A good method of avoiding incrustations in steam boilers is evidently
a preliminary purification of the feed-water, provided it can be done
by means sufficiently simple. This is a problem which it is claimed has
been solved by M. Dehne of Halle, by means of an arrangement which we
will herewith describe. The fresh water, which is taken up by a feed
pump, is sent into a heater where it is raised to a temperature that
will be favorable to chemical reaction. It then passes into a mixer
where it encounters certain reacting agents which have been pumped in
there by a pump of special design. These reacting agents are composed
of a mixture of carbonate of soda and of caustic soda, the carbonate
of soda serving to precipitate the sulphate of lime contained in the
feed water, while the caustic soda precipitates the carbonate of lime
and the magnesia. The relative dimensions between the special pump
and the feed pump are calculated in such a way that the proportions
of carbonate of soda and caustic soda in the mixture have always a
certain relation to the amount of lime and magnesia to be precipitated.
The water of the mixture is frequently very much disturbed by the
precipitations which are formed, and passes into a filter where all the
matters that are held in suspension are retained. It then goes into the
boiler. In cases where the feed-water is taken from a tank, the heater,
the mixer, and filter are put in the suction pipe of the feed pump, but
if, as often happens, the water is already under pressure and will pass
directly through the three, the feed pump will take the water directly
from the filter and pump it directly into the boiler.