EP2906873B1

EP2906873B1 - Method and device for intensifying the burning of solid fuels in a fireplace

Info

Publication number: EP2906873B1
Application number: EP13844960.8A
Authority: EP
Inventors: Jouko Kettunen
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-10-09
Filing date: 2013-10-08
Publication date: 2019-12-18
Anticipated expiration: 2033-10-08
Also published as: EP2906873A4; WO2014057172A1; RU2015117059A; FI20126055A; EP2906873A1; FI127234B

Description

The invention relates to a method for intensifying the burning of solid fuels in a fireplace and a device for applying the method.
In conventional fireplaces, such as e.g. in furnaces, solid fuels, such as wood or other materials including gasifiable components and carbon, are burned usually in a similar way. A fuel filling is put in the fireplace, the filling is lit and the fireplace starts to heat up gradually along with the lighting of wood, the burning proceeds to the gasifying stage and char burning of fuels, such as e.g. pieces of wood.
Depending of the structure of the fireplace, the quality of wood and its setting in the fireplace, the way of lighting, the control of combustion air, draught, and some other factors, the quality of the burning process varies. When the draught is weak in the smoke flue due to the weather, other environmental factors, low pressure in the indoor air or some other reason, smoke can even come inside.
Solutions for improving the burning have been developed. There are, inter alia, different ways to supply air. Primary air and secondary air are supplied to the fire chamber in different ways. There are also various shapes of fire chambers as well as combustion space and smoke flue solutions.
There are other types of fireplaces in boilers, particularly in those which produce heat at a larger scale. Their problems are partially similar. A problem is uneven and incomplete burning. Varying amounts of smoke and other results of imperfect burning are discharged to the surroundings during burning.
Heating devices provided with a fire chamber often have a large mass which is used for storing heat. They heat up slowly and first give heat slowly to the surroundings.
Those with a lighter structure heat up more quickly and also give heat to the surroundings more quickly but also cool down more quickly.
A method and a device according to the prior art are described by document US4766876 .
In conventional wood burning occurring in a fire chamber, an air flow goes below, between and partially on top of the pieces of wood. Flames are formed according to the release of burning gas and the flows of air varyingly. Burning in an oxygen-rich section occurs from the surface layer of the flame towards the inside of the flame.
First, there is sufficiently oxygen for burning. Heat builds up well. When burning proceeds towards the inside of, between and amongst the flame, a carbon dioxide layer is formed which slows down and prevents the progress of burning. In a deeper, oxygen-poor section, carbon monoxide is formed and the reaction changes into one which absorbs heat. Burning slows down and can even be totally prevented. Slow-burning mixed gas is formed which prevents burning in its surroundings and in the later stages. Burning is mixed burning in the sense that gasifiable burning materials and char burn at the same time. Forming carbon monoxide disturbs burning.
The reason for this problem is usually the fact that the temperature in the fire chamber does not increase quickly enough to a good burning temperature or the temperature in the fire chamber has no prerequisites to increase suitably high for good burning in any stage of burning. This can be due to the great and quick heat absorption of stone material surfaces or metal or water surfaces. The heat-absorbing capacity of the surfaces is so good that heat is absorbed to it at a greater speed than it is formed. Thus, temperature close to the surface only increases so much as the heating of burning material and the flame enables. And it is nowhere near enough to the temperature enabling good burning. For instance, wood starts to gasify in about 200°C. The temperature which enables good burning is quite high; carbon monoxide does not start to burn until in the temperature of about 700°C.
Another factor which affects by hindering burning is the quick flow of combustion air through the fire chamber. The flow continuously brings new cool air to the burning surroundings, even inside the flames, thus cooling them effectively. Furthermore, the flow takes with it formed heat, transfers it from the burning section elsewhere in the surroundings of the fire chamber, to the flue and even outside. In addition to cooling the surroundings and burning effectively, the quick flow of air caused by draught provides an accelerating flow the boundary of which to the stationary or slower-moving air becomes harder and tighter, which further hinders swirling and mixing which are a prerequisite for good burning.
It is important to notice the difference between various flows, what they are, how they operate and what their results are. A turbulent flow is whirling. A pressure-based flow is often turbulent.
Another type is a laminar flow which causes the mainly parallel transfer of materials, and its speed and extent can vary. This is based on suction or underpressure which causes it.
An object of the invention is to introduce a method for intensifying the burning of wood and other fuels including gasifiable components and carbon in a fireplace as well as a device and means for applying the method, which eliminate disadvantages related to current methods, devices and means. A particular object of the invention is to introduce a method and a device which improve the burning of fuel in the fire chamber.
