High-Calcium Limestone Flux
High-calcium limestone flux is a coarsely crushed calcareous stone with at least 95% calcium carbonate content, specifically used in blast furnaces to remove impurities during steel production. It falls under HTS 2521.00.00.00 because it is limestone of a kind used for lime or cement manufacture, distinguished by its chemical purity and fluxing properties. This raw material is essential for slag formation in metallurgical processes.
Import Duty Rates by Country of Origin
Alternative Classifications
This product could be classified differently depending on its characteristics or intended use.
If quicklime produced domestically from the limestone
Quicklime (calcined limestone) is classified separately under 2522, not raw flux stone.
If further processed into marble slabs or tiles
Worked monumental or building stone from calcareous materials falls under Chapter 68.
If used as pebbles or gravel for construction rather than flux
Pebbles, gravel, and crushed stone for general use (not specifically for lime/cement) go to 2517 per chapter notes.
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Import Tips & Compliance
• Verify chemical composition certificates showing high CaO content to confirm classification under 2521.00.00.00 and avoid misclassification as general crushed stone
• Ensure documentation specifies end-use for lime/cement manufacture, as flux properties must be evidenced for duty-free entry in some cases
• Watch for particle size specs; overly processed stone may shift to heading 2522 if not raw flux material
Related Products under HTS 2521.00.00.00
Cement Kiln Feed Limestone
Cement kiln feed limestone consists of medium-to-coarse crushed calcareous rock selected for its consistent calcium carbonate levels, fed directly into rotary kilns for clinker production. It qualifies for HTS 2521.00.00.00 as limestone expressly used in cement manufacturing. The material's purity ensures optimal lime reactivity during calcination.
Lime Production Quarry Limestone
Quarry-run limestone blocks or crushed stone from high-purity deposits, intended for quicklime production via calcination in lime kilns. Classified under HTS 2521.00.00.00 due to its specific suitability for lime manufacture, characterized by uniform reactivity and low contaminants. This feedstock is critical for industries like steel, chemicals, and water treatment.
Fluxing Calcareous Stone for Steel Mills
Coarse angular calcareous stone flux, sized 1-4 inches, used in steel mill basic oxygen furnaces to form slag and protect furnace linings. HTS 2521.00.00.00 covers this as limestone flux specifically for lime-related industrial processes. Its high melting point and impurity-binding properties define its metallurgical role.
Hydrated Lime Manufacturing Limestone
High-brightness limestone suitable for producing hydrated lime used in construction and chemical applications. Falls under HTS 2521.00.00.00 as raw material expressly for lime production. Its fine reactivity post-calcination defines industrial suitability.
Chemical-Grade Flux Limestone
Ultra-pure limestone flux for chemical processes requiring consistent calcium source, such as precipitated calcium carbonate production. HTS 2521.00.00.00 applies to its role in lime-based chemical manufacturing. Low silica ensures purity in end products.
Glass Manufacturing Calcareous Stone
Calcareous stone flux for soda-lime glass production, providing network stabilization. Though glass-making, classified under HTS 2521.00.00.00 as limestone used for lime manufacture (soda-lime process). Specific silica-calcia ratios required.