CN212777312U - Flue gas recirculation system for ultra-supercritical secondary reheating boiler - Google Patents
Flue gas recirculation system for ultra-supercritical secondary reheating boiler Download PDFInfo
- Publication number
- CN212777312U CN212777312U CN202021685315.1U CN202021685315U CN212777312U CN 212777312 U CN212777312 U CN 212777312U CN 202021685315 U CN202021685315 U CN 202021685315U CN 212777312 U CN212777312 U CN 212777312U
- Authority
- CN
- China
- Prior art keywords
- flue gas
- main pipe
- gas recirculation
- nozzle
- hearth
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
Landscapes
- Chimneys And Flues (AREA)
Abstract
The utility model relates to a flue gas recirculation system for ultra supercritical double reheat boiler, which comprises a hearth, wherein a flue gas recirculation lower layer nozzle, a burner, an over fire air nozzle and a flue gas recirculation upper layer nozzle are arranged on the side wall of the hearth, the flue gas recirculation upper layer nozzle is positioned vertically above the uppermost over fire air nozzle, and the flue gas recirculation lower layer nozzle is positioned vertically below the lowermost burner; a recirculated flue gas main pipe is arranged between the hearth and the outlet flue of the dust remover, the recirculated flue gas main pipe comprises an upper recirculated flue gas main pipe and a lower recirculated flue gas main pipe, one end of the upper recirculated flue gas main pipe is communicated with an upper nozzle of the flue gas recirculation, and the other end of the upper recirculated flue gas main pipe is communicated with the lower recirculated flue gas main pipe; one end of the lower-layer recirculated flue gas main pipe is connected with the lower-layer nozzle of the flue gas recirculation, and the other end of the lower-layer recirculated flue gas main pipe is communicated with the outlet flue of the dust remover through the air preheater and the recirculation fan in sequence. The utility model discloses can realize the nimble adjustment of once reheat and the reheat steam temperature of secondary, promote boiler thermal efficiency effectively.
Description
Technical Field
The utility model belongs to the technical field of thermal power, especially, relate to a flue gas recirculation system for ultra supercritical secondary reheat boiler.
Background
At present, China still uses coal-fired thermal power generation as the most main power generation mode, and the adoption of a clean coal combustion technology with high efficiency and low pollution is an effective measure for meeting the current energy-saving and emission-reducing requirements under the background of gradual reduction of fossil energy and increasing environmental protection pressure. The double reheating technology is a method capable of effectively improving the thermoelectric conversion efficiency of a unit, and is one of the development directions of high-capacity and high-parameter ultra-supercritical units.
The existing double reheating technology has the following technical defects:
1) flexible adjustment of the primary reheat and secondary reheat steam temperatures cannot be achieved.
2) The smoke temperature at the outlet of the hearth is uneven, so that slag is formed on convection heating surfaces such as a screen superheater.
3) The combustion disturbance of the hearth is large.
4) The primary air side is easy to leak to the smoke side.
5) The recirculated flue gas main pipe is easy to block dust, and the recirculated fan blade is easy to wear.
6) The thermal efficiency of the boiler is low.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a flue gas recirculation system for ultra supercritical secondary reheat boiler to solve above-mentioned technical problem.
The utility model provides a flue gas recirculation system for an ultra-supercritical secondary reheating boiler, which comprises a hearth, wherein a hearth outlet is sequentially connected with a horizontal flue at the upper part of the hearth, a vertical flue at the right side of the hearth and a flue at the tail part of the hearth; an SCR catalyst layer, an air preheater and a dust remover are sequentially arranged in the flue at the tail part of the hearth, and the flue at the outlet of the dust remover is connected with a chimney through an induced draft fan;
the side wall of the hearth is provided with a flue gas recirculation lower-layer nozzle, a burner, an over-fire air nozzle and a flue gas recirculation upper-layer nozzle, the flue gas recirculation upper-layer nozzle is positioned vertically above the uppermost over-fire air nozzle, and the flue gas recirculation lower-layer nozzle is positioned vertically below the lowermost burner;
a recirculated flue gas main pipe is arranged between the hearth and an outlet flue of the dust remover, the recirculated flue gas main pipe comprises an upper recirculated flue gas main pipe and a lower recirculated flue gas main pipe, one end of the upper recirculated flue gas main pipe is communicated with an upper nozzle of the flue gas recirculation, and the other end of the upper recirculated flue gas main pipe is communicated with the lower recirculated flue gas main pipe; one end of the lower-layer recirculated flue gas main pipe is connected with the flue gas recirculation lower-layer nozzle, and the other end of the lower-layer recirculated flue gas main pipe is communicated with the dust remover outlet flue through an air preheater and a recirculation fan in sequence; the inlet of the upper nozzle of the flue gas recirculation is provided with an upper flue gas recirculation baffle door, and the inlet of the lower nozzle of the flue gas recirculation is provided with a lower flue gas recirculation baffle door.
