Classifications

• • 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 
  • F23C6/00—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion
  • F23C6/04—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection
  • F23C6/045—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with staged combustion in a single enclosure
  • F23C6/047—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with staged combustion in a single enclosure with fuel supply in stages
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
  • F23K3/00—Feeding or distributing of lump or pulverulent fuel to combustion apparatus
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements
  • F23N5/247—Preventing development of abnormal or undesired conditions, i.e. safety arrangements using mechanical means
• • 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 
  • F23C2201/00—Staged combustion
  • F23C2201/30—Staged fuel supply
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
  • F23K2201/00—Pretreatment of solid fuel
  • F23K2201/10—Pulverizing
  • F23K2201/1006—Mills adapted for use with furnaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
  • F23K2203/00—Feeding arrangements
  • F23K2203/008—Feeding devices for pulverulent fuel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
  • F23K2203/00—Feeding arrangements
  • F23K2203/10—Supply line fittings
  • F23K2203/105—Flow splitting devices to feed a plurality of burners

Definitions

• the invention relates, as set forth in the present specification, to a solid fuel combustion system (for example coal or biomass) sprayed in a boiler and a method, associated with said system, for the optimization of the process with a view to reducing emissions of polluting gases, such as nitrogen oxides, as well as to optimize the performance and operation of the boiler.
• a solid fuel combustion system for example coal or biomass
• polluting gases such as nitrogen oxides
• NO x mainly comprise NO and NO 2 and are among the Gaseous pollutants more harmful to health and the environment.
• Nitrogen oxides are precursors of photochemical smog and acid rain, phenomena with direct effects on the health of animals, vegetation and humans.
• the technologies applied to reduce ⁇ emissions in this type of facilities can be classified mainly into two groups: modifications and adjustments of the combustion process, or primary measures, and post-combustion abatement, or secondary measures.
• some of the strategies applied are those based on the stratification of air and fuel contributions to the boiler.
• the lines of action in existing units range from the adjustment of the operating parameters of the thermal group to the implementation of boiler modifications such as the installation of low NO x burners, OFA (Over Fire Air) registers. , UFA (Under Fire Air), etc.
• Stratification pursues combustion in two or more stages, of which the first or initial is rich in fuel and the second or subsequent are poor in fuel. It is about reducing the oxygen available in those areas where it is critical for the formation of ⁇ and reducing the amount of fuel burned at the maximum flame temperature. This procedure acts on the thermal NO (disadvantaged by rich mixtures) and on the NO of the fuel (promoting its transformation to N 2 in the fraction from the combustion of volatiles).
• JP 59145406 defines a NO x low-generation pulverized coal boiler equipped with a plurality of burners grouped into several levels or stages. The burners are divided into two groups, depending on the air / fuel ratio they are fed with: main burners and denitrification burners.
• the boiler has several levels of main burners and several levels of denitrification burners being in the latter the air / fuel ratio in the range 0.2-0.8.
• hydrocarbon radicals generated by sub-stoichiometric conditions in denitrification burners cause a global reduction of NO x emissions.
• the coal supply system to the boiler is designed in such a way as to guarantee the feeding to the levels of denitrification burners considered as keys for the process of global reduction of NO x , even in cases of a mill stop.
• the invention itself does not advocate any type of adjustment in the fuel inputs to each group of burners. In its conception it is established as a purely operational objective that, regardless of the mill that may be out of service, the design conditions with respect to coal injection are maintained.
• the present invention relates firstly to an optimized system for the combustion of pulverized solid fuel with a view to reducing emissions of polluting gases, such as nitrogen oxides, and / or improving the performance and operation of industrial boilers, such as those in power generation units.
• polluting gases such as nitrogen oxides
• Said system consists of a boiler equipped with a plurality of burners distributed in several groups arranged at different levels or in areas, each group consisting of several burners, a group of solid fuel mills that exceeds at least one the number of mills necessary to generate the maximum load of the boiler and means of transport of solid fuel that The mills communicate with the burners.
• the main particularity that introduces the invention is that it allows to establish patterns of differential contribution of solid fuel between each group of burners, associated to the achievement of a certain operational objective (reduction of NO x , improvement of performance, reduction of unburned, etc. ), so that these patterns are not modified by the specific unavailability of one of the mills.
• main burners located in different areas or levels, through which the solid fuel sprayed preferentially is injected into the boiler.
