Performance analysis of an O_2/ CO_2 power plant based on chemical looping air separation

The process of an O2//CO2 power plant based on chemical looping air separation （CLAS） is modeled using the Aspen Plus software. The operating parameters and power consumption of the CLAS unit are analyzed. The CLAS system, thermal power generation system and flue gas cooling and compression unit （CCU） are coupled and optimized, and the temperature and flow of the flue gas extraction are determined. The results indicate that the net plant efficiency of CLAS O2/CO2 power plant is 39.2%, which is only 3.54% lower than that of the conventional power plants without carbon capture. However, the O2/CO2 power plant based on cryogenic air separation technology brings 8% to 10% decrease in the net plant efficiency. By optimizations, the net plant efficiency increases by 1.65%. The energy consumption of the CCU accounts for 59.7% and the pump accounts for 27.1%. The oxygen concentration from the chemical looping air separation unit is 12.2%.

Insights in active pulsing air separation technology for coarse coal slime by DEM-CFD approach

To research a novel technology for dry coarse coal slime beneficiation and extend its application, active pulsing air separation technology was investigated by DEM-CFD coupling simulation approach. The results show that the ash content of feed is reduced by 10% 15% and the organic efficiency is up to 91.78% by using the active pulsing air separation technology. The gas solid flow in the active pulsing air classifier was simulated. Meanwhile, the characteristics of particle motion and the separation process of different particles were analyzed, and the mechanical structure of the classifier was also modified to achieve high separation efficiency. Therefore, a novel high-efficiency dry beneficiation technique was advanced for coarse coal slime.

Numerical simulation of the pulsing air separation field based on CFD

The flow field of pulsing air separation is normally in an unsteady turbulence state.With the application of the basic principles of multiphase turbulent flows,we established the dynamical computational model,which shows a remarkable variation of the unstable pulsing air flow field.CFD(computational fluid dynamics) was used to conduct the numerical simulation of the actual geometric model of the classifier.The inside velocity of the flowing fields was analyzed later.The simulation results indicate that the designed structure of the active pulsing air classifier provided a favorable environment for the separation of the particles with different physical characters by density.We shot the movement behaviors of the typical tracer grains in the active pulsing flow field using a high speed dynamic camera.The displacement and velocity curves of the particles in the continuous impulse periods were then analyzed.The experimental results indicate that the effective separation by density of the particles with the same settling velocity and different ranges of the density and particle size can be achieved in the active pulsing airflow field.The experimental results provide an agreement with the simulation results.

Simulation and experiment of six-bed PSA process for air separation with rotating distribution valve

In this work,a six-bed pressure swing adsorption(PSA)process was investigated to produce medical oxygen from air,which uses the combination of six-way rotating distribution valve and PSA and has the main advantage of effectively saving space compared to the traditional two-bed or four-bed PSA process and can obtain greater productivity.The mathematical model of adsorption beds was developed based on the separation mechanism and the interaction among different equipment.Moreover,a pilot-scale device has been constructed to verify the accuracy of mathematical model by experiment.The oxygen product conformed to the medical standard(>93%(vol))with a recovery of over 57%.Some related parameters were also discussed in detail,such as step time,ratio of length to the diameter,flow rate of product.

Enrichment of carbon recovery of high ash coal fines using air fluidized vibratory deck separator

Coal is primarily beneficiated by wet gravity methods. The wet processing of coal is an efficient practice. However, it introduces the moisture in the range of 6%-15%, depending upon the size of coal which is as detrimental as ash content to the heating value of coal. Dry beneficiation of coal fines was carried out using an air fluidized vibrating table in which the coal particles get separated from the heavier mineral particles as a result of horizontal and vertical stratification. Two level factorial design matrix was used to optimize and assess the interactive effects of the operational parameters of a pneumatic table viz. deck eccentric, side tilt and air flow rate on the clean coal yield and its ash content. Double stage processing was found to be more effective for reducing the ash content of the clean coal. Initial stage of processing at a higher ash level generates a reject of high ash with low combustibles. Cleaning of the rougher concentrate at 34%-35% ash level shows significant improvement in the organic efficiency （88.6%） and useful heat value of clean coal （15690 kJ/kg）. The performance of air fluidized vibrating deck was measured by Ep value which is 0.18.

MATHEMATICAL AND EXPERIMENTAL ANALYSIS OF AIR SEPARATION BY HOLLOW FIBER MEMBRANES

Approximate solutions for gas separation by hollow fiber membranes have been developedby several investigators.However,there are few reports of experimental verification of the models forhigh stage cut separations.In this work,an approximate mathematical model was developed and wasexperimentally verified for high stage cut air separation.Both countercurrent and cocurrent now pat-terns were used.In addition,the applicability of feed-inside mode for low stage cut air separation byhollow fiber membrane was examined.It was found that feed-inside mods was more advantageousthan feed-outside mode when used for the generation of oxygen-enriched air.

