EP0023000A2

EP0023000A2 - Boiler with pressurized firebox

Info

Publication number: EP0023000A2
Application number: EP80104044A
Authority: EP
Inventors: Placido Zampieri
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-07-20
Filing date: 1980-07-12
Publication date: 1981-01-28
Also published as: BR8004489A; FI802132A; EP0023000A3; AU6048680A

Abstract

The invention relates to a boiler (1) with pressurized firebox, particularly suitable for use in combination with a blue flame burner; the boiler (1) comprises a firebox area (11) which is surrounded by a tank (7) containing the water to be heated. The tank (7) is divided into two compartments (18,19): an inner one (18) surrounding the firebox area (11), and an outer one (19) arranged around the inner compartment (18) and in heat exchange relationship therewith. The inner compartment (18) may be intended, for instance, for supplying the radiators of a heating system, whilst the outer compartment (19) may be intended for supplying sanitary water. The boiler (1) further comprises a muffler (17) which may accommodate a superheater assembly for quick hot water production, even when starting from cold, such as where used as a water heater.

Description

This invention relates to a boiler with pressurized firebox, particularly for use in combination with a blue flame burner.
Experiments have already been made with oil-burning turbo-boilers, which were operated with a "blue" flame, such as to release virtually non-polluting fumes. However, such known turbo-boilers involve, for the flue fumes and the water to be heated, long and tortuous paths through inner conduits before they are discharged. Along such conduits, there occur high pressure drops, the formation of deposits and scales of various natures, as well as an unbalanced distribution of the thermal loads. This may lead to the undesirable formation of small steam pockets in the water to be heated, which affect to a considerable extent the subsequent circulation of the hot water.
It has been found that under certain pressure, temperature combustion and thermodynamic conditions the color of the burning oil, in particular gas oil becomes blue. It has been found that with such a blue flame the combustion is highly efficient and the thermal characteristics of the flame very advantageous.
This invention sets out to provide a boiler of the specified kind wherein a fully homogeneous distribution of temperature can be achieved throughout the water to be heated, while doing away with the presence of complex paths and/or tube nest for that water.
Within that general aim, it is possible to arrange that the boiler according to this invention can be also utilized to generate steam.
It is further possible to arrange that the boiler of this invention is a highly efficient one, easily manufactured, and economical to run.
According to one aspect of the present invention, there is provided a boiler with pressurized firebox, particularly for use in combination with a blue flame burner, the boiler comprising a firebox area whereinto the burner is intended to blow its flame, a tank for the water to be heated located adjacent said firebox area and in heat exchange relationship therewith, and a thermally insulating coating around said tank, characterized in that it further comprises a radiating element removably installed in said firebox area at an opposite location with respect to said burner and effective, during the boiler operation, to radiate toward said tank the heat absorbed from said blue flame and to control the outflow of the combustion gases or fumes from said firebox area.
Advantageously, the tank or reservoir for the water to be heated comprises an inner compartment surrounding said firebox area, and an outer compartment arranged around said inner compartment ..and in heat exchange relationship therewith.
Further features and advantages of this invention will be more clearly understood by making reference to the following detailed description of preferred but not limitative embodiments thereof, in conjunction with the accompanying drawings, where:

Figure 1 is a cut-away elevation view, as sectioned along the longitudinal axis of a boiler and related burner;
Figure 2 is a left side view of the boiler of Figure 1;
Figure 3 is a one-half elevational and one-half sectional view of a radiating element intended to be placed within the boiler;
Figure 4 is an enlarged scale, schematical partial view of the left side of the boiler of Figure 1;
Figure 5 is a reduced scale, cross-sectional schematic view of a superheater device ; and
Figure 6 is a reduced scale, schematic cross-section of a further embodiment of the superheater device.

