NOx Emission Model Research Articles

Satellite measurements of daily variations in soil NOx emissions

Soil NOx emission from agricultural regions in the western United States has been investigated using satellite observations of NO2 from the SCIAMACHY instrument. We show that the SCIAMACHY observations over a 2 million hectare agricultural region in Montana capture the short intense NOx pulses following fertilizer application and subsequent precipitation and we demonstrate that these variations can be reproduced by tuning the mechanistic parameters in an existing model of soil NOx emissions.

Modeling of NOx Emissions from the Laboratory Regeneration of Spent Fluid Catalytic Cracking Catalyst

We have collected data on the emissions of NO, HCN, and N2 during the regeneration of spent fluid catalytic cracking catalyst in two different laboratory-scale units. We have developed a model that describes how coke nitrogen is converted into gas-phase nitrogen-containing species during catalyst regeneration. In this model, the combustion of coke causes the volatilization of nitrogen as HCN, which then can be oxidized to NO or hydrolyzed to NH3. In the presence of coke, NO can be reduced to N2; this reaction is accelerated by the presence of CO. Our model accurately describes the main elements of the collected emissions data.

Modelling of NOx and Co Emissions of a Small Gas Turbine Unit Based on Operational Data and Neural Networks

Compact models of NOx and CO emissions of a small gas turbine power plant are discussed, to be used in a plant simulator; the models are based either on semiempirical correlations or neural networks. Experimental data collected during five months of operation are used to calibrate and validate the models. The results obtained with the different models are shown: semi-empirical correlations fail to accurately describe the observed emissions, while neural-network based models perform well, provided their structure is carefully selected.

Fractional conversion of char N to no in an entrained flow reactor

Char samples have been produced, under oxidative pyrolysis conditions, from Australian bituminousand subbituminous coals under high heating rate conditions in an entrained flow reactor. The samples were collected, characterized, and stored under iner gas. The chars were then combusted in the entrained flow reactor, using Ar/O2 mixtures (to eliminate thermal NOx formation and to enable determination of formed N2), and the amounts of NO and N2 produced were determined for a range of temperatures and residence times. The fractional conversion of NO to nitrogen-containing products was determined from the NO and N2 measurements. This is the first time this technique has been applied at this scale to determine the selectivity of char N conversion to NO. It is not possible to discern significant differences between the four chars studied. The results show that, under stoichiometric conditions (=1), char N will be released at a rate determined by the char burnout. An overall fractional conversion of char N to NO of 0.5±0.1 for =1 represents a reasonable summary of the data. Under fuel-lean conditions, fractional conversions as high as 0.7–0.8 are observed, while under fuel-rich conditions, fractional conversions as low as 0.3–0.4 are observed. These results include chars prepared from parent coals with N contents ranging from 1.07 to 2.20 wt. % (dry ash-free basis) and coal types including subbituminous and bituminous. The implications for predictive methods and modeling of NOx emissions are discussed.

A Mathematical Modeling and Validation Study of NOx Emissions in Metal Processing Systems.

The model is based on separate calculations of prompt and thermal NO x and is accomplished using CFD code for flow, temperature and concentration fields in the combustion system. Thermal NO x is calculated with the Zeldovich model. The prompt NO x is considered to be independent of residence time and is computed with detailed kinetic data based GRI-Mech version 2.11 and CHEMKIN code by assuming that every computational cell is a perfectly stirred reactor. Three main parameters are considered to be critical in NO x production: 1) air equivalence ratio, 2) temperature, and 3) mixture dilution with combustion products. All of these parameters and methane oxidation reaction rates are readily available in every cell of the CFD domain. Once NO x emission index is computed by GRI-Mech in every cell, NO x reaction rate is easily evaluated by multiplying it with the methane oxidation reaction rate. The NO x concentration field is then calculated using known CFD transport parameters. Comparison of model predictions with measurements is made for a wide range of industrial natural gas-fired burners installed in combustion chambers and furnaces. The flame temperatures were in the range of 1 400-2 100 K, velocities were in the range of 10-200 m/s, burner nozzles were in the range of diameters 5-550 mm, and the combustion chamber or furnace internal equivalent size in the range of 0.05-3.5 m. Good agreement has been obtained in most cases.

Nonlinear Identification and Adaptive Control of Combustion Engines

Advanced engine control systems require accurate models of the thermodynamic-mechanical process, which are substantially nonlinear and often time-variant. After briefly introducing the identification of nonlinear processes with grid-based look-up tables and a special local linear Radial Basis Function network (LOLIMOT), a comparison is made with regard to computation effort, storage requirements and convergence speed. A new training algorithm for online adaptation of look-up tables is introduced which reduces the convergence time considerably. Application examples and experimental results are shown for a multidimensional nonlinear model of NOx emissions of a Diesel engine, and for the adaptive feedforward control of the ignition angle of a SI engine.

A MLP Prediction Model for Power Plant NOx Emission

In this paper, a MLP (Multi-Layer Perceptron) model is developed for long time period prediction of NOx emission in a coal-fired power generation plant. In order to achieve this purpose, a novel training algorithm is used to improve the generalisation capacity of the model. The application results show the merits of this MLP model.

