DeNOx System Research Articles

Optimization and Numerical Simulation of the Flow Characteristics in SCR System

Selective Catalytic Reduction (SCR) DeNOx is the main flue gas denitrification technology, and the efficiency of SCR DeNOx system depends on whether the flue gas and ammonia distributions of the velocity and concentration fields are uniform in the reactor. Combined with the porous medium model and component transport equations, the numerical simulations were carried on for the SCR system of the 1000MW coal-fired station, and the velocity fields and concentration fields in different cases were obtained. The results showed that: the corner vane cascades and rectifier grills installed, the non-uniformity of flue gas velocity is less than 15% at the catalyst inlet within the reactor. Under the premise of the best flow field, the vortex mixers can ensure the full blending of the ammonia and flue gas in the reactor. The reliability of numerical simulation is verified through the cold model test, and then the design of the SCR system is guided effectively by the numerical simulations.

Effects of various mixer types on the spatial distribution of a De-NOx reductant

De-NOx catalytic systems generally perform better in rich or stoichiometric engine operating conditions due to high hydrocarbon (HC) concentrations in the exhaust gas. However, the hydrocarbon concentration in a diesel engine is typically low, so post or supplemental fuel injections into the exhaust gas have been employed in order to increase the HC concentration. A hydrocarbon-type lean NOx trap (HC-LNT) catalyst system that is a De-NOx system based on NOx-absorbing catalyst has also been developed to optimize control of the external HC injection into the diesel exhaust pipe. The system has a secondary injector that injects diesel fuel (HC) into an exhaust manifold. The typically high temperature (250–350°C) in the exhaust manifold affects the spray behavior of the secondary injector, and the high temperature also makes it particularly difficult to achieve uniform distribution of the reducing agent in the manifold. Thus, it is necessary to use a mixer to improve the fuel distribution in the exhaust manifold. In this study, the effects of various mixer types on the spatial distribution of the LNT reducing agent were investigated to improve the performance of the LNT catalyst system. While the LNT reducing agent was injected directly toward the mixers in a transparent manifold, spray images were collected using a high-speed camera, and the spatial distribution of the spray was analyzed using image processing techniques. The analysis on the spatial distribution of the spray represented that mixers were beneficial to achieve uniform distribution of the reducing agent in exhaust pipe and improve the performance of LNT catalyst system.

Development of Di-Air - A New Diesel deNOx System by Adsorbed Intermediate Reductants

Development of Di-Air - A New Diesel deNOx System by Adsorbed Intermediate Reductants

CATALYSTS TO TREAT POLLUTION GASES OF THE INCINERATORS

Incineration is a useful way to treat industrial and medical waste. However, the combustion process in the incinerators can produce many toxic gases like nitrogen oxides (NOx), monoxide carbon (CO), hydro cacbon (HC). In this paper we present the study and design of the deNOx and oxidation catalyst system, which can be used to treat pollution gases NOx, CO, HC that are produced in the incinerators. The study results show good prospect for applying the treatment system in Vietnam industry.

연료 개질장치의 적용에 따른 디젤 LNT 환원성능 개선 특성

디젤엔진은 높은 열효율과 우수한 연비 성능 등의 장점을 가지고 있으나, 기화된 연료와 주변 공기가 혼합된 후 착화되는 과정을 거치기 때문에 이론 공연비 영역에서는 질소산화물(NOx) 배출이 증가되는 문제점을 가지고 있다. 최근 활발히 연구되고 있는 높은 정화 효율을 가진 LNT촉매는 희박 분위기 조건에서는 NOx를 흡장하게 되고 과농한 분위기에서는 환원 분위기 형성을 통하여 를 NOx저감시키게 된다. 희박 공연비에서 동작하는 디젤 엔진에서는 이러한 환원 과정을 이루기 위해 주기적으로 과농한 분위기를 형성해주어야만 하는데, 이러한 연구는 NOx저감을 위해 HC를 포함한 환원제의 농도를 제어하는 기술로서 본 연구에서는 디젤을 연료로 하는 수소농후가스 발생장치를 이용하여 LNT 촉매에 환원제로서 수소농후가스를 직접 공급하는 방식으로 LNT촉매의 NOx저감 특성을 파악하였다.

305 アンモニアラジカルインジェクションによる同時脱硫脱硝(大気環境保全・改善技術(2))

A unique De-NOx system by ammonia radical injection using an intermittent dielectric barrier discharge (DBD) have been developed for an incinerator. .In this paper, characteristics of simultaneous NOx/SO_2 removal was investigated. SO_2 removal was decreased with increasing applied voltage under NO/SO_2/O_2 system. However, NOx removal was strongly increased in the presence of SO_2. NHi radicals generated by the DBD may have selective reaction with NO. Simultaneous NOx/SO_2 removal by ammonia radical injection is available at a reaction temperature of 700℃ and an applied voltage of 3 kV.

