Catalytic effect of char for tar cracking in pyrolysis of citrus wastes, design of a novel experimental set up and first results

This study describes the design of a novel fixed bed lab scale down-draft ‘multiple layer’ reactor, aimed to investigate the effect of chars as means to catalyze tar cracking during pyrolysis of agro-industrial wastes. Preliminary experiments were carried out on pyrolysis of citrus wastes at 500, 700 and 800 °C for 30 minutes holding time in N2 atmosphere. Tar obtained from pyrolysis of same feedstock at 650 °C and 800 °C were used as cracking catalyst. Tests showed that tar yields of pyrolysis of approximately 2 g of oven dried lemon pulp could be reduced when approximately 0.4 g of chars were used as a catalytic means. Results of runs conducted at 500, 700 and 800 °C show no significant cracking effect at the lower temperature and a moderate (3% reduction in tar yield) at the higher temperatures. Results show that catalytic effect of char may be foreseen in downdraft set-ups but mainly in sections close to the gasifying zone. Overall, the system described showed to be a valid tool in evaluating the effectiveness of using chars in tar cracking during pyrolysis of citrus wastes. Moreover, important insights were obtained for future more in depth analyses of the issue.