Experimental Study on Ammonia Co-Firing with Coal for Carbon Reduction in the Boiler of a 300-MW Coal-Fired Power Station

To reduce CO_(2) emissions from coal-fired power plants,the development of low-carbon or carbon-free fuel combustion technologies has become urgent.As a new zero-carbon fuel,ammonia(NH_(3))can be used to address the storage and transportation issues of hydrogen energy.Since it is not feasible to completely replace coal with ammonia in the short term,the development of ammonia-coal co-combustion technology at the current stage is a fast and feasible approach to reduce CO_(2) emissions from coal-fired power plants.This study focuses on modifying the boiler and installing two layers of eight pure-ammonia burners in a 300-MW coal-fired power plant to achieve ammonia-coal co-combustion at proportions ranging from 20%to 10%(by heat ratio)at loads of 180-to 300-MW,respectively.The results show that,during ammonia-coal co-combustion in a 300-MW coal-fired power plant,there was a more significant change in NO_(x) emissions at the furnace outlet compared with that under pure-coal combustion as the boiler oxygen levels varied.Moreover,ammonia burners located in the middle part of the main combustion zone exhibited a better high-temperature reduction performance than those located in the upper part of the main combustion zone.Under all ammonia co-combustion conditions,the NH_(3) concentration at the furnace outlet remained below 1 parts per million(ppm).Compared with that under pure-coal conditions,the thermal efficiency of the boiler slightly decreased(by 0.12%-0.38%)under different loads when ammonia co-combustion reached 15 t·h^(-1).Ammonia co-combustion in coal-fired power plants is a potentially feasible technology route for carbon reduction.

SO_2 emission characteristics from co-firing of petroleum coke and coal in circulating fluidized bed

Combustion and sulfur retention experiments of mixed fuel of petroleum cokeand coal were conducted on a pilot-scale circulating fluidized bed (CFB) combustor with the thermalinput of 0. 6 MW. The effects of several parameters, such as the primary air percentage, excess aircoefficient, bed temperature, Ca/S molar ratio and mass ratio of petroleum coke to coal on SO_2emission were verified. Experimental results show that when the ratio of petroleum coke to coal inthe mixed fuel increases, the SO_2emission increases. The maximum SO_2 emission appears when purecoke burns. The SO_2 concentration in flue gas reduces with the increase in the primary airpercentage, excess air coefficient and Ca/S molar ratio for all kinds of fuel mixtures. Therangebetween 830 t and 850 t is the optimal temperature for sulfur retention during co-firing ofpetroleum coke and coal with the mass ratio R of 1 and 3 in CFB.

Emissions of SO_2, NO and N_2O in a circulating fluidized bed combustor during co-firing coal and biomass

This paper presents the experimental investigations of the emissions of SO2, NO and N20 in a bench scale circulating fluidized bed combustor for coal combustion and co-firing coal and biomass. The thermal capacity of the combustor is 30 kW. The setup is electrically heated during startup. The infuence of the excess air, the degree of the air staging, the biomass share and the feeding position of the fuels on the emissions of SO2, NO and N2O were studied. The results showed that an increase in the biomass shares resulted in an increase of the CO concentration in the flue gas, probably due to the high volatile content of the biomass. In co-firing, the emission of SO2 increased with increasing biomass share slightly, however, non-linear increase relationship between SO2 emission and fuel sulfur content was observed. Air staging significantly decreased the NO emission without raising the SO2 level. Although the change of the fuel feeding position from riser to downer resulted in a decrease in the NO emission level, no obvious change was observed for the SO2 level. Taking the coal feeding position R as a reference, the relative NO emission could significantly decrease during co-firing coal and biomass when feeding fuel at position D and keeping the first stage stoichiometry greater than 0.95. The possible mechanisms of the sulfur and nitrogen chemistry at these conditions were discussed and the ways of simultaneous reduction of SO2, NO and N2O were proposed.

