US2354246A - Apparatus for using normally gaseous solvents to separate wax and oil - Google Patents

Description

MON. SOLUTION AND DISINTEGRATED WAX UID ANE

v INVENTORS: E. M. DONS o. c. MAURO BY m%&m*% I ATTORNEYS. v

'GAS

Filed March 2, 1942 E. M. DONS ET AL APPARATUS FOR USING NOBMALLY GASEOUS SOLVENTS TO SEPARATE WAX AND OIL July 25, 1944.

wAxY' on. CHARGE A ED UTION DEWAXING CHAMBER DEOlL-ED WAXY Patented July 25, 1944 APPARATUS FOR USING NORMALLY GASEI- f @OUS soLvEN'rsTo SEPARATE WAX AND OIL ' Eddie M. Dons and Oswald G. Mauro, Tulsa, Okla, ass'ignors to Mid-Continent Petroleum Corporation, Tulsa, Okla, a corporation of Delaware? Application March 2, 1942 Serial Nansen 2 Claims. (o1, 196-18) This invention relates to apparatus for using normally gaseous solvents to separate wax'and oil. The invention may be employed in separating wax and oil found in various kinds of mate rials including mineral oils, petrol-atum and slack wax. It can be conveniently usedin dewaxing petroleum lubricating oils to produce low pour point lubricants. I

The main object of the invention is to produce a relatively simple and inexpensiveapparatus for using normally gaseous dewaxing solvents lacking several serious objections found in prior disclosures. The commercial development of dewaxing systems has passed through a series of stages, which eventually led to the modern dewaxing systems wherein extremely large filters are employed to separate Wax from diluted oil.

Nevertheless, thehighly developed conventional filtering plants now in general use are,

complex systems, involving considerable trouble and expense, andlacking the desired efficiency in the separation of wax from oil. In commercial practice, clusters of wax crystals are deposited on the filters withportions-of the oil solution trapped'or occluded in the wax clusters. The filtration does not remove this occluded oil solution from the wax clusters, and additional portions of the solution are trapped between the clusters on the filter. I

A primary object of the invention is to advance this art by producing a very simple and inexpensive commercial system, lacking inherent defects, or objections, found in the dewaxing systemswhch have been generally adopted forcommercial use in this industry. v

A specific object of the present invention is to produce an entirely feasible dewaxing system wherein normally gaseous dewaxing solvents'are deliberately employed. to forcibly disintegrate the wax. We realize that experts in this art have regarded even .a' slight or incidental disintegration of the wax as a nuisance or'objectionable conditionto be carefully avoided in the separae tion of wax and oil. However, a study of the plan herein set forth will show that we have established novel conditions wherein this radical. departure from the usual practice is employed to obtain substantial advantages Instead of exercising precautions to avoid a possibility of slight disintegration, we have created cooperative conditions wherein rather severe disintegration of the wax is an outstanding factor tending to promote separation of the wax and oil. g

For example, propane .is a .:very.: popular ;nor' mally gaseous solvent havin'g 'special advantages for. dewaxing,1. including :the .intense-o -chihling which occurs; when ipropane is evaporated inlthe oil solution. :I-Iowever,*--in commercial practice special precautions areexercised tojavoidta sudden expansion; which would rupture-the i pre'cip itated wax clusters, or otherwise IeSll1t in':disin==l tegration, of the wax: This usual commercial I practice hasresulted in so. called critical rates of chilling, requiring ,gradual evapoiationx of propane, intended-{to avoid shock chilling whichwould runtur'ethe :wax clusters, or otherwiseinterfere with the usual methods of-separating' the; wax from :the propane: solution; In this popular commercial procedure, the free oil' solution. is transmitted through a :fiiteni while substantial portions of the solution are' trapped,.=or occluded, in the wax cake deposited on .the'nfilter;

