CA2833523A1 - Method for the separation of slurry into a solid fraction and a liquid fraction, and the associated installation - Google Patents
Method for the separation of slurry into a solid fraction and a liquid fraction, and the associated installation Download PDFInfo
- Publication number
- CA2833523A1 CA2833523A1 CA2833523A CA2833523A CA2833523A1 CA 2833523 A1 CA2833523 A1 CA 2833523A1 CA 2833523 A CA2833523 A CA 2833523A CA 2833523 A CA2833523 A CA 2833523A CA 2833523 A1 CA2833523 A1 CA 2833523A1
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- Prior art keywords
- fraction
- accordance
- flotation tank
- mixture
- installation
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Classifications
-
- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01C—PLANTING; SOWING; FERTILISING
- A01C3/00—Treating manure; Manuring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
- B03D1/00—Flotation
- B03D1/14—Flotation machines
- B03D1/1443—Feed or discharge mechanisms for flotation tanks
- B03D1/1462—Discharge mechanisms for the froth
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
- B03D1/00—Flotation
- B03D1/14—Flotation machines
- B03D1/24—Pneumatic
- B03D1/247—Mixing gas and slurry in a device separate from the flotation tank, i.e. reactor-separator type
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/24—Treatment of water, waste water, or sewage by flotation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
- C02F11/123—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using belt or band filters
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
- C02F11/147—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using organic substances
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/20—Nature of the water, waste water, sewage or sludge to be treated from animal husbandry
Abstract
Described is a method whereby slurry with solid and liquid constituents is separated, comprising the addition to the slurry of a flocculating agent in order to obtain a first mixture, the formation of air bubbles in a fluid medium in order to obtain a second mixture, the introduction of the mixtures to a flotation tank and the initiation therein of a separation of a floating and a sinking fraction, and the removal of both fractions from the flotation tank, whereby the fluid medium is at least partly composed of the sinking fraction.
Description
. .
, METHOD FOR THE SEPARATION OF SLURRY INTO A SOLID FRACTION AND A
LIQUID FRACTION, AND THE ASSOCIATED INSTALLATION
The invention relates to a method and installation for the separation of slurry into a solid fraction and a liquid fraction.
A similar method is known and is applied to separate slurry, in the form of the excreta of pigs and similar animals from the animal husbandry sector, into a solid fraction and a liquid fraction, following which further processing can take place to provide for example compost and potable water respectively. This processing makes it possible to reduce the burden on the environment in comparison to processing of the slurry by spreading it over open land. Such separation is applied on a large scale as a consequence of increasingly stringent environmental legislation.
The method described has the disadvantage that the separation is slow and insufficiently thorough.
The invention has the objective of providing an installation and a method whereby the faster and yet at least as effective separation takes place between the solid and the liquid components is possible in a way which imposes a lower burden on the environment.
This objective is achieved by a method in accordance with the introduction, with characteristics in accordance with claim 1.
Using the method in accordance with the invention it is unnecessary to create air bubbles in the flotation tank. Further, it appears that the addition of rising air bubbles there has a retardant effect on the separation there of the floating fraction and the sinking/falling fraction.
, METHOD FOR THE SEPARATION OF SLURRY INTO A SOLID FRACTION AND A
LIQUID FRACTION, AND THE ASSOCIATED INSTALLATION
The invention relates to a method and installation for the separation of slurry into a solid fraction and a liquid fraction.
A similar method is known and is applied to separate slurry, in the form of the excreta of pigs and similar animals from the animal husbandry sector, into a solid fraction and a liquid fraction, following which further processing can take place to provide for example compost and potable water respectively. This processing makes it possible to reduce the burden on the environment in comparison to processing of the slurry by spreading it over open land. Such separation is applied on a large scale as a consequence of increasingly stringent environmental legislation.
The method described has the disadvantage that the separation is slow and insufficiently thorough.
The invention has the objective of providing an installation and a method whereby the faster and yet at least as effective separation takes place between the solid and the liquid components is possible in a way which imposes a lower burden on the environment.
This objective is achieved by a method in accordance with the introduction, with characteristics in accordance with claim 1.
Using the method in accordance with the invention it is unnecessary to create air bubbles in the flotation tank. Further, it appears that the addition of rising air bubbles there has a retardant effect on the separation there of the floating fraction and the sinking/falling fraction.
. With the application of the method in accordance with the invention, when the slurry to be separated is led into the flotation tank the air bubbles are already within that slurry and the flocculating agent, so that they do not disturb the separation of the slurry in the flotation tank.
A further advantage of the method in accordance with the invention is that the air in the flotation tank is located immediately in the place where it is used, namely with the flocculating agent to which it attaches. Also no thinning occurs.
