2 in the total liquid volume here is the liquid a mixture of fresh cooking chemicals wl m added to a circulation with screen s 2 pump p 2 and a central pipe cp 2 ending above screen s 2 in order to establish appropriate temperature conditions for the subsequent cooking stage in the second lower volume z 2 of liquid in the total liquid volume heating is performed by heater he in the same first liquid circulation having a screen s 2 in the wall of the vessel in first end of the first circulation conduit and an outlet pipe cp 2 in the center of the vessel at the second end of the circulation conduit and a pump p 2 in the circulation conduit wherein the liquid in the circulation conduit is passing the heater he for heating the liquid circulated in the circulation conduit as shown in the table in preceding part of the description a cooking temperature of 140 u00b0 c could easily be implemented if this circulation i e the outlet of central pipe cp 2 ends up more than 26 meters below the second liquid level if pressure in vessel top is held at 0 bar g i e at the total distance h 1 h 2 in the figure the means for heating the cooking liquids includes preferably a heater in form of an indirect heat exchanger where the heating medium.