The mechanism of mercury oxidation/adsorption on an NH4Br modified fly ash (NH4Br-FA) was discussed. The effect of flue gas component including O2, SO2 and NO, and the roles of main fly ash compositions on the Hg0 oxidation/adsorption capability by the NH4Br-FA was evaluated on a fixed-bed reactor. The mercury adsorption species on the spent sorbent were then identified by the temperature programmed decomposition desorption (TPDD) method. The results show that NH4Br modification on the fly ash not only improves Hg0 oxidation, but also promotes Hg0 adsorption. Due to the generation of Br-containing functional groups, HgBr2 is the main adsorption form on the surface of the NH4Br-FA. O2 cannot promote Hg0 oxidation or adsorption, but leads to the generation of little HgO. NO cannot promotes Hg0 oxidation, while significantly improves the Hg0 adsorption on the NH4Br-FA with the adsorbate of HgBr2, HgO or Hg2(NO3)2. SO2 has little effect on Hg0 oxidation, but significantly inhibits Hg0 adsorption on the surface of the NH4Br-FA, because SO2 can destroy the Br activate sites leading to deactivation, in which there is no HgS or HgSO4 formation. The main metal oxides in the NH4Br-FA include Fe2O3, TiO2, CaO, and Al2O3, which display poor mercury removal capability. However, after the modification of NH4Br solution, the NH4Br-Fe2O3 and the NH4Br-TiO2 demonstrate excellent Hg0 oxidation capability with poor Hg0 adsorption performance.

Unburned carbon(UBC)and metal oxides have a certain adsorption and oxidation abilities of mercury. Fly ash has been considered as a cheap and potential mercury removal adsorbent in coal-fired power plant,but the efficiency is to be improved. In this paper,two kinds of fly ash with different contents of UBC were chosen and modified by 1%NH4Br solution. Effect of flue gas components(O2,SO2and NO)and metal oxides on mercury removal by the modified fly ash was investigated in fixed-bed reactor,in order to obtain high efficiency mercury removal adsorbent and adsorption mechanism. The results showed that O2has a little positive effect on the mercury oxidation. SO2has a certain inhibitory effect. NO promotes the oxidation of Hg0obviously. Fe2O3and TiO2in bromine modified fly ash played a major role in the oxidation of Hg0. The reason was that bromine modification increases the lattice oxygen content of Fe2O3and TiO2which promotes the catalytic oxidation of Hg0,and mainly follows the Mars-Maessen mechanism. UBC content of fly ash has a great impact on the removal of Hg0. When the bromide was embedded in the UBC of the fly ash surface,the activity of the neighborhood was enhanced. As a result,the adsorption capacity of the carbonaceous surface to Hg0was enhanced,and the subsequent reaction was promoted.

Three different crude high sulfur petroleum cokes were activated with SO2to prepare samples of the petroleum coke with high sulfur content.The physical and chemical properties of the samples were characterized using surface area and porosity analyzer,X-ray photoelectron spectroscopy and ultimate analysis.Experimental studies on mercury removal were investigated in a fixed bed reactor system.The results showed that the process of modification of petroleum coke with SO2 effectively loaded sulfur on the surface.A large amount of organic sulfur(thiophene)was detected on the surface of the high-sulfur-content petroleum coke,which indicated its great ability of mercury removal.The sulfur content and sulfur formd on the surface of petroleum coke with high sulfur content have a great influence on the mercury removal capacity.The microstructure and micro morphology on surface of the petroleum coke played a remarkable role on mercury removal ability.The Hg0 penetration rate decreased and the mercury removal ability of high-sulfur-content petroleum coke increased with reduction of adsorption temperature in a certain range.

