US1982620A - Apparatus for determining critical temperatures - Google Patents

Description

Dec. 1934- G. ALLEMAN ET AL. 1,982,620

APPARATUS FOR DETERMINING CRITICAL TEMPERATURES Filed May 15, 1932 WMAM Patented Dec. 4, 1934 UNITED STATES PATENT OFFICE APPARATUS FOR DETERMINING CRITICAL TEMPERATURES poration of New Jersey Application May 13, 1932, Serial No. 611,024

9 Claims.

The object of the invention is to provide an apparatus for determining critical temperature, that is, that temperature above which, irrespective of the pressure applied, a substance which is capable of being converted into a gas cannot be liquefied. For the determination of the critical temperature of many substances, including stable hydrocarbons, satisfactory means are known; but such means are not reliable or practicable, if indeed they can be said to be operative, as applied to other substances, particularly those complex mixtures of hydrocarbons which comprise crude petroleum oil and fractions thereof such as fuel oil, gas oil, kerosene, heavy naphtha and gasoline.

In the determination of the critical temperatures and of the critical pressures of compounds such as water and benzene, no special contrivances for rapid heating are required, because these compounds are stable and do not break down during the time required to make the determinations. In the determination of the critical temperatures and of the critical pressures of a mixture of petroleum hydrocarbons, heating at a slow rate, through the range of temperatures under the critical temperature, effects cracking of the mixture; that is, many of the hydrocarbons break down to produce new hydrocarbons. These new hydrocarbons individually have critical temperatures different from those which are broken down to produce them. Since (it is believed) the critical temperature of a mixture of substances is the average of the critical temperature of the individual components (assuming equal amounts of all components), it will be understood that when a mixture of hydrocarbons is substantially cracked, necessarily it has a critical temperature different from that of the mixture before cracking. Cracking is a factor of both temperature and time. If the hydrocarbon mixture is heated with sufficient rapidity through its cracking range, there will be no substantial amount of cracking. We have found that, in the case of gas oila typicalmineral oil fraction-not over about three minutes should elapse from the time it reaches a temperature of 700 F. until it reaches its critical temperature. Such slight amount of cracking as occurs in this short period of time does not interfere with the attainment of reasonably and sufilciently accurate results. By a. long series of experiments employing various petroleum hydrocarbons, it was determined that satisfactory and reliable results can be obtained if the determinations are made in a period of not over about seven minutesfour minutes of which are required for the oil to attain the temperature of its immediate heating agent, as hereinafter described.

One difliculty, therefore, in devising a suitable critical temperature determination apparatus is to provide an apparatus wherein the oil may be heated up with sufficient rapidity through its cracking zone to avoid an amount of cracking that will substantially change its critical temperature.

Another difficulty is to determine what available materials are required that will possess properties permitting of their use and that will, at the same time, withstand the very high pressures produced.

- Another difiiculty is the placement of the thermometer or other temperature recording instrument in such a way as to reliably indicate the temperature of the oil. 75

Another difficulty is to provide means whereby the operator can make the necessary observations. The high pressures produced often cause explosions of the tubes containing the oil. The operator must therefore be some distance from the .tube containing the hydrocarbon mixture and from the temperature indicating scale and must be protected by a shield. It is therefore necessaryto provide special means for specially illuminating the upper level of the liquid oil, since it is requisite that he should closely observe the meniscus, since its sudden disappearance indicates that the critical temperature has been reached. This cannot be done without special illuminating means largely concentrated on the oil and the avoidance of dissemination of light by the heating medium. This latter requirement excludes the employment of such convenient and otherwise satisfactory methods of heating as incandescent electrically heated resistant wire, since the light radiated thereby interferes with the field of vision of the operator. We have, however, solved this difficulty by heating the tube contain ing the oil by the radiant heat from a dark object. We have also devised means whereby light may be concentrated upon the oil at its upper level before, and when, it reaches its critical temperature.

Another difficult requirement is to provide means for uniformly heating the entire body of oil.

All these difliculties we have overcome by long experimentation; The invention is capable of embodiment in different forms. The apparatus shown in the drawing is an embodiment which has been successfully used and the accuracy of which has been demonstrated by using it to determine the critical temperatures of stable substances whose critical temperatures have been repeatedly determined by other means and which are given in various printed publications.

In the drawing:

Fig. 1 is a perspective view of the apparatus.

Fig. 2 is a plan view of the apparatus.

Fig. 3 is a perspective view of the heating element with thermometer in position.

Fig. 4 is a view of the tube containing the material whose critical temperature is to be determined.

