Coking coal is an important raw material for coke production. In this study, in an inert atmosphere, two Chinese coking coal samples were, respectively, heated gradually to 1200 °C to release volatile and form char and coke in succession, then cooled naturally to close room temperature to age the coke. The whole heating and cooling process on carbonization were monitored in situ by simultaneous small and wide-angle X-ray scattering (SAXS-WAXS) technique based on a synchrotron radiation platform. The simultaneous structural changes of pore and skeleton in coal during carbonization are revealed for the first time. The two raw coal samples, with similar carbon content and slightly different coalification degree, undergone a carbonization process similar in whole and different in parts. The carbonization presents approximately three stages during heating process and one stage during cooling process. The coal structure changes wavily during heating and monotonously during cooling. The corresponding structural change mechanism is analyzed.

    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Samples
        2.2 In-situ SAXS-WAXS characterization
        2.3 True density measurement
    3 Results and discussion
        3.1 Nature of raw coal
        3.2 In-situ SAXS and WAXS
        3.3 Structure evolution during heating
        3.4 Structure evolution during cooling
    4 Summary
    References

• Yuexiang Wang(Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology)
• Zhihong Li(Beijing Synchrotron Radiation Facility, Institute of High Energy Physics)
• Jiao Kong(State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology)
• Liping Chang(State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology)