NOx Analyzer Research Articles

Artificial neural network (ANN) assisted prediction of transient NOx emissions from a high-speed direct injection (HSDI) diesel engine

The understanding and prediction of NOx emissions formation mechanisms during engine transients are critical to the monitoring of real driving emissions. While many studies focus on the engine out NOx formation and treatment, few studies consider cyclic transient NOx emissions due to the low time resolution of conventional emission analysers. Increased computational power and substantial quantities of accessible engine testing data have made ANN a suitable tool for the prediction of transient NOx emissions. In this study, the transient predictive ability of artificial neural networks where a large number of engine testing data are available has been studied extensively. Significantly, the proposed transient model is trained from steady-state engine testing data. The trained data with 14 input features are provided with transient signals which are available from most engine testing facilities. With the help of a state-of-art high-speed NOx analyser, the predicted transient NOx emissions are compared with crank-angle resolved NOx measurements taken from a high-speed light duty diesel engine at test conditions both with and without EGR. The results show that the ANN model is capable of predicting transient NOx emissions without training from crank-angle resolved data. Significant differences are captured between the predicted transient and the slow-response NOx emissions (which are consistent with the cycle-resolved transient emissions measurements). A particular strength is found for increasing load steps where the instantaneous NOx emissions predicted by the ANN model are well matched to the fast-NOx analyser measurements. The results of this work indicate that ANN modelling could strongly contribute to the understanding of real driving emissions.

Development of a 443 nm diode laser-based differential photoacoustic spectrometer for simultaneous measurements of aerosol absorption and NO2

Measurement of ambient aerosol and nitrogen dioxide (NO2) is important as they are major pollutants from the burning of fossil fuel and biomass. In the present work, a differential photoacoustic spectrometer (D-PAS) was developed for simultaneous, online measurements of aerosol optical absorption and NO2 concentration. A novel photoacoustic resonator was designed and employed in the D-PAS for controlling a large flow rate, improving response time, and keeping the flow noise at a low level. The detection limits of 1.0 Mm−1 and 0.87 ppb for aerosol absorption and NO2 concentration measurements were achieved with a lock-in amplifier time constant of 1 s. The D-PAS accuracy was demonstrated by performing a long-time, continuous measurement of aerosol, and NO2 in ambient air. The measured results of NO2 are consistent with the NOx analyzer and environmental monitoring station results.

Nitrous acid formation on Zea mays leaves by heterogeneous reaction of nitrogen dioxide in the laboratory

Nitrous acid (HONO) is of considerable interest because it is an important precursor of hydroxyl radicals (OH), a key species in atmospheric chemistry. HONO sources are still not well understood, and air quality models fail to predict OH as well as HONO mixing ratios. As there is little knowledge about the potential contribution of plant surfaces to HONO emission, this laboratory work investigated HONO formation by heterogeneous reaction of NO2 on Zea mays. Experiments were carried out in a flow tube reactor; HONO, NO2 and NO were measured online with a Long Path Absorption Photometer (LOPAP) and a NOx analyzer. Tests were performed on leaves under different conditions of relative humidity (5–58%), NO2 mixing ratio representing suburban to urban areas (10–80 ppbv), spectral irradiance (0–20 W m−2) and temperature (288–313 K). Additional tests on plant wax extracts from Zea mays leaves showed that this component can contribute to the observed HONO formation. Temperature and NO2 mixing ratios were the two environmental parameters that showed substantially increased HONO emissions from Zea mays leaves. The highest HONO emission rates on Zea mays leaves were observed at 313 K for 40 ppbv of NO2 and 40% RH and reached values of (5.6 ± 0.8) × 109 molecules cm−2 s−1. Assuming a mixing layer of 300 m, the HONO flux from Zea mays leaves was estimated to be 171 ± 23 pptv h−1 during summertime, which is comparable to what has been reported for soil surfaces.

