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.

Modeling of aerated upflow fixed bed reactors for nitrification

1999 ◽  
Vol 39 (4) ◽  
pp. 85-92 ◽  
Author(s):  
J. Behrendt
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Liquid Phase ◽  
Gas Phase ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Bulk Liquid ◽  
Initial Value ◽  
Fixed Bed Reactors ◽  
Number Of Cells

A mathematical model for nitrification in an aerated fixed bed reactor has been developed. This model is based on material balances in the bulk liquid, gas phase and in the biofilm area. The fixed bed is divided into a number of cells according to the reduced remixing behaviour. A fixed bed cell consists of 4 compartments: the support, the gas phase, the bulk liquid phase and the stagnant volume containing the biofilm. In the stagnant volume the biological transmutation of the ammonia is located. The transport phenomena are modelled with mass transfer formulations so that the balances could be formulated as an initial value problem. The results of the simulation and experiments are compared.

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.

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.

Nitrogen-Bearing Emissions From Burning Corn Straw in a Fixed-Bed Reactor: Effects of Fuel Moisture, Torrefaction, and Air Flowrate

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Emad Rokni ◽  
Yu Liu ◽  
Xiaohan Ren ◽  
Yiannis A. Levendis
Keyword(s):  
Moisture Content ◽  
Hydrogen Cyanide ◽  
Fossil Fuels ◽  
Environmental Pollutants ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Fuel Moisture ◽  
Corn Straw ◽  
Renewable Biomass ◽  
Torrefied Biomass

Combustion-generated emissions of acid gases, such as nitrogen-bearing species, constitute environmental pollutants and some are subjected to environmental regulations. Assessment of such emissions is important to decide what systems need to be put in place for their control. This applies to both conventional fossil fuels and for alternative environmentally friendlier fuels, such as renewable biomass. This research investigated the emissions of nitrogen-bearing gases, which evolve from combustion of biomass (corn straw) in a fixed bed furnace, as a function of specific air flowrate (m˙air) through the bed and of moisture content of the fuel. The effect of torrefaction of corn straw on the combustion-generated nitrogen bearing emissions was also examined. The predominant nitrogen-bearing species in the combustion effluents were hydrogen cyanide (HCN), nitrogen oxide (NO), and ammonia (NH3). Increasing m˙air through the bed, to enhance the combustion rate, increased the emissions of HCN, NO, and NH3. As the m˙air through the bed increased by a factor of 5, the amounts of HCN, NO, and NH3 gases increased by factors of 3–4. As the moisture content of the biomass was reduced by drying, the combustion-generated emissions of NO increased mildly, whereas those of both NH3 and HCN decreased. Furthermore, the combustion-generated emissions of NO and NH3 from torrefied biomass were found to be higher than those from raw biomass. In contrast, the combustion-generated emissions of HCN from torrefied biomass were found to be lower than those generated from raw biomass.

Dynamic modelling of a gas phase catalytic fixed bed reactor—III

1976 ◽  
Vol 31 (6) ◽  
pp. 473-479 ◽  
Author(s):  
Sten Bay Jørgensen ◽  
Knud Waede Hansen
Keyword(s):  
Gas Phase ◽  
Fixed Bed ◽  
Dynamic Modelling ◽  
Fixed Bed Reactor

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.

A 2-D observer to estimate the reaction rate in a stopped flow fixed bed reactor for gas phase olefin polymerization

AIChE Journal ◽  
2014 ◽  
Vol 60 (10) ◽  
pp. 3511-3523 ◽  
Author(s):  
Barbara Browning ◽  
Nida Sheibat-Othman ◽  
Isabelle Pitault ◽  
Timothy F. L. McKenna
Keyword(s):  
Gas Phase ◽  
Reaction Rate ◽  
Olefin Polymerization ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Stopped Flow

scholarly journals The Grindability of Biochars from Agroforestry Biomass Prepared under Different Torrefied Conditions

2019 ◽  
Vol 118 ◽  
pp. 01051
Author(s):  
Hewei Jiang ◽  
Yangtian Ye ◽  
Ping Lu
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Wheat Straw ◽  
Size Distribution ◽  
Mass Fraction ◽  
Fixed Bed ◽  
Holding Time ◽  
Fixed Bed Reactor ◽  
Corn Straw ◽  
Agricultural Biomass

