Opposed Multi-burner Gasifier Research Articles

Post-mortem analysis of Cr2O3-Al2O3-ZrO2 refractory bricks used in an industrial opposed multi-burner gasifier

Periodical relining of the gasifier due to refractory corrosion and failure is a major cost driver in the coal gasification industry. In the present work, the failure mechanisms of Cr2O3-Al2O3-ZrO2 refractory bricks taken from different areas of an industrial opposed multi-burner (OMB) gasifier were investigated by post-mortem analysis. The results demonstrated that a densified (Mg, Fe)O-n(Al, Cr)2O3 complex spinel layer was attained on surface of refractory, which inhibited the further infiltration of slag. The SiO2 and CaO in slag were the main corrosive components and infiltrated into the refractory through pores and cracks. Damage of used bricks was mainly due to crack growth as well as structural spalling caused by different thermal expansion coefficient of de-zirconium layer, infiltration layer and original brick layer. In addition, the failure mechanisms of refractory bricks in different areas were also different owing to unique flow field and structure of OMB gasifier. The dome brick has the smallest wear, which was mainly destroyed by thermal corrosion, the strong scouring of upward flow unit and folded back flow unit. The sidewall brick was damaged by the scouring of high-speed airflow, chemical corrosion and high temperature creep. The damage of lower cone brick was mainly caused by strong mechanical scouring and structural spalling, which has the shortest service life.

Opposed multi-burner gasification technology: Recent process of fundamental research and industrial application

Opposed multi-burner (OMB) gasification technology is the first large-scale gasification technology developed in China with completely independent intellectual property rights. It has been widely used around the world, involving synthetic ammonia, methanol, ethylene glycol, coal liquefaction, hydrogen production and other fields. This paper summarizes the research and development process of OMB gasification technology from the perspective of the cold model experiment and process simulation, pilot-scale study and industrial demonstration. The latest progress of fundamental research in nozzle atomization and dispersion, mixing enhancement of impinging flow, multiscale reaction of different carbonaceous feedstocks, spectral characteristic of impinging flame and particle characteristics inside gasifier, and comprehensive gasification model are reviewed. The latest industrial application progress of ultra-large-scale OMB gasifier and radiant syngas cooler (RSC) combined with quenching chamber OMB gasifier are introduced, and the prospects for the future technical development are proposed as well.

Numerical simulation for size optimization of refractory support frame in OMB gasifier

The refractory support frame in opposed multi-burner (OMB) gasifier is used to support the refractory bricks. However, excessive thermal stress in OMB gasifier at high temperature will damage it and cause refractory bricks to collapse. The effect of size and structure on the thermal stress of refractory support frame has remained unclear. A three-dimensional physical structure model of industrial refractory support frame was established. The numerical simulation of temperature distribution and thermal behavior with different thickness and length of the support plate was detailedly investigated by the analysis modules of steady-state thermal and static structural through ANSYS. When the temperature of end face of hot-face brick was 1300°C, the outer surface temperature of steel shell was 210.4°C, which matched well with the measured temperature. As the thickness of support plate increased, the equivalent stress at the center of support plate gradually decreased. With increasing the length of support plate, the value and whole saltation of stress were both the smallest at the length of 230 mm. The optimal size of support plate which was beneficial to decrease the stress and prolong the service life of the refractory support frame was obtained. It could be a better guidance for the size optimization of the refractory support frame.

Refractory failure in entrained-flow gasifier: Investigation of partitioned erosion characteristics in an industrial opposed multi-burner gasifier

Based on an industrial opposed multi-burner (OMB) gasification plant, a complete review of spent refractory materials inside a gasifier, including a study of the macrostructure and partitioned erosion characteristics, is reported based on systemic industrial data. The results are compared with those from a bench-scale gasification platform as well as numerical simulation. Five heavily eroded regions of the refractory were observed in the industrial OMB gasifier: two in the impinging up-flow zone, one in the burner plane, one in the impinging down-flow zone, and one in the cone zone. The erosion of the refractory material in the dome zone and the plug-flow zone is mild. The spalling on the lower side wall is uneven; therefore, the bricks below the region between two adjacent burners are more eroded in the longitudinal direction. Herein, the results can be used for the development of new refractory structure and the optimization of ultra-large-scale gasifiers.

