TECHNOLOGICAL FIELD
[0001] Embodiments of the present disclosure relate to a gas burner membrane. Some relate
to a gas burner combustion system comprising the gas burner membrane and some relate
to a method of forming the gas burner membrane.
BACKGROUND
[0002] In gas burners used, for instance, in boilers, cookers, gas fires or other systems
for combusting gaseous fuels, a burner membrane is usually provided which has a pattern
of through holes through which a gas or a mixture of gases passes. The mixture is
ignited on an outer side of the membrane. Burner membranes may also be called flame
strips, flame skins, burner skins or burner heads.
[0003] Conventionally gases such as methane have been used in gas burners in a number of
locations. In some instances, different gases could be used in gas burners, such as
pure hydrogen gas or a hydrogen rich gas mixture.
BRIEF SUMMARY
[0004] According to various, but not necessarily all, embodiments there is provided a gas
burner membrane for use with pure hydrogen gas or a hydrogen blend gas which includes
at least 30 vol. % hydrogen gas, the gas burner membrane comprising a sheet of material
with a plurality of holes, and wherein a ceramic coating is provided on the sheet
of material.
[0005] Possibly, the thickness of the ceramic coating is up to 2000 microns. Possibly, the
thickness of the ceramic coating is 30 - 300 microns. Possibly, the thickness of the
ceramic coating is 50 - 200 microns. Possibly, the thickness of the ceramic coating
is 100 - 150 microns.
[0006] The ceramic coating may comprise zirconium oxide. The ceramic coating may comprise
yttrium oxide. The ceramic coating may comprise yttria-stabilized zirconia.
[0007] At least a majority of the holes may have a diameter equal to or less than 1.3 times
the thickness of the sheet of material. At least a majority of the holes may have
a diameter of between 0.1 and 1 mm.
[0008] The gas burner membrane may include at least 100 holes.
[0009] The coating may be located on the outer surface of the gas burner membrane.
[0010] The gas burner membrane may be a flat gas burner membrane, a linear gas burner membrane
or a cylindrical gas burner membrane.
[0011] Possibly, the sheet of material is formed from sheet metal. Possibly, the sheet of
material is formed from sheet steel.
[0012] The ceramic coating may cover only a portion of the sheet of material. Substantially
all of the holes in the sheet of material may be provided in the portion of the sheet
of material covered by the coating.
[0013] According to various, but not necessarily all, embodiments there is provided a gas
burner membrane for use with hydrogen gas, the gas burner membrane comprising a plurality
of holes, and wherein a ceramic coating is provided on the gas burner membrane.
[0014] According to various, but not necessarily all, embodiments there is provided a gas
burner including: the gas burner membrane of any of the preceding paragraphs; and
a hydrogen gas supply. The hydrogen gas supply is a pure hydrogen gas supply or a
hydrogen blend gas supply which includes at least 30 vol. % hydrogen gas.
[0015] According to various, but not necessarily all, embodiments there is provided a method
of forming a gas burner membrane, the method comprising: forming a plurality of holes
in a sheet of material; and applying a ceramic coating onto the sheet of material.
[0016] The ceramic coating may be applied using thermal spraying. The ceramic coating may
be applied using thermal plasma spraying.
[0017] Prior to application, the ceramic may be in powder form with an average particle
size of up to 100 microns.
[0018] The gas burner membrane may be the gas burner membrane of any of the preceding paragraphs.
[0019] According to various, but not necessarily all, embodiments there is provided a method
of forming a gas burner combustion system comprising: providing the gas burner membrane
of any of the preceding paragraphs; and providing a hydrogen gas supply.
[0020] The hydrogen gas supply may be a pure hydrogen gas supply or a hydrogen blend gas
supply. The hydrogen blend gas supply may include at least 30 vol. % hydrogen gas.
[0021] According to various, but not necessarily all, embodiments there is provided a gas
burner membrane for use with hydrogen gas, the gas burner membrane comprising a sheet
of material with a plurality of holes, and wherein a ceramic coating is provided on
the sheet of material.
[0022] According to various, but not necessarily all, embodiments there is provided examples
as claimed in the appended claims.
BRIEF DESCRIPTION
[0023] Some examples will now be described with reference to the accompanying drawings in
which:
Fig. 1 schematically shows a gas burner combustion system according to the disclosure;
Fig. 2 schematically shows a further gas burner combustion system according to the
disclosure;
Fig. 3 schematically shows a yet further gas burner combustion system according to
the disclosure;
Fig. 4 shows a side view of an example gas burner membrane according to the disclosure;
Fig. 5 shows a cross sectional view of the example gas burner membrane along the line
A-A of Fig. 4; and
Fig. 6 shows a magnified cross sectional view of the example gas burner membrane within
the circle B of Fig. 5.
