超临界碳化对水泥基材料性能和孔径结构的影响

为了考察超临界碳化技术在水泥基材料改性方面的应用,研究超临界碳化对水泥基材料微观和宏观性能的影响,基于此设计了超临界二氧化碳碳化试验研究水泥砂浆、水泥净浆和混凝土试件的碳化深度、强度、孔径分布以及二氧化碳吸收量的变化.试验分析表明,超临界碳化可以快速实现水泥基材料的碳化,大幅提高试件强度,改善材料的孔径分布,使材料的中细径孔大幅降低,提高材料的抗渗透能力,为改善重金属等危害废物的水泥基固化效果提供了依据.同时超临界碳化可以将大量二氧化碳转化在碳酸钙中沉淀吸收,具有重要的环境保护意义.

几种水泥基材料的渗透率及其超临界碳化的应用

孔隙度和渗透率是水泥基等多孔材料的重要指标,是水泥基材料内部离子迁移多物理场耦合预测模型中的关键材料参数。针对水泥基材料超亚临界碳化预测模型的质量控制方程,采用稳态法试验分析得到了液体渗透率、氮气渗透率、固有渗透率,采用体积法得到了材料孔隙度和含水饱和度,试件包括水泥砂浆、混凝土、水泥瓦、纤维水泥板等材料。其中水泥砂浆和混凝土材料固有渗透率分别为0.001mD和0.0001mD数量级,其他试件为0.01mD数量级;而混凝土的固有渗透率最低为9e-4mD。木纤维等纤维材料的掺加,将大幅增加材料的孔隙度和渗透率。最后使用得到的各项渗透率、孔隙度、含水饱和度,对水泥砂浆和水泥瓦的超亚临界碳化试验进行了多物理场耦合模拟,模拟结果与试验吻合较好。

不同骨料形状的超临界碳化模型对比分析

利用积累分布函数建立了二维随机骨料模型,在超临界碳化理论模型中引入圆形和椭圆形随机骨料模型,通过多物理场模拟软件分别建立均质超临界碳化模型和引入随机骨料的超临界碳化模型,验证了引入骨料后超临界碳化模型的有效性,分析了骨料形状对超临界碳化过程的影响。研究表明引入随机骨料的超临界碳化模型会因为骨料的存在而产生不规则的碳化边界。以最大碳化深度来描述碳化过程时,圆形随机骨料模型得到的最大碳化深度16.1mm,椭圆形随机骨料模型得到的最大碳化深度17.1mm,椭圆形随机骨料比圆形随机骨料更适用。

Effect of Allelochemicals of Chinese-fir root extracted by supercritical CO_2 extraction on Chinese fir

Allelochemicals of Chinese-fir root was extracted by technology ofsupercritical CO_2 extraction under orthogonal experiment design, and it was used to analyzeallelopathic activity of Chinese-fir through bioassay of seed germination. The results showed thatas to the available rate of allelochemicals, the pressure and temperature of extraction were themost important factors. The allelochemicals of Chinese-fir root extracted by pure CO_2 and ethanolmixed with CO_2 have different allelopathic activities to seed germination, and the allelochemicalsextracted by ethanol mixed with CO_2 had stronger inhibitory effects on seed germination than thatextracted by pure CO_2.

Optimization of Supercritical Carbon dioxide Extraction of Ginger Essential Oil by Response Surface Method

[Objective] Ginger essential oil （GEO） is widely used in food production and medical field in recent years due to its prominent biological functions, and this study was conducted to obtain high-quality and high-purity ginger essential oil from the fresh ginger. [Method] GEO was extracted from ginger roots by supercritical fluid extraction （SFE） method. The effects of flow rate of CO2, mesh size of ginger powder and volume of entrainer were investigated by single-factor experiments and response surface method. The content and extraction rate of 6-gingerol represented the extraction index of GEO. [Result] The conditions were optimized as follows： flow rate of CO2 at 25 L/h, mesh size of ginger power of 80 mesh, and volume of anhydrous ethanol as entrainer of 92.46 ml. The optimal extraction rate of 6-gingerol was 3.21%, which was predicted by RSM. [Conclusion] The optimal process of supercritical carbon dioxide extraction of ginger essential oil was identified by singlefactor experiments and response surface method. The present study provides a satisfactory method for purifying GEO from ginger for industrial purpose.

