Abstract
Biomass energy has been used for decades in lieu of fossil fuels. However, biomass, such as wheat straw, typically contains a high concentration of alkali elements, which is likely to induce unfavorable conditions during combustion, such as slagging, agglomeration, and corrosion in the boiler. This study investigated the effects of leaching on the chemical compounds and sintering temperatures of wheat straw ash before and after leaching by tap water. Ash melting and sintering degree tests were conducted using hot-stage microscopy and a scanning electron microscope, respectively. The results show that the ash content in wheat straw decreased by 26.09% (from 4.14% to 3.06%) following leaching, as did the chlorine (Cl), sulfur (S), and nitrogen (N). Meanwhile, the ash-related elements such as potassium (K), magnesium (Mg), and silicon (Si) reduced after leaching too. Additionally, the higher heating value increased slightly, from 19.25 to 19.53 MJ/kg. At the same time, leaching improved the ash melting temperatures of wheat straw during combustion and minimized the ash sintering degree. Similar results were also shown in scanning electron microscope (SEM) images, which clearly indicated that the leached samples had a lighter sintering degree than the original samples. Overall, the leaching process had a positive effect on the ash sintering problems of wheat straw.
Highlights
Human activities demand a vast amount of energy
Similar results were shown in scanning electron microscope (SEM) images, which clearly indicated that the leached samples had a lighter sintering degree than the original samples
This study evaluates the effect of leaching on the chemical compounds and sintering temperature of ash, as well as ash sintering degrees, using tap water
Summary
Human activities demand a vast amount of energy. Fossil fuel has been the most prevalent energy source for the past several decades. The sediments, such as sinters on the super heater, agglomerate on the water wall, and corrosion of the tube surface occurs in fluidized boilers, and in grate furnaces, and has obvious negative effects on boiler efficiency [10,11,12,13,15] Various measures, such as water or acidic leaching, mineral addition, and co-firing with fossil fuels, have been adopted to solve the aforementioned biomass ash-related problems by optimizing the fuel chemical compositions with low vaporized alkaline compounds [15]. A discussion of the partial correlation between ash-related elements and the shrinkage start temperature is provided
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