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In solid-liquid separation selection there is no “one size fits all” process solution. I began this blog back in 2015 saying, with a nod to Sherlock Holmes, we have to avoid “jumping to conclusions.” That’s because selecting a separation technology requires a systems approach. We must incorporate our solution with other solids processing equipment such as reactors, dryers, solids handling, etc.   

All this means that before selection we must look at the universe of technologies for bulk separation available. We also have to consider which high solids slurries we’re working with and whether the production process is for a chemical, pharmaceutical, battery chemical, or other application. The many separation technologies include:

  • Nutsche Filter-Dryer
  • Rotary Pressure Filter
  • Indexing Vacuum Belt Filter
  • Rubber Belt Filter
  • Rotary Vacuum Drum Filter
  • Candle Filter
  • Pressure Plate Filter
  • Filter Press
  • Pressure Leaf
  • Tower Press
  • Backwashing Rotating Screen Filter
  • Decanter Centrifuges
  • Pusher Centrifuges
  • Batch Peeler Centrifuges

Each of these is more fully discussed in my Handbook of Solid-Liquid Filtration. In the meantime, though P&ID has developed a matrix to help guide your decision-making process. We’ve made the Decision Matrix available here for download as a pdf, free of charge, for your use.

Separation Selection Systemized with Matrix

Let me provide a quick overview. The Decision Matrix has three main components: material properties, mechanical properties of the technology, and then the separation technology performance. To use the matrix, you’ll complete each box relevant to your application and then discuss your options. Evaluate your ranked choices with operational, economic, and plant (internal and external) objectives in mind.

For solids, the engineer will need to know the total suspended solids (TSS) and solids concentration, particle size distribution (PSD), and particle shape. The PSD should be based upon particle counts at different sizes rather than by weight or volume. For example, the particle shapes can be spherical, rounded, angular, flaky, or thinly flaked. These shape variations will influence the filtration rates for the process. The shapes will also impact the PSD due to the nature of particle size measuring equipment.

Your selection of the right solid-liquid separation technology also requires a holistic systems approach. This means incorporating your selection with other solids processing such as reactors, dryers, and solids handling, etc. Your full scope includes the actual upstream and downstream equipment. My book, Integration & Optimization of Unit Operations, discusses holistic chemical engineering with topics ranging from reaction/fermentation to equipment, controls, techno-economic evaluations, and project management.

Please let me know if this new tool is helpful to you. P&ID is also here to help you to complete this Decision Matrix to meet your process needs. Contact me if you want an Excel version of this matrix.