## 4 Conclusions  
This study successfully developed and validated a laboratory-scale pilot system based on a dry fixed-bed reactor for FGD experiments under mild conditions (75/160 \({}^{\circ}\)C and 30/45 RH%). The system was systematically monitored using a custom-designed data acquisition system and mass-flow controllers. COMSOL Multiphysics software provided valuable insights into the reactor's internal temperature distribution and air-flow operational dynamics. Two materials, portlandite and 13X zeolite, were used to validate the system. The breakthrough sulfur capacity of PC was consistent with the existing literature. Furthermore, the breakthrough curves indicated that an increase in temperature had a more pronounced favorable effect on PC absorption than an increase in relative humidity. It can be reasonably assumed that at a temperature of 160 \({}^{\circ}\)C, the PC catalytic activity in relation to SO\({}_{2}\) chemisorption will increase. 13X zeolite exhibited a superior breakthrough sulfur capacity to PC, due to its microporosity, large surface area, and high catalytic activity. XRPD analyses revealed that 13X underwent structural changes upon interaction with H\({}_{2}\)O and SO\({}_{2}\), highlighting its potential for efficient sulfur capture. Notably, the breakthrough sulfur capacity of 13X zeolite was higher at 30%RH, suggesting the complex role of water in facilitating or hindering sulfur adsorption. The results underscore the potential of dry fixed-bed FGD systems, particularly in applications where sulfur capture from fine gases is critical, as in the petrochemical industry. These systems offer significant advantages, including high efficiency, scalability, and operational flexibility under varying environmental conditions. Future research should focus on optimizing material properties, system design, and operating conditions to further enhance sulfur capture efficiency and develop robust solutions for large-scale industrial applications, including the petrochemical sector. Continued exploration of the interaction between temperature, humidity, and adsorbent materials will be essential to fine-tune performance and ensure sustainable, cost-effective sulfur removal. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app142311364/s1](https://www.mdpi.com/article/10.3390/app142311364/s1)]([https://www.mdpi.com/article/10.3390/app142311364/s1](https://www.mdpi.com/article/10.3390/app142311364/s1)), Figure S1: (a) Three-dimensional model representation of the reactor design with the main components described. (b) Picture of the reactor and accessories used for the fixed-bed FGD process; Figure S2: Photo of the DaQ system, consisting of a single custom-made circuit which allows readings up to 8 TC-K, two air humidity/temperature sensors (model: SHIT75, produced by Sensirion), and one air humidity/temperature sensor (model: AHT25, produced by Asaij); Figure S3: Three-dimensional model representation of the reactor, with red circles indicating the TC-K positions. The numbers correspond to the ones mentioned in Table S1; Table S1: Temperature values measured by the TCs-K in positions 1-5 represented in Figure S3; Table S2: Experimental conditions and labels. The values in the \"Temperature\" column refer to the temperature of the adsorbent during FGD experiments, which correspond to position 5 in Table S1; Figure S4: Reactor geometry reproduced using the geometry drawing tool in Comsol. The orange disk inside the reactor represents the porous material made of portlandite and air with 30% porosity; Figure S5: Representative chromatogram showing the retention times of O\({}_{2}\), SO\({}_{2}\), and H\({}_{2}\)O. N\({}_{2}\) is not detected by the TCD. The synthetic flue gas was used with a SO\({}_{2}\) composition of 600 ppm in a complement of air.