Furthermore, the air preheater is sequentially provided with a recirculating flue gas side, a primary air side, a secondary air side and a flue gas side along the clockwise direction, and two sides of the recirculating flue gas side are respectively and closely adjacent to the flue gas side and the primary air side; the lower-layer recirculating smoke main pipe is arranged close to the primary air side and the smoke side.
Furthermore, a partition screen superheater, a rear screen superheater, a final superheater, a first primary high-temperature reheater and a first secondary high-temperature reheater are sequentially arranged in the horizontal flue at the upper part of the hearth.
Further, be equipped with the low temperature reheater of the second time, second secondary low temperature reheater, economizer and the baffle that adjusts the temperature in the vertical flue in furnace right side, the low temperature reheater of the second time, second secondary low temperature reheater are arranged side by side along the horizontal direction, the economizer correspond to arrange in low temperature reheater, second secondary low temperature reheater below are once to the second, the baffle that adjusts the temperature is arranged in the left side low temperature reheater of the second time, economizer and right side second secondary low temperature reheater, economizer along vertical direction.
Borrow by above-mentioned scheme, through the flue gas recirculation system of ultra supercritical secondary reheat boiler, have following technological effect:
1) part of flue gas extracted from the side surface of a flue at the outlet of a dust remover is heated by an air preheater and then is fed into a boiler furnace, the flue gas amount in the furnace is increased, the retention time of the flue gas in the boiler is shortened, the radiation heat absorption capacity of the furnace is reduced, the heat transfer capacity of a convection heating surface is increased, the heat absorption capacity of the heating surface positioned at the downstream of the flue gas flow is increased more, and the reheating steam temperature is obviously increased, so that the heat absorption capacity share of each heating surface in the furnace is changed, and the flexible adjustment of the primary reheating steam temperature and the secondary reheating steam temperature is realized.
2) When the recirculated flue gas enters the hearth through the upper-layer nozzles of the flue gas recirculation, the radiant heat absorption capacity of the hearth is reduced, meanwhile, the temperature of the flue gas at the outlet of the hearth is also reduced, the temperature of the flue gas at the outlet of the hearth can be reduced and uniform by adjusting the opening degree of the upper-layer flue gas recirculation baffle door, the slag bonding of convection heating surfaces such as a screen superheater and the like is prevented, the thermal deviation of the convection heating surfaces is reduced, and a good protection effect is achieved.
3) The opening degree of the upper baffle plate and the lower baffle plate of the flue gas recirculation system is coordinated and adjusted, so that combustion disturbance of the hearth can be reduced, combustion in the furnace is more reasonable, and reasonable combustion of the hearth and the temperature of reheated steam can be effectively improved.
4) The two sides of the recirculating flue gas side of the air preheater are close to the primary air side and the flue gas side, so that air leakage from the primary air side to the flue gas side is effectively reduced;
5) the flue gas recirculation system extracts part of flue gas from the outlet of the dust remover, and the flue gas only contains a small amount of fly ash particles, so that ash blockage of a main pipe of the recirculated flue gas and abrasion of blades of a recirculation fan are effectively reduced, and the output of an induced draft fan is reduced;
6) the recirculated flue gas is heated by the air preheater, so that the temperature of the recirculated flue gas can be increased, the temperature of exhaust gas is reduced, and the thermal efficiency of the boiler is effectively improved.
The above description is only an overview of the technical solution of the present invention, and in order to make the technical means of the present invention clearer and can be implemented according to the content of the description, the following detailed description is made of preferred embodiments of the present invention.
Drawings
FIG. 1 is a schematic structural diagram of a flue gas recirculation system of an ultra-supercritical double reheat boiler of the present invention;
fig. 2 is the structural schematic diagram of the flue gas recirculation system air preheater of the ultra-supercritical double reheat boiler of the present invention.
Reference numbers in the figures:
1-hearth; 2-flue gas recirculation lower layer nozzle; 3-a burner; 4-over-fire air nozzle; 5-flue gas recirculation upper nozzle; 6-split screen superheater; 7-rear screen superheater; 8-a finishing superheater; 9-a first primary high temperature reheater; 10-a first secondary high temperature reheater; 11-a second primary low temperature reheater; 12-a second secondary low temperature reheater; 13-a coal economizer; 14-temperature regulating baffle; 15-SCR catalyst layer; 16-an air preheater; 17-a dust remover; 18-a draught fan; 19-a chimney; 20-a recirculation fan; 21-a recirculated flue gas main pipe; 22-lower layer flue gas recirculation baffle door; 23-upper layer flue gas recirculation baffle door; 24-recirculated flue gas side; 25-primary air side; 26-secondary air side; 27-flue gas side.
