摘要:
Finely divided powdery materials such as, e.g., precipitated silica are granulated by means of two rolls, one of which has a filter surface and the other has a profiled covering, in which the shafts of these rolls are arranged vertically one above the other and the finely divided powdery material is introduced into the gap between the rolls by means of at least one feed screw.
摘要:
A finely divided silicic acid having a pH>6 is prepared by spray drying, in the presence of a base or basic-reacting substance, a highly concentrated silicic acid suspension having excess, unwanted acidity.
摘要:
A silicic acid filter cake and suspension agent are fed to a container equipped with a stirrer having a peripheral speed of about 20-30 m/sec. The ratio of container diameter to stirrer diameter is about 3:1. The ratio of container diameter to level of filling is a maximum of about 1:2. The container contains at least about 1.5 to about 2 kg of silicic acid suspension, for each 1 kg of silicic acid filter cake which is added to the container. The contents of the container is mixed while maintaining a pH of at most about 4. A portion of the resulting silicic acid suspension is drawn off from the zone of highest turbulence in the container. An apparatus for carrying out the process is provided.
摘要:
A silicic acid filter cake and suspension agent are fed to a container equipped with a stirrer having a peripheral speed of about 20-30 m/sec. The ratio of container diameter to stirrer diameter is about 3:1. The ratio of container diameter to level of filling is at most about 1:2. The container contains at least about 1.5 to about 2 kg of silicic acid suspension, for each 1 kg of silicic acid filter cake which is added to the container. The contents of the container is mixed while maintaining a pH of at most about 4. A portion of the resulting silicic acid suspension is drawn off from the zone of highest turbulence in the container.
摘要:
A cutting tool or pick on a rotary excavating head has a substantially flat body with leading and trailing flanks, one of these flanks having an arcuate recess or projection matingly engaged by a complementarily curved formation on an adjacent wall of a pocket of a tool holder defining therewith a rotary joint about which the body of the pick is swingable upon insertion of its shank into the pocket. A screw clamp inside the pocket wedges the pick firmly in a position which in one embodiment is adjustable by the provision of a toothed and an indented surface of the rotary joint enabling selective interfitting. The pick may be further braced by one or more additional screws threaded into it and bearing upon other pocket walls.