The Experts below are selected from a list of 5268 Experts worldwide ranked by ideXlab platform

Haifeng Liu - One of the best experts on this subject based on the ideXlab platform.

  • Modeling study of the Slag behaviors and SiC refractory wall corrosion on the top cone of a membrane wall entrained-Flow gasifier
    Energy & Fuels, 2020
    Co-Authors: Binbin Zhang, Jing Jin, Haifeng Liu
    Abstract:

    The Slag behaviors on the top cone are significant characteristics that relate to the refractory wall corrosion and safe operation in a membrane wall gasifier. The Slag Flow and heat transfer model...

  • Modelling of Slag Flow and prediction of corrosion state of refractory bricks in an entrained-Flow gasifier
    Fuel, 2020
    Co-Authors: Kuo Lin, Zhongjie Shen, Qinfeng Liang, Haifeng Liu
    Abstract:

    Abstract The corrosion rate of refractory brick is a key factor for long-term and stable operation of a gasifier. In situ measurement of refractory brick corrosion was always a challenging topic due to the extreme temperature and pressure in the gasifier. In this paper, numerical simulations were adopted to accurately predict the corrosion depth of the refractory brick. Models for Slag Flow and refractory brick heat transfer were built, and various models of refractory brick corrosion rate were derived in detail. Heat transfer and brick corrosion models were validated with available industry data and the prediction accuracies of the different models were compared and discussed. Results showed that the external diffusion model could accurately predict the corrosion state, and the correlation coefficient with industry data was 0.998. The Slag shear rate on the surface of the refractory brick was a key control parameter for corrosion, especially for a top single-burner down-Flow gasifier.

  • Study on the Fragmentation Behaviors of Deposited Particles on the Molten Slag Surface and Their Effects on Gasification for Different Coal Ranks and Petroleum Coke
    Energy & Fuels, 2018
    Co-Authors: Zhongjie Shen, Haifeng Liu, Qinfeng Liang, Kuang-fei Lin
    Abstract:

    Coal char particles were deposited on the molten Slag surface and continued to react with the gas near the gasifier wall Slag surface in an entrained Flow gasifier, which significantly affected the total carbon conversion and Slag Flow properties. The current research work is to investigate the fragmentation and gasification characteristics of coal char particles, which were captured on the molten Slag surface. A high-temperature stage microscope was used to study and analyze the particle evolution and char gasification process on the molten Slag surface with the effects of different coal ranks. Results indicated that char particles first shrank and then broke into several fragments during the gasification on the molten Slag surface. Char particles with fragmentation behaviors on the molten Slag surface had higher reaction rates and carbon conversions than the particles in the shrinking period. The initial fragmentation time of a char particle showed an increasing linear relationship with the initial part...

  • modeling study of residence time of molten Slag on the wall in an entrained Flow gasifier
    Fuel, 2018
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Haifeng Liu
    Abstract:

    Abstract In an entrained Flow coal gasifier, the Slag viscosity property is of great importance to the Slagging process. The Slag viscosity is affected by the crystal mineral and the crystallization process has a time effect. The molten Slag residence time in gasifier was calculated by Slag Flow model to estimate the isothermal time or crystal growth time during the cooling process. The residence times of tracer Slag unit were calculated by the Slag velocity. The residence time distribution (RTD) curve was obtained and the mean residence time was about 100–500 s in this study. Moreover, the molten Slag mean residence time decreases significantly with increasing ash contents in coal, decreases slightly with increasing operating temperatures, and increases with increasing Slag critical viscosities and temperatures. In addition, a plug Flow reactor (PFR) series a similar laminar Flow tubular reactor model was used to analysis the RTD curves of molten Slag with different operating conditions.

