Patent GB-1231823-A (GB)
IPC: C10G33/06
Filed: 1968-07-09
Abstract: 1,231,823. Forming and breaking emulsions. ESSO RESEARCH & ENG. CO. 9 July, 1968 [14 July, 1967], No. 32774/68. Headings B1C, B1D and B1V. An emulsion comprising 75 to 99% hydrocarbon fuel as the dispersed phase is used in aircraft, where its high viscosity reduces fire risk in crashes, and is broken immediately before delivery to the jet engines. The continuous phase may be water or any one or more of a comprehensive list of polar organic liquids. Two particular emulsions comprise jet fuel dispersed in formamide containing 20% dissolved urea, with an emulsifier which may be a 75-25 mixture of ethyoxylated polyhydric long chain alkyl alcohol and ethyoxylated tridecyl alcohol or a 37-63 mixture of sorbitan mono-oleate and polyoxyethylene sorbitan mono-oleate. Other emulsions exemplified comprise 75 to 99% halogenated or oxygenated hydrocarbon derivatives, dispersed in water of formamide, and fluoro-alkenes in lubricating oil. Many emulsifiers are exemplified; gum tragacanth and gum acacia are mentioned: In manufacture, the continuous phase liquid enters emulsifier stage 5 by inlet 2 and aliquot portions of hydrocarbon are added upstream of each emulsifier stage 5, 15, 25 by inlets 3, 13, 23, pumps 8, 18, 28 recycling the major proportion of the emulsion leaving each stage (Fig. 3). The emulsifier stages each comprise 20 to 300 wire mesh screens 12 separated by perforate spacers 11, Fig. 2. In Fig. 3, the screens in successive stages 5, 15, 25 may have 20, 10 and 5 wires per inch in both directions, but the screens in a single stage could vary in mesh size from one end to the other. The respective shear rates produced in the liquids pumped through the different stages may be 10,000; 4,000 and 2000 reciprocal seconds (velocity gradient) respectively, and the recycle volume ratios of pumps 8, 18, 28 may be 10, 20 and 50 to 1. Wire screens of 4 to 30 wires per inch are envisaged in the emulsifier stages. In demulsifying (Fig. 4) the emulsion is first subjected to a shear rate greater than that which it experienced in the last emulsifier stage by at least 5000 and possibly up to 100,000 reciprocal seconds. This process occurs in zone 34 whose construction is identical to that of the emulsifier stage illustrated in Fig. 2 except that the wire screens may have 4 to 300 wires per inch. The partly separated phases then pass through coalescer 36, which could be a tube filled with glass wool, steel wool, coiled wire, porous foamed glass or plastics, and could be combined with zone 34 in a common housing. The coalesced liquids are then separated by gravity in vessel 38, whence unseparated emulsion may pass to a second gravity separation vessel 42. Unseparated emulsion from vessel 38 or 42 may be recycled to upstream of any stage of the Fig. 4 circuit or may pass to the inlet end of a second and similar circuit involving a higher shear rate. A proportion of separated fuel from coalescer 36 or vessel 42 may be recycled to both or either of stages 34, 36 to assist the initial formation of continuous phase fuel. Alternatively 1 to 5% of methyl or ethyl alcohol may be added to the emulsion at inlet 33.