http://hdl.handle.net/10366/138522 Tue, 21 Apr 2026 07:25:19 GMT 2026-04-21T07:25:19Z http://hdl.handle.net/10366/169667 [EN]This work presents a two-stage optimization procedure for the conceptual design and operation of A-frame dry cooling systems for concentrated solar power facilities. First, the optimal geometry of the A-frame including sizing, number of fans and blade geometry, and unit parameters such as pipe length, configuration and number is determined. Finally, the operation of the system over a year for minimum energy consumption is computed. The geometry problem is formulated as a mixed-integer non linear programming (MINLP) problem. A tailor-made branch and bound algorithm is used to solve the complex non-linear programming sub-problems. The second problem consists of a multi-period MINLP. A fixed geometry is used to evaluate the usage of fans over time. The solution suggests an apex angle of 63°, one row of 75 pipes of 13.5 m long with a diameter of 3.3 mm, and 4 fans are used but they only operate at full capacity during summer. This design allows reducing the energy required by 20% by using the appropriate pipe configuration and number. The unit consumes around 4% of the energy produced by the CSP plant that serves. It is a promising result that can be affected by plant layout and ground availability. Mon, 01 Jan 2018 00:00:00 GMT http://hdl.handle.net/10366/169667 2018-01-01T00:00:00Z http://hdl.handle.net/10366/168230 [EN]The operation performance of air-coolers in concentrated solar power plants decays due to particulate deposition on heat transfer surfaces. The deposition process can be seen as a stochastic phenomenon. A modelling approach is proposed to capture the uncertainty and the effect of extreme events, such as sandstorms, affecting the performance of plants located in dry places through dust or sand deposition on the air coolers. A case study of a concentrated solar power plant located in Dubai is analysed. Sandstorms generate acute and drastic fouling of the air coolers, and this is modelled as a stochastic process using historical aerosol dispersion data. Ten scenarios are generated by sampling the probability distribution of sandstorms occurrence and intensity. The optimal operation (cleaning schedule and airflow profiles) of the air coolers is established using Benders decomposition to solve the resulting large-scale mixed integer non-linear programming problem. The results of the stochastic scenarios demonstrate that substantial savings of $ 0.6 M − $ 2.7 M per year are achieved by the optimal operation. Cost is minimized by a combined reactive and proactive cleaning policy which accounts for the frequency, intensity and seasonal variability of sandstorms, in addition to the variability on local radiation and weather conditions. Wed, 01 Jan 2020 00:00:00 GMT http://hdl.handle.net/10366/168230 2020-01-01T00:00:00Z http://hdl.handle.net/10366/168228 [EN]This work presents a parametric programming framework for the optimal design and operation of systems with performance loss over time. A two-stage procedure is proposed. The unit is designed for the operating conditions just before maintenance. In a second stage, a multiperiod problem is solved for the optimal the operation of the unit over time including cleaning costs. The minimum operating cost as a function of the cycle length determines the operating cycle and the unit design. The methodology is applied to A-frame cooling systems under fouling conditions, where fouling affects the pressure drop and the global heat transfer coefficient. The sigmoidal deposition profile results in an optimal cycle time of 8 years. This design allows reducing the energy required to around 4% of the energy produced by the concentrated solar power plant. It is a promising result that can be affected by plant layout and ground availability. Tue, 01 Jan 2019 00:00:00 GMT http://hdl.handle.net/10366/168228 2019-01-01T00:00:00Z http://hdl.handle.net/10366/163046 [EN] This work presents the development of a reduced order compartment model for a counter-current spray dryer. The compartment model is formulated using adaptable compartments and introducing the use of correlations based on dimensionless groups. These correlations can capture the mean residence time they but are unable to reproduce the variance of the entire residence time distribution (RTD). Limitations are also observed in the evaluation of internal fluxes. The application of these correlations to a specific zone requires the inclusion the geometrical modifications in any part of the unit. A small internal modification in one geometry not only modifies a zone, but also influences the remaining regions so that the zones cannot be independently scaled-up. The methodology is complemented with an analysis of the RTD showing that most of the dispersion generated takes place in the bottom cone. Wed, 19 Jan 2022 00:00:00 GMT http://hdl.handle.net/10366/163046 2022-01-19T00:00:00Z http://hdl.handle.net/10366/163043 [EN]We optimized the operation of the process thatreforms biogas with CO 2 and/or steam for the production ofmethanol using a mathematical