  • Modeling the Slag Flow and heat transfer on the bottom cone of a membrane wall entrained-Flow gasifier
    Fuel, 2018
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Haifeng Liu
    Abstract:

    Abstract The Slag behaviors on the bottom cone are crucial characteristics that relate to the Slag blockage in a gasifier. The Slag Flow and heat transfer model on the bottom cone was built to calculate the Slag Flow velocity, Slag thickness and heat flux density. The results shown the Slag Flow velocity decreased and the Slag thickness increased with the increasing cone angle. The Slag heat flux density decreased with the increasing cone angle, and specially, the heat transfer rate of the overall bottom cone decreased significantly with the increasing cone angle. The Flow Slag residence time model was established to calculate the residence time distribution (RTD) of molten Slag, and the results shown the mean residence time decreased with the increasing cone angle. In addition, this study preliminary analyzed the blockage possibility, and the results shown the Slag thickness was significantly influenced by the critical temperature interval.

Qinfeng Liang - One of the best experts on this subject based on the ideXlab platform.

  • Modelling of Slag Flow and prediction of corrosion state of refractory bricks in an entrained-Flow gasifier
    Fuel, 2020
    Co-Authors: Kuo Lin, Zhongjie Shen, Qinfeng Liang, Haifeng Liu
    Abstract:

    Abstract The corrosion rate of refractory brick is a key factor for long-term and stable operation of a gasifier. In situ measurement of refractory brick corrosion was always a challenging topic due to the extreme temperature and pressure in the gasifier. In this paper, numerical simulations were adopted to accurately predict the corrosion depth of the refractory brick. Models for Slag Flow and refractory brick heat transfer were built, and various models of refractory brick corrosion rate were derived in detail. Heat transfer and brick corrosion models were validated with available industry data and the prediction accuracies of the different models were compared and discussed. Results showed that the external diffusion model could accurately predict the corrosion state, and the correlation coefficient with industry data was 0.998. The Slag shear rate on the surface of the refractory brick was a key control parameter for corrosion, especially for a top single-burner down-Flow gasifier.

  • Study on the Fragmentation Behaviors of Deposited Particles on the Molten Slag Surface and Their Effects on Gasification for Different Coal Ranks and Petroleum Coke
    Energy & Fuels, 2018
    Co-Authors: Zhongjie Shen, Haifeng Liu, Qinfeng Liang, Kuang-fei Lin
    Abstract:

    Coal char particles were deposited on the molten Slag surface and continued to react with the gas near the gasifier wall Slag surface in an entrained Flow gasifier, which significantly affected the total carbon conversion and Slag Flow properties. The current research work is to investigate the fragmentation and gasification characteristics of coal char particles, which were captured on the molten Slag surface. A high-temperature stage microscope was used to study and analyze the particle evolution and char gasification process on the molten Slag surface with the effects of different coal ranks. Results indicated that char particles first shrank and then broke into several fragments during the gasification on the molten Slag surface. Char particles with fragmentation behaviors on the molten Slag surface had higher reaction rates and carbon conversions than the particles in the shrinking period. The initial fragmentation time of a char particle showed an increasing linear relationship with the initial part...

  • modeling study of residence time of molten Slag on the wall in an entrained Flow gasifier
    Fuel, 2018
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Haifeng Liu
    Abstract:

    Abstract In an entrained Flow coal gasifier, the Slag viscosity property is of great importance to the Slagging process. The Slag viscosity is affected by the crystal mineral and the crystallization process has a time effect. The molten Slag residence time in gasifier was calculated by Slag Flow model to estimate the isothermal time or crystal growth time during the cooling process. The residence times of tracer Slag unit were calculated by the Slag velocity. The residence time distribution (RTD) curve was obtained and the mean residence time was about 100–500 s in this study. Moreover, the molten Slag mean residence time decreases significantly with increasing ash contents in coal, decreases slightly with increasing operating temperatures, and increases with increasing Slag critical viscosities and temperatures. In addition, a plug Flow reactor (PFR) series a similar laminar Flow tubular reactor model was used to analysis the RTD curves of molten Slag with different operating conditions.

