Selective mining
Separate clay horizons and contaminants. Blend lots to stabilize montmorillonite, swelling, color and moisture.
BENTONITE POWDER ENGINEERING GUIDE
Designing a stable bentonite grinding process.
A process-led reference for mineral identification, moisture control, crushing, conveying, dry grinding, air classification and application-specific powder design.
- Smectite clay
- Layered, water-sensitive mineral
- 5-74 um
- CRGM catalogue product range
- 50+ years
- Manufacturing heritage
01Know the clay
02Control moisture
03Define the PSD
04Validate performance
01 / Mineral fundamentals
Bentonite is a functional clay, not merely a fine filler
Bentonite is a clay-rich material dominated by smectite minerals, commonly montmorillonite. Its layered crystal structure carries exchangeable cations and can adsorb water between layers. That mechanism gives useful swelling, thixotropy, binding and adsorption behavior.
Sodium bentonite generally develops stronger swelling and gel formation, making it important in drilling fluids, geosynthetic clay liners and slurry walls. Calcium bentonite usually swells less but can offer useful adsorption and bleaching behavior. Sodium activation with soda ash may improve selected calcium clays, but dosage, aging and moisture must be tested rather than assumed.
Grinding exposes more surface area and improves dispersion, yet excessive heat, uncontrolled drying, soluble salts or over-grinding can change hydration and rheology. A successful plant therefore protects the clay's function, not just its mesh number.
02 / Global occurrence
Commercial deposits occur across several geological belts
The chart is a qualitative supply-intensity guide compiled from public geological summaries. Bentonite statistics are reported with different scopes by country, so it is not presented as a market-share table.
Reference context: USGS clay statistics and national geological reporting. Confirm the current annual tonnage and whether “bentonite” includes fuller's earth or other clays before commercial use.
Deposit origin predicts process behavior
Wyoming-type sodium deposits, Mediterranean calcium deposits and Asian volcanic-ash clays can differ in swelling, grit, iron, carbonate, moisture and activation response. Representative bench testing is the first sizing step.
Data discipline: Production tonnage is revised annually and definitions vary. For a published market report, insert the latest USGS Mineral Commodity Summaries - Clays table and state the exact year and units.
03 / Process engineering
A dry bentonite line has six linked control points
Moisture management is usually the key difference between a generic mineral line and a reliable clay line.
Primary crushing
Break lumps gently to a uniform feed while limiting metal and stone contamination.
Activation / aging
When required, meter soda ash or another modifier and allow controlled moisture-assisted reaction time.
Controlled drying
Reduce free moisture without overheating the clay. Dryer temperature is not the same as product temperature.
Grinding
Compression and shear reduce the prepared feed; steady metering prevents mill load and PSD swings.
Classification
Return coarse particles, collect on-size powder under negative pressure, then blend or pack by grade.
CRGM grinding circuit in operationCompact web video with a persistent Cronus identification layer.
Clay stockpile
→
Crusher
→
Dryer / conditioner
→
CRGM mill
→
Classifier & collector
Optional activation can occur before drying or during conditioning. The best sequence depends on clay chemistry and the customer's performance test.
Sticky feed can bridge bins, coat rollers and destabilize the classifier. Measure free moisture by lot.
Aggressive drying may reduce rehydration performance. Track product temperature and final application results.
Quartz and hard inclusions drive wear and coarse residue. Screening or pre-separation may be economical.
Fine clay is easily airborne. Enclosed transfer, negative pressure and pulse filtration are core process equipment.
