CA1303965C - Storage and transportation of liquid co - Google Patents

Abstract

ABSTRACT
A system for transportation and storage of liquid CO 2 at low pressures in the region of 1600-2300 KPa comprises a mobile supply tank and an on site storage tank . The mobile supply tank and the on site storage tank are thermally insulated and each tank is refrigerated by a refrigeration system with an evaporator located in the upper gas space of each tank. The on site storage tank is filled with liquid CO2 by a conduit extending from near the bottom of the mobile tank via a filling port on the on site tank to an opening near the bottom of the on site tank. A
closed circuit system is achieved by a further conduit extending from the gas space near the top of the on site tank to a gas space near the top of the mobile tank.

Description

1. ` ~l3~f365 STOR~G~: AND TRANSPORTATION OF LIQUID CO 2 ~ HIS INVENTION is concerned with the storage and -transportion of liquld carbon dioxide ~CO2 ) and in particular to the storage and transportation of liquid C02 at relatively low pressures.
Carbon dioxide in gaseous form is used in large quantities in many industries. One of the major consumers of CO2 is the hotel trade in the provision of draught carbonated beer and other carbonated beverages through a reticulated supply system.
Other consumers include manufacturers of carbonated beverages, manufacturers of dry ice, operators of welding machines requiring an inert CO2 welding atmosphere, manufacturing operations using an inexpensive inert gas such as CO2 for spraying of hollow vessels and the like.
For the sake of simplicity the following prior ar~
discussion will be limited to the use of CO2 by ho-teliers but it should be understood that the problems and limitations associated with storage and transportation of ~0 CO2 by prior art systems is generally common -to all users.
Traditional prior art methods of storage and transportation of CO2 required the use of steel cylinders measuring approximately 1.5 metres in length and about 0.25 metres in diameter. Such cylinders have a capacity of about 32 kg of CO2 at about 14000 KPa. Because o~ the very high storage pressures required, the storage cylinders of necessity were extremely robust and in consequence e~tremely heavy to handle. The steel storage cylinders were designed . . .

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for upright storage on a flat base and i~ consequence were extremely unstable due to small hase area and a relatively high centre of mass. There are many recorded instances of injury and damage being caused by falling cylinders. In some cases the exposed filling/outlet valve has been broken during such a fall enabling the contents of the cylinder to be discharged at very high pressure. Work related injuries such as back injury, crushed limbs and the like can be attributed to handling of C~- cylinders.
10Apart from the dangerous aspects of handling of C~
cylinders there are many inefficiencies associated with the storage and transportation of CO2 in such cylinders, particularly for consumers of large amounts of C~ .
The CO~-cylinders are usually filled at a gas producing plant and then are transported great distances by road and/or rail to a user destination. When empty, the cylinders must be returned to the gas producing plant for refiling. Apart from excessive handling re~uirements and ( transportation charges, this necessitates the use of a very ~0 large number of cylinders to take into account turn around time from consumers, transportation time and maintenance and testing time. The high capital costs, handling, transportation, testing and maintenance costs are passed on to the consumer, usually in the form of a rental charge for the cylinders.
Steel cylinders, although durable from a physical handling point of view, are subject to internal corrosion .~
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~;13~6~ ,i due to molsture en~rained ln thc CO~ con~ained there~n ~nd ~af~y regul~tiQn3 requlr~ f~equent pre~sur~ ~e~lng a~ w~
A~ phy~lcal ill8peCtiOllq ~0~ t}~ey are ultlm~tely rejected a~ un~a~e- i O~ recent tim~ there has been an at~empt to overcome some of the problems associated with ~igh pr~sure steel gas cyllnde~ by utilizing aluminiu~ cylinder5.
Al~hough aluminlum cylln~ers h~v~ a significantly reduced ma~ any adYan~age gained in ~a~ of slandling i8 offse~ or even tot~lly n~gated by increased manu~acturlng C08t~
com~ined wlth a lacX of durability which necessita~e~
requent replAcement.
Ye~ anot~er pro~m a~sociated with ~he use of high pre~u~e cylinders is tslat most ~os~ulners actually use ~he 1~ C02 at relati~ely low pressures. ~ox example a retlcul~t~d beer llne in a hotel o~ bar may operate a about 70-125 KPa~ This necessitates the us~ o a pre~ure x~ducing devlce, u~ually o~ the diaphragm ~ype, ~o ob~aLn a source of 02 at ~ required workln~ pr~ u~e Prom a i~ource of C~Oi stored at about 14000 KPa, It ls impo~t~nt ~o be a~l2 ~o con~xol user pres~ure with consider~ble accuracy ln or~r to a~oi~ was~age of ga~
due to exce~isl~ flow rates and also to avoid w~itag~ o~
beer aue to ex~e~lve ~b~rption of CO2 l~a~ing to eXCessive f~othing a~ t~e beer pouril~g ta~.
Further problems are ~xperl~nced by u~e~6 o~ l~r~e ~olume~ o~ CO2 ~irs~ly, ln or~er to provl~e ready acc~

O .. ... . ..

