MOBILIZATION OF SLUDGE IN HORIZONTAL CYLINDRICAL TANKS WITH SUBMERGED NOZZLES

Over 378,000 m³ (100 million gal) of radioactive waste is being stored in hundreds of tanks at several U.S. Department of Energy (DOE) sites. The environment within the tanks is highly radioactive and chemically harsh. The waste typically consists of a heterogeneous sludge layer covered by a layer of supernatant. A few of the tanks have leaked to the environment, while others are corroding. Removing the waste from the tanks and processing it to a stable final form are desired to prevent any additional contamination of the environment. The tanks vary in size and geometric shape and do not have systems for removing the sludge waste.

Mobilization and mixing studies were conducted with a surrogate sludge (e.g., kaolin clay) using submerged jets in two sizes of horizontal tanks with nominal capacities of 0.87 m³ (230 gal) and 95 m³ (25,000 gal). Mobilization efficiencies and mixing times were determined for single and bidirectional jets in both tanks with the discharge nozzles positioned at various locations in the tanks. Approximately 80% of the surrogate sludge was mobilized in the 95-m³ tank using a fixed bidirectional jet (inside diameter = 0.035 m) and a jet velocity of 6.4m/s (21 ft/s). The effective cleaning length, which is defined as the distance between the jet and the edge of the remaining sludge bank, was approximately 3.2 m (10 ft) on each side of the bidirectional jet.     

2000m3低温丙烯球罐球壳板型式和材料的选择

大型球罐球壳板型式和材料的选择是设计的首要环节,从这两方面论述了设计时选择的过程。     

Characterisation of the adsorption sites of hydrogen on Pt/C fuel cell catalysts

A key component of a hydrogen fuel cell is a catalyst to dissociate dihydrogen to hydrogen atoms. In the present study, the adsorption of hydrogen on Pt/C fuel cell catalysts has been investigated by inelastic neutron scattering spectroscopy.

Monitoring a clean Pt(50%)/C catalyst with low energy neutron spectroscopy, after exposure to dihydrogen at 20 K, as it was heated to room temperature, showed three distinct temperature regimes: (i) a decrease in intensity from 10 to 60 K, (ii) a rise to a maximum between 60 and 120 K and then (iii) a slow fall-off towards room temperature. We assign the three regions as: (i) desorption of physisorbed dihydrogen, (ii) dissociation of dihydrogen to give an adsorbed layer and (iii) damping of the response by an increasing Debye–Waller factor.

The vibrational INS spectra of a series of Pt/C catalysts prepared under varying conditions were similar indicating that the same types of site are common to all the catalysts, although the relative proportions of each site are sample dependent. Features at 520, 950 and part of the intensity at 1300 cm⁻¹ are assigned to hydrogen on (1 1 1) faces, in good agreement with single crystal data. The mode at 640 cm⁻¹ is assigned as the doubly degenerate asymmetric stretch of Pt(1 0 0) faces with the symmetric stretch near 550 cm⁻¹.

We assign the bending mode of the on-top site to the feature at 470 cm⁻¹. The Pt–H stretch mode was observed at 2079 cm⁻¹. This is a significant result: this is the first time that hydrogen on the on-top sites has been observed on nanosized platinum particles supported on high surface area carbon black. The width of the INS peak is surprisingly large and may give additional information on the type and relative proportions of the crystallographic faces present on the catalyst particles.     

基于FLUENT振荡浮子式波浪能转换装置浮子的数值仿真

基于VOF模型,运用三种不同的造波方法建立了二维数值波浪水槽,并对其进行了比较,选取了在特定波况下较为合适的数值水槽。基于该数值波浪水槽,考察了波浪作用下的运动状态以及受力状态,为波能转换器的设计提供指导。     

坦克装甲车辆用橡胶履带板的研究开发

探讨了坦克装甲车辆用橡胶履带板（ＴＴＲＰ）的损坏摸式及其机理，从胶料配合，性能测试等方面评 ＴＴＲＰ的研究开发进展，并对我国ＴＴＲＰ的研究提出了建议。     

Modeling of solid—liquid adsorption: Effects of adsorbent loads on model parameters

The adsorption of cobalt phthalocyanine dye onto activated carbon in a continuous stirred tank adsorber was studied. The variables investigated were: adsorbent mass, adsorbent particle size and fluid flowrate. Several models based on film, pore and surface diffusion were constructed and fitted to the experimental data. Experimental results showed: (i) the increasing importance of the film mass transfer resistance for increasing adsorbent loads; (ii) the increasing importance of the surface diffusion mechanism for increasing adsorbent loads; and (iii) the better discrimination among different models for higher adsorbent loads and lower flowrate.     

3-D hydrodynamics generated in a stirred vessel by a multiple-propeller system

The aim of this study is to optimize the position and the number of propellers in a non-standard tall vessel. Laser sheet flow visualization experiments were carried out for selected geometrical arrangements which produced stable flow patterns and good transport between the propellers. Four double-propeller arrangements corresponding to frequent industrial cases and a three-propeller system have been chosen. Comparison of LDA measurements in the r-z plane, dimensionless global parameters N_Qp, Nt_m, N_p, E_p and spatial distribution of local energy dissipation rate ? shows that a three-propeller system is the most efficient.     

Conceptual design of a novel hybrid fuel cell/desalination system

A novel concept for integrating fuel cells with desalination systems is proposed and investigated in this work. Two unique case studies are discussed — the first involving a hybrid system with a reverse osmosis (RO) unit and the second — integrating with a thermal desalination process such as multi-stage flash (MSF). The underlying motivation for this system integration is that the exhaust gas from a hybrid power plant (fuel cell/turbine system) contains considerable amount of thermal energy, which may be utilized for desalination units. This exhaust heat can be suitably used for preheating the feed in desalination processes such as reverse osmosis which not only increases the potable water production, but also decreases the relative energy consumption by approximately 8% when there is an increase of just 8°C rise in temperature. Additionally, an attractive hybrid system application which combines power generation at 70%+ system efficiency with efficient waste heat utilization is thermal desalination. In this work, it is shown that the system efficiency can be raised appreciably when a high-temperature fuel cell co-generates DC power in-situ with waste heat suitable for MSF. Results indicate that such hybrid system could show a 5.6% increase in global efficiency. Such combined hybrid systems have overall system efficiencies (second-law base) exceeding those of either fuel-cell power plants or traditional desalination plants.     

液氨贮存设计分析

氨是生产含氮肥料及尿素的基本原料，为确保原料供应，必须设置其贮存设施。介绍了常温中压、降温低压和低温常压三种不同的液氨贮存工艺及其特点，并以某大型氨站设计为例，分析了液氨贮存工艺流程、主要设备、材料的选型和工艺参数的确定。     

中压汽包法兰断裂失效原因分析及改进措施

本文针对中压汽包法兰断裂失效原因进行分析，指出汽包上两个法兰同时断裂的原因在于安全阀排汽管路设计上的失误，并提出对安全阀排汽系统的改进措施。