Coal Pyrolysis Process Research Articles

C1∼C2 hydrocarbons generation and mutual conversion behavior in coal pyrolysis process

Different hydrocarbon species in coal pyrolysis gases have the NOx reduction potential. To investigate hydrocarbons CxHy mutual conversion in the coal pyrolysis gases, four typical coals were pyrolyzed under slow and fast heating rate conditions below 1200 °C. Results show that the yield of the hydrocarbon species has positive relation to coal volatiles. In fast heating condition CH4 is the major pyrolysis products. In addition, the alkanes generation behavior is quite different from that of olefins and alkynes. In the range of 600–1200 °C, as the pyrolysis temperature increases, the yield of C2H4 and C2H2 increases while CH4 and C2H6 decreases. The yield of C2H2 is significant at the temperature above than 1000 °C. Fourier transform infrared (FTIR) analysis show a close relationship between the coal functional group from 2800 to 3000 cm−1 and the alkanes yield. In the slow heating condition, five CH4 and two C2H6 evolution paths are proposed by the mathematic fitting method. The ethylene in the high temperature produced from the decomposition of C2H6. When the heating rate is low, no C2H2 is detected which illustrates that the formation of acetylene is closely related with the heating rate.

Pemanfaatan Asap Cair Hasil Pirolisis Batubara sebagai Pestisida Organik pada Rayap (Coptotermes curvignathus Holmgren)

Pyrolysis is a process of chemical decomposition of materials through a heating method in the absence of oxygen or a little oxygen. The utilizing coal as a raw material for making liquid smoke, it is hoped that it will be able to produce pesticides that have economic value and can be used as a termite exterminator. The use of coal as a raw material for making liquid smoke is expected to produce pesticides that have economic value and can be used as a termite repellent. This research aimed to determine the optimum concentration and time of liquid coal smoke as a pesticide against termite insect mortality (Coptotermes curvignathus Holmgren). The method used is the coal pyrolysis process at a temperature of 300 0C. The process of testing the mortality of termites with time and concentration variables. The determination of the liquid smoke content of coal is carried out by qualitative and quantitative analysis. The results showed that the optimum time for termite mortality was 25 minutes with an optimum concentration of 80%, where the termite mortality was obtained by 100%. Based on the results of UV/VIS Spectrophotometer Analysis, the sulfur content of liquid coal smoke was 46.92 mg/kg, and the degree of acidity (pH) was 3.00. The acidity content is high enough to allow pesticides from liquid coal smoke to be widely used in agriculture.

Integrated Process of Coal Fast Pyrolysis in a Fluidized Bed Reactor With Reforming Reaction of Simulated Fuel Gas to Promote Light Tar Evolution

The evolution behavior of the light tar during coal fast pyrolysis under inert gas, simulated fuel gas (SFG) atmosphere, and catalytic reformation of simulated (CRS) fuel gas over Ni/Al2O3 was studied in this article. The light tar was recovered from the distillation of the crude tar at the temperature of 300°C and subsequently subjected to detection through the GC-MS analysis. It was found that both SFG and CRS over Ni/Al2O3 significantly enhanced the light tar yield, but a little effect was shown on the heavy tar yield. According to the molecular structure characteristics, the compounds in the light tar could be classified into several groups: aromatic components, phenol components, aliphatic components, heteroatom components, and O-containing components (phenol compounds excluded). It was demonstrated that the selectivity of each component in the light tar varied significantly with the pyrolysis atmosphere and temperature. The evolution of the aromatic components took the dominant role in the light tar produced at high temperature. The SFG and CRS contributed markedly to enhancing the evolution of the O-aromatic components in the light tar, whereas they suppressed the evolution of the O-aliphatic components and the phenol components in the light tar at high temperature.

