Densification characteristics of chromia/alumina castables by particle size distribution
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Densification characteristics of chromia/alumina castables by particle size distribution Jingming Zhao1, Taesuk Kim1, Gichul Kim1, Kyuhong Hwang1* and Dongsik Bae2
Abstract The quality of the refractories applied on integrated gasification combined cycle should be a key factor that affects both the reliability and the economics of gasifier operation. To enhance the workability of chromia/alumina castables, three types of ultrafine alumina powder were added to improve the workability. Densification behavior of such castables in the presence of ultrafine alumina was assessed through the measurement of parameters like flow value, viscosity, bulk density, apparent porosity, and microstructure evaluation by an SEM study. It’s proved that the specific surface area and particle size distribution of ultrafine powders in matrix parts greatly influence the densification behavior of these castables. Keywords: densification, chromia/alumina, castables, IGCC
Introduction The gasification process converts carbonaceous materials such as coal, petroleum coke, and biomass to synthesis gas consisting of H2 and CO that can be utilized as a chemical feedstock or for powder generation. The ash from the carbon feedstock is liquefied into slag in the gasification chamber and can corrode, penetrate, and interact with the refractory liner at the elevated temperatures, severely limiting refractory service life and gasifier operation [1]. Reaction can occur between refractory materials and slag oxides of Fe, Si, and/or V or with H2 and CO gasification products. Chromia/alumina castables have been widely used in integrated gasification combined cycle [IGCC]. It provides a number of advantages such as high resistance to slag corrosion and low slag penetration. However, the current generation refractory liners installed in gasifier systems have a short service life [2]. This paper discusses efforts to increase refractory service life through the development of refractory densification. The densification effect was examined by adding ultrafine alumina powder to reduce the amount of water and improve the flow ability of the chromia/alumina refractory castable.
* Correspondence: [email protected] 1 Engineering Research Institute, i-Cube Center, Gyeongsang National University, Jinju, 660-701, South Korea Full list of author information is available at the end of the article
Experimental procedure The particle size distribution of the castable was adjusted to a theoretical self-flowing continuous curve based on the Andreassen model [3]. The white fused alumina was used as aggregate, and the distributions were 3 to approximately 5 mm, 1 to approximately 3 mm, and approximately 1 mm with optimized distribution. Chromia and alumina were used as matrix taken at mass ratios of 0, 0.5, and 1.0. The following additions were introduced into the mixture: high grade alumina cement, 3%; ultrafine fumed silica powder, 1%; two types of polycarboxylate ether based on polycarboxylic acid, 0.1%. Three types of ultrafine alumina were adde
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