4~ 65 ~or cylinder changeovex~ the ayllnde~s are ~ lly Gonnec~d to ~ manifold ~rranged ln a slngle b~nk extending ~or con~lderable ~istance along, ~ay, a wall. Due to delays in ~upply or unexpected demands oSI ~s con~umption, lt is ~ot uncommon to have on hand S0-100~ a~ditlonal supplles o gas ~nd apart f~om ~torage problems, ~hi~ n~ce~sltat~s con~ldera~le addltional revenue being tled up in exces~
~torage.
with a manl~old supply ~ys~em belng ~ed by a lQ plurallty of cylinders, lt is very dl1cult to determine reserves of gas supply in eac~l ~ylinder. U~ually a cellarm~n is requi~ed to constantly moni~or pres~ure gauge~
associa~ed wlth tsle manifold supp1y system. When a cyllnd~r becomes empt~ and r~guires csha~lying thi~ allow~ a certain amount o~ ~ir an~ po~si~ly for~ign mat~er to enter t~l~ gas ~upply li~le. Accvrdingly ~efore a fresh cy~lnder o~ g~ can ~e use~ it i8 necessary to sparge the g~s s~pply an~ beer supply lineS and to flush ~he beer supply 11ne wlth ~r~h beer ~o avoid contatnisl~tion. Apart ~ro~ beln~ very ~a~te~ul ~o o be~r this can be very disruptlve to bar ~ra~lng i~ thi5 occurs durlng trading hours. I~ 1~ no~ uncommon ther~ore ~or ho~eliers to have to change vv~r cylinders ~fter trading hourq ~n~ then ~parge and ~lush the gas and bee~ lin~ in a sinqle ~aily ope~ation. This opera~ion i~ no~ only very tlme consumin~ but i very wast~ful of b~th ~a~ and be~x.
It i~ an aim o~ the present inventlon tv pro~ide a i sy~tem for low pres~ure ~torag~ an~ tran~portation of llquld .