To overcome these problems, weuwill sl'i'ow how the waxfican' bev deliberately subjected' to-a forcible disintegrating operation, which liberates practically all of: the oil :solution from' thew'ax. This may be regarded as a' de'sirablepreliminary step in the new sequence of conditionswherein the departure from'conventional theories is em: ploy-ed to improve the art of using. normally gaseousdewaxingsolvents. A i-" f 3 v A special advantage is gained by' suddenly evaporating portionsof" thenormally gaseous materialin the precipitated wax, as this will result in a sudden-explosive force-which forcibly disintegratesthe wax, thereby positively releasing oil-solution which is usually trappedin the .wax. The liberated oil solution'will' then be free to separate from the wax in' 'our' dewa'xing or deoiling operation. This is a substantial a'd vantage over the usual commercial practice,

wherein trapped or;occluded oil is inevitably re tainedwithin and betweenwax clusters deposited Y A 'separateand distinct object ofthe present invention is to obttain advantages'of using a normally gaseous:- solvent, including the advan= tage of evaporating portions of the solvent to produce the desired degree ofdchillirigarrd at the same time avoid the usual troubie expense and ineflicienc'y involvedin the ordinary-filtering plants. This phase"of the invention may -be advantageously employed in a sequence of operations which include forcible disintegration'o'f the wax, but it has-special advantages which' may be gained without subjecting the wax tosaid forcible.dis-integration. .r i Briefly stated, the liquefied normally gaseous and oil solution, this mixture is preferably transmitted into a settling chamber. A rising stream of dewaxed solution may be discharged from an upper portion of the settling chamber, thereby dewaxing a major portion of the oil solution. A descending stream of wax with portions of the oil solution is preferably-discharged from a lower portion of the settling chamber to a counterfiow deoiling system, where the wax is subjected to a deoiling operation and then discharged from the system. The deoiling operation may be performed by transmitting a rising stream of liquefied normally gaseous solvent through a descending stream of wax, so as to dissolv'e'oil solution carried by the wax, and we will hereafter show how a stream of the used deoiling solvent, with the oil solution dissolved therein, may be transmitted to the wax-containing charging stock, so as to recycle the dissolved 'oil from the deoiling system. and at the same time utilize the 'deoiling solvent'in forming the dewaxing solution. I

With the foregoing'and other objects in view, the invention comprises a novel combination and arrangement of devices hereinafter more specif ically described and shown in the accompanying drawing to illustrate one form of the invention.

Howeveryit is to be understood that the invention comprehen'ds changes, variations and modiflcations within thescope of the "claims hereunto appended.

The accompanying drawing is a diagrammatical view of an apparatus which'may be employed'to carry out one form of the invention.

A continuousregulated stream'of the waxbearing charging stock; for example, alubricating oil stock, enters the system through a pipe I which may be provided with a pump 2 and a regulating value 3. A'continuous stream'o'f liquefled normally gaseous dewaxing solvent; from sources to be hereafter described, is conducted through a pipe 4 to the oil supply pipe I. The continuous-streams of oila'nd dewaxing solvent are united in the pipe land transmittedthrough a mixing'nozzle 5 where-the oil and solvent'are mixed at a temperature high enough to form the desired solution.

The continuous stream of solution from the mixer 5 asses through a heat exchanger 6 to a pipe 'l'leadingto an insulated chamber 8, said pipe 1 being equippedwith a pressure-reducing valve 9 to provide-for a reduction in the pressure of the stream entering the chamber 8. The valve 9 is adjusted" to provide for evaporation of portions of the normally gaseous solvent, thereby chilling the remaining oil solution to precipitate wax therein.

- Any suitable normally gaseous dewaxing solvents may be employed in this system. Examples appear in propane, methane, ethane, and mixtures including theserelatively light hydrocarbons. However, for convenience in describing the invention, we will refer to propane as a suitable normally gaseous solvent, without limiting the-invention to this specific solvent.

To provide the desired ratio of solvent in oil to be dewaxed, a regulated stream of cold liquid propane may be transmitted through a pipe I 0 to the pipe I, said pipe I 0 being equipped with a pump II and regulating valve I2. An advantage can be gained by introducing the propane from pipe ID in a very cold condition, for example, at a temperature lower than about 40 F., so as to suddenly chill the relatively warm solution to a temperature of about 10 F. More specifically stated, the incoming solution may pass from the 'tively large to provide the desired capacity, and

a series of such chambers may be employed, instead of using a single chamber 8.

