WO2005024301A1

WO2005024301A1 - Hydrogen burning method and burner, and water heating system using it

Info

Publication number: WO2005024301A1
Application number: PCT/EP2004/010146
Authority: WO
Inventors: Luca Giacomini
Original assignee: Giacomini S.P.A.
Priority date: 2003-09-11
Filing date: 2004-09-10
Publication date: 2005-03-17
Also published as: ITMI20031741A1

Abstract

In a method and burner or combustor (1) for burning hydrogen, hydrogen is mixed with air and burned in a burning chamber (3) on a catalyzer (4) at a low temperature and in a flame free manner. In the combustor or burner (1) the hydrogen burning chamber (3) is encompassed by a thermal exchange chamber (6) containing a hot burned gas conveying tube nest (7) and being traversed by cooling water, or water to be heated, the air-hydrogen to mixture being supplied at a low pressure. Advantageously, the burner (1) is arranged in a stage (41) for generating electric power from renewable sources, a buffer battery stage (42), an electrolytic hydrogen making stage (43), an hydrogen accumulating stage (44), provided for accumulating hydrogen by transforming hydrides, and an optional heated water storing stage (46).

Description

"HYDROGEN BURNING METHOD AND BURNER, AND WATER HEATING SYSTEM USING IT"

Background of the invention The present invention relates to a method and a burner for burning hydrogen, according to the features of claims 1 and 10. The invention relates moreover to a water heating system using said burner or combustor and, more specifically, operating on a stored hydrogen supply, and on autonomously made hydrogen, according to the features of claims 17 and 18. Hydrogen is broadly used in fuel cells as a fuel for generating electric power. Said fuel cells have low output voltages, for example from 0.3 to IV, and, for providing higher voltages, a plurality of fuel cells are series coupled. The electric power provided by said fuel cells is used in different applications, for example for driving motor vehicles by electric motors. Thus, it should be apparent that the use of electric power from fuel cells for heating water would not be economically advantageous. Is likewise known to make hydrogen by electrolysis, the made hydrogen being stored at a high pressure (10 - 200 bars) in storing tanks or bottles.

Summary of the invention Accordingly, in the light of the above discussion, and due to the very high heat power of hydrogen as used as a fuel, and to a substantial absence of combustion noxious products, the present inventor has set out to provide an economically advantageous method for using hydrogen for operating heating system and sanitary hot water. Thus, the aim of the present invention is to provide such a method and burner for directly burning an air-hydrogen mixture for generating heat, for example for heating a fluid, such as water, in a manner which can be easily controlled and in very high safety conditions, thereby allowing to use them for heating houses. Within the scope of the above mentioned aim, a main object of the present invention is to provide a hot water producing system, containing a burner of the above mentioned type, as well as a like system for autonomously providing and storing hydrogen. The above mentioned aim, in its aspect related to a method and burner for burning hydrogen, is achieved, according to the present invention, by a method and burner or combustor having the features stated respectively in claims 1 and 10. Said aim, in the aspect thereof related to a hot water system, for example for providing hot water for heating houses and providing sanitary water, by burning hydrogen, which can be produced and stored in situ, is achieved, according to the invention, by hydrogen burning systems having respectively the features of claims 17 and 18. Further modified embodiments and advantageous developments of the subject matter of the present invention are stated by the features of the respective dependent claims. The method and burner for burning/oxidating hydrogen by the inventive systems provide a lot of different and important advantages. With respect to the method and burner they can be operated under absolutely safe conditions, with a very high efficiency and an easy adjustment. In fact, hydrogen is supplied to the burner with a very low pressure of the order of about 20 millibars, as it would be conventional in a methane delivery system. By using catalyzers for burning air-hydrogen mixtures, it is possible to provide a hydrogen combustion or oxidation, without flames and at a low temperature, for example from 200 to 450°C, said combustion/oxidation being started by a simple contact of the air- hydrogen mixture with the catalyzer, thereby allowing to omit igniting systems and related components. By a thermal exchange chamber, encompassing the burning chamber, it is possible to achieve the above mentioned high thermal efficiency. For adjusting the temperature of the generated hot water, formed by the same cooling water passing through said thermal exchange chamber, it is possible to easily control, in addition to the combustion chamber temperature (by changing the amount of hydrogen present in the air-hydrogen mixture supplied to the burner), the cooling water amount passing through the thermal exchange chamber in a time unit. A further advantage of the burner according to the present invention is that said burner has a very small size, and being adapted, for example, for heating civil buildings, thereby allowing the burner to be also easily installed in kitchens, or other small rooms, apartments or houses. Moreover, the inventive system for supplying low pressure hydrogen and water to be heated and stored for heating and sanitary systems, can be made without any problems and by using conventional components, i.e. easily commercially available elements. With respect to the implementation of the inventive system, comprising an autonomous generation of hydrogen, a plurality of advantages are likewise obtained. At first, the provision of an electric power generating stage using renewable sources (for example including aeolic generators or photovoltaic panels) allows to generate electric power at a very low cost, and for an alternating succession of electric power making periods and periods in which no electric power is generated. The thus generated electric power, in particular, is advantageously used for autonomously making hydrogen by electrolysis. The electric power supply continuity can be advantageously assured by buffer battery assemblies, both the elctrolysis apparatus and said buffer batteries being known per se. According to an important aspect of the present invention, by the above mentioned system, it is accordingly possible to make hydrogen at any time, independently from the operation of the hot water using system, the heating system or the sanitary system. Accordingly, hydrogen can be made and stored before its use, for example during the year before the domestic heating season. According to a further important aspect of the present invention, the made hydrogen is stored in storing tanks in a hydride form. Advantageously, for promoting the reaction of hydrogen to provide hydrides, metals allowing to operate at about an atmospheric pressure and environmental temperature, such as titanium, iron, manganese, nickel, chrome and the like and alloys thereof are selected. Under these conditions, the made hydrogen can be stored at a low pressure, advantageously without any dangers, in storing tanks which can be also installed immediately near the houses or inside the latter.