The Ontario Hydro Method (OHM) was applied to determine the mercury speciation and concentration in the flue gas emitted from a 100MW boiler system. Mercury speciation transformation and removal characteristics of selective catalytic reduction (SCR) system, electrostatic precipitators (ESP) and wet flue gas desulfurization (WFGD) had been obtained. Temperature programmed decomposition (TPD), Scanning electron microscope (SEM) and X ray fluorescence (XRF) were used to investigate the adsorption characteristic of mercury by fly ashes and thermal stability after adsorption. T The results show that the overall mercury (Hg) removal efficiencies over SCR + ESP + WFGD combination were 0 92.83% and 81.66% under 75% MCR and 85% MCR, respectively. The oxidation of element mercury (Hg 02+) by SCR catalyst was greatly promoted by the chlorine (Cl) content in coal and 96.18% Hgwas oxidized to oxidized mercury (Hg) P by SCR when the Cl concentration in burned-coal contained 500mg/kg. Hgcould be effectively removed by ESP, 02+removal efficiencies with 12.73% of Hgand 27.79% of Hgwere observed. Unburned carbon and metal oxides (Al2O3, Fe2O3) were the main components of ESP fly ash to adsorb gaseous mercury. HgCl2, HgS (red), and HgO were the main mercury compounds in the ash after adsorption which would decompose when the temperature reached 190 degrees. The 2+average removal efficiencies of Hgby WFGD were 91.10%. Meanwhile, the phenomenon of mercury re-emission due to part of Hg 2+was reduced to Hg 0 in WFGD was found.

Fly ash from coal combustion has been recognized as an effective sorbents for mercury removal in flue gases.However,the mechanism between fly ash and mercury reaction is unclear due to the complicated composition of it,so the oxidation and adsorption on the surface of fly ashes are crucial to mercury control.In this study,the mercury adsorption and oxidation mechanisms on the surface of four bromine-modified electrostatic precipitator (ESP) fly ashes were explored based on the experimental results of a fixed-bed reactor and temperature programmed desorption (TPD) technique.The fly ashes were characterized by the X-ray fluorescence spectrometry (XRF),Scanning electron microscope (SEM) to study the reaction mechanism.The results indicated that bromine-modified fly ashes played a significant role in mercury oxidation and adsorption compared with raw ones,about 75％ elemental Hg transformed into oxidized Hg was achieved.The heterogeneous oxidation process has been confirmed that follows the Langmuir-Hinshelwood and Eley-Ridea mechanism,while the inorganic material in fly ashes oxidizing mercury follows the Mars-Masessen mechanism in the second.

Effects of acidic gases (CO2, SO2, NO, and HCl) in coal-fired-plant flue gas on mercury removal by a raw activated carbon (AC) under oxy-fuel atmosphere were studied on a laboratory-scale fixed-bed reactor. The temperature programmed-desorption (TPD) method was used to determine mercury forms in the AC. Some characterization methods (BET, FTIR, XRF, and EDS) are adopted to characterize the physical and chemical properties of the AC. Results show that NO and HCl can strongly promote mercury removal, and the mercury species formed on AC are Hg-2(NO3)(2), HgO, and HgCl2, respectively, which all desorb around 300 degrees C. SO2 is not beneficial for mercury removal because it will change into SO3 to occupy the active sites competing with Hg. In addition, Hg2+ adsorbed on AC would be reduced to He in the presence of SO2. Two different kinds of HgS (black and red) are generated after SO2 is introduced; they desorb at 240 and 340 degrees C, respectively. For the oxy-fuel combustion atmosphere, high concentration of CO2, almost has no effect on mercury removal.

Mercury adsorption capability of raw activated carbon (R-AC) and NH4Br modified activated carbon (NH4Br-AC) was evaluated in a fixed-bed reactor. The effect of inlet Hg-0 concentration and flue gas components on mercury adsorption was investigated. The mercury adsorption species on the sorbent surface was analyzed by the Temperature Programmed Desorption (TPD) method. Finally, the mercury adsorption equilibrium of R-AC and NH4Br-AC was explored. Mercury adsorption results show that the mercury adsorption capability of NH4Br-AC is significantly larger than that of R-AC and increased with higher inlet Hg-0 concentration. O-2 and NO promote mercury adsorption on NH4Br-AC, but SO2 inhibits the mercury adsorption. The TPD result shows that mercury adsorption on RAC is mainly physical in nature, enhanced by chemisorption with the product of HgO. Mercury adsorption on NH4Br-AC is in the major form of chemisorption with the product of HgBr2. O-2 has little effect on the mercury adsorption mechanism. SO2 reduces the generation of HgBr2, but promotes little of HgS generation on NH4Br-AC. NO significantly improves the generation of Hg-2(NO3)(2) on NH4Br-AC. Adsorption equilibrium analysis shows that Langmuir and Temkin equations are more suitable to describe the mercury adsorption on R-AC, indicating the uniformity of the R-AC surface. Mercury adsorption on the NH4Br-AC surface can be described well by the Freundlich equation, illustrating the nonuniformity of the NH4Br-AC surface.

