scholarly journals Reaction Characteristics of NOx and N2O in Selective Non-Catalytic Reduction Using Various Reducing Agents and Additives

Atmosphere ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1175
Author(s):  
Poong-Mo Park ◽  
Young-Kwon Park ◽  
Jong-In Dong
Keyword(s):  
Sodium Carbonate ◽  
Fossil Fuels ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Nox Emissions ◽  
Chemical Modeling ◽  
Reduction Techniques ◽  
Modeling Software ◽  
Ammonia Addition ◽  
Nox Control

Artificial nitrogen oxide (NOx) emissions due to the combustion of fossil fuels constitute more than 75% of the total NOx emissions. Given the continuous reinforcement of NOx emission standards worldwide, the development of environmentally and economically friendly NOx reduction techniques has attracted much attention. This study investigates the selective non-catalytic reduction (SNCR) of NOx by methane, ammonia, and urea in the presence of sodium carbonate and methanol and the concomitant generation of N2O. In addition, the SNCR mechanism is explored using a chemical modeling software (CHEMKIN III). Under optimal conditions, NOx reduction efficiencies of 80–85%, 66–68%, and 32–34% are achieved for ammonia, urea, and methane, respectively. The N2O levels generated using methane (18–21 ppm) were significantly lower than those generated using urea and ammonia. Addition of sodium carbonate and methanol increased the NOx reduction efficiency by methane to ≥40% and 60%, respectively. For the former, the N2O level and reaction temperature further decreased to 2–3 ppm and 850–900 °C, respectively. The experimental results were well consistent with simulations, and the minor discrepancies were attributed to microscopic variables. Thus, our work provides essential guidelines for selecting the best available NOx control technology.

Kinetics Modeling on NOx Emissions of a Syngas Turbine Combustor Using RQL Combustion Method

2019 ◽  
Author(s):  
Haoyang Liu ◽  
Wenkai Qian ◽  
Min Zhu ◽  
Suhui Li
Keyword(s):  
Gas Turbine ◽  
Residence Time ◽  
Air Flow ◽  
Nox Reduction ◽  
Outlet Temperature ◽  
Nox Emissions ◽  
Gas Turbine Combustor ◽  
Kinetics Modeling ◽  
The Rich ◽  
Nox Control

Abstract To avoid flashback issues of the high-H2 syngas fuel, current syngas turbines usually use non-premixed combustors, which have high NOx emissions. A promising solution to this dilemma is RQL (rich-burn, quick-mix, lean-burn) combustion, which not only reduces NOx emissions, but also mitigates flashback. This paper presents a kinetics modeling study on NOx emissions of a syngas-fueled gas turbine combustor using RQL architecture. The combustor was simulated with a chemical reactor network model in CHEMKIN-PRO software. The combustion and NOx formation reactions were modeled using a detailed kinetics mechanism that was developed for syngas. Impacts of combustor design/operating parameters on NOx emissions were systematically investigated, including combustor outlet temperature, rich/lean air flow split and residence time split. The mixing effects in both the rich-burn zone and the quick-mix zone were also investigated. Results show that for an RQL combustor, the NOx emissions initially decrease and then increase with combustor outlet temperature. The leading parameters for NOx control are temperature-dependent. At typical modern gas turbine combustor operating temperatures (e.g., < 1890 K), the air flow split is the most effective parameter for NOx control, followed by the mixing at the rich-burn zone. However, as the combustor outlet temperature increases, the impacts of air flow split and mixing in the rich-burn zone on NOx reduction become less pronounced, whereas both the residence time split and the mixing in the quick-mix zone become important.

