Effect of NO2 in exhaust gas from an oxyfuel combustion system on the cap rock of a proposed CO2 injection site

Kosuke Tanaka, Hirokazu Okawa, Keiichiro Hashimoto, Ryohei Takahashi, Akira Imai, Katsuyasu Sugawara

Research output: Contribution to journalArticle

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Abstract

A laboratory geochemical study was conducted using a drill core sample of cap rock from the Surat Basin, Australia, to investigate the effect of NO2 contained in the CO2 gas exhausted from the oxyfuel combustion process (oxyfuel combustion CO2) on the cap rock. A gas (CO2 containing NO2) was prepared to simulate the exhaust gas produced from the oxyfuel combustion process. Two types of gases (pure CO2 and CO2 containing SO2) were also prepared as reference gases. The effect of NO2 on cap rock was studied experimentally using these gases. No differences in the amounts of leached ions and pH changes for CO2 containing NO2 (36 ppmv), pure CO2, and CO2 containing SO2 (35 ppmv) existed. The pH values decreased immediately after CO2 gas injection but increased with time as a result of mineral buffering. Leaching of Fe, Mg, Ca, and K was suggested to have occurred as the result of dissolution of Fe-chlorite, prehnite and illite-smectite mixed layer clay in the shale sample. The amounts of Ca, Fe, and Mg leached with CO2 containing NO2 (318 ppmv) were higher than those for pure CO2. For the mixture containing 318 ppmv NO2, the pH increased more than that for the other gas conditions immediately after the pH fall at the start of the experiment, because oxidation-reduction reactions occurred between Fe2+ and NO3 -. Moreover, the results indicated that some of the leached Ca and Fe were deposited on the shale sample because of the pH increase. Therefore, we concluded that the effects of NO2 on mineral dissolution and pH changes of formation water are negligible when oxyfuel combustion CO2 containing about 30 ppmv of NO2 is injected into an underground aquifer. In addition, even if about 300 ppmv NO2 is accidentally injected into the underground aquifer, mineral dissolution is suppressed due to the buffering of pH decrease after gas injection.

Original languageEnglish
Pages (from-to)17-26
Number of pages10
JournalApplied Geochemistry
Volume70
DOIs
Publication statusPublished - Jul 1 2016

Fingerprint

cap rock
Exhaust gases
combustion
Gases
Rocks
gas
Minerals
Dissolution
Shale
Aquifers
dissolution
buffering
shale
Core samples
mineral
Redox reactions
aquifer
prehnite
Leaching
effect

All Science Journal Classification (ASJC) codes

  • Environmental Chemistry
  • Pollution
  • Geochemistry and Petrology

Cite this

Effect of NO2 in exhaust gas from an oxyfuel combustion system on the cap rock of a proposed CO2 injection site. / Tanaka, Kosuke; Okawa, Hirokazu; Hashimoto, Keiichiro; Takahashi, Ryohei; Imai, Akira; Sugawara, Katsuyasu.

In: Applied Geochemistry, Vol. 70, 01.07.2016, p. 17-26.

Research output: Contribution to journalArticle

Tanaka, Kosuke ; Okawa, Hirokazu ; Hashimoto, Keiichiro ; Takahashi, Ryohei ; Imai, Akira ; Sugawara, Katsuyasu. / Effect of NO2 in exhaust gas from an oxyfuel combustion system on the cap rock of a proposed CO2 injection site. In: Applied Geochemistry. 2016 ; Vol. 70. pp. 17-26.
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