Synthesis of sorbents for co2 capture from biogenesis calcium waste
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Date
2018-07-01
Authors
Tan Sei Ling
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Abstract
Global warming has become one of the essential global issues as the world concentration of CO2 is rising. Carbon dioxide (CO2) capture by using calcium oxide (CaO) derived from natural waste shells has attracted the attentions of many researchers. Utilization of these green sorbents for CO2 capture is able to minimize the cost of the sorbents which is favourable to the whole production cost. In this research, the natural waste shells which are anadara granosa shells, meretrix meretrix shells and textile venus clam shells were utilized as the sources to obtain CaO. In the X-ray fluorescene (XRF) analysis, more than 97 wt % of CaO was found in the natural waste shells after calcination process at 900 ℃. Several parameters were investigated including carbonation duration, carbonation temperature, type of metal additives added and weight percentage of metal additive added to sorbent. The highest sorption capacity was found when the carbonation duration was 60 minutes. The range of the carbonation temperature studied in this research was 400 – 800 ℃. The highest sorption capacities for calcined anadara granosa shells (CaO – AGS) and calcined meretrix meretrix shells (CaO – MMS) were at 800 ℃ while calcined textile venus clam shells (CaO – TVCS) and commercial CaO had their highest carbonation conversion at 700 ℃. However, commercial CaO had the highest sorption capacity as compared to others since it had the highest surface area (100.63 m2/g). Regenerability study also had been carried for all the sorbents at 700 ℃ for 11 cycles. CaO – TVCS had been found as the best sorbent due to its higher carbonation conversion and minor
efficiency drop (24.27 %). Kinetic study of the sorbent samples was evaluated. The activation energy for CaO – AGS, CaO – MMS, CaO - TVCS and commercial CaO during the chemical reaction controlled stage of carbonation reaction were 47.13, 18.19, 26.98 and 30.18 kJ/mol respectively. The activation energy for CaO – AGS, CaO – MMS, CaO - TVCS and commercial CaO during the product layer diffusion controlled stage of carbonation reaction were 20.19, 20.74, 21.09 and 15.81 kJ/mol respectively. The sorption capacities of the CaO – TVCS added with metal additives (Al2O3 and ZrO2) were decreased with the increasing weight percentage of metal additives. The sorption capacities of the sorbent samples added with metal additives were found relied on the weight percentage of CaO in the sorbent samples. After conducting the regeneration study, CaO:ZrO2 with 90:10 weight percentage had been found as the best sorbent samples owing to its lower efficiency drop (19.05 %) in comparison to CaO:Al2O3 with 90:10 weight percentage (22.47 %) and CaO – TVCS (38.04 %). Therefore, it can be concluded that CaO:ZrO2 with 90:10 weight percentage is a potential alternative to CaO as it has higher durability and stability than CaO.