• main mills Solid fuel mills, called main mills, each connected to the main burners of a group. These mills will be in operation whenever the demand of load requires it.
• a solid fuel mill called a replacement mill, that would only operate at the stop of one of the main mills.
• Said mill would be connected to the burners of each of the main burner groups and, optionally, to a group of auxiliary burners. In this way, each group of main burners would be connected to their corresponding main mill and all of them parallel to the replacement mill.
• the mill feed Substitution in its entirety would result, through the connections and the appropriate gate sets, to the group of main burners whose mill has suffered a stop.
• Each distributor connects the replacement mill with a burner of each of the main burner groups to which the two-phase solid air-fuel current derives, in case of stopping of its associated main mill,
• a solid fuel mill called a support mill, also connected to each of the main burner groups and, optionally, to an additional group or level of auxiliary burners. Said mill would always be in operation, generating a solid fuel flow that would be added to the main burner groups. Therefore, each group of main burners would transport the solid fuel produced by its associated main mill plus a percentage of the distribution of the solid fuel flow produced by the support mill.
• Each divider connects the support mill with a burner of each of the main burner groups and generates adjustable flow flows of biphasic solid air-fuel mixture that are added to the vehicular currents through said burners to which it is connected.
• the division of the currents The output of the dividers is carried out by means of flow deflectors that are positioned according to the required distribution.
• connections between the inlet sections of the distributors and the flow dividers is contemplated. These connections would be enabled when a stop of the support mill occurs. In this way the replacement mill would fulfill the functions of the support mill in case of failure of the latter.
• the present invention therefore, allows to ensure and adjust the Contributions of fuel to certain groups of main burners, allowing to establish feeding patterns that can lead to a large stratification between different groups of burners, without the need to operate the mills away from their normal design point and regardless of the mill that may eventually be left out of service for maintenance or other purpose.
• the object of this invention is also an operation method that, using the elements described, allows the fuel to be stratified through the following process:
• Figure 1 shows a preferred embodiment of the invention applied to a tangential boiler equipped with 24 burners, arranged in 6 levels of 4 burners each located in the corners The burners and the transport ducts associated to one of the corners are represented, the arrangement being analogous to the other three.
• a typical pattern of solid fuel feed (coal typically) in conventional boilers is shown in Figure 2, with a view to producing a stratification of the fuel by levels for the reduction of NO x emissions.
• Figure 3 shows a pattern of fuel stratification, more pronounced than in the case of Figure 2, obtained by application of the present invention for achieving a greater reduction of NO x .
• Figure 4 shows a pattern obtained by application of the present invention for the reduction of NO x in compromise with the control of the level of unburned fuel.
• the tangential boiler (1) represented in Figure 1, equipped with 24 burners grouped in 6 levels or heights in groups of burners (2A, 2B, 2C, 2D, 2E, 2F) each comprising 4 burners per level located in the corners of the boiler (1), where the burner groups of the four lower levels consist of groups of main burners (2F, 2E, 2D, 2C) and the groups of burners of the two upper levels consist of groups of auxiliary burners (2A, 2B).
• the solid fuel feed (coal typically) to the boiler (1) comes from 6 mills (3A, 3B, 3C, 3D, 3E, 3F), from which a two-phase solid air-fuel mixture is distributed to the burners (2A, 2B, 2C, 2D, 2E, 2F) through a network of pneumatic transport ducts.
• the full load of the boiler (1) can be obtained with the contribution of only 5 of the mills in operation operating at their nominal point.
• the transport ducts to the burners of the groups (2A, 2B, 2C, 2D, 2E, 2F) located in one of the corners of the boiler (1) have been represented for simplicity, being the distribution for the rest of the three corners totally analogous.
• mills (3A, 3B, 3C, 3D, 3E, 3F) we distinguish firstly some main mills (3F, 3E, 3D and 3C), which feed respectively the main burner groups (2F, 2E, 2D, 2C ). From each of said main mills (3F, 3E, 3D and 3C), 4 pipes that transport fuel to the main burners of their corresponding level are derived.
• a replacement mill (3B) is also distinguished, from which 4 transport ducts also start, one for each corner. These ducts ascend to the level where the first group of auxiliary burners (2B) is located where they branch through first three-way connections (4) (one per corner) into 2 groups of alternative lines; some towards the first group of auxiliary burners (2B) and others towards the distributors (5) (there are 4 distributors, one per corner) descending with exits to the 4 lower levels.
• the first three-way connections (4) have guillotine valves (6, 7) connected to their 2 outputs to guarantee the total closure of one of the lines when the opposite is activated. Additionally they have a first deflector (8) to minimize the load losses caused by the change of direction.
