Soil NOx Emission Prediction via Recurrent Neural Networks

This paper presents designing sequence-to-sequence recurrent neural network(RNN)architectures for a novel study to predict soil NOx emissions,driven by the imperative of understanding and mitigating environmental impact.The study utilizes data collected by the Environmental Protection Agency(EPA)to develop two distinct RNN predictive models:one built upon the long-short term memory(LSTM)and the other utilizing the gated recurrent unit(GRU).These models are fed with a combination of historical and anticipated air temperature,air moisture,and NOx emissions as inputs to forecast future NOx emissions.Both LSTM and GRU models can capture the intricate pulse patterns inherent in soil NOx emissions.Notably,the GRU model emerges as the superior performer,surpassing the LSTM model in predictive accuracy while demonstrating efficiency by necessitating less training time.Intriguingly,the investigation into varying input features reveals that relying solely on past NOx emissions as input yields satisfactory performance,highlighting the dominant influence of this factor.The study also delves into the impact of altering input series lengths and training data sizes,yielding insights into optimal configurations for enhanced model performance.Importantly,the findings promise to advance our grasp of soil NOx emission dynamics,with implications for environmental management strategies.Looking ahead,the anticipated availability of additional measurements is poised to bolster machine-learning model efficacy.Furthermore,the future study will explore physical-based RNNs,a promising avenue for deeper insights into soil NOx emission prediction.

Impact of Aircraft NOx Emission on NOx and Ozone over China

A three-dimensional global chemistry transport model (OSLO CTM2) is used to investigate the impact of subsonic aircraft NOZ emission on NOX and ozone over China in terms of a year 2000 scenario of subsonic aircraft NOX emission. The results show that subsonic aircraft NO* emission significantly affects northern China, which makes NOX at 250 hPa increase by about 50 pptv with the highest percentage of 60% in January, and leading to an ozone increase of 8 ppbv with 5% relative change in April. The NOX increase is mainly attributed to the transport process, but ozone increase is produced by the chemical process. The NOX increases by less than 10 pptv by virtue of subsonic aircraft NOX emission over China, and ozone changes less than 0.4 ppbv. When subsonic aircraft NOX emission over China is doubled, its influence is still relatively small.

Changes in PM2.5 sensitivity to NOx and NH3 emissions due to a large decrease in SO2 emissions from 2013 to 2018

The authors evaluated and compared the behavior of PM2.5 with respect to NOx and NH3 emission changes in high(the year 2013)and low(the year 2018)SO2 emission cases.Two groups of simulations were conducted based on anthropogenic emissions from China in 2013 and 2018,respectively.In each group of simulations,a respective 25%reduction in NOx and NH3 emissions were assumed.A sensitivity factor(β)was defined as the relative change in PM2.5 concentration due to 1%change in NOx or NH3 emissions.In the high SO2 emissions case,PM2.5 was more sensitive to NH3(0.31)emissions change than NOx(0.21).Due to the significant decrease in SO2 emissions from the high to low SO2 emissions case,the sensitivity of PM2.5 to NOx increased to 0.33,while its sensitivity to NH3 decreased to 0.22.The result implies that now and in the future,PM2.5 is/will be less sensitive to NH3 emissions change,while NOx emissions control is more effective in reducing the surface PM2.5 concentration.Seasonally,in the low SO2 emissions case,the sensitivities of PM2.5 to NOx and NH3 in winter were higher than those in summer,indicating that to dealwith severewinter hazemore attention should be paid to the emissions control of inorganic PM2.5 precursors,especially NOx.

Emissions of SO2, NOx and PMs from Cement Plant in Vicinity of Khoms City in Northwestern Libya

Estimated emissions of gases and particulate matter from two Portland cement plants near Khoms city in northwestern Libya by computer simulation reveal that the SO2, NOx and dust emissions exceed selected international standard limits. The results highlight the need for improved operational procedures to minimize emissions and avoid any possible adverse environmental effects.

