Primary Investigation Of Synergy Effect In Co-pyrolysis Of Ximeng Lignite And Corncob

With the increase of demand for energy source and the severity of environmental requirement around the world, much more focus is being placed on the utilization of biomass due to its features of environment-friendliness and renewability. However, biomass has the critical disadvantage of low heating value, which restricts the alone utilization range of biomass. In order to relief the situation of energy emergency, the co-utilization of coal and biomass has become the research hotspot based on the integrated advantages of both coal and biomass. There exist the interactions between coal and biomass in the co-utilization process, which influence the distribution and yields of products. The relevant information obtained by analyzing the interactions during the co-utilization of coal and biomass is beneficial for the process design of co-utilization of coal and biomass.Our work is to study the behaviors of lignite/corncob blend under the conditions of both temperature-programmed pyrolysis and fast pyrolysis by means of designing novel reactor and the relevant experimental results. And the effect of the interactions on the distribution and quality of products is also studied in this paper. And some conclusions are drawn from the experiments as follows:(1) During the temperature-programmed pyrolysis, the total volatile and tar yields of lignite are smaller than that of corncob, which is related with the components and properties of lignite and corncob. As compared to lignite, corncob has higher oxygen and aliphatic moieties and the lower content of aromatic moieties, which are easy to decompose. So, the total volatile yield, tar yield, and gases releasing amount of lignite/corncob blends during pyrolysis decrease with the increase of blend ratio of lignite.(2) During the temperature-programmed pyrolysis, the total volatile yield and tar yield of lignite/corncob blends are different from the relevant theoretical values, indicating that there exists the synergic effect in the process of co-pyrolysis of lignite and corncob, and this effect mainly occurs in the secondary reactions of between lignite volatile and corncob volatile. Meanwhile, the presence of synergic effect increases the yield of tar, decreases the yield of gaseous products, but does not change the yield of total volatile. According to the analyses of different experimental results, the main reason of this effect is the interactions between corncob volatile and nascent char of lignite during co-pyrolysis. And the synergic effect also influences the oxidizing reactivity of char from pyrolysis. The reactivity of chars from pyrolysis is in direct proportion to the blend ratio of corncob and lignite, which is closely related to the abundant potassium in corncob and the content of potassium decreases with the increase of lignite blend ratio. What’s more, the interactions between corncob volatile and lignite nascent char change the structure of char, which is one of the factors affecting the reactivity of char.(3) The conversion behaviors of lignite and corncob during fast pyrolysis are different from that during temperature-programmed pyrolysis. In the temperature range of500-900℃, the total volatile yield and gases releasing amount of corncob are higher than that of lignite.700℃is the turning point of tar yield. When the temperature is lower than700℃, the tar yield of lignite is larger than that of corncob, and then with the temperature increasing, the result is opposite. The total volatile of lignite/corncob blend increases with the pyrolysis temperature, increasing by17%.(4) During fast pyrolysis, the total volatile and tar yields of lignite/corncob blend are not accordant to the relevant theoretical values, illustrating that there exists synergic effect in the co-pyrolysis of lignite and corncob. The synergy increases the tar yield slightly, and decreases the formation of gaseous products below700℃, but not changes the total volatile yield. When the temperature is in the range of700℃-900℃, the synergy obviously decrease the formation of total volatile and tar, but increase the release of gaseous products. The interactions between corncob volatile and nascent char of lignite are the main factor of the synergic effect during co-pyrolysis. The interactions between lignite volatile and corncob nascent char and the interactions between volatile of corncob and nascent char of lignite during fast co-pyrolysis restrain the formation of volatile and tar, but the interactions between corncob volatile and lignite volatile improves the release of total volatile but decrease tar yield. Meanwhile, the interactions between volatile and char of lignite and corncob influence the migration of K, Na, Ca, Mg, and Fe in char.