Compressed Water Research Articles

Investigation of nanocrystallization behaviour of AISI 316 stainless steel under adiabatic and non-adiabatic severe plastic deformation conditions

Abstract Of late surface nanocrystallization of steels has become an important topic for researchers due to the exceptional properties obtained after nanocrystallization. Austenitic stainless steel is very important alloy for industrial applications due to its corrosion resistance and versatile mechanical properties. However, austenitic stainless steel lacks in surface wear resistance. Surface nanocrystallization of austenitic stainless steel component can eliminate this drawback. This work involved fabrication of nanocrystallized layer on specimens of AISI 316 stainless steel. Nanocrystallized layer was synthesized by shot-peening process. Shots were propelled towards target surface by newly developed surface mechanical attrition treatment like process. The principal objective of the present work was to investigate nanocrystallization behaviour of AISI 316 stainless steel under adiabatic and non-adiabatic severe plastic deformation conditions. Two types of flow were used to propel the shots. In first method, only compressed air was used whereas in second method mixture of compressed air and water was used. Water is used to extract rapidly the heat generated during shot-peening so as to produce non-adiabatic conditions. After shot-peening, specimens were characterized by micro-hardness testing, optical microscopy, SEM and XRD. Results showed that nanocrystallized layer on AISI 316 stainless steel specimens can be easily synthesized by severe shot-peening. Hardness traverse as well as optical microscopy showed that with rise in velocity of shot, surface hardness, depth of nanocrystallized layer and total deformed layer increased for shot-peening with both types of flow. However, surface hardness, depth of nanocrystallized layer are higher for the specimen shot-peened using mixture of air and water. No strain induced martensite was observed when specimens were shot-peened by using only air, however, significant volume fraction of strain induced martensite (17.5 to 28.3%) was observed when shot peened with air/water mixture.

Wet torrefaction pre-treatment of yard waste to improve the fuel properties

The utilization of biomass has emerged as an attainable alternative for energy production. However, the intrinsic properties of biomass including hygroscopic behaviour, heterogeneity in structure and high moisture content constraint the usage of biomass in bioenergy applications. Wet torrefaction enhance the fuel properties of the lignocellulosic biomass by treating in hot compressed water. The present study aimed to identify the effectiveness of wet torrefaction to improve the properties of yard waste as an energy resource. Wet torrefaction operating parameters investigated in this study were water-to-biomass ratio (10:1–30:1) and reaction temperature (180–220 °C). The energy yield varies from 63.9% - 74.4% in these operating conditions. Temperature was found to have greater impacts on the fuel properties of biomass compared to water-to-biomass ratio. The higher heating value (HHV) of yard waste achieved was 24.2 MJ/kg after undergoing the wet torrefaction process at 220 °C with water-to-biomass ratio of 10:1. The enhanced properties for wet-torrefied biomass were observed as lower moisture content, lower ash content, higher fixed carbon content and higher heating value in relative to raw yard waste. Torrefied biomass had reduced oxygen content and higher carbon content in comparison with raw biomass, which implied that wet torrefaction is capable in improving the fuel properties.

Local Heat Transfer Control using Liquid Dielectrophoresis at Graphene/Water Interfaces

Graphene-based materials are considered for the solution of the thermal management problem of current and next generation micro/nano-electronics with high heat generation densities. However, the hydrophobic nature of few-layer graphene makes passing heat to a fluid very challenging. We introduced an active and local manipulation of heat transfer between graphene and water using an applied, non-uniform electric field. When water undergoes electric field induced orientation polarization and liquid dielectrophoresis, a substantial increase in heat transfer develops due to a decrease in interfacial thermal resistance and increase in thermal conductivity. By using two locally embedded pin and plate electrodes of different sizes, we demonstrated a two-dimensional heat transfer control between two parallel few-layer graphene slabs. We obtained local heat transfer increase up to nine times at pin electrode region with an ultra-low Kapitza resistance through the studied non-uniform electric field strength range creating highly-ordered compressed water in the experimentally measured density limits. With this technique, heat can be (i) distributed from a smaller location to a larger section and/or (ii) collected to a smaller section from a larger region. Current results are important for hot spot cooling and/or heat focusing applications.