Simulation and heat exchanger network designs for a novel single-column cryogenic air separation process

To realize the industrialization of the novel single-column air separation process proposed in previous work,steady-state simulation for four different configurations of the single-column process with ternary(nitrogen,oxygen and argon)is developed.Then,exergy analysis of the single-column processes is also carried out and compared with the conventional double-column air separation process at the same capacity.Furthermore,based on the steady-state simulation of single-column processes,the different heat exchanger networks(HENs)for the main heat exchanger and subcooler in each process are designed.To obtain better performance for this novel process,optimization of process configuration and operation is investigated.The optimal condition and configuration for this process is consisted as:feedstock is divided into two streams and the reflux nitrogen is compressed at the approximate temperature of 301 K.In addition,HEN is optimized to minimize the utilities.HENs without utilities are obtained for the four different configurations of single-column process.Furthermore,capital costs of the HEN for different cases are estimated and compared.

Characteristics and management strategy of the devices configured in Baosteel's domestically-integrated 60000 m^3/h air separation unit

Baosteel＇ s No. 8 air separation unit（ASU） is the first domestically-integrated 60 000 m^3/h ASU. This paper describes the mechanical equipment, the design and the configuration characteristics of this unit. The potential failure modes of the mechanical devices are deduced via analyses on the failure history of similar devices in other ASUs. Finally, this paper also brings up suggestions on daily maintenance, overhaul and purchases of spare parts.

Independent integration and innovation of the first domestically-integrated 60000 m^3/h air separation unit

Baosteel＇s 60000 m……3/h air separation unit （ASU）, the first domestically-integrated unit of its class, is a milestone in the Chinese air separation industry. In this paper,the process characteristics of the unit and the application of the original techniques are expatiated. Some difficulties in the process design, the risk control, the quality control, the control system integration and the system commissioning are analyzed and appraised. The mode of the project integration and innovation, the cooperation among industries and the user-orientated project management mode are introduced. Finally,the successful experiences in innovation are summarized with the focus on the integration of the project.

Baosteel's No.8 air separation unit and the practice of its system commissioning

This paper introduces the process flow, technical parameters and relevant features of Baosteel＇s No. 8 air separation unit （ASU） with a capacity of 60000m^3/h. It summarizes the commissioning work, which includes the adjustment of the air compressor,the system＇s naked cooling,the precooling system and the operation adjustment. It also provides detailed analyses on some failures which occurred in the commissioning. Through the modification of the design and the interlocks, the tripping probability of the air compressor was greatly reduced. Through the heating of the system and the control of the water cooler＇s nitrogen flow,the overproof content of carbon dioxide and fluctuation of oxygen flow were avoided. Nitrogen-block in the argon system was eliminated by the precise control of the argon rectification flow and argon content. All these solutions have been proved to be effective by practice.

Experimental Study on the Performance of an Onboard Hollow-Fiber-Membrane Air Separation Module

Onboard air separation devices,based on hollow fiber membranes,are traditionally used for the optimization of aircraft fuel tank inerting systems.In the present study,a set of tests have been designed and executed to assess the air separation performances of these systems for different air inlet temperatures(70°C∼110°C),inlet pressures(0.1∼0.4 MPa),volume flow rates of nitrogen-enriched air(NEA)(30∼120 L/min)and flight altitudes(1.5∼18 km).In particular,the temperature,pressure,volume flow rate,and oxygen concentration of air,NEA and oxygen-enriched air(OEA)have been measured.The experimental results show that the oxygen concentration of NEA,air separation coefficient,and nitrogen utilization coefficient decrease with the rising of air inlet temperature,air inlet pressure,and flight altitude.The effect of air inlet pressure on the above three parameters is significant,while the influence of air inlet temperature and flight altitude is relatively small.

Characteristics and experience in the electrical design of the first domestically-integrated large-scale air separation unit

The first domestically-integrated large-scale air separation unit （ASU） with a capacity of 60 000 m^3/h was successfully built and put into operation at Baosteel. Compared with the electrical design of the imported equipment of the same type,this ASU has an electrical protection interlink that is independent from the distribution control system （DCS）. With the design idea of simplicity, the ASU features a simplified configuration and an audio alarm system for electrical failures. It helps reduce the failure rate of the electrical equipment and detect failures quickly and accurately. It will effectively enhance safe and stabilized production. The ASU can not only reduce the cost of investment, but also ensure a smooth and stable running of the whole electrical equipment. This study focuses on the experience and understanding of the unit design and commissioning.

Performance Prediction of Structured Packing Column for Cryogenic Air Separation with Hybrid Model

A detailed investigation of a thermodynamic process in a structured packing distillation column is of great impor- tance in prediction of process efficiency. In order to keep the simplicity of an equilibrium stage model and the accu- racy of a non-equilibrium stage model, a hybrid model is developed to predict the structured packing column in cryogenic air separation. A general solution process for the equilibrium stage model is developed to solve the set of equations of the hybrid model, in which a separation efficiency function is introduced to obtain the resulting tri-diagonal matrix and its solution by the Thomas algorithm. As an example, the algorithm is applied to analyze an upper column of a cryogenic air separation plant with the capacity of 17000 m3·h-1. Rigorous simulations are conducted using Aspen RATEFRAC module to validate the approach. The temperature and composition distributions are in a good agreement with the two methods. The effects of inlet/outlet position and flow rate on the temperature and composition distributions in the column are analyzed. The results demonstrate that the hybrid model and the solution algorithms are effective in analvzin~ the distillation process for a a cryogenic structured packing column.