DETAILED DESCRIPTION
[0024] Fig. 1 shows a typical gas burner combustion system 10 with a mixing chamber 12 with
a burner membrane 14 on top of the mixing chamber 12. Air and gas is blown into the
mixing chamber 12 using a fan 20. The gas is supplied to the fan 20 via a pipe 18
from a supply 16. The burner 10 is controlled by a control unit 22. The fan 20 could
for instance operate at 2000 rpm at 5 kW.
[0025] Fig. 2 shows a further typical gas burner combustion system 50 with the mixing chamber
12 with the burner membrane 14 on top of the mixing chamber 12. The mixing chamber
12 receives gas directly from a supply 16 via a pipe 19, without passing through the
fan 20. Air is blown into the mixing chamber 12 using the fan 20, and the burner 10
is controlled by the control unit 22.
[0026] Fig. 3 shows part of a yet further typical gas burner combustion system 60 with the
mixing chamber 12, with the burner membrane 14 on top of the mixing chamber 12. The
mixing chamber 12 receives gas from a supply 16 via a pipe 21. In this example, a
venturi 23 is provided at the mixing chamber 12 entrance, to cause the gas to accelerate
prior to entering the mixing chamber 12. The pressure in a narrow passage of the venturi
23 is lower than atmospheric pressure, which causes air surrounding the venturi 23
to be sucked into the venturi 23 via apertures in the venturi 23, and then into the
mixing chamber 12.
[0027] In other examples, the venturi 23 might not be included in the gas burner combustion
system 60, so only the gas from the supply is present in the chamber 12. In the examples
where the gas burner combustion system 60 of Fig. 3 does not include a venturi 23,
no mixing takes place in the chamber 12, and thus the chamber 12 is not referred to
as a "mixing" chamber.
[0028] The typical gas burner combustion systems 10, 50, 60 each also include an igniter
(not shown) to initiate the burning of the gas. The gas is combusted on the outside
(topside in the examples of Figs. 1 to 3) of the burner membrane 14.
[0029] The gas burner combustion systems 10, 50, 60 are intended to be used with hydrogen
gas. The term hydrogen gas used herein refers to pure hydrogen gas or hydrogen blend
gas (i.e. a mixed gas including at least some hydrogen). Hydrogen has a greater flame
velocity than natural gas, which increases the risk of flashback (i.e. an uncontrolled
upstream propagation of the flame, due to a local imbalance in the flow velocity and
the flame speed). If the exit velocity of an air/fuel mixture through the holes in
a burner membrane is lower than the flame speed of hydrogen, there is a risk of flashback.
Flashback can be explosive and thus dangerous, especially when hydrogen gas is used
as a fuel. Increasing the air/hydrogen ratio can reduce the risk of flashback, but
at the expense of combustion efficiency and flame stability.
[0030] It has been found that the size of the holes in the burner membrane is an important
factor for reducing the risk of flashback and efficient burning of hydrogen gas. Relatively
small holes are required when compared to conventional natural gas burners.
[0031] Fig. 4 shows a side view of an example gas burner membrane 100, which can be used
in the example gas burner combustion systems 10, 50, 60 of Figs. 1 to 3. Fig. 5 shows
a cross sectional view of the gas burner membrane 100 along the line A-A of Fig. 4.
The gas burner membrane 100 comprises a sheet of material 110 with a plurality of
holes 120. The section of the sheet of material 110 containing the holes 120 is shaded
in Figs. 4 and 5. The gas burner membrane 100 further comprises a ceramic coating
130, which is provided on the sheet of material 110.
[0032] In this example, the gas burner membrane 100 is a flat gas burner membrane. The sheet
of material 110 of the example flat gas burner membrane includes a flat section 112
and a raised section 114. The raised section 114 may be in the form of a half-cylinder.
In this example, the plurality of holes 120 are provided in the raised section 114.
In other examples, the gas burner membrane 100 may be a cylindrical gas burner membrane
or a linear gas burner membrane. A cylindrical gas burner membrane includes a sheet
of material which is formed into a substantially cylindrical shape.
