The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Lingxue Kong - One of the best experts on this subject based on the ideXlab platform.
-
viscosity temperature property of coal ash slag at the condition of Entrained Flow gasification a review
Fuel Processing Technology, 2021Co-Authors: Lingxue Kong, Jin BaiAbstract:Abstract Viscosity-temperature property of coal ash slag plays the key role for stable and long term operation of Entrained Flow Gasifiers, which is the quantitative parameter for slag tapping process. It is described by a curve of slag viscosity as a function of temperature, which includes three aspects: viscosity value dependence on temperature, temperature of critical viscosity (TCV), and pattern of slag viscosity-temperature curve. A clear and comprehensive understanding of viscosity-temperature property of coal ash slag and its influencing factors is really important for slag tapping, operation and design of a gasifier. This review begins with essence of slag viscosity-temperature property and requirement for slag tapping, and then focused on utilization of basic oxides to adjust slag viscosity-temperature property. It was found that TCV of a crystalline slag is vitally dependent on crystallization behavior of slag, and crystallization kinetics of slag needs further to be investigated in the future. In addition, residual char in slag, water vapor in syngas, and temperature program in viscosity measurement significantly affect the slag viscosity-temperature property and slag tapping process. Finally, based on results reported in the literatures, several perspectives were proposed for future studies on slag viscosity-temperature property of coal ash slag.
-
crystallization kinetics and tcv prediction of coal ash slag under slag tapping conditions in an Entrained Flow gasifier
Fuel, 2020Co-Authors: Lingxue Kong, Bernd Meyer, Jin Bai, Zongqing Bai, Xi Cao, Huiling Zhao, Stefan GuhlAbstract:Abstract Slag blockages in the bottom of Gasifiers cause unplanned shutdowns and huge losses for syngas utilization downstream of gasification. The sudden viscosity increase by crystal precipitation leads to slag blockage during slag tapping in Entrained Flow Gasifiers. The temperature at which the viscosity abruptly increases is the temperature of critical viscosity (TCV), which is the strict low limit temperature for slag tapping. A comprehensive investigation of slag crystallization kinetics was performed to illustrate TCV in this work. Five slag samples with three different dominant mineral phases that commonly appear in coal ash slag were selected by thermodynamic calculations. The single hot thermocouple technique (SHTT) was applied to analyze the crystallization kinetics based on Avrami and JMA theory. The kinetic analysis indicated that anorthite showed heterogeneous nucleation and grew with a two-dimensional crystalline pattern. The temperature range for anorthite crystallization was approximately 150 °C. Corundum exhibited heterogeneous nucleation and one-dimensional growth pattern. The maximum crystal ratio was 52% for corundum at the temperature of 98 °C. Mullite showed a low E c value, resulting in a high Ton. Rapid crystallization of mullite was observed at 60 °C due to homogeneous nucleation and two-dimensional crystallization. In this work, TCV was revealed by crystallization kinetics for the first time. The relationship between TCV and the activation energy, maximum crystalline rate, and initial crystallization temperature was built to illustrate the influence of crystallization on TCV. Three equations were used for TCV prediction to guide coal selection and slag tapping in Entrained Flow Gasifiers.
-
effect of cao fe2o3 ratio on slag viscosity behavior under Entrained Flow gasification conditions
Fuel, 2019Co-Authors: Bernd Meyer, Jin Bai, Lingxue Kong, Zongqing Bai, Xi Cao, Huiling Zhao, Stefan GuhlAbstract:Abstract The key factor for smooth slag tapping of Entrained Flow Gasifiers was slag viscosity behavior. Shanxi coals can’t meet the requirement for discharging slag due to its high SiO2 + Al2O3 contents. The single fluxing agent (CaO or Fe2O3) was also inoperative for Shanxi coals. Hence, the development of binary composite flux was urgent and necessary. The effect of CaO-Fe2O3 binary composite flux on slag viscosity temperature behavior was investigated in this work. As the CaO/Fe2O3 ratio decreased, the slag viscosity at same temperatures decreased. Furthermore, a linear relationship between the slag viscosity and CaO/Fe2O3 ratio was established at high temperatures. Characterization of slag structure showed that the polymerization degree decreased with the decreasing CaO/Fe2O3 ratio. The calculated BO/(BO + NBO) (fraction of bridging oxygen) also presented an excellent linear relationship with CaO/Fe2O3 ratio. This indicated that CaO/Fe2O3 ratio affected the slag structure, leading to the variation of slag viscosity. During the cooling step, the crystallization activation energy E c was used to describe the effect of CaO/Fe2O3 ratio on slag crystallization behavior quantitatively. Besides, the growth pattern of crystal phases transformed from the surface crystallization to the bulk crystallization with the decreasing CaO/Fe2O3 ratio, and the bulk crystallization was more easily to promote the crystallization behavior. In brief, slag viscosity and crystallization behavior could be modified via adjusting CaO/Fe2O3 ratio. These results can provide a guide for using CaO-Fe2O3 binary composite flux to improve the slag viscosity behavior in Entrained Flow gasification.
