CN205461179U - Sedimentation basin - Google Patents

Sedimentation basin Download PDF

Info

Publication number
CN205461179U
CN205461179U CN201620103936.1U CN201620103936U CN205461179U CN 205461179 U CN205461179 U CN 205461179U CN 201620103936 U CN201620103936 U CN 201620103936U CN 205461179 U CN205461179 U CN 205461179U
Authority
CN
China
Prior art keywords
mud
sedimentation tank
sludge
mudhole
qualified
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
Application number
CN201620103936.1U
Other languages
Chinese (zh)
Inventor
何新华
Original Assignee
何新华
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by 何新华 filed Critical 何新华
Priority to CN201620103936.1U priority Critical patent/CN205461179U/en
Application granted granted Critical
Publication of CN205461179U publication Critical patent/CN205461179U/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Abstract

The utility model provides a sedimentation basin, includes the sedimentation basin body of vertical setting, is equipped with sewage import and clear water export on the sedimentation basin body, the inside of sedimentation basin body is down set gradually to settling zone, mud transition district, mud extrusion drying zone and qualified mud district by last, is equipped with the clear device of drawing of mud of qualified mud in drawing sedimentation basin clearly in qualified mud district, and mud is clear draws the device including establishing the bottom center was located in the sedimentation basin body mudhole and pushing qualified mud the eccentric scraper blade of mudhole to, be equipped with outside the sedimentation basin body with mudhole complex mud output device. The utility model discloses the mud that need not to produce the sedimentation basin body discharges, also need not to dewater with mechanical means such as centrifuge, and direct self the action of gravity extrusion sludge dewatering who loses mobile mud that utilizes can.

