Saturated Steam Pressure Research Articles

Breakthrough in allergy mitigation using an innovative steam pressure-based processing technique

Peanuts are recognized as one of the most common allergenic foods, known to induce severe Th2-mediated allergic reactions. The resulting global health concern has fostered the necessity to design innovative technologies capable of mitigating allergenicity. This study investigated the effect of an innovative thermomechanical process, “Intensification of Vaporization by Decompression to the Vacuum” (IVDV), on the protein content and immunogenicity of whole peanuts. Through animal studies using peanut allergy BALB/c mouse models, this research revealed a clear reduction in allergic symptoms once challenged with IVDV-treated peanut protein extract, compared to those receiving raw or deep-fried peanut protein extracts. Significant changes in immune response markers in animals were observed, including reduced levels of histamine, Th1/Th2 cytokines, and antibodies, thus confirming the efficacy of IVDV in mitigating allergenicity in peanuts. Saturated steam pressure was demonstrated to have a highly significant positive effect on the reduction of protein content in IVDV-treated samples through degradation, with a noteworthy reduction ranging from 42.3% to 89.2%. This pilot study embarked on a pioneering exploration into the ability of IVDV to offer a viable solution in reducing peanut allergenicity, opening new avenues for enhanced food safety and inclusivity. The ease of scalability of IVDV technology to an industrial level, along with its cost-efficiency, further enhance its appeal for widespread adoption.

Instant Controlled Pressure Drop (DIC) as an innovative pre-treatment for extraction of natural compounds from the brown seaweed Sargassum muticum (Yendo) Fensholt 1955 (Ochrophytina, Fucales)

The effects of the Instant Controlled Pressure Drop (DIC) technology on the recovery of natural compounds from the brown seaweed Sargassum muticum (Yendo) Fensholt 1955 (Ochrophytina, Fucales) were investigated. Fresh biomass of S. muticum was collected on the Brittany Coast, France. Both fresh and Air Impingement-Dried (AID) thalli of 3 and 10 cm length were submitted to DIC during 20 s or 90 s of processing time under 100 or 800 kPa of saturated steam pressure. DIC treatment significantly improved the extraction of sulphate groups at 90 s, and carotene at 20 s under 100 kPa in thalli of 10 cm. While, coupling AID to DIC, the content of neutral sugars, proteins and antioxidants were higher in AID + DIC treatments. Further, a significant increase of 20 % in fucose-containing sulfated polysaccharides and 30 % in sodium alginate under 100 kPa during 90 s, compared to oven-dried, was observed. The biomass of the invasive S. muticum treated by DIC and AID + DIC represented a valuable contribution for extraction of natural compounds. Advantages for industrial integration of DIC were discussed.

Analysis on cause of erosion of guide vane of high‐head Francis turbine in sandy river

AbstractThe Kizilsu River Basin in China is located in the desert Gobi area with high sediment content and high hardness. After 4798h operation, the maintenance of a high‐head Francis turbine in this basin found that the guide vane was seriously worn, and even most of the top and lower skirts of the front of the guide vane were worn off. In this study, the k‐ε turbulence model, ZGB cavitation model and sediment erosion prediction model were used to simulate the solid‐liquid two‐phase flow and cavitation of guide vane. The research results show that the guide vane of a high‐head Francis turbine in a sandy river has a high sediment velocity and serious surface erosion, with the maximum erosion rate of 1.0 × 10−6 kg/(m2·s), while the area near the skirt of the guide vane is a low‐pressure area lower than the saturated steam pressure, and cavitation is very easy to occur, with the maximum vapor volume fraction of 0.9. Serious cavitation erosion occurs near the skirt of the guide vane, and the combined effect of sand erosion and cavitation erosion on the surface of the skirt of the guide vane aggravates the damage of the skirt structure. The research results provide a technical basis for the antiabrasion design of the guide mechanism of the high‐head Francis turbine and the operation and maintenance of the hydropower station in the sandy river.

Kinetic Study and Catalytic Activity of Cr3+ Catalyst Supported on Calcium Silicate Hydrates for VOC Oxidation.

