CA2130241A1 - Low cost equipment for cleaning using liquefiable gases - Google Patents
Low cost equipment for cleaning using liquefiable gasesInfo
- Publication number
- CA2130241A1 CA2130241A1 CA002130241A CA2130241A CA2130241A1 CA 2130241 A1 CA2130241 A1 CA 2130241A1 CA 002130241 A CA002130241 A CA 002130241A CA 2130241 A CA2130241 A CA 2130241A CA 2130241 A1 CA2130241 A1 CA 2130241A1
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- cleaning chamber
- cleaning
- chamber
- liquefiable
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
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- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
- D06F43/00—Dry-cleaning apparatus or methods using volatile solvents
- D06F43/007—Dry cleaning methods
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
- B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
- B08B3/12—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration by sonic or ultrasonic vibrations
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
- B08B7/0021—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by liquid gases or supercritical fluids
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
- D06F19/00—Washing machines using vibrations for washing purposes
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
- D06F43/00—Dry-cleaning apparatus or methods using volatile solvents
- D06F43/08—Associated apparatus for handling and recovering the solvents
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/22—Secondary treatment of printed circuits
- H05K3/26—Cleaning or polishing of the conductive pattern
Abstract
LOW COST EQUIPMENT FOR CLEANING
USING LIQUEFIABLE GASES
ABSTRACT OF THE DISCLOSURE
Precision cleaning of parts (20) is performed with liquefiable gases (12), such as CO2, without the use of a complex and costly processor system. Rather, simplified and reliable performance for small scale and "low end"
cleaning applications is accomplished without the use of pumps and condensers. The apparatus (10) for removing undesired material from a chosen substrate comprises: (a) an enclosed cleaning chamber (17) in a walled vessel (10) for containing a liquid (12') derived from the liquefiable gas and the substrate containing the undesired particulates and contaminants the walled vessel adapted to withstand a maximum pressure of about 1,500 pounds per square inch (105.4 kg/cm2) at ambient temperature; (b) means (21) for supporting the substrate in the cleaning chamber; (c) ultrasonic energy-producing transducer means (18) attached to the walled vessel within the cleaning chamber; (d) inlet means (16) attached to the walled vessel for introducing the liquiefiable gas into the cleaning chamber under a pressure less than about 900 pounds per square inch (63.3 kg/cm2); (e) temperature control means (27) connected to the cleaning chamber for controlling the temperature within the chamber up to about 50°C; (f) reservoir means (14, 44) for providing the liquefiable gas to the inlet means; (g) means for changing the liquefiable gas to the liquid; and (h) outlet means (22) in the chamber for removing the liquid from the cleaning chamber. The liquid may then be further treated to remove particulates and organic contaminants and either recycled to the cleaning chamber or vented to the atmosphere. The process is especially applicable for gen-eral degreasing and particulate removal processes, when high precision cleaning is not required.
USING LIQUEFIABLE GASES
ABSTRACT OF THE DISCLOSURE
Precision cleaning of parts (20) is performed with liquefiable gases (12), such as CO2, without the use of a complex and costly processor system. Rather, simplified and reliable performance for small scale and "low end"
cleaning applications is accomplished without the use of pumps and condensers. The apparatus (10) for removing undesired material from a chosen substrate comprises: (a) an enclosed cleaning chamber (17) in a walled vessel (10) for containing a liquid (12') derived from the liquefiable gas and the substrate containing the undesired particulates and contaminants the walled vessel adapted to withstand a maximum pressure of about 1,500 pounds per square inch (105.4 kg/cm2) at ambient temperature; (b) means (21) for supporting the substrate in the cleaning chamber; (c) ultrasonic energy-producing transducer means (18) attached to the walled vessel within the cleaning chamber; (d) inlet means (16) attached to the walled vessel for introducing the liquiefiable gas into the cleaning chamber under a pressure less than about 900 pounds per square inch (63.3 kg/cm2); (e) temperature control means (27) connected to the cleaning chamber for controlling the temperature within the chamber up to about 50°C; (f) reservoir means (14, 44) for providing the liquefiable gas to the inlet means; (g) means for changing the liquefiable gas to the liquid; and (h) outlet means (22) in the chamber for removing the liquid from the cleaning chamber. The liquid may then be further treated to remove particulates and organic contaminants and either recycled to the cleaning chamber or vented to the atmosphere. The process is especially applicable for gen-eral degreasing and particulate removal processes, when high precision cleaning is not required.
Description
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~1, 5 I,OW COST 13iQUIlP~TT FOR CLJ3ANII~G
USING LIQUE:FIABLE~ GAS~æS
i 10 ~he presQnt applicaltion i8 2 con~in~aa~ion-in part Or appli~ation Ser1al ~o. 07/927,4~3, ~ila~ Augu~t lo, 1992.
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j~i Th8 preserlt invention relate~ to 'che u~e oi~ ~upercrit-`' ic~l ~luids to clean sub~trateE~, and, mOrQ particularly, to a process and apparatus e;l~ploying 21 ligue~iabl~ ga i, uch ~ ~:
as liquid carbon dioxide, in c~ na3:ion with ultra~30ni~
cavitation to provide high clQaning e~ficiency ~or general .
degreasing and particulate re~oval without the need for ex-i, pensive high pressure eguipment.
`~ 25 2. Descriptio~_of_Related Art J
Ultrasonic cleaning ha~ been utilized by indu~try for a ~umber of year~. In the conventional proces~s, the ~on~
icating media are organic 801v2nt6, ~ater, or aqueous solu~
~ tions, and ultrasonic ener~y is applied to the media to .1 30 promote cavitation, i.e., the for~ation of bubbles and ~ heir subsequent collap~e. Alt~ough us~ally qsi~e adeguate .I for the re~oval of undesired contamination, ~oth type~ o~
c solvent have disadvantages. Many substrates reguire a rigorous drying process following exposure to an aqueous medium, and this is often a time-consuming thermal excur sion. The use of organic solvent~ a~ sonicating media pre- r `, sent~ the problem of che~ical disposal and is subject to ~trict re~llatory controls. An additional disadvantage re-lates to handling of the re~oved contaminantls), whether ' ,~
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organic or particul~te. When the c:olltamin~nt 1 ~ con-trolled ~n~teri~ uch as 21 radioactive p~rtic:le, once ln solution or ~uY3pen~3ion, itE~ ~olu~e i~ E~ub~t~ntially ~n-creased, and thia preserlts an additional pretreat~ent/di~-posal proble~.
In t~ese conventional ultrasonic cleaning proces~ea, ranmduc~ar~ are ofl~en used ~o produce t2~e ~oniLc energy. In oth~r processe~, a cavltation nozzle may ~ u~ed. For ex-ample, U.~;. Patent No~ 4,906,3,B7, i~sued ~arch 6, 1990, to J. P~san~ for ~2~ethod for Removing Oxidiz~ble Contaminan~
~' in Cooling Water Used in Con~ nction wi~ a Cooling Tower:
.j and U.S. Patent No. 4,990,260, isE~ued February 5, 199l, to J. Pisani for UXethod and Apparatus for Removing Oxidizable Contahlinants in Water to Achieve High Purity ~ater ~or In-! 15 dustri2~ en di~;close Dlethods for xemovlng contaminants fro~ water by Lnducing cavitation in t~e water to cause the water to di sc~i~te to prc~uce hydroxyl free-r~icals ~hich act a~ ox~dizing agent~. In ghe proces~e o~ Pisani, ul txa~iolet radiation i5 u~ed in combination ~it~ cavitation to continue the oxidation proces~ which wa initiated by the hydroxyl free-radical~. The cavitat~on in the Pisani ~ processes is pro~uced by a ~critical flow~ nozzle.
