Coke Combustion Research Articles

Multithreaded Acceleration of 3D Mathematical Model for Ore Sintering

One of the widely used methods to accelerate a numerical solver is implementation of multithreading. The problem of thread allocation on-demand at runtime is latency, caused by periodical instantiation of threads. The article is devoted to parallelization of solver for 3D mathematical model of ore sintering, based on software threads reusing them during computation. Computational domain is equally shared among available threads. Each thread writes only to own data partition. A looped barrier is proposed for guaranteed synchronization of all threads after iteration. The method allows scaling performance without recompilation of the solver by using similar CPU with more cores. Measurement of solver performance with 220 nodes using different thread count confirms scalability around 95% for double and single precision arithmetics. Presented pictures of perspective view with three slices of temperature field show influence of heat loss from pallets walls. A cross section of temperature field in layer after 16 minutes of sintering is calculated with appearance of two high-temperature regions inside. Comparison of temperature field with literature data gives good correspondence. The computer model takes into account important chemical reactions, such as, coke burning, carbonate dissolution, water vaporization, as well as mass-heat transfer inside the sinter layer and can be used in metallurgical plants to increase effectiveness of sintering.

CFD-DEM modelling of raceway dynamics and coke combustion in an ironmaking blast furnace

In this study, a CFD-DEM reacting model featuring thermochemical sub-models is developed for describing gas–solid reacting flow related to raceway dynamics and coke combustion in an ironmaking blast furnace (BF). The simulation results show that a ring-type zone is formed around the cavity where the coke combustion and gasification occur with a large amount of heat released, leading to intense momentum and thermochemical exchanges in this zone. Heat fluxes contributed from radiation and reaction dominate total heat transfer during the coke combustion, while conductive heat transfer is insignificant. Then, the impacts of key operating parameters on raceway evolution are quantified. The simulation results indicate increasing the blast gas velocity from 210 m/s to 230 m/s and oxygen mass fraction from 0.17 to 0.27, the cavity depth is increased by 42.3% and 20.8%, respectively; lower inlet velocity, higher bed temperature, higher oxygen mass fraction leads to more CO production and the resulting better BF performance.

A Model of Catalytic Cracking: Product Distribution and Catalyst Deactivation Depending on Saturates, Aromatics and Resins Content in Feed

The problems of catalyst deactivation and optimization of the mixed feedstock become more relevant when the residues are involved as a catalytic cracking feedstock. Through numerical and experimental studies of catalytic cracking, we optimized the composition of the mixed feedstock in order to minimize the catalyst deactivation by coke. A pure vacuum gasoil increases the yields of the wet gas and the gasoline (56.1 and 24.9 wt%). An increase in the ratio of residues up to 50% reduces the gasoline yield due to the catalyst deactivation by 19.9%. However, this provides a rise in the RON of gasoline and the light gasoil yield by 1.9 units and 1.7 wt% Moreover, the ratio of residue may be less than 50%, since the conversion is limited by the regenerator coke burning ability.

Numerical modelling of a three-zone combustion for heavy fuel oil in inert porous media reactor

Numerical model for heavy fuel oil and air mixtures combustion is presented to simulate the behavior of the fuel in an inert porous medium reactor for hydrogen production. Three-zone combustion of oil and petroleum cokes separated by temperature ranges starting from ambient temperature to 560 K, from 560 K to 673 K, and above 673 K, is presented. Hydrogen production is achieved using water gas shift equilibrium reaction on the combustion products at different temperatures. Results show a high enthalpy contribution due to coke combustion formed in the low temperature oxidation reaction, being the most important reaction in relation to its zone size. Simulations increasing filtration velocity (from 0.05 to 0.9 m/s) has a favorable effect on the maximum temperature and the combustion front velocity. The effect of the simplified combustion model lowers computational time, with acceptable results for temperature as well as hydrogen production in contrast to laboratory tests and other software simulation such as COMSOL Multiphysics.

Formation and Reduction of NO from the Combustion of the Fuels Used in the Sintering Process of Iron Ore in the Presence of Additives

Iron and steel companies account for more than 10% of global emissions of NO. The iron ore sintering process represents more than 40% of the total emission of NO. At present, there is no economical and effective method of inhibiting NO emissions from sintering flue gas. Therefore, controlling the conditions of fuel combustion is highly required for the reduction of NO. The current research investigated the effects of adding different materials to anthracite coal and coke on the formation of NO. The addition of CaO and FeO decreased the conversion of nitrogen to NO during coke combustion. CaO was found to play a significant role in both the formation and reduction of NO. However, its was less effective in the case of coke, which suggested replacing anthracite coal with coke in the sintering process to decrease NO emission. Two mixing procedures of fuel and BOF slag were adopted with increasing BOF slag. NO was reduced in the combustion of fuels prepared by both uniform distribution and coating using BOF slag. In the uniform distributed sample, the highest addition of BOF slag (20 wt%) provided the highest NO reduction. In BOF slag-coating fuel, the slightest addition of BOF slag (5 wt%) provided the highest reduction of NO. The difference in each mixing procedure's combustion characteristics is the key to the proposed reduction mechanism of NO. As the amount of BOF slag increased in uniform distribution, more catalysts were available to reduce the NO formed. In the coated sample, two factors were considered: temperature and additional amount. With increasing temperature, the BOF slag started to melt and exposed the fuel surface to react with O2, resulting in a higher formation of NO. Based on that, 1000 °C was defined to be a suitable temperature for the coated sample. Besides, CaO and iron oxides work as catalysts for the formation of NO at 1000 °C; minor addition of BOF slag is advantageous. The addition of BOF slag to fuel was done by two different mixing procedures; uniform distribution and coated fuel. Three additional amounts of BOF slag were used; 5, 10, and 20 wt%. Both mixing methods decreased the conversion of nitrogen to NO (XNO) above 1000 °C when compared to the fuel baseline. In the case of a uniformly distributed sample, the highest additional amount (20 wt%) promoted the highest reduction ratio, while in the coated sample, the lowest (5 wt%). The diagram expressed the XNO for the different layouts combusted at 1000 °C.

Thermal and kinetic analyzing of pyrolysis and combustion of self-heating biomass particles

As a renewable fuel, the application of biomass fuel gets more and more attention. Fire and explosion are the main safety problems in the biomass fuel storage process. The characteristic parameters and kinetic analysis of pyrolysis and combustion are significant to guide the safe storage of biomass fuel. In this work, the thermogravimetric analysis (TGA) was used to obtain the pyrolysis and combustion characteristics of corn straw powder, poplar wood chip and rice husk in nitrogen and air, respectively. The Thermogravimetry-Differential Thermogravimetric (TG-DTG) profile shows that the pyrolysis process of these biomass includes three stages of drying, pyrolysis and carbonization, while the combustion process includes three stages of drying, devolatilization and coke combustion. The main reaction stage of biomass pyrolysis and combustion are roughly between 170∼400 °C and 180∼530 °C, respectively. With the increase of the heating rate, TG and DTG profiles shifts to the high temperature side. Furthermore, the kinetic analysis was performed by using Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), Friedman, and Coats-Redfern (CR) methods, based on the thermogravimetric experimental data. The activation energy of biomass pyrolysis is shown to be between 70∼100 kJ/mol. For the activation energy of biomass combustion, the calculated value from isoconversional methods is between 140∼180 kJ/mol. The calculated value from CR method is between 80∼150 kJ/mol, and the activation energy of the coke combustion stage is greater than that of the devolatilization stage. Finally, the auto-ignition experiment of biomass particles was designed and conducted, indicating that the corn straw powder is more prone to spontaneous combustion, followed by rice husk and poplar wood chip, which corresponds to the results of activation energy. And the fire hazard of the biomass particles was analyzed according to the characteristic parameters. This work provides fundamental data to promote the development of storage techniques and facilitate the safe production of biomass particles.

