Mass transfer correlation for phenol biodegradation in a fluidized bed bioreactor

Experiments have been carried out in a draft tube fluidized bed bioreactor to study biodegradation of synthetic wastewater containing phenol. The microorganism employed in the study Psuedomonas putida has been immobilized on solid support particles. Studies have been carried out at different feed concentrations of phenol, air flow rates and feed flow rates. The mass transfer coefficient for phenol transfer from bulk phase to the surface of the biofilm on the solid particle has been estimated from observed experimental data using the conservation equations. The mass transfer coefficient was found to be in the range of 0.0726 x 10(-5) to 0.2012 x 10(-5) m s(-1). It was found to increase with increase in feed concentration, air flow rate and feed flow rate. A dimensionless correlation has been developed for the mass transfer coefficient in terms of Sherwood, Reynolds and Schmidt numbers, and the same has been compared with correlations available in literature.     

Kinetic analysis and energy efficiency of phenol degradation in a plasma-photocatalysis system

Combination of two kinds of advanced oxidation processes (AOPs) is an effective approach to control wastewater pollution. In this research, a pulsed discharge plasma system with multi-point-to-plate electrode and an immobilized TiO(2) photocatalysis system is coupled to oxidize target pollutant in aqueous solution. Kinetic analysis (pseudo-first order kinetic constant, k) and energy efficiency (energy yield value at 50% phenol conversion, G(50)) of phenol oxidation in different reaction systems (plasma alone and plasma-photocatalysis) are reviewed to account for the synergistic mechanism of plasma and photocatalysis. The experimental results show that higher k and G(50) of phenol oxidation can be obtained in the plasma-photocatalysis system under the conditions of different gas bubbling varieties, initial solution pH and radical scavenger addition. Moreover, the investigation tested hydroxyl radical (OH) is the most important species for phenol removal in the synergistic system of plasma-photocatalysis as well as in the plasma alone system.     

对称型内平动齿轮系统的非线性动力学分析

摘要：基于拉格朗日方程,建立了含有两个呈对称布置的平动齿轮的内平动齿轮传动机构的动力学模型,通过啮合相对位移函数分析及无量纲化处理,得到系统的无量纲6自由度运动微分方程。通过对系统可能存在的不对称因素(平动齿轮支撑轴承不对称、啮合间隙不对称以及平动齿轮受载不对称)对系统动力学特性的影响进行分析,表明三种不对称因素均会引起系统的分岔,且混沌区域随非对称因素的不同表现出不同的分布规律,并且使得周期解呈现出不同的特性。     

Optimizing aeration rates for minimizing membrane fouling and its effect on sludge characteristics in a moving bed membrane bioreactor

In MBR processes, sufficient aeration is necessary to maintain sustainable flux and to retard membrane fouling. Membrane permeability, sludge characteristics, nutrient removal and biomass growth at various air flow rates in the membrane and moving bed biofilm reactor (MBBR) compartments were studied in a pilot plant. The highest nitrogen and phosphorous removal rates were found at MBBR aeration rates of 151 and 85 L h(-1) and a specific aeration demand per membrane area (SAD(m)) of 1.2 and 0.4 m(air)(3) m(-2) h(-1), respectively. A linear correlation was found between the amount of attached biofilm and the nutrient removal rate. The aeration rate in the MBBR compartment and SAD(m) significantly influenced the sludge characteristics and membrane permeability. The optimum combination of the aeration rate in the MBBR compartment and SAD(m) were 151 L h(-1) and 0.8-1.2 m(air)(3) m(membrane)(-2) h(-1), respectively.     

Simultaneous removal of phenol, ammonium and thiocyanate from coke wastewater by aerobic biodegradation

A laboratory-scale activated sludge plant composed of a 20 L volume aerobic reactor followed by a 12 L volume settling tank and operating at 35 degrees C was used to study the biodegradation of coke wastewater. The concentrations of ammonium nitrogen (NH(4)(+) -N), phenols, chemical oxygen demand (COD) and thiocyanate (SCN(-)) in the wastewater ranged between 504 and 2,340, 110 and 350, 807 and 3,275 and 185 and 370 mg/L, respectively. The study was undertaken with and without the addition of bicarbonate. The addition of this inorganic carbon source was necessary to favour nitrification, as the alkalinity of the wastewater was very low. Maximum removal efficiencies of 75%, 98% and 90% were obtained for COD, phenols and thyocianates, respectively, without the addition of bicarbonate. The concentration of ammonia increased in the effluent due to both the formation of NH(4)(+) as a result of SCN(-) biodegradation and to organic nitrogen oxidation. A maximum nitrification efficiency of 71% was achieved when bicarbonate was added, the removals of COD and phenols being almost similar to those obtained in the absence of nitrification. Batch experiments were performed to study the influence of pH and alkalinity on the biodegradation of phenols and thiocyanate.     

