Yilmaz S.

Article | 2019 | Combustion Science and Technology

In this study, considering a specific coal fired power plant, fly ash samples were analyzed in terms of unburned carbon (UBC) and amount of UBC in these samples were compared to coal volatile matter content. UBC which can be used as an expression to tell efficiency of power plants is basically reasoned by either coal properties or by the conditions of combustion environment in boiler. Coal combustion boilers are utilized in terms of their design conditions and they are really hard to utilize them out of these ranged conditions. That is why in order to investigate the effect of these abovementioned parameters, either laboratory scale . . . or pilot scale combustion tests should be conducted. Briefly in this study, a period of same conditions of same boiler utilization of different types of coals considered, and different amounts of UBC in fly ashes were correlated with high or low amount of volatile matter content in coal. Obtained correlation between coal volatile matter and UBC in ash showed that volatile matter content of coal is dominantly affecting the coal burnout. © 2019, © 2019 Taylor & Francis Group, LLC Daha fazlası Daha az

Kizgut S. | Bilen M. | Toroğlu I. | Bariş K.

Article | 2016 | Combustion Science and Technology188 ( 3 ) , pp.439 - 450

The unburned carbon (UBC) content of ash from coal-fired thermal power stations and plants that use massive amount of coal can sometimes be 6-7% or more; this simply means loss of carbon and decrease in efficiency. Carbon loss not only causes a decrease in efficiency but is also an economical issue. Decreasing the carbon content would provide the usage of ash from thermal power stations as cement additives. Many factors cause low combustion efficiency and a high amount of UBC. In the course of this study, fly ash and bottom ash were divided into size fractions and accumulation of UBC at coarser size fractions was observed. In this s . . .tudy, a ground coal sample from a mill was sieved, and the accumulation of UBC at coarser size fractions was associated to a lack of grinding of pulverized coal. Ground coal has a size distribution where 54.45% was below 75 µm, and 45.55% was still over this critical size. A significant amount (35.48%) of the UBC accumulated in the size fraction over 75 µm in fly ash, whereas almost 70% accumulated in the size fraction over 0.5 mm in bottom ash. Coal and ash samples were observed under a microscope to deduce origins of UBC. © 2016 Taylor & Francis Daha fazlası Daha az

Bilen M. | Kizgut S.

Article | 2016 | Fuel Processing Technology143 , pp.7 - 17

Unburned carbon (UBC) percentage in coal ash can be considered as an economic and environmental constraint since it is not only an important characteristic in terms of combustion efficiency but also it becomes more of an issue of further utilization of ash. In this study, particle size distribution (PSD) effect on UBC in fly ash (FA) was discussed and efficient size parameter of PSD in terms of UBC formation was determined. At the first stage of the study, regarding ash formation, percentage of any set of coal particles which are more likely to form fly ash (FA) was theoretically determined. For this purpose, a formulation including . . . the size parameters was proposed. Secondly, with the help of a 3-day long systematical control of power, the effect of size distribution on UBC was obtained. The size distributions of these samples showed that an increase in D32 size parameter causes an increase in the amount of UBC as well. Relationships between the amount of UBC and mean values of size parameters (D10, D50, D90, D32, D43)were all statisticallymeaningful for both units of power plant concerned but D32 size parameter has a better fit among all the size parameters. In summary, D32 & UBC have a regression coefficient of 0.90 (R2 ~ 0.9),while other size parameters (D10, D50, D90, D43) & UBC have regression coefficients of 0.2 (R2 ~ 0.2) for both units. Finally, a model including these size parameters was proposed to predict UBC in FA. The model proposed was in good agreement with the measured UBC in FA. © 2015 Elsevier B.V Daha fazlası Daha az