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COMBUSTION APPARATUS USING FLUENT FUEL (combustion apparatus for solid fuel only F23B; burners F23D; constructional details of combustion chambers not otherwise provided for F23M; combustion chambers for generating combustion products of high pressure or high velocity F23R)
Definition statement
This subclass/group covers:

General function-oriented aspects of methods and apparatus for combustion of

  • Fluent fuels, alone or in combination with other fluent or non-fluent fuels
  • Fluent fuels alternately with non-fluent fuels
  • Pulverised solid fuel suspended in a stream of air or other gas, e.g. combustion in fluidised beds or combustion of pulverised fuel using burners where the fuel is transported into the combustion chamber by an air stream
  • Solid fuel suspended in a liquid, e.g. combustion of coal-water slurry
Relationship between large subject matter areas

F23G, Cremation furnaces; Consuming waste by combustion is to be seen as an application place in relation to the function-oriented aspects of combustion covered by this subclass. In case of doubt, classification should be made in both subclasses, or in both F23G and detail subclasses of class F23.

Classification is made in F23C if the methods or apparatus:

  • are of general interest for combustion of different types of fluent fuel, for example not specially adapted for a particular fuel, or
  • specially adapted for fluent fuels other than those provided for in F23G, see the list below, for example "normal" commercial fluent fuel, such as oil, natural gas or pulverised coal.

Classification is made in F23G if the methods or apparatus are specially adapted for combustion of the following types of substances:

  • Fuels, e.g. waste, presenting particular fuel-related environmental problems requiring specially adapted methods or apparatus for combustion, for example toxic, explosive, radioactive or corrosive fuels
  • Waste having a special physical form requiring specially adapted methods or apparaus for combustion, for example packaged waste
  • Low-grade fuels presenting particular problems of combustion requiring specially adapted methods or apparatus for combustion, for example contaminated oil or gas of low heating value.

F23R, Generating combustion products of high pressure or high velocity, is also to be seen as an application place in relationship to this subclass.

Classification is made in F23R if the apparatus or method is specially adapted for generating combustion products of high pressure or high velocity.

Relationship between this subclass and other application places

Combustion of fluent fuel is often used for the purpose of heating or performing different operations. Apparatus for combustion of fluent fuel can be self-contained devices, but are often part of, or used in connection with, heat-consuming apparatus, such as heating boilers. This subclass is therefore related to several places providing for uses of heat. In many of these fields the fluent fuel combustion apparatus can be considered a detail of a bigger entity. A non-exhaustive list of examples of such classes or subclasses will be found under the heading "Informative references" below.

Combinations of combustion apparatus with other apparatus, where the combustion apparatus can be seen as a detail of the complete apparatus, e.g. a steam boiler, are classified as a whole, in the place for the other apparatus. Additional classification is made in this subclass only if features relating to the combustion apparatus per se are of interest apart from its application.

Relationship between this subclass and detail subclasses of class F23

Subclass F23D covers burners per se, as defined in the section "Glossary" below. Classification is made in F23C if the subject matter to be classified, in addition to a burner, includes further features that are of interest, such as a particular form of combustion chamber or a particular arrangement of burners in a combustion chamber. Air supply means that are arranged in immediate connection with the fuel-feeding conduit of a burner, for example concentric with it, should be considered to be part of the burner. Means for feeding air otherwise than in immediate connection with the fuel-feeding conduit of a burner are classified in F23C or F23L, for example arrangements for feeding secondary air at points distant from a burner.

Subclasses F23J - F23Q are to be seen as detail places in relation to this subclass. Classification is made in this subclass if the apparatus as a whole is of interest, or if a detail is of use only for a particular type of combustion apparatus and not specifically provided for in any of subclasses F23J - F23Q. If a detail of a combustion apparatus is of interest, classification is made in the relevant subclass providing for such matter.

References relevant to classification in this subclass
This subclass/group does not cover:
Candles
Burners

Examples of places where the subject matter of this class is covered when specially adapted, used for a particular purpose, or incorporated in a larger system:

Baking ovens
Cooking apparatus
Gas turbine plants
Lighting
Generating steam
Combustion specially adapted for waste or low grade fuel
Generating combustion products of high temperature or high pressure
Domestic stoves or ranges for cooking or local heating
Domestic heating systems or space-heating systems
Heating of fluids, e.g. air or water
Drying
Heat treatment of material or articles
Informative references
Attention is drawn to the following places, which may be of interest for search:
Chemical or biological purification of waste gases
Chemical or physical processes or apparatus in general
Combustion using solid fuel only
Removal or treatment of combustion products, e.g. flue gases or combustion residues, e.g. ash
Feeding fuel
Supplying air or other non-combustible liquids or gases, e.g. water or steam
Constructional details of combustion chambers, not otherwise provided for
Regulating or controlling combustion
Ignition
Heat-producing reactions of chemical substances, other than combustion, e.g. of hydrogen peroxide and methane, or iron oxide and aluminium
Special rules of classification within this subclass

In this subclass methods are classified in the groups that cover the apparatus used.

