US2786626A - Process for the compression of gases - Google Patents

Description

March 26, 1957 A. K. REDCAY PROCESS FOR THE COMPRESSION OF GASES Filed Aug. 7, 1952 F1 Ci. 1. -t 1o 6 ,ucauxb l COOQLHIN'T NJCTIOQN 1] 2 Shets-Sheet 1 IN V EN TOR. *VKR N B- RE AY ms ATTo mey March 26, 1957 K REDCAY 2,786,626

PROCESS FOR THE COMPRESSION OF GASES Filed Aug. 7; 1952 2 Sheets-Sheet 2 FIG. 2.

GAS COMPRESSION WITHOUT LIQUID INJlEC/IION 0R INT/ERSTBGF COOLING 6 PSIR 132 mix-:0. --1soo 6 0 $377,351}; HP '25"? 3) 174 105"? FI G. 25.

GAS C MPRE SION WITH INTERSTAGE COOLING.

53.'? Pau 75%EFF-- 2220 96 MPRE I N ITH LIQUID INJECTION- I H-P THO.--- 125 P5126 FF---168O 105? wsmn INJE CT ION IN VEN TOR.

AARON K- RED A flIS ETTORNEY United States Patent PROCESS FOR THE COMPRESSION OF GASES Aaron K. Redcay, MountLebanon, Pa., assignor to Gulf Oil Corporatiomlittsburgh, Pa., a corporation of Pennsylvania Application August 7, 1952, Serial No. 303,181 1 Claim. or. 230-209 This invention relates to a process for the compression of gases and more particularly to an improved method for the handling of ajgas or mixture of gases undergoing compression in a centrifugal compressor.

In the case of a purely adiabatic compression of a gas, which is, by definition, one in which no heat is added to or removed from the gas during compression, there is nevertheless an increase in the temperature of the gas. This increase in temperature is a manifestation of a change in form of the mechanical work done on the gas into heat energy within the gas. In addition, the inefficiency of a centrifugal compressor changes gas conditions within the compressor so that in practice an adiabatic compression is not achieved. For example, various energy losses taking place within the compressor such as mechanical friction, gas friction and turbulence are all transformed into heat and raise the temperature of the gas beyond that calculated from adiabatic compression conditions.

This increase in temperature, or internal energy res-ulting from those causes discussed above may haveparticularly detrimental effects. In the case of any gas the increased internal energy of the gas makes further compression more diflicult and expensive by virtue of the extra work required. In the case of many normally gaseous hydrocarbons, particularly hydrocarbon-containing gases such as inflammable gas-es like gas mixtures containing acetylene; and refinery gases and those derived from the cracking of normally gaseous hydrocarbons, such as ethane and propane, at the elevated temperatures resulting during compression, the gases or mixtures of gases may be thermally sensitive; that is, they may be reactive at the temperatures attained during compression to undergo decomposition, alkylation, or polymerization reactions and the like. p 7

Since the foregoing hydrocarbon-containing gases contain valuable constituents, such as ethylene, it has become can polymerize eitherlby themselves or-in a-copolyn'ieri'za tion reaction with the mono-olefinic hydrocarbons'{ to form solid polymers which tend to plug up subsequent-i separating apparatus and represent a loss-of valuable" components. Similarly the diene hydrocarbons or the; mono-olefinic hydrocarbons can become involved in at: kylationr'eac'tions with each other or with the saturated hydrocarbons, againresulting'in 'a loss of valuable centponents. V

Conventional methods for controllingthe 'increasein temperature 'of gases being compressed have employed 1 multistage compressors with interstagecooling by means of indirect heat exchange. The volume of ordinary cooling media in such a case is so great, however, as to entail a large capital investment for coolers. Furthermore, a considerable increase is required in the number of cornpression stages to achieve sufiicient finalcompressionof customary to subject such gases to various separationprocesses to recover the valuable constituents therefrom; The separation processes employed have included fractional distillation, oil absorption or extraction, or combinations of such processes. In any of these processes, it is necessary to at least partially liquefy the initial gaseous mixture, such liquefaction involving compression of the gases followed by cooling. in compressing thermally sensitive hydrocarbon-containing gases for the purpose of liquefying them, the controlled temperatures attained during compression tend to cause thermal reactions, thereby resulting in a loss of valuable components of the gaseous I standard design. I through suction inlet 10 at which point vaporizable liquid the gases. 7, H

It is therefore an object of this invention to compress a thermally sensitive, hydrocarbon-containing gaseous mix ture while avoiding thermal reactions of such mixture.

