Optimisation of Mare’s Tail coalescer technology.
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VIJAYAKUMAR, B. 2014. Optimisation of Mare’s Tail coalescer technology. Robert Gordon University, MPhil thesis.
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 the 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, which 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 to the Mare’s Tail Coalescer and SEM2 can be used to predict the coalescence efficiency of the Mare’s Tail Coalescer, based on the growth of the oil droplet size. SEM1 was developed and tested using experimental and offshore data while SEM2 was developed and tested only using the experimental data. The results show that the optimum porosity is between 0.54 to 0.51 for a spool diameter from 2′′ to 20′′. It was identified that, as the pack structure increases the coalescence efficiency increases. The optimum velocity was identified as 0.4m/s. It was proved both experimentally and theoretically that increase in inlet oil droplet sizes 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 to be used in the software as it depicts only the performance of the Mare’ Tail and not the separation equipment downstream. The method to evaluate the drople size and their respective concentration were identified to calculate the efficiency of the Mare’s Tail. In this project the difference between coalescence efficiency and seperation efficiency were distinguished and the method to evaluate them were addressed to the sponsoring company. Even though most of the model was derived from a paper published by (Oyeneyin, Peden, Hosseini, Ren & Bigno 1992) it was then modified to suit the requirements of the Mare’s Tail.