WO2009110841A1

WO2009110841A1 - Device and method for producing a gaseous medium comprising steam

Info

Publication number: WO2009110841A1
Application number: PCT/SE2009/050199
Authority: WO
Inventors: Anders Holmgren
Original assignee: Safesam Ab
Priority date: 2008-03-04
Filing date: 2009-02-23
Publication date: 2009-09-11
Also published as: SE534619C2; SE0800508L

Abstract

The invention relates to a device for producing a gaseous medium comprising steam intended for heating, said steam being arranged to be produced from water, comprising means for supplying energy for heating the water by means of burning a fuel, wherein the device is arranged to mix water in droplet form with combustion gas from said combustion, comprising means for supplying the water for the formation of said gaseous medium in the form of a water mist. The invention also relates to a method for producing a gaseous medium comprising steam.

Description

DEVICE AND METHOD FOR PRODUCING A GASEOUS MEDIUM

COMPRISING STEAM

TECHNICAL FIELD

The invention relates to a device for producing a gaseous medium comprising steam according to the preamble of claim 1. The invention also relates to a method for producing a gaseous medium comprising steam according to the preamble of claim 8.

BACKGROUND ART

It is already known to, by introducing water into a chamber, vaporize the water by means of combustion gas generated during combustion in the chamber for producing a mixture of combustion gas and steam.

WO 2004/005797 discloses a direct fired steam generator for generating steam at atmospheric pressure for disinfection of horticultural growing media such as soil. The steam generator comprises a burner for burning a fuel, a chamber from the top portion of which the flame from the burner is introduced, a system for spraying water on the inner wall of the chamber for providing a water film about the circumference of the chamber and an outlet through which steam generated from the water film on the wall is discharged.

The steam generator further comprises a spray system arranged in connection to the outlet and directed towards the outlet in order to regulate the temperature of said generated steam by spraying cold water, wherein the temperature of the generated steam may be substantially reduced to a desired temperature of about 70° - 80° C.

US 4,397,356 discloses a high pressure combustion device comprising a chamber wherein a flame is produced from the top portion of the chamber, where water is sprayed in the chamber such that it is vaporized by means of the combustion gases, wherein the mixture of steam and combustion gas is forced through a catalyst for complete combustion, wherein the steam is intended to be introduced directly into an oil reservoir.

OBJECT OF THE INVENTION

An object of the present invention is to provide a device for producing a gaseous medium comprising steam which efficiently uses supplied energy.

An additional object of the present invention is to provide a device for producing a gaseous medium which is independent of its orientation.

An additional object of the present invention is to provide a device for producing a gaseous medium which has a quick start up time.

An additional object of the present invention is to provide a device for producing a gaseous medium which has a simple construction.

An additional object of the present invention is to provide a method for producing a gaseous medium comprising steam which is efficient and has a quick start up time.

SUMMARY OF THE INVENTION

These and other objects, apparent from the following description, are achieved by a device and method of the type stated by way of introduction and which in addition exhibits the features recited in the appended independent claims 1 and 8. Preferred embodiments of the inventive device and method are defined in appended dependent claims 2-7, and 9-14. According to the invention the objects are achieved by means of a device for producing a gaseous medium comprising steam intended for heating, said steam being arranged to be produced from water, comprising means for supplying energy for heating the water by burning a fuel, wherein the device is arranged to mix water in droplet form with combustion gas from said combustion, comprising means for supplying the water for the formation of said gaseous medium in the form of a water mist.

Hereby is facilitated a very quick energy transfer from the combustion gases to the water, since the total surface of the water droplets is very big when the water is supplied in the form of a water mist. Further the falling velocity of the microscopically small water droplets in the water mist is so low that they essentially are not affected by gravity and thus do not fall down but rather hover as a mist. Thus it is avoided that water falls down to the bottom of the chamber. Droplets with an initial velocity in a certain direction are slowed down quickly during collisions with molecules in surrounding gas. Hereby arbitrary orientation of the device during use and arbitrary placement of the means for supplying energy, according to a variant a burner unit, is facilitated. Further a quick start up time of the device is achieved. Such a device may further be given a simple construction.

According to an embodiment of the device said water mist is constituted by water droplets in the range of 2-50 micrometer, preferably 2-30 micrometer. This is a suitable size range of the water droplets of the water mist. The advantage with very small droplets is that the smaller droplets of the water mist, the shorter life expectancy they get in the combustion gas, i.e. the quicker they are vaporized. Further, small droplets according to said range have very low falling velocity and tend to hover. Further they are retarded quickly towards surrounding gas and appear as part of that.

