Co-firing Of Coal Research Articles

Effect of Blending Ratio of Coal and Biomass on NOx Emission Regarding Co- Firing

Greenhouse gas emission had a huge effect on global warming as well as cause of acid rain. Regarding this study was made to investigate the effect of blending ratio on coal and biomass on NOx emission through co-firing. Different biomass was used to measure the considerable value of biomass with coal on NOx emission. Fluidized bed combustor was used at 3000C optimum temperature for co firing of coal and biomass. The maximum emission of NOx measured at tree leaves 40% and lignite coal 60% and minimum range of NOx at 80/20 ratio for coal and banana tree waste. This could be healthfully beneficial when utilizing biomass with coal.

Co-firing of coal/biomass blends in a pilot plant facility: A comparative study between Opuntia ficus-indica and Pinus radiata

Chile has begun to promote the use of biomass to replace a fraction of the energy produced from coal. However, the power plants are located in the world driest desert, the Atacama Desert, and far from the forest resources. Fortunately, a cactaceous species named Opuntia ficus-indica, has proven to be able to grow under climate desert conditions. In this study the behavior of Opuntia ficus-indica under co-firing conditions with coal, is evaluated and compared to that of Pinus radiata, in terms of heat transfer, ash deposits formation and pollutant emissions in a 150 kW fluidized bed pilot plant. The results revealed a variation of the temperature profile inside the reactor, as well as a relationship between the efficacy factor and the base-acid ratio. The heat transfer coefficients in the dense bed evidenced a decrease in the heat transfers mechanisms attributed to a variation of the mean particle diameter and a greater presence of fuel particles. Under coal-Pine co-firing conditions, an increase in NO formation and a decrease of PM and SO2 concentrations was observed. While co-firing coal with Opuntia showed an increase in the particulate matter and a reduction of NO and SO2 concentrations.

Effect of Operating Conditions on the Combustion Characteristics of Coal, Rice Husk, and Co-firing of Coal and Rice Husk in a Circulating Fluidized Bed Combustor

This study was performed to investigate the combustion characteristics of coal and rice husk and their co-combustion in a 100 kW circulating fluidized bed combustor (diam.: 150 mm, height: 6000 mm). Gaining insights into the effects that the primary and secondary excess air ratios (λPA and λSA), biomass fraction, and secondary air (SA) position have on CO and NOx emissions was also an aim of this study. In contrast to coal combustion, and co-combustion of coal and rice husk, the combustion of rice husk could not be sustained without the aid of an external heat source, and the released volatiles were found to be fired chiefly above the bottom bed. Air-staging substantially decreased NOx (40–75% reduction), but with a high CO penalty, compared to no air-staging. However, the effect of the SA position which was profoundly engaged with the char inventory in the bed was pronounced for coal combustion but not for rice husk combustion. Increase in λPA and λSA tended to reduce CO levels but enhanced NOx formation...

Co-firing of coal and rice straw pellet in a circulating fluidized-bed reactor

This paper presents the experimental investigation of co-firing of coal with rice straw pellet in terms of combustion efficiency, gaseous emissions (CO, NOx and SO2) and occurrence of bed agglomeration. The influence of excess air ratio (EA) and mass share of rice straw in the mixed fuel were investigated in a lab-scale circulating fluidized bed (CFB) reactor. The fuel feed rate was fixed at 14 kg/hr, while the air supply was varied to achieve EA 1.28-1.94. Rice straw pellet was mixed with coal at 25% and 50% mass fraction. The results show that increasing EA generally reduced CO emission. However, at excessively high EA, CO emission started to rise due to the insufficient residence time for complete combustion and the cooling effect. The CO emission clearly reflected the combustion efficiency trend. Higher CO emission was also found when increasing biomass, which may be influenced by the lower combustion temperature and the incomplete combustion of biomass volatiles. NOx and SO2 emission strongly depended on N and S content in the fuel that is the higher rice straw addition the lower NOx and SO2. At lower EA, the observed lower NOx emission could be the effect of reduction by CO and carbon present; while the opposite effect was found at high EA. SO2 emission was more temperature dependent and continuously decreased with increasing EA. System pressure monitoring and visual observation of the spent bed showed no occurrence of bed agglomeration even at 50% addition of rice straw pellet. However, the size distribution of spent bed moved slightly towards a larger particle size range indicating a tendency of agglomeration.

