Model-based Design, Operation and Control of Pressure Swing Adsorption Systems

This thesis is concerned with the design, operation and control of pressure swing adsorption (PSA) systems, employing state of the art system engineering tools. A detailed mathematical model is developed which captures the hydrodynamic, mass transfer and equilibrium effects in detail to represent the real PSA operation. The first detailed case study presented in this work deals with the design of an explicit/multi-parametric model predictive controller for the operation of a PSA system comprising four adsorbent beds undergoing nine process steps, separating 70 % H2, 30 % CH4 mixture into high purity hydrogen. The key controller objective is to fast track H2 purity to a set point value of 99.99 %, manipulating time duration of the adsorption step, under the effect of process disturbances. To perform the task, a rigorous and systematic framework is employed comprising four main steps of model development, system identification, the mp-MPC formulation, and in-silico closed loop validation, respectively. Detailed comparison studies of the derived explicit MPC controller are also performed with the conventional PID controllers, for a multitude of disturbance scenarios. Following the controller design, a detailed design and control optimization study is presented which incorporates the design, operational and control aspects of PSA operation simultaneously, with the objective of improving real time operability. This is in complete contrast to the traditional approach for the design of process systems, which employs a two step sequential method of first design and then control. A systematic and rigorous methodology is employed towards this purpose and is applied to a two-bed, six-step PSA system represented by a rigorous mathematical model, where the key optimization objective is to maximize the expected H2 recovery while achieving a closed loop product H2 purity of 99.99 %, for separating 70 % H2, 30 % CH4 feed. Furthermore, two detailed comparative studies are also conducted. In the first study, the optimal design and control configuration obtained from the simultaneous and sequential approaches are compared in detail. In the second study, an mp-MPC controller is designed to investigate any further improvements in the closed loop response of the optimal PSA system. The final area of research work is related to the development of an industrial scale, integrated PSA-membrane separation system. Here, the key objective is to enhance the overall recovery of "fuel cell ready" 99.99 % pure hydrogen, produced from the steam methane reforming route, where PSA is usually employed as the purification system. In the first stage, the stand-alone PSA and membrane configurations are optimized performing dynamic simulations on the mathematical model. During this procedure, both upstream and downstream membrane configuration are investigated in detail. For the hybrid configuration, membrane area and PSA cycle time are chosen as the key design parameters. Furthermore, life cycle analysis studies are performed on the hybrid system to evaluate its environmental impact in comparison to the stand-alone PSA system

