# Special Issue \"Thermochemical Conversion Processes for Solid Fuels and Renewable Energies\"
## 2 Special Issue Findings
At a higher inlet gas flow rate, the gas/liquid interfacial area was significantly decreased. A pressure increase leads to a decrease in the gas/liquid interfacial area and thus decreases the absorption rate of carbon dioxide. * The eighth paper resulted from the collaboration of two universities (Technical University of Darmstadt, Germany) and (Military Technical College, Egypt). The paper, authored by [PERSON]; [PERSON]; [PERSON], [PERSON]; [PERSON]; [PERSON], [PERSON] investigated the performance of an existing 135 MW integrated solar combined cycle (ISCC) power plant in Kureimat, Egypt [25]. The existing ISCC power plant that consists of a solar field and a solar steam generator integrated into a combined cycle power plant (CCPP) was thermodynamically studied under Kureimat climatic conditions using the concept of energy and exergy analyses. The overall thermal efficiency, the exergetic efficiency, and the exergy destruction of each component in the power plant were calculated at different ambient temperatures (5, 20, and 35 \({}^{\circ}\)C) and different solar heat inputs (0, 50, 75 MW). The results show that the solar field has the lowest exergetic efficiency, followed by the condenser. Furthermore, it was found that the thermal efficiency and the exergetic efficiency of the ISCC and the CCPP (when no solar field heat input is supplied) decrease with increasing the ambient temperature. * The authors ([PERSON]; [PERSON]; [PERSON]) from the Technical University of Darmstadt, Germany presented a combined experimental/numerical study on circulating fluidized bed boilers (CFBs) [26]. The ninth paper of this Special Issue contributes to close the knowledge gap for the operational flexibility of CFB. Corresponding to industrial standards, a long-term campaign on Polish lignite combustion during transient operation has been performed at a 1 MW\({}_{\text{th}}\) scale (see Figure 2). A load following sequence for fluctuating electricity generation/demand was reproduced experimentally by four load changes from 60% to 100% load and vice versa. Based on the design data obtained from the test facility, a core-annulus dynamic process simulation model was developed. The core-annulus model was tuned with experimental data of a steady-state test point and validated with the load cycling tests. The simulation results reproduce the key characteristics of CFB combustion with good accuracy. Further numerical results can also be found in [27]. Detailed measurement data were provided during the load change for the most important parameter in the system, such as the pressure and temperature profiles along the riser, the flue gas concentrations, and the solid compositions at different locations of the test facility. * The last paper of this Special Issue was published by [PERSON]; [PERSON]; [PERSON]; [PERSON], from the University of Stuttgart, Germany. In this work, a novel sorption enhanced gasification (SEG) in a dual fluidized bed gasification system was presented [28]. The SEG system is considered a promising and flexible method for the tailored syngas production to be used in chemical manufacturing or power generation (see Figure 3). A simulation model was developed, describing the hydrodynamics in a bubbling fluidized bed gasifier and the kinetics of gasification reactions and CO\({}_{2}\) capture (defined by the number of carbonation/calcination cycles and the make-up of fresh limestone). Experimental data of a 200 kW pilot plant were applied to model validation. The authors claimed that the developed model can successfully predict the performance of the pilot plant at different operation conditions. With the help of the validated model, different operational parameters such as gasification temperature, steam-to-carbon ratio, solid inventory, and fuel mass flow were investigated.