The Ejffect of Vertical Internal Baffles on Fluidization Hydrodynamics and Grain Drying Characteristics

The effect of vertical internal baffles on the particle mixing and grain drying characteristics in a batch fluidized bed column is investigated. Experimental work was carried out in a 3m high rectangular fluidized bed dryer of cross sectional area of 0.15 m×0.61 m at different operating conditions using paddy, a group D particle, as the fluidizing material. The results of the study showed that the fluidized bed dryer system with vertical internal baffles gave better particle mixing effect in the bed of particles than that without vertical internal baffles. This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking up the large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bed of particles before finally erupting at the bed surface. This improves the contacting efficiency and enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate was obtained in the falling rate period because the higher con     

Advanced Ramming Mix Based on Fused Zirconia Stabilized by Com-bined Additives of CaO and MgO for Lining of Carbon Black Production Reactor

Fused materials from ZrO_2 stabilized by CaO or MgO,or the combined additive consisting of CaO and MgO are made. With using chemical,petrographic,Xray phase and electron microscopic researches the main characteristics of these materials are determined. It is shown that,the materials of all compositions have low water absorption; they are characterized by equal structure. The materials stabilized by the combined additive consisting of CaO and MgO are presented by generally the cubic phase and a small amount of tetragonal and monoclinic ZrO_2 phases. Depending on CaO∶ MgO ratio in the materials the tetragonal ZrO_2 phase settles down in a cubic matrix in the form of separate grains,and sites of net like structure in the form of a "woven"interlacing( 2. 9% of CaO and 2. 6% of MgO). An influence of the above mentioned fused stabilized ZrO_2 materials and quantity of monoclinic zirconia,on the forming of zirconia mix on a phosphate bond and properties of fired samples is studied. The samples from mix based on ZrO_2 stabilized by the combined additive consisting of 2. 9% CaO and 2. 6% MgO with 20% of monoclinic ZrO_2 are characterized by the highest properties: after firing at 1 580 ℃ open porosity of 14. 3%-14. 8%,apparent density of 4. 67-4. 69 g·cm~(-3),cold crushingstrength of 62-68 MPa, thermal shock resistance( 1300℃air) of 15 thermal cycles,linear growth of 0. 2%. The manufacturing technology of powders mixture for ramming mix based on the new fused material from ZrO_2 stabilized by the combined additive is developed and its production is mastered. From this mixture the large-size,shaped products on the phosphate bond are made at one carbon black production plant,which are installed in the combustion chamber of the carbon black production reactor.     

用高露点空气干燥小木块时挥发性有机物的释放

Emission of volatile organic compounds (VOCs) during drying of wood particles for particleboard manufacture, or for production of refined biofuels, is a potential environmental problem. The aim of this work is to study the emissions of VOCs during drying, and the influence on the emissions by different drying parameters. The experiments have mainly been done in a batch fluidized bed dryer, but measurements have also been done in a, pilot scale, continuous fluidized bed dryer. The parameters studied are air flow rate through the bed, air temperature, air dewpoint, and bed height. Since the present trend in biofuels and particle drying is towards very high dewpoints during drying, some measurements have been made at dewpoints up to 95℃, corresponding to a water content of 3.2 kg water per kilogram dry air. The emissions have been measured in two different ways, online during drying with a flame ionization detector and through wood analyses of the terpene content in the wood particles before and after dryi     

垂直内挡板对流态化流体动力学及谷物干燥特性之影响

The effect of vertical internal baffles on the particle mixing and grain drying characteristics in a batch fluidized bed column is investigated. Experimental work was carried out in a 3 m high rectangular fluidized bed dryer of cross sectional area of 0.15 mx0.61 m at different operating conditions using paddy, a group D particle, as the fluidizing material. The results of the study showed that the fluidized bed dryer system with vertical internal baffles gave better particle mixing effect in the bed of particles than that without vertical internal baffles. This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking up the large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bed of particles before finally erupting at the bed surface. This improves the contacting efficiency and enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate was obtained in the falling rate period because the higher contactin efficiency increases the evaporation rate at the particle surface. However, the drying rate in the diffusion regiol shows little improvement because the moisture diffusivity does not depend on the contacting efficiency. The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapid drying stage in a two stage drying strategy for paddy. The insertion of vertical internal baffles into a fluidized bed system improves the processing of Group D particles in a fluidized bed system especially if the system is large in scale.     

