US2045425A - Wax sweating - Google Patents

Description

June 23, Y1936. v. vooRHEl-:s

WAX SWEAT ING Filed Jan. l5, 1934 2 Sheets-Sheerl l mwN( gah

INVENTOR VczfzdevcaerVoofzee ATTORNEY Lmh m um# June 23, 1936. v v. vooRHEl-:s 2,045,425

WAX SWEATING Filed Jan. 13, 1934 2 sheets-sheet 2' Lawaai-mg uid mvENToR Vanderoeer' Voorz eas ATTORNEY Patented June 23, 1936 PATENT ortiev 2,045,425 WAX sWEA'rINo Vanderveer Voorhees,

to Standard l` Company,

' poration of Indiana` Hammond, Ind.,A assignor Chicago, Ill., a cor- .Application January 13, 1934, Serial No. 706,514

s'ol'aims. A(o1. 19e- 20) p This invention relates to a process of separating oils from waxes and particularly for separating petroleum oils from parafn wax by an improved sweating process.

In the refining of parain wax, `it is common practice. to chill the lubricating oil distillate fractions and lilter the parafiin therefrom, thereby producing a wax cake'. This cake which may originally contain about 50% of Vvwax, is then melted and charged into a large tank known as a sweating oven where the temperature is lowered by means of water circulated through closed pipe coils in order to solidi-fy the wax. Warm water is then circulated through the coils and the temperature gradually raised until the wax begins to sweat, the sweat oil being drawn 01T, leaving the oil-free wax in the oven.` By the use of this process it has been dilicult' to make a sharp separation between the oil and the wax; there was either a loss of considerable wax` in the drips or a retention of considerable` oil in the wax` product. An object of the present invention is toobtain more temperature control in the sweating oven, both during the period of wax solidiiicationand during'the sweating operation'with the result that larger yields of drier wax are obtained than has been heretofore possi-ble.l Another'objectl of the invention is' to economize on the heat required A for carrying out the operation.

The invention may be readily understood by referring toV the accompanying drawings which form a part of this specification and wherein:

Figure 1 shows an elevational View partially in section of a simple form including only two sweating ovens. Y

Figure 2 shows a cross section of a sweating oven, and Figure 3-shows a layout for an inderlnte number of sweating ovens withfpipeconnec- Z tions. l

Y Referring to Figure 1, a sweating oven |10 consists of a vertical cylindrical tank containing trays Il with suitable outlets for the drips- I2' leading to manifold 'Cooling and heating of the Wax charge is effected by passing a low-boiling liquid or vapor throughv suitable pipes. I5 which are shown in cross section in FigureZ. These pipes pass vertically through the oven and are manifoldedl intotop gmanifold I6 and bottom manifold I'I. The construction lof-the otl er sweating OvenA I8 is substantially identical. A pump I9y is connected between the lower manifolds of the two ovensfand a compressorV 20 is connected between the upper 55,'manifolds of the two ovens.

accurate and uniform I3V and outlet valve I4.`

The operation of the process is substantiallyl j as follows: Melted wax, containing a considerable amount of oil, for charged into the oven I0 through the charging valve 2 Il.: When the oven has been fully charged a suitable low-boiling liquid is forced by pump .Y

I9 through valves 22 and 23 into the header Il and heat exchange tubes I5. VThe liquid vaporizes in these rtubes and the vapors are passed by headers I6 through valve 36 andfby-passline 3'I tothe inlet of compressor 20, thence through valve 25, line 29 and valve 23 to header Ilia, valves 24 and 21 being closed, in oven i8. Oven I8, being already charged'with solidiedwax, is

gradually heated by condensation or the'vapors v example, may be in the coils therein and the condensed vapors.

tinually increasing pressure differential between headers I.6 and |r by meansof compressor 2U. At the beginning of the operation, however, the pressure of the vapors in header greater than the pressure in header Ilia and at that stage it is-not necessary to operate -com. that condition prevails pressor- 20. Aslong as the compressor 20 is out out by closing valvesv 25 and 21 and regulating the rate of flow of they 28 in by-pass l-ine 29..

vapors by means of valve Similarly when vcompressor 2@ is operating it may be unnecessary to use pump I9 and valves 23 and 3Ir may be Opened or a storage tank or collector may be connected in the system at this point. i

When all the wax in oven I0 is solidified the direction of ow of theliquid is reversed by resetting the valves on the by-passes around ,pump I9. Valves 23 and and 3l are opened, permitting liquid to flow from header I1 through by-pass line 32 to the inlet of pump I3, then through valve 22 and by-pass line 33 to header I'Ia. the header I6 under suicient pressure to condense in the oven Il) and thereby cause the oil andV low melting Wax to liquefy and flow from the oven through the drip line I3 as previously described. After the sweating has proceeded to V a sufficient point substantially all the ,oil is removed from the wax, the valve in drip line I3 is closed and the remaining wax inthe sweater is allowed to melt, either by increasing thelpressure on the vapors in the heating pipes header Ila, and are re- It will be 26 areiclosed and valves 3l)V Vapors are allowedto enter mitting live steam directly to the oven through steam line 35. The melted wax is withdrawn from drain outlet lA and also from drip line i3 by opening valve I4, the melted Wax being directed to a separate receptacle from the drips. Wax is withdrawn from oven I8 in the same manner, live steam being admitted at connection 35A and wax being withdrawn from the drain line |8A and drip line MA. The vapor flow between headers |6 and lSa is conveniently reversed by closing valves 28 and 3S and opening valves 24, 25 and 21.