The eventual consequence is that less air bubbles are necessary to achieve the same result.
Since the liquid medium is at least to some extent formed by the sinking fraction, there is the advantage that no process water from outside is needed, whereby there is also less burden on the environment.
In the variant in claim 2, where both mixtures are already added together before they are brought together into the flotation tank, the foam from the second mixture already has the opportunity to attach itself to the floccules from the first mixture as it passes through the supply line to the flotation tank. In other words the air bubbles are then already present with the flocculating agent in the slurry to be separated, before this arrives in the flotation tank. This also appears to have a positive effect on the separation process.
In an advantageous embodiment, the addition of the first and/or second mixture to the flotation tank takes place in or just below the fraction floating on the liquid surface. In this way the mixture is immediately in almost the correct position and no time therefore needs to be lost in getting it to the correct -3-.
, position in the flotation tank by means of convection. Also in this manner it minimally disturbs the motion of the sinking fraction. This supply may take place at a location at a fixed height, this being particularly suitable for a continuous and stable process, and may alternatively take place at a location at a variable height, this being particularly suitable for a non-continuous process and for continuous processes with variations in throughput.
In another embodiment the addition of the first and/or second mixture to the flotation tank takes place in the vertical direction, raised to a height. In this manner the floating fraction already has the correct direction of movement, and the separation will take place more quickly, in particular where the supply takes place into or just below the separation area. The vertical supply rate is then also advantageously lower than 30 cm/minute.
In another embodiment the supply of the second mixture takes place via a vertical riser pipe, widening as it approaches the discharge end. In this manner the outflow from the riser pipe is delayed with respect to the inflow into the riser pipe, preventing turbulence at the outflow to a large extent, with the consequence that the flows in the separation area are disturbed still less.
In a further embodiment the step of removing the floating fraction is carried out by an endless conveyor belt provided with transverse partitions attached to the belt, whereby the scooping or pushing transverse partitions are active at the level of the floating fraction and the conveyor belt moves upwards with CA 02833523 2013-11.-15 =
A further advantage of the method in accordance with the invention is that the air in the flotation tank is located immediately in the place where it is used, namely with the flocculating agent to which it attaches. Also no thinning occurs.
The eventual consequence is that less air bubbles are necessary to achieve the same result.
Since the liquid medium is at least to some extent formed by the sinking fraction, there is the advantage that no process water from outside is needed, whereby there is also less burden on the environment.
In the variant in claim 2, where both mixtures are already added together before they are brought together into the flotation tank, the foam from the second mixture already has the opportunity to attach itself to the floccules from the first mixture as it passes through the supply line to the flotation tank. In other words the air bubbles are then already present with the flocculating agent in the slurry to be separated, before this arrives in the flotation tank. This also appears to have a positive effect on the separation process.
In an advantageous embodiment, the addition of the first and/or second mixture to the flotation tank takes place in or just below the fraction floating on the liquid surface. In this way the mixture is immediately in almost the correct position and no time therefore needs to be lost in getting it to the correct -3-.
, position in the flotation tank by means of convection. Also in this manner it minimally disturbs the motion of the sinking fraction. This supply may take place at a location at a fixed height, this being particularly suitable for a continuous and stable process, and may alternatively take place at a location at a variable height, this being particularly suitable for a non-continuous process and for continuous processes with variations in throughput.
In another embodiment the addition of the first and/or second mixture to the flotation tank takes place in the vertical direction, raised to a height. In this manner the floating fraction already has the correct direction of movement, and the separation will take place more quickly, in particular where the supply takes place into or just below the separation area. The vertical supply rate is then also advantageously lower than 30 cm/minute.
In another embodiment the supply of the second mixture takes place via a vertical riser pipe, widening as it approaches the discharge end. In this manner the outflow from the riser pipe is delayed with respect to the inflow into the riser pipe, preventing turbulence at the outflow to a large extent, with the consequence that the flows in the separation area are disturbed still less.
In a further embodiment the step of removing the floating fraction is carried out by an endless conveyor belt provided with transverse partitions attached to the belt, whereby the scooping or pushing transverse partitions are active at the level of the floating fraction and the conveyor belt moves upwards with CA 02833523 2013-11.-15 =
respect to the horizontal over a first processing section in the direction of the motion of these partitions, with a gradient of less than 1:20 and preferably 1:25. In this way the floating fraction is made to move vertically to only a small degree and the flow in the separation area below it is hardly disturbed, again resulting in a faster separation. The conveyor belt may also preferably have a running speed of less than 25 cm/minute, so as to disturb the flow particularly in the horizontal direction still less than in known installations, where the speed is higher.
