| In recent years, supercritical circulating fluidized bed boilers have rapidlydeveloped, and it is an efficiently clean coal power generation technology with bothsupercritical steam cycle technology and circulating fluidized bed combustiontechnology. As supercritical circulating fluidized bed boilers have been put into use inour country, the annual amount of Sulfur fixing ashes and Sulfur fixing slags washundreds of millions of tons. Most of ashes and slags can only be used for landfill dueto the huge amount and poor understanding of their properties, and the using wayaffects the environment of human survival seriously.In this paper, taking four kinds sulfur fixing ashes and two kinds sulfur fixingslags of supercritical circulating fluidized bed coal from power plant in Huaibei miningarea as the research object, their characteristics were systematically analyzed.Chemical analysis method, micro-testing techniques of energy dispersive X-rayspectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS)micro-testing techniques were used to analyze the chemical compositions of sulfurfixing ashes and sulfur fixing slags. The mineral components were analyzed by X-raydiffraction spectrum (XRD), and the surface morphology and microstructure of ashesand slags were investigated by scanning electron microscope (SEM). At the same time,their pozzolanic activity were studied by using the rapid evaluation method of activityrate, and the effect of the temperature and ages on playing the activity of sulfur fixingashes and sulfur fixing slags was investigated. This article was mainly focusing onstudying the effect on system strength when replaced part of the cement by sulfurfixing ashes or sulfur fixing slags. The impact of different amount of substitution,different water cement ratio and different varieties of sulfur fixing ashes and sulfurfixing slags on the strength of the system were observed.The results of the characteristics of sulfur fixing ashes and sulfur fixing slagsshow that, firstly, the main elements of sulfur fixing ashes and sulfur fixing slags are Si,Al, Ca, S, K, Fe, Mg, Na and Ti, and there are some heavy metal elements such as Cd,Cu, Cr, Pb and As (a kind of metalloid), which are harmful to the environment. What’smore, the content of silicon oxide and aluminium oxide in chemical composition ismore than70%, and it is far more than the content of them in cement. The content ofsulfur is also higher than that in cement. Through the analysis of ignition loss, A1, A2, A3and S2belong to the first level, but A4and S1belongs to secondary level. Secondly,mineral compositions of sulfur fixing ashes and sulfur fixing slags mainly includequartz, anhydrite, calcite, hematite, free lime and amorphous calcined clay mineralsrepresented by partial kaolinite. Thirdly, the particle size of sulfur fixing ashes issmaller than that of the sulfur fixing slags obviously, so the sulfur fixing slags need tobe grinded fine before use. The particle size of sulfur fixing ashes is mostly below10microns, but the particle size of sulfur slags is from10microns to50microns. Theirparticle shape is irregular, and their structure is loose. In addition, there are manymicro pores in sulfur fixing ashes and sulfur fixing slags, the size is about tens ofnanometers. Finally, the activity rate of sulfur fixing ashes and sulfur fixing slagsincreases with the increases of temperature, and the activity rate of sulfur fixing ashesand sulfur fixing slags increases with thegrows of age.When sulfur fixing ashes or sulfur fixing slags replace part of cement, theresearch results of influence of the strength to the system show that, firstly, when at7days, with the increases of the content of sulfur fixing ashes, the flexural strength andcompressive strength shows a trend of decline after the first growth; at28days,flexural strength and compressive strength of the composite system fall with theincrease of the dosage of sulfur fixing ashes. Secondly, with the increases of watercement ratio, the system of flexural strength and flexural strength decrease. Thirdly,under the condition of same water-cement ratio, at28days, strength of compoundslurry mixed with sulfur fixing ashes and strength of compound mixed with sulfurfixing slags are higher than that of the pure cement system. Fourthly, there is a certaincorrelation between the activity rate and the compressive strength, and using theactivity rate to evaluate the activity of sulfur fixing ashes and sulfur fixing slags has acertain scientific nature. Fifthly, macroscopic strength of system has a certainconnection with micro structure and composition of the system. Finally, only takingstrength into consideration, as an admixture of cement, the sulfur fixing slags are moresuitable than sulfur fixing ashes, and sulfur fixing slags and cement has bettersynergistic effect. |
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