Novel modeling and control approach for performance improvement of an industrial copper solvent extraction process

More than 20% of the cathode copper is annually produced by copper leaching, solvent extraction and electrowinning processes. The focus in process technology has been on research and capital intensive development of the process equipment and chemicals. However, the financial benefits gained through an advanced control system would be significant. An advanced control system would maximize production by running the process closer to the optimal operating point, and increase the production of the first quality copper cathode by decreasing the variation in key process variables. The lack of adequate dynamic process models for industrial applications has, to date, prevented the development of advanced process control systems. Therefore, the first aim of this thesis is to develop dynamic models to describe the behaviour of an industrial copper solvent process and to facilitate control system development. The second aim of this thesis is to develop an advanced control system for the copper solvent extraction process, and to verify that the performance and profitability of an industrial copper solvent extraction process can be significantly increased by utilizing the advanced process control system. In the process model, the mass transfer of copper in the mixer-settler units is described by means of dynamic, modified ideal mixing and plug flow models. The equilibrium value for the ideal mixing model is calculated on the basis of the steady state McCabe-Thiele diagram. The model utilizes industrial online and offline measurements. The unit process models are combined according to the case plant flowsheet. Based on the process models, a control hierarchy is developed for the case copper solvent extraction process. The optimization level in the hierarchy consists of an optimization algorithm that maximizes the production of the copper solvent extraction process and provides setpoints for the stabilizing control level. The stabilizing control level consists of a single input-single output control strategy employing two PI controllers or, alternatively, a multi input-multi output control strategy using the model predictive control (MPC). The dynamic models are tested by comparing the simulated data with the industrial data. The controller performances are tested for setpoint tracking and disturbance rejection in the simulation environment with step input changes. The benefits of the control system are assessed by comparing the variation in the controlled variables and the total copper production to the data collected from the process under manual control. The dynamic models are tested with two data sets representing the normal operation of the industrial case copper solvent extraction plant. The models follow the output copper concentration trends smoothly for the major input changes in the flow rates and copper concentrations, and the residuals between the simulated data and the industrial measurements are sufficiently small. The average absolute error is 1-3 % of the mean value of the output copper concentrations. The performance of the control system for setpoint tracking and disturbance rejection is very good. As expected, the model predictive controller performs better than the PI controllers. The disturbance rejection capabilities are further improved by adding four feedforward compensators to the control strategies. Compared to manual control, the variation in the rich electrolyte copper concentration was decreased by 70-80 % with the PI controllers and 80-90 % with the model predictive controller. The copper mass production was increased by about 3-5 % with both control strategies. The modeling and control results are very encouraging for the further testing of the control system in an industrial copper solvent extraction plant.Katodikuparista vuosittain yli 20 % tuotetaan kuparin liuotus - uutto - elektrolyysi -menetelmällä. Prosessiteknologian painopisteenä on ollut prosessilaitteiden ja -kemikaalien kehittäminen, joka vaatii paljon tutkimusta ja runsaasti taloudellista pääomaa. Kehittyneitä säätömenetelmiä soveltamalla voitaisiin saavuttaa merkittäviä taloudellisia hyötyjä kuluttamalla huomattavasti vähemmän resursseja. Kehittyneellä säätöjärjestelmällä kuparin uuttoprosessin tuotantoa sekä parhaan katodilaadun osuutta koko tuotannosta voidaan kasvatettaa, koska prosessia voidaan ajaa lähempänä optimaalista operointipistettä ja prosessin laatuparametrien vaihtelua voidaan pienentää. Kuparin uuttoprosessille soveltuvien dynaamisten mallien puute on tähän mennessä estänyt ylemmän tason säätöjärjestemien kehityksen. Tämän työn ensimmäinen tavoite oli kehitettää dynaaminen malli, joka kuvaa teollisen kuparin uuttoprosessin käyttäytymistä ja mahdollistaa säätöjärjestelmän kehityksen. Työn toisena tavoitteena oli kehittää säätöjärjestelmä ja todistaa että sen avulla kuparin uuttoprosessin tehokkuutta ja tuottavuutta voidaan merkittävästi parantaa. Dynaaminen prosessimalli perustuu kuparin massansiirrolle vesi- ja orgaanisen faasin välilla sekoitus-selkeytys-prosessilaitteissa. Sekoittimen malli perustuu modifioituun ideaalisekoitin malliin, jossa tasapaino lasketaan McCabe-Thiele diagrammista. Selkeyttimen malli perustuu tulppavirtaukseen. Prosessimalli laadittiin yhdistelemällä sekoitin-selkeytin-yksikkömalleja teollisen sovellusprosessin virtauskaavion mukaisesti. Tämän mallin perusteella implementoitiin prosessisimulaattori. Prosessimalliin perustuen prosessille kehitettiin säätöhierarkia, joka koostuu optimointitason optimointialgoritmista ja stabiloivan säädön tason yksikkösäätöstrategiasta (PI- ja myötäkytkentäsäätimet) tai monimuuttujasäätöstrategiasta (MPC-säädin). Dynaamisten malleilla saatua simulointidataa verrattiin teolliseen prosessidataan hyvin tuloksin. Simuloitu data seurasi kuparikonsentraatioiden ja virtausten vaihteluista johtuvia muutoksia ja keskimääräinen ero simuloidun ja oikean datan valilla oli noin 1-3% testatuissa kahdessa datajoukossa. Säätösysteemiä testattiin prosessisimulaattorilla, jonka sisääntuloina käytettiin prosessidataa. Manuaaliseen säätöön verrattuna, rikkaan elektrolyytin kuparikonsentraation vaihtelu pienentyi 70-80% PI-säätimillä ja 80-90% MPC-säätimellä. Kuparin tuotanto kasvoi 3-5% käyttämällä kumpaakin säätöstrategiaa. Mallitus- ja säätötulokset luovat vahvan pohjan säätösysteemin testaukselle teollisella kuparin uuttolaitoksella.reviewe

