About
155
Publications
22,614
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,411
Citations
Introduction
Additional affiliations
January 2008 - present
Università degli studi di Cagliari
Position
- Università degli Studi di Cagliari
January 2004 - present
January 1985 - June 1985
Publications
Publications (155)
Fokker-Planck (FP) partial differential equation (PDE) theory is applied to characterize the stochastic dynamics of a class of open-loop (OL) 2-state nonlinear exothermic continuous reactors with: (i) zero and time-varying mean noise disturbances, and (ii) linear proportional-integral (PI) temperature control. The characterization includes: (i) the...
Ribbed surfaces are widely employed in heat exchangers to enhance the convective heat transfer and hence the overall thermal efficiency. This study aims to investigate the effect of two important assumptions made in computational fluid dynamics simulations, i.e. the thermal boundary conditions and the turbulence modeling, using a popular test case...
In this contribution, the problem of NGL separation control is addressed by dealing with the most common process schemes. The main goal is to achieve a specified ethane recovery as well as maintaining certain levels of methane impurity in the demethanizer column. An indirect control of composition through the temperature control in the column is pr...
In recent years the attention on natural gas production and utilization is growing due to different fundamental aspects. First, the availability of natural gas has increased thanks to technological improvements in the extraction techniques that have made possible the production from unconventional reservoirs. Second, the interest in clean energy is...
In this work, a combination of a Convolutional Neural Network (CNN) based measurement sensor and a reinforcement learning (RL) framework that speeds up the control loop is presented. The objective of the controller is to reach a target mean size and to reduce the variability of the crystal sizes. The CNN based sensor improves the quality of crystal...
Recent technological improvements have driven the rapid increase in natural gas production from unconventional reservoirs. The heaviest hydrocarbon fraction of this fossil fuel, the so-called natural gas liquids (NGL), have greater economic interest justifying the attention on its separation process from the raw gas. Various process schemes have be...
The nonlinear stochastic dynamics of a class of two-state bioreactors with isotonic or nonisotonic kinetics is analytically characterized with Fokker–Planck (FP) theory, with emphasis on: (i) the spatiotemporal geometry of the two-state probability density function (PDF) motion, (ii) conditions for metastability-based bio-extinction/revival (inexis...
During the last years, machine learning-based control and optimization systems are playing an important role in the operation of wastewater treatment plants in terms of reduced operational costs and improved effluent quality. In this paper, a machine learning-based control strategy is proposed for optimizing both the consumption and the number of r...
In this contribution, the monitoring and control problem of the natural gas liquids (NGL) extraction process is addressed by exploiting a data-driven approach. The cold residue reflux (CRR) process scheme is considered and simulated by using the process simulator Aspen HYSYS®, with the main targets of the achievement of 84% ethane recovery and low...
Recent technological improvements have driven the rapid increase in natural gas production from unconventional reservoirs. The heaviest hydrocarbon fraction of this fossil fuel, the so-called natural gas liquids (NGL), have greater economic interest justifying the attention on its separation process from the raw gas. Various process schemes have be...
The stochastic dynamics of a two-state bioreactor model with random feed flow fluctuations and non-monotonic specific growth rate is analyzed. Using the Fokker-Planck equation approach for describing the probability density function (PDF) evolution the lack of stochastic robustness due to deterministic bifurcation phenomena for the open-loop reacto...
The growth process of a Chlamydomonas reinhardtii cell population is modelled with experimental data obtained in a batch reactor. To describe the growth process of this culture, the Droop model, extended by cell population balance model, is considered. On the basis of available measurements and the mathematical model, an optimization problem is def...
Nowadays the improvements on the extraction methods of natural gas has increased the availability of natural gas liquids (NGL), which represent a valuable source of energy and industrial feedstock. Several process schemes have been developed in the past for an economical, safe and efficient recovery of these components including the conventional, c...
Intensified processes where reaction and separation are simultaneously carried out in the same equipment represent an attractive option to substitute the traditional reaction-separation sequences. Reactive absorption is already applied in different processes at industrial scale, but its modeling still represents an open topic where researchers are...
The solvent recovery section from the exhaust gas represents an important auxiliary part for an industrial CO2 post-combustion capture plant by the reactive absorption-stripping process. In this work, a partial condenser and a water-wash section configuration were designed to reach 1 ppm of solvent in the exhaust gas, and compared using the Total A...
In this work, a geometric observer (GO) is formulated and tested using experimental data from the Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP) system for a semi-batch free-radical polymerization reactor that synthetizes polyacrylamide. The available measurements include the weight-average molecular weight, the concentr...
