Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/12—Radiant burners
  • F23D14/18—Radiant burners using catalysis for flameless combustion
  • F23D14/181—Radiant burners using catalysis for flameless combustion with carbon containing radiating surface
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C13/00—Apparatus in which combustion takes place in the presence of catalytic material
  • F23C13/02—Apparatus in which combustion takes place in the presence of catalytic material characterised by arrangements for starting the operation, e.g. for heating the catalytic material to operating temperature

Definitions

• the present invention describes an oxidant supply system for a catalytic hydrogen burner setup, the use of a highly porous ceramic foam as an oxidant diffuser and a catalytic hydrogen burner setup, comprising a layer like arrangement of a first catalytic hydrogen burner and a second catalytic hydrogen burner forming part of a gas distribution setup which is integrated in a burner containment.
• a layer like burner setup 0, comprising a gas distribution setup 1, with a first catalytic burner 10 and a second catalytic burner 12 separated by an intermediate free space 14, is build .
• the first and the second burner 10, 12 are preferably formed like plates and are inserted and hold in a burner containment 2.
• An oxidant can be fed through an oxidant inlet 20 in the burner containment 2 into the intermediate free space 14, while hydrogen can be fed through a hydrogen inlet 21 into the burner containment 2.
• Both catalytic burners 10, 12 are formed by plates of nobel metals (Pt, Pd, Rh, Ir, ...) coated porous SiC foams.
• the introduced oxidant and the hydrogen 14 are building one reaction zone in and above the first catalytic burner 10 and a second reaction zone underneath and in the second catalytic burner 12 in direction of the longitudinal axis L.
• the lower flammability limit is therewith only reached inside these reaction zones in the near of the intermediate free space 14 between both catalytic burner 10, 12.
• the hydrogen slip above the reaction zone, above the second catalytic burner 12, reached was promising low, the reachable mixing of hydrogen and oxidant was not satisfying and should be improved to make indoor applications with secure catalytic hydrogen burner possible.
• the object of the present invention is to improve the hydrogen combustion in a hydrogen catalytic burner with high efficiency showing an improved controllable homogenous distribution of combustible (hydrogen) and the oxidant, leading to a needful combustible/oxidant ratio inside the catalytic combustion zone of the hydrogen catalytic burner setup and a decreased hydrogen slip.
• the problem is solved by building an improved mixing setup using a special oxidant supply system, which is part of a self igniting catalytic hydrogen burner setup.
• Such self igniting catalytic hydrogen burner setups can for example be used as parts of glass-ceramic cooktops.
• Figure 1 shows a schematic sectional view of a catalytic hydrogen burner according to the prior art. shows a schematic sectional view of a layer like mixing setup, comprising a first and a second catalytic burner separated by a oxidant diffuser, while
• FIG. 1 shows a schematic sectional view of one embodiment of a catalytic hydrogen burner setup, comprising a containment including the mixing setup, an additional hydrogen diffuser, hydrogen inlet and two oxidant inlets. shows the burner setup according to figure 3 with a glass- ceramic cover.
• a catalytic hydrogen reaction burner setup 0 is described.
• the fundamental idea is to bring the combustible, preferably hydrogen and the oxidant, air or pure oxygen together in a porous medium in the presence of a catalyst and thus producing heat without an open flame.
• no ignition is necessary and the process starts from below room temperature due to the nobel metal (Pt, Pd, Rh, Ir), preferred Pt-based catalyst.
• the reaction temperature consequently is lowered in relation to conventional H 2 combustion without Pt catalyst and no NO x emissions occur, while at the same time an ideal power modulation of the burner setup 0 is possible by adjusting the oxygen to hydrogen supply and lambda ratio.
• This burner setup 0 can be used for applications like cooking stoves, room heating, cars applications (heating, preheating of PEMS, etc.), barbeque and hydrogen safety applications.
• This novel catalytic hydrogen diffusion burner setup don't need a H 2 -air premix. By preventing gaseous hydrogen and oxygen from mixing prior to the catalytic reaction zone, a high passive safety standard is assured.
• an optimized gas distribution setup 1' functioning as oxidant supply system, comprising a first catalytic burner 10', a second catalytic burner 12' and an oxidant diffuser 16 separating both catalytic burner 10', 12' forming a sandwich structure.
