Significant economic savings can be generated by micro-pelletizing waste oxides, through the raw material replacement and elimination of landfill charges. Micro-pelletized steel mill by-products can be directly inserted into the sintering process, as a substitute for low-grade iron ore or scrap.
In conjunction with direct savings, micro-pelletizing of by-products has also been shown to deliver improvements in sinter plant productivity. Traditionally, when by-products have been recycled via sinter plant operations they are added in a less-than-homogenous manner, resulting in a sinter mix that varies dramatically from one day to the next. This variability has a direct impact on the sintering process efficiency.
In contrast, the use of a consistently-sized and homogenous mix improves the sintering process allowing it to operate with reduced variation, leading to improvements in sinter plant productivity of up to 5%.
A variety of by-products can be included in the mix of materials for micro-pelletizing, including converter sludge (BOS sludge), blast furnace sludge, ladle slags, sinter fines, millscales, bag house dusts, iron ore fines, lime and dolomite dusts.
The input by-products are prepared, blended, mixed and conditioned correctly before being fed in a controlled manner into the pelletizing disc. The material is then granulated to a size and shape that can be tailored to suit each customer’s individual requirements.
A number of critical factors influence the micro-pelletizing process, namely:
• The chemical and physical properties of by-products to be processed
• The number of by-products to be pelletized
• The moisture content of the blend
Benefits of micropelletizing
• Improves sinter plant productivity
• Minimizes disposal costs (lowest possible volume of material is sent to landfill)
• Converts heterogenous waste streams into a homogeneous lump agglomerate suitable for material handling
• Contributes to reduction of overall Co2 emissions
• Helps comply with environmental regulations on airborne dust emissions
• Promotes sustainable steelmaking
Briquetting is an agglomeration process utilized to make products for a variety of applications, notably BOS briquettes, BF briquettes, and coke breeze briquettes. Slags, dusts, fines, slurries, millscale and hydrated limes are all processed to recover the iron units within these by-products.
The briquetting process converts individual by-products into a homogenized agglomerated form by a process of compaction via a hydraulic roll (briquetting press) and binder (molasses). This generates a briquette which can be used in conventional iron and steelmaking facilities.
A number of critical factors influence the roll briquetting process:
• The chemical and physical properties of by-products to be briquetted
• The number of by-products to be agglomerated
• The required temperature and moisture of the briquette blend
• The binder to be used
• The feed rate of materials