CA1229524A - Heat generator - Google Patents

Abstract

Abstract A heat generator comprising a fuel supply chamber (7a), having at its lower end an inwardly tapered section (12), comprising at its lower end a burner plate (14) with mixing strips (33) and a combustion pipe (20), said tapered section (12) being provided with apertures (8) for primary air in its upper part, apertures (13) for secondary air at a level just above the level of the burner plate (14) and apertures (22) for tertiary air at a level just below the level of the burner plate (14) at the level of mixing strips (33). Preferably all air supplies are preheated. The combustion pipe (20) stands in closed connection with an outlet-pipe, preferably provided with an adjustable ventilator.

Description

Heat generator This invention relates to a heat generator. More particularly it relates to a wood gas generator in working cooperation with a burner, suitable for use in combination with a heat exchanger. This invention relates especially to a wood gas generator in working cooperation with a burner, wherein the burner comprises a burner plate with mixing strips and a combustion pipe.

Wood generators as such have been known for many decades and their use has been aimed at the utilization of the wood gas thus generated in combustion motors. On the other hand wood has been used and is still used in open and closed wood fires. The circumstances under which this has been achieved are such that inconvenient tar formation will occur, requiring frequent sweeping of the chimney, such fireplaces being unsuitable for unproblematic burning of used wood or wood cuttings, in particular when it has been painted or has been plasticized. The heat yield of wood according to that procedure is also relatively small. These open or closed wood fires use a grate to support the fuel, i.e. the wood logs.
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It is an object of the present invention to provide a simple, efficient heat generator with a high yield, especially suitable for use of wood as a fuel, in ~25 particular small pieces of wood, hereinafter referred to was "piece-goods", which, if desired, may also be painted "3~2~

or plasticized, while avoiding the disadvantages of wood for heating purposes, as encountered with installations known hitherto.

In accordance with the present invention a heat generator is provided by a wood gas generator in comb-nation with a burner, incorporated in the fire-bed of the wood gas generator. This combination may in turn be combined with a fire box and a subsequent heat exchanger, as will be described in more detail hereinafter.

By suitable adjustment of the air-supply it is possible to achieve complete combustion of the gas generated in the wood gas generator by means of the heat generator according to the invention, in the burner, and if desired in the fire box. The heat thus released can be used substantially completely for heating purposes by means of a heat-exchanger.

The heat generator according to the invention comprises an upper fuel supply section constituting a fuel supply chamber, provided with a feed port with a lid, and at the lower end an inwardly tapered section, comprising in its lower end a burner plate with mixing strips and a combustion pipe with a collar, in which a continuous gas flow can be maintained from the tapered section towards a gas discharge pipe, connected therewith.

More specifically the tapered section is provided with a supply line for primary air in its upper part, a supply for secondary air at a level just above the level of the burner plate, and a supply for tertiary air at a level just below the level of the burner plate.

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The upper fuel supply section may consist of any material that it not self-combustible at temperatures below SKYE, and as such normal steel may be used.

The inwardly tapered section is exposed to some-what higher temperatures up to 800C, and may consist of materials capable of being exposed to such temperatures, such as special stainless steel of fire steel.

The burner plate, provided with eccentrically positioned mixing strips at its side, facing away from the inwardly tapered section, is exposed to substantially higher temperatures in a range of 1000C to 1200C and consequently will consist preferably of a suitable refract tory material, such as for example fire steel, ceramics or aluminum hydroxide.

The capacity of the heat generator is dictated by the primary air supply. This primary air supply may be provided by apertures in the upper part of the inwardly tapered section. Alternatively the primary air may be provided by one or more air lances which release air at that level. The primary air provides gasification.

The secondary air supply may be provided by apertures in the wall of the inwardly tapered section at a level just above the level of the burner plate. The secondary air has to maintain the ignition temperature of the gas in the combustion pipe at low load. Preferably the secondary air is preheated in order to minimize any possible cooling effect of the secondary air on the gas stream, with which it is going to be mixed. This preheat-in may be achieved in a suitable manner by contacting a wall of the secondary air supply with the gas flow emanating from the gasification stage.

The tertiary air supply may be provided by apertures in the wall of the inwardly tapered section at a level just below the level of the burner plate. The tertiary air thus provides the oxygen for combustion of the combustible gas generated in the preceding stages.

A part of the ashes is carried along through the combustion pipe with the outflowing gas. This ash will stinter or melt respectively at a temperature of about 1000 to 1200C thus leaving substantially no minute ash particles in the flue gases. Thus the need for expensive devices for trapping ash from the flue gases is avoided.

