Study On Syntheses And Properties Of Dispersants Based On Humic Acid And Tannic Acid For Coal-water Slurry

Coal water slurry (CWS), a type of novel liquidized fuel, consists ofpulverized coal of different particle size (approximately60-75wt%), water(about25-40wt%), and dispersant (1wt%). It has many advantages such ashigh combustion efficiency, lower pollutant emissions as well as easytransmission. During the process, the dispersant plays an important role. But thedispersants commercialized all have its disadvantages. For example, naphthalenesulfonic acid-formaldehyde condensates (NSF) perform excellent dispersity,rheology, and lower apparent viscosity as well, but the stability of CWSprepared is poor and it is expensive. The CWS prepared by lignin sulfonate (SL)has poor dispersity so that it usually used with other dispersants. The humic acid(HA) and the tannic acid (TA) are two natural macromolecules which weregrafted and copolymered in the experiment. And the two dispersants which canprepare the CWSs that are high concentrations, good stability and available to different coals were got.A novel humic acid based dispersant, a black copolymer produced bymodification of humic acid (MHA), has been successfully synthesized inaqueous solution through the grafting copolymerization of maleicanhydride-polyethylene glycol400monoester (MAPEG), methacrylatoethyltrimethyl ammonium chloride (DMC) and humic acids (HA). MAPEG wasobtained by esterification of polyethylene glycol400and maleic anhydride inour laboratory. The MHA was successfully synthesized through the analysis ofinfrared spectra. The optimization of reaction conditions as follows: the massratio of MAPEG and HA was2.42:1, the mass of initiator and DMC accountedfor4.0wt%,5.0wt%of the sum mass of MAPEG and HA respectively, thereaction time was2.75h and the more available reaction temperature was70oC.MHA was a surfactant and the critical micelle concentration was10g/L. TheMHA was applied in Jinyang coal. The available MHA dosages was0.6%thatthe CWS (consisted67%coal samples) prepared has best performance. Theresult demonstrates that the rheological behavior and stability of CWS preparedby the MHA, which contain67%pulverized coal and0.6%additives, both werebetter than that made by NSF and SL. In addition, the possible reaction route forMHA was offered.a novel tannic acid based dispersant, a copolymer produced bymodification of tannic acid (MTA), has been successfully synthesized inaqueous solution through the grafting copolymerization of tannic acid(TA) and acrylamide (AM). TA was firstly oxidized0.5h by potassium persulfate(oxidant)before grafting copolymerization. The MTA was successfully synthesizedthrough the analysis of infrared spectra. The optimization of reaction conditionsas follows: the mole ratio of TA and AM was1:20, the mass of oxidantaccounted for8.5wt%of the mass of TA, the reaction time was3h and the moreavailable reaction temperature was85oC. The MTA was applied in Taiyuan coal.The available MTA dosages was0.4%that the CWS (consisted68%coalsamples) prepared has best performance. The result demonstrates that thestability of CWS prepared by the MTA, which contain67%pulverized coal and0.6%additives, was one level. The bleeding ratio of MTA was4.44%less thanSL, and was6.16%less than NSF. And the CWS presented yield pseudoplasticfluids. In addition, the possible reaction route for MTA was offered.At last, the MHA, MTA, SL and NSF were applied in Jinyang coal，Taiyuancoal, Linfen coal and the Jet coal. The performances of CWS prepared by themwere researched. Compared with SL and NSF, the dispersity of CWS preparedby MHA and MTA were slightly weaker, but the static stability of CWSprepared by MHA and MTA were far superior. And the CWS prepared by firstthree coal with MTA and MHA that presented yield pseudoplastic fluids. Thebest match coal to MHA was Jinyang coal and to MTA was Taiyuan coal.