Dynamic Control Of Alternative Bioethanol Purification Processes

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2016Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2016Biyoetanol, biyokütleden biyokimyasal bir reaksiyonla genel olarak elde edilen alternatif bir yakıttır. Biyoetanol; temizleme, ekstraksiyon, işleme, sakarifikasyon, fermantasyon, damıtma ve dehidrasyon adımları ile üretilir. Etanol hammadde, katkı maddeleri ve çözücü olarak da kullanılabilir. Bu nedenle, biyokütleden elde edilen etanol geleceğin yakıtı olarak kabul edilmektedir. Avantajlarından en önemlisi çevre açısından yararlı olan, yenilenebilir enerji kaynaklarından üretilmesidir, bunun nedeni; benzinden daha düşük sera gazı emisyonlarını açığa çıkarmasıdır. Etanol aynı zamanda yüksek oktan sayısına, geniş yanıcılık sınırlarına ve benzinden daha yüksek buharlaşma ısıları vardır. Buna ek olarak, benzin katkı maddesi olarak kullanılabilir ve hatta doğrudan kullanılabilir.  Tez iki aşamadan oluşmaktadır. İlk aşamada, seçilen üç biyoetanol ayırma prosesi Aspen Plus'ta simüle edilmiştir. Proseslerin ilki ön yoğunlaştıncı kolon, ekstraktif kolon, solvent geri kazanım kolonu ve yoğunlaştırıcı kolonu içeren dört kolonlu bir prosestir. Birinci kolonda, fermentasyon suyundan % 85 etanol ve % 15 su içeren karışım elde edilirken, saf etanol üretmek için etilen glikol ikinci kolona gönderilir. İkinci kolonun distilatından susuz etanol elde edilirken, kolonun dip akımı çözücü geri kazanımı için bir sonraki kolona gönderilir. Solventin küçük bir miktarının, bu geri dönüşüm sırasında kaybını önlemek için telafi olarak makeup eklenir. Solvent geri kazanım kolonundan su ve azetropik karışım elde edilir. Buradaki azeotropik karışım ilk kolona geri gönderilir. Ikinci proses (CLR), üç kolondan oluşmaktadır: ön yoğunlaştıncı kolon, ekstraktif kolon, solvent geri kazanım kolonu. Dört kolonlu sistemden farkı bir kolon indirgenmesi bunu takiben üçüncü kolonun distilatının birinci kolona gönderilmesidir. Son proses SSVR denilen iki kolonlu prosestir. Burada ön derişiklendirme kolonu aynı çalışırken ekstraktif kolon buhar yan akımına sahiptir ve bu akımla birinci kolna dönüş yapar. Ektraktif kolonun distilatı saf etanol içerirken; dip akım solvent içerir ve sisteme geri beslenir. Aspen Dynamics'e gönderilmeden önce gerekli kolon boyutlandırılmaları yapılarak yapılar Aspen Dynamics'e gönderilir. Yeterli literatür araştırması sonucunda proseslere kontrol yapıları kurulmuştur. Yapılara ± %20 besleme akış ve %0.4 ve %0.6 mol besleme kompoziyonu distürbansı uygulanmaktadır ve veriler 10 saat boyunca toplanmaktadır. Elde edilen veriler sonucu MATLAB'te grafikler oluşturularak   incelenmiştir. Sistemlerin distürbanslara karşı verdiği cevaplar çok düşük değişimlere sahiptir ve kısa zamanda yatışkın hale ulaşmıştır. Sonuç olarak her üç yapının da dinamik davranışlarının iyi olduğu gözlemlenmiştir.Bioethanol is an alternative fuel obtained generally by biochemical reaction of biomass. Bioethanol is produced efficiently and economically with cleaning, extraction, treatment, saccharification, fermentation, distillation and dehydration steps of sugarcane, corn, wheat and cellulose, simultaneously. Ethanol can be used as raw material, additives and solvent, such as cosmetics, sprays, perfumery, paints, medicines, food, varnishes and explosives industries. Therefore, ethanol produced from biomass is regarded as the fuel of the future. Due to the fact that ethanol has important advantages like it is produced from renewable energy sources that are environmentally beneficial; it has the lower greenhouse gas emissions than gasoline. Ethanol has also a higher octane number, wider flammability limits, and higher heats of vaporization than gasoline. Furthermore, it can be used as additive with gasoline and also used directly. On the contrary, the major disadvantages of ethanol are including lower energy density, lower vapor pressure and miscibility with water. Several alternative processes are applied to produce bioethanol: ordinary distillation,  pervaporation, adsorption, pressure-swing distillation, extractive distillation, azeotropic distillation, liquid–liquid extraction, adsorption as well as hybrid methods combining these options. In this thesis, the simulation and control of bioethanol production processes using extractive distillation method  are studied. The thesis consists of two stages. In the first stage, the processes selected are simulated in Aspen Plus using the data in the relevant article. Three bioethanol separation processes formed by Errico et al have been selected. The first one is a four-column configuration which includes the preconcentrator column, the extractive distillation column, the solvent recovery column, and the concentrator column. In first column, fermentation broth is converted into the azeotropic mixture, and also the mixture is sent to the second column to produce pure ethanol using ethylene glycol as a solvent. While this is obtained from the distillate   of the second column, the bottom of the column is sent to the next column for solvent recovery. A small amount of fresh solvent is added as make up to prevent any losses of solvent during this recycle. The distillate of the solvent recovery column is separated as water and an azetropic mixture and also the mixture is turned back to the first column in the last column. The second configuration is called conventional separation sequences with liquid recycle (CLR) and also consists of three columns: preconcentrator, extractive and solvent recovery column. While the same sequences occurs in both preconcentrator and extractive column, changes are made in the solvent recovery column. The solvent is obtained from the bottom of the solvent recovery column and is turned to the second column (extractive column) not to the first column. The last configuration is called SSVR, includes two column: preconcentrator column and extractive column. The preconcentrator column is performed same in the other processes. In the extractive column, , pure ethanol is obtained from the distillate, the solvent is recovered at the bottom. The vapor side stream includes a mixture of water and ethanol and also is turned to the preconcentrator column. Before being sent to Aspen Dynamics, column sizing is applied to the columns of these three structures to determine the diameter and length of the vessel. Then, the procedure for "exporting" is performed. Three process control structure has been established by examining the control structure in the literature. In the control structures of four column and three column configurations: reflux drum levels for all columns are controlled by manipulating the distillate flow rates in the first configuration. In the CLR and SSVR, the control of the partial condenser is applied. The base levels for all columns except the solvent recovery column are controlled by manipulating the bottoms flow rates. The base level for  recovery column is controlled by manipulating the makeup flow rate. The top pressures of both columns are controlled by manipulating the corresponding condenser duties. The entrainer flow rate is ratioted to the azeotropic feed and the ratio is controlled by manipulating the bottoms flow rate of the recovery column. Reflux ratios are held constant in each column at their nominal values during disturbances. The fresh feed to the preconcentrator column is flow control in order to guarantee the constant flowrate. The entrainer feed temperature is controlled by manipulating cooler duty. The reboiler duties of both columns are used to control the temperature in a particular stage of each column.   In the two column process, reflux drum level for extractive column is controlled by manipulating the distillate flow rate. The reflux drum level for preconcentrator column is controlled by manipulating reflux. The base level for preconcentrator column is controlled by manipulating the bottoms flow rates. The base level for second column is controlled by manipulating the makeup flow rate. The top pressures of both columns are controlled by manipulating the corresponding condenser duties. The entrainer flow rate is ratioted to the azeotropic feed and the ratio is controlled by manipulating the bottoms flow rate of the recovery column. Reflux ratio is held constant in extractive column at their nominal values during disturbances. Distillate flow rate of the preconcentrator column is ratioed to the reflux flow rate. The fresh feed to the preconcentrator column is flow control in order to guarantee the constant flowrate. The entrainer feed temperature is controlled by manipulating cooler duty. The reboiler duties of both columns are used to control the temperature in a particular stage of each column. The temperature of the vapor sidestream is controlled by manipulating the bottom of the second column. After the design of the structures, two type distorbances are given to the processes: ethanol composition disturbances and Fresh feed flow disturbances. Ethanol composition disturbances, from 5 to 6 mol% ethanol and from 5 to 4 mol% ethanol, for 10 hours. Therefore, fresh feed flow disturbances of ±20% are applied for 10 hours. The results are recorded and shown by using MATLAB. Dynamic responses of the all systems are given in the Figures. The designed three control structures are affected from disturbance with small changes and soon stabilize and so the systems give good dynamic behaviours.Yüksek LisansM.Sc

