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.
Highlights
The growth of population and limitation of hydrocarbon sources in the world have resulted in higher demand which, in turn, continuously affect the price of these products
- According to the API and AGA standards, acceptable accuracy of single phase fiscal flow measurement for gaseous is 1% and for liquids is 0.15%, using this soft sensor, RMSE metric for the liquid flow measurement is better than 0.12% and for the gas flow measurement is better than 0.34%
The Kalman filter is a recursive estimator, which estimates the states and parameters of a linear systems by integrating measured data in real-time. It is initially developed for linear systems but several extensions of that exist for nonlinear systems which Unscented Kalman filter (UKF) is one of the most popular extensions because of its ease of implementation and simple concept
Summary
The growth of population and limitation of hydrocarbon sources in the world have resulted in higher demand which, in turn, continuously affect the price of these products. The main contribution of this paper is, presenting a new form of the soft sensor using the new decentralized Lyapunov-based observer to measure the multiphase flow at the entrance of a gas refinery, which leads to better performance, higher accuracy, and repeatability. - According to the API and AGA standards, acceptable accuracy of single phase fiscal flow measurement for gaseous is 1% and for liquids is 0.15%, using this soft sensor, RMSE metric for the liquid flow measurement is better than 0.12% and for the gas flow measurement is better than 0.34% This technique can be used as an alternative to the costly multiphase measurement systems or lowaccuracy conventional systems and serves as a fault-detection system or as a backup when the existing measurement system is in fault or removed due to maintenance or replacement. - Consistency of both estimators with the real process in a gas refinery in the South Pars Gas Complex (SPGC) in Iran is shown
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