US2067627A - Method for flashing mineral oils - Google Patents

Description

Jan. 12, I M R FENSKE E AL METHOD FOR FLASHING MINERAL OILS Filed Sept. 13, 1933 2 Sheets-Sheet 1 STZ'AM Joukc:

Elma/who'd Jan. 12, 1937. M. R. FENSKE ET AL METHOD FOR FLASHING MINERAL OILS 2 Sheets-Sheet 2 Filed Sept. 15, 1933 STEAM+ 8 W m m M m ynmc o Q r 0 0. Mm W0 \I Away- Patented Jan. 12, 1937 UNITED STATES PATENT OFFICE METHOD FOR FLASHING MINERAL OILS Pennsylvania Application September 13, 1933, Serial No. 689,330

3 Claims.

This invention pertains to the flashing of mineral oils. It is particularly applicable to the frac tionation of mineral oils containing both high and low boiling fractions such as an overall crude oil, although it is also applicable to the fractionation of either high boiling or low boiling portions for instance to the fractionation of bright stock. 'As is well known, crude oils contain fractions which range all the way from highly volatile materials (as well as dissolved gases) to materials of very low volatility. In fractioning by way of distillation, considerable difiiculty is experienced in vaporizing the high boiling fractions since excessive heat for extended periods must be avoided to prevent cracking. In the usual distillation processes, the fractions are taken off substantially in the order of their volatility and as the higher boiling fractions are approached, reduced overhead pressures are resorted to in view of the very low vapor pressures of the materials to be vaporized.

The low vapor pressures of the higher boiling fractions has led to a process known generally as steam distillation. In this process the materials are mixed with and agitated by steam which exerts a partial pressure of its own so that the difiicultly volatile portions of the oil can be vaporized, and so distilled over, even though the total pressure on the oil, or steam and oil, is greater than the vapor pressure of the oil.

The use of steam, however, is a mere expedient to effect the application of heat, the turbulence of the oil, and the increased vaporization. It has many disadvantages among which are inefficiency in the use of heat energy, contamination of'the fractions with water, etc.

The entire process of taking off the fractions in the order of their volatility, or substantially in such order, consumes considerable time and labor, and requires a relatively large amount of equipment, compared to the amount of material treated per unit of time.

In contrast to the foregoing and in accordance with this invention, all of the fractions which it is desired to vaporize, are vaporized simultaneously, leaving very viscous oils or impurities such as free carbon or coloring materials in the bottoms. The more volatile constituents when present in the material to be fractionated are employed to function in the manner of steam in steam distillation, and the vaporized oil is separated into its fractions by fractional condensation. Steam may be added to assist or supplement the action of the mo e volatile constituents if desired, or desired fractions may be recycled for this purpose, or both may be resorted to, if desired. Low boiling fractions may also be added to the oil before processing if desired, particularly if it is high boiling.

Other features of the invention reside in the construction, arrangement and combinations of parts, and in the steps and combinations and sequences of steps of the process, all of which together with further features, will become more apparent to persons skilled in the art as this specification proceeds, and upon reference to the accompanying drawings in which:

Figure 1 is a diagrammatic illustration of apparatus for carrying out the above process; and

Figure 2 is an illustration of a suitable temperature control for the condenser sections.

Referring now more particularly to the drawings which illustrate one embodiment of the invention, at I is shown a column adapted for fractional condensation. Column I 0 is particularly designed to effect heat economy and afford fractionation. It is to be understood that other constructions may be employed to serve the fundamental purpose of the column illustrated.

Column I0 is divided vertically into a plurality of sections, each section serving to condense and separate one fraction. The sections may be of any number. For the purpose of illustration, five sections, ll, l2, l3, l4, and l5have been shown, but are not necessarily intended to be a representative number. The number of sections employed will depend upon the number of different fractions desired. It is conceivable that the column l0 may be made with a large number of sections, in which case the number of sections desired for any operation might be selected beginning from the bottom and proceeding upward, leaving the surplus sections at the top inoperative.

Sections II to I 5 have heat transfer coils IE to 20 respectively. These coils are connected in ,series. Temperature control means is inserted between each pair of coils so thatthe oil entering each coil may be at the desired temperature. Each temperature control means, as illustrated, comprises a heat responsive control member of any suitable type represented generally at 2 I, and oil cooling and heating apparatus represented generally at 22.

