US2038624A - Separation of wax from oils - Google Patents

Description

April 28, 1936. c, ADAMS E AL 2,038,624

' SEPARATION OF WAX FROM OILS Filed March 18, 1932 3 Sheets-Sheet l April 28, 1936. E, ADAMS AL 2,038,624

SEPARATION OF WAX FROM OILS Filed March 18, 1952 SSheets-Sheet 2 Jrzverztow GfiwtevEfldama Jzeci (0. jakerze mm c. E. ADAMS ET AL SEPARATION OF WAX FROM OILS I Filed March 18, 1932 3 SheetsSheet 3 Jrzuerztow 61m: $1905. Ada/m5 5% (dJc/Zememrz/ Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE 2,038,624 SEPARATION OF WAX FROM OILS Chester E. Adams, Hammond, Ind., and Fred W. Scheineman, Chicago, Ill., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application March 18, 1932, Serial No. 599,730 19 Claims. (Cl. 196-19) This invention relates to the separation of wax by a gas line, all parts of said system being opfr m i s an t p a ns more particularly o an eratively connected with said line. Vaporized mpr v System for the use f normally gaseous propane from all parts of the system are sucked d u nt fri ants. such as liquid propane. from this line by suitable pumps, compressed, The object of our invention is to provide a condensed and returned to storage for re-use. commercial a ge-scale dewaxing pl t fo D This tying together of the whole system by suctroleum refineries in which inflammable volatile tion gas lines insures safety, and at the same time diluents or refrigerants may be used with safetyit enables the temperature of each respective In other words, our object is to provide a closed element of the combination to be separately consystem and means for regulating the pr ssure in trolled in a very simple and expeditious manner. all Parts Of the y t m 80 t l a age of propane In other words, the tying together of the whole w be p v d. W wa t to av d the n sdewaxing system with a suction gas line makes it y Opening t s a d th s, in turn, possible to employ volatile and expensive refrigthat We must Provide a System whereby the filter erants and diluents which were heretofore too leaves will not become clogged with amorphous dangerous for commercial use and makes it posflnely divided wax. Our Object i to P i sible to improve the operation of filters, chillers, p l de i n for fi r that w fit into P etc. so that the operation is uninterrupted over cially designed filter system to accomplish the a long period of time. continuous dewaxing Of Oil in a 010566. system Another feature of our invention is the com. wh c will not have to be frequently interrupted bination with our suction gas line of an improved, 20 for repair or cleaning. t closed vertical filter in which reverse flow and A further ob ect of our invention it to provide pressure regulation cmact to remove the filt r an improved System and method of chfllmg cake and clean the filter cloth. Another feature luted oil-wax mixtures so that the optimum wax of our invention is the combination of wash crystal formation may be obtained. In other propane and used wash propane tanks with e words we s to determine sequePce of chillers and filters so that practically all of the steps, the relative volumes of diluent refrigerant on can be removed from the wax without the 333 221 3;? at :ggtf; sgfi fig z gfifi g melting or redissolving the same in oil or diluent. handling the crystals which will prevent them gggg x ggzrg 2 gfi g ifigg gfig fizg gig 38: g fi gig gs g fgz giggg zg ggfizg figg used to cool the waxy oil without the formation and the method of handling these. crystals is of g; wax cryfstals on sides g g so v e use 0 scrapers s avo e e nven on $53? Importance commercml dewa'xmg sys will be more clearly understood from the following 35 A further object of our invention provide a description taken in connection with the accomsystem for obtaining mafimuni mechanical, therpanying drawings which form part of the mal, and operating emciency we want to specification and in which similar parts are desigmnge heat exchangers and chillers so that it nated bylike reference characters throughout the will be possible to abstract all of the heat from several vlewsthese drawings:

wax-bearing oil without the use of the conven- Figure 1 is a diagrammatic Plan of our entire tional wax chillers wherein scrapers are necessystemsary for removing wax from cold walls. We also Figure 15 an elevation our improved Vern" want to obtain the maximum benefit from the cal filter, parts thereof being shown in section. 3 is a horizontal section of said filter 45 low temperatures of dewaxed oil and diluent so Figure that the expense of refrigeration may be reduced taken along the l e of g e Figure 4 is a vertical section at a filter leaf outto a minimum. A further object ing oils having high flash points and low pour points, and to obtain wax which is substantially oil free. Other objects will be apparent as the Figure 5 is an elevational plan of our improved detailed description of our inventionproceeds. filter element, parts of the same being broken Certain features of our invention may be briefly away to illustrate the construction.

