Tube Furnace Experiments Research Articles

Investigation of the mechanism and interaction of nitrogen conversion during lignin/glutamic acid co-pyrolysis

Biomass pyrolysis has the potential to be transformed into valuable chemicals and fuels. Nitrogenous chemicals exert a substantial influence on the quality of bio-oil. Studying the impact of lignin on the transformation of nitrogen-containing elements in biomass during biomass pyrolysis is crucial for achieving efficient and effective utilization of biomass resources. In this study, tube furnace experiments, thermogravimetric infrared experiments (TG-FTIR), and gas chromatography-mass spectrometry (Py-GC/MS) were used to investigate the interactions of typical lignins (vanillin and syringol), nitrogenous components (glutamic acid), and the effect of lignin on the pyrolysis gas release of glutamic acid and the pyrolysis products during the co-pyrolysis process. In addition, the impact of lignin on the effect of pyrrolidone formation from glutamic acid was investigated in this study in conjunction with quantum chemical calculations. The experimental findings demonstrated that the co-pyrolysis of lignin and glutamic acid resulted in a reduction in the pyrolysis temperature. This reduction facilitated the release of HCN, NH3, and CO2 while notably impeding the formation of nitrogen-containing compounds in the oil. The nitrogen concentration in the pyrolysis oil declined from 97 % to a range of 51.06–79.63 %, and the inhibitory impact decreased as the pyrolysis temperature increased. At an elevated pyrolysis temperature of 800 °C, lignin facilitated the decarboxylation process of glutamic acid, resulting in an increased production of pyrrolidone.Simulation results demonstrated that the lowest energy barrier paths were the dehydration condensation process and the Maillard reaction involving glutamic acid and lignin and their pyrolysis intermediates, with a particular competitive connection between the two pathways. The results explained the interaction mechanism between the two pyrolysis products and provided a fundamental theoretical basis for nitrogen conversion in biomass pyrolysis.

The effect of additives on the co-pelletization of sewage sludge and extraction residue on combustion behavior and off-gas emission reduction

Co-combustion of biomass and sludge is a promising method for waste treatment and power generation. In this study, additives such as ammonium dihydrogen phosphate (ADP), calcium oxide (CaO), attapulgite (AT), and their combinations were added into the co-pelletization of semi-dry sludge (with approximately 50% water content) and extraction residue from vegetable oil processing. The objective of the studies was to examine the pelletization behavior, reduce off-gas emissions during the combustion, and investigate the mechanisms influenced by these additives through the thermogravimetric analysis and the tube furnace combustion experiment. The results of the analysis of variance (ANOVA) indicated an increase in pellet density due to the addition of additives. During the combustion, the addition of AT and compound additives generated more complex compounds with high melting temperatures, thereby mitigating the high slagging tendency. Meanwhile, additives facilitated the conversion of ultrafine particles (PM0.1) to fine particles, leading to a reduction in PM0.1 emissions by 15.60–42.40%. The additives exhibited efficacy in reducing SO2 emissions, with a reduction range of 5.00–23.20%. However, the addition of ADP additives resulted in a 12.00% increase in NO emissions. Consequently, adding additives to pellets could address the slagging issue and reduce the emission of air pollutants during combustion.

Co-pyrolysis of thermoplastic polyurethane with paulownia wood: Synergistic effects on product properties and kinetics