This book focuses on modelling issues and their implications for the correct design of reactive absorption–desorption systems. In addition, it addresses the case of carbon dioxide (CO2) post-combustion capture in detail. The book proposes a new perspective on these systems, and provides technological solutions with comparisons to previous treatment...
In this chapter, the absorption section of two pilot-plant facilities, different in dimensions and operating conditions, is modeled. A discussion on the typical temperature bulge, which gives important indications on the behavior of the absorber, is reported. The Peclet number is evaluated for both the cases with reference to the material and the e...
In this chapter, the implementation in Aspen Plus® of the CO2 post-combustion capture by reactive absorption-stripping process model is presented. Components and thermodynamics in the Properties Environment are considered in the first place. Then, in the Simulation environment, the set-up of the RadFrac™ model—Rate-Based mode, considered mandatory...
In this chapter, the stripping section is modeled and experimental data from two different pilot-plant facilities are used for the validation. In Aspen Plus®, two different sets of degrees of freedom are chosen for the two plants, in order to study the effect of the proposed procedure on the evaluation of the output streams features in one case and...
In this chapter, the design of the absorption section of an industrial CO2 post-combustion capture system using MEA as solvent is analyzed. After the process description, the gas and liquid feed streams are characterized. A two-steps procedure is adopted for the design. Initially, the minimum number of units and the minimum solvent flow rate are de...
In this chapter, the design of the cross heat-exchanger, which interconnects the absorption and the stripping section, is examined in the first place. In this context, the stripper feed temperature is discussed in relation to its influence on the reboiler duty. Then, the flowsheet is completed with the design of the section dedicated to the recover...
The analysis of the stripping section design procedure of an industrial CO2-MEA post-combustion capture system is considered in this chapter. An alternative plant configuration without reflux is adopted with the aim of reducing the consumption of steam in the reboiler. Then, the most important operating parameters are described in detail. After the...
The global-nonlinear stochastic dynamics of a class of two-state two-parameter continuous exothermic chemical reactors subjected to noise disturbances is studied with Fokker-Planck's (FP's) partial differential equation (PDE) theory. The dependency of the stochastic on deterministic dynamics is formally established, and the fundamental characterist...
A high order Geometric Observer (GO) and a hybrid discrete-time extended Kalman filter (h-DEKF) are assessed in real-time towards data reconciliation and comprehensive polymer characterization. The nonlinear estimators are tested under a set of experiments using the data provided by the state-of-the-art smart sensor Automatic Continuous Online Moni...
This article focuses on the design and implementation of model-based control strategies for real time control of crystal size distribution (CSD) in semi batch crystallization processes. The objective of the feedback controller is to reach a desired particle mean size while the standard deviation is controlled in a feedforward fashion. Alternative m...
The open and closed-loop global state probability density function PDF behavior of a class of single-state nonlinear chemical processes subjected to additive and multiplicative white noises is characterized with analytic formulae through Fokker Planck (FP) theory, in terms of: (i) stationary state probability density function (PDF), (ii) PDF evolut...
The process analysis for the post-combustion CO2 capture using amine-based solvents is nowadays a fundamental step in its industrial scale design. In this work, the absorption-solvent regeneration system is deeply analyzed for different values of the loading in the solvent entering the absorber. The importance of the temperature and composition col...
The application of a multivariable predictive controller to the mixing process for the production of a non-Newtonian fluid is discussed in this work. A data-driven model has been developed to describe the dynamic behaviour of the rheological properties of the fluid as a function of the operating conditions using experimental data collected in a pil...
This paper presents a gain-scheduling design technique that relies upon neural models to approximate plant behaviour. The controller design is based on generic model control (GMC) formalisms and linearization of the neural model of the process. As a result, a PI controller action is obtained, where the gain depends on the state of the system and is...
This work aims to develop a control system capable to maintain the viscosity curve measured in-line during the continuous production of a non-Newtonian fluid inside a range of values of viscosity which represent the target. Rheological models capable of relating the viscosity curve of the final product to the input variables were introduced to mimi...
The complexity of the phenomena involved in CO2 chemical absorption and solvent regeneration systems results in the necessity to develop reliable models to describe the steady state and the dynamic behavior of the process. In the present work, the modeling of the regeneration section of a post-combustion CO2-MEA system have been examined. A rigorou...
Nowadays in many industrial continuous production processes of complex fluids, the rheological properties of the products are studied and verified only after the production is finished, with random checks and using off-line instruments like rheometers. This can lead to final products not meeting specifications. If this happens, products could not b...
