Thermal Drying Process Research Articles

Supercritical, Freezing and Thermal Drying Process of Resorcinol‐Formaldehyde Polymer based Nano‐carbons and their Highly Loaded PtRu Anode Electrocatalyst for DMFC

AbstractThe capillary condensation is affected by micropore and nanopore of catalyst layer on fuel cell. Due to limitation of sluggish mass transport and electrocatalytic activity, to retain the pore skeleton of carbon and metal nanoparticles are very significant for enhanced utilizations of pore structure in electrochemical reaction. Besides, thickness of electrocatalyst layer is very crucial due to one of the factor affected by cell performance of direct methanol fuel cell. Highly loaded four Pt−Ru anode catalysts supported on resorcinol‐formaldehyde (RF) polymer based on meso‐porous carbons (80 wt.% Pt−Ru/carbon cryogel, 80 wt.% Pt−Ru/carbon xerogel and 80 wt.% Pt−Ru/carbon aerogel) and conventional carbon (80 wt.% Pt−Ru/Vulcan XC‐72) were prepared by colloidal method for direct methanol fuel cell. These catalysts were characterized by X‐Ray diffraction (XRD), High resolution transmission electron microscopy (HR‐TEM) and X‐ray photoemission (XPS). The results of CO stripping voltammetry, cyclic voltammetry (CV) and single cell test performed on DMFC show that Pt−Ru/carbon cryogel and Pt−Ru/carbon aerogel exhibits better performances in comparison to Pt−Ru/carbon xerogel and Pt−Ru/Vulcan XC‐72. It is thus considered that particle size, oxidation state of metal and electrochemical active surface area of these catalysts are important role in electrocatalytic activity in DMFC.

Thermodynamic investigation on gasification performance of sewage sludge-derived hydrochar: Effect of hydrothermal carbonization

Compared with the conventional thermal drying process, hydrothermal carbonization (HTC) can reduce the energy cost of water removal from sewage sludge prior to its steam gasification. However, less attention is paid on the interactions between HTC and gasification. In this study, the thermodynamic evaluation on hydrochar gasification performance under different operating conditions including HTC duration (τ), HTC temperature (THTC), gasification temperature (Tg), and steam/hydrochar mass ratio (S/C ratio) is performed. Two indicators including carbon conversion rate (CC) and cold gas efficiency (CGE) are used to assess the gasification performance. The results show that elevating both gasification temperature and S/C ratio can enhance the H2 production, which also result in the increase of CC and CGE. The content and gasification activity of fixed carbon increase under moderate HTC duration and temperature, favoring the H2 formation despite of the apparent loss of volatiles species in the hydrochar. Longer HTC duration or higher HTC temperature declines the H2 production due to the sharp reduction of carboxyl and hydroxyl groups, weakening water gas reaction and on-site reforming reaction of tar occurred on the hydrochar surface. In terms of the values of CC = 93.9% and CGE = 64.38%, the optimum HTC conditions of τ = 30min and THTC = 200 °C can be determined. The data provided here favor guiding HTC treatment of sewage sludge targeting gasification and thus promoting the development of this promising waste-to-energy technology.

The relevance between water release behavior and pore evolution of hard lignite during the thermal-drying process

As known, the shrinkage of coal and the pore collapsed during the drying process due to water removal. The relevance between water release behavior and pore evolution of lignite during the thermal-drying process was studied in this work. From N2 adsorption of traditional pretreated samples and freezing wet samples, most of moisture was in the pores in the range of 26–100 nm, and results from low-field nuclear magnetic resonance (LFNMR) confirmed this conclusion that the removed moisture was in the pores with pore size smaller than 200 nm, while from the mercury intrusion porosemitry (MIP) results, the most obvious reduction of macropores was in the range of pore dimeter larger than 1 μm and there was almost no change of pore volume in the range of pore diameter smaller than 200 nm, which was completely different from traditional ideas that the pore shrunk or collapsed due to water removed. The macropores were more prone to collapse than mesopores and micropores, maybe due to its structural mechanical characteristics. And the effect of pore evolution on moisture release behavior was related to the specific drying methods and mass transfer processes.

Elliot and Symmetric Elliot Extreme Learning Machines for Gaussian Noisy Industrial Thermal Modelling

This research proposes an Elliot-based Extreme Learning Machine approach for industrial thermal processes regression. The main contribution of this paper is to propose an Extreme Learning Machine model with Elliot and Symmetric Elliot activation functions that will look for the fittest number of neurons in the hidden layer. The methodological proposal is tested on an industrial thermal drying process. The thermal drying process is relevant in many industrial processes such as the food industry, biofuels production, detergents and dyes in powder production, pharmaceutical industry, reprography applications, textile industries and others. The methodological proposal of this paper outperforms the following techniques: Linear Regression, k-Nearest Neighbours regression, Regression Trees, Random Forest and Support Vector Regression. In addition, all the experiments have been benchmarked using four error measurements (MAE, MSE, MEADE, R 2 ).