Figure 6 is a horizontal section taken along the is to obtain improved lubricatlet showing the detail construction of the flexible coupling and showing the insulation at the top 50 joint of the filter.

characterized as follows: In the first place, we employ a dewaxing system which is tied together lines 6-6 of Figure 5.

Figure 7 is a detail section showing the means for holding the filter cloth on the leaf.

Our invention will be described as used for the separation of wax from a treated distillate lubricating oil from Mid-Continent crude petroleum, the particular distillate having a viscosity of about 100 seconds Saybolt at 210 F. and an A. P. I.

gravity of 21.3. It should be understood. however, that the invention is equally applicable to any wax-bearing oils.

In the description of our preferred embodiment we will disclose the use of commercial propane as a combined diluent and refrigerant. It should be understood that other normally gaseous hydrocarbons, such as butane, iso-butane, butylene, ethane, ethylene, propane, propylene, etc. may be used either separately or in admixture with each other. By suitably reducing the pressures we may use hydrocarbons in the boiling range of pentane or even hexane. The waxy oil may be diluted all through the system with a small amount of filter naphtha or other light oil which may be useful as a viscosity breaker. Instead of using normally gaseous hydrocarbons we may use normally gaseous ethers such as methylether or we may use chlorinated or fluorinated hydrocarbons such as methyl chloride or dichlordifiuor-methane or oxygenated compounds such as ethylene oxide; the last named substances are useful in the dewaxing process because they have a tendency to throw wax out of solution. We may use normally liquid antisolvents for wax, such as acetone, acid esters, etc. or mixtures of liquid antisolvents with miscibility agents such as benzene or mixtures of benzene with naphtha. If liquids of this type are mixed with the oil they may be considered in the following description as a part of the oil. In our preferred embodiment we efiect practically complete dewaxing of the oil by the use of commercial propane.

The propane enters the system through line I0 and is introduced by pipes II into storage tanks I2 which are designed to hold the propane at temperatures as high as F. at which temperature the propane may exert a pressure of 165 pounds gauge (above atmospheric). The liquid propane may be selectively removed from one of these storage chambers through line I4, passed through heat exchanger I 5, and thence into wash tank I6. The propane is usualy at a temperature of- 95 F. in line I4 and it is cooled in exchanger I 5 to a temperature of about -20 F. The propane in wash tank I6 is cooled to a temperature of -40 F. by the evaporation of a part of the propane, vapors being removed from the tank through conduit I! and line I8 to compressor I9 which is designed to maintain atmospheric pressure in line I8. The gases may then be passed through pipe 20 to compressor 2I which boosts them to a pressure of about 200 pounds, or compressor I9 may be designed to boost them to this pressure, in which case compressor 2| is cut out by pipe 22. either case, the highly compressed vaporsare passed through line 23 and condensers 24 back to storage tanks I2. The cold propane from wash tank I6 is pumped through pipe 25 by pump 26 to the filter system.

The wax-bearing oil is pumped from storage tank 21 by pump' 28 through one branch of pipe v 29 into one of the gauging tanks 30, one of these tanks being filled while the other is being emptied. v

The oil from the gauging tanks is transferred by pump 3I to mixer 32 where it is mixed with pro pane, forced by pump 33 through pipe 34, and the mixture of waxy oil and propane is cooled in exchanger 35 to a temperature of about 90 F. to F., this temperature being preferably selected so that the wax will be completely dissolved in the diluted oil. The mixture of wax and diluent is then selectively introduced through one of the pipes 36 into one of the chill chambers A. B, C, or D. When one of these chambers is about one-third full the flow thereto is cut off and the propane-oil mixture is introduced into the following chamber. While this mixture is being charged into the tank the vapor outlets 31 and 38 are preferably closed so that no appreciable cooling by evaporationof diluent takes place.