基于魏格纳分布的鼓泡流化床中结焦早期诊断

An experimental verification is reported on the early predicting index of agglomeration in bubbling fluidized bed. Coarse quartz sand, which has the same density but larger diameter than the bed material, was used to simulate the initial agglomerated particle. Wigner distribution was used to analyze the pressure fuctuation of the tested bed, and the average amplitude of local domain frequency （LDF） and local peak weighted average frequency （LPWA） under different operating conditions were measured and compared. The results showed that the LDF is sensitive to the agglomeration phenomena and had quick response to the incipient agglomeration in fluidized beds. It can be concluded from the results that these two parameters could be taken as the characteristic indexes to the agglomeration in fuidized beds.     

Performance and Application of CaO—rich MgO—CaO Coating Material for Tundish

On the base of MgO-CaO coating material TD-CA12 for tundish ,a new TD-CA32 with high CaO content was developed,Its CaO content is 30%-36% and MgO content is 45%-55%,The application result in Baosteel shows that TD-CA32 not only has the same properties as TD-CA12 but alao has the improved properties of disintegration and steelpurifing.     

循环流化床的沸腾传热

A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. To verify the model, experiments are conducted in a stainless steel column with 39 mm ID and 2.0 m height, in which the heat transfer coefficient is measured for different superficial velocities, steam pressures, particle concentrations and materials of particle. As the steam pressure and particle concentrations increase, the heat transfer coefficient in the bed increases. The heat transfer coefficient increases with the liquid velocity but it exhibits a local minimum.The heat transfer coefficient is correlated with cluster renewed model and two-mechanism method. The prediction of the model is in good agreement with experimental data.     

THERMAL CONDUCTIVITY OF THF CLATHRATE HYDRATE FROM 243 K TO 263 K

Using transient plane source technique, we measured THF hydrate thermal conductivity from 243 K to 263 K. The sample THF solution is over saturated in order to avoid the effect of ice. And also to avoid the effect of crystal anisotropy, the THF hydrate was crushed to measure. In the test temperature range of the experiment, the THF hydrate has a thermal conductivity about 0.45W·m~(-1)·K~(-1), and the value increases with the temperature increasing.     

Hydrodynamics of three-phase fluidization of homogeneous ternary mixture in a conical conduit——Experimental and statistical analysis

Hydrodynamics of conical fluidized bed differ from that of columnar beds by the fact that a velocity gradient exists along the axial direction of the bed.The gas–liquid–solid fluidized bed has emerged in recent years as one of the most promising devices for three-phase operations.Such a device is of considerable industrial importance as evident from its wide applications in chemical,refining,petrochemical,biochemical processing,pharmaceutical and food industries.To explore this,a series of experiments have been carried out for homogeneous well-mixed ternary mixtures of dolomite of varying compositions in a three-phase conical fluidized bed.The hydrodynamic characteristics determined included the bed pressure drop,bed fluctuation and bed expansion ratios.The single and combined effects of operating parameters such as superficial gas velocity,superficial liquid velocity,initial static bed height,average particle size and cone angle on the responses have been analyzed using response surface methodology(RSM).A 25 full factorial central composite experimental design has been employed.Analysis of variance(ANOVA) showed a high coefficient of determination value and satisfactory prediction second-order regression models have been derived.Experimental values of bed pressure drop,bed fluctuation and bed expansion ratios have been found to agree well with the developed correlations.     

