Dissertations / Theses on the topic 'PH control system'

Uma das técnicas de controle avançado que vem ganhando destaque no cenário econômico e ecológico, focando maior sustentabilidade e a otimização dos processos, é o controle preditivo, o qual já vem sendo aplicado em indústrias químicas e petroquímicas. Esta dissertação trata do desenvolvimento de um controle preditivo aplicado a uma planta piloto de neutralização de pH, presente no Laboratório de Controle de Processos Industriais da Escola Politécnica da Universidade de São Paulo. O desenvolvimento do projeto pode ser dividido em quatro etapas: implementação das malhas de controle regulatório, identificação dos sistemas, construção do controlador preditivo, aplicações e análises experimentais. Na primeira etapa foi necessário estudar o sistema em questão e implementar algumas malhas internas usando controladores PID. Na segunda etapa foi realizada a identificação do modelo da planta, ressaltando que pontos de operação e ajuste de parâmetros internos são determinantes para a modelagem. Já na terceira etapa desenvolveu-se um controlador preditivo, através de softwares auxiliares como o MATLAB e o IIT 800xA da ABB, que foram utilizados para o desenvolvimento e implementação do algoritmo de controle. Por fim, na última etapa, foi feita a análise e comparação dos resultados, quando se submete à planta a um controlador PID, quando aplicado um controlador preditivo em cascata com controladores PID e quando se utiliza apenas o controlador preditivo com ação direta nos atuadores.
The predictive control is an advanced control technique which has gained evidence in the economic and ecological context because the search for sustainability and process optimization. This control has already been applied by the chemical and petrochemical industries. The purpose of this project is to develop a predictive controller which will be applied in a pH neutralization plant located in the Industrial Processes Control Laboratory at Polytechnic School of the University of São Paulo. The development of this project can be divided into four stages: implementation of regulatory control loops, identification of the system, construction of the predictive controller, applications and experimental analysis. The first step is necessary in order to study the plant and to implement some internal loops using PID controllers. In the second step, the identification process of the plant model will be done. It is important to note that operating points and internal parameter settings are very important for modeling. In the third stage, using the model obtained from the identification process, a predictive controller is built from auxiliary software such as MATLAB and IIT 800xA (by ABB), which will be used for the development and implementation of the control algorithm. Finally, the last step consists in collecting and analyzing the results of the pH neutralization plant. At this stage the responses of each controller will be compared: PID controller, MPC controller in cascade mode with PID and MPC controller acting directly on actuators.

A identificação para controle é baseada especificamente na construção de modelos matemáticos a partir de dados experimentais, cuja finalidade é encontrar uma relação entre um conjunto de entradas e saídas de um processo dinâmico. Estes modelos são de fundamental importância para o projeto de controladores em processos industriais. No presente trabalho é realizada a identificação e o desenvolvimento do sistema de controle para uma planta piloto de neutralização de pH. O procedimento de identificação é baseado na coleta de dados reais do processo de neutralização de pH, operando em malha fechada. A estimativa dos modelos é realizada de duas formas: (1) estimar modelos que representem o comportamento de todo o sistema, incluindo os controladores PID do processo e (2) estimar modelos do processo com os dados coletados dos sinais de controle e as variáveis de saída do processo. Com os modelos do processo estimados projeta-se uma estratégia de controle MPC (Model Predictive Control), envolvendo dois esquemas de controle. O primeiro esquema calculará os set points ótimos que ingressarão nas malhas do processo. O segundo esquema calculará os sinais de controle ótimos que ingressarão diretamente no processo. O tipo de controlador MPC adotado é o QDMC (Quadratic Dynamic Matrix Control), permitindo restringir os sinais de entrada e saída do processo. A avaliação destes esquemas de controle é realizada mediante a mudança do set point das malhas do processo e a influência de perturbações. As perturbações são baseadas no aumento da vazão do ácido que ingressa no reator.
Identification for control system is based specifically on the mathematical models construction from experimental data, whose aim is to find a relationship between a set of inputs and outputs of a dynamic process. These models are fundamentally important for the industrial processes controllers design. In this work is performed the identification and development of the control system for a pH neutralization pilot plant. The identification procedure is based on the real data collected from pH neutralization process, operating in closed loop. The models estimation is performed in two forms: (1) estimating models that represent all system behavior, including process PID controllers and (2) estimating process models with collecting data of the control signals and process output variables. The process models parameters estimation is performed with the algorithms studied in Chapter 4. With the estimated process models is a MPC (Model Predictive Control) control strategy was designed, creating two control schemes. First scheme will compute the optimal set points that will enter to the process-loops. The second scheme will compute the optimal control signals that will enter to the process. The type of MPC controller adopted is a QDMC (Quadratic Dynamic Matrix Control), allowing restriction of the input and output signals. The control schemes evaluation is performed by changing the set point of the process-loops and the disturbance influence. This disturbance is based on acid flow increased that enters the reactor.

