The significance of fly ash in wet-dry scrubbing of SO2

A bench scale flue gas desulphurization spray dry scrubbing unit was employed to study the effect of fly ash on the removal of SO₂. The equipment consisted of a spray dryer with and ultrasonic nozzle for atomization and a pulse jet baghouse. The flue gas rate was 1500 l_N/h (dry gas). Four fly ashes, originating from different countries were investigated. The alkalinity and reactivity of the fly ashes were determined in a pH-stat equipment. Pure fly ash removed SO₂ in both the spray dryer and in the baghouse. An increase of humidity divided the fly ashes into two groups. The high calcium fly ash gave a considerably higher SO₂ removal than the medium and low calcium fly ashes which showed similar SO₂ removals. Fly ash did not enhance the removal of SO₂ when added to a lime slurry because lime suppresses the dissolution of the alkali in the fly ashes. The pressure drop build-up in the fabric filter showed a strong dependence on material properties.     

Cansolv[R] SO2洗涤系统在新建冶炼烟气制酸项目中的应用

一套新建的间歇式硫化矿熔炼系统在设计上存在着若干挑战.熔炼炉产生的烟气在极高与极低的二氧化硫浓度之间波动,而硫酸装置需要稳定的烟气流量及二氧化硫浓度,以符合环保法规.采用Cansolv[R]洗涤系统可将间歇操作的熔炼炉与硫酸装置以某种方式整合,从而优化投资并使硫酸装置以放热模式运行.Cansolv[R] SO2洗涤系统可通过改变送入SO2洗涤塔的贫液流量来匹配熔炼炉所产生的SO2量,并利用贫液和富液储槽来均衡送入硫酸装置的SO2流量.进一步优化系统的方法是将流量恒定的冶炼烟气送入硫酸装置,而将流量波动的冶炼烟气通过旁路送入SO2洗涤系统.Cansolv[R]再生塔排出的SO2可确保硫酸装置始终在高于其自热平衡极限的浓度下运行.     

A study on simultaneous removal of NO and SO2 by using sodium persulfate aqueous scrubbing

Nitric oxide(NO) removal and sulfur dioxide(SO_2) removal by sodium persulfate(Na_2S_2O_8) were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO_2 removal are discussed. The effects of temperatures(35–90 °C), Na_2S_2O_8(0.05–0.5 mol·L~(-1)), Fe SO4(0.5–5.0 m mol·L~(-1)) and H_2O_2(0.25 mol·L~(-1))on NO and SO_2 removal were investigated. The results indicated that increased persulfate concentration led to increase in NO removal at various temperatures. SO_2 was almost completely removed in the temperature range of 55–85 °C. Fe~(2+)accelerated persulfate activation and enhanced NO removal efficiency. At 0.2 mol·L~(-1) Na_2S_2O_8 and 0.5–1.0 mmol·L~(-1) Fe~(2+), NO removal of 93.5%–99% was obtained at 75–90 °C, SO_2 removal was higher than 99% at all temperatures. The addition of 0.25 mol·L~(-1) H_2O_2 into 0.2 mol·L~(-1) Na_2S_2O_8 solution promoted NO removal efficiency apparently until utterly decomposition of H2 O2, the SO_2 removal was as high as98.4% separately at 35 °C and 80 °C.     

Trickle‐bed scrubbing of flue gas SO2 using non‐aqueous solvents

Experiments were carried out on the performance of several ketone solvents for the scrubbing of dilute SO₂ from a gas stream and its conversion to sulfuric acid in a trickle‐bed reactor packed with activated carbon. Using a bench‐scale trickle bed packed with a structured packing based on Sulzer static mixers coated with Centaur^TM activated carbon and a Teflon binder, measurements of SO₂ removal, conversion to acid and catalyst productivity showed that all were considerably greater than levels achieved with water flushing. The combination of Teflon‐coated Centaur activated carbon with a non‐aqueous solvent as the flushing agent provided from 10 to 100 times higher catalyst productivity than those obtained with water alone and other activated carbons. Also, the productivities obtained by this combination were up to 40 times higher than the productivity of typical vanadium pentoxide catalyst operating at 350°C to 400°C.     