The Role of Inverter-based Generation in Future Energy Systems: An Oriented Decentralized Strategy for Reactive Power Sharing in Islanded AC Microgrids and a Techno-Economic Approach to Inertia Requirements Assessment of the Italian Transmission Network

One of the most impacting changes in the electricity energy scenario of the latest decades is the extensive increase of Distributed Energy Resources (DER) including Electrical Storage Systems (EES), fuel cells and Renewable Energy Sources (RES), such as Photovoltaic (PV) and Wind Turbines (WT). The integration of a rapidly increasing share of inverter-based generation poses relevant challenges in terms of frequency and voltage control both in Islanded Microgrids (MG) and traditional transmission networks. For the sake of complementarity, the thesis focuses on reactive power and voltage regulation in MG and frequency instability problems in a future Italian transmission network. In MG with converter-based energy production, one of the main problems is the proper reactive power sharing among DER and related voltage regulation. In this concern the most used approach is based on the conventional droop control; however, it presents some relevant drawbacks. In SECTION A an Advanced Droop Control strategy (ADC) and an Advanced Boost Control strategy (ABC) are proposed, to approach primary voltage control and reactive power sharing among Grid-Supporting inverters in islanded MG. The strategies are presented defining their control laws and the control schemes together with the relevant stability analysis. Then, an analytical procedure is developed for each control methods to set proper control parameters. Next, a comparison between the new strategies and droop conventional control is performed with simulations on a common benchmark MG, in order to show that new strategies, according to their specific control logics, are able to guarantee improved performance in terms of the combined regulation of voltage and reactive power. Considering the traditional electric system, one of the main consequences of the increasing penetration of RES is, besides of the decrease of the system short-circuit power, the reduction of the electric system inertia: this could lead to frequency instability problems in case of severe perturbations, especially for what concerns the Rate of Change of Frequency (RoCoF)and the frequency nadir. In SECTION B, the thesis provides a technical-economic methodology for the estimation of the amount of additional inertia that will be needed in the Italian Transmission Network in a prospective 2030 scenario, in order to limit the RoCoF within sustainable values. Moreover, the algorithm optimally commits synthetic inertia contribution from RES and Battery Energy Storage Systems (BESS) and installation of Synchronous Compensators (SC) among the Italian market areas. The method is designed to be sufficiently simple to process a relevant number of working scenarios in order to exploit the relevant quantity of information owned by the TSO. Results have shown to be highly accurate as outline by comparison with detailed time domain simulations