Co-firing of coal and biomass in oxy-fuel fluidized bed for CO2 capture: A review of recent advances

The co-firing of coal and biomass in oxy-fuel fluidized beds is one of the most promising technologies for capturing CO2.This technology has attracted wide attention from academia and industry in recent years as a negative emission method to capture CO2 produced by carbon contained in biomass.In the past decades,many studies have been carried out regarding experiments and numerical simulations under oxy-fuel combustion conditions.This paper firstly briefly discusses the techno-economic viability of the biomass and coal co-firing with oxycombustion and then presents a review of recent advancements involving experimental research and computational fluid dynamics(CFD)simulations in this field.Experimental studies on mechanism research,such as thermogravimetric analysis and tube furnace experiments,and fluidized bed experiments based on oxy-fuel fluidized beds with different sizes as well as the main findings,are summarized as a part of this review.It has been recognized that CFD is a useful approach for understanding the behaviors of the co-firing of coal and biomass in oxyfuel fluidized beds.We summarize a recent survey of published CFD research on oxy-fuel fluidized bed combustion,which categorized into Eulerian and Lagrangian methods.Finally,we discuss the challenges and interests for future research.

Waste biomass from production process co-firing with coal in a steam boiler to reduce fossil fuel consumption:A case study

Waste biomass is always generated during the production process in industries. The ordinary way to get rid of the waste biomass is to send them to landfill or burn it in the open field. The waste may potentially be used for co-firing with coal to save fossil fuel consumption and also reduce net carbon emissions. In this case study, the bio-waste from a Nicotiana Tahacum （NT） pre-treatment plant is used as the biomass to co-fire with coal. The samples of NT wastes were analysed. It was found that the wastes were of the relatively high energy content which were suitable for co-firing with coal. To investigate the potential and benefits for adding NT wastes to a Fluidised Bed Combustion （FBC） boiler in the plant, detailed modelling and simulation are carried out using the European Coal Liquefaction Process Simulation and Evaluation （ECLIPSE） process simulation package. The feedstock blending ratios of NT waste to coal studied in this work are varied from 0% to 30%. The results show that the addition of NT wastes may decrease the emissions of CO2 and SOx without reducing the boiler performance.

Low SO_2 emission from CFB co-firing MSW and bituminous

Influence of co-firing rate on SO 2 emission from co-firing municipal solid waste(MSW) and bituminous containing high amount of sulfur(1.79%) was studied in a 0.15 MWt circulating fluidized bed(CFB). The temperature selected is 1123 K, typical for MSW incineration using CFB. The particle concentration in the dilution zone of the furnace, the alkali metal concentration and sulfate concentration in the recirculating ash and fly ash, and flue gas composition were determined. The results showed that the addition of MSW leads to a significant decrease in SO 2 emission. Concentration of SO 2 in flue gas decreased to 0 with the co-firing rate greater than 51%. This reduction in SO 2 emission is attributed both to the high particle concentration in the dilution zone of the furnace, the high content of alkali metals in the bed material, and to the comparatively high concentration of HCl in flue gas during co-firing of MSW and bituminous.

Effects of Flue Gas Internal Recirculation on NOx and SOx Emissions in a Co-Firing Boiler

Volumetric combustion has been developed to realize a high substitution ratio of biomass in co-firing boilers, which features an intensive flue gas internal recirculation inside furnace. However, the characteristics of NOx and SOx emissions in large-scale boilers with volumetric combustion were not fully clear. In this paper, an Aspen Plus model of volumetric combustion system was built up based on a co-firing boiler. In order to characterize the reductions of NOx and SOx, three biomass substitution ratios were involved, namely, 100% biomass, 45% biomass with 55% coal, and 100% coal. The effects of flue gas recirculation ratio, air preheating temperature, oxygen concentration, and fuel types on pollutants emission in the volumetric combustion system were investigated. According to the results, it was concluded the higher substitution ratio of biomass in a co-firing boiler, the lower emissions of NOx and SOx. Moreover, flue gas internal recirculation is an effective pathway for NOx reduction and an increased recirculation ratio resulted in a significant decreasing of NOx emission;however, the SOx increased slightly. The influences of air preheating temperature and O2 concentration on NOx emission were getting weak with increasing of recirculation ratio. When 10% or even higher of flue gas was recycled, it was observed that almost no NOx formed thermodynamically under all studied conditions. Finally, to reach a low emission level of NOx, less energy would be consumed during biomass combustion than coal combustion process for internal recirculation of flue gas.

