Microwave-Only Heating Concepts for Industrial CO₂ Regeneration System Design

Abstract

This study presents various microwave reactor designs specifically engineered for continuous microwave CO₂ desorption, marking a significant advancement in microwave-heating systems. This study explored both horizontal and vertical continuous microwave reactor configurations. The horizontal design incorporates a modified conveyor belt system with cleated belts and Teflon sidewalls, rendering it particularly suitable for the regeneration of gas. Conversely, the vertical design utilizes a cascade gate opening mechanism, facilitating precise control over the microwave intensity and exposure duration. The efficiency of microwave power utilization was enhanced through the numerical modeling and optimization of the reactor dimensions. This study assessed the impact of waveguide placement, cavity size, and sorbent material thickness on power absorption and heating. The findings indicate that strategic waveguide positioning and optimal cavity dimensions significantly influence the microwave energy distribution and absorption, leading to reduced hotspots and more uniform heating. This study offers valuable insights into the design and optimization of microwave reactors for CO₂ desorption, contributing to more efficient and effective commercial applications of this technology. These results underscore the potential of microwave technology to revolutionize desorption processes and pave the way for further advancements in this domain. Design 2 exhibited more uniform heating owing to its slower and controlled temperature increase, making it more suitable for applications requiring consistent thermal performance over extended periods.

1. Introduction

Microwave heating is a method that employs microwave radiation to induce heat in a material. This thermal energy is generated through the interaction of microwaves with the molecules of the substance, particularly through molecular rotation and frictional resistance to ion movement [1]. Microwave heating is notably efficient and has extensive applications in various domains. For instance, microwaves are extensively used in the food industry for uniform cooking and reheating [2]. Industrial conveyor belt microwave systems have been applied in diverse industrial contexts, including food processing, drying, and wood processing [3,4,5,6,7,8,9,10]. Microwave-dried specimens exhibit a more organized microstructure owing to uniform energy absorption and heat and moisture distribution [11,12,13,14]. Carbon dioxide (CO₂) significantly contributes to global warming and climate change. Efforts are underway to identify effective methods for CO₂ desorption, and microwave heating has emerged as a promising strategy. Researchers aim to enhance the regeneration efficiency of CO₂ from sorbent materials through microwave heating, thereby providing a more environmentally sustainable approach for mitigating the carbon dioxide emissions. Microwave heating has consistently demonstrated a substantial increase in the rate of CO₂ desorption from various materials, including microporous activated carbon, zeolite 13X, and metal-organic framework/graphene oxide composites [15,16,17,18]. Experimental investigations have assessed the feasibility of microwave regeneration of two commercial adsorbents within a dynamic carbon capture swing adsorption system [15]. Microwave-assisted regeneration surpasses conventional methods in terms of CO₂ purity, recovery, and productivity [15]. Microwave heating of chemisorbents facilitates CO₂ desorption under near-isothermal conditions at ambient temperature, with the desorption rate increasing with increasing microwave power [16]. The reduced activation energy associated with microwave-accelerated sorbent regeneration enhances the CO₂ desorption kinetics through microwave-induced rotational-vibrational coupling transitions [16]. The optimal dimensions for a continuous flow radial desorption bed were determined via numerical analysis [19]. A prototype designed with these optimal dimensions was developed to desorb CO₂ from a commercially available amine sorbent in both fixed-bed and moving-bed configurations, demonstrating the concept and evaluating the performance parameters [19]. Compared to conventional hybrid temperature vacuum swing adsorption (TVSA), the energy consumption remains comparable, whereas the productivity is significantly enhanced [19]. However, this design was only prototype with only one waveguide. Gyoung et al. [20] introduced the concept of employing the current large-scale, continuous microwave dryer for regeneration at 915 MHz using a conveyor belt. Nevertheless, this concept is predicated on existing industrial microwave dryers, which are primarily designed for food and wood processing and are not inherently suitable for CO₂ regeneration applications. In their present configuration, the desorbed CO₂ is merely released back into the environment rather than being captured, rendering them incompatible with carbon-capture applications without significant redesigning. Microwave heating has been extensively studied for sorbent synthesis, desorption processes, and adsorption heat pumps, offering advantages such as rapid and selective heating and energy efficiency across various applications [21,22,23,24,25,26]. Continuous microwave systems are commonly used for food processing and drying. However, no current design has been specifically developed for microwave-assisted CO₂ regeneration on an industrial scale. This study introduces innovative reactor designs for continuous microwave-assisted regeneration. Numerical modeling was employed to optimize the dimensions and waveguide positions to enhance the heating uniformity and power utilization efficiency. The numerical analysis provides guidelines for designing continuous microwave reactors specialized in CO₂ desorption, addressing a significant gap in the design of microwave heating systems for this application. The improved design has the potential to enhance performance and energy efficiency.

