This paper describes behaviour of solid plugs pneumatically conveyed in a horizontal and vertical pipe whose purpose is to establish a basis for design of shch a conveying system, in which it is required to estimate the minimum air velocity, the velocity of the solid plug and the pressure loss of air. On the assumption that ideal flow of alternate solid plugs and air takes place, the minimum air velocity is obtained from force balance on the solid plug, and the plug velocity is also obtained from comparison of energy of air with that of the solid plug. The Ergun equation is adopted to compute the pressure loss of air passing through the solid plug. Computed results are favourably compared with results obtained from plug phase conveying for some polyethylene pellets. The particle diameter and its density, the voidage of the solid plug, the angle of internal friction and the frictional angle between the particle and the pipe wall are important. In this conveying system, there is an optimum air velocity at which the maximum power coefficient is reached, and the horizontal conveying is superior in power consumption to the vertical one.

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The analyses of Janssen, Jenike, Walker and Walters for the wall pressure distribution in the bunker have been drawn attention of many investigators. However, only several experiments have been performed against these analyses, there have been few reported date measured with various experimental condition.
In this paper, the authors measured static and dynamic pressures of the bulk materials (powders of GB 733 and granular materials of GB 708) in the modle bunkers using three defferent hopper angles which retained from horizontal to 75°, 45° and 90°, and discussed.
As the results, the following conclusions are obtained:
(1) Dynamic pressures in the bunker are roughly dependent of the change of discharge velocity but slightly increase in the hopper part closed cylindrical part (within the limited about 300cm³/s).
(2) In mass flow conditions using hopper angle of 75°, dynamic pressures of the cylindrical part closed to the hopper part do not saturate a constant value for sufficient depth as the analysis of Walters, and become higher.
(3) In case of mass flow conditions with powders, dynamic pressures increase slightly than static pressures, but do not greatly increase as dynamic pressures of granular materials.
(4) In case of funnel flow, the peak of dynamic pressures occurs to two parts of the wall in the bunker, that is in the part changed from mass flow to funnel flow and in the part closed to the discharge opening.
(5) In case of set an obstruction on the wall in the bunker, the dynamic pressures become higher in the part closed to the obstruction, consequently it is found that the obstruction corresponds to the top of the dead space in funnel flow.
(6) Dynamic bottom pressures in a flat-bottom bunker become higher in the part closed to side of wall where correspond to the top of the dead space.

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