The torrefaction experiments of four biomass including agricultural biomass (corn straw (CS) and wheat straw (WS)) and forestry biomass (polar wood (PW) and cedar wood (CW)) were carried out in a fixed bed reactor at torrefaction temperature of 200-300°C and holding time of 10-60min, the effects of torrefaction temperature and holding time on biochar grindability based on the component analysis and the particle size distribution of ground biomass and biochars. The obtained results indicated that the mass fraction of ground biochar with particle size less than 150 μm increases with increasing torrefaction temperature, and the mass fraction of ground biochar with particle size less than 150 μm achieves 100%. The larger the λC, the better the grindability of biochar. The correlation between the grindability of the woody biochar and the λC is not as good as that of the straw biochar. The grindability of corn straw biochar and cedar wood biochar is improved with the increase of holding time at the same torrefaction temperature, however, the grindability of wheat straw biochar and polar wood biochar gets a little change, which can keep good grindability at higher torrefaction temperature large than 275°C.

scholarly journals Gas-phase elemental mercury removal by nano-ceramic material

2020 ◽  
Vol 10 ◽  
pp. 184798041989975
Author(s):  
Tao Zhu ◽  
Weidong Jing ◽  
Xing Zhang ◽  
Wenjing Bian ◽  
Yiwei Han ◽  
...  
Keyword(s):  
Gas Phase ◽  
Gas Flow ◽  
Removal Rate ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Mercury Removal ◽  
Bet Surface Area ◽  
Mercury Adsorption ◽  
Experimental Conditions ◽  
Physical And Chemical

The nano-ceramic which is mesoporous silica material was applied to test the removal efficiency of gas-phase Hg0 using a fixed-bed reactor. The physical and chemical properties of nano-ceramic were investigated by various techniques such as BET surface area (BET), X-ray diffraction, fourier transform infrared spectrometer (FTIR), and scanning electron microscope (SEM); then, the sample was tested for mercury adsorption under different conditions. The mercury adsorption tests shown that different Hg0 concentration, adsorption temperature, gas flow rate, and different gas components have significant effects on the mercury removal performance of nano-ceramic, and the adsorption removal rate of nano-ceramic can be 75.58% under the optimal experimental conditions. After fitting the experimental data to the adsorption model, it was found that the theoretical maximum mercury adsorption amount q max of nano-ceramic is 1.61 mg g−1 and there were physical and chemical adsorption at the same time. The adsorption kinetics fitting results shown that the adsorption process of nano-ceramic exhibits multi-segment characteristics of “transmembrane–diffusion–adsorption.”

scholarly journals Synthesis of carbon nanotube using ferrocene as carbon source and catalyst in a vertical structured catalyst reactor

2018 ◽  
Vol 67 ◽  
pp. 03038 ◽  
Author(s):  
Praswasti PDK Wulan ◽  
Ghassan Tsabit Rivai
Keyword(s):  
Carbon Nanotube ◽  
Carbon Source ◽  
Gas Phase ◽  
Carbon Deposition ◽  
Fixed Bed ◽  
Catalyst Particle ◽  
Fixed Bed Reactor ◽  
Structured Catalyst ◽  
Catalyst Particle Size

Development of nano-carbon technology in the world has recently occurred due to its excellent electric, thermal, and mechanical properties and it diverse of applications such as electronics, biology, and material. Fixed bed reactor run into blocked due to carbon deposition on the catalyst that cause pressure drop enhancement. Whereas, application of fluidized bed reactor as an alternative of prior reactor have some trouble for complicated of feed flow control that can cause change of catalyst particle size during reaction since agglomeration and adhesion of nanoparticles transpire. Synthesis of carbon nanotube material used a vertical structured catalyst gauze reactor with double furnace system to maintain the catalyst and carbon source in the form of gas phase. This will lead growth of CNT on the surface of the substrate proved by SEM and XRD characterization. Furnace 1 used to ferrocene vaporizer at 400°C and furnace 2 provide substrate placement for CNT growth at 850°C. CNTs characterization confirmed yield and CNT diameter 29.33% and 11.38 nm respectively. Characterization of SEM show that CNT grows on stainless steel type 316 substrate preferable with oxidative heat treatment. Nevertheless, CNTs product still contain many of impurities such as Fe3O4, Fe2O3, Fe3C, hexagonal graphite, and amorphous carbon.

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