Sharif Digital Repository

In this research, self-optimizing method has been used to design a plant-wide control structure for processes containing purge and recycle streams. The method is based on the concept of self-optimizing variables to maximize the process profitability in the presence of possible disturbances. The purpose of this thesis is to perform this procedure on ammonia and methanol processes containing purge and recycle streams.Using the results obtained for the ammonia process and considering the constraints and operating conditions of the problem, the active constraints of this process were detected which were cooling water flow rates to exchangers. According to local analysis method, self-optimizing... 

One of the model based control strategies that has been proposed in recent years for the control of process systems is the one based on the economic models, in which objective functions with an economic basis are used along with the equations and constraints to perform control calculations. In this work, the control of a multiproduct continuous stirred reactors is discussed, in which, it is possible to produce different products based on changes in the market demand, the price of the products or the primary raw materials according to a specific schedule. One of the recently used methods is the economic predictive control method based on the Lyapunov function. In this method a quadratic... 

In this thesis titled "Enhancing Energy Efficiency in Ideal Binary Distillation tower with a Dynamic Process Intensification," operational methods in distillation units are explored and improved. Given the high cost of energy, limited energy resources, and environmental considerations, increasing energy efficiency in process industries has become significantly important. In this context, this research attempts to enhance the performance of the distillation unit by utilizing dynamic process intensification with two operational points corresponding to the production of products with purities both higher and lower than the desired product purity, and switching between these two points. The... 

In the present work, the integration of production scheduling and process control in a multi-product CSTR reactor is addressed. In order to reduce the complexity of solving this integrated problem, in the scheduling layer, a reduced closed-loop model, named scale bridging model, based on neural network concept is used. In the control layer, a neural network-based controller is used to achieve control objectives such as tracking, stability and robustness against model uncertainty. In addition, the designed closed loop system is used to obtain offline setpoint-output data set in order to train neural network based scale bridging model. In a comparative study, both simultaneous and sequential... 

The aim of this thesis is investigating the approaches proposed for controlling switched systems and designing a controller for MIMO switched systems. The system under consideration is in strict feedback form with unknown dynamics, unmodeled dynamics, state-dependent delays and disturbances and input nonlinearity (saturation, backlash, dead-zone). In this work, the unknown dynamics are estimated by an intelligent approximator. The arbitrary switching law is assumed and for control purpose the switching instances are not required. The backstepping technique has been utilize for controller design and by using a nonnegative switching function and a common lyapunov function, the closed loop... 

Due to advances of biotechnology, control of bioprocess has become very important. The goal of this project is to simulate the acetic acid production bioreactor and designing an adaptive PI controller for this reactor. For this goal, a suitable model has been selected from the literature and simulation has shown that the system has a nonlinear dynamical behavior. In order to control the system in a wide range of operating conditions, the adaptive PI controller was designed. In single input-single output case, the concentration of the product is controlled in such a way that the production rate is maximized, assuming that the pH and temperature are kept constant. Then a two input-two... 

Due to the successful experience gained in the process intensification and implementation of Reactive Distillation and Divided Wall Column in industry, Reactive Divided Wall Column have also been considered as a further step in process intensification. One important research area in implementation of RDWCs is their control issue. In the present study, the dynamic simulation of reactive divided wall columns and their control were studied and the adaptive model predictive control was used for the control objectives. Aspen Dynamics software was used for simulation and MATLAB software was utilized for applying the control strategy. The advantage of the applied control method is the use of... 

According to the competitive nature of process industries and the necessity of increasing the efficiency of supply, manufacturing, and distribution operations, the optimization of such activities with an integrated attitude has become a major goal of research in the field of Process Systems Engineering. Lying at the interface of Chemical Engineering and Operations Research, enterprise-wide optimization has become a tool that enables the integrated optimization of different components of an industry to maximize the net profit. Design, Planning, Scheduling, and Control are four major operational items within such an optimization that may be simultaneously considered; among which, Planning and... 

The “hypothalamus-pituitary-adrenal” axis is one of the most important axes of the human body, and cortisol is one of its key products, which plays an essential role in the immune system, stress management, and many diseases. Appropriate modeling and simulation of this axis can help us to understand how the body reacts to stress and inflammation, to examine relevant diseases, and how drugs affect the body. In this study, by combining an axial model of the hypothalamic-pituitary-adrenal axis with a model of adrenal cells, a bi-level model including several time delays has been developed that can predict the effect of stress on this axis. Some parameters of the model have been modified through... 

Nowadays, due to increasing attention to produce a wide range of fuels through bioprocesses, in the present work, simulation and control of a continuous reactor to produce biodiesel from food-wastes has been addressed. In this regard, the transesterification reaction of triglyceride (a mixture of 10% (wt) Jatropha oil and 90% (wt) of edible oil residue) with methanol (6:1 molar ratio of methanol to oil) in the presence of 1% (wt) potassium hydroxide catalyst in a continuous stirred tank reactor has been simulated. For the control purposes, the bioreactor temperature and the product concentration have been controlled by manipulating heat duty and reactant feed flow rate, respectively. An... 