7-90-8 アンモニアラジカルインジェクション法脱硝装置の開発(Session 7 環境対策・リサイクル,ポスター発表)

7-90-8 アンモニアラジカルインジェクション法脱硝装置の開発(Session 7 環境対策・リサイクル,ポスター発表)

304 ラジカルインジェクション脱硝反応におけるNHラジカルの挙動(大気環境保全・改善技術(1))

An ammonia radical injection DeNOx system using an intermittent dielectric barrier discharge (DBD) with a one-cycle sinusoidal-wave power source has been developed to reduce NOx from incinerators. When DBD plasma-generated radicals (NH_2, NH, N and H) are injected into a flue gas containing NOx, NOx is removed efficiently by chain reaction in gas phase. Energy efficiency of DeNOx in this system is 120 g-NO/kWh, which is the higher efficiency than other DeNOx systems using different plasma techniques. However, we have not been explained detailed reaction mechanism yet. In this study, emission spectrum of NH radical was investigated by emission spectroscope. Maximum emission spectrum of NH radical was obtained at an applied voltage of 12 kV for a NOx reduction agent flow rale of 15 L/min and a NH_3 concentration of 500 ppm.

Numerical Study on the Optimum Injection of Urea–Water Solution for SCR DeNOx System of a Heavy-Duty Diesel Engine to Improve DeNOx Performance and Reduce NH3 Slip

Optimization of the urea dosing system to maximize deNOx performance and to minimize NH3 slip during load changes is one of the main challenges for the mobile application of the urea–SCR (selective catalytic reduction) system. A mobile SCR system is restricted to a short distance between the engine exhaust and the catalyst entrance. Therefore, it is likely that urea residence time may not be adequate for complete thermolysis at the catalyst entrance. The key factors affecting the automobile application of SCR technology are the rapid thermolysis, good mixing of ammonia and gas, and reduction of ammonia slip. To this end, in the present study, the effects of the injection angle, urea injector location, and number of injection holes on the uniformity of the ammonia concentration distribution at the entrance of the SCR monolith as well as the maximum ammonia conversion efficiency have been examined in detailed three-dimensional numerical simulations under various engine loads of a heavy-duty diesel engine. A...

Spark ignition natural gas engines—A review

Natural gas is a promising alternative fuel to meet strict engine emission regulations in many countries. Natural gas engines can operate at lean burn and stoichiometric conditions with different combustion and emission characteristics. In this paper, the operating envelope, fuel economy, emissions, cycle-to-cycle variations in indicated mean effective pressure and strategies to achieve stable combustion of lean burn natural gas engines are highlighted. Stoichiometric natural gas engines are briefly reviewed. To keep the output power and torque of natural gas engines comparable to those of their gasoline or Diesel counterparts, high boost pressure should be used. High activity catalyst for methane oxidation and lean deNOx system or three way catalyst with precise air–fuel ratio control strategies should be developed to meet future stringent emission standards. 2006 Elsevier Ltd. All rights reserved.

Efficient decomposition of NO by ammonia radical-injection method using an intermittent dielectric barrier discharge

Although many NO decomposition systems have been developed using plasmas such as dielectric barrier discharges (DBDs), corona discharges, surface discharges, glow discharges, and microwave discharges, the present system is unique on the viewpoint of the use of an intermittent one-cycle sinusoidal power source to generate DBD plasma. There are several features of the system: (1) easy control of the electric power consumed in the DBD plasma, and (2) DBD-plasma generation used only for the production of ammonia radicals. The system employs a radical injection system, where the radicals are produced in a separate discharge chamber, called radical injector, from NO flow field. This enables an efficient production of ammonia radicals being appropriate for DeNOx. It is shown from the temperature dependence of NO removal (DeNOx) characteristics that the present system is a low-temperature DeNOx system compared to a conventional thermal DeNOx system, and NO decomposition is performed over a wide range of gas temperature containing NO. Surveying parametric characteristics of DeNOx, the energy efficiency is improved by a factor of 30% compared to the previously obtained result.

Development and evaluation of a DeNOx system based on urea SCR

DeNOx system comprising a single, highly active SCR catalyst with a catalyst volume of about twice the swept volume of the engine was set up and evaluated at Liebherr Machines Bulle SA in Switzerland. Various control algorithms have been tested with this system. A novel NOx sensor became available for these experiments being used to measure NOx and NH3 after the catalyst. It allowed a NOx closed-loop control system to be used for the adjustment of the urea dosage. This article presents the results of the tests.

液体炭化水素を還元剤として用いた舶用脱硝プラントの研究

The exhaust gas of marine diesel engine contains a lot of NOx, SOx and PM, that is, it contributes to global warming and air pollution, and the IMO has regulated the NOx emissions for the vessels built after January 1st, 2000.KHI has the experience of research about DeNOx methods, for example, timing retard, EGR, fuel-water emulsion, natural gas and methanol ignited with pilot fuel oil, and SCR with NH3 or HC.This paper introduces the test results of DeNOx system for marine diesel engine by SCR with liquid hydrocarbon extracted from marine diesel oil, which has the advantage in cost, treatment and supply compared with troublesome NH3 system.

