Clean Preparation of Formed Coke from Semi-coke by the Carbonated Consolidation Process

In order to address the low thermal efficiency of low-rank coal combustion and the accompanying serious environmental issues, formed coke was prepared using a carbonization consolidation method with low-rank coal semi-coke. The test for briquetting and carbonation consolidation conditions revealed that the optimal parameters were a briquetting pressure of 93.63 MPa, moisture content of 16%, Ca(OH)₂ binder amount of 10%, and a CO₂ concentration of 30% at 20 °C. Under these conditions and a carbonation consolidation time of 60 min, high-quality formed coke was produced, exhibiting a compressive strength of 1256.2 N/a, redrying strength of 286.2 N/a, and a dropping strength of 10.6 number/a. The combustion characteristics of the prepared formed coke were investigated, revealing that ignition temperatures (345.39 °C), burnout temperatures (495.57 °C), and peak of the maximum weight loss rate temperatures (437.93 °C) are slightly higher than those of bituminous coal. The low calorific value of the briquette was 20.4 MJ/kg. During the combustion process, the emission concentrations of SO₂, NO, and solid particles from the formed coke were significantly lower than those of bituminous coal, indicating that it is a cleaner energy source. Moreover, adding Ca(OH)₂ effectively reduced SO₂ emissions and achieved sulfur fixation and emission reduction.