烧结复合式烧结金属丝网颗粒移动床过滤器研究

A new gas clean-up process called “integrated sintered metal screen moving granular bed“ (ISMSMGB) for the integrated gasification combined cycle (IGCC) and pressured fluidized bed combustion (PFBC) was developed on the basis of a sintered metal candle filter and a cross-flow moving granular bed filter. This is a combination of the surface and deep bed filtering processes. A set of facilities was established and a series of cold model tests were carried out. The dust removal efficiency and the pressure drop of the filter were measured and analyzed. The results show that this process features the advantages of the moving bed for high capacity as well as high inlet dust load and the surface filter for high efficiency. Meanwhile, the granules moving downward cleans the cake on the screen surface, so that the system is operated at steady state.     

Surface Properties of CaO (or BaO)–La2O3–MgO Catalysts and Their Performance in Oxidative Coupling of Methane

CaO–La₂O₃–MgO and BaO–La₂O₃–MgO catalysts with different compositions have been studied for their bulk and surface properties (viz. crystal phases, surface area, acidity/acid strength distribution, basicity/base strength distribution, etc.) and catalytic activity/selectivity in the oxidative coupling of methane (OCM) at different processing conditions (reaction temperature, 700–850°C; CH₄/O₂ ratio in feed, 3·0, 4·0 and 8·0 and GHSV, 102000 and 204000 cm³ g⁻¹ h⁻¹). The surface acidity and strong basicity of La₂O₃–MgO are found to be increased due to the addition of a third component (CaO or BaO), depending upon its concentration in the catalyst. The addition of CaO or BaO to La₂O₃–MgO OCM catalyst causes a significant improvement in its performance. Both the CaO- and BaO-containing catalysts show a high activity and selectivity at 800°C, whereas, the activity and selectivity of BaO-containing catalysts at 700°C is lower than that of CaO-containing catalysts. © 1997 SCI.     

Oxidative coupling of methane to C2-hydrocarbons over lithium–cerium-promoted MgO and MgO–CaO catalysts

The oxidative coupling of methane to ethylene and ethane was studied over lithium–cerium-promoted MgO and MgO–CaO catalysts in the presence of molecular oxygen at 730°C and at atmospheric pressure in a continuous flow, fixed bed quartz reactor. The catalysts were prepared by an impregnation method and finally calcined at 900°C. The surface area, pore size distribution and pore volume of the catalysts were determined. The feed consisted of only methane and oxygen in the molar ratio of 2:1. The results obtained over the catalyst systems, viz. (i) lithium–cerium-promoted MgO and (ii) lithium–cerium-promoted MgO–CaO, have been compared. A relatively high C₂-selectivity has been obtained with Li–Ce-promoted MgO–CaO catalysts. The optimum yield and selectivity for C₂-hydrocarbons were found to be 21·5% and 76·8% respectively at a methane conversion of 28% over Li (7 wt%)–Ce (2 wt%)-doped MgO–CaO (3:1 wt ratio) catalyst. The various factors governing the activity and the selectivity of the catalyst systems have been discussed.     

Research on the mechanism of bed agglomeration and superheater fouling in CFB boiler fired pure petroleum coke

Circulating fluidized bed combustion is an effective method for the clean and efficient utilization of high-sulphur petroleum coke. In the actual production and operation process, there are serious problems of bed agglomeration and superheater fouling. The chemical and mineral compositions of the deposition were analyzed by X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF), and the effects of CaO sulphation and V₂O₅ on bed agglomeration and superheater deposits were studied through targeted experiments. The research results show that the sulphation process of CaO is the cause of bed agglomeration, and the superheater fouling is the result of the combined action of K₂SO₄ condensation and CaO sulphation; V₂O₅ in petroleum coke ash catalyzes the oxidation reaction of SO₂ to accelerate the sulphation of CaO, thereby accelerating the development of bed agglomeration and superheater fouling.     

