Effect of oxygenated liquid additives on the urea based SNCR process

An experimental investigation was performed to study the effect of oxygenated liquid additives, H₂O₂, C₂H₅OH, C₂H₄(OH)₂ and C₃H₅(OH)₃ on NO_x removal from flue gases by the selective non-catalytic reduction (SNCR) process using urea as a reducing agent. Experiments were performed with a 150 kW pilot scale reactor in which a simulated flue gas was generated by the combustion of methane operating with 6% excess oxygen in flue gases. The desired levels of initial NO_x (500 ppm) were achieved by doping the fuel gas with ammonia. Experiments were performed throughout the temperature range of interest, i.e. from 800 to 1200 °C for the investigation of the effects of the process additives on the performance of aqueous urea DeNO_x. With H₂O₂ addition a downward shift of 150 °C in the peak reduction temperature from 1130 to 980 °C was observed during the experimentation, however, the peak reduction efficiency was reduced from 81 to 63% when no additive was used. The gradual addition of C₂H₅OH up to a molar ratio of 2.0 further impairs the peak NO_x reduction efficiency by reducing it to 50% but this is accompanied by a downward shift of 180 °C in the peak reduction temperature. Further exploration using C₂H₄(OH)₂ suggested that a 50% reduction could be attained for all the temperatures higher than 940 °C. The use of C₃H₅(OH)₃ as a secondary additive has a significant effect on the peak reduction efficiency that decreased to 40% the reductions were achievable at a much lower temperature of 800 °C showing a downward shift of 330 °C.     

Control of combustion-generated nitrogen oxides by selective non-catalytic reduction

Controlling nitrogen oxides (NO(x)) emissions is becoming a daunting technical challenge as increasingly strict emission limits are being imposed. The stringent regulations have prompted the innovation and characterization of NO(x) control technologies suitable for various applications. This paper presents a review on NO(x) removal techniques with particular reference to selective non-catalytic reduction (SNCR) technology. This includes initially how SNCR emerged as a technology along with a comparison with other relevant technologies. A review of various features related to selective non-catalytic gas phase injection of ammonia and ammonium salts (as reducing agent) is presented. The use of urea solution as a reducing agent and its performance in laboratory and pilot scale tests as well as large-scale applications is also discussed. Use of cyanuric acid as a potential reducing agent is also presented. The underlying reaction mechanisms have been reviewed for ammonia, urea and cyanuric acid for the explanation of various observations. Computational fluid dynamics (CFD) modeling as applied to SNCR is also presented. Subsequently the use of SNCR coupled with other in-combustion and post-combustion NO(x) control techniques is elaborated. Additionally, a two-stage NO(x) removal strategy to control un-reacted ammonia slip and to improve overall efficiency is discussed. At the end a summary is given which highlights various areas needing further research.     

Photo-oxidation of NO using an exterior paint--screening of various commercial titania in powder pressed and paint films

The present work aims to evaluate the photocatalytic activity of photo-TiO(2) from various producers (Evonik, Kemira, Kronos, Millennium, Sachtleben and Tayca), in the form of powder pressed films and upon incorporation in a water-based paint, for outdoor NO abatement. The photocatalytic activity of the different samples was evaluated in terms of NO conversion and selectivity towards nitrite and nitrate ions following approximately the ISO 22197-1:2007(E) standard. The highest yields obtained for powder pressed films were achieved with VLP7000 (0.70), followed by VLP7101 (0.55) and UVLP7500 (0.55), all from Kronos. On the other hand, when incorporated in paint films, the highest yields were obtained with PC500 and PC105 from Millennium and UV100 from Sachtleben (ca. 0.15). The paint matrix plays an important role on the photocatalytic activity. In particular, the time for steady state is one or two orders of magnitude higher when the photocatalysts are incorporated in paint films in relation to the powder pressed films. The paint films were activated following the procedure recommended by the above-mentioned standard. However, the photocatalytic activity of films incorporating P25 (Evonik) was displayed only when higher power radiation and higher humidity conditions were used. This allowed for similar levels of photocatalytic activity as the other paint films.     

Performance evaluation of Nahar oil–diesel blends in a single cylinder direct injection diesel engine

This study attempts to use plentiful available high oil content (67% of Nahar seed kernel) non-edible feedstock as a source for powering diesel engine. Various performance and emission characteristics of prepared Nahar oil–diesel blends (5%, 10%, 20%, 30%, and 40%) are analyzed in a single cylinder direct injection diesel engine at different load spectrum, in order to judge the optimum blend, which can be efficiently used in a diesel engine. 10% blending of Nahar oil with diesel fuel has shown a reduction in hydrocarbon and carbon monoxide emission by 8.64% and 8.34%, respectively. With the increase in blend concentration, the nitrogen oxide emission decreased considerably and smoke emission increased slightly. Further pressure crank angle and heat release rate analysis of 10% blending of Nahar oil with diesel confirms its smooth combustion inside the engine combustion chamber.     

