Air and Power Requirements for the Pneumatic Transport of Crushed Coal in Horizontal Pipelines

Empirical equations were developed giving minimum air and power requirements for the vacuum and pressure transport of crushed coal through horizontal pipelines. The test system included 2-, 4-, 6-, and 8-in.-dia pipelines, each with a 200-ft straight section followed by three shorter runs connected by 90-deg bends of different radii. Air requirements were found to be a function of coal rate and specific gravity, pipe diameter and length, and the ratio of the cross-sectional area of the pickup section to that of the pipe. Although coal size was not a significant variable, the maximum size cannot exceed four-tenths the diameter of the pipe. The highest coal rate—55 tons per hr—was achieved in pressure operation with 1.35 specific, gravity coal transported through the 8-in.-dia pipeline. In this experiment with a pickup to pipe area ratio of 3 to 1, about 2200 actual cu ft per min of air at the pipeline entrance was required to keep the coal moving in full suspension with a 7.5-psi drop in pressure. The equations can be used to design horizontal pipeline systems operated under either vacuum or pressure with different types of pick-up devices and varying conditions of coal gravity and rate and pipe diameter and length. For example, assuming a pressure drop of 20 psi and a pickup to pipe area ratio of 3 to 1, 380 tons per hr of 5- by 0-in. coal (sp. gr. 1.40) could be transported through 1000 ft of straight 12-in.-dia pipe by 7300 actual cu ft per min (17,300 standard cu ft per min) at the pipeline entrance at the expense of 1080 theoretical horsepower.