Low-temperature Drying Process Research Articles

Efficacy of mosquito repellent finishes on polyester fabrics using four essential oils against the vector of the West Nile virus, Culex pipiens (Diptera: Culicidae)

One of the most common ways to prevent mosquito bites is to use treated textiles, which can be used to repel mosquitoes in the form of nets, clothing, uniforms, and other items. Four eco-friendly essential oils: lemongrass (Cymbopogon citratus), eucalyptus (Eucalyptus camaldulensis), clove (Dianthus caryophyllus), and marjoram (Origanum vulgare), were evaluated and used to finish polyester fabrics (PE) to give them a pleasant odor and antibacterial properties, as well as mosquito repellent as medical textiles. A low-temperature drying process and thermal stabilization technique were used to bond the polyester to the fragrance-containing compounds. The effect of essential oil finishes on polyester textile properties has been studied using various techniques such as mechanical measurements, contact angle, ultraviolet tests, infrared spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, GC-MS analysis, etc. Scanning electron microscopy showed the physical adsorption of oil on PE surfaces and the penetration of oil droplets between PE fibers. The ability of polyester textiles treated with essential oils of lemongrass, eucalyptus, clove, and marjoram to kill Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus niger was also tested. Polyester fabrics treated with clove showed the strongest antibacterial effect, surpassing that of eucalyptus oil. 12 essential oils were screened to determine their superiority in repelling mosquitoes at a concentration of 1% through the CDC bottle and WHO cone tests. Cymbopogon citratus (LT50 = 60.03 min) oil was the most effective against Cx. pipiens, followed by Eucalyptus camaldulensis (LT50 = 61.65 min) and Dianthus caryophyllus (LT50 = 64.73 min) with CDC tests. It was found that finishing PE with clove and eucalyptus oils provided 76 and 68% protection from Culex pipiens mosquitoes, even after 6 cycles of washing. This approach is innovative because it meets the goal of having antibacterial, mosquito-repellent, and pleasant-smelling fabrics as requirements for economically viable medical textiles. There is an urgent need to engineer textiles, with or without insecticides, to effectively repel mosquitoes. Our data showed the efficiency of polyester fabric treated with clove and eucalyptus oils in repelling mosquitoes after 6 washings.

Effect of drying process on survival of environmental starter culture and nutritional value

Since Poland is one of the largest producers of rapeseed, the products of its processing – oil cake and rapeseed meal – could be promising alternatives in animal nutrition and, in the future, could also be used as food additives for humans. Fermentation, of these post-waste raw materials, eliminates the bitter taste and enriches the ferment with nutrients. Due to the fact that fermented rapeseed meal has a high water activity, it is possible to develop virtually all groups of microorganisms in it. Therefore, it is advisable to use a fixation method that will ensure the microbiological stability of the fermented product. The purpose of this study was to develop a starter culture for the fermentation of rapeseed meal and to investigate the effect of the drying process of fermented rapeseed meal on the survival rate of the starter culture. Fermented rapeseed meal was dried at 48°C for 33 h. After 30 days of storage of the dried meal, the survival rate of the starter culture was checked. Since the fermented rapeseed meal was meant to be used as feed for pigs, a low-temperature drying process was used in the study. Drying the fermented rapeseed meal made it possible to stabilize the product and allowed it to be stored safely, without signs of mold, for 30 days. The drying temperature of 48°C did not negatively affect the biological value of the nutrients or the survival of the starter culture in dried rapeseed meal after rehydration.