With reference to the cited drawing figures, the boiler 1 comprises a supporting structure having two side members 2 and 3 provided with resting feet 4, and two end members, namely a front one 5 and rear one 6.
The boiler 1 is formed from a tank or reservoir 7 for the water or other liquid to be heated, which is surrounded externally by an insulating material layer 8, e.g. of glass wool adjacent its body, and two layer of an asbestos-based material, one on the front member and the other on the rear member, as indicated respectively at 9 and 10.
At the longitudinal central portion of the tank 7, the latter defines a firebox area or tubular chamber 11, acceded by a nozzle 12 of a burner generally indicated at 13, preferably a transparent blue flame burner, as disclosed in the concurrently filed Patent Application No..
The burner 13 is attached to and supported by the front wall 5 of the boiler, and penetrates with its nozzle a receiving seat 14 formed in the tank 7. The chamber 11 also accommodates a radiating element or radiator 15, which can be inserted therein and withdrawn therefrom through an appropriate opening 16 provided in the rear wall or end member 6.
On the outside of the rear wall 6, there is mounted, at the opening or port 16, a muffler, generally indicated at 17, which will be described more in detail hereinafter with reference to some possible versions thereof and to Figures 1,2,5 and 6.
The tank 7 is divided into an inner compartment 18 and outer compartment 19, both compartments being intended for containing water therein, and in heat exchange relationship with each other through a metal wall 20 acting as. a partition wall. The inner compartment 18, which surrounds the chamber 11, is intended for containing hot water (at a temperature in the 80°C to 90°C range), and is fed from a conduit 21, which from the rear end member 6 extends beneath the boiler and,through a bent portion 22, communicates with an inlet port 23.
Onto the conduit 21, there is mounted a pump 24 which has its suction end connected to a T-like manifold 25. The manifold 25 is in turn connected to a first conduit 26 which can be closed or shut off by means of a gate valve 27 and functions to feed water, such as from a water supply network and/or the radiators of a heating system. The manifold 25 is also connected to a second conduit 28 (Figure 2), also equipped with a shut-off valve 29 and communicating with the mouth 30 of an outlet or discharge pipe 31 from the compartment 18. The pipe 31 is connected to the outlet end 32 of the compartment 18 and, downstream of the mouth 30 it has a shut-off valve 33 effective to control the hot water outflow for delivery to a utilization system, such as a heating system including a set of radiators (not shown).
The outer compartment 19 is instead fed with cold water from a conduit 34 (Figure 1) located beneath the boiler and connected to the inlet 35, and is discharged through an outlet pipe 36 leading, for example, to sanitary appliances (not shown). The water contained in the compartment 19 is heated indirectly by the water of the compartment 18 through the wall 20, and, accordingly, it actsatonetimeas a cooler and distributor and homogenizer device for the thermal loads in the boiler.
At the top of the front end member 5, there is formed externally thereto a console 37 (Figure 4), accommodating a plurality of instruments and gauges for controlling and monitoring the boiler operating conditions. More specifically, the reference numeral 38 designates a temperature displaying device for the temperature of the water passed through the conduit _ 21 and directed to the compartment 18. The numeral 39 designates a tell-tale or indicator relative to the pump 24, the numeral 40 a tell-tale or indicator for the electrodes 41 of the burner 13, 42 designates a safety thermostat,and 43 amains ON/OFF switch. The temperature of the water leaving the compartment 18 through the outlet conduit 31 is, in turn, displayed by a device 44, whilst the temperatures of the water in the compartment 19 and outlet pipe 36 are respectively displayed by devices 45 and 46. The console 37 further includes a water temperature adjustment thermostat 47, a timer 48, a burner tell-tale 49, a clock 50, a tell-tale 51 for a fuel feed control solenoid valve, and a tell-tale 52 for an air control valve 53 in the burner 13.
