Sludge processing system and storage medium storing a program for controlling an operation of a sludge processing system thereon

A sludge processing system comprising:

• a centrifugal separator which concentrates the sludge,
• a furnace which heat-treats the concentrated sludge, and
• an automatic control device which receives, from the furnace, the information regarding a heat-treatment state of the concentrated sludge and, controls the centrifugal separator based on the received information,
• wherein the centrifugal separator includes a bowl by which centrifugal force is applied to the sludge so as to separate the sludge into the concentrated sludge and the separated liquid, a screw conveyor to convey the concentrated sludge contained in the bowl to an exhaust port, a drive motor to rotate the bowl, a differential speed generator to cause the screw conveyor to rotate at a differential speed relative to the bowl,
• wherein the information received from the furnace to the automatic control device include a moisture content of the concentrated sludge fed into the furnace and, VTS/TS (Volatile Total Solids/Total Solids) or the information required to compute the VTS/TS of the concentration sludge, the automatic control device determines either a current target value of the moisture content is maintained or a new target value is set based on VTS/TS of the concentrated sludge and controls as follow (a) to (c):
• (a) the automatic control device previously stores the information indicative of a correlation relationship between a moisture content of the concentrated sludge and the centrifugal force and a concentrated sludge convey torque, sets a variable range of a differential speed between the bowl and the screw conveyor, operates the centrifugal force determined based on the VTS/TS, and performs a variable control of the differential speed so that the concentrated sludge convey torque of the screw conveyor achieves a torque corresponding to the target moisture content within the variable range,
• (b) the automatic control device performs the variable control of the differential speed so that, when the differential speed varies within a certain range being previously set and the concentrated sludge convey torque of the screw conveyor maintains the torque corresponding to the target moisture content for a certain period of time being previously set, a control value of the centrifugal force is decreased as well as the concentrated sludge convey torque achieves a torque corresponding to the target moisture content in the centrifugal force being set to the new control value, and
• (c) the automatic control device performs the variable control of the differential speed so that, when the differential speed remains at a minimum value within the variable range and the concentrated sludge convey torque of the screw conveyor is lower than the torque corresponding to the target moisture content, the control value of the centrifugal force is increased as well as the concentrated sludge convey torque achieves a torque corresponding to the target moisture content in the centrifugal force being set to the new control value.

A storage medium storing a program for controlling an operation of a sludge processing system, the sludge processing system comprising:

• a centrifugal separator which concentrates the sludge,
• a furnace which heat-treats the concentrated sludge, and
• an automatic control device which receives, from the furnace, the information regarding a heat-treatment state of the concentrated sludge and, controls the centrifugal separator based on the received information,
• wherein the centrifugal separator includes a bowl by which centrifugal force is applied to the sludge so as to separate the sludge into the concentrated sludge and the separated liquid, a screw conveyor to convey the concentrated sludge contained in the bowl to an exhaust port, a drive motor to rotate the bowl, a differential speed generator to cause the screw conveyor to rotate at a differential speed relative to the bowl,
• wherein the information received from the furnace to the automatic control device include a moisture content change request regarding the concentrated sludge, and
• wherein, in response to the moisture content change request, the program for controlling the operation of the sludge processing system causes the automatic control device to perform as follow (a) to (c):
• (a) the automatic control device previously stores the information indicative of a correlation relationship between a moisture content of the concentrated sludge and the centrifugal force and a concentrated sludge convey torque, sets a variable range of a differential speed between the bowl and the screw conveyor, and performs a variable control of the differential speed so that the concentrated sludge convey torque of the screw conveyor achieves a torque corresponding to a moisture content requested by the furnace within the variable range,
• (b) the automatic control device performs the variable control of the differential speed so that, when the differential speed varies within a certain range being previously set and the concentrated sludge convey torque of the screw conveyor maintains the torque corresponding to the moisture content requested by the furnace for a certain period of time being previously set, a control value of the centrifugal force is decreased as well as the concentrated sludge convey torque achieves a torque corresponding to the moisture content requested by the furnace in the centrifugal force being set to the new control value, and
• (c) the automatic control device performs the variable control of the differential speed so that, when the differential speed remains at a minimum value within the variable range and the concentrated sludge convey torque of the screw conveyor is lower than the torque corresponding to the moisture content requested by the furnace, the control value of the centrifugal force is increased as well as the concentrated sludge convey torque achieves a torque corresponding to the moisture content requested by the furnace in the centrifugal force being set to the new control value.