Co-combustion Characteristics Research Articles

Research on the co-combustion characteristics and kinetics of rice husk hydrochar with anthracite

Co-combustion of anthracite and hydrochar derived from hydrothermal carbonization with process water recirculation was proposed as an effective way to achieve a transition to low-carbon energy in industries that rely heavily on coal combustion. In this study, thermogravimetric analysis and model-free methods were employed to investigate the co-combustion characteristics and kinetics of anthracite and hydrochar. The results demonstrate that the carbon content of hydrochar is lower than that of anthracite, but the volatile content is higher than that of anthracite, indicating that hydrochar has better combustion performance. There is a synergistic effect in the co-combustion reaction of hydrochar and anthracite. With the increase of the hydrochar addition ratio, the ignition and burnout temperatures of anthracite decrease gradually. With the increase of temperature rise rate, the combustion reaction is enhanced and the combustion performance of anthracite is improved under the fixed mixing ratio. According to the calculation of combustion activation energy by Flynn-Wall-Ozawa and Kissenger-Akahira-Sunose methods, the apparent activation energy of the mixed samples gradually decreases with the increase of combustion conversion rate. When the addition of hydrochar is 60 %, the average apparent activation energy of the mixed sample is the lowest, which is 66.51 kJ mol−1 and 54.62 kJ mol−1, respectively.

Thermogravimetric analysis of co-combustion characteristics of sewage sludge and bamboo scraps combined with artificial neural networks

The increasing amount of sludge resources has brought great challenges to the ecological environment and sustainable development. Co-combustion of low calorific value sewage sludge and biosolid waste has become a new and effective way to treat sludge. The co-combustion characteristics of sewage sludge and bamboo scraps in air were studied by thermogravimetric mass spectrometry and artificial neural network. The thermogravimetric analysis of combustion at three different heating rates was performed with five different mixing ratios. Through comprehensive combustion index and cooperative analysis, it is concluded that the co-burning effect and cooperative effect of sludge and bamboo are better. Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose were used to calculate the apparent activation energy. The average activation energy of the sludge mixed with 75% bamboo scraps was the lowest (126.3 kJ mol−1) under the co-combustion condition. The ion current of combustion gas products during combustion was studied by mass spectrometry. Co-combustion can increase NOx and reduce SO2, and 75% bamboo slag mixed sludge has the least gas production. Finally, the prediction model of sludge co-combustion is established by artificial neural network, which provides a prospective guidance for the resource utilization of solid waste.

Study on the Co-combustion characteristics and synergistic effect of semi-coke and dust coal produced from biomass briquette in fluidized bed gasification

Biomass briquette semi-coke (BFSC) is one of the byproducts of biomass gasification. It is difficult to reuse due to its inadequate carbonization, unsatisfactory pore structure, and surface properties. Co-combustion of BFSC with coal-fired boilers can be a cost-effective usage of biomass gasification semi-coke while also improving dust coal's combustion characteristics. However, research on the optimal blending ratio, co-combustion properties, and synergistic effects of BFSC and dust coal is lacking. This study conducted experimental and theoretical research on the co-combustion and reaction kinetic characteristics of BFSC and dust coal with a 0.3 MW pilot experimental system. The findings indicate that during co-combustion, sawdust semi-coke (SC), eucalyptus bark semi-coke (EBC), rice husk semi-coke (RHC), and corn straw semi-coke (CSC) exhibit favorable synergistic effects. At a 25 % blending ratio, the corresponding synergistic parameter indexes (SPIs) were 1.313, 1.053, 1.001, and 1.042. Adding EBC and SC may significantly promote the combustion of dust coal and make it enter the combustion stage sooner, improving combustion stability. When 25 % RHC or CSC is co-combusted, the activation energy predicted by the kinetic control equations is 17 kJ/mol and 5 kJ/mol lower than theoretical values, with a relative error of less than 3 %. The annual EBC output from a 1-ton biomass boiler may replace roughly 706 tons of normal coal, lowering CO2 emissions by approximately 634 tons and producing a direct economic gain of $33300. Therefore, BFSC is a low-carbon and low-cost coal boiler fuel with great potential for large-scale industrial applications.

