Microwave-induced cracking of pyrolytic tars coupled to microwave pyrolysis for syngas production

Herein a new process is proposed to produce a syngas-rich gas fraction (>80 vol% H2 + CO) from biowaste based on microwave heating within two differentiated steps in order to avoid tars production. The first step consists of the microwave pyrolysis of biowaste induced by a char-based susceptor at 400–800 °C; tars, char and syngas-rich gas fractions being produced. The tars are then fed into the second step where a portion of the char from the first step is used as a bed material in a 0.3:1 wt% ratio. This bed is heated up by microwaves up to 800 °C, allowing thermal cracking of tars and additional syngas (>90 vol% H2 + CO) being then produced. This new concept arises as an alternative technology to the gasification of biowastes for producing syngas with no need for catalysts or gasifying reagents to minimise tars production.