Iron Ore with Lime Pelletizing Case Study

The Bottom Line:

Pilot trial of FLOTICOR PA 8000 in the production of blast pellets showed substantial improvements over the use of lime binding agent only, including...

• 37% increase in green pellet resistance
• 137% increase in dried pellet resistance
• 52% increase in burned pellet compressive strength
• Improved iron pellet finishing and maximized production throughput

Picture A (test 4) show the cracks from pellets using Hydrated CaO. Picture B (test 7) show the quality finish from pellets using Hydrated CaO plus FLOTICOR PA 8000.

Objectives

Increasing iron ore pellet throughput without adding plant equipment can result in challenges to maintain product quality when using a hydrated lime binding agent alone. This was the experience of a blast furnace pellet producer when increasing its pellet production. The producer approached Clariant to develop a pelletizing additive that would help to increase its current burned pellet compressive strength to 300 daN. Clariant engineers tested numerous additives in our lab facilities, and the three top-performing agents were chosen for pilot trials by the customer. In addition to increasing product quality, the strategy was to incorporate the right balance of pelletizing additive and hydrated lime binder in order to maintain per-ton production costs. Beyond achieving a significant increase over the minimum compressive strength goal, a clear improvement of pellet finish quality – including no visible cracks of pellet surface fracture and reduced rate of abrasion – was realized. The combination of exceeding compressive strength targets and improvement in finish quality can represent a significant production increase.

Table 1 – Green and burned pellets resistance, using different dosages.

Background

To keep pace with increased global demand for iron ore, blast furnace pellet producers are testing the limits of their plant capacities. Increasing plant throughput without making significant capital equipment expenditures often sacrifices pellet quality. Clariant is at the forefront in developing new additive technologies to improve hydrated lime binder performance in the production of iron ore pellets. In one application, we are working with a customer to increase the quality of the blast furnace pellet circuit, allowing the circuit to produce more than its designed capacity without installing additional equipment. Higher product throughput rates reduces the amount of time the fine iron ore spends at each stage of the production process, including mixer inputs, balling disks and traveling grate furnace. When increasing plant capacity, producers can experience more surface cracks and reduced compression resistance with the blast furnace products when using hydrated lime binder alone. Clariant tested many different pelletizing additives to improve the binding properties of hydrated lime in the production of blast furnace pellets. Seven top performers were considered by the customer for trail to increase pellet quality, reduce the per-ton levels of hydrated lime consumption and keep production costs virtually the same.

Actions

From the seven considered options, three pelletizing additives went through pilot trial using samples of the customer’s iron ore. While the customer’s customary pelletizing process uses dry binders, Clariant proved the effectiveness of incorporating our liquid pelletizing agents. With a goal of meeting or exceeding targeted compressive strength quality, a pellet reference sample using only the concentrated iron ore and the hydrated lime binder served as the baseline. Multiple tests with the three liquid Clariant additives were conducted with dosages ranging from100 to 500 grams/ton. Hydrated lime dosages were reduced to find the optimum balance of pelletizing additive and binder that improved pellet quality. After analyzing drop test, compression strength, abrasion resistance and humidity results, FLOTICOR PA 8000 performed the best. It increased pellet strength from 275 to 340 daN at a dosage of 250 grams/ton. Hydrated lime dosage was reduced by 7 kg/ton, allowing production costs to remain the same. Moving from pilot trial to customer field evaluation, Clariant Mining Solutions custom-designed and installed a complete liquid additive system for production trail of the FLOTICOR PA 8000 additive.

Results

Clariant’s FLOTICOR PA 8000 pelletizing additive resulted in the highest quality of green and burned pellets, significantly outperforming the reference

Table 2 – Green and burned pellets resistance comparison using FLOTICOR PA 8000 sample points in all tested areas and exceeding quality standards established by the customer.

FLOTICOR PA 8000 delivered a compressive strength reaching as high as 340 daN, exceeding the customer’s target of 300 daN and offering an opportunity for the customer to significantly increase production throughput. This will be evaluated during plant trial.

FLOTICOR PA 8000 Opportunities...

• Significantly increases iron pellet quality when using only lime as the binding age
• Substantial compressive strength increases offer real opportunities of increased production throughput
• Maximizing plant capacities without significant equipment investment while maintaining desired product quality
• By reducing the per-ton rate of hydrated lime required to make the pellets, production costs are kept virtually identical

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