Abstract
The article presents the results of the analysis of straw obtained from ripening wheat, which
was subjected to four water soaking cycles in demineralized water. The soaking was carried out
under laboratory conditions at 20°C. As a result, part of mineral matter, including a significant
amount of alkaline sodium and potassium salts and substances containing sulfur and phosphorus,
was washed out. The process of soaking has a great impact on the chemical composition of ash
obtained from water-treated straw, which increased its acidity. The Na2O content in the analyzed
ash has decreased by 78%, while the K2O content has decreased by 60%. In turn, the content of
water-insoluble, acid-forming SiO2 has increased by 80%. As a consequence, a positive change in
the values of indices, on the basis of which the tendency of straw to slagging and deposit formation
during the combustion and gasification processes is assessed, has been observed. Already after the
second water soaking cycle it became apparent, based on the AI alkali index, that the examined fuel
should not cause difficulties resulting from the increased intensity of use of the boiler during the
combustion process. Meanwhile, the value of the BAI bed agglomeration index was considered to
be safe, indicating a low possibility of bed agglomeration during the combustion or fluidized bed
gasification, after the third water soaking cycle. The third of the analyzed indices, the Fu fouling
index, did not indicate any tendency to deposit formation during the combustion; however, four
water soaking cycles reduced its initial value by 80%. The last of the analyzed indexes, the SR, slag
viscosity index did not change its value during the experiment, which, both for the raw straw and after subsequent soaking cycles, indicated that the fuel should have a low tendency to accumulate
slag during the combustion process.
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