CA2355575A1 - Thickeners with vibrating inclined plates - Google Patents
Thickeners with vibrating inclined plates Download PDFInfo
- Publication number
- CA2355575A1 CA2355575A1 CA002355575A CA2355575A CA2355575A1 CA 2355575 A1 CA2355575 A1 CA 2355575A1 CA 002355575 A CA002355575 A CA 002355575A CA 2355575 A CA2355575 A CA 2355575A CA 2355575 A1 CA2355575 A1 CA 2355575A1
- Authority
- CA
- Canada
- Prior art keywords
- thickener
- liquid
- suspension
- holding tank
- inclined plates
- 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.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D21/00—Separation of suspended solid particles from liquids by sedimentation
- B01D21/28—Mechanical auxiliary equipment for acceleration of sedimentation, e.g. by vibrators or the like
- B01D21/283—Settling tanks provided with vibrators
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D21/00—Separation of suspended solid particles from liquids by sedimentation
- B01D21/24—Feed or discharge mechanisms for settling tanks
- B01D21/245—Discharge mechanisms for the sediments
- B01D21/2455—Conveyor belts
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Separation Of Suspended Particles By Flocculating Agents (AREA)
Abstract
A thickener with vibrating inclined plates placed inside is disclosed for separating solids from feed liquor of suspended solids, by gravity settling, to form a thickened suspension as thickener underflow effluent and recovering clarified liquid as thickener overflow effluent. The thickener is composed of a liquid-holding tank of rectangular or circular geometry, preferably with triangular or conical bottom section. Inside the thickener, vibrating inclined plates are placed, preferable in the compression zone of the thickener.
The number and geometry of the plates, and their inclination angles are adjusted depending on the sliding characteristics of the sedimenting suspension. The inclined plates vibrate continuously or periodically at selected vibration directions, amplitudes and frequencies. Thickener overflow or the clarified fluid, which is the process water for most of industrial applications, is collected in a launder and continuously discharged.
Thickener underflow is the thickened suspension, which is continuously discharged from the bottom of the thickener using screw conveyer. The present invention can be used for thickening of suspensions by means of batch or continuous operating modes.
The number and geometry of the plates, and their inclination angles are adjusted depending on the sliding characteristics of the sedimenting suspension. The inclined plates vibrate continuously or periodically at selected vibration directions, amplitudes and frequencies. Thickener overflow or the clarified fluid, which is the process water for most of industrial applications, is collected in a launder and continuously discharged.
Thickener underflow is the thickened suspension, which is continuously discharged from the bottom of the thickener using screw conveyer. The present invention can be used for thickening of suspensions by means of batch or continuous operating modes.
Description
Descriution Background of the Innovation The present invention relates generally to the sedimentation process also called thickening, caused by natural gravity, which is used for the separation of suspended solids from solid-liquid suspensions.
Sedimentation apparatus, called thickeners, operating by gravity settling are used to separate suspended solids from streams of liquid, such as water and wastewater. A
thickener is also called a clarifier, siince the recovered liquid would contain a very minor amount, i.e., generally less than 0.1 % by weight solids. The objective of the use of a thickener apparatus could be obtaining the thickened pulp, recovering the liquid, or both.
In most industrial applications, the feed stream contains about 5 % to 30 % by weight solids, while the thickened suspensions contain about more than 30 % by weight solids.
Particle size and particle density of suspended solids, suspension temperature, fluid viscosity, fluid density and thickener geometry are the paramount parameters affecting thickener performance. To accelerate liquid-solid separation, especially when the size of suspended particles is small, it is a common practice to employ chemical additives, which are called flocculating and/or coagulating reagents. 'These chemical additives reduce the solid-liquid interfacial tension in i;he suspension, by which the very fine suspended particles cannot be wetted strongly by the liquid and they form aggregates, which are also called flocs. These aggregates can settle rapidly since their sizes are sufficiently large.