The PID controller has been widely used in the industry for many years because of its simple structure and satisfactory performance. If the process is time-varying or has a nonlinear dynamic, the PID controller with constant parameters can not control the process in a wide range of operation and adaptive PID controller should be used. In this thesis, two adaptive controllers proposed in the literature, one for multi-input multi-output (MIMO) affine nonlinear systems and another for single-input single-output (SISO) non-affine nonlinear systems both in the normal form that both of them are extended in to the general form. The latter extended controller includes the MIMO systems. The main... 

In the upstream part of the natural gas supply chain, the refinery is one of the most complex and energy-intensive sectors that has received little attention. Enterprise-wide optimization, that uses mathematical programming in a centralized and multi-scale point of view, and nonlinear models of the manufacturing sector, can provide optimal plans and operational variables for the production goals of the supply chain. In this research, a multi-scale formulation is presented with a production planning model in one to two-year horizon and six-month time periods and production operational scheduling models with six-month horizon to approach the enterprise-wide optimization of a general gas... 

In the upstream part of the natural gas supply chain, the refinery is one of the most complex and energy-intensive sectors that has received little attention. Enterprise-wide optimization, that uses mathematical programming in a centralized and multi-scale point of view, and nonlinear models of the manufacturing sector, can provide optimal plans and operational variables for the production goals of the supply chain. In this research, a multi-scale formulation is presented with a production planning model in one to two-year horizon and six-month time periods and production operational scheduling models with six-month horizon to approach the enterprise-wide optimization of a general gas... 

Due to global warming and its environmental effects caused by increasing greenhouse gases concentration there are various agreement between different countries that forced countries to reduce greenhouse gas emissions, especially carbon dioxide. In this research, we using a nonlinear model and focusing on Assaluyeh region and identifying the sources of carbon dioxide emissions and the oil reservoir for carbon dioxide injection, we optimize the pipeline network for carbon dioxide transportation.Different values of input pressure, oil prices and carbon tax have been investigated. According to the results in the base case, the profit is equal to 149.28 million USD in year. If carbon tax is... 

Because of lower energy consumption and lower capital cost, divided wall columns attracted wide attention. The main challenge of these units is their controllability. In this thesis dynamic simulation and control of a divided wall column is investigated and an adaptive model predictive controller has been used for control purpose. For dynamic simulation the Aspen Dynamics software and for applying control strategy the MATLAB software have been utilized. The model used for model predictive controller has been obtained by using open loop responses of the system. The main advantage of presented work over the existing ones is using the input-output transfer function of the system model instead... 

Anaerobic digestion of waste and wastewater has attracted researchers’ attention due to its important effect on reducing greenhouse gas emissions and reducing the level of environmental pollution and production of methane as a renewable energy source. This process is highly sensitive and can become unstable due to the presence of complex biochemical reactions and containing various types of chemical in it. In order to understand and improve the performance of this process, modeling and design of an appropriate control strategy is needed. ADM1 is the most accurate model for this process which is used in this study to describe and simulate the anaerobic reactor. Constrained and unconstrained... 

Anaerobic digestion of waste and wastewater has attracted researchers’ attention due to its important effect on reducing greenhouse gas emissions and reducing the level of environmental pollution and production of methane as a renewable energy source. This process is highly sensitive and can become unstable due to the presence of complex biochemical reactions and containing various types of chemical in it. In order to understand and improve the performance of this process, modeling and design of an appropriate control strategy is needed. ADM1 is the most accurate model for this process which is used in this study to describe and simulate the anaerobic reactor. Constrained and unconstrained... 

Researchers have paid more attention to greenhouse cultivation, due to the exacerbation of food and water crisis. Higher production with lower cost could be achieved through greenhouse climate control (temperature, humidity, carbon dioxide concentration). However, greenhouse climate control is a challenging task, because greenhouses have highly interactive nonlinear dynamics and model uncertainties and are subject to input saturation. In light of the fact that Iran is a country with a warm and arid climate, tunnel greenhouses equipped with evaporative cooling system are very common in Iran. Accordingly, this type of greenhouse is considered for modelling, simulation and control in this... 

Study on fish oil Supercritical Fluid Fractionation (SFF) is still an open issue with the objective of large scale production. A fundamental issue for scaling up the process is the knowledge of phase behaviour of the mixtures involved in SFF. So, development of reliable models to describe phase behaviour of the mixtures is crucial. Some thermodynamic models have been suggested which is able to predict solubility of fatty acid ethyl esters in supercritical phase. Some relevant experimental data is necessary to fit and validate the models. In this work, the experiments are designed to collect equilibrium data in the FeyeCon pilot plant. A validated model becomes a fundamental tool for the... 

process design and decision-making about it are challenging activities that involve optimizing conflicting goals such as cost, technical feasibility, and environmental impacts. These conflicting goals can be analyzed by considering the complete life cycle of a process or product in the initial design and decision-making. Life cycle analysis follows the environmental effects throughout the life cycle of a product, including extraction, transportation, production, consumption, and disposal. Life cycle assessment includes four fundamental stages: goal and scope definition, inventory analysis, life cycle impact assessment, and interpretation of results. The aim of this project is to investigate...