Desulfurization Devices Research Articles

The effect of air pollution control devices in coal-fired power plants on the removal of condensable and filterable particulate matter.

Total particulate matter (TPM), including condensable and filterable particulate matter (CPM and FPM), is one of the pollutants that need to be controlled in the coal combustion process. In this study, CPM and FPM were sampled from sixteen coal-fired power units and two coal-fired industrial units. The removal effects of air pollution control devices equipped in the units on the migration and emission of particles were investigated by analyzing samples from inlets and outlets of apparatus. The average removal efficiency of TPM by dry-type dust removal equipment, wet flue gas desulfurization devices, and wet-type precipitators reached 98.57 ± 0.90%, 44.89 ± 15.01%, and 28.45 ± 7.78%, respectively. The removal efficiency of dry-type dust removal equipment and wet-type precipitators to TPM is mainly determined by the purification effect of FPM and CPM, respectively, and both types of particles contribute to the removal efficiency of desulfurization systems to total TPM. The concentrations of CPM (12.01 ± 5.64mg/Nm3) and FPM (1.95 ± 0.86mg/Nm3) emitted from ultra-low emission units were the lowest, and CPM is the dominant particle, especially the higher proportion of organic components in CPM.

Experimental and Mechanistic Study of Synergistic Removal of Hg by Evaporation from Desulfurization Wastewater

The flue evaporation of desulfurization wastewater can solve the problem that it is difficult to remove some heavy metal ions and chloride ions by conventional methods. A large amount of chloride ions in desulfurization wastewater can also promote the catalytic oxidation removal of Hg in the flue gas. The migration character of chloride ions in the flue evaporation process of desulfurization wastewater was studied by using the coal-fired thermal state experimental platform. The concentrations of Hg0 and Hg2+ in the flue gas at the inlet and outlet of selective catalytic reduction denitration (SCR), electrostatic precipitator (ESP), and wet desulfurization (WFGD) devices were tested, and the synergistic removal of traditional pollutant removal equipment by flue evaporation of desulfurization wastewater was analyzed. The influence of Hg and the effect of the evaporation of desulfurization wastewater at different positions on the removal of Hg in the flue gas were compared and analyzed, and the catalytic mechanism of Hg on the SCR surface was further revealed. The results show that 10% chloride ions enter the flue gas after the desulfurization wastewater evaporates. The content of chlorine elements and evaporation temperature influence the evaporation of desulfurization wastewater. The mechanism of SCR catalytic oxidation of Hg0 was explored; oxygen atoms have catalytic oxidation effects on Hg0 at different positions in the V2O5 molecule in SCR; and chloride ions can enhance the catalytic oxidation of Hg0 by V2O5. The intermediate product HgCl is generated, which is finally converted into HgCl2. The oxidation efficiency of Hg0 in electrostatic precipitation (ESP) is increased from 3% to 18%, and the removal efficiency of Hg is increased from 5% to 10%. The removal efficiency of Hg2+ in WFGD is basically maintained at approximately 85%. In addition, a small amount of Hg2+ was restored to Hg0 in WFGD. The removal efficiency of Hg0 in the flue gas of evaporative desulfurization wastewater before SCR is 65%, and the removal efficiency of gaseous Hg is 62%. When the evaporative desulfurization wastewater before ESP, the synergistic removal efficiency of Hg0 is 39%, and the gaseous Hg removal efficiency is 39%, and the removal efficiency of Hg is 40%. Evaporation of the desulfurization wastewater before SCR was more conducive to the coordinated removal of Hg by the device.

Application of adjacent heating technology in thermal power unit

There are many problems in the start-up stage of thermal power unit, which seriously affect the safe and economic operation of the unit. Therefore, it is of great significance to study the energy-saving technology of thermal power unit in the start-up stage. The adjacent heating technology is put forward to solve these problems in the boiler start-up stage. Thermal power unit USES the adjacent machine heating technology, improve the conditions of the boiler ignition and steady combustion conditions, improve the safety of the boiler start-up, saves the costs of fuel oil, coal, electricity, strengthened the flushing efficiency, shorten the flush time, improve the economic benefit of the adjacent machine, and prevent the scale caused by dramatic change wall temperature fall off, It can also ensure the safe operation of desulfurization, denitration and dust removal devices, and reduce the emission of pollutants, so it has a broad application prospect.

