Comprehensive Evaluation of Deinking Performance of Waste Paper Deinking Agent

At present, most domestic DIP production lines use imported soap deinking agents. With the increasing number of inks and the decline in the quality of waste paper, the demand for deinking agents has also increased. We should vigorously research and develop new and efficient deinking agents, non-ionic deinking agents, and biological enzyme deinking agents. Meet the needs of the domestic market. At present, the evaluation methods and methods for deinking agent are different. For flotation deinking technology, the deinking performance of deinking agent should be comprehensively evaluated from two aspects of pulping and flotation.

1 pulping

Pulp is the first step in waste paper treatment. Its purpose is to maintain the original strength of the fiber to the utmost, and to effectively remove the ink from the fiber without changing the shape of various impurities as much as possible. The repulping effect is usually evaluated by the combined residual ink concentration (ER IC junction), over-wash whiteness, and total effective residual ink concentration (ERIC total) of pulp after pulping (referred to as comminuted pulp).

1.1 Combined with effective residual ink concentration

The combined effective residual ink concentration (ERIC junction) value reflects the concentration of ink that has remained unstripped on the fiber. The smaller the ERIC knot, the better the effect of the ink peeling off the fibers. The determination method is: take a certain amount of crushed slurry, placed in the bottom of the 80 mesh copper mesh funnel, fully washed until the filtrate becomes clear, and then collect the residue of the plasma sample, in the Buchner funnel suction filter The amount of cake is about 170 g/rn2 (the opacity of the cake is required to be greater than 97%). The ERIC of the two sides of the cake was measured on a CTP-ISO ERIC 950 detector and averaged.

1.2 Washing whiteness

The whiteness of the deinked pulp reflects the whiteness of the pulp. It excludes the influence of inks, fillers and other substances in the pulp on the whiteness of the pulp. Under the same pulping conditions, the higher the washed whiteness of the crushed pulp, the more the ink peeled off the fibers. The whiteness of the washed deinked pulp was measured on a whiteness meter using a slurry cake with a measured ERIC value in 1.1. The degree of washing whiteness of the crushed slurries, in addition to the ERIC knot value, also depends on the proportion of waste paper in the pulp, the quality of waste paper, and the amount of chemicals added.

1.3 Total effective residual ink concentration

The total effective residual ink concentration (ERIC total) mainly includes the released free ink in the deinked pulp and the bound ink that is still attached to the fibers. The total height of the ERIC depends on the amount of ink and the size of the ink particles. The greater the amount of ink, the greater the total ERIC. With a certain amount of ink, the higher the total ERIC, the smaller the ink particles in the paste. Flotation deinking is different from wash deinking. Flotation deinking ink particles are relatively small, which is beneficial to washing and deinking; while in the flotation deinking process, free ink particles are relatively large and can be better from the slurry. Separation, and the deinking production workshop white water with less fine ink, is conducive to the reuse of white water. Therefore, in the case of a certain ratio of waste paper, the smaller the ERIC of the crushed slurry is, the better. The total measurement method of ERIC has not yet met the detection standard. The key is how to make the free ink in the slurry remain in the cake even when the cake is pumped. The filtrate should be clear. Aluminum compound, fixing agent, CPAM, etc. can be added for retention before the cake is formed. The filtered cakes (having a quantitation of approximately 170 years old with an opacity greater than 97%) were tested on a CTP-ISO ERIC 950 tester to determine the mean and negative ERIC values ​​of the cakes.

2 Flotation

Flotation is the use of different particle surface physical and chemical characteristics of the different separation. During the flotation process, hydrophobic particles or surfactants that convert hydrophilicity to hydrophobicity are adsorbed on the air bubbles in the pulp suspension, float upwards and separate from the pulp. The flotation effect of the deinking pulp is often evaluated by the value of flotation whiteness, flotation ink removal rate, and flotation slurry loss.

2.1 Flotation Whiteness Value Added
Flotation Whiteness Addition refers to the difference between the whiteness of floatation pulp and the whiteness of pulp into pulp. The higher the value of whiteness, the better the effect of flotation. Special emphasis should be placed on the fact that deinked pulp contains fibers, inks, fillers, pigments, etc., and its whiteness measurement is different from other pulp types. The whiteness test piece (pulp cake) must be filtered by a Buchner funnel. It is not possible to use an ordinary film copying machine, and it is necessary to uniformly regulate the pulp volume and pulp consistency of the slurry before the formation of the cake, and the positive and negative sides of the cake. The difference in whiteness is large and should be averaged.

2.2 Flotation ink removal rate

The flotation ink removal rate was 2 ((Feeding ERIC Total One Equivalent Paste ERIC)/(Introduction ERIC Total-Introduced ERIC Junction)) x 100%. In general, the better the ink trapping performance during flotation, the greater the ink removal rate and the higher the whiteness increase.

2.3 Flotation slurry

If the solid content of the flotation slurries is too high, the yield will inevitably be low. Especially when the fiber content is high, the large loss of fibers will increase the production cost. During flotation, the foam is too small and the amount of foam is too high, which easily leads to air bubbles and increases the loss. In actual production, if the defoaming time of the foam is long, not only will the foam overflow condition of the flotation tank be poor, but some of the ink will re-enter the slurry and the flotation effect will be reduced, and the flotation ink tank will often be caused. It is in an overflow state, increasing the loss of the workshop trench and affecting the workshop's production environment.

3 Comparison of deinking effects of several deinking agents

Under the same pulping conditions, due to the large ERIC, g, of the crushed slurries, indicating that the deinking agents B and C cause the ink to disintegrate to a greater extent. A reasonable amount of deinking agent (131) can be used to obtain a better ink peeling effect, which is reflected in the washed whiteness of the crushed pulp. During flotation, the devitrification agent B1 has higher flotation whiteness and ink removal rate than the deinking agent A. With the increase of the amount, the solid content and fiber content in the flotation slurry increased. However, the deinking agent B1 and the deinking agent C are too rich in foam during flotation, and the defoaming time is long and should not be used in actual production. Therefore, in order to select an appropriate deinking agent, it is necessary to comprehensively consider the pulping and flotation. effect.

4 Conclusion

4.1 When deinking during flotation, the deinking performance evaluation of deinking agent should be comprehensively considered from pulping and flotation, in which flotation whiteness increment and flotation ink removal rate are two main indicators.

4.2 Foaming and foam defoaming time is an important indicator to evaluate the deinking agent in the flotation process. The foam size distribution, the number of foams, and foam defoaming time must be moderate to reduce the loss of flotation yield.