A typical wastewater effluent of a chemical process can contain several strong acids/bases, weak acids/bases as well as their salts. They must be neutralized before being discharged to the environment in order to protect aquatic life and human welfare. However, neutralization process is highly non&ndash
linear and has time&ndash
varying characteristics. Therefore, the control of pH is a challenging problem where advanced control strategies are often considered. In this study, the aim is to design a pH control system that will be capable of controlling the pH-value of a plant waste-water effluent stream having unknown acids with unknown concentrations using an on&ndash
line identification procedure. A Model Predictive Controller, MPC, and a Fuzzy Logic Controller, FLC, are designed and used in a laboratory scale pH neutralization system. The characteristic of the upstream flow is obtained by a small identification reactor which has ten times faster dynamics and which is working parallel to actual neutralization tank. In the control strategy, steady&ndash
state titration curve of the process stream is obtained using the data collected in terms of pH value from the response of the identification reactor to a pulse input in base flow rate and using the simulated response of the identification reactor for the same input. After obtaining the steady&ndash
state titration curve, it is used in the design of a Proportional&ndash
Integral, PI, and of an Adaptive Model Predictive Controller, AMPC. On the other hand, identification reactor is not used in the FLC scheme. The performances of the designed controllers are tested mainly for disturbance rejection, set&ndash
point tracking and robustness issues theoretically and experimentally. The superiority of the FLC is verified.

Two important membrane transport processes involved in the regulation of intracellular pH (pH) and Na* activity (ave) are the plasmalemmal Na*-H* exchanger and Na*-K* pump. In several non-cardiac tissues exposure to a hyperosmolar or hypoosmolar (anisosmolar) extracellular milieu modulates the activity of the Na*-H* exchanger. The response of the Na*-K* pump to alterations of extracellular osmolarity is, however, largely unknown. In cardiac muscle the effects of changes in extracellular osmolarity and hence cell volume on the activity of the Na*-H* exchanger and Na*-K* pump has not been studied. Such a study is desirable since pH, and am are important determinants of contractility in cardiac muscle and because the myocardium may be exposed to an anisosmolar milieu in several clinical settings. The studies described in this thesis examine the effect of shrinkage and swelling of cardiac tissue during exposure to anisosmolar solutions on the regulation of pH. and a'. by the sarcolemmal Na*-H* exchanger and Na*-K* pump. Ion-selective microelectrodes were used to determine pH; and a'v. in guinea-pig ventricular muscle. Exposure of tissue to HEPES-buffered Tyrode's solution made hyperosmolar by the addition of 100 mM sucrose (418 mosM) produced an intracellular alkalinization of O.10 units and hyperpolarization of the membrane potential. When the Na*-H* exchanger was inhibited by 5-(N,N-dimethyl) amiloride (DMA) or by reducing extracellular Na* to 15 mM (choline substituted) exposure to hyperosmolar solution caused a small decrease in pH. The Na+-dependence and DMA-sensitivity of the intracellular alkalinization in hyperosmolar solution together with the demonstration of a DMA-sensitive rise in ax, during such exposure suggested that the sarcolemmal Na*-H* exchanger was activated by cell shrinkage in hyperosmolar solution. Further evidence for osmotic activation of the Na*-H* exchanger was obtained from experiments showing that the recovery of pH, from an intracellular acidosis, induced by brief exposure to NIL, CI, was faster in hyperosmolar than in isosmolar solution.

Neuro-Fuzzy systems are the systems that neural networks (NN) are incorporated in fuzzy systems, which can use knowledge automatically by learning algorithms of NNs. They can be viewed as a mixture of local experts. Adaptive Neuro-Fuzzy inference system (ANFIS) is one of the examples of Neuro Fuzzy systems in which a fuzzy system is implemented in the framework of adaptive networks. ANFIS constructs an input-output mapping based both on human knowledge (in the form of fuzzy rules) and on generated input-output data pairs. Effective control for distillation systems, which are one of the important unit operations for chemical industries, can be easily designed with the known composition values. Online measurements of the compositions can be done using direct composition analyzers. However, online composition measurement is not feasible, since, these analyzers, like gas chromatographs, involve large measurement delays. As an alternative, compositions can be estimated from temperature measurements. Thus, an online estimator that utilizes temperature measurements can be used to infer the produced compositions. In this study, ANFIS estimators are designed to infer the top and bottom product compositions in a continuous distillation column and to infer the reflux drum compositions in a batch distillation column from the measurable tray temperatures. Designed estimator performances are further compared with the other types of estimators such as NN and Extended Kalman Filter (EKF). In this study, ANFIS performance is also investigated in the adaptive Neuro-Fuzzy control of a pH system. ANFIS is used in specialized learning algorithm as a controller. Simple ANFIS structure is designed and implemented in adaptive closed loop control scheme. The performance of ANFIS controller is also compared with that of NN for the case under study.

