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1.
Previous workers have shown that simultaneous SO 2/NO X removal can be obtained in a dry scrubbing system with Ca(OH) 2 promoted by an additive such as NaOH, and that fly ash and product recycle improve the reactivity of the solids toward SO 2. To test SO 2/NO X removal with fly ash and product recycle, bench-scale experiments with a packed bed reactor were performed at bag filter conditions. The most reactive solid for NO X removal was prepared by slurrying Ca(OH) 2 with fly ash, CaSO 3, and NaOH. The best conditions for NO X removal were the greatest temperature (125°C) and greatest concentrations of SO 2 (1500 ppm) and O 2 (20 percent). At the best conditions, NO X removed in 1 hour was 3-4 moles per 100 moles Ca(OH) 2, compared to 5-10 moles SO 2 removed per 100 moles Ca(OH) 2. The best SO 2 removal was obtained at the highest relative humidities/lowest temperatures (55% RH/ 65°C) with solids prepared by slurrying Ca(OH) 2 with fly ash and NaOH. At these conditions, SO 2 removed In 1 hour was 60-80 moles per 100 moles Ca(OH) 2, compared to 0.5 to 1 moles NO X removed per 100 moles Ca(OH) 2. 相似文献
2.
ABSTRACT This article presents the results of an industrial-scale study (on 400 MW e lignite fired unit) of simultaneous NO x, SO 2, and Hg T removal in FGD absorber with oxidant injection (NaClO 2) into flue gas. It was confirmed that the injection of sodium chlorite upstream the FGD (Flue Gas Desulfurization) absorber oxidize NO to NO 2, Hg 0 to Hg 2+, and enhancing NO x and Hg T removal efficiency from exhaust gas in FGD absorber. Mercury removal efficiency grows with the rise of degree of oxidation NO to NO 2 and was limited by the phenomenon of re-emission. For NO x removal the most critical parameters is slurry pH and temperature. There was no negative effect on sulfur dioxide removal efficiency caused by oxidant injection in tested FGD absorber. Based on the data provided, NO x and Hg T emissions can be reduced by adjusting the FGD absorber operating parameters combined with oxidant injection. 相似文献
3.
Abstract Efforts to develop multipollutant control strategies have demonstrated that adding certain oxidants to different classes of Ca-based sorbents leads to a significant improvement in elemental Hg vapor (Hg 0), SO 2, and NO x removal from simulated flue gases. In the study presented here, two classes of Ca-based sorbents (hydrated limes and silicate compounds) were investigated. A number of oxidizing additives at different concentrations were used in the Ca-based sorbent production process. The Hg 0, SO 2, and NO x capture capacities of these oxidant-enriched sorbents were evaluated and compared to those of a commercially available activated carbon in bench-scale, fixed-bed, and fluid-bed systems. Calcium-based sorbents prepared with two oxidants, designated C and M, exhibited Hg 0 sorp-tion capacities (~100 μg/g) comparable to that of the activated carbon; they showed far superior SO 2 and NO x sorption capacities. Preliminary cost estimates for the process utilizing these novel sorbents indicate potential for substantial lowering of control costs, as compared with other processes currently used or considered for control of Hg 0, SO 2, and NO x emissions from coal-fired boilers. The implications of these findings toward development of multipollutant control technologies and planned pilot and field evaluations of more promising multipollutant sorbents are summarily discussed. 相似文献
4.