Effects of water on pyridine pyrolysis: A reactive force field molecular dynamics study

The emission of nitrogen oxides (NOx) from coal combustion causes serious environmental problems. Fuel splitting and staging is a promising method for NOx control by combustion modification. In this process, nitrogen-containing compounds generated from pyrolysis gas play an important role in regulating NOx generation. Water from coal could potentially change reactions during the coal pyrolysis process. Adjusting the content of water in coal may be an effective way to control coal pyrolysis reactions. This work aims to investigate the effects of water on pyridine (a main nitrogen-containing compound in coal) pyrolysis via reactive force field (ReaxFF) molecular dynamics (MD) simulations. Results indicate that the addition of water during the pyridine pyrolysis process increases the number of OH radicals in the system and accelerates the consumption of pyridine at the initial stage. However, at a later stage, water inhibits the consumption of pyridine as it impedes the condensation reaction of pyridine molecules. Common and unique intermediates are identified and quantified under various water-content conditions. Results suggest that water also reduces the proportion of nitrogen atoms in the polycondensation product. Furthermore, ring opening processes of pyridine molecules are reproduced at the atomic level. The changes in reaction pathways due to the presence of water are also revealed. The new insights into the mechanisms of pyridine pyrolysis under water and water-free conditions provide a possibility to control nitrogen migration during the pyrolysis process, which is of great significance to emission reduction from coal combustion.

Study on pyrolysis characteristics of lump coal in the context of underground coal gasification

Coal reaction in dry distillation zone, as an essential step in underground coal gasification (UCG), is of great significance to be studied about its characteristics in a comprehensive way. This study simulated the pyrolysis process of lump coal in UCG tunnel in a laboratory. Lump coal samples were heated in nitrogen environment at 200–600 °C. The functional groups, pore structure, and microcrystalline structure of coal samples were analyzed by Fourier transform infrared spectrometer, scanning electron microscope, and X-ray diffractometer. The results showed that, as final pyrolysis temperature increased, the contents of hydroxyl, aliphatic, and aromatic groups all showed decreasing trends. The escalation of CHar/CC and CH2/CH3 implied that the condensation degree of aromatic structure and the branching degree of fatty chain increased. With the temperature increasing, volatile substances such as CO2 and CH4 were released. Coal samples had higher porosity and gradually turned hollowed. The d002 (Interlinear Spacing of Microcrystalline) of the coal sample decreased, Lc (final stacking height) increased and Lc/d002 (stacking layer numbers) decreased, indicating that the crystal structure of coal samples tended to be more disordered.

Effects of CO2 and H2O on coal pyrolysis with the ultrafast heating rate in a concentrating photothermal reactor

A novel concentrating photothermal reactor with the ultrafast heating rate at around 1800 °C/min was developed to study the effects of CO2 and H2O on coal pyrolysis for oxy-fuel combustion. The mass loss rate with the ultrafast heating rate increased by several decuples than that with the slow heating rate. Coal pyrolysis process with the ultrafast heating rate was promoted by CO2 within 50% concentration but inhibited for a further higher concentration (70%). The addition of H2O into 30% CO2 exhibited a continuous positive role in coal pyrolysis with the ultrafast heating rate. Different from the satisfied prediction of chemical reaction models with the slow heating rates, diffusion models were of higher correlation coefficients for the ultrafast-heating pyrolysis process. The correction factors for CO2 and H2O were determined accordingly, and the modified three-dimensional diffusion mechanism model based on Jander equation (D3 model) well described the ultrafast-heating coal pyrolysis process.