Flotation is an important and versatile mineral processing technique that is used to separate hydrophobic materials from hydrophilic. This technique makes it possible to mine complex ores that otherwise would have been regarded as uneconomic and non-beneficial. In this case flotation is used to separate copper from the unwanted gangue. The addition of lime is used to control the pH level in the flotation’s pulp, which governs the selectivity of the process, i.e. which minerals are recovered. Currently, fluctuating concentration grades of the produced metals have been observed in Boliden Aitik. Therefore, Boliden proposes a new control strategy which aims to maintain a constant ratio between the added lime and the incoming ore flow, but at the same time ensuring that the pH level is maintained within allowed limits. The aim of this thesis is to develop a model that captures the most essential dynamics of a process stage where lime is added, and then evaluate the suggested control strategy by studying suitable control structures. A linear model describing the system dynamics in a specific operating region is obtained by conducting step response experiments on the process. The model is then used to obtain a model describing the disturbances of the process, thereby yielding a complete model that describes the most important dynamics. The most promising control structure utilizes the concept of selective control, where a ratio controller is allowed to maintain a constant ratio as long as the pH level is within allowed boundaries. The pH level is maintained within the boundaries with upper and lower bound pH controllers that utilize the concept of an equivalent control objective (known as the strong acid equivalent) in order to achieve satisfying pH control. The results show that the control structure is able to maintain a constant ratio, and also ensure that the pH level is kept within the allowed limits. A cascade inspired pH ratio controller is also studied and evaluated. The results show that this pH ratio controller is only able to maintain a constant ratio as long as the incoming ore flow is constant. However, the outcomes also suggest that the concentration grades are either sensitive to variations in the ratio between added reagent and incoming ore flow, or that there is something else that causes them to vary.

Introduction: The desire to have a biological child transcends race, religion and socio-economic status. However for those faced with infertility, the financial resources needed to conceive are often not available. Current research in assisted reproduction has gravitated towards cost reduction to address restricting financial factors, without compromising quality of treatment. One such initiative is the development of a low-cost embryo culture method by The Walking Egg foundation. This method utilizes a standard chemical reaction and simple equipment to equilibrate culture media pH and to regulate temperature; both aspects were investigated in this study. An exploration into the insemination concentration to achieve oocyte fertilization was also undertaken. Methods: Quality control of temperature regulation on six different heating devices, including a comparison of inter- and intra-variations was carried out. The utilization of citric acid and bicarbonate of soda for carbon dioxide production, which subsequently facilitate setting of pH values, was tested by injecting increasing citric acid volumes (1.2 ml – 3.0 ml in 0.2 ml increments) into set volumes of bicarbonate of soda. Further investigation evaluated gas production at various temperatures (37°C, 25°C and 15°C), at increasing intervals (16 – 30 hours) of equilibration and these were compared by measuring pH of the culture media. The influence of altitude on pH was explored by repeating the chemical reaction experiment at five different locations in South Africa. Furthermore, the addition of water to citric acid before gas generation was explored. The minimal insemination concentration needed for fertilization was determined by the addition of decreasing numbers of spermatozoa to non-fertilized bisected oocytes. The experiment was repeated with a selected sperm insemination number in 1 ml or 50 μl culture media to compare the tested culture system with conventional culture. Spermatozoa bound to the hemi-zonae were counted with the aid of an inverted phase contrast microscope. Hemi-zonae with bound sperm were also stained with ethidium homodimer and evaluated using a confocal laser-scanning microscopy system. After removal of hemi-zonae, the spermatozoa in culture were isolated for deoxyribonucleic acid fragmentation analyses and reactive oxygen species presence in the culture media was measured. Additionally, reactive oxygen species generation in simulated culture was measured over time. Results: All the equipment tested bar one, the warming oven, proved useable with the simplified Walking Egg in vitro fertilization culture system. By decreasing the citric acid volumes, it was indicated that 1.8 ml citric acid, diluted with 1.2 ml water, is the optimal volume to facilitate the required culture media pH. Omitting the water dilution from citric acid volumes affected the culture media pH adversely, however reducing the temperature during gas equilibration did not. A change in altitude had no effect on culture media pH. Lower insemination numbers resulted in decreased sperm binding, with 2 x 103 motile sperm insemination providing the lowest number to still obtain sufficient sperm–zona binding (≥20 sperm bound). Incubation in 1 ml vs. 200 μl culture media indicated decrease in sperm bound. Sperm deoxyribonucleic acid fragmentation and the presence of reactive oxygen species in the culture media were similar in both the test and control groups. A comparison over time revealed less reactive oxygen species in 1 ml culture media, from the simplified Walking Egg in vitro fertilization culture system after three days of culture, than 200 μl culture media drops under oil, from conventional culture after 18 hours, however the results were not statistically significant. Discussion: Purpose-made heating devices provide superior stabilization of culture media temperature. When selecting a heating device, intra-variations should be considered. Culture media can be manipulated to the required pH by carbon dioxide production, with meticulous attention paid to the citric acid volumes used. However, if gas generation is performed at room temperature, equilibration time must be increased. In conventional culture, the minimum insemination number can be reduced to 2 x 103 motile sperm. Due to lower binding of sperm in large volumes of culture media, 2 – 5 x 103 motile sperm should be considered for the simplified culture system, depending on a holistic consideration of all sperm parameters. Extended culture for at least three days with the simplified culture system can be performed without increasing reactive oxygen species present in culture media. Further research of this novel culture method should include the application of the culture method in a South African environment.
Dissertation (MSc)--University of Pretoria, 2017.
Obstetrics and Gynaecology
MSc
Unrestricted

