CN204469531U - Membrane separation circulating fluid bed desulfation dust-extraction device - Google Patents
Membrane separation circulating fluid bed desulfation dust-extraction device Download PDFInfo
- Publication number
- CN204469531U CN204469531U CN201420671610.XU CN201420671610U CN204469531U CN 204469531 U CN204469531 U CN 204469531U CN 201420671610 U CN201420671610 U CN 201420671610U CN 204469531 U CN204469531 U CN 204469531U
- Authority
- CN
- China
- Prior art keywords
- fluid bed
- venturi tube
- extraction device
- membrane separation
- circulating fluid
- 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
Landscapes
- Treating Waste Gases (AREA)
Abstract
Membrane separation circulating fluid bed desulfation dust-extraction device, comprise the bottom ash discharge groove distributed successively from bottom to up, the tube bank of cyclone separator, venturi, cylinder fluid bed and membrane separator, Integral vertical is arranged, be followed successively by ash discharge section, pretreatment section from bottom to top, flue gas accelerating sections, conversion zone and top dedusting section; Venturi tube top is provided with atomizer and desulfurization absorbent shower nozzle; Cyclone separator sidewall is provided with air inlet, and cylinder fluid bed has ash bucket; Membrane separator top is exhanst gas outlet; The ash releasing tube of cyclone separator connects bottom ash discharge groove; The gas outlet of cyclone dust collectors is connected with Venturi tube.
Description
Technical field
The utility model relates to one (partly) dry desulfurization, flue-gas dust-removing and desulfurization integrated technique, is specially a kind of stack gas desulfurization and dust removal of circulating fluid bed integrated apparatus and technique, belongs to smoke gas treatment technical field.
Background technology
In recent years, country puts into effect a series of severe Air Pollution Control standard, the such as SO of key area coal fired thermal power plant
2discharge standard is 50mg/m
3, dust emission standard is 20mg/m
3, along with the requirement of Environmental protection is more and more stricter, exhaust gas dust and SO
2discharge standard can be more and more higher.
Pottery (metal) membrane material compare organic fiber filter material, its intensity is large, high temperature resistant, resistance to acids and bases, corrosion-resistant, long service life, easy-to-clean ash, in some rugged environments, advantage is clearly.Membrane filtration technique can improve filter effect when not increasing resistance, realizes retaining PM2.5, reaches minimum discharge; And make it while dedusting, have the effect of other gas pollutants of purification by supported catalyst or adsorbent, be the important development direction of membrane separation technique in gas solid separation.
At present for circulating fluidized bed desulfurization technique, all add deduster after desulfurizing tower technique, by Recycle of material system, absorbent is turned back to desulfurizing tower recycle, make a whole set of desulfation dust-extraction device floor space larger, and for the desulfurizing fly ash engineering of many units, often place is very nervous, too much should not arrange other equipment; Because reaction can produce a large amount of ultra-fine granule PM2.5, comprising unreacted absorbent granules completely, existing deduster can not effectively reclaim and run off, and adds production cost, causes that exiting flue gas is granular material discharged to exceed standard simultaneously.
Chinese patent application publication number CN102671535 A describes a kind of stack gas desulfurization and dust removal of circulating fluid bed in damp dry type integrated purifying technique and device.The method by desulfurizing tower and deduster arranged apart, the coarse granule absorbent in cyclone separator separating flue, is entering secondary ash collector, the fine grained absorbent in separating flue, is separated the absorbent that obtains and again enters reaction tower Inner eycle.The method and device technique complexity, energy consumption is high, and so-called integration is the combination of technique, and be not proper integrated apparatus, and do not have pretreatment measure, the flying dust in flue gas can have a strong impact on desulfurized effect.
Chinese patent application publication number CN102210973 A describes a kind of for SO
2semi-dry desulphurization dust removal integrated plant, Disengagement zone is arranged on whole device top, eliminates circulation ash-transmission system, be applicable to SO
2concentration is lower than 1500mg/Nm
3in time, uses.But device is square, and device inside exists dead angle, there is the possibility that air flow method is uneven in easy fouling, blocking.