A PSA Process for an Oxygen Concentrator

Oxygen is used in a variety of chemical processes and for medical purposes throughout the world. Pressure swing adsorption (PSA) has become a viable alternative to cryogenic distillation for the separation of oxygen from air with the development of advanced adsorbents like zeolites. PSA processes are inherently complex because it is a dynamic process. Efficient operation of a PSA process is necessary in order to utilize the capacity of the adsorbent as much as possible and reduce the power requirements of the process.In this thesis, a novel zeolite adsorbent was utilized in a PSA process for oxygen generation with the goal of designing cycles for high recovery and a low bed size factor (BSF). A secondary goal was to determine the kinetic limit of the novel zeolite to determine how fast of an adsorption rate the zeolite has and if it is a candidate for rapid PSA processes. This thesis demonstrates cycles that efficiently utilize the new adsorbent at different operating conditions. This provides a range of operating conditions from which to determine how to best utilize the zeolite to develop larger PSA processes. Also, it was found that this novel zeolite is in fact an enhanced zeolite with a fast adsorption rate capable of supporting rapid PSA processes. Unfortunately due to system constraints, the kinetic limit was not foun

Electrically conductive composite sorbents for CO2 capture from industrial effluents

The capture of CO2 from stationary sources of emission is one of the fundamental approaches of climate change mitigation. One of the main obstacles in the way of implementing many of the introduced technologies for CO2 capture from stationary sources of emission is the associated high cost. For this purpose, dynamic research is focusing on the development of low cost CO2 capture technologies. Knowing that two of the highest cost components of CO2 capture are the capture and the regeneration steps, many research studies are focusing on improving and optimizing CO2 capture and sorbent regeneration to reduce their associated costs. This can be achieved through increasing the amount of CO2 captured by a sorbent, and regenerating the sorbent without using excessive energy. In this context, this thesis targeted the improvement of CO2 adsorption capacity of electrically conductive activated carbon by combining it with materials with a higher adsorption capacity, namely; zeolite type-A and layered double hydroxide. The resulting composite materials can be directly heated and regenerated using Joule effect, potentially reducing the costs of material regeneration using electrical swing adsorption. In this thesis, four types of electrically conductive composite CO2 sorbents were synthesised and characterized: carbonized Purolite® MN200/zeolite NaA composite; carbon supported zeolite NaA composite (zeolite NaA/AC), carbon supported dual-cation containing zeolite type-A composite (ZMG/AC), and carbon supported layered double hydroxide composite (LDH/AC). For the first composite material, a new method was explored for the synthesis of carbonized Purolite® MN200/zeolite NaA composite, where zeolite NaA was synthesised inside the pores of phenolic resin. After synthesis, the composite material was carbonized and activated. The resulting composite material has a unique spherical carbon beads cluster morphology that is expected to reduce pressure drop during CO2 capture. Additionally, the material can easily be shaped and customized according to the shape of the reactor or application requirements. Improving the porosity, mechanical strength, and electrical conductivity of the developed material is expected to make it a suitable material for CO2 capture using electric swing adsorption. Activated carbon beads from MatrixCarbon™ were chosen to be the support material for zeolite NaA, dual-cation containing zeolite type-A (ZMG), and layered double hydroxide (LDH), to synthesise the remaining three composite materials. MatrixCarbon™ activated carbon beads were chosen due to their high porosity and superior electric conductivity. Scanning Electron Microscopy analysis of the internal formation of the composite materials showed the successful growth of zeolites and LDH in the macropores of the carbon beads. The ion exchange process with magnesium in zeolite NaA proved that the material’s CO2 adsorption properties can be modified to work under different sets of operation temperatures. Energy Dispersive X-Ray and X-Ray Diffraction analyses confirmed the formation zeolite NaA, dual-cation containing zeolite type-A, and LDH in the pores of the synthesised composite materials. The amounts of impregnated zeolites or LDH in the composite material was found to range between 4.5 and 6.0 wt% in the composite material. Brunauer-Emmett-Teller (BET) analysis showed that zeolite NaA/AC, ZMG/AC, and LDH/AC composite materials maintained high surface areas of 911, 917, and 1043 m2/g respectively. Temperature Programmed Desorption showed that combining activated carbon with zeolites or LDH crystals not only increases CO2 adsorption capacity but also decreases the desorption temperature of CO2, potentially increasing the cost effectiveness of the materials. Flux response technology was used to investigate CO2 adsorption by the synthesised materials at isothermal and non-isothermal temperatures. The technique proved to be an effective tool for the measurement of CO2 adsorption in solid sorbents. This was demonstrated by the ability to detect the non-linear CO2 adsorption in zeolite NaA and LDH at increasing temperatures (22, 100, 200, and 300 °C), which was reported in previous studies.Open Acces