Process modeling and techno-economic analysis of a solar thermal aided low-rank coal drying-pyrolysis process

This study investigated the feasibility of integration of concentrated solar power (CSP) to low-rank coal pyrolysis process from the economic and technical perspective. Victorian brown coal is generally used in local power plants with low efficiency and great greenhouse gas emissions. Therefore, the development of low-emission technologies for an efficient use of such vast resources is paramount. The principal objective of this process is to upgrade Victorian brown coal to alternative fuels through a solar-assisted pyrolysis process. Upon a robust design of four different scenarios for the process integration, the effects of a variety of key variables have been examined, including different types of solar collectors, heat transfer fluids (HTF) and pyrolysis temperature. The plant operation analysis showed that integrating solar tower (ST) to provide heat for both coal drying and pyrolysis within the plant can save an average of 12.8% of the annual thermal energy demand. For the optimum solar tower design, it requires a solar multiple of 2, using carbonate salts as HTF, a design point DNI of 750 W/m2 and a heat storage capacity of 8 h to maximize its total solar energy output over a year. However, from an economical perspective, the use of solar tower for both drying and pyrolysis is economically infeasible. Instead, the parabolic trough solar collectors (PTC) designed to cover the heat required for coal drying only is most economically viable. It even shows a slightly better economic performance than the conventional pyrolysis process. The parabolic trough solar assisted pyrolysis process has the potential to reach a high net present value (NPV) of $81.1 million and a short payback period of 4.9 years, relative to an NPV of $52.8 million and a payback period of 5.1 years for the conventional pyrolysis process.

Effect of Fe2O3 on the pyrolysis of two demineralized coal using in-situ pyrolysis photoionization time-of-flight mass spectrometry

Influence of Fe2O3 on the pyrolysis products distribution of demineralized Hongshaquan (HSQ) and Daliuta (DLT) coal was investigated by a novel in-situ pyrolysis vacuum ultraviolet single photon ionization time-of-flight mass spectrometry. The experiment samples were obtained by mechanical mixing of Fe2O3 and demineralized coal from acid elution with the mass ratio of 10:1, 5:1 and 2:1. Due to the characteristics of in-situ sampling, soft ionization and high vacuum environment, the initial pyrolysis volatiles including alkenes, aromatic hydrocarbons, phenols, bi-phenols and a small amount of sulfur and nitrogen-containing substances can be detected. The results show that Fe2O3 has similar influence on the products distribution of two demineralized coal, and it is relatively stronger on DLT coal than that on HSQ. With the increase of Fe2O3 content, the light fraction content is promoted such as alkenes and aromatic hydrocarbons, but bi-phenols are obviously inhibited. Correspondingly, the heavy products are also decreased, and the evolution peak temperatures of the product increase. Fe2O3 is successively reduced to FeO and Fe while transforming heavy components into light components. The increase of aliphatic carbon (or aromatic hydrocarbon substituted carbon) during coal pyrolysis process is mainly responsible for the decrease pyrolysis peak temperature.

Pyrolysis behavior of coal in a moving bed with baffled internals under different residence times

In view of the problems faced by a conventional moving bed coal pyrolysis process, such as the inability to deal with pulverized coal, low light tar yield, poor tar quality, etc., a moving bed pyrolysis process with baffled internals was developed to control heat and mass transfer of the gas-solid two-phase and the pyrolysis reaction process. The multi-stage gas gathering system can collect the oil and gas products released in different pyrolysis stages of coal in time. The pyrolysis behavior and product quality of Naomaohu coal at different temperatures and residence times were investigated. The results show that the baffle internals enhance heat and volatile matter transfer among particles, enabling it to process 0.4–6.0 mm pulverized coal. When pyrolysis temperature is 550°C and residence time is 3.0h, the pyrolysis tar yield reaches the highest 11.38%, which is 86.87% of the Gray-King assay yield, and the mass fraction of light components below 360°C in the tar fraction is 85.0%. With the extension of the residence time, the H2 volume fraction in the pyrolysis gas increases from 22.1% to 35.1%, and the CO volume fraction increases from 8.0% to 9.5%. Tar yield in the first and second layer reactors increases with increasing residence time, and the tar yield in the third and fourth layer reactors isobtained when the residence time is 2.0 h. As the number of beds increases, content of light components in the tar simulated distillation fraction increases; content of tar aliphatic hydrocarbon compounds decreases, and that of monocyclic aromatic hydrocarbons and bicyclic aromatic hydrocarbons gradually increases. Based on the above results, it provides technical support for large-scale industrial processing of small particle size pulverized coal, and preparation of higher yield and quality tar.