Catalytic combustion behaviors of petroleum coke with hematite catalyst in a micro fluidized bed thermogravimetric analysis

Both conventional TGA and fluidized bed have some inherent limitations in the accurate measurement of gas–solid reaction. To characterize the gas–solid process under the fluidization state, a micro fluidized bed thermogravimetric analysis (MFB-TGA) was developed based on the real-time measurement with precision of 0.1 mg mass, 0.1°C temperature, and 0.01 kPa pressure. In this study, we preliminarily applied the MFB-TGA in evaluating catalytic combustion of petroleum coke with respect to deducing Fe2O3 catalytic mechanism, lattice oxygen migration pathway, and apparent combustion kinetics. The measurement stability of MFB-TGA was impacted by various factors, such as inhomogeneous temperature distribution and slight gas disturbance. Even char combustion heat could destabilize the weight signal by inducing vigorous particle collisions. The lightweight design and several structural optimizations were implemented to improve the MFB-TGA performance with the result of realizing smooth weight loss curves with 0.1 mg errors during the entire experiment. The experimental analysis revealed that the catalytic mechanism of hematite was identified as CO homogeneous catalysis. Hematite accelerated the char combustion rate by intensifying the driving force of bulk oxygen diffusion to the carbon surface. It served as an oxygen carrier, transferring lattice oxygen to oxidize carbon monoxide surrounding char particles. The apparent intrinsic kinetics of 33.73 kJ/mol was determined by the isothermal differential approach, which was lower than the published results measured in regular TGA. The zero-order model exhibited an excellent linear correlation in describing combustion behaviors based on a function fitting process. The MFB-TGA had the potential for extensive application by providing a reliable and straightforward method in characterizing gas–solid reactions under a fluidization state.

MP-PIC simulation of the effects of spent catalyst distribution and horizontal baffle in an industrial FCC regenerator. Part II: Effects on regenerator performance

Improving distribution uniformity of spent catalyst and adding horizontal baffles are two effective measures to improve the regeneration performance of a fluid catalytic cracking (FCC) unit. In this study, the effects of the spent catalyst distribution and horizontal baffle on the regeneration performance of an industrial coaxial compact FCC regenerator is simulated using an Eulerian-Lagrangian multi-phase particle in cell (MP-PIC) method with coupled hydrodynamic and coke-burning kinetics models. The coke-burning kinetics model developed by Arbel et al. (Ind Eng Chem Res, 1995, 34(4): 1228–1243) is used in the simulation. The MP-PIC simulations successfully predicted agreeable temperatures in the industrial regenerator. Serious afterburning in the freeboard was also successfully predicted. The effectiveness of the two intensification measures in enhancing the performance of an industrial FCC regenerator were proved, as indicated by the restrained afterburning in the freeboard, the increased coke burning efficiency, the lower coke content in the regenerated catalysts. Comparatively, adding a properly design horizontal baffle was proved to be more effective and should be a primary intensification measure used in industrial regenerators. A better spent catalyst distributor was suggested to be used to help the inserted horizontal baffles further improve the performance of the regenerator. By the simulation, more flow-reaction coupling mechanisms during the regeneration process are capable to be understood in more depth. The effectiveness of different intensification measures depends both on the resulted matching quality between the distributions of spent catalyst and oxygen in the main air, and the solids residence time distribution.

GENERALIZATION OF ALGORITHMIC MODELS FOR ORE SMELTING FURNACE OPERATION

This article establishes the relationship between the various processes that take place in the furnace. Specifically: - heating of the charge due to its electrical resistance; - introduction of additional heat due to coke burning; - heat transfer processes in the volume of the furnace bath; - formation of melt and slag due to chemical reactions. The complete algorithm of operation of the ore-thermal furnace is presented. By means of which it becomes possible to model in dynamics the technological process of obtaining ferroalloys. Literature sources are presented, where a more detailed mathematical description of modeling the ferroalloy smelting process is presented. The model is reconfigured when changing the parameters of the charge, depending on its component composition and temperature value. Such as: - electrical resistivity; - mass heat capacity; - specific density; - thermal conductivity. The described algorithmic model is universal for obtaining different brands of ferroalloys.

