In carbon black production, lignosulfonate is used as a pelletizing binder: fluffy carbon black is wet-pelletized with water containing a binder, then dried into dust-free beads. Lignosulfonate, molasses and nitric acid are the classic pelleting agents. The binder raises pellet hardness and reduces fines and dust during handling, while the low ash and low insolubles of a carbon-black grade keep the purity of the black.
Why Carbon Black Is Pelletized
Freshly produced carbon black is a very light, dusty powder. Wet pelletizing in a pin mixer forms small beads that flow, convey and dose easily and release much less dust. Without a binder, dried pellets are weak and break into fines; dissolved binders such as lignosulfonate remain in the pellets after drying and increase their strength.
Requirements for a Carbon Black Grade
| Parameter | Lignosulfonate Carbon Black Grade (GAC-LS-CB) | Why it matters |
|---|---|---|
| Solid content | 95% min | Consistent dosing |
| Ash | 10% max | Ash ends up in the carbon black; ash content is a key black specification |
| Water-insoluble matter | 0.5% max | Insolubles can show up as grit or sieve residue |
| Lignosulphonate content | 55% min | Binding capacity |
| pH | 7.5 ± 0.8 | Affects pelletizing water and black surface pH |
| Solubility | Fully water-soluble | Even distribution in the pelletizing water |
Process Points
- Dosing: lignosulfonate is dissolved in the pelletizing water; patent literature describes aqueous solutions of about 1–2 wt% lignosulfonate, in some processes combined with nitric acid. The optimum depends on the black grade and the pelletizer.
- Pellet properties: monitor individual pellet hardness, fines content, attrition and pellet size distribution.
- Drying: binder content and drying temperature together set final hardness; very hard pellets can be harder to disperse in rubber.
- Dispersion in use: check that pellets still disperse well in rubber or plastic compounds; harder is not always better.
- Specifications: verify that ash, sulfur and sieve residue of the black stay within its grade limits after the binder is added.
Trial Plan
| Step | Measurement |
|---|---|
| Baseline with water only (or current binder) | Pellet hardness, fines, attrition, ash, sieve residue |
| Lignosulfonate at 2–3 concentrations in pelletizing water | Same measurements |
| Dispersion check in the customer compound | Dispersion rating and compound properties |
| Cost per tonne of black | Binder cost plus effect on yield and dust losses |
Frequently Asked Questions
Why is lignosulfonate used in carbon black pelletizing?
It acts as a binder that stays in the pellets after drying, increasing their hardness and reducing fines and dust during handling.
Why does carbon black need a low-ash lignosulfonate?
Because the ash of the binder remains in the carbon black, and ash is a controlled property of carbon black grades.
Can pellets become too hard?
Yes. Very hard pellets may disperse less easily in rubber or plastics, so binder level should be balanced against dispersion in the end use.
References
- US patent literature on carbon black pelleting with aqueous lignosulfonate solutions (e.g. US 3969457, “Carbon black pelleting”)
- Green Agrochem TDS GAC-LS-CB, Lignosulfonate Carbon Black Grade
Related Pages
- Sodium lignosulfonate dispersant grade
- Sodium lignosulfonate
- Lignosulfonate as a natural industrial binder
Questions about a specification, a test method or a trial: contact us or email info@greenagrochem.com.
