Clinker cooling rate

Rate of clinker cooling (rate of temperature change from maximum to approximately 1200 C)... 

J.D. Dorn (personal communication, 1985) stated that clinkers less than approximately 25 mm are virtu ally the same and that larger clinkers exhibit effects of different cooling rates. Dorn recommended passing a liter of clinker through a crusher, producing particles of approximately 5-mm diameter, followed by riffling to a volume of 1/4 liter and pulverizing to less than 0.59 mm. The 0.59- to 0.30-mm (No. 30 to 50 mesh) fraction is used for a polished section. 

CgA2F-C3A and C2p-C2A F-MgO with laboratory-made clinkers. They related ferrite crystal morphology and optics to cooling rates, showing that in slowly cooled clinker, ferrite occurs as fernlike crystals and in quickly cooled clinker the crystals resemble bamboo leaves. 

Photograph 7-74 Prismatic alkali aluminate crystals in crushed clinker powder mount. High maximum temperature, long burning time, slow heating rate, moderately quick to moderately slow cooling rate. Gas- and coal-fired, wet-process kiln, 500 tons/day. (S A6692)... 

In the formed clinker the Mj modification of C3S prevails. Belite is present mostly in its modification, but some ti- and a -C2S may also be formed. At high cooling rates the amount of these high-temperature modifications increases at the expense of -C2S. 

Another factor that affects the coefficient of reflection is the cooling rate of the cUnker, which influences the composition of the formed glass phase. It has been reported that the highest whiteness is obtained if the composition of the glass phase is close to eutectic (Gaidzhurov and Zhubar, 1994). To achieve this, a fast cooling rate of the clinker is necessary. 

In the bnming of clinker the rate of cooling must be speeded up as much as possible. 

It has been found that very effective activation may be achieved by combining an increased alkali content of the raw meal and a veiy rapid cooling of the clinker formed, in particular in the temperature range 1300-900°C (Stark et al, 1979, 1986 Gies and KnOfel, 1986 Lampe, 1986 Milke, 1992). In this way the a -CjS phase, which is more reactive than P-C2S and exists in the resultant clinker at high temperatures, is at least partially preserved in the cooled product. Moreover, defects are introduced into the crystalline lattice, which increase the reactivity of the dicalcium silicate present even further. To effectively prevent the a - 28 conversion, cooling rates of up to 1000 K/min were found to be necessary. About 5% of alkali oxides and other foreign ions are typically present in the stabilized a -C2S phase. 

Another dopant that may be considered for increasing the reactivity of belite cements is S04 ions (Gies and Knofel, 1987 Stark et al, 1987). Under these conditions the final clinker contains the rather than the a -CjS phase, even if high cooling rates have been employed however, the SO -doped form of yff-dicalcium silicate is much more reactive than its SO -free counterpart. The doped C S typically contains about 3% each of SO3 and AI2O3 in its crystalline lattice. If an SO3-doped belitic clinker that also contains some alite is to be produced, the amoimt of SO3 in the raw meal must not exceed... 

Kuznetsova et al. (1992) produced activated belite cements by introducing into the raw meal industrial waste products containing phosphoras, chromium, and titaniiun, and by employing cooling rates of up to 5000 K/min, Such clinkers contained dicalcium silicate mainly in its form, but a and a modifications were also present. By adding carbon to the raw mix, regions with local temperatures above 2100 °C were obtained before the bulk of limestone present was decarbonated. This resulted in a non-stoi-chiometry of the produced clinker minerals and along with it an increase of reactivity. 

Kanaya, M., Matsumi, M., and Ichikawa, M. (1998) Effect of cooling rate on fine texture and hydraulic activity of clinker in the C3S-C2S-CjjA2-CaF2-C4AF system (in Japanese). MmL Materiaru 5 (274), 215-219 [ref CA 119/84891]. 

The recuperative zone is followed by the final cooling zone, where the clinker is cooled from about 750° K to its final temperature. The grate area for final cooling is nearly three times as large as that for heat recuperation. The reason for this is the cooling rate, which decreases as the difference in temperature between the cooling air and the clinker to be cooled becomes less. 

The differences in cooling rate in the significant temperature range and for the commonly employed raw material compositions between the various clinker... 

The operation of planetary and rotary coolers requires no special attendant personnel for control. The cooling air flow rate, the clinker discharge rate and the secondary air temperature automatically adjust themselves in relation to the clinker output of the kiln, the heat consumption and the temperature of the clinker on entering the cooler. Fluctuations in the discharge rate or temperature of the clinker on leaving the kiln which are caused by, for example, dislodgment of coating cannot be compensated in the cooler... 

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