Hitachi, Ltd.

Babcock-hitachi Kabushiki Kaisha

Babcock-hitachi K.k.

Hidetoshi Akimoto

Yukio Hishinuma

Fumito Nakajima

Yoshijiro Arikawa

Hideo Kikuchi

Ryuichi Kaji

Shigeru Azuhata

Norio Arashi

Kenichi Gomi

Takeo Komuro

Akira Kato

Yoji Ishibashi

Makoto Sasaki

Yoshihiro Uchiyama

Yasushi Muranaka

Shimpei Matsuda

Zensuke Tamura

Toshikatsu Mori

Sadao Takahashi

Ryoichiro Oshima

Teruo Kumagai

Osamu Kanda

Hajime Iinuma

Hiroshi Terada

Mineral impurities can be effectively removed from coal by introducing oil droplets into an aqueous slurry of pulverized coal. Coal, which is lipophilic, attaches to the surface of the oil droplets and floats upwardly along with the oil droplets utilizing their buoyancy. On the other hand, mineral impurities, which are hydrophilic, are left in the aqueous slurry.

Process for removing ash from coal

Sulfur oxides contained in the flue gas from coal-fired boiler are adsorbed by an adsorbent prepared by dry-distilling a portion of fuel coal, thereby producing semi-coke, and activating the semi-coke by steam, and then the sulfur oxides-adsorbed adsorbent is heated to desorb the adsorbed sulfur oxides at a high concentration. The desorbed sulfur oxides are passed through a bed of semi-coke before the activation to recover the sulfur oxides as elemental sulfur.

Process for dry desulfurization of flue gas

Sulfur oxides contained in the flue gas from coal-fired boiler are adsorbed by an adsorbent prepared by dry-distilling a portion of fuel coal satisfying at least one of requirements of an ash content lower than 15% by weight and a fixed carbon content of at least 50% by weight, thereby producing semi-coke, and activating the semi-coke by steam, and then the sulfur oxides-adsorbed adsorbent is heated to desorb the adsorbed sulfur oxides at a high concentration. The desorbed sulfur oxides are passed through a bed of semi-coke before the activation to recover the sulfur oxides as elemental sulfur.

A coal or petroleum combustion flue gas containing sulfur oxides and dust is treated by contacting the flue gas with a sulfur dioxide-oxidizing catalyst, thereby converting sulfur dioxide to sulfur trioxide, allowing the resulting sulfur trioxide to react with components of dust, absorbing the trioxide into the dust as a sulfate, and removing the dust. Catalytic oxidation of sulfur dioxide can be efficiently carried out at a low temperature and sulfur oxides can be efficiently removed from the flue gas.

Process for treating flue gas

An apparatus for removing nitrogen oxides from a flue gas comprises a first stage of injecting ammonia in a combustion flue gas and then hydrogen peroxide thereto, thereby decomposing nitrogen oxides in the combustion flue gas to nitrogen and water by gas phase reduction, and a second stage of passing the combustion flue gas leaving the first stage through a bed of catalyst whose temperature is controlled by cooling water passing through a cooling pipe provided through the bed of catalyst, thereby conducting decomposition of excess ammonia exiting from the first stage and further reaction of nitrogen oxides at the same time.

Apparatus for removing nitrogen oxides from flue gas

A hot gas containing nitrogen oxides is admixed with ammonia and hydrogen peroxide to reduce the nitrogen oxides to nitrogen and water. Reduction reaction of the nitrogen oxides by ammonia is considerably promoted in a temperature range of 400.degree. to 800.degree. C. by the addition of hydrogen peroxide, and also ammonia present in excess of the nitrogen oxides is decomposed thereby, eliminating an unreacted ammonia effluent.

Process for removing nitrogen oxides from gas by ammonia

Nitrogen oxides in a combustion flue gas are removed by reduction in a gaseous phase at a low temperature in the absence of any catalyst by adding urea and an oxidizing agent for decomposition of urea, such as ozone, nitric acid, hydrogen peroxide, chlorine, chlorine dioxide, or oxy acids of chlorine or their salts. NO.sub.x removal can be carried out in a very simplified manner with high percent NO.sub.x removal.

Process for abating concentration of nitrogen oxides in combustion flue

Nitrogen oxides are removed from a flue gas by wet process, where the flue gas is contacted with a solution of transition metal complex compounds capable of reacting with oxygen in the presence of oxygen, thereby forming oxygen complexes, and the nitrogen oxides are oxidized and absorbed by the oxygen complexes.

Method for removing nitrogen oxides from flue gas by absorption

The present invention relates to a process for removing nitrogen oxides contained in a gaseous mixture such as combustion flue gas, etc. by reduction of the nitrogen oxides with ammonia, and a cuprous or cupric halide is used as a catalyst to carry out the reduction in a low temperature range. As a result, nitrogen oxides can be satisfactorily removed by the reduction even at about 150.degree. C.

Process for making nitrogen oxides contained in flue gas harmless

Nitrogen oxides (NOx) are removed from combustion waste gases by injecting gas (NH.sub.3) into the combustion waste gases in the presence of a metallic catalyst to deoxidize the nitrogen oxides to nitrogen and water, within a reaction tower having the catalysts moving through the reaction tower, so that thereafter the dust may be separated from the catalysts and the catalysts may be regenerated continuously, so that the regenerated catalysts may be returned to the reaction tower. The catalyst moves in a substantially closed path, and preferable downwardly through the reaction tower, with the ammonia gas and combustion waste gases moving in cross current through the reaction tower, with mixing being enhanced by a plurality of angled baffle plates. Regeneration is accomplished by washing the catalysts, particularly ferrous catalysts with water to remove ferric sulfates, thereafter providing ferrous sulfates on the surface of the ferrous catalysts, and thereafter heating the catalysts with combustion gases separate from the ammonia gases, to dry the catalysts prior to their moving into the portion of the reaction tower having therein the mixed ammonia gas and combustion waste gases.

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Ibaraki, Japan

Hidetoshi Akimoto