Provided is a desulfurization method for sulfur oxide gas that includes: bringing a first sulfur oxide gas into contact with a humidifying liquid to obtain a second gas; separating at least part of the humidifying liquid from the second gas to obtain a third gas; contacting the third gas with an alkaline agent-containing liquid and oxygen to remove sulfur oxide from the third gas; using the alkaline agent-containing liquid as the humidifying liquid to be brought into contact with the first gas in the humidifying liquid contact step; acquiring at least part of the humidifying liquid separated from the second gas; removing gas from the humidifying liquid; and recovering a by-product, the alkaline agent-containing liquid, and oxygen from the humidifying liquid from which the gas has been removed in the gas removal step, the by-product recovery step being performed only downstream of the humidifying liquid acquisition step.

A control device for a scrubber includes a converter which calculates a minimum amount of seawater: a minimum amount of seawater necessary for an absorption reaction of the sulfur oxide by the seawater, from an engine output and a sulfur content of fuel oil; another converter which calculates a corrected amount of seawater: an amount of seawater at which the sulfur oxide in the exhaust gas discharged from the scrubber is equal to or less than a set value; a summing element which calculates a set amount of seawater by summing the minimum amount and corrected amount of seawater; a pump control device which implements control such that seawater corresponding to the set amount is supplied to the scrubber; and an alkalinity setting device which sets the alkalinity of the seawater in accordance with traveled waters. The amount of seawater supplied to the scrubber is adjusted based on the alkalinity.

Apparatus and methods for denitrification and desulfurization of and dust removal from an FCC tail gas by an ammonia-based process. The apparatus may include a first-stage waste heat recovery system, a denitrification system, a dust removal and desulfurization system, a tail gas exhaust system, and an ammonium sulfate post-processing system. The dust removal and desulfurization system may include a dedusting tower and an absorption tower disposed separately. The top and the bottom of the absorption tower may be connected respectively to the tail gas exhaust system and the ammonium sulfate post-processing system. The absorption tower may include sequentially, from bottom to top, an oxidation section, an absorption section, and a fine particulate control section. The methods may be implemented with the apparatus.

The present invention relates to a method and a system for the removal of impurities from a flue gas. In particular, the present invention relates to a method and a system for the removal of impurities such as SO.sub.3 (acid mist), SO.sub.2 (sulphur dioxide), NO.sub.2 (nitrogen dioxide) from a CO.sub.2 (carbon dioxide) rich flue gas.

A process for converting gypsum into precipitated calcium carbonate including reacting a mixture comprising gypsum and a seed, a mineral acid, or both with at least one carbonate source, whereby precipitated calcium carbonate is produced in the form of calcite and/or aragonite directly without conversion from a vaterite polymorph. Also, a process for converting gypsum into precipitated calcium carbonate including providing a mixture comprising i) gypsum ii) a seed, a mineral acid, or both iii) at least one additive selected from the group consisting of ammonium sulfate, an organic acid, or an iron material, and reacting the mixture with at least one carbonate source to produce precipitated calcium carbonate in the form of vaterite. The precipitated calcium carbonates having desired and unique compositions, polymorph and crystal size characteristics formed by these processes.

A process for converting gypsum into precipitated calcium carbonate including reacting a mixture comprising gypsum and a seed, a mineral acid, or both with at least one carbonate source, whereby precipitated calcium carbonate is produced in the form of calcite and/or aragonite directly without conversion from a vaterite polymorph. Also, a process for converting gypsum into precipitated calcium carbonate including providing a mixture comprising i) gypsum ii) a seed, a mineral acid, or both iii) at least one additive selected from the group consisting of ammonium sulfate, an organic acid, or an iron material, and reacting the mixture with at least one carbonate source to produce precipitated calcium carbonate in the form of vaterite. The precipitated calcium carbonates having desired and unique composition, polymorph and crystal size characteristics formed by these processes.

Methods, apparatus, and compositions for cleaning gas. The use of segmented multistage ammonia-based liquid spray with different oxidation potentials to remove sulfur compounds from gas. The use of different oxidation potentials may reduce unwanted ammonia slip.

Apparatuses, systems, and methods for removing acid gases from a gas stream are provided. Gas streams include waste gas streams or natural gas streams. The methods include obtaining a hypochlorite and a carbonate or bicarbonate in an aqueous mixture, and mixing the aqueous mixture with the gas stream to produce sulfates or nitrates from sulfur-based and nitrogen-based acidic gases. Some embodiments of the present disclosure are directed to produce the carbonate and/or bicarbonate scrubbing reagent from CO.sub.2 in the gas stream. Still others are disclosed.

The invention relates to a process for preparing potassium thiosulfate, potassium sulfite or potassium bisulfite comprising the following steps:

Step (1a): providing a potassium hydroxide or potassium carbonate solution for neutralizing acid forming components such as dissolving SO.sub.2 or H.sub.2S;

Step (1b): providing an SO.sub.2 contacting solution, containing at least some potassium sulfite or potassium bisulfite or potassium thiosulfate;

Step (2): providing SO.sub.2 gas;

Step (3): reacting these to absorb the SO.sub.2 gas and to form an intermediate reaction mixture comprising potassium sulfite, or potassium bisulfite or a mixture thereof, and optionally recovering the potassium sulfite, or potassium bisulfite or a mixture thereof, and/or optionally using steps 4 and 5;

Step (4): adding sulfur or sulfide containing compound containing sulfur having the oxidation state of 0, ?2 or of between 0 and ?2 to the reaction mixture and optionally potassium hydroxide or potassium carbonate, and reacting the mixture under suitable conditions to form potassium thiosulfate; and

Step (5): recovering the potassium thiosulfate, and optionally concentrating the potassium thiosulfate.

A process for preparing sulfuric acid may involve melting elemental sulfur in a melting stage to give molten sulfur. Sulfuric acid is subsequently produced from the molten sulfur. Further, sulfur-containing offgases formed in the melting stage may be subjected to oxidation in a supplementary oxidation stage in which sulfur-containing components of the offgases are oxidized to sulfur dioxide. The process may further involve processing the sulfur dioxide to give at least one reaction product. The melting stage may be operated without emissions by processing all of the offgases from the melting stage. An apparatus may be employed for carrying out such a process.