'Instea of adhering to the generally accepted critical rate of very gradual chilling, we preferably regulate the valve 9 to very suddenly reduce the pressure'in a, disintegrating zone formed by the chamber 8. An instantaneous reduction of this pressure will result in sudden evaporation of portions of the solvent, so as to suddenly chill and precipitate wax fractions in a liquid solution of the oil and solvent. Furthermore, this violent flash chilling will suddenly expand the evaporating portions of the solvent to produce an explosive effect, thereby forcibly disintegrating the wax. The oil solution is thus liberated from the wax, and there is no opportunity for the usual formation of wax clusters which occlude or trap portions of the oil solution in the wax.

Of course, this violent disintegration may not produce readily filterable wax. However, one of the objects of the invention is to dewax the oil without resorting to trouble and expense of employing the conventional filter plants, and as a preliminary step, we preferably disintegrate the wax to liberate all of the oil solution for the dewaxing operation.

The distintegrating chamber 8 is provided with a gas outlet pipe l3 at the top, and a valve M in said pipe may be regulated to control the discharge of gas. Any suitable recovery system may be employed to liquefy this gas for reuse in the system.

We will now refer to a settling chamber, or dewaxing chamber, l5 surrounded by the upper portion of an insulated column I 6. An annular space may be formed around said settling chamber I5 to provide an outer settling chamber I! to be hereinafter described. The chamber [5 may be open at the bottom to form a wax outlet l9, and the top of said chamber l 5 may be provided with a pipe 20 having a valve 2| to regulate the discharge of dewaxed solution.

A continuous stream of disintegrated wax and oil solution is discharged from the bottom of the chamber 8, through a pipe 22 leading into the dewaxing chamber l5 as shown in the drawing This pipe 22 is equipped with a pump 23 and valve 24 to regulate the flow of wax and oil solution to the dewaxing chamber I5. The incoming stream of cooled solution and wax may be delivered to this chamber at approximately the temperature selected for precipitation of, wax in the disintegrating chamber 8. For example, in using propane to dewax lubricating oils, this temperature may be about -40 F., although higher and lower temperatures may be employed inseparating various kinds of waxy materials.

We are now assuming that a. relatively light solvent has been selected. for the de'waxing oper-' ation'in the chamber I5, and that the viscosity and: interfacial tension are low enough to allow. the wax particles to descend in the relatit ly;

light. solution. In this event, the major port of the light solution will rise to the top: of e dewaxing chamber l5, where it is discharged in the form of a continuousstream through the pipe 20. wThis outgoing'solution is free of wax, and'it may be distilled in any suitable manner to removethesdlvent fromv the dewaxed' oil.

Attention is now directed to the separating zone, or dewaxing zone, established near thepoint where the incoming mixture of cooled solution and wax begins to separate in the chamber l5.

The disintegrated wax particles move downward 1y" and carry with them portions of the oil solution, including oily films and relatively free portions of the solution between the descending cover oil-solution carried by the wax.

For example, the wax Toilllustrate a suitable condition of this kind,

we. have shown a counterflow deoiling system in-' eluding theinsulated column l6 associated with the dewaxing. chamber l5. Thev mass of wax descending from the cham-" ber passes through a relatively light rising stream which may be produced by continuously introducing a stream of deoiling solvent througha pipe leading into th lower portion ofpthecolumn [6. The pipe 25 is equipped with a pump 25 and a regulating valve 21 adjusted to regulate the flow of" the incoming deoiling solvent. The stream of deoiling solvent from the pipe 25 will rise in direct contact with the descending stream of wax particles, so as to selectively-dissolve the free portions of oil solution carried-by the wax, and also forcibly scrub oily films from the descending wax particles. This action rn'ay be aidedby any suitable mechanical appliances. For example, the column I 5 maybe provided with alternatingbaflles including a series of rings 28 extending-inwardly from theinnerface of the column l6 and a series of central baille' mem bers 29 arranged as shown in the drawing to produce an elongated tortuous passageway where in the descending wax particles move backand forth in 'a' zigzag course. The stream of selective deoiling solvent rises through the descending stream of wax particles, and the counterflowing streams are divided into numerous layers of different specific gravities contacting with each other and advancing in intersecting paths as they flow from one bafile to another. These baffies are preferably provided with downwardly in-' clined top and bottom faces to permit free movement of the descending wax particles... It will be observed that the descending layers-of wax particles move downwardly while in contact with the downwardly inclined top faces of the baflles, and that said wax particles repeatedly intersect the rising solvent while descending from one inclined plane to another. A continuous stream vent may be 'discha'rged'through apipe 30 below theinlet for the deoiling solvent.