Cooling between coils is provided for since the latent heat liberated upon condensation in any one section, which heat is absorbed by the oil flowing through the coil of that section, generally raises the oil to a higher temperature than is ordinarily desired for effective heat absorption in the coil of the next section in the series. Preferably the 011 should enter each coil at a predetermined temperature which is determined by the amount of latent heat to be absorbed by the coil to effect condensation of the desired fraction and the rate of flow of oil through the coil. For a very close out it might be necessary in some cases to actually heat the oil to bring it to the desired temperature. Therefore, 22 preferably comprises both heating and cooling means as illustrated.

It is preferred that the fraction condensed in any one section shall not reflux into a lower section. Means for taking ofi a side stream is therefore provided at the bottom of each section. This means has been represented as a plate 2 3 of the bubble cap type in each section with a draw oif pipe 25, although any means which would collect all of the condensate, and yet permit the upward flowof uncondensed vapors, may be employed. Draw-off pipe 25 is positioned so as to keep the plate 2% effectively drained to any suitable level so as to prevent the condensate from overflowing into the next lower section.

If desired, scrubbing may take place within the sections. Means for this purpose has been diagrammatically represented in each section as a plate 26 but any effective means for this purpose may be employed. It is obvious that any desired number of theoretically perfect plates may be employed in each section and that plate 26 might also be employed for scrubbing purposes.

The crude, bright stock or other oil enters the coil 16 of the upper section at 28 and after flowing therethrough, is brought to the desired temperature prior to entering the coil ll of the next lower section. The same is true of the oil that leaves any one section and before it enters the next. The oil is finally delivered in a preheated condition from the coil of the lowermost section, represented as 20.

The use of the oil to be processed, whether it is crude, bright stock, or other oil, in the coils I6 to 20 for the purpose of absorbing heat from the ascending vapors to cause selective condensation in the individual sections, is for the purpose of heat conservation, for in this way such oil is delivered to the first pipe still 33 in a preheated condition. Any other suitable means might therefore be substituted for this preheating arrangement provided, of course, that the desired results are obtained.

The oil to be processed flows preferably continuously and preferably under elevated pressure through pipe still 3Q, whether preheated or not, and is rapidly heated therein to a relatively high temperature. The temperature to which the oil is heated in still 34 need not exceed a safe noncracking temperature, but since cracking not only involves heat and/or pressure but also time, it is preferred that the oil be heated to a higher temperature and that the time of heating be kept below that which would effect cracking. This time interval decreases with rise in temperature as'is well known in the art. The limit in the temperature to be employed for any one type of oil is therefore conditioned upon the time required for the oil to flow from the point where it reaches a cracking temperature to the point where it is brought back to below a cracking temperature, upon the rate of temperature rise in the oil, the highest temperature reached and the rate of cooling of the oil. The latter point will be more fully described hereinafter.

The oil is preferably maintainedin still 33 under a sufficiently elevated pressure to keep as much of the oil as possible in the liquid phase and to keep that portion of the oil which may be in the vapor phase of a. relatively high density. Under these conditions separation of the low boiling constituents is maintained at a minimum. It is preferred to avoid substantial separation in order that the relatively volatile portions may more intimately contact and bubble through the less volatile portions and bring about to a greater degree the desired effects which result from the use of steam in steam distillation processes.

The pressure in still 34% may be brought about by any suitable means. As illustrated, a high pressure pump 35 is provided at the inlet of still 33 and a constricted portion 36, represented as an expansion valve, is provided at its outlet. To maintain the pressure in still 3d more or less con stant, valve 36 may be made to respond to pressure, opening slightly further when the pressure exceeds the desired value and closing slightly when the pressure falls below such value. Any suitable device may be employed for this purpose. Valve 35 may be operated manually to control the pressure in a similar manner, and gauge 37 may be provided to guide the manual operation of valve 36.

The pressure on the oil is released as it passes through valve 36. In view of the high temperature of the oil the highly volatile constituents immediately vaporize and expand carrying with them the less volatile portions.

