Search Results (44)

The drying process of microcrystalline cellulose and adipic acid particles in a cylindrical fluidized bed was investigated using the Gaussian spectral technique to monitor fluid–dynamic regime transitions associated with surface moisture loss. Pressure fluctuation signals were recorded and analyzed to assess hydrodynamic behavior. Excess moisture significantly alters the bubbling characteristics of the bed, leading to instability in the fluidization regime. The results demonstrated that the Gaussian spectral technique effectively captured these hydrodynamic changes, particularly at the critical moisture content threshold, when compared with the drying rate curves of the materials. For microcrystalline cellulose and adipic acid particles, it is reasonable to conclude that a mean central frequency above 5.75–6.0 Hz and a standard deviation exceeding 3.7–3.8 Hz correspond to a bubbling regime, indicating that the critical drying point has been reached. This approach provides a non-intrusive and sensitive method for identifying transitions in the drying process, offering a valuable tool for real-time monitoring and control. The ability to track fluidization regime changes with high precision reinforces the potential of this technique for optimizing drying operations in the pharmaceutical, food, and chemical industries. Full article

In this study, alkali-activated mortars were prepared using two different types of fine aggregates: natural sand and biomass bottom ash. These mortars were used as a repair material for structures constructed using old reinforced concrete structures based on Ordinary Portland cement (OPC). Experimental studies have shown that the alkali-activated slag mortar with biomass bottom ash (BBA) from the bubbling fluid bed meets the repair mortar class R1 according to EN 1504-3. The suitability of such repair mortar is determined by the good adhesion properties of the alkali-activated slag binder to old OPC concrete. The adhesion after 28 days was 0.31 MPa and the samples broke off at the repair matrix. The AAC/BBA repair mortar had a compressive strength of 18.69 MPa, the shrinkage due to drying deformations consisted of 0.1903% after 28 days. Alkali-activated slag mortars are effective in repairing, renewing and rebuilding damaged OPC concrete structures. Full article

The heat transfer (HT) characteristics of cylindrical biomass particles (CBPs) in fluidized beds (FBs) are important for their drying, direct combustion, and thermochemical transformation. To provide a deeper insight into the complex mechanisms behind the HT behaviors involving CBPs, this study developed a cylindrical particle HT model within the framework of computational fluid dynamics coupled with the discrete element method (CFD-DEM) in which the CBPs were characterized by the super-ellipsoid model, which has the unique merit of striking a balance between computational accuracy and efficiency. The newly developed heat transfer model considers particle–particle (P-P), particle–wall (P-W), and fluid–particle (F-P). Its accuracy was verified by comparing the numerical results with the experimental infrared thermography measurements in terms of the temperature evolution of the cylindrical particles. The effects of the gas velocity, inlet temperature, and thermal conductivity of particles on the HT behaviors of the CBPs were investigated comprehensively. The results demonstrated the following: (1) Gas velocity can improve the uniformity of bed temperature distribution and shorten the fluctuation process of bed temperature uniformity. (2) A 26.8% increase in inlet temperature leads to a 13.4% increase in the proportion of particles with an orientation in the range of 60–90°. (3) The thermal conductivity of particles has no obvious influence on the bed temperature, convective HT rate, or orientation of particles. Full article

Many biological markers of normal and disease states can be detected in saliva. The benefits of saliva collection for research include being non-invasive, ease of frequent sample collection, saving time, and being cost-effective. A small volume (≈1 mL) of saliva is enough for these analyses that can be collected in just a few minutes. For “dry” saliva paper matrices, additional drying times (about 30 min) may be needed, but this can be performed at room temperature without the need for freezers and specialized equipment. Together, these make saliva an ideal choice of body fluid for many clinical studies from diagnosis to monitoring measurable biological substances in hospital settings, remote, and other general locations including disaster areas. For these reasons, we have been using saliva (dry as well as wet) from astronauts participating in short- and long-duration space missions for over two decades to conduct viral, stress, and immunological studies. We have also extended the use of saliva to space analogs including bed rest, Antarctica, and closed-chamber studies. Saliva is a biomarker-rich and easily accessible body fluid that could enable larger and faster public health screenings, earlier disease detection, and improved patient outcomes. This review summarizes our lessons learned from utilizing saliva in spaceflight research and highlights the advantages and disadvantages of saliva in clinical diagnostics. Full article