Volatile organic compounds (VOCs) are pollutants that pose significant health and environmental risks, necessitating effective mitigation strategies. Catalytic oxidation emerges as a viable method for converting VOCs into non-toxic end products. This study focuses on synthesizing a catalyst based on calcium silicate hydrates with chromium ions in the CaO-SiO2-Cr(NO3)3-H2O system under hydrothermal conditions and evaluating its thermal stability and catalytic performance. A catalyst with varying concentrations of chromium ions (10, 25, 50, 100 mg/g Cr3+) was synthesized in unstirred suspensions under saturated steam pressure at a temperature of 220 °C. Isothermal curing durations were 8 h, 16 h, and 48 h. Results of X-ray diffraction and atomic absorption spectroscopy showed that hydrothermal synthesis is effective for incorporating up to 100 mg/g Cr3+ into calcium silicate hydrates. The catalyst with Cr3+ ions (50 mg/g) remained stable up to 550 °C, beyond which chromatite was formed. Catalytic oxidation experiments with propanol and propyl acetate revealed that the Cr3+ catalyst supported on calcium silicate hydrates enhances oxygen exchange during the heterogeneous oxidation process. Kinetic calculations indicated that the synthesized catalyst is active, with an activation energy lower than 65 kJ/mol. This study highlights the potential of Cr3+-intercalated calcium silicate hydrates as efficient catalysts for VOC oxidation.

THERMOPHYSICAL PROPERTIES OF ALTERNATIVE FUEL IN A WIDE RANGE OF PARAMETERS

In the presented article, butanol-1 and diesel B0 fuel are degassed in special flasks and their purity is checked using a Karl Fischer 756 KF titratron. Then binary mixtures are prepared in appropriate mole fractions xb-1=(0.0, 0.1773, 0.3493, 0.5514, 1.0) or Vb-1=(0.0, 7.0, 15.79, 30.04 and 100.0)% )in volume percentages by using special connected flasks. Two different static devices with high accuracy were used to measure the saturated vapor pressure of butanol-1, diesel B0 fuel and their binary mixtures [8]. Glass gauge sockets (3, 4, 27) are used to measure saturated vapor pressure at subatmospheric pressure and temperature T=(274.15÷323.15) K (Fig. 1). The metal gauge socket is used to measure the saturated vapor pressure at temperatures T= (323.15÷473.15)K (Fig. 2). The experimentally obtained results of saturated vapor pressure of butanol-1 and diesel B0 fuel mixtures were fitted to analytically by means of Clausius-Clapeyron type equations.Experiments to measure the isobaric heat capacity cp/(C·kg-1·K-1) of butanol-1, diesel B0 fuel and their mixtures at atmos-pheric and saturated vapor pressures were measured in a Pyris 1 type differential scanning calorime-ter (Fig. 4) [10] . The measuring chamber is resistant to a temperature of T=573.15 K and a pressure of 24 bar. Measurements were carried out at temperatures (263.15÷468.15) K, atmospheric p=0.101 MPa and saturated steam pressures Ps/MPa. The experimentally obtained results of heat capacity of butanol-1 and diesel B0 fuel mixtures were analytically written by means of an empirical polynomial equation.

Enhancing Wheat Sprout Attributes Using “Intensification of Vaporization by Decompression to the Vacuum”, an Innovative Drying–Texturizing Technology

Highly valued for their nutritional benefits, sprouts are characterized by high water content, which promotes microbial proliferation, potentially leading to toxicity and a reduced shelf life. To address this challenge, the present study explores the application of a novel drying–texturizing approach, named IVDV (Intensification of Vaporization by Decompression to the Vacuum), to sprouts. This technique would enable faster drying of the sprouts and better preservation of their nutritional content, compared to traditional hot-air drying. Using Response Surface Methodology, optimal IVDV parameters (saturated steam pressure P, processing time t, and water content W) for wheat sprouts were defined, with a focus on preserving vitamins, proteins, and lipids, and optimizing the expansion ratio. This optimization process identified optimal experimental conditions at 5.5 bars, a duration of 15 s, and 8.8% d.b. water content. Under these conditions, the use of IVDV endowed the expanded sprouts with a crunchier and more friable texture. In addition, it significantly improved the preservation of vitamins B6 and E by 412% and 42%, respectively, compared to traditional mild hot-air drying, without significantly affecting vitamin B2, proteins, and lipids. When combined with conventional hot-air drying, IVDV not only enhanced the preservation of the sprouts’ nutritional content but also reduced drying time and energy consumption. This marks a significant advancement in sprouts preservation techniques, paving the way for novel potential applications.

