Dense-phase pneumatic conveying of solids offers many advantages over dilute-phase conveying. The lower air velocities, and, consequently, lower particle velocities, result in lower pipe wear and lower particle attrition. This paper describes an experimental program that has been undertaken to study the flow pattern of cohesionless solids in vertical transport and to measure the parameters influencing the pressure drop required to move a single plug of solids. Highspeed photographic techniques have been used to observe the flow pattern of polyethylene particles (diameter 5 3 mm) in the vertical riser section of a circulating unit constructed from pipes with an internal diameter of 50.8 mm. The flow pattern resembles that of square-nosed slugging in a fluidized bed. The solids move up as "plugs" of bulk solids that occupy the entire cross-section of the pipe. Particles are seen to "rain" down from the back of one plug and then to be collected by the front of the next plug. Collecting these particles causes a stress on the plug front which is transmitted by powder mechanics forces axially through the plug and radially to the wall. The pressure drop required to move a single plug of cohesionless solids through the transport pipeline was measured as a function of the plug length, particle properties, pipe diameter, and the frontal stress. The results of these experiments are compared with a theoretical model.Le transport pneumatique en phase dense de solides prksente de nombreux avantages pour le transport en phase diluke.Les vitesses d'air les plus basses et, en conskquence, les vitesses de particules les plus basses, entrainent une faible usure des conduites et une faible attrition des particules. Nous dtkrivons dans le prksent article un programme expinmental mis sur pied pour etudier le diagramme d'kcoulement de solides sans cohtsion dans le transport vertical et pour mesurer les paramktres qui influencent la perte de charge ntcessaire pour dkplacer un seul bouchon de solides. Nous avons fait appel B des techniques photographiques B haute vitesse pour observer le diagramme d'tcoulement de particules de polyethylkne (diamktre 3 mm) dans la section montante verticale d'un systkme de circulation compost de conduites de 50,8 mm de diamttre intkrieur. Le diagramme d'tcoulement resemble au bouillonnage a profil c a d dans un lit fluidist. Les solides se deplacent vers le haut comme des bouchons solides en occupant toute la section transversale de la conduite. I1 semble que les particules tombent en "pluie" de I'arritre d'un bouchon et qu'elles sont collectkes a I'avant du bouchon suivant. La collecte de ces particules cause une tension B I'avant du bouchon qui se transmet par les forces de mkchanique des poudres dans le sens axial dans le bouchon et dans le sens radial vers le mur. La perte de charge nkcessaire pour dkplacer un simple bouchon de solides sans cohtsion dans une conduite de transport a ktt mesurCe en fonction de la lonueur de conduit, des proprittes des particules, du diamktre du conduit et de la contrain...
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