Supplementary material for Chemical looping of synthetic ilmenite. Part I: Addressing challenges of kinetic TGA measurements with H2 [Dataset]
2. Experimental runs An exemplary for an entire isothermal experiment is given in Fig. 2. It shows the initial conditioning, consisting of ten redox cycles, followed by the actual experiment, consisting of seven isothermal plateaus. These isothermal plateaus each consist of four redox cylces employi...
| Autores: | , , , , , , , , |
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| Tipo de recurso: | conjunto de datos |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/357787 |
| Acceso en línea: | http://hdl.handle.net/10261/357787 |
| Access Level: | acceso abierto |
| Palabra clave: | TGA Kinetics Hydrogen http://metadata.un.org/sdg/7 Ensure access to affordable, reliable, sustainable and modern energy for all |
| Sumario: | 2. Experimental runs An exemplary for an entire isothermal experiment is given in Fig. 2. It shows the initial conditioning, consisting of ten redox cycles, followed by the actual experiment, consisting of seven isothermal plateaus. These isothermal plateaus each consist of four redox cylces employing the following H2 volume fractions: 50, 50, 30, 16.66 vol%. The 50 vol% run was repeated to possibly detect inconsistencies introduced through the preceding temperature change. Between reduction and oxidation or when changing from one temperature to another, the system was purged with nitrogen. 3. Reproducibility In order to reach the kinetic regime small sample masses (< 2 mg) and high gas flow rates (> 300 ml · min−1) were required. The reproducibility of the measurements was assessed at these conditions. All isothermal runs were repeated six times, all on different days using fresh solid samples and the same TGA programs. Fig. 3 shows the conversion rate dX/dt. for the individual runs during reduction at T = 900 ◦C. Even though, there were noticeable deviations between individual sets, the overall reproducibility of results was convenient. 4. Gas conversion The hydrogen conversion XH2 during the TGA experiments was estimated to ensure sufficient gas supply and negligible impact of steam produced. Low gas conversion signifies that enough gas was present and the atmosphere did not change significantly during the experiments. The mass balance ˙V | in · ci{nz· yH2,i}n n˙ H2,in − (m0 − m∞) MO · (dX/dt)max = ˙V| out · cou{tz· yH2,ou}t n˙ H2,out (1) was used calculate the molar flow n˙ H2,out of unreacted H2 leaving the reactor at maximum reactivity. This gives the highest possible gas conversion for a specific case, i.e. the worst case scenario for reaching the kinetic regime. The n˙ H2,out was used to calculate the conversion XH2 = n˙ H2,in − n˙ H2,out n˙ H2 in at different temperatures and H2 contents. The results are summarized in Table 1. As can be seen, the hydrogen conversion XH2 was low (< 2 %) for all cases, which means that neither gas starvation nor limitations due to steam generation should have played a significant role. 5. Isoconversional methods The additional plots for the isoconversional methods (i.e. evaluation of linear regression and R2) which were referenced in our main work are given in this section. Figure 4 shows the differential isoconversional method for one exemplary experiment with higher mass at 50 vol%H2. Except for the first point (X=0.1) a reasonably high R2 was again achieved. Figure 5 depicts the analysis of the nonisothermal reductions with the differential isoconversional method. Figure 6 shows the results for the integral isoconversional KAS method [1]. For both methods high R2 values were achieved.-- Under a Creative Commons license CC-BY 4.0 Deed. |
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