UV辐照强化NaClO_2溶液脱硝实验研究

NaClO_2具有非常强的氧化性,在湿法脱硝方面具有良好的应用前景,但该方法存在氧化剂成本较高、利用率偏低等不足。针对该问题,文中采用UV对NaClO_2溶液进行辐照预处理,分别研究了NaClO_2浓度、UV辐照预处理时间、溶液初始pH值对NO脱除效果的影响。结果表明:UV辐照可以明显增强NaClO_2溶液的NO脱除率。当UV辐照预处理时间为1 min时,NaClO_2浓度越低,NO脱除强化效果越明显。当NaClO_2浓度为2 mmol/L时,随UV辐照预处理时间的增加,NO脱除率不断提高,且与无UV辐照预处理时相比,NO脱除强化率最高可达87.5%。当UV辐照预处理时间大于5 min时,NO脱除率可达94%以上。UV辐照预处理前溶液pH值对NO脱除率也会有影响,当NaClO_2溶液初始pH值在5—9范围内时,NO脱除率在60%左右,而当pH值降为3时,NO脱除率可迅速提高至75.3%。利用分光光度法测定了NaClO_2光解后主要产物ClO_2的质量浓度。     

Simultaneous removal of SO2, SO3 and H2SO4 mist from the gas after TiO2 calcining

Absorption of SO₂ and SO₃ in the solutions of waste ferrous sulfate (so-called ‘green salt’) and in the spent acid after TiO₂ hydrolysis, at H₂SO₄ concentrations ranging from 0–5 to 15 g/m³ (STP), was studied. The rate of SO₃ absorption has been found to rise linearly with increasing SO₃ concentration in the gas and to be independent on H₂SO₄ concentration in solution. The SO₂ absorption also rises linearly with increasing SO₂ content in the gas, but diminishes as H₂SO₄ concentration increases—an upper limit of 100 g H₂SO₄/kg H₂O is indicated. The initial concentration of the solution must not be higher than 40 g H₂SO₄/kg H₂O.     

K2SO4-Na2SO4系统相变材料的热物性分析

利用已有的热力学数据,对硫酸钠和硫酸钾相变材料的热力学稳定性、饱和蒸汽压等热物性进行了计算分析,探讨了莫来石作为硫酸盐相变材料基体的可行性.由热力学计算和分析可以看出,硫酸钠和硫酸钾在1100℃的高温下发生分解反应的平衡常数都极小,很难发生分解.硫酸钠即使在1200℃的饱和蒸气压也很低,是一种很有前途的相变材料,同时混合熔盐也表现出了非常低的蒸气压,计算数据和实验的热失重分析相吻合.研究结果表明,通过热物性相关参数的设计计算可以为相变储能材料的实际应用提供依据.     

Multilevel surrogate modeling of an amine scrubbing process for CO2capture

Surrogate models provide a powerful method for simplifying calculations within complex simulations. While surrogate models are broadly applied within chemical engineering, little research exists investigating the level of surrogacy's impact on a simplified process model. In this work, artificial neural networks (ANN) and Kriging models are used as surrogate models at the process, process unit, and thermodynamic levels for a CO₂ amine scrubbing process. The surrogated models are evaluated against an Aspen Plus simulation for accuracy, convergence behavior, computational cost, and ability to extrapolate. The thermodynamic and process unit models can better handle discontinuous, non-smooth behavior, and convergence issues in the surrogated truth model, but poor conditioning in the final system of equations results in a lower accuracy and convergence rate than the process level surrogate. Beyond model accuracy, availability of diverse data, intended re-usability, and the desired outputs must be considered when selecting a level of abstraction.     

SO2 Oxidation and H2O-H2SO4 Binary Nucleation by Radon Decay

The oxidation of SO₂ by ·OH radical produced by radon decay and binary nucleation of H₂SO₄-H₂O were studied using a thermal diffusion cloud chamber. A kinetic model was developed to examine the oxidation of SO₂ by ·OH to H₂SO₄ to estimate airborne concentration of the critical species. The kinetic modelling calculations suggested that ·OH radical production is the rate control step among the gas-phase reactions proposed. The experimental results showed that nucleation rates increase with increasing radon and SO₂ concentrations. Two distinct types of nucleation, mist and rain, were observed at different super-saturation in the thermal diffusion cloud chamber. The experimental observations suggest that both SO₂ and H₂SO₄ can cause binary nucleation with water vapor. It is necessary to further distinguish between these two nucleation mechanisms in the future in order to obtain a better understanding of this combined oxidation and nucleation mechanism.     

SO2-Assisted Simultaneous Reduction of SO2 and NO by CO on SnO2-TiO2 Solid Solution

Sn_0.5Ti_0.5O₂ shows excellent catalytic performance both for the CO-SO₂ reaction and the CO-SO₂-NO reaction. At 350 ° C, 525 ppm SO₂/520 ppm NO/2085 ppm CO, SV = 3000 h^-1, the conversion of SO₂ is nearly complete in the CO-SO₂ reaction and above 89% in the CO-SO₂-NO reaction; NO conversion is above 98% in the latter reaction. The selectivities of S and N₂ are both close to 100%. SO₂ shows a significant promoting effect on the activity of the Sn_0.5Ti_0.5O₂ catalyst for NO reduction by CO. Combining transient response experiments, catalytic tests and TPD results, we propose a SO₂-assisted NO-CO reaction concept. The existence of a surface sulfur species, which was formed during the CO-SO₂ or CO-SO₂-NO reaction, is proved by XPS analysis. It is the active site for NO reduction in the CO-SO₂-NO reaction, and through which SO₂ accomplishes its promoter role. On the basis of the results obtained, the SO₂-assisted redox mechanism of simultaneous reduction of SO₂ and NO by CO is proposed.     

Modification of SO4 2--ZrO2 and Pt/SO4 2--ZrO2 properties during n-hexane isomerization

The modification of the textural properties and crystalline structure of SO₄ ^2--ZrO₂ and Pt/SO₄ ^2--ZrO₂ during n-hexane reaction at 473 K and 6 kg cm^-2 has been studied in the presence of either hydrogen or nitrogen. Sulfur content before and after reaction and the amount of coke at the end of the reaction were measured. The coke deposited on the catalysts blocks the pores of small size and decreases the surface area of the used catalysts. After regeneration, surface area is not completely restored. The loss of sulfur during reaction, probably associated to the reaction medium, also produces a decrease in surface area by the collapse of the smallest pores which generates larger ones. The transformation of tetragonal to monoclinic crystalline structure of zirconia begins to occur when sulfur content drops below a critical value. This revised version was published online in July 2006 with corrections to the Cover Date.     

用AgNO3-H2SO4溶液代替Ag2SO4-H2SO4溶液测定水质COD值的可行性探讨

研究了用硝酸银代替昂贵的硫酸银作催化剂,在H2SO4介质中,重铬酸钾回流法测定油田污水COD的新方法.通过t检验,验证该方法与标准法的测定结果一致,精密度符合国家监测标准要求.表明AgNO3可代替Ag2SO4作为重铬酸钾回流法的催化剂测定含油污水的COD.     

富氧燃烧烟气冷凝塔钠碱法脱硫过程SO2和CO2共吸收建模与实验研究

建立SO₂与CO₂共吸收到钠基溶液中的吸收速率模型,假设该模型中SO₂的水解反应为瞬间反应;关于CO₂水解反应存在两种假设：有限动力学假设和瞬间反应假设。由这两种方法计算分别获得SO₂的吸收速率并与完全预混气液反应器中的的动态实验进行对比。采用瞬间反应假设可以预测反应速率的趋势,绝对反应速率误差仍然较大。而采用有限动力学假设的模拟值与实验值在pH>3吻合良好。CO₂对SO₂吸收速率的影响主要通过影响气相传质系数和相同pH下溶液总硫浓度产生。根据CO₂存在与否对SO₂吸收速率的影响,获得五个不同的相互作用pH的区间。pH>11.42时,SO₂/N₂吸收速率大于SO₂/CO₂,主要由于气相传质系数影响;7.8 < pH < 11.42时,SO₂/N₂的吸收速率和SO₂/CO₂吸收速率相似,主要由于气相传质系数和溶液总硫影响抵消;5.41 < pH < 7.8时,SO₂/CO₂的吸收速率相对较高,主要由于溶液总硫影响更大;2.8 < pH < 5.41时,SO₂/CO₂的吸收速率相对较低,主要由于气相传质系数影响;pH < 2.8时,SO₂/N₂和SO₂/CO₂吸收速率相似,主要受液相传质的控制。模拟同时获得不同pH下溶液中碳和硫相关离子的转化规律和SO₂吸收速率的控制步骤,为富氧燃烧冷却塔同时脱硫设备的设计和运行提供参考。     

SO2/O2 dehydrogenation of ethylbenzene

In the SO₂ dehydrogenation of ethylbenzene to styrene using alkalized alumina or titania catalysts, addition of small amounts of oxygen results in (1) higher styrene yields at equivalent SO₂ concentrations, or (2) equivalent styrene yields with lower SO₂ requirements. By staging the oxygen additions, styrene yields of greater than 80% are achieved at SO₂ levels as low as 0.15 mole/mole ethylbenzene when 0.45 mole O₂ is added in increments of 0.15 mole. The low SO₂ concentration and staging of the oxygen result in a high selectivity (94%) for the reaction to styrene by minimizing both byproduct formation and combustion.     

硫酸钾-硫酸-水体系液固相平衡及其应用

在研究30℃下K2SO4－H2SO4－H2O体系相图特性的基础上，探讨了常温下在液相中用水分解硫酸氢钾制取硫酸钾的相平衡原理，并初步拟定了原则流程。研究表明，该流程主要由常温下固体的溶解与液固分离这些技术上非常成熟的单元操作组成，是一种值得研究开发的具有光明前景的新工艺。     

氯化钾硫酸液相转化生产硫酸钾新工艺研究

本文在研究30℃下K2SO4－H2SO4－H2O体系相图特性的基础上，探讨了常温下在液相中用水分解硫酸氢钾制取硫酸钾的相平衡原理，并拟定了原则流程。研究表明，该流程主要是由常温下固体的溶解与液固分离这些技术上非常成熟的单元操作组成，易于实现工业化，是一种值得研究开发的具有光明前景的新工艺。