Ammonia Injection Research Articles

Negative effect of industrial waste residue additives (IWRA) on NOx reduction by selective non-catalytic reduction (SNCR) in cement plant: A comparison between copper slag and iron-ore slag

The rapid development of cement plants necessitates the involvement of IWRA to improve the production performance of cement, which leads to the suppression of SNCR de-NOx process. However, the specific performance and mechanism of iron-rich waste materials on SNCR remain unclear. This study specifically addresses the effects of iron-ore slag (Fe2O3) and copper slag (Fe3O4) on the SNCR de-NOx process using fixed bed reactor in a simulated precalciner atmosphere ranging from 400 to 1000 °C. The results show that iron-ore slag had a strong inhibitory effect on the SNCR de-NOx process at low-medium temperatures (400 ∼ 800 °C), whereas copper slag could promote the NOx reduction reactions under slightly excessive NH3/NO ratio (NSR) conditions (NSR = 1.3). Both types of slag exhibited a more significant restraining effect on SNCR as ammonia concentration increased. In addition, the influence of trace elements in IWRA is not significant, which proved IWRA has incomparable substitutability and better economy than traditional catalysts. Consequently, these findings offer theoretical guidance for the subsequent implementation of IWRA in actual cement production processes. Additionally, it is advisable to avoid using Fe2O3-containing IWRA and ensure that ammonia injection points are positioned in the high-temperature region (900 ∼ 1000 °C) to achieve higher de-NOx efficiency.

EXPERIMENTAL STUDY ON FLASH BOILING SPRAY OF HIGH-PRESSURE LIQUID AMMONIA JET WITH ROUND AND ELLIPTICAL HOLE NOZZLES

Ammonia is an ideal alternative fuel for mitigating carbon emissions. High-pressure direct injection of liquid ammonia (LNH<sub>3</sub>) offers significant advantages in enhancing energy efficiency and minimizing emissions. Due to the high saturation vapor pressure, the injection of LNH<sub>3</sub> is susceptible to flash boiling. In this study, we used high-speed micro-imaging technology with backlight lighting to establish a high-pressure common-rail LNH<sub>3</sub> jet experimental platform and investigate the flash boiling spray characteristics of nozzles with round and elliptical holes. The results demonstrated that under non-flash boiling conditions, the residual LNH<sub>3</sub> in the sac chamber and nozzle can rapidly corrode the acrylic material of the nozzle, leading to deformation and failure of the nozzle structure. Under flash boiling conditions, LNH<sub>3</sub> ejected from the hole will produce spherical macroscopic spray morphology. Then, the spray gradually transitions from an elliptical profile to a conical profile as the back pressure increases. Compared to nozzles with round holes, nozzles with elliptical holes exhibit higher flow velocity, which enhances oil-gas mixing and promotes more pronounced flash boiling phenomena. Flash boiling occurs at an earlier stage with an increase in the spray cone angle, thereby improving the atomization characteristics under both flash and non-flash boiling conditions. The tail jet of nozzles with elliptical holes terminates earlier while exhibiting a higher decrease rate in the average gray value, which improves the atomization quality in the tail spray stage and meets the requirements of timing, quantification, and precise control of the fuel injection system.

A multi-indicator prediction method for NOx emission concentration and ammonia escape value for cement calciner system

It is particularly important to accurately predict NOx emission concentration in cement production. As the cement industry is a process industry, there are many chemical reactions, coupling of front and back processes, and large fluctuations in production, resulting in time-delayed denitration data, strong coupling, and uncertainty, which makes it difficult to adequately extract the characteristics of the denitration data to achieve accurate prediction of NOx concentration. At the same time, excessive ammonia is used in production to reduce NOx concentration, resulting in increased ammonia escape and secondary hazards to the environment, therefore it is necessary to perform accurate multi-step prediction of NOx concentration and ammonia escape. To address these issues, this paper presented a new multicriteria deep learning hybrid model MI-ITBA. The model is constructed by connecting an improved causal dilated temporal convolutional network (ITCN) with bidirectional gated recurrent units (BiGRU) and a special attention mechanism, which enhances the ability to extract features from denitration sequence, using the attention mechanism to weigh the importance of different time steps and highlight the influence of key features on the prediction results. In addition, the time series (TS) of denitration containing time-delay information is designed in the input of the model to minimize the influence of time delay. Dynamic information support for denitration control was provided by multi-step prediction of NOx concentration at seven moments and ammonia escape value at three moments to retain the dynamics of the data. Compared with TCN, BiGRU, and TCN-BiGRU, MI-ITBA has a high prediction accuracy, which can provide an effective guide to realizing NOx emission reduction and accurate ammonia injection.

Numerical analysis and optimization of combustion and emissions in an ammonia-diesel dual-fuel engine using an ammonia direct injection strategy

To reduce greenhouse gases in accordance with stringent emission regulations, interest in ammonia, a carbon-free fuel, is increasing in the heavy-duty engine industry. Pre-mixed ammonia-diesel dual-fuel combustion showed better results than diesel combustion in efficiency and greenhouse gas emissions, but NO and unburned NH3 levels were significant. Therefore, a liquid ammonia direct injection strategy should be considered, and that requires detailed combustion and emission formation process analyses. Therefore, in this study, a numerical analysis of the direct injection ammonia-diesel combustion process was conducted, and an optimal injection strategy was sought. Compensating for the slow flame speed of ammonia by supplying additional momentum to the ammonia through direct injection could improve combustion characteristics. Furthermore, NO removal could be promoted by widening the thermal DeNOx reaction region compared to that in pre-mixed ammonia-diesel combustion. At injection timing was −7 CAD for the ammonia injection and −15 to −10 CAD for the diesel injection, the efficiency increased by 8 %, NO emissions were reduced by up to 13.5 %, and GHG emissions were reduced by about 91 % compared with diesel alone. In addition, unburned ammonia was reduced to least 58.4 ppm, a significant improvement over pre-mixed ammonia combustion.

Combustion of liquid ammonia and diesel in a compression ignition engine operated in high-pressure dual fuel mode

This study investigates the characteristics of a compression ignition engine fuelled by ammonia and diesel in high-pressure dual fuel mode. The study focuses on the effect of injection strategies on engine performance and important emissions like NH3, NO/NO2 and N2O. The engine was operated with fixed intake air conditions and at an engine speed of 1500 rpm for all operating points, and liquid ammonia was directly injected at 180 bar using a GDI injector. The ammonia energy shares tested were 40 %, 50 % and 60 %. Various combustion modes were achieved by fixing the diesel injection timing at −15 CAD aTDC and varying the ammonia injection timing between -80 and 2.5 CAD aTDC. Injecting ammonia early (-80/-60 CAD aTDC) led to premixed-type combustion with very high ammonia slip (65 %). Delaying the ammonia injection to -30 CAD aTDC, i.e. 15 CAD before the diesel injection, yielded a very long ignition delay due to the strong influence of the ammonia injection on the diesel injection, resulting in premixed combustion of ammonia and diesel. Injecting ammonia simultaneously or after diesel did not affect the diesel ignition, yielding stable combustion where the ammonia burned during the mixing-controlled phase. Temporally overlapping injections of ammonia and diesel resulted in the highest combustion efficiency, lowest ammonia slip, highest NOx emissions, and lowest N2O emissions, i.e., the optimal cases found. For temporally overlapping ammonia and diesel injections, extending the ammonia injection to after the end of diesel injection was found to increase ammonia slip compared to injecting ammonia before diesel, due to the limited time for liquid ammonia to vaporise, mix and combust in the expansion stroke. The NOx and N2O emissions were found to have opposite trends, where the highest NOx and lowest N2O concentrations were achieved for the operating points with the highest combustion efficiency. Delaying the combustion phasing improved the combustion efficiency for the 40 % and 50 % ammonia energy share cases, while for the 60 % cases, it deteriorated, which can be explained by the injection of ammonia after the end of diesel injection for the 60 % ammonia energy share cases.