Manganese Ore-based Wet Flue-Gas Desulfurization: A Review

The removal of SO2 from flue gases is necessary for eliminating haze and controlling acid rain. However, developing the traditional wet and dry flue-gas desulfurization (FGD) is challenging due to the disposal issue of several byproducts. Manganese (Mn) orebased wet FGD possesses many advantages, including good desulfurization property, low cost, and high economic benefit. The environment friendliness and reusability of MnSO4 provide new ideas and methods in the future research direction of FGD. This review summarizes the background information of Mn ore slurry desulfurization, the desulfurization mechanism, the technological process, and the desulfurization devices. The role of operating parameters, such as temperature, liquid/solid ratio, pH, SO2 concentration, and particle size, in the desulfurization efficiency and manganese leaching rate are also discussed. The temperature (20°C-80°C) has exerted little effect on the desulfurization efficiency, whereas a low pH value is beneficial for SO2 removal. Moreover, a low inlet SO2 concentration and small particle size are beneficial for SO2 removal. The control and digestion techniques related to the byproduct (manganese dithionate) are also presented, along with the future development direction of Mn ore-based wet FGD in different industries.

Long-term (2006–2015) variations and relations of multiple atmospheric pollutants based on multi-remote sensing data over the North China Plain

In this analysis, the Aqua/MODIS aerosol optical thickness (AOD), Aura/OMI tropospheric NO2 and SO2 column concentration from 2006 to 2015 were used to statistically analyze the spatial distribution characteristics and variation trends of three polluted parameters from three temporal scales of monthly, seasonal and annual average. The results showed that the minimum values of NO2 and SO2 column concentrations both appeared in July and August, and the maximum values appeared in December and January, which was contrary to the variations in AOD. The highly polluted levels were mainly distributed in Shijiazhuang, Xingtai, and Yancheng cities of Hebei Province, and gradually transported to Zhengzhou, Henan Province, north and southwest of Shandong Province, and Tianjin, along the main line of Taiyuan-Linyi, Shanxi Province. AOD and NO2 had significant differences on the seasonal average scale, whereas SO2 had little changes. These pollutants had declined year by year since 2011, in the 10-year period, AOD and SO2 respectively decreased by 17.14% and 10.57%, and only NO2 rose from 8.69 × 1015 molecules/cm2 in 2006 to 9.10 × 1015 molecules/cm2 in 2015 with the increase rate of 4.79%. Integrated with MODIS-released fire products and the Multi-resolution Emission Inventory for China (MEIC), high AOD values in summer were usually accompanied by frequent biomass burning, and heavy heating demand of coal burning led to largest NO2 and SO2 levels in winter. Both inter-annual variations of MEIC NOx and OMI-observed NO2 responded to emission reductions of vehicle exhaustions positively, but vehicle population in Henan and Shandong provinces need to be further controlled. The significant decline of SO2 is mainly attributed to the enforcement of de-sulfurization devices in power plants. Our study found that in the treatment of complex atmospheric pollution, in addition to strict control of common sources of emissions from AOD, NO2 and SO2, it is also necessary to consider their individual characteristics.

Field measurements on the generation and emission characteristics of PM2.5 generated by industrial layer burning boilers

Particle size distributions, concentrations, morphological characteristics, and elemental compositions of PM2.5 from 15 industrial layer-burning boilers were determined experimentally in air, before and after dust removal and after desulfurization processes. The morphological characteristics and elemental compositions were analyzed using scanning electron microscopy and X-ray fluorescence, respectively. The concentrations and particle size distributions of PM2.5 were monitored and sampled using an electrostatic low pressure impactor. We found that before and after dust removal, the number concentration distributions of PM2.5 displayed obvious unimodal distributions, with peaks in the range 0.07–0.38 μm. In both instances, the particle concentrations of PM2.5 depended mainly on submicron particles (less than 1 μm in diameter), formed by gasification-condensation mechanisms. The concentration of the particles larger than 0.38 μm reflected aggregation of carbon black particles; this fraction tended to gradually decrease in concentration with increasing size. Total number and mass removal efficiencies of PM2.5 indicate that fabric filters were superior to mechanical precipitators, although mechanical precipitators were superior to integrated dust removal and desulfurization devices. Typically, the number concentration increased after desulfurization, suggesting that better demisters need to be implemented in these systems. The PM2.5 generated by industrial layer-burning boilers mainly comprised soot aggregates. However, the mass percentages of S, Si, K, and Al in PM2.5 decreased after dust removal but increased after the desulfurization. In contrast, the mass percentage of Na in PM2.5 increased after both dust removal and desulfurization processes, while the mass percentages of Ca and Fe in PM2.5 decreased after dust removal but remained constant after desulfurization. These data clearly show that the composition of PM2.5 changes as dust and sulfur are removed by air pollution control devices. Data generated in this study are useful for selecting the most effective strategy for reducing PM2.5 emitted by industrial layer-burning boilers of various sizes.

