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.

scholarly journals REDUCTION OF NOX CONCENTRATIONS IN BOILER FLUE GAS BY INJECTING SELECTIVE REAGENTS

2005 ◽  
Vol 13 (2) ◽  
pp. 91-96 ◽  
Author(s):  
Kestutis Buinevičius ◽  
Egidijus Puida
Keyword(s):  
Flue Gas ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Boiler Furnace ◽  
Gas Cleaning ◽  
Operation Conditions ◽  
Cleaning Equipment ◽  
Primary Means ◽  
Reduction Of Nox ◽  
Nox Control

Present EU regulations promote search for efficient means of reducing environmental pollution caused by fuel‐burning equipment. Primary means of NOx reduction are of a limited efficiency. The aim of this study is investigation and development of Selective Non‐Catalytic Reduction (SNCR) for NOx Control. This method can be applied in the existing boilers that have no external flue gas cleaning equipment, and that is the main advantage of the method. Experimental investigation of the influence of various reagent solutions on NOx concentration was carried out in a stand simulating a boiler furnace. Reagents and their operation conditions were selected, desirable efficiency of SNCR method was determined. The experimental results indicated positive application perspectives of this method. Reduction of NOx concentration by 40 % was reached. It was determined that improperly selected SNCR technology can even increase NOx concentration.

scholarly journals Combined NOx and NH3 Slip Reduction in a Stoker Boiler Equipped with the Hybrid SNCR + SCR System FJBS+

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8599
Author(s):  
Robert Wejkowski ◽  
Sylwester Kalisz ◽  
Przemysław Garbacz ◽  
Izabella Maj
Keyword(s):  
Fly Ash ◽  
Flue Gas ◽  
Full Range ◽  
Nox Reduction ◽  
Main Idea ◽  
Cost Effective ◽  
Combustion Products ◽  
Ammonia Removal ◽  
Ammonia Content ◽  
Ammonia Slip

The application of secondary NOx control methods in medium to low-capacity furnaces is a relatively new topic on the energy market and thus requires further research. In this paper, the results of full-scale research of SNCR and hybrid SNCR + SCR methods applied into a 29 MWth solid fuel fired stoker boiler is presented. The tests were performed for a full range of boiler loads, from 33% (12 MWth) to 103% (30 MWth) of nominal load. A novel SNCR + SCR hybrid process was demonstrated based on an enhanced in-furnace SNCR installation coupled with TiO2-WO3-V2O5 catalyst, which provides extra NOx reduction and works as an excess NH3 “catcher” as well. The performance of a brand-new catalyst was evaluated in comparison to a recovered one. The emission of NOx was reduced below 180 mg NOx/Nm3 at 6% O2, with ammonia slip in flue gas below 10 mg/Nm3. Special attention was paid to the analysis of ammonia slip in combustion products: flue gas and fly ash. An innovative and cost-effective method of ammonia removal from fly ash was presented and tested. The main idea of this method is fly ash recirculation onto the grate. As a result, ammonia content in fly ash was reduced to a level below 6.1 mg/kg.

scholarly journals In situ measurements of O<sub>2</sub> and CO eq.  in cement kilns

2017 ◽  
Vol 6 (2) ◽  
pp. 327-330 ◽  
Author(s):  
Olga Driesner ◽  
Fred Gumprecht ◽  
Ulrich Guth
Keyword(s):  
Flue Gas ◽  
Oxygen Sensor ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Raw Material ◽  
Delayed Response ◽  
Plant Operator ◽  
In Situ Sensors ◽  
Cement Kilns

Abstract. The simultaneous in situ measurement of O2 and CO eq.  in cement kilns is a great challenge due to the high process temperatures and high dust load. The standard method for measurement for flue gas in cement kilns is extractive. Extractive measurements have a higher response time due to the flue gas conditioning including the length of heated extraction lines for electrochemical or optical analysis. This delayed response is not optimal for fast process control.A probe was developed for this purpose in which the in situ solid electrolyte oxygen sensor and an in situ CO eq.  mixed potential sensor are implemented. Due to the high temperatures, the probe is cooled by a water–coolant mixture. In order to prevent deposits of raw material forming and sintering on the probe, it rotates 90° in programmable intervals. In addition, an automated probe plunger pneumatically removes plugging at the probe flue gas entrance, also in programmable intervals. These self-cleaning functions allow the probe to continually stay in the process for combustion optimisation (low excess O2 and CO) and enable the plant operator to measure additional process-related gas components (NO, SO2, HCl etc.) and optimise the SNCR (selective non-catalytic reduction) for NOx reduction. Combustion air supply can be adapted very quickly due to the in situ sensors, which has been demonstrated by a CEMTEC® probe over years (Märker Cement Harburg, 2017).

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.

