A Prototype Microwave Pyrolyzer for Solid Wastes

摘要

This paper continues previous work on pyrolysis processing of solid wastes for spacecraft and planetary surface applications. A prototype microwave pyrolyzer apparatus was designed, constructed and tested. Experiments were done with cellulose, wheat straw and two formulations of a feces simulant. A central microwave absorber was used consisting of a quartz tube filled with activated carbon. The pyrolyzer included a primary pyrolysis zone and a secondary cracking zone consisting of a SiC bed. The cracking zone temperature ranged from ~ 850 to 1000 °C. The sample was inserted into the (primary) microwave heating zone after the cracking bed temperature was stabilized to ～ 950 °C. Analysis of the gas products was performed by both FTIR spectroscopy and mass spectrometry. The sample sizes were 15-20 g for wheat straw, 40 g for cellulose and 100 g for the feces simulants. The cellulose sample was not run to completion, but was interrupted to provide photographic evidence that microwave heating using a central microwave absorber results in pyrolysis beginning near the center of the sample and proceeding in an outward fashion. For the wheat straw and feces simulant samples, it was found that, on a per-gram basis, the yields of ethylene, methane, and hydrogen were significantly higher than a previous pyrolyzer that was based on a modified domestic microwave oven. This result was mainly attributed to the presence of a separate cracking zone in the current pyrolyzer.