In a particular embodiment the conveyor belt runs upwards with respect to the horizontal in the direction of motion of these partitions over a second processing section which lies downstream of the first processing section, and a guide partition sloping upwards lies below and close to the first section. This measure also has the consequence that the flow in the flotation tank, in particular in the separation area, remains to a large extent undisturbed.
In a further embodiment the stage of adding the air bubbles to the first mixture is preceded by the preparation of the air bubbles by mixing the air bubbles with the sinking fraction from the flotation tank or located downstream of it. Using no water but instead tapping off the sinking fraction and returning it again to the flotation tank together with air, flocculating agent and slurry saves on the consumption of water. This reduces costs and less water needs to be removed from the floating fraction downstream of the flotation tank and/or less sinking fraction needs to be purified, which again reduces the costs of the method.
In a particular embodiment the conveyor belt runs upwards with respect to the horizontal in the direction of motion of these partitions over a second processing section which lies downstream of the first processing section, and a guide partition sloping upwards lies below and close to the first section. This measure also has the consequence that the flow in the flotation tank, in particular in the separation area, remains to a large extent undisturbed.
In a further embodiment the stage of adding the air bubbles to the first mixture is preceded by the preparation of the air bubbles by mixing the air bubbles with the sinking fraction from the flotation tank or located downstream of it. Using no water but instead tapping off the sinking fraction and returning it again to the flotation tank together with air, flocculating agent and slurry saves on the consumption of water. This reduces costs and less water needs to be removed from the floating fraction downstream of the flotation tank and/or less sinking fraction needs to be purified, which again reduces the costs of the method.
The method is preferably carried out as a continuous process, as in this way the highest speed of separation is achieved in the flotation tank, as the flows can be near enough unvarying or laminar.
The invention further relates to an installation in accordance with claim 10. Such an installation offers similar advantages to those described above.
Other advantageous embodiments are defined in the sub-claims.
The invention will now be further explained on the basis of the figures below, in which similar elements have been provided with the same reference numbers. In this:
Figures lA and 1B show schematic partial representations of an installation in accordance with a first embodiment of the invention.
Figure 2A shows a schematic representation of an embodiment of the method in accordance with the invention, as can be embodied in the installation in Figure 1.
Figure 23 shows a schematic representation of a stage from Figure 2A broken down into several sub-stages.
Figure 3A shows a schematic representation of a cleaning installation for the installation from Figures 1A and 13, and Figure 38 shows a detail of the transverse section through 3B-3B.
Figure lA shows the pre-processing section of an installation 1 for the separation of slurry into a solid fraction and a liquid fraction in accordance with the invention. The installation 1 includes a storage tank 2 for a mixture of the , . .
The invention further relates to an installation in accordance with claim 10. Such an installation offers similar advantages to those described above.
Other advantageous embodiments are defined in the sub-claims.
The invention will now be further explained on the basis of the figures below, in which similar elements have been provided with the same reference numbers. In this:
Figures lA and 1B show schematic partial representations of an installation in accordance with a first embodiment of the invention.
Figure 2A shows a schematic representation of an embodiment of the method in accordance with the invention, as can be embodied in the installation in Figure 1.
Figure 23 shows a schematic representation of a stage from Figure 2A broken down into several sub-stages.
Figure 3A shows a schematic representation of a cleaning installation for the installation from Figures 1A and 13, and Figure 38 shows a detail of the transverse section through 3B-3B.
Figure lA shows the pre-processing section of an installation 1 for the separation of slurry into a solid fraction and a liquid fraction in accordance with the invention. The installation 1 includes a storage tank 2 for a mixture of the , . .
= solid and liquid fractions of slurry. Storage tank 2 has a supply line 3 and a drain line 4 which leads to a mixing unit 5. A
polymer production station 6 has a supply line 7 for a standard solution and a supply line for water 8, and an outlet line 9 and which runs to the mixing unit 5. From the mixing unit 5 a line 10 runs via an aeration station 10a and via A to a flotation tank 11 shown in Figure 1A. Also visible in Figure lA is a pressure vessel 12, in which are located a large number of PVC rings 13.
The pressure vessel 12 has a drain line 14 which leads to line 10 and two supply lines, namely a supply line 15 for compressed air and a supply line 16 for the liquid fraction of slurry, arriving - via C - from flotation tank 11 via inter alia a filter 17 installed in the supply line 16, which filter has a tap-off line 18 for flushing purposes.
In Figure 1B the flotation tank 11 has side and bottom walls 112, an open upper face 113 and riser pipe 114, into which A
emerges. A drain line 115 for the liquid fraction is provided close to the floor of flotation tank 11 and emerges at overflow tank 116 which itself has a drain line 117 leading to a water production unit 118, using reverse osmosis. This water production unit 118 has two outlets, one outlet 19 for pure water, and another outlet 20 for filtered out residual matter.
