A Koppers-Totzek reactor (there seems to be only a German Wikipedia page) is an entrained flow gasifier that blows coal dust, oxygen and water (as steam, of course) into a burning chamber where the coal burns at about 1600 °C. The output contains around 60% $\ce{CO}$ and 33% $\ce{H2}$, plus some $\ce{CO2}$ and (very little) $\ce{CH4}$.

When burning coal, I would expect $\ce{CO2}$ and $\ce{H2O}$ as output, is the reactor simply providing too little oxygen, or is there something about the process that produces the output observed?

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    $\begingroup$ I believe the question may apply equally to other gasification processes. $\endgroup$ – Hanno Fietz Nov 13 '12 at 13:18

The reaction occurs in two stages: in first $\ce{C}$ oxidized to $\ce{CO2}$ and then $\ce{CO2}$ is reduced to $\ce{CO}$.

The process of having carbon react with oxygen and water vapor is called steam-oxygen conversion. It is used, because in reality, due to the high reaction temperatures, the allothermic principle is hard to provide.

$$\ce{C + O2->CO2}$$ $$\ce{C + 2H2O->CO2 + 2H2}$$ $$\ce{C + H2O->CO2 + H2}$$ $$\ce{C + CO2->2CO}$$

The equilibrium concentrations of $\ce{O2}$ and $\ce{H2O}$ in the gasification products at all temperatures are negligible. Steam-oxygen gasification products are a mixture of $\ce{CO2}$, $\ce{CO}$ and $\ce{H2}$.

Before carrying out the reaction of the shift $$\ce{CO + H2O->CO2 + H2}$$ from a mixture of $\ce{CO2}$, $\ce{CO}$ and $\ce{H2}$ must be separated $\ce{CO2}$. To this must be expended work division (again burn some $\ce{C}$).

  • $\begingroup$ OK, so the key is the reduction of the CO2, then? And, if I understand you correctly, the rate at which that occurs is a temperature-dependent equilibrium? $\endgroup$ – Hanno Fietz Nov 13 '12 at 22:58
  • $\begingroup$ Yes, the main thing is the reduction of CO2. The result depends on the temperature. Need to find a ratio of steam and oxygen when the temperature is 1800 K. And at high temperatures resins and other macromolecular compounds decompose, making it easier to clean the gas. $\endgroup$ – Calypso Nov 14 '12 at 8:09
  • $\begingroup$ OK, great, thank you. I tried to edit your answer because I had some difficulties with the English, but I'm not a native speaker either, and I don't speak Chemist-English. Maybe someone else will jump in. $\endgroup$ – Hanno Fietz Nov 14 '12 at 12:52

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