Size distributions of fine and ultrafine particles in the city of Strasbourg: correlation between number of particles and concentrations of NO(x) and SO(2) gases and some soluble ions concentration determination

An Electrical Low Pressure Impactor (ELPI) was used during spring and autumn 2003 in the centre of Strasbourg for the measurement of atmospheric aerosols size distribution. The concentration of NO(x) and SO(2) in air was simultaneously measured with specific analysers. Samples were collected in the range 0.007-10 microm in equivalent aerodynamic diameter size. Number distributions are representative of a pollution originating from urban traffic with a particle size distribution exhibiting a nucleation mode below 29 nm and an accumulation mode around 80 nm in size. A mean particle density equal to 39000+/-35000 total particles per cm(3) with a size ranging from 7 to 10 microm was obtained after a sampling period of 2 weeks in spring. About 86.9% of the number of particles have an aerodynamic diameter below 0.1 microm and 13.1% between 0.1 and 1 microm. Correlation coefficients between the number of particles impacted on each ELPI plate and gas concentrations (SO(2) and NO(x)) showed that the numbers of particles with diameter between 0.10 and 0.62 microm are highly related to the NO(x) concentration. This result indicates that particles are traffic induced since NO(x) is mainly emitted by cars as shown by measurements on various sites. Particles are less clearly correlated to the SO(2) concentration. Particle analysis on different ELPI plates for a sampling period of 2 weeks in autumn showed high level of soluble NO(3)(-), SO(4)(2-) and NH(4)(+) ions. Indeed, up to 90% b.w. of these three species were found in the particle range 0.1-1 microm. The formation of particulate NH(4)NO(3) is favoured by high NO(x) concentration, which induces the formation of gaseous HNO(3).     

Thermodynamic and Economic Aspects of the Hard Coal Based Oxyfuel Cycle

The present study shows a new approach in modelling the hard coal fired Oxyfuel Cycle on the whole. The static process model comprises an Oxyfuel combustion principle applied to an existing state-of-the-art hard coal power plant located in Rostock, Germany. It includes the air separation unit and the flue gas liquefaction unit, which are modelled in detail. As one of the main advances to previous work, the closed simulation of all components in one model delivers a coherent solution with a significantly reduced number of assumptions. The model needs no interfaces between different stand alone simulation tools or manual iteration and transfer of internal variables. Results from a thermodynamic and economic feasibility study on this process are shown and areas relevant for future research are identified.

The present study shows the feasibility and prospective key figures of the technology under realistic, comparable and reproducible assumptions and boundary conditions. The basic engineering of the process with a detailed study of the necessary gas separation and flue gas handling technologies is undertaken in the effort to a first stage optimisation of the process.

The flowsheet tool Aspen Plus (TM) was used to simulate the overall process. This particular tool was chosen because it offers an advanced data library on chemical substances and allows the calculation of phase equilibria and real gas behaviour during air separation and flue gas liquefaction. Emissions, coal consumption and investment costs of the Oxyfuel power plant are compared to those of the original state-of-the-art hard coal power plant which is used as the reference case.     

One way to reduce the NOX Emission of biodiesels: The increase of cetane number

Compared to conventional diesel fuels, biodiesels normally have lower smoke and particulate matter, while higher nitrogen oxides (NO_X) emissions. In our study, an attempt was made to reduce the NO_X emissions of biodiesels by increasing the cetane numbers (CNs). Three kinds of biodiesels with extremely high CNs (70.1, 76.9, 80.9, respectively) were developed. Their main physical and chemical properties were tested. With a two-cylinder direct injection diesel engine, their emission performances were experimentally investigated. The results indicate that, CN, freezing point, as well as viscosity of biodiesels are linearly increased with the increase of carbon number. The NO_X emission for biodiesels with high CNs is lower than that of conventional diesel fuels. High CN promotes smoke formation as well while lower smoke emissions are still obtained for biodiesels when certain oxygen contents are present. That is, the smoke/NO_X tradeoff is broken. Besides, as fuel CN is elevated, NO_X for biodiesels decreases but smoke and carbon monoxide emissions are increased.     

