The Application Of Surfactants In Particle Size Distribution Determination And Ultrafine Grinding Of Fine Graphite Powder

In the carbon industry, the technology of particle size determination for finecarbonaceous/graphite powder, accurately and rapidly, has great significance. Butthe agglomeration of the carbonaceous/graphite powder in the water make it difficultto get a true data result from the determination of particle size distributioncharacteristics by laser method. However, the decentralized property of the surfactantcan reduce or even eliminate the agglomeration of carbonaceous/graphite powder inthe water and thereby improving the accuracy of the results of laser method. Thisthesis first studied the error may be caused by the application of surfactants in thelaser method and summed up the general standard of screening dispersing aids. On theother hand, accurately characterize the dispersion properties of the surfactant havegreat significance for the grinding aids selecting for the Graphite wet ultrafinegrinding. This thesis compared the accuracy of laser particle method and traditionalsettlement method in characterize the dispersion properties of the surfactant, and thelaser particle method can be used as a new approach for grinding aids selecting isproposed. The conclusions are as follows.First, the results show that when the surfactant (especially anionic surfactants)added in the laser method of particle size measurement, the foaming properties ofsurfactant may produce serious interference leaving the measurement resultscompletely distortion. Only the surfactant solution without produce microbubbles,during the measurement process, can be used for laser method. Anionic surfactantslauryl alcohol polyoxyethylene ether ammonium sulfate and non-ionic surfactant fattyalcohol polyoxyethylene ether with either good dispersion of artificial graphite (HAG)samples and without produce micro-bubbles in the testing process which will affectthe measurement accuracy are suitable for be used as laser method’s dispersionadditives. For different types of carbonaceous/graphite particles, the requiredoptimum dispersant concentration and the best scatter time are different.Second, in the graphite ultrafine grinding experiment, the laser particle method andsedimentation method were contrastively used to determine the dispersion propertiesof dodecyl alcohol polyoxyethylene ether sulfate and fatty alcohol ethoxylates. Afterthat using colloid mill for grinding equipment, graphite ultrafine grinding experimentsis carried out to study the effect of the dispersion property difference of two surfactants above, as well as particle size, to the grinding result of HAG powder. Theresults show that, the dispersion performance of fatty alcohol polyoxyethylene ethersolution, to HAG sample, is higher than the lauryl alcohol polyoxyethylene etherammonium sulfate. So under the optimum conditions, respectively, the grinding aideffect of fatty alcohol polyoxyethylene ether is better than the lauryl alcoholpolyoxyethylene ether ammonium sulfate. This means that the grinding aid effect andthe dispersion properties of surfactant are related. In a addition, the result of laserparticle size analysis indicated that only when the particle size of HAG sample wasgrinding to the level that manifest aggregation can appear, the addition of grindingaids can demonstrate a significant grinding aid effect. This result proves that themechanism of action of the grinding aids in experiments above is match to the ‘slurryrheology adjustment mechanism’ theory, which statements is that action of thegrinding aids is to reduce the particles aggregation and thereby increasing the graphiteultrafine grinding efficiency.