Bench Scale Process Evaluation of Reburning for In-Furnace NOx Reduction

1986 ◽  
Vol 108 (3) ◽  
pp. 450-454 ◽  
Author(s):  
S. B. Greene ◽  
S. L. Chen ◽  
D. W. Pershing ◽  
M. P. Heap ◽  
W. R. Seeker
Keyword(s):  
Molecular Nitrogen ◽  
Nox Reduction ◽  
Plug Flow ◽  
Firing Zone ◽  
Pulverized Coal ◽  
Process Variables ◽  
Fuel Type ◽  
Bench Scale ◽  
Utility Boilers ◽  
Coal Type

Reburning involves the injection of a secondary fuel above the main firing zone of pulverized coal-fired utility boilers to produce a reducing zone which acts to reduce NOx to molecular nitrogen. Overfire air is added above the reburn reducing zone to complete the combustion. Bench scale evaluations of the process carried out in a plug flow furnace at 23 KW have indicated that NOx reductions of up to 70 percent can be achieved depending on a number of process variables. The dominant variables include the initial NOx level that is to be reduced, the reburning fuel type (pulverized coal type or natural gas), and the residence time and temperature in the reducing zone. The reburning process has been combined with the injection of calcium-based sorbents (limestone) to investigate the potential for combined NOx and SOx reduction.

scholarly journals Nitrogen Oxide Reduction by Staged Combustion of Biomass Gas in Gas Turbines — A Modeling Study of the Effect of Mixing

1999 ◽  
Author(s):  
Edgardo G. Coda Zabetta ◽  
Pia T. Kilpinen ◽  
Mikko M. Hupa ◽  
Jukka K. Leppälahti ◽  
C. Krister O. Ståhl ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Nox Reduction ◽  
Plug Flow ◽  
Chemical Kinetic ◽  
Process Variables ◽  
Staged Combustion ◽  
Fuel Gas ◽  
Effective Option ◽  
Fuel Mixing ◽  
Lower Temperature

Detailed chemical kinetic modeling has been used to study the reduction of nitrogen oxides at gas turbine (GT) combustor conditions. A gas from gasification of wood with air has been used as the fuel. An air-staged combustion technique has been adapted. In our previous study a simple plug flow model was used to study the effects of pressure and temperature among others process variables. The air-fuel mixing was assumed perfect and instantaneous. Results showed the NOx reduction mainly affected by both pressure and temperature. The aim of the present work is to establish the effect of air-fuel mixing delay on NOx predictions and to extrapolate indications options for GT. To model the mixing delay, a varying number of air sub-streams are mixed with the fuel gas during different time periods. Alternatively, a combination of a perfectly mixed zone followed by a plug flow zone is illustrated. Results by any air-fuel mixing model show similar affect of process variables on NOx reduction. When a mixing delay is assumed instead of the instantaneous mixing the NOx reduction is enhanced, and only with delayed mixing NOx are affected by CH4. Lower temperature and higher pressure in the GT-combustor can enhance the NOx reduction. Also air staging is an effective option: a 3 stages combustor designed for low mixing speed appear competitive compared to more complicate combustors. The fewer hydrocarbons in the gasification gas the high NOx reduction.

Coal Quality and Its Impact on Power Stations Emissions Control

2005 ◽  
Author(s):  
J. W. Allen ◽  
K. R. Parker ◽  
A. Sanyal
Keyword(s):  
Nox Reduction ◽  
Operating Efficiency ◽  
Original Design ◽  
Power Stations ◽  
Generation Plant ◽  
Emission Regulations ◽  
Power Generation Plant ◽  
Boiler Operation ◽  
Firing Mode ◽  
Coal Type

Although coal fired power generation plant was originally designed to operate on a particular coal, increasingly stringent emissions regulations have led to modifications to both the coal type and firing mode. Low sulphur (S) coals minimize the requirement for sulphur dioxide (SO2) scrubbing plant combustion modifications are used as the primary measure to reduce the emission of nitrogen oxides (NOx) and these changes in the firing regime and/or the coal type can also impact on the in boiler ash deposition, particulate collection and the overall efficiency of the boiler operation. Emission regulations requiring maximum NOx levels of 0.15lbs./MM.Btu. are at, or just below, the limit of NOx reduction achievable by primary measures and at this limit significant increases in unburnt carbon (UBC) in ash levels can be expected, which affect boiler efficiency and also the operation of any SO2 and particulate collection plant. Coals are usually purchased, in addition to price, on quality based on the well established proximate and ultimate analyses, whereas parameters derived from these basic analyses may be more effective in defining the behaviour of a coal, substituted for the original design coal, in order to meet current emissions regulations whilst still maintaining an acceptable operating efficiency.

Effect of Pulverized Coal Preheating on NOx Reduction during Combustion

2017 ◽  
Vol 31 (4) ◽  
pp. 4436-4444 ◽  
Author(s):  
Yanqing Niu ◽  
Tong Shang ◽  
Jun Zeng ◽  
Shuai Wang ◽  
Yanhao Gong ◽  
...  
Keyword(s):  
Nox Reduction ◽  
Pulverized Coal

Studies of sintering of coal ash relevant to pulverized coal utility boilers

Fuel ◽  
1984 ◽  
Vol 63 (12) ◽  
pp. 1664-1670 ◽  
Author(s):  
Richard E. Conn ◽  
Leonard G. Austin
Keyword(s):  
Coal Ash ◽  
Pulverized Coal ◽  
Utility Boilers

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.

Surface Characterization of the Mechanism for Decreased Boiler Slagging via Fly Ash Surface Modification

1985 ◽  
Vol 65 ◽  
Author(s):  
Christopher J. Macey
Keyword(s):  
Fly Ash ◽  
Flue Gas ◽  
Surface Characterization ◽  
Depth Profiling ◽  
Pilot Scale ◽  
Pulverized Coal ◽  
Pulverized Coal Combustion ◽  
Utility Boilers ◽  
Combustion Experiment

ABSTRACTSlagging difficulties encountered in large, pulverized coal-fired utility boilers can be alleviated by using recently developed chemical conditioners designed to inhibit the agglomeration of molten fly ash particles. Slagging results from the impaction and accretion on the boiler interior surfaces of molten ash particles in the flue gas resulting from the combustion of coal. Electron Spectroscopy for chemical Analysis (ESCA) and ion sputtering depth profiling were utilized to examine the mechanism whereby a fuel conditioner containing copper oxychloride effectively reduced slag deposition rates during a pilot-scale, pulverized coal combustion experiment.

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