According to an embodiment of the device the water for providing said water mist is arranged to be supplied under pressure. This facilitates to efficiently providing water mist. According to an embodiment of the device said pressure is in the range of 30-220 bars, preferably 40-120 bars. High pressure of the water facilitates efficient provision of water mist with small droplet size.

According to an embodiment of the device said means comprises at least one nozzle arranged to disintegrate the water into water mist. Nozzle facilitates efficient way of providing water mist.

According to an embodiment the device comprises means for pressurizing said gaseous medium to a pressure above atmospheric pressure. Hereby the range of application from the produced mixture increases.

According to an embodiment the device comprises a chamber to which said means for supplying energy is connected wherein said combustion is arranged to be effected in a combustion zone in the chamber, the chamber further comprising an evaporator zone in which a mixture of said water mist and combustion gases is arranged to be effected for providing said gaseous medium, and an outlet through which said formed gaseous medium is arranged to be guided. By substantially allowing the combustion to be completely effected in one zone and allowing the combustion gases to be mixed with the water mist for vaporization of the water mist in another zone and see to that the supplied energy leaves the chamber as a warm mixture of steam and combustion gases an even more efficient device is achieved.

According to one embodiment of the device said combustion zone is present mainly at a lower level than said evaporator zone. An advantage with the combustion zone being provided lower than the evaporator zone, i.e. arranging the burner unit in the lower portion of the chamber, is that the hot flue gases rises, which gives a reduced resistance in the flow at certain applications. Further the energy is then developed in the lower part of the chamber which results in that possible larger droplets move slowly towards increasing temperature and are vaporized, and not away from the heat source such that water flowing downwards is formed as is the case when the burner unit is arranged in the upper part of the chamber.

According to the invention the object are also achieved with a method for producing a gaseous medium comprising steam intended for heating, said steam being produced from water, comprising the steps of supplying energy for heating the water by means of burning a fuel, and mixing water in droplet form with combustion gas from said combustion, comprising the step of: supplying the water for the formation of said gaseous medium in the form of a water mist.

Hereby a very quick energy transfer from the combustion gases to the water is facilitated, since the total surface of the water droplets is very large when the water is supplied in the form of water mist. Further the falling velocity of the microscopically small droplets in the water mist is so low that they can be assumed not to be affected by gravitation and thus do not fall down but hovers as a mist. Thus water falling down to the bottom of the chamber is avoided. Droplets with an initial velocity in a certain direction are slowed down quickly during collisions with molecules in surrounding gas.

According to an embodiment of the method said water mist is constituted by water droplets with a size in the range of 2-50 micrometer, preferably 2-30 micrometer. This is a suitable range of the water mist.

According to an embodiment the method comprises the step of supplying the water for providing said water mist under pressure. This facilitates efficiently providing water mist.

According to an embodiment of the method said pressure is in the range of 30-220 bars, preferably 40-120 bars. High pressure of the water facilitates efficient provision of water mist with a small droplet size. According to an embodiment the method comprises the step of disintegrating the water to water mist by means of a nozzle. Nozzle facilitates an efficient way of providing water mist.

According to an embodiment the method comprises the step of pressurizing said gaseous medium to a pressure above atmospheric pressure. Hereby the range of application for the produced mixture increases.

According to an embodiment the method comprises the steps of: burning the fuel in a combustion zone of a chamber; mixing water mist with combustion gas for providing said gaseous medium in an evaporator zone of said chamber, and directing said gaseous medium out through an outlet of said chamber for use of said gaseous medium. By essentially allowing the combustion to be effected completely in one zone and then allowing the combustion gases to be mixed with the water mist for evaporation of the water mist in another zone an even more efficient method is achieved.

According to an embodiment of the method said combustion zone is provided mainly at a lower level than said evaporator zone. An advantage with the combustion zone being provided at a lower level than the evaporator zone is that the hot flue gases rises, which gives a reduced resistance in the flow at certain applications. Further the energy is then developed in the lower part of the chamber which results in that possible larger droplets move slowly towards increasing temperature and are vaporized, and not away from the heat source such that water flowing downward is formed which is the case when the burner unit is arranged in the upper part of the chamber.

DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention will be had upon the reference to the following detailed description when read in conjunction with the accompanying drawings, wherein like reference characters refer to like parts throughout the several views, and in which:

Fig. 1a schematically shows a device for producing a gaseous medium comprising steam according to an embodiment of the present invention;

Fig. 2 schematically shows a device for producing a gaseous medium comprising steam according to an embodiment of the present invention;

Fig. 3 schematically shows a device for producing steam according to an embodiment of the present invention;

Fig. 4 schematically shows a device for producing steam according to an embodiment of the present invention;

Fig. 5 schematically shows a device for producing steam according to an embodiment of the present invention;

Fig. 6 schematically shows a device for producing steam according to an embodiment of the present invention;

Fig. 7 schematically shows a device for producing steam according to an embodiment of the present invention; and

Fig. 8 schematically shows a device for producing steam according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 schematically shows a device 1 for producing a gaseous medium according to an embodiment of the present invention.

