Azd Zayoud | UCLouvain (University of Louvain) (original) (raw)
Papers by Azd Zayoud
HAL (Le Centre pour la Communication Scientifique Directe), Oct 11, 2021
Global warming is potentially the greatest challenge of this century, with anthropogenic CO2 emis... more Global warming is potentially the greatest challenge of this century, with anthropogenic CO2 emissions the main source of greenhouse gas (GHGs) emissions. Recently, ammonia (NH3) has gained attention as a potential carbon-free energy vector (carrier). NH3 can be produced from waste sources, renewable energy, coupled with already existing infrastructures for production and distribution. However, pure NH3 suffers from low flame speed and potentially important nitrogen oxide (NOx) emissions. As such, blending fuels such as methane (CH4) or hydrogen (H2) with NH3 could potentially address NH3's poor combustion capacities. Therefore, the program FLEXnCONFU has been conceived, supporting bespoke research to tackle some of the fundamental and applied challenges of using these blends. This paper addresses some of the current FLEXnCONFU's progress. Firstly, a series of experiments using a spherical expanding flame setup was employed to investigate potential increases in reactivity of NH3 and its blends with H2 and CH4. Secondly, direct numerical simulation (DNS) modelling of NH3/H2 turbulent expanding spherical flames was performed at lean and rich conditions. Finally, this study also discusses experimental results from an industrial scale swirl burner with varying content of CH4/NH3/H2 under rich condition (Φ = 1.2), in terms of radicals and exhaust emissions. The work is a step towards using non-conventional fuels such as NH3 and H2 and scaling up the technology from lab to industrial level.
33rd Ethylene Producers' Conference (EPC 2021), Proceedings, 2021
Thermochemical recycling of plastic waste to base chemicals via pyrolysis followed by a minimal a... more Thermochemical recycling of plastic waste to base chemicals via pyrolysis followed by a minimal amount of upgrading and steam cracking is expected to be the dominant chemical recycling technology in the coming decade. However, there are substantial safety and operational risks when using plastic waste pyrolysis oils instead of conventional fossil-based feedstocks. This is due to the fact that plastic waste pyrolysis oils contain a vast amount of contaminants which are the main drivers for corrosion, fouling and downstream catalyst poisoning in industrial steam cracking plants. Contaminants are therefore crucial factors to evaluate the steam cracking feasibility of these alternative feedstocks. Indeed, current plastic waste pyrolysis oils exceed typical feedstock specifications for numerous known contaminants, e.g. nitrogen (~10000 vs. 100 ppm max.), oxygen (~1000 vs. < 100 ppm max.), chlorine (~2300 vs. 3 ppm max.), iron (~33 vs. 0.001 ppm max.) and calcium (17 vs. 0.5 ppm max.). Pyrolysis oils produced from post-consumer plastic waste can only meet the current specifications set for industrial steam cracker feedstocks if they are upgraded, with hydrogen based technologies being the most effective, in combination with an effective pretreatment of the plastic waste such as dehalogenation. Moreover, steam crackers are reliant on a stable and predictable feedstock quality and quantity representing a challenge with plastic waste being largely influenced by consumer behavior, seasonal changes and local sorting efficiencies. Nevertheless, with standardization of sorting plants this is expected to become less problematic in the coming decade.
Journal of Analytical and Applied Pyrolysis
Waste Management, 2022
Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking... more Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking of pyrolysis oils shows great potential to overcome the limitations in present means of plastic waste recycling. In this scenario, the largest concern is the feasibility. Are plastic waste pyrolysis products acceptable steam cracking feedstocks in terms of composition, product yields and coke formation? In this work, steam cracking of two post-consumer plastic waste pyrolysis oils blended with fossil naphtha was performed in a continuous bench-scale unit without prior treatment. Product yields and radiant coil coke formation were benchmarked to fossil naphtha as an industrial feedstock. Additionally, the plastic waste pyrolysis oils were thoroughly characterized. Analyses included two dimensional gas chromatography coupled to a flame ionization detector for the detailed hydrocarbon composition as well as specific analyses for heteroatoms, halogens and metals. It was found that both pyrolysis oils are rich in olefins (∼48 wt%) and that the main impurities are nitrogen, oxygen, chlorine, bromine, aluminum, calcium and sodium. Steam cracking of the plastic waste derived feedstocks led to ethylene yields of ∼23 wt% at a coil outlet temperature of 820 °C and ∼28 wt% at 850 °C, exceeding the ethylene yield of pure naphtha at both conditions (∼22 wt% and ∼27 wt%, respectively). High amounts of heavy products were formed when steam cracking both pyrolysis oils, respectively. Furthermore, a substantial coking tendency was observed for the more contaminated pyrolysis oil, indicating that next to unsaturated hydrocarbons, contaminants are a strong driver for coke formation.