Co-pyrolysis of plastics and biomass offers an effective approach for waste disposal. In this study, the synergistic effects during the co-pyrolysis of thermoplastic polyurethane (TPU) and paulownia wood (PAW) were investigated in terms of pyrolysis kinetics and product properties using tube furnace, TG-FTIR and GC/MS. The results revealed that co-pyrolysis promoted the material pyrolysis and facilitated the pyrolysis process taking place at low temperatures. By adopting the Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO) and Starink methods, the average activation energies of pure TPU, PAW, and TPU/PAW blends with a 1:1 mass ratio were determined to be 139 kJ/mol, 288 kJ/mol, and 126 kJ/mol. It is indicated that co-pyrolysis significantly reduced the activation energies and enhanced reactivity. Tube furnace experiments demonstrated that TPU/PAW blend with 1:1 mass ratio exhibited the highest synergism. The TPU melt acted as a physical barrier, leading to increased production of char and oil, and lower production of volatile gas. In the pyrolysis oil, the synergistic effect effectively hindered a formation of alcohol phenols. In the meanwhile, the synergistic effect also boosted generations of aliphatic compounds and ketones, increasing the heat value use of pyrolysis oil. Furthermore, a reaction pathway and mechanism of co-pyrolysis of TPU and PAW was proposed. The active molecules and free radicals generated by the pyrolysis of PAW promote the hydrogen transfer cyclization of polyester polyols decomposed by TPU, and the hydrogen free radicals released by TPU promote the depolymerization and activation of PAW. Moreover, the catalytic effect of alkali metal elements in PAW promotes the synergistic effect. The results of the study provide a basis for the co-pyrolysis of waste plastics and biomass to achieve high value utilization of waste.

Preparation of municipal solid waste incineration fly ash/ granite sawing mud ceramsite and the morphological transformation and migration properties of chlorine

Municipal solid waste incineration (MSWI) fly ash is a hazardous waste containing high chlorine and harmful substances generated during the waste incineration disposal, and its resource utilization has a positive effect on reducing environmental pollution. In this study, the feasibility of preparing lightweight MSWI fly ash/granite sawing mud ceramsite (MG ceramsite) was investigated by evaluating the influence of Al2O3 addition, MSWI fly ash content and sintering temperature on the ceramsite properties. The microstructure of MG ceramsite was investigated by using SEM, the chlorine morphological transformation and migration behaviors were simultaneously explored by using the tube furnace experiment, XRD and XRF analyses. The experimental results show that the maximum MSWI fly ash content is about 30 wt%∼35 wt%, with the Al2O3 addition of at least 10 %. By controlling the MSWI fly ash content of 30 wt%, MG ceramsite can be obtained with bulk density of 986 kg/m3, cylindrical compressive strength of 19.67 MPa, 1 h water absorption of 0.31 %, and chlorine content of 0 after sintering at 1150 °C for 20 min. Chlorine in MG ceramsite enters into the tail gas or secondary fly ash in the form of chlorine salts and chlorine-containing gas when the sintering temperature is above 800 °C. The MG ceramsite prepared from MSWI fly ash meets the lightweight aggregate standard and are environmentally friendly. However, the disposal of tail gas and secondary fly ash needs attention when the MSWI fly ash is used as one of the main raw materials to prepare ceramsite.

Analysis of hydrogen-rich syngas generation in chemical looping gasification of lignite: Application of carbide slag as the oxygen carrier, hydrogen carrier, and in-situ carbon capture agent

Chemical looping gasification (CLG) has become a popular method for producing hydrogen-rich syngas due to its environment-friendliness. Recently, a method of using industrial solid waste carbide slag as an oxygen carrier, hydrogen carrier, and in-situ carbon capture agent in the CLG process has been proposed. However, the actual experiment was affected by heat and mass transfer, and the detailed reaction pathway of the carbide slag was not fully understood. In the present study, the process of the CLG process for producing hydrogen-rich syngas with lignite and carbide slag was analyzed using tube furnace experiments, FactSage calculations, and joint characteristic experiment of carbide slag. The result showed that to achieve a gas phase product with a hydrogen concentration exceeding 90 vol% (with dry N2 excluded), a molar ratio of lignite to carbide slag of greater than 1:5 and a reaction temperature of 923 K should be maintained. In terms of the reaction pathway of carbide slag in the CLG process, it was revealed that calcium hydroxide, the primary component of carbide slag, directly participated in the reaction at temperatures of less than 773 K. Overall, this work provides a novel idea for the preparation of hydrogen-rich syngas during CLG process.

