NETL researchers have developed a refractory brick that can increase the service life of refractories that are used to line entrained flow slagging gasifiers, reducing wear from molten mineral impurities (slag) in carbon feedstock, and resulting in reduced replacement costs and an increased gasifier availability and efficiency.

The brick is composed primarily of chromium oxide (Cr₂O₃), aluminum oxide (Al₂O₃), and carbon (C); and is designed to decrease molten slag corrosion, which is a dissolution of the refractory into the slag and pore penetration that causes spalling—a repetitive wear process where layers of the brick porosity penetrated by slag break off at the slag refractory interface. Corrosion and spalling are the two primary wear mechanisms causing refractory replacement in the high-pressure, high-temperature environment of these types of advanced energy systems.

Traditional high chrome oxide refractory bricks fail by spalling or corrosion—dissolving of the refractory into slag over time—reducing the refractory lining thickness that protects the gasifier steel shell. Visual inspections and thermal monitoring are needed to determine refractory wear, requiring process shutdowns and physical entry into the gasifier. Worn refractory lining are removed and replaced with new bricks to keep the gasification chamber operating efficiently and to reduce the risk of the steel containment vessel have catastrophic failure caused by the severe service gasification environment, something that would cause system shutdown, and something that could result in personnel injuries.

The gasification chamber, with its protected refractory lining, is where a carbon feedstock, like coal, petcoke, and/or biomass, is converted to CO and H₂ in a process called gasification. CO and H₂ is the gasification product. The CO/H₂ mixture is commonly called synthesis gas, or syngas, and can be used to generate power, or as a feedstock material to generate other chemical compounds.

Impurities in the carbon feedstock can vary from under a percent for most petcoke, to 10 percent or higher in coal. Biomass varies from a few percentage points to 50 weight-percent or higher. In an entrained bed slagging gasifier, the ash byproducts melt to form slag, which attacks the refractory lining.

NETL’s novel chromia refractory brick was developed using carbon treatment to fill void space. It can be used at gasification temperatures between 1250 degrees Celsius and 1575 degrees Celsius, pressures of between 300 and 1000 psi, and under reducing conditions of gasification. It improves refractory service life by reducing slag corrosion and spalling of the gasifier refractory lining.

The invention was developed by NETL’s James Bennett and Keyi-Sing Kwong and is available for licensing and/or further collaborative research. The technology was awarded a patent on March 21, 2017 (U.S. Patent No. 9,590,318) “Chromia Refractory Brick with Carbon Treatment.”

The innovation is one more example of how NETL develops technology solutions to enhance the nation’s energy foundation.