The device comprises means 10, 10' for burning a fuel. The means 10, 10' preferably is a burner unit 10. The device further comprises a chamber 20 to which the burner unit is connected such that burning of a fuel by means of the burner unit 10 is effected in the chamber 20. The burning of the fuel is effected in the chamber 20 in a combustion zone. Z1.

The device further comprises means 30 for introducing water in the form of a water mist 32 into the chamber 20. The chamber 20 comprises inlets through which the introduction of water mist is arranged to be provided.

The chamber 20 is configured such that the water mist introduced into the chamber 20 is mixed with the reaction products, i.e. the combustion gases, from said combustion. Hereby the water droplets in the shape of water mist 32 are vaporized such that a gaseous medium being constituted by a mixture of steam and reaction products from the combustion is achieved.

The chamber 20 further comprises an outlet 22 through which said mixture of steam and combustion gases is arranged to be directed. Consequently a transport of the mixture of combustion gases and steam in the direction towards said outlet 22 occurs, wherein said mixture may be used for desired application such as heating of a space for cleaning.

The space in the chamber 20 where vaporization of water mist 32 mixed with combustion gases is effected is termed evaporator zone Z2. The chamber 20 is consequently preferably dimensioned such that all droplets in the water mist 32 have evaporated in the evaporator zone Z2 such that a mixture of steam and combustion gases leaves the outlet of the chamber 20.

Preferably the chamber 20 is configured such that essentially complete combustion is effected in the combustion zone Z1 such that in the evaporator zone Z2 the water mist 32 is vaporized by means of combustion gases from said complete combustion. However, certain vaporization of water mist 32 may be effected in the combustion zone Z1 and certain combustion may occur in the evaporator zone Z2.

Preferably the walls of the chamber 20 are of a suitable heat insulating material such that heat is not lead out through the walls from the chamber to the surrounding. The radiation then heats inner parts being cooled by water mist and generates steam. In this way the major part of the supplied energy is used to supply heat to the water droplets.

The technical effect of introducing and mixing water mist 32 with reaction products/combustion gases from combustion of a fuel is that a very quick energy transfer from the combustion gases and radiation from the combustion to the water in the form of the water mist 32 is achieved. Further the falling velocity of the microscopically small droplets in the water mist 32 is so low that they essentially are not affected by gravity and thus do not fall down but hover as a mist. Thus water falling down to the bottom of the chamber 20 is avoided. Hereby arbitrary orientation of the device by use and arbitrary placement of the burner unit 10 is facilitated, where the burner unit 10 advantageously may be arranged in the bottom of the device, without the risk of the flame 12 being extinguished. This facilitates construction of a device which may be oriented differently depending on application and/or space and/or construction, such that at one occasion the chamber 20 is horizontally oriented, with the burner unit arranged at a side of the chamber 20 such that the mixture of steam and combustion gas is released sideways through the outlet, and at another occasion is vertically arranged with the burner unit at the bottom or the burner unit at the top of the chamber 20, or with any desired inclination of the chamber 20 and consequently of the burner unit. An advantage with placing the burner unit in the lower part of the chamber is that the hot flue gases rises, which renders a decreased resistance in flow at certain applications. Further the energy is developed in the lower part of the chamber which results in that potential larger droplets move slowly towards increasing temperature and are evaporated, and not from the heat source such that water flowing downwards is formed which is the case when the burner unit is in the upper part of the chamber.

The reason for these effects is that the relationship between volume and surface is changed in a favourable way as the droplets become so small that water mist 32 is reached. The surface of the droplets bearing against the reaction products is very large relative to the volume of water to be vaporized. The larger surface of the water droplets relative to its volume results in them being rapidly vaporized in contact with the hot flue gases, wherein the water droplets gets an extremely short life expectancy. It will take a water droplet of 5 micrometer about 0,0002 seconds to vaporize in combustion gas with a temperature of about 600 ⁰C and at a temperature of about 150 °C about 0,004 seconds, the falling velocity in both cases being essentially 0 m/s. Even a water droplet of 50 micrometer at such a low temperature as 150 ⁰C is vaporized in about 0,4 seconds and has a falling velocity of about 0,08 m/s such that the falling distance before the droplets has vaporized is negligible in the context.

The quick vaporization of the water droplets being effected during contact with the hot flue gases results in that a water droplet is vaporized after a certain time. The chamber 20 is dimensioned such that the transport of combustion gases and steam occurring in a direction towards said outlet of the chamber 20 results in that after a certain distance in the chamber 20, termed evaporator zone Z2, a vaporization to steam of all water droplets has been effected. Hereby is facilitated to use the portion of the chamber 20 being used for transporting the steam away from the combustion zone, and/or even connected heat isolated pipe/channel/hose in which also vaporization may be effected such that the pipe/channel/hose constitutes the evaporator zone or a portion of the evaporator zone.

The very quick vaporization and thereby in terms of control short dead time facilitates quick control such that the device may be controlled against desired steam content and/or temperature in a simpler way.

The device is configured such the amount of water being supplied per time unit is adapted to the energy being released per time unit during combustion. Hereby the start up time before steam is produced becomes as no reservoir has to be heated for boiling. During combustion of a fuel, i.e. during combustion of a hydrocarbon, steam is also formed as reaction product. Hereby both the steam generated during combustion and the steam generated by the water mist 32 during contact with the combustion gases is utilized during the mixture. Since the water mist 32 is mixed directly with the reaction products and is vaporized the efficiency is very high.

The transport velocity of the mixture of steam and combustion gases is controlled inter alia of how much steam being generated and the dimension of the chamber 20, e.g. the diameter in the case the chamber 20 has a circular cylindrical shape.

Fig. 2 schematically shows a device 2 for producing a gaseous medium according to an embodiment of the present invention.

The embodiment of the device according to fig. 2 comprises the features in fig. 1. Thus, the device comprises means 10 for burning a fuel, such as a burner unit 10, connected to a chamber 20, where the combustion of the fuel is effected.

The walls 24 of the chamber 20 comprise a heat insulating material such that heat is prevented from being guided out through the walls from the chamber to the surrounding. The heat radiation then heats the inner parts of the chamber being cooled by means of water mist and generates steam at the same time as the water mist also absorbs radiation and thereby is heated and steam is generated. In this way the larger part of the supplied energy is used to supply heat to the water droplets.

The device further comprises in accordance with the embodiment in fig. 1 means 30 for introducing water in the form of water mist 32 into the chamber 20. Preferably said means 30 comprises a set of nozzles 34 through which pressurized water is arranged to be pressed, whereby the water is disintegrated such that atomized water in the form of water mist 32 is introduced into said chamber 20. The high pressure of the water is achieved according to an embodiment by means of a pump configuration 36. The pump configuration 36 may comprise one or more pumps 36. The pressure by means of which the water is pressed through respective nozzle lies according to an embodiment in the range of 30-220 bars, preferably 40-120 bars. The size of the water droplets being introduced as a water mist 32 into the chamber 20 lies according to an embodiment in the range of 2-50 micrometer, preferably 2-30 micrometer.

According to a preferred embodiment the means 30 comprises a high pressure system 34, 36 with at least one high pressure pump 36 and a set of nozzles 34, the nozzles 34 according to the invention being constituted by high pressure nozzles 34, so called "jet pin nozzles". Hereby the water being supplied is arranged to be filtered on the water side of each nozzle 34, i.e. the side from which water is supplied to the nozzle 34 and disintegrated during passage through the nozzle 34, by means of a high pressure on the water side, the pressure preferably being in the range 30-220 bars, preferably 40-120 bars.

There are alternative methods/systems for providing water mist 32. According to a variant of the means 30 an air stream is allowed to pass a fluid pipe in a nozzle 34 at high speed such that the water is disintegrated to water mist 32. This method/system is not preferred as the supplied air dilutes and cools the combustion gases whereby the efficiency of the device is reduced.

An additional way of providing water mist is to disintegrate the water to water mist by means of piezoelectric crystal. Hereby no nozzles are required.

According to a variant of the invention the device comprises means for controlling the amount of water supplied to the chamber 20. According to an embodiment this is achieved by activating/deactivating one or several of the nozzles 34 in the set of nozzles 34. The set of nozzles 34 preferably is arranged to inject the water mist 32 towards the centre area of the chamber 20. In the set of nozzles 34 these are preferably mutually arranged around the chamber 20 such that the water mist 32 being injected from the different nozzles mainly does not collide. Thus coagulation is avoided, i.e. that larger water droplets are formed taking longer time to vaporize.

In order for the device to be as efficient as possible and not giving undesired rest products in the mixture of steam and combustion gases complete combustion of the fuel is desired. In order to achieve complete combustion of the fuel a sufficiently high temperature in the combustion zone Z1 is required.

During combustion heat radiation from the combustion zone is generated, which assists in vaporizing the droplets, which also to a certain extent is absorbed by surrounding walls of the chamber 20, particularly the portions of the walls surrounding the combustion zone. In order to avoid the walls being too hot so that too high combustion temperature is achieved, and in order to prevent the temperature in the walls to exceed their thermal durability the device according to a variant of this embodiment comprises means 40 for cooling the walls. Said means 40 for cooling the walls is not an essential feature for the function of the device. Cooling of the walls in connection to the combustion zone Z1 is depending on thermal durability of the walls, and temperature and radiation level in the combustion zone Z1 during combustion of a fuel.