optimization approach. Theraw biogas is cleaned up before reforming. Part of the biogas isused to provide energy for the process. Next, the unreactedhydrocarbons and CO 2 are removed. Subsequently, syngascomposition may be adjusted, using either water gas shiftreaction or membrane-pressure swift adsorption. Finally,methanol is synthesized. The process is modeled using massand energy balances, chemical and phase equilibria, and rulesof thumb. The problem is formulated as an NLP problem with simultaneous heat integration for the optimal biogas compositionand methanol production. Two objective functions are considered: a simplified production cost and an environmental onedeveloped based on carbon footprint. Biogas is expected to have around 50−52% of CH 4 and 45−47% of CO 2 , depending on theobjective function. The production cost of methanol is $1.75/gal, for a plant size that uses 10% of the potential biogas to beproduced in Madrid, Spain, with an investment of $46 MM. Wed, 18 May 2016 00:00:00 GMT http://hdl.handle.net/10366/163043 2016-05-18T00:00:00Z http://hdl.handle.net/10366/162154 [EN] Methanol and ammonia emerge as two of the most important energy carriers in a new decarbonized society. In this work, a systematic assessment of the power generation based on these chemicals is performed using two different alternatives: direct utilization as green fuels in fuel cells or as carriers for hydrogen. Despite the need for a previous stage for hydrogen production, the use of these chemicals as hydrogen carriers demonstrates higher efficiencies (around 40%), mainly due to the higher degree of maturity of the hydrogen fuel cells. This is reflected in the cost of electricity for the different alternatives with around 700 €/MWh for hydrogen carrier options and about 1200 €/MWh for the direct utilization as green fuels. Compared to hydrogen, the use of methanol or ammonia has a higher electricity production cost. However, future improvements in the efficiency of fuel cell units could convert these fuels is competitive options. In addition, for different scenarios combining transportation and power generation, methanol and ammonia emerge as technically and economically feasible alternatives, especially for distances over 3000 km. Consequently, both hold a pivotal role in addressing the challenges associated with hydrogen within a future energy systems characterized by high renewable penetration. Fri, 01 Nov 2024 00:00:00 GMT http://hdl.handle.net/10366/162154 2024-11-01T00:00:00Z http://hdl.handle.net/10366/162151 [EN] Methanol is one of the most important chemical compounds, as it is the basis for producing a wide variety of derivatives. Its production through fossil sources such as natural gas in countries like Mexico is not entirely viable due to the fluctuations in the availability of this resource. The use of renewable sources to produce methanol represents an interesting area of opportunity to reduce the dependence on a single raw material. This work proposes the design of the methanol supply chain in Mexico using residual materials, finding a solution with the best compromise between profit, social impact, and CO2 emissions. The solution with the best compromise corresponds to a profit of 7,334,100 USD/y, a marginalization index of 2592.536 and CO2 emissions of -0.021 Mt/y. This solution has 8 different types of raw materials, 18 process plants and the use of three processing technologies: gasification, anaerobic digestion, and catalysis from CO2. Sun, 01 Sep 2024 00:00:00 GMT http://hdl.handle.net/10366/162151 2024-09-01T00:00:00Z http://hdl.handle.net/10366/162148 [EN] The defossilization of household heating systems is one of the paramount goals of renewable energy, where pellets are regarded as a promising option. A multiscale techno-economic analysis is performed to determine first the raw material yield to pellets as well as estimating CAPEX and OPEX as a function of the biomass processed. Next, the location of the facilities is evaluated in the agricultural counties of Castilla y León through the formulation of an MILP facility location problem, including economic, social, and environmental objectives. The lignocellulosic materials considered are pinewood, eucalyptus wood, corn stover, and switchgrass. For substituting the natural gas-powered boilers in towns with over 500 inhabitants, 860,000 t/yr of pellets will be necessary. 