Saturated Steam Pressure Research Articles

Impact of Instant Controlled Pressure Drop Treatment on Dehydration and Rehydration Kinetics of Green Moroccan Pepper (Capsicum Annuum)

Abstract A comparative study of various drying techniques were carried out on Green Moroccan Peppers GMPs, Traditional Hot Air Drying, Swell Drying SD, and freeze drying, in order to compare the dried product's behavior during drying and rehydration. Moreover, starting accessibility, and water effective diffusivity during drying and rehydration were studied. The water holding capacity of dried GMPs were investigated as well. The impacts of Instant Controlled Pressure Drop process (DIC) on dehydration and rehydration kinetics and functional properties (water holding capacity) were compared to Freeze Drying (FD) and Traditional Hot Air Drying processes (THD). DIC treatment was carried out on pre-dried peppers (classical hot air drying at 50 °C, 265 Pa initial partial pressure of vapor in the air flux, 1.2 m s-1) to reach a moisture content of 20% dry basis varying the saturated steam pressure (ranged from 0.1 to 0.6 MPa) and heating time (ranged from 9 to 35 s) and keeping the initial water content constant at 20% db. Drying and rehydration kinetics of DIC-textured and untreated peppers were well interpreted by a specific model coupling a starting superficial interaction with Fickian diffusion. Response parameters (dependent variables) were the dehydration and rehydration starting accessibility Ws (g H2O/g dry matter), effective diffusivity D eff (m 2 s -1 ) and drying time t d0,05% (min). Response Surface Methodology RSM was employed. Compared to THD, DIC treatment dramatically increased the starting accessibility and the effective water diffusivity during hot air drying; it allowed the drying time needed to get a final water content of 0.05% db, to decrease by 1.7 times. Regarding the rehydration ability, the time needed to reach 300% db, were reduced 3.7 times under optimum DIC conditions. Fickian diffusion model could not explain FD rehydration, which appeared as a pure water/surface interaction. Water Holding Capacity of DIC dried products was higher than FD and THD.

In situ time-resolved X-ray diffraction of tobermorite formation process under hydrothermal condition: Influence of reactive al compound

Hydrothermal formation reaction of tobermorite in the autoclaved aerated concrete (AAC) process has been investigated by in situ X-ray diffraction. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used. XRD measurements were conducted in a temperature range 100–190°C throughout 12 h of reaction time with a time interval of 4.25 min under a saturated steam pressure. To clarify the tobermorite formation mechanism in the AAC process, the effect of Al addition on the tobermorite formation reaction was studied. As intermediate phases, non-crystalline calcium silicate hydrate (C-S-H), hydroxylellestadite (HE), and katoite (KA) were clearly observed. Consequently, it was confirmed that there were two reaction pathways via C-S-H and KA in the tobermorite formation reaction of Al containing system. In addition, detailed information on the structural changes during the hydrothermal reaction was obtained.

Optimizing thermomechanical pretreatment conditions to enhance enzymatic hydrolysis of wheat straw by response surface methodology

Abstract Wheat straw was pretreated with a thermomechanical process developed in our laboratory to improve the enzymatic hydrolysis extent of potentially fermentable sugars. This process involves subjecting the lignocellulosic biomass for a short time to saturated steam pressure, followed by an instantaneous decompression to vacuum at 5 kPa. Increasing of the heat induced by saturated steam result in intensive vapour formation in the capillary porous structure of the plant material and the subsequent release of the pressure to vacuum allows fixing the expanded structure. Response surface methodology (RSM) based on central composite design was used to optimize three independent variables of the pretreatment process: processing pressure (300–700 kPa), initial moisture contents of wheat straw (10–40%) and processing time (3–62 min). The process was optimised for hydrolysis yield and initial hydrolysis rate obtained by enzymatic hydrolysis on the pretreated solids by Celluclast (1.5 L). The analysis of variance (ANOVA) revealed that, among the process variables, processing pressure and processing time have the most significant effect on the hydrolysis yield and on initial rate of hydrolysis whereas initial moisture content observed significantly lower effect on the two responses. The predicted hydrolysis yield and in a lesser extent the predicted initial rate of hydrolysis agreed satisfactorily with the experimental values with R2 of 96% and 86% respectively.