The cooling of the oil to eflect complete precipitation of wax is preferably effected by the introduction of liquefied propane at 40 F. at a rate suflicient to lower the temperature of the oil about 1 per minute. This is accomplished by withdrawing the cooled wash propane from the filter system (which will be hereinafter described) at a temperature of about -40 F. through one of the pipes 39. The physical structure of the wax slurry.

After a particular chill chamber has-been filled system, and which is evacuated by compressor I9 Thus at about -20 F. to 40 F. the wax slurr is withdrawn through one of the pipes 4I, pum 42, line 43, and one of the feed pipes 44 to a vertical filter L, M or N. Pump 42 should be of th rotary, or sliding vane type; if a pulsating pum isused a suitable gas cushioned surge chambe should follow it to obtain uniform, non-pulsatin propane the so-called wash propane" filtrate passes by gravity through pipes 50 to used wash tank from which it is transferred by pump 52 into pipes 39. The propane in the used wash tank 5| is maintained at40 F. by the vaporization of a part thereof, the vapors-being removed through pipe 53 to line l8.

We connect the filtersto line l8 by valved pipes 54. These valves are closed during actual filter operation, but for purposes of cooling the filter or removing the filter cake, the valves may be opened.

Wax is removed from the base of the filter in the manner hereinafter described through one of pipes 55, thence through pipe 56 to wax pumping drum 51. The wax lines are preferably large conduits provided with screw conveyors although in some instances the wax slurry may be pumped by ordinary methods. Wax from drum 5! is forced by pump 58 into high pressure heater 59 which is maintained under a pressure of about 200 pounds gauge. Steam coil 60 maintains a temperature in the heater of about 235 F. Liquid wax, together with some propane, is withdrawn from the base of the heater through pipe 6| and passes through regulating valve 62 into atmospheric flash drum 63. Valve 62 is automatically controlled to maintain a constant liquid level in heater 59. The propane vaporized in wax heater 59 is withdrawn through pipe 23 which leads directly to condensers 24. Propane from atmospheric flash drum 63 is withdrawn to line l8.

The wax from the base of the flash chamber is withdrawn in amounts controlled by liquid level operated valve 64 and introduced into wax stripper 65 in which steam or other suitable stripping gas may be injected. The steam from the top of the stripper is condensed by the water in jet condenser 66, the liberated propane being vented to propane line l8. Finally the wax which has been freed from oil and propane is forced by pump 61 through cooler 68 into storage tank 69.

Returning to the filtrate in tanks 48, this filtrate is withdrawn through one of pipes and pump 19a to heat exchanger l5 wherein it cools the incoming propane which is to be used in washing the filters. The filtrate then passes through heat exchanger H and heat exchanger 12 to the top plate of the oil heater 13. Heat may be supplied thereto by steam coil 14 so that a temperature of about 235 F. at a pressure of 200 pounds is maintained in the heater. Oil is withdrawn from'the base of the heater by pipe through a regulating valve 16 to low pressure flash drum ll. Regulating valvefilfi is automatically controlled to maintain a constant liquid level in heater l3. Propane vapors are removed from the fiash drum to line IS. The oil from the base of the fiash drum is passed in amounts regulated by liquid level control valve I8 into steam stripping chamber 19'where it is stripped with steam or other suitable gas. The steam is withdrawn through exchanger H and thence to jet condenser BEL-the liberated propane being returned to line l8.

The oil from the base of the stripper 79 is withdrawn through heat exchanger 12 and to oil storage tank 8i.

It will be observed from the above description that the chill chambers, unused wash propane,

.used wash propane, filtrate receivers and wax pumping drum are all maintained at temperatures slightly below dewaxing temperatures by A the direct vaporization of. propane, these vapors being withdrawn by propane line l8 and compressed in compressor l9 to about 200 pounds.

tures may be controlled, however, by regulating the valves leading to line' Hi.

If the pressure in the system exceeds ab ut 200 pounds it will be released through vent 82 by the opening of release valve 83. Pressure in the storage tanks I2 is usually about 150 pounds to 165 pounds gauge and use may be made of this pressure to blow the filter cake from the filter leaves (as will be hereinafter described), the propane gas being conducted through line 84 to the respective filtrate discharge pipes 45, suitable by-passes and valves being provided so that propane can be used to discharge the filter cake without interfering with the normal filtrate discharge.

