the permeability of a mixture to be agglomerated is measured by means of ateast one permeability - measuring device situated upstream of a mixer directly preceding a feed hopper feeding an agglomerating apparatus . water is added to the mixture in the mixer . the measured permeability value is utilized to influence the quantity of water added in the mixer by means of an automatic feed - forward regulating loop so as to obtain a given permeability at the output of the mixer . the feed - forward loop may be combined with a feedback regulating loop .