.1 Another type of cleaning process, utili2ing phase shifting of dense pha~e gases, has been di~closad and claimed in U.S. Patent No. 5,013,366, i~ued to D.P. Jack-son et ~1 and assigned to the sa~e assig~ee a~ ~he present application. The proces~ employs a dense pha~e gas at or above the critical pressure. The phase of the dense phase gas i~ then shifted between the liquid state and the super-~ 30 critical state by varying ~he temperature of the dense flu~
! id in a series of steps between temperatures above and be-;j low the criti~al temperature o~ the dense fluid, while maintaining the pressure above the critical value. ~xam-ples o~ ~luids include (1) hydrocarbons, such as methane, ethane, propane, butane, pentane, hexane, ethylene, and . propylene; (2) halogenated hyc~ocarbons, such as tetraflu-3 oro3ethane, chlorodifluoromethane, and perfluoropropane;
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(3) lnorganic~, uch as carbon dioxid2, a~mo~ia, h~liuDI, krypton, argon, ~ul~ur hexa~luoride, and nltroll~ oxid~; an~
( 4 ) mixture~ therQof . In alternatlv~ eE bodliEIen~s ~ ~he d~n~e pha~e g~ ~ay be expo~ed to ultraviolet (lDV) radia tion during the c:leaninsT proce~s or ultra~onic enerqy ~ay be applied during the cleaning proce~s to agit~t~ the dQn~e phas~a ga~ ~nd the sub~tra . e ~urfac~.
In y~t another approac:h to cleaning, co2llponen~3 ar~
placed in ~ c:leaning cha~er that i~ ~aintainod at a pr~-sure above a2~bient ~t~osph~ric: pr28~ and a spray of liq !~1 uid $olvent, such a~ auid carbon diox~ de, umder hi~h ~, pressur~ i8 directed onto the co~ponents ~o ~ to di~lodse ;i any contaminant particles therefroDI. Such an ~ppro~ch i~
diE~clo~ed, for exa~ple, in U.S. Patent~3 4,832"53 and ~; 15 4,936,922 by P~.L. Cherry et al. The pray o~E tiny ~olvent dropletn act ~8 "fluid ha~sners" to lcnock very ~mall, ~;ub--~icrometer particle~ o~ of the componer~ to l~e cleaned, dispersing the particleEs into tha c:hambar where th~y are carried a~y by ~ ~trea~ of ~lean, dry air flowing over the 2 0 components and through the chan~er .
Systems based on supercritical ~luid cleaning tec~nol-ogy, ~uch as the SUPERSCRUBTI~ preci~ion cleaning equipment (a trademark of Hughes Aircraft colspany~, typically include a pressure vessel, a fluid pump, a fluid reservoir, a sep-arator and condenser ~ystQ~, and various v~lves, transduc-ers, and temperature ~ensors. The pressure ~essel that is employed is capable of containing pressures up to 5,000 psi (351.5 kg/c~2) and temperature~ up to about 100C. Thi~
technology provides the conditions required to exceed the cri~ical points of most candidate supercritical fluids, such as nitrogen, oxygen, argon, helium, methane, propane~
carbon dioxide, and nitrous oxide. Systems o~ this nature ~i are expensive. The C05t of such systems i~ well-justified for high precision cleaninq; however, for ~any particulate and organic contaminants, the cleaning process criteria ~ay 3 often be me~ without using these fluids in their supercrit-ical state.
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Thu~, ~ need ex~ t,~ ~or a ~y~t,~ tll~t provlde~ ~or pli~ied and relia~le pf~rIor~ance, il~or ~all ~c~lef an~l ;, " low endW cleaning applic:at~ On8 .
,i -~, 5 .` , ~1 ~n accordance wlth the lnYention, apparatu~ ~or r~f,-ving undesired matf,r,r1~1 fr~ chc>~s2n ub~tr~t~ Gola-pri~3:
(a) an enlo~ed cle~ning cha~nber in za ~allff~d ves-~;el ~or cont~ining a li~id de!rive,d groDII a liqa~,eriabl~ g~
and the ~;ubstrate containill~ the lmde~ired part~culate~ and ~ conta~inant~, 'che ~alled vessel adapted to wlth~tand a ~
3 iDau~ pre~;&ur~ OI about 1, 500 pounds per sguare~ inch ( 105 . 4 kq/c~) at a~bient 'ceD~per~tur~;
(b) means ~or ~upportinç~ trat~ in the -1 cleaning cha~ber;
.3 (c) ultra~sonis: energy-producins~ tran~ducer mea~
attas::hed to the walled ve~el within the c:leaning chalaber;
~! 20 (d) inlet ~ans attached lto the walled vessQl for introducing the liquuefiable gas into the cleaning chamber under a pressure less than about 900 pOlll~dB per square inc~
( 63 . 3 kg/cm2);
~3 ( e) temperature control ~eans connected to ~e cleaning chamber for controlling the temperature wi~hin the chamber up to about 50C;
(f) reservoir means for pro~iding the liquefiable gas to ~e inlet ~Deans;
(g) means for changing the lique~iable gas to the liquid; and (h) outlet means in the cham~er ~or remov~ng t~e liquid from the cleaning chamber.
The removed liquid ~ay then be ~urther treated to re move particulates and organic contaminants and either re~
cycled to ~he cleaning chamber or Yented to the atmosphere.
The process is especially appl~cable for general degrea~ing ,;,..........
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and partlculate removal process, when h.lgh preci~ion clean-iny i~ not required.
The adv~ntage o~ tha pre~ant inventiorl 1~ tllat it eliminate~ the need ~or a cond~nl~er ;~nd recycle E~y8tllal!~, ', 5 e~ch of ~ich ~re ~or cl~st ite~ o~ prior ;~rt syste~a.
In addition, the pre~l3ure rzlting required Por tha c:l~nin5~
cha~bar o~ the inv~ntion i~ 3rslativ21y lo~d (i.e, ~1,500 p~i, or ~105.4 kg/c212), which ~ubstanti~lly r~d~ce~ its co~t over thst of typical ~upercritical cleaninq ~y~t~s.
Egu~pDIent cost~ for the present in-,rention ar~ e~ti~ated at le~3 than ona-hal~ the co~t o~ th8 prior art ~y~t~ e present invention will al~o permit the application o li~
uefiable fluid cleanin51 for reDIote or inacc:e~ibl~ cleani~
application, and ~or r~pid, ~211 ~e bate~, and ~seJai-continuou~ proce~se~. Both o~ t~e~;e requirealents are not easily ~et ~ri~ current supercritic;~l fluid cleaning equip-7 ~nent pack~ge~.
