Temperature gasification

Characteristics of moving-bed gasifiers are low gasification temperatures, relatively low oxygen requirements, relatively high methane content in... 

A potential source of particulates is char formed when the biomass feedstock is incompletely gasified. These particles undergo devolatilization and subsequent reactions at gasification temperatures that leave them less reactive than fresh biomass feedstock. They can pass through the gasifier before they are completely gasified, particularly in those configurations with turbulent beds. Char entrained in the product gas also represents unconverted biomass that contributes to lower conversion efficiencies. 

The percentage of hydrogen in gaseous products from the samples of hazelnut shell, tea waste and spruce wood increased from 43.3 to 56.9%, 41.0 to 53.9% and 40.0 to 51.5% by volume, respectively, while the final air-steam gasification temperature was increased from 900 to 1250 K (Figs. 6.14 to 6.16). 

When metal oxide particles are used as oxidizers, metal particles are used as fuel components. Since the melting point and gasification temperatures of metal oxide particles are very high, the oxidation reaction only occurs when the metal particles... 

Figure 6 shows the exergetic efficiency as a function of pressure at various gasification temperatures. In the case of alternative I (waste heat boiler), the efficiency is independent of... 

Figure 4. Exergy after waste heat recovery (I) and quench (II) for different gasification temperature (H O/coal =...

Once the char sample is introduced into the PTGA, it is first dried in N during 10 min at 200 °C. then is heated at 24 °C/min to 1000 C and held at this temperature for 30 min. After this the sample is cooled to the gasification temperature and when conditions are stable, the steam is allowed into the reaction chamber. The sample is hold isothermal until the gasification reaction is complete and then the temperature is raised to 1000 °C to complete the reaction. The sample size is ca. 10 mg and the gas flow lOOOml/min. 

Once pyrolysed, the char was sieved to 32-45 ttm. This particle size was found to avoid heat transfer limitations. Based on previous research on the same equipme t a sample of about 5 mg and a gas flow of 200 ml/min during gasification were used for all experiments. The char sample was first dried in (99,999%) at 110 °C for 30 min, then heated up at 30 C/min to 1000 °C, kept at 1000 "C for 20 minutes and then brought to the gasification temperature of the experiment. After 10 minutes for... 

The slope and shape of the reactivity profile depends to a certain extent on the gasification temperature. This trend has been observed in all the experiments, both with and without CO addition. However, the differences between reactivity profiles at the same temperature are relatively large and therefore do not suggest any further conclusion. 

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