Technical feasibility of a 1000 MWe pulverized coal power plant under ammonia co-combustion conditions

Ammonia has attracted the attention as a practical way to reach carbon free power generation. Ammonia co-combustion characteristics in 1000MWe pulverized coal power plant was simulated by using Aspen Plus and evaluated under an excess air ratio of 1.0–1.2, air of 2642–3457 ton/hr, coal of 208.2–355.5 ton/hr, ammonia of 0–186.14 ton/hr and various coals. The influence of co-combustion ratios of different coals on emission characteristics and net efficiency was compared. For carbon dioxide emission reduction, the respective CO2 intensity reduction for KPU and BG was 36.44 and 37.76% in calorific value basis, 32.51 and 31.90% in weight basis. The net efficiencies of the power cycle showed a lower decrease as the fuel was supplied on the weight basis compared to the calorific value basis. Based on the obtained results, the KPU on the weight basis showed the lowest net efficiency decrement of 3.1%, but in terms of CO2 intensity reduction, BG on calorific value basis showed most drastic reduction of 37.76%. Consequently, these results showed an effective carbon reduction with ammonia co-combustion and provides a promising solution for the pulverized coal power plants to compass a meaningful reduction of carbon emissions and conservation of combustion efficiency.

Co-combustion characteristics and reaction mechanism of coal slime and sewage sludge using a novel multilateral double volumetric parallel model and dendrite neural network

The co-combustion of coal slime (CS) and sewage sludge (SS) presents an effective method for significantly reducing solid waste on large-scale. This study conducted experimental research to investigate the combustion and co-combustion characteristics of CS and SS, focusing on exploring the synergistic effects and mechanisms during co-combustion processes. Novel multilateral double parallel models (Multi-DPM) were proposed to analyze the contributions of volatile and char components in CS/SS mixtures across different ratios during co-combustion. The effects of temperature, mixing ratio, and heating rate on the co-combustion process were evaluated using a new novel dendrite neural network (DD-NN) model. The results revealed varyied degrees of interaction between CS and SS during co-combustion. Kinetic and thermodynamic analyses revealed that the most significant enhancement in the CS/SS mixing ratio of 6:4. Both the double parallel volumetric model (DPVM) and the newly proposed multilateral double parallel volumetric models (Multi-DPVM) demonstrated the best fit with experimental conversion and proved their suitability for analyzing the co-combustion process of CS and SS. These models were further employed to predict the combustion kinetic parameters and conversion profiles of total volatiles and total char of single and mixed materials, as well as the volatiles and char of the individual CS and SS materials within the mixture. The obtained conversion data and activation energy values from the DPVM and Multi-DPVM were used to assess the best fit reaction mechanism using the master-plots method. This validation underscored the reliability of the DPVM and Multi-DPVM based on integral fitting model solution. Moreover, the application of the new DD-NN model demonstrated good predictive performance for the co-combustion process of CS and SS, identifying key transfer functions influencing the co-combustion process. Overall, this study provides valuable insights into comprehensively understanding the co-combustion mechanism of CS and SS, providing crucial information for industrial product design.

Co-combustion characteristics and kinetics of sludge/coal blends in 21%–50% oxygen-enriched O2/CO2 atmospheres

This research investigated the thermogravimetric analysis (TGA) and combustion kinetics of sewage sludge and Australian sub-bituminous coal and their blends with different mixing ratios (sludge/coal = 100/0, 80/20, 50/50, 20/80, 0/100 by weight) under air atmosphere (O2/N2 = 21/79 by volume), oxy-fuel combustion (O2/CO2 = 21/79, 25/75, 35/65, and 50/50 by volume), and pyrolysis (pure N2 atmospheres). The gaseous products that evolved from the TGA experiments were also analyzed using a Fourier transform infrared (FTIR) spectrometer under pyrolysis conditions. Results showed that the mixed fuel with higher coal blending ratio had higher ignition temperature, lower burnout temperature and larger combustion characteristic index. Furthermore, TGA–FTIR experiments of the 20 % sludge + 80 % coal blended fuel under nitrogen atmospheres showed more gasification components in pure coal than in sludge. The combustion kinetics analytical results via the Flynn–Wall–Ozawa method indicated that the larger the conversion degree, the smaller the obtained activation energy value. Under the oxy-fuel combustion conditions, when the oxygen concentration increased from 21 % to 50 % for the 20 % sludge + 80 % coal blended fuel, the ignition and burnout temperatures decreased, and the combustion characteristic index increased nearly three times. Oxygen enrichment can clearly improve combustion characteristics and flammability.