In a variant of the flotation tank in Figure 1B which is not shown, the riser pipe 114 has a variable length, being fabricated in the cylindrical section at the lower end in the form of two cylinders, sliding one within the other. This variable length can if necessary be continually adjusted to the current level of the underside of the floating fraction, so that the end of the riser pipe 114 is always just below this underside.
A scraper unit 21 is provided at the upper surface of flotation tank 11, having an endless conveyor belt 22 with . rollers 23 which guide the belt 24, and there are transverse partitions fitted to the belt 24, transverse to the surface of the belt 24 and serving to scrape solid constituents above the flotation tank 11, as will be described in further detail below.
At the end of conveyor belt 22 the side wall 112 of the flotation tank 11 is formed with a rising inclination, approximately parallel to the belt 24 immediately above it. While this is not shown in the Figure, the lower surface of the conveyor belt can also be installed with an inclination to the left of the bend in the belt at the middle guide roller 23 (viewed horizontally), rising from left to right in Figure 1B.
The dimensions of the flotation tank are approximately: a height of 3.5 metres, a length of 6 metres and a width of 3.5 metres, with a normal water level of 3.3 metres and the end of the riser pipe 14 at a height of around 3.25 metres.
A conveyor belt 26 runs from the output end of the conveyor belt 22 to a belt press 27 of a known type, in this case the BPF
1200 WR 11 Greenland supplied by Sernagiotto (a subsidiary of Siemens). The latter has two endless mesh screen belts 28 which run between rollers in a filtering section of the belt press 27 and between rollers in a press section of belt press 27. A
flushing and brushing unit 29 designed by the applicant for screening belts 28 has been provided in the press section of the belt press, which is shown in Figure 3A with detail 3B.
The operation of the installation shown in Figure lA and Figure 1B is described below, by means of reference to Figures 2A
and 2B.
The stages in the process are represented in Figure 2A, with the component from the installation shown in Figures lA and 1B in which the stage in question takes place specified in brackets.
Slurry consisting of a solid fraction and a liquid fraction . .
, ' .
is preferably continuously or virtually continuously fed in and stored in storage tank 2 which serves as a buffer, and a flocculating agent is added in mixing unit 5, in this case a polymer with a positive charge of the brand Breustedt Chemie type BC FLOC EM 1750 or Brenntag type Sedipur CL 343, but some other agent is also possible. In some cases it will also be necessary to add a coagulating agent, such as for example Digi-Floc by Breustedt Chemie, in order to obtain stable floccules. However the addition of a coagulating agent leads to an elevated salt content in the fractions, which may be undesirable as requiring further processing.
The working solution of the polymer is prepared in the polymer production station 6, as for example supplied by Melspring, Axflow or ProMinent, by means of mixing of a so-called standard solution with liquid, in this case water, although if desired the liquid fraction from the flotation tank 11 may be used.
In order to obtain a sufficiently homogeneous first mixture Ml, mixing unit 5 includes a pump with an eccentric worm, after which is installed a constricted polymer injector. This sequence has the advantage that the slurry is first brought into a rotary motion by the worm pump, before the polymer is injected into the slurry, so that good mixing occurs, better than if no worm pump were used. The constriction amplifies this effect.
The result of the aforementioned mixing is a first mixture Ml, which is subsequently mixed in air mixing station 10a with air bubbles dissolved in the liquid fraction arriving from pressure vessel 12 where air is mixed with the liquid fraction under elevated pressure, in this case around 6 Bar. The mixing of the air bubbles in the liquid fraction in the pressure vessel 12 is improved by the presence of the PVC rings 13 in the in the pressure vessel 12 which come into motion and break up the air bubbles entering pressure vessel 12 to create smaller air bubbles and sometimes foam. The first mixture M1 mixed with air bubbles and liquid fraction forms a second mixture M2 which is led via A
to flotation tank 12 where it is separated. This separation takes place in sub-stages shown in Figure 2B, namely inflow (Si), in this example via riser pipe 114, followed by the separation proper (S2), whereby the liquid fraction sinks under the influence of gravity and the solid fraction with air attached to it rises, that is to say it commences to float.
The inflow is of importance since in this example and in accordance with a preference for the invention this takes place just below the region where the floating fraction consolidates and comes to a standstill, at least in the vertical direction, close to the surface of flotation tank 11 or a little further from it, depending on the quantity of floating fraction present, before being led off by conveyor belt 21.
In this way the floating fraction fed in only has to cover a small distance and therefore disturbs the natural convectional flow of the sinking fraction little or not at all. The fact that the outflow orifice of riser pipe 114 is large so that there is only a minor vertical speed component from the slurry fed in with its solid and liquid fraction contributes to this, as does the vertical position of riser pipe 14.