Summary of the invention
The utility model object is, in order to overcome, conventional recycle fluid-bed sweetening floor space is comparatively large, desulfuration efficiency ground, absorbent utilization rate are low and the dust emission not easily shortcoming such as up to standard of giving vent to anger, provide and integrate membrane separation technique, adsorption technology, fluidization and Cyclone Separation Technology, high-efficient purification can be carried out to boiler smoke, realize minimum discharge, and technique is simple, and energy consumption is low, the UF membrane smoke eliminator that floor space is less.
Technical solutions of the utility model are: a kind of membrane separation circulating fluid bed desulfation dust-extraction device, comprise the bottom ash discharge groove distributed successively from bottom to up, the tube bank of cyclone separator, venturi, cylinder fluid bed and membrane separator, Integral vertical is arranged, the pretreatment section be followed successively by ash discharge section from bottom to top, forming primarily of cyclone separator, is configured with flue gas accelerating sections, primarily of the conversion zone of cylinder fluid bed formation, the top dedusting section primarily of membrane separator formation primarily of venturi tube bank; Venturi tube top is provided with atomizer and desulfurization absorbent shower nozzle; Cyclone separator sidewall is provided with air inlet, and cylinder fluid bed has ash bucket.Membrane separator top is exhanst gas outlet.The ash releasing tube of cyclone separator connects bottom ash discharge groove.Cyclone separator can according to exhaust gas volumn size adjustment separator quantity, and cyclone separator is arranged in parallel, and the gas outlet of cyclone dust collectors is connected with Venturi tube, and is provided with mozzle, makes flue gas smoke distribution even.
Described membrane separator comprises separating film module, flue gas heater, blowback system, and separating film module is made up of film pipe bracing frame and the film pipe be fixed on bracing frame; Flue gas heater is arranged on the neat stress outlet section of membrane separator, and film pipe inside is provided with and adds electric device; The top of film pipe bracing frame is provided with upper cover, is collection chamber between upper cover and film pipe bracing frame; Upper cover top has exhanst gas outlet and pulse backblowing gas access.
The tubular type that described separating film module is made up of pottery, metal or metallic composite, cellular hexagonal diffusion barrier form, and described film pipe diameter is 5-20cm, average pore size 0.01-100 μm.
Described film Guan Weiyi section closes one section of uncovered tubular type or cellular diffusion barrier, the structure of more than four layers or four layers of rete, transition zone, porous supporting body layer, absorbent particles layer and inline layer that the tube wall ecto-entad of described film pipe sets gradually.
The aperture of described rete is 0.01-1 μm, transition zone 10-20 μm, porous supporting body layer aperture be 10-100 μm, and inline layer aperture is 10-100 μm.
Described absorbent particles is active carbon or activated coke, and grain diameter is 0.1-1mm, for adsorbing SO
2, to nitrogen oxide, mercury, bioxin, furans, heavy metal and volatile organic matter.The regeneration of adsorbent adds electric device heating desorption by what be placed on film pipe inside.Adsorbent can desorb online, separates the high concentration SO of sucking-off
2gas pumped enter storage tank, for the production of sulfuric acid.Above-mentioned diffusion barrier long service life, at least 6 years replacement cycles.
The described edge of venturi tube bank for being positioned at cylindrical shell circumference.The intrafascicular heart of described Venturi tube is ash bucket, and ash bucket connects bottom ash-pit.Described Venturi tube is made up of the ingress pipe being positioned at bottom, superposed convergent divergent channel and link ingress pipe and the trunnion of convergent divergent channel.The charging aperture of absorbent is located at the top of venturi tube bank, and distance Venturi tube 800-1200mm, atomizer is positioned at charging aperture top, distance 1000-1500mm.
The gas approach of described desulfurizer, ash bucket and bottom ash-pit are all provided with outer ash discharging hole and anti-block apparatus.
Flue gas provides power by blower fan, and blower fan is roots blower, before can being arranged on gas approach, after also can being arranged on exhanst gas outlet.
Described fluidized system is made up of cylinder and Venturi tube and ash bucket, is followed successively by accelerating sections, conversion zone, top exit section from bottom to top; Venturi tube top is provided with atomizer and lime slurry shower nozzle.