The oil whose critical temperature is to be determined is placed in a tube e of barometer tubing composed of strong and well annealed boro-silica glass. The tubes may be composed of any other sufiiciently transparent material which will withstand the high pressures incidental to the critical temperature determination procedure.

This tube containing the oil is placed in a heating block which we construct as follows: A cylindrical forging is made of a material which will absorb and radiate heat while remaining dark or comparatively dark. A suitable material is manganese bronze. Manganese bronze will not readily oxidize and will radiate the heat to the glass barometer tube quite rapidly. Other materials than manganese bronze may be employed, but they should be composed of alloys which will not oxidize and which will rapidly transfer the heat to the glass barometer tube. A cylindrical forging a of this material is made of a diameter of about 6 inches and a height of about '7 inches. A hole of one inch diameter is bored through the axis of the cylinder. Holes of suitable diameter are drilled at various places to form thermometer and tube wells. A slit or slits about one-eighth of an inch in width and intersecting the tube well or wells and the center of the cylinder are sawed through the cylinder. To simplify the disclosure, we show in the drawing a cylinder provided with only two wellsone awell b to receive the oilholding tube, the other a well 0 to receive the lower end of a thermometer, and a diametrical slit d intersecting the well b. The two wells must be so relatively positioned that the temperatures therein will be the same, so that the thermometer will accurately register the temperature of the oil. This may be rendered certain by sealing a thermocouple in a barometer tube, inserting this tube in well b, inserting the thermometer in well 0, and comparing their readings.

As an example of dimensions and locations that have proved to give satisfactory results, the tube well may be drilled to a depth of 5 inches and may be of a diameter of one-half inch. The thermometer well may be drilled to a depth of 3 inches and may be 11/32 inch in diameter. The wells may be drilled about one inch from the circumference of the block and about five-eighths of an inch from each other.

The oil-holding tube e is filled with such quantity of oil that, at the critical temperature, the meniscus will be very near the top of the tube; that is, the liquid at this temperature will nearly fill the tube. Experience has shown that the tubes filled to about one-third their volume, at room temperature, fulfill this condition.

Since it is necessary for the operator to observe only the meniscus and not the entire column of oil, the slit d need be of the height required to expose only the upper portion of the tube to the operator's vision.

The block a is mounted upon or above any suitable heater, such as a gas stove g. The block is surrounded and covered with heat insulating or refractory insulating material I such as a porous silica brick made from diatomaceous earth. This insulating enclosure may be conveniently formed in two parts which, when brought together, form an enclosure which is complete at sides and top except for slits i and a hole 7'. The enclosure 1 and block a are so relatively positioned that slits i and d align with each other and hole :i aligns with the thermometer well 0 as shown in Fig. 2.

At one side of the heating contrivance described is an adjustable micro lamp is provided with a focusing condensing lens so positioned as to throw its light rays through slits i and d and thus illuminate the critical temperature tube at the upper part thereof. On the other side of the described heating contrivance is a metal shield m provided with a glass window n, which is in line with the slits i and d. In front of the upper part of shield m and extending above it is a shield o of polished wire glass.

A thermometer p is placed in the well 0 and extends through hole a to a considerable height above the roof of the refractory enclosure f. The exposed part of the thermometer is housed within a glass tube 12 in order to prevent the (relatively) cold air from contacting with the thermometer. Instead of using a thermometer, a thermocouple may be employed, but experience has shown that accurately calibrated thermometers are more convenient than thermocouples.

After the block R: has been heated to a temperture below the critical temperature of the contained oil but as near to that temperature as can be safely estimated, the tube containing the oil is placed in the well b and the block is rapidly heated by means of gas flames at the bottom. This operation and subsequent observations are made in a dark room. The operator carefully observes the meniscus; this observation being made possible by the special illumination of the upper end of the oil tube in contrast with the darkness of the heating block a. Immediately upon observing the disappearance of the meniscus, he views the temperature scale through a properly positioned vertical slot 1 in the shield m. This indicated temperature is the critical temperature of the-oiL- The temperature scale is illuminated by a special lamp s.

It is diflicult to determine the exact time at which the meniscus disappears. To facilitate observation we have successfully used a specially designed magnifying lens with a fiat field. This lens (t) may be positioned as shown in Fig.1. We have also used a periscope and actinic spectacle glasses. We have also found that a planar objective greatly aidsv in making accurate observations.

The accuracy of the thermometer should be determined by calibration. The accuracy of the entire apparatus is proved by using it to determine the critical temperatures of substances, such as benzene and naphthalene, whose critical temperatures have been previously determined with great care by other observers by means of other devices which have been found reliable in the determination of stable substances.