Phase stabilities and thermodynamic properties of crystalline phases in CaO–SiO2–H2O above 100 °C

The current study revises the phase diagram of the CaO–SiO2–H2O system at saturated steam pressure between 100 and 250 °C by combining experimentally observed phase relations, solubility data and thermodynamic restrictions. A new self-consistent thermodynamic dataset for crystalline C-S-H phases is reported. The dataset revises known thermodynamic properties and derives values for phases for which no data have been published up to now. Chemical compositions and molar volumes of the phases were updated based on recent crystal structure refinements. Additionally, thermodynamic properties are deduced for hydroxylellestadite, scawtite and spurrite as they are relevant for autoclaved concrete and metamorphism/metasomatism of rocks. Portlandite dominates together with hillebrandite, xonotlite and low-quartz the equilibrium phase assemblage up to 250 °C. If the formation of the latter three phases is delayed by kinetic reasons, numerous metastable phases can occur.

The Impact of Hydrolysis Regime on the Physical and Mechanical Characteristics of Medium-Density Fiberboards Manufactured from Recycled Wood Fibers

Recycling medium-density fiberboards (MDF) presents notable technological challenges, primarily due to the deteriorated properties of the recycled wood fibers obtained from MDF waste. On the other hand, the enhanced valorization of recycled wood in the manufacturing of wood composites represents a viable approach for implementing the principles of a circular bio-economy in the wood-based panel industry and lowering its carbon footprint. This research aimed to investigate and evaluate the impact of the hydrothermal hydrolysis regime on the physical and mechanical properties of recycled MDF panels (rMDF). The hydrolysis temperature was varied from 121 °C (saturated steam pressure 0.2 MPa) to 134 °C (saturated steam pressure 0.3 MPa), and three hydrolysis durations, i.e., 30, 45, and 60 min, were applied. A control MDF panel, manufactured in laboratory conditions from industrial pulp, was used to perform the comparative analyses. It was observed that the degradation of the rMDF panels occurred when the hydrolysis temperature was increased from 121 °C to 134 °C. The research confirmed the deteriorated physical and mechanical properties of rMDF compared to the panels manufactured from natural wood fibers. Markedly, no significant differences were detected between the density profiles of the rMDF panels and the control boards fabricated from industrial pulp. As a result of the study, it was found that the hydrolysis temperature has a more significant effect than the processing time. It was also established that, in the preliminary preparation of the MDF panels into samples with dimensions similar to those of pulp chips, the optimal hydrolysis regime is at a temperature of 121° C (saturated steam pressure 0.2 MPa) and a time of 30 min.

READY-TO-EAT CHICKPEA PURÉE POWDER BY DRUM DRYING; PHYSICOCHEMICAL AND RHEOLOGICAL PROPERTIES OF POWDER PRODUCT

This study aims to convert raw chickpea (Cicer arietinum L.) into dried chickpea puree powder form using a drum dryer having a high rehydration ratio and for ready-to-use consumption form maintaining its healthy properties. The effects of the drying conditions on the physical, chemical, and rheological properties of chickpea puree powders were investigated. Before drying, raw chickpeas were soaked in water at 25°C for 12 hours and boiled at 100°C for 55 minutes. In the drying process, saturated steam pressures (2, 3, and 4 bar) and drum rotation speeds (2.0, 3.0, 4.0, and 5.0 rpm) were chosen as process variables. The most appropriate process conditions were determined as 3 bar of steam pressure and 2 rpm of drum rotation speed targeting the maximum protein content (30.35±0.18%), maximum rehydration ratio (515±0.01%), and as low as possible browning index (BI)(59.28±4.90) values. It was determined that chickpea puree had the appropriate rheological characteristics when the shear stress and shear rate values for chickpea puree powders with various dry matter contents (%25, %26, %27.5, %30) produced under suitable process parameters were examined.