Compressed hot water pretreatment enhanced bioethanol production from corn stalk

Finding alternative use for corn stalk (CS), an abundant agricultural waste, in energy production would solve the problem of it becoming environmental encumbrance and increases energy availability. CS used in this study was exposed to compressed hot water (CHW) pretreatment at 100, 120, 140, 160, 180 and 200 °C for reaction time 10 min and the slurry was used for production of ethanol in a simple bioreactor kept at 30 °C. Optimal performance was recorded with the 180 °C pretreated corn stalk (PCS). Filtration of the slurry improved ethanol production to 31.06 g/L. Under optimal conditions, 73.8% degradation of hemicellulose was recorded. Scanning Electron Microscope images showed induced porosity and increased surface area in the PCS. Crystallinity index of the PCS increased as revealed by X-ray diffraction analysis. CHW pretreatment shows potential as a promising pretreatment method for lignocellulosic materials use for large-scale production of bioethanol that is useable as fuel.

Effect of Dodecyl Trimethyl Ammonium Bromide on the Migration of Water Molecules in the Pores of Lignite: An Experimental and Molecular Simulation Study.

Molecular dynamics simulations and experiments were used to study the influence of dodecyl trimethyl ammonium bromide (DTAB) on the migration of water molecules in the pores of lignite. To simulate the accuracy, 13C NMR was used to confirm the structure of Shengli lignite. It was found through adsorption experiments that DTAB reduces the specific surface area and pore volume of lignite. Molecular simulations indicate that the lignite and water molecules are primarily connected by hydrogen bonding. DTAB impedes the movement of water molecules in the pores of lignite and the storage space of compressed water molecules. Water molecules are mainly present in the pores of lignite in a posture parallel to the XOY plane, which facilitates the formation of hydrogen-bonding networks. However, this also leads to a decrease in the mobility of water molecules. Experimental and simulation results show that DTAB can enter lignite pores, reducing the water absorption in lignite. This is highly significant for the processing and utilization of lignite.

Hydrolysis of Dimethyl Methylphosphonate (DMMP) in Hot-Compressed Water.

Dimethyl methylphosphonate (DMMP) is often used as a chemical surrogate for organophosphate nerve agents, as it exhibits similar physiochemical properties while having significantly lower toxicity. Continuous hydrolysis of DMMP in hot-compressed water is performed at temperatures from 200 to 300 °C, pressures of 20 and 30 MPa, and residence times from 30 to 80 s to evaluate the effects of pressure and temperature on reaction kinetics. DMMP hydrolysis is observed to follow pseudo-first-order reaction behavior, producing methylphosphonic acid and methanol as the only detectable reaction products. This is significant for the practical implementation of a continuous hydrothermal reactor for chemical warfare agent neutralization, as the process only yields stable, less-toxic compounds. Pressure has no discernible effect on the hydrolysis rate in compressed liquid water. Pseudo-first-order Arrhenius parameters are determined, with an activation energy of 90.17 ± 5.68 kJ/mol and a pre-exponential factor of 107.51±0.58 s-1.

Characterization of thermally stable compliant structures with internal fluidic channels

This paper represents a novel method to suppress the thermal effects of flexure mechanism-based nanopositioning system by fluid (air or water) flow under certain pressure conditions through the internal fluidic channels of the compliant structure. The nanopositioning system made of stainless steel was additively manufactured, and the rectangular fluidic channels were formed on each side of the double compound type flexure mechanism-based compliant structure. The motion behavior was characterized by measuring the stiffness and frequency responses of the compliant structure with the hammering test while filling compressed air or the water through the fluidic channels. The thermal behavior was characterized by measuring the temperature distribution over the compliant structure and thermal displacement under the various compressed air pressure and water flow-rate conditions. Dynamic behaviors of the nanopositioning system under various fluid-fed conditions were also characterized by the Finite Element Method and were validated with experimental results. As a result, the compressed air- or water-fed mechanisms have the following characteristics: (1) the damping may increase when the fluid exists in the channels, (2) the compressed air-fed mechanism can move the stage with nanometer precision with fast response time, and (3) the media filled in the fluidic channels significantly lower the temperature increase and reduce thermal displacement error. Interestingly, two-fluid flows of the compressed air and water showed a similar tendency in suppressing the temperature increase. The proposed method is expected to meet the increasing needs for nanometer motion accuracies and the efforts achieving high precision in the thermally stable environments requiring from semiconductor industries and precision machine tool industries.

