Application Of Bamboo Pulp Lignin-based Efficient Dispersant Used In CWS

In recent years, it is still very popular in industry how to achieved the energy recycling,emission reduction and the sustainable utilization of resources. As a new type of clean fuel,the coal water slurry （CWS） has been widely applied. It is known that the pulp and paperblack liquor contains a lot of lignin, thus abandoning the black liquor wantonly is not onlycaused rivers polluted, but also a waste of natural resources. So useing the black liquor-ligninproducts to improve its added value is an effective way to take advantage of the waste andprevent the pollution. On the other hand, there is a great deal of ceramic enterprise inGuangdong province, the ungasified coal and poisonous phenol water in the production wouldbring some economic and environmental problems. It would turn out to be a good method thatuse phenol water to prepare coal water slurry.In this paper, the modified lignin dispersant of CWS has been synthetized by the methodof sulfonation and graft copolymerization while the bamboo pulp black liquor was used as theoriginal material. The effort of reaction liquid concentration, sulfonation agent and the blackliquor content on the performance of CWS was studied. The molecular structure of syntheticdispersant samples was characterized by UV, FTIR, GPC,1H-NMR ect.analysis method. Theinfluence of different pulping condition on the viscosity of CWS and adsorption behavior inthe water-coal interface such as dispersant dosage, pulping temperature, pH value etc. hasbeen studied, which contains adsorption isotherm and adsorption kinetics. In addition, thelignin efficient dispersant used in phenol water CWS was prepared on the basis of aboveresearch, and the effect of dispersant on viscosity and stability of slurry was studied.The molecular weight and sulfonation degree of samples could be increased byimproving the reaction liquid concentration and sulphonated agent dose respectively, but withthe dispersant of medium molecular weight and high sulfonation degree,we can got the slurryhas better performance. The apparent viscosity of slurry was only930mPa· s with theconcentration of CWS is58.5%and the dispersant GCL3S-B is0.5%. The pulping propertiesof GCL3S-B is better than naphthyl sulfonate formaldehyde condensate FDN, which intrinsicviscosity is5.42ml·g^-1and sulfonation degree is2.20mmol·g^-1. It is showed that theweight average molecular weight of GCL3S-B is16592, while the number average molecularweight is4699, and the molecular weight distribution is wide. Compared to bamboo pulpblack liquor, GCL3S-B has a bigger molecular weight and more sulfonate content, but lesscarboxyl and phenolic hydroxyl groups. According to the result of IR and1H-NMR spectrums,more sulfonate group and aliphatic side chain was introduced. It is0.75%of the optimum quantity of GCL3S-B that make the apparent viscosity ofCWS minimum. The slurry could be improved by increasing water pH or pulping temperature.When water pH changed from2to12, the apparent viscosity of slurry from1110mPa·s downto949mPa·s. When pulping temperature from15℃increased to55℃, the slurry’sapparent viscosity decreased to62.24%. Furthermore, it could also improve the slurrysignificantly by adding few of electrolytes （20%of sodium carbonate,15%of sodiumtripolyphosphate） or surfactants （1%of TX-10）, which apparent viscosity of CWS is only672mPa· s.The saturated adsorption of GCL3S-B is higher than FDN in the water-coal interface, butthe adsorption capacity is weaker. The adsorption of GCL3S-B on the coal particles obeyedthe Langmuir monolayer adsorption, which adsorption kinetic process fittedpseudo-second-order equation, while the correlation coefficient is more than0.99. Theadsorption rate of GCL3S-B increased significantly when reducing pH or adding metal ioninto the system, such as Na⁺, Ca²⁺, Al³⁺or Fe²⁺. The adsorption rate would be slowed downand the adsorption decreased by adding some additives, such as1%of TX-10,20%of sodiumcarbonate or15%of sodium tripolyphosphate. The adsorption of GCL3S-B decreased withpH value increasing, and there exists not only electrostatic interaction in adsorption processbut also other adsorption driving force. The adsorption of GCL3S-B is changed after addinginorganic salts and urea in the system. It is concluded that there is hydrophobic interactionand hydrogen bonding interaction exist in the process, but electrostatic adsorption is the mainforce.The research showed that performance of CWS prepared by phenol water was better thantap water. On the base of above research, efficient dispersant of CWS used in phenol waterGCL3S-FB was prepared by the modified synthetic samples remixed with15%sodiumtripolyphosphate, and the dispersant with medium molecular weight （intrinsic viscosity is6.66mL·g-1） and medium sulphonation degrees （sulfonation degree is2.37mmol·g-1） hasbetter performance.The apparent viscosity of slurry was only803mPa· s with58.5%of theconcentration of CWS and0.5%of the dispersant GCL3S-FB, which it is similar with thepulping performance of FDN. The rheological curve of phenol water CWS is fitted forHerschel-Bulkley model, and the slurry is yield dilatant fluid. The apparent viscosity of slurrychaged from1370mPa·s down to659mPa·s by the content of GCL3S-FB varing from0.3%to1.0%, while the yield stress τ0decreased, but dilatant enhanced. With the increasing ofpulping temperature, the apparent viscosity is decreased at first and then increased. The liquidity index n constantly decreased and then a sharp increased when the minimum value is487mPa s at55℃, whose n is1.0613. The Turbiscan Lab type dispersion stability analyzerwas used in system of phenol water CWS. It is found that the coal particles began to reunionand settled with the extension of time, while the clear liquid height and stability coefficientincreased, which the stability of slurry become poor. Meanwhile, the change of system withdifferent dispersant dosage and different pulp concentration is rather different.