Instead of Vusing only two ovens in the'process, I may employ a series of ovens connected as shown in Figure 3. The ovens are designated by the letters A, B, C, D, E and F. A suitable heat transfer liquid is contained in tank 50 and may be transferred by pump 5| and line 52 vto header 53 connected with the lower pointV ofthe heat exchange coils in each oven. The vapors in each oven pass through header54 from Vone oven to the other or they may be returned by lines 55A, 55B', 55C, 55D, 55E and 55E' to header 56 and compressor 5'! where they are compressed and condensed in condenser 58, returning them to the storage tank 50. The vapors may also be passed from manifold 54 by compressor 59 and manifold 60 to any other desired oven through connections GIA-B-C, etc., in which case compressor 51 may be shunted.

In operation the process may be conducted as follows: Oven A may be freshly charged with melted wax at a temperature of 15G-200 F.; oven B may be cooling; the wax in oven C may be solidified and ready for the sweating operation; oven D may be undergoing sweating; oven E may be also undergoing sweatingrand oven F may be discharging sweated wax. The cooling liquid may be passing through pump 5|, lines 52 and manifold 53 through lines 62, into the coil in oven B. The vapor from this oven may pass by valve 64B to manifold 54 and compressor 5S to manifold 66 and thence into the heat exchange coil in sweating ovens D and E through lines SID and GIE, valves 64D, 64E, 66D and 66E being closed. The liquid condensing in ovens D and E flows by gravity through lines 62D and 62E back to liquid manifold 53. If at any time there is more vapor collecting in the system than is needed for sweating it may be withdrawn from any oven at will through lines 55A, B, etc., to vapor header 56 and pump 51 where it isv condensed in condenser 58 and returned to the liquid storage.

In view of the fact that the temperature in oven E will be higher than that in oven D, which is at an earlier stage of the sweating cycle, it ispossible to employ vapor at different pressures for these ovens. For example, vapor for Aoven D may be led directly from one other oven, for example, oven B, which is cooling through line 55B and manifold 56, thence through line 55D and into sweater D. At the same time vapor from oven C, which is completing the cooling cycle, may pass by valve 64C, through manifold 54 and compressor 59, to manifold 6l) and thence through line GIE to oven E, valves 64E and 66E being closed. The temperature obtained in the oven is a direct function of the pressure applied to the vapor and this can be controlled in any way desired by the operation of variable compressor 59 and by proper control of valves.

The next stage of the process above outlined is the charging of oven'F with fresh stock and valve 63 and the. higher pressure are suitable for use directly in sweating another oven at a somewhat lower f temperature, thus avoiding the necessity of recompression. When the cooling has proceeded to @the stage where the vapor pressure is no longer sufficient to effect sweating in the other oven the vapors may then be boosted in pressure or diverted to a diiferent oven which is at a lower temperature. By routing the vapors in this manner a maximum economy can be obtained with a minimum cost for both heat and compression. Under some conditionsof operation it may be desirable to employ a separate refrigerating liquid charging pump for each oven, this pump being suitably located in-line 62A, B, C, etc.

As a suitable yheat exchange fluid I may use propane, butane, pentane', hexane, methyl and ethyl ethers, methyl chloride, sulfur dioxide, etc.

In selecting a suitable cooling Afluid it is desirable that `the boiling point of the liquid be below the freezing point of the wax undergoing sweating. Inthe case of paraffin wax this temperature is about 'l0-80 F. However, higher boiling liquids might be employed if a vacuum were used to bring about their evaporation. YThis is undesirable on account ofv the increased cost of handling the larger Volumes of vapors entailed by this operation. It is also important that the heat exchange liquid have a fairly denite boiling point, i. e., that its boiling range be within a very few degrees in order that more accurate temperature control can be obtained and fractionation be avoided. The liquid which I prefer to use is butane whose boiling point is 1 C. at ordinaryV pressure. By maintaining a moderate pressure on the system the boilingpoint of thebutane can be regulated to any desired degree.