Brief description of the drawings Further advantages, details and characteristics of the method and burner for making air-hydrogen mixtures and systems according to the invention, will become more apparent from the following disclosure of some exemplary embodiments which are given only by way of an example and being schematically illustrated in the accompanying drawings, where: Figure 1 shows a burner or combustor for burning hydrogen by a method according to the invention; Figure 2 shows a hot water system, comprising a burner as shown in figure 1; and Figures 3 is a block diagram of an autonomous system, also allowing to provide and store hydrogen, for providing hot water for heating and sanitary systems.

Description of the preferred embodiments The operating steps of the method according to the present invention will become more apparent hereinafter from the following disclosure of a burner or combustor for carrying out the inventive method as hereinbelow disclosed. Reference is at first made to figure 1. The burner or combustor according to the invention, for burning, that is oxidating, hydrogen in an air-hydrogen mixture, has been generally indicated by the reference number 1. Said burner comprises a vessel 2 defining, in the shown embodiment, an inner combustion/oxidating chamber 3, holding catalyzers 4, and an annular outer thermal exchange chamber 6, holding a tube nest 7, for conveying exhausted gases therethrough. In the shown embodiment, the tube sheet 7 comprises tube sectors 7A which are mutually coupled, on a side, through an annular chamber 15 and, on the other side, through a further chamber 17. the reference numbers 9 and 11 respectively show the inlet and outlet of the cooling water circuit, i.e. of the water to be heated, which has been only partially shown. The reference number 8 shows the exhausted gas outlet, and the reference number 10 shows a condensate material outlet. On the inlet side 12 of the burner 1, a fan 13 is provided, for supplying air for forming, in a mixing chamber 14, the air- hydrogen burning or combustion mixture, the hydrogen coming from the hydrogen inlet 16 through the hydrogen supply circuit 19 which has been schematically illustrated. The air-hydrogen combustible mixture will enter the combustion chamber 3, as schematically shown by the arrows, and hydrogen is supplied to the low pressure burner 1, for example, at a pressure of 20 millibars, and being burnt or oxidated, by causing it to react with the catalyzers 4, without flame and at a low temperature, for example from 200 to 450°C. Good results have been achieved by using as catalyzers palladium and platinum. The flow rates of said fan 13, hydrogen and cooling water can be advantageously varied and controlled by apparatus well known per se and not further herein disclosed. The burner or combustor 1 operates as follows: In the mixing chamber 14 the air-hydrogen mixture is formed with a ratio less than 4% (start of the exploding range) for example 3.5% and being supplied to the burning or combustion chamber 3 in which, upon contacting the catalyzer 4, the hydrogen combustion/oxidation at a low temperature, for example in a 200- 450°C range and without forming flames is performed. The burnt gases, which are substantially constituted by combustion air and do not include oxides or polluting compounds, pass through the tube nest 7 and are collected in an annular chamber 18, therefrom they are discharged as schematically shown at 8. The cooling water, or water to be heated, enters the inlet 9, passes through the thermal exchange chamber 6, and being heated by contact with the hot tube nest 7, and then exits the outlet fitting 