Study on Low Temperature Drying Characteristics of Chicken Manure in a Humid Environment

Drying chicken manure with exhaust air from a chicken house is a new manure management method developed in recent years. The majority of the heat for this drying method comes from the waste heat of ventilation in a poultry house or ambient air, so the drying process is carried out at a low temperature. When met with continuous rain or when the wet curtain in the chicken house is turned on, the relative humidity of the exhaust air from the chicken house will rise to high levels, and the drying process will be under the condition of high relative humidity. In order to explore the low-temperature drying characteristics of chicken manure in a humid environment, drying experiments were carried out in an experimental cross-flow drying system. The experiment mainly studied the effect of process parameters such as drying temperature, air velocity, and manure layer thickness on the low-temperature drying characteristics of chicken manure in a humid environment. The results showed that the low-temperature drying process of chicken manure in a humid environment only had a falling rate period, with no accelerated or constant rate period. Additionally, five common thin-layer drying models (Lewis model, Page model, Henderson and Pabis model, Wang and Singh model, and Exponential model) were applied to simulate the performance of the manure drying process. The exponential model was considered to be more suitable for describing the low temperature drying process in a humid environment, and the effective diffusivity changed between 6.37 × 10−7 and 2.17 × 10−6 m2/h.

Experimental research of the low-temperature drying process of tomato

The scientific research presents the results of studies aimed at studying the patterns of tomato drying, the change in moisture released per unit time over the entire surface of the raw material and the change in temperature in the product layers, as well as the dependence of the mass of the product per unit surface on the drying speed. Wavelength ranges with a high level of liquid absorption during tomato drying were experimentally determined. It has been established that the acceleration of the movement of liquid drops in a capillary-porous structure in the direction from the inner layer to the surface is carried out by creating the appropriate temperature and pressure in the inner layer of the product. The isotherms of desorption and sorption of tomato raw materials during the drying process are given.

Numerical Simulation of Heat and Mass Transfer in Sludge Low-Temperature Drying Process.

Based on the sludge mass transfer flux model, this paper conducts a simulation study on the drying characteristics of sludge under low-temperature environment and compares it with the previous experimental results. It is found that when the sludge moisture content is low, the change of its drying curve is basically consistent with the experimental results, but there is a large error when the sludge moisture content is 0.4-0.6. In order to better simulate sludge drying characteristics, a model of cracking and shrinkage coefficients based on sludge moisture content is proposed, and the effective diffusion coefficient and mass transfer coefficient are modified. The maximum error between simulation and experiment is reduced to 23.78%. Based on this model, the sludge drying mechanism was studied. It was found that heat transfer and diffusion played a major role in the initial stage of sludge drying, and diffusion played a major role in sludge drying 30 min later.

Experimental Study of the Volume Drying Shrinkage Characteristics of Lignite under Low Temperatures.

Low-temperature and humid drying experiments [temperatures of 20–30 °C; relative humidity (RH) of 40–60%] were conducted to investigate the drying shrinkage of lignite at low temperatures. The moisture content and volume variations of lignite during low-temperature drying were measured to analyze the change in the water content and volume drying shrinkage rate under low-temperature drying conditions. The results show that in the first 48 h of drying, the water evaporated rapidly. The amount of external water evaporated and lost accounted for 70–90% of the total water lost during the entire low-temperature drying period, and the average water content is reduced to about 12.8%. When the rapid loss of external water decreased to less than 12.8%, the water adsorbed on the external surfaces, the movable water between large particles was completely lost, and saturated lignite underwent heterogeneous volume shrinkage. The drying shrinkage was slow during the first 48 h, accounting for 20.8% of the total drying shrinkage in the entire low-temperature drying process. The volume shrinkage occurred in four stages as the water content decreased with time. With increasing drying time, the decrease in the water content occurred in four stages: the thermal expansion stage, rapid shrinkage stage, slow shrinkage stage, and stable shrinkage stage. The dry shrinkage rate has a significant positive correlation with the water evaporation quality and significant negative correlations with the water content and evaporation rate. The lower the evaporation rate, the greater the dry shrinkage rate when the saturated lignite is dried under low-temperature and humid conditions (temperature of <30 °C; RH of <60%). There is a time lag between volume shrinkage and water loss, and there is also a difference in their quantities. The volume shrinkage is lower than the water loss, and the difference is largest about 48 h into the initial stage of low-temperature drying. As the low-temperature drying time increases, the shrinkage due to drying becomes stable, and the moisture content remains unchanged. The larger the ratio of RH to temperature, the larger the stable shrinkage.