The entire mass is preferably carried first through pipe still 38 before entering chamber 3!. Pipe still 38 is preferably designed as to the diameter of its tubes taking into consideration the rate of fluid flow so as to cause considerable turbulence in the material passing therethrough.

The highly volatile material boils through the material of low volatility much the same as steam boils through the oil in steam distillation. The result is a substantially increased vaporization due to the increased vapor volume formed by the vaporization of the low boiling materials.

The vaporized and non-vaporized materials fiow from still 38 to chamber 3| through pipe 380. and separate in chamber 3|. The vapors pass up through the bottom 30 of the lowest section of column in. From this point on up through column l0 fractional condensation takes place, the fractions condensing successively in successive sections in the reverse order of their volatility.

Once the desired portions of the oil are vaporized it becomes a relatively simple matter to separate them into fractions by the means previously described.

The non-vaporized portion which is dropped in chamber 3| contains a large proportion of those materials which are responsible for color and the formation of carbon. The percentage of non-vaporized material is a matter for choice. It may be relatively small or may for instance be sufii-- cient to correspond to a cylinder stock.

As the oil passes through valve 36 it begins to cool due to the heat absorbed by vaporization. If the oil were heated as it passed through still 38 to a point above a safe non-cracking temperature it would eventually in cooling, return to a safe non-cracking temperature. The highest temperature to which any particular type of oil may be heated in still 34 may be determined by actual trial of the equipment or by calculation.

The rate of travel of the oil through still 34, the design of still 34, and the type of material under treatment will obviously have a direct bearing in such calculations.

It is, of course, unnecessary to operate at the highest possible temperature, taking into consideration the time factor. This temperature is referred to, merely to point out that there is a limit in time of heating for each temperature above a safe non-cracking temperature beyond which cracking might occur.

The highest safe non-cracking temperature will of course vary with each type of oil as is well known. It will generally correspond to the limit in temperature employed in an ordinary distillation process for the particular mineral oil.

As the material passes through still 38 more and more vapor is formed and more and more latent heat is absorbed. In order to bring more of the materials of low volatility into the vapor phase, heat may be added to the vaporizing oil in still 38 to compensate for that absorbed. The heating in still 38 is not intended to bring the materials above a safe non-cracking temperature, unless of course the rate of travel of the oil is so great that the safe time interval above referred to is not exceeded before the material is finally released into chamber 3| and sufliclently cooled by vaporization therein, in which case this could be done, if desired.

Considered broadly still 38 is to beregarded as a heat transfer device for the purpose of controlling the temperature of the vapors and liquid passing therethrough. It might therefore actually have cooling means for instance to assure a non-cracking temperature.

When the material is delivered to chamber 3|, the non-volatile portions are dropped along with the non-vaporized relatively non-volatile portions. If desired, means for dispersing the material such as a closed drum 3|a upon the surface of which the material impinges upon leaving pipe 38a may be provided.

In the event that it is desired to increase the effects of the highly volatile constituents of the oil, or if the oil is deficient in highly volatile portions and an increased effect is desired, one or more of the lower'boiling fractions may berecycled by adding them to the fresh oil. Means for this purpose is illustrated diagrammatically in the drawings.

At 40 is shown a tap on draw-off pipe 25 of top section II to which is connected pipe 4| which in turn is connected to the inlet of pump 35. By this means any desired portion of this fraction may be recycled, valve 42 in pipe 4| affording a control for this purpose.

A similar tap is shown at 43 on draw-off pipe 25 of the next lower section I2, which is connected to the inlet of pump 35 through pipe 44 and pipe 4|, valve 45 in pipe 44 affording a control of the amount of this fraction to be recycled.

Similar arrangements may be made for recycling the condensate from any desired section.

If one or more lower boiling fractions have been added to higher boiling material, for instance, a gas oil or lower fraction to bright stock, prior to processing to obtain the desired effects accruing therefrom during processing, these lower boiling fractions may be continuously recycled, thus making it unnecessary to continue to add such lower boiling materials to the higher boiling material, except to make up for unavoidable losses.

The column l0 may operate at atmospheric super-atmospheric or at reduced pressures. Re duced pressures would of course facilitate the vaporization of the higher boiling constituents. Reduced pressures would generally be preferred when operating with oils having a relatively high percentage of higher boiling constituents, such as bright stock. Atmospheric pressures would generally be preferred when operating with overall crudes since they contain all of the low boiling constituents and vaporization of the high boiling constituents would thus be much easier. Reduced pressures, however, may be employed with oils containing low boilers, particularly if the increased effect on vaporization is desired.

As previously referred to, steam might be used to assist or supplement the more volatile materials. This is illustrated diagrammatically in the drawings. represents a steam source, 5| a header, 52 a pipe leading to the inlet of still 34 and 53 a control valve in pipe 52. 54 represents a pipe leading from header 5| to the downstream side of valve 36. Steam flow is controlled by a valve 55. 56 represents a pipe leading from header 5| to the outlet of still 38 and 51 is a control valve in said pipe. 58 represents a pipe leading from header 5| to and into the chamber 3|. Flow of steam through pipe 58 is controlled by valve 59.

The point at which the steam enters the system depends first of all upon the temperature of the steam. If the temperature of the steam is less than that of the oil leaving still 34, it will generally be introduced into still 34 through pipe 52 so as to avoid reducing the oil temperature. Water might be used in place of steam in which case it would be introduced at this point. Steam regardless of temperature might be introduced into still 34 to get the effect of steam passing through valve 36 along with the oil. Or, the steam may be introduced on the downstream side of valve 36 through pipe 54, particularly if it is at the same temperature or is of a higher temperature than the oil, unless perchance a quicker cooling is desired to avoid cracking. The steam may also be introduced through pipes 56 or 58 which is substantially the same except that pipe 58 directs the steam upward in chamber 3|. The connection 38a between the outlet of still 38 and chamber 3| would obviously be one which would avoid substantial heat loss and therefore would generally be considerably shorter than represented in the drawings.

While higher pressures are preferred, other pressures may be maintained on the oil in still 34 having in mind the purposes thereof. For instance, and broadly speaking, the pressure at pump 35 might vary from that which is just required to cause the oil to flow at the desired rate with valve 36 wide open or eliminated, to that which is required to keep all fractions in the liquid phase, except those which have reached their critical temperatures.

To obtain the benefits of a high degree of subdivision of the heated oil as it passes out of still 34, whether it goes directly to chamber 3| or by way of still 38, an atomization of the oil may take place. Valve 36, for instance, may be of an atomizing type, or atomizing means may be provided at the inlet to chamber 3|. Valve 36 might be used for the latter purpose when still 38 is not employed. Or atomization at both points may be provided for if still 38 is employed, but preferably without an appreciable increase in pressure drop between the outlet of still 38 and the inlet of chamber 3|.

While the invention has been described in connection with the processing of oils, it is to be understood that it is applicable to the fractionaing water.

tion of any other materials, particularly where similar problems are involved.

The temperature control means at El and 22 may obviously be of any suitable character known in the art. In Figure 2 for instance is schematically illustrated such a control which will be considered as being inserted between coils l6 and ii. Pipe iii leads from coil l6 and connects to heating means 62 comprising a coil 53 for the oil and a chamber Mi for steam for heating coil 63. An electrically controlled valve 65 controls the flow of steam into chamber E l, said valve being opened when current flows through solenoid 66 thereof. Solenoid $6 is in a circuit comprising battery El and relay 68. Relay 68 is normally open so that valve 65 is normally closed.

Coil 63 of heater 62 is connected in series with coil 70 of cooler ll.

Coil 10 is surrounded by a chamber H for cool- The flow of water through chamber 72 is controlled by an electrically controlled valve 13, said'valve being opened when current flows through the solenoid Hi thereof. Solenoid it is in a circuit which comprises battery '15 and relay 76. is normally closed.

A temperature gauge 78 is connected in pipe l9 which leads from coil 70 to coil ll. Gauge 78 has an indicator 80 which registers on a dial 8H, said indicator moving clockwise with increase in temperature and counterclockwise with decrease in temperature.

A contact 82 is adjustably supported at 83 and may be placed opposite any desired point on dial 8i. Contact 82 is contacted by indicator 80 to close a circuit through relay 68, when the temperature of the oil falls below a desired point. This opens steam valve 65, permitting steam to enter chamber 62 to heat the oil flowing through coil 63. As soon as the desired temperature is restored, Valve 65 will close because of the opening of relay 68. This opening of relay 68 is caused by indicator 80 leaving contact 82,. The cycle is repeated when the temperature of the oil falls below the desired value.