For large particles, gravity forces easily overcome viscous drag forces exerted on the particles by the upward motion of the release fluid and the downward motion of the suspended particles. In most cases, mixing of chemical additives in the suspension is accomplished outside the thickener, for example in a transportation pipeline, in a feedwell or in a mixing tank. In army case, sufficient retention time and mixing intensity are needed for the formation of the aggregates. Some chemical additives work better when the solid concentration of the; suspension is within a narrow concentration range, i.e., for some suspensions this range: is about 4 % to 8 % by weight solid concentration.
If the solid concentration in the feed suspension is large, then dilution of the feed Thickeners with Vibrating Inclined Plates suspension is needed, so that the chemical additive would work effectively to form aggregates.
Standpipe tests, I L or 2 L ( 1 L. is 0.001 cubic meter) capacity, are generally used to understand thickening mechanism for a given suspension. Thickening of suspensions takes place in four distinct zones, which are formed in the thickener:
~ Zone I, composed of clear recovered liquid.
~ Zone II or hindered settling zone, composed of pulp with uniform concentration with constant settling velocity.
~ Zone III, a thin transition zone between Zone II and Zone IV.
~ Zone IV or compression zone, composed of thickened pulp, in which solid concentration gradient exists.
In standpipe tests, the settling characteristics of the pulp and operating conditions such as temperature and pulp solid concentration determine the thickness of each zone.
In thickeners however, the thickness of each zone is a function of additional variables such as thickener geometry, thickener type, raking mechanism, etc.
It is well known that the settling .capacity of a thickener is related to the cross sectional area of the thickener and settling velocity of the particles in the pulp. The settling capacity of a thickener is definedf as the solid flux per unit cross sectional area of the thickener, i.e., kilogram solids fed into the thickener per square meter cross sectional area of the thickener, per hour. The minimum hindered settling velocity of Zone II
will eventually control the settling cal>acity and therefore exerts a primary influence on the cross sectional area of the thickener.
Batch settling tests are generally suitable to measure hindered settling rates and pulp concentrations and are useful for predicting the required surface area of the thickener.
The hindered settling rate can be determined by observing the motion of the interface between Zone I and Zone II as a function of time. The height of the thickener and slow raking of the pulp in Zone IV will affect the performance of the sediments within the compression zone. The best supporting data for the performance of Zone IV, the compression zone, can be obtained by operating a continuous pilot unit, which is usually only economically feasible for large projects.
Summary of the Invention A primary objective of the present invention is to provide an improved sedimentation apparatus for treating industrial suspension and tailings. The present invention could be used for the thickening of oil sands tailings, industrial tailings such as pulp and paper, food processing and malting wastewater, mineral slurnes such as coal and mineral processing tailings, municipal sewage, and others.
The present invention increases the settling capacity of the thickener. As a result, with the present invention, a thickener with a fixed cross sectional area would have a high settling capacity, therefore would handle the thickening of a high suspension feed rate.
At the same time, the thickener still would provide good clarity in the supernatant liquid, Thickeners with Vibrating Inclined Plates -which is the thickener overflow effluent. It would also provide a high solid concentration in the compression zone and therefore a high solid concentration in the thickener underflow effluent.
The present invention uses vibrating inclined plates placed in the thickener, triangular or conical thickener bottom cross sectional geometry and rotating screw conveyer mounted in the bottom of the thickener. The present invention uses the combined effects of vibrating inclined plates, thickener bottom geometry and rotating screw conveyer for the most effective use of natural gravity to thicken the suspension. Using the present invention, high solid concentration in the compression zone is achieved without conventional raking mechanisms and the thickened suspension is easily discharged from the thickener.
The present invention is a sedimentation process apparatus with inclined vibrating plates placed in the thickener, preferably in the compression zone, Zone IV, of the thickener.
