气—固反应法酯化改性纤维素

通过气—固反应,利用顺丁烯二酸酐(MA)对纤维素进行了酯化改性。元素分析和红外光谱分析(FTIR)表明MA与纤维素发生了酯化反应。依据质量增加百分率(Wpg)和取代度(Ds)的测定结果确定了酯化反应条件:m(MA)∶m(纤维素)=1.2∶1.0,反应温度150℃,反应时间2.5h,催化剂用量10%,在此条件下酯化纤维素相对纤维素质量增加45%,Ds为0.8。热重分析(TGA)表明,酯化纤维素的热稳定性相对纤维素有所降低,但残留量明显提高,在高温条件下更为稳定。X射线衍射(XRD)表明,酯化反应使得纤维素的结晶度下降,但没有改变纤维素的构型。

气氛条件对铁碳合金薄带气—固反应脱碳的影响

试验以初始碳含量为4.25%,厚度为1 mm铁碳合金薄带为研究对象,利用Ar-H2O-H2弱氧化性气氛在高温条件下,开展气—固反应脱碳研究。通过正交试验和单因素方法研究了水浴温度、初始H2含量、气体流量对1mm铁碳合金薄带脱碳的影响。试验结果表明:在脱碳温度一定的条件下,气氛条件相关的气体流量、初始H2含量、水浴温度对脱碳效果影响的显著性递减。本试验条件下,在200500 mL·min-1范围内增大气体流量,能显著改善脱碳效果;当水浴温度超过333 K时,铁碳合金薄带表面铁元素开始发生氧化,表面形成致密的铁氧化层导致脱碳速率显著下降。在1 413 K脱碳温度下,固态脱碳适宜的气氛条件为:气体流量500 mL·min-1,初始H2含量为15%,水浴温度333 K。

Fluidized-bed chlorination thermodynamics and kinetics of Kenya natural rutile ore

Natural rutile and gaseous chlorine with carbon as reductant were used to prepare titanium tetrachloride. Thermodynamics and kinetics of chlorination of Kenya natural rutile particles in a batch-type fluidized bed were studied at 1173-1273 K. Thermodynamic analysis of this system revealed that the equation of producing CO was dominant at high temperatures. Based on the gas-solid multi-phase reaction theory and a two-phase model for the fluidized bed, the mathematical description for the chlorination reaction of rutile was proposed. The reaction parameters and the average concentration of gaseous chlorine in the emulsion phase were estimated. The average concentration of emulsion phase in the range of fluidized bed was calculated as 0.3 mol/m^3. The results showed that the chlorination of natural rutile proceeded principally in the emulsion phase, and the reaction rate was mainly controlled by the surface reaction.

Gas-solid catalytic reactions over ruthenium-based catalysts

Ruthenium （Ru）‐based catalysts are widely employed in several types of gas‐solid reactions because of their high catalytic activities. This review provides theoretical research on Ru‐based catalysts and an analysis of their basic properties and oxidation behavior. There is particular emphasis on Ru‐catalyzed gas‐solid catalytic reactions, including the catalytic oxidation of VOCs, preferential oxidation of CO, synthesis of ammonia, oxidation of HCl and partial oxidation of CH4. Recent litera‐ture on catalysis is summarized and compared. Finally, we describe current challenges in the field and propose approaches for future development of Ru‐based catalysts.

Preparation and characteristic research of anhydrous magnesium chloride with dehydrated ammonium carnallite

Taking the saline lake bischofite and NH4Cl that was removed with the ammonia method and continuously followed by filtration as raw materials with a molar ratio of 1∶1 of MgCl2 to NH4Cl, ammonium carnallite was synthesized. And then the ammonium carnallite was dehydrated to some extent at 160℃ for 4 h. Ammonium carnallite reacted with ammonia at 240℃ for 150 min and the ammonation ammonium carnallite was produced. Finally, the ammonation ammonium carnallite was calcined at 750℃ into anhydrous magnesium chloride containing only 0.1%（mass fraction） of MgO. On the other hand, dehydrated ammonium carnallite was mixed with the solid ammonium chloride at mass ratio 1∶4 at high temperature and with the differential pressure of NH3 above 30.5kPa. The dehydrated ammonium carnallite of mixture was dehydrated at 410℃, and then calcined at 700℃ into anhydrous magnesium chloride with only 0.087%（mass fraction） of MgO. X-ray diffraction and electron microscopy analysis results prove that anhydrous magnesium chloride obtained by both methods hasn’t mixed phases, the particle is large and even has good dispersion, which is suitable for preparation of metal magnesium in the electrolysis.