Porous solids for biogas upgrading

In this work, we will present sorption equilibrium, kinetic and fixed bed data of CO2, CH4 in MOF-508b and zeolite 13X at 303, 323 and 343 K and partial pressures up to 4.5 bar. These data are fitted with appropriate isotherm models. At the same time single, binary and ternary breakthrough curves were measured to provide required data to develop and validate a mathematical model based on the LDF approximation for the mass transfer, which could be used in the design (simulation) of a cyclic adsorption processes (PSA) for the purification of biogas and CO2 sequestration

Dynamic Modeling, Predictive Control and Optimization of a Rapid Pressure Swing Adsorption System

Rapid Pressure Swing Adsorption (RPSA) is a gas separation technology with an important commercial application for Medical Oxygen Concentrators (MOCs). MOCs use RPSA technology to produce high purity oxygen (O2) from ambient air, and provide medical oxygen therapy to Chronic Obstructive Pulmonary Disease (COPD) patients. COPD is a lung disease which prevents O2 from entering a patient\u27s blood, and reduces the blood oxygen level. The standard therapy for COPD is to provide the patient with high purity (~90%) O2. MOCs have become more popular than traditional O2 gas cylinders due to their improved safety, and smaller device size and weight. The MOC market is growing rapidly and was expected to grow from $358 million in 2011 to$1.8 billion in 2017. Recently, a novel, single-bed MOC design was developed and tested to further reduce the size and weight of the device, and provide a continuous supply of O2 to the patient. This single-bed design uses a complex RPSA cyclic process with many nonlinear effects. Flow reversals, discrete valve switching, nonlinear adsorption effects, and complex fluid dynamics all make operating the RPSA system very challenging. Feedback control is necessary in a final commercial product to ensure the device operates reliably, but feedback control of PSA systems is not well studied in the current literature.In this work, a study of dynamic modeling, predictive control and optimization of this single-bed RPSA device is presented. A detailed, nonlinear plant model of the RPSA device is used to study the dynamics of the system as well as design a Model Predictive Controller (MPC) for the RPSA system. The plant model is a fully coupled, nonlinear set of Partial and Ordinary Differential Equations (PDEs and ODEs) which act as a representation of reality when design and evaluating the MPC. A sub-space model identification technique using Pseudo-Random Binary Sequence (PRBS) input signals generate a linear model which reduces the computational cost of MPC, and allows the algorithm to be implemented as an embedded controller for the RPSA device. The multivariable MPC independently manipulates the RPSA cycle step durations to control both the product composition and pressure. This MPC strategy was designed and tested in simulation before being implemented on a lab-scale device.The MPC is implemented onto a lab-scale MOC prototype using Raspberry Pi hardware, and evaluated using several MOC-relevant disturbance scenarios. The MPC is also expanded using piece-wise linear modeling to improve the performance of an RPSA device for other concentrated O2 applications. The embedded MPC features a convex quadratic optimization problem which is solved in real time using online output measurements. Additional hardware in the embedded controller operates the RPSA cycle and implements control actions supplied by the MPC.Design and optimization of RPSA systems remains an active area of research, and many PSA models have been used to optimize RPSA cycles in simulation. In this work, a model-free steady state optimization approach using the embedded hardware is presented which does not require a detailed process model, and uses experimental data and a nonlinear solver to optimize the RPSA operation given various objectives