The object of the invention is achieved with a method and a device which are characterised by what is presented in the claims.
In a method according to the invention in the burning of fuel, the burning of gases in it is separated from the burning of solid carbon in the fuel by releasing gases from the fuel by means of heat and by conveying them to a uniform, planar flow of combustion air in the top part of the fire chamber, where they are burned. Then during burning, combustion air is not supplied amongst or is not allowed directly to the fuel, but only heat is used for releasing the gases.
In the method according to the invention, combustion air of combustion gases is conveyed after lighting only to the top part of the fire chamber, from gaps opening from air channels being all around in its sides in the top part, directed at the middle on top of the flames as a planar flow supporting itself on the top surface of the fire chamber, becoming denser as it moves forward, whereby the flames when rising upwards in the fire chamber hit the flow, are cut along with rising becoming merged to it for its every part, and the combustion gases are removed to an exit opening in the crown of the fire chamber being in the middle of said crown and from there to an afterburner, the inside volume of which is greater than the volume flow of holes of inlet flow entering from the exit opening, whereby the flow and the whirl first become quicker and then slow down, heavier particles of the gas flow first fly on the edges of the afterburner and turn to the slow flow directed downwards and lighter particles of the gas flow move slower and along a different route and at a different pace downwards than the heavier particles of the flow. The partially insulated structure and the little heat-absorbing material of the inner surface of the fire chamber enable a quick increase of temperature to high in connection with lighting, whereby heat releases gasifiable particles of the fuel thus helping the bonds of the gasified fuel to open and transform into a form which burns better. Char is burned separately by a method based on time or section, thus conveying the main part of combustion air from below chars amongst them. In the method according to the invention in the fire chamber, heat affects the fuels, heat provides the release of gases separated from char burning and the mixing of burning gases to a uniform combustion air flow. This and variation in pressure ratios together achieve good burning.
In an application of the method according to the invention in the next stage, char remaining of the fuel after gas burning is burned separately, in batch-burning devices, in the fireplace or, in continuous-burning fireplaces, in a separate section provided for char burning, whereby at the start of char burning the inlet of combustion air going through the gap in the top part is decreased and combustion air is supplied from below and through the chars increasing combustion air when the temperature increases in the chars and intensifies their burning.
In an embodiment of the invention in a conical inlet part of the afterburner, a burner provided with narrow, directed inlet openings increases the speed and direction of the gas flow, directing the flow from different directions to a rising whirl in the middle, whereby intense coarse mixing occurs in it. The whirl collides with the top part thus spreading and directing downwards. Also buoyancy caused by heat causes differences in pace in the particles of the gas flow. When flowing in different paces, molecules and atoms collide with each other, thus becoming totally oxidised. In the bottom part, gas flow turns directing upwards to a channel around the burner at the same time delivering heat to the walls of the channel and exits the afterburner through an opening being in the top middle. Also variations in pressure ratios help the bonds to open and form new ones which burn better. Burning can be controlled by monitoring the carbon monoxide content of burning gases. If carbon monoxide occurs in exiting gases during char burning despite of the slow start, it is possible to carefully supply combustion air to the top part of the fire chamber or the afterburner e.g. through the gap in the top part, whereby carbon monoxide will burn out in the afterburner.
According to the invention, the release of gasifiable components from fuel occurs by means of heat and their burning is separated from char burning, char is burned in batch-burning devices in a way based on time and in continuous-burning burning devices in a way based on sections separately, gasifiable components first and char after them.
The inventive method includes dividing the burning event exactly into two different stages. As the first stage, gasifiable particles of burning material are gasified by means of heat and gas is burned, the burning of which supplies more heat. As the second stage, remaining char is burned in a way well suited for it by supplying a correct amount of combustion air for chars at the correct point.
When using the method, fuel is first lit in the fireplace, if required, combustion air is supplied for a while in the starting stage from below the fuel and the fuel and the fireplace are let to warm and heat up, the supply of combustion air is then totally changed to occur from the gap in the top part, gasifiable components of the fuel are gasified by heat and the gasifiable components of the fuel are burned, supplying combustion air to the top part of the fire chamber from the edges all around, along the roof, crown of the fire chamber to an exit flue being advantageously in the middle, whereby gases burn with a hot flame releasing more gas from the fuel. After gas burning has stopped, the second stage, char burning, is entered by decreasing the supply of combustion air from the gap in the top and by moving the supply of air to occur below and through chars.
Another possible way of burning is suitable for continuous-burning fireplaces, which many boilers are. In them, the burning section is divided into different sections. In them, fuel enters to a grate continuing its travel forward there by means of either gravity or inclination according to the progress of burning or transported by the moving grate.