-
effect of cao na2o on slag viscosity behavior under Entrained Flow gasification conditions
Fuel Processing Technology, 2018Co-Authors: Jin Bai, Lingxue Kong, Xiaodong Chen, Zongqing BaiAbstract:Abstract The Entrained Flow gasification is becoming a predominant and efficient way for coal clean utilization. And the smooth operation of Entrained Gasifiers strongly depends on steady and reliable removal of the ash slag. In order to reduce the additive amount of flux and improve gasification efficiency, the influence of CaO/Na2O (weight ratio) at constant total content of CaO/Na2O on the viscosity-temperature behavior was studied in this work. Slag structure at high temperatures, and crystallization behavior of the coal ash slag with different CaO/Na2O were investigated in detail. As the CaO/Na2O of the slag decreased, the viscosity increased at same temperatures. Meanwhile, the slag viscosity which exhibited a rapid increase in viscosity transformed into the behavior of a glassy slag, of which the viscosity gradually increases as the temperature decreased. The slag structure depended on network polymerization degree and charge compensation effect of Na+ on Al3+. The polymerization degree of the slag was intensified with the decreasing CaO/Na2O, and the charge compensation effect of Na2O on Al3+ was promoted by CaO. The formation of anorthite was attributed to the rapid increase of viscosity at higher CaO/Na2O, while the decrease of CaO/Na2O was not favor of anorthite crystallization during cooling. In addition, the best ratio of CaO/Na2O in the slag was 6:4, and the slag viscosity behavior was suitable for the smooth operation of the Entrained Flow Gasifiers.
-
Effect of CaO/Na2O on slag viscosity behavior under Entrained Flow gasification conditions
Fuel Processing Technology, 2018Co-Authors: Lingxue Kong, Jin Bai, Xiaodong Chen, Zongqing BaiAbstract:Abstract The Entrained Flow gasification is becoming a predominant and efficient way for coal clean utilization. And the smooth operation of Entrained Gasifiers strongly depends on steady and reliable removal of the ash slag. In order to reduce the additive amount of flux and improve gasification efficiency, the influence of CaO/Na2O (weight ratio) at constant total content of CaO/Na2O on the viscosity-temperature behavior was studied in this work. Slag structure at high temperatures, and crystallization behavior of the coal ash slag with different CaO/Na2O were investigated in detail. As the CaO/Na2O of the slag decreased, the viscosity increased at same temperatures. Meanwhile, the slag viscosity which exhibited a rapid increase in viscosity transformed into the behavior of a glassy slag, of which the viscosity gradually increases as the temperature decreased. The slag structure depended on network polymerization degree and charge compensation effect of Na+ on Al3+. The polymerization degree of the slag was intensified with the decreasing CaO/Na2O, and the charge compensation effect of Na2O on Al3+ was promoted by CaO. The formation of anorthite was attributed to the rapid increase of viscosity at higher CaO/Na2O, while the decrease of CaO/Na2O was not favor of anorthite crystallization during cooling. In addition, the best ratio of CaO/Na2O in the slag was 6:4, and the slag viscosity behavior was suitable for the smooth operation of the Entrained Flow Gasifiers.
Ahmed F Ghoniem - One of the best experts on this subject based on the ideXlab platform.
-
impact of finite rate kinetics on carbon conversion in a high pressure single stage Entrained Flow gasifier with coal co2 slurry feed
Applied Energy, 2013Co-Authors: Cristina Botero, Randall P Field, Howard J Herzog, Ahmed F GhoniemAbstract:Coal–CO2 slurry feed has been suggested as an attractive alternative to coal–water slurry feed for single-stage, Entrained-Flow Gasifiers. Previous work demonstrated the system-level advantages of gasification-based plants equipped with CO2 capture and CO2 slurry feed, under the assumption that carbon conversion remains unchanged. However, gasification in carbon dioxide has been observed to be slower than that in steam. In view of this, the impact of CO2 slurry feeding on gasification kinetics and ultimately on carbon conversion and oxygen consumption in a pressurized, single-stage Entrained-Flow gasifier processing bituminous coal is studied here using a 1-D reduced order model. Results show that the CO2 gasification reaction plays a dominant role in char conversion when the feeding system is CO2 slurry, increasing the CO content in the products by up to a factor of two. CO inhibition of the gasification reaction and a higher degree of internal mass transport limitations lead to an up to 60% slower gasification rate, when compared to a system based on coal–water slurry. Accordingly, a gasifier with CO2 slurry feed has 15% less oxygen consumption but a 7%-point lower carbon conversion for a given reactor outlet temperature. The gasifier outlet temperature must be raised by 90K in order to achieve the same conversion as in a water slurry-fed reactor; the peak reactor temperature increases by 220K as a result. Net oxygen savings of 8% are estimated for a system with a CO2 slurry-fed gasifier relative to one with water slurry and the same level of conversion.
