scholarly journals Thermodynamic Characteristics of Methane Adsorption of Coal with Different Initial Gas Pressures at Different Temperatures

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Tingting Cai ◽  
Zengchao Feng ◽  
Yulong Jiang ◽  
Dong Zhao
Keyword(s):  
Adsorption Process ◽  
Thermodynamic Characteristics ◽  
Methane Adsorption ◽  
Gas Pressure ◽  
Adsorption Heat ◽  
Mathematical Function ◽  
Adsorption Time ◽  
Free Gas ◽  
Different Temperatures ◽  
Gas Pressures

The adsorption of methane in coal depends on both pressure and temperature, and the adsorption gas content decreases as the temperature rises while increases as the pressure increases. When the gas molecule switches between the free state and adsorbed state, energy exchange is accompanied. To study the thermodynamic characteristics (adsorption heat, adsorption content, and adsorption time) of the methane adsorption of coal, the isothermal methane adsorption experiments of coal with different initial free gas pressures at different temperatures (30–90°C) were conducted. In this paper, a well-defined mathematical function of the adsorption heat was established on the basis of the actual gas state equation, Boltzmann energy distribution theory, and the two-state energy model, and the function was verified by the experimental data. The results show that the mathematical function of the adsorption heat can well describe the relationship among the adsorption heat, temperature, and initial free gas pressure in the closed adsorption system, and the adsorption heat involves the initial free gas pressure. The greater the initial free gas pressure, the less the adsorption heat is. In the adsorption process with different initial free gas pressures at different temperatures, the real-time free gas content increases with time and the adsorption system shows desorption process generally. For the adsorption process with the same initial free gas pressure, the adsorption time increases with the rising temperature. For the adsorption process with different initial free gas pressures at the same temperature, the greater the initial free gas pressure, the shorter the adsorption time it takes to reach an equilibrium state. The results help to understand the thermodynamic characteristics and the heat and mass transfer of methane in coal adsorption.

scholarly journals Variation law of adsorption heat of methane and coal with inhomogeneous potential well

2018 ◽  
Vol 36 (7-8) ◽  
pp. 1538-1549 ◽  
Author(s):  
Zeng-Chao Feng ◽  
Chen Wang ◽  
Dong Zhou ◽  
Dong Zhao
Keyword(s):  
Adsorption Process ◽  
Methane Adsorption ◽  
Adsorption Heat ◽  
Potential Well ◽  
Coal Surface ◽  
Isothermal Adsorption ◽  
Potential Wells ◽  
Preferential Adsorption ◽  
Coal Deposits ◽  
High Temperature Stage

The non-uniform structures of coal deposits make potential well distribution on the coal surface inhomogeneous. Deep potential wells adsorb methane molecules more easily than shallow potential wells. The methane adsorption heat release differs according to the depths of the potential wells. During isobaric adsorption, the adsorption heat in the high-temperature stage is significantly higher than that in the low-temperature stage. A lower adsorption pressure results in greater adsorption heat variation during a temperature increase. During the isothermal adsorption process, the adsorption heat is higher in the low-pressure stage, with the preferential adsorption characteristics of deep potential wells.

scholarly journals Study on Adsorption Properties of Modified Corn Cob Activated Carbon for Mercury Ion

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4483
Author(s):  
Yuyingnan Liu ◽  
Xinrui Xu ◽  
Bin Qu ◽  
Xiaofeng Liu ◽  
Weiming Yi ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Photoelectron Spectroscopy ◽  
Adsorption Process ◽  
Physical Adsorption ◽  
Raw Material ◽  
Order Kinetic ◽  
Mercury Ions ◽  
Corn Cob ◽  
Adsorption Time ◽  
X Ray

In this study, corn cob was used as raw material and modified methods employing KOH and KMnO4 were used to prepare activated carbon with high adsorption capacity for mercury ions. Experiments on the effects of different influencing factors on the adsorption of mercury ions were undertaken. The results showed that when modified with KOH, the optimal adsorption time was 120 min, the optimum pH was 4; when modified with KMnO4, the optimal adsorption time was 60 min, the optimal pH was 3, and the optimal amount of adsorbent and the initial concentration were both 0.40 g/L and 100 mg/L under both modified conditions. The adsorption process conforms to the pseudo-second-order kinetic model and Langmuir model. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Zeta potential characterization results showed that the adsorption process is mainly physical adsorption, surface complexation and ion exchange.

