吸附法烟气脱硫

燃油和煤炭在燃烧过程中会产生SO2 ,这些SO2 排入大气中 ,形成酸雨 ,严重破坏生态环境 ,危害人类健康。一个世纪以来 ,人们对烟气脱硫作出了很大的努力 ,但常见的脱硫技术具有投资大、运行费用高 ,甚至有二次污染等问题。吸附法烟气脱硫工艺简单、脱硫效率高 。

氨法脱硫技术分析

烟气中含有的二氧化硫会对大气环境产生非常严重的污染,严重的破坏生态平衡,并对动植物以及人类的健康产生了极大的危害,还会在很大程度上出现酸雨,对建筑物进行腐蚀与破坏,严重的影响着生态环境与生存环境。为了降低二氧化硫产生的危害,需对烟气进行脱硫处理。

石灰石(CaCO3)的石膏法脱硫技术——在钢厂烧结机上的实际应用的探讨

石灰石—石膏法脱硫法是火力发电厂及钢厂烧结机上脱硫的主要方法之一,它具有技术应用广成熟,原料成本低等多种优点。本文主要详细介绍了石灰石—石膏法脱硫技术的主要原理,以及对其在钢厂烧结机上的实践与应用作出初步探讨。

我国钢铁废气末端治理之脱硫技术类比

随着现代化工业化的发展,钢铁废气末端治理的技术手段也越来越先进,其废弃物中所含二氧化硫导致诸多环境污染问题,是土地酸化的罪魁祸首。现阶段我国钢铁废气的废料残余物中所含的二氧化硫治理是控制土地污染和大气污染问题的重要环节,文章就钢铁废气末端治理的众多脱硫技术进行类比,讨论研究现阶段工业发展收益最高的脱硫技术,分析相关影响和重要性。

Fabrication and characterization of tungsten-containing mesoporous silica for heterogeneous oxidative desulfurization

A series of functional,tungsten-containing mesoporous silica materials（W-SiO2） have been fabricated directly from an ionic liquid that contained imidazole and polyoxometalate,which acted as mesoporous template and metal source respectively.These materials were then characterized through X-ray diffraction（XRD）,transmission electron microscopy（TEM）,Raman spectroscopy,Fourier transform infrared spectra（FTIR）,diffuse reflectance spectra（DRS）,and N2 adsorption-desorption,which were found to contain tungsten species that were effectively dispersed throughout the structure.The as-prepared materials W-SiO2 were also found to possess a mesoporous structure.The pore diameters of the respective sample W-SiO2-20 determined from the TEM images ranged from 2 to 4 nm,which was close to the average pore size determined from the nitrogen desorption isotherm（2.9 nm）.The materials were evaluated as catalysts for the heterogeneous oxidative desulfurization of dibenzothiophene（DBT）,which is able to achieve deep desulfurization within 40 min under the optimal conditions（Catalyst（W-SiO2-20）= 0.01 g,temperature = 60℃,oxidant（H2O2）= 20 μL）.For the removal of different organic sulfur compounds within oil,the ability of the catalyst（W-SiO2-20） under the same conditions to remove sulfur compounds decreased in the order：4,6-dimethyldibenzothiophene Dibenzothiophene Benzothiophene 1-dodecanethiol.Additionally,they did not require organic solvents as an extractant in the heterogeneous oxidative desulfurization process.After seven separate catalytic cycles,the desulfurization efficiency was still as high as 90.3%.From the gas chromatography-mass spectrometer analysis,DBT was entirely oxidized to its corresponding sulfone DBTO2 after reaction.A mechanism for the heterogeneous desulfurization reaction was proposed.

Ultra-deep oxidative desulfurization of fuel with H_2O_2 catalyzed by phosphomolybdic acid supported on silica

A highly active catalyst of phosphomolybdic acid ~HPMo） was prepared and applied in the catalytic oxidative desulfurization （CODS） system. The catalyst was characterized by FT-IR, XRD, XPS and superconducting NMR. The influences of rn（catalyst）/m（oil）, V（H202）fV（oil）, reaction temperature and reaction time on the fractional conversion of benzothiophene （BT） and dibenzothiophene （DBT） were investigated. GC-MS and micra-coulometric methods were employed to investigate the reaction. The catalyst has high desulfurization activity in the removal of BT and DBT under mild conditions. The recycling experiments indicated that DBT and BT removal could still reach 95.2% and 95.7% after 10 cycles.

