US1744599A - Treating hydrocarbon oil - Google Patents

Description

Jan. 2l, 1930.

C. W. WATSON TREATING HYDROCARBON OIL Filed Nov. l1. 1927 Sgam@ SO bv@ Lullbm. SQ

Patented Jan. Z1, 193@ trasse UNllEI) STATES PATEN @FFICE CLAUDE W. VJATSONy OF PORT ARTHUR, TEXAS, ASSIGNOR T THE TEXAS COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE TREATING HYDROCARBON OIL Application led November 11, 1327. Serial N'O. 232,661.

This invention relates to a process of treating hydrocarbon oil and more particularly to a process for the separa-tion of the various components of petroleum by fractional distillation. rlhe'iiwention comprises a continuous process in which petroleum oil may be subjected to distillation by passing through a battery consisting of a series of stills fitted with suitable fractionating towers, the ino dividual stills of the series being maintained at progressively higher temperatures. Various fractions of the oil charged to the battery are collected from corresponding groups of stills of the series. In each group of stills the oil is conveyed from each individual still directly to the next succeeding` still with the exception of the final still of each group, in which case the oil is conveyed from the preceding still to the fractionating tower of the 2o final still.

In the distillation of petroleum, wherein the various fractions such as gasoline, ker-osene, gas oil, lubricating oil, and the like are separated, it is desirable to eect the separation as thoroughly and in as efficient tain any of the kerosene fraction as the presence of such material will tend to raise the end point and change the desired distillation range of the Ovasoline. From the same standpoint it is undesirable that a kerosene fraction shall contain any part of the gasoline fraction as this would result in the lowering of the initial boiling point of the kerosene and would also change its desired distillation range.

In the ordinary methods of distilling petroleum in which a continuous battery of stills is employed the boiling range of the distillates obtained from the stills is not such as to permit of thorough separation between the various fractions, and as a result, it is found that products from such ordinary processes usually have to be redistilled to eliminate appreciable quantities of other products of diilferent boiling' range. For example the fraction containing the gasoline constituents complete separation of the various fractions collected.

The present invention provides a method of distilling petroleum oil in a continuous battery of stills whereby a substantially complete separation of the various fractions collected may be brought about. The invention may be more clearly understood when considered in connection witha suitable apparatus such as that shown in the accompanying drawing which illustrates in diagrammatic form an apparatus and flow chart in which the invention is embodied. It will be understood that the invention is in no way limited by the diagrammatic representation of apparatus, this being provided solely for illustrative purposes.

Referring to the drawing, the diagram illustrates a battery of six shell type stills so arranged for distilling crude petroleum that distillates will be obtained from the first three stills which, after condensing, will be found suitable for blending to produce a gasoline fraction. From the fourth and fifth stills are obtained distillates suitable for blending to form a kerosene fraction, while from the last still a distillate corresponding to gas oil may be collected. In the drawing the siX stills are represented by the numerals 10a, 10b, etc., the first five of these stills being iitted with suitable fractionating towers, preferably of the type usually known as bubble towers, lla, 1l, etc. The last still of the series, 10f, from which a gas oil fraction is to be collected, is fitted with a vapor heat exchanger 12 instead of the fractionating towers of the type used on the other stills in the battery. A source of supply 13 of the oil which is to be charged to the battery of stills is provided, the oil being conveyed to the stills through the connections 14 by charging pump 15. The charge oil may enter the battery through the first still 10a or through the tower 11, or may be distributed between the still and the tower, and the point of entry may be controlled by means of the valves 26 and 17. Suitable piping connections 18a, 18), etc. are provided for the removal of the vapors from the tops of the fractionating towers 11, 11, etc. and from the vapor heat exchanger 12 and extend to suitable condensers (not shown). The several vapor lines 18, 18, etc. are connected as indicated in the drawing for the purpose of combining vapors from the corresponding stills to produce the desired distillate. Connections'lSa, 19h, etc. are provided for the introduction of reflux cooling to the fractionating towers and the valves 20a, 20", etc. are provided for the regulation of the quantity of reflux liquid supplied. Overflow lines 21, 21, and 21e are provided for intercommunication of stills 10a-10", 10C-10d, and 10C-10i, while stills 10b- 102 10d-10e are connected through the lines 22h, 23", 22, and 23d, respectively, and the pumps 24 and 25. From the final still in the battery 10i, the connection 21f is provided for the withdrawal of the undistilled residuum.

In operating the process comprising the invention in connection with the apparatus illustrated, the procedure may be as follows:

A suitable charging stock is provided which may consist of any petroleum oil which it is desired to separate into several fractions by means of distillation. Thus the charging stock may consist of a distillate oil, a residual oil, or a crude petroleum but in the present description and for the purpose of illustrating the invention the operation when charging a crude petroleum of the type obtained from the North Central Texas fields will be discussed.

The crude charging stock from the source of supply 13 is forced by the pump 15 through the line 14C to the battery, passing first through the vapor heat exchanger 12 wherein an exchange of heat is effected between the hot vapors from the still 10 and the cool charge. In the particular example under consideration the charge may be heated to approximately 200 F. while passing through the vapor heat exchanger. From the vapor heat exchanger 12 the heated charge passes through the residuum exchanger 16 wherein its temperature is further elevated by the heat absorbed from the hot residuum which is withdrawn from the final still of the series, 10f. From the exchanger 16, the heated charge is carried by the line 14 to the first of the battery of stills. The charge may be introduced directly into the still 10a or it may be introduced into the fractionating tower 11a, preferably at a mid-point, and in the present example it is desirable to introduce the charge into the tower 11a at a midpoint.

The stills 10a, 10b, etc. are maintained at successively higher temperatures by means of suitable furnaces (not shown). The arrangen ment of stills as shown in the drawing may be in three groups, the first three stills, 10, 10, and 10c constituting the first group, from which a gasoline fraction is collected. The next two stills, 10d and 10e, constitute the second group of the series and from these stills a kerosene distillate is collected. Still 10f may be considered as the third group, and 'from this still a gas oil distillate is obtained.

.The charge after entering still 10n undergoes distillation therein and overflows into still 10b through the overflow line 21a. After undergoing further distillation in still 10b the oil is pumped from still 10b through the lines 22b and 231 by means of the pump 24 into a mid-point in the tower 11C. The pump 24 may be any suitable typeof reciprocating or rotary pump and it has been found that a steam lift may be satisfactory for use in elevating the oil at this point. rIhus it will be observed that in the group of three gasoline stills the oil overflows from the first still to the second still but is pumped from the next to the last still of the group into a mid-point of the tower of the last still of the group. The contents of the stills may be maintained atany desired temperature but in the particular operation described herein still 10a may be maintained at a temperature of 410 F., still 10b at- 4800 F. and still 10c at 525 F. The distillate fractions taken from the tops of the corresponding towers are condensed and combined to form the gasoline fraction of the crude charge, which fraction is so distilled as to have an end point of approximately 400 F. Steam may be introduced into any or all of the stills during distillation by means of suitable conections (not shown) as is well known to those familiar with the art of petroleum refining, and the exact temperatures of the stills will vary somewhat in accordance with the amount of steam thus introduced. In order that propel' fractionation may be obtained from the fractionating towers 11a, 11b, and 11, cooling is supplied to the top of the towers by means of the reflux conections at 19a, 19h, and 19. The material used for reflux may consist of the liquid condensate from corresponding towers or any other suitable material, the quant-ity supplied the individual towers being regulated by means of the valves 20, 20h, and 20c.

From the last still, 10C, of the group of gasoline stills the charge overows into the first of the group of kerosene stills. In this particular illustration of the process there are only two kerosene stills, 10l and 10e, and accordingly the charge is pumped from the first of the group of kerosene stills, 10d, to a midpoint in the tower` of the second or last still of the group, e. These stills may be maintained at temperatures of approximately 5&0O F. and 560O F., respectively. Suitable reflux is supplied the fractionating towers of the kerosene stills through the connections 19d and 19e, the quantity being regulated by means of the valves 20 and 20e. The vapors from the fractionating towers lld and il@ u are condensed and combined to form the kerosene fraction obtained from the crude charge, the distillation being so regulated that the kerosene will have an end point of approximately 500O F. From the last still, 10Q, of the group of kerosene stills the oil overflows into the still l0f in which a portion or all of the gas oil fraction of the charge is distilled over` head through the vapor heat exchanger 12, the vapors givine` up their heat to the incoming charge, as has been mentioned before. The residuum is withdrawn from the still 10" through the connection 2li and the exchanger 1G wherein it gives up a portion of its heat to the charge. The residuum may be suitable for fuel oil or for lubricating oil stock or for other purposes.

The illustration of the invention which has been given in the preceding paragraphs has shown, 'n a continuous battery of stills, groups of stills producing distillates suitable for gasoline, kerosene, and gas oil fractions. Itis to be understood of course that any nurnber of stills may be employed in the series and that the individual groups within the series may contain any desired number of stills, which may vary in accordance with the characteristics of the charging stock. For example, a certain charging stock may contain a large quantity of gasoline and very little "f kerosene in which case the group of gasoline stills may contain four or even more stills, while the kerosene group may even consist of a single still. However, it is possible that a charging stock may be used which would contain a larOe proportion of kerosene but practically no gasoline in which case thefirst group of stills may yield a kerosene distillate.

The advantages obtained from the practice of the invention in connection with the operation of a continuous battery of shell stills consist chiefly in the more thorough separation of the various fractions which it is desired to obtain from the charging stock. For example, in ordinary operation of a battery of stills, even those equipped with eliicient fractionating towers, it will be found that if the gasoline fraction is run to a required end point, say for example 400 F., the kerosene fraction will contain some gasoline and will have an initial boiling point well below 400 F., say for example 360 F. This condition is due to the fact that the charge, in overflowing through the series of stills, reaches the last gasoline still in such a condition that it contains an appreciable quantity of material which may be considered as gasoline, that is, boiling below 400 F. Due to the equilibrium conditions obtaining in the still in accordance with the well-known laws of partial vapor pressures it is very diicult to avoid having the charge flowing out of the last gasoline still thoroughly stripped of the lower boiling or gasoline constituents and accordingly this charge, when flowing into the first kerosene still, which is maintained at a somewhat higher temperature, immediately vaporizes the lighter constituents which accordingly pass overhead into the kerosene fraction. However, when the battery is operated' in accordance with the present invention the charge from the next to the last of the group of gasoline stills is pumped into the fractionating tower of the last of the group of gasoline stills. Thus the charge, in flowing downward through the fractionating column on the last of the group of stills, meets the upward flowing heated vapors and is stripped of its entire gasoline content before it reaches the still itself. It is found that the oil within the last of the group of gasoline stills contains practically no material within the gasoline range of distillation and accordingly when carrying on the distillation in connection with the present invention, a gasoline may be easily obtained which will have an end point not exceeding, and in some instances several degrees lower than, the initial boiling point of the kerosene.

The foregoing discussion of the operation of the group of gasoline stills applies also to the group of kerosene stills. Thus, in ordinary operation of a continuous battery of stills in which the oil merely overflows from one still to the next, due to the insufficient fractionation and separation, a portion of the kerosene will pass into the gas oil still and will accordingly be distilled overhead with the gas oil fraction. However, when operating a continuous battery of stills in accordance with the present invention it will be found that a kerosene of a given end point, say for example 5000 F., may be obtained, together with a gas oil fraction having an initial boiling point in excess of 500 F. thus showing that there is approximately no kerosene passing over into the gas oil fraction.

Further advantages resulting from the operation of a continuous battery of stills in accordance with the invention, in addition to the more thorough separation of the various fractions collected, is experienced in the increase in the charging capacity of the battery, its more flexible operation, and the saving in fuel effected.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

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tI cla-im:

1. lThe method of distilling petroleum oils which comprises establishing a series ofpools of oil maintained underv conditions Aofv distillation, each pool communicating Witha fracvtionating Zone, said seriesjof pools of oil being divided into two or more separate groups, continuously.charging oil-into the iirst pool of 'the series, collecting separate distillate fractions from each ofthe said groups and introducing oil from the next to the lastpool of each group to an intermediate point in the'fractionating Zone or' the'last pool of the 2. The vmethod of distilling crude petroleum which comprises establishing a series ofipools 'of oil maintained under conditions of distillation, each'pool communicating with ya :fractionating Zone, taking olf distillates suitable forforming a fraction of substantially the boiling range of gasoline from a group comprisingthe'firstseveral pools of the series, taking off distillates suitable 'for forming a fraction of substantiallythe boiling range of kerosene .ffromza group comprising the next succeeding pools of the series andintroducing the oil into the last pool of each of said groups at an intermediatepointiin the corresponding fractionating Zones.

In Witness whereof .I have hereunto set my'hand and seal thisQGthfday oOctober,

.CLAUDE WV. 'VATSON

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