Lime/limestone

Theory of Calcination. The reversible reaction involved in the calcination and recarbonation of lime—limestone is one of the simplest and most fundamental of all chemical reactions. In practice, lime burning can be quite complex, however, and many empirical modifications are often necessary for efficient performance. 

Desulfurization with Dry Lime Limestone or lime or dolomite (CaCO,3-MgCO,3) in a fluidized bed coal combustor reacts with SO9 in... 

Lime is among a family of chemicals which are alkaline in nature and contain principally calcium, oxygen and, in some cases, magnesium. In this grouping are included quicklime, dolomitic lime, hydrated lime, dolomitic hydrated lime, limestone, and dolomite. The most commonly used additives are quicklime and hydrated lime, but the dolomitic counterparts of these chemicals (i.e., the high-magnesium forms) are also widely used in wastewater treatment and are generally similar in physical requirements. 

Soda ash, slaked lime, limestone, or sodium bicarbonate. Cover spills with vermiculite, diatomaceous earth, clay, or fine sand followed by one of the decontaminants. 

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. 

Lead, lead oxide, leather wastes, LD-dust, lignite, lime, limestone, lithium carbonate, lithium fluoride, lithium hydroxide... 

Reactions between gases and liquids may involve solids also, either as reactants or as catalysts. Table 17.9 lists a number of examples. The lime/limestone slurry process is the predominant one for removal of S02 from power plant flue gases. In this case it is known that the rate of the reaction is controlled by the rate of mass transfer through the gas film. 

Chemical scrubbing systems for SO/ absorption fall into two broad categories (a) Disposable systems and (b) regenerative systems. Typical of systems in use for a number of years are those that use an aqueous slurry of an insoluble caldum compound, which can be discarded after use. Disposable 02-removal systems use aqueous slurries of finely ground materials, such as lime, limestone or dolomite, to produce a mixture of insoluble sulfites and sulfates. On passing through the scrubber, S02 from the waste gas dissolves to form sulfurous acid S02 ... 

While the development of flue gas clean-up processes has been progressing for many years, a satisfactory process is not yet available. Lime/limestone wet flue gas desulfurization (FGD) scrubber is the most widely used process in the utility industry at present, owing to the fact that it is the most technically developed and generally the most economically attractive. In spite of this, it is expensive and accounts for about 25-35% of the capital and operating costs of a power plant. Techniques for the post combustion control of nitrogen oxides emissions have not been developed as extensively as those for control of sulfur dioxide emissions. Several approaches have been proposed. Among these, ammonia-based selective catalytic reduction (SCR) has received the most attention. But, SCR may not be suitable for U.S. coal-fired power plants because of reliability concerns and other unresolved technical issues (1). These include uncertain catalyst life, water disposal requirements, and the effects of ammonia by-products on plant components downstream from the reactor. The sensitivity of SCR processes to the cost of NH3 is also the subject of some concern. 

A preliminary-level economic evaluation (13) performed by EPRI (Electric Power Research Institute) and TVA (Tennessee Valley Authority) indicates that a combination of electrostatic precipitators (or bag house), ammonia-based SCR system, and wet lime/limestone FGD scrubber range between 20% to 185% cheaper than wet process for complete control of particulates, N0X and S02 The lower percentage is for the second type and higher percentage for the first type of process. Therefore, the second type of process appears to be more promising and will be the subject of further discussion in this paper. 

Laslo, D., J. C. S. Chang, and J. D. Mobley, "Pilot Plant Tests on the Effects of Dissolved Salts on Lime/Limestone FGD Chemistry," In Proceedings Eighth Symposium on Flue Gas Desulfurization, New Orleans, LA, November 1983, Volume 1, EPA-600/9-84-017a (NTIS PB84-223031), July 1984. 

Lead, lead oxide, leather wastes, LD-dust, lignite, lime, limestone, lithium carbonate, lithium fluoride, lithium hydroxide Magnesia, magnesium carbonates, magnetite, maleic anhydrate, manganese dioxide, metal powders, molding compounds, molybdenum, monocalciumphosphate (MCP)... 

Costs of 10 alternative ECTs were calculated for three hypothetical and three actual coal-cleaning plants, and the cost of lime-limestone slurry coating was analyzed. 

Option 10. Lime-Limestone Slurry Coating of Waste Before Disposal. One major... 

A highly acidic Illinois Basin coal waste was mixed in plastic-lined 55-gal. barrels with wet slurries containing lime ranging from 0.17 to. LS wt% of the waste. In one case, 1.1% limestone slurry was mixed in after 0.3.3% lime had been used. These slurries were screened to remove excess water and placed in specially designed disposal boxes. Six boxes of each of the six lime/limestone/waste mixes were then placed in a pattern to await wet and dry weathering cycles. 

The iron values closely parallel the effluent acidities that is, when the acidity is high (low pH) the iron contents of the leachates are high. When the acidity is low (high pH) the iron concentrations in the leachates are also low. The lime-limestone-treated material is particularly interesting because the iron levels remain low as long as the pH is maintained in the neutral region. Consequently, this treatment effectively controlled the pH and the release of iron for nearly 4 months. 

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