11 in the form of hot water, i.e. the target or desired product. The tube nest 7, in turn, is heated by heat generated in the combustion chamber 3 upon burning/oxidating hydrogen. It should be apparent that either increasing the hydrogen amount in the burning mixture or reducing the cooling water flow- rate, higher temperatures of generated hot water will be provided and, reversely, by reducing the hydrogen flow-rate or increasing the cooling water flow-rate, a hot water of less temperature will be provided. The thus generated hot or warm water can be used in different applications, for example for supplying heating systems, sanitary water generating systems, and so on, for use in houses and the like. The hydrogen combustion/oxidation can be simply interrupted or switched off by shutting off the air-hydrogen mixture supply. Reference is now made to figure 2, which illustrates in a more detailed manner the hydrogen supply circuit 19 and the cooling water or water to be heated supply circuit 21, associated with the burner 1 shown in figure 1. In said hydrogen supply circuit 19, the reference number 22 shows, for example, an adjusting flow meter, 23 a gauge for displaying the hydrogen pressure, 24 a shut-off solenoid valve, 26 a flow-rate measurement device, and 27 a further gauge for displaying the pressure in the mixing chamber 14, including an injector 29 for supplying to the combustion chamber 3 the air- hydrogen mixture. Said circuit 19 is supplied with hydrogen at a low pressure, for example from 1 to 5 bars, said hydrogen pressure being reduced, for example, to 20 millibars, by a not shown pressure reducing unit, arranged before the burner inlet. The circuit 21 for supplying cooling water, to be heated, comprises, for example a recirculation pump 31 at its burner 1 inlet side, and a hot water accumulator 32, at the water outlet. The reference number 33 shows a calorie counter and 34 an expansion tank. For measurement purposes, a thermometer 36 and an exhausted gas manifold 37, having an outlet 38 leading to a hydrogen analyzer, not shown, can be provided. From the system diagram shown in figure 2, it is moreover possible to see other components, which can be identified by their symbols, as conventionally provided in hydraulic and gas distribution systems. It should be apparent that the selection, number and arrangement of the shut off measurement, adjustment, pressure reduction and so on components, can be set at will by one skilled in the art, depending on the considered system and the teachings of the present invention. Thus, for example, hydrogen can be taken from a storing tank which can be filled-in with hydrogen through autotanks, or in bottles, (with corresponding pressure reduction units), or with low pressure hydrogen directly generated according to the invention, as shown, by way of an example, in the system of figure 3, which system comprises the following mutually connected operating or functional stages as shown in figure 3:

- an electric power generating stage 41 for generating electric power from renewable sources, such as aeolic generators, photovoltaic panels and the like,

- a buffer battery stage 42, for continuously supplying, at any desired time, electric power,

- a stage 43 for generating hydrogen by electrolysis, which can be supplied with electric power from the stages 41 or 42,

- an accumulator stage 44 for accumulating the generated hydrogen, preferably at a low pressure and being accumulated by forming hydrides,

- a combustion or oxidation stage 45 for burning or oxidating hydrogen, including, for example, the burner or combustor according to the invention shown in figure 1, and