Description

A kind of sedimentation tank
Technical field
This utility model relates to a kind of sewage purification field, particularly a kind of sedimentation tank.
Background technology
At present, sedimentation tank (the including depositing reservoir) precipitating sludge that water treatment field commonly uses, great majority are all to be discharged by mud with waterpower sludge discharging method.Mud owing to discharging is mobility, moisture content is the highest, the mud discharged must be carried out processed, in most of the cases, the sludge dehydrating agent (such as PAMC etc.) of costliness need to be added in the mud discharged, make macromolecule medicament and the sludge reaction of addition, produce the bulky grain floccule of easily dehydration, the most again with sludge dewatering equipments such as centrifuges by sludge dewatering, form the relatively low mud of moisture content or earth.Such sludge treatment technique, the most loaded down with trivial details, the most uneconomical, equipment investment is big, and processing cost is the highest.
And the industry such as thermal power plant, colliery processes the coal slime that the sedimentation tank of black water is precipitated out, great majority use grab claw coal slime to be pulled out to sedimentation tank bottom from waterborne, grab claw is used to drag for mud in sedimentation tank, having severely impacted black water sedimentation tank deposition efficiency, effluent quality of sedimentation tank is excessively poor.Sedimentation tank water outlet must be carried out agent-feeding treatment, just can be continuing with or discharge.The most not only waste substantial amounts of medicament, waste substantial amounts of manpower and materials.
Summary of the invention
The technical problems to be solved in the utility model is for the deficiencies in the prior art, proposes one and had both saved device for dehydrating sladge waste, saves again the sedimentation tank of medicament.
The technical problems to be solved in the utility model is achieved through the following technical solutions, a kind of sedimentation tank, including vertically arranged sedimentation tank body, sedimentation tank body is provided with wastewater inlet and clear water output, it is characterized in: the inside of described sedimentation tank body sets gradually as settling zone from top to bottom, mud transition region, mud extrusion dehydration district and qualified mud district, the sludge clearing device of qualified mud in drawing clearly sedimentation tank it is provided with in qualified mud district, sludge clearing device includes being located at the mudhole of sedimentation tank body inner bottom part center and qualified mud being pushed to the eccentric scraper plate of mudhole, the sludge output coordinated with mudhole it is externally provided with at sedimentation tank body.
The technical problems to be solved in the utility model can also be come to realize further by the following technical programs, and described wastewater inlet is located on sedimentation tank body upper part outer wall, to having the vertical guide plate coordinated with wastewater inlet in sedimentation tank body;Be provided with center set tank near center at the top of sedimentation tank body, described clear water output is connected with center set tank by outlet pipe.
The technical problems to be solved in the utility model can also be come to realize further by the following technical programs, sewage water inlet pipe is installed at wastewater inlet, the water side of sewage water inlet pipe is arranged on the intrinsic center of sedimentation tank, to having the vertical sewage guide plate coordinated with sewage water inlet pipe water side in sedimentation tank body;Being provided with water leg in the outer, top of sedimentation tank body, described clear water output is connected with water leg by Graceful water pipe.
The technical problems to be solved in the utility model can also be come to realize further by the following technical programs, described sludge output includes the conveying worm being arranged on below mudhole, conveying worm is provided with mud import and sludge outlet, described mud import is connected by the mudhole of sludge bucket with sedimentation tank body, is provided with sludge carrier pipe road at the sludge outlet of conveying worm.
The technical problems to be solved in the utility model can also be come to realize further by the following technical programs, is provided with sludge outlet in the outer end in sludge carrier pipe road and closes end cap.
The technical problems to be solved in the utility model can also be come to realize further by the following technical programs, is fixed with towards eccentric scraper plate direction of rotation at the top of eccentric scraper plate and cuts mud plate every mud.
The technical problems to be solved in the utility model can also be come to realize further by the following technical programs, and described eccentric scraper plate includes that periphery is scraped mud section, middle transition section and mud is pushed to the centre pilot section of mudhole.
The technical problems to be solved in the utility model can also be come to realize further by the following technical programs, and described periphery is scraped mud section, middle transition section and centre pilot section and arranged continuously.
The technical problems to be solved in the utility model can also be come to realize further by the following technical programs, and the intersegmental disconnected setting of mud section, middle transition section and centre pilot is scraped in described periphery.
The technical problems to be solved in the utility model can also be come to realize further by the following technical programs, described periphery is scraped mud section, middle transition section, centre pilot section and is connected with the drive shaft being arranged on sedimentation tank body interior center by linking arm respectively, is provided with the driving means driving drive shaft to rotate at the top of sedimentation tank body.
Compared with prior art, this utility model utilizes the eccentric scraper plate that qualified mud is pushed to mudhole, qualified mud can be collected from mudhole equably, with sludge output, mud is transported out again, utilize the gravity (including water layer gravity) of mud above qualified mud district itself, moisture in qualified mud is squeezed out, the most both the equipment such as sludge dewatering equipment had been eliminated, need not again the medicaments such as expensive dehydrant, meanwhile, also need not discharge, to surrounding, the waste water that sludge dewatering treatment produces.And, sedimentation tank body effluent quality after precipitation is the most fine;Utilize the sludge outlet being arranged on outer end, sludge carrier pipe road to close end cap, quit work period at sludge output, can prevent internal pressure from being extruded from sludge carrier pipe road by mud.This utility model, without being ejected by the mud that sedimentation tank body produces, is dehydrated without with mechanical means such as centrifuges, directly utilizes the self gravitation effect extruding sludge dewatering of the mud that loses flowability.
