GB726804A - Improvements in or relating to the deaeration of viscose - Google Patents

Abstract

<PICT:0726804/IV (a)/1> Viscose is deaerated by introducing it into a closed vessel provided with a vacuum conduit in which a sufficient high vacuum is maintained to cause the viscose to boil and in which cooling means are provided between the level of liquid viscose in the vessel and the entrance to the vacuum conduit, so that foam formed by the deaeration is caused to break on reaching the cooling means and coming into contact therewith and is prevented from entering the vacuum conduit, and that the formation of films is prevented by substantial condensation of water vapour contained in the foam by contact with the cooling means. As shown in Fig. 1, viscose continuously enters a closed vacuum vessel (which is evacuated through the conduit 2) through an inlet conduit 1 and starts to foam and boil, all the air present in the viscose, including any dissolved air, being thus expelled. The foam rising from the surface of the viscose in the vacuum vessel reaches a system of closely-spaced parallel tubes 3 near the top of the vessel, through which tubes a cooling medium flows from the inlet 4 and inlet manifold 4a to the outlet manifold 5a and outlet 5. As soon as the foam comes into contact with the cooling tubes 3 it is broken and the vapour present in the foam bubbles condenses. In this manner the foam is prevented from passing the tubes 3 and entering the vacuum conduit 2. The deaerated viscose is continuously pumped off from the barometric discharge tube 6 by the pump 7. In an alternative construction, the top of the vacuum vessel and the upper portion of its walls are provided with cooling jackets, the tubes 3 being omitted. U.S.A. Specification 2,355,057 is referred to.ALSO:<PICT:0726804/III/1> Liquids are de-aerated by introducing the liquid into a closed vessel provided with a vacuum conduit in which a sufficiently high vacuum is maintained to cause the liquid to boil and in which cooling means are provided between the level of liquid in the vessel and the entrance to the vacuum conduit, so that foam formed by the de-aeration is caused to break on reaching the cooling means and coming into contact therewith and is prevented from entering the vacuum conduit, and that the formation of films is prevented by substantial condensation of water vapour contained in the foam by contact with the cooling means. As shown in Fig. 1, viscose continuously enters a closed vacuum vessel (which is evacuated through the conduit 2) through an inlet conduit 1 and starts to boil, all the air present in the viscose, including any dissolved air, being thus expelled. The foam rising from the surface of the liquid in the vacuum vessel reaches a system of closely-spaced parallel tubes 3 near the top of the vessel, through which tubes a cooling medium flows from the inlet 4 and inlet manifold 4a to the outlet manifold 5a and outlet 5. As soon as the foam comes into contact with the cooling tubes 3 it is broken and the vapour present in the foam is prevented from passing the tubes 3 and entering the vacuum conduit 2. The de-aerated liquid is continuously pumped off from the barometric discharge tube 6 by the pump 7. In an alternative construction, the top of the vacuum vessel and the upper portion of its walls are provided with cooling jackets, the tubes 3 being omitted. U.S.A. Specification 2,355,057 is referred to.