Specific surface fractionator

A method of separating a pulp on the basis of specific surface into a plurality of samples comprising;

• providing an arrangement of hydrocyclones in series, each of said hydrocyclones having a conical section with a base, a base outlet, an apex outlet and a tangential inlet adjacent said base;
• the apex outlet of each hydrocyclone connected to the inlet of the succeeding hydrocyclone in the arrangement, feeding a slurry of said pulp to the inlet of a first hydrocyclone in said arrangement at a pressure sufficiently high to overcome the pressure drop through the arrangement and at a consistency to ensure that consistency of the feed to the last hydrocyclone in the arrangement is no greater than 0.25%, adjusting the flows through the base outlet of at least some of the cyclones in said arrangement to ensure that the pressure and flow at the apex outlet of each of said cyclones are sufficiently high to overcome the pressure drop in the succeeding cyclones in said series and provide pulp flow in the required amount and consistency for operation of the succeeding cyclones in said series, collecting fractions issuing from at least some of said outlets of said hydrocyclones.