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C 2 whlch ov~rcome~ or ~ len~ allevia~e~ the p~oblem~
a~qo~iated with prior art high pre~sure sto~ge ~n~
tran~port~lon o liquid Co 2 and ultlmat~ u8e of 6uch gas ~rom a high pre~uro source.
As used llexeirl the expression "hlgh pres~lre" a~ it rel~te3 to pr~ or ~rt storag~ and t:ransportatlon o liquiQ CO 2 meang pres~ures of the order of about 14000 KPa and "low pre~sure " a~ it relate:s to storage an~ tran~portation c~f liquid CO 2 ~ccor~in~ ~o the ln~ention m~an~ pressur~ of the order of about 1600-2300 KPa sllghtly 128~ than 1 or~Qr of .
magnitude in di~er~nc~ between the respectl~e pressure~.
Ao~oral~g to one ~epec~c o4 thc ln~nt~on th~re i~
pro~lded a st~r~ge ~ystem ~or ~torage of liquid ~2 at low pre~ure, ~ia 3tor~ge ~y~tem compri~ing:-a pres~ure vessel h~ving inlet me~ns and outl~t me~n~ for 111ing ~id ve~sel, said inlet mean~ comprising a condui~c having an operling communlc~tlng wl1:h the ~n~erl~r of ~ald ve~el ~d~acent a bo~om w~l~ of ~ai~ ve~el and ~a~a outlet me~ns h~vi~g an opening con~ul~icating wlth the 2~ interior o~ SAld Ve8Bel ad~cent an upper wall of ~ai~
~sselt a coollng mcans located wi~hls~ v~el in ~n upper part thereo~ ln ~ ~egion normally occupied b~ gaseous C0~ ~ and~
a ~pply conduit for ~upply o~ gaseous C~ , said ~upply conduit communic~ting w~ th ~a~ d region no~mAlly o~upled by g~8eo~4 CO 2 ' 6. :~l3~3~6~i Su~t~bly ~ald ooollng mea~s co~prl~e3 ~ny me~ns ~b~
coollng g~aeo~ CO~ and may include a h~at exchang~r s~oh ~
a Pel~ier effec~ t~lermocouple or alternatlvely ~n evaporator a6s~cia~ed wi~h a compressio~ or a~orption r~rlg~ration apparatus, Prefera~ly tlle coollng means compr~es a~
evapor~tor associate~ with a compr~sion r~frigera~ion appAr~tus .
Pr~er~bly the storage system lnclu~e~ moan~ to lndlcate a llquid le~el within said pre sure ve~
Pre~er~bly ~ heAtlng mea~ i~ located within ~he low~r portion of ~aid press~re vess~l ln a region normally o~cupied by liquld CO~ . Sui~ably said he~tlng me~ns may be heated ~y waste heat from a con~enser a~ociated with sal~
re~riger~tlon ~y3tem.
Preferably ~aid heatlng n~eans colnprlse~ ~n .
electrlcally en~rgized hea~ing element ~nd ~ore p~e~erably said heatlng el~ment iB ~hermos~a~ically con~rolled to m~int~ln ~ vol~me o liquid Co~ in Gaid pre~Dur~ v4szol wlth~n predetermined temperatur~ limits.
Mo~t preferably s~id pres~ure vessel is the~m~lly insulatod.
~ u~tably ~ald stol-ag~ ~ys~m aompri~e~ an in~egral struct~re ~cluding a refrigera*ioll App~ratus ~s~oclated ~ with said evapora~or.
: ~5 A~cordin~ to another a~pect of the ln~ention ~her~
is pro~ded a 3y~tem for ~rall6portation ~nd delivery of low p~ec~ure liquid CO2 compri~lng;-.
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at le~8t one ~torage tank having ~ ga~ inlet por~
commun~c~tlng with an uppex ~nt~rior part of ~a~d tank and a ll~uid lnlet/outle~ por~ com~unicating wlth a lower lnterior part o~ ~ald tank;
coollng mean6 for main~aining liquid C02 containet withln ~id ~essel wlthin ~ede~ermine~ ~mpera~ure llml~s;
pump means ~ssociated wlth 3aid liq~ld lnlet/ou~le~
port ~or digcharge o~ liqui~ C02 to a ~e~eivlng ~e~l; and,.
~ storage vessel ~illin~ mean~ lncludlng a ~lr~t conduit connected to said pump for ~ischarge o~ liquld C0~
to an lnlet means o~ a stvrag~ ~es~el and a ~econd conduit to recelve ~aseous C02 from an outlet m~an~ of ~aid fi~orage ves~el or return of said gaseous C0~ to 3ald ga~ inl~t por~
a6socl~ted with sal~ storage ~ank.
~uitably said 8y~tem for t~an~portatlon and del~ery of low pressUre liquid C2 i~ adapted fo~ mounting on a moblle vehicle. Pr~ferably s~id syst~m or transpor~ation and dell~ery o~ liquid C02 i~ moun~ed on ~ ( base an~ ls r~m~vably attachab~ to said mobLle vehlcl~.
; ~o Pre~ei~ably ~ald aooling ~e~ns aomprl~ an ev~pora~or meAns a~30~iated with ~ ro~rlgoratio~ system, s~id evaporato~ m~an~ l~eing los;:ated ~rithin said at l~a5t ons i tank in ~n upper rcgion normally occupied by ga~eou~ CO2 .
Pre~erably sa~d at lea,st: one tank i8 i:h~rmzllly ln~ul~t~d.
Pre~er~l~ly sa~ d pump mean is adapted ~o ~ c~ar~e liquld CO2 selec~;ively at high pressur~ ~or f~ ~ llng high -- . . - . _ . ~ .. ..... .. ... ..... .. ...

-- 8. ~3~35~65 pre~sure liquid C02 storage ve ~el3 an~ a~ low p~e~ ure for fllllng lo~ pres~ure liq~id CO2 ~tor~ge ~eBsel~O
P~e~er~ly s~ld flrat i~nd ~ecorld conduit~ comprl~e xet~actAhle flexl~le hose a~emblies.
Accordlng to y~t a further aspecl: o~ t:he inventlon there is provided a ~yQtem ~or sto~ag~ and transportation of 1 liquid C02 at low pressures, ~ald sy~ten~ oharacterizsd in l;he provl sion o~ a clv~ed clrcuit for fllling of pressure ve~el~ cont~inlng low preS ur~ C02, B~id clo~ed circuit 1~ oomprlsing~
a flrst ~ondui~ connec~abl~ at ~ne en~ to a sourc~
o~ low pressuxe llquld C02 below ~he liquid level of 6~i~
sourc~ ~nd connectable ~t ~n opposed en~ to an inlet por~ of ~ uid C02 sto~age ves6el, said inlst port having an opening adjacent a low~r wall of said 6tor~ge vessel; ~d a second condult conn~ ble ~ one en~ ~o ~ gas outlet port con~unichting wlt~ the lnt~rlor o~ sal~ ~torage ve~el at an upper par~ thereof normally oc~upied by gA3eous C02 and conne~ta~le at an opposed end w~h a g~ lnlet port .
~s30ci~ed wi~h said ~o~rce, ~ld ~y~tam ln u~e cau~lng low pres~u~e llq~ld C02 ~o be intrvduaed in~o a ~to~age ve3~1 aaja~en~ ~ l~w~ wall ~he~eo~ and simul~ane~u~ly ga~ou3 CO~
ocoupying ~ 6pace between th~ 1@Y~1 of liquîd wl~hin 6aid ~torage tar~k ~eing r~turned to s~ld sour~o vla s~ld econd conduil: l:o prevent exc-3ss gas pre~ure oca~ring in ~ai~

storage tank during a f illin~ vp~ration .

