Water gas shift reactor modelling and new dimensionless number for thermal management/design of isothermal reactors

Distributed ammonia production has the potential to revolutionize the food and energy industries of the future. Small-scale ammonia production systems can convert stranded renewable resources to ammonia for long-term energy storage during times of excess energy production or fertilizers during times of resource availability. While their intermittent operation with an uncertain feedstock may be economically feasible in some applications, in this work, we explore the technical feasibility of smallscale ammonia production systems. Ammonia synthesis reactors are particularly sensitive to disturbances and can exhibit oscillatory behavior detrimental to the system when perturbed. Therefore, to determine the technically feasibility of distributed ammonia production from a variable feed, we simulated a conventional ammonia production process fed by stranded natural gas. The conventional plant model was then scaled down and subjected to disturbances in the natural gas flow and process conditions. Three ammonia production models were simulated in Aspen Plus at small-, medium-, and large-scales with a production capacity of 135, 675, and 1350 tNH 3 /d, respectively. It was shown that decreasing the ammonia production capacity increases the sensitivity of the production plant to disturbances. A 5% change in natural gas feed resulted in oscillations in the small-scale ammonia synthesis reactor of 21.4% of its nominal value. Additionally, while the conventional large-scale plant was able to withstand up to a 15% increase in natural gas flow rate before exhibiting instabilities, the small-scale plant exhibited instabilities at a 3% increase in flow. Findings from disturbance tests performed in this work were used to propose methods of stabilizing the ammonia synthesis reactor at the small scale via improved ammonia separation techniques and new reactor designs.

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“…Validation plots for the (a) primary reformer against its reference in ref and (b) MTH against its reference in ref .…”

Section: Resultsmentioning

confidence: 99%

“…Water gas shift reactor validation for the (a) HTS reactor and (b) LTS reactor models against reference data …”

Section: Resultsmentioning

confidence: 99%

Stability Assessment of Small-Scale Distributed Ammonia Production Systems

Burrows

Bollas

2022

Ind. Eng. Chem. Res.

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“…These tubes are packed with the catalyst and fed with a reaction mixture with a flow of 2670.61 kg.h −1 . This flux was chosen to study a feed flux of real order of magnitude, because it corresponds to one of the total fluxes feeding the pilot reactors as reported by van Dijk et al [19] and Rosner et al [20]…”

Section: Process Descriptionmentioning

confidence: 99%

“…To diagnose, size and predict the behavior of these converters, the mono-dimensional heterogeneous model offers great precision for the design of reactors oper-ating in steady state [17]. Many authors have adopted this model for the study of WGS reactors operating at medium and high pressures [4,[18][19][20]. These works have shown that generally, the catalytic pellet can be considered isothermal, but the limitations to the intraparticle transfer of mass cannot be neglected [4].…”

Section: Introductionmentioning

confidence: 99%

“…This model can correctly describe the behaviour of industrial reactors despite the presence of H2S in the reaction mixture [19]. The use of the optimization rate Ro in thermal management and in the design of the reactor allows considerably reducing the catalytic masses [20]. Another study was interested in reactors operating at low pressures [1-4 atm] and temperatures compared this model to 2Dmodel.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Study of a Water Gas Shift Fixed Bed Reactor Operating at Low Pressures

Bazi

Bideq

El-Abidi

et al. 2022

Bull. Chem. React. Eng. Catal.

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Today, hydrogen has become one of the most promising clean energy. Several processes allow obtaining hydrogen, among them there is the Water Gas Shift (WGS) reaction. On an industrial scale, WGS reaction takes place at high pressure [25–35 bar]. At high pressure, the cost of the process rises due to the energy consumed by compression, and the reduction in the lifetime of the equipment and the catalyst. At low pressures, catalyst lifetime can reach many years and the energy cost is reduced. It is for this reason that we are interested in modelling and simulation of a WGS converter operating at low pressures close to atmospheric pressure. In this work, a numerical study was conducted in order to determine the conditions allowing good rector operating at low pressure. A number of drawbacks of the process were identified. These drawbacks are essentially the non-negligible pressure drops and the strong intraparticle diffusion resistances. The prediction of the concentrations and the reaction rate within the pellet showed that the active zone of the pellet is located near the particle surface. It has also been shown that the resistances to interfacial mass and heat transfer are insignificant. The study of pressure effect showed that the pressure increase reduces the required catalyst mass to achieve equilibrium. Finally, this work revealed that the decrease in temperature and the increase in the concentrations of the reactants by increasing their fluxes, make it possible to increase the effectiveness factor of the catalyst and the conversion of carbon monoxide. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

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