US2588296A - Gas treatment and apparatus therefor - Google Patents

Description

March 4, 1952 G, F. RUSSELL, JR

GAS TREATMENT AND APPARATUS THEREF'OR lFiled Feb. 15, 194e Patented Mar. 4, 1952 GAS TREATMENT AND APPARATU THEREFOR George Franklin Russell, Jr., Baton Rouge, La.,` `assgnor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania Application `February 15, 1946, Serial No. 647,750

5 Claims. 1

This invention relates to improved methods for recovering from wells gaseous hydrocarbon fluids, particularly natural gas, and to improved systems for receiving, handling and treating such gases.

Among the problems encountered in the re covery of gaseous hydrocarbon fluids, such as natural gas, from the earth and placing the gas in usable form are the diiculties encountered in protecting from corrosion the recovery apparatus and particularly thecasing elements of the well and the pipe or tube through which the gas is withdrawn from the well. Another problem encountered is the provision of eflicient `means by which the gas maybe "driedf i. e., stripped of its moisture content. Since the corrosion difculties just referred -to are inlarge part caused bythe moisture carried by the gas, these problems are, in a sense, related. Natural gas as it is recovered from the earth usuallyfbears considerable moisture. As the gas moves upwardly from the relatively warm subterranean levels to the relatively cool levels, this moisture condenses upon the well casing and the gas carrying tube disposed therein and causes thecorrosion `herein referred to. When'the natural gas also bears acidic components the corrosion effect may be considerably increased.

An important object of this invention is `the provision of methods by which such corrosion may be minimized or substantially eliminated. Another object of the invention is to provide an efficient gas handling and treating system by which the rst mentioned object may be realised.

A further object of the invention is provision `of an improved gas handling and drying system having new and novel features including an efficient combination of means for drying the gas by use of a sorbent and means for reactivating said sorbent. Yet `another object is the provision of an efficient gas handling system in which the pressure of the recovered gas is utilized to effect certain operations in said system. These and further objects of the invention, as well as the advantages and benefits obtainable bythe practice thereof, will more particularly appear from the following description.. The drawing, which will be referred to insa-id description, illustrates in diagrammatic form a preferred system ernbodying the principles of this invention.

Referring to the drawing, the well illustrated therein consists of a conventional casing lll, which, extends into the producing formation Il. Casing head (l2 is likewise conventional and through it passes the `tubel I3 which collects the gas .and delivers the same to the gas handling and treating system. It is on the surfaces of the tube, the casing and the` casing head that much of the corrosion difficulties occur. As the moisture-bearing gas passes .from the earth to the relatively cool conditions existing abovethe surface of the earth, moisture .condenses on ,the casing and particularly on the inner surface of tube t3. The resultant corrosion `limits the useful life of `tube I3 and, often, the lifeof casing I0. The method of this. invention designed t0 minimize or eliminate these corrosion effects consists in mixing with the gas at the bottom` of the casing and prior to its travel to the` surface of the ground, ofsuch amounts ,of `a dry gas `as are calculated `to reduce the moisture content ofthe mixture thus formed below the point ,at

