Shenmu Coal Research Articles

Insight into the stabilization mechanism of Zn during co-gasification of sewage sludge and coal: Perspective of solid-liquid transition

In this study, the underlying mechanism of zinc (Zn) stabilization during the co-gasification of sewage sludge (SS) with Shenmu coal (SM) was investigated using an in-situ visual furnace to analyze the distribution of Zn species. The findings classified two distinct stages within the co-gasification process: the organic matter gasification stage, occurring below 1000 °C, and the inorganic mineral melting stage, occurring above 1000 °C. The addition of SM can extend the organic matter gasification phase, in which the porous carbon structure of the SM char aids in the capture of Zn released during the devolatilization of SS. However, a sustained reducing atmosphere promoted the formation of Fe3O4, causing Zn destabilization. Subsequently, during the inorganic mineral melting stage, the complete reaction of carbon released Zn, which was adsorbed onto the carbon surface. Furthermore, the ash from SM contributes to the melting of the co-gasification residues, enhancing Zn stabilization through encapsulation by the molten phase and stabilization within the spinel lattice. This study highlights the critical role of liquid encapsulation in Zn stabilization during co-gasification.

Oxy-fuel co-combustion properties and N-containing pollutants release characteristics of biomass/coal blends

Thermal properties and NO release characteristics during oxy-fuel co-combustion of pine sawdust (PS) and Shenmu coal (SM) were investigated based on the effects of various parameters, including atmosphere, temperature, blending ratio, and oxygen concentration in this research. The results indicate that the release of NO decreased with the increasing temperature during decomposition process of PS and SM. The content of N-Q and N-X in semicoke (SC) increased at higher torrefaction temperature. The N-Q and N-X content for SC at the temperature of 1000 °C was 36.9 % and 23.2 %, respectively. When 40 % PS was added to the SM, the NO release amount was significantly reduced by 16.3–23.1 % in the oxy-fuel atmosphere compared to the O2/N2 atmosphere, and the ignition time was reduced from 4.0s to 0.66s. The NO emission initially increased and then decreased as the combustion temperature increased from 800 to 1000 °C. Furthermore, increasing the oxygen concentration from 10 % to 40 % shortens the combustion time and increases the emissions of NO. Conversely, increasing PS blending ratios from 10 % to 40 % decreased NO emission and the conversion ratio. These findings emphasize that adding biomass can effectively improve coal ignition, increase combustion rates, reduce NO emissions, and address the air pollution problems associated with NOx emissions.

Comparative experimental study of ash formation behaviors during the fixed-bed gasification of coal water slurry and dry pulverized coal prepared from Shenmu coal

The mechanism of ash formation during coal gasification is very important for the safety and stability of gasifier operation. This study comparatively investigated the ash formation behaviors during the gasification of coal water slurry and dry pulverized coal. Shenmu coal was gasified in a CO2 atmosphere at 900 °C using a fixed-bed reactor to prepare chars and ashes. Computer-controlled scanning electron microscopy was employed to characterize the compositions and particle sizes of minerals in the raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash. Morphological characteristics reveal that, during gasification, coal water slurry gasification char exhibits obvious agglomeration compared to the dry pulverized coal gasification char. The changes of mineral compositions indicate that, during both coal water slurry and dry pulverized coal gasification, minerals follow nearly identical transformation pathways, but the degrees of transformation are different. The influence of char agglomeration on heat transfer may be the reason for the less transformation of K Al-silicate and kaolinite during the coal water slurry gasification. Furthermore, in comparison to dry pulverized coal gasification, more Ca in calcite and S in pyrite transfer into gypsum during the coal water slurry gasification. The results from thermodynamic equilibrium calculations indirectly suggest that this may be attributed to the limited internal diffusion of CO2 within coal water slurry gasification char resulting from char agglomeration during gasification. Overall particle size distributions of minerals in raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash demonstrate that the degrees of mineral fragmentation are almost consistent during both coal water slurry and dry pulverized coal gasification. However, differences in the degrees of mineral transformation led to different particle size distributions of various minerals between coal water slurry gasification ash and dry pulverized coal gasification ash. This study mainly focuses on the influence of water in coal water slurry on ash formation, and it has not considered the influence of other factors, such as ash content, hydrophilicity, caking property, and gasification reactivity of coal, which need further research to explore.

