November 27, 2002
Kurita Water Industries Ltd.
Kurita Water Industries (President Takahide Santo) and Komatsu Limited (President Masahiro Sakane) have successfully developed a supercritical water oxidation unit of practical use, which is an ultimate water treatment technology decomposing various waste fluids, wastes and sludges to harmless materials. The two companies will collaborate on business to manufacture and sale this processing system, under the product name "AquaFlame."
The Supercritical Water Oxidation (SCWO) technology oxidatively decomposes organic matter into water as well as carbon dioxide in the aqueous phase above the critical point of water (374 ℃ and 22 MPa). The technology has been receiving considerable attention as a means to detoxify toxic substances of social issues, such as dioxins and PCB. However, practical application has been delayed because of technical problems, such as the unit plugging by accumulated salt that is generated during the reaction, and the unit corrosion.
After obtaining the basic technologies from General Atomics of the United States, the two companies began joint development in 1997. Consequently, the companies succeeded in developing a unit equipped with the means to remove accumulated salt, which also incorporates an anti-corrosion feature as well as the outstanding performance in decomposing of organic matter that is peculiar to the SCWO technology. An operation test lasting more than 1,000 hours using a demonstration plant (with a processing capacity of 10 m3 per day) confirmed stable performance in decomposing organic matters, in removing accumulated salt, and also demonstrated strong anti-corrosion performance and safety. Combining the strengths of both companies, namely Kurita's excellent water treatment technologies and Komatsu's outstanding technologies in developing and manufacturing machines and devices, the companies are convinced that they embody world-leading performance and quality in SCWO.
The new SWCO unit co-developed by Kurita Water Industries and Komatsu Limited represents a world first in that it can deal with high salt concentrations. With the ability to process a wide range of waste fluids, wastes and sludges, it is set to find a broad array of applications for zero waste discharge.
[Demonstration Plant Flow Chart]
[Major features of the co-developed SCWO unit]
1) Decomposition performance
Waste fluid is injected from the upper part of the vertical cylinder-shaped reactor through a nozzle. It is instantly heated to 650 ℃ to react, and completely decomposed to be discharged from the lower part of the reactor. Leaving no residual undecomposed substance, it features both high-decomposition performance and a compact reactor. Furthermore a specially devised preheating method enables a quicker start.
2) Salt removal mechanism
The salt precipitated over the reactor wall is removed by the scraper, and dissolved in water in the lower part of the reactor to enable continuous discharge. This mechanism enables SCWO processing of waste fluid including salt.
3) Anti-corrosion feature
Corrosion-resistant materials are used for each part of the unit considering conditions such as temperature and oxygen concentration for that part. In particular, a replaceable internal lining using corrosion-resistant materials has been introduced to provide the outstanding anti-corrosion feature.