Ray Allen - Academia.edu (original) (raw)
Papers by Ray Allen
Across the World there is a significant R&D effort concentrated on the Sulphur Iodine cycle, with... more Across the World there is a significant R&D effort concentrated on the Sulphur Iodine cycle, with a view to efficient hydrogen production from water. This paper investigates the application of Nafion membranes to both the HIx and H2SO4 processing sections. Flux and selectivity data using a stirred batch process for the dewatering of HI-H2O-I2 solutions have previously been presented. Here, this work is continued by using a continuous flow set up similar to those used in industrial membrane processes. Excellent separation factors were achieved and the data collected correlated closely with that from previous experiments. Simulations have been performed to identify the potential benefits of dewatering the H2SO4 solution leaving the Bunsen section. An experimental programme has also been carried out, assessing the stability and applicability of Nafion membranes for water separation by pervaporation. Different thickness Nafion membranes have been investigated, across a range of temperat...
The Sulphur family of thermochemical cycles shows great promise for the massive scale production ... more The Sulphur family of thermochemical cycles shows great promise for the massive scale production of hydrogen from water. The decomposition of sulphuric acid is a common stage in the cycles and poses design problems due to the corrosive nature of the solution, the high temperatures involved and the difficult separations required. The work considered here focuses on the oxygen separation stage of the process where, in order for a science based design approach to be taken, thermodynamic data are required for multicomponent phase equilibrium relationships between water, sulphur dioxide and oxygen; H2O-SO2-O2. A bespoke vapour-liquid-equilibrium still is used to measure the simultaneous solubilities of the ternary solution. The results are presented, along with a comparison to a model based on weak electrolyte thermodynamics. The model can be used for flash calculations, necessary for the design of the separation equipment.
Thermochemical cycles have great potential for massive scale, carbon-neutral hydrogen production.... more Thermochemical cycles have great potential for massive scale, carbon-neutral hydrogen production. Of particular interest are the Sulphur Iodine (SI) and the Hybrid Sulphur (HyS) cycles, both having a common step consisting on the high temperature thermal decomposition of H2SO4. The energy requirements are large and there is no known thermodynamic data for this particular system. In order for a design-based approach to be taken for the low temperature separation, accurate vapour-liquid equilibrium data is needed for the decomposition products: SO2-H2O-O2. This work experimentally investigates both the binary SO2-H2O and ternary SO2-O2-H2O system at pressures up to 15 bar and temperatures up to 80° C. Results are compared to a theoretical model based on weak electrolyte thermodynamics. Good correlation between the model and experimental results is seen at low pressures for the binary solution and across the pressure range for the ternary solution. The divergence at high pressures in t...
… International hydrogen …, 2005
The objective of HYTHEC-HYdrogen THErmochemical Cycles-is to investigate the effective potential ... more The objective of HYTHEC-HYdrogen THErmochemical Cycles-is to investigate the effective potential for massive hydrogen production of the S_I thermo-chemical cycle, and to compare it with the hybrid S cycle, also called Westinghouse cycle, which have in common the H 2 SO 4 decomposition reaction (technical feasibilities, industrial and economic viabilities, including the safety aspects). The main goals of the project are the comparison of advantages and drawbacks of the S_I and WH cycles (flow-sheeting, industrial scale-up, safety and costs), the improvement of the fundamental knowledge and efficiency of the S_I cycle H 2 production step, and investigation of a solar primary energy source for the H 2 SO 4 step common to both cycles.
