DE102006020968A1 - Flotation plant for depolluting aqueous fiber suspension, e.g. for paper-making, comprises aerated flotation cells in series connected by additional tubing to allow extra volume flow - Google Patents

Abstract

In a flotation plant (1) for removing pollutants (PL) from an aqueous fiber suspension (FS), by passing the FS through several flotation cells (2 - 5) in series, where each cell has an aerator for forming a PL-enriched flotation foam (removed as overflow) and an outlet for the refined material (RM), an additional tubing system forms connections between the cells, to overcome hydraulic over-capacity in the form of an additional volume flow of FS. A flotation plant (1) is for removing pollutants (PL) from an aqueous fiber suspension (FS), by passing the FS through several flotation cells (2 - 5) in series. Each cell has a first aerator for forming a PL-enriched flotation foam (removed as overflow) and an outlet for the refined material (RM). The novel feature is that the plant has an additional tubing system, forming FS-conducting connections between the cells, to overcome hydraulic over-capacity in the form of an additional volume flow of FS. The additional flow of initial FS is fed through a first tube past the first cell (2) to the second cell (3), the same increased amount of RM formed in the first cell is fed past the second cell to the third cell (4) and most of the RM formed in the first cell is fed to the second cell. This sequence is repeated in the remaining cells (i.e. part of the RM formed in the second cell is fed past the third cell to the fourth cell (5) etc.), until part of the RM formed in the penultimate cell is fed past the final cell to the outlet and most of the RM formed in the penultimate cell is fed via the final cell to the outlet. An independent claim is included for a corresponding pollutant removal process.

Description

The The invention relates to a flotation plant for the removal of contaminants according to the generic term of claim 1.

From the DE 10 2004 020 339 A1 is a method for flotation of impurities from an aqueous paper pulp suspension known. Such a method is used to precipitate a portion of the suspended contaminant particles contained therein from a pulp suspension. In a flotation containing the excreted substances containing foam or scum is formed. A typical application of such a method is the treatment of a paper pulp suspension obtained from recovered paper, in which the ink particles are already detached from the fibers, so that they can be floated. This flotation process makes use of the fact that the pulp is hydrophilic and remains in the suspension while the ink particles are hydrophobic and therefore rise and form a foam together with the air bubbles which are introduced into the suspension. In addition to the ink particles there are a variety of other substances that are hydrophobic and therefore can be separated by flotation of the pulp, such. As adhesives, plastic particles and possibly also resins.

From the DE 41 16 916 A1 are - in particular according to figure for the summary - Flotationszellen known, which are suitably operated with level control to allow optimum effect.

In the DE 10 2004 020 339 A1 is in 1 a system is shown with a plurality of flotation cells, each of which may have a single level control. Such flotation cells are limited to a respective throughput volume flow (nominal volume flow) due to the hydraulic surface loading. The maximum production possible with these flotation cells is thus determined by the nominal volume flow and the maximum flotation density. For subsequent production increase in such a flotation plant was previously the opportunity to arrange the existing flotation cells as parallel lines and also to expand the system with new, larger flotation cells. The parallel arrangement of the existing flotation cells doubles the hydraulic throughput of the flotation plant. However, if only 10, 20, 30, 40, 50 or 60% production increases are needed, which is the main area of desired production increases, then the parallel arrangement of the flotation cells is uneconomic (energy, space, maintenance).

It The object of the invention, an increased volume flow with a to cope with existing flotation plant.

According to the invention this Task in a flotation of the type mentioned by solved, that the flotation plant to cope with a hydraulic overcapacity in shape an additional one Volumetric flow of pulp suspension an additional pipe system for the production of additional, the pulp suspension of leading compounds between the flotation cells, wherein the additional Volume flow in the output pulp suspension through a first pipeline past the first flotation cell to the second flotation cell feasible is that, at least in essence, an equally high proportion of the accepts formed in the first flotation cell at the second Flotation cell is passed over to the third flotation cell and that the biggest part of the accepts formed in the first flotation cell in the second Flotation cell is conductive that part of the second flotation cell formed Acceptance of the third flotation cell over to the fourth flotation cell is conductive and that the largest part of the accepts formed in the second flotation cell to the third Flotation cell is conductive, ... that part of the in the (n - 1) formed Acceptance agent at the nth flotation cell over to an outlet and the biggest part of the (n - 1) th Flotationszelle formed accepts to the n-th flotation cell is conductive, and that this, after he went through the n-th flotation cell has, to the outlet is conductive.

