Apparatus and methods for controlling aerosol production during absorption in ammonia desulfurization, by removing sulfur dioxide in flue gas with an absorption circulation liquid containing ammonium sulfite, so as to control the aerosol production during absorption in ammonia desulfurization. Efficient desulfurization and dust removal may be achieved by staged solution composition control and reaction condition control. At the same time ammonia escape and aerosol production during absorption may be controlled. The flue gas may be subjected to preliminary temperature lowering and purification, and may be allowed to contact with an absorption circulation liquid and a fine particle washing circulation liquid sequentially. Levels of solution compositions and reaction temperatures may be controlled.

A process for cleaning process gas removes sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter (PM) to produce a tail gas substantially free of these pollutants. The process oxidizes and absorbs SOx and NOx for storage as liquid acids. In some embodiments a PM removal stage and/or a SOx removal stage are provided in a close-coupled higher-pressure environment upstream from a turbocharger turbine. The process has example application in cleaning exhaust gases from industrial processes and large diesel engines such as ship engines.

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.

A composite material for purifying air includes a porous foam material which is an open-cell polyurethane foam net; and a mixture sprayed on the interior and/or the surface of the porous foam material, the mixture including an absorbent material, a treating agent and an adhesive; wherein the adsorptive material is diatomite, and the treating agent is alkali solution.

A sorbent composition with improved acid gas reactivity comprising calcium hydroxide particles is provided. In the calcium hydroxide composition, about 90% percent of the calcium hydroxide particles are less than or equal to about 10 microns; the ratio of 90% of the calcium hydroxide particles below a specified size to the ratio of 10% of the calcium hydroxide particles above a specified size is less than about 8; and the calcium hydroxide particles have a BET surface area of about 18 m.sup.2/g or greater.

A method for treating a flue gas, comprising: step (A) desulfurizing a flue gas to obtain a desulfurized flue gas, comprising NO.sub.x, SO.sub.x, and CO.sub.2; step (B) providing oxygen for an oxidization to obtain an oxidized flue gas; step (C) rinsing the oxidized flue gas with water to obtain a rinsed flue gas and a nitric acid solution; and step (D) contacting the rinsed flue gas with a basic solution to absorb the CO.sub.2 in the rinsed flue gas. The method for treating a flue gas can largely reduce the content of CO.sub.2 and NO.sub.x in the flue gas. Besides, the obtained product can be used as a carbon source and nitrogen source for algae cultivation.

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.

Apparatus and methods for controlling aerosol production during absorption in ammonia desulfurization, by removing sulfur dioxide in flue gas with an absorption circulation liquid containing ammonium sulfite, so as to control the aerosol production during absorption in ammonia desulfurization. Efficient desulfurization and dust removal may be achieved by staged solution composition control and reaction condition control. At the same time ammonia escape and aerosol production during absorption may be controlled. The flue gas may be subjected to preliminary temperature lowering and purification, and may be allowed to contact with an absorption circulation liquid and a fine particle washing circulation liquid sequentially. Levels of solution compositions and reaction temperatures may be controlled.

A method for improving effectiveness of a steam generator system includes providing air to an air preheater in excess of that required for combustion of fuel and providing the air at a mass flow such that the air preheater has a cold end metal temperature that is no less than a water dew point temperature in the air preheater and such that the cold end metal temperature is less than a sulfuric acid dew point temperature. The method includes mitigating SO.sub.3 in the flue gas which is discharged directly from the air preheater to a particulate removal system and then directly into a flue gas desulfurization system. Flue gas reheat air is fed from the air preheater to heat the flue gas prior to entering a discharge stack to raise the temperature of the flue gas to mitigate visible plume exiting and to mitigate corrosion in the discharge stack.

Conversion methods and equipment for converting a calcium-based flue gas desulfurization (FGD) system to an ammonia-based FGD systems, including modifying a reagent system and absorber system of the calcium-based FGD system to be capable of, respectively, delivering an ammonia-based reagent to the absorber system rather than the calcium-based reagent, and modifying the absorber system to increase capacity of a reaction tank thereof.