Chemical Engineering Science, 2012
The separation of one component from a multicomponent fluid solution is commonly achieved by brin... more The separation of one component from a multicomponent fluid solution is commonly achieved by bringing the solution into contact with a second immiscible phase, as in liquid-liquid or gas-liquid contactors. Counter-current flow of the phases allows high purity separations and existing approaches typically force one of the phases to disperse into the other, producing the close contact necessary for the solute species to be distributed by diffusion throughout the volume of each phase. This phase mixing leaves the contacting strongly dependent on fluid and interface mechanical properties. Thus an approach that suits one phase and solute system will not necessarily suit others. In addition, it is then necessary to separate the dispersed phase which can be a major drawback of the operation sometimes posing substantial difficulties in easily emulsified liquid-liquid systems or in easily foamed gas-liquid systems. A new approach, which has recently been demonstrated experimentally for microchannels, uses a rotating spiral channel to allow controlled contacting giving a very high ratio of interfacial surface area to fluid volume but avoids phase mixing. Its application to larger channels, up to millimetres in size, is considered here. The two phases are forced to flow side by side in parallel layers along the narrow spiral channel. Selection of spiral parameters, rotation rate and pressure gradient along the channel controls the flow rate ratio of the phases and the relative thickness of the phase layers. This allows adjustment to reach the optimum mass transfer (limited strongly neither by one phase nor the other) and adaptation to phase and solute systems having widely differing fluid viscosities, densities, solute diffusivities and interface equilibria. With appropriate control over these parameters, a single device is, in principle, capable of application to a wide range of separation requirements. This rotating spiral contacting is, however, a new technology and remains to be investigated and tested in detail. The present work develops a model yielding both quantitative prediction of flow and mass transfer in the contacting channel and a framework for determining suitable designs, operating conditions and mass transfer performance for liquid-liquid and gas-liquid operations.
Chemical Engineering Research and Design, 2006
ABSTRACT Slotted wall axial flow cyclones with a conventional center-body swirler are found to ex... more ABSTRACT Slotted wall axial flow cyclones with a conventional center-body swirler are found to exhibit significant flooding at low air velocities. This was observed to be due to significant liquid hold-up on the vanes which eliminated the swirl and led to a pulsating frothing behaviour. At higher velocities, the liquid dispersed and separated through the wall slots. The onset of entrainment of liquid was determined visually. In the low velocity frothing region liquid was entrained directly but coalesced and fell back down the vortex finder. At higher gas velocities entrainment occurred due to several mechanisms. Design changes were introduced to improve performance. The center body was replaced by a new design of vane swirler around the periphery of the tube inlet. This significantly increased the swirl in the tube. Adapting four of the vanes to operate as liquid drainage channels eliminated the flooding phenomenon observed at low gas velocity and enabled the tube slot area to be reduced. This, combined with a larger diameter vortex finder, significantly increased the fraction of flow through the vortex finder, with no extra overall pressure drop. Liquid entrainment in the new design was reduced by positioning liquid slots at the top of the tube and by the use of a skirt. Grade efficiency was determined for the improved cyclone design operating over a range of gas flowrates. The cut size for outflow to the vortex finder was found to vary from about 7 μm at an air velocity of 4.5 ms−1 to about 4.5 μm at 11 ms−1.
Chemical Engineering Research and Design, 2008
ABSTRACT A new concept of micro-channel contactor–separator is developed for operation with immis... more ABSTRACT A new concept of micro-channel contactor–separator is developed for operation with immiscible liquids. It has potential for application with micro-reactors or for mass transfer operations. A prototype device is made in glass using a photo-chemical etching process, including etching across a gap to produce sections of shallow channel. It is tested using oil and water, and the behaviour studied using a microscope in conjunction with a digital video camera. The basis of operation is to use a simple T-junction to produce slugs of typically the oil phase in the water phase. The slugs then flow along a straight channel toward a separation section, which consists of small side channels running perpendicular from the main channel. The side channels carry water to the water outlet, whilst the oil flows out along the main channel. The side channels have a restricted opening where they join the main channel and the extra interfacial force at this point is intended to prevent the oil phase from entering. The operating conditions over which the system operated successfully were determined experimentally. These were found to agree reasonably well with conditions predicted based on CFD analysis.
Chemical Engineering Journal, 2010
The objective of HYTHEC- HYdrogen THErmochemical Cycles- is to investigate the effective potentia... more The objective of HYTHEC- HYdrogen THErmochemical Cycles- is to investigate the effective potential for massive hydrogen production of the S_I thermo-chemical cycle, and to compare it with the hybrid S cycle, also called Westinghouse cycle, which have in common the H2SO4 decomposition reaction (technical feasibilities, industrial and economic viabilities, including the safety aspects). The main goals of the project are the comparison of advantages and drawbacks of the S_I and WH cycles (flow-sheeting, industrial scale-up, safety and costs), the improvement of the fundamental knowledge and efficiency of the S_I cycle H2 production step, and investigation
The sulphur-iodine (SI) and Hybrid Sulfur (HyS) cycles are promising processes for massive scale ... more The sulphur-iodine (SI) and Hybrid Sulfur (HyS) cycles are promising processes for massive scale hydrogen production. These thermochemical cycles take water as a feedstock and produce only hydrogen and oxygen, with no additional waste streams. Both cycles employ ...