Pyrolysis of shenmu coal to prepare blue-coke used as reductant

Blue-coke is a form of granular char prepared by medium-low temperature pyrolysis of low-rank coal. As a reductant, it has been widely used in calcium carbide production, ferroalloy, copper pyro refining, and ferrosilicon production in China due to the abundant reserves of raw coal and its excellent performance. However, there is little research on the pyrolysis process of granular coal to produce blue-coke and its characteristics as a reductant. Thus, the effects of pyrolysis temperature, heating rate, particle size and holding time at the final temperature on blue-coke preparation were investigated in a rotary kiln reactor. The quality index of blue-coke as a reductant and its properties, including the element composition, surface function groups, carbon forms, reactivity and lower heating value under different pyrolysis temperatures, were analyzed in detail. It is demonstrated that the pyrolysis temperature had a more significant impact on the quality of blue-coke compared to other pyrolysis conditions. With the rise of pyrolysis temperature, the blue-coke’s C/O and C/H increased. With the particle size and heating rate increased, the temperature gradients developed within the granular coal during the pyrolysis process led to the volatile release shifting to higher temperature zone and more secondary reaction occurrence. Nevertheless, the secondary reaction was restrained in the rotary kiln with good heat and mass transfer. The indexes of blue-cokes as reductants were met by the chars produced at temperatures from 550 oC to 750 oC with a holding time 60 min at this temperature and a heating rate of 10 oC/min. As the key index of blue-coke, the electrical resistivity decreased with the increase of pyrolysis temperature. It was found to be closely related to the removal of H and O heteroatom at the pyrolysis temperature below 700 °C. While at the higher temperature, the development of graphitized carbon structure took a major role on it. Nonetheless, the crystallite sizes of the blue-coke obtained under this low temperature pyrolysis were small and the carbon forms were turbostratic. These resulted in the blue-coke's high combustion reactivity, which would gradually decline with the rise of pyrolysis temperature.

A novel coal purification-combustion system: Product and efficiency of coal purification process

A novel coal purification-combustion technology is presented to realize the efficient and clean utilization of coal under carbon peaking and carbon neutrality goals. Central to this technology is the implementation of a purification process, the product characteristics, and energy properties of which are the focus of this study. An experimental test of coal purification was conducted using Shenmu coal. The results demonstrate increased coal reactivity following the moderate temperature activation (MTA) process. The high temperature reduction (HTR) phase promotes the production of higher amounts of amorphous carbon, reduces aromatic carbon content, and further decreases fuel particle size. The composite combustion characteristic index(S) of the purified fuel reaches its peak when the excess air coefficient of secondary air (λ2) is 0.36. As λ2 increases from 0.1 to 0.36, the energy in the gas product of the purification system increases from 13700 kJ/kg coal to 25351 kJ/kg coal, while exergy increases from 6530 kJ/kg coal to 11030 kJ/kg coal. The energy efficiency of the purification process ranges from 74.74 % to 80.88 %, with exergy efficiency varying between 60.51 % and 70 %. These findings offer significant insights into refining the coal purification process, ultimately contributing towards maximizing the utility of coal resources.

Unraveling the intrinsic mechanism behind the retention of arsenic in the co-gasification of coal and sewage sludge: Focus on the role of Ca and Fe compounds

Minimizing the emission of arsenic (As) is one of the urgent problems during co-gasification of Shenmu coal (SM) and sewage sludge (SS). The intrinsic mechanism of As retention was obtained by analyzing the effect of different SM addition ratios on the As form transformation during co-gasification at 1000 °C under CO2 atmosphere. The results showed that the addition of SM effectively promoted the enrichment of As in the co-gasified residues. Especially, the best As retention rate of 65.71% was achieved with the 70 wt% addition ratio of SM. The addition of SM promoted the adsorption and chemical oxidation of As(III) to the less toxic As(V) through the coupling of Ca and Fe compounds in the co-gasified residues. XRD and XPS results indicated that Fe2O3 adsorbed As2O3(g) after partial conversion to Fe3O4 by the Boudouard reaction, while part of As2O3 was oxidized to As2O5 by lattice oxygen. Finally, the generated As2O5 was successively trapped by CaO and Fe2O3 to form stable Ca3(AsO4)2 and FeAsO4. HRTEM and TEM analysis comprehensively proved that As(III) was stabilized by the lattice cage of CaAl2Si2O8. In conclusion, the co-oxidation of Ca and Fe compounds and lattice stabilization simultaneously played a crucial role in the retention of As2O3(g) during co-gasification.

