OPTIMIZED FUEL INJECTOR DESIGN FOR MAXIMUM IN-FURNACE NOx REDUCTION AND MINIMUM UNBURNED CARBON

Biomass reburn is a low NOx alternative to cofiring that effectively uses the high volatility and high char reactivity of biomass for NOx reduction. In this paper, computational fluid dynamics (CFD) and thermal modeling, and a NOx prediction model were used to evaluate the impacts of sawdust/coal reburn on the performance of a 250 MW opposed-fired boiler burning bituminous coal as the primary fuel. The results showed that the reburn system maintained overall boiler performance with a 50 – 70 °F reduction in the furnace exit gas temperature. Predicted losses in thermal efficiency were caused by the lower biomass fuel heating value (similar to biomass cofiring) and increase in unburned carbon. The higher unburned carbon emissions were attributed to an order of magnitude larger biomass mean particle size relative to bituminous coal. Thus, LOI emissions can be improved significantly by reducing the biomass mean particle size. The NOx predictions showed that for reburn rates above about 19%, adding dry sawdust biomass to a coal reburn system can improve NOx reduction; i.e., using pure dry sawdust as reburn fuel at 30% of the total heat input can lead to NOx levels about 30% less than those for pure coal reburn under for similar firing conditions.

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Optimization of Air Distribution to Reduce NOx Emission and Unburned Carbon for the Retrofit of a 500 MWe Tangential-Firing Coal Boiler

Energies ◽

10.3390/en12173281 ◽

2019 ◽

Vol 12 (17) ◽

pp. 3281 ◽

Cited By ~ 3

Author(s):

Hyunbin Jo ◽

Kiseop Kang ◽

Jongkeun Park ◽

Changkook Ryu ◽

Hyunsoo Ahn ◽

...

Keyword(s):

Negative Impact ◽

Nox Reduction ◽

Standard Technique ◽

Unburned Carbon ◽

Air Distribution ◽

Reference Case ◽

Design Data ◽

Secondary Air ◽

Coal Boiler ◽

Air Staging

The use of separated overfire air (SOFA) has become a standard technique of air staging for NOx reduction in the coal-fired boiler and can also be applied to existing boilers by retrofit. This study was to optimize the air distribution for the proposed SOFA installation in a 500 MWe tangential-firing boiler that has 20 identical units in Korea. Using computational fluid dynamics (CFD) incorporating advanced coal combustion submodels, the reference case was established in good agreement with the design data, and different flow ratios of burner secondary air, close-coupled OFA (CCOFA), and SOFA were evaluated. Increasing the total OFA ratio effectively suppressed NO formation within the burner zone but had a negative impact on the boiler performance. With moderate air staging, NO reduction became active between the CCOFA and SOFA levels and, therefore, the OFA distribution could be optimized for the overall boiler performance. For total OFA ratios of 25% and 30% with respective burner zone stoichiometric ratios of 0.847 and 0.791, increasing the SOFA ratio to 15% and 20%, respectively, was ideal for decreasing the unburned carbon release and ash slagging as well as NO emission. Too high or low SOFA ratios rapidly increased the unburned carbon because of inefficient mixing between the strong air jets and char particles. Based on these ideal cases, the actual air distribution can be adjusted depending on the coal properties such as the ash slagging propensity.

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

2002 International Joint Power Generation Conference ◽

10.1115/ijpgc2002-26081 ◽

2002 ◽

Cited By ~ 8

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.

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Development of a Liquid-Fueled, Lean-Premixed Gas Turbine Combustor

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2906743 ◽

1993 ◽

Vol 115 (3) ◽

pp. 554-562 ◽

Cited By ~ 8

Author(s):

L. H. Cowell ◽

K. O. Smith

Keyword(s):

Gas Turbine ◽

Performance Testing ◽

Operating Conditions ◽

Operating Parameters ◽

Nox Emissions ◽

Fuel Injector ◽

Design Variables ◽

Lean Premixed ◽

Annular Combustor ◽

Injector Design

Development of a lean-premixed, liquid-fueled combustor is in progress to achieve ultra-low NOx emissions at typical gas turbine operating conditions. A filming fuel injector design was tested on a bench scale can combustor to evaluate critical design and operating parameters for low-emissions performance. Testing was completed using No. 2 diesel. Key design variables tested include premixing length, swirler angle, injector centerbody diameter, and reduced liner cooling. NOx emissions below 12 ppmv at 9 bar pressure were measured. Corresponding CO levels were 50 ppmv. An optimized injector design was fabricated for testing in a three injector sector of an annular combustor. Operating parameters and test results are discussed in the paper.

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Dynamic Modeling of a Piezoelectric Actuated Fuel Injector

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.4003095 ◽

2011 ◽

Vol 133 (5) ◽

Cited By ~ 13

Author(s):

Chris A. Satkoski ◽

Gregory M. Shaver ◽

Ranjit More ◽

Peter Meckl ◽

Douglas Memering ◽

...

