WO2022269476A1 - Filtre rotatif amélioré - Google Patents

Filtre rotatif amélioré Download PDF

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Publication number
WO2022269476A1
WO2022269476A1 PCT/IB2022/055729 IB2022055729W WO2022269476A1 WO 2022269476 A1 WO2022269476 A1 WO 2022269476A1 IB 2022055729 W IB2022055729 W IB 2022055729W WO 2022269476 A1 WO2022269476 A1 WO 2022269476A1
Authority
WO
WIPO (PCT)
Prior art keywords
drum
rotary filter
screen
water
cylindrical section
Prior art date
Application number
PCT/IB2022/055729
Other languages
English (en)
Inventor
Andrew James Barclay
Reuben John MILLER
David Jethro MILLER
Kent William STEWART
Original Assignee
Wyma Engineering (Nz) Limited
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 Wyma Engineering (Nz) Limited filed Critical Wyma Engineering (Nz) Limited
Publication of WO2022269476A1 publication Critical patent/WO2022269476A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/44—Regenerating the filter material in the filter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/06—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums
    • B01D33/067—Construction of the filtering drums, e.g. mounting or sealing arrangements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/06—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums
    • B01D33/11—Filters with filtering elements which move during the filtering operation with rotary cylindrical filtering surfaces, e.g. hollow drums arranged for outward flow filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/44—Regenerating the filter material in the filter
    • B01D33/48—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
    • B01D33/50—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps with backwash arms, shoes or nozzles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2201/00—Details relating to filtering apparatus
    • B01D2201/28—Position of the filtering element
    • B01D2201/282—Filtering elements with a horizontal rotation or symmetry axis