Effect of AES anionic surfactant on the microstructure and wettability of coal

The paper object is high-quality Shenmu bituminous coal modified by fatty alcohol polyoxyethylene ether sodium sulfate (AES) surfactant. The changes in functional groups, free radicals, Zeta potential, and contact angle of coal modified in AES anionic surfactant were analyzed. Based on the molecular structure of Shenmu coal, a coal-AES-water three-phase dynamic model was constructed. The wetting mechanism of coal was studied by molecular dynamics. The research has demonstrated that as the mass fraction of AES surfactant increases, the proportion of polar groups (-OH, C–O–C, –COOH, –CO), free radical content and Zeta potential increased significantly. The size of contact angle displayed a major negative linear correlation with the proportion of polar groups and free radicals, but positively linearly correlated with the Zeta potential. In the coal-AES-water three-phase dynamic model, the AES molecules adhere to coal molecules as hydrophobic group, while hydrophilic groups extended into the water. This increased H2O diffusion coefficient, enhanced action energy between coal and water interface, decreasing surface tension and achieving effective wetting of the coal. This paper supplies s a new idea for selecting efficient surfactants to change the coal microstructure. It is of major importance for improving coal wettability and offers a theoretical foundation for gas drainage and disaster prevention.

Effects of pyrolysis temperature and atmosphere on grinding properties of semicoke prepared from Shenmu low-rank coal

This study investigated the effect of temperature and atmosphere on the grindability of the semicoke prepared via a mid–low temperature pyrolysis of low-rank Shenmu coal, analyzed the variation in its grinding characteristics with the increase of ball grinding duration, and explored the influence mechanism of the pyrolysis conditions on the grindability of semicoke based on the pyrolysis process and semicoke structure evolution. The results show that as the pyrolysis temperature increases (400–700 °C), grindability and grinding mechanism of the semicoke change significantly; the grindability first increases and then decreases with the increase of the pyrolysis temperature. As the grinding duration increased, high-Hardgrove grindability index (HGI) semicoke underwent intensive bulk grinding at a specific grinding time. Additionally, the varying contents of the proximate analysis during devolatilization are not the main cause of the varying HGI during pyrolysis. Using thermogravimetric and thermomechanical analyses, the optimal grindability of the semicoke was found to occur at the transition stage of the pyrolysis to pyrocondensation reactions (approximately 600 °C). During the transition, the intense pyrolysis reaction led the semicoke to have abundant pores and cracks, a highly disordered chemical structure, and low matrix hardness. The porous semicoke which has high grindability first underwent surface grinding; subsequently, the loose cores were more prone to bulk grinding, whereby the optimal grindability was obtained. HGIs of the semicoke prepared in the reductive atmospheres such as H2, CO and CH4 are lower than that of the semicoke prepared in N2 atmosphere at the same pyrolysis temperature. Moreover, the reductive atmospheres inhibited pore development in the semicoke and made its carbon structure more ordered, which densified the structure and decreased the grindability of the semicoke.

Migration behavior of chlorine during co-gasification of Shenmu coal and corn straw

Migration behavior of chlorine during co-gasification of Shenmu coal and corn straw

Thermal Behavior and Kinetics of Shenmu Coal Pyrolyzed under Hydrogen-Rich or Methane-Gas-Rich Atmosphere