Sodium hypochlorite (NaClO) has been widely used as a chemical additive for enhancing nitrogen oxide (NO x; NO + NO 2), sulfur dioxide (SO 2), and mercury (Hg 0) removals in a wet scrubber. However, they are each uniquely dependent on NaClO (aq) pH, hence making the simultaneous control difficult. In order to overcome this weakness, we sprayed low liquid-to-gas (L/G) ratio (0.1 L/Nm 3) of NaClO (aq) to vaporize quickly at 165 °C. Results have shown that the maximized NO x, SO 2, and Hg 0 removals can be achieved at the pH range between 4.0 and 6.0. When NO x and Hg 0 coexist with SO 2, in addition, their removals are significantly enhanced by reactions with solid and gaseous by-products such as NaClO (s), NaClO 2(s), OClO, ClO, and Cl species, originated from the reaction between SO 2 and NaClO (aq). We have also demonstrated the feasibility of this approach in the real flue gases of a combustion plant and observed 50%, 80%, and 60% of NO x, SO 2, and Hg 0 removals, respectively. These findings led us to conclude that the spray of NaClO (aq) at a relatively high temperature at which the sprayed solution can vaporize quickly makes the simultaneous control of NO x, SO 2, and Hg 0 possible. Implications: The simple spray of NaClO(aq) at temperatures above 165 °C can cause the simultaneous removal of gaseous NOx, SO2, and Hg0 by its quick vaporization. Their maximized removals are achieved at the pH range between 4.0 and 6.0. NOx and Hg0 removals are also enhanced by gaseous and solid intermediate products generated from the reaction of SO2 with NaClO(aq). The feasibility of this approach has been demonstrated in the real flue gases of a combustion plant. 相似文献
5.
ABSTRACT To explore environmentally benign solvents for the absorption of NO and NO 2, a series of caprolactam tetrabutyl ammonium halide ionic liquids were synthesized. The solubility of NO and NO 2 was measured at temperatures ranging from 298.2 to 363.2 K and atmospheric pressure, and the following trend in the solubility of NO and NO 2 in ionic liquids with various halide anions was observed, respectively: F > Br > Cl and Br > Cl > F. Moreover, as the temperature increased from 308.15 to 363.15 K and the mole ratio of caprolactam increased from 2:1 to 6:1, the solubility of NO increased. Alternatively, the solubility of NO 2 decreased as the temperature increased from 298.15 to 363.15 K, and the mole ratio of caprolactam increased from 2:1 to 6:1. The absorption and desorption of NO and NO 2 was practically reversible in the ionic liquids, which was characterized by nuclear magnetic resonance. The method, which is at least partially reversible, offers interesting possibilities for the removal of NO and NO 2. IMPLICATIONS Basic ionic liquids with amino groups were synthesized and used to capture CO 2, SO 2, and H 2S, and to promote hydrogenation of CO 2. In this paper, the authors used caprolactam tetrabutyl ammonium halide ionic liquid (IL) as absorbing medium in which NO x could be absorbed. NO x desorbed from the absorbent could be efficiently reduced by right catalysts at high temperature. The absorbed NO and NO 2 gas could be desorbed at higher temperature, allowing the ionic liquids to be reused several times without loss of capability. It was believed that caprolactam tetrabutyl ammonium bromide (CPL-TBAB) ILs may be useful for NO x removal reagent for pollution control. 相似文献
6.
Abstract The proposed mercury (Hg) oxidation mechanism consists of a 168-step gas phase mechanism that accounts for interaction among all important flue gas species and a heterogeneous oxidation mechanism on unburned carbon (UBC) particles, similar to established chemistry for dioxin production under comparable conditions. The mechanism was incorporated into a gas cleaning system simulator to predict the proportions of elemental and oxidized Hg species in the flue gases, given relevant coal properties (C/H/O/N/S/Cl/Hg), flue gas composition (O 2, H 2O, HCl), emissions (NO X, SO X, CO), the recovery of fly ash, fly ash loss-on-ignition (LOI), and a thermal history. Predictions are validated without parameter adjustments against datasets from lab-scale and from pilot-scale coal furnaces at 1 and 29 MW t. Collectively, the evaluations cover 16 coals representing ranks from sub-bituminous through high-volatile bituminous, including cases with Cl 2 and CaCl 2 injection. The predictions are, therefore, validated over virtually the entire domain of Cl-species concentrations and UBC levels of commercial interest. Additional predictions identify the most important operating conditions in the furnace and gas cleaning system, including stoichiometric ratio, NO X, LOI, and residence time, as well as the most important coal properties, including coal-Cl. 相似文献
7.