Combined conventional thermal and microwave drying process for typical Chinese lignite

A combined conventional and microwave drying process for Ximeng lignite was investigated in this paper. Samples were firstly dehydrated by hot air to achieve a conversion moisture content, and then were managed to final moisture content by microwave drying. Results showed that the drying rate was significantly improved in the decreasing rate period by microwave drying, approximately 3–5 times faster than that of conventional drying. Finally, the orthogonal test was used to clarify the effects of each factor on the energy consumption, and the magnitude ranking order was conversion moisture content > microwave power > hot air temperature.

Free-conditioning dewatering of sewage sludge through in situ propane hydrate formation

The propane hydrate formation was proposed to have potentials in realizing free-conditioning dewatering of sewage sludge with implications to simultaneous clean water extraction and highly efficient volume reduction. Primarily, the investigation on phase equilibrium of propane hydrates found that the organic components of sewage sludge promoted the propane hydrate formation in terms of decreasing equilibrium pressure by up to 19.2%, compared with that in pure water. Further, the feasibility of hydrate-based dewatering was verified through the observation of propane hydrate formation in sewage sludge and also the quality analysis of water generated from decomposition of up-floated formed hydrates. The formation of up-floated propane hydrates extracted water molecules from sewage sludge into homogeneous crystal phase, which actually excluded sludge particles from hydrate phase and realized the reduction of water in sludge phase. The efficiency of water conversion into hydrates was determined by monitoring propane pressure, which indicated that 14 batch runs decreased the water content of sludge from 98.81wt.% to 44.3wt.% under free-conditioning conditions. The chemical oxygen demand, total nitrogen and total phosphorus of hydrate-extracted water were measured to be 21 ± 1 mg/L, 10.5 ± 0.2 mg/L and 0.4 ± 0 mg/L, respectively, which reflected the excellent separation performance and also indicated that the hydrate-extracted water can be directly discharged without further treatments. Finally, the unit energy consumption of hydrate-based dewatering process based on a continuous operation mode was calculated to be 2673.96 kW h/t dry solid of sewage sludge, which was nearly half of that in thermal drying process. Therefore, the propane hydrate-based process is believed to maximize the green operation of enhanced sludge dewatering while minimizing the energy and additional material consumption.

Upgrading of lignite using a combined novel drying and the FGX dry separation process

ABSTRACT Lignite is a fossil fuel that will become increasingly important in the futurebecause it is an alternative raw material for the oil, gas, energy, and chemical industries. Based on an analysis of the nature of raw coal, this study investigated the upgrading of the lignite by a novel thermal drying process and processing the material on the FGX dry separation process. In the drying step the effects of airflow, temperature, and drying time on the drying characteristics of different bed materials were examined. For the FGX separation process effects of air (gas) velocity, frequency, and amplitude of the table on the separation efficiency of the machine were investigated. The results showed that the lignite could be upgraded effectively using the dual step-drying and processing process. The optimum drying parameters were v = 0.64 m3/s, T = 195°C, t = 5 min and with the best FGX sorting parameters were v = 0.56 m3/s, A = 3 mm, f = 30 Hz. Using these conditions from a feed ash of 32.0%, a clean coal with a yield of 64.82%, ash and sulfur contents 17.4% and 0.96%, respectively, and the calorific value was 14.53 MJ/kg was obtained. Gangue yield was 35.18% with ash and sulfur contents of 62.93% and 25.53%, respectively, and the calorific value was 4.52 MJ/kg. The partisan coefficient E-value was 0.155 g/cm3, which indicated that the effects of drying and sorting were effective.

Surface chemistry of thermal dry etching of cobalt thin films using hexafluoroacetylacetone (hfacH)

A mechanism of thermal dry etching process of cobalt thin films by using 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone, hfacH) was investigated. This process, relevant to atomic layer etching (ALE) technology directed towards oxidized cobalt films, requires adsorption of molecular organic precursor, such as hfacH, at moderate temperatures and is often thought of as releasing water and Co(hfac)2 at elevated temperatures. The reaction was analyzed in situ by temperature-programmed desorption (TPD) and the resulting surface was investigated ex situ by X-ray photoelectron spectroscopy (XPS). The changes in surface morphology during the process were monitored by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The removal of Co(hfac)2 from the surface was observed above 650 K, a temperature well above commercially desired etching conditions, suggesting that the thermal etching process is more complex than originally envisioned. In addition, the upper limit of thermal treatment is established at 800 K, as the microscopic techniques clearly indicated surface morphology changes above this temperature. In addition, the structure of the surface at the nanoscale is observed to be affected by the presence of surface bound organic ligands even at room temperature. Thus, further mechanistic studies should address the kinetic regime and surface morphology to make inroads into mechanistic understanding of the dry etching process.