The pyrolysis characteristics of Shenmu coal under an atmosphere containing H2 (40%) and another containing CH4 (40%) were studied via a thermogravimetric analysis, and the kinetic parameters of pyrolysis were calculated by using a distributed activation energy model (DAEM). The results showed that H2 promoted the cleavage of CH-like functional groups by providing reactive hydrogen groups to combine with CH groups and –OH groups in the coal. However, the H2 and CH4 atmosphere inhibits the cleavage of oxygen-containing functional groups such as carbonyl groups and C–O groups, and this is unfavorable to the production of CO2 and CO. The pyrolysis weight-loss rate of raw coal decreases with the increase of the heating rate, and the weight-loss curve shifts to the high-temperature region. At the same conversion rate and pyrolysis temperature, the activation energy of pyrolysis under the H2 and CH4 atmospheres is lower than that under the N2 atmosphere, and the activation energy does not conform to the Gaussian distribution. The activation energy of pyrolysis was distributed in a narrow range, in which the activation energy of the H2 and CH4 atmospheres was concentrated in the range of 175–215 kJ/mol and 225–230 kJ/mol, respectively, and the activation energy of the H2 atmosphere was lower than that of the CH4 atmosphere under the same conversion rate.

Effect of the pore structure of coal-based activated carbon and hydrogen addition on methane decomposition for the preparation of carbon nanotubes

Activated carbon with a hierarchical micro/mesoporous carbon structure was synthesized using Shenmu coal as the raw material, which was impregnated with KOH (K) in different K/C ratios before carbonization at various temperatures. The obtained material was loaded with nickel and then employed as catalyst for the catalytic methane decomposition (CMD) to prepare carbon nanotubes. Using a constant nickel loading, the effects of the pore structure of the different activated carbon materials and hydrogen addition on the preparation of carbon nanotubes were investigated. The results show that the coal-based activated carbon with a micropore content of 0.8, synthesized at a carbonization temperature of 850 °C and a K/C ratio of 2, is the most suitable carrier for the methane cracking catalyst to produce carbon nanotubes. The diameter of the prepared carbon nanotubes is in the range of 50–120 nm with a length of 5–15 μm. The addition of hydrogen can prevent the high-temperature decomposition of oxygen-containing functional groups, and the activity of the catalyst can be maintained by inhibiting carbon deposition. Furthermore, the hydrogen present in the CMD process can promote the formation of carbon nanotubes with larger diameters (50–350 nm) and shapes. The nanotubes are more curved, and their length is reduced to 5–11 μm. Finally, the formation mechanism of carbon nanomaterials is discussed according to the morphological changes of the products after hydrogen addition and the existing theories. In conclusion, appropriate amounts of oxygen-containing functional groups and larger micropore volumes facilitate the pyrolysis of coal-based activated carbon catalysts in the preparation of carbon nanotubes.

Reaction characteristics of Shenmu coal pyrolysis volatiles with an iron-based oxygen carrier in a two-stage fixed-bed reactor

The reaction of volatiles with oxygen carriers (OCs) is a common issue in the chemical looping combustion of coal or chemical looping reforming of hot pyrolysis gas. A two-stage fixed-bed reactor was used to determine the characteristics of the reaction of pyrolysis volatiles of Shenmu coal with an Fe-based OC. The effects of the oxygen/carbon ratio (O/C, φ, 0–1.31) and temperature (750–900 °C) on the three-phase products (carbon deposition, tar, and gas) were systematically studied. The results showed that an increase in φ caused a decrease in the carbon content in tar, whereas carbon deposition and the gaseous carbon content increased. Moreover, the amount of reducing gases slowly decreased while CO2 significantly increased, indicating that the increase in CO2 mainly originates from the carbon in tar. Additionally, phenols decreased fast, but naphthalene decreased rapidly at φ > 0.63. Rise in temperature decreased carbon deposition, and tar substances, whereas increased the CO content, notably, naphthalene significantly decreased only when the temperature exceeded 800 °C. The reaction of volatiles with OCs consisted of volatiles complete oxidation, tar catalytic cracking, and carbon deposition oxidation, for which the effects of the O/C ratio and temperature were evaluated.