Hydrothermal liquefaction of wood using a modified multistage shrinking-core model

Wood liquefaction in hot compressed water is modeled using the hydrolysis of Cellulose, Hemicellulose, and Lignin. These three components are reacted under catalyst-free subcritical conditions in a temperature range from 553 K to 640 K, and the heating rate ranges from 2 K/min to 6 K/min. Using a simplified reaction scheme, water-soluble products11WSP: - Water soluble products (WSP), Biocrude, char, and gas are generated through intermediates with each wood component. A modified multistage shrinking core model is employed to simulate biomass particle degradation. The reaction and kinetic regime of the hydrothermal liquefaction22HTL: -Hydrothermal Liquefaction (HTL) process are treated separately for each wood component. Although the lack of initial fast reaction kinetic data limits the development of more accurate models, computed results displayed a generous fit to data from the literature. At 593 K for a 2 K/min heating rate and particle size of 0.08 mm, biocrude shows the maximum yield of 26.87% for wood liquefaction. Although lower heating rates show fast initial lignin hydrolysis, for longer residence times, and close to the critical point, yield outputs show similar yields. Meanwhile, char and gas yields of cellulose model show maximums of 55 wt% and 25 wt% respectively at 640 K with a 2 K/min heating rate. Nevertheless, char yield values become very similar at 640 K for different heating rates for the cellulose hydrolysis model. Both cellulose and lignin hydrolysis models show better hydrolysis with smaller particle sizes. Besides, lignin decomposition shows more dependence on the particle size, where it decomposes much faster with 0.08 mm particle and slower than Cellulose with the 1 mm particle.

Dielectric and structural relaxation of compressed water: Decoupling of motions

Effects of hydrostatic pressure on the dielectric spectra of water are discussed, primarily with a view to the reorientation time of the individual molecular dipole moments. In conformity with the wait-and-switch model of the dielectric relaxation of associating liquids, the reorientation time of pressurized water decreases with density and thus with the concentration of hydrogen bonding abilities. Unlike variations of temperature, however, variations of pressure cause smaller changes in the dipole moment reorientation time than in the structure relaxation time of the liquid. Obviously, the autocorrelation time of density fluctuations does not control the dielectric relaxation in compressed water as strictly as otherwise. This difference between the behaviors at normal and enhanced pressure is discussed in the light of potential pressure-induced changes of the water structure and resulting modifications in the activated rate processes of relaxation.

Hydrothermal carbonization of waste biomass: An experimental comparison between process layouts

This paper contributes to the knowledge on waste biomass conversion processes occurring in the presence of hot compressed water. The experimental procedure detailed herein assesses different process schemes based on the low-temperature reaction known as hydrothermal carbonization. The performances of two lab-scale reactor configurations, with and without a downstream flash expansion step, were evaluated and compared. Each setup was tested with six different types of waste biomass. Fir, beech, and olive prunings are representative of lignocellulosic raw materials, while potato, pea, and carrot are representative of non-lignocellulosic wastes from processing in the local agro-food industry. The batch reactions (200 °C, water/solid = 7/1) were carried out for up to 120 min. The hydrochars were characterized by elemental composition, humidity, heating value, and mass and energy yields. The extent of difference between the results obtained for the two procedures varied significantly with the material treated. At a residence time of 30 min, the solid yields increased due to expansion, ranging from 10 to 36% for lignocellulosic material and 50 to 220% for agro-food industry scraps. The downstream flash expansion step causes an increase of the solid yields, especially for hydrochars from lignocellulosic materials, leading to higher energy recovered compared to the configuration without expansion. Lignocellulosic and agro-food wastes behaved dissimilarly, likely because of different hydrothermal reaction pathways. The additional expansion step can considerably increase the efficiency of energy recovery in full-scale plants, the extent of which depends on the biomass waste substrate used.