Detailed Description
The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.
Referring to fig. 1, the present embodiment provides a flue gas recirculation system for an ultra-supercritical secondary reheat boiler, including a furnace 1, a flue gas recirculation lower nozzle 2, a burner 3, an over-fire air nozzle 4, a flue gas recirculation upper nozzle 5, a split screen superheater 6, a rear screen superheater 7, a final superheater 8, a first primary high temperature reheater 9, a first secondary high temperature reheater 10, a second primary low temperature reheater 11, a second secondary low temperature reheater 12, an economizer 13, a temperature regulation baffle 14, an SCR catalyst layer 15, an air preheater 16, a dust remover 17, an induced draft fan 18, a chimney 19, a recirculation fan 20, a recirculation flue gas main pipe 21, a lower flue gas recirculation baffle door 22, and an upper flue gas recirculation baffle door 23.
The upper nozzles 5 of the flue gas recirculation are symmetrically distributed on the side wall of the hearth 1, the lower nozzles 2 of the flue gas recirculation are positioned below the burner at the lowest layer, the upper nozzles 5 of the flue gas recirculation are positioned above the overfire air nozzles 4 at the uppermost layer, the partition screen superheater 6, the rear screen superheater 7, the final superheater 8, the first primary high-temperature reheater 9 and the first secondary high-temperature reheater 10 are sequentially arranged in a horizontal flue at the upper part of the hearth 1, the second primary low-temperature reheater 11, the second secondary low-temperature reheater 12, the economizer 13 and the temperature adjusting baffle 14 are arranged in a vertical flue at the right side of the hearth 1, the second primary low-temperature reheater 11 and the second secondary low-temperature reheater 12 are arranged in parallel along the horizontal direction, the economizer 13 is correspondingly arranged below the second primary low-temperature reheater 11 and the second secondary low-temperature reheater 12, and the temperature adjusting baffle 14 is arranged in the vertical direction at the left side of the second, The economizer 13 is arranged between the second secondary low-temperature reheater 12 and the economizer 13 on the right side;
the SCR catalyst layer 15, the air preheater 16 and the dust remover 17 are sequentially arranged in a flue at the tail part of the hearth 1 at the outlet of the economizer 13, the outlet of the economizer 13 is connected with the SCR catalyst layer 15 and the inlet of the air preheater 16 through pipelines, the inlet of the dust remover 17 is connected with the outlet of the air preheater 16 through a pipeline and a draught fan 18, and the draught fan 18 and a chimney 19 are connected through pipelines;
the recirculating flue gas main pipe 21 comprises an upper recirculating flue gas main pipe and a lower recirculating flue gas main pipe, one end of the upper recirculating flue gas main pipe is communicated with the upper nozzle 5 of the flue gas recirculation through an upper flue gas recirculating baffle door 23, and the other end of the upper recirculating flue gas main pipe is communicated with the lower recirculating flue gas main pipe; one end of the lower-layer recirculated flue gas main pipe is connected with the flue gas recirculation lower-layer nozzle 2 through a lower-layer flue gas recirculation baffle door 22, and the other end of the lower-layer recirculated flue gas main pipe is communicated with an outlet flue of the dust remover 17 through the air preheater 16 and the recirculation fan 20 in sequence. The upper layer of flue gas recirculation baffle door 23 is arranged at the inlet of the upper layer of flue gas recirculation nozzles 5, and the lower layer of flue gas recirculation baffle door 22 is arranged at the inlet 2 of the lower layer of flue gas recirculation nozzles.
Referring to FIG. 2, the air preheater 16 includes a recirculated flue gas side 24, a primary air side 25, a secondary air side 26 and a flue gas side 27 in a clockwise direction, and the recirculated flue gas side 24 is adjacent to the flue gas side 27 and the primary air side 25. The lower-layer recirculating flue gas main pipe is arranged close to the primary air side and the flue gas side of the air preheater, so that air leakage from the primary air side to the flue gas side is effectively reduced.
