US1945581A - Oil refining - Google Patents

Description

J. S. WALLIS Feb. 6, 1934.

on. REFINING Filed July 12, 1930 2 Sheets-Sheet l INVENTOR 4% Mum/d424,.- Y M 92;,

if: ATTORNEY if S. WALLIS OIL REFINING Filed July 12, 1930 2 Sheets-Sheet 2 1 wii lNV NTOR d" /.14;

BY n

. 'J' ATTORNEY Patented Feb. 6, l34

UNHTED 2 S teaser PATENT @FFIQE Application July 12,, 1930. Serial No. 467,499

3 Claims.

My invention relates to treatment of oil and more particularly to fractionating systems.

One phase of my invention comprisesa novel iractionating system wherein a greater amount of 5 heat is abstracted from. the flue gases of heaters used for raising oil to fractionating or cracking temperature than has heretofore been accomplished. In this phase of my invention I generate steam by means of flue gases which have previously been used for the raising of temperature of oil, and this steam is used in the system, for example, for operating the auxiliaries such as pumps.

In another phase of my invention I provide a novel combination of oil heater and steam generator capable of extracting a greater amount of heat from products of combustion than previously known oil heaters.

The nature of the invention and other objects and the advantages thereof willbecome apparent from a consideration of the following description taken in conjunction with the accompanying drawings constituting a part of this specification, of which:

Fig. 1 shows a fractionating system in accordance with the invention; I I 4 Fig. 2 is a sectional view of my improved oil heater and steam generator taken on the line 2-2 of Fig. 3; and

Fig. 3 is a cross-sectional view taken on the line 33 of Fig. 2.

The system shown in Fig. 1 comprises an atmospheric fractionating tower 10 and a vacuum tower 11. Heater 12 supplies heated oil through conduit 13 to the atmospheric tower 10. This heater may be of the usual type having a bridge wall 14 behind which is a series of oil heating tubes 15, and in the roof of which are radiant heat tubes 16, the tubes being connected in series. A supe'rheater may be included in the setting behind the bridge wall as indicated at'1'7.

Tower 10 contains the usual bubble trays 18 and stripping sections 19. The heated oil, which is partially vaporized, is admitted into the tower behind a baflie 20. Vapor leaves the top of the tower through the conduit 21, passes through a heat exchanger 22 and a condenser 23 and is in part returned to the tower as liquid through conduit 24 by means of reflux pump 25. Side streams are taken ofi from the tower at 27. Steam is introduced into the tower by means of conduits 28. Bottoms from tower 10 pass through conduit 29 and bottoms pump 30 into heater 31. In heater 31 the oilpasses through tubes 32 behind the bridge wall 33 and thence through roof tubes 34,

and thence through conduit 35 into tower 11 behind baflie 36.

Tower 11 also contains bubble trays 18 and stripping sections 19. Side streams are also withdrawn as at 27. Vapors are withdrawn from the tower through conduit 38, pass through a heat exchanger 39 and to a surface condenser 40; in

' which the oil vapors are condensed, the oil passing by gravity through conduit41 to run-down tank 42 and stream passing through conduit 43 to baro-' c5 metric condenser 44. Some of the oil is refluxed from run-down tank 42 through conduit 45,,in which is inserted reflux pump 46. Pumps 47, 48, 49 and 50 pump oil from the vacuum run-down tanks 42, 51, 52 and 53 to storage or other point of reception. The vacuum run-down tanks 51, ,52 and 53 are connected to the side stream con duits 2'7. There may be any number of side streams takenirom the towers. Bottoms are withdrawn from the vacuum tower 11 through conduit 53' and pumped, by means of pumps 54,-

to storage or use. Oil is supplied to the system by means of pipe 76 and is pumped by pump 75 first through heat exchanger 22, thence through heat exchanger 39, thence through heat ex- 30 changers in various side stream conduits, and thence into heater 12.

Incorporated in the setting of heater 31 is a steam generator diagrammatically illustrated in Fig. 1 and indicated generally by reference char- 8 actor 56. The steam generator comprises a. steam and water drum 57. Water is fed to the steam generator by means of conduit 58 and through feed water heater 59 which is situated in the path of flow of the products of combustion behind the bridge wall 33. A thermosyphon circuit 60 comprises a conduit extending downwardly from. the steam and water drum 57 and conduits connected theretoin the heater setting behind the bridge wall and arranged to be contacted by theproducts of combustion and a conduit connecting these tubes with the steam and water drum. Steam is withdrawn fromthe top of the steam and water drum 5'7 and passes through superheater 61, which is also behind the bridge wall and arranged to be heated by the products of combustion, and thence through conduit 62.

I use the steam produced in the steam generator 56 to operate various pumps. A conduit 63 0011- ducts steam to pump 30, or, more accurately, to the steam motor for driving pump 30. A branch conduit 64 conducts steam from conduit 62 to the motor for running pump 25. All the various motors are designated by the reference character 65. Conduit 62 is connected to a conduit 66, from which branch pipes 67, 68, 69, 70, '71, '72, '13 and 74 lead to the motors for operating pumps '75, 46, 47, 48, 49, 5c and 54 respectively.

lf desired, some of the steam may be supplied to other consumers as indicated at 79. If the steam developed by the steam generator 56 is not sufiicient for the various auxiliaries additional steam may be supplied through conduit 80.