Carbon dioxide capture and utilization by VPSA: a sustainable development

El continu increment en l'ús de les energies renovables i els objectius per a la reducció de les emissions de diòxid de carboni (CO2) requereixen canvis significatius tant a nivell tècnic com a nivell normatiu. La captura i utilització de diòxid de carboni (CCU, per les sigles en anglès) és un mètode eficaç per aconseguir la mitigació del CO2 i al mateix temps mantenir de forma segura els subministraments d'energia. Si bé la demanda a la reducció de les emissions de CO2 està augmentant, l'eficiència energètica i el cost dels processos de captura de CO2 segueixen sent un factor limitant per a les aplicacions industrials. En el present treball s'estudia l'ús del procés d'adsorció per oscil·lació de pressió i buit (VPSA, per les sigles en anglès) amb adsorbents d'alta selectivitat per separar el CO2 dels gasos de combustió, com un mètode alternatiu al procés d'absorció tradicional amb amines. Es realitza un estudi preliminar mitjançant Anàlisi Tèrmica per determinar la capacitat d’adsorció i el comportament cíclic de la captura de CO2 per deu adsorbents comercials, inclosos els tamisos moleculars de carboni (CMS) i les zeolites. L'anàlisi es va fer amb CO2 pur, N2 pur i mescles dels dos gasos en la proporció 15%/85% que correspon a la composició d’un gas de combustió normal; s’usen les zeolites comercials 13X, 5A, 4A sense i amb aglomerants i tres tamisos moleculars de carboni (CMS) en l’interval de pressió de 0 a 10 bar i a 283K, 298K, 232K i 323 K de temperatura. Els resultats s’han ajustat amb els models Toth, Sips i Dual Site Langmuir (DSL). Es va realitzar una selecció entre deu adsorbents comercials per a la captura de CO2, inclosos els tamisos moleculars de carbó (CMS, per les sigles en anglès) i les zeolites. Es van determinar les propietats texturals, la capacitat d'adsorció i el comportament cíclic dels adsorbents per comparar el seu comportament a la separació del diòxid de carboni del nitrogen. Posteriorment, es van mesurar les isotermes d'adsorció d'un sol component en la balança de suspensió magnètica a quatre temperatures diferents (283, 298, 232 i 323 K) i en un ampli marge de pressions (de 0 a 10 bara). Les dades sobre les isotermes de components purs es van correlacionar utilitzant els models Toth, Sips i Dual Site Langmuir (DSL). Es van dissenyar i construir tres unitats de laboratori per realitzar l'experimentació del procés VPSA. La primera unitat es va usar per a la producció i el control de mescles gasoses de CO2 i N2 a una pressió màxima de 9 bara. En la segona unitat es van dur a terme la determinació dels equilibris d'adsorció amb una barreja de composició semblant a la dels gasos de combustió (15/85% de CO2/N2 v/v). Amb el programa Aspen Adsorption® es va simular el sistema experimental, obtenint que les prediccions del model DSL reprodueixen suficientment bé els resultats experimentals de les corbes de ruptura i els perfils de temperatura en el llit fix. A més, es van fer estudis dinàmics per avaluar les zeolites 5ABL i 13XBL usant el procés VPSA discontinu per a la separació CO2 de N2. La unitat dos es va dotar d'un sistema de control amb una interfície PLC que facilita la seva operació i automatització, usant una estratègia de control desenvolupada en aquest treball. En base als resultats obtinguts amb la unitat dos, tant experimentals com simulats, es va trobar que la zeolita 13XBL era la més adequada per al procés VPSA proposat. Els resultats experimentals es van emprar per alimentar el disseny de la unitat dos a Aspen Adsorption® i validar el model usat que al seu torn es va utilitzar per realitzar un disseny complet d'experiències de dos factors (26) en configuració continua. La tercera unitat experimental consta de tres columnes d'adsorció on es va incloure l'estratègia de control desenvolupada per la unitat dos i es va incloure la recirculació dels corrents rics en N2 i CO2. Es van dur a terme tres experiments del procés VPSA cíclic de 8 passos canviant els paràmetres de control del procés automatitzat i usant la zeolita 13XBL com adsorbent. Es va aconseguir satisfer els objectius en termes puresa de CO2 (> 80%) i consum energètic (<2.5 kWh/kgCO2). Sobre la base dels resultats experimentals i simulats, es va realitzar una demostració a escala pilot de la captura de CO2 del gas de combustió d'una caldera de vapor en una planta industrial a situada a la província de Barcelona.La planta pilot de captura de CO2 consta d'un procés de pretractament dels gasos de combustió, una unitat VPSA acoblada amb una unitat de deshumidificació i una aplicació industrial per a l'ús del CO2. A la unitat de pretractament, els gasos de combustió es van refredar de 70ºC a 25ºC i es van desnitrificar. A la unitat de deshumidificació, es va eliminar el vapor d'aigua del gas desnitrificat mitjançant adsorció sobre alúmina. Posteriorment, es va emprar el procés VPSA de vuit passos amb tres columnes usant zeolita 13XBL, en la qual es va obtenir un corrent enriquit de CO2 de 85 a 95% de puresa de CO2, amb una recuperació del 48 a 56%, una productivitat de 0,20-0,25 gCO2/(gads·h) i un consum energètic de 1.48 