Den fundamentala principen för tillverkning av papper är inte en särskilt komplicerad sådan. Men för att pappret skall erhålla specifika egenskaper blir processen alltmer komplicerad. Bland annat tillsätts olika typer av kemikalier och processen övervakas ständigt av olika system. Ett av dessa system mäter pH-halten i pappersmassan. Mätsystemet är dock utsatt för frekventa mätfel vilket medför en felaktig dosering av den koldioxid som används för att sänka pH-värdet. Detta kan slutligen ha negativ påverkan på papprets egenskaper. Syftet bakom arbetet är att mätsystemet ska bidra till en jämn reglering av pH och därigenom garantera jämn papperskvalitet. För detta arbete har en frågeställning och ett antal mål och delmål etablerats. De övergripande målen omfattar att etablera en statistisk modell över mätfel och beräkna eventuella ekonomiska besparingar. För att uppfylla mål och besvara frågeställningen måste en grunduppfattning byggas uppför berörda delar av tillverkningsprocessen, pH-värdets påverkan i processen, pH-sensorns mätprincip, mätsystemets utformning och rutiner som berör mätsystemet. Med denna grund undersöks uppkomsten av mätfel för de sex mätpunkterna. Detta utförs med två tillvägagångssätt: Sammanställning av lagrade historiska data och sammanställningar avprovtagningar utförda under kontrollerade förhållanden. De aspekter som undersöks är magnitud, frekvens och hur dessa förhåller sig till olika processrelaterade värden. En kalkyl för kostnader berörande mätsystemet upprättas även. Denna omfattar aktuella kostnader för koldioxid och underhåll. I resultatet presenteras en statistisk modell över mätfel, uppdelat på historiska och i närtid. Den historiska modellen visar, för samtliga behandlade positioner, en medelavvikelse på <0,3 pH-enheter. Den min- och maximala avvikelsen kan däremot uppgå till >0,8 pH-enheter. Modellen för närtid visar på kraftiga avvikelser för fyra av de sex behandlade systempositionerna, som relaterar både till papperskvalitet och ytvikt. Denna statistiska modell används sedan för att beräkna möjliga besparingar. Här påvisades att viss besparing fanns, både för koldioxid och för underhållskostnader. Slutsatsen för detta arbete är att ett mätfel existerar för majoriteten av de behandlade positionerna. Det har även kunnat påvisas ett samband med de undersökta processrelaterade aspekterna, men resultatet kan inte garanteras fullständigt. Med detta kunde även en möjlig besparing av koldioxid uppskattas vid bättre mätnoggrannhet. Besparingen uppgick till c:a 200 tkr, vilket i jämförelse med företagets omsättning endast utgör 0,075‰ av denna.
The fundamental principle for manufacturing paper is not a complicated one. However, for the paper to acquire specific properties, the process becomes increasingly complicated.Among other things, different chemicals are added, and the process is continuouslymonitored by various systems. One of these systems measures the pH-level of the pulp. This system is however constantly affected by measuring errors, which in turn leads to the incorrect dosage of the carbon dioxide used to lower the pH-level. This could in turn have a negative impact on the properties of the final paper. The underlaying purpose of this project is for the measuring system to ensure an even regulation of pH and therethrough guarantee an even paper quality. For this project, several question at issue, goals and subgoals have been established. The general goals cover establishing a statistical model for the error and estimate possible economical savings. To fulfil the goals and answer the questions at issue, firstly a basic understanding must be established for: concerned parts of the manufacturing process, the effect pH-level has on the process, the measuring principle of the pH-sensor, the design of the measuring systemand the routines concerning the measuring system. With this basis, the occurrence of measuring error is examined for the six measuring points. This is accomplished with two methods: The compilation of historical data and the compilation of manual measurementsexecuted under controlled conditions. The aspects examined are magnitude, frequency and the relation to process related values. Finally, a calculation for costs regarding the measuring system was established. This includes current carbon dioxide and maintenance costs. The result presents a statistical model for the measuring error, divided into historical and near time. The historical model shows that for all the addressed positions, a mean deviation occurred <0.3 pH-units. However, the minimum and maximum deviation could reach >0.8 pH-units. The model for near time shows significant deviations for four out of the six covered positions, which in turn shows relations to both paper quality and surface weight. With this statistical model possible savings were calculated. This in turn showed the possibility of savings for both carbon dioxide and maintenance. The conclusion for this project is the existence of a measuring error. Also, a connection between this and the process related aspects could be established. Although, the result cannot be completely guarantied. With this, possible savings through better accuracy could be estimated. Though, these were only in the size of 0.075‰ of the company’s total revenue.

