I would like to ask about the calculation of the theoretical focal length

The coking rate (i.e., coal-to-coke ratio) is the percentage by which charged coal (dry) is converted into coke (dry) through high-temperature dry distillation. The coking rate mainly depends on the coal quality, and is also affected by coking conditions and furnace type. The main methods for calculating the coking rate are as follows: 2.1.1 Determine the coking rate by using the relationship between the ash content of coal and coke. ? Kd·j = Ad·m / Ad·j × 100% (1) ? In this formula, Kd·j represents the coking rate of dry coke relative to dry coal ； Ad·m and Ad·j represent the ash content on a dry basis (%) for coal and coke, respectively. The focalization index calculated using equation (1) is often lower than the measured value. Apart from reasons such as sampling and analysis errors, this is mainly due to changes in the ash composition during the high-temperature carbonization process, as well as loss due to burning of the coke inside the carbonization chamber and during quenching, which increases the ash content. 2.1.2 Calculating the coking rate using the volatiles of the coal and coke used in furnace charging: ?Kd·j=100-Vd·m/100-Vd·j×100+Q (2) ?Where Vd·m and Vd·j represent the dry-base volatiles (%) of coal and coke, respectively ； The correction factor Q refers to the carbon increase resulting from secondary cracking after the volatiles in coal have escaped; it is related to factors such as the volatiles in the coal fed into the furnace, the structure of the coke oven, and the operating procedures of the coke oven. Typically, Q is set to 1. 2.1.3 How can the coking rate be determined using the relationship between the volatiles in coal and coke? The formula is Kd·j = 99 – 5/6 Vd·m; here, Vd·m represents the dry-base volatiles of the coal, while the dry-base volatiles of coke are assumed to be Vd·j = 1.2%. 2.1.4 How to determine the coking rate from coal quality and coking operation conditions? Kd·j=103.17-0.75Vd·m-0.0067tJ. In the formula, Vd·m represents the dry-base volatiles of the coal loaded ； tJ is the center temperature of the coke cake (°C, measured 15 minutes before coke pushing). This formula was proposed by Japan; the Kryvorizhia coking plant in the former Soviet Union found it to be suitable for its operational conditions after calibration, and China also recommends its use

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