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- Modeling the deactivation of CaO-based sorbents during multiple Ca-looping cycles for CO2 post-combustion capturePublication . Abreu, Miguel; Teixeira, Paula; Filipe, Rui; Domingues, Luís; Pinheiro, Carla; Matos, Henrique A.A novel model is presented for the estimation of natural CaO-based sorbents carbonation reactivity decay during Calcium Looping carbonation-calcination cycles. The model consists of a cyclic framework of two sub-models, the Overlapping Grain Model and the novel proposed modified Rate Theory for the Pore Size Distribution model. The model was implemented in gPROMS ModelBuilder (R) and parameter estimation was used for model validation using experimental data from three CaO-based sorbent precursors. The carbonation profile for the three sorbents was simulated with average deviations under 5%. The calcination sub-model predicted the evolution of total porous volume and total surface area for the calcination and sintering of dolomite, with an error of 3%. The cyclic framework successfully predicted the carbonation behavior of dolomite for 20 carbonation-calcination cycles. The model can be used for other CaO-based sorbents and the flexible modular structure allows the integration of other modules or approaches.
- Recovering value from organic waste materials: Supercritical fluid extraction of oil from industrial grape seedsPublication . Coelho, Jose; Filipe, Rui; Robalo, Maria Paula; Stateva, Roumiana P.Supercritical extraction of oil from grape seed samples obtained from a Portuguese industry was carried out at temperatures from (313-333) K, pressures up to 40.0 MPa and different scCO(2) flow rates. The qualitative analysis of the crude oil was carried out by NMR. The fatty acids were analyzed by GC-Fid with reference to the parameters in Annex I to European Commission Regulation. The results show similar content of TAGs and DAGs both in the n-hexane and scCO(2) extraction methods, but the latter have higher PUPA and lower saturated fatty acids content. A dynamic model was used to simulate the extraction curves in gPROMS ModelBuilder. The grape seed oil was represented as either a one or a three component mixture of triacylglycerols, and the deviation between the experimental and calculated extraction yields was in the range (2-9) % for the first, and (4-11) % for the second case.
- Modelling the kinetics of supercritical CO2 extraction of biomassPublication . R. M. Filipe; Coelho, Jose; Robalo, Maria Paula; Cholakov, Georgi; Stateva, R. P.This work addresses the modelling and simulation of the kinetics of CO2 supercritical extraction of oils from biomass. Experimental and simulation results from different matrices and models are presented. gPROMS Model Builder is used to find solutions to three different models applied to study the extraction of three different volatile oils from aromatic plants (coriander, fennel and savoury), and from a bioresidue, industrial grape seeds. The supercritical extraction experiments performed at different temperature, pressure and flow rate conditions provide the data to the modelling studies and for model parameter estimation. The qualitative and quantitative agreement between the experimental and simulated extraction profiles in terms of yields was good for the cases investigated.
- Influence of co-solvents on the supercritical extraction kinetics of spent coffee grounds: experimental and modelling studiesPublication . Coelho, Jose; Filipe, Rui; Robalo, Maria Paula; Boyadzieva, Stanislava S.; Cholakov, Georgi; Stateva, Roumiana P.Coffee is one of the most widely used beverages. An estimated 3.5 billion cups of coffee are drunk worldwide every day. In EU alone, for the period 2011-2013, 2.5 Mt of coffee were consumed. Taking into consideration that the production of coffee in 2015 was approximately 9 Mt and that from each kg of coffee 0.91 kg of solid waste is produced, the importance of a further valorization of this residue becomes obvious. In recent years, the biorefinery concept has been identified as the most promising route for employment of the full potential of a biomass by maximizing its conversion into high value products. Its main bottleneck, however, is how to extract the energy and non- energy compounds from the biomass without damaging one or more of the components, e.g. those which are heat sensitive. Spent coffee grounds (SCGs) contain large amounts of fatty acids, lignin, cellulose, hemicellulose, etc. and can be exploited as an excellent source of value-added energy and non-energy related products (e.g, antioxidants and other functional additives).
- ProGreS 2nd Workshop: from biomass characterization to process synthesis (book of extended abstracts)Publication . Coelho, Jose; Matos, Henrique A.; Filipe, Rui; Robalo, Maria Paula; Braz, Catarina G.
- Semi-empirical models and a cubic equation of state for correlation of solids solubility in scCO(2): dyes and calix[4]arenes as illustrative exemplesPublication . Coelho, Jose; Filipe, Rui; Naydenova, Greta P.; Yankov, Dragomir S.; Stateva, Roumiana P.Knowledge of a compound's solubility in the supercritical solvent is crucial to the definition of the optimal operating conditions and consequently to the development of supercritical applications. The present paper examines the performance of two of the most widely used groups of models for correlating the solubility of solid solutes in supercritical carbon dioxide – equations of state (EoSs) and semi-empirical density based models. The Soave-Kwong-Redlich (SRK) EoS with the one-fluid van der Waals mixing rule represents cubic EoSs, while the group of the density-based models includes Chrastil, Kumar and Johnston, Bartle et al., Méndez-Santiago and Teja, Garlapati and Madras, Nejad et al. and Khansary et al. models. The seven solutes chosen as illustrative examples are compounds of interest to the dry dyeing processing techniques and biotechnological processes and have diverse structural complexity. The results obtained reveal that the more recently advocated density-based models (Garlapati and Madras, Nejad et al. and Khansary et al. models) perform better with overall average absolute deviations, AARD, of 6.5, 9.0 and 9.3%, respectively. The 6.7% overall AARD for the SRK CEoS is acceptable and it can be used as a reliable thermodynamic model to predict the solubility of any compound for which there is no sufficient experimental data available.
