Kureha Kagaku Kogyo Kabushiki Kaisha

Tetsuya Watanabe

Shigeru Saitoh

Koji Konno

Tadashi Nakamura

Tamotsu Miyamori

Kunihide Yaguchi

Katsutoshi Komahashi

Kenji Kodama

Oxides of nitrogen can be removed efficiently from a gas containing such oxides of nitrogen by bringing said gas into contact with an aqueous solution containing an organic acid alkali salt and a salt of metal selected from the group consisting of Fe, Co, Ni, Cu and Mn in the presence of a sulfurous acid alkali salt. The efficiency for removing oxides of nitrogen is much improved by use of a polybasic acid alkali such as ethylenediamine tetracarboxylic acid alkali salt or nitrilo-tricarboxylic acid alkali salt as said organic acid alkali salt.

An absorbing solution for the removal of nitrogen oxide form a gas

A method of removing nitrogen oxides from a gas containing nitrogen oxides and converting same to a salt of imidodisulfonic acid, wherein the gas containing nitrogen oxides is brought into contact with an aqueous solution which contains at least one ferrous salt and at least one sulfurous acid alkali salt to absorb the nitrogen oxides in solution in the form of imidodisulfonic acid alkali salts.

Method of removing nitrogen oxides from a gas as a salt of

Disclosed is a method for removing hydrogen chloride from an exhaust gas containing same without discharging any waste water from the system, which method includes bringing the exhaust gas into contact with a slurry containing calcium carbonate or calcium hydroxide to absorb the hydrogen chloride in the form of calcium chloride and then recovering the calcium chloride as solid calcium chloride hydrate.

Method for removing hydrogen chloride from exhaust gas containing same

A method of effectively removing nitrogen oxides which are entrained in a gas, wherein a nitrogen oxide-containing gas is brought into contact with an aqueous solution which contains at least one ferrous salt and one sulfurous acid alkali salt to absorb the nitrogen oxides in the solution in the form of imidodisulfonic acid alkali salt, hydrolyzing the imidodisulfonic acid alkali salt to obtain a hydrolyzate-containing solution, and adding nitrous acid, nitrous acid anhydride, or nitrite to the hydrolyzate-containing solution to generate nitrogen.

Method of removing nitrogen oxides from a gas containing nitrogen oxides

A method of removing nitrogen oxides from a gas containing nitrogen oxides and converting same to ammonium sulfate, wherein the gas containing nitrogen oxide is brought into contact with an aqueous solution which contains at least a ferrous salt and a sulfurous acid alkali salt to absorb the nitrogen oxides in the solution in the form of imidodisulfonic acid alkali salts, and the imidodisulfonic acid alkali salt is converted into ammonium sulfate by hydrolysis at a temperature higher than 100.degree. C after separation and recovery of the salt from solution.

Method of removing nitrogen oxides from a gas and for converting same to

A sulfur dioxide-containing exhaust gas is scrubbed by contact with an aqueous solution containing an alkali salt of an organic acid to dissolve sulfur dioxide in the aqueous solution in the form of alkali sulfite. The alkali sulfite in the solution is converted by oxidation into alkali sulfate, which is contacted for reaction with a calcium compound to form calcium sulfate. The calcium sulfate so formed is separated by filtration from the aqueous solution for recovery while the filtrate is recycled for use as the aqueous solution for scrubbing the exhaust gas. The concentration of alkali sulfite in the scrubbing aqueous solution is maintained at a level of less than 1% to ensure efficient removal of sulfur dioxide from the exhaust gas in the form of calcium sulfate.

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Iwaki, Japan

Tetsuya Watanabe