共查询到20条相似文献,搜索用时 15 毫秒
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用微波辅助疏水性离子液体[Bmim]PF6萃取分离红霉素,考察了微波辐射功率、辐射时间、离子液体用量、pH值对红霉素萃取率的影响。结果表明,微波辅助离子液体萃取分离红霉素的最佳工艺条件为:在303.15 K的温度下,调节体系pH=6~7,微波辐射功率为210 W,采用间歇辐射的方式,单次辐射时间为20 s,辐射3次,离子液体的用量为3 g,萃取率为90.7%。同时,建立微波辅助离子液体富集分离分析牛奶中红霉素的方法,该方法的检出限为4μg/kg,线性范围在5~50μg/L,RSD=1.7。 相似文献
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用NaH2PO4-Na2HPO4缓冲盐溶液反萃醋酸丁酯相中的红霉素,以纯化酯相中的红霉素A。分别考察了缓冲盐pH值、相比(体积比)、温度对红霉素A、C反萃取的影响。实验结果表明:随着pH值的增加,红霉素A的反萃率大大减少,红霉素C的反萃率先增加后减小,当pH=8时,酯相中红霉素A纯度最高且损失最低;随着相比(A/O)的增加,红霉素A、C的反萃率及酯相中的红霉素A纯化效果都略有提高,但综合考虑反萃剂用量和红霉素A损失,可知相比(A/O)为2∶1时较优;随着温度的增加,红霉素A、C的反萃率都大大减小,且酯相中的红霉素A纯度略有下降,但因红霉素A反萃损失较少,可考虑在328 K时,反萃2次,除去大量红霉素C的同时损失较少的红霉素A。 相似文献
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Jung Hoon Yang 《Fuel Processing Technology》2010,91(3):285-289
Mass transfer limitations on fixed-bed for Fischer-Tropsch synthesis were investigated by changing synthesis gas superficial velocity, catalyst pellet size, and catalyst amount. To study external mass transfer limitation, synthesis gas superficial velocity was changed from 8.47 × 10− 4 m s− 1 to 3.39 × 10− 3 m s− 1. As a result, the synthesis gas superficial velocity of 3.39 × 10− 3 m s− 1 was most suitable for hydrocarbon chain growth resulting to liquid hydrocarbon formation. In case of internal mass transfer limitations, the effects of catalyst pellet size and catalyst amount (Wcat/F) were discussed. The large catalyst pellet showed higher C5+ selectivity and a lower α value compared to the small pellet because of more severe internal mass transfer limitations of α-olefin and long-chained hydrocarbons in the large pellet, respectively. Catalyst amount (Wcat/F) was inversely proportional to the internal mass transfer limitation because increased catalyst amount gave more time for liquid hydrocarbon products to diffuse from the catalyst pellet and, therefore, the catalyst amount of 4.5 g (Wcat/F = 45 gcat min L− 1) was most appropriate for liquid hydrocarbon formation. 相似文献
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介绍了固定层制气技术的发展过程,指出了今后固定层制气的发展方向。针对目前固定层制气生产过程中存在的工艺配套、设备及操作等问题,提出了解决问题的方法和思路:①增大炉径,提高单个煤气发生炉的产气量;②在解决好工艺配置的前提下,大胆使用先进技术和设备;③采用富氧空气进行加氮。 相似文献
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Many mass transfer kinetic models are used to study varying pressure steps of a pressure swing adsorption (PSA) cycle, namely pressurization and blowdown steps. It is shown that the choice of an appropriate model to account for intra-particle diffusional limitations is essential to simulate accurately PSA processes. It has been demonstrated that, besides mathematical approximations (parabolic profile within the particle), a very important factor that can affect simulation results remarkably is the correctness of the mass transfer kinetic model when regarded as being a mass balance for the adsorbent particle. In fact, neglecting intra-particle gas phase leads to erroneous simulations. Some models widely used in the literature, such as the classic linear driving force (LDF) and the solid diffusion models prove inadequate. It is recommended to use pore diffusion model as well as a new version of the solid diffusion model to get reliable predictions. 相似文献
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A fixed-bed coal gasification reactor was set up which specifically simulated the devolatilization zone in a gasifier. Samples (100 g) of lignite coal in three size ranges; ?2+1 mm, ?3+2 mm and ?4+3 mm, were devolatilized in the temperature range 350–550 °C with a steam-oxygen mixture, at 1 atm. The effect of these operating variables on tar yield and composition, melting point, viscosity, specific gravity, and molecular weight distribution was determined. A first-order reaction model was fitted to the experimentally observed total loss in weight of the lignite. 相似文献
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Fixed-bed adsorption on activated carbon is a common blood detoxification technique implemented in liver support devices to remove different types of toxins, among which is tryptophan. 相似文献
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通过理论分析,综合加压固定床煤气化工艺和烃类转化工艺的技术特点,提出加压固定床粗煤气再转化工艺。加压固定床粗煤气再转化工艺取消了现有加压固定床煤气化工艺中煤气水分离、酚氨回收、废气焚烧、变换工艺洗涤塔、低温甲醇洗工艺萃取系统和石脑油分离系统等装置,降低固定资产投资46.9亿元(现用煤气化工艺化工固定资产投资117.25亿元);每年减少使用原料煤96.84万~118.18万t,约合1.29亿元(以褐煤120元/t计);取消使用二异丙基醚0.21万t/a、减少甲醇用量0.96万t/a和质量分数32%的NaOH用量0.36万t/a;取消含尘煤气水和含油煤气水排放量1585.71 t/h(原排放污水1761.9 t/h);减少废水处理装置土地使用面积17790 m2以上。提高CO2利用率,提高硫回收率。加压固定床粗煤气再转化工艺具有工艺、设备和工程建设投资少,工艺运行成本低,环境保护好等显著特点。 相似文献
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利用浸渍溶剂的多孔介质进行萃取是一种有效的分离方法,本文根据固定床溶剂萃取的特点,假定其过程为内扩散控制,采用扩散传质模型,建立了浸渍溶剂的多孔介质提取红霉素的固定床数学模型。 相似文献
