A Study of Chemical Reactivity in Ceramic Heat Exchangers

Past techniques to evaluate the resistance to chemical attack of rotary ceramic regenerator structures and materials have been used as screening tests with some success. The major drawback, though, has been the lack of simulation of the thermal and chemical characteristics of the exhaust stream. A new technique has been developed which allows one to reproduce more closely the environment of the regenerator and therefore determine the response of structures and materials to various chemical species and thermal gradients. Sulfur attack results from this test are compared with those from previous laboratory tests and also gas turbine engine tests. Materials considered include both β-spodumene and cordierite compositions. The essential conclusions from this study are: 1 – The SO₂-gradient furnace can simulate the chemical and thermal environments of a rotary regenerator in operation; 2 – Sulfuric acid vapor ion-exchange is the predominant sulfur related reaction in β-spodumene rotary regenerators; 3 – Leaching of cordierite regenerators by sulfuric acid will not be observed unless the temperature on the cold face of the regenerator lies below the sulfuric acid dew point of the combustion gases.