98.1% substitution is achieved deploying 13 pellet plants, 11 based on pinewood and 2 on corn stover, representing 26.4% of the resources available and it is necessary to invest 164.8 M€ with an annual profitability of 133.0 M€. The emissions substituting these boilers are reduced by 94.8%. Switchgrass is studied separately as it is not currently grown in Castilla y León, although, its introduction would decrease the OPEX from 127.5 €/t to 63.9 €/t while the social and environmental impact is adversely affected. Mon, 01 Jul 2024 00:00:00 GMT http://hdl.handle.net/10366/162148 2024-07-01T00:00:00Z http://hdl.handle.net/10366/162145 [EN] Renewable ammonia can be the path to decarbonization of food, chemicals, and the transport system. While lately, electrochemical hydrogen and air separation are gaining support, biomass-based ammonia can provide an alternative to contribute to green ammonia deployment with possible synergic with the current ammonia facilities. Different processing paths have been considered, depending on the wet content of the biomass. Wet biomass yield to ammonia is low, but it is more interesting as a waste management procedure. Biomass gasification has attracted most of the attention and results in promising ammonia production prices using technologies already in the toolbox of the process industry. The combination of ammonia and urea production solves one of the most significant challenges in biomass-based ammonia, the released CO2. These integrated facilities allow for the full utilization of biomass in the green chemical industry. Sat, 01 Jun 2024 00:00:00 GMT http://hdl.handle.net/10366/162145 2024-06-01T00:00:00Z http://hdl.handle.net/10366/162121 [EN] This work introduces a compartment model based on a discreteelement method (DEM) model. The DEM model determines the residence times(RTs) of particles in the active (in contact with air) and passive zones. Theextracted RT is combined with the heat and mass transfer models into acompartment model, where particles are modeled by employing a populationbalance. Heat and mass transfer models contain efficiency coefficients that aremodeled with surrogates generated from a reduced set of experiments. Theresulting surrogate models are validated with additional experiments in anindustrial facility. It accurately reproduces the heat and mass transfer in the dryer(±10% of relative error in temperature prediction) and provides a guess of thedistribution of the properties of the particles (e.g., moisture content andtemperature) across particle sizes and locations within the dryer. Fri, 01 Mar 2024 00:00:00 GMT http://hdl.handle.net/10366/162121 2024-03-01T00:00:00Z http://hdl.handle.net/10366/162117 [EN] Glycerol carbonate (GC) is one of the most attractive green chemicals involved in several applications such as polymer synthesis, e. g., the production of polyurethanes and polycarbonates. This relevant chemical can be produced, in a green way, using CO2 (from carbon capture) and glycerol (a byproduct from biodiesel manufacturing). Therefore, in this work, a comprehensive analysis of the GC production process is conducted based on the following synthesis route: urea-dimethyl carbonate-GC using carbon dioxide and glycerol as the main raw materials where the synthesis pathway was efficiently integrated using Aspen Plus. A techno-economic analysis was performed in order to estimate the required capital investment and operating cost for the whole GC process, providing insights on individual capital cost requirements for the urea, dimethyl carbonate, and GC production sections. A total capital cost of $192.1 MM, and a total operating cost of $225.7 MM/y were estimated for the process. The total annualized cost was estimated as $1,558 USD/t of GC produced, competitive with current market price. Fri, 01 Mar 2024 00:00:00 GMT http://hdl.handle.net/10366/162117 2024-03-01T00:00:00Z http://hdl.handle.net/10366/162115 [EN] A systematic techno-economic analysis for the comparison of different routes for grape seed oil extraction was performed, which included hexane extraction as benchmark process, and the use of supercritical fluids (SC), specifically SC-CO2 and SC-CO2+ethanol as co-solvent. The processes have been modeled rigorously using Aspen Plus. The results show that the use of hexane is the most efficient (13.06 % recovery) and, only by using a co-solvent together with SC-CO2, the yield is similar (12.98 %). However, the cost increases from 6.31 USD/kg of extracted grape oil to 8.61 USD/kg of oil extracted, even though it is cheaper than the use of SC-CO2 alone. The investment cost is almost twice using the co-solvent compared to the traditional one ($9.72 MM vs $4.95 MM). SimaPro has been used to perform the lifecycle assessment (LCA). Similar results are found when the LCA analysis is performed as long as the energy mix is the current one. The high energy consumption of SC based systems results in high carbon emissions. However, combining electrification and renewable energy allowed the SC-CO2+ethanol system to reduce by 25 % the CO2 emissions per kg of oil produced by the hexane system. The economic evaluation performed provides the estimation of the CAPEX and OPEX for each alternative. Thu, 01 Feb 2024 00:00:00 GMT http://hdl.handle.net/10366/162115 2024-02-01T00:00:00Z http://hdl.handle.net/10366/162113 [EN] A mechanistic model to evaluate the stability of amylase and protease under food stain removal conditions has been developed. The mechanism was determined identifying the significant factors for each enzyme based on response surface methodology. The amylase stability was jeopardized by the deprotonated peracid-based bleach, the interaction pH–temperature, and the protonated peroxide-based bleach promoted by manganese-based bleaching catalyst. The stability of the protease decreased in presence of protonated peracid-based bleach, acid-base