The main function of this unit is to accumulate the materials and collect them, homogenize them, provide for a decent reserve of the materials and separate the functions of pelletizing and direct reduction plant. The plant has been designed in a way to account for the unloading and homogenizing of 4.5 million ton raw materials including iron ore powder and pellets per year. Now the unloading capacity is 6.5 million ton. This unit allows the storage of maximum 2 million iron ore powder and pellets.
A great portion of the iron ore is supplied from the internal mines of Golegohar and Chadormalu on rails. The cars are weighed on rail weighbridge and move to car dumper for unloading. The car indexer, or locomotive picks the cars and moves them to the car dumper unit and places them inside the car dumper while adjusts their position there. The cars are unloaded by the car dumper and move to the storage yard (parks). The empty car weighs 30 ton and can hold 90 tons that can increase to 120 tons. Three 950 X 38 m parks store and mix the iron ore powder and three 950 X 38 m parks store iron ore powder and pellets.
Coarse-grained iron ore has its granulation reduced from 95 percent below 1 mm to granulation of 70 to 80 percent below 45 microns. The iron ore thus milled enters the pelletizing discs after it has been mixed with fine-grained iron ore coming from the mine with the granulation of 80 to 85 percent below 45 microns, bentonite (as binder), and water for the preparation of raw pellets. The pelletizing discs the iron ore mix is changed into iron ore pellets with the size of 5 to 25 millimeters. After the raw pellets have been sieved through rotary sieves pellets with the size of 8 – 18 millimeters enter the curing furnace.
In the curing furnace the raw pellets undergoes drying, preheating, curing, and cooling down and achieve enough strength for going through the direct reduction process. The oxide pellets either go to the direct reduction plant for consumption or are sent to the raw material storage yard for storage.
3.Lime calcinating plant:
The lime calcinating kiln consists of 2 rotary kilns with the length of 38 meters designed for the production of 270,000 ton calcinated lime needed by the steel making plant. First, limestone with the granulation of 18-15 millimeters arrived from Hozemahi mine enters the rotary kilns and goes through a temperature of 1250 – 1350 degrees Celsius and loses its carbon dioxide by oxidation. The calcinated lime thus produced is sieved and the product with the granulation of 5 – 50 millimeters goes to the electric arc furnaces in the steel making plant.
Lime grains with the size of below 5 millimeters in diameter go to the hydration plant where the lime is treated with water to change into hydrated lime which is used in the pelletizing, briquetting, and water treatment facilities. In recent years, with the addition of the burned dolomite to the additives of the steel making process, a dolomite calcinating plant has been built where raw dolomite is changed into burned dolomite. The product is sent to the electric arc furnaces in the steel making plant after it has lost its fine grains through the sieves.
4.Direct reduction plant:
Direct reduction plant consists of 5 Midrex 600 and 1 Midrex 800 modules whose production capacity has increased to 5 million ton sponge iron per year with improvements implemented on it. In direct reduction plant, the oxide pellets produced in the pelletizing plant enters the reduction plant from the top into the furnace after it has had its chemical and physical properties checked, and loses its oxygen to the reducing gas which flows upwards from the bottom of the module.
H2 and CO is the initial mixture of the reducing gas with the ratio of 1.5 to 1.7. This mixture absorbs the oxygen content of the pellets and changes into CO2 and H2O and gets out of the furnace from the top. 2/3 of the exit gas goes through a cooling and water washing process and enters the reformer with natural gas added to it. The mixture recycles to H2 and CO while passing over a nickel-based catalyst and re-enter the furnace. The remaining 1/3 created due to the expansion resulting from the reforming operation gets out of the cycle and is burned in the reformer as a source of energy with air and provides heat needed for the operation of the reformer. Finally the product gets out of the direct reduction plant in the form of sponge iron pellets with the metallization of over 92 percent and carbon content of over 1.7 percent. The product gets out from the bottom of the furnace after it has been cooled down by the cooling gas to the ambient temperature and is sent to the steelmaking plant after it has lost its fine grains.