Lecture Notes in Mechanical Engineering, 2016
In the present investigation, the effect of aeration rate on bed hydrodynamics in the riser of a ... more In the present investigation, the effect of aeration rate on bed hydrodynamics in the riser of a pressurized circulating fluidized bed (PCFB) has been studied. Experiments are conducted with two different bed inventories, viz. 500 and 750 g. Aeration superficial velocities, U sup = 0.65, 1.94, and 3.23 m/s respectively are used to observe the change of bed hydrodynamics of the PCFB. Operating velocities of 2.72, 3.4 and 4.08 m/s and pressures of 100, 200, and 250 kPa are maintained for each inventory and aeration rate. It has been observed that the suspension density increases along the riser height with the decrease in aeration rate. The solid circulation rate increases with the increase in aeration rate as well as primary air flow rate. The present study will help in optimizing the aeration rate for smooth operation of the non-mechanical valve or the stand pipe without obstruction of inventory material.
Waste Management, 2022
Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking... more Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking of pyrolysis oils shows great potential to overcome the limitations in present means of plastic waste recycling. In this scenario, the largest concern is the feasibility. Are plastic waste pyrolysis products acceptable steam cracking feedstocks in terms of composition, product yields and coke formation? In this work, steam cracking of two post-consumer plastic waste pyrolysis oils blended with fossil naphtha was performed in a continuous bench-scale unit without prior treatment. Product yields and radiant coil coke formation were benchmarked to fossil naphtha as an industrial feedstock. Additionally, the plastic waste pyrolysis oils were thoroughly characterized. Analyses included two dimensional gas chromatography coupled to a flame ionization detector for the detailed hydrocarbon composition as well as specific analyses for heteroatoms, halogens and metals. It was found that both pyrolysis oils are rich in olefins (∼48 wt%) and that the main impurities are nitrogen, oxygen, chlorine, bromine, aluminum, calcium and sodium. Steam cracking of the plastic waste derived feedstocks led to ethylene yields of ∼23 wt% at a coil outlet temperature of 820 °C and ∼28 wt% at 850 °C, exceeding the ethylene yield of pure naphtha at both conditions (∼22 wt% and ∼27 wt%, respectively). High amounts of heavy products were formed when steam cracking both pyrolysis oils, respectively. Furthermore, a substantial coking tendency was observed for the more contaminated pyrolysis oil, indicating that next to unsaturated hydrocarbons, contaminants are a strong driver for coke formation.
Lecture Notes in Mechanical Engineering, 2016
In the present investigation, the effect of aeration rate on bed hydrodynamics in the riser of a ... more In the present investigation, the effect of aeration rate on bed hydrodynamics in the riser of a pressurized circulating fluidized bed (PCFB) has been studied. Experiments are conducted with two different bed inventories, viz. 500 and 750 g. Aeration superficial velocities, U sup = 0.65, 1.94, and 3.23 m/s respectively are used to observe the change of bed hydrodynamics of the PCFB. Operating velocities of 2.72, 3.4 and 4.08 m/s and pressures of 100, 200, and 250 kPa are maintained for each inventory and aeration rate. It has been observed that the suspension density increases along the riser height with the decrease in aeration rate. The solid circulation rate increases with the increase in aeration rate as well as primary air flow rate. The present study will help in optimizing the aeration rate for smooth operation of the non-mechanical valve or the stand pipe without obstruction of inventory material.