3D Numerical Simulations of Selective Catalytic Reduction of NOx With Detailed Surface Chemistry

2017 ◽  
Author(s):  
Zhaoyu Luo ◽  
Parvez Sukheswalla ◽  
Scott A. Drennan ◽  
Mingjie Wang ◽  
P. K. Senecal
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Surface Chemistry ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Water Solution ◽  
Nox Reduction ◽  
Nox Emissions ◽  
Detailed Surface ◽  
Exhaust After Treatment

Environmental regulations have put stringent requirements on NOx emissions in the transportation industry, essentially requiring the use of exhaust after-treatment on diesel fueled light and heavy-duty vehicles. Urea-Water-Solution (UWS) based Selective Catalytic Reduction (SCR) for NOx is one the most widely adopted methods for achieving these NOx emissions requirements. Improved understanding and optimization of SCR after-treatment systems is therefore vital, and numerical investigations can be employed to facilitate this process. For this purpose, detailed and numerically accurate models are desired for in-cylinder combustion and exhaust after-treatment. The present paper reports on 3-D numerical modeling of the Urea-Water-Solution SCR system using Computational Fluid Dynamics (CFD). The entire process of Urea injection, evaporation, NH3 formation and NOx reduction is numerically investigated. The simulation makes use of a detailed kinetic surface chemistry mechanism to describe the catalytic reactions. A multi-component spray model is applied to account for the urea evaporation and decomposition process. The CFD approach also employs an automatic meshing technique using Adaptive Mesh Refinement (AMR) to refine the mesh in regions of high gradients. The detailed surface chemistry NOx reduction mechanism validated by Olsson et al. (2008) is applied in the SCR region. The simulations are run using both transient and steady-state CFD solvers. While transient simulations are necessary to reveal sufficient details to simulate catalytic oxidation during transient engine processes or under cyclic variations, the steady-state solver offers fast and accurate emission solutions. The simulation results are compared to available experimental data, and good agreement between experimental data and model results is observed.

Observer-Based Estimation of Aging Condition for Selective Catalytic Reduction Systems in Vehicle Applications

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Yao Ma ◽  
Junmin Wang
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Estimation Error ◽  
Nox Reduction ◽  
Observer Design ◽  
Accurate Estimation ◽  
Nox Emissions ◽  
Aging Condition ◽  
Entire Vehicle ◽  
Scr System

This paper presents two observers for estimating the aging condition of selective catalytic reduction (SCR) systems in vehicle applications. SCR systems have been widely recognized as one of the leading engine exhaust gas aftertreatment systems for reducing diesel powertrain tailpipe NOx emissions in ground vehicle applications. While fresh SCRs are quite effective in reducing tailpipe NOx emissions, their NOx reduction capabilities and performances may substantially degrade with in-service aging. To maintain the emission control performance of a SCR system for a diesel engine during the entire vehicle service life, it is thus critical to have an accurate estimation of the SCR system aging condition. In this paper, two Lyapunov-based observers utilizing the measurements of NOx and ammonia concentrations are analytically developed and verified in simulations for estimating the SCR aging condition. The measurement uncertainty is explicitly considered in the observer design process. A sufficient condition for the boundedness of the estimation error is derived. Simulation results under the US06 test cycle demonstrate the effectiveness of the proposed observers.

Scenario Analysis of Denitration for Chinese Coal-Fired Power Generation

2015 ◽  
Vol 814 ◽  
pp. 425-429 ◽  
Author(s):  
Xian Ce Meng ◽  
Chen Li ◽  
Su Ping Cui ◽  
Li Li Zhao ◽  
Xian Zheng Gong ◽  
...  
Keyword(s):  
Power Generation ◽  
Scenario Analysis ◽  
Power Plants ◽  
Fossil Fuels ◽  
Catalytic Reduction ◽  
Thermal Power ◽  
Power Industry ◽  
Nox Emissions ◽  
Technology Applications ◽  
Chinese Coal

