Refine
Document Type
Way of publication
- Open Access (12)
Keywords
- CO2 methanation (7)
- Biogas upgrading (3)
- Biomethane production (3)
- Waste valorization (3)
- CO2 waste valorization (2)
- CeO2 (2)
- Cu catalysts (2)
- Green energy (2)
- Mixed-integer linear programming (2)
- Ni catalysts (2)
Institute
BTU
This work analyses the catalytic activity displayed by Cu/SiO2, Cu-Fe/SiO2 and Cu/FSN (Fe-SiO2 nanocomposite) catalysts for the Reverse Water Gas Shift reaction. Compared to Cu/SiO2 catalyst, the presence of Fe resulted on higher CO’s selectivity and boosted resistances against the constitution of the deactivation carbonaceous species.
Regarding the catalytic performance however, the extent of improvement attained through incorporation Fe species strongly relied on the catalysts’ configuration. At 30 L/gh and H2:CO2 ratios = 3, the performance of the catalysts’ series increased according to the sequence: Cu/SiO2 < Cu-Fe/SiO2 << Cu/FSN. The remarkable catalytic
enhancements provided by Fe-SiO2 nanocomposites under different RWGS reaction atmospheres were associated to enhanced catalyst surface basicity’s and stronger Cu-support interactions. The catalytic promotion achieved by Fe-SiO2 nanocomposites argue an optimistic prospective for nanocomposite catalysts within future
CO2-valorising technologies.
By evaluating the functional modifications induced by Zr and Fe as dopants in Pt/CeO2‐MOx/Al2O3 catalysts (M = Fe and Zr), the key features for improving water gas shift (WGS) performance for these systems have been addressed. Pt/ceria intrinsic WGS activity is often related to improved H2 surface dynamics, H2O absorption, retentions and dissociation capacities which are influenced greatly by the support nature. Two metals, iron and zirconia, were chosen as ceria dopants in this work, either in separate manner or combined. Iron incorporation resulted in CO‐redox properties and oxygen storage capacities (OSC) improvement but the formation of Ce‐Fe solid solutions did not offer any catalytic benefit, while the Zr incorporation influenced in a great manner surface electron densities and shows higher catalytic activity. When combined both metals showed an important synergy evidenced by 30% higher CO conversions and attributed to greater surface electron densities population and therefore absorption and activity. This work demonstrates that for Pt/ceria catalysts OSC enhancement does not necessarily imply a catalytic promotion.
The circular economy is calling for the rapid use of already-developed renewable energies. However, the successful implementation of those new fuels is limited by economic and political issues. For instance, in the Brandenburg region, Germany, biogas production from anaerobic digestion of biomass and wastes is a current alternative. However, the upgrading biogas to biomethane is still challenging and the economic viability is unknown. Therefore, we performed an economic analysis for biogas upgrading to biomethane in the Brandenburg region. Five biogas plant sizes were analyzed by the method of discounted cash flow. This method yields the net present value of the projects, thus revealing the profitability or non-profitability of the plants. Results indicate profitable outputs for medium and large plants, with net present values between 415 and 7009 k€. However, the smallest plants have net present values from -4250 to -3389 k€, thus needing further economic efforts or subsidies to reach profitability. Indeed, biomethane prices should range between 52.1 and 95.6 €/MWh to make these projects profitable. Combinations of 50% of investment subsidized and 11.5 €/MWh feed-in tariffs subsidies could make the projects reach profitability. These findings reveal that political actions such as green policies and subsidies are needed to implement green energy. This case study should serve as a potential tool for policy-makers toward a sustainable bioeconomy.
Herein a novel path is analysed for its economic viability to synergize the production of biomethane and dimethyl ether from biogas. We conduct a profitability analysis based on the discounted cash flow method. The results revealed an unprofitable process with high cost/revenues ratios. Profitable scenarios would be reached by setting prohibitive DME prices (1983–5566 €/t) or very high feed-in tariffs subsidies (95.22 €/MWh in the best case scenario). From the cost reduction side, the analysis revealed the need of reducing investment costs. For this purpose, we propose a percentage of investment as incentive scheme. Although the size increase benefits cost/revenues ratio, only the 1000 m3/h biogas plant size will reach profitability if 90% of the investment is subsidized. A sensitivity analysis to check the influence of some important economical parameters is also included. Overall this study evidences the big challenge that our society faces in the way towards a circular economy.
