Large-scale Raw Materials Handling at Bushan Steel's Integrated Steel Plant

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Base Mix and Product Sinter

The base blending building is the heart of the base blending system and it comprises of 20 bins each of capacity 360 m³ to store iron ore, lux (crushed limestone and dolomite), coke, mill scale and sinter fines. The bins are provided with bin level indicators and air blaster system. The raw materials stored in the base blending building are reclaimed at required proportion with the help of belt weigh feeders to form the base mix. The base mix produced is stacked in either of the stock yards by the twin boom stacker machine and the barrel reclaimer is used to retrieve base mix across the full width. The barrel reclaimer machine will be transferred to either of the beds by transfer car. One bed will have the formation of the base mix while the other will be under reclamation. The reclaimed base mix is conveyed to the sinter plant after necessary trimming, addition of coke fines and lime fines. There is also a provision of transportation of base mix directly to the sinter plant without stacking and reclaiming.

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Product sinter received from the sinter plant is either conveyed to an emergency sinter storage building or directly to the blast furnace stock house. The emergency sinter storage building consists of 16 bins each having a volume of 485 m³ to store sinter as emergency stock.

Coal and Coke Handling

This system comprises of the coal circuit which carries coking coal from the yard to the coal tower and the coke circuit that conveys the product coke to the blast furnace and base blending system. The details of the system are given in the following section.

The coal handling system is designed for a nominal capacity of 750 t/h and caters to the total coal requirement of two coke oven batteries and the plant will operate 365 days per year (two shifts per day). Its major sub systems are coal reclaiming from yard, coal blending, coal crushing and mixing and coal tower feeding.

Coking coal stored in the yard is reclaimed by a stacker/reclaimer machine and fed to one of 12 storage bins in the coal blending building. The bins are designed for a total storage capacity of 8800 t (735 t each) corresponding to 20 hours storage availability and Nitrogen inertising system is provided in each of the bins to avoid any risks. To achieve the desired blend, coal stored in the bins is reclaimed at the required proportion with the help of belt weigh feeders installed below each of the bins.

The blended coal is fed to the rotating conveyor in the coal crushing building which can feed to any of the four surge hoppers (one in future). Vibro feeders installed below the surge hoppers feed the coal to four reversible hammer mill crushers (2W+2S). The feed (0 to 50 mm) is ground to predominantly (-3 mm).

After crushing, the coal is transported to the mixing station using high angle conveyors. A distribution system consisting of reversible belt feeders and diverter gates feeds the material to three 750 t/h mixers (BSL scope). Subsequently after crushing and mixing the blended coal is fed to the coal tower through a series of conveyors. A coal sampler station is also installed in one of the conveyors to collect samples to check the quality of blending.

The 500 t/h coke handling system is designed to operate continuously on three shifts per day, 365 days a year. The quenched coke is dumped on the wharf and fed to the wharf conveyor by means of 400 t/h plough feeders (BSL Scope). A cooling water system is installed in both the wharf conveyors to avoid damage of belt conveyors due to hot pieces (if any).

The material is then fed to the two vibrating grizzly screens (separation -80 mm) inside the coke treatment building. The oversize material is fed onto two smooth double roll crushers (BSL scope) to reduce the grain size. Subsequently the screened out and crushed material (-80 mm) is screened by three double deck screens (BSL scope) to segregate coke fines (0 to 15 mm), nut coke (15 to 25 mm) and coke for blast furnace (15 to 80 mm).

The blast furnace coke is conveyed to either of the Blast Furnace 1,2 (and, in the future, 3) as per requirement and the excess coke is stacked in a covered storage yard and reclaimed by a scraper type reclaimer. The coke fines and nut coke are stored in eight bins (each of 1000 m³ capacity) inside the coke fines and nut coke building. Each of these bins is provided with the option of discharging coke to trucks or feed to the sinter plant. The coke fines and the nut coke can be conveyed directly to the base blending building through the sinter plant feeding conveyors.

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