US2501276A - Vacuum production apparatus - Google Patents

Description

March .21, 1950 K. c. D. HlcKMAN 2,501,276

vAcuuu PRODUCTION APPARATUS Filed June 14, 1945 Q Ww- FROM SYSTEM 7U 5E EVACUATED g U) n N U 5 n Q u no 5 I KENNETH C.D.H1CK1\4AN Q Si: INVENTog ATTORNEY named Mu. 21, 195o A VACUUM PRODUCTION APPARATUS Kenneth C. D. Hickman, Rochester, N. Y., as-

signor, by mesne assignments, to Eastman Kodak Company, Rochester, N. Y., a corporation oi' New Jersey Application June 14, 1945, Serial No. 599,381

6 Claims. (CL423Il-101) 1 'mais invention relates to improvements in process and apparatus for producing rarefied atmospheres by means of ejector orv condensation Dumps.

Condensation and ,ejector pumps actuated by.

organic working uids are well known in the art. It has also been known to utilize multistage ejector or condensation pumps actuated with organic working fluids and to fractionate the working iluid during operation and to deliver appropriate fractions to appropriatev jets, i. e., high vapor pressure fractions are delivered to jets operating against the higher pressures, while low vapor pressure constituents are delivered to jets operating against low pressures.

This invention has for its Object to provide improved ejector and condensation pumps of the foregoing type. Another object is to provide improved pumping procedure whereby a system can be evacuated with an organic working fluid lssuing through an ejector or condensation pump nozzle. A still further object is to provide a multistage pump actuated with an organic vapor propellant which, during operation, will have high speed when large volumetric capacity is required lied atmosphere with an organic vapor propellant pump by delivering organic propellant to the jet of the pump so that high vapor pressure components are used during the stage in the pumping operation when large volumetric capacity and moderate pressures are required and by .delivering low vapor pressure propellant components during the stage when lower pressures and lower volumetric capacity are required.

In the following examples and description I have set forth several of the preferred embodiments'of my invention but it is to be understood these are given by way of illustration and not in limitation thereof.

In the accompanying drawing I have illustrated in a single figure a vertical section of a multistage organic vapor propellant pump embodying the principles of my invention. Referring to the drawing, numerals 6, 8 and`I0 designate a plurality of pumps connected ln series by conduits I2 and I4, respectively. Pump III operates against the lowest pressure and produces the lowest pressure in its low pressure end I6, which is to be connected to the system to be evacuated (not shown). Pump 6 operates against the highest backing pressure and its high pressure end I8 is connected to a backing pump (not shown). Numerals 28, 22 and 26designate boilers which supply actuating vapor to pumps 6, 8 and I0 respectively by way of conduits 28, 30, and 32. These conduits terminate in jet nozzles 34, 36 and 38. Pumps 6, 8 and I0 are provided with diffuser tubes 40, 42 and 48 respectively, which cooperate with the jet nozzles 34, 36 and 38, to form a pumping unit. Each of these diiusers is surrounded by a jacket through which cooling fluid is circulated.

Numeral 50 designates a conduit which serves to collect spent pumping iiuid draining from the high pressure end of pumps 6, 8 and I0. This conduit is provided with U tubes 52 and 54 which,

- during operation, are filled with liquid and thus prevent passage of gas from the high pressure end of one pump into the high pressure end of the other. Conduit 5U drains into a reservoir 5| containing pump fluid 53 which is connected by conduit 56 to circulating pump 58. Conduit 60 leads from the outlet of pump 58 to boiler 2D, provided with a plurality of baiiies 62. A U tube 64 connects boiler 20 with boiler 22, which is also provided with a plurality of bales 66. U tube 68 connects boiler 22 with boiler 26, also provided with bales 10. Numeral 'I2 indicates a conduit through which liquid overflowing from boiler 26 flows into reservoir 5I. Numerals 14, 'I6 and I8 designate heaters for boilers 20, '22 and 26, respectively.

Numeral designates an electric motor which drives pump 5B, the source of electric energy being designated at 82. One terminal of the source of electric power leads to a manometer device 84 filled with an electrical conducting liquid, s uch as mercury. One end of the manometer is connected to the high pressure end of pump 6 by conduit 86. Numerals 88, and 92 designate electric leads which terminate inside manometer 84 and make electrical contact with the mercury therein, depending on its height, and which lead to an electric resistor 94, one end of which leads to motor 80 and delivers current thereto in cooperation with the other lead wire 96. This arrangement constitutes a monitoring device automatically supplying pump fluid according to variations in pressure in the pump.

