Limestone/Lime injection process

LIMB [Lime/limestone injection into a multi-stage burner] A flue-gas desulfurization process used in Germany and Finland. Dry, ground limestone is injected directly into the combustion chamber. This reacts with the sulfur dioxide, and the dry particulate product is collected downstream together with the ash. The process is suitable only for those systems which limit the maximum combustion temperature by staging, in order to minimize the production of oxides of nitrogen. 

Dry Lime/Limestone Processes Furnace Sorbent Injection Processes... 

SONOX A process for simultaneously removing S02 and NOx from flue-gas. A slurry of lime or limestone, with a proprietary nitrogen-based additive, is injected into the furnace. Developed by Ontario Hydro (the largest electricity supplier in North America) and marketed by Research-Cottrell. 

There are several processes for the removal of sulfur dioxide from stack gas (Table 25.1) (Chapter 23) but to date scrubbing process utilizing limestone (CaCOj) or lime [Ca(OH)J slurries have received more attention than other stack gas scrubbing processes. Attempts have been made to use dry limestone or dolomite (CaCOs MgCOj) within the combustor as an in situ method for sulfur dioxide removal, thus eliminating the wet sludge from wet processes. This involves injection of dry carbonate mineral with the coal followed by recovery of the calcined product along with sulfite and sulfate salts. 

Flue gas desulfurization (FGD) Removal of the sulfur gases from the flue gases (stack gases) of a coal-fired boiler—typically using a high-calcium sorbent such as lime or limestone three primary types of flue gas desulfurization processes commonly used by utilities are wet scrubbers, dry scrubbers, and sorbent injection. 

Dry injection of limestone and hydrated lime particles in desulfurization processes is currently under active development (Stouffer et al, 1986 Weinstein, 1989 Yoon et al, 1986). Furnace dry sorbent injection for SO2 control consists of injecting a dry pulverized calcium based material directly into furnace cavity of a coal fired boiler. The product CaS04 and unreacted sorbent particles are removed from the furnace together with fly ash. Fan and Satija (1984), Milne et al (1990b) Krammer and Staudinger (1991) reported kinetic data and model expressions which are applicable to dry injection systems. 

In the discussions that follow, dry sorption processes are categorized on the basis of the sorbent utilized i.e, dry lime/limestone, sodium salt injection, alkalized alumina, dry MgO-based, and copper oxide processes. 

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