Dynamic Efficiency Analysis of an Off-Shore Hydrocyclone System, Subjected to a Conventional PID- and Robust-Control-Solution

Abstract

There has been a continued increase in the load on the current offshore oil and gas de-oiling systems that generally consist of three-phase gravity separators and de-oiling hydrocyclones. Current feedback control of the de-oiling systems is not done based on de-oiling efficiency, mainly due to lack of real-time monitoring of oil-in-water concentration, and instead relies on an indirect method using pressure drop ratio control. This study utilizes a direct method where a real-time fluorescence-based instrument was used to measure the transient efficiency of a hydrocyclone combined with an upstream gravity separator. Two control strategies, a conventional PID control structure and an H ∞ robust control structure, both using conventional feedback signals were implemented, and their efficiency was tested during severely fluctuating flow rates. The results show that the direct method can measure the system's efficiency in real time. It was found that the efficiency of the system can be misleading, as fluctuations in the feed flow affect the inlet concentration more than the outlet oil concentration, which can lead to a discharge of large oil quantities into the ocean.

Online Backwash Optimization of Membrane Filtration for Produced Water Treatment

“…The mechanical stirrers have a combined electrical effect of 2.2 kW and a mixing intensity of 1469 m3/h. The droplet size distribution during stirring was analyzed in [21] and is shown in Figure 2. Based on the results, 95% of the droplets are between 5.4 μm and 46.6 μm, which are close to the 5 μm–50 μm range reported in [22].…”

“…Droplet size distribution histogram based on measurements from the ViPA monitor with a mean and median of 18.473.33333ptsans-serifμm and 15.473.33333ptsans-serifμm, respectively [21]. …”

Non-target screening of organic compounds in offshore produced water by GC×GC-MS

“…The latter is largely removed by physical methods, i.e. separators, hydrocyclones and gas flotation tanks/degassers implemented in series on the platform, typically resulting in levels below 10 mg/L at the discharge point (Meldrum, 1988;Saththasivam, Loganathan & Sarp, 2016;Durdevic & Yang, 2018). In contrast, the removal of dissolved organics requires chemical treatment, e.g.…”

Modeling and Control of Membrane Filtration Systems for Offshore Produced Water Treatment

“…The plant was initially constructed to investigate how slugging is formed and how advanced control can be deployed to negate the negative effects slugging can have on the downstream processes. In addition, advanced control and monitoring of the combined separator and hydrocyclone system have been carried out using H ∞ control and model predictive control (MPC) solutions [40,[64][65][66][67][68].…”

“…To control the droplet size distribution and ensure a uniform distribution of oil throughout the large mixing tank, two large mechanical stirrers (variable speed) with a combined maximal mixing intensity of 1469m 3 /h were used. To evaluate if the artificially created emulsion has a reasonable droplet size distribution, the emulsion was analyzed using the Jorin ViPA (video microscopy) [66]. The identified droplets size distribution is illustrated in Fig.…”