Fragmentation of a Turkish Low Rank Coal During Fixed-bed Evaporative Drying Process

ABSTRACT In the present study, a new approach was utilized to investigate the fragmentation of low rank coal during the thermal drying process. Drying experiments were conducted at different drying air temperatures (70, 100, 110 and 130°C), drying air velocities (0.4 and 0.7 m/s), bed heights (100, 150 and 250 mm) and particle fractions (20–50, 28–50 and 35–50 mm) for a Turkish lignite (Konya-Ilgın lignite) in a fixed-bed dryer. Konya-Ilgın lignite was used in the heating sector. Particle sizes used in these experiments were coarser than the studies in the literature due to legal constraints. The effects of drying parameters on coal fragmentation were evaluated. The fragmentation increased as the drying air temperature and the velocity increased, and it decreased as the bed height and the particle size increased. Results of this study may be used in the design of a suitable dryer for low rank coal.

Volatilization of mercury in coal during conventional and microwave drying and its potential guidance for environmental protection

During the thermal drying process of coal, the sufficient attention has been paid to the changes in the properties of coal before and after the drying process. However, the volatility characteristics of harmful trace elements in coal during the drying process are always neglected to date, whereas the volatilization of harmful trace elements not only has significant effects on the surrounding atmosphere environment but also influence the following utilization of dried coal. In this study, the volatility characteristics of both the moisture and mercury in the coal sample during conventional (electric blast oven) and microwave (microwave oven) drying processes were investigated. In addition, the changes in the surface properties of coal before and after the drying process were studied using X-ray photoelectron spectroscopy (XPS) analysis. The results show that the moisture content of coal decreases in non-line format (decreases slowly at the first and then quickly according to the drying time) in the conventional drying process, while it decreases in line format in the microwave drying. The microwave drying process needs much shorter time required to obtain the dried coal of a certain moisture content than the conventional drying process. Under the same volatilization rate of moisture, the volatilization rate of mercury in the microwave drying process is always greater than that in the conventional drying process. Nearly half or more (49.73% and 59.26%, respectively) of the mercury in the coal slime evaporates into the atmosphere after the drying processes. XPS results show the content of CC and CH groups on the coal surface increased, but the CO content decreased after the drying processes and the microwave drying process has a stronger ability to remove oxygen-containing functional groups than the conventional drying process.

Effect of Drying, Polarity and Molecular Weight on Oat Chemical Content and Bioactivity

This study’s outcome brings some information about oat phenolic compounds characteristics and response to thermal drying process, and fractionation by polarity and molecular weight; also suggests that Moroccan oat varieties may serve as a good source of natural antioxidants. In this study, total phenolic (TPC) and total flavonoid (TFC) of two Moroccan oat varieties (Amlal and Tissir) were investigated. Additionally, oat extracts and fractions were analyzed with regard to their antioxidant activities (AA) using DPPH radicals’ cation, and ferric reducing/antioxidant power (FRAP) methods. The results indicated that TPC ranged from 8.12 ± 0.11 to 27.56 ± 0.40 mg of gallic acid equivalent/gram of extract dry weight (edw). While, TFC ranged from 6.66 ± 0.90 to 27.60 ± 0.71 mg RE/g of edw. The results demonstrated that the hydro-methanolic fraction has the highest TPC and TFC compared to other extracts in both varieties, and that thermal drying process increase oat phenolic content and AA. A significant correlation was found between phytochemical contents and AA.

A Natural Based Method for Hydrophobic Treatment of Natural Fiber Material.

A treatment for hydrophobic functionalization of natural fiber materials is developed. This hydrophobic treatment is based mainly on natural products. As hydrophobic component the natural Tung Oil is used, which is originally a compound used for wood conservation purposes. The application on textile is done in a padding process under presence of an oxidative agent. For the current investigations a fiber felt from linen was used. The hydrophobic effect is determined by the concentration of Tung Oil and the duration of a thermal drying process. The hydrophobic effect is investigated by capillary rise tests and contact angle measurements. Scanning electron microscopy SEM is used to investigate the surface topography of the fiber material and the deposited hydrophobic material. Altogether, an interesting and promising method for hydrophobisation of natural fibers is developed, which could especially be used as part of a production process of a fiber reinforced composite material, mainly based on natural products.