BP~IEF 3~SCRIPTIQN ~F T}~ 12Rl~ lG~i ~j FIG. 1 is a schematic: diagram, partly in section, of :~ a first embodiment of apparatus employed in the practice o~ the invention; and F}G. 2 i~ a 6cheslatic diagram, partly in section, of a second embodi3nent of apparatu~ employed in the practice of ~he invention, ~ho~ing the apparatu~ prior to fill~g with cleaning liquid (FIG. 2A) and filled with cleaning liquid (FIG. 2B).
pESCRIPTION OF ~HE PRE:FERR~D_ElqBODIME~TS
The typical equipment require~ents for using super-critical fluids results in rQlatively high capital cost~ in 3 some cases. The present invention provides for hiqh clean~
ing efficiency without resorting to the high pressures u~u-ally reguired when employing fluid~ in their supercri~ical stat~.
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: 6 There ~re many fluid~ whlch nre typical c:andldate~ ~or llquefiable fluid cleaning in con~unction with ultri~on~c energy. The~e include nitrogen, oxyg~n, argon, hellu~, methane, propane, carbon dioxids, ~nd ni1:rou~ oxid~3.
,~, 5 FIGS~ 1 and 2 d~pict two e~di3aQnt~ o~ present~.
inv~ntion. In ~ch embodi~aent, ~ s~all ~1 to 20 liter) `. ve~3~el 10 i~3 u~ilized, provided wi~h a lid 10~. Fluid ~2 is supplied ~rom a pre~urized re~ervoir a~ t~rough nozzles along tl:~ ves~l wall$ ~0g, ldhich define ~ cleaninq cha~b~r 17. AlE~o, the ve~;el ~L0 i~ ~quipped ~ith an ultra-sonic transducer 18. ~uring op~ration, t:hQ ve~el ~0 i c:harged with ~luid ~2 through the nozzles 1~. Onc3 ch2~rged ~ with fluid a2, ultra30n~c~ ar~ appli~d to ~inal-clean the i', part 20 ~nd to remove the l~Rt tracea o~ contamlnation.
The part 20 ls ~upported in the ve~el 10 by ~upport ~e~ns 21. ~luid ~2 is withdrawn ro~ the ~e~el ~0 through out-let 22 a~er ~leaning and ~ 5 trea~ed by filtar~ 2~ and a separator 26 to re~ove particulat~ and srganic conta~na tion.
While the following descrip~ion is pre~ented in terms of employing C02, other liquefiable fluid~ ~ay be used in 1 the practice of the invention.
3~ Intermediate_Cleanin~_svstem FIG. 1 illustrate~ the fir~t embodi~ent, which repre-¦ ~ents an intermediate ~ersion, of ~h~ prs~ent invention.
The steps used in thi cleaning process are as follows: : -(1) ChaFae the Vessel wi~h ~iquid ~2-~he parts ~0 to ~e cleaned are placed in the vessel 10, ~hich is then closed, and C02 12 is intrs-duced into the vessel through nozzles 1~ in the vessel wall. Initially, snow will be formed, but the state :;
o~ the fluid 12 is controlled by the temperature in ~eat ~xchanger 27. ~s pressure builds, C02 is con - ~:
densed a~ a liquid 12' using cooli~g coils 28 in the vessel 10. The liquid C02 ~2' may be above or ~elow :
the critical point ~or C02, which is de~ined by pres-., .
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`~.,? 7 i~ ~ure and temper~ture. The IDaxl~ r~ssure c~ntem-. pl~ted by thl~ proc~ About 1, 000 p~si 170O 3 kg/~
c~2 ) a.t ~ bien tsmper~ture .
1~2-After char~ing wi~h f luid, ~Q te~perature 1~
ad~usted a~ resuired - to ~a~nt~in th~ id ~t~te (i.e., 25C:, 800 psl, or 56.2 kg)~2~0 ~I!he ~lu~d l~v ad~ustesl froD~ thQ rao~rvoir 1~11 aE~ r~quirss31 t~
i~er~e the part~ 20, by ~ean~ o~ a le~l lndlic~tor 30 in t ve~el 10 ~ Sonic:ation i~ ~en perfc~aed in the liquid C02 129 u~ing one or ~ore ~on~catl~ horn~ 1 a~ a ~reguesls:y ranqing ~ro~ about S to 100 ~iloheri:z.
(3? 3eq~e~e ~ Q2-The liquid 12 ' i~ now he~ted b?ll:h hea~ing coil~
~8 to above 32C. As; an option, thi~ 8y3tl aquipped with a 3~0nitor 29 of thla ~f~luent ~rols th~
~8S~l. The ~on~tor 29 ~onitors th~ p2~rticulate and ~, organic conta~inant l~vels. If repeated cleanings ar~
;~, p~rformed, t~e particulate and organic level~ decrea~e until the part i~ deemed to be ~clean". Steps 2 and 3 are then repeated a~ deter~nined by the ~onitor re-~ult.
(4~ ~o1npression.
After cleanin~ i~ c:olap~:ete, fluid 12 i~ recyc:led and compressed into the re~ervoir 1~, using a co~pre~-~or 32.
In this f irst e~bodiment, cleaning ~luid ~2 is recy cled, but only rough or ~fir~t level~ puri~icat~on ~8 per ~ormed, inste2d of ~he high level prov~ded by ~he prior art SUPERSCRUBTN preci~ion cleaning eguip~ent. Particulate re-moval i8 stepwise, with ~he final step down to only 10 ~m ;l size, before final ~iltration, to minimize filter clogging and Da~ntenance. larqe particulate~, on the order of 10 to 100 ~m, are ~iltered pr~or ~o entry to the separator 26, ; 35 u~ng ~lter 24, to provide ~or easier ma~ntenance and I operation. A cyclone separator 3~ i3 u~ed to remove small ¦ particulates, on the order of 0.1 to 10 ~m, ~hich gives `
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le~ e~cient ~eparation o~ organic conta~inat1Or~ an tha3 known ~ilter/demi~t6~r approach, Ibut provldQ~ for e~ier maintenance an~ down-tiJ~. The compres~or sa i~ u~ed to Xill and pressurize th~ liquid re~ervoir â~l. Th~ præs-~ure of the re~ervoir ~erve~ t:o ~ill ~e ~e~ol O, co~-pleting the~ ~luld cycle. Thi8 ~!lpproac:~ ell~irlatQI~ tbe r~Qed ~or zl liquid puap and cond~n~r, and ~ford~ ~uch sllDpl~
c~perzltion. However, by providing a recycl~ capabillty, it i~ po~sible to puri~y tAIa gA~ supply to en~ure that it meets any required cleanline ~ criterl~. ~n thi8 ~ di-ment, thQ ~onitor 2~ can b~ utilized to dete~n~d ~hen ~he part 20 i~ ~leaned, by determ~n{ng ~hen ~he liguid 12' con tain~ par~icul~e~ and cont~inants below a pr~determinQd level.
