Comparison of three methods for natural gas dehydration

This paper compares three methods for natural gas dehydration that are widely applied in industry:(1) absorption by triethylene glycol, (2) adsorption on solid desiccants and (3) condensation. A comparison is made according to their energy demand and suitability for use. The energy calculations are performed on a model where 105 Nm3/h water saturated natural gas is processed at 30 °C. The pressure of the gas varies from 7 to 20 MPa. The required outlet concentration of water in natural gas is equivalent to the dew point temperature of -10 °C at gas pressure of 4 MPa.     

Adsorption isotherms and kinetic characteristics of methane on block anthracite over a wide pressure range

It is important to quantitatively understand the methane adsorption and transport mechanism in coal for an evaluation of the reserves and for its production forecast. In this work, a block coal sample was chosen to perform the CH4 adsorption experiments using the gravimetric method at temperatures of 293.60 K, 311.26 K, 332.98 K and 352.55 K and pressures up to 19 MPa. The excess adsorption capacity of CH4 in dry block anthracite increased, followed by a sequence decrease with the increasing pressure. High temperature restrained the growth of the excess adsorption due to that the adsorption is an intrinsically physical and exothermic process. The excess adsorption peak decreased slowly with the increase of temperature and intersected at a pressure of more than 18 MPa; meanwhile, the pressure at the excess adsorption peak increased.The existing correlations were examined in terms of density rather than pressure. The DR+k correlation, with an average relative deviation of ±0.51%, fitted our data better than the others, with an average relative deviation of up to 2.29%. The transportation characteristics of CH4 adsorption was also investigated in this study, including the adsorption rate and diffusion in block coal. The kinetic data could be described by a modified unipore model. The adsorption rates were found to exhibit dependence on pressure and temperature at low pressures, while the calculated diffusivities exhibited little temperature dependence. In addition, the kinetic characteristics were compared between CH4 and CO2 adsorption on the block coal. The excess adsorption ratios of CO2 to CH4obtained from the DR+k model decreased with the increasing pressure.     

Electroosmotic Driving Liquid Using Nanosilica Packed Column

The packed-bed electroosmotic pump (p-EOP) can manipulate liquid with pressure as high as 50 MPa and micro flowrate ranging from several nL/ min to several μL/min1-3. The p-EOP is matching to micro systems and suitable for developing chip liquid chromatography/electrochromatography for proteomics and high throughput HPLC for drug discovery4-6. There are some efforts to improve the performance p-EOP7-8 recently. In this paper, the nanosilica was chosen as the electroosmotic carrier to i…     

Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

Adsorption/desorption isotherms of supercritical methane on superactivated carbon have been measured in the range of 0-10 MPa and 233-333 K (20 K interval). The reversibility of the physical adsorption process is acknowledged. The heat of adsorption of 16.5 kJ/mol is determined from the isotherms, and a new modeling strategy for isotherms with maximum is presented. The model yields fits to the experimental isotherms with precision of ?%, maintaining the constancy of the characteristic energy of adsorption. The exponent of the model equation expresses the pore size distribution feature of the adsorbent. The density of the supercritical adsor-bate is evaluated as a parameter of the model. It is shown that the conventional isotherm theory works too at supercritical condition if the limit state of supercritical adsorption is introduced into isotherm modeling.     

Preparation of activated carbons and their adsorption properties for greenhouse gases: CH4 and CO2

Three kinds of activated carbons were prepared using coconut-shells as carbon precursors and characterized by XRD, FT-IR and texture property test. The results indicate that the prepared activated carbons were mainly amorphous and only a few impurity groups were adsorbed on their surfaces. The texture property test reveals that the activated carbons displayed different texture properties, especially the micropore size distribution. The adsorption capacities of the activated carbons were investigated by adsorbing CH4, CO2, N2 and O2 at 25 ?C in the pressure range of 0-200 kPa. The results reveal that all the activated carbons had high CO2 adsorption capacity, one of which had the highest CO2 adsorption value of 2.55 mmol/g at 200 kPa. And the highest adsorption capacity for CH4 of the activated carbons can reach 1.93 mmol/g at 200 kPa. In the pressure range of 0-200 kPa, the adsorption capacities for N2 and O2 were increased linearly with the change of pressure and K-AC is an excellent adsorbent towards the adsorption separation of greenhouse gases.     

