In-Line Milk of Lime Production for PCC Crystallization
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Solution Overview
Problem
In-line production of milk of lime for precipitated calcium carbonate (PCC) in the paper industry faces challenges due to particle size deviations and agglomeration issues, which affect the efficiency and quality of PCC production, particularly when produced directly in the fibrous web machine, as existing methods require lengthy settling times and storage, leading to suboptimal crystallization and increased crystal size deviations.
Innovation Solution
A method and apparatus for in-line production of milk of lime using a rotating comminuting apparatus to achieve fine particle sizes quickly, followed by immediate processing to prevent agglomeration, ensuring efficient energy and water usage, and incorporating a cyclone cleaning system to separate oversized particles, allowing for direct introduction into the fibrous web machine's approach system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If milk of lime is stored in a tank waiting for further use, then the production process can be continuous, but calcium hydroxide agglomerates grow which degrades the quality of milk of lime
Solution Approach 1:
The patent applies preliminary action by performing comminuting of calcium hydroxide particles immediately before use, rather than storing them. The mill disintegrator continuously comminutes the particles in the milk of lime stream right before it enters the PCC production process, ensuring particles remain fine and uniform without agglomeration even during continuous operation
Solution Approach 2:
The patent implements continuity of useful action by integrating the mill disintegrator into the continuous flow line between milk of lime production and PCC production. The comminuting action continues throughout the entire process without interruption, maintaining constant particle size reduction and preventing agglomeration while enabling continuous production
2Ease of manufacture
If an excess of water is directed into the impact mill disintegrator, then quick lime slaking is facilitated, but comminuting of calcium carbonate is impaired due to dampening and lubricating effect
Solution Approach 1:
The patent segments the water addition process into two distinct stages: first, a limited amount of water is added in the impact mill disintegrator to facilitate slaking while maintaining comminuting efficiency; second, the remaining water is added in the post-slaker tank after comminuting is complete. This segmentation allows each stage to optimize its function without interfering with the other
Solution Approach 2:
The patent applies preliminary action by completing the comminuting operation in the impact mill disintegrator before adding the majority of water in the post-slaker. This ensures that particle size reduction occurs when mechanical action is most effective, before water dampening and lubricating effects would interfere with the comminuting process
3Ease of manufacture
If a large mixer and slaking tank are used for slaking quick lime, then slaking can be completed, but the process requires large space and time for settling and separation
Solution Approach 1:
The patent replaces the traditional large mechanical mixer and settling tank system with a mill disintegrator that combines comminuting and slaking functions in one compact unit. The mill disintegrator uses mechanical impact and attrition forces to both reduce particle size and facilitate slaking, eliminating the need for separate large mixing vessels and subsequent settling tanks
Solution Approach 2:
The patent applies universality by designing the mill disintegrator to perform multiple functions simultaneously: it comminutes calcium oxide particles, facilitates slaking with water, and separates fine calcium hydroxide particles from unreacted material all in one device. This multi-functionality consolidates what traditionally required multiple large pieces of equipment into a single compact unit
4Manufacturing precision
If settling is performed for tens of minutes to separate impurities, then impurity removal is achieved, but production time increases and particle size deviations worsen
Solution Approach 1:
The patent applies preliminary action by performing comminuting of all particles including potential impurities in the mill disintegrator before the settling stage. This preliminary comminuting breaks down any oversized particles or agglomerates that would otherwise require lengthy settling to separate, enabling faster and more effective impurity removal in the subsequent settling tank
Solution Approach 2:
The patent applies parameter changes by using the mill disintegrator to dramatically reduce particle size and create a more uniform particle size distribution before settling. This parameter change in particle size enables the settling process to separate impurities much more quickly, reducing settling time from tens of minutes to a fraction of that time while maintaining or improving separation effectiveness
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 enables rapid and efficient production of milk of lime with particle sizes optimized for quick dissolution, reducing reaction time and crystal size deviations, thus enhancing the quality and yield of PCC while minimizing energy and water consumption.
Implementation Method 1
a rotating comminuting apparatus (50) forming a first part of the slaking apparatus and creating large shearing forces
Implementation Method 2
creating large shearing forces
Implementation Method 3
as the calcium oxide reacts with water, it is converted to calcium hydroxide (Ca(OH)2). Simultaneously heat is released
Implementation Method 4
it is converted to calcium hydroxide (Ca(OH)2). Simultaneously heat is released
Implementation Method 5
incorporating a cyclone cleaning system to separate oversized particles
Data Source
AI summary
A method and apparatus for in-line production of milk of lime into an in-line production process of PCC arranged in connection with a fibrous web machine. In the solution, lime is slaked in a slaking apparatus at a temperature of at least 80 degrees. The produced milk of lime is cleaned by separating excessively large calcium hydroxide particles immediately prior to introducing the milk of lime into the production process of PCC. The milk of lime is introduced into the in-line production process of PCC located in the production line of the end or intermediate product of the fibrous web machine.