Urea Mixing in Selective Catalytic Reduction Systems

2007 ◽  
Author(s):  
Fawaz Fadul ◽  
Amarnath Nelli ◽  
Ahmad Fakheri
Keyword(s):  
Gas Flow ◽  
Catalytic Reduction ◽  
Particulate Emissions ◽  
Exhaust Gas ◽  
Selective Catalyst ◽  
Emission Standards ◽  
Aqueous Mixture ◽  
Catalyst Reduction ◽  
The Impact ◽  
State Of Art

The tightening of emission standards mandates NOx and particulate emissions to be reduced by more than 90 percent by 2010 in Europe, United States, and Japan. Selective Catalyst Reduction (SCR) using Urea as the NOx reducing agent is fast becoming the preferred technology. This paper provides an overview of the state of art on the topic. It also examines the use of urea vapor instead of spraying an aqueous mixture and the impact of different spraying strategies on mixing. It is shown that by injecting urea vapor opposite to direction of the exhaust gas flow, better mixing with the exhaust and thus better conversion can be achieved as compared with injecting the urea vapor parallel to the gas. The increase in pressure drop does not appear significant.

Selective Catalytic Reduction Impact on Heat Recovery Steam Generator Design and Operation

1986 ◽  
Author(s):  
James S. Davis ◽  
G. C. Duponteil
Keyword(s):  
Selective Catalytic Reduction ◽  
Gas Turbine ◽  
Steam Generator ◽  
Heat Recovery ◽  
Gas Flow ◽  
High Efficiency ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Heat Recovery Steam Generator ◽  
The Impact

Selective Catalytic Reduction (SCR) is a post-combustion method to reduce the oxides of nitrogen (NOx), present in flue gases such as gas turbine exhaust streams, to N2 and water. It involves the injection of ammonia and the use of a catalyst module to promote the reaction to obtain high efficiency (60–86+%) NOx reduction. Several operating parameters can influence catalyst performance to include temperature, gas flow distribution, presence of sulfur compounds and catalyst age. This paper examines the impact of a SCR integration in a gas turbine heat recovery steam generator (HRSG) design/operation. Limitations on HRSG load and following capabilities, effect on capital cost and overall performance and current SCR system experience represent a number of areas that are examined.

scholarly journals Application of the F-statistic of the Fisher-Snedecor distribution to analyze the significance of the effect of changes in the compression ratio of a diesel engine on the value of the specific enthalpy of the exhaust gas flow

2021 ◽  
Author(s):  
Patrycja Puzdrowska
Keyword(s):  
Diesel Engine ◽  
Compression Ratio ◽  
Gas Flow ◽  
Test Stand ◽  
Specific Enthalpy ◽  
Experimental Investigations ◽  
Exhaust Gas ◽  
Exhaust Gases ◽  
Measurement Results ◽  
The Impact

The paper discusses the impact of changes in the compression ratio on the operating parameters of a diesel engine, e.g. on the temperature of exhaust gases. It presents the construction of the laboratory test stand, on which experimental measurements were realized. It is characterized how the actual changes of the compression ratio were introduced to the existing engine. The program of experimental investigations taking into account the available test stand and measurement possibilities was described. A statistical and qualitative analysis of the obtained measurement results was made. The use of F statistics of the Fisher-Snedecor distribution was proposed to assess the significance of the effect of compression ratio changes on the specific enthalpy of the exhaust gas stream. The specific enthalpy of exhaust gases was analysed for one cycle of diesel engine work, determined on the basis of the course of quickly varying temperature of exhaust gases. The results of these analyses are discussed and the utilitarian purpose of this type of evaluation in parametric diagnostics of piston engines is presented.

Interpretation of the Oscillating Signals of the Smart NOx Sensors Used in Urea Selective Catalyst Reduction Systems via Spectral Analysis

2013 ◽  
Vol 479-480 ◽  
pp. 719-723
Author(s):  
Chih Cheng Chou ◽  
Chia Jui Chiang ◽  
Yu Hsuan Su ◽  
Yong Yuan Ku
Keyword(s):  
Spectral Analysis ◽  
Catalytic Reduction ◽  
Ammonia Concentration ◽  
Nonlinear Characteristic ◽  
Sensor Signal ◽  
Reciprocating Motion ◽  
Selective Catalyst ◽  
Nox Sensor ◽  
Higher Harmonic ◽  
Catalyst Reduction

The oscillating signals of NOx sensor observed in urea selective catalytic reduction (SCR) tests are explained via spectral analysis. The NOx sensor built by NGK / Continental requires decoding following the SAE J1939 protocol and thus higher harmonic induced by the discretization is observed in the spectral analysis. The reciprocating motion of the urea pump induces fluctuation of the ammonia dosage, which combined with the nonlinear characteristic from ammonia dosage to NOx downstream SCR result in oscillating NOx sensor readings with different amplitude. The cross-sensitivity of the NOx sensor to ammonia concentration for higher-than-stoichiometric ammonia dosage also results in oscillating NOx sensor signal at lower frequencies.