Described Venturi tube is by the top being positioned at the ingress pipe of bottom, the charging aperture of absorbent is located at venturi tube bank, and distance Venturi tube 800-1200mm is very little to the wearing and tearing at nozzle place, is long-time protection, the steel about 4-10mm thicker in other in this region.Atomizer is positioned at charging aperture top, distance 1000-1500mm.
Described cyclone separator can according to exhaust gas volumn size adjustment separator quantity, and cyclone separator is arranged in parallel, and the gas outlet of cyclone dust collectors is connected with Venturi tube, and is provided with mozzle, makes flue gas smoke distribution even.The ash releasing tube of cyclone separator connects bottom ash discharge groove.
Outer ash discharging hole and anti-block apparatus is all provided with bottom the gas approach of described desulfurizer, ash bucket and ash-pit.
Dust-removing and desulfurization process on said apparatus basis, boiler flue gas out enters cyclone separation system bottom desulfurizer, cyclone separation system the coarse granule that carries in flue gas is removed laggard enter fluid bed, the desulfurization absorbent that sour gas in flue gas and fluid bed spray into and water react, and (flying dust, calcium sulfite and unreacted be Ca (OH) completely to produce a large amount of fine particle
2), wherein containing a large amount of PM2.5, these particles are directly tackled by the membrane separator at top, get back to fluidized bed reaction zone by reverse gas cleaning to continue to participate in reaction, realize recycling of absorbent, remove PM2.5 simultaneously, secondary desulfuration is carried out during the adsorption layer of the clean flue gas after desulfurization and dedusting in filmed passing tube, part nitrogen oxide, mercury, bioxin, furans, heavy metal and volatile organic matter are adsorbed in the lump simultaneously, eventually pass blower fan and enter chimney discharge, the desulfurizing byproduct particle in desulfurizer is delivered to bottom ash-pit by ash bucket.
The beneficial effects of the utility model are, the present invention overcomes that traditional circulating fluidized bed desulfur technology floor space is comparatively large, desulfuration efficiency ground, absorbent utilization rate are low and the dust emission not easily shortcoming such as up to standard of giving vent to anger, volume of the present invention is little, integrate membrane separation technique, adsorption technology, fluidization and Cyclone Separation Technology, can carry out high-efficient purification to boiler smoke, clean-up effect can reach the new standard of country.
Accompanying drawing explanation
Fig. 1 is the structural representation of the membrane separation circulating fluid bed embodiment of the utility model;
Fig. 2 is venturi Pipe bundle structure schematic diagram;
Fig. 3 is tubular separation membrane structural representation.
In figure, critical piece illustrates: 1 air inlet; Ash-pit bottom 2; 3 cyclone separators; 4 venturi tube banks; 5 ash buckets; 6 atomizer interfaces; 7 desulfurizing agent interfaces; 8 fluid beds; 9 membrane separators; 91 retes; 92 transition zones; 93 support body layer; Absorbent particles layer; 10 gas outlets.
Detailed description of the invention
Inventive principle and plant running is set forth further below in conjunction with film desulfurizer shown in Fig. 1-Fig. 3 and parts thereof.
Membrane separation circulating fluid bed desulfurizer as shown in Figure 1, cyclone separator 3 exhanst gas outlet connects venturi tube bank by mozzle, fluid bed cylindrical shell top 8 junctional membrane separator 9.Venturi tube 4 top is provided with atomizer interface 6 and desulfurizing agent interface 7, and the center of venturi tube bank 4 is provided with ash bucket 5, and ash bucket 5 connects bottom ash-pit 2.
As shown in Figure 2, the venturi tube bank of the present embodiment includes six Venturi tubes 4 being evenly distributed on cylindrical shell edge, and tube bank center is ash bucket 5.
