Control-Oriented Modeling and Experimental Validation of a Deoiling Hydrocyclone System

Abstract

As the treated water from offshore oil and gas production is discharged to the surrounding sea, there is an incentive to improve the performance of the offshore produced water treatment, to reduce the environmental pollutants to the sea. Regulations determine both the maximum allowed oil concentration and the total annual quantity. It is reasonable to assume that when better separation equipment or methods are developed, the regulation will become more strict, and force other producers to follow the trend towards zero harmful discharge. This paper develops and validates a hydrocyclone model to be used as a test-bed for improved control designs. The modeling methodology uses a combination of first-principles to define model structure and data-driven parameter identification. To evaluate and validate the separation performance, real-time fluorescence-based oil-in-water (OiW) concentration monitors, with dual redundancy, are installed and used on sidestreams of a modified pilot plant. The installed monitors measure the inlet and outlet OiW concentration of the tested hydrocyclone. The proposed control-oriented hydrocyclone model proved to be a reasonable candidate for predicting the hydrocyclone separation performance.

Feedforward, Cascade and Model Predictive Control Algorithms for De-Oiling Hydrocyclones: Simulation Study

“…A control-oriented model for de-oiling hydrocyclone with a swirl element was developed by Das and Jäschke (2018). In Bram et al (2020), a virtual flow resistance model with an extended trajectory model was developed and performance of hydrocyclone was compared using the model and experimental data from a scaled pilot plant. A first-principles model for de-oiling hydrocyclones based on pressure-flow relationship, separation efficiency and dynamic mass balance was developed by Vallabhan K G et al (2020).…”

The Impact of Riser-Induced Slugs on the Downstream Deoiling Efficiency

“…This section describes the model framework for used in this paper. This model framework is based on previous works, which is well-described and validated in [33], expanded by a separator-tank model and two valve controllers. The model framework is illustrated in Figure 2.…”

“…A virtual flow resistance (VFR) model, proposed in [27], estimates the flow rates leaving the hydrocyclone: Underflow flow rate (Q u ) and overflow flow rate (Q o ). Finally, an oil droplet trajectory (ODT) model, proposed in [42], extended in [43], and validated in [33], estimates the deoiling performance of the hydrocyclone.…”

“…which are are chosen to emulate the valve properties of the used pilot plant, as described in [33]. To solve this system of equations, the boundary pressures P i , P ub , P ob are required to be known.…”

“…The work examined in [31] concluded that the separation performance decreased when severe riser-induced slugs are presents, however, the oil-in-water (OiW) concentration was not measured or estimated due to the challenges and limitations associated with online OiW monitoring [32]. Hence, in this paper, the recently developed hydrocyclone model from [33,34] will be utilized to quantify the riser-induced slug's impact on the OiW concentrations after the downstream separation processes.…”