ITCO20100003A1 - "HYDROGEN GENERATOR SYSTEM FOR A HYDROGEN CATALYTIC COMBUSTOR" - Google Patents

Description

â € œHydrogen generator system for a hydrogen catalytic combustorâ €

Description of the invention

Field of use

The present invention relates to a hydrogen generator system for a hydrogen catalytic combustor according to the preamble of claim 1.

Technological background and state of the art

Recently, as an alternative to the known liquid fuel or gas boilers for the production of heat, respectively for heating systems, combustors have been developed for the catalytic combustion of hydrogen with initiation of the reaction at room temperature, without flame formation, with reaction below the NOx formation temperature, with exhaust formed by hot humid air only, and with the transfer of heat completely to a heat exchanger for heating the water of a heating system, for example of the radiant type, in particularly for homes, i.e. with surfaces for example up to about 250-300 m <2>. Hydrogen catalytic combustors of the indicated type are disclosed, for example, by the applicant's document WO 2005/024301. In them the hydrogen supply is foreseen at low pressures, for example of the order of 2 - 5 bar, where the hydrogen supply must be ensured in a reliable, safe and continuous way. Industrially, hydrogen is produced by electrolysis of distilled water in alkaline electrolysers, obtaining oxygen and hydrogen. The electrolysers are supplied with suitably demineralized mains water and the necessary electrical energy is supplied from the mains using an A / C transformer / converter unit, generally fed with three-phase current due to the high current values and the low voltage values required. , where heat is developed during the electrolysis process.

For the practical use of the aforementioned catalytic hydrogen combustors, it is necessary to supply a suitable supply of hydrogen, ie continuous, at low pressure and with a suitable degree of hydrogen price. Such a power supply is currently available with plants or systems for the sole generation of hydrogen and oxygen assembled with devices or components on the market, generally envisaged for the industrial production of hydrogen.

They therefore have the following drawbacks:

- they are generally made up of components or devices occasionally recovered from the market, possibly modified and not designed according to the intended use,

- they are systems as a whole rather complex for plumbing and electrical installers, which require rather long assembly and installation times, errors are possible and require a large footprint, - they have an improved performance,

- proton exchange membrane electrolytic cells (PEM) are often used, which indeed provide a greater purity of hydrogen than the use of electrolytic cells envisaged according to the invention, but have correspondingly high costs and a longer duration limited,

- during the electrolysis heat is developed, which lowers the efficiency of the system,

- an interruption of electricity leads to an interruption in the production of hydrogen,

- only the production of hydrogen and oxygen is foreseen,

Summary of the invention

At the basis of the present invention there is therefore the task of creating a hydrogen generator system for the supply of hydrogen catalytic combustors of the type indicated which eliminates the disadvantages of the systems of the prior art and is able to supply hydrogen produced with the sufficient degree of purity reliably and continuously, is achievable economically and with improved performance.

It is part of the indicated task to propose a hydrogen generator system simplifying its construction and installation

The indicated aim is achieved with a hydrogen generator system for hydrogen catalytic combustors having the characteristics of claim 1.

Further advantageous developments and embodiments can be seen from the dependent claims.

With the hydrogen generator system according to the invention, several important advantages are achieved starting from the known production of hydrogen by electrolysis of distilled water and adopting the most rational formation criteria for the individual blocks into which the hydrogen generator system can be divided. proposed as illustrated in more detail below.

A further advantage of the proposed hydrogen generator consists in the exploitation of the heat that develops inside the electrolyser during the electrolysis process, which heat can be advantageously used as an integration of the planned heating and / or production plant. hot sanitary water.

In a further development of the basic hydrogen generator, a reliable continuous supply of the hydrogen produced can be guaranteed even during possible interruptions of the electrolysis process.

In still a further development of the hydrogen generator according to the invention, a suitable purification of the hydrogen is obtained with simple and economical means.

Furthermore, an advantage common to all the embodiments of the hydrogen generator according to the invention consists in providing a targeted choice, design and sizing of the individual components necessary to make the proposed hydrogen generator, so that said circuit can be advantageously compactly assembled and housed in a housing that can be installed inside or outside a home.

