US2355892A

US2355892A - Means for supporting heater tubes

Info

Publication number: US2355892A
Application number: US446299A
Authority: US
Inventors: Frank H Praeger
Original assignee: Alcorn Combustion Co
Current assignee: Alcorn Combustion Co
Priority date: 1942-06-08
Filing date: 1942-06-08
Publication date: 1944-08-15
Anticipated expiration: 1961-08-15

Description

Aug. l5, 1944. F. H. PRAl-:GER l 2,355,892l

MEANS FOR SUPPORTING HEATER TUBES l Filed June 8, 1942 2 /2 F/G. l

Hai 3 lNvENToR. @HAK/ Pewfae awww' Patented ug. 15, 1944 MEANS FOR SUPPORTING HEATER, 'TUBES Frank H. Praeger, Merion, Pa., assignor to Alcorn Combustion Company, Philadelphia, Pa., a corporation of Delaware Application June 8, 1942, Serial No. 446,299

l(Cl. 122-510) l8 Claims.

My invention relates to heaters, more particularly to heaters of the type used for heating petroleum, its components and similar fluids, and has for an object the provision of fluid cooled columns to support intermediate supports for tubes extending through or across the re chamber of the heater.

In the past it has been customary to construct petroleum heaters with tubes disposed along the walls and roof of the fire chamber of the heater. Ordinarily, tube sheets of refractory metal were by contact with the tubes maintained sufliciently low in temperature as to retain the required vstrength for the support of the tubes. Such tube sheets cannot withstand direct exposure to the 11;'

high temperatures of a re chamber Without material loss in strength. Erven where tube sheets have been used for the support of a bank of tubes extending vertically in single row through the fire chamber, the temperature rise, due to the direct application of heat thereto, has been sufcient to cause failure of such tube sheets. For that reason tubes in double row have been disposed in vertical rows through the fire chamber with the tube sheet between the rows and shielded by them from the direct heat of the re chamber.

In carrying out my invention in one form thereof, I have provided satisfactory means for supporting a single row of tubes which extends across the fire chamber. More particularly, I provide uid cooled pillars each of which conssts of concentric pipes, heat insulated by a series of refractory discs surrounding the outer pipe. the inner pipe and is discharged near the upper closed end of the outer pipe which forms a pillar for the intermediate support ofthe tubes. The relative diameters .of thetwo pipes vare of size such that adequate cooling fluid mayflow through them and at such velocity as to prevent more than a predetermined `rise in .temperature of the outer .tube-supporting pipe. The cooling lluid may be low temperature steam or circulation of cool.- ing air may be accomplished by subjecting .the outlet of .each outer vpipe to the stack draft. Aeluitable inlet and outlet headers intercorlrlect the several tube-supporting means or pillars.

For a more complete understanding of ,my inventiOn, reference should be had to the accom- Ipanying drawing in which:

Fig. .1 is a sectional elevation of a Aheater embodying my invention;

Fig. 2 is ,an :enlarged View lof one of the pillars of Fig. 1; and

The cooling fluid is Vintroduced through l Fig. 3 is Aa section taken on the line 3-3 of jFig. 2.

Features of the heating system of Fig. 1 are .disclosed and claimed in my accompanying application, Serial No. 492,653 filed June 26, 1943, and entitled Petroleum heaters, which in turn is a divisional application of Serial Number 446,298 filed June 8, 1942.

Referring to the drawing, I have shown my invention in one form as applied to a single vend red heater I0 comprising a bank of floor tubes I I disposed horizontally and in single row adjacent the refractory floor I2. A single row lof tubes I3 is diposed adjacent the sloping roof portion I4 and a single row of tubes I5 extends yhorizontally across the fire chamber `and about midway thereof. Heat is generated by the combustion of fuel, preferably gas or oil, introduced into the heater in a plurality of streams by means of a series of burners I6 and I'I, respectively provided with burner control valves I8 and I9. Each burner is provided with `a mule for directing burning gases yover .and Vabove the bank of tubes .below it. For example, the Inutile 20 for the `burner I6 directs burning gases above the intermediate bank of tubes I5 and below the lroof tubes I3. Similarly, the muflle 2I directs burning gases above the ioor vtubes II and below the intermediate tubes I5. The number of burners and munies depends upon the length of the tubes of the severalbanks and it is to be understood that a plurality of burners IB and I'I and their associated' inutiles `20 and 2I may be provided in horizontal array along the front wall 22 of the heater i. For tubes having .a length of twenty feet, six burners and associatedmuiiles may be provided above and below the intermediate bank I5.