The application of the hydrodynamic method has enhanced the extraction of coal bed methane (CBM). In this method, fracturing fluid rapidly penetrates the coal reservoir, altering its intrinsic pore structure and microscopic mechanical properties. These changes impact the properties of the coal reservoir and CBM depletion. It is, therefore, crucial to explore how these micro-characteristics evolve following water invasion. In this context, using nanoindentation tests, the microscopic characteristics of three coal samples were measured under dry conditions and at water saturations corresponding to 44% and 75% relative humidity. The influence of water immersion on the pore structure was also assessed using mercury injection experiments. Moreover, cluster analysis was used to categorize the extensive measured data into three sub-components: fractures (large pores), inertinite, and vitrinite, to investigate the impact of water saturation on microscopic properties. The findings indicate that cluster analysis is well-suited to these data, showing excellent agreement with porosity and maceral tests. The relationship between the elastic modulus and hardness of dry and wet coal samples varies across the sub-components. There is a notable dependency in the case of vitrinite, whereas water content tends to reduce this dependency. It is also found that water content negatively affects elastic modulus and hardness and reduces the anisotropy ratio. The mechanical properties of inertinite are highly responsive to water immersion, whereas vitrinite exhibits lesser sensitivity. The softening mechanisms of coal when immersed in water, such as calcite phase dissolution, swelling stress fracturing, and weakening of macerals, are identified. This study offers new perspectives on the impact of moisture on the alteration of micromechanical properties in coal. Full article

Recent research advances and technological developments of spouted bed reactors (SBRs) have been discussed in this work. SBR has aroused increasing interest since their invention in 1955 due to its flexibility in processing different feedstocks and the high process yields that can be achieved due to its characteristic fluid dynamics. However, even though highly satisfactory results have been obtained at the laboratory scale for different applications (i.e., drying or thermochemical reactions, among others), their full implementation at an industrial level is still scarce, mainly due to the challenges encountered for their scale-up. In this work, an initial short description of SBR and configurations is followed by a review of the main experimental activities that have been conducted at different scales in the period 2013–2023. Advanced solutions such as multi-unit reactors and the use of rectangular geometries instead of the classical cylindrical ones have arisen as potential areas for further study and development to achieve a reliable implementation of the spouted bed technology at an industrial scale. Full article

The peel from mango (Mangifera indica L.) var. “Kent” is a good source of bioactive compounds (BC). BC are sensitive to oxygen, temperature, humidity, light, and gastrointestinal digestion, which change their biological function and health benefits. This study was aimed at the extraction of the bioactive compounds present in the peel from mango var. “Kent” and their microencapsulation using spray drying (SD) and spout-fluid bed drying (SFB). The bioaccessibility of BC was also evaluated. Two consecutive extractions of 90 min at 30 °C and 80% v/v ethanol were used. The microcapsules produced via SD and SFB presented high retention and encapsulation percentages of the bioactive compounds; nevertheless, SFB showed better protection during in vitro gastrointestinal digestion. The non-encapsulated extract showed a decrease (p ≤ 0.05) of BC at the end of in vitro gastrointestinal digestion. The results show that these microcapsules might be used in the food industry as an ingredient to produce functional foods and, thereby, to obtain the health benefits that the bioactive compounds provide. Full article

Probiotic bacteria confer a range of health benefits and are a focus of a growing number of studies. One of the main issues is their stability during drying and storage, which is why techniques, such as fluid bed drying and coating or treatment with stress factors during culturing, are utilized. The methods of the evaluation of probiotic viability and quality are, however, lacking and we need a way of distinguishing between different subpopulations of probiotic bacteria. To address this issue, imaging flow cytometry (IFC) has been utilized to assess cells after simulated in vitro digestion of dried and coated preparations treated with pH stress and heat shock. Samples were analyzed fresh and after 12 months of storage using RedoxSensor green and propidium iodide dyes to assess metabolic activity and cell membrane integrity of the cells. The results were then used to design a drying process on an industrial scale and evaluate the economic factors in the SuperPro Designer v13 software. Based on the number of biologically active and beneficial cells obtained utilizing tested methods, the coating process and treatment with heat shock and pH stress have been the most effective and up to 10 times cheaper to produce than only by drying. Additionally, samples after 12 months of storage have shown an increase in the proportion of cells with intermediate metabolic activity and small amounts of cell membrane damage, which are still viable in probiotic products. This subpopulation of bacteria can still be considered live in probiotic products but is not necessarily effectively detected by pour plate counts. Full article

