Overview

The crucible swelling number (CSN) quantifies the volumetric expansion of a coal sample when heated under standardized conditions, which directly influences the swelling pressure exerted by the resulting coke in a blast furnace. A higher CSN indicates a greater tendency for the coke to expand, affecting gas permeability and furnace stability. Understanding CSN allows operators to select coals that produce coke with the desired mechanical strength and porosity for efficient ironmaking.

Technical Specifications

Typical ranges for key properties of CSN‑graded coking coal are presented below. Values are indicative and can be adjusted according to project requirements.

Measurement Method

CSN is determined by placing a finely crushed coal sample (typically <0.2 mm) into a standardized porcelain crucible, heating it in an inert nitrogen atmosphere at 800 °C for a fixed duration, and measuring the increase in sample volume relative to the initial volume. The test follows ISO 11714/ASTM D7208 procedures, ensuring reproducibility across laboratories. Results are expressed as a dimensionless number representing the percentage volume increase.

Applications in Metallurgy

In blast furnace operations, coke must support the column burden while allowing sufficient gas flow. Coal with an appropriate CSN yields coke that expands enough to create a porous structure, enhancing permeability without causing excessive pressure that could disrupt burden descent. Coals with low CSN may produce rigid coke, leading to channeling and uneven reduction, while excessively high CSN can cause over‑expansion, fines generation, and increased pressure drop. Thus, CSN serves as a key parameter for matching coal selection to furnace design and operating conditions.

Quality Control and Testing

Consistent CSN performance is maintained through a multi‑stage inspection regime that verifies both raw material properties and final product specifications.

• Lot‑by‑lot proximate analysis (volatile matter, ash, sulphur)
• CSN determination according to ISO 11714
• Particle size distribution screening
• Moisture content measurement
• Visual inspection for foreign matter and agglomeration

Customization Options

Depending on downstream coke‑making constraints, the coal can be adjusted to meet specific CSN targets and handling requirements.

• Size fraction selection (e.g., <6 mm, 6–13 mm, or custom blends)
• Moisture reduction via drying to <5 % if required
• Blending with low‑sulphur or high‑volatile coals to fine‑tune CSN
• Pre‑carbonization treatments to modify swelling characteristics

Supply and Packaging

The product is delivered in formats designed to minimize segregation, moisture uptake, and handling losses while preserving the measured CSN value.

• Bulk rail gondolas or truckloads for large‑volume shipments
• Sealed polyethylene‑lined bulk bags (25 kg net)
• Containerized lots with optional nitrogen purging to limit oxidation
• Custom palletizing and stretch‑wrapping upon request

Request for Quotation

To obtain a quotation, please provide the following details so we can tailor the offer to your specific technical and logistical needs.

• Desired CSN range (or target value)
• Quantity required (metric tons per month or per shipment)
• Delivery destination (nearest port or inland terminal)
• Preferred packaging option
• Any additional analysis required (e.g., ash, sulphur, phosphorus)

Submit your inquiry via the link below, and our technical team will respond with a detailed proposal and lead‑time estimate.