Emissions of SO2, NOx, CO2, and HCl from Co-firing of coals with raw and torrefied biomass fuels

This work examined acid gas emissions of sulfur dioxide, nitrogen oxide, carbon dioxide, and hydrogen chloride from co-firing biomass (corn straw and rice husk) with either a high-sulfur bituminous coal or a low-sulfur sub-bituminous coal. Pulverized neat coals, neat biomass, either raw or torrefied, and 50–50wt% blends thereof were introduced to a laboratory-scale electrically-heated drop-tube furnace (DTF), operated at a gas temperature of 1350K, and experienced high heating rates. Emissions from the combustion of the fuels in air were measured at the furnace effluent. Coal particles were in the range of 75–90µm and biomass particles in the range of 90–150 µm. Results revealed that blending of both coals with raw and torrefied biomass drastically reduced the coal’s SO2 and NOx emission yields to values that were below those predicted by linear interpolation of the corresponding emission yields of the two neat fuels. The SO2 emission yields from torrefied biomass were lower than those of their raw biomass precursors due to their lower sulfur contents. Similarly to the emission yields, the SO2 emission factors (based on the energy content of each sample) from the blends of coal with torrefied biomass were also lower than the blends of coal with raw biomass. NOx emission yields from neat torrefied biomass were mildly higher than those from raw biomass, as the latter had higher nitrogen content per unit mass. There was no discernible trend in NOx emissions from the blends based on their nitrogen contents. HCl emission from torrefied corn straw was lower than that from its raw precursor, as the former had a lower chlorine content. The HCl emission yields from the blends of corn straw with coal were much higher than those from neat coal combustion. Finally, the HCl emission yield from blends of the high-sulfur coal with corn straw were higher than those from the blends of the same biomass with the low-sulfur coal.

Characteristics of fine particulate matter formation during combustion of lignite riched in AAEM (alkali and alkaline earth metals) and sulfur

The high contents of AAEM (alkali and alkaline earth metals) and sulfur in zhundong coal result in more fine particulate matter during coal combustion. In this paper, the emission of fine particulates from zhundong coal riched in AAEM-sulfur and zhunnan coal riched in aluminum-silicon was investigated in a drop tube furnace. Co-combustion of zhundong coal and zhunnan coal was further investigated to study the effect of interaction among different elements in coal on the PM formation. The size distribution, concentration and composition of the particulates were analyzed by low pressure impactor (DLPI) and scanning electron microscopy (SEM). The distribution of sodium, magnesium, calcium, iron and sulfur in fine particulates and their effects on the generation of fine particulates were obtained. The results show that the fine particulates from AAEM-sulfur rich coal combustion mainly consist of sulfates and oxides of AAEM. The amount of fine particulates from burning aluminum-silicon rich coal decreased significantly. The composition of PM0.4 and PM0.4+ are significantly different. Co-firing of AAEM-sulfur rich coal with aluminum-silicon rich coal has an obviously synergetic effect of reducing the fine particulates emission. The capture of AAEM and iron by aluminum-silicon compounds plays an important role in PM10 reduction during blended coal combustion. The change of sulfur content in PM0.4 is consistent with the change of AAEM content.

