CN104896495A - In-boiler flue gas heat exchange heat system providing urea pyrolysis heat source - Google Patents
In-boiler flue gas heat exchange heat system providing urea pyrolysis heat source Download PDFInfo
- Publication number
- CN104896495A CN104896495A CN201510315955.0A CN201510315955A CN104896495A CN 104896495 A CN104896495 A CN 104896495A CN 201510315955 A CN201510315955 A CN 201510315955A CN 104896495 A CN104896495 A CN 104896495A
- Authority
- CN
- China
- Prior art keywords
- heat exchanger
- boiler
- gas
- air compartment
- flue gas
- 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.)
- Granted
Links
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
- Y02E20/30—Technologies for a more efficient combustion or heat usage
Landscapes
- Treating Waste Gases (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
The invention discloses an in-boiler flue gas heat exchange heat system providing a urea pyrolysis heat source, and belongs to the field of power station boiler flue gas denitration. The system comprises a boiler and a gas-gas heat exchanger; the gas-gas heat exchanger comprises multiple rows of a heat exchanger tube coil, an inlet wind chamber communicated with an inlet of the heat exchanger tube coil, an inlet wind chamber interface of the inlet wind chamber, an outlet wind chamber communicated with an outlet of the heat exchanger tube coil, and an outlet wind chamber interface of the outlet wind chamber; the inlet and outlet wind chamber interfaces are connected with a ventilation pipeline through expansion joints; the heat exchanger tube coil is arranged into the multiple rows in parallel between a left-side wall enclosure and a right-side wall enclosure, and is hung onto boiler hanging tube overheater tubes through a fixing device; the inlet and outlet wind chambers are fixed and arranged in a manner that the inlet and outlet wind chambers are tightly attached to a rear wall enclosure, and are composed of multiple sections of wind chambers which are connected through expansion joints in the boiler width direction; and the various sections of the wind chambers are symmetrically arranged according to the center line of the boiler. The system has the small influence on the boiler and has good heat exchanger performance, and the system overcomes the problems of heat exchanger dust deposition and obstruction, which are resulted from a high-dust flue gas, of a conventional shell and tube type heat exchanger arranged outside a boiler.
Description
Technical field
The invention belongs to flue gas in power station boiler denitration field, particularly relate to gas-gas heat exchanger in a kind of stove that denitrification reducing agent urea pyrolysis thermal source is provided.
Background technology
Urea is adopted by power plant more and more as denitrification reducing agent.Urea pyrolysis method technique comparatively conventional in current engineering is that cold (heat) First air of air or boiler is heated to about the 600 DEG C thermals source as urea pyrolysis by heater or heat exchanger.
Heater adopts electrical heating or burner heating usually; Heat exchanger is then cold (heat) First air utilizing high temperature flue-gas from boiler to add hot-air or boiler.For energy-conservation object, heat exchanger technology is applied to denitrating flue gas urea pyrolysis field more and more.
Patent document: notification number CN202609955U, Chinese utility model patent prospectus proposes a kind of denitration urea pyrolysis Ammonia Process device, at boiler exterior, heat exchanger is set, according to diagram, the shell-and-tube heat exchanger that heat exchanger structure pattern is arranged horizontally, the air in flue gas inflow heat exchanger shell heating tube bundle is drawn, for SCR denitration reducing agent urea pyrolysis from boiler; Its defect is: even if installed soot blower in heat exchanger inside, but because the boiler smoke of drawing is owing to can cause heat exchanger dust stratification, blocking and affect air heat containing the flue dust of high concentration.Notification number CN203824376U, it is the improvement that heat exchanger carries out on the basis of notification number CN202609955U, horizontal heat exchanger is modified into the pipe shell type heat exchange structure of vertical, the air of the flue gas shell of the high dust concentration of circulation in tube bank, though this arrangement can slow down dust stratification, blocking in tube bank, can not high concentration flue dust blockage problem be solved at all and affect heat exchange.
Patent document: publication No. CN103191640A, Chinese invention patent application prospectus proposes a kind of SCR denitration reducing agent urea pyrolysis thermal source supply method and device, heat exchanger is arranged in boiler smoke region, the heating of the First air of heat is used for SCR denitration reducing agent urea pyrolysis, the structural shape of undeclared heat exchanger.
Hinge structure is arranged in the simple and easy to do of heat exchanger outside boiler, the heat exchanger difficulty be arranged in boiler is higher, prior art is also only often the general simple imagination proposing to arrange in a stove heat exchanger, there are no the scheme of specific implementation, solved because it exists two remarkable difficult problems always:
1) gas-gas heat exchanger is on the impact of boiler, heat exchanger is arranged in boiler, will inevitably cause significant impact to boiler, and first is the impact of the configuration aspects of boiler own, be exactly the impact on running environment original in boiler on the other hand, as the impact etc. on boiler efficiency and swelling heat stress.
