US2276528A - Apparatus for heating fluids - Google Patents

Description

March 17, 1942. w. THROCKMQRTON "ET AL APPARATUS FOR HEATING FLUIDS Filed May 2, 1941 .2 Sheets-Sheet l INVENTORS. (Jo/7x7 l M ThracK Mafl/ar.

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March 17, 1942- J. w. THROCKMORTON ET AL 2,276,528

APPARATUS FOR HEATING FLUIDS INVENTORS.

ATTORNEY.

Patented Mar. 17, 1942 APPARATUS FOR. HEATING FLUIDS John W. Throckmorton, Wilton, and John S. Wallis, Darien, Conn., assignors to Petro-Chem Development Compan poration of Delaware y, New York, N. Y., a cor- Application May 2, 1941, Serial No. 391,522

2 Claims.

Our invention relates to afurnace construction for heating fluids and more particularly to a tubular furnace in which the heat exchange elements or tubes are verticallyipositioned in a combustion chamber around the perimeter of a circle and the combustion gases circulated over the tubes and through the combustion chamber to transfer relatively uniform radiant and convection heat to the tubes throughout their lengths.

The furnace is adaptable for use in any connection Where fluids are to be heated, as for instance the chemical industry for processingand distillation, and in the oil ind try for distillation, cracking and for other ty s of thermal processing as well as boilers and steam generation. 1

This invention is an improvement over the furnace shown in our copending applications, Serial No. 343,272, filed June 29, 1940, and Serial No. 384,892, filed March 24, 1941.

One object of our invention is to provide a furnace in which uniform heat intensity is distributed throughout the full length of all of the heat exchange elements or tubes.

Another object is to provide a furnace of high efliciency in-which radiant heat is uniformly supplied to the lower portions of the tubes and convection heat to the upper portions of the tubes.

A further object of the invention is to provide a furnace setting in which a plurality ,of heating elements such as tubes are arranged in the setting and fired'in such a. manner that uniform heat distribution is obtained circumferentially and longitudinally of the tubes.

Another object of our invention is to provide radiant reflecting surfaces and sources of combustion gases outside of the heat exchange elements which will supplement the radiant heat furnished from the combustion gases inside of the heat exchange elements to distribute'radiant' heat more uniformly over the entire heat transfer surfaces of the tubes or heat exchange elemerits.

Other and further objects of our invention will appear from the following description.

In the accompanying drawings which form part of the instant specification and are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views;

Fig. 1 is a sectional view of a furnace showing one embodiment of our invention.

Fig. 2 is a view-taken along the line 2-2 in Fig. 1.

Figs. 3, 4, 5, and 6 are half sections" showing.

modifications of the construction shown in Fig. 1.

Referring to the drawings, supported on a concrete base is a pedestal I which carries tube supports 2 and a prefabricated metal sheathing. 3. An internal alloy sheathing 4 is spaced from the sheathing 3 and'between the outer casing 3 and inner reflecting surface '4 is insulation 5.

While an internal alloy sheathing 4 is shown as in our previous copending applications, when utilizing the double firing both inside and outside of the tube circle the alloy sheathing may be dis- Y pensed with and the conventional type of refractory setting used. This insulating material is preferably mono-block, high temperature, or may be arranged inlayers with rcck wool blanket or the like. Vertically positioned within the combustion chamber 6 are a plurality of vertical heat exchange elements or tubes 1 arranged around the perimeter of a circle-within the combustion chamber and held in place at their upper extremities by a U-shaped channelm which renders accessible the removable return bend connections shown at 9. Similar return bend.con-

nections are available through the tube supports 2 at the lower ends of the tubes. At the bottom and positioned centrally of the combustion chamber is a combustion pct 10 in which are located burners ll. These burners are preferably 6 arranged tangentially of the combustion pot and The flow of combustion gases is may be of the directional type'so that the combustion heating gases produced from the burning of: liquid or gaseous fuel can be directed into the combustion chamber according to the direction: in which the burners are arranged. These burners ll furnish the heating gases to the combustion space inside of the circle of tubular heating elements. Outside of the heating elements and within the space 6 are burners l2 extending rise and join the combustion gases from burners II in a constricted passageway between the cone l4 and the upper truncatedcone section of the combustion chamber adjacent the conical -refleeting baflle. The cone I4 is ofalloy metal or other reflective material including refractories and is supported from the inverted funnel-shaped flue l5 by" rods l6, fastened to the base of the cone and to supports l1 arranged around the inside of the flue. The inverted funnel-shaped flue 16 has, mounted at its top, a chimney or stack l8. The lower base of the flue I5 is supported upon the channel 8 through which the ends of the heating tubes extend. Into the base of the flue l5 rises a cylindrical throat of insulating material l9, which has a widened base to collect the combustion gases passing around the base of the reflecting cone l4 and direct them into the flue l5 and to stack l8.

In the modification shown in Fig. 3, combustion gases are generated within the combustion pot I0 by burners II in a similar manner to that shown in Fig. 1. The combustion chamber, however, is somewhat differently shaped, being tapered both at the top and bottom and fired outside of the tube near a central position at burners l3. The remainder of the construction is substantially identical to that explained in connection with Fig. l with the exception that the reflecting cone I4 is somewhat larger in order to supply a larger reflecting surface.

The modification shown in Fig. 4, in so far as the combustion chamber is concerned, is similar to that shown in Fig. l, the space 6 outside of the tubes being fired by burners l2 and I3, and the combustion space within the tubes fired by burners II within the combustion pot In. In this modification, however, the conical baflie or reflecting cone l4 has a cylindrical portion Ma at its base which produces a considerably longer restricted passage between the cylindrical portion of the cone and the upper cylindrical portion of the combustion chamber. In this modification also there are two rows or banks of tubes 1 in place of the single row shown in Figs. 1 and 3.

The modification shown in Fig. 5 is similar to that shown in Fig. 4, except that the inner bank of tubes adjacent the reflecting cone M are somewhat longer than the outer bank of tubes. This outer bank of tubes receivesradiant heat from the combustion gases emitted from burners l2 and I3 and the reflecting wall of the combustion chamber. The long tubes which constitute the inner bank receive radiant heat from combustion taking place in combustion pot I0 from gases produced by fuel consumed in burners II. In Fig. 1 and in the modifications shown in Figs. 3, 4, and 5, the burners H and I3 are tangentially arranged, while burners I2 are of the directional type, discharging the gases at an angle toward the outer surface of the heat exchange elements.

'In Fig. 6, the combustion chamber, tube banks and reflecting cone are similar to the construction shown in Fig. 5. Burners l3 are arranged tangentially of the combustion chamber and centrally thereof, while the burners through the bottom of the chamber, II and I2, are arranged to supply heat inside and outside of the combustion chamber similarly to the previous figures except that burners II are raised to the floor of the chamber as the combustion pot It has been eliminated. The design eliminating the ignition or combustion pot I may be applied as well to the proceeding modifications, if desired.

The modification shown in Fig. 6, in which' a baflie wall 20 is used, offers a design in which two separate heating circuits are mounted in the same furnace setting and have controlled heat supply to each circuit. Such conditions arise in the cracking of petroleum where the heating and soaking circuits require variable heat loads; also in two stage distillation, different amounts of heat are required for the separate stages. By varying the firing of burners l2 and I3 outside the bafile wall 20 with respect to the firing of burners ll inside the bailie wall, the above desired variance of heat load and controlled conditions of heat supplied to each circuit is obtained.

The tapering of the top of the combustion chamber in the form of a truncated cone and the inverted baffle cone offer reflecting surfaces for radiant heat generated in the spaces inside and outside of the tubes and direct this radiant heat more uniformly upon the upper portion of the tubes. The shape of the combustion chamber and the baflle cone also serve to constrict the passageway through which the combustion gases flow from inside and outside of the tubes to the flue, increasing the velocity of the gases as their temperature decreases, thus obtaining a better heat exchange upon the upper portions of the tubes. The burners II and I3 are arranged tangentially as shown in Figs. 1 to 5 inclusive, to give the gases a whirling motion, both inside and outside of the tube banks. The reflected or radiant heat from both the cone and the cylindrical and conical surfaces of the combustion chamber, as well as from both sides of the cylindrical wall 20 in Fig. 6, distributes evenly over the lower portions of the heating elements radiant heat generated inside and outside of the tube banks. The convection heat supplied principally to the upper portions of the tubes is concentrated and the velocity of the gases increased by restricting the passageway through which the gases must pass from the combustion chamber to the flue.

In the modifications shown in Figs. 4, 5, and 6, where a short convection zone exists between the combustion chamber and flue, it is contemplated that extended surfaces such as fins may be used on the tubes to distribute more uniformly the convection heat of the combustion gases.

By the use of such a convection zone in the upper part of the combustion or heating chamber, it maybe unnecessary to use brickwork in the top of the furnace, because the flue gasis sufiiciently low in temperature to be introduced directly into the stack. By the construction shown in Fig. l, and the subsequent modifications, there is provided a furnace of-high efliciency wherein the heat of the combustion gases is distributed as radiant and convection heat throughout the full-length of the tubes, all of the tube surfaces operating at the maximum possible heat transfer rate. The interior of the tubes is rendered accessible for cleaning by suitable cleanout connections at the top and bottom, and the construction is such that it lends itself easily to replacement or repairs of either the tubes or combustion chamber.

Observation ports may be placed at convenient locations in order that the operators can at all times determine conditions within the furnace.

It will be undersood that certain features and sub-combinations are of utility and may be employ-ed without reference to other features and sub-combinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, we claim: 1. A furnace including in combination a combustion chamber of circular cross section, the

upper portion simulatingv a truncated cone, av

plurality of vertically disposed heat exchange elements positioned in said combustion chamber and substantially around the perimeter of a circie, means positioned within said combustion chamber within said space surrounded by said heat exchange elements and located in that portion of the combustion chamber simulating a truncated cone having the form of a. cone with its apex depending, said cone and truncated por-' tion or the combustion chamber adapted to progressively decrease the cross sectional area of the upper part of said combustion chamber, and separate sources of combustion heating gases positioned inside and outside of the circle of heat exchange elements.

2. A furnace including in combination a combustion chamber or circular cross section, the upper portion simulating a truncated cone, a plu-' rallty of substantially vertical heat exchange elements positioned in' said combustion-chamber and substantially around the perimeter of a circle, means positioned within said combustion chamber within said space surrounded by said heat exchange elements and located in that portion of the combustion chamber simulating a truncated cone having the form of a cone with its apex depending, said cone and truncated portion of the combustion chamber adapted-to progressively decrease the cross sectional area of the upper part of said combustion chamber, and

separate sources of combustion -heating gases positioned inside and outside of the circle of heat exchange elements and'tangentiaily in the combustion chamber wall adjacent its mid-section. JOHN W. THROCKMORTON.

JOHN S. WALLIS.

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