Selective Catalytic Reduction Process Research Articles

A survey study on arsenic speciation in coal fly ash and insights into the role of coal combustion conditions

Coal fly ashes (CFAs) are the low-density byproducts of the coal combustion process. Improper or uncontrolled CFA disposal poses significant environmental and health concerns due to the potential leaching of toxic heavy metals such as arsenic (As). Previous studies have investigated the content and speciation of As in different CFA samples, yet systematic information on As speciation in CFA with representative coal source and combustion conditions is still missing. Based on a recent survey study on the typical coal sources and combustion conditions across the U.S., this study selected 19 representative CFA samples to systematically investigate As speciation and potential correlations with these parameters. The composition, morphology, mineralogy, and As speciation of these CFA samples were characterized by complementary analytical, microscopic, and spectroscopic techniques. Synchrotron X-ray spectroscopy and microscopy analyses revealed the dominant As oxidation state to be As(V) and with strong associations to Ca, with the exception of 3 samples that had 19–51% As(III), likely due to the use of selective catalytic reduction (SCR) process. Principal component analysis was conducted to identify potential correlations of As concentration and oxidation state with parameters such as major element content, loss on ignition (LOI), average particle size, coal source, and combustion condition. Al2O3 and FeO content were found to capture a majority of the variability. Results from this study provide fundamental basis for understanding the correlations between coal source, combustion conditions, CFA characteristics, and As speciation, and providing insights for downstream beneficial utilization or disposal management.

Elucidating the role and enhancement mechanisms of CH4 on the coupling abatement of N2O & NO over Fe-SSZ-13 catalysts

CH4 + NH3 + NOx + N2O coupling system was proposed for high-effective simultaneous catalytic reduction of both NO and N2O from flue gas generated by nitric or adipic acid industries. The Fe-SSZ-13 catalyst performed both elegant activity for NOx and N2O at 400–600 °C. Based on experimental studies, the active Fe species were illustrated and the transforming of Fe species during the N2O decomposition (deN2O) and selective catalytic reduction (SCR) processes was clarified. It found that deN2O could cause the main active sites of [Fe-O2-Fe]2+ transform to [Fe-O-Fe]2+ and consequently inhibited the NH3-SCR process over the Fe-SSZ-13 catalyst. Meanwhile, the αO* generated via N2O decomposition would strengthen NO oxidation to NO2, which is advantageous to NH3-SCR. More importantly, the functions of CH4 for deN2O and NH3-SCR were also investigated. CH4 could work as reductant to convert N2O over the Fe-SSZ-13. CH4 could also facilitate the reduction of NO; however, NH3 has stronger activity to NO than that of CH4. And CH4 was easily oxidized by O2 rather than N2O or NO, which significantly limit the CH4-SCR for N2O with present of O2. At the same time, CH4 can also accelerate αO* consumption that somehow enhance deN2O efficiency. Moreover, the consumption of αO* by CH4 prevent the transforming of [Fe-O2-Fe]2+ to [Fe-O-Fe]2+, and CH4 play an important role on turnover rates of [Fe-O2-Fe]2+ and [Fe-O-Fe]2+ active sites, guaranteeing both satisfactory purifying efficiency for NO and N2O. This work reveals the positive promoting effect of CH4 on simultaneous reduction of NOx and N2O, and proposes a potential catalyst for implementation.

The study of NH3‐SCR mechanism on γFe2O3 supported LaMnO3 catalyst based on DFT

AbstractFe2O3 supported LaMnO3 is an effective selective catalytic reduction (SCR) denitrification catalyst, but its reaction mechanism has not been reported yet. This article is based on the density functional theory (DFT) method to study the denitrification reaction mechanism of LaMnO3/Fe2O3 catalyst, in order to guide the development and application of denitrification catalysts. The conclusion is as follows: NH3, NO, and O2 molecules can form stable adsorption on the surface of La MnO3/γFe2O3 catalysts, and NH3 molecules are more likely to be adsorbed on Mn ions. Under the oxidation of lattice oxygen, NH3 will gradually dehydrogenate to form NH2, and then will react with NO in the air to form the transitional intermediate NH2NO, to produce N2 and H2O. The mechanisms are same on Mn and Fe sites. The dehydrogenate of NH3 to form NH2 is rate determining step. Compared with pure γFe2O3, the energy barrier decreases to promote the SCR process.

