Clinkering process

Operation with the experimental furnaces has shown that the material properties of coal or ash are only part of the clinkering processes. The geometric shape of the flame, reaction characteristics and heat transmission processes near the wall of the corresponding heating surfaces and on individual particles are coupled with melting, vaporization and condensation processes of mineral substance to form deposits. 

It is convenient to follow the advancement of clinkering process by determining the free calcium oxide in the raw mix, called frequently free lime . The content of this component on the beginning is increasing quickly, as a result of calcium carbonate decomposition, and then is gradually decreasing (Fig. 2.1), as the new compounds are formed with silica, alumina and iron. 

The simple formnla for the calculation of free CaO in the clinkering process by Johansen [15] was given he admitted that the limiting of the process rate factor is diffusion ... 

The invariant point 2 of 1338 °C C2S-C3S-C3A-C2(A, F)-melt has the same temperature. Both these points Swayze [37] treated as peritectic. In the equilibrium condition the clinkering process ends in point 2, and the composition of ferrite phase is which corresponds to the ratio A/F=0.85. Both invariant... 

In the system Ca0-Si02-CaS04 the compound 2C2S CaSO is formed [72], stable at the range 1000-1200 °C. This is important in the production of expansive clinkers [73]. As it was mentioned earlier, at low quantities the sulphur presence has advantageous effect on clinkering process, principally by modification of the melt properties. 

To the most important factors influencing the clinkering process in rotary kiln are the following ... 

The formulae for these calculations can be found in Babnshkin et al. book [13]. The heats of several reactions, which constitute the overall clinkering process, are given in the Table 2.1, and specific heats of components participating in this process in Table 2.2. On the basis of these data the theoretical thermal balance of clinkering can be obtained and heat of this process can be calculated (Table 2.3). 

Table 2.1 Heat of elemental leaetions participating in clinkering process [96]...

Table 2.3 Thermal balance of clinkering process, J/g of clinker...

Similarly cuprum enhances the clinkering process, however, worsens cement properties [215]. Chromium, bariitm, phosphoms, boron and titanium added in small quantities to raw materials increase cement strength after 3 days of hardening... 

As it is known, that the heat consiunption of the clinkering process is mainly due to the calcium carbonate decomposition and the long period (about 20 min) of clinker heating in sintering zone at maximirm temperamre, to assirre full alite formation. Therefore the energy consirmption increases with lime saturation factor (see Chap. 2). 

---