Carbon black — a dusting material: transloading, occupational safety and storage

Definition

Carbon black is a fine-grained carbon material with a very large specific surface area, produced by controlled, incomplete combustion or thermal decomposition of hydrocarbons, supplied in pelletised (beaded) form or as a fluffy powder, used above all as a reinforcing filler in rubber and tyres and as a black pigment in plastics, paints and inks.

From the terminal’s perspective carbon black is a material with two faces. In one form it behaves almost like granulate — it is transferred gently and controllably. In the other it is the lightest and dirtiest powder we come across, requiring full transloading discipline. The whole difference lies in the delivery form, which is why we always start the conversation about carbon black with it.

What carbon black is

Carbon black is not chimney soot or “dirt” — it is a precisely manufactured industrial product. It is created by incomplete combustion or pyrolysis of hydrocarbons (most often heavy oil or gas fractions) under controlled conditions. The most popular method is the furnace process (furnace black); alongside it, thermal and channel processes are used. The result is almost pure elemental carbon in the form of aggregates of very fine particles.

The key feature of carbon black is its enormous specific surface area — individual particles have dimensions of the order of tens of nanometres, and their total internal surface reaches hundreds of square metres per gram. It is precisely this developed surface that determines the reinforcing action of carbon black in rubber and its intense blackness as a pigment. On the other hand, this same feature makes the material light, free-flowing and prone to dusting.

In circulation there are dozens of grades of carbon black, differing in specific surface area, structure and purity — from tyre grades to high-quality pigment and conductive carbon blacks. These grades are sometimes designated by standardised codes describing their characteristics, but from the logistics point of view these chemical differences are secondary; what matters primarily is the physical form in which carbon black comes to transport, and the dusting and bulk density that result from it.

Forms of carbon black: pellet versus fluffy powder

This is the most important practical division. Carbon black is supplied in two fundamentally different forms, which are handled completely differently.

Pelletised carbon black (beaded, in the form of beads — beaded carbon black) is created by compacting the fine powder into fine, spherical granules, most often in a wet pelletisation process with a small addition of water or binder, followed by drying. This form dusts much less, transfers better and is easier to transport in bulk. Its bulk density is about 0.3-0.5 t/m³ — comparable to lighter bulk materials.

Fluffy carbon black (fluffy, powder) is the original powder form — uncompacted, very light, with a bulk density of the order of just 0.03-0.1 t/m³. It is an extremely voluminous material: at a small mass it occupies a great deal of space. It dusts strongly, easily rises into the air and is difficult to transfer in a controlled way. It is used where the recipient needs the powder form (e.g. certain pigment and processing applications), but in bulk transport it is always a challenge.

In terminal practice we prefer the pellet. If the customer has a choice, the granulated form means less dusting, cleaner handling, better use of payload and a lower risk of material loss. Fluffy carbon black we accept, but with a full regime of dedusting and protection.

Bulk density and transport volume

The low bulk density of fluffy carbon black has direct logistical consequences. At a density of the order of 0.03-0.1 t/m³ it is volume, not the permissible combination weight, that becomes the limiting factor. A silo tanker with a capacity of ~60 m³ will fill up geometrically before it reaches the weight limit — the reverse of heavy mineral materials, where the tank is sometimes full by weight at half its volume.

That is why with fluffy carbon black the economics of transport are worse: one is carrying mainly the air trapped between the particles. Pelletisation partly solves this problem — the higher bulk density of the granulated form allows the trailer’s volume to be used better and the number of trips per tonne of material carried to be reduced. This is one of the reasons why the tyre industry in bulk transport operates above all with pelletised carbon black.

The same mechanism — the relationship between bulk density and volume — we describe more broadly under silo transport, because it concerns all the bulk materials we handle in silo tankers.

ADR classification — is carbon black hazardous

Here a common misunderstanding must be dispelled. Standard carbon black in its non-activated, mineral form is not classified as a dangerous good and is not subject to ADR regulations. Contrary to the intuition of a “black carbon powder”, this material is not a self-igniting substance: according to the relevant UN tests (including the self-heating test) standard furnace black does not show self-heating properties at a level requiring classification.

This means carbon black fits into the standard stream of bulk materials we handle in Chorula — alongside PE, PP and other plastics as well as mineral materials — as a non-ADR material. It requires no dangerous-goods transport documentation, ADR marking or driver qualifications in this respect.

With one practical caveat: some special grades (e.g. highly activated conductive carbon blacks or activated carbon products of another type) may have a different classification. That is why, when accepting a load, we always verify the safety data sheet of the specific batch, rather than assuming the status in advance. This is the same principle of caution we apply to every new material entering the terminal.

Occupational safety and dusting — work hygiene, not ADR

The fact that carbon black is not subject to ADR does not mean it is handled without a regime. On the contrary — because of dusting and soiling, carbon black requires one of the most rigorous occupational-hygiene regimes among the non-ADR materials we handle.

The most important elements of safe handling:

• Limiting dusting at the source — tight packaging (big bags with a liner), a closed transfer path between packaging and tank, minimising the free fall of material.
• Local extraction and dedusting — dust extraction at the transfer station, so the black dust does not spread through the hall and settle on other loads.
• Respiratory protection — dust masks and half-masks for staff when working with the fluffy form; fine carbon dust is a nuisance for the respiratory system.
• Protective clothing and hygiene — carbon black soils permanently; workers use dedicated clothing, and the work zone is separated from the rest of the terminal.

It must be emphasised: these are occupational-hygiene requirements, not a consequence of dangerous-goods classification. The material is safe in transport in the ADR sense, but its physical nature — lightness and dustiness — forces a transloading discipline comparable to the most difficult powders. A gentle, gravity-fed transfer by the method of pneumatics-free transloading is especially important here, because pneumatic conveying of carbon black would generate dust clouds that are hard to control.

Storage

Carbon black is stored under dry and clean conditions, in tight packaging, away from strong oxidisers and ignition sources. Although standard carbon black is not classified as self-igniting, as a carbon material with an enormous surface area it should not come into contact with strong oxidisers or be exposed to open flames.

Moisture and soiling lower the quality of the material, which is why big bags of carbon black are kept under a roof, on a dry surface, preserving the cleanliness of the packaging. At the terminal carbon black occupies a dedicated zone — the black, light dust easily contaminates light-coloured materials, so we keep it away from the stream of polymer granulates and light mineral powders. This is an element of the broader cleanliness discipline we describe under bulk material storage and the control of cross-contamination.

Applications

Carbon black is one of the most mass-produced industrial fillers and pigments. The most important directions of application:

• Tyres and rubber products — by far the largest recipient. Carbon black is a reinforcing filler in rubber compounds, raising the abrasion resistance, rigidity and durability of tyres, conveyor belts, seals and hoses.
• Plastics — a black pigment and filler in masterbatches, profiles, films and technical products; carbon black imparts blackness and UV resistance.
• Inks and paints — an intense black pigment in printing inks, paints, varnishes and coatings.
• Cables and conductive products — conductive carbon blacks are used in cable insulation and sheathing and in antistatic materials.

These are applications of enormous scale, which is why carbon black is constantly present in the stream of industrial loads in Central Europe. From the terminal’s perspective it is important that, regardless of the final purpose, it is handled according to the physical form — pellet versus powder — and not according to the chemical grade.

It is worth adding that quality requirements rise along with the end use. Tyre carbon black allows a certain tolerance, but pigment and conductive carbon blacks require high purity and batch repeatability — any contamination with foreign material disqualifies the load. This raises the importance of clean, controlled handling and unambiguous batch traceability already at the transloading stage at the inland terminal, on the last leg of the material’s road to the processor.

Transloading carbon black at the terminal

Carbon black reaches us in big bags with a liner — most often from import containers — and is transferred into silo tankers on the last leg of the road to the processor. The 2000-big-bag warehouse allows deliveries to be buffered between import and the rhythm of the tyre plant’s collections, and the transfer line itself works with a throughput of up to 200 tonnes per day. Unlike with granulates, however, we start every carbon black batch with one question: pellet or fluffy powder. The answer determines both the choice of transfer station and the level of dedusting we must engage.

Pelletised carbon black is handled similarly to granulate: by a gentle, gravity-fed flow through a sieve, without pneumatics, which limits dusting and does not break up the beads. Fluffy carbon black we transfer with a full regime: a tight transfer path, local extraction, respiratory protection for staff and control of the cleanliness of the surroundings. In both cases we use cleaning sieves, to catch any contaminants and maintain the uniformity of the stream.

As a non-ADR load, carbon black fits into the same stream as the polymer granulates and bulk mineral materials we handle — with one distinction: because of its colour and dusting we keep it separate, so the black dust does not come into contact with light plastics and fillers. The big-bag-to-silo-tanker transfer itself we describe on the big bag to silo tanker transloading page, and the buffering of deliveries — in the storage section. A broader context of bulk material transport can be found on the PHS Magnum portal.

Related topics

Carbon black is best understood through the prism of its physical form and the handling regime that results from it. Pelletisation brings it close to granulates, but the fluffy form requires discipline known from the most difficult powders — hence the key role of pneumatics-free transloading and cleaning sieves. The basic packaging remains the big bag (FIBC), and the target means of bulk transport — the silo tanker. The low bulk density and voluminous character of carbon black link this topic with the question of silo transport and bulk material storage.

Sources

• ISO standards series on carbon black (ISO 1124, ISO 1126, ASTM D1799/D1513 — determination of bulk density and dusting).
• UN guidelines on material classification tests (self-heating test N.4) — the basis for assessing the absence of ADR classification of standard carbon black.
• Technical materials and safety data sheets of carbon black producers.
• Experience from transloading pelletised and fluffy carbon black at the SMIALA terminal, Chorula — Aleksy Pasternak.