Preliminary Design Precipitated Calcium Carbonate from Blast Furnace Gas and Steel Slag Plant

The steel industries account for 6% of the world's CO₂ emissions. The number of emissions will continue to increase as the steel industry in Indonesia grows. Generally, steel production uses blast furnaces which can produce large CO₂ emissions. The blast furnace process emissions called blast furnace gas (BFG) contain 20.7% mol of CO₂. The high CO₂ content also causes the calorific value of the gas to be low, so the gas must be purified to increase its calorific value to be used for power generation. In addition, the steel industry also produces steel slag as waste with a high CaO content (45.2%) but with low economic value. To increase its economic value, CaO content can be used to absorb CO₂ from BFG to produce Precipitated Calcium Carbonate (PCC). The use of PCC is very broad for various industrial needs, such as a filler in the paper industry which can increase paper brightness. Therefore, the "Precipitated Calcium Carbonate from Blast Furnace Gas and Steel Slag" plant is expected to be a solution to reduce CO₂ emissions from the steel industry. BFG and steel slag as raw materials were obtained from PT. Krakatau Posco. The PCC production process consists of three main stages, namely: (1) Pre-Treatment Steel Slag; (2) Carbonation; and (3) Purification. In the pre-treatment stage, the pH-swing method was used to extract CaO with NH4Cl solvent using pH control. The use of NH4Cl solution is advantageous because it can be recycled. This process obtained a solution of CaCl₂ and NH₄OH, which was then reacted with CO₂ from BFG in a bubble column reactor, resulting in a carbonation process. In the reactor, PCC (CaCO₃) and several impurities are formed. The PCC solids formed will then be filtered, dried, and reduced in size so that the moisture content and size are under PCC specifications for the paper industry. Besides producing PCC, purified BFG will be recycled and used as fuel for power generation. The plant location is integrated with PT. Krakatau Posco in the industrial area, Cilegon, Banten, West Java, with a production capacity of 12,750 tons/year. From the results of the economic analysis, with the capital expenditure (capex) of about IDR 337 million and operational expenditure (OPEX) of about IDR 89 million: the payback period is about 6.35 years, and the break-even point (BEP) is 32.38%.