If desired, propane from line 23 may be bypassed into line 84 by line 95. When gas is used to blow back the filter cake there will be'a condensation of propane in the filter cloth due to its cold temperature, and there will be an almost instantaneous boiling or revaporization of this propane due to the low pressure on the other side of the filter cake and,as a result, the filter cake is quickly and thoroughly removed from the filter cloth and the cloth is washed by the reversed fiow of propane. The same end may be accomplished by the reverse fiow of a slight amount of used wash propane liquid.

Before going into detail about filter cake removal we should get a more accurate idea of the structure of this filter by referring to Figures 2 to 7. Each filter is mounted on suitable supports 86 and it consists generally of a vertical, cylindrical wall 81, tapered hopper bottom 88, and concave, tightly fitting removable cover 33. Suspended in the body of the filter or in the cylindrical casing are a plurality of filter leaves 90. Each leaf consists of a reinforcing frame 9|, the sides of which are extended and provided with apertured lugs or hooks 92 by means of which the plates may be suspended. The plates or leaves 90 may be spaced by suitable brackets 93, their outer surfaces being about 1 5" to 2" apart. At the bottom of the leaf there is a channel 94 to collect filtrate, and this filtrate is removed up through the center of the leaf through flattened conduit 95, fiexible conduit 96 and valved outlet 91 to filtrate discharge pipe 45.

Each leaf may consist of a coarse screen or perforated plate 98, covered by a finer supporting screen 99 which supports the canvas filter element I00, said element being held in place by suitable buttons Illl. These buttons may consist of short bolts I02 extending through the leaf, holding the filter element between washers I93 and I04 (see Figure '7). The filter element is preferably a bag adapted to slide over the frame.

The operation of our improved filter is as follows: Propane from tank 5| or tank I6 is first introduced into the filter and evaporated by the bestos or other suitable material I05. When the filter is cooled, the chilled mixture of wax crystals and diluted oil from chillers A, B, etc. is forced by rotary pump 42 into the base of the filter through pipe 44 The rotary pump is designed to move relatively slowly and, in effect, to push the slurry along the pipe without violent agitation and without destroying the structure of the wax crystals. We prefer to maintain a substantially con-. stant flow of filtrate from pipes 45 and we regulate pump 42 accordingly; the pressure on the filter leaves is preferably held below 50 pounds per square inch. Filtrate is forced through the filter medium IOU, it collects in channel 94 and is forced up through flattened pipe 95, flexible conduit 96 and outlet pipes 91 to filtrate discharge pipe 45. During the filtering operation it is, of course, necessary to close vapor outlets 54. I

Filtration is continued until a cake about to l" is built up on the leaf, at which time the fiow of the wax slurry is stopped by closing outlet valves in line 45, and the wash propane from tank I5 is introduced at the top of the filter through line 49a. The flow of this liquid propane is continued until all of the unfiltered oil in the filter is forced back (through bypass 42a.) to the chillers by displacement. The flow of the wash propane is then changed so as to enter the filter at the bottom and to pass through the wax cake and the filter leaves and out through line'45. The flow of this propane is continued until practically all of the oil is washed out of the wax cake. The first Wash propane may contain large amounts of oil and it may therefore be discharged with the filtrate into filtrate receivers 48 through pipes 41. Later amounts of washpropane are removed from thefilter leaves through pipe 50 to used wash pro-- pane tank 5 I.. Propane from the latter tank, as stated above, is used for diluting incoming waxy oil in chillers A, B, C, etc.

Finally the flow of Wash propane from tank [6 is stopped and the remaining propane liquid is pumped from the bottom of the filter back to wash tank l6. During this operation a small pressure is maintained inside the filter (outside of the leaves) by means of vapors admitted through lines 84 and 54. To remove the filter cake we may employ a reverse flow of wash propane or we may employ gas from line 84. In either case, liquid propane will be formed in the filter medium and it will be violently expanded by opening the valve in pipe 54, this expansion causing the immediate and thorough removal of the cake from the leaf. The filter cake is directed by the hopper bottom ,88 into an enlarged conduit 56 wherein a screw conveys it to wax sump 51. If desired, a spray of liquid propane may be used to assist in washing the outside of the leaves.