-
reduced order modeling of the shell prenflo Entrained Flow gasifier
Fuel, 2013Co-Authors: Matteo Gazzani, Giampaolo Manzolini, Ennio Macchi, Ahmed F GhoniemAbstract:Abstract Pre-combustion capture applied to an integrated gasification combined cycle is a promising solution for greenhouse gas emission’s mitigation. For optimal design and operation of this cycle, detailed simulation of Entrained Flow Gasifiers and their integration in the Flowsheet analysis is required. This paper describes the development of a reduced order model (ROM) for the Shell–Prenflo gasifier family, used for chemicals and power production because of its high efficiency and compatibility with a wide range of coal quality. Different from CFD analysis, ROM is computationally very efficient, taking around 1 min in a typical desktop or laptop computer, hence enabling the integration of the gasifier model and the overall power plant Flowsheet simulation. Because of the gasifier complexity, which includes several gas recirculation loops and a membrane wall, particular attention is paid to: (i) the two-phase heat exchange process in the gasifier wall; and, (ii) the syngas quench process. Computed temperature, composition, velocity and reaction rate profiles inside the gasifier show good agreement with available data. The calculated cold gas efficiency is 82.5%, close to the given value of 82.8%. Results and several sensitivity analyses describe the implementation of the model to explore the potential for operating Gasifiers beyond the design point.
-
a dynamic reduced order model for simulating Entrained Flow Gasifiers part ii model validation and sensitivity analysis
Fuel, 2012Co-Authors: Rory F D Monaghan, Ahmed F GhoniemAbstract:Abstract Part I of this series describes a dynamic reduced order model (ROM) that has been developed in Aspen Custom Modeler (ACM) for a range of Entrained Flow Gasifiers (EFGs) [1] . The ROM incorporates submodels for multiple feedstocks, mixing and recirculation, particle properties, drying and devolatilization, chemical kinetics, fluid dynamics, heat transfer, pollutant formation, slag behavior and syngas cooling. This paper describes ROM validation for steady-state simulation of four Entrained Flow Gasifiers for which experimental data is available, and sensitivity analysis for the GE gasifier design. The throughputs of these Gasifiers range from 0.1 to 1000 metric tonnes per day (tpd) (3 kW th –240 MW th ). Gasifier designs vary widely and simulations encompass the following configurations: dry and slurry feed, oxygen and air blowing, up and down Flow, one and two stages, membrane and refractory lining, and quench and radiant cooling. Available experimental data consists of axial profiles for temperature, gas composition and carbon conversion, as well as exit values for temperature, composition, carbon conversion, char Flow rate, syngas heating value and cold gas efficiency. Results show satisfactory ROM accuracy for all four gasifier designs simulated, which increases with knowledge of design, operating conditions and experimental data. In cases, where more detailed models that incorporate computational fluid dynamics (CFD) have been used for gasifier simulation, the ROM exhibits comparable accuracy. In sensitivity analysis, important input parameters are identified and varied 10% around their base case (validation) values. The resulting changes in ROM-predicted gasifier performance revealed that the most important parameters are those that determine reactor network model (RNM) geometry (reactor sizes and mass Flow rates), particle physical (porosity, surface area, density, etc.) and kinetic properties, and slagging. In addition, the ROM takes about 1 min to run on a desktop PC, while CFD-based models can take multiple days on multiple processors.
-
Simulation of a Commercial-Scale Entrained Flow Gasifier Using a Dynamic Reduced Order Model
Energy & Fuels, 2012Co-Authors: Rory F D Monaghan, Ahmed F GhoniemAbstract:The development of accurate, flexible, and robust dynamic reduced order models (ROMs) of Entrained Flow Gasifiers (EFGs) is an important step toward greater commercialization of that technology. Previous work by the authors described the development, validation, and sensitivity analysis of such a ROM.(1, 2) This paper presents the results of dynamic simulation of a commercial-scale General Electric (GE or Texaco) gasifier and syngas cooling system. The base case for simulation is introduced, and the ROM is used to simulate six cases of dynamic gasifier operation. The objective of this work is to develop a computationally efficient simulator to assess steady-state and dynamic performance of Entrained Flow Gasifiers under a wide range of realistic operating conditions. The six cases simulated are (1) removal of fluxant, (2) load following, (3) feed switching, (4) coal–petroleum coke cofiring, (5) coal–biomass cofiring, and (6) gasifier cold start. The results of dynamic simulation show that slagging propert...
-
a dynamic reduced order model for simulating Entrained Flow Gasifiers part i model development and description
Fuel, 2012Co-Authors: Rory F D Monaghan, Ahmed F GhoniemAbstract:Abstract The development of accurate, flexible and robust dynamic reduced order models (ROMs) is an important step towards greater commercialization of Entrained Flow Gasifiers (EFGs). This two-part series of papers describes the development of such a ROM. Part I, below, describes the model, while Part II presents its validation for four EFG designs and sensitivity analysis. The ROM employs a reactor network model (RNM) that approximates fluid mixing and recirculation using a series of idealized chemical reactors; well-stirred reactors and 1-D plug Flow reactors. The RNM is constructed such that the ROM is capable of simulating the operation of a range of commercial or research Gasifiers and syngas cooler configurations. The ROM incorporates submodels for multiple feedstocks, mixing and recirculation, particle properties, drying and devolatilization, chemical kinetics, fluid dynamics, heat transfer, pollutant formation, slag behavior and syngas cooling. It is the first experimentally-validated gasifier simulator to incorporate all of the above submodels as well as possess dynamic capability. Modifications to some of the submodels from their original form to improve ROM accuracy, flexibility and robustness are also discussed. The ROM performs the steady-state simulations presented in Part II of this series in 1–5 min on a desktop personal computer, compared to multiple days on multiple processors for more detailed CFD-based simulations.