Investigation of the Acceleration Region in a Gas-Solid Co-current Down-flow Circulating Fluidized Bed

In this work, a mathematical model is established to describe the axial variation of the characteristic flow parameters (particle velocity, solid holdup and pressure gradient) in a downer. An empirical correlation is developed to estimate the particle velocity at the constant velocity section. Experimental investigations are made to validate the downer model. The model simulations have a good agreement with experimental data. Moreover, a formula is derived to predict the first acceleration section length and the whole acceleration section length.

SO_2/Hg removal from flue gas by dry FGD

To study the mechanism of SO2 and Hg removal from flue gas, an experimental packed bed reactor was designed to simulate the dry FGD, where a mixture of lime and fly ash in ratio 1：3 w/w was used as the S02 and Hg sorbent, and steam at temperature of 100 ℃ was applied for activation of the sorbent, while the activation time set to 20 rain. The experimental factors including the SO2/Hg sorbent characteristics, 50% breakthrough time for SO2/Hg removal, sorbent packed bed depth and reaction temperature were investigated. The experimental results show that after steam activation, the BET specific surface area and specific pore volume increased from 37.8 to 45.5 m^2/g and from 0.42 to 0.51 cm^3/g, respectively. With activation of the sorbent by steam, the 50% breakthrough times of SO2 and Hg removal increased from 34 to 42 rain and from 23 to 45 rain, respectively. When the packed bed depth was increased from 5 to 25 ram. the 50% breakthrough times for Hg and S02 removal increased from 12 to 52 rain and from 6 to 47 rain, respectively. With the increase of the reaction temperature, the 50% breakthrough of SO2/Hg removal decreased accordingly. Steam activation can efficiently improve SO2/Hg removal simultaneously.

Cobalt-free gadolinium-doped perovskite Gd_xBa_(1-x)FeO_(3-δ) as high-performance materials for oxygen separation

Cobalt-free oxides GdxBal-xFeO3-σas（0.01 _〈 x _〈 0.1 ） were achieved by a solid state reaction method. It is found that GdxBal-xFeO3-σas（0.025 _〈 x _〈 0.1） exhibits the cubic perovskite structure. Among GdxBal-xFeO3-σas （0.025 -〈 x -〈 0.1 ）, the GdxBal-xFeO3-σas （GBF2.5） membrane shows the outstanding phase structure stability and the highest oxygen permeation, which can reach 1.44 ml. cm- 2. rain- 1 at 950 ℃ under air/He oxygen partial pressure gradient. The GBF2.5 membrane was successfully operated for more than 100 h at 800 ℃ and the oxygen permeation flux through the membrane is 0.62 ml. cm- 2. rain- 1. After 100 h oxygen permeation experiment at 800℃, X-ray diffraction （XRD） and energy dispersive X-ray spectrometer （EDXS） demonstrate that the GBF2.5 exhibits phase structure stability even at intermediate temoerature.

Local Gas Phase Flow Characteristics of a Gas-Liquid-Solid Three-Phase Reversed Flow Jet Loop Reactor

The local gas-phase flow characteristics such as local gas holdup(εg), local bubble velocity (V_b) and local bubble mean diameter(d_b) at a specified point in a gas-liquid-solid three-phase reversedflow jet loop reactor was experimentally investigated by a five-pointconductivity probe. The effects of gas jet flow rate, liquid jet flowrate, solid loading, nozzle diameter and axial position on the localεg, V_b and d_b profiles were discussed. The presence of solids atlow solid concentrations not only increased the local εg and V_b,but also decreased the local d_b. The optimum solid loading for themaximum local εg and V_b together with the minimum local d_b was0.16×10^-3 m^3, corresponding to a solid volume fraction ε_S＝2.5/100.