Harnessing the potential of common water hyacinth as an industrial raw material for the production of quality biofuel briquettes

Eichhornia crassipes has a high cellulose and hemicellulose content, which are easily converted to simple sugars, thus making the plant suitable for the production of biofuel briquettes. The main purpose of this proposed work, therefore, was to investigate the production of bio briquettes from E. crassipes. The plant was harvested from a wastewater effluent management system, chopped, sun-dried and pulverized to a particle size of < 5 mm and mixed with various binders (Eucalyptus globulus leaves powder, molasses and phytoplankton scum). The binders were appropriately prepared and added to E. crassipes at the ratios of 10%, 20% and 30%. The quality of biofuel briquettes was evaluated using compressed density, relaxed density, water resistance, durability and calorific values (CV) parameters and compared to those of charcoal briquettes already on the market. The results showed a water resistance capacity of 45%, relaxation ratios of between 1.08 and 1.33, CV of 1148.35 kJ/kg for 20% molasses-based briquettes, CV of 1090.43 kJ/kg for 20% E. globulus leaf-based briquettes and CV of 1422.97 kJ/kg for charcoal-based briquettes. In conclusion, therefore, E. crassipes may become a viable raw material for producing quality biofuel briquettes that are durable with the desired calorific value and may be able to withstand mechanical handling and be useful for household and cottage industries locally.

Raman spectroscopic technique towards understanding the degradation of phenol by sodium persulfate in hot compressed water

Degradation of phenol by sodium persulfate (SPS) in hot compressed water (HCW) was investigated in a lab-built fused quartz tube reactor (FQTR) coupled with Raman spectroscopy system. The species of S2O82−, SO42−, HSO4−, SO32− and HSO3− in the reaction system were qualitatively and quantitatively analyzed by Raman spectroscopy. The hydrothermal stability of phenol and SPS at different temperature and the degradation of phenol by SPS were also studied. The results indicated that phenol was not stable in aqueous solution above 200 °C, and that only SO42− was generated in the hydrolysis of SPS at temperatures below 50 °C, and SO42− and HSO4− were generated at higher temperatures. The maximum conversion rate (90.93%) and mineralization efficiency (38.88%) of phenol by SPS was obtained at reaction temperature of 300 °C with 180 min reaction time. During the degradation of phenol by SPS, HSO4− was the main product and S∗ (not detected by Raman spectroscopy) exhibits a positive correlation with temperature. In addition, a degradation pathway of phenol by SPS was proposed. The degradation data for the kinetic analysis indicated that the reaction followed pseudo first-order kinetics, and the reaction rate constants (ks) were given as k50 °C = 0.0083 min−1, k100°C = 0.0197 min−1, k200 °C = 0.0498 min−1, k300 °C = 0.0619 min−1 and k400°C = 0.0505 min−1 at 30 min reaction. Moreover, the activation energy (12.580 kJ mol−1), the enthalpy change (9.064 kJ mol−1) and the entropy change (−222.104 J mol−1) of the reaction were also calculated.

Biohydrogen production improvement using hot compressed water pretreatment on sake brewery waste

Most hydrogen is derived from fossil fuels. Therefore, more environmentally friendly methods for hydrogen production have been investigated. The present report describes a hot compressed water (HCW) pretreatment to increase hydrogen production using sake lees, which is an industrial waste of sake production. The inoculum is obtained from treated biogas slurry. The temperatures of HCW are 130 (0.3 MPa), 150 (0.5 MPa), and 180 °C (0.8 MPa) for 15–120 min. Gas production was analyzed using gas chromatography; fermentation liquid analyses were performed using HPLC. The modified Gompertz model was used to determine hydrogen potential, lag time, and production rate. Results show an increase in the degradation of sake lees with longer holding time and higher temperature. Total sugar and organic acids also are influenced by HCW pretreatment. The maximum hydrogen yield was obtained at 130 °C for 60 min with the result 112.07 mL H2/g COD. The HCW pretreatment successfully decreased the lag phase of biohydrogen production and increased the degree of acidification. Clostridium butyricum, C. acetobutylicum, and other Clostridium sp. were identified in all samples, while Pantoea agglomerans was detected in two samples.