A validação de modelos lineares é uma etapa importante em um projeto de Identificação de Sistemas, pois a escolha correta do modelo para representar a maior parte da dinâmica do processo, dentro de um número finito de técnicas de identificação e em torno de um ponto de operação, permite o sucesso no desenvolvimento de controladores preditivos e de controladores robustos. Por tal razão, o objetivo principal desta Tese é o desenvolvimento de um método de validação de modelos lineares, tendo como ferramentas de avaliação os métodos estatísticos, avaliações dinâmicas e análise da robustez do modelo. O componente principal do sistema de validação de modelos lineares proposto é o desenvolvimento de um sistema fuzzy para análise dos resultados obtidos pelas ferramentas utilizadas na etapa de validação. O projeto de Identificação de Sistemas é baseado em dados reais de operação de uma Planta-Piloto de Neutralização de pH, localizada no Laboratório de Controle de Processos Industriais da Escola Politécnica da USP. Para verificar o resultado da validação, todos os modelos são testados em um controlador preditivo do tipo QDMC (Quadratic Dynamic Matrix Control) para seguir uma trajetória de referência. Os critérios utilizados para avaliar o desempenho do controlador QDMC, para cada modelo utilizado, foram a velocidade de resposta do controlador e o índice da mínima variabilidade da variável de processo. Os resultados mostram que a confiabilidade do sistema de validação projetado para malhas com baixa e alta não-linearidade em um processo real, foram de 85,71% e 50%, respectivamente, com relação aos índices de desempenho obtidos pelo controlador QDMC.
Linear model validation is the most important stage in System Identification Project because, the model correct selection to represent the most of process dynamic allows the success in the development of predictive and robust controllers, within identification technique finite number and around the operation point. For this reason, the development of linear model validation methods is the main objective in this Thesis, taking as a tools of assessing the statistical, dynamic and robustness methods. Fuzzy system is the main component of model linear validation system proposed to analyze the results obtained by the tools used in validation stage. System Identification project is performed through operation real data of a pH neutralization pilot plant, located at the Industrial Process Control Laboratory, IPCL, of the Escola Politécnica of the University of São Paulo, Brazil. In order to verify the validation results, all modes are used in QDMC type predictive controller, to follow a set point tracking. The criterions used to assess the QDMC controller performance were the speed response and the process variable minimum variance index, for each model used. The results show that the validation system reliability were 85.71% and 50% projected for low and high non-linearity in a real process, respectively, linking to the performance indexes obtained by the QDMC controller.