Pressure Assisted Sintering of an Aluminium Alloy

2009 ◽  
Vol 618-619 ◽  
pp. 627-630
Author(s):  
Stephen J. Bonner ◽  
Graham B. Schaffer ◽  
Ji Yong Yao
Keyword(s):  
Aluminium Alloy ◽  
Gas Flow ◽  
Isothermal Holding ◽  
Horizontal Tube ◽  
Elevated Pressure ◽  
Nitrogen Pressure ◽  
Gas Pressure ◽  
Densification Rate ◽  
Conventional Press ◽  
Gas Pressures

An aluminium alloy was sintered using a conventional press and sinter process, at various gas pressures, to observe the effect of sintering gas pressure on the densification rate. Compacts of aluminium alloy 2712 (Al-3.8Cu-1Mg-0.7Si-0.1Sn) were prepared from elemental powders and sintered in a horizontal tube furnace under nitrogen or argon at 590°C for up to 60 minutes, and air cooled. The gas flow was adjusted to achieve specific gas pressures in the furnace. It has been found that increasing the nitrogen pressure at the start of the isothermal holding stage to 160kPa increased the densification rate compared to standard atmospheric pressure sintering. Increasing the nitrogen pressure further, up to 600kPa, had no additional benefit. The densification rate was increased significantly by increasing the gas pressure to 600kPa during both heating and isothermal holding. Under argon the elevated pressure did not increase the densification rate. Results seem to suggest that the beneficial effect of the elevated pressure on the rate of densification is related to nitride formation.

scholarly journals Removal of toxic metals from aqueous solution by biochars derived from long-root Eichhornia crassipes

2018 ◽  
Vol 5 (10) ◽  
pp. 180966 ◽  
Author(s):  
Qiang Li ◽  
Lizhou Tang ◽  
Jiang Hu ◽  
Ming Jiang ◽  
Xiaodong Shi ◽  
...  
Keyword(s):  
Toxic Metals ◽  
Eichhornia Crassipes ◽  
Adsorption Process ◽  
Correlation Coefficients ◽  
Sorption Ability ◽  
Different Temperatures ◽  
Lead Zinc ◽  
Pseudo Second Order ◽  
Cyano Groups ◽  
Maximum Removal

Biochars were produced from long-root Eichhornia crassipes at four temperatures: 200, 300, 400 and 500°C, referred to as LEC200, LEC300, LEC400 and LEC500, respectively. The sorption ability of lead, zinc, copper and cadmium from aqueous solutions by four kinds of biochars was investigated. All the biochars had lower values of CEC and higher values of pH. LEC500 was the best one to bind toxic metals which can be reflected in the results of SEM, BET and elemental analyser. It was also found that alkyl, carboxyl, phosphate and cyano groups in the biochars can play a role in binding metals. In addition, the sorption processes of four metals by the biochars in different metal concentration were all excellently represented by the pseudo-second-order model with all correlation coefficients R 2 > 0.95. And the sorption processes of four metals in different temperatures could be described satisfactorily by the Langmuir isotherms. According to calculated results by the Langmuir equation, the maximum removal capacities of Pb(II), Zn(II), Cu(II) and Cd(II) at 298 K were 39.09 mg g −1 , 45.40 mg g −1 , 48.20 mg g −1 and 44.04 mg g −1 , respectively. The positive value of the Δ H 0 confirmed the adsorption process was endothermic and the negative value of Δ G 0 confirmed the adsorption process was spontaneous. The sorption capacities were compared with several other lignocellulosic materials which implied the potential of long-root Eichhornia crassipes waste as an economic and excellent biosorbent for eliminating metal ions from contaminated waters.

scholarly journals Adsorption Study for Chromium (VI) on Iraqi Bentonite

2010 ◽  
Vol 7 (1) ◽  
pp. 745-756
Author(s):  
Baghdad Science Journal
Keyword(s):  
Adsorption Isotherm ◽  
Adsorption Process ◽  
Kinetic Equations ◽  
Bentonite Clay ◽  
Sorption Process ◽  
Adsorption Study ◽  
Chromium Vi ◽  
Freundlich Adsorption Isotherm ◽  
Different Temperatures ◽  
The Subject

The subject of this research involves studying adsorption to remove hexavalent chromium Cr(VI) from aqueous solutions. Adsorption process on bentonite clay as adsorbent was used in the Cr(VI) concentration range (10-100) ppm at different temperatures (298, 303, 308 and 313)K, for different periods of time. The adsorption isotherms were obtained by obeying Langmuir and Freundlich adsorption isotherm with R2 (0.9921-0.9060) and (0.994-0.9998), respectively. The thermodynamic parameters were calculated by using the adsorption process at four different temperatures the values of ?H, ?G and ?S was [(+6.582 ? +6.547) kJ.mol-1, (-284.560 ? -343.070) kJ.mol-1 and (+0.977 ? +1.117) kJ.K-1.mol-1] respectively. This data indicates the spontaneous sorption process. The kinetic study of adsorption process was studied depending on three kinetic equations: 1- Lagergren equation 2- Morris-Weber equation 3- Reichenberg equation

Correlation between global thermodynamic functions and experimental data in multicomponent heterogeneous systems

2016 ◽  
Vol 94 (2) ◽  
pp. 113-119 ◽  
Author(s):  
Igor Povar ◽  
Oxana Spinu
Keyword(s):  
Experimental Data ◽  
Thermodynamic Functions ◽  
Solid Phase ◽  
Heterogeneous Systems ◽  
Thermodynamic Characteristics ◽  
Alkaline Solutions ◽  
Precipitation Process ◽  
Mutual Transformation ◽  
Homogeneous Solutions ◽  
Different Temperatures

