What is the reason for the large difference between the actual coal-coke ratio and the theoretical coal-coke ratio?

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This post was last edited by Xiaoxiaogu on 2018-7-23 08:00. Our plant’s coke ovens are of the rammed-type, and they are used to produce dry quenched coke. In June, the volatile matter content on a dry basis of the coal used was 26.96%, while that of the coke was 0.98%. Using these values, the overall coke yield was calculated to be 74.76%, which implies a coal-to-coke ratio of 1.338. However, the actual coal-to-coke ratio in our plant in June was 1.387. What is the reason for this large difference? Even considering a burn loss rate of 1.5% for dry quenching of coke, 1.338/0.985=1.358, which is far below 1.387. Question 1: With an overall coke ratio of 74.76%, this should refer to the dry basis of coke; does the overall coke amount include the dust removed during dry quenching of coke? Question 2: The dust removed during the dry quenching of coke is not included in the coke production volume. When comparing the actual coal consumption with the theoretical value, aside from the losses due to combustion, does the impact of this dust also need to be taken into account? Is the proportion of this dust around 2%?