2) hinge structure is arranged in the heat exchanger outside boiler, and boiler internal running environment is complicated, in this complex environment, how to ensure a superperformance difficult problem especially for gas-gas heat exchanger.
Summary of the invention
The object of the invention is to: the hot heat-exchange system of inner flue gas of the stove proposing a kind of pyrolysis thermal source of supplying urea, on the impact of boiler is little and heat exchange property good, and overcome heat exchanger dust stratification, the blockage problem that shell-and-tube heat exchanger that conventional stove arranges causes due to high cloud of dust conductance outward.
The object of the invention is realized by following technical proposals:
A kind of hot heat-exchange system of inner flue gas of the stove of pyrolysis thermal source of supplying urea, comprise boiler and gas-gas heat exchanger, described gas-gas heat exchanger comprises some row's heat exchanger pipeloops, with import air compartment and the import air compartment interface thereof of heat exchanger pipeloop inlet communication, with the outlet air compartment of Tube Sheet of Heat Exchanger circle outlet and export air compartment interface, described enter, outlet air compartment interface is connected with ventilation shaft by expansion joint, described heat exchanger pipeloop is the some rows of one-tenth arranged in parallel between left side bag wall to right side bag wall, and by fixture lodge on boiler hanging pipe superheater pipe, described heat exchanger pipeloop is by Tube Sheet of Heat Exchanger horizontal-extending come back to be bent to form pipeloop on perpendicular on bag wall to mid-board direction after boiler, Tube Sheet of Heat Exchanger from pass between the band steel of bag wall after boiler described enter, in outlet air compartment, and Tube Sheet of Heat Exchanger is entered described in close, outlet air compartment place is bent to form fork configuration, described enter, outlet air compartment is close to rear bag wall fixed and arranged, and connected and composed by expansion joint on boiler width direction by some sections of air compartments, each section of air compartment is arranged symmetrically with by boiler center line.
As selection, described heat exchanger pipeloop is provided with shoe near mid-board one end.
In such scheme, reduce flue gas to the erosive wear of gas-gas heat exchanger.
As selection, described heat exchanger pipeloop entirety is in nearly " Y " font.
As selection, the Tube Sheet of Heat Exchanger of described heat exchanger pipeloop is bent to form fork configuration part at described import and export air compartment place is 10 ° ~ 90 ° with horizontal plane angle.
In such scheme, minimize the differential expansion of heat exchanger pipeloop along boiler for deeply direction.
As selection, described heat exchanger pipeloop is also provided with pipe clamp and fixes its Tube Sheet of Heat Exchanger bent back and forth.
As selection, described gas-gas heat exchanger is arranged in boiler tail vertical shaft low temperature superheater or low-temperature reheater region.
In such scheme, heat exchanger is arranged in boiler rear steering room place, and comparatively large to washing away of gas-gas heat exchanger from stokehold toward stove rear to flue gas in this position, heat exchange property is better.
The main scheme of aforementioned the present invention and each further selection scheme thereof can independent assortment to form multiple scheme; be the present invention can adopt and claimed scheme: as the present invention; each selection can select any combination with other; those skilled in the art can understand there is multiple combination according to prior art and common practise after understanding the present invention program; be the claimed technical scheme of the present invention, do not do exhaustive at this.
The course of work is: denitrification apparatus is as the important component part of thermal power plant, and boiler and denitration are integrally considered by the present invention, makes full use of residual heat from boiler fume and provides thermal source for SCR denitration urea pyrolysis, can create good economic benefit for power plant.Flue gas-air heat exchanger is preferably arranged in boiler tail vertical shaft low temperature superheater or low-temperature reheater region by this invention, flue-gas temperature is between 400 DEG C ~ 900 DEG C, heat exchanger is connected with the device producing heat (cold) First air and introduces the flue gas of First air by above-mentioned boiler smoke region, and the hot blast after heat exchanger heating is incorporated into urea pyrolysis reactor again provides pyrolysis thermal source for it.
Beneficial effect of the present invention: the present invention is by position, arrangement form, the arrangement of specific restriction heat exchanger, and the combination of this three aspect, had both decreased as far as possible and in turn ensure that good heat exchange property to the impact of boiler.