A multi-laser hybrid absorption sensor for simultaneous measurement of NH3, NO, and temperature in denitrification flue gas

The real-time monitoring of NH3, NO, and flue gas temperatures is critical to controlling NOx emissions from coal-fired power plants, reducing ammonia slip, and realizing accurate ammonia injection. However, few previous studies have utilized laser absorption sensors to measure these three indicators simultaneously. In this paper, a multi-laser hybrid sensor is designed based on tunable diode laser absorption spectroscopy (TDLAS) for simultaneous measurement of NH3, NO, and flue gas temperature. The sensor uses a distributed feedback (DFB) laser to target the NH3 and the H2O lines, and a quantum cascade laser (QCL) is used to target the NO line. In the measurements of NH3 and NO using calibration-free wavelength-modulated spectroscopy (CF-WMS), we employ a method to obtain the laser wavelength response by fitting the demodulated signal of a standard gas. Additionally, temperature measurements are obtained using the time-division multiplexing (TDM) strategy and direct absorption spectroscopy (DAS) techniques with the help of the absorption spectrum of H2O. Under static conditions, the relative accuracy of NH3 and NO detected by the sensor is 4.2% and 2%, respectively, and the maximum relative standard deviation of temperature is 1.3%. When tested under flowing conditions, the sensor can accurately capture NH3, NO, and temperature changes. The relative accuracy of NH3 and NO is 4.7% and 2.2%, and the relative standard deviation of temperature is 0.9%. The sensor has great potential in optimizing denitrification processes in thermal power plants.

Evaluation of coal ammonia flames using a non-adiabatic three mixture fraction flamelet progress variable approach

A highly resolved large eddy simulation (LES) modeling of the co-firing of ammonia with pulverized coal in a single-burner test furnace of the Central Research Institute of Electric Power Industry (CRIEPI) has been performed using a non-adiabatic three mixture fraction flamelet/progress variable (3Z-FPV) approach. To parametrize the thermochemical space, a six-dimensional tabulation method based on non-premixed flamelets is introduced, which uses three mixture fractions, for ammonia, coal volatiles, and char-off gases, respectively, as well as variance of mixture fraction, reaction progress variable, and total enthalpy. The accuracy of non-adiabatic model has been tested by comparing it with experimental data and previously computed adiabatic FPV results for two different ammonia injection cases. The results show that the non-adiabatic FPV model accurately predicted the peak temperature and its location, while the peak NO, overpredicted by approximately 150 % in the adiabatic FPV model, is slightly underpredicted in the non-adiabatic FPV model. Ammonia injection in the primary reaction zone lowered NO concentrations in both cases, primarily due to dominant NO reduction reactions with ammonia under the reducing environment. Reactive conditions and higher temperature caused NH3 dissociation, increasing H2 and H2O concentrations near burner exit in burner ammonia injection case.

Effects of Pre-Injection Strategy on Combustion Characteristics of Ammonia/Diesel Dual-Fuel Compression Ignition Mode

As a zero-carbon clean fuel, the use of ammonia in internal combustion engines is of great significance to achieve the “two-carbon” goal. This paper investigates the effect of the ammonia energy ratio and diesel injection timing on combustion and emissions. Based on Computational fluid dynamics (CFD) and the simulation analysis software, Converge, three-dimensional modeling is carried out for a direct injection diesel engine with a Compression Ignition (CI) mode. Under the initial full-load conditions of 1200 r/min, the engine simulation was calculated. The results show that the peak cylinder pressure increases and then decreases as the ammonia energy ratio increases, the ignition delay time increases, and the CO2 and N2O emissions decrease. With pre-injection, the peak cylinder pressure increases at the same energy ratio and the combustion stage advances, resulting in improved indicated thermal efficiency. In comparison to the pure diesel mode, the pre-injection strategy shows an obvious reduction in greenhouse gas (GHG) emissions with a decrease of 40.9% by adjusting the injection timing, while the single injection strategy shows a reduction of 36.5%. The soot emission peak occurs in the diesel-only mode with 98.13% and 99.6% reductions in emissions under single and pre-injection, respectively. The ammonia–diesel dual-fuel (ADDF) engine with an ammonia-to-energy ratio of 70% and optimized ammonia and diesel injection timing significantly reduces the NH3 emissions and GHG emissions by 69.34%.