The steam, after passing through motors 65,

passes through conduits 81 and'into a conduit 82 which supplies steam to the stripping sections of the vacuum tower. If desired, this steam may be superheated in a superheatcr 83 which may be incorporated in the heater 31.

The exhaust steam from the motors may also be introduced into tower 10. I have indicated this by showing the pipe 81 connected to the inlet of superheater 17 and heater 12. Suitable valves are to be used in the various conduits to take care of flows and pressures.

It will be seen that the condensers 39 and 44 and the ejector 87 a vacuum in the tower 11. This vacuum is communicated back through conduit 82, which supplies steam to this tower, and thusthe exhausts of the motors for driving the auxiliaries is caused to be at lowpressure due to the same apparatus which. produces the vacuum in the tower.

By incorporating the steam generator in the setting of heater 2-1 1 am able to reduce the flue gas temperature at the exit from the heater by several hundred degrees over what would be possible without the use of a steam generator in the setting. This means that there is a saving in respect of the fuel used for raising the tempera ture of the oil, inasmuch as I utilize the steam produced in the steam generator for driving the steam-driven pumps of the system and thereby save the introduction of more or less steam into the system from another source for driving these pumps. The system as a whole therefore, coop crates to reduce the amount of heat necessary to obtain the ultimate products of fractionation.

In certain cases there is some difficulty in vaporizing the heavy oil extracted from the bottom of, for example, an atmospheric tower for further treatment in a vacuum tower. This vaporization can be assisted by the introduction of steam into the inter-stage heater, because by the introduction of steam the partial pressure of the oil is lowered and it therefore has a lower boiling point. To accomplish this I simply provide a branch conduit 90 connecting conduit 62 with the inlet to the oil heating tubes 32 of heater 31. Some of the steam may be passed through conduit 90 from the superheater 61 into the oil heating tubes of heater 31. The control of this steam may be accomplished by means of a hand valve in conduit 90.

While it will be apparent that various kinds of combined steam generators and oil heaters may be employed, so far as the system as a whole is concerned, I have shown as one phase of my invention, in Figs. 2 and 3, a structure which I consider particularly suitable for the purpose set -also at a relatively low temperature, giving a high efficiency for heater 12. The reduced crude from tower 10 leaves at a relatively high temperature (500 F.). Therefore the charging stock will enter the oil surface of heater 31 at relatively high temperature (500 F.) and the products of combustion leaving the oil heating surface of heater 31 will be of a high temperature, say 700 F. or higher. If this were the final exhaust temperature, the heating for the second stage would be inefficient. Consequently, my invention is particularly applicable to plants having fundamentally a high exit flue gas temperature from the oil surface.

The heater of Figs. 2 and 3 comprises walls 100 forming a setting. Extending upwardly from the base of the heater is a bridge wall 101 which terminates short of the roof 102 and which divides the setting into a combustion chamber 103 and a heating chamber 104. A burner 105 of the usual type supplies the fuel for combustion.

Behind the bridge wall and within the chamber 10% and near the top of the bridge wall is a series of oil conveying tubes 106, two rows being shown. This group of tubes may be termed the convection group since it is heamd by convection. The tubes are connected in series, the oil passing in at 10'? through the tubes of the lower row and thence through the tubes of the upper row. From the upper row of this group oil passes through a connection 108 to the roof tubes 1&9. The roof tubes may be connected so that the oil passes either through the upper or lower tubes first and thence through the other. The tubes in each row are connected by connections 110. The heated and vaporized oil. leaves the heater through conduit 111 to pass to the tower such as tower 1G or 11 of Fig. 1. The roof tubes, which are radiant tubes, being heated by radiant heat, are bare tubes as contrasted tothe convection tubes, which are preferably encased in cast iron extended. surface members 112. This type of extended surface is well known per se. Below the convection group in chamber 104 are the heat absorbing tubes or the steam generator. There arethree groups-of these tubes, the feed heater group 113, the boiler or thermo-syphon group 114, and the superheater group 115. Feed water is supplied through connection 116 and thence passes through the horizontal tubes of the feed water section 113. These tubes are connected in staggered relation as shown in Fig. 3. The tubes may be connected either in series in the same row with the rows in series, or in series first as to one row and then the other as shown in the drawings. The water, after passing through the feed water heating section, passes through conduit 117 anzl into the steam and water drum 118, which is situated outside the boiler setting and at a higher level than the boiler tubes 114. Water flows downwardly through pipe 119 from the steam and water drum and passes into a manifold 120 wherefrom it is distributed to the tubes of the lowermost horizontal row of the group 114. The tubes of the lowermost row. are connected in series with adjacent tubes of the next lowest row. The various tubes of any row are connected in parallel and the rows are connected in series. Steam and water pass upwardly through conduit 121 and back to the steam and water drum. Circulation is produced due to the heating of the tubes 114. All the tubes of groups 113, 114 and 115 are encased in corrosion resisting extended surface material such as cast iron. Circulation is produced through the tubes 114 due to the thermo-syphon action produced by the heating of these tubes. This circulation is produced upwardly in the thermo-syphon section 114, upwardly in conduit 121 and. downwardly in conduit 119, although the tubes lid are in a hori= zontal position. The side walls of this chamber are made up of plates, either solid or sectional ized plates. and the ends of the tubes extend through the plates. The connections between the tubes are outside the plates and therefore out of contact with respect to the hue gases. It is thus seen that the steam generator is very erficiently designed for resisting corrosive effects of low temperature flue gases.