Bench-scale demonstration of an integrated deSoot–deNOx system

A catalytic deSoot–deNOx system, comprising Pt and Ce fuel additives, a Pt-impregnated wall-flow monolith soot filter and a vanadia-type monolithic NH3-SCR catalyst, was tested with a two-cylinder DI diesel engine. The soot removal efficiency of the filter was 98–99mass% with a balance temperature (stationary pressure drop) of 315°C at an engine load of 55%. The NOx conversion ranged from 40 to 73%, at a NH3/NOx molar ratio of 0.9. Both systems were measured at a GHSV of 52000l/(lh). The maximum NOx conversion was obtained at 400°C. The reason for the moderate deNOx performance is discussed. No deactivation was observed after 380h time on stream. The NOx emission at high engine loads is around 15% lower than that of engines running without fuel additives.

1727 内航船エンジン排ガス浄化用の新しい脱硝触媒システムの研究

New purification technology of the nitrogen oxide discharged from vessels, such as a small coaster, was developed. A new de-NOx system by the combination of an "adsorbent-selective reduction catalyst" was studied as a method of solving the problem that a former type SCR catalyst does not fully operate on the conditions that the exhaust gas temperature is low (below 300℃). Mn-Zr oxide was effective in removing NO at 100-300℃ by absorption in the solid as nitrate. Nitrogen oxides were first stored in the Mn-Zr oxide below 300℃. Then, the stored NOx was released above 300℃ and reduced by the SCR catalyst in the down-stream. As a result of the purification examination using marine diesel engine exhaust gas, it was found that 80% of NOx discharged in a low-temperature region was removable by this system.

P33-05 燃料油(液体炭化水素)からの還元剤を用いた選択的脱硝システムの舶用エンジン排ガスへの適用

P33-05 燃料油(液体炭化水素)からの還元剤を用いた選択的脱硝システムの舶用エンジン排ガスへの適用

Dual-bed Catalytic System for the Selective Reduction of NOx with Propene

For the removal of NO x from exhausts containing excess oxygen, the selective catalytic reduction of NO x using hydrocarbons (HC-SCR) is highly interesting, especially for car applications (lean deNO x ). Two types of HC-SCR catalysts can be distinguished. High-temperature catalysts operate at temperatures above 573 K, showing moderate activity, and (mostly) low heat and poison resistance, but high N 2 selectivity. Low-temperature catalysts, usually based on Pt, operate between 473 and 573 K, showing opposite features: very high activity, as well as heat and poison resistance, and a low N 2 selectivity by forming N 2 O. The strategy for developing an active and stable deNOx system without N 2 O emission is the implementation of a separate catalytic function for N 2 O removal as a second stage.

303 水吸収による道路沿道大気の NOx 浄化システムに関する研究 : 微細気泡による水への NOx 吸収特性とシミュレーションモデルの検討

303 水吸収による道路沿道大気の NOx 浄化システムに関する研究 : 微細気泡による水への NOx 吸収特性とシミュレーションモデルの検討

炭化水素系還元剤を用いた小規模脱硝システムの特性

Authors have carried out experiments for deNOx performance of small size deNOx plant with platinum-zeolite catalyst and propylene reduction agent, for development of deNOx system with hydrocarbon reduction agent.As result of experiments, following have been found.(1) . The deNOx equipment with hydrocarbon reduction agent is higher reduction efficiency by control of exhaust gas temperature at catalyst.(2) . Supply method of reduction agent influences reduction performance of deNOx equipment, so that divide supply of reduction agent is higher reduction efficiency.(3) . NOx reduction effect of this system with other deNOx method, as fuel injection retard and water emulsified fuel, is comparable without other deNOx method.(4) . After driving this system at about 200 hr, NOx reduction efficiency is not drop.

Modeling a Boiling-Liquid, Expanding-Vapor Explosion Phenomenon with Application to Relief Device Design for Liquefied Ammonia Storage

This paper addresses a fictitious accident scenario involving an ammonia storage tank in a refinery. Ammonia is used in a deNOx system. In a selective catalytic reduction environment, a refinery stack gas containing nitric oxide and nitrogen dioxide is decomposed into nitrogen and water vapor. In this study, a cylindrical ammonia tank is “bleved” (boiling-liquid, expanding-vapor explosion (BLEVE)) with an external fire. We developed a computer model in order to determine the thermal response of a horizontal ammonia tank involved in fire engulfment accidents. The assessment of the separation distance between tanks and protection measures such as water spray cooling were also discussed. Further, we examined the relief device design and studied the open-system thermal response as well as pressure response effects in the event of a BLEVE for the ammonia tank.