9. ~13~3965 By way o~ illustratio~ ~riou~ p~ ed embotlment~ o~ ~he lnvention will now be ~eacrlb~d with re~erence ~o the ao~ompanyi~g drawlngs in which ~ig 1 i a 3ch~matlc ~iew o~ a system ~ox manufac~ure, tr~n~port~ion and 6torage of low pre~sure liquid ~arbon ~loxide;
~ ig 2 i6 a schematic view of a moblle delivery ~y~tem for low pres~ure li~uld C02;
~ ig 3 is a schematic view o~ a ~oola~t sy~tem ~or t~e mob~le del~very v~hicle stor~g~ tank ~y~em ~hown in Fig ( ~o 2:
Fig ~ ia a 3chem~ic ~ie~ o~ an on 6ite ~to~age ~tem for recel~ing ~nd ~toring low pres~ur~ l~que~ied carbon ~loxide dellvered by the ~ystem 6hown generally i~
~ig ~, In ~lg 1 gaseous carbon dioxid~ ~ produced by a conventlonal CO 2 gene~ating ~ystem ~hown q~nerally at 1.
~uch a generating ~ys~em may comprise a ga~ er 2 to pro~ide a ~ou~oe of producer g~6 from a carbona~eou~ f~
~u~h ~3 co~l, preferably ant~ cite. ~aste mln~ral oil~ may ~o be in~roduoed into the top o t~le ga~ifier 2 and a8 the wa~e oll pA~e dow~ the in~erior o~ t~e ~a~i~ler o~r the an~h~clte~ pOr~iOIl of the oil i~ volatllized an~ por~ion ~nde~goes aom~u~tlon while impurlt~e~ and t~rs are collected a~ the bo~tom of the gasifie~ 20 Oil ~nriched producer ga~ ~h~n p~ 8~ to a ~a6 scrubber 3 of con~enkional design ~or washlng and coollng wl~h wAt~r. I