O presente texto tem por objetivo avaliar diferentes aplicações do algoritmo PLS-PH (Partial Least Squares Prediction Horizon), desenvolvido por (LAURI et al., 2010) para a identificação de sistemas, com o objetivo de desenvolvimento de controladores MPC. Desta maneira, é avaliada a capacidade do algoritmo gerar modelos lineares para realizar predições múltiplos passos à frente, para sistemas SISO e MIMO, com dados coletados em malha fechada. É também avaliada a capacidade do algoritmo de identificar modelos não-lineares baseados na estrutura NARX polinomial.
The objective of this work consists in evaluating different applications of the PLS-PH (Partial Least Squares Prediction Horizon) algorithm, developed by (LAURI et al., 2010), in order to identify models for MPC controllers. The algorithms capacity of producing linear models capable of performing multiple steps-ahead prediction for both SISO and MIMO systems, with data collected in closed-loop. The algorithms capability of identifying non-linear models with the NARX polynomial structure is also evaluated.

This paper presents the design, simulation, assembly and testing of a force-compensated hydrogel-based pH sensor. In the conventional deflection method, a piezoresistive pressure sensor is used as a chemical-mechanical-electronic transducer to measure the volume change of a pH-sensitive hydrogel. In this compensation method, the pH-sensitive hydrogel keeps its volume constant during the whole measuring process, independent of applied pH value. In order to maintain a balanced state, an additional thermal actuator is integrated into the close-loop sensor system with higher precision and faster dynamic response. Poly (N-isopropylacrylamide) (PNIPAAm) with 5 mol% monomer 3-acrylamido propionic acid (AAmPA) is used as the temperature-sensitive hydrogel, while poly (vinyl alcohol) with poly (acrylic acid) (PAA) serves as the pH-sensitive hydrogel. A thermal simulation is introduced to assess the temperature distribution of the whole microsystem, especially the temperature influence on both hydrogels. Following tests are detailed to verify the working functions of a sensor based on pH-sensitive hydrogel and an actuator based on temperature-sensitive hydrogel. A miniaturized prototype is assembled and investigated in deionized water: the response time amounts to about 25 min, just half of that one of a sensor based on the conventional deflection method. The results confirm the applicability of the compensation method to the hydrogel-based sensors.

On se pose le problème de commander une certaine classe de réacteurs (réacteurs fermés agités) dans le cas non isotherme, sièges de certaines réactions chimiques caractérisées entre autres par la notion de déficience. Les modèles de connaissance de ces systèmes sont intrinsèquement non-linéaires, du fait de l'utilisation des lois cinétiques (par exemple la loi d'Arrhenius. . . ), des bilans enthalpiques, etc. . . Pour décrire les réactions chimiques. Certaines réactions peuvent être exothermiques donnant lieu à des phénomènes dits d'emballement. Le but est, donc, de traiter la stabilité asymptotique globale de cette classe de réacteurs en utilisant une loi de commande géométrique par retour d'état, assurant la poursuite de la sortie (température du réacteur) et la stabilité interne. L'implémentation d'une loi de commande géométrique nécessite la connaissance de l'état. On montre pour certains exemples de ces systèmes l'observabilité forte et que toute demi-trajectoire peut être observée par un observateur grand gain à convergence exponentielle. * le traitement de l'eau au même titre que celui des déchets est un enjeu majeur pour l'environnement. On se pose le problème de neutralisation des eaux usées avant d'être évacuées dans la nature : ramener la sortie à un pH donné et la maintenir à ce point, avec stabilité interne asymptotique au point d'équilibre correspondant. Cet objectif est atteint par feedback via une loi de commande géométrique dans un premier temps et par feedback dynamique de sortie via la synthèse d'un observateur dans un deuxième temps.

This experiment was designed to study iron control systems in fracking and well stimulation jobs at higher pH. Experimental study of iron control at high pH of this kind has not previously been reported in the literature. In addition, almost all of the widely used iron control chemicals today work at lower pH (≤4).

In this experiment, newly enhanced chemicals, such as EnerFlow 780, SC803, EDTA, Poly Itaconic acid, and TN801 were used and the following new result were found. In the absence of iron control chemicals, iron precipitation occurred at pH of 1.85 and completely precipitated at 3.5. SC803 has shown a very unique characteristic. The chelating characteristic of this product increases with pH. At lower pH (≤4), this product has shown weaker performance in curbing iron precipitation. Only 37% (average) initial iron was prevented from precipitating at this pH. However, when the pH was increased to above 4, its sequestering characteristic became more and more until it reached pH 13. Minimum precipitation was observed at pH of 11 & 12, which are 4.3% and 4.7%, respectively. Furthermore, SC803 was observed to cause unforeseen yellowish iron precipitation at lower pH.