- Multi-scale modelling and simulation of Ca-looping cycle process for CO2 post-combustion capturePublication . Pinheiro, Carla; Filipe, Rui; Torres, Miguel Abreu; Silva, João; Matos, Henrique A.The present work focuses on one of the more promising new post-combustion technologies using calcium-based materials, known as the “Ca-looping cycle” process, which endeavors to scrub CO2 from flue gases and syngases by using natural lime-based sorbents and which appears to potentially offer limited CO2 capture costs. So, the major driving force is to improve overall efficiency, reduce the cost, and minimize adverse environmental impacts of post-combustion Ca-looping cycle CO2 capture, as compared to more conventional technologies (e.g., amine-based solvent scrubbing). There is a large energy penalty with amine scrubbing, the closest to market technology. The main objective of this work is to develop a first principles model to simulate different natural sorbents looping cycle performance in a fixed bed reactor laboratory scale system. A rigorous non-linear dynamic model of the looping cycle process was developed in gPROMS, based on the multiscale concept. The multiscale modeling is an emerging technique, where the characteristic length for each phenomena that occurs is taken into consideration, leading to a set of submodels with different scale lengths. These submodels when coupled together allow the simulation of a macrosystem (Hangos and Cameron, 2001). After the identification of the characteristic dimensions involved in the models, the first step is the development of a single particle model, which takes into account the energy and material transport, undergoing reactions (carbonation and calcination) and structural changes inside the particle. The material and heat transport inside the particle take into account the structural changes. Detailed models of single particle undergoing cycles of calcination and carbonation are developed. An improved decay approach is introduced in the model for those sorbents exhibiting carbonation decay with the number of cycles. The experimental characterization of the samples gave vital information on the physicochemical changes occurring during testing that need to be described in the model in the carbonation decay function. The conversion decay does not only depend on the number of cycles, but also on the conditions of the previous cycles, temperature, pressure, gas phase composition and characteristics of the material used for the carbonation. Model parameters are estimated from experimental results obtained for different sorbents tested (Santos et al., 2012)(Pinheiro et al., 2016). Several simulations for different sorbents and operating conditions were performed and the model was validated with experimental data obtained in a fixed bed reactor. It was also important to ensure that the model is numerically stable within a large range of values.
- Computer aided control projects as main assessment component of master's advanced control coursesPublication . Pinheiro, Carla I. C.; Filipe, RuiThis paper addresses the assessment methodology used in the advanced process control courses of the Chemical Engineering master degrees at the departments where the authors are affiliated. The details of the assessment methodology used are presented, and two examples of case study processes used in the computer aided control projects assessment are presented. The advantages and drawbacks of this approach, students feedback and success rates are discussed.
- Supercritical CO2 extraction of spent coffee grounds. Influence of co-solvents and characterization of the extractsPublication . Coelho, Jose; Filipe, Rui; Robalo, M. Paula; Boyadzhieva, Stanislava; Cholakov, Georgi; Stateva, RoumianaSpent coffee grounds (SCGs) were extracted with supercritical CO2 at temperatures of 313 K and 333 K, pressures up to 50.0 MPa and different scCO(2) flow rates. The addition of co-solvents isopropanol, ethanol and ethyl lactate decreased the time to achieve the maximum oil yield, to half of that with pure CO2. Analysis of the extracted oils by NMR, showed that caffeine content was (0.56-3.96) % and DUFA and MUFA contents changed within (39.8-42.0) % and (12.9-15.8) %, respectively. The analyses of fatty acids performed by GC-FID revealed the composition of the oils being 76 % of the total constituted by palmitic and linoleic esters. The DPPH antioxidant capacity was improved up to 12.5 times with co-solvents. The kinetics of oil extraction from SCGs with pure scCO(2) was modeled successfully by combining for the first time representation of the oil mixture by a single virtual molecule with group contribution methods.
- Supercritical CO2 extraction of feed stocks to generate high added value bio-productsPublication . Coelho, Jose; Boyadjieva, S.; R. M. Filipe; Robalo, Maria Paula; Cholakov, Georgi; Stateva, R. P.The huge amounts of waste generated every year by the industry, in addition to the great loss of valuable materials, pose serious organisational problems, both from an economic and ecological point of view. Many of the residues, however, have the potential to be reused and utilized completely via integrated bio-refining technologies. Extraction techniques which play a very important part in biorefineries should provide swift processing and yield quantitative recovery without degradation, complemented by easy separation of extracts from the solvent. In this work, focussed on two generic biomass examples - grape seeds and spent coffee grounds, we outline the perspectives of introducing mild, efficient and with low environmental impact techniques that apply compressed fluids in biorefineries for obtaining high value-added products with a wide spectrum of applications.