基于神经网络的重型车辆远程监控NOx传感器露点保护过程数据修复方法

为解决重型车辆远程监控数据中NOx传感器露点保护过程的数据无效问题,利用一辆国六重型车辆的PEMS测试对露点保护期间的高NOx排放问题进行探究,验证了利用神经网络算法修复数据和提高远程监测数据利用率的可行性。结果表明,NOx传感器露点保护过程会导致30%以上的NOx排放量未被统计;在露点保护期间,超过90%的数据显示车辆速度低于54 km/h、发动机冷却液温度低于82℃、SCR入口温度低于245℃、SCR出口温度低于225℃。神经网络算法可有效修复露点保护过程中失效的NOx测量值,对发动机原始排放和车辆尾管排放的累计排放量误差都在4%以内。

基于某装载机高原环境下NOx排放的模拟研究

为了探讨工程机械在高原环境下的燃烧排放特性,本文以某装载机柴油发动机为原型,建立高原环境下的数值计算模型,研究该柴油机在高原环境下的燃烧排放特性。结果表明:NOx的产生与发动机缸内温度密切相关。且当发动机转速不变时,随着海拔的上升,发动机NOx的排放有着先上升后下降的趋势;当海拔不变时,发动机转速提高,其NOx的排放也逐渐增加。

Study on effect of heat transfer space non-uniformity of combustion chamber components on in-cylinder NOx emission formation in internal combustion engine

The components of combustion chamber (cylinder head-cylinder liner-piston assembly-oil film) were taken as a coupled body.Based on the three-dimensional heat transfer numerical simulation of the coupled body,a coupled three-dimensional calculation model for in-cylinder working process and the combustion chamber components was built with domain decomposition and boundary coupled method,which implements the coupled three-dimensional simulation of in-cylinder working process and the combustion chamber components.The model was applied in the influence investigation of the space non-uniformity in heat transfer among combustion chamber components on the generation of in-cylinder emissions:NOx.The results showed that the heat transfer space non-uniformity of combustion chamber components directly influences the formation of in-cylinder NOx.The main area being influenced was the accessory area on the wall,while the influence on the generation of NOx in the central area couold be omitted.

Numerical Study on NOx Emissions of Methane Re-Combustion in a 600 MWe Coal-Fired Boiler

The fuel staging combustion technology is a promising low NOx combustion technology for coal-fired boiler. In order to reduce NOx emissions, the burners of a 600?MWe coal-fired boiler are retrofitted in which methane gas is selected as a secondary fuel for re-combustion. The CFD models of combustion process are built to investigate?effects of the methane gasratio on combustion process and NOx emissions. A total of 4 cases are numerically studied, including the pure coal combustion case, the coal combustion with 7.5%, 10%, 12.5% of methane gas re-combustion cases respectively. The results show that the re-combustion of methane can reduce the temperature at primary combustion zone, but increase the temperatures at the re-combustion area and the furnace outlet. The NOx concentration at the furnace outlet reduces with the increasing methane gas ratio.?Methane re-combustion can greatly benefit to the NOx emissions reduction.

Angle Scattering Method for Soot Concentration Measurement under Ultra-Low Emissions Condition

Aiming at the problem of soot concentration measurement under ultra-low emission conditions,a forward small angle soot concentration measurement method is proposed.Taking a typical boiler emission of 0.1μm-3.0μm bimodal distribution soot as an object,the particle scatter simulation calculation under different parameters is carried out,and the influence of detection angle and particle size on the angular scatteringmeasurement of ultra-low emission soot is analyzed.The influence of detection angle and particle size on the angular scatteringmeasurement of ultra-lowemission soot is analyzed.Preferably,thewavelength of incident light is 650 nm,and the forward detection angle parameter is 15◦for the design of forward small angle soot concentration measurement system.An experimental system for measuring soot with standard concentration is built.Experiments of particle concentration measurement of 1.0μm and 3.0μm under ultra-low emission conditions are carried out.The results show that the average deviation of soot concentration measurement is less than 0.10 mg/m3 under the condition of ultra-low emission by using 15◦of forward detection,which provides an effective way for monitoring ultra-low emission soot concentration in coal-fired power plants.