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Th~ washed and aooled ga~ ~ ~ then dir~c~e~ to the in~ke manifold o~ an ~n~ernal oombu6~10n engl~e 4 vla a suit~ble metering devlc~ ~uch a~ a carburettor or the like and pro~ides a ~uel source ~or the ~ngin~. The engine 4 ln 5 tUL'n i~ connec~ed to ~n electrical pow~r ge~ration system 5 . whlch ln ~urn provides electri~al po~er o~ a carbon dioxide pl~nt ;6. An isola~ing 6witch ~ ~solate~ power ~upply to a con~rol panel 8 a~ociated wi~h ~he carbon dioxlde plant 6.
The exh~u~t gase~ fa-om the engine 4 are ~hen ~ed to .
0 ~ ga8 burner lO of known type to comple~e ~he combustlon o any carbon monoxide in the exhaust ga~. Al~ernatively or addi~lo~ally the gas burner 10 may receive ~ source 11 of carbonaceous ga~ in tl~e form of w~te ~lue ~n~ fro~ a oomhustion proce~ employlng a c~rbonaoeou~ f~
lS Afte~ recombustion o~ tlle 0xhau~t ga~ea ln.g~s bu~ner 10 the 1ue gas f~om the gas b~ner are washed &nd cooled ln ~ w~er scrubber and then dlrected to an absorp~lon ~ower for extractl~n o C0 2 Su~tably ~he C0 2 g~s ls selectlv~ly ab60rbed from the flue g~s ln ~n a~ue~u~
M~A/~od~ ~6~ 601ution.
The ~a enrlclled a~sor~er llquor 1~ then pr~h~ated in ~ ~e~t exchangel- ~efore pa6sing ~o a conventlonal ~ ~trippe~re~ctiv~or ~o re}ease absorbed C0 2 ~rom th~
enriched absorbe~ llquor. R~leased CV2 i~ then di~ected ~t plant operating pressure to a conden~el- to ~ool ~he C0 2 gas and to remo~e w~ter ~apour ro~ th~ ga~0 ., .
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- ~ contr~l valve maintaln~ ~ cQn~tant pxe~sur~
within ~he stripper/reactiv~t~r ~nd a~ter p~s~ge ~hrough a .
compre~or of conventional type, liquefled ~O~ iJ pass~d to a bulk ~torage ~ank 12 ~or ref~lg~rated storage a~ a p~-e~u~e of 1500-2300 XPa and a tem~erature of - 10~ C ~o 25 C prefer~bly - 17 C. .
~lq~id CO~ m~y then be used to ma~e ~ry ice u~illzlng a convent~onal dry ice manuf~cturing apparatUs 13. I~ ~ typl~al dry ic~ manu~acturing ~pparatus, liqui~
Co~ is allowed ln a ~now cone to form ~ "snow" o~ ~olld CO~
cry~al~. The CO~ l'6now" fall~ into a rain openiny and the ram compres~e6 ~he snow ~nto ~olld blocks o~ de~ire~ ~hape and ~ize. 5uita~1y ~he "snow" is compr~s~e~ ~galn~t a di~
plate having a plurali~y o~ shaped ori~lces. The ~omp~essive ~ction o~ the ram ~xtrud~3 the ~olid C0~ tllroug~
the ~ie pla~e ori~ices to form ~ha~ed, l.e. cylin~rical~
~luge o dry i~e.
In the dry ice m~nu~actuxlng Appara~u~, ga~ou~ C0 ~i formed by ev~poratlon o the liquid CO~ or ~ubli~tlon o~
the ~olid CO2 is collect~ and pass~d to a compre~or be~ore bein~ retu~ned to bulk storage vla the ~aln compre~or.
Th~ bulk ~tored li~uid CO2 may ~160 ~e decatlted lnto a mobile refrigerated low pr~s~ure ~toxage ~ank 14 on a delivery ~rehicle 15. The liquid C2 i~i; maintaine~ ln thf~
mobile s~orage tank 14 un~er conditions similar to the bulk qtorage t~nk 12. As deserlbetl h~r~ina~ft~r in more de~ail the ~rehicle mounte~ mo~lle storag~ tank is adapted ~or i -3~3965 ~illlng oonventlonal high pressure CO ~ cylln~ra 16 A~ well ~8 O~ ~ite low pre~sure ~torage t~nk~ 17a,17b,17c And 17d e~ch of ~iffering cap~cities, ~or ~xam~le 140kg, 300kg, SOOkg and BOOkg r~spectively.
Fig 2 ~hows s~he~atic~lly a flow ~y~tem for liquid ~nd g~qeous CO2 in a vehicle mounted moblle tran~portation and aellvery ey~tem.
The ~eli~er~ v~hi~le 6~ita~1y comp~ A ~lat top ~ray truck and ~he mo~ile liqui~ C02 t~ansport~tlon and delivery 5y6t~m shown ~chematically in ~ig 2 i~ afi~emble~ a n compl~te ~nit moun~ed on a s~d base or ~upport frame.
For re~son~ of ~ompactness and economy the llqu~d c4 i~
s~ored for transportation in a pair of tanks 20a~0~ mouslt~d on a skld ba~e. The ~anks ~Oa,20~ ar~ refri~ra~ed and 1~ insul~ted wit~ polyurethane foam. The re~rigeration e~stem (de~rlbed later with reference ~o Fi~ 3) lS pow~red by a ~m~ll p~trol ~uelled internal combus~ion engille mounte~ on ~he ~kld ~se ~uppor~ g tanks 20a,20~. The ~n~ne lB
~onnec~ed to ~n alternator ~o provide a source o~ el~ctrlcal 2~ power~
The tankB 20a~20~ axe ~11ed ~rom the bulk ~orage t~nk ~ys~em ~own ln ~ig 1. The ~nks 20al20b ~e ~illed vl~ illing v~lve 21 wtth valva 2~ clo~d ~n~ ~alves 23~4$
op~n. Val~e 39 i8 oonn~cted to a return line ~or collec~ion of g~seous CO2 abo~e the liquid level in ~anks 20&,20b~
Coltected g~ re~urne~ to ~u}~ storage tank 12 or ~onden8q~0n to a ~l~ui~. Valves 24 ~nd 25 are then openea 13. ~Q3S~65 ~opara~ly ~o selec~lvely ~111 rcspective ~ank~ 20A,~b~ A
~igh~ gla~ 2~ en~bles an operatox to d~termine when each tank 1~ full. The mobil~ tank i~ ~aintained at ~
temper~ture o - 17 C and a pres~le o~ abo~t 1800 RPa, S 31mllar kO the ~ulk storage ~ank ~rom w~lich the mobile tank 1~ f~
When filling an on ~ite s~ora~e tank eith~x o v~lve~ 24 or 25 may ~e opened a~ r~quired as well a~ valv~
23,22,27 and 28 and depending on whlch tan~ i~ t~ be used elther of valves 29 or 29a are al~o opene~.
Valve~ 21,30,31,32,33 and 34 are main~alned 1~ a closed pos~tlon and pump 35 ~ a~tuated ~o recirculats liquid CO~ ~rom ~ t~nk, say ~ank 20a, via oùtle~ ~alve ~4 ~d then~e to inle~ Yalve 29. Thls s~rve~ to ensure tha~
pump 35 i~ primed Wit~l llq~id CO~ . .
Hosos on ho~e re~l~ 36 and 37 Ar~ ~hen run out to th~ on ~i~e ~torage tank ~nd connector 36A i~ connec~ed ~o the lnlet ~al~o of ~he st~r~e tank ~nd connector 37a i~
connected to the ou~let v~lve o~ the ~orage tank. Wh~n the ho~e~ nre conn~c~ed ~o the storage ~ank val~e 28 ls clo~ed ; then val~ 24,23,22,27,31 ~nd 32 on the lnlet line ~rs operled ~nd ~alve~ 34, 33 an~ 29 on ~}le r~turn llne are op~ned. The vol~ of liquid COa belng dell~r~r~ to ~che on sito storage tank is mete~d by met~r 38.
.25 When t~e low pre~ure on 61~e storage tanX i8 ~illed, liqui~ CO~ enters a~ ~he ~ottom o~ ~ha tank and g~seou~ CO~ oe~upies the upper part o~ the tank, Rather ,. . , ~ !