Influence of temperature on decomposition reaction of compressed hot water to valorize Achatina fulica as a functional material

Achatina fulica, which is one of the land snails with high protein content, was decomposed by compressed hot water at various temperatures (100–300°C) and characterized its physicochemical properties, Angiotensin I-converting enzyme (ACE) inhibitory, acetylcholinesterase (AChE) inhibitory, and antioxidant activities. The physical properties of water such as an ionic product changed with increasing temperature produced polysaccharides and peptides by decomposition of the cell structure of A. fulica, indicating various physiological activities. The ACE inhibitory activity represented an IC50 value of 5.60μg/mL at 200°C; 75.88% of AChE inhibitory activity was determined, and ABTS radical scavenging activity was 311.06±0.00mM Trolox equivalent/g at 250°C. This study found that compressed hot water can be used to selective producing of bioactive substances, depending on the temperature of water.

Effect of temperature on the hydrolysis of levan treated with compressed hot water fluids.

The hydrolysis of levan using compressed hot water for the production of functional fructooligosaccharides (FOSs) was investigated. Levans from Erwinia herbicola (EH) and Halomonas smyrnensis (HS) were characterized using scanning electron microscopy and light scattering techniques, and hydrolyzed using compressed hot water at four temperatures (120, 140, 160, and 180°C). The hydrolysates were analyzed using high‐performance liquid chromatography and electrospray ionization‐mass spectrometry. Levan HS showed a crystalline morphology, whereas levan EH showed an aggregated structure. Both levans had molar masses on the order of 106 g/mol, but levan EH had a smaller radius of gyration, hydrodynamic radius, and intrinsic viscosity. Levan EH hydrolyzed into FOSs at approximately 120°C, whereas levan HS required a temperature of at least 160°C, possibly because of differences in the degree of branching of the two levans. Both samples were degraded to fructose when treated at 180°C.

Fire extinguishing efficiency of compressed air foam, water and gel forming agents in a standard class A test fire

Fire extinguishing efficiency of compressed air foam, water and gel forming agents in a standard class A test fire

Extraction and characterization of pectic polysaccharides from Chaenomeles sinensis fruit by hot compressed water

The effects of extraction conditions on the yield of polysaccharides from the fruit of Chaenomeles sinensis (FCS) using a hot compressed water method were investigated. The results showed that an appropriately high temperature (150 °C) and a moderate extraction time (45 min) at a material to water ratio of 1 to 10 g/mL led to a high yield of alcohol precipitation polysaccharide (PA). The purified polysaccharides (CSP-1, CSP-2, and CSP-3) were successfully obtained using a DEAE-52 chromatographic column. Chemical analysis showed that CSP-2 and CSP-3 were homogenous and exhibited characteristics of esterified pectins, whereas CSP-2 mainly consisted of galacturonic acid (GalA), galactose (Gal), arabinose (Ara), rhamnose (Rha), and mannose (Man) with an average molecular weight of 59.1 kDa. Furthermore, CSP-1 possessed stronger antioxidant ability according to DPPH scavenging and reducing power compared with CSP-2 and CSP-3. However, it was weaker with respect to OH scavenging. The technical data presented in this study could help the industry make use of polysaccharides from FCS as a source of pectin for a range of pharmaceutical, culinary, and cosmetic products.