Visualization study on the ignition and diffusion combustion process of liquid phase ammonia spray ignited by diesel jet in a constant volume vessel

Ammonia fueled engines applying diffusion combustion mode is expected to further improve the thermal and combustion efficiencies with high burning rate and high ammonia energy replacement. However, there is a lack of the fundamental studies about ammonia diffusion combustion characteristics. Therefore, the fundamental optical experiments of liquid phase ammonia spray and combustion, which is ignited by pilot diesel injection, were performed to investigate the ignition and diffusion combustion characteristics of liquid phase ammonia. According to the high-speed photography, interaction processes between the liquid phase ammonia spray and the diesel spray had been described, and the whole ignition and combustion processes were also recorded in detail. The discussion about the effect of diesel jet ignition location on ammonia ignition process shows that the effective ammonia ignition zone by diesel spray is the region of gas entrainment zone except for the liquid phase ammonia volume under evaporated condition, where the interval on ammonia spray axis is about 16 mm ∼ 35 mm away from the ammonia nozzle exit under the current experimental conditions, and the ammonia spray is failed to be ignited at any region out of the effective ignition zone. Moreover, the ammonia diffusion combustion characteristics under various ammonia injection durations reveals that the entrainment, including both the diesel flame and the surrounding ambient gas, into the effective ignition zone of liquid phase ammonia spray, is the effective way to achieve reliable ignition and the subsequent diffusion combustion of ammonia, which can increase the energy ratio (ammonia to pilot diesel) up to at least 2.9. Finally, based on the control of combustion mode of the pilot diesel, utilizing premixed diesel flame to induce the diffusion combustion of ammonia is proved to be an effective regulation scheme to enhance the performance of ammonia combustion under engine-like thermal conditions.

Large eddy simulation investigation of ammonia spray characteristics under flash and non-flash boiling conditions

Ammonia is an ideal zero-carbon fuel for energy systems, and it can be used directly in a liquid state. However, liquid ammonia is susceptible to flash boiling due to its unique physical and chemical properties, which brings challenges for liquid ammonia spray and combustion simulations. In the present study, high-pressure liquid ammonia injection under flash boiling and non-flash boiling conditions was investigated. Large eddy simulations were conducted in an Eulerian–Lagrangian framework. The aim is to explore in detail the influence of the critical parameters on the characteristics of liquid ammonia spray. Under the flash boiling condition, the effects of ambient pressure were examined. Comparisons of the measured and predicted spray penetration and morphology demonstrate that the present simulations can reproduce liquid ammonia spray characteristics well. Varying ambient pressures causes the ammonia spray to be at different superheat levels, resulting in significant changes in spray features. Under the non-flash boiling condition, the effects of injection pressure and ambient pressure were investigated. The higher injection pressure feature a higher gas velocity and improves the mixing of ammonia and air. The ammonia spray propagates more rapidly and the spray width becomes wider at lower ambient pressure.

Visualization study on ammonia/diesel dual direct injection combustion characteristics and interaction between sprays

Ammonia is regarded as a highly promising green fuel. Nevertheless, its auto-ignition temperature is exceptionally elevated, posing challenges for its direct utilization in compression ignition engines. Using highly active fuel as the ignition source seems a solution. In this paper, based on the RCEM experimental platform, the diesel/ammonia diffusion combustion mode was studied in detail. The experimental parameters included the ammonia injection pressure, ammonia and diesel injection interval (including ammonia in advance of diesel and diesel in advance of ammonia), diesel injection pressure, and ammonia nozzle diameter. The results indicated that injecting ammonia on diesel flame contributed to the completeness of ammonia combustion. Injecting ammonia before diesel achieved a higher peak heat release rate but aggravated the incomplete combustion. The injection pressure of diesel had no significant impact on the combustion effect of ammonia. Increasing the ammonia injection pressure resulted in enhanced air entrainment, consequently enhancing the effective combination of fuel with air, which improved the peak heat release rate more effectively. Increasing the diameter of the ammonia nozzle was a necessary way to achieve a high ammonia energy substitution ratio, but a large amount of ammonia sprayed simultaneously caused a portion of the ammonia to not burn in time, resulting in aggravation of incomplete combustion. In addition, the interaction between diesel spray and ammonia spray was also studied. The results showed that, due to the higher quantity of ammonia compared to diesel, the two sprays would gather and develop toward the direction of ammonia injection roughly, and the final development direction of the spray was also related to the fuel injection pressure.