Separation of CO_2–N_2 using zeolite NaKA with high selectivity

The adsorption method based on solid adsorbents is one of feasible ways to capture and store CO_2. Using the ion exchange method, different zeolites Na KA varying in K+content were produced. The adsorption isotherms and kinetic uptakes were measured. The experimental results show that the optimal NaKA could adsorb significant quantities of CO_2 and little N_2. On the zeolite Na KA with 14.7 at.% K+, the adsorption capacity for pure CO_2 is over 3.10 mmol g~(-1) and the CO_2–N_2 selectivity is about 149 at ambient pressure and temperature. The kinetic CO_2–N_2 selectivity could also achieved 200 within 3 min according to the uptake data. To demonstrate the separation effectiveness, breakthrough curves of pure components and binary mixtures were investigated experimentally and theoretically in a fixed bed. It is found that the breakthrough points of CO_2 and N_2 are almost at the same time under the atmospheric pressure at 348 K with the raw gas composition CO_2/N_2(20:80, v/v). If the pressure has been increased higher than 0.1 MPa, CO_2 would break through the bed much slower than N_2. Therefore, the pressure may become the limiting factor for the separation performance of zeolites NaKA.     

TiO2担载镍催化剂上硝基苯液相加氢（英文）

The catalytic hydrogenation of nitrobenzene to aniline employing nickel impregnated on rutile,anatase,and high surface area titania supports has been investigated.The nickel is present in elemental state as fcc phase on the catalyst as evidenced by X-ray diffraction results.The Ni crystallite size was found to be greater for Ni/anatase.The temperature-programmed reduction results suggest a greater metal-support interaction for Ni/rutile.The observed order of catalytic activity for the hydrogenation of nitrobenzene is Ni/rutile > Ni/anatase > Ni/TiO2.A conversion of 99% was observed for Ni/rutile at 140 oC and hydrogen pressure of 1.96 MPa.Interestingly,aniline is the only product formed which demonstrates the catalytic hydrogenation of nitrobenzene proceeds with atom economy.Both Ni/rutile and Ni/anatase exhibited a better stability than Ni/TiO2.The hydrogenation proceeds with the preferential adsorption of hydrogen on nickel present in the catalyst surface,possibly assisted by TiOx species.     

亚氨基二乙酸树脂吸附钇(Ⅲ)的研究

The adsorption behavior and mechanism of a novel chelate resin, iminodiacetic acid resin (IDAAR) for Y(Ⅲ) were investigated. The statically saturated adsorption capacity is 102mg·g^-1 resin at 298K in HAc-NaAc medium at pH 5.7. Y(Ⅲ) adsorbed on IDAAR can be reductively eluted by 1.0～4.0mol·L^-1 HCl used as eluant and the elution percentages are almost as high as 100%. The resin can be regenerated and reused without apparent decrease in adsorption capacity. The apparent adsorption rate constant is k₂₉₈=3.36×10^-5s^-1. The adsorption behavior of IDAAR for Y(Ⅲ) conforms to Freundlich′s model reasonably. The thermodynamic adsorption parameter, enthalpy change ΔH of IDAAR for Y(Ⅲ) is 18.6kJ·mol^-1. The complex molar ratio of the functional group of IDAAR to Y(Ⅲ) is about 3∶1. The adsorption mechanism of IDAAR for Y(Ⅲ) was examined by using chemical method and IR spectrometry.     

A Study of Estimating the Safe Storage Life, Self-accelerating Decomposition Temperature and Critical Temperature of Thermal Explosion of Double-base Propellant Using Isothermal and Non-isothermal Decomposition Behaviours

The pressure exponent (γ) equation of the burning rate (u) of the title propellant is u=apγ=4.350p0.192 at 4-10 MPa, having very good combustion characteristics. It has the potential for possible use as solid rocket propellant from the point of view of …     

Adsorption studies of tannic acid by commercial ester resin XAD-7

<正>Tannic acid and its related compounds are known as refractory organic pollutants,and it can create serious problems for the environment.The adsorption and desorption studies of tannic acid on commercial resins XAD-7 and D-201 are performed,and all data indicates resin XAD-7 can be used as an effective adsorbent for removing tannic acid during water/wastewater treatment.Furthermore,adsorption thermodynamics studies indicate different adsorption mechanisms for TA on XAD-7 and D-201.FT-IR and solid state ~(13)C-NMR spectroscopy are used to explain the adsorption force between XAD-7 and TA.It suggests that hydrogen bonding is the main adsorption force for TA.Finally,XAD-7's adsorption capacity in the presence of different metal ions is investigated,which indicates that heavy metal ions in solutions can decrease the adsorption capacity for TA on ester resin XAD-7.     

