| Shannxi Binchang coal and Inner Mongolia Huolinhe coal are both poor-quality coal, with high oxygen/carbon ratio and water content and low metamorphic degree, they are hard to prepare high concentration coal water slurry(CWS). In this paper, a new generation of polycarboxylate dispersant of coal water slurry were prepared according to the two coal preparation. This kind of dispersant is of excellent performance, high slurrying concentration, low additive amount and simple preparation process. But it has not been widely used because of the high cost of preparation due to expensive monomers. So the preparation of polycarboxylate dispersant with excellent performance and low price is the key to develop polycarboxylate dispersant.In this paper, a series of polycarboxylate dispersants were prepared and the most economical and effective monomers were selected, in order to reduce the cost of synthesis and improve application value.In the first section, using methacrylic acid (MAA) and sodium allyl sulfonate (SAS) as monomers, sodium hypophosphite of 10% of the total mass as chain transfer agent, perchloric acid ammonia of 4wt%(mass fraction) as the initiator, PMAS system polycarboxylate dispersant was prepared through free radical copolymerization reaction when the reaction temperature is 80 ? and the reaction time is about 5 hours. In the five kinds of MAA:SAS ratio of 20.83, 9.21,4.60,3.63 and 2.22, five kinds of binary dispersants were prepared, recorded as PMAS-0?PMAS-1?PMAS-2?PMAS-3 and PMAS-4. Through the aqueous potentiometric titration measurement, the actual ratio of-COO-1/-SO3-1 is 15.67,6.93,3.23,1.78 and 0.94. And through the Infra-Red spectrum (FT-IR) and gel permeation chromatography(GPC), the molecular structure were characterized. As were used in slurrying of Binchang coal at the dosage of 0.4wt%, when the water coal slurry concentration was 65%, we explored the relationship between the apparent viscosity and the-COO-1/-SO3-1 ratio, Zeta potential in different concentrations and influence of pH value on the application of coal water slurry. The results showed that when the ratio of-COO-1/-SO3-1 was 3.23, the apparent viscosity is the lowest and the stability was best. What's more, Zeta potential can reach-38mV and the coal water slurry viscosity gradually decreased with the increase of pH, but tends to be stable when pH is more than 10.The second part was to introduce polyether macromer based on binary dispersant, and change the sulfonate monomer, to explore its application performance. Using MAA, APEG500 and SSS, SAS, SMAS, AMPS in a certain proportion, four kinds of tribasic dispersants were prepared, named PCS, PCSM, PCS A, PCSS. Through Infra-Red spectroscopy(FT-IR) and gel permeation chromatography(GPC), the structure was characterized. Through the thermogravimetry(TA) and differential scanning(DSC) analysis, the thermal properties were studied. Using these four kinds of dispersants in slurrying of Huolinhe coal, analyzed the appropriate dosage of APEG500 macromer and explored performance of slurry apparent viscosity, stability and rheology, slurrying concentration and optimum amount. Zeta potential, adsorption, and its contact angle between coal and dispersant were analyzed and compared. Then we selected the polycarboxylate dispersant corresponding to the best sulfonate monomer.The results showed that when MAA:S(sulfonate monomers):APEG500 ratio is 4:1.3:2, the best slurrying concentration of Huolinhe coal is 57% and its appropriate dosage is 0.4%. In these dispersants, PCSS had the best performance, meanwhile, it showed good apparent viscosity, stability and rheological model. PCSS exhibited adsorption amount can be 3.19mg/g, the apparent viscosity is 503.7 mPa · s under 57% slurry concentration, Zeta potential is-36mV, and the contact angle with coal is 49.84°.It showed that sodium p-styrenesulfonate with aromatic ring was the best sulfonate monomer of the tribasic dispersants.The third part was to prepare 3 kinds of quaternary dispersants through copolymerization reaction of MAA and SAS, APEG50, styrene(St) and SMAS, AMPS, named PCST, PCSMT, PCSAT. Through Infra-Red spectroscopy, thermogravimetry, gel permeation chromatography and other means, we characterized and analyzed the structure, thermal properties, relative molecular mass and its distribution of the dispersants. Using these dispersants for Huolinhe coal, the appropriate dosage of St was discussed, and the performance like apparent viscosity, stability, rheology, slurrying concentration and optimum amount were explored. Then, Zeta potential, adsorption, and its contact angle between coal and dispersant were analyzed and compared.When the dosage of St is 3.5wt%, PCST showed the best performance, and its adsorption amount can be 3.19mg/g. When the slurry concentration is 57%, the apparent viscosity is 503.7 mPa · s, Zeta potential is-36 mV, and the contact angle with coal is 49.84°. After comparing their performance, we found that aromatic ring can effectively increase the adsorption capacity and the dispersion performance. |
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