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METHODS OR APPARATUS FOR COMBUSTION USING ONLY SOLID FUEL ( {for combustion of fuels that are solid at room temperatures, but burned in melted form, e.g. candle wax, C11C 5/00, F23C, F23D ; using solid fuel suspended in air F23C, F23D 1/00 ; using solid fuel suspended in liquids F23C, F23D 11/00; using solid fuel and fluent fuel simultaneously or alternately F23C, F23D 17/00; burning of low grade fuel F23G; grates F23H; feeding solid fuel to combustion apparatus F23K; combustion chambers, not otherwise provided for F23M; domestic apparatus F24; central heating boilers F24D; package boilers F24H} )
Definition statement
This subclass/group covers:

General function-oriented aspects of methods and apparatus for combustion of solid fuel wherein the main body of fuel is either

  • essentially stationary during combustion or
  • mechanically transported, as opposed to pneumatically transported or suspended in air, during combustion

and wherein the combustion does not involve liquid or gaseous fuels, or pulverulent fuel burned in suspension.

The solid fuel can be in the form of lumps or pieces, e.g. coal, briquettes or firewood, or pulverulent or granulated, e.g. coal powder, wood pellets or wood chips.

Relationship between large subject matter areas

Relationship between this subclass and application subclasses of class F23.

Subclass F23G, Cremation furnaces; Consuming waste by combustion is to be seen as an application place in relation to the function-oriented aspects of 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 this subclass if the method or apparatus is:

  • of general interest for combustion of different types of solid fuel, for example not specially adapted for a particular fuel, or
  • specially adapted for specific solid fuels other than those provided for in F23G, see the list below, for example "normal" commercial fuel, such as coal, firewood, wood chips, wood pellets or straw.

Classification is made in F23G if a method or apparatus is specially adapted for combustion of any of the following types of substances:

  • Human corpses or amputated body parts;
  • Animal carcasses or their discarded body parts;
  • 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 apparatus for combustion, for example packaged waste, rubber tyres or discarded cars;
  • Low-grade fuels presenting particular problems of combustion requiring specially adapted methods or apparatus for combustion, for example fuels containing high amounts of water or other non-combustible substances;
  • Fuels that vary considerably in composition or form and therefore require specially adapted methods or apparatus for combustion;
  • Household, municipal, or similar waste that is solely or primarily burned for the purpose of its destruction.

Subclass F23R, Generating combustion products of high pressure or high velocity, especially group F23B 5/00, 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 solid fuel is often used for purpose of heating or performing different operations. Apparatus for combustion of solid 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 solid 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.

Subclasses F23H - 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 F23H - F23Q. If a detail of a combustion apparatus is of interest, classification is made in the relevant subclass providing for such matter.

Relationship between this subclass and places for gasification or destructive distillation.

C10B covers destructive distillation of carbonaceous material for production of gas, coke, tar or similar matter.

C10J covers production of combustible gases containing carbon monoxide from solid carbonaceous fuels.

Classification is made in these subclasses if the combustible substances produced, e.g. gases or coke, are burned in an apparatus separate from the gasification or distillation apparatus.

Classification is made in this subclass if complete combustion takes place in the same apparatus as the gasification, for example in different parts of the same combustion chamber or in an afterburner immediately connected to a primary combustion chamber.

References relevant to classification in this subclass
This subclass/group does not cover:
Combustion of both solid fuel and fluent fuel, simultaneously or alternately
Combustion of solid fuel suspended in a stream of air, 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
Combustion of solid fuel suspended in a liquid, e.g. combustion of coal-water slurry
Combustion of fuels that are solid at room temperatures, but burned in melted form, e.g. candle wax

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
Lighting
Generating steam
Combustion specially adapted for waste or low grade fuel
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 apparatus using fluent fuel
Burners for fluent fuel, e.g. pulverulent fuel
Grates, cleaning or raking of grates
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, the first place priority rule is applied, i.e. at each hierarchical level, classification is made in the first appropriate place.

In this subclass methods are classified in the groups that cover the apparatus used. Methods that are of general applicability are classified in group F23B 90/00.

When classifying in this subclass, add the Indexing Codes:

R23B900/001-F23B 2900/99001.

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 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 term "secondary air" covers "tertiary air" etc.
Ash
means any solid combustion residues, for example remaining in the fuel bed or suspended in the flue gases
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
Combustion
means 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 the apparatus where the reaction takes place between air and fuel
Firebridge
a low wall separating the fuel bed from adjacent flue gas passages in apparatus for combustion of solid fuel, for example in reverberatory furnaces or fire-tube boilers
Flue gases
any gaseous products of combustion
Grate
a perforated surface, e.g. a grid, which supports or delimits a bed of burning fuel and serves to supply primary air
Synonyms and Keywords

In patent documents the expression/word "boiler" is often used with the meaning "combustion apparatus".

In patent documents the expression/word "burner" is often used with the meaning "combustion apparatus".

Combustion apparatus using only lump fuel
Definition statement
This subclass/group covers:

Combustion apparatus using only lump fuel.

Special rules of classification within this group

F23B 1/00 to F23B 1/12 are not used anymore for classification, please refer to groups F23B 10/00 - F23B 99/00 instead.

Combustion apparatus which is portable or removable with respect to the boiler or other apparatus which is heated
Definition statement
This subclass/group covers:

Combustion apparatus which is portable or removable with respect to the boiler or other apparatus which is heated.

Special rules of classification within this group

F23B 3/00 is not used anymore for classification, please refer to groups F23B 10/00 - F23B 99/00 instead.

Combustion apparatus with arrangements for burning uncombusted material from primary combustion { (combustion apparatus characterised by the combination of two or more combustion chambers F23C 6/00; the primary combustion being pulverulent fuel F23C 9/003) }
Definition statement
This subclass/group covers:

Combustion apparatus with arrangements for burning uncombusted material from primary combustion.

Special rules of classification within this group

F23B 5/00 to F23B 5/04 are not used anymore for classification, please refer to groups F23B 10/00 - F23B 99/00 instead.

Combustion techniques; Other solid-fuel combustion apparatus
Definition statement
This subclass/group covers:

Combustion techniques; Other solid-fuel combustion apparatus.

Special rules of classification within this group

F23B 7/00 to F23B 7/007 are not used anymore for classification, please refer to groups F23B 10/00 - F23B 99/00 instead.

Combustion apparatus characterised by the combination of two or more combustion chambers
Definition statement
This subclass/group covers:

Combustion apparatus characterized by the combination of two or more combustion chambers.

References relevant to classification in this group
This subclass/group does not cover:
Combustion methods including secondary combustion in the same combustion chamber
F23B99/04
including separate secondary combustion chambers
Definition statement
This subclass/group covers:

Combustion apparatus including two or more combustion chambers in which one of the combustion chambers works as a secondary combustion chamber.

Combustion apparatus including two or more physically separated combustion zones, e.g. by a perforated partition wall in a single enclosure in which one of the combustion zones works as a secondary combustion chamber.

Informative references
Attention is drawn to the following places, which may be of interest for search:
Waste or low grade fuel incinerators with separate secondary combustion chamber
Combustion methods or apparatus adapted for combustion of waste gases or noxious gases, e.g. exhaust gases
Combustion apparatus using fluent fuel with two or more combustion chambers in series connection
Combustion apparatus specially adapted for portability or transportability
Informative references
Attention is drawn to the following places, which may be of interest for search:
Portable or movable incinerators for waste
Combustion apparatus with driven means for agitating the burning fuel; Combustion apparatus with driven means for advancing the burning fuel through the combustion chamber
Definition statement
This subclass/group covers:

Combustion apparatus using e.g. rotary, vibrating or travelling grates, reciprocating bars or pushers, rocking bars, screw conveyors or any other means located inside the combustion chamber for agitating or advancing the fuel.

References relevant to classification in this group
This subclass/group does not cover:
Combustion grates or details of grates per se
with fuel-supporting surfaces that are rotatable around a horizontal or inclined axis and support the fuel on their inside, e.g. cylindrical grates
Informative references
Attention is drawn to the following places, which may be of interest for search:
Waste incinerators having rotating drums
Revolving cylindrical grates per se
with fuel-supporting surfaces that move through the combustion zone, e.g. with chain grates
Informative references
Attention is drawn to the following places, which may be of interest for search:
Travelling grates per se
with fuel-supporting surfaces having fuel advancing elements that are movable, but remain essentially in the same place, e.g. with rollers or reciprocating grate bars
Informative references
Attention is drawn to the following places, which may be of interest for search:
Grates with movable bars per se
Combustion apparatus with driven means for feeding fuel into the combustion chamber
Definition statement
This subclass/group covers:

Combustion apparatus using e.g. throwing devices, reciprocating pushers, screw conveyors or other driven means located outside the combustion chamber for supplying fuel directly into the combustion chamber.

References relevant to classification in this group
This subclass/group does not cover:
Combustion apparatus wherein the driven means, located outside the combustion chamber, advance the fuel only up to a location above the burning bed, from where it proceeds by gravity, e.g. on a slide or chute
the fuel being fed by scattering over the fuel-supporting surface
Informative references
Attention is drawn to the following places, which may be of interest for search:
Pneumatic feeding arrangements per se
Spreader stokers per se
the fuel being fed from below through an opening in the fuel-supporting surface
Informative references
Attention is drawn to the following places, which may be of interest for search:
Under-feed arrangements per se
Combustion apparatus in which the fuel is fed into or through the combustion zone by gravity, e.g. from a fuel storage situated above the combustion zone
Definition statement
This subclass/group covers:

Combustion apparatus using gravity as sole means for feeding the fuel into the combustion zone.

Informative references
Attention is drawn to the following places, which may be of interest for search:
Over-feed arrangements per se
Stoves with fuel storage in hoppers
Combustion apparatus in which the fuel burns essentially without moving
Definition statement
This subclass/group covers:

Combustion apparatus wherein the fuel is loaded on a grate or on a support on which it rests till complete exhaustion without further move or agitation.

Combustion apparatus characterised by means returning solid combustion residues to the combustion chamber
Definition statement
This subclass/group covers:

Combustion apparatus wherein solid combustion residues, e.g. ashes or fly-ashes are returned to the chamber for complete burning.

References relevant to classification in this group
This subclass/group does not cover:
Fluidised bed combustors for solid fuels.
Combustion apparatus characterised by means creating a distinct flow path for flue gases or for non-combusted gases given off by the fuel
Definition statement
This subclass/group covers:

Combustion apparatus having either means guiding the flue gas along specific path, e.g. for increasing heat transfer to the heat recovery means or creating longer permanence time of the gases in the combustion chamber, or for flue gas recirculation.

Informative references
Attention is drawn to the following places, which may be of interest for search:
Devices for conducting smoke or fumes per se
Flue gas circulation on or around stoves
by means for guiding the flow of flue gases, e.g. baffles
Informative references
Attention is drawn to the following places, which may be of interest for search:
Baffles or deflectors for combustion products per se
Combustion methods not related to a particular type of apparatus
Definition statement
This subclass/group covers:

Methods for starting the combustion, for staged combustion, i.e. a first combustion in a oxidant deficient atmosphere followed by secondary combustion in oxidant rich atmosphere, or for catalytic combustion.

Start-up techniques
Informative references
Attention is drawn to the following places, which may be of interest for search:
Ignition in general
Controlling combustion
including secondary combustion (in separate combustion chambers F23B 10/02)
References relevant to classification in this group
This subclass/group does not cover:
Combustion apparatus including separate secondary combustion chambers
Informative references
Attention is drawn to the following places, which may be of interest for search:
Waste or low grade fuel incinerators with secondary combustion
Combustion methods or apparatus adapted for combustion of waste gases or noxious gases, e.g. exhaust gases
Supplying secondary air
F23L/00
the primary combustion being a gasification or pyrolysis in a reductive atmosphere
Definition statement
This subclass/group covers:

Among combustion methods including secondary combustion, those involving gasification or pyrolysis in a reductive atmosphere in the primary zone, and, involving combustion in an oxidative atmosphere in the secondary zone.

Informative references
Attention is drawn to the following places, which may be of interest for search:
Combustion methods or apparatus adapted for waste or low grade fuel including pyrolising or gasifying as pretreatment
Destructive distillation of carbonaceous materials
in the presence of catalytic material
Informative references
Attention is drawn to the following places, which may be of interest for search:
Combustion apparatus using fluent fuel in which combustion takes place in the presence of catalytic material
Combustion methods or apparatus adapted for combustion of waste gases or noxious gases, e.g. exhaust gases, in which combustion takes place in the presence of catalytic material
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Last Modified: 10/11/2013