Novel dynamic equipment with gas in and out continuously was developed to study the capture capacity of CO 2. Municipal solid waste incineration (MSWI) fly ash has a high capture rate of CO 2 in CO 2-rich gas. Fly ash can sequester pure CO 2 rapidly, and its capacity is 16.3 g CO 2/100 g fly ash with no water added and 21.4 g CO 2/100 g fly ash with 20% water added. For simulated incineration gas containing 12% CO 2, the capture rate decreased and the capacity was 13.2 g CO 2/100 g fly ash with no water added and 18.5 g CO 2/100 g fly ash with 20% water added. After accelerated carbonation, the C and O contents increased, indicating CO 2 capture in the fly ash; CO 2 combines with Ca(OH) 2 to form CaCO 3, which increased the CaCO 3 content from 12.5 to 54.3%. The leaching of Pb markedly decreased from 24.48 to 0.111 mg/L. 相似文献
8.
Four different mixed fuels consisted of leather waste, coal, and sewage sludge were combusted in a lab-scale entrained flow fluidized bed furnace. The influence of blending ratio on emission characteristics of SO2, NOx, HCl, particulate matter (PM), heavy metals, and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) was studied. Results showed that the mixing of coal with sewage sludge had a complex effect on the emission characteristics. On the one hand, with more sewage sludge blending in the mixed fuel, the acid gas pollutant (SO2, NOx) decreased a lot, and the recovery of volatile heavy metals (Cd, Pb) increased at the same time. Furthermore, the leaching toxicity of Cr in the fly ash and bottom ash went down below the national standard with the adding of sewage sludge. On the other hand, the mixing of sewage sludge which consisted of more ash content resulted in the increase of the PM emission. Moreover, the high content of Cu and chlorine in the sewage sludge can promote the formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) when the fuel 3 and 4 were combusted. Most importantly, the concentration of toxic PCDD/Fs in the flue gas produced from fuel 3 and fuel 4 was successfully controlled down below 0.20 ng I-TEQ/Nm3 by the active carbon. 相似文献
9.
ABSTRACT At conditions typical of a bag filter exposed to a coal-fired flue gas that has been adiabatically cooled with water, calcium hydroxide and calcium silicate solids were exposed to a dilute, humidified gas stream of nitrogen dioxide (NO 2) and sulfur dioxide (SO 2) in a packed-bed reactor. A prior study found that NO 2 reacted readily with surface water of alkaline and non-alkaline solids to produce nitrate, nitrite, and nitric oxide (NO). With SO 2 present in the gas stream, NO 2 also reacted with S(IV), a product of SO 2 removal, on the exterior of an alkaline solid. The oxidation of S(IV) to S(VI) by oxygen reduced the availability of S(IV) and lowered removal of NO 2. Subsequent acidification of the sorbent by the removal of NO 2 and SO 2 facilitated the production of NO. However, the conversion of nitrous acid to sulfur-nitrogen compounds reduced NO production and enhanced SO 2 removal. A reactor model based on empirical and semi-empirical rate expressions predicted rates of SO 2 removal, NO 2 removal, and NO production by calcium silicate solids. Rate expressions from the reactor model were inserted into a second program, which predicted the removal of SO 2 and NO x by a continuous process, such as the collection of alkaline solids in a baghouse. The continuous process model, depending upon inlet conditions, predicted 30-40% removal for NO and 50-90% removal for SO 2. These x 2 results are relevant to dry scrubbing technology for combined SO 2 and NO x removal that first oxidizes NO to NO 2 by the addition of methanol into the flue duct. 相似文献
10.
低温选择性催化还原(SCR)脱硝是国内外脱硝技术研发的热点,但目前主要集中在实验室小试范围,无法完全反映催化剂在实际烟气中的运行状况。在30 t/h循环流化床燃煤锅炉脱硫除尘装置后建设了2 000~5 000 m3/h的SCR脱硝中试装置,经系统研究发现,中试使用的蜂窝式催化剂对SO2和NO具有很强的吸附能力,且反应温度、喷氨速率和气体空速均会影响催化脱硝效率。为期5 d的连续运行实验结果表明,催化剂的脱硝效率一直稳定在30%~50%,并未发现明显的失活,这证明设计除雾除尘器、较大的混合器、混合器与反应器间较长的管路均有利于缓解催化剂因SO2、H2O和飞灰中的碱性金属导致的失活。 相似文献
11.