The de facto separation is followed by the draining of the sinking, predominantly liquid fraction via the drain line 15 (S3) and the skimming off of the floating fraction from the liquid surface (S4), which is largely solid, by scraper unit 21 and specifically by its transverse partitions 25, which as they move to the right in Figure 1B very gradually and falling with an inclination of 1:25 (20 cm in 5 metres) in the flotation tank 11, = and moreover with a very low speed of around 0.25 m/minute or 15 m/hr, take the floating solid fraction to the right where it is gradually moved upwards due to the inclined rising side wall 112 of the flotation tank 11 and so led off, subsequently falling onto conveyor belt 26, which leads on to the belt press 27 for further separation, where it first drains and is then pressed, and the residual component is led off in the form of compost.
Stage S5 achieves level control for the material in flotation tank 11, obtained through overflow tank 116.
Because of the careful manner of taking off the floating fraction described above, the actual separation resulting from gravity is so little negatively affected that it can take place quickly.
The sinking fraction led off from flotation tank 11 consists of a liquid fraction and possibly a very small quantity of small solid elements, and this is separated in the water production unit 118 by means of reverse osmosis into water, via 18 and residual matter, in particular salts, via 20.
In Figure 3A the flushing and brushing unit 29 lies against and here below the belt 28, and consists of a tube 30 which is oriented transversely to the belt 28 and runs parallel to it, horizontally in this example, and is provided on its upper surface with a number of spray orifices 31 as well as a feed orifice 32 and a rotating rod 33 lying along the longitudinal axis of the tube 30 which is connected to an electric or other motor 34 and which carries brushes 35 (see Figure 3B) which lie against the interior surface of the tube 30. A flushing valve 36 is connected to a drain line 37 and offers the possibility to flush the tube 39 by allowing the liquid fed in via the feed orifice 32, including the soiling brushed loose by the brushes 35, to flow away when flushing valve 36 is opened.
polymer production station 6 has a supply line 7 for a standard solution and a supply line for water 8, and an outlet line 9 and which runs to the mixing unit 5. From the mixing unit 5 a line 10 runs via an aeration station 10a and via A to a flotation tank 11 shown in Figure 1A. Also visible in Figure lA is a pressure vessel 12, in which are located a large number of PVC rings 13.
The pressure vessel 12 has a drain line 14 which leads to line 10 and two supply lines, namely a supply line 15 for compressed air and a supply line 16 for the liquid fraction of slurry, arriving - via C - from flotation tank 11 via inter alia a filter 17 installed in the supply line 16, which filter has a tap-off line 18 for flushing purposes.
In Figure 1B the flotation tank 11 has side and bottom walls 112, an open upper face 113 and riser pipe 114, into which A
emerges. A drain line 115 for the liquid fraction is provided close to the floor of flotation tank 11 and emerges at overflow tank 116 which itself has a drain line 117 leading to a water production unit 118, using reverse osmosis. This water production unit 118 has two outlets, one outlet 19 for pure water, and another outlet 20 for filtered out residual matter.
In a variant of the flotation tank in Figure 1B which is not shown, the riser pipe 114 has a variable length, being fabricated in the cylindrical section at the lower end in the form of two cylinders, sliding one within the other. This variable length can if necessary be continually adjusted to the current level of the underside of the floating fraction, so that the end of the riser pipe 114 is always just below this underside.
A scraper unit 21 is provided at the upper surface of flotation tank 11, having an endless conveyor belt 22 with . rollers 23 which guide the belt 24, and there are transverse partitions fitted to the belt 24, transverse to the surface of the belt 24 and serving to scrape solid constituents above the flotation tank 11, as will be described in further detail below.
At the end of conveyor belt 22 the side wall 112 of the flotation tank 11 is formed with a rising inclination, approximately parallel to the belt 24 immediately above it. While this is not shown in the Figure, the lower surface of the conveyor belt can also be installed with an inclination to the left of the bend in the belt at the middle guide roller 23 (viewed horizontally), rising from left to right in Figure 1B.
The dimensions of the flotation tank are approximately: a height of 3.5 metres, a length of 6 metres and a width of 3.5 metres, with a normal water level of 3.3 metres and the end of the riser pipe 14 at a height of around 3.25 metres.
A conveyor belt 26 runs from the output end of the conveyor belt 22 to a belt press 27 of a known type, in this case the BPF
1200 WR 11 Greenland supplied by Sernagiotto (a subsidiary of Siemens). The latter has two endless mesh screen belts 28 which run between rollers in a filtering section of the belt press 27 and between rollers in a press section of belt press 27. A
flushing and brushing unit 29 designed by the applicant for screening belts 28 has been provided in the press section of the belt press, which is shown in Figure 3A with detail 3B.
