US2660519A

US2660519A - Fluid heater

Info

Publication number: US2660519A
Application number: US22782A
Authority: US
Inventors: Lawrence J Mccarthy
Original assignee: Chemical Construction Corp
Current assignee: Chemical Construction Corp
Priority date: 1948-04-23
Filing date: 1948-04-23
Publication date: 1953-11-24
Anticipated expiration: 1970-11-24

Description

Nov. 24, 1953 Filed Apr i1 25, 1948 L. J. M CARTHY FLUID HEATER 6 Sheets-Sheet 1 67" (60 7 INVENTOR lflW/Pf/VCf C/ MC 64/5 7):

ATTO RN EY Nov. 24, 1953 L. J. Mcc 2,660,519

FLUID HEATER Filed April 25, 1948 6 Sheets-Sheet 2 INVENTOR 30 A .u. MC 644 7921 BYQ 9 ATTORN EY L. J. MCCARTHY FLUID HEATER Nov. 24, 1953 e Sheets-Sheet 5 Filed April 25, 1948 V INVENTOR .4 fll MQf/VCF 1 Ma" (WET/,0;

' BYgf 9 S ATTORNEY NOV. 24, 1953 J MCCARTHY 2,660,519

FLUID HEATER Filed April 25, 1948 6 Sheets-Sheet 4 BY 6*. 9. M%

ATTORN EY NOV. 24, 1953 L J MCCARTHY 2,660,519

FLUID HEATER Filed April 23, 1948 6 Sheets-Sheet 5 HIHII" INVENTOR A flWif/VCA a. Mo (3427/7 11 ATTORN EY Nov. 24, 1953 Filed April 23, 1948 J. M CARTHY FLUID HEATER 6 Sheets-Sheet 6 .IVIIII ATTORNEY Patented Nov. 24, 1953 UNITED STATES PATENT OFFICE FLUID HEATER Lawrence J. McCarthy, Hawthorne, N. J assignor to Chemical Construction Corporation, New York, N. Y., a corporation of Delaware Application April 23, 1948, Serial No. 22,782

1 2 Claims.

This invention relates to an improved apparatus for the application of heat to fluids. It is particularly adapted to conducting endothermic reactions such as gas reforming.

In Patent 2211,3 63, issued to me on August 20, 1940, there is described a heater for fluids having a radiant heating chamber with fluid conducting tubes extending vertically through the chamber where the tubes are arranged in a plurality of banks radiating substantially from the central portion of the chamber to divide it into a plurality of heating cells so that at least one cell is disposed on each side of each bank of tubes and where the tubes in each bank are connected in series and with the tubes of one or more banks so that the fluid to be heated flows successively through a plurality of banks in the single heating chamber. Radiant heat is supplied to the tubes by heating the walls with burners disposed in the bottom of each cell adjacent the wall and also by wall burners.

The present invention relates to new and useful improvements in the furnace described in my patent referred to above. My improved furnace is intended. to be a heater for fluids generally and is particularly useful for conducting endothermic reactions. For convenience it will be described in connection with the production of hydrogen by the catalytic reaction of methane with steam, although the invention is not limited thereto.

One of the obiets of my invention is to improve the heater or furnace described in my patent referred to above. Another object is to provide a furnace in which the hot gases of combustion will flow substantially longitudinally and parallel to the reaction tubes for that portion of their length exposed to radiant heat. Another object is to equalize the draft in the various cells formed by the plurality of radial banks of tubes disposed in a combustion chamber. A further object is to provide an overhead suspension arrangement for the reaction tubes in which the tubes will be free to expand, downwardly into the furnace from the point of their suspension. Another object is to supply preheated air to burners located in the floor of the furnace and adjacent the tubes by a manifold in each cell which is an integral part of the fioor thereof. Still another object is to provide overhead suspended reaction tubes in which the fluid in ets and outlets for the tubes are adjacent each other.