Jin Bai - One of the best experts on this subject based on the ideXlab platform.
-
viscosity temperature property of coal ash slag at the condition of Entrained Flow gasification a review
Fuel Processing Technology, 2021Co-Authors: Lingxue Kong, Jin BaiAbstract:Abstract Viscosity-temperature property of coal ash slag plays the key role for stable and long term operation of Entrained Flow Gasifiers, which is the quantitative parameter for slag tapping process. It is described by a curve of slag viscosity as a function of temperature, which includes three aspects: viscosity value dependence on temperature, temperature of critical viscosity (TCV), and pattern of slag viscosity-temperature curve. A clear and comprehensive understanding of viscosity-temperature property of coal ash slag and its influencing factors is really important for slag tapping, operation and design of a gasifier. This review begins with essence of slag viscosity-temperature property and requirement for slag tapping, and then focused on utilization of basic oxides to adjust slag viscosity-temperature property. It was found that TCV of a crystalline slag is vitally dependent on crystallization behavior of slag, and crystallization kinetics of slag needs further to be investigated in the future. In addition, residual char in slag, water vapor in syngas, and temperature program in viscosity measurement significantly affect the slag viscosity-temperature property and slag tapping process. Finally, based on results reported in the literatures, several perspectives were proposed for future studies on slag viscosity-temperature property of coal ash slag.
-
crystallization kinetics and tcv prediction of coal ash slag under slag tapping conditions in an Entrained Flow gasifier
Fuel, 2020Co-Authors: Lingxue Kong, Bernd Meyer, Jin Bai, Zongqing Bai, Xi Cao, Huiling Zhao, Stefan GuhlAbstract:Abstract Slag blockages in the bottom of Gasifiers cause unplanned shutdowns and huge losses for syngas utilization downstream of gasification. The sudden viscosity increase by crystal precipitation leads to slag blockage during slag tapping in Entrained Flow Gasifiers. The temperature at which the viscosity abruptly increases is the temperature of critical viscosity (TCV), which is the strict low limit temperature for slag tapping. A comprehensive investigation of slag crystallization kinetics was performed to illustrate TCV in this work. Five slag samples with three different dominant mineral phases that commonly appear in coal ash slag were selected by thermodynamic calculations. The single hot thermocouple technique (SHTT) was applied to analyze the crystallization kinetics based on Avrami and JMA theory. The kinetic analysis indicated that anorthite showed heterogeneous nucleation and grew with a two-dimensional crystalline pattern. The temperature range for anorthite crystallization was approximately 150 °C. Corundum exhibited heterogeneous nucleation and one-dimensional growth pattern. The maximum crystal ratio was 52% for corundum at the temperature of 98 °C. Mullite showed a low E c value, resulting in a high Ton. Rapid crystallization of mullite was observed at 60 °C due to homogeneous nucleation and two-dimensional crystallization. In this work, TCV was revealed by crystallization kinetics for the first time. The relationship between TCV and the activation energy, maximum crystalline rate, and initial crystallization temperature was built to illustrate the influence of crystallization on TCV. Three equations were used for TCV prediction to guide coal selection and slag tapping in Entrained Flow Gasifiers.
-
effect of cao fe2o3 ratio on slag viscosity behavior under Entrained Flow gasification conditions
Fuel, 2019Co-Authors: Bernd Meyer, Jin Bai, Lingxue Kong, Zongqing Bai, Xi Cao, Huiling Zhao, Stefan GuhlAbstract:Abstract The key factor for smooth slag tapping of Entrained Flow Gasifiers was slag viscosity behavior. Shanxi coals can’t meet the requirement for discharging slag due to its high SiO2 + Al2O3 contents. The single fluxing agent (CaO or Fe2O3) was also inoperative for Shanxi coals. Hence, the development of binary composite flux was urgent and necessary. The effect of CaO-Fe2O3 binary composite flux on slag viscosity temperature behavior was investigated in this work. As the CaO/Fe2O3 ratio decreased, the slag viscosity at same temperatures decreased. Furthermore, a linear relationship between the slag viscosity and CaO/Fe2O3 ratio was established at high temperatures. Characterization of slag structure showed that the polymerization degree decreased with the decreasing CaO/Fe2O3 ratio. The calculated BO/(BO + NBO) (fraction of bridging oxygen) also presented an excellent linear relationship with CaO/Fe2O3 ratio. This indicated that CaO/Fe2O3 ratio affected the slag structure, leading to the variation of slag viscosity. During the cooling step, the crystallization activation energy E c was used to describe the effect of CaO/Fe2O3 ratio on slag crystallization behavior quantitatively. Besides, the growth pattern of crystal phases transformed from the surface crystallization to the bulk crystallization with the decreasing CaO/Fe2O3 ratio, and the bulk crystallization was more easily to promote the crystallization behavior. In brief, slag viscosity and crystallization behavior could be modified via adjusting CaO/Fe2O3 ratio. These results can provide a guide for using CaO-Fe2O3 binary composite flux to improve the slag viscosity behavior in Entrained Flow gasification.