Such a case will therefore be equipped on the outside with only inlet and outlet fittings, which further facilitates the connection of said case, or the hydrogen generator according to the invention, during the execution of the relative connections.

Providing a supply of electricity produced from renewable sources (solar, wind, biogas) together with the presence of a hydrogen storage, an independent, continuous and economical operation is obtained, where hydrogen can be substantially produced continuously when the renewable source is available and stored for its use when really necessary.

It is also advantageous to provide a plurality of embodiments of the proposed hydrogen generator system, which are able to satisfy the different characteristics to be considered depending on the user to be fed with hydrogen, for example in relation to the degree of purity hydrogen, which is essential if you decide to feed the catalytic combustor or another user, such as a fuel cell, or the pressure or flow rate.

Brief description of the drawings

Further characteristics, advantages and details of the hydrogen generator system for a user operating on hydrogen, such as for example a hydrogen catalytic combustor, can be seen from the following description of some preferred embodiments, illustrated by way of example in the attached drawings, to which please also refer to any details not described in detail in the following description, and in which they schematically show:

Figure 1 is a first embodiment of a hydrogen generator system for a user running on hydrogen, and

Figures 2 to 5 are further embodiments of the hydrogen generator system according to the invention.

Description of the preferred embodiments

In the various figures, identical or functionally equivalent components of the proposed system have the same reference indices.

Reference is first made to the basic embodiment illustrated in Figure 1, in which 1 indicates as a whole the hydrogen generator system according to the invention. The proposed system 1 comprises an electrolyser 2, that is an electrolytic cell, containing an alkaline-based solution (KOH) for the electrolysis process of distilled water for the production of oxygen and hydrogen. Alkaline electrolysers are cost-effective. Alternatively, it is also possible to use PEM electrolysers, or proton exchange membrane electrolysers, which are more expensive but better for the purity of the hydrogen supplied. In the case of a catalytic combustor 3, hydrogen is supplied for example at a pressure of 5 bar, where production control takes place via the pressure value.

The oxygen produced 4 can be released into the atmosphere.

The water to be subjected to electrolysis is taken from the network and demineralized in a demineralizer 5, advantageously of the reverse osmosis type, which provides a high purity of distilled water suitable for the requirements for electrolysis of water.

Advantageously, the demineralizer 5 is connected to a tank 6, which automatically requires its filling with demineralized water when the water level in it drops below an adjustable minimum threshold level. The sizing of the tank 6, designed to have the desired operating autonomy, is also carried out in order to have as little space as possible. With tank 6, continuous operation safety is obtained even in the event of a possible interruption of the mains water.

The electrical energy necessary for the electrolysis process can be taken from the electricity network, for example from a three-phase network following the high absorption of the electrolysis process (about 5 KW per cubic meter of hydrogen produced), by means of an intermediate unit 7 A / C converter transformer equipped with a control system, not shown.

Alternatively, it is planned to take electricity from a renewable source, for example from a solar, wind or biogas plant, not illustrated.

As mentioned above, hydrogen is produced at a very low pressure, for example 5 bar for reasons of safety and duration of the system, whereas hydrogen produced by alkaline electrolysis could contain traces of basic solution, however it has a purity higher than 99%, and therefore sufficient for a catalytic combustor, while the remainder is formed by water in a vapor state or very small traces of oxygen. It should be emphasized here that these impurities are irrelevant if it is decided to store hydrogen at low pressures (as illustrated in more detail below) or if hydrogen is used in combustion processes, as in the case of catalytic combustors, while they are relevant in the case of feeding fuel cells, which require higher purities in order not to be damaged.

A further purification of the gas could require, as known, a stage 8 of condensation of hydrogen through a cooling unit (chiller), not illustrated, with which a very high degree of purity of 4 can be reached, 5 (99.995%). However, these chillers are very bulky and consume a lot of electricity to break down any water residues, which are indeed irrelevant for combustion, which generates water vapor.

As mentioned above, however, in the case of catalytic combustors, the hydrogen must have a lower purity, for example at least 99.5%, which is undoubtedly obtainable with the aforementioned condensation stages 8 powered by a chiller. .

According to the invention it is possible to forego the use of chillers and instead add an activated carbon and Teflon filter 9 to the condensation stage 8 to eliminate any electrolytic residues. In this way a more economical and compact solution is obtained. Any traces of oxygen are indeed irrelevant, since hydrogen is destined for combustion.

A further teaching of the invention consists in recovering the heat generated in the electrolyser, or in the electrolytic cell 2 during the electrolysis process, by providing a heat exchanger device 10 associated with the electrolyser 2. The primary circuit 11 of the heat exchanger heat 10 is inserted in the electrolyser 2 and contains a circulation pump 12. The secondary circuit 13 has a delivery 14 and a return 15 associated with a heating system 16. This heat exchanger device 10 constitutes a heat source which allows to raise the efficiency and energy balance of the hydrogen generator system 1, whereas the heat exchanger 10 also serves to cool the electrolyser 2.

In this sense it is observed that, generally, to produce 1 Nm <3> of hydrogen about 5.3 KW of electricity are required, of which 3.5 KW are actually used for electrolysis, while the rest is substantially dissipated in heat and by the hydrogen generator system 1 itself, for example through its electrical control panel, sensors, fans and so on. With the recovery illustrated above, the efficiency of the electrolytic cell 2 reaches over 90%.

According to a further important teaching of the present invention, a storage device for the hydrogen produced is provided, figures 2, 3, 4 and 5. For reasons of space and at the same time of hydrogen purification, the storage device provided can be based either on a pressure storage, possibly raised by a compressor, or on a storage based on the absorption of hydrogen through metal hydrides, which have the ability to absorb hydrogen inside them and then release it, where this solution allows to have low pressure accumulators with an excellent capacity with respect to the volume.

As known, metal hydrides must be cooled when they absorb hydrogen while they develop heat when they release it. This heat input can be more or less relevant depending on the composition of the alloy of the aforementioned metal hydrides, where the ideal would be to work at room temperature, or just above it.

According to the invention, the necessary heat input can come from the heat recovery 10 of the electrolysis process, so in this sense the system 1 can be autonomous, figures 2 and 3. In this case, two three-way valves 22 are provided and 23 electrically piloted, of which the first (22) serves to bypass the storage device 17 while the second (23) regulates the temperature according to needs by mixing the water. Alternatively this heat could be produced by an external heat source, for example by an electrical resistance, not shown. Another important advantage achieved with the storage of hydrogen on a solid basis, or with metal hydrides, must be seen in the fact that, in addition to storing a good amount of hydrogen inside them, the metal hydrides also allow an additional purification of the hydrogen, advantageous for its combustion, where in this way a purification unit is obtained per se included in the storage device 17.

Therefore, in the event that the user does not need a particular purity, as in the case of a catalytic combustor 3, it can directly withdraw hydrogen from the electrolyser 2 and / or from the storage device 17. Therefore the generator system of hydrogen 1 can have two gas outlets, fig. 3, i.e. an outlet 18 for hydrogen purified only by the filter 9 and not further by the storage device 17 supplied directly by the electrolyser 2, and an outlet 19 for the purest hydrogen, i.e. purified both by the filter 9 and from the accumulator device 16, and coming from the latter. The two outputs 18 and 19 can supply the same user or, as illustrated, two users requiring different degrees of hydrogen purity.

Alternatively, the storage of hydrogen can be achieved with a container under pressure, which can be the same as supplied by the electrolyser 2 or can be raised by a compressor, not shown, fig. 5.

The embodiment of Figure 4 shows a hydrogen generator system 1 with separate heat management and storage.

The embodiment of Figure 5 illustrates a hydrogen generator system 1 according to the invention with storage of hydrogen under pressure, without compressor.

In all the embodiments illustrated above, in order to improve efficiency and consumption, it is necessary to manage in the most rational way all the circuit components and devices of the proposed system 1. According to the invention, it is therefore proposed to use a logic, assisted by software, suitable for making the entire system work, where for example the production of hydrogen must work only if the accumulation of sterilized water in the tank 6 of the demineralizer 5 and the accumulation of hydrogen in the storage device 17 falls below the set thresholds. For the production of hydrogen and the management of hydrogen storage, a pressure control is envisaged; where up to a certain level or lower threshold hydrogen is taken from the accumulator device 17, after which it is recharged and / or the user 3 is supplied with hydrogen directly from the electrolyser 2. These examples are exemplary and are which can be produced with corresponding circuit arrangements of hydrogen generator systems 1 as illustrated in the drawings.

