{'fraction_non_alphanumeric': 0.026599568655643422, 'fraction_numerical': 0.015815959741193385, 'mean_word_length': 4.898305084745763, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Detrimental effects of low-rank coal utilization to the operational condition of large capacity updraft moving-bed gasifier

ABSTRACT The feedstock of updraft Fixed-Bed Gasifier must meet very strict criteria such as low fragmentation, non-caking property and high ash fusion temperature (AFT), which represent the general characteristic of medium rank coal. In this paper, the properties of low-rank coal were carefully selected according to literature recommendations such as high AFT (above 1500°C), low grindability (HGI 55), swelling index (FSI 1) and lump size ranging from 30 to 80 mm. Thermal fragmentation was also evaluated by using sieve analysis and show Fd value of 0.81. After 90 h of service time, the temperatures of the vessel body declined gradually and 580 kg/h gasifier reactor was forced to shut down after 300 h. The rotating grate was found severely damaged with a large deposit of char. The OES, SEM, EDS and XRD analysis results confirmed each other that rotating grate has experienced excessively high temperature during gasification. It is likely that high breakage during devolatilization is the root cause of all operational problems. It causes melting of the cone, block the air exit ports, localize pressure drop, aggravate bed channeling, and so on. It is possible that FSI value is not necessarily to be low to maintain uniform pressure drop of the gasifier.