Chip Refiner Control via Fibre Filling Factor Estimation
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Solution Overview
Problem
Current methods for controlling wood pulp quality in chip refiners fail to effectively address the issues of insufficient or excessive fibre mass in the refining zone, leading to difficulties in loading the refiner and deterioration of pulp quality, as they do not account for the fibre mass in the refining zone.
Innovation Solution
A method that estimates the fibre filling factor by determining the mass of fibre in the refining zone and when the refiner is full, using this information to adjust operating parameters and maintain the refiner within a suitable operating range to avoid pulp quality deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydraulic pressure is increased to increase refiner motor load, then shear force on fibre increases and motor load increases, but fibre mass in refining zone may become insufficient leading to difficulties in loading refiner and deterioration of pulp quality
Solution Approach 1:
The invention implements feedback control by continuously monitoring the filling factor (ratio of actual fibre mass to maximum fibre mass in refining zone) and adjusting hydraulic pressure accordingly. When filling factor drops below threshold, hydraulic pressure is reduced to prevent fibre mass depletion; when filling factor is adequate, pressure can be increased to maintain motor load. This closed-loop feedback resolves the contradiction by dynamically balancing motor load requirements against fibre mass availability.
Solution Approach 2:
The system performs preliminary estimation of fibre mass in the refining zone using measurable parameters (production rate, residence time, density) before actual refining occurs. By calculating the filling factor in advance, the system can predict when fibre mass will become insufficient and adjust operating parameters proactively, preventing the deterioration of pulp quality before it occurs.
2Productivity
If refiner is operated beyond maximum motor load, then production capacity increases, but fibre cutting occurs and pulp strength properties are lost
Solution Approach 1:
The feedback mechanism monitors the filling factor and motor load simultaneously. When motor load approaches maximum capacity, the system checks whether adequate fibre mass (filling factor above threshold) is available to support higher loads. If fibre mass is insufficient, the system prevents motor load from exceeding safe levels, avoiding fibre cutting and strength loss. This resolves the contradiction by using real-time fibre mass information to gate production capacity increases.
Solution Approach 2:
The system dynamically changes operating parameters (hydraulic pressure, motor load setpoint) based on the calculated filling factor. When filling factor indicates sufficient fibre mass, parameters are adjusted to maximize production capacity. When filling factor drops, parameters are reduced to protect pulp strength. This adaptive parameter adjustment resolves the contradiction between productivity and strength by making production capacity a function of real-time fibre mass conditions.
3Power
If fibre mass in refining zone is insufficient, then refiner cannot be properly loaded, but increasing hydraulic pressure to compensate causes fibre cutting and quality deterioration
Solution Approach 1:
The feedback control system uses filling factor as a key indicator of fibre mass status. When filling factor drops below the threshold, the system automatically reduces hydraulic pressure to prevent fibre cutting, even if this means accepting lower motor load. This resolves the contradiction by prioritizing fibre integrity over maximum loading when fibre mass is insufficient, using real-time monitoring to prevent harmful effects.
4Ease of operation
If empirical corrective measures and plate gap adjustments are used to address loading difficulties, then refiner operation can be maintained, but the problem is not corrected at the source and requires continuous manual intervention
Solution Approach 1:
The system implements self-service control by automatically calculating the filling factor from readily available process data (production rate, residence time, density) and autonomously adjusting hydraulic pressure and motor load without operator intervention. The refiner monitors its own fibre mass status and corrects loading issues automatically, eliminating the need for continuous manual plate gap adjustments and reducing operational complexity.
Solution Approach 2:
The invention replaces manual mechanical adjustments (plate gap changes) with an automated control system based on computational estimation and electronic control of hydraulic pressure. By substituting mechanical intervention with an automated feedback loop, the system simplifies operation while providing more precise and timely corrections to loading issues.
Data Source
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AI summary
A method has been developed that estimates from the on line measurements of readily available process variables the proportion of the mass of fibre in the refining zone of a chip refiner relative to the mass with a full refining zone. This estimate of the filling factor is used to determine the margin available to load the refiner and the control action needed to avoid abnormal operation.