kWh/kgCO2. El CO2 recuperat es va usar per reemplaçar l'ús d'àcids minerals en l'etapa de regulació del pH de la planta de tractament d'aigües residuals existent a la fàbrica. Per tant, el procés desenvolupat és una alternativa efectiva per separar el CO2 dels punts d'emissió de gasos de combustió industrial i utilitzar el CO2 recuperat com a matèria primera per a aplicacions industrials. L'ús de CO2 capturat en aquestes fonts d'emissió té dos avantatges clars. D'una banda, es van reduir les emissions de CO2 a la atmosfera. De l'altra, va permetre reutilitzar i transformar un contaminant ambiental en compostos neutres.El continuo incremento en el uso de las energías renovables y los objetivos para la reducción de las emisiones de dióxido de carbono (CO2) requieren cambios significativos tanto a nivel técnico como a nivel normativo. La captura y utilización de dióxido de carbono (CCU, por sus siglas en inglés) es un método eficaz para lograr la mitigación del CO2 y al mismo tiempo mantener de forma segura los suministros de energía. Si bien la demanda en la reducción de las emisiones de CO2 está aumentando, la eficiencia energética y el costo de los procesos de captura de CO2 siguen siendo un factor limitante para las aplicaciones industriales. En el presente trabajo se estudia el uso del proceso de adsorción por oscilación de presión y vacío (VPSA, por sus siglas en inglés) con adsorbentes de alta selectividad para separar el CO2 de los gases de combustión, como un método alternativo al proceso de absorción tradicional con aminas. Se realizó una selección entre diez adsorbentes comerciales para la captura de CO2, incluidos los tamices moleculares de carbón (CMS, por sus siglas en inglés) y las zeolitas. Se determinaron las propiedades texturales, la capacidad de adsorción y el comportamiento cíclico de los adsorbentes para comparar su comportamiento en la separación del dióxido de carbono del nitrógeno. Posteriormente, se midieron las isotermas de adsorción de un solo componente en la balanza de suspensión magnética a cuatro temperaturas diferentes (283, 298, 232 y 323 K) y en un amplio margen de presiones (de 0 a 10 bara). Los datos sobre las isotermas de componentes puros se correlacionaron utilizando los modelos Toth, Sips y Dual Site Langmuir (DSL). Se diseñaron y construyeron tres unidades de laboratorio para realizar la experimentación del proceso VPSA. La primera unidad se usó para la producción y el control de mezclas gaseosas de CO2 y N2 a una presión máxima de 9 bara. En la segunda unidad se llevaron a cabo las mediciones de los equilibrios de adsorción con una mezcla de composición semejante a la de los gases de combustión (15/85% de CO2/N2 v/v). Con el programa Aspen Adsorption® se simuló el sistema experimental, obteniendo que las predicciones del modelo DSL reproducen suficientemente bien los resultados experimentales de las curvas de ruptura y los perfiles de temperatura en el lecho fijo. Además, se hicieron estudios dinámicos para evaluar las zeolitas 5ABL y 13XBL usando el proceso VPSA discontinuo para la separación CO2 de N2. La unidad dos se dotó de un sistema de control con una interfaz PLC que facilita su operación y automatización, usando una estrategia de control desarrollada en este trabajo. En base a los resultados obtenidos con la unidad dos y su simulación, se encontró que la zeolita 13XBL era la que la más adecuada para el proceso VPSA propuesto. Los resultados experimentales se usaron para alimentar el diseño de la unidad dos en Aspen Adsorption® y validar el modelo usado que a su vez se utilizó para realizar un diseño completo de experiencias de dos factores (26) en configuración discontinua. La tercera unidad experimental consta de tres columnas de adsorción donde se incluyó la estrategia de control desarrollada para la unidad dos y se incluyó la recirculación de las corrientes ricas en N2 y CO2. Se llevaron a cabo tres experimentos en el proceso VPSA cíclico de 8 pasos cambiando los parámetros de control del proceso automatizado y usando la zeolita 13XBL como adsorbente. Se logró satisfacer los objetivos en términos pureza de CO2 (>80%) y consumo energético (<2.5 kW·h/kgCO2). Sobre la base de los resultados experimentales y simulados, se realizó una demostración a escala piloto de la captura de CO2 del gas de combustión de una caldera de vapor en una planta industrial situada en la provincia de Barcelona. La planta piloto de captura de CO2 consta de un proceso de pretratamiento de los gases de combustión, una unidad VPSA acoplada con una unidad de deshumidificación y una aplicación industrial para el uso del CO2. En la unidad de pretratamiento, los gases de combustión se enfriaron de 70ºC a 25ºC y desnitrificaron. En la unidad de deshumidificación, se eliminó el vapor de agua del gas desnitrificado mediante adsorción con alúmina. Posteriormente, se empleó el proceso VPSA de ocho pasos con tres columnas usando zeolita 13XBL, en la que se obtuvo una corriente enriquecida de CO2 de 85 a 95% de pureza de CO2, con una recuperación del 48 a 56%, una productividad de 0.20 a 0.25 gCO2/(gads٠h-) y un consumo energético de 1.48 kWh/ kgCO2. El CO2 recuperado se usó para