Argumentation for critical parameters and operating modes in the process of underwater mining of placers

The purpose of the article is to study the connection between the parameters of the formation of the suction funnel, such as the scattering speed and concentration of the suction mixture, and the concentration of the slurry in the suction pipe, which provides supercritical flow conditions. This connection is considered in terms of the most common process of underwater mining of placers for the open mining technology by suction dredger. The importance of the research is conditioned by the well-known but not yet thoroughly studied phenomenon of a decrease in the performance of the dredger pump on solid material without breaking the vacuum, which in most cases leads to a hydraulic shock in the pressure line. It is argued that the cause of this occurrence is the onset of a critical flow regime in the suction pipe due to inconsistency of the parameters of the hydrotransport modes and suction funnel formation. A combined analysis of the known dependences for the critical rate of hydro transportation in an inclined pipeline and for the geometric parameters of the suction funnel made it possible to establish restrictions on the concentration of solid particles on the surface of the erosion funnel.

A Practical Solution for Reducing Critical Height in Drain Sink Problem during Ladle Teeming Process

A common problem that affects the continuous casting process is the formation of a sink funnel or a vortex funnel in the end of the teeming process of a steel ladle. This causes the slag to be carried over with the molten steel to the tundish, generating inclusions in the produced steel ingot. In this work we propose an innovative device designed to delay the sink-funnel formation and hence decrease the critical draining height. The apparatus consists of an air-suctioning spear that induces a reduced pressure gradient just above the slag/air interface, in a position vertically alignedwith the draining nozzle axis. The device operation was modeled with Computational Fluid Dynamics (CFD). The results showed that the introduction of the suctioningspear allowedfor an optimizedladle teeming process, resulting in a shorter critical draining height, thus, reducing the amount of leftover steel to be recycled.

Characterization and Modeling of Ladle Teeming Process

In the continuous casting process, significant amounts of molten steel are left in the ladle during teeming as an established practice to avoid vortexing funnel formation in the end of the teeming process, preventing the ladle slag to be carried over to the tundish. Thus, it was the objective of this work to experimentally and numerically analyze the funnel formation in ladle teeming process. Experiments were designed and carried out to verify the numerical results.