Use of CFD Modeling for Design of NOx Reduction Systems in Utility Boilers

2002 ◽  
Author(s):  
Bradley Adams ◽  
Marc Cremer ◽  
James Valentine ◽  
Venkata Bhamidipati ◽  
David O’Connor ◽  
...  
Keyword(s):  
Nox Reduction ◽  
Field Testing ◽  
Nox Emission ◽  
Injection System ◽  
Cfd Modeling ◽  
Unburned Carbon ◽  
Port Placement ◽  
Utility Boilers ◽  
Ammonia Slip ◽  
Combustion Optimization

CFD modeling has found increasing use in the design and evaluation of utility boiler retrofits, combustion optimization and NOx reduction technologies. This paper reviews two recent examples of CFD modeling used in the design and evaluation of NOx reduction technologies. The first example involves the staging of furnace combustion through use of overfire air (OFA) to reduce NOx emission in a B&W opposed-wall fired pc furnace. Furnace simulations identified locations of highest flue gas mass flows and highest CO concentrations and were used to identify OFA port placement for maximum NOx reduction with lowest increases in unburned carbon in fly ash and CO emission. Simulations predicted a 34% reduction in NOx emission with OFA. The second example summarizes the design and application of RRI with OFA and SNCR in a 138 MW cyclone-fired boiler. Simulations were used to design an aminebased injection system for the staged lower furnace and to evaluate NOx reduction and ammonia slip of the RRI system. Field-testing confirmed modeling predictions and demonstrated that the RRI system alone could achieve 25–30% NOx reduction beyond OFA levels with less than 1 ppm ammonia slip and that RRI in combination with SNCR could achieve 50–55% NOx reduction with less than 5 ppm slip.

CFD Modeling of NOx Reduction Technologies in Utility Boilers

2000 ◽  
Author(s):  
Marc A. Cremer ◽  
Bradley R. Adams ◽  
David H. Wang ◽  
Michael P. Heap
Keyword(s):  
Nox Reduction ◽  
Electric Utility ◽  
Cfd Modeling ◽  
Nox Formation ◽  
Modeling Tools ◽  
Chemical Mechanisms ◽  
Utility Boilers ◽  
Clean Air ◽  
Nox Control ◽  
Selective Noncatalytic Reduction

Abstract This paper discusses the development and application of CFD modeling tools that have been utilized to assess and design NOx reduction systems that are currently being evaluated by the electric utility industry. Stringent limits on NOx emissions have been imposed by the Clean Air Act Amendments, and a number of NOx reduction technologies are available to help meet these limits including selective noncatalytic reduction (SNCR) and reburning, as well as various combinations of these. This paper discusses the development and implementation of global and reduced chemical mechanisms for NOx formation/destruction into a comprehensive CFD code so that these various options for NOx control can be evaluated. Also, some examples showing the application of these tools to full-scale utility boilers utilizing low-NOx burners, air staging, and SNCR are presented.

Application Analysis on the Bias and Air Staged Combustion Technology in the Opposed Firing Boiler

2011 ◽  
Author(s):  
Tai-sheng Liu
Keyword(s):  
Recirculation Zone ◽  
Nox Reduction ◽  
Pulverized Coal ◽  
Nox Emission ◽  
Unburned Carbon ◽  
Staged Combustion ◽  
Bias Model ◽  
Combustion Technology ◽  
Radial Model ◽  
Low Nox Emission

The bias combustion technology has been widely used in the swirling burner. Take the distribution of the pulverized-coal concentration at the primary air outlet as the division principle, there are three kinds of bias combustion models: radial model with inside dense and outside lean, radial model with outside dense and inside lean, and circumferential model. Considering stable ignition and low NOx emission, at the phase of the pulverized-coal ignition, the dense pulverized-coal flow should be heated by the high temperature flue gas intensively and quickly to ensure the coal’s timely ignition and form an In-flame NOx reduction zone for low NOx emission. Hence the bias combustion technology should be in accordance with the recirculation zone. So the radial bias model with inside dense and outside lean suits to central recirculation zone while radial bias model with outside dense and inside lean suits to annular recirculation zone. The circumferential bias model suits to both recirculation zones. Furthermore, appropriate measures should be taken on the burner’s arrangement and furnace’s design to prevent the obvious increase of slagging problem and unburned carbon in fly ash when using bias and air staged combustion technology.

