Rapid Pyrolysis Of Coal Research Articles

Investigating pyrolysis characteristics of Shengdong coal through Py-GC/MS

Abstract Shengdong coal was single-step and multi-step pyrolyzed by pyrolysis-gas chromatography/mass spectrometry. In the single-step pyrolysis process, Mono-ring aromatics contents reach a maximum value at 800°C, while phenolic contents are significantly reduced, which might be attributed to the dehydroxylation of phenolics. Naphthalene content also reaches a maximum value at 800°C in the single-step pyrolysis process; however, naphthalene was not detected in the multi-step pyrolysis process. So naphthalene might come from the ring-opening of multi-ring aromatics or the cyclization of mono-ring aromatics in the single-step pyrolysis process. Only phenol and o-cresol were detected, but no p-cresol in the multi-step pyrolysis process; however, p-cresol content reaches a maximum value at 800°C, meanwhile, phenol content was decreased and o-cresol was disappeared in the single-step pyrolysis process, which suggests that p-cresol may be derived from isomerization of o-cresol or alkylation of phenol. It provides an idea for strengthening more basic research related to the rapid pyrolysis of coal.

Release characteristics of AAEMs and physicochemical structural evolution of char during rapid coal pyrolysis

Rapid pyrolysis experiment of Zhundong coal was conducted in a high-frequency furnace to investigate release characteristics of alkali and alkaline earth metals (AAEMs) and its correlation with changes of physical and chemical properties of char. Residence time and atmosphere during pyrolysis were important process parameters that affected the migration characteristics of AAEMs and physicochemical structural evolution of char. Experimental results show that the release of AAEMs in coal char increases over time. The maximum release rate of Na, Mg and Ca is 61.05%, 64.47%, and 44.01%, respectively. Promoting effect of CO2 on release of Na mainly occurs in the initial stage of rapid pyrolysis, nevertheless the promoting effect on release of Mg and Ca mainly is in the middle and late stage. CO2 accelerates release of AAEMs by promoting release of volatiles, facilitating decomposition of oxygen-containing functional groups and aliphatic functional groups, and promoting formation of cracks on surface of coal char.

Oxidation characteristics of soot in different entrained flow gasification processes

The morphological structure of six samples including the rapid pyrolysis soot of solid fuels (coal, biomass), the soot from non-catalytic partial oxidation(NCPOX) of natural gas in a laboratory pilot plant and an industrial plant, the commercial carbon black in natural gas furnace/coal tar furnace, were characterized by using a transmission electron microscope. Based on atmospheric thermogravimetric analyzer, the non-isothermal method (50–800 °C) was adopted to study the ignition point and the oxidation reaction rate of soot, and the oxidation reaction kinetic parameters of soot was obtained. Studies showed that the physical and chemical properties of various soot were quite different. The soot from the rapid pyrolysis of coal and biomass presented a higher sphericity and a larger particle size. The Lab-NCPOX-soot was formed at a lower temperature which caused the particle being wrapped by a carbon capsule. The Ind-NCPOX-soothad a hollow structure and a small particle size. The reactivity of the Lab-NCPOX-soot is close to that of the Ind-NCPOX-soot, which is 3.1 times that of the commercial natural gas furnace carbon black and 3.2 times that of the commercial coal tar furnace carbon black; the reactivity of NCPOX-soot is 9.0 times of the rapid pyrolysis soot of coal, and 26.6 times of the rapid pyrolysis soot of biomass. The activation energy of 2 kinds of NCPOX-soot and 2 kinds of commercial carbon blacks present staged forms with increasing temperature. The activation energy of the 2 rapid pyrolysis soot was basically unchanged with increasing the temperature.

