Study On Slurrying Mechanism Of Coal Slurry Prepared From Coking Wastewater

Coking wastewater is used to prepare coal slurry,which can be used as combustion and gasification fuel.This promising technology simultaneously achieves resource utilization and wastewater management.Slurrying properties are essential to the industrial application of coal slurry.These properties are considerably influenced by coal surface properties and the adsorption of an additive by coal.By studying the comprehensive slurry forming characteristics of CWCS,such as maximum slurry concentration,rheology and stability,the pulping performance of coking wastewater prepared from coal slurry is macroscopically mastered.It is learned that the effective content of coking wastewater can promote the slurryability and stability of coal water slurry,and grasp the potential of coking wastewater as a pulping dispersant and stabilizer.By investigating the influence of various contents of coking wastewater on the surface characteristics of coal water,the mechanism of CWCS pulping was learned from the microscopic level,which provided important theoretical support for the large-scale popularization and application of CWCS technology.In this paper,the adsorption amount of additives on the coal surface and the surface characteristics of coal water were determined.The adsorption kinetic was obtained by fitting the additive adsorption data using pseudo-first-rate,pseudo-second-rate and intra-particle diffusion models.In addition,the effects of the internal components?e.g.,phenol,ammonia nitrogen,and metal ions?of coking wastewater on the adsorption of an additive by coal and on coal surface properties were also measured.Furthermore,the mechanism of the internal components in coking wastewater on the pulping characteristics of CWCS was analyzed.The results show that the adsorption process follows the pseudo-second-order kinetic equation and is controlled by liquid membrane diffusion,surface adsorption and intraparticle diffusion.The internal components exhibited different influences on the adsorption rate k₂ by increasing or decreasing its value.Moreover,their influences on the k₂ disagreed with that on the q_e.This may be due to the fact that the pseudo-second-order model did not consider the adsorption competing and promoting effects between the multi components.Results showed that the competitive adsorption between phenol and the additive reduced the amount of additive adsorbed on coal,when the initial concentration of the additive is 1000 mg·L^-1.However,phenol acted as an additive to improve the wettability of coal particles.When the initial concentration of the additive is160 mg·L^-1,the adsorption amount of the additive on the coal in the phenol-containing water environment increased compared with the deionized water environment.This may be due to the fact that when the concentration of the additive is low,its adsorption mode on the coal surface was different from the high concentration condition,and the additives and phenols promoted each other in the process of adsorption to the coal surface.Cations(Ca²⁺,NH₄⁺,and Na⁺)adversely affected the slurrying because they weakened the negative charges of coal.Furthermore,a large amount of water was adsorbed due to the ionic bonding effects,thereby reducing the free water in the coal slurry system.The maximum slurrying concentration of CWCS was 0.8 percentage points higher than that of CWS,suggesting that coking wastewater enhanced the slurrying capability of the coal slurry by integrating the various effects induced by the different internal components.