Syngas Methanation

Methanation of coal-derived syngas

Special consideration must be given to the availability of commercial catalysts for the methanation process. The layout of the gas conditioning has to consider the high sulphur content of coal. Therefore long-term screenings of catalysts and adsorbents with real coal derived syngas from an existing labscale gasifier is planned for Work Package 2.

Process layout for Coal-to-Methane plants

The methanation of coal allows efficiencies up to 65%. The SNG fed into an existing natural gas grid may be used in existing natural gas fired combined cycle plants with efficiencies of nearly 60%. Thus the  total  efficiency  for  the  conversion  of  coal  into  power  may  reach  approximately  40%.  The  high temperature level of the waste heat of gasification and methanation may be used on site in a steam cycle, which increases the total conversion efficiency by up to 10% as shown in Fig. 4.

Figure 4:  Energy and carbon balance of coal-to-SNG plants with allothermal gasification

Thus, upgrading coal into SNG will not necessarily reduce the total efficiency of the power production from coal or lignite.
 
However detailed thermodynamic analysis are necessary to specify feasible efficiencies and cycle layouts  with  an  adequate  use of  the  process  heat  (Work Package 1).

CO2  removal  from CO2/CH4 mixtures 

The  methanation  provides a  gas,  which  consists  of approximately  50%  CO2 and  50%  CH4  (dry  base) with  an  additional  amount of  excess  steam.  The  high CO2  concentration  favours its  removal  by  scrubbing technologies  (preferably physical  adsorption), membrane  technologies  or pressure  swing  adsorption. (Work Package 1 task 1.4) Detailed  cycle  calculations will compare state-of-the-art  gas  conditioning and  CO2  removal technologies.