-
effect of cao na2o on slag viscosity behavior under Entrained Flow gasification conditions
Fuel Processing Technology, 2018Co-Authors: Jin Bai, Lingxue Kong, Xiaodong Chen, Zongqing BaiAbstract:Abstract The Entrained Flow gasification is becoming a predominant and efficient way for coal clean utilization. And the smooth operation of Entrained Gasifiers strongly depends on steady and reliable removal of the ash slag. In order to reduce the additive amount of flux and improve gasification efficiency, the influence of CaO/Na2O (weight ratio) at constant total content of CaO/Na2O on the viscosity-temperature behavior was studied in this work. Slag structure at high temperatures, and crystallization behavior of the coal ash slag with different CaO/Na2O were investigated in detail. As the CaO/Na2O of the slag decreased, the viscosity increased at same temperatures. Meanwhile, the slag viscosity which exhibited a rapid increase in viscosity transformed into the behavior of a glassy slag, of which the viscosity gradually increases as the temperature decreased. The slag structure depended on network polymerization degree and charge compensation effect of Na+ on Al3+. The polymerization degree of the slag was intensified with the decreasing CaO/Na2O, and the charge compensation effect of Na2O on Al3+ was promoted by CaO. The formation of anorthite was attributed to the rapid increase of viscosity at higher CaO/Na2O, while the decrease of CaO/Na2O was not favor of anorthite crystallization during cooling. In addition, the best ratio of CaO/Na2O in the slag was 6:4, and the slag viscosity behavior was suitable for the smooth operation of the Entrained Flow Gasifiers.
-
Effect of CaO/Na2O on slag viscosity behavior under Entrained Flow gasification conditions
Fuel Processing Technology, 2018Co-Authors: Lingxue Kong, Jin Bai, Xiaodong Chen, Zongqing BaiAbstract:Abstract The Entrained Flow gasification is becoming a predominant and efficient way for coal clean utilization. And the smooth operation of Entrained Gasifiers strongly depends on steady and reliable removal of the ash slag. In order to reduce the additive amount of flux and improve gasification efficiency, the influence of CaO/Na2O (weight ratio) at constant total content of CaO/Na2O on the viscosity-temperature behavior was studied in this work. Slag structure at high temperatures, and crystallization behavior of the coal ash slag with different CaO/Na2O were investigated in detail. As the CaO/Na2O of the slag decreased, the viscosity increased at same temperatures. Meanwhile, the slag viscosity which exhibited a rapid increase in viscosity transformed into the behavior of a glassy slag, of which the viscosity gradually increases as the temperature decreased. The slag structure depended on network polymerization degree and charge compensation effect of Na+ on Al3+. The polymerization degree of the slag was intensified with the decreasing CaO/Na2O, and the charge compensation effect of Na2O on Al3+ was promoted by CaO. The formation of anorthite was attributed to the rapid increase of viscosity at higher CaO/Na2O, while the decrease of CaO/Na2O was not favor of anorthite crystallization during cooling. In addition, the best ratio of CaO/Na2O in the slag was 6:4, and the slag viscosity behavior was suitable for the smooth operation of the Entrained Flow Gasifiers.
Zongqing Bai - One of the best experts on this subject based on the ideXlab platform.
-
crystallization kinetics and tcv prediction of coal ash slag under slag tapping conditions in an Entrained Flow gasifier
Fuel, 2020Co-Authors: Lingxue Kong, Bernd Meyer, Jin Bai, Zongqing Bai, Xi Cao, Huiling Zhao, Stefan GuhlAbstract:Abstract Slag blockages in the bottom of Gasifiers cause unplanned shutdowns and huge losses for syngas utilization downstream of gasification. The sudden viscosity increase by crystal precipitation leads to slag blockage during slag tapping in Entrained Flow Gasifiers. The temperature at which the viscosity abruptly increases is the temperature of critical viscosity (TCV), which is the strict low limit temperature for slag tapping. A comprehensive investigation of slag crystallization kinetics was performed to illustrate TCV in this work. Five slag samples with three different dominant mineral phases that commonly appear in coal ash slag were selected by thermodynamic calculations. The single hot thermocouple technique (SHTT) was applied to analyze the crystallization kinetics based on Avrami and JMA theory. The kinetic analysis indicated that anorthite showed heterogeneous nucleation and grew with a two-dimensional crystalline pattern. The temperature range for anorthite crystallization was approximately 150 °C. Corundum exhibited heterogeneous nucleation and one-dimensional growth pattern. The maximum crystal ratio was 52% for corundum at the temperature of 98 °C. Mullite showed a low E c value, resulting in a high Ton. Rapid crystallization of mullite was observed at 60 °C due to homogeneous nucleation and two-dimensional crystallization. In this work, TCV was revealed by crystallization kinetics for the first time. The relationship between TCV and the activation energy, maximum crystalline rate, and initial crystallization temperature was built to illustrate the influence of crystallization on TCV. Three equations were used for TCV prediction to guide coal selection and slag tapping in Entrained Flow Gasifiers.
