Effect of temperature and additives on the yields of products and microwave pyrolysis behaviors of wheat straw

The microwave pyrolysis of wheat straw has been studied in the laboratory using a fixed-bed microwave reactor. The effects of both the temperature and the presence of additives on the yields and properties of products and pyrolysis behaviors are the focus of this work. The results showed that at constant temperature (500 °C) pyrolysis, the yield of solid products decreased with the increase in microwave power during the heating up stage, whereas the yield of gas products was the opposite; H2 concentration increased by approximately 20 vol.% with the increase in microwave power, leading to a high heating rate. The lowest concentration of CO2 was obtained when adding CaO. The yields of H2 and CO increased with the promotion of gasification reactions between carbon and CO2 and the dry reforming and cracking reaction of CH4 under high temperature by K2CO3. Two gas release peaks occurred when the sample continued to be heated after pyrolysis at a constant temperature. The first peak was the release of most volatiles, and the second one was the release of residual volatiles after temperature control canceled. The final temperature and presence of additives had strong effects on the yields and properties of the final products.

► A special microwave pyrolysis reactor (MWR) has been built for the pyrolysis of biomass.
► The microwave pyrolysis at a constant temperature or constant microwave power, and adding different additives were carried out.
► The product yields and compositions, as well as fuel properties at different reaction conditions was investigated.