Nippon Steel Corporation

Nippon Steel & Sumikin Engineering Co., Ltd.

Teruhiko Hayashi

Kazuhiro Takahashi

Michio Kaneko

Kiyonori Tokuno

Kinichi Kimura

Junichi Tamenari

Hiroshi Shimizu

Hideki Fujii

Akira Kawakami

Akihiro Itoh

Shoichi Maruyama

Keita Suzumura

Masayuki Igarashi

Provided is a multiplex pipe and a system for recovering steam from a geothermal well, which are capable of solving all of the various problems with a neutralization pipe prepared by painting or the like of an alkali-resistant coating on the inner face of an acid-resistant single pipe. A multiplex pipethat is configured to recover steam from a geothermal well GT, includes: a casing pipelocated outside; and a duplex pipethat is slidable relative to the casing pipein the casing pipe, and has a first gapwith an inner face of the casing pipe, the duplex pipe including an outer pipehaving acid-resistance and an inner pipehaving alkali-resistance, the outer pipeand the inner pipedefining a second gaptherebetween. An alkali solution is injected to acid hot-water stored in an acid geothermal well GT via a hollowof the inner pipeto neutralize the acid hot-water, and the neutralized hot-water V is allowed to spout to the ground via the first gap, thus recovering flashing steam.

Multiplex pipe and system for recovering steam from geothermal wells

Titanium material less susceptible to discoloration and method for thereof are provided. Titanium materials less susceptible to discoloration in the atmosphere are obtainable by controlling the fluorine and carbon contents in the oxide film on the surface thereof and the thickness of the oxide film. Such titanium materials are obtainable by dissolving the surface thereof in an aqueous fluonitric acid solution with a nitric acid concentration of not higher than 80 g/l or heat-treating at between 300 and 900&#xb0; C. in a vacuum or in an inert gas atmosphere of argon or helium after dissolving in the aqueous fluonitric acid solution.

Titanium material less susceptible to discoloration and method for production thereof

Titanium resistant to discoloration in an atmospheric environment characterized by having an average carbon concentration of 14 at % or less in a range to a depth of 100 nm from the surface and having an oxide film of a thickness of 12 to 40 nm at its surface. Titanium resistant to discoloration in an atmospheric environment characterized in that, in X-ray diffraction of its surface, a ratio (X/X) of a (200) peak intensity Xof TiC to a (110) peak intensity Xof titanium is not more than 0.18 and by having an oxide film of a thickness of 12 to 40 nm at its surface.

Titanium resistant to discoloration in atmospheric environment and process of production of same

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Hikari, Japan

Teruhiko Hayashi