Part-load performance of direct-firing and co-firing of coal and biomass in a power generation system integrated with a CO2 capture and compression system

Bioenergy with Carbon Capture and Storage (BECCS) is recognised as a key technology to mitigate CO2 emissions and achieve stringent climate targets due to its potential for negative emissions. However, the cost for its deployment is expected to be higher than for fossil-based power plants with CCS. To help in the transition to fully replace fossil fuels, co-firing of coal and biomass provide a less expensive means. Therefore, this work examines the co-firing at various levels in a pulverised supercritical power plant with post-combustion CO2 capture, using a fully integrated model developed in Aspen Plus. Co-firing offers flexibility in terms of the biomass resources needed. This work also investigates flexibility within operation. As a result, the performance of the power plant at various part-loads (40%, 60% and 80%) is studied and compared to the baseline at 100%, using a constant fuel flowrate. It was found that the net power output and net efficiency decrease when the biomass fraction increases for constant heat input and constant fuel flow rate cases. At constant heat input, more fuel is required as the biomass fraction is increased; whilst at constant fuel input, derating occurs, e.g. 30% derating of the power output capacity at firing 100% biomass compared to 100% coal. Co-firing of coal and biomass resulted in substantial power derating at each part-load operation.

Investigation on co-firing of coal mine waste residues in pulverized coal combustion systems

Millions of tonnes of coal mine waste residues are piled up in dumping sites, causing serious environmental problems. Co-combustion in fluidized bed facilities is the most widespread alternative for the energy utilization of these by-products. However, no experiences have been so far reported of coal mine waste residues co-firing under pulverized fuel combustion technology. This work proves the technical feasibility of co-firing coal with up to 20% coal mine waste residues and investigates the impacts of transferring this co-firing alternative into a commercial unit. Experimental co-firing tests of coal mine waste residues were conducted on a 500 kWth pulverized fuel pilot plant. Regulated emissions (CO, CO2, SO2 and NOx) and visible flame radiation were monitored, obtaining regular and stable flicker and acceptable emissions levels for CO (200 mg/m3N) and NOx (700–800 mg/m3N). Finally, the impact analysis of co-firing coal mine waste residues in a full-scale pulverized fuel plant was performed by simulating the power cycle and combustion process in a 160 MWe pulverized coal combustion unit. Simulation results show the viability of this alternative in terms of plant efficiency, increase in power consumptions of auxiliary equipment and pollutant emissions for co-firing ratios under 10% in energy basis.

Fouling and Slagging Characteristics during Co-combustion of Coal and Biomass

The effects of different kinds (cotton stalk, rice husk, and sawdust) and proportions (0%, 10%, 20%, and 30% based on weight) of biomass and operating conditions (temperature and excess air coefficient) were evaluated relative to the ash deposition characteristics during the co-firing of Huang Ling (HL) coal with biomass. The experiments were performed in a drop-tube furnace. The chemical compositions and mineral phase characteristics of the collected ash particles were analyzed using scanning electron microscopy with energy dispersive X-ray (SEM-EDX) and X-ray diffraction (XRD), respectively. The results showed that the most severe agglomeration, from co-firing coal with cotton stalk, was due to the higher content of alkali metals, especially K. The amount of K in the ash increased with an increasing proportion of cotton stalk, and ultimately, agglomeration was more serious. When the combustion temperature increased from 1050 °C to 1300 °C, the dystectic solid compounds were transformed into eutectic compounds. The increased excess air coefficient accelerated the sulfur reaction, but did not relieve the heavy sintering. Consequently, limiting the content of biomass in the fuel blends, maintaining a lower combustion temperature, and a suitable level of excess air were determined to be necessary for the co-firing of coal and biomass.