l 4 . 13Q3965 than bleeding o~f the ga~ occupying the upp~r part of the tank., this ga~ i~ collec~ed ln ~he re~urn line vla the hoee conn~c~ed to ho3e ~-eel 37 and ~he ga~ return~ t~ the upper pa~t o ~ank 20a wh~re $t ix cond~nsed to a llqul~ ~t~te ~y S a refrlger~tl~n e~apoxator (not ~hown) loca~ed in the ~pp~r part o~ tank 20a.
~ae~y relie~ valves 39,40 ar~ connected to tank~
70~ 20b respectl~ely to r~lieve pressure bull~ ~p in ~he tan~s ~eyond a prede~exmined ~e v~lue. Pressure gaug~s 41, 4~ provi~e a ready ~isual indication o~ the pres~ures re3p~ctlvely ln ~nkfi 20~,20~, A pre ~ure ac~uated ~wi~ch meRns 43 operate~ ~o ~wl~ch on the refrigeration sy~tem Illot ~hown) as~ociated with the stoxage tanks 2~a,20b to reduce the temperature o~
~he ga~eous CO~in the upper portion o~ the tank~. ~h~
r~rlgeration o~ the ga~ cau~e$ ~he tempe~ure o the g~seous and llquid CO~ ~o drop and thus lower~ the gas pressure in the tanks ~o a predetermined lev~l at which ~he : refrlgeration syst~m is deac~iva~ed.
An Alarm 44, pref~ra~ly au~lbl~ pr~vlded ~o ~ignal ~he f~t ~hat the gas pressure lnside the ~orage t~nk~ 20a,20b ha6 ~eached an un3a~e level and in the ~vQn~
of ~allure o~ the r~friger~tion sys~em val~e~ 29,29~ may be opene~ to all~w gas to oscape v~a p~e~s~e ~lief valve~ ;
2~ 39,40. ~lternatlve~y valve 45 may be opened ~o relle~e pressure in both ~ank~ ~imultaneously.
Pump 35 i~ a dual p~essure pump o~ con~en~ional .. ...

