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.

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.

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.

Simultaneous Optimization of Configuration and Control for a Passive SCR System

2018 ◽  
Author(s):  
Pingen Chen ◽  
Qinghua Lin
Keyword(s):  
Catalytic Reduction ◽  
Simultaneous Optimization ◽  
Computationally Efficient ◽  
System Architectures ◽  
Aftertreatment System ◽  
In Series ◽  
System Configurations ◽  
Scr System ◽  
And Control ◽  
Passive Scr

The configuration and control of aftertreatment systems have a significant impact on their functionalities and emission control performance. The traditional aftertreatment system configurations, i.e., connections from one aftertreatment subsystem to another subsystem in series, are simple but generally do not yield the optimal aftertreatment system performance. New aftertreatment configurations, in conjunction with new engine and aftertreatment control, can significantly improve engine efficiency and emission reduction performance. However, new configuration design requires human intuition and in-depth knowledge of engine and aftertreatment system design and control. The purpose of this study is to develop a general systematic and computationally-efficient method which enables automated and simultaneous optimization of passive selective catalytic reduction (SCR) system architectures and the associated non-uniform cylinder-to-cylinder combustion (NUCCC) controls based on a newly proposed highly reconfigurable passive SCR model structure and integer partition theory. The proposed method is general enough to account for passive SCR systems with two or more TWC stages. We demonstrate through this case study that the optimized passive SCR configuration, in conjunction with the optimized NUCCC control, can reduce the NH3 specific fuel consumption by up to 21.90%.

scholarly journals Direct Measurement of Ammonia Storage on Passive SCR Systems for Lean Gasoline NOx Reduction Using Radio Frequency Sensing

2019 ◽  
Author(s):  
Paul Ragaller ◽  
Josh Mandelbaum ◽  
Luc Lapenta ◽  
Alexander Sappok ◽  
Josh Pihl ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Real Time ◽  
Gasoline Engine ◽  
Nox Reduction ◽  
Practical Implementation ◽  
Engine Operation ◽  
Ammonia Storage ◽  
Scr System ◽  
Lean Gasoline ◽  
Passive Scr

Abstract Lean gasoline engine operation provides clear efficiency benefits relative to conventional stoichiometric combustion approaches. One of the key hurdles to the widespread, practical implementation of lean gasoline combustion remains the challenge of lean NOx control. One of the potential approaches for controlling NOx emission from lean gasoline engines is the so-called passive selective catalytic reduction (SCR) system. In such systems, periods of rich operation generate ammonia over a three-way catalyst (TWC), which is then adsorbed on the downstream SCR and consumed during lean operation. Brief periods of rich operation must occur in response to the depletion of stored ammonia on the SCR, which requires reliable measurements of the SCR ammonia inventory. Presently, lean exhaust system controls rely on a variety of gas sensors mounted up- and downstream of the catalysts, and which only provide an indirect inference of the operation state. In this study, a radio frequency (RF) sensor was used to provide a direction measurement of the amount of ammonia adsorbed on the SCR in real-time. The RF sensor was calibrated and deployed on a BMW N43B20 4-cylinder lean gasoline engine equipped with a passive SCR system. Brief periods of rich operation performed at lambda values between 0.98 and 0.99 generated the ammonia, subsequently stored on the SCR for consumption during periods of lean operation. The experiments compared real-time measurements of SCR ammonia inventory from the RF sensor with estimates of ammonia coverage derived from exhaust gas composition measurements upstream and downstream of the catalyst. The results showed a high degree of correlation between the RF measurements and SCR ammonia storage inventory, and demonstrated NOx conversion efficiencies above 98%, confirming the feasibility of the concept. Relative to stoichiometric operation, lean-gasoline operation resulted in fuel efficiency gains of up to 10%, which may be further improved through direct feedback control from the RF sensor to optimize lean–rich cycling based on actual, measured SCR ammonia levels.

scholarly journals Investigation of Urea Uniformity with Different Types of Urea Injectors in an SCR System