A CFD Model Based Evaluation of Cost Effective NOx Reduction Strategies in a Roof-Fired Unit

2003 ◽  
Author(s):  
James Valentine ◽  
Marc Cremer ◽  
Kevin Davis ◽  
J. J. Letcavits ◽  
Scott Vierstra
Keyword(s):  
Fly Ash ◽  
Nox Reduction ◽  
Water Injection ◽  
Cost Effective ◽  
Cfd Modeling ◽  
Unburned Carbon ◽  
Cfd Model ◽  
Reduction Strategies ◽  
Nox Control ◽  
The Impact

To meet aggressive NOx reduction requirements, a range of NOx reduction strategies are currently available for application to pulverized coal fired furnaces. Utilities must assess the benefits and drawbacks of each viable NOx control technology to develop the best strategy for unit specific NOx control that fits within the utilities’ overall compliance plan. The installation of high capital and operating cost NOx reduction technologies, such as selective catalytic reduction, is cost prohibitive on many units. Lower cost technologies, although not capable of SCR level NOx reductions, can provide a more cost-effective approach and still achieve compliance over the fleet. This paper describes how computational fluid dynamic (CFD) modeling has been utilized by an experienced group of combustion engineers to evaluate and design cost effective NOx reduction strategies applied to a relatively unique PC fired unit, a B&W 150 MW roof-fired furnace. The unit fires bituminous coal through 10 multi-tip burners and is equipped with 10 NOx ports located below the burners. A baseline CFD model was first constructed and the predicted model results were compared with available data including NOx and CO emissions, as well as unburned carbon in fly ash. Upon completion of the baseline model, combustion alterations, including deeper staging, were evaluated. Specific burner adjustments were evaluated to allow for the deeper staging without significantly increasing unburned carbon in the fly ash, CO emissions, or near burner slagging. The CFD model was also utilized to evaluate the impact of water injection. AEP has previously utilized water injection to reduce peak combustion temperatures and thermal NOx formation rates in coal fired units for incremental NOx reductions. It is crucial that the NOx production zones in the downstream portion combustion field be identified, since these regions are most likely to produce NOx that will not be subsequently reduced prior to exiting the furnace. The CFD model was utilized to identify the most appropriate regions for water injection combined with the other combustion alterations. The results showed that NOx emissions could be reduced in this unit by approximately 37% from baseline full load emissions with no associated increase in unburned carbon in the fly ash or furnace exit CO. Burner alterations and water injection equipment based on the CFD model evaluation are currently being installed. Comparisons between the model predictions and the post retrofit performance will be provided.

Comprehensive Modeling Study on Fuel Gas Reburn in an Opposed Wall Fired Boiler

2007 ◽  
Author(s):  
Q. H. Nguyen ◽  
W. Zhou ◽  
G. Xu ◽  
L. W. Swanson ◽  
D. K. Moyeda
Keyword(s):  
Gas Flow ◽  
Nox Reduction ◽  
Injection System ◽  
Cfd Modeling ◽  
Performance Impact ◽  
Fuel Gas ◽  
Gasification Process ◽  
Underground Gasification ◽  
Coal Deposits ◽  
Economical Feasibility

GE conducted engineering and modeling studies to evaluate the feasibility of applying gas reburn technology on Eskom’s Majuba Unit 5 (710 MWe). The key objective of the study was to evaluate the technical and economical feasibility of utilizing a low-calorific fuel gas as a reburn fuel. The fuel gas is produced from an underground gasification process of the Majuba coal deposits, which are difficult to mine. The studies include: (1) develop a conceptual gas reburn injection system that will serve as a basis for the boiler performance impact and economic studies, (2) evaluate mixing performance of the gas reburn system and evaluate impacts of gas reburn on the furnace thermal and species profiles using computational fluid dynamics (CFD) modeling, (3) evaluate impacts of gas reburn on the boiler thermal performance using heat transfer modeling, (4) evaluate NOx reduction potential of the gas reburn systems, and (5) evaluate the economical feasibility of applying gas reburn technology to the Majuba boiler. The study indicates that the proposed reburn fuel and OFA injection systems will provide adequate mixing and reasonable residence time for the reburn application. The potential impacts on boiler performance with injection of the low-calorific fuel gas include the flue gas flow rate, attemperation rate and ID fan capacity. The detailed modeling approach and results are presented in this paper.