- a heat storing stage 46, for example for accumulating hot water in an accumulating tank, as shown in figure 2. Figure 3 shows moreover a stage 47 for using the generated heat comprising, for example, domestic and industrial heating systems, sanitary hot water generating systems, greenhouse heating systems, de-salting systems, industrial process fluid heating systems and so on. Advantageously, said aeolic generators, photovoltaic panels, and buffer batteries and electrolysis apparatus for generating hydrogen are components individually known per se, thereby they can be freely chosen by one skilled in the art. As to accumulating hydrogen by reaction thereof with metals to form hydrides, therefrom hydrogen can then be derived, it is per se well known that some metals, in particular titanium, iron, manganese, nickel, chrome alloys, react with hydrogen to form hydrides according to the following reversible reaction: M + H₂ < ► MH₂. According to this reversible reaction, and proceeding to the right, i.e. the hydride formation region, the reaction will slightly exothermal. On the contrary, as hydrogen is released, i.e. to the left, the reaction is likewise endothermal. The metals used in said hydride forming reactions can be advantageously selected to operate at about atmospheric pressure and environment temperature. By way of an example, the following metals or alloys thereof, i.e., titanium, iron, manganese, nickel and chrome would be suitable, without limiting the scope of the invention. Actually, hydrogen is supplied with a supplying pressure slightly larger than atmospheric pressure, the reaction occurring from the left to the right. The cooling can be carried out by a simple air ventilation, and, during this reaction, the pressure will be held at a constant value, whereas said pressure will increase at the end of the reaction. According to the invention, it is provided to store hydrogen at low pressure from 1 to 5 bars, preferably about 2 bars, the burner hydrogen supplying pressure being further reduced to a smaller value, preferably about 20 millibars. As hydrogen is used for burning, or oxidating applications, said reaction will occur in said burner with a reversed direction, i.e. from the right to the left, the heating power necessary to this end being comparatively small, and being advantageously provided by a hot water circuit supplied with water, for example, by the hot water storing tank 32. As hydrogen in its metal tank or in the stage 44 is nearly exhausted, said tank can be filled-in again by hydrogen generated in the electrolysis stage 43, as above shown. Thus, one skilled in the art can be easily select the metals to be reacted with hydrogen to provide hydrides according to the teachings of the present invention. With respect to the burning 45, heat storing 46 and heat using 47 stages, reference should be made to the above disclosure. From the above constructional and functional disclosure, and from the steps of the method according to the invention, it would be apparent that the invention fully achieves its aim and objects, while providing the above mentioned advantages. Thus, instead of burning hydrogen for generating electric power, as it would be conventional in fuel cells, according to the teachings of the present invention, in heated fluid, for example heated water applications, heat is not generated by electric power from hydrogen combustion but, on the contrary, hydrogen preferably generated in situ by electrolysis and, more specifically, by a low temperature flame free combustion, i.e. in very safe conditions without generating oxides or polluting compounds is directly used. The air-hydrogen mixture combustion/oxidation being automatically started upon contacting the catalyzer. The inventive autonomously hydrolitically generated hydrogen from renewable electric power available in alternating year to be accumulated in batteries, as well as said hydride generated hydrogen, advantageously allow to operate in fully independent manner from the electric net and, accordingly, the inventive systems can be advantageously also installed in insulated regions without electric supplies and on aircraft, vessels, sea platforms and so on. Moreover, since the invention operates at a low pressure, dangers related to hydrogen accumulation at a high pressure are consequently obviated, and the low pressure hydrogen accumulating tank of the invention can be advantageously installed immediately near houses or industrial buildings, or inside the latter. While in the above disclosure reference has been made to water as a cooling fluid, or a fluid to be heated, it should be apparent that in actual practice it would be also possible to use any other fluids or fluid mixtures as a thermal support. Moreover, it should be apparent that, in addition to heating water for heating and sanitary system purposes, said heated water or fluid can also be used for chemical and industrial processes in general, requiring to heat fluids. Finally, it should be also apparent that in practicing the invention, one skilled in the art can modify the shown and disclosed burner and systems, for example depending on a selection of the burner components and apparatus, and enlarge or limit the disclosed circuits depending on applications, without departing from the inventive scope, as disclosed, shown and claimed.

Claims

1. A method for burning hydrogen in a burner, characterized in that said method comprises the steps of: - mixing hydrogen and air to provide a combustible mixture,

- supplying said mixture to said burner on a catalyzer, so as to start a combustion by contacting said mixture and catalyzer,

- burning at a low temperature said hydrogen without forming flames.

2. A method according to claim 1, characterized in that palladium (Pd 46), platinum (Pt 78) or other metals or alloys thereof are used as said catalyzer.

3. A method according to claim 1, characterized in that said hydrogen is supplied at a low pressure in a 16 to 25 millibar range, preferably 20 millibars.

4. A method according to claim 1, characterized in that said hydrogen is burnt at a temperature range from 200 to 450°C, preferably about 300°C.

5. A method according to claim 1, characterized in that heat from said combustion is used for heating a cooling fluid, such as cooling water.

6. A method according to claim 5, characterized in that said cooling water is heated by causing it to pass through a heat exchanger traversed by burnt gases, said burnt gases being free of oxides or polluting compounds.

7. A method according to claim 5, characterized in that said cooling water, or heated water, is stored in a storing tank and used, for example, for heating purposes or for prociding sanitary hot water.

8. A method according to claim 1, characterized in that said hydrogen is produced by electrolysis in a same system, or place, where the hydrogen combustion is performed.

9. A method according to claim 8, characterized in that said hydrogen is stored in a storing tank and is used for forming hydrides by reacting it with metals, or alloys thereof, such as titanium, iron, manganese, nickel, chrome or the like.