which substantial condensation will occur in the gas carrying tube, i..e below the dew point of the gas-dry gas mixture. The amount of drygas necessary to this purpose will, of course, depend upon the original moisture content of the gas .to be recovered and thetemperature conditions pre,- vailing during passage of that gas from the.earth to the surface ,or to the next step of the gas handling operati-ons, but is readily.. calculated when these conditions, which .are easily ascertainable, are known. The naturev of the .dry gas is-not important to this invention, in so far as concernsthe reduction of the dew `point of ,the gasbeing recovered. However, it is preferable to use as the dry gas aportion of the recovered gas which has been previously dried and, in any event, the dry gas should Abe substantially .nonreactive with the materialsfrom which the .gas handling apparatus is formed and should. preferably be a type which does not form explosive mixtures with the recovered gas. The manner in which the mixture between drygas and the moisture-bearing gas is `formed may vary with the choice of the operator, butconveniently the dry gas is merely forced Aunder pressure` .downf wardly to the `bottom of the casing. Forthis purpose the dry gas-may Ibe furnished through the casing headby, a pipe or tube,l such as tube lli shown in the drawing. AThe gas handling and treating apparatus which is particularly useful in the practice of the aforestated method ofthis invention is shown 'inthe drawing Aand-will now be specifically described. The general purpose rof the system is to prepare anatural' gasforH-de livery toa consumer orto storageffor later use. A `specific purpose is to deliver to the' ywell a quantity of dry gas for' the purpose 'above stated. The general function "of f the 1 system isfto dry 1and I purify the gas, the principal drying means being a sorbent, such as adsorbent alumina, silica gel, or other known sorbent which is capable of being revived or reactivated. The adsorbent corn-mercially availabe as Activated Alumina is particularly suitable. The preparation of such material is described in U. S. Patents 1,868,869 and 2,015,543. To these ends the specc system shown includes three identifiable but mutually interdependent circuits, viz., a receiving and treating circuit, a sorbent reactivating circuit, and a feed circuit designed to furnish dry gas under pressure to the well casing. Each of these circuits will now be described.

The receiving and treating circuit The circuit is fed by gas issuing from the well through tube I3. The gas passes through heat exchanger I5, tube I6 and separator I'I. From separator I'I the bulk of the gas moves through tube I8 and thence through one of the drying towers I9 or 20 for treatment with a sorbent. From the tower the gas flow continues through pipe 2I, the bulk of the gas then passing through expansion motor 22, pipe 23, heat exchanger I5, and then through pipe 24 to the consumer or to storage. It will be noted that during the time the natural gas is being puriiied and dried, it is under substantially the pressure at which it entered the system, subject, of course, to changes in temperature and incidental losses. However, when the gas iiow reaches expansion motor 22, the gas is expanded to cool it and the energy thus released is used to operate motor 22 to drive a compressor 34 for purposes later described. To this end the motor is any conventional device adapted to expand the gas and permit the expansion to operate a piston or like driving part. As the unpuriiied natural gas iiows through heat exchanger I5, its temperature is reduced by the cooling action of the dried and puried gas which, having been expanded at expansion motor 22, passes through tube 23 to and through said heat exchanger. The unpuried and undried natural gas, now partially cooled by the action of the heat exchanger I5 just described, next is subjected to the action of separator II. Here the condensate which may have resulted from the cooling action is collected and discharged through pipe 40 to a suitable place, while the gas passes to the drying tower. While, for convenience of illustration, only two drying towers are shown, it will be realized that any number of such towers may be used, the principle being that at any given time one or more of said towers are available for use, while one or more towers previously used are being reconditioned ior future use. Thus, in the device shown, by manipulation of valves 4I and 42, one of the towers I9 and 20 may be placed in circuit with separator I'I and expansion motor 22, while the other tower is excluded from said circuit. For the purposes of drying, the tower contains a sorbent of the type above described.

The sorbent reactiuating or reconditioning circuit The purpose of this circuit is to divert from the receiving and treating circuit a portion of gas which is then heated to a proper temperature and passes through the inactive tower to recondition or reactivate the sorbent held therein. Thereafter this gas is returned to the receiving and treating circuit of the system. Referring now to' that point in the receiving and treating circuit where the gas leaves separator Il, a

portion of the gas is diverted through tube 25 to heater 21, the amount diverted being controlled by valve 26. Heater 2'I is conventional. It is, of course, desirable, all other conditions being equal, to use as a reactivating gas a gas which has at least been partially dried. It is for that reason that it is preferred to take the reactivating gas from the circuit after the gas has passed through separator I'I. Fuel for the heating is delivered thereto from any convenient source (including a point in the system) by pipe 4l. The temperature of the heater is regulated to deliver therefrom gas at reconditioning or reactivating temperature. These temperatures are known and depend upon the sorbent used in the drying tower. For instance, when adsorbent alumina is the sorbent used, the temperature of the gas as it leaves the heater should preferably be in the range of 350 to 600 degrees Fahrenheit. On leaving the heater, the diverted and now heated gas passes through tube 28 to a drying tower and thence from the tower through tube 29, then through heat exchanger 30, where the gas is somewhat cooler, then through separator SI and tube 32, which directs the gas iiow into the drying tower then being used in the receiving and treating circuit, at which point the diverted gas rejoins the receiving and treating circuit and becomes a part thereof. The function of heat exchanger 30 will be later described. The function of separator 3| is to separate condensate, which condensate passes through pipe 48 to a suitable place. It Will be noted that by manipulation of valves 43 and 44 this sorbent reactivation circuit is diverted through and includes the drying tower which is not, at that moment, a portion of the receiving and treating circuit, while the gas diverted to the sorbent reactivation circuit is finally returned to the redried in the other drying tower.

