Diatomaceous Earth Filter Aids with Low Crystalline Silica
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Solution Overview
Problem
Conventional methods for producing diatomaceous earth filter aids result in high levels of crystalline silica, which is a health risk, and fail to achieve a wide range of permeabilities, limiting the production of filter aids with permeabilities greater than 1.0 darcy while maintaining less than 1% crystalline silica by weight.
Innovation Solution
The method involves milling diatomaceous earth ore to a specific size range, calcining it at controlled temperatures between 900° C and 980° C for a controlled residence time, and further processing to achieve a wide range of permeabilities from 0.01 darcy to 20 darcy, all while minimizing crystalline silica formation through the use of uniform heating and adjustable milling and classification systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional calcining processes are used to produce diatomaceous earth filter aids, then the filter aids achieve adequate permeability, but the crystalline silica content increases to greater than 1% by weight
Solution Approach 1:
The patent applies parameter changes by precisely controlling calcining temperature (900-980°C range) and residence time (0.5-5 hours) to achieve the optimal balance between permeability development and crystalline silica minimization. This quantitative parameter optimization resolves the contradiction by finding the specific processing window where both requirements are satisfied.
Solution Approach 2:
The patent implements dynamics through adjustable milling and classification systems that can be dynamically tuned to produce different particle size distributions. This allows the same calcining process to produce filter aids with varying permeabilities (0.01 to 20 darcy) while maintaining low crystalline silica content, resolving the contradiction across multiple product specifications.
2Object-affected harmful factors
If efforts are made to reduce crystalline silica through flash calcining or eliminating calcining, then crystalline silica content decreases, but the range of achievable permeabilities is restricted
Solution Approach 1:
The patent applies segmentation by dividing the processing into distinct stages: controlled calcining to minimize crystalline silica, followed by separate milling and classification stages to achieve desired permeability. This multi-stage approach with independent control of each function resolves the contradiction by decoupling crystalline silica formation from permeability development.
Solution Approach 2:
The patent implements universality through a multi-functional processing system that can produce filter aids across the full permeability range (0.01 to 20 darcy) using the same low-crystalline-silica calcining process. The adjustable milling and classification equipment provides universal adaptability to meet different permeability requirements without compromising crystalline silica control.
3Quantity of substance
If calcining temperature and residence time are increased to achieve higher permeability, then permeability improves, but crystalline silica formation accelerates
Solution Approach 1:
The patent applies parameter changes by establishing the optimal calcining window of 900-980°C with residence times of 0.5-5 hours. This specific parameter range achieves sufficient permeability development through controlled sintering while minimizing the thermal conditions that accelerate crystalline silica formation, resolving the contradiction between these two competing requirements.
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 allows for the production of diatomaceous earth filter aids with permeabilities greater than 1.0 darcy and less than 1% crystalline silica by weight, overcoming previous limitations and achieving a broader range of permeabilities than previously possible.
Implementation Method 1
the addition of heat, such as in a conventional calcining step, causes some sintering of the diatoms, drives off the water of hydration, reduces the specific surface area of the particles
Implementation Method 2
the addition of heat, such as in a conventional calcining step, causes some sintering of the diatoms
Implementation Method 3
the conversion from amorphous silica to crystalline silica occurs at high temperatures, whether flux is added or not, and that the conversion is accelerated when a sodium-based flux is added
Data Source
AI summary
A method of producing a range of diatomaceous earth filter aids having selectable permeabilities and less than about 1 percent by weight total crystalline silica. The method includes milling diatomaceous earth ore to a size range of between about 100 micrometers and about 1400 micrometers; calcining the milled diatomaceous earth in a calciner; and milling the calcined diatomaceous earth in an adjustable milling and classification system to produce diatomaceous earth filter aids. Systems to implement such methods and compositions produced by such methods are also described.