Centrally to the console 37, and protruding therefrom, is an inspection window 54 for inspecting the inside of the chamber 11, for example to check and, if necessary, control the color (transparent blue) of the flame emerging from the nozzle 12 of the burner. Finally, on the side member 5, a socket (not shown) is provided for connecting the boiler to the electric power supply, while on the side member 3, there may be provided a pressure gauge 55 (shown, for clarity reasons, facing the reader in Figure 4), for monitoring the pressure prevailing within the chamber 11.
The chamber 11 has of preference a cylindrical cross-section, for practical reasons both during the manufacturing and maintenance thereof, and is occupied for approximately one half thereof by the radiating element 15 (Figures 1 and 3), which also functions as a shut-off/admission element for the flue gases or fumes. The element 15 comprises a body 58, the outer configuration whereof is of preference slightly frusto-conical, and has all over its outer surface a plurality of fins 59 of substantially radial pattern with respect to the body 58 and having outline dimensions such as to accommodate the taper of the body 50, thereby it contacts the inner cylinderical wall of the chamber 11. Furthermore, the body 58 shown in the drawings is hollow internally, but could be solid, at least over a predetermined length (e.g. over one half thereof), starting from its end 60 intended to be swept by the flame issueing from the burner 13. The end 60 of the body 58 has preferably a frusto-conical shape, with an apex angle which is much more inclined over the body 58, such as to present a front surface 61 which is flat and comparatively small, and intended to position itself, while in operation, along the longitudinal axis of the chamber 11, which axis is coincident with the axis of the nozzle 12, and accordingly of the flame.
At its other end, the body 31 carries, e.g. through uprights 62, a manifold conical element 63 formed with a central calibrated hole 64, whereat there is attached, such as by threading, a nozzle 65 extending axially to the outside of the manifold 63. The nozzle 65 has its inside hole 66 conically tapered'from the manifold 63.
The manifold 63 has a rim 67, which may be cylindrical or at any rate of such a shape as to mate the shape of the chamber 11 wherein the element 15 is to be installed. The rim or lip 67 functions to seal off (with the boiler in operation) the chamber 11' such as to force the flue gases to flow along a path defined by the manifold 63 and nozzle 65. To accommodate the element 15, the chamber 11 extends, at its port 16, outwardly beyond the rear end member 6 of the boiler (Figure 1).
Externally to the port 16, on the rear end member 6, there is hingedly connected, such as by means of hinges 68, a muffler 17 which, as is more clearly shown in Figure 2, comprises a first outer box-like body 69 having one end hingedly connected through the hinges 68 for attachment to the wall 6. Inside the box-like body 69, there is provided an insulating and sound absorbing coating layer 70, e.g. of glass wool, which is applied to the inner wall of the body 69 such as to leave unobstructed the central portion of the space defined by the body 69 itself. At its end facing the opening 16, the body 69 has an opening 71 with a diameter or span which is equal to or smaller than the opening 16, thereby the inner volume of the body 70 constitutes, at least conceptually, an axial extension of the chamber 11.
The other end of the box-like body 69 carries a second box-like body 72, which is flanged and removably attached, as by bolting at 73, too a tubular body 74 located within the body 69 adjacent the insulating layer 70.
Between the flanged body 72 and body 74, there is inserted a support 75 for a plurality of conduit portions 76, e.g. uniformly distributed parallel to the axis 77 of the inner cavity of the muffler, which is also the axis of the chamber 11 and element 15.
That portion of the body 72 which remains external to the body 69 encloses an insulating layer 78 and supports therein a conduit 79 which is coaxial with the axis 77 and has preferably an extension 80.
As may be seen in Figure 1, the nozzle 65 protrudes out of the chamber 11 to reach within the inner cavity defined by the muffler 17 and is readily accessible from the outside owing to the muffler being movable away from the opening 16 by rotation on its hinges 68, as shown in Figure 2.
Between the opening 16,at the bottom,and the muffler, there is further provided a collecting pan 81 for collecting any condensation therein, as usually containing a high percentage of SO₃ and other toxic and/or polluting components. The pan 81 can be removed and emptied periodically, for example on the occasion of normal and regular boiler maintainance operations.
Figure 5 shows a variation of this boiler, wherein the muffler 17, instead of being hinged to the wall 6, is fixed thereon and has larger dimensions than the boiler shown in Figures 1 and 2. In particular, the inner walls 74 define a thermally insulated chamber 85 intended for - accommodating a superheater device 86 which comprises an elbow conduit 87 having one end connected, through a fitting 88, to the nozzle 65.
The conduit 87 has an intermediate widening, whereat there is formed an aperture 89 wherethrough the conduit 31 is passed to communicate with the compartment 18 of the boiler. Onto the conduit 31, again within the chamber 85, there is inserted and fixed in position, such as by welding, a baffle element 90 in the shape of a hood, whereto the free end of the elbow 87 opens. Within the chamber 85, there is also located a portion of the conduit 36 which communicates directly with the compartment 19 of the boiler. As may be seen from the drawings, the flue gases exiting the nozzle 65, instead of being discharged at once into the conduits 76 of the muffler, are conveyed by the elbow 87 to sweep the conduit 31, whereto.they transfer a part of their heat content such as to further heat the water passed through the same. They are then deflected by the hood element 90 to partly sweep the conduit 36 and then exhausted through the conduits 76, like with the muffler shown in Figures 1 and 2.
Since upon leaving the nozzle 65 the flue gases are at a temperature approximately in the 180°C to 200°C range, they are still apt to effectively heat the water within the conduits 31 and 36, owing to the considerable thermal gradient existing between the same and the water within the tubes.
In the embodiment shown in Figure 6, the elbow 87 is considerably wider at its intermediate area, the conduit 31 portion extending within the elbow 87 being spiralled such as to expose a much larger surface to the eaxhaust gases from the nozzle 67 and thus provide a more effective heat transfer between the flue gases and the water inside the conduit 31. This embodiment is particularly advantageous where the boiler must be used to generate steam within a very short time, e.g. within a few minutes from the start of the boiler operation, even when started from cold.
The operation of the boiler according to this invention is quite unique. With specific reference to the instance where the burner 13 is a pressurized blue flame burner, the flame emerging therefrom is directed, from the nozzle 12, into the chamber 11 of the boiler against the central region 61 of the radiator element 15. The latter, after a short time (e.g. 3 minutes) begins to glow up to about one half its own length. The blue flame is ejected under pressure from the burner .13 into the chamber 11, which thus becomes pressurized, e.g. to 20-80 mm H₂0, preferably to about 40-60 mm H₂0, and this regardless of the dimensions of the chamber 11 and power of the burner 13.
The very hot combustion products are quickly diverted both from the surface 61 and frusto-conical region 60, to expand radially, or almost so, against - the inner wall of the chamber 11 and flow upwards toward the nozzle 65, being obliged to undergo several deviations, against and around the fins 52, such as to effect an efficient heat exchange between the gaseous combustion products and the inner wall of the chamber 11. After climbing up along the body 58, the flue gases, now less hot than before, are obliged to enter the conical manifold 63 and exit through its nozzle 65 to be directed into the box-like body 69 of the muffler 17. Here, they follow a fountain-like path, being obliged to reverse their flow direction against the support 75, which has the function of a baffle-admitter or directing device, and to leave rearwards through the conduits 76. Upon exiting the conduits 76, the flue gases largely impinge on the abutting wall 82 of the body 72, whereat they are again deflected and obliged to start along the comparatively narrow conduits 80,79 adjacent the insulating material 78 arranged inside the outer box-like body 72. Finally, the gas enter a stack (not shown) and are then discharged into the atmosphere, or alternatively, discharged through an absorbing bed, or possibly a sewer system.
The fume temperature can be adjusted at will by adjusting the nozzle 65, namely by suitably selecting the diameter of the hole 66, and considering that,with nozzles having small diameter holes 66, higher pressures can be preserved in the chamber 11, thereby the outlet flue gases or combustion fumes will be colder, whereas larger diameters will result in hotter fumes.
It will be appreciated, moreover, how the radiating element 15 functions to trap the fumes and favor the turbulence within the chamber 11 such as to prevent the formation of stagnant pockets and/or of a jacket of hot fumes adjacent the comparatively cold wall of the chamber 11, as well as of allowing the extent of the heat exchange occurring between the hot gases and tank 7 to be adjusted, and accordingly the temperature of the gases leaving the boiler through the nozzle 65. The economics of the direct heat transfer to the tank 7,should take into account, moreover, the considerable radiating effect developed by the radiating element 15, which radiates in all directions toward the inner wall of the chamber 11 the heat absorbed at its end 60 from the flame and that delivered thereto by.the flue gases. The water inside the compartment 18, which is smaller than the compartment 19, although in contact with the firebox area 11, is not brought to boiling owing to to the thermal inertia of the large amount of water contained in the compartment 19 acting as a coolant. Furthermore, there being no tube nests provided, and the water being distributed in the compartment 18, it will, in addition to the external cooling applied by the water in the compartment 19, remain free to circulate, thereby there exists no chance that overheated spots may form, which could result in the release of steam. Thus, it is possible to keep the compartment 18 relatively small in size, such as to only allow a small amount of water to circulate therethrough, which is particularly advantageous from the standpoint of the boiler efficiency.
It has been surprisingly found that with a boiler according to this invention a 92% to 95% efficiency can be achieved, with the flue gases outlet being at a temperature level within the 180°C to 210°C range.
Since the burner 13 employed is preferably a stoichiometric burner, the fumes that leave the boiler are colorless, because thoroughlly stripped of soot or other solid particulate, such as carbon, and will leave no visible marks, with obvious attendant advantages of an environmental nature.
Furthermore, whereas with conventional type boilers some 25-50% excess air is required over the stoichiometric amount in order to eliminate the presence of carbon monoxide from the fumes, with the boiler according to this invention, by virtue of its operating with a blue flame stoichiometric burner, a 5-10% excess air is quite adequate, preferably a 5-6% excess over the theoretically required amount of air.
One of the specific advantages to be secured with the boiler of this invention resides in that, thanks to its extremely simple construction, the boiler has all its internal parts readily accessible and within arm's reach from the outside. For instance, to gain access to the chamber 11, it will be sufficient to rotate the muffler about its hinges 68 and to withdraw the radiating element 15 which is simply inserted into the chamber 11 (without any special locking or retaining devices). Moreover, a cleaning operation for the chamber 11 reduces to simply handling a cylindrical surface rather than a complex layout of tube nests as with conventional boilers. Lastly, all the boiler components can be quickly disassembled because they are held together almost exclusively by bolting or detachable pieces.
As regards the size of the chamber 11, it should be considered that it should not be too long, for otherwise the flame emerging from the burner 13 might grow turbulent and be extinguished. The same would occur where the chamber 11 is too wide, because the blue flame must be confined. By contrast, if the chamber 11 were too short or narrow, the blue flame would meet with excessive resistance, would be dispersed and produce soot in the combustion chamber inside the nozzle 12 of the burner 13. The volume of the chamber 11 is preferably established while considering that_/at the operating pressure, e.g. at about 40 mm H₂0, a flow is required for the blue flame which corresponds to the hourly fuel consumption wherefor the boiler and related burner 13 have been designed. The blue flame could otherwise undergo undesired changes (e.g. turn into a white or dark blue flame) which, as mentioned, could result in the formation of soot within the burner and in an unstable blue flame.
The invention as described is susceptible to many modifications and variations, all falling within the true spirit and scope thereof.