[0033] It has been surprisingly found that the application of the ceramic coating 130 to
the sheet of material 110 with the holes 120 reduces the size of the opening of the
holes through the gas burner membrane 100, and enables the size of the opening to
be finely tuned. Thus a gas burner membrane 100 with a ceramic coating is able to
more efficiently burn hydrogen gas with a lower risk of flashback. The size of the
opening to the hole can also be more effectively tailored to a particular hydrogen
blend gas or gas burner type using the ceramic coating 130.
[0034] A magnified cross sectional view within the circle B of Fig. 5 is shown in Fig. 6,
illustrating the coating 130 on the sheet of material 110. In this example, the ceramic
coating 130 is located only on the outer surface of the gas burner membrane 100 (i.e.
the ceramic coating 130 is located on the opposite face of the sheet of material 110
to the mixing chamber 12). In other words, the ceramic coating 130 is applied to the
same side of the sheet of material 110 as the flame when the gas burner combustion
system 10, 50, 60 is in use (i.e., the upper side in Figs. 4 - 6). In other examples,
the ceramic coating 130 may be located on the inner surface of the gas burner membrane
100, or both the inner and outer surfaces of the gas burner membrane 100.
[0035] In this example, the ceramic coating 130 covers substantially all of the outer face
of the sheet of material 110. In other examples, the ceramic coating 130 may cover
only a portion of the sheet of material 110. For instance, the ceramic coating may
cover only the raised section 114 of the example sheet of material 110. Substantially
all of the holes 120 in the sheet of material 110 may be located in the portion of
the sheet of material 110 covered by the ceramic coating 130.
[0036] In some examples, the ceramic coating 130 comprises zirconium oxide (i.e. zirconia).
Preferably, the ceramic coating 130 also comprises yttrium oxide (i.e. yttria). Most
preferably, the ceramic coating 130 comprises at least 50 wt.% zirconium oxide. The
ceramic coating 130 may be yttria-stabilised zirconia, such as 8 % yttria-stabilised
zirconia (i.e. 8 mol.% yttrium oxide). Other suitable ceramic materials may be used
to provide the ceramic coating 130 in other examples.
[0037] In some examples, the ceramic coating 130 has a thickness of up to 2000 microns (µm).
In some examples, the thickness of the ceramic coating 130 is at least 30 microns.
In some examples, the thickness of the ceramic coating 130 is 30 - 300 microns. Preferably,
the thickness of the ceramic coating 130 is 50 - 200 microns. Most preferably, the
thickness of the ceramic coating 130 is 100 - 150 microns, such as 125 microns. The
coating thickness referred to herein is the average thickness, which could be determined
using a coating thickness gauge such as an Elcometer
®. The ceramic coating 130 may be of substantially uniform thickness across the sheet
of material 110. Thin ceramic coatings are often prone to cracking. However, it has
been found that the gas flow through the burner membrane 100 is able to significantly
reduce the incidence of cracking by cooling the ceramic coating 130.
[0038] The burner membrane 100 of Figs. 4 to 6 is a single skin burner membrane. Preferably,
the sheet of material 110 onto which the ceramic coating 130 is applied is formed
from sheet metal. Most preferably, the sheet of material 110 is formed from sheet
steel, such as ferritic stainless steel. Thus, the sheet of material is preferably
made from metal, or most preferably is made from steel. The sheet of material 110
may be an impermeable material (i.e. non-porous when discounting the plurality of
holes 130 cut into the sheet of material 110). In some examples, the sheet of material
110 has a thickness of at least 0.3 mm. In some examples, the sheet of material 110
has a thickness of up to 3 mm. Preferably, the sheet of material 110 has a thickness
of 0.4 - 1.5 mm, such as 0.6 mm.
[0039] The burner membrane 100 includes a pattern of holes 120, which are relatively small
holes when compared to those in traditional natural gas (methane) burner membranes.
The holes 120 are through holes extending through the sheet of material 110. In some
examples, the majority of the holes 120 have a diameter of up to 1 mm, such as 0.1
mm, 0.25 mm, 0.5 mm, 0.75 mm or 1 mm. Preferably, the holes 120 have a diameter of
0.1 mm - 1 mm. Most preferably, the holes 120 have a diameter of 0.25 mm - 0.75 mm.
At least a majority of the holes 120 may have a diameter equal to or less than 1.3
times the thickness of the sheet of material 110. Preferably, at least the majority
of the holes 120 may have a diameter equal to or less than the thickness of the sheet
of material 110. Most preferably, at least the majority of the holes 120 may have
a diameter equal to or less than 0.75 times the thickness of the sheet of material
110. The holes 120 may have a substantially circular cross-section.
[0040] In this example, at least 100 holes 120 are provided in the sheet of material 110.