Model Based Analysis and Control Design of a Urea-SCR deNOx Aftertreatment System

2005 ◽  
Vol 128 (3) ◽  
pp. 737-741 ◽  
Author(s):  
Devesh Upadhyay ◽  
Michiel Van Nieuwstadt
Keyword(s):  
Sliding Mode ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Control Design ◽  
Observer Design ◽  
Lumped Parameter Model ◽  
Control Synthesis ◽  
Model Based ◽  
Ammonia Slip ◽  
Controllability And Observability

In this paper we tackle issues relevant to model based control design for a Urea based Selective Catalytic Reduction (SCR) process relevant to automotive applications. A three state, control oriented, lumped parameter model of the system is used to investigate essential controllability and observability properties of the Urea-SCR plant. Results from the controllability and observability analysis of both nonlinear and linearized models are shown to have realistic implications. Observer design for predicting gas phase ammonia slip is outlined and results presented. An altered definition of the catalyst efficiency is used in control design. It is shown that this altered definition lends itself readily to control synthesis in the Sliding Mode framework while satisfying the dual control objectives of maximizing NOx reduction and minimizing ammonia slip.

NOx Reduction: The Challenge for Innovative Concepts in Europe

2011 ◽  
Author(s):  
Ralf Koralewska
Keyword(s):  
Catalytic Reduction ◽  
Catalytic Converter ◽  
Nox Reduction ◽  
Waste Incineration ◽  
Reaction Rates ◽  
Limit Values ◽  
Average Value ◽  
Ammonia Slip ◽  
Emission Limit ◽  
The Eu

During combustion, most of the waste’s nitrogen content is transferred to the flue gases as nitrogen oxide, NOx. The EU Waste Incineration Directive defines a maximum emission limit value for NOx of 200 mg/Nm3 as a daily average value referred to 11% O2. Based on National Emission Ceilings (NEC) defined by the Gothenburg Protocol, it can be expected that the limit values for NOx in the EU will become even more stringent. In some European countries (e.g. The Netherlands, Austria, Switzerland) a lower emission limit has already been introduced. Selective Catalytic Reduction (SCR) technologies are used in many cases to achieve the above-mentioned NOx limits. However, there are drawbacks to SCR systems such as high investment cost. Operation cost is also quite high due to the energy consumption necessary for the reheating of the flue gas as well as the increased pressure loss. Innovative technologies are therefore required to make it possible to reconcile both requirements: reduced emissions and increased energy efficiency. Selective Non-Catalytic Reduction (SNCR) systems are based on the selective reaction of ammonia or urea injected into the upper furnace. In many cases SNCR technologies are limited by the ammonia slip which increases in case of more stringent NOx requirements. According to the relevant BREF document, an ammonia slip limit of 10 mg/Nm3 is generally required at the stack. In order to achieve reduced NOx values, it is necessary to implement measures to reduce ammonia slip, by means of either a wet scrubber or a High-dust catalytic converter. EfW plants in Mainz (Germany) and Brescia (Italy) are examples of operational plants combining SNCR with such a catalytic converter type. In addition R&D activities are carried out on the development of simplified reaction mechanisms to be implemented in Computational Fluid Dynamics (CFD) codes. With these tools it will be possible to describe the interaction between turbulent mixing, radiation and chemical reaction rates. Another option to achieve low NOx values (below 100 mg/Nm3) is the reduction of NOx by so-called primary measures, e.g. the Very Low NOx process (VLN), which has been developed by MARTIN jointly with its cooperation partners. The VLN process is based on a grate-based combustion system. The “VLN gas” is drawn off at the rear end of the grate and is reintroduced into the upper furnace in the vicinity of the SNCR injection positions. NOx will be reduced significantly, ensuring low NOx emission values at the stack as required, at low values for ammonia slip. The new EfW plant in Honolulu (USA) will be equipped with the VLN process. In Coburg (Germany), the VLN process will be retrofitted in an existing installation. This paper documents the potential and the limitations of different measures for NOx reduction as well as examples of recent innovative EfW plants in Europe using MARTIN technologies successfully.

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.

Enhanced Selective Non-Catalytic Reduction (SNCR) for Refinery Applications: Pilot-Scale Test Data With a Hydrogen Promoter

2011 ◽  
Author(s):  
Larry Swanson ◽  
Wei Zhou ◽  
David Moyeda ◽  
Christopher Samuelson
Keyword(s):  
Flue Gas ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Pilot Scale ◽  
Gas Temperature ◽  
Wide Range ◽  
Lower Temperature Range ◽  
Scale Test ◽  
Lower Temperature ◽  
Pilot Scale Test

Selective non-catalytic reduction technology (SNCR) is an effective and economical method of reducing NOX emissions for a wide range of industrial combustion systems. It is widely known that the traditional SNCR temperature window is centered around 1,200 to 1,255 K [1]. However, for some applications, the flue gas temperatures in boilers, oxidizers, and heaters range from 950 to 1150 K. At these lower temperatures, injection of an amine reagent into flue gas no longer actively reduces NOX, but instead passes through the system and exits as ammonia slip. Earlier studies have shown that at lower temperatures, hydrogen and other promoters can be added to the system to shift the SNCR window to a lower temperature range, enhancing or promoting SNCR NOX reduction performance [2–5]. This extended abstract describes pilot-scale test results for an enhanced SNCR process (ESNCR) that uses hydrogen as the SNCR promoter. The impacts of flue gas temperature, hydrogen concentration, CO concentration, and SO2 concentration on ESNCR NOX reduction performance are presented.

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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