Powering the future: a comprehensive review of battery energy storage systems

Global society is significantly speeding up the adoption of renewable energy sources and their integration into the current existing grid in order to counteract growing environmental problems, particularly the increased carbon dioxide emission of the last century. Renewable energy sources have a tremendous potential to reduce carbon dioxide emissions because they practically never produce any carbon dioxide or other pollutants. On the other hand, these energy sources are usually influenced by geographical location, weather, and other factors that are of stochastic nature. The battery energy storage system can be applied to store the energy produced by RESs and then utilized regularly and within limits as necessary to lessen the impact of the intermittent nature of renewable energy sources. The main purpose of the review paper is to present the current state of the art of battery energy storage systems and identify their advantages and disadvantages. At the same time, this helps researchers and engineers in the field to find out the most appropriate configuration for a particular application. This study offers a thorough analysis of the battery energy storage system with regard to battery chemistries, power electronics, and management approaches. This paper also offers a detailed analysis of battery energy storage system applications and investigates the shortcomings of the current best battery energy storage system architectures to pinpoint areas that require further study.This publication is part of the project TED2021-132864A-I00, funded by MCIN/ AEI/10.13039/501100011033 and by the European Union “NextGenerationEU”/PRTR”.Peer ReviewedPostprint (published version

Algebraic synthesis methods for linear multivariable control systems

The mathematical formulation of various control synthesis problems , (such as Decentralized Stabilization Problem , (DSP) , Total Finite Settling Time Stabilization for discrete time linear systems, (TFSTS) , Exact Model Matching Problem, (EMMP), Decoupling and Noninteracting Control Problems) , via the algebraic framework of Matrix Fractional Representation . (MFR) - i.e. the representation of the transfer matrices of the system as matrix fractions over the ring of interest - results to the study of matrix equations over rings , such as : A . X + B . Y = C , (X. A + Y . B =C) (1) A· X = B , (y. A = B) (2) A·X·B = C (3) A·X + Y·B = C, X·A + B·Y = C, A·X·B + C·Y·D = E (4) The main objective of this dissertation is to further investigate conditions for existence and characterization of certain types of solutions of equation (1) ; develop a unifying algebraic approach for solvability and characterization of solutions of equations (1) - (4), based on structural properties of the given matrices, over the ring of interest. The standard matrix Diophantine equation (1) is associated with the TFSTS for discrete time linear systems and issues concerning the characterization of solutions according 'to the Extended McMillan Degree, (EMD) , (minimum EMD , or fixed EMD) , of the stabilizing controllers they define , are studied . A link between the issues in question and topological properties of certain families of solutions of (1) is established . Equation (1) is also studied in association with the DSP and Diagonal DSP (DDSP) , for continuous time linear systems . Conditions for characterizing block diagonal solutions of (1) , (which define decentralized stabilizing controllers) , are derived and a closed form description of the families of diagonal and two blocks diagonal decentralized stabilizing controllers is introduced. The set of matrix equations (1) - (4) is assumed over the field of fractions of the ring of interest , ℛ , (mainly a Euclidean Domain, (ED) , and thus a Principal Ideal Domain , (PID)) , and solvability as well as parametrization of solutions over ℛ is investigated under the unifying algebraic framework of extended non square matrix divisors , projectors and annihilators of the known matrices over ℛ . In practice the ring of interest is either the ring of polynomials ℝ [s] , or the rings of proper

A study of some molecular interactions on alumina surfaces by inelastic electron tunnelling spectroscopy

