Abstract: Methanol and cyclohexane are recovered from a condensed methanol-cyclohexane azeotrope by allowing the condensed azeotrope to separate in a vessel into an upper phase rich in cyclohexane and a lower phase rich in methanol, fractionating the upper phase in a first column whereby the methanol-cyclohexane azeotrope is taken off the top and returned to the vessel while cyclohexane is removed from the lower portion of the first column, and fractionating the lower phase in a second column whereby the methanol-cyclohexane azeotrope is taken off the top and returned to the vessel while methanol is removed from the lower portion of the second column.

Abstract: A process and apparatus are provided controlling the heat input of an extractive distillation column. The bottom of the column is heated with a major stream of thermal energy which is either slowly varying in time or controlled by the amount of starting material mixture and with a minor stream of thermal energy which is controlled by sensing the thermodynamic state in the upper half of the column during the process. The major stream can provide about 90 percent and the minor stream about 10 percent of the heat fed to the column. The minor stream can be controlled by the temperature at one point in the upper half of the column, by the temperature difference at two points in the upper half of the column or by gas chromatographic analysis of the extract material concentration near the top of the column. The process allows one to keep a low concentration of the extract material in the raffinate.

Abstract: An improved distillation method and apparatus are provided for recovering anhydrous ethanol from fermentation or synthetic feedstocks. The system includes at least one stripper-rectifier tower, a dehydrating tower, and an azeotropic agent stripping tower. Substantial energy savings are realized by operating the dehydrating tower, and preferably also the azeotropic agent stripping tower, at a higher pressure than the stripper-rectifier tower and by condensing the overhead vapors from the dehydrating tower (or dehydrating tower and azeotropic agent stripping tower) to provide the heat required in the stripper-rectifier tower. In a preferred embodiment, two stripper-rectifier towers are used, one operating at a higher pressure than the other, in which case the higher pressure tower is heated as just described and the overhead vapors from the higher pressure tower are condensed to supply the heat required in the lower pressure tower.

Abstract: A process of extractive distillation for separating components easily soluble in a polar solvent from at least two hydrocarbon mixtures having different contents of the easily soluble components by extractive distillation using said polar solvent, which comprises feeding a hydrocarbon mixture containing a larger amount of the easily soluble components, as a gas, into the middle or lower portion of an extractive distillation column, feeding a hydrocarbon mixture containing a smaller amount of the easily soluble components, as a liquid, to the upper portion of the extractive distillation column, and subjecting them to extractive distillation.

Abstract: In a fractional distillation process in which a heating fluid and waste heat stream are utilized to supply heat to a fractional distillation column and in which the heat supplied from the waste heat stream is not controllable, control of the liquid level in the fractional distillation column is accomplished by manipulating the flow rate of the heating fluid so as to maintain a desired liquid level until such time as the flow rate of the heating fluid becomes zero at which time the flow rate of the external reflux to the fractional distillation column is manipulated to maintain a desired liquid level in the fractional distillation column. A switching of control of the liquid level provides a means by which an uncontrollable heat input may be provided to the fractional distillation column without losing control of the liquid level in the fractional distillation column.

Abstract: An improved distillation method and apparatus are provided for recovering hydrous ethanol from fermentation or synthetic feedstocks. Substantial energy savings are realized by utilizing a pair of stripper-rectifier towers in which overhead vapors from one tower operating at a higher pressure supply the heat required for the other tower operating at a lower pressure and by preheating the feedstock in multiple heat exchange steps. The feedstock is split into two portions of unequal size, the larger portion being supplied to the higher pressure tower and the smaller portion to the lower pressure tower.

Abstract: In a distillation process, the heats of distillates and bottom product are recovered to preheat the feed and to generate the steam of higher than 5 kg/cm.sup.2 G which in turn may be utilized to improve the distillation efficiency.