Filtration & Separation, 1996
... 3 Morris, K., Clift, Ft. and Allen, RWK: Adhesion of filter cakes. Fourth World Filtration Co... more ... 3 Morris, K., Clift, Ft. and Allen, RWK: Adhesion of filter cakes. Fourth World Filtration Congress, Ostend, Belgium, 1986. ... III, Elsevier, Amsterdam (1986). 3. K. Morris, R. Clift and RWK Allen, Adhesion of filter cakes. In: Fourth World Filtration Congress (1986). ...
Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer, 2006
Computer Aided Chemical Engineering
2009 IEEE International Frequency Control Symposium Joint with the 22nd European Frequency and Time forum, 2009
Ionic liquids are becoming of increasing interest for an extensive range of applications. Small s... more Ionic liquids are becoming of increasing interest for an extensive range of applications. Small scale characterization processes are being continually researched to find cheap and efficient methods for processing ever smaller sample volumes. This work presents a dual Quartz Crystal Microbalance (QCM) setup with one smooth, and one patterned surface using chemically compatible materials allowing separate viscosity and density measurements
The Chemical Engineering Journal and the Biochemical Engineering Journal
An industrial scale Venturi scrubber pilot plant has been used to provide detailed measurements o... more An industrial scale Venturi scrubber pilot plant has been used to provide detailed measurements of pressure drop as a function of a broad range of operating conditions. Modelling approaches suitable for design predictions of ΔP have been examined. While numerical models provide clearer understanding of the phenomena occurring in scrubbers, analytical models offer the most promise of improving industrial design practice. These models concentrate on the work done on the liquid phase and ignore turbulence-induced gas phase accelerational (dry pressure drop) losses. However, the experiments show that the latter are important even in well-designed, classical Venturi shapes. Available models are compared, for the first time, with actual wet pressure drop data and agreement is shown to be good. By isolating the dry pressure drop effect, design models can be applied to a wider range of Venturi geometries.
Across the World there is a significant R&D effort concentrated on the Sulphur Iodine cycle, with... more Across the World there is a significant R&D effort concentrated on the Sulphur Iodine cycle, with a view to efficient hydrogen production from water. This paper investigates the application of Nafion membranes to both the HIx and H2SO4 processing sections. Flux and selectivity data using a stirred batch process for the dewatering of HI-H2O-I2 solutions have previously been presented. Here, this work is continued by using a continuous flow set up similar to those used in industrial membrane processes. Excellent separation factors were achieved and the data collected correlated closely with that from previous experiments. Simulations have been performed to identify the potential benefits of dewatering the H2SO4 solution leaving the Bunsen section. An experimental programme has also been carried out, assessing the stability and applicability of Nafion membranes for water separation by pervaporation. Different thickness Nafion membranes have been investigated, across a range of temperat...
The Sulphur family of thermochemical cycles shows great promise for the massive scale production ... more The Sulphur family of thermochemical cycles shows great promise for the massive scale production of hydrogen from water. The decomposition of sulphuric acid is a common stage in the cycles and poses design problems due to the corrosive nature of the solution, the high temperatures involved and the difficult separations required. The work considered here focuses on the oxygen separation stage of the process where, in order for a science based design approach to be taken, thermodynamic data are required for multicomponent phase equilibrium relationships between water, sulphur dioxide and oxygen; H2O-SO2-O2. A bespoke vapour-liquid-equilibrium still is used to measure the simultaneous solubilities of the ternary solution. The results are presented, along with a comparison to a model based on weak electrolyte thermodynamics. The model can be used for flash calculations, necessary for the design of the separation equipment.