Experimental tests performed using vibrating plates with inclining angles of 30, 45 and 60 degrees from the horizontal planes showed that small inclining angle from the horizontal plane for the vibrating plates performs betters. Small inclining angles however, would limit the downward sliding motion of the settled solids on the vibrating plates by the gravitational force. The most effective inclining angle for vibrating plates from the horizontal plane would not be universally constant. The optimal value of the inclining angle for the vibrating plates from the horizontal plane would be a function of the amplitude, frequency and direction of the vibration of the plates, as well as the physical characteristics of the thickened suspension. Therefore, the optimal value of the inclining angle from the horizontal plane would be determined experimentally.
The optimal inclining angle for the triangular or conical bottom section of the thickener would be experimentally determined using a laboratory scale thickener.
Preferably, the inclining angle for the triangular or conical bottom section of the thickener will be parallel to the inclining angle of the vibrating plates.
As an example, a brief description of a rectangular thickener with a triangular bottom section using the art described in the present invention is depicted in Figure 1.
Other prior art considers thickening; apparatus of interest hereto includes U.S. Pat. Nos.
4,787,978; 4,681,683; 4,544,487; 4,515,698; 4,263,137; 4,178,243; 4,151,084;
4,142,970;
4,055,494 and 3,975,266.
Sedimentation apparatus, called thickeners, operating by gravity settling are used to separate suspended solids from streams of liquid, such as water and wastewater. A
thickener is also called a clarifier, siince the recovered liquid would contain a very minor amount, i.e., generally less than 0.1 % by weight solids. The objective of the use of a thickener apparatus could be obtaining the thickened pulp, recovering the liquid, or both.
In most industrial applications, the feed stream contains about 5 % to 30 % by weight solids, while the thickened suspensions contain about more than 30 % by weight solids.
Particle size and particle density of suspended solids, suspension temperature, fluid viscosity, fluid density and thickener geometry are the paramount parameters affecting thickener performance. To accelerate liquid-solid separation, especially when the size of suspended particles is small, it is a common practice to employ chemical additives, which are called flocculating and/or coagulating reagents. 'These chemical additives reduce the solid-liquid interfacial tension in i;he suspension, by which the very fine suspended particles cannot be wetted strongly by the liquid and they form aggregates, which are also called flocs. These aggregates can settle rapidly since their sizes are sufficiently large.
For large particles, gravity forces easily overcome viscous drag forces exerted on the particles by the upward motion of the release fluid and the downward motion of the suspended particles. In most cases, mixing of chemical additives in the suspension is accomplished outside the thickener, for example in a transportation pipeline, in a feedwell or in a mixing tank. In army case, sufficient retention time and mixing intensity are needed for the formation of the aggregates. Some chemical additives work better when the solid concentration of the; suspension is within a narrow concentration range, i.e., for some suspensions this range: is about 4 % to 8 % by weight solid concentration.
If the solid concentration in the feed suspension is large, then dilution of the feed Thickeners with Vibrating Inclined Plates suspension is needed, so that the chemical additive would work effectively to form aggregates.
Standpipe tests, I L or 2 L ( 1 L. is 0.001 cubic meter) capacity, are generally used to understand thickening mechanism for a given suspension. Thickening of suspensions takes place in four distinct zones, which are formed in the thickener:
~ Zone I, composed of clear recovered liquid.
~ Zone II or hindered settling zone, composed of pulp with uniform concentration with constant settling velocity.
~ Zone III, a thin transition zone between Zone II and Zone IV.
~ Zone IV or compression zone, composed of thickened pulp, in which solid concentration gradient exists.
In standpipe tests, the settling characteristics of the pulp and operating conditions such as temperature and pulp solid concentration determine the thickness of each zone.
In thickeners however, the thickness of each zone is a function of additional variables such as thickener geometry, thickener type, raking mechanism, etc.
It is well known that the settling .capacity of a thickener is related to the cross sectional area of the thickener and settling velocity of the particles in the pulp. The settling capacity of a thickener is definedf as the solid flux per unit cross sectional area of the thickener, i.e., kilogram solids fed into the thickener per square meter cross sectional area of the thickener, per hour. The minimum hindered settling velocity of Zone II
will eventually control the settling cal>acity and therefore exerts a primary influence on the cross sectional area of the thickener.
