Combustion efficiency optimization by adjusting the amount of excess air

2014 ◽  
Author(s):  
Mehdi Parsa ◽  
Ali Vahidian Kamyad ◽  
Mohammad Bagher Naghibi Sistani
Keyword(s):  
Combustion Efficiency ◽  
Efficiency Optimization ◽  
Excess Air

Modeling and Experiment on Combustion Characteristics for Biomass Rotary Burner

2020 ◽  
Vol 04 ◽  
Author(s):  
Guohai Jia ◽  
Lijun Li ◽  
Li Dai ◽  
Zicheng Gao ◽  
Jiping Li
Keyword(s):  
Combustion Chamber ◽  
Combustion Temperature ◽  
Combustion Efficiency ◽  
Middle Part ◽  
Combustion Characteristics ◽  
Maximum Temperature ◽  
Excess Air ◽  
Element Simulation ◽  
Excess Air Coefficient ◽  
Secondary Air

Background: A biomass pellet rotary burner was chosen as the research object in order to study the influence of excess air coefficient on the combustion efficiency. The finite element simulation model of biomass rotary burner was established. Methods: The computational fluid dynamics software was applied to simulate the combustion characteristics of biomass rotary burner in steady condition and the effects of excess air ratio on pressure field, velocity field and temperature field was analyzed. Results: The results show that the flow velocity inside the burner gradually increases with the increase of inlet velocity and the maximum combustion temperature is also appeared in the middle part of the combustion chamber. Conclusion: When the excess air coefficient is 1.0 with the secondary air outlet velocity of 4.16 m/s, the maximum temperature of the rotary combustion chamber is 2730K with the secondary air outlet velocity of 6.66 m/s. When the excess air ratio is 1.6, the maximum temperature of the rotary combustion chamber is 2410K. When the air ratio is 2.4, the maximum temperature of the rotary combustion chamber is 2340K with the secondary air outlet velocity of 9.99 m/s. The best excess air coefficient is 1.0. The experimental value of combustion temperature of biomass rotary burner is in good agreement with the simulation results.

Effects of Air Flowrate on the Combustion and Emissions of Blended Corn Straw and Pinewood Wastes

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Xiaoxiao Meng ◽  
Wei Zhou ◽  
Emad Rokni ◽  
Honghua Zhao ◽  
Rui Sun ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ignition Delay Time ◽  
Fixed Bed ◽  
Combustion Efficiency ◽  
Fixed Bed Reactor ◽  
Corn Straw ◽  
Excess Air ◽  
Burning Rates ◽  
Excess Air Coefficient ◽  
Hazardous Pollutants

This research investigated the effects of the specific primary (under-fire) air flowrate (m˙air) on the combustion behavior of a 50–50 wt % blend of raw corn straw (CS) and raw pinewood wastes in a fixed-bed reactor. This parameter was varied in the range of 0.079–0.226 kg m−2 s−1, which changed the overall combustion stoichiometry from air-lean (excess air coefficient λ = 0.73) to air-rich (excess air coefficient λ = 1.25) and affected the combustion efficiency and stability as well as the emissions of hazardous pollutants. It was observed that by increasing m˙air, the ignition delay time first increased and then decreased, the average bed temperatures increased, both the average flame propagation rates and the fuel burning rates increased, and the combustion efficiencies also increased. The emissions of CO as well as those of cumulative gas phase nitrogen compounds increased, the latter mostly because of increasing HCN, while those of NO were rather constant. The emissions of HCl decreased but those of other chlorine-containing species increased. The effect of m˙air on the conversion of sulfur to SO2 was minor. By considering all of the aforesaid factors, a mildly overall air-rich (fuel-lean) (λ = 1.04) operating condition can be suggested for corn-straw/pinewood burning fixed-bed grate-fired reactors.

Numerically Study on Combustion and NOx Emission Characteristics in Tangentially Fired Boiler Co-Firing Semi-Coke

2018 ◽  
Author(s):  
Yongbo Du ◽  
Chang'an Wang ◽  
Pengqian Wang ◽  
Qiang Lv ◽  
Defu Che
Keyword(s):  
Bituminous Coal ◽  
Combustion Efficiency ◽  
Low Rank ◽  
Operation Performance ◽  
Combustion Heat ◽  
Practical Utilization ◽  
Excess Air ◽  
Utility Boilers ◽  
Excess Air Coefficient ◽  
Char Burnout

Semi-coke is a specific solid fuel, which is mainly produced by upgrading low-rank coal. The poor reactivity of semi-coke makes a difficulty to its practical utilization in utility boilers. Previous research was mainly focused on the combustion behavior of semi-coke, while the industrial application has to be understood. In this paper, the effect of co-firing semi-coke and bituminous coal on the operation performance of pulverized boiler was numerically studied. The work was conducted on a 300 MW tangentially fired boiler, and the temperature distribution, the char burnout and NOx production were mainly examined. The results indicate that the incomplete combustion heat loss drops with the increase in semi-coke blending ratio. The NOx concentration increases from 186 mg/Nm3 for only firing the bituminous coal to 200, 214, and 255 mg/Nm3, when the blending ratio was 17%, 33% and 50%, respectively. With enhancing excess air coefficient for the co-firing condition, the combustion efficiency got improved, while NOx production increased very slightly. In general, the boiler is well adapted to co-firing semi-coke, and the semi-coke blending ratio of 1/3 with an excess air coefficient of 1.235 is recommended.