单平动轮驱动内平动齿轮副动力学分析

考虑了内平动齿轮副的多齿接触造成的多谐啮合刚度的影响以及齿侧间隙和齿轮支撑轴承的间隙,建立了单个平动轮驱动内齿轮的内平动齿轮副的运动微分方程,对其在不同转速情况下的动力学分岔特性进行了研究,分析结果显示,各运动副碰撞振动情况不仅随着转速变化,且各个运动副间隙的碰撞振动特性在相同转速下也会表现出不同的特性。     

Production of a fluidized bed moving along an inclined gas-distributing grid

Results are presented from analytical and experimental studies on how the height of a fluidized bed is dependent on the major parameters when it moves up an inclined gas-distributing grid.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 2, pp. 261–264, February, 1984.     

Modelling of simulated moving bed adsorption system: a more precise approach

A mathematical model for a simulated moving bed adsorption system is presented using a more precise approach. In this precise approach the differential equations along with appropriate boundary conditions are written for each adsorption column as distinct from the section approach adopted by previous workers in order to examine the column dynamics of the actual system. An axially dispersed plug flow model with linear driving force rate expression for mass transfer and nonlinear Langmuir equilibria are considered. The time-dependent boundary conditions for each column are formulated and related to switching time. Computations are performed for several cycles till the cyclic steady state is reached. The results obtained from the present model for the limiting cases of linear glucose-fructose and nonlinear monoethanolamine-methanol systems are compared with available experimental data and are found to agree well. The effect of various process parameters on the performance of systems are investigated and the distinction from the section approach is emphasized. The present study reveals that the system performance and dynamics are strongly dependent on axial dispersion, eluent-to-feed ratio, bed length and switch time. It is observed that there exists a set of optimum values of all the parameters for best process performance, which can be evaluated from the present simulation.     

加压下颗粒移动床空隙率实验研究

在移动床排料装置上,研究加压条件下移动床表观颗粒速度、表观气速及入口压力对并流移动床空隙率的影响。结果表明,在表观颗粒速度或表观气速不变的情况下,移动床空隙率随入口压力的升高而减小;在入口压力不变的情况下,移动床空隙率基本不随表观颗粒速度和表观气速变化。对实验结果进行非线性拟合,得到气固并流移动床空隙率的压力拟合公式,利用该拟合公式和Ergun方程可计算移动床压降,在实验数据范围内,计算压降与实验压降的最大偏差小于±10%。     

Biological phenol removal using immobilized cells in a pulsed plate bioreactor: effect of dilution rate and influent phenol concentration

The continuous aerobic biodegradation of phenol in synthetic wastewater was carried out using Nocardia hydrocarbonoxydans immobilized over glass beads packed between the plates in a pulsed plate bioreactor at a frequency of pulsation of 0.5s(-1) and amplitude of 4.7 cm. The influence of dilution rate and influent phenol concentration on start up and steady state performance of the bioreactor was studied. The time taken to reach steady state has increased with increase in dilution rate and influent phenol concentration. It was found that, as the dilution rate is increased, the percentage degradation has decreased. Steady state percentage degradation was also reduced with increased influent phenol concentration. Almost 100% degradation of 300 and 500 ppm influent phenol could be achieved at a dilution rate of 0.4094 h(-1) and more than 99% degradation could be achieved with higher dilution rates. At a higher dilution rate of 1.0235 h(-1) and at concentrations of 800 and 900 ppm the percentage degradation has reduced to around 94% and 93%, respectively. The attached biomass dry weight, biofilm thickness and biofilm density at steady state were influenced by influent phenol concentration and dilution rate.     

