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Optimizing the gasification characteristics of bio-oil distillation sludge by obtaining co-pyrolysis char with walnut shells
Get PDFThe presence of bio-oil distillation sludge (DS) disrupts biomass refining and poses health risks. This study investigates DS utilization in industrial bio-oil refining through co-pyrolysis with walnut shell (WS). Char characterization elucidates structural changes induced by co-pyrolysis. Observations show increased DS ratios smoothened the pleated structure of W3D1, with heightened graphitized structure observed at higher DS ratios through Raman analysis. Gasification indices (R0.5 and R0.9) indicate significant enhancements through co-pyrolysis. Mineral composition analysis revealed silicon in DS reduced ash deposition, while WS blending increased deposition risks due to potassium and calcium content. Investigation into the synergistic relationship between biochar’s carbonaceous structure parameters and gasification indices emphasized stronger correlations with R0.9, indicating pronounced synergy in later gasification stages.Optimizing the gasification characteristics of bio-oil distillation sludge by obtaining co-pyrolysis char with walnut shellspublishedVersio
Enhancing Extrusion Performance: Macroscopic Analysis of Dispersive Mixing Sections
Get PDFDispersion is a critical process within the extrusion industry. The attention of this study is drawn to the deficiency in dispersive mixing quality in single screw extruders compared to their twin screw counterparts. This study outlines an approach that is used to evaluate and quantify the quality of dispersive mixing sections, which are commonly added to single screw extruders to compensate for this inherent lack of dispersive mixing quality. The approach centers around employing micro-level dispersion models that describe the macro-breakup of agglomerates—specifically, rupture and erosion. These models are integrated with Computational Fluid Dynamics to quantify the particle size of solid additives before, during, and after traversing these crucial mixing sections. Using a non-isothermal Generalized Newtonian Fluid model with particle tracking and dispersion kinetics modeling. This new methodology facilitates swift analysis of mixing sections and offers a fresh avenue to study and optimize the extrusion process.publishedVersio
Simulating Vortex-Induced Vibrations in Sheared Current by Using an Empirical Time-Domain Model with Adaptive Parameters
No full textSlender marine structures, such as risers and power cables are subject to various loads, where Vortex-Induced Vibrations (VIV) is known to have a significant impact on accumulation of fatigue damage in the materials. The stochastic nature of VIV makes it challenging to do accurate fatigue predictions even when the underlying numerical model is deterministic. The current state-of-the-art is to model VIV response in the time-domain, where semi-empirical models have shown promising results. However, there are significant uncertainties in the fatigue prediction associated with assuming the values of the empirical model parameters. In the present paper, an efficient gradient-free optimization method is proposed to adapt the empirical parameters based on curvature measurements from model tests. Prior to the optimization problem, a global sensitivity analysis was applied to determine which parameters that have the largest influence on relevant quantities of interest. A variance-based sensitivity analysis method using Sobol’ indices was used together with a Polynomial Chaos Expansion to increase the computational efficiency of the method. The yearly fatigue damage was computed for model tests with a riser in sheared current and simulated using the optimal, adaptive parameters. Using adaptive parameters improved the prediction of curvatures, including both the maximum curvature and identification of the dominating frequency related to the given curvature. The predicted maximum fatigue damage was also improved, especially for the in-line direction.publishedVersio
Nonlinear interpolated Variational Autoencoder for generalized fluid content estimation
Get PDFGeneralizing machine learning models for petroleum applications, especially in scenarios with limited and less varied training data compared to real-world conditions, remains a persistent challenge. This study introduces a novel method combining interpolation mixup with a Variational Autoencoder (VAE) and adaptable interpolation loss for downstream regression tasks. By implementing this approach, we generate high-quality interpolated samples, yielding accurate estimations. Experimental validation on a real-world industrial dataset focused on fluid content measurement demonstrates the superior performance of our method compared to other interpolation and regularization techniques. Our approach achieves over a 15% improvement on generalized out-of-distribution datasets, offering crucial insights for fluid content estimation and practical implications for industrial applications.publishedVersio
Novel Recuperated Power Cycles for Cost-Effective Integration of Variable Renewable Energy
Get PDFThe ongoing transition to energy systems with high shares of variable renewables motivates the development of novel thermal power cycles that operate economically at low capacity factors to accommodate wind and solar intermittency. This study presents two recuperated power cycles with low capital costs for this market segment: (1) the near-isothermal hydrogen turbine (NIHT) concept, capable of achieving combined cycle efficiencies without a bottoming cycle through fuel combustion in the expansion path, and (2) the intercooled recuperated water-injected (IRWI) power cycle that employs conventional combustion technology at an efficiency cost of only 4% points. The economic assessment carried out in this work reveals that the proposed cycles increasingly outperform combined cycle benchmarks with and without CO2 capture as the plant capacity factor reduces below 50%. When the cost of fuel storage and delivery by pipelines is included in the evaluation, however, plants fired by hydrogen lose competitiveness relative to natural gas-fired plants due to the high fuel delivery costs caused by the low volumetric energy density of hydrogen. This important but uncertain cost component could erode the business case for future hydrogen-fired power plants, in which case the IRWI concept powered by natural gas emerges as a promising solution.publishedVersio