The correlation between global thermodynamic functions and such experimental data, which quantitatively characterize the precipitation–dissolution processes of sparingly soluble compounds, as the degree of precipitation and residual concentrations of the solid-phase components in saturated solutions under real conditions, taking into account the complex formation reactions, has been deducted. The paper intends also to introduce widely formal thermodynamic methods for forecasting the conditions of mutual transformation of solid phases through chemical synthesis by precipitation methods, optimization of coprecipitation methods, fractional precipitation from homogeneous solutions, and separation and analysis of chemical compounds. Within the method of residual concentrations, the thermodynamic parameters of the process of precipitating cadmium ions with potassium decanoate from acid and alkaline solutions for different temperatures were investigated. On the basis of the experimentally determined degree of precipitation and its dependence on temperature, the temperature coefficients and overall thermodynamic characteristics of the precipitation process ([Formula: see text], [Formula: see text], and [Formula: see text]) were determined. The optimum conditions of the investigated process of precipitation have been established.

Study of Adsorption Process and Performance of Neutral Red Dye Wastewater by Bamboo Shoot Hulls

2013 ◽  
Vol 295-298 ◽  
pp. 1647-1653 ◽  
Author(s):  
Xin Long Jiang ◽  
Yi Hua Jiang ◽  
Cheng Gang Cai
Keyword(s):  
Adsorption Process ◽  
Ph Value ◽  
Physical Adsorption ◽  
Neutral Red ◽  
Rate Equations ◽  
Bamboo Shoot ◽  
Dye Wastewater ◽  
Adsorption Time ◽  
Freundlich Isotherms ◽  
Red Dye

Surface response optimization of adsorption process of neutral red dye wastewater by bamboo shoot hulls with the factors of pH value, amount of adsorbent, adsorption temperature, adsorption time and the response of adsorption rate were studied. The optimal parameters for adsorption process were of adsorbent concentration of 100 mg·L-1, adsorbent particle size of 60~80 mesh, pH 4.49, adsorbent amount of 3.65 g·L-1, adsorption time and temperature of 2.23 h and 39.70 °C, respectively. The maximal absorption rate got 98.37%. The adsorption follows the Langmuir and Freundlich isotherms, its dynamic behavior was consistent with the second-order reaction rate equations, the adsorption quantity was 179.3201 mg·g-1 at 30 °C. The apparent thermodynamic calculation of infrared spectroscopy showed that the adsorption process were of a spontaneous heat-emitting physical adsorption other than a simple chemical adsorption. Mechanical study showed that the functional groups were of hydroxyl and carbonyl groups on the pore and rough surfaces inside the hulls of bamboo shoots. Bamboo shoot hulls are good biological adsorption materials.

A Study on Gas Pressure for Superplastic Forming of Titanium Alloy Bellows

2005 ◽  
Vol 475-479 ◽  
pp. 3051-3054 ◽  
Author(s):  
Gang Wang ◽  
Jun Chen ◽  
X.Y. Ruan
Keyword(s):  
Titanium Alloy ◽  
Thin Shell ◽  
Deformation Theory ◽  
Shell Theory ◽  
Superplastic Forming ◽  
Gas Pressure ◽  
Forming Process ◽  
Compressive Axial Load ◽  
Thin Shell Theory ◽  
Gas Pressures

The complex superplastic forming (SPF) technology applying gas pressure and compressive axial load is an advanced forming method for bellows made of titanium alloy, which forming process consists of the three main forming phases namely bulging, clamping and calibrating phase. The influence of forming gas pressure in various phases on the forming process are analyzed and models of forming gas pressure for bellows made of titanium alloy are derived according to the thin shell theory and plasticity deformation theory. Using model values, taking a two-convolution DN250 bellows made of Ti-6Al-4V titanium alloy as an example, a series of superplastic forming tests are performed to evaluate the influence of the variation of forming gas pressure on the forming process. According to the experimental results models are corrected to make the forming gas pressures prediction more accurate.

Adsorption of Cobalt Ions on Molded Magnesium Silicate

2013 ◽  
Vol 807-809 ◽  
pp. 704-707
Author(s):  
Li Li Mao ◽  
Hai Zeng Wang ◽  
Qing Wang
Keyword(s):  
Adsorption Process ◽  
Average Pore Size ◽  
Chemical Properties ◽  
Magnesium Silicate ◽  
Average Pore ◽  
Cobalt Ions ◽  
Adsorption Time ◽  
Physico Chemical ◽  
Adsorption Desorption ◽  
Adsorbent Dose

The groundwater contaminated with cobalt is attracted more and more concern. In this study, molded magnesium silicate (MMS) was successfully prepared and the physico-chemical properties were determined by N2 adsorption/desorption isotherm and Scanning Electron Microscopy (SEM). Surface area and the average pore size were 333.19 m2·g-1 and 4.442 nm. Adsorption experiments of removal of cobalt ions was investigated as the function of initial concentration, adsorbent dose and adsorption time. Adsorption process was rapid and adsorption equilibriums were achieved soon.

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