电气石/TiO2复合体系光催化降解苯酚溶液的反应动力学

采用电气石微粒表面钛盐水解包覆纳米TiO2的方法,在不同条件下构建电极性矿物/TiO2体系,分别采用扫描电子显微镜、傅里叶红外吸收光谱、高效液相色谱仪等对催化体系进行了表征。以苯酚溶液为目标物,考察了动态条件下催化体系对苯酚的去除效果,结果表明复合光催化体系对苯酚具有良好的分解性能,当比例为0.2时,催化效果增长的趋势非常明显,当反应时间为120min时,降解率达到了96.29%,高出了纯相TiO2的70%降解率将近26个百分点;在苯酚浓度不断变化时的速率常数从-0.0012～-0.0503变化,证明在苯酚浓度变化的条件下对催化剂的催化效率有明显的影响。在加入的催化剂量不断变化时的催化速率常数从-0.0105～-0.0051,降解苯酚符合Langmuir-Hinshelwood动力学方程。     

Metal precipitation in an ethanol-fed, fixed-bed sulphate-reducing bioreactor

A batch upflow fixed-bed sulphate-reducing bioreactor has been set up and monitored for the treatment of synthetic solutions containing divalent iron (100mg/L and 200mg/L), zinc (100mg/L and 200mg/L), copper (100mg/L and 200mg/L), nickel (100mg/L and 200mg/L) and sulphate (1700 mg/L and 2130 mg/L) at initial pH 3-3.5, using ethanol as the sole electron donor. The reactor has been operated at the theoretical stoichiometric ethanol/sulphate ratio. Complete oxidation of ethanol has been achieved through complete oxidation of the intermediately, microbially produced acetate. This is mainly attributed to the presence of Desulfobacter postgatei species which dominated the sulphate-reducing community in the reactor. The reduction of sulphate was limited to about 85%. Quantitative precipitation of the soluble metal ions has been achieved. XRD and SEM-EDS analyses performed on samples of the produced sludge showed poorly crystalline phases of marcasite, covellite and wurtzite as well as several mixed metal sulphides.     

Kinetic modeling of electrochemical degradation of phenol in a three-dimension electrode process

For giving a reasonable design method of electro-chemistry reactor, based on law of conservation of energy and law of conservation of charge, using a series of assumption, theoretical energy model was proposed in this study. By proper mathematics simplification method for the new model which demonstrats the relation between energy demanding and providing of the three-dimension electrode (TDE) reactor, the most important characteristic parameters (K(1), K(2)) which are constant for a certain matter during electro-oxidation process were obtained. Experiments about phenol degradation using TDE reactor filling with granular activated carbon (GAC) were conducted to examine the fitness of new energy equation and experimental data. Results from experiments revealed that the oxidation behavior could be reasonably described using new model and the energy providing can be calculated by following equation: W=1.56x10(14)eta(d(2)/V)C(0)EQ(2)(1+square root of (1+(V lnK)/(3.63x10(13)eta(2)d(2)Q(2)C(0)E))). The calculated results obtained from above equation were in good agreement with experimental data especially at higher phenol removal efficiency. The new energy equation illustrates energy could be easily obtained through the solution of the value of characteristic parameters by simple lab-scale experiments.     

Calculation of heating and cooling of products moving longitudinally in a fluidized bed

An analysis is made of the problem of the heating and cooling of a metal product moving through two sequentially arranged chambers containing a fluidized bed in the presence of a return flow of heat by thermal conduction along the axis of the product.     

Mathematical model of heat and mass transfer in a moving bed of dispersed material

A moving bed of moist dispersed material is treated as a continuous medium in investigation of the temperature field and as a discrete medium in the determination of the moisture content field. A simplified combined transport system is presented.     

Synthesis, growth and characterization analysis of nickel mercury thiocyanate crystal (NMTC)

The nonlinear optical single crystal of NiHg(SCN)₄ has been successfully synthesized and good quality single crystal has been grown by slow cooling solution growth technique. The grown single crystals have been analyzed by different characterization analyses in order to know its suitability for various applications. The functional groups have been identified from the FTIR analysis. The TG/DTA analysis reveals the thermal behavior of NMTC. The optical behaviour was assessed by UV–Vis analysis and was found with no absorption in the entire visible region and it may be useful for second harmonic and other relevant applications. The relative second harmonic generation efficiency was evaluated by Kurtz powder technique and was found to be good in comparison with the standard inorganic potassium dihydrogen phosphate.     