Alkalis atomic emission spectroscopy and flame temperature measurement of diesel impinging flames in an opposed multi-burner gasifier

Atomic emission spectroscopy can well characterize atom release properties and flame temperature. This work aims to investigate the spectroscopic characteristics of alkalis atoms and measurement method of flame temperature in diesel impinging flames, based on a bench-scale opposed multi-burner (OMB) gasifier. A fiber-optic spectrometer and a CCD camera coupled with multiple bandpass filters are used to obtain the spectral emission lines and two-dimensional emission distributions of Na∗ and K∗, respectively. The results indicate that alkalis atoms can be released and excited in impinging region and four jet regions. The emission intensities of Na∗ and K∗ under different O/C are the strongest in the impinging region, suggesting that the atom release concentration and flame temperature are the highest. Moreover, the thermal excitation degree is related to the type of atom, and Na atom is much easier to be excited than K atom. It is confirmed that alkalis atom content and flame temperature were the two main influence factors on the emission intensity, and emission intensity can be used to qualitatively characterize flame temperature under the same O/C. In addition, atomic emission spectroscopy (AES) was given to quantitatively calculate the flame temperature. It is verified that the AES method is and feasible to derive diesel flame temperature and monitor the temperature changes of OMB gasifiers in real time.

Investigations of CH∗ chemiluminescence and blackbody radiation in opposed impinging coal-water slurry flames based on an entrained-flow gasifier

The characteristics of excited CH radical (CH∗) chemiluminescence and blackbody radiation in opposed impinging coal-water slurry (CWS) flames were investigated in this paper based on a bench-scale opposed multi-burner (OMB) gasifier. CH∗ chemiluminescence is a significant radical species in flame spectral diagnostics, and blackbody radiation can reflect the spatial distribution of solid particles produced in flame. A fiber-optic spectrometer and a CCD camera coupled with multiple bandpass filters are used to obtain the spectral emission lines and two-dimensional spectral distributions, respectively. The results show that CH∗ emission peak at 431 nm and continuous blackbody radiation can be detected in CWS flames. The differences of spectral distributions between diesel and CWS impinging flame are analyzed. Impinging zone is the core chemical reaction region, and solid particles are also concentrated in impinging zone, indicating that four-burner impinging can well restrict the reactants and flames in the impinging zone, thereby greatly reduce the damage to the refractory walls. Moreover, according to the time-averaged distributions, the intensity and area of CH∗ emission and blackbody radiation are enhanced with the increase of oxygen and carbon molar ratio (O/C), demonstrating that improving O2 velocity promotes the chemical reactions, and flame temperature plays more dominant role than solid particle quantity in blackbody radiation. The time-dependent blackbody radiation evolution presents periodical change. Besides, it is found that O/C or syngas concentration can be feasibly estimated using CH∗ chemiluminescence in OMB gasifier.

Refractory failure in entrained-flow gasifier: Vision-based macrostructure investigation in a bench-scale OMB gasifier

As the key component of the entrained-flow gasifier, the refractory experiences high temperature, while also suffering the impacts of high speed gas flow and massive particle impacts accompanied with molten slag. These issues are causing corrosion and erosion that shorten the gasifier service life. Based on a bench-scale opposed multi-burner (OMB) gasifier, the refractory macrostructure failure is investigated by vision-based techniques. The whole refractory is cut into cross-sections and along the vertical direction to study the corrosion. From these samples, it is possible to classify the refractory failure into six zones by utilizing the penetration depth (calculated by area) coupled with simulations of particle trajectories. Refractory surface erosion is investigated through contour arithmetical mean deviation by employing a light field camera to measure the surface height distribution in each cross section. The space distributions of refractory corrosion and erosion present different characteristics which could guide the future design and optimization of OMB gasifiers. The extent of corrosion distribution can be concluded as follows: impinging up-flow zone>impinging down-flow zone>dome zone>impinging/burner zone>plug-flow zone>cone zone. Meanwhile, the extent of surface erosion distribution can be concluded as follows: impinging down-flow zone>impinging/burner zone>cone zone>dome zone>impinging up-flow zone and plug-flow zone.

Experimental Study on the Spectroscopy of Opposed Impinging Diesel Flames Based on a Bench-Scale Gasifier

This paper applies spectral diagnostics (SD) to study the characteristics of diesel flames in opposed burners and monitor the operation of an entrained-flow opposed multi-burner (OMB) gasifier. On the basis of a bench-scale OMB gasifier, the spectral emissions of opposed impinging diesel flames were obtained for different planes and equivalence ratios. The emission lines of OH*, CH*, C2*, Na*, Ar*, and K* radicals were found in diesel flame, and OH* was considered as a good indicator of the impinging flame height. The time-averaged and time-dependent OH* emission intensities can characterize the reaction zone and pulsation magnitude of the flame. The OH*, CH*, and C2* emission intensities of two- and four-burner impinging flames under different [O/C]e were analyzed, indicating that the strengthening effects of four-burner impinging on chemical reactions are superior to those of two-burner impinging. Moreover, whether varying the O2 velocity or diesel flow rate, the OH*/C2* intensity ratio in the impinging...

