The Ontario Hydro Method (OHM) recommended by the United States EnvironmentalProtection Agency (EPA) was used to determine mercury speciation in the combustionflue gas across wet FGD systems.Four coal-fired units with...The Ontario Hydro Method (OHM) recommended by the United States EnvironmentalProtection Agency (EPA) was used to determine mercury speciation in the combustionflue gas across wet FGD systems.Four coal-fired units with wet FGD systemswere chosen to evaluate mercury speciation and mercury removal efficiencies throughthese wet FGD systems.Chlorine content in coal had been suggested as a main factorthat affects mercury speciation in flue gas.It is shown that the higher the chlorine concentrationin coal is, the higher the percentage of oxidized mercury (Hg^(2+)) is removed in wetFGD systems, which can increase overall mercury removal efficiencies through wet FGDsystems.The selective catalyst reduction (SCR) system has a function of oxidizing elementalmercury (Hg^0) to oxidized mercury.A higher percentage of oxidized mercury in thetotal vapor mercury at the FGD inlet is observed when SCR is in service.Therefore, higheroverall mercury removal efficiencies through wet FGD are attained.Because of differentwet FGD operating conditions, there are different mercury removal efficiencies in differentunits.Elemental mercury reemission took place when a fraction of oxidized mercury absorbedin the slurry is reduced to elemental mercury, and Hg^0 is reemitted from stack,which results in decreases in mercury removal efficiencies through wet FGD systems.展开更多
By using the advanced instrumentation of a Computer Controlled Scanning Electron Microscope (CCSEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF), the ash composition and the mineral components of six typical ...By using the advanced instrumentation of a Computer Controlled Scanning Electron Microscope (CCSEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF), the ash composition and the mineral components of six typical Huainan coals of different origins were studied. The transformation of mineral matter at high temperatures was tracked by XRD in reducing conditions. The quartz phase decreased sharply and the anorthite content tended to increase at first and then decreased with increasing temperatures. The formed mullite phase reached a maximum at 1250 ℃ but showed a tendency of slow decline when the temperature was over 1250 ℃ . The mullite formed in the heating process was the main reason of the high ash melting temperature of Huainan coals. Differences in peak intensity of mullite and anorthite reflected differences in phase concentration of the quenched slag fractions, which contributed to the differences in ash melting temperatures. The differences in the location of an amorphous hump maximum indicated differences of glass types which may affect ash melting temperatures. For Huainan coal samples with relatively high ash melting tempera- tures, the intensity of the diffraction lines for mullite under reducing condition is high while for the samples with rela- tively low ash melting temperature the intensity for anorthite is high.展开更多
文摘The Ontario Hydro Method (OHM) recommended by the United States EnvironmentalProtection Agency (EPA) was used to determine mercury speciation in the combustionflue gas across wet FGD systems.Four coal-fired units with wet FGD systemswere chosen to evaluate mercury speciation and mercury removal efficiencies throughthese wet FGD systems.Chlorine content in coal had been suggested as a main factorthat affects mercury speciation in flue gas.It is shown that the higher the chlorine concentrationin coal is, the higher the percentage of oxidized mercury (Hg^(2+)) is removed in wetFGD systems, which can increase overall mercury removal efficiencies through wet FGDsystems.The selective catalyst reduction (SCR) system has a function of oxidizing elementalmercury (Hg^0) to oxidized mercury.A higher percentage of oxidized mercury in thetotal vapor mercury at the FGD inlet is observed when SCR is in service.Therefore, higheroverall mercury removal efficiencies through wet FGD are attained.Because of differentwet FGD operating conditions, there are different mercury removal efficiencies in differentunits.Elemental mercury reemission took place when a fraction of oxidized mercury absorbedin the slurry is reduced to elemental mercury, and Hg^0 is reemitted from stack,which results in decreases in mercury removal efficiencies through wet FGD systems.
基金Projects 2003001 supported by the key project of Huainan city, & 2004kj125 by the Science Funding of Department of Education of Anhui Province
文摘By using the advanced instrumentation of a Computer Controlled Scanning Electron Microscope (CCSEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF), the ash composition and the mineral components of six typical Huainan coals of different origins were studied. The transformation of mineral matter at high temperatures was tracked by XRD in reducing conditions. The quartz phase decreased sharply and the anorthite content tended to increase at first and then decreased with increasing temperatures. The formed mullite phase reached a maximum at 1250 ℃ but showed a tendency of slow decline when the temperature was over 1250 ℃ . The mullite formed in the heating process was the main reason of the high ash melting temperature of Huainan coals. Differences in peak intensity of mullite and anorthite reflected differences in phase concentration of the quenched slag fractions, which contributed to the differences in ash melting temperatures. The differences in the location of an amorphous hump maximum indicated differences of glass types which may affect ash melting temperatures. For Huainan coal samples with relatively high ash melting tempera- tures, the intensity of the diffraction lines for mullite under reducing condition is high while for the samples with rela- tively low ash melting temperature the intensity for anorthite is high.