Study on Pressure Swing Adsorption Removing C+2 from Natural Gas as Raw Material for Thermal Chlorination

The experimental investigation demonstrates that a satisfactory result can be expected for pressure swing adsorption (PSA) purification of natural gas as raw material for thermal chlorination process. Using hh-4 molecular sieve as adsorbent for removing C2 components, the suitable adsorption pressure is 0.4-0.45 MPa, desorption vacuum is 0.08-0.09 MPa and circulation time is 20-21 min.     

Adsorption of nitrogen on granular activated carbon: experiment and modeling

A carbon adsorbent was produced and used to volumetrically measure nitrogen adsorption isotherms from 93 to 298 K and up to 7 MPa. The isosteric heat of adsorption was determined to range between -9.5 and -16 kJ/mol. The excess adsorption isotherms were modeled using an approach based on a modified Dubinin-Astakhov adsorption model, adapted for excess adsorption, which provided an accurate fit for all supercritical isotherms. An expression for the differential energy of adsorption as a function of pressure was developed using the Dubinin-Astakhov isotherm. The energy of adsorption for the isotherms measured was found to range from -8 to -15 kJ/mol as a function of pressure.     

Hydrogen adsorption on nanoporous carbon adsorbents prepared from furaldehyde by thermochemical synthesis

Hydrogen adsorption on two samples of active carbon (FAS) produced from furaldehyde by the thermochemical synthesis method is investigated. Maximum hydrogen adsorption on these active carbons at hydrogen boiling temperature of 20.38 K and a pressure of 0.101 MPa is calculated in terms of the theory of the volume filling of micropores. Hydrogen adsorption on FAS-1-05 active carbon at temperatures of 77, 196, and 300 K and pressures of 7 and 20 MPa is calculated using the condition of linear isosteres. The calculated data are compared with the experimental results obtained for the same adsorbent at temperatures of 77 and 293 K and pressures below 5.1 and 16.1 MPa, respectively. The maximum adsorption value of hydrogen on FAS-1-05 amounts to 6.2 wt % at 5.1 MPa and 77 K.     

氢在活性炭、石墨烯和金属有机骨架上的吸附平衡

为比较不同物理吸附材料的结构参数对其储氢性能的影响,制备和选取了具有超高比表面积的活性炭、石墨烯以及金属有机骨架（MOFs）作为低温吸附储氢的典型材料。首先,利用77 K下氮气在材料上的吸附数据确定了其BET比表面积以及孔径分布的主要结构参数。其次,利用3Flex全自动微孔吸附仪在77-87 K测试了0-0.1 MPa低压下氢在各材料上的吸附量,而后在0.1-8 MPa高压条件下利用PCTPro测试了氢在各材料上的过剩吸附量。最后,分析了各材料的储氢量与其结构参数间的关系。结果表明,在低压下,影响物理吸附材料储氢量的主要因素为孔径分布小于1 nm的微孔;而高压下,氢在多孔材料上的最大过剩吸附量与材料的BET比表面积呈正相关关系,斜率为0.0059 mmol/m²。     

Adsorption of hydrogen on nanoporous carbon adsorbents

Four samples of active carbons with specific micropore volumes of 0.4—1.33 cm³g^-1 at 77 K and pressures up to 5 MPa were used to study hydrogen adsorption. The highest amount of of hydrogen adsorbed on these active carbons at the boiling point 20.38 K and pressure 0.101 MPa was calculated by methods derived from the theory of volumetric filling of micropores (TVFM). The adsorbent FAS-1-05 prepared by the liquid-phase polymerization of furfurol was shown to have the highest adsorption capacity. The amounts of hydrogen adsorbed on FAS-1-05 at temperatures 77, 196, and 300 K and pressures 7 and 20 MPa were calculated using the TVFM methods with allowance for linearity of the isosters. The results were compared with the experimental values obtained at 77 K and pressure below 5.1 MPa and at 293 K and pressures up to 16.1 MPa. The highest amounts of hydrogen adsorbed (6.2 wt.% for the adsorbent FAS-1-05) were obtained under pressures below 5.1 MPa and at 77 K.     