2. The Microwave-Assisted Regeneration Reactor Designs

In this study, two distinct microwave desorption reactors were introduced. The proposed reactor designs aim to leverage the unique heating characteristics of microwave radiation to enhance the desorption process, thereby improving its efficiency and its selectivity. The two proposed microwave desorption reactor designs incorporate the essential components of a microwave system, including a microwave cavity, rectangular waveguide, high-powered magnetron serving as the microwave generator, rotary vane vacuum pump for gas evacuation, and infrared thermometers for temperature monitoring. These critical elements are intentionally integrated to exploit the unique properties of microwave radiation, facilitating the desorption process and enabling precise control and analysis of the system performance. Multiple portable infrared thermometers continuously monitored the temperature distribution across the sorbent pellet bed at various locations, providing real-time data on the bed temperature. A programmable logic controller recorded and displayed the data on a human-machine interface screen to assist in performance optimization. The proposed designs permit the sequential cycling of several adsorption reactors, which supply sorbents to a single desorption unit. Given the discrepancy between the brief microwave desorption duration and the longer adsorption cycle times, the regenerated sorbent pellets may be adsorbed in one reactor and desorbed in another reactor. Consequently, the device can concurrently serve multiple adsorption reactors in parallel using a single microwave cavity. This cascaded structure with interchangeable sorbent pellets facilitates continuous operation and separation, overcoming the limitations of conventional paired adsorption-desorption systems. Therefore, the proposed design offers enhanced productivity and efficiency.

2.1. The Cleated Conveyor Belt Reactor

Horizontal conveyor belt microwave systems have been previously employed in various industrial heating applications, such as wood processing [8] and drying [13,27]. However, the design presented in this study incorporates a distinctive modification specifically tailored for gas desorption. Figure 1 illustrates a schematic of the continuous horizontal microwave desorption reactor used in this study. The horizontal belt microwave system was adapted to accommodate the gas desorption process by replacing the standard conveyor belt with a cleated belt, thereby creating trays suitable for handling the sorbent pellets. The trays were enclosed within fixed Teflon sidewalls. This strategic reconfiguration facilitates consistent and effective gas desorption from the sorbent pellets, enhancing the system performance while preserving the integrity of the desorption operation. The Teflon covers were perforated with small holes to permit the escape of carbon dioxide. The sequential operating process is delineated as follows:

• The sorbent pellets are deposited onto the tray on the belt through the feeding opening.
• A variable frequency motor subsequently activates the cleated conveyor belt, advancing the trays into the microwave cavity at a meticulously regulated speed, determined by the duration required for carbon dioxide to be desorbed from the sorbent pellets.
• At the top of the microwave cavity, a specified number of magnetrons generate microwave radiation at a frequency of 2450 MHz; the multi-port design ensures uniform microwave heating patterns, thereby facilitating effective desorption.
• Under microwave irradiation, the sorbent rapidly heats up, releasing the CO₂. Temperature feedback control utilizing infrared sensors modulates the forward power of the system.
• A rotary vane vacuum pump employs a negative pressure gradient to swiftly evacuate the desorbed gas via the outlet port.
• Following the desorption process, the sorbent pellets are conveyed to a collection container at the end of the belt.

