A large amount of sulfur dioxide (SO2) will be released during rural household coal combustion, causing serious environmental pollution. Therefore, it is very urgent to develop a clean and efficient fuel to substitute rural household coal controlling SO2 emission. In this paper, a new strategy toward scattered coal combustion with remarkably reducing SO2 emission was proposed. Coal and compound additive of Al2O3 and CaCO3 were blended and then copyrolysis at 1050 °C was performed to produce clean coke. First, the sulfur content of clean coke was reduced, meanwhile, generating sulfur fixation precursor during pyrolysis. Then, clean coke is used for efficient sulfur fixation during the subsequent combustion process to reduce SO2 emissions. The effects of combustion temperature, Al/S molar ratio, and the mechanism of sulfur retention during clean coke combustion were studied in the tube furnace and muffle furnace. The mechanism can be attributed the following reason: (a) CaS produced during pyrolysis and CaO decomposed by complex additives were oxidized during combustion, and CaO captured the SO2 released from clean coke combustion, which formed CaSO4. (b) CaSO4 reacts with Al2O3 to produce calcium sulfoaluminate at high temperatures, which improves the sulfur fixation efficiency of clean coke combustion at high temperatures. In a word, this new strategy can greatly reduce the emission of SO2, thus helping to solve rural household coal pollution problems.

For alleviating of the shortage of coking coal resource and efficient cleaning and utilization of low-rank coal, hydro-plasticization of low-rank coal was carried out. However, the caking property of low-rank coal cannot be obviously improved under mild conditions in the traditional tetralin-H 2 system. This study is to investigate the feasibility of mixed tetralin-glycerol as a solvent in the process of low-rank coal hydro-plasticization. The solvent ratios of tetralin-glycerol, reaction pressure, and atmosphere were varied to evaluate their effects on hydro-plasticization. The results show that the caking index (G RI ) of long-flame coal increases from 0 to 78 at mild conditions, and the hydrogen transfer mechanism might be directly from H 2 to coal rather than through hydrogen-donor solvents in the mixed solvent case. The solvent extraction and the G RI of modified coals were measured and found that the G RI of modified coal has a good linear relationship with PAA yield, and its R 2 is .985.

High strength clean briquettes production by using recycling coal fines is of great realistic significance in saving coal resources and protecting the environment. Blends consisting of a long‐flame coal fines and coal slime (CS) and polyvinyl alcohol (PVA) as binders were used in the preparation of briquettes. To produce a qualified clean briquette with enough briquette strength, the effects of the binder content, briquetting pressure, and moisture content were systemically investigated. The results indicated that the briquettes prepared by using blended binder with 20 wt.% of CS and 1 wt.% of PVA showed better compressive strength (10.2 MPa) and drop strength (98.3%). CS with particle size less than 0.2 mm could fill in the gap between the coarse coal particles uniformly, thus reinforcing the embedded state and leading to a higher briquette strength. Moreover, the strength of the briquettes was also affected by the briquetting pressure and moisture content. At briquetting pressure of 60 kN and optimum moisture content of 14%, the highest briquette strength was achieved. The hydroxyl content of the briquettes by adding CS and PVA increased significantly. In this condition, a highly viscous network colloid was formed when the PVA and water were mixed together. When the briquettes were dried, the colloid could produce a dendritic structure, which was mechanically embedded between adjacent coal particles.

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