The feed circuit which delivers dry gas to the well circuit This circuit begins at a point in the receiving and treating circuit between the drying tower and expansion motor 22 and terminates when it delivers the dried gas to the well casing for mixture there with the moisture-bearing natural gas being recovered. Thereafter the dried gas is returned to the receiving and treating circuit in said mixture subject, of course, to incidental losses which may occur at the bottom of the well casing. The dried gas enters this circuit through tube 33, the amount so diverted from the principal circuit being controlled by valve 46. The gas then passes through compressor 34, where it is compressed to a pressure desirable or necessary for its subsequent entry into the well. From the compressor 34 the compressed dry gas passes through tube 35 to and through heat exchanger 3U and thence through pipe I4 to the Well. In heat exchanger 30 the temperature of the dried gas is raised by the heat loss of the heated gas from the reactivation circuit which, as above described, likewise passes through said exchanger. The heating of the dry gas prior to the time it enters the well is desirable as additional assurance that corrosion condensate will not form on the walls of the well elements. The amount of gas diverted to this circuit will depend, as above described, on the temperature conditions existing in the well and at the surface and the moisture content of the natural gas being recovered.

From the above description of the illustrated, and preferred, form of gas handling system, it will bezamiarentthat,V viewedtas af, who1e; the systemA circuit including atleasttoneoi` saidtowers and` in whichnatural gasfdelivered-from a. gas well is rdried=` at substantially `the pressure ofi delivery,

a` reactivating` circuitfrcceiving undried gas from` the 'drying circuit, including atleast oneof .said

towers and also including means for heating the.

undriedgas prior toits entry into said tower, this reactivatirrg circuitA terminating; in: thedrying circuit at a point prior toinal drying,-v anda feed circuit i adapted to f divert'. a f portion of the` dried gas from the drying circuit to the Well, this feed circuit including` means for compressing` the gas operable jby` expansion lof` the driedz gas I.traveling through the=drying circuit and also includingheating rmeans f or raising the temperature of the compressed gas;- saidxl'ieatingbeingc electedby transfer of heat from-the gas traveling` in the:

reactivation circuit.

Thus far the. above describedsystem has been considered asan improved meansi'or` carrying out the Apreviously described corrosion preventing` methods of the invention.. It will` betnotedthat even in thisform `the reactivation circuit may be eliminatedwithout destroying the systems usefulness as applied to such methods. For instance, if the drying `agent usedv in the dryingtower is of. a type which cannot be revived or` reactivated after useor inthe reactivationV force or fluid` is best furnished separately ofthe system, then the system described may be modified by removing the reactivation circuit or by shutting valves 2.?, ill` andli, in whichcaseif heating of. thecompressed gas in the dry gas feedsystem is desirable, i

this heating may be. accomplished by separate means or, Where the gas. issuing. through: tube I3 is quitewarm, by heat exchange withdrying circuit.

Likewise the. above described system may be. used solely as adryingsystemin casestwhere no,

feed of dry gasto, the wellisdesirable or neces-i- -sary or where dry gas `is fed; to the well fromanother source. Inthiscase the feed circuit may` be eliminated or,. equivalently,.valve.46 may be closed. In such. case, if. cooling of the reactivating gas Ais desired, the cooling4 may be effected by other means or by heat exchange with a portion of the dried gas after expansion. Likewise the expansion motor maybe eliminated, and` replaced.

by a conventional expansion chamber, or the motor may be retainedand the expansion energy translated thereby into useful work of any kind.