This paper shows the design of an injector, using carbon nanotubes as inkjet material, implemented in a 3D printer. According to the available literature, few injectors are capable of depositing material. Due to the lack of information, the central part of this research is to develop a suitable device for ink injection that is capable of applying the Fused Deposition Modeling (FDM) method to print nanomaterial ink. The injector was designed using a CAD program based on an open-source desktop 3D printer, which allows it to be modified according to the needs of the injector. This prototype was manufactured in aluminum alloy 7075T6. Computational fluid dynamics (CFD) were carried out to analyze the behavior of the fluid when it passes through the injector, obtaining parameters such as pressure, velocity, and vorticity. An experimental matrix of the injector operation was carried out to achieve an adequate printing speed. The results show that the optimum speed was 250 ms, considering that a temperature of 100 °C is needed in the heated bed to dry the ink so that it does not undergo expansion. Full article

The pharmaceutical industry is in the midst of a transition from traditional batch processes to continuous manufacturing. However, the challenges in making this transition vary depending on the selected manufacturing process. Compared with other oral solid dosage processes, wet granulation has been challenging to move towards continuous processing since traditional equipment has been predominantly strictly batch, instead of readily adapted to material flow such as dry granulation or tablet compression, and there have been few equipment options for continuous granule drying. Recently, pilot and commercial scale equipment combining a twin-screw wet granulator and a novel horizontal vibratory fluid-bed dryer have been developed. This study describes the process space of that equipment and compares the granules produced with batch high-shear and fluid-bed wet granulation processes. The results of this evaluation demonstrate that the equipment works across a range of formulations, effectively granulates and dries, and produces granules of similar or improved quality to batch wet granulation and drying. Full article

Adhesion is one of the main factors responsible for the probiotic properties of bacteria in the human gut. Membrane proteins affected by cellular damage are one of the key aspects determining adhesion. Fluid-bed-dried preparations containing probiotic bacteria were analyzed in terms of their stability (temperature of glass transition) and shelf life in different conditions (modified atmosphere, refrigeration). Imaging flow cytometry was utilized to determine four subpopulations of cells based on their physiological and morphological properties. Lastly, adhesion was measured in bacteria cultured in optimal conditions and treated with heat shock. The results show that the subpopulations with no or low levels of cell membrane damage exhibit the ability to adhere to Caco-2 cells. The temperature of protein denaturation in bacteria was recorded as being between 65 °C and 70 °C. The highest glass transition temperature (Tg) value for hydroxypropyl methylcellulose (used as a coating substance) was measured at 152.6 °C. Drying and coating can be utilized as a sufficient treatment, allowing a long shelf-life (up to 12 months). It is, however, worth noting that technological processing, especially with high temperatures, may decrease the probiotic value of the preparation by damaging the bacterial cells. Full article