Okra (Abelmoschus esculentus) Powder Production and Application in Gluten-Free Bread: Effect of Particle Size

Okra (Abelmoschus esculentus) has interesting nutritional and technological properties and is naturally gluten-free (GF). This study investigated the physicochemical properties of okra powder obtained by a low-temperature drying process and its impact on GF bread. Its potential synergy with other hydrocolloids (i.e., hydroxypropylmethylcellulose (HPMC) and Psyllium fibre (Psy)) was also studied. As the importance of powder particle size in food design is well known, whole okra powder (WOP; ≤ 1000 µm) and fine okra powder (FOP; ≤ 250 µm) were produced. Compared to the standard formulation, WOP and FOP doughs required less water to reach the desired dough consistency (200 ± 20 Brabender unit) and generally showed higher stability during mixing. Dough development was affected by HPMC more than okra powder particle size. Breads containing WOP or FOP in combination with HPMC exhibited high specific volume and soft texture, while the combination with Psy resulted in a less-developed, harder and darker bread. The combination with HPMC also guaranteed a longer shelf-life, regardless of okra powder particle size. These results may prove useful for the agri-food industry, as they demonstrate that okra can be used as an innovative natural hydrocolloid.

Water intercalation strategy to fabricate low-potential and dense grapheme film anode for high energy density K-ion batteries

Carbon materials have appealing potential as anode for Potassium ion batteries (KIBs), but achieving low-potential plateau curve and high energy density for anode materials is a primary challenge. Herein, a 3D holey reduced graphene oxide/ carbon nanotubes (L-HRGO/CNT) film was constructed via chemical etching and low- temperature drying method. The micro/mesoporous in graphene oxide (GO) sheets are created by chemical etching, which shorts ion transfer distance, and thus increases the K+ intercalation/deintercalation rate. During low-temperature drying process, the water molecules inside the GO interlayer serve as self-sacrificial spacers for extending the stacked structure and maintaining integrity, increasing capacity contributed from K+ intercalation for a low discharge voltage. And the CNTs introduced into the film via vacuum co-filtration can enhance the conductivity and mechanical strength of the film. The optimized L-HRGO/CNT film delivered a high K+ storage capacity of 307.0 mA h g−1, high-rate capability, and the capacity retention reaches 72.6% at 200 mA g−1 for 200 cycles. When assembled with the KVPO4F cathode, the reversible capacity remains 93.8 mAh g−1 after 100 cycles, and 473.0 Wh kg−1(776.9 Wh L−1) of the energy density is achieved.

Coupling electro-dewatering and low-temperature air-drying for efficient dewatering of sludge

This study investigated the effects of electro-dewatering on subsequent low-temperature drying at various potentials and the characteristics of low-temperature air-drying sludge were explored through experiments and multi-physical modeling. Experimental results showed that the extracellular polymeric substance (EPS) content in the sludge was reduced during electro-dewatering process, even the species of organic matter was changed, as well as the dewatered cake tend to form many seepage channels, crack and a certain number of holes. These changes in the properties and structure were conducive to the subsequent low-temperature drying process. For air-drying process, the mass of the sludge cake variation was simulated and results were consistent with the experimental phenomenon. Firstly, the weight of the sludge cake was decreased approximately linearly with time, then tended to stable and reached the dewatering limitation finally. The applied higher electric field intensity (25 V cm−1) in the front-end electro-dewatering were conducive to promote water vapor diffusion activity in air-drying stage. Energy consumption and yield analysis results indicated that the combined technology has lower energy consumption and higher yield than that of directly low-temperature drying.

Facile and Scalable Fabrication of High-Performance Microsupercapacitors Based on Laser-Scribed In Situ Heteroatom-Doped Porous Graphene.

