Grinding and shipment of burnt lime

Burnt lime is sent to consumers in the Federal Republic of Germany, mainly in the form of a fine lime. This underlines the importance attached to the process of production and consumption. Burnt lime is one of hard grind materials. Soft burnt lime grinding easier than more strictly (strongly) burned. Heavy fragmentation produced in the impact crusher, while the fine grinding is carried out in a ball or roller tube mills.

Burnt lime is sent to consumers in the Federal Republic of Germany, mainly in the form of a fine lime. This underlines the importance attached to the process of production and consumption. Burnt lime is one of hard grind materials. Soft burnt lime grinding easier than more strictly (strongly) burned. Heavy fragmentation produced in the impact crusher, while the fine grinding is carried out in a ball or roller tube mills. The conveyor circuit crushing plant is shown in Figure 1.54. There are several stages of quicklime powder lime. Snachala absorbed water and raw powder is compacted by the formation of oxide hydroxide - CaO • 2H2O. Then a homogeneous dense mass turns into a "raging" powdered product. This releases a major amount of heat, leading to the heating supply and steam generation, as a result of spontaneous razlozheniya oxyhydrate by the equation:

 

CaO • 2H2O → Ca (OH) 2 + H 2 O

 

The final stage - the formation of fluff, ie the appearance of aggregates of calcium hydroxide as a result of the mutual attraction of oppositely charged areas of single crystals of Ca (OH) 2...

For powder lime slaking in theory, must be 32.13% water by weight of quicklime. Practically water take 2 - 3 times more, since much of it evaporates. With a lack of water is overheated masses and "burnout" lime rezultate in which some of its grain that failed to extinguish priobretayut dense structure, difficult to further gidratatsii, and products cause a decrease in strength due to the late cancellation.

The amount of water required for slaking the dough depends on the quality of the lime, quenching method, and other factors. On average, it is approximately 2.5 liters per 1 kg of quicklime. The fatter the lime, the more water is needed. The water content in the final product - the limy test - usually no more than 50%.

The process of clearing burnt lime occurs [33] the faster and more completely:

- The more quality burnt lime, ie The higher content of CaO;

- More than svezheobozhzhennaya lime;

- The smaller pieces of lime;

- The lower the firing temperature of lime;

- The higher the temperature of the water supplied to the vapor pressure or quench.

1 - Crusher Lump lime 2 - bucket elevator, 3 - silage quicklime, 4 - dispenser, 5 - mixing screw, 6 - gasilny drum 7 - bucket elevators hydrate, 8 - separator 9 - screw 10 - shaker, 11 - fan humid air, 12 - spray chamber

Slaked lime

CaO in the hydration reaction of Ca (OH) 2 occurs at a considerable heat release (1159 kJ / kg CaO at 20 ° C) and technically referred to as hydrated lime. When 1 kg CaO slaking liberating sufficient heat to heat about 2.8 liters of water of 0 ° to 100 ° C. When slaked lime, depending on the amount of water can obtain lime - powder lime with a moisture content of not more than 5%, lime paste with a moisture content of about 50%, or milk of lime.

Blanking - special technological process used in the production of lime tolko. This process proceeds by the reaction:

 

CaO + H2O → Ca (OH) 2 + 1160 kJ / kg CaO

 

When slaked lime is released znachitelnoe amount of heat 1160 kJ per 1 kg of calcium oxide. Vydelyayuschayasya heat causes boiling water, so called izvest quicklime quicklime. Penetrating deep into the grain, the water enters into chemical interaction with CaO, and the heat released at the same time, turns the water into steam. The sharp increase of steam compared to the amount of liquid causes the internal stresses in rastyagivayuschie lime grains and their destruction [165, 166, 167].