Re-understanding and Thinking about Environmental Impact of Coal-fired Power Plants under Ultra-low Emission

From the perspective of development background,concepts and related policies of ultra-low emission,according to work practice,some issues and difficulties that need to be paid attention to in the environmental impact assessment of ultra-low-emission thermal power projects were discussed from the aspects of evaluation criteria,evaluation grade and scope,pollution control technical lines,environmental benefit accounting,and total emission control,and corresponding recommendations were put forward.

Combined Effect of a Catalytic Reduction Device with Waste Frying Oil-Based Biodiesel on NOx Emissions of Diesel Engines

Internal combustion engines with application in automobiles and other relevant industries constitute significant environmental pollution via the release of toxic exhaust gasses like carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM), and nitrogen oxide (NOx). Engine researchers and manufacturers are challenged to develop external and internal measures to ensure environmentally friendly solutions to accommodate and conform to the growing list of emission standards. Therefore, this work presents an experimental investigation of the NOx emission profile of a diesel engine that is fuelled and fitted with waste frying oil-based biodiesel and catalytic converter. Using a single-cylinder, four-stroke air-cooled CI engine at a constant speed of 1900 rpm and different loadings of 25%, 50%, 75%, and 100%;fitted with a catalytic converter at the exhaust outlet of the engine and linked to a dynamometer and a gas analyser, an experiment was conducted at biodiesel/diesel volume blends of B0 (0/10), B5 (5/95), B20 (20/80), B30 (30/70), B70 (70/30), B100 (100/0);and 30% concentration (v/v), 0.5 litre/hr flow rate of aqueous urea from the catalytic converter. The results show an increasing NOx emission as the biodiesel component increased in the blend. The catalytic converter showed a downward NOx reduction with a significant 68% reduction in efficiency at high exhaust gas temperatures. It is concluded that the combined utilisation of waste frying oil-based biodiesel and the catalytic converter yields substantial NOx emission reduction.

基于智能算法的重型车辆NOx排放量预测方法

重型车辆NOx排放量的传统预测方法中,由于没有利用误差反馈来修正预测算法,导致预测出的NOx排放量数据与真实数据相差较大。为此提出基于智能算法的重型车辆NOx排放量预测方法。收集大量的重型车辆真实的NOx排放数据,计算出重型车辆NOx综合排放因子,基于智能算法构建BP人工神经网络,设置隐含模式的工作层,输入收集到的真实数据对智能算法进行训练,利用BP神经网络误差反传的功能对每个数据对进行训练,通过误差反馈修正算法的预测误差。设计道路预测实验,将基于智能算法得出的重型车辆NOx排放量数据与真实排放量数据进行对比,得出两者数据结果高度一致的结论,表明该方法的预测数据误差较小,能够进行有效的重型车辆Nox排放量预测。

带式焙烧机球团NOx超低排放技术研究现状与展望

总结了带式焙烧机NOx的产生机制,揭示了带式焙烧机产生NOx的主要因素,探索从焙烧过程中可降低NOx产生的措施;并结合最新烟气强化脱硝技术和强化手段,为带式焙烧机烟气脱硝技术改造做理论支持和铺垫。

Effect of Light Quality and Intensity on N_2O and NO_X(NO, NO_2)Emissions from Rice Phyllosphere and Roots at Tillering Stage in a Liquid Culture Medium System

