US2221518A - Desalting system - Google Patents

Description

Nov. 12, 1940. "G, A. JENNINGs DESALTING SYSTEM Filed May 14, 1940 bv kum@ l .WW Wmo W mDNNM.

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f2s a system lfor elevating thetemperature ofth as currently, a salt-free stream of petroleum is ranging between 275 and 350 F.,with the pres- Patented Nov. 12, 1940 y l UNITED STATES PATENT ,oFFIclazjfl DESALTIN G SYSTEM George A. Jennings, Wichita Falls, Tex., assignor to Alcorn Combustion Company, a corporation i of Delaware Application May 14, 1940, Serial No. 335,157

' 14 claims. (ci. 252-348) My invention relates to treating systems for the condensing temperature of steam so that petroleum, more particularly to methods and the water fraction of the overhead stream is in means of desalting a water and salt-,bearing the form of water vapor. The overhead stream. petroleum, and has for an object the provision including vaporized petroleum then passes 5 of a highly eii'ectlve desalting system which 'is through a condenser and into a separator w` ere both simple and eflicient in operation. the water 'is withirawn from the lower portion It has long been known that chloride salts of and the condensed lighter fraction of the pecalcium, magnesium, Vand sodium may be found troleum withdrawn from the upper portion therein crude oils and that in certain crude oils the of. The reflux1 is derived from the petroleum salt content is so great that' the crude oil must condensate. be subjected to a desalting operation ,before :itv For a. more complete understariding of my inmay be charged to a cracking, or distillation unit. vention reference 'may be had to the accompany- Many diil'erent methods .of salt removal have been ing drawing in which: proposed, such as electrical, chemical, centrifugal, Fig. 1 illustrates diagrammatically a system l5 andthose utilizing heat and pressure. My inembody-ing my invention; and l vention is particularly concerned with a method Fig. 2 is a cross-section of the settling d rum of removing the salt or salts by flashing or vaportaken on the line 2-2 of F18. 1. izmgv the water content of the petroleum, thus Referring to the drawing, a salt-bearing peproducing crystallization ofthe salt. Heretofore troleumis withdrawn from storage by line Il, l the salt was deposited on the very heating sur-y -pump II, and iiows, by way of line I2l under the y F faces which were provided for -the elevationof control of a valve I2a, through a heat exchanger the temperature to a'poi'nt where the water con- I3 and by line I4 into a mixing zone or tube I5. tent could be vaporized. v The mixing tube I5 extends'into the vapor space It isa further object of my 'invention topro,vi ie l of an enlarged zone or dehydrator I 6,. which is H itself in direct communication with a precipitator petroleum without subjecting thel saltbeaingfor settling zone I1. petroleum toy any conditions which would pro.v vAs more fully explained hereinafter, a salt-free duce the precipitationl or crystallization oi' vthe petroleum is withdrawn by way of line Il under salt upon heating surfacea(v control of valve Ita and by pump I9 is vforced In carrying out my invention in one form through the tube banks 20 and 2I of a heater a thereof ,`a stream of salt-bearing petroleum, pref- 22 provided with a burn'er 23. Y 'I'he salt-free erably by heat exchange, is elevated to a ,temstream is discharged through line 24 from the perature safely below one which would cause heater 22 at a temperature adequate tov produce the salt to be precipitated or.crystallized. Conin the mixing tube or zone I a mix-temperature heated to a temperature such that when the surebetween 50 to 150# per square inch stream is commingled with the salt-bearing pegauge. This temperature may be indicated by troleum stream, sufficient heat units are added any suitable means such as the thermometer lia. to raise the commingled streams to well above 'Ihe mixing zone or tube I5 is of sum-cient length 40 the vaporization temperature of the water orto insure thoroughmixng of the two streams water-content thereof. During the heating and during passage therethrough. The commingled commingling thereof, a substantial pressure is streams disch ge through a back pressure valve maintained upon both streams.A Thereafter the 25, a movable element 26 of which, controlled by pressure is suddenly released to produce the a hand wheel 21, serves to control. the rate of flashing or complete vaporization of the water discharge ofthe commingled streams into the content. The resulting crystallized salt and lenlargedzone or dehydrator I6. This back presheavy petroleum collects in the bottom of a sepasure valve, asshown, has the characteristics of rating 4zone. Thecrysta1lized salt settles to the producing the reduction of pressure as the combottom, where it is removed,l and the aforesaid mingled stream enters the enlarged zone and o1' stream of salt-free petroleum is withdrawn from maintaining the pressure within the tube 'or zone this zone. The lighter portion of the petroleum, l5, up to the outmost end thereof. vThus when including the water vapor, passes upwardly the stream enters the lenlarged zone the water through a scrubbing or fractionating zone, the *content vaporizesor flashes. The salt is immeditop temperature of which is controlled by reiux. ately crystallized and .passes with the heavier It This temperature is preferably approximately liquid component of the petroleum into the settling chamber or precipitator I1. While I have referred herein to salt in the singular, both in the description and claims, it is to be understood I have used the term salt to include all of the salt content of the petroleum regardless of whether it is a salt of one kind or another.

