Arturo Jiménez

Design of energy-efficient Petlyuk systems

A strategy for the energy-efficient design of the fully thermally coupled distillation column (Petlyuk system) is presented. The strategy is based on a dynamic model and uses two recycle streams as search variables. The optimization procedure with the dynamic model provides the conditions under which a given design minimizes the heat duty supplied to the reboiler. Several case studies are presented, and some trends of the optimal values of the recycle streams are identified.

A comparison of the feedback control behavior between thermally coupled and conventional distillation schemes

A comparative analysis of the feedback control responses to set point changes of three thermally coupled distillation schemes and two conventional distillation sequences for the separation of ternary mixtures is presented. Designs for the thermally coupled schemes were obtained and optimized for energy consumption to link their energy characteristics to their dynamic behavior. For the comparison of the dynamic behavior, responses to set point changes under closed loop operation with proportional-integral (PI) controllers were obtained. For each separation scheme, the parameters of the PI controllers of the three composition control loops were optimized using the integral of the absolute error criterion. The effects of feed composition and of the ease of separability index were considered. The dynamic tests showed that in many cases the thermally coupled distillation schemes outperformed the dynamic responses of the conventional distillation sequences. The results indicate that there exist cases in which the energy savings provided by the thermally coupled systems do not conflict with their dynamic properties.

Control Behaviour of Thermally Coupled Distillation Sequences

The controllability properties of thermally coupled distillation sequences for the separation of ternary mixtures are compared with those of the conventional direct and indirect sequences. Closed loop responses to set point changes were performed, and controllers were tuned to minimize their ISE values. The results indicate that the integrated systems exhibit better control properties than sequences based on conventional distillation columns. This result provides a further incentive for the use of those integrated systems.

Analysis of dynamic properties of alternative sequences to the Petlyuk column

The Petlyuk distillation configuration has received considerable attention because of its efficiency to reduce the energy required for the separation of ternary mixtures. The structure of the Petlyuk system offers some control challenges arising from the transfer of vapor streams back and forth between the columns. This means that neither of the columns can have a uniform lower nor higher pressure. Recently, some alternate Petlyuk-like schemes that might provide better operational properties than the Petlyuk column have been proposed. In this work, we analyze the control properties of six alternative thermally coupled distillation schemes to the Petlyuk system. The theoretical control properties are analyzed with the application of the singular value decomposition technique. Rigorous closed loop simulations are used to supplement the theoretical analysis. The results indicate that a reduction in the number of interconnections of the Petlyuk configuration does not necessarily provide an improvement of its controllability properties.

A study of the development of a mexican petrochemical industry using mixed-integer programming☆

Abstract A large interactive system such as the petrochemical industry requires a model that can account for the different interactions among units, providing at the same time a suitable mathematical representation of the variables of interest. In this work, a model for the development of a Mexican petrochemical industry is presented. The system is formulated as a Mixed-Integer Programming model, where installing a process is compared on an economic basis to importing its corresponding product. This formulation lets the model take economies-of-scale into account which are shown to be a very decisive factor in the selection of chemical processes, since a simple linear model does not seem to provide an adequate tool for the planning and development of a Mexican petrochemical industry. A heuristic approach using multiple linear programs is also discussed.

CONTROL AND ENERGY SAVINGS OF THE PETLYUK DISTILLATION SYSTEM

Abstract The Petyuk distillation system has gained considerable attention because of the energy savings it can provide with respect to the conventional distillation sequences. Since the structure of the Petlyuk system is more complex, its controllability properties may be adverse with respect to the conventional systems. In this work a closed-loop analysis of the Petlyuk distillation system is presented. Special attention is given to show how the control properties change when different operating conditions are used. The results show that the control properties of the Petlyuk column can improve if some degradation in the energy consumption level is allowed.

Dynamic control of a Petlyuk column via proportional-integral action with dynamic estimation of uncertainties

Abstract A three point control configuration based on a proportional-integral controller with dynamic estimation of unknown disturbances was implemented in a Petlyuk column. The proposed controller comprises three feedback terms: proportional, integral and quadratic actions. The first two terms act in a similar manner as the classical PI control law, while the quadratic term (double integral action) accounts for the dynamic estimation of unknown disturbances. Comparison with the classical PI control law was carried out to analyze the performance of the proposed controller in face to unknown feed disturbances and set point changes. The results show that the closed-loop response of the Petlyuk column is significantly improved with the proposed controller.

Dynamic study of thermally coupled distillation sequences using proportional-integral controllers

Abstract A comparative study of the energy requirements and control properties of three thermally coupled distillation schemes and two conventional distillation sequences for the separation of ternary mixtures is presented. The responses to set point changes under closed loop operation with proportional-integral (PI) controllers were obtained. Three composition control loops were used, and for each separation scheme, the parameters of the PI controllers were optimized using the integral of the absolute error criterion. The effects of feed composition and of the ease of separability index were considered. The results indicate that there exist cases in which integrated systems may exhibit better control properties than sequences based on conventional distillation columns.

AN INTEGRATION PROGRAM FOR THE MEXICAN PETROCHEMICAL INDUSTRY

Abstract The integration of the petrochemical industry has been a major objective of the Mexican government because ot its ample oil resources. Using a recursive mixed-integer programming model, we detect an optimal integration sequence for the Mexican petrochemical industry. The model provides the yearly expansions necessary to achieve a long-term industrial structure. We show that the construction of complete industrial segments provide a proper integration strategy for the industry. The economic aspects of the development plan are reported.