It is also an object of this invention to limit the in-; crease in temperature normally encountered in the centrif-1i ugal compression of athermal-ly sensitive hydrocarboncontaining gas. 4

A further object of this invention is to reduce the power" required to compress a thermallyv sensitive, hydrocarbon. containing gas in a centrifugal compressor.

These and other objects areachieved by the presentinvention wherein, in the centrifugal'compression of hyi', drocarbon-containing gases also containing thermally sensitive constituents, there is injected into the gases undergoing compression a vaporizable liquid. The vaporization of the vaporizable liquid in the stream of gases undergoing compression serves to cool the compressed gases, and thus produces a temperature level within said gases lower than the temperature which would otherwisebe attained by reason of the normal heat of compression. Thermal reaction of the thermally sensitive gases isthereby avoided. Furthermore, as compared with conventional compression, less power is required to compress the gases to the same pressure.

- In order more fully to describe my invention reference is made to the accompanying drawings in which:

Fig. 1 is a cross-sectional view of a standard centrifugal compressor, four pressure stages of compressionbeingrepresented, in which liquid injectors have been incorporated;

Fig. .2'is a diagrammaticalrepresentation of operating conditions and eifects'where gascompression is achieved without either liquid injection'or interstage cooling;

Fig. 3 is a diagrammatical representation of operating conditions and effects where'gas compression is achieved with interstage cooling;

Fig. 4 is adiagrammaticalrepresentation of operating; conditions and effects Where liquid 'is injected in accordance with my invention.

The centrifugal compressor shown in Fig. 1 is of The gases to be compressed enter-i may be injected through atomizer 11. The vaporizable; liquid vaporizes within the stream of gases to becom pressed, and in so doing an amount 'of heat equaljtothe heat of evaporation of the vaporizable liquid is abstracted. from the stream of gases being compressed, thereby cooling the gases. The cooled gases then pass through inlet guide vane '12 into impeller 13 attached to rotating shaft 14. The high angular velocity of the shaft and impeller throws the gases centrifugally through passage way 15 into deflector 16 at which point more vaporizable liquid can be injected through atomizer 17 to achieve a direct cooling of the gases being compressed in the same jection or interstage cooling the gaseous mixture requires seven stages of compression to be raised from 33.7 p. s. i. a. to 85 p. s. i. a'., with a power requirement of 1740 horsepower. In compressing the gases through pellers 1-9 and 20, in eachof-which the gases undergo 5 the seven stages they are heated from an initial temfurther eompressiontwithcooling betweentpressure stages perature of 105 F. to a discharge temperature of 280 by the injection of vaporizable liquid-from atomizers 21 F. Such a discharge temperature will tend to cause therand 22. Finally, the compressed. gases are discharged mal reaction of the thermally sensitive constituents.- through-outlet 23. Elements 24 through 28 inclusive, Fig. 3 indicates that, to achieve the same degree of represent drainplugs located inthe lower portion of the compression With interstage cooling of the gases at the compressor casing for removal of any liquids that may points indicated, eight stages'are required with a horsecollect at those points during compression. power requirement of 2220. The discharge temperature As vaporizable liquids'for injection into the gases being of the gases is 214 F. compressed I can employ any liquid which is vaporized When water is injected into the gases being compressed toa substantial extent at the pressures and temperatures in accordance with my invention, as represented in Fig. 4, existing at the point of injection. For example, water only six stages of compression and only 1680 horsepower can be used to good'elfect, sutficient vaporization taking are required to compress the gases to the same pressure, place even at temperaturesbelow its boiling. point at the namely, 85 p. s. i. a., achieved in the methods shown pressurev involved to exert a cooling. effect. A liquefied in' Figs} 2 and 3. The discharge temperature of the gases normally gaseous hydrocarbon, such. as liquid ethane, or is 219 F; it is to be borne in mind that" the discharge propane, or low boiling normally liquid hydrocarbon,- temperature and power requirements may be even further such as pentane or hexane can also be employed. In reduced by injection of water into a greater number of some cases mixtures of water and hydrocarbons can be pressure stages. employed, or water can be employed in some compres- The foregoing example clearly shows the temperature sion stages such as the initial stages, and hydrocarbons control achieved and the powersavings and reduction in in the other compression stages, such as the later stages. compressor size that are made possible by the injection It. is'preferred to employ asthe vaporizable liquid' water of vaporizable liquidsinto a stream of a thermally sensiobtained from cooling the compressed gas to at least partive, hydrocarbon-containing gaseous mixture undergoing tially liquefy the vwater component. compression. Such temperature control effectuates econ- The' following example shoWs the elfect of water inomies by preventing (l) costly losses of a portion of jection in the compression of a hydrocarbon-containing reactive gases through their polymerization, alkylation gaseous mixture,- the results being illustrated diagram and the like, and (,2) operating difficulties that may be matically in Figs. 2, 3 and 4. The charge gas has the folcaused thereby. The reduction in'compressor size that 1Wlfig0mP0$1tl01E is possible by the method of my invention is another Charge gas economy attained. In addition, heavy and expensive Component. v01. percent heat exchangers and piping such as are used in Figure 3 Hydrogen 2&1 to achieve indirect cooling, can be ellmmated with re- Methane sultant reduction of installation costs. Ethykm. 3L9 Although I have disclosed the use of water as the va- Acetylene 0'4 40 porizable liquid-in the specific example, it will be ob- Ethane 261 vious that any other vaporizable liquid which vaporizes propylene 1.2 at the pressures and temperatures existing at the point of propane; ()5 injection can. be employed. In addition, compressors Bm 1 5 having more or less pressure stages thanthat shown in Water 3 7 Figure 1 can be employed. Furthermore, the vaporizable liquid can be injected into the gases entering the 100.0 suction of the compressor, directly into the compressor Flg}; 2 a 4 No Water Injection Interstage Cooling Water Injection or Interstage Cooling Press, Temp., Press, Temp., Press, Temp, p. s. i. a. T. p..s .1 a T. p. s.i :1 F.

