Keywords: multi-stage flotation cell; working principle; energy-saving; high-efficiency Finnish Valmet mechanical pulping company has developed a new flotation device, which is a single-stage multi-stage flotation cell. The summary is introduced below, for reference when we improve the flotation cell and develop a new flotation cell.
This article is based on data from two international conferences (Paper Recycling, 1998 and 5th Research Forum on Recycling, 1999).
1 The structure and working principle of the monomer five-stage flotation cell for the intermediate test Figure 1 (simply) the internal simple structure of the monomer five-floatation cell (MUST5 cell) and the working principle of the deinking slurry flow path and flotation . It can be seen that the monomer five-stage flotation cell has a structure of 2 laps and 9 cells, and the inner ring is divided into a, b, c, and d4 cells, all of which are inflating and mixing regions. There is a special slurry mixing rotor at the bottom of each cell; There are small cells (1) and (2), and large cells (3), (4) and (5), except that the cell (1) is an aeration mixing zone, and the others are flotation separation zones. The deinked pulp enters from the bottom of the outer ringlet (1) and is aerated (low-pressure compressed air) mixed (mixed with a special rotor) and then enters the (overflow) compartment (3) for flotation separation, which is equivalent to the usual The first level flotation. Scum (foam, ink, etc.) overflows out of the cell (3). The slurry continues to flow from the bottom of the cell (3) into the inner cell a-cell for aeration and mixing, and then into the outer cell (3) to float. Select separation, which is equivalent to the second-stage flotation. The scum is still overflowing from the outer ring (3), and the good slurry enters the inner ring (b) at the bottom of the cell (3) to be aerated and mixed, and then enters the outer ring (4) for flotation separation. This is equivalent to the third-stage flotation. The good slurry is further inflated and mixed at the bottom of the outer ring (4) into the inner ring c, and then into the outer ring (5) to perform flotation separation, which is equivalent to the fourth-stage flotation. The slurry continues to inflate through the bottom of the outer ring (5) into the inner d-cell, and then enters the outer cell (2) for flotation separation, which is equivalent to the fifth-stage flotation. The good slurry flowing from the bottom of the outer cell (2) is the first flotation paste after the five-stage flotation. The scum overflowed from the outer rims can be subjected to a second flotation to recover the fibers in the scum.
As can be seen from Figure 1, this flotation tank with five-stage flotation in one unit saves four sets of slurry pumps and their pipelines. The flow of slurry is only handled by one slurry pump. The difference in level is to send the flow. In addition, slurry mixing with low-pressure compressed air and a mixing rotor also avoids slurry jams that may occur when using ejectors in general. At the same time, the air volume and rotor speed can be adjusted, which means that the size of the air bubble can be adjusted.
From the structural features and operating conditions of this multi-cell flotation cell, summarize its advantages:
(1) The dross concentration is large (4% to 6%), which means that the pumping amount and the processing amount of dross are saved, and the floor space is saved. At the same time, the amount of wastewater treatment and the fresh water consumption are both low.
(2) automation and easy operation.
(3) Low energy consumption.
(4) The inflation system does not block.
(5) Inflation in multiple stages in the flotation cell and internal circulation of the slurry.
(6) The average bubble size can be adjusted.
(7) The ratio of air to pulp can be adjusted.
(8) The dross concentration can be adjusted.
2 Computer fluid dynamics simulation and pilot test results The computer simulation of single-cell multi-stage flotation cell simulation results showed that in the outer flotation separation zone, the pulp flow velocity is very important, and the flow rate of the most uniform slurry flow rate is lower than 5cm/s, otherwise, the removal efficiency of air will be weakened, with the result that the ink is carried away by the slurry. Therefore, it is not good for the flotation system to use too much air. In addition, the pulp concentration is also very important. When the pulp concentration is low, the non-uniformity of the pulp flow is quickly increased.
The pilot test is performed in parallel with a conventional deinking system in a deinking mill. That is, after the first flotation, the main flatation, the second flotation, and the post flotation, if necessary, it is usually set before and after bleaching. . The effect of the total flotation, in general, is better when using single-stage multi-stage flotation cells, with a higher value of whiteness, and only a slightly lower value of whiteness.
In addition, the results of the pilot tests also confirmed that the flotation separation of the outer ring flotation separation anti-slurry flow speed is good, the slurry whiteness is higher. At the same time, it was confirmed that the flotation efficiency (whiteness increase) when the slurry concentration is 1.5% when the monomer multi-stage flotation cell is used can be equivalent to the flotation efficiency (whiteness) when the slurry concentration is 1.1% when the conventional flotation cell is used. Added value, which shows that the monomer multi-stage flotation cell can use a higher slurry concentration, so that the slurry flow is more stable.
