US2429916A - Heating apparatus - Google Patents

Description

Oct. 28, 1947. R. c. BELGAU HEATING APPARATUS Filled Aug. 20, 1945 2 Sheets-Sheet 1 IN V TOR.

1 stringent in the case Patented Oct. 28, 1947 UNITED STATES ATENT OFFICE HEAI -IN'G APPARATUS :Robert 'C. Belgau, Detroit, Mich. Application August 20, 1945, Serial N 0. 611,462

.8 Claims. 1

This invention relates to heating apparatus, and more particularly :to heating apparatus utilizing combustible fuel 'as *a source of heat.

One form of the invention disclosed herein comprises a boiler wherein a liquid heating medium is vaporized by the heat derived from the combustion of gaseous fuel, the vaporized heating medium being passed into heat exchanging relation with the material to be heated and then returned to the boiler in a closed circulatorysystem.

There are many industrial processes wherein it is desired to heat a material at a rapid rate, while insuring that no part or the material is brought toa temperature which would produce burning or deterioration thereof. The requirement for accurately controlled heating means is especially of pharmaceutical and chemical compounds, thermo-plastic compositions, foodstuffs and similar products whichdeteriorate rapidly when raised to excessive temperatures.

Such materials have in the past been heated by various methods. In one known system, a central steam generating plant, utilizing coal or other fueLsupplies steam to a plural ty of vessels containing the material to be heated. The temperature of the steam may in; such installations be accurately controlled-so ,as to limit the temperature to which the material will be subjected. Such a system is wasteful and unsatisfactory in many cases, however, since it is necessary, in order to heat .a single container, that th entire central plant be put into operation, with consequent fuel waste when ;this central system :is operating on a partial-load. Heat losses in conveying the steam from the central plant to the point of use may also be considerable, and the system as a whole lacks flexibility, while the ori inal installation is :cost ly. and requires costly maintenance of the steam lines, valves, pumps and other accessories.

The present inventionie 1 bodies .a designrwhich eliminates many of. the :obiections hereinheiore ointed out, and provides a degree of flexibility andeconomy not possible with devices :ofrthe prior art above indicated.

An Object of thepresentinvention iS'ltO provide a heating idevicegof simplified :constructioniwhich will avoid the disadvantages of the prior :artdevices above outlined, in that it will hei-ndependent of other units and dependentzonly ,uponia supply of fuel at the site .of-heati-ng."

'2 aheating device which a high percentage of the heat units developed by combustion of the fuel are transferred to the material to be heated.

A further object is to provide acornplete vapor heating unit which may be made in any suitable size and shape, a d of any suitable material, but which is complete unto itself and depends only upon a supply of fuel.

A further object of the invention is to provide a heating unit utilizing heat of combustion, wherein the heating mediumis circulated rapidly to avoid the formation of bubbles in the heating medium and to render the heating process more efficient.

Another object of the invention is to provide a heating unit of the type indicated, wherein overrunning of the heating cycle is reduced to a minimum.

Another object of the invention is to provide heating apparatus utilizing combustible fuel .and automatically controlled to maintain the pressure and. temperature ,of the vaporized heating medium within predetermined limits, wherein the automatic control operates to control separately the combustion in separate systems, to minimize I .verrunn'ing of the heating operation.

Further objects and advantages of the invention will be apparent from the following description, taken in connection with the a pended. drawings, in which:

Fig. 1 is a view in vertical section of a, device embodying the invention;

Fig. 2 is a vertical sectional view of the boiler and its connections;

Fig. 3 is a horizontal section taken on the line 3-3 of Fig. 1; and

Fig. 4 i a schematic showing of the automatic control mechanism.

It is to be understood that the invention is not limited in :its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since. the invention is capable of other embodiments and of being racticed or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

The heating apparatus shown in the drawings comprises ashell of sheetmetal or the like, made up of a cylindrical base section l0, a cylindrical :body section I2,'a'trusto-conical section l4, anda stack 16. Surrounding the shell and spaced therefrom is a jacket made up of a lower section A iurtherpbjeot' oj the invention is'zto provide l8 and an upper section 20, the space between the shell and jacket being sealed with heat insulating material 22.