scholarly journals The High-Rate Sealed MRPC to Promote Pollutant Exchange in Gas Gaps: Status on the Development and Observations

2021 ◽  
Vol 11 (11) ◽  
pp. 4722
Author(s):  
Botan Wang ◽  
Xiaolong Chen ◽  
Yi Wang ◽  
Dong Han ◽  
Baohong Guo ◽  
...  
Keyword(s):  
Gas Flow ◽  
High Rate ◽  
Stable Operation ◽  
Beam Test ◽  
High Luminosity ◽  
Rate Test ◽  
3D Printed ◽  
Resistive Plate Chambers ◽  
The Impact ◽  
Current Behavior

This work reports the latest observations on the behavior of two Multigap Resistive Plate Chambers (MRPC) under wide high-luminosity exposures, which motivate the development and in-beam test of the sealed MRPC prototype assembled with low-resistive glass. The operation currently being monitored, together with previous simulation results, shows the impact of gas pollution caused by avalanches in gas gaps, and the necessity to shrink the gas-streaming volume. With the lateral edge of the detector sealed by a 3D-printed frame, a reduced gas-streaming volume of ~170 mL has been achieved for a direct gas flow to the active area. A high-rate test of the sealed MRPC prototype shows that, ensuring a 97% efficiency and 70 ps time resolution, the sealed design results in a stable operation current behavior at a counting rate of 3–5 kHz/cm2. The sealed MRPC will become a potential solution for future high luminosity applications.

scholarly journals The Impact of Pressure and Hydrocarbons on NOx Abatement over Cu- and Fe-Zeolites at Pre-Turbocharger Position

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 336
Author(s):  
Deniz Zengel ◽  
Simon Barth ◽  
Maria Casapu ◽  
Jan-Dierk Grunwaldt
Keyword(s):  
Catalytic Reduction ◽  
Elevated Pressure ◽  
Systematic Investigation ◽  
Diesel Oxidation Catalyst ◽  
Zeolite Catalysts ◽  
Oxidation Catalyst ◽  
Pollutant Concentrations ◽  
Oxidation Of Hydrocarbons ◽  
Negative Effect ◽  
The Impact

Positioning the catalysts in front of the turbocharger has gained interest over recent years due to the earlier onset temperature and positive effect of elevated pressure. However, several challenges must be overcome, like presence of higher pollutant concentrations due to the absence or insufficient diesel oxidation catalyst volume at this location. In this context, our study reports a systematic investigation on the effect of pressure and various hydrocarbons during selective catalytic reduction (SCR) of NOx with NH3 over the zeolite-based catalysts Fe-ZSM-5 and Cu-SSZ-13. Using a high-pressure catalyst test bench, the catalytic activity of both zeolite catalysts was measured in the presence and absence of a variety of hydrocarbons under pressures and temperatures resembling the conditions upstream of the turbocharger. The results obtained showed that the hydrocarbons are incompletely converted over both catalysts, resulting in numerous byproducts. The emission of hydrogen cyanide seems to be particularly problematic. Although the increase in pressure was able to improve the oxidation of hydrocarbons and significantly reduce the formation of HCN, sufficiently low emissions could only be achieved at high temperatures. Regarding the NOx conversion, a boost in activity was obtained by increasing the pressure compared to atmospheric reaction conditions, which compensated the negative effect of hydrocarbons on the SCR activity.

Hydrogen Concentration Analysis in Pecvd and Rtcvd Silicon Nitride Thin Films and It's Impact on Device Performance

2001 ◽  
Vol 664 ◽  
Author(s):  
C. Y. Wang ◽  
E. H. Lim ◽  
H. Liu ◽  
J. L. Sudijono ◽  
T. C. Ang ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Threshold Voltage ◽  
Vapor Deposition ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Gate Oxide ◽  
Nitride Film ◽  
Device Performance ◽  
Gas Flow Ratio ◽  
The Impact

ABSTRACTIn this paper the impact of the ESL (Etch Stop layer) nitride on the device performance especially the threshold voltage (Vt) has been studied. From SIMS analysis, it is found that different nitride gives different H concentration, [H] in the Gate oxide area, the higher [H] in the nitride film, the higher H in the Gate Oxide area and the lower the threshold voltage. It is also found that using TiSi instead of CoSi can help to stop the H from diffusing into Gate Oxide/channel area, resulting in a smaller threshold voltage drift for the device employed TiSi. Study to control the [H] in the nitride film is also carried out. In this paper, RBS, HFS and FTIR are used to analyze the composition changes of the SiN films prepared using Plasma enhanced Chemical Vapor deposition (PECVD), Rapid Thermal Chemical Vapor Deposition (RTCVD) with different process parameters. Gas flow ratio, RF power and temperature are found to be the key factors that affect the composition and the H concentration in the film. It is found that the nearer the SiN composition to stoichiometric Si3N4, the lower the [H] in SiN film because there is no excess silicon or nitrogen to be bonded with H. However the lowest [H] in the SiN film is limited by temperature. The higher the process temperature the lower the [H] can be obtained in the SiN film and the nearer the composition to stoichiometric Si3N4.