Modification of Inclusions by Rare Earth Elements in a High-Strength Oil Casing Steel for Improved Sulfur Resistance

Steel casing pipes used in the construction of deep oil wells usually require both high strength and corrosion-resistant behavior. Due to the exploration of deep H2S-bearing oil reservoirs, sulfide stress cracking (SSC) is becoming an increasingly serious concern for casing steel. The nonmetallic inclusions in the steel are among the key reasons for its service failure. The rare earth element Ce can be used to modify the inclusions in casing steel and improve its SSC resistance. Here, taking C110 grade casing steel (the highest class currently in service) as the investigated object, the modification behavior of Ce inclusions in the steel and the effect of the addition of Ce in varying amounts (0.01, 0.024, and 0.042 wt.%) on the modified products were studied through high-temperature tube furnace experiments and thermodynamic calculations. The results showed that Ce had an obvious modification effect on the CaO·Al2O3 inclusions in casing steel, and the diffusion of dissolved Ce in the steel was the limiting step of the modification reaction. With the extension of reaction time, the sequence describing the modification of inclusions in the steel was determined as follows: CaO·Al2O3 → CeAlO3 → Ce2O3/Ce2O2S. The final stable product after modification depended on the amount of Ce added. With 0.01 wt.% Ce, the stable phase in molten steel was Ce2O3; on the other hand, upon adding ≥0.024 wt.% Ce, the stable phase became Ce2O2S. In addition, the thermodynamic stability of Ce2O3 decreased, and it was transformed into CeAlO3, Ce2O2S, Ce2S3, and CeS during solidification. On the basis of our results and the considerations for smooth casting, the addition of a proper amount of a rare earth element is suggested for industrial trials, following the achievement of a significant and surprising improvement in the qualified rate of SSC resistance for the final steel products. The relevant mechanism is also analyzed.

Emission Characteristics and Formation Mechanism of Carbonyl Compounds from Residential Solid Fuel Combustion Based on Real-World Measurements and Tube-Furnace Experiments.

This study updated carbonyl compound (CC) emission factors (EFs) and composition for residential solid fuel combustion based on real-world measurements of 124 fuel/stove combinations in China and explored the CC formation mechanism using tube-furnace experiments with 19 fuels and low/high temperatures to explain the impact of fuel and stove on CC emission characteristics. The average EFCC values for straw, wood, and coal were 1.94 ± 1.57, 1.50 ± 0.88, and 0.40 ± 0.54 g/kg, respectively. Formaldehyde and acetaldehyde were the most abundant species, accounting for 40-60% of CCs, followed by acetone (∼20%), aromatic aldehydes (∼10%), and unsaturated aldehydes (∼5%). Different from formaldehyde and acetaldehyde, other species showed significant variation among fuel types. All these characteristics could be explained by the difference in the volatile content and chemical structure of fuel, such as aromatic in coal versus lignin in biomass. The improvement in stove technology reduced CC emissions by 30.4-69.7% (mainly formaldehyde and acetaldehyde) among fuels but increased the proportion of aromatic aldehydes by 24.3-89.4%. Various CC species showed different formation mechanisms related to fuel property and burning temperature. The volatile matter derived from thermal pyrolysis of fuel polymers determined CC composition, while higher temperature preferentially degraded formaldehyde and acetaldehyde but promoted the formation of acetone and aromatic aldehydes. This study not only revealed emission characteristic of CCs from RSFC but also contributed to the improvement of clean combustion technology.

Research on Combustion Properties and Pollutant Emission Characteristics of Blends of Maltol Byproduct/Pine Sawdust.

In this paper, the combustion and pollutant emission characteristics of maltol byproduct, pine sawdust, and their blends were experimentally studied by thermogravimetry, tube furnace experiment, and scanning electron microscopy. The results show that the combustion process of maltol byproduct, pine sawdust, and their blends can be divided into three stages, in which the volatile release of the maltol byproduct includes two stages. The ignition temperature of the blended fuel is lower than that of sawdust. The NOx produced by combustion of the blended fuel is lower than that produced by sawdust combustion alone, and the SO2 emission is always at a low level. There is a certain synergy between maltol byproduct and pine sawdust mixed combustion. Comprehensively comparing the combustion characteristics and emission characteristics, the blended fuel made by adding less than 10% maltol byproduct into pine sawdust can improve the combustion characteristics and reduce emissions, and 10% is the best proportion of the blended fuel.