In some examples up to 100,000 holes 120 are provided in the sheet of material 110.
Preferably between 1000 and 6000 holes are provided in the sheet of material.
[0041] To form the gas burner membrane 100, the holes 120 are formed in the sheet of material
110. The holes 120 could be formed by laser cutting or using a water jet cutter. The
laser cutting may comprise laser drilling, such as single pulse or multi beam laser
drilling.
[0042] The sheet of material 110 may be formed into a desired shape, for instance by bending
sheet metal 110. The sheet of material 110 may be shaped to provide a flat gas burner
membrane, a linear gas burner membrane or a cylindrical gas burner membrane. The sheet
of material 110 may be formed into the desired shape prior to, or after, the holes
120 are formed in the sheet of material 110.
[0043] The ceramic coating 130 is applied to the sheet of material 110. The coating 130
is preferably applied after the holes 120 have been formed in the sheet of material
110. In some examples, the ceramic coating 130 is applied using thermal spraying.
Preferably, the ceramic coating 130 is applied using thermal plasma spraying.
[0044] In this example, thermal plasma spraying comprises introducing the ceramic material
into a plasma jet from a plasma torch. The ceramic material may be provided in powder
form, and the average particle size of the ceramic powder may be up to 100 microns,
when measured by laser diffraction. In this example, the ceramic material is yttria-stabilised
zirconia. When introduced into the plasma jet, the ceramic particles in the ceramic
powder melt, and are directed towards the sheet of material 110. The molten ceramic
particles then solidify and form a deposit on the sheet of material 110, to form the
ceramic coating 130 on the sheet of material 110.
[0045] In some examples, the surface of the sheet of material 110 is pre-treated prior to
the application of the ceramic coating 130. For instance, the pre-treatment may include
at least one of: a cleaning step, a surface roughening step (e.g., grit blasting),
or a surface primer step (e.g., the application of an aluminium oxide primer to the
sheet of material 110).
[0046] Once the ceramic coating 130 has been applied to the sheet of material 110, the diameter
of the opening of the holes 120 in the sheet of material 110 is reduced by the ceramic
coating 130.
[0047] To form a gas burner combustion system, the gas burner membrane 100 is provided and
a hydrogen gas supply is provided. The hydrogen gas supply could for instance be a
connection to a mains gas supply or a hydrogen gas canister. The hydrogen gas supply
may be a pure hydrogen gas supply or a hydrogen blend gas supply. The hydrogen blend
gas may include at least 30 vol.% hydrogen gas. The gas burner combustion system could
be the example gas burner combustion systems 10, 50, 60 of Figs. 1 to 3.
[0048] There is thus described a gas burner membrane, a gas burner combustion system, and
a method of forming a gas burner membrane with a number of advantages. The size of
the opening to the holes in the burner membrane can be adjusted to enable hydrogen
gas to be burned efficiently with a low risk of flashback. The burner membrane is
also more durable due to the heat resistance provided by the ceramic coating.
[0049] Although examples have been described in the preceding paragraphs with reference
to various examples, it should be appreciated that modifications to the examples given
can be made without departing from the scope of the claims. For instance, the size,
shape and pattern of holes can be chosen as required. Different ceramics may be used.
The gas burner membrane may be differently shaped. The ceramic coating may be applied
using a different method. The burner membrane can be used with pre-mix gas burners,
post-mix gas burners or naturally aspirated gas burners. The burner membrane may be
for a boiler, cooker, a gas fire or other systems for combusting gaseous fuels.
[0050] The term 'comprise' is used in this document with an inclusive not an exclusive meaning.
That is any reference to X comprising Y indicates that X may comprise only one Y or
may comprise more than one Y. If it is intended to use 'comprise' with an exclusive
meaning then it will be made clear in the context by referring to "comprising only
one" or by using "consisting".
[0051] In this description, reference has been made to various examples. The description
of features or functions in relation to an example indicates that those features or
functions are present in that example. The use of the term 'example' or 'for example'
or 'can' or 'may' in the text denotes, whether explicitly stated or not, that such
features or functions are present in at least the described example, whether described
as an example or not, and that they can be, but are not necessarily, present in some
of or all other examples. Thus 'example', 'for example', 'can' or 'may' refers to
a particular instance in a class of examples. A property of the instance can be a
property of only that instance or a property of the class or a property of a sub-class
of the class that includes some but not all of the instances in the class. It is therefore
implicitly disclosed that a feature described with reference to one example but not
with reference to another example, can where possible be used in that other example
as part of a working combination but does not necessarily have to be used in that
other example.