equilibria species from peroxide-based bleach as well as temperature and pH. This work integrates the main mechanisms based on non-linear differential equations for each enzyme. In addition, a kinetic dissolution model was included for the enzymatic spherical particles. The models were validated, obtaining a determination coefficient of 0.84 and 0.90 for amylase and protease respectively for the training data set. For the validation set, a determination coefficient of 0.91 and 0.90 were obtained for amylase and protease, respectively. Mon, 01 Jan 2024 00:00:00 GMT http://hdl.handle.net/10366/162113 2024-01-01T00:00:00Z http://hdl.handle.net/10366/162110 [EN]This work evaluates a systematic comparison between the production of methanol and methane using CO2 and renewable hydrogen. CO2 is captured from point and dilute sources using aqueous MEA solutions and a conventional DAC process. Hydrogen is obtained through water electrolysis, powered by PV panels and wind turbines. First, a techno-economic evaluation is developed to detail the characteristics of the production facilities and the renewable energy systems. Finally, a Facility Location Problem (FLP) is developed to determine the centralized and decentralized CO2 use across Spain. This supply network is formulated as a mixed-integer linear programming (MILP) problem, selecting the optimal amount of CO2 to capture, the number and location of the facilities, the distribution of the PV panels for a fixed available area in the territory, and the number of wind turbines across the 47 Spanish peninsular provinces. Methanol is the selected product, with prices between 1,000–2,600 €/tMethanol. MEA solutions are preferred over DAC. Methane production is also considered through decentralized CO2 capture due to abundant CO2 availability and high transportation costs. A sensitivity analysis was performed, obtaining prices from 18.97 to 20.36 €/MMBTU to 8.90–9.09 €/MMBTU in the years 2022 and 2050, covering 5 times the methane production for that period. The implementation of carbon taxes could lower methane prices to around 2–3 €/MMBTU by 2050, aligning closely with natural gas prices. Mon, 01 Jan 2024 00:00:00 GMT http://hdl.handle.net/10366/162110 2024-01-01T00:00:00Z http://hdl.handle.net/10366/162109 [EN]An integrated facility to produce surfactants from manure and CO2 is conceptually designed avoiding the use of external chemicals. Cow and pig manure is anaerobically digested to produce biogas and digestate. The biogas is used to produce hydrogen via reforming. The digestate provides the nutrients for algae growing. From the algae, lipids and starch are extracted and broken down to produce oil, and glucose. Finally, the alkyl polyglucoside surfactant (APG) is produced from hydrogenated oil and glucose. The yield of the facility reaches 0.08 kgAPG/kgmanure (0.47 kgAPG/kgalgae). A facility of 252 kt/yr of APG, consumes 17.7 MW of thermal energy and steam and 7.9 MW of electricity, capturing 788 kt/yr of CO2. The investment adds up to 196 M€ with a production cost of 0.17€/kgAPG. A scale down study is also developed. Current market price of APG can be achieved processing the waste of over 1.4 k cows and 11.4 k pigs. Thu, 01 Feb 2024 00:00:00 GMT http://hdl.handle.net/10366/162109 2024-02-01T00:00:00Z http://hdl.handle.net/10366/156617 [EN]The effects of climate change, such as droughts and decreased rainfall, as well as population growth and globalization are aggravating the availability of water, energy and food. As a result, meeting the population's demand will be a major challenge in the near future. For this reason, assessing the situation of the water-energy-food (WEF) nexus is of great importance to know the vulnerabilities of the system and take actions to correct or improve them. The contribution of this work is the formulation of a composite index called the WEF-Waste index that includes 13 indicators, 4 of which are indicators to measure aspects of the water sector that include availability, independence, treatment and recycling; 3 energy indicators that include availability, independence and renewable energy; 4 food indicators that measure availability, food independence, ecological area planted and food waste; and 2 urban solid waste indicators that measure the level of separation and reuse. The WEF-Waste index was evaluated in Spain at the national level and in the 17 autonomous communities over a period of 10 years in order to focus on the spatial and temporal distribution pattern of the WEF nexus. Results show that the indicator with the lowest scores over the years was water availability, which indicates a very important water deficiency. On the other hand, high values in the water treatment indicator were obtained, showing that a high percentage of the water supplied to the network and used is processed in wastewater treatment plants. The WEF-Waste index has an improving trend from 2010 to 2014. However, by 2016 it suffered a decay and from that year to 2020, it again presented a positive trend in the scores of the communities. Sun, 01 Jan 2023 00:00:00 GMT http://hdl.handle.net/10366/156617 2023-01-01T00:00:00Z