Interference from alkenes in chemiluminescent NO<sub><i>x</i></sub> measurements

Abstract. Nitrogen oxides (NOx=NO+NO2) are critical intermediates in atmospheric chemistry and air pollution. NOx levels control the cycling and hence abundance of the primary atmospheric oxidants OH and NO3 and regulate the ozone production which results from the degradation of volatile organic compounds (VOCs) in the presence of sunlight. They are also atmospheric pollutants, and NO2 is commonly included in air quality objectives and regulations. NOx levels also affect the production of the nitrate component of secondary aerosol particles and other pollutants, such as the lachrymator peroxyacetyl nitrate (PAN). The accurate measurement of NO and NO2 is therefore crucial for air quality monitoring and understanding atmospheric composition. The most commonly used approach for the measurement of NO is the chemiluminescent detection of electronically excited NO2 (NO2∗) formed from the NO + O3 reaction within the NOx analyser. Alkenes, ubiquitous in the atmosphere from biogenic and anthropogenic sources, also react with ozone to produce chemiluminescence and thus may contribute to the measured NOx signal. Their ozonolysis reaction may also be sufficiently rapid that their abundance in conventional instrument background cycles, which also utilises the reaction with ozone, differs from that in the measurement cycle such that the background subtraction is incomplete, and an interference effect results. This interference has been noted previously, and indeed, the effect has been used to measure both alkenes and ozone in the atmosphere. Here we report the results of a systematic investigation of the response of a selection of commercial NOx monitors to a series of alkenes. These NOx monitors range from systems used for routine air quality monitoring to atmospheric research instrumentation. The species-investigated range was from short-chain alkenes, such as ethene, to the biogenic monoterpenes. Experiments were performed in the European PHOtoREactor (EUPHORE) to ensure common calibration and samples for the monitors and to unequivocally confirm the alkene levels present (via Fourier transform infrared spectroscopy – FTIR). The instrument interference responses ranged from negligible levels up to 11 %, depending upon the alkene present and conditions used (e.g. the presence of co-reactants and differing humidity). Such interferences may be of substantial importance for the interpretation of ambient NOx data, particularly for high VOC, low NOx environments such as forests or indoor environments where alkene abundance from personal care and cleaning products may be significant.

Significant influences of TiO2 crystal structures on NO2 and HONO emissions from the nitrates photolysis

The emissions of NO2 and HONO from the KNO3 photolysis in the presence of TiO2 were measured using a round-shape reactor coupled to a NOx analyzer. TiO2 played important roles in the emission flux density of NO2 (RNO2) and HONO (RHONO), depending on crystal structures and mass ratios of TiO2. RNO2 and RHONO significantly decreased with increasing the rutile and anatase mass ratios from 0 to 8 and 0.5 wt.%, respectively. Nevertheless, with further increasing the anatase mass ratio to 8 wt.%, there was an increase in RNO2 and RHONO. RNO2 on KNO3/TiO2/SiO2 had positive correlation with the KNO3 mass (1–20 wt.%), irradiation intensity (80–400 W/m2) and temperature (278–308 K), while it had the maximum value at the relative humidity (RH) of 55%. RHONO on KNO3/TiO2/SiO2 slightly varied with the KNO3 mass and temperature, whereas it increased with the irradiation intensity and RH. In addition, the mechanism for NO2 and HONO emissions from the nitrates photolysis and atmospheric implications were discussed.

Unprecedented Ambient Sulfur Trioxide (SO3) Detection: Possible Formation Mechanism and Atmospheric Implications.

Sulfur trioxide (SO3) is a crucial compound for atmospheric sulfuric acid (H2SO4) formation, acid rain formation, and other atmospheric physicochemical processes. During the daytime, SO3 is mainly produced from the photo-oxidation of SO2 by OH radicals. However, the sources of SO3 during the early morning and night, when OH radicals are scarce, are not fully understood. We report results from two field measurements in urban Beijing during winter and summer 2019, using a nitrate-CI-APi-LTOF (chemical ionization-atmospheric pressure interface-long-time-of-flight) mass spectrometer to detect atmospheric SO3 and H2SO4. Our results show the level of SO3 was higher during the winter than during the summer, with high SO3 levels observed especially during the early morning (∼05:00 to ∼08:30) and night (∼18:00 to ∼05:00 the next day). On the basis of analysis of SO2, NOx, black carbon, traffic flow, and atmospheric ions, we suggest SO3 could be formed from the catalytic oxidation of SO2 on the surface of traffic-related black carbon. This previously unidentified SO3 source results in significant H2SO4 formation in the early morning and thus promotes sub-2.5 nm particle formation. These findings will help in understanding urban SO3 and formulating policies to mitigate secondary particle formation in Chinese megacities.

On-Road NOx and Smoke Emissions of Diesel Light Commercial Vehicles-Combining Remote Sensing Measurements from across Europe.