Hydrothermal solidification of municipal solid waste incineration fly ash

Hydrothermal solidification of municipal solid waste incineration (MSWI) fly ash has been conducted under saturated steam pressure at 200 °C for up to 48 h with quartz addition. To enhance the strength of solidified specimens further, the raw fly ash was pre-treated by water-washing and mixed with NaOH solution (2 M) as reaction solvent. Experimental results showed that curing time and temperature had significant effects on strength development. Strength development was found to be mainly due to tobermorite formation, and addition of quartz and NaOH solution promoted tobermorite formation. The raw fly ash could also be used as an additive to solidify MSWI bottom ash, and with raw fly ash addition (10%) the flexural strength of solidified specimens reached more than 21 MPa, suggesting high potential to recycle 100% MSWI ash (e.g. as 10% fly ash + 90% bottom ash). Leaching tests were conducted to determine amounts of heavy metals dissolved from solidified specimens. The results showed that under the hydrothermal conditions of this study, leaching of heavy metals was very low. As such, the hydrothermal processing method might have high potential for recycling/reusing MSWI fly ash on a large scale.

Hydrothermal synthesis of porous materials from sepiolite

In order not only to manufacture a tough porous material from sepiolite but also to sustain the inherent properties of the sepiolite, a hydrothermal experiment was carried out under saturated steam pressure at 473 K for up to 24 h by mixing slaked lime. The experimental results show that the addition of slaked lime exerts a positive effect on the strength development, and the strength enhancement is found to be due to tobermorite and calcium silicate hydrate (CSH) gel formation. Curing time seems to condition the strength development. A fine particle size of sepiolite improves its activity during the hydrothermal process, thus offering a higher strength and quicker hardening rate of the synthesized specimen. The acid activation also has a beneficial effect on the strength development. The hardening mechanism of the synthesized specimen is different between the specimens synthesized with or without acid activation. The strength enhancement for sepiolite with acid activating is due mainly to CSH gel formation, instead of tobermorite formation without acid activation.

Extraction of essential oils from Algerian myrtle leaves using instant controlled pressure drop technology

In the present work, the new extraction process of Détente Instantanée Contrôlée DIC (French, for instant controlled pressure drop) was studied, developed, quantitatively and qualitatively compared to the conventional hydrodistillation method for the extraction of essential oils from Algerian myrtle leaves. DIC was used as a thermomechanical treatment, DIC subjecting the product to a high-pressure saturated steam. The DIC cycle ends with an abrupt pressure drop towards vacuum, and this instantly leads to an autovaporization of myrtle volatile compounds. An immediate condensation in the vacuum tank produced a micro-emulsion of water and essential oils. Thus, an ultra-rapid cooling of residual leaves occurred, precluding any thermal degradation. An experimental protocol was designed with 3 independent variables: saturated steam pressure between 0.1 and 0.6 MPa, resulting in a temperature between 100 and 160 °C, a total thermal processing time between 19 and 221 s, and between 2 and 6 DIC cycles. The essential oils yield was defined as the main dependent variable. This direct extraction gave high yields and high quality essential oil, as revealed by composition and antioxidant activity (results not shown). After this treatment, the myrtle leaves were recovered and hydrodistilled in order to quantify the essential oil content in residual DIC-treated samples. Scanning electron microscope (SEM) showed some modification of the structure with a slight destruction of cell walls after DIC treatment.

In Situ Time‐Resolved X‐Ray Diffraction of Tobermorite Formation Process Under Autoclave Condition

Hydrothermal formation reaction of tobermorite has been investigated by in situ X‐ray diffraction (XRD) using high‐energy X‐rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon‐counting pixel array detector. XRD measurements were conducted in a temperature range of 100°–190°C throughout 7.5 h of reaction time with a time interval of 4.25 min under a saturated steam pressure. Two samples using different types of cements were compared: high early strength Portland cement and ordinary Portland cement. In both cases, noncrystalline calcium silicate hydrate (C–S–H), hydroxylellestadite (HE), and katoite were clearly observed as intermediate materials. A possible mechanism that the consumption of noncrystalline C–S–H and HE as precursors of tobermorite occurs sequentially rather than simultaneously has been suggested. Four tobermorite peaks corresponding to different reflections started to be detected at the same timing, suggesting tobermorite is formed without any preference for a particular crystal axis at the beginning. A decrease in the Bragg spacing of the basal reflection during the reaction was observed, implying the increase of periodicity along the c‐axis.

