화학공학소재연구정보센터
Energy & Fuels, Vol.31, No.11, 12570-12581, 2017
Combustion Performance of Sewage Sludge in a Novel CLC System with a Two-Stage Fuel Reactor
Chemical looping combustion (CLC) is a promising and efficient technology for sewage sludge (SS) combustion with carbon capture. The CLC reactor configuration is crucial to the intimate contact between the solid phase and the gas phase species. This work proposed a novel CLC unit with a two-stage fuel reactor. Different from the conventional CLC unit with a single-stage bubbling bed as fuel reactor, two-stage fuel reactor design can make gas phase and solid phase be in adequate contact and achieve gas flow redistribution in the fuel reactor. On this unit, both cold and hot experiments were conducted. The gas-solid flow characteristics were studied on the cold model, and the system was successfully commissioned and in stable operation. No gas leakage occurred between reactors. In the hot experiments, SS from the municipal wastewater treatment plant was chosen as solid fuel and hematite with a size range of 0.3-0.45 mm was used as oxygen carrier. To thoroughly evaluate the performance of this noval CLC system, the combustion compensation efficiency and carbon supplementation efficiency were proposed. The results showed that the two-stage fuel reactor design was beneficial to improving the carbon conversion efficiency of the whole system. The carbon conversion efficiency, carbon capture efficiency, and combustion compensation efficiency increased within the temperature range of 800-900 degrees C, while the carbon supplementation efficiency decreased at high temperature. Besides, the effect of SS feed rate was also investigated. High SS feed rate resulted in lower carbon conversion efficiency due to the large bubbles produced during the SS gasification process. At last, the phase characteristics of fresh oxygen carrier and oxygen carrier extracted from the both fuel reactors were detected. Fe3O4 was the main reduced phase of hematite in the FR.