Figure 1. Horizontal cleated conveyor belt continuous microwave reactor.

Figure 1. Horizontal cleated conveyor belt continuous microwave reactor.

2.2. Cascade Gate Opening System

The installation of belts equipped with bearings and rotating shafts facilitated the continuous movement of trays containing sorbent pellets. However, this belt assembly requires substantial power for rotation, which increases the overall weight of the system. The implementation of a cascade gate opening system driven by an integrated linker mechanism addresses the limitations of the cleated conveyor belt design. Controlled exposure of the material to the microwave radiation field within the desorption reactor was achieved by incorporating cascade gate apertures. These sequential gate openings allow for the precise modulation of the microwave intensity and exposure duration, thereby optimizing the desorption kinetics and efficiency. Figure 2 illustrates the cascade gate opening of the vertical microwave reactor. The cascade gate system employs a sequential operating mechanism to manage the transfer and exposure of the sorbent material to the microwave desorption reactor. The process is initiated by opening the bottom gate, which facilitates the removal of the desorbed sorbent from the preceding trays. Subsequently, the gate above is closed, permitting the transfer of the sorbent material to the next tray. This procedure was repeated for each gate, culminating at the top gate. The duration of each phase was meticulously calculated based on the required desorption time, ensuring optimal exposure and effective removal of the target gas species from the sorbent pellets.

3. Numerical Method

3.1. Governing Equations

COMSOL Multiphysics 6.1 is a robust simulation tool designed to address problems involving coupled physical phenomena in scientific and engineering contexts. This numerical study employed COMSOL Multiphysics software to compute the interaction between electromagnetic and heat transfer physics. The software utilizes the finite element method (FEM) to resolve the electromagnetic heating problem [28]. Maxwell’s equations were employed to describe the electromagnetic field distribution within the sorbent bed, microwave cavity, and waveguide [29].

$$\begin{array}{cc}\hfill \nabla \times \mathbf{H}& =\mathbf{J}+{\displaystyle \frac{\partial \mathbf{D}}{\partial t}}\hfill \end{array}$$

(1)

$$\begin{array}{cc}\hfill \nabla \times \mathbf{E}& =-{\displaystyle \frac{\partial \mathbf{B}}{\partial t}}\hfill \end{array}$$

(2)

$$\begin{array}{cc}\hfill \nabla ·\mathbf{B}& =0\hfill \end{array}$$

(3)

$$\begin{array}{cc}\hfill \nabla ·\mathbf{D}& ={\rho }_e\hfill \end{array}$$

(4)

where $\mathbf{H}$ is the magnetic field intensity, $\mathbf{E}$ is the electric field strength, $\mathbf{B}$ is the magnetic induction intensity, $\mathbf{D}$ is the electric displacement vector, $\mathbf{J}$ is the ampere density, t is the time, and ${\rho }_e$ is electric charge density.

The constitutive equations governing the interaction between the material and electromagnetic waves in an electromagnetic field are as follows [29]:

$$\begin{array}{cc}\hfill \mathbf{D}& ={\epsilon }_0{\epsilon }_r·\mathbf{E}\hfill \end{array}$$

(5)

$$\begin{array}{cc}\hfill \mathbf{B}& ={\mu }_0{\mu }_r·\mathbf{H}\hfill \end{array}$$

(6)

$$\begin{array}{cc}\hfill \mathbf{J}& =\sigma ·\mathbf{E}\hfill \end{array}$$

(7)

where ${\epsilon }_0$ is the free space permittivity ($8.854\times {10}^{-12}$ V/m), ${\mu }_0$ is the free space permeability ($4\pi \times {10}^{-7}$ H/m), ${\epsilon }_r$ is the material relative permittivity, ${\mu }_r$ is the material relative permeability, and $\sigma$ is the material electrical conductivity.