With the above and other objects in view the invention therefore consists in the various arn e ents and m t o s of a paratus clements hereinafter to be specifically described with particular reference to the preferred embodiments thereof illustrated in the accompanying drawings. In the drawings:

Fig. 1 is a vertical section taken along the line |--l and in the direction of the arrows of Fig. 2;

Fig. 2 is a section taken along the line 22 and in the direction of the arrows of Fig. 1;

Fig. 3 is a section partly broken away along the line 33 and in the direction of the arrows of Fig. 1;

Fig. 4 is a view in perspective of the gas collecting chamber showing the manifold arrangement;

Fig. 5 is a section taken along the line 5-5 and in the direction of the arrows of Fig. 1;

Fig. 6 is a section taken along the line li-B and in the direction of the arrows of Fig. 5;

Fig. 7 is a vertical section partly broken away of a reaction tube;

Fig. 8 is a section in detail showing the suspension of a tube;

Figs. 9 and 10 are end views of the bottom of one of the tubes with the cover plate removed.

Referring to the drawings, in Fig. 1 a furnace assembly shows a combination in which a foundation made of a suitable structure of iron I- beams supports cylindrical load-bearing walls 2 which enclose a radiant heating section 3, a gas collecting section 4 and a space 5 in which are located the suspension means and inlet and outlet manifolds. Banks of vertical heating tubes or catalytic tubes 6 preferably in cruciform arrangement extend downwardly through both the gas-collecting chamber s and the radiant heating chamber 3 and divide both chambers into four heating cells, the tubes being free to expand into the wells I placed in the floor of the furnace.

Transverse trusses or beams s mounted at the top of the load-bearing walls 2 and supported by them extend across the central portion of the furnace. Preferably two transverse trusses or beams 9 are used and attached to them at one end and to the load-bearing walls 2 at the other are support angles 8 which together with beams 9 frame the top of the furnace. On this structure cover plates 8a rest. Suspended from the beams 9 are the tension members it which extend downwardly into the central portion of the furnace. An upper set of transverse beams l I and a lower set 12 are attached at their inner ends to the suspension members it and at their outer ends to the load-bearing walls 2. The tension members E E3 and the sets of transverse beams H and I2 cooperate with the load-bearing walls 2 to outline the general contours of the gascollecting chamber which in turn takes the outline of the tube bank arrangement.

The walls It and the ceiling I4 of the radiant heating section 3 and the walls 15 and top iii of the gas-collecting chamber 4 are composed of suitable refractory material which protects the load-bearing walls 2 and the suspension means including members 8, 9, H], II, and I2 from the hot products of combustion. To further cool the suspension means, ventilating ports ll are provided in the space 5 to permit circulation of air therein. The bustle pipe l8 surrounds the furnace and supplies preheated air to a manifold under each cell which forms an integral part of the floor for the cell. The air flows from the manifold into the banks of burners which are placed in each cell adjacent the ends of the vertical tubes.

The flow of the fluid reactants through the furnace can best be illustrated by referring to Fig. 4, which shows a perspective arrangement of the gas headers or manifolds which are located in the space and to Fig. '7. The mixture of relatively cool methane and steam is led into the inlet manifolds E9 provided for the tubes of each cell and passes through pipes 26 into the catalytic reaction tubes '5. In the catalytic reaction tubes which are the nested tube type, the fluids pass downwardly between the outer and inner tube and in contact with the catalyst, where the reaction takes place, and then pass up through the inner tube and into the tubes 2| which lead them to the outlet manifolds 22 from which the fluids are withdrawn from the furnace. Instead of passing the fluids countercurrently to the hot products of combustion as shown, they may be passed concurrently with the hot gases by introducing the fluids into the tubes through manifolds 22 and withdrawing them from manifolds l9.

The flow of the heating gases during the furnace operation is best shown by referring to Figs. 1, 4, 5, and 6. Preheated air enters the furnace from bustle Hi passing into the manifold which vforms a part of the floor in each cell and passes up alongside the burners embedded therein and which are adjacent the tubes. In each cell the hot products of combustion pass from the burners substantially parallel to the portion of the tubes in the radiant heating chamber and collect in the

sections

23, 24, 25, and 26 which constitute the gas-collecting chamer 4. In chamber 4 the gases pass transversely to the tubes, leaving the chamber through section 26 which connects with a stack.

