Effect of CaO additive on co-pyrolysis behavior of bituminous coal and cow dung

Co-pyrolysis of coal and biomass has an important function on high efficient and clean utilization of coal and biomass. Effect of CaO additive on the co-pyrolysis behavior of Meihuajing (MHJ) bituminous coal and cow dung (CD) and the synergistic effect between them were investigated by using TG and Py-GC/MS. The results show that both the heating rate and the addition of CaO have an important influence on the co-pyrolysis of coal and cow dung. As the heating rate increases from 5 to 25 degrees C/min, the negative synergistic effect for the yield of char weakens during the co-pyrolysis when no CaO is added to the MHJ and CD. CaO partly delays the pyrolysis of CD and declines the pyrolysis temperature of MHJ, providing an overlapping pyrolysis range for the two fuels at around 370 degrees C. The synergies between CD and MHJ are enhanced by the addition of CaO during their co-pyrolysis at the range of 350 to 450 degrees C. The positive role of CaO increases with the increasing heating rate, and reaches its maximum at the heating rate of 15 degrees C/min. It is also worth noting that the addition of CaO raises the content of high-valued tar products such as benzenes and nephthalenes.