On the grate of the fuel close to the supply point, there is a hot gasifying section in which the fuel first warms and heats up and gaseous components release from it by rising upwards from the effect of their lightness and buoyancy. During first lighting, warming and heating up, combustion air is carefully supplied to the fuel e.g. from below, after that, combustion air is supplied to the gasifying section only through the top part of the fire chamber, directing starting from the gap on the edge along the top part, the crown to the exit channel advantageously being located in its middle or one of the sides.
When mixing to the combustion air flow, gas releasing from the fuel burns with a hot flame further enhancing gasifying and heat formation.
At a distance from the supply point behind a separating wall or some other suitable obstacle, there is another section to which char enters through an opening in the bottom part of the separating wall as the supply process proceeds. At its point below and amongst chars, combustion air is supplied thus burning the chars all the way effectively. The gasifying section is separated from the char burning section by the separating wall or some other suitable obstacle, such as e.g. a gas curtain, such that chars enter past the wall to their own burning section. It is important that the gases of both burning sections stay on their own sides. Otherwise, they will mix the burning on the other side, and clean burning is not possible. On both sides of the burning section, there are their own pressure sensors which control the moving of air by means of suction fans and blowers and the supply and suction on both sides. The pressure sensors observe the pressure levels of the sections such that no significant flow occurs from one side to the other.
Also the quantitative forming of gases is different on different sides. The gasifying of fuel increases volume significantly. In the method, combustion gases and flames released by heat rise upwards in the fire chamber due to their lightness and buoyancy, mixing into the uniform flow of combustion air thus merging to it as they hit it. Various burning compounds and atoms and molecules of combustion gases always hit the oxygen-rich fresh flow of combustion air, mix to it well and burn out.
Combustion air in gas burning is controlled totally from the edges of the top part of the fire chamber, from a narrow gap, to be directed advantageously to the middle such that a thin, unbroken planar flow is formed which supports itself of its top side to the level ceiling of the fire chamber, flowing from different sides to the exit opening advantageously located in the middle. The flow directed to the middle partially accelerates of its speed, at the same time, the flow thickens as its volume and area decrease.
In the device according to the invention around the edges of the fire chamber, there is/are a gap or gaps entering from a combustion air channel or channels the direction of which is along the bottom surface of the top part of the fireplace towards an exit opening advantageously in the middle section. From the exit opening, the flow channel extends to the afterburner being above. The inner surface of the fire chamber is of heat-resistant material having a low heat capacity, and there is a heat insulator layer behind it which decelerates the transfer of heat from the fireplace to the other structures of the fireplace and the medium of heat transfer.
In a batch-burning fireplace, there is a grate or a char basket inside the grate and an adjustable supply mechanism of combustion air, such as a tight ash box or a damper. In continuous-burning fireplaces, the burning section has two parts, at the inlet end of fuel on top of the grate there is a section for fuel entering, warming, heating up and gasifying and on the top part of that section a gap circulates its edges in which from the edges combustion air is supplied as a planar flow to the middle towards an exit opening for gas burning. At a distance behind a separating wall or some other suitable obstacle, there is a section to which the grate extends and the fuel having gasified out, char, burns by means of combustion air supplied from below the base or the grate after the process has reached this stage.
In a continuous-burning fireplace, there is advantageously a separating wall or some other suitable obstacle which separates the different burning events from each other and prevents different combustion gases from mixing to each other. From below it, chars are able to transfer to the char burning section, and it features a control mechanism which includes pressure sensors on both sides of the fire chamber, suction and pressure blowers controlled by them, which control the travel of gases in the fireplace keeping the pressure level the same on both sides the fireplace, in the gas burning and char burning section, and preventing the flow of gases occurring under the separating wall.
In the bottom part of a continuous-burning fireplace, there is advantageously a fixed inclined grate or a moving grate having one or more parts as the base of fuel and transferring it from one stage to another and the operation of which is controlled and driven by sensors and actuators monitoring the burning as it proceeds. In the char burning section, a supply mechanism of combustion air is connected to the grate or the base by means of which combustion air is arranged to be supplied below and amongst chars.
In the moving grate, the amount of burning and heat formed is controlled by the batching of fuel on the grate and by adjusting the moving speed of the grate. The first end of a two-part grate is in the gasifying section as a receiver, base and forward transferer of fuel. At the point of char burning, there is the second part of the grate below and inside of which there are a combustion-air supply apparatus and channels for supplying combustion air to chars. Advantageously, the different parts of the grate having two or more parts move independently such that their moving can be controlled based on signals given by sensors monitoring the progress of burning, according to the requirements of the progress of burning. It enables a more extensive power-adjustment range and cleaner burning such that both sections, the gas burning and the char burning sections, burn out the fuel entering the section.
There are fireplaces different of their mode of operation, and the method can be applied in different fireplaces in different ways, in accordance with the mode of the operation of the fireplace. The fireplace should also be designed such that its structures enable sufficiently quick rising of temperature in places necessary for burning, such as in the fire chamber, the heat formed is recovered in the other structures of the fireplace.
In small-scale fireplaces, the so-called batch-burning mode is common. It means charging the fire chamber with fuel, lighting it and burning it for the most part before adding fuel or burning the chars. A batch of fuel is burned at a time. For the batch-burning mode, most suitable is the division based on time for burning gasifiable components and, on the other hand, char. The structure of the fireplace must be such that the supply of air can be controlled accurately based on requirements.
The inner structure of the fire chamber includes a top part all around the edges of which there is a supply gap of combustion air opening from air channels which controls the flow of combustion air from the air channels along the bottom surface of the top part as planar towards the exit opening in the middle section. It is important that the flow remains planar, thin and laminar of its nature.
Then, the flow can be continuously uniform and even small side flows are not released from it which could possibly go amongst the fuel, but it is continuously ready to receive burning gases. As the atoms and molecules of burning materials rise to the flow of combustion air, there are continuously fresh oxygen atoms to receive them. When the rising gases and flames as turbulent meet the planar flow, they as if become cut, merge into it and the oxidation, i.e. burning, is effective. The earlier notion of the importance of a turbulent flow in connection with mixing does not operate here properly.
A planar top part is an advantageous shape of the top part, but it is possible to use also other shapes, however such that there is a uniform support on top of the planar flow which enables the flow remaining uniform. In the structure, it is possible to use one or more inner panes or blocks of the top part of the fire chamber being upwards at different angles on inclination or even such that the inclination is inside downwards, i.e. the edges of the exit opening are lower than the other section of the crown of the fireplace. It is still essential that the shape supports the flowing of the planar flow of combustion air as whole and uniform below it such that the flames and gases rising in the fire chamber meet it well.
The inner surface material inside the fire chamber is material having a low heat capacity as is the heat insulation layer below it. The insulation layer is dimensioned according to its heat production capacity such that, after lighting, the temperature of the fire chamber starts to rise quickly. Hence, it is possible to reach good burning temperature quickly.
The insulation layer should still be thin enough in order for the heat transfer speed in a higher temperature to the other structure of the fireplace to increase thus preventing the fire chamber from heating up too much and to be damaged due to too high a temperature. It is advantageous that the height of the fire chamber is quite small, in a batch-burning device about 0.8-1.2 times the width of the fire chamber such that the radiation heat of flames burning in the top part will heat up and gasify the fuel.
In a continuous-operating fireplace, the mutual sizes of the sections required by gas burning and char burning are partially dependent on the shape, size and power of the fireplace. A prerequisite for good burning is that gases are able to burn out totally before the fuel flows to the char burning section. Similarly, the total burning of char in its own section reserved for it is important. Then, the yield of thermal energy is the best possible, the burning result is clean and the amount of ashes little.
An advantageous distribution of the burning section is for gas burning about 2/3 and for char burning about 1/3 of the length of the grate. When desiring a burning result as good and clean as possible, it is advantageous to have a grate of two or more parts, whereby there is one grate at the point of gas burning and one at the point of char burning. It is advantageous that the grates can be controlled independently. Then, the power-adjustment range of the fireplace and the possibility to adjust accurately between low and high power is greater.
The shape of the bottom side of the top surface of the fire chamber can be planar, straight, sloping or inclined into one or more directions directed at the exit opening which can be e.g. on top or on the side, still such that the principle presented in the claims of a planar laminar flow of combustion air and of flames and gases rising to it will be realised.
The device also includes a suitably insulated afterburner in which the unburned particles of combustion gases mix to combustion air and burn out in a suitable temperature. The parts of the afterburner are an inlet/acceleration section, a conical inlet section provided with directed holes in which the speed of a scattered gas flow increases, its direction changes to uniform and a rising whirl is formed in the middle of the cone which whirl turns from the effect of a ceiling part all around to the sides. At the same time, the volume of the flow part increases and the speed of the gas flow decreases. Particles of gas flown close to the separating wall fall quickly to the downwards-directed flow, lighter particles of gas flow slower and buoyancy caused by heat affects them more also by decelerating. At micro level, particles of gas flowing at different speeds hit each other and then burn out. Via a circular opening in the bottom part of the separating wall, the flow turns to rise upwards, rising between the walls and exiting via the opening in the middle of the ceiling part further to the structures of the heating device.