Catalytic Steam Reforming of Fast Pyrolysis Bio‐Oil in Fixed Bed and Fluidized Bed Reactors

Catalytic steam reforming of bio‐oil is an economically‐feasible route which produces renewable hydrogen. The Ni/MgO‐La₂O₃‐Al₂O₃ catalyst was prepared with Ni as active agent, Al₂O₃ as support, and MgO and La₂O₃ as promoters. The experiments were conducted in fixed bed and fluidized bed reactors, respectively. Temperature, steam‐to‐carbon mole ratio (S/C), and liquid hourly space velocity (LHSV) were investigated with hydrogen yield as index. For the fluidized bed reactor, maximum hydrogen yield was obtained under temperatures 700–800 °C, S/C 15–20, LHSV 0.5–1.0 h^–1, and the maximum H₂ yield was 75.88 %. The carbon deposition content obtained from the fluidized bed was lower than that from the fixed bed. The maximum H₂ yield obtained in the fluidized bed was 7 % higher than that of the fixed bed. The carbon deposition contents obtained from the fluidized bed was lower than that of the fixed bed at the same reaction temperature.     

Simultaneous oxidative conversion and CO2 or steam reforming of methane to syngas over CoO–NiO–MgO catalyst

CO₂ reforming, oxidative conversion and simultaneous oxidative conversion and CO₂ or steam reforming of methane to syngas (CO and H₂) over NiO–CoO–MgO (Co: Ni: Mg=0·5: 0·5:1·0) solid solution at 700–850°C and high space velocity (5·1×10⁵ cm³ g⁻¹ h⁻¹ for oxidative conversion and 4·5×10⁴ cm³ g⁻¹ h⁻¹ for oxy-steam or oxy-CO₂ reforming) for different CH₄/O₂ (1·8–8·0) and CH₄/CO₂ or H₂O (1·5–8·4) ratios have been thoroughly investigated. Because of the replacement of 50 mol% of the NiO by CoO in NiO–MgO (Ni/Mg=1·0), the performance of the catalyst in the methane to syngas conversion process is improved; the carbon formation on the catalyst is drastically reduced. The CoO–NiO–MgO catalyst shows high methane conversion activity (methane conversion >80%) and high selectivity for both CO and H₂ in the oxy-CO₂ reforming and oxy-steam reforming processes at ⩾800°C. The oxy-steam or CO₂ reforming process involves the coupling of the exothermic oxidative conversion and endothermic CO₂ or steam reforming reactions, making these processes highly energy efficient and also safe to operate. These processes can be made thermoneutral or mildly exothermic or mildly endothermic by manipulating the process conditions (viz. temperature and/or CH₄/O₂ ratio in the feed). © 1998 Society of Chemistry Industry     

Comparison of Alkali Metal Promoted MgO Catalysts for Their Surface Acidity/Basicity and Catalytic Activity/Selectivity in the Oxidative Coupling of Methane

Alkali metal (viz. Li, Na, K, Rb and Cs) promoted MgO catalysts (with an alkali metal/Mg ratio of 0·1) calcined at 750°C have been compared for their surface properties (viz. surface area, morphology, acidity and acid strength distribution, basicity and base strength distribution, etc.) and catalytic activity/selectivity in the oxidative coupling of methane (OCM) to C₂-hydrocarbons at different temperatures (700–750°C), CH₄/O₂ ratios (4·0 and 8·0) in feed, and space velocities (10320 cm³ g⁻¹ h⁻¹). The surface and catalytic properties of alkali metal promoted MgO catalysts are found to be strongly influenced by the alkali metal promoter and the calcination temperature of the catalysts. A close relationship between the surface density of strong basic sites and the rate of C₂-hydrocarbons formation per unit surface area of the catalysts has been observed. Among the catalysts calcined at 750°C, the best performance in the OCM is shown by Li–MgO (at 750°C). © 1997 SCI.     

