GB893773A - Apparatus and method for dehumidifying gases - Google Patents

Abstract

893,773. Drying air and gases. PUREGAS EQUIPMENT CORPORATION. Jan. 5, 1961 [April 25, 1960], No. 530/61. Class 34(1) A method of removing an impurity that is a moisture from a gas comprising passing the gas through a cooling chamber having a heat exchange surface that is maintained at a temperature below the freezing temperature of the impurity so as to cool the gas to a temperature at which the impurity is precipitated, allowing the cooled gas from the cooling chamber to pass continuously over an absorbent or adsorbent material which is capable of absorbing or adsorbing the impurity, a certain portion of the impurity being condensed and frozen on the heat exchange surface of the cooling chamber during a first part of the operating cycle; then, when sufficient impurity has been deposited on the heat exchange surface to interfere with the cooling of the gas, defrosting the cooling surface by heating it above the melting point of the frozen impurity and allowing a part of the melted impurity to drain out of the cooling chamber while continuing to pass the gas through the cooling chamber and over the absorbent or adsorbent material, the gas flowing from the cooling chamber during this second part of the operating cycle being at a temperature above the precipitation temperature and having a surplus of impurity so that the absorbent or adsorbent material absorbs or adsorbs the impurity from the gas; and, finally, when the heat exchange surface has been defrosted, cooling the heat exchange surface to the predetermined temperature and repeating the operating cycle so that during the first part of each operating cycle impurity in the gas is removed in the cooling chamber and the absorbent or adsorbent material is regenerated by slowly reabsorbing the impurity into the purified gas. In the apparatus described the gas is introduced under pressure from a compressor 1 into a cooling chamber 2 which is cooled by a refrigeration system 15, 16, 17 and heated by an electrical heating element 17 and which is connected to a drying chamber 5 containing an absorbent or adsorbent material. In operation, the moist gas is pumped into the chamber 2 to freeze out the moisture content of the gas and then the gas leaves the chamber in a drier state than required and passes through the material in the chamber 5 to absorb any moisture therein. The duct which connects the chambers 2, 5 is surrounded by the local atmosphere so that the gas is warmed before passing to the chamber 5 to improve its absorbent capacity. When the frozen moisture reaches a predetermined limit in the chamber 2 a pressure or time switch 6 operates the heating element 7 to defrost the chamber, the condensate being removed to a condensate tank 9. The gas which passed through the chamber 2 during the defrosting portion of the cycle is dried within the chamber 5 until the defrosting cycle is completed and the regeneration cycle is restarted and the moisture content in the gas is frozen. The drying material is silica gel when water vapour is to be removed but when the impurity is other than water vapour other adsorbent or absorbent materials such as activated aluminium oxide, activated charcoal, Fuller's earth, diatomite, kaolin, bentonite, or a molecular sieve material may be used depending on the impurity to be removed.