Patent ID: 8579103

Claim:
A system, comprising: a solid feed pump configured to transport a solid feedstock, comprising: at least one passage for the transport of the solid feedstock; at least one movable wall configured to move along the passage; and at least one retractable gripping element configured to extend from the at least one movable wall into the at least one passage to grip a portion of the solid feedstock, and the at least one retractable gripping element is configured to retract away from the at least one passage, wherein the at least one movable wall comprises first, second, and third wall portions surrounding the at least one passage, the first and second wall portions are disposed opposite from one another, the third wall portion is disposed crosswise to the first and second wall portions, and the at least one retractable gripping element is configured to extend from the first wall portion, to extend from the second wall portion, or to extend from the third wall portion.