Research On Pipeline Fouling Process And Mechanism Of Coal Chemical Salty Wastewater Treatment

Due to the complex composition of high salinity wastewater from coal-chemical industry and high salt and organic content,zero liquid discharge(ZLD)treatment process pipelines and equipment for high-salt wastewater often cause various types of fouling and corrosion problems.Component damage affects long-term stable operation of equipment and processes.Therefore,it is necessary to study the formation mechanism and influencing factors of pipeline salt fouling in coal chemical wastewater treatment.The common fouling materials in the treatment of coal chemical salt wastewater are mainly calcium carbonate and a small amount of salt such as silica and sodium chloride.This paper analyzes the formation and influencing factors of pipeline salt scale in coal chemical wastewater treatment.A self-designed soil static experiment was carried out in a simulated wastewater treatment environment.The effects of fouling temperature,steel type,experimental time and wall roughness on the average growth thickness of the fouling layer were investigated by microscopy and weighing method.The content of dirt and dirt was qualitatively and quantitatively analyzed by XRD and EDS,and the morphology of the scale was observed by SEM.The experimental results show that the fouling rate increases with the increase of temperature;the common pipeline materials used in the treatment of four kinds of coal chemical wastewater:Q235,Q345r,20#,N80 steel,Q235 steel is the most difficult to scale,which is the minimum fouling rate,and is the most preferred material in the process;the fouling rate is obviously reduced at 12?48 h,gradually becoming stable at 48?96 h;The scaling thickness increases with the increase of roughness.Under different roughness conditions of 1?10 h,the scale thickness is linearly correlated with time;the scale component is analyzed:the scale product increases with time.It is mainly calcium carbonate and is converted from calcite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.The relationship between fouling rate and time in actual wastewater and simulated wastewater all satisfy the function of y=ax-0.494,and the relationship between actual wastewater and simulated wastewater is ya=1.085ys.According to the static experiment results,the dynamic fouling experiment was simulated by using Fluent software in the simulated 35?,Q235 steel wastewater treatment environment.The inlet flow rate and wall shear force were investigated by microscope and weighing method to observe the surface morphology of the fouling rate and the average growth thickness of the fouling.Experimental results show:(1)at the same position,the formation of fouling increases first and then decreases with the increase of flow velocity.It can be concluded that when v=0.4 m/s,the thickness of the fouling layer is the thickest,and the increase of the fouling layer is relatively fast.The later period is relatively slow.(2)When v=0.2?0.4 m/s,the fluid flow state is mainly laminar and transitional flow,and the thickness of the fouling layer increases with the increase of flow velocity;Different wall shear forces at different locations,the thinner the wall layer,the thinner,denser and tighter the fouling layer.(3)When v=0.4?0.7 m/s,the fluid flow state is turbulent,and the thickness of the fouling layer decreases as the flow rate increases;The turbulent flow can be different at different locations,and the thicker and denser the fouling layer is,the larger the turbulent energy is.(4)The density of the fouling layer at the 90°elbow is relatively large.Due to the large impact of the water flow,the thickness of the fouling layer is low and the thickness of the fouling layer is low,but the retained fouling is hard and dense,and it is difficult to handle and clean the formed fouling.According to the main component of the fouling is calcium carbonate,a model of calcium carbonate fouling deposition is summarized.The calcium carbonate fouling deposition was simulated by UDF custom compilation in Fluent software.The simulation results show that the fouling deposition rate,erosion rate and thickness of the fouling layer tend to increase first and then tend to be gentle in the whole pipeline;90°The net deposition rate of fouling and the thickness of the fouling layer are the smallest in the elbow;the experimental value is larger than the simulated value,and the trend is basically the same.The research results in this paper determine the optimal operating conditions for slowing scaling,the type of steel,the surface roughness of steel,and the distribution of fouling deposits at 90°bends,which lays the foundation for slowing pipeline fouling in the treatment of high-salt wastewater from coal chemical industry.