Study On Flow Properties Of Powders And Characterization Techniques

Traditional testing techniques and the methodologies provided by the FT4Powder Rheometer were used to measure the flow parameters of8typical powders. Correlation between characterization techniques and application range for powders were also determined. Effects of particle size, internal and external moisture content and the coal quality on the flow properties of several industrial pulverized coals were investigated. With the measurements of flowability parameters, such as the angle of repose, apparent density, HR index, Carr flow index FI and discharge rates, the flow properties as well as the particle interaction were further studied by related model calculation. Influence on the flow characteristics by the addition of the common addictive to industrial powders cement and starch was showed with the help of FT4powder rheometer.It was found angle of repose test is a simple method but is not accurate enough for high cohesive powder, while Hausner Ratio is a well established method that allows good differentiation over a wide range of powders but the test process is complicated. Carr flow index is a common parameter which can fully characterize the flowability of powders, while the discharge rate can characterize the discharge characteristics intuitively and quantitatively. Basic Flow Energy (BFE) and Flow Rate Index (FRI) can explain some behavior of powders, but it is complex to interpret them. For the effect of particle size, it was pointed out that the particle size boundries between the strong adhesiveness, general adhesiveness and easy flow are80μm and150μm respectively. Exponential equation of AOR, HR and FI as a function of particle sizes were also achieved. The internal moisture content will almost not while the external moisture content will significantly affect the flowability of pulverized coals. Greater degree of coalification makes better flow while ash content had marginal or even no effect on the flowability of pulverized coals.Coke has the worse flowability than coal powders, and linear or nonlinear relationship of flow parameters between the calculation value and experimental value for the mixture were obtained, and explanation was carried out through the packing state. From the influence of additives on the flow behavior of starch and cement, it can be found the acting mechanisms between them were different or opposite. Additives increased the spacing between starch particle centers, thus improving flowability, while influence on the flowability of cement was fluctuating.