The environmental loads are made due to the natural resources and fossil fuels use and pollutants emissions by Chinese thermal power industry. To explore the realistic coal-fired power generation and its denitration strategies, the input and output of coal-fired power generation in China were identified and quantified. The scope of this paper is defined in the boundary of coal-fired electricity generation system all over China. The methodology follows the principal of ISO 14040 and ISO 14044. The functional unit is “1 kWh of electricity generated”. The inventory data of Chinese coal-fired power generation in 2009 without denitration technology applications were measured. The output data include the CO, N2O, CH4, CO2, NOx, PM and SO2 emissions. NOx emissions are the major contributor of acidification and photochemical in China. To avoid catastrophic environmental damages, the air pollution especially NOx emissions from coal-fired power plants are advised to be cut. For scenario analysis, in the assumption of 100%of selective non-catalytic reduction (SNCR) technology applications, China still has denitration potential. In the coming several decades, the SNCR technology will be decisive for the Chinese coal-fired power industry to reach deeper NOx emission reductions. However, the reduction agents of ammonia and urea usage bring ammonia slip, and extra natural resource and fossils consumption. The urea use also brings extra CO2 emissions. This limits the applications of SNCR technology to reduce NOx emissions.

Comparison of NOx Emissions Decreasing Methods for Biofuel Boilers

2017 ◽  
Author(s):  
Titas Sereika ◽  
Kęstutis Buinevičius ◽  
Adolfas Jančauskas
Keyword(s):  
Catalytic Reduction ◽  
Nox Reduction ◽  
Main Idea ◽  
Nox Emissions ◽  
Reduction Methods ◽  
Reduction Of Nox ◽  
Secondary Air ◽  
Nitrogen Oxides Reduction ◽  
Gas Recirculation ◽  
Co Emission

The main idea of research is to figure out the emissions of nitrogen oxides reduction using various type of reduction methods. In experiments were used NOx reduction methods: high CO emissions generation, flue gas recirculation, water and water vapor supply, selective non-catalytic reduction (SNCR), and SNCR with flammable additive. This study presents emission and combustion results obtained burning furniture production waste which generates higher rate of NOx emissions. The result of research shows, that CO emission has the biggest impact factor -on reducing NOx emission. Burning fuel in combustion zone with first and secondary air ratio (40/60) and using methods for higher generation CO emissions reached 3.000 mg/m3 which reduces NOx emissions up to 83%. Using selective non-catalytic reduction with traditional and flammable additives reduction of NOx emissions reached up to 55%.

Implementation of SCR Systems for Three Boilers at the TVA Paradise Fossil Site

2002 ◽  
Author(s):  
Donald Schreyer ◽  
Arnold Manaker ◽  
Scot Pritchard
Keyword(s):  
Flue Gas ◽  
Bituminous Coal ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Ammonia Slip ◽  
Catalyst Life ◽  
Fossil Site ◽  
Full Power ◽  
Nox Control ◽  
And Storage

In 1998, TVA undertook the implementation of Selective Catalytic Reduction systems at the Paradise Generating Station. The station has three fossil-fired cyclone boilers totaling 2515 Mw of power generation which have been online since the early 1960s for Paradise Units 1 and 2, and since 1970 for Unit 3. Design efforts started late 1998 with Paradise Unit 2, a 704 Mw cyclone-fired unit that went into operation for the May 2000 ozone season. This was followed by Paradise Unit 1, an identical 704 Mw unit that went into operation for the May 2001 ozone season. Paradise Unit 3, an 1107 Mw unit, is currently in manufacture and erection for placement into service for the 2003 ozone season. The Paradise Units 1 & 2 SCR modules are among the largest single modules in service for treating the entire flue gas path. The system design considered the operation of the boiler without overfire air NOx control, where the emission of NOx would be 688.5 g/GJ (1.6 lb/MMBtu) and with overfire air NOx emission of 370 g/GJ (0.86 lb/MMBtu). Paradise Units 1 & 2 are fitted with scrubbers and burn a high sulfur fuel. Paradise 3, not currently fitted with a scrubber, fires a blend of PRB and Utah bituminous coal. The SCR is configured with two modules. The SCR project guarantees are 90% NOx reduction, 2-ppm ammonia slip and a catalyst life of 20,000 hours. Each of the cyclone units retained their tubular air heaters. Each unit required the erection of either temporary or new ductwork from the air heater to the downstream equipment to allow the demolition of equipment that had been part of the gas path but is no longer in service. The old equipment had to be removed to permit the building of the SCRs. Each SCR unit is equipped with a full flow bypass and man-safe dampers. These man-safe dampers permitted the construction and maintenance of the SCR while the boiler was in operation. Paradise Unit 2’s SCR was fitted with steam soot blowers. Sonic horns were tested on a section of Unit 2 and based on the results, Paradise Unit 1 was fitted only with sonic horns for catalyst cleaning. The anhydrous ammonia unloading and storage facility is more than a mile from the ammonia vaporizers that are located at grade adjacent to their respective SCR unit. The monthly ammonia consumption under full power conditions for Paradise Units 1 & 2 and 90% NOx reduction is 1,703.3 m3 (450,000 gallons) per month with the overfire air system in service. This paper addresses the issues and decisions related to integration of the SCR systems and the experiences of manufacturing and erecting each of the SCR units.

