Roasting system with clean emissions and high thermal efficiency

A bean roasting system, comprising:

• a plurality of components at least partly defining a recirculating gas flow path;
• a roasting chamber coupled to the recirculating gas flow path;
• a blower coupled to the recirculating gas flow path, the blower configured to provide a flow stream of gas through the recirculating gas flow path;
• a variable diverter coupled to the recirculating gas flow path, the variable diverter configured to split the gas flow path into at least two flow paths including a treated flow path and a bypass flow path, the treated flow path including a series arrangement of a gas heater and a catalytic converter, the variable diverter configured to control a percentage of a flow stream of gas that is diverted into the bypass flow path;
• and
• a controller configured to activate a plurality of different predetermined operating modes for the bean roasting system by controlling a state of the variable diverter and a state of the heater, gas flows along the recirculating gas flow path out of the roasting chamber through the variable diverter and through the treated flow path and bypass flow path before returning to the roasting chamber, the plurality of different predetermined operating modes are partly defined by a temperature in the catalytic converter and a temperature in the roasting chamber.

A bean roasting system, comprising:

• a roasting chamber having a gas inlet and a gas outlet fluidically coupled to the gas inlet by a recirculating gas flow path;
• a blower coupled to the recirculating gas flow path and configured to establish a flow stream of gas through the recirculating gas flow path;
• a variable diverter coupled to the recirculating gas flow path and configured to split the recirculating gas flow path into at least two gas flow path segments including a treated gas flow path segment and bypass gas flow path segment, the variable diverter configured to control a percentage of the flow stream of gas that is diverted to the bypass gas flow path segment;
• a catalytic converter coupled to the treated gas flow path segment;
• a heater in series with the catalytic converter and coupled to within the treated gas flow path segment, the blower, the variable diverter, and the treated and bypass flow paths segments define portions of the recirculating gas flow path between the gas inlet and gas outlet of the roasting chamber;
• a fluidic junction at which the at least two gas flow path segments are recombined before the flow stream of gas reaches the gas inlet of the roasting chamber;
• and
• a controller configured to control a state of the variable diverter and a state of the heater to provide closed loop temperature control of both the catalytic converter and the roasting chamber such that an increase in the percentage of the flow stream of gas that is diverted to the bypass gas flow path segment reduces a temperature in the roasting chamber relative to a temperature of the catalytic converter, the controller is configured to define and activate a plurality of different operating modes that are defined at least in part upon a temperature of the roasting chamber and a temperature of the catalytic converter, the controller configured to activate the different operating modes by controlling at least the states of the blower, the variable diverter, and the heater.