Definitions

  • the present invention relates to a rotary filter for screening particles out of wastewater.
  • the invention has been developed with especial reference to screening water used for washing fruit and vegetables and therefore will be described with particular reference to that application.
  • the rotary filter of the present invention is suitable for screening out soils and organic matter from wastewater such as dairy effluent, stormwater, sewage, excavation run-off, and food processing waste water.
  • the filter of the present invention can be used to filter a wide range of particle sizes, but it is particularly useful for screening particle sizes less than 1 mm.
  • the problem of screening particle-carrying water has been approached in a number of ways for at least 90 years, and the equipment which has been proposed for this purpose includes both equipment for screening wastewater containing soil particles and/or organic material, and equipment for screening predominantly organic fibrous material such as wood pulp.
  • the screening of predominantly organic fibrous material poses fewer problems in that the fibres’ shape is such that they tend to lie across a screen and each other rather than lodging in the apertures of the screen. This results in longer run times before blinding, and the screen being easier to clean. It follows that screening apparatus which works satisfactorily for screening out fibres does not work adequately when it is used to screen waste water containing soil and/or organic material with small screen sizes (less than 1 mm).
  • Water spraying on the outside of the screen whilst effective in clearing particles blinding the screen, requires the use of a large volume of freshwater and of course introduces a great deal more water into the wastewater system.
  • Fresh or clean water is generally required for back washing to allow the use of smaller nozzles at high pressure for cleaning.
  • the filtered water is often not suitable for spray bars as despite the filtration, the particles remaining may either erode and or clog the pipework.
  • One of the objectives of screening wastewater in the first place is to conserve water, the idea being that the screened wastewater can be reused for further washing or for other purposes. Thus, having to use freshwater to wash off the screen is undesirable.
  • Air blasts do not have the drawbacks of water sprays, but they do require a considerable amount of pressure to be effective. Compressed air is expensive to produce, requiring additional power and thus reduces the cost effectiveness of the overall system.
  • a rotary filter includes a cylindrical screen 2 which is mounted on, and rotatable with, a horizontal driveshaft 3 which extends along the longitudinal axis of the cylinder.
  • a conical portion is mounted on the end of the cylinder 2 opposite to the intake 18 into the rotary filter.
  • the intake 18 extends into the corresponding end of the cylinder 2 by about one third of the overall length of the cylinder 2.
  • the rotary filter is provided with an internal helix 13 which extends from adjacent the end of the intake 18 inside the cylinder 2, to the end of the conical portion.
  • a curved plate 14 is mounted underneath the rotary filter, arranged so that the lowermost section of the screen cylinder is continuously partially immersed in liquid held on the plate 14.
  • liquid to be processed enters the rotary filter through the intake 18 and is sprayed onto the screen at diametrically opposite areas.
  • the rotary filter is rotated on the driveshaft 3, and as the rotary filter rotates, the lowermost section of the screen is washed by the liquid reservoir on the curved plate 14, assisting in keeping the screen clear.
  • the screen is designed to separate, clean and recover larger clean particles of wood from a pulp stream with the fibrous pulp stream, being the underflow and waste. This is the opposite of what is required in this invention, where the underflow is screened to as fine a level as practically possible for reuse, with the screened out soil and fibre being sent to waste.
  • the tray which holds water providing the water head is relatively small, with low depth and width. As a result, this water will tend to move in the same direction as the screen rotates, and thus be ejected from the tray by the rotation of the drum, diminishing the effective water head created to limit differential pressures that assist to slow down the blinding of the screen.
  • the water rotating on the curved tray results in a less turbulent flow being created below the screen, limiting the amount of backwash, which is a critical requirement for the continuous clearing of the screen.
  • the internal helix 13 does not start until about one third of the distance along the longitudinal axis of the cylinder 2; this means that particles in the water being processed tend to lodge in the first portion of the cylinder 2, rather than being carried to the end of the rotary filter by the internal helix 13. Presumably, this is not a significant problem when paper pulp is being processed, because the rotary filter is used to screen out comparatively large particles only:- the equipment is designed to allow the finer wood fibres pass through the filter with the water.
  • An object of the present invention is the provision of a rotary filter suitable for processing waste water at a high rate of throughput, without requiring air blasters and/or water sprayers as an essential mechanism for cleaning off the screens of the filter, but capable of removing a high proportion of solid particles in the waste water.
  • the filter of the present invention may incorporate air blasters and/or water sprayers, but these will not be the primary mechanism for cleaning off the filter screens.
  • the present invention provides a rotary filter which includes:
  • an auger mounted inside the drum and arranged for rotation coaxially with the drum, wherein the auger extends substantially the full length of the drum;
  • the drum having an inlet at one end for the admission of wastewater to be processed and an outlet at the other end for the discharge of filtered solid particles;
  • the drum being mounted so that the lowermost surface of the drum at said other end of the drum is higher than the lowermost surface of the drum at said one end of the drum, in a horizontal plane;
  • the rotatable drum includes a first cylindrical section one end of which opens into a frusto-conical section, which in turn opens into a second cylindrical section of smaller diameter than the first cylindrical section.
  • the rotatable drum is cylindrical along the whole of its length, but the axis of rotation of the drum is inclined at an acute angle to the horizontal such that the inlet end of the drum is lower than the outlet end of the drum.
  • the rotatable drum is rotated by drive means which are external to the drum and do not intrude into the interior of the drum; however, a driveshaft extending through the interior of the drum may be feasible.
  • the rotary filter is capable of removing solid particles from the waste water with a screen size of 10 - 1000 pm.
  • Figure 1 is a vertical section through a first embodiment of a rotary filter in accordance with the present invention
  • Figure 2 is a detail of part of the screen of the rotary filter of Figure 1 ;
  • Figure 3 is a vertical section through a second embodiment of a rotary filter in accordance with the present invention.
  • a rotary filter includes a drum 10 which is suspended in a housing 11 for rotation about a substantially horizontal axis.
  • the drum 10 may be rotated by any suitable means e.g. a drive belt arranged adjacent each end of the drum.
  • suitable types of drive may be substituted, and the drive is not shown in detail.
  • the drive means is such that the drive means does not intrude into the interior of the drum, to avoid fouling.
  • the lower part of the housing 11 incorporates a tank 12.
  • the drum 10 includes a first cylindrical section 13 with an inlet 14 at one end; the other end of the cylindrical section opens into the wider end of a frusto-conical section 15.
