GB474976A - Improvements in or relating to the drying of gases - Google Patents

Abstract

<PICT:0474976/III/1> <PICT:0474976/III/2> <PICT:0474976/III/3> In a process for drying protective gases suitable for use in metal heat treatment apparatus and obtained by the thermal decomposition or partial combustion of certain gases, for example, ammonia, in which the drying is effected by means of two or more driers containing adsorbents, alternately used for drying and subjected to regeneration, the hot drier or driers after regeneration is or are cooled at least in part by the passage therethrough of cooled protective gases taken either from the active drier or driers or from the heat treatment apparatus. In the arrangement indicated in Fig. 1, protective gases produced in a gas generator 1 pass through a cooler 2, catchpot 3 for condensed moisture, valve 4, active drier 5, valve 7, heat-treatment furnace 8, gascirculator 9, oil catchpot 10, valve 7, exhausted drier 6 and valve 4 back to the generator 1. The driers 5, 6 contain electric heaters (not shown) which are switched in during regeneration. Air may be added at 11 or 12 to the gases returning from the furnace 8. When the drier 6 has been regenerated the heater is turned off and relatively cool gases from the furnace cool the drier. Other cooling means may be provided in addition. Afterwards the valves 4, 7 are changed over so that the drier 6 takes over the duties of drying and the drier 5 is subjected to regeneration and cooling. In the arrangement shown in Fig. 2, gas from the generator 1 passes through cooler 2, catchpot 3, valve 4, active drier 5, valve 7, furnace 8, gas blower 9 and catchpot 10 to the generator. The drier 6 is regenerated and cooled by an auxiliary circulating system as follows: A gas insulator 11 circulates gas through catchpot 12, valve 7, drier 6, valve 4 and cooler 13. From this system there is a controlled outlet of gas via pipe line 14 to the suction side of the blower 9, a corresponding supply being provided from the drier 5 to the insulator 11. In a further arrangement shown in Fig. 3, gas from the generator 1 flows through active drier 5, furnace 8 and exhaust drier 6 back to the generator. When the moisture in drier 6 has been driven off, valves 11, 12 are changed over so that return gas from the furnace 8 instead of passing through the drier 6 passes back to the generator by way of valves 11 and 12. The drier 6 is cooled by gas passing through a circulator 13, catchpot 14, valves 11, 7, drier 6, valves 4, 12 and cooler 15 back to the circulator 13. The supply of gas to the circulator 13 is from the drier 5 by line 17, discharge being by line 16 to the blower 9. In a further arrangement, three driers are used in rotation so that while one is drying, another is being regenerated and the third is being cooled after regeneration.