A pressure drop in the inwardly tapered section is maintained from its upper wider part towards its narrower lower part by either feeding pressurized air or alterna-lively by a ventilator positioned downstream of the inwardly tapered section. By suitable adjustment of the gas flow, and in particular the air supply at the various levels, it will be possible to comply with the desired capacity. The air supplies are used both for gasification and for complete combustion of the gases formed in the wood gas generator. An additional advantage is that in the heat generator according to the invention any possible other materials present in the fuel supply, which arrive together with the gas flow in the combustion pipe, will be completely combusted or be nearly completely combusted as a consequence of the prevailing temperature in the combustion pipe.

The invention will be elucidated in more detail ; with reference to the accompanying drawings, without limiting the invention to the embodiments of the invention as presented therein.

With reference to the accompanying drawings Fig. 1 shows a longitudinal section of a heating system in accordance with the invention comprising a heat generator according to the invention.

Fig. 2 shows a top view of the heating system of Fig. 1;

Fig. 3 shows a combined air supply adjustor;

Fig. 4 shows a top view of a burner plate according to the invention;

Fig. 5 shows a cross-section of the burner plate and its immediate vicinity;

Fig. 6 shows a modification of the heating system as presented in Fig. 1;

Fig. 7 shows another modification of the heating system as presented in Fig. 1; and Fig. 8 shows a cross-section of the heating system of Fig. 7.

With reference to Fig. 1 a longitudinal section is shown of the heat generator and the heating system accord-in to the invention, wherein a flue connection with an adjustable ventilator (1), coupled to a thermostat ~39) and a switch (16) for minimum level, after boiler pipes

(2), is arranged in a boiler (pa) with insulation (3).
The boiler (pa) is provided with a cleaning hatch (24), provided with a connection (4) for suction from a suction lid (5) of a generator vessel (pa). The generator vessel (pa) is provided with an insulating wall (7), a cover (6), 52~

inlet apertures (8) for supply of primary air, as well as a control valve (9) for the primary air. In addition there is a control valve (10) for supply of secondary air to secondary air inlet apertures (13) in a lower part of an inwardly tapered section (12), which forms a duct with concentric insulation (11). At the lower part of the inwardly tapered section (12) a burner plate (14) is located, as will be described in more detail with reference to Figs. 4 and S. Tertiary air is introduced at a level just below burner plate (14) by means of a duct (aye), provided with a control valve (15). Below burner plate I is a combustion pipe (20). The tertiary air is introduced through inlet apertures (22). At the lower end of boiler (pa) is an ash pan (21) and just above the ash pan a lead strip (23) for condensed water. The combined air supply is adjusted in a suitable manner by an extension rod (19), provided with an automatic control valve (15), a switch for minimum level (16), an adjustment screw (17) for the minimum level and an adjustment screw (18) for the tertiary air supply.

In Fig. 2 similar parts are indicated by the same reference numbers as in Fig. 1. For easy removal of ash, the wood gas generator, resting on a fire-box, may be positioned thereon in an easily removable manner, such as by means of lifting means (25). Instead thereof the ; burner plate may be shaken, for example by means of a suitable lever.

A combined air supply adjustor is presented in Fig. 3, wherein identical reference numbers have been used as in Fig. 1 for similar parts. The supply of air to an inlet for tertiary air (aye) is controlled by a control valve (15), connected by a pivot point (31), which is con-netted with outer wall (32), and is adjusted by extension ~.Z~S2~

rod (19). The functioning of this arrangement is self-evident and does not require more detailed elucidation.

In order to prevent the gases emanating from the heat generator from reaching the heat exchanger in the boiler uncombusted, a certain minimum temperature of the parts of the burner plate and of the active part of the charcoal bed present in the heat generator, when function-in, should be maintained. To this end a flame is main-twined in the relatively narrow combustion pipe (20) with complete combustion of the gas, but with a very small capacity. For adjustment of the so-called minimum load a switch (16) for the minimum level is provided, which is controlled by means of a lever (26) by the combined action of pivot point (30) for lever (26), which is connected with lever (29) and extension rod (19). For proper adjustment of switch t16) an adjustment screw (17) with an appropriate biasing spring (27) are provided. For adjust-mint of the supply of tertiary air, control valve (15) is connected with pivot point (31) by means of lever (29), whereby an adjustment screw I on extension rod (19) allows for proper adjustment.

In use for a heating system according to the invention the generator vessel (pa) is ignited in a customary manner and filled with suitable fuel, usually wood blocks and wood residues, by means of lid (6). After a very short time, usually less than one minute, a charcoal bed is formed in the inwardly tapered section (12), from where wood gas is sucked by ventilator (1) through burner plate (14) into combustion pipe (20). The temperature of the flame emanating therefrom amounts to at least about 800C and the system shown above for control of air supply takes care of maintaining a desired combustion. The combustion products, mainly carbon it it dioxide and aqueous vapor, are passed through the heat exchanger, where the gases and vapor release their heat.
The functioning of the heat exchanger is customary and does not require further elucidation.