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1269
Author(s):  
Muhammad Khristamto Aditya Wardana ◽  
Kwangchul Oh ◽  
Ocktaeck Lim
Keyword(s):  
Diesel Engine ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Heavy Duty ◽  
Ammonia Gas ◽  
Experimental Parameters ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel ◽  
Scr System

Heavy-duty diesel engines in highway use account for more than 40% of total particulate and nitrogen oxide (NOx) emissions around the world. Selective catalytic reduction (SCR) is a method with effective results to reduce this problem. This research deals with problems in the urea evaporation process and ammonia gas distribution in an SCR system. The studied system used two types of urea injectors to elucidate the quality of ammonia uniformity in the SCR system, and a 12,000-cc heavy-duty diesel engine was used for experimentation to reduce NOx in the system. The uniformity of the generated quantities of ammonia was sampled at the catalyst inlet using a gas sensor. The ammonia samples from the two types of urea injectors were compared in experimental and simulation results, where the simulation conditions were based on experimental parameters and were performed using the commercial CFD (computational fluid dynamics) code of STAR-CCM+. This study produces temperatures of 371 to 374 °C to assist the vaporization phenomena of two injectors, the gas pattern informs the distributions of ammonia in the system, and the high ammonia quantity from the I-type urea injector and high quality of ammonia uniformity from the L-type urea injector can produce different results for NOx reduction efficiency quality after the catalyst process. The investigations showed the performance of two types of injectors and catalysts in the SCR system in a heavy-duty diesel engine.

Modelling and parametric investigation of NOx reduction by oxidation precatalyst-assisted ammonia-selective catalytic reduction

2009 ◽  
Vol 223 (9) ◽  
pp. 1193-1206 ◽  
Author(s):  
S-C Jung ◽  
W-S Yoon
Keyword(s):  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Volume Ratio ◽  
Kinetic Scheme ◽  
Space Velocity ◽  
Gas Temperature ◽  
Scr System ◽  
Very High

Nitrogen oxide (NO x) reduction by the selective catalytic reduction (SCR) system assisted by an oxidation precatalyst is modelled and analytically investigated. The Langmuir—Hinshelwood SCR kinetic scheme with vanadium-based catalyst and ammonia (NH3) reductant in conjunction with the NO—NO2 conversion reaction over a platinum-based catalyst is used. The effects of the ratio of the oxidation precatalyst to the SCR monolith volume, the gas temperature, the space velocity, and the NH3-to-NO x concentration ratio on the de-NO x performance are parametrically examined. The oxidation precatalyst promotes NO x conversion at low temperatures. At intermediate temperatures, the NO x reduction is either activated or deactivated with increase in the space velocity. A higher oxidation precatalyst-to-SCR monolith volume ratio tends to promote the NO x reduction of higher space velocities. At high temperatures, the de-NO x efficiency is very high and insensitive to the space velocity. The NO x conversion efficiency depends on the NH3-to-NO x ratio at low temperatures.

scholarly journals The Development and Implementation of Model-Based Control Algorithm of Urea-SCR Dosing System for Improving De-NOx Performance and Reducing NH3-Slip

2011 ◽  
Author(s):  
Soo-Jin Jeong ◽  
Woo-Seung Kim ◽  
Jung-Kwon Park ◽  
Ho-Kil Lee ◽  
Se-Doo Oh
Keyword(s):  
Control Algorithm ◽  
Catalytic Reduction ◽  
Fluid Model ◽  
Nox Reduction ◽  
Reaction Model ◽  
Urea Solution ◽  
Model Based Control ◽  
Model Based ◽  
Nh3 Emission ◽  
Scr System

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia (NH3) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and NH3 slip reduction in the SCR system. This paper investigated NOx and NH3 emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and O2 for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm cannot estimate NH3 absorbed on the catalyst Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated based on the analytic model for SCR system. The channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.