Hydrothermal solidification of municipal solid waste incineration bottom ash with slag addition

Hydrothermal solidification of municipal solid waste incineration (MSWI) bottom ash has been carried out under saturated steam pressure (1.56 MPa) at 200 °C for up to 24 h by mixing quartz, slaked lime and water-cooled blast furnace slag (WBFS). The strength enhancement for the WBFS addition was best. The strength development was shown to be due mainly to tobermorite formation, and the tobermorite formation densified matrix, thus promoting the strength development. WBFS seemed to have a higher reactivity than the quartz during the initial hydrothermal process, which provided more silica available to harden the solidified specimens. However, a longer curing time (24 h) was favorable to the quartz dissolution for tobermorite formation, which in turn, enhanced the strength for quartz addition. Curing time affected the crystal morphology evolution, and the stubby plate of tobermorite seemed to result in a high strength enhancement in this study. Laboratory leaching tests were conducted to determine the amount of heavy metals dissolved from the final solidified specimens, and the leaching results showed that after hydrothermal processing the heavy metals dissolved from the solidified specimens were reduced effectively. As such, the hydrothermal processing may have a high potential for recycling/reusing MSWI ash on a large scale.

Saturated-Steam Pressure Drop in Flow Through Porous Media

Summary This note provides a simple steady-state method for estimating the pressure drop for steam vapor flowing at a constant mass rate through porous media. The derived formula includes the relevant properties of saturated steam and allows for their distribution along the zone of pressure variation. It also eliminates the need for steam tables within the applicable pressure range (10-2,900 psia). The method can also be extended to cases in which the rate varies in a known manner because of heat loss or other factors.

A new formula for saturated water steam pressure within the temperature range −25 to 220°C

Instead of approximation formula ln(E(t)/E(0)) = [(a − bt)t/(c + T)] commonly used at present for representing dependence of pressure of saturated streams of liquid water E upon temperature we suggested new approximation formula of greater accuracy in the form ln(E(t)/E(0)) = [(A − Bt + Ct2)t/T], where t and T are temperature in °C and K respectively. For this formula with parameters A = 19.846, B = 8.97 × 10−3, C = 1.248 × 10−5 and E(0) = 6.1121 GPa with ITS-90 temperature scale and for temperature range from 0°C to 110°C relative difference of approximation applying six parameter formula by W. Wagner and A. Prus 2002, developed for positive temperatures, is less than 0.005%, that is approximately 15 times less than accuracy obtained with the firs formula. Increase of temperature range results in relative difference increasing, but for even temperature range from 0°C to 220°C it does not higher than 0.1%. For negative temperatures relative difference between our formula and a formula of D. M. Murphy and T. Koop, 2005, is less than 0.1% for temperatures higher than −25°C. This paper also presents values of coefficients for approximation of Goff and Grach formula recommended by IMO. The procedure of finding dew point Td for known water steam pressure en based on our formula adds up to solving an algebraic equation of a third degree, which coefficients are presented in this paper. For simplifying this procedure this paper also includes approximation ratio applying a coefficient A noted above, in the form Td(en) = \( \frac{{AT_0 }} {{A - \varepsilon }} \) + 0.0866ɛ2 + 0.0116ɛ10/3, where ɛ = ln(en/E(T0)). Error of dew point recovery in this ratio is less than 0.005 K within the range from 0 to 50°C.

A thermoeconomic analysis of biomass energy for trigeneration

The principal objective of this study is to formulate a calculation process, based on the second law of exergy, for evaluating the thermoeconomic potential of a steam-turbine plant for trigeneration. The plant employs biomass, namely, waste wood as its energy source. Four different plant configurations are presented and assessed. ‘Their cost effectiveness is evaluated with varying economic and operating parameters’, because only the fuel price and electricity price are varied. In case 1, high pressure superheated steam generated is supplied to meet the demand for process heat as well as chilled water production in an absorption chiller. In cases 2 and 3, steam is extracted at appropriate stages of the turbine and supplied to meet the demand for process heat and chilled water production in an absorption chiller. Steam generated in case 2 produces sufficient power to meet internal demands while case 3 generates excess electricity for sale back to the utility. In case 4, low pressure saturated steam is generated to meet the demand for process heat and electricity is bought from the utilities, including those used to power an electric vapour-compression chiller. For all cases, it was found that exergy destruction is most extensive in the furnace, amounting to nearly 60%. Exergy destruction in the steam drum is the next most extensive ranging from 11% to 16%. It was also observed that the overall production cost decreases with steam pressure and increases with steam temperature.

