# A Detailed One-Dimensional Hydrodynamic and Kinetic Model for Sorption Enhanced Gasification
## 3 Results and Discussion
### Validation with Experimental Data
#### 3.2.1 Effect of Gasification Temperature on Fractions of Syngas Components  
In Figure 7a-e, the simulated volume fractions of synthesis gas components (H\({}_{2}\), CO, CO\({}_{2}\), and CH\({}_{4}\)) and non-condensable hydrocarbons (in the form of C\({}_{2}\)H\({}_{4}\)) are plotted over a gasification temperature between 600-850 \({}^{\circ}\)C. For each synthesis gas component, the curves of three different make-up flows (0.2 kg/h, 6.6 kg/h, and 15 kg/h) are shown to demonstrate its influence on the gas  
Figure 6: Simulated temperature profiles of the gasifier for various \(\alpha\) (ranging from 0.8 to 0.98); \(\dot{M}_{BM,ref}\) = 29.7 kg/h, \(S\)/C = 2.2 mol/mol, \(WHSV\) (weight hourly space velocity) = 0.68 1/h, limestone make-up 6.6 kg/h, and comparison with experimental data from 200 kW dual fluidized bed (DFB) pilot plant [11].  
volume fraction. Additionally, experimental results derived from both 200 kW (Experiment 1) and 20 kW (Experiment 2) DFB systems are included to evaluate the simulated volume fractions.  
Figure 7: **(a–e)** Simulated syngas components: **(a)** H\({}_{2}\), **(b)** CO, **(c)** CO\({}_{2}\), **(d)** CH\({}_{4}\), and **(e)** C\({}_{2}\)H\({}_{4}\) for gasification temperatures in the range of 600–850 \({}^{\circ}\)C (lines for limestone make-up of 0.2, 6.6, and 15 kg/h); comparison with experimental results from 200 kW (Experiment 1) and 20 kW (Experiment 2) DFB systems (data points).  
For sorption enhanced gasification, one important characteristic is the strong dependency of the gas composition on the gasification temperature, which is affected by CO\({}_{2}\) capture through the carbonation reaction [19; 22]. Beside gasification reactions, the pyrolysis step also has an important impact on the initial gas composition in the fluidized bed [34]. The results from a 20 kW system were additionally included in the present work, as it enables operation temperatures up to 850 \({}^{\circ}\)C due to its electrical heating system. For low gasification temperatures, there is a larger distance between the actual CO\({}_{2}\) concentration and the equilibrium curve for the carbonation/calcination regime [37; 38]. This leads to a strong capture of CO\({}_{2}\) and, hence, low CO\({}_{2}\) concentrations in the syngas. With higher temperatures, the CO\({}_{2}\) capture rate decreases and, consequently, the CO\({}_{2}\) concentration in the syngas rises. Furthermore, this influences the water-gas shift reaction, resulting in decreased H\({}_{2}\) concentrations and increased CO concentrations. When the CO\({}_{2}\) concentration reaches the equilibrium concentration at around 750 \({}^{\circ}\)C, an inflection in the concentrations of CO\({}_{2}\) and H\({}_{2}\) can be observed. This demonstrates the strong coupling of the carbonation reaction with the water-gas shift reaction. Particularly for low gasification temperatures, there is also a distinctive influence of the make-up flow. Presumably, the reason for this effect is a reduced circulation mass flow of fresh CaO from the regenerator with a simultaneously higher CO\({}_{2}\) capture rate due to lower temperatures. For instance, at a gasification temperature of 600 \({}^{\circ}\)C, the delivered circulation mass flow is around ten times lower, compared to that when operating at 850 \({}^{\circ}\)C. This can lead to a higher content of carbonated particles if the bed inventory is hardly exchanged. In this operating range, an increase of the limestone make-up rate can increase the activity in the bed and, thus, the CO\({}_{2}\) capture rate.