Factory Scale Up in Milling of Raw Materials

By AZoNano.com Staff Writers

Topics Covered

Introduction
Common Areas of Inconsistency
Scale Up Idea
Accurate Quality Conclusions
Accurate Particle Analysis
Correlation Between Particle Size and Qualitiative Properties
Conclusion
About Hockmeyer Equipment Corporation

Introduction

It is a challenging task to reproduce dispersion in a production facility that has already been successfully done in the laboratory. Even after reaching the appropriate grind, the qualitative characteristics of a 7 Hegman produced in the factory may be different from that of a 7 Hegman from a laboratory.

The raw materials taken from the same lots and dispersions read the same value in a draw down on the grind gauge. This article discusses the factory scale-up in milling of raw materials and the measures required for improving scale-up consistency.

Common Areas of Inconsistency

Some common areas of inconsistency that can take place between the factory and the laboratory on a product with same raw materials and ratios:

  • Premix grinds are of different quality
  • Reading a grind gauge can be subjective
  • Media size, density, and wear may differ
  • Operating temperature of mill-base
  • Throughput rates/liter of media are different
  • Mill wear
  • Actual power input/liter of media. 

Scale Up Idea

One scale up idea examined recently is that of controlling the work input to mill-base to ascertain its consistency. There is an ambiguity in the conclusion of scale-up accuracy when other key aspects are not considered. Describing mill performance based on erroneously applied design criteria is risky. The scale problem is further complicated because of the introduction of an additional, deceptive baseline assessment due to the dependence on a grind gauge to support conclusions of quality, which expands the window of misleading conclusions.

Correcting for these aspects is essential to eliminate scale-up inaccuracy. There are several other factors of scale to be considered without increasing the complexity of the problem by using the inaccurately measured data. This approach can only result in many incorrect conclusions supported by failed reasoning.

Accurate Quality Conclusions

Accurate quality conclusions are one of the critical factors of scale up often overlooked. The accuracy of scale in the dispersion process is a function of the accuracy of measure and control of the particle distribution band within a fixed time. The accuracy of measure and control improve the certainty of the properties of the finished product.

Accurate Particle Analysis

Particle size analysis is an integral part of designing necessary scale-up techniques. The use of a particle analysis system enables a formulator to expect the quality control and scale-up assistance required for production accuracy. One can set formulation guidelines, pre-test raw materials for quality standards, benchmark production process times to anticipated particle standards, explore reports and document for historical libraries.

The advantage of this structured testing method is the ability to scale-up and improve development processes and to achieve repeatability in the production cycle and accuracy in research and development. Laser technology can provide 3D particle analyses with improved accuracy. Both visual and 3D measuring methods are inadequate in their ability to measure the size of non-spherical particles accurately. However, industrial particles to be measured are mostly non-spherical. Although the data generated by the two technologies vary slightly, their product quality predictability is much better than a hand-held grind gauge.

Correlation Between Particle Size and Qualitiative Properties

There is a positive correlation between particle size and qualitative characteristics of the dispersion. It is a challenging task to control the dispersion by following a particle distribution band. There are many different factors that can affect the homogeneity of the band. One broad area is ‘chemical’ wherein particles bond more or less intensely due to the influence of a foreign substance. Another broad area is ‘mechanical’ wherein particles bond more or less intensely due to the influence of an external force.

Energy uniformly applied to a wide particle distribution band is prone to narrow and shift the band as a function of time. The largest agglomerates continue to break down into tinier agglomerates until the energy needed to break them apart is no longer adequate. The reduction trend can be continued by increasing the energy input until the next stabilization level is achieved. The continual addition of homogenous energy input to the dispersion will pose a challenge to the inventiveness of the machinery designer to control the conversion of shear rate into shear stress without exceeding stress and temperature limitations of the dispersion.

The scale must be driven more by the quantifiable reproduction of particle distribution band per unit of time (performance) and the elimination of subjective variables. It is possible to design lab equipment to duplicate production equipment using quantifiable baselines. Machine makers can add the common baseline of particle size distribution into the performance data on dispersion equipment utilizing published, standardized formulas, which can become universal performance standards.

Users must be trained in the proper techniques of scale. Equipment makers can concentrate more on establishing uniform standards of scale and milling consistency instead of impressing users with the performance of a lab mill that can be reproduced in the factory.

Conclusion

The standardization of measure through these new technologies will assist manufacturers survive in a highly competitive industry, especially the integration of particle size analysis as a basis for scale and a measure of quality.

About Hockmeyer Equipment Corporation

Hockmeyer Equipment Corporation has been providing process solutions for over 70 years. It is a leader in the wet grinding and dispersion industry and offers custom designed process equipment for mixing, blending, dispersing and particle size reduction as fine as 25 nano-meters. The Hockmeyer Team is dedicated to building and designing processing equipment that is the highest quality available. Our goal is to increase the profitability of our customers through continuous innovations in process technology.

We are committed to learning our customer’s process so that we can provide the best possible equipment for the application. We will build equipment that is as efficient as possible to reduce the energy requirements, and therefore, the environmental impact of the industries we serve. Hockmeyer offers a state of the art customer service laboratory for product testing and process development.

This information has been sourced, reviewed and adapted from materials provided by Hockmeyer Equipment Corporation.

For more information on this source, please visit Hockmeyer Equipment Corporation.

Date Added: Mar 11, 2014 | Updated: Mar 14, 2014
Ask A Question

Do you have a question you'd like to ask regarding this article?

Leave your feedback
Submit