OMI satellite observations of decadal changes in ground-level sulfur dioxide over North America

Abstract. Sulfur dioxide (SO2) has a significant impact on the environment and human health. We estimated ground-level sulfur dioxide (SO2) concentrations from the Ozone Monitoring Instrument (OMI) using SO2 profiles from the Global Environmental Multi-scale – Modelling Air quality and CHemistry (GEM-MACH) model over North America for the period of 2005–2015. OMI-derived ground-level SO2 concentrations (r = 0. 61) and trends (r = 0. 74) correlated well with coincident in situ measurements from air quality networks over North America. We found a strong decreasing trend in coincidently sampled ground-level SO2 from OMI (−81 ± 19 %) and in situ measurements (−86 ± 13 %) over the eastern US for the period of 2005–2015, which reflects the implementation of stricter pollution control laws, including flue-gas desulfurization (FGD) devices in power plants. The spatially and temporally contiguous OMI-derived ground-level SO2 concentrations can be used to assess the impact of long-term exposure to SO2 on the health of humans and the environment.

PM2.5 Emission Reduction by Technical Improvement in a Typical Coal-Fired Power Plant in China

ABSTRACTTo investigate PM2.5 reduction by technical improvement in typical Chinese coal-fired power plants, two units built in different time with different particulate matter (PM) control technologies but with the same coal-fired boiler type were selected to characterize the concentrations of PM2.5 generated and emitted from coal-fired power plants. We found that significant benefit of PM2.5 emission reduction was achieved by technological improvement. Due to the increase in the installed capacity and the application of low NOx burner alone, PM2.5 emission factor without adopting other air pollution control devices decreased from 0.153 kg t–1 (the 100 MW unit) to 0.123 kg t–1 (the 300 MW unit). With the help of an improved electrostatic precipitator (ESP) of which removal efficiency increased from 76.4% to 97.5%, PM2.5 emission factor further decreased from 0.014 kg t–1 (the unit with a normal ESP) to 0.003 kg t–1 (the unit with a cold-side ESP and a wet flue gas desulphurization (WFGD)). However, the application of flue gas denitrification and desulfurization devices may alter PM2.5 compositions and their emissions. For instance, the installation of a WFGD was found to largely increase the emissions of water-soluble ions in PM2.5 (e.g., SO42–, Ca2+, and NH4+).

Spatial and temporal evaluation of long term trend (2005–2014) of OMI retrieved NO2 and SO2 concentrations in Henan Province, China

Tropospheric NO2 and SO2 concentrations are of great importance with regard to air quality, atmospheric chemistry, and climate change. Due to lack of surface monitoring stations, this study analyzes long term trend of NO2 and SO2 levels (2005–2014), retrieved from Ozone Monitoring Instrument (OMI) board on the NASA's Aura satellite, in an important region of China – Henan Province. Henan Province, located in North China Plain, has encountered serious air pollution problems including extremely high PM2.5 concentrations and as one of the most polluted region in China. The satellite spatial images clearly show that high levels of both NO2 and SO2 are concentrated in north and northeastern regions with much lower levels observed in other parts of Henan. Both pollutants exhibit the highest levels in winter with the least in summer/spring. The temporal trend analysis based on moving average of deseasonalized and decyclic data indicates that for NO2, there is a continuous increasing pattern from 2005 to 2011 at 6.4% per year, thereafter, it shows a decreasing trend (10.6% per year). As for SO2, the increasing trend is about 16% per year from 2005 to 2007 with decreasing rate 7% per year from 2007 to 2014. The economic development with incredible annual 11% GDP growth in Henan is responsible for increasing levels of NO2 and SO2. The observed decreasing SO2 level starting in 2007 is due to reduced SO2 emission, utilization of flue gas desulfurization (FGD) devices and to some extent, in preparation of Beijing 2008 Olympic Games. On the other hand, increasing vehicle numbers (155% from 2006 to 2012) and coal consumption (37% during the same span), along with the lack of denitration process for removing flue/exhaust gas NOx are responsible for increasing NO2 trend until 2011. The ratio of SO2/NO2 started decreasing in 2007 and dropped significantly from 2011 to 2013 indicating good performance of FGD and ever increasing NOx contribution from mobile sources. Unlike those observed in developed countries (US, EU and Japan) where a decreasing trend for both SO2 and NO2 has been observed since 1990s, the observed upward and downward trend found in Henan is similar to those found in North China Plain and other parts of China. The spatial and temporal trend analyses of SO2 and NO2 in four other regions in Henan further indicate a similar trend to those observed in Henan Province, albeit with different increasing and decreasing rate. The results provide regulatory agency to develop action plans to combat air pollution problem in general and SO2 and NO2 problems in particular in Henan. The implications of our findings and recommendations for decision makers are discussed in the paper.