Optimizations of energy fraction and injection strategy in the ammonia-diesel dual-fuel engine

Fuel consumption and emissions are growing concerns, driving the need for cleaner alternative fuels in engine research. Ammonia is a competitive alternative fuel. To enhance the effective utilization and provide a new direction for the marine application of ammonia, an ammonia-diesel dual-fuel engine model with the pre-combustion chamber structure was designed. Numerical simulations were carried out in this paper, considering variations in diesel energy fraction, ammonia injection timing, diesel injection pressure, and diesel injection timing. The findings indicate that an appropriate amount of pilot diesel accelerates jet flame formation, improving combustion efficiency. Advancing ammonia injection timing improves mixture homogeneity but increases ammonia slip, while delaying ammonia injection timing leads to mixture stratification. Locally rich areas in the mixture improve combustion efficiency. The timing and pressure of diesel injection significantly impact both combustion efficiency and emissions. Advancing diesel injection timing improves power output but increases NOX emissions. Increasing diesel injection pressure improves combustion efficiency, but excessive pressure leads to deterioration. Overall, this study provides valuable insights into the potential use of ammonia as a sustainable fuel for marine low-speed engines, selecting the optimal energy fraction and injection strategy to achieve efficient and environmentally friendly combustion.

Influence of Hydrogen on the Performance and Emissions Characteristics of a Spark Ignition Ammonia Direct Injection Engine

Because ammonia is easier to store and transport over long distances than hydrogen, it is a promising research direction as a potential carrier for hydrogen. However, its low ignition and combustion rates pose challenges for running conventional ignition engines solely on ammonia fuel over the entire operational range. In this study, we attempted to identify a stable engine combustion zone using a high-pressure direct injection of ammonia fuel into a 2.5 L spark ignition engine and examined the potential for extending the operational range by adding hydrogen. As it is difficult to secure combustion stability in a low-temperature atmosphere, the experiment was conducted in a sufficiently-warmed atmosphere (90 ± 2.5 °C), and the combustion, emission, and efficiency results under each operating condition were experimentally compared. At 1500 rpm, the addition of 10% hydrogen resulted in a notable 20.26% surge in the maximum torque, reaching 263.5 Nm, in contrast with the case where only ammonia fuel was used. Furthermore, combustion stability was ensured at a torque of 140 Nm by reducing the fuel and air flow rates.

Effect of Ammonia Injection on the Iron Ore Sintering Process: Reducing Fossil Fuel Consumption and Carbon Emissions

Effect of Ammonia Injection on the Iron Ore Sintering Process: Reducing Fossil Fuel Consumption and Carbon Emissions

Experimental and numerical study on direct injection of liquid ammonia and its injection timing in an ammonia-biodiesel dual injection engine

