A fluidised-bed membrane reactor for the catalytic partial oxidation of methane to synthesis gas

doi:10.1016/0009-2509(96)00218-7

Chemical Engineering Science

Volume 51, Issue 11, June 1996, Pages 3187-3192

https://doi.org/10.1016/0009-2509(96)00218-7 Get rights and content

Abstract

A fluidised-bed membrane reactor was proposed as reaction engineering means for performing the catalytic partial oxidation of methane to synthesis gas (syngas) in a safe and stable manner, and to achieve high syngas yields at elevated pressures and low temperatures. In order to analyse the potential of this reactor design a reaction engineering model was developed. Simulation studies performed with this model for palladium and ceramic membranes indicated that in the fluidised-bed membrane reactor higher syngas yields can be achieved compared to the fluidised bed. Furthermore, under certain conditions the integrated product separation allowed to overcome the thermodynamic constraints. Syngas yield in the fluidised-bed membrane reactor strongly depended on the permeation rate and the selectivity of the separation. For the ceramic membrane the interaction between membrane and bed hydrodynamics was found to be of primary importance; in order to achieve high syngas yields the separation unit should contact mainly with the emulsion phase.

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This study investigates the hydrodynamics of a fluidized bed with flat vertical membranes for selective species dosing. A custom designed pseudo-2D column, equipped with a multi-chamber area on the back for gas permeation, was used to emulate a membrane assisted fluidized bed (MA-FB). The effect of global and local gas additions on bubble properties, solids hold up, solids circulation patterns and regime transition was investigated using Digital Image Analysis, Particle Image Velocimetry and pressure fluctuation measurements. Gas addition throughout the entire permeable area substantially reduced bubble size and velocity, while increasing the number of bubbles. In addition, a significant reduction in gas channelling through the centre of the column was observed. Concentrating gas addition towards the sides of the column further enhances bubble distribution over the lateral direction and totally removes gas channelling. Gas addition also caused an earlier transition to turbulent fluidization. The estimated bubble-to-emulsion mass transfer rate could be doubled when 30% gas addition was applied in the turbulent regime. These benefits maximise the potential of process intensification for fluidized bed reactor concepts using selective dosing through flat vertical membranes.
A technical and financial analysis of two recuperated, reciprocating engine driven power plants. Part 1: Thermodynamic analysis
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This paper is the first of a two part study that analyses the technical and financial performance of particular, recuperated engine systems. This first paper presents a thermodynamic study of two systems. The first system involves the chemical recuperation of a reciprocating, spark ignited, internal combustion engine using only the waste heat of the engine to power a steam–methane reformer. The performance of this system is evaluated for different coolant loads and steam–methane ratios. The second system is a so-called ’hybrid’ in which not only the waste heat of the engine is used, but also a secondary heat source – the combustion of biomass. The effects of the reformer’s temperature and the steam–methane ratio on the system performance are analysed.
These analyses show that the potential efficiency improvement obtained when using only the engine waste heat to power the recuperation is marginal. However, results for the hybrid show that although the overall efficiency of the plant, defined in terms of the energy from both the methane and biomass, is similar to that of the conventional, methane fuelled engine, the efficiency of the conversion of the biomass fuel energy to work output appears to be higher than for other biomass fuelled technologies currently in use. Further, in the ideal limit of a fully renewable biomass fuel, the burning of biomass does not contribute to the net ${CO}_{2}$ emissions, and the ${CO}_{2}$ emission reduction for this second plant can be considerable. Indeed, its implementation on larger internal combustion engine power plants, which have efficiencies of around 45–50%, could result in ${CO}_{2}$ emissions that are as much as 10–20% lower than typical natural gas combined cycle (NGCC) power stations. This appears to be a significant result, since NGCCs are commonly considered to have the lowest ${CO}_{2}$ emissions of all forms of fossil fuelled, power generation currently in use.
Novel Developments in Fluidized Bed Membrane Reactor Technology
2014, Advances in Chemical Engineering
This chapter outlines recent and ongoing investigations on the effect of using membranes in a fluidized bed reactor (FBR), using numerical simulations and experiments.
Fluidized bed membrane reactors are a novel, integrated type of reactors where heterogeneously catalyzed reactions can be performed with simultaneous reactant feeding or product extraction in a single unit operation. While this operating technique is beneficial for various reasons (e.g., shift of chemical equilibrium, very good mass and heat transfer), addition or extraction of components can significantly change the behavior of the fluidized bed compared to traditional FBRs, hydrodynamics (bubble and emulsion phase behavior), and mass and heat transfer may be severely affected by the presence of the membranes.
A number of experimental measurement techniques are discussed, with a focus on noninvasive optical techniques such as particle image velocimetry and digital image analysis, as well as a number of academic numerical modeling tools such as discrete particle model and two-fluid model. Not only hydrodynamic aspects, such as the emergence of defluidized zones and solids circulation profile inversion, but also the effect on the bubble size distributions are discussed for wall-mounted membranes and horizontally immersed membranes.
The development of two novel experimental techniques, which may be used for studying concentration profiles in the gas phase, and for studying the fluidized bed at reaction conditions, are outlined in Section 5.
Experimental study on the hydrodynamic effects of gas permeation through horizontal membrane tubes in fluidized beds
2013, Powder Technology
Citation Excerpt :