Since the crystallized salt is heavier than the liquid petroleum, this gradually settles to the bottom of the chamber I1 along withi any other solid foreign matter which is heavier than the liquid petroleum. 'I'he chamber I1 is relatively large and long to provide adequate time, twenty to thirty minutes, for the settling operation. As best shown in Fig. 2 the chamber I1 is provided with inclined bottom portions 36 and 3I, which terminate in a trough 32 along which extends a conveyor 33. 'Ihe conveyor, shown by way of example as a spiral or screw conveyor, is driven by a motor or prime mover 34 in a direction to move the crystallized salt and the heavy foreign matter into an accumulator 35. o

Preferably the conveyor 33 is operated intern mittently. To this end, a valve or plug-cock 36 is retained in the closed position, when the conveyor is at a standstill. When the salt is to be removed, the valve 36 is turned to the open position, shown in the drawing, to provide an open passage from the end of the conveyor into the accumulator 35, the conveyor bearing adjacent valve 36 occupying a sufliciently small space as not to interfere with the passage of salt. It may be necessary by means of a reamer 31, operated by a wheel 38, to clean the opening through the valve 36. At the same time, a valve 46 in line 4I is opened to equalize the pressure within the accumulator 35 with that of the enlarged zone I6. A valve 42 in a steam line 43 during this operation is closed, as is valve 44 in discharge line 45. Operation of the conveyor now results in the discharge of the crystallized salt and other solids into the accumulator 35. When it is filled to any desired level, the valve or plug cock 35 and valve are closed. If continuous removal of salt is desired, it is to be understood a second accumulator may be provided to receive the salt after 1the 1accumulator 35 has been vfilled to a desired eve.

The accumulator 35 may now be emptied by closing valve 40 in line 4I and by opening the valve 44 in discharge line 45, followed by the opening of the valve 42 in the steam line 43. 'I'he application of a relatively high steam pressure for example forces the crystallized salt and other solids out of the accumulator 35.

A stream of salt-free petroleum may be withdrawn from an upper level of the settling chamber I1 and, as I have described, a part of this streamgpasses throughthe line.I3 and pump I3 to form the heat-carrier for the salt-bearing stream entering through line I0. Under the control of a liquid level controller 48, a second stream of salt-free petroleum ows by way of line 56, pump 5I, liquid level controller valve 52, and by way of line 53 to the heat exchanger I3. The quantity may vary somewhat, the purpose of the controlled being to maintain constant the liquid level in settling drum I1. 'I'he salt-freestrearr; in exchanger I3 gives up a part of its heat to raise somewhat the temperature of the incoming stream of salt-bearing petroleum. The salt-free stream is withdrawn by way of line 54 to storage.

As I have stated, upon lowering the pressure upon the commingled streams in zone I6 the water content of the petroleum is vaporized and passes upwardly through the enlarged zone or dehydrator I6. Light fractions contained in the petroleum also vaporize and rise upwardly therethrough; A mixture of these light fractions and the vaporized water comprises the overhead stream withdrawn through line 66 and it passes through condenser 6I and into an accumulator 62, within which the water and petroleum sepa. arate. Water 1s Withdrawn from the lower part of the accumulator 62' by way of line 62a under control of valve 62h, and the lighter petroleum fraction from the upper part thereof through line 65. Through a line 63, under control of valve 64, gas is withdrawn from the system. The light fractions pass by way of line 65 into an accumulator 66, from which reux is withdrawn by line 61 and pump 68 and returned by way of line 69 under control of valve 69a to the top of the enlarged zone or dehydrator I6. 'Ihe reflux flows over a plurality of baiiies 10. From accumulator 66, light fractions in excess of those required for the reux are sent by line 1I under control of valve 12 to storage.