TN801, a blend of SC803, EDTA and Poly Itaconic acid, showed the best result of the all the individual chemicals tested. It effectively curbed an average of 96% iron precipitation in all pH less than 13. EDTA and Poly Itaconic acid were added to enhance the performance of SC803 at lower pH. The result showed 86.8% maximum enhancement at lower pH and 0.3% at higher pH. TN801 was also able to dissolve 50% of crystalline iron sulfide, despite the fact that it is insoluble in nature. Furthermore, TN801 was tested on field and the anticipated result was achieved.

Nitrous oxide (N2O) is a greenhouse gas (GHG) with 300 times the radiative forcing in the atmosphere of carbon dioxide (CO2), and has recently become a subject of great concern because the nitrogen (N) fertilizers which have been necessary to increase agricultural productivity have also dramatically increased N2O emissions from agroecosystems. Many N control practices have been suggested and implemented in agroecosystems, but their ability to simultaneously remove reactive N from the environment and prevent the production of N2O is, at best poorly understood. The goal of this work is to characterize environmental controls on production of N2O in denitrifying bioreactors. The review portion of this work first discusses the geologic history of the N cycle, how its past and present processes differ, and how it is being affected by human activity. It then explores the N cycle's biochemical pathways, reviews the controls for each of its steps, and discusses the environmental drivers of these controls. The review closes with a discussion of environmental N management strategies. The experimental portion of this work further explores these concepts by observing how biochar amendment and the modification of pH affect N2O production in the denitrification pathway in denitrifying bioreactors. Both pH and biochar have previously been shown to affect N2O production and many N management practices utilize biochar or manipulate pH to increase N retention. The objectives of the experiment were to: 1) Examine headspace N2O concentration in sealed, biochar-amended, denitrifying bioreactors; 2) Determine if the effects of pH on N2O production differ in biochar-amended systems versus controls (under acidic, unbuffered, and buffered conditions); 3) Quantify key denitrification genes (nirK, nirS, nosZ) in each treatment combination. Experimental results showed biochar treatment to significantly increase N2O emissions, a result which runs contrary to most, but not all studies regarding its effects on N2O production. Differences between treatments decreased with increasing pH levels. Biochar did not exhibit significant effects on individual denitrification genes, but it did show influence on the ratios of their populations. On the other hand, pH was found to have significant effects on nirS and nosZ populations. Differences in N2O production between biochar and controls were thus explained by biochar's chemical effects, likely its ability to increase denitrification activity. Developing an understanding of the mechanisms behind these differences will require using a combination of isotope tracing, enzyme assays, and mass balance approaches. Future microbial work in biochar-amended systems should attempt to characterize differences in gene expression, overall community structure, and long-term population trends in the genes of interest. The combination of these approaches should allow researchers to better predict where N2O production will occur and develop strategies to mitigate it while simultaneously increasing food production to meet the demands of a growing population.
Master of Science

碩士
國立雲林科技大學
電子與光電工程研究所碩士班
100
In this thesis, the sensing properties of the chlorine and the pH sensing devices were discussed, and the chlorine and pH sensing devices applied to wireless measurement system and water quality monitoring system. The pH sensing membrane (ruthenium dioxide (RuO2)) was deposited on the silicon substrate by radio frequency (R. F.) sputtering system. The selective membrane of chlorine ion was prepared on the pH sensing membrane thin film by spin coating method. As well as, the sensing performance of the chlorine and pH sensing device with different manufacturing conditions were analyzed by using voltage-time system (V-T system) and electrochemical impedance spectroscopy (EIS). The quality of sensing device was measured by EIS before measurement, and the sensitivity and linearity of the sensing device was measured by V-T measurement system. The response time of the chlorine and pH sensing devices were less than 30 s and 10 s, respectively. The sensitivity and linearity of the pH sensing device were 55.27 mV/pH and 0.999, respectively. The sensitivity and linearity of the chlorine sensing device were 10.04 mV/ppm and 0.996 in sodium chloride (NaCl) solution, respectively. The sensitivity and linearity of the chlorine sensing device were 15.33 mV/ppm and 0.990 in sodium hypochlorite (NaClO) solution, respectively. Moreover, the lifetime of the chlorine sensing device was immersed at least 14 days in NaCl or NaClO solutions; the lifetime of the pH sensing device was immersed at least 15 days in pH buffer solutions. According to the experimental results, chlorine and pH sensing devices can be applied to water quality monitoring system with wireless measurement system for real-time measurement and long-term measurement.

