US2140462A - Refrigerating method and apparatus - Google Patents

Description

Dec. 13, 1938. c. w. sTRATFoRD 2,140,452

REFRIGERATING METHOD AND APPARATUS Filed Jan. 18, 1937 ATTORNEY.

Patented-Dec'. 13, 193:5

' UNITED STATES',

PATENTA oFFlcE 2,140,462 REFRIGERATING METHOD AND APPAaA'rU Charles W. Stratford, Kansas ity, Mo., assignor to Stratford Development Corporation, Kansas City,y Mo., a corporation of Delaware Application January 18, 1937, Serial No. 121,033 6 Claims. (Cl. 62-126) My invention relates to a refrigerating method and apparatus, 4and more particularly to a refrigerating method and apparatus for use in refrigerating hydrocarbon oils vundergoing treatmentjin which exothermic reactions take place,`

as, for example, the treatment of hydrocarbon oil with sulphuric acid.

One object of my invention is to provide a method of and apparatus for maintaining 'a con- 10 stant maximum temperature to which the chemical reaction between sulphuric acid and hydro-l carbon oil is allowed to proceed.

Another object of my invention is to provide a method of and apparatus for, in the processing 16 of materials in which an exothermic reaction takes place, absorbing the heat of reaction at vide a method of and apparatus for refrigerating inl which the heat transfer rate of a chillerheat exchanger is increased by continuously evaporating -a liquefied refrigerant gas from a vheat exchanger coil positioned within an evaporating zone, through which heat exchanger coil fluid to be processed is passedn 'A further object of my invention is to provide -a method of and apparatus for refrigerating in which a high heat transferrate within a heat exchange zone is maintained by the circulation of a large quantity of liquefied refrigerant gas.

A still further object of my invention is` to' provide a method of-and apparatus for regulating the temperature of reactants in-response to the iinaltemperature of these leaving thetreating zone. A

Other and further objects ofy myinvention will appear from the following description,

describe my m thod and the operation lof my apparatus with eference to ammonia gas as therefrigerant uid. *It is to be understood, however, that this is only for 'the purpose of clarity i and illustration, and that any suitable refrig- A further object of my invention is to pro- For purposes of clarity and convenience, I will erant fluid, such as ethyl chloride, sulphur dioxide or the like, may be used.

As is well known to the art, in a mechanical refrigerating system a refrigerant gas is compressed, the heat of compression removed by heat exchange in what is known 4as a condenser". ,The condensed refrigerant gas (which is then usually in a liquid state) `is then expanded through an expansion valve into `a zone of reduced pressure, as for example, into an elongated conduit in the form of a coil which isv usually termed the refrigerating coil. Upon expansion the liquefied refrigerant reassumes a gaseous state and passes to the compressor for re-compression and recycling. The eiliciency of an ammonia compressor will vary as a function of the suction pressure.

My apparatus and method has in view the absorbing of the heat of reaction as rapidly as it is created in order to reduce the temperature range, whereby I am enabled to operate my system at a high suction pressure of the compressor.

The accompanying drawing represents a diagrammatic view of a refrigerating system .for

contacting hydrocarbon oil with acid in the acid treatment thereof, in which the temperature is controlled by refrigeration, embodying apparatus of my invention which is capable of carrying out the process ofmy invention.

While my process and apparatus will be described with reference to: hydrocarbon oilsfor purposes of illustration,lit is to be understood that it is applicable to any chilling or refrigerating use.

The hydrocarbon distillate to be treated is stored intank l, from which it is pumped by pump 2 through'line to a settling tank 4 in which bottom settlings, water and other impurities are permitted to settle and periodically drained through line 5, controlledby valve ii. The distillate after settling is withdrawn from the settler l through line 1 and passes through heat exchanger 8, in which the oil is' cooled by heat exchange against the treated distillate entering heat exchanger through line 9 and leaving it` through line l0. The treated distillate, as will be hereinafter seen, has been refrigerated and after leaving the separating step ii which thetmtreating agent is separated, is pumpedl through line 9. The heat exchange is usually `vsuiiicient to lower the temperature of the dxistillate considerably, for examp1e, to say'404F. for purposes of illustration.- The cooled distillate leaves the heat exchanger through line Il and maybe passed directly to the distillate4 inducthe position of valve I6 controlling line I3, and

the position of valves I1 and I8 controlling coil I4. If desired, a portion of the distillate may be passed both through line I3 and through coil I4 by partially opening valves I6, I1 and I8. Coil I4 is positioned within a chilling chamber I9, which will be hereinafter more fully described. The distillate to be chilled is admxed in line I5 with the treating agent, as for example acid, lbeing pumped from any suitable supply by pump 22, through line 28, controlled by valve 2l.