Thermal Science, 2017
Pressurized circulating fluidized bed technology is a potentially promising development for clean... more Pressurized circulating fluidized bed technology is a potentially promising development for clean coal technologies. The current work explores the hydrodynamics of a small-scale circulating fluidized bed at elevated operating pressures ranging from 0.10 to 0.25 MPa. The initial experiments were performed at atmospheric pressure with air and O2/CO2 environments as the fluidization gas to simulate the hydrodynamics in a circulating fluidized bed. A comparison between the effects of air and O2/CO2 mixtures on the hydrodynamics was outlined in this paper for particles of 160 ?m diameter. A small but distinct effect on axial void-age was observed due to the change in gas density in the dense zone of the bed at lower gas velocity, while only minimal differences were noticed at higher gas velocities. The hydrodynamic parameters such as pressure drop and axial voidage profile along the height were reported at two different bed inventories (0.5 and 0.75 kg) for three mean particle sizes of 1...
Chemical Engineering Journal, 2008
The hydrodynamics and flow regimes identification in fast-fluidized bed for single systems consis... more The hydrodynamics and flow regimes identification in fast-fluidized bed for single systems consisting of FCC, sand, coal, iron ore and mixed systems of FCC-sand and coal-iron ore were investigated in a perspex column (0.1016 m ID × 5.62 m high). The real voidage profiles have been found out by incorporating gas and solid friction factor and shear stress at the wall of column in the momentum balance equation. To study the flow regimes, the transport velocity (U tr) was determined from the (P L /L)-U g-G s relationship. The gas velocity at which solid holdup in the upper dilute region exhibits a maximum value is defined as the fast transition velocity (U TF) and the transition velocity to pneumatic transport as U FD. In the present work, two correlations have been proposed for both the transition velocities. It has been found that the proposed correlation is in good agreement with experimental values of axial voidage.
Fuel Processing Technology
Materials Today: Proceedings, 2018
Materials Today: Proceedings
Current Science
In the present study, a new method is proposed for temperature controlling by combustion staging.... more In the present study, a new method is proposed for temperature controlling by combustion staging. Two combustion stages can be used with two stages of fuel feeding. A high stoichiometric ratio (SR) > 1 is used at the first stage to mitigate adiabatic flame temperature (AFT) in case of high O 2 % in the oxidant. For validation, a series of experiments are conducted using mini-CFB (circulating fluidized bed), and an oxidant of 100% O 2 concentration is used with three SR ratios, i.e. = 1.25, 2.0 and 3.0. The resulting average temperatures along the riser for biomass are 1031C, 950C and 798C; and for coal 1129C, 1051C and 961C respectively. The controlling of AFT with pure oxy-fuel combustion eliminates the recycled flue gas in oxy-fuel CFB combustion and flue gas recirculation section; this simplifies design, fabrication and installing-operating costs of the power plants. Familiarizing this concept can accelerate adapting oxy-fuel combustion in CFB power plants for carbon capturing and sequestration. This study can help commercialize the third generation of oxy-fuel CFB combustion with zero RFG. Finally, the concept of controlling AFT by SR is validated experimentally.
The hydrodynamics and flow regimes identification in fast-fluidized bed for single systems consis... more The hydrodynamics and flow regimes identification in fast-fluidized bed for single systems consisting of FCC, sand, coal, iron ore and mixed systems of FCC-sand and coal-iron ore were investigated in a perspex column (0.1016 m ID × 5.62 m high). The real voidage profiles have been found out by incorporating gas and solid friction factor and shear stress at the wall of column in the momentum balance equation. To study the flow regimes, the transport velocity (U tr ) was determined from the ( P L /L)-U g -G s relationship. The gas velocity at which solid hold-up in the upper dilute region exhibits a maximum value is defined as the fast transition velocity (U TF ) and the transition velocity to pneumatic transport as U FD . In the present work, two correlations have been proposed for both the transition velocities. It has been found that the proposed correlation is in good agreement with experimental values of axial voidage.