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type ~nd i8 capahle ~ ~igh volume lo~ pre~su~ 1Ow ~or filllng on 31te sto~Age t~nk~ a3 well A8 low vol~me, high presSuxe rlow ~or illlng collventlorlal high pre~u~e gas cylin~ers ~o pressur~s o ~bout 14000 ~Pa. High pres~ur~
S gas cylinders a~e filled via valve 30 wlth which ts as~ociat~d a pre~ur~ ~auge 46 ~o moni~or ~he filling o~ the cyllnder. Becau~e the high pre~sure cylinders are ~illed fro~ t~e top, there is no need or a return lln~ to return-aocumulatod gaseous CO 2 ~
Fig 3 shows t~le xe~rigeratlon sy~tem a~socia~d wlth the mobil~ tanks of ~ig 2.
The r~frlgeratlng sy~em shown generally a~ 5D i6 of a conven~lonal type ~nd e~ loys dual refrlgerant co~pre~sors 51, 52 to ena~le cOntinuea op~ratlon ln th~
lS event o fallure or main~enance requlre~en~ for one of ~he comp~e6sors, One way check ~alves 53,54 are ~sociat~
respec~ively witll compre~sors ~1,52 on the high pr~ure ou~let lines o~ the compres30r~. Refrigeratlon ~y~tem 50 incl~de~ a conden~er 55 a li~uid re~rigeran~ re~ei~er 56 and an l~ola~ing ~alve 57.
B~tween the hig~ pre~sure outlet side o~ the re~rlgeratlng ~y~tem 50 and ~he mobile liquld CG 2 ~torage tanks 20a,20b are a conve~tional ~llter/drler ~evlce ~7 ~
sig}~t gla~ ~8, an olectrically acl;uable ~olenold valve 58, isolating valve~ ~2, ~3 and thermostatic ~xp~ns~on valve~
60, 61 respectively~ all of ~oIIve~sltlvnal ty~.
I.o~atea is~ the upper porl;ion of each ~ank 23a, 2~b , 16. ~3~3~9~5 , ~re re~igeran~ evaporatOrB 64,65 whl~ are located in ~pac~ normally occupi~d by gaseou~ C0~ . ~he evaporator~
6~,65 ar~ c~nllec~ed via low pressure accumulator 6~ wh~re any ab~orbed moi~ture in ~he ho~ re~riger~nt vapour i~
S removea to pre~eslt its entry lnto ~he refrigerant compr~aor.
Connected betw~en the high pressure refrigerant ou~let line ~nd low pressure r~turn llne i8 a dual pre~sure con~rol swi~h 59, When excess pres~ure occur~ in tanks 20a,20b, pressure actuated ~wltch 43 (~n Fig 21 actu~t~s soLenol~ valve 28 which permits refrlgerant to cir~ul~te ~hrough e~aporators 64,~5 to lower th~ tank.pr~ure~ by lowering ~he ~emperature o~ the CO~ ~n the ~tor3ge tank.
Pre6~ure control swit~h S9 Al#o ser~ to electrically isolate compr~sors Sl,52 in the even~ of failure of condelser 55 or ln the event o~ a blockage ln th~
ref~igerant l~ne.
~ig 4 show~ 6ch~ma~ically an on ~lte 8torage tan~.
' Th~ ~ank 70 comprisas a pres~ure ve~ ~1 (pre~erably cylindri~l) whioh ls in6ula~ed with polyure~han~ ~oam. The lnlet ~or llquid CO~ compri~e~ an inle~ valve 72 connec ea ~o ~hlch 1~ an elongat~ lnlet c~ndult 72~ extending ~o near the bottom of tank 70. An outle~ for gaseous ~2 comprl~s an outl~t ~al~e ~3 ConnecLed ~o a ~hor~ collduit 73a po.~ltioned in the uppel- Le~ion of tha tank. A liquid level dete~t~on d~vice of conventlon~l type ha~lng ~n olong~te rvd ~l ~nd ~ c~lv~ ~lo~ ~2 ls l~aL~ wi~hln t~l~ tan~ ana ~

.. . . . ~ . .
.. . . . . . . . .................................... . .. . ..
(.. , ,...... -~3Q~9~S
7.

level y~uge 83 indioate~ thc li~uid le~elO
~ocatQd within tha upper part o~ tank 70 1~ a r~frig~rant evaporator 85 connec~ed in cirouit wlth conventlonal re~rigeratlon sy~t:em shown gener~lly at 71 ~nd compri61ng a compre9sor 84, capilliary 86, ~rier/~ilter 87 and con~en~er 88.
On the CO2 take o~Ç llne ~4 i~ a branched c~nnection one 8ide of which is the supply line 76 having ( ~ ssoclatea therewith an isolation valv~ ~S an~ a ~iafety r~lief valve 77 to vent gaseous CO2 in ~e even~ o~ exce~6 pressure ln the ~ystam.
On the other side of ~he ~rAnc~le~ line ~4 i~
loc~ted a pressure gaiugo 80 and a pres~ure ~ctuable swi~ch 78 ~hich 1~ ope~lble when a predetermlned pre~ure i8 reached wi~hin th~ ta~k to ac~uate th~ refrig~r~itin~ By~t~m i, 71 ~o oool ~he g4seous CO 2 a~ 1:h op o~ cylinder 7~ ~nd thereby re~uoe 1;ank pxesi3ur~ to A pred~te~min~d level At whioh the re~rlgeratiny 6ystem is swl~c~le~ of.
A furthe-- pres~ure ac~uabl~ switch 79 1~ provl~ed ~0 ~o actuate ~n alarm system ln the ~V~ of exce6s prei~ure bulld up du~ to ~exlgerati~n ysten~ ~ailure or ~he 11ke.
In the event of excosslve demand on the s~orage ~ank, heavy dr~w-of~ ~ CO2 ~an cause the liquid CO~ to boil thu6 resulting in a tampe~ture reduction and con~squent re~uctlon or ~t least va~idtlvn ~n th~ llne pre~sure in ~uppIy line 76. To overcome ~hi~ dif~icul~y ~
thermo~t~tically con~rolle~ he~till~ element 89 1~ provi~ed ~3t~3~iS

~o rn4int~in the llquld CO;~ within predetermine~ temper~ re l irnl t~ .
From the ~oregoing de~xiption lt can be 3e~n that the lnvention, in il;s ~arious ~sp~cts, provld~ ~n ~nexpen~ e 3~ut~ elegantly el~'ectlve alternative to th~ use of high pr~s~re CO~ cylin~ers as a sourc~ o~ low pressure ~a~aous CO~ .