Coordinated Active Thermal Management and Selective Catalytic Reduction Control for Simultaneous Fuel Economy Improvement and Emissions Reduction During Low-Temperature Operations

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Pingen Chen ◽  
Junmin Wang
Keyword(s):  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Thermal Management ◽  
Catalytic Reduction ◽  
Coordinated Control ◽  
Nox Emissions ◽  
Total Cost ◽  
Nox Conversion ◽  
Ammonia Slip ◽  
Nox Conversion Efficiency

The low-temperature operations of diesel engines and aftertreatment systems have attracted increasing attention over the past decade due to the stringent diesel emission regulations and excessive tailpipe emissions at low temperatures. The removal of NOx emissions using selective catalytic reduction (SCR) systems during low-temperature operations remains a significant challenge. One of the popular techniques for alleviating this issue is to employ active thermal management via in-cylinder postinjection to promote aftertreatment system temperatures. Meanwhile, numerous studies have focused on ammonia coverage ratio controls with the aim to maintain high NOx conversion efficiency and low tailpipe ammonia slip. However, most of the active thermal management and SCR controls in the existing literatures were separately and conservatively designed, which can lead to higher cost of SCR operation than needed including diesel fuel consumption through active thermal management and urea solution consumption. The main purpose of this study is to design and coordinate active thermal management and SCR control using nonlinear model predictive control (NMPC) approach to minimize the total cost of SCR operation while obtaining high NOx conversion efficiency and low tailpipe ammonia slip. Simulation results demonstrate that, compared to the baseline control which consists of separated active thermal management and SCR control, the coordinated control is capable of reducing the total cost of SCR operation by 25.6% while maintaining the tailpipe NOx emissions and ammonia slip at comparable levels. Such an innovative coordinated control design concept shows its promise in achieving low tailpipe emissions during low-temperature operations in a cost-effective fashion.

Factors Affecting Mercury Oxidation by SCR Catalysts

2014 ◽  
Vol 986-987 ◽  
pp. 755-760
Author(s):  
Wen Du ◽  
Li Bao Yin ◽  
Yu Qun Zhuo ◽  
Qi Sheng Xu ◽  
Liang Zhang ◽  
...  
Keyword(s):  
Active Sites ◽  
Catalytic Reduction ◽  
Space Velocity ◽  
Injection Rate ◽  
Mercury Oxidation ◽  
Factors Affecting ◽  
Scr Catalysts ◽  
Negative Effect ◽  
Oxidation Efficiency ◽  
Scr System

The application of selective catalytic reduction (SCR) system may affect mercury speciation in coal-combustion flue gas. The factors affecting mercury oxidation efficiency by SCR catalysts have been evaluated in this research. The influencing factors investigated included hydrogen chloride (HCl), sulfur dioxide (SO2), ammonia (NH3) injection rate and space velocity. HCl had been found to promote mercury oxidation significantly. The Eley-Rideal mechanism was proven to be suitable to explain the reaction of Hg0 and HCl. NH3 injection had a strong negative effect to mercury oxidation. The deactivation of aged SCR catalysts was mainly due to loss of active sites.

A Simple Gas Turbine Combustor NOx Correlation Including the Effect of Vitiated Air

1977 ◽  
Vol 99 (2) ◽  
pp. 145-152 ◽  
Author(s):  
D. A. Sullivan
Keyword(s):  
Gas Turbines ◽  
Laboratory Tests ◽  
Nox Reduction ◽  
Nox Emissions ◽  
Gas Turbine Combustor ◽  
Gaseous Fuels ◽  
Fuel Flow ◽  
In Series ◽  
Data Points ◽  
Regenerative Cycle

A set of parametric laboratory tests are used to develop a simple NOx correlation. The correlation is then compared with over 100 data points from various gas turbines operating on liquid and gaseous fuels. The correlation agrees well with constant speed simple cycle and regenerative cycle NOx data. The effect of vitiated air on NOx emissions is also determined from full scale laboratory tests and machine data. The NOx correlation with vitiated air is used to demonstrate the NOx emissions from two combustors operated in series with a variable fuel flow split between them. The nonlinear effect of fuel-to-air ratio on NOx production is shown to be responsible for the NOx reduction which occurs when two combustors are operated in series as opposed to single combustor operation.

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