A roll-type coal-dust press brings two synchronized, pocketed rolls together to compact fine material into briquettes. Matching half-pockets form one cavity at the nip. This calculator counts those cavity opportunities and shows how roll speed, diameter and pocket arrangement relate.
Separate positioning actuators
The illustrated rolls have a rotary drive. This calculator does not size that drive or the force needed to compact coal. If a separate linear actuator positions auxiliary equipment, size it from that component’s load, mounting geometry, travel and cycle requirements.
For a FIRGELLI positioning actuator, consult the power-supply sizing guide and duty-cycle calculator, then check the exact specifications in the linear actuator range. These links do not establish suitability for the roll press, its compaction load or a coal-dust environment.
Coal Dust Press Interactive Calculator
Adjust diameter, circumferential pockets per row, roll speed and the number of rows across the roll width. The calculator reports an ideal cavity-count rate, circumferential speed and pitch. It does not predict mass output or briquette strength.
Equation Used
- Matching pockets remain in phase on equal-diameter counter-rotating rolls.
- Uniform circumferential spacing and identical rows.
- Complete filling and no rejected or broken briquettes for the ideal rate.
- No pressure, binder or strength prediction.
The synchronized pair forms one cavity per matching pair of half-pockets. Ideal count assumes complete filling and no losses. Pocket shape, feed flow and discharge are schematic; compaction pressure, material behavior, strength and mass throughput are not calculated.
Two registered rolls and one forming cavity
The rolls turn in opposite directions so their facing surfaces draw feed downward. Their pockets are indexed: each pocket on one roll meets its counterpart on the other. The animation shows an end section through one row, with the surrounding covers omitted to expose the mechanism.
The green marks identify one matching pair. Recesses around the roll perimeter are pocket halves, not meshing gear teeth. The lower diagram unwraps a short strip of one roll surface: columns represent the entered rows across the width. It is an explanatory surface map, not a second pair of rolls.
KOMAREK describes registered matching pockets and either gravity or screw feeding for its roll-press arrangements. Here the hopper and falling shapes show the material route schematically. Their dimensions and motion do not calculate fill, deformation or release dynamics.
Roll briquetting of fines
Pocketed rolls are used to agglomerate fine materials, including coal fines. Material preparation, binder use, temperature and tooling depend on the feed and desired briquette. A particular moisture, binder percentage or compaction pressure cannot be inferred from the four inputs in this tool.
The illustration is a rotary roll press. Historical reciprocating ram presses and ring-die pellet mills have different motion and output relationships.
Count whole cavities, not pocket halves
For N circumferential pockets per row, n revolutions per minute and R axial rows, ideal cavity rate = NnR. Each matched pair contributes one cavity. There is no additional factor of two for the second roll.
Per-row rate is Nn. With diameter D in millimetres, circumferential surface speed is πDn/1000 m/min, and circumferential pocket pitch is πD/N millimetres. Diameter affects pitch and surface speed, while the cavity-count rate stays fixed if N, n and R are unchanged.
Actual saleable briquette output also depends on filling, breakage and downstream losses. A mass rate requires briquette mass and yield; neither is supplied here.
Worked pocket-count example
A 1000 mm roll with 80 pockets per row at 12 rpm presents 960 cavities/min in one row. Three rows present 2880 cavities/min. The roll surface speed is 37.70 m/min and pocket pitch is 39.27 mm.
Increasing diameter to 1200 mm, while keeping the pocket count and rpm, raises surface speed to 45.24 m/min and pitch to 47.12 mm. It does not create additional pockets or increase the ideal count rate.
Use the outputs for geometric comparisons
More rows or circumferential pockets increase the ideal count at a fixed rpm. More circumferential pockets on the same diameter reduce pitch. Changing diameter changes the spacing and peripheral speed. The animation draws the actual entered number of recesses around each roll, with simplified pocket shape.
These relationships do not establish allowable speed, compaction pressure, material strength, tooling life, machine price or a guaranteed production rate. Input ranges and pictured pocket proportions are illustrative rather than a machine specification.
Coal-dust press calculator questions
Should I double the rate because there are two rolls?
No. One half-pocket on each roll forms one complete cavity. Count pairs, not individual halves.
Why does a larger diameter leave the count rate unchanged?
At fixed pocket count, rows and rpm, the same number of cavities passes the nip each minute. Diameter changes surface speed and pocket pitch.
Are the rows extra pockets around the circumference?
No. Rows are distributed across the roll width. The unwrapped surface panel shows them as separate columns.
Does ideal cavity rate equal actual briquettes delivered?
Only in the assumed fully filled, loss-free case. Material feed, filling, deformation, release, breakage and processing losses can reduce actual output.
References & further reading
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