A method for processing pulp in an apparatus for washing and dewatering pulp comprising two rotatable press rolls (102, 104) having a permeable outer surface (106, 108), and a vat (114, 116, 118) in which the press rolls (102, 104) are installed, the press rolls (102, 104) defining a press nip between them, in which press nip the pulp is pressed, and the apparatus is arranged to feed the pulp in the direction of rotation of the press rolls through the press nip, wherein the processing of the pulp in the apparatus is determined by at least two variable operating parameters which are variable during operation, wherein at least one of the press rolls (102, 104) is movable in relation to the other press roll (102, 104) to vary the press nip, characterized in that the method comprises: • including (310; 320) the rotation speed of the press roll (102, 104) and the distance between the press rolls (102, 104) as variable operating parameters; • including (311; 321) vat pressure and linear load which acts on the pulp in the press nip as control parameters, each being associated with a predetermined threshold value wherein a desired maximum value is set as the predetermined threshold value for the respective control parameter; • measuring (313; 323; 402; 502) the control parameters; • comparing (314; 324; 403, 404, 406, 408; 503, 505, 506, 508) measured control parameters and respective predetermined threshold value; • if a measured control parameter and the respective predetermined threshold value deviates from each other, adjusting and/or maintaining (315; 325; 405, 407, 409; 504, 507, 509) the rotation speed during operation according to a first set of control process rules wherein the rotation speed is reduced when the vat pressure and linear load are below their respective maximum values to reduce the difference between the measured value and maximum value; • if a measured value of a linear load and/or vat pressure and the respective predetermined threshold value deviates from each other, adjusting (315; 405, 407, 409; 504, 507, 509) the distance between the press rolls during operation according to a second set of control process rules wherein the distance between the press rolls is decreased if the linear load is below the maximum level and the vat pressure is at the maximum level and the distance between the press rolls is increased if the vat pressure is below the maximum level and the linear load is at the maximum level, wherein said second set of control process rules are operated in synchronism with said first set of control process rules. • including (310; 320) the rotation speed of the press roll (102, 104) and the distance between the press rolls (102, 104) as variable operating parameters; • including (311; 321) vat pressure and linear load which acts on the pulp in the press nip as control parameters, each being associated with a predetermined threshold value wherein a desired maximum value is set as the predetermined threshold value for the respective control parameter; • measuring (313; 323; 402; 502) the control parameters; • comparing (314; 324; 403, 404, 406, 408; 503, 505, 506, 508) measured control parameters and respective predetermined threshold value; • if a measured control parameter and the respective predetermined threshold value deviates from each other, adjusting and/or maintaining (315; 325; 405, 407, 409; 504, 507, 509) the rotation speed during operation according to a first set of control process rules wherein the rotation speed is reduced when the vat pressure and linear load are below their respective maximum values to reduce the difference between the measured value and maximum value; • if a measured value of a linear load and/or vat pressure and the respective predetermined threshold value deviates from each other, adjusting (315; 405, 407, 409; 504, 507, 509) the distance between the press rolls during operation according to a second set of control process rules wherein the distance between the press rolls is decreased if the linear load is below the maximum level and the vat pressure is at the maximum level and the distance between the press rolls is increased if the vat pressure is below the maximum level and the linear load is at the maximum level,