HAL (Le Centre pour la Communication Scientifique Directe), Oct 11, 2021
Global warming is potentially the greatest challenge of this century, with anthropogenic CO2 emis... more Global warming is potentially the greatest challenge of this century, with anthropogenic CO2 emissions the main source of greenhouse gas (GHGs) emissions. Recently, ammonia (NH3) has gained attention as a potential carbon-free energy vector (carrier). NH3 can be produced from waste sources, renewable energy, coupled with already existing infrastructures for production and distribution. However, pure NH3 suffers from low flame speed and potentially important nitrogen oxide (NOx) emissions. As such, blending fuels such as methane (CH4) or hydrogen (H2) with NH3 could potentially address NH3's poor combustion capacities. Therefore, the program FLEXnCONFU has been conceived, supporting bespoke research to tackle some of the fundamental and applied challenges of using these blends. This paper addresses some of the current FLEXnCONFU's progress. Firstly, a series of experiments using a spherical expanding flame setup was employed to investigate potential increases in reactivity of NH3 and its blends with H2 and CH4. Secondly, direct numerical simulation (DNS) modelling of NH3/H2 turbulent expanding spherical flames was performed at lean and rich conditions. Finally, this study also discusses experimental results from an industrial scale swirl burner with varying content of CH4/NH3/H2 under rich condition (Φ = 1.2), in terms of radicals and exhaust emissions. The work is a step towards using non-conventional fuels such as NH3 and H2 and scaling up the technology from lab to industrial level.
33rd Ethylene Producers' Conference (EPC 2021), Proceedings, 2021
Thermochemical recycling of plastic waste to base chemicals via pyrolysis followed by a minimal a... more Thermochemical recycling of plastic waste to base chemicals via pyrolysis followed by a minimal amount of upgrading and steam cracking is expected to be the dominant chemical recycling technology in the coming decade. However, there are substantial safety and operational risks when using plastic waste pyrolysis oils instead of conventional fossil-based feedstocks. This is due to the fact that plastic waste pyrolysis oils contain a vast amount of contaminants which are the main drivers for corrosion, fouling and downstream catalyst poisoning in industrial steam cracking plants. Contaminants are therefore crucial factors to evaluate the steam cracking feasibility of these alternative feedstocks. Indeed, current plastic waste pyrolysis oils exceed typical feedstock specifications for numerous known contaminants, e.g. nitrogen (~10000 vs. 100 ppm max.), oxygen (~1000 vs. < 100 ppm max.), chlorine (~2300 vs. 3 ppm max.), iron (~33 vs. 0.001 ppm max.) and calcium (17 vs. 0.5 ppm max.). Pyrolysis oils produced from post-consumer plastic waste can only meet the current specifications set for industrial steam cracker feedstocks if they are upgraded, with hydrogen based technologies being the most effective, in combination with an effective pretreatment of the plastic waste such as dehalogenation. Moreover, steam crackers are reliant on a stable and predictable feedstock quality and quantity representing a challenge with plastic waste being largely influenced by consumer behavior, seasonal changes and local sorting efficiencies. Nevertheless, with standardization of sorting plants this is expected to become less problematic in the coming decade.
Journal of Analytical and Applied Pyrolysis
Waste Management, 2022
Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking... more Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking of pyrolysis oils shows great potential to overcome the limitations in present means of plastic waste recycling. In this scenario, the largest concern is the feasibility. Are plastic waste pyrolysis products acceptable steam cracking feedstocks in terms of composition, product yields and coke formation? In this work, steam cracking of two post-consumer plastic waste pyrolysis oils blended with fossil naphtha was performed in a continuous bench-scale unit without prior treatment. Product yields and radiant coil coke formation were benchmarked to fossil naphtha as an industrial feedstock. Additionally, the plastic waste pyrolysis oils were thoroughly characterized. Analyses included two dimensional gas chromatography coupled to a flame ionization detector for the detailed hydrocarbon composition as well as specific analyses for heteroatoms, halogens and metals. It was found that both pyrolysis oils are rich in olefins (∼48 wt%) and that the main impurities are nitrogen, oxygen, chlorine, bromine, aluminum, calcium and sodium. Steam cracking of the plastic waste derived feedstocks led to ethylene yields of ∼23 wt% at a coil outlet temperature of 820 °C and ∼28 wt% at 850 °C, exceeding the ethylene yield of pure naphtha at both conditions (∼22 wt% and ∼27 wt%, respectively). High amounts of heavy products were formed when steam cracking both pyrolysis oils, respectively. Furthermore, a substantial coking tendency was observed for the more contaminated pyrolysis oil, indicating that next to unsaturated hydrocarbons, contaminants are a strong driver for coke formation.