-
effect of cao fe2o3 ratio on slag viscosity behavior under Entrained Flow gasification conditions
Fuel, 2019Co-Authors: Bernd Meyer, Jin Bai, Lingxue Kong, Zongqing Bai, Xi Cao, Huiling Zhao, Stefan GuhlAbstract:Abstract The key factor for smooth slag tapping of Entrained Flow Gasifiers was slag viscosity behavior. Shanxi coals can’t meet the requirement for discharging slag due to its high SiO2 + Al2O3 contents. The single fluxing agent (CaO or Fe2O3) was also inoperative for Shanxi coals. Hence, the development of binary composite flux was urgent and necessary. The effect of CaO-Fe2O3 binary composite flux on slag viscosity temperature behavior was investigated in this work. As the CaO/Fe2O3 ratio decreased, the slag viscosity at same temperatures decreased. Furthermore, a linear relationship between the slag viscosity and CaO/Fe2O3 ratio was established at high temperatures. Characterization of slag structure showed that the polymerization degree decreased with the decreasing CaO/Fe2O3 ratio. The calculated BO/(BO + NBO) (fraction of bridging oxygen) also presented an excellent linear relationship with CaO/Fe2O3 ratio. This indicated that CaO/Fe2O3 ratio affected the slag structure, leading to the variation of slag viscosity. During the cooling step, the crystallization activation energy E c was used to describe the effect of CaO/Fe2O3 ratio on slag crystallization behavior quantitatively. Besides, the growth pattern of crystal phases transformed from the surface crystallization to the bulk crystallization with the decreasing CaO/Fe2O3 ratio, and the bulk crystallization was more easily to promote the crystallization behavior. In brief, slag viscosity and crystallization behavior could be modified via adjusting CaO/Fe2O3 ratio. These results can provide a guide for using CaO-Fe2O3 binary composite flux to improve the slag viscosity behavior in Entrained Flow gasification.
-
effect of cao na2o on slag viscosity behavior under Entrained Flow gasification conditions
Fuel Processing Technology, 2018Co-Authors: Jin Bai, Lingxue Kong, Xiaodong Chen, Zongqing BaiAbstract:Abstract The Entrained Flow gasification is becoming a predominant and efficient way for coal clean utilization. And the smooth operation of Entrained Gasifiers strongly depends on steady and reliable removal of the ash slag. In order to reduce the additive amount of flux and improve gasification efficiency, the influence of CaO/Na2O (weight ratio) at constant total content of CaO/Na2O on the viscosity-temperature behavior was studied in this work. Slag structure at high temperatures, and crystallization behavior of the coal ash slag with different CaO/Na2O were investigated in detail. As the CaO/Na2O of the slag decreased, the viscosity increased at same temperatures. Meanwhile, the slag viscosity which exhibited a rapid increase in viscosity transformed into the behavior of a glassy slag, of which the viscosity gradually increases as the temperature decreased. The slag structure depended on network polymerization degree and charge compensation effect of Na+ on Al3+. The polymerization degree of the slag was intensified with the decreasing CaO/Na2O, and the charge compensation effect of Na2O on Al3+ was promoted by CaO. The formation of anorthite was attributed to the rapid increase of viscosity at higher CaO/Na2O, while the decrease of CaO/Na2O was not favor of anorthite crystallization during cooling. In addition, the best ratio of CaO/Na2O in the slag was 6:4, and the slag viscosity behavior was suitable for the smooth operation of the Entrained Flow Gasifiers.
-
Effect of CaO/Na2O on slag viscosity behavior under Entrained Flow gasification conditions
Fuel Processing Technology, 2018Co-Authors: Lingxue Kong, Jin Bai, Xiaodong Chen, Zongqing BaiAbstract:Abstract The Entrained Flow gasification is becoming a predominant and efficient way for coal clean utilization. And the smooth operation of Entrained Gasifiers strongly depends on steady and reliable removal of the ash slag. In order to reduce the additive amount of flux and improve gasification efficiency, the influence of CaO/Na2O (weight ratio) at constant total content of CaO/Na2O on the viscosity-temperature behavior was studied in this work. Slag structure at high temperatures, and crystallization behavior of the coal ash slag with different CaO/Na2O were investigated in detail. As the CaO/Na2O of the slag decreased, the viscosity increased at same temperatures. Meanwhile, the slag viscosity which exhibited a rapid increase in viscosity transformed into the behavior of a glassy slag, of which the viscosity gradually increases as the temperature decreased. The slag structure depended on network polymerization degree and charge compensation effect of Na+ on Al3+. The polymerization degree of the slag was intensified with the decreasing CaO/Na2O, and the charge compensation effect of Na2O on Al3+ was promoted by CaO. The formation of anorthite was attributed to the rapid increase of viscosity at higher CaO/Na2O, while the decrease of CaO/Na2O was not favor of anorthite crystallization during cooling. In addition, the best ratio of CaO/Na2O in the slag was 6:4, and the slag viscosity behavior was suitable for the smooth operation of the Entrained Flow Gasifiers.