Modeling of combustion characteristics and NOx emission in highly preheated and diluted air combustion

The gas diffusion combustion in a regenerative furnace with highly preheated and diluted air has been numerically investigated in this paper. The highly preheated air combustion possesses high combustion intensity and high level temperature, but the NO x emission also has an unwanted high level. Decreasing the oxygen concentration in the highly preheated air could decrease the NO x emission and improve the uniformity of temperature distribution in the furnace. The combustion characteristics of highly preheated and diluted air combustion have been studied, including temperature distribution, soot formation, OH radical distribution, as well as NO x emission. The influence of the preheated air temperature, the oxygen concentration, and the air diluent has also been investigated. The optimal combinations of the preheated air temperature and the oxygen concentration have been predicted in the case of flue gas recirculation, which could provide the highest possible temperature in the furnace while keeping the NO x emission lower than the permitted value.

Modelling of Combustion and Emissions for a Cyclic Power Plant

Within a power plant, it is highly desirable to improve efficiency and reduce pollutant emissions. Consequently this interest has led to the modelling of combustion and emissions which can be used for boiler operation and control system design. This paper presents a model of combustion and NOx emissions for a power plant boiler. The major inputs are fuel flow, air flow, and burner tilt positions. The outputs are concentrations of the components in the flue gas. The model is verified by experiments on a 300 MW boiler.

Modelling of NOx Emissions Based on a Fuzzy Logic Neural Network

This paper concerns the process modelling based on fuzzy logic neural networks. Fuzzy systems are implemented in the form of distributed logic processors. Derivatives required by gradient descent training methods are given, and recursive prediction error training method is used to adjust the model parameters. The approach is illustrated with a modelling example where nitrogen emission (x) data from a fluidized-bed combustion district heating plant is used. The method presented in this paper is general, and can be applied to other complex processes as well.

Flamelet and PDF modeling of CO and NOx emissions from a turbulent, methane hydrogen jet nonpremixed flame

Modeling of NO formation in a turbulent, nonpremixed jet flame with a fuel mixture of 31% methane and 69% hydrogen has been performed using the joint scalar probability density function (PDF) approach and the traditional flamelet model. The importance of various effects such as transients, flame interaction, preferential diffusion, and radiative heat loss on NO formation is evaluated by comparisons of predictions with experimental data. The radiative heat loss is included in the PDF approach using the optically thin limit model. A simple model to account for the effect of temperature decrease on thermal NO formation is used in the flamelet model. The model results suggest that radiative heat loss becomes increasingly important for NO predictions in the far field, and it can lower the predicted values by a factor of 3 leading to a better agreement with the experimental data. Preferential diffusion, which is not included in the PDF model, is found to be insufficient to account for the overprediction in the NO levels by the flamelet approach. Comparisons of the predicted CO concentrations from the two models indicate that transient and flame interaction may be important for describing the flame behavior in the near field.

ChemInform Abstract: Modelling of Combustion and NOx Emissions in Industrial Equipment

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Modelling of combustion and NOx emissions in industrial equipment

Abstract

The NOx Emission Levels of Unconventional Fuels for Gas Turbines

An experimentally verified NOx emission model for gas turbines has been reported previously. The model has been modified to determine the NOx emission levels of various fuels as compared to No. 2 distillate oil. The NOx emission levels of various conventional and unconventional gas turbine fuels of interest are predicted. The predicted NOx emission levels for these fuels, including methanol, ethanol, propane, and hydrogen, are in good agreement with available laboratory and field data from stationary, aircraft, and automotive gas turbine combustors. The predicted results should be applicable to other fuel-lean, heterogeneous combustion systems.

A Potential Low NOx Emission Combustor for Gas Turbines Using the Concept of Hybrid Combustion

An experimentally verified NOx emission model has been described previously to predict accurately the NOx emission characteristics of conventional gas turbine combustors as well as laboratory scaled premixed combustor. Experimental data and analyses indicated that a hybrid combustor, which utilizes features of both the conventional and the premixed combustors, has the potential to be a viable low NOx emission combustor. Initial calculations indicated low NOx emission levels for the hybrid combustor. This hybrid combustion concept was tested in the laboratory. The measured NOx emissions from this laboratory-scaled hybrid combustor were in excellent agreement with the analytical predictions. The emissions of carbon monoxide and unburned hydrocarbons were also measured. It has been concluded from an analysis of the measured data that a gas turbine combustor, designed with the hybrid combustion concept, has the best potential to be a near-term viable combustor in meeting the EPA proposed gas turbine emission regulations. The experimental effort thus far has focused on the emission characteristics. Other areas of the design, such as the vaporization of liquid fuels, require additional development work prior to the incorporation of this concept into a viable system for an engine application.

Operating and Ambient Condition Influences on Aircraft Gas Turbine NOX Emissions

This paper deals with a simplified NOx emission model which analyzes the effects of humidity and primary zone flame temperature on the NO formation processes. Ambient temperature and humidity corrections are proposed. Methods of predicting stratospheric NOx emissions and of correcting reduced-pressure combustor rig data to full pressure conditions are also proposed. Emission levels and trends of future combustors designed to minimize N() are examined.