Accompanying drawing explanation
Fig. 1 is structural representation of the present utility model;
Fig. 2 is the structural representation of this utility model another embodiment;
Fig. 3 is the structural representation of eccentric scraper plate;
Fig. 4 is that the A-A of Fig. 3 is to structural representation;
Fig. 5 is the structural representation of eccentric a kind of embodiment of scraper plate;
Fig. 6 is the structural representation of eccentric scraper plate another embodiment.
Detailed description of the invention
A kind of sedimentation tank, including vertically arranged sedimentation tank body 13, sedimentation tank body 13 is provided with wastewater inlet and clear water output, the inside of described sedimentation tank body sets gradually as settling zone 3 from top to bottom, mud transition region 4, mud extrusion dehydration district 5 and qualified mud district 11, the sludge clearing device 6 of qualified mud in drawing clearly sedimentation tank it is provided with in qualified mud district 11, sludge clearing device 6 includes being located at the mudhole 22 of sedimentation tank body inner bottom part center and qualified mud being pushed to the eccentric scraper plate 21 of mudhole, the sludge output coordinated with mudhole it is externally provided with at sedimentation tank body.Described sedimentation tank body overall structure form is in addition to plain base version, it is also possible to use top be cylindrical shape bottom be the overall structure form of reverse taper shape;Can also use settling zone, top be large diameter cylinder type, sludge solids district be roundlet cylindricality, intermediate sludge transition region be the overall structure form of truncated cone-shaped;Can also be used in combination with conventional conventional precipitation pond (depositing reservoir), the mud discharged with conventional conventional precipitation pond (depositing reservoir) is sent into novel sedimentation tank (depositing reservoir) and carries out Treatment of Sludge, Treatment of Sludge become qualified sludge solids remove, by the original water inlet of water outlet loopback (recovery) to conventional conventional precipitation pond (depositing reservoir).
Described settling zone is equivalent to commonly use the sediment fraction of equipment in the past;Described mud transition region is similar with the bottom sludge part commonly using equipment in the past, it it is the part being specifically used to make sludge settling get off, along with mud precipitates downwards, sludge concentration is gradually increased, when mud sinks to bottom mud transition region, mud loses flowability because moisture content is relatively low, the mud so lost flowability is referred to as " sludge solids ", the sludge solids that the sedimentation tank (depositing reservoir) in the past commonly used uses the devices such as mud scraper to prevent from losing flowability produces, otherwise, mud cannot lean on waterpower to discharge.Such as, the mud scraper of mechanical agitation accelerating purifying pool, all the time operate and the mud divided bottom pond is swept, pool bottom sludge precipitation is not allowed to solidify, otherwise, just it is difficult to be discharged by mud by waterpower once sludge settling solidification, for another example, the cleaning shoe device of radical sedimentation basin, also it is equally to remain operating, the mud that stirring precipitates from settling zone, it is made to keep mobility, to discharge by waterpower, and way of the present utility model is on the contrary, it is then to produce sludge solids by every means, the sludge solids lost flowability precipitated from mud transition region, sink to mud extrusion dehydration district;Described mud extrusion dehydration district is one of key of design, the sludge solids lost flowability precipitated from mud transition region, moisture content is the highest, must continue to remove by its internal moisture, this district is the gravity utilizing upper part sludge solids, the sludge solids of extruding lower part, sludge solids layer above extrudes following sludge blanket as piston, it is similar to and as extruding sponge, the moisture in lower floor's sludge solids is squeezed out, form the mud that moisture content is the lowest, the moisture being extruded out from mud is less than sludge solids proportion because of proportion, upwards emersion return to mud transition region, must there be the highest height in mud extrusion dehydration district, so sludge solids of upper part could produce the biggest pressure to the sludge solids of lower part, moisture in mud could be extruded, reach the purpose of sludge dewatering.Such as, if the sludge solids proportion in mud extrusion dehydration district is when about 1.45 grams/cc, so, the solid coal mud layer of 1 meter high will produce the pressure of 0.0145MPa to lower floor, plus the pressure of the 0.06MPa that the water layer height (height overall is about 6 meters) of settling zone and mud transition region produces, total can produce 0.0145MPa+0.06MPa= The pressure of 0.0745 MPa.In other words, the sludge solids floor in mud extrusion dehydration district often increases by 1 meter high, and the squeeze pressure that the sludge solids bottom mud extrusion dehydration district is subject to is increased by 0.0145MPa.As a example by water layer total height by settling zone and mud transition region is 6 meters below, the corresponding relation of mud extrusion dehydration district height and squeeze pressure is described:
1m----0.075 MPa
5m----0.133 MPa
10m----0.205 MPa
15m----0.278 MPa
20m----0.350 MPa
Can be seen that from above-mentioned data, in mud extrusion dehydration district, the most down the squeeze pressure suffered by sludge solids is the biggest, the moisture being extruded out is the most, sludge solids moisture content is the lowest, utilize sludge dewatering district internal upper part to divide the action of gravity extruding lower part sludge solids of sludge solids (including settling zone and transition region water), the moisture in lower part sludge solids is extruded, thus reaches the purpose of sludge dewatering.Sludge solids bottom described mud extrusion dehydration district is by after the long extrusion dehydration of sludge solids above, in sludge solids, moisture major part is extruded, when the moisture content of sludge solids low to can with received degree time, it is possible to cleared out, such sludge solids, the most qualified mud.In the intrinsic bottom of sedimentation tank, retain the qualified mud of certain altitude, for preventing above water and underproof mud from surprisingly spilling, calculate according to processing the water yield, how many sludge solids can be produced in a period of time, just periodically the qualified sludge solids of qualified mud district lowermost part correspondence water treating capacity be drawn out clearly.
