Abstract: Methods and systems for controlling speed of a turboexpander receiving a working fluid from an oxy-fuel combustor. A first valve modulates flow of a working fluid into the combustor between a minimum and a maximum working fluid flow rate. A first pipe between the first valve and the combustor has a first volume to hold the working fluid at an inlet pressure. A discharge chamber receives a fluid, the discharge chamber being at an outlet pressure, wherein the inlet pressure is greater than the outlet pressure. A diverter valve connects the pipe and the discharge chamber when the diverter valve is open. A controller detects a condition where the turboexpander accelerates above a maximum acceleration, a maximum speed, or both, and opens the diverter valve and closes the first valve upon detection of the condition, thereby reducing a pressure differential across the turboexpander.

Abstract: Systems and methods for processing gases are disclosed. A first cryogenic fluid stream is cryogenically separated from an air stream through an O2 production system. A first cryogenic column in a CO2 production system transfers heat to a first portion of the first cryogenic fluid stream. The CO2 production system separates carbon dioxide from a combustion product stream. A second cryogenic column in an N2 rejection system transfers heat to a second portion of the first cryogenic fluid stream. The N2 rejection system separates a second cryogenic fluid stream from a combustible carbonaceous gas fuel stream. The air stream transfers heat to a first portion of the second cryogenic fluid stream.