5.2　Proportioning

5.2.1　For large and medium-scale pellet plants with multiple induration lines，each line should be provided with independent material handling，preparation and proportioning system.The configuration of multiple induration lines sharing a common upstream system should be avoided.

5.2.2　All materials shall be proportioned by weight automatically to accuracy of±0.5%.The proportioning systems shall be concentrated.

5.2.3　Each kind of material shall be stored in proportioning bins for at least 8 hours of operation.

5.2.4　At least three bins shall be installed for iron-bearing materials and for the rest each of them should be provided with two sets of proportioning equipment.

5.2.5　The materials should be withdrawn from proportioning bins and fed on common collect belt conveyors in a proper order of raw materials，additives，solid fuels，recycled dust and finally the binders along the conveyor traveling direction.

5.2.6　The ratios of all materials shall be preset exactly according to the stoichiometric calculations and adjusted online to accommodate any variation of chemistries.

5.2.7　Except for iron-bearing materials，the others should be pneumatically conveyed into proportioning bins.Bin top dust collectors shall be installed where pneumatic conveying is applicable.

5.2.8　The combination of table feeder and weigh belt feeder should be adopted for weight proportioning of iron-bearing materials，and weight belt feeders with good seal performance and accuracy for binders and additives.