Abstract
We have recently presented two new pyrolysis methods: one is the flash pyrolysis of coal preswollen with hydrogen donor solvent in an inert atmosphere (method I). This method drastically increased the yields of total volatiles and liquids. The other is the pyrolysis of coal in the atmosphere containing a solvent vapor (method II). In this method, the BTX yield reached 5 times larger than that in an inert atmosphere.In this paper an Australian brown coal (Morwell) preswollen by tetralin at 100°C was pyrolyzed in a free fall pyrolyzer to examine the validity of the method I in a practical operation. The yields of total volatiles and tar increased at all temperatures. At 850°C the BTX yield increased up to 3.9% which was twice as large as that obtained from the pyrolysis of the raw coal. Apart from the tetralin in the gas phase, the tetralin in the swollen coal was found only to be dehydrogenated to naphthalene during the pyrolysis. This indicates that the incrases in the yields of total volatiles and tar are caused by the effective hydrogen radical transfer from tetralin to coal fragments in the micropores. Thus it is clarified that the method I is also valid in an actual industrial pyrolyzer.Next, the method I and the method II were combined (method III) to realize effective hydrogen transfer from solvent to coal fragments both in the micropore of the coal and in the gas phase. To examine the validity of the method III, Morwell coal swollen by tetralin was pyrolyzed in a stream of 2-methyl-1-propanol vapor. Both the coal conversion and the liquid yield increased significantly through effective hydrogen transfer within coal particles, and simultaneously the BTX yield increased up to 6.2kg/100kg-coal through the acceleration of the gas phase reaction. Thus it is clarified that the method III is an attractive method to obtain valuable chemicals in high yields and in high selectivities.