The amount of water is arranged to be adjusted such that the temperature in the material of the walls around the combustion zone Z1 are optimized. This can be achieved by suitable temperature control, which will be apparent from further embodiments below.

Fig. 3 schematically shows a device 3 for producing gaseous medium according to an embodiment of the present invention. The embodiment of the device according to fig. 3 comprises the features in fig. 1. Thus the device 3 comprises means 10 for burning a fuel, such as a burner unit 10, connected to a chamber 20, where the combustion of the fuel is effected.

The device further comprises in accordance with the embodiment in fig. 1 means 30 for introducing water in the form of water mist 32 into the chamber 20, where the means comprises nozzles 34 through which pressurized water is disintegrated into a water mist 32.

The walls 24 of the chamber 20 comprise a heat insulating material such that heat is prevented from being guided out through the walls from the chamber to the surrounding. The heat radiation then heats inner parts of the chamber being cooled by means of water mist and generates steam at the same time as the water mist also absorbs radiation and thereby is heated and generates steam. In this way the larger part of the supplied energy is used to supply heat to the water droplets.

The device 3 according to this embodiment comprises means 50 for providing a pressure above atmospheric pressure of the mixture of steam and combustion gases in the chamber. The means comprises a device 52 for adding air and fuel to the burner unit 10 under a certain overpressure.

The device for adding air and fuel to the burner unit 10 under a certain overpressure is constituted according to an embodiment by a fan 52 configured and dimensioned in such a way that it gives an amount of air being adapted to the amount of fuel to be supplied. A fan 52 is suitable when a relatively low overpressure of the mixture of steam and combustion gases is to be provided.

According to another embodiment the device 52 for adding air and fuel to the burner unit 10 under a certain overpressure is constituted by a compressor 52. One or more compressors are suitable when a higher overpressure of the mixture of steam and combustion gases is to be provided. The means 50 for providing a pressure above atmospheric pressure of the mixture of steam and combustion gases comprises according to this embodiment also the introduction of flow resistance in the flow of the mixture of steam and combustion gases out of the chamber in the form of a restriction 54. The restriction 54 is constituted by a tapering 54 or constriction of the chamber 20 in connection to the outlet of the chamber 20 or in the end of a pipe, channel or the like connected to the chamber, which restriction 54 holds a certain pressure in both the combustion zone Z1 and the evaporator zone Z2.

An advantage with providing an overpressure in the combustion zone Z1 is that when the flame 12 is not operating a weak air stream from the compressed air may be provided which prevents moist air from entering into the combustion zone Z1 , and that possible moist therein dries out. In that way the reliability of the device 3 is improved.

Fig. 4 schematically shows a device 4 for producing a gaseous medium comprising steam according to an embodiment of the present invention.

The embodiment of the device according to fig. 4 comprises the features in fig. 1. Thus, the device comprises means 10 for burning a fuel such as a burner unit 10, connected to a chamber 20, where the combustion of the fuel is effected.

The walls 24 of the chamber 20 comprise a heat insulating material such that heat is prevented from being guided out through the walls from the chamber to the surrounding. The heat radiation then heats inner parts of the chamber which are cooled by means of water mist and generates steam at the same time as the water mist also absorbs radiation and thereby is heated and generates steam. In this way the larger part of the supplied energy is used to supply heat to the water droplets.

The device 4 further comprises in accordance with the embodiments in fig. 1 and 2 means 30 for introducing water in the form of water mist 32 into the chamber 20, the means comprising nozzles 34 through which pressurized water has been disintegrated to a water mist 32.

The device further comprises a device 60 for preventing that the injected water mist 32 disrupts the combustion in the combustion zone ZL The device according to this embodiment is arranged in connection to the burner unit 10 and its flame 12 and is configured in such a way that the combustion gases easily reaches the evaporator zone Z2 but that the water mist 32 is prevented from entering into the combustion zone Z1. According to a variant the device 60 comprises a so called honeycomb structure 60 of similar type as of catalysts. Such a honeycomb structure may be arranged directly above the flame with a first portion 62, or both above the flame with the first portion 62 and around the flame with a second portion 64, i.e. essentially surrounding the flame, as is apparent from fig. 4.

Fig. 5 schematically shows a device 5 for producing a gaseous medium comprising steam according to an embodiment of the present invention.

The embodiment of the device 5 according to fig. 5 comprises the feature in fig. 1. Thus the device comprises means 10 for burning a fuel, such as a burner unit 10, connected to a chamber 20, where the combustion of the fuel is effected.

