US2385749A - Heater - Google Patents

Description

Patented Sept. 25, 1945 HEATER John S. Wallis, Darlen, and' John W. Throckmorton, Wilton, Gonn assignors to Petra-Chem Process Company, Incorporated, New York, N. Y., a corporation of Delaware Application April 29, 1944, Serial No. 533,421

1 Claim.

This invention relates to a vertical furnace or tubular heater employing predominantly radiant heat in the transmission of heat energy from combustion gases to the fluid circulating through its heat exchange elements. The furnace is particularly adapted for small size installations where reduction in capital cost of the installation is a major factor, the furnace being particularly adaptable to units of 10,000,000 B.t.u. per hour heat absorption. Among the salient objects are to provide a heater construction including the following structural features:

a. A vertical heating chamber having vertical tubular heating elements arrangedabout its interior wall fired at the bottom and with a top flue gas outlet.

b. A depending funnel shaped baflle open at top and bottom, positioned in the upper part of the heating chamber.

c. Inlet ports for the admission of a tempering gas such as air at atmospheric temperature into the top of the heatin chamber above the baffle where the heating gases enter the flue.

d. Inverted U-shaped tubular units supported at their lower extremities and held in position by guides adjacent the wall of the chamber near the top.

e. The top of the furnace and chimney being removable to facilitate withdrawing the bafile and tubular units from the heating chamber.

Generally, it may be said that "the invention resides in a furnace consisting of a series ofv inverted U-tube heating elements (each unit in so far as their upper extremities are concerned being identical in design) so that the upp r return bends of the heating elements remain entirely within the flue gas passage (requiring no top tube sheets ortop header box doors) and the lower end of the heating elements interconnected with removable cleanout plugs outside of the flue gas passage, so that all tubes may be cleaned tion of a furnace in which a modified type of baiile is used.

Referring to the drawing and particularly to Fig. 1, the heating chamber of the furnace comprises a cylindrical steel casing l lined with fire brick I l and insulation l2 of a suitable type which will satisfactorily withstand the temperatures existing within the chamber. The floor of the furnace is also lined with fire brick as shown'at l3.

Centrally of the furnace floor is positioned a burner M which is fired with gas or 011 fuel through pipe l5. Instead of gas or liquidfuel the furnace may be fired with coal, in which event the burner will be replaced by grates and suitable stoking apparatus. In the sides of the furnace chamber are observation plates l6 through which the furnace operation may be viewed.

The furnace is supp rted on standards I! which are bolted to any suitable type of foundation. The furnace structure is built essentially in three pieces including a main cylindrical portion surrounded by the casing ID, a truncated section l8 and the stack or chimney 19. Sections I8 and I9 may be separate or may be shop fabricated as a single unit. Hung from the truncated section by means of rod supports 20 suitably insulated from the heat of the furnace gases is a funnel shaped baflle 2| open at the top and bottom to permit circulation of the furnace gases in the direction indicated by the arrows.

Adjacent the interior wall of the furnace are arranged a plurality of heating tubes 22, adjacent tubes connected by return bends 23 at their upper extremity and by cross-over connections 24 at the bottom. The bottom connections are equipped with removable plugs 25 in alignment with the internal y from below and eliminate the conventubes Which permit cleaning of the tubes from below. The bottom connections 24 are equipped with shoulders or lugs 24a which rest upon an annular tube sheet 25 positioned beneath the tubes and supported by plates or angles 26 which form the lower structural members of the furnace. These connections are protected from the furnace heat by segmental blocks of insulation l3, as shown in Fig. 2. To maintain the relative position .of the tubes along the wall of the furnace and to prevent Warping of the tubes due to temperature changes tube guides 21 surround the upper extremities of the tubes and are fastened I to the furnace wall by suitable supports 21a.

The tube surfaces exposed principally to radiant heat are bare surfaced while the sections of the tubes within the annular space formed by the vertical wall of the bafile and the furnace wall where convection heat predominates extended surface is attached to the tubes. This extended surface preferably takes the form of longitudinal radial fins shown at 28. r I

In the modified form of constructionshown in Fig. 3, the structural features of the furnace are identical to those shown in Fig. 1 with the exception that an inverted conical baille 2ia, slightly truncated at its lower end, has been substituted for the funnel shaped baiiie shown in Fig. 1. The

.and by removing stack i9 and support rods 20 the entire baille may be lifted through the top opening. Likewise, tubes may be installed or removed baiiie shown in Fig. 3 is open ended as is the baffle shown in Fig, 1 permitting circulation of the combustion gases from top to bottom so that there is constantly circulating through the bailie a relatively cooler gas than the gas surrounding the outside of the baiile. In the modified form shown in Fig. 3, the extended surface section has been eliminated since the tubes are subjected 'to considerably more radiant heat throughout their length and substantially to their upper extremities in the construction shown in Fig. 3.

Both furnaces are equipped in the truncated section above the baffle with air inlet ports 29 which have closure plates adjustable to permit the admission of a desired amount of tempering or diluting gas, such as atmospheric air. Air introduced in this section of the furnace serves to temper the heat of the gases passing to the chimney and reduces excessive and troublesome oxidation occurring at the base of the chimney and within the stack.

While a single burner is shown in the bottom of the furnace, it is contemplated that a plurality of burners may be used or grates, if solid fuel is burned, as a source of the heating gases.

In operation the furnace is fired from the bottom, combustion gases passing upwardly transmitting both radiant and convection heat to the vertical tubes positioned against the interior furnace wall surface. The battle positioned in the upper part of the heating chamber diverts the heating gases outwardly against the upper sections of the tubes. Where extended surface section is employed adjacent the balile additional heat is absorbed due to this extended surface.

The gases after passing the annular space between the baffle and furnace wall are diluted with air or any suitable cooler gas introduced through ports 29 before being discharged through the flue or stack IS. The amount of air or cooling gas introduced through ports 29 will depend upon the temperatures existing within the furnace above the baiile. A portion of the heating gases tend to circulate downwardly through the baflie and out through its lower end to join or blend with the furnace gases. These eddy currents circulating downwardly through the baiiie are relatively coolin the same manner from the top of the furnace by removal of the truncated section and chimney.

In brief, the improvement lies in the combination of structural features which include a vertical furnace employing vertical tubes arranged against its interior wall supported at the bottom upon a tube sheet and having permanent return bend connections at their upper extremities. The tubes are held in position within the furnace by upper guide members which prevents lateral displacement or warping of the tubes which would alter their position relative to the baiiie member. The design is also original in the ining and stack from high temperature oxidation.

' Further protection to the upper portion of the furnace" is afforded by a lining of insulation shown at 30 within the upper truncated section of the fumace. All tubes are cleanable internally from below and no ladders or platforms are required for access to the top of the heating elements.

From the foregoing, it will be seen that the invention is one well adapted to attain all of the ends and objects hereinbefore set forth together with other advantages which are obvious and which are inherent to the furnace structure.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

Having thus described our invention, we claim: In a furnace of the vertical type comprising an upright chamber fired at the bottom and with a flue gas discharge at the top wherein tubular heat exchange elements are arranged about the interior wall, a funnel shaped baflie open at top and b0ttom in the upper part of the chamber be-

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