Improving Separation of Oil and Water With a Novel Coalescing Centrifugal Pump

Abstract

Summary A novel centrifugal pump that increases oil-droplet sizes in produced water has been developed. This paper investigates a concept of pumping-pressure optimization, with respect to downstream separation efficiency, for the new pump. The investigation shows that the coalescing centrifugal pump always increased the separation efficiency of a downstream hydrocyclone. Furthermore, it is shown that the pumping pressure can be adjusted to maximize the improvement. Experimental results demonstrate how pumping conditions that minimize the volume fraction of droplets with a diameter smaller than the cut size of the hydrocyclone maximize the separation efficiency. Finally, it is demonstrated how the concept of pumping-pressure optimization can be implemented in a typical produced-water-treatment plant.

Variable Step Size P&O Algorithms for Coalescing Pump/Deoiling Hydrocyclone Produced Water Treatment System

“…The figure indicates the modeled downstream oil concentration before and after the environmental change, using black numerals. Due to the reduced size of the droplets entering the pump, the size of the droplets leaving the pump is also reduced, therefore lowering the hydrocyclone efficiency and increasing the downstream oil concentration (Husveg et al, 2018). After the environmental change, the system adapts to the new conditions, increasing the pumping pressure and eventually encircling ∆p = 7.3 bar.…”

“…The investigated control routines determine this setpoint. The coalescing pump used in this investigation is designed according to the principles of Typhonix AS and is the same pump as used by Husveg et al (2016Husveg et al ( , 2018Husveg et al ( , 2019. It is emphasized that the resulting coalescing effect is partly a design parameter and partly process related, and therefore varies from one pump application to another.…”

“…As a continuation of van Teeffelen's work, Husveg et al (2016Husveg et al ( , 2018 performed several studies of the pump's coalescing effect when operated outside of BEP. They studied 1) the droplet growth at various pumping pressures and flow rates, 2) how produced water characteristics-including oil type, oil-in-water concentration, and droplet size distribution-affected the droplet growth, and 3) how the enlarged droplets further affected the separation efficiency of a downstream deoiling hydrocyclone.…”

“…Based on the findings of Husveg et al (2016Husveg et al ( , 2018, Husveg et al (2019) presented a control routine which continuously optimized the droplet growth according to the downstream separation efficiency. By repeatedly changing the pumping pressure in steps of a fixed size, the routine tracked the optimal point of operation, i.e., the combination of pumping pressure and flow rate, without affecting the overall process plant.…”