The operation of the installation shown in Figure lA and Figure 1B is described below, by means of reference to Figures 2A
and 2B.
The stages in the process are represented in Figure 2A, with the component from the installation shown in Figures lA and 1B in which the stage in question takes place specified in brackets.
Slurry consisting of a solid fraction and a liquid fraction . .
, ' .
is preferably continuously or virtually continuously fed in and stored in storage tank 2 which serves as a buffer, and a flocculating agent is added in mixing unit 5, in this case a polymer with a positive charge of the brand Breustedt Chemie type BC FLOC EM 1750 or Brenntag type Sedipur CL 343, but some other agent is also possible. In some cases it will also be necessary to add a coagulating agent, such as for example Digi-Floc by Breustedt Chemie, in order to obtain stable floccules. However the addition of a coagulating agent leads to an elevated salt content in the fractions, which may be undesirable as requiring further processing.
The working solution of the polymer is prepared in the polymer production station 6, as for example supplied by Melspring, Axflow or ProMinent, by means of mixing of a so-called standard solution with liquid, in this case water, although if desired the liquid fraction from the flotation tank 11 may be used.
In order to obtain a sufficiently homogeneous first mixture Ml, mixing unit 5 includes a pump with an eccentric worm, after which is installed a constricted polymer injector. This sequence has the advantage that the slurry is first brought into a rotary motion by the worm pump, before the polymer is injected into the slurry, so that good mixing occurs, better than if no worm pump were used. The constriction amplifies this effect.
The result of the aforementioned mixing is a first mixture Ml, which is subsequently mixed in air mixing station 10a with air bubbles dissolved in the liquid fraction arriving from pressure vessel 12 where air is mixed with the liquid fraction under elevated pressure, in this case around 6 Bar. The mixing of the air bubbles in the liquid fraction in the pressure vessel 12 is improved by the presence of the PVC rings 13 in the in the pressure vessel 12 which come into motion and break up the air bubbles entering pressure vessel 12 to create smaller air bubbles and sometimes foam. The first mixture M1 mixed with air bubbles and liquid fraction forms a second mixture M2 which is led via A
to flotation tank 12 where it is separated. This separation takes place in sub-stages shown in Figure 2B, namely inflow (Si), in this example via riser pipe 114, followed by the separation proper (S2), whereby the liquid fraction sinks under the influence of gravity and the solid fraction with air attached to it rises, that is to say it commences to float.
The inflow is of importance since in this example and in accordance with a preference for the invention this takes place just below the region where the floating fraction consolidates and comes to a standstill, at least in the vertical direction, close to the surface of flotation tank 11 or a little further from it, depending on the quantity of floating fraction present, before being led off by conveyor belt 21.
In this way the floating fraction fed in only has to cover a small distance and therefore disturbs the natural convectional flow of the sinking fraction little or not at all. The fact that the outflow orifice of riser pipe 114 is large so that there is only a minor vertical speed component from the slurry fed in with its solid and liquid fraction contributes to this, as does the vertical position of riser pipe 14.
The de facto separation is followed by the draining of the sinking, predominantly liquid fraction via the drain line 15 (S3) and the skimming off of the floating fraction from the liquid surface (S4), which is largely solid, by scraper unit 21 and specifically by its transverse partitions 25, which as they move to the right in Figure 1B very gradually and falling with an inclination of 1:25 (20 cm in 5 metres) in the flotation tank 11, = and moreover with a very low speed of around 0.25 m/minute or 15 m/hr, take the floating solid fraction to the right where it is gradually moved upwards due to the inclined rising side wall 112 of the flotation tank 11 and so led off, subsequently falling onto conveyor belt 26, which leads on to the belt press 27 for further separation, where it first drains and is then pressed, and the residual component is led off in the form of compost.
Stage S5 achieves level control for the material in flotation tank 11, obtained through overflow tank 116.
Because of the careful manner of taking off the floating fraction described above, the actual separation resulting from gravity is so little negatively affected that it can take place quickly.
The sinking fraction led off from flotation tank 11 consists of a liquid fraction and possibly a very small quantity of small solid elements, and this is separated in the water production unit 118 by means of reverse osmosis into water, via 18 and residual matter, in particular salts, via 20.
