变压吸附制氧过程传质特性数值分析

研究了变压吸附制氧过程中吸附时间对制氧性能的影响,提出了利用浓度波传递模型分析变压吸附制氧过程传质特性、计算最佳吸附时间的方法。结果表明,吸附过程中吸附床内氮气浓度波形状随着时间和轴向位置而变化,理想传热传质条件下,氮气浓度波传递速度比实际吸附过程浓度波传递速度快,实际过程中由于传质和传热阻力,浓度波传递速度减少26%。基于浓度波传递模型计算的最佳吸附时间与实验值误差在0.5 s以内。

制氧过程循环冷却水系统中低温结垢的研究

针对制氧过程循环冷却水系统中低温易结垢的现象,通过采用新型高效复配药剂进行了一系列试验。试验表明,该复合配方的特点是具有缓蚀、阻垢、分散的多功能作用,在高钙高碱度的条件下,对碳酸钙、磷酸钙、硫酸钙和氢氧化铁等沉积物有良好的抑制和分散作用,同时很好地解决了制氧循环冷却水中长期以来存在的水温较低的沉积垢问题。

真空变压吸附空分制氧等温与非等温过程模拟比较

应用动态柱穿透法测定的空气中氮-氧吸附平衡数据模拟两床真空变压吸附(VSA)空分制氧中等温与非等温过程;在VSA过程模拟中探讨了吸附压力、进料流量和冲洗比等过程操作条件以及吸附过程中温度的变化对产品气氧的纯度、收率和产率的影响,为VSA空分制氧过程提供一定的设计依据。

Process control technology of low NO_x sintering based on coke pretreatment

Process control is an effective approach to reduce the NOx emission from sintering flue gas.The effects of different materials adhered on coke breeze on NOx emission characteristics and sintering performance were studied.Results showed that the coke breeze adhered with the mixture of CaO and Fe2O3 or calcium ferrite significantly lowers the NOx emission concentration and conversion ratio of fuel-N to NOx.Pretreating the coke with the mixture of lime slurry and iron ore fines helped to improve the granulation effect,and optimize the carbon distribution in granules.When the mass ratio of coke breeze,quick lime,water and iron ore fines was 2:1:1:1,the average NOx emission concentration was decreased from 220 mg/m3 to 166 mg/m3,and the conversion ratio of fuel-N was reduced from 54.2%to 40.9%.

Mathematical models and expert system for grate-kiln process of iron ore oxide pellet production.Part Ⅱ:Rotary kiln process control

Rotary kiln process for iron ore oxide pellet production is hard to detect and control.Construction of one-dimensional model of temperature field in rotary kiln was described.And the results lay a solid foundation for online control.Establishment of kiln process control expert system was presented,with maximum temperature of pellet and gas temperature at the feed end as control cores,and interval estimate as control strategy.Software was developed and put into application in a pellet plant.The results show that control guidance of this system is accurate and effective.After production application for nearly one year,the compressive strength and first grade rate of pellet are increased by 86 N and 2.54%,respectively,while FeO content is 0.05% lowered.This system can reveal detailed information of real time kiln process,and provide a powerful tool for online control of pellet production.

pH variation mechanism of high sulfur-containing bauxite

In order to fundamentally solve the acidification problem of high sulfur-containing bauxite during storage, by simulating the environment of minerals storage in laboratory, the acidification mechanism and influencing factors of high sulfur-containing bauxite were studied and confirmed using the single variable method to control the atmosphere, water and other variables. The results show that the acidification is mostly caused by the oxidation of sulfur-containing bauxite, which is mainly the natural oxidation of Pyrite(Fe S2), then the alkaline minerals dissolute in the presence of water, leading to the acidification phenomenon, which is influenced by moisture and air flow. Finally, more acid-producing substances are formed, resulting in the acidification of high sulfur-containing bauxite. The acidification of high sulfur-containing bauxite results from the combined effect of the oxygen in the air and water, which can be significantly alleviated by controlling the diffusion of the oxygen in air.

Control for Modified University of Cape Town Process Using Oxidation-Reduction Potential in the Second Anoxic Zone

The aim of this work is to evaluate the feasibility of applying the technology of oxidation-reduction potential （ORP） control on the municipal wastewater treatment system for nitrogen and phosphorus removal. Meanwhile the relation between the optimal ORP （ ORPopt ） and influent C/N ratio was evaluated, in which the influent chemical oxygen demand （ COD ） concentration was stabilized at （290 ± 10 ） mg/L, the influent total phosphorus （TP） concentration was stabilized at （7.0 ± 0.5 ） mg/L. The results indicated that： （1） the ORP in the second anoxic zone had effect on nitrogen and phosphorus removal capability, and the average percentages of phosphorus uptake in ANO2 zone （ ηa ） increased with increasing ORP, i. e. , increasing from 12. 0% at - 143 mV to 22.0%,30.0%,37.0%, and45.0% at -123, -111, -105 and -95 mV, respectively; （2） the ORPopt as function of influent C/N ratio could be calculated by the equation： y ffi 252. 73e〈 -x/3.39） _ 131.01 ; the maximum percentage of phosphorus uptake in ANO2 as function of the ORPopt could be calculated by the equation： y ffi -0.49e（x/15.58） ＋ 1. 51. The ORPopt was the important process control parameter that must be optimized for operation of enhanced biological phosphorus removal （ EBPR ） system. Moreover, ORP sensor is very simple, and the industrial applications of this strategy is practical.