In a further modification of the system, whether used solely as a drying system or also as a means of furnishing dry gas to the well, the return of the gas in the reactivation circuit to the dryingoperationmay be eliminated. This case presupposes either that mixture of the reactivationgas directly with the dried gas. will not unduly raise moisture content. ofy the mixture or thatthe reactivation gas isof. such small quantity thatwastage thereof is of noimportance. In the rst case the valve i5 may be closed and the gasA issuing from separator 3l delivered through a by-pass tube 36 to tube24, or tube 32 may be directly connected to the consumer line and its connections with the drying towers eliminated. In the second case the reactivation gas could be delivered to the atmosphere from separator 3! or delivered and burned at some convenient point.

Another modiiication of my system now to be explained is particularly adapted to carry out a modified method of corrosion prevention in which lack of moisture in the gas.

with the natural gas inthe volume desired,` the total mixture will be at suchv temperature that no substantial condensation will occur duringpas-` sageof the mixture from theearth to thehandling system. Thus, in this method thefeed gas is preconditioned with respect to temperature rather than with respect to moisture content, the result being the same. The system above described mayfconveniently be used to achieve this result by bleeding a portion of the undried` heated gas from the heater 2.1 directly to tube I4, as through tube 50, in which case the valves Miwould be closed or the dry feed circuit to the well, apart from tube I4, entirely eliminated.

These and similar modifications will suggest themselves to those skilled in the art, in the practice of my improved methods, as will such details as the fact that the casing may be utilized as the carrier for the up-coming gas in the well,

while an auxiliary tube may be used to transmit conditioned incoming gas to the lower regions of the well, and all such modications are within. the purview of this invention, except as limited by the terms of the appended claims.

The advantages of the gas handling systems herein described are manifold. The preferred form described, comprising the three interdependent circuits, eiiiciently utilizes the energy `inherent in the pressure of the gas issuing from the well and likewise cuts heat losses to a minimum, while at the same time conditioning the gas to be fed to the well. Considered as a drying system, and without reference to the i conditioning of gas for well use, my system allows well, said system comprising, in combination, a i

receiving and treating circuit comprising, in recited sequence, means for receiving the gaseous fluid from said well, means for holdingV a mass of gas drying sorbent in the. path of.flow of said gaseous fluid, and means for expanding the dried` gaseous fluid prior to delivery thereof from the circuit, said circuit being adapted to maintain the gaseous iiuid. at the approximate pressure of its receipt, subject to changes in temperatureand the herein recited diversions of fluid from. said circuit, until said gaseous fluid enters said expansion means, a sorbent reactivating circuit including, in recited` sequence, means for diverting thereto` a. portion of theY gaseousfluid flowing in. said. receiving and treating circuit, means. for heating the diverted gaseousnuid, means for holding a mass of sorbent in. the path of flow of the thus heated gaseous fluid and means for returning said gaseous flow to said receiving and holding circuit, and a feed circuit for feeding dried gaseous :duid from said receiving and holding circuit into said well, said feed circuit including, in recited sequence, means for diverting thereto a portion of said dried gaseous fluid, means for compressing the diverted dried gas and means for delivering said compressed gas into said well, said compressing means being operable by the expansion means of the said receiving and treating circuit, and a heat exchanging means disposed in said system to transfer a portion of the heat content of the gaseous fluid flowing through said returning means of the said reactivation circuit to the gaseous fluid flowing through said delivery means of the said feed circuit.