The walls 24 of the chamber 20 comprise a heat insulating material such that heat is prevented from being guided out through the walls from the chamber to the surrounding. The heat radiation then heats inner parts of the chamber being cooled with water mist and generates steam at the same time as the water mist also absorbs radiation and thereby is heated and generates steam. In this way a larger part of the supplied energy is used to supply heat to the water droplets.

The device 5 further comprises in accordance with the embodiment in fig. 1 means for introducing water in the form of water mist 32 into the chamber 20, the means comprising nozzles 34 through which pressurized water is disintegrated into a water mist 32.

The device according to this embodiment further comprises a catalyst 70.

The catalyst 70 is arranged in connection to the combustion zone Z1 such that the reaction products/ combustion gases passes the catalyst 70. Hereby a complete combustion is achieved such that the combustion gases essentially are constituted by carbon dioxide and steam. According to an embodiment of the invention water mist 32 is arranged to be introduced also upstream of the catalyst. In such a way the temperature of the catalyst may be controlled such that the catalyst does not become to hot.

The device 5 according to this embodiment further comprises a heat insulating device 80. The heat insulating device 80 is arranged in such a way in the combustion zone Z1 that the emission of heat from the combustion zone Z1 to surrounding walls of the chamber 20 is reduced. According to a variant the heat insulating device 80 comprises a tubular casing which is arranged about the flame 12 of the burner unit 10. The heat insulating device 80 is according to a variant constituted by a refractory ceramic material having good insulating properties. Hereby heat emission to the space outside the chamber 20 is reduced whereby efficiency of the device 5 is further increased.

During combustion heat radiation is generated from the combustion zone Z1 which also partly is absorbed by surrounding walls of the heat insulating device 80. To avoid that the walls become too hot such that too high combustion temperature is reached, and to avoid that the temperature in the walls exceed their thermal durability the device comprises according to a variant of this embodiment means 40 for cooling the walls. This is according to a variant effected by spraying them with water in such a form that it is vaporized, for example in the form of water mist, wherein the wails of the heat insulating device 80 is cooled to a suitable temperature. According to a variant said means 40 comprises a set of nozzles 44 for supplying water to said nozzles 44. Said means 40 for cooling the walls is not an essential feature for the function of the device 5. Cooling of the walls in connection to the combustion zone Z1 is depending on thermal durability of the walls, and temperature in the combustion zone Z1 during combustion of a fuel.

Fig. 6 schematically shows a device for producing a gaseous medium comprising steam according to an embodiment of the present invention.

The embodiment of the device 6 according to fig. 6 comprises the features in fig. 1. Thus the device 6 comprises means 10 for burning a fuel such as a burner unit 10, connected to a chamber 20, where combustion of the fuel is effected.

The walls 24 of the chamber 20 comprise a heat insulating material such that heat is prevented from being guided out through the walls from the chamber to the surrounding. The heat radiation then heats inner parts of the chamber which are cooled with water mist and generates steam at the same time as the water mist also absorbs radiation and thereby generates steam. In this way the larger part of the supplied energy is used to supply heat to the water droplets.

The device 6 further comprises in accordance with the embodiment in fig. 1 means 30 for introducing water in the form of water mist 32 into the chamber 20, the means 30 comprising nozzles 34 through which pressurized water is disintegrated to a water mist 32.

The device 6 further comprises in accordance with the embodiment in fig. 3 pressure means 50 for providing pressure of the mixture of steam and combustion gases.

The device 6 according to this embodiment further comprises a catalyst 70, and a heat insulating device 80 according to the embodiment in fig. 5.

The device 6 according to this embodiment further comprises means 90 for controlling the steam content such that maximum level of the steam content is achieved for a certain developed effect in the combustion zone Z1. The means 90 is arranged to measure in connection to the end of the evaporator zone Z2 whether there exist water droplets which have not been evaporated or whether there exist water droplets which have been formed due to the fact that the mixture of steam and combustion gases started to condense.

According to a variant said means 90 comprises an optical sensing device 90. The optical sensing device 90 is according to a variant arranged to measure transparency in the path of propagation of the light between a transmitter and a receiver. According to an alternative variant the optical sensing device 90 is arranged to measure diffused scattered light from the mixture of steam and combustion gases. Hereby is used the fact that when the steam starts to condense as small water droplets in the mixture of steam and combustion gases the diffused scattered radiation increases substantially.

The device 6 according to this embodiment further comprises means 100 for controlling the temperature of the mixture of steam and combustion gases. The means comprises a temperature measurement device 102 which is arranged to measure the temperature at the end of the evaporator zone Z2. The means further comprises a device 104 for controlling the amount of injected water mist 32 in the evaporator zone Z2. The device for controlling the amount of injected water mist is according to a variant arranged to activate/deactivate nozzles 34 in the set of nozzles 34. An alternative variant is to control the pressure of the water being supplied to the nozzles between e.g. 30-220 bars, or other desired range so as to in such a way controlling the amount of injected water mist.

The device 6 may be provided with either the sensing device 90 or the temperature measurement device 100, or as in fig. 4 both.

Fig. 7 schematically shows a device 7 for producing a gaseous medium comprising steam according to an embodiment of the present invention. The embodiment of the device 7 according to fig. 7 comprises the features in fig. 1. Thus, the device 7 comprises means 10 for burning a fuel, such as a burner unit 10, connected to a chamber 20, where the combustion of the fuel is effected.

The device 7 further comprises in accordance with the embodiment in fig. 1 means 30 for introducing water in the form of water mist 32 into the chamber 20, the means 30 comprising nozzles 34 through which pressurized water is disintegrated to a water mist 32.

The walls 24 of the chamber 20 comprise a heat insulating material so that heat is prevented from being guided out through the walls from the chamber to the surrounding. The heat radiation then heats inner parts of the chamber being cooled with water mist and generates steam at the same time as the water mist also absorbs radiation and thereby is heated and generates steam. In this way the larger part of the supplied energy is used to supply heat to the water droplets.

The device 7 further comprises as an alternative or a complement to the embodiment in fig. 3 pressure means 50' for providing pressure of the mixture of steam and combustion gases. The pressure means comprises according to this embodiment a compressor 56 arranged at the outlet downstream of the evaporator zone Z2. The mixture of steam and combustion gases is arranged to pass via the low pressure side 56a of the compressor 56, to be pressurized at the compressor 56 and then being sprayed out form the high pressure side 56b of the compressor 56. Connecting a compressor 56 beyond the end of the evaporator zone Z2 is an alternative which gives a smaller pressurized volume in the chamber which in turn leads to reduced problems with CE-marking/approval.

Fig. 8 schematically shows a device 8 for producing a gaseous medium comprising steam according to an embodiment of the present invention. The embodiment of the device 8 according to fig. 8 comprises the features in fig. 1. Thus the device 8 comprises means 10' for burning a fuel, connected to a chamber 20, where the combustion of the fuel is effected.

The walls 24 of the chamber 20 comprise a heat insulating material such that heat is prevented from being guided out through the walls from the chamber to the surrounding. The heat radiation then heats inner parts of the chamber which is cooled with water mist and generates steam at the same time as the water mist also absorbs radiation and thereby is heated and generates steam. In this way the larger part of the supplied energy is used to supply heat to the water droplets.

The device 8 further comprises in accordance with the embodiment in fig. 1 means 30 for introducing water in the form of water mist 32 into the chamber 20, the means 30 comprising nozzles 34 through which pressurized water is disintegrated to a water mist 32.

In the device 8 the means for burning a fuel is constituted by a catalytic burner unit 10'. The catalytic burner unit comprises burner means 10", a catalyst means 70' and walls 80' provided with catalyst material, for example in the form of a porous mat coated with e.g. platinum, through which a mixture of air and e.g. liquefied petroleum gas is arranged to be guided and combusted catalytically. A catalytic burner unit provides good performance when the combustion temperature is lower and the radiation level decreases which provides a more even temperature distribution in the chamber. This results in the released energy being in the flue gases which heavily interact with the small droplets. The combustion zone is here constituted by the catalyst means 70' and the walls 80' provided with catalyst material. According to a variant only catalyst means 70' is used, which protects against water mist such that water mist can be injected proximate to the catalytic burner unit 10'. Alternatively only the walls provided with catalyst material are used. Above, a number of embodiments have been described with reference to different figures, in order to provide said combustion a fuel is used. Any fuel in the form of a solid, liquid or gaseous fuel may be used for providing said reaction products/combustion gases, and where catalytic combustion is used any fuel suitable for catalytic combustion may be used. Advantageously e.g. propane is used, which provides cleaner combustion gases mainly constituted by carbon dioxide and water, such that the mixture of steam and combustion gases is relatively clean, and does not contain rest products such as soot. Thereby the range of application for the mixture is increased.

Above, embodiments of the present invention have been described with different features. The features in the different embodiments may be combined such that features in one embodiment may be used in another embodiment. The embodiments may thus be combined both by taking separate features from one embodiment such as adding or removing means for cooling of walls in connection to the combustion space, removing or adding heat insulating device, means for providing pressure, sensor devices etc.

According to the embodiment above the chamber comprises an outlet through which said mixture of steam and combustion gases is arranged to be guided. The chamber according to the embodiments above may naturally comprise several outlets through which said mixture may be guided.