Thus, Maxwell’s equations for the electric field can be derived and written as [30]:

$$\nabla \times {\displaystyle \frac{1}{{\mu }_r}}(\nabla \times \mathbf{E})-k_0^2\left({\epsilon }_r-j{\displaystyle \frac{\sigma }{\omega {\epsilon }_0}}\right)\mathbf{E}=0$$

(8)

$$k_0=\omega \sqrt{{\epsilon }_0{\mu }_0}$$

(9)

$$\omega =2\pi f$$

(10)

where $\omega$ is the angular frequency, f is the frequency, and $k_0$ is the wave number in free space.

The material permittivity can be expressed as [31]:

$$\epsilon ={\epsilon }_0{\epsilon }_r={\epsilon }^{\prime }-j{\epsilon }^{\prime \prime }$$

(11)

where ${\epsilon }^{\prime }$ is the dielectric constant, which is a measure of a material’s capacity to be polarized by an external electric field and store energy inside it, and ${\epsilon }^{\prime \prime }$ is the dielectric loss factor, which measures the capacity of the material to disperse absorbed electromagnetic energy and convert it into heat [32].

The materials used were non-magnetic and had a relative permeability of approximately 1. The penetration depth is a characteristic length that reflects the progressive absorption of microwave energy by the material. At this depth, incident microwaves lose approximately 37% of their initial power at the surface [32]. The penetration depth of non-magnetic materials can be expressed as [32]

$$\begin{array}{cc}\hfill D_p& ={\displaystyle \frac{c}{2\sqrt{2}\pi f{[\sqrt{{\left({\epsilon }_r^{\prime }\right)}^2+{\left({\epsilon }_r^{\prime \prime }\right)}^2}-{\epsilon }_r^{\prime }]}^{1/2}}}\hfill \end{array}$$

(12)

$$\begin{array}{cc}c\hfill & ={\displaystyle \frac{1}{\sqrt{{\epsilon }_0{\mu }_0}}}={\lambda }_{0}f\hfill \end{array}$$

(13)

where c is the speed of light, and ${\lambda }_0$ is the electromagnetic wavelength in vacuum.

The wavelength of electromagnetic wave propagation within the material (${\lambda }_m$) can be expressed as [31]:

$${\lambda }_m={\displaystyle \frac{c\sqrt{2}}{f{[\sqrt{{\left({\epsilon }_r^{\prime }\right)}^2+{\left({\epsilon }_r^{\prime \prime }\right)}^2}+{\epsilon }_r^{\prime }]}^{1/2}}}$$

(14)

The propagation constant of the material (${\kappa }_m$) [33]:

$${\kappa }_m=\alpha +j\beta ={\displaystyle \frac{2\pi f}{c}}\sqrt{{\epsilon }_r^{\prime }-j{\epsilon }_r^{\prime \prime }}$$

(15)

The real part ($\alpha$) is the attenuation constant, which indicates the decrease in wave amplitude as it passes through a material. The imaginary part ($\beta$), known as the phase constant, characterizes the progression of the wave [33].

The Landau–Lifshitz–Looyenga equation is a simple equation that can be used to calculate the effective permittivity of porous materials [34].

$${\epsilon }_{ff}={(v_s{\epsilon }_s^{1/3}+v_f{\epsilon }_f^{1/3})}^3$$

(16)

where $v_s$ is the solid volume fraction, and $v_f$ is the fluid volume fraction (porosity).

The following equation calculates the total volumetric power produced by the microwave [35]:

$$Q_e={\displaystyle \frac{1}{2}}\omega {\epsilon }_0{\epsilon }_r^{\prime \prime }{\left|\mathbf{E}\right|}^2$$

(17)

The heat transfer equation was used to calculate the temperature distribution [28] as follows:

$${\left(\rho C_p\right)}_{eq}{\displaystyle \frac{\delta T}{\delta t}}-\nabla ·(k_{eq}\nabla T)=Q_e$$

(18)

where T is the temperature, ${\left(\rho C_p\right)}_{eq}$ is the equivalent volumetric heat capacity, $Q_e$ is the microwave heat source, and $k_{eq}$ the equivalent thermal conductivity.

