Available lime

Available lime, 15 26 Available net positive suction head (NPSHA), 21 85... 

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. 

After washing the fmits, a screw press is employed to produce a juice-water emulsion. Subsequently, this emulsion is subjected to steam distillation. More than 85% of all commercially available lime oils derive from a distillative process. Sensorially, they differ considerably from cold-pressed oils. 

While the cost per tonne of available lime increases progressively from option (a) to (c), the capital costs decrease and the ease of handling/automation increases. Large users generally prefer options (a) or (b), while small users tend to prefer option (c). In addition, some countries have a small, but growing market for milk of lime, generally prepared at the lime works. 

Sandlime brick plants using hydrated lime (see Fig. 26.4) are relatively simple to operate and low in capital cost. The operating costs, however, tend to be higher than for quicklime, owing to the higher delivered cost of hydrated lime per unit weight of available lime. 

A high available lime content is desirable, not only for economic reasons, but because it reflects low levels of impurity. The % CaC03 should be as low as practicable, while meeting the reactivity requirements. Much of the CaC03 can be removed by screening the milk of lime, albeit at the cost of losing some slaked lime. 

ASTM C911 (formerly ASTM C433) specifies the required quality of quick- and hydrated lime for chemical uses including the production of hypochlorite bleach. High purity products are required with high available lime contents, low levels of sludge-forming impurities and a low iron oxide content (iron oxide is understood to catalyse the decomposition of calcium hypochlorite) [31.1]. 

The calcium hydroxide should have a high available lime content, a low level of residual CaCOs (typically less than 2 %) and be free of grit. 

TTie principal properties of hydrated lime for this purpose are its available lime content and its particle size distribution, which help to produce the required rheological characteristics. 

Available lime is an analytical term for the calcium oxide content of quicklime or hydrated lime that is able to react with a sucrose solution in the available lime test (e.g., as specified in BS 6463 and ASTM C25). 

Determination of available lime or free CaO in industrial lime or in milk of lime or determination of caustic value of agricultural lime iodi-metrically... 

Determination of available lime (after extraction with sucrose solution) with standard acid... 

How does long exposure of a lime sample to atmosphere affect its available lime ... 

Its available lime therefore goes on decreasing on continued exposure to air. 

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