Within the insulated chamber thus formed is mounted a boiler comprising an upper head 23 and a lower head 2%, connected together by vertical tubes 23, which are secured in fluid-tight relation to the lower wall 25 of the upper head and to the upper wall 26 of the lower head in any suitable known manner, as by welding. The boiler, when in operation, is filled with liquid heating medium to a level indicated at 363, the heating medium being any suitable material such as a non-volatile oil, diethylene glycol, Dowtherm or the like, having suitable characteristics as to high boiling point, low latent heat of vaporization, and other qualities. In order to permit continuous circulation of the heating medium by thermosiphon action, return tubes 32, 33 lead from the upper head below the liquid level therein to the lower head, to permit downward flow of heating medium therein and thus balance the upward flow caused by heating of the liquid heating medium in the tubes 28.

A vapor outlet 36 leads from the upper head 23 above the liquid level therein and connects with a transverse vapor tube 38 which connects with a conduit 39 leading to the interior of a jacket 40 on a process vessel 42, adapted to contain material to be heated. Condensed heating medium from the vapor space of jacket lo is returned to the boiler by a conduit 44, which passes through the jacket section I3 and communicates with the lower head 24, the return tube 32 being connected thereto by means of a coupling 45. A manually operated valve 48 is mounted in the conduit 39, to cut oil the flow of heat to the vessel 22 when desired. A'similar valve 50 is mounted in the return conduit 46, both valves being preferably of the packless diaphragm type indicated in the drawing.

The upper head 23 is suspended by brackets 52 from the tube 38, the tube in turn being suspended from the jacketby means of brackets 56. The lower head 24 is suspended from the inner shell by means of a horizontal annular plate cured to the head by welding, and fitting between flanges on the base section I6 and the body section I2 of the shell. A cylindrical deflector 58 surrounds the upper portion of the tubes 23, and is suspended in any convenient manner, as by means of spaced connecting elements Gil welded thereto and to the upper head 23, the deflector being spaced by a short distance from the upper head 23 so that the deflector will not entrap lighter-than-air gases, such as producers gas, which might be present in the apparatus because of leakage or other cause.

The tubes 23 will, in the operation of the apparatus, be filled with liquid heating medium, and will be surrounded by hot gases imparting their heat to the heating medium within the tubes. As an additional heating means for the heating medium, smaller tubes 62 are threaded through tubes 28 in concentric relation thereto, and are secured in the known manner to the upper wall 66 of the upper head 23 and to the lower wall of the lower head 24. The smaller tubes are preferably of equal number with the tubes 28, and are designed to pass hot gases and transfer the heat therefrom to the heating medium in the upper and lower heads and in the tub-es 28, as well as to act as staybolts for the heads. The tubes 28 and 62 are preferably spaced rather close to each other, as indicated in Fig. 3, so as to pro-- vide a rapid and economical heating action.

Beneath the lower head 24 is a horizontal wall 10 formed of heat insulating material and provided with apertures 'II which register with the smaller tubes 62. Below the wall and spaced therefrom is a second horizontal wall '52, the two bein joined together by an annular insulating member 74, thus forming an annular combustion chamber 76 which communicates through the smaller tubes 52 with the chamber 18 at the upper portion of the shell. The chamber '56 is supplied with a combustible mixture through a conduit provided at its outlet with an electric igniting device Si of known type. The mixture is forced through conduit 80 by means of a centrifugal fan 32 driven by an electric motor 83, the flow of IniXture being controlled by a valve 84 actuated by a solenoid 85. It will be seen that when the flow of combustible mixture is turned on and the motor started and the mixture ignited, the mixture will burn in the chamber 16 and the hot gases will pass upwardly through the tubes e2, giving up their heat to the heating medium in the boiler, and passing through chamber 78 to the stack I6.

Disposed centrally in the lower head 24 is a due 86, within which is housed the main gas jet 88. The jet 88 is provided with an electrical igniting device 89, and is supplied through a conduit 90 with a mixture of air and combustible gas, the conduit being controlled by an automatically controlled valve 92, actuated by a solenoid S4 in the known manner. The conduit 90 and combustion chamber 16 are insulated by means of the insulating wall 72, which includes a metallic plate 96 and fibrous heat insulation 98 held in position by means of pins I ll!) welded to the plate 96. The space below the plate 96 is filled with heat insulation 99. It will be apparent that when a combustible mixture is permitted by the Valve 92 to pass through the conduit 90 to the jet 88 and is ignited, the hot gases of combustion will pass through the flue 86 and upwardly into the space between the tubes 28, and will thence be deflected downwardly below the lower edge of deflector 58, whence they will pass upwardly to the chamber l8 and out at the stack I6.

It will be understood that instead of the gasburning equipment just described, apparatus for burning other types of fuel, such as liquid hydrocarbons, may be used.

For automatic control of the heating process a pressurestat IDI of known type is mounted upon the upper section I8 of the jacket by means of a bracket I02. A pressure tube I84 is connected between the tube 38 and the pressurestat to communicate to the pressurestat the pressure of vaporized heating medium therein. The pressurestat contains a pressure responsive bellows I65 which is operative, upon the occurrence of pressures of a predetermined value set by adjustment of an adjusting screw I06, to open a switch, indicated at I08 in Fig. 4, in a relay circuit H2 which controls a circuit H4 leading to the solenoid 94. Upon the occurrence of a somewhat higher pressure, corresponding to a higher temperature of the vaporized heating medium, the bellows I05 will open a second switch, indicated at H0, in a second relay circuit H6 which controls a circuit II 8 leading to the electric motor 83 and the solenoid 85, thus successively shutting oiT the supply of fuel to conduits 90 and 86. The circuits are supplied through leads I20 which are controlled by a manual switch I22.

In the operation of the device, the heating means will be put into operation by manually closing the switch I22. Thi will result in enerfaca e 1's 5 sizing thesolenoid 29.4, permitting mixture to allow through :the -.conduit 0 to :thejet :88 where itrwill he ignited by the igniting device 9 and-will supply heat to the heating medium'athrough tubes &8 as 'hereinbeiore. indicated, :Closing .of .the switch J22 will also cause {the solenoid :85 .and 1 391 91 13:3 to be pnergizedgwhich will result in the valve .85 being opened and the gas in .conduit so bein :icrced into the combustion chamber 1.6, Where :it-will be, ignited :by .meansiof the igniting device 81.- pIThe hot products of combustion will pass irromzthe combustionchamber :16 upwardl throu h the smaller tubes :52 and thence into the chamber. andput the stack :l-fi. -l3y reason of like large amount .of heat transfer area repre- -,s ented bythe tubes :28 and $2, the heatingmedium will .be rapidly iheated, causing generation of yaporsin the vapor space of the :head 12%, which yapgrs willf ll the conduit 3.8 and be superheated therein, but will be prevented from passing to the cket es of the process vessel 42 by reason of valves i8 and 59 being closed. During the heating operation, heating medium will flow upwardly from the lower head 24 through the tubes 28 to the upper head 23, and thence downwardly through return tubes 32, 33 to the lower head. Such circulation is brought about by thermosiphon action in the known manner, and because of the arrangement of the parts as shown is rapid enou h to k up any vapor bubbles which may 170 1 n th system, and thus to insure against the formatien of bubbles in lower head 25 or in the space between tube 28 and tubes 62., or elsewhere in the boiler, which bubbles wouldtend to cause burning of the tubes due to the low rate of heat transfer away from the metal adjacent such bubbles.

As the vapor in the boiler approaches the desired temperature, the valves 48 and 50 may be opened, permitting the vapor to pass through conduit 38 tothe jacket 40 of the process vessel to heat the contents thereof, the condensate returning to the boiler through conduit M. As the temperature of the vapors approaches the predetermined temperature set by adjustment of the screw I95 of the pressurestat, the bellows I05 will be actuated to cause the switch I08 to be opened, thus deenergizing the solenoid 94 and closing the valve 92. The closing of this valve cuts oil the flow of combustible mixture to the gas jet 38, and thus reduces the heat intake to that supplied by conduit 89, which is of considerably less capacity than the conduit 90. Upon further increase in pressure, the bellows H35 will open the switch H0, which will deenergize the electric motor 83 and cause valve 84 to cut off the supply of gas passing through conduit 89.

By means of the apparatus above described, the rate of heating which is utilized when starting the apparatus up from cold is maintained at maximum rate until a certain pressure is reached which is slightly below that for which the screw 16 is set, then as the temperature approaches the predetermined temperature the heating rate is out down by the closing of the valve 92, leaving the heating process to be carried on at a relatively slow rate by means of the gases burning in combustion chamber it. Finally the supply of heat is cut off altogether by opening the switch H0, at a temperature which is still somewhat below the desired temperature of the vapors in the conduit 38. However, by reason of the residual heat in the tubes and other elements heated directly by the hot gases, heat will continue to flow to the heating medium for a short time after the motor =83 has been stopped, :so that the upper limit of temperatures within the permissible range is closely approached but not exceeded, and no .burning .or other damage to the material results. By this means, the heating rate may be maintained at .a maximum during most of the heating .cycle While overshooting due to hysteresis is prevented by the use of heating :de- -vices of relatively large and small capacity, and by so constructing the device that the residual heat of the boiler is small compared to that of the usual central heating system. Since in the present device the heat generated in individual systems at the site of use, each heating apparatusor system may be of capacity sufiicient merely to supply its associated vessels or other equipment, and may be started lip-or shut down independently of other :units in the :plant, and in minimum time.

