Influence of Na2CO3 on the rheology of Hongshaquan lignite water slurry
Aiming at the difficulty in preparing high concentration lignite water slurry(LWS),a compound dispersant was prepared based on the compound of Na2CO3 and sodium methylene dinaphthalene sulfonate(NNO).The effects of NNO and the compound dispersant on the LWS properties were investigated.The changes in zeta potential,contact angle,pore structure and pore size distribution of LWS particles with different agents were analyzed to explain the mechanism in slurry concentration and rheological properties.The results show that the mass concentration increased from 59.89％to 60.53％,and the yield stress increased from 24.12 Pa to 38.85 Pa when the slurry was made with the compound dispersant.Besides,the fluidity index decreased from 0.69 to 0.56 indicating that the pseudoplasticity was increased by Na2CO3.The absolute value of zeta potential increased from 28.3 mV to 36.1 mV and the contact angle decreased from 74.5° to 65.3° after NNO adsorption on lignite.With the addition of Na2CO3,the absolute value of zeta potential decreased to 34.6 mV and the contact angle decreased to 57.5°.Compared with NNO,the specific surface area of the particles decreased from 2.7442 m2/g to 2.4264,the content of macropores decreased from 70.71％to 54.15％,while the content of mesopores increased from 25.68％to 41.27％.These results indicated that Na2CO3 optimizes the ionic environment in the coal-water slurry system and promotes the adsorption of NNO on the surface of lignite particles,which reduces the contact angle and zeta potential,causing the viscosity reduction.In addition,Na2CO3 formed precipitates with the metal ions dissolved in LWS system so that the pores was plugged and drove more free water releasing,thus reducing the apparent viscosity of LWS.
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