Particuology and climate change

The global concern over the greenhouse gas emissions and its effect on global warming and climate change has focused attention on the necessity of carbon dioxide capture and sequestration. There are many processes proposed to capture carbon either before or after combustion and these processes invariably involve investigation and application of traditional particuology. The solids employed are of different sizes, densities, morphologies, and strengths. Their handling, transportation, recirculation, and reactor applications are the essence of ＇particuology＇. Particuology can play an important and vital role in achieving cost-effective removal of carbon and minimize emissions of greenhouse gases. In this paper, the existing and developing carbon capture processes are briefly reviewed and the opportunities for application of particuology are identified. The review was not intended to be exhaustive. It is only in sufficient detail to make connection between particuology and climate change. For immediate and future challenges of reducing global warming and carbon capture and sequestration, innovative reactor design and application of parricuology is imperative. Expertise and innovation in particuology can greatly enhance the speed of development of those technologies and help to achieve cost-effective implementation. Particuology is indeed intimately related to the climate change and global warming.     

A novel application of fluidization – Integrating three processes in reclaiming foundry sand

Immersion of automotive parts in a fluidized bed of foundry sand is used to both strip the castings free from moulding sand and to heat-treat the castings at 500℃. The fluid bed is heated by hot gases from a burner directed first into a serpentine heat exchanger located near one side-wall of the rectangular tank, and then into a distributor consisting of horizontal sparger pipes having maintenance standpipes fixed into their upper surfaces.     

包层氚增殖球床不同装载方案的有效热导率研究

针对聚变堆固态包层的产氚载体中锂陶瓷颗粒组成的氚增殖球床,建立了基于离散元-计算流体力学(DEM-CFD)方法的球床传热分析模型,进行了离散元(DEM)几何模型有效性验证、网格敏感性分析和计算流体力学(CFD)传热模型有效性验证。用该模型模拟计算了粒径分布球床、不同粒径的一元球床、二元球床的有效热导率,研究了相同填充率下,粒径分布、不同粒径及粒径混合对球床有效热导率的影响。研究结果表明,对于填充率相近的钛酸锂球床,粒径分布球床与一元等效粒径球床的有效热导率结果相差不大;在辐射换热可以忽略的情况下,粒径尺寸对一元球床有效热导率的影响可以忽略不计;二元混合钛酸锂球床相较于一元钛酸锂球床有更高的球床填充率和有效热导率。     

Validation of a discrete element model using magnetic resonance measurements

The discrete element model(DEM)is a very promising modelling strategy for two-phase granular systems.However,owing to a lack of experimental measurements,validation of numerical simulations of two-phase granular systems is still an important issue.In this study,a small two-dimensional gas- fluidized bed was simulated using a discrete element model.The dimensions of the simulated bed were 44 mm×10 mm×120 mm and the fluidized particles had a diameter dp=1.2 mm and density p=1000 kg/m3.The comparison between D...     

医疗资源影响下具有潜伏期的一类传染病模型建立及性态分析

建立了医疗资源影响下的考虑疾病具有潜伏期的一类传染病模型,并分析了模型的动力学性态.发现疾病流行与否由基本再生数和医院病床数共同决定,并得到了病床数的阈值条件.当基本再生数R_0大于1时,系统只存在惟一正平衡点,且通过构造Dulac函数证明了正平衡点只要存在一定是全局渐近稳定的;当R_01,我们得到系统存在两个正平衡点及无正平衡点的条件,且只有当医院的病床数小于阈值时,系统会经历后向分支.因此,可根据实际情况使医院病床的投入量不低于阈值条件,不仅有利于疾病的控制而且不会出现医疗资源过剩的现象.     

Heat transfer and hydrodynamic studies on two- and three-phase fluidized beds of floating bubble breakers

Heat transfer characteristics in three-phase fluidized beds of floating bubble breakers have been studied in a 0.142 m I.D. x 2.0 m high Plexiglas column fitted with an axially mounted cylindrical heater.Effects of the liquid and gas velocities, the particle size, the volume ratio of floating bubble breaker to particles on phase holdup, the vertical bubble length, and the heat transfer coefficient have been determined.In the bubble-coalescing regime, the heat transfer coefficient in three-phase fluidized beds having the volume ratio V_f/V_s of 10–15% produced a maximum increase in heat transfer coefficient of about 20% in comparison to that in the bed without floating bubble breakers. Also, bubble length and gas-phase holdups exhibited their maximum and minimum values at a volume ratio of 10–15%. The heat transfer coefficient in three-phase fluidized beds of floating bubble breakers can be estimated from the surface renewal model with isotropic turbulence theory.Heat transfer coefficients expressed in terms of the Nusselt number have been correlated with the particle Reynolds number and the volume ratio of floating bubble breakers to particles.     

红层M形路堑边坡特征及病害的初步研究

在对红层地区渝綦、綦万高速公路路堑边坡调查的基础上,提出了M形路堑边坡的概念,并总结了其特点;简要分析了红层和坡残积层物质的岩土矿物成分和结构特征,探讨了红层M形路堑边坡病害发生的类型及形成原因,为边坡稳定性评价与采取合理的边坡加固措施提供了依据。     

污泥的热解提油-半焦燃烧工艺的实验研究

本文提出了双流化床中污泥的热解提油-半焦燃烧工艺,组织实验论证并进行了探索研究。结果表明,双流化床中可以实现污泥热解提油工艺和半焦燃烧工艺的耦合,即获得了污泥热解产生的油和气,又实现了污泥的焚烧无害化处理。污泥在双流化床中发生热解反应时,干燥无灰基污泥的油产率为24.1%,是煤的2.4倍,干燥无灰基污泥的轻油产率为8.44%,是煤的9倍。该工艺中,污泥中热量的43.1%转化为油,10.4%转化为热值10.54MJ/m~3的气体燃料,46.5%的热量残留在污泥半焦中,在燃烧炉内燃烧放热。     

MODELING NONLINEAR DYNAMICS OF CIRCULATING FLUIDIZED BEDS USING NEURAL NETWORKS

In the present work, artificial neural networks (ANNs) were proposed to model nonlinear dynamic behaviors of local voidage fluctuations induced by highly turbulent interactions between the gas and solid phases in circulating fluidized beds. The fluctuations of local voidage were measured by using an optical transmittance probe at various axial and radial positions in a circulating fluidized bed with a riser of 0.10 m in inner diameter and 10 m in height. The ANNs trained with experimental time series were applied to make short-term and long-term predictions of dynamic characteristics in the circulating fluidized bed. An early stop approach was adopted to enhance the long-term prediction capability of ANNs. The performance of the trained ANN was evaluated in terms of time-averaged characteristics, power spectra, cycle number and short-term predictability analysis of time series measured and predicted by the model.     

OVERLAPPING GRIDS FOR THE SIMULATION OF PARTICLE INTERACTION AT THE MICRO SCALE

This paper describes the use of overlapping grids for the calculation of flow around single and multipleparticle configurations at the micro scale. The basic equations for calculation are those for conservation of mass and momentum which are solved using a common Finite-Volume formulation. The hydrodynamic particle-particle and particle-wall interaction can be calculated by using an overlapping or Chimera grid scheme. With the grid structuring procedure it is possible to use simple and structured grids around the particles and the overall main grid geometry. The particle grids are lapped over the main grid such that they can move independently after each time step without remeshing the whole geometry. The paper gives results for the validation of the code developed for general test cases, for a rotating ellipsoid in simple shear flow, the flow around particles attached to a wall, the motion of a particle in the vicinity of a wall and some results for the flow through a packed bed configuration.