Mercury stability of byproducts from wet flue gas desulfurization devices

Mercury released from wet flue gas desulfurization (WFGD) devices can be inhibited by additives that can transfer mercury to its solid phase. However, the use of additives increases the mercury content in desulfurization gypsum, and the mercury is released again during the calcination process. In this study, NaHS, 2,4,6-trimercaptotiazine, trisodium salt nonahydrate (Na3(C3N3S3)·9H2O, or TMT) and sodium dithiocarbamate (DTCR) were used as additives to control mercury emissions in simulated WFGD devices. Then, different calcination methods were adopted to study mercury release behaviors from calcination process. The transformation of mercury compound species on gypsum was also investigated to explain its behavior during calcination. The result showed that the mercury content in the solid phase increased significantly in the presence of additives. Among three additives, simulated desulfurization slurry with TMT had the highest trapping efficiency over mercury. The mercury thermal stability in gypsum increased in the order of using DTCR, TMT and NaHS. Due to the migration of mercury to the solid phase and the stronger thermal stability of resultants, the residual content of mercury in gypsum with additives after calcination were higher than that without additives. In general, using TMT coupled with slow-speed calcination had the best effect on controlling mercury contamination from WFGD slurry and WFGD byproducts. Moreover, it was verified by temperature programmed decomposition experiments that, after using NaHS, TMT and DTCR, the mercury compound in the gypsum was mainly in the form of HgS, Hg3(TMT)2, Hg(DTCR)2, respectively, which explained the mercury release behaviors during calcination.

Actual mercury speciation and mercury discharges from coal-fired power plants in Inner Mongolia, Northern China

Mercury species distribution in the flue gas from three typical coal-fired power plants have been investigated using a C-5000 sampler for Ontario Hydro Method (OHM) to evaluate specified Hg emission inventories in the largest coal-production province of China, Inner Mongolia. The feed coal, bottom ash, fly ash and gypsum have also been sampled in the field. Mercury emissions are in the dominant form of Hg0 (>85%). The Hg2+ (<15%) and the Hgp (<2%) emissions are minor fractions of Hgt in the flue gas. The wet limestone flue gas desulfurization device (WLFGD) showed much higher removal efficiency for Hg2+ (87–95%) than for the other two Hg species. The input Hg/output Hg varied from 92% to 115% for the tested 3 coal-fried utility boilers during sampling time. We obtained comprehensive Hg discharge factors, including direct atmospheric Hg emission factors and indirect discharge factors of Hg associated with bottom ash, fly ash and gypsum, to the environment, designating the fates of Hg in coal. We estimated the Hg discharges from coal-fired power plants in Inner Mongolia in 2008–2014 and expanded to China. The maximum of direct Hg emissions from coal-fired power plants of Inner Mongolia was 24Mg in 2012. The Chinese coal-fired power plants emitted directly 100Mg Hg to the atmosphere every year at the nationwide air control actions. The maximum discharges of Hg associated with fly ash and gypsum of Inner Mongolia was 81Mg and 11Mg in 2012, respectively. The national Hg discharges with fly ash and gypsum every year are respectively about 300Mg and 82Mg, majority of which may be reemitted to the atmosphere by the utilization industry. Therefore, mercury emissions from coal-fired power plants are not the largest single source of Hg to the atmosphere in normal operation of the current efficient denitrification, particles control and desulfurization devices. Instead, the utilization industry of fly ash and gypsum would be emitting more Hg to the atmosphere.