A further teaching of the present invention consists in housing in a housing 20 a pre-assembled hydrogen generation circuit or system 1 according to the invention, made as compactly as possible according to the criteria illustrated above. In this way said case 20 and the hydrogen generator system 1 housed therein form a compact unit 21 which can be installed in a simple and rapid way and with the exclusion of any errors in the formation of the various circuits provided. Unit 21 will only have the necessary inlet and outlet connections on the outside. This will therefore make the execution of the various connections provided simple, quick and safe, for example to the mains water pipeline, to the source of electricity, as well as to the output pipeline (s) 18, 19 of the Hydrogen for the utilities provided, as well as the delivery pipes 14 and return 15 of the exchanger 10 to be connected to a heating system 16, for example of the radiant type of a house, integrated by a solar system.

From the structural and functional description above it can be seen that with the hydrogen generator systems according to the invention for catalytic combustors the indicated task is effectively solved and the mentioned advantages are achieved.

What disclosed above in relation to a catalytic combustor obviously also applies conceptually to other utilities operating on hydrogen, such as in the case of fuel cells, which can be advantageously used for the production of electricity as a back-up service, for example in hospitals to replace the usual accumulator batteries, in which hospitals can also use the oxygen produced and, for heating purposes, if in combination with a catalytic combustor similarly fed with the hydrogen produced. Two examples of sizing of a hydrogen generator system 1 according to the criteria and teachings of the invention illustrated above are now indicated, respectively for a catalytic combustor and a fuel cell.

Example 1 (catalytic combustor)

Project data:

User: thermal catalytic combustor with 5.8 kW, hydrogen consumption 1.67 Nm3 / h

Accumulation duration: 12 hours

Charging cycle duration: 12 hours

Hypothesis of withdrawing only from the accumulation and not directly from the producer.

Sizing:

<m> 3

1,67â ‹… 12h = 20m <3> = 20000l Minimum storage size = h

m3

2

Minimum electrolyser flow rate = <h>

Where the flow required for a safety factor and to approach the flow rates available on the market has been approximated by excess.

20 m 3 l â ‹… 0,873 = 17, 4 l Required distilled water to fill storage tank = m

Where 0.87 is the standard consumption of an electrolyser. For safety, an accumulation of 20 liters is assumed.

Minimum water treatment flow rate = 20là · 12h = 1, 67 <l>

h

N.B. In this calculation example the m <3> are to be understood under normal conditions.

Results:

Water treatment (minimum flow rate) = 1.67 l / h

Storage of demineralized water = 20 liters

Electrolysis (recommended flow rate) = 2 Nm3 / h

Hydrogen storage = 20000 liters

Example 2 (fuelcell)

Project data:

User: 1 kW fuel cell, hydrogen consumption 14 liters / minute Storage duration: 8 hours

Charging cycle duration: 12 hours

Hypothesis of withdrawing only from the accumulation and not directly from the electrolyser.

Sizing:

<itri> 60 <3>

User = <l m3> m

14 â ‹… = 0.84â ‰ ˆ1

min 1000 h h

In this dimensioning, the maximum consumption of hydrogen has been approximated by excess to have a safety margin.

3

Minimum accumulation size = 1 <m> â ‹… 8h = 8m <3> = 8000l

h

3

Minimum electrolyser flow rate = 8m <3> Ã · 12h = 0, 67 <m>

h

Required distilled water to fill accumulation = 3 l

8 m â ‹… 0.873 = 6.96 l m

Where 0.87 is the standard consumption of an electrolyser. For safety, an accumulation of 10 liters is assumed.

Minimum water treatment flow rate = 10là · 12h = 0, 83 <l>

h

In this calculation example the m <3> are to be understood under normal conditions. Results:

Water treatment (minimum flow rate) = 0.83 l / h

Storage of demineralized water = 10 liters

Electrolysis (minimum flow rate) = 0.67 Nm <3> / h

Hydrogen storage = 8000 liters

In this case, considering the important accumulation of hydrogen, the accumulator can be provided outside the housing 20, or unit 21.