Nickel Phosphide Catalysts as Efficient Systems for CO2 Upgrading via Dry Reforming of Methane
(2021)
This work establishes the primordial role played by the support’s nature when aimed at the constitution of Ni2P active phases for supported catalysts. Thus, carbon dioxide reforming of methane was studied over three novel Ni2P catalysts supported on Al2O3, CeO2 and SiO2-Al2O3 oxides. The catalytic performance, shown by the catalysts’ series, decreased according to the sequence: Ni2P/Al2O3 > Ni2P/CeO2 > Ni2P/SiO2-Al2O3. The depleted CO2 conversion rates discerned for the Ni2P/SiO2-Al2O3 sample were associated to the high sintering rates, large amounts of coke deposits and lower fractions of Ni2P constituted in the catalyst surface. The strong deactivation issues found for the Ni2P/CeO2 catalyst, which also exhibited small amounts of Ni2P species, were majorly associated to Ni oxidation issues. Along with lower surface areas, oxidation reactions might also affect the catalytic behaviour exhibited by the Ni2P/CeO2 sample. With the highest conversion rate and optimal stabilities, the excellent performance depicted by the Ni2P/Al2O3 catalyst was mostly related to the noticeable larger fractions of Ni2P species established
Profitability studies are needed to establish the potential pathways required for viable biomethane production in the Brandenburg region of Germany. This work study the profitability of a potential biomethane production plant in the eastern German region of Brandenburg, through a specific practical scenario with data collected from a regional biogas plant located in Alteno (Schradenbiogas GmbH & Co. KG). Several parameters with potential economic influence such as distance of the production point to the grid, waste utilization percentage, and investment, were analyzed. The results illustrate a negative overall net present value with the scenario of no governmental investment, even when considering trading the CO2 obtained throughout the process. Subsidies needed to reach profitability varied with distance from 13.5 €/MWh to 19.3 €/MWh. For a fixed distance of 15 kms, the importance of percentage of waste utilization was examined. Only 100% of waste utilization and 75% of waste utilization would reach profitability under a reasonable subsidies scheme (16.3 and 18.8 €/MWh respectively). Concerning the importance of investment, a subsidized investment of at least 70% is demanded for positive net present values. Besides, the sensitivity analysis remarks the energy consumption of the biogas upgrading stage, the electricity price, and the energy consumption of biogas production as major parameters to be tackled for the successful implementation of biogas upgrading plants. The results here obtained invite to ponder about potential strategies to further improve the economic viability of this kind of renewable projects. In this line, using the CO2 separated to produce added-value chemicals can be an interesting alternative.
This study delivers useful understanding towards the design of effective catalytic systems for upgrading real CO2erich residual streams derived from biomass valorization. Within this perspective, a catalysts' series based on (5 wt%) Cu - (X wt%) Mn/Al2O3with X¼0, 3, 8, and 10 is employed. The improved catalyst performance achieved through Mn incorporation is ascribed to enhanced Cu dispersions and promoted surface basic concentrations. Under standard RWGS conditions, the highest reaction rates achieved by(5 wt%) Cu - (8 wt%) Mn/Al2O3catalyst were associated to improved Cu dispersions along with the constitution of highly active Cu-MnOxdomains. Remarkably, variations on the optimal Cu to Mn ratios were detected as a function of the RWGS reaction conditions. Thus, under simulated CO2-rich residual feedstock's, i.e., in presence of CO and CH4, the further promotion on the Cu dispersion attained by the larger amounts of MnOxrendered the (5 wt%) Cu - (10 wt%) Mn/Al2O3catalyst as the best performing sample. Overall, the presented outcomes underline operative strategies for developing catalytic systems with advanced implementation potentialities.