  • the narrower end of the frusto-conical section 15 opens into a second cylindrical section 16 which terminates in a solids outlet 17.
  • the first cylindrical section 13, frusto conical section 15, and second cylindrical section 16 all are coaxial; the common axis is substantially horizontal, and is the axis of rotation of the drum 10.
  • Auger blades 18 are attached around the inside of the drum 10 in each of the sections 13, 15 and 16.
  • the auger blades rotate with the drum 10 and are angled so that as the drum 10 rotates, the auger blades move solid particles in the drum 10 from the inlet 14 to the outlet 17.
  • the auger blades 18 start adjacent the inlet 14, and extend the full length of the drum. Alternatively, a separate auger where the blades are not attached to the screen, could be used.
  • each of the three sections 13, 15 and 16 of the drum 10 is formed by a supporting metal grid 19 with relatively large apertures (typically 130 x 90 mm).
  • the grid 19 supports a filter screen 20 which provides apertures, (depending on requirements) ranging from 10-1000 pm in width/height and extends around the whole of the interior surface of the drum 10.
  • the drum 10 is supported in the housing 11 such that the lower part of the first cylindrical section 13 of the drum 10 lies inside the tank 12.
  • the level of water inside the tank 12 is controlled by any suitable means, for example, by an adjustable weir 21 , the height of which can be raised or lowered by an adjustment mechanism (not shown). This water level may also be controlled by a transducer and valve or similar.
  • the tank 12 is provided with a filtered water outlet 22 and also with a dump valve 23 fitted to the bottom of the tank, so that any fine particles which have settled out of the filtered water in the tank can be removed from the tank.
  • the tank 12 must be dimensioned to hold a sufficient volume of water that the section 13 of the drum can rotate in the tank without significantly affecting the water level.
  • the above described apparatus is used as follows:- wastewater to be filtered enters the drum 10 through the inlet 14. Water can leave the drum 10 through the apertures in the screen 20, but any particles larger than the screen size are retained by the screen.
  • the drum 10 may be rotated constantly or intermittently; preferably, the drum is rotated constantly at a rate of rotation which provides a screen tangential velocity of at least 0.6 ms 1 . Rotation of the drum 10 causes the auger blades 18 to move the larger particles accumulating inside the drum 10 in the direction of arrow A i.e. towards the outlet 17.
  • the deposit of the particles on the screen 20 tends to blind the screen, and these particles must be removed continually, or the efficiency of the apparatus will be seriously compromised.
  • each section of screen 20 in the first cylindrical portion 13 is cleared via the resulting tangential and radial forces of the water pushing the blinding waste out of the screen and back inside the drum 10.
  • the depth to which the drum 13 is submersed in the water of the tank 12 depends upon a number of factors, including the screen size, the throughput rate and the particle loading in the water. Typically, the drum 13 is submersed by 55-215 mm. Water in the tank 12 which rises above the level of the weir 21 flows over the weir as indicated by arrow B and is removed through the filtered water outlet 22.
  • the solid particles retained in the drum 10 are moved continually down towards the outlet 17 as the drum 10 is rotated and are collected at the outlet 17.
  • the second cylindrical section 16 is used to dewater the solid particles as they are transported via the auger blades 18 to the outlet 17.
  • the duration of time which solid particles are held in section 16 (controlled by the length, rotational speed, and auger pitch of section 16) (which is above the water in the tank 12) determines the degree to which the solid particles are dewatered before being collected at the outlet 17.
  • the throughput rate depends upon a number of interdependent factors: obviously, the greater the length and the diameter of the first cylindrical section 13, the greater the area of screen 20 which can be supported, and the greater the capacity of the filter.
  • the throughput rate naturally will reduce as the particle loading in the water increases, and also will reduce as the screen aperture size reduces.
  • a further factor affecting the throughput rate is the proportion of the first cylindrical section 13 which can be submerged in the tank 12; this depends on the dimensions of the tank and also upon the length and diameter of the first and second cylindrical sections 13, 16. The deeper the drum 13 is submersed in the water within the tank 12, the smaller the pressure differential from the outside to the inside of the screen; this reduces the forces required to clean the screen by rotation of the first cylindrical section 13 in the tank 12.
  • the diameter of the second cylindrical section 16 also affects the efficient operation of the filter:- if the section 16 is too small a diameter, it may not have a sufficient capacity to auger out the trapped particulates. However, if the smaller section is too large a diameter, then it can prevent a sufficiently large proportion of the first cylindrical portion 13 being submerged in the tank 12, and in addition it can mean that when the filter is rotated, the tangential velocity of the section 16 is so high that the filtered product in this section is flung onto the walls of the section, rather than being extracted by the auger.
  • a filter constructed as shown in Figure 1 was used to filter vegetable wash line water with a total suspended solids loading of approximately 2%, using a screen aperture of 150 pm.
  • the diameter of the first cylindrical section 13 was 1 m and the length of the first cylindrical section 13 was 1.5 m; a throughput of over 40 L per second was achieved.
  • the rotary filter includes a drum 30 which is suspended in a housing 31 for rotation about an axis inclined at an acute angle to the horizontal, so that the intake end 32 of the drum is lower than the output end 33, in a horizontal plane.
  • the drum 30 is rotated by any suitable means, for example a drive belt arranged adjacent each end of the drum.
  • the drive means preferably does not include any components extending into the interior of the drum, to avoid fouling.
  • the whole of the drum 30 is cylindrical. Auger blades 34 are attached around the inside of the drum, extending the full length of the drum. The auger blades rotate with the drum and are angled so that as the drum rotates, the auger blades move solid particles inside the drum from the inlet 32 to the outlet 33.
  • the exterior surface of the drum 30 is formed in the same manner as the exterior surface of the drum 10 described with reference to Figures 1 and 2.
  • the drum 30 is supported in the housing 31 such that a large portion of the length of the drum 30 lies with its lowermost portion inside a tank 35 which is incorporated in the housing 31.
  • the level of water inside the tank 35 is controlled by any suitable means, for example, by an adjustable weir 36, the height of which can be raised or lowered by an adjustment mechanism (not shown). This water level may also be controlled by a transducer and valve or similar.
  • the tank is provided with a filtered water outlet 37 and a dump valve 38. Similar to Figure 1 , the latter section of the drum 30 is then used to dewater the solid particles as they are transported to via the auger blades 34 to the outlet 33.
  • the apparatus of Figure 1 and Figure 3 may be provided with a spray bar 40 which extends along substantially the full length of the drum 10/30.
  • This spray bar is connected to a supply of water (e.g. the filtered water from the base of the tank) and may be used to clean off the grid 19 and screen 20 at the end of operation, to avoid waste drying on to the grid or the screen.
  • the spray bar 40 may be used for additional cleaning of the grid and screen, especially (in the case of the Figure 1 embodiment) to unblind the tapered section 15 and the second cylindrical section 16, using periodic spraying (e.g. 5 second sprays every 3 minutes).

