Pulp Tower White Water Separation for Effluent Reduction
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Solution Overview
Problem
Pulp mills face challenges in minimizing water consumption and effluent production, particularly during situations where excess water from pulp drying cannot be recycled back to the fiberline, leading to increased water usage and effluent handling needs.
Innovation Solution
A method and system that involve storing pulp from the fiberline in a first pulp tower, directing it to pulp drying, and storing white water from drying into a first water tower. When the fiberline cannot receive the white water, it is diverted to a second pulp tower where it remains separated from the pulp, and when conditions allow, it is evacuated and returned to the first pulp tower, ensuring continuous operation and balanced water usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If excess white water from pulp drying is diverted to effluent when fiberline cannot receive it, then water consumption and effluent handling need increase, but this provides a simple solution for managing excess water
Solution Approach 1:
A second pulp tower is introduced as an intermediary storage facility between the water tower and effluent discharge. This intermediate tower allows excess white water to be temporarily stored and later transferred back to the water tower when capacity is available, rather than being immediately discharged to effluent. The second pulp tower acts as a buffer that decouples the water recycling system from direct effluent discharge.
Solution Approach 2:
The system performs preliminary storage of excess white water in the second pulp tower before final effluent discharge is considered. By preemptively capturing and storing excess water in the intermediate tower, the system prepares for future recycling opportunities, preventing premature effluent discharge and reducing overall water consumption and effluent volume.
2Device complexity
If white water is stored in a pulp tower with pulp of certain consistency, then the white water and pulp remain substantially separated in different layers, but this requires a second pulp tower with specific pulp consistency
Solution Approach 1:
The second pulp tower is assigned a specific local quality - containing pulp with consistency of about 3.5 to 12% - that is different from the first pulp tower. This localized difference in pulp consistency creates the necessary density gradient that allows white water to remain separated from pulp in distinct layers, enabling the tower to function as a water storage facility while maintaining pulp integrity.
Solution Approach 2:
Instead of mixing white water with pulp to store excess water (as in conventional pulp towers), the system inverts the approach by using a pulp tower where white water and pulp remain separated. The white water forms a separate layer above the pulp, allowing the tower to store white water without compromising pulp quality or requiring mixing operations.
3Measurement precision
If a measurement element is used to monitor white water consistency in the second pulp tower, then accurate detection of white water evacuation status is achieved, but this increases system complexity
Solution Approach 1:
A measurement element is installed in the second pulp tower to continuously monitor the consistency of the pulp-white water mixture. This measurement system provides feedback on the white water storage level and evacuation status, enabling automated control of the system. When the measured consistency indicates that white water has been substantially emptied from the second tower, the system automatically initiates evacuation operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces water usage and effluent production, maintains uninterrupted pulp drying operations, and enhances environmental sustainability by optimizing water circulation and minimizing effluent handling needs.
Implementation Method 1
directing the white water to second pulp tower comprising pulp with such consistency that the white water and the pulp remain substantially separated in different layers in the second pulp tower
Data Source
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AI summary
A method and system for control of flows of in a pulp mill, comprising storing pulp from fiberline in a first pulp tower (10); directing the pulp from the first pulp tower (10) to pulp drying; storing white water from the pulp drying into a first water tower (30) and directing the water therefrom back to the fiberline; and when the fiberline is not able to receive the white water from the first water tower (30), directing the white water to second pulp tower (10) comprising pulp with such consistency that the white water and the pulp remain substantially separated in different layers in the second pulp tower (20).