Light commercial vehicles (LCVs) account for about 10-15% of road traffic in Europe. There have only been few investigations on their on-road emission performance. Here, on-road remote sensing vehicle emission measurements from 18 locations across four European countries are combined for a comprehensive analysis of NOx and smoke emission rates from diesel LCV in the past two decades. This allows differentiating the performance by emission standards, model years, curb weights, engine loads, manufacturers, vehicle age, and temperature, as well as by measurement devices. We find a general consistency between devices and countries. On-road NOx emission rates have been much higher than type approval limit values for all manufacturers, but some perform systematically better than others. Emission rates have gone down only with the introduction of Euro 6a-b emission standards since the year 2015. Smoke emission rates are considered a proxy for particulate emissions. Their emissions have decrease substantially from the year 2010 onward for all countries and size classes measured. This is consistent with the substantial tightening of the particulate matter emission limit value that typically forced the introduction of a diesel particulate filter. The average NOx emission rate increases with engine load and decreasing ambient temperatures, particularly for Euro 4 and 5 emission classes. This explains to a large extent the differences in the absolute level between the measurement sites together with differences in fleet composition. These dependencies have already been observed earlier with diesel passenger cars; they are considered part of an abnormal emission control strategy. Some limited increase of the NOx emission rate is observed for Euro 3 vehicles older than 10 years. The strong increase for the youngest Euro 6 LCVs might rather reflect technology advances with successively younger models than genuine deterioration. However, the durability of emission controls for Euro 6 vehicles should be better monitored closely. Smoke emission rates continuously increase with vehicle age, suggesting a deterioration of the after-treatment system with use.

Anticipatory NH3 injection control for SCR system based on the prediction of the inlet NOx concentration

The anticipatory NH3 injection control strategy with a prediction-assisted feed-forward was proposed to improve the accuracy of the outlet NOx control. The large lag of SCR system was ascribed to the lag duration by flue gas sampling for inlet NOx analysis. A 660 MW power plant equipped tangentially fired pulverized coal boiler was involved in the process of theoretical analysis and engineering application. 22 key running parameters of the studied power plant were determined to influence the inlet NOx concentration of SCR system substantially through the multiple linear regression (MLR) method. Multiple input single output (MISO) model was adopted to predict the non-lag inlet NOx concentration based on a multi layer perception (MLP) model with three hidden layers. An optimization strategy for MISO model application was proposed to improve the prediction accuracy of inlet NOx concentration. The root mean square error (RMSE) was decreased to be 5.52 mg·Nm−3 and the mean absolute percentage error (MAPE) was only 1.12%. The maximum absolute deviation was also decreased by 41.28% compared with the deviation in the direct application case. The average constant control deviation (CCD) of the outlet NOx concentration was calculated to be 2.27 mg·Nm−3 in the case analysis of engineering application. The technology can be developed as a potential strategy for improving the NH3 injection performance of SCR system.

Boiling and drying accident of high-level liquid waste in a reprocessing plant: Examination of the NO2 and NO generation using the simulated waste

ABSTRACT NO2 and NO generated during a boiling and drying accident, which affects the release of volatilized radioactive Ru into the atmosphere, were examined using various samples including simulated high-level liquid waste and a thermogravimetric analyzer. NO2 and NO in the gas flowing out of the analyzer were measured separately using a NOx analyzer equipped with NO2 and NO sensors. The samples were heated to 600°C at constant heating rates of mainly 0.2 and 1°C min−1 that was adopted taking into account the decay heat of high-level liquid waste. It was found that under 180°C some nitrates in the liquid waste mainly separated their nitrate groups as HNO3 without generating NOx (a mixture of NO and NO2) and above 300°C the residual HNO3 in the waste participated in thermal decomposition generating NOx. The generation rates of NO2 and NO were obtained as a function of time using Arrhenius type equations, and the O2 rate was derived from these equations using the stoichiometry of the reactions that generate NO2, NO, and O2.