Catalytic upgrading of coal volatiles with Fe2O3 and hematite by TG-FTIR and Py-GC/MS

Pyrolysis plays a critical role in clean coal technology and energy conversion and is also conducive to the early peaking of carbon dioxide emissions. Light tar production from traditional coal pyrolysis using various iron-based catalysts for chemicals and fuel oil has gained attention recently. In this study, waste hematite was initially used for catalytic upgrading of rapid coal pyrolysis. Subsequently, thermogravimetric analyzer coupled with Fourier-transform infrared spectrometry (TG-FTIR) and pyrolysis gas chromatography mass spectrometry (Py-GC/MS) were utilized to compare the performances, kinetic parameters, and volatile composition of coal pyrolysis with Fe2O3 and hematite. The results showed that the maximum weight loss rate of coal pyrolysis increased by 1.55 %/min and 0.32 %/min with the addition of Fe2O3 and hematite, respectively, indicating that the pyrolysis reaction became more rapid and intense with iron-based catalysts. Both Kissinger Akahira Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods revealed that the catalysts reduced the apparent activation energy of coal pyrolysis. Online FTIR showed the emission temperature and content of coal volatiles, suggesting iron-based catalysts were conducive to the cracking of oxygen-containing functional groups and the directional cracking of groups to CO. Py-GC/MS illustrated the presence of Fe2O3 and hematite could reduce polycyclic aromatic hydrocarbons and oxygenates. In addition, a mechanism for rapid coal pyrolysis with iron-based catalysts was proposed to provide fundamental information for the transformation of aliphatic hydrocarbons, oxygenates, and polycyclic aromatic hydrocarbons. It is believed that iron-based catalysts have great potential for future research on upgrading coal volatiles and tar.

Process modelling of two-stage entrained-bed gasification composed of rapid pyrolysis and gasification processes

A novel two-stage entrained-bed gasification system composed of the rapid pyrolysis of pulverized coal and the gasification of char is proposed to obtain high-quality synthetic gas with low tar content and high methane content. A new framework containing a modified multi-step kinetic pyrolysis model and a non-linear programming (NLP) process is developed to simulate the rapid pyrolysis process of pulverized coal. The method can be used to simulate the volatile composition, which includes only the high-weight hydrocarbons/distillable liquids (benzene, toluene, xylene, naphthalene, pyrene, phenol) based on the proximate and ultimate analysis data of coal. The framework for coal rapid pyrolysis and the simulation of the two-stage entrained-bed gasification are validated by experimental data and semi-industrial data, respectively. This paper analyses the effects of the final pyrolysis temperature, the gas residence time, and the steam/coal ratio on the performance of the two-stage entrained-bed gasification system. The results indicate that by adjusting the gas residence time to 15.5 s at the final pyrolysis temperature of 1000 °C, the tar yield can be reduced to less than 500 mg/Nm3, the molar fraction of methane in the syngas can be approximately 5.84%, the exit temperature can be approximately 943 °C, and the higher heating value (HHV) of syngas and the cold gas efficiency (CGE) will be 11.41 MJ/(Nm3) and 91.23%, respectively.

Rapid Pyrolysis of Pulverized Coal for the Preparation of Nanostructured Powder Activated Coke

By rapid pyrolysis of pulverized coal in oxygen and steam atmosphere, powder activated coke (PAC) nanostructured carbon material was derived by one step. Then, nitrogen adsorption measurement, scanning electric measurement (SEM) and Fourier transform infrared spectroscopy (FTIR) test were conducted to analyse the detail characteristic of the obtained PACs. The results showed that the one-step pulverized coal rapid pyrolysis process was an effective method for the production of PAC powders. The mixture of oxygen and steam as the activating agent was essential during the pyrolysis progress. Oxygen act as the most important fast activating agent for the pore formation, while steam activation protected the material matrix and weakly affected pore growth. The composition and concentration of oxygen and steam had a great effect on pore structure, surface micromorphology and functional groups of PACs. The mixed oxygen and steam atmosphere exhibited a tightly tailored micropore structure. By further optimizing activating oxygen and steam composition, the PAC products could have considerable pore structures, respectable surface morphology and functional groups.

