Abstract
The increased number of modern high-pressure steam boilers emphasizes the need for high-quality feedwater make-up of minimum scale-forming and minimum total-solids content consistent with the desired sulphate-carbonate ratio. The usual sodium zeolites hitherto known, which exchange their sodium base for calcium and magnesium (hardness), reduce this hardness to a minimum, but do not reduce total solids or alkalinity. The new hydrogen zeolites described in this paper retain the simplicity and complete hardness-removal characteristics of zeolite softeners and at the same time eliminate the alkalinity with (a) a corresponding reduction in total solids and CO2 content of steam, and (b) an increase in the sulphate-carbonate ratio. Furthermore, they remove alkalinity present in any form; thus, for the first time in history it is possible, by simple economical means, to remove sodium alkalinity often found in raw waters.
When the capacity of these hydrogen zeolites is exhausted, they are regenerated by dilute acid solutions in the same manner as a salt solution is used to regenerate sodium-zeolite softeners. By combining the hydrogen- and sodium-zeolite effluents in correct proportions, or by alkali neutralization, it is a simple matter to obtain a feedwater completely free from hardness and of any predetermined desired alkalinity.
These hydrogen zeolites are made of carbonaceous substances and are therefore practically free from silica. They can also be regenerated with common salt, and with such regeneration they can function in the usual sodium-zeolite cycle. Being extremely resistant to low pH waters and practically free from silica, and of relatively high capacity, they also possess great advantages when used in the usual sodium-zeolite cycle, especially where it is desired to avoid any increase in silica content, a condition that is gaining favor rapidly in the high-pressure-boiler feedwater field.