Preparation and Application of Slag‐Based Catalyst for Steelmaking

This study focuses on utilizing ground granulated blast furnace slag (GGBS) from a steel plant as the main raw material, with water and calcium‐based montmorillonite as binders, with manganese and alkali metal nitrates (Na, K, Mg, Ca). A series of supported denitration catalysts are prepared using the equal volume impregnation method. These catalysts are then employed in the selective catalytic reduction process to investigate their impact on denitration effectiveness. Furthermore, the mechanism of low‐temperature denitration in selective catalytic reduction is analyzed by combining catalyst activity tests and characterization techniques. The activity of catalysts is assessed through Fourier transform infrared spectrometer (FT‐IR), X‐Ray diffraction (XRD), and search engine marketing (SEM) characterization tests, along with examining its denitration and sulfur resistance capabilities to determine the denitration mechanism. Experimental results indicate that Mn–Mg/GGBS exhibit the most efficient low‐temperature denitrification effect, and it demonstrates certain sulfur resistance with a 5% Mn loading and a 3% second active component. Introducing Ce as the third active component further enhances the sulfur resistance of Mn–Mg–Ce/GGBS when loaded at 1%.

Potential Risk of Significant N2O Emission without Changing NOx Conversion on Commercial V2O5/TiO2 Catalyst under Working Conditions.

Vanadium-based catalysts play a pivotal role in the emission control of industrial NOx via selective catalytic reduction (SCR) technology. However, little attention has been paid to the potential emission of greenhouse gas N2O under complex working conditions. This work reports that a commercial V2O5/TiO2 catalyst may lead to significant N2O emission without greatly changing the outlet NOx concentration after chromium (Cr) deposition. With a Cr loading of 2 wt %, N2O concentration increased from 27.8 to 199.2 ppm at 350 °C with the value of outlet N2O/(N2O+N2) from 2.5% to 19.4%. Experimental results combined with DFT+U calculations suggest that nonselective catalytic reduction (NSCR) is the main route for N2O formation in a wide temperature range of 250 ∼ 400 °C. It is stemmed from the fact that the covalent interaction between Cr and V species on the V2O5/TiO2 surface accelerates the conversion of V4+ + Cr6+ → V5+ + Cr3+, leading to a larger proportion of surface V5+. More importantly, surface V5+ is highly related to the redox property of the V2O5/TiO2 catalyst, which is beneficial to NSCR reaction rather than the standard SCR process. The work suggests that to better inhibit the emission of greenhouse gases during the NH3-SCR process, monitoring N2O emission should be included along with the NOx concentrations, especially in complex flue gases.

Monitoring ammonia slip from large-scale selective catalytic reduction (SCR) systems in combined heat and power generation applications with field effect gas sensors