The top temperature of the zone I6 is maintained at about the condensing temperature of steam so that the vaporized water passes overhead in the form of water vapor, or in the form of steam in as wet a condition as possible, or close to its condensation temperature, for overhead passage. A temperature of between 180 F. and 200 F. will be found satisfactory, depending, of course, upon the partial pressure conditions as determined by the percentage of the lighter petroleum fractions present. This particular temperature requirement is an important feature of my invention since I have found that if high top temperatures are maintained in the zone Il the water-content in the form of relatively dry steam, condenses at some pointintermediate the inlet and outlet of the condenser 6I. Such a condensing condition results in a high concentration of hydrochloric acid which products severe corrosion on the condenser tubes. However, bymaintaining the top temperature so that the steam is as wet as possible, or close to its condensation temperature, any acid which may be formed is immediately diluted by relatively great quantities of water, and the aforesaid corrosive action is greatly minimized, if not entirely eliminated. Stated differently, this top temperature is such that the vaporized water is in the form of mist, or comprises tiny dropletsof water, which will rise and pass outwardly with the overhead stream, and will serve to dilute the acid-forming constituents to a point where little corrosion results.

Instead of the thermometer I5a and the other thermometers shown in the drawing indicating instruments oi' the thermocouple type may be utilized. Similarly, suitable pressure gauges are provided, such as at the mixing tube I5.

In the specification and claims wherever the term salt-free petroleum has been used it means petroleum whose salt-content has been materially reduced and below a salt-content which will result in deposition of salt when the stream is heated in tubes to high temperatures, as upwardly of 700 E.

While I have shown a particular embodiment of my invention, it will be understood that I do not limit myself thereto, since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as follow within the spirit and scope of my invention.

What I claim is: 1. The method of desalting a water and saltbearing petroleum, which comprises heating a salt-free petroleum uid materially to raise its temperature, commingling under pressure a stream of said uid with a stream of saidwater heat units adequate to raise the temperatureiof said petroleum stream to above the vaporization temperature of its water-contentat reduced Dressure, -in an enlarged zone crystallizing the -salt content of the ,petroleum by reducing the pressure upon said commingled streams and vaporiz` ing the water-:content ofthe petroleum, and in an enlarged zone gravity-settling from liquid petroleum therein said crystallized salt.

2. 'I'he method of desalting a water and saltabearing petroleum, which comprises heatinga salt-free petroleum iluid materially to raise its temperature, commingling under pressure a stream -of said iluid with a stream of Isaid water and salt-bearing petroleum, said fluid supplying heatl units adequate to raise the temperature of said petroleum stream to above the vaporization temperature of its water content for a reduced pressure thereupon, in an enlarged zone crystal. lizing the salt content of the petroleum by reduc: ing the pressure upon said commingled streams and vaporizing the water-content of the petroleum, and withdrawing from said enlarged zone salt-free petroleum. j

3. The method of desalting a. water and saltbearing, petroleum, which comprises heating a temperature, commingliig under pressure a v Astream of said uid with a'stream of said water and salt-bearing petroleum,l'said uid supplying `heat units adequate to raise [the temperature of said petroleum stream to above the vaporization 40 temperature of its water-content at reduced pressure, in an enlarged zone crystallizing the salt content of the petroleum by reducing the pressure upon said commingled streams and vaporizing the water-content of the petroleum, withdrawing 45 from said enlarged zone salt-free petroleum in liquid phase, the latter comprising said salt-free uid.

4.' The method of desalting a water and saltbearing petroleum, which .comprises heating a y 50 salt-free petroleum fluid materially to raisel its temperature, commingling under pressure a stream ofsaid uid with a stream of said water and salt-bearing petroleum, said iluid supplying heat units adequate to raise the temperature of 55 said petroleum stream to above the vaporization temperature of its water cgitent for a lower presv sure thereupon, in an enlarged zone crystallizing the salt content of the petroleum by reducing the pressure upon said commingled streams and 60 vaporizing the water content of the petroleum,

withdrawing from said enlarged zone salt-free petroleum in liquid phase, the latter comprising said salt-free uid, and separately withdrawing from the lower portion of said enlarged zone crys- 65 tallized salt and other foreign matter which settles to the bottom thereof.

' 5. 'I'he method of desalting a water and saltbearing petroleum which comprises initially heating a stream of said petroleum to a temperature 70 below 212 F., heating a stream of salt-free petroleum to a temperature which will produce,

when mixed with said initially heated salt-bearing stream, a mim-temperature of between-275 and 350 F., commingling said streams, said salt- 75 free petroleum supplying the heat units to raise salt-free petroleum uid materially to raise its thev temperature of said salt-bearing petroleum to above the vaporization temperature of its water-content, in an enlarged zone crystallizi-ng the salt-content of-V the petroleum by reducing lthe pressure upon said lcommingled streams'and vaporizing the water-content of the petroleum,

stream of salt-free petroleum, and removing irom the lower portion of said last-named zone crystal-A lized salt. A