1 The: inclined faces of the names tend to prevent? the wax: particlesfrom clinjgg g to said baflles; However; any suitable mechan a1 means may be employed to prevent or limitthe growing of waxcrystals :whichmight otherwise; extend from the top faces of the baffles; For example, the central bafiies 29 may be fixedto a slowly rotating shaft 3|. "so as to rot'ate "with the shaftfand scrapers 32"may extend fr bottom faces of these rotary-baffles to remove, waxy material from the tops of the stationary bafilef' rings 28;. wThese stationary baffles may be likewise provided with scrapers 33 extending from their bottom: faces to remove waxy'material from the topiaces-of the rotating'baflles'. v

interesting condition-appears "in the effective cleansingof the des ding wax particles due-to the forcible scrubbing and dissolving actionof "the selectivedeoilirig solvent which"repeate'dly crosses the path of thewax in the de'-' oilingzonefi Attention is also directed to the condition at the" up'perportionbf this deoiling.

zonewhere the rising solvent stream is'diverted" from'rthe interior" of the deyvaxing chamber l5.

This deflection of the rising jsolvent is due partly to theydownwardforce of the descen'dingstream of wax particles issuing from the "bottom of said chamber"l5,"and partly to afrising current in the surrounding'ch'amber or passageway 11. highestce'ntral baffle 29 alsofte nds to deflect the rising'solvent toward the chamber l1;

tling chamber "I 1', but these wax particles are relatively heavy, so they will eventually fallin the lighter solvent and return to the mass of wax, instead of'pa-ssing tothe top? of said settling chamber' l1.

The selectivedeoiling solvent'performs a very important function in selectively removing oil carried by the waxp'articl'es'. However, most of valve 36'ins'aid pipe which leads to the heat exchanger 6; and thence through pipe 4 to the continuous incoming stream of wax-bearing oil' in the pipe I.

The velocity and time or the deoiling action may be regulated to dissolvegpractically all ofthe oil carriedby the wax, 'or anyde'sired percentage of "oil may be discharged with the" wax, dependina upon the commercial requirements.

It is to be understood that the invention is not limited to the specific arrangements of chambers and zones herein disclosed to illustrate one form of the invention, and that any suitable solvents may be employed to producethe counterflow of wax and solvent in the deoiling system. However, when the deoilin solvent admitted through the pipe 25 is eventually transmitted to the incoming charge in the pipe I, so as to serve as a dewaxing solvent, an advantage may be gained by selecting a solvent suitable for both operations. For example, if the primary dewaxing solvein; is propane, a stream of "fresh cold propane of deoiled w'ax with a minor 'portion or: the sol--' The Some ofthewax particles may be; swept into the set in a liquid state may be admitted through the pipe 25, andafter performing itsdeoiling function in the counterflow system, this liquid propane and the oil dissolved therein, may be transmitted through the pipes 34 and 4 to the incoming streamof charging stock in the pipe I. The oil recovered-in the deoiling operation is thus very economically recycled to the charging stock; while the used deoiling solvent is employed as a solvent for the dewaxing operation. s.