Gas–Liquid Mass Transfer Characteristics in a Gas–Liquid–Solid Bubble Column under Elevated Pressure and Temperature

abstract The volumetric mass transfer coefficient kLa of gases （H2, CO, CO2） and mass transfer coefficient kL on liquid par-affin side were studied using the dynamic absorption method in slurry bubble column reactors under elevated temperature and elevated pressure. Meanwhile, gas-holdup and gas-liquid interfacial area a were obtained. The effects of temperature, pressure, superficial gas velocity and solid concentration on the mass transfer coeffi-cient were discussed. Experimental results show that the gas-liquid volumetric mass transfer coefficient kLa and interfacial area a increased with the increase of pressure, temperature, and superficial gas velocity, and decreased with the slurry concentration. The mass transfer coefficient kL increased with increasing superficial gas velocity and temperature and decreased with higher slurry concentration, while it changed slightly with pressure. Ac-cording to analysis of experimental data, an empirical correlation is obtained to calculate the values of kLa for H2 （CO, CO2） in the gas-paraffin-quartz system in a bubble column under elevated temperature and elevated pressure.

Syngas Production from Crude Glycerol Using Pyrolysis

Glycerol pyrolysis is carried out in a fixed bed reactor filled with alumina oxide. The packing material diameter was examined according to each one, but in general it was varied between 0.1-5.0 mm. The reaction temperature was varied in the range of 700-900 ℃, the reaction time from 10 to 50 min and flow rate of carrier gas from 0 to 60 mL/min. The process parameters listed above （factors） were used to evaluate the syngas production yield （response）. Also, syngas properties such as composition and heat value were evaluated. The experiments were carried out according to a 23 factorial design plus three central points. At last, a technical-economical analysis is carried out to examine the feasibility of syngas production from glycerol pyrolysis considering not only feedstock, catalyst and energy required costs but also conventional procedures used nowadays to produce syngas such as water electrolysis and natural gas catalytic reform.

LOCAL LIQUID-PHASE OHARAOTERISTIOS OF THE SELF-ASPIRATED REVERSED FLOW JET LOOP REAOTOR

The local liquid--phase characteristics of the gas--liquid two-phase and gas--liquid--solid threephase self-aspirated reversed flow jet loop reactor with a concentric gas--liquid injection nozzle were studied experimentally. They facilitate the evaluation of local phenomena. The local instantaneous liquid velocities at different axial positions of the reactor were measured by using the modified pilot tube.The local liquid-phase turbulent structural parameters such as time-averaged velocity. turbulent nuctuating velocity and turbulent micro scale were calculated with the aid of the statistical theory of turbulence. In particular, effects of liquid jet flowrates and solid loadings on the profiles of the liquid--phase turbulent structural parameter both in the jet effective region and in the tubular region inside the draft tube were discussed.

Conversion and reaction kinetics of coke oven gas over a commercial Fe-Mo/Al_2O_3 catalyst

Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst(T-202) were studied in a continuous flow fixed bed reactor under pressures of 1.6-2.8 MPa, space time of 1.32-3.55 s and temperatures of 240-360 °C. Though the COG contains about 0.6 mol/mol H2, hydrogenation of CO and CO2 is not significant on this catalyst. The conversions of unsaturated hydrocarbons depend on their molecular structures. Diolefins and alkynes can be completely hydrogenated even at relatively low temperature and pressure. Olefins, in contrast, can only be progressively hydrogenated with increasing temperature and pressure. The hydrodesulfurization(HDS) of CS2 on this catalyst is easy. Complete conversion of CS2 was observed in the whole range of the conditions used in this work. The original COS in the COG can also be easily converted to a low level. However, its complete HDS is difficult due to the relatively high concentration of CO in the COG and due to the limitation of thermodynamics. H2 S can react with unsaturated hydrocarbons to form ethyl mercaptan and thiophene, which are then progressively hydrodesulfurized with increasing temperature and pressure. Based on the experimental observations, reaction kinetic models for the conversion of ethylene and sulfur-containing compounds were proposed; the values of the parameters in the models were obtained by regression of the experimental data.