The recycling fan 20 extracts partial flue gas as recycling flue gas at the outlet of the dust remover 17 and the side surface of the flue at the inlet of the draught fan 18, the recycling flue gas enters the hearth along the flue gas recycling main pipe 21 through the air preheater 16, the lower layer flue gas recycling baffle door 22 and the flue gas recycling lower layer nozzle 2), the upper layer flue gas recycling baffle door 23 and the flue gas recycling upper layer nozzle 5, and the amount of the recycling flue gas entering the hearth is adjusted through the lower layer flue gas recycling baffle door 22 and the upper layer flue gas recycling baffle door 23. Flue gas not drawn by the recirculation fan 20 is exhausted from the stack 19 through the boiler back pass.
This a flue gas recirculation system for on ultra supercritical secondary reheat boiler, the low-load operation of unit is particularly useful for, has following technological effect:
1) part of flue gas extracted from the side surface of a flue at the outlet of a dust remover is heated by an air preheater and then is fed into a boiler furnace, the flue gas amount in the furnace is increased, the retention time of the flue gas in the boiler is shortened, the radiation heat absorption capacity of the furnace is reduced, the heat transfer capacity of a convection heating surface is increased, the heat absorption capacity of the heating surface positioned at the downstream of the flue gas flow is increased more, and the reheating steam temperature is obviously increased, so that the heat absorption capacity share of each heating surface in the furnace is changed, and the flexible adjustment of the primary reheating steam temperature and the secondary reheating steam temperature is realized.
2) When the recirculated flue gas enters the hearth through the upper-layer nozzles of the flue gas recirculation, the radiant heat absorption capacity of the hearth is reduced, meanwhile, the temperature of the flue gas at the outlet of the hearth is also reduced, the temperature of the flue gas at the outlet of the hearth can be reduced and uniform by adjusting the opening degree of the upper-layer flue gas recirculation baffle door, the slag bonding of convection heating surfaces such as a screen superheater and the like is prevented, the thermal deviation of the convection heating surfaces is reduced, and a good protection effect is achieved.
3) The opening degree of the upper baffle plate and the lower baffle plate of the flue gas recirculation system is coordinated and adjusted, so that combustion disturbance of the hearth can be reduced, combustion in the furnace is more reasonable, and reasonable combustion of the hearth and the temperature of reheated steam can be effectively improved.
4) The two sides of the recirculating flue gas side of the air preheater are close to the primary air side and the flue gas side, so that air leakage from the primary air side to the flue gas side is effectively reduced;
5) the flue gas recirculation system extracts part of flue gas from the outlet of the dust remover, and the flue gas only contains a small amount of fly ash particles, so that ash blockage of a main pipe of the recirculated flue gas and abrasion of blades of a recirculation fan are effectively reduced, and the output of an induced draft fan is reduced;
6) the recirculated flue gas is heated by the air preheater, so that the temperature of the recirculated flue gas can be increased, the temperature of exhaust gas is reduced, and the thermal efficiency of the boiler is effectively improved.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (4)
1. A flue gas recirculation system for an ultra-supercritical secondary reheating boiler is characterized by comprising a hearth, wherein a hearth outlet is sequentially connected with a hearth upper horizontal flue, a hearth right vertical flue and a hearth tail flue; an SCR catalyst layer, an air preheater and a dust remover are sequentially arranged in the flue at the tail part of the hearth, and the flue at the outlet of the dust remover is connected with a chimney through an induced draft fan;
the side wall of the hearth is provided with a flue gas recirculation lower-layer nozzle, a burner, an over-fire air nozzle and a flue gas recirculation upper-layer nozzle, the flue gas recirculation upper-layer nozzle is positioned vertically above the uppermost over-fire air nozzle, and the flue gas recirculation lower-layer nozzle is positioned vertically below the lowermost burner;
a recirculated flue gas main pipe is arranged between the hearth and an outlet flue of the dust remover, the recirculated flue gas main pipe comprises an upper recirculated flue gas main pipe and a lower recirculated flue gas main pipe, one end of the upper recirculated flue gas main pipe is communicated with an upper nozzle of the flue gas recirculation, and the other end of the upper recirculated flue gas main pipe is communicated with the lower recirculated flue gas main pipe; one end of the lower-layer recirculated flue gas main pipe is connected with the flue gas recirculation lower-layer nozzle, and the other end of the lower-layer recirculated flue gas main pipe is communicated with the dust remover outlet flue through an air preheater and a recirculation fan in sequence; the inlet of the upper nozzle of the flue gas recirculation is provided with an upper flue gas recirculation baffle door, and the inlet of the lower nozzle of the flue gas recirculation is provided with a lower flue gas recirculation baffle door.
2. The flue gas recirculation system for the ultra-supercritical double reheat boiler according to claim 1, wherein the air preheater is sequentially arranged with a recirculation flue gas side, a primary air side, a secondary air side, and a flue gas side in a clockwise direction, and the recirculation flue gas side is respectively adjacent to the flue gas side and the primary air side; the lower-layer recirculating smoke main pipe is arranged close to the primary air side and the smoke side.
