9
$\begingroup$

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?

Improve this question
$\endgroup$
1
  • 1
    $\begingroup$ I believe the question may apply equally to other gasification processes. $\endgroup$ – Hanno Fietz Nov 13 '12 at 13:18
3
$\begingroup$

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 $\ce{C}$).

Improve this answer
$\endgroup$
3
  • $\begingroup$ 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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.