Microstructure and chemical analysis of NOx and particle emissions of diesel engines

This study was carried out to investigate the micro and chemical structure of particulate matter and nitrogen oxide from motor vehicle exhaust fumes. In this context, particulate matter microstructure was determined with the help of scanning electron microscope; elements such as C, O, N, F, Na, Mg, Br, Al, Si, Hg, S, Pb, Cl, Cd, K, Ca, Ba, Ti, V, Mn, Fe, Ni, V and Zn which constitute the source of pollution were determined by energy dispersive spectrometer; nitrogen oxide compounds were determined with X-ray diffraction spectrometer; and photonic properties were determined by means of photoluminescence spectrophotometer. The data obtained in this study provide important source information to understand the effects of exhaust fume on environmental pollution.

Reactive uptake of NO2 on volcanic particles: A possible source of HONO in the atmosphere

The heterogeneous degradation of nitrogen dioxide (NO2) on five samples of natural Icelandic volcanic particles has been investigated. Laboratory experiments were carried out under simulated atmospheric conditions using a coated wall flow tube (CWFT). The CWFT reactor was coupled to a blue light nitrogen oxides analyzer (NOx analyzer), and a long path absorption photometer (LOPAP) to monitor in real time the concentrations of NO2, NO and HONO, respectively. Under dark and ambient relative humidity conditions, the steady state uptake coefficients of NO2 varied significantly between the volcanic samples probably due to differences in magma composition and morphological variation related with the density of surface OH groups. The irradiation of the surface with simulated sunlight enhanced the uptake coefficients by a factor of three indicating that photo-induced processes on the surface of the dust occur. Furthermore, the product yields of NO and HONO were determined under both dark and simulated sunlight conditions. The relative humidity was found to influence the distribution of gaseous products, promoting the formation of gaseous HONO. A detailed reaction mechanism is proposed that supports our experimental observations. Regarding the atmospheric implications, our results suggest that the NO2 degradation on volcanic particles and the corresponding formation of HONO is expected to be significant during volcanic dust storms or after a volcanic eruption.

New Route to Toxic Nitro and Nitroso Products upon Irradiation of Micropollutant Mixtures Containing Imidacloprid: Role of NOx and Effect of Natural Organic Matter.

In this study, we reveal the capacity of imidacloprid (a neonicotinoid insecticide) to photoinduce the nitration and nitrosation of three aromatic probes (phenol, resorcinol, and tryptophan) in water. Using a gas-flow reactor and a NOx analyzer, the production of gaseous NO/NO2 was demonstrated during irradiation (300-450 nm) of imidacloprid (10-4 M). Quantum calculations showed that the formation of NOx proceeds via homolytic cleavage of the RN-NO2 bond in the triplet state. In addition to gaseous NO/NO2, nitrite and nitrate were also detected in water, with the following mass balance: 40 ± 8% for NO2, 2 ± 0.5% for NO, 52 ± 5% for NO3-, and 16 ± 2% for NO2-. The formation of nitro/nitroso probe derivatives was evidenced by high-resolution mass spectrometry, and their yields were found to range between 0.08 and 5.1%. The contribution of NO3-/NO2- to the nitration and nitrosation processes was found to be minor under our experimental conditions. In contrast, the addition of natural organic matter (NOM) significantly enhanced the yields of nitro/nitroso derivatives, likely via the production of triplet excited states (3NOM*) and HO•. These findings reveal the importance of investigating the photochemical reactivity of water contaminants in a mixture to better understand the cocktail effects on their fate and toxicity.

Effects of Oil Drops and the Charcoal’s Proximate Composition on the Air Pollution Emitted from Charcoal Barbecues

ABSTRACT This research investigated the emission rates (ERs) and emission factors (EFs) of air pollutants generated from charcoal barbecues and the influence of temperature, the charcoal’s proximate composition (moisture, volatile matter, fixed carbon, and ash), and oil drops. Charcoal briquettes, longan charcoal, and binchotan (commonly used for indoor barbecues) were selected for combustion experiments, and the exhaust gas was collected for the analysis of air pollutants, viz., CO, CO2, NOx, hydrocarbons (HCs), benzene, toluene, formaldehyde, acetaldehyde, PM2.5, and trace metals (Al, Cr, Cu, Fe, and Zn). A linear regression model was employed to verify the major factors affecting the EFs. The EFs of HCs measured during the dripping of oil and sauce on the charcoal ranged from 2486.2 to 9305.2 mg kg–1, 76.4–357% higher than those measured during no dripping. For PM2.5, the EFs measured during dripping ranged from 3080.4 to 3926.5 mg kg–1, 8–19 times higher than those measured during no dripping. The EFs of benzene, toluene, formaldehyde, and acetaldehyde also significantly increased during dripping. In addition, increasing the combustion temperature reduced the EFs of HCs, formaldehyde, and CO but increased those of Fe and Zn. The charcoal moisture content was significantly positively correlated with the EF of HCs, whereas the volatile matter content was significantly positively correlated with those of HCs and benzene. Positive correlations existed between the charcoal ash content and the EFs of CO, Fe, and Zn. The fixed carbon content was significantly positively correlated with the EF of CO2 but negatively correlated with those of CO, Al, and Zn.