In a mcdifica~ion o~ ~h~ above apparatu~, th~ ~ep~ra-tor 2~ 2nd the cyclone 34 ~ay be by-passed, using in~t~ad a pressure reduction valve 35, me valve 3~ allo~ ~e liquid 12 to expand to ~he ga~eous state, whereafter it 1~
compressed to the liquid state by the co~pres30r 32. [It will be appreciated ~hat the separator 26 includes such a valve 3S.) The u~e of the co~pressor 32 in either case en~
sures filling ~he reservoir 14. In this case, the ~oni~or 29 can be used to determine if the l~quid 12 i8 atill u~e-ful, by whether the particulate and contaminant levels ex-ceed a predeter~ined level.
The liquefiable gas ~ay be u~ed wi~h modifiers. Typi-cally ~ ~inor percentage (less ~han about 50 vol/vol per-cent) of a condensed phase solvent, or ~odifier, i8 added to the bulk c~pressed gas. These modifiers are mixed with the compreæsed gas to form a non-flammable, non-toxi~ mix-ture. The ~odifiers c~ange the critical point of the mix-ture so t~at higher pressures (up to about 1,500 pound~ per square inch, or 105.4 ~g/cm2) and temperatures (up to about 50C) can ~e used, which provides improved sonication. In addition, the ~odifiers change the chemical properties of the condens~d gas to improve the solubility properties of the mixture~ The modi~ier or ~odifiers used depend on the ~ ~ 2~2~
:~ 9 ;, contarninant being removed~ For removing polar organic con-;' t~inant3, a ~odif i~r uch ~ o-propanol or aceton~ i ., employed~ For reDloving polar inorgAni~ cont~inant~t w~er ` 1 18 desirably employed. For re~oving low niolecular w~ight ;~ 5 non-polar organic ~C6 to C18) conta~nants, a ~i~ier ~uch `j a~ hexane ~ay be uied. For r~ ring high ~olecular weight non-polar organic (>Cl~) contal~hinan~s, ~ ~odigler ~uc~h za~
kero~sn~ may be u~e~., Optionally, any ~nodi~ier re~aining on the surface o~
:~ 10 the part 20 to be cleaned may be removed follo~ding removal of the liquid CO2 froffl thle ve~el 10 by introducing CO2 in the 6upercritical state and ~onicating.
i ;~ 15 The second eibodi~ent of the present invention, d~-'~,! picted in PIG. 2, i3 intended ~or low end ~i.e., low-co~t) ~, use, wit~ irregular, frequent and small bat~h ize require;~
men~s and when ~ringent purity cri~ri~ ~or th~ ~upply ~luid 12 are not requlred. Thi~ e~bodi~ent con~itute~ th~
bare minimum for lique~iable fluid cleaninq; and provides for the ultimate in si~plicity, flexibility and cost effec-tive operation. The step~ used in thi~ process are as fol-lows:
(1) Charqe ~he Ve~el with Liqul~ Ç2-The parts 20 to be cleaned are plac~d in ~he ves-. 3el 10, which is then closed, and C02 12 i5 in~roduc~d 31 into the vessel through nozzles 16 in t~e vessel wall.
Initially, snow ~ay be formed, but is replaced with liquid 12' to charge the vessel. As above, the physical tate of the fluid is controlled by tempera~
ture, using a heat exchanger 3~.
!2~ SQnicate In Li~ui~ ~Q2.
Final cl~aning is accomplished with ultrasonics, a~ described above. FIG. 2B shows the liquid C02 12' 3 35 filling the vessel 10.
(3) Ve~
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A~ter ~onic~tlng, the ~luid 12 1~ vented through BeparatOr 3~ to re~ove "he orgzlnic and part~culate contamln2nts. Prior to venting through the ~parator 38, large particulat~s (10 to 100 ~DI) 2r~ re~nov~d ~y ,' 5 ~ilter 40 in the bottoD; of the veEi~el lOo acond embodi~2nt, l~ke the ~r~at ~i~ent, al~so ~upplle~ Pluid 12 into t:~e ~Je~el ~0 throug~ ln'ce~rn~
nozzl~ . HOWQVer, thi~ ~<aclond eDIbodi~ent d~ not r~-cyclQ the ~luld 12, but ln~adl vent~ it to ~he 2l~0~pher~
by exl~aust ~neans ~a ~fter removal o particulat~ and org~n-ic cont~ninants in the ~eparator 3~
Pre~suriza~ion of the ves~el 10 i~ acco~plished with ~ tank or cylinder pressure fro~ the CO2 ~upply ~ource ~ on~
j ly. Pres~ur~ i~ increased by heating ~he CO2 i~ the tank ¦ 15 ~ by ~eans of ~ heater ~6. ~ypically, th~ teEperature o~
~ the CO2 i ~aintained at about 30C, provlding a pre~sure 3 of about 1,000 p3~ (70.3 kg/c~2). ~hi3 eliminate~ the need for a reservoir 1~ (n~ shown in FIG. 1) ~nd pu~p and re~
duces ~he sy~te~'s upper pressure requirement, thereby re-! 20 sulting in much simpler and less expen~i~e process equip~
~ ~ent. However~ this approach limits the process to sub-1 critical condition~, which mean~ that the cleaning advan-tages of the ~upercritical state cannot be used. In thi~
embodi~ent, cleaning efficiency in liquid cO2 12 is opti~
mized through ~he use of ultrasonics, which overco~e~ the cleaning efficiency ~hortcomings of using the less powerful solvent.
The present invention is applicabl~ to ~any processes involving.liquefiable fluids for preci~ion cle~ning, ex-tractions, particulate removal, and degrea~ing. Exe~plary applications include cleaning during ~anufacture of contact lenses, fuel in~ectors, engine blocks, watches, s~all elec-¦ trical appliance~, and razor blade , bearing degreasing, and engine repair shop3.
Thu~, there has been disclo6ed ~ process for re~oving contarinantD rom nubstrate~, u~ing lique~ied g~s. It vill -~ 2~2~
' ~1 be apprec~atzd by tho~e skilled ln the art that varioua modif ic~t1ons and changes o~ an obvious nsture ~y be D~de without departing ~roDI the ~cop~a o~ th~ ~nvention, and ~11 ~uch modii~ication~ ~nd change~ ar~ intended to ~all with$n the ~cope o~ the ~nvention, 218 de~in~d by the ~ppende~l cla$~s.
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~1, 5 I,OW COST 13iQUIlP~TT FOR CLJ3ANII~G
USING LIQUE:FIABLE~ GAS~æS
i 10 ~he presQnt applicaltion i8 2 con~in~aa~ion-in part Or appli~ation Ser1al ~o. 07/927,4~3, ~ila~ Augu~t lo, 1992.
~D~
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ield_Q~ the~ç~iQD
j~i Th8 preserlt invention relate~ to 'che u~e oi~ ~upercrit-`' ic~l ~luids to clean sub~trateE~, and, mOrQ particularly, to a process and apparatus e;l~ploying 21 ligue~iabl~ ga i, uch ~ ~:
as liquid carbon dioxide, in c~ na3:ion with ultra~30ni~
cavitation to provide high clQaning e~ficiency ~or general .
degreasing and particulate re~oval without the need for ex-i, pensive high pressure eguipment.