Performance of Anaerobic Reactors during Pseudo-Steady-State Operation

Four anaerobic reactors were studied for the purposes of this work: two anaerobic fluidized bed reactors (AFBR) using diatomaceous earth and granular activated carbon as immobilization media (R1 and R2, respectively), a packed-bed reactor (R3), and a suspended growth reactor (R4). A nutrient-supplemented wastestream with glucose as the main carbon source was treated. Successful reactor start-up was achieved for all four anaerobic reactors. These reactors were able to handle organic loading rates of more than 12000, 7500, 6000 and 650 mg dm⁻³ day⁻¹ for R1–R4, respectively. Anaerobic fluidized bed reactors were less affected by interruptions and adverse operating conditions than were packed-bed and suspended growth reactors. Immobilized cell reactors and, specifically, AFBRs were clearly superior to conventional high-rate digesters. This enhanced performance is primarily due to the very high cell retention ability of such reactors. High total organic carbon (TOC) removal efficiencies were achievable under pseudo-steady state operation. Removal efficiencies above 98% were observed for all reactors. Specific biogas production rates of 1·5–1·7, 1·4–1·7, 1·1–1·5 and 0·9–1·3 dm³ of methane per gram of TOC removed for R1–R4, respectively, were attained. A consistent biogas methane content of 52·5–55·9% was observed. Biomass concentrations of 84, 91, 21 and 1·9 g VS dm⁻³ were measured for R1–R4, respectively. Extremely high biomass concentrations in AFBRs were possible due to the high available specific surface area. © 1997 SCI.     

Ring opening metathesis polymerization of dicyclopentadiene catalyzed by titanium tetrachloride adduct complexes with nitrogen‐containing ligands

Ring opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) catalyzed by titanium tetrachloride adduct complexes such as TiCl₄ · 2L [L = pyridine (1), 2‐methylpyridine (2), 2,4,6‐trimethylpyridine (3), 3‐aminopyridine (4), 2‐hyroxypyridine (5)] and CH₃Li as cocatalyst was reported. The polymer was characterized by IR and ¹H‐NMR methods. Five influencing factors were also discussed. The catalyst systems TiCl₄ · 2L/CH₃Li (L = 2‐methylpyridine, 2,4,6‐trimethylpyridine) appeared to be very active for the ROMP of DCPD. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3247–3251, 2000     

Effect of alkali concentrations and operating conditions on agglomeration/defluidization behavior during fluidized bed air gasification

Biomass gasification plays an important role in finding a solution to the energy crisis, and the fluidized bed (FB) is recognized as an important technique for using biomass. However, this process significantly tends toward bed material agglomeration. Accordingly, the aim of this study is to emphasize the effects of operating conditions and different Na concentrations on agglomeration behavior during FB air gasification. Defluidization time decreases as Na concentration increases from 0.8 to 3%. Defluidization time decreases as temperature and the amount of bed materials increase. In addition, no significant change in the trend for this process occurs as the equivalence ratio increases. Adding CaO and Al₂O₃ can significantly prolong this process, and the inhibition level follows the sequence: Al₂O₃ > CaO. The same observations are noted during both incineration and air gasification in the FB at various operating conditions.     

Biological Nutrient Removal Using a Novel Laboratory‐Scale Twin Fluidized‐Bed Bioreactor

The capability of biological nutrient removal from wastewater of a novel laboratory‐scale twin fluidized‐bed bioreactor (TFBBR) was studied. The work showed approximately 96 % organic matter, 84 % nitrogen, and 12 % phosphorus removal efficiencies in the first three phases of the study at influent synthetic municipal wastewater (SMW) flow rates of 150, 190, and 240 L/d, with corresponding organic loading rates of 1.3, 1.7, and 2.3 kg COD m^–3 d^–1 and nitrogen loading rates of 0.14, 0.18 and 0.25 kg N m^–3 d^–1. The TFBBR effluent was characterized by <1.0 mg NH₄‐N/L, <4.3 mg NO₃‐N/L, <6 mg TN/L, <6 mg SBOD/L, and 6–10 mg VSS/L. For the three phases, biomass yields of 0.06, 0.066, and 0.071 g VSS/g COD were observed, respectively, which was a significant further reduction in yield compared to the liquid‐solid circulating fluidized‐bed bioreactor technology developed and patented by this research group, of 0.12–0.16 g VSS/g COD. The very low yield was due to a longer solid retention time of 72–108 d.