Abstract. Following tightened regulations, selective catalytic reduction (SCR) of nitrogen oxides (NOx) by ammonia (NH3) has over the last couple of decades found wider adoption as a means of reducing NOx emissions from e.g. power production and district heating plants. As in the SCR process NH3 injected into the flue gas reacts with and reduces NOx to nitrogen (N2) and water (H2O) on the surface of a specific catalyst, the NH3 injection has to be dynamically adjusted to match both instant and long-term variations in flue gas nitrogen oxide concentration in order to minimize NOx and NH3 emissions. One possibility of realizing such NH3 dosing control would be the real-time monitoring and feedback of downstream flue gas NOx and NH3 concentrations to the NH3 injection control unit. In this study the sensing characteristics and performance of SiC-based Metal Oxide Semiconductor Field Effect Transistor (MOSFET) sensors with a structurally tailored gas-sensitive gate contact of iridium (Ir) for in situ NH3 monitoring downstream from the SCR catalyst in a combined heat and power (CHP) plant have therefore been investigated and evaluated. The sensor's NH3 sensitivity and selectivity as well as the cross-sensitivity to common flue gas components – oxygen (O2), water vapour (H2O), nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO), and a model hydrocarbon, ethene (C2H4) – were thereby investigated for relevant concentration ranges under controlled conditions in the laboratory. While, at the prescribed sensor operation temperature of 300 ∘C, the influence of H2O, CO, and C2H4 on the sensor's NH3 concentration reading could be regarded as practically insignificant, a moderate cross-sensitivity was observed between NH3 and NO2 and, to a lesser extent, between NH3 / NO and NH3 / O2. As the NOx concentration downstream from the SCR catalyst under normal SCR and power plant operation is expected to be considerably smaller than the NH3 concentration whenever any appreciable ammonia slip occurs, the observed NH3 / NOx cross-sensitivities may, however, be of less practical significance for ammonia monitoring in real flue gases downstream from the SCR catalyst. Furthermore, if required, the small influence of O2 concentration variations on the sensor reading may also be compensated for by utilizing the signal from a commercially available oxygen sensor. Judging from in situ measurements performed in a combined heat and power plant, the structurally tailored Ir gate field effect sensors also exhibit good NH3 sensitivity over the relevant 0–40 ppm range when directly exposed to real flue gases, offering an accuracy of ±3 ppm as well as low sensor signal drift, the latter most likely to further improve with regular zero-point calibration and thereby make the Ir gate MOSFET ammonia sensor a promising alternative for cost-efficient real-time ammonia slip monitoring or SCR system control in heat and/or power production plants.

Commercial SCR catalyst modified with Cu metal to simultaneously efficiently remove NO and toluene in the fuel gas.

Developing an environmentally friendly selective catalytic reduction (SCR) catalyst to effectively eliminate both nitric oxides (NO) and toluene has garnered significant attention for regulating emissions from automobiles and the combustion of fossil fuels. This study synthesized a series of novel commercial V2O5-WO3/TiO2 catalysts modified with Cu through the wet impregnation method, which was employed to simultaneously remove NO and toluene from the fuel gas. The assessment of catalyst removal performance was conducted at a selective catalytic reduction system, and the experimental results showed a significant increase in the catalytic activity due to the modification of the copper metal. The 10% Cu/SCR catalyst showed a superior activity that the NO and toluene conversion reached 100% and 95.56% at 300 °C, respectively. Subsequently, various characterization techniques were employed to investigate the crystal phase, morphology, physical features, chemical states, and surface acidity properties of the synthesis catalysts. According to the characterization results, the presence of Cu metal did not have a noticeable impact on the physical property. However, the redox performance was enhanced, and the number of surface acidic sites was also increased after adding Cu to the SCR catalyst. Furthermore, the redox cycle of Cu metal and V species was facilitated to produce more active oxygen which helped to improve the NO and toluene conversion. This work offered a novel perspective into the synergistic oxidation of both NO and toluene, which was potentially relevant for improving the selective catalytic reduction process in coal-fired power plants.

Redox on Mn-Ce interface and its effects on low temperature selective catalytic reduction for NOx removal

The objective of this work was to clearly elucidate the interactions on Mn-Ce interface and understand how they affect low temperature selective catalytic reduction (SCR) for NOx removal. In this work, three Mn-Ce catalysts in similar particle size and morphology with different Mn-Ce interface areas were prepared. MnO2@CeO2-F had the tightest and largest amount of Mn-Ce interfaces compared with MnO2@CeO2-P and MnO2-CeO2-M, and also exhibited the highest NO conversion degree at 100–150 °C as well as the strongest activity of Mn species and lowest generation of N2O. The TG-DTG, XPS and electrochemical impedance spectroscopy results proved the redox of Ce4+ + Mn3+ ↔ Ce3+ + Mn4+ on the Mn-Ce interface, and MnO2@CeO2-F had the highest Mn4+, Ce3+, Oα concentrations. The results of the study on the redox reactions during the NH3-SCR process provided powerful evidence of the Mn4+/Mn3+ and Ce3+/Ce4+ recycles that are important for low temperature NH3-SCR process. Moreover, the Mn-Ce interface was directly proved to benefit the surface acid sites, redox ability, and activity of the adsorbed intermediates. Both the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction mechanisms were observed in the SCR reaction with prepared Mn-Ce materials, where “fast SCR” can be observed with MnO2@CeO2-F. Moreover, the Mn-Ce interface also lowers the activation energy of the low-temperature SCR process, with MnO2@CeO2-F having the lowest activation energy. The results from this work offered powerful evidences for the interactions of Mn/Ce redox at the Mn-Ce interface and elucidated clear understanding of the effects of Mn-Ce redox on low-temperature SCR process, which is expected to promote the NOx removal process.