Extraction of betulin from bark of Betula platyphylla by supercritical carbon dioxide extraction

Betulin, which is a medicinal pentacyclic triterpene, is abundant in the bark of white birch (Betula platyphlly). The bark of birch was collected at Tayuan Forest Farm of Jiagedaqi, Heilongjiang Province in September 2000. Supercritical fluid extraction (SFE) that is a new separation technology has been used for the processing pharmaceutical and natural products. In this paper, the extraction of betulin from the bark of birch by supercritical CO2 extraction was studied. The authors investigated and analyzed a few parameters such as modifier dosage, extraction pressure and extraction temperature. The optimal extrac-tion conditions showed that the modifier dosage used for per gram bark powder was 1.5 mL, the extraction pressure was at 20 Mpa, and the extraction temperature was at 55 C. The velocity of flow of liquid CO2 was at 10 kg/h. The pressure and tem-perature in separation vessel were at 5.5 Mpa and 50 C, respectively.

Extraction of Perilla Seed Oil Using Supercritical Carbon Dioxide and GC-MS Analysis

[Objective] This study was aimed to determine the optimal parameters for the extraction of perilla seed oil to obtain high-quality perilla seed oil and analyze its compositions. [Method] In this study, perilla seed oil was extracted using supercritical CO2 （SC-CO2）. The effects of extraction time, temperature and pressure were investigated by single-factor experiments and orthogonal array testing （ORT）. The chemical compositions of extracted perilla seed oil were investigated by GC-MS. [Result] The optimal conditions for the extraction of perilla seed oil using SC-CO2 were extraction time of 4 h, extraction temperature at 40 ℃, and extraction pressure at 23 MPa. Under these conditions, the extraction yield of perilla seed oil was maximized to 12.43%. GC-MS analysis revealed that perilla seed oil was a complex mixture containing 76.183% α-linolenic acid. [Conclusion] Supercritical CO2 extraction was proven to be an effective technology to extract oil from perilla seed, and GCMS was also a satisfactory method for analyzing the compositions of perilla seed oil.

微管壳式换热器在能量转换循环中的应用

目前,超临界二氧化碳(S-CO_(2))布雷顿循环普遍采用印刷电路板换热器(PCHE)来保证其相对其他能量转换循环的紧凑性优势。PCHE芯体为整体结构,若内部出现泄漏或结垢等问题,很难进行维护与检修。本文提出了一种微管壳式换热器(MSTE),其结构与传统管壳式换热器类似,但其管径缩小至微通道级。由于MSTE的流道横截面积占总截面积之比较PCHE大,在典型的回热器与冷却器设计工况下,相对PCHE而言,采用MSTE可将体积与质量均减小30%以上。灵敏性分析结果显示,采用本文设计的MSTE结构的回热器与冷却器,回热器冷热流道入口温度升高20℃左右,压缩机入口温度变化均不超过1℃,说明该种结构换热器的换热能力足够支撑能量转换循环的一般工况波动。

Measurement and Correlation of the Solubility of Ligusticum Chuanxiong oil in Supercritical CO_2

Extraction of the Ligusticum Chuanxiong oil with supercritical CO2 （SC-CO2） was investigated at the temperatures ranging from 55℃ to 70℃ and pressure from 25 MPa to 35 MPa. The mass of Ligusticum Chuanxiong oil extracted increased with pressure at constant temperature. The initial slope of the extraction was considered as the solubility of oil in SC-CO2. Chrastil equation was used to correlate the solubility data of Ligusticum Chuanxiong oil. An improved Chrastil equation was also presented and was employed to correlate the solubility data, The correlation results show that the values of the average absolute relative deviation are 5.94% and 3.33% respectively, indicating the improved version has better correlation accuracy than that of Chrastil equation.

Effects of CO_2 Compression and Decompression Rates on the Physiology of Microorganisms

The influence of compression and decompression rates of carbon dioxide on the physiology of Absidia coerufea and Saccharomyces cerevisiae was investigated. Besides parameters such as pressure, temperature, exposure time, water content, and initial pH, the influence of either compression or decompression rate on the biological behavior of microorganisms was quite essential. For both microorganisms studied, an optimal rate for either compression or decompression process exists due to the integrated effect of pressure, exposure time as well as compression or decompression speed. The decompression rate has no significant effect on cell's viability after 180 min exposure in compressed CO_2 because almost all the microorganisms were died before decompression.

Fabrication of Co-Ni-P film with excellent wear and corrosion resistance by electroplating with supercritical CO_2 emulsion

To avoid the defects caused by the hydrogen evolution and improve the corrosion and wear properties of the electroplated films in the traditional aqueous bath electrodeposition,a supercritical carbon dioxide(Sc-CO2)emulsion was proposed to electrodeposite ternary nanocrystalline Co-Ni-P alloy films.Microstructure,corrosive and tribological properties of the Co-Ni-P films were investigated and compared with the ones electroplated by conventional method.The results show that the Co-Ni-P films produced with Sc-CO2assisted electrodeposition exhibit a more compact microstructure.The preferred orientation plane of hcp(110)for the Co-Ni-P films produced in conventional aqueous bath is changed to be hcp(100)for the one prepared in emulsified Sc-CO2bath.The microhardness,corrosion resistance and tribological properties of the Co-Ni-P films are substantially improved with the assistance of Sc-CO2in the electrodeposition bath.

Measurement and Correlation of Solubilities of C.I. Disperse Red 73,C.I. Disperse Blue 183 and Their Mixture in Supercritical Carbon Dioxide

The solubility of disperse dyes and their mixture in supercritical carbon dioxide is an important property in study and development of supercritical fluid dyeing technology.In this study,solubilities of C.I.Disperse Red 73,C.I.Disperse Blue 183 and their mixture in supercritical CO2 are measured at temperatures from 343.2 to 383.2 K and pressures from 12 to 28 MPa with a static recirculation method.Under the experimental conditions for the binary(C.I.Disperse Red 73+CO2 or C.I.Disperse Blue 183+CO2) and ternary(C.I.Disperse Red 73+C.I.Disperse Blue 183+CO2) systems,the solubilities increase with pressure.The solubility of C.I.Disperse Blue 183 decreases with the increase of temperature when the pressure is lower than 16 MPa,and the trend is opposite when the pressure is higher than 16 MPa.However,there is no crossover pressure for C.I.Disperse Red 73.The solubilities are also affected by molecular polarity of dyes.The co-solvent effect exhibited in the dissolving process of mixed dyes promotes their dissolution in supercritical CO2.The experimental data of solubilities of C.I.Disperse Red 73,C.I.Disperse Blue 183,and their mixture are correlated with the Chrastil model and Mendez-Santiago/Teja model. The former is more accurate.

Supercritical Carbon Dioxide Extraction of Andrographolide from Andrographis paniculata： Effect of the Solvent Flow Rate, Pressure, and Temperature

Andrographis paniculata Nees has been extensively used for traditional medicine and help against fever dysentery, diarrhoea, inflammation, and sore throat. In this study, andrographolide, the main component of this plant was extracted from the leaves of A. paniculata using supercritical carbon dioxide. The operating pressures were varied from 7.50 to 20MPa, the temperatures were varied from 30℃ to 60℃, and the flow rates were varied from 0.5 to 4ml.min^-1. The best extraction condition occurred at 10MPa, 40℃, and a flow rate of 2ml.min^-1 for a 3g sample of A. paniculata ground-dried leaves. The measured extraction rate was found to be about 0.0174g of andrographolide per gram of andrographolide present in the leaves per hour of operation. The future studies must focus on the interaction between the various operating parameters such as temperature, pressure, and flow rate of supercritical carbon dioxide.

Study on the Phase Behavior of Coating Matrix in Supercritical or Sub-critical Carbon Dioxide

The high-pressure phase behavior of coating-solvent-supercritical or sub-critical carbon dioxide system was investigated experimentally. The coating matrix used was 108-acrylic resin at concentration ranging from 10% to 50% (by mass) in mixtures with n-butyl acetate. The experiments were conducted in a high-pressure view cell for temperatures from 35℃ to 65℃ and for pressures from 3.0MPa to 8.0MPa. The effect of temperature, pressure and content of every component on the phase behavior of the systems was observed. Finally, the ternary phase diagram for resin-solvent-CO2 was plotted.

