Improved Refractory Liner for Coal Gasification

Refractoryliner

Researchers from the Department of Energy’s National Energy Technology Laboratory (NETL) in Albany, Oregon, have developed a novel refractory material that could overcome one of the major challenges preventing the widespread adoption of the next generation of advanced power plants based on coal gasification. The newly developed refractory material has a longer service life, leading to greater online availability of the gasifier for coal processing.

Coal gasification is an important part of the nation’s efforts to obtain the most energy from its abundant coal supplies. It involves reacting coal with high-temperature, high-pressure steam in a shortage of oxygen, and converting it to a carbon monoxide and hydrogen gas mixture called synthesis gas, or syngas.

Syngas can be used to make gasoline, diesel, and aviation fuels in the coal-to-liquids process, or can be combusted to drive turbines producing electricity. Hydrogen can also be separated from syngas to power advanced fuel cells. Carbon dioxide can be captured for reuse in other processes such as enhanced oil recovery, or it can be sequestered underground to prevent it from contributing to global climate change. The versatility and carbon capture ability of coal gasification highlights its need as an economically viable process.

Gasification is not always viewed as the technology of choice by industry, in part because of the high costs associated with rapidly deteriorating refractory linings. Refractories are heat-resistant materials that protect the metal gasification chamber from its service environment. Investigation by NETL researchers revealed that the major causes of refractory wear are:

  • Penetration of corrosive molten material (slag) that originates from coal mineral impurities into the re-fractory brick
  • Corrosion of the refractory by that molten slag. Once slag is inside the brick, it generates cracks parallel to the brick?s face. Eventually these cracks link and cause flaking (spalling) of the brick?s surface as pieces up to one-inch deep, leading to premature lining failure.

Refractory linings typically cost $1 million or more to replace, depending on the gasifier size and the amount of lost production during the plant shutdown. For that reason, refractory service life has slowed the adoption of gasification technology.

NETL researchers targeted altering the internal structure of the refractories through chemical changes to prevent slag penetration, with the goal of eliminating spalling as a wear mechanism. The addition of a few percent of phosphate compounds to the chromia brick formulation was found to be successful.

Once the technology was patented, NETL entered into a CRADA with Harbison-Walker Refractories Company to scale the process for field trials. The resulting refractory was found to increase refractory service life by up to 50 percent. HarbisonWalker licensed the technology from NETL, conducted additional field trials, and commercialized the product as AUREXTM 95P. It has received reviews of “exceptional” and “excellent” at test sites, and is the refractory of choice in high wear areas of a gasifier. One gasifier site has lined almost the entire gasifier with the product.