Effect of CO2 on the characteristics of soot derived from coal rapid pyrolysis

The present work aims to investigate the effects of a CO2-rich atmosphere on the characteristics of coal-derived soot. The rapid pyrolysis of Shenfu bituminous coal was conducted in a Drop tube furnace (DTF) in N2 and CO2 atmospheres with a wall temperature of 1073–1473 K and residence time below 700 ms. The yields and microstructure characteristics of N2-soot and CO2-soot were analysed by using a series of techniques (elemental analysis, HRTEM, Raman, XRD, FT-IR and thermogravimetry techniques). CO2 enhanced the soot formation and proceeded the dehydrogenation. CO2 improved the order of internal carbon lattices, enhanced the lateral extension of carbon nanostructures, decreased the interplanar spacing of the graphene layers and also promoted the stack of polyaromatic layers. The variations of the SOLO, DUO, TRIO and QUARTO structures were also analysed, and the contribution of CO2 was found to reduce the defects of the basic structure units (BSU). The defects of soot were an important indication of the initial gasification reactivity. Overall, CO2-soot was more mature and low active than N2-soot.

Effects of CO2 on coal rapid pyrolysis behavior and chemical structure evolution

Rapid pyrolysis of Shenfu bituminous coal was conducted with a wall temperature 1073–1473K and residence time 0–750ms in both CO2 and N2 atmospheres to study the pyrolysis mechanism in CO2 atmosphere. The interest was focused on mass loss, gas yield, element content of chars and a series of chemical structure parameters (CH2/CH3, Har/H, fa and (R/C)u) obtained by FT-IR analyses. The results show that varied impacts dominated on pyrolysis at different temperatures in CO2 atmosphere. Mass loss decreased at 1073K but increased at 1273 and 1473K. Both heterogeneous reaction of CO2 with char and homogeneous reactions of CO2 with volatile occurred during pyrolysis in CO2 atmosphere. The combined effect of enhanced polycondensation of aromatic rings and C-CO2 reaction has been found to increase the mass loss of char. More H-containing free radicals generated during polycondensation, which consequenctly increase combination possibility with other radical fragments to inhibit the cross-linking reaction.

Characteristics of Soot from Rapid Pyrolysis of Coal and Petroleum Coke

Rapid pyrolysis of several types of solid carbonaceous materials [lignite, bituminous coal, and petroleum coke (petcoke)] was conducted in a drop-tube furnace at 1300 °C under atmospheric pressure. Soot properties, including yield, particle size, microstructure, and reactivity, were studied, with focus on the key factors that influence soot gasification reactivity. Results show that the soot yield of bituminous coal is up to 15–20 wt %, which is nearly half of the volatile matter, while those of lignite and petcokes are merely several percentages of the raw material. The reactivity of soot is lower than that of coal char and higher than that of petcoke char. Among several soots, lignite soot is most active, while petcoke soot displays the lowest reactivity. The catalytic effect of the mineral content is excluded because no alkali metal and alkaline earth metal were detected in soot samples. The reactivity difference is independent of the particle size but closely related to the microstructure. The soot pa...

Effects of CO2 on the fuel nitrogen conversion during coal rapid pyrolysis

To investigate the fuel nitrogen conversion during rapid pyrolysis, the tests with Genesee bituminous coal and Petroleum coke were accomplished under N2 and CO2 atmosphere in a fixed bed reactor equipped with a Fourier transform infrared analyzer. The samples were analyzed by an X-ray photoelectron spectroscopy (XPS) to determine the fuel nitrogen conversion mechanism during rapid pyrolysis. Furthermore, the fuel nitrogen distribution in pyrolysis products were also calculated based on the testing results. It was found that higher temperature can enhance the conversion of fuel nitrogen in the char to both HCN and NH3. The effects of CO2 on coal pyrolysis depended heavily on the temperature of rapid pyrolysis. There were more quaternary nitrogen (N-Q) consumed during rapid pyrolysis in CO2 atmosphere than that in N2 atmosphere, causing more NH3 formation in CO2 atmosphere. Higher temperature can restrain the formation of N2 as a result of the generation of more H free radicals. Besides, NO was also one of the major products during coal rapid pyrolysis.

