present invention can quite advantageously be incorporated into an existing digester such as shown in fig1 from this point on the components of the digester system 100 described in the following text with reference to fig2 are those which are newly added as part of the present invention there is a solvent tank 130 having in the upper portion of the tank 130 a steam region 132 containing high pressure steam that is at a pressure higher than the operating pressure inside the digester 102 in the lower part of the solvent tank 130 there is a section containing a solvent composition 134 there is also a solvent recirculating tank 136 having an upper high pressure steam region 138 and a lower solvent containing region 140 and also a third solvent tank which is a solvent makeup tank 142 having an upper steam region 144 and a lower solvent region 146 there is a source of high pressure steam indicated at 148 leading into a steam line 149 that communicates with each of the aforementioned solvent tanks 130 136 and 142 through steam inlets 150 152 and 154 respectively the inlets 152 and 154 each have control valves 156 and 158 respectively and another valve 159 is provided in the line 149 upstream of the steam inlet 150 the system of the present invention will first be described with reference to the upper liquor extracting area 118 there is a steam inlet valve 160 which leads from the steam line portion 162 into.