Influence Of Modified Sodium Lignosulfonate/Polycarboxylate Dispersant On The Properties Of Carbon-based Slurry And Mechanism Research

As a kind of low value byproduct with high carbon content,coal pitch(CP)and waste tire pyrolysis residue(WTPR)has the advantages of wide source and low price.However,their application value has been limited due to low comprehensive utilization rate and serious environmental pollution.Slurry technology is a clean energy technology,which has been widely used in fuel preparation because of its multiple advantages such as low cost and high efficiency.Sodium lignosulfonate(LS)is a kind of biomass dispersant with extensive sources and low-cost.However,due to its poor dispersion and stability,it needs to be modified to improve its dispersion performance.In addition,polycarboxylic acid is also widely used as dispersant because of its high design and structural flexibility.In this paper,modified sodium lignosulfonate(MLS)dispersant was prepared,and amphoteric polycarboxylic acid(AAD-1,AAD-2,AAD-3)dispersants were synthesized.On this basis,the effects of MLS/AAD-2 compound dispersant on the properties of CP water slurry(CPWS)and waste tire pyrolysis residue water slurry(WTPRWS)were investigated,respectively,and the slurry-making mechanism of the compound dispersant was analyzed by means of experiments and simulations.The main research contents include as follow:(1)The MLS dispersant was prepared by sulfomethylation and condensation reaction.It was applied to prepare CPWS.The effects of preparation parameters on the dispersion performance of MLS dispersant were mainly studied.The effects of MLS dispersant under the optimal conditions on the slurry properties were investigated.The changes of surface properties of CP by MLS dispersant were explored by adsorption,contact angle and Zeta potential,and compared with sulfomethylated sodium lignosulfonate(S-LS)and condensed sodium lignosulfonate(C-LS).The results showed that,compared with LS,S-LS and C-LS dispersants,MLS dispersant had the best dispersion and viscosity-reducing ability,and the flow pattern of slurry was better,which belonged to yield pseudoplastic fluid with small yield stress and good stability of slurry.The adsorption capacity of MLS dispersant on the CP surface was 4.37 mg/g,and the thickness of adsorption layer reached 6.31 nm.The MLS dispersant could effectively improve wettability and Zeta potential of CP surface,which was beneficial to improve the electrostatic repulsion and steric hindrance between CP particles in slurry.(2)Three AADs dispersants with different side-chain lengths were prepared by the free radical polymerization using 2-acrylamide-2-methylpropanesulfonic acid(AMPS),allyl polyoxyethylene ether(APEG)and methacryloyloxyethyl trimethylammonium chloride(DMC)as reaction monomers.They were applied to prepare CPWS.The effect of side-chain length of dispersant on the properties of slurry under the optimum conditions was studied.The surface properties of CP and slurry microstructure of CPWS were characterized by adsorption,contact angle,XPS,Zeta potential,optical microscope,and so on.The results showed that the side-chain length of AADs dispersant had a great influence on its performance.The AAD-2 dispersant with appropriate side-chain length had the best dispersity and stabilization ability for CPWS,and the slurry conformed to the yield pseudoplastic fluid with minimum yield stress.When the concentration of AAD-2 dispersant was 600 mg/L,the adsorption capacity was 4.55 mg/g,the contact angle of AAD-2 dispersant solution on the CP surface was 75.8°,and the Zeta potential was-28.7 mV.(3)Based on the excellent dispersibility of MLS dispersant and the excellent stability of AAD-2 dispersant,the CPWS was prepared after the combination of MLS/AAD-2 dispersant,and the effects of the compound ratio of MLS/AAD-2 dispersant on the slurry characteristics were investigated.The effects of MLS/AAD-2 compound dispersant on the surface properties of CP was analyzed by adsorption,XPS,contact angle and Zeta potential.The dispersion and stability mechanism of MLS/AAD-2 compound dispersant on slurry was revealed by quantum chemical,molecular dynamics simulation and EDLVO theory.The results showed that the MLS and AAD-2 had a good good synergistic effect.When m(MLS):m(AAD-2)wasequal to 1:1,the MLS/AAD-2 compound dispersant had the best dispersion and viscosity-reducing ability,and the slurry conformed to yield pseudoplastic fluid with minimum yield stress.The adsorption capacity of MLS/AAD-2 compound dispersant on the CP surface was 5.23 mg/g and accorded with Langmuir model.The adsorption layer thickness was 7.22 nm,the contact angle of CP surface was 74.5°,and the Zeta potential was-32.5 mV.Simulation results showed that hydrogen bonds were formed between MLS/AAD-2 compound dispersants and CP.The hydrophobic group could effectively adsorb with CP,while the hydrophilic group could adsorb water particles,the adsorption energy was-169.36 kcal/mol.According to the EDLVO calculation,the total interaction energy between adjacent CP particles after adsorption of MLS/AAD-2 compound dispersant was greater than 0,which indicated that CP particles could be stably dispersed in water after adsorption of dispersant.(4)Based on the good synergistic effects of MLS/AAD-2 compound dispersant in CPWS,it was applied to preparing WTPRWS.The effects of dispersant type,compound ratio and dosage,pyrolysis temperature and residue content on the slurryability were investigated,and the effects of dispersant on the surface properties of residue,the rheology and stability of slurry were analyzed.In addition,the dispersion and stability mechanism of WTPRWS were studied by simulation and EDLVO theory.The results showed that compared with LS,cetyl trimethyl ammonium chloride and nonylphenol polyoxyethylene ether,the MLS/AAD-2 compound dispersant had the best dispersion and viscosity-reducing effect,and the slurry was a yield pseudoplastic fluid with lowest yield stress.The adsorption amount of MLS/AAD-2 compound dispersant on the WTPR surface was 6.20 mg/g,the contact angle of WTPR surface was 77.9°,the Zeta potential was-31.2 mV,the content of C-O bond increased to 43.04%,and the surface was rough.Simulation results showed that hydrogen bonds were formed between the MLS/AAD-2 compound dispersant and WTPR,and the adsorption energy between MLS/AAD-2 compound dispersant and WTPR was-141.09 kcal/mol.According to the EDLVO calculation,the total interaction energy between adjacent WTPR after adsorption of MLS/AAD-2 compound dispersant was greater than 0,and was greater than that of the WTPR after adsorption of other three dispersants,which indicated that the MLS/AAD-2 compound dispersant had the strongest dispersion and stability to WTPR.In this paper,the CPWS and WTPRWS were prepared with MLS,AAD-2 or compound dispersants,the effects on the slurry properties were studied,and theslurry-making mechanism was revealed,which hadthe important theoretical and practical significance for the synthesis of high-efficiency dispersants and preparation of slurry with industrial carbon-containing solid waste.