2. A system for receiving, handling and treating moisture bearing gaseous hydrocarbon uid issuing, under relatively high pressure, from a Well, said system comprising, in combination, a receiving and treating circuit comprising, in recited sequence, means for receiving the gaseous fluid from said well, means for holding a mass of gas drying sorbent in the path of flow of said gaseous uid, and means for expanding the dried gaseous fluid prior to delivery thereof from the circuit, said circuit being adapted to maintain the gaseous fluid at the approximate pressure of its receipt, subject to changes in temperature and the herein recited diversions of fluid from said circuit, until said gaseous fluid enters said expansion means, a sorbent reactivating circuit including, in recited sequence, means for diverting thereto a portion of the gaseous uid nowing in said receiving and treating circuit, means for heating the diverted gaseous fluid, means for holding a mass of sorbent in the path of now of the thus heated gaseous fluid and means for returning said gaseous ilow to said receiving and holding circuit, and a feed circuit for feeding dried gaseous uid from said receiving and holding circuit into said well, said feed circuit including, in recited sequence, means for diverting thereto a portion of said dried gaseous fluid, means for compressing the diverted dried gas and means for delivering said compressed gas into said well, said compressing means being operable by the expansion means of the said receiving and treating circuit, a heat exchanging means disposed in said system to transfer heat from gaseous fluid owing through the returning means of said reactivation circuit t gaseous fluid flowing through the delivery means of said feed circuit and another heat exchanging means disposed in said system to transfer heat from gaseous fluid flowing through the receiving means of the receiving and treating circuit to gaseous fluid flowing from the expansion means of the same circuit. Y

3. A system for receiving, handling and treating moisture bearing gaseous hydrocarbon fluid issuing, under relatively high pressure, from a Well, said system comprising, in combination, a receiving and treating circuit comprising, in recited sequence, means for receiving the gaseous fluid from said well, means for holding a mass of gas drying sorbent in the path of flow of said gaseous fluid, and means for expanding the dried gaseous fluid prior to delivery thereof from the circuit, said circuit being adapted to maintain the gaseous fluid at the approximate pressure of its receipt, subject to changes in temperature and the herein recited diversions of uid from said 8 circuit, until said gaseous fluid enters said expansion means, and a feed circuit for feeding dried gaseous fluid frbm said receiving and holding circuit into said well, said feed circuit including, in recited sequence, means for diverting thereto a portion of said dried gaseous fluid, said means being positioned to divert said portion prior to its entry into the expansion means i of the receiving and treating circuit, means for compressing the diverted dried gas and means for delivering said compressed gas into said well, said compressing means being operable bv the expansion means of the said receiving and treating circuit.

4. A system for receiving, handling and treatine.r moisture bearing gaseous hydrocarbon fluid issuing, under relatively high pressure, from a well, said system comprising, in combination. a receiving and treating circuit, including gas drying sorbent and means for transmitting said gas from the well through a portion of said sorbent, a sorbent reactivating circuit, including a heater and means for transmitting a portion of the gas from said well through said heater and through another portion of said sorbent to reactivate the same, and thence to said receiving and` treating circuit, a feed circuit for feeding a portion of the dried gaseous iiuid from said, receiving and treating circuit into said well, and a heat exchanger disposed in said system to transfer heat from the heated gas flowing in the reactivating circuit to the gas flowing to the well through said feed circuit.

5. A system for receiving, handling and treating moisture bearing gaseous hydrocarbon fluid issuing, under relatively high pressure, from a well, said system comprising, in combination, a receiving and treating circuit, including gas drying sorbent and means for transmitting said gas from the well through a portion of said sorbent, a sorbent reactivating circuit, including a heater and means for transmitting a portion of the gas from said well through said heater and through another portion of said sorbent to reactivate the same, and thence to said receiving and treating circuit, a feed circuit for feeding a portion of the dried gaseous fluid from said receiving and treating circuit into said well, and a heat exchanger disposed in said system to transfer heat from undried gas flowing from said well to dried gas discharging from said receiving and treating circuit.

GEORGE FRANKLIN RUSSELL, J r..

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 956,058 Elten Apr. 26, 1910 1,763,984 Husted July 1, 1930 1,978,655 Straight Oct. 30, 1934 2,160,831 Colby et al June 6, 1939 2,204,042 Legatiski June 11, 1940 2,309,075 Hill Jan. 19, 1943 2,323,524 Downs, Jr. July 6, 1943 2,342,165 Plummer Feb. 22, 1944V 2,355,167 Keith Aug. 8, 1944,

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