In operating the apparatus illustrated in the drawing a suitable pump fluid, such as a fraction of a petroleum oil, such as described in Hickman Patent 2,379,436, dated July 3, 1945, or a synthetic duid, such as di-amyl phthalate, di-octyl phthalate, or mixtures thereof, is introduced into the boilers 20,22 and 26 and reservoir 5I. The backing pump connected to conduit I8 is actuated and conduit I6 is connected to the system to be evacuated. Pump 58 is then actuated by current supplied to leads 82. Heating units 14, 16 and 18 are put into operation. Vapors from boiler 28 pass through conduit 28 and issue as a pump stream through nozzle 34. 'The vapors entrain gases from conduit l2 and force them into the opposite and high pressure end of pump 6. The spent pump fluid is condensed on the cool walls of diffuser 40 and flows by gravity into U tube 52 and thence into conduit 50. Gases from the high pressure end of pump 6 are removed by the backing pump connected to conduit I8. The same action takes place in connection with pump 8, vapors from boiler 22 passingthrough jet nozzle 86 and forcing vapors from conduit I4 into con'- duit I2. Spent condensed pump fluid flows through U tube 54 into conduit 50. Similarly vapors from boiler' 26 pass through nozzle 38 of pump I 8, forcing gases from I6 into conduit I4. Spent pump fluid :flows into conduit 58 and thence into reservoir I. The liquid in reservoir 5i is then withdrawn by pump 58 and returned to boiler 28. Any over-supply of liquid thus returned or unvaporized overflows into U tube 64 and flows thence into boiler 22. Liquid unvaporized in boiler 22 overflows into U tube 68 and flows into boiler 26. Excess liquid is then returned to reservoir 5I through conduit 12.

Manometer 84 is adjusted so that when high pressures exist in pump 6 the column of mercury makes contact with lead wire 88 and then supplies the full current to motor 88. Pump 58 is, therefore, run at high speed and supplies a large volume of pump fluid to boiler 26 when high pressures exist in pump 6. On the other hand, when low pressures exist in pump 6 the column of mercury falls and makes contact only with lead wire 92, which necessitates passage of the electric current through the entire resistor 94. This cuts down the speed of motor 80 and consequently the speed of pump 58 so that low volumes of pump fluid are delivered to boiler when the pressure in pump 6 is low. The pressures in pumps 6, 8 and l0 vary together so that the conditions of supply of pump fluid to pumps 8 and i8 are the same as for pump 6. Intermediate lead 90 gives an intermediate speed to motor 80 and pump 56 when the pressure in pump 6 is intermediate. It will be appreciated that there is fractionation of the pump fluid in each of the boilers 2l), 22 and 26. This fractionation is particularly effective when low volumes of liquid are supplied. The baffles 62, 66 and 10 somewhat 4slow the passage of the pump iluid in the boilers and increase the fractonating effect.

While I have illustrated heating the boilers with an electric resistor, other methods of heating such as, for instance, steam may be used. The boilers may be all heated to the same temperature or graduated heat may be employed. A constant heat input is preferred, i. e., one using a constant l t. u. input (electric or gas heat) with variable temperature or a constant temperature input (such as steam heat) with a variable B. t. u.

supply.

Let it be supposed that all of the boilers 2U, 22 and 26 are surrounded by steam jackets heated by steam at 180 C. and that a mixed organic liquid is furnished by the reservoir 6l such that l. pressure of 1/2 an atmosphere is produced in boiler 20 during the ilrst few minutes of oper ation. As vaporization of the pump fluid takes place, the lighter constituents will be distilled out and will pass through jet nozzle 34 and the pressure in boiler 20 would, therefore, fall. however, pump fluid is supplied to the boiler at such a rate as to supply the volatile constituents as fast as they are evaporated, the pressure in boiler 20 will remain ilxed at about 1A an atmos- This condition implies that a quantity of pump uid freed of these more volatile constituents will overflow through 64 into the boiler 22. Here evaporation continues but, since the volatiles have been removed and the temperature is substantially the same as the boiler 20, the pressure of vapors in the boiler 22 will be less at say I/m of an atmosphere. The process continuing, the residue from boiler 22 will pass through 68 into boiler 26 which, in turn, will discharge the final pump fluid residue through conduit l2 into reservoir 5i. The pressure in boiler 26 may be only a few inches by oil manometer.

