Abstract:
PURPOSE: A production method of clinker and eco-cement using ash generated during the incineration of domestic waste and sewage sludge is provided, which recycles waste materials and saves energy due to low sintering temperature. CONSTITUTION: The clinker is produced by mixing 87-92wt.% of limestone, 1-4wt.% of alumina-based materials, 1-2wt.% of clay, 2-6wt.% of sewage sludge, 6-10wt.% of incineration ash, decarbonating the mixture at 900deg.C for 1hr and sintering it at 1250-1350deg.C for 1hr. Eco-cement is produced by grinding produced clinker to become powder having specific surface of 2000-6000cm¬2/g and adding 8-12wt.% of gypsum, preferably anhydrous gypsum obtained by heating gypsum selected from phosphogypsum byproduct, FGD gypsum, natural gypsum, etc. at 700-900deg.C.
Abstract:
PURPOSE: Provided is a preparation method of aragonite-type calcium carbonate through a carbonation process by reacting CO2 gas with dust generated from a stainless steel refining process. The resultant aragonite(CaCO3) is applied to high functional materials requiring mechanical strength and optical property. CONSTITUTION: The aragonite-type calcium carbonate is prepared by the following steps of: preprocessing dust generated from stainless steel refining process through sieving, gravity separating, magnetic separating, filtering and drying; preparing Ca(OH)2 slurry by adding dust containing 1-15wt.% of Ca(OH)2 to 2L of Mg(Cl)2 solution containing 0.1-1.0M of Mg(Cl)2 in a glass reactor; flowing high purity CO2 gas at a rate of 0.1-1.0L/min between 40 and 80deg.C into the reactor with stirring for carbonation of Ca(OH)2 sludge; washing, filtering and drying.
Abstract:
PURPOSE: Provided is a preparation method of β-gypsum hemihydrate by using sludge generated by a refining process of stainless steel and waste sulfuric acid generated by a plating process. The method recycles waste resources and decreases environmental problems. CONSTITUTION: The preparation method of β-gypsum hemihydrate(CaSO4·1/2H2O) comprises the steps of: preparing Ca(OH)2 suspension by preprocessing sludge generated by refining processes of stainless steel through sieving, gravity separating, magnetic separating, filtering and drying; removing impurities such as iron ions from waste sulfuric acid; reacting Ca(OH)2 suspension with sulfuric acid in a molar ratio of 1:0.4 - 1:1.2 at 20-100deg.C; adding 1-20wt.% of NaCl; drying it at 50deg.C for 24hrs to stabilize gypsum hemihydrate.