Efficient utilization of coal slime using anaerobic fermentation technology

In order to increase the utilization of coal slime, realize efficient utilization of resources and protect the environment, the feasibility of anaerobic fermentation technology employing coal slime was explored. The biodegradation of coal slimes and its influence on the utilization characteristics were analyzed using biogas production simulations, drying dehydration and thermogravimetric (TG) analysis. The results showed that the organic matter in various coal slimes could be converted to biomethane. In addition, the main methanogenic pathway was the reduction of CO2. Moreover, lower the metamorphic degree of coal slimes and higher the ash content, more conducive were they to the dehydration of coal slimes. After biodegradation, the temperatures of four coal slimes during the stages of release of moisture, volatile combustion, residual coke combustion and burnout advanced to varying degrees. Moreover, the combustion performance improved. The research results provided a novel idea for the efficient utilization of coal slime.

Seasonal variations, gas-PM2.5 partitioning and long-distance input of PM2.5-bound and gas-phase polycyclic aromatic hydrocarbons in Shanghai, China

The sources of PAHs in the urban atmosphere are particularly complex. This study focused on the local emissions and long-distance input of PAHs in the urban atmosphere, which will contribute to the reduction of air pollution. PM2.5-bound and gas-phase concentrations of 16 atmospheric polycyclic aromatic hydrocarbons (PAHs) were investigated during different seasons in Shanghai. The results showed that total concentration of 16 PAHs ranged from 3.19 to 22.26 ng m−3 and 6.13–53.97 ng m−3 in PM2.5 and gas phase, respectively. The seasonal variation is in the following orders: winter > autumn > spring > summer for PM2.5-bound PAHs and winter > summer > autumn > spring for gas-phase PAHs, respectively. The result of gas-particle partitioning between PM2.5 and gas phase indicated that PAHs were most easily adsorbed in particles in autumn. Concentrations of other major air pollutants (PM2.5, SO2, NO2, and CO) had a significant positive correlation with the PM2.5-phase PAHs suggesting both local and regional coal combustion emissions were one of the important sources. Positive Matrix Factorization (PMF) was applied to identify the sources of atmospheric PAHs. It was found that the PM2.5-bound PAHs in Shanghai were mainly from coke and coal combustion (38.71%), traffic emission (23.55%) and biomass combustion (20.98%). However, the sources of gas-phase PAHs were biomass combustion/petroleum combustion and leakage (45.96%), natural gas combustion (29.98%), coke and coal combustion (24.06%). Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLT) showed that Shanghai was more susceptible to atmospheric pollutants from the north of China in spring and winter. The results of Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) indicated that gas-phase PAHs in Shanghai were greatly affected by long-distance input, while the potential source area of PM2.5-bound PAHs mainly distributed in the local and surrounding industrial areas of Shanghai.

Modelling the effect of sinter machine speed on bed temperature and coke combustion characteristics in iron ore sintering process

ABSTRACT In the present study, the influence of industrial sinter machine speed on the temperature distribution of the bed is evaluated using a one-dimensional transient mathematical model. The model is developed considering the law of conservation of mass, momentum, and energy of solid and gas phases. The prediction of bed temperature from the model is compared with the measured lab scale pot test and the exit gas temperature of an industrial sinter machine wind boxes shows a reliable agreement. The effect of machine speed on the temperature of the bed is quantified using Maximum Temperature, and the coke combustion characteristics are expressed in terms of Duration Time of Coke Combustion and Combustion Zone Thickness. Eventually, the Melting Zone Thickness and melt fraction of the bed is evaluated. This model result demonstrates that the increasing industrial sinter machine speed significantly affects the temperature distribution of the top layer of the sinter bed.

Coke deactivation and regeneration of HZSM-5 zeolite catalysts in the oligomerization of 1-butene

The deactivation phenomenon of HZSM-5 catalysts (SiO2/Al2O3 ratio = 30–280) in the 1-butene oligomerization has been studied. Experiments were performed in a fixed-bed reactor at 175−325 °C; 1.5−40 bar; and, 2−6 g h molC−1. Used catalysts were analyzed by: temperature-programmed sweeping with N2 (TPS-N2), soluble coke analysis by gas chromatography/mass spectrometry (GC/MS); Fourier-transform infrared spectroscopy (FTIR); temperature-programmed oxidation (TPO), and; combined TPO/FTIR. The main deactivation cause is the oligomer (soft coke) confinement in the catalyst matrix, which depends on the reaction conditions (temperature and pressure). Soft coke is removed by TPS-N2 at 400 °C, whereas the remaining hard coke, by combustion. Two types of hard coke are distinguished, which are located in the catalyst matrix and in the zeolite micropores, being the second fraction more refractory to combustion. The low developed nature of soft coke facilitates catalyst regeneration, which is fully achieved by the combustion of hard coke at 500 °C.