Lignite oxidative desulphurization. Notice 2： effects of process parameters

The influence of main characteristics upon conversion directions of the lignite organic part during its oxidation desulphurization was studied. The optimum temperature values, the ratio oxidant ： raw material, and time of coal stay in the reaction zone, which provide the maximum degree of sulphur conversion and hydrogen sulphide content in desulphur- ization gases, were calculated. The process implemented under these conditions will decrease environment pollution by sulphur dioxide during further lignite burning at least to 55 %-60 % and utilize sulphur in coal in the form of desul- phurization gases with hydrogen sulphide content of 7 %. Such obtaining sulphur. The effect of the above three factors on the depth was studied. gases can be reprocessed by the known methods of and character of the coal organic matter transformation

Experimental Research on Flue Gas Desulfurization by Superfine Titanium Dioxied

The mechanism of all present adopted desulfurization technologies is chemical reaction. A new kind of desulfurization medium - TiO 2 particle having large fraction void and specific surface area which is made from TiO 2 with superfine size sintered at low temperature and processed with surface activation is tested and investigated. The mechanism of desulfurization is mainly physical adsorption instead of traditional chemical reaction. Four samples of such TiO 2 particles were characterized by advanced instruments and tested for adsorption dynamics at the temperature range of 90?℃ to 240?℃ in a fixed bed. The results show that its adsorption ability for SO 2in flue gas is dependent strongly on three factors: quality of TiO 2particles, adsorption temperature and SO 2 concentration in flue gas. Titanium dioxide has well desulfurization character and pretty good prospect in engineering application. Sintered at temperature range from 440?℃ to 540?℃, it has the best adsorption ability. In practical use the best adsorption temperature is around 120?℃.

Oxidative desulfurization of diesel fuel with caprolactam-based acidic deep eutectic solvents: Tailoring the reactivity of DESs by adjusting the composition

Despite the significance of hydrogen bonding in deep eutectic solvents（DESs） for desulfurization processes, little is understood about the relationship between the DES composition, hydrogen-bonding strength, and oxidative desulfurization activity. In this study, a new family of caprolactam-based acidic DESs was prepared with different molar ratios of caprolactam and oxalic acid. The prepared DESs were characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, 1 H nuclear magnetic resonance, and thermogravimetric analyses. These DESs were employed for oxidative desulfurization reactions and the desulfurization efficiency was found to vary regularly with the DES composition. The factors influencing the removal of dibenzothiophene were systematically investigated and the desulfurization efficiency of the caprolactam-based acidic DESs reached as high as 98% under optimal conditions. The removal of different sulfur compounds followed the order： dibenzothiophene 4,6-dimethyldibenzothiophene benzothiophene. The combined experimental data and characterization results revealed that the oxidative desulfurization efficiency of the system was influenced by the hydrogen bonding interactions with the DES, which can be optimized by adjusting the DES composition. These findings regarding hydrogen bonding in DESs provide new insight for better understanding of the mechanism of diesel deep desulfurization processes.

Carbon Dioxide Captured from Flue Gas by Modified Ca-based Sorbents in Fixed-bed Reactor at High Temperature

Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors： calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350-650 ℃. It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450 ℃. The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299 mg.g-1. The mor- phology of those sorbents was examined by scanning electron microscope （SEM）, and the changes of composition before and after carbonation were also determined by X-ray diffraction （XRD）. Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca（OH）2], and CaCO3 is the main component after carbonation reaction. The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction, and became much denser than before. The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area. lar2er oore volume and anoropriate pore size distribution than that of CaO-CaO and Ca（OH）2-CaO.

Experimental Study on Refinery Gas Desulfurization Using Gas-Liquid Membrane Contactor

Gas-liquid contactors equipped with polytetrafluoroethylene （PTFE） or polypropylene （PP） hydrophobic membranes were applied for removal of sulfur dioxide from refinery gas. Pure water, NaOH solution and MDEA were adopted as the absorbents. The performance of the two kinds of membranes for separation of SO2 was evaluated in terms of the concentration of absorbent solution, the concentration of SO2, and the feed flow rate. The efficiency for removal of SO2 increased with an increasing absorbent concentration. Upon increasing the concentration of SO2 and the feed flow rate, the desulfurization efficiency was decreased.

Separation of Sulfur/Gasoline Mixture with Polydimethylsiloxane/ Polyetherimide Composite Membranes by Pervaporatlon

Worldwide environment has resulted in a limit on the sulfur content of gasoline.It is urgent to investigate the desulfurization of gasoline.The polydimethylsiloxane(PDMS)/polyetherimide(PEI)composite membranes were prepared by casting a PDMS solution onto porous PEI substrates and characterized by scanning electron microscope(SEM).The membranes were used for sulfur removal from gasoline by pervaporation.The effects of feed temperature,sulfur content in the feed and PDMS layer thickness on membrane performance were investigated,and an activation energy of permeation was obtained.Experimental results indicated that higher feed temperature yielded higher total flux and lower sulfur enrichment factor.The total flux varied little with the increase of sulfur content in the feed,but the sulfur enrichment factor first increased with the amount of thiophene added into the gasoline,and then the variation was little.The increase of PDMS layer thickness resulted in a smaller flux but a larger sulfur enrichment factor.The result indicates that the PDMS/PEI composite membranes are promising for desulfurization by pervaporation.

Review on the latest developments in modified vanadium-titanium-based SCR catalysts

Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, insufficient Hg^0 oxidation activity, SO_2 oxidation, ammonia slip, and other disadvantages,modifications to traditional vanadium-titanium-based selective catalytic reduction（SCR）catalysts have been attempted by many researchers to promote their relevant performance. This article reviewed the research progress of modified vanadium-titanium-based SCR catalysts from seven aspects, namely,（1） improving low-temperature deNO_x efficiency,（2） enhancing thermal stability,（3） improving Hg^0 oxidation efficiency,（4） oxidizing slip ammonia,（5） reducing SO_2 oxidation,（6） increasing alkali resistance, and（7） others. Their catalytic performance and the influence mechanisms have been discussed in detail. These catalysts were also divided into different categories according to their modified components such as noble metals（e.g., silver, ruthenium）, transition metals（e.g., manganese, iron, copper, zirconium, etc.）, rare earth metals（e.g., cerium, praseodymium）,and other metal chlorides（e.g., calcium chloride, copper chloride） and non-metals（fluorine,sulfur, silicon, nitrogen, etc.）. The advantages and disadvantages of these catalysts were summarized.Based on previous studies and the author＇s point of view, doping the appropriate modified components is beneficial to further improve the overall performance of vanadium-titanium-based SCR catalysts. This has enormous development potential and is a promising way to realize the control of multiple pollutants on the basis of the existing flue gas treatment system.

Sulfur Dioxide Emission Control,Blockade and Drainage

This paper presents the present status of sulfur dioxide emission from thermal plants in China, tells the main problems existing in its emission control and finally gives out suggestions to the problems, that is, to constitute complete standards and regulations and enhancesupervision accordingly.

Synthesis of Silica-Dispersed NiMo Hydrodesulfurization Catalysts

Silica-dispersed NiMo hydrodesulfurization catalysts were synthesized by the deposition-precipitation method. For comparative purposes, bulk NiMo catalysts were obtained by co-precipitation. The silica-dispersed NiMo catalyst had highly active metals content. Silica was employed to disperse active metals for full utilization of active components. The BET analysis showed that the silica-dispersed NiMo catalysts had a high surface area （147.0 m2/g） and pore volume （0.27 mL/g）, whereas the bulk NiMo catalysts exhibited a very low surface area （87.5 m2/g）. Transmission electron microscopy results proved that the active components were dispersed on the SiO2 substrate. X-ray diffraction patterns of the silicadispersed NiMo catalyst and the bulk NiMo catalyst were indexed to NiMoO4. The hydrodesulfurization activity of silicadispersed NiMo catalysts was much higher than that of reference catalysts and could be up to twice greater than those of commercial NiMo alumina-supported systems per gram of catalyst. The activity testing results also demonstrated that the silica-dispersed NiMo catalyst was an effective hydrodesulflarization catalyst.

Enhanced Performance of Denitrifying Sulfide Removal Process by 1,2-Naphthoquinone-4-Sulphonate

The denitrifying sulfide removal(DSR) process with bio-granules comprising both heterotrophic and autotrophic denitrifiers can simultaneously convert nitrate, sulfide and acetate species into di-nitrogen gas, elemental sulfur and carbon dioxide, respectively, at high loading rates. This study has determined that the reaction rate of sulfide oxidized into sulfur could be enhanced in the presence of 1,2-naphthoquinone-4-sulphonate(NQS). The presence of NQS mitigated the inhibition effects of sulfide species on denitrification. Furthermore, the reaction rates of nitrate and acetate to nitrogen gas and CO_2, respectively, were also promoted in the presence of NQS, thereby enhancing the performance of DSR granules. The advantages and disadvantages of applying the NQS-DSR process are discussed.

Challenges from the New Emission Standards for SO_2 and NO_X

The Emission Standards of Air Pollutants from Thermal Power Plants (GB 13223-2011) prescribe a stricter limitation to air pollutants than ever before. As set in the new emission standard, the limitations of SO2 and NOX for sensitive areas under normal conditions are 50 mg/m3 and 100 mg/m3, respectively. The objective analysis and suggestions are proposed. The recent status and operational experience of desulfurization and denitrification equipment are discussed. From the discussions, thermal power plants face a huge challenge to satisfy the new emission standards. For further reducing of the emission concentrations of SO2 and NOX, three methods were introduced, including: seriously implementing the emission standards, improving treatment equipment, and increasing the efficiencies of desulfurization and denitrification.

Oxidation of Benzothiophenes Using Tert-amyl Hydroperoxide

Homogeneous oxidation using an oil-soluble oxidant, tert-amyl hydroperoxide （TAHP）, for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts. Dibenzothio- phene （DBT）, benzothiophene （BT） and 4, 6-dimethyl-dibenzothiophene （DMDBT）, which are the refractory sulfur compounds for hydrodesulfurization （HDS）, were employed as model substrates for a simulated diesel fuel. Activity of molybdenum oxide supported on a macroporous weak acidic resin was investigated. The mass conversion of DBT reached near 100% at 90℃ and a TAHP/DBT molar ratio of 3 with 1% of molybdenum oxide supported on Amberlite IRC-748 resin for 1 h. It was further found that the activities of the model substrates decreased in the or- der of DMDBT 〉DBT 〉BT. In the flow oxidation using TAHP as the oxidant, mass conversion of DBT increased remarkably from 61.3% to 98.5% when dropping the weight hourly space velocity （WHSV） from 40 h^-1 to 10 h^-1. A series of experiments dealt with selectivity of this oxidation using TAHP revealed that the model unsaturated compounds, i.e. 4, 6, 8-trimethyl-2-nonylene, and 2-methylnaphthalene did not affect the oxidation of DBT. Carbazole had nearly no effect on the conversion of DBT using TAHP, but had some influence on the one using tert-butyl hydroperoxide （TBHP）. The mass conversion of DBT decreased remarkably from 75.2% to 3.6% when the content of carbazole increased from 0 to 500μg·g^-1. In the flow oxidation using TAHP as the oxidant, the concentration of DBT in model fuels was reduced from 500 μg·g^-1 to 7.2 μg·g^-1 at WHSV of 10 h^-1, and then reduced to 3.8 μg·g^-1 by adsorntion of Al2O3.

火电厂烟气脱硫脱硝一体化技术分析

酸雨会产生多种气体,其中包括二氧化硫(SO2)与二氧化氮(NO2)等.SO2会对环境造成污染,同时会危害人们的健康.因此,在火力发电过程中要科学运用脱硫技术,在此基础上减少SO2的排放量.在发电中会形成烟气,其中包含氮氧化物,常见氮氧化物的混合物被称之为硝气,这是对人体有危害的气体,因此要科学处理火电厂的烟气,尽量减少对该类硝气的排放量.在应用脱硫脱硝工艺时,不仅能达到环保的目的,而且还不会对正常发电产生影响.本文对常见的脱硫脱硝一体化方法进行介绍,希望可以为火电厂提供一定的参考.

Desulphurization Technology in China Is Maturing Day by Day

In China, a number of power plants are installed with large imported FGD equipment. As from 1990s, China has built several demonstration projects with wet limestone-gypsum, simplified wet limestonegypsum, spray semi-drying, seawater, LIFAC and EBA processes along with vigorous introduction of foreign FGD equipment and technologies. As seen by FGD projects being under invitation for bid, large-sized units will generally be fitted with limestone-gypsum FGD equipment. Although theefficiency of FGD equipment is being raised rapidly, especially that of limestone/gypsum FGD equipment can reach 90%, such a technology has much room for improvement. In the coming ten years, China should exert itself to institute design and construction specification and standards, improve operation and maintenance techniques and develop new materials, etc.