Cobalt-/pH-Modified V2O5-MoO3/TiO2 Catalyst with Enhanced Activity for the Low-Temperature Selective Catalytic Reduction Process

Currently, the elimination of gaseous pollutants—particularly nitrogen oxides—has emerged as a significant concern. Among various deNOx technologies, selective catalytic reduction (SCR) has gained prominence as the primary approach for NOx abatement, owing to its superior performance. In this study, novel low-temperature SCR catalysts were developed by regulating the pH value and doping cobalt based on a V2O5-MoO3/TiO2 (VMT) catalyst. The results show an increased SCR performance with 82.8% and 91.1% for catalysts after pH (=10) modification (VMT-10) and (1 wt%) Co/pH (=10) modification (1CoVMT-10), respectively. H2-TPR, NH3-TPD, XPS and DRIFTS confirmed that the pH regulation transformed polymerization V species into isolated V5+=O, thus leading to an increase in the number of acid sites, which enhanced the NH3 and NO2 adsorption capacity. Furthermore, the DRIFTS study indicated that the NH3-SCR reaction over 1CoVMT-10 followed the E–R and L–H mechanism.

Synergistic Chemical Looping Process Coupling Natural Gas Conversion and NOx Purification

We present a novel low-temperature chemical looping combustion scheme for simultaneous natural gas conversion into a sequestration-ready CO2 stream and NOx purification. The scheme employs nickel oxide (NiO) supported on ZrO2 as the oxygen carrier. In the process, CH4 reduces the oxidized carrier to Ni/ZrO2 in a co-current moving bed reactor, which is then oxidized back to NiO/ZrO2 by the NOx-laden flue gas in a fluidized bed reactor, completing the oxygen carrier loop. Thermodynamic studies demonstrate that the presence of CO2 does not significantly affect NOx purification performance at different flue gas flow rates. The operating temperatures of the reactors are selected based on NOx-temperature programmed oxidation (TPO) and CH4-temperature programmed reduction (TPR) experiments. Results show that the process can optimally operate at temperatures close to the combustion plants’ flue gas temperature of 400–500 °C, reducing the need for hot utilities. The study conducts comprehensive isothermal and autothermal analyses of the process to evaluate the effects of temperature and carrier flow rate on CH4 conversion, CO2 selectivity, carbon deposition, and NOx conversion. For the autothermal analysis, the CH4 reactor operates adiabatically, while the NOx reactor operates isothermally. Comparative studies with the conventional NOx selective catalytic reduction (SCR) process indicate an exergy efficiency and effective thermal efficiency (ETE) improvement of 9 and 18 percentage points, respectively. The findings suggest that this low-temperature chemical looping process is a promising solution for flue gas NOx treatment, utilizing cheaper natural gas as the reductant and eliminating environmental concerns, such as ammonia or urea slippage. Overall, this study contributes to the development of more efficient and sustainable methods for reducing NOx emissions.