碩士
國立中央大學
環境工程學系
84
For open and dynamic systems, the conventional steady- state control strategies applied in wastewater treatment plants usually could not result in the best performance. From recent research results, it has been found that the breakpoint of the ORP and pH monitorning curves of biological treatment processes are correlated to the disappearance of nitrogen compound. Therefore, a real-time control strategy built by ORP and pH was used to control the single tank continuous- flow SBR in this study. The experimental procudures of this study contain two main sections as follows: (1) Fixed-time control study: to prove the feasibility of using ORP and pH as the control parameters under different operation conditions. Results obtained from fixed-time studies reflect that the ORP and pH profiles can represent the system''s dynamic characteristics, especially in pointing out the ends of nitrification and denitrification in form of breakpoint. It is noted that the locations and values of ORP and pH, on those endpoints, are highly correlated to F/M ratio with linear relationship. This result provided the primary ideas for set-point and set-time control. The breakpoints, set- point and set-time on the ORP and pH profiles were used to establish the real-time control strategy; (2) Real-time control study: some results had found in real-time study including: (a) pH was more appropriate parameter for controlling aerobic stage and ORP for controlling anoxic stage; (b) six mathematical calculation methods were appliced to determine the transfers of operation stages, and the multiplication of two slopes of ORP was appropriate for determining the breakpoint on ORP profile, and the differential of pH was more practical for determining the breakpoint of pH; (c) The real-time control study show a good proformane in COD and nitrogen removeal, approxicaty 93% COD , 88.68% NH4+-N, 86.54% T-N be reducted. In addition, the real-time study required less retention time than fixed-time study, it is approxicately 2.5 hours can be abridged. Thus, it can save the cycle time and aeration energy.

abstract: Microbial fuel cells(MFC) use micro-organisms called anode-respiring bacteria(ARB) to convert chemical energy into electrical energy. This process can not only treat wastewater but can also produce useful byproduct hydrogen peroxide(H2O2). Process variables like anode potential and pH play important role in the MFC operation and the focus of this dissertation are pH and potential control problems. Most of the adaptive pH control solutions use signal-based-norms as cost functions, but their strong dependency on excitation signal properties makes them sensitive to noise, disturbances, and modeling errors. System-based-norm( H-infinity) cost functions provide a viable alternative for the adaptation as they are less susceptible to the signal properties. Two variants of adaptive pH control algorithms that use approximate H-infinity frequency loop-shaping (FLS) cost metrics are proposed in this dissertation. A pH neutralization process with high retention time is studied using lab scale experiments and the experimental setup is used as a basis to develop a first-principles model. The analysis of such a model shows that only the gain of the process varies significantly with operating conditions and with buffering capacity. Consequently, the adaptation of the controller gain (single parameter) is sufficient to compensate for the variation in process gain and the focus of the proposed algorithms is the adaptation of the PI controller gain. Computer simulations and lab-scale experiments are used to study tracking, disturbance rejection and adaptation performance of these algorithms under different excitation conditions. Results show the proposed algorithm produces optimum that is less dependent on the excitation as compared to a commonly used L2 cost function based algorithm and tracks set-points reasonably well under practical conditions. The proposed direct pH control algorithm is integrated with the combined activated sludge anaerobic digestion model (CASADM) of an MFC and it is shown pH control improves its performance. Analytical grade potentiostats are commonly used in MFC potential control, but, their high cost (>$6000) and large size, make them nonviable for the field usage. This dissertation proposes an alternate low-cost($200) portable potentiostat solution. This potentiostat is tested using a ferricyanide reactor and results show it produces performance close to an analytical grade potentiostat.
Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2018

碩士
國立中央大學
環境工程研究所
83
Modified single continuous-flow activated sludge system is a small and compact system which includes the functions of equalization, aeration and sedimentation, and can be used to remove organic carbon, nitrogen and phosphorus, simultaneously As a small and compact system, automatic monitoring and control of the system has become a basic requirement from the view- point of practical engineering. In concern of process automation, the main purpose of this study is to find the relationships between automatic monitoring and control parameters and system characterics. Furthermore, the study of the operation and control of the system based on previous relationships was also discussed. The ORP, pH, DO, and MLSS meters were used, which include some advantages of inexpensive, convienient, quic Two stages of the experiment have been conducted. The purpose of the first stage is to find the stable conditions for system operation. According to the result of the first stage,the results have shown that the characteristics of the system can be reflected adequately by using ORP、pH and DO to be as the automatic monitoring and control parameters. The end point of denitrification in anoxic phase, the end point of nitrification and the fully oxidation state of carbon source in aerobic phase can be determined by differentialing to the ORP and pH profiles. Furthermore, the F/M ratio of the system can be predicted by the ORP of the end point of denitification from the relation equation of ORP versus log(F/ M).