There are several stages of quicklime powder lime. Snachala absorbed water and raw powder is compacted by the formation of oxide hydroxide - CaO • 2H2O. Then a homogeneous dense mass turns into a "raging" powdered product. This releases a major amount of heat, leading to the heating supply and steam generation, as a result of spontaneous razlozheniya oxyhydrate by the equation:

 

CaO • 2H2O → Ca (OH) 2 + H 2 O

 

The final stage - the formation of fluff, ie the appearance of aggregates of calcium hydroxide as a result of the mutual attraction of oppositely charged areas of single crystals of Ca (OH) 2...

For powder lime slaking in theory, must be 32.13% water by weight of quicklime. Practically water take 2 - 3 times more, since much of it evaporates. With a lack of water is overheated masses and "burnout" lime rezultate in which some of its grain that failed to extinguish priobretayut dense structure, difficult to further gidratatsii, and products cause a decrease in strength due to the late cancellation.

The amount of water required for slaking the dough depends on the quality of the lime, quenching method, and other factors. On average, it is approximately 2.5 liters per 1 kg of quicklime. The fatter the lime, the more water is needed. The water content in the final product - the limy test - usually no more than 50%.

The process of clearing is slow due to the formation on the surface of the lime particles doughy layer prepyatstvuyuschego access of water to unslaked inner layers. To speed up the process of extinction of lime is recommended mechanical effect - mixing vibration, as this breaks with the unreacted particles of shell Ca (OH) 2.

The rate of interaction of calcium oxide with water and sootvetstvenno speed damping at higher temperatures for every 10 ° C increase in 2 times, so it is advisable to extinguish lime at elevated steam pressure in special drums.

On quenching speed is also influenced by various additives vvodimye water. For example, chloride salts (NaCl, SaS12i al.) Increase the rate of quenching, gypsum and additives and surfactant significantly slow the hydration of CaO.

The character blanking process is dependent on the presence of impurities. When quenching in fluff grains silicates and calcium aluminates, a converted-on during firing is not blanked and not converted into a powder - they must be separate, and be mixed with comminuted fluff to improve its properties.

Figure 1.55 shows a flow chart gasilnoy lime plant.

The process of clearing burnt lime occurs [33] the faster and more completely:

- The more quality burnt lime, ie The higher content of CaO;

- More than svezheobozhzhennaya lime;

- The smaller pieces of lime;

- The lower the firing temperature of lime;

- The higher the temperature of the water supplied to the vapor pressure or quench.

1 - Crusher Lump lime 2 - bucket elevator, 3 - silage quicklime, 4 - dispenser, 5 - mixing screw, 6 - gasilny drum 7 - bucket elevators hydrate, 8 - separator 9 - screw 10 - shaker, 11 - fan humid air, 12 - spray chamber

The use of lime products

Figure 1.56 - Scheme of areas the use of lime [168]

 

- White lime (cl): Lime, which are mainly composed of oxide or calcium hydroxide without any additions of hydraulic or pozzolanic materials.

- Dolomitic lime (dl): Lime, which are predominantly magnesium or calcium hydroxide and magnesium hydroxide without addition of hydraulic or pozzolanic materials.

- Hydraulic lime (CB): lime, which consist mainly of calcium hydroxide, calcium silicates and aluminates, and obtained by mixing suitable materials. They grasped in the air and then solidified underwater. Atmospheric carbon dioxide contributes to the process of hardening due to carbonation processes of hydration products.

- Lime high gidravlichnosti (NHL): Lime, which are obtained by calcination of carbonate rocks containing high amount of clay or rich in silica. All NHL-lime after setting the air can continue to harden under water. Atmospheric carbon dioxide contributes to the hardening process.

The area and the possible use of burnt lime and calcium hydroxide in the construction industry are varied: they are the raw material for the manufacture of lime sandstone, porous concrete, for wall mortar and plaster (lime, cement + lime plaster), which are mixed either manually on site, or more often delivered - ready-made as dry mortar in the tank (silo) or fresh mortar to a mixing vehicle to the construction site. Of those manufactured and lime paint sludge is used as a filler in asphalt, land drainage and stabilization. Mortars and plasters have proved to be reliable binders with a long tradition.