Co-combustion strategy of waste energetic materials with pine sawdust for efficient NOx emissions reduction

Excessive NOx emissions during incineration of waste energetic materials (EMs) is harmful to the environment. Co-combustion technologies with biomass have demonstrated remarkable advantages in reducing NOx emissions. Herein, the co-combustion characteristics and NOx emission behaviors of waste double-base propellant (DP) and pine sawdust (PS) were investigated via thermogravimetric (TG) and fixed-bed experiments firstly. Meanwhile, the general full factorial design (GFFD) was performed to explore the effects of different factors on the NOx emissions of co-combustion. The interaction mechanism between DP and PS was discussed as well. Moreover, the interaction of three other typical waste EMs (RDX, TNT, and triple-base propellant) co-combustion with PS in NOx emissions was studied utilizing orthogonal experiments. The kinetics under air atmosphere indicated that the mixing of PS slightly diminished the combustion reactivity of DP, conversely, the remaining residue of DP combustion promoted the combustion of PS. Oxygen concentration, temperature and mixing ratio all had significant effects on NOx emissions of co-combustion between DP and PS, the degree of effect decreased in turn. Overall, the mixing of PS all suppressed the NOx emissions with significant synergistic effects, optimal synergistic effect at 20 wt% of PS mixing. The synergistic effect in oxygen environment was lower than that in oxygen-free environment. Meanwhile, increasing temperature contributed to enlarging the synergistic effect. Additionally, there was synergistic effect of TNT and PS co-combustion, whereas RDX, TP exerted inhibition effect of co-combustion with PS. Therefore, the co-combustion strategy of waste EMs with PS provides reliable data support and guidance for the control of NOx emissions during the incineration of waste EMs.

Study on co-slurry and co-combustion characteristics of coal and modified-coal gasification fine slag

In this study, hydrocarbon oil was used to modify coal gasification fine slag(CGFS) to improve its hydrophobic performance. The modified CGFS(MCGFS) was then mixed with coal to prepare MCGFS-coal water slurry(MCGFS-CWS), and the slurry’s flowability and combustion characteristics of MCGFS-CWS were investigated. XPS analysis and contact angle experiments revealed an increase in the non-polar groups on the surface of MCGFS, resulting in enhanced hydrophobicity with higher hydrocarbon oil content. The viscosity of MCGFS-CWS decreases as the amount of hydrocarbon oil increased, significantly improving its fluidity compared to CGFS-CWS. Under the conditions of this study, when the amount of hydrocarbon oil is 8%, the constant-viscosity concentration of MCGFS-CWS is 0.46% higher than that of CWS. Combustion characteristic studies revealed that the addition of CGFS increased the concentrations of alkali metals and alkaline earth metals in the slurry, promoting the catalytic combustion reaction. When the amount of hydrocarbon oil is large, the hydrocarbon oil in MCGFS ignites and burns at a lower temperature. The temperature released during the combustion of hydrocarbon oil is beneficial to promote the ignition of slurry and reduce the ignition temperature of MCGFS-CWS. These results demonstrate that hydrocarbon oil modification enhances the hydrophobicity of CGFS and reduces the ignition temperature of MCGFS-CWS.