Microstructure analysis of fluidized preheating pulverized coal under O2/CO2 atmospheres

The high efficient and clean coal combustion with fundamental deep low pollution emission was extensively explored worldwide. In this work, the Shenmu bituminous coal was preheated in a circulating fluidized bed (CFB) and this modified fuel including the preheated fuel and the coal gas was burned in a down-fired combustor (DFC) under the O2/CO2 atmospheres. The microstructure change of fuel was analyzed to reveal the reaction process and particle change behavior during high temperature coke combustion. Analysis at the micro scale was important for understanding macro phenomena and achieving deep low pollution emission. The results showed that the main forms of N, C, and O elements in coal were pyrrole, hydrocarbon (aromatics or aromatic substituted alkanes), and carbon-oxygen single bond (including ether and hydroxyl) respectively. During the preheating process, pyrrole converted to pyridine, the coal char reached a state of deep oxidation on the surface, and the stable structure between carbon and oxygen was destroyed. Besides, the number of reacting sites increased after preheating process, which was beneficial to the further combustion.

Combustion comparison analysis on two typical Shenhua chars

Shenhun and Shitan coal are two types of typical Shenhua coals in Shenhua Group. To compare the ignition and burn out characters of this two coals, the pyrolysis process was adopted and Shenhun, Shitan two chars were acquired. The thermogravimetric method(TGA) was used to evaluate two chars combustion characters. Results show that the combustibility of Shenhun char samples are better than that of Shitan char samples. Both the two types of chars DTG peak temperature are approximate 600-650 °C, indicating an easier ignition tendency. The increase of pyrolysis temperature is adverse to the coke combustion. The DTG peak temperature in 700 °C pyrolysis temperature condition is 50 °C larger than that in 900 °C. In addition, the larger particle size is not beneficial to burn out. From the results in this paper, the particle size below 125 μm is recommended.

Faujasite silicalites for oxidative dehydrogenation of n-octane: Influence of alkali metals, gallium, and boron on catalyst activity

• Faujasite silicalites made using sol-gel method and tested in ODH of n-octane. • Extraframework barium reduced the acid site density, hence also COx formation. • Framework B gave more selective to octene isomers compared to framework Ga. • Ga facilitated burning of coke on the surface of the catalyst, prolonging activity. The sol-gel method was used to synthesize faujasite type silicalites bearing gallium and boron in the framework. Barium and sodium were used as charge balancing cations since isomorphic substitution of Si 4+ by Ga 3+ or B 3+ results in a negative excess charge of the framework. The successful synthesis of this type of silicalites (GaBaY-S, BBaY-S, GaBBaY-S(IE), GaNaY-S) was confirmed using powder-XRD. SEM analysis showed that the morphology of the catalysts with respect to particle size depended on the framework metals and the charge balancing cation used. Framework Ga containing catalysts showed smaller particle size compared to B containing catalysts. Sodium also yielded a smaller particle-sized catalyst compared to barium. The catalysts were tested in the continuous flow oxidative dehydrogenation (ODH) of n -octane, and the catalytic results showed dependence on the active metal reducibility and acid-base character of the catalysts. At iso-conversion of 8 ± 1 %, the least acidic BBaY-S gave the highest selectivity to octenes (40 %) and the lowest selectivity to COx (28 %), and the most acidic GaNaY-S showed the opposite results with octenes at 17 % and COx at 56 %. The catalysts (BaBY-S and GaBBaY-S(IE) with least total acidity had the greatest quantity of strong acid sites which were attributed to Lewis acid sites, confirmed by the pyridine IR analysis. The GaNaY-S, with the highest total acidity, had the least strong acid sites.

