A modulating burner apparatus includes a burner and a blower placed upstream of the burner. A venturi is placed upstream of the blower. A damper valve is placed upstream of the venturi. The damper valve has an open position and a restricted position. A smaller gas valve and a larger gas valve are communicated with the venturi. A controller is operably associated with the system to select a position of the damper valve and to select the appropriate one of the gas valves so as to provide a low output operation mode and a high output operation mode, which in combination provide an overall turndown ratio of at least 25:1.

An example exhaust system for a biochar kiln includes a chimney of the biochar kiln. The example exhaust system for a biochar kiln also includes a first forced air inlet on the chimney to draw smoke through the chimney during a preheating stage to prime the chimney. The example exhaust system for a biochar kiln also includes a second forced air inlet operatively coupled with the chimney. The second forced air inlet activated to increase airflow when air naturally occurring in a smoke stream in the chimney is insufficient, the second forced air inlet deactivated when there is sufficient air.

A furnace includes a combustion blower and one or more pressure switches. In some cases, the one or more pressure switches may be used to calculate one or more operating points for the combustion blower. Additional operating points may be calculated by interpolation and/or extrapolation, as appropriate. The furnace may temporarily alter these operating points as necessary to keep the furnace safely operating in response to minor and/or transient changes in the operating conditions of the furnace.

An example flow regulation system for a biochar kiln includes an air inlet port of the biochar kiln. The example flow regulation system also includes a port cover coupled to the air inlet ports. The example flow regulation system also includes an external flow regulation assembly coupled with the port cover. The example flow regulation system also includes a controller operating the external flow regulation assembly based on monitoring conditions of the biochar kiln to open and close the air inlet port.

An example managed biochar kiln includes drum walls, a drum floor, and a lid formed to be fitted to a top edge of the drum walls to close a top end of the drum walls and form a combustion chamber between the lid, the drum walls, and the drum floor. The example managed biochar kiln also includes a chimney stack attachable to the lid. The example managed biochar kiln also includes a valve on the lid operable by an electronic controller to vary airflow through the chimney and out of the lid.

An example exhaust system for a biochar kiln includes a chimney of the biochar kiln. The example exhaust system for a biochar kiln also includes a first forced air inlet on the chimney to draw smoke through the chimney during a preheating stage to prime the chimney. The example exhaust system for a biochar kiln also includes a second forced air inlet operatively coupled with the chimney. The second forced air inlet activated to increase airflow when air naturally occurring in a smoke stream in the chimney is insufficient, the second forced air inlet deactivated when there is sufficient air.

A control module for preventing acoustic resonance noise generation from a heat exchanger of a heating furnace, comprising a control signal generated by the control module. The control signal is configured to operate an induction fan of the heating furnace at more than one speed for a given heat demand mode of the heating furnace.

A control module for preventing acoustic resonance noise generation from a heat exchanger of a heating furnace, comprising a control signal generated by the control module. The control signal is configured to operate an induction fan of the heating furnace at more than one speed for a given heat demand mode of the heating furnace.

A motor controller for a blower in a gas-burning appliance. The motor controller includes a processor configured to receive a measured pressure differential measured by a sensor disposed in an airflow generated by the blower. The processor is configured to compute a motor speed based on the measured pressure differential and a pressure differential set-point for the gas-burning appliance. The processor is configured to operate the blower at the motor speed to drive the measured pressure differential toward the pressure differential set-point.

A controlled kiln and manufacturing system for biochar production includes control systems and subsystems. An example biochar kiln exhaust apparatus, includes a chimney configured for heating by pyrolysis and for exhausting smoke from the combustion chamber. The example biochar kiln exhaust apparatus also includes a plurality of exhaust inlet pipes configured to pass smoke from the combustion chamber to the chimney.