Coal cleans up its act

Researchers from Imperial College London have designed a system which uses coal to generate hydrogen.

Team leader Rafael Kandiyoti believes that the ZECA (zero emissions carbon alliance) technology could make a significant contribution to low-emissions energy generation.

The technology combines several different systems. First, the coal is brought into contact with hydrogen at 70 bar and 700 degrees C using hydrogasification, which converts the carbon in the coal into methane. Steam is then pumped into the reactor, absorbing some of the heat given off by hydrogasification, and providing the reaction mixture for the second phase.

Here, gases pass into another reactor containing calcium oxide (lime) and a catalyst which promotes the 'water-shift' reaction, converting the methane and steam into carbon dioxide and hydrogen. The lime reacts with the CO2 to form calcium carbonate (limestone), leaving near-pure hydrogen.

Next, the limestone is passed into a third reactor called a calciner, where it is heated, reversing the first reaction and releasing a pure steam of CO2. This, say the researchers, can be captured and sequestered.