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G. H. Sedahmed H. A. Farag A. A. Zatout F. A. Katkout 《Journal of Applied Electrochemistry》1986,16(3):374-378
Mass transfer rates at a gas-sparged fixed-bed electrode made of stacks of vertical screens were studied by measuring the limiting current for the cathodic reduction of potassium ferricyanide. Variables studied were air flow rate, physical properties of the solution and bed thickness. The mass transfer coefficient was found to increase with increasing air flow rate up to a certain point and then remain almost constant with further increase in air flow rate. Increasing bed thickness was found to decrease the mass transfer coefficient. Mass transfer data were correlated by the equation $$J = 0.2(ReFr)^{ - 0.28} ({L \mathord{\left/ {\vphantom {L d}} \right. \kern-\nulldelimiterspace} d})^{ - 0.28} $$ For a single vertical screen electrode the data were correlated by the equation $$J = 0.187(ReFr)^{ - 0.26} $$ 相似文献
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This study introduces a dynamic mass transfer model for the fixed-bed adsorption of a flue gas. The derivation of the variable mass transfer coefficient is based on pore diffusion theory and it is a function of effective porosity, temperature, and pressure as well as the adsorbate composition. Adsorption experiments were done at four different pressures (1.8, 5, 10 and 20 bars) and three different temperatures (30, 50 and 70 °C) with zeolite 13X as the adsorbent. To explain the equilibrium adsorption capacity, the Langmuir-Freundlich isotherm model was adopted, and the parameters of the isotherm equation were fitted to the experimental data for a wide range of pressures and temperatures. Then, dynamic simulations were performed using the system equations for material and energy balance with the equilibrium adsorption isotherm data. The optimal mass transfer and heat transfer coefficients were determined after iterative calculations. As a result, the dynamic variable mass transfer model can estimate the adsorption rate for a wide range of concentrations and precisely simulate the fixed-bed adsorption process of a flue gas mixture of carbon dioxide and nitrogen. 相似文献
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A.A. Mobarak M.S.E. Abdo M.S.M. Hassan G.H. Sedahmed 《Journal of Applied Electrochemistry》2000,30(11):1269-1276
Rates of mass transfer were studied at a vertical array of closely packed screens under single and two phase (gas–liquid) flow by measuring the limiting current for the cathodic reduction of ferricyanide ions. Variables studied were screen characteristics (mesh number and wire diameter), physical properties of the solution, solution flow rate, gas flow rate and the effect of surface active agents. The single phase data were correlated by the equation:J = 0.52 ReL-0.55while the two phase data were correlated by the equations:Sh=0.87 Sc0.33 ReL0.35 Reg0.12for the conditions 10 < Re < 125 and 1.4 < Reg < 77; andSh=0.62 Sc0.33ReL0.11Reg0.25for the conditions 1.1 < ReL < 22 and 1.4 < Reg < 77. The presence of surfactant was found to reduce the rate of mass transfer in both single phase and two phase flow, the percentage reduction being higher in the case of single phase flow. 相似文献
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E. Gonzlez-Pradas M. Villafranca-Snchez A. Gallego-Campo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,54(3):291-295
The adsorption process of phosphate ions on a bentonite from Almería (East-Andalucía, Spain) was studied at 30°C over a range of experimental conditions such as saline (0.1 M KCl) or non-saline medium, natural or calcium homoionic bentonite and different pH values. In order to calculate the adsorption capacities (Xm) of the samples, the experimental data points were fitted to the Langmuir equation. Xm values ranged from 0.42 μg P g?1 for the natural sample in non-saline medium to 0.74 μg P g?1 for the same sample in saline medium, the Xm value corresponding to the calcium homoionic bentonite sample being intermediate. At different pH conditions, Xm increased from 0.28 μg P g?1 at a pH of 1.3 to 1.53 μg P g?1 at a pH of 4.4, and then decreased to 0.42 μg P g?1 at a pH of 8.7. 相似文献
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Carrousel型模拟移动床在红霉素提取中的应用 总被引:2,自引:0,他引:2
为将模拟移动床技术推广到红霉素提取中,采取了以下步骤:首先通过固定床的吸附穿透和洗脱实验,确定树脂的基本吸附和洗脱参数;其次结合移动床设备指标,确定移动床循环工艺和运行参数;最终利用30柱Carrousel型模拟移动床,使用Amberlite XAD-16大孔吸附树脂,从实际的工业红霉素发酵液中提取红霉素。在树脂体积仅为2 700 mL,循环时间405 min,进料流速125 mL/min,进料液效价大约2 700 U/mL时,可连续提取得到效价高于45 000 U/mL的红霉素产品,同时产品收率在98%以上。该系统操作方便,运行成本低,环保压力轻,经计算其工业规模设备可替代红霉素提取工艺中的传统固定床系统。 相似文献