Air Quality Impact of Biomass Co-Firing with Coal at a Power Plant in the Greater Houston Area

The Houston-Galveston-Brazoria (HGB) area of Texas is a moderate nonattainment region for ozone, and has a history of severe summer ozone episodes. W. A. Parish power plant (WAP) located in the greater Houston area is the largest coal and natural gas based electricity generating unit (EGU) in Texas. Forest residue is an abundant renewable resource, and can be used to offset coal usage at EGUs. This study evaluates the impact of co-firing 5%, 10%, and 15% (energy-basis) of forest residue at WAP on the air quality of the HGB area. Photochemical modeling with Comprehensive Air Quality Model with Extensions (CAMx) was conducted to investigate the air quality at three air quality monitoring sites (C696, C53, C556) in the HGB area, under two source scenarios (all-sources, point + biogenic sources). Significant reduction of SO2 and O3 was observed for 10% and 15% co-firing ratios at monitoring station (C696) close to WAP. The maximum reduction of ozone observed for 15% co-firing is 4.7% and 6.3% for all-sources and point + biogenic sources scenarios respectively. The reduction in other criteria air pollutants is not significant at all locations. The overall results from this study indicate that biomass co-firing at WAP would not lead to a significant reduction in ozone concentrations in the region during periods of peak ozone.

Emission Factors of Particulate Matter Emitted from Co-Firing of Thai Lignite and Agricultural Residues in Fixed Bed Combustor

Emission factors （EFs） of particulate matter （PM） derived from mono and co-firing of Thai lignite and agricultural residues have been investigated. Two sampling methods for PM, total filtration （TF） and electrical low-pressure impactor （ELPI）, were used together. The study is focused on the influence of fuel mass fraction, and of secondary air to total air; SA：TA on EFs of PM. The results have shown that EFs of PM in mass-basis given by TF method are 8.9, 5.3 and 8.1 mg/kgfuel, while 3.3, 2.7 and 3.3 mg/kgfuel when using ELPI, for firing at constant SA：TA （30%） of lignite, rice husk and bagasse, respectively. For co-firing with 30%SA of coal/rice husk, higher EFs of PM is observed. They are 7.17 and 10.9 mg/kgfuel （TF） for 40 and 70% rice husk share, respectively, or 4.18 and 5.19 mg/kgfuel （ELPI）. However, lower PM emission; 1-3.3 mg/kgruel （TF） or 0.72-2.83 mg/kgfuel （ELPI） are obtained during co-firing of coal/rice husk with lower degree of air staging （i.e. 0-10% SA：TA）. For the influence of oxygenation state, increasing of SA： TA leads to a low formation of ultrafine particles （Dp 〈 0.1 μm）. Apart from PM, major gases （CO, NO, SO2） will be documented in this paper.

Wood Pellet Co-Firing for Electric Generation Source of Income for Forest Based Low Income Communities in Alabama

Alabama imports coal from other states to generate electricity. This paper assessed the direct and indirect economic impacts of wood pellet production to be co-fired with coal for power generation in Alabama. Four sizes of wood pellet plants and regional input-output models were used for the analysis. The results showed that the economic impact increases with the size of the plant. Wood pellet production will have a multiplier effect on the economy especially, forest-related services, retail stores, the health service industry, and tax revenue for the government. Domestic wood pellet production can reduce the use of imported coal, allow the use of local woody biomass, and create economic activities in Alabama’s rural communities. Policies that support the production of wood pellet will serve to encourage the use of wood for power generation and support the rural economies.

