US2022695A - Method and apparatus for controlling the flow of volatile liquids - Google Patents

Description

De z 3, 1935.

- K. E. STUART METHOD AND APPARATUS FOR CONTROLLING THE] FLOW OF VOLATILE LIQUIDS Filed Dec. 1, 193

IN VEN TOR.

Patented Deco 3, 1935 UHTED STATES METHOD AND APPARATUS FOR CONTROL- LING THE FLOW F VOLATILE LIQUIDS Kenneth E. Stuart, Niagara Falls, N. Y., assignor to Hooker Electrochemical Company, New York, N. Y., a oorporation of New York Application December 1, 1933, Serial No. 700,461

11 Claims.

In a sense, of course, all liquids are volatile, but in this application I shall use the term todenote any liquid that is at or near its boiling point.

In controlling the flow of volatile liquids, as by g at the same time prevent the chlorine from throttling the stream, difificulty is experienced owing to the propensity of such liquids to break into vapor phase. This is especially true when the point of control is at a higher level or remote from the storage container, and results from the reduced pressure upon the liquid either from increased elevation or from frictional loss of head or heat absorption, in the piping system. Under these conditions, a sufficient proportion of the liquid must necessarily break into vaporphase to cool the remainder to its equilibrium temperature at the reduced pressure. This may amount to very little, but in any case it will result in slugs of vapor coming along the pipe. When such a slug of vapor reaches the needle valve, it for all practical purposes momentarily shuts ofi the flow, since the volume of the vapor is so enormous compared with that of the liquid that, notwithstanding the higher velocity of the vapor, the weight passing the needle valve in vapor phase in a given time is negligible compared with the weight passing'in the same time in liquid phase. When it is desired, as part of the control, to meter the liquid, the dimculty is in creased; for the meter cannot distinguish be tween vapor and liquid and will give too high a reading. In some cases the meter may even be damaged by the high velocity of the slugs of vapor.

' An instance in which such difiiculties of control frequently arise is afforded by the use of liquid chlorine under pressure in a drum, as when used in chemical processes, such as chlorination of paper pulp. In such processes accurate control of the chlorine is very important; The drum or tank car containing the chlorine is usually at ground level and the point of use may be several stories'higher and at a horizontal distance of several hundred feet from the source. Not only does such a condition involve a substantial reduction of pressure, but heat is liable to be absorbed on the way. To prevent the chlorine from breaking into vapor phase at the point of controL it has hitherto been customary to raise the pressure upon the drum or tank car well above equilibrium pressure by pumping. in air. This is objection able, as the air, even when, carefully dried, is liable to introduce moisture and the dryer itself is liable to fail. When this happens the chlorine becomes wet and attacks the shell of the con= tainer, which not only dangerously deteriorates the container, but contaminates the chlorine it self with iron. Even when this does "not occur, the air is objectionable, as it is more or less soluble in liquid chlorine, and is given up again by the chlorine under reduced pressure, so that it becomes necessary to provide an air trap ahead of the point of control.

My invention therefore has for its object to obviate the necessity for excess air pressure and breaking into vapor phase. This is accomplished by extracting the heat of vaporization and expansion of the chlorine as it passes the needle valve, by means of a heat exchanger, from the chlorine approaching the meter. or needle valve, to cool the latter below its equilibrium temperature and thus reliquefy any chlorine that may have broken into vapor phase..

Referring to the drawing:

Figure 1 is an elevational view of a chlorine meter, needle valve and heat exchanger, arranged in accordance with my invention, the source of the volatile liquid being indicated diagrammatically.

Figure 2 is an elevational View of an equivalent 2o arrangement in which the meter is of a difierent' type.

Figure 3 is an elevational view of a needle valve and heat exchanger only, the meter being in this case omitted.

Referring to Figure 1:

The source of chlorine is indicated at I, in this case a standard drum of the type in which it is customary to ship liquid chlorine. The heat exchanger is indicated at 2, the meter at 3, and the control valve at 4. The meter illustrated is of the type shown in my co-pending application, Serial No. 640,399.- The needle valve may be of the type shown in my co-pending application Serial No. 582,031.

In the control of flow by this method, chlorine is drawn in liquid phase from the drum I through pipe 5, which extends to the bottom of the drum. Pipe 5 after traversing the building and perhaps rising several stories, as indicated by the break 40 in its continuity, connects with a coil 6 in the heat exchanger, which may be of copper, closely wrapped about the inner cylinder l and closely enclosed by outer cylinder 8. The exit from coil 6 is connected through pipe 9 to the meter. The construction of the meter is such that the flow is upward through the left leg, across the top yoke and downward through the right leg. The meter 3 is connected through pipe Hi to valve 4, thence through pipe 8 l to the annular chamber l2 be tween inner and outer cylinders l and 8 respectively. From this'chamber the chlorine issues through pipe l3 and is delivered to the point of use, whatever it may he as the chlorination of paper pulp described. in co-pending applications Serial Nos. 547,755 and 694,171. The pressure upon a chlorine drum under equilibrium conditions at ordinary temperatures will be about lbs. per square inch. The drop in pressure in the.

piping may easily be 15 lbs. The back pressure to at the point of use may be 40 lbs. leaving a net drop of 45 lbs. at the needle valve. This will cause suflicient chlorine to vaporize beyond the needle valve and in the chamber I 2 to reliqueiy any chlorine that may have broken into gas on the way from drum i.