'I'he mixture of treating agent and distillate enters the heat Yexchanger I2 in which the heat of reaction is removed, it being my purpose to remove the heat of reaction as fast as it is liberated and to employ as small a mean temperature difference as is permitted bythe amount of heat transfer surface and the velocity of iiow of the refrigerant and reacting mixture through the heat exchanger. 'The chilled distillate-acid mixture vleaves the heat exchanger I2 through `line 23, `which is iitted with a thermometerwell supplied with a cooling medium through line f 32, which leaves through line 33.

In the condenser 3| the compressed ammonia gasI will be liquefied and will leave in liqueed condition through line 34 and pass into receiver 35,' fromwhich it is withdrawn through line 36 and discharged through liquid levelcontrol 31 into the chiller I9. The liquid level control is well known to the art -and in general comprises a valve controlled by the level of the liquid within a vessel. In the instant case, the liquid llevel control 31' will maintain a body of liquid aml monia 38 within the chilll chamber` I9. When the desired level is reached, the liquid level control opera'tes to prevent the induction of further liquidy ammonia. When the level of the ammcnia within chill chamber I9 drops, the level control operates to permit further ammonia toy ow into the chill chamber to bring the level to monia and liquid ammonia. This is discharged intolchill chamber I9 through a spray head 43. Liquid ammonia falling downwardly, as indicated by the arrows, allows separated gaseous ammonia to be withdrawn through line 44 for passage through control valve 26 into line 29 to the suction of thecompressor. y

l,Considering now the operation of my system with valves I1 and I8 closed, and valve I6 open,

`all of the hydrocarbon distillate to be treated will bypass chilling coil I4. Let us' assume that it is desired to conduct the treating reaction so that the outlet temperature of the distillatefacid mix ture will not be in excess of F. and the temperature of the incoming distillate to be treated has been pre-cooled by heat exchanger 8 to a temperature of F. r v

As the outlet temperature of the distillate-acid mixture tends to exceed 20 F., the arrangement is such that pressure controller 25 is operated to reduce the air pressure impressed upon control diaphragm through line 46 to permitvvalve 26 to open to a greater extent. This reduces the back pressure upon thechill chamber I9 and permits a larger volume of liquid ammonia to evaporate, which in turn lowers the temperature of the body of liquid ammonia 38, as well as permitting a greater expansion of ammonia within the heat exchange elements of heat exchanger I2. 1

Since the heat transfer surface of the heat exchange elements within heatexchanger I2 is limited, it will be obvious that under certain con- 'ditions the back pressure in thev ammonia sys- ,tem of the heat exchanger may be reduced to such a point that compressor 21 will be operat- 'ing under a considerably lowered suction pressure. As pointed out hereinbefore, this renders the operation of the ammonia compressor inefcient. I

Let us now consider the operation withV the (valve I6 closed, and valves I1 and I8 open. I'he distillate will be further chilled by heat exchange with ammonia being sprayed` over the coil from spray head 43. The temperature will be lowered by the evaporation of ammonia through heat supplied from the distillate by heat exchange. This reduction in temperature can be effected without decreasing l the back pressure of the ammonia system in heat exchanger I2, since in effect coil I4 acts as the heating coil of a still and the evaporation of additional ammonia by transfer of heat from the coil I4 .to ithe liquid ammonia being sprayed thereover will in effect raise the su'ction pressure at which the ammonia gas is passed to the compressor 21.

Since the distillate is 'much greater volume than the treating agent, and the distillate is precooled, aqnuch smaller load is placed upon the heat exchanger I 2. Should the temperature tend to be lowered under the desired treating tem-4 perature of 20 F., the temperature responsive element in well 24 will operate temperature controller 25 to ,increase the air pressure impressed upon diaphragm 45 through line 46. This will cause'the valve 26 to tend to close, thus further increasing the back pressure upon the chill chamber I9 and enabling the compressor to. operate at a `higher suction pressure andthus more efficiently. Should the temperature of the distillate-acid mixture tend to exceed the desired treating temperature of 20 F.,vthe valve 26 is moved to open somewhat, decreasing the back pressure upon the chill chamber I9. This enables, the liquid ammonia being sprayed over the coil I4 toevaporate to Va greater extent, that is,

la, larger quantity of ammonia will be evaporated by the heat supplied from the distillate in coil I4. 'I'his in turn will cool the distillateV to a greater extent and will, in addition, ,permit a greater quantity of heat to beremoved in heat exchanger I2, thus enabling the additional'heat load to be carried at a -smaller decrease of back pressure than would otherwise be possible.