The heating system according to the invention obtains substantially complete combustion of piece goods, that is small pieces of wood or other cellulosic material, possibly provided with a paint- or plastic-layer. This system can be used to replace partly or completely lo customary installations using natural gas, coal or fuel oil as fuel. The heating system according to the present invention avoids the formation of undesired by-products, in particular Selfware containing compounds, as occurs with coal and fuel oil, whereas with respect to natural gas substantial savings are obtained as waste products of wood processing, sawdust, dead wood or compressed blocks of sawdust or wood clippings can be used as a fuel. These fuels for the heating system according to the present invention can be used as such or in combination with other useful components, such as agricultural and horticultural waste materials, regardless of a Herr low moisture content.

A suction lid (5) of generator vessel (pa) is positioned above lid (6) in order to prevent gas formed in the generator from causing an obnoxious smell in the surrounding space by minor leakage of the lid (6), in particular when at low load. To that end the suction lid (5) is connected with the chimney stack by means of a connection (4), which extends through cleaning hatch (24), thus removing possible leaking gas by means of the ventilator (1). This is desirable for indoor use in particular.
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In order to avoid heat losses as much as possible not only a good insulation is desirable but it is also recommended to burn the wood/gas as close as possible to the charcoal bed using preheated air. It is also useful that the air is mixed as thoroughly as possible with the gases to be burned. Thus the charcoal bed is boosted with secondary air, increasing the temperature in such a manner that the ignition temperature of the gases is achieved.
For preheating of the air, the air is introduced radially through a number of apertures (13) positioned along the periphery of the charcoal bed, after said air has been passed for some distance along the hot wall of the inward-lye tapered section (12), in which the charcoal is present.

The charcoal bed rests on a round burner plate (14) of which the annular opening with inwardly tapered section ~12) of generator (pa) is large enough to allow fly ash to pass together with the gases in order to prevent clogging by fly ash.

Mixing can occur thereafter with the tertiary air, which is introduced through numerous small apertures (22) and thus provides optimal combustion.

The gas/air mixture thus formed is then passed into the combustion pipe (20) by means of some eccentrically positioned vertical strips (in the present case 4), wherein the gas mixture is concentrated from the rim of the burner plate (14) towards the center. This is desirable for obtaining an optimal mixture of gas and air, and is necessary to maintain a small flame at minimum load at a temperature which is high enough to avoid pollution of the installation. At a temperature which is too low soot would be given off by incomplete combustion.

In order to maintain a temperature as high as possible, all parts of the burner, that is burner plate and mixing strips, are positioned as close as possible to the charcoal bed. At the same time the burner should be positioned in such a way that heat dispersion by conduct lion is avoided as much as possible, which can be achieved by insulation and also by having a contact surface with other parts of the installation as small as possible.

The gas supply from the generator is not smooth.
Thus continuous adjustment of the air supply is desirable, when fairly coarse piece goods are used. The control of the air supply as described hereinabove is eminently suited for this purpose.

The boiler can be any customary heat exchanger.

As the burner will not function on interruption of the electricity supply to the ventilator (for whatever reason), a safety device for the boiler should be provided if the boiler should be brought back to minimum load within a short time, such as is done in a known manner for customary central heating boilers By mounting various types of ventilators, different capacities can be achieved with one and the same size of burner, depending on the application of refractory materials, which is also determined by the ash throughput and the type of piece goods to be burned.

Removal of ash and refilling in continuous processing are simple actions, which for a properly chosen size of heating installation according to the invention, will be required not more than once a day.

it The burner plate with mixing strips is further elucidated in Figs 4 and 5, wherein similar parts are referred to with the same reference number. Burner plate (14) is positioned over combustion pipe (20) and is kept in this position by mixing strips (33), which rest on the bottom of inwardly tapered section (12) and which at the same time take care of centering of the burner plate.
Inlet apertures (13) for secondary air are present in the inwardly tapered section (12) above the level of burner plate (14) and inlet apertures (22) for tertiary air are present below the level of the burner plate (14) at the level of the mixing strips (33). Gas present in the charcoal bed in the generator (34) is then mixed with secondary air, flows along the burner plate (14) and past the mixing strips (33) and is mixed there with tertiary air and is subsequently removed whirling through combs-lion pipe (20). with a view to the high temperatures to which the burner plate and the mixing strips are exposed it is advisable that these be made of refractory material. For relatively small installations, such as for home use foundry iron will usually be sufficient. For larger installations, such as those for industrial apply-cation, higher temperatures have to be taken into account, with as a consequence a preference for ceramic materials, more specifically refractory materials, in order to ascertain a reliable functioning of the installation. I-t is advisable that the diameter of the combustion pipe (20) is at most half the diameter of the lower end of the inwardly tapered section (12), with the length of the combustion pipe being at least 1.5 times its diameter.

