Thermal insulating device for high temperature reactors and furnaces which utilize highly active chemical gases

Thermal insulating device comprising:

• (i) a first hollow, self-supporting cylindrically shaped, vertically extending shell for use as a heat shield surrounding a radiant heat source, said shell being in the form of multiple layers of a spiral wound roll-pressed anisotropic sheet of graphite separated by and bonded to an in situ cured phenolic resin coated on both sides of a sheet of heat decomposable carbon based material co-extensive with said spiral wound sheet of graphite, said heat decomposable sheet of carbon based material providing a porous carbon network path for the escape of gases, produced in the course of in situ curing of the phenolic resin, between spiral wound sheets of graphite and also enabling contact between resin on both sides of the sheet of carbon based material after the in situ curing of the phenolic resin;
• (ii) a second vertically extending shell essentially identical to said first shell except for being larger in cross-section, said second shell surrounding said first shell to define an annular chamber therebetween;
• and
• (iii) individual uncompressed particles of expanded graphite essentially filling said annular chamber.