Described wastewater inlet 1 is located on sedimentation tank body upper part outer wall, to having the vertical guide plate 2 coordinated with wastewater inlet 1 in sedimentation tank body;Be provided with center set tank 15 near center at the top of sedimentation tank body, described clear water output is connected with center set tank 15 by outlet pipe 14.This utility model can also be provided with sewage water inlet pipe 18 at wastewater inlet, and the water side of sewage water inlet pipe 18 is arranged on the intrinsic center of sedimentation tank, to having the vertical sewage guide plate 19 coordinated with sewage water inlet pipe water side in sedimentation tank body;Being provided with water leg 17 in the outer, top of sedimentation tank body, described clear water output is connected with water leg 17 by Graceful water pipe 20.
Described sludge output includes the conveying worm 8 being arranged on below mudhole, conveying worm is provided with mud import and sludge outlet, described mud import is connected by the mudhole of sludge bucket 7 with sedimentation tank body, is provided with sludge carrier pipe road 9 at the sludge outlet of conveying worm.Sludge output can also be drag conveyor import or the material transfer equipment import such as concrete pump entrance or piston type delivery pump import.It is provided with sludge outlet in the outer end in sludge carrier pipe road and closes end cap 10.After sludge solids exports, sludge solids can be extruded by internal gravity by conveying equipment and conveyance conduit, so the design has installed one section of sludge carrier pipe road and the sludge outlet closedown end cap of suitable length additional in the outlet of sludge solids conveying equipment.After sludge solids conveying equipment is out of service, sludge outlet is closed end cap and is automatically switched off, and the sludge solids at this moment retained in sludge carrier pipe road is the formation of a sludge solids post, and outlet conduit " is clogged " by this sludge solids post just as one " bottle stopper ".Sludge outlet closes end cap the most again to this " bottle stopper " (i.e. sludge solids post) pressure, prevents this " bottle stopper " (i.e. sludge solids post) to be extruded by internal pressure.This prevents internal mud to be extruded by internal pressure by the passage of sludge solids conveying equipment.End cap can also be closed without sludge outlet, sludge carrier pipe road can be extended upward, make the pressure pressure more than or equal to device interior of pipeline internal solid mud, be so also possible to prevent internal mud and extruded by internal pressure by sludge solids conveying equipment passage.Valve can also be installed additional in the outlet of sludge solids conveying equipment, open during conveying equipment work, close during stopping, equally, also can prevent internal mud from being extruded by internal pressure by sludge solids conveying equipment passage.According to different needs, use the different methods preventing internal mud from being extruded by internal pressure by sludge solids conveying equipment passage.
It is fixed with towards eccentric scraper plate direction of rotation at the top of eccentric scraper plate and cuts mud plate 26 every mud.Described cut mud plate 26 and eccentric scraper plate vertical (according to different needs, it is also possible to the most vertical) the front being welded on scraper plate rotary-top direction every mud.When eccentric scraper plate rotates and scrapes mud, mud plate is cut in front sludge solids is first cut in scraper plate front every mud, separate cutting the sludge solids above mud plate every mud and the sludge solids of top is held, scraper plate is made the most only to scrape the sludge solids rotating front one blade height, will not sludge solids above scraper plate.So scraper plate often rotates a circle, will be by the sludge solids Ceng Guaru pond bottom centre mudhole of a blade height (height calculated by a scraper plate).When scraper plate rotates continuously, will by the sludge solids in qualified mud district from bottom Gua Ru pond bottom centre mudhole the most continuously.So, the mud in qualified mud district (including mud extrusion dehydration district) declines the most equably, will not form the logical hole of " funnel " shape, and the sewage on top would not be through the entrance bottom, logical hole of " funnel " shape.
Described eccentric scraper plate includes that periphery is scraped mud section 23, middle transition section 24 and mud is pushed to the centre pilot section 25 of mudhole.Described periphery is scraped mud section 23, middle transition section 24 and centre pilot section 25 and is arranged continuously.The intersegmental disconnected setting of mud section, middle transition section and centre pilot is scraped in described periphery.Described eccentric scraper plate is that the rectangular slab of the setting not passing through pond centrage around the rotation of pond centrage is (according to different needs, may not be flat board rectangle, can be the other shapes of plates such as arc), when scraper plate rotates around pond centrage, the horizontal line of the point on any point and same level upper storage reservoir centrage on scraper plate, with the angle of eccentric scraper plate both greater than (or being equal to) 90 degree, such scraper plate just pushes the sludge solids in rotation front to mudhole.Described eccentric scraper plate every section can also divide multilamellar to install not all on a horizontal plane as required up and down.Utilize eccentric scraper plate by sludge solids in bottom layer by layer bottom pond each position " equably " scrape the mudhole of Chi Dibuzhongxinchu, in other words, being exactly scraper plate every revolution, the mud in qualified mud district the most integrally declines the height of an eccentric scraper plate.As the height that qualified mud district (including mud extrusion dehydration district) each position declines is necessary, otherwise, will result in the logical hole declining fast position formation " funnel " shape, the sewage on top will pass through bottom the entrance pond, logical hole of " funnel " shape.
Described periphery is scraped mud section, middle transition section, centre pilot section and is connected with the drive shaft 12 being arranged on sedimentation tank body interior center by linking arm respectively, is provided with the driving means 16 driving drive shaft 12 to rotate at the top of sedimentation tank body.Described linking arm is that drive shaft and eccentric scraper plate link together and the torque of drive shaft passed to the component that eccentric scraper plate promotes scraper plate to rotate, and generally doubles as scraper plate pivoted arm by cutting mud plate every mud.Described driving means can be located at the lower section of sedimentation tank body, it is also possible to be located at sedimentation tank body top.If be positioned below, it is necessary to install shaft seal additional, by getting up through the gap sealing at the bottom of the axle at the bottom of pond and pond, prevent the water in pond and mud from spilling.