• a first reaction zone rl between the first catalytic burner 10' and the oxidant diffuser 16 and a second reaction zone r2 between oxidant diffuser 16 and catalytic burner 12' are building up. Due to the laminary diffusion of the oxidant a homogenous combustion between the three layers 10 ⁇ 16, 12 ⁇ is achieved.
• the first and the second catalytic burner 10', 12' are formed of open- pored ceramics, preferably based on highly porous silicium carbide (SiC) ceramic foams, coated with fine dispersed Al 2 0 3 washcoat giving a high surface area and a nobel metal, preferred a platinum (Pt) or Pt and/or Pd and/or Rh and/or Ir-based catalyst to enhance the catalytic reaction .
• platinum platinum
• Pt platinum
• Rh platinum
• SiC based (SiC, SiSiC, clay bonded SiC, etc.) materials have a high thermal stability (up to 1400°C), a high thermal shock resistance high thermal conductivity and low Coefficient of Thermal expansion (CTE) meaning low material expansion and thus low mechanical stresses during heating and cooling .
• CTE Coefficient of Thermal expansion
• the porous SiC based (SiC, SiSiC, clay bonded SiC, etc.) ceramic itself is heated by the release of the heat, the catalytic burner 10', 12' are glowing in the visible part of the spectra, therefore giving optical feedback of the operation of the device.
• SiC based foams of 60 to 100 PPI (pores per inch) are used for the first and second catalytic burner 10', 12'. Due to their high temperature stability as well as high thermal conductivity and thermal shock resistance, the SiC based foam ceramic, for example SiC, SiSiC, clay bonded SiC, is predestinated for high temperature applications and long lifetime.
• the first and the second catalytic burner 10', 12' are formed like plates working as hydrogen distributer leading to a homogenous hydrogen distribution. The best results could be reached by using highly porous (60-95%) foam ceramics (60-100 PPI), with fine dispersed Al 2 0 3 for high surface area and Platinum based catalyst (Pt, Pd, etc.).
• FIG 3 shows a catalytic burner setup 0' with the gas distribution setup 1', hold in a burner containment 2'.
• the oxidant air or pure oxygen
• the oxidant is fed through multiple oxidant inlets 20 in the oxidant diffuser 16, sandwiched between the first and the second catalytic burner 10', 12'.
• an optional hydrogen diffuser 15' is placed in the burner containment 2'.
• At the bottom of the burner containment 2' at least one hydrogen inlet 21' is provided . Due to the sandwich structure an intrinsic prevention of H 2 leakage is insured and thus leading to a quite simple design.
• the oxidant is diffused laminary by the oxidant diffuser 16.
• the optional hydrogen diffuser 15' is diffusing the hydrogen in a laminar way.
• the thermal power can easily be regulated by adjusting the hydrogen and air flow rate so that temperatures between RT and 1200 °C on the SiC based surface can be adjusted. This is not possible for open flame hydrogen combustion processes without catalytic reaction.
• the catalytic combustion of hydrogen with air produces no polluting carbon oxides.
• the catalytic combustion is a low temperature reaction ( ⁇ 1000 °C) nitrogen oxide is not generated, the only exhaust product from the reaction is water vapour.
• the new developed catalytic burner setup 0' can thus be used safely indoors even without air ventilation systems.
• the step like design of the burner containment 2' helps to prevent leakage of hydrogen.
• the hydrogen cannot escape on the casing rim of the burner containment 2', it all has to pass at least the first reaction zone.
• the gas under glass technology was introduced by using a conventional glass ceramic cover 30, covering the burner setup 0' for a comfortable and convenient appliance.
• the gas distribution setup 1', hold in the burner containment 2' is covered at a cooking side by the glass ceramic cover 30, on the side opposed to the hydrogen inlet 21'.
• hydrogen pipe 41 hydrogen is fed from a hydrogen tank 42.
• a pump 43 or pressurised bottles air is fed via the oxidant pipe 40 in the oxidant diffuser 16.
• burner setups 0' comprising the improve gas d istribution setup 1 '
• preheating systems e.g . for PEM systems in cars etc.
• the air supply system or gas distribution setup 1' comprising the oxidant diffuser 16 in form of a porous ceramics a hydrogen-air homogenization is possible improving the hydrogen combustion.
• the resulting air turbulences in the porous foam structure of the oxidant diffuser 16 are used to reach a very homogenous air distribution in the two reaction zones rl, r2 between the catalytical burner 10', 12' and the oxidant diffuser 16.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Gas Burners (AREA)

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• 2014
  • 2014-01-15 EP EP14700860.1A patent/EP2946142A1/de not_active Withdrawn
  • 2014-01-15 WO PCT/EP2014/050712 patent/WO2014111427A1/en active Application Filing

Non-Patent Citations (2)

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