Advantages of invention compared to prior art

The method according to the invention resolves some of the problems related to imperfect burning. The method alters the earlier used supply method of combustion air from distributing combustion air amongst burning material and gases into batching combustion air to a continuous whole flow of air such that the gas flow and flames will be cut and as if merge to it of their each part simultaneously as they meet it. Then, the interiors of flames will not be lacking the effect of oxygen but all atoms and molecules can possible react with oxygen by burning. A prerequisite for it is that there are no separate carbon atoms amongst gas entering oxygen-rich combustion air. If there are those, they will take over the second oxygen atom from carbon dioxide during burning and carbon monoxide is formed, after the reaction has continued, it starts to strengthen by taking most part of burning thus effectively mixing up the good burning process and disturbing burning for a long time. The result is carbon monoxide and solid carbon and other compounds in combustion gases.
According to the method, gasifiable components in fuel are burned by releasing gasifiable components first from the fuel by means of heat. Heat also incurs the reaction of oxygen possibly in the fuel with burning gases and, then, less extra oxygen is required. When no oxygen at all is added to the fuel layer during gas burning, the burning components gasify and solid char remains. According to the method after the gases have released from the fuel, char burning is started by decreasing the supply of combustion air in the top part of the fire chamber and by carefully opening the supply of combustion air from below chars to flow through chars. According to the increase in the temperature of char burning, the supply of combustion air can be increased. Then if there is carbon monoxide in the exiting flow, there is too much air at the beginning in relation to the heating speed of chars.
Devices having different operating principles require different arrangements to provide burning according to the method. A problem of the burning of fuels is the variation in reactions between exothermic reactions releasing heat and endothermic reactions absorbing heat.
When burning occurs correctly and with sufficient combustion air, the burning process proceeds well and releases heat continuously, the fuel burns out and the amount of heat formed is the one possible from that fuel. When burning components do not oxidise and burn sufficiently, the burning process is interrupted and reverses a little. Instead of separate carbon atoms to burn out, they take a little oxygen from carbon dioxide and change into carbon monoxide, which gas absorbs oxygen very effectively from its surroundings.
The carbon monoxide reaction is intense and controls burning for some time in the immediate area and absorbs heat and forms solid carbon at the same time as it cools down its surroundings. The most prolonged burning compounds will not light until in the temperature of over 700°C burning explosively when burning is otherwise accurate.
It is important in the method that the burning proceeds controlledly, because the amount of heat formed is greater than in burning which makes much smoke. If the filling is large in relation to the fireplace and it burns very quickly, there is a risk that heat has no time to transfer evenly in the structures of the fireplace. There form heat accumulations which, when reoccurring, might damage the structures of the fireplace. In a fireplace operating with the method according to the invention and being according to the invention, there is even draught and the fuel burns without smoking for the whole duration of the burning event.
According to the method in burning wood, gas burning in wood is separated from the burning of solid carbon in it. No combustion air is supplied directly to fuel, amongst it during burning, but gases are released from wood by means of heat and burned by conveying them to a whole, uniform, planar flow of combustion air in which they all are oxidised well changing into carbon dioxide. After gas burning has stopped, a flow of combustion air is conveyed below chars or, in another embodiment, chars are burned in a different section by conveying combustion air below and amongst them according to requirements.
Next, the invention will be described in more detail referring to some of its advantageous embodiments and the attached drawings in which

Figs. 1 and 2 show schematical front and side views of a sauna stove structure according to the invention,
Figs. 3 and 4 show schematical front and side views of a furnace according to the invention,
Fig. 5 shows a schematical view of a boiler structure according to the invention, and
Fig. 6 shows the structure principle of an afterburner.

Figs. 1 and 2 show a sauna stove according to the invention which is implemented in a way required by the method. In the sauna stove, an inlet door 1 of a fire chamber 8 is in front of the fire chamber and an air supply shutter 2 at the beginning of an air channel behind the stove. Combustion air gaps 3 in the fire chamber circulate a top part 5 of the fire chamber. An exit opening 4 is in the middle of the fire chamber connecting to other heat-release channels. A route of combustion air is shown in Figs. 1 and 2 by a thick dashed line and arrows.
An ash box 6 is tight enabling the supply of combustion air in the first stage only though the gaps 3 in the top part of the fire chamber and, in the second stage, during char burning, after gas burning has stopped, decreasing the supply of combustion air from above from the gaps 3 by adjusting the air supply shutter 2 and directing combustion air to chars from below via the ash box 6 from below a grate 7. The burning of fuel in the stove is intermittent; first, burning gases are released and burned and, after they have burned out, the supply of combustion air is switched to below chars and chars are burned.