Claims (9)

1. a sedimentation tank, including vertically arranged sedimentation tank body, sedimentation tank body is provided with wastewater inlet and clear water output, it is characterized in that: the inside of described sedimentation tank body sets gradually as settling zone from top to bottom, mud transition region, mud extrusion dehydration district and qualified mud district, the sludge clearing device of qualified mud in drawing clearly sedimentation tank it is provided with in qualified mud district, sludge clearing device includes being located at the mudhole of sedimentation tank body inner bottom part center and qualified mud being pushed to the eccentric scraper plate of mudhole, it is fixed with towards eccentric scraper plate direction of rotation at the top of eccentric scraper plate and cuts mud plate every mud, the sludge output coordinated with mudhole it is externally provided with at sedimentation tank body.
Sedimentation tank the most according to claim 1, it is characterised in that: described wastewater inlet is located on sedimentation tank body upper part outer wall, to having the vertical guide plate coordinated with wastewater inlet in sedimentation tank body;Be provided with center set tank near center at the top of sedimentation tank body, described clear water output is connected with center set tank by outlet pipe.
Sedimentation tank the most according to claim 1, it is characterized in that: sewage water inlet pipe is installed at wastewater inlet, the water side of sewage water inlet pipe is arranged on the intrinsic center of sedimentation tank, to having the vertical sewage guide plate coordinated with sewage water inlet pipe water side in sedimentation tank body;Being provided with water leg in the outer, top of sedimentation tank body, described clear water output is connected with water leg by Graceful water pipe.
Sedimentation tank the most according to claim 1, it is characterized in that: described sludge output includes the conveying worm being arranged on below mudhole, conveying worm is provided with mud import and sludge outlet, described mud import is connected by the mudhole of sludge bucket with sedimentation tank body, is provided with sludge carrier pipe road at the sludge outlet of conveying worm.
Sedimentation tank the most according to claim 4, it is characterised in that: it is provided with sludge outlet in the outer end in sludge carrier pipe road and closes end cap.
Sedimentation tank the most according to claim 1, it is characterised in that: described eccentric scraper plate includes that periphery is scraped mud section, middle transition section and mud is pushed to the centre pilot section of mudhole.
Sedimentation tank the most according to claim 6, it is characterised in that: described periphery is scraped mud section, middle transition section and centre pilot section and is arranged continuously.
Sedimentation tank the most according to claim 6, it is characterised in that: the intersegmental disconnected setting of mud section, middle transition section and centre pilot is scraped in described periphery.
Sedimentation tank the most according to claim 8, it is characterized in that: described periphery is scraped mud section, middle transition section, centre pilot section and connected with the drive shaft being arranged on sedimentation tank body interior center by linking arm respectively, is provided with the driving means driving drive shaft to rotate at the top of sedimentation tank body.
CN201620103936.1U 2016-02-02 2016-02-02 Sedimentation basin Active CN205461179U (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201620103936.1U CN205461179U (en) 2016-02-02 2016-02-02 Sedimentation basin