Claims

1. A boiler with pressurized firebox,particularly for use in combination with a blue flame burner, the boiler comprising a firebox area whereinto the burner is intended to blow its flame, a tank for the water to be heated located adjacent said firebox area and in heat exchange relationship therewith, and a thermally insulating coating around said tank, characterized in that it further comprises a radiating element (15) removably installed in said firebox area (11) at an opposite location with respect to said burner (13) and effective, during the boiler operation, to radiate toward said tank (7) the heat absorbed from said blue flame and to control the outflow of the combustion gases or fumes from said firebox area (11).

2. A boiler according to Claim 1, characterized in that said radiating element (15) comprises an elongate body (58) having outline dimensions which are smaller than the span of said firebox area (11), a plurality of lugs (59) protruding cantilever-fashion from the outer surface of said body, and a manifold (63) connected to said body (58) and adapted for defining a conveying path for the combustion gases extending from the outside of said body to an outlet calibrated passage (66) discharging from said firebox area (11).

3. A boiler according to Claim 2, characterized in that said manifold (63) has a frusto-conical configuration with an outer rim having a shape and dimensions such as to match the inside ones of said firebox area (16) wherein it is intended to be mounted.

4. A boiler according to either Claim 2 or 3, characterized in that said calibrated outlet passage (66) for the combustion gases is defined by a nozzle (65) removably mounted on or in said manifold (63).

5. A boiler according to Claim 4, characterized in that said nozzle (65) is a control nozzle effective to control the pressure and temperature to be maintained within the boiler.

6. A boiler according to any of Claims 2 to 5, characterized in that said body (58) of said radiating element (15) is at least partly solid.

7. A boiler according to any of Claims 2 to 5, characterized in that said body (58) of said radiating element (15) is hollow.

8. A boiler according to any of Claims 2 to 7, characterized in that said body (58) has a substantially frusto-conical outer configuration.

9. A boiler according to any of Claims 2 to 8, characterized in that said lugs (59) comprise fins arranged to extend substantially radially to said body (58) and with outline dimensions such as to contact, in the assembled condition thereof, the inner wall of said firebox area (11).

10. A boiler according to any of Claims 1 to 9, characterized in that said firebox area (11) is fully confined within and along said tank (7).

11. A boiler according to Claim 10, characterized in that said tank (7) comprises an inner compartment (18) surrounding said firebox area (11) and an outer compartment (19) arranged around said inner compartment (18) and in heat exchange relationship therewith.

12. A boiler according to Claim 11, characterized in that said outer tank compartment (19) has larger dimensions than said inner tank compartment (18), the water contained in said outer tank compartment (19) being intended to function as a coolant for said inner tank compartment (18).

13_c A boiler according to either Claim 11 or 12, characterized in that said inner tank compartment (18) is separated from said outer tank compartment (19) by means of a metal partition wall (20).

14. A boiler according to any of the preceding claims, characterized in that it further comprises a muffler device (17) located externally to the boiler (1) at the oulet end of said calibrated nozzle (65) and adapted for defining a tortuous path for the combustion gas flow therein.

15. A boiler according to Claim 14, characterized in that said muffler (17) comprises a first box-like body (69) and a second box-like body (72) arranged as an extension of said first box-like body (69), and a baffle-admitter body (75) effective to define a tortuous path for the combustion fumes.

16. A boiler according to Claim 15, characterized in that said first box-like body (69) and second box-like body (72) are lined with an insulating material layer (70,78).

17. A boiler according to Claim 16, characterized in that said second box-like body (72) is removably mounted cantilever-fashion by bolts (73) inside said first box-like body (69).

18. A boiler according to Claim 17, characterized in that said muffler defines a chamber therein, inside said chamber there being arranged a portion of an outlet conduit (36;87) of at least one of said compartments (18;19) of said tank (7).

19. A boiler according to Claim 7, characterized in that a superheater device (86) is arranged within said muffler (17).

20. A boiler according to Claim 19, characterized in that said superheater device (86) comprises a manifold (87) for the combustion gases from said calibrated nozzle (65), said manifold (87) being adapted for directing the combustion gases to sweep said outlet conduit (31) of the inner compartment (18) of said tank (7).

21. A boiler according to Claim 20, characterized in that said outlet conduit (31) of said inner compartment (18) of said tank (7) has a coiled portion located within said muffler (17).

22. A boiler according to any of the preceding claims, characterized in that it comprises a condensate collecting vessel (81) at the outlet end of said firebox area (11).

23. A boiler according to any of the preceding claims, characterized in that it is operated at a pressure in the 40,to 120 mm H₂0 range, preferably at about 40 mm H₂O.

24. A boiler according to any of the preceding claims, characterized in that it further comprises actuating and control means (38,39,40,42,43,44,45,46, 47,48,49,50 and 55) for the automated operation thereof.