reemplazar el uso de ácidos minerales en la etapa de regulación del pH de la planta de tratamiento de aguas residuales existente en la fábrica. Por lo tanto, el proceso desarrollado es una alternativa efectiva para separar el CO2 de los puntos de emisión de gases de combustión industrial y utilizar el CO2 recuperado como materia prima para aplicaciones industriales. El uso de CO2 capturado en estas fuentes de emisión tiene dos ventajas claras. Por un lado, redujeron las emisiones de CO2 a la atmósfera. Por otro lado, permitió reutilizar y transformar un contaminante ambiental en compuestos neutros.The continuously increasing share of renewable energy sources and European Union targets for carbon dioxide (CO2) emission reduction need significant changes both on a technical and regulatory level. Carbon dioxide capture and utilization (CCU) is an effective method for achieving CO2 mitigation while simultaneously keeping energy supplies secure. While the demand for reduction in CO2 emissions is increasing, the improvement of energy-efficiency and the cost of CO2 capture processes remains a limiting factor for industrial applications. The present work studies the Vacuum Pressure Swing Adsorption process (VPSA) using high selectivity adsorbents for separating CO2 from flue gas as an alternative method to the traditional absorption process with amines. A screening analysis for CO2 capture was conducted on ten commercial adsorbents, including carbon molecular sieves (CMS) and zeolites. The textural properties, the adsorption capacities and the adsorbent cyclic behaviors were determined to compare their performance in the context of CO2 separation from nitrogen (N2). Subsequently, the single component adsorption isotherms were measured in a magnetic suspension balance at four different temperatures (283, 298, 232 and 323 K) and over a large range of pressures (from 0 to 10 bara). Data on the pure component isotherms were correlated using the Toth, Sips and Dual Site Langmuir (DSL) models. Three laboratory units were designed and built to perform the VPSA experiments. The first was used for the production and control of CO2 and N2 gas mixtures at a maximum pressure of 9 bara. Adsorption equilibrium measurements with a mixture that resembles the composition of combustion gases (15/85% CO2/N2 v/v) were obtained using the second unit that was built. Afterwards, the Aspen Adsorption® program was used to simulate the experimental system, where the predictions of the DSL model agree with the breakthrough curves and the temperature profiles of the experimental fixed bed results. In addition, dynamic studies were performed to evaluate the zeolites 5ABL and 13XBL using a discontinuous VPSA process for the CO2 separation of N2. The process was automated and operated with a PLC interface, using a control strategy developed in this work. Based on the comparison results of the zeolites, it was found that the 13XBL zeolite was the one most suitable for the proposed VPSA process. The experimental results were verified by numerical simulations in the Aspen Adsorption® software and the validated model was used to perform a two-factor complete design of experiments (26) using 13XBL simulations in a discontinuous configuration. The third experimental unit was built with three adsorption columns which included the developed control strategy and the recirculation of N2 and CO2 rich streams. Three experiments were carried out using zeolite 13XBL as an adsorbent for the proposed 8-step VPSA cyclic process by changing the control parameters of the automated process. Through the experiments, the objectives were achieved in terms of CO2 purity (> 90%) and energy consumption (> 2.5 kWh/kgCO2). Based on the experimental and simulated results, a pilot-scale demonstration plant for CO2 capture from flue gas in an existing industrial boiler in a Spanish company was carried out. The pilot-scale CO2 capture plant consisted of a pre-treatment process for flue gases, a VPSA unit coupled with a dehumidification unit and an industrial application for the use of CO2. In the pretreatment unit the flue gases were cooled from 70°C to 25°C and then denitrified. In the dehumidification unit, the water vapor was removed from the denitrified gas by adsorption with alumina. Subsequently, the three columns’ eight-step VPSA process developed with zeolite 13XBL was used. The results were a product purity of 85 to 95% of CO2, a recovery of 48 to 56%, a productivity of 0.20 to 0.25 gCO2/(gads٠h) and an energy consumption of 1.48 kWh/kgCO2. The recovered CO2 was then used to replace the use of mineral acids in the pH regulation stage of the existing wastewater treatment plant. Therefore, it is concluded that the developed process is an effective alternative to separate the CO2 from the emission points of industrial combustion gases and to use the recovered CO2 as raw material for industrial applications. The use of CO2 captured in these emission sources has two clear advantages. On the one hand, it reduces the CO2 emissions to the atmosphere. On the other hand, it allows the reuse and transformation of an environmental pollutant into neutral compounds