Effect of Hydrolysis Regime on the Properties of Fibers Obtained from Recycling Medium-Density Fiberboards

Unlike the recycling of particleboards, the recycling of medium-density fiberboards (MDF) is not a widespread industrial practice, and currently, most waste MDF panels are landfilled or incinerated after the end of their life cycle. Therefore, it is of great importance to develop cost-effective methods for MDF recycling. The extraction of resins used for bonding the panels, mostly urea–formaldehyde (UF) resins, is carried out mainly with hydrolysis. Hydrothermal hydrolysis is a more environmentally friendly and cheaper recycling technique compared to acid hydrolysis and allows obtaining a high yield of recycled fibers. The aim of this research work was to investigate and evaluate the effect of hydrolysis regime applied on its efficiency and on the properties of the recycled MDF fibers. For this purpose, thermal hydrolysis was carried out in an autoclave with saturated steam as a heat carrier. The main novelty of the research is the preliminary preparation of the recyclable MDF in samples with dimensions close to those of pulp chips. The effect of hydrolysis regime characteristics, i.e., process time and temperature on the properties of recycled MDF wood fibers, was studied. The hydrolysis temperatures used were 121 °C (saturated steam pressure of 0.2 MPa) and 134 °C (saturated steam pressure of 0.3 MPa); for each temperature, three durations were applied—30, 45, and 60 min. After hydrolysis, the resulting fiber fraction was refined using a hammer mill. The fractional and elemental composition of the recycled fibers obtained were evaluated. The hemicellulose content after each hydrolysis treatment was also determined. The chemical oxygen demand (COD) was defined as an indicator of wastewater contamination and as an indirect indicator of the quantitative yield of the process. The results revealed no significant changes in the elemental composition of the recycled fibers, and the hydrolysis regimes used showed no decrease in pentosan content. The recycled MDF fibers exhibited similar fiber morphology and fractional composition, being shorter than fibers from industrial pulp. The increased temperature and time of hydrolysis resulted in a significant increase in COD values. Based on the obtained results, with a view to the slightest contamination of wastewater (as determined by COD), the most promising hydrolysis regime was at a temperature of 121 °C and a time of 30 min. It should be emphasized that for a confirmation of this statement, the properties of MDF panels fabricated with fibers recycled in different regimes should be subsequently investigated.

Swelling of beech wood (Fagus sylvatica L.) during gaseous ammonia treatment as a function of pressure

AbstractThis paper deals with the optical observation and evaluation of the swelling of beech wood samples (Fagus sylvatica L.) during gaseous ammonia treatment. The pressure level was varied in several experiments from ambient pressure to almost saturated steam pressure at isothermal conditions at 20 °C. The initial moisture content of the wood was oven dried and also conditioned (65% RH/20 °C). All experiments were carried out in a self-developed experimental setup. It consisted of three parts: a pressure vessel with a glass pane at the top, a camera with additional lighting above it and an algorithm for the semi-automatic evaluation of the data. Parallel investigation of the maximum swelling in water of specimens of the same origin showed that ammonia leads to a higher swelling in tangential direction (up to 23%). The swell-inhibiting influence by the wood rays can be observed on the basis of the comparison to the water swelling in radial direction. Furthermore, the results visualise the change in crystal structure from cellulose I to ammonia-cellulose I.

Optimization of DIC-Tripolium Ecofriendly Extraction Process: Recovery of Hesperidin from Orange Byproducts, Antioxidant and α-Amylase Inhibition of Extracts.

This study aimed to investigate the effect of an innovative ecofriendly process-instant controlled pressure drop technology, also known as "détente instantanée contrôlée" or DIC-coupled with Tripolium extraction (DIC-Tripolium), on the hesperidin recovery, and antioxidant and antidiabetic activities of orange byproduct extracts. A DIC pretreatment was applied to partially dried orange byproducts (~16% wet basis). A central composite rotatable design (CCRD), composed of 13 experimental trials (four factorial points, four-star points, and five repetitions for the central point), was followed by a Tripolium process consisting of successive intermittent extraction periods using ethanol/water solvent at 20 ± 1 °C, 5 kPa for 5 min and m/v ratio = 5 g/50 mL. The DIC pretreatment, coupled with the Tripolium process, increased the extractability of hesperidin (from 1.55- to 4.67-fold compared to untreated DIC orange byproducts). The radical scavenging activities of the extracts were also enhanced or preserved in different DIC-Tripolium extracts. The α-Amylase inhibition percentage varied between 55.6 ± 0.02 and 88.30 ± 0.01% according to DIC-Tripolium conditions. The multi-criteria optimized condition of DIC-Tripolium extraction, allowing for the maximization of the hesperidin content, radical scavenging activities, iron chelating activity, and α-amylase inhibition of extracts, corresponds to a DIC saturated steam pressure of 599.4 kPa and a DIC pretreatment time of 38 s.

