Failure Mechanisms in High Chrome Oxide Gasifier Refractories
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asification
GASIFICATION as a modern high-temperature, high-pressure industrial process was first used by the oil industry in the 1950s to process low-value petroleum and by-products from petroleum refining into higher value products. Since that time, gasification has expanded to other uses, including processing low-cost carbon materials for power generation and producing CO and H2 feedstock for use by the chemical industry (for applications from fertilizer to Fischer–Tropsch liquids), and is considered a leading candidate to produce H2 for a hydrogen-based economy. It is one of several technologies expected to see increased use in the future. Gasification is being evaluated, in part, because of its high efficiency, ability to capture CO2 for sequestration or reuse in other applications, and fuel flexibility. As a process, gasification converts a carbon feedstock (typically methane, coal, or by-products from petroleum processing such as petcoke) into CO and H2 (called synthesis gas or syngas). The process of gasification JAMES P. BENNETT and KYEI-SING KWONG, Ceramic Engineers, are with the National Energy Technology Laboratory– USDOE, Albany, OR 97321. Contact e-mail: [email protected] Manuscript submitted April 9, 2010. Article published online March 3, 2011 888—VOLUME 42A, APRIL 2011
occurs in a facility similar to the general flow sheet shown in Figure 1, with major downstream processing and applications or proposed applications for the syngas product shown. Gasification can occur using any of a number of gasifier designs, including dry ash gasifiers such as the Sasol–Lurgi* and Foster Wheeler designs *Disclaimer: The use of commercial products and brand names does not imply endorsement by the DOE.
(slag typically does not fuse due to the low temperature of operation), water-cooled entrained bed slagging gasifiers such as the Shell and Siemens designs (gasification occurs at temperatures that create a molten slag from ash which is contained by a water-cooled refractory liner), and the air-cooled entrained-bed slagging gasifiers that include the ConocoPhillips and General Electric designs (these gasifiers operate at temperatures where ash liquefies into molten slag that flows down an air-cooled refractory liner surface). Each gasifier design has advantages and disadvantages that determine the amount and type of carbon feedstock it can process and the syngas composition produced. Gasifiers are used to contain the severe service reaction between carbon feedstock (typically coal, petroleum coke, or biomass), water (or steam), and oxygen in a reducing environment (shortage of oxygen, with the oxygen partial pressure typically between 107 and 109 atm), producing a primary product of CO and
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METALLURGICAL AND MATERIALS TRANSACTIONS A
Fig. 1—Schematic of the overall gasification process.
H2 from the feedstock materials. The air-cooled slagging gasifiers currently used by industry (shown in Figure 1) are high-temperature, high-pressure reaction chambers, typically operating be
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