Thermodynamic Analysis of Carbon Capture and Pumped Heat Electricity Storage

This work can be divided into two parts: the first part is focused on carbon capture; the second part is devoted to the study of pumped heat electricity storage processes. Thermodynamic analysis of energy requirement for adsorption and chemical looping processes is investigated. It enables us to compare various technology platforms under the same separation target. Sorption-enhanced reaction is a novel intensified process by combining catalyst and adsorbent in a single fixed bed reactor. Experimental studies of sorption-enhanced water gas shift and steam methane reforming have been done by previous members of our group. Here numerical studies on the interactions between reaction and sorption in a sorption-enhanced reactor are carried out. Water-gas shift reaction, hydrogen sulfide decomposition and propene metathesis reaction are studied. Our results suggest that the produce purity depend on factors such a reaction kinetics, stoichiometry, equilibrium and adsorption isotherm. Mass transfer resistance can also play an important role in product purity. Experimental studies on high temperature carbon dioxide capture by pressure swing adsorption using Na-promoted alumina are undertaken for the first time. The effects of steam during regeneration are discussed. Pumped heat electricity storage processes are a novel thermal energy storage technique recently proposed. It does not require specific geological structure sites and is environmentally friendly. When combined with renewable energy resources, e.g. solar, wind and tidal, it can supply stable power throughout the day. During the charging and delivery cycle a cyclic steady state temperature distribution is formed inside the storage tank. In order to reduce the computing time to simulate this process, a novel matrix exponential solution is provided. Dimensionless analysis on the process performance is discussed

CO2 Capture by the Integrated VSA/Cryogenics method including Pipeline Transportation

This thesis proposes a hybrid technology of vacuum swing adsorption and cryogenic liquefaction to capture CO2 at high recovery with an energy penalty comparable with the traditional amine absorption process. After the capture, this thesis also proposes a pipeline transportation system which utilizes the ground/ambient temperature to retain its liquid phase. Significant amount of laboratory experiment and software simulation have been conducted and conclusions and recommendation have been provided for future research work

Recuperación de hidrógeno de corrientes gaseosas residuales de origen industrial para su aplicación en pilas de combustible

RESUMEN: La necesidad de promover una economía circular aprovechando los recursos da lugar a la importancia de la recuperación de corrientes gaseosas residuales que contienen hidrógeno. Por ello, el objetivo global de la tesis es contribuir en la recuperación de mezclas de gases residuales de origen industrial investigando principalmente dos tipos de tecnologías de separación de hidrógeno: membranas poliméricas y procesos de adsorción por cambio de presión (PSA, por sus siglas en inglés), con objeto de obtener hidrógeno de elevada pureza. Para conseguir tal objetivo general, la investigación se ha centrado en proporcionar cuestiones metodológicas relacionadas con la recuperación de hidrógeno; evaluar el comportamiento de membranas comerciales poliméricas selectivas de hidrógeno usando mezclas de gases multi-componentes; y producir hidrógeno con la calidad apta para alimentar pilas de combustible a partir de una corriente gaseosa residual de origen industrial mediante un proceso de PSA.ABSTRACT: The need to promote the circular economy by upcycling the resources leads to a great relevance of hydrogen-containing waste gas streams recovery. Thus, the overall objective of this thesis is the contribution to the recovery of hydrogen from industrial waste gas mixtures by investigating two different separation technologies: polymeric membranes and pressure swing adsorption (PSA) processes, in order to obtain high-purity hydrogen. To achieve such general goal, the research has been centered in providing methodological issues to surplus hydrogen recovery; evaluating the performance of commercial hydrogen-selective polymeric membranes using multicomponent gas mixtures; and producing fuel cell grade hydrogen from an industrial waste gas stream via PSA process