Study on Coupling Effect of Additives on NOx Control in Coal Pyrolysis-Combustion

A large amount of nitrogen oxides produced by loose coal combustion has an important impact on the ecological environment. To solve this problem, it is proposed to prepare clean coke instead of loose coal combustion to reduce the emission of nitrogen oxides from civil coal combustion. Clean coke is prepared by pyrolysis raw coal adding additives, and the gas generated by pyrolysis is collected uniformly, thus avoiding the emission problem in the process of loose burning. In addition, the clean fuel catalyzes the reduction of nitrogen oxides to produce N2 in the combustion process, thus reducing the emission of combustion nitrogen oxides. In this paper, the additives were investigated, and finally it was found that loading 1 wt.% Fe and Ni had a better effect of decrease nitrogen content in coke through pyrolysis of coal and denitrification during the combustion of coke, and had a coupling effect on nitrogen oxide control in the pyrolysis-combustion process.

Effect of the Pressure of a Gas Mixture on the Ignition, combustion, and Spontaneous Extinction of Cokes of Coals of Different Polymorphisms

Effect of the Pressure of a Gas Mixture on the Ignition, combustion, and Spontaneous Extinction of Cokes of Coals of Different Polymorphisms

Experimental Study on the Catalytic Reduction of NOX by Fe and Ce During the Coke Combustion Process

NOX emissions during the combustion of coal would cause serious pollution to the atmosphere. It is particularly important to reduce NOX pollution during the combustion process by replacing loose coal with clean coke. The use of clean coke for civil is one of the main ways to reduce NOX emissions, which is mainly formed by the mixed dry distillation of metal additives and coal. The coke samples with different proportions of metal additives were prepared by physical mixing method, and the NOX emission law of clean coke at different temperatures was studied in a high-temperature tube furnace reactor. The results show that the addition of Fe alone has a significant effect on the control of NOX emissions, and the co-doping with Ce can further promote the reduction of NOX, so as to achieve the final low emission of NOX. While the reaction temperature is 1000 ℃ and the addition ratio is 2:1, the NOX reduction rate is 73%. It has important practical value and scientific significance for the clean utilization of coal and the treatment of NOX in the atmosphere.

Combined scheme of solid fuel combustion in low power boilers

Different constructive schemes of solid fuel combustion in heating boilers up to 100 kW with the analysis of their efficiency depending on the quality of the burned solid fuel are considered. It is established that low-power solid fuel boilers with various types of combustion devices depending on the characteristics of the burned fuel and the accepted level of service are used in heat supply systems of premises, buildings and structures: from simple furnaces with manual maintenance to automated combustion devices of complex design. Mostly pre-prepared high-quality fuel is used for combustion: fuel pellets, briquettes, high-quality coal, the high cost of which significantly increases operating costs. In order to reduce capital and operating costs, it is advisable to introduce relatively inexpensive models of low-power heating boilers with an acceptable level of mechanization of combustion technology of cheap fuel, including local, with minimal costs for its preparation. The design of a heating water boiler with a semi-mechanical furnace and a technological scheme of combustion is proposed, which combines the processes of drying, gasification and combustion of fuel in a shaft with a clamping grate and combustion of coke in a layer on a moving grate. It is noted that the periodic supply of fuel in the furnace with a moving grate is maintained the stability of the combustion process in the combustion chamber, in the period between cleaning of ash and slag, without significant changes in the composition of above-layer gases. Due to the smooth movement of the next portion of hot coke from the fuel shaft to the combustion chamber on the rotating grate, conditions are created to maintain the uniformity of the boiler with the normative indicators. A reduction in harmful emissions in the exhaust gases was achieved during the combustion of the reaction fuel by passing a secondary blast of air through a collector and directing it to the combustion zone of light substances at the outlet of the clamping grate. Analytical equations for determining the size of the combustion zone according to the regime and design parameters of the combustion process are given. The efficiency of application of the combined (shaft-layer) technological scheme in low-power boilers was tested during testing of combustion of different quality coal in a semi-mechanical furnace with a rotating grate in the electric coal boiler with a heat output of 50 kW for railway carriages.