Thermodynamic Description of Excess Isotherms in High-Pressure Adsorption of Methane, Argon and Nitrogen

In the present work the supercritical fluids argon, methane and nitrogen were picked out as examples, and the results of analysis concerning the adsorption of these fluids at activated carbon Norit R1 (Norit company, Germany) and SCS-3 (ISPE, Kiev) at different temperatures up to a pressure of 50 MPa are presented and discussed in this paper. The principle of working of the measuring device is described in this context as well.A three-parameter isothermal equation is used to represent the adsorption equilibrium. The isothermal equation is based on a physical model concept which has already been used for the modelling of adsorption processes with a pressure up to 15 MPa.     

Gas adsorption process in activated carbon over a wide temperature range above the critical point. Part 1: modified Dubinin-Astakhov model

Simulations of the thermal effects during adsorption cycles are valuable tools for the design of efficient adsorption-based systems such as gas storage, gas separation and adsorption-based heat pumps. An analytical representation of the measured adsorption data over the wide operating pressure and temperature swing of the system is necessary for the calculation of complete mass and energy conservation equations. In Part 1, the Dubinin-Astakhov (D-A) model is adapted to model hydrogen, nitrogen, and methane adsorption isotherms on activated carbon at high pressures and supercritical temperatures assuming a constant microporous adsorption volume. The five parameter D-A type adsorption model is shown to fit the experimental data for hydrogen (30 to 293 K, up to 6 MPa), nitrogen (93 to 298 K, up to 6 MPa), and for methane (243 to 333 K, up to 9 MPa). The quality of the fit of the multiple experimental adsorption isotherms is excellent over the large temperature and pressure ranges involved. The model’s parameters could be determined as well from only the 77 K and 298 K hydrogen isotherms without much reducing the quality of the fit.     

Determination of the quasi-saturated vapor pressure of supercritical gases in the adsorption potential theory application

Equilibrium data on supercritical N(2) and CH(4) adsorption on K02 activated carbon are presented in the temperature range 273-333 K and the pressure range 0-12 MPa. The adsorption potential theory was adopted to predict the adsorption equilibria of N(2) and CH(4) in the whole range utilizing a single experimental isotherm. The methods in literatures for calculating the quasi-saturated vapor pressure and the adsorbate density of supercritical gases have been investigated in detail. It is demonstrated that the predicting accuracy is considerably more sensitive to the quasi-saturated vapor pressure than to the adsorbate density. Moreover, for different adsorbates, the appropriate approach to the important quasi-saturated vapor pressure is various in the same experimental range. A new viewpoint, based on the relationship between the research temperature ranges and the critical temperatures of adsorbates, was proposed to determine the exact method for the quasi-saturated vapor pressure in the application of the adsorption potential theory.     

The magnetic suspension balance in high pressure measurements of pure gases

In the present work the supercritical fluids argon, methane, nitrogen, carbon dioxide, ethane, ethylene and propane were picked out as examples, and the results of analysis concerning the adsorption of these fluids at activated carbon Norit R1 (Norit Company, Germany) and SCS-3 (ISPE, Kiev) at different temperatures up to a pressure of 50 MPa are presented and discussed in this paper. The principle of working of the measuring device is described in this context as well.A three-parameter isothermal equation is used to represent the adsorption equilibrium. The isothermal equation is based on a physical model concept which has already been used for the modelling of adsorption processes with a pressure up to 15 MPa.This revised version was published online in November 2005 with corrections to the Cover Date.     

甲烷在活性炭上吸附平衡模型的研究

比较吸附模型分析甲烷在活性炭上吸附平衡的适用性,为吸附式天然气(ANG)的工程应用提供准确的预测模型。基于在温度268.15～338.15 K、压力0～12.5 MPa测试的甲烷在Ajax活性炭上的吸附平衡数据,选择Langmuir、Langmuir-Freundlich和Toth方程,应用非线性回归拟合方程参数后,确定绝对吸附量和甲烷吸附相态,并比较方程在不同压力区域内的预测精度。结果表明,甲烷吸附相密度随平衡温度和压力变化;由绝对吸附量确定的甲烷在Ajax活性炭上的平均等量吸附热为15.72 kJ/mol,小于由过剩吸附量的标绘结果;Langmuir、Langmuir-Freundlich和Toth方程预测结果在0～0.025 MPa的累积相对误差为6.449 8%、7.918 4%和0.910 0%,在1～10 MPa为0.491 1%、0.161 3%和0.369 4%。Toth方程在整个压力范围内的预测结果最为准确,但Langmuir-Freundlich方程在较高压力区域内具有较高的预测精度。