Thermochemical cycles have great potential for massive scale, carbon-neutral hydrogen production.... more Thermochemical cycles have great potential for massive scale, carbon-neutral hydrogen production. Of particular interest are the Sulphur Iodine (SI) and the Hybrid Sulphur (HyS) cycles, both having a common step consisting on the high temperature thermal decomposition of H2SO4. The energy requirements are large and there is no known thermodynamic data for this particular system. In order for a design-based approach to be taken for the low temperature separation, accurate vapour-liquid equilibrium data is needed for the decomposition products: SO2-H2O-O2. This work experimentally investigates both the binary SO2-H2O and ternary SO2-O2-H2O system at pressures up to 15 bar and temperatures up to 80° C. Results are compared to a theoretical model based on weak electrolyte thermodynamics. Good correlation between the model and experimental results is seen at low pressures for the binary solution and across the pressure range for the ternary solution. The divergence at high pressures in t...
… International hydrogen …, 2005
The objective of HYTHEC-HYdrogen THErmochemical Cycles-is to investigate the effective potential ... more The objective of HYTHEC-HYdrogen THErmochemical Cycles-is to investigate the effective potential for massive hydrogen production of the S_I thermo-chemical cycle, and to compare it with the hybrid S cycle, also called Westinghouse cycle, which have in common the H 2 SO 4 decomposition reaction (technical feasibilities, industrial and economic viabilities, including the safety aspects). The main goals of the project are the comparison of advantages and drawbacks of the S_I and WH cycles (flow-sheeting, industrial scale-up, safety and costs), the improvement of the fundamental knowledge and efficiency of the S_I cycle H 2 production step, and investigation of a solar primary energy source for the H 2 SO 4 step common to both cycles.
Chemical Engineering Science, 2012
The separation of one component from a multicomponent fluid solution is commonly achieved by brin... more The separation of one component from a multicomponent fluid solution is commonly achieved by bringing the solution into contact with a second immiscible phase, as in liquid-liquid or gas-liquid contactors. Counter-current flow of the phases allows high purity separations and existing approaches typically force one of the phases to disperse into the other, producing the close contact necessary for the solute species to be distributed by diffusion throughout the volume of each phase. This phase mixing leaves the contacting strongly dependent on fluid and interface mechanical properties. Thus an approach that suits one phase and solute system will not necessarily suit others. In addition, it is then necessary to separate the dispersed phase which can be a major drawback of the operation sometimes posing substantial difficulties in easily emulsified liquid-liquid systems or in easily foamed gas-liquid systems. A new approach, which has recently been demonstrated experimentally for microchannels, uses a rotating spiral channel to allow controlled contacting giving a very high ratio of interfacial surface area to fluid volume but avoids phase mixing. Its application to larger channels, up to millimetres in size, is considered here. The two phases are forced to flow side by side in parallel layers along the narrow spiral channel. Selection of spiral parameters, rotation rate and pressure gradient along the channel controls the flow rate ratio of the phases and the relative thickness of the phase layers. This allows adjustment to reach the optimum mass transfer (limited strongly neither by one phase nor the other) and adaptation to phase and solute systems having widely differing fluid viscosities, densities, solute diffusivities and interface equilibria. With appropriate control over these parameters, a single device is, in principle, capable of application to a wide range of separation requirements. This rotating spiral contacting is, however, a new technology and remains to be investigated and tested in detail. The present work develops a model yielding both quantitative prediction of flow and mass transfer in the contacting channel and a framework for determining suitable designs, operating conditions and mass transfer performance for liquid-liquid and gas-liquid operations.
Chemical Engineering Research and Design, 2006
ABSTRACT Slotted wall axial flow cyclones with a conventional center-body swirler are found to ex... more ABSTRACT Slotted wall axial flow cyclones with a conventional center-body swirler are found to exhibit significant flooding at low air velocities. This was observed to be due to significant liquid hold-up on the vanes which eliminated the swirl and led to a pulsating frothing behaviour. At higher velocities, the liquid dispersed and separated through the wall slots. The onset of entrainment of liquid was determined visually. In the low velocity frothing region liquid was entrained directly but coalesced and fell back down the vortex finder. At higher gas velocities entrainment occurred due to several mechanisms. Design changes were introduced to improve performance. The center body was replaced by a new design of vane swirler around the periphery of the tube inlet. This significantly increased the swirl in the tube. Adapting four of the vanes to operate as liquid drainage channels eliminated the flooding phenomenon observed at low gas velocity and enabled the tube slot area to be reduced. This, combined with a larger diameter vortex finder, significantly increased the fraction of flow through the vortex finder, with no extra overall pressure drop. Liquid entrainment in the new design was reduced by positioning liquid slots at the top of the tube and by the use of a skirt. Grade efficiency was determined for the improved cyclone design operating over a range of gas flowrates. The cut size for outflow to the vortex finder was found to vary from about 7 μm at an air velocity of 4.5 ms−1 to about 4.5 μm at 11 ms−1.
