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Scale up of chemical reactors
Abstract
This review will not go into discussion on issue related to the market, nor will deal with the attitude of companies and management to promote innovation. We shall focus instead on the technical knowledge and on the tools that are necessary to change an invention into a true innovation.
... Furthermore, it is important to carefully consider whether scaling up is cost-effective because if the costs are too high compared to the volume of production, the advantages of continuous flow may be lost. [120,141,188,189] ...
The present work reviews the continuous‐flow hydrogenation of nitroaromatic compounds (NACs) to aromatic amines, highlighting its significance in sustainable chemical manufacturing. These processes offer enhanced efficiency, scalability, and safety compared to traditional batch methods, addressing the environmental concerns associated with NACs contamination. In this context, the flow‐mode processes of NACs hydrogenation may be considered as tools for catalytically driven extraction of fine chemical products. Within this review, key aspects, including an overview of flow reactor designs—such as packed‐bed and microreactors—optimizing heat and mass transfer are discussed. Additionally, various catalytic materials, including bimetallic nanoparticles and metal‐organic frameworks, are explored for their improved stability and selectivity in NACs reduction. The kinetics of these reactions aids in understanding the factors affecting reaction, and mass transfer rates. Despite the advantages, challenges remain, including catalyst deactivation and reactor design complexities, particularly during scale‐up for industrial applications. Future trends indicate a shift toward hybrid systems integrating photocatalysis and biocatalysis, enhancing the versatility of continuous‐flow processes. Ultimately, the adoption of these technologies is anticipated to play a crucial role in the circular economy by converting hazardous waste into valuable products, thereby fostering innovation and environmental preservation in the chemical industry.
... The transition to larger scales introduces greater complexity in the ALD chamber, which can potentially lead to nonideal film growth and impact the uniformity of films. [39][40][41] As the scale increases, the inherent limitations of CFD simulations become more apparent. It becomes increasingly important to pay careful attention to CFD simulations for ALD systems with nonideal growth. ...
Atomic layer deposition (ALD) can be used to fabricate protective coatings including moisture barrier layers for organic light emitting diodes, anticorrosion layers for photoelectrodes, and plasma-resistant coating for semiconductor manufacturing equipment, which necessitates the deposition of large and thick ALD films via batch ALD. However, batch ALD for the fabrication of large-area and thick coatings exhibits nonideal film growth, a phenomenon that cannot solely be explained by transient concentration distribution within the deposition chamber. This paper describes the application of precursor “exposure” (in the unit of Langmuir, or Pa s), defined as the integral of concentration over time, as a metric to assess the growth per cycle (GPC) distribution under nonideal ALD conditions, demonstrating that the local GPC correlates well with the cumulative precursor exposure at that site. Consequently, this measure can effectively predict the nonuniformity (NU) distribution of film thickness and facilitate the determination of optimal operating conditions that ensure maximal uniformity of exposure. Under this condition, the intrafilm NU of ALD-grown Al2O3 film (nominal thickness 300 nm) was reduced to 1.2%, and the interfilm NU is diminished to as low as 3.3%. These values represent reductions of 40% and 45%, respectively, compared to the NU levels observed under nonideal conditions (insufficient trimethylaluminum, TMA exposure downstream). The plasma etch rate of ALD-deposited films is merely 4.3 nm/min, representing a reduction of one-half compared to films deposited under nonideal conditions (9.8 nm/min) with overload TMA exposure downstream leading to chemical vapor deposition-like reactions.
The application of Direct Air Capture (DAC) for extracting CO 2 from the atmosphere has a great potential to reduce net CO 2 emissions and help achieve climate goals. Besides storing the...
A general programme for the solution of large sparse systems of non-linear equations is presented that allows to afford in a general way most computational problems in chemical engineering.Equipments and plants can, in fact, be represented as networks of “unit cells” to which material and energy balance equations are applied in finite form.The lay-out of the network and the assessment of the equations is a matter of the engineer's judgment and depends upon the aims of the computation and the complexity and importance of the phenomena involved.The solution of the equations then becomes a straightforward procedure that may be committed to the computer.Examples of application to a variety of chemical equipments and to process computation are given.
The description of the kinetics of the ammonia synthesis reaction has been deepened by means of a new model building technique. A number of kinetic models are offered as an alternative to these already proposed.
An easily applied method for predicting binary gas-phase diffusivities is based on the use of special diffusion volumes coupled with extensive experiment and nonlinear least squares analysis of the data. Comparison with eight other correlations demonstrates the relative reliability and simplicity of the new method.
The expression for the rate of formation of ammonia at pressures from 150 to 300 atm. derived here is the simplest available for a modern catalyst, is suitable for design, optimization, and control studies, and is believed to be as accurate as the most complex expressions in the composition, temperature, and pressure regions of commercial importance. The rate expression is based on the Temkin and Pyzhev expression corrected for high pressures and fitted to recently reported kinetic measurements of Nielsen, Kjaer, and Hansen for an industrially used catalyst. In addition, simple expressions permit rapid calculation of effectiveness factors for 6- to 10-mm. particles for the process conditions found in modern synthesis units.