Coal rapid pyrolysis in a transport bed under steam-containing syngas atmosphere relevant to the integrated fluidized bed gasification

An integrated fluidized bed (IFB) consisting of an upper transport bed section and a bottom fluidized bed section was adopted to investigate the transport bed coal pyrolysis by varying its reaction temperature and reaction atmosphere adjusted to simulate steam-containing syngas produced by the bottom fluidized bed char gasification. Steam and syngas, in comparison with N2, as the reaction atmosphere little affected the tar yield below 600°C but significantly decreased it for the former and increased it for the latter at rather higher temperatures. The presence of H2 in the syngas increased tar yield significantly because it could suppress polymerization and condensation reactions through providing H as radical stabilizer and hydrogenation agent. In the steam-containing syngas atmosphere, the tar yield obtained from transport bed rapid pyrolysis increased rapidly with raising temperature to a peak value of 10.5wt.% (daf) at 600°C, about 1.1wt.% higher than the Gray–King assay yield, and then decreased due to the excessive secondary reactions. Analyzing tar composition further showed that steam-containing syngas combined their respective advantages that syngas improved the yields of both light and heavy tars while steam reduced the heavy tar yield, especially at temperatures above 600°C. The steam-containing syngas atmosphere also promoted CH4 production in comparison with syngas atmosphere below 700°C.

Evolution of NOx Precursors during Rapid Pyrolysis of Coals in CO2 Atmosphere

To understand the effect of CO2 on fuel N evolution during rapid coal pyrolysis, pyrolysis/gasification of EH lignite and HL bituminous coal were carried out in a suspension-bed reactor under N2 or CO2 atmosphere. The chemical and physical structures of the chars were measured by Fourier transform infrared spectrometry and X-ray diffractometry. The results show that higher temperature is favorable for the evolution of HCN and NH3. Thermally stable quaternary N is believed to be the important intermediate for the formation of NH3. The presence of CO2 can promote HCN and NH3 generation through the creation of H radicals and the cracking of N-containing groups. However, the HCN yields of HL coal pyrolyzed in CO2 at 700 and 800 °C are lower than that in N2, and a similar result was obtained for EH coal at 1000 °C, which are caused by the blocking effect of CO2 and the reaction of HCN with CO2, respectively. Structural analyses of the chars show that in the initial stage of coal pyrolysis/gasification, CO2 can...

Study on Carbocoal as Microwave Absorber in Microwave Field

The present paper decribed the effects of carbocoal on temperature rising characteristic during coal pyrolysis at different temperature in microwave field. Different mixture rate of carbocoal with coal and different final temperature on coal pyrolysis tempereature rising characteristics were studied in the work. The results indicate: Coal is a poorly microwave absorbing material. Because carbocoal can be fast heated in microwave field, so it can be used as additive for coal pyrolysis. Carbocoal otained from different pyrolysis temperature have different heating rate, along with the increase of carbocoal pyrolysis temperature, carbocoal heating rate increases in microwave field. Using carbocoal as microwave absorbent for coal rapid pyrolysis in microwave field is feasible.

Release of Nitrogen Species during Rapid Pyrolysis of Model Coals

To gain an in-depth insight into the release of nitrogen species during rapid pyrolysis of coals, two model coals containing pyrrolic or pyridinic nitrogen are synthesized, and rapid pyrolysis of model coals is performed in an entrained flow system between 800 and 1300 °C. The effects of pyrolysis temperature, minerals, particle size, and the interaction between the two forms of nitrogen are discussed. The results show that a moderate amount of HCN and small amounts of NO and NO2 rather than NH3 are formed. As the temperature rises, the HCN release increases first and then decreases, and exhibits very similar trends for the two forms of nitrogen. Because of the better thermal stability of pyridinic nitrogen, the releases of both HCN and NOx are lower for pyridinic nitrogen than for pyrrolic nitrogen. When the two forms of nitrogen are pyrolyzed together, the interaction between the nitrogen species released makes the HCN release decrease and approach the HCN release from pyridinic nitrogen alone. For pyrrolic nitrogen, Fe addition suppresses the HCN release at all temperatures and Na addition promotes the HCN release obviously at 1000 °C or above, whereas Ca addition increases the HCN release with increasing temperature first and then decreases. For pyridinic nitrogen, all the metal additions suppress the HCN release and Fe has the strongest catalytic effect. As the catalyst content increases, the HCN release decreases drastically. The HCN release from pyridinic nitrogen increases slightly with increasing particle size at 800 or 1000 °C. When the temperature achieves 1200 or 1300 °C, the particle size dependence of HCN release is not observed.

