Particle size distribution

What it is for

Tracking the particle size distribution of each stream: % retained per size class, % passing, P80, P50 and % passing at control sizes. It is required by the units that separate or produce size by model (hydrocyclone by the curve, ball mill, vibrating screen by aperture).

Projects without particle size do the mass and water balance only (and grades).

Turn on particle size

• In the new project wizard, step 2, tick Particle size; or
• Project ▾ → Particle size… → Turn on particle size.

When turned on, the project starts from the Grinding and concentration sieves.

The project sieve series

The project has one sieve series, used in every stream. Tick the sieves in the list (from 4" to 2500#, ASTM E11 apertures). Shortcuts:

Each shortcut ticks only those sieves.

• Mesh number: ASTM (default) or Tyler. The apertures are the same; the number changes for some sieves (0.212 mm is 70# in ASTM and 65# in Tyler). The choice also applies to the aperture shown on the screens.
• Control sizes: up to two, chosen from the sieves of the series. The stream table shows the % passing at these sizes (e.g. 0.150 mm in the grinding product, 10 µm for slimes, 0.045 mm in pellet feed).
• Ticking or unticking sieves rebuilds the Feed particle size distributions from what was typed in them: going back and forth does not accumulate error.

Why a single series? Mixtures add size class by size class. Different series per stream would require re-interpolating at every mixture.

Feed particle size distribution

In the Feed panel, under Particle size → Entry method, choose:

1. % retained per sieve — one % per sieve of the series and on the pan. The sum must be 100; Adjust to 100 % corrects small differences.
2. % passing at points — two or more points (aperture and % passing), with the aperture in mm, µm, inches or mesh. Useful for a lab report with sieves different from the project's. Between the points, the curve is interpolated on a log-log scale; beyond them, it follows the slope of the last two.
3. Curve (P80 and slope) — P80 and slope, by the Gates-Gaudin-Schuhmann or Rosin-Rammler model.

Switching the entry method converts what was there. The panel shows the feed P80 already on the project series.

Without the particle size distribution of a Feed with solids, the balance does not calculate. The summary asks you to enter it, as it does with the SG.

Results per stream

• Stream table: Particle size group, collapsible, with P80, P50, % passing at the control sizes and the % retained in each size class ("+ 200#", …, "Pan (− 400#)"), from the largest sieve to the smallest. Empty classes at the top and bottom, across all streams shown, are hidden.
• Stream panel: P80, P50 and control sizes; chart of % passing × aperture on a log-log scale, with the P80 marked and, dashed, the feed of the unit the stream comes from (it shows the cut of a cyclone or screen); and the table by size class (% retained, % passing and t/h).
• PDF: the stream table carries P80, P50 and control sizes. The particle size box (% retained per size class) is printed for the streams you tick in the Export PDF dialog.

P80 and P50 are read by log-log interpolation between the two neighboring sieves.

Units that use the particle size distribution

• Vibrating screen by particle size: aperture and undersize efficiency per deck.
• Hydrocyclone by the curve: split by size class from the corrected d50 and the sharpness.
• Ball mill: product with the specified P80 and modulus.
• The other units (mass splits, separators) apply the same split to all size classes.

Turn off particle size

Turn off particle size is refused while the project has a hydrocyclone by the curve, a ball mill or a screen calculated by aperture. Change or remove these units first.

Common warnings and limits

• A mill P80 finer than the smallest sieve of the series is refused: tick finer sieves.
• The top size class extends slightly above the largest ticked sieve. If the Feed material is coarser, tick larger sieves.
• Grade by size class does not exist yet (see Grades).
• 800#, 1250# and 2500# are not standard sieves; they are the nominal equivalents used in lab reports.