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1.
富氧燃烧技术是目前最有可能大规模推广和商业应用的碳捕集与封存技术之一,其中,烟气压缩净化及CO 2提纯对于整个富氧燃烧系统至关重要。然而,目前研究多聚焦于富氧燃烧后烟气压缩净化的工艺验证,而对烟气压缩纯化各单元运行特性的研究仍不深入,特别是烟气压缩净化过程杂质污染组分的迁移转化、系统运行参数与污染物脱除效率的关联仍不明确。且现有研究对净化后烟气的深度提纯及高浓度CO 2制备的关注也相对较少,直接关系到富氧燃烧系统运行经济性。因此,针对富氧燃烧烟气净化及CO 2提纯需求,系统探究了富氧燃烧烟气压缩纯化过程SO 2、NO x吸收脱除以及CO 2深度提纯等各子系统的运行特性,其中SO 2与NO x脱除采用压缩-酸液吸收,CO 2深度提纯采用低温精馏。结果表明:通过烟气净化可实现SO 2脱除效率达100%,NO脱除效率达99%,同时实现纯度为99.99%的食品级液态CO 2制备。烟气净化过程中,气相反应占据主导,提高压力可缩短反应时间;当SO 2吸收塔运行压力超过0.8 MPa时,SO 2脱除效率可达100%;当NO吸收塔运行压力超过3.0 MPa时,NO排放浓度可达超低排放标准。CO 2提纯过程中,提高压力会降低液体CO 2纯度。SO 2吸收塔运行压力为1.6 MPa、NO吸收塔运行压力为3.0 MPa、CO 2提纯塔运行压力为3.8 MPa时,系统整体功耗最低,为0.37 MJ/kg。 相似文献
2.
The reactivity of four pulverised Australian coals were measured under simulated air (O 2/N 2) and oxy-fuel (O 2/CO 2) environments using a drop tube furnace (DTF) maintained at 1673 K and a thermogravimetric analyser (TGA) run under non-isothermal (heating) conditions at temperatures up to 1473 K. The oxygen concentration, covering a wide and practical range, was varied in mixtures of O 2/N 2 and O 2/CO 2 in the range of 3 to 21 vol.% and 5 to 30 vol.%, respectively. The apparent volatile yield measured in CO 2 in the DTF was greater than in N 2 for all the coals studied. Pyrolysis experiments in the TGA also revealed an additional mass loss in a CO 2 atmosphere, not observed in a N 2 atmosphere, at relatively high temperatures. The coal burnout measured in the DTF at several O 2 concentrations revealed significantly higher burnouts for two coals and similar burnouts for the other two coals in oxy-fuel conditions. TGA experiments with char also revealed higher reactivity at high temperatures and low O 2 concentration. The results are consistent with a char–CO 2 reaction during the volatile yield experiments, but additional experiments are necessary to resolve the mechanisms determining the differences in coal burnout. 相似文献
4.
The emissions of CO 2, NO x and SO 2 from the combustion of a high-volatile coal with N 2- and CO 2-based, high O 2 concentration (20, 50, 80, 100%) inlet gases were investigated in an electrically heated up-flow-tube furnace at elevated gas temperatures (1123–1573 K). The fuel equivalence ratio, φ, was varied in the range of 0.4–1.6. Results showed that CO 2 concentrations in flue gas were higher than 95% for the processes with O 2 and CO 2-based inlet gases. NO x emissions increased with φ under fuel-lean conditions, then declined dramatically after φ=0.8, and the peak values increased from about 1000 ppm for the air combustion process and 500 ppm for the O 2(20%)+CO 2(80%) inlet gas process to about 4500 ppm for the oxygen combustion process. When φ>1.4 the emissions decreased to the same level for different O 2 concentration inlet gas processes. On the other hand, NO x emission indexes decreased monotonically with φ under both fuel-lean and fuel-rich combustion. SO 2 emissions increased with φ under fuel-lean conditions, then declined slightly after φ>1.2. Temperature has a large effect on the NO x emission. Peak values of the NO x emission increased by 50–70% for the N 2-based inlet gas processes and by 30–50% for the CO 2-based inlet gas process from 1123 to 1573 K. However, there was only a small effect of temperature on the SO 2 emission. 相似文献
5.
