Coal combustion technologies are changing in order to burn coal more cleanly.Many 'clean combustion' and post-combustion technologies are developed to remove SO_2 and NO_xgases, particulate matter during combu...Coal combustion technologies are changing in order to burn coal more cleanly.Many 'clean combustion' and post-combustion technologies are developed to remove SO_2 and NO_xgases, particulate matter during combustion, or from the flue gases leaving the furnace. This paperfocuses on three types of fly ash (flue gas desulfurization (FGD) residuals, atmospheric fluidizedbed combustion (AFBC) residuals and sorbent duct injection (SDI) residuals) which produced by 'theclean combustion' and post-combustion technologies. The residuals formed by FGD are PCFA (pulverizedcoal fly ash) grains entrained with reacted and unre-acted sorbent and have lower bulk densitiesthan PCFA grains because it contains higher concentrations of calcium and sulfur, and lowerconcentrations of silicon, aluminum and iron than PCFAs. AFBC residuals consist of spent bed whichis a heterogeneous mixture of coarse-grained bed material and irregularly shaped, unfused, sphericalPCFAs. The main crystalline phases in AFBC residuals are anhydrite (reacted sorbent), quartz andlime (unreacted sobent), calcite, hematite, periclase, magnetite and feldspars. The residualsproduced by SDI contained 65 percent-70 percent PCFA with the larger sizes material beingirregularly shaped, fused or rough-edged. The reaction products of sorbent (portlandite and lime)included calcium sulfate (anhydrite) and calcium sulfate. The chemical properties of these residualsare similar to those of high calcium PCFAs because of the high alkalinity and high pH of theseresiduals.展开更多
文摘Coal combustion technologies are changing in order to burn coal more cleanly.Many 'clean combustion' and post-combustion technologies are developed to remove SO_2 and NO_xgases, particulate matter during combustion, or from the flue gases leaving the furnace. This paperfocuses on three types of fly ash (flue gas desulfurization (FGD) residuals, atmospheric fluidizedbed combustion (AFBC) residuals and sorbent duct injection (SDI) residuals) which produced by 'theclean combustion' and post-combustion technologies. The residuals formed by FGD are PCFA (pulverizedcoal fly ash) grains entrained with reacted and unre-acted sorbent and have lower bulk densitiesthan PCFA grains because it contains higher concentrations of calcium and sulfur, and lowerconcentrations of silicon, aluminum and iron than PCFAs. AFBC residuals consist of spent bed whichis a heterogeneous mixture of coarse-grained bed material and irregularly shaped, unfused, sphericalPCFAs. The main crystalline phases in AFBC residuals are anhydrite (reacted sorbent), quartz andlime (unreacted sobent), calcite, hematite, periclase, magnetite and feldspars. The residualsproduced by SDI contained 65 percent-70 percent PCFA with the larger sizes material beingirregularly shaped, fused or rough-edged. The reaction products of sorbent (portlandite and lime)included calcium sulfate (anhydrite) and calcium sulfate. The chemical properties of these residualsare similar to those of high calcium PCFAs because of the high alkalinity and high pH of theseresiduals.