Ash deposition behavior under coal and wood co-firing conditions in a 300 kW downfired furnace

Growth of ash deposits when wood was co-fired with coal was visually investigated in a 300 kW pilot-scale furnace. For comparison, combustion of pure coal was also conducted. A total of 10% and 20% wood were mixed with coal. The thickness and heat flux were obtained. The collected ash deposits and fly ash were characterized by a series of analysis methods to determine the physical and mineral properties. Their relationships were also revealed. Results showed that co-firing of coal with wood dramatically increased the ash deposition propensity. During the coal combustion, shedding of ash deposit occurred and the maximum deposit thickness was 15.33 mm. A deposit thickness of up to 27.02 mm was achieved for 10% wood, and the thickness increased to 34.20 mm for 20% wood. The variation in heat flux with deposit thickness substantially changed when wood was co-fired. A significant change was also observed in the mineral composition of ash deposit with the increase in wood ratio. The proportion of anorthite increased because that of lime in fly ash increased with wood ratio. In addition, the mean diameter of fly ash particles increased as wood ratio increased.

Technological aspects of sunflower biomass and brown coal co-firing

The technological problems occurring in the co-firing of biomass and brown coal (lignite) prompted this research project. During the fuel preparation, accidental self-ignition and explosions were several times reported by power plants operators. The aim of this study was to evaluate brown coal, sunflower husks and sunflower husk pellets as fuels for co-firing in energetic boilers. Sunflower husk had a lower ash content and calorific value than the pellets. The range of the combustion temperatures of the biomass (200–300 °C) was narrower than that of brown coal (200–800 °C). The formation of highly alkaline ash from the biomass resulted in the formation in boiler of agglomerates of ash. The elemental composition, thermogravimetric and biological analyses suggested that the pellets contained synthetic additives difficult to identify. The biological method was proposed for evaluating biomass additives. The use of additional agents in the pelletizing process may influence on the combustion parameters. Mixing biomass with brown coal may occasionally result in self-ignition in the logistic chain. Plastic additives and biological activity may contribute to self-ignition.

Математична модель процесів спільного спалювання біомаси з вугіллям в котлі теплової електростанції

Математична модель процесів спільного спалювання біомаси з вугіллям в котлі теплової електростанції

Effect of carbonization temperature on composition of carbonized woody biomass

Co-firing coal and carbonized woody biomass is an effective method for reducing $$\hbox {CO}_\mathrm{2}$$ emission from coal-fired power generation plants because biomass absorbs $$\hbox {CO}_\mathrm{2}$$ when growing. In this study, we used thermogravimetry along with mass spectrometry and with gas chromatography–mass spectrometry to analyze the effects of carbonization temperature on the composition of carbonized woody biomass prepared from Douglas fir, spruce and pine feedstocks. The obtained carbonized biomass contained both holocellulose and lignin when the feedstocks were carbonized below $$400\,^\circ \hbox {C}$$ and contained mainly lignin when the feedstocks were carbonized above $$400\,^\circ \hbox {C}$$ , because almost all the holocellulose in the biomass feedstocks decomposed at around $$400\,^\circ \hbox {C}$$ .

Hydrothermally-treated Empty Fruit Bunch Cofiring in Coal Power Plants: A Techno-Economic Assessment

Abstract Co-firing biomass with coal is believed to be able to improve the domestic energy security in Indonesia. Hydrothermal treatment process prior to the combustion is needed to convert raw biomass into coal-like product. The main objective of this research is to demonstrate the technological, economic and environmental feasibility of the cofiring coal with hydrothermally-treated empty fruit bunch (HT-EFB) through extensive laboratory investigations, simulations, system analyses and economic assessments from literature. Based on computational fluid dynamics (CFD) simulation, HT-EFB mass fraction of 10 to 25% seems to be the most preferable cofiring condition in term of temperature and produced gas compositions including CO 2 , CO, NO and SOx. An aspen plus simulation showed combining hydrothermal treatment with cofiring in an integrated system power plant could be a positive way to generate electricity with overall energy efficiency 37.09%. Moreover, fuel production cost, EFB supply capacity from palm mills surrounding the power plants, and transportation cost are required parameters to be considered for developing large scale biomass cofiring and integrated supply chain.