Metal-Doped Mesoporous MnO2-CeO2 Catalysts for Low-Temperature Pre-Oxidation of NO to NO2 in Fast SCR Process

Selective catalytic reduction (SCR) is an effective system for treating nitrogen oxides (NOx; mainly NO), and fast SCR requires the equimolar reactants of NO and NO2. This study focused on catalysts for oxidizing 50% of NO to NO2. A series of catalysts composed of a variety of components, such as mesoporous mMnO2-nCeO2 as carrier catalysts (m:n = 9:1 and 7:3) and transition metals (e.g., Fe, Co, Ni, Cu, and Cr), were synthesized and characterized using N2 adsorption, in situ XRD, TEM, and XPS. All samples had a mesoporous structure with pore size around 8 nm. XPS results demonstrated that addition of cerium ion increased the surface area and provided oxygen vacancy due to the formation of Ce3+ within the structure. NO oxidation activity was tested using a feed (205~300 ppm NO and 6% O2) that simulated typical flue gas conditions. Doped mesoporous mMnO2–nCeO2 has higher NO oxidation activity than pristine mMnO2–nCeO2. The doped mMnO2-nCeO2 catalyzed 50% of NO to NO2 at between 140 and 200 °C resulting in an equivalent amount of NO and NO2. Among the transition metals, Cu, Ni, Co, Fe, and Cr have the highest to lowest oxidation activity, respectively. The precatalytic oxidation of NO can potentially be combined with the current SCR system without changes to existing equipment and can be applied to the exhaust gas treatment for de-NOx.

Insight into blast furnace dust for selective catalytic reduction of NOx: An experimental and DFT study

Blast furnace dust (BFD), a solid waste generated from the ironmaking process, causes the environmental problems of soil and water pollution. In this work, we develop the selective catalytic reduction (SCR) catalyst for the nitric oxides (NO) reduction using BFD as the raw material by the co-precipitation method. To guarantee the strongest catalytic capability, different calcined temperatures are tested to activate the catalysts, where the prepared catalysts are labeled as BFD-T with the capital letter T to represent the calcination temperature. α-Fe2O3 is the main crystal phase in BFD-T catalyst and the mesoporous structure is mainly concentrated in 2–15 nm. The BFD-400 catalyst presents the best SCR performances and further increasing of the calcination temperature for the catalyst preparation reduces the reducibility, specific surface area and surface adsorbed oxygen of the catalyst. In the temperature range of 225 ℃ to 350 ℃, the BFD-400 catalyst presents the nitrogen oxides (NOx) conversion of more than 90%, which is attributed to the increase of ferric ion on the catalyst surface. Meanwhile, density functional theory (DFT) is applied to study the adsorption states of the reactant molecules on the catalyst surface and reaction mechanism. During the SCR process, this catalyst shows the excellent resistance to sulfur and water in the coal-fired flue gas due to the weak adsorption energy calculation.

Improvement in the resistance to KCl and PbCl2 synergistic poisoning of the commercial SCR catalyst by Ce(SO4)2 modification: A combined experimental and spin-polarized DFT study

The commercial selective catalytic reduction (SCR) catalysts are vulnerable to the synergistic poisoning of K and Pb species in flue gas, two common and typical components that can trigger severe damage on the physical and chemical properties of the catalysts. In this study, a Ce(SO4)2-V2O5-MoO3/TiO2 catalyst with 15 wt% Ce(SO4)2 loading was developed which maintained high activity under the synergistic poisoning of 2 wt% KCl and PbCl2. The resistance mechanisms were explored by a series of characterization techniques and density functional theory (DFT) calculations. The results indicated that the enhancement on the resistance to the synergistic poisoning of K and Pb species by the introduction of Ce(SO4)2 could be elucidated in three aspects. Firstly, the interactions between Ce(SO4)2 and K/Pb species protected the V and Mo species from the synergistic poisoning. Secondly, the Ce4+/Ce3+ redox couples and large amounts of chemisorbed oxygen improved the redox ability of the catalyst. Finally, the Ce(SO4)2 modified catalyst maintained a high surface acidity despite the synergistic poisoning of K and Pb species, which was beneficial for the adsorption of NH3 species and the following SCR process.

Density Functional Study on Adsorption of NH3 and NOx on the γ-Fe2O3 (111) Surface.