Dynamics analysis of distributed parameter system subjected to a moving oscillator with random mass, velocity and acceleration

The problem of calculating the response of a distributed parameter system excited by a moving oscillator with random mass, velocity and acceleration is investigated. The system response is a stochastic process although its characteristics are assumed to be deterministic. In this paper, the distributed parameter system is assumed as a beam with Bernoulli–Euler type analytical behaviour. By adopting the Galerkin's method, a set of approximate governing equations of motion possessing time-dependent uncertain coefficients and forcing function is obtained. The statistical characteristics of the deflection of the beam are computed by using an improved perturbation approach with respect to mean value. The method, useful to gathering the stochastic structural effects due to the oscillator–beam interaction, is simple and leads to results very close to Monte Carlo simulation for a wide interval of variation of the uncertainties.     

TBM试验台刀盘混合驱动系统设计与仿真分析

针对全断面硬岩隧道掘进机(TBM)在施工时因驱动扭矩不足引发的刀盘卡死情况,提出了由变频电机和泵控马达混合驱动的方案.采集电机转矩跟随主从控制系统下的电机速度信号,叠加一个预设的常量来实时调节变量泵的排量,利用比例溢流阀溢流多余流量实现对马达工作压差的比例调节,从而实现泵马达系统对电机系统的转速跟随和扭矩可调,并基于○/2.5mTBM实验台的刀盘驱动系统指标要求完成了设计选型.在AMEsim仿真平台上搭建了负载敏感变量泵控系统(LSCS)、流量反馈比例变量泵控系统(FFPCS)和变量缸位移反馈比例变量泵控系统(DFPCS)的模型,分析对比了不同系统在同一电机系统速度信号下泵的压力和流量响应,并对比了不同比例控制策略下变量泵的效率.结果表明:LSCS无法响应电机系统转速跳变,且不适用于闭式系统,FFPCS和DFPCS均能较好地跟随电机系统的转速变化,尽管FFPCS有着更高的控制精度和效率,DFPCS的高可靠性、模块化和低成本优势更符合实际施工要求.     

Dynamic analysis of an axially moving sandwich beam with viscoelastic core

A development of the beam model of the axially moving sandwich continua with elastic faces and the core characterized by viscoelastic properties is presented in this paper. Two-parameter Kelvin–Voigt rheological model is used to describe material properties of the core. The Galerkin method is used to solve the governing partial differential equation. Dynamic analysis of the composite with two aluminum facings and a polyurethane core is carried out. The effect of the transport speed, the core thickness and the internal damping of the core material on the dynamic behavior of the system is investigated in undercrtitical and supercritical range of transport speed.     

Kinetic studies of elemental mercury adsorption in activated carbon fixed bed reactor

Activated carbons are suitable materials for Hg(0) adsorption in fixed bed operation or in injection process. The fixed bed tests provide good indication of activated carbons effectiveness and service lives, which depend on the rates of Hg(0) adsorption. In order to correlate fixed bed properties and operation conditions, with their adsorptive capacity and saturation time, Hg(0) adsorption tests were realized in a bench-scale unit, consisted of F400 activated carbon fixed bed reactor. Hg(0) adsorption tests were conducted at 50 degrees C, under 0.1 and 0.35 ng/cm(3) Hg(0) initial concentrations and with carbon particle sizes ranging between 75-106 and 150-250 microm. Based on the experimental breakthrough data, kinetic studies were performed to investigate the mechanism of adsorption and the rate controlling steps. Kinetic models evaluated include the Fick's intraparticle diffusion equation, the pseudo-first order model, the pseudo-second order model and Elovich kinetic equation. The obtained experimental results revealed that the increase in particle size resulted in significant decrease of breakthrough time and mercury adsorptive capacity, due to the enhanced internal diffusion limitations and smaller external mass transfer coefficients. Additionally, higher initial mercury concentrations resulted in increased breakthrough time and mercury uptake. From the kinetic studies results it was observed that all the examined models describes efficiently Hg(0) breakthrough curves, from breakpoint up to equilibrium time. The most accurate prediction of the experimental data was achieved by second order model, indicating that the chemisorption rate seems to be the controlling step in the procedure. However, the successful attempt to describe mercury uptake with Fick's diffusion model and the first order kinetic model, reveals that the adsorption mechanism studied was complex and followed both surface adsorption and particle diffusion.