In recent years unfired burner assemblies of complex configuration made of refractory concretes have been widely used in various furnace equipment.The purpose of this investigation was the development of a composition of concrete for production of highly resistant burner assemblies directly at the user in the absence of specialized refractory production facilities.Crushed type MKS-72 high-alumina parts to GOST 24704-81, high-alumina chamotte with an AI203 content of not less than 85%* to Technical Instructions 199-0-4-85 produced by Semiluki Refractory Plant, and type PKPS-97 or PKPS-98 electrofused corundum to Technical Specification 14-8-394-81 were tested as the filler in development of the composition of concrete.Aluminum-calcium quick-hardening high-alumina to Technical Specification 14-8-242-77 with a specific surface of about 9000 cm2/g and a chemical composition of 73.48% AI203, 25.90% CaO, 0.22% Fe203, and 0.44% SiO= was used as the binder.The use of alumina cement was undesirable as the result of its low refractoriness (1480~ The high-alumina cement consisted of 80-85% calcium dialuminate (CaO'2AI203) and 10-15% calcium monoaluminate.The refractoriness of the cement is 1750~ Specimens for laboratory investigation in the form of cubes with an edge of 40 mm were prepared from cement mixed with water and concretes with the use of these fillers by pouring into a sectional mold. After drying the specimens were fired at 500, 800, 1200, 1350, and 1580~ with a hold of 6 h. The compressive strength, the open porosity, the apparent density, and the linear shrinkage were determined for the fired specimens.The maximum firing temperature (1580~ corresponded to approximately the temperature of the surface axial channel of the blockin which combustion of natural gas occurs.The properties of specimens of high-alumina cement mixed with water to a water content of 30% are shown in Table i. The specimens were characterized by quite high compressive strengths and during firing at 1580~ partially fused.Firing at 1350~ caused high linear shrinkage of the specimens (15-16%).For the purpose of reduction of shrinkage of the burner assemblies in service it was desirable to use highly refractory fillers based on corundum or high-alumina chamotte with an AI=O 3 content of 70-85% for preparation of the concretes.Specimens with contents of i0, 20, and 30% of high-alumina cement were prepared with the use of crushed MKS-72 high-akumina parts as the refractory filler. The chemical analysis of the filler was 75.8% AI=O 3, 23.2% SiO 2, and 0.40% Fe203 (tot.). The grain distribution of the filler was 21.3% 5-3 mm fraction, 16.42% 3-2 mm, 19.5% 2-1 mm, 14.0% I-0.5 mm, 23.5% 0.5-0.09 ~m, and 5.28% finer than 0.09 mm.The compressive strength and the linear shrinkage of specimens of concrete mixed with water to a water content of 12-15% after firing at different temperatures are shown in Table 2.An increase in cement content in the composition of the concrete from i0 to 30% significantly reduced its refractoriness and after firing at 1580~ ...
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