Characteristics of pyrolytic wastewater incineration and effects on NOx emissions of shenmu coal

The wastewater produced in the process of coal pyrolysis is difficult to decompose with conventional chemical and physical methods. To solve this dilemma, incineration is found to be an efficient way to deal with pyrolytic wastewater. For this study, experiments were conducted to investigate the characteristics of pyrolytic wastewater incineration at different temperatures as well as its effects on the characteristics of coal combustion and NOx emissions when injected into a post-combustion chamber. The results show that CO emissions during the incineration of pyrolytic wastewater decreased when temperature or residence time increased. NOx emissions fluctuated little from 700 ℃ to 850 ℃, but NOx emissions declined when temperatures increased from 900 ℃ to 1000 ℃. Phenols could be removed when the residence time was 5 s at 950 ℃ or 4 s at 1000 ℃. In the incineration process of pyrolytic wastewater, it is more beneficial to reduce NOx by setting the injection position in an environment with low particle concentration under the premise that the residence time in the high temperature region is greater than 2 s. The NOx emissions increased 1.3% when pyrolytic wastewater was injected from middle of furnace, the NOx emissions decreased 3.4% when pyrolytic wastewater was injected from top of furnace, and the NOx emissions decreased 15.3% when pyrolytic wastewater was injected from top of post-combustion chamber.

Reaction Characteristics of Shenmu Coal Pyrolysis Volatiles with an Iron-Based Oxygen Carrier in a Two-Stage Fixed-Bed Reactor

Reaction Characteristics of Shenmu Coal Pyrolysis Volatiles with an Iron-Based Oxygen Carrier in a Two-Stage Fixed-Bed Reactor

Char structural evolution characteristics and its correlation with reactivity during the heterogeneous NO reduction in a micro fluidized bed reaction analyzer: The influence of reaction atmosphere

Experiments were conducted on chars prepared from R- and H- form sawdust (SD) and Shenmu coal (SM) to investigate NO reduction in different atmospheres, and physicochemical structures of chars after the reaction were analyzed. The effects of atmospheres on NO reduction reactivities and structural evolution characteristics of different chars were discussed. The NO reduction reactivity of SD chars was always better than that of SM chars, and there were some differences in the specific reactivity of four chars under different atmospheres. When NO, CO2 and O2 were sequentially involved, the char ordering degree tended to increase, which also had a clear positive impact on the pore development. With the participation of CO2 and O2 in the reaction, some N-6 and N-X in R SD char were converted into N-5 and N-Q, while N-6, N-5 and N-X in the other three chars were converted into N-Q.

Roles of moisture and cyclic loading in microstructures and their effects on mechanical properties for typical Chinese bituminous coals

This work aimed at studying the roles of moisture and cyclic loading in microstructures and their effects on mechanical properties for typical Chinese bituminous coals. Different relative moisture contents (100%, 75%, 50%, 25%, and 0%) for Shenmu coal (SM), Hongshaquan coal (HSQ), and Wucaiwan coal (WCW) were chosen to study the effects of moisture. The raw SM was then further selected to investigate the effects of cyclic loading. Images of coals surfaces and mechanical properties during simulated crushing process were recorded and combined to be analyzed. The results showed that the moisture possessed significant effects on coal mechanical properties, which strongly depended on their porosities. As for low porosity coal (SM), the adsorption of moisture can soften and lubricate the microstructures, weakening mechanical properties. While the drying process would destroy the microstructures and decease mechanical properties for high porosity coals (HSQ and WCW). Under the cyclic loading process, the cumulative effects of strain showed a step-up state and the first cyclic loading can typically cause the biggest change of microstructures and produce the largest strain under different stress levels. Finally, a normalized quantitative relationship (σr=-0.67Dr2+1.62Dr+0.07) between the relative fractal dimension and relative stress was built.

Effect of active alkali and alkaline earth metals on physicochemical properties and gasification reactivity of co-pyrolysis char from coal blended with corn stalks