10. A burner for carrying out a method according to one or more of claims 1 to 9, characterized in that said burner comprises, in a burner vessel (2), a hydrogen combustion chamber (3) holding a catalyzer (4) and encompassed by a thermal exchange chamber (6) holding a tube nest (7) for conveying hot burnt gases and therethrough cooling water or water to be heated is caused to pass, in that on an inlet side (12) of the combustion chamber (3) an adjustable low pressure air and hydrogen mixture is supplied, in that in said combustion chamber (3) said hydrogen combustion is performed at a low temperature and without flames by contacting said catalyzer, in that on a burnt gas outlet side (17) converging means to convey said burnt gases from said combustion chamber (3) to the tube nest (7) are provided, a burnt gas collecting and discharging chamber (18) being moreover provided, wherein said thermal exchange chamber (6) comprises a cooling water inlet (9) and outlet (11) and a condensate outlet (10).

11. A burner according to claim 10, characterized in that said low temperature hydrogen oxidation is performed in a temperature range from 200 to 450°C, preferably about 300°C, and that said low pressure with which hydrogen is supplied to said burner, is included in a range of 16-24 millibars and preferably being of about 20 millibars.

12. A burner according to claim 10, characterized in that upstream of said burner (1) inlet side (12) is provided an air and hydrogen supply assembly, forming, in a mixing chamber (14) a combustible mixture, to be supplied to said combustion chamber (3) through an injection nozzle (29).

13. A burner according to claim 10, characterized in that said water heated in said thermal exchange chamber (6) is accumulated in a hot water accumulator (32).

14. A burner according to claim 10, characterized in that said generated hot water is used in domestic and industrial heating systems, sanitary hot water delivery systems and in industrial systems in general.

15. A burner according to one or more of claims 10 to 14, characterized in that said air and hydrogen in said combustible mixture are present in a maximum ratio of 3.5%.

16. A burner according to claim 10, characterized in that, as a catalyzer (4) in said combustion chamber (13), palladium, platinum and the like catalyzers or alloys thereof, on a support, for example alumina, on in a single piece form, for example as small balls, grains and the like are used.

17. A heating system for heating water comprising a burner (1) according to claims 10 to 16, and being characterized in that said heating system further comprises: A) in said low pressure hydrogen supplying circuit (19):

- a flow meter (22) for adjusting an hydrogen flow- rate,

- a display gauge (23) for displaying the hydrogen pressure,

- a flow-rate measurement device, and

- a further display gauge (27) for displaying the pressure in said mixing chamber (14),

- a thermometer (28) for measuring the temperature in said mixing chamber (14) or at the inlet side (12) of the combustion chamber (3), and

B) in said cooling water or water to be heated supplying system (21):

- a recirculating pump (31) on the inlet side,

- a calorie-counter (33) on the outlet side, - at least a hot water accumulator (32), and

- an expansion tank (34), wherein said circuits A) and B) optionally further comprise shut-off and/or adjusting and/or discharging components like those conventionally used in hydraulic and gas delivery circuits.

18. A system for producing heat water heated by a burner for burning hydrogen, i.e. a burner according to one or more of claims 10 to 16, characterized in that said system comprises the following operating stages: - an electric power producing stage (41) for producing electric power for renewable sources (for example aeolic generators, photovoltaic panels and so on),

- a buffer battery stage (42),

- a hydrogen producing stage (43) for producing hydrogen by electrolysis,

- a hydrogen accumulating stage (44),

- a burning stage (45) for burning hydrogen, and

- a cooling water respectively a water to be heated storing stage (46).

19. A system according to claim 18, characterized in that said hydrogen is accumulated in a time in which no electric power is generated from said renewable sources and/or in which no hydrogen combustion is performed in said burner, i.e. in an automatic manner for holding a "full" status in said hydrogen accumulating tank.

20. A system according to claim 18, characterized in that said hydrogen is accumulated in said accumulating tank by forming hydrides, derived by reacting said hydrogen with metals or alloys of titanium, iron, manganese, nickel, chrome and the like.

21. A system according to claims 18 to 20, characterized in that said hydrogen is accumulated at a low pressure, in a 1 to 5 bar range, preferably from 1.5 to 3 bar, and more preferably about 2 bars.

22. A system according to claim 18, characterized in that said hydrogen burning burner (1) is of a type according to claims 10 to 16.

23. A system according to claim 18, characterized in that the generated hot water is stored in at least a hot water storing tank.

24. A system according to claim 18, characterized in that said electric power generating stage (41) for generating electric power from a renewable source comprises herein an emergency connection for connecting it to an electric power distributing net.

25. A system according to claim 17, characterized in that said hydrogen is supplied by hydrogen tanks or bottles, at a high pressure, through an associated pressure reduction stage.