-
the precipitation of metallic iron from coal ash slag in the Entrained Flow coal gasifier by thermodynamic calculation
Fuel Processing Technology, 2017Co-Authors: Jin Bai, Lingxue Kong, Stefan Guhl, Daniel Schwitalla, Zongqing BaiAbstract:Abstract A smooth slag Flow out of gasifier bottom is key to a reliable operation of Entrained Flow gasifier. Therefore, avoiding slag blockage at the bottom of gasifier is very essential. Under the gasifier reduction operation conditions, precipitation of metallic iron from the liquid slag sometimes occurred. This solidified slag resulted in the gasifier outlet blockage. Consequently, gasifier operation has to stop. In this study, the thermodynamic software FactSage was used to predict the behavior of iron in the liquid slag within the temperature range of gasifier normal operation. From the results of this study, the mechanism of iron precipitation was revealed. The study showed that due to the higher reducing gas ratio in the syngas, the precipitation of metallic iron only occurred in the pulverized coal Gasifiers instead of the coal water slurry Gasifiers. When weight ratio of SiO 2 /Al 2 O 3 is too low, or CaO content is too high in the slag, Fe 2 + is not able to be saturated in the liquid phase. As a result, precipitation of metallic iron from slag was observed. A β value (β = Si 4 + / (Ca 2 + + Al 3 + ), mole basis) of 1.25 was regarded as the boundary of metallic iron precipitation when 18.4% Fe 2 O 3 content in coal ash. Finally, a metallic iron precipitation predicting model was given by using ternary phase diagram to guide the feedstock selection for the coal application in the Entrained Flow Gasifiers.
Rory F D Monaghan - One of the best experts on this subject based on the ideXlab platform.
-
a dynamic reduced order model for simulating Entrained Flow Gasifiers part ii model validation and sensitivity analysis
Fuel, 2012Co-Authors: Rory F D Monaghan, Ahmed F GhoniemAbstract:Abstract Part I of this series describes a dynamic reduced order model (ROM) that has been developed in Aspen Custom Modeler (ACM) for a range of Entrained Flow Gasifiers (EFGs) [1] . The ROM incorporates submodels for multiple feedstocks, mixing and recirculation, particle properties, drying and devolatilization, chemical kinetics, fluid dynamics, heat transfer, pollutant formation, slag behavior and syngas cooling. This paper describes ROM validation for steady-state simulation of four Entrained Flow Gasifiers for which experimental data is available, and sensitivity analysis for the GE gasifier design. The throughputs of these Gasifiers range from 0.1 to 1000 metric tonnes per day (tpd) (3 kW th –240 MW th ). Gasifier designs vary widely and simulations encompass the following configurations: dry and slurry feed, oxygen and air blowing, up and down Flow, one and two stages, membrane and refractory lining, and quench and radiant cooling. Available experimental data consists of axial profiles for temperature, gas composition and carbon conversion, as well as exit values for temperature, composition, carbon conversion, char Flow rate, syngas heating value and cold gas efficiency. Results show satisfactory ROM accuracy for all four gasifier designs simulated, which increases with knowledge of design, operating conditions and experimental data. In cases, where more detailed models that incorporate computational fluid dynamics (CFD) have been used for gasifier simulation, the ROM exhibits comparable accuracy. In sensitivity analysis, important input parameters are identified and varied 10% around their base case (validation) values. The resulting changes in ROM-predicted gasifier performance revealed that the most important parameters are those that determine reactor network model (RNM) geometry (reactor sizes and mass Flow rates), particle physical (porosity, surface area, density, etc.) and kinetic properties, and slagging. In addition, the ROM takes about 1 min to run on a desktop PC, while CFD-based models can take multiple days on multiple processors.
-
Simulation of a Commercial-Scale Entrained Flow Gasifier Using a Dynamic Reduced Order Model
Energy & Fuels, 2012Co-Authors: Rory F D Monaghan, Ahmed F GhoniemAbstract:The development of accurate, flexible, and robust dynamic reduced order models (ROMs) of Entrained Flow Gasifiers (EFGs) is an important step toward greater commercialization of that technology. Previous work by the authors described the development, validation, and sensitivity analysis of such a ROM.(1, 2) This paper presents the results of dynamic simulation of a commercial-scale General Electric (GE or Texaco) gasifier and syngas cooling system. The base case for simulation is introduced, and the ROM is used to simulate six cases of dynamic gasifier operation. The objective of this work is to develop a computationally efficient simulator to assess steady-state and dynamic performance of Entrained Flow Gasifiers under a wide range of realistic operating conditions. The six cases simulated are (1) removal of fluxant, (2) load following, (3) feed switching, (4) coal–petroleum coke cofiring, (5) coal–biomass cofiring, and (6) gasifier cold start. The results of dynamic simulation show that slagging propert...