`~ 25 2. Descriptio~_of_Related Art J
Ultrasonic cleaning ha~ been utilized by indu~try for a ~umber of year~. In the conventional proces~s, the ~on~
icating media are organic 801v2nt6, ~ater, or aqueous solu~
~ tions, and ultrasonic ener~y is applied to the media to .1 30 promote cavitation, i.e., the for~ation of bubbles and ~ heir subsequent collap~e. Alt~ough us~ally qsi~e adeguate .I for the re~oval of undesired contamination, ~oth type~ o~
c solvent have disadvantages. Many substrates reguire a rigorous drying process following exposure to an aqueous medium, and this is often a time-consuming thermal excur sion. The use of organic solvent~ a~ sonicating media pre- r `, sent~ the problem of che~ical disposal and is subject to ~trict re~llatory controls. An additional disadvantage re-lates to handling of the re~oved contaminantls), whether ' ,~
' ' ~` ` 213~2~
organic or particul~te. When the c:olltamin~nt 1 ~ con-trolled ~n~teri~ uch as 21 radioactive p~rtic:le, once ln solution or ~uY3pen~3ion, itE~ ~olu~e i~ E~ub~t~ntially ~n-creased, and thia preserlts an additional pretreat~ent/di~-posal proble~.
In t~ese conventional ultrasonic cleaning proces~ea, ranmduc~ar~ are ofl~en used ~o produce t2~e ~oniLc energy. In oth~r processe~, a cavltation nozzle may ~ u~ed. For ex-ample, U.~;. Patent No~ 4,906,3,B7, i~sued ~arch 6, 1990, to J. P~san~ for ~2~ethod for Removing Oxidiz~ble Contaminan~
~' in Cooling Water Used in Con~ nction wi~ a Cooling Tower:
.j and U.S. Patent No. 4,990,260, isE~ued February 5, 199l, to J. Pisani for UXethod and Apparatus for Removing Oxidizable Contahlinants in Water to Achieve High Purity ~ater ~or In-! 15 dustri2~ en di~;close Dlethods for xemovlng contaminants fro~ water by Lnducing cavitation in t~e water to cause the water to di sc~i~te to prc~uce hydroxyl free-r~icals ~hich act a~ ox~dizing agent~. In ghe proces~e o~ Pisani, ul txa~iolet radiation i5 u~ed in combination ~it~ cavitation to continue the oxidation proces~ which wa initiated by the hydroxyl free-radical~. The cavitat~on in the Pisani ~ processes is pro~uced by a ~critical flow~ nozzle.
.1 Another type of cleaning process, utili2ing phase shifting of dense pha~e gases, has been di~closad and claimed in U.S. Patent No. 5,013,366, i~ued to D.P. Jack-son et ~1 and assigned to the sa~e assig~ee a~ ~he present application. The proces~ employs a dense pha~e gas at or above the critical pressure. The phase of the dense phase gas i~ then shifted between the liquid state and the super-~ 30 critical state by varying ~he temperature of the dense flu~
! id in a series of steps between temperatures above and be-;j low the criti~al temperature o~ the dense fluid, while maintaining the pressure above the critical value. ~xam-ples o~ ~luids include (1) hydrocarbons, such as methane, ethane, propane, butane, pentane, hexane, ethylene, and . propylene; (2) halogenated hyc~ocarbons, such as tetraflu-3 oro3ethane, chlorodifluoromethane, and perfluoropropane;
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(3) lnorganic~, uch as carbon dioxid2, a~mo~ia, h~liuDI, krypton, argon, ~ul~ur hexa~luoride, and nltroll~ oxid~; an~
( 4 ) mixture~ therQof . In alternatlv~ eE bodliEIen~s ~ ~he d~n~e pha~e g~ ~ay be expo~ed to ultraviolet (lDV) radia tion during the c:leaninsT proce~s or ultra~onic enerqy ~ay be applied during the cleaning proce~s to agit~t~ the dQn~e phas~a ga~ ~nd the sub~tra . e ~urfac~.
In y~t another approac:h to cleaning, co2llponen~3 ar~
placed in ~ c:leaning cha~er that i~ ~aintainod at a pr~-sure above a2~bient ~t~osph~ric: pr28~ and a spray of liq !~1 uid $olvent, such a~ auid carbon diox~ de, umder hi~h ~, pressur~ i8 directed onto the co~ponents ~o ~ to di~lodse ;i any contaminant particles therefroDI. Such an ~ppro~ch i~
diE~clo~ed, for exa~ple, in U.S. Patent~3 4,832"53 and ~; 15 4,936,922 by P~.L. Cherry et al. The pray o~E tiny ~olvent dropletn act ~8 "fluid ha~sners" to lcnock very ~mall, ~;ub--~icrometer particle~ o~ of the componer~ to l~e cleaned, dispersing the particleEs into tha c:hambar where th~y are carried a~y by ~ ~trea~ of ~lean, dry air flowing over the 2 0 components and through the chan~er .
Systems based on supercritical ~luid cleaning tec~nol-ogy, ~uch as the SUPERSCRUBTI~ preci~ion cleaning equipment (a trademark of Hughes Aircraft colspany~, typically include a pressure vessel, a fluid pump, a fluid reservoir, a sep-arator and condenser ~ystQ~, and various v~lves, transduc-ers, and temperature ~ensors. The pressure ~essel that is employed is capable of containing pressures up to 5,000 psi (351.5 kg/c~2) and temperature~ up to about 100C. Thi~
technology provides the conditions required to exceed the cri~ical points of most candidate supercritical fluids, such as nitrogen, oxygen, argon, helium, methane, propane~
carbon dioxide, and nitrous oxide. Systems o~ this nature ~i are expensive. The C05t of such systems i~ well-justified for high precision cleaninq; however, for ~any particulate and organic contaminants, the cleaning process criteria ~ay 3 often be me~ without using these fluids in their supercrit-ical state.
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Thu~, ~ need ex~ t,~ ~or a ~y~t,~ tll~t provlde~ ~or pli~ied and relia~le pf~rIor~ance, il~or ~all ~c~lef an~l ;, " low endW cleaning applic:at~ On8 .
,i -~, 5 .` , ~1 ~n accordance wlth the lnYention, apparatu~ ~or r~f,-ving undesired matf,r,r1~1 fr~ chc>~s2n ub~tr~t~ Gola-pri~3:
(a) an enlo~ed cle~ning cha~nber in za ~allff~d ves-~;el ~or cont~ining a li~id de!rive,d groDII a liqa~,eriabl~ g~
and the ~;ubstrate containill~ the lmde~ired part~culate~ and ~ conta~inant~, 'che ~alled vessel adapted to wlth~tand a ~
3 iDau~ pre~;&ur~ OI about 1, 500 pounds per sguare~ inch ( 105 . 4 kq/c~) at a~bient 'ceD~per~tur~;
(b) means ~or ~upportinç~ trat~ in the -1 cleaning cha~ber;
.3 (c) ultra~sonis: energy-producins~ tran~ducer mea~
attas::hed to the walled ve~el within the c:leaning chalaber;
~! 20 (d) inlet ~ans attached lto the walled vessQl for introducing the liquuefiable gas into the cleaning chamber under a pressure less than about 900 pOlll~dB per square inc~
( 63 . 3 kg/cm2);
~3 ( e) temperature control ~eans connected to ~e cleaning chamber for controlling the temperature wi~hin the chamber up to about 50C;
(f) reservoir means for pro~iding the liquefiable gas to ~e inlet ~Deans;
(g) means for changing the lique~iable gas to the liquid; and (h) outlet means in the cham~er ~or remov~ng t~e liquid from the cleaning chamber.
