With the concentration of CO₂in the atmosphere increasing beyond sustainable limits, much research is currently focused on developing solutions to mitigate this problem. Possible strategies involve sequestering the emitted CO₂for long-term storage deep underground, and conversion of CO₂into value-added products. Conventional processes for each of these solutions often have high-capital costs associated and kinetic limitations in different process steps. Additionally, CO₂is thermodynamically a very stable molecule and difficult to activate. Despite such challenges, a number of methods for CO₂capture and conversion have been investigated including absorption, photocatalysis, electrochemical and thermochemical methods. Conventional technologies employed in these processes often suffer from low selectivity and conversion, and lack energy efficiency. Therefore, suitable process intensification techniques based on equipment, material and process development strategies can play a key role at enabling the deployment of these processes. In this review paper, the cutting-edge intensification technologies being applied in CO₂capture and conversion are reported and discussed, with the main focus on the chemical conversion methods.

The spinning disc reactor (SDR) uses surface rotation to produce thin film flow with improved mixing and reduced residence times in chemical processing applications. Solvent-antisolvent precipitation is one such process that can benefit from these properties. This study investigates the film hydrodynamics and precipitation of starch nanoparticles by contacting starch dissolved in sodium hydroxide with ethanol as the antisolvent. One objective of this study is to understand how interactions of the disc surface topography (grooved and smooth) with other parameters such as liquid flowrate, antisolvent to solvent flow ratio and disc speed impact the mixing and precipitation processes. Results indicate that an increase in flow rate and rotational speed leads to smaller nano-particles and narrower size distributions, which is attributed to increased shear and instabilities within the liquid film. It was also observed that an increased antisolvent to solvent ratio caused a reduction in particle size, as increased antisolvent generated higher supersaturation. Results showed that although particle size was not significantly influenced by the disc texture, the size distribution was narrower and higher yields were obtained with the grooved disc surface. The grooved disc therefore offers the opportunity for higher throughput in the solvent-antisolvent precipitation of starch particles with better product quality.

The feasibility of performing an ortho-lithiation reaction in a T-reactor and a spinning disc reactor (SDR) at ambient temperature has been demonstrated and compared experimentally to a conventional batch stirred tank reactor (STR) process performed at a cryogenic temperature of −70 °C. The benefits of significantly improved mixing and much shorter residence times in the flow reactors eliminated the need for cryogenic cooling in batch processing which is a costly requirement. A theoretical evaluation of a scaled up process with a design product output of 3 tons per year highlights that significant process intensification is achievable in the flow reactors which demonstrate higher energy efficiency, better volume efficiency, smaller processing inventory, and smaller equipment footprint. For this reaction, the performance of the T-reactor is the best among the three reactors leading to much lower reactor investment and operating cost. The SDR was also demonstrated to be effective, even though this reaction did not take advantage of its inherent capabilities in solid handling or rapid heat removal through evaporation/gas disengagement, all of which present major challenges in enclosed channel geometries such as the T-reactor.

Despite abundant experimental work on intensification aspects of spinning disc reactors (SDRs), research on control characteristics of such novel devices are rather scarce. Control of SDRs may be challenging due to fast dynamics and high responsiveness of the system. However, the readily controllable rotational speed of the disc may offer an extra degree of freedom in control system design. In the present work, two test processes, namely, neutralization of HCl and NaOH and precipitation of barium sulfate, are chosen to investigate the control aspects of SDRs experimentally. The most commonly used controllers based on PI/PID algorithms implemented in LabVIEW, coupled with commercially available instrumentation, are employed to achieve the control objectives. The pH control of the neutralization process was successfully achieved using a PID controller which manipulated the flow rate of the base stream to the SDR. Addition of a disturbance observer scheme resulted in further enhancement of the control performance by suppressing the undesired effects of pH system nonlinearity. The conductivity control of the precipitation process was successfully achieved by manipulating the disc rotational speed, which presents a vastly appealing potential for adopting an innovative approach to process control for SDRs.

Cu nanoparticles are known to be very active for methanol (MeOH) synthesis at relatively low temperatures, such that smaller particle sizes yield better MeOH productivity. We aimed to control Cu nanoparticle (NP) size and size distribution for catalysing MeOH synthesis, by using the spinning disk reactor. The spinning disk reactor (SDR), which operates based on shear effect and plug flow in thin films, can be used to rapidly micro-mix reactants in order to control nucleation and particle growth for uniform particle size distribution. This could be achieved by varying both physical and chemical operation conditions in a precipitation reaction on the SDR. We have used the SDR for a Cu borohydride reduction to vary Cu NP size from 3 nm to about 55 nm. XRD and TEM characterization confirmed the presence of Cu₂O and Cu crystallites when the samples were dried. This technique is readily scalable for Cu NP production by processing continuously over a longer duration than the small-scale tests. However, separation of the nanoparticles from solution posed a challenge as the suspension hardly settled. The Cu NPs produced were tested to be active catalyst for MeOH synthesis at low temperature and MeOH productivity increased with decreasing particle size.