The present invention relates to pulverizers. Pulverizers have been suggested, for example, in European Pat. No. 0017367 in which the pulverizer chamber is provided with bottom, top and side walls and the material to be pulverized, such as coal, is introduced thereinto and is taken up by jets of high velocity fluid, such as steam, the jets extending along lines which are between a radius and a tangent to the chamber. In theory the coarser particles descend as a curtain protecting the side walls of the chamber from wear. In practice it has been found that this does not work fully satisfactorily and while a central vortex is formed in the chamber, there is a tendency for the heavier particles not to move downwardly, but rather to move upwardly as a sleeve and for these to exit from the pulverizer with the finer particles. This is clearly unsatisfactory if one wishes to obtain really very fine particles indeed.