In practice, blooms made
by this process have been so red-short that they could not be hammered
at all.
It would be impracticable in this process to employ ore and carbon in
as fine particles as Wilson does, as a very large portion of the
charge would be carried off by the draught, and a sticking of the
material to the sides of the rotating furnace could scarcely be
avoided. I do not imagine that a division of the material into
anything like the supposed size of molecules is necessary; we know
that the graphitic carbon in the pig-iron employed in puddling is not
so finely divided, but it is much smaller particles than bean or pea
size, and by approximating the size of the graphite particles in pig
iron, Wilson has succeeded in obtaining good results.
If we examine the utilization of the heat developed by the combustion
of a given quantity of coal in this process, and compare it with the
result of the combustion of an equivalent amount of fuel in a blast
furnace, we shall soon see the theoretical economy of the process. The
coal is burned on the grate of the puddling-furnace, to carbonic acid,
and the flame is more fully utilized than in an ordinary
puddling-furnace, for besides the ordinary hearth there is the second
or rear hearth, where additional heat is taken up, and then the
products of combustion are further utilized in heating the retorts in
which the ore is partly reduced.
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