Theoretical Model and Experimental Study of Slurry Erosion by Flowing Dilute Sulfuric Acid Under Turbulent Conditions

Abstract

Sewage pipes and acid rain, as the surface of concrete materials in buildings, are often eroded by sulfuric acid turbulence. In this paper, the influence of sulphuric acid with different velocity on the erosion rate of concrete mortar under turbulent conditions is studied. The thickness expression of the viscous inner layer is obtained by using the turbulent boundary layer theory, and the relationship between the viscous inner layer and the concentration boundary layer (CBLr) in the acidic solution near the mortar wall is established by using the Schmidt number. On this basis, a theoretical model of the relationship between the velocity of sulfuric acid and the erosion rate of mortar under turbulent conditions is derived, combining with the dissolution reaction process of dilute sulfuric acid erosion mortar (DSAEM). The results show that the erosion rate increases with the increase of the velocity, but decreases with the exponential relation of the velocity. In order to verify the rationality of the theoretical model, a simulated flow erosion test device was used to test 10 groups of cement mortar specimens for 800 h, and the experimental data of erosion rate and dilute sulfuric acid consumption of mortar specimens with water-binder ratio of 0.5, pH value of 3.4 and flow rate of 1.70 m/s ~ 2.87 m/s were obtained, and compared with the theoretical model. The experimental results show that the relationship between the amount of flushing and the flow rate is in good agreement with the theoretical results.

Keywords

• cement mortar
• flow corrosion model
• sulfuric acid
• turbulence