Highly conductive metal interconnects on three-dimensional objects fabricated with omnidirectional ink jet printing technology

In this work, we demonstrate that highly conductive metal interconnects can be fabricated on the surface of three-dimensional objects using “omnidirectional ink jet” (OIJ) printing technology. OIJ printing technology makes it possible to perform ink jet printing in all directions by combining the motion of a 6-axis vertically articulated robot with precise positioning and a thermal drying process, which allows for the printing of stacked layers. By using OIJ technology, we were the first to successfully fabricate printed interconnect layers having a very low electrical resistance of 12 mΩ over a 10 mm length. Moreover, the results of the high-current test demonstrated that the printed interconnects can withstand high-current-flow of 5 A for 30 min or more.

Learning FCMs with multi-local and balanced memetic algorithms for forecasting industrial drying processes

In this paper, we propose a Fuzzy Cognitive Map (FCM) learning approach with a multi-local search in balanced memetic algorithms for forecasting industrial drying processes. The first contribution of this paper is to propose a FCM model by an Evolutionary Algorithm (EA), but the resulted FCM model is improved by a multi-local and balanced local search algorithm. Memetic algorithms can be tuned with different local search strategies (CMA-ES, SW, SSW and Simplex) and the balance of the effort between global and local search. To do this, we applied the proposed approach to the forecasting of moisture loss in industrial drying process. The thermal drying process is a relevant one used in many industrial processes such as food industry, biofuels production, detergents and dyes in powder production, pharmaceutical industry, reprography applications, textile industries, and others. This research also shows that exploration of the search space is more relevant than finding local optima in the FCM models tested.

Influence of oxidation temperature on the interfacial properties of n-type 4H-SiC MOS capacitors

The effect of oxidation temperature on interfacial properties of n-type 4H-SiC metal-oxide-semiconductor capacitors has been systematically investigated. Thermal dry oxidation process with three different oxidation temperatures 1200°C, 1300°C and 1350°C were employed to grow SiO2 dielectric, following by the standard post-oxidation annealing (POA) in NO ambience at 1175°C for 2h. The root mean square (RMS) roughness measured by Atomic Force Microscopy for the thermally grown SiO2 before POA process is reduced with increasing the oxidation temperature, obtaining an atomically flat surface with a RMS of 0.157nm from the sample oxidized at 1350°C. Several kinds of electrical measurements were used to evaluate the densities of near interface traps and effective fixed dielectric charge for the samples, exhibiting a trend reduced with increasing the oxidation temperature. The interface state density of 3×1011cm−2eV−1 at 0.2eV from the conduction band edge was achieved from conductance method measurement for the sample oxidized at 1350°C. The results from Secondary Ion Mass Spectroscopy and X-ray Photoelectron Spectroscopy demonstrate that high oxidation temperature can reduce the width of transition layer, the excess Si and silicon suboxide compositions near the interface, leading to effective improvement of the interfacial properties.

Increasing thermal drying temperature of biosolids reduced nitrogen mineralisation and soil N2O emissions.

Previous studies found that thermally dried biosolids contained more mineralisable organic nitrogen (N) than the raw or anaerobically digested (AD) biosolids they were derived from. However, the effect of thermal drying temperature on biosolid N availability is not well understood. This will be of importance for the value of the biosolids when used to fertilise crops. We sourced AD biosolids from a Danish waste water treatment plant (WWTP) and dried it in the laboratory at 70, 130, 190 or 250°C to >95% dry matter content. Also, we sourced biosolids from the WWTP dried using its in-house thermal drying process (input temperature 95°C, thermal fluid circuit temperature 200°C, 95% dry matter content). The drying process reduced the ammonium content of the biosolids and reduced it further at higher drying temperatures. These findings were attributed to ammonia volatilisation. The percentage of mineralisable organic N fraction (min-N) in the biosolids, and nitrous oxide (N2O) and carbon dioxide (CO2) production were analysed 120days after addition to soil. When incubated at soil field capacity (pF 2), none of the dried biosolids had a greater min-N than the AD biosolids (46.4%). Min-N was lowest in biosolids dried at higher temperatures (e.g. 19.3% at 250°C vs 35.4% at 70°C). Considering only the dried biosolids, min-N was greater in WWTP-dried biosolids (50.5%) than all of the laboratory-dried biosolids with the exception of the 70°C-dried biosolids. Biosolid carbon mineralisation (CO2 release) and N2O production was also the lowest in treatments of the highest drying temperature, suggesting that this material was more recalcitrant. Overall, thermal drying temperature had a significant influence on N availability from the AD biosolids, but drying did not improve the N availability of these biosolids in any case.