Experimental study of particle evolution characteristics in an opposed multi-burner gasifier

Based on a bench-scale opposed multi-burner (OMB) gasifier and advanced visualization techniques, the particle evolution characteristics in the gasifier was studied. Particle images of different focusing planes were obtained by optical sectioning tomography (OST) method. Particle types and the principles of transformation between them, particle shape and particle size distribution (PSD), particle fragmentation characteristics were statistically analyzed after image processing. The results show that the burner plane contains all of the particle types, most of them are high temperature particle without wake (HTP), low temperature particle without wake (LTP), high temperature particle with high temperature wake (HTP-HTW) and low temperature particle with high temperature wake (LTP-HTW). Particle shapes in the burner plane are mainly round or round-like. The particle fragmentation process in the burner plane is violent and usually accompanied by sudden bursts that would result in the change of particle motion status, but the probability of which is relatively low (only about 7%). The space between 100mm and 300mm above the burner plane is the main regions of particle pyrolysis, particle types are mainly the low temperature particle with low temperature wake (LTP-LTW). Particles at 100mm above the burner plane have a higher fragmentation probability (10.53%) than that at 200mm (9.51%) and 300mm (8.73%) above the burner plane because of the more intense pyrolysis. In these regions, particle shapes become more irregular and the median particle diameter (D50) are slightly increased. There are plenty of LTP in the space between 400mm above the burner plane to the refractory dome. The probability of fragmentation around 400mm (16.84%), 500mm (11.35%) and 580mm (9.32%) above the burner plane are all higher than the probability around 100mm, 200mm and 300mm above the burner plane, which indicates that the particle fragmentation has more probability to take place in the char gasification stage than in the pyrolysis stage in the OMB gasifier. The closer to the refractory dome, the less the number of large particle is and the smaller the D50 is. About 85% of the particles near the refractory dome have a diameter less than 500μm.

Numerical study of the particle residence time and flow characters in an Opposed Multi-Burner gasifier

As one of the most efficient and reliable entrained flow coal gasification technologies, the Opposed Multi-Burner (OMB) coal-water slurry gasification technology has been applied in 38 plants. The particle residence time in a commercial scale OMB gasifier is studied in this work by using a 3D numerical model. The Realizable k-ε model and discrete particle stochastic trajectory model are employed to solve the gas–solid two-phase flow. The model is validated with the particle residence distribution (RTD) obtained from the bench scale gasifier. The Direct Simulation Monte Carlo (DSMC) method and hard sphere model are used to calculate the gas–solid flow in gasifier impinging zone to consider the effects of the inter-particle collision. In order to reveal the intrinsic factors that dominate the particle residence time, the particle flow behavior is investigated and the mechanical analysis is conducted. A criterion is proposed and used to evaluate the dominant factor of particle flow in different flow regions of the OMB gasifier. The following results are obtained: The inter-particle collisions in Jet Zones and Impinging Zone of the OMB gasifier slightly reduce the particle residence time in these regions. In the regions close to the Impinging Zone, nearly all of the particles are completely controlled by the drag force, while the gravity is the dominant factor to most of the particles in the Outlet Zone. In the middle part of the down flow Impinging Flow Zone, the dominant factor of particle flow can be significantly affected by the particle diameter and inlet gas velocity.

Numerical Simulation and Assessment of a Two‐Stage Gasifier Modified from an Opposed Multi‐Burner Gasifier

AbstractAn opposed multi‐burner (OMB) entrained‐flow gasifier with coal water slurry feeding is developed by the East China University of Science and Technology. A 3D model is employed to numerically simulate the gas flow field, motion of char particles, and distributions of temperature and gaseous components in an OMB gasifier and in a conceptual two‐stage gasifier modified from the OMB gasifier (TS‐OMB gasifier). Results show that the TS‐OMB gasifier produces higher concentration and productivity of the effective gases (CO+H2) with a slightly higher carbon conversion than the OMB gasifier. The reasons for the differences between these two types of gasifier are discussed by means of numerical simulation. This information is valuable for guiding the design of an advanced OMB gasifier.