Investigation on the characteristics of dispersion mass transfer associated matter in the silicone oil and water interface

In this manuscript, taking into account the dispersion mass transfer reported in the previous article, the main features of the associated matter in the interface region during the mass transfer process were further investigated (In the study of dispersion mass transfer, the interface associated matter is considered to be a mixture containing both water and silicone oil components. It has a loosely network-like microstructure and exists in the mesoscopic interface region between silicone oil and water.). Especially the structural characteristics of interface associated matter, the transfer and distribution characteristics of associated matter in the interface region, and the influence of the distribution characteristics of the associated matter on the interface pressure were investigated. For the structural characteristics of the associated matter, a structural observation experiment was carried out using a Cryo-scanning electron microscope (Cryo-SEM) to observe its microstructure characteristics, and the intrinsic composition of the interface associated matter was analyzed using Energy Dispersive Spectrometer (EDS). According to the distribution characteristics of the associated matter in the interface region, a Cryo-SEM was used to observe the higher magnification and measure the distance between the silicone oil phase and the water phase in the interface region, that is, the distribution characteristics. According to the distribution characteristics of the associated matter in the interface region, the influence degree of the compression directions on the interface pressure is different when the associated matter is compressed, and an upgraded dual interface pressure synchronous measuring device (DIMD) is designed and fabricated to simultaneously measure interface pressures in different compression directions. The results show that the associated matter of the interface region exhibits obvious network structure characteristic which is significantly different from water and silicone oil, and the EDS test shows that the silicone component has accumulated in the interface region. When the associated matter is formed in the interface region, it will be closer to the silicone oil under the attraction, which indicates that the associated matter is more likely to migrate to the silicone oil in the interface region to alienate the water. The measured interface pressure in different compression directions is different, and the interface pressure of the compressed water -silicone oil is greater than the interface pressure of the compressed silicone oil - water.

Extraction of Polysaccharide from Dendrobium nobile Lindl. by Subcritical Water Extraction.

Subcritical water extraction (SWE) uses hot compressed water as an effective solvent for both polar and nonpolar compounds and has been developed as an environmentally benign extraction technology for natural materials. Polysaccharides as one of the main ingredients in Dendrobium plants showed obvious biological activity. Thus, SWE of polysaccharides obtained from Dendrobium nobile Lindl. was investigated in this work. The response surface methodology (RSM) was combined with a Box–Behnken design to evaluate the influence that the three independent variables had on the response. The optimal extraction conditions (determined via RSM) were 129.83 °C extraction temperature, 16.71 min extraction time, and 1.12 MPa extraction pressure. The maximum predicted polysaccharide yield was 20.67%, which corresponded well with the experiential extraction (21.88%). The polysaccharides obtained from either the stirring extraction, refluxing extraction, ultrasound extraction, or SWE methods were compared, and the extraction processes were modeled. The molecular weight, monosaccharide composition, and antioxidative activities of the polysaccharides were analyzed.

Single reagent treatment and degradation of switchgrass using iron(III)chloride: The effects on hemicellulose, cellulose and lignin

The possibility of using abundant metal chlorides as a single reagent for pretreatment and degradation of switchgrass biomass was studied. Three metal chlorides: MgCl2, CaCl2 and FeCl3 were tested in the initial phase and FeCl3 at 2% w/w loading was found as the most effective reagent for treatment and hydrolysis of switchgrass in hot compressed water. Therefore, FeCl3 was selected for the detailed study and the heat treatment at 140–160 °C or microwaving for 6–10 min was required to activate the FeCl3 after impregnation of switchgrass. These samples could be hydrolyzed in water at 160 °C, without additional catalyst or reagent to produce reducing sugars. In the hydrolysis experiments, FeCl3 impregnated and micro waved switchgrass produced slightly higher total reducing sugar (TRS) yields of 31.5%; whereas the samples heated at 140 °C after FeCl3 impregnation produced 28.6% TRS yield. In a thermogravimetric analysis study, the decomposition temperature of lignin fraction showed the highest shift (ΔTdecomp ~ - 42 °C) after adding 2% w/w FeCl3 and microwaving for 10 min, indicating that strong interactions between FeCl3 and lignin is likely the primary cause of enhancement in polysaccharide degradation.