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201620103936.1U CN205461179U (en) 2016-02-02 2016-02-02 Sedimentation basin

Publications (1)

Publication Number Publication Date
CN205461179U true CN205461179U (en) 2016-08-17

Family

ID=56672342

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201620103936.1U Active CN205461179U (en) 2016-02-02 2016-02-02 Sedimentation basin

Country Status (1)

Country Link
CN (1) CN205461179U (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107265792A (en) * 2017-08-14 2017-10-20 马鞍山市顺达环保设备有限公司 A kind of sewage disposal device
CN109591223A (en) * 2018-12-07 2019-04-09 佛山科学技术学院 A kind of separator for separation soil and micro- plastics in soil

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107265792A (en) * 2017-08-14 2017-10-20 马鞍山市顺达环保设备有限公司 A kind of sewage disposal device
CN109591223A (en) * 2018-12-07 2019-04-09 佛山科学技术学院 A kind of separator for separation soil and micro- plastics in soil
CN109591223B (en) * 2018-12-07 2021-02-19 佛山科学技术学院 A separator that is arranged in soil to separate earth and little plastics

Similar Documents

Publication Publication Date Title
KR101180639B1 (en) Moving type screw dewatering equipment
CN205461179U (en) Sedimentation basin
CN104843955A (en) Oil and gas field drilling mud waste while-drilling processing system and processing method thereof
CN103351090A (en) Method and device for collecting and treating sludge in shallow lake
KR101319395B1 (en) Dewatering centrifuge decanter comprising thickening function
CN104829070A (en) Oil and gas field drilling fluid waste treatment-while-drilling system
CN205500982U (en) Sewage quickly separating clarifier
CN203382620U (en) Device for collecting and treating sludge in shallow lake
CN202729923U (en) Backflow type high-efficiency air-dissolved air flotation device
CN202089878U (en) Sludge concentrator
CN101823829B (en) Extrusion sludge dewatering system
KR20120091553A (en) A solid-and-liquid seperating apparatus for treating effluents, a screw dehydration apparatus and a treatment using them
CN201686602U (en) Extrusion type sludge dewatering system
CN204644081U (en) A kind of oilfield drilling mud waste is with brill treatment system
CN202193677U (en) High-efficiency sedimentation device used for mines
CN204281365U (en) Equipment for processing industrial sewage
CN207347372U (en) A kind of mud thickening system
CN107473339B (en) Mine water magnetic coagulation treatment device and process
CN204400789U (en) Mud is except gravel slurrying integrated apparatus
CN206198830U (en) A kind of novel sewage filtering machine
CN106698713B (en) Solid-liquid separation system in sewage treatment
KR101517285B1 (en) A Sludge turnkey treatment system for a basin
CN204644080U (en) A kind of oilfield drilling mud waste is with brill treatment system
KR101431161B1 (en) Filtering, dehydrating equipment of sand and impurities
CN202538428U (en) Sludge concentrator

Legal Events

Date Code Title Description
GR01 Patent grant
C14 Grant of patent or utility model