04 / Powder design
Fineness should follow the application test
Mesh values are approximate screening references. Critical contracts should use laser PSD D-values, sieve residue and a named functional test.
| Typical powder band | Application examples | Why the range is used | Verify beyond fineness |
|---|---|---|---|
| 80-200 mesh 180-75 um reference | Cat litter granulation feed, low-cost absorbent, civil-engineering blends | Preserves throughput and granule structure where rapid dispersion is unnecessary. | Absorption, dust, granule strength, moisture |
| 200-325 mesh 75-45 um reference | Foundry bonding, iron-ore pelletizing, drilling-fluid base grades | Provides dispersible surface area while keeping process cost and dust manageable. | Wet compression strength, pellet drop, yield point, API tests |
| 400-800 mesh 38-18 um reference | Construction rheology, coatings, adhesives, agricultural carriers | Lower grit and faster wet-out improve smoothness, suspension and formulation consistency. | Residue, viscosity curve, gel strength, color |
| 1250-2500 mesh 12-5 um reference | Specialty rheology, polymer and paper formulations, purified or modified clay systems | High surface area and low coarse tail can improve finish and dispersion, but only if platelets remain functional. | D10/D50/D90, surface treatment, purity, dispersion energy |
Drilling & geotechnics
Hydration, filtrate control and gel structure matter more than headline mesh.
Foundry & pelletizing
Binder performance is measured in green strength, hot behavior and pellet durability.
Construction & coatings
Low grit, repeatable rheology and easy dispersion protect surface quality.
Paper & specialty clay
Purity, brightness, particle distribution and modification route become decisive.
Important: finer is not automatically better. Over-grinding can increase dust, energy demand and formulation viscosity without improving the customer's final test.
05 / Equipment selection
Raymond mill, ball mill or CRGM ring roller mill?
Select the circuit from feed behavior, target PSD, contamination tolerance, capacity and maintenance strategy.
Robust conventional powder
- Commonly used for roughly 80-400 mesh products.
- Simple layout and familiar maintenance.
- Strong fit for general bentonite grades with moderate residue targets.
- Fine-end capacity can decline rapidly as the cut point tightens.
Choose it when: the market accepts a conventional PSD and capital simplicity is the priority.
Flexible large circuit
- Can operate with a separate dynamic classifier.
- Large installation and media inventory deserve review.
- Potential iron contamination and over-grinding must be assessed.
- Useful where ball-mill infrastructure already exists.
Choose it when: plant scale, existing utilities or a specific impact/attrition profile justify the footprint.
Dry ultrafine closed circuit
- Multi-stage compression and shear in a compact main unit.
- Integrated high-efficiency classifier controls the coarse tail.
- Catalogue range covers 5-74 um for CRGM80/100 and 7-74 um for CRGM125.
- No grinding media charge; wear system centers on rollers and rings.
Choose it when: ultrafine PSD control, compact layout and multi-grade production are central.
Target mainly 80-325 mesh?Start by comparing Raymond and CRGM on tested capacity and kWh/t.
Need D97 near 10 um or below?Prioritize classifier performance, feed moisture and full PSD testing.
Clay is sticky or above moisture limit?Design drying and feed conditioning before selecting nominal mill power.
Application is performance-certified?Run customer-specific swelling, rheology, foundry or pellet tests on trial powder.
06 / CRGM technical data
CRGM80, CRGM100 and CRGM125
Catalogue values below are reference ranges, not a bentonite performance guarantee. Moisture, mineralogy and target PSD can materially change output.