Effects of Co-Firing Biomass and Pulverized Coal on NO Reduction in Cement Precalciner

With increased awareness of the large-scale CO_(2) emissions from the cement industry,there has been growing focus on greenhouse gas reduction strategies.Among all these strategies,fuel substitution using biomass fuel is extensively used to achieve CO_(2) zero-emission in cement production.Due to the avoidable high-temperature-generated thermal nitrogen oxides during cement production,research on the impact of biomass application on nitrogen oxide emissions shall be carried out.Three types of biomass fuel and bituminous coal were used to investigate the NO reduction characteristics under different O_(2) concentrations on experimental benches.It was found that the change in oxygen concentration from 9% to 1% increased the reaction time in the reactor from 555 s to 1425 s,which means the increase in oxygen concentration can lead to shorter reaction time,and correspondingly,the existing time of nitric oxide in the flue gas is also shortened,but the peak value of nitric oxide rises,during the process of O_(2) concentration changing from 1% to 9%,the peak NO concentration in the flue gas increased from 5.4×10^(-5) to 1.05×10^(-4).An increase in O_(2) concentration greatly reduces the total reduction of NO and the minimum change in NO concentration.The peak NO concentration during the combustion process of corn stalk is 4.56×10^(-4),which is approximately 7 times higher than that of coal,and it is caused by the high amount of N in corn stalk.The addition of raw meal has an inhibitory effect on the reduction of NO:after adding raw meal,the effective reduction time of NO by fuel decreased by about 20%,but adding raw meal raises CO_(2) concentration of fuel gas in the early stage of reaction.

Flame Morphology and Characteristic of Co-Firing Ammonia with Pulverized Coal on a Flat Flame Burner

Ammonia as a new green carbon free fuel co-combustion with coal can effectively reduce CO_(2)emission,but the research of flame morphology and characteristics of ammonia-coal co-combustion are not enough.In this work,we studied the co-combustion flame of NH_(3)and pulverized coal on flat flame burner under different oxygen mole fraction(X_(i,O_(2)))and NH_(3)co-firing energy ratios(E_(NH_(3))).We initially observed that the introduction of ammonia resulted in stratification within the ammonia-coal co-combustion flame,featuring a transparent flame at the root identified as the ammonia combustion zone.Due to challenges in visually observing the ignition of coal particles in the ammonia-coal co-combustion flame,we utilized Matlab software to analyze flame images across varying E_(NH_(3))and X_(i,O_(2)).The analysis indicates that,compared to pure coal combustion,the addition of ammonia advances the ignition delay time by 4.21 ms to 5.94 ms.As E_(NH_(3))increases,the ignition delay time initially decreases and then increases.Simultaneously,an increase in X_(i,O_(2))results in an earlier ignition delay time.The burn-off time and the flame divergence angle of pulverized coal demonstrated linear decreases and increases,respectively,with the growing ammonia ratio.The addition of ammonia facilitates the release of volatile matter from coal particles.However,in high-ammonia environments,oxygen consumption also impedes the surface reaction of coal particles.Finally,measurements of gas composition in the ammonia-coal flame flow field unveiled that the generated water-rich atmosphere intensified coal particle gasification,resulting in an elevated concentration of CO.Simultaneously,nitrogen-containing substances and coke produced during coal particle gasification underwent reduction reactions with NO_(x),leading to reduced NO_(x)emissions.

Development and application of ferrite materials for low temperature co-fired ceramic technology

Development and application of ferrite materials for low temperature co-fired ceramic （LTCC） technology are dis- cussed, specifically addressing several typical ferrite materials such as M-type barium ferrite, NiCuZn ferrite, YIG ferrite, and lithium ferrite. In order to permit co-firing with a silver internal electrode in LTCC process, the sintering temperature of ferrite materials should be less than 950 ℃. These ferrite materials are research focuses and are applied in many ways in electronics.

Computational Analysis of Gas Phase Mixing in a Co-Fired Burner with Two Different Designs

The study of swirling jet combustor for biomass coal co-firing is of great interest for energy industry. The biomass co-firing can serve as a NOx reduction method as well as the better use of renewable energy source. Large eddy simulation (LES) and RANS modelling have been performed with two different burner designs. Usually pulverized coal-biomass mixture enters the furnace along with primary air through primary pipe, and the secondary pipe provides necessary air and mixing for combustion. The improved model has three passages including primary, secondary and middle passage for swirling. The simulations on two geometries have been compared, and the aim is to design a better and improved burner model for better pre-combustion mixing in the biomass co- fired furnace. The results from two-way and three-way geometry have been compared with each other as well as with the results from the furnace model used by Apte and Mahesh [8].

