Patent PL-189580-B1 (PL)
Title: Method of obtaining an medium for simultaneous reduction of nitrogen oxides and oxidation of sulphur dioxide to sulphur trioxide contained in flue gas
Inventor: GRZEGORCZYK WIESLAW
IPC: B01D53/60
Filed: 1998-04-03
Abstract: 1. The method of obtaining a substance for a simultaneous reduction of nitrogen oxides and oxidation of sulphur dioxide to sulphur trioxide in waste gases from boiler facilities consists in dispersing and depositing pulverised substances on the old carrier, and in creating the catalysis field and binding toxic products in the fuel combustion zone by means of the carrier precursor in the form of dolomite. It is characterised in that the active phase - consisting of metal oxides and/or metal salts that decompose thermally into oxides, consisting of: 40 percent by mass to 85 percent by mass of MgO; from 2 percent to 20 percent by mass of Na2CO3 and/or K2CO3, used in any mutual ratio; from 3 percent to 10 percent by mass of ZnO; from 1 percent to 7 percent by mass of V2O5; and from 1 percent to 6 percent by mass of MoO3 and/or from 1 percent to 2 percent by mass of TiO2, used in any mutual ratio - is subjected to dispersion in an open technological container until it assumes a dense liquid form. The process is carried out at the temperature of at least 50 degrees Celsius, while the substrates are homogenised by intensive mixing for the period of at least 180 minutes. In this form, it is deposited on Mg oxide or on Ca oxide or on salts of these metals, preferably on the natural dolomite which is a mixture of the former. The dolomite should be pulverised by grinding, preferably in a ball grinder, until the grain size does not exceed 0.005 mm. The deposition is realised through intensive homogenising mixing for the period of at least 180 minutes, while the environment temperature remains the same, but not lower than 50 degrees Celsius. The pulverised dolomite is used in the amount of 2 percent to 20 percent by mass, with respect to the mass of the dispersed mixture of the active phase. Then, the resultant mixture is diluted with technological water, preferably distilled water, until the substance assumes the form of a thin liquid. The process is carried out by intensive mixing, which lasts at least 30 minutes. The resulting substance is left for the period of at least 24 hours to get conditioned and cool naturally down to the room temperature, which does not exceed 20 degrees Celsius, at the environment pressure. The resultant precipitate is filtered through a negative pressure filter, especially through a nutsche filter, or it is separated, preferably by centrifugation in a centrifugal separator. The resultant filtrate, being a useful waste substance, is returned into the process, while the separated precipitate is subjected to drying in a drier, at atmospheric pressure, for the period of at least 10 hours, at the temperature of drying, which does not drop below 150 degrees Celsius. Then, the resultant dry half-product is calcinated in the air atmosphere of the environment at the temperature of at least 500 degrees Celsius for the period of at least 4 hours. The solid phase obtained in this way - after cooling down to the temperature of the environment for at least 6 hours, while the air humidity does not exceed 12 percent - is ground in a grinder, preferably a ball grinder, until the resultant grain size is between 0.05 and 0.005 mm, while the fine-grained fraction of 0.005 mm is dominant. Thus, a dry substance is obtained, which is characterised by the geometrical surface between 100 and 130 m2>/g and the apparent bulk density between 0.118 g/cm3> and 0.077 g/cm3>. The useful waste obtained from the filtration or the centrifugation, before being returned into the preferably continuous process, is subjected to purification to remove the excess of sodium ions and of carbonates and acetates, until only trace amounts of the substances and of ions of magnesium and ions of zinc are left in the substance.