Two-Phase Flows in Mini-/Micro-Gas Flow Channels of PEM Fuel Cells

2013 ◽  
Author(s):  
Sung Chan Cho ◽  
Yun Wang
Keyword(s):  
Pressure Drop ◽  
Gas Flow ◽  
Fluid Model ◽  
Pem Fuel Cells ◽  
Two Phase ◽  
Micro Gas Flow ◽  
Two Fluid Model ◽  
The Impact ◽  
Two Fluid ◽  
Phase Pressure

In this paper, two-phase flow dynamics in a micro channel with various wall conditions are both experimentally and theoretically investigated. Annulus, wavy and slug flow patterns are observed and location of liquid phase on different wall condition is visualized. The impact of flow structure on two-phase pressure drop is explained. Two-phase pressure drop is compared to a two-fluid model with relative permeability correlation. Optimization of correlation is conducted for each experimental case and theoretical solution for the flows in a circular channel is developed for annulus flow pattern showing a good match with experimental data in homogeneous channel case.

High Performance MEMS Thermal Gyroscope

2012 ◽  
Author(s):  
Nilgoon Zarei ◽  
Albert M. Leung ◽  
John D. Jones
Keyword(s):  
External Force ◽  
High Performance ◽  
Gas Flow ◽  
Element Model ◽  
Minimal Impact ◽  
Mems Gyroscope ◽  
Force Finding ◽  
Dimensional Finite Element ◽  
To Come ◽  
The Impact

This paper reports modeling a new design of Thermal MEMS gyroscope through the use of the Comsol Multiphysics software package. Being very small and having no movable parts have made thermal MEMS gyroscope very practical. Previously designed Thermal MEMS gyroscope shows some limitation such as being vulnerable to gravity force. Finding a technique to increase the range of thermal MEMS gyroscope reliability motivated us to come up with a new design that we will refer to as the ‘Forced Convection MEMS gyroscope’. A two-dimensional finite-element model of the device has been developed to investigate its performance. An external force has been introduced to the system to create a higher-velocity hot gas stream that will be deviated more in response to rotation. The external force should be great enough that convection currents resulting from gravity or acceleration will have minimal impact on the gyroscope sensitivity. A heating element can still be used, but its primary purpose is now to warm the flowing gas so that it can be detected by the sensors. In this paper we will also show that, in order to completely eliminate the impact of gravity and increase the sensitivity of the gyroscope, it is possible to eliminate the heaters entirely and instead use heated sensors to detect gas currents. In other words, the sensors are working as hot-wire anemometers. Our simulations suggest that this design variant results in higher sensitivity. We have also carried out optimization studies to identify the best location for the heaters and sensors. A prototype of this device has been fabricated based on MEMS techniques, and an external pump is used to produce an oscillating gas flow within the device.

scholarly journals The influence of physical parameters on the in-situ metal carbonyl complex formation studied with the Fast On-line Reaction Apparatus (FORA)

2021 ◽  
Vol 109 (4) ◽  
pp. 261-281
Author(s):  
Yves Wittwer ◽  
Robert Eichler ◽  
Dominik Herrmann ◽  
Andreas Türler
Keyword(s):  
Gas Flow ◽  
Metal Carbonyl ◽  
Fission Products ◽  
Reaction Chamber ◽  
Single Atom ◽  
Physical Parameters ◽  
Carbonyl Complex ◽  
Reaction Conditions ◽  
On Line ◽  
The Impact

Abstract The Fast On-line Reaction Apparatus (FORA) was used to investigate the influence of various reaction parameters onto the formation and transport of metal carbonyl complexes (MCCs) under single-atom chemistry conditions. FORA is based on a 252Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes. Those are recoiling from the spontaneous fission source into a reaction chamber flushed with a gas-mixture containing CO. Upon contact with CO, fission products form volatile MCCs which are further transported by the gas stream to the detection setup, consisting of a charcoal trap mounted in front of a HPGe γ-detector. Depending on the reaction conditions, MCCs are formed and transported with different efficiencies. Using this setup, the impact of varying physical parameters like gas flow, gas pressure, kinetic energy of fission products upon entering the reaction chamber and temperature of the reaction chamber on the formation and transport yields of MCCs was investigated. Using a setup similar to FORA called Miss Piggy, various gas mixtures of CO with a selection of noble gases, as well as N2 and H2, were investigated with respect to their effect onto MCC formation and transport. Based on this measurements, optimized reaction conditions to maximize the synthesis and transport of MCCs are suggested. Explanations for the observed results supported by simulations are suggested as well.

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