The equivalent volumetric heat capacity can be calculated as [28]:

$$k_{eq}=v_s{k}_s+v_f{k}_f$$

(19)

The equivalent thermal conductivity can be calculated as [28]:

$${\left(\rho C_p\right)}_{eq}=v_s{\left(\rho C_p\right)}_s+v_f{\left(\rho C_p\right)}_f$$

(20)

The microwave energy utilization efficiency can be expressed as:

$$\eta ={\displaystyle \frac{P_{abs}}{P_{in}}}$$

(21)

where $P_{abs}$ is the absorbed power, and $P_{in}$ is the forward power.

3.2. Assumptions

Throughout the model’s development, several assumptions were made to simplify the process and reduce computational time.

• Thermal properties and permittivity were assumed to be independent of temperature.
• The Teflon covering the catalyst bed within the microwave was considered fully transparent to microwaves.
• The walls of the wave cavity and waveguide were treated as perfect electrical conductors.
• Given the low movement speed of the conveyor belt, it was assumed that there is no relative motion between the sorbent pellets layer and the belt.
• Due to Teflon’s significantly lower permittivity compared to the sorbent materials, heat transfer for Teflon was not considered.
• The simulation focused solely on the sensible heating of the sorbent materials to optimize dimensions and maximize the power absorbed by the sorbent material.

3.3. Boundary Conditions

3.3.1. Electromagnetic Boundary Conditions

The cutoff frequency $f_c$ of a rectangular waveguide with $T_{mn}$ mode of propagation, width a, and height b can be calculated as [32]:

$$f_c={\displaystyle \frac{c}{2}}\sqrt{{\left({\displaystyle \frac{m}{a}}\right)}^2+{\left({\displaystyle \frac{n}{b}}\right)}^2}$$

(22)

The operating frequency f should be between $1.25f_c$ and $1.89f_c$ [32].

The rectangular waveguide input port supplies the microwave energy to the cavity with a 2.45 GHz operating frequency and $T_{10}$ propagation mode.

The impedance boundary conditions used to define the cavity and waveguide walls are described as follows [28]:

$$\sqrt{{\displaystyle \frac{{\mu }_0{\mu }_r}{{\epsilon }_0{\epsilon }_r-j\left(\frac{\sigma }{\omega }\right)}}}\mathbf{n}\times \mathbf{H}+\mathbf{E}-(\mathbf{n}·\mathbf{E})\mathbf{n}=(\mathbf{n}·{\mathbf{E}}_s)\mathbf{n}-{\mathbf{E}}_s$$

(23)

3.3.2. Heat Transfer

The thermal insulation boundary condition was used to define the material boundaries, which can be described as follows [28]:

$$-\mathbf{n}·(-k\nabla T)=0$$

(24)

3.4. Mesh Size

A mesh independence study was performed using microwave energy use efficiency to ascertain the optimal mesh sizes for the proposed model (see Figure 3). When the value of $\eta$ remained unchanged with finer mesh sizes, it could be inferred that convergence was achieved and that the results obtained with that mesh size were accurate.

4. Results

4.1. The Effect of Microwave Dimensions and Waveguides Position

The simulation model consists of three components: a cavity functioning as a heating oven, a waveguide for the delivery of microwave power, and the sorbent material. The construction of the model is depicted in Figure 4. In this study, the waveguide is characterized by a rectangular cross-section and operates in the $T_{10}$ propagation mode at a frequency of 2.45 GHz, with an input power of 1 kW per input port.

