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.

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.

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 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.

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.

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.

Product Model Evolvement and Configuration Knowledge Reuse Method

Configuration knowledge is a dynamic information set which is evolving and enriching on and on. Product model is the instantiation of configuration knowledge and the evolution of configuration knowledge is the essential inherent reason which causes the models dynamic evolvement. In the traditional model evolvement process, the inheriting and reuse of configuration knowledge was always ignored. Aim at solving the above problem, the multistage rhombus evolution mode of configuration knowledge is discussed in this paper. The product model based on configuration knowledge is put forward in different levels to achieve the models dynamic evolvement and automatic upgrading. The evolving configuration knowledge drives the product model to evolve directly according to the rule of up-layer evolvement. Furthermore, a new configuration knowledge reuse and optimization technology is presented to inheriting and reuse the foregone configuration knowledge in the course of model evolvement. At last, the air separation equipment which is related with the project is taken as an example to illuminate that the presented model evolvement and configuration knowledge reuse technology are validity and practical.

Synthesis gas production using oxygen storage materials as oxygen carrier over circulating fluidized bed

A novel process for synthesis gas production over Circulating Fluidized Bed （CFB） using oxygen storage materials as oxygen carder was reported. First, oxygen in the air was chemically fixed and converted to lattice oxygen of oxygen storage materials over regenerator, and then methane was selectively oxidized to synthesis gas with lattice oxygen of oxygen storage materials over riser reactor. The results from simulation reaction of CFB by sequential redox reaction on a fixed bed reactor using lanthanum-based perovskite LaFeO3 and La0.8Sr0.2Fe0.9CO0.1O3 oxides prepared by sol-gel, suggested that the depleted oxygen species could be regenerated, and methane could be oxidized to synthesis gas by lattice oxygen with high selectivity. The partial oxidation of methane to synthesis gas over CFB using lattice oxygen of the oxygen storage materials instead of gaseous oxygen should be possibly applicable.

Economical operation of Baosteel's oxygen generating system

Baosteel＇s 60000 m^3/h air separation unit （ASU） is the largest oxygen generating system in China. The operational cost of such a giant system is very high. How to reduce the operational cost is a critical issue. This paper discusses the system＇s characteristics,the current operational status and the difficulties in reducing the cost,and analyzes relevant indicators, such as the technical and economical indicators of individual units and systems as well as the indicators concerning the costs. The relationship between the cost and each economical indicator and measures to optimize an economical operation of the oxygen generating system are also discussed in this paper.

Numerical Investigation into the Distributor Design in Radial Flow Adsorber

Air flow distribution in radial flow adsorber was numerically investigated using computational fluid dynamics(CFD)method,which was proved to be applicable to study the problem of non-uniform distribution in radial flow adsorber.Results showed that the degree of non-uniformity was more serious in desorption process than that is adsorption process.Therefore,it was considered that the non-uniform distribution of flow in a radial flow adsorber was mainly manifested in the desorption process.Optimum design of distributor parameters can improve the flow distribution in adsorber.Meanwhile,three different structures of distributor and the effect of breathing valve were analyzed.Results revealed that truncated cone is more effective than tubular and conical distributors in flow distribution.By inserting the truncated cone in central channel,desorption uniformity was increased by 6.56%and the breakthrough time of CO_(2)was extended from 564s to 1138s in the adsorption process.The“dead zone”problem at the top of adsorber during the desorption process was solved by opening breathing valve,which prolonged the working life of adsorber and was proved to have less effect on the uniform of airflow.

Comparison of aerodynamic characteristics between a novel highly loaded injected blade with curvature induced pressure-recovery concept and one with conventional design

This paper introduces a novel design method of highly loaded compressor blades with air injection.CFD methods were firstly validated with existing data and then used to develop and investigate the new method based on a compressor cascade.A compressor blade is designed with a curvature induced pressure-recovery concept.A rapid drop of the local curvature on the blade suction surface results in a sudden increase in the local pressure,which is referred to as a curvature induced ‘Shock＇.An injection slot downstream from the ‘Shock＇ is used to prevent ‘Shock＇ induced separation,thus reducing the loss.As a result,the compressor blade achieves high loading with acceptable loss.First,the design concept based on a 2D compressor blade profile is introduced.Then,a 3D cascade model is investigated with uniform air injection along the span.The effects of the incidence are also investigated on emphasis in the current study.The mid-span flow field of the 3D injected cascade shows excellent agreement with the 2D designed flow field.For the highly loaded cascade without injection,the flow separates immediately downstream from the ‘Shock＇;the initial location of separation shows little change in a large incidence range.Thus air injection with the same injection configuration effectively removes the flow separation downstream from the curvature induced ‘Shock＇ and reduces the size of the separation zone at different incidences.Near the endwall,the flow within the incoming passage vortex mixes with the injected flow.As a result,the size of the passage vortex reduces significantly downstream from the injection slot.After air injection,the loss coefficient along spanwise reduces significantly and the flow turning angle increases.

Synergistic impacts of anthropogenic and biogenic emissions on summer surface O_3 in East Asia

A factor separation technique and an improved regional air quality model （RAQM） were applied to calculate synergistic contributions of anthropogenic volatile organic compounds （AVOCs）,biogenic volatile organic compounds （BVOCs） and nitrogen oxides （NOx） to daily maximum surface O3（O3DM） concentrations in East Asia in summer （June to August 2000）.The summer averaged synergistic impacts of AVOCs and NOx are dominant in most areas of North China,with a maximum of 60 ppbv,while those of BVOCs and NOx are notable only in some limited areas with high BVOC emissions in South China,with a maximum of 25 ppbv.This result implies that BVOCs contribute much less to summer averaged O3DM concentrations than AVOCs in most areas of East Asia at a coarse spatial resolution （1×1） although global emissions of BVOCs are much greater than those of AVOCs.Daily maximum total contributions of BVOCs can approach 20 ppbv in North China,but they can reach 40 ppbv in South China,approaching or exceeding those in some developed countries in Europe and North America.BVOC emissions in such special areas should be considered when O3 control measures are taken.Synergistic contributions among AVOCs,BVOCs and NOx significantly enhance O3 concentrations in the Beijing-Tianjin-Tangshan region and decrease them in some areas in South China.Thus,the total contributions of BVOCs to O3DM vary significantly from day to day and from location to location.This result suggests that O3 control measures obtained from episodic studies could be limited for long-term applications.