Modeling of an Opposed Multiburner Gasifier with a Reduced-Order Model

A reduced-order model (ROM) is considered a promising solution for engineering simulation of a gasifier. In this study, a ROM of a commercial-scale opposed multiburner gasifier is developed based on a reactor network model (RNM). The RNM blocking for this gasifier is established and validated based on analysis of the gasifier flow field. The particle flow in the gasifier is characterized by the particle residence time in each reactor of the RNM. The random pore model and the “effective factor” method are employed to model the char gasification rate under high pressure and temperature. The interphase heat transfer and heat loss through the refractory wall are calculated. In model validation, the simulation results show well agreement with the industrial data. The model provides distributions of the gas temperature and compositions in the gasifier. Effects of the particle size on the particle temperature and carbon conversion are discussed quantitatively. It is observed that fine particles can be completely...

Impinging Flame Characteristics in an Opposed Multiburner Gasifier

On the basis of the bench-scale opposed multiburner (OMB) gasifier, industrial light field camera and high speed cameras combined with high temperature endoscopes and image processing technology are proposed and applied to study characteristics of impinging flame height including impinging height and pulsation frequency in coal–water slurry (CWS) gasification. The results show that the mean flame height and the max flame height rise with the increase of mole ratio of oxygen to carbon (O/C) while the general increase trends decrease. The restriction of refractory dome to the flow field in impinging stream recirculation region enhance with the increase of O/C. The impinging flame heights calculated by light field camera combined with axial high temperature endoscope are proved to be reliable. Flame pulsation frequency is investigated by correlation coefficients and frequency spectra calculated from lateral high temperature endoscopes of 90° and 45° optical axis-to-target angle combined with high speed camer...

Comparative Study of Gasification Performance between Bituminous Coal and Petroleum Coke in the Industrial Opposed Multiburner Entrained Flow Gasifier

A comprehensive three-dimensional numerical model for simulating Shenfu bituminous coal and petroleum coke in the industrial opposed multiburner (OMB) gasifier is established. The “effectiveness factor” method is used to extrapolate the intrinsic char reactivity data to industrial gasifier conditions. With the proposed models, the predicted gasification performance of Shenfu coal is in good agreement with industrial operating data, and the predicted carbon conversion of petroleum coke is about 96.7%. Comparing with Shenfu coal, the specific solid fuel consumption of petroleum coke is lower, while the specific oxygen consumption is higher. The characteristic of char gasification in the entrained flow gasifier is investigated. In the high temperature jet flow region and impinging flow region, when the particle diameter is above 200 μm, the Thiele modulus of the char gasifying with steam for Shenfu coal and petroleum coke are 15.4 and 4.8, respectively. Therefore, pore diffusion has a significant effect on the apparent char reactivity. While for the char gasifying with CO2, the Thiele modulus is below 5 in different regions of the OMB gasifier, and the apparent char reactivity is affected by the chemical reaction and pore diffusion. When the char reactivity of petroleum coke is accelerated at 5 times by catalysis effects, the carbon conversion reaches 99.2% and the consumption of oxygen and feedstock decrease obviously. Importantly, the temperature at the dome of the gasifier decreases to 1345 °C, which prolongs the life of refractory wall and favors a long period of availability for the gasifier.

Three-Dimensional Temperature Distribution of Impinging Flames in an Opposed Multiburner Gasifier

Based on the bench-scale opposed multiburner (OMB) gasifier, a new combination of the optical sectioning tomography (OST) and two-color method has been proposed and applied to reconstruct the three-dimensional (3-D) temperature distribution of the gasifier by employing a single charge-coupled device (CCD) camera installed on the top of the gasifier. The reconstruction method is first applied in diesel gasification and the reconstructed results are validated by calibrated thermocouples and a side imaging system; thus the 3-D temperature distribution of coal–water slurry (CWS) gasification is reconstructed. The results show that the temperature distribution is more spatially homogeneous and the average temperature is higher with blurry contours of flame than that of diesel. The overall temperature of the gasifier rises with the increase of oxygen to carbon ratio, and the high temperature region which ranges from 1700 to 2200 K remains in the axis of the gasifier steadily and remains a safe distance from the...

Numerical Simulation of Industrial Opposed Multiburner Coal–Water Slurry Entrained Flow Gasifier

A comprehensive three-dimensional numerical model is developed for simulation of the industrial opposed multiburner (OMB) coal–water slurry (CWS) entrained flow gasifier. The CWS gasification process is divided into several submodels, including water evaporation, coal pyrolysis, and homogeneous and heterogeneous char reactions. The “effectiveness factor” method is used to extrapolate the intrinsic char reactivity data to industrial CWS gasifier conditions. Numerical simulations with the proposed models are performed on the industrial OMB gasifier, and the predicted temperature and gas compositions at the outlet of the gasifier are in good agreement with industrial operating data. The profiles of flow field, temperature, and gas composition in the gasifier are described. In addition, the effects of the slurry concentration and oxygen/coal ratio on the gasifier performance are also studied, which reveal that the lower oxygen/coal ratio or higher slurry concentration leads to higher cold gas efficiency, whil...

Numerical and experimental investigations on gas–particle flow behaviors of the Opposed Multi-Burner Gasifier

Numerical and experimental study on the gas–particle flow field has been carried out in the large Opposed Multi-Burner (OMB) Gasifier (I.D. 1.0 m) at high temperature and pressure. A 3D numerical model based on the Eulerian–Lagrangian model is used to simulate the gas–particle flow behaviors. The gas phase is treated as continuous phase with an Eulerian method while the Lagrangian method is applied to trace of the particles, and the interaction between gas and particles is considered. The behavior of slag/ash particle collision and its effects on particle dispersion are presented. The simulations are validated by available experimental data. The results showed that material residence time increased with the straight section height above the burner, and the deposition flux increased with the inlet velocity. The axis profiles of particle concentrations at high temperature and pressure have the similar characteristic shapes to those at ambient pressure and temperature. And the highest turbulence intensity and collision flame are converged around the centre of impingement zone. Though the inter-particle collision led to the phenomenon of particle agglomeration, the holistic distribution of particle concentration was reasonable. Finally, the effect of operating pressure and particles Stokes number were studied.

Experimental investigations on temperature distributions of flame sections in a bench-scale opposed multi-burner gasifier

Based on a flame image processing technique, the temperature distributions of flame sections in a bench-scale opposed multi-burner (OMB) gasifier is visualized. With the assumption of the gray radiation, a charge-coupled device camera installed on the top of the gasifier is used to capture the approximately monochromatic radiant images under the visible wavelengths. To reduce the errors, the camera is calibrated by a blackbody cavity. By using the two-color method, the radiant intensity captured by the camera is calculated from the pair of red/green with reference to the calibration data. Based on the assumption of rotational symmetry, the temperature distributions of flame sections are reconstructed by the Filtered back-projection method. The results show that the temperature distributions of flame sections are consistent with the flame structure. The flame temperature distribution at the burner plane ranges from 1700 to 2100 °C. The section is farther from the burner plane, the temperature is lower. The relative errors between the calculated temperatures and the measured temperatures by a B-type thermocouple are no greater than ±6.4%. The research results establish the foundation for understanding the flame internal structure and temperature distribution in the OMB gasifier.

Stochastic Modeling of the Particle Residence Time Distribution in an Opposed Multi‐Burner Gasifier

AbstractThe gasification technology of impinging streams has been extensively applied to chemical production and power generation. Particle residence time distribution (RTD) is an important parameter required for modeling, designing and optimization of an impinging stream gasifier. A stochastic mathematical model based on the Markov chains model is developed for the opposed multi‐burner gasifier (OMBG), which closely describes the behavior of the flow pattern and particle RTD in the gasification system. The model simulates the motion of single particle moving in the gasifier using the Markov chains. The predicted results give a reasonable fit to the experimental data. This shows that the flow process of particles in the gasifier has recirculation eddies, which have a downward flow direction near the downflow core and an upward flow direction near the wall, but no short‐circuit. Finally, the effect of particle flux rate on the RTD is predicted, and the contrast between gas and particles RTDs at a laboratory scale and in an industrial gasifier are presented.

Reaction of brown coal and lignin during briquetting

Opposed multi-burner (OMB) gasification technology is the first large-scale gasification technology developed in China with completely independent intellectual property rights. It has been widely used around the world, involving synthetic ammonia, methanol, ethylene glycol, coal liquefaction, hydrogen production and other fields. This paper summarizes the research and development process of OMB gasification technology from the perspective of the cold model experiment and process simulation, pilot-scale study and industrial demonstration. The latest progress of fundamental research in nozzle atomization and dispersion, mixing enhancement of impinging flow, multiscale reaction of different carbonaceous feedstocks, spectral characteristic of impinging flame and particle characteristics inside gasifier, and comprehensive gasification model are reviewed. The latest industrial application progress of ultra-large-scale OMB gasifier and radiant syngas cooler (RSC) combined with quenching chamber OMB gasifier are introduced, and the prospects for the future technical development are proposed as well.