Numerical study of rope formation and dispersion of non-spherical particles during pneumatic conveying in a pipe bend

For AM processes—specifically Laser Powder Bed Fusion (L-PBF) processes—powder flowability is essential for the product quality, as these processes are based on a thin layer spreading mechanism. However, the available techniques to measure this flowability do not accurately represent the spreading mechanism. Hence, this paper presents two novel applicator tools specifically designed to test the spreadability of l -PBF powders in thin layer application. The results were checked by running standard tests to analyze the powder morphology, moisture content, chemical composition and flowability using the Hall-flowmeter. For this study, four common l -PBF metal powders were selected: Inconel 718, Ti6Al4V, AlSi10Mg and Scalmalloy. From the as-received state, drying (vacuum and air) and moisturizing treatments were applied to compare four humidity states and investigate the feasibility of pre-treating the powders to remove moisture, which is known to cause problems with flowability, porosity formation and enhanced oxidation. The tests reveal that AlSi10Mg is the most susceptible alloy to moisture and oxygen pick-up, considerably decreasing the spreadability and relative density on the build platform. However, the results also reveal how challenging the direct measurement of moisture levels in metal powders is.

Measuring the spreadability of pre-treated and moisturized powders for laser powder bed fusion

Theoretical and experimental investigation on angle of repose of biomass–coal blends

The utilization of biomass has been increasing in recent years, how to achieve successful feeding of biomass into the different utilization systems is a common problem. Reliable information on flow properties are required for the design of storage, processing and handling equipment. In this paper, the flow properties of four representative agricultural biomass powders (soybean straw, corn straw, rice straw and rice husk) and their torrefied powders were investigated experimentally by two different testing methods (angle of repose test and packing properties test) with a powder synthetic characteristic tester. The effects of mean particle size, particle shape, biomass species and their interaction on different characterization parameters (angle of repose, bulk density, tapped density, Hausner ratio and compressibility index) were investigated. The results of the two different testing methods were compared, and it was found that Hausner ratio and compressibility index cannot always accurately characterize the flowability of biomass powders compared with angle of repose. Meanwhile, the effect of torrefaction pretreatment on the flowability of biomass powders was discussed. The results showed that torrefaction pretreatment can improve biomass powder flowability, however, it cannot change the relative relationship between the flowability of different biomass powders.

Experimental investigation on flow properties of different biomass and torrefied biomass powders

Correlation of powder flow properties to interparticle interactions at ambient and high temperatures

Investigation on characterization of powder flowability using different testing methods

This paper presents a review and analysis of the research that has been carried out on dynamic calibration for optical-fiber solids concentration probes. An introduction to the optical-fiber solids concentration probe was given. Different calibration methods of optical-fiber solids concentration probes reported in the literature were reviewed. In addition, a reflection-type optical-fiber solids concentration probe was uniquely calibrated at nearly full range of the solids concentration from 0 to packed bed concentration. The effects of particle properties (particle size, sphericity and color) on the calibration results were comprehensively investigated. The results show that the output voltage has a tendency to increase with the decreasing particle size, and the effect of particle color on calibration result is more predominant than that of sphericity.

https://www.mdpi.com/1424-8220/13/7/9201/pdf

Investigation on Dynamic Calibration for an Optical-Fiber Solids Concentration Probe in Gas-Solid Two-Phase Flows

Investigation of influence of coal properties on dense-phase pneumatic conveying at high pressure

https://www.tpbin.com/Uploads/Subjects/54725089-0452-4ab7-adca-8444e6fcc5f6.pdf

Effect of moisture content on conveying characteristics of pulverized coal for pressurized entrained flow gasification

Experiments of high-pressure dense-phase pneumatic conveying of pulverized coal with different mean particle sizes using nitrogen were carried out in an experimental test facility with a conveying pressure of up to 4 MPa. The effects of three representative operating parameters (solids-to-gas mass flow ratio, conveying pressure, mean particle size) on the total pressure drop were examined. The pressure drops across the horizontal and vertical bends were analyzed by experimental and analytical calculation. The results show that the pressure drop due to gas friction is of much less significance, while the pressure drop due to the solids friction component of the total pressure drop dominates. There exists a relationship between the pressure drop due to solids kinetic energy loss and mass flux of solids.

Pan Xu

Papers

Investigation on characterization of powder flowability using different testing methods

Investigation on Dynamic Calibration for an Optical-Fiber Solids Concentration Probe in Gas-Solid Two-Phase Flows

Investigation of influence of coal properties on dense-phase pneumatic conveying at high pressure

Effect of moisture content on conveying characteristics of pulverized coal for pressurized entrained flow gasification

Resistance Properties of a Bend in Dense-Phase Pneumatic Conveying of Pulverized Coal under High Pressure