An aqueous composition including an NOx reducing agent or a precursor of such an agent, in particular urea, and at least one paraffin dispersed in the aqueous phase. Such a composition can be used for reducing the formation of deposits in an SCR exhaust system while preventing foaming during the handling of same.

Processes and systems for producing potassium sulfate as a byproduct of a desulfurization process. Sulfur dioxide is absorbed from a flue gas using an ammonia-containing solution to produce an ammonium sulfate solution that contains dissolved ammonium sulfate. At least a first portion of the ammonium sulfate solution is heated before dissolving potassium chloride therein to form a slurry that contains potassium sulfate crystals and an ammonium chloride solution. The slurry is then cooled to precipitate additional potassium sulfate crystals, after which the potassium sulfate crystals are removed to yield a residual ammonium chloride solution that contains dissolved ammonium chloride and residual dissolved potassium sulfate. Ammonia is then absorbed into the residual ammonium chloride solution to further precipitate potassium sulfate crystals, which are removed to yield a residual ammonium chloride solution that is substantially free of dissolved potassium sulfate.

The present invention describes a fluid which is suitable for the decontamination of heat engines which can carry out both, at the same time, the catalytic reduction of oxides of nitrogen (NOx) contained in exhaust gases and assist in the regeneration of the particulate filter (PF). The invention also describes several embodiments of said fluid.

Organic sulfur compounds contained in refinery off gas streams having either high ort low concentrations of olefins are converted to hydrogen sulfides which can be then be removed using conventional amine treating systems. The process uses a catalytic reactor with or without a hydrotreater depending on the olefin concentration of the off gas stream. The catalytic reactor operates in a hydrogenation mode or an oxidation mode to convert a majority of organic sulfur compounds into hydrogen sulfides.

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.

The present invention describes a fluid which is suitable for the decontamination of heat engines which can carry out both the catalytic reduction of oxides of nitrogen (NOx) contained in exhaust gases and assist in the regeneration of the particulate filter (PF), said fluid being in the form of a stable suspension of colloidal particles, these colloidal particles being dispersed in an aqueous solution containing at least one reducing agent or at least one precursor of a reducing agent for NOx. The invention also describes several embodiments for the preparation of said fluid.

Disclosed herein are methods for treating an exhaust stream comprising NOx, the methods comprising receiving an exhaust stream and combining it with at least one nitrogen-containing reagent to form a combined stream, heating the combined stream to a reaction temperature ranging from about 870 C. to about 1100 C. to react at least a portion of the nitrogen-containing component, cooling the reacted stream in a first cooling step to a first temperature, and optionally further cooling the reacted stream in a second cooling step to a second temperature, wherein the first cooling step comprises heat exchange between at least a portion of the exhaust stream and at least a portion of the reacted stream. Exhaust treatment systems are also disclosed herein.

A catalyst for treating an exhaust gas comprising SO.sub.2, NO.sub.x and elemental mercury in the presence of a nitrogenous reductant comprises a composition containing oxides of: (i) Molybdenum (Mo) and optionally Tungsten (W); and (ii) Vanadium (V); and (iii) Titanium (Ti); and(iv) Phosphorus (P), wherein, with respect to the total metal atoms in the composition, the composition comprises: (i) Mo in an amount of less than 2 at. %, and optionally up to 9 at. % W; (ii) from 2.5 to 12 at. % V; (iii) from 85 to 96 at. % Ti, and wherein the composition comprises (iv) P in an atomic ratio to the sum of atoms of Mo, W and V of from 1:2 to 3:2. The values expressed must total 100%.

A catalyst for treating an exhaust gas comprising SO.sub.2, NO.sub.x and elemental mercury in the presence of a nitrogenous reductant comprises a composition containing oxides of: (i) Molybdenum (Mo) and/or Tungsten (W); (ii) Vanadium (V); (iii) Titanium (Ti), and (iv) an MFI zeolite, wherein the composition comprises, based on the total weight of the composition: (i) 1 to 6 wt % of MoO.sub.3 and/or 1 to 10 wt % WO.sub.3; and (ii) 0.1 to 3 wt % V.sub.2O.sub.5, and (iii) 48.5 to 94.5 wt % TiO.sub.2; and (iv) 35 to 50 wt % MFI zeolite.

A combustion system operated at low cost is provided. A combustion system 1 includes a combustion device 10 that burns fuel, an exhaust line L1 through which exhaust gas flows, the exhaust gas being generated through combustion of the fuel in the combustion device 10, an air preheater 30 that is disposed in the exhaust line L1 and that recovers heat from the exhaust gas, and a denitration device 40 that is disposed in the exhaust line L1 and that removes nitrogen oxide from the exhaust gas using a denitration catalyst. The denitration device 40 is disposed downstream from the air preheater 30 in the exhaust line L1, and the denitration catalyst contains 43 wt % or more of vanadium pentoxide and has a BET specific surface area of 30 m.sup.2/g or more.