Suction Sta-gem tone-"- 3: 3313 $3 1313 .133 3335 i2? Stage 2eDischarge 47. 0 160 47. 0 160 47. 0 160 Stage 3 ischar e 64 0 186 iit b e iiis ltfl sta es Discharge- 62:0 210 a i C 191, W 84 i t 196 SW DH v ers a e 00 er ater njec ion at 227 iii a I a stage-1 mscnsrgennua 85.0 280 000E557 Y? j l f i sta spsDischarges 85 214 B. P,.The0. 1, 00 1,667 1 259 B. H. P. 1, 740 2,220 1; 680

v In'the example and in Figs. 2, 3 and 4, the theoretical itself, between the stages of a multistage compressor, or horsepower requirement of'the variou methods repreat any or all of these points. Moreover, an amount of sented therein is the calculated horsepower required. to vaporizable liquid can be injected into the stream of gases compress thegases delivered by the compressor through undergoing compression in excess of that completely vathe sgecl f iedrange' of pressures. The actual horsepower porized. The unvaporized liquid would be discharged in requirement isbas'edon a percent effi'eiency. the compressed gases at the compressor outlet.

Fig. 2 shows that without either vaporizabl'e liquid in 75 Qbviously 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.

I claim:

A method of centrifugally compressing a gaseous mixture containing as constituents hydrogen, methane, acetylene, ethylene, ethane, propylene, propane, butanes, butylenes, related dienes and water while controlling the temperature of compression to avoid reactions to which the constituents would be subject under normal uncontrolled compression, which comprises compressing said mixture, injecting into said mixture,a vaporizable liquid, which liquid is vaporized to a substantial extent at the pressures and temperatures existing at the point of injection, atomizing said vaporizable liquid, and continuing the injection and atomization until said vaporizable liquid is vaporized to a substantial extent in said gaseous mixture, thereby lowering the temperature of the aforesaid mixture to avoid thermal reactions of the constituents in the mixture undergoing compression.

References Cited in the file of this patent UNITED STATES PATENTS 1,400,813 Graerniger Dec. 20, 1921 1,751,537 Vianello Mar. 25, 1930 2,164,761 Ashley July 4, 1939 2,280,845 Parker Apr. 28, 1942

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