High-efficiency cogeneration boiler bagasse-ash geochemistry and mineralogical change effects on the potential reuse in synthetic zeolites, geopolymers, cements, mortars, and concretes

Abstract

Sugarcane bagasse ash re-utilisation has been advocated as a silica-rich feed for zeolites, pozzolans in cements and concretes, and geopolymers. However, many papers report variable success with the incorporation of such materials in these products as the ash can be inconsistent in nature. Therefore, understanding what variables affect the ash quality in real mills and understanding the processes to characterise ashes is critical in predicting successful ash waste utilisation. This paper investigated sugarcane bagasse ash from three sugar mills (Northern NSW, Australia) where two are used for the co-generation of electricity. Data shows that the burn temperatures of the bagasse in the high-efficiency co-generation boilers are much higher than those reported at the temperature measuring points. Silica polymorph transitions indicate the high burn temperatures of ≈1550 °C, produces ash dominated α −quartz rather than expected α-cristobilite and amorphous silica; although α-cristobilite, and amorphous silica are present. Furthermore, burn temperatures must be ≤1700 °C, because of the absence of lechatelierite where silica fusing and globulisation dominates. Consequently, silica-mineralogy changes deactivate the bagasse ash by reducing silica solubility, thus making bagasse ash utilisation in synthetic zeolites, geopolymers, or a pozzolanic material in mortars and concretes more difficult. For the ashes investigated, use as a filler material in cements and concrete has the greatest potential. Reported mill boiler temperatures discrepancies and the physical characteristics of the ash, highlight the importance of accurate temperature monitoring at the combustion seat if bagasse ash quality is to be prioritised to ensure a usable final ash product.

Influence of Ground Calcium Carbonate Waste on the Properties of Green Self-Consolidating Concrete Prepared by Low-Quality Bagasse Ash and Rice Husk Ash

“…The original BA was unsuitable for applications as low-reactivity pozzolanic materials in concretes because of their high porosity and large particle sizes. Chao and Kuo [ 2 ] and Clark et al [ 3 ] revealed that the filler effects and pozzolanic activities of industrial ashes depend on their fineness and particle size. Therefore, using a Los Angeles grinding machine (ELE International, Bedfordshire United Kingdom) for 3.0 h at a rotating speed of 33.0 rpm, the original BA was dried to reduce their moisture contents to about 1.0–2.0% (dry basis) and was ground until the particles were less than 15% by mass and retained on a 45 micrometer (µm) sieve.…”

“…The gSCC specimens were utilized to establish the optimal percentages of GCW associated with BA and RHA [ 3 ]. At a constant of 1:2.15, a binder to aggregate mortars was set by mass as outlined by ASTM C39 [ 24 ].…”

“…The cement industry is becoming a severe threat to ecology due to its emission of carbon dioxide (CO 2 ). The modern world is looking for alternatives so that the environment can be saved for the next generation [ 1 , 2 , 3 , 4 ]. To combat climate change, cement producers have tried to minimize the consumption of Portland cement through the application of supplementary cementitious materials, such as natural pozzolanic materials, to minimize emission of carbon dioxide (CO 2 ) and partly substitute Portland cement in concretes.…”

“…The compressive strength of the concrete containing ground BA improves greatly when the BA is ground into fine particles. According to Clark et al [ 3 ], fine or ground BA can be utilized as a substitute for up to 30% of the weight of ordinary Portland cement (OPC), and the 28-day and 90-day compressive strengths of concretes can be lower than those of concretes without BA. Thus, other biomass ashes such as rice husk ash (RHA) are also possible alternative cement replacement materials.…”

Utilização de cinzas do bagaço de cana-de-açúcar como material de preenchimento estrutural ou pozolânico para a produção de argamassas cimentícias: uma revisão

“…Durante o processo de combustão do bagaço, a temperatura das caldeiras (300ºC a 1.000ºC) pode produzir cinzas com diferentes tonalidades de cor [49], bem como determinará o aparecimento das diferentes fases estruturais (amorfa ou cristalina) de sílica [13,47]. Além da temperatura, o tempo de queima também pode afetar a forma estrutural, a quantidade e as características físicas da sílica [48,50].…”