The removed liquid ~ay then be ~urther treated to re move particulates and organic contaminants and either re~
cycled to ~he cleaning chamber or Yented to the atmosphere.
The process is especially appl~cable for general degrea~ing ,;,..........
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and partlculate removal process, when h.lgh preci~ion clean-iny i~ not required.
The adv~ntage o~ tha pre~ant inventiorl 1~ tllat it eliminate~ the need ~or a cond~nl~er ;~nd recycle E~y8tllal!~, ', 5 e~ch of ~ich ~re ~or cl~st ite~ o~ prior ;~rt syste~a.
In addition, the pre~l3ure rzlting required Por tha c:l~nin5~
cha~bar o~ the inv~ntion i~ 3rslativ21y lo~d (i.e, ~1,500 p~i, or ~105.4 kg/c212), which ~ubstanti~lly r~d~ce~ its co~t over thst of typical ~upercritical cleaninq ~y~t~s.
Egu~pDIent cost~ for the present in-,rention ar~ e~ti~ated at le~3 than ona-hal~ the co~t o~ th8 prior art ~y~t~ e present invention will al~o permit the application o li~
uefiable fluid cleanin51 for reDIote or inacc:e~ibl~ cleani~
application, and ~or r~pid, ~211 ~e bate~, and ~seJai-continuou~ proce~se~. Both o~ t~e~;e requirealents are not easily ~et ~ri~ current supercritic;~l fluid cleaning equip-7 ~nent pack~ge~.
BP~IEF 3~SCRIPTIQN ~F T}~ 12Rl~ lG~i ~j FIG. 1 is a schematic: diagram, partly in section, of :~ a first embodiment of apparatus employed in the practice o~ the invention; and F}G. 2 i~ a 6cheslatic diagram, partly in section, of a second embodi3nent of apparatu~ employed in the practice of ~he invention, ~ho~ing the apparatu~ prior to fill~g with cleaning liquid (FIG. 2A) and filled with cleaning liquid (FIG. 2B).
pESCRIPTION OF ~HE PRE:FERR~D_ElqBODIME~TS
The typical equipment require~ents for using super-critical fluids results in rQlatively high capital cost~ in 3 some cases. The present invention provides for hiqh clean~
ing efficiency without resorting to the high pressures u~u-ally reguired when employing fluid~ in their supercri~ical stat~.
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: 6 There ~re many fluid~ whlch nre typical c:andldate~ ~or llquefiable fluid cleaning in con~unction with ultri~on~c energy. The~e include nitrogen, oxyg~n, argon, hellu~, methane, propane, carbon dioxids, ~nd ni1:rou~ oxid~3.
,~, 5 FIGS~ 1 and 2 d~pict two e~di3aQnt~ o~ present~.
inv~ntion. In ~ch embodi~aent, ~ s~all ~1 to 20 liter) `. ve~3~el 10 i~3 u~ilized, provided wi~h a lid 10~. Fluid ~2 is supplied ~rom a pre~urized re~ervoir a~ t~rough nozzles along tl:~ ves~l wall$ ~0g, ldhich define ~ cleaninq cha~b~r 17. AlE~o, the ve~;el ~L0 i~ ~quipped ~ith an ultra-sonic transducer 18. ~uring op~ration, t:hQ ve~el ~0 i c:harged with ~luid ~2 through the nozzles 1~. Onc3 ch2~rged ~ with fluid a2, ultra30n~c~ ar~ appli~d to ~inal-clean the i', part 20 ~nd to remove the l~Rt tracea o~ contamlnation.
The part 20 ls ~upported in the ve~el 10 by ~upport ~e~ns 21. ~luid ~2 is withdrawn ro~ the ~e~el ~0 through out-let 22 a~er ~leaning and ~ 5 trea~ed by filtar~ 2~ and a separator 26 to re~ove particulat~ and srganic conta~na tion.
While the following descrip~ion is pre~ented in terms of employing C02, other liquefiable fluid~ ~ay be used in 1 the practice of the invention.
3~ Intermediate_Cleanin~_svstem FIG. 1 illustrate~ the fir~t embodi~ent, which repre-¦ ~ents an intermediate ~ersion, of ~h~ prs~ent invention.
The steps used in thi cleaning process are as follows: : -(1) ChaFae the Vessel wi~h ~iquid ~2-~he parts ~0 to ~e cleaned are placed in the vessel 10, ~hich is then closed, and C02 12 is intrs-duced into the vessel through nozzles 1~ in the vessel wall. Initially, snow will be formed, but the state :;
o~ the fluid 12 is controlled by the temperature in ~eat ~xchanger 27. ~s pressure builds, C02 is con - ~:
densed a~ a liquid 12' using cooli~g coils 28 in the vessel 10. The liquid C02 ~2' may be above or ~elow :
the critical point ~or C02, which is de~ined by pres-., .
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`~.,? 7 i~ ~ure and temper~ture. The IDaxl~ r~ssure c~ntem-. pl~ted by thl~ proc~ About 1, 000 p~si 170O 3 kg/~
c~2 ) a.t ~ bien tsmper~ture .
1~2-After char~ing wi~h f luid, ~Q te~perature 1~
ad~usted a~ resuired - to ~a~nt~in th~ id ~t~te (i.e., 25C:, 800 psl, or 56.2 kg)~2~0 ~I!he ~lu~d l~v ad~ustesl froD~ thQ rao~rvoir 1~11 aE~ r~quirss31 t~
i~er~e the part~ 20, by ~ean~ o~ a le~l lndlic~tor 30 in t ve~el 10 ~ Sonic:ation i~ ~en perfc~aed in the liquid C02 129 u~ing one or ~ore ~on~catl~ horn~ 1 a~ a ~reguesls:y ranqing ~ro~ about S to 100 ~iloheri:z.
(3? 3eq~e~e ~ Q2-The liquid 12 ' i~ now he~ted b?ll:h hea~ing coil~
~8 to above 32C. As; an option, thi~ 8y3tl aquipped with a 3~0nitor 29 of thla ~f~luent ~rols th~
~8S~l. The ~on~tor 29 ~onitors th~ p2~rticulate and ~, organic conta~inant l~vels. If repeated cleanings ar~
;~, p~rformed, t~e particulate and organic level~ decrea~e until the part i~ deemed to be ~clean". Steps 2 and 3 are then repeated a~ deter~nined by the ~onitor re-~ult.
(4~ ~o1npression.
After cleanin~ i~ c:olap~:ete, fluid 12 i~ recyc:led and compressed into the re~ervoir 1~, using a co~pre~-~or 32.