Aura OMI observations of regional SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; and NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; pollution changes from 2005 to 2015

Abstract. The Ozone Monitoring Instrument (OMI) onboard NASA's Aura satellite has been providing global observations of the ozone layer and key atmospheric pollutant gases, such as nitrogen dioxide (NO2) and sulfur dioxide (SO2), since October 2004. The data products from the same instrument provide consistent spatial and temporal coverage and permit the study of anthropogenic and natural emissions on local-to-global scales. In this paper, we examine changes in SO2 and NO2 over some of the world's most polluted industrialized regions during the first decade of OMI observations. In terms of regional pollution changes, we see both upward and downward trends, sometimes in opposite directions for NO2 and SO2, for different study areas. The trends are, for the most part, associated with economic and/or technological changes in energy use, as well as regional regulatory policies. Over the eastern US, both NO2 and SO2 levels decreased dramatically from 2005 to 2015, by more than 40 and 80 %, respectively, as a result of both technological improvements and stricter regulations of emissions. OMI confirmed large reductions in SO2 over eastern Europe's largest coal-fired power plants after installation of flue gas desulfurization devices. The North China Plain has the world's most severe SO2 pollution, but a decreasing trend has been observed since 2011, with about a 50 % reduction in 2012–2015, due to an economic slowdown and government efforts to restrain emissions from the power and industrial sectors. In contrast, India's SO2 and NO2 levels from coal power plants and smelters are growing at a fast pace, increasing by more than 100 and 50 %, respectively, from 2005 to 2015. Several SO2 hot spots observed over the Persian Gulf are probably related to oil and gas operations and indicate a possible underestimation of emissions from these sources in bottom-up emission inventories. Overall, OMI observations have proved valuable in documenting rapid changes in air quality over different parts of the world during last decade. The baseline established during the first 11 years of OMI is indispensable for the interpretation of air quality measurements from current and future satellite atmospheric composition missions.

Mercury mass flow in iron and steel production process and its implications for mercury emission control

The iron and steel production process is one of the predominant anthropogenic sources of atmospheric mercury emissions worldwide. In this study, field tests were conducted to study mercury emission characteristics and mass flows at two iron and steel plants in China. It was found that low-sulfur flue gas from sintering machines could contribute up to 41% of the total atmospheric mercury emissions, and desulfurization devices could remarkably help reduce the emissions. Coal gas burning accounted for 17%–49% of the total mercury emissions, and therefore the mercury control of coal gas burning, specifically for the power plant burning coal gas to generate electricity, was significantly important. The emissions from limestone and dolomite production and electric furnaces can contribute 29.3% and 4.2% of the total mercury emissions from iron and steel production. More attention should be paid to mercury emissions from these two processes. Blast furnace dust accounted for 27%–36% of the total mercury output for the whole iron and steel production process. The recycling of blast furnace dust could greatly increase the atmospheric mercury emissions and should not be conducted. The mercury emission factors for the coke oven, sintering machine and blast furnace were 0.039–0.047gHg/ton steel, and for the electric furnace it was 0.021gHg/ton steel. The predominant emission species was oxidized mercury, accounting for 59%–73% of total mercury emissions to air.

Analysis on Effectiveness of SO2 Emission Reduction in Shanxi, China by Satellite Remote Sensing