The state of aiairs just described is for normal operation. However, suppose that there is a heavy load on the system in the starting period. This will be reflected quite exactly in increased forepressure in pump 6. This will increase the height of the mercury ln manometer 84 and will increase the speed of pump 58, with the result that more volatile oil will enter boiler 20 and consderably more volatile fractions will overflow into boilers 22 and 25. This will raise the pressure in all the boilers and will result in increased volumetric pumping capacity at the expense 4of ultimate vacuum. However, ultimate vacuum is not now important, since the system is overloaded and throughput alone is of importance.

Consider the opposite case. The system to be evacuated has steadied down, i. e., the volume of gases to be removed is lower, the vacuum is improving and the forepressure in i8 falls to an abnormally low value. The manometer control then shifts to lower the speed of pump 58, which lowers the speed of delivery of pump iluid to the boilers 20, 22 and 26. The more volatile constituents are more or less completely removed in boiler 20 so that only intermediate constituents ilow into boiler 22 and only the lowest vapor pressure constituents into boiler 26. The operating pressure, therefore, falls in all of the boilers but the average boiling point of the operating iluid in each of the boilers rises and, therefore, the ultimate vacuum ofthe system improves and there is a large increase in degree cf evacuation, as well as pumping speed at the low pressure.

What I claim is:

1. A fractionating multistage organic vapor propellant pump which comprises a plurality of vapor condensation pumps, a plurality of interconnected boiler compartments to each of which is connected one of said vapor condensation pumps, heating means for each boiler compartment, a circulatory passage for pump iluid through said boiler compartments, means for conveying condensed pump fluid from each vapor condensation pump to said circulatory passage, and a controllable pump means in said circulatory passage for regulating the rate of ilow of pump fluid through said boiler compartments whereby the degree of fractionation of pump fluid may be controlled.

2. A fractionating multistage organic vapor propellant pump which comprises a plurality of vapor condensation pumps, a plurality of boiler compartments to each of which is connected one of said vapor condensation pumps, heating means for each boiler compartment, a circulatory passage for pump iluid through said boiler compartcirculating pumping iiuid through said channeling means, heating means along said channeling means for producing vapors of pumping iluid at a plurality of zones along said channeling means, vapor condensation pumping means communicating with said channeling means at said zones, means connecting said pumping means with said channeling means for returning condensed pumping iiuid from said pumping means to said channeling means, and pressure-responsive controlling means communicating with said pumping means and connected with said circulating means for varying the circulatory rate of said circulating means in response to variations in pressure in said apparatus.

4. Vacuum pumping apparatus comprising in combination liquid-channeling means, circulating means associated with said channeling means for maintaining in continuous circulation through said channeling means a stream of organic liquid comprising constituents boiling at diierent temperatures, a plurality of heating means at spaced apart zones along said channeling means for ments, a pump fluid comprised of constituents neling means at the iirst of said zones along said channeling means, and pressure-responsive controlling means associated with said circulating means for controlling the rate of circulation of liquid through said channeling means, said controlling means being eiective to accelerate said rate of circulation with increases in pressure in said apparatus and to decelerate said rate of producing in said zones vapors oi different compositions, vapor condensation pumping means communicating with said channeling means at each of said zones, condensing means for said pumping means, means for returning condensate from said condensing means to said chancirculation as said pressure decreases.

A5. A fractionating multistage organic vapor propellant pump which is adapted to fractionate the organic working iiuid and deliver fractionated components to appropriate stages of the pump, which pump comprises in combination a plurality of boiler compartments, a plurality of jets, means connecting each said boiler compartment with at least one of said jets for delivering-vapors from said compartments to said jets, means for supplying pumping fluid to said boiler compartments, and means for varying the' composition of pump iluid supplied-to each said boiler compartment so that components of relatively high vapor pressure are vaporized during that part of the pumping operation when large volumetric capacity and moderate pressures are required and so that components of relatively low vapor pressure are vaporized during that part of the pumping operation when lower pressures and lower volumetric capacity are required.

6. Apparatus as defined in claim 5 wherein said means for varying the composition of pump uid comprises a monitoring device actuated by variations in` pressure in the pump for automatically varying the composition oi pump fluid supplied to the pump. y Y

KENNETH C. D. HICKMAN.

REFERENCES CITED The following references iile of this patent:

UNI'IED STATES PATENTS l Date Number a Name 2,153,189 Hickman Apr. 4, 1939 2,379,436

Hickmanet al. vJuly 3, 1945 are of record in the

Images