• 제목/요약/키워드: Caustic Cracking

검색결과 16건 처리시간 0.051초

API-581 절차에 의한 정량적 위험기반검사에서 부식성 균열에 의한 응력부식의 사고발생 가능성 해석 (Analysis of Likelihood of Failure for the Stress Corrosion Cracking by Caustic Cracking through the Quantitative Risk Based-Inspection using API-581 BRD)

  • 이헌창;최성규;조지훈;함병호;김태옥
    • 대한안전경영과학회지
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    • 제9권1호
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    • pp.65-76
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    • 2007
  • The likelihood of failure for the stress corrosion cracking (SCC) of caustic cracking, which affect to a risk of facilities, was analyzed through the risk based-inspection using API-581 BRD. We found that SCC of the caustic cracking was occurred above 5 % NaOH concentration, and the technical module subfactor (TMSF) was maximized for above 50 % concentration. The heat traced and monitoring were not sensitive to the TMSF with NaOH concentration and temperature. But the steam out was more of less affect minimum value of the TMSF. Also, the inspection number, the inspection effectiveness, and the year since inspection were very sensitive to the TMSF with NaOH concentration and temperature. Therefore, the plan of next inspection will be established with compositively considering those at once.

Effect of Additives on the Stress Corrosion Cracking Behavior of Alloy 600 in High Temperature Caustic Solutions

  • Hur, Do Haeng;Kim, Joung Soo;Baek, Jae Sun;Kim, Jung Gu
    • Corrosion Science and Technology
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    • 제3권1호
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    • pp.6-13
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    • 2004
  • The effect of inhibitors on the electrochemical behavior and the stress corrosion cracking resistance of Alloy 600(UNS N06600) was evaluated in 10% sodium hydroxide solution at $315^{\circ}C$. The specimens of a C-ring type for stress corrosion cracking test were polarized at 150 mV above the corrosion potential for 120 hours with and without inhibitors such as titanium oxide, titanium boride and cerium boride. The chemical compositions of the films formed on the crack tip in the C-ring specimens were analyzed using a scanning Auger electron spectroscopy. The cerium boride, the most effective, was observed to decrease the crack propagation rate more than a factor of three compared with that obtained in no inhibitor solution. It was found that the changes of the active-passive transition potentials and the film compositions were related to the resistance to stress corrosion cracking in high temperature caustic solution.

Stress Corrosion Cracking of Alloy 600 and Alloy 690 in Caustic Solution

  • Kim, Hong Pyo;Lim, Yun Soo;Kim, Joung Soo
    • Corrosion Science and Technology
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    • 제2권2호
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    • pp.82-87
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    • 2003
  • Stress corrosion cracking of Alloy 600 and Alloy 690 has been studied with a C-ring specimen in 1%, 10% and 40% NaOH at $315^{\circ}C$. SCC test was performed at 200 mV above corrosion potential. Initial stress on the apex of C-ring specimen was varied from 300 MPa to 565 MPa. Materials were heat treated at various temperatures. SCC resistance of Ni-$_\chi$Cr-10Fe alloy increased as the Cr content of the alloy increased if the density of an intergranular carbide were comparable. SCC resistance of Alloy 600 increased in caustic solution as the product of coverage of an intergranular carbide in grain boundary, intergranular carbide thickness and Cr concentration at grain boundary increased. Low temperature mill annealed Alloy 600 with small grain size and without intergranular carbide was most susceptible to SCC. TT Alloy 690 was most resistant to SCC due to the high value of the product of coverage of an intergranular carbide in grain boundary, intergranular carbide thickness and Cr concentration at grain boundary. Dependency of SCC rate on stress and NaOH concentration was obtained.

Hybrid Bardenpho 공정에서 Spent Sulfidic Caustic의 주입을 통한 독립영양 탈질에 관한 연구 (Study on Autotrophic Denitrification by the Injection of Spent Sulfidic Caustic in a Hybrid Bardenpho Process)

  • 이재호;박소라;박정진;변임규;박태주
    • 한국물환경학회지
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    • 제24권5호
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    • pp.563-568
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    • 2008
  • In petroleum refining industry, caustic (NaOH) solution is used to remove $H_2S$ from hydrocarbon streams in naphtha cracking process. Once $H_2S$ is absorbed in caustic solution, the solution becomes known as spent sulfidic caustic (SSC), which contains high concentrations of hydrogen sulfide and alkalinity. This study was focused on the evaluation of autotrophic denitrification by SSC in a hybrid Bardenpho process. SSC was injected to the anoxic (1) and anoxic (2) tank at different S/N ratio. In a previous lab-scale study, as we operated a modified Ludzack-Ettinger process, it was observed that the COD increment of effluent and nitrification failure happened because of non-biodegradable matters in SSC and high pH, respectively. Thus cilia media was packed at 2.4%(v/v) in all aerobic tanks and the pH of SSC was neutralized from 13.3 to 11.5 with addition of sulphuric acid ($H_2SO_4$). Consequently, these strategies were successful because no COD increment of effluent was observed and nitrification failure did not happen. The maximum TN removal efficiency was 77.5% when SSC was injected to both the anoxic (1) and anoxic (2) tanks. The mean TN concentration of effluent in this condition was 5.8 mg/L.