The SO2 emissions from coal-fired power plants in China have been regulated since 2005 by a mandatory installation of flue gas desulfurization (FGD) devices. In order to verify the effectiveness of FGD systems applied in power plants, Shanxi (a province well-known for the largest coal reserves in China) was selected, and the characteristic and evolution of SO2 densities over 22 regions with large coal-fired power plants during 2005–2012 were investigated by using the satellite remote sensing data from the Ozone Monitoring Instrument (OMI). A unit-based inventory was also employed to study the trend of SO2 emissions from coal-fired power plants in Shanxi. The results show that the operation of FGD systems was successful in reducing SO2 emissions from power plants during 2005–2010: the mean SO2 densities satellite-observed over those regions with power plants operated before 2005 showed a notable decrease of approximate 0.4 DU; the mean SO2 densities over other regions with power plants newly built behind 2006 did not show a statistical increasing trend overall; the mean SO2 density over the whole Shanxi also showed a moderate decline from 2008 to 2010. However, the polluted conditions over Shanxi during 2011–2012 rebounded and the declining trend in mean SO2 density over the whole Shanxi disappeared again. In comparison of unit-based emission inventory, the emissions calculated show a similar trend with SO2 densities satellite-observed during 2005–2010 and still maintain at a lower volume during 2011–2012. By investigating the developments of other emission sources in Shanxi during 2005–2012, it is considered that the rapid expansion of industries with high coal-consumption has played an important role for the increment rise of SO2 emissions. Lack of an independent air quality monitoring network and the purposeful reduced operation rate of FGD systems occurring in some coal-fired power plants have reduced the effectiveness of SO2 emission reduction policy applied in Shanxi. In view that the SO2 pollution in Shanxi has not been well ameliorated, more reasonable and mandatory policies, such as a national-wide independent monitoring network and installation of FGD systems in other large emission sources, should be pushed out in the near future.

Measurement of slurry droplets in coal-fired flue gas after WFGD.

China owns the world's largest capacity of coal-fired power units. By the end of 2012, the capacity of installed national thermal power has been 819.68 million kilowatts. The latest standard requires that newly built power plants emit SO2 in no more than 100 mg/m(3) and the emission of old ones be lower than 200 mg/m(3) while in some key areas the emission should be controlled under 50 mg/m(3). So by the end of 2012, 90% of the active coal-fired units have been equipped with flue gas desulfurization devices. Among the desulfurization methods adopted, limestone-gypsum wet flue gas desulphurization accounts for 92%, causing the problem of fine droplets in the exhaust gas after defogger, which may even form "gypsum rain." At present, sampling methods are widely used at home and abroad, such as magnesium ion tracer method, modified magnesium ion tracer method and chemical analysis. In addition, some scholars use aerodynamic methods, such as ELPI, to measure the diameter distribution and concentration. The methods mentioned above all have their own demerits, such as the inability to on-line, continuous measurements and the need of prolonged measuring time. Thus, in this paper some potential optical on-line methods are presented, such as Fraunhofer diffraction pattern analysis and wavelength-multiplexed laser extinction. Also brought up are their measuring scope and merits. These methods have already been utilized to measure small liquid droplets and their demonstrations and evaluations are as well stated. Finally, a 3D imaging method based on digital holographic microscope is proposed for in-line measurement of size and concentration of slurry droplets. The feasibility of this method is demonstrated by preliminary experimental investigation.

Influence of flue gas cleaning system on characteristics of PM2.5 emission from coal-fired power plants

AbstractThis study investigated the influence of precipitators and wet flue gas desulfurization equipment on characteristics of PM2.5 emission from coal-fired power stations. We measured size distribution and removal efficiencies, including hybrid electrostatic precipitator/bag filters (ESP/BAGs) which have rarely been studied. A bimodal distribution of particle concentrations was observed at the inlet of each precipitator. After the precipitators, particle concentrations were significantly reduced. Although a bimodal distribution was still observed, all peak positions shifted to the smaller end. The removal efficiencies of hybrid ESP/BAGs reached 99 % for PM2.5, which is considerably higher than those for other types of precipitators. In particular, the influence of hybrid ESP/BAG operating conditions on the performance of dust removal was explored. The efficiency of hybrid ESP/BAGs decreased by 1.9 % when the first electrostatic field was shut down. The concentrations and distributions of particulate matter were also measured in three coal-fired power plants before and after desulfurization devices. The results showed diverse removal efficiencies for different desulfurization towers. The reason for the difference requires further research. We estimated the influence of removal technology for particulate matter on total emissions in China. Substituting ESPs with hybrid ESP/BAGs could reduce the total emissions to 104.3 thousand tons, with 47.48 thousand tons of PM2.5.

Study on Molecular Sieve Catalyst for Selective Catalytic Reduction of Nox at Low Temperature

Low temperature SCR method has caused concern for the scholars in recent years. This SCR unit can be installed downstream of the desulfurization and particulate control devices, which is conducive to match the existing boiler system. It can relief the poisoning and blocking of SO2 and dust, so as to extend the life of catalyst. This paper summarizes the research progress of molecular sieve catalyst of low temperature SCR.