During co-pyrolysis, active alkali and alkaline earth metals (AAEMs) can influence the synergistic effect of coal and biomass. For exploring the influence of active AAEMs on the co-pyrolysis process, this paper studied the physicochemical properties and gasification reactivity of co-pyrolysis char of four blends: raw coal and raw corn stalks (RC&RCS), pickling coal and raw corn stalks (HC&RCS), raw coal and pickling corn stalks (RC&HCS), and pickling coal and pickling corn stalks (HC&HCS). The results show that the synergistic effects on char yields are within 3%. During co-pyrolysis, the presence of corn stalks is beneficial to the generation of spherical particles from coal char, and the promotion effect of pickling corn stalks is greater than that of the raw corn stalks. The active AAEMs have an inhibitory effect on the decomposition of aliphatic C–H, CO and –CH3 in Shenmu coal, and also on the decomposition of O–H, aliphatic C–H and C–O in the corn stalks. The experimental values of gasification residual carbon of RC&RCS/HC&RCS co-pyrolysis char are 24–77% of the calculated values, while that of RC&HCS/HC&HCS co-pyrolysis char are 86–103% of the calculated values. The interaction between the blends promotes the reactivity of co-pyrolysis char.

High-temperature fast pyrolysis of coal: An applied basic research using thermal gravimetric analyzer and the downer reactor

The study explored the influence of temperature and particle size on the high-temperature fast pyrolysis behaviors of Shenmu(Yulin) coal through thermal gravimetric analyzer and the downer reactor. Results of TG-FTIR show that the thermal hysteresis causing by high heating rate make TG and DTG curves shift to high-temperature zone. The infrared spectra reveal that the release characteristics of typical products and functional groups are consistent with the weight loss curve. Moreover, experimental results of the downer reactor reveal that the content of coal-char and coal-tar decreased and coal-gas increased with the increment of temperature. Better syngas can be obtained at 900 °C. The yield of coal-char firstly increases and then decreases with the decrease of particle size and the coal-tar is opposite. More importantly, during the pyrolysis process of 35–60 mesh coal, the largest amount of coal-char and the smallest amount of coal-tar are not only obtained, but high-quality syngas is also obtained. Through the characterization of coal-tar, it is found that coal-tar is mainly composed of aromatic compounds, and the content can reach more than 50%. Moreover, the change of infrared absorption intensity of O–H, CO and C–O groups in coal-char varies with the change in pyrolysis parameters.

Characteristics of small molecule compounds produced from the co-pyrolysis of cotton stalk and coal

Pyrolysis experiments of cotton stalk (CS) and Shenmu coal (SM) were conducted in a tubular furnace. The pyrolysis temperature was 600 °C at 5 °C/min and sustained for 15 min. The water-soluble small molecule compounds (WSMC) were derived from the liquid products obtained during pyrolysis with the methods of toluene entrainment and ultrasonic extraction. The compositions of WSMC were further characterized by gas chromatography–mass spectrometry (GC-MS). The components of the syngas were analyzed by gas chromatography (GC). The results showed that the phenol yield was promoted by the interaction of CS and SM during co-pyrolysis. Moreover, the co-pyrolysis interaction blocked the radical reaction pathway that produces amides and accelerated the formation of pyridines. Because the ester yield increased, the esterification was clearly enhanced and the yield of carboxylic acids in WSMC was reduced during co-pyrolysis. In addition, the inhibition of furan generation resulted in an increased yield of C2–C4 hydrocarbons in the co-pyrolysis syngas. The maximal yields of C2–C4 hydrocarbons all occurred at a 20/100 ratio of CS/SM. Lastly, the formation mechanisms of small molecule compounds were proposed.

Study of the Influence of Biodegradation on Coal Micro-Nano Pore Structure Using Low-Temperature N₂ Adsorption.

An experimental study of biodegradation of Shenmu coal was carried out by using Ochrobactrum cytisi, Novospingobium naphthalenivorans, Alcaligenes faecalis and Pseudomonas fluorescens. The micro-nano pore structure of coal samples before and after biodegradation was studied by low-temperature N₂ adsorption. For biodegraded coal, the results showed that micropores and mesopores are primarily open pores with good connectivity, including parallel plate pores and cylinder pores with two open ends; the specific surface area of biodegraded coal decreased from 2.2174 m²/g to 1.6255˜2.0537 m²/g, and the pore size of the coal biodegraded by the four bacteria decreased following biodegradation from 250 nm to 170˜200 nm, which may be due to collapse of the coal structure due to the bacterial degradation. Coal biodegradation by the dominant bacterium P. fluorescens led to a diminished mesopore size and an increased number of smaller mesopores, with the smaller mesopores gradually taking on dominant roles.