The body of Information presented in this paper is directed to those Individuals concerned with the removal of NO x in combustion flue gases. A catalytic process for the selective reduction of nitrogen oxides by ammonia has been investigated. Efforts were made toward the development of catalysts resistant to SO x poisoning. Nitrogen oxides were reduced over various metal oxide catalysts in the presence or absence of SO x(SO 2 and SO 3). Catalysts consisting of oxides of base metals (for example, Fe 2O 3) were easily poisoned by SO 3, forming sulfates of the base metals. A series of catalysts which are not susceptible to the SO x poisoning has been developed. The catalysts possess a high activity and selectivity over a wide range of temperatures, 250—450°C. The catalysts were tested in a pilot plant which treated a flue gas containing 110-150 ppm NO x, 660-750 ppm SO 2, and 40-90 ppm SO 3. The pilot plant was operated at 350°C and at a space velocity of 10,000 h -1. The removal of nitrogen oxides was more than 90% for several months. A mechanism of the NO-NH 3 reaction has also been investigated. It is found that NO reacts with NH 3 at a 1:1 mole ratio in the presence of oxygen and the reaction is completely inhibited by the absence of oxygen. The experimental data show that the NO-NH 3 reaction in the presence of oxygen is represented byNO + NH 3 + 1/4 O 2 = N 2 + 3/2 H 2O. 相似文献
12.
A decentralized emission inventories are prepared for road transport sector of India in order to design and implement suitable technologies and policies for appropriate mitigation measures. Globalization and liberalization policies of the government in 90's have increased the number of road vehicles nearly 92.6% from 1980–1981 to 2003–2004. These vehicles mainly consume non-renewable fossil fuels, and are a major contributor of green house gases, particularly CO 2 emission. This paper focuses on the statewise road transport emissions (CO 2, CH 4, CO, NO x, N 2O, SO 2, PM and HC), using region specific mass emission factors for each type of vehicles. The country level emissions (CO 2, CH 4, CO, NO x, N 2O, SO 2 and NMVOC) are calculated for railways, shipping and airway, based on fuel types. In India, transport sector emits an estimated 258.10 Tg of CO 2, of which 94.5% was contributed by road transport (2003–2004). Among all the states and Union Territories, Maharashtra's contribution is the largest, 28.85 Tg (11.8%) of CO 2, followed by Tamil Nadu 26.41 Tg (10.8%), Gujarat 23.31 Tg (9.6%), Uttar Pradesh 17.42 Tg (7.1%), Rajasthan 15.17 Tg (6.22%) and, Karnataka 15.09 Tg (6.19%). These six states account for 51.8% of the CO 2 emissions from road transport. 相似文献
13.
