Improvement to hydrocyclone used in separating particles from produced water in the oil and gas industry.

Adewoye, Adebola Jumoke

Abstract

Hydrocyclone is used to separate particles from produced water. It can be used in different industries, including oil and gas, water treatment and pharmaceutical (among others). The hydrocyclone can effectively separate particles larger than 10μm, but the efficiency is greatly reduced when the particle size is less than 10μm. This research work therefore aimed to improve the efficiency of separating small oil droplets (particle size of 0-20μm) in liquid-liquid hydrocyclone. In order to achieve this, the use of micro particles was employed and magnetism was later induced into the system. The hydrocyclone with micro-doped oil is referred to as the micro-hydrocyclone, while the hydrocyclone that includes both micro-doped oil and induced magnetism is referred to as magnetic hydrocyclone. Computational fluid dynamics (CFD) were employed for analysis of the fluid flow in the hydrocyclone; a review of the turbulence model shows that the Reynold stress model (RSM) and Large eddy simulation (LES) are the best turbulence models for the analysis. RSM was employed because of the reduced computational time when compared to the LES model. A pressure-based solver with transient time was used for the simulations. The discretization was done using SIMPLE for the pressure velocity coupling, QUICK was used for all other discretization. The review of the turbulence model was done to evaluate the best RANS model for hydrocyclone simulation, as a reduction in computational time would be greatly appreciated. Results of the eddy viscosity models with curvature correction terms and RSM model were compared to Hseih’s experimental results. The fluid flows in liquid-liquid and solid-liquid hydrocyclones were analysed using different geometrical parts, which established that - as reviewed in the literature - the geometrical parts cannot be used to effectively separate particles less than 10μm. A comparison of the fluid flows in liquid-liquid and solid-liquid hydrocyclone was also reviewed using the same hydrocyclone geometry. The impact of microparticles and microparticles with magnetic induction on the separation oil-emulsion was compared to the conventional hydrocyclone. A review of the magnetic permeability, charge density, magnetic particle density and effect of flowrate was also performed. From turbulence model analysis, it was concluded that RSM better predicts the flow in the hydrocyclone in comparison to the other evaluated RANS model. However, the use of the eddy viscosity model with curvature correction can also be used with a slight reduction in efficiency. The eddy viscosity without curvature correction terms cannot be used to predict the anisotropy flow in the hydrocyclone. The results of the micro-doping analysis show that the magnetic hydrocyclone can improve the efficiency of separating particles smaller than 10μm by approximately 30%. However, the micro-doped hydrocyclone provides better efficiency for separating particles sized between 10-30μm, while the conventional hydrocyclone is better used for particles that are larger than 30μm at a higher flowrate. It was also concluded that the density difference caused by doping oil with magnetic particles is the most important factor influencing the separation. Increasing the density of the microparticle increases the separation efficiency. For the split ratio, however, increasing from a density of 2175kg/m3 to 3175kg/m3 increases the split ratio, whereas a further increase of the density from 3175kg/m3 to 5175kg/m3 did not significantly affect the split ratio. Decreasing the magnetic permeability increases the drag force, lift force and moment while hydrocyclones with lower permeability have a higher velocity profile than hydrocyclones with high permeability. The pressure and split ratio also decrease with increasing permeability. Finally, increasing the microparticle charge density increases separation, while very slightly decreasing the split ratio.

Citation

ADEWOYE, A.J. 2020. Improvement to hydrocyclone used in separating particles from produced water in the oil and gas industry. Robert Gordon University, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-1357822

• Thesis Type: Thesis
• Deposit Date: Jun 7, 2021
• Publicly Available Date: Jun 7, 2021
• Keywords: Hydrocyclones; Particle separation techniques; Micro-doped oil; Induced magnetism; Industrial applications
• Public URL: https://rgu-repository.worktribe.com/output/1357822
• Publisher URL: https://doi.org/10.48526/rgu-wt-1357822
• Award Date: Jun 30, 2020