Multi-objective optimization of marine nuclear power secondary circuit system based on improved multi-objective particle swarm optimization algorithm

The mathematical model for the main equipment and auxiliary equipment of the marine nuclear power secondary circuit system and the system heat balance calculation model are established. A complete mathematical model of the secondary circuit system is obtained by coupling the above model. In addition, an adaptive multi-objective particle swarm optimization algorithm based on angle penalized distance (AMOPSO-APD) for complex and strong coupling marine nuclear power system is obtained by introducing the angle penalized distance and the adaptive adjustment strategy of algorithm parameters based on convergence factor in the MOPSO algorithm. By optimizing the benchmark test problems to compare the performance of the improved algorithm, the original one, and the NSGA-II algorithm. It is discovered that the improved algorithm has greatly enhanced search capability and optimization efficiency. Sensitivity analysis is used to choose parameters for optimization that have a significant impact on the equipment structure and system performance, such as the secondary circuit saturated steam pressure, the U-tube outer diameter, and the coolant flow velocity in U-tube. Satisfying the safety, performance, and structure constraints, taking the lightest weight, minimum volume, and highest effective efficiency of the secondary circuit system as the optimization objectives, the optimal design for the system is carried out with the AMOPSO-APD algorithm, the Pareto optimal solutions and Pareto front are obtained, and the TOPSIS method is used to choose the compromise optimization scheme. In the optimized secondary circuit system, the weight is reduced by 10.57%, the volume is reduced by 13.68%, and the effective efficiency is increased by 4.26%.

A comprehensive novel approach for fire analysis of tunnels structural design

The main purpose of this paper is to present a comprehensive novel methodology for fire analysis of infrastructures, viz. tunnels, via studying the effects of a major fire event on a case study tunnel, Louis Hippolyte Lafontaine Tunnel (TLHL). A weak thermo-mechanical coupling analysis is performed via a staggered scheme to evaluate the structural integrity of the precast tunnel caissons when subjected to fire. The effect of explosive spalling on the tunnel’s structural integrity was evaluated based on saturated steam pressure (SSP) with a cut-off peak. In-situ tests were conducted to assess the spalling of concrete in the TLHL and calibrate the spalling parameters in the numerical models. Both in-situ tests and numerical models predicted that spalling occurs approximately within two minutes in the fire event, which leads to a reduction in tunnel cross-section and structural capacity and impacts the long-term durability of the tunnel. In this study, based on the analysis results, passive fire protections were suggested to prevent the loss in structural integrity. Furthermore, the numerical simulations considering ground-structure interaction were carried out to firstly predict the response of ground and tunnel caissons, secondly, confirm the adequacy of the structural design of the tunnel, and finally, to ascertain the performance of fire protection when the tunnel is subjected to fire.

Prediction of energy and cavitation characteristics of high specific speed Francis hydraulic turbines

BACKGROUND: Cavitation is a phenomenon that occurs in vane hydraulic machines: pumps, hydraulic turbines, when the pressure in a certain area of the flow reaches the level of saturated steam pressure. Its occurrence depends on the design and mode of operation of the hydraulic turbine. In order to design a hydraulic turbine with high cavitation qualities, it is necessary to be able to reliably predict this phenomenon.
 AIMS: The article describes approaches to modeling the operation of Francis hydraulic turbines based on the ANSYS software package.
 METHODS: Using quasi-3D methods was modeled turbine blade system with 75 meters head. Hydrodynamic computation carried out in single-phase and two-phase formulations using the ANSYS CFX package.
 RESULTS: The design of a flow path Francis turbine 3D solid model with a specific speed coefficient ns =283 has been completed. The flow part of the hydraulic turbine includes a spiral case, a stator, a guide vane, an impeller and a draft tube. Computational modeling of the flow of a single-phase viscous fluid in a hydraulic turbine in different modes was carried out to construct a universal characteristic. The optimal efficiency is found and the flow characteristics are calculated. The losses in the elements of the flow part of the hydroturbine under various operating modes are determined, the zone of optimal operation is found. The cavitation flow is calculated using a two-phase flow model (water-steam). For both sides of the impeller blade, a pressure distribution was obtained, which can be used to judge the possibility of cavitation in areas where the pressure of the water column is less than the vaporization pressure. The value of the critical cavitation coefficient for the three most unfavorable modes was determined, and the dependence of the efficiency on the cavitation coefficient was constructed. The area occupied by steam on the blade during cavitation flow is visualized, its area is determined relative to the surface area of the blade.
 CONCLUSIONS: The designed hydraulic turbine has good energy and cavitation qualities, confirmed by the calculation. This version of the hydroturbine can be used as the initial one with further optimization of the blade system and elements of the flow path, to improve the energy and cavitation qualities.