Lecture Notes in Mechanical Engineering, 2016
In the present investigation, the effect of aeration rate on bed hydrodynamics in the riser of a ... more In the present investigation, the effect of aeration rate on bed hydrodynamics in the riser of a pressurized circulating fluidized bed (PCFB) has been studied. Experiments are conducted with two different bed inventories, viz. 500 and 750 g. Aeration superficial velocities, U sup = 0.65, 1.94, and 3.23 m/s respectively are used to observe the change of bed hydrodynamics of the PCFB. Operating velocities of 2.72, 3.4 and 4.08 m/s and pressures of 100, 200, and 250 kPa are maintained for each inventory and aeration rate. It has been observed that the suspension density increases along the riser height with the decrease in aeration rate. The solid circulation rate increases with the increase in aeration rate as well as primary air flow rate. The present study will help in optimizing the aeration rate for smooth operation of the non-mechanical valve or the stand pipe without obstruction of inventory material.
Waste Management, 2022
Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking... more Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking of pyrolysis oils shows great potential to overcome the limitations in present means of plastic waste recycling. In this scenario, the largest concern is the feasibility. Are plastic waste pyrolysis products acceptable steam cracking feedstocks in terms of composition, product yields and coke formation? In this work, steam cracking of two post-consumer plastic waste pyrolysis oils blended with fossil naphtha was performed in a continuous bench-scale unit without prior treatment. Product yields and radiant coil coke formation were benchmarked to fossil naphtha as an industrial feedstock. Additionally, the plastic waste pyrolysis oils were thoroughly characterized. Analyses included two dimensional gas chromatography coupled to a flame ionization detector for the detailed hydrocarbon composition as well as specific analyses for heteroatoms, halogens and metals. It was found that both pyrolysis oils are rich in olefins (∼48 wt%) and that the main impurities are nitrogen, oxygen, chlorine, bromine, aluminum, calcium and sodium. Steam cracking of the plastic waste derived feedstocks led to ethylene yields of ∼23 wt% at a coil outlet temperature of 820 °C and ∼28 wt% at 850 °C, exceeding the ethylene yield of pure naphtha at both conditions (∼22 wt% and ∼27 wt%, respectively). High amounts of heavy products were formed when steam cracking both pyrolysis oils, respectively. Furthermore, a substantial coking tendency was observed for the more contaminated pyrolysis oil, indicating that next to unsaturated hydrocarbons, contaminants are a strong driver for coke formation.
Lecture Notes in Mechanical Engineering, 2016
In the present investigation, the effect of aeration rate on bed hydrodynamics in the riser of a ... more In the present investigation, the effect of aeration rate on bed hydrodynamics in the riser of a pressurized circulating fluidized bed (PCFB) has been studied. Experiments are conducted with two different bed inventories, viz. 500 and 750 g. Aeration superficial velocities, U sup = 0.65, 1.94, and 3.23 m/s respectively are used to observe the change of bed hydrodynamics of the PCFB. Operating velocities of 2.72, 3.4 and 4.08 m/s and pressures of 100, 200, and 250 kPa are maintained for each inventory and aeration rate. It has been observed that the suspension density increases along the riser height with the decrease in aeration rate. The solid circulation rate increases with the increase in aeration rate as well as primary air flow rate. The present study will help in optimizing the aeration rate for smooth operation of the non-mechanical valve or the stand pipe without obstruction of inventory material.
