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Concentrated sodium lignosulfonate (NaLS) solutions have wide industrial applications. Therefore, the viscoelastic properties of NaLS in concentrations of 55%-63% have been investigated between 5°C and 55°C by means of a dynamic rheological technique, namely, the oscillatory rheological experiments were conducted in a rheometer in the small amplitude oscillatory mode. All solutions showed 'shear-thinning' behavior over frequency. The complex viscosity ( η*) increased and the loss tangent (tanδ) decreased with increasing concentrations. Both the storage modulus ( G′) and the loss modulus ( G″) increased with increasing frequencies and concentrations. The change in viscoelastic behavior was probably caused by stronger aggregation effects. However, the effects of temperature on the viscoelastic properties are more complex. For 60% NaLS, G′, G″, and η* decreased, but tanδ increased with increasing temperatures. When the temperature exceeded 20°C, G′, G″, and η* increased, but tanδ decreased, and the relaxation times were increased as a function of temperature. The change in viscoelasticity as a function of temperature may also be related to intermolecular aggregation and the swelling of aggregates. The conductivity experiments indicated that the formation of a greater strength of network structures at higher levels of concentrations between 55% and 63% and temperatures between 20°C and 55°C was probably responsible for elasticity enhancement. [ABSTRACT FROM AUTHOR]

Five interfacial agents with different hydrophilic groups (DBS, SDS, SO, TX, CTAB) are used as model additives to prepare coal-water slurry (CWS). The effects of different interfacial agents on the rheological properties of CWS are systemically investigated, the microscopic aggregation behavior of coal particles in the suspensions and the zeta potentials in coal-water interface are also studied. Based on the interpretation of the results, the rheological behavior of CWS is greatly influenced by the adsorption pattern of the interfacial agents in coal-water interface. The adsorption patterns of anionic interfacial agents on coal surface are mainly influenced by the combining force between the anionic hydrophilic groups with Ca2+, the stronger combining force with Ca2+leads to the apparent viscosity increase and heavier pseudo-plastic property of CWS. The adsorption pattern of nonionic interfacial agent on coal surface is seldom influenced by the hydrophilic polyoxyethylene chain, and the addition of nonionic interfacial agent reduces the apparent viscosity of CWS. The adsorption pattern of cationic interfacial agent on coal surface is determined by its cationic head, and the addition of cationic interfacial agent increases the apparent viscosity of CWS. The concluded adsorption models of the interfacial agents with different hydrophilic groups can be guidance for the molecular design of high-performance additives of CWS. [ABSTRACT FROM AUTHOR]

Abstract: High solid content coal–water slurries (abbreviated as CWS) with low viscosity and excellent stability are ideal for the combustion and storage, but it is very difficult to prepare the CWS with both properties in industry. In this study a new Polycarboxylic Acid (abbreviated as PC) hyper-dispersant containing fundamental chain, sulfonic groups, carboxyl and polyoxyethylene branches is designed and synthesized as additive to prepare the CWS with ideal solid content, viscosity and stability. The synthesized PC hyper-dispersant under optimized conditions can be used to prepare CWS with the 68.13wt.% solid content and 645mPa·s apparent viscosity at 0.4wt.% dosage, and the CWS have no sediments during three days. The rheological property investigation shows that the CWS prepared using PC exhibit markedly shear-thinning characteristic, which is very advantageous to the static stability, pipe pumping and spray combustion under high-shear condition. Fundamental analysis considers that the carboxyl anchor on coal surface, exhibiting firm adsorption affinity. The sulfonic groups orient towards the solution, providing electronegativity on coal surface. The flexible polyoxyethylene branches orient towards the solution, forming a thick hydrophilic polyoxyethylene layer on coal surface. The excellent dispersing and stabilizing effects of PC hyper-dispersant for CWS are concluded to be due to the combined effects of steric hindrance, lubrication action and electrostatic repulsion force. [Copyright &y& Elsevier]

The Haake rheometer is used to determine the rheological property of coal-water suspension (CWS) made up from Datong coal, and the obtained rheological curves are fitted using power-law, Binghamplastic, Herschel-Bulkley, Casson, and Sisko models, respectively. The fitted parameters indicate that the Herschel-Bulkley model has the maximum correlation coefficient of all the rheological models, so the Herschel-Bulkley model is selected to study the rheological property of the prepared CWS. By means of the Herschel-Bulkley model, the effects of coal concentration, dispersant dosage and electrolyte addition on rheological property of CWS are studied. The results show that CWS with higher coal concentration tend to be pseudoplastic behavior, and CWS prepared using excessive dispersant show shear-thickening flow characteristic. The addition of high-valence cationic electrolyte increase the yield value and the pseudoplastic behavior of CWS, while the addition of anionic adjusting agent decrease the yield value of CWS, and the CWS tend to be shear-thickening flow characteristic. [ABSTRACT FROM AUTHOR]

Abstract: The paper making waste liquor is a great water pollution source and much work has been done over the years to overcome this challenge. We present here a solution of black liquor used as dispersant of coal–water slurry (abbreviated as CWS) following chemical treatment. The treated black liquor (abbreviated as TBL) is used to prepare CWS for three bituminous coals, and the factors influencing its dispersing ability and the properties of CWS are investigated. The results show that the increasing sulfonating agent and formaldehyde dosage increase the sulfonic group content while reducing the molecular weight of TBL. The comparison with a naphthalene dispersant shows that TBL has a similar or better dispersing ability, and the large quantity of sulfonic groups engrafted in lignin molecules and the markedly increase of molecular weight are considered the key reason for the excellent performance of TBL. Moreover, the change of the molecular configuration from globular to flocculent in solution observed by TEM is also considered as an important reason for the excellent dispersing effect of TBL for CWS. [Copyright &y& Elsevier]