[0052] Features described in the preceding description may be used in combinations other
than the combinations explicitly described above.
[0053] Although functions have been described with reference to certain features, those
functions may be performable by other features whether described or not.
[0054] Although features have been described with reference to certain examples, those features
may also be present in other examples whether described or not.
[0055] The term 'a' or 'the' is used in this document with an inclusive not an exclusive
meaning. That is any reference to X comprising a/the Y indicates that X may comprise
only one Y or may comprise more than one Y unless the context clearly indicates the
contrary. If it is intended to use 'a' or 'the' with an exclusive meaning then it
will be made clear in the context. In some circumstances the use of 'at least one'
or 'one or more' may be used to emphasis an inclusive meaning but the absence of these
terms should not be taken to infer any exclusive meaning.
[0056] The presence of a feature (or combination of features) in a claim is a reference
to that feature or (combination of features) itself and also to features that achieve
substantially the same technical effect (equivalent features). The equivalent features
include, for example, features that are variants and achieve substantially the same
result in substantially the same way. The equivalent features include, for example,
features that perform substantially the same function, in substantially the same way
to achieve substantially the same result.
[0057] In this description, reference has been made to various examples using adjectives
or adjectival phrases to describe characteristics of the examples. Such a description
of a characteristic in relation to an example indicates that the characteristic is
present in some examples exactly as described and is present in other examples substantially
as described.
[0058] Whilst endeavoring in the foregoing specification to draw attention to those features
believed to be of importance it should be understood that the applicant may seek protection
via the claims in respect of any patentable feature or combination of features hereinbefore
referred to and/or shown in the drawings whether or not emphasis has been placed thereon.
1. A gas burner membrane for use with pure hydrogen gas or a hydrogen blend gas which
includes at least 30 vol. % hydrogen gas, the gas burner membrane comprising a sheet
of material with a plurality of holes, and wherein a ceramic coating is provided on
the sheet of material.
2. A gas burner membrane according to claim 1, wherein the thickness of the ceramic coating
is up to 2000 microns, and optionally wherein the thickness of the ceramic coating
is 30 - 300 microns, and optionally wherein the thickness of the ceramic coating is
50 - 200 microns.
3. A gas burner membrane according to any of the preceding claims, wherein the ceramic
coating comprises zirconium oxide, and optionally wherein the ceramic coating comprises
yttrium oxide.
4. A gas burner membrane according to any of the preceding claims, wherein the ceramic
coating comprises yttria-stabilized zirconia.
5. A gas burner membrane according to any of the preceding claims, wherein at least a
majority of the holes have a diameter equal to or less than 1.3 times the thickness
of the sheet of material.
6. A gas burner membrane according to any of the preceding claims, wherein at least a
majority of the holes have a diameter of between 0.1 and 1 mm.
7. A gas burner membrane according to any of the preceding claims, wherein the coating
is located on the outer surface of the gas burner membrane.
8. A gas burner membrane according to any of the preceding claims, wherein the gas burner
membrane is a flat gas burner membrane, a linear gas burner membrane or a cylindrical
gas burner membrane.
9. A gas burner membrane according to any of the preceding claims, wherein the sheet
of material is formed from sheet metal, and optionally wherein the sheet of material
is formed from sheet steel.
10. A gas burner membrane according to any of the preceding claims, wherein the ceramic
coating covers only a portion of the sheet of material, and optionally wherein substantially
all of the holes in the sheet of material are provided in the portion of the sheet
of material covered by the coating.
11. A gas burner combustion system including:
the gas burner membrane of any of the preceding claims; and
a hydrogen gas supply, wherein the hydrogen gas supply is a pure hydrogen gas supply
or a hydrogen blend gas supply which includes at least 30 vol. % hydrogen gas.
12. A method of forming a gas burner membrane, the method comprising:
forming a plurality of holes in a sheet of material; and
applying a ceramic coating onto the sheet of material.
13. A method according to claim 12, wherein the ceramic coating is applied using thermal
spraying, and optionally wherein the ceramic coating is applied using thermal plasma
spraying.
14. A method according to claim 12 or 13, wherein, prior to application, the ceramic is
in powder form with an average particle size of up to 100 microns.
15. A method of forming a gas burner combustion system comprising:
providing the gas burner membrane of any of the preceding claims; and
providing a hydrogen gas supply, wherein the hydrogen gas supply is a pure hydrogen
gas supply or a hydrogen blend gas supply which includes at least 30 vol. % hydrogen
gas.