Characteristics of Confined Dense Phase Flow of Granular Solids Driven by Compressed Air

摘要

The transport of sand was studied in 1, 2, 3, and 4-inch transparent plastic pipes of lengths ranging from 75 to 800 feet. Several distinctly different modes of sand transport were observed; they might be described as (1) shifting-dune; (2) a transition region of air velocity in which the dunes become more like plugs filling the whole pipe section, and (3) slug flow. There is a gain in lineal velocity of sand particles through the first half of the line length, after which velocity remains constant; this effect is thought to be due in part to the rapid expansion of the carrying air in the first half of the pipe. Flow up inclines and vertical flow were also studied. The effect of a wooden driving piston to assist in horizontal flow is reported. Considerable effort was devoted to the problem of deriving theoretical expressions which will describe solids flow and gas flow as a function of applied pressure, amount of sand in the conveyance pipe, cross-sectional areas of pipe and sand size. (Author)