Although the invention has been described with reference to a particular embodiment thereof, it may 'be embodied in other forms within the skill of artisans in this art. The invention is therefore not limited to the .form disclosed, nor other wise except in accordance with the language of the following claims.

I claim:

1. In heating apparatus, a boiler for vaporizable heating medium comprising :upper and lower heads, tubes connecting the heads, :a burner located adjacent the lower head and designed to supply hot gases to the exteriors of said tubes, a second set of tubes extendin through both heads and through the first mentioned tubes, a burner for supplying hot gases to the interiors of said second mentioned tubes, said second burner including forced draft means, means responsive to a predetermined pressure in the boiler for rendering said first mentioned burner inoperative, and means responsive to a predetermined higher pressure in the boiler for rendering said second mentioned burner inoperative.

2. The invention defined in claim 1, wherein said pressure responsive means comprises a pressure responsive element and electrical circuits successively opened and closed by the pressure responsive element and operative to control the respective burners.

3. The invention defined in claim 1, wherein the pressure responsive means comprises separate valves controlling the flow of fuel to said burners, separate circuits controlling said valves, and

a pressure responsive element subject to pressures in the boiler for successively opening and closin said circuits at different predetermined pressures.

4. In heating apparatus, a boiler for vaporizable heating medium comprising upper and lower heads, tubes connecting said heads, a vapor outlet conduit leading from the upper head and adapted to be connected to the point of use, a condensate return conduit leading to the lower head and adapted to return condensate from the point of use, a return conduit leading directly from the upper head to the lower head to permit circulation of heating medium therein by thermosiphon action, an insulating shell surrounding said boiler, said lower head being provided with a central aperture, a burner communicating with said aperture for supplying heated gases to said tubes, a combustion chamber beneath the lower head, tubes extending from the combustion chamher and through both heads and the first mentioned tubes, and a separately controlled burner for supplying hot gases to said combustion chamber.

5. In heating apparatus, a process vessel comprising a heatin jacket, a boiler for vaporizable heating medium, conduits connecting said boiler and said jacket for conveying vaporized heating medium to the jacket and returning condensate to the boiler, said boiler comprising upper and lower heads, tubes connecting the heads and communicating therewith to permit flow of heating medium therebetween by thermo-siphon action, means including a burner of relatively large capacity for passing hot gases into contact with the exterior surfaces of said tubes, tubes extending through said heads and said first mentioned tubes and secured to said heads to act as staybolts for the boiler, means including a burner of relatively small capacity for passing hot gases through said second mentioned tubes and means responsive to pressures in theboilerto'separately and successively render said burners operative and inoperative.

6. The invention defined in claim 5, wherein the pressure responsive means includes separately operable valves controlling the supply of fuel to said burners, a plurality of electrical circuits controlling said valves, switches controlling said circuits, and a, pressure responsive element operative by a predetermined pressure in the boiler to open one of said switches and operative upon a predetermined higher pressure in the boiler to open another of said switches.

7. The invention defined in claim 5, comprising in addition heat insulation separating said burners, a fuel conduit connected to said small capacity burner, and a valve and a compressor in said conduit, said pressure responsive means being operative to simultaneously close said valve and shut off said compressor.

8. In heating apparatus, a boiler for vaporizable heating medium comprising upper and lower heads, tubes connecting the heads, a vapor outlet conduit leading from the upper head, means for passing hot gases into contact with the exteriors of said tubes and of said conduit to heat the heating medium therein, return conduits to permit flow of heating medium from the upper head to the lower head by thermo-siphon action, means responsive to pressures within the boiler for rendering the first mentioned means inoperative, and a deflector plate extending downwardly from the upper head and surrounding said tubes, said deflector plate being provided adjacent the upper head with bleed apertures to permit escape of combustible gas.

ROBERT C. BELGAU.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 635,710 Blackden Oct. 24, 1899 2,127,172 Hermitte Aug, 16, 1938 475,850 Dimmick May 31, 1892 1,304,496 MacLachlan May 20, 1919 1,963,624 Kroger June 19, 1934

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