To improve Hg and SO2 removal efficiency of calcium-based composite sorbent,the simple and efficient non-chemical treatment method was proposed.Calcium-based composite sorbent was treated by non-thermal plasma in air environment and characterized with Fourier transform infrared spectroscopy (FT-IR) and Brunauer-Emmett-Teller (BET) surface area to study the influence of non-thermal plasma modification on the surface physical and chemical properties.Demercuration and desulfurization experiments were carried out in a fixed bed adsorption experimental stage.The mass ratio of AC/CaO and hydration conditions on mercury adsorption effect were explored,and the desulfurization performance of the adsorbent was also considered.Under the optimized conditions,the effects of non-thermal plasma modification time and power on removal of Hg and SO2 were investigated.The results showed that the compound calcium-based sorbents prepared under optimum conditions with good surface area and pore structure,can effectively remove Hg and SO2 in flue gas.Compound calcium-based sorbents treated with non-thermal plasma had higher mercury and SO2 removal efficiency.The main reason was that non-thermal plasma treatment increased functional groups,which played an important role in Hg and SO2 absorption.Compared with the unmodified calcium-based sorbent,mercury and SO2 removal efficiency of sorbent treated by non-thermal plasma with 40W and 10 min was increased 33.10％ and 34.71％ respectively.Non-thermal plasma modification has obvious advantages,which is a potential technology for the removal of pollutants.

Removing mercury technology of activated carbon in flue gases is very mature. However, the mechanism of the mercury reaction is seldom.Experiments on mercury capture by a commercial activated carbon and a 1% NH4Br-modified activated carbon were carried out in a fixed-bed reactor under simulated flue gas to study the reaction path among the mercury,flue gas and activated carbon. The effect of single component such as O2,CO2,SO2 and NO was investigated. Then the temperature programmed desorption technique was used to identify the mercury species on the adsorption products. The results showed that the bromine impregnation on the activated carbon has a great promotion on the mercury capture. O2 and CO2 play a positive role in the mercury capture process,while the SO2 plays a negative function. According to the TPD analysis results,NO promotes mercury capture significantly because of the formation Hg2(NO3)2 on the activated carbon surface. The elemental mercury was oxidized to generate HgO when O2 was injected.SO2 competed with Hg0on the surface functional groups of activated carbon and HgS was formed because of C—S was formed to react with Hg0.CO2 has little effect on the adsorption mechanism of NBAC.

在管式炉上模拟烟气气氛下实验研究了650～950℃范围内选择性非催化还原(SNCR)技术的脱硝特性及添加CO对其脱硝特性的影响,分析了相关反应机理.结果表明:不添加CO时,SNCR最佳脱硝温度为900℃;反应器尾部N2O和NO2排放质量浓度均随反应温度的增加,先增大后减小,在850℃时N2O和NO2排放质量浓度达到峰值,高温可降低氨逃逸量;反应温度低于700℃,增大氨氮摩尔比对脱硝效率、N2O与NO2排放质量浓度没有影响,而氨逃逸显著增大;反应温度高于800℃,增大氨氮摩尔比,脱硝效率与N2O排放质量浓度均增大,而NO2排放质量浓度减小.添加微量CO时,最佳脱硝效率略有增大,最佳脱硝温度、脱硝温度窗口及氨逃选曲线向低温移动,脱硝温度窗口的下限降低至750℃;N2O排放温度范围变宽且峰值增大,NO2排放质量浓度接近于零.增加CO添加量易引起低温下反应器尾部CO逃逸量的增大,应尽量减少CO的添加量.实际应用中,可通过加入微量的CO降低SNCR脱硝温度,减少NO2排放质量浓度及低温时的氨逃逸量等.