Precoats or filter aids may be employed to increase filter rates and prevent clogging. Some oils are readily dewaxed with the ordinary filter elements, but other oils show a cloud at low temperatures after dewaxing. It is highly desirable that lubricating oil should be zero-bright.

may be used, either as a precoat or admixed with the wax slurry.

While we prefer to cool the diluted wax-oil mixture as hereinabove described, it shoul be understood that we may simultaneously move propane vapors and add propane liquid to the chillers, we may cool by evaporating propane and subsequently adding more cold propane, or we may add all of the propane before we start to chill by evaporation.

While we have described a preferred embodi ment of our invention it is to be understood that we do not limit ourselves to any of the details hereinabove set forth except as defined by. the following claims, which should be constructed as broadly as the prior art will permit.

. We claim:

1. In apparatus of the class described, a closed system comprising a propane storage tank, a suction gas line, a compressor and condenser between said gas line and said storage tank, a plurality of chillers, a plurality of filters, a filtrate receiver, a

wash propane tank, a used wash propane tank, means for connecting all of said elements to said suction gas line whereby the escape of propane is prevented and whereby the temperature of said elements may be easily controlled by the vaporization of propane.

2. In apparatus of the class described, a closed chill chamber, a closed filter, and a closed filtrate receiver, connections whereby a liquid comprising a liquefied refrigerant may be passed into said chill chamber, thence to said filter, and thence to said filtrate receiver, means for compressing and condensing refrigerant vapors, and a refrigerant vapor line for collecting vapors from said chill chamber, filter and filtrate receiver to said compressing and condensing means whereby the low temperature in various parts of the system may be maintained by vaporization of refrigerant therein.

3. In a dewaxing system for employing a normally gaseous diluent, means for mixing a waxy oil with said diluent, a chill chamber, means for introducing said mixture into the chill chamber, means for withdrawing vapors from said chill chamber whereby the temperature of the oilwax' mixture is reduced at the rate of about 1 to 3 per minute, means for condensing said vapors and returning them for reuse, means including a closed filter for mechanically separating solidified wax from diluted oil, a filtrate receiver, means for removing diluent, from said wax and said filtrate, a low'pressure gas line, connections from said low pressure gas line to said chill chamber, said filtrate receiver and said diluent removal means, a compressor with its intake side connected to said low pressure .gas line, a condenser connected to the discharge side of said compressor, a liquefied diluent storage tank, and means for conducting a condensed diluent from said condenser to said storage tank.

i. In a dewaxing system of the class described wherein a high boiling hydrocarbon is diluted with a diluent having a vapor pressure of about 100 to 200 pounds per square inch at 95 F., the method of separating the diluent from the high boiling hydrocarbon which comprises heating the mixture to a' temperature at which the partial pressure of the diluent exceeds its vapor pressure final diluent vapors with thevapors removed from the flash step.

5. In a dewaxing system of the type described, means for storing a normally gaseous diluent in a liquid state, means for mixing said diluent with wax-bearing oil, means for refrigerating said mixture to dewaxing temperature, a closed pressure filter for separating the wax from the oil-diluent mixture, means for introducing fresh diluent to wash the separated wax in filter, and means for applying said diluent gas from said storage system to remove said separated wax from said filter.

6. In apparatus of the class described, a warm propane storage tank, a cold propane storage tank serving as a reservoir for liquid propane at substantially dewaxing temperature, means for transferring propane from said warm storage tank to said cold storage tank, means for cooling the propane which is so transferred, means for withdrawing propane from the warm storage tank, means for dissolving a waxy oil in said warm propane, means for chilling said solution to form a filterable wax slurry, a closed filter, means for introducing said slurry into said filter, means for introducing cold propane from said cold storage tank into said filter, means for separately removing and storing filter cake and filtrate from said filter, means for removing propane from said filtrate and said filter cake respectively, a low pressure propane gas line connected to said cold propane storage tank, to said cooling means and to said propane recovery means, a condenser connected to said warm propane storage tank, and a compressor with its intake side connected to said gas line and its discharge side connected to said condenser.

7. The apparatus of claim 6 which includes means for effecting heat exchange between said filtrate and the propane which is transferred from the warm storage to the cold storage tank.

8. In apparatus of the class described, a closed system comprising a liquefied propane storage tank, a propane gas line, a compressor and condenser connected between said gas line and saidfiltrate receiver and said propane gas line for removing propane from the filtrate, and means connected with said Wax receiver and said propane gas line for removing propane from wax.

9. The apparatus of claim 8 which includes asecond propane storage tank, means for introducing propane into said second tank from said first tank, and means for introducing vapors from said second tank into said gas line for cooling the propane in the second tank.

10. The apparatus defined by claim 8 which includes a second propane tank, means for introducing propane from the first storage tank to said second tank, means for transferring heat from said propane to the cold filtrate, and means for removing vapors from the top of said tank and introducing them into said propane gas line.

11. The apparatus of an additional propaii storage tank, cans for introducing propane'from said filter t said addiclaim ,8 which includes tional storage tank, means for introducing propane from said additional storage tank to said chillers, and means for connecting the top of said additional storage tank to said propane gas line.

12. The apparatus of claim 8 which includes means for blowing propane gas from the upper part of said storage tank tosaid filter.

13. The apparatus of claim 8 which includes a direct connection between said propane recovery means and said condenser whereby said propane is condensed without further compression.

14. In a dewaxing system of the class described wherein a high boiling hydrocarbon is diluted with a diluent having a vapor pressure of about 100 to 200 pounds per square inch at 95 F., the method of separating the diluent from the high boiling hydrocarbon which comprises heating the mixture to a temperature at which the partial pressure of-the diluent exceeds its vapor pressure at about 95 F. whereby diluent vapors are drawn from the mixture, cooling said vapors to temperatures of about 95 F. to condense said vapors, flashing the residual oil mixture at about atmospheric pressure to release further amounts of diluent vapors, compressing said released vapors to the pressure of said first named vapors, and stripping the flashed residue to remove the last traces of propane therefrom.

15. In a system for dewaxing a wax-bearing mineral oil by means of a liquefied normally gaseous hydrocarbon diluent such as propane, means for storing liquefied propane at substantially atmospheric temperatures and superatmospheric pressures, means for withdrawing liquefied propane from said storing means and for admixing the withdrawn propane with a wax-bearing oil, a chiller, means for transferring said propane and wax-bearing oil to said chiller, a filter having a wax outlet and a filtrate outlet, means for transferring slurry. from said chiller to said filter, a filtratestorage tank connected to said filtrate outlet, a wax storage tank connected to said wax outlet, a high pressure propane recovery still connected to said filtrate tank, a low pressure propane recovery still connected to said high pressure propane recovery still, a similar high pressure propane recovery still connected to said wax tank, a low pressure propane recovery still connected to said high pressure wax-propane still, a propane compressor, a propane condenser connected between the discharge of said compressor and the propane storing means, connections between said high pressure propane recovery stills and said condenser, a low pressure propane gas line, and connections between said low pressure gas line and said chiller, said low pressure filtrate-propane and wax-propane stills respectivey.

16. The apparatus of claim 15 which further includes an independent means for passing high pressure propane vapors from said chiller to said condenser.

17. A propane dewaxing system which comprises a tank. for storing liquefied propane at or nected to said filter, a propane recovery system connected to said filtrate storage tank, a separate propane recovery system connected to said wax storage tank, a low pressure propane gas line, a compressor with its suction side connected to said gas line, a condenser connected between said propane storage tank and the discharge side of said compressor, a connection from said 10w pressure gas line to said chilling means and to each of said propane recovery systems, and means for introducing propane gas into said filter through said filtrate discharge connection whereby wax cake may be dislodged from the filter element by blowing back with propane without the introduction of non-condensible gases into the system.

18. The system of claim 17 which includes a I connection from the upper part of said propane storage tank to said propane blow-back gas means.

19. The apparatus 01' claim l'l'which includes a connection between the propane recovery system and the condenser and a connection from the aforesaid connection to the propane blow-back 10 means for discharging filter cake.

CHESTER E. ADAMS. FRED W. SCHEIN'EMAN.

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