Experimental Study On Ash Fusion Characteristics Of Straw Biomass

Coal, oil and other conventional energy sources are gradually exhausted, thepollution which has been from large energy consuming has an adverse effect on thesurvival and development of human and other living beings. Compared with othercountries, china was facing more serious issues on energy resources andenvironmental conditions. Biomass as a renewable clean energy, which can achievedCO₂zero-emission, was a excellent fuel to replace fossil fuels and solved the energyand environmental issues. As a large agricultural country, china has sufficientbiomass production, development of biomass industry was helpful to achievesustainable and low carbon requirements.Given the advantages of the low ash fusion temperature and slaggingcharacteristics of crop straw, they were mianly researched in this thesis. Experimentsabout ash slagging were made, scanning electron microscopy, infrared spectrum,X-ray diffraction detection methods are used to analysis the alkali metals problemswhich limited the slagging of straw combustion, from the micro perspective.At first, the work was carried out on ash slagging experiments. In order toreduce the slagging of straw combustion, CaO, MgO, Al₂O₃, Fe₂O₃, SiO₂, TiO₂andMnO₂as additives added to corn stalk pellets respectively, the slagging underdifferent situation indicated that MgO, Al₂O₃and Fe₂O₃had a certain effect onreducing slagging tendency, and the MgO showed the evident effect; the higher theratio of the additives, the better effect on controlling of slagging, while the CaO andSiO₂had little effect, TiO₂and MnO₂made it even worse. Based on hardnessstandard, the methods for distinguishing slagging were made, and used it to judgethe slagging degree of different fuel ash; the experiment also could conclude that theslagging tendency had a close connection with temperature: the higher thetemperature was, the more serious the slagging took place.Then, the microstructure and phases transformation of different fuel ash were analyzed thoroughly from the micro perspective. The microstructure observed byelectron microscopy showed that adding different additives with differenttemperature of the ash sample performed different surface structure: ashes withoutslagging showed very loose organizations with lots of gaps, there were connect ordiscrete section; weak or moderate slagging showed the form of discrete irregularstrips, blocks and nets, there was little space between them; ashes with seriousslagging showed smooth surface with lots of small pits, there was no gap on it. Thealkali composition of different ashes were analyzed via fourier transform infraredspectrum and X-ray diffraction. It showed that except TiO₂, remaining otheradditives were involved chemical reaction and the new substances formed, the newsubstances were majored in silicate metals, and with the increase of the proportionof additives, the content of new substances varied with it. The spectrum of asheswith MgO, Al₂O₃, Fe₂O₃showed that the potassium and magnesium salts couldeffectively reduce the corn stalk slagging tendencies, the content level of calciumsalts played a decisive role: the more the content of it, the worse the slagging, andthe temperature also had an influence on it. It proved that the straw slagging can bechanged by controlling the level of calcium salts and combustion temperature.At last, the experiment of ash melting character of crop straw pellet addedFe₂O₃, MgO and Al₂O₃was made respectively, the results showed that the threeadditives had better effect on improving the ash melting temperature, Al₂O₃had themost effect, then the MgO, the last is Fe₂O₃. In order to obtain the fuel suit forbiomass boiler, which had a low slagging tendency and higher ash meltingtemperature. This paper choosed Fe₂O₃, MgO and Al₂O₃to add them to crop strawpellet, the orthogonal test was made for compound fuel, and obtained severalmatching programs.