Upper access doors 21 and lower access or explosion doors (not shown) are placed in the walls 2. Access to the space .5 may also be had through the top of the furnace by removing plates 8a. The doors 2? may also cooperate with the ports ll to circulate cooling air to this space.

Since the heat for the reactions is supplied principally by radiant heat and since the reaction in each of the tubes should proceed equally, it is desirable that the hot gases pass substantially parallel and longitudinally of the portion of the tubes in the radiant heating chamber. When the gases pass through the radiant chamber in this manner they radiate heat to the tubes and to the walls of the chamber which in turn reradiate heat to the tubes so that all of the tubes are heated alike. The flow of the hot gases longitudinally of the tube in the radiant heating zone is accomplished by having the burners in the 4 bottom of the furnace and adjacent the tubes and by placing the gas-collecting chamber above the radiant heating chamber and also by varying the of the openings between the two chambers in such a way that the draft in each of the

sections

23, 24, 25, and 25 of the collecting chamher is substantially equal.

The arrangement to equalize the draft is illustrated in Figs. 1 and 2. In these figures the walls is of the gas-collecting chamber are shown; below these walls and at the entrance from the radiant heating chamber 3 to the gas-collecting chamber 5 are the baffles 23. These baffles which may be extensible, are a continuation of the roof of the radiant heating chamber. They extend beyond the walls 65 for varying distances in such a way as to equalize substantially the draft within each cell and one cell with respect to another. Thus in each

section

23, 24, and 25 of the gascollecting chamber 4, the cross sectional area of the opening into the section is reduced progressively from the walls 2 to the center of the furnace substantially as shown in Fig. 2. In section 26, however, which contains the outlet 29 to the stack, the cross sectional area decreases progressively from the center of the furnace to the walls 2. With this draft equalizing arrangement and by locating the burners adjacent the tubes, there is substantially no tendency for the gases to deviate from their path longitudinally of the tube in the radiant heating chamber or for the gases to pass therein from one cell to another in the direction of the flue outlet. These features are among the principal advantages of my in vention.

I will now describe the manner in which the tubes are suspended. In Fig. l the I-beams 35) which are located at suitable intervals external to the gas-collecting chamber 4 are fastened at their lower ends to the transverse beams 12. They are attached at their upper ends to channel beams H by means of clips 32. The channels ll are attached at their inner ends to the tension members H) by means of clips BI and on the channels 1 l rest tube support plates 33.

The manner in which the plates rest on the channels is shown more fully in Fig. 3. This figure shows the general relationship between the I-bealns 30, the clips 32, the channels Ii, and the tube support plates 33. Also shown are the tension members [0 an clips 3|. There is an individual support plate 33 for each of the tubes and each plate is provided with a hole 3 1 in the center of the plate through which the tube is inserted. The four tubes around the center of the furnace are supported by the four triangular type plates 35, which, as shown, rest on channels ll. These four plates are also supported by diagonal tie members (not shown) which are framed beneath the plates 35 and are attached. to tension members H].

The suspension of the tubes is shown in more detail in Fig. 8 which shows the vertical I-beams 30, the clips 32, channels II, and the tube support plate 33 all fastened together by rivets although this fastening may also be by bolts or by welding. The hole 34 through which the tube is inserted is sufficiently large so that the lower edge of the lugs 31 which are attached to the tube 6 will fit down into the hole and between the plates 33 and tube 6.

The manner in which the suspension means supports the weight of the insulation which forms a. part of the ceiling of the radiant heating chamber and the walls and top of the gas-collecting chamber as well as the bafile between the two chambers is shown by Figs. 1 and 2. It will be seen that the ceiling M- of the radiant heating chamber and the walls I of the gas-coll cting chamber are supported by the transverse beams l2 which comprise two angles fastened together as illustrated by the numeral 211 in the Fig. l. The individual pieces of refractory in the walls l5 may also be attached to prong-like projections attached to angles which may be attached to I- beams 33 and spaced above and parallel to l2a. The rods 33 are supported at one end by the load-bearing walls 2 and at the other end on the angles i2a. From this system of rods which is shown in Fig. 2 the individual pieces of refractory in the ceiling H are hung by means of hooks 39 shown in Fig. 1. The top of the gas-collecting chamber is is hung in a like manner from the channels II. This is done by attaching angles to the lower edge of the channels H which support the rods to which the hooks, which are fastened to the individual pieces of refractory, are attached. For clarity in the drawing, the angles, rods and hooks attached to the channels H are not shown.

The weight of the baiile 28 which is an extension of the ceiling I4 is also borne by the transverse beam l2. Since the draft in the gascollecting chamber is equalized by extending the bafile for various distances into the opening between the gas-collecting chamber ti and the radiant heating chamber 3, some of the pieces of refractory material which form the baffle will extend farther into the opening and may require additional support. Such pieces of refractory as Well as the smallest ones may be supported by attaching a plate or plates or prong-like plates to the bottom of the transverse member l2. By providing a hole or a slot in the piece of refractory into which the plate attached to the transverse member is insertable, the refractory will be supported. It should be noted that the plates referred to above may be extensible plates.

The burner arrangement and the means for supplying preheated air to the burners is shown in Fig. 5. This figure shows the bustle pipe l3 which surrounds the lower portion of the furnace and which is attached to it by the clips 4 i. The ducts 42 leads the preheated air from the bustle it into the manifolds which constitute an integral part of the floor of each cell of the furnace. In the preferred form of the furnace there are twenty tubes in cruciform arrangement and for each cell formed by the tubes there are five burners placed in the manifold of each cell and adjacent the tubes. The burners are indicated generally by the numeral cc.

This construction is shown in more detail in Fig. 6. This figure also shows the clips ll, bustle it, the duct 42 provided with the damper 63, the manifold 44, the burner Ml. The flow of the preheated air is shown generally by the arrows, the air flowing from the bustle through the duct and into the manifold. From the manifold the air passes through the opening 45 in the bottom of the burner and then passes up through the burner where it contacts the fuel issuing from the burner nozzles.

The top of the manifold is formed by the plate 46 which is attached to the load-bearing wall 2. On this top plate rests the insulation 1 3. The top plate it rests on the channels ll which form the sides of the manifold and which are also a part of the iron construction I, shown in Fig. 1, which is the load-bearing foundation referred to earlier.

The bottom of the manifold is formed by the plate 48. The duct 42 is attached to the bottom of the manifold and to the bustle ill by the angles 49. The walls and the bottom of the manifold are suitably insulated with the insulation 56.

Fig. 6 also shows the well construction which accommodates the tube expansion referred to earlier. Each reaction tube extends through individual holes 5! which are also shown in Fig. 5 and which are located in the insulation of the floor of the furnace. Below each hole individual wells 1 are attached to form a substantially gastight cell with the floor. As shown, the well 1 is cup-like in construction with an insulated interior and an access plug 53 on its bottom which may be used to attach a thermocouple to any part of the tube 6. Each well is attached to the chan nels 4'! by clip angles 52. Instead of providing an individual well for each tube, a continuous well or trough for each bank may be used.

Tube details are shown in Figs. 7, 9, and 10. Fig. 7 shows the general assembly of the gas-tight reaction tube 6 in which 54 is an outer tube con taining an extensible inner tube having two sections, the upper section of which is 55 and the lower section 56. The lower portion of the space between the inner and outer tubes is filled with filler elements such as Raschig rings to a height above the perforations 51 in the section 55. These flller elements prevent the loss of catalyst by dusting in that they prevent the catalyst from being carried along by the moving fluids. Above the filler elements and to any desirable level the tube is filled with a catalyst 58 such as a catalyst required for the reaction between methane and steam. The path of the fluids through the reaction tube 6 is shown generally by the arrows. A thermocouple (not shown) may be placed in the bed of the catalyst.

