Method for monitoring and controlling water content in paper stock in a paper making machine
AssigneeHoneywell-Measurex Corporation
InventorsHung-Tzaw Hu, Francis Tu
Life of this patent
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Abstract
A method of predicting the dry stock weight of paper that is produced by a papermaking machine based on simultaneousness measurements of (1) the water weight of the paper stock on the fabric or wire of the papermaking machine and of (2) the dry stock weight of the paper product is provided. The invention which provides a linearized model of the de-watering process is based in part on that creation of drainage characteristic curves that provides an effective means of predicting the drainage behavior of the paper stock on the fabric of a de-watering system.
Claims22
A method of predicting the dry stock weight of a sheet of material that is on a moving water permeable fabric of a de-watering machine that includes a dryer section located downstream from the water permeable fabric said method comprising the steps of:
- a) placing three or more water weight sensors adjacent to the fabric wherein the sensors are positioned at different locations in the direction of movement of the fabric and placing a sensor to measure the dry weight of the sheet material after exiting the dryer section;
- b) operating the machine at predetermined operating parameters aid measuring the water weights of the sheet of material at the three or more locations on the fabrics with the water weight sensors and simultaneously measuring the dry weight of a part of the sheet of material exiting the dryer section;
- c) performing bump tests to measure changes in water weight in response to perturbations in three or more operating parameters wherein each bump test is performed by alternately varying one of the operating parameters while keeping the others constant, and calculating the changes in the measurements of the three or more water weight sensors and wherein the number of bump tests correspond to the number of water weight sensors employed;
- d) using said calculated changes in the measurements from stop c to obtain a N.times.M matrix that expresses changes in the three or more water weight sensors as a function of changes in the three or more operating parameters about the predetermined operating parameters wherein N is equal to the number of water weight sensors employed and M is equal to the number of bump tests performed and N is equal to or greater than M;
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- e) developing an inverted N.times.M matrix that provides the predicted dry weight for a segment after being dried in the dryer section based on measurements from the three or more water weight sensors for said segment of the sheet of material on the moving fabric.
A method of controlling the dry stock weight of a sheet of material that is on a moving water permeable fabric of a de-watering machine that comprises the steps of:
- a) placing three or more water weight sensors adjacent to the fabric wherein the sensors are positioned on different locations along the direction of movement of the fabric;
- b) operating the machine at predetermined parameters and measuring the water weights of the sheet of material with the sensors;
- c) performing bump tests to measure changes in water weights in response to perturbations in three or more operating parameters wherein each bump test is performed by alternately varying one of the operating parameters while keeping the others constant, and calculating the changes the measurements of three or more water weight sensors, wherein the number of bump tests corresponds to the number of sensors employed;
- d) using said calculated changes in the measurements from step C to obtain an N.times.M matrix that expresses changes in the three or more water weight sensors in response to changes in the three or more operating parameters about the predetermined operating parameters wherein N is equal to the number of sensors employed and M is equal to the number of bump tests performed and N is equal to or greater than M;
- e) inverting the matrix to derive a functional relationship which correlates changes in measurements from the three or more operating parameters to changes in the three water weight sensors;
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- f) employing said inverse function for controlling operation of the dewatering machine to produce a sheet of material having a desired dry stock weight.
Dependencies are inferred from the claim text.