Enhanced trace pollutants removal efficiency and hydrogen production in rice straw gasification using hot gas cleaning system

• Published in: International journal of hydrogen energy 2019-02, Vol.44 (6), p.3363-3372
• Main Authors: Ngoc Lan Thao, Ngo Thi, Chiang, Kung-Yuh, Wan, Hou-Peng, Hung, Wei-Chun, Liu, Chiung-Fang
• Format: Article
• Language: English
• Subjects: Catalyst; Gasification; Hot gas cleaning; Rice straw; Syngas
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2018.07.133

This study investigates the enhancement of tar and trace gaseous pollutants (e.g. hydrogen sulfide (H2S) and hydrogen chloride (HCl) removal efficiency derived from rice straw gasification using an integrated hot-gas cleaning system. A bubbling fluidized bed gasifier was used by controlling the temperature at 800 °C and equivalence ratio (ER) ranging 0.2 to 0.4. The hot gas cleaning system was operated at 250 °C and designed to combine three types of absorbents including zeolite, calcined dolomite, and activated carbon. Tar, H2S, and HCl removal efficiency and enhanced hydrogen production were also discussed. The experimental results indicated that light fraction tar removal efficiency was higher than 90% and the overall tar removal efficiency was approximately 70%. In the case of ER 0.4, the syngas tar content was decreased from 71.88 g/Nm3 (without hot gas cleaning system) to 16.53 g/Nm3 (with hot gas cleaning system). The tar removal efficiency is nearly 77% using the hot gas cleaning system. The HCl and H2S removal efficiency ranged from 94% to 98% and from 80.7% to 83.92%, respectively. In the case of ER 0.3 and with the hot gas cleaning system, the HCl and H2S concentrations in cleaned syngas gas were less than 40 ppm and 100 ppm, respectively. Meanwhile, the hydrogen concentration of produced gas was also increased from 6.82% to 9.83% with hot gas cleaning system used. It means that the hot gas cleaning system can effectively remove HCl and H2S from produced gas in gasification, but also it has good potential for improving syngas quality and enhancing gas turbine application in the future. •Hot gas cleaning system for removing trace pollutants has successfully developed.•The overall tar removal efficiency was nearly 70% by hot gas cleaning system.•The HCl and H2S removal efficiency were approximately 95% and 80%, respectively.•Hot gas cleaning system could play a key role in improving syngas quality.