Heat is transferred largely by radiation from the burning gases to the oil oruid conducting tubes II, I3, and I5, and transfer thereto by convection is minimized. The gases from the burners 2,0 exit through openings 23 in the rear wall of the heater and convectively heat a bank ,of convection tubes24. The gases and products of combustion from the burners -2I exit through a plurality 0f openings 25 in the rear Wall of the heater and convectively heat a bank of convection tubes 2 6. The gases from the lower .part of Vtheheater after passage through the bank 126 mingle with those entering through the openings 23 and the combined streams together heat the convection `bank 24. The gases exit by way of a stack 2.1.

The roof tubes I3 are supported by means .of

.low space within the column 3|.

tube sheets 23 suspended by means of a plurality of anchor bolts 29 extending from associated structural steel (not shown). The floor tubes are supported on refractory brick (not shown) which may be laid upon the oor I2. The intermediate bank of tubes l is supported by means of a plurality of tube sheets 30, carried by a number of pillars 3| and 32. Since the pillars 3| and 32 are subjected to the direct heat from the re chamber, the metal temperature thereof must not be permitted to rise above a predetermined amount.

As is well understood, after a metal reaches a certain temperature the strength rapidly decreases. It is an important object of my invention to provide pillars having fluid cooled means for maintaining the metal temperature below a value which would cause material loss of strength of the metal. As best shown in Fig. 2, each pillar, for example, the pillar 3|, comprises a relatively large cylindrical pipe 34 of heat-refractory metal, which may be fabricated with a closed upper end or the upper end may be closed by a member 35 welded thereto and having an intermediate portion 33 adapted suitably to engage the tube sheet 30 for the support of the tube sheet and its tubes I5. The lower open end of the cylindrical pipe 34 embedded in the concrete foundation is Welded to a header 3l also cmbedded in the foundation and of sufficient strength for the support of its proportionate part of the weight of the tubes l5. To insulate and to provide protection for the pipe 34, heat insulating refractory material, preferably of a ceramic or fire brick character, is preformed into washerlike shapes 38 Whose inner diameters are approximately equal to the outer diameter of the tube 34. These washer-like members or discs 38 are piled one on top of the other and in encircling relation with respect to the tube 3'4. Insulating discs 38a, of lesser diameter are used between tubes lla, and Hb. In this manner the tube 34 is shielded from the direct heat of the fire chamber. Additional plastic refractory insulation (not shown) may be molded around the closure member 35 and also molded around the base of the pipe 34 or around the point where it passes between the adjacent floor tubes lla, and Hb.

The cooling of the supporting pipe 34 of pillar 3| may be conveniently accomplished by injection of low temperature steam in headers 43 and by means including a pipe 40 of relatively small diameter which extends upwardly into the hol- Cool air or steam introduced through the pipe 40 is discharged from its upper end toward and against the closure member 35. The air and/or steam then flows downwardly along the inner wall of the pipe 34 and maintains the temperature thereof withina safe Working range by absorption of heat therefrom.

As shown in Fig. l, each pipe corresponding with that of pipe 33 is connected with a large' header or duct 3l which terminates at the stack 21 and is connected into it. The header 3l and the several pipes corresponding with the pipe 34 are thereby subject to stack draft. The inner pipes corresponding with the pipe 4!) are connected to a header or duct 43 which may preferably be open to the atmosphere for the introduction of cooling air. As shown, headers 43 connect with a header 44 open to atmosphere at a point to one side of the heater structure.

In a typical embodiment of my invention the pipe 34 may be four inches in diameter and will be surrounded with insulating discs 38 providing about four inches of heat insulation around the pipe 34. The inner pipe 40 may be two and a half inches in diameter and provides for the flovl of 30 cu. ft. of cooling air per minute through each inlet tube 40. Cooling air in this quantity maintains the metal of tube 34 within a safe working range of temperature, of from 400 F. to 700 F. If air entering through the pipes 40 is at a temperature of approximately '75 F. then its temperature upon entering the outlet header or duct 3l will be about 375 F. The loss of heat as a result of the air-cooled pillars represents less than 1/2% of the heat released by the combustion of the fuel, a percentage which is inconsequentially small when considered in connection with the advantages of the intermediate bank of tubes l5. When low temperature steam is also used as above explained, an even greater cooling effect is obtained.

It is to be understood when the pipe 34 is of carbon steel, greater cooling must be provided than for a more heat resisting alloy, such as one including substantial percentages of nickel and chromium for the reason that the strength of carbon steel decreases more rapidly with temperature than does that of the heat resisting alloy.