Thermal conversion property and NO emission characteristics of oxy-fuel co-combustion of biomass and semicoke

Thermal conversion property and NO emission characteristics of oxy-fuel co-combustion of biomass and semicoke

Numerical Study on Coal–Sludge Cocombustion Characteristics and NOx Emission Behaviors in a 330-MW Wall-Fired Boiler

Numerical Study on Coal–Sludge Cocombustion Characteristics and NOx Emission Behaviors in a 330-MW Wall-Fired Boiler

Synergy mechanism of biochar and petcoke co-combustion based on potassium migration and transformation

Co-combustion of biochar and pet-coke can reduce environmental pollution, provide fuel energy supply and improve fuel reaction characteristics. In this study, the co-combustion characteristics and synergistic behavior of rice straw char (BC) and petcoke (PC) were analyzed based on thermogravimetric analysis and kinetic analysis. The combustion corroborative experiments were conducted based on a fixed bed reactor, and the contents of different forms of potassium (K) during combustion of semi-char were characterized. Raman spectroscopy and X-ray photoelectron spectroscopy were used to characterize the carbon structure order and surface elements distribution characteristics of the semi-char after the combustion. The results showed that the co-combustion reactivity improved with the temperature and the BC blended ratio increase. Moreover, the synergistic effect increased with the temperature decrease and the BC blended ratio increase. The synergistic effect was confirmed to be related to the K migration and transformation, and its behavior was varied with active K content adsorbed by PC. The H2O-soluble K would be transformed into -COOK during PC combustion. -COOK would reduce the order of PC and increase the content of amorphous carbon during combustion.

Investigation of Co-Combustion Characteristics of Waste Biomasses and Anthracite by TG-DTG/DSC and Machine Learning Method

ABSTRACT The co-combustion characteristics and thermodynamics of waste biomasses, namely coconut shell and corncob, with anthracite were investigated using TG-DTG/DSC analysis and artificial neural networks. TG-DTG experiments were conducted at different ratios of CS-AN and CC-AN, and the samples were heated from 293 K to 1273 K at heating rates of 10, 15, 20, 25, and 30 K·min−1. The results indicated three main stages in the combustion process of the mixtures and the combustion profiles shifted to higher temperatures with increasing heating rates. As the mass fraction of biomass in the mixtures increased from 10 wt.% to 90 wt.%, the residual mass of the co-combustion mixture decreased by 19.50 wt.% and 21.78 wt.% for CS-AN and CC-AN, respectively. The comprehensive combustion index of CS-AN increased from 24.645%2·min−2·K−3 to 167.274%2·min−2·K−3, while that of CC-AN increased from 26.262%2·min−2·K−3 to 102.654%2·min−2·K−3. The DSC results showed a peak of heat absorption followed by an exotherm in the co-combustion process. As the mass fraction of anthracite in the mixtures increased, the curve shifted toward the high temperature region and the exothermic time increased. The apparent activation energies (E) for CS, CC, and AN were 75.36, 112.08, and 90.90 kJ·mol−1, respectively. Additionally, 50 wt.% CS and 50 wt.% CC were more conducive to CS-AN and CC-AN co-combustion processes. 63 ANN models were utilized to predict the post-combustion residual weight of CS5-AN5. ANN56 was identified as the best performer, with error results (RSME = 1.482, MBE = 1.120, R 2 = 0.9982) and a topology of (3 × 15 * 5 × 1), which proved to be the most suitable model for the co-combustion characteristics of this mixture. This study provides theoretical and practical guidance for solving engineering problems related to the energy utilization of waste biomasses (coconut shell and corncob) with anthracite.

Slagging Characteristics of Co-Combustion of Water Hyacinth Biomass and Coal

Slagging Characteristics of Co-Combustion of Water Hyacinth Biomass and Coal

Co-combustion characteristics of paper sludge and combustible construction and demolition waste