In this work the economic performance of valorizing the gaseous stream coming from hydrothermal carbonization (HTC) of olive tree pruning is presented as a novel strategy to improve the competitiveness of HTC. The valorization of the commonly disregarded gaseous stream produced in this thermochemical treatment was proposed via the Reverse Water–Gas Shift reaction. This allows to obtain syngas for selling and therefore improving the overall economic performance of the process. To this end, three plant sizes were selected (312.5, 625 and 1250 kg/h of biomass processing). The parameters with a higher share in the total cost distribution along with the revenues from the hydrochar and the syngas selling were further evaluated. The results evidenced that with the assumptions taken, the overall process is still not profitable. To reach profitability, syngas selling prices between 2.2 and 3.4 €/m3 are needed, revealing that this proposal is not economically attractive. Alternatively, a lack of competitiveness in the current market is revealed with hydrochar selling prices between 0.41 and 0.64 €/kg to make the project profitable. The catalyst cost, sharing approximately 20% of the total cost, is the parameter with the highest impact in the total economics of the process. The second one is the hydrogen price production, representing almost 16% of the total. Investment subsidies are also examined as a potential tool to cover part of the initial investment. These results evidenced that further efforts and measures are needed to push forward in the path towards circular economy societies.
Seeking for advanced catalytic systems for the CO2 methanation reaction, the use of Ni supported catalysts over redox materials is often proposed. Profiting the superior redox properties described for layered perovskite systems, this work has investigated a series Ni supported YMn1-xAlxO3 (x = 0, 0.2, 0.5, 0.8, 1) perovskite catalysts.
The obtained results evidenced the impact of the support nature on the systems redox properties and Ni-support interactions. Within the catalysts series, the greater methanation rates displayed by Ni/YMn0.5Al0.5O3 catalyst (0.748 mmolCO2,conv.s–1 gNi –1 at 400 ◦C and 60 L/gh) were associated to the interplay between the support redox
properties and superior Ni dispersion. The improved redox behavior attained through the Al-incorporation (up to x = 0.5) was associated to the layered perovskite structures which, being distorted and constituted by smaller crystal sizes, facilitated the behavior of Mn redox couples as surface species readily interconverted. Exhibiting
catalytic performances comparable to precious metals based catalysts, this work proposes the Ni/YMn0.5Al0.5O3 catalyst as an effective system for the CO2 methanation reaction.
CO2 methanation: on the modeling of reacting laminar flows in structured Ni/MgAl2O4 catalysts
(2022)
CO2 methanation: on the modeling of reacting laminar flows in structured Ni/MgAl2O4 catalysts
(2022)
State-of-the-art approaches for membrane cleaning scheduling have focused on the Mixed-Integer Nonlinear Programming (MINLP) formulation so far, a strategy leading to a combinatorial problem that does not capture accurately the dynamic behaviour of the system. In this work, the Reverse Osmosis (RO) cleaning scheduling problem is solved using a novel approach based on the Multistage Integer Nonlinear Optimal Control Problem (MSINOCP) formulation. The approach produces an automated solution for the membrane cleaning scheduling, which also obviates the need for any form of combinatorial optimisation. Two different simulations, for 26 and 52 periods of operation (each period with a duration of one week), are carried out to illustrate the application of the proposed framework and the total cost is 1.17 and 2.48 10⁷ €, respectively. The RO network configuration considers 2 stages, each with 3 individual RO modules. The results show evidently that the new proposed solution framework can solve successfully this type of problems, even for large scale configurations, long time horizons and arbitrary realistic complexity of the underlying dynamic model of the RO process considered.
Various pests which diminish the quality of the fruit have a big influence on the organic banana production in the Piura region of Peru (and not only) and prevent it from being sold on the international market. In this study, a framework for facilitating the prediction of the pest incidence in organic banana crops is developed. To achieve this, a data acquisition system with smart sensors is implemented to monitor the meteorological variables that influence the growth of the pests. The proposed framework is utilised for the assessment of various mathematical representations of the pest incidence. These models are adapted from population growth functions and built in such way as to predict the behaviour of the insects at non-regular time intervals. A hybrid approach, combining mechanistic and data-based methods is utilised for the development of the models. Both linear and nonlinear dynamic relationships with the temperature are assumed. The results show that nonlinear model representations have greater accuracy (a fit index of more than 70%), which provides a basis for improving pest management actions on the organic banana farms.
