Computational fluid dynamics analysis of a novel continuous cementing slurry mixer

Abstract

To improve the uniformity of continuous slurry mixing in well cementing, a novel continuous mixing system is proposed in this paper. The CFD model of the mixing system is established by employing the Eulerian multiphase flow model, k-ε model, and Multiple Reference Frames (MRF) method to simulate the flow of the two-phase fluids and the rotation of the agitator, respectively. A segmented control simulation method, which includes a dynamic “monitoring-assignment” approach capable of handling secondary mixing processes in engineering, is proposed to calculate the slurry mixing process in the continuous system. A comparative analysis of the control effectiveness is conducted to demonstrate the feasibility of this method. Using the validated model and method, the mixing process of the slurry in the system is investigated. The obtained data is analyzed based on four indicators: uniformity calculation, power, velocity component, and solid volume fraction, to evaluate the effects of impeller diameter and rotational speed on slurry uniformity. The data shows that both impeller diameter and rotational speed significantly affect the slurry uniformity in the continuous mixing system, while only impeller diameter has a greater impact on the flow field and flow pattern inside the stirred tank. It is observed that increasing the impeller diameter and rotational speed beyond a certain point does not further improve slurry uniformity, and excessive impeller diameter and rotational speed may lead to a decrease in uniformity due to stratification in the tank, along with a significant increase in power consumption. The proposed novel structure and method can provide valuable references for the industry, and the research findings can offer scientific guidance for achieving efficient well cementing operations in engineering.