Abstract: A control system for a multiple feed fractional distillation column is disclosed in which the flow rate signals of the multiple feed streams are delayed and combined for use in feedforward predictive control of the upper reflux flow, intermediate reflux flow and/or reboiler fluid flow to the fractional distillation column. Temperature measurements of the upper vapor stream, the upper reflux stream, the intermediate vapor stream and the intermediate reflux stream as well as analysis of a product stream can be utilized to provide feedback control of the fractional distillation column.

Abstract: A process for separating two close-boiling chemical compounds by fractionation wherein a vapor stream removed from the overhead receiver is superheated by indirect heat exchange and is then further heated by compression. The thus-heated high pressure stream is cooled by heat exchange against the overhead vapor and split into at least two portions. One portion of the high pressure stream is passed through a reboiler at an intermediate point in a fractionation column. Preferably, both portions of the high pressure stream are subcooled and returned to the overhead receiver except for the overhead product drawn off.

Abstract: The recovery of dimethylacylamides from solutions which are formed during the production of fibres is particularly economical if the solution is concentrated in a separating column to produce a sump product having a DMA content of 30 to 90% at pressures of more than 300 Torr, using the evaporation heat of the head product for heating the column, with the aid of a compressor and then separating the sump product which is concentrated in DMA by distillation.

Abstract: Crude phenol is recovered from CHP reaction products by continuously feeding to a main column separating in its uppermost section phenol from crude acetone, this fraction being removed overhead, and in the lower section crude phenol from higher boilers, including acetophenone and carbinol, the crude phenol being removed as a sidestream fraction from the main column at a point in the column above the feed-point wherein the total concentration of acetophenone plus carbinol is less than 1,000 ppm and the higher boiling compounds being removed as a base fraction.

Abstract: Impurities such as hydrogen sulfide and carbon dioxide are removed from fluids such as natural gas, synthesis gas or liquid or gaseous hydrocarbons by contact with an aqueous alkanolamine solution which absorbs said impurities from the fluid. The resultant spent impurity-enriched absorbent amine stream containing the absorbed impurities is split into two streams; one stream being routed directly to the top of an amine regenerator column and the second stream being routed to a heat exchanger where it is heated en route to an intermediate point of the regenerator column by heat exchange with the hot regenerated solution coming from the bottom of the regenerator column. The spent amine stream which is passed without prior heating directly to the top of the regenerator column is heated by condensing steam in the column which would normally escape therefrom, thereby reducing the amount of "saturation" steam which is lost from the system.

Abstract: Process for the continuous preparation of organic solutions of percarboxylic acids by reaction of aqueous hydrogen peroxide with the corresponding carboxylic acid in the presence of an acid, water-soluble catalyst, extraction of the resulting reaction mixture with an organic solvent and recycle of the raffinate, containing hydrogen peroxide, after reconcentration by the removal of water by distillation into the reaction. The raffinate is fed, together with the whole of that amount of hydrogen peroxide which essentially to the consumption of hydrogen peroxide in the reaction or with a part thereof, into the distillation for the removal of water. The amount of water which essentially corresponds to the sum of the water of reaction formed during the reaction and the water introduced into the process with the feed products is distilled off under reduced pressure. The sump product, thus obtainable, from the distillation is recycled into the reaction.

Abstract: An improved aromatics extraction process is disclosed. Key feature of the present invention is use of the fractionator in the hydrodealkylation unit or other unit with a benzene fraction to fractionate not only hydrodealkylated benzene but also extracted benzene. The extracted benzene is used as "pseudo" reflux in the hydrodealkylation unit fractionator, thereby reducing the reflux requirement. The conventional re-run fractionator for clay treated benzene extract is eliminated, since polymerized olefins in this extract are removed as a bottoms fraction from the hydrodealkylation fractionator.

Abstract: A control method and system for regulating the heat input to the reboiler section of a distillation column having attendant thereto a first external heat-recovery reboiler. Flow-measuring means, disposed within a substantially liquid-free environment, produces a signal which is representative of the quantity of vapor flowing from the reboiler section upwardly into the fractionation section of the column. This signal is transmitted to heat-varying means whereby the heat input to a second external reboiler heater is regulated in response to the quantity of vapor flow.