Crushed Pellets

Crushed Pellets

At the Kakogawa works of Kobe Steel. Ltd., the agglomeration facilities are composed of a pelletizing plant and sintering plant. This aim is to utilize raw materials efficiently and stabilize the raw material resources. Therefore at Kakogawa works, the blast furnaces (BF) have been operated with high pellet ratio and various developments for pellet properties have been achieved to improve the blast furnace performance. These developments include dolomite-fluxed pellets, new-porous pellets and crushed pellets. As a results of these improvements, pellets have achieved almost the same performance as sinter at high temperature regarding properties such as the softening, melting and reduction behaviour.


To decrease production cost of crushed pellets, it is important to get high yield in crushing. The target for this yield was above 80%.

crushed-pellets flowsheet


crushed-pellets qualities

In crushing and sizing of jumbo pellets, the following characteristics should be controlled.

  1. Crushing ratio (the rate of non-spherical pellets to total pellets) This should be high to improve the shape of pellets.
  2. Size distribution This should be narrow and stable to keep constant the reducibility pellets and the permeability of the BF. To this end, the portion of large and small size should be controlled,
  3. Crushing yield This should be high for economy.

crushed-pellets comparison of various crusher


crushed-pellets improvement of crushing system


crushed-pellets operating data

crushed-pellets stacking method

crushed-pellets effect

crushed-pellets size segregation

Blast furnace operation test using crushed pellets


crushed-pellets properties

crushed-pellets coke layer


crushed-pellets sinking

crushed-pellets gas velocity

Further, the influence of crushed pellets on burden distribution was studied by test model of the Kakogawa No. 3 BF which is full sized and that of 40° segment. In this study ordinary pellets were replaced by crushed pellets.

crushed-pellets relation

crushed-pellets full scale model

Influence of size and shape on properties

the properties of crushed pellets are influenced considerably by the size. This suggest that the size distribution should be as narrow as possible. The reducibility increases with increase in the number of new surface generated by crushing, but the effect is small.

crushed-pellets results

crushed-pellets distribution of porosity

crushed-pellets effect of size

crushed-pellets results of test

Results of blast furnace operation test with crushed pellets

A BF operation test with crushed pellets was carried out from September, 1981 to December 1981 at Kakogawa No. 2 BF (inner volume: 3,850m³, hearth diameter : 13.1m). Ordinary pellets were replaced by crushed pellets, and other burdens were kept almost constant.


crushed-pellets pressure

So it is considered that the replacement of ordinary pellets by crushed pellets caused the improvement in pellet behavior at the upper zone of the BF and this in turn is affected by the shape-based characteristics of crushed pellets.

crushed-pellets profile meter

crushed-pellets comparison of heat balance

Test operation using crushed pellets were carried out at Kobe Steel’s Kakogawa No. 2 BF and successful results obtained. The furnace permeability was improved by replacing ordinary pellets with crushed pellets, the fuel rate also being lowered.

development of crushed pellets in kakogawa works