Understanding Ash Sintering Variation Behaviors of Low-Rank Coals with Municipal Sludge Addition Based on Mineral Interactions

Abstract

Co-gasification with coal provides an economically viable way to use sludge. To investigate the effect of municipal sludge (MS) on the sintering behaviors of low-rank coals (LRCs) and their modification mechanisms, the initial sintering temperature ( T s ) of three LRCs and their mixtures with MS addition were tested by a T s analyzer, an X-ray diffractometer, and FactSage calculation. The results show that the T s values of Xiaolongtan coal (XLT), Xiangyuan coal (XY), and Daliuta coal (DLT) all increase with MS addition. The 9–12% MS mass ratio is suitable during LRC fluidized-bed gasification to mitigate ash-related issues. The T s is closely related to the liquid-phase content or the transmissions of microparticles (e.g., atoms and ions) or blank spots during heating, while the ash fusion temperatures (AFTs) are mainly determined by acid/base ratios. The T s values of high-Fe XLT and XY mixed ashes increased gradually with increasing MS proportion because the sintering mechanisms transferred from liquid phase to solid phase, while for relatively high-Mg DLT ashes, the T s values increased with increasing MS proportions, which might result from the formations of high-melting-point minerals (e.g., Ca 3 (PO 4 ) 2 and Mg 2 SiO 4 ). The results deepen the understanding of ash sintering behaviors and provide references to alleviate ash-related issues during gasification.

Review of Phosphorus Chemistry in the Thermal Conversion of Biomass: Progress and Perspectives

“…Generally, it appears as if sewage sludge has a positive influence on the silicon- and potassium-rich biomasses wheat straw, corn stalk, and sugar cane bagasse. The effect of blending sewage sludge with coals is also positive, except for one iron-rich coal . When blending coal rich in silicon and aluminum with chicken or swine manure the AFT decreased …”

“…Normally, XRD analysis is only performed on the final biomass residues, and does therefore not provide a lot of information on the transformation pathways, but it gives an indication of the fate of phosphorus in thermal conversion of biomass. In an attempt to investigate what crystalline phosphates are most commonly found in biomass residues, the reported phases detected in 384 samples, from 65 references (refs , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , – , , , – , , , , – ) were compiled in this work. The result of the compilation is shown in Figure .…”

“…Crystalline phosphorus phases reported to be present in residues from different types of biomass, including biomass blends (left) (refs , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , – , , , – , , , , – ) grain- and seed-based biomass (upper middle) (refs , , , , , , , , ) animal biomass (upper right) (refs , , , , , – ) sewage sludge (lower middle), (refs , , , , , , , , , , , , , , , , …”

“…The effect of blending sewage sludge with coals is also positive, except for one iron-rich coal. 626 When blending coal rich in silicon and aluminum with chicken or swine manure the AFT decreased. 616 5.1.3.…”

Correlation between the Flow Temperature and Mineral Factor for Coal Ashes Based on FactSage Calculation

“…Under the pressure of rapid increase of energy demand and strict environmental pollution requirements, coal gasification has attracted worldwide attention as an effective way to produce synthetic natural gas, liquid fuels, chemicals, and power. − Among the existing gasification technologies, entrained-flow bed (EFB) gasification is widely used in industrial practice because of its high carbon conversion, high thermal efficiency, wide feedstock flexibility, and environmental friendliness. − The fusion and flowing behaviors of ash/slag are the keys to successful operation for an EFB gasifier. − To keep slag tapping smoothly during coal EFB gasification, it is required that the ash flow temperature [FT, the temperature when the ash cone is completely melted or expanded into a thin layer with a height of <1.5 mm during the ash fusion process, which is an important characteristic temperature to illustrate ash fusion temperature (AFT)] ranges from 1200 to 1400 °C. , Therefore, a simple method is required to predict coal FT for evaluating whether it is suitable for EFB gasification.…”