Effect of synthetic zeolite on tobermorite synthesis

This paper presents the results of a study of the effect of synthetic zeolite addition on the formation of tobermorite in a burnt lime-quartz mixture. Synthetic zeolite was obtained by thermal activation of halloysite followed by boiling in sodium hydroxide solution. In this study, the formation of tobermorite was investigated at a constant CaO/SiO2 molar ratio of 0.86 under autoclaving conditions corresponding to saturated steam pressure at 180ºC. The synthesis times were 4 and 12 hours. Synthetic zeolite was added at 5%, 15% and 30%. Studies have shown that synthetic zeolite infl uences the formation of hydrated calcium silicates with poor crystallinity. After 4 hours of autoclaving for samples with synthetic zeolite, a small peak of tobermorite can be found on the XRD pattern. In samples where the molar ratio of Al/(Al+Si) > 0.15 was exceeded, hydrogarnets of the hibschite-katoite group appear. The paper shows that hydrogarnets of the hibschite-katoite group appear for samples with 15% and 30% zeolite after 4 hours of hydrothermal treatment. The intensity of the katoite reflection decreases with increasing autoclaving time and disappears for the sample with 15% zeolite after 12 hours of autoclaving. The presence of portlandite was also demonstrated in these samples.

Effect of Steam Flash-Explosion on Physicochemical Properties and Structure of High-Temperature Denatured Defatted Rice Bran Protein Isolate.

The effects of Steam Flash-Explosion (SFE) on the physicochemical properties and molecular structure of high-temperature denatured defatted rice bran protein isolate (RBPI) were investigated. The mechanism of SFE treatment on high-temperature denatured defatted RBPI was revealed. The analysis of the physical and chemical properties of RBPI showed that the surface hydrophobicity, characteristic viscosity, and thermal stability of rice bran protein isolate were significantly affected by the pressure of saturated steam and pressure holding time. Under the conditions of 2.1 MPa and 210 s, the surface hydrophobicity index decreased significantly from 137.5 to 17.5, and the characteristic viscosity increased significantly. The peak temperature of denaturation decreases from 114.2 to 106.7 °C, and the enthalpy of denaturation decreases from 356.3 to 231.4 J/g. The higher structure (circular dichroic spectrum and endogenous fluorescence spectrum) of rice bran protein isolate was analyzed by volume rejection chromatography (SEC). The results showed that steam flash treatment could depolymerize and aggregate RBPI, and the relative molecular weight distribution changed greatly. The decrease in small molecules with poor solubility was accompanied by the increase in macromolecules (>550 kDa) soluble aggregates, which were the products of a Maillard reaction. The contents of free sulfhydryl and disulfide bonds in high-temperature rice bran meal protein isolate were significantly increased, which resulted in the increase in soluble aggregates containing disulfide bonds. Circular dichroism (CD) analysis showed that the α-helix content of the isolated protein was significantly decreased, the random curl content was increased, and the secondary structure of the isolated protein changed from order to disorder. The results of endogenous fluorescence spectroscopy showed that the high-temperature rice bran meal protein isolate was more extended, tryptophan was in a more hydrophilic microenvironment, the fluorescence intensity was reduced, and the tertiary structure was changed. In addition, the mean particle size and net surface charge of protein isolate increased in the aqueous solution, which was conducive to the development of the functional properties of the protein.