Adaptive and Efficient Ammonia Storage Distribution Control for a Two-Catalyst Selective Catalytic Reduction System

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Ming-Feng Hsieh ◽  
Junmin Wang
Keyword(s):  
Catalytic Reduction ◽  
Nox Reduction ◽  
Injection Rate ◽  
Nox Emissions ◽  
System A ◽  
Ammonia Slip ◽  
Ammonia Storage ◽  
In Series ◽  
Storage Distribution ◽  
Scr System

This paper presents an adaptive urea-SCR dosing control design for a two-catalyst SCR system. A novel SCR ammonia storage distribution control (ASDC) approach aiming to simultaneously increase the SCR NOx conversion efficiency and reduce the tailpipe ammonia slip was proposed and experimentally validated. Based on the insight into SCR operational principles, a high ammonia storage level at the upstream part of the catalyst can generally yield a higher NOx reduction efficiency while a low ammonia storage level at the downstream part of the catalyst can reduce the undesired tailpipe ammonia slip. To achieve such an ammonia storage distribution control, a two-catalyst (in series) SCR system with NOx and NH3 sensors was devised. Grounded in a newly developed SCR control-oriented model, an adaptive (with respect to the SCR ammonia storage capacity) controller was designed to control the urea injection rate for achieving different ammonia storages in the two catalysts. Experimental data from a US06 test cycle conducted on a medium-duty Diesel engine system showed that, with the similar total engine-out NOx emissions and NH3 (AdBlue) consumptions, the proposed ASDC strategy simultaneously reduced the tailpipe NOx emissions by 57% and the ammonia slip by 74% in comparison to those from a conventional controller.

scholarly journals Emissions of a Euro 6b Diesel Passenger Car Retrofitted with a Solid Ammonia Reduction System

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 180 ◽  
Author(s):  
Barouch Giechaskiel ◽  
Ricardo Suarez-Bertoa ◽  
Tero Lahde ◽  
Michael Clairotte ◽  
Massimo Carriero ◽  
...  
Keyword(s):  
Catalytic Reduction ◽  
Nox Reduction ◽  
Cold Start ◽  
Nox Emissions ◽  
Passenger Car ◽  
The Road ◽  
Diesel Vehicles ◽  
Hot Start ◽  
On The Road ◽  
Solid Ammonia

Nitrogen oxides (NOx) emissions from diesel vehicles are a serious environmental concern. Prior to the introduction of on-road tests at type approval, vehicle on-road NOx emissions were found many times higher than the applicable limits. Retrofitting an existing vehicle is a short/mid-term solution. We evaluated a NOx reduction retrofit system installed on a Euro 6b diesel passenger car both in the laboratory and on the road. The retrofit consisted of an under-floor SCR (selective catalytic reduction) for NOx catalyst in combination with a solid ammonia-based dosing system as the NOx reductant. The retrofit reduced NOx emissions from 25% (50 mg/km) to 82% (725 mg/km) both in the laboratory and on the road. The minimum reduction was achieved at cold start cycles and the maximum at hot start cycles. The retrofit had small effect on CO2 (fuel consumption). No ammonia emissions were detected and the N2O increase was negligible at cold start cycles, but up to 18 mg/km at hot start cycles. The results showed that the retrofit technology could be beneficial even for high emitting Euro 6b diesel vehicles.