• the distributors (5) derive the solid fuel flow from the replacement mill (3B) to one of the main burner groups (2F, 2E, 2D, 2B, 2C), the one whose corresponding main mill is out of service.
• the selection of the group of main burners (2F, 2E, 2D, 2B, 2C) fed by the replacement mill (3B) is carried out by means of guillotine valves (9, 10, 1 1, 12) and flow deflectors ( 13, 14, 15) associated with each exit of the distributors (5).
• outlets of the distributors (5) are connected to the ducts from the main mills (3F, 3E, 3D and 3C) through junctions (1 6, 17, 18, 19) located downstream of the guillotine valves (9, 10, 1 1, 12).
• a support mill from which 4 transport ducts, one for each corner, that rise to the level where a second group of auxiliary burners (2A) are located where they fork middle of a second three-way connections (20) (one per corner) in 2 groups of alternative lines; some towards the second group of auxiliary burners (2A) and others towards flow dividers (21) (there are 4 dividers, one per corner) descending with outputs to the lower 4 levels of burners.
• the second three-way connections (20) have two guillotine valves (22, 23) in their 2 outlets to guarantee the total closure of one of the lines when the opposite is activated. Additionally it has a second deflector (24) to minimize the load losses caused by the change of direction.
• the divider (21) of each corner divides the flow of solid fuel from the support mill (3A) in 4 streams of two-phase solid air-fuel mixture directed towards the burners of that corner belonging to the main burner groups (2F, 2E, 2D, 2C).
• Each of these support currents is connected to each duct that connects the distributor outlets (5) of that corner with the burners belonging to the main burner groups (2F, 2E, 2D, 2C) through the junctions (25 , 26, 27, 28) located between the guillotine valves (9, 10, 1 1, 12) and the junctions (1 6, 17, 18, 19) with the pipes coming from the main mills (3F, 3E, 3D , 3C).
• the distribution of the two-phase support mixture between the main burner groups (2F, 2E, 2D, 2C) is regulated by flow deflectors (29, 30, 31, 32) equipped with mechanisms for intermediate positioning depending on the distribution required in flows and granulometry of solid fuel.
• the distributor (5) and the divider (21) are connected through a connecting duct (33) provided with a guillotine valve (34) and third flow deflectors (35, 36). This connection allows the replacement mill (3B) to do the work of the support mill (3A) when it is out of service.
• the described configuration of the fuel transport system to the boiler (1) allows the application of operating methodologies that are not feasible or maintainable in conventional combustion units, in which each level of burners is fed exclusively by a single mill.
• FIG. 3 shows in percentage the production of each mill, the distribution of the production of the support mill (3A) between each level of groups of main burners (2F, 2E, 2D, 2C) and the total flow of vehicles per level of group of burners.
• the position of the guillotine valves and baffles that allow the achievement of the pattern is also represented.
• the 4 levels of groups of main burners (2F, 2E, 2D, 2C) would be fed through their respective mills (3F, 3E, 3D, 3C) operating at their nominal load.
• the replacement mill (3B) would remain stationary while the support mill (3A) would be in nominal operation contributing its production to the 4 lower divided levels, based on the position of the baffles (29, 30, 31, 32), in fractions of 30% for the two lower levels and 20% for the third and fourth.
• the guillotine valves (34) of the connecting ducts (33) would be opened.
• the distributors (5) and the dividers (21) communicate and the second deflectors (35, 36) would be activated to derive the currents from the replacement mill (3B) to the dividers (21), performing this mill the function of the support mill ( 3A).
• Figure 4 shows, with the same symbology as Figure 3, the configuration that allows establishing an operating pattern according to the defined strategy.
• the production of the replacement mill (3B) is derived to the fifth level where the first group of auxiliary burners (2B) is located by opening the guillotine valves (6), closing the guillotine valves (7) and activating the baffle (8) of the first 3-way connections (4).
• the only level of burners without power would be that corresponding to the second group of auxiliary burners (2A), while the main burner groups (2F, 2E, 2D, 2C) would be fed by their corresponding mills, operating slightly below of its nominal load and additionally each of them for a percentage of the production of the support mill (3A), which would also work below its nominal load.
• This injection pattern allows a better control of the unburned fuel in compromise with a significant reduction of NO x .

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Combustion Of Fluid Fuel (AREA)

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• 2010
  • 2010-01-22 US US13/521,970 patent/US20130040251A1/en not_active Abandoned
  • 2010-01-22 CN CN201080062160.9A patent/CN102822600B/zh not_active Expired - Fee Related
  • 2010-01-22 ES ES10707560.8T patent/ES2473990T3/es active Active
  • 2010-01-22 WO PCT/ES2010/070039 patent/WO2011089283A1/es active Application Filing
  • 2010-01-22 EP EP10707560.8A patent/EP2527735B1/en not_active Not-in-force
  • 2010-01-22 PL PL10707560T patent/PL2527735T3/pl unknown

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