' This recycling .device enables aisingle solventto very effectively perform two successive functions, whilerecycling recovered-oil to the incom ing charge. It also eliminates a distilling operation which would otherwise be required to sep-' arate the deoiling solvent from its-recovered oil;- and if any of the valuable wax should be inciden tally dissolved in the deoiling solvent, such wax willbe recycled to the incomingcharging stock,

The term disintegrating as used in the claims refers to the effect of sudden expansion which forcibly separates a crowdedmass of wax particles. In some cases, portions of the solvent may be securely trapped, or occluded, in relatively large clusters of the wax particles, so as to provide an internal bursting force when the pressure is suddenly reduced. In other cases, the disintegrating efi'ect occurs in a crowded mass of individual wax crystals before they have an opportunity to unite in the form of relatively large wax clusters. For example, an intense flash chilling'at the chamber 8 will produce a crowded mass of elementary wax crystals,-but the disintegrating effect of the sudden expansion will forcibly disintegrate or scatter this crowded mass; so; as to avoid the usual trapping of oil-solution in the precipitated wax.

sWe claim: 1. In an apparatus for using normally gaseous solvents to separate oil and wax, a wax-di'sin-te grating device wherein wax is precipitated and disintegrated, said wax-disintegrating:-device comprising a disintegrating chamber having an inlet conductor communicating with sources-of wax-containing oil and normally gaseous-solvent;

pumps-to transmit the oil and liquefied normally gaseous solvent to said inlet conductor under pressure, a pressure-reducing valve insaid-inlet conductor. set to suddenly; reduce the .pressure,

thereby suddenly expanding portions of said 501-,

vent to forcibly disintegrate the precipitated wax 'insaid disintegrating chamber, dewaxing means including a Settling chamber having an inlet communicating with said disintegrating chamberto receive a mixture of liquid oil solution and disintegratedwax, said settling chamber having a wax outlet lower than its inlet to provide for the, discharge of a wax stream, and a solution outlet higher than its inlet. to provide for discharge of, dewaxed, oil. solution, andlfdeoiling means comprising a countercurrent deoiling system located below and communicating with the wax outlet of said settling chamber to receive a descending stream of wax and oil solution, the lower portion of said countercurrent deoiling system having an outlet for the wax, means for transmitting a rising stream of relatively light deoiling solvent through a descending stream of wax in said countercurrent deoiling system, and alternating bafiies located in said deoiling system to deflect the wax and solvent into'intersecting paths, the upper portion of said deoiling system being provided with an outlet for the used deoiling solvent, and the last mentioned outlet being higher than the wax outletof said settling chamber, 1 a

2. In an apparatus for using normally gaseous solvents to separate oil andwax, a wax-disinte grating device wherein wax is precipitated and disintegrated, said wax-disintegrating device comprising a. disintegrating chamber having an inlet conductor communicating with sources of wax-containing oil and'normally gaseous solvent, and pumps to transmit the oil and liquefied normally gaseous solvent to said inlet conductor under pressure, said disintegrating device also including a pressure-reducing valve in said inlet conductor set to suddenly reduce the pressure, thereby suddenly expanding portions of said solvent to forcibly disintegrate the precipitated wax in said disintegrating chamber, dewaxing means including a settling chamber having an inlet communicating with said disintegrating chamber to receive a mixture of liquid oil solution and disintegrated wax, said settling chamber having a wax outlet lower than its inlet to provide for the discharge of a wax stream, and a solution outlet higher than itsinlet to provide for discharge of dewaxed oil solution, deoiling means comprising a countercurrent deoiling system located below and communicating with the wax outlet of said settling chamber to receive a descending stream of wax and oil solution, the lower portion of said countercurrent I deoiling system having an outlet for the wax, means for transmitting a rising stream of relatively light deoiling solvent through a descending stream of wax in said countercurrent deoiling system, the upper portion of said deoiling system being provided with an outlet for the used deoiling solvent higher than the wax outlet of said settling chamber, and means for transmitting the used deoilingsolvent from the last mentioned outlet to the inlet conductor of said disintegrating chamber, so as to recycle the oil recovered in said deoiling system, the last mentioned means including a return conductor provided with a pump to force .theused deoiling solvent into the wax-containing oil. v

- EDDIE M. DONS.

OSWALD G. MAURO.

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