In practice, those skilled in the art will be able to introduce various modifications and variations, such as for example providing some component outside the enclosure 20 or unit 21 described, replacing some component with others that are substantially functionally equivalent, as well as providing for different fields of use, such as heating systems for industrial uses, such as for the heating of greenhouses, or use oxygen to oxygenate the water of tanks of pitches in fish farming and so on, without escaping from the The scope of the present invention as described and claimed in the attached claims.

Claims (1)

â € œHydrogen generator system for a hydrogen catalytic combustorâ € Claims 1. Hydrogen generator system for a user running on hydrogen, such as a hydrogen catalytic combustor or a fuel cell, comprising an electrolyzer for the electrolysis of distilled water, with production of hydrogen and oxygen, containing , on the inlet side, an associated demineralizer device and an associated A / C transformer / converter unit for the power supply for the electrolysis process and, on the outlet side, a purification device for the hydrogen produced with subsequent release of hydrogen to be fed to the user running on hydrogen, as well as a production of oxygen, characterized by the fact that it also includes: - a device (10) for recovering the heat produced by the electrolysis process associated with the electrolyser (2), - and / or a storage device (17) for the storage of the hydrogen produced, and by the fact that the entire hydrogen generator system (1) is housed in a housing (20), which externally has only connection fittings inlet, for mains water and electricity for the power supply of the electrolyser (2), and outlet fittings for the hydrogen produced and for the delivery and return pipes of a heating, for example of a house, to be connected to said heat recovery device 2. Hydrogen generator system (1), according to claim 1, characterized in that the electrolysis heat recovery device (10) is formed by a heat exchanger (10), whose primary circuit (11) is arranged in the electrolyser (2) and whose secondary circuit (13) is connected to a heat user (16), for example to a domestic or industrial heating system. 3. Hydrogen generator system (1) according to claim 1, characterized in that the hydrogen storage device (17) is a pressurized tank or contains metal hydrides and forms or comprises a storage tank for the hydrogen hydrogen, where said hydrogen storage takes place at low pressure, for example at a maximum of 6 bar. 4. Hydrogen generator system (1), according to claim 1, characterized in that the hydrogen storage device (17) is a pressure storage device with or without a compressor. 5. Hydrogen generator system (1), according to one or more of the preceding claims, characterized in that it provides a direct output of the hydrogen produced, which can be associated with a hydrogen inlet / outlet of a device ( 17) for the storage of hydrogen with metal hydrides, and by the fact of providing a derivation in the secondary circuit (13) of the heat exchanger (10) for the supply of heat to the storage device (17). (Fig. 2) 6. Hydrogen generator system (1) according to one or more of the preceding claims, characterized in that it provides a double hydrogen outlet, i.e. a first outlet derived directly from the low pressure electrolyser (2) and preliminarily purified, as well as a second outlet of the hydrogen coming from the hydrogen accumulator (16) with metal hydrides and having a higher degree of purification, metallic, and by providing a derivation in the secondary circuit (17) of the heat exchanger (10) for providing heat to the storage device (17). (Fig. 3) 7. Hydrogen generator system (1), according to one or more of the preceding claims, characterized by the fact of comprising a centralized control device assisted by a programmable software and able to manage in the most rational way the control and adjustments of all the devices and circuit components that can be controlled to obtain the best performance and consumption. 8. Hydrogen generator system (1), according to claims 1 and 3, characterized by the fact of using an alloy of metal hydrides which in the hydrogen release phase requires a heat input allowing to work at room temperature or slightly higher, where said heat input is preferably derived from the heat recovery of electrolysis. 9. Hydrogen generator system (1), according to claims 1 and 2, characterized in that the heat exchanger device (10) cools the electrolyser (2). 10. Hydrogen generator system (1), according to one or more of the preceding claims, characterized by forming with said housing (20) for housing the system (1) a preassembled unit (21) ready for its installation and ™ direct connection to the inlet and outlet lines.