Integrated process of coal pyrolysis with dry reforming of low carbon alkane over Ni/La2O3-ZrO2 with different La/Zr ratio

Integrated coal pyrolysis with dry reforming of low carbon alkane (CP-DRA) is an effective method to improve tar yield. The development of dry reforming catalyst is the key for the integrated process. Ni/La2O3 shows a good performance in improving tar yield during CP-DRA, but the carbon deposition of catalyst is still a lot. To solve this problem, Zr was used as modifier to prepare Ni/La2O3-ZrO2 with different La/Zr ratios (1:1, 2:1, 4:1 and 8:1) by co-precipitation to improve catalyst stability. Results indicated that Ni4LaZr (La/Zr ratio being 4) shows a good performance and high anti-carbon deposition in DRA and CP-DRA as compared to other catalysts. The highest tar yield of CP-DRA over Ni4LaZr at 600 °C is 20.5 wt.%. Ni4LaZr catalyst also shows a good regenerability, and tar yield keeps at 20.3 wt.% within 5 times regeneration, indicating a good stability of Ni4LaZr. The high performance and stability are due to the formation of a stable pyrochlore La2Zr2O7 and present of excess La2O3 in Ni4LaZr that can inhibit carbon deposition.

Dynamic trends for char/soot formation during secondary reactions of coal pyrolysis by large-scale reactive molecular dynamics

Coal char formation depends on its precursor properties and pyrolysis time-temperature history that has a significant impact on subsequent coal conversion processes and desired tar products. With the intention for getting comprehension of char/soot formation in coal pyrolysis, a simulation strategy combining the pyrolysis simulation for raw coal model and the secondary pyrolysis simulation for nascent tar radical model with ReaxFF MD method was employed. The models around 100,000 atoms were used in order to describe the large char/soot precursors formed and their chemical structure transformation statistically that is only accessible by large-scale model and long-time simulation. The simulations revealed that an optimal condition (1700–1800 K in this case) exists during coal pyrolysis process to produce high yields of light tar and few char/soot formation. The char precursors of C100+ are mostly originated from heavy tar (C14–C40) of recombination of methylene and Car–Car bonds with significant aromaticity increasing at high temperature. The obtained overall competitive spectrum among condensation, stabilization and decomposition reactions at different typical conditions provides a more complete understanding for char/soot formation from the pyrolysis reaction perspective.

Co-pyrolysis characteristics of camellia oleifera shell and coal in a TGA and a fixed-bed reactor

The pyrolysis characteristics of camellia oleifera shell (COS), coal and their mixture were investigated using a thermogravimetric analyzer (TGA) and fixed-bed reactor. The decomposition reactions and kinetic analyses of COS, coal and their mixture from using TGA were compared. The results showed that during the pyrolysis process of COS and coal lonely, heat transfer hysteresis would occur with the increase of heating rates, and the synergistic effects during the co-pyrolysis of COS and coal could be enhanced by increasing the proportion of COS. In addition, from the results of kinetic analyses, in the range of 666∼750 °C, the activation energy (Ea) was gradually decreased with the increase of COS content, which was from about 59.7 kJ/mol to 12.7 kJ/mol. The effects of mixing ratio of COS to coal, pyrolysis temperature and heating rate on the pyrolysis process were further evaluated by using the fixed-bed reactor, and the optimal operating conditions were found (60% COS mixing ratio, 600 °C, and 10 °C/min) to obtain a higher yield of liquid around 30% and modifying the product composition. Gas products containing hydrogen, carbon-monoxide, carbon-dioxide and hydrocarbons were analyzed by gas chromatography (GC). Interestingly, the tar produced by co-pyrolysis of the blends was mainly composed of small molecule such as phenols, and there were basically no polycyclic aromatic hydrocarbons. For the fixed-bed reactor, the synergistic effects mainly impacted on the product composition, rather than the % distribution of the products.

Formation Characteristics of PCDD/Fs in the Co-combustion and Pyrolysis Process of Coal and Sewage Sludge

ABSTRACT Co-combustion technology of coal and sewage sludge (SS) was encouraged and recommended in China. Previous studies most focused on its influence on combustion characteristics, migration characteristics of heavy metals in fly ash, and emission of conventional pollutants, etc., but less reported the formation characteristics of polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/Fs). To well reveal it, this study carried out five parallel experiments, including the pyrolysis of SS, the combustion of SS, the co-combustion of coal and SS with the proportion of 0%, 2.5% and 5%, respectively. The emission concentration of PCDD/Fs respectively increased from 0.42 ng g–1 (0.0022 ng I-TEQ g–1) to 0.54 ng g–1 (0.0030 ng I-TEQ g–1) and 1.70 ng g–1 (0.0305 ng I-TEQ g–1) with increasing blending proportion of SS. The dominant part was also changed from PCDF (0.32 ng g–1 in M-0%, 0.38 ng g–1 in M-2.5%) to PCDD (1.11 ng g–1 in M-5%). The formation concentration of PCDD/Fs in the combustion process of SS was about 0.34 ng g–1 (0.0019 ng I-TEQ g–1). In the pyrolysis process of SS, the concentration of PCDD/Fs was 0.59 ng g–1 (0.0037 ng I-TEQ g–1). The de novo synthesis should be the major formation pathway of PCDD/Fs in the co-combustion process of coal and SS. On the basis of sufficient carbon sources, the PCA analysis revealed the chlorine source (Cl) and metal catalyst (Fe) should contribute a lot on the formation of PCDD/Fs. The results paved the way for further optimization on the operation of co-combustion of coal and SS and assist in controlling the PCDD/F emission from co-combustion process.

Pyrolysis of a typical low-rank coal: application and modification of the chemical percolation devolatilization model.

The chemical percolation devolatilization (CPD) model can simulate the formation of various products during the coal pyrolysis process and predict the products composition relatively accurately. In this study, the pyrolysis products of a typical low-rank coal were calculated using the CPD model, and several model improvements were proposed by combining the experimental results in a lab-scale pyrolysis system. The chemical structural parameters calculated from the Genetti correlations were verified by adjusting the initial fraction of char bridges (c0) from 0.098 to 0.25. A yield difference (Δftar) was defined in this paper to analyze the consumption of tar fragments in the model, and it was found that the deviations between experiments and calculations resulted from the weak influence of crosslinking. A modification expression was adopted to amplify the tar consumption: , which improved the accuracy of the model on the tar yield with errors of less than ±0.5 wt%. Furthermore, this paper also developed a correlation in an exponential form about gas composition, which attempted to extend the application of the CPD coalification reference mesh for the coal away from interpolation triangles. The improved model by the correlation predicted CH4, CO, and CO2 yields for this typical low-rank coal accurately in most cases. Compared with the original CPD model, the modified model showed better agreement with the experimental results and predicted 71.4% and 88.6% of the data points in this work within ±10% and ±20% errors, respectively.

Effect of temperature on Shenfu coal pyrolysis process related to its chemical structure transformation

Revealing the pyrolysis reaction pathway related to coal structure evolution under different temperatures is important for the industry to design reactors and process operations. In this study, all the pyrolysis products obtained under different pyrolysis temperatures were comprehensively analyzed by multiple techniques. The results showed that the aromatic nucleus were inclined to react with methyl radicals, forming char with abundant methyl substitution aromatic structure at low pyrolysis temperature. At medium pyrolysis temperature, dramatically condensation reaction occurred, resulting in the formation of aromatic protonated carbon and abundant polycyclic aromatic hydrocarbons (PAHs) containing benzenoid rings joined by a carbon‑carbon single bond remaining in char. The concentration of aliphatic hydrocarbons in light tar decreased dramatically and converted into light hydrocarbon gas compounds (especially H2 and CH4). At high pyrolysis temperature, severe carbonation of char led to the formation of abundant PAHs with reduced aliphatic side chain in light tar. Tar precursors preferred to form larger PAHs due to occurrence of drastic secondary reaction. The contents and diversity of oxygen−/nitrogen-containing heteroatom compounds in heavy tar were significantly reduced with the increase of temperature. Finally, the devolatilization mechanism responsible for the evolution of chemical structure of Shenfu coal pyrolyzed at elevated temperatures was proposed.

Process intensification on suspension pyrolysis of ultra-fine low-rank pulverized coal via conveyor bed on pilot scale: Distribution and characteristics of products

From the perspective of intensifying the pyrolysis process, suspension pyrolysis characteristics of ultra-fine low-rank coal via conveyor bed (1500 kg/h) were studied. The effects of coal particle size, pyrolysis temperature, and heating rates on the distribution of products were investigated. The relationship between the pyrolysis process and product quality, such as gas, tar, and char, was analyzed. The results showed that suspension pyrolysis enhanced the heat and mass transfer of the upgrading process. When the pyrolysis temperature was between 550 and 650 °C and coal particle size in the range of 0.075 ~ 0.105 mm, the yield of tar reached about 145% of the Gray-King tar yield. The analysis of group composition and four main components of tar showed that each fraction contained a certain amount of chain hydrocarbons or saturated hydrocarbons, which were mainly aromatic hydrocarbon compounds. The effective gas content from pyrolysis was H2 (19.32 vol%), CH4 (17.59 vol%), CO (12.53 vol%), and the low calorific value was about 900 kcal/Nm3. With the increase of pyrolysis temperature, the overall yield of pyrolysis gas increased, and the yields of H2 and CH4 increased linearly with temperature. The mass fraction of volatiles in char was less than 8%, while the mass content of fixed carbon was more than 80%. With the increase of pyrolysis temperature, the fixed carbon and ash content of the char increased, but the volatile matter decreased. This study provides a fundamental basis for the improvement of the pulverized coal pyrolysis process on large-scale installation.

Effect of density on physicochemical and thermal conversion characteristic of Naomaohu coal

Three coal samples with different density (d < 1.35, 1.35 < d < 1.40 and d > 1.40 g cm−3) which were separated using ZnCl2 specific gravity liquid from Naomaohu (NMH) coal were investigated to understand the difference in their physicochemical and thermal properties. Fourier transform infrared spectrometry (FTIR), Raman, X-ray diffraction (XRD), solid-state 13C Nuclear Magnetic Resonance (13C NMR) and scanning electron microscopy (SEM) methods were used to determine the physicochemical characteristics of the coal sample. In addition, a TG-FTIR analyzer was used to investigate the key thermal conversion characteristics and volatile emissions of the three coal samples. Typical volatile contents including CO2, CO, CH4, and Aromatic CC were analyzed. Results showed that the density has great effect on functional groups and crystalline structure on coal sample. Four distinct peaks are showed in DTG curves, indicating that four reaction stages, namely, drying, desorption, pyrolysis, and polycondensation, were involved in the pyrolysis process of NMH coal. The TG/DTG curves of the three densities indicate that the low-density coal assumes the highest weight loss rate at the pyrolysis stage and the trend becomes weaker at the polycondensation stage. Two obvious emission peaks vividly showed that light gases such as CO2, CO, and CH4 can be separated into two stages at the pyrolysis and polycondensation stage.