In-Furnace Sulfur Capture by Cofiring Coal With Alkali-Based Sorbents

This manuscript presents experimental results on the reduction of sulfur oxide emissions from combustion of a high-sulfur content pulverized bituminous coal (Illinois #6 Macoupin) using a dry sorbent injection method. The coal particles were in the size range of 90–125 μm and were blended with calcium-, sodium-, potassium-, and magnesium-containing powdered sorbents at different proportions. The alkali/sulfur molar ratios were chosen to correspond to stoichiometric proportions (Ca/S = 1, Mg/S = 1, Na2/S = 1, and K2/S = 1) and the effectiveness of each alkali or alkali earth based sorbent was evaluated separately. Combustion of coal took place in a drop-tube furnace, electrically heated to 1400 K under fuel-lean conditions. The evolution of combustion effluent gases, such as NOx, SO2, and CO2 was monitored and compared among the different sorbent cases. The use of these sorbents helps to resolve the potential of different alkali metals for effective in-furnace sulfur oxide capture and possible NOx reduction. It also assesses the effectiveness of various chemical compounds of the alkalis, such as oxides, carbonates, peroxides, and acetates. Reductions in SO2 emissions were in the range of 5–72%, with sodium being the most effective metal followed by potassium, calcium, and then magnesium. Acetates were effective as dual SO2 and NOx reduction agents.

Life cycle assessment of co-firing coal and wood pellets in the Southeastern United States

Coal-fired power plants produce nearly 40% of the electricity in the United States, contributing more than three-quarters of all carbon dioxide emissions from the electricity sector. While many European coal-fired power plants have been transitioning to wood pellets to abate carbon dioxide emissions, such a changeover has not occurred in the United States electricity sector. This analysis examines the environmental implications of co-firing coal and wood pellets in the Southeastern United States, where the vast majority of wood pellet exports to Europe originate. Utilizing primary data from existing wood pellet manufacturers, a life cycle inventory is presented that characterizes the full cradle-to-grave environmental performance of co-firing coal and wood pellets for electricity generation. Furthermore, the avoided life cycle emissions related to shipping wood pellets to Europe are calculated. Life cycle assessment modeling scenarios for co-firing wood pellets in existing coal-fired power plants within the Southeastern United States result in reductions in eight of nine impact categories. The results presented here indicate that co-firing with wood pellets could be a viable interim solution for the aging fleet of coal-fired power plants within the Southeastern United States, particularly if stricter emission regulations and renewable portfolio standards are implemented.

Porosity development and reactivity changes of coal–biomass blends during co-pyrolysis at various temperatures

While co-firing of coal and biomass represents an inexpensive, efficient, short-range future method to incorporate more renewable fuels into our energy generation portfolio, we know little about how U.S. domestic coals and biomasses behave together. Computational fluid dynamics models are routinely used to model combustion of solids in packed and fluidized beds, for which porosity changes are a key variable to predicting heterogeneities in transport and fuel reactivity. This work probes the changes in carbon contents, thermal reactivities, surface areas, and porosities as a function of blend ratio and pyrolysis temperature for a series of Pennsylvania coal and feed corn stover biomass blends. There is a fairly linear trend between both percent biomass in a blend and pyrolysis temperature with volatile matter content of the char; this additive nature of the blended streams does not extend to surface area and porosity. Surface areas (measured by N2 adsorption isotherms) peaked for the pure coal and 10wt% biomass peaks around 600°C, and for the 20 and 50wt% biomass and pure biomass between 600 and 750°C. The surface area decreases for all samples when the pyrolysis temperature reaches 900°C. Generally, higher temperatures led to enhanced microporosity across all fuels and blends, though this was not a linear trend. Of keen interest to co-firing scenarios was the disappearance of segregated oxidation behavior of the coal–biomass blends at pyrolysis temperatures as low as 300°C, suggesting that co-firing could be improved by preheating the comingled fuels and low temperatures before their introduction into the boiler.

