the cooking vessel f w u2267 7 0 equivalent to a concentration just over 14 on exit from the cooking vessel f w u2267 6 0 equivalent to a concentration just over 16 the calculation above is based on the original wood content and since the pulp is delignified during the cooking and the released organic material principally lignin is withdrawn for recovery the actual concentration on exit from the cooking vessel will be significantly lower a concentration of 9 6 for a yield of 60 from the cooking phase approximately 1 tonne condensate per tonne sawdust approximately 1 tonne white liquor per tonne sawdust approximately 5 tonnes washing filtrate black liquor per tonne sawdust the large amount of black liquor that is returned at an elevated temperature to the steaming vessel ensures a very good energy economy for the process and essentially only the sawdust usually having the temperature of the surroundings 20 u00b0 c and the white liquor which however normally has a temperature of 70 85 u00b0 c need to be heated the consistency of the sawdust in a slurry formed with cooking fluid is maintained during the complete process such that it does not exceed 20 and it is appropriate that it is held at a maximum level in the interval 15 17 from the point of view of process technology the low consistency ensures a system that is easy to manage with a minimum of interruptions of the process a significant characteristic of the process is that more than 95 and preferably 100 of the cooking fluid that is added to the sawdust from the initial mixing with cooking fluid until it is transferred to the digester accompanies the sawdust in a mixture of cooking fluid and sawdust right up.