3. The flue gas recirculation system for the ultra-supercritical double reheat boiler according to claim 1, wherein a partition screen superheater, a rear screen superheater, a final superheater, a first primary high temperature reheater and a first secondary high temperature reheater are sequentially arranged in the horizontal flue at the upper part of the furnace.
4. The flue gas recirculation system for the ultra-supercritical double reheat boiler according to claim 3, wherein a second primary low temperature reheater, a second secondary low temperature reheater, an economizer and a temperature regulation baffle are arranged in the vertical flue on the right side of the furnace, the second primary low temperature reheater and the second secondary low temperature reheater are arranged in parallel along the horizontal direction, the economizer is correspondingly arranged below the second primary low temperature reheater and the second secondary low temperature reheater, and the temperature regulation baffle is arranged between the left second primary low temperature reheater, the economizer and the right second secondary low temperature reheater and the economizer along the vertical direction.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021685315.1U CN212777312U (en) | 2020-08-13 | 2020-08-13 | Flue gas recirculation system for ultra-supercritical secondary reheating boiler |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021685315.1U CN212777312U (en) | 2020-08-13 | 2020-08-13 | Flue gas recirculation system for ultra-supercritical secondary reheating boiler |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN212777312U true CN212777312U (en) | 2021-03-23 |
Family
ID=75053651
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202021685315.1U Active CN212777312U (en) | 2020-08-13 | 2020-08-13 | Flue gas recirculation system for ultra-supercritical secondary reheating boiler |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN212777312U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114659099A (en) * | 2022-04-20 | 2022-06-24 | 西安热工研究院有限公司 | Flue gas circulation system for improving combustion characteristics and thermal characteristics of pulverized coal fired boiler |
-
2020
- 2020-08-13 CN CN202021685315.1U patent/CN212777312U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114659099A (en) * | 2022-04-20 | 2022-06-24 | 西安热工研究院有限公司 | Flue gas circulation system for improving combustion characteristics and thermal characteristics of pulverized coal fired boiler |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108758651A (en) | A kind of circulating fluidized bed boiler suitable for waste incineration | |
| CN103776020B (en) | Double reheat power station boiler with three rear flues and double rear baffles and capable of recycling jet flow flue gas | |
| CN107270274B (en) | Novel starting mode of ultra-supercritical coal-fired unit realizes unit full-load denitration input | |
| WO2015014233A1 (en) | Circulating fluidized bed boiler having secondary reheat | |
| CN110822418A (en) | Low NO of pi-shaped boiler under low loadXLow temperature flue gas recirculation system and method | |
| CN107101187B (en) | Heating system and heating method for supercritical carbon dioxide boiler | |
| CN107477564A (en) | A kind of biomass recirculating fluidized bed boiler flue gas waste heat recovery system and method | |
| CN103486563A (en) | Supercritical once-through boiler capable of firing eastern Junggar coal | |
| WO2022088686A1 (en) | Gas boiler tail flue gas energy-saving and emission-reduction system | |
| CN212777312U (en) | Flue gas recirculation system for ultra-supercritical secondary reheating boiler | |
| WO2023202634A1 (en) | Flue gas circulation system for improving combustion characteristics and thermal characteristics of pulverized coal fired boiler | |
| CN103438418A (en) | Double-n-shaped boiler | |
| CN111981469A (en) | Flue gas recirculation system for ultra-supercritical secondary reheating boiler | |
| CN109084319B (en) | Flue gas recirculation system adopting two stages for heat exchange | |
| CN111486440A (en) | System and method for adjusting reheating steam temperature of W flame boiler by adopting flue gas recirculation | |
| CN106287680A (en) | Small-sized biomass shaped fuel recirculating fluidized bed steam boiler | |
| CN106765035A (en) | Improve SCR temperature of reactor system and device and method | |
| CN109705920A (en) | Gasification of biomass couples coal unit power generator | |
| CN210050992U (en) | Coal-fired boiler type hot-blast stove | |
| CN103486574B (en) | Large-scale low First air power consumption supercritical circulating fluidized bed boiler | |
| CN102889585A (en) | Environment-friendly energy-saving vertical boiling boiler | |
| CN209944289U (en) | Double-hearth composite combustion corner tube boiler | |
| CN208652579U (en) | A kind of circulating fluid bed boiler structure suitable for waste incineration | |
| CN207990606U (en) | A kind of boiler is for exhaust system | |
| CN207162509U (en) | Improve SCR temperature of reactor system and devices |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant |