铁矿石含碳球团中碳的气化反应速度对球团熔融的影响

利用气化反应速度不同的焦炭和石墨作为还原剂,考察了铁矿石含碳球团在高温加热时还原铁的渗碳、熔融及球团结构的变化规律。根据研究的结果,得到以下结论:①碳的气化反应速度对铁的渗碳及熔融有重要影响;②气化反应速度较快的焦炭混合球团在1350℃加热9 min时球心部首先出现熔融铁粒,而气化反应速度较慢的石墨混合球团在1250℃加热9 min时在球团表面首先出现熔融铁粒;③反应中物料混合状态的变化以及反应后球团内部空洞的大小都受到碳的气化反应速度的影响。

长脉冲激光与硅相互作用气化过程的数值模拟

为了研究毫秒量级脉宽激光与半导体材料的相互作用机理,建立了一维有限元模型,对长脉冲激光与硅相互作用的气化现象进行了数值模拟。在计算中,利用热焓法处理了固-液相变过程,并根据热流方程考虑了气化产生的能量损失。在入射激光功率密度相同的条件下,定量地描绘了不同脉宽激光辐照材料的温度分布,前表面的温度历史,以及气化速度和气化深度,并估算出气化深度为0.5μm时,物质蒸汽使激光产生光学自聚焦现象的激光功率阈值仅为0.2 W,此阈值远小于长脉冲激光的功率。因此,在长脉冲激光与硅材料相互作用过程中,气化的物质蒸汽会使后续激光产生光学自聚焦现象。得到的结果可为长脉冲激光的应用提供理论依据。

多点两阶段煤炭地下气化方法

鉴于在急倾斜煤层中进行地下气化所存在的煤气热值不稳定问题 ,提出了多点两阶段煤炭地下气化工艺。介绍了模型试验系统 ,阐述了多点两阶段地下气化方法 ,研究了两阶段时间之比、产出的煤气热值、组份和气化速度 ,并对试验结果进行了分析。模型试验结果表明 ,多点两阶段煤炭地下气化方法 ,使产生高热值水煤气的时间较固定点供风 (汽 )模式提高 0 .6 7～ 1.5倍。从而在煤炭地下气化现场试验过程中 ,为生产和技术参数的设计 ,提供了重要的理论依据。

急倾斜煤层移动点两阶段地下气化模型试验

鉴于在急倾斜煤层中进行地下气化所存在的煤气热值不稳定问题 ,提出了移动点两阶段煤炭地下气化工艺 .介绍了多功能工艺技术模型试验台结构 ,阐述了移动点两阶段地下气化方法 ,研究了两阶段时间之比、产出的煤气热值、组份和气化速度 ,并对试验结果进行了分析 .模型试验结果表明 ,移动点两阶段煤炭地下气化方法 ,使产生高热值水煤气的时间较固定点供风 (汽 )模式提高 0 .67～ 1 .5倍 .从而在煤炭地下气化现场试验过程中 ,为生产和技术参数的设计 ,提供了重要的理论依据 .

高效节能调温气化炉

项目简介该炉是我院最新发明的高科技成果,煤柴两用适合于农村一家一户,也适用于乡镇集体小食堂,其突出特点是以烧湿柴、生柴为主。干柴还需水泡1～2分钟,一次放足柴草,做饭期间基本不添柴,即方便又卫生。此外,本炉膛深浅,炉火温度,气化速度及柴草燃烧时间都可调。一般情况下,比传统炉灶可节省柴三至五倍,而且起火速度快捷。

毫秒激光与硅靶相互作用靶材后表面温度的干涉法测量

研究了毫秒激光与硅靶相互作用后表面的蒸气速度和后表面温度变化。由实验得到了脉宽为1 ms、能量密度为5.82×10~3J/cm^2的激光与厚度为0.3 mm的硅靶相互作用过程的序列干涉图。观察该序列干涉图发现,激光辐射466μs时,硅靶的前表面和后表面均产生了气化现象;激光作用699μs后,硅靶的前表面和后表面均有液态喷溅物出现。通过相邻两幅干涉图的干涉条纹位置变化及时间间隔,计算得到了激光辐射466~699μs时后表面蒸气的膨胀速度为20.47±0.08 m/s。根据Rankine-Hugoniot关系、气体动力学理论以及Knudsen层的质量、动量、能量守恒方程,计算得到硅靶后表面附近的蒸气压强。考虑物质蒸气压强满足克拉伯龙—克劳修斯方程,计算得到激光作用466~699μs时硅靶后表面的平均温度为3551.2±2 K,计算结果与文献基本吻合。最后,根据计算的温度分析了熔融喷溅的产生机理。

Converted-wave diodic moveout and application in the land gas cloud area

PS converted-waves （C-waves） have been commonly used to image through gas clouds but the C-wave imaging may also be degraded by the diodic effect introduced by the gas cloud. It may be compensated for using a velocity perturbation method which decouples the diodic moveout into two parts： the base velocity and the velocity perturbation. Gas clouds are widely distributed in the Sanhu area in the Qaidam basin of northwest China which is rich in natural gas. A land 2D3C seismic dataset is analyzed from the Sanhu area and significant diodic effects are observed in the data which harm the C-wave imaging. The diodic correction is applied to this data and the resultant C-wave imaging and the details of the reservoir structure are significantly improved. The diodic moveout plays an important role in working out the residu~ shear wave statics and the association of diodie correction and shear wave residual statics computation is a key step of C-wave high fidelity imaging in the gas cloud area. Finally, the new process workflow with diodic moveout is given.

话说“煤气罐”

话说“煤气罐”长安随着我国石油工业的迅速发展，城市里许多家庭都使用了煤气罐。“煤气罐”似乎可以顾名思义——里边装的是煤气。其实不然，里边装的并不是煤气，而是液化石油气。“液化石油气”跟“煤气”不同，煤气是用煤制造的，它的主要成分是氢气、一氧化碳和甲烷...

节能与环保

1.CL130型高效节能调温气化炉 该炉属高科技成果,煤柴两用适合农村一家一户和乡镇小食堂使用。其突出优点是以烧湿柴生柴为主,干柴还需浸水1—2分钟使用,一次放足柴草,做饭期间基本不需添柴,既方便又卫生。该炉膛深浅、炉火温度、气化速度及柴草燃烧时间都可调,起火快捷,做饭省时,该炉采用上点火,从上而下燃烧,火焰温度可达1000℃以上,又采用二次进气。

Fabrication of Hydrogenated Microcrystalline Silicon Thin Films at Low Temperature by VHF-PECVD

Using H 2 diluted silane,series of μc Si∶H films are fabricated at low temperature with VHF PECVD.The thickness measurements reveal that the deposition rates are obviously enhanced with higher plasma excitation frequency or working pressure,but increase firstly and then decrease with the increase of plasma power density.Raman spectra show that the crystallinity and the average grain sizes of the films strongly depend on the temperature of substrate and the concentration of silane.However,the plasma excitation frequency only has effect on the crystallinity,and a maximum occurs during the further increase of plasma excitation frequency.From XRD and TEM experiments,three preferential crystalline orientations (111),(220) and (311) are observed,and the average grain sizes are different for every crystalline orientation.

Reflection and transmission of bottom simulating reflectors in gas hydrate-bearing sediments: Two-phase media models

The bottom simulating reflector （BSR） in gas hydrate-bearing sediments is a physical interface which is composed of solid, gas, and liquid and is influenced by temperature and pressure. Deep sea floor sediment is a porous, unconsolidated, fluid saturated media. Therefore, the reflection and transmission coefficients computed by the Zoeppritz equation based on elastic media do not match reality. In this paper, a two-phase media model is applied to study the reflection and transmission at the bottom simulating reflector in order to find an accurate wave propagation energy distribution and the relationship between reflection and transmission and fluid saturation on the BSR. The numerical experiments show that the type I compressional （fast） and shear waves are not sensitive to frequency variation and the velocities change slowly over the whole frequency range. However, type II compressional （slow） waves are more sensitive to frequency variation and the velocities change over a large range. We find that reflection and transmission coefficients change with the amount of hydrate and free gas. Frequency, pore fluid saturation, and incident angle have different impacts on the reflection and transmission coefficients. We can use these characteristics to estimate gas hydrate saturation or detect lithological variations in the gas hydrate-bearing sediments.

The anthropogenic acceleration and intensification of flash drought over the southeastern coastal region of China will continue into the future

The frequent and rapid onset of flash drought poses a serious threat to agriculture and ecosystems.Detecting human influences on flash droughts and estimating their future risks under climate change have attracted great attention.Focusing on a record-breaking flash drought event in the southeastern coastal region of China in summer 2020,the authors found that the suppression of convective precipitation and high temperature caused by the persistent high geopotential height anomalies and land-atmosphere dry coupling were important reasons for the rapid onset and strong intensity of the flash drought.Event attribution analysis with the latest CMIP6 data showed that anthropogenic climate change has not only increased the likelihood of an onset speed and intensity like those of the 2020 flash drought event,by about 93%±20%and 18%±15%,respectively,but also increased the chance of their simultaneous occurrence,by about 86%±38%,according to their joint probability distribution.Under a business-as-usual future scenario(SSP2-4.5),the likelihood of such an onset speed,intensity,and their simultaneous occurrence will further increase,by 85%±33%,49%±8%,and 81%±48%,respectively,as compared with current climate conditions.This study highlights the importance of anthropogenic climate change for accelerating and intensifying flash drought in the southeastern coastal region of China.

Effect of agitation on the characteristics of air dense medium fluidization

In order to study the effect of agitation on the characteristics of air dense medium fluidization, we designed and constructed an agitation device. Analyses were then conducted on the fluidization characteristics curves, the bed density stability and the average bubble rise velocity Uaunder different agitation conditions. The results indicated that a lower bed pressure drop(without considering lower gas velocity in a fixed bed stage) and higher minimum fluidized velocity are achieved with increasing agitation speed.The height d(distance between the lower blades and air distribution plate) at which the agitation paddle was located had a considerable effect on the stability of the bed density at 9.36 cm/s < U < 10.70 cm/s. The higher the value of d, the better the stability, and the standard deviation of the bed density fluctuation r dropped to 0.0364 g/cm^3 at the ideal condition of d = 40 mm. The agitation speed also had a significant influence on the fluidization performance, and r was only 0.0286 g/cm^3 at an agitation speed of N = 75 r/min. The average bubble rise velocity decreased significantly with increasing agitation speed under the operating condition of 1.50 cm/s < U–U_(mf)< 3.50 cm/s. This shows that appropriate agitation contributes to a significant improvement in the fluidization quality in a fluidized bed, and enhances the separation performance of a fluidized bed.

Analytical Model for Predicting the Heat Loss Effect on the Pyrolysis of Biomass Particles

This paper presents the combined influence of heat-loss and radiation on the pyrolysis of biomass particles by considering the structure of one-dimensional, laminar and steady state flame propagation in uniformly premixed wood particles. The assumed flame structure consists of a broad preheat-vaporization zone where the rate of gas-phase chemical reaction is small, a thin reaction zone composed of three regions: gas, tar and char combustion where convection and the vaporization rate of the fuel particles are small, and a broad convection zone. The analysis is performed in the asymptotic limit, where the value of the characteristic Zeldovich number is large and the equivalence ratio is larger than unity(i.e.u≥1). The principal attention is made on the determination of a non-linear burning velocity correlation. Consequently, the impacts of radiation, heat loss and particle size as the determining factors on the flame temperature and burning velocity of biomass particles are declared in this research.

Seepage laws of two kinds of disastrous gas in complete stress-strain process of coal

The similarities and differences in seepage flow evolution laws of CH4 and CO2 during complete stress- strain process of samples were comparatively analyzed. The results show that the seepage flow evolution laws of CH4 and CO2 are extremely similar during the stress-strain process, showing that the character- istic first decreased and then increased. A mathematical model was also established according to the rela- tionship of seepage velocity and axial strain. However, due to the strong adsorption ability of CO2, the coal samples generated a more serious ''Klinkenberg effect'' under the condition of CO2. Owing to this, the CO2 seepage flow resulted into occurrence of ''stagnation'' phenomenon during the late linear elastic stage II. In the strain consolidation stage III, the increment rate of CH4 seepage velocity was significantly greater than that of CO2. In the stress descent stage IV, when the axial load reached the peak pressure of coal, the increment rates of CH4 seepage velocity presented a turning point. But the changing rate of CO2 seepage velocity still remained slow and a turning point was presented at one time after the peak of thestrain pressure, which showed an obvious feature of hysteresis.

Ozonation of Sulfur Dioxide in Sulphuric Acid Solution

In this study, the oxidation rates of sulfur dioxide （SO2） in sulphuric acid solution by ozone and oxygen were compared, and the oxidation mechanism of ozone on SO2 was investigated. The results showed that the oxidation-reduction potential of the acidic solution was enhanced, the transformation rate of sulfuric acid to sulphuric acid was increased and the absorption driving force was improved in the presence of ozone. By comparing the amount of sulfate ions measured in the experiments and the theoretical amount of sulfate ions calculated from the amount of ozone consumed in the reaction, it can be confirmed that oxygen free radicals from dissociation of ozone are reactive as an efficient oxidant and oxygen from ozone generator participates in the reaction with SO2. 0.602 mol of effective oxygen was introduced into the reaction by one mole of ozone in 10.15 rain at sulphuric acid concentration of 3% （by mass）, SO2 concentration of 1.33% （by volume） and oxygen flow rate of 1.5 L.min^-1 from ozone generator.

Optimization of the Design and Drying Process Adapted to Pineapple Slices

The present work is a study on the influence of temperature and the velocity of air on the drying kinetics of pineapple slices. The main objective is to define from this drying kinetics rules to help a designer choose an adequate principle or drying configuration and optimize the design of dryers adapted to the use of it. The experiments were made in an electric dryer using a parallel flow system. The air was used at three different temperatures （40, 50 and 60 ~C） and at four different velocities （0.27, 0.5, 1 and 1.8 m/s） during the experiment. The results show that an increase of 10 ℃ of the drying temperature reduced the drying time by 45% and increased the drying velocity by 30%. On the set of air velocities tested, it was noticed that the influence of air velocity on drying was more striking at the beginning than at the end of the drying process （variation of less than 20%）. Whatever the variation of parameters during the drying process, the best performance was observed when the products water content during the drying process was between 50% and 80%.

Numerical Study of the Mixing of Density-Stratified Fluid with a Jet

Density stratification of LNG （liquefied natural gas） is produced in a storage tank when one LNG is loaded on top of another LNG in the same tank. Mixing LNG by a jet issued from a nozzle on the tank wall is considered to a promising technique to prevent and eliminate stratification in LNG storage tanks. This study is concerned with the numerical simulation of a jet flow issued into a two-layer density-stratified fluid in a tank and the resultant mixing phenomena. The jet behavior was investigated with the laboratory-based experiment of the authors＇ previous study. A numerical method proposed by the authors is employed for the simulation. The upper and lower fluids are water and a NaCl-water solution, respectively, and the lower fluid is issued vertically upward from a nozzle on the bottom of the tank. The Reynolds number （Re） defined by the jet velocity and the nozzle diameter ranges from 95 to 2,378, and the mass concentration of the NaCl-water solution Co is set at 0.02 and 0.04. The simulation highlights the jet-induced mixing between the upper and lower fluids. It also clarifies the effects of Re and C0 on the height and horizontal spread of the jet.

Determination of Trihalomethanes in Water Samples Using Headspace Solid-Phase Microextraction Gas Chromatography

The chlorination process is one of the water treatment method used for the disinfection of water. The disinfection by products are trihalomethanes such as chloroform, dichloromethane, dibromochloromethane and bromoform. A headspace solid-phase microextraction method has been developed for determination oftrihalomethanes in water samples. The experimental parameters such as the stirring rate, extraction time, extraction temperature and desorption time were investigated. The linearity, detection limits and percentage recovery were evaluated. The optimum conditions were stirring rate 800 rpm/min, extraction time 6 min, extraction temperature 20 ~C, desorption time 2.5 min and desorption temperature 220 ~C. The detection limits were 0.01 ~g/L and the recoveries were in the range of 86-110 %, The proposed method was successfully applied to determination of THM4 in tap water samples. The THM4 contents were varied depending on the sample sites and the season. The total THM4 contents in cool, summer and rainy season were in the range of 27.58-41.89, 32.06-60.73 and 46.26-69.87 p.g/L, respectively. Confirmation of the detected compounds in water samples were performed by gas chromatograph-mass spectrometer. The mass spectra of the target compounds in water samples is in good agreement with trihalomethanes standard spectra.