Materials, Methods & Technologies, Volume 5, 2011

Rezumat: The presented investigations are connected with creation of a new suitable for small and middle capacity boilers technology for removal of SO2 from flue gases by absorption with CaCO3 slurry, producing gypsum for building material. To reduce the capital investments it was decided to eliminate the hydrocyclone block and the centrifuge of the existing technologies and to dry the slurry of CaSO4.2H2O directly in a spray dryer by flue gases, utilizing the heat of evaporation in a contact economizer system. This decision required practically full oxidation of the CaSO3 to CaSO4 in the oxidizer. A construction of a new oxidizer, divided by vertical partitions into 4 chambers with regular distribution of the air in the slurry by means of perforated horizontal tubes, is described. Some possibilities for cleaning of the orifices of the tubes are specially investigated and a solution is found. It is shown that at presence of catalysts, Fe and Mn ions, more than 99% of the slurry can be oxidized in 9 hours. The obtained after the drying of the slurry gypsum is white. The test of its compressive strength shows a value of 3.5 MPa, i.e. 40% higher than the requirements of the Bulgarian national standard for building gypsum. The obtained data are used for designing the oxidizer of an industrial installation for purification of flue gases from SO2. Key wards: purification of flue gases, SO2.removal, absorption degree, new technology, catalyst, CaSO3 oxidation, slurry, gypsum compressive strength.