A second example is a furnace of heating type according to Figs. 3 and 4. A fire chamber of the furnace includes a door 11 for adding wood to the fire chamber, an inlet door 12 in an outer covering for adding wood and for controlling combustion air and the supply of combustion air from the top part of the fire chamber from edges 13 towards the middle. Inner walls of the fire chamber and a crown 14 of a ceiling part are advantageously of material having a low heat capacity.
Furthermore, the furnace includes an exit channel 15, in the bottom part a tight ash box door 16 and a box, above it a grate 17 or a netlike base for chars. The fire chamber is insulated by a heat-resistant insulation 18, insulation circulates its bottom part as a seal 19 and above the fire chamber there is an insulation 20. When using the furnace, pieces of wood are put to the fire chamber by opening the inlet door 12 and the door 11 of the fire chamber. Pieces of wood are put in the fire chamber, kindling amongst and on top of the pieces of wood. The kindlings are lit at several points. In the lighting stage, a little combustion air is supplied via the ash box door 16. The burning method is intermittent; first, pieces of wood are lit in the fire chamber, they are let to warm and heat up, heat releases and burns burning gases, after the gas burning has stopped, it is possible to add pieces of wood to the fire chamber without smoke forming or, after gas burning has stopped, the supply of combustion air is decreased from above through the air control parts of the inlet door, the supply of combustion air is changed to below and amongst the chars and the chars are burned, e.g. on top of the grate or in a netlike char basket provided inside or below the grate of the fire chamber.
The route of combustion air inside the fire chamber is first adjustably via the inlet door 12 distributing outside the fire chamber between the structure to different sides and via the gap 13 inside the fire chamber from where combustion gases flow advantageously along the top part, the crown of the furnace to the exit channel 15 being in the middle of the crown which channel extends to an afterburner 31.
A third example is a continuous-operating boiler shown in Fig. 5 which is implemented with a moving 22 or a fixed inclined grate. Its burning method is different. It is based on various sections. At the beginning of the boiler, there is a section 22 in which fuel enters from a container 21 and in which it starts to move forward and dries up, heats up and gasifies on top of the grate. At the beginning in the gas burning section, no combustion air is supplied below the grate.
In the middle section of the fire chamber, there is a separating wall 29 or some other suitable obstacle almost extending to fuels, at the beginning of the fire chamber in the gas burning section in the top part, there is on the edges a narrow opening 23, a gap, opening from the combustion air flues, also at the point of the separating wall 29, from which combustion air enters the fire chamber and is directed as a planar flow along the separating wall of a fire chamber 24 advantageously in the direction of an exit opening 25 being in the middle of the ceiling of the fire chamber.
Combustion air is conveyed to the gas burning section of the fire chamber all around only via the gap 23 in the top part. Otherwise, air entering below the grate disturbs the burning process of gases. It lights fire to char and, at the same time, generates separate carbon atoms. They start a carbon monoxide reaction which, when mixed with burning gases, prevents good burning. Behind the separating wall at the end of the fire chamber, there is a section for char burning 27 to which combustion air is supplied from below a grate 26 starting carefully and adjusting along the way in order for no carbon monoxide to occur in exiting combustion gases. There can also be for gases exiting the char burning section the afterburner 31 as an extension of the exit channel 30. Walls 28 and 29 as well as the ceiling 24 of the fire chamber are of material which allows and endures the increase of temperature sufficiently high.
Additionally, it is important that there is a sufficiently sensitive control mechanism of pressure and flows such that pressure levels can be kept the same on both sides, in gas burning and char burning sections, by means of measuring sensors and suction and pressure blowers controlled by them such that no flow of gases under the separating wall occurs from one side to the other to disturb the burning on the other side.
Here, we did not describe technique known as such which relates to the control and management of gas flows and pressure levels, but we simply described those modes of operation and principles which are important and essential to understand the inventive method and the operation of devices and means required by it.
As an extension of the exit channel 15, there can be in batch burning and also in continuous burning the afterburner 31 in which the possible unburned particles of combustion gases will mix to combustion air and burn. A middle part 32, an inlet section, of the afterburner 31 according to Fig. 6 is an upwards expanding and circularly conical part closed of its bottom end on the side of which there are all around wavelike folds parallel in the vertical direction in the side directed in the middle of which there is a row of holes 33. The common size of the holes enables a smaller volume flow than in the other flow section where the speed of the gas flow in the holes increases and a rising whirl 34 is formed in the middle of the cone. The inlet section is open of its top part in the middle and, in the top end of the conical part 32, there is a flange open in the middle the edges of which extent/turn downwards thus forming an interior wall 36.