Design and control of a p-xylene oxidation process

The p-xylene(PX) oxidation process is of great industrial importance because of the strong demand of the global polyester fiber.A steady-state model of the PX oxidation has been studied by many researchers.In our previous work,a novel industrial p-xylene oxidation reactor model using the free radical mechanism based kinetics has been developed.However,the disturbances such as production rate change,feed composition variability and reactor temperature changes widely exist in the industry process.In this paper,dynamic simulation of the PX oxidation reactor was designed by Aspen Dynamics and used to develop an effective plantwide control structure,which was capable of effectively handling the disturbances in the load and the temperature of the reactor.Step responses of the control structure to the disturbances were shown and served as the foundation of the smooth operation and advanced control strategy of this process in our future work.

Design of an Expert Control System for Biogas Fermentation Process

Controlling the biogas fermentation process is the key for maintaining stable operation of biogas system and increasing gas yield. Aiming at features of biogas fermentation process and difficulties of control, a practical control scheme is proposed combining the abundant experience of biogas experts. And it discussed the structural design and hardware configuration of the expert control system, established the database and role base, and designed the control strategy of production system inference. The design scheme with ZigBee and PDA technology as core is employed so as to solve problems of environmental factor detection and data transfer management. The test result shows that the deviation of temperature is controlled within ± 0.9℃, the deviation of pH is controlled within ±0.3, the deviation of oxidation-reduction potential is controlled within ±30mV, the deviation of gas production is controlled within ± 9mL and that of methane concentration is controlled within ±4.5%. This system is easily expandable and applicable to biogas engineering at various scales.

Evaluation of Porous Structure of Cement Pastes Made with Residual Rice Husk Ash

In several countries, the residual RHA （rice husk ash） has been produced in rice processing industries or in thermoelectric plants that use rice husk to generate heat and/or electrical energy, usually without burning process control. This causes a reduction in the amorphous silica content of residual RHA, which distinguishes them from the RHA produced according to controlled burning process, which is totally amorphous and considered a highly reactive pozzolan. In this paper, the hydration products and the porous structure of binders paste were studied by replacing, in weight of 5%, 10% and 20% of Portland cement OPC （ordinary Portland cement）, by residual RHAs named A and B, which have high and low content of amorphous silica, respectively, using microstructure evaluation techniques as XRD （X-ray diffraction）, TG （thermogravimetric） tests and MIP （mercury intrusion porosimetry）. A reducing the size of the pores of the pastes was observed according to the increase of content replacement of RHA A and RHA B.

Electrocatalytic water-splitting for the controllable and sustainable synthesis of deuterated chemicals

Tandem water electrolysis for the transformation of universal feedstock to value-added chemicals integrated with hydrogen generation and in situ utilization is a promising approach to address the economic challenges of electrochemical hydrogen evolution and storage.Herein,we present the controllable electrocatalytic deuteration of halides using inexpensive and reusable heavy water(D2 O)as a D-source for the preparation of valuable D-labelled chemicals and pharmaceuticals under mild conditions.This electrochemical deuteration method with high efficiency and selectivity furnishes a series of D-labelled chemicals and pharmaceuticals in high yields with excellent D-incorporation.The reaction efficiency and selectivity,that is,the precise substitution of deuterium atoms at different halogen positions,can be tuned by varying the applied voltages.The results show the great potential of green and economical electrocatalytic methods for producing value-added fine chemicals in addition to hydrogen evolution.

Theoretical analysis on expansion mechanism in carbon dioxide expander

The expansion mechanism inside carbon dioxide expander is analyzed theoretically in this paper.The mechanism analysis of metastable equilibrium indicates that there is a potential barrier during phase change process.That is to say energy is required to overcome the potential barrier when the new interface is formed from primary phase.The superheat of liquid is the impetus of phase change and has an exponential decrease with the increase of the saturated temperature of fluid.The analysis also indicates that there is a critical radius during the phase change process.The bubble will grow up when its radius is larger than the critical value,otherwise,will disappear.When considering the metastable phase change,calculation of P and V during expansion process indicates that the phase-change will be delayed with the decline of pressure,which is called lag phenomenon.The phase-change delay time decreases with the increase of initial temperature.When the initial temperature is close to the critical temperature,the delay time is close to zero.The phase-change delay brings energy losses,which decrease with the increase of initial temperature and its decrease ratio also has a decrease trend.When the initial pressure is 10 MPa,the energy loss will be 1.06 W with an initial temperature of 10℃ while 0.34 W with that of 20℃.