Hydrothermal formation of tobermorite studied byin situX-ray diffraction under autoclave condition

Hydrothermal formation of tobermorite from a pre-cured cake has been investigated by transmission X-ray diffraction (XRD) using high-energy X-rays from a synchrotron radiation source in combination with a newly designed autoclave cell. The autoclave cell has a large and thin beryllium window for wide-angle X-ray diffraction; nevertheless, it withstands a steam pressure of more than 1.2 MPa, which enables in situ XRD measurements in a temperature range of 373 to 463 K under a saturated steam pressure. Formation and/or decomposition of several components has been successfully observed during 7.5 h of reaction time. From the intensity changes of the intermediate materials, namely non-crystalline C-S-H and hydroxylellestadite, two pathways for tobermorite formation have been confirmed. Thus, the newly developed autoclave cell can be used for the analyses of reaction mechanisms under specific atmospheres and temperatures.

The effect of elevated inlet air temperature and relative humidity on cogeneration system

The effect of elevated inlet air temperature and relative humidity on a gas turbine (GT) cogeneration system performance was investigated. The analysis was carried out on a GT of a capacity 171 MW at ISO condition, which is integrated with a dual pressure heat recovery steam generator (HRSG), the cogeneration system had been tested under Kuwait summer climate conditions. A computational model was developed and solved using engineering equation solver professional package to investigate the performance of a dual pressure GT-HRSG system. The suggested HRSG is capable of producing high-pressure superheated steam at 150 bar and 510°C to operate a power generation steam turbine cycle, and a medium pressure saturated steam at 15 bar to run a thermal vapor compression (TVC) desalination system. In this research, the influence of elevated inlet air temperature and relative humidity on the energy assessment of the suggested cogeneration system was thoroughly investigated. Results indicated that operating GT under elevated values of inlet air temperatures is characterized by low values of net power and thermal efficiency. At elevated inlet air temperatures, increasing relative humidity has a small positive impact on GT cycle net power and thermal efficiency. Integrating the GT with HRSG to generate steam for power generation and process heat tends to increase energy utilization factor of the system at elevated inlet air temperatures. Increasing inlet air temperature plays a negative impact on power to heat ratio (PHR), while relative humidity has no effect on PHR. Copyright © 2009 John Wiley & Sons, Ltd.

Kinetics of hydrothermal crystallization under saturated steam pressure and the self-healing effect by nanocrystallite for hydroxyapatite coatings

Hydroxyapatite coatings (HACs) with a low crystalline state were prepared using the plasma spraying process followed by hermetic autoclaving hydrothermal treatment at 100, 150 and 200 °C. Experimental evidence confirmed that the HACs became significantly crystallized and the content of amorphous calcium phosphate decreased by performing the autoclaving hydrothermal treatment in an ambient saturated steam pressure system. The obvious chemisorbed hydroxy groups (OH) peak in the X-ray photoelectron spectra detected from the hydrothermally crystallized HAC specimens means that the hydroxyl-deficient state of plasma-sprayed HACs is significantly improved by the abundant replenished OH groups. The HA nanocrystallite observed from scanning electron microscopy and transmission electron microscopy images within hydrothermally treated HACs is the result of nucleation and grain growth through the replenishment of OH groups into the hydroxyl-deficient HA crystal structure. The microstructural self-healing effect is a result of reduction in defects (pores, microcracks and lamellar boundaries) due to new-growth HA nanocrystallite. According to the systematic derivation of the Arrhenius equation, the HA crystallization is a second-order Arrhenius reaction kinetics. Besides the effects of heating temperature and an atmosphere with abundant water molecules, the saturated steam pressure is a crucial factor which significantly improves the crystallization rate constant and further reduces the activation energy for the hydrothermal HA crystallization.

The influence of impurities on the saturated vapor pressure hydrocarbon media

Here are presented experimental result due to the research of the impact non – volatile admixture on the pressure of saturated steam of Hydrocarbonic medium. It is showed, that in their presence is watched the positive deflection from ideal state due to the Raul's low. Also is watched an appropriate decrease of the quantity of positive deflection of saturated steam from Raul's law in Hydrocarbonic consequence C­6H14 - C13H28 – C16H34,, which could be explained by increasing of depressive intermolecula cooperation energy with increasing of molecule's possibility to polarize.

Potential utilization of riverbed sediments by hydrothermal solidification and its hardening mechanism

Hydrothermal solidification of riverbed sediments (silt) has been carried out in a Teflon (PTFE) lined stainless steel hydrothermal apparatus, under saturated steam pressure at 343–473 K for 2–24 h by calcium hydrate introduction. Tobermorite was shown to be the most important strength-producing constituent of the solidified silt. A longer curing time or a higher curing temperature was shown to be favorable to the tobermorite formation, thus promoting strength development; however, overlong curing time (24 h) seemed to affect the strength development negatively. The hardening mechanism consisted of the crystal growth/morphology evolution during the hydrothermal process. The species dissolved from the silt were precipitated first as fine particles, and then some of the particles seemed to build up the rudimental morphology of calcium silicate hydrate (CSH) gel. The CSH gel, with precipitated particles, appeared to cause some reorganization within the matrix, which made the matrix denser and thus gave an initial strength development. Tobermorite, transformed inevitably from the CSH gel, reinforced the matrix with its interlocked structure, and thus further promoted the strength development.

Isolation of Indonesian Cananga Oil by Instantaneous Controlled Pressure Drop

The isolation of cananga oil by a new process, Instantaneous Controlled Pressure Drop (DIC), was investigated. This process consists in heating the dry cananga (Cananga odorata Hook. fil. et Thomson, forma macrophylla) flowers for a short time period by steam, followed by an abrupt pressure drop into a vacuum (about 5 kPa). This pressure drop provokes auto-vaporization of the volatile compounds, puffing of flowers, breaking of cell walls and cooling. The effect of the process parameters, namely number of DIC cycles (1–9), saturated steam pressure (0.2–0.6 MPa), and heating time (0.5–20 min) on the oil yield and oil composition was examined. The results indicated a significant increase of oil yield with increasing processing pressure and number of DIC cycles, however the total heating time was not a significant parameter. The DIC oil was compared with the oil obtained using steam distillation (SD). DIC exhibited better results than SD concerning rapidity (4 min versus 24 h), oil yield (2.74% versus 2.60%) and also oil quality.

Influence of tobermorite formation on mechanical properties of hydrothermally solidified blast furnace slag

A hydrothermal processing method has been used to solidify blast furnace water-cooled slag (BFWS), in which the BFWS could be solidified in an autoclave under saturated steam pressure (1.56 MPa) at 200 °C for 12 h by the additions of quartz or coal fly ash. The experimental results showed that the addition of the quartz or fly ash was favorable to the formation of tobermorite, and the tobermorite formation in turn exerted a signifiant influence on tensile strength. The strength development depended on both tobermorite formation and the density of the tobermorite formed. The excessive addition of quartz appeared to cause strength deterioration due to the fact that the residual quartz affected the formation of tobermorite in the solidified specimens. Fly ash could be used as an additive for the hydrothermal solidification of BFWS, which may offer both energy saving and cost reduction.

Hydrothermal synthesis and characterization of aluminium and sulfate substituted 1.1nm tobermorites

Substitutions of sulfate and aluminum ions in calcium silicate hydrate (tobermorite) were investigated at 175 °C under saturated steam pressure. Structure and morphology of different tobermorite samples were investigated using XRD, FTIR and SEM. A sample of pure xonotlite was prepared to assist in FTIR band assignment of different tobermorites. Al 3+ decreases the degree of crystallinity at short curing time and increases crystallinity at longer curing times, with a sort of stabilization of small crystals. Al 3+ changes the morphology of tobermorite from platy-shape to lath-shape. Sulfate ion increases imperfection of tobermorite crystal structure and the morphology of tobermorite change magnificently to leafy shape. The FTIR spectra of all 1.1 nm tobermorite samples are nearly similar. All tobermorite samples have a significant concentration of Q 3 Si sites, which indicates cross-linking of the chains. Sulfate substitution for silicate in tobermorite structure is associated with the appearance of the bands at 1610 and 631 cm −1 which indicates the incorporation of CaO–H group in tobermorite structure. This indicated the charge compensation mechanism; SiO 4 4− is substituted by SO 4 2− and 2OH − .

Hygrothermal Failures From Small Defects in Lead-Free Solder Reflowed Electronic Packages

Steam-driven delamination failure is a main failure mode in electronics packages during solder reflow. Steam pressures built up within interfaces in packages are sensitive functions of the reflow temperature. The switch to lead-free soldering will raise re-flow temperature by more than 20degC and double the equilibrium saturated steam pressure within defects in the package. The effects of saturated steam driven interfacial failure was analyzed using finite element in this study. Analyses revealed that packages which are thin and made using high thermal conductivity materials are at higher risk of failure than conventional packages made using standard materials. This suggests that electronics made with thick and inexpensive encapsulants are less prone to failure when switched to lead-free solder. Portable and mobile electronics which have low profiles and are made of high thermal conductive encapsulants are at higher risk when switched to lead-free solder reflow. Moreover, the study found that the critical temperature for failure is dependent on the defect size in the package. Reduction of initial defect size can reduce failures in high risk packages in lead-free solder reflow.