  • Modeling the Slag Flow and heat transfer on the bottom cone of a membrane wall entrained-Flow gasifier
    Fuel, 2018
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Haifeng Liu
    Abstract:

    Abstract The Slag behaviors on the bottom cone are crucial characteristics that relate to the Slag blockage in a gasifier. The Slag Flow and heat transfer model on the bottom cone was built to calculate the Slag Flow velocity, Slag thickness and heat flux density. The results shown the Slag Flow velocity decreased and the Slag thickness increased with the increasing cone angle. The Slag heat flux density decreased with the increasing cone angle, and specially, the heat transfer rate of the overall bottom cone decreased significantly with the increasing cone angle. The Flow Slag residence time model was established to calculate the residence time distribution (RTD) of molten Slag, and the results shown the mean residence time decreased with the increasing cone angle. In addition, this study preliminary analyzed the blockage possibility, and the results shown the Slag thickness was significantly influenced by the critical temperature interval.

  • Numerical study of dynamic response analysis of Slag behaviors in an entrained Flow gasifier
    Fuel, 2018
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Haifeng Liu
    Abstract:

    Abstract The characteristics of Slag Flow and heat transfer are significant for the stability and security of gasifier. A Slag Flow and heat transfer model under unsteady conditions was built to study the Slag behaviors dynamic response with transient and periodic operating conditions change. The results show that Slag behaviors changed at the beginning and tended to be stable as time increasing with the coal ash content and operating temperature transient changed. The trend of Slag heat flux and SiC surface temperature are opposite of Slag thickness. Moreover, periodic operating temperature variance was considered and the results show that the Slag behavior changes were also periodic within a specific frequency range. The amplitude of the Slag behavior change increased with the increasing amplitude of the operating temperature, but decreased with the increasing frequency of the operating temperature.

Lian Zhang - One of the best experts on this subject based on the ideXlab platform.

  • xinjiang lignite ash Slagging and Flow under the weak reducing environment at high temperatures Slag viscosity and its variation with ash type and addition of clay
    Fuel, 2019
    Co-Authors: Baiqian Dai, Jie Zhao, Lian Zhang
    Abstract:

    Abstract In this study, five different ashes derived from Xinjiang lignite were tested for Slagging at 1300–1400 °C in a weak reducing environment (1% CO in nitrogen), at different exposure time from 10 min to 2 h. The apparent viscosities for different Slags were determined by using a modified inclined plane (M-IP) method with an inclination of 25° based on the Slag travel length per unit mass. In particular, the variation on Slag viscosity upon the blending of additives including clay and MgO was examined in detail. As have been confirmed, the Slags derived from the original basic and neutral ashes start to Flow from 1400 °C onwards. The viscosities calculated based on the M-IP method at 1400 °C are in the range from ∼1 Pa·s for neutral ash to ∼5 Pa·s for the basic ash Slags. For both neutral and acidic Slags, their viscosities calculated by the M-IP method show a good agreement with some of the existing empirical models that have been validated for high-rank coal Slags. Upon the addition of 10 wt% clay, the viscosity of basic ash at 1300 °C was reduced to 1.53–1.71 Pa·s, demonstrating a comparable Flow-ability and viscosity to that of the original ash at 1400 °C. The addition of MgO promotes the Slag Flow-ability and reduces the Slag viscosity to a relatively small extent in comparison to clay. Instead of melting with other elements in the ash matrix to form Slag, the discrete Mg grains are observed in the Slag matrix. It could even partially react with the alumina plate. The precipitation of Mg may promote the Slag Flow-ability by alleviating the Slag penetration into the alumina plane and the resultant friction between them. Additionally, the viscosities for both the original Slags and those blended with clay decrease quickly upon the increase of the exposure time, substantiating a non-linear Slagging propensity and hence, probably non-Newtonian property. A minimum exposure time of 40 min is essential to ensure these Slags to settle down and reach their equilibrium viscosities in the M-IP method.