As more fully explained in my aforesaid copending application, the maximum density of heat application is the same for the intermediate bank of tubes I5 as it is for the floor and roof tube banks and I3. A greater uniformity in the average rate of heat application per square foot of heat absorbing surface may be accomplished by a relatively close spacing of the tubes I5 as compared with the spacing of the tubes and |3; more specifically, for approximately the same maximum intensity of heat applications per square foot of heat absorbing surface. the tubes in each of banks and I3 may be spaced one from the other approximately four tube diameters, While the tubes in bank I5 are spaced one from the other by only about one and onehalf tube diameters.

The flow of fluid, ordinarily petroleum or one of its components, may be as desired. For eX- ample, it may pass through heat-absorbing tubes 26, 24, I3, l5, and in the order named or the several banks may be connected for a different sequence of flow.

While I have described particular embodiments of my invention, it is to be understood that I do not limit myself thereto, since many modifications maybe made, and I therefore contemplate by the appended claims to cover any such modications as fall within the spirit and scope of my invention.

What I claim is:

1. In a heater having a fire chamber and a bank of fluid-conducting, heat-absorbing tubes extending as a bank across said re chamber, the combination of means within said re chamber providing support of the tubes of said bank intermediate the ends thereof comprising hollow pillars closed at one end, a 'tube sheet for the tubes of said bank supported on the closed ends of said pillars, means forming an inlet passage and an outlet passage for ingress and egress of a cooling medium to and from the interior of each said pillar, and means connected to said passages for circulating said cooling medium through each of said pillars in heat exchange therewith.

2. The combination as set forth in claim 1, in which the area of said outlet passage is substantially larger than the area of said inlet passage, the inlet passage extending into and through the major part of said outlet passage and arranged to discharge its cooling medium adjacent the tube supporting end of each pillar.

3. The combination as set forth in claim 1, in which said outlet passage consists of a pipe of heat refractory metal and of substantial diameter and closed at one end and in Which said inlet passage consists of a pipe of materially less diameter, said inlet pipe nesting within said outlet pipe and arranged to discharge said cooling medium near the upper closed end of said outlet pipe.

4. The combination as set forth in claim 1, in which headers are provided for the inlet and outlet passages of said pillars, the headers extending to said inlet passages being open at one end to atmosphere and the headers extending to said outlet passages being subject to stack draft for inducing circulation of said cooling medium through said inlet passages and out of said outlet passages.

5. A heater having a re chamber and a bank of tubes extending horizontally across said fire chamber, a tube sheet interconnecting and supporting said tubes, and means within said lire chamber for supporting said tube sheet comprising a hollow pillar of heat refractory metal extending from the door of said heater into abutting and supporting relation with said tube sheet, refractory heat-insulating material surrounding said pillar and minimizing the flow of heat to said pillar, a pipe extending into said hollow pillar for discharge of cooling air adjacent the closed end thereof, means subject to stack draft connected to the opposite end of said pillar for inducing flow of air through said inlet pipe and into cooling relation with said holloW pillar, and means connected with said inlet pipe for flow of air from atmosphere into said pillar.

6. In a heater having a lire chamber, a bank of tubes extending across said fire chamber, means providing intermediate support of said tubes comprising a cylinder of heat refractory metal closed at its upper end, means supported from its closed end for providing said intermediate support of said tubes, a plurality of Washerlike elements of refractory heat-insulating material stacked one above the other for protecting and insulating said cylinder from the heat of said re chamber, and an inlet cylinder extending from the open end of said outlet cylinder to a point adjacent the closed end thereof for ingress of cooling air, said inlet and outlet cylinders having diameters adequate to provide for the circulation of cooling air in sufficient quantity to maintain the temperature of said outlet cylinder below a predetermined degree, and means connected to one of said cylinders for producing iloW of said cooling air into one and out of the other of said cylinders.

7. In combination with a heater having a supporting foundation and a fire chamber, of an intermediate tube-supporting means comprising a uid cooled pipe of heat-refractory metal closed at one end, means carried by said closed end of said pipe and forming an intermediate tube-support, a header for cooling fluid extending laterally of said pipe and through said supporting foundation, said pipe opening into and supported by said header, heat-insulating means surrounding said pipe throughout the length thereof Within the fire chamber of said heater, and means for supplying cooling uid to said pipe.

8. The combination as set forth in claim 7, in Which said last-named means includes a pipe of smaller diameter nesting Within said firstnamed pipe, and a header for cooling luid disposed Within said foundation connected to and supporting said pipe of smaller diameter.

FRANK H. PRAEGER.