GB488638A - Improvements in or relating to the treatment of materials, for example fumigation thereof - Google Patents

Abstract

488,638. Fumigating and adjusting the moisture content of food and other materials. GUARDITE CORPORATION. Oct. 8, 1936, Nos. 21909 and 21910. Convention dates, Dec. 12, 1935 and July 10, 1936. [Classes 49, 81 (i), and 130] [Also in Group I] Materials or articles, e.g. tobacco, furs, wool, food products such as rice, cereals, or dried fruit, having interstices containing a fairly readily vaporized liquid are subjected to such a degree of vacuum in a chamber maintained at atmospheric temperature that the liquid boils, the boiling is continued under reduced pressure whilst the material is maintained at substantially atmospheric temperature until substantially all of the air and/or other non-condensible gas in the interstices of the material or articles is driven out by the generated vapour, and the interstices are then filled at substantially high pressure with a fumigating gas or vapour, or with water vapour to adjust the moisture content of the materials. The readily vaporized liquid may be water, ether, alcohol or gasoline, and may be naturally present in the materials or previously introduced. For example, the materials may be moistened with water, water vapour or steam. As shown, the moist materials are placed in tank 1 which is exhausted by pump 6 through lines 7, 11, 12 and oil separator 10. At 20‹ C., the exhaustion is preferably to below 15 mm. Heat losses are made up by conduction through the steel walls of the tank or by means of heating coils or other means. During the evacuation, dry steam at a pressure higher than that prevailing in the tank, e.g. at atmospheric pressure, may be passed thereinto, the quantity being such as not to alter substantially the prevailing temperature conditions. The exhaustion may be followed by the introduction of water vapour and a further exhaustion, and these operations may be repeated. The water vapour drawn off is condensed in condenser 19 maintained at 33‹ F. or lower. When the air is completely removed, and it is desired to adjust the moisture content of the material, water vapour or steam is admitted to the chamber. Thus, rice with an initial moisture content of 8À52 per cent evacuated to 13 mms. and treated with water vapour at 23 mms. had a final moisture content of 8À87 per cent. When it is desired to fumigate the product, the fumigant, for example, pure ethylene oxide, a mixture of carbon dioxide and ethylene oxide in a ratio of less than 9:1, methyl formate, methyl bromide, hydrogen cyanide or mixtures of the latter gases with other gases, is introduced through lines 15, 5, 3, 4 from pressure vessel 14. A steam heating coil 16, 17 is disposed in this vessel. A supply tank 18 for the fumigant is provided. The pressure of the fumigant in tank 1 may be 250 mm. above atmospheric. The fumigant may be circulated via lines 7, 11, 15, 5, 3, 4, condenser 19 being byepassed, if desired. After fumigation, the gas is removed by pump 20 and stored in tank 14 for reuse. A separator 21 is provided for oil and condensed water. The fumigant may be left in the materials, or removed by exhaustion with the aid of steam. If the moisture content of the material is thereby undesirably reduced, it is restored by steaming preferably at low temperatures and pressures. Air, sterilized air, or an inert gas such as carbon dioxide may be then introduced into the tank. The fumigant withdrawn from the tank 1 may be treated for the removal of oxygen, and the water collected in the condensers 19, 21 for the recovery of the fumigant. British Specifications 3137/02, [Class 81], 369,391, and 473,842, and U.S.A. Specification 1,952,781 are referred to. The Specification as open to inspection under Sect. 91 comprises also preliminarily heating the materials before evacuation, e.g. to 122‹ F. This subject-matter does not appear in the Specification as accepted.