In this f irst e~bodiment, cleaning ~luid ~2 is recy cled, but only rough or ~fir~t level~ puri~icat~on ~8 per ~ormed, inste2d of ~he high level prov~ded by ~he prior art SUPERSCRUBTN preci~ion cleaning eguip~ent. Particulate re-moval i8 stepwise, with ~he final step down to only 10 ~m ;l size, before final ~iltration, to minimize filter clogging and Da~ntenance. larqe particulate~, on the order of 10 to 100 ~m, are ~iltered pr~or ~o entry to the separator 26, ; 35 u~ng ~lter 24, to provide ~or easier ma~ntenance and I operation. A cyclone separator 3~ i3 u~ed to remove small ¦ particulates, on the order of 0.1 to 10 ~m, ~hich gives `
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le~ e~cient ~eparation o~ organic conta~inat1Or~ an tha3 known ~ilter/demi~t6~r approach, Ibut provldQ~ for e~ier maintenance an~ down-tiJ~. The compres~or sa i~ u~ed to Xill and pressurize th~ liquid re~ervoir â~l. Th~ præs-~ure of the re~ervoir ~erve~ t:o ~ill ~e ~e~ol O, co~-pleting the~ ~luld cycle. Thi8 ~!lpproac:~ ell~irlatQI~ tbe r~Qed ~or zl liquid puap and cond~n~r, and ~ford~ ~uch sllDpl~
c~perzltion. However, by providing a recycl~ capabillty, it i~ po~sible to puri~y tAIa gA~ supply to en~ure that it meets any required cleanline ~ criterl~. ~n thi8 ~ di-ment, thQ ~onitor 2~ can b~ utilized to dete~n~d ~hen ~he part 20 i~ ~leaned, by determ~n{ng ~hen ~he liguid 12' con tain~ par~icul~e~ and cont~inants below a pr~determinQd level.
In a mcdifica~ion o~ ~h~ above apparatu~, th~ ~ep~ra-tor 2~ 2nd the cyclone 34 ~ay be by-passed, using in~t~ad a pressure reduction valve 35, me valve 3~ allo~ ~e liquid 12 to expand to ~he ga~eous state, whereafter it 1~
compressed to the liquid state by the co~pres30r 32. [It will be appreciated ~hat the separator 26 includes such a valve 3S.) The u~e of the co~pressor 32 in either case en~
sures filling ~he reservoir 14. In this case, the ~oni~or 29 can be used to determine if the l~quid 12 i8 atill u~e-ful, by whether the particulate and contaminant levels ex-ceed a predeter~ined level.
The liquefiable gas ~ay be u~ed wi~h modifiers. Typi-cally ~ ~inor percentage (less ~han about 50 vol/vol per-cent) of a condensed phase solvent, or ~odifier, i8 added to the bulk c~pressed gas. These modifiers are mixed with the compreæsed gas to form a non-flammable, non-toxi~ mix-ture. The ~odifiers c~ange the critical point of the mix-ture so t~at higher pressures (up to about 1,500 pound~ per square inch, or 105.4 ~g/cm2) and temperatures (up to about 50C) can ~e used, which provides improved sonication. In addition, the ~odifiers change the chemical properties of the condens~d gas to improve the solubility properties of the mixture~ The modi~ier or ~odifiers used depend on the ~ ~ 2~2~
:~ 9 ;, contarninant being removed~ For removing polar organic con-;' t~inant3, a ~odif i~r uch ~ o-propanol or aceton~ i ., employed~ For reDloving polar inorgAni~ cont~inant~t w~er ` 1 18 desirably employed. For re~oving low niolecular w~ight ;~ 5 non-polar organic ~C6 to C18) conta~nants, a ~i~ier ~uch `j a~ hexane ~ay be uied. For r~ ring high ~olecular weight non-polar organic (>Cl~) contal~hinan~s, ~ ~odigler ~uc~h za~
kero~sn~ may be u~e~., Optionally, any ~nodi~ier re~aining on the surface o~
:~ 10 the part 20 to be cleaned may be removed follo~ding removal of the liquid CO2 froffl thle ve~el 10 by introducing CO2 in the 6upercritical state and ~onicating.
i ;~ 15 The second eibodi~ent of the present invention, d~-'~,! picted in PIG. 2, i3 intended ~or low end ~i.e., low-co~t) ~, use, wit~ irregular, frequent and small bat~h ize require;~
men~s and when ~ringent purity cri~ri~ ~or th~ ~upply ~luid 12 are not requlred. Thi~ e~bodi~ent con~itute~ th~
bare minimum for lique~iable fluid cleaninq; and provides for the ultimate in si~plicity, flexibility and cost effec-tive operation. The step~ used in thi~ process are as fol-lows:
(1) Charqe ~he Ve~el with Liqul~ Ç2-The parts 20 to be cleaned are plac~d in ~he ves-. 3el 10, which is then closed, and C02 12 i5 in~roduc~d 31 into the vessel through nozzles 16 in t~e vessel wall.
Initially, snow ~ay be formed, but is replaced with liquid 12' to charge the vessel. As above, the physical tate of the fluid is controlled by tempera~
ture, using a heat exchanger 3~.
!2~ SQnicate In Li~ui~ ~Q2.
Final cl~aning is accomplished with ultrasonics, a~ described above. FIG. 2B shows the liquid C02 12' 3 35 filling the vessel 10.
(3) Ve~
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A~ter ~onic~tlng, the ~luid 12 1~ vented through BeparatOr 3~ to re~ove "he orgzlnic and part~culate contamln2nts. Prior to venting through the ~parator 38, large particulat~s (10 to 100 ~DI) 2r~ re~nov~d ~y ,' 5 ~ilter 40 in the bottoD; of the veEi~el lOo acond embodi~2nt, l~ke the ~r~at ~i~ent, al~so ~upplle~ Pluid 12 into t:~e ~Je~el ~0 throug~ ln'ce~rn~
nozzl~ . HOWQVer, thi~ ~<aclond eDIbodi~ent d~ not r~-cyclQ the ~luld 12, but ln~adl vent~ it to ~he 2l~0~pher~
by exl~aust ~neans ~a ~fter removal o particulat~ and org~n-ic cont~ninants in the ~eparator 3~
Pre~suriza~ion of the ves~el 10 i~ acco~plished with ~ tank or cylinder pressure fro~ the CO2 ~upply ~ource ~ on~
j ly. Pres~ur~ i~ increased by heating ~he CO2 i~ the tank ¦ 15 ~ by ~eans of ~ heater ~6. ~ypically, th~ teEperature o~
~ the CO2 i ~aintained at about 30C, provlding a pre~sure 3 of about 1,000 p3~ (70.3 kg/c~2). ~hi3 eliminate~ the need for a reservoir 1~ (n~ shown in FIG. 1) ~nd pu~p and re~
duces ~he sy~te~'s upper pressure requirement, thereby re-! 20 sulting in much simpler and less expen~i~e process equip~
~ ~ent. However~ this approach limits the process to sub-1 critical condition~, which mean~ that the cleaning advan-tages of the ~upercritical state cannot be used. In thi~
embodi~ent, cleaning efficiency in liquid cO2 12 is opti~
mized through ~he use of ultrasonics, which overco~e~ the cleaning efficiency ~hortcomings of using the less powerful solvent.