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Filtration Of Liquid (AREA)

Abstract

Un filtre rotatif comprend : un tambour rotatif qui a au moins une partie de sa paroi extérieure formée par des tamis ; une vis sans fin est montée à l'intérieur du tambour et s'étend sensiblement sur toute la longueur du tambour ; la vis sans fin tourne de manière coaxiale avec le tambour ; le tambour comporte une entrée d'eaux usées à une extrémité et une sortie à l'autre extrémité pour décharger les particules solides filtrées ; le tambour est monté de telle sorte que la surface la plus basse du tambour au niveau de l'extrémité de décharge est supérieure à l'extrémité d'entrée de tambour ; un réservoir d'eau est disposé au-dessous du tambour et positionné de telle sorte qu'une partie inférieure du tambour se trouve à l'intérieur du réservoir.
PCT/IB2022/055729 2021-06-24 2022-06-21 Filtre rotatif amélioré WO2022269476A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NZ777539 2021-06-24
NZ77753921 2021-06-24

Publications (1)

Publication Number Publication Date
WO2022269476A1 true WO2022269476A1 (fr) 2022-12-29

Family

ID=84545487

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2022/055729 WO2022269476A1 (fr) 2021-06-24 2022-06-21 Filtre rotatif amélioré

Country Status (1)

Country Link
WO (1) WO2022269476A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3938434A (en) * 1973-03-19 1976-02-17 Cox Clyde H Sludge dewatering
EP2012901B1 (fr) * 2006-05-04 2012-04-25 Huber SE Procede et dispositif de separation de solides grossiers d'un fluide visqueux
US20160115065A1 (en) * 2013-07-26 2016-04-28 Ishigaki Company Limited Recovery device and recovery method for recovering specific material from sludge
CN112661365A (zh) * 2020-12-14 2021-04-16 沈阳中城生态环境与能源研究发展有限公司 一种通沟污泥分离脱水系统

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3938434A (en) * 1973-03-19 1976-02-17 Cox Clyde H Sludge dewatering
EP2012901B1 (fr) * 2006-05-04 2012-04-25 Huber SE Procede et dispositif de separation de solides grossiers d'un fluide visqueux
US20160115065A1 (en) * 2013-07-26 2016-04-28 Ishigaki Company Limited Recovery device and recovery method for recovering specific material from sludge
CN112661365A (zh) * 2020-12-14 2021-04-16 沈阳中城生态环境与能源研究发展有限公司 一种通沟污泥分离脱水系统

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