previously described. 
     The solvent section pump assembly  121  is operably connected to the solvent section  72  of the tank  70  to provide the operator with the ability to add solvent to the device  30  from the source independent of the plate processor  22  and to mix solvent within the solvent section  72  to provide solvent having uniform quality. The solvent section pump assembly  121  has the tank pump  80  mounted to the frame  32 , and the tank pump discharge conduit  81  mounted to the tank pump discharge port  80   a  of the tank pump  80 . The tank pump discharge conduit  81  is operably connected in fluid communication with the solvent section  72  and is discussed further below. Mounted to the tank pump suction port  80   b  is a suction conduit  122 . A recycle conduit  123  is mounted to one port of the three-way valve  82  and is operably connected in fluid communication with the solvent section  72 , and the hollow wand  85  is mounted to another port of the three-way valve. The third port of the three-way valve  82  is mounted to the suction conduit to provide operable fluid communication to the recycle conduit  123  and the wand with the tank pump  80 . By placing the three-way valve  82  in one position of fluid flow and by engaging the tank pump  80 , solvent is drawn from the source and delivered to the solvent section  72  through the tank pump  80  and the tank pump discharge conduit  81 . Alternatively, by placing the three-way valve  82  in the alternative position of fluid flow and by engaging the tank pump  80 , solvent is drawn from the solvent section  72  through the recycle conduit  123  and recycled back to the solvent section  72  through the tank pump  80  and the tank pump discharge conduit  81 . The recycling action of drawing and returning solvent creates turbulence within the solvent section  72  and mixes the solvent therein. By mixing solvent within the solvent section  72 , uniform quality or consistent chemical makeup of the solvent is established. 
     With continuing reference to FIGS. 11 and 12 and particularly to FIG. 13, the reservoir  124  is mounted to the top of the tank  70  and has a reservoir top wall  125  and four reservoir side walls  126  extending downwardly from the reservoir top wall  125  to the tank  70  to define a reservoir interior  127 . Disposed within the reservoir interior  127  is a sample cube  128  and a baffle section  129 . The tank pump discharge conduit  81  is operably connected to the sample cube  128  to provide fluid communication with the tank pump  80 . Extending upwardly through the top of the solvent section  72  into the sample cube  12  is a cube conduit  130 . Mounted to the reservoir  124  and operably connected in fluid communication with the sample cube  124  is a sample port valve  75   a  from which samples of the solvent can be taken for quality determination. This valve  75   a  is vertically disposed below the upper most portion of the cube conduit  130 . Solvent delivered from the tank pump  80  by the tank pump discharge conduit  81  accumulates within the sample cube  124  until the fluid level reaches the height of the upper most portion of the cube conduit  130 , thereby maintaining solvent within the sample cube  124  for sampling. Two baffle walls  131  extend downwardly from the reservoir top wall  125  and are mounted to adjacent reservoir side walls  126  to form the baffle section  129 . The lower most portions of the baffle walls  131  are vertically disposed above the top of the tank  70  to provide fluid communication between the interior of the baffle section  129  and the reservoir interior  127 . The solvent delivery conduit  94  extends into the baffle section  129  and discharges solvent withdrawn from the still interior  41  by the vacuum pump  90 . The baffle section  129  is provided to dampen turbulence created by solvent delivery from the solvent delivery conduit  93 . A reservoir conduit  132  provides operable fluid communication between the reservoir interior  125  and the interior of the solvent section  72 . The upper most portion of the reservoir conduit  132  is vertically disposed above the lower most portions of the baffle walls  131  to receive solvent from the non-turbulent region of the reservoir interior  127 . Extending into the reservoir  124  is the solvent priming conduit  94 . 
     As shown in FIGS. 11 and 14, the waste fluid meter  133  is operably connected to the controller  101  and is operably disposed in fluid communication with the waste fluid conduit  76  to measure the amount of waste photopolymer fluid drawn from the waste fluid section  73  of the tank  70  through the waste fluid conduit  76  and the control valve  77  and delivered into the still interior  41 . During the operational cycle of the device  30 , the control logic of the controller  101  records the flow rate of the waste photopolymer fluid and the cumulative amount of waste photopolymer fluid delivered to the still interior  41 . 
     Referring to FIGS. 11,  12  and  14 , the solvent meter  134  is operably connected to the controller  101  and is operably disposed in fluid communication with the reservoir conduit  132  to measure the amount of solvent drawn from the still interior  41  through the solvent discharge conduit  91 , the condenser  86 , the vacuum pump  90 , the solvent delivery conduit  93 , the reservoir  124  and the reservoir conduit  132  and delivered into the solvent section  72  of the tank  70 . During the operational cycle of the device  30 , the control logic of the controller  101  records the flow rate of the solvent and the cumulative amount of solvent delivered to the interior of the solvent section  72 . A solvent sight glass  135  is operably disposed in fluid communication in the reservoir conduit  132  between the solvent meter  134  and the solvent section  72  to provide the operator with a visual indication of solvent flow into the solvent section  72 . 
     In operation of this embodiment of the device  30 , waste photopolymer fluid containing a solvent desired to be distilled from the fluid and recovered is supplied from the plate processor  22  through the waste photopolymer fluid conduit  26  to the waste fluid section  73  of the tank  70 . 