Thermal Science, 2017
Pressurized circulating fluidized bed technology is a potentially promising development for clean... more Pressurized circulating fluidized bed technology is a potentially promising development for clean coal technologies. The current work explores the hydrodynamics of a small-scale circulating fluidized bed at elevated operating pressures ranging from 0.10 to 0.25 MPa. The initial experiments were performed at atmospheric pressure with air and O2/CO2 environments as the fluidization gas to simulate the hydrodynamics in a circulating fluidized bed. A comparison between the effects of air and O2/CO2 mixtures on the hydrodynamics was outlined in this paper for particles of 160 ?m diameter. A small but distinct effect on axial void-age was observed due to the change in gas density in the dense zone of the bed at lower gas velocity, while only minimal differences were noticed at higher gas velocities. The hydrodynamic parameters such as pressure drop and axial voidage profile along the height were reported at two different bed inventories (0.5 and 0.75 kg) for three mean particle sizes of 1...
Chemical Engineering Journal, 2008
The hydrodynamics and flow regimes identification in fast-fluidized bed for single systems consis... more The hydrodynamics and flow regimes identification in fast-fluidized bed for single systems consisting of FCC, sand, coal, iron ore and mixed systems of FCC-sand and coal-iron ore were investigated in a perspex column (0.1016 m ID × 5.62 m high). The real voidage profiles have been found out by incorporating gas and solid friction factor and shear stress at the wall of column in the momentum balance equation. To study the flow regimes, the transport velocity (U tr) was determined from the (P L /L)-U g-G s relationship. The gas velocity at which solid holdup in the upper dilute region exhibits a maximum value is defined as the fast transition velocity (U TF) and the transition velocity to pneumatic transport as U FD. In the present work, two correlations have been proposed for both the transition velocities. It has been found that the proposed correlation is in good agreement with experimental values of axial voidage.
Fuel Processing Technology
Materials Today: Proceedings, 2018
Materials Today: Proceedings
Current Science
In the present study, a new method is proposed for temperature controlling by combustion staging.... more In the present study, a new method is proposed for temperature controlling by combustion staging. Two combustion stages can be used with two stages of fuel feeding. A high stoichiometric ratio (SR) > 1 is used at the first stage to mitigate adiabatic flame temperature (AFT) in case of high O 2 % in the oxidant. For validation, a series of experiments are conducted using mini-CFB (circulating fluidized bed), and an oxidant of 100% O 2 concentration is used with three SR ratios, i.e. = 1.25, 2.0 and 3.0. The resulting average temperatures along the riser for biomass are 1031C, 950C and 798C; and for coal 1129C, 1051C and 961C respectively. The controlling of AFT with pure oxy-fuel combustion eliminates the recycled flue gas in oxy-fuel CFB combustion and flue gas recirculation section; this simplifies design, fabrication and installing-operating costs of the power plants. Familiarizing this concept can accelerate adapting oxy-fuel combustion in CFB power plants for carbon capturing and sequestration. This study can help commercialize the third generation of oxy-fuel CFB combustion with zero RFG. Finally, the concept of controlling AFT by SR is validated experimentally.
The hydrodynamics and flow regimes identification in fast-fluidized bed for single systems consis... more The hydrodynamics and flow regimes identification in fast-fluidized bed for single systems consisting of FCC, sand, coal, iron ore and mixed systems of FCC-sand and coal-iron ore were investigated in a perspex column (0.1016 m ID × 5.62 m high). The real voidage profiles have been found out by incorporating gas and solid friction factor and shear stress at the wall of column in the momentum balance equation. To study the flow regimes, the transport velocity (U tr ) was determined from the ( P L /L)-U g -G s relationship. The gas velocity at which solid hold-up in the upper dilute region exhibits a maximum value is defined as the fast transition velocity (U TF ) and the transition velocity to pneumatic transport as U FD . In the present work, two correlations have been proposed for both the transition velocities. It has been found that the proposed correlation is in good agreement with experimental values of axial voidage.