As shown in Figure 1, flue gas enters two cyclone separators 3 in parallel simultaneously, for removing the bulky grain thing in flue gas, dust clearance is more than 50%, Cyclone outlet connects mozzle and enters Venturi tube 4, flue gas is by the acceleration of Venturi tube, form turbulent flow, fully mix with water droplet and lime stone slurry, at the conversion zone generation gas-liquid-solid phase reaction of fluid bed 8, generate calcium sulfite particles thing, flue gas is entrained with particle tunicle separation period 9 and retains, particle under retaining is continued reaction by the conversion zone that blowback drops on fluid bed 8, simultaneously clean flue gas is through the adsorption layer of diffusion barrier, by the SO of remnants
2absorption, eventually passes blower fan, is discharged by chimney.Because sour gas most of in flue gas is removed by fluid bed 8, and diffusion barrier has retained nearly all particle, so the service life of active carbon extends greatly.Particle in fluid bed 8 is delivered to bottom ash-pit 2 by ash bucket 5, then supplements fresh lime stone slurry and continues circular response.
Membrane module comprises the tubular membrane that multiple ceramic material is formed, and the internal diameter of this film pipe is 100mm, and outer membrane aperture is 0.5 μm, and transition zone is 10-50 μm μm, and porous supporting body layer aperture is 50-100 μm.As shown in Figure 3, diffusion barrier comprises four-layer structure, is followed successively by rete 91, transition zone 92, support body layer 93, absorbent particles layer 94.Absorbent particles layer is for adsorbing remaining SO
2, also have certain adsorption effect to part nitrogen oxide, mercury, bioxin, furans, heavy metal and volatile organic matter.Adsorbent is activated carbon granule.Diffusion barrier pipe one section of opening, the other end is closed.The minimum theca externa in diffusion barrier aperture is arranged on flue gas upstream end, for trapped particles thing, protects absorbent particles layer simultaneously.Flue gas is successively by theca externa, the transition zone of diffusion barrier, and porous supporting body layer, after the purification of absorbent particles layer, through film inner channel, is discharged by openend.
Finally brightly be, above embodiment is only in order to illustrate the technical solution of the utility model and unrestricted, although with reference to preferred embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that, can modify to form of the present utility model and details or replace on an equal basis, and not depart from the spirit and scope of the present utility model that institute's additional copy claims limit.
Claims (9)
1. a membrane separation circulating fluid bed desulfation dust-extraction device, it is characterized in that, comprise the bottom ash discharge groove distributed successively from bottom to up, the tube bank of cyclone separator, venturi, cylinder fluid bed and membrane separator, Integral vertical is arranged, be followed successively by ash discharge section, pretreatment section from bottom to top, flue gas accelerating sections, conversion zone and top dedusting section; Venturi tube top is provided with atomizer and desulfurization absorbent shower nozzle; Cyclone separator sidewall is provided with air inlet, and cylinder fluid bed has ash bucket; Membrane separator top is exhanst gas outlet; The ash releasing tube of cyclone separator connects bottom ash discharge groove; The gas outlet of cyclone dust collectors is connected with Venturi tube.
2. membrane separation circulating fluid bed desulfation dust-extraction device according to claim 1, is characterized in that, described membrane separator comprises separating film module, flue gas heater, blowback system, and separating film module is made up of film pipe bracing frame and the film pipe be fixed on bracing frame; Flue gas heater is arranged on the neat stress outlet section of membrane separator, and film pipe inside is provided with heating element heater; The top of film pipe bracing frame is provided with upper cover, is collection chamber between upper cover and film pipe bracing frame; Upper cover top has exhanst gas outlet and pulse backblowing gas access.
3. membrane separation circulating fluid bed desulfation dust-extraction device according to claim 2, it is characterized in that, the tubular type that described separating film module is made up of pottery, metal or metallic composite, cellular hexagonal diffusion barrier form, described film pipe diameter is 5-20cm, average pore size 0.01-100 μm.
4. membrane separation circulating fluid bed desulfation dust-extraction device according to claim 3, it is characterized in that, described film Guan Weiyi section closes one section of uncovered tubular type or cellular diffusion barrier, the structure of more than four layers or four layers of rete, transition zone, porous supporting body layer, absorbent particles layer and inline layer that the tube wall ecto-entad of described film pipe sets gradually.
5. membrane separation circulating fluid bed desulfation dust-extraction device according to claim 4, is characterized in that, the aperture of described rete is 0.01-1 μm, transition zone 10-20 μm, porous supporting body layer aperture be 10-100 μm, and inline layer aperture is 10-100 μm.
6. membrane separation circulating fluid bed desulfation dust-extraction device according to claim 4, is characterized in that, the absorbent particles of described absorbent particles layer is active carbon or activated coke, and grain diameter is 0.1-1mm, for adsorbing SO
2, nitrogen oxide, mercury, bioxin, furans, heavy metal and volatile organic matter.
7. according to the membrane separation circulating fluid bed desulfation dust-extraction device one of claim 1-6 Suo Shu, it is characterized in that, the described edge of venturi tube bank for being positioned at cylindrical shell circumference; The intrafascicular heart of described Venturi tube is ash bucket, and ash bucket connects bottom ash-pit; Described Venturi tube is made up of the trunnion of ingress pipe, convergent divergent channel and link ingress pipe and convergent divergent channel; The charging aperture of absorbent is located at the top of venturi tube bank, and distance Venturi tube 800-1200mm, atomizer is positioned at charging aperture top, distance 1000-1500mm.
8. membrane separation circulating fluid bed desulfation dust-extraction device according to claim 7, it is characterized in that, described Venturi tube is by the top being positioned at the ingress pipe of bottom, the charging aperture of absorbent is located at venturi tube bank, distance Venturi tube 800-1200mm, the steel plate of the feed hole area of absorbent thickeies 4-10mm.
9. membrane separation circulating fluid bed desulfation dust-extraction device according to claim 7, is characterized in that, described atomizer is positioned at charging aperture top, distance charging aperture 1000-1500mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420671610.XU CN204469531U (en) | 2014-11-11 | 2014-11-11 | Membrane separation circulating fluid bed desulfation dust-extraction device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420671610.XU CN204469531U (en) | 2014-11-11 | 2014-11-11 | Membrane separation circulating fluid bed desulfation dust-extraction device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN204469531U true CN204469531U (en) | 2015-07-15 |
Family
ID=53625267
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201420671610.XU Active CN204469531U (en) | 2014-11-11 | 2014-11-11 | Membrane separation circulating fluid bed desulfation dust-extraction device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN204469531U (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104437069A (en) * | 2014-11-11 | 2015-03-25 | 南京中电环保科技有限公司 | Desulfurization and dust-removal device and desulfurization and dust-removal method of membrane separation circulating fluidized bed |
| CN108159872A (en) * | 2018-02-11 | 2018-06-15 | 佛山市三水区广顺自动化设备有限公司 | A kind of pure dry-method desulfurization device |
| CN108295613A (en) * | 2018-04-18 | 2018-07-20 | 无锡红旗除尘设备有限公司 | It is a kind of can automatic desludging multitube is cooling and agglomeration device |
| CN108619794A (en) * | 2018-06-11 | 2018-10-09 | 兰州大学 | Deduster and cleaner |
| CN110548355A (en) * | 2019-10-24 | 2019-12-10 | 镇江市恒升达化工科技有限公司 | High-efficiency membrane separation dust removal device |
| WO2020140821A1 (en) * | 2018-12-31 | 2020-07-09 | 中国石油化工股份有限公司 | Separation device and separation method |
-
2014
- 2014-11-11 CN CN201420671610.XU patent/CN204469531U/en active Active
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104437069A (en) * | 2014-11-11 | 2015-03-25 | 南京中电环保科技有限公司 | Desulfurization and dust-removal device and desulfurization and dust-removal method of membrane separation circulating fluidized bed |
| CN108159872A (en) * | 2018-02-11 | 2018-06-15 | 佛山市三水区广顺自动化设备有限公司 | A kind of pure dry-method desulfurization device |
| CN108295613A (en) * | 2018-04-18 | 2018-07-20 | 无锡红旗除尘设备有限公司 | It is a kind of can automatic desludging multitube is cooling and agglomeration device |
| CN108295613B (en) * | 2018-04-18 | 2024-05-14 | 无锡红旗除尘设备有限公司 | Multi-pipe type cooling and agglomerating device capable of automatically descaling |
| CN108619794A (en) * | 2018-06-11 | 2018-10-09 | 兰州大学 | Deduster and cleaner |
| CN108619794B (en) * | 2018-06-11 | 2023-10-24 | 兰州大学 | Dust remover and dust removing equipment |
| WO2020140821A1 (en) * | 2018-12-31 | 2020-07-09 | 中国石油化工股份有限公司 | Separation device and separation method |
| US11958011B2 (en) | 2018-12-31 | 2024-04-16 | China Petroleum & Chemical Corporation | Separation device and separation method |
| CN110548355A (en) * | 2019-10-24 | 2019-12-10 | 镇江市恒升达化工科技有限公司 | High-efficiency membrane separation dust removal device |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN204469531U (en) | Membrane separation circulating fluid bed desulfation dust-extraction device | |
| CN104437069A (en) | Desulfurization and dust-removal device and desulfurization and dust-removal method of membrane separation circulating fluidized bed | |
| CN102228788B (en) | Device and method for removing sulfur dioxide and dioxin from sintering flue gas | |
| CN106390652B (en) | A kind of Wet-type high-efficient eddy flow removing fine particle device | |
| CN102824846A (en) | Axial and radial cross flow moving bed reactor and activated coke flue gas desulfurization and denitration technology thereof | |
| CN101822942B (en) | Wet purification method for dioxin and heavy metals in solid waste incineration gas | |
| CN205461778U (en) | Semidry method circulating fluidized bed flue gas is SOx/NOx control device simultaneously | |
| CN203886406U (en) | Tail gas purification device of circulating fluid bed garbage incinerator | |
| CN102059045A (en) | Venturi atomization compound wet type electrostatic flue gas treatment reactor | |
| CN104548809A (en) | Active coke desulfurization and denitrification and membrane separation dust removal integrated system and treatment method | |
| CN102716622B (en) | Integrated bag-type dust removal and fluidized adsorption device | |
| CN102423593A (en) | Method for simultaneously dedusting, desulphurizing and denitrating boiler flue gas in coal-fired industry | |
| CN202173882U (en) | Device for removing sulfur dioxide and dioxin in sintering flue gas | |
| CN105251300A (en) | Waste gas dedusting device and method for tunnel kiln | |
| CN102266718A (en) | Semi dry process flue gas desulfurization method of circulating fluidized bed based on circulation, and apparatus thereof | |
| CN102512901B (en) | Composite dust-removing and collaborative desulfurization and denitration device capable of wetting flue gas | |
| CN109865414A (en) | A kind of novel absorbent charcoal desulfuring and denitrifying apparatus | |
| CN112675698A (en) | Desulfurization, denitrification and dust removal device of turbulent bed in separate bin and process thereof | |
| CN111991991A (en) | Active coke turbulent bed desulfurization tower, system and method | |
| CN202715332U (en) | Dry-method aftertreatment system | |
| CN214597998U (en) | SO in flue gas after wet desulphurization3Device of high-efficient desorption | |
| CN202191838U (en) | Flue gas disposing device of coal-fired industrial boiler | |
| CN105276999A (en) | Sintering flue gas waste heat utilization and deep purification method and system thereof | |
| CN111603890B (en) | Adsorption tower for preventing dust deposition in air chamber and method for treating flue gas by using adsorption tower | |
| CN107569937A (en) | A kind of incinerator smoke desulfuring and denitrifying apparatus |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| EE01 | Entry into force of recordation of patent licensing contract |
Assignee: NANJING CEC ENVIRONMENTAL PROTECTION CO., LTD. Assignor: Nanjing Zhongdian Environmental Protection Technology Co., Ltd. Contract record no.: 2016320000021 Denomination of utility model: Desulfurization and dust-removal device and desulfurization and dust-removal method of membrane separation circulating fluidized bed Granted publication date: 20150715 License type: Exclusive License Record date: 20160202 |
|
| LICC | Enforcement, change and cancellation of record of contracts on the licence for exploitation of a patent or utility model |