The present invention is applicabl~ to ~any processes involving.liquefiable fluids for preci~ion cle~ning, ex-tractions, particulate removal, and degrea~ing. Exe~plary applications include cleaning during ~anufacture of contact lenses, fuel in~ectors, engine blocks, watches, s~all elec-¦ trical appliance~, and razor blade , bearing degreasing, and engine repair shop3.
Thu~, there has been disclo6ed ~ process for re~oving contarinantD rom nubstrate~, u~ing lique~ied g~s. It vill -~ 2~2~
' ~1 be apprec~atzd by tho~e skilled ln the art that varioua modif ic~t1ons and changes o~ an obvious nsture ~y be D~de without departing ~roDI the ~cop~a o~ th~ ~nvention, and ~11 ~uch modii~ication~ ~nd change~ ar~ intended to ~all with$n the ~cope o~ the ~nvention, 218 de~in~d by the ~ppende~l cla$~s.
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Claims (9)
1. Apparatus for removing undesired particulates and contaminants from a major surface of a chosen substrate (20) comprising:
(a) an enclosed cleaning chamber (17) in a walled vessel (10) for containing a liquid (12') derived from a liquefiable gas (12) and said substrate (20) containing said undesired particulates and contaminants, said walled vessel (10) adapted to withstand a maximum pressure of about 1,500 pounds per square inch (105.4 kg/cm2) at ambient temperature;
(b) means (21) for supporting said substrate in said cleaning chamber;
(c) ultrasonic energy-producing transducer means (18) attached to said walled vessel (10) within said cleaning chamber (17);
(d) inlet means (16) attached to said walled vessel (10) for introducing said liquefiable gas (12) into said cleaning chamber (17) under a pressure less than about 900 pounds per square inch (63.3 kg/cm2);
(e) temperature control means (27) connected to said cleaning chamber (17) for controlling the temperature within said chamber (17) up to about 50°C;
(f) reservoir means (14, 44) for providing said liquefiable gas (12) to said inlet means (16);
(g) means (28) for changing said liquefiable gas (12) to said liquid (12'); and (h) outlet means (22) in said cleaning chamber (17) for removing said liquid (12') from said cleaning chamber (17).
(a) an enclosed cleaning chamber (17) in a walled vessel (10) for containing a liquid (12') derived from a liquefiable gas (12) and said substrate (20) containing said undesired particulates and contaminants, said walled vessel (10) adapted to withstand a maximum pressure of about 1,500 pounds per square inch (105.4 kg/cm2) at ambient temperature;
(b) means (21) for supporting said substrate in said cleaning chamber;
(c) ultrasonic energy-producing transducer means (18) attached to said walled vessel (10) within said cleaning chamber (17);
(d) inlet means (16) attached to said walled vessel (10) for introducing said liquefiable gas (12) into said cleaning chamber (17) under a pressure less than about 900 pounds per square inch (63.3 kg/cm2);
(e) temperature control means (27) connected to said cleaning chamber (17) for controlling the temperature within said chamber (17) up to about 50°C;
(f) reservoir means (14, 44) for providing said liquefiable gas (12) to said inlet means (16);
(g) means (28) for changing said liquefiable gas (12) to said liquid (12'); and (h) outlet means (22) in said cleaning chamber (17) for removing said liquid (12') from said cleaning chamber (17).
2. The apparatus of Claim 1 further including filter-ing means (24, 40) for removal of particulates from said liquid (12'), said filtering (24, 40) means associated with said outlet means (22).
3. The apparatus of Claim 2 wherein said apparatus comprises a closed, recycling system, with said filtering means (24) associated with said outlet means (22) for re-moval of particulates on the order of 10 to 100 µm from said liquid (12') after removal from said cleaning chamber (17), wherein said means for providing said liquid from said liquefiable gas comprises a compressor means (32) be-tween said filtering means (24) and said reservoir means (14) for ensuring that said liquefiable gas (12) is in its liquid state (12'), said apparatus further including a heat exchanger (27) between said reservoir means (14) and said inlet means (16) for controlling the temperature of said liquid (12) prior to introduction thereof into said clean-ing chamber (17).
4. The apparatus of Claim 3 further including a pres-sure reduction valve (35) between said filtering means (24) and said compressor means (32) for converting said filtered liquid (12') to its gaseous state (12).
5. The apparatus of Claim 3 further including (a) a separator means (26) following said filtering means (24) and before said compressor means (32) for (1) removing par-ticulates on the order of 0.1 to 1 µm and organic matter from said liquid and (2) converting said filtered liquid (12') to its gaseous state (12), and (b) a cyclone means (34) for removing small particulates.
6. The apparatus of Claim 3 further including monitor-ing means (23) for monitoring particulate and organic con-taminant levels, said monitoring means associated with said outlet means (22) to monitor said liquid (12') after remov-al thereof from said cleaning chamber (17).
7. The apparatus of Claim 2 wherein said apparatus comprises a vented system, with said filtering means (40) associated with said outlet means (22) for removal of par-ticulates on the order of 10 to 100 µm from said liquid (12') prior to removal from said cleaning chamber (17).
8. The apparatus of Claim 7 further including a sep-arator (38) associated with said outlet means (22) for re-moval of particulates on the order of 0.1 to 1 µm from said liquid (12') following passage of said liquid (12') through said filter (40) and prior to venting.
9. The apparatus of Claim 7 further including a heat-ing means (46) within aid reservoir (44) for heating said liquefiable gas (12) contained therein.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/082,866 US5339844A (en) | 1992-08-10 | 1993-09-07 | Low cost equipment for cleaning using liquefiable gases |
| US08/082,866 | 1993-09-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2130241A1 true CA2130241A1 (en) | 1995-03-08 |
Family
ID=22173939
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002130241A Abandoned CA2130241A1 (en) | 1993-09-07 | 1994-08-16 | Low cost equipment for cleaning using liquefiable gases |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5339844A (en) |
| EP (1) | EP0641611B2 (en) |
| JP (1) | JP2922791B2 (en) |
| KR (1) | KR950007963A (en) |
| CA (1) | CA2130241A1 (en) |
| DE (1) | DE69410192T3 (en) |
| TW (1) | TW438631B (en) |
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-
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-
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- 1994-08-16 CA CA002130241A patent/CA2130241A1/en not_active Abandoned
- 1994-09-02 EP EP94113814A patent/EP0641611B2/en not_active Expired - Lifetime
- 1994-09-02 DE DE69410192T patent/DE69410192T3/en not_active Expired - Lifetime
- 1994-09-05 TW TW083108181A patent/TW438631B/en active
- 1994-09-06 KR KR1019940022320A patent/KR950007963A/en not_active Application Discontinuation
- 1994-09-07 JP JP6213728A patent/JP2922791B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DE69410192T2 (en) | 1999-01-14 |
| EP0641611B1 (en) | 1998-05-13 |
| JP2922791B2 (en) | 1999-07-26 |
| TW438631B (en) | 2001-06-07 |
| EP0641611B2 (en) | 2002-07-31 |
| DE69410192T3 (en) | 2004-01-08 |
| JPH07171527A (en) | 1995-07-11 |
| DE69410192D1 (en) | 1998-06-18 |
| EP0641611A1 (en) | 1995-03-08 |
| KR950007963A (en) | 1995-04-15 |
| US5339844A (en) | 1994-08-23 |
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