In order to illustrate that my method of control is not limited to any one type of meter, in Figure 2 I have shown a common type of metering orifice and U tube for indicating the flow.

To illustrate that my method of control is applicable broadly .to valve control, with or without metering, in Figure 3 I have shown the valve and heat exchanger connected in accordance with my method, the meter being omitted altogether.

By the use of this simple arrangement of known elements, the necessity of using excess air pressure is avoided and the difllculties arising from such a pressure, or without it from the chlorine breaking into bubbles, is completely obviated. The source of chlorine may be placed at any convenient point and the meter and control valve located wherever desired within reasonable limits. The heat exchanger required is a simple, durable and inexpensive affair. Within a few seconds after turning on a flow of chlorine that may have been standing in pipe 5 and become completely vaporized, the chlorine in the meter and control valve will be 100 per cent liquid and from that time on no vapor can occur at this point. The control of the flow of chlorine is thereby rendered simple, accurate and reliable.

What I claim is: l. The method of metering the flow of volatile ture below the equilibrium temperature of saidfluid at the up-stream side of said point by efleoting a transfer of heat from said stream to vaporize liquid of the stream leaving said point.

3. The method of metering the flow oi fluid, including components thereof in liquid and vapor phase, which includes the step of cooling the stream of fluid approaching the point of metering to a temperature below the equilibrium temperature of said fluid corresponding to the pressure at the up-stream side of said point by eifecting a transfer of heat from said stream-*to vaporize liquid of the stream leaving said point.

4. The method of metering the.flow of fluid.

including components thereof in liquid and vapor phase, which includes the step of cooling the stream of fluid approaching the point of metering to a temperature-below the equilibrium temperature or said fluid corresponding to the lowest pressure likely to develop at the up-stream side of said point, thereby reliquefying the fluid in vapor phase and stabilizing the stream in liquid phase, by effecting a transfer c1 heat from said stream to vaporize liquid of the stream leaving said point.

5. The method of metering the flow of volatile fluids which includes the step of vaporizing a part of the stream of fluid leaving the point of metering and eflecting a transfer of heat to said stream from thestream of fluid approaching said point to cool said last mentioned stream to a temperature below the equilibrium temperature of said fluid at the up-stream side of said point.

6. The method of metering the flow of volatile fluids which includes the step of restricting the flow for regulation thereof, thereby causing drop of pressure and vaporization of a part of the stream of fluid leaving the point of restriction, and efiecting a transfer of heat to said stream fromthe stream offluid approaching said point of restriction to cool said last mentioned stream to a temperature below the equilibrium temperature of said fluid at the up-stream side of said point of. restriction and metering the stream approaching said point of restriction in liquid phase.

7. The method of controlling the flow of a stream of volatile fluid which comprises regulating the rate of flow thereof, eifecting a heat transfer from the stream approaching the point of regulation to the stream leaving said point of regulation and metering'said approaching stream in liquid phasebetween the point of heat transfer and said point of regulation.

8. The method of metering a stream of volatile fluid including components thereof in liquid and vapor phase which comprises reducing the pressure upon said stream and vaporizing a portion thereof, effecting a heat transfer from said stream in advance of the point of pressure reduction to supply the heat of vaporization of said vaporized ao portion, and metering said stream between said point of heat transfer and said point of pressure reduction in liquid phase.

9. The method of metering and controlling, inv

liquid phase, at a point higher than its point of origin, the rate of flow of, a stream of volatile fluid under equilibrium conditions of temperature and pressure, which comprises regulating said flow, efiecting a heat transfer from the stream approaching the point of regulation to the stream 40 leaving said point of regulation and metering said approaching stream in liquid phase between the point of heat transfer and said point of regulation.

10. The method of metering and controlling in liquid phase, at a point remote from its source, the rate of flow of a stream of volatile fluids from a source under equilibrium conditions of temperature and pressure, which consists in regulating said flow, effecting a heat transfer from the stream approaching the point of regulation to the stream leaving said point oi regulation and metering said approaching stream in liquid phase between the point of heat transfer and said point of regulation.

11.' An apparatus for metering and controlling the rate of flow of a stream of volatile liquid comprising a heat exchanger, a conduit for conveying said stream theret ugh, a meter, 9. conduit for conveying said ream from said heat exchanger to said meter, a control valve, a conduit for conveying said stream from said meter to said control valve, a conduit for conveying said stream from said control valve through said heat exchanger and a conduit for delivering said 66 stream from said heat exchanger, whereby the pressure upon said stream is reduced by said. control valve and a portion of said stream vaporized at and beyond said control valve and the heat-of vaporization of said portion is ex- 70 tracted from the stream approaching said meter to maintain said last mentioned stream in liquid phas KENNEI'H n. STUART.

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