Two measurement campaigns were carried out at ENERGI E2's Asnæs Power plant, unit 5. The unit has a capacity of 620 MW e and is equipped with a wet flue gas desulphurisation (FGD) plant employing a counter-current spray absorber with five spray levels. In the first campaign, the power plant was firing Orimulsion ® with 2.85 wt% S resulting in a flue gas concentration of SO 2 exceeding 2000 ppmv. In the second campaign, the fuel applied was a low-S blended coal and the SO 2 concentration in the raw gas was around 400 ppmv. A novel probe for in situ sampling of gas phase concentrations in wet FGD spray absorbers was developed and applied for measuring axial profiles of the SO 2 gas phase concentrations in the absorber. The expected decrease in SO 2 concentrations along the height of the absorber was found in the spray section (from height 26.5 to 36.2 m) whereas the SO 2 concentration above the holding tank and below the gas inlet was quite low probably due to long local residence times in the region. Horizontal variations, due to somewhat different flow conditions near the column wall were investigated and the SO 2 concentrations were found to be higher near the wall. Measurements at different gross loads showed that the SO 2 gas phase concentration at a given position inside the absorber was roughly linearly related to the L/G ratio in the measuring interval. Turning off one of the lower spray levels, while burning coal with low S content, did not lower the overall removal efficiency of the absorber. However, the SO 2 gas phase concentration inside the lower part of the absorber was increased by a factor of 2-3. Measurements of slurry pH at different positions showed a decrease of approximately 0.5 units from the upper to the lower part of the absorber. The full-scale measurements provide a detailed set of experimental data for validation of mathematical models of a wet FGD spray absorber. 相似文献
6.
为实现富氧燃烧技术的广泛推广,对煤粉燃烧在富氧气氛下的颗粒物排放特性进行了研究。在1800 K管式炉内进行煤焦燃烧试验,研究了富氧气氛下H 2O(g)体积分数(0、5%、10%、20%、30%)对煤焦燃烧超细颗粒物的影响;采用荷电低压撞击器(ELPI+)获得超细颗粒物质量和数量浓度粒径分布并进行分析。结果表明,H 2O(g)对超细颗粒物质量浓度和数量浓度粒径分布无影响,但会导致超细颗粒物的峰值波动。超细颗粒物总数量由最小粒径超细颗粒物决定,5种水蒸气浓度下EL?PI+第1级撞击器收集到的超细颗粒物数量占比均超过65%。超细颗粒物总质量由最大粒径超细颗粒物决定,5个水蒸气浓度下ELPI+第7级撞击器收集到的超细颗粒物质量占比均超过94%。低H 2O(g)浓度会抑制超细颗粒物生成,H 2O(g)体积分数为5%时的抑制作用最显著;高H 2O(g)浓度会促进超细颗粒物生成。这是因为一方面H 2O(g)与煤焦发生气化反应,使煤焦颗粒周围产生还原性气氛,促进矿物质还原为单质,进一步促进矿物质蒸发;另一方面气化反应是吸热反应,会降低煤焦颗粒燃烧温度,同时H 2O(g)加入也导致烟气热容增加进一步降低,煤焦燃烧温度抑制煤中矿物质的蒸发,导致超细颗粒物生成减少,是2种作用相互竞争的结果。此外,H 2O(g)的加入使超细颗粒物平均粒径增大,0~5%H 2O(g)时超细颗粒物平均粒径增大最迅速。 相似文献
7.
Combustion of a Chinese bituminous coal was carried out in a laboratory-scale drop tube furnace (DTF) to clarify the variation of ash properties with bulk gas composition. The combustion conditions tested include three bulk gases, air, 21% O 2/79% CO 2 and 27% O 2/73% CO 2, two furnace/gas temperatures close to the fluidized bed reactor temperature range, 1073 K and 1273 K, and three particle residence times. Apart from bulk properties analysis, individual ash particles and the original mineral species in coal were characterized using Computer - Controlled Scanning Electron Microscopy (CCSEM). The results indicate that, under the given experimental conditions, shifting bulk gas from air to O 2/CO 2 mixtures is insignificant in terms of the elemental composition of bulk ash, in agreement with the literature. However, changes in the properties of individual species/metals are noticeable, including the extent of the vaporization of volatile elements, ash particle-size distribution (PSD), crystallization extent of K alumino-silicate associate, pyrite decomposition and oxidation rate and formation propensity of liquidus in ash. These changes were mostly considered to be caused by the evolution of included mineral grains in the distinct char particles in the O 2/CO 2 environment. Reduction in char particle temperature with bulk gas shifting from air to O 2/CO 2 mixtures was primarily crucial, which, however, could be overweighed by the existence of a fairly strong local reducing condition on the char surface in O 2/CO 2. Consequently, vaporization of the volatile elements such as Na and P was promoted; formation of the crystalline leucite in air was in contrast inhibited. Furthermore, the extent of coalescence of included minerals and oxidation rate of pyrite (or its derivative, pyrrhotite) were also influenced by char consumption rate, i.e. the receding extent of char surface. These parameters exerted a combined effect on ash formation, requiring detailed mathematical modeling to describe the dynamics of the formation of oxy-fuel ash. This study also indicated that the differences of ash properties formed between air and O 2/CO 2 mixtures can be greatly reduced and eventually eliminated by increasing furnace temperature. Increase in the turbulence of gas flow should also benefit the elimination of the side effects of local reducing gases on char surface. 相似文献
8.
Activated carbon-supported copper, iron, or vanadium oxide catalysts were exposed to incineration flue gas to investigate the simultaneous catalytic oxidation of sulfur dioxide/hydrogen chloride and selective catalytic reduction of nitrogen oxide by carbon monoxide. The results show that AC-supported catalysts exhibit higher activities for SO 2 and HCl oxidation than traditional γ-Al 2O 3-supported catalysts and the iron and vanadium catalysts act as catalysts instead of sorbents, and can decompose sulfate with evolution of SO 3 and then regenerate for more SO 2 adsorption to take place. The AC-supported catalysts also display a high activity for NO reduction with CO generated from a flue gas incineration process and the presence of SO 2 in the incineration flue gas can significantly promote catalytic activity. Using CO as the reducing agent for NO reduction is more effective than using NH 3, because NH 3 may be partially oxidized in the presence of excess O 2 (12 vol%. in the incineration flue gas used) to form N 2, which can decrease the overall extent of NO reduction. 相似文献
9.
The paper presents a model of coal combustion in air and oxygen-enriched CFB environment. A computer program to calculate the CO 2, CO, SO 2, NO x and O 2 emissions from the combustion of solid fuels in a circulating fluidized bed boiler was created. The validity of this program was verified by measurements on a 0.1MW th OxyFuel-CFB Test Rig.The calculations have been carried out for air and so-called oxy-fuel conditions, i.e. when combustion runs in a gas mixture based on O 2 and N 2, with various fractions of oxygen.The comparison between measured and predicted by model CO, SO 2, NO x and O 2 emissions is shown in this paper. The results of the calculation showed, that the kinetic equations of some reaction have to be modified. Authors propose to use the reaction surface area instead of the specific internal surface area of char in rate constant formulas as the combustion nature changes from internal-kinetic to external-diffusion controlling regime. 相似文献
10.
Ca(OH) 2/silica fume sorbents were prepared with various Ca(OH) 2/silica fume weight ratios and slurrying times at 65°C and a water/solid ratio of 10/1. Dry sorbents prepared were characterized, and their reactivities toward SO 2 were measured in a differential fixed-bed reactor at the conditions similar to those in the bag filters in the dry and semidry flue gas desulfurization (FGD) processes. The reaction between Ca(OH) 2 and silica fume in the slurry was very fast. The formation of calcium silicate hydrates, which were mainly C-S-H(I), resulted in sorbent particles with a highly porous structure that seemed compressible under high pressures. The sorbents were mesoporous, and their specific surface areas and pore volumes were much larger than those of Ca(OH) 2 alone. The utilization of Ca of sorbent increased with increasing silica fume content mainly due to the increase in the specific surface area of sorbent. The sorbent with Ca(OH) 2 had the maximum SO 2 capture. Sorbents with Ca(OH) 2 contents less than and greater than would have a SO 2 capture greater than that of Ca(OH) 2 alone. Both the utilization of Ca and SO 2 capture per unit specific surface area of sorbent decreased in general with increasing specific surface area. At the same Ca(OH) 2 content, the utilization of Ca or SO 2 capture of the Ca(OH) 2/silica fume sorbent was greater than that of the Ca(OH) 2/fly ash sorbent; however, the amount of SO 2 captured per unit surface area of the former sorbent was smaller than that of the latter sorbent. The results of this study are useful to the preparation of silica-enhanced sorbents for use in the dry and semidry FGD processes. 相似文献
12.
Oxidation kinetics of natural (110) diamond by oxygen and water were investigated using in situ Fizeau interferometry. Apparent activation energies of 53 and 26 kcal mol −1 were obtained for the etching of (110) type Ia diamond by O 2 and H 2O respectively. The etch rate was found to follow second-order kinetics with respect to O 2 pressure in the pressure range 0.04–10 Torr. For water over the vapour pressure range 0.1–2 Torr, the reaction has a reaction order near unity. The diamond (110) surface was impervious to etching by molecular fluorine at all temperatures up to 1300 °C. Fluorine, hydrogen fluoride and water were found to inhibit the molecular oxygen etching of diamond. Below 900 °C, oxidation is inhibited by the addition of F 2 and HF presumably by blocking reactive sites on the diamond surface through formation of C---F bonds. Above 900 °C, the fluorine is thought to desorb from the diamond (110) surface, rendering the surface susceptible to further oxidation. Addition of water below 800 °C was found to retard etching by molecular oxygen. This is attributed to the formation of C---OH bonds, analogous to C---F. 相似文献
13.
The objective of this research is to asses the impact of the addition of H 2O, SO 2, and both in the SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths. The sulphated catalyst keeps a 100% conversion and total selectivity to N 2 in the low temperature range, i.e. 473–500 K, when either H 2O or SO 2 is added to the gas feed. However, a decline of steady state conversion and selectivity occurs when both H 2O and SO 2 are added simultaneously because H 2O speeds up the deposition of ammonium sulphate salts. This decrease of catalyst performance is reversed when the reaction is carried out under dry conditions at temperatures higher than 473 K but not at lower temperature (453 K). Thus, the catalyst has demonstrated to be a good candidate for the SCR of NO at low temperatures even in stack gases containing traces of undesired components. 相似文献
14.
Free acids of the iron substituted heteropoly acids (HPA), H 7[(P 2W 17O 61)Fe III(H 2O)] (HFe1) and H 18[(P 2W 15O 56) 2Fe III2(H 2O) 2] (HFe2) were prepared from the salts K 7[(P 2W 17O 61)Fe III(H 2O)] (KFe1) and Na 12[(P 2W 15O 56) 2Fe III4(H 2O) 2] (NaFe4), respectively. The iron-substituted HPA were adsorbed on to XC-72 carbon based GDLs to form HPA doped GDEs after water washing with HPA loadings of ca. 1 μmol. The HPA was detected throughout the GDL by EDX. Solution electrochemistry of the free acids are reported for the first time in sulfate buffer, pH 1-3. The hydrogen oxidation reaction was catalyzed by KFe1 at 0.33 V, with an exchange current density of 38 mA/cm 2. Moderate activity for the oxygen reduction reaction was observed for the iron substituted HPA, which was dramatically improved by selectively removing oxygen atoms from the HPA by cycling the fuel cell cathode under N 2 followed by reoxidation to give a restructured oxide catalyst. The nanostructured oxide achieved an OCV of 0.7 V with a Tafel slope of 115 mV/decade. Cycling the same catalysts in oxygen resulted in an improved catalyst/ionomer/carbon configuration with a slightly higher Tafel slope, 128 mV/decade but a respectable current density of 100 mA/cm 2 at 0.2 V. 相似文献
15.
A two-step process to generate H 2 gas; first by milling polystyrene (PS) or poly(vinyl alcohol) (PVA) with Ni(OH) 2 and Ca(OH) 2, followed by heating of the milled product in the second-step was performed in this work. Polymer and hydroxide mixtures obtained after milling for 60 min and heating to 700 °C showed H 2, CH 4, H 2O, CO, and CO 2 as the main gaseous products with H 2 as the dominant gas generated between 350 and 500 °C. Analysis of the gaseous products by TG-MS and gas-chromatography, and solid products by TG-DTA and XRD shows that CO 2 gas was fixed as CaCO 3 at temperatures between 350 to 600 °C allowing generation of H 2 gas with concentrations over 95% for PS and over 98% for PVA. The results in this study show that milling of solid based hydrocarbon compounds with nickel and calcium hydroxides allows dispersion of nickel to hydrocarbon surfaces and facilitates C-C bond rupture in polymer(s) during heating at temperatures below 500 °C, at the same time calcium adsorbs CO 2. This process could be developed to treat hydrocarbon based wastes such as plastics, biomass or combinations at low temperatures avoiding syngas purification and separation steps. 相似文献
16.
In this paper a global reaction kinetic model is used to understand and describe the NO x storage/reduction process in the presence of CO 2 and H 2O. Experiments have been performed in a packed bed reactor with a Pt–Ba/ γ-Al 2O 3 powder catalyst (1 wt% Pt and 30 wt% Ba) with different lean/rich cycle timings at different temperatures (200, 250, and ) and using different reductants (H 2, CO, and C 2H 4). Model simulations and experimental results are compared. H 2O inhibits the NO oxidation capability of the catalyst and no NO 2 formation is observed. The rate of NO storage increases with temperature. The reduction of stored NO with H 2 is complete for all investigated temperatures. At temperatures above , the water gas shift (WGS) reaction takes place and H 2 acts as reductant instead of CO. At , CO and C 2H 4 are not able to completely regenerate the catalyst. At the higher temperatures, C 2H 4 is capable of reducing all the stored NO, although C 2H 4 poisons the Pt sites by carbon decomposition at . The model adequately describes the NO breakthrough profile during 100 min lean exposure as well as the subsequent release and reduction of the stored NO. Further, the model is capable of simulating transient reactor experiments with 240 s lean and 60 s rich cycle timings. 相似文献
17.
This work evaluates both the removal efficiencies of HCl and SO 2 at different points in a spray dryer using Ca(OH) 2 as the absorbent. The operating conditions were specified in terms of the temperature of the flue gas (200-300 °C), the HCl concentration (120-1000 ppm), the SO 2 concentration (150-500 ppm) and the amount of CaCl 2 added (10-30 wt.%).The experimental results showed that the SO 2 removal efficiencies were higher in the presence of HCl (120-500 ppm) than in the absence of HCl at 250 °C and 20% relative humidity (RH). However, the removal efficiency of SO 2 decreased as the HCl concentration increased. The removal efficiency of SO 2 also increased with the amount of CaCl 2 in the spray dryer. 相似文献
18.
This paper reports results of studies on structure and activity in soot combustion of nanocrystalline CeO 2 and CeLnOx mixed oxides (Ln = Pr, Tb, Lu, Ce/Ln atomic ratios 5/1). Nano-sized (4–5 nm) oxides with narrow size distribution were prepared by a microemulsion method W/O. Microstructure, morphology and reductivity of the oxides annealed up to 950 °C in O 2 and H 2 were analyzed by HRTEM, XRD, FT-IR, Raman spectroscopy and H 2-TPR. Obtained mixed oxides had fluorite structure of CeO 2 and all exhibited improved resistance against crystal growth in O 2, but only CeLuOx behaved better than CeO 2 in hydrogen. The catalytic activity of CeO2, CeLnOx and physical mixtures of CeO2 + Ln2O3 in a model soot oxidation by air was studied in “tight contact” mode by using thermogravimetry. Half oxidation temperature T1/2 for soot oxidation catalysed by nano-sized CeO2 and CeLnOx was similar and ca. 100 °C lower than non-catalysed oxidation. However, the mixed oxides were much more active during successive catalytic cycles, due to better resistance to sintering. Physical mixtures of nanooxides (CeO2 + Ln2O3) showed exceptionally high initial activity in soot oxidation (decrease in T1/2 by ca. 200 °C) but degraded strongly in successive oxidation cycles. The high initial activity was due to the synergetic effect of nitrate groups present in highly disordered surface of nanocrystalline Ln2O3 and enhanced reductivity of nanocrystalline CeO2. 相似文献
19.
Flue-gas recycling combustion of a sub-bituminous coal and its rapid pyrolysis char at 1120 K has been simulated experimentally in a bubbling fluidized-bed. O 2, CO 2 and H 2O, and NO or N 2O were pre-mixed and fed into the bed together with coal/char particles with the O 2 concentration in the exit gas maintained at 3.5 vol%. Increasing the inlet O 2 concentration, thus increasing the O 2 consumption rate and decreasing the flue-gas recycling ratio, caused the once-through conversion of fuel-bound nitrogen into N 2O to decrease while the conversion to NO to remain unchanged. The in-bed reductions of NO and N 2O were both first order with respect to the respective nitrogen oxide, with the rate constants to increase linearly with the rate of O 2 consumption in the bed and thus also with that of char/volatiles consumption. This finding, which indicated linear increase in the concentrations of reactive species involved in NO/N 2O reduction with the rate of O 2 consumption, enabled consideration that the homogeneous and heterogeneous reduction rates of NO and N 2O were proportional to the consumption rates of O 2 by the volatiles and char, respectively. The rate analysis of the kinetic data revealed the relative importance of burning volatiles and char as the agents for the reduction of NO and N 2O. While the reduction in the gas phase was fully responsible for the NO-to-N 2O conversion, the reactions over the char surface governed the NO-to-N 2 reduction. The volatiles and char had comparable contributions to the reduction of N 2O to N 2. The NO-to-N 2 and N 2O-to-N 2 reductions over the char surface were, respectively, accelerated and decelerated by increasing the H 2O concentration. 相似文献
20.
Hexanuclear 4d–4f heterometallic complexes, [Ln 2Ag 4(ina) 8(H 2O) 10][NO 3] 2 · 4H 2O [Ln = Sm ( 1), Eu ( 2), Dy ( 3) and Hina = isonicotinic acid], have been synthesized by the hydrothermal reaction of lanthanide oxides, Ag I, and isonicotinic acid at a suitable temperature. Single-crystal X-ray diffraction studies indicate that these 4d–4f complexes consist of extended 1D zigzag chains structure built upon [Sm 2Ag 4(ina) 8(H 2O) 10] subunits connected by Ag–Ag interactions. Furthermore, the photoluminescent properties of the complex 2 were studied. 相似文献
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