[Objective] N2Oand NOX（NO, NO2） are important nitrogen oxides gases（NOGs） in paddy fields, and rice plants play important roles in NOG emissions in paddy fields. However, the source of NOG emissions from rice phyllosphere and roots and their relationship to light quality and intensity still remain unclear. In this study, the relationship between light quality, intensity and N2 O, NOX（NO, NO2） emissions from rice phyllosphere and roots at tillering stage was investigated to clarify the contribution of rice plants to N2Oand NOX（NO, NO2） emissions and analyze the mechanism of light control, aiming at providing a scientific basis for revealing how light-control technology affects NOG emissions from rice at tillering stage in paddy fields. [Method] In this study, nitrogen content was controlled by a hydroponic system. A small electric incubator was used for light control. A simultaneous determination was designed to investigate the effect of different weak light qualities（yellow, green, white, red and blue lights） and intensities（dark, 0 lx; very weak, 2 000lx; weak, 4 000 lx; moderate, 6 000 lx; strong, 8 000 lx） on N2Oand NOXemissions from rice phyllosphere and roots at tillering stage in a liquid culture medium system. N2Oconcentration in air samples was determined by gas chromatography within 12 h, and NOX（NO, NO2） concentration was analyzed using 42 i NO- NO2-NOXgas analyzer. [Result] The results showed that：（1） Under a constant nitrogen condition（NH4NO3-N, 90 mg/L） when rice seedlings were treated with moderate（6 000lx） and strong（8 000 lx） light, the average emission rate of N2Oand NO from rice phyllosphere at tillering stage was 27.08, 32.33 μg/（pot·h） and 0.114, 0.057 μg/（pot·h）,respectively, accounting for 57.38%, 58.65% and 9.65%, 4.52% of the total release of N2Oand NO from the whole rice plant, respectively. It implicated that rice phyllosphere is an important source of N2Oemission at tillering stage in paddy fields.（2）When rice seedlings were treated with yellow, green, white, red and blue LED lights under a constant light intensity（1 600 lx）, the average emission rate of N2Ofrom rice phyllosphere was 6.83, 9.40, 9.73, 2.82 and 4.08 μg/（pot·h）, respectively. Compared with green and yellow LED lights, N2Oemission from rice phyllosphere and roots at tillering stage was inhibited markedly by red（3 000 lx） and blue（2 500 lx）LED lights（P0.01）. In addition, NO emission from rice phyllosphere was enhanced significantly by white and red LED lights, while NO emissions from rice phyllosphere and roots were inhibited by blue light synchronously. Nevertheless, no evident NO2 emission from rice phyllosphere and roots was detected under the same condition.（3） Within the range of 0-8 000 lx, NO and N2Oemissions from rice roots and N2Oemission from rice phyllosphere increased with the enhancement of light intensity. In contrast, NO emission from rice phyllosphere was inhibited remarkably by moderate（6 000 lx） and strong（8 000 lx） light（P〈 0.01）. [Conclusion] Rice seedlings mainly exhibited net emissions of NO2 from the phyllosphere and roots.N2Oand NOX（NO, NO2） emissions from rice phyllosphere and roots at tillering stage could be inhibited by adjusting the composition of visible light（synchronously increasing the proportions of red and blue lights） and appropriately controlling daytime light intensity.

On Countermeasures and Suggestions to Control NO_X Emissions from Utility Boilers

In combination with low NOX combustion techniques inChina and in view of limits of the Standard of Discharging Atmo-spheric Pollutants from Thermal Power Plants to be published soon,this paper presents corresponding technical countermeasures andkey subjects to be studied.

基于BWOA-GAM-BiGRU的火电厂SCR系统出口NOx排放预测

提出了一种基于数据驱动结合全局注意力机制与双向门控循环单元深度神经网络的选择性催化还原系统出口NOx排放预测模型,并使用黑寡妇优化算法对网络超参数进行自动寻优。对某300MW电厂选择性催化还系统的历史运行数据进行深度挖掘,确定模型输入变量并校准各输入变量与NOx排放量之间的时延并重构样本序列。实验结果显示,所提出模型的预测结果比典型预测模型具有更高预测精度和更好的泛化能力。

Distribution and bioavailability of mercury in size-fractioned atmospheric particles around an ultra-low emission power plant in Southwest China