According to the invention Thus, a control and pipeline interconnection is created, the one for that Caring, that at the respective production increase the associated throughput volume flow from flotation cell to flotation cell is distributed so that each Flotation cell always works on the volume flow optimum. Thereby will be less new extra Flotation cells needed and the specific energy consumption per pulp suspension to be processed remains as before the production expansion.

advantageous Further developments of the invention are in the dependent claims, the Description and drawings included.

With Advantage is according to the invention also provided that the second, third, fourth, ..., (n - 1) th, nth Flotation cell respectively first ventilation elements for the of the first, second, third, fourth or (n-1) -th cell received accepts and second ventilation elements for the additional Volumetric flow or obtained from the Vorogheraus flotation cell Accepted good.

Particularly suitable is a flotation plant ge, in which the first and second ventilation elements in each of the flotation cells are each combined separately with its own suspension distributor.

Eben case It is advantageous if the second ventilation elements of the n-th flotation cell in each case operate at the same pressure level as the first ventilation elements the previous (n - 1) th Flotation cell.

Preferably is also provided that between the flotation cells control devices for Control of the volume flow of the (n-1) -th flotation cell to the n-th flotation cell to conductive accept and the volume flow of the volume flow or the good to be passed by it the pre-existing flotation cell.

As well The invention also relates to a method for removal of impurities from an aqueous Pulp suspension, in particular a paper pulp suspension, successively a first, second, third, fourth, ..., (n - 1) -th, flows through the n-th flotation cell, each flotation cell having first ventilation elements for production one with impurities enriched flotation foam, which flows through an overflow, and a flow for having the accepts formed in the flotation cell.

This is according to the invention A method characterized in that a first of the capacity of the flotation plant corresponding volume flow and an additional, exceeding the capacity of the flotation plant Volumetric flow of pulp suspension through the flotation cells flows through one after the other, wherein the first part of the volume flow is the first flotation cell flows through that the second part of the volume flow past the first flotation cell the second flotation cell flows through that a first larger part of the effluent from the first flotation cell accept in the second Flotation cell flows and that a second, smaller part of the second flotation cell past the third flotation cell, etc. flows through to the nth flotation cell for the most part the accepts from the (n - 1) th Flotation cell and to a lesser extent the accepts from the (n - 2) th Flotation cell flows through, while the smaller part of the accept from the (n - 1) th flotation cell the nth flotation cell flows past to an outlet.

below the invention will be described in exemplary embodiments closer to the drawings explained. Show it:

1 the scheme of successively arranged flotation cells in a flotation plant,

2 the example of a volume flow increase by 16.7% in a flotation plant with seven successive flotation cells and

3 the example of a 50% increase in volume flow in a flotation plant with seven flotation cells connected in series.

A flotation plant 1 according to the 1 includes four flotation cells 2 to 5 ,

From a feed 6 becomes the flotation plant 1 supplied a volume flow that is higher than the regular for the plant 1 provided volume flow. Therefore, the entire volume flow, for example, in a valve 17 or by a controller, split into a share A and a share B. The proportion A corresponds approximately to the volume flow which is regular in the first flotation cell 2 can flow through, and flows through a supply line 8th into this. In this case, the supply line 18 be designed as a loop, which introduces the flow in several places. The portion B is through a bypass or a bypass line 19 at the flotation cell 2 passed and passes directly into the flotation cell 3 , The level of the flotation cell 2 comes with a valve 14 controlled by a level transmitter.

From the flotation cell 2 pour both foam 10 as well as accept 11 out. The foam 10 is disposed of or sent to a secondary school. The accepts 11 is through a pump 13 promoted and divided into two parts C and D. The first portion C flows together with the portion B from the flotation cell 2 into the downstream flotation cell 3 while the proportion D at the flotation cell 3 over into the third flotation cell 4 is directed.