According to a variant (not shown) a limitation of the combustion zone circularly could be provided by a so called fused silica pipe which is intended to be arranged in connection to the burner unit for transmitting the radiation from said burner unit to the part of the chamber along the sides where water mist is present for absorbing the radiation. Outside this partition the water droplets may be arranged to interact with the radiation and be evaporated without the droplets ending up in the flame. The device according to the embodiments above is dimensioned such that it is adapted to the power of the burner being used/required. By controlling the temperature of the mixture of steam and combustion gases the device may be adapted to different applications. For example during heating of a space for cleaning different temperatures are required depending on what is supposed to be removed during cleaning, i.e. the temperature of the mixture of steam and combustion gases are adapted to the melting temperature of the substance/dirt to be removed. An advantage with introducing into and mixing water mist with combustion gases is that the energy transport from the device, i.e. the heat source, to the surfaces to be heated becomes efficient and that the temperature may be kept relatively low, and adapted to application. The risk of the dirt being heatedly stuck or is ignited by hot flue gases is minimized. Moist steam transfers the heat more easily than dry stem.

The figures describing above mentioned embodiments is as mentioned only schematic, and the chamber may be longer relative to other dimensions. Further the evaporator zone may be longer such that water mist is introduced in the beginning of the evaporator zone at a certain distance from the outlet.

In the embodiments according to fig. 2-8 the walls 24 have heat insulating material, the walls 24 also including the portion around which the burner unit 10; 10' is arranged.

Water mist is here defined as water disintegrated to a droplet size which results in that they as they are introduced and mixed with combustion gas essentially hovers, and consequently are not affected by gravitation, but are very quickly vaporized in said combustion gas.

The invention should thus not be limited to the above indicated embodiments but could be varied within the scope of the appended claims.

Claims

1. A device for producing a gaseous medium comprising steam intended for heating, said steam being arranged to be produced from water, comprising means (10; 10') for supplying energy for heating the water by means of combusting a fuel, wherein the device is arranged to mix water in the form of droplets with combustion gas from said combustion, characterized by means (30) for supplying the water for the formation of said gaseous medium in the form of a water mist (32).

2. A device according to claim 1 , wherein said water mist (32) is constituted by water droplets with a size in the range of 2-50 micrometers, preferably 2-

30 micrometers.

3. A device according to claim 1 or 2, wherein the water for providing said water mist (32) is arranged to be supplied under pressure.

4. A device according to claim 3, wherein said pressure lies in the range 30- 220 bars, preferably 40-120 bars.

5. A device according to any of claims 1-4, wherein said means (30) comprises at least one nozzle (34) arranged to disintegrate the water to a water mist (32).

6. A device according to any of claims 1-5, comprising means (50; 50') for pressurizing said gaseous medium to a pressure above atmospheric pressure.

7. A device according to any of claims 1-6, comprising a chamber (20) to which said means (10) for supplying energy is connected wherein said combustion is arranged to be effected in a combustion zone (Z1) in the chamber (20), the chamber (20) further comprising an evaporator zone (Z2) in which mixture of said water mist (32) and combustion gases is arranged to be effected for providing said gaseous medium, and an outlet (22) through which said formed gaseous medium is arranged to be guided.

8. A device according to claim 7, wherein said combustion zone (Z1) mainly is present at a lower level than said evaporator zone (Z2).

9. A method for producing a gaseous medium comprising steam intended for heating, said steam being produced from water, comprising the steps of supplying energy for heating the water by means of combusting a fuel, and mixing water in droplet form with combustion gas form said combustion, characterized by the step of: the water for the formation of said gaseous medium is supplied in the form of a water mist (32).

10. A method according to claim 9, wherein said water mist (32) is constituted by water droplets with a size in the range 2-50 micrometers, preferably 2-30 micrometers.

11. A method according to claim 9 or 10, comprising the step of supplying the water for providing said water mist (32) under pressure.

12. A method according to claim 11 , wherein said pressure lies in the range of 30-220 bars, preferably 40-120 bars.

13. A method according to any of claims 8-11 , comprising the step of disintegrating the water to water mist by means of at least one nozzle (34).

14. A method according to any of claim 9-13, comprising the steep of pressurizing said gaseous medium to a pressure above atmospheric pressure.

15. A method according to any of claims 8-13 comprising the steps of: burning the fuel in a combustion zone (Z1) of a chamber (20); mixing water mist with combustion gas for providing said gaseous medium in an evaporator zone (Z1) of said chamber (20), and guiding said gaseous medium through an outlet (22) of said chamber (20) for use of said gaseous medium.

16. A method according to claim 15, wherein said combustion zone (Z1) mainly is situated at a lower level than said evaporator zone (Z2).