Abstract: The treatment of a fluid containing a high concentration of particulate matter is enhanced by preventing the accumulation of particulate matter which falls from solution in the lower areas of the treatment vessel. The foregoing is accomplished by withdrawing fluid having a relatively low concentration of particulate matter at the axis of the vessel and subsequently reinjecting the withdrawn fluid as a jet or jets directed downwardly and tangentially to the wall of the vessel in the vicinity of the bottom thereof.

Abstract: To permit the output of a vertical fluidizing-cell column to be increased, its cross-sectional area to be enlarged, and the installation of plates in the column to be simplified, the plates are made conical or pyramidal with their concave and convex sides alternately directed upwardly. The plates have central openings for the passage of one stream of material, and are mounted in the column with peripheral passages for another stream of material. Preferably the plates are movable relative to each other and have movable center pieces variably closing some of the central openings for varying the operation of the column.

Abstract: A process for the production of a crude dimethyl terephthalate suitable for hydrolyzing into a fiber grade terephthalic acid involves separating a crude ester obtained from the production of dimethyl terephthalate by the Witten process by vacuum distillation at elevated pressure in a three-column series arranged distillation system. In the first distillation column of the system the crude is separated into a methyl p-toluate-rich fraction as head product; in a second column of the series, into a fraction rich in methyl ester of terephthalaldehydic acid as head product; and in a third distillation column, a crude dimethyl terephthalate fraction. The crude dimethyl terephthalate fraction has a methyl ester of terephthalaldehydic acid content of 0.01-0.1% by weight as a head product.

Abstract: A process for the production and maintenance of a fluidized layer in a heterogeneous system includes the steps of:(1) setting a heterogeneous mass stream having a liquid as the continuous phase and a solid and/or gas as the disperse phase into fluidized motion in a column between two plates arranged superimposed and inclined in opposition to each other with respect to the horizontal, said plates forming a fluidizing cell and said fluidized motion being promoted by the force of gravity;(2) enriching a heavier phase above the lower plate, especially in the lower region thereof, and causing said heavier phase to flow from there into the space below the lower plate;(3) enriching a lighter phase below the upper plate, especially in the upper region thereof, and causing the lighter phase to flow from there into the space above the upper plate and/or to be discharged from there from the column; and(4) conducting the disperse phase in case of a density higher than that of the continuous phase, in a direction from the

Abstract: In a process for the preparation of fiber-grade terephthalic acid from intermediate stage crude dimethyl terephthalate, the crude dimethyl terephthalate, which has a limited content of intermediate oxidation products including a content of terephthalaldehydic acid methyl ester of up to 0.1% by weight based on the weight of the crude dimethyl terephthalate, is hydrolyzed with water at a weight ratio of the crude dimethyl terephthalate to water of between 3:1 and 0.1:1 and at a temperature between 140.degree. C. and 350.degree. C. and under a pressure required to maintain a liquid phase (e.g., from 6 to 200 bars) to produce a reaction mixture containing crystalline fiber-grade terephtalic acid and thereafter the terephthalic acid is recovered from the reaction mixture.

Abstract: A process for mass transfer between heterogeneous systems or phases in a vertical exchange column having at least one plate, a heavier stream of matter being introduced above the plate and, a lighter stream of matter being introduced countercurrently thereto from the bottom of the plate, wherein (a) a heavier stream of matter fed from the top is deflected, above the plate, into a mixing zone in which the heavier stream undergoes vertical rotary movement and is mixed with a lighter stream of matter passing from below through a first passgeway of the plate and introduced into the mixing zone to also undergo vertical rotary movement, (b) a heavier phase, suspension, or the like fluid-like mass forming in the mixing zone during the mass transfer therein is accumulated in a zone superjacent to a second passageway of the plate; and (c) after a sufficient pressure gradient has been built up, the accumulated mass flows as another heavier stream through the second passageway into a space underneath the plate and is at