Kobe Steel, Ltd.

Isao Furuta

Kazuhito Yagaki

Masami Takao

Toyohiko Masuda

Akira Uragami

Osamu Yoshida

Hiroshi Tamura

Toshihiko Masuda

Yoshimi Takiguchi

In a process for preventing the formation of gypsum scale in a flue gas desulfurization process, in which a gas containing SO.sub.2 is subjected to a desulfurization treatment by a lime-gypsum process, the concentration of Ca(OH).sub.2 in an absorbing solution is maintained at not more than 0.1% by weight, and the absorbing liquid contains not more than 40% by weight of CaCl.sub.2.

Process for preventing formation of gypsum scale in a flue gas

A process for removing nitrogen oxides from exhaust gases which comprises;

Process for denitration of exhaust gas

The present invention provides a method of converting NO.sub.3.sup.- ions which are contained in denitration waste liquids to nonpoisonous N.sub.2 gas or to valuable by-products. In the method of the invention, concentrated sulfuric acid is added to the waste liquid which results from denitration of exhaust gases which contains calcium nitrate and calcium chloride to obtain a mixed solution of nitric acid, hydrochloric acid, sulfuric acid and calcium sulfate. The ratio of the chloride ions to nitrate ions in the mixed solution is adjusted within the range of Cl.sup.- /NO.sub.3.sup.- = 2-3; the mixed solution is heated to 110.degree. to 150.degree. C after adjusting the concentration of sulfuric acid in the solution to 10 to 70% by weight to thereby convert the mixed solution to a mixed gas essentially including NOCl, Cl.sub.2 and nitrogen oxides. The mixed gas is then passed through concentrated sulfuric acid having a concentration higher than 80% which is maintained at a temperature of 80.degree. to 150.degree. C to obtain a nitrosylsulfuric acid solution. A mixed gas containing SO.sub.2 and H.sub.2 O is passed into the thusly formed nitrosylsulfuric acid solution to obtain a mixed gas containing NO, NO.sub.2 and SO.sub.2 which is then introduced into a reducing solution to convert the nitrogen oxides to N.sub.2 gas.

Method of treating calcium nitrate contained in denitration waste liquid

Exhaust gases are denitrated by a method comprising removing NO from exhaust gases which comprises washing the exhaust gas with a first aqueous solution containing a chloride of Mg or Ca, and a hypochlorite of Mg or Ca, and washing said washed gas with a second aqueous solution of an alkali.

Method for denitrating exhaust gases

Sulphur dioxide is removed from a stack gas by bringing said gas containing SO.sub.2 into contact with an absorbing solution prepared by adding an hydroxide of a metal from either Groups II, III and VIII of the periodic Table to an aqueous solution of a halide of said metal, wherein the hydroxide is present in an amount of from 0.3 to 0.8 weight percent.

Desulfurization process

A gas-liquid contacting method and a scrubber used therefor are disclosed which are adapted to remove harmful components, such as SOx, NOx, CO, Cl.sub.2 and HCl contained in exhaust gases. According to this invention, liquid is sprayed to follow a conical form and the mist of liquid which is thus being diffused in a conical form is encompassed with a gas flowing in parallel relation therewith. To this end, at least one nozzle for spraying liquid and an encompassing tube for ejecting gas are arranged to specific forms and relations to the effect that an excellent contacting efficiency will result, without increasing energy consumption due to pressure loss.

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Mitaka, Japan

Isao Furuta