Steam leaves the upper part of the drum 118 and passes through conduit 123 and into the superheater section 115. The steam passes out through conduit 12% to the various motors as de-= scribed in connection with Fig. 1. A connection 125, containing a hand valve 126, serves to permit steam to pass into the oil heating section of the heater to assist in the vaporization of the oil. The flue gases flow upwardly in chamber 103 and downwardly in chamber 104 and thence to any suitable outlet such as a stack. It will be seen that the coldest heat absorbingmedium, namely, the cold feed water, is in contact with the end of the path of now or the products of combustion, which is conducive to the highest efiiciency.

The side walls or plates of chamber 104 may be made of cast iron or may be made of such heavy steel plate that they will stand up for a long period. The corrosive action of products of combustion, resulting from the burning of the fuel usually used for heating oil, is of a serious nature. This has been observed in connection with air preheaters used to save heat in such flue gases. It will become apparent that by the use of a steam generator, and particularly the steam generator which I have proposed, the problem of corrosion is taken ,careof, because cast iron surfaces can be used, and cast iron is relatively non-corrosive.

In order to vary the amount of heating of the steam generator independently of the heating supplied by burner 105, I have provided an auxiliary combustion chamber 130, heated by an auxiliary burner 131. The products of combustion pass from chamber 130 through flue 132 and branches 133 and 134 to the convection chamber 104 ahead of the superheater section 115 and the boiler section 114 respectively. Dampers 135 and 136 are providedin the branches 133 and 134, whereby the degree of heating with respect to the difierent parts can be regulated at will.

While I have. described certain features more or less in detail and a given system it will be understood that the invention may be embodied in other systems and that the invention is not limited to this specific apparatus described. It will be understood that the invention may be utilized in cracking processes as well as in fractionating processes. The scope of the invention is not to be limited except by the appended claims taken in connection with the state of the prior art.

What I claim is:

1. A combined oil heater and steam generator comprising walls forming a setting and means within said setting providing a path of flow of products of combustion, an oil heating section in said path of flow and a steam generating section in said path of flow, the aforesaid sections being arranged in the path of flow so that the products of combustion first contact the oil heating section and then contact the steam generating section; said steam generating section comprising a plurality of horizontal rows of tubes, a steam and water drum, means connecting said tubes with said drum to produce thermo-syphon circulation upon heating of said tubes by the products of. combustion, a feed water section in said path of how behind said tubes section and a superheater section in said path of flow ahead of the said tubes.-

2. Fluid heating apparatus comprising a furnace chamber and a tube chamber, a group of oil heating tubes inthe tube chamber, a group of water heating tubes, a group of steam generating tubes and a group of steam superheating tubes in the tube chamber, a steam and water drum, said groups of tubes being disposed in the tube chamber so that the stream of hot gases from the furnace chamber comes into contact first with the oil heating tubes, then with the steam superheatioo ing tubes, then with the steam generating tubes and finally with the water heating tubes, means for forcing water through the water heating tubes and into said drum, conduits connecting the inlet and outlet of the group of steam generating tubes 1% and said drum to cause thermo-siphon circulation through the steam generating tubes, a conduit for conducting steam from said drum. through thesuperheating tubes, means for forcing oil through the oil heating tubes and means for varying the temperatureand quantity of the hot gases in zones intermediate tube groups.

3. Fluid heating apparatus comprising a furnace chamber and a tube chamber, a group of oil heating tubes in the tube chamber, a group of water heating tubes, a group of steam generating tubes and a group of steam superheating tubes in the tube chamber, a steam and water drum, said groups of tubes being disposed in the tube ,sei.

chamber so that the stream of hot gases from 120.

the furnace chamber comes into contact first with the oil heating tubes, then with the steam superheating tubes, then with the steam generating tubes and finally with the water heating tubes, means for forcing water through the water heating tubes and into said drum, conduits connecting, the inlet and outlet of the group of steam generating tubes and said drum to cause thermosiphon circulation through the steam generating tubes, a conduit for conducting steam from said drum through the superheating tubes, a connection between the steam superheating tubes and the oil heating tubes whereby steam may be introduced into the oil flowing through the oil heating tubes, means for forcing oil through the oil heating tubes and means for varying the temperature and quantity of the hot gases in zones intermediate tube groups.

JOHN SAMUEL WALLIS. MG

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