Further developments have been carried out to improve the resolution and sensitivity of the spectrometer by introducing a dual phase lock-in amplifier and using new software to enhance the flexibility of the computer interfaced with the spectrometer. The spectrometer has been utilised to study a variety of molecular orientations on an alumina substrate. These have included an investigation to distinguish optical and geometrical isomers together with some alkynes in order to explore the validity of the previously proposed Selection Rule. The new observation that the triple bond is detected even when parallel to the substrate surface is reported. An attempt to study the polymerisation of ethylene on an alumina substrate has been carried out and some evidence is presented to support an increase in polymerisation with time. It has been shown that formic acid is produced 'in situ' within an aluminium-aluminium oxide-lead tunnelling junction from atmospheric carbon dioxide and water. A mechanism to account for this reaction is proposed. Junction structure has been studied particularly by utilising a modified crystal oscillator thickness monitor to investigate the influence of electrode and insulating oxide thickness both on junction electrical integrity and the mechanism of doping completed tunnelling junctions

Design and Control of Power Converters 2019

In this book, 20 papers focused on different fields of power electronics are gathered. Approximately half of the papers are focused on different control issues and techniques, ranging from the computer-aided design of digital compensators to more specific approaches such as fuzzy or sliding control techniques. The rest of the papers are focused on the design of novel topologies. The fields in which these controls and topologies are applied are varied: MMCs, photovoltaic systems, supercapacitors and traction systems, LEDs, wireless power transfer, etc

Tools for Nonlinear Control Systems Design

This is a brief statement of the research progress made on Grant NAG2-243 titled "Tools for Nonlinear Control Systems Design", which ran from 1983 till December 1996. The initial set of PIs on the grant were C. A. Desoer, E. L. Polak and myself (for 1983). From 1984 till 1991 Desoer and I were the Pls and finally I was the sole PI from 1991 till the end of 1996. The project has been an unusually longstanding and extremely fruitful partnership, with many technical exchanges, visits, workshops and new avenues of investigation begun on this grant. There were student visits, long term.visitors on the grant and many interesting joint projects. In this final report I will only give a cursory description of the technical work done on the grant, since there was a tradition of annual progress reports and a proposal for the succeeding year. These progress reports cum proposals are attached as Appendix A to this report. Appendix B consists of papers by me and my students as co-authors sorted chronologically. When there are multiple related versions of a paper, such as a conference version and journal version they are listed together. Appendix C consists of papers by Desoer and his students as well as 'solo' publications by other researchers supported on this grant similarly chronologically sorted

An electron cooler for ultra-low energy cryogenic operation

Zusammenfassung: Es werden grundlegende Konzepte zur Erzeugung eines kalten und extrem niederenergetischen, magnetisch geführten Elektronenstrahls entwickelt, welcher als Elektronen-Kühler und -Target am elektrostatischen kryogenen Speicherring CSR dienen soll. Die Machbarkeit sehr langsamer Elektronenstrahlen, mit kinetischen Energien unterhalb eines Elektronenvolts und Stromdichten, die den Anforderungen von Elektronenkühlung und ElektronIonKollisionsexperimenten genügen, wurde durch Experimente am Elektronen-Target des Speicherrings TSR unter Verwendung einer kryogenen Kathode unter Beweis gestellt. Ein Vakuum- und Magnetfeldsystem wurde konzipiert, das die Verwendung dieses extrem niederenergetischen Elektronenstrahls im CSR ermöglicht. Ein neuartiges Verfahren zum Zusammenführen von Elektronen- und Ionenstrahlen wurde entwickelt und mit Hilfe numerischer Magnetfeldund Teilchenspur-Simulationen analysiert. Ein Konzept zur Herstellung von Hochtemperatur- Supraleiter-Spulen, welche von Kryogen durchströmt werden, wird vorgestellt. Ein darauf basierender Spulenprototyp wurde gebaut und unter realistischen Bedingungen erfolgreich getestet. Um die Magnetspulen unabhängig von der Hauptkälteanlage des CSR zu betreiben, wurde ein auf tiefkaltem Neon basierendes zwei-Phasen- Niederdruck-Kühlsystem entwickelt, aufgebaut und erfolgreich in Betrieb genommen. Die hier vorgestellte Arbeit liefert somit ein experimentell getestetes Konzept für den Bau des CSR-Elektronen-Kühlers