减污降碳协同增效的关键路径与政策研究

全面推动实现减污降碳协同增效是新发展阶段我国兑现碳达峰碳中和庄严承诺、深入打好污染防治攻坚战、建设美丽中国的必然要求。环境污染物与二氧化碳排放的高度同源性是实现减污降碳协同增效的理论基础。本文首先就目标指标、管控区域、控制对象、措施任务、政策工具五个方面的协同性系统讨论了减污降碳协同增效的基本内涵。其次,着眼于当前大气环境治理与碳减排在中国的重要性,本文在国家层面讨论了二者的中长期协同控制路线图,阐述了重点协同区域的识别方法和重点部门的协同治理思路,系统提出了大气环境治理与碳减排的协同路径。再次,本文还就“无废城市”建设和生态保护这两个领域与碳减排的协同治理思路展开分析讨论。最后,针对减污降碳协同治理对政策体系的需求,提出了统筹优化减污降碳协同目标、建立协同法规标准、建立减污降碳协同管理制度三个方面的建议。本研究将有助于厘清各方对减污降碳协同增效的认识,对各级政府后续推进减污降碳协同治理工作提供理论和科学基础。     

Emission of CO2, CH4 and N2O from freshwater marsh in northeast of China

The wetlands play an important role in carbon storage, especially at high latitudes, at which they store nearly one-third of global soil carbons. However, few studies have investigated the emissions of CO(2), CH(4) and N(2)O in the long-term, especially effects of freeze-thaw cycles on these gases emissions in freshwater marsh ecosystems. In this paper, we collected greenhouse gas emission data from a freshwater marsh area in China for 4 years, evaluated their release variables and speculated on their potential atmospheric impact. For this paper, we report on the CO(2), CH(4) and N(2)O emission rates recorded from June 2002 to November 2005 in the Sanjiang Plain of northeast China. We measured their interannual variations and fluctuations, as well as factors affecting their emissions, and estimated their regulation and freeze-thaw cycle impacts. Our results revealed obvious CO(2) and CH(4) emission fluctuations during the winter months, and during the freeze-thaw cycle, and a strong interannual variation during the growing season. Overall, we documented a close relationship between the CO(2) and CH(4) emissions, implicating some regulatory commonality. We determined that the marsh was a N(2)O sink during the winter, but a significant source of N(2)O during the freeze-thaw cycle as the temperature increased, especially in early summer. During the thaw-freeze period, the N(2)O levels were positively correlated with the water depth. Additionally, water depth greatly governed the interannual variation of the N(2)O emissions from the marshes during the thaw-freeze period.     

Clove as antioxidant additive in diesel–biodiesel fuel blends in diesel engines

Increased NOx emission from usage of biodiesel is a burning issue to be dealt with. Many techniques have been adopted to reduce NOx emissions from diesel engines. The present experimental study deals with the analysis of performance and emission characteristics of Cotton Seed oil biodiesel with the addition of natural antioxidant extract of clove. FTIR analysis characterized the antioxidant by the presence of hydroxyl groups denoted by the corresponding wave number. The oxidation stability of the test samples was determined in terms of induction period by means of Rancimat test. The induction periods of the test fuel samples B100, B20, B20+CL1000, and B20+CL2000 were found to be 2.20 h, 2.73 h, 10.19 h, and 11.12 h, respectively. Thus, the addition of Clove antioxidant increased the oxidation stability of the biodiesel. Results show that the addition of antioxidant to biodiesel blend has increased the Brake Thermal Efficiency to a maximum of 4.71% and decreased the Brake Specific Fuel Consumption to a maximum of 6.25% at full-load conditions compared to Cotton Seed biodiesel blend. The addition of Clove extract antioxidant at a concentration of 1000 ppm and 2000 ppm decreases the NOx emission by 23.03% and 26.7%, respectively, at full-load conditions. However, CO emissions increased by 1.12% and 4.49% with the addition of CL1000 and CL2000 to B20, respectively. Similarly, HC emissions increased by 4.19% and 7.35% by the addition of CL1000 and CL2000 to B20, respectively. The increases in smoke with the addition of CL1000 and CL2000 to B20 were 42.48% and 47.71%, respectively.     

济宁市区2013-2015年降水中阴离子浓度分析

2013-2015年对济宁市两个点位降水中4种阴离子（氟、氯、硫酸盐、硝酸盐）浓度进行连续监测。结果表明, AQI与氟、氯、硫酸盐和硝酸盐浓度相关系数分别为0.16、0.46、0.52和0.32,呈现一定的正相关性。因采暖期燃煤排放,在采暖期降水中氟、氯以及硫酸盐平均浓度分别高于非采暖期平均浓度26%、38%、35%,靠近燃煤电厂的2^#点位处降水中氟、氯和硫酸盐浓度总体上高于1^#点位。降水中的硝酸盐来自燃煤排放和机动车尾气排放,1^#点位和2^#点位处降水中硝酸盐浓度相差不大。