Numerical investigation on combustion and NOx emissions of a down-fired 350 MWe utility boiler with multiple injection and multiple staging: Effect of the air stoichiometric ratio in the primary combustion zone

2013 ◽  
Vol 109 ◽  
pp. 32-42 ◽  
Author(s):  
Min Kuang ◽  
Qunyi Zhu ◽  
Zhengqi Li ◽  
Xiang Zhang
Keyword(s):  
Numerical Investigation ◽  
Combustion Zone ◽  
Stoichiometric Ratio ◽  
Nox Emissions ◽  
Multiple Injection ◽  
Utility Boiler

Numerical investigation of NOx emissions from a tangentially-fired utility boiler under conventional and overfire air operation

Fuel ◽  
2008 ◽  
Vol 87 (7) ◽  
pp. 1259-1269 ◽  
Author(s):  
Luis I. Díez ◽  
Cristóbal Cortés ◽  
Javier Pallarés
Keyword(s):  
Numerical Investigation ◽  
Nox Emissions ◽  
Utility Boiler

scholarly journals NOx Emissions and Nitrogen Fate at High Temperatures in Staged Combustion

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3557
Author(s):  
Song Wu ◽  
Defu Che ◽  
Zhiguo Wang ◽  
Xiaohui Su
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Combustion Zone ◽  
Combustion Temperature ◽  
Stoichiometric Ratio ◽  
Nox Emissions ◽  
Mechanism Analysis ◽  
Staged Combustion ◽  
Atom Concentration ◽  
Reducing Atmosphere

Staged combustion is an effective technology to control NOx emissions for coal-fired boilers. In this paper, the characteristics of NOx emissions under a high temperature and strong reducing atmosphere conditions in staged air and O2/CO2 combustion were investigated by CHEMKIN. A methane flame doped with ammonia and hydrogen cyanide in a tandem-type tube furnace was simulated to detect the effects of combustion temperature and stoichiometric ratio on NOx emissions. Mechanism analysis was performed to identify the elementary steps for NOx formation and reduction at high temperatures. The results indicate that in both air and O2/CO2 staged combustion, the conversion ratios of fuel-N to NOx at the main combustion zone exit increase as the stoichiometric ratio rises, and they are slightly affected by the combustion temperature. The conversion ratios at the burnout zone exit decrease with the increasing stoichiometric ratio at low temperatures, and they are much higher than those at the main combustion zone exit. A lot of nitrogen compounds remain in the exhaust of the main combustion zone and are oxidized to NOx after the injection of a secondary gas. Staged combustion can lower NOx emissions remarkably, especially under a high temperature (≥1600 °C) and strong reducing atmosphere (SR ≤ 0.8) conditions. Increasing the combustion temperature under strong reducing atmosphere conditions can raise the H atom concentration and change the radical pool composition and size, which facilitate the reduction of NO to N2. Ultimately, the increased OH/H ratio in staged O2/CO2 combustion offsets part of the reducibility, resulting in the final NOx emissions being higher than those in air combustion under the same conditions.

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.

Numerical investigation of air-staged combustion to reduce NOX emissions from biodiesel combustion in industrial furnaces

2019 ◽  
Vol 92 (3) ◽  
pp. 704-716 ◽  
Author(s):  
Jiaxu Shen ◽  
Fashe Li ◽  
Zhouhang Li ◽  
Huage Wang ◽  
Yicheng Shen ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Nox Emissions ◽  
Staged Combustion

Numerical investigation on the lifetime decline of burners in a wall-fired dual-fuel utility boiler

2015 ◽  
Vol 82 ◽  
pp. 141-151 ◽  
Author(s):  
Mahdi Pourramezan ◽  
Mohsen Kahrom ◽  
Mohammad Passandideh-Fard
Keyword(s):  
Numerical Investigation ◽  
Dual Fuel ◽  
Utility Boiler

Performance of Multiple-Injection Dry Low-NOx Combustor on Hydrogen-Rich Syngas Fuel in an IGCC Pilot Plant

2014 ◽  
Author(s):  
Tomohiro Asai ◽  
Satoschi Dodo ◽  
Mitsuhiro Karishuku ◽  
Nobuo Yagi ◽  
Yasuhiro Akiyama ◽  
...  
Keyword(s):  
Pilot Plant ◽  
Gas Turbines ◽  
Coal Gasification ◽  
Maximum Load ◽  
Combined Cycle ◽  
Nox Emissions ◽  
Multiple Injection ◽  
Test Results ◽  
Low Nox Combustion ◽  
Combustion Of Hydrogen

Successful development of oxygen-blown integrated coal gasification combined cycle (IGCC) technology requires gas turbines capable of achieving dry low-nitrogen oxides (NOx) combustion of hydrogen-rich syngas for low emissions and high plant efficiency. The authors have been developing a “multiple-injection burner” to achieve the dry low-NOx combustion of hydrogen-rich syngas. The purposes of this paper are to present test results of the multi-can combustor equipped with multiple-injection burners in an IGCC pilot plant and to evaluate the combustor performance focusing on effects of flame shapes. The syngas fuel produced in the plant contained approximately 50% carbon monoxide, 20% hydrogen, and 20% nitrogen by volume. In the tests, the combustor that produced slenderer flames achieved lower NOx emissions of 10.9 ppm (at 15% oxygen), reduced combustor liner and burner plate metal temperatures, and lowered the combustion efficiency at the maximum load. The test results showed that the slenderer flames were more effective in reducing NOx emissions and liner and burner metal temperatures. These findings demonstrated that the multiple-injection combustor achieved dry low-NOx combustion of the syngas fuel in the plant.

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