Impact of co-firing lean coal on NO x emission of a large-scale pulverized coal-fired utility boiler during partial load operation

The present work aimed at combustion optimization of a 1,000 MW tower-type ultra-supercritical boiler co-firing a lean coal with bituminous coals for reducing NOX emission particularly at low load operations. Historic operation data were systematically analyzed to investigate the characteristics of NOX emission. Through comparing between lean coal co-firing and sole bituminous coal firing, it was confirmed that, besides the big difference in quality and combustion characteristics of the lean coal from the bituminous coals, the excess air ratio in main combustion zone had a significant effect on NOX emission. Keeping the ratio at properly lower level achieved lower NOX emissions at low load operations. Based on the analyses, in-situ tests successfully brought NOX emissions of co-firing down close to 300 mg/m3 at the load of 700 MW, demonstrating the effectiveness of combustion optimization for controlling NOX emissions at partial load operation of co-firing.

Effect of co-firing coal and biomass blends on the gaseous environments and ash deposition during pilot-scale oxy-combustion trials

This paper presents the experimental results from co-firing blends of El Cerrejon (EC) coal and cereal co-product (CCP) using several ratios (100/0; 75/25; 50/50; 0/100 (w/w)) under air- and oxy-firing conditions, in a retrofitted 100kWth pulverised fuel combustor. An on-line high-resolution multi-component Fourier Transform Infra-red (FTIR) analyser was used to measure CO2, O2, H2O, CO, NO, NO2, N2O, NH3, SO2, HCl, HF and CH4. A comprehensive evaluation of the major and minor species present in the flue gas was carried out to study the effects of the addition of biomass, the firing mode (air/oxy) and the type of recycle (wet/dry) on the gaseous environment in the combustor. It was found that similar CO2 levels can be reached when using pure coal or pure biomass, on a dry basis. For the minor species, the increase in the share of biomass had the effect of decreasing the SO2 levels reached in the flue gas and increasing the HCl content. No significant variation in the NOx levels was observed as a consequence of using high percentages of biomass. For ash deposit characterisation, two probes were used for which surface temperatures were controlled at 650° and 750°C. Environmental scanning electron microscopy (ESEM) with energy dispersive X-ray (EDX) analysis, supported by X-ray diffraction (XRD), were used to study the deposits. The ESEM/EDX and XRD results showed similar sulphur levels in the deposits when varying the share of biomass even though EC coal contains 3.5times more sulphur than CCP. This is thought to be a consequence of the reaction of sulphur with the alkalis, especially potassium, present at higher levels in the CCP, which produces higher levels of K2SO4 in the combustion gas. Chlorine was only found in the deposits generated using pure CCP under oxy-firing conditions. An evaluation of the different mineral species formed when varying the biomass share and the firing mode was also performed. Results obtained comparing the mineral species in deposits when using 100% CCP, switching from air to oxy-firing conditions, showed that in air-firing CCP deposits had higher levels of aluminium phosphate and arcanite (K2SO4). Also, under oxy-firing conditions, 100% CCP-derived deposits had a higher level of potassium magnesium chloride compared 100% EC.

Organic carbon emissions from the co-firing of coal and wood in a fixed bed combustor

Co-firing of biomass and coal and biomass reduces the emission of pollutants and the overall effects have been extensively studied, but many aspects of the detailed mechanism remain uncertain. A number of studies have been previously made by us of emissions from the combustion in a fixed-bed furnace of bituminous coal and wood, both individually and together, and it was observed that biomass produced less soot and lower NOX emissions. These data are combined with recent measurements of emissions of black carbon (BC) and organic carbon (OC), which are an important source of climate forcing, from the combustion of a number of solid fuels. Conclusion are drawn about the nature of the OC and how the values are dependent on the measurement technique used. Complementary analytical-scale combustion and pyrolysis experiments were also carried out. The results of the analysis of emissions and reaction products, mainly by gas chromatography–mass spectrometry (GC–MS), were interpreted so as to construct a model for pollutant formation during co-firing.There is a reduction of smoke from the combustion of torrefied biomass and this is considered in relation to the torrefaction processes.