34 GHz Bandpass Filter for Low-temperature Co-fired Ceramic System-in-Package Application

Modern electronic circuit requires compact,multifunctional technology in communication systems.However,it is very difficult due to the limitations in passive component miniaturization and the complication of fabrication process.The bandpass filter is one of the most important passive components in millimeter（mm）-wave communication system,attracting significant interest in three-dimension（3D） miniaturized design,which is few reported.In this paper,a bandpass filter structure using low-temperature co-fired ceramic（LTCC） technology,which is fully integrated in a system-in package（SIP） communication module,is presented for miniaturized and high reliable mm-wave application.The bandpass filter with 3D end-coupled microstrip resonators is implemented in order to achieve a high performance bandwidth characteristic.Specifically,all of the resonators are embedded into different ceramic layers to decrease the insertion loss and enhance the out-of-band rejection performance by optimizing the coupling coefficient and the coupling strength.A fence structure,which is formed by metal-filled via array with the gap less than quarter wavelength,is placed around the embedded bandpass filter to avoid electromagnetic（EM） interference problem in multilayer structure.This structural model is validated through actual LTCC process.The bandpass filter is successfully manufactured by modifying the co-fireablity characteristics,adjusting the sintering profile,releasing the interfacial stress,and reducing the shrinkage mismatch with different materials.Measured results show good performance and agree well with the high frequency EM full wave simulation.The influence of layer thickness and dielectric constant on the frequency response in fabricated process is analyzed,where thicker ceramic sheets let the filter response shift to higher frequency.Moreover,measured S-parameters denote the center frequency is also strongly influenced by the variation of ceramic material＇s dielectric constants.By analyzing the relationship between the characteristics of the ceramic tape and the center frequency of the filter,both theoretical and experimental data are accumulated for broadening application filed.With the coupling resonators embedded into the ceramic layers,the bandpass filter exhibits advantages of small size and high reliability compared to conventional planar filter structure,which makes the bandpass filter suitable for SIP communicational application.

Analysis on Micro Complex Shape Via Hole Punching on Low Temperature Co-Fired Ceramics

The quality of a via hole on a multilayer stack of Low Temperature Co-fired Ceramic (LTCC) tape is of utmost importance to its functionality. This paper investigates a substitute for the commonly used circular shape hole to a more complex one and its implications when different parameters such as sheet thickness, punch speed, travel distance and tool clearance are?changed. Fabrication of the punch tools and the punching process is carried out at the same machine, ensuring alignment. Two types of non-circular shape are chosen to carry out the experiment. Pre-sintered complex shape hole measurements show that while punch conditions such as speed and tool gap have?little effect on the size, sheet thickness and travel depth play a vital role in the overall dimension. Albeit having only a slight effect on the size, those parameters are significant in other aspects of hole quality. Post-sintering investigation is also observed and discussed.

Co-milling as a synergy factor for co-firing.A case study of wood/coal blends

It is known that simple adding of wood allows one to accelerate the ignition of powder mixtures compared to the situation when pure coal is used.This study focuses on testing the hypothesis about the effect of co-milling coal and wood on their co-firing:is the case of composite powdered fuels should ensure the maximum possible efficiency of heat and mass transfer?Firstly,we will show that co-milling of coal and wood leads not independent size reduction of two materials but gives composite powder-coal-covered wood.For the composite fuel further reduction of the ignition delay time of air suspension and reduction of the limit volume concentration required for flame propagation have demonstrated.Obtained synergy also manifests in thermogravimetry.Here we propose a simple method for analyzing the mass loss curves.For any coal-to-wood sawdust ratio,combustion of the composites and mixtures both can be viewed as a weighted sum of the curves of individual components.But only in the case of composites calculated sawdust content is higher than the actual one:the mass loss is redistributed towards the stage occurring at lower temperatures due to geometry of wood/coal contact.