Experimental and theoretical calculations study on heterogeneous reduction of NO by char/NH3 in the reduction zone of ammonia co-firing with pulverized coal: Influence of mineral Fe

As a carbon-free fuel, NH3 can be co-firing with pulverized coal to reduce CO2 emissions in pulverized coal-fired boilers, which has attracted increasing attention in recent years. However, the source of N in NH3 can lead to the increase in NO emissions. Studies on the NO reduction mechanism in the reduction zone by the co-firing of NH3 in a pulverized coal-fired boiler have been reported rarely. The mechanism for the heterogeneous reduction of NO with char and NH3 in the reduction zone is still not known, and the influence mechanism of mineral Fe on the char/NH3/NO heterogeneous reaction system is still not clear. In this study, high-temperature tube-furnace experiments and quantum chemical theoretical calculations are used to investigate the NO heterogeneous reduction mechanism in the reduction zone of NH3 co-firing with pulverized coal, and in-depth analysis of the influence mechanism of mineral Fe on the heterogeneous reduction of NO by char/NH3. Experimental results revealed that the heterogeneous reduction efficiency of iron-impregnated char/NH3 to NO is less than that of demineralized char/NH3 to NO. Fe inhibits the reduction of NO by char and NH3 in the reduction zone. Theoretical calculation results revealed that Fe is not conducive to the adsorption of NH and NO on the char surface. In the heterogeneous reduction of char/NH3/NO, Fe increases the activation energy of N–H bond dissociation and OH formation on the char surface, resulting in a 32.34 kJ/mol higher energy barrier value for the rate-determining step in the heterogeneous reduction of NO on the iron-impregnated char surface (IM2-Fe3 structure) than that for the heterogeneous reduction of NO on the surface of the iron-free char (IM2 structure). Fe is not conducive to the reduction of NO by char and NH3. This study provides new insights into the NO reduction mechanism in the reduction zone by the co-firing of ammonia in the pulverized coal-fired boiler and provides theoretical support for the application of this technology.

Determination on the activity of formed CaSO4 for arsenic adsorption during arsenic capture by CaO with the presence of SO2: Experimental and density functional theory study

Impact of SO2 on arsenic capture by CaO during oxy-coal combustion was investigated. The key question was to reveal the role of formed CaSO4 for arsenic capture. Drop tube furnace experiments verified that SO2 largely inhibited arsenic capture by CaO, and the adverse effect was assigned to the plugging and sulfation of CaO. Density functional theory study was further conducted to determine the impact of CaO transition to CaSO4 on arsenic adsorption. While, the feeble gap of adsorption energy between hexahedral As2O3 on CaO (001) surface and hexahedral As2O3 on CaSO4 (001) surface was incongruous with the apparently weakened arsenic capture capability of CaO by SO2. Then deformation of hexahedral As2O3 to chain As2O3 was firstly proposed to improve theoretical calculations, since the high combustion temperature and low deformation energy. Finally, huge adsorption energy gap between chain As2O3 on CaO (001) surface and chain As2O3 on CaSO4 (001) surface was observed. It not only demonstrated the much weaker activity of CaSO4 as opposed to CaO for As2O3 adsorption, but also confirmed the validity of As2O3 deformation. The widely applied hexahedral As2O3 structure was not the factual structure in flue gas during coal combustion, and the deformation should be concerned. Additionally, it was identified that Ca and O sites in CaO (001) surface were active for As2O3 adsorption. While, sulfur atoms in CaSO4 (001) surface were idle for As2O3 adsorption, and restricted the activity of surface O sites for As2O3 adsorption. Meanwhile, the activity of surface Ca sites was not affected by sulfur atoms.