NOx Reduction of a Medium Speed Diesel Engine Using a Charge Air Moisturizer System

2006 ◽  
Author(s):  
Hyoung-Keun Park ◽  
Sang-Hak Ghal ◽  
Byong-Seok Kim ◽  
Ki-Doo Kim ◽  
Jong-Suk Kim
Keyword(s):  
Diesel Engine ◽  
Combustion Chamber ◽  
Nox Reduction ◽  
Water Injection ◽  
Combustion Process ◽  
Hot Water ◽  
Nox Emission ◽  
Injection System ◽  
Medium Speed ◽  
A Charge

It is well known that water can be used to prevent NOx formation during a combustion process. It is based on the principle by decreasing flame temperature with increasing the specific heat capacity of combustion air by adding water to a combustion chamber. Introducing water into a charge air enables much more water addition into a combustion chamber than other methods, which can reduce NOx emission to lower level than the others. The method has also the advantage of low installation cost. In a general water injection system for a charge air only hot water is sprayed into the charge air and vaporized, but more effective means to introduce water into the charge air is needed because only small amount of water is evaporated in hot water injection system. In this study, steam and hot moisturizing water are injected simultaneously. The steam supplies steady additional energy for evaporation of the water and can be vapor by itself. The new method was evaluated for NOx reduction performance on a medium speed diesel engine. NOx emission was reduced to 10∼38% on the 27∼59gram water per kilogram dry air.

Combination of Field Testing and CFD Modeling for Optimum Clarifier Design

2015 ◽  
Vol 2015 (19) ◽  
pp. 991-1025
Author(s):  
Irene Chu ◽  
Alonso Griborio ◽  
Paul Pitt ◽  
Meei-Lih Ahmad ◽  
Guoji Chiu ◽  
...  
Keyword(s):  
Field Testing ◽  
Cfd Modeling

Reduction of NOx Emission of Heavy Duty Gas Turbines by Improving Mixing Quality Using CFD Tools

2003 ◽  
Author(s):  
Weiqun Geng ◽  
Douglas Pennell ◽  
Stefano Bernero ◽  
Peter Flohr
Keyword(s):  
Gas Turbines ◽  
Mass Fraction ◽  
Cross Flow ◽  
Nox Emission ◽  
Injection System ◽  
Water Tunnel ◽  
Injection Hole ◽  
Fuel Mass ◽  
Mixing Quality ◽  
Fuel Mass Fraction

Jets in cross flow are one of the fundamental issues for mixing studies. As a first step in this paper, a generic geometry of a jet in cross flow was simulated to validate the CFD (Computational Fluid Dynamics) tool. Instead of resolving the whole injection system, the effective cross-sectional area of the injection hole was modeled as an inlet surface directly. This significantly improved the agreement between the CFD and experimental results. In a second step, the calculated mixing in an ALSTOM EV burner is shown for varying injection hole patterns and momentum flux ratios of the jet. Evaluation of the mixing quality was facilitated by defining unmixedness as a global non-dimensional parameter. A comparison of ten cases was made at the burner exit and on the flame front. Measures increasing jet penetration improved the mixing. In the water tunnel the fuel mass fraction within the burner and in the combustor was measured across five axial planes using LIF (Laser Induced Fluorescence). The promising hole patterns chosen from the CFD computations also showed a better mixing in the water tunnel than the other. Distribution of fuel mass fraction and unmixedness were compared between the CFD and LIF results. A good agreement was achieved. In a final step the best configuration in terms of mixing was checked with combustion. In an atmospheric test rig measured NOx emissions confirmed the CFD prediction as well. The most promising case has about 40% less NOx emission than the base case.