The Influence of bipolar plate wettability on performance and durability of a proton exchange membrane fuel cell
Get PDFA significant surface wettability transition from hydrophobicity to hydrophilicity after long-term operation is observed in graphite bipolar plates of a proton exchange membrane fuel cell (PEMFC). Extensive in-situ electrochemical characterization was performed to investigate the impact of bipolar plate wettability on the performance and durability of two PEMFCs (named “New cell” and “Old cell”), which use the same membrane electrode assemblies but have new and aged bipolar plates, respectively. Two-phase flow simulations are conducted to analyze water transport within bipolar plate channels with different wettabilities, utilizing the volume of fluid method. The Old cell is found to have reduced performance and accelerated degradation compared to the New cell. The degradation is attributed to increased liquid water at the cathode, which increases mass transport resistance by obstructing active catalyst sites. Simulations further demonstrated that as the hydrophobicity of the channel surface decreases, liquid water flow transitions from discrete droplet flow to semi-slug/film flow, and ultimately to slug flow. This transition results in greater water accumulation in hydrophilic channels, leading to higher pressure drops, intensified pressure oscillations, and more frequent sharp pressure drop peaks. These effects amplify the risk of cathode flooding, relating to experimentally observed performance losses and accelerated degradation in the Old cell.publishedVersio
Development of CO2 dry ice heat pump system
Get PDFA refrigeration temperature below −50.0°C is highly required for the storage of vaccines and fishery catches using natural refrigerants such as CO2 (carbon dioxide). In this study, we have proposed and developed a unique refrigeration system using solid-state CO2 (dry ice) to achieve ultra-low temperatures below −70°C. The initial challenge was the evaporator blockage due to dry ice aggregation, causing system instability. A stainless-steel spiral coil (swirl promoter) was introduced at the evaporator/sublimator inlet to enhance heat transfer and alleviate the blockage problem. The system, which operates effectively at the triple point of approximately −60°C and 0.5 MPa, is further advanced to its limits by using a cyclone separator/evaporator in its latest stage. By integrating a cold recovery heat exchanger in a cylindrical vessel, the system can maintain ultra-low temperatures of approximately −70°C inside the recovery section, achieving a coefficient of performance of this system (COPsystem) of 1.2. Keywords: Natural Refrigerant, CarbonDdioxide, CO2 Refrigeration System, Dry Ice, Ultra-low TemperatureDevelopment of CO2 dry ice heat pump systemacceptedVersio
Industrial cold storage of fruit and berries - specific energy use and operational processes
Get PDFFruits and berries require due to their perishable nature specific storage conditions. During harvest season, products are stored in large quantities within the storage, resulting in high peak power requirements of the refrigeration system to maintain the setpoint temperature. Furthermore, the energy consumption is dependent on the type of system and their operational procedures. The present study showcases the specific energy consumption (SEC) of four Norwegian fruit and berry cold storages, with annual production volumes of 500 – 7000 ton/year. The SEC varies greatly between the factories due to the annual production volume, product types, frozen vs. fresh storage, equipment and operational procedures. Values of the overall SEC are found in the range between 85 – 512 kWh/ton of processed product and year. Additionally, waste from plum production is measured to be within 6 – 18.5% of the total production across the factories and years and the temperature and rel. humidity profile during storage is showcased.acceptedVersio
Comparative Assessments of At-Sea and Inland Low- and Medium-Pressure CO2 Transport
Get PDFDeveloping cost-efficient systems for transporting CO2 is key to accelerate the deployment of carbon capture and storage. The present work explores the impact of reducing the pressure of tank-based inland and at-sea transport on their techno-economic performance. The study uses established techno-economic models for CO2 transport, adjusted with the most up-to-date knowledge on costs of low-pressure containment and transport. Particularly, the impact of cargo tank material and design on the transport costs shows that low-pressure cargo tank systems can be 50% less expensive than medium-pressure systems if materials with similar price and strength can be used. This results in reductions in transport costs as high as 30% for long distances. This is partly driven by the currently suggested size limitation on medium-pressure shipping which limits its economies of scale. If this limitation is alleviated, the cost advantage of low-pressure shipping compared to medium-pressure is more limited (10-20%) although it remains advantageous. The same scaling effects on capacity were not found for truck and barge inland transport, thus yielding 1-10% cost reductions of low- relative to medium-pressure transport. These results imply that future systems may combine medium-pressure inland and low-pressure at-sea transport, and that efficient solutions connecting the two must be investigated.Comparative Assessments of At-Sea and Inland Low- and Medium-Pressure CO2 TransportpublishedVersio