Adris et al. [2–4], who patented a reactor concept for selectively removing hydrogen from a fluidized bed for methane steam reforming, were the first in this field, quickly followed by Chen et al. [7], Gallucci et al. [18], Grace et al. [19], Patil et al. [27] and Rakib et al. [29], who continued to explore the subject of hydrogen production with fluidized bed membrane reactors in the bubbling or fast fluidization regimes. Another interesting application of fluidized bed membrane reactors is selective dosing of a reactant, which was extensively studied by Mleczko et al. [25]. Later, also Abashar et al. [1], Ahchieva et al. [5], Al-Sherehy et al. [6], Deshmukh et al. [15,16] and Rahimpour et al. [28] devoted their research to various applications of selective reactant dosing via membranes.
Fluidized Bed Membrane Reactors gain worldwide increasing interest for various applications. Nevertheless, fundamental research on the hydrodynamics of these reactors is required in order to improve the predictive capabilities of numerical models and to improve reactor performance. This study comprises an experimental investigation in a pseudo-2D gas–solid fluidized bed containing horizontal submerged membrane tubes, through which gas can be added to – or extracted from – the fluidized suspension. Employing Particle Image Velocimetry (PIV) combined with a novel Digital Image Analysis (DIA) technique, the effect of the presence of, and permeation of gas through the membranes, on both the solids flux profiles as well as the bubble properties has been investigated in great detail for different membrane configurations.
It has been shown that merely the presence of the membrane tubes decreases the solid fluxes by about a factor three, but does not significantly change the overall circulation patterns in the bed. The permeation ratio and the membrane tube arrangement (in-line vs. staggered, size and number of membranes) hardly influence the time-averaged solid flux profiles. In addition, it has been found that, compared to a fluidized bed without inserts, the average bubble size with horizontally submerged membrane tubes decreases by a factor of approximately three, but is hardly dependent on the permeation ratio. The average total superficial gas velocity is more important than the permeation ratio. With respect to bubble size and number of bubbles, the staggered membrane arrangement with 9.6 mm tubes outperforms the in-line arrangement, the arrangement with smaller tubes and the arrangement with fewer membrane tubes, which is of great benefit to reduce bubble-to-emulsion phase mass transfer limitations in fluidized bed membrane reactors under reactive conditions.
Membrane-assisted fluidized beds-Part 2: Numerical study on the hydrodynamics around immersed gas-permeating membrane tubes
2012, Chemical Engineering Science
Citation Excerpt :
The integration of membranes in the reactor enables overcoming equilibrium limitations of conventional reactors. Another potential application area is the selectively dosing of oxygen, resulting in inherently safe reactor operation (Mleczko et al., 1996; Al-Sherehy et al., 2005; Deshmukh et al., 2005a,b). For more examples of potential future fluidized bed membrane reactor applications the reader is referred to Deshmukh et al. (2007) and de Jong et al. (2011).
Among many research studies on fluidized bed membrane reactors, only very few focus on the details of the effects of gas permeation through the membranes on the hydrodynamic properties of the membrane-assisted fluidized bed. For this reason, in the first part of this paper, a novel hybrid Immersed Boundary Method (IBM) Discrete Particle Model (DPM) has been developed. In the second part of the paper, this model is employed to investigate fluidized bed membrane reactors in more detail. Simulations without membrane inserts (having vertical membranes at the side walls instead), with membrane tubes in an in-line arrangement and membranes in a staggered arrangement are compared with each other.
The time-averaged particle fraction maps display a lower bed height for the simulations with inserts. A very important aspect of the simulation with gas extraction/addition via the side walls is the solids circulation; an inversion of the solids circulation is observed when gas is added via the side walls with altered bubble properties. Because of this phenomenon, the bubble size counter-intuitively decreases when gas is added, and increases slightly when gas is extracted. The latter is a result of the existence of compacted zones near the membranes.
For the simulation cases with membrane inserts, the solids circulation and bubble properties are different; in these cases they mainly depend on the local fluidization velocity, and not so much on the extent of permeation itself. Although the arrangement of the membrane tubes plays only a minor role in this matter, their presence has a pronounced influence on the bubble size. The system's energy and energy dissipation are both smaller for the simulations with inserts compared to those with permeation via the side walls. Also in this respect, the local fluidization velocity is found to be more important than the extent of permeation.
Experimental study on the effects of gas permeation through flat membranes on the hydrodynamics in membrane-assisted fluidized beds
2011, Chemical Engineering Science
Recently, many novel reactor concepts based on membrane fluidized bed reactors have been proposed. In this work, the effects of gas permeation through flat membranes on the hydrodynamics in a pseudo-2D membrane-assisted gas–solid fluidized bed have been investigated experimentally. A combination of the non-invasive techniques (Particle Image Velocimetry (PIV) and Digital Image Analysis (DIA)) was employed to simultaneously investigate solids phase and bubble phase properties in great detail. Counter-intuitively, addition of secondary gas via the membranes, that constituted the confining walls of a gas–solid suspension at conditions close to incipient fluidization, did not result in a larger, but in a smaller equivalent bubble diameter, while gas extraction on the other hand, resulted in a larger equivalent bubble diameter, although in this case the effect was less pronounced. This could be explained by changes in the larger scale particle circulation patterns due to gas extraction and addition via the membranes.

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A fluidised-bed membrane reactor for the catalytic partial oxidation of methane to synthesis gas

Abstract

Chem. Eng. Sci.

Fuel Process. Technol.

J. Membr. Sci.

Acta Met.

Chem. Eng. Sci.

Can. J. Chem. Eng.

Fluidised Particles