Chemical Engineering Research and Design, 2008
ABSTRACT A new concept of micro-channel contactor–separator is developed for operation with immis... more ABSTRACT A new concept of micro-channel contactor–separator is developed for operation with immiscible liquids. It has potential for application with micro-reactors or for mass transfer operations. A prototype device is made in glass using a photo-chemical etching process, including etching across a gap to produce sections of shallow channel. It is tested using oil and water, and the behaviour studied using a microscope in conjunction with a digital video camera. The basis of operation is to use a simple T-junction to produce slugs of typically the oil phase in the water phase. The slugs then flow along a straight channel toward a separation section, which consists of small side channels running perpendicular from the main channel. The side channels carry water to the water outlet, whilst the oil flows out along the main channel. The side channels have a restricted opening where they join the main channel and the extra interfacial force at this point is intended to prevent the oil phase from entering. The operating conditions over which the system operated successfully were determined experimentally. These were found to agree reasonably well with conditions predicted based on CFD analysis.
Chemical Engineering Journal, 2010
The objective of HYTHEC- HYdrogen THErmochemical Cycles- is to investigate the effective potentia... more The objective of HYTHEC- HYdrogen THErmochemical Cycles- is to investigate the effective potential for massive hydrogen production of the S_I thermo-chemical cycle, and to compare it with the hybrid S cycle, also called Westinghouse cycle, which have in common the H2SO4 decomposition reaction (technical feasibilities, industrial and economic viabilities, including the safety aspects). The main goals of the project are the comparison of advantages and drawbacks of the S_I and WH cycles (flow-sheeting, industrial scale-up, safety and costs), the improvement of the fundamental knowledge and efficiency of the S_I cycle H2 production step, and investigation
The sulphur-iodine (SI) and Hybrid Sulfur (HyS) cycles are promising processes for massive scale ... more The sulphur-iodine (SI) and Hybrid Sulfur (HyS) cycles are promising processes for massive scale hydrogen production. These thermochemical cycles take water as a feedstock and produce only hydrogen and oxygen, with no additional waste streams. Both cycles employ ...
Filtration & Separation, 1996
... 3 Morris, K., Clift, Ft. and Allen, RWK: Adhesion of filter cakes. Fourth World Filtration Co... more ... 3 Morris, K., Clift, Ft. and Allen, RWK: Adhesion of filter cakes. Fourth World Filtration Congress, Ostend, Belgium, 1986. ... III, Elsevier, Amsterdam (1986). 3. K. Morris, R. Clift and RWK Allen, Adhesion of filter cakes. In: Fourth World Filtration Congress (1986). ...
Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer, 2006
Computer Aided Chemical Engineering
2009 IEEE International Frequency Control Symposium Joint with the 22nd European Frequency and Time forum, 2009
Ionic liquids are becoming of increasing interest for an extensive range of applications. Small s... more Ionic liquids are becoming of increasing interest for an extensive range of applications. Small scale characterization processes are being continually researched to find cheap and efficient methods for processing ever smaller sample volumes. This work presents a dual Quartz Crystal Microbalance (QCM) setup with one smooth, and one patterned surface using chemically compatible materials allowing separate viscosity and density measurements
The Chemical Engineering Journal and the Biochemical Engineering Journal
An industrial scale Venturi scrubber pilot plant has been used to provide detailed measurements o... more An industrial scale Venturi scrubber pilot plant has been used to provide detailed measurements of pressure drop as a function of a broad range of operating conditions. Modelling approaches suitable for design predictions of ΔP have been examined. While numerical models provide clearer understanding of the phenomena occurring in scrubbers, analytical models offer the most promise of improving industrial design practice. These models concentrate on the work done on the liquid phase and ignore turbulence-induced gas phase accelerational (dry pressure drop) losses. However, the experiments show that the latter are important even in well-designed, classical Venturi shapes. Available models are compared, for the first time, with actual wet pressure drop data and agreement is shown to be good. By isolating the dry pressure drop effect, design models can be applied to a wider range of Venturi geometries.