DRY OUT OF DENSE REFRACTORY CASTABLES VIA USE OF PERMEABILITY ENHANCING ACTIVE COMPOUND

摘要

The removal of 'free' and 'bonded' water is a critical step in the preparation of dense refractory castables for use in modern furnaces, with the risk of premature failure due to an incompatible dry-out schedule commonly referred to as 'explosive steam spalling'. The risk of this mode of failure increasing with highly deflocculated castables with very low permeability is well documented and creates a significant safety concern during the installation process as well as potential financial implications. This paper discusses the impact of REFPAC MIPORE 20 (MP20), an innovative permeability enhancing active compound (PEAC) for calcium aluminate cement bonded castables. Investigations show how the MP20-powder interacts with the cement hydration path creating a new microstructure that significantly improves gas permeability at temperatures above 100°C while for example the traditionally used Polypropylene-fibers are effective only above 150°C. Test results show that the new microstructure allows more water removal at lower temperatures and lower pressure build-up. A more permeable microstructure is formed and investigations show how it can effectively release moisture prior to critical temperatures being reached which avoids high steam pressure build-up in the pores. This paper also explores how formulation types, curing conditions, and dimensions of the monolith impact the water release.