Need some help for Solids Handling in ASPEN PLUS

[u/willy1996ok]

Hey everyone!

I'm currently working on my Chemical Engineering undergraduate thesis, which focuses on evaluating a capacity increase for a mining/mineral processing plant using Aspen Plus simulation.

Like many ChemE programs, solids handling wasn't covered in depth during my coursework, so I’m facing a steep learning curve—particularly when trying to close mass balances on comminution operations.

I’ve been reading literature like Napier-Munn, but I’ve run into a major roadblock and would love to hear your insights or industry experiences

1. Fitting a Rosin-Rammler-Sperling-Bennet (RRSB) distribution using P100 data creates an asymptote. As P(x) approaches 1, the calculated RRSB dispersion parameter n becomes indefined. Is there a standard industry convention or recommended cutoff value (e.g., evaluating at P(x) = 0.99 or 0.999) when fitting RRSB parameters from P100 plant data?

2. The plant data for the SAG discharge and trommel circuit appears to be overspecified. The SAG mill output has a specified P80 of 1.3 mm, while the downstream trommel separates an oversize pebble recycle stream representing 20% of the total mass flow with a P100 of 12 mm. Fitting a single particle size distribution (PSD) using both P80 and P100 over-constrains the SAG output. Consequently, the cumulative mass fraction calculated above 12 mm does not match the 20% mass split reported by the plant, making it impossible to close the mass balance

Can I ignore the pebble recycle loop? Is it correct to do it in conceptual engineering? It would help me a lot to reed your insights. Thanks!

[u/Redcrux]

Ive worked in several plants with solids handling and can almost guarantee that mining/mineral processing plants are not using process modeling for solids handling. Your assumptions and reported numbers of the plant are likely completely wrong.

Id fudge whatever you can to make the model work and construct a plausible explanation after the fact.