US 6,485,296 B1Granted

Variable moisture biomass gasification heating system and method

OwnerRobert J. Bender, John P. Tomassi +1inventors

InventorsRobert J. Bender, John P. Tomassi, Frank Asplund

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Abstract

A sloping fuel grate allows primary air to flow up into a thick biomass fuel bed in a gasifier producing combustible gases. Fuel feed screws keep the fuel bed at a nearly constant height in response to a level indicator. A burner above the fuel bed admits swirling secondary air and combustible gases, burning the gases to produce a flame to heat a boiler or other heat applying device. A donut shaped collar in the burner prevents gases from leaking back into the burner. A programmable logic controller maintains the system at a desired optimum level of operation based on signals from oxygen, moisture, pressure, temperature and fuel bed height sensors. The controller sends signals to controls for primary air valves and dampers, fuel feeder, and an induced draft fan and optional combined primary and secondary air fan controlling the pressure and flow of air and gases for the system.

Claims20

Dependent claims

A controlled thick-fuel-bed elevated-burner biomass gasification heating system comprising:

a gasifier for gasification of a variety of types and qualities of biomass fuels with a means for supporting a thick fuel bed and distributing a primary air flow in such a way to get an even gas flow through the fuel bed, and a means for directing the primary air flow, a means for controlling fuel bed height, the gasifier being capable of transforming the biomass fuels into combustible gases and ash;
a variable means for feeding biomass fuel into the gasifier at a controlled rate;
a means for removing the ash from the gasifier;
a burner positioned above the fuel bed and leading out of the gasifier for receiving and igniting the combustible gases from the gasifier and burning the gases by creating a flame out of the burner providing heat and exhaust gases, the burner having a means for preventing the exhaust gases from passing back into the burner outlet part;
a means for controlling a flow of air into the gasifier and into the burner;
a heat exchange chamber for receiving the flame from the burner and for housing a means for receiving and applying heat produced from the system, including a means for monitoring temperature and pressure of the means for applying heat;
a means for variably controlling pressure throughout the system and for transporting the exhaust gases from the heat exchange chamber at a variable rate;
a means for removing particulates from the exhaust gases to produce clean emission exhaust gases;
a means for diverting a portion of the clean emission exhaust gases through a conduit and into the gasification chamber and diverting the remainder of the clean emission exhaust gases up an exhaust stack and out into the atmosphere;
a means for monitoring the oxygen content of the exhaust gases;
a means for monitoring the moisture content of the exhaust gases;
a means for sending feedback signals from all of the means for monitoring to control all of the means for controlling in the system.

9 more elements

A controlled heating method for biomass gasification and combustion in a thick-fuel-bed elevated-burner heating system, the heating method comprising:

the step of loading biomass fuel by a variable means for feeding biomass fuel at a controlled rate into a gasifier, without disturbing the pressure in the gasifier, to form a thick fuel bed on a means for supporting a thick fuel bed and a means for evenly distributing a primary air flow through the fuel bed and maintaining a nearly constant fuel bed height by adding fuel in response to a means for controlling fuel bed height;
the step of igniting the fuel bed by a conventional means;
the step of monitoring and controlling the gasification of any of a variety of types and qualities of biomass fuels to transform the biomass fuels into combustible gases and ash;
the step of removing the ash from the gasifier by an ash removal means without disturbing the pressure in the gasifier;
the step of creating a flame out of a burner positioned above the fuel bed and leading out of the gasifier by receiving and igniting the combustible gases from the gasifier in a swirling stream of air in the burner, the burner having a means for preventing the gases from passing back into the burner, the flame extending into a heat exchange chamber for receiving the flame from the burner and for housing a means for applying heat produced from the system, the heat from the flame being transferred to the means for applying heat;
the step of controlling a flow of air into the gasifier and into the burner by a means for controlling the flow of air;
the step of monitoring temperature and pressure in the means for applying heat by a means for monitoring temperature and pressure;
the step of variably controlling pressure throughout the system and transporting exhaust gases from the heat exchange chamber at a variable rate by a means for controlling pressure and for transporting the exhaust gases;
the step of removing particulates from the exhaust gases to produce clean emission exhaust gases by a means for removing particulates;
the step of diverting a portion of the clean emission exhaust gases through a conduit and into the gasifier and diverting the remainder of the clean emission exhaust gases up an exhaust stack and out into the atmosphere;
the step of monitoring oxygen content of the exhaust gases by an oxygen monitoring means;
the step of monitoring moisture content of the exhaust gases by a moisture monitoring means;
the step of sending feedback signals from all of the means for monitoring to control all of the means for controlling in the system.

10 more elements

Dependencies are inferred from the claim text.