Miura Co., Ltd.

Other

Junichi Nakajima

Masazumi Yamashita

Kenichi Kimura

Yuuji Ukena

Kazuhiro Tachino

Hiroyuki Mitsumoto

Yoshitami Tsubota

Sadatoshi Takechi

Katsufumi Isshiki

Takeshi Fukumura

Takashi Ninomiya

Junichi Kato

Yoshiro Kaminokado

Keita Mizogami

Boiler water is heated in a steam boiler while feed water, which has a hardness of 5 mg CaCO/L or less and is used as the boiler water, is supplied to the steam boiler. A part of the boiler water is appropriately disposed of. A chemical aqueous solution containing an alkaline metal silicate, an alkaline metal hydroxide and at least one kind of scale preventive agents of ethylenediamine tetraacetate, and its alkaline metal salt, is supplied to the feed water so that a concentration of the scale preventive agent is at least 1.5 mol equivalent times relative to the hardness of the feed water. In the steam boiler, a condensation rate of the boiler water is set so that the concentration of the scale preventive agent in the boiler water is 40 mg EDTA/L or less.

Method of operating steam boiler

It is intended to effectively suppress corrosion of a feed-water supply pipe in a preheater, by means of recirculation of boiler water to feed-water to be supplied to a steam boiler, even if a concentration of an alkaline component of the feed-water is relatively high. An alkali metal hydroxide is added from an agent-adding unit () to feed-water after removing therefrom a water hardness component in a water-softener unit () using a cation exchange resin and then removing therefrom dissolved gas in a degasifier unit (). Then, the feed-water is supplied to a steam boilervia a feed-water supply linewhile being heated by a preheater (). A part of boiler water having a pH value increased along with an increase in concentration of the alkali metal hydroxide resulting from enrichment thereof in the steam boiler () is mixed with the feed-water via a recirculation line (). An alkaline component of the feed-water in the feed-water supply line () reacts with hydrogen ions from the cation exchange resin to form a carbonic acid, so that a concentration of the alkaline component is reduced. Thus, when the boiler water is mixed with the feed-water, a pH of the feed-water is increased without being influenced by a buffering ability of the alkaline component, to suppress corrosion of the feed-water supply line ().

Steam boiler apparatus and operating method therefor

A hardness indicator composition, and a method of water hardness analysis, capable of measuring hardness even with higher-hardness water without requiring titration by a two-liquid system. The hardness indicator composition is formulated of a metal indicator with a desensitizer added thereto.

Hardness indicator composition and method of water hardness analysis

The invention effectively prevents occurrence of corrosion in water tubes or the like of boilers. The invention provides a method for operating a boiler, including regulating a concentration of sulfate ions SO in boiler water to under 500 ppm, and a method for injecting a sulfite base oxygen scavenger, including setting a concentration of residual dissolved oxygen in boiler feed water to 2-4 ppm. The invention further provides a sulfite base oxygen scavenger composition comprising: 3-30 weight % of at least one selected from a group consisting of Na SO , K SO , NaHSO and KHSO ; 1-20 weight % of NaOH or KOH; 0.2-2 weight % of potassium sorbate; and 5-500 ppm of CoSO .

Composition for preventing corrosion using a sulfite-based oxygen scavenger

A harness indicator is highly reactive to a trace amount of Ca,, and is slow to degrade in a high temperature environment of greater than 50&deg; C. In one embodiment, the hardness indicator contains EBT, a pH buffer, and a masking agent as main components, and an admixture of Mg-EDTA. In another embodiment, the hardness indicator contains EBT, a pH buffer, and a masking agent as main components, and an admixture of anhydrous Mg-EDTA. In another embodiment, the hardness indicator contains EBT, a pH buffer, and a masking agent as main components, and an admixture of anhydrous Mg-EDTA and potassium sorbate. In a further embodiment, the hardness indicator contains EBT, a pH buffer, and a masking agent as main components, and an admixture of Mg-EDTA and potassium sorbate. In a further embodiment, the hardness indicator contains EBT, a pH buffer, and a masking agent as main components, and an admixture of potassium sorbate.

Hardness indicator

The invention effectively prevents occurrence of corrosion in water tubes or the like of boilers. The invention provides a method for operating a boiler, including regulating a concentration of sulfate ions SO.sub.4.sup.2- in boiler water to under 500 ppm, and a method for injecting a sulfite base oxygen scavenger, including setting a concentration of residual dissolved oxygen in boiler feed water to 2-4 ppm. The invention further provides a sulfite base oxygen scavenger composition comprising: 3-30 weight % of at least one selected from a group consisting of Na.sub.2 SO.sub.3, K.sub.2 SO.sub.3, NaHSO.sub.3 and KHSO.sub.3 ; 1-20 weight % of NaOH or KOH; 0.2-2 weight % of potassium sorbate; and 5-500 ppm of CoSO.sub.4.

Growing community of inventors

Matsuyama, Japan

Junichi Nakajima