Fig. 6 shows a modification of the heating system as presented in Fig. 1, wherein the same reference numbers have been used for similar parts. In addition it come proses a lever (40) for securing the cover (6) on top of cj~

generator vessel (pa); a central air inlet (41) provides air for the primary, secondary and tertiary apertures (8), (13) and (22) respectively. The combustion pipe (20) is provided with a lever (42) for shaking the burner plate (14), mixing strips (33) and combustion pipe (20) to remove any ash assembled thereon. A fire-box, whereon the generator vessel (pa) is resting, is formed by refractory bricks (43), said fire-box also having a door (44) for easy removal of ashes. In the exhaust pipe an adjustable servo valve I is located.

Figs. 7 and 8 show a longitudinal section and a cross-section, respectively, of another modification of the heating system as presented in Fig. 1, using the same reference numbers for similar parts as used in Figs. 1 and 6. In addition a flue gas duct I is shown in Fig. 7 and in Fig. 8 fire-tubes (47) are present as heat exchangers.

As will be evident from Fig. 6 it is possible to provide a suitably adjustable generator vessel without any more or less complicated controls for the various air flows, the capacity and load being largely dictated by the ventilator (1) (not shown in Fig. 6).

The modification as shown in Figs. 7 and 8 has the advantage of a minimum heat loss as both heat generator and heat exchanger are confined within one and the same insulating wall.

If desired the novel heat generator can be used for destruction of wood as a consequence of the burner and combustion pipe present thereon, without the disadvantages with respect to pollution of the environment, as occurs by burning wood on grids causing smoke and tar formation.

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In particular from the viewpoint of environmental hygiene it is considered to be of major importance, that the heating system and the heat generator according to the invention does not only expel hardly any harmful components, if any, but in essence only carbon dioxide, but also provide a solution for the fly ash problem. Thus no dust filters are required and the stack or chimney needs cleaning considerably less frequently than most conventional systems, with the possible exception of natural gas.

It will be obvious to persons skilled in the art that the invention encompasses other advantages and modifications than those recited above.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A heat generator comprising an upper fuel supply section, constituting a fuel supply chamber provided with a feed port with a lid, and at the lower end an inwardly tapered section, comprising at its lower end a burner plate with mixing strips and a combustion pipe with a collar, in which a continuous gas flow can be maintained from the tapered section concentrating into the combustion pipe, said tapered section being provided with a supply line for primary air emerging in its upper part, a supply line for secondary air emerging in its lower part at a level just above the level of the burner plate, and a supply line for tertiary air emerging in its lower part at a level just below the burner plate at the level of the mixing strips.

2. A heat generator according to claim 1, wherein the burner plate is provided with eccentrically positioned mixing strips between said burner plate and the combustion pipe.

3. A heat generator according to claim 1, wherein primary air is provided by a supply line emerging in a number of apertures in the upper part of the wall of the inwardly tapered section.

4. A heat generator according to any one of claims 1, 2 and 3, wherein primary air is provided by at least one air-lance releasing air within the inwardly tapered section at the level of the upper part thereof.

5. A heat generator according to any one of claims 1, 2 and 3, wherein secondary air is provided by a supply line emerging in a number of apertures at the lower end of the inwardly tapered section at a level just above the level of the burner plate.

6. A heat generator according to any one of claims 1, 2 and 3, wherein the secondary air is preheated.

7. A heat generator according to any one of claims 1, 2 and 3, wherein tertiary air is provided by a supply line emerging in a number of apertures in the lower end of the wall of the inwardly tapered section at a level just below the burner plate, said tertiary air being preheated.

8. A heat generator according to claim 1, comprising a fuel supply vessel, provided with an insulating wall, a feed port with a lid, and at the lower end provided with an inwardly tapered section having inlet holes for the supply of primary air, inlet holes for the supply of secondary air, said inwardly tapered section forming a duct in cooperation with concentric insulation, said inwardly tapered section in its lower end being provided with a burner plate with mixing strips and a subsequent combustion pipe, said combustion pipe being in closed connection with an outlet-pipe.

9. A heat generator according to claim 8, wherein the outlet pipe is provided with a ventilator.

10. A heat generator according to any one of claims 1, 2 and 3, modified in that the heat generator together with a heat exchanger connected with said heat generator, are confined within a common insulating wall.