OneA of the advantages of the process is that extremely'uniform cooling and heating are obtained because of the close relationship between the boiling point and condensing point of the liquid'and 'vapors and the pressure which is imposed thereon. Thus, a large sweating oven containing several hundred barrels of Wax can be cooled at substantially uniform rate throughout the entire oven, as long as the coils are interiorly submergedY with cooling liquid. Likewise, during'sweating exactly the same temperature will prevail inevery part of the oven which is in contact with condensing vapors. In this operation it is' necessary, of course,A to removercondensed vapors as rapidly as the condensate is formed. rIfhis Vis a' decided improvement over previous practice using water for cooling and heating in which case the temperature gradient from the bottom to the top of the oven will usually be 10 F. or more. The reason for this high gradient is the necessity of transferring all the heat by changing the temperature of the water, whereas in the present process, the heat transferred is the latent heat of vaporization and condensation, no change in temperature being involved. The gradient -from the top to the bottom of the oven in this casev is well below 10 F. and usually below 5 F.

visting within said Although I have described my invention with respect to a specific embodiment thereof, the scope of the invention is intended to be limited. only by the following claims:

I claim:

1. The method of removing oils from waxes, which comprises solidifying an oil wax mixture, liquefying the oil without liquefying the wax in said mixture by condensing a vaporized material which is normally a gas at the sweating temperature employed, in heat exchange relation to all parts of said solidified oil wax mixture whereby uniform and readily controllable temperatures are obtained throughout the body of solidified oil wax mixture and withdrawing the liquefied oil from the solidified wax.

2. The method of uniformly controlling crystallization and melting of wax mixed with oil in a sweating oven which comprises introducing into the heat exchange coil disposed throughout the interior of said oven a working fluid having a boiling point, under the pressure conditions excoil, close to the melting point of the wax-oil mixture, and regulating the pressure-on the working fluid so as to produce a change of state of the working fluid thereby producing a material change in heat content of the wax-oil mixture sufficient to bring about the desired change, with only minor change in temperature.

3. The method of regulating the exchange of heat in a wax sweating system employing a plurality of sweating ovens, which comprises vaporizing a refrigerant in heat exchange relation with Y a liquid oil wax mixture contained in a sweating oven whereby the mixture is uniformly solidified and condensing the vapors from said sweating oven in indirect heat exchange relation to a solidified oil wax mixture in another sweating oven, whereby the temperature is raised gradually and uniformly and the oil and low melting wax are sweated from the high melting wax with minimum liquefaction of the latter.

4. In apparatus of the class described, a sweating oven, a plurality of trays in said oven, a pair of manifolds, a plurality of heat exchange pipes connected between said manifolds and arranged in heat exchange relation to said trays, means for introducing or withdrawing a liquefied refrigerant into or out of one of said manifolds, means for withdrawing or introducing vapors from or into the other manifold, means for controlling the pressure within said heat exchange pipes whereby liquid refrigerant introduced into one manifold, may be evaporated and discharged as vapor from the other manifold, or vapor introduced into one manifold may be condensed and discharged as liquid from the other manifold and means for withdrawing from said trays the liquid products of the sweating operation.

Yliquid at a pressure equal 5. In apparatus of the class described, a plurality of sweating ovens, means for supporting a solidified oil wax mixture in said sweating ovens, a pair of manifolds associated with each sweating oven, heat exchange means in each sweating oven connected with both manifolds and in heat exchange relation to said cil wax supporting means, whereby either a refrigerant liquid may be introduced through one manifold, vaporized in said heat exchange means and withdrawn through the other manifold or whereby refrigerant vapors may be introduced through one manifold liquefied in said heat exchange means and withdrawn through the other and means for circulating a refrigerant, whereby it is vaporized in one sweating oven to solidify an oil wax mixture and condensed in another oven to cause the sweating of the oil from the wax therein.

6. In apparatus of the class described, a plurality of sweating ovens, means for obtaining uniform heating and cooling in each of said sweating ovens by the condensation and vaporization, respectively, of refrigerants therein, a low pressure manifold, a high pressure manifold, a compressor for withdrawing vapors from the low pressure manifold and compressing them into the high pressure manifold, means for selectively connecting the top ofV each of said sweating ovens with the high or low pressure connected to th'e base of each sweating oven for introducing liquefied refrigerant into the ovens or withdrawing condensed refrigerant from the ovens and means for condensing and storing surplus refrigerant liquid.

7. The method of gradually and uniformly increasing the temperature throughout all parts of a wax sweating oven equipped with coils or other indirect heat exchange means disposed throughout the interior thereof, which comprises supplying to said heat exchange means vapors of a to or slightly above the condensing pressure corresponding to the temperature prevailing in the oven at any particular moment and withdrawing condensed vapors from said heat exchanging surfaces.

8. The process of gradually and uniformly reducing the temperature of a sweating oven equipped with coils or `other indirect heat exchange means, comprising introducing a liquid within said heat exchange means until the surfaces thereof are substantially submerged, gradually reducing the pressure of the vapors above said liquid thereby causing said liquid to boil at a temperature equal to or slightly below the temperature prevailing in said sweating oven at the moment and continuously withdrawing the vapors evolved from said liquid.

VANDERVEER VOORHEES.

manifolds, a manifold

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