     Upon reaching a predetermined level of waste photopolymer fluid in the waste fluid section  73 , the control logic of the device  30  activates the vacuum pump  90 , creating a vacuum pressure in the still  40 . After sufficient vacuum pressure is developed, the control valve  77  opens to permit a predetermined amount of waste photopolymer fluid to travel through the waste fluid feed conduit  76  to the still interior  41 . Also, the control logic of the device  30  activates the tank pump  80  to recycle the solvent within the solvent section  72  of the tank  70 . A signal is sent from the waste fluid meter  133  to the controller  101  indicating the amount of waste photopolymer fluid being delivered to the still interior  41 . After the predetermined amount of waste photopolymer fluid is received by the still  40 , control logic of the device  30  causes a signal to be sent to the control valve  77 , causing it to close and interrupt the supply of waste photopolymer fluid to the still interior  41 . While waste photopolymer fluid is being supplied to the still interior  41 , the controller  101  signals the agent control valve  99  to open to permit a supply of flash-point-increasing agent to travel through the agent conduit  97  to the waste fluid feed conduit  76  where the agent is commingled with the waste photopolymer fluid and supplied to the still interior  41 . After a predetermined amount of the flash-point-increasing agent is supplied to the still interior  41 , the control logic of the device  30  causes a signal to be sent to the agent control valve  99 , causing it to close and interrupt the supply of flash point increasing agent to the still interior  41 . 
     At this point in the operation of the device  30 , the control logic of the device  30  controls the electric heaters  67  to heat the oil contained in the oil filled jacket  66  surrounding the still  40  to a desired temperature. The heated oil surrounding the still  40  heats the volume of waste photopolymer fluid and volume of flash point increasing agent supplied to the still interior  41  to the waste photopolymer fluid boiling point. As previously described, the solvent is distilled out from the mixture of waste photopolymer fluid and flash-point-increasing agent, and the flash-point-increasing agent remains with the waste photopolymer fluid. The thermocouple monitors the waste photopolymer fluid vapor temperature in the still interior  41  and provides an indication of the temperature to the operator at the control panel and to the control logic of the device  30  for safety monitoring of the temperature by the control logic. The auto-fill probe monitors the level of the waste photopolymer fluid with in the still interior  41  and provides a signal to the controller  101  and to the control logic of the device  30 . A signal is sent by the auto-fill probe to the controller  101  and the control logic of the device  30  when the boiling fluids in the still interior  41  are no longer detected and the control valve  77  opens to permit additional waste photopolymer fluid to travel through the waste fluid feed conduit  76  to the still interior  41 . The amount of additional waste photopolymer fluid delivered to the still interior  41  is measured by the waste fluid meter  133  and the cumulative amount of waste photopolymer fluid delivered to the still interior  41  is monitored by the control logic of the device  30 . Once the auto-fill probe detects the boiling components, control logic of the device  30  causes a signal to be sent to the control valve  77 , causing it to close and interrupt the supply of waste photopolymer fluid to the still interior  41 . The sequence of supplemental waste photopolymer addition to the still interior  41  continues until a total predetermined amount of waste photopolymer fluid is received by the still  40 . Upon reaching the total predetermined amount of waste photopolymer fluid, the control logic of the device  30  prevents the control valve  77  from opening for the remainder of the device  30  distillation cycle. At this point in the operation of the device  30 , the control logic of the device  30  begins the final cycle which is controlled by the signal sent to the controller  101  by the solvent meter  134 . 
     Operation of the vacuum pump  90  supplies vacuum pressure through the solvent discharge conduit  91  to the still interior  41 . The increased temperature of the waste photopolymer fluid contained in the still interior  41  and the vacuum pressure supplied to the still interior  41  together cause the solvent contained in the waste photopolymer fluid to vaporize. However, the flash-point-increasing agent does not vaporized and remains with the waste photopolymer fluid in the still interior  41 . The solvent vapor distilled from the waste photopolymer fluid is drawn through the solvent discharge conduit  91  by the vacuum pressure created by the vacuum pump  90 . The solvent vapor is drawn through the condenser  86  where the vapor is condensed into a liquid. The liquid solvent is drawn from the condenser  86  through the solvent discharge conduit  91 , the solvent check valve  92 , and the vacuum pump  90  and is supplied by the vacuum pump  90  through the solvent delivery conduit  93  to the reservoir  124 , the solvent meter  134 , the solvent sight glass  135  and the interior of the solvent section  72  of the tank  70  where the distilled solvent is collected and stored. 
     As described above, the flash-point-increasing agent prevents the concentrated fluid residue from being completely reduced to an amorphous solid incapable of flowing out of the tank interior by suspending and lubricating the coalesced particles. Likewise, the flash-point-increasing agent lubricates the still interior  41  to prevent bonding and caking of the concentrated fluid residue on the still  40  within the still interior  41 . 
     The solvent meter  134  measures the amount of solvent delivered to the solvent section  72  and the control logic of the device  30  monitors the cumulative amount of solvent delivered to the solvent section  72 . Upon delivery of a predetermined amount of solvent to the solvent section, the control logic of the device  30  controls the electric heaters  67  to terminate heating the oil contained in the oil filled jacket  66  surrounding the still  40  and disengage the tank pump  80 . At this point in the operation of the device  30 , a control command generated at the controller  101  by the control logic of the device  30  signals the actuatable dump valve  63  to open, permitting the concentrated residue, a Class III residue, to drain in a molten state from the still interior  41  into the residue container  64  disposed within the drum cavity  103 , wherein the residue solidifies upon cooling. 
     With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. Further, the various components of the embodiments of the invention may be interchanged to produce further embodiments and are these further embodiments are intended to be encompassed by the present invention. 
     Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, various modifications may be made of the invention without departing from the scope thereof and it is desired, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and which are set forth in the appended claims.