Combustion characteristics and hazardous gas emissions were investigated by using TG-FTIR under individual and co-combustion of paper sludge (PPS), combustible construction and demolition wastes (CCDW) and its components. The interaction between PPS and CCDW during co-combustion at different PPS ratios was predicted by mass-weighted method. Kinetic parameters under individual and co-combustion of PPS and CCDW were calculated by using three model-free methods involving Flynn-Wall-Ozawa (FWO), Kissinger-Akah-Sunose (KAS) and Starink. The obtained results indicated that the residue of co-combustion with PPS and CCDW gradually increased when PPS ratio increased from 30% to 70%. Co-combustion of PPS and CCDW improves combustion characteristics and mass-weighted method can be used to predict their TG/DTG curves. A significant interaction between PPS and CCDW was clarified, especially at the high temperature stage greater than 400 °C. The activation energy calculated by FWO method has higher accuracy for co-combustion of PPS and CCDW. Co-combustion of PPS and CCDW can effectively reduce the emission of hazardous gases. A suggested PPS ratio of 50% was proposed for improving combustion characteristics and reducing the hazardous gas emissions during co-combustion of PPS and CCDW.

Investigation of intake air temperature effect on co-combustion characteristics of NH3/gasoline in naturally aspirated high compression ratio engine with sub-chamber

Recently, ammonia (NH3), which has a higher energy density than hydrogen, has gained attention for zero-carbon emission goals in the transportation sector. However, in a conventional internal combustion engine (ICE), NH3 combustion mechanism is still under investigation. In this paper, to further expand the knowledge on the adoption of NH3 in ICEs, authors conducted NH3/gasoline co-combustion experiments in a modified, 17.7:1 compression ratio, naturally aspirated spark-assisted CI engine with sub-chamber. The sub-chamber was chosen in order to enhance the combustion speed of NH3. In addition, the sub-chamber was equipped with glow and spark plugs to overcome the high auto-ignition temperature of NH3. Engine performance and NOX emissions were studied under three different intake air temperatures. During the experiments, NH3 content was increased gradually where the engine was run under lean conditions. Although higher NH3 content was achieved compared to our previous work, increasing the intake air temperature resulted in decreased charging efficiency. In addition, corrosion was found on the piston ring after 120 h of operation, negatively affecting the engine performance. Furthermore, NH3/gasoline co-combustion duration was shortened drastically with the influence of the sub-chamber, where the longest combustion duration under the present conditions was found to be 17°CA.

Decoupling combustion characteristics of biomass pellets and their mixture with bituminous briquettes

Co-firing coal and biomass has been thought to be a promising way to achieve the efficient and clean combustion of them, but few researches were concentrated on the application of the co-firing technology in the residential field. In this study, the decoupling co-combustion characteristics of bituminous briquettes (BB) and biomass pellets (BP) were first evaluated by thermalgravimetric mass spectrometer (TG/MS) measurements, followed by the experiments on the pollutant emissions of burning blending fuels in a typical household decoupling stove as well as the thermodynamic equilibrium calculation and X-ray powder diffractometer (XRD) analysis of their slagging/fouling characteristics. The synergistic effect of co-firing coal and biomass is clarified. The addition of BP improves the combustion performance of blending fuels, while bituminous briquettes enhance the combustion stability of blending fuels. In the decoupling combustion stove, the stable coal char layer together with biomass pyrolysis gases plays an important role in the suppression of NOx, which also promotes the burnout of combustibles and thus favors the reduction of CO emission. Possible ash-related issues of ultrafine/fine particle emissions and severe slagging/fouling tendency caused by burning BP alone can be effectively alleviated by the capturing and regulating effect of BB. Co-firing bituminous briquettes and biomass pellets directly in the decoupling furnace can be anticipated to find wide use in the residential field.

Investigation of co-combustion characteristics of distillery sludge and sugar mill waste: kinetics, synergy, and ash characterization

Investigation of co-combustion characteristics of distillery sludge and sugar mill waste: kinetics, synergy, and ash characterization

Experimental investigation on co-combustion characteristics of semi-coke and coal: Insight into synergy and blending method

