Optimisation of Mare's Tail coalescer technology.

Vijayakumar, Bhavani

Abstract

The Mare's Tail technology was invented in ERT (Orkney) as a joint industrial project to reduce the use of chemicals in the produced water treatment process. The Mare's Tail is a fibrous type of coalescer used in the coalescence of oil droplets that are finely dispersed in the produced water stream with less or no chemicals. This thesis describes the work done under the auspices of the knowledge transfer partnership (KTP) between Opus Plus Ltd. and Robert Gordon University (RGU), which is concerned with optimising the existing Mare's Tail technology. A number of parameters - like surface energy, flow rate, viscosity, density, length of the fibre, porosity, inlet oil droplet size, oil concentration and spool diameter - that affect both the coalescence efficiency and the separation efficiency were identified. These parameters were then grouped together to form an initial semi-empirical model (SEM). From the initial SEM, SEM1 and SEM2 were developed based on experiments conducted in the bespoke test rig. SEM1 was developed to predict the separation efficiency of a hydrocyclone or compact floatation unit (CFU) downstream of the Mare's Tail Coalescer. SEM2 can be used to predict the coalescence efficiency of the Mare's Tail coalescer based on the growth of oil droplet size. SEM1 was developed and tested using experimental and offshore data, while SEM2 was developed and tested using only the experimental data. The results show that the optimum porosity is between 0.54 to 0.51 for a spool diameter between 2" to 20". It was identified that the coalescence efficiency increases as the pack structure increases. The optimum velocity was identified as 0.4m/s. It was proved both experimentally and theoretically that increasing the inlet oil droplet size decreases the coalescence efficiency, but increases separation efficiency. At the final stage of the project, even though SEM1 (R2 = 0.85) had higher accuracy level, SEM2 (R2 = 0.66) was selected for use in the software, as it depicts only the performance of the Mare’ Tail and not the separation equipment downstream. A method to evaluate the droplets' size and their respective concentration were identified in order to calculate the efficiency of the Mare's Tail. This project distinguished the difference between coalescence efficiency and seperation efficiency, and proposed to the sponsoring company the method used to evaluate them. Even though most of the model was derived from a previously-published paper (Oyeneyin, Peden, Hosseini, Ren and Bigno 1992), it was then modified to suit the requirements of the Mare's Tail.

Citation

VIJAYAKUMAR, B. 2014. Optimisation of Mare's Tail coalescer technology. Robert Gordon University, MPhil thesis.

• Thesis Type: Thesis
• Deposit Date: Jul 16, 2019
• Publicly Available Date: Jul 16, 2019
• Keywords: Water treatment process; Coalescer; Mare's Tail technology
• Public URL: https://rgu-repository.worktribe.com/output/322195
• Award Date: Jul 31, 2014