25 , :, .

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Claims (16)

1. A storage system for storage of liquid CO2 at low pressure, said storage system comprising:
a pressure vessel having inlet means and outlet means for filling said vessel, said inlet means comprising a conduit having an opening communicating with the interior of said vessel adjacent a bottom wall of said vessel and said outlet means having an opening communicating with the interior of said vessel adjacent an upper wall of said vessel;
a cooling means located within said vessel in an upper part thereof in a region normally occupied by gaseous CO2; and a supply conduit for supply of gaseous CO2, said supply conduit communicating with said region normally occupied by gaseous CO2.

2. A storage system as claimed in claim 1 wherein said cooling means comprises an evaporator associated with a refrigeration apparatus.

3. A storage system as claimed in claim 1 wherein said cooling means comprises an evaporator associated with a refrigeration apparatus and said storage system includes means to indicate a liquid level within said pressure vessel.

4. A storage system as claimed in claim 1 wherein said cooling means comprises an evaporator associated with a refrigeration apparatus, said storage system includes means to indicate a liquid level within said pressure vessel and wherein a heating means is located within the lower portion of said pressure vessel in a region normally occupied by liquid CO2.

5 . A storage system as claimed in claim 4 wherein said heating means is heated by waste heat from a condenser associated with said refrigeration system.

6. A storage system as claimed in claim 4 wherein said heating means comprises an electrically energized heating element which is thermostatically controlled to maintain a volume of liquid CO2 in said pressure vessel within predetermined temperature limits.

7. A storage system as claimed in claims 1, 2, 3, 4, 5 or 6 wherein said pressure vessel is thermally insulated.

8. A storage system as claimed in claims 1, 2, 3, 4, 5 or 6 wherein said pressure vessel is thermally insulated and wherein said storage system comprises an integral structure including a refrigeration apparatus associated with said evaporator.

9. A system for transportation and delivery of low pressure liquid CO2 comprising:
at least one storage tank having a gas inlet port communicating with an upper interior part of said tank and a liquid inlet/outlet port communicating with a lower interior part of said tank;
cooling means for maintaining liquid CO2 contained within said vessel within predetermined temperature limits;
pump means associated with said liquid inlet/outlet port for discharge of liquid CO2 to a receiving vessel; and a storage vessel filling means including a first conduit connected to said pump for discharge of liquid CO2 to an inlet means of a storage vessel and a second conduit to receive gaseous CO2 from an outlet means of said storage vessel for return of said gaseous CO2 to said gas inlet port associated with said storage tank.

10. A system for transportation and delivery of low pressure CO2 as claimed in claim 9 wherein said system is adapted for mounting on a mobile vehicle.

11. A system as claimed in claim 10 wherein said system is mounted on a base and is removably attachable to said mobile vehicle.

12. A system as claimed in claims 9, 10 or 11 wherein said cooling means comprises an evaporator means associated with a refrigeration system, said evaporator means located within said at least one tank in an upper region normally occupied by gaseous CO2 .

13. A system as claimed in claims 9, 10 or 11 wherein said cooling means comprises an evaporator means associated with a refrigeration system, said evaporator means located within said at least one tank in an upper region normally occupied by gaseous CO2 and wherein said at least one tank is thermally insulated.

14. A system as claimed in claim 9 wherein said pump means is adapted to discharge liquid CO2 selectively at high pressure for filling high pressure liquid CO2 storage vessels and a low pressure for filling low pressure liquid CO2 storage vessels.

15. A system as claimed in claim 9 wherein said first and second conduits comprise retractable flexible hose assemblies.

16. A system for storage and transportation of liquid CO2 at low pressures, said system characterized in the provision of a closed circuit for filling of pressure vessels containing low pressure CO2, said closed circuit comprising:

a first conduit connectable at one end to a source of low pressure liquid CO2 below the liquid level of said source and connectable at an opposed end to an inlet port of a liquid CO2 storage vessel, said inlet port having an opening adjacent a lower wall of said storage vessel; and a second conduit connectable at one end to a gas outlet port communicating with the interior of said storage vessel at an upper part thereof normally occupied by gaseous CO2 and connectable at an opposed end with a gas inlet port associated with said source, said system in use causing low pressure liquid CO2 to be introduced into a storage vessel adjacent a lower wall thereof and simultaneously gaseous CO2 occupying a space between the level of liquid within said storage tank being returned to said source via said second conduit to prevent excess gas pressure occurring in said storage tank during a filling operation.