' It will be apparent that by the use of my method and apparatus the back pressure in the chill vchamber will vary as an exponential function of the outlet temperature of the acid-distillate mixture, instead of as an aritl'nnetical4 In this manner function of said temperature. it will be obvious to those skilled in the art that I have provided a very flexible refrigerating system in which a refrigerating heat exchanger of a given size in connection with a refrigerating system of a given rating, can be used to carry a refrigerating load far in vexcess of what would otherwise `be possible.- It will be obvious, therefore, that I am thus enabled to use smaller size equipment both with respect to the refrigerating heat exchanger and the ammonia compressor, thus enabling savings not `only in installation cost, but also in operating cost. 'I'his saving is largely effected by enabling a given ammonia compressor to operate at its most efficient point. It is to be understood, of course, that my method and apparatus can be used in connection with any refrigerating problem where it is desired to refrigerate any substance or mixtures of substances and that I have described my method and apparatus with respect to the acid treatingof hydrocarbon oil for the purpose of illustration only, and not by way of limitation.

It will be understood that certain features and sub-combinations are of utility and may be employedfwithout reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims, Without kdeparting from the spirit of my invention'. Itiis,

therefore, to be understood that my invention is not to be limited to the specific details shown and described. l

Having thus described my invention, what/I claim is: I

1. In a refrigerating system, a chamber,

means for supplying liqueed gaseous refrigerant to said chamber, a heat exchanger, a heat exchange means positioned within said chamber and means for circulating a liquefied refrigerant gas from saidl chamber'throug'h said heat exchanger and back into said chamber, and means for passing returned liquefied refrigerant gas over said heat exchange means in said chamber.

2. In a refrigerating system,'a chamber, means for supplying liquefied refrigerant gas .to lsaid chamber, a refrigerant gas outlet from said chamber, a valve for controlling said outlet, a heat exchanger, means for' introducing iiuid to be refrigerated into said heat exchanger, means for withdrawing refrigerated fluid from said heat exchanger, means for circulating liquefied refrigerant gas from said chamber through said heat exchanger back into"l said chamber, and r-means responsive to the temperature of the refrigerated uid leaving said heat exchanger for controlling said valve.

3. In a refrigerating system, a chamber, means for supplying liquefied refrigerant gas to said chamber, heat exchange means positioned in saidv uid from said heat exchanger, means for circulating liquefied refrigerant gas from said chamber through said heat exchanger back into said chamber, a refrigerant gas outlet from said chamber, a valve for controlling said outlet and means responsive to the temperature of the refrigerated fluid leaving said heat exchanger for controlling said valve.

4. A method of refrigerating fluids including the steps of passing a fluid to be refrigerated in heat exchange relation with a liquefied refrigerant gas, permitting a portion of said liquefied gas to gasify during said heat exchange step, maintaining a body of liquefied refrigerant gas in a confined zone under a predetermined pressure, circulating liquefied refrigerant gas from said Zone through said heat exchange step and back to said 'zone, withdrawing gasified refrigerant in said zone in response to the temperature of -the fluid being refrigerated.

between said heat exchange means and said heat exchanger, means for` withdrawing refrigerated 5. A method as in claim 4 in .which the fluid being refrigerated is pre'cooled by heat exchange with a liquefied refrigerant gas in said confined Zone whereby heat supplied from the fluid to be refrigerated will evaporate a portion of said liquefied refrigerant gas without decreasing the pressure in said confined zone.

6. In a method of contacting a hydrocarbon 'oil and a treating agent at reduced temperatures, including the steps of admixing said hydrocarbon oil and said treating agent and permitting them toreact ina refrigerated heat exchange' zone, maintaining a bodylof liquefied gaseous refrigerant, continuously withdrawing liquefied gaseous refrigerant from said body and introducing it into said refrigerated zone in heat exchange relation with said reacting oil and treating agent, withdrawing the refrigerant iiuid from said heat exchange zone and separating it into gas and liquid, and continuously returning said liquid to said body of liquefied refrigerant gas, wherein said separated liquid is passed in heat exchange relation with hydrocarbon oil being charged to the process in a heat exchange zone maintained under super-atmospheric pressure,

whereby to evaporate additional liquefied re-

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