Motivated by problems in process design, monitoring and control, the effect of multiplicative
stochastic uncertainty injection on the behavior of nonlinear dynamical system is studied with Fokker
Planck theory for two rather simple case examples selected to draw rigorous results with analytic
formulae. The effect of noise multiplicativeness on the...
A generalized formulation for the development of stochastic models to predict the crystal size distribution (CSD) in antisolvent crystallization processes is proposed. Exploiting the result of the noise induced dynamic in stochastic processes, new results are provided to represent the CSD as function of the operational parameters. The generalized f...
Recent studies into the estimation and control of an activated sludge process (ASP) at a wastewater treatment plant suggest that artificial-intelligence methods, such as neural networks, fuzzy systems and genetic algorithms, can improve the plant performance in terms of reduced operation costs and improved effluent quality. In this paper, a neural-...
The problem of robustly controlling a highly exothermic gas-phase packed-bed tubular reactor on the basis of feed and reactor temperature measurements is addressed. First, advanced nonlinear control yields a detailed model-based output feedback (OF) control design with passivity and observability solvability conditions, sensor location criterion, a...
Motivated by problems in process design, monitoring and control, the effect of multiplicative stochastic uncertainty injection on the behavior of nonlinear dynamical system is studied with Fokker Planck theory for two rather simple case examples selected to draw rigorous results with analytic formulae. The effect of noise multiplicativeness on the...
In this work, we discuss the application of multivariable predictive control for the activated sludge process in a full-scale municipal wastewater treatment plant. Emphasis is given to the selection of a control configuration that contributes to minimising the economic costs while improving the removal efficiency of the nitrogen compounds. For this...
The issues regarding the design and implementation of on-line optimal control strategies of crystal properties in noniso- thermal antisolvent crystallization processes to control particles’ mean size and standard deviation are dealt. The one- dimensional Fokker–Planck equation is used to represent the dynamic characteristics of the crystal growth a...
The problem of regulating the effluent concentration in an open-loop unstable exothermic jacketed reactor is addressed. The coolant temperature must be adjusted according to temperature as well as flow measurements. First, the robust nonlinear feedforward-output feedback stabilizing control problem is addressed with advanced control theory, yieldin...
The problem of reducing the energy consumption in an industrial multicomponent distillation column is addressed. The column is subjected to step feed and distillate flow rates, the distillate impurity is regulated by adjusting the heat duty with a PI temperature controller, and the objective is to save energy through control upgrade. First, the non...
This paper focuses on the design and implementation of on-line optimal control strategies of crystal properties for non-isothermal antisolvent crystallization processes. The one-dimensional Fokker-Planck equation (FPE) is used to represent the dynamic characteristics of the crystal growth and to generate iso-mean and iso-standard deviation curves....
A complete framework to measure and anticipate the salt concentration during crystallization process is presented. On-line monitoring of the solute concentration based on conductivity of the solution is implemented. The conductivity of the dissolved compound is dependent on its concentration in the solvent, as well as the temperature of the solvent...
In this work, we discuss a recently proposed approach for supervised dimensionality reduction, the Supervised Distance Preserving Projection (SDPP) and, we investigate its applicability to monitoring material's properties from spectroscopic observations. Motivated by continuity preservation, the SDPP is a linear projection method where the proximit...
This paper deals with the issues regarding the design and implementation of on-line optimal control strategies of crystal properties in non-isothermal antisolvent crystallization processes to control particles' mean size and standard deviation. The one-dimensional Fokker-Planck equation (FPE) is used to represent the dynamic characteristics of the...
The problem of regulating the distillate impurity content in a two-feed (paraffin-olefin) industrial multicomponent distillation column (iso-normal butane splitter) by manipulating the heat duty according to olefin-to-total feedflow load disturbance and tray temperature measurements is addressed. First, the detailed model-based nonlinear state-feed...
Motivated by the need to reconstruct blends properties and their behavior in industrial distillation columns for control and monitoring purposes, the problem of the C7+ fractions modeling is addressed with substitute mixture of real components. The reliability of the proposed approach (comparable with the employment of hypothetical component as mad...
In the last decades, a huge number of studies on carbon dioxide removal have been presented in the literature. The non-equilibrium nature of the process involves an accurate definition of the parameters' correlations and of the model's assumptions. One of the most important assumptions when developing a process model is the definition of the number...
In this work an image-based multi-resolution sensor for online prediction of crystal size distribution (CSD) is proposed. The mean and standard deviation of lognormal probability density function as the CSD can be predicted through the on-line sensor. In the proposed approach, texture analysis (fractal dimension (FD) and energy signatures) as chara...
In this article the problems of input multiplicities arising in non-isothermal crystallization process is first considered. Using controllability tools it was found that the system, along a certain trajectory is ill conditioned. Furthermore, the singularity loci of the gain matrix, calculated at asymptotic condition, were obtained. The ill-conditio...
The goal of the present work is to model the crystal growth processes mediated by both antisolvent feed and temperature variations through the time evolution of the Particle Size Distribution (PSD). The study is carried out by exploiting two different approaches. In the first approach a Population Balance Equation (PBE) model is devised, where crys...
In this work, we discuss a recently proposed approach for supervised dimensionality reduction, the Supervised Distance Preserving Projection and, we investigate its applicability to monitoring material's properties from spectroscopic observations. Motivated by continuity preservation, the SDPP is a linear projection method where the local geometry...
The problem of on-line estimating on the basis of temperature measurements the distillate NC4 impurity in an industrial IC4-NC4 splitter is addressed within an adjustable-structure Geometric Estimation approach, yielding: (i) suggestive sensor location guidelines drawn from detectability measures, and (ii) conclusive results obtained from estimator...
In this work, we discuss a recently proposed approach for supervised dimensionality reduction, the Supervised Distance Preserving Projection (SDPP) and, we investigate its applicability to monitoring material's properties from spectroscopic observations using Local Linear Regression (LLR). An experimental evaluation is conducted to show the perform...
A stochastic formulation for the description of cooling-antisolvent mediated crystal growth processes based on the Fok- ker-Planck equation is discussed. Previous results are further extended to include not only the additional degree of free- dom (temperature) in the approach, but also to formulate the model parameters dependencies with the input m...
The effect of the temperature on the Crystal Size Distribution (CSD) in antisolvent crystallization operation, for systems where the solubility is weakly dependent on the temperature, is analyzed. The hydrogen bonding properties of the solvents used that influence the supersaturation of the solution and consequently the growth and the nucleation dy...
An image-based multi-resolution sensor for online prediction of crystal size distribution (CSD) is proposed. The mean and standard deviation (std) of lognormal probability density function as the CSD can be predicted through the on-line sensor. Texture analysis, through wavelet-texture algorithm, as characteristic parameters to follow the crystal g...
The problem of on-line estimating on the basis of temperature measurements the distillate NC4 impurity in an industrial IC4/NC4 splitter (operating at Saras refinery at Sarroch in Italy) is addressed. The application of the adjustable model-based Geometric Estimation approach yields a dynamic data processor that adequately performs the estimation t...
A stochastic global formulation for the description of antisolvent mediated crystal growth processes is discussed based on the Fokker-Planck equation (FPE). The obtained global model is used to define an operating map of the crystallization process, where asymptotic iso-mean and iso-variance curves are reported in an antisolvent flowrate – temperat...
A new formulation of the recent stochastic approach for the description of the particle-size distribution (PSD) time evolution in antisolvent crystal-growth processes is presented. In this new approach, the crystals size is modeled as a random variable driven by a Gompertz growth term and the corresponding Fokker-Planck equation is carried out. Thi...
The problem of designing the state estimation structure for staged process is addressed within a geometric estimation (GE) framework, with the class of binary columns as case study. The structure consists of the complete or reduced model, the number of measurements and their locations, and the innovation mechanism. The structure is chosen to execut...
In this paper, we present an application of data derived approaches for analyzing and monitoring an industrial deethanizer column. The discussed methods are used in visualizing process measurements, extracting operational information and designing an estimation model. Emphasis is given to the modeling of the data obtained with standard paradigms li...
Nel presente lavoro è trattato il problema del design di sensori software al fine di stimare il set completo, o una sua parte, delle composizioni di una colonna di distillazione multicomponente a partire da misure di temperatura. Lo sviluppo del sensore software è basato sull’analisi del diagramma dei gradienti di temperatura con contributo per com...
Recently, a novel stochastic formulation based on the Fokker–Planck equation (FPE) for the description of anti-solvent mediated crystal growth process was proposed. Here, we further expand these results by analyzing the asymptotic (end of the batch) solution of the FPE for the CSD. In this regard, the analytical solution of the stationary FPE is ex...
a b s t r a c t The problem of assessing the short and long time effects of stochastic fluctuations on the global-nonlinear dynamics of a class of closed-loop continuous exothermic reactors with temperature control and mono or bistable isothermal dynamics is addressed. The consideration of the problem within a Fokker–Planck (FP) stochastic framewor...
