Computational method for multiphase flow characterization in the gas refinery

Abstract

This paper presents a new computational method for the decentralized multiphase flow measurement based on the interconnections between the two subsystems to precisely estimate the states of the multiphase flow at the gas refinery. The states of the condensate and gas sub-systems were separately estimated using the Differential Mean Value Theorem by considering the relationship between two subsystems, designing an observer and converting the conditions to linear matrix inequality. To check the stability and performance of the system against the changes, the Lyapunov theory has been used. The states behavior investigated with and without disturbance in the system output and dynamics. Additionally, the Unscented Kalman Filter based on the simplified drift flux model was used to estimate the states. It is found that both observers are capable to identify the states with some differences in performance and drift flux model is sufficient for estimation of parameters and states.

Sliding Mode Observer Design for decentralized multi-phase flow estimation

“…The available measurements are acquired by pressure sensors, outlet single-phase flow meters and analyzers. By considering interconnection term H(s,t) as a disturbance, the proposed observer is defined as [44]:…”

“…The available measurements are acquired by pressure sensors, outlet single-phase flow meters and analyzers. By considering interconnection term as a disturbance, the proposed observer is defined as [45] : where is the estimated states, is the flux estimation, L is the observer gain, denotes the signum function of σ and the sliding surface is defined as: In the Sliding Mode technique, the state trajectory of the system is bounded in a chosen manifold by an appropriate control action. This manifold is termed as switching surface or a sliding surface.…”

“…Multi-phase flows in many environmental and industrial processes are subject to nonlinear and complex changes in the flow regime, composition of different phases, temperature and pressure fluctuations [40] , [41] , [42] , [43] , [44] . These nonlinearities in multi-phase flow systems are further intensified due to the existence of disturbance sources, the effects of environmental conditions, and specifications of the multi-phase flow system.…”