Compact production
- Ring diameter
- 800 mm
- Ring / rollers
- 3 / 21
- Main shaft
- 230-240 rpm
- Product range
- 5-74 um
- Catalogue capacity
- 0.5-4.5 t/h
- Total power
- 143 kW
Balanced multi-grade line
- Ring diameter
- 1000 mm
- Ring / rollers
- 4 / 28
- Main shaft
- 180-200 rpm
- Product range
- 5-74 um
- Catalogue capacity
- 1.8-5 t/h
- Total power
- 244 kW
Higher-throughput platform
- Ring diameter
- 1250 mm
- Ring / rollers
- 4 / 32
- Main shaft
- 135-155 rpm
- Product range
- 7-74 um
- Catalogue capacity
- 1.5-12 t/h
- Total power
- 401 kW
| Parameter | CRGM80 | CRGM100 | CRGM125 |
|---|---|---|---|
| Maximum feed size | 20 mm | ||
| Overall dimensions (L x W x H) | 15.9 x 4.2 x 6.1 m | 19.7 x 4.7 x 7.7 m | 23.2 x 4.7 x 7.7 m |
| Main unit power | 75 kW | 132 kW | 185 kW |
| Classifier power | 18.5 kW | 30 kW | 75 kW |
| Blower power | 45 kW | 75 kW | 132 kW |
| Discharge valve | 0.75 x 2 kW | 1.1 kW | 1.5 kW |
| Screw conveyor | 3 kW | 4 kW | 4 kW |
Source: Cronus Grinding Mill Catalog, CRGM technical parameter tables. Capacity must be confirmed against representative bentonite, feed moisture, required residue and agreed test method.
07 / Working principle
Multi-stage grinding with closed-circuit classification
The main motor drives stacked turnplates. Rollers travel against fixed grinding rings, and prepared bentonite is dispersed by centrifugal force through successive grinding zones. Compression, shear and particle-to-particle interaction reduce the material.
A high-pressure blower carries fine particles upward to the classifier. The variable-speed rotor releases particles below the selected cut point; coarse particles lose lift and return for another pass. Cyclones and a pulse bag filter recover product while maintaining negative pressure.
01 Adjustable classifier speed
02 Coarse-particle recirculation
03 No loose grinding media
04 Enclosed dust collection
05 VFD-based process control
06 Multi-layer roller-ring contact
08 / Engineering features
What the CRGM architecture contributes
Claims are framed as design features. Project results still depend on feed and operating conditions.
Precise coarse-tail control
A vertical turbine classifier and variable speed help tune the cut point without changing the grinding chamber.
Compact dry circuit
Main unit, classifier, cyclone, bag filter, fan and conveying form an integrated negative-pressure line.
Wear-focused maintenance
Rollers, rings, pins and classifier parts are accessible, traceable consumables rather than an uncontrolled media charge.
Recipe flexibility
Feed rate, classifier speed and airflow can be recorded as repeatable recipes for multiple saleable grades.
Fine product potential
The catalogue states one-pass product potential down to D97 less than or equal to 5 um under suitable conditions.
Noise-management options
Sound-insulation room and muffler design can reduce transmission from the fan and grinding system.
09 / Project evidence
Built equipment, customer sites and process testing
Photos are from Cronus-owned project and factory archives. Final bentonite selection requires a material-specific test; these images document manufacturing and installation capability.
A useful bentonite trial report should include
FeedSource, moisture, grit, swelling index, montmorillonite proxy
PowderD10/D50/D90, sieve residue, moisture and bulk density
ProcessFeed rate, classifier speed, airflow, temperature and kWh/t
FunctionAPI, foundry, pellet, absorption or customer formulation test
10 / Wear parts
Original parts with known fit and metallurgy
Cronus supplies the components that determine availability and powder consistency. The company has its own casting capability and dimensional records for original equipment, helping balance quality, lead time and lifecycle cost.
Visit the main product catalogueGrinding rollers & ringsMatched profiles and selected wear materials for stable pressure distribution.
Classifier rotor & bladesBalanced replacement parts protect cut-point repeatability.
Pins, shafts & turnplatesOriginal dimensions reduce field fitting and alignment time.
Gearbox & drive itemsModel-matched parts and documented installation support.
Filter bags & pulse valvesConsumables selected for clay dust load and operating temperature.
Feed and discharge partsValves, screws and feeder components support stable mass flow.
11 / About Cronus
Shanghai response, Guilin manufacturing heritage
Shanghai Cronus Machinery Co., Ltd. is a wholly owned subsidiary of Guilin Mining Machinery Co., Ltd. Guikuang was founded in 1973 and has more than 50 years of experience in mineral powder equipment manufacturing.
The organization combines Shanghai-based international communication with engineering, casting, machining, assembly and testing resources in Guilin. Its portfolio includes Raymond mills, CRGM ultrafine mills, vertical roller mills and associated powder-processing equipment.
High-tech enterpriseInvention & utility patentsCE certificationISO 9001ISO 14001ISO 45001
Powder-equipment team backed by a manufacturing organization established in 1973.
12 / Lifecycle support
Service from sample definition to stable operation
Clear acceptance criteria at the start make commissioning faster and protect both parties.
Material review
Review moisture, mineralogy, feed size, target PSD, capacity and application test.
Process design
Define crushing, drying, storage, activation, milling, collection and packing interfaces.
Manufacturing QA
Inspection records, assembly checks and model-matched component documentation.
Installation guidance
Foundation, erection, alignment, electrical and piping support for the agreed supply scope.
Commissioning
Establish safe startup, airflow balance, classifier settings and product recipes.
Operator training
Daily checks, lubrication, vibration, filter differential pressure and PSD sampling.
Parts planning
Recommended startup spares and wear monitoring based on actual feed abrasiveness.
Remote follow-up
Operating-data review and troubleshooting through documented measurements.
International customer visitsFactory tours, material discussions and process review with customers from Asia, Africa, the Middle East and Latin America.
13 / FAQ
Questions to resolve before buying a bentonite mill
These answers are engineering starting points. A final proposal needs a representative sample and a written product acceptance method.
Can wet bentonite feed directly into the CRGM mill?
Normally no. High free moisture promotes bridging, coating and classifier instability. The line should include stockpile control, drying or conditioning to a tested limit.
What is the best fineness for drilling-grade bentonite?
There is no universal mesh answer. Specify the applicable API or customer rheology and filtrate tests, then determine the PSD that passes those tests economically.
Can calcium bentonite be converted to sodium bentonite?
Selected calcium clays can be sodium-activated with soda ash. Success depends on mineralogy, dosage, water distribution and aging time, so activation trials are required.
Does finer bentonite always swell more?
No. Finer powder may wet faster, but swelling also depends on smectite content, exchangeable cations, salts, drying history and dispersion conditions.
Can one CRGM produce 325 mesh and ultrafine grades?
Usually it can produce multiple grades within its classifier range. Each grade requires a validated recipe, and throughput changes with the cut point.
How should capacity be specified?
State dry tonnes per hour at a defined feed moisture, feed size, target D-values or residue, and application acceptance test. A catalogue maximum alone is not sufficient.
When is a Raymond mill the better choice?
For conventional 80-400 mesh products with moderate PSD requirements, a Raymond circuit may offer a simpler and economical solution.
When is a ball mill worth considering?
Consider it for large established circuits, special impact/attrition requirements or sites that already have ball-mill infrastructure and classifier experience.
What causes high wear in bentonite grinding?
Quartz, sand, hard stones and metal contamination often matter more than the clay itself. Test grit and abrasiveness and remove tramp material upstream.
Which wear parts should be stocked?
Typical items include rollers, rings, pins, classifier wear parts, filter bags, pulse valves, seals and selected drive or discharge components.
How is dust controlled?
Use enclosed transfer, negative pressure, cyclones and a correctly sized pulse bag filter. Housekeeping and explosion or fire risk assessment must follow the actual material and local rules.
What sample data should we send?
Send 20-50 kg of representative material where feasible, plus source, moisture, feed size, current test results, target PSD, capacity, final use and any additive recipe.
14 / Technical enquiry
Start with the clay and the acceptance test
Share the bentonite source, sodium or calcium type, moisture, feed size, target fineness, required t/h and end-use test. That information lets the first discussion focus on a workable flowsheet.
Phone / WhatsApp+86 199 2122 1418Emailsales@shcronus.comMain websitewww.shcronus.com
Room 801, Building 2, Shanghai Zhicheng, No. 8666 Hunan Road, Pudong New Area, Shanghai, China