Method for continuous cleaning of process water in waste paper treatment with control of the content of inorganic solids

Device for processing waste paper (100), and/or paper machine (200) of a machine for manufacturing paper from waste paper, the device (100) and/or the paper machine (200) comprising a process water processing unit (116a, 116b, 216) for cleaning process water circulating in the device (100) and/or the paper machine (200), and comprising at least one unit selected from one or more of a pulper (105), sorting device (110a, 110b), dewatering unit (115a, 115b), oxidation/reduction unit (112), centrifugal sorter (202), fine sorting device (204), paper-machine mold part (206), paper-machine press part (208), reject treatment unit (118a, 118b, 212), fiber recovery unit (214) and drying part (210), and the process water processing unit (116a, 116b, 216) comprising:

• i) an anaerobic reactor (125a, 125b, 225) comprising one or more gas separators (504), for anaerobic cleaning of process water, comprising at least one supply line (500) for supplying process water to be cleaned to the anaerobic reactor (125a, 125b, 225), and at least one discharge line (512) for conveying away cleaned process water out of the reactor (125a, 125b, 225), the process water processing unit (116a, 116b, 216) being connected to at least one of the at least one unit, such that, during operation of the device (100) and/or paper machine (200), process water to be cleaned is supplied from the at least one unit to the process water processing unit (116a, 116b, 216) and, therein, the anaerobic reactor (125a, 125b, 225), and after the process water processing step cleaned process water is returned into the at least one unit, and
• ii) a solid-liquid separator (126a, 126b, 226) for separating process water conveyed away from the anaerobic reactor (125a, 125b, 225) into a fraction depleted of inorganic solids and a fraction enriched with inorganic solids, comprising a discharge line (127a, 127b, 227) for the fraction enriched with inorganic solids and comprising a return line (128a, 128b, 228) for returning the fraction depleted of inorganic solids into the anaerobic reactor (125a, 125b, 225), at least in part, a further line leading from the anaerobic reactor (125a, 125b, 225) to the solid-liquid separator (126a, 126b, 226) for supplying process water conveyed away from the anaerobic reactor (125a, 125b, 225),
• wherein this further comprises iii) a measuring device for measuring the content of inorganic solids in the process water contained in the anaerobic reactor (125a, 125b, 225), and in that this also comprises a control means which can receive measuring data regarding the content of inorganic solids in the process water contained in the anaerobic reactor (125a, 125b, 225) and into which a limit value and optionally a threshold value can be input, the control means being designed such that it automatically starts the continuous removal of process water from the anaerobic reactor (125a, 125b, 225) and the supply thereof into the solid-liquid separator (126a, 126b, 226), when an input limit value for the inorganic solids content in the process water contained in the anaerobic reactor (125a, 125b, 225) is exceeded, and automatically ends the continuous removal of process water from the anaerobic reactor (125a, 125b, 225), and the supply thereof into the solid-liquid separator (126a, 126b, 226), in the event of falling below the limit value or an input threshold value for the inorganic solids content in the process water contained in the anaerobic reactor (125a, 125b, 225).