When classifying in this subclass, add codes F23C 2200/00 - F23C 2206/103 and F23C 2900/10001 - F23C 2900/09002.

Indexing Codes F23C 2700/00 - F23C 2700/066 shall not be used.

Glossary of terms
In this subclass/group, the following terms (or expressions) are used with the meaning indicated:
Air
a mixture of gases containing free oxygen and able to promote or support combustion
Primary air
air supplied to the burning fuel, e.g. together with the fuel in order to liberate combustible gases
Secondary air
air supplied to the combustible gases liberated by the primary air in order to complete their combustion. The expression "secondary air" covers "tertiary air" etc.
Burner
a device by which fluid fuel or solid fuel suspended in air is passed to a combustion space where it burns to produce a self-supporting flame. A burner includes means for feeding air that are arranged in immediate connection with a fuel feeding conduit, for example concentric with it.
Combustion
the direct combination of oxygen gas, e.g. in air, and a burnable substance
Combustion chamber
a chamber in which fuel is burned to establish a self-supporting fire or flame and which surrounds that fire or flame
Combustion zone
the part of an apparatus where the reaction takes place between air and fuel
Synonyms and Keywords

In patent documents the following abbreviations are often used:

CFB
Circulating fluidised bed
CWS
Coal-water slurry
EHC
Electrically-heated catalyst
FBN
Fuel bound nitrogen
HC
Hydrocarbons
NOx
Nitrous oxides
PFBC
Pressurised fluidised bed combustion
SOx
Sulfur oxides
UHC
Unburned hydrocarbons

In patent documents the word "boiler" is often used with the meaning "combustion apparatus", even when heating of water or other liquids is of no interest.

In patent documents the expression/word "burner" is often used with the meaning "combustion apparatus", and not in the restricted meaning defined above.

Combustion apparatus specially adapted for combustion of two or more kinds of fuel simultaneously or alternately, at least one kind of fuel being fluent ( combustion apparatus characterised by the combination of two or more combustion chambers F23C 6/00 ; pilot flame igniters F23Q 9/00)
Informative references
Attention is drawn to the following places, which may be of interest for search:
Combustion apparatus characterised by the combination of two or more combustion chambers
Waste incinerators having supplementary heating by gaseous or liquid fuel
Combustion apparatus wherein one fuel is used for igniting the other
Combustion apparatus characterised by the shape of the combustion chamber
Definition statement
This subclass/group covers:

Combustion apparatus wherein the shape or the location of the combustion chamber is of particular relevance, e.g. radiant tubes, cyclonic combustors and submerged combustors

Illustrative example: EP2299175, US547981, US2900930, WO2010/090453

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Informative references
Attention is drawn to the following places, which may be of interest for search:
Cyclonic combustion for waste
{the chamber being arranged for submerged combustion (F23C 3/002 takes precedence ) }
References relevant to classification in this group
This subclass/group does not cover:
Combustion apparatus wherein the combustion chamber is specially arranged for submerged combustion
Disposition of burners with respect to the combustion chamber or to one another; Mounting of burners in combustion apparatus (F23C 1/00 , F23C 15/00 take precedence )
Informative references
Attention is drawn to the following places, which may be of interest for search:
Arrangements or dispositions of combustion apparatus in steam boilers
Arrangement or mounting of burners in fluid heaters
to obtain a single flame of concentrated or substantially planar form, e.g. pencil or sheet flame (F23C 5/32 takes precedence )
References relevant to classification in this group
This subclass/group does not cover:
Disposition of burners to obtain rotating flames, i.e. flames moving helically or spirally
Combustion apparatus characterised by the combination of two or more combustion chambers {or combustion zones, e.g. for staged combustion}
References relevant to classification in this group
This subclass/group does not cover:
Consuming smoke or fumes in separate combustion apparatus
Informative references
Attention is drawn to the following places, which may be of interest for search:
Heat supply in steam boilers by installation of two or more combustion apparatus
Waste incinerators with secondary combustion in a separate combustion chamber
Water heaters having plural combustion chambers
Special rules of classification within this group

When classifying in this group, add codes F23C 2201/10 - F23C 2201/401.

Combustion apparatus characterised by arrangements for air supply ( inlets for fluidisation air F23C 10/20)
Definition statement
This subclass/group covers:

Aspects of the air supply related to the introduction of the combustion air into the combustion chamber in proximity of the burner, e.g. passages, swirling vanes, flow controlling means, limited to apparatus of methods for fluid fuels only.

