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While in scientific literature much focus is directed toward model validation, comparison, and even parametric investigations on individual model parameters, the possible effects of the used computational fluid dynamics (CFD) software on the results are largely neglected. In this article, CFD modeling of circulating fluidized beds (CFB) are performed with Ansys Fluent and OpenFOAM to investigate the effect of software implementation on the simulation results. Transient Eulerian–Eulerian simulations are performed of two different laboratory‐scale CFB cold models in turbulent and circulating fluidized bed conditions. The same mesh and as identical models and settings as possible are utilized on both software. The obtained time‐average profiles of pressure, velocity, and solids volume fraction are compared between the software and with available measurements. A difference in the granular energy equation was identified between the software, and a modification was made to achieve the same formulation. The effect of boundary conditions was also investigated. It was found that depending on the case, the software could have a notable effect on the results. These differences are found especially in particle distribution, visible in the vertical pressure and solids volume fraction profiles as well as in external circulation mass flow rates. [ABSTRACT FROM AUTHOR]

Currently waste incineration is a widely used method of waste management in China. Effective incineration requires understanding and tools to analyze the incineration process leading to good incinerator performance and efficiency as well as lower emissions. In this work, a Chinese circulating fluidized bed (CFB) incinerator firing municipal solid waste (MSW) and coal is modeled with a three-dimensional CFB furnace model to evaluate the incineration process. First, the modeling results are verified with measurement data from the incinerator. Then, the furnace model is applied in the simulation of a case with more dry MSW without coal. The objective of the research is to provide insight and increase understanding of the MSW incineration process. The simulation case of MSW with the lower moisture content highlights the possible reductions of fossil carbon emissions associated with the utilization of coal. To achieve this, a moderate reduction in the moisture content of MSW is required. A comparison between the MSW and coal versus only the MSW shows minor differences in the performance of the incinerator. Utilization of modeling in incinerator studies can aid in development of more efficient CFB incinerators, improving the waste management and reducing the utilization of fossil coal. [ABSTRACT FROM AUTHOR]

An experimental characterization of a stream of falling particles impacting a stationary sphere is conducted in which the diameter of the sphere is two orders of magnitude larger than the diameter of a single particle. A novel method is applied for measuring the instantaneous collisional force between the sphere and dilute particle stream using a strain gauge-based force sensor in combination with high-speed imaging. The objective of this work is to understand the effects of particle velocity, size, and density on the collisional force when there is a significant size difference between two interacting granular phases. Additionally, discrete element method (DEM) simulations are conducted. The DEM closely represents the experimental behavior in low particle velocities, whereas the discrepancies between the experimental and computational data increase with the stream velocity corresponding to the falling distance. The presented experimental methodology and data can be applied for the development and validation of numerical modeling of particle collisions. [Display omitted] • Novel experimental method is presented for measuring contact force with a strain gauge in dilute particle flows. • Collisional (drag) force of falling particles impacting a large sphere is measured and modeled. • The effects of particle velocity, size, and density are studied on collisional forces. • The characterization of falling particles is performed using high-speed video image analysis. [ABSTRACT FROM AUTHOR]

The discrete element method (DEM) is utilized to calculate the drag force on big spherical objects exerted by the cloud of small particles as they are subjected to an initial relative velocity. The drag force is calculated as the average over single collisions within a certain time interval. Then it is comparable to the calculated values obtained from Eulerian simulations, which are performed on the same particulate system by keeping the big spherical objects in discrete form and turning the cloud of small particles into a continuum phase. The DEM simulations indicate that the average drag force on a big particle in a cluster is lower than that on a single big particle. The decrease in drag force is even larger when the big particles in the cluster are arranged in an ordered configuration such as a simple cubic array. In Eulerian simulations, it is found that the model for kinetic viscosity plays an influential role in the calculated drag force. The two models known as Syamlal–O'Brian and Gidaspow models for kinetic viscosity are employed. Considering the DEM simulation results as the reference cases, it is shown that the Gidaspow model is suitable for the clusters of big particles, while the Syamlal–O'Brian model can reproduce the single big particle motion in a cloud precisely. It is discussed how the distribution of shear stress over the surface of particles in Eulerian simulations may explain the observed differences. [ABSTRACT FROM AUTHOR]