Type selection and maintenance of the control system of large-scale air separation units

Based on the practice of Baosteel＇ s 60000 m3/h air separation unit （ASU） ,which is the first domestically- integrated unit of such a scale, this paper studies the principles of type selection of the distribution control system （DCS）. It discusses the design of the unit＇s control system,which involves a compressor system,a purification system （molecular sieving）, a turbo expansion system and an air separation system. The final part of the paper discusses the maintenance and future development of the ASU control system at Baosteel.

TEMPERATURE DEPENDENCE OF AIR SEPARATION OF LIQUID CRYSTALLINE TRIHEPTYL CELLULOSE/ETHYL CELLULOSE MEMBRANES

Triheptyl cellulose/ethyl cellulose(3/97)binary blend membranes were prepared from tetrahydrofuran,chloroform and dichloromethane solutions and their air separation capabit- ities were studied at different temperatures.With increasing temperature from 25 to 85℃,the flux QOEA of O_2-enriched air(OEA),O_2 permselectivity and the O_2 concentration Yo_2 in the OEA all increase.The membranes show a unique trend in their Yo_2～QOEA relationship,that is,the air separation capability increases simultaneously with the OEA permeation capability.The magnitudes of QOEA and Yo_2 for 17μm-thick membrane after the testg time of 36hours at 70℃ are 5×10^(-4)cm^3 (STP)/s·cm^2 and 37.6%,respectively.The air separation capability depends slightly on membrane forming solvents.

NaOH-NaNO_3-Air体系低温碱性熔炼处理废弃电路板多金属粉末

研究Na OH-Na NO3-Air体系低温碱性熔炼处理废弃电路板多金属粉末的工艺流程,在熔炼过程中对各因素对两性金属的影响进行系统研究,优化得到较为适宜的熔体组成与工艺条件:Na NO3,Na OH和多金属粉末质量比为0.6:2.5:1.0,温度为350℃,空气流量为1.5 L/min,熔炼时间为30 min。研究结果表明:在此条件下Sn,Pb,Al和Sn的转化率分别为100%,83.99%,93.26%和91.97%。针对含两性金属的碱性浸出液,设计Ca(OH)2沉锡和Na2S·9H2O沉铅锌的分离工艺,得到纯度(质量分数)98%以上的Sn O2及Pb S-Zn O混合物。

Feasibility Research on the High Speed Rotary Positive Air Filter

The structure, separation principle and feasibility research for a new type of vehicle air filter called the high speed rotary positive air filter were described. The analysis of the experimental data showed that the principle and structure of it were feasible and it possessed high separation efficiency and great self cleaning ability. Compared with the conventional air filter it also has lower air intake loss. So it is worth further practical research.

Applications of metal–organic frameworks for green energy and environment: New advances in adsorptive gas separation, storage and removal

The separation of gas molecules with similar physicochemical properties is of high importance but practically entails a substantial energy penalty in chemical industry. Meanwhile, clean energy gases such as H_2 and CH_4 are considered as promising candidates for the replacement of traditional fossil fuels. However, the technologies for the storage of these gases are still immature. In addition, the release of anthropogenic toxic gases into the atmosphere is a worldwide threat of growing concern. Both in academia and industry, considerable research efforts have been devoted to developing advanced porous materials for the effective and energy-efficient separation, storage, or capture of the related gases. In contrast to conventional inorganic porous materials such as zeolites and activated carbons, metal–organic frameworks(MOFs) are considered as a type of promising materials for gas separation and storage. In this contribution, we review the recent research advance of MOFs in some relevant applications, including CO_2 capture, O_2 purification, separation of light hydrocarbons, separation of noble gases, storage of gases(CH_4,H_2, and C_2 H_2) for energy, and removal of some gaseous air pollutants(NH_3, NO_2, and SO_2). Finally, an outlook regarding the challenges of the future research of MOFs in these directions is given.

Three-Dimensional Numerical Investigation of the Separation Process in a Vortex Tube at Different Operating Conditions

Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hilsch vortex tube cleaning （cooling） system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-c turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows in the air separators. Results present a comprehensive and practical solution for use in future numerical studies.

A time-optimal aircraft-following model based on Pontryagin's minimum principle

A time-optimal aircraft-following model is introduced to address air traffic flow interference by velocity reduction. The objective function is set up as minimizing the recovery time during which the separation minima are not infringed and the separation of the air traffic flow returns to the initial separation at the terminal time. Pontryagin＇s minimum principle is used to solve the optimum aircraft-following velocity control law. An analytical minimum safe following separation is also provided under the time-optimal control law. The simulation results show that the precision first-order tracking accuracy is achieved without losing the separation.