The influence of waveguide positioning on the microwave power efficiency is depicted in Figure 5. The waveguide transmits electromagnetic waves into the microwave cavity. Within the cavity, an electromagnetic field is generated by the superposition of the initial electromagnetic wave and the wave reflected by the cavity walls and sample surfaces. The position of the waveguide determines the entry point of the microwaves into the cavity, thereby influencing the field distribution and standing wave patterns. This can result in regions of high and low electric field intensities within the cavity, consequently altering the power absorption characteristics of the sample. Typically, the sample is positioned in an area with the maximum electric-field intensity to ensure efficient power absorption. Deepshikha and Phadungsak underscore the necessity of optimal waveguide placement to enhance power efficiency [36]. Figure 5 demonstrates that the strategic placement of the waveguide relative to the sample is crucial for maximizing power absorption and achieving effective heating in a microwave cavity, with SPH and SPV values of 0.15 and 0.0875, respectively. The electric field distributions exhibit significant variations contingent on the waveguide location [37].

The multi-mode cavity is characterized by dimensions exceeding the wavelength, resulting in electromagnetic wave propagation in various directions within the cavity, leading to multiple maxima and minima in the electric field intensities. This phenomenon causes an uneven distribution of the electric field strength within the material layer, manifesting as regions of high and low intensity. The microwave cavity functions as a resonator, implying that its frequency and standing-wave patterns are determined by its dimensions. Figure 6 illustrates the impact of the microwave cavity width and depth on the efficiency of microwave power utilization. The depth and width of the microwave cavity are crucial for determining the power absorbed by the sample in a microwave heating system. As reported by Walker [38], the distribution of the electric field within a microwave cavity varies with changes in its dimensions. As depicted in Figure 6, the optimal width and depth of the microwave cavity for maximizing power absorption and achieving effective heating are when the ratios of cavity depth to electromagnetic wave wavelength and cavity width to electromagnetic wave wavelength are 4.41 and 4.57, respectively, which approximate $\left(n{\lambda }_0\right)/2$, where n is an integer.

Controlling the processing of small loads within large cavities presents challenges owing to impedance mismatch. The limited penetration depth of microwaves results in slower heat transfer, necessitating the determination of the optimal reactor size prior to microwave heating [39,40]. Figure 7 demonstrates the impact of the microwave cavity height and sorbent material thickness on the microwave power utilization efficiency. Research indicates that variations in the material height within the microwave cavity affect the power absorbed by the sample, energy absorption efficiency, and temperature distribution [41]. The height of the microwave cavity influences the energy absorbed by the sample during the microwave heating. The cavity was designed to generate a standing wave pattern, with the cavity height playing a crucial role in determining the distribution and intensity of the electric field. Samples located in regions of high electric-field intensity absorb more energy than those in low-intensity regions. As depicted in Figure 7, the optimal cavity height for maximizing power absorption occurs when the ratio of cavity height to wave wavelength is 24.92, approximately $\left(n{\lambda }_0\right)/2$, where (n) is an integer. Another study highlighted the significance of wave interaction within food as a function of the thickness of food slabs irradiated on both sides, demonstrating that the power per volume unit at the food center is proportional to food thickness [42]. The power absorbed by a sample in a microwave cavity varies with the chamber thickness owing to the penetration depth of microwave radiation and the interaction between the sample and the electric field distribution within the cavity. As illustrated in Figure 7, the optimal thickness of the microwave cavity for maximizing the power absorption is 26 mm.

4.2. The Microwave Heating of the Optimized Microwave Designs

This study assessed the thermal behaviors of the two distinct microwave designs, as depicted in Figure 8. An optimization study was conducted for each design to enhance the microwave power absorption of the sorbent, while minimizing the hotspot effect. The electric field strength and power dissipation density were determined by solving Maxwell’s equations using an electromagnetic wave frequency domain module. Fourier’s equations were solved using the solids module heat transfer to calculate the temperature distribution. COMSOL Multiphysics and MATLAB R2023a programming were integrated to model material movement. The sorbent pellets were introduced into the first tray and heated for a specific duration. Subsequently, they were transferred to the subsequent trays through the reactor until they reached the final tray. This sequential movement facilitates regulated and staged heating throughout the equipment, as shown in Figure 9. The final average temperature from the preceding step was used as the initial temperature for the subsequent step. Following the desorption process simulation of the sorbent pellets at various trays along the reactor, all individual solutions at different trays were integrated to obtain the total simulation results. The heterogeneous temperature distribution can be improved by adjusting the electrical field configuration by moving the product through the cavity. This adjustment causes the microwave radiation from the waveguide to form high- and low-energy zones. By absorbing microwave energy, the sorbent pellets alter the electric field upon their introduction [43].