References relevant to classification in this group
This subclass/group does not cover:
All aspects of air supply for non fluid fuels, e.g. solid waste
General aspects of air supply, independently from the type of fuel, e.g. secondary or overfire air passages, blowers or draft inducing means, details of dampers, heat recovery means
Special rules of classification within this group

Multiple classification should be applied when:

the subject matter to be classified deals with air supply means which are part of a burner and no relevant subgroup is available in F23D, e.g. arrangements of swirling vanes in a premix gas burner have to be classified in F23C 7/004 and F23D 14/02;

the subject matter to be classified, in addition to a burner, includes further features of the air supply means that are of interest, for example a particular form of a swirling vane, even if a relevant subgroup is available in F23D, e.g. an arrangement of adjustable swirling vanes in a non-premix gas burner having separate air and gas feed conduits have to be classified in F23C 7/006 and F23D 14/24

Combustion apparatus characterised by arrangements for returning combustion products or flue gases to the combustion chamber ( fluidised bed combustion apparatus with means for recirculation of particles entrained from the bed F23C 10/02 ; fluidised bed combustion apparatus with devices for removal and partial reintroduction of material from the bed F23C 10/26)
References relevant to classification in this group
This subclass/group does not cover:
Fluidised beds with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
Combined with devices for partial reintroduction of material into the bed, e.g. after separation of agglomerated parts
Fluidised bed incinerators with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
Informative references
Attention is drawn to the following places, which may be of interest for search:
Combustion apparatus using solid fuel with means for returning combustion products or flue gases
Special rules of classification within this group

When classifying in this group, add codes F23C 2202/10 - F23C 2202/50.

Fluidised bed combustion apparatus
Informative references
Attention is drawn to the following places, which may be of interest for search:
Fluidised bed apparatus comprising two or more beds
Fluidised bed apparatus comprising a rotating bed
Fluidised bed apparatus comprising a bed of catalytic particles
Fluidised bed apparatus comprising means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
Fluidised bed apparatus specially adapted for operation at super-atmospheric pressures, e.g. by the arrangement of the combustion chamber and its auxiliary systems inside a pressure vessel
Details and/or accessories for fluidised bed apparatus, e.g. inlets for fluidizing air, fuel feeders, controlling devices
Devices for removal of material from the bed combined with devices for partial reintroduction of material into the bed, e.g. after separation of agglomerated parts
Chemical or physical processes according to "fluidised-bed" technique in general
Waste incinerators having a fluidised bed
Fluidised bed furnaces or other similar apparatus for heat treatment of materials or articles
Special rules of classification within this group

When classifying in this group, add codes F23C 2206/10 - F23C 2206/103.

Other combustion apparatus using fluent fuel
Informative references
Attention is drawn to the following places, which may be of interest for search:
Applying electric means or magnetism to combustion in combustion engines
Using sound or vibrations in combustion engines
Special rules of classification within this group

F23C11/00 to F23C11/00M are not used anymore for classification, please refer to subgroups F23C 99/00 - F23C99/40 instead.

Apparatus in which combustion takes place in the presence of catalytic material ( in a fluidised bed of catalytic particles F23C 10/01 ; radiant gas burners using catalysis for flameless combustion F23D 14/18)
References relevant to classification in this group
This subclass/group does not cover:
Combustion in a fluidised bed of catalytic particles
Radiant gas burners using catalysis for flameless combustion
Informative references
Attention is drawn to the following places, which may be of interest for search:
Incinerators for waste gases or noxious gases in which combustion takes place in the presence of catalytic material
Combustion chambers for generating combustion products of high pressure or high velocity, characterised by the use of catalytic means
characterised by the catalytic material
Informative references
Attention is drawn to the following places, which may be of interest for search:
Catalysts per se
Apparatus in which combustion takes place in pulses influenced by acoustic resonance in a gas mass { ( for generating combustion products of high pressure or high velocity F23R 7/00 ; starting devices F23D 11/42) }
Informative references
Attention is drawn to the following places, which may be of interest for search:
Intermittent or explosive combustion chambers for generating combustion products of high pressure or high velocity
Starting devices
Special rules of classification within this group

When classifying in this group, add codes F23C 2205/10 - F23C 2205/20 if appropriate.

[N: Applying electric means or magnetism to combustion (for combustion engines F02B 51/04, F02M 27/04)
Informative references
Attention is drawn to the following places, which may be of interest for search:
Applying electric means or magnetism to combustion in combustion engines
[N: Combustion process using sound or vibrations (for combustion engines F02B 51/06, F02M 27/08; liquid fuel burners using ultrasonic means for spraying the fuel F23D 11/34)]
Informative references
Attention is drawn to the following places, which may be of interest for search:
Using sound or vibrations in combustion engines
Liquid fuel burners using ultrasonic means for spraying the fuel
[N: Suspension-type burning, i.e. fuel particles carried along with a gas flow while burning (fluidized-bed combustion apparatus F23C 10/00)]
References relevant to classification in this group
This subclass/group does not cover:
Fluidised bed apparatus
[N: Flameless combustion stabilised within a bed of porous heat-resistant material (F23C 13/00 takes precedence; gas burners with radiant combustion on a porous surface F23D 14/16)]
References relevant to classification in this group
This subclass/group does not cover:
Apparatus in which combustion takes place in the presence of catalytic material
Radiant gas burners with combustion on or in a porous body
Radiant gas burner with a catalyst flameless combustion
[N: Combustion methods wherein flame cooling techniques other than fuel or air staging or fume recirculation are used]
Special rules of classification within this group

When classifying in this subgroup, add codes F23C 2203/10 - F23C 2203/30 if appropriate.

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Last Modified: 10/11/2013