In Figure 3A the flushing and brushing unit 29 lies against and here below the belt 28, and consists of a tube 30 which is oriented transversely to the belt 28 and runs parallel to it, horizontally in this example, and is provided on its upper surface with a number of spray orifices 31 as well as a feed orifice 32 and a rotating rod 33 lying along the longitudinal axis of the tube 30 which is connected to an electric or other motor 34 and which carries brushes 35 (see Figure 3B) which lie against the interior surface of the tube 30. A flushing valve 36 is connected to a drain line 37 and offers the possibility to flush the tube 39 by allowing the liquid fed in via the feed orifice 32, including the soiling brushed loose by the brushes 35, to flow away when flushing valve 36 is opened.
= The flushing and brushing unit 29 of belt press 27 serves to spray the belt clean with sinking fraction from the flotation tank 11, through the openings 31 which are formed to act as sprayers. Experience has shown that the orifices 31 block up from time to time as a result of the presence of an extremely small quantity of solid components which have remained present in the sinking fraction. In order to prevent such blockages the flushing valve 36 is opened after a preset time (typically 15 minutes) and the electric motor 34 is activated for some time, and subsequently in the reverse direction of rotation, so that the brushes 35 clean the interior of the tube 30 and in particular unblock the orifices 31. Soiling is thereby led off via flushing valve 36. Following this process the flushing valve is closed again and orifices 31 again spray the belt 28 clean.
Because the cleaning of the belt 28 takes place using the sinking fraction from flotation tank 11, and not with water, no water is introduced to the process and there is eventually less moisture to be purified in unit 118.
Because the moisture from belt press 27 is fed back to the storage tank, whereupon it passes once again through the separation process, a more complete separation of the solid and liquid fraction of the slurry is achieved, and also an element of the added flocculant, in this case polymer, is reused, so that less polymer is required, which is advantageous from the cost and environmental perspectives.
While the method in accordance with the invention is illustrated using the installation 1 in Figures 1A and 1B, the method can also be implemented in other separation installations.
Because the cleaning of the belt 28 takes place using the sinking fraction from flotation tank 11, and not with water, no water is introduced to the process and there is eventually less moisture to be purified in unit 118.
Because the moisture from belt press 27 is fed back to the storage tank, whereupon it passes once again through the separation process, a more complete separation of the solid and liquid fraction of the slurry is achieved, and also an element of the added flocculant, in this case polymer, is reused, so that less polymer is required, which is advantageous from the cost and environmental perspectives.
While the method in accordance with the invention is illustrated using the installation 1 in Figures 1A and 1B, the method can also be implemented in other separation installations.
Claims (15)
1. A method whereby slurry is separated into solid and liquid constituents, consisting of:
- the addition of a flocculating agent to the slurry to obtain a first mixture;
- the formation of air bubbles in a fluid medium to obtain a second mixture;
- the introduction of the mixtures to a flotation tank and the initiation of a separation of a floating and a sinking liquid fraction by means of gravity;
- the removal from the flotation tank of both fractions, whereby the liquid medium is at least in part formed by the sinking fraction.
- the addition of a flocculating agent to the slurry to obtain a first mixture;
- the formation of air bubbles in a fluid medium to obtain a second mixture;
- the introduction of the mixtures to a flotation tank and the initiation of a separation of a floating and a sinking liquid fraction by means of gravity;
- the removal from the flotation tank of both fractions, whereby the liquid medium is at least in part formed by the sinking fraction.
2. A method in accordance with claim 1, characterised in that the first and second mixtures are combined, subsequently to be introduced to the flotation tank.
3. A method in accordance with claim 1 or 2, characterised in that the addition of the first and/or second mixture takes place at a level in the flotation tank which is below the underside of the floating fraction.
4. A method in accordance with one of the foregoing claims, characterised in that the addition of the first and/or second mixture to the flotation tank takes place through a virtually vertically positioned riser pipe.
5. A method in accordance with one of the foregoing claims, characterised in that the removal of the floating fraction is carried out by an endless conveyor belt provided with protruding transverse partitions which remove the floating fraction virtually without the creation of any turbulence in the floatation tank.
6. A method in accordance with claim 5, characterised in that the floating fraction from the flotation tank is dewatered until it takes on a pasty consistency.
7. A method in accordance with claim 6, characterised in that the liquid is pressed out of the fraction brought to a pasty consistency.
8. A method in accordance with claim 6 or 7, characterised in that the liquid forming part of the first or second mixture obtained by means of dewatering and/or pressing is reused.
9. A method in accordance with one of the foregoing claims, characterised in that it is carried out as a continuous process.
10. An installation for the separation of slurry into solid and liquid components, consisting of:
- a mixing unit suitable for the addition of a flocculating agent to slurry containing a solid fraction and a liquid fraction, in order to form a first mixture;
- a pressure vessel filled with a fluid medium suitable to form a second mixture by means of the addition of air bubbles to it;
- a flotation tank connected to the mixing unit and the pressure vessel, in which a separation is brought about between a floating and a sinking liquid fraction therein purely by the force of gravity, and - drainage equipment connected to the flotation tank used for the removal from the tank of the floating and the sinking fraction respectively, whereby the drainage equipment for the sinking fraction is connected to the mixing unit and/or the pressure vessel.