The average temperature over time for the two designs is shown in Figure 10a. The growth rates of the designs differed significantly. Design one demonstrated a rapid increase in temperature in the initial trays, whereas design two exhibited a more gradual and consistent increase. This variation is primarily attributed to the distinct power absorption characteristics of each design, as shown in Figure 10b. Two heating processes were designed to be slow and steady, maintaining consistent thermal performance. Consequently, this design is more suitable for applications that require sustained thermal stability over an extended period.

The distributions of the electrical field intensity and temperature within the heating materials for both designs are depicted in Figure 11 and Figure 12, respectively. The absorption of microwave energy within the sorbent pellets governs the variations in temperature and CO₂ concentration during desorption, which are influenced by the electric field strength and dielectric properties of the sorbent pellets. The movement of the sorbent pellets across different trays induced dynamic interactions between the microwaves and materials, potentially mitigating excessive microwave radiation heating within the same hot/cloud spots during the heating period. The reflection from the cavity walls and sorbent pellets generated multimode resonance in the microwave cavity, which may alleviate the non-uniform distribution of the electromagnetic field within the sorbent pellets. The temperature of the sorbent progressively increased over time during desorption. The temperature distribution exhibited spatial variations throughout the tray, indicating a heterogeneous electrical field distribution along the reactor. The thermal extrema (hot and cold spots) varied between trays, diminishing their cumulative effect as the sorbent pellets moved sequentially at each time step. This dynamic approach facilitates more consistent heat exposure of sorbent materials.

5. Conclusions

This study presents various microwave reactor designs specifically engineered for continuous microwave CO₂ desorption, marking a significant advancement in microwave heating systems. This study aims to address these existing gaps by proposing innovative methods for optimizing reactor size and configuration. It introduces novel reactor designs that leverage the unique heating properties of microwave radiation to enhance the efficiency and selectivity of desorption. This optimization is crucial because it facilitates a more targeted approach to CO₂ removal, achieving the desired outcomes with minimal energy expenditure. The proposed designs seek to improve the performance and energy efficiency compared to standard desorption techniques. The reactors are designed for continuous operation by cycling sorbent pellets through multiple adsorption reactors into a single desorption unit, thereby overcoming the limitations of conventional paired adsorption-desorption systems and resulting in increased production and efficiency. This study also explored horizontal and vertical continuous microwave reactor concepts. Horizontal designs incorporate a modified conveyor belt system with cleated belts and Teflon sidewalls, making them ideal for the regeneration of gas. The vertical design utilizes a cascade gate opening mechanism, allowing for precise control of the microwave strength and exposure duration, thereby maximizing the desorption kinetics and efficiency. The efficiency of microwave power utilization has been enhanced through numerical modeling and reactor-dimension optimization studies. This study examined the impact of waveguide placement, cavity size, and sorbent material thickness on power absorption and heating, concluding that strategic waveguide positioning and optimal cavity dimensions significantly affect microwave energy distribution and absorption, leading to fewer hotspots and more uniform heating. This study offers valuable insights into the design and optimization of microwave reactors for CO₂ desorption, paving the way for more efficient and effective commercial applications. These findings underscore the potential of microwave technology to revolutionize desorption processes and facilitate further advancements in this domain. Design 2 demonstrated more uniform heating owing to its slower and controlled temperature increase, potentially making it more suitable for applications requiring consistent thermal performance over extended periods. Nevertheless, these designs necessitate further experimental and simulation efforts, including the investigation of CO2 deposition kinetics (mass transfer) and examination of permeability as a function of temperature. Additionally, further research is essential to ascertain the optimal speed of conveyor belts and the timing for the opening and closing of gates to improve disposition performance. This study offers a framework for employing and refining these designs for industrial-scale applications.