三氯化铁和硫酸亚铁除砷的比较研究

分别采用三氯化铁和硫酸亚铁作为化学沉淀除砷药剂,比较研究了三氯化铁和硫酸亚铁处理高浓度模拟含砷（V）废水的工艺条件。试验结果表明,在最佳条件下三氯化铁砷去除率为99．92％,硫酸亚铁的砷去除率为99．97％;三氯化铁的用量少且产生的含砷沉淀物也较少。但由于三氯化铁中氯离子较高,导致滤液中氯离子严重超标,不利于废水的达标排放。因此,硫酸亚铁更适合处理工业高浓度含砷废水。     

硫磺掺烧硫酸亚铁制酸装置生产实践与装置特点

主要介绍了龙蟒集团的硫磺掺烧硫酸亚铁制酸装置的工艺流程、主要设备及生产运行情况。硫酸装置掺烧硫酸亚铁比例为20%~30%,各项技术经济指标均达到了设计要求。300 kt/a硫酸装置日产w(H2SO4)98%硫酸最高达1 kt,3.82 MPa蒸汽产量为28 t/h;400 kt/a硫酸装置日产w(H2SO4)98%硫酸最高达1 280 t,3.82 MPa蒸汽产量为35 t/h,成品酸质量全部达到优等品的要求。龙蟒集团开发的硫磺掺烧硫酸亚铁制酸技术提高了资源综合利用效率,减少了环境污染。     

硫铁矿掺烧硫酸亚铁制酸经济效益分析

介绍了硫铁矿掺烧一水硫酸亚铁制酸原理及技术进展。通过对掺烧前后硫酸亚铁中硫、铁资源价值理论分析,探讨了30%掺烧比例下中、高品位硫铁矿掺烧硫酸亚铁的综合经济效益情况。中、高品位硫铁矿掺烧一水硫酸亚铁制酸不但能解决钛白粉副产七水硫酸亚铁出路问题,还能获得一定的经济效益。建议企业建立掺烧硫酸亚铁数学模型,以便在不同状况下处理七水硫酸亚铁。     

400 kt/a硫酸亚铁和硫磺、硫铁矿混合制酸工程设计

针对硫酸法钛白粉生产中排出的w（H2SO4）20％硫酸和硫酸亚铁,提出一种以焙烧硫酸亚铁、硫磺和硫铁矿生产硫酸的新工艺.重点介绍了焙烧硫酸亚铁制酸的工艺特点、工程难点及主要设备.焙烧硫酸亚铁制酸装置的成功运行从根本上解决了困扰硫酸法钛白粉生产工艺的废渣及副产物问题,使硫酸法钛白粉生产装置大型化得以实现.     

Growth of Thiobacillus ferrooxidans on ferrous iron in chemostat culture: Influence of product and substrate inhibition

Thiobacillus ferrooxidans was grown at pH 1.6 in continuous flow chemostat culture on ferrous sulphate as growth limiting substrate at dilution rates between 0.02–1.33 h^?1. Iron oxidation and growth were subject to product inhibition by ferric iron and under some conditions substrate inhibition by ferrous iron. Product inhibition could be predominantly competitive or non-competitive, and the mode observed depended partly on previous steady state conditions. The inhibition phenomena resulted in unique anomalous washout curves and complex relationships between steady-state substrate, product and biomass concentrations, for which mathematical models are developed. For the growth states subject to non-competitive inhibition by Fe³⁺ at D 0.073–0.99 h^?1, the growth yield coefficient corrected for maintenance (Y_G) was 1.33 g dry wt (g atom Fe²⁺ oxidized)^?1 and the maintenance coefficient (m) was 0.43 g atom Fe²⁺ oxidized (g dry wt)^?1 h^?1). For predominantly competitive states (D, 0.05–0.268 h^?1) with 2–70 mM Fe³⁺ in steady states, Y_G was 0.36–0.38 and m was 0–0.04. A consequence of product inhibition and substrate inhibition was the possibility of more than one steady state product value and yield for a single steady state substate concentration. This was demonstrated experimentally. Substrate saturation coefficient, K_s (giving half maximum specific growth rate) for Fe²⁺, was 0.7–2.4 mM and maximum specific growth rate (μ_m) 1.25–1.78 h^?1. The results presented reveal unusual and novel properties of T. ferrooxidans relevant to describing its activities in natural environments or in mineral leaching systems.     