The present invention, by being close to importing and exporting air compartment the mode that bag wall is fixing after boiler, making the thermal stress difference between air compartment and boiler greatly reduce, avoiding the destruction to steam generator system; Importing and exporting air compartment is one section every a segment distance, adopts expansion joint to connect between air compartment, reduces differential expansion between boiler and air compartment further, safe and reliable.
Structure of the present invention and arrangement form, the impact minimized for boiler internal running environment maximizes heat exchange efficiency simultaneously, can save again gas-gas heat exchanger tube connector tubing simultaneously, reduce the cost of gas-gas heat exchanger equipment; And be not required to be the erecting by overhang that import and export header arranges complexity.
Structure of the present invention is simple, and conveniently, the flue gas heat making full use of large-sized station boiler adds the thermal source of hot-air as urea pyrolysis for manufacture and in-site installation, will create significant commercial value on power plant runs.
Accompanying drawing explanation
Fig. 1 is the gas-gas heat exchanger arrangement schematic front view of the embodiment of the present invention;
Fig. 2 is the gas-gas heat exchanger arrangement schematic top plan view of the embodiment of the present invention;
Wherein heat exchanger pipeloop 1, import air compartment 2, import air compartment interface 3, outlet air compartment 4, outlet air compartment interface 5, air compartment fixture 6, smoke sealing device 7, shoe 8, pipe clamp 9, pipeloop fixture 10, boiler hanging pipe superheater pipe 11, rear bag wall 12, mid-board 13, left side bag wall 14, right side bag wall 15.
Detailed description of the invention
Following non-limiting examples is for illustration of the present invention.
Shown in figure 1,2, a kind of hot heat-exchange system of inner flue gas of the stove of pyrolysis thermal source of supplying urea, comprises boiler and gas-gas heat exchanger, and gas-gas heat exchanger is arranged in boiler tail vertical shaft low temperature superheater or low-temperature reheater region.Gas-gas heat exchanger comprises some row's heat exchanger pipeloops 1, with import air compartment 2 and the import air compartment interface 3 thereof of heat exchanger pipeloop 1 inlet communication, with the outlet air compartment 4 of heat exchanger pipeloop 1 outlet and export air compartment interface 5, enter, outlet air compartment interface 3, 5 are connected with ventilation shaft by expansion joint, heat exchanger pipeloop 1 is the some rows of one-tenth arranged in parallel between bag wall 14 to right side, left side bag wall 15, and (utilize boiler original hanging pipe superheater pipe to carry out hanging to fix on boiler hanging pipe superheater pipe 11 by pipeloop fixture 10 lodge, harmless boiler structure), heat exchanger pipeloop 1 is by Tube Sheet of Heat Exchanger horizontal-extending come back to be bent to form pipeloop on perpendicular on bag wall 12 to mid-board 13 direction after boiler, Tube Sheet of Heat Exchanger from pass between the band steel of bag wall 12 after boiler into, outlet air compartment 2, in 4, and Tube Sheet of Heat Exchanger near enter, outlet air compartment 2, 4 places are bent to form fork configuration, part and the horizontal plane angle a of this fork configuration are 10 ° ~ 90 °, heat exchanger pipeloop 1 entirety is in nearly " Y " font (see Fig. 1).Heat exchanger pipeloop 1 is provided with abrasionproof cladding system 8 near mid-board 13 one end, in order to reduce from stokehold toward stove rear to flue gas the erosive wear of gas-gas heat exchanger, heat exchanger pipeloop 1 is also provided with pipe clamp 9 and fixes its Tube Sheet of Heat Exchanger bent back and forth, pipe clamp 9 fixes in order to heat exchanger pipeloop 1.Import and export air compartment 2,4 is close to rear bag wall 12 fixed and arranged, and is connected and composed by expansion joint on boiler width direction by some sections of air compartments, and each section of air compartment is arranged symmetrically with by boiler center line.
Said system is arranged, workflow:
The pipeline of power plant fans outlet is connected with gas-gas heat exchanger import air compartment interface 3 by expansion joint, and outlet air compartment interface 5 is connected with outlet hot-blast pipe line by expansion joint equally.Boiler First air is incorporated into gas-gas heat exchanger import air compartment 2 by blower fan, air enters in several rows of heat exchanger pipeloop 1 again, through after vertical shaft high-temperature flue gas heating after enter into heat exchanger exit air compartment 4, the hot air duct then through being connected with outlet air compartment interface 5 is incorporated in urea pyrolysis reactor as pyrolysis thermal source.