These all show that the monomer multi-stage flotation tank has a better flotation effect. Chen Jiaxiang (State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, 510641)
This article is based on data from two international conferences (Paper Recycling, 1998 and 5th Research Forum on Recycling, 1999).
1 The structure and working principle of the monomer five-stage flotation cell for the intermediate test Figure 1 (simply) the internal simple structure of the monomer five-floatation cell (MUST5 cell) and the working principle of the deinking slurry flow path and flotation . It can be seen that the monomer five-stage flotation cell has a structure of 2 laps and 9 cells, and the inner ring is divided into a, b, c, and d4 cells, all of which are inflating and mixing regions. There is a special slurry mixing rotor at the bottom of each cell; There are small cells (1) and (2), and large cells (3), (4) and (5), except that the cell (1) is an aeration mixing zone, and the others are flotation separation zones. The deinked pulp enters from the bottom of the outer ringlet (1) and is aerated (low-pressure compressed air) mixed (mixed with a special rotor) and then enters the (overflow) compartment (3) for flotation separation, which is equivalent to the usual The first level flotation. Scum (foam, ink, etc.) overflows out of the cell (3). The slurry continues to flow from the bottom of the cell (3) into the inner cell a-cell for aeration and mixing, and then into the outer cell (3) to float. Select separation, which is equivalent to the second-stage flotation. The scum is still overflowing from the outer ring (3), and the good slurry enters the inner ring (b) at the bottom of the cell (3) to be aerated and mixed, and then enters the outer ring (4) for flotation separation. This is equivalent to the third-stage flotation. The good slurry is further inflated and mixed at the bottom of the outer ring (4) into the inner ring c, and then into the outer ring (5) to perform flotation separation, which is equivalent to the fourth-stage flotation. The slurry continues to inflate through the bottom of the outer ring (5) into the inner d-cell, and then enters the outer cell (2) for flotation separation, which is equivalent to the fifth-stage flotation. The good slurry flowing from the bottom of the outer cell (2) is the first flotation paste after the five-stage flotation. The scum overflowed from the outer rims can be subjected to a second flotation to recover the fibers in the scum.
As can be seen from Figure 1, this flotation tank with five-stage flotation in one unit saves four sets of slurry pumps and their pipelines. The flow of slurry is only handled by one slurry pump. The difference in level is to send the flow. In addition, slurry mixing with low-pressure compressed air and a mixing rotor also avoids slurry jams that may occur when using ejectors in general. At the same time, the air volume and rotor speed can be adjusted, which means that the size of the air bubble can be adjusted.
From the structural features and operating conditions of this multi-cell flotation cell, summarize its advantages:
(1) The dross concentration is large (4% to 6%), which means that the pumping amount and the processing amount of dross are saved, and the floor space is saved. At the same time, the amount of wastewater treatment and the fresh water consumption are both low.
(2) automation and easy operation.
(3) Low energy consumption.
(4) The inflation system does not block.
(5) Inflation in multiple stages in the flotation cell and internal circulation of the slurry.
(6) The average bubble size can be adjusted.
(7) The ratio of air to pulp can be adjusted.
(8) The dross concentration can be adjusted.
2 Computer fluid dynamics simulation and pilot test results The computer simulation of single-cell multi-stage flotation cell simulation results showed that in the outer flotation separation zone, the pulp flow velocity is very important, and the flow rate of the most uniform slurry flow rate is lower than 5cm/s, otherwise, the removal efficiency of air will be weakened, with the result that the ink is carried away by the slurry. Therefore, it is not good for the flotation system to use too much air. In addition, the pulp concentration is also very important. When the pulp concentration is low, the non-uniformity of the pulp flow is quickly increased.
The pilot test is performed in parallel with a conventional deinking system in a deinking mill. That is, after the first flotation, the main flatation, the second flotation, and the post flotation, if necessary, it is usually set before and after bleaching. . The effect of the total flotation, in general, is better when using single-stage multi-stage flotation cells, with a higher value of whiteness, and only a slightly lower value of whiteness.
In addition, the results of the pilot tests also confirmed that the flotation separation of the outer ring flotation separation anti-slurry flow speed is good, the slurry whiteness is higher. At the same time, it was confirmed that the flotation efficiency (whiteness increase) when the slurry concentration is 1.5% when the monomer multi-stage flotation cell is used can be equivalent to the flotation efficiency (whiteness) when the slurry concentration is 1.1% when the conventional flotation cell is used. Added value, which shows that the monomer multi-stage flotation cell can use a higher slurry concentration, so that the slurry flow is more stable.
These all show that the monomer multi-stage flotation tank has a better flotation effect. Chen Jiaxiang (State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, 510641)
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