The interior wall 36 is directed from the flange directly downwards at a distance where it turns circularly as a base 37 outwards turning at a distance upwards forming a piece 38 of the shape of a circular cylinder, and the top part turns inwards as if a cover 39 in the middle of which there is an exit opening 40.
Inside, there is an interior part 35 of the shape of an overturned cylindrical vessel inside of which there is a channel 43 for downwards going flow and, at the bottom between the base 37 and a wall 44 of the inside extending downwards, there is an opening 42 all around.
Outside the wall 44, there is a channel 45 for the upwards directed flow and between the cover part 39 and the bottom at the top of the cylinder 35 there is a flow path 41 to the exit opening in the middle.
At the point of the top part of the whirl, the volume of the flow section increases, whereby the speed of the gas flow decreases. Above the whirl, there is the top part 35 of the cylindrical vessel, a ceiling the edges 44 of which are directed downwards forming an upturned circular vessel-like separating wall all around. Via an circular opening 42 in the bottom part of the side wall 44, the flow turns to rise upwards, rising between the walls 38 and 44 and exiting via the opening 40 in the middle of the ceiling part 39 further to the structures of the heating device.
Bernoulli's principle states the interdependency of pressure and flow speed: when speed increases, pressure decreases and vice versa. In the afterburner, the phenomenon operates by increasing the speed of the gas flow at the point of the holes and the decrease of volume decreases it at another point. In addition to increasing mixing, variations in speed change the pressure ratios of flow in the different sections of the afterburner. Variations in pressure have a positive effect on the discharge of molecules in burning and in the forming of new better-burning compounds.
In the conical section 32, the afterburner provided with the narrower directed inlet holes 33 directs the direction of a scattered gas flow to the rising whirl 34 in the middle rotating in the same direction, whereby intense coarse mixing occurs in it. The volume of the inside of the afterburner is larger, whereby the flow and the whirl decelerate, the heavier particles of the gas flow fly first on the edges and turn to a slower flow directed downwards. The effect of centrifugal force on the molecule level sorts out molecules and atoms to a new order and breaks even the last ribbon-like flows which prevent mixing. Particles of gas flown close to the side wall 44 fall quickly to the slower flow directed downwards, lighter particles of gas flow slower and buoyancy caused by heat affects them more also by decelerating their speed. On micro level, gas particles, molecules and atoms flowing at different speeds collide each other thus becoming oxidised.
The remainder is carbon dioxide. If after the start carbon monoxide occurs in exit gases during char burning despite a careful start, it is possible to carefully supply the afterburner with more combustion air from the gap in the top part, whereby it burns out carbon monoxide.
There are various types and shapes of fireplace structures. When applying the inventive method to them, the most essential factors are sufficient burning temperature, separating the burning of burning gases and char, the mixing of burning gases and controlling combustion gases up to a uniform planar flow of combustion air and burning the most difficult-to-burn particles in the afterburner. Then, the burning process can proceed to the end without hindrances, and the carbon monoxide will not interrupt or cool it down.
The invention is not limited to the embodiments and advantageous applications described, but it can vary in different ways within the scope of the inventive ideas presented in the claims.

Claims

A method for intensifying the burning of solid fuels in fireplaces, in which fuel is heated up and gasified in a fire chamber (8), said method comprising separating in the burning of fuel the burning of gases in it from the burning of solid carbon in the fuel by releasing gases from the fuel in the fire chamber by means of heat, conveying combustion air of combustion gases after lighting only to the top part of the fire chamber (8) characterized in that said air is conveyed from gaps (3, 13, 23) opening from air channels being all around the sides of the fire chamber in the top part of said fire chamber, said air being directed in the middle on top of flames as a planar flow supporting itself on the bottom surface of the top part of the fire chamber, thickening when proceeding forward, and the method also comprising removing combustion gases to an exit opening (4, 15, 25) located in the middle of a crown (5, 14, 24) of the fire chamber.
