Conversion efficiency, carbon

Carbon conversion efficiency is defined as the experimental number of moles of H2 produced per mole of carbon substrate consumed as a percentage of the theoretical maximum.129 Based on the organic acid substrate used, the theoretical maximum can be calculated according to the Eq. 7, assuming that all of the substrate is used for H2 production ... 

The influence of carbon conversion efficiency on the requirement of limestone for a fixed value of sulfur absorption efficiency is also computed. The generation of sulfur dioxide is found to be directly related to the amount of carbon combusted. 

The generation rate of sulfur dioxide reduces with the decrease in carbon conversion efficiency and hence the limestone requirement also decreases. A reduction in the carbon conversion efficiency from 99.5 to 70.0% causes a reduction in dolomite requirement from 27.5 to 18.9 g/s for a 99% sulfur absorption efficiency. 

Figure 1 illustrates the critical role played by step 2 in cellulose gasification. By increasing the temperature achieved by the gas phase volatile matter from 500°C to 750°C, the carbon conversion efficiency nc is increased from qc = 0.1 to nc = 0.76. 

The carbon conversion efficiency is emphasized here because (for non-oxidative conversion processes) nc provides an excellent measure of how well the energy and chemical content of the solid fuel feedstock is converted to gaseous fuels and chemicals. 

Figure 1. Cellulose carbon conversion efficiency rjC as a function of gas-phase residence time for various gas-phase temperatures...

Developmental goals considered to be necessary for acceptable performance include a turndown ratio of 3 1 or better, minimum burner-tip life of 2000 h, air preheating of less than 150°C (300°F), maximum droplet size of 300 rm, and carbon conversion efficiencies of greater than 99%. Small-scale tests suggest that these coals are achievable, but what is yet required is long-term demonstration in large electric-utility-size boilers in the 100-500 MW range. 

Energetically independent carbon conversion efficiency (CCE) in %. Serine pathway. 

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