Developments in the understanding of gas–solid contact efficiency in the circulating fluidized bed riser reactor:A review

In the last several decades, circulating fluidized bed reactors have been studied in many aspects including hydrodynamics, heat and mass transfer and gas–solid two phase contacting. However, despite the abundance of review papers on hydrodynamics, there is no summary paper on gas–solid contact efficiency to date, especially on high density circulating fluidized beds(CFBs). This paper gives an introduction to, and a review of the measurement of contact efficiency in circulating fluidized bed riser. Firstly, the popular testing method of contact efficiency including the method of heating transfer experiment and hot model reaction are discussed, then previous published papers are reviewed based on the discussed methods. Some key results of the experimental work are described and discussed. Gas–solid contact efficiency is affected by the operating conditions as well as the particle size distribution. The result of the contact efficiency shows that the CFB riser is far away from an ideal plug flow reactor due to the characteristics of hydrodynamics in the riser. Lacunae in the available literature have been delineated and recommendations have been made for further work.

Oxygen Gasification of Municipal Solid Waste in a Fixed-bed Gasifier

Four waste materials, paper, wood, textile and kitchen garbage, in municipal solid waste were gasified separately with oxygen in a fixed bed reactor. The yields of products char. tar and gas, the composition of gas components H2, CO, CO2 and CH4, and the lower heating value （LHV） were examined at temperatures between 700 and 900 ℃ and equivalence ratio （ER） between 0.14 and 0.32. Characteristics of gas evolution during gasification were inves- tigated. Results show that a higher temperature improves the formation of H2 and CO while lowers the yield of CO2 and CH4. The LHV of syngas increases with temperature and varies in the range of 6-10 MJ. m-3 reaching the maximum at 800 ℃ or above. As ER increases, both combustible gas component and LHV of syngas decrease while the yield of CO2 rises linearly. The appropriate ER for obtaining high quality gas is in the range of 0.18-0.23. Temperature and ER have significant effects on the product distribution. Higher temperature and ER are favorable for higher gas yield and lower yield of char and tar in the gasification of textile and kitchen garbage. At 800 ℃, the gas evolution may be divided into two regions. In the first region, the flow rate of gas increases and then de- creases ranidlv, while in the second reuion the flow rate decreases monotonically to lower level.

H2 Generation from Thermochemical Water-Splitting Using Sol-Gel Derived Ni-Ferrite

H2 generation from a thermochemical water-splitting reaction was performed using a sol-gel derived Ni-ferrite. The sol-gel synthesis involved addition of nickel chloride hexahydrate （NiCl2@6H2O） and ferrous chloride tetrahydrate （FeCl2·4H2O） in ethanol followed by gelation using propylene oxide. The gels were aged, dried and calcined at 900 ℃in air or N2 environment. The powders thus obtained were characterized using X-ray diffraction （XRD）. This analysis revealed a nominally phase pure Ni-ferrite （NiFe204） composition for the gels calcined in air, whereas those calcined in N2 environment exhibited primarily Ni04Fe2.604 composition mixed with metallic Ni. Particle size and specific surface area （SSA） of the ferrite powders were analyzed using scanning electron microscopy （SEM） and Brauner-Emmett-Teller （BET） surface area analyzer, respectively. The ferrites were placed in a packed bed reactor and water-splitting reaction was carried out at 700 ℃, 800 ℃, and 900 ℃. After water-splitting reaction, oxidized ferrites were regenerated at 900 ℃ for 2 h in N2 environment. Together water-splitting and regeneration steps designated as one thermochemical cycle. In four consecutive thermochemical cycles performed using NiFe204, an average of 40 mL of H2/g per cycle was generated at water-splitting temperature of 900 ℃, which was about five times higher than the average H2 produced at 700 ℃.

System Validation Tests for an SOFC Power System at INER

This research presents the results of system validation tests for an SOFC power system. In the study, the system was heated up without electric device, i.e., the fuel providing the required thermal energy through an integrated BOP （balance of plant）. The ex-situ experiments, without an SOFC stack installed in the system, were fast conducted to investigate the operability of a BOP apparatus. It was found that the BOP possessed high conversion rates for both steam reforming and water gas shift reactions. The total fuel concentration of hydrogen and carbon monoxide from the reformer was around 91.2%. The system validation tests showed that, with the natural gas as fuel, the output power from the stack reached to 1,060 W, while the fuel utilization efficiency and electrical efficiency were 67.16% and 45.0%, respectively. A steady 600-hour system operation test was carried out at an average system temperature of 694℃. Of which, a 36-cell stack was employed for the test. Meanwhile, the current, voltage and output power were 26 A, 32.3 V and 840 W, respectively, and its electrical efficiency was around 33.4%.