This study proposes an efficient, facile, and scalable strategy to synthesize in situ heteroatom-doped porous graphene via laser direct writing on the precursor-doped polyimide (PI) film, which is fabricated for the first time through incorporating PI powder and precursors with sodium carboxymethyl cellulose (CMC) binder by a drop-casting and low-temperature drying process. The resulting microsupercapacitors (MSCs) based on the as-prepared heteroatom-doped porous graphene exhibit remarkable capacitive performance. The typical boron-doped MSC prepared on borax-doped polyimide film possesses an ultrahigh areal capacitance of 60.6 mF cm-2 at 0.08 mA cm-2, which is approximately 20 times larger than that of undoped MSC. Furthermore, the boron-doped MSC has impressive cycling stability (with the capacitance retention of 96.3% after 20 000 cycles), exceptional mechanical flexibility, tunable capacitance, and voltage output through arbitrary modular serial and parallel integration. Besides, the nitrogen-doped porous graphene with excellent capacitive performance is also prepared by laser direct scribing on the sulfonated melamine-doped polyimide film, demonstrating excellent scalability and generality of this strategy. Hence, one-step laser direct writing on precursor-doped polyimide films can realize in situ heteroatom doping and generation of hierarchical porous graphene electrodes simultaneously, which opens a new avenue for the facile, cost-effective, and scalable fabrication of heteroatom-doped porous graphene, thus promising for MSCs and various flexible and wearable electronics at large-scale production.

Flexible Solar Cells: Low‐Temperature‐Deposited TiO2 Nanopillars for Efficient and Flexible Perovskite Solar Cells (Adv. Mater. Interfaces 3/2021)

Sunlight can be converted to electricity via solar cells, with which then light can be generated the other way around. In this regard, skyscrapers performing light show during night or the bright Karst landscape under the ground are exemplified, echoing the geometry of the TiO2 nanopillars which are fabricated via a low-temperature dry process and work as the efficient electron-transporting layer in flexible perovskite solar cells. More details can be found in article number 2001512 by Zhifeng Huang, Zijian Zheng, and co-workers.

Heat pump technologies of low temperature drying of capillary-porous materials spherical shape

Heat pump technologies have become widely used in space heating and air conditioning systems, and the heat pump can be used for low-temperature drying of capillary-porous materials.&#x0D; Recuperative and condensing heat pumps, which allow both drying and cooling of the material, have become the most widespread.&#x0D; The developed condensing heat pump drying unit with a mine chamber implements a low-temperature drying process of spherical capillary-porous materials at a drying agent temperature of 40-50°C with a decrease in material humidity by 11% to a final humidity of 8%.&#x0D; Experimental studies on a heat pump drying unit for drying capillary-porous materials of spherical shape indicated a significant reduction in average energy costs per process up to 3700 - 4100 kJ/kg of evaporated moisture. The increase in energy consumption increases significantly in the second part of the second period, where heat consumption can reach 5000 - 5350 kJ/kg of evaporated moisture.&#x0D; The use of condensing heat pumps for low-temperature drying of capillary-porous materials has shown high energy efficiency compared to existing drying technologies.

Optimization of low-temperature drying of laying-hen manure using response surface methodology

ABSTRACT Manure-drying system using exhausted air from laying hen houses or ambient air has been extensively used in China to dewater the manure for easy transportation and to reduce pathogen levels prior to land application. Due to the climate influence or inappropriate setting of technological parameters, there are some issues in this manure-drying system, such as low dehydration rate, high energy consumption, and high ammonia emission. A purpose-designed experimental drying apparatus was set up to simulate the commercial manure drying system. Drying experiments were carried out to assess the impacts of hot air temperature (15–35°C), air velocity (0.6–1.8 m/s) and manure layer thickness (60–140 mm) on fan’s energy consumption, dehydration rate, and nitrogen loss rate. The response surface analysis method and sub-stepping method was used to analyze the relationships between the response variables and the influence factors. The drying curves were drawn, and the quadratic regression mathematical models that described the relations between the experimental indices and the influence factors were established. The optimal combination of technological parameters for drying laying-hen manure was obtained through conducting a multi-objective function optimization by function-expected optimization. The optimal parameters are as follows: hot air temperature of 35°C, air velocity of 1.60 m/s, and manure layer thickness of 85 mm. The results also indicate that raising the hot air temperature increased the value of synthesis objective function when the hot air temperature was in 26–35°C. The results can provide a theoretical basis for low-temperature drying of laying-hen manure in actual production. Implications: A large amount of poultry manure is produced yearly in China, which has become a tremendous pressure on the environment when it cannot be utilized as resources. A more sustainable solution using the residual heat from the poultry house ventilation or ambient hot air has been widely used in China. This drying method can significantly reduce energy consumption compared to the traditional way. However, due to the influence of climate or inappropriate setting of technological parameters, issues such as high energy consumption and high ammonia emission still exist in this method. It is necessary to optimize the low-temperature drying process of laying-hen manure, to reduce energy consumption and nitrogen loss rate.