Ultra-low emission(ULE)technology retrofits significantly impact the particulate-bound mercury(Hg)emissions from coal-fired power plants(CFPPs);however,the distribution and bioavailability of Hg in size-fractioned particulate matter(PM)around the ULE-retrofitted CF-PPs are less understood.Here,total Hg and its chemical speciation in TSP(total suspended particles),PM_(10)(aerodynamic particle diameter≤10μm)and PM_(2.5)(aerodynamic particle diameter≤2.5μm)around a ULE-retrofitted CFPP in Guizhou Province were quantified.Atmospheric PM_(2.5)concentration was higher around this ULE-retrofitted CFPP than that in the intra-regional urban cities,and it had higher mass Hg concentration than other sizefractioned PM.Total Hg concentrations in PM had multifarious sources including CFPP,vehicle exhaust and biomass combustion,while they were significantly higher in autumn and winter than those in other seasons(P<0.05).Regardless of particulate size,atmospheric PM-bound Hg had lower residual fractions(<21%)while higher HCl-soluble fractions(>40%).Mass concentrations of exchangeable,HCl-soluble,elemental,and residual Hg in PM_(2.5)were higher than those in other size-fractioned PM,and were markedly elevated in autumn and winter(P<0.05).In PM_(2.5),HCl-soluble Hg presented a significantly positive relationship with elemental Hg(P<0.05),while residual Hg showed the significantly positive relationships with HCl-soluble Hg and elemental Hg(P<0.01).Overall,these results suggested that atmospheric PM-bound Hg around the ULE-retrofitted CFPP tends to accumulate in finer PM,and has higher bioavailable fractions,while has potential transformation between chemical speciation.

Advances in reduction of NO_x and N_2O emission formation in an oxy-fired fluidized bed boiler

Fossil fuel combustion is one of the major means to meet the mounting global energy demand. However, the increasing NO_x and N_2 O emissions arising from fossil fuel combustion process have hazardous effects. Thus, mitigating these gases is vital to attain a sustainable environment. Interestingly, oxy-fuel combustion in fluidized bed for carbon capture and minimized NO_x emissions is strongly sustainable compare to the other approaches. It was assessed that NO_x formation and fuel-N conversion have significant limitation under oxy-fluidized bed compared to air mode and the mechanism of NO_x formation is still deficient and requires further development. In addition, this review paper discussed the potential of primary measure as low emission process with others supplementary techniques for feasible NO_x reduction. The influences of combustion mode, operating parameters, and reduction techniques such as flue gas recirculation, oxygen staging, biomass co-firing, catalyst, influence of fluidized bed design and structure, decoupling combustion and their merges are respectively evaluated. Findings show that significant minimization of NO_x emission can be achieved through combination of primary and secondary reduction techniques.

NO_x emission model for coal-fired boilers using partial least squares and extreme learning machine

To implement a real-time reduction in NOx,a rapid and accurate model is required.A PLS-ELM model based on the combination of partial least squares(PLS)and the extreme learning machine(ELM)for the establishment of the NOx emission model of utility boilers is proposed.First,the initial input variables of the NOx emission model are determined according to the mechanism analysis.Then,the initial input data is extracted by PLS.Finally,the extracted information is used as the input of the ELM model.A large amount of real data was obtained from the distributed control system(DCS)historical database of a 1 000 MW power plant boiler to train and validate the PLS-ELM model.The modeling performance of the PLS-ELM was compared with that of the back propagation(BP)neural network,support vector machine(SVM)and ELM models.The mean relative errors(MRE)of the PLS-ELM model were 1.58%for the training dataset and 1.69%for the testing dataset.The prediction precision of the PLS-ELM model is higher than those of the BP,SVM and ELM models.The consumption time of the PLS-ELM model is also shorter than that of the BP,SVM and ELM models.

Extra Low NO_x Emission Furnace with HTAC Technology

HTAC (High Temperature Air Combustion) technology needs high temperature air and low oxygen atmosphere to complete its unique combustion and achieve extra low NOx production. In order to apply HTAC technology to forge furnace and meet the NOx emission standard, exhaust gas regeneration technology in combination with no-fuel-switch and U-shape air circulation methods was applied on forge furnace. The results show that extra low NOx emission (NOx = 2.9 x 10(-5), in volume fraction) could be obtained, the NO, emission meets the standards of Japan and US, HTAC mechanism is discussed finally.