Ammonia is an alternative carbon-free fuel that can be easily stored in a liquid phase, unlike hydrogen, and then directly utilized in diesel engines. Hence, a single-cylinder diesel engine was retrofitted for direct injection of liquid ammonia with pilot ignition of biodiesel in dual fuel combustion mode. The effects of the liquid phase of ammonia and ammonia energy share (AES) on combustion, emissions, and engine performance were investigated and compared with pure biodiesel operation. Moreover, various ammonia injection timings were studied to improve ammonia/biodiesel combustion and reduce emissions. A CFD model was developed and validated with experimental data to study ammonia/biodiesel sprays, combustion characteristics, and emissions formation. The results showed higher AES significantly reduced the local cylinder temperature due to the strong cooling effects of ammonia, therefore, a maximum AES of 50% was achieved. Increasing AES to 50% decreased combustion duration and combustion phasing by 26.2 and 4.4 CAD, respectively. However, it deteriorated the indicated thermal efficiency (ITE) by 1.3 percent point compared to pure biodiesel. Furthermore, retarding ammonia injection from −25 to −10 CAD significantly reduced NOx, CO, and ammonia emissions by 31.4%, 39.6%, and 31.3%, respectively. Ultimately, the optimal operating condition was suggested when ammonia was injected at −10 CAD and biodiesel at −16 CAD with AES of 50%.

Effects of ammonia combustion on skin friction characteristics for supersonic flow

Boundary layer combustion is an effective method to reduce friction in scramjet combustors. In existing research on drag-reducing fuels, hydrocarbons pose challenges related to carbon deposition and emissions. Meanwhile, hydrogen presents significant difficulties in storage and transportation. For the first time, this paper explores ammonia as a drag-reducing alternative. We employed the Reynolds-averaged Navier-Stokes (RANS) method to investigate the characteristics of drag reduction by ammonia combustion in supersonic flow. Numerical results indicate that the local drag reduction by ammonia combustion is better than hydrocarbon and worse than hydrogen compared to existing research. Ammonia exhibits superior potential for drag reduction. However, the overall drag reduction at room ammonia injection temperature is limited due to the significant distance between the ammonia self-ignition point and the injection port. To address this challenge, we proposed two optimization strategies: increasing the ammonia injection temperature and increasing the inlet ammonia decomposition ratio. As the ammonia injection temperature increases, the self-ignition position moves towards the inlet, and the combustion drag reduction region expands upstream. Interestingly, a higher ammonia inlet decomposition ratio does not necessarily lead to a better drag reduction effect. In fact, an excessively high decomposition ratio can inhibit the combustion drag reduction effect. The most effective drag reduction occurs when the ammonia inlet mass fraction is 50%, resulting in a 42.8% reduction in integrated drag compared to the case without NH3 injection. Overall, this paper offers critical insights into the utilization of ammonia combustion in scramjets to reduce drag.

Design and Verification of Key Components of a New Selective Catalytic Reduction System in a Petrochemical Captive Power Plant

A new selective catalytic reduction (SCR) system for captive power plants in the petrochemical industry was analyzed. The key components suitable for the target SCR system were obtained using computational fluid dynamics (CFD) numerical simulation combined with a cold physical model. The structural characteristics of the SCR system were studied, and corresponding design schemes were obtained for the key components, such as the guide plate, the ammonia injection grid (AIG), the static mixer, and the rectifier grille. The distributions of the flue gas velocity and the NH3 concentration within the flue cross-section in front of the first layer catalyst were studied in detail. Synchronously, the pressure loss and the temperature reduction characteristics in the SCR system were also considered. CFD results showed that the average standard deviation of the flue gas velocity was about 11.61%, and the average standard deviation of the NH3 concentration distribution could reach about 3.79% under the five operating conditions. It could be concluded that the uniformity of the flue gas velocity and the NH3 concentration distribution within the above flue cross-section was guaranteed by comparing to the design standard of 15% and 5%, respectively. It was further found that the maximum pressure loss between the inlet and the first layer catalyst was about 106.64 Pa, and the temperature reduction characteristic of the entire SCR system could be maintained within ±0.01 °C, which indicated that no extreme adverse effect arose due to the introduce of the key components. The cold physical model experiment was accordingly conducted to verify the reliability of the above CFD results. The cold physical model experiment results showed that the average standard deviation of flue gas velocity was about 8.82%, and the average standard deviation of NH3 concentration distribution could reach about 4.21%. The maximum biases for the standard deviations of the flue gas velocity and the NH3 concentration distribution were approximately 4.83% and 1.18% under the five operating conditions. Based on the good agreement of the research results via the two different methods, the designed key components of a new SCR system could be confirmed to be feasible, which would benefit the deNOx performance of the SCR system.

