Coal Gangue Ash Research Articles

Co-melting mechanisms for municipal solid waste incineration fly ash with fine slag from coal gasification and coal gangue

Vitrification is a promising treatment for municipal solid waste incineration fly ash (MSWI-FA); however, high energy consumption due to the high MSWI-FA fusion temperature limits the development and application of this technique. In this study, fine slag ash (FSA) derived from coal gasification and coal gangue ash (CGA) were mixed with MSWI-FA to reduce the ash fusion temperature. The transformation of minerals in ash during thermal treatment was examined via X-ray diffraction and thermodynamic equilibrium calculations. The ash flow behaviour was observed using a thermal platform microscope, and the silicate structure was quantified using Raman spectra. The co-melting mechanisms for the mixed ash were systematically investigated. Results indicate that the flow temperature (FT) of the mixed ash exhibited an initial decrease and subsequent increase as a function of the addition ratio of FSA or CGA. Lowest ash FT of 1215 °C and 1223 °C were recorded for addition of 50% FSA and 50% CGA, respectively; further, these temperatures were lowered by > 285 °C and >277 °C respectively, relative to FT of the MSWI-FA. The transformation of minerals and silicate structure during mixed ash heating was responsible for the variation in the ash fusion temperature. CaO in MSWI-FA tended to react with mullite, quartz and haematite in FSA and CGA, forming minerals such as anorthite, gehlenite, and andradite with relatively low melting points. The addition of FSA or CGA caused changes in the silicate network structure of the mixed ash. In particular, 50% FSA incorporation caused the transformation of Q4 and Q3 to Q2, whereas 50% CGA introduction resulted in the conversion of Q4 and Q2 into Q3 and Q1 + Q0, respectively. The silicate network depolymerised, causing reduction in the ash fusion temperature and increasing the melting rate.

Prospective application of coal gangue as filler in fracture-healing behavior of asphalt mixture

Coal gangue powder, which is an environmental waste, was used as filler to investigate its facilitation effect on microwave heating and self-healing of asphalt mixture. In this work, two types of fillers named coal gangue powder (CGP) and coal gangue ash (CGA) were utilized to prepare various mixtures to replace conventional limestone powder (LMP) by six rates of 0%, 15%, 35%, 50%, 75%, and 100%. Firstly, the micromorphology and composition properties of different fillers were performed by scanning electron microscopy (SEM) and X-ray fluorescence (XRF) test. Secondly, the semi-circular bending (SCB) test was conducted to analyze the low-temperature fracture performance of mixtures. Then, the microwave heating capacity and behaviors of fillers and mixtures were studied on the basis of infrared thermography imaging. Ultimately, the mixtures healing efficiency was evaluated with five fracture-healing-fracture cycles and the electromagnetic parameters were determined via a microwave network vector analyzer. Test results reveal that mixtures with appropriate CGA and CGP filler proportion both possess better microwave heating effect, while the excessive dosage of CGA or CGP filler will result in mixtures’ uneven surface temperature distribution. It is found that 50% CGA or 50% CGP can be a prospective substitution because this rate not only obtains excellent healing effectiveness at 60-s microwave heating but also improve the low-temperature crack resistance of mixture. Moreover, the higher dielectric and magnetic losses of CGA and CGP provide an explanation for promoting microwave heating. The aforementioned results show that coal gangue powder waste has prominent application in asphalt mixture cracking and self-healing and thus improve its utilization in this method.

Effect of Promoters on Steam Reforming of Toluene over a Ni-Based Catalyst Supported on Coal Gangue Ash.

The exploration of high-value-added materials using inorganic solid waste is a very important contribution to sustainable development. Coal gangue ash (CGA) as a solid waste was chosen as catalyst support. Five low-cost catalysts modified by different promoters (Co, Ce, Fe, Mn, and Mo) were prepared using a co-impregnation method. The toluene steam reforming tests were carried out at 800 °C under S/C = 2 (steam-to-carbon mole ratio). Catalyst characteristics were evaluated using X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method, temperature-programmed reduction (TPR), and Raman spectroscopy. The results showed that most promoters could interact with a Ni active compound and enhance the toluene conversion and H2 yield. The Mo-Ni/CGA-1d (1d means the acid pretreatment time) catalyst performed the best catalytic activity, and corresponding toluene conversion and H2 yield was equal to 92.6 and 62.3%, respectively, and it should be due to the formation of Mo-Ni alloy. Meanwhile, the Mo-Ni/CGA-1d catalyst exhibited higher stability during the runtime of 300 min compared with the Mn-Ni/CGA-1d catalyst, which can be attributed to the formation of the Mo2C structure with high-carbon-resistance ability. This is perhaps because the dissociation of CO2 or H2O on the Mo2C structure surface is beneficial to the production of free oxygen species, which can accelerate the removal of carbon deposition on the catalyst surface.

Steam reforming of toluene over nickel catalysts supported on coal gangue ash

Abstract The development of high performance and low-cost catalyst is very important to remove tar during biomass gasification. Solid waste coal gangue ash (CGA), which mainly contains SiO2, Al2O3, Fe2O3 and CaO, was selected as support for Ni-based catalyst. The prepared low-cost catalysts were characterized suitably by XRD, BET, TPR, SEM, TG and Raman techniques. Toluene was selected as typical biomass tar model compounds to test the catalyst performance and compared with traditional catalysts Ni/Al2O3 and Ni/SiO2. Ni/CGA-1d exhibited the highest catalytic performance with the toluene conversion and H2 yield accounting for 91.5% and 58.2% respectively, at 800 °C. It was showed that the performance of Ni/CGA-1d was higher than traditional catalysts Ni/Al2O3 and Ni/SiO2, and comparable with other polymetallic reforming catalysts. Due to the good resistance of carbon deposition, the Ni/CGA-1d catalyst also performed better catalytic activity stability. The ability should be attributing to the existence of some metal elements such as Fe, Mg, K, Ca et al. in coal gangue ash support.

Character of the Si and Al Phases in Coal Gangue and Its Ash

Abstract:Analysis of the Si and Al phases in coal gangue fuel and its ash is important for use of coal gangue ashes. A comprehensive study by theoretical and experimental analyses with differential thermal analysis, X‐ray diffraction and Infrared Spectroscopy has been made in the present article to explore the diagram of the Si and Al phases in coal gangue fuel and its ashes. It is found that kaolinite and quartz are the main phases in coal gangue fuel. The ratio of moles Al2O3to SiO2 (i.e., Al2O3 (mole)/ SiO2 (mole)) is usually no more than 0.5 in most coal gangue fuel and its ashes. The kaolinit at about 984°C releases a large quantity of SiO2, which makes calcine coal gangue more active than coal gangue itself. The relationship between the ratio Al2O3 (mole)/SiO2 (mole) and the components of coal gangue ash is analyzed, resulting in a formula to calculate the quantity of each phase. Applying the formula to the testing samples from an electric plant in north China supports the above conclusions.