Thermal expansion coefficient calcining coke

Properties of Calcined Coke. Table II shows the properties of calcined cokes A, B, C, D and F by the new and traditional methods. Regardless of the green coke type, the thermal expansion coefficient of calcined coke by the new method was lower than that of traditional calcination method. Porosity values for calcined cokes by the new method have a higher value, regardless of the coke type, than... 

Theoretical Explanation. The major factors of the thermal expansion coefficient of calcined coke are the degree of preferred orientation of the crystallites and void structure (12-14). For example, the thermal expansion coefficient is low for needle coke because it is strongly affected by the preferred orientation of its crystallites. 

We found the latter factor-voids to be important. Experimental results showed that when green coke was calcined under the new methods, and the derived calcined coke was observed by scanning electron microscopy (Figure 2) and its pore size distribution was measured by mercury porosimetry (Figure 3), microcracks of significant sizes (1 to 60 microns) were developed. This was an important contribution to the reduction of the thermal expansion coefficients of the calcined coke processed under the new method. 

During the primary processing, the thermal expansion coefficient of calcined coke changes, and that treatment at the range of 700°C to 900°C is effective. 

The coefficient of thermal expansion of calcined shot coke is too high, making it unsuitable for high-quality anode production. 

A key factor in the suitabihty of cokes for graphite production is their isotropy as determined by the coefficient of thermal expansion. After the calcined coke was manufactured into graphite, the axial CTE values of the graphite test bars were determined using a capacitance bridge method over a temperature range of 25 to 100°C. The results are summarized in Table 24. Also included in the table are bulk density measurement of calcined cokes and the resistivity values of their graphites. 

A specialized application of petroleum coke is the production of electrodes for the steel industry. For this application, it is necessary to use needle coke because its low coefficient of thermal expansion and low resistivity. The needle coke must have low sulfur and low metals content. After production in a delayed coker, needle coke is crushed and calcined in preparation for electrode production. 

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