Modeling ash deposition and shedding during oxy-combustion of coal/rice husk blends at 70%inlet O_(2)

Co-firing rice husk(RH)and coal with carbon capture using oxy-combustion presents a net carbon negative energy produc-tion opportunity.In addition,the high fusion temperature of the non-sticky,silica rich,RH can mitigate ash deposition as well as promote shedding of deposits.To identify the optimum operating conditions,fuel particle sizes,and blend ratios that minimize ash deposition,a Computational Fluid Dynamic methodology with add-on ash deposition and shedding models were employed to predict outer ash deposition and shedding rates during co-combustion of coal/RH in AIR and O2/CO_(2)(70/30 vol%,OXY70)oxidizer compositions.After ensuring that the fly-ash particle size distributions and particle Stokes numbers near the deposition surface were accurately represented(to model impaction),appropriate models for coal ash and RH ash viscosities that were accurate in the temperature region(1200-1300 K)of interest in this study were identified.A particle viscosity and kinetic energy(PKE)based capture criterion was enforced to model the ash capture.An erosion/shed-ding criterion that takes the deposit melt fraction and the energy consumed during particle impact into account was also implemented.Deposition rate predictions as well as the deposition rate enhancement(OXY70/AIR)were in good agreement with measured values.While the OXY70 scenario was associated with a significant reduction(60%-70%)in flue gas velocities,it also resulted in larger fly-ash particles.As a result,the PKE distributions of the erosive RH ash were similar in both scenarios and resulted in similar shedding rates.

Effects of Blending Ratio on Combustion and NO Emission Characteristics during Co-Firing of Semi-Char and Lignite in a 350 kW Pulverized Coal-Fired Furnace

The influence of the blending ratio of pyrolyzed semi-char(SC)on the ignition,NO emission and burnout characteristics of lignite co-fired with SC was investigated in a 350 kW fuel-rich/lean combustion furnace.The flame temperature and concentrations of gaseous species including O_(2),CO,and NO,were measured in detail.The results indicated that the ignition characteristics of the blended fuel worsened with increasing SC blending ratio,such as an elongated ignition standoff distance.The addition of SC to lignite delayed the appearance of a stable flame boundary,and the stable combustion zone moved down,but the final combustion stability was gradually strengthened in the later combustion stage.NO emission concentration at the primary combustion zone(PCZ)outlet was the lowest at 472.6 mg/m^(3)@6%O_(2)when the SC blending ratio was 25%.The combustion zone and reducing zone areas in PCZ were defined to evaluate the NO reduction characteristics,and quantitative analysis using a multiple linear regression model showed that heterogeneous reduction was more important than homogeneous reduction in lowering NO emissions.The Raman spectrum of the char sample indicated that the addition of lignite promoted the formation of small aromatic rings in the early ignition stage,corresponding to a higher char reactivity.The burnout ratio of pure lignite was maximal and was decreased by increasing the SC blending ratio.Synthetically,considering the ignition standoff distance,NO emission,and burnout ratio,the optimum SC blending ratio was estimated to be 25%.

含钡玻璃陶瓷LTCC粉体的表面修饰及其对玻璃陶瓷性能的影响

为了降低BaO-TiO2-B2O3-SiO2玻璃陶瓷中钡离子的析出,通过化学沉淀法和硫酸处理法对玻璃陶瓷粉体进行了表面修饰,在玻璃陶瓷粉体的表面形成了一层不溶于水的无机膜(氧化铝或BaSO4),不仅阻断了LTCC中钡离子与水的接触途径,使LTCC玻璃陶瓷粉体制备可适用于水基流延工艺的浆料,且操作简便,无毒副作用。研究发现用共沉淀法包覆氧化铝对玻璃陶瓷的性能影响不大,但是硫酸包覆处理后大大提高了玻璃陶瓷的烧结温度,限制了LTCC的应用。