Thermodynamic cycles using thermal diluent

A method providing a carbon-rich fluid, using a reactor with an inlet, a reaction chamber, and an outlet in fluid communication with an expander which is upstream of and in fluid communication with a downstream hot fluid heat exchanger, the method comprising:

• delivering a reactant fluid comprising a reactant including carbon to the reactor;
• delivering a co-reactant fluid, comprising a co-reactant including oxygen, to the reactor;
• delivering, upstream of the reactor outlet, a diluent fluid, comprising a vaporizable diluent;
• reacting the reactant fluid together with the co-reactant fluid in the reaction chamber to form an energetic fluid comprising products of reaction, diluent, and residual components of the reactant fluid, co-reactant fluid, and diluent fluid;
• extracting mechanical energy from the energetic fluid while expanding it through the expander and forming an expanded fluid;
• cooling one of the energetic fluid and the expanded fluid by a coolant fluid using the hot fluid heat exchanger, to obtain a cooled carbon-rich fluid, the cooling resulting in a heated coolant fluid;
• delivering mechanical energy to a mechanical use;
• delivering the heated fluid to a thermal fluid use;
• delivering the cooled carbon-rich fluid to a carbon fluid use;
• controlling the reactant fluid delivery to provide a thermal energy sufficient to deliver the mechanical energy and the thermal fluid;
• controlling the oxidant to reactant ratio to less than 334% of the stoichiometric ratio;
• thereby forming the carbon-rich fluid comprising greater than 6.40% carbon dioxide by mass on a dry basis;
• controlling the diluent fluid delivery upstream of the reactor outlet to constrain the peak temperature of the energetic fluid entering the expander to below a specified expander inlet temperature;
• and
• controlling the delivery of coolant fluid through the hot fluid heat exchanger;
• wherein recovering
• heat from the energetic fluid to control the temperature of the heated coolant fluid to greater than a predetermined minimum temperature.