Methods for feedstock pretreatment and transport to gasification

7) A method for pretreating feedstock for gasification comprising:

• mixing a coal based feedstock with supercritical carbon dioxide to increase the volatile content of the feedstock;
• passing at least a portion of the feedstock to a gasifier to produce a synthesis gas;
• combusting at least a portion of the synthesis gas to form an exhaust gas comprising carbon dioxide;
• purifying, compressing and heating the carbon dioxide to produce carbon dioxide;
• and
• recycling at least a portion of the carbon dioxide at supercritical conditions to the feedstock prior to the gasifier.

14) A system for gasification comprising:

• a feedstock pretreatment unit comprising:
• one or more lockhoppers;
• one or more intermediate vessels;
• and
• one or more flow control valves, wherein a feedstock to be treated is contacted with supercritical carbon dioxide within the one or more intermediate vessels to provide a treated feedstock;
• a gasification unit comprising one or more gasifiers;
• a compression unit;
• and
• a combustion turbine,
• wherein the flow control valves pass the treated feedstock to the gasification unit, and the supercritical carbon dioxide decreases leakage across the flow control valves.