Trend Analysis of NOX and SO2 Emissions in Indonesia from the Period of 1990 -2015 using Data Analysis Tool

Trend Analysis of NOX and SO2 Emissions in Indonesia from the Period of 1990 -2015 using Data Analysis Tool

The Photocatalytic Activity Of Cement In Reducing Air Pollutants

Air pollution is the major concern in the recent years because of causing imbalance to the ecosystem and also increases global warming and climate change. This paper, tries to investigate the applicability of photo catalytic cement in removing the pollutants under partially controlled and simpler experimental conditions such that it mimics the ideal state of its use, that is the natural open environment where it always is susceptible to complex physical and chemical interactions. It also gives an overview of the concentrations of the contaminants reduced not limiting to NOx residues alone, by employing Ion Chromatography instead of NOx analyzers.

Estimation of NO<sub><i>x</i></sub> and SO<sub>2</sub> emissions from Sarnia, Ontario, using a mobile MAX-DOAS (Multi-AXis Differential Optical Absorption Spectroscopy) and a NO<sub><i>x</i></sub> analyzer

Abstract. Sarnia, Ontario, experiences pollutant emissions disproportionate to its relatively small size. The small size of the city limits traditional top-down emission estimate techniques (e.g., satellite) but a low-cost solution for emission monitoring is the mobile MAX-DOAS (Multi-AXis Differential Optical Absorption Spectroscopy). Measurements were made using this technique from 21 March 2017 to 23 March 2017 along various driving routes to retrieve vertical column densities (VCDs) of NO2 and SO2 and to estimate emissions of NOx and SO2 from the Sarnia region. A novel aspect of the current study was the installation of a NOx analyzer in the vehicle to allow real time measurement and characterization of near-surface NOx∕NO2 ratios across the urban plumes, allowing improved accuracy of NOx emission estimates. Confidence in the use of near-surface-measured NOx∕NO2 ratios for estimation of NOx emissions was increased by relatively well-mixed boundary layer conditions. These conditions were indicated by similar temporal trends in NO2 VCDs and mixing ratios when measurements were sufficiently distant from the sources. Leighton ratios within transported plumes indicated peroxy radicals were likely disturbing the NO–NO2–O3 photostationary state through VOC (volatile organic compound) oxidation. The average lower-limit emission estimate of NOx from Sarnia was 1.60±0.34 t h−1 using local 10 m elevation wind-speed measurements. Our estimates were larger than the downscaled annual 2017 NPRI-reported (National Pollution Release Inventory) industrial emissions of 0.9 t NOx h−1. Our lower-limit estimate of SO2 emissions from Sarnia was 1.81±0.83 t SO2 h−1, equal within uncertainty to the 2017 NPRI downscaled value of 1.85 t SO2 h−1. Satellite-derived NO2 VCDs over Sarnia from the ozone monitoring instrument (OMI) were lower than mobile MAX-DOAS VCDs, likely due to the large pixel size relative to the city's size. The results of this study support the utility of the mobile MAX-DOAS method for estimating NOx and SO2 emissions in relatively small, highly industrialized regions, especially when supplemented with mobile NOx measurements.

On the use of data from commercial NOx analyzers for air pollution studies

Reactive oxidized nitrogen species play a central role in environmental pollution, and long term monitoring is widespread. But conventional NOx (defined as NO + NO2) analyzers employing heated converters respond to many species in addition to the compounds NO and NO2. The response of these instruments to nitric acid, peroxyacetyl nitrate, alkyl nitrates and other oxidized nitrogen species (the sum of these plus NOx is defined as NOy) is well established, but the ratio of NOx to NOy varies widely in time and space making the accuracy of commercial NOx monitors uncertain. Care must be taken when comparing spectroscopic measurements of NO2 or numerical models to output from commercial NOx monitors. Correction factors can be developed for specific conditions, and long term trends can be meaningful. Recent studies comparing modeled NOx to measurements with large interferences can involve errors of a factor of two or more and produce misleading guidance on science and policy; the need for rigorous model evaluation adds urgency to the deployment of “true NOx” monitors.

