System and method for laser ignition of fuel in a coal-fired burner

A system, comprising:

• a coal fuel source;
• an air source;
• a furnace;
• a fuel transport tube to transport a mixture of coal from the coal fuel source and air from the air source to the furnace for combustion thereof;
• a laser igniter configured to ignite the mixture of coal and air carried through the fuel transport tube to the furnace, the laser igniter including:
• a laser source;
• a laser tube to deliver a beam of laser light from the laser source to the mixture of coal and air in the fuel transport tube, wherein a portion of the laser tube is disposed within the fuel transport tube;
• and
• an ignition tube disposed within the fuel transport tube to receive a portion of the mixture of coal and air flowing through the fuel transport tube, wherein an inlet of the ignition tube is separated from the portion of the laser tube disposed in the fuel transport tube by a predetermined spacing, wherein the beam of laser light heats and ignites the mixture of coal and air in the predetermined spacing and in the ignition tube in a multiple of ignition stages;
• a plurality of flow directing devices, wherein each of the flow directing devices is configured to direct a portion of the flow of the mixture of coal and air to flow about the ignition tube for irradiation by the beam of laser light;
• and
• the flow control directing devices are configured to reduce a velocity of air coming out of the laser tube to a velocity that is slower than a velocity of the flow of the mixture of coal and air in the fuel transport tube, creating a recirculation zone in a region between an outlet of the laser tube and an inlet to the ignition tube, wherein the mixture of coal and air carried in the fuel transport tube recirculates for more exposure in the recirculation zone to the beam of laser light prior to entering the ignition tube.

A method of igniting fuel for combustion in a burner assembly, comprising:

• transporting a flow of a mixture of fuel from a fuel source and air from an air source to a furnace with a fuel transport tube;
• directing a portion of the flow of the mixture of the fuel and air through an inlet of an ignition tube placed within the fuel transport tube;
• directing a beam of laser light from a laser tube into the fuel transport tube towards the mixture of the fuel and air carried through the ignition tube;
• heating and igniting the mixture of the fuel and air carried through the ignition tube in a multiple of stages;
• supplying the heated and ignited mixture of the fuel and air from the ