US2349482A - Automatic aniline point recorder - Google Patents

Description

.I i i I I .l .I 1 ANAL nv I canrrA/Aren I 28 i y 1944- A. B. WELTY, JR 2,349,482 AUTOMATIC ANILINE POINT RECORDER Filed Oct. 30, 1941 3 Sheets-Sheet l 'rzMP I! A Tall y 1944- A. B.'WELTY, JR 2,349,482

AUTOMATIC ANILINE POINT RECORDER Fil-ed Oct. 30, 1941 3 Sheets-Sheet 2 /LTER Fla-2 nmuv .sma-AM WATER DRIP 25" FILTER-- la 1 t ,Mnav JmEAM i I F/Gty 23, 1944- A. B. WELTY, JR 2,349,482

AUTOMATIC ANILINE fOINT RECORDER Filed Oct. 30, 1941 3 Sheets-Sheet 5 THBEMOCOUPLE 7'0 RECORDER PHOTO CE!- PNoTO c514,;

PHO TO 25 M54 TIA/C ELEMENTM AT/N ELEMzNr 1V9 2 ICEBATH F/GZ-5 Patented May 23, 1944 AUTOMATIC AN ILINE POINT RECORDER Albert 13. Welty, Jr., Mountainside, N. 1., assignor to Standard Oil Development Company, a

corporation of Delaware Application October 30, 1941, Serial No. 417,215

4 Claims. (CI. 73-51) This invention relates to a method and apparatus for continuously recording the aniline point of a hydrocarbon oil. The aniline point is the temperature at which an approximately equal volumetric mixture of aniline and oil becomes immiscible. When immiscible the mixture becomes milky and does not transmit light readily.

The invention will be fully understood from the following description taken in connection with the accompanying drawings, in which latter- Fig. 1 is adiagr'ammatic view of a preferred form of apparatus for carying out the invention when the main stream of hydrocarbon oil is under superatmospheric pressure, which pressure is irregular.

Fig. 2 is a diagrammatic representation of an apparatus for sampling the main oil stream, which latter is at or near atmospheric pressure.

Fig. 3 is a diagrammatic representation of apparatus -for sampling the main oil stream which is maintained at a constant superatmospheric pressure and'is formed of a reasonably clean hydrocarbon stock.

Fig. 4 is a diagrammatic view of a simplified arrangement for sampling a stream of hydrocarbon under pressure; and

Fig. 5 is a diagrammatic represention of an alternative arrangement for recording the aniline point.

Referring particularly to Fig. 1 of the drawings, referencenumeral l0 designates a main stream of hydrocarbon from a refining process operated at greater than atmospheric pressure and subject to variations in the amount of pressure. stream of the hydrocarbons, which may be gasoline, isdiverted through a pipe II. The gasoline which, depending upon the type of operation being carried out may boil anywhere from 100 F. to 400 or 500 F., is preferably sampled in such a way as to prevent gas or water getting into the sample. For this reason, the sampling pipe ll protrudes into approximately the middle point l2 of the horizontal main conduit l0. Gas, if any, normally would be in the upper portion of the conduit Ill and water would be in the bottom of the conduit l0 so that the sample obtained by pipe ll would be relatively free of gas or water.

The sampling pipe H contains a throttling valve or needle valve H by means of which the pressure of the gasoline can be reduced to essen which may consist merely of cotton waste, in

A small minimize the temperature rise.

order to remove any foreign particles. such as rust. Combined with the filter 20 is a small water knock-out which should remove any water not previously removed in knock-out Hi; this water is carried off through water drip 22. The sample then passes through a pipe 2| to a small drier 23 which may contain lumps of calcium chloride or anhydrous aluminum oxide and thence by means of a pump 24 is passed through line 25 to join with a stream of aniline coming from line 21. The aniline is fed from a container 28 through a filter 29, check valves 30, and pump 3|.

The amount of oil pumped per minute is not critical, except that it should be approximately the same as the amount of aniline. Preferably the amount used should be kept at a minimum in order to reduce the aniline recovery problem. To this end, the size of the filter, water knockout, dehydrator and all connecting lines are preferably kept at a minimum. By way of example, 5 cubic centimeters of oil per minute can be used.

The combined stream of aniline and oil passes through line 35 into a coil 36 in an ice bath 31. The coil 36 is made as short as practicable in order to decrease the amount of hold-up. The temperature at which the ice bath 3'! is maintained is determined by the lowest aniline point which it is desired to record. Thus, if it is desired to record aniline points no lower than 32 to 40 F., a temperature of 32 F. may be maintained in the bath. For lower aniline points, such as 15 to 20 F., salt can be mixed with the ice or some other expedient such as the use of kerosene through a tube 40 surrounded by a heating element 4| and thence to a glass cell 43. The tube 40, heating element 4|, and cell 43, are encased in a jacket which preferably is evacuated by means of a vacuum pump 46. The vacuum in the Jacket 45 eliminates convection currents inside the jacket and thus the heat transfer to or away from the various parts of the apparatus is minimized. If desired, the inner wall of the jacket can be silvered, except at those points through which a beam of light can be passed, as will be later described. Also, the tube is made as short as possible and aswell insulated as possible to The glass cell 43 always contains liquid through which a beam of light is passed from a light source 50. Preferably an oil resistant rubber connection is used to connect the metal tubing 40 to the glass cell 43. The liquid in the cell is mildly agitated by means The liquid in the cell 43 is maintained at the.

aniline point in the following manner: Light is admitted to cell 43 only from the light source 58 and, depending upon the light transmitting characteristics of the mixture in the cell, very little or very much light passes through to a photocell 51 on the opposite side of the cell. Thus, when the liquid mixture in the cell is at :a temperature higher than the aniline point, under which conditions the mixture is miscible'and clear, abundant light will pass through to the photocell and the photocell will in turn energize a relay 60. This relay 60 serves to turn off the heating element 4| surrounding the tube 48 through which the liquid mixture enters the cell 43, thus allowing the oil-aniline mixture to enter the cell 43 at a lower temperature. When the liquid mixture in the cell 43 has reached the point of immiscibility, the light will be denied the photocell in any appreciable amount, due to the milkiness of the mixture. The relay 50 'will be de-energized automatically then, allowing the current to pass through the heating element 4|, which will increase the temperature of the liquid entering 'the cell 43. As soon as the mixture becomes clear again, light reaches the photocell, the relay 68 is energized, and the current is shut off. Thus the heating element is alternately turned on and off in 'such a way as to keep the liquid at the temperature corresponding to its aniline point.

In order to widen the scope of use of the instrument, a compensating cell 55 is provided to take care of those cases in which the oil is fairly dark colored. A stream of oil from pipe 23a is diverted continuously through line 66 to the compensating cell 65. The rate at which it flows is not critical. A convenient layout is to have a single motor operate small pumps for the aniline, for the oil to be mixed with the aniline, and for the compensating oil stream. The same light source 50 is used for both the main cell 43 and the compensating cell 65 in order to eliminate difiiculties due to change in intensity of the light source as the lamp 50 becomes older. The main photocell 51 and a compensating photocell 68 are so connected that the voltage applied to the relay 60 represents only the difference in light transmission through the two cells 48v and 55. Two potentiometers are required, connected as illustrated, and initially-adjusted with the same oil in both cells so as to exert no potential across the relay 60.

With reference to the heating element 4| which may be mechanically separated from the tube 40 by means of longitudinal strips of insulating material since the entering tube is constructed of metal and would otherwise short circuit, the illustration shows the use of a 110 volt alternating current circuit for heating purposes In order to minimize the resistance necessary in the heating element 4|, it is desirable to reduce the voltage across it and this may be accomplished by means of a small transformer or by means of a variable resistance 1| having a minimum fixed resistance, in series with the heating element. The aniline point is recorded as a sine curve corresponding to the on and oil periods of the heating element 41. It is desirable to minimize the amplitude of the wave and this is accomplished by minimizing the heat capacity of the tube 40 surrounded by the heating element matic adjustment of the heater 4|, as described heating element, as for example by the variable resistance 1|. The relay 68 is of the vacuum tube amplifier type. A rheostat 12 is included in the photocell circuit in order to permit adjusting the sensitivity to changes in light intensity.

In a typical operation of the aniline point recorder, a filtered, .dry stream of the oil, the aniline point of which it is desired to record, is mixed with a substantially equal amount of pure aniline. This mixture is cooled, for example to 32 F., in the refrigerator coil 36 and then passes into the special apparatus contained in the Jacket 45. Normally the highest aniline point which might be recorded would be of the order of 125 F. and the lowest aboutv 40 F. By means of the autoabove, the mixture will be heated just to the temperature which is its aniline point. This temperature will 'be recorded on the continuous automatic potentiometer 55. The'used anilineoil mixture is continuously discharged from the apparatus and the aniline is recovered.

Referring now to Fig. 2, in which a sample of oil is diverted from the main stream which is at or near atmospheric pressure, the sampling line ll opens into a filter 15 inorder to remove any foreign particles such as rust. Combined with this filter 15 is a small water knock-out, which should remove most of any water getting into the sample. The sample then passes through a small drier 11 and thence through a pump 1 to join the aniline stream in pipe 25.

Referring to Fig. 3, in which the sample is diverted from the main stream maintained at a constant superatmospheric pressure and using a reasonably clean stock, the diverting line I i opens into a'filter 15 combined with a water knock-out. The thus treated oil passes into a drier 11, as previously described, after which it is conducted through an orifice or needle valve 88 and thence to line 25. The line 66 to the compensating cell 65 contains an orifice or needle valve 81. This modification is satisfactory in those cases where gas is not released when the pressure on the oil is reduced.

Referring to Fig. 4, a simplified sample diverting structure is illustrated for those cases in which the oil is free from water, the sample passing directly from the filter 15 into the line 25.

Referring to Fig. 5, an arrangement is illustrated in which several degrees of variation are allowed before the heater is turned on or oilf, as the case may be. The apparatus comprises two transparent cells 86 and 81 connected in series by the conduit 88. The on and off heating ele ment which precedes the first cell 86 is made into two elements 89 and 90. Element 89 is adjusted by rheostat SI and element is adjusted by rheostat Bla. Heating element 80 is constantly on and heatingelement 89 is controlled by the photocells. A small heater which is always on through glass cells I03 and I04 through which a stream of pure oil is passed, as described in connection with Fig. 1. These photocells are con- I they are immiscible.

nected as illustrated with the vacuum tube relay I06 so that the on-off heater 89 is turned off when the solution in the first cell 86 becomes clear and is turned on when the mixture in the second cell 81 becomes cloudy. In this way, the instrument will allow several degrees variation before the heater is turned on or oil, as the case may be. In operations where the aniline point remains reasonably constant, the heater which precedes the first cell 86 and which is constantly on, is adjusted to supply most of the heat required so that the heater operated by-the relay can be oflf most of the time. By looking in the two cells, it will be possible to tell where the aniline point is with respect to the temperature being recorded. If the first cell 86 is cloudyand the second cell 81 is clear, the aniline point being recorded is correct. If both cells 86 and 81 are clear, the aniline point being recorded is too high. If both cells 86 and 81 are cloudy, the aniline point being recorded is too low. The line 35 in Fig. is connected with the main stream of oil as described in connection with Figs. 1 to 4, inclusive.

By determining the aniline point continuously, as above described, an indication is obtained of relative increase or decrease in anti-knock rating of the gasoline being refined. Gasolines may be pictured as being produced from two different crude products; namely, virgin naphtha, and distillates or residues boiling at a higher temperature than marketed gasolines. These crude products are converted to gasoline by cracking methods and the crude naphthas thus formed which boil largely within the gasoline range are usually reformed to further increase the volatility and to increase the anti-knock rating. It is with these reforming operations that the invention is particularly concerned. It has been found that for a given feed stock, a certain sample inspection of the product may be quite accurately correlated with the anti-knock characteristics. This inspection is referred to as the aniline point and is defined as the lowest temperature above which a mixture of oil and aniline in equal parts is miscible. Thus at all temperatures above the aniline point temperature, the two liquids are entirely miscible while at all temperatures below the aniline point temperature, When the two liquids are immiscible, the mixture assumes a milky appearance, whereas when miscible, the mixture is quite clear.

The relationship between aniline point and octane number is different for diiferent feed stocks and this relationship must be established before the aniline point can be interpreted in terms of octane. However, the aniline point of itself is of great value because of its indication of relative increase or decrease in anti-knock rating as the operation proceeds. By continuously recording the aniline point of the product, in-

stant detection of any change in the process is observed.

In the case of catalytic reforming or hydroforming operations of petroleum oil, the aniline point changes continuously as the run progresses due to gradual coke deposition on the catalyst surface. In the case of such catalytic'operations it may be desirable to segregate the product according to its anti-knock rating. The continuous automatic aniline point recorder above described makes possible instant determination of the point where segregation should be made.

I claim:

1. In the refining of oil, apparatus for continuously indicating the aniline point of the oil, which comprises means for diverting a small stream of the refined oil, means for mixing a substant ally equal volume of aniline in a stream with the diverted oil, a transparent cell, means for passing the mixture through the cell, means for successively cooling the mixture entering the cell to just below its point of miscibility and for heating the mixture entering the cell to just above its point of miscibility to maintain the mixture at its aniline point in the cell. and means for continuously indicating the temperature of the mixture in the cell.

2. In the refining of oil. apparatus for continuously indicating the aniline point of the oil. wh ch comprises means for diverting a small stream of the refined oil, means for mixing a substantially equal volume of aniline in a stream with the diverted oil, a cooler adapted to cool the stream of mixture below its point of miscibility, a heater adapted to heat the cooled stream of mixture above its point of miscibility, a transparent cell adapted to receive the thus treated mixture, means for directing a beam of light through the cell, means governed by the light issuing from the cell for deactivating the heater when the liquid is miscible and for activating the heater when the liquid is immiscible whereby the mixture is maintained at its aniline point, and means for continuously indicating the temperature of the mixture in the cell.

3. In the refining of oil, apparatus for continuously indicating the aniline point of a stream of oil maintained under superatmospheric pressure, which comprises means for diverting a small stream of the refined oil, means for filtering and drying the diverted oil, means for reducing the pressure on the dried oil to atmospheric pressure, means for mixing a substantially equal volume of aniline in astream with the thus treated oil, a cooler adapted to cool the stream of mixture below its point of miscibility, a heater adapted to heat the cooled stream of mixture above its point of miscibility, a transparent cell adapted to receive the thus treated mixture, means for directing a beam of light through the cell, means governed by the light issuing from the cell for deactivating the heater when the liquid is miscible and for activating the heater when the liquid is immiscible whereby the mixture is maintained at its aniline point, and means for continuouslyindicating the temperature of the mixture in the cell.

4. In the refining of oil, apparatus for continuously indicating the aniline point of the oil, which comprises means for diverting a small stream oi the refined oil, means for mixing a substantially equal volume of aniline in a stream with the diverted oil, a plurality of transparent cells, means for passing the mixture through the cells in series, means for maintaining the mixture in the cells at successively higher temperatures, means for cooling to just below its point otiniscibility the mixture entering the first cell when the mixture inthe first cell becomes clear whereby the

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