Association of Plasma Levels of Nitric Oxide Oxidative Metabolites with Acute Stroke in Patients Presenting to the Emergency Department of a Low-Middle Income Country.

Introduction Acute stroke incites an inflammatory reaction in the brain's microvasculature, activating formation of nitric oxide oxidative metabolites, nitrate and nitrite (NOx, collectively), measurable in plasma. Our objectives were to investigate plasma NOx in patients with acute stroke presenting to the Emergency Department (ED) and to determine if it could (i) differentiate between ischemic and hemorrhagic stroke; (ii) predict clinical outcomes. Methods A cross-sectional study was conducted in the ED of Aga Khan University Hospital, from January 1 to December 31, 2016. Participants were enrolled if they had clinical acute stroke with confirmatory brain imaging to differentiate between ischemia and hemorrhage. Clinical demographic information, ancillary blood, and diagnostic specimens were collected as per standard of care since the center follows stroke algorithmic guidelines. Plasma NOx analysis was performed using high performance liquid chromatography. Clinical outcomes were assessed using Barthel Index and Modified Rankin Score. Data was analyzed using SPSS 19 and expressed in medians with interquartile ranges. Nonparametric tests were applied for comparing among groups. Pearson's correlation was used to determine associations with aforementioned stroke severity and disability scales. Results Seventy-five patients were enrolled, with median age of 57 years (IQR 47-66 years), 53 (71%) were males, and 46 (61%) had ischemic stroke. Overall, median NOx was 20.8 μM (IQR 13.4-35.3); there was no statistically significant difference between NOx in ischemic versus hemorrhagic stroke (21.2 μM vs. 17.9 μM; p=0.2). However, there was a significant positive correlation between NOx levels and aforementioned acute stroke scales [r(73)=0.417, p=0.0001], for both. Conclusion Although plasma NOx could not differentiate between ischemia and hemorrhage, higher levels of the biomarker did show associations with poststroke disability scales. Further study with more patients in a multicenter trial is warranted to establish the real biomarker potential of plasma NOx in acute stroke.

Preparation, Characterization and Application on Catalytic Removal of NOx for Ni/Cu/Fe Mixed Metal Oxides

Ni/Cu/Fe mixed metal oxides (Ni/Cu/Fe-MMOs) were prepared by calcination of Ni/Cu/Fe layered double hydroxides (Ni/Cu/Fe-LDHs) precursors. Their composition, structure and morphology were characterized by ICP, XRD, FT-IR, BET and SEM. Ni/Cu/Fe-MMOs were used for catalytic removal of NOx by hydrocarbon. Their catalytic activities were studied by NOx analyzer. The results show that Ni/Cu/Fe-MMOs have homogeneous distribution of hexagon with particles size around 30~50nm and specific surface areas of 10~35 m2∙g–1. Ni/Cu/Fe-MMOs sample with molar ration of Ni/Cu/Fe = 5:1:3 exhibits the highest NOx conversion of 15.3%. Ni/Co/Cu/Fe-MMOs have better catalytic activities than both Ni/Cu/Fe-MMOs and Cu/Co/Fe-MMOs. For Ni/Cu/Fe-MMOs, propene is the better reductant than octane.

Analysis of Influence of Adjusting Air Distribution Mode on Boiler Combustion under Different Loads

In view of the main problems faced by power plants, many scholars in China have focused on the problem of distribution adjustment of secondary air. This paper also conducted research on the adjustment of secondary air distribution. In this paper, a 200MW four-corner tangential boiler of a power plant is taken as the research object, and the overall size of the boiler and the modification of the damper are clarified. The boiler is tested under different loads and different working conditions. Through the inverse balance calculation of boiler thermal efficiency on the SCR inlet NOX analysis, the combination of numerical simulation and test method provides an important reference for the four-corner tangential boiler optimization and variable load operation in the future. At present, the domestic research on the numerical simulation of boiler combustion is mainly to change the different secondary air distribution methods. In this paper, the analysis of the effects of different number of tertiary air nozzles on the combustion of boilers under different loads is studied under the condition of equal secondary air.