This study quantifies the trade-offs and synergies between climate and air quality policy objectives for the European power and heat (P&H) sector. An overview is presented of the expected performance data of CO 2 capture systems implemented at P&H plants, and the expected emission of key air pollutants, being: SO 2, NO X, NH 3, volatile organic compounds (VOCs) and particulate matter (PM). The CO 2 capture systems investigated include: post-combustion, oxyfuel combustion and pre-combustion capture.For all capture systems it was found that SO 2, NO x and PM emissions are expected to be reduced or remain equal per unit of primary energy input compared to power plants without CO 2 capture. Increase in primary energy input as a result of the energy penalty for CO 2 capture may for some technologies and substances result in a net increase of emissions per kWh output. The emission of ammonia may increase by a factor of up to 45 per unit of primary energy input for post-combustion technologies. No data are available about the emission of VOCs from CO 2 capture technologies.A simple model was developed and applied to analyse the impact of CO 2 capture in the European P&H sector on the emission level of key air pollutants in 2030. Four scenarios were developed: one without CO 2 capture and three with one dominantly implemented CO 2 capture system, varying between: post-combustion, oxyfuel combustion and pre-combustion.The results showed a reduction in GHG emissions for the scenarios with CO 2 capture compared to the baseline scenario between 12% and 20% in the EU 27 region in 2030. NO x emissions were 15% higher in the P&H sector in a scenario with predominantly post-combustion and lower when oxyfuel combustion (?16%) or pre-combustion (?20%) were implemented on a large scale. Large scale implementation of the post-combustion technology in 2030 may also result in significantly higher, i.e. increase by a factor of 28, NH 3 emissions compared to scenarios with other CO 2 capture options or without capture. SO 2 emissions were very low for all scenarios that include large scale implementation of CO 2 capture in 2030, i.e. a reduction varying between 27% and 41%. Particulate Matter emissions were found to be lower in the scenarios with CO 2 capture. The scenario with implementation of the oxyfuel technology showed the lowest PM emissions followed by the scenario with a significant share allocated to pre-combustion, respectively ?59% and ?31%. The scenario with post-combustion capture resulted in PM emissions varying between 35% reduction and 26% increase. 相似文献
14.
Abstract Air pollutants were collected in Logan, Cache County, UT, in February 1993 during two periods of atmospheric inversion accompanied by fog. The following atmospheric species were determined: (1) gaseous SO 2, NO 2 (semi-quantitatively),HNO3, NH3, and HF; (2) fine particulate SO 4 =, NO 3 -, NH 4 +, F–, H +, C, Si, S, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Pb, Se, Br, and Sr, and; (3) fine particulate mass, which was calculated. The major components of fine particulate matter were carbonaceous material, ammonium nitrate, and ammonium sulfate, while the soil component was small. Calculated, fine particulate mass averaged 80 μg/m 3 and reached concentrations as high as 120 μg/m 3. SO 2/So x and NO 2/NO y mole ratios generally varied between 0.2 and 0.1 during inversions. These ratios also showed moderate but consistent diurnal patterns. The emission inventory for Cache County indicates sources of SO 2 and NO x but not significant amounts of primary sulfate and nitrate. The observations reported here indicate there is significant conversion of SO 2 and NO x in the presence of excess oxidants to sulfuric and nitric acid that are neutralized by excess ammonia. 相似文献
15.
This study proposes an easy-to-apply method, the Total Life Cycle Emission Model (TLCEM), to calculate the total emissions from shipping and help ship management groups assess the impact on emissions caused by their capital investment or operation decisions. Using TLCEM, we present the total emissions of air pollutants and greenhouse gases (GHGs) during the 25-yr life cycle of 10 post-Panamax containerships under slow steaming conditions. The life cycle consists of steel production, shipbuilding, crude oil extraction and transportation, fuel refining, bunkering, and ship operation. We calculate total emissions from containerships and compare the effect of emission reduction by using various fuels. The results can be used to differentiate the emissions from various processes and to assess the effectiveness of various reduction approaches. Critical pollutants and GHGs emitted from each process are calculated. If the containerships use heavy fuel oil (HFO), emissions of CO 2 total 2.79 million tonnes (Mt), accounting for 95.37% of total emissions, followed by NO x and SO x emissions,which account for 2.25% and 1.30%, respectively.The most significant emissions are from the operation of the ship and originate from the main engine (ME).When fuel is switched to 100% natural gas (NG), SO x, PM 10, and CO 2 emissions show remarkable reductions of 98.60%, 99.06%, and 21.70%, respectively. Determining the emission factor of each process is critical for estimating the total emissions. The estimated emission factors were compared with the values adopted by the International Maritime Organization (IMO).The proposed TLCEM may contribute to more accurate estimates of total life cycle emissions from global shipping. Implications: We propose a total life cycle emissions model for 10 post-Panamax container ships. Using heavy fuel oil, emissions of CO2 total 2.79 Mt, accounting for approximately 95% of emissions, followed by NOx and SOx emissions. Using 100% natural gas, SOx, PM10, and CO2 emissions reduce by 98.6%, 99.1%, and 21.7%, respectively. NOx emissions increase by 1.14% when running a dual fuel engine at low load in natural gas mode. 相似文献
16.
The emissions of exhaust gases (NO x , SO 2, VOCs, and CO 2) and particles (e.g., PM) from ships traversing Busan Port in Korea were estimated over three different years (the years 2006, 2008, and 2009). This analysis was performed according to the ship operational modes (“at sea,” “maneuvering,” and “in port”) and ship types based on an activity-based method. The ship emissions for current (base year 2009) and future scenarios (years 2020 and 2050) were also compared. The annual emissions of SO 2, VOCs, PM, and CO 2 were highest (9.6?×?10 3, 374, 1.2?×?10 3, and 5.6?×?10 5 ton year ?1, respectively) in 2008. In contrast, the annual NO x emissions were highest (11.7?×?10 3 ton year ?1) in 2006 due mainly to the high NO x emission factor. The emissions of air pollutants for each ship operational mode differed considerably, with the largest emission observed in “in port” mode. In addition, the largest fraction (approximately 45–67 %) of the emissions of all air pollutants during the study period was emitted from container ships. The future ship emissions of most pollutants (except for SO 2 and PM) in 2020 and 2050 are estimated to be 1.4–1.8 and 4.7–6.1 times higher than those in 2009 (base year), respectively. 相似文献
17.
Electric utilities considering atmospheric fluidized-bed combustion (AFBC) as an economic way to reduce SO 2 and NO x emissions at coal-fired power plants must evaluate the impact AFBC will have on existing or planned plant systems and components. Because fly ash in AFBC units can have characteristics significantly different from that generated in pulverized-coal-fired boilers, a particular concern in this regard is the performance of the plant's particulate control equipment. 相似文献
18.
We present measurements of several trace gases made at a subtropical coastal site in Hong Kong in October and November 1997. The gases include O 3, CO, SO 2, and NO x. The surface measurement data are compared with those from an aircraft study [Kok et al. J. Geophys. Res. 102 (D15) (1997) 19043–19057], and a subset of the latter is used to show the vertical distribution of the trace gases in the boundary layer. During the study period, averaged concentrations at the surface site for O 3, CO, NO x, and SO 2 were 50, 298, 2.75, and 1.65 ppbv, respectively. Their atmospheric abundance and diurnal pattern are similar to those found in the “polluted” rural areas in North America. The measured trace gases are fairly well mixed in the coastal boundary layer in the warm South China region. Large variability is indicated from the data. Examination of 10-day, isentropic back trajectories shows that the measured trace gases are influenced by maritime air masses, outflow of pollution-laden continental air, and the mixing of the two. The trajectories capture the contrasting chemical features of the large-scale air masses impacting on the study area. CO, NO x and SO 2 all show higher concentrations in the strong outflow of continental air, as expected, than those in the marine category. Compared with previously reported values for the western Pacific, the much higher levels found in the marine trajectories in our study suggest the impacts of regional and/or sub-regional emissions on the measured trace gases at the study site. The presence of abundant O 3 and other chemically active trace gases in the autumn season, coupled with high solar radiation and warm weather, suggests that the South China Sea is a photochemically active region important for studying the chemical transformation of pollutants emitted from the Asian continent. 相似文献
20.
The removal of triphenyltin chloride from contaminated simulated seawater with adsorption method was discussed. The adsorbents used are fly ash, nSiO 2, and nSiO 2/fly ash composite. The results showed that the adsorption of the adsorbents increases with increase in the adsorbent dose, contact time, pH, stirring speed, initial TPT concentration, and decreased with increase in temperature. The adsorption fitted well with the Freundlich isotherm, showing that the adsorbent and TPT combined with function groups and the adsorption kinetics followed the pseudo-second-order kinetic model. The thermodynamic parameters were also evaluated. Optimal conditions for the adsorption of TPT from simulated seawater were applied to TPT removal from natural seawater. A higher removal efficiency of TPT (>99 %) was obtained for the nSiO 2/fly ash composite but not for fly ash and nSiO 2. 相似文献
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