-
a dynamic reduced order model for simulating Entrained Flow Gasifiers part i model development and description
Fuel, 2012Co-Authors: Rory F D Monaghan, Ahmed F GhoniemAbstract:Abstract The development of accurate, flexible and robust dynamic reduced order models (ROMs) is an important step towards greater commercialization of Entrained Flow Gasifiers (EFGs). This two-part series of papers describes the development of such a ROM. Part I, below, describes the model, while Part II presents its validation for four EFG designs and sensitivity analysis. The ROM employs a reactor network model (RNM) that approximates fluid mixing and recirculation using a series of idealized chemical reactors; well-stirred reactors and 1-D plug Flow reactors. The RNM is constructed such that the ROM is capable of simulating the operation of a range of commercial or research Gasifiers and syngas cooler configurations. The ROM incorporates submodels for multiple feedstocks, mixing and recirculation, particle properties, drying and devolatilization, chemical kinetics, fluid dynamics, heat transfer, pollutant formation, slag behavior and syngas cooling. It is the first experimentally-validated gasifier simulator to incorporate all of the above submodels as well as possess dynamic capability. Modifications to some of the submodels from their original form to improve ROM accuracy, flexibility and robustness are also discussed. The ROM performs the steady-state simulations presented in Part II of this series in 1–5 min on a desktop personal computer, compared to multiple days on multiple processors for more detailed CFD-based simulations.
-
dynamic reduced order modeling of Entrained Flow Gasifiers
2010Co-Authors: Rory F D MonaghanAbstract:Gasification-based energy systems coupled with carbon dioxide capture and storage technologies have the potential to reduce greenhouse gas emissions from continued use of abundant and secure fossil fuels. Dynamic reduced order models (ROMs) that predict the operation of Entrained Flow Gasifiers (EFGs) within IGCC (integrated gasification combined cycle) or polygeneration plants are essential for understanding the fundamental processes of importance. Such knowledge can be used to improve gasifier reliability, availability and maintainability, leading to greater commercialization of gasification technology. A dynamic ROM, implemented in Aspen Custom Modeler, has been developed for a range of EFGs. The ROM incorporates multiple feedstocks, mixing and recirculation, particle properties, drying and devolatilization, chemical kinetics, fluid dynamics, heat transfer, pollutant formation, slag behavior and syngas cooling. The ROM employs a reactor network model (RNM) that approximates complex fluid mixing and recirculation using a series of idealized chemical reactors. The ROM was successfully validated for steady-state simulation of four experimental Gasifiers. The throughputs of these Gasifiers range from 0.1 to 1000 metric tonnes per day (3 kWth - 240 MWth). Sensitivity analysis was performed to identify the parameters most important to ROM accuracy. The most important parameters are found to be those that determine RNM geometry, particle physical and kinetic properties, and slagging. The ROM was used to simulate the steady-state and dynamic performance of a full-scale EFG system. In steady-state mode, the ROM was used to establish base case and fluxant requirements. The base case performance agreed with design specifications. Steady-state simulation was also used to determine important states for dynamic simulation. Six cases were examined in dynamic mode, including gasifier cold start. Dynamic results showed agreement with industrial experience for gasifier start-up times.
-
Reduced Order Modeling of Entrained Flow Solid Fuel Gasification
Proceedings of the Asme International Mechanical Engineering Congress and Exposition, 2009Co-Authors: Rory F D Monaghan, Simcha L Singer, Mayank Kumar, Cheng Zhang, Ahmed F GhoniemAbstract:Reduced order models that accurately predict the operation of Entrained Flow Gasifiers as components within integrated gasification combined cycle (IGCC) or polygeneration plants are essential for greater commercialization of gasification-based energy systems. A reduced order model, implemented in Aspen Custom Modeler, for Entrained Flow Gasifiers that incorporates mixing and recirculation, rigorously calculated char properties, drying and devolatilization, chemical kinetics, simplified fluid dynamics, heat transfer, slag behavior and syngas cooling is presented. The model structure and submodels are described. Results are presented for the steady-state simulation of a two-metric-tonne-per-day (2 tpd) laboratory-scale Mitsubishi Heavy Industries (MHI) gasifier, fed by two different types of coal. Improvements over the state-of-the-art for reduced order modeling include the ability to incorporate realistic Flow conditions and hence predict the gasifier internal and external temperature profiles, the ability to easily interface the model with plant-wide Flowsheet models, and the flexibility to apply the same model to a variety of Entrained Flow gasifier designs. Model validation shows satisfactory agreement with measured values and computational fluid dynamics (CFD) results for syngas temperature profiles, syngas composition, carbon conversion, char Flow rate, syngas heating value and cold gas efficiency. Analysis of the results shows the accuracy of the reduced order model to be similar to that of more detailed models that incorporate CFD. Next steps include the activation of pollutant chemistry and slag submodels, application of the reduced order model to other gasifier designs, parameter studies and uncertainty analysis of unknown and/or assumed physical and modeling parameters, and activation of dynamic simulation capability.