  • Xinjiang lignite ash Slagging and Flow under the weak reducing environment at high temperatures – Slag viscosity and its variation with ash type and addition of clay
    Fuel, 2019
    Co-Authors: Baiqian Dai, Jie Zhao, Lian Zhang
    Abstract:

    Abstract In this study, five different ashes derived from Xinjiang lignite were tested for Slagging at 1300–1400 °C in a weak reducing environment (1% CO in nitrogen), at different exposure time from 10 min to 2 h. The apparent viscosities for different Slags were determined by using a modified inclined plane (M-IP) method with an inclination of 25° based on the Slag travel length per unit mass. In particular, the variation on Slag viscosity upon the blending of additives including clay and MgO was examined in detail. As have been confirmed, the Slags derived from the original basic and neutral ashes start to Flow from 1400 °C onwards. The viscosities calculated based on the M-IP method at 1400 °C are in the range from ∼1 Pa·s for neutral ash to ∼5 Pa·s for the basic ash Slags. For both neutral and acidic Slags, their viscosities calculated by the M-IP method show a good agreement with some of the existing empirical models that have been validated for high-rank coal Slags. Upon the addition of 10 wt% clay, the viscosity of basic ash at 1300 °C was reduced to 1.53–1.71 Pa·s, demonstrating a comparable Flow-ability and viscosity to that of the original ash at 1400 °C. The addition of MgO promotes the Slag Flow-ability and reduces the Slag viscosity to a relatively small extent in comparison to clay. Instead of melting with other elements in the ash matrix to form Slag, the discrete Mg grains are observed in the Slag matrix. It could even partially react with the alumina plate. The precipitation of Mg may promote the Slag Flow-ability by alleviating the Slag penetration into the alumina plane and the resultant friction between them. Additionally, the viscosities for both the original Slags and those blended with clay decrease quickly upon the increase of the exposure time, substantiating a non-linear Slagging propensity and hence, probably non-Newtonian property. A minimum exposure time of 40 min is essential to ensure these Slags to settle down and reach their equilibrium viscosities in the M-IP method.

  • xinjiang lignite ash Slagging and Flowability under the weak reducing environment at 1300 c a new method to quantify Slag Flow velocity and its correlation with Slag properties
    Fuel Processing Technology, 2018
    Co-Authors: Baiqian Dai, Lian Zhang
    Abstract:

    Abstract In this study, a novel measurement method for the direct visualisation and quantification of lignite Slag Flowability has been established. The ash Slagging was tested under a weak reducing environment (1% CO 2 in nitrogen) at temperature range from 1000 to 1300 °C to mimic a cyclone combustion furnace for the Chinese Xinjiang lignite. Five different ash samples with a broad variation on the basicity, i.e. base/acid ratio from 1.98 to 0.27, and their blends with up to 40 wt% clay were loaded on a 25°–inclined corundum substrate and exposed to the above-mentioned reducing gases in a pre-heated horizontal furnace. The thermodynamic equilibrium software, FactSage 6.4 and typical viscosity equations were also employed to quantify the liquid fraction in each Slag and its viscosity, respectively. Efforts were further made to correlate the calculated liquid fraction and viscosity of a Slag and its Flow velocity. As has been found, the neutral ash with the lowest ash fusion temperature is the only original ash sample that can melt and Flow at 1300 °C without the use of clay additive, although its Flow velocity is quite marginal. The addition of clay into basic ashes, at 8–10 wt% is able to improve the Slag Flow velocity by 6–7 times at 1300 °C. Both ash basicity and liquid fraction within an ash are critical in determining the Slag Flow velocity. However, neither has proven to be a sole and sufficient factor affecting the Slag Flowability. The Slag viscosity is believed to be a key factor counter balancing the liquid fraction within a Slag. This hypothesis was proven by the addition of 5–10 wt% MgO into a basic ash that decreased both the liquidus fraction and Slag viscosity. Since the decrease on the Slag viscosity (based on the calculation) was more remarkable than the liquidus fraction, the Slag Flow velocity was improved consequently. Apart from providing a new method to quantify Slag Flowability, this study also paved a direction for the future study focusing on lignite ash Slag viscosity and modelling approach to correlate lignite Slag properties and its Flow velocity. A universal method has yet to be established for either of them.