NOx Emissions in a Steel Reheat Furnace Firing By-Product Fuels

2001 ◽  
Author(s):  
Bradley R. Adams ◽  
Dave H. Wang
Keyword(s):  
Low Cost ◽  
Nox Reduction ◽  
Coke Oven ◽  
Cfd Modeling ◽  
Stoichiometric Ratio ◽  
Nox Emissions ◽  
Confined Space ◽  
Nox Formation ◽  
Reheat Furnace ◽  
Bottom Zone

Abstract A DOE-funded program was used to understand the mechanisms that control the formation of NOx during the combustion of steelmaking by-product fuels and to investigate possible low-cost control options to minimize the NOx emissions. This paper discusses the CFD modeling results of NOx emissions in a reheat furnace. The reheat furnace has a total of 20 burners distributed over three firing zones. The furnace is fired at a rate of 250 × 106 Btu/hr and an overall stoichiometric ratio of 1.06 (fuel lean). Fuels with heating values of approximate 500 Btu/SCF were examined, including coke oven gas (COG), blast furnace gas (BFG) and a blend of COG, BFG, natural gas (NG) and nitrogen. A good range of process variables was modeled to examine effects of fuel type, air preheat, stoichiometric ratio, firing rate and burner stoichiometry distribution on NOx emissions. Modeling results indicated that NOx formation in the reheat furnace is dominated by thermal NO, with some variation depending on the fuel fired. Temperature profiles showed an effective separation of the furnace interior into top and bottom zones as a result of the steel slab barrier. Higher temperatures characterized the bottom zone and elevated NOx levels as a result of the confined space and enhanced fuel air mixing provided by the slab supports. Results also showed that reburning of NOx plays a significant role in final NOx emissions with 30–40% of NOx formed being reduced by reburning in most cases. Modeling identified that operating the side burners in each burner zone slightly substoichiometric (while maintaining the overall furnace stoichiometry at 1.06) provided significant NOx reduction via reburning. NOx reductions of 23% and 30% were predicted when firing with COG and COG-NG-Air fuels, respectively. Overall furnace exit temperatures and heat flux profiles were not significantly affected by the biased firing.

Water Addition in Diesel Engine Intake for NOx Reduction: Comparison of Modeling and Experiments

2003 ◽  
Author(s):  
Bhaskar Tamma ◽  
Juan Carlos Alvarez ◽  
Aaron J. Simon
Keyword(s):  
Diesel Engine ◽  
Fuel Efficiency ◽  
Nox Reduction ◽  
Engine Performance ◽  
Thermodynamic Cycle ◽  
Nox Emission ◽  
Water Addition ◽  
Predictive Tool ◽  
Fuel Flow ◽  
Influence Of Water

Reduction in emissions, especially NOx has been the main study of various engine researchers in the light of stringent emission norms. To reduce the time and cost involved in testing these technologies, engine thermodynamic cycle predictive tools are used. The present work uses one such predictive tool (GT Power from Gamma Technologies) for predicting the influence of water addition in a turbocharged 6-cylinder diesel engine intake on engine performance and NOx emissions. The experiments for comparison with modeling included the introduction of liquid water in the engine intake stream, between the compressor and intercooler ranging from 0 to 100% of fuel flow rate. NOx emission reduced linearly with water addition with reduction of 63% with less than 1% penalty on fuel efficiency at 100% water addition. The GT Power model predicted the performance within 5% of experimental data and NOx emission within 10% of the experiments.

NOx Reduction Review on Fuel Alternative in Cement Kiln

2013 ◽  
Vol 864-867 ◽  
pp. 1626-1629
Author(s):  
Hai Bing Liu ◽  
Xiao Dong Chen ◽  
Jun Gu
Keyword(s):  
Nitrogen Content ◽  
Fossil Fuels ◽  
Nox Reduction ◽  
Reducing Agent ◽  
Environmental Benefits ◽  
Nox Emission ◽  
Cement Kiln ◽  
Cement Kilns ◽  
Low Nitrogen

The paper first discusses the relativity between alternative combustion andNOx emissions by a test in dry cement kiln, and a lot of case on fuel alternative The main findings of the study are that the use of RDF in cement kilns instead of coal or coke offers environmental benefits and reduce NOx emission. The conclusion is that the NOx generation can probably be lower because of lower flame temperatures or lower air excess and low nitrogen content in comparison with fossil fuels also is impartment reason., another a fact that most of the nitrogen (N) in biomass is released as ammonia (NH3) which acts as a reducing agent with NOx to form nitrogen (N2).

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