Biological oxidation of ferrous iron: study of bioreactor efficiency

The bio‐oxidation of ferrous iron is a potential industrial process for the regeneration of ferric iron in the removal of H₂S. In the first stage, H₂S is selectively oxidized to elemental sulfur using ferric sulfate. The ferrous sulfate produced is oxidized to ferric sulfate using Thiobacillus ferrooxidans for recycle and reuse in the process. The aim of the work described here was to investigate continuous oxidation of ferrous iron by immobilized T ferrooxidans and the factors which can directly affect the oxidation rate in order to assess the feasibility of this technique on an industrial scale. An analysis of the evolution of bioreactor performance with time (125 days) was performed in order to assess the feasibility of this technique on an industrial scale. A good oxidation rate was obtained despite the transport problems encountered due to occlusion of the porous support. On the other hand, the toxic effects due to absorption in the ferric solution of one or more compounds from the gas digester were studied using a ferric iron solution from the absorption process. The results indicate the feasibility of the biological system for the regeneration of the ferric‐absorbing solution. Finally, a previous study for the design of an industrial bioreactor to regenerate ferric sulfate solutions, used to remove H₂S from biogas in a wastewater‐treatment plant (Jerez de la Frontera, Spain), is introduced. Good biological oxidation performances have been obtained using a pilot plant bioreactor of 500 dm³. Copyright © 2003 Society of Chemical Industry     

Combined biological and chemical oxidation of ferrous sulfate using immobilised Thiobacillus ferrooxidans

Thiobacillus ferrooxidans immobilised in biomass support particles with activated carbon coating were used in a packed‐bed bioreactor to study the combined effects of chemical and biological catalysis on the oxidation of ferrous iron. The effect of ferrous iron concentration (in the range 5–30 kg m⁻³) and of its volumetric loading on the kinetics of reaction were investigated. With low concentrations of ferrous iron, 5–10 kg m⁻³, the combined catalysis did not offer a significant advantage to oxidation of ferrous iron and the kinetics of reaction were slightly faster than those achieved with just the biological catalyst. With ferrous iron at a concentration of 20 kg m⁻³, the combination of chemical and biological catalysis resulted in a remarkable enhancement of the reaction rate. The maximum oxidation rate of ferrous iron in the presence of combined catalysts, 21.9 kg m⁻³ h⁻¹, was twice as high as that achieved with just the biological catalyst. © 1999 Society of Chemical Industry     

Development of a hybrid neural network model to predict feeding method in fed‐batch cultivation for enhanced recombinant streptokinase productivity in Escherichia coli

BACKGROUND: A simple and efficient model for enhancing production of recombinant proteins is essential for cost effective development of processes at industrial scale. A hybrid neural network (HNN) model is proposed combining an unstructured model and neural network to predict the feeding method for the post‐induction phase of fed‐batch cultivation for increased recombinant streptokinase activity in Escherichia coli. RESULTS: The parameters of the unstructured model were estimated from experiments conducted with various feeding methods. The simulated model described the dynamics of the process satisfactorily, however, its predictive capability of the process for different feeding methods is limited due to wide disparity in process parameters. In contrast, a neural network model trained to map the variations in process parameters to state variables complements the ‘first principle’ model in predicting the state variables effectively. CONCLUSIONS: The HNN model is able to predict the product profile for different substrate feed rates. Further, the average volumetric streptokinase activity predicted by the HNN model matches closely the experimental values for fed‐batches having high as well as low streptokinase activity. The HNN model developed in this study could facilitate development of a process for recombinant protein production with minimum number of experiments. Copyright © 2011 Society of Chemical Industry     

Mathematical modelling of chemical processes—obtaining the best model predictions and parameter estimates using identifiability and estimability procedures

Chemical engineers who develop fundamental models often have difficulties estimating all model parameters due to problems with parameter identifiability and estimability. These two concepts are reviewed, as are techniques for assessing identifiability and estimability. When some parameters are not estimable from the data, modellers must decide whether to conduct new experiments, change the model structure, or to estimate only a subset of the parameters and leave the others at fixed values. Estimating a reduced number of parameters can lead to better model predictions with lower mean squared error (MSE). MSE‐based techniques for parameter subset selection are discussed and compared. © 2011 Canadian Society for Chemical Engineering     

Forced thermal cycling of catalytic reactions: Experiments and modelling

Recent studies of catalytic reactions subjected to fast forced temperature oscillations have revealed a rate enhancement increasing with temperature oscillation frequency. We present detailed studies of the rate enhancement up to frequencies of 2.5 Hz. A maximum in the rate enhancement is observed at about 1 Hz. A model for the rate enhancement that includes the surface kinetics and the dynamic partial pressure variations in the reactor is introduced. The model predicts a levelling off of the rate enhancement with frequency at about 1 Hz. The experimentally observed decrease above 1 Hz is explained by dynamic thermal limitations of the reactor.     