Catalytic Oxidation Activity of NO on TiO&lt;sub&gt;2&lt;/sub&gt;-Supported Mn-Co Composite Oxide Catalysts

Globally, NOx is one of the most widespread pollutants. It is generated mainly from the burning of fossil fuels, and NO is very difficult to remove because of its capacity to be dissolved in water. The catalytic oxidation method can be used to convert NO to NO2, which is soluble in water and can be removed using desulfurization devices. Here, a series of TiO2-supported Mn-Co composite oxide catalysts were prepared using the impregnation method. The results of catalytic activity tests showed that the addition of Mn enhanced the efficiency of NO oxidation. Significantly, with 6% doping amounts, Mn (0.3)-Co(0.7)/TiO2 showed the best activity of 88% NO conversion at 300 degrees C. X-ray diffraction (XRD), N-2 adsorption/desorption, hydrogen temperature-programmed reduction (H-2-TPR), oxygen temperature-programmed desorption (O-2-TPD), and in-situ diffuse reflectance Fourier transform infrared (in-situ DRFTIR) spectroscopy were used to characterize the catalysts. The results indicated that when the doping amount was 6%, the Mn enhanced the specific surface areas and pore volumes, which improved the dispersion of the active component over the TiO2 support. The co-doping of manganese into the Co/TiO2 also enhanced the oxygen desorption capabilities of the catalysts, which improved their reduction abilities. In addition, bridge NO3-, the key intermediate, was converted into NO2; this conversion was also enhanced by the presence of Mn on the Co/TiO2 catalyst. All of the above reasons account for the high NO catalytic oxidation activity of the supported Mn-Co composite oxide catalysts.

Interannual variation in the fine-mode MODIS aerosol optical depth and its relationship to the changes in sulfur dioxide emissions in China between 2000 and 2010

Abstract. Anthropogenic SO2 emissions increased alongside economic development in China at a rate of 12.7% yr−1 from 2000 to 2005. However, under new Chinese government policy, SO2 emissions declined by 3.9% yr−1 between 2005 and 2009. Between 2000 and 2010, we found that the variability in the fine-mode (submicron) aerosol optical depth (AOD) over the oceans adjacent to East Asia increased by 3–8% yr−1 to a peak around 2005–2006 and subsequently decreased by 2–7% yr−1, based on observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA's Terra satellite and simulations by a chemical transport model. This trend is consistent with ground-based observations of aerosol particles at a mountainous background observation site in central Japan. These fluctuations in SO2 emission intensity and fine-mode AOD are thought to reflect the widespread installation of fuel-gas desulfurization (FGD) devices in power plants in China, because aerosol sulfate is a major determinant of the fine-mode AOD in East Asia. Using a chemical transport model, we confirmed that the contribution of particulate sulfate to the fine-mode AOD is more than 70% of the annual mean and that the abovementioned fluctuation in fine-mode AOD is caused mainly by changes in SO2 emission rather than by other factors such as varying meteorological conditions in East Asia. A strong correlation was also found between satellite-retrieved SO2 vertical column density and bottom-up SO2 emissions, both of which were also consistent with observed fine-mode AOD trends. We propose a simplified approach for evaluating changes in SO2 emissions in China, combining the use of modeled sensitivity coefficients that describe the variation of fine-mode AOD with changes in SO2 emissions and satellite retrieval. Satellite measurements of fine-mode AOD above the Sea of Japan marked a 4.1% yr−1 decline between 2007 and 2010, which corresponded to the 9% yr−1 decline in SO2 emissions from China during the same period.

Technical Evaluation of the Selection of Flue Gas Purifying Device of Power Plant

The paper introduced several ash separator, desulfurization devices and denitrification devices which were widespread used in thermal power plant in recent years and respectively compared the technicality efficiency of them. It comes to the conclusion that: in the choice of ash separators, bag filter which has more merits than ESP, it has the advantages of reliable operation, simple maintenance, adapting to change in different coal and higher efficiency. In the choice of desulfurization technology, wet limestone-gypsum desulfurization technology is the most mature, which has stable operation and wide adaptability. Therefore, the thermal power plant prefer to it. In the choice of denitrification devices, SCR with low NH3 escape rate and easy to maintain, so it has become the mature and mainstream technology at home and abroad.