| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 106 === The steel reducing slag (SRS) from electric arc furnace (EAF), byproduct of the steel industry, exhibits high potential for carbon dioxide absorption due to its plenty content of free-calcium oxide (f-CaO). The SRS will be stable after carbonization reaction, can be further applied as the additive of cement with low expansion ratio. The process is able to achieve the goal of resource recycle and CO2 utilization.
In this study, SRS of different electric arc furnaces in steel factory was evaluated in the gas-solid-liquid reaction in semi-batch and packed bed reactor, respectively. The SRS reacted with pure carbon dioxide stream continuously under ambient condition. The effects of water contents, temperature, and reaction time on the carbonation efficiency for this process were systematically investigated in detail, where the degree of carbonization was determined by thermogravimetric analyzer (TGA), nondispersive infrared CO2 detector, and Field-emission scanning electron microscope equipped with energy dispersive spectroscopy. (FE-SEM-EDS). The results indicated that the CO2-absorption capacity of the pre-washed SRS was 0.1338 gCO2/gSRS in the small semi-batch reactor. A packed bed reactor was further designed and established for SRS raw material to simulate the filed condition. The largest CO2-absorption capacity of different SRS (US and DS) was obtained with adjusting the water content to 20±3 wt%, where the slag diameter is about 0.5 mm and reaction time is 2 hours. The maximum CO2 adsorption was 0.1 g CO2/g SRS-US and 0.075 g CO2/g SRS-DS under room temperature. Moreover, the properties of autoclave expansion and compressive strength for blended cement with using 20 wt% SRS as additive was examined according to CNS standards (CNS1258 and CNS 15286). The expansion ratio of carbonated US sample was only 11.1 %, which was much less than that of the raw material. The test result of compressive strength also met the requirement of regulation. Finally, the system was magnified to 20 liters semi-batch reactor to ensure the practicability of utilization of SRS from different EAF for CO2 absorption and the economic potential of carbonated product.
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