Ammonia emission characteristics and ammonia injection control from stationary source in flue gas denitrification system

With the implementation of ultra-low emission of nitrogen oxides, denitrification technologies, such as selective catalytic reduction, selective non-catalytic reduction or selective non-catalytic reduction combined with selective catalytic reduction, have been widely used in gas-fired power plants, cement plants and municipal solid waste incineration power plants. These three denitrification industries have become the main potential fixed sources of ammonia emissions in urban areas, however the studies on ammonia emissions are lacking. In order to study the ammonia emission characteristics and ammonia injection control of gas-fired power plants, cement plants and municipal solid waste incineration power plants, field tests were carried out on five typical denitrification enterprises using three monitoring methods. The multi-form ammonia manual monitoring method proposed in this study distinguished and defined all possible ammonia in the flue gas into filterable ammonia, residual ammonia, condensable ammonia and gaseous ammonia according to the migration and transformation behavior during the collection process. The monitoring results of the multi-form manual monitoring method can more accurately reflect the actual ammonia emission level with the simultaneous collection and monitoring of different ammonia forms. The ammonia emission levels in cement plants (more than 20 mg/m³) were higher than that of gas power plants and waste incineration plants (almost less than 4 mg/m³). The condensed ammonia was the dominant form of ammonia, accounting for 58.4%～88.7%. The humidity and temperature of flue gas at the chimney outlet had significant influence on residual ammonia. For the denitration enterprises using a single denitrification technology, the ammonia emission had a linear negative correlation with that of nitrogen oxide with changing ammonia injection amount, while for that using combined denitrification technology, the degree of collaboration between selective non-catalytic reduction ammonia injection control and selective catalytic reduction ammonia injection control played a decisive role in the control of nitrogen oxide emission and ammonia emission, especially the selective catalytic reduction ammonia injection control.

Multi‐model predictive control ofSCRflue gas denitrification system in coal‐fired power plant based on kernel fuzzy c‐means clustering and integrated model

AbstractA multi‐model predictive control strategy based on kernel fuzzy c‐means (KFCM) clustering and integrated model is proposed for the complex problem of rapid and accurate control of ammonia injection in selective catalytic reduction (SCR) denitrification systems of coal‐fired power plants under a wide range of variable load conditions. First, the SCR data samples are clustered using the KFCM clustering algorithm, and the number of clusters is determined by introducing the Xie‐Beni index. Second, the prediction model of the SCR denitrification system is established by an integrated modelling approach, and the sub‐learners of the integrated model are the genetic algorithm optimized back propagation (GA‐BP) neural network model and the least squares support vector machine (LSSVM) model. Third, a multi‐model prediction controller based on the particle swarm optimization (PSO) algorithm and the integrated model is designed and developed. To ensure the stability of the system, a model‐switching strategy based on the minimum Euclidean distance is proposed. Finally, simulation verification and industrial field application verification are fulfilled by comparing with proportion integral differential (PID) control and single model predictive control (MPC). The results show that the multi‐model predictive control method proposed in this paper can obtain higher control accuracy and better control stability and meet the control requirements for the long‐term operation of the SCR denitrification system.

Study and management of flow and concentration field problems in 600 MW SCR unit

With the increasingly stringent national requirements for environmental protection, the control of pollutants in coal-fired power plants has been gradually strengthened. In order to meet the NOx emission standard, some coal-fired units achieve ultra-low emissions by excessive ammonia injection, which seriously affects the unit operation economy. This paper takes the SCR denitrification unit of a 600 MW coal-fired unit with a Π-type furnace in China as the research object and studies the distribution of flow and concentration fields inside the unit under a 60% load section by means of CFD numerical simulation. It points out the problems of flow and concentration fields at local locations under current operating conditions and proposes the rectification of the corresponding area of the inflow equipment and the idea of a zonal ammonia injection optimization method. It provides a certain reference value for the optimized management of the denitrification system of coal-fired units in the future.