NORDEN FGD (Flue Gas Desulphurization) plants are based on the wet limestone technology with production of gypsum, which is readily usable by manufacturers of gypsum based products.
The limestone wet process has become the most popular process for flue gas desulphurization; NORDEN has the experience and the know-how for the design and the construction of complete FGD plant, with main characteristics as follow: 1- High removal efficiency (> 96%), 2-Limestone consumption closely approximating stoichiometric requirements, 3- Reduced space requirements due to compact construction, 4- Scrubbing tower complete with integral absorption, oxidation, crystallizing and mist separation stages, 5- Low residual moisture in effluent gas by optimal location of the demister, 6- High gypsum purity in the final product as a result of high oxidation efficiency
Flue gas ducts connect flue gas system to absorber and from absorber to stack. After the flue gas cleaning a reheating system for clean gases is required before they enter the stack.
The absorber consists of a vertical cylindrical vessel, with a flue gas inlet and outlet opening. The part of the absorber between the gas inlet and gas outlet (the gas section) may be subdivided in "the spray section" and in "the mist eliminator section". The part of the absorber below the gas inlet contains the absorber slurry (the sump). In the spray section, the flue gas will be in contact with a fine spray of limestone slurry droplets, as produced by the slurry spray banks, equipped with spray nozzles.
The SO2 and other acid gases are absorbed to a large extend in the slurry droplets and react with the limestone present in the slurry to form gypsum. In order to obtain nearly 100% oxidation of sulphite to sulphate, the absorber is provided with an oxidation air injection system for the injection of a certain flow of oxidation air, supplied from a compressor system.
The bleed system consists essentially of an absorber bleed pump and a gypsum cyclone battery, supplied with absorber slurry by the absorber bleed pump.
The underflow of the cyclones flows to the mechanical dewatering that produces dry commercial gypsum with a maximum water content of 10%.