Batch settling tests are generally suitable to measure hindered settling rates and pulp concentrations and are useful for predicting the required surface area of the thickener.
The hindered settling rate can be determined by observing the motion of the interface between Zone I and Zone II as a function of time. The height of the thickener and slow raking of the pulp in Zone IV will affect the performance of the sediments within the compression zone. The best supporting data for the performance of Zone IV, the compression zone, can be obtained by operating a continuous pilot unit, which is usually only economically feasible for large projects.
Summary of the Invention A primary objective of the present invention is to provide an improved sedimentation apparatus for treating industrial suspension and tailings. The present invention could be used for the thickening of oil sands tailings, industrial tailings such as pulp and paper, food processing and malting wastewater, mineral slurnes such as coal and mineral processing tailings, municipal sewage, and others.
The present invention increases the settling capacity of the thickener. As a result, with the present invention, a thickener with a fixed cross sectional area would have a high settling capacity, therefore would handle the thickening of a high suspension feed rate.
At the same time, the thickener still would provide good clarity in the supernatant liquid, Thickeners with Vibrating Inclined Plates -which is the thickener overflow effluent. It would also provide a high solid concentration in the compression zone and therefore a high solid concentration in the thickener underflow effluent.
The present invention uses vibrating inclined plates placed in the thickener, triangular or conical thickener bottom cross sectional geometry and rotating screw conveyer mounted in the bottom of the thickener. The present invention uses the combined effects of vibrating inclined plates, thickener bottom geometry and rotating screw conveyer for the most effective use of natural gravity to thicken the suspension. Using the present invention, high solid concentration in the compression zone is achieved without conventional raking mechanisms and the thickened suspension is easily discharged from the thickener.
The present invention is a sedimentation process apparatus with inclined vibrating plates placed in the thickener, preferably in the compression zone, Zone IV, of the thickener.
Experimental tests performed using vibrating plates with inclining angles of 30, 45 and 60 degrees from the horizontal planes showed that small inclining angle from the horizontal plane for the vibrating plates performs betters. Small inclining angles however, would limit the downward sliding motion of the settled solids on the vibrating plates by the gravitational force. The most effective inclining angle for vibrating plates from the horizontal plane would not be universally constant. The optimal value of the inclining angle for the vibrating plates from the horizontal plane would be a function of the amplitude, frequency and direction of the vibration of the plates, as well as the physical characteristics of the thickened suspension. Therefore, the optimal value of the inclining angle from the horizontal plane would be determined experimentally.
The optimal inclining angle for the triangular or conical bottom section of the thickener would be experimentally determined using a laboratory scale thickener.
Preferably, the inclining angle for the triangular or conical bottom section of the thickener will be parallel to the inclining angle of the vibrating plates.
As an example, a brief description of a rectangular thickener with a triangular bottom section using the art described in the present invention is depicted in Figure 1.
Other prior art considers thickening; apparatus of interest hereto includes U.S. Pat. Nos.
4,787,978; 4,681,683; 4,544,487; 4,515,698; 4,263,137; 4,178,243; 4,151,084;
4,142,970;
4,055,494 and 3,975,266.