Insight into the high-temperature adsorption of PbO/PbCl2 by kaolinite: An experimental and DFT study on the role of H2O/–OH

Water vapor and surface hydroxyl groups were considered to participate in the high-temperature adsorption of metal vapor by kaolinite; however, the effect and the mechanisms were not clear yet. In this study, we investigated the effect of H2O on PbO/PbCl2 adsorption by kaolinite at high temperatures by drop tube furnace (DTF) experiments at 800-1300℃, and further investigated the role of H2O/–OH in adsorption by DTF experiments and density functional theory (DFT) calculations. It was found that H2O inhibited the PbO adsorption but enhanced the PbCl2 adsorption. No significant interactions between H2O and PbO/PbCl2 were found before adsorption, so the interactions between H2O and kaolinite surface were considered to be responsible for the effect of H2O. At high temperatures, H2O inhibited the conversion of –OH on kaolinite surface to H2O mainly by the reverse conversion of H2O to –OH. The residual –OH on kaolinite surface inhibited the adsorption of PbO molecule and PbCl2 molecule by the occupation of the adsorption sites. However, dechlorination was another important step for PbCl2 adsorption, which made the unstable chloride adsorption (adsorption energy ≈ 200 kJ/mol) transform to stable oxide adsorption (adsorption energy > 500 kJ/mol). –OH on the surface could lower the dechlorination energy from around 400 kJ/mol to around 200 kJ/mol. Therefore, H2O enhanced the adsorption of PbCl2 by increasing the amount of –OH on kaolinite surface. The optimum adsorption temperatures of PbO adsorption and PbCl2 adsorption were 1200℃ and 1000℃, respectively.

Performance evaluation of biomass pretreated by demineralization and torrefaction for ash deposition and PM emissions in the combustion experiments

Biomass combustion is a promising method in combustion facilities to reduce CO2 emissions. Biomass fuel has unfavorable characteristics, such as low temperature ash minerals and high particulate matter (PM) emission in the combustion facility, which influences operation and creates environmental issues. In this work, different types of empty fruit bunch (EFB) and palm kernel shell (PKS) biomass samples, such as raw biomass, demineralized biomass, and its biomass pretreated by torrefaction were studied to identify their char combustion characteristics by thermogravimetric analysis (TGA) and their ash deposition behaviors and PM emissions in a drop tube furnace (DTF) experiment. Regarding the char combustion characteristic results obtained by TGA, demineralization pretreatment did not clearly influence the char combustion reactivity compared to that of raw biomass, but torrefaction pretreatment lowered the char combustion reactivity at low temperatures. In the DTF experiments, torrefaction pretreatment led to increasing ash deposition and PM emissions during biomass combustion. However, demineralization pretreatment clearly lowered the amount of ash deposition and PM emissions because potassium (K), chlorine (Cl), and sulfur (S) were significantly removed by demineralization pretreatment. In particular, scanning electron microscopy with dispersive X-ray spectroscopy (SEM-EDX) analysis results showed that the demineralized biomass samples having low K, Cl, and S components emitted relatively large PM compared to untreated biomass. Therefore, demineralization pretreatment might be a good method to produce cleaner biomass fuel.

Fate of chromium with the presence of HCl and steam during oxy-coal combustion: Quantum chemistry and experimental study

Quantum chemistry combined with kinetic simulation and drop tube furnace (DTF) experiments were conducted to reveal the transformation behavior of chromium at the presence of steam and HCl under oxy-coal combustion. A completed kinetic system Cr‒O‒H‒Cl containing 107 elementary reactions was firstly proposed. The unknown microcosmic reaction paths and corresponding Arrhenius parameters were calculated via quantum chemistry. Kinetic simulations on the basis of Cr‒O‒H‒Cl system clarified that HCl promoted the oxidation of chromium to hexavalent CrO2Cl2. Coexistence of HCl and steam divided the transition of chromium into two stages. At the early stage, reaction rate between chromium and steam was faster than chromium with HCl, chromium mainly transformed to CrO(OH)2. Hereafter, HCl was dominant in the transformation of chromium, then chromium mainly presented as CrO2Cl2. Moreover, DTF experimental results indicated that introduction of HCl into combustion atmosphere induced more chromium release. Presence of steam reinforced the effect of HCl on chromium attributing to the significant transition of CrOx(OH)y to CrO2Cl2. Although CaO and Fe2O3 both exhibited good reactivity with chromium, presence of HCl largely suppressed chromium capture by CaO and Fe2O3. Moreover, the inhibition effect of HCl on Fe2O3 was stronger than CaO for Cr capture.

Characteristics of coal tar residue treated with microwave-assisted hydrothermal treatment

To achieve an efficient large-scale use of the coal tar residue (CTR), a microwave-assisted hydrothermal treatment was investigated to reduce its viscosity. The CTR was treated at various temperature with various liquid/solid (L/S) ratio by microwave-assisted hydrothermal. Then the thermogravimetry (TG) and the tube furnace combustion experiment were employed to study the combustion behavior and the NOx and SO2 emissions of the treated CTR. The results indicated that the microwave-assisted hydrothermal treatment with higher temperature and higher L/S ratio was beneficial to the viscosity reduction of the CTR. The TG results suggested that the treated CTR achieved a complete combustion only at a heating rate of 10 °C/min. Moreover, increasing the temperature and the L/S ratio reduced the comprehensive combustion characteristic index of the treated CTR. The results of combustion experiment indicated that the NOx emission of the treated CTR was less than 140 mg·m−3, while the SO2 emission was less than 100 mg·m−3. The microwave-assisted hydrothermal treatment is a promising method for the CTR, and the treated CTR can be applied as the fuel of circulating fluid beds (CFB) for industrial production.

Influence of phosphorus on ash fouling deposition of hydrothermal carbonization sewage sludge fuel via drop tube furnace combustion experiments

Phosphorus effect on ash fouling deposition produced during combustion process of sewage sludge solid fuel is a very important factor. Previous studies have only focused on decrease of the ash melting temperature and increase of slagging and sintering by phosphorus content. Therefore, research regarding combustion fouling formation and its effect on temperature reduction of deposit surface by phosphorus content is insufficient. Ash fouling is an important factor, because ash in the combustion boiler process deposits on the surface of heat exchanger and interferes with heat exchange efficiency. In particular, temperature reduction of heat exchanger surface via fouling should be considered together with fouling deposition, because this is related to the heat exchanger efficiency. Synthetic ash, phosphorus vaporization, and drop tube furnace experiments were performed to investigate effect of phosphorus on ash fouling formation and temperature reduction of deposit surface under combustion condition. Phosphorus was highly reactive and reacted with ash minerals to produce mineral phosphate, which promoted ash fouling deposition during the combustion experiments. In contrast, the occurrence of sintering on deposited fouling resulted in formation of a large hollow structure, which alleviated the temperature reduction on the deposit surface. Phosphorus content had a substantial correlation with fouling deposition behavior and influenced reduction in the surface temperature of the heat exchanger, because it led to generating low temperature mineral phases.

Effect of ash components and atmospheres on slagging characteristics of high-AAEM lignite gasification

Two kinds of high alkali and alkaline earth metal (AAEM) lignite (TTc and ZDc) were used as fuels, and three atmospheres of CO2, CO/CO2, and H2O (g) were used in the horizontal tube furnace experiments to simulate the gasification conditions in different parts of the boilers. The relevant thermodynamic calculations on the atmospheres and ash compositions were conducted in FactSage 7.2. The results show that both two coals have a high risk of slagging. Decreasing the relative content of SiO2 or increasing the relative content of Al2O3 can increase the ash fusion temperatures (AFTs) of TTc; increasing the relative content of CaO can increase the AFTs of ZDc. Besides, it is not recommended to adjust the relative content of Fe2O3. The proportion of the liquid phase of ZDc ash in CO/CO2 atmosphere is much higher than that of CO2 and H2O (g) in a typical circulating fluidized bed (CFB) gasification temperature interval, while the generation of liquid phase of TTc ash is less affected by atmospheres. The bottom of boilers is the most severe slagging zone, and purging with H2O (g) is a good way to alleviate the low-temperature slagging of the return feeder.

Experimental study on combustion and NO formation characteristics of semi-coke

Pyrolysis condition is vital to physicochemical properties of semi-coke, influencing the subsequent combustion and NO formation. In this study, the combustion behaviors and NO formation characteristics of semi-cokes obtained from various pyrolysis conditions in a fixed-bed reactor were investigated by thermogravimetric analysis and drop tube furnace experiments. Experimental results indicated that the combustion reactivity of semi-coke lowered as pyrolysis temperature, residence time increased and coal particle size decreased. Addition of CO2 or O2 in pyrolysis atmosphere improved the reactivity. NO conversion ratio of semi-coke decreased initially and increased afterwards with the elevation of pyrolysis temperature with a turning point at 800 °C, arose from the fact that higher surface area was helpful for NO reduction during combustion. For mild pyrolysis semi-coke, a critical particle size range was found corresponding to the lowest NO conversion ratio, and it reduced with increasing residence time. O2 addition in pyrolysis atmosphere significantly lowered the NO conversion ratio and burnout ratio, because some combustibles in coal had been oxidized during the foregoing pyrolysis. CO2 addition in pyrolysis atmosphere exhibited relatively slight effect on the burnout or NO conversion, since the gasification between CO2 and char was weak at this temperature. Quantitative relationship was established to reflect major factors affecting NO formation, and the surface area was observed to have the most prominent influence.

Structure and Reactivity of Low-Rank Coal Chars Prepared from Fluidized Bed and Moving Bed Pyrolyzers and the Potential for Using Them in Pulverized Coal Injection (PCI)

Utilizing pyrolysis chars as the injection fuel in a blast furnace can reduce the dependence on high-quality pulverized coal injection (PCI) coal. In this study, the physical properties and reaction characteristics of chars prepared from two different industrial-scale pyrolyzers (fluidized bed and moving bed) are investigated. The results reveal remarkable component segregation in the char particles with different particle sizes. The properties of large-size char particles are found to better satisfy the PCI fuel requirement in a blast furnace. Compared with PCI coal, the char particles exhibit a rough surface, well-developed pore structure, and less-ordered chemical structure of carbon. Results from isothermal combustion, isothermal gasification, and drop tube furnace experiments show that both types of chars exhibit a better reactivity than PCI coal. The excellent reactivity of chars is closely related to its high Brunauer–Emmett–Teller surface area and relatively poor chemical ordering during conversion. Based on these characteristics, both fluidized bed char (FBC) and moving bed char (MBC) have a great potential to be used as PCI fuels. The application method of chars for PCI in a blast furnace is proposed finally.

Characteristics of volatile release rate and fuel nitrogen conversion for three typical coals under high temperature fast pyrolysis

Drop Tube Furnace experiments were carried out to investigate the fast pyrolysis characteristics of three typical coals. The process of fast pyrolysis was simulated by a one-step pyrolysis model as well as a Chemical Percolation Devolatilization (CPD) model. The results indicate that coal rank, reaction temperature and residence time have complex influences on volatile release and nitrogen conversion. Both activation energy and frequency factor, which decrease with increasing coal rank, show obvious differences for the three considered coals. The volatile release coefficient QR is relative to coal rank and heating rate which fluctuates from 1.02 to 1.72. Predictions of volatile release and coal nitrogen conversion obtained from CPD model agree well with experiments. In addition, the one-step pyrolysis model could predict the volatile release of low-rank coal, whose precision is related to coal rank.

Evaluation of the adhering layer ratio of iron ore granules and its influence on combustion-generated NO x emission in iron ore sintering

In iron ore sintering, the granulation process is the first and an important step. As the fine particles adhere to the coarse coke particles, the NO x emission generated from coke combustion may be expected to be influenced by that adhering layer. In this study, the granule size distributions and adhering ratios were evaluated by a granulation model. Granulation experiments were also carried out to obtain the granule size distribution and adhering ratio. The influence of the adhering layer on NO x emissions from the combustion of S type granules was studied by tube furnace experiments. Conclusions include: (1) The adhering ratio predicted from the granulation model can be used as a qualitative index for the evaluation of NO x emission from coke combustion. (2) The influence of the adhering layer on NO x emissions was enhanced with increasing adhering layer thickness of S type granules, and the NO x reduction was enhanced at higher temperatures (around 1373 K), but weakened at lower temperatures (around 1173 K).