| Coal water slurry (CWS) is a new type of coal-base liquefaction technology, which was developed in1970s since the global oil crisis, It aims to change the traditional way of coal combustion, reduce pollutant emissions and improve the efficiency of coal utilization. Compared with the direct way of burning coal, CWS has a higher combustion efficiency, less pollution, lower cost and high heat value. Dispersant is a key factor of the preparation of high concentration CWS with low viscosity. Currently, the most widely used dispersant is naphthalene sulfonate series, its synthetic material derived from petroleum chemical products. As oil prices rise much further, raw material prices have also gone up. Therefore, the development of low prices, excellent dispersion and eco-friendly of dispersant is particularly important.In this paper, a novel dispersant was developed by sodium lignosulfonate which derived from paper wastemter, graft copolymerization of sodium lignosulfonate and acrylamide was taken after materials was purified, the product demonstrated excellent dispersivity performance and stability, it can Reduce the surface tension of solution effectively. The optimal conditions for the synthesis of modified dispersant is determined by means of single factor experiment method. The mass ratio of ligninsulfonate and acrylamide was5:1, the amount of initiator was3%, the reaction temperature was40℃, the reaction time is2.5h, and the ratio of K2S2O8and NaHSO3is3:2. The IR results shown many characteristic absorption peaks, At3415cm-1is the adsorption peak of free-NH2,3205cm-1is the absorption peak of associated amide group, The adsorption peak in1566cm-1is the bending vibration absorption peak of N-H in-CONH. When the contents of dispersant is0.8w%, the apparent viscosity of CWS prepared is550mPas, lower about60mPas than before modified. The maximum concentration is69%, compared with the CWS prepared commercial sodium naphthalene sulfonate, the former has7.82%higher penetration and4.45%lower dehydration rate than the latter, shows excellent stability.Another kind of dispersant was developed by humic acid which is very similar with the structure of the coal, It was modified with acrylic acid and maleic acid in the role of initiator, When the concentration of hydrochloric acid is20%, the concentration of NaOH solution is15%, the humic acid is purified. The optimized conditions of synthesis humic acid-based polycarboxylic dispersant were as following:the mass ratio of humic acid and monomer was1:1.08, the initiator dosage was5%, the reaction temperature was75oC, the reaction time was3h, the ratio of K2S2O8and NaHSO3is4:2. IR spectra indicated that the existence of C=O and COO-stretching vibration of carboxylic acid in1712cm-1and1610cm-1,and the dispersant can reduce the surface tension of water significantly. When the contents of dispersant is0.5w%, the apparent viscosity of CWS prepared is505mPa·s, lower about245mPa·s than before modified. The concentration was improve about2%and the maximum concentration is70%,compared with the CWS prepared commercial sodium naphthalene sulfonate, the former has8.87%higher penetration and1.85%lower dehydration rate than the latter at72h.Meanwhile, the stability of CWS prepared above dispersants is measured in the case of ultrasound, the viscosity of both CWS prepared decreases evidently when ultrasonic power is80W and100W for3min, and stability performance is better than mechanical mixing pulping. The CWS prepared for the above kinds of dispersants performed excellent mobility than prepared naphthalene dispersant; the liquidity shows A-level, better than the latter D-level. It indicated that the hydrophilic active groups were introduced successfully, and can effectively decrease the viscosity increase the concentration. |
PDF Full Text Request