Pretreatment of Corn Stover Using Supercritical CO2 with Water-Ethanol as Co-solvent

Supercritical carbon dioxide,with water-ethanol as co-solvent,was applied to pretreat corn stover to enhance its enzymatic hydrolysis.The efficiency of pretreatment was evaluated by the final reducing sugar yield obtained from the enzymatic hydrolysis of cellulose.Under the operation conditions of pretreatment pressure 15 MPa,temperature 180 ℃ and time 1 h,the optimal sugar yield of 77.8℅ was obtained.Scanning electron microscopy(SEM) and chemical composition analysis were applied to the pretreated corn stover.The results showed that the surface morphology and microscopic structure of pretreated corn stover were greatly changed.After the pretreatment,the contents of hemicellulose and lignin were reduced obviously.Thus more cellulose was exposed,increasing the sugar yield.

Microparticle Formation and Crystallization Rate of HMX with Supercritical CO_2 Antisolvent Recrystallization

Microparticle formation and crystallization rate of 1,3,5,7-tetranitro-l,3,5,7-tetraazacyclooctane (HMX) in acetone solution using supercritical carbon dioxide antisolvent (GAS) recrystallization were studied. Scanning electronic microscopy, X-ray diffraction and infrared radiation were used to examine particle size, crystallinity and chemical structure. The results show that B-HMX microparticle in different average size (2-9.5um) and with narrow size distribution were obtained by controlling the expansibility, expansion speed, initial concentration and temperature during recrystallization of HMX. The formation of nuclei may be a main cause of consumption of solute when the solution is expanded rapidly enough and the equilibrium concentration is lower, in which almost monodisperse microparticle can be obtained.

Kinetics of Reactive Extraction of Nd from Nd2O3 with TBP-HNO3 Complex in Supercritical Carbon Dioxide

The process based on supercritical fluid extraction for reprocessing of the spent nuclear fuel has some remarkable advantages over the plutonium-uranium extraction(PUREX) process.Especially,it can minimize the generation of secondary waste.Dynamic reactive extraction of neodymium oxide(Nd2O3) in supercritical carbon dioxide(SC-CO2) containing tri-n-butyl phosphate-nitric acid(TBP-HNO3) complex was investigated.Temperature showed a positive effect on the extraction efficiency,while pressure showed a negative effect when the unsaturated TBP-HNO3 complex was employed for the dynamic reactive extraction of Nd2O3 in SC-CO2.Both temperature and pressure effects indicated that the kinetic process of the reactive extraction was controlled by the chemical reaction.A kinetic model was proposed to describe the extraction process.

Experimental and Simulating Study of Supercritical CO_2 Extraction of Ginger Essential Oil

An experimental setup for separating ginger essential oil by supercritical fluid extraction is established. The effects of the extraction pressure, temperature, CO2 flow rate and particle size of raw material on the extraction rate are investigated, and the optimum process conditions of supercritical CO2 extraction are determined. A mathematical simulation model is established based on the mass conservation in differential units of extraction bed. The total mass transfer driving force and the equilibrium absorption constant are evaluated by the linear driving force theory. The results from numerical simulation agree well with the experimental data.

Dynamic Supercritical Fluid Devolatilization of Polymers

A number of studies have been reported on the applications of supercritical fluids to polymeric processes. The presence of volatiles can affect the end-use properties of polymer materials. Therefore, these volatiles must be reduced to a level below the maximum permissible limit. Conventional heat-relevant techniques for polymer devolatilization sometimes have limited effectiveness. Devolatilization with supercritical fluids, however, can enhance removal of volatiles from polymers. A model for diffusion-limited extraction is used to characterize dynamic supercritical fluid devolatilization of spherical polymer particles. The rate of supercritical fluid devolailization for styrene/polystyrene system is measured at 343 K and 18 MPa and at CO2 flow rate of 1.93, 3.27 and 5.62 L·min^-1, respectively. The model analysis, which is consistent with experimental results, indicates that the supercritical fluid devolatilization is not solubility-limited but diffusion-limited when CO2 flow rate is above 4.00 L·min^-1.

Separation of Erucic Acid from Rape-Seed Oil Using Supercritical Carbon Dioxide with Entrainer

Separation of erucic acid from rape-seed oil using supercritical carbon dioxide with entrainer was carried on a pilot column with an inner diameter 14 mm and an effective total height 2.2 m. Experiments were focused on the effects of entrainers, i.e. acetone, ethanol and ethyl acetate, on the extraction. It is showed that entrainers made selectivity lower, but separation time shorter.