A method according to claim 1, characterised by conveying gases exiting the fire chamber to an afterburner (31), wherein a middle part (32) of the afterburner (31) is an upwards expanding and circularly conical part closed of its bottom end on the sides of which there are all around wavelike folds parallel in the vertical direction in the side directed in the middle of which there is a row of holes (33), the common size of the holes enabling a smaller volume flow than in the other flow section of the afterburner, wherein the conical part is open of its top part in the middle and the edges of the top part are fast by a horizontal flange to an interior wall (36), the interior wall is directed downwards from the flange at a distance where it turns circularly outwards (37), turning at a distance upwards forming a circular cylindrical piece (38), turning in the top part inwards into a cover (39) in the middle of which there is an exit opening (40), wherein inside said afterburner is provided an inner part (35) of the shape of an upturned cylindrical vessel, inside of which there is a channel for downwards directed flow, in the bottom of which there is an opening (42) all around for a flow changing its direction, outside of which there is a channel (45) all around for a flow directed upwards and wherein between the cover part (39) and the bottom at the top end of the cylinder there is a flow path (41) to the exit opening (40) in the middle.
A method according to claim 1 or 2, characterised by burning chars remaining of the gas burning separately, in a batch-burning fireplace in the fire chamber (8) based on division based on time, whereby in the batch-burning fireplace at the start of char burning the supply of combustion air going through the gap (3, 13) in the top part is decreased and combustion air is supplied from below and through chars (6, 16) and the supply of combustion air is increased as the temperature rises in the chars and intensifies their burning.
A method according to claim 1, characterised by burning chars remaining of the gas burning separately, in a continuous-burning fireplace based on different sections, wherein chars are burned in their own section provided for char burning (27), combustion air is supplied below and amongst the chars and the access of burning gases is prevented from the other side to the char burning section.
A device for intensifying the burning of solid fuels in fireplaces, which device includes a fire chamber (8) for the heating up and gasifying of fuel, wherein in the fire chamber there is in the bottom part a grate (7, 17) or inside the grate a char basket and an adjustable supply mechanism of combustion air, such as a tight ash box (6, 16) or a damper, wherein the device is adapted to convey a combustion air of combustion gases after lighting only to the top part of the fire chamber (8), and characterized in that on the edges of the top part of the fire chamber there is all around a gap (3, 13, 23) entering from a combustion air channel/channels which is directed towards an exit opening (4, 15, 25) along a bottom surface (14, 24) of the top part of the fire chamber in the middle section, wherein the inner surface of the fire chamber is of heat-resistant material having a low heat capacity, and wherein it there is a heat insulator layer (18).
A device according to claim 5, characterised in that in continuous-burning fireplaces the burning section has two parts, at the inlet end of fuel on top of a grate (22) there is a section for fuel entering, warming, heating up and gasifying and in the top part of its section for gas burning at a distance, behind a separating wall or some other suitable obstacle there is a section (27) to which the grate extends and the totally gasified fuel, char, is arranged to burn by means of combustion air (26) supplied from below the grate after the process has reached that stage.
A device according to claims 5 and 6, characterised in that in a continuous-burning fire chamber there is a control mechanism which includes pressure sensors on both sides of the fire chamber, in the gas and char burning sections, suction and pressure blowers controlled by them are arranged to control the travel of gases in the fire chamber keeping the pressure level on both sides of the fire chamber the same and preventing the flow of gases occurring under the separating wall.
A device according to any one of claims 5-7, characterised in that in a continuous-burning fireplace there is in the bottom part the fixed inclined or the moving grate (22, 27) having one or more parts as the base of fuel and arranged to transport fuel from one stage to another, and the operation of which are arranged to control and drive sensors monitoring burning according to the progress of burning, and that in the char burning section the grate or the other burning section includes a supply mechanism of combustion air (26) by which combustion air is arranged to be supplied below and amongst the chars.
A device according to any one of claims 5-8, characterised in that a flow channel extends from the exit opening (4, 15, 25) to an afterburner (31) located above it, wherein a middle part (32) of the afterburner (31) is an upwards expanding and circularly conical part closed of its bottom end on the sides of which there are all around wavelike folds parallel in the vertical direction in the side directed in the middle of which there is a row of holes (33), wherein the common size of the holes enables a smaller volume flow than in the other flow section of the afterburner, the conical part is open of its top part in the middle and the edges of the top part are fast by a horizontal flange to an interior wall (36), the interior wall is directed downwards from the flange at a distance where it turns circularly outwards (37) turning at a distance upwards forming a circular cylindrical piece (38), turning in the top part inwards into a cover (39) in the middle of which there is an exit opening (40), wherein inside said afterburner there is an inner part (35) of the shape of an upturned cylindrical vessel, inside of which there is a channel for downwards directed flow, in the bottom of which there is an opening (42) all around for a flow changing its direction, and wherein outside there is a channel (45) all around for a flow directed upwards and between the cover part (39) and the bottom at the top end of the cylinder there is a flow path (41) to the exit opening (40) in the middle.