Method for separating a liquid waste finish composition

A method is provided for separating a liquid mixture into its aqueous and non-aqueous liquid phases. The method comprises the steps of introducing the liquid mixture into a gas-tight vessel; rotating the vessel at a surface speed of approximately 19 to 190 ft/min (0.095 to 0.950 m/s) to cause filming of the liquid composition, while simultaneously heating the vessel to cause the aqueous phase to evaporate; removing the water vapor under vacuum; and condensing the water vapor for removal.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to the separation of a liquid mixture into 
its aqueous and non-aqueous liquid phases. More particularly, the 
invention is related to the separation of the aqueous and non-aqueous 
phases of a finish composition diluted with water and having a Brookfield 
viscosity at 25.degree. C. of 2 to 115 centipoise. 
2. The Prior Art 
In the production of multifilament synthetic polymer yarn, especially 
polyester and polyamide yarns, it is conventional to coat the solidified 
filaments with a spin finish or overfinish composition to improve 
processing of the yarn and ultimate yarn properties. These finish 
compositions may be applied to the yarn in a variety of ways, for example 
by contact with a roll rotating in a trough of the composition or with a 
surface to which the composition is metered. The waste finish composition 
is diluted with distilled or deionized water for removal from the process 
equipment and then fed to a collection point for disposal. There may be 
components of the non-aqueous phase of the waste finish composition which 
require disposal of the composition in a hazardous waste disposal facility 
approved by the Environmental Protection Agency. As the water content of 
the waste finish composition may be quite high, for example as high as 99 
percent, it is desirable to develop a method to separate the aqueous and 
non-aqueous phases for disposal of the non-aqueous phase; transportation 
and disposal costs necessary for ultimate disposal of the waste would 
accordingly be greatly decreased. 
FIG. 1 of British Patent Specification No. 1,019,099 to Snia Viscosa, 
hereby incorporated by reference, describes apparatus (a rotary dryer) 
similar to that used in practicing the method of the present invention. 
U.S. Pat. Nos. 3,870,475 and 3,787,481, both to Siclari et al., and 
3,296,709 to Barsch, all of which are hereby incorporated by reference, 
also describe apparatus that have potential use for practicing the method 
of the present invention, specifically a vertical wall evaporator with a 
high speed rotor and a rotating drum chip dryer, respectively. 
SUMMARY OF THE INVENTION 
The present invention provides a method for separating a liquid mixture 
into its aqueous and non-aqueous liquid phases. The method comprises the 
steps of introducing the liquid mixture into a gas-tight vessel, 
preferably via a spray nozzle which discharges jets of the liquid mixture 
onto the inside surface of the vessel; rotating the vessel at a surface 
speed of approximately 19 to 190 ft/min (0.095 to 0.950 m/s) to cause 
filming of the liquid composition, while simultaneously heating the 
vessel, preferably to a temperature of about 90.degree. to 92.degree. C., 
to cause the aqueous phase to evaporate; removing the water vapor under 
vacuum, preferably under vacuum of 203 to 508 torr; and condensing the 
water vapor for removal. It is preferred that the liquid mixture be a 
finish composition diluted with water and having a viscosity of 2 to 115 
centipoise (cps). It is also preferred that the liquid mixture be filtered 
with a 40 to 100, preferably the latter, micron filter prior to being 
introduced into the vessel. 
In the most preferred embodiment the present invention provides a method 
for separating the aqueous and non-aqueous phases of a finish composition 
diluted with water and having a viscosity of 2 to 115 cps. The method 
comprises the steps of filtering the diluted finish composition with a 40 
to 100 micron filter; injecting the diluted finish composition into a 
gas-tight vessel via a spray nozzle which discharges jets of the 
composition onto the inside surface of the vessel; rotating the vessel at 
a surface speed of approximately 19 to 190 ft/min (0.095 to 0.950 m/s) to 
cause filming of the composition, while simultaneously heating the vessel 
to a temperature of about 90.degree. to 92.degree. C. to cause the aqueous 
phase to evaporate; removing the water vapor under vacuum of 203 to 508 
torr; and condensing the water vapor for removal. 
The invention will be more clearly understood and additional objects and 
advantages will become apparent upon reference to the discussion below and 
to the drawings which are given for illustrative purposes.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to the accompanying drawings, like numbers indicate like 
apparatus. With reference to FIG. 1, a gas-tight vessel 10 is held 
eccentrically at two diametrically opposed ends by tires 13 that run on 
trunnion rolls (unshown) and are driven for rotation of vessel 10 by 
conventional motor 14. Vessel 10 is preferably about 6 ft (1.8 m) in 
diameter and 8 ft (2.4 m) in length, and is rotated at a speed of 1 to 10 
revolutions per minute, perferably 3 revolutions per minute, to give a 
surface speed of about 19 to 190 ft/min (0.095 to 0.950 m/s). Steam inlet 
15 and steam condensate outlet 16 connect through a rotary steam joint to 
the volume between vessel 10 and jacket 11. With reference to FIG. 2, 
dimpled jacket flights 20 are connected in a conventional manner with the 
volume between vessel 10 and jacket 11. In this manner, vessel 10 and 
angled flights 20 are heated. It is preferred that a sufficient amount of 
heat be supplied to bring vessel 10 to a temperature of about 90.degree. 
to 92.degree. C. 
In FIG. 1, heat traced feed line 17 feeds water diluted finish composition 
having a Brookfield viscosity at 25.degree. C. of about 2.8 to 2.9 cps 
through a conventional bag filter 18 having a mesh size, preferably, of 40 
to 100 microns. The composition is then pumped continuously by a Milton 
Roy Diaphragm metering pump (not shown) at a flow rate of up to 2.5 
gal/min (0.0002 m.sup.3 /s) through a pipe connection in a rotary joint to 
injection nozzle 19, which discharges jets of the composition onto the 
heated inner surface of vessel 10 and angled flights 20 attached thereto 
(see FIG. 2). Heated flights 20 function in conjunction with the rotation 
of vessel 10 to cause filming of the composition for more rapid 
evaporation of the aqueous phase. With reference to FIG. 2, numeral 21 
represents a film of the composition and numeral 22 represents the 
accumulating pool of the composition, which with time becomes concentrated 
with the non-aqueous phase. 
The water vapors are removed from vessel 10 by a vacuum generating device 
24 at the end of the process. Vacuum generating device 24 may be a 
conventional vacuum jet or vacuum pump, preferably the latter, under 
pressure of 203 to 508 torr, most preferably 304 torr. The water vapors 
are removed through the introductory rotary joint through condenser system 
23, which comprises two conventional condensers cooled by chilled water 
and operating in parallel with a condensing capacity of approximately 2.4 
gal/min (0.0002 m.sup.3 /s). The remaining vapors are combined and moved 
through a third condenser where an additional condensate flow of 
approximately 0.1 gal/min (0.0000003 m.sup.3 /s) combines with the flow 
from the first two condensers. All three of these condensers have a level 
control in the tank section which will open drain valves and start 
condensate pumps to transfer the water condensate to a contaminated drain. 
Vacuum generating device 24 draws all remaining vapors from the third 
condenser and exhausts them through a scrubber designed to remove vacuum 
pump oil vapors from the remaining water vapors. These remaining water 
vapors are exhausted to the atmosphere. The minute amounts of vacuum pump 
oil carryover that are removed by the scrubber are returned to a 
contaminated drain. The concentrated non-aqueous phase of the composition 
that collects as pool 22 in vessel 10 is periodically removed by stopping 
rotation of vessel 10, connecting a flexible hose to drain 12, opening a 
valve (unshown) to complete a flow path from vessel 10 through the hose 
into a receiver tank (unshown) with a vent to the atmosphere. This 
arrangement allows relief of the vacuum on vessel 10 (a valve in the vapor 
line to the condensers is closed prior to connecting the drain hose). The 
concentrated non-aqueous phase may be stored for subsequent removal and 
shipping according to established procedures. At the time of discharge 
from vessel 10, the concentrated non-aqueous phase has a Brookfield 
viscosity at 25.degree. C. of approximately 115 cps. 
It is preferred that feed of the diluted finish composition to rotating 
heated vessel 10 continue uninterrupted for twenty-three hours, followed 
by a one hour period without feed. Rotation of the vessel 10 is stopped 
and the concentrated non-aqueous phase is removed via drain 12. 
Thereafter, the equipment may be restarted.