US2398279A - Fluid heater - Google Patents

Description

Patented Apr. 9, 1946 FLUID HEATER Herbert L. Barnebey, Oakmont, and Harry T.

Needham, Blawnox, Pa., assignors :to Blaw- Knox Company, Blawnox, Pa., a corporation of New Jersey Application January 21, 1944, Serial No. 519,128

6 Claims. (01. 122-451) This invention relates to heat-exchange apparatus and, in particular, to a boiler capable of delivering vapor for heating to high temperatures jacketed pipes, vessels, tanks and other apparatus used in the process industries.

It is now quite common in the process industry to utilize vaporizable liquid other than Water for delivering heat ,to-reactor vessels. Examples of such liquids are diphenyl and diphenyl oxide, tetrahydron'aphthalene, and ethylene glycol. It has heretofore been the practice to heat such liquids in boilers constructed in about the same manner as ordinary steam boilers. Serious difficulties have been experienced, however, in the use of such boilers for the purpose indicated. For example, the boilers used heretofore have been subject to fouling as a result of overheating of the tubes in certain portions. They have also exhibited "a tendency to develop leaks and have proved to have only a relatively short life. Frequently leakage is due to inadequate provision for thermal expansion, which is considerable, at the high temperatures employed. A further objection is that stay bolts must be used in the portions of tube sheets of fire-tube boilers which are not taken up by the tubes. At the high operating temperatures which are common in theprocess industry, leaks developgat the connections between the stay bolts and the tube sheets. Finally, conventional boilers have a fairly high liquid level and this usually makes it necessary to pump condensate into the boiler against a substantial liquid head when the boiler is located, as it usually is, on about the same floor level as the reactor vessel. The pumping of hot liquids such as those employed for heating applications is attended with considerable diificulty.

We have invented .a novel form of heat-exchange apparatus particularly suited for vaporizing special liquids useful for supplying heat to reactor vessels. Our invention .has important advantages such as low head-room requirement, unique provision for thermal expansion, the absence of stay bolts and a simple construction throughout as well as a low liquid level. In a preferred embodiment of the invention, We provide a horizontal boiler composed of an elongated pressure vessel having a bundle of tubes extending therethrough, a fire box removably positioned adjacent one end of the vessel and a smoke box and stack removably positioned adjacent the other end of the vessel. The vessel itself is cruciform or T-shaped inplan and includes a generally cylindrical section which is substantially filled by the tube bundle and a merging chamber adjacent oneend providing a vapor space and a large area of liquidsurface. Each of the several units, viz., fire box, pressure vessel .and smoke box has its own feet and is thereby fully self-supporting whetherrin cooperative relation to the other parts or separated therefrom. When the several units are properly assembled, they constitute a complete boiler. When ,the fire box and smoke box are removed from the pressure vessel, the tubes throughthe latter are fully exposed for inspection or cleaning.

Further details, novel features and advantages of our invention will become apparent during the following complete description and explanation which refer to the accompanying drawings illustrating the preferred embodiment.

In the drawings:

Figure 1 is a longitudinal vertical section through the apparatus of our invention;

Figure 2 is an end view such as would be seen by looking on the structure of Figure 1 from the left; line I-I of Figure 2 indicates the plane on which the section of Figure 1 is taken; and

Figure .3 is a partial plan View.

Referring in detail to the drawings, the apparatus of our invention comprises a fire box III, a pressure vessel H, and a smoke box H. The several units are assembled on a common axis, the fire box being disposed at one end of the vessel l l and the smoke ,box at the other. Each of the units has feet I3 whereby it is self-supporting whether disposed together with the other unitsorapart therefrom. The fire box and smoke box are freely removable from the ends of the vessel.

Considering first the vessel II, it is composed of a substantially cylindrical portion l4 substantially filled with a bundle of tubesl5 extending between tube sheets 16 at the ends of the vessel, the tube ends being exposed on the exterior of the tube sh'eets. The vessel also includes a generally cylindrical enlargement ll near one end merging into the portion I4. .As shown in Figures 1 and 3, the enlargement I 1 extends upwardly and laterally from the cylindrical portion 14, so as to provide a large area in horizontal planes at the top of the tube bundle and for a desirable distance thereabove, the bottoms of the two parts of the vessel being nearly at the same level. The bottom of portion I1 is made preferably somewhat lower than the bottom of portion 14, sufiicient to allow a continuous curvature of the merg ing surfaces at the transition with suitable radii. This construction also provides for relative expensioner the tubes and :shell. The actual amount by which the bottom of portion I1 is lower than the bottom of portion l4 would be small, from three to eight inches, for example; and it would vary somewhat with the size of the vessel. While the portion I4 has been referred to as substantially cylindrical, it is preferably somewhat frusto-conical as shown in the drawings, the diameter thereof adjacent the enlargement I! being slightly greater than the diameter adjacent the smoke box. The wall of the portion I4 thus slopes upwardly toward the enlargement l1. This facilitates the travel of vapor from the smoke-box end of the vessel to the enlargement I! thereof which constitutes a vapor space.

A manway I8 is formed in the side of the enlargement ll remote from the fire-box end of the vessel H. A vapor outlet connection I9 is formed on the upper side of the enlargement H. A liquid inlet 20 is formed adjacent the smokebox end of the vessel. A liquid outlet or drain connection 21 extends laterally from the bottom of the enlargement IT. The foregoing functions ascribed to connections:l9, 20 and 2] are illustrative of typical cases only, it being understood, of course, that these and other connections may be provided and selected as inlets or outlets for fluidswhen desired in a particular case. Other connections extend from the enlargement H to a liquid-level gauge 22, a liquid-level alarm or control device 23, a vapor-pressure gauge 24 and safety valve 25.

When the boiler has been filled with cold liquid 7 sumcient to cover the tubes, the surface .lies in the region of portion ll having a relatively large horizontal area; and as the cold liquid is heated and expands volumetrically, a small change in level will accommodate a relatively large change in volume. This is important particularly in maintaining low liquid level. A mixture of diphenyl and diphenyl oxide, for example, having a volume of 1'78 gallons at 70 F., expands to a total volume of 252 gallons at 700 F., a commonly used temperature. This is a volumetric expansion of about 40%, yet in the boiler of our invention it is accommodated with a change in level of only a few inches.

The fire box I is simply a combustion chamber composed of a refractory lining laid up within a sheathing of metal plate. As shownin Figures 1 and 3, the outer end of the fire box is provided with a burner 26. While a fluid-fuel type of burner is shown, any suitable means for burning solid or fluid fuels may be used. A clean-out 0r inspection door 21 is mounted below the burner. The other end of the fire box is shaped to fit closely around the adjacent end of the vessel II and its enlargement l'l, having an opening adapted to receive the extreme end of the vessel whereby the flame and hot gases produced in the fire box by combustion of fuel supplied through pipe connctions to the burner 26, pass through the tubes Hi to heat the liquid contained in the vessel I I.

The smoke box l2 comprises simply a, cylindrical drum 28 of suitable metal plate open at one side, having a stack 29 projecting upwardly therefrom. As shown, the drum I2, like the fire box I0, is disposed in overlapping relation with the adjacent end of the vessel H whereby the combustion gases, after traversing the tubes 15, collect within the drum I2 and then pass upwardly through the stack to the atmosphere. It will immediately be apparent that when the fire box and smoke box are withdrawn from the positions in which they are illustrated, the tubes 15 are exposed at both ends of the vessel II for the reactor at a height much above the floor level and it is notconvenient to mount the heating apparatus on the fioor below the reactor since accepted practice requires in a majority of cases a separate heating apparatus for each reactor to provide flexibility of control, and it is desirable to have the heating apparatus near the reactor, there usually being a fireproof partition between them. The low liquid level characteristic of our apparatus permits the return of condensate by gravity flow and without pumping. We thus avoid in many instances the difficulties involved in pumping hot liquids.

The construction of our apparatus also has several structural and mechanical advantages. Stay bolts are not necessary. The curvature at the merging of small and large ections of the shell provides adequately for thermal expansion of the shell and tubes. A multiplicity of inspection hand holes and manways are obviated, furthermore, since the single manway provided opens into the enlargement which is of sufiicient size to permit entry of an inspector.

Our apparatus has numerous applications in addition to the. production of heated vapor. It may be used to deliver hot liquid or for the concentration of dilute solutions. In the former case, the vapor outlet I9 may be blanked off and the hot liquid may be delivered from the outlet 2|, which in that case would be somewhat larger than illustrated, preferably about the same size as the liquid inlet 29. When the apparatus is used for concentration, the dilute solution is introduced through the inlet'Zll, the vapor driven off is removed through outlet l9 and the concentrated solution delivered from outlet 2 I Although we have illustrated and described but a preferred embodiment, it will be recognized that changes in the construction and arrangemerit, ofthe parts may be made without deviating from the principle of theinvention or the scope of the appended claims. 1

We claim:

1. In a heat-exchange apparatus: a pressure vessel adapted to be fired, said vessel comprising spaced tube sheets forming the ends of the vessel; a generally cylindrical shell joined to said' sheets, horizontal tubes extending between said sheets and substantially filling said shell, said shell having a generally cylindrical enlargement adjacent one end ofthe shell, and a fire box removably positioned at the end of the shellat which said enlargement is located, said fire boxcomprising a generally cylindrical chamber of substantially the same diameter as said enlargement and being disposed coaxially therewith. p

2. A vaporgenerator comprising an elongated cylinder having a tube sheet at each end and a bundle of tubes extending between said sheets and substantially filling said cylinder, said cylinder merging gradually into a generally cylindrical enlargementadjacent one' end, the axis of at the level of the top of said cylinder, whereby the liquid surface in the enlargement is a maximum at liquid levels which cover the tubes.

3. The apparatus defined by claim 2 characterized by the bottom of said enlargement being at substantially the same level as the bottom of said cylinder.

4. A vapor generator comprising an elongated cylinder having a tube sheet at each end and a bundle of tubes extending between said sheets and substantially filling said cylinder, said cylinder merging gradually into a generally cylindrical enlargement adjacent one end, the axi of said enlargement being substantially parallel to the axis of the cylinder and located substantially at the level of the top of said cylinder, whereby the liquid surface in the enlargement is a. maximum at liquid levels which cover the tubes, a firebox at the end of the cylinder adjacent which said enlargement is located, the fire-box having its top and bottom substantially at the levels of the top and bottom of'the enlargement, respectively.

5. A vapor generator comprising spaced tube sheets, an elongated cylinder joined to said sheets, horizontal tubes extending betweensaid sheets and substantially filling said shell, and a generally cylindrical enlargement near one end of the shell, the axis of the enlargement being parallel to that of the cylinder but located substantially at the level of the top of the cylinder so that horizontal sections through the enlargement have maximum area substantially at liquid levels submerging said tubes.

6. A horizontal boiler comprisin two intersecting and merging cylinders of difierent lengths and diameters disposed with their axes parallel, the longer cylinder having the smaller diameter and being filled with heat-exchange tubes, the shorter cylinder being disposed adjacent one end of the longer cylinder with its axis at substantially the level of the top of the longer cylinder.

whereby said tubes are submerged when said

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