Mathematical modelling and its use for design of feeding strategies for L‐Sorbose fermentation

Batch sorbitol to sorbose bioconversion by Acetobacter suboxydans using initial sorbitol concentration (S₀ = 100 g/L) yielded a productivity of 10.11 g/L‐h and 98.6% conversion in 10 h time. The batch kinetics was then used to develop an unstructured mathematical model. Model parameters were identified using a nonlinear regression technique assisted by a computer program which minimized the deviation between the model predictions and actual batch experimental data. F test indicated 99% confidence on the prediction of model using optimized parameters. The batch model was eventually extrapolated to identify nutrient feeding strategies to maintain constant noninhibitory sorbitol supply and eliminate substrate limitation for fed‐batch fermentation in order to improve the sorbose productivity. The adequacy of the fed‐batch model was established by excellent agreement between experimental data and model simulation (except towards the end of fermentation).     

Biohydrogenation of fumarate using Desulfovibrio desulfuricans: experimental results and kinetic rate modelling

The biological hydrogenation of organic compounds using sulphate-reducing bacteria was investigated. A high pressure stainless steel bioreactor and an atmospheric pressure reactor were constructed so that identical reactions at different pressures could be compared. The mesophillic sulphate-reducing bacteria Desulfovibrio desulfuricans (ATCC 7757) were used. Qualitative tests showed that Desulfovibrio desulfuricans was able to retain its viability at hydrogen pressures up to 35 atmospheres at a temperature of 37°C when exposed to fumarate. Evidence of fumarate dismutation was observed since half of the fumarate was converted to succinate. The effect of bacterial cell concentration was also studied under hydrogen gas. For a doubling of the bacterial cell (reactivated) concentration, the conversion of fumarate doubled from 40% to 80% in 12 h. A first-order reaction rate model was fit to the fumarate concentration data. The first-order reaction rate constant was found to be a linear function of the bacterial cell concentration. ©1997 SCI     

Properties and paper sizing application of waterborne polyurethanemicroemulsions: Effects of extender,cross‐linker,and polyol

A series of waterborne polyurethane (WPU) microemulsions were synthesized through self‐emulsification methodology, using toluene‐2,6‐diisocyanate, polytetramethylene glycol (PTMG), poly‐caprolactonediol (PCL), and dimethylol propionic acid (DMPA) as monomers; isophorone diamine (IPDA) as chain extender; and aziridine as cross‐linking agent. The resultant WPU microemulsions were utilized as surface‐sizing agents for cellulose fiber paper. The influences of IPDA content, PTMG/PCL molar ratio, and aziridine content on the physicochemical properties of the resultant emulsions and sized paper have been investigated in detail. The WPU microemulsion displayed better surface sizing properties when it was prepared under the following conditions: the IPDA content of 2.96%, PTMG/PCL molar ratio of 0:4, and aziridine content of 2.0 wt %. The relationships between the WPU structure and properties of WPU films and sized paper were clearly illustrated. The mechanical properties and water resistance of sized paper were not only depended on the interactions, chain entanglements, and cross‐linking density among the WPU chains, but also relied on the interactions among polymers and fibers, as well as the polarity and stiffness of surface sizing agent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43211.     

From compressibility to structural investigation of sodium dodecyl sulphate — Part 1: Powder and tablet physico-chemical characteristics

As a part of a study on detergent tablets, investigations were carried out to elucidate the compression behavior of a powdered surfactant, sodium dodecyl sulphate (SDS), based on a comparison with the main component of the formulation, i.e. the chorine provider (DCCNa). The compacted SDS exhibited poor cohesion as well as delayed dissolution whatever the compression pressure. The microscopic observations and the mercury porosimetry measurements both demonstrated that a residual porosity existed in the tablets but the dissolution times were always long. A modification of SDS in contact with water, forming a structure like a gel, probably occurred, inducing the closing of the pores and thereby limiting the water intrusion into the tablets.     