The Effect of Drying Temperature on Nitrogen Loss and Pathogen Removal in Laying Hen Manure

Exhaust air from the poultry houses or ambient hot air are normally utilized to dry the laying hen manure extensively in the summer in China. The drying process can not only reduce the moisture of lay hen manure but can also have a degerming effect. However, the ammonia emission is considered as one of the major issues of laying hen manure drying and air pollution scouse. Then, it is not clear that whether the ammonia emission increased using the hot ambient air to dry laying hen manure in summer and whether increasing the temperature can inactivate more bacteria during low temperature drying process. Therefore, the main works of this study were to investigate the evolution of ammonium nitrogen (NH4-N) content, organic nitrogen (Org-N) content, and total bacteria count vs. time during the low-temperature drying process of laying hen manure at different drying temperatures. The results showed that increasing drying temperature can reduce the energy consumption of the manure drying system, but can increase the loss of NH4-N. The Org-N content among the three drying temperatures within same drying time was not significantly different (p &gt; 0.05), which suggested that increasing the temperature did not accelerate the degradation of Org-N during low-temperature drying process. Low-temperature drying had weak destruction of bacteria in laying hen manure and the end dried manure still had a great number of bacteria.

An experimental method to investigate the water-based suppression of smoldering peat fire

Smoldering wildfire in peatlands is one of the largest and most persistent fire phenomena on Earth, which contributes importantly to global carbon emissions. However, very few studies are available on how to extinguish these smoldering wildfires. Herein, we develop an experimental method to explore the effectiveness of the water-based suppression on smoldering peat fire, and the proposed method can also be used to simulate fire suppression by rain. The low-temperature drying process avoids the variation of hydrophobicity of peat soil. The validation shows that the proposed approach can provide a wide range of water-spray intensities with time variation, and two examples of successful suppression of smoldering peat fire and flaming wood crib fire were presented.•The design of small-scale combustion reactor for peat can mimic the smoldering peat fire in the field.•The effectiveness of water-based fire suppression technologies on peat fire are explored in the lab.•The proposed method can evaluate the effect of rain and weather on suppressing the smoldering wildfire.

Experimental Research of Drying Red Chili by Two Methods: Solar Drying and Low - Temperature System Drying

The objective of this research was to experiment of solar drying and Low-Temperature system drying (45-50%RH, 27-30°C) for drying red chili. Solar drying during daytime (greenhouse dryer) and during at night using climate control system to coordinate with air conditioner in drying. The Low-Temperature system consists the humidity control unit (ultrasonic), air-conditioner, temperature and relative humidity sensor, heating coil and microcontroller unit. For Low-Temperature drying process, climate control system controls the compressor in the air conditioner by turn on-off to control the temperature and relative humidity in the chamber. The dehumidification process by controlling the temperature of the surface evaporator coil is decreased to the dew point temperature, making water vapor in the air condensed to be water drops. The result of solar drying and Low-Temperature system takes 52h to reduce the moisture content of about 74% to 13.5% (w.b). For temperature and relative humidity of the solar drying at 50 °C and 36%RH by average, in during daylight and at night with Low-temperature drying system by the climate control system coordinate with air conditioning system in moisture reduction at 27-30°C and relative humidity at 45-50%RH for drying chili in the night. These processes were found to have average temperatures and relative humidity for drying at 27.55°C, 47.37% RH., moisture condensation rate and specific energy consumption at 2.16 kgwater/h and 0.75 MJ/kg.