However, the aerators are the second flotation cell 3 containing the suspension from the feed of the flotation cell 2 , ie supplied with the portion B, a separate suspension distributor 15 not associated with the suspension distributor 16 the remaining ventilation elements of the flotation cell 3 connected is. As a result, the ventilation elements of the flotation cell work 2 and the flotation cell 3 (Proportion B) at the same pressure level, so that there is no need for control in this pipeline. The number of aeration elements operating in the flotation cell n at the same pressure level as in the preceding flotation cell n-1 can be determined individually for the production increase. As many as 10, 20, 30, 40 or 50% of the hydraulic excess flow to the flotation cell 2 at the flotation cell 3 be led past. The hydraulic overcapacity attached to the first flotation cell 2 has been passed, is thus only in the second flotation cell 3 ventilated. As a result, the hydraulic excess is in by cut n - 1 times less aerated than the remaining suspension. By a proportionate expansion, for example, at 20% overproduction by using 20% more flotation cells, this additional proportion of the volume flow can be processed in exactly the same way as without overproduction. In this way, can be achieved according to the invention by additional use of one, two or three additional flotation cells, according to the overproduction to be managed, at the end of the flotation with the same energy consumption the same flotation effect as in the system without overproduction.

In the same way as the flotation cells 2 and 3 are arranged to each other and connected by lines, are also the subsequent flotation cells 4 and 5 with the flotation cells 2 and 3 connected. This means that, in addition to the foam, which is not shown here, which is discharged in each flotation cell, accepts good that is split again into two parts: a first, which flows directly to the subsequent flotation cell, in which also a remaining fraction from the Vorgerhergehend flotation cell is vented, and a second portion, the second flotation cell, ie of the flotation cell 3 to the flotation cell 5 continues to flow.

Explained on a numerical example ( 2 ), this means that from an incoming liquid quantity of 18900 l / min only 16200 l / min to the flotation cell 2 be conducted while 2700 l / min over the valve 17 at the flotation cell 2 over to the flotation cell 3 continue to flow.

After in the flotation cell 2 Foam were separated in an amount of 500 l / min, flow out of it 15700 l / min, which are split into a main part of 13100 l / min, in the flotation cell 3 flow in, so that these together with those at the flotation cell 2 via the bypass flows past 2600 l / min 15700 l / min.

The flotation cell 3 again emits 500 l / min of foam. Of the 15,300 l / min flowing out of it, 12800 l / min are sent directly to the flotation cell 4 continued, while 2500 l / min to the flotation cell 5 continue to flow.

In the flotation cell 4 Thus, 2600 l / min of the suspension from the flotation cell 2 and 12800 l / min from the flotation cell 3 , a total of 15600 l / min processed.

In a corresponding manner, the indication of the volume of the pulp suspension, in each case in liters per minute, in the other flotation cells 5 to 8th specified.

In this case, the mass flow is reduced by a foam formation of in each case 500 l / min, from initially 18900 l / min to 18400 l / min in the area of the flotation cell 2 , at 17900 l / min in the area of the flotation cell 3 , at 17400 l / min in the area of the flotation cell 4 , to 16900 l / min in the area of the flotation cell 5 , at 16400 l / min in the area of the flotation cell 6 , at 15900 l / min in the area of the flotation cell 7 and at 15400 l / min in the area of the flotation cell 8th , which are thus available at the output as accepts, said flotation cell 8th has a processing capacity greater than that of the flotation cell 3 but smaller than the flotation cell 2 so they also control the volume flow from the flotation cell 6 can take over.

Thus, in the in 2 instead of the regular 16200 l / min, the nominal volume flow of the flotation cell 2 , now process 18,900 l / min, representing a capacity increase of 16.7% of the plant 1 equivalent.

In another embodiment ( 3 ) is using the same attachment 1 realized a production increase of 50%, being at the end after the flotation cell 8th still further, not shown flotation cells can be added.

From 24300 l / min thus flow in a known manner 16200 l / min through the flotation cell 2 passing the flotation cell at 8100 l / min 3 be directed. The further throughput data are analogous to the representation in FIG 2 inserted in the drawing; It is also assumed in this embodiment that in each flotation cell 2 to 8th 500 l of foam will be removed per minute.

Claims (6)

Flotation plant ( 1 ) for the removal of impurities from an aqueous pulp suspension, in particular a paper pulp suspension, which comprises a plurality of first, second, third, fourth, ..., (n-1) th, n-th flotation cells ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ), each flotation cell ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ) first aerating elements for producing an enriched with impurities flotation foam, which flows through an overflow, and a drain for the in the flotation cell ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ), characterized in that the flotation plant ( 1 ) to handle a hydraulic overcapacity in the form of an additional volume flow of pulp suspension, an additional pipe system for producing additional, the pulp suspension leading connections between the flotation cells, wherein the additional volume flow in the starting pulp suspension through a first pipeline at the first flotation cell ( 2 ) over to the second flotation cell ( 3 ) is feasible, that, at least substantially, an equally high proportion of the in the first flotation cell ( 2 ) formed on the second flotation cell ( 3 ) over to the third flotation cell ( 4 ) is conductive and that most of the in the first flotation cell ( 2 ) formed accepts in the second flotation cell ( 3 ) is conductive, that a part of the in the second flotation cell ( 3 ) formed on the third flotation cell ( 4 ) over to the fourth flotation cell ( 5 ) is conductive and that most of the in the second flotation cell ( 3 ) to the third flotation cell ( 4 ) is conductive, ... that a part of the accepts formed in the (n - 1) past the n-th flotation cell to an outlet and the majority of the accepts formed in the (n-1) -th flotation cell to the n The flotation cell is conductive, and that this, after he has passed through the n-th flotation cell, can be conducted to the outlet. Flotation plant ( 1 ) according to claim 1, characterized in that the second, third, fourth, ..., (n-1) th, n-th flotation cell ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ) has in each case first ventilation elements for the accepts received from the first, second, third, fourth or (n-1) th flotation cell and second ventilation elements for the additional volume flow or the accepts received from the preceding flotation cell. Flotation plant ( 1 ) according to claim 2, characterized in that the first and second venting elements in each of the flotation cells ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ) are each summarized separately with its own suspension distributor. Flotation plant ( 1 ) according to claim 3, characterized in that the second ventilation elements of the n-th flotation cell ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ) are each operable at the same pressure level as the first aeration elements of the preceding (n-1) th flotation cell ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ). Flotation plant ( 1 ) according to one of claims 1 to 4, characterized in that between the flotation cells ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ) Regulating devices for controlling the volume flow of the acceptor to be passed from the (n-1) -th flotation cell to the n-th flotation cell and the volume flow of the volume flow or the accept from the preceding flotation cell ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ). Process for removing impurities from an aqueous pulp suspension, in particular a paper pulp suspension, which successively comprises a first, second, third, fourth, ..., (n-1) th, n-th flotation cell ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ), whereby each flotation cell ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ) first aerating elements for producing an enriched with impurities flotation foam, which flows through an overflow, and a drain for the in the flotation cell ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ), characterized in that a first of the capacity of the flotation plant ( 1 ) corresponding volume flow and an additional, the capacity of the flotation plant ( 1 ) exceeding volume flow of pulp suspension by the flotation cells ( 2 . 3 . 4 . 5 . 6 . 7 . 8th . 9 ) flows through successively, wherein the first part of the volume flow, the first flotation cell ( 2 ) flows through that the second part of the volume flow at the first flotation cell ( 2 passing the second flotation cell ( 3 ) flows through that a first larger part of the first flotation cell ( 2 ) flowing out into the second flotation cell ( 3 ) and that a second, smaller part of the second flotation cell ( 3 ) into the third flotation cell ( 4 ) flows, etc., to the n-th flotation cell, through which most of the accepts pass from the (n-1) -th flotation cell and to a smaller extent the accepts from the (n-2) -th flotation cell, while the smaller one Part of the accept from the (n-1) -th flotation cell flows past the n-th flotation cell to an outlet.