Claims (2)
- Claim 1. A process apparatus for continuously separating suspended solids from liquor feed streams by gravity settling comprising:
a. a liquid-holding tank of rectangular or circular geometry, preferably with a triangular or conical bottom section, for continuous thickening of a body of liquid suspension;
b. triangular or conical bottom section of the said liquid-holding tank according to Claim 1-a provides greater surface area in upwards direction, by which the linear velocity of the release liquid in an upwards direction in the thickener is reduced, which decreases the interaction between the settling particles and the release liquid, and consequently causes an increase in the rate of particle settling;
c. triangular or conical bottom section of the said liquid-holding tank according to Claim 1-a improves the compaction of the thickened suspension caused by natural gravity, which results in a better compression of the thickened suspension, therefore high solid concentration;
d. vibrating inclined plates placed inside the thickener, which could be in varying number and geometry, mounted preferable within the compression zone of the said liquid-holding tank according to Claim 1-a;
e. vibrating inclined plates according to Claim 1-d, vibrating continuously or periodically, at selected directions, amplitude and frequency in the said liquid-holding tank according to Claim 1-a provide disruptive energy to the solids suspension structure resulting in accelerated reduction in excess fluid pressure, accelerated compression of the thickened suspension and faster release of the liquid. - Claim 2. A process apparatus according to Claim 1, further including a mechanism for continuous discharge of thickened suspensions comprising:
a. a machine according to Claim 2 further consisting of a continuously rotating screw conveyer mounted in the bottom section of the said liquid-holding tank according to Claim 1-a, which continuously discharges the thickened suspension; and, b. a machine according to Claim 2-a the said continuously rotating screw conveyer further increases the compression of the thickened suspension during its discharge.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002355575A CA2355575A1 (en) | 2001-08-03 | 2001-08-03 | Thickeners with vibrating inclined plates |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002355575A CA2355575A1 (en) | 2001-08-03 | 2001-08-03 | Thickeners with vibrating inclined plates |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2355575A1 true CA2355575A1 (en) | 2003-02-03 |
Family
ID=4169794
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002355575A Abandoned CA2355575A1 (en) | 2001-08-03 | 2001-08-03 | Thickeners with vibrating inclined plates |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2355575A1 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010031107A1 (en) * | 2008-09-17 | 2010-03-25 | Outotec Oyj | Method and apparatus for disturbing networked pulp |
| WO2011091722A1 (en) * | 2010-01-27 | 2011-08-04 | 昆明理工大学 | Vibratile micro-distance settling module |
| US20130284641A1 (en) * | 2012-03-20 | 2013-10-31 | Syncrude Canada Ltd. In Trust For The Owners Of The Syncrude Project | Bitumen separation process and apparatus for problem ores |
| CN105031964A (en) * | 2015-07-07 | 2015-11-11 | 苏州珍展科技材料有限公司 | Improved thickener apparatus |
| CN111603809A (en) * | 2020-07-01 | 2020-09-01 | 长沙矿山研究院有限责任公司 | Thickener and using method thereof |
-
2001
- 2001-08-03 CA CA002355575A patent/CA2355575A1/en not_active Abandoned
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010031107A1 (en) * | 2008-09-17 | 2010-03-25 | Outotec Oyj | Method and apparatus for disturbing networked pulp |
| US8641909B2 (en) | 2008-09-17 | 2014-02-04 | Outotec Oyj | Method and apparatus for disturbing networked pulp |
| AU2009295249B2 (en) * | 2008-09-17 | 2016-02-04 | Metso Outotec Finland Oy | Method and apparatus for disturbing networked pulp |
| AU2009295249C1 (en) * | 2008-09-17 | 2016-04-28 | Metso Outotec Finland Oy | Method and apparatus for disturbing networked pulp |
| WO2011091722A1 (en) * | 2010-01-27 | 2011-08-04 | 昆明理工大学 | Vibratile micro-distance settling module |
| US20130284641A1 (en) * | 2012-03-20 | 2013-10-31 | Syncrude Canada Ltd. In Trust For The Owners Of The Syncrude Project | Bitumen separation process and apparatus for problem ores |
| CN105031964A (en) * | 2015-07-07 | 2015-11-11 | 苏州珍展科技材料有限公司 | Improved thickener apparatus |
| CN111603809A (en) * | 2020-07-01 | 2020-09-01 | 长沙矿山研究院有限责任公司 | Thickener and using method thereof |
| CN111603809B (en) * | 2020-07-01 | 2023-07-04 | 长沙矿山研究院有限责任公司 | Thickener and use method thereof |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |