Refractory Problems in Production of Hydrogen by Pyrolysis of Natural Gas*

A bstract The severe attack of the refractory checkerwork in a regenerative furnace was encountered at temperatures over 2500°F. Pilot‐plant tests, supplemented by a laboratory investigation, were made of silicate refractories varying in alumina content from 0 to 70%. These tests indicate that the attack was primarily caused by the reduction, to a volatile form, of free and combined silica by carbon. This left a granular residue of mullite and/ or corundum, depending on the original alumina content. Secondary reactions occurred, the most notable of which was the recombination of the corundum with locally deposited silica to form secondary mullite. The laboratory test showed that carbon reacted with mullite at a temperature as low as 2470°F. A petrographic study has shown that the decomposition of the refractory material takes place in well‐defined stages from the initial removal of free silica to the breakdown of mullite. The rate of decomposition increases with temperature.