Macromolecular structure evolution and its significance for perhydrous coal under drying and pyrolysis conditions

ABSTRACTNo. 13-1 perhydrous coal (PHC) was dried by fluidized bed drying with N2 used as the fluidizing medium in drying characteristics experiments. The PHC was characterized before and after the low-temperature drying process by Fourier transform infrared (FTIR). The drying temperatures tested were 100, 150, and 200°C. Changes in the major functional groups of PHC before and after the drying process were examined on the basis of the FTIR curve-fitting analysis. In addition, the PHC was pyrolyzed through a thermogravimetric analyzer. The pyrolysis temperature ranged from 300 to 650°C, and the temperature increment value was 50°C. The macromolecular structure of PHC before and after pyrolysis was characterized by Raman. The Raman parameters were obtained by spectral curve-fitting analysis. The FTIR results show that following the drying process, the aliphatic hydrocarbons in PHC progressively weakened with increasing drying temperature. Compared with the methyl groups, the oxidation activity of the methylene groups was higher in the low-temperature drying process. As the drying temperature increased, the main oxygen functional groups decreased. Overall, drying provides the chemical environment for hydrogen transfer in PHC, leading to a decline in aliphatic hydrocarbons and a rise in aromatic hydrocarbon content, and accelerates the polycondensation and ordering of large molecules in PHC. The Raman results show that with increasing pyrolysis temperature, the macromolecular structure of PHC becomes more and more similar to that of graphite. The Raman spectral parameters are closely correlated to reflectance. Considering the stability and reliability of the Raman parameters, the full width at half maximum (FWHM) of D2- and G-band was used to characterize the metamorphic grade of the PHC. The FWHM of the D2- and G-bands showed a linear relationship with PHCR0 in the range of 2.0–7.6%, indicating that the FWHM parameters can be used to determine the PHC rank.

New Ultrasonic Controller and Characterization System for Low Temperature Drying Process Intensification

Process intensification constitutes a high interesting and promising industrial area. It aims to modify conventional processes or develop new technologies in order to reduce energy needs, increase yields and improve product quality. It has been demonstrated by this research group (CSIC) that power ultrasound have a great potential in food drying processes. The effects associated with the application of power ultrasound can enhance heat and mass transfer and may constitute a way for process intensification.The objective of this work has been the design and development of a new ultrasonic system for the power characterization of piezoelectric plate-transducers, as excitation, monitoring, analysis, control and characterization of their nonlinear response. For this purpose, the system proposes a new, efficient and economic approach that separates the effect of different parameters of the process like excitation, medium and transducer parameters and variables (voltage, current, frequency, impedance, vibration velocity, acoustic pressure and temperature) by observing the electrical, mechanical, acoustical and thermal behavior, and controlling the vibrational state.

Basics and Application of Low-Temperature Drying Process with High Drying Rate－Superheated-Steam Fluidized Bed Drying under Reduced Pressure－

Basics and Application of Low-Temperature Drying Process with High Drying Rate－Superheated-Steam Fluidized Bed Drying under Reduced Pressure－

The Preliminary Study of the Manufacturing Process of Veneer Composite Plank

This study focuses on the manufacturing process of veneer composite plank and test the mechanical properties.The results showed that: ① In the dipping process, when the dipping time was 20min and adhesive solids was 25%,the veneer composite plank can get a better mechanical properties; ②In the low-temperature drying process, according to the mechanical properties and drying efficiency, low drying temperature appropriate select 50°C; ③Considering the mechanical properties and the cost issue as the density increases, select the density of 1.0g/cm3 is appropriate. Prove that the production technology is feasible, its products have uniform texture and good mechanical properties can be widely used for furniture, flooring and structural materials and other fields.