γ-Fe2O3 is considered to be a promising catalyst for the selective catalytic reduction (SCR) of nitrogen oxide (NOx). In this study, first-principle calculations based on the density function theory (DFT) were utilized to explore the adsorption mechanism of NH3, NO, and other molecules on γ-Fe2O3, which is identified as a crucial step in the SCR process to eliminate NOx from coal-fired flue gas. The adsorption characteristics of reactants (NH3 and NOx) and products (N2 and H2O) at different active sites of the γ-Fe2O3 (111) surface were investigated. The results show that the NH3 was preferably adsorbed on the octahedral Fe site, with the N atom bonding to the octahedral Fe site. Both octahedral and tetrahedral Fe atoms were likely involved in bonding with the N and O atoms during the NO adsorption. The NO tended to be adsorbed on the tetrahedral Fe site though the combination of the N atom and the Fe site. Meanwhile, the simultaneous bonding of N and O atoms with surface sites made the adsorption more stable than that of single atom bonding. The γ-Fe2O3 (111) surface exhibited a low adsorption energy for N2 and H2O, suggesting that they could be adsorbed onto the surface but were readily desorbed, thus facilitating the SCR reaction. This work is conducive to reveal the reaction mechanism of SCR on γ-Fe2O3 and contributes to the development of low-temperature iron-based SCR catalysts.

Getting insight into the oxidation of SO2 to SO3 over P modified VW/Ti catalyst: Effect and inhibition mechanism

Commercial VW/Ti catalyst used in selective catalytic reduction (SCR) process is one of the major sources of SO3 in coal-fired boiler, and modification of VW/Ti catalyst by adding catalytic promoter has been demonstrated to be an effective way to inhibit SO3 generation. In this study, the effect of P addition on the activity of NOx conversion and SO2 oxidation over VW/Ti catalyst was investigated. The results showed that the P-modified VW/Ti catalyst not only enhanced the catalytic activity at low temperature, but also reduced the oxidation rate of SO2. The 1.5PVW/Ti catalyst exhibited the lowest SO2 oxidation rate at 360 °C and achieved about 30 % reduction in SO2 oxidation rate when compared to 0PVW/Ti catalyst, whereas the conversion of NOx was still above 95 %. The physicochemical properties of catalysts were comprehensively characterized with N2 adsorption, XRD, H2-TPR, NH3-TPD, XPS and DRIFTS. The results illustrated that the W-O-W structure was also the main reason for SO2 oxidation on P-modified VW/Ti catalyst, which oxidized SO2 to form intermediate products HSO4− and constantly replenished in the presence of O2. The oxidation of SO2 was weakened by the generation of VOPO4 on P-modified VW/Ti catalyst surface, which inhibited the formation of VOSO4 by reducing the adsorption of SO2 on the catalyst. In addition, the release of P-OH and W=O were promoted with the addition of P, which led to a significant increase in the intensity of the Brønsted and Lewis acid sites, resulting in the increase in the conversion of NOx at low temperatures.

Nitric oxide (NO) and nitrous oxide (N2O) emissions during selective non-catalytic reduction and selective catalytic reduction processes in a pulverized coal/Ammonia Co-fired boiler

The global warming and climate change are accelerated by the emissions of CH4, chlorofluorocarbon, and N2O gases along with CO2 resulting from the use of fossil fuels. Recently, a new combustion technology that combines carbon-free ammonia (NH3) fuel and coal has been proposed to reduce CO2 emissions from thermal power plants. In this study, we examined the emission levels of NO and greenhouse gas N2O from the existing coal-fired and future carbon-neutral coal/ammonia co-fired thermal power plants. As a result, a correlation between the amounts of NO and N2O gases generated during combustion in the furnace of a thermal power plant was established, and possible relationships between NO and N2O emissions during the selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) of NOx were experimentally analyzed. In addition, a linear correlation between the CO and N2O concentrations was observed. The air-staged combustion during SCR (300 °C, urea) produced the lowest total emission concentration of NO and N2O (9 ppm) under the utilized conditions. The findings of this study can help control the emission levels of air pollutant NO and greenhouse gas N2O throughout the entire process of thermal power plants.