The outer tube 54 is provided with a flange 59 at its upper end and flange 58 at its lower end. The fluid inlet 5! is located below the upper edge of the tube 54 and is provided with a flange 62 by means of which the fluid inlet is attached to the inlet manifold. Three lugs 31 are placed equidistantly around the circumference of the tube and below the fluid inlet. In the lower portion of the outer tube 54 the walls slope inward to form section 63 of a reduced diameter. The upper edge of the restricted diameter portion 63 is provided on its inner side with a flange 54 and spaced below this flange and equidistantly around the inside diameter are placed three lugs 65. The flange 64 and the lugs 55 cooperate with a notched flange 56 on the outside of the lower section 56 of the inner tube such that when this section is inserted and turned it will be held in place. The cover plate 87 equipped with sealing ring 68 may be attached to the bottom of the outer tube 54 by bolting it to flange with bolts 69.

The diameter of the upper section 55 of the inner tube is smaller than that of the lower section 55 and the lower part of tube is inserted into the upper part of tube 51% so that the two tubes are slideably engaged. In its upper portions, the pipe 55 bends toward the walls of the outer tube 54 as shown in Fig. 7 and emerges from the outer tube thrcugh closure iii which is an integral part of this upper tube but which may be detachably joined with it. The end of the tube 55 is provided with the flange 1! by means of which the inner tube is attached to the outlet manifold.

The closure ill is provided with the opening Ha through which the filler elements and the catalyst may be introduced to the tube 5. This openin is sealed with the closure 12 which is bolted to the closure 10 by means of bolts 13. The closure 10 may be attached to the tube 54 by clamping it to the flange 59 by means of the bolts 14 and the ring flange 15.

As described above the inner surface of the pipe 55 having the perforations 51 engages the outside of the pipe 55 to form a slideable joint. The notches on the flange 66 which is attached to the lower portion of the pipe 56 permit this pipe to be inserted past the lugs 65 which are attached to the inside of the tube 54. When this pipe is so inserted and turned by means of a suitable tool which is applied to the indentations T5, the pipe 56 is supported by the lugs 65 and is prevented from moving upward by the flange 64. Two advantages are derived from the sectional structure of the inner pipe. One of these is that any difference in expansion between the inner and outer tubes is easily accommodated by the slideably engaging joint and the other is that the lower portion only of the inner tube need be removed to remove the rings and the catalyst.

Figs. 9 and 10 show the manner in which the tube 56 is inserted into tube 54. Fig. 9 shows the relationship of tube 56 with respect to tube 55 after the former tube is inserted in the latter and without turning. This figure shows the flange EU, the recess H in which the sealing ring 83 is inserted and the walls 18 of the restricted portion 63 of the tube 54 to which are attached the lugs 65. Also shown are the inner tube 58 and the notched flange 55 which is attached to it, the notches in the flange 66 being spaced equidistantly around its circumference and corresponding as shown with the lugs '55.

Fig. 10 shows the same elements shown in Fig. 9 but in this figure the tube 56 has been rotated clockwise through an angle of 60 by inserting a suitable tool in the indentations it. This figure shows how the unnotched portion of the notched flange 66 rests on the lugs 65.

In the production of hydrogen from steam and methane where the reactants make a single reactive pass through a furnace, three problems are involved. The problems are:

(1) All of the tubes should be heated uniformly-J11 order that the reaction may proceed equally in each tube, heat must be supplied'uniformly to the tubes and to similar portions of the tubes in each cell.

(2) Precision must be made for the expansion of the tubes.Since the usual length of the reaction tubes is about 28 and an expansion of about in the tubes is not uncommon for the operating temperatures, adequate provision must be made for the expansion.

(3) The problem of suspension.--An overhead suspended type of tube is desirable for the furnace, and an adequate load-bearing structure must be provided. Moreover this structure must be protected from the hot products of combustion.

From the foregoing description of a preferred embodiment it will be apparent that all three of these problems are solved by the apparatus of by invention. The first problem is solved by the combination of two novel features. The gas-collecting chamber 4 is mounted on the radiant heating chamber 3, the side walls [5 and top I6 of the gas-collecting chamber cooperating to outline the general contours of the tube bank arrangement in the radiant heating chamber. The

her toward the flue gas outlet or outlets.

horizontal partition I4 which constitutes the celling for the radiant heating chamber has openings communicating with the gas-collecting chamber. This partition extends beyond the walls [5 of the gas-collecting chamber to form the baflies 28 which restrict the openings to areas of varying cross section so as to equalize the draft in the gas-collecting chamber.