q 6. Themethod'of desalting a1 water and salt'- bearing petroleum which comprises elevating the temperature. of an elongated stream thereof by contact with a heating surface whosetempera-f ture does not exceed'the flash point of `the water or salt brine in said stream, heatinglstream artisan-bearing petroleum, saidriiuid supplying ,gaand withdrawing frOm an enlarged zone said of salt-free petroleum to a temperature materially above said :dash point,'commi nglingj isaid streams, said salt-free stream supplying heatunits adequate to raise the temperature of fsaid saltbearing stream to above the-vaporizationf'vtemperature of the water and saltY brine thereof;v in an Vvenlarged zone crystallizing thefsalt-content of the petroleum by vreducing the pressure :upon said commingled streams and vaporizing therefrom the water content of the petroleumand of the saltabrinelthereimand withdrawingirom an `enlarged zone saidsalt-free petroleum stream.

7. The method of desaltingn a 'saltfbearing petroleum which comprises heating underfprese sure a salt-free petroleum stream 'materially to raise its temperature, under pressure commingling said stream with a stream of said salt-bearing petroleum, discharging said commingled streams intoan enlarged zone, concurrently releasing said pressure Yand discharging said streams-into said enlarged zone to produce vaporization` of the water-content of said streams and thefresultant crystallization of the contained salt, andvremov-l ing said crystallized salt. ,f f!

8. A petroleum desalting system which. comprises, heat exchange means for heating affwater and salt-bearing stream of petroleum, said -heatexchange means having a heating Asurface the maximum temperature of which doesnot for the existing pressure exceed' the ash point of the water content of said stream of petroleum, means for heating a salt-free petroleum stream to a temperature materially above the 'flash point of the water in said petroleum stream, an elongatedthey ilow into said enlarged chamber, means for chamber salt which settles thereto, and means for withdrawing from said chamber said salt-free petroleum stream. L

9. In a petroleum desalting system, the combination of an enlarged chamber provided along its lower portion with an elongated passage, conveyor means disposed in said passage for transporting material, .means for driving said conveyor means, an outlet in communication with said passage, a valve for opening and closing said outlet, a container for receiving material transported by said conveyor means, and means operable during operation of said conveyor means for equalizing the pressure between said chamber and said container.

10. In a petroleum desalting system, the combination of a settling chamber provided along its lower portion with an elongated narrow U-shaped passage, a conveyor disposed within and extending along said passage for transporting material, a container for receiving material transported by said conveyor, means operable during operation of said conveyor for equalizing the pressure between said chamber and said container, means including a valve for opening and clos-l ing one end of said passage, a reamer disposed in operative relation with said valve, and means for operating said reamer through the valve when in open position to provide an unobstructed passageway for the transport of material by said conveyor from said chamber to said container.

11. In a petroleum desalting system, the conrbination 'of an enlarged chamber, an' elongated mixing tube, one end of which extends into said chamber, means for introducing into the opposite end of said tube a hot salt-free stream of petroleum and a cooler salt-bearing stream of petroleum, and valve means cooperating with the end of the tube Within said chamber for reducing the pressure upon said commingled streams only as they leave said mixing tube.

12. In a petroleum desalting system a combination of an enlarged chamber, an elongated mixing tube, one end of which extends into said chamber, means for introducing into the opposite end of said tube a hot salt-free stream of petroleum and a cooler salt-bearing stream of petroleum, valve means cooperating with the end of the tube within said chamber for reducing the pressure upon said commingled streams as they leave said mixing tube, means disposed in the upper part of said chamber for contacting petroleum and water vapor with reflux, the lower portion of said veslselproviding a substantial interval of time for the settling out of crystallized salt, and conveyor means disposed in the lower portion of said vessel for removing said salt therefrom.l

13. The method of desalting a water and salt bearing petroleum which comprises heating a stream of said petroleum to above the vaporization temperature of its water-content under temperature and pressure conditions which avoid deposition of salt, in an enlarged zone reducing the pressure upon said stream to vaporize said Water-content and to crystallize the salt, removing from said zone an overhead stream, reuxing said stream to hold its temperature as low as will permit the vaporized water to pass overhead, and cooling said overhead stream to condense the water in the vaporized petroleum, said low temperature resulting in the condensation of said water and dilution of acidic products immediately `after said overhead streamisy withdrawn from said zone.

14. A system as set forth in claim 8 in which the upper part of said chamber is provided with countercurrent vapor and liquid contact means, and an outlet for passage of van overhead stream, means for introducing reux over said contact means to control the top temperature of said chamber and thereby insure the -withdrawal of said vaporized water-content near its condensation temperature, and means for cooling the overhead stream from said chamber.

GEORGE A. JENNINGS.

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