The Effect of Additive on Temperature Rising Characteristics during Coal Pyrolysis in Microwave Field

The pesent paper decribed the effects of additive on temperature rising characteristic during coal pyrolysis at different temperature in microwave field. Different mixture rate of carboncoal with coal and different final temperature on coal pyrolysis tempereature rising characteristics were studied in the work. The results indicate: Coal is a poorly microwave absorbing material, and its pyrolysis in microwave field need to add a certain amount of microwave absorbent for higher heating rate; Because carbocoal can be fast heated in microwave field, so it can be used as additive for coal pyrolysis. Carbocoal otained from different pyrolysis temperature have different heating rate, along with the increase of carbocoal pyrolysis temperature, carbocoal heating rate increases in microwave field. Using charcoal as microwave absorbent for coal rapid pyrolysis in microwave field is feasible.

Analysis of particle heating and devolatilization during rapid coal pyrolysis in a thermal plasma reactor

Using thermal plasma for coal pyrolysis to acetylene provides a direct route to make chemicals from coal resources, where the temperature field in the reactor plays a dominant role in the performance of coal devolatilization. A comprehensive computational fluid dynamics with discrete phase model (CFD-DPM) has been established to describe the rapid coal pyrolysis process in a reactor under ultra-high temperatures. The simulations based on this model helped to understand the complex gas–particle reaction behavior in the millisecond process of coal pyrolysis. The particle-scale physics such as the heat conduction inside solid materials, diffusion of released volatile gases, coal devolatilization, and tar cracking reactions were incorporated. The improved chemical percolation devolatilization (CPD) model was applied to describe the devolatilization behavior of rapidly heated coal based on the physical and chemical transformations of the coal structure. This model was proved to be qualified for describing the complex gas–particle reaction behavior with milliseconds residence time by the operation experience of a 5-MW plasma reactor. Then the simulations revealed the fact that the particle heating and devolatilization are strongly affected by the grade of the temperature and the residence time of coal particles in the high temperature zone(s). Highly concentrated energy input in the reactor may not intensify the reactor performance. As a potential solution, multi-stage heating design would provide more flexibilities to effectively adjust the devolatilization performances under the same energy input.

Mixing behaviors of cold–hot particles in the downer of a triple-bed combined circulating fluidized bed

In a triple-bed combined circulating fluidized bed (TBCFB) gasifier, consisting of a downer for rapid pyrolysis of coal, a bubbling fluidized bed for gasification of char, and a riser for combustion of unreacted char to produce heat, it is necessary to transfer the heat carried by inert particles from the riser rapidly and effectively to coal particles injected into the downer. In order to evaluate the quality of mixing between injected coal from the inlet of the downer and circulating inert solids in the TBCFB, hot sand particles which are substitute of coal were injected into the downer through two kinds of injection nozzle arrangements, i.e., normal and tangential arrangements. The hot sand particles were mixed with the cold sand particles circulated in a large-scale TBCFB, and the temperatures of the sand were measured using thermocouples below the injection nozzle. A mixing index was suggested to quantify the degree of mixing. Simultaneously, Eulerian–Eulerian method was adopted to simulate the hydrodynamics of hot sand, cold sand and air, as well as the heat transfer among them. The mixing index was also calculated based on the temperature distributions, and was compared with the experimental data. In experiment, it was found that the tangential arrangement gave better mixing just below the injection nozzle than the normal arrangement. This may be due to the fact that the hot sand branches into two flows at the inlet in the tangential arrangement. However, uniform temperature distribution was observed along the downer in the normal arrangement and gave better mixing than in the tangential arrangement. The simulation result agreed well with the experimental observations in the normal arrangement just below the injection nozzle. Tangential arrangement gave better mixing indices as mixing between the hot sand and cold sand proceeded.

Nitrogen conversion during rapid pyrolysis of coal and petroleum coke in a high-frequency furnace

Rapid pyrolysis of three typical Chinese coals, lignite from Inner Mongolia, bituminous from Shenfu coalfield, and anthracite from Guizhou, as well as a petroleum coke were carried out in a drop-style high-frequency furnace. The reactor was induction coil heated and had a very small high-temperature zone, which could restrain secondary conversions of nitrogen products. The effects of temperature and coal rank on conversions of fuel-N to primary nitrogen products (char-N, HCN–N, NH 3–N and (tar + N 2)–N) have been investigated. The results showed that, the increasing temperature reduced the yields of char-N and promoted the conversion of fuel-N to N 2. Char-N yields increased, while volatile-N yields decreased as the coal rank increased. In most of the conditions, NH 3–N yields were higher than HCN–N yields during rapid pyrolysis of coal. In the case of petroleum coke, NH 3–N yields increased gradually with the increasing temperature, but no HCN was detected. We argue that NH 3–N can be formed directly through the primary pyrolysis without secondary reactions. Although volatile-N yields of lignite were higher than those of bituminous, yields of (HCN + NH 3)–N in volatile-N of lignite were lower than those of bituminous. While the (HCN + NH 3)–N yields of anthracite were the lowest of the three coals. Both of the (HCN + NH 3)–N yields and (HCN + NH 3)–N proportions in volatile-N of petroleum coke were lower than the three coals.

06/02096 Two-stage desulfurization process for hot gas ultra cleanup in IGCC: Park, N. -K. et al. Fuel, 2006, 85, (2), 227–234.

The formation and fate of polycyclic aromatic hydrocarbons (PAH) during the pyrolysis and fuel-rich combustion of primary tar generated under rapid heating conditions have been studied. Experiments were performed using a quartz two-stage reactor consisting of a fluidized-bed reactor coupled to a tubular-flow reactor. Primary tar was produced in the fluidized-bed reactor by rapid coal pyrolysis at 600°C. The freshly generated tar was subsequently reacted in the tubular-flow reactor at 1000°C under varying oxygen concentrations covering the range from pyrolysis to stoichiometric oxidation. PAH species present in the tars recovered from the tubular-flow reactor were analyzed by high-performance liquid chromatography (HPLC). Twenty-seven PAH species, varying from 2-ring to 9-ring structures, were identified, including benzenoid PAH, fluoranthene benzologues and indene benzologues. The majority of PAH species identified from pyrolysis were also identified in the samples collected from oxidation experiments. However, three products, 9-fluorenone, cyclopenta[def]phenanthrene and indeno[1,2,3-cd]fluoranthene, were produced only during oxidizing conditions. The addition of a small amount of oxygen brought about measurable increases in the yields of the indene benzologues and 9-fluorenone, but the yields of all PAH products decreased at high oxygen concentrations, in accordance with their destruction by oxidation. Possible formation and destruction mechanisms of PAH under fuel-rich conditions have been discussed.

Application of TG–FTIR to the determination of organic oxygen and its speciation in the Argonne premium coal samples

During rapid pyrolysis of coal, TG–FTIR (thermogravimetry – Fourier transform infrared) technique can be effectively used to simultaneously detect and measure the three main O-containing gases, namely H 2O, CO and CO 2. Their sum corresponds to the quantitative amount of oxygen in the coal and is, in general, inherently more accurate than the ‘by-difference’ values. In this paper, we first attempt to relate the ‘by-difference’ values for %O reported for the Argonne premium coal samples (lignite to bituminous rank) (Argonne Users Handbook) to those determined from a TG–FTIR examination of the pyrolysis gases evolved. Another objective of the work is to relate the pyrolysis gases (H 2O, CO and CO 2) evolved to oxygen-containing functional groups found in coals as well as the evolution of these functional groups as a function of rank. Correlations are also developed between the TG–FTIR oxygen values and other parameters determined for the Argonne Premium Coals. In particular, comparisons of our results using TG–FTIR with analyses carried out by other workers on functional group analysis of acidic groups are considered.