What we claim and desire to protect by Letters Patent is:

1. A critical temperature determination apparatus comprising a block provided with a well for the reception of the substance whose critical temperature is to be determined, said block being of a material adapted to absorb and radiate heat while remaining relatively dark, means to heat the block and thereby heat said substance, a protective shield for the block, and means to illuminate and render visible the upper part of said well.

2. An apparatus for determining that critical temperature of a substance convertible into a gas above which, irrespective of the pressure applied, it cannot be liquefied, comprising a substantially solid block adapted to absorb and radiate heat and transmit heat to said substance and to the temperature indicating instrument hereinafter specified, said block being provided with passages of restricted dimensions into which a tube containing said substance and a temperature indicating instrument are insertable so as to occupy loci subject to the same degree of heat, means to heat the block and a. shield of heat insulating material enclosing the block.

3. An apparatus for determining that critical temperature of a substance convertible into a gas above which, irrespective of the pressure applied, it cannot be liquefied, comprising a block adapted to absorb and radiate heat and transmit heat to said substance and to the temperature indicating instrument hereinafter specified, said block being provided with wells adapted to receive respectively a tube containing said substance and a temperature indicating instrument and provided also with a slit through which the meniscus of said substance may be observed, said block being otherwise substantially solid, and means to heat the block, said wells being so relatively positioned as to insure the subjection, at the same time, of said substance and the temperature indicating instrument to the same degree of heat.

4. A critical temperature determination apparatus comprising a block provided with a well for the reception of the substance whose critical temperature is to be determined, said block being of a material adapted to absorb and radiate heat while remaining relatively dark, said block being provided with a slit intersecting said well, and a lamp so positioned that light rays therefrom pass through said slit and illuminate the substance contained therein so that its meniscus may be observed by the operator.

5. A critical temperature determination apparatus comprising a block provided with a well for the reception of the substance whose critical temperature is to be determined, said block being of a material adapted to absorb and radiate heat while remaining relatively dark, a shield of heat insulating material surrounding and overlying the block, said block and shield being provided with aligning slits, the slit in the block intersecting said well, and a lamp so positioned that light rays therefrom pass through said slits and illuminate the substance therein so that its meniscus may be observed by the operator.

6. A critical temperature determination apparatus comprising a block provided with a well for the reception of the substance whose critical temperature is to be determined, said block being of a material adapted to absorb and radiate heat that its meniscus may be observed by the operwhile remaining relatively dark, a shield of heat insulating material surrounding and overlying the block, said block and shield being provided with aligning slits, the slit in the block intersecting saidrwell, a lamp so positioned that light rays therefrom pass through said slits and illuminate the substance therein, and a shield at the side of said block opposite said lamp and provided with a transparent area in line with said slits and through which the operator may observe the illuminated meniscus of the substance contained in said well.

7. A critical temperature determination apparatus comprising a block provided with a well for the reception of a temperature-indicating instrument and a well for the reception of a tube containing the substance whose critical temperature is to'be determined, the block being provided with a slit intersecting the second named well, means to heat the block, said block being of a material adapted to absorb and radiate heat while remaining relatively dark, and a' lamp so positioned that light rays therefrom pass through said slit and illuminate the substance therein so ator.

8. A critical temperature determination apparatus comprising a block provided with a well for the reception of a temperature-indicating instrument and a well for the reception of a tube containing the substance whose critical temperature is to be determined, the block being provided with a slit intersecting the second named well, means to heat the block, said block being of a material adapted to absorb and radiate heat while remaining relatively dark, a lamp so positioned that light rays therefrom pass through said slit and illuminate the substance therein so that its meniscus may be observed by the operator, and a shield of heat insulating material extending around and above the block, said shield having slits aligning with the slit in the block and having a hole through and above which a temperature-indicating instrument inserted in the first named well, may extend to permit temperature readings.

9. A critical temperature determination apparatus comprising a block adapted, when heated to the required temperature, to radiate heat with out radiating a substantial amount of light and provided with wells, a tube, adapted to contain the material whose critical temperature is to be determined, inserted in one of said wells, a thermometer inserted in and projecting above another of said wells, the block being provided with a slit intersecting the first named well for passage of light through the block, a glass tube housing the projecting portion of the thermometer, heat insulating bricks forming a shield for the block, means to heat the block, a lamp provided with a focusing condensing lens adapted to transmit 135 light through said slit, a metal shield opposite the lamp and provided with a transparent area in line with the slits, and means outside said'shield to receive the light rays passing through said slit and transmit them to the eyes of the operator.

GELLERT ALLEMAN. AUGUSTINE FRANCIS STEPHEN MUSANTE.

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