Power Improvement and NOx Reduction Strategies for a Hydrogen-Fueled Multicylinder Internal Combustion Engine

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Jayakrishnan Krishnanunni ◽  
Divesh Bhatia ◽  
Viresh Dutta ◽  
Lalit Mohan Das
Keyword(s):  
Internal Combustion Engine ◽  
Selective Catalytic Reduction ◽  
Power Output ◽  
Catalytic Reduction ◽  
Combustion Engine ◽  
Nox Reduction ◽  
Internal Combustion ◽  
Nox Emissions ◽  
Spark Timing ◽  
Reduction Strategies

Abstract The conventional operation of a hydrogen internal combustion engine (ICE) under lean conditions results in low NOx emissions, however, at the cost of power generated. In this study, the power output of a hydrogen-fueled ICE was increased while maintaining the NOx emissions at low levels. The power output was increased by turbocharging, relatively richer operation, and spark timing optimization, whereas a combination of exhaust gas recirculation (EGR) and H2-selective catalytic reduction (H2-SCR) aftertreatment was used to reduce NOx emissions. Turbocharging resulted in a maximum torque output of 168 N·m at 3200 rpm as compared to 70 N·m at 1600 rpm for the naturally aspirated operation. However, the turbocharger could not generate enough boost at low speeds and the equivalence ratio was increased to obtain a high power output which resulted in a substantial increase in the NOx emissions. The use of EGR resulted in an average reduction of 72% in the NOx emissions. Retarding of spark timing significantly reduced the NOx emissions too, but was limited by the adverse impact on the torque. Since hydrogen would be available onboard a hydrogen-fueled vehicle, we for the first time report external injection of H2 for use as a reductant in the selective catalytic reduction unit. Even under extremely oxidizing conditions, the efficiency of aftertreatment was found to be 35.4% averaged over various speeds. A maximum of 83.7% overall reduction in NOx emissions was achieved by using the combined EGR and H2-SCR strategies.

DyNOR™ DeNOx Performance Confirmed in Further MSW Plants

2010 ◽  
Author(s):  
Fred Sigg ◽  
Roland Halter ◽  
Peter Chromec
Keyword(s):  
Distribution System ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Reduction Process ◽  
Process Conditions ◽  
Nox Emissions ◽  
Commercial Unit ◽  
Catalytic Systems ◽  
Industrial Installation ◽  
Ammonia Slip

Von Roll Inova’s innovative new SNCR process is up to the task. This new approach takes the well known Selective non-catalytic reduction process to new heights (lows). By monitoring process conditions very closely and implementing a quick-reacting, highly precise mechanical system for distribution of the reducing agent, emissions can be limited to levels comparable to those demonstrated by SCR. Von Roll Inova’s DyNOR™ (Dynamic NOx Reduction) process takes advantage of fast and precise infrared pyrometer measurements in the exact locations where reagent is needed. Coupled with a patented distribution system, reagent injection is continuously directed to the optimal location in the furnace. The system is capable of responding to changes in a matter of seconds and thus can correct for uneven temperature profiles which are typical in combustion systems with inhomogeneous waste fuel such as MSW. Good combustion control can limit uncontrolled NOx emissions to less than 200 ppmv and forms the platform upon which secondary NOx reduction measures should build. The conventional Von Roll Inova SNCR process limits NOx emissions to 100 ppmv. DyNOR™ pushes the envelope further towards 70 ppmv NOx and less than 10 ppmv ammonia slip and closes the gap towards capital intensive catalytic systems. Long term trials at a full scale industrial installation have demonstrated emission levels well below 75 ppmv with ammonia slip below 15 ppmv. Now this process has successfully been implemented as a retrofit in a commercial unit. Results confirm that these levels can be safely achieved without compromising furnace air distribution and residence time.

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