Research and Improvement on Calculation Method of Optimal Excess Air Ratio

2014 ◽  
Vol 536-537 ◽  
pp. 1583-1586
Author(s):  
Jun Xiong Qi
Keyword(s):  
Heat Loss ◽  
Correction Factor ◽  
Calculation Method ◽  
Traditional Method ◽  
Combustion Efficiency ◽  
Exhaust Gas ◽  
Incomplete Combustion ◽  
Excess Air

By analyzing the relations of the excess air ratio to heat loss due to exhaust gas, chemical incomplete combustion and combustibles in refuse, the traditional method for solving the optimal excess air ratio is improved. A correction factor is proposed for heat loss due to combustibles in refuse, making the solving method more accurate, which is of great importance for improving the combustion efficiency of the boiler.

An Experimental Investigation of Wood Combustion

1994 ◽  
Vol 116 (3) ◽  
pp. 186-193 ◽  
Author(s):  
A. Dadkhah-Nikoo ◽  
D. J. Bushnell
Keyword(s):  
Experimental Investigation ◽  
Particle Size ◽  
Moisture Content ◽  
Combustion Products ◽  
Combustion Efficiency ◽  
Particulate Emissions ◽  
Fuel Particle ◽  
Wood Combustion ◽  
Part Load ◽  
Excess Air

This paper presents the results from an experimental investigation of wood combustion. Variables chosen for investigation are fuel moisture content, fuel particle size, excess air, fraction and temperature of under-fire air. Influence of the off-design (part load) operation of the combustion unit on combustion efficiency and particulate emission is also investigated. Data recorded during the experiments include the composition and temperature of the combustion products, particulate emissions, and combustible fraction of the particulate. Based on the experimental data, a linear regression model was developed to investigate the variables affecting the combustion process. A computer model was used to calculate the temperature and composition of the combustion products under adiabatic conditions. Results of the adiabatic model and the experimental regression analysis are compared and discussed. According to the results presented, it is concluded that the combustion efficiency and particulate emissions are most influenced by the factors that increase the volume of the combustion products in the combustion chamber. These variables include excess air, moisture content of the fuel, and the combustion air temperature. Fuel particle size and the fraction of under-fire air did not significantly affect the combustion efficiency and particulate emissions. It is also concluded that the off-design (part-load) operation of the combustion unit, results in higher particulate emissions and lower combustion efficiency.

Optimization Process of Biomass Combustion in the Advanced FBC Using Factorial Design and Response Surface Methodology

2005 ◽  
Author(s):  
Shijun Zhu ◽  
Yun Liu ◽  
Seong Lee
Keyword(s):  
Response Surface Methodology ◽  
Moisture Content ◽  
Factorial Design ◽  
Poultry Manure ◽  
Combustion Efficiency ◽  
Air Injection ◽  
Excess Air ◽  
Secondary Air Injection ◽  
Carbon Combustion ◽  
Secondary Air

This paper studied the optimization process of the combustion of poultry waste material (i.e. poultry manure) in an advanced fluidized bed combustor (FBC) with the secondary air tangential injection. In order to test the influences of combustion parameters on the carbon combustion efficiency, factorial design (FD) and response surface methodology (RSM) were applied in the experimental process and data analysis. The parameters studied were moisture content, waste/natural gas ratio, excess air ratio, secondary/total air ratio, and the height levels of the secondary air injection. Using the 25−1 fractional factorial design, moisture content, excess air and secondary air injection height were found to be significant for the carbon combustion efficiency at the critical level of type-I error α = 0.1. The RSM was used to approach the optimal combustion condition. The optimal condition regarding the significant factors was found. Then the data from a validation experiment was compared with the computed combustion efficiency under the optimal condition. The result showed the combustion efficiency for poultry manure can reach up to 83%, which indicated that the poultry manure could be effectively burned in the advanced FBC.

The Influence of Excess Air Coefficient of Boiler Efficiency

2013 ◽  
Vol 409-410 ◽  
pp. 548-552
Author(s):  
Jiu Sheng Shi ◽  
Fei Peng ◽  
Bing Wen Zhang
Keyword(s):  
Thermal Efficiency ◽  
Linear Relation ◽  
Combustion Efficiency ◽  
Efficiency Analysis ◽  
Furnace Temperature ◽  
Excess Air ◽  
Important Impact ◽  
Boiler Efficiency ◽  
Excess Air Coefficient ◽  
One To One

Excess air coefficient has an important impact on the combustion conditions of boiler and thermal efficiency, analysis shows that the furnace temperature and the combustion efficiency is the linear relation of one to one correspondence. Any combustion conditions, there is an optimum excess air coefficient makes the top of furnace temperature, thus it can establish a control relationship, furnace temperature is optimization index, excess air coefficient is disturbance.It can achieve the purpose of improving the efficiency of boiler combustion.

Effect of Operating Variables on the Performance of a Highly Loaded Annular Combustor

2015 ◽  
Vol 32 (1) ◽  
Author(s):  
S. K. Muduli ◽  
R. K. Mishra ◽  
R. K. Satpathy ◽  
S. Chandel
Keyword(s):  
Pressure Loss ◽  
High Pressures ◽  
Combustion Efficiency ◽  
Performance Parameters ◽  
Operating Variables ◽  
Excess Air ◽  
Discharge Velocity ◽  
Annular Combustor ◽  
Exit Temperature ◽  
Highly Loaded

AbstractA highly loaded full-scale annular combustor is studied in the air-flow facility for the effect of operating variables such as compressor discharge velocity and fuel-air ratio on the performance parameters. The combustor is designed to operate at high pressures and high exit temperatures that impose stringent limitations on its performance such as pressure loss, exit temperature profiles and combustion efficiency. The effect of excess air ratio on performance parameters is found to be marginal over the range tested. Increasing the excess air ratio decreases the pressure loss, exit pattern factors and combustion efficiency. The inlet Mach no. is found to influence the pressure loss strongly and exit temperature patterns marginally. Combustion efficiency is found to deteriorate with increase in Mach number. This will in turn affect the integrity and life of hot end components of the aero engine.

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