- a mixing unit suitable for the addition of a flocculating agent to slurry containing a solid fraction and a liquid fraction, in order to form a first mixture;
- a pressure vessel filled with a fluid medium suitable to form a second mixture by means of the addition of air bubbles to it;
- a flotation tank connected to the mixing unit and the pressure vessel, in which a separation is brought about between a floating and a sinking liquid fraction therein purely by the force of gravity, and - drainage equipment connected to the flotation tank used for the removal from the tank of the floating and the sinking fraction respectively, whereby the drainage equipment for the sinking fraction is connected to the mixing unit and/or the pressure vessel.
11. An installation in accordance with claim 10, characterised in that the equipment for the introduction of the first and/or second mixture includes a virtually vertically oriented riser pipe.
12. An installation in accordance with claim 11, characterised in that at least one riser pipe is provided with an outlet widening towards the top.
13. An installation in accordance with one of the claims 10 to 12, characterised in that the flotation tank is provided with an endless conveyor belt with transverse partitions attached to the belt, and in that the conveyor belt moves upwards with respect to the horizontal with an inclination of less than 1:20 in the direction of motion of the transverse partitions over a first processing section.
14. An installation in accordance with claim 13, characterised in that the conveyor belt moves upwards with respect to the horizontal in the direction of motion of the transverse partitions over a second processing section, which lies downstream of the first processing section, and that under and close to the second processing section a guide partition sloping upwards virtually parallel to the second processing section is provided on the upper side of the flotation tank.
15. An installation in accordance with claim 13 or 14, characterised in that the installation is provided with a belt press connected to the endless conveyor belt, having an outgoing fluid line connected with the mixing unit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2010263A NL2010263C2 (en) | 2013-02-07 | 2013-02-07 | METHOD FOR SEPARATING MANURE IN A FIXED FRACTION AND A LIQUID FRACTION AND ASSOCIATED DEVICE. |
| NLNL-2010263 | 2013-02-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2833523A1 true CA2833523A1 (en) | 2014-08-07 |
Family
ID=48366523
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2833523A Abandoned CA2833523A1 (en) | 2013-02-07 | 2013-11-15 | Method for the separation of slurry into a solid fraction and a liquid fraction, and the associated installation |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2833523A1 (en) |
| NL (1) | NL2010263C2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106423585A (en) * | 2016-11-30 | 2017-02-22 | 丹东东方测控技术股份有限公司 | Plunger type flotation chemical feeding machine |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB687296A (en) * | 1950-06-20 | 1953-02-11 | Francois Laurenty | Process and apparatus for the anaerobic fermentation of vegetable products and more particularly for producing manure and gas |
| US3788478A (en) * | 1971-08-19 | 1974-01-29 | Shell Oil Co | Waste water treatment |
| HU184526B (en) * | 1972-07-29 | 1984-09-28 | Tatabanyai Szenbanyak | Method and apparatus for purifyng thin manures and sewages of plantlike animal keeping |
| GB1400064A (en) * | 1972-08-03 | 1975-07-16 | Electricity Council | Treatment of an effluent using an activated sludge process |
| US5310485A (en) * | 1992-09-30 | 1994-05-10 | Darling-Delaware Company, Inc. | Process for dissolved gas flotation in anaerobic wastewater treatment |
| US5660718A (en) * | 1993-02-10 | 1997-08-26 | M.D. Research Company Pty, Ltd. | Method and apparatus for separation by flotation |
| RU2046759C1 (en) * | 1993-05-25 | 1995-10-27 | Акционерное общество Научно-производственная фирма "Бифар" | Method of saturating liquid by pressurized gas |
| US5540836A (en) * | 1994-06-16 | 1996-07-30 | Coyne; Thomas J. | Wastewater treatment system and method |
| CA2380797A1 (en) * | 2002-04-09 | 2003-10-09 | Institut National De La Recherche Scientifique | Manure treatment method |
-
2013
- 2013-02-07 NL NL2010263A patent/NL2010263C2/en active
- 2013-11-15 CA CA2833523A patent/CA2833523A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106423585A (en) * | 2016-11-30 | 2017-02-22 | 丹东东方测控技术股份有限公司 | Plunger type flotation chemical feeding machine |
Also Published As
| Publication number | Publication date |
|---|---|
| NL2010263C2 (en) | 2014-08-11 |
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| Date | Code | Title | Description |
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| FZDE | Discontinued |
Effective date: 20191115 |