  • Xinjiang lignite ash Slagging and Flowability under the weak reducing environment at 1300 °C – A new method to quantify Slag Flow velocity and its correlation with Slag properties
    Fuel Processing Technology, 2018
    Co-Authors: Baiqian Dai, Lian Zhang
    Abstract:

    Abstract In this study, a novel measurement method for the direct visualisation and quantification of lignite Slag Flowability has been established. The ash Slagging was tested under a weak reducing environment (1% CO 2 in nitrogen) at temperature range from 1000 to 1300 °C to mimic a cyclone combustion furnace for the Chinese Xinjiang lignite. Five different ash samples with a broad variation on the basicity, i.e. base/acid ratio from 1.98 to 0.27, and their blends with up to 40 wt% clay were loaded on a 25°–inclined corundum substrate and exposed to the above-mentioned reducing gases in a pre-heated horizontal furnace. The thermodynamic equilibrium software, FactSage 6.4 and typical viscosity equations were also employed to quantify the liquid fraction in each Slag and its viscosity, respectively. Efforts were further made to correlate the calculated liquid fraction and viscosity of a Slag and its Flow velocity. As has been found, the neutral ash with the lowest ash fusion temperature is the only original ash sample that can melt and Flow at 1300 °C without the use of clay additive, although its Flow velocity is quite marginal. The addition of clay into basic ashes, at 8–10 wt% is able to improve the Slag Flow velocity by 6–7 times at 1300 °C. Both ash basicity and liquid fraction within an ash are critical in determining the Slag Flow velocity. However, neither has proven to be a sole and sufficient factor affecting the Slag Flowability. The Slag viscosity is believed to be a key factor counter balancing the liquid fraction within a Slag. This hypothesis was proven by the addition of 5–10 wt% MgO into a basic ash that decreased both the liquidus fraction and Slag viscosity. Since the decrease on the Slag viscosity (based on the calculation) was more remarkable than the liquidus fraction, the Slag Flow velocity was improved consequently. Apart from providing a new method to quantify Slag Flowability, this study also paved a direction for the future study focusing on lignite ash Slag viscosity and modelling approach to correlate lignite Slag properties and its Flow velocity. A universal method has yet to be established for either of them.

Baiqian Dai - One of the best experts on this subject based on the ideXlab platform.

  • xinjiang lignite ash Slagging and Flow under the weak reducing environment at high temperatures Slag viscosity and its variation with ash type and addition of clay
    Fuel, 2019
    Co-Authors: Baiqian Dai, Jie Zhao, Lian Zhang
    Abstract:

    Abstract In this study, five different ashes derived from Xinjiang lignite were tested for Slagging at 1300–1400 °C in a weak reducing environment (1% CO in nitrogen), at different exposure time from 10 min to 2 h. The apparent viscosities for different Slags were determined by using a modified inclined plane (M-IP) method with an inclination of 25° based on the Slag travel length per unit mass. In particular, the variation on Slag viscosity upon the blending of additives including clay and MgO was examined in detail. As have been confirmed, the Slags derived from the original basic and neutral ashes start to Flow from 1400 °C onwards. The viscosities calculated based on the M-IP method at 1400 °C are in the range from ∼1 Pa·s for neutral ash to ∼5 Pa·s for the basic ash Slags. For both neutral and acidic Slags, their viscosities calculated by the M-IP method show a good agreement with some of the existing empirical models that have been validated for high-rank coal Slags. Upon the addition of 10 wt% clay, the viscosity of basic ash at 1300 °C was reduced to 1.53–1.71 Pa·s, demonstrating a comparable Flow-ability and viscosity to that of the original ash at 1400 °C. The addition of MgO promotes the Slag Flow-ability and reduces the Slag viscosity to a relatively small extent in comparison to clay. Instead of melting with other elements in the ash matrix to form Slag, the discrete Mg grains are observed in the Slag matrix. It could even partially react with the alumina plate. The precipitation of Mg may promote the Slag Flow-ability by alleviating the Slag penetration into the alumina plane and the resultant friction between them. Additionally, the viscosities for both the original Slags and those blended with clay decrease quickly upon the increase of the exposure time, substantiating a non-linear Slagging propensity and hence, probably non-Newtonian property. A minimum exposure time of 40 min is essential to ensure these Slags to settle down and reach their equilibrium viscosities in the M-IP method.

  • Xinjiang lignite ash Slagging and Flow under the weak reducing environment at high temperatures – Slag viscosity and its variation with ash type and addition of clay
    Fuel, 2019
    Co-Authors: Baiqian Dai, Jie Zhao, Lian Zhang
    Abstract:

    Abstract In this study, five different ashes derived from Xinjiang lignite were tested for Slagging at 1300–1400 °C in a weak reducing environment (1% CO in nitrogen), at different exposure time from 10 min to 2 h. The apparent viscosities for different Slags were determined by using a modified inclined plane (M-IP) method with an inclination of 25° based on the Slag travel length per unit mass. In particular, the variation on Slag viscosity upon the blending of additives including clay and MgO was examined in detail. As have been confirmed, the Slags derived from the original basic and neutral ashes start to Flow from 1400 °C onwards. The viscosities calculated based on the M-IP method at 1400 °C are in the range from ∼1 Pa·s for neutral ash to ∼5 Pa·s for the basic ash Slags. For both neutral and acidic Slags, their viscosities calculated by the M-IP method show a good agreement with some of the existing empirical models that have been validated for high-rank coal Slags. Upon the addition of 10 wt% clay, the viscosity of basic ash at 1300 °C was reduced to 1.53–1.71 Pa·s, demonstrating a comparable Flow-ability and viscosity to that of the original ash at 1400 °C. The addition of MgO promotes the Slag Flow-ability and reduces the Slag viscosity to a relatively small extent in comparison to clay. Instead of melting with other elements in the ash matrix to form Slag, the discrete Mg grains are observed in the Slag matrix. It could even partially react with the alumina plate. The precipitation of Mg may promote the Slag Flow-ability by alleviating the Slag penetration into the alumina plane and the resultant friction between them. Additionally, the viscosities for both the original Slags and those blended with clay decrease quickly upon the increase of the exposure time, substantiating a non-linear Slagging propensity and hence, probably non-Newtonian property. A minimum exposure time of 40 min is essential to ensure these Slags to settle down and reach their equilibrium viscosities in the M-IP method.

  • xinjiang lignite ash Slagging and Flowability under the weak reducing environment at 1300 c a new method to quantify Slag Flow velocity and its correlation with Slag properties
    Fuel Processing Technology, 2018
    Co-Authors: Baiqian Dai, Lian Zhang
    Abstract:

    Abstract In this study, a novel measurement method for the direct visualisation and quantification of lignite Slag Flowability has been established. The ash Slagging was tested under a weak reducing environment (1% CO 2 in nitrogen) at temperature range from 1000 to 1300 °C to mimic a cyclone combustion furnace for the Chinese Xinjiang lignite. Five different ash samples with a broad variation on the basicity, i.e. base/acid ratio from 1.98 to 0.27, and their blends with up to 40 wt% clay were loaded on a 25°–inclined corundum substrate and exposed to the above-mentioned reducing gases in a pre-heated horizontal furnace. The thermodynamic equilibrium software, FactSage 6.4 and typical viscosity equations were also employed to quantify the liquid fraction in each Slag and its viscosity, respectively. Efforts were further made to correlate the calculated liquid fraction and viscosity of a Slag and its Flow velocity. As has been found, the neutral ash with the lowest ash fusion temperature is the only original ash sample that can melt and Flow at 1300 °C without the use of clay additive, although its Flow velocity is quite marginal. The addition of clay into basic ashes, at 8–10 wt% is able to improve the Slag Flow velocity by 6–7 times at 1300 °C. Both ash basicity and liquid fraction within an ash are critical in determining the Slag Flow velocity. However, neither has proven to be a sole and sufficient factor affecting the Slag Flowability. The Slag viscosity is believed to be a key factor counter balancing the liquid fraction within a Slag. This hypothesis was proven by the addition of 5–10 wt% MgO into a basic ash that decreased both the liquidus fraction and Slag viscosity. Since the decrease on the Slag viscosity (based on the calculation) was more remarkable than the liquidus fraction, the Slag Flow velocity was improved consequently. Apart from providing a new method to quantify Slag Flowability, this study also paved a direction for the future study focusing on lignite ash Slag viscosity and modelling approach to correlate lignite Slag properties and its Flow velocity. A universal method has yet to be established for either of them.

  • Xinjiang lignite ash Slagging and Flowability under the weak reducing environment at 1300 °C – A new method to quantify Slag Flow velocity and its correlation with Slag properties
    Fuel Processing Technology, 2018
    Co-Authors: Baiqian Dai, Lian Zhang
    Abstract:

    Abstract In this study, a novel measurement method for the direct visualisation and quantification of lignite Slag Flowability has been established. The ash Slagging was tested under a weak reducing environment (1% CO 2 in nitrogen) at temperature range from 1000 to 1300 °C to mimic a cyclone combustion furnace for the Chinese Xinjiang lignite. Five different ash samples with a broad variation on the basicity, i.e. base/acid ratio from 1.98 to 0.27, and their blends with up to 40 wt% clay were loaded on a 25°–inclined corundum substrate and exposed to the above-mentioned reducing gases in a pre-heated horizontal furnace. The thermodynamic equilibrium software, FactSage 6.4 and typical viscosity equations were also employed to quantify the liquid fraction in each Slag and its viscosity, respectively. Efforts were further made to correlate the calculated liquid fraction and viscosity of a Slag and its Flow velocity. As has been found, the neutral ash with the lowest ash fusion temperature is the only original ash sample that can melt and Flow at 1300 °C without the use of clay additive, although its Flow velocity is quite marginal. The addition of clay into basic ashes, at 8–10 wt% is able to improve the Slag Flow velocity by 6–7 times at 1300 °C. Both ash basicity and liquid fraction within an ash are critical in determining the Slag Flow velocity. However, neither has proven to be a sole and sufficient factor affecting the Slag Flowability. The Slag viscosity is believed to be a key factor counter balancing the liquid fraction within a Slag. This hypothesis was proven by the addition of 5–10 wt% MgO into a basic ash that decreased both the liquidus fraction and Slag viscosity. Since the decrease on the Slag viscosity (based on the calculation) was more remarkable than the liquidus fraction, the Slag Flow velocity was improved consequently. Apart from providing a new method to quantify Slag Flowability, this study also paved a direction for the future study focusing on lignite ash Slag viscosity and modelling approach to correlate lignite Slag properties and its Flow velocity. A universal method has yet to be established for either of them.

Binbin Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Modeling study of the Slag behaviors and SiC refractory wall corrosion on the top cone of a membrane wall entrained-Flow gasifier
    Energy & Fuels, 2020
    Co-Authors: Binbin Zhang, Jing Jin, Haifeng Liu
    Abstract:

    The Slag behaviors on the top cone are significant characteristics that relate to the refractory wall corrosion and safe operation in a membrane wall gasifier. The Slag Flow and heat transfer model...