Soft-sensors for estimating in real-time important quality variables are a key technology in modern process industry. The successful development of a soft-sensor whose performance does not deteriorate with time and changing process characteristics is troublesome and only seldom achieved in real-world setups. The design of soft-sensors based on loca...
In this paper a new stochastic approach for the description of antisolvent crystal growth processes is presented. In this approach, the trajectory of crystals mean size is modeled as a Gompertz equation and the time evolution of the Particle Size Distribution (PSD) is modeled as a Fokker-Planck equation. In the new formulation the problem is reform...
A stochastic formulation for the description of antisolvent mediated crystal growth processes is discussed. In the proposed approach, the crystal size growth dynamics is driven by a deterministic growth factor coupled to a stochastic component. The evolution in time of the particle size distribution (PSD) is then described in terms of a Fokker−Plan...
The time behavior of the crystal size distribution in anti-solvent based crystal growth processes is investigated via statistical tools. The data are provided by the NaCl-water-ethanol anti-solvent crystallization system in a bench-scale fed-batch crystallization unit. It was found that the crystal population can be reasonably described in terms of...
Efficient and accurate methods for numerical simulation of time evolution of distributed dynamical systems are presented and discussed. As case example, stochastic models based on the Fokker-Planck equation are considered, describing the evolution of the probability density function (PDF) of the state variables. Unlike most of the methods presented...
In this paper, we define and implement the design of an optimized control structure for the activated sludge process given as COST/IWA benchmark simulation model No.1. Emphasis is given to the identification of controlled variables that contribute to minimize economic costs while the effluent requirements are met. This is achieved considering the s...
The problem of controlling binary distillation column effluents by manipulating the reflux and vapor flow rates on the basis of four temperature measurements is addressed. The problem is motivated by the need of understanding and systematizing two-point control industrial schemes driven by four temperature measurements. On the basis of the relative...
The Delaunay tessellation and topological regression is a local simplex method for multivariate calibration. The method, developed within computational geometry, has potential for applications in online analytical chemistry and process monitoring. This study proposes a novel approach to perform prediction and extrapolation using Delaunay calibratio...
In this work, the problem of estimating the concentration of exothermic rectors with temperature measurement is addressed. The problem is treated within a global nonlinear stochastic framework, according to the Fokker Plank-based Kushner filtering theory. The on-line solution of the associated two-dimensional partial differential equation driven by...
A stochastic formulation for the description of antisolvent mediated crystal growth processes is discussed. In the proposed approach the crystal size growth dynamics is driven by a deterministic growth factor coupled to a stochastic component. The evolution in time of the particle size distribution is then described in terms of a Fokker-Planck equa...
In this work, the problem of designing the estimation structure to infer some of the effluent compositions in a multicomponent distillation column is addressed, with the aim to determine the structure that yields the best estimator functioning in the sense of a suitable compromise between performance versus complexity, regardless of the particular...
In this paper, we overview and discuss the implementation of topology-based approaches to modeling and analyzing industrial process data. Emphasis is given to the representation of the data obtained with the self-organizing map (SOM). The methods are used in visualizing process measurements and extracting relevant information by exploiting the topo...
A phenomenological model for the description of antisolvent mediated crystal growth processes is presented. The crystal size growth dynamics is supposed to be driven by a deterministic growth factor coupled to a stochastic component. Two different models for the stochastic component are investigated: a Linear and a Geometric Brownian motion terms....
This work discusses a stochastic approach for the calculation of robust anti-solvent addition policies for controlling the mean crystal size (MCS) and prediction of the crystal size distribution (CSD) in semi-batch crystallization operations. The proposed strategy is based on a structured-like population balance where uncertainties associated with...
In this work, the problem of estimating the concentration of exothermic rectors with temperature measurement is addressed. The problem is treated within a global nonlinear stochastic framework, according to the Fokker Plank-based Kushner filtering theory. The on-line solution of the associated two-dimensional partial differential equation driven by...
In this paper, we define and implement the design of an optimized control structure for the activated sludge process given as COST/IWA benchmark simulation model No.1. Emphasis is given to the identification of controlled variables that contribute to minimize economic costs while the effluent requirements are met. This is achieved considering the s...
The Delaunay tessellation and topological regression is a local simplex method for multivariate calibration. The method, developed within computational geometry, has potential for applications in online analytical chemistry and process monitoring. This study proposes a novel approach to perform prediction and extrapolation using Delaunay calibratio...
