Co-Combustion of Low-Rank Coal with Woody Biomass and Miscanthus: An Experimental Study

Abstract

This paper presents a research on ash-related problems and emissions during co-firing low-rank Bosnian coals with different kinds of biomass; in this case woody sawdust and herbaceous energy crops Miscanthus. An entrained-flow drop tube furnace was used for the tests, varying fuel portions at a high co-firing ratio up to 30%wt woody sawdust and 10%wt Miscanthus in a fuel blend. The tests were supposed to optimize the process temperature, air distribution (including OFA) and fuel distributions (reburning) as function of SO 2 and NO x emissions as well as efficiency of combustion process estimated through the ash deposits behaviors, CO emissions and unburnt. The results for 12 co-firing fuel combinations impose a reasonable expectation that the coal/biomass/Miscanthus blends could be successfully run under certain conditions not producing any serious ash-related problems. SO 2 emissions were slightly higher when higher content of woody biomass was used. Oppositely, higher Miscanthus percentage in the fuel mix slightly decreases SO 2 emissions. NO x emissions generally decrease with an increase of biomass co-firing rate. The study suggests that co-firing Bosnian coals with woody sawdust and Miscanthus shows promise at higher co-firing ratios for pulverized combustion, giving some directions for further works in co-firing similar multi-fuel combinations.

Emission Behaviors of Inorganic Ultrafine Particles during Zhundong Coal Oxy-Fuel Combustion with Characterized Oxygen Input Fractions Comparable to Air Combustion

“…The newly discovered Zhundong coal field is the largest intact coalfield with a predicted reserve of~390 billion tons, located in Junggar Basin in the Xinjiang Autonomous Region of China. Zhundong coal was reported to show the typical combustion characteristics of a low-rank coal [7,8], i.e., it consisted of sequential and overlapping stages of volatile release and char combustion [9,10]. To better utilize it in a power boiler, Chinese researchers have paid attention to the obvious ash deposition problems, such as slagging, fouling and corrosion, which are mainly caused by the high sodium and calcium content of Zhundong low-rank coal [11][12][13][14][15][16].…”

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“…The final results of the investigation point out a few critical conclusions related to the additive type and ratio to reduce deposits formation on heat transfer surfaces, referred to as slagging and fouling problems of CFB boilers. Other papers published in the previous SDEWES Special Issues in this field studied the ash/emissions-related problems during co-firing low-rank Bosnian coals with different kinds of biomass [42], and ash deposit formation during the combustion of pulverised grape pomace in a drop tube furnace [43].…”

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