  • modeling study of residence time of molten Slag on the wall in an entrained Flow gasifier
    Fuel, 2018
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Haifeng Liu
    Abstract:

    Abstract In an entrained Flow coal gasifier, the Slag viscosity property is of great importance to the Slagging process. The Slag viscosity is affected by the crystal mineral and the crystallization process has a time effect. The molten Slag residence time in gasifier was calculated by Slag Flow model to estimate the isothermal time or crystal growth time during the cooling process. The residence times of tracer Slag unit were calculated by the Slag velocity. The residence time distribution (RTD) curve was obtained and the mean residence time was about 100–500 s in this study. Moreover, the molten Slag mean residence time decreases significantly with increasing ash contents in coal, decreases slightly with increasing operating temperatures, and increases with increasing Slag critical viscosities and temperatures. In addition, a plug Flow reactor (PFR) series a similar laminar Flow tubular reactor model was used to analysis the RTD curves of molten Slag with different operating conditions.

  • Modeling the Slag Flow and heat transfer on the bottom cone of a membrane wall entrained-Flow gasifier
    Fuel, 2018
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Haifeng Liu
    Abstract:

    Abstract The Slag behaviors on the bottom cone are crucial characteristics that relate to the Slag blockage in a gasifier. The Slag Flow and heat transfer model on the bottom cone was built to calculate the Slag Flow velocity, Slag thickness and heat flux density. The results shown the Slag Flow velocity decreased and the Slag thickness increased with the increasing cone angle. The Slag heat flux density decreased with the increasing cone angle, and specially, the heat transfer rate of the overall bottom cone decreased significantly with the increasing cone angle. The Flow Slag residence time model was established to calculate the residence time distribution (RTD) of molten Slag, and the results shown the mean residence time decreased with the increasing cone angle. In addition, this study preliminary analyzed the blockage possibility, and the results shown the Slag thickness was significantly influenced by the critical temperature interval.

  • Numerical study of dynamic response analysis of Slag behaviors in an entrained Flow gasifier
    Fuel, 2018
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Haifeng Liu
    Abstract:

    Abstract The characteristics of Slag Flow and heat transfer are significant for the stability and security of gasifier. A Slag Flow and heat transfer model under unsteady conditions was built to study the Slag behaviors dynamic response with transient and periodic operating conditions change. The results show that Slag behaviors changed at the beginning and tended to be stable as time increasing with the coal ash content and operating temperature transient changed. The trend of Slag heat flux and SiC surface temperature are opposite of Slag thickness. Moreover, periodic operating temperature variance was considered and the results show that the Slag behavior changes were also periodic within a specific frequency range. The amplitude of the Slag behavior change increased with the increasing amplitude of the operating temperature, but decreased with the increasing frequency of the operating temperature.

  • Effects of the bubbles in Slag on Slag Flow and heat transfer in the membrane wall entrained-Flow gasifier
    Applied Thermal Engineering, 2017
    Co-Authors: Binbin Zhang, Qinfeng Liang, Zhongjie Shen, Dong Han, Haifeng Liu
    Abstract:

    Abstract The Slag from the industrial gasifier has porous structure, which has a non-ignorable influence on the characteristics of Slag layer. The Slag Flow and heat transfer model were modified based on the effective thermal conductivity and viscosity, to predict the Slag characteristics for the effects of bubbles in Slag. The results show that bubbles inside Slag reduce the Slag thermal conductivity and viscosity. The modified model predicts the liquid Slag velocity, Slag layer thickness and heat flux of Slag layer. The liquid Slag Flow velocity increases with the increase of bubbles inside Slag, while the thickness of Slag layer decreases. In addition, the increasing gas volume fraction of bubbles inside Slag decreases the heat flux of Slag layer. Two models are applied to calculate the bubbly Slag effective thermal conductivity. The Maxwell-Eucken thermal conductivity model is more accurate than geometric mean model from the result of Slag layer heat flux.