Molecular reaction dynamics simulation of pyrolysis mechanism of typical bituminous coal via ReaxFF

A reasonable and effective macromolecular model of bituminous coal was established. The molecular dynamics method based on reactive force field (ReaxFF) was used to simulate the pyrolysis process of typical bituminous coal in the range of 1400–2600 K. The distribution of products and evolution of intermediate radicals were analyzed. Calculation results showed that with increase of pyrolysis temperature, yield of char firstly increased and then decreased, while the trend in tar production was opposite. Yield of pyrolysis gas increased monotonously with increasing temperature. The pyrolysis of coal at low temperature mainly experienced primary reaction with formation of tar free radical fragments and small molecular gases. At high temperature, the secondary reaction of tar fragments was remarkable, and char with more content but less quantity and small molecular gas with more content and quantity were produced. The temperature turning point from the primary reaction to the second one was 2000 K. Under the high temperature pyrolysis conditions, C and H in coal gradually migrated into char and tar, while oxygen-containing functional groups were more active, resulting in migration of O to pyrolysis gases. In the secondary reaction stage, comparing chemical properties of the three elements C, H and O, O was the most active, H was the second, and C was the most stable. H2O was firstly released during pyrolysis. NH3 mainly came from secondary reactions during which H2S was consumed and converted into other products. Yield of H2 was the highest, and increased with increasing pyrolysis temperature. A large amount of H2 was generated in secondary reactions, which was mainly from collision of hydrogen radicals generated from pyrolysis and condensation of aromatic structures. Based on ReaxFF simulation results, the weightless activation energy of coal pyrolysis was 39.45 kJ/mol.

Strength degradation mechanism of iron coke prepared by mixed coal and Fe2O3

Iron coke, as a new type of blast furnace burden is helpful for energy saving, emission reduction and green production of iron making. This study aims to investigate the strength degradation mechanism of iron coke prepared by mixed coal and Fe2O3 to provide a theoretical direction to improve its strength. Coking and pyrolysis experiments of mixed coal and Fe2O3 were carried out between 400 and 500 ℃ temperature. Gieseler plastometer and derivative thermogravimetric (DTG) showed that added Fe2O3 inhibited the thermoplasticity and pyrolysis process of mixed coal during coking. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) results showed that added Fe2O3 decreased the aromaticity and average stacking height, but increased the interlayer spacing of crystallite, aliphatic chain length and hydrocarbon-generating potential of mixed coal during coking. Further, gas chromatography-mass spectrometer (GCMS) analysis suggested that the added Fe2O3 inhibited the cleavage of CalO, CalS, CalN, CalCar and CalCal bonds, reduced the generation of ethylbenzene, o-xylene and unbranched alkanes with carbon atoms in 24–26, thus decreased the amount of fluid phase generated in coking and ultimately degraded the strength of iron coke.

Multi-scale Cleaner Analysis of Chemical Looping Gasification Coupled Coal Pyrolysis Process

Coal is one of combustion fuel sources that occupies an important position in the world energy resource structure. Coal pyrolysis is a very complex process involving myriad coupled reaction pathways. An in-depth mechanism investigation of coal pyrolysis will improve the efficient and cleaner coal conversion and utilisation. In this paper, a novel Coal Pyrolysis (CP) - Chemical Looping Gasification (CLG) integration strategy is proposed with the aid of multi-scale analysis to realise cleaner production of coal chemical products. First, ReaxFF molecular dynamics (MD) simulation is used to model the chemical reactions in the pyrolysis process to obtain the optimal parameters with the highest carbon conversion rate. The pyrolysis temperature should be set below 900 °C through mechanism analysis. Second, the CP-CLG system is simulated and analysed with Aspen Plus software to obtain high purity synthesis gas for synthesising cleaner coal chemical products. The mass flow of synthesis gas can reach 616.5 kg/h. Finally, one control scheme of multiple reactors is proposed to verify the stability of synthesis gas production with Aspen Dynamics software. The quality of synthesis gas is stable under different 10 % disturbances.