Dynamic synergistic modelling for cobalt removal process in zinc hydrometallurgy and the research of parameter estimation based on unscented Kalman filter

The cobalt removal process with arsenic salt of zinc hydrometallurgy has serious non-linearity, uncertainty, and mutual coupling. Its accurate dynamic modelling has always been a challenging problem. On the basis of in-depth analysis of cobalt removal process and reaction mechanism, considering the cascade relationship between the reactors, a dynamic synergistic continuously stirred tank reactor (SCSTR) mechanism model of the cobalt removal process was constructed. Aiming at the unknown parameters in the SCSTR model, the idea of the Kalman filter was introduced, and the unknown parameters were characterized as unknown states; a method of estimating the unknown model parameters was developed using the augmented state equation and the unscented Kalman filter (UKF) algorithm. Simulation results with industrial data of a zinc smeltery showed that the parameter estimation model has high accuracy, and the estimated parameters can be used in the SCSTR model. An intensive simulation analysis of the dynamic characteristics of the complete SCSTR model was carried out to verify the influence of different input disturbances on the output ion concentration of each reactor, which demonstrated the excellent dynamic performance and potential of the model. Ultimately, according to the industrial calculation analysis, the SCSTR model has a guiding effect on the addition of zinc powder in the reactors, overcomes the blindness in the production process, and provides a momentous basis for the optimization control of the cobalt removal process.     

Reductive roasting of nickel laterite ore with sodium sulphate for Fe-Ni production. Part II: Phase transformation and grain growth

In Part II, the correlation between Fe–Ni grain growth and characteristic fusion temperatures of the Na₂SO₄–laterite mixtures, and phase transformations of the reduced pellets were investigated. For the mechanism of sodium sulphate, Na⁺ is able to liberate the hosted nickel and iron within lizardite, while SO₄^2– is the sulphur source for the formation of Fe–FeS eutectic compound which can decrease the characteristic fusion temperatures to promote the growth of ferronickel grains. The mean particle size of ferronickel increased from 7.4 μm to 48.6 μm with the addition of 20 wt% Na₂SO₄.     

The decrease of carbonation efficiency of CaO along calcination-carbonation cycles: Experiments and modelling

Successive calcination-carbonation cycles, using CaO as sorbent, have been performed either in a classical fixed bed reactor or using a thermogravimetric analyser. Significant differences in carbonation efficiencies were obtained, possibly due to different conditions prevailing for CaO sintering during the calcination stage. The effect of the presence of CO₂ on sintering was confirmed.A simple model of the decay of the carbonation capacity along cycles based on the specific surface area of non-sintered micrograins of CaO is able to predict the decrease of the extent of conversion obtained after 40 carbonations along calcination-carbonation cycles. The asymptotic extent of conversion is obtained when all the micrograins present within a grain are sintered. A detailed model of the carbonation shows that the voids present between the micrograins are filled up by carbonate when a critical thickness of the carbonate layer around each micrograin reaches 43 nm. Then, carbonation becomes controlled by diffusion at the scale of the whole grain, with the CO₂ diffusion coefficient decreasing (at ) from 2×10^-12 to as carbonation proceeds from 50% conversion to 76% (first cycle). This scale change for diffusion is responsible for the drastic decrease of the carbonation rate after the voids between micrograins are filled up.     

五箱一体化活性污泥工艺的数学模拟与校正

对五箱一体化活性污泥工艺进行了数学模拟研究, 针对模型中的动力学参数提出了一种迭代计算的校正方法。该方法结合了6个批式实验模拟(氨氮吸收速率AUR、硝氮吸收速率NUR、耗氧速率OUR、厌氧释磷速率PRR、好氧吸磷速率PUR_aerobic和缺氧吸磷速率PUR_anoxic)、灵敏度分析以及数学优化方法(遗传算法):通过迭代计算确定合适的污泥组分比例, 完成对6个批式实验的模拟;灵敏度分析可以分别确定各个批式实验模拟中参数对模拟结果的影响程度, 挑选待优化参数, 完成参数识别;数学优化方法可以自动对参数进行校正。结果显示, 校正后的模型对五箱一体化活性污泥工艺的模拟效果较好:6个批式实验的模拟值与测量值之间的平均相对误差(ARD)分别为5.65%、17.27%、6.02%、7.11%、13.07%和6.98%;30 d动态出水COD、NH₄⁺-N、TN和TP的ARD值分别为4.72%、18.87%、9.45%和38.11%。研究结果表明, 提出的迭代方法可以用来对活性污泥模型进行校正, 而且校正效果较好。