A second contact 8% is adjustably supported at 85 in a similar manner. Contact 85 is contacted by indicator 80 to close a circuit through relay 15 when the temperature of the oil exceeds a desired point. This opens valve 73 and permits water or other refrigerant to flow through chamber 12 to cool the oil flowing through coil 10. As soon as the desired temperature of the oil is restored, valve 13 closes because of the breaking of the circuit through relay 16. This circuit is broken when indicator 8!] leaves contact at. The cycle is repeated when the temperature of the oil again exceeds the desired value.

Current for the operation of relays 58 and i6 is supplied by battery 86. Any other suitable arrangement may be provided.

The fractions and bottoms are of course preferably collected in individual receivers. This is illustrated in the drawings in which 88, 39, 90, ill, and 92 are individual receivers for sections l l to I5 respectively and 93 is a receiver for the bot toms. The receivers are, of course, preferably operated at the same pressure as the column, as is Well understood in the art.

The apparatus particularly described and exemplified in the drawings is of the continuous type. The invention may be likewise applied to batch operation. Suitable apparatus therefore will occur to persons skilled in the art upon becoming familiar with this invention.

Relay i6 is normally open so that valve '63 While in the above description it is contemplated that the oil shall reach its highest, or in other words, final temperature in still 341, if desired, and provided still 38 has sumcient heat transfer capacity, the highest temperature may actually be reached in still 38.

Although the vapors produced are preferably fractionally condensed since they are recovered in an excellent condition for this purpose, they may be condensed as a whole, the net result of which will be the separation of the condensate from the residue.

A single embodiment of the invention has been described for the purpose of illustration. It is therefore to be understood that changes, omissions, additions, substitutions and modifications may be made without departing from the spirit thereof, or avoiding the scope of the claims which are intended to be limited only as required by the prior art.

While the invention has been more particularly described in connection with relatively nonvolatile materials and in connection with relatively non-volatile materials mixed with volatile materials it is to be understood that it may be applied to any mixture which is separated by fractional distillation whether such mixture is in the vapor, liquid or solid phase at atmospheric pressure and ordinary temperatures.

Any of the parts used in connection with the still 38 may also be constructed so as to cause turbulence of the fluids flowing therethrough and' the dispersing means represented at 3la in chamber 3! may have any desired construction. It will be understood that any devices and constructions known in the art may be employed for carrying out the invention and it will of course be obvious that heat insulation will be employed where desired.

In separating given materials either elevated or reduced pressure might be used to take advantage of diiferent temperature slopes of the vapor pressure curves at difierent pressures.

We claim:

l. A continuous process for vaporizing relatively high boiling lubricating oil components contained in a mineral oil, said mineral oil also containing relatively lower boiling components, comprising flowing a continuous stream of oil through a heating zone wherein said oil is brought to a cracking temperature for said oil While being subjected to superatmospheric pressure sufficiently high to keep as much of the oil as possible in the liquid phase and to keep that portion of the oil which may be in the vapor phase at a relatively high density, projecting the oil of said stream after it reaches a cracking temperature but before any substantial cracking takes place and with reduction in pressure into an inter mediate vaporization zone of substantial length wherein vaporization is restricted and takes place over an extended period with reduction in temperature of said oil to at least a non-cracking temperature for any component present, thoroughly mixing vaporized oil with liquid oil as said materials flow co-currently through said intermediate vaporization zone while holding the temperature below a cracking temperature for any component present, and then projecting said mixture of vaporized oil and liquid oil into a flash vaporization zone to cause additional vaporization.

2. A process as claimed in claim 1 wherein heat is added to the oil in said intermediate vaporiza- 75 tion zone to partially compensate for loss of heat due to vaporization while maintaining the temperature of said oil below the point of decomposition.

3. A process as claimed in claim 1 wherein heat is abstracted from said 011 while flowing through said intermediate vaporization zone in addition to that absorbed due to vaporization to reduce the temperature of said oil below the point of decomposition.

MERRELL R. FENSKE. WILBERT B. McCLUER.

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