Characteristics of Heavy Metal Species Transformation of Pb, Cu, Zn from Municipal Sewage Sludge by Thermal Drying

Thermal process allow for a significant reduction in the weight and volume of transformed sewage sludge. The high heavy metal content in sewage sludge effectively reduces the possibility of its agricultural use. This study investigated heavy metals transformation from municipal sewage sludge using a combination of thermal drying process. The experiments were conducted using furnace as a heating apparatus to dry the municipal sewage sludge at different temperature and analyze the species of heavy metal in municipal sewage sludge after drying. Results show that the contents of heavy metal are different in municipal sludge. The species of heavy metal obviously transformed after drying at different temperature. Additionally, the transform amount of metals varies in the species of metal as well as the type of heavy metal after drying. The effect of high temperature can transfer the acid-soluble, the reducible and the oxidizable species into the residual species. High temperature has the ability of stabilizing the heavy metals in municipal sewage sludge.

Energy potential and alternative usages of biogas and sludge from UASB reactors: case study of the Laboreaux wastewater treatment plant

This work assessed the energy potential and alternative usages of biogas and sludge generated in upflow anaerobic sludge blanket reactors at the Laboreaux sewage treatment plant (STP), Brazil. Two scenarios were considered: (i) priority use of biogas for the thermal drying of dehydrated sludge and the use of the excess biogas for electricity generation in an ICE (internal combustion engine); and (ii) priority use of biogas for electricity generation and the use of the heat of the engine exhaust gases for the thermal drying of the sludge. Scenario 1 showed that the electricity generated is able to supply 22.2% of the STP power demand, but the thermal drying process enables a greater reduction or even elimination of the final volume of sludge to be disposed. In Scenario 2, the electricity generated is able to supply 57.6% of the STP power demand; however, the heat in the exhaust gases is not enough to dry the total amount of dehydrated sludge.

Oxidation behavior of Cr(III) during thermal treatment of chromium hydroxide in the presence of alkali and alkaline earth metal chlorides.

The oxidation behavior of Cr(III) during the thermal treatment of chromium hydroxide in the presence of alkali and alkaline earth metal chlorides (NaCl, KCl, MgCl2, and CaCl2) was investigated. The amounts of Cr(III) oxidized at various temperatures and heating times were determined, and the Cr-containing species in the residues were characterized. During the transformation of chromium hydroxide to Cr2O3 at 300 °C approximately 5% of the Cr(III) was oxidized to form intermediate compounds containing Cr(VI) (i.e., CrO3), but these intermediates were reduced to Cr2O3 when the temperature was above 400 °C. Alkali and alkaline earth metals significantly promoted the oxidation of Cr(III) during the thermal drying process. Two pathways were involved in the influences the alkali and alkaline earth metals had on the formation of Cr(VI). In pathway I, the alkali and alkaline earth metals were found to act as electron transfer agents and to interfere with the dehydration process, causing more intermediate Cr(VI)-containing compounds (which were identified as being CrO3 and Cr5O12) to be formed. The reduction of intermediate compounds to Cr2O3 was also found to be hindered in pathway I. In pathway II, the alkali and alkaline earth metals were found to contribute to the oxidation of Cr(III) to form chromates. The results showed that the presence of alkali and alkaline earth metals significantly increases the degree to which Cr(III) is oxidized during the thermal drying of chromium-containing sludge.

Determination of drying characteristics of biomass residues to be used as a renewable fuel

In the present work, a study of the thermal drying process of biomass residues has been developed. The residues used were woodchips which have been dried in a thermal cylindrical dryer designed according to these types of residues. An experimental facility has been built in order to measure the temperature inside the dryer. The raw material was characterized by elemental and proximate analyses as well as by Higher Heating Value. Hot gases and air were used as drying medium using different flow rates. The experiments were carried out at various drying medium temperatures. The rotation speed of the dryer screw was varied for each experiment. The biomass residue was fed to a dryer and dried many times in the same drying conditions in order to determine the reduction of moisture content and temperature variation of the residue along the time. The variation of moisture content and drying temperature are determined under different drying conditions. It was found that by increasing drying medium flow rate and decreasing the rotation speed of the screw, the drying rate is increased. Finally, it could be concluded that the dried biomass residue can be used as a solid fuel with a moisture content of about 10% in direct combustion to produce thermal energy, and in gasifying processes to produce syngas.