CO2 catalytic gasification with NaAlO2 addition for its low-volatility and tolerant to deactivate

Abstract

Although catalytic gasification has many natural advantages, its industrial application is still hindered by catalysts deactivation for the reaction between catalysts and mineral in coal, slagging that arises from the fluxing effect of catalyst, fouling and corrosion for the volatility of alkali. Yet, we find that NaAlO2, with a high melting point, can alleviate the above problems. In this study, NaAlO2 catalytic gasification behaviors were firstly investigated, and its catalytic gasification reactivity was compared with Na2CO3, the latter is the traditional catalyst for gasification. Meanwhile, the deactivation behaviors, Na distribution and ash fusion temperatures (AFTs) of the catalytic gasification ash were comprehensively investigated by TG, ICP-OES, and XRD. The results show that NaAlO2 is more tolerant to deactivate than Na2CO3. Part of Na2CO3 reacts with mineral in coal to form deactivated sodium aluminum silicate at 700 °C, but NaAlO2 deactivates until 900 °C. Compared with Na2CO3, NaAlO2 is more difficult to volatilize during catalytic gasification, alleviating fouling and corrosion problems. Meanwhile, NaAlO2 increases the AFTs, yet Na2CO3 decreases the AFTs. The softening temperature (ST) of the gasification ash with NaAlO2 addition is 249 °C higher than that of Na2CO3 with the same Na loaded content 0.94 mmol Na/g char, which is very useful to alleviate the slagging problems. Therefore, NaAlO2 is an excellent catalyst for gasification with more tolerant to deactivation, lower Na volatility, and higher AFTs.