Co-combustion of semi-coke and coal is a prospective technique for large-scale disposal or utilization of the solid waste. In this paper, the co-combustion behaviors and kinetics of semi-coke and coal were studied by thermogravimetric analysis with a focus on the influence of blending method and synergy. The results indicated that the semi-coke combustion was improved by blending with coal, and the interaction between fuels tended to promote the co-combustion. The ignition and burnout temperatures were positively correlated with the carbon content of the mixture, while the comprehensive combustion index and stability index were negatively correlated with it. The layer blending and partition blending method seemed to show stronger promotion than uniform blending method, and the layer blending method with coal in the upper layer was recommended due to the better combustion behavior. The promotion of coal on semi-coke combustion was less affected in devolatilization stage but weakened by the decrease of O2 concentration in char burnout stage. The apparent activation energy (Ea) of the mixture decreased with the increasing faction of coal. The layer blending method with coal in the upper layer had the lowest Ea in devolatilization stage and relatively high Ea in char burnout stage. The work can give some new insights into waste co-disposal strategy and carbon emission reduction in China.

Effect of modified diatomaceous earth on the heavy metal volatilization characteristics of aged refuse co-combustion

ABSTRACT This paper investigated the adsorption performance of natural and modified diatomaceous earth (DE) for six heavy metal species (Cu, Zn, Ni, Cd, Pb, Cr) during the co-combustion of aged refuse (AR) and municipal solid waste (MSW) in a lab-scale tubular furnace. The aim was to examine the effects of temperature, sorbents, and modification methods on heavy metals’ adsorption performance. The capture rates of calcined diatomaceous earth (CDE) were higher than those of DE, especially for Ni at 700°C, whose capture rate increased to 78.6%. Modified sorbents with NaOH or Na2CO3 significantly reduced the volatility of six heavy metals at 700°C, with the volatilization rates (VR) of Ni and Zn decreasing by at least 50%. Meanwhile, for Cu, Pb, and Zn, the fixation of heavy metals in the bottom ash increased with rising the sorbents mass. However, when the combustion temperature was equal to or above 800°C, the effects of modification on the VR of Cd, Pb, and Zn diminished, except for 10 wt% DE and CDE-10%NaOH. Using NaOH-modified DE at higher temperatures increased the VR of Ni, Pb, and Zn, particularly for Ni whose VR increased by 21.13%. This work contributes to understanding DE’s control mechanism of heavy metals and investigates new heavy metal control strategies during the co-combustion of MSW and AR.

Simulation study on fuel-nitrogen migration characteristics of oxy-fuel co-combustion of various ultra-low volatile coal-based solid fuels

The co-combustion of various ultra-low volatile coal-based solid fuels (UVCFs) under oxy-fuel condition could consume semi-coke and residual carbon cleanly and efficiently. However, the fuel-nitrogen (fuel-N) migration behaviors of various UVCFs blends in O2/CO2 atmosphere are still unclear. In addition, the heterogeneous reactions on surfaces of char could also affect the synergistic effects between various UVCFs blend. Here, the fuel-N migration features of various UVCFs in O2/CO2 atmosphere were investigated by Chemkin simulation and the oxy-fuel co-combustion mechanism of various coal-based solid fuels (OCF mechanism) included heterogeneous reactions was developed. Moreover, the methods of sensitivity and rate of production analyses were both employed to clarify the synergistic effects on nitrogen conversion pathways of various blends. The heterogeneous reaction between char and NO (R15) is the key reaction for NO reduction in primary zone. The free radicals OH and H provided by UVCFs could react with main NO precursors NCO, HNCO, HOCN, NH and NH2 to generate NO. The conversion pathways of HCN to NO are more complex than those of NH3 to NO. The rises of residual carbons proportions and temperature in primary zone (T1) could both reduce the NO formation amount due to the promoted R15. The sensitivity coefficients (S) on NO formation of 50% SS/50% CR blend in the burnout zone are lower than those of 50% SS/50% FR blend. The transformations of HNCO, HNO and NO2 to NO and the heterogeneous reactions of NO could both be enhanced with the O2 concentration in burnout zone. The increasing burnout air position (Pb) results in the rise of NO generation owing to that the NO reducing reactions R15 and R16 are greatly inhibited with the Pb raised. The present study could be beneficial for the clean and effective utilization of UVCFs, together with the reduce of NOx emission and realization of carbon neutral in China.