To investigate the pore structure distribution and the coupled heat and moisture transfer during the drying process of the grains, this study focuses on fixed-bed corn drying with varying levels of broken kernel rate. A model of internal flow and conjugate heat and mass transfer was established for the drying process. Random packing models of whole and half corn kernels with different proportions were generated using rigid body dynamics (RBD), and the porosity, airflow distribution, and coupling of temperature and moisture transfer in fixed beds with different levels of broken kernel rate were analyzed. A fixed-bed corn drying device was developed, and the effects of broken particle contents of 0%, 10%, 20%, and 30% on drying characteristics were studied. The research findings reveal that the radial porosity in the fixed bed exhibits an oscillating distribution, with the localized porosity decreasing as the broken kernel rate increases. Increasing the broken kernel rate intensifies the curvature of the airflow paths within the fixed bed, increasing the pressure drop in the bed. The broken kernels fill the gaps between the whole kernels, improving the uniformity of the velocity distribution within the fixed bed. Under various packing models, the average discrepancy between pressure drop obtained from Particle-resolved Computational Fluid Dynamics (PRCFD) simulations with experimental remains below 15%. The increase in broken kernel rate within the fixed bed enlarges the heat transfer area, resulting in an elevation of the transient heat transfer characteristic parameters during drying. Simultaneously, the broken kernel rate increases the surface area of mass transfer, thereby enhancing the moisture transfer rate within the fixed bed. Compared to the fixed bed without broken kernels (0%), which requires 560 min to dry the corn pile to a safe moisture of 14% (d.b.), the drying time is reduced by 60 min, 100 min, and 130 min for the respective broken kernel contents of 10%, 20%, and 30%, respectively. The PRCFD method successfully simulates the processes of convective heat and mass transfer in the fluid phase and thermal and mass diffusion in the solid phase, exhibiting a strong correlation with experimental data. Full article

Replacing the conventionally used steam reforming of methane (SRM) with a process that has a smaller carbon footprint, such as dry reforming of methane (DRM), has been found to greatly improve the industry’s utilization of greenhouse gases (GHGs). In this study, we numerically modeled a DRM process in lab-scale packed and fluidized beds using the Eulerian–Lagrangian approach. The simulation results agree well with the available experimental data. Based on these validated models, we investigated the effects of temperature, inlet composition, and contact spatial time on DRM in packed beds. The impacts of the side effects on the DRM process were also examined, particularly the role the methane decomposition reaction plays in coke formation at high temperatures. It was found that the coking amount reached thermodynamic equilibrium after 900 K. Additionally, the conversion rate in the fluidized bed was found to be slightly greater than that in the packed bed under the initial fluidization regime, and less coking was observed in the fluidized bed. The simulation results show that the adopted CFD approach was reliable for modeling complex flow and reaction phenomena at different scales and regimes. Full article

A thermal energy storage–updraft gasification device is a type of reactor that should be considered for use in solid waste gasification research that can save energy. However, the operating parameters and internal flow field during its operation remain unclear. In this study, a numerical model of the thermal energy storage–solid waste gasification device based on the computational fluid dynamics dense discrete phase model (CFD-DDPM) which had almost never been used before was established, and an innovative method that causes particles to be piled to simulate the gasification process was proposed according to the updraft fixed bed gasification characteristics; meanwhile, solid waste gasification experiments were conducted on the device. This study focused on the influence of moisture content and excess air coefficient on the gasification process of solid waste particles, and the velocity, pressure, temperature, and species distribution of the internal flow field of the device were analyzed. Simulation results showed that the higher the moisture content of particles, the greater the amplitude of changes in the internal physical field of the device. The fluid pressure drop is around 25 Pa–75 Pa for different working conditions. The combustible species of the gas of moist particles raise slightly with the increase in excess air coefficient, while the dry particles have the opposite effect. Compared with other gasification devices of the same type, the hydrogen production of this device is about 2–3 times higher. Our findings could facilitate the analysis, predict the operation status, and provide a theoretical basis for the improvement of this device. Full article

In this paper, a data preprocessing methodology, EDA (Exploratory Data Analysis), is used for performing an exploration of the data captured from the sensors of a fluid bed dryer to reduce the energy consumption during the preheating phase. The objective of this process is the extraction of liquids such as water through the injection of dry and hot air. The time taken to dry a pharmaceutical product is typically uniform, independent of the product weight (Kg) or the type of product. However, the time it takes to heat up the equipment before drying can vary depending on different factors, such as the skill level of the person operating the machine. EDA (Exploratory Data Analysis) is a method of evaluating or comprehending sensor data to derive insights and key characteristics. EDA is a critical component of any data science or machine learning process. The exploration and analysis of the sensor data from experimental trials has facilitated the identification of an optimal configuration, with an average reduction in preheating time of one hour. For each processed batch of 150 kg in the fluid bed dryer, this translates into an energy saving of around 18.5 kWh, giving an annual energy saving of over 3.700 kWh. Full article