Mitsubishi Jukogyo Kabushiki Kaisha

Masumi Atsukawa

Naoharu Shinoda

Atsushi Tatani

Naohiko Ukawa

Toshikuni Sera

Naruo Yokoyama

Yoshihiko Nishimoto

Hiroyuki Ushio

Taku Shimizu

Kenji Inoue

Kenichi Yoneda

Toru Seto

Naoyuki Takahashi

Kyoji Kubo

Kazuhiro Matsumoto

Takeji Tanaka

Kazumi Kamei

Haruo Kuwabara

Yasuyuki Inoue

A wet process for stack gas treatment wherein the stack gas is scrubbed with a suspension containing calcium hydroxide and/or calcium carbonate to remove sulfur oxides from the gas, characterized in that (1) air or oxygen-containing gas is supplied to the gas scrubber so as to oxidize at least 18% of the sulfur oxides absorbed by the scrub liquid to gypsum, and then part of the gypsum from the gypsum-containing scrub liquid partly taken out is recycled to the scrubber, or (2) part or whole of the scrub liquid is taken out from the scrubber into an oxidizer, where it is oxidized with the supply of air or oxygen-containing gas, and, after the oxidation, part of the scrub liquid from the oxidizer is recycled to the scrubber, whereby at least 18% of the sulfur oxides absorbed from the gas by the scrub liquid is oxidized to gypsum.

Process for stack gas treatment

In a process and an apparatus for controlling oxides of nitrogen in exhaust gases from combustion equipment by decomposing the oxides, in the presence of oxygen, with ammonia blown into the equipment and associated ducting at temperatures within the range from 700.degree. to 1300.degree. C., a catalyst assembly is arranged, with the catalytic surfaces of the component units substantially in parallel to the direction of exhaust gas flow, in a region where the temperature of the gas after the decomposing treatment is between 300.degree. and 500.degree. C., and the gas after the decomposing treatment is caused to pass through the catalyst assembly to decompose residual nitrogen oxides and ammonia in the gas to innocuous substances. An additional supply of ammonia, in an amount from 0.5 to 1.5 times equivalent (in molar ratio) to the amount of nitrogen oxides in moles in the gas is introduced into the space immediately upstream of the catalyst assembly, thereby to accelerate the decomposition of the oxides in the gas to make it harmless.

Process for controlling nitrogen oxides in exhaust gases and apparatus

A catalyst for the selective catalytic reduction of nitrogen oxides by the use of ammonia as a reducing agent composed of a catalytically active constituent on a carrier having a honeycomb or parallel plate structure, the carrier being prepared from a slurry of crystallized calcium silicate prepared by mixing silicic acid and lime and heating the mixture under pressure, the calcium silicate having the structure of xonotrite and the formula 6 CaO.6 SiO.sub.2. H.sub.2 O.

Catalyst for selectively reducing nitrogen oxides from oxygen-containing

A catalyst for selective catalytic reduction of nitrogen oxides by use of ammonia as a reducing agent is prepared by mixing a silicic acid material with a lime material, heating the mixture under pressure to form a slurry of calcium silicate crystals, forming the slurry into a carrier, and then allowing the carrier to carry a catalytically active ingredient.

A process for exhaust gas desulfurization by the wet lime-gypsum process comprises an absorption step for scrubbing the exhaust gases with a calcium hydroxide slurry as an absorbent; an oxidizing step for oxidizing a slurry composed chiefly of calcium sulfite from the absorption step; and a solids-liquid separation step for separating a slurry composed mainly of gypsum from the oxidizing step, characterized in that the liquid from said solids-liquid separation step is passed into a sulfate impurity reaction step where said liquid reacts with added calcium hydroxide and is thereby freed from water-soluble sulfate impurities; and the so purified liquid is supplied to the absorbent preparation step where it is mixed with calcium hydroxide to form said absorbent. Also, precipitates formed in said sulfate impurity reaction step are supplied to said absorbent preparation step.

Process for treating exhaust gases

A process for the wet-treatment of an exhaust gas in which nitrogen oxide and sulfur oxide contained in the exhaust gas are removed by use of an absorbent comprising a lime slurry containing an alkali metal or alkaline earth metal iodide, wherein an oxidizing agent is supplied to at least a part of iodide containing liquid retrieved from the wet-treatment to oxidize the iodide and thereby recover said iodide as iodine.

Wet-treatment of exhaust gases

A method of desulfurizing exhaust emissions which comprises pulverizing slag from a blast furnace, converter, open-hearth furnace or the like which is composed principally of Ca.sub.2 Al.sub.2 SiO.sub.7, suspending the resulting minute particles in water, and bringing the aqueous suspension of pulverized slag into contact with the exhaust that contains sulfur dioxide and oxygen, while supplying the slag at a rate to keep the pH of the suspension within a range of 1.5 to 4.0 and thereby to remove the sulfur dioxide from the exhaust.

Method of desulfurizing exhaust emission using pulverized slag as

A spray type wet scrubber includes a plurality of spray nozzles installed in parallel banks across the path of gas stream within the scrubber body, and partition walls held upright in grating fashion to divide the path of gas stream into a plurality of passages, each of which accommodates one of the spray nozzles.

Spray type wet scrubber

A wet waste flue gas desulfurizing process using lime as absorbent, wherein a sulfur oxide-containing waste flue gas is washed with a liquid absorbent containing calcium hydroxide or calcium carbonate for the purpose of removing the sulfur oxide from said waste flue gas, characterized in that an absorbing device is divided into two stages, i.e. a former stage absorbing device and a latter stage absorbing device, arranged in tandem with respect to the flow of said waste flue gas, and the liquid absorbent is circulated in the former stage absorbing device at a lime available percentage of more than 96% and in the latter stage absorbing device at a lime available percentage of 85 - 95%.

Wet waste flue gas desulfurizing process using lime as absorbent

A process for wet-treating an exhaust gas to remove oxides of sulfur and of nitrogen including: 1. washing the exhaust gas with a slurry containing one or more magnesium compounds to remove oxides of sulfur from the exhaust gas; 2. washing the exhaust gas treated in step (1) with an aqueous solution of an alkali metal iodide and/or an alkaline earth metal iodide to remove the oxide of nitrogen; and 3. contacting the slurry from step (1) with the aqueous solution from step (2) to regenerate the solution of alkali metal iodide and/or alkaline earth metal iodide and to decompose any nitrite formed in step (2) to nitrogen.

Process for removing oxides of nitrogen and sulfur from exhaust gases

Nitrogen oxides and sulfur oxides are removed from exhaust gases in a two step process including a slurry removal of the sulfur oxides followed by washing the gases with an aqueous solution of an alkali metal iodide and/or an alkaline earth metal iodide.

Process for the removal of SO.sub.x and NO.sub.x from waste gases using

The present invention relates to a process for wet-treating an exhaust gas which comprises simultaneously removing a nitrogen oxide (NO.sub.x) and a sulfur oxide (SO.sub.x) from an exhaust gas containing these oxides by treating exhaust gas containing oxides of nitrogen and sulfur with a lime or limestone slurry containing alkali metal or alkaline earth metal iodide.

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Hiroshima, Japan

Masumi Atsukawa