Another feature of my improved furnace is that the burners 40 for each cell are placed in the floor of the furnace adjacent the tubes 6. All of the burners in a cell are supplied with preheated air by a manifold 44 for each cell which constitutes an integral part of the floor thereof.

This novel arrangement substantially eliminates the tendency of the hot products of combusticn to channel in the radiant heating cham- This is so because the draft in the gas-collecting chamher is the same above each tube and each bank of tubes. The hot products of combustion therefore pass from the burners which are placed in the floor of the furnace and adjacent the tubes through the radiant heating zone substantially longitudinally and parallel to the entire portion of the tubes disposed therein. Thus all of the tubes and similarly units of lengths of the tubes are heated alike and the reaction in each of the tubes proceeds uniformly one with respect to the other. This is one of the principal features and advantages of my improvements.

By withdrawing the fluids at a point adjacent to their inlet to the tubes, the expansion of the tubes is confined to the tubes alone. This is accomplished with a novel reaction tube 6 by placing a return tube having two slideably engaging sections, 55 and 56, inside the catalytic tube and placing the catalyst between the outer tube and the inner tube. The reactant fluids or gases then pass from an inlet manifold [9 down between the outer tube 54 and the inner tube and in contact with the catalyst therein. They then reverse their flow at the lower end of the outer tube, pass into and up through the inner tube to an outlet manifold 22 which is located at a point adjacent to the inlet manifold. In addition to having the catalyst in the form of an annulus which thereby facilitates the problem of supplying heat to the endothermic reaction taking place therein, this arrangement permits the overhead suspended tubes to expand downwardly without the necessity of providing means to allow the outlet manifold to accompany this expansive movement. Moreover their arrangement is flexible in that the reactant fluids may be passed countercurrently or concurrently with the hot products of combustion. These advantages are also features of my invention.

The suspension means by which the tubes are supported from their upper ends also bears the weight of the novel gas-collecting chamber 4 and the refractory which protects these means from the hot products of combustion. This is accomplished by placing on a foundation I substantially vertical load-bearing walls 2 which enclose the radiant heating chamber 3 and the gas-collecting chamber 4. Transverse beams 9 extending across the central portion of the furnace are mounted at the top of the walls 2 and are supported by them. Tension members [0 are suspended from the beams 9 and extend downwardly into the central portion of the furnace. An upper and a lower set of transverse beams H and I2 are attached at their inner ends to the tension members I0 and at their outer ends to the vertical walls 2. The

tension members and the transverse beams co operate with the walls to outline the surmounted chamber 4 and from them are hung the tubes 6, the inlet and outlet manifolds l9 and 22, the ceiling of the radiant heating chamber l 4 and the walls 15 and top 16 of the gas-collecting chamber. The suspension of these elements is carried out in such a way that the suspending means are protected from the hot products of combustion in the furnace.

One advantage of the suspension feature of the invention is that the tube supports do not shield any of the so-called working part of the tubes from the heat. Another advantage of the suspension feature is that the upper portion of the tubes and the means by which they are suspended from their upper portion are placed. adjacent that part of the furnace where the hot gases are at their lowest temperature. This arrangement also allows the furnace to be operated up the those temperatures where the'working portion of the metalalloy tubes becomes soft.

Although in the preferred form my furnace is circular in shape with twenty reaction tubes disposed in cruciform arrangement, there are a number of alternate forms within the scope of my invention. Thus for example any number and size of tubes supported from their upper or lower portions may be arranged in any number of banks which radiate symmetrically or unsymmetrically from the center of the furnace. Likewise the gascollecting chamber may be made to function as a convection-heating chamber and where fiuid heating tubes are used they may have attached to them on those portions of the tubes that extend into the convection heating zone suitable extensions or fins to control the flow of heat into these portions of the tubes. Where reaction tubes are used, whether or not the gas-collecting chamber functions as a convection heating chamber,

they may also have extensions or fins on either or both sides of the outer tube and on the outside and inside of the inner tube.

Although it is preferred to have a single row of tubes in any bank and to carry out the same reaction at the same rate in all the cells formed by the banks of tubes, a plurality of rows of tubes may be used in a bank and the same reaction can be carried out at various temperatures in the various cells of the furnace and even different reactions can be carried out in the various cells if so desired.