Keyword(s):

Control System ◽

Injection Rate ◽

Fuel Injector ◽

Fuel Injectors ◽

Response Characteristics ◽

Rate Shaping ◽

System Verification ◽

Reduce Emissions ◽

And Control ◽

Injector Design

As engine designers look for ways to improve efficiency and reduce emissions, piezoelectric actuated fuel injectors for common rail diesel engines have shown to have improved response characteristics over solenoid actuated injectors and may allow for enhanced control of combustion through multipulse, closely spaced injections or rate shaping. This paper outlines the development of an 11 state simulation model for a piezoelectric fuel injector and associated driver that can be used for injector design and control system verification. Nonmeasureable states of the model are plotted and analyzed, while measurable quantities including injection rate, piezo stack voltage, and piezo stack current are validated against experimental injector rig data for two different rail pressures.

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NOx Reduction of a 165 MW Wall-Fired Boiler Utilizing Air and Fuel Flow Measurement and Control

2002 International Joint Power Generation Conference ◽

10.1115/ijpgc2002-26131 ◽

2002 ◽

Cited By ~ 1

Author(s):

Marion Cherry ◽

Dave Earley ◽

David Silzle

Keyword(s):

Measurement System ◽

Flow Measurement ◽

Power Plants ◽

Nox Reduction ◽

Capital Requirements ◽

Unburned Carbon ◽

Front Wall ◽

Future System ◽

Reduction Strategies ◽

Coal Flow

As a result of increasingly stringent emissions limitations being imposed on coal-fired power plants today, electric utilities are faced with having to make major compliance related modifications to their existing power plants. While many utilities have elected to implement expensive post-combustion NOx reduction programs on their largest generating units, infurnace NOx reduction offers a less expensive alternative suitable to any size boiler, to reduce NOx while also improving overall combustion. In-furnace NOx reduction strategies have proven that, when used with other less expensive approaches (Overfire air, fuel switching, and/or SNCR), levels less than 0.15 lb./MMBtu can be economically achieved. Furthermore, when implemented in conjunction with an expensive post-combustion SCR program, initial capital requirements and ongoing operating costs can be cut to save utilities millions of dollars. For the purpose of developing a system-wide NOx reduction strategy, Santee Cooper, a southeastern U.S. utility applied pulverized coal flow and individual burner airflow measurement systems to Unit 3 at its Jefferies Station, a 165MW, 16-burner front wall-fired boiler. The airflow measurement system, in service for many years, applied a well-proven averaging Pitot tube technology to measure individual burner secondary airflow. The coal flow measurement system utilized low energy microwaves to accurately measure coal density and coal velocity in individual coal pipes. The combination of these two systems provided the accurate measurements necessary for controlled manipulation of individual burner stoichiometries, giving the plant the ability to improve burner combustion, yielding a reduction in NOx levels approaching 20%. Optimized burner combustion also resulted in a leveling of the excess O2 profile, which will enable the plant to pursue further reductions in excess air as well as staged combustion, thus allowing for further NOx reductions in the future. How this program produced a significant NOx reduction will be presented in detail in this paper. The paper will also discuss the effects on excess O2, opacity, and unburned carbon. In addition, this program will allow for future system-wide planning with regard to possible SCR implementation.

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Pengaruh Penyelitan Plat Orifis dalam Mengurangkan Emisi dari Pembakar

Jurnal Teknologi ◽

10.11113/jt.v37.550 ◽

2012 ◽

Author(s):

Mohammad Nazri Mohd Jaafar ◽

Mohd. Rosdzimin Abdul Rahman ◽

Mohamad Shaiful Ashrul Ishak ◽

Kiran Babu Appalanaidu

Keyword(s):

Nox Reduction ◽

Orifice Plate ◽

Dual Fuel ◽

Fuel Injector ◽

Co2 Emission Reduction ◽

Flow Rates ◽

Fuel Flow ◽

Back Plate ◽

Vane Angle ◽

Fuel Burner

Penyelidikan telah dijalankan ke atas plat orifis pelbagai saiz yang dipasangkan pada keluaran pemusar udara sebuah pembakar berbahan api cecair yang berdiameter dalam 163 mm dan panjangnya 280 mm. Pembakar ini menggunakan kerosin sebagai bahan api. Terdapat dua saiz plat orifis yang setiap satunya berdiameter 25 mm dan 30 mm telah digunakan dengan pemusar udara aliran jejarian yang mempunyai sudut bilah 30°. Dalam ujikaji ini, penyelitan plat orifis ini akan menyebabkan peningkatan terhadap kehilangan tekanan di bahagian keluaran pemusar dan seterusnya meningkatkan aliran gelora yang akan menambah kadar percampuran bahan api dengan udara. Pemancit bahan api semburan paksi yang mempunyai dua lubang keluaran telah dipasangkan di bahagian belakang pemusar udara. Kadar alir bahan api menjadi parameter yang diubah dalam ujikaji yang dijalankan. Keputusan yang diperolehi menunjukkan dengan penyelitan plat orifis, emisi NOx berjaya dikurangkan sebanyak 50% bagi penyelitan plat orifis 25 mm, manakala CO sebanyak 5% dan CO2 sebanyak 20% jika dibandingkan dengan kes tanpa penyelitan plat orifis. Kata kunci: Plat orifis; emisi NOx; pemusar udara; emisi CO; pemancit bahan api A liqued fuel burner system with different orifice plate sizes mounted at the exit plane of the radial air swirler outlet has been investigated using 163 mm inside diameter combustor of 280 mm length. All tests were conducted using kerosene as fuel. Two different orifice plates with diameter of 25 mm and 30 mm were used with a 30° radial air swirler vane angle. The purpose of orifice plate insertion was to create the swirler pressure loss at the swirler outlet so that the swirler outlet shear layer turbulence was maximized to assist in the mixing of fuel and air. Fuel was injected at the back plate of the swirler outlet using central fuel injector with dual fuel nozzles pointing axially outwards. The fuel flow rates were varied. The results show that orifice plate enhances better mixing and reduces NOx emmisions. NOx reduction of more than 50% was obtained using the 25 mm diameter orifice plate compared to the test condition without orifice plate. CO emissions were also reduced by 5%. CO2 emission reduction of more than 20% was achieved for the same condition. Key words: Orifice plate; NOx emissions; air swirler; CO emissions; fuel atomiser

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Emission Reduction From Burner System By Varying Swirler Blade Angle

Jurnal Teknologi ◽

10.11113/jt.v51.151 ◽

2012 ◽

Author(s):

Mohammad Nazri Mohd Jaafar ◽

Muhamad Shukri Abdul Mookmin ◽

Ismail Samat

Keyword(s):

Liquid Fuel ◽

Radial Flow ◽

Swirling Flow ◽

Nox Reduction ◽

Oxides Of Nitrogen ◽

Fuel Injector ◽

Blade Angle ◽

Back Plate ◽

Curved Blade ◽

Fuel Burner

Kertas kerja ini mempersembahkan pengaruh mengubah sudut bilah pemusar udara aliran jejarian yang kecil dalam mengurangkan emisi seperti oksida nitrogen (NOx) dan karbon monoksida (CO). Dalam kajian ini, satu sistem pembakar berbahan api cecair menggunakan empat pemusar udara aliran jejarian yang berlainan sudut bilah diuji di dalam kebuk pembakar berdiameter 163 mm dan panjang 280 mm. Ujian dijalankan menggunakan kerosin sebagai bahan api. Pemusar udara aliran jejarian dengan bilah terlengkung berdiameter keluaran 40 mm dipasang pada satah masukan pembakar bagi menjana aliran berpusar. Bahan api dipancitkan pada plat belakang keluaran pemusar menggunakan pemancit bahan api pusat dengan dua nozel bahan api menghala keluar secara paksi. Sudut pemusar udara dan nisbah setara diubah–ubah. Ujian dilaksanakan menggunakan empat pemusar udara yang berlainan sudut, iaitu masing–masing 30°, 40°, 50° dan 60°. Pengurangan NOx melebihi 50 peratus dicapai untuk sudut bilah 60° berbanding pada sudut bilah 30°. Emisi CO juga dikurangkan sebanyak 72 peratus pada sudut bilah 60° berbanding pada sudut bilah 30°. Kata kunci: Aliran berpusar; pembakar industri; emisi NOx; emisi CO; bilah terlengkung This paper presents the effect of varying the blade angle of a small radial air swirler on reducing emissions such as oxides of nitrogen (NOx) and carbon monoxide (CO). In this research a liquid fuel burner system with four different radial air swirler blade angles has been investigated using 163 mm inside diameter combustor of 280 mm length. Tests were conducted using kerosene as fuel. A radial flow air swirler with curved blades having 40 mm outlet diameter was inserted at the inlet plane of the combustor to produce swirling flow. Fuel was injected at the back plate of the swirler outlet using central fuel injector with two fuel nozzles pointing axially outwards. The swirler blade angles and equivalence ratios were varied. Tests were carried out using four different air swirlers having 30°, 40°, 50° and 60° blade angles, respectively. A NOx reduction of more than 50 percent was achieved for blade angle of 60° compared to the 30° blade angle. CO emissions were also reduced by 72 percent for 60° blade angle compared 30° blade angle. Key words: Swirling flow; industrial burner; NOx emissions; CO emissions; curved blade

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