In this contribution, a dynamic first principles model of an existing 3.01 MW natural gas fired water bath heater (WBH) in operation at the Takoradi Distribution Station (TDS) in Ghana is developed primarily to predict the outlet temperature of the natural gas stream being heated. The model is intended to be applied during operations to provide useful data to optimise material and energy consumption, as well as minimise CO2 emissions. Due to the low thermal efficiencies of WBHs, even small improvements in efficiency can result in significant savings. The firetube and process coils are both modelled as onedimensional (1D) thin-walled tubes and the entire model incorporates mass and energy conservation equations, heat transfer rate relations and rigorous thermodynamic p-V-T relations. In contrast to what commonly exists in literature, this model accurately estimates the enthalpy change of the natural gas stream being heated by accounting for its enthalpy departure correction term due to pressure, in addition to the ideal gas heat capacity relation which is a function of only temperature. The coupled ordinary differential and algebraic equations are implemented using gPROMS® ModelBuilder® V4.2.0, a commercial modelling and simulation software. Verification of the model results showed good agreement between the model predictions and actual on field measurements. With excess air at 15%, the simulation results closely approximate measured data with an absolute error of about 0.31 %. More importantly, the results show that significant savings of up to 30% per annum can be made through optimal operation of the water bath heater.
A first contribution of this paper is an overview of the research efforts and contributions over several decades in the area of scheduling maintenance optimization for decaying performance dynamic processes. Following breakthrough ideas and implementation in the area of heat exchanger networks for optimal scheduling of cleaning actions subject to exchanger surface fouling, these concepts were transferred successfully to the area of scheduling catalyst replacement actions in catalytic reactor networks. This necessary overview leads to the main, second contribution aimed with this work: its application to restorative maintenance scheduling in the area of RON regeneration actions planning, as well as point to new areas where this approach can be fruitfully applied to and extended into in the near future – particularly enhancing model descriptions that include general types of planning uncertainty. The effectiveness and efficacy of the approach is demonstrated computationally in this work.
Spray drying is a basic unit operation in several process industries such as food, pharmaceutical, ceramic, and others. In this work, a Eulerian-Lagrangian three-phase simulation is presented to study the drying process of barbotine slurry droplets for the production of ceramic tiles. To this end, the simulated velocity field produced by a spray nozzle located at the Institute of Ceramic Technology in Castelló (Spain) is benchmarked against measurements obtained by means of laser Doppler anemometry in order to validate the numerical model. Also, the droplet size distribution generated by the nozzle is obtained at operating conditions by means of laser diffraction and the data obtained are compared qualitatively to those found in the literature. The characteristic Rosin-Rammler droplet size from the distribution is introduced thereafter in the three-phase simulation to analyse the drying kinetics of individual droplets. The model predicts the theoretical linear evolution of the square diameter (D²-law), and the temperature and mass exchange with the environment. The proposed model is intended to support the design and optimization of industrial spray dryers.
Nature has provided some of the most ingenious and elegant solutions to complex problems over millions of years of refining through evolution. The adaptation of Nature´s solutions to engineering problems is a recent trend which has opened opportunities for improvement in many areas ranging from Architecture to Chemical Engineering. In particular, the use of fractal geometries on heat exchangers is a recent design trend. Recent investigations highlight the benefit of implementing fractal-based geometries on the tube side of shell and tube heat exchangers. A complete evaluation of such devices by assessing the performance of the shell side has not been undertaken, though. Here, we present a systematic numerical assessment of the shell side of a tree-like shaped heat exchanger. Key performance parameters, i.e. temperature change, pressure drop and coefficient of performance, are obtained and compared to those of a straight tube, in order to fully understand the potential of the application of fractal-based shapes to the design of heat exchangers.
Traditional food supply chains are often centralised and global in nature. Moreover they require a large amount of resource which is an issue in a time with increasing need for more sustainable food supply chains. A solution is to use localised food supply chains, an option theorised to be more sustainable, yet not proven. Therefore, this paper compares the two systems to investigate which one is more environmentally friendly, cost efficient and resilient to disruption risks. This comparison between the two types of supply chains, is performed using MILP models for an ice cream supply chain for the whole of England over the period of a year. The results obtained from the models show that the localised model performs best environmentally and economically, whilst the traditional, centralised supply chain performs best for resilience.