Instead of the single stack outlet disclosed above, two or more stack outlets may be used as well as a stack outlet for each section of the surmounted chamber and this may be particularly desirable when this chamber is used primarily as a convection heating chamber. Wherever a stack outlet is used the baffle construction should conform to that of section 26 in Fig. 2 in that proceeding from the center of the furnace to the 10 walls the baflies should extend progressively farther into the openings in such a way as to equalize the draft within a section and one section with respect to another.

What I claim is:

1. A furnace for conducting endothermic reaction having a heating chamber and a plurality of overhead suspended reaction tubes extending into said chamber below their point of suspension and being free to expand into said chamber below said suspension point, said tubes comprising an outer tube having a closure at its lower end, an inner tube nested therein and removably attached in its upper portion to the top of said outer tube, fluid openings for each tube in the upper portion thereof, the opening for the inner tube being outside the outer tube a flange on the inner lower surface of said outer tube, lugs on said tube spaced below said flange and a concentric foraminous cylinder slideably engaged at its upper end with the lower end of said inner tube and having a notched flange on its outside lower portion adapted to permit insertion of said cylinder past said lugs and upon rotation of said cylinder to be supported by said lugs and to abut on said flange on said outer tube.

2. In a furnace for conducting endothermic reaction a vertical reaction tube comprising an outer tube closed at its lower end, an inner tube nested therein and removably attached in its upper portion to'the top of said outer tube, fluid openings for each tube in the upper portions thereof the opening for the inner tube being outside of the outer tube, and a concentric foraminous cylinder attached to the lower inside portion of said outer tube and slideably engaged with the lower end of said inside tube.

LAWRENCE J. MCCARTHY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,737,173 Pratt Nov. 26, 1929 1,738,620 Umpleby Dec. 10, 1929 1,881,275 Huff Oct. 4, 1932 1,894,140 Wietzel et al. Jan. 10, 1933 1,917,357 Burk et al. July 11, 1933 2,028,326 Hanks et al Jan. 21, 1936 2,038,807 Synnott Apr. 28, 1936 2,173,984 shapleigh Sept. 26, 1939 2,198,555 Wilson et al Apr. 23, 1940 2,211,903 McCarthy Aug. 20, 1940 2,273,826 Bates Feb. 24, 1942 2,276,527 Throckmorton et al. Mar. 17, 1942 2,394,631 Neuhart Feb. 12, 1946 2,495,665 Spring Jan. 24, 1950 FOREIGN PATENTS Number Country Date 330,872 Great Britain June 19, 1930

Claims

1. A FURNACE FOR CONDUCTING ENDOTHERMIC REACTION HAVING A HEATING CHAMBER AND A PLURALITY OF OVERHEAD SUSPENDED REACTION TUBES EXTENDING INTO SAID CHAMBER BELOW THEIR POINT OF SUSPENSION AND BEING FREE TO EXPAND INTO SAID CHAMBER BELOW SAID SUSPENSION POINT, SAID TUBES COMPRISING AN OUTER TUBE HAVING A CLOSURE AT ITS LOWER END, AN INNER TUBE NESTED THEREIN AND REMOVABLY ATTACHED IN ITS UPPER PORTION TO THE TOP OF SAID OUTER TUBE, FLUID OPENINGS FOR EACH TUBE IN THE UPPER PORTION THEREOF, THE OPENING FOR THE INNER TUBE BEING OUTSIDE THE OUTER TUBE A FLANGE ON THE INNER LOWER SURFACE OF SAID OUTER TUBE, LUGS ON SAID TUBE SPACED BELOW SAID FLANGE AND A CONCENTRIC FORAMINOUS CYLINDER SLIDEABLY ENGAGED AT ITS UPPER END WITH THE LOWER END OF SAID INNER TUBE AND HAVING A NOTCHED FLANGE ON ITS OUTSIDE LOWER PORTION ADAPTED TO PERMIT INSERTION OF SAID CYLINDER PAST SAID LUGS AND UPON ROTATION OF SAID CYL-