Thermal stability of synthetic high basicity calcium silicate hydrates substituted with Cr3+ ions

In this work, the formation mechanism, the thermal stability (280–1000 °C) and the surface area properties of calcium silicate hydrates substituted with Cr3+ ions under hydrothermal conditions were investigated. In this experiment, CaO, amorphous SiO2·nH2O raw materials and Cr(NO3)3·9H2O (5 or 15 g Cr3+/dm3 (accordingly, Cr:Ca:Si:H2O ratios were equal to 0.002:1.5:1:1.098 and 0.006:1.5:1:1.094)) solutions were used. Hydrothermal synthesis was performed in unstirred suspensions, in an autoclave, under saturated steam pressure (∼ 10 bar) at a temperature of 200 °C for 1 h. The thermal stability of the synthesized samples was investigated at 280, 500 and 1000 °C with a temperature increase rate of 8.33 °C/h. It was determined that Cr3+ ions changed the formation mechanism of high basicity calcium silicate hydrates and yielded different synthesized compounds: a lower amount of Cr3+ ions accelerated the reaction of the raw material and promoted the crystallization of α-C2SH and xonotlite, while a higher concentration of Cr3+ ions effected only the formation of semicrystalline type compounds (C-S-H (I) and C-S-H (II)). Calcium silicate hydrates substituted with Cr3+ ions remained stable up to 250 °C temperature because, at a higher temperature, calcium chromate started to form. Also, when the calcination temperature was equal to 1000 °C, the Cr3+ ions additive accelerated the crystallinity of calcium silicates (wollastonite and belite). The results of the SBET measurements showed that the Cr3+ ions additive positively influenced the values of the specific surface area (total of 76.17 m2/g). However, these values decreased after the samples were calcinated at a temperature of 500 °C (the value dropped to 48.02 m2/g).

Study on the influence of structural parameters on the flow and cavitation characteristics of tandem multi-stage pressure-reducing valves

Tandem multi-stage pressure-reducing valves (TMSPRV) are widely used for piping systems in the process industry. The flow coefficient is a central factor in valve design. The cavitation was caused by the local pressure of the fluid passing through the pressure-reducing valve being lower than the saturated steam pressure. Would cause serious damage to the pipeline system. Therefore, it is important to investigate systematically the effect of throttling structure parameters on the flow and cavitation characteristics of valves. In this paper, a combination of experimental and numerical simulations was used to study the effect of different structural parameters of valves on the flow coefficient. The results showed that increasing the flow channel inclination is beneficial to enlarging the flow coefficient. Meanwhile, the effects of different structural parameters on pressure and velocity of pressure reducing valves are discussed, the results indicated that increasing the inclination of the flow channel would reduce the vortex volume at the outlet. With the increase of the chamfer, the low-pressure area caused by the vortex in the near-wall surface decreases. Numerical simulations are conducted to investigate the effect of different structural parameters on the cavitation characteristics of valves. The numerical results showed that the flow channel inclination angle is 60° and the flow channel chamfer is less than 6 mm as the optimal value. In summary, considering the influence of structural parameters on flow coefficient, flow characteristics, and cavitation characteristics. The runner inclination angle is 60°, and the runner chamfer is 4 mm as the best value. The research work in this paper could provide technical support to achieve a better fluid pressure reducing and flow state of the TMSPRV under severe working conditions.

Effect of intercalated metal ions on the specific surface area and porosity of dibasic calcium silicate hydrate

This work aims to determine the influence of adsorbed Cu2+, Co2+, and Cr3+ ions on the porosity of synthetic calcium silicate hydrate by analyzing nitrogen adsorption and desorption isotherms. The calcium silicate hydrate sample was synthesized under saturated steam pressure at a 175 °C temperature when the duration of isothermal curing was 16 h. The intercalation of Cu2+, Co2+, or Cr3+ ions was based on the adsorption experiment at 25 °C temperature. It was obtained that after adsorption 100 mg of metal ions were intercalated in 1 g of the sample. The analysis of nitrogen adsorption-desorption isotherms showed, that the nature of intercalated metal ions strongly affects the specific surface area and porosity of adsorbent. It was calculated that the specific surfaces area of the adsorbent increases during adsorption of Cu2+ and Co2+ ions and decreases during adsorption of Cr3+ ions. During calcination, adsorbent and adsorbent with intercalated Co2+ ions became non-porous materials, while samples with intercalated Cr3+ and Cu2+ ions showed a different tendency. The classification of hysteresis loops and calculations by using the corrected Kelvin equation and Orr et al. scheme revealed that the shape of pores depends on the nature of adsorbate. The obtained results were confirmed by analysis of nitrogen adsorption-desorption isotherms as well as SEM and TEM analysis.