Supercritical water oxidation corrosion

General Atomics. 1997. Supercritical Water Oxidation Corrosion Studies Technical Report, Vols. 1 and 2. Aberdeen Proving Ground, Md. Program Manager for Assembled Chemical Weapons Assessment... 

Hayward, T., Svishchev, I. and Makhija, R. (2003). Stainless steel flow reactor for supercritical water oxidation corrosion tests, J. Supercrit. Fluid, 27, pp. 275-281. 

The formation of acids from heteroatoms creates a corrosion problem. At the working temperatures, stainless steels are easily corroded by the acids. Even platinum and gold are not immune to corrosion. One solution is to add sodium hydroxide to the reactant mixture to neutralize the acids as they form. However, because the dielectric constant of water is low at the temperatures and pressure in use, the salts formed have low solubiHty at the supercritical temperatures and tend to precipitate and plug reaction tubes. Most hydrothermal processing is oxidation, and has been called supercritical water oxidation. 

Reaction vessels for supercritical water oxidation must be highly corrosion resistant because of the aggressive nature of supercritical water and oxidation reaction products at extreme temperatures and pressures. Supercritical oxidation of PCBs and some chlorinated hydrocarbons can be difficult... 

L.B. Kriksunov and A.A. Me Donald, Corrosion in Supercritical Water Oxidation Systems a Phenomenological Analysis, J. Electrochemical Society, 142, (1995), 4069. 

T. A. Danielson, Corrosion of Selected Alloys in Sub-and Supercritical Water Oxidation Environments, Thesis, University of Texas USA, (1995). 

Corrosiveness of supercritical water oxidation (SCWO) media and technical issues that need to be resolved for practical use of SCWO technology... 

Kriksunov LB, Macdonald DD. Corrosion in supercritical water oxidation systems—a phenomenological analysis. J Electrochemical Sci 1995 142(12) 4069, 4073. 

As said earlier, this hazard must be evaluated prior to treating any fluid/co-solvent/raw material in the equipment. A considerable corrosion hazard is related to supercritical water oxidation equipments, where special alloys are required. 

Supercritical water oxidation poses a unique corrosion problem that has not been experienced in other chemical processes. Development of new materials is needed to address the problem. The material needs to withstand a chemically harsh environment along with the high temperature and pressure conditions. Even if some current materials are available for... 

Residence time for supercritical water oxidation systems may be as short as several minutes at temperatures of 600 to 650°C. More than 99.9 percent conversion of EPA priority pollutants such as chlorinated solvents has been achieved in a pilot-scale plant with retention time less than 5 minutes. The system is limited to treatment of liquid wastes or solids less than 200 microns in diameter. Char formation during reaction may impact the oxidation time of the organics, while separation of inorganic salts during the process may be a problem. Typical materials for the reactor are Hastelloy C-276 and Iconel 625 (high nickel alloys), which can withstand high temperatures and pressmes and the corrosive conditions. 

K. M. Garcia and R. Mizia, Corrosion Investigation of Multilayered Ceramics and Experimental Nickel Alloys in SCWO Process Environments, First International Workshop on Supercritical Water Oxidation, Amelia Island, Florida, February, 1995. 

Recommendation (Demo I) GA-2. Before construction of a full-scale supercritical water oxidation (SCWO) system, additional evaluations of constraction materials and fabrication techniques will be necessary because corrosion and plugging prevent continuous operation with the present design. If the new construction materials do not solve these problems, then alternative SCWO reactor designs should be investigated. 

Finding (Pueblo) GA-7. Corrosion remains a serious operating problem with the GATS supercritical water oxidation system. Failure to shut down in time to replace a perforated reactor liner could result in rapid corrosion of the high-pressure reactor shell. 

Recommendation (Pueblo) GA-3. Methods for monitoring the extent of corrosion in the supercritical water oxidation reactor other than by measuring effluent turbidity should be investigated. Outputs from the monitors should identify corrosion that exceeds safe operating limits, enabling operators to take corrective action when necessary. 

Supercritical water oxidation (SCWO) Strong oxidizing capability pollution prevention High temperatures and pressures make system complex and prone to failures corrosion and plugging due to precipitated salts are problems Batch SCWO could address problems of continuous SCWO but requires significant further develc jment... 

Supercritical fluid, especially supercritical water (SCW), that is above the thermodynamic critical point of water (374"C, 22.1 MPa), has attracted increasing attention in various applications, such as in supercritical water oxidation (SC WO), in supercritical water gasification (SCWG), and for the continuous synthesis of nanoparticles. The environment of reactors presents a big challenge for structural materials used in the components. Many kinds of materials including stainless steel, alloys, and ceramics have been studied for using in SCW atmosphere. However, the details of the corrosion mechanism of each ceramic in an SCW environment were not fully clarified. 

Supercritical aqueous electrolytes are perhaps the most challenging supercritical mixtures to study experimentally, and are currently the focus of renewed interest because of the significant role played by ion speciation in new environmentally-friendly technologies — such as the supercritical water oxidation of toxic wastes [10,11,13] — and significant complications with current technologies — such as solid deposition [196] and metal corrosion [197] in electric power generators. 

Latanision, R.W. and Shaw, R.W. (1993) Corrosion in supercritical water oxidation systems Workshop Summary. MIT-EL 93-006. 

There is a background of relevant knowledge arising from the nuclear power industry and the Energy Laboratory at the Massachusetts Institute of Technology (Boston) is a centre for supercritical water corrosion studies. A workshop on Corrosion in Supercritical Water Oxidation Systems was held in May 1993. A copy of the report subsequently produced is available from Professor Latanision at MIT. 

Garcia, K., and Mizia, R. (1995). Corrosion investigation of multilayered ceramics and experimental nickel alloys in SCWO process environments, Proc. 1st Int. Workshop on Supercritical Water Oxidation, WCM forums, Amelia Island, Florida. 

Fauvel, E., Joussot-Dubien, C., Tanneur, V., et al. (2005). A porous reactor for supercritical water oxidation Experimental results on salty compounds and corrosive solvents oxidation,... 

While supercritical water oxidation (SCWO) chemistry conditions are much more aggressive than those expected in an SCWR core, there is some synergy between these systems and SCWO data can provide insights into corrosion phenomena in an SCWR core [11]. 

The selection of materials for use in many industrial environments, including supercritical thermal power plants (SCTPPs) and Supercritical Water Oxidation (SCWO) systems requires a broad study of the forms and the rates of corrosion of various metals and alloys in supercritical (T > 374°C) aqueous environments. Nickel is an important component of many corrosion resistant alloys and is a classic model for corrosion studies. Extensive electrochemical polarization studies of this metal in... 

L. B. Kriksunov, D. D. Macdonald Corrosion in Supercritical Water Oxidation Systems A Phenomenological Analysis, J. Electrochem. Soc. 142, 1995, 4069. X.Y. Zhou, S.N. Lvov, X.J. Wei, L.G. Benning, D.D. Macdonald, Quantitative Evaluation of General Corrosion of Type 304 Stainless Steel in Subcritical and Supercritical Aqueous Solutions via Electrochemical Noise Analysis , Corrosion Science, 44 (2002) 841. 

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