Ceria-Promoted and stabilized copper and iron oxides cooperatively catalyze NO efficient degradation by CO

The copper and iron oxides highly dispersed on CeO2 composite system was successfully synthesized by solid-state based methods for NO reduction by CO with a certain sulfur and water resistance. The conversion of NO at 100, 150 and 220 °C can reach ∼40 %, ∼80 % and ∼100 % respectively, at space velocity = 65,000 mL·g−1·h−1. Here, some ex/in-situ characterization techniques are used to explore the active species and catalytic mechanism in the reaction process. The results show that the catalyst system has a large number of defects and contains highly reactive oxygen species. During the reaction, the dominant Ce species can promote the formation of Cu+ active species and enhance its relative stability. Also, under higher temperature reaction atmosphere, Ce species can stabilize Fe3+ and maintain the catalytic performance. The stabilization effect of Ce species on copper and iron makes the catalyst have a quite wider active window. To understand the selective catalytic reduction process of NO by CO, a possible reaction mechanism was proposed by in-situ DRIFTS. Overall, this work provides a possible foundation for understanding the structure, catalytic stability, and activity.

Cascade and Override Structure of SCR Process by LQR Scheme

This paper describes the development and application of the Linear Quadratic Regulator (LQR) to the Selective Catalytic Reduction (SCR) process in a Combined Cycle (CC) Power Plant. The whole closed-loop control is implemented by the actual plant Distributed Control System (DCS). To improve control dynamics, we are proposing a cascade override controller system. The effectiveness of the designed controller is evaluated by not only the simulation study but also the actual plant operation data during commercial operation. The controller covers all the operating conditions and has been continuously used from the commissioning stage to this day.

Machine Learning Approach to NOx Prediction for SCR Process of Thermal Power Plant

This paper presents a machine learning application, to predict the formed nitrogen-oxides (NOx) in thermal power plants, and used in the control loops of the selective catalytic reduction (SCR) process. To deal with the big plant operation data, data reduction methods are also described. The predictions are applied for the feed-forward (FF) control and show improvement of control performance in the simulation study.

Revealing M (M = Cu, Co and Zr) oxides doping effects on anti-PbCl2 poisoning over Mn-Ce/AC catalysts in low-temperature NH3-SCR reaction

Lead salts poisoning was a great challenge for the catalysts application in selective catalytic reduction (SCR) reaction of NOx with NH3 in stationary sources. Herein, several typical transition metal (Cu, Co and Zr) oxides modified Mn-Ce/AC catalysts were prepared by impregnation method, and the effects of Cu, Co and Zr doping on resistance PbCl2 poisoning for the catalyst were investigated. The addition of three transition metal oxides improved the PbCl2 resistance of Mn-Ce/AC catalyst and maintained excellent low-temperature denitrification activity of the catalyst. The lead resistance performance of the three metal oxides followed: Cu > Co > Zr oxides. The NO conversion of Cu-doping catalyst after PbCl2 poisoning was only ca. 10% lower than that of fresh Mn-Ce/AC catalyst at 225 °C. Cu, Co and Zr doping could decrease the loss of specific surface area caused by poisoning, while Cu-doped catalyst showed lowest crystallinity of active components. Meanwhile, the contents of Mn4+ and chemisorbed oxygen in Cu-doped catalyst were higher than those in Co- or Zr-doped catalysts. Cu, Co and Zr doping improved the surface acidity and redox performance of the poisoned catalysts, with Cu-doped poisoned catalyst exhibiting nearly the same surface acidity and redox performance as the fresh Mn-Ce/AC catalyst. Furthermore, Cu doping could also improve NO adsorption and was in favor to the SCR process. Besides, in situ DRIFTS results showed that the catalytic reaction pathways of all the poisoned or modified catalysts were in accordance with both Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. Finally, a possible anti-PbCl2 poisoning mechanistic model of (Cu, Co and Zr) oxides modified on Mn-Ce/AC catalyst was proposed.