Heat exchanger inlet and outlet air compartment 2,4 does not adopt monoblock type on boiler width direction, and consider and to reduce after boiler differential expansion between bag wall 12 and air compartment, importing and exporting the every certain distance of air compartment is one section, adopts expansion joint to connect, be arranged symmetrically with by boiler center line between air compartment.By calculating, import and export air compartment 2,4 arranges air compartment fixture 6 every a segment distance.After boiler, Bao Qiang relevant position is preset with the built-in fitting be sealed and matched with heat exchanger inlet and outlet air compartment 2,4, wears bag wall place and is also provided with smoke sealing device 7, prevent flue gas from entering in air compartment at import and export air compartment 2,4 pipeloop.On the outer surface and hot air duct of air compartment, certain thickness insulation material is arranged after in-site installation is good.
Heat exchanger is arranged in boiler rear steering room place, comparatively large to washing away of gas-gas heat exchanger from stokehold toward stove rear to flue gas in this position, so be provided with abrasionproof cladding system 8 at the high order end of heat exchanger pipeloop 1.Calculated the reasonability determining pipeloop transverse pipe row amount and longitudinal pipe row amount by performance, and relative set pipe clamp 9 heat exchanger pipeloop 1 fixes.
The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. the hot heat-exchange system of inner flue gas of the stove of a pyrolysis thermal source of supplying urea, comprise boiler and gas-gas heat exchanger, it is characterized in that: described gas-gas heat exchanger comprises some row's heat exchanger pipeloops, with import air compartment and the import air compartment interface thereof of heat exchanger pipeloop inlet communication, with the outlet air compartment of Tube Sheet of Heat Exchanger circle outlet and export air compartment interface, described enter, outlet air compartment interface is connected with ventilation shaft by expansion joint, described heat exchanger pipeloop is the some rows of one-tenth arranged in parallel between left side bag wall to right side bag wall, and by fixture lodge on boiler hanging pipe superheater pipe, described heat exchanger pipeloop is by Tube Sheet of Heat Exchanger horizontal-extending come back to be bent to form pipeloop on perpendicular on bag wall to mid-board direction after boiler, Tube Sheet of Heat Exchanger from pass between the band steel of bag wall after boiler described enter, in outlet air compartment, and Tube Sheet of Heat Exchanger is entered described in close, outlet air compartment place is bent to form fork configuration, described enter, outlet air compartment is close to rear bag wall fixed and arranged, and connected and composed by expansion joint on boiler width direction by some sections of air compartments, each section of air compartment is arranged symmetrically with by boiler center line.
2. to supply urea as claimed in claim 1 the hot heat-exchange system of inner flue gas of the stove of pyrolysis thermal source, it is characterized in that: described heat exchanger pipeloop is provided with shoe near mid-board one end.
3. to supply urea as claimed in claim 1 the hot heat-exchange system of inner flue gas of the stove of pyrolysis thermal source, it is characterized in that: described heat exchanger pipeloop entirety is in nearly " Y " font.
4. to supply urea as claimed in claim 1 the hot heat-exchange system of inner flue gas of the stove of pyrolysis thermal source, it is characterized in that: the Tube Sheet of Heat Exchanger of described heat exchanger pipeloop is bent to form fork configuration part at described import and export air compartment place is 10 ° ~ 90 ° with horizontal plane angle.
5. to supply urea as claimed in claim 1 the hot heat-exchange system of inner flue gas of the stove of pyrolysis thermal source, it is characterized in that: described heat exchanger pipeloop is also provided with pipe clamp and fixes its Tube Sheet of Heat Exchanger bent back and forth.
6. to supply urea as claimed in claim 1 the hot heat-exchange system of inner flue gas of the stove of pyrolysis thermal source, it is characterized in that: described gas-gas heat exchanger is arranged in boiler tail vertical shaft low temperature superheater or low-temperature reheater region.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510315955.0A CN104896495B (en) | 2015-06-10 | 2015-06-10 | In-boiler flue gas heat exchange heat system providing urea pyrolysis heat source |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510315955.0A CN104896495B (en) | 2015-06-10 | 2015-06-10 | In-boiler flue gas heat exchange heat system providing urea pyrolysis heat source |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN104896495A true CN104896495A (en) | 2015-09-09 |
| CN104896495B CN104896495B (en) | 2017-04-12 |
Family
ID=54029325
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510315955.0A Active CN104896495B (en) | 2015-06-10 | 2015-06-10 | In-boiler flue gas heat exchange heat system providing urea pyrolysis heat source |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN104896495B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105423323A (en) * | 2015-12-23 | 2016-03-23 | 哈尔滨锅炉厂有限责任公司 | Surface type gas-gas heater for tail flue and heat exchange method thereof |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4350100A (en) * | 1979-11-13 | 1982-09-21 | James Howden Australia Pty. Limited | Air infiltration and mixing device |
| CN101050854A (en) * | 2007-05-18 | 2007-10-10 | 哈尔滨工业大学 | W-shape flame boiler for preventing side wall water cooling wall slagging scorification |
| US7615200B2 (en) * | 2000-12-01 | 2009-11-10 | Fuel Tech, Inc. | Selective catalytic reduction of NOx enabled by urea decomposition in heat-exchanger bypass |
| CN202074503U (en) * | 2011-04-23 | 2011-12-14 | 淄博齐林贵和热电有限公司 | Energy-saving coal economizer for boiler |
| CN103191640A (en) * | 2013-04-11 | 2013-07-10 | 东方电气集团东方锅炉股份有限公司 | SCR (Selective Catalytic Reduction) denitration reducing agent urea pyrolysis heat source supply method and device |
| CN203464242U (en) * | 2013-08-29 | 2014-03-05 | 山东华鲁恒升化工股份有限公司 | High-medium-low temperature overall economizer for coal-fired boiler |
-
2015
- 2015-06-10 CN CN201510315955.0A patent/CN104896495B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4350100A (en) * | 1979-11-13 | 1982-09-21 | James Howden Australia Pty. Limited | Air infiltration and mixing device |
| US7615200B2 (en) * | 2000-12-01 | 2009-11-10 | Fuel Tech, Inc. | Selective catalytic reduction of NOx enabled by urea decomposition in heat-exchanger bypass |
| CN101050854A (en) * | 2007-05-18 | 2007-10-10 | 哈尔滨工业大学 | W-shape flame boiler for preventing side wall water cooling wall slagging scorification |
| CN202074503U (en) * | 2011-04-23 | 2011-12-14 | 淄博齐林贵和热电有限公司 | Energy-saving coal economizer for boiler |
| CN103191640A (en) * | 2013-04-11 | 2013-07-10 | 东方电气集团东方锅炉股份有限公司 | SCR (Selective Catalytic Reduction) denitration reducing agent urea pyrolysis heat source supply method and device |
| CN203464242U (en) * | 2013-08-29 | 2014-03-05 | 山东华鲁恒升化工股份有限公司 | High-medium-low temperature overall economizer for coal-fired boiler |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105423323A (en) * | 2015-12-23 | 2016-03-23 | 哈尔滨锅炉厂有限责任公司 | Surface type gas-gas heater for tail flue and heat exchange method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN104896495B (en) | 2017-04-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN205690425U (en) | A kind of residual heat from boiler fume Multi-class propagation combines condensation water heating supply air system | |
| CN207706077U (en) | A kind of temperature difference electricity generation device using boiler back end ductwork fume afterheat | |
| CN204853528U (en) | Hot heat transfer system of boiler flue gas | |
| CN104896495A (en) | In-boiler flue gas heat exchange heat system providing urea pyrolysis heat source | |
| CN202757144U (en) | Parallel-connection hybrid multistage air pre-heater | |
| CN205402781U (en) | Air heater of node tubular | |
| CN207865428U (en) | A kind of biomass boiler fume afterheat utilizes energy saver | |
| CN203824376U (en) | High-temperature flue gas heat exchanger for urea pyrolysis process and urea pyrolysis ammonia-producing device for denitration | |
| CN106370034A (en) | Flue gas heat exchange system for urea pyrolysis | |
| CN206496367U (en) | Helical finned tube type steam air heater | |
| CN102080935A (en) | Device for recovering waste heat of industrial waste gas | |
| CN205482504U (en) | But fluoroplastics tubular heat exchanger structure that level was placed | |
| CN108267032A (en) | A kind of heat-exchanger rig and system with honeycomb | |
| CN106369825B (en) | gas water heater and waste heat recovery method | |
| CN206919709U (en) | A kind of flue gas heat-exchange unit | |
| CN102635941B (en) | Dual-liner type hot water and hot air two-functional boiler | |
| CN201819587U (en) | Flue heat exchanger of cremator | |
| CN203010934U (en) | Heat energy recovery device of air heating furnace | |
| CN207317577U (en) | A kind of anhydrous cell type efficient heat exchanger of single channel | |
| CN110057209A (en) | A kind of shell and tube light pipe evaporator and its welding method | |
| CN212719811U (en) | Boiler heat exchange equipment and urea pyrolysis system | |
| CN209588013U (en) | A kind of horizontal three return smokes fire tube steam boiler | |
| CN104100957A (en) | Boiler waste heat recovery system | |
| CN205227314U (en) | Gas heating system | |
| CN204943525U (en) | A kind of device improving SCR reactor cigarette temperature |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |