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.     

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.     

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.     

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.     

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.     

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.     

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.     

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。     

Reaction of SO2 and NO2 with polymers

A number of polymers have been exposed to SO₂ and NO₂ gas under various conditions. Chain scission, crosslinking reactions, and changes in infrared spectra have been noted. All polymers suffer some deterioration, which may be considerable with exposure over long periods of time. Elastomers form a separate group, being appreciably more susceptible to these gases than saturated polymers; however, they are still more sensitive to ozone.     

High-Temperature Crystal Chemistry of Na2SO4–K2SO4 Sulfate System

Glass Physics and Chemistry - In the Na2SO4–K2SO4 system, nine phases are known. In this study, for the first time, the values of the thermal expansion coefficients of continuous...     

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。     

Removal of NO from flue gas by wet scrubbing with NaClO2/(NH2)2CO solutions

The experiments were performed in a countercurrent packed column in a continuous mode to study the absorption of nitric oxide in sodium chlorite/urea solutions. Sodium chlorite mainly works as an agent to oxidize NO to NO₂. A combined SO₂/NO removal system was also tested. On the basis of high SO₂ removal efficiency, the NO removal efficiencies under various experimental conditions were emphatically measured. Among the operating variables such as initial NaClO₂ concentration, urea concentration, temperature and initial pH value, the pH value of the absorbing liquid was found to have a great impact on both NO removal efficiency and NO₂ concentration. NO removal efficiency was increased with increasing NaClO₂ concentration and temperature. Urea almost has no negative effect on NO removal efficiency, however it aids the abatement of NO₂ greatly. The anions in the spent scrubbing liquor were analyzed by ion chromatography.