Optimización del Proceso de Separación de Gases por Membranas

Este trabajo trata sobre la optimización del diseño del proceso de captura de CO2 por membranas a partir de gases generados en una planta de combustión de carbón. Diferentes configuraciones alternativas son embebidas simultáneamente en una superestructura a partir de la cual se deriva el modelo matemático que permite determinar la configuración óptima del proceso de separación, el área de membrana y consumo de potencia en cada etapa, y las correspondientes condiciones de operación. Precisamente, se propone minimizar el área total de membrana, adoptando como metas de diseño una recuperación de CO2 del 85.00% y pureza de 98.00% en la corriente enriquecida de CO2. Dicho problema se resolverá para dos tipos de flujos: contra-corriente y co-corriente. Las soluciones óptimas obtenidas para cada tipo de flujo son analizadas y comparadas en términos de la distribución de áreas, flujos, composiciones y la contribución individual de cada compresor al consumo total de potencia

Optimización del Proceso de Separación de Gases por Membranas: determinación del número óptimo de etapas de membrana y condiciones de operación para la captura de co 2 a partir de gases efluentes de plantas de generación de electricidad a base de carbón.

This work deals with the optimal design of membrane-based separation processes for CO2 capture from coal fired power plant flue gasses. Different alternative configurations are simultaneously embedded in a superstructure from which a mathematical model is derived with the main aim to determine the optimal configuration of the separation process, the membrane area and the power consumption in each stage, and the corresponding operating conditions.Precisely, the total membrane area is proposed for minimization, assuming as main design targets, 85 % CO2 recovery and 98 % of purity on the CO2-rich stream. The mentioned problem will be solved for two flow types: counter-current and co-current. The optimal solutions obtained for each flow type will be analyzed and compared in terms of membrane area distribution, flows, compositions and the individual contribution of each compressor to the total power consumption.Este trabajo trata sobre la optimización del diseño del proceso de captura de CO2 por membranas a partir de gases generados en una planta de combustión de carbón. Diferentes configuraciones alternativas son embebidas simultáneamente en una superestructura a partir de la cual se deriva el modelo matemático que permite determinar la configuración óptima del proceso de separación, el área de membrana y consumo de potencia en cada etapa, y las correspondientes condiciones de operación. Precisamente, se propone minimizar el área total de membrana, adoptando como metas de diseño una recuperación de CO2 del 85.00% y pureza de 98.00% en la corriente enriquecida de CO2. Dicho problema se resolverá para dos tipos de flujos: contra-corriente y co-corriente. Las soluciones óptimas obtenidas para cada tipo de flujo son analizadas y comparadas en términos de la distribución de áreas, flujos, composiciones y la contribución individual de cada compresor al consumo total de potencia

Optimization of Cogeneration Power-Desalination Plants

The design of new dual-purpose thermal desalination plants is a combinatory problem because the optimal process configuration strongly depends on the desired targets of electricity and freshwater. This paper proposes a mathematical model for selecting the optimal structure, the operating conditions, and sizes of all system components of dual-purpose thermal desalination plants. Electricity is supposed to be generated by a combined-cycle heat and power plant (CCHPP) with the following candidate structures: (a) one or two gas turbines; (b) one or two additional burners in the heat recovery steam generator; (c) the presence or missing a medium-pressure steam turbine; (d) steam generation and reheating at low pressure. Freshwater is supposed to be obtained from two candidate thermal processes: and (e) a multi-effect distillation (MED) or a multi-stage flash (MSF) system. The number of effects in MED and stages in MSF are also discrete decisions. Different case studies are presented to show the applicability of the model for same cost data. The proposed model is a powerful tool in optimizing new plants (or plants under modernization) and/or improving existing plants for desired electricity generation and freshwater production. No articles addressing the optimization involving the discrete decisions mentioned above are found in the literature

Membrane-Based Processes: Optimization of Hydrogen Separation by Minimization of Power, Membrane Area, and Cost

This work deals with the optimization of two-stage membrane systems for H2 separation from off-gases in hydrocarbons processing plants to simultaneously attain high values of both H2 recovery and H2 product purity. First, for a given H2 recovery level of 90%, optimizations of the total annual cost (TAC) are performed for desired H2 product purity values ranging between 0.90 and 0.95 mole fraction. One of the results showed that the contribution of the operating expenditures is more significant than the contribution of the annualized capital expenditures (approximately 62% and 38%, respectively). In addition, it was found that the optimal trade-offs existing between process variables (such as total membrane area and total electric power) depend on the specified H2 product purity level. Second, the minimization of the total power demand and the minimization of the total membrane area were performed for H2 recovery of 90% and H2 product purity of 0.90. The TAC values obtained in the first and second cases increased by 19.9% and 4.9%, respectively, with respect to that obtained by cost minimization. Finally, by analyzing and comparing the three optimal solutions, a strategy to systematically and rationally provide ‘good’ lower and upper bounds for model variables and initial guess values to solve the cost minimization problem by means of global optimization algorithms is proposed, which can be straightforward applied to other processes

EXPERIMENTAL AND THEORETICAL INVESTIGATION OF ANAEROBIC FLUIDIZED BED BIOFILM REACTORS

Abstract -This work presents an experimental and theoretical investigation of anaerobic fluidized bed reactors (AFBRs). The bioreactors are modeled as dynamic three-phase systems. Biochemical transformations are assumed to occur only in the fluidized bed zone. The biofilm process model is coupled to the system hydrodynamic model through the biofilm detachment rate; which is assumed to be a first-order function of the energy dissipation parameter and a second order function of biofilm thickness. Non-active biomass is considered to be particulate material subject to hydrolysis. The model includes the anaerobic conversion for complex substrate degradation and kinetic parameters selected from the literature. The experimental set-up consisted of two mesophilic (36±1ºC) labscale AFBRs (R1 and R2) loaded with sand as inert support for biofilm development. The reactor start-up policy was based on gradual increments in the organic loading rate (OLR), over a four month period. Step-type disturbances were applied on the inlet (glucose and acetic acid) substrate concentration (chemical oxygen demand (COD) from 0.85 to 2.66 g L -1 ) and on the feed flow rate (from 3.2 up to 6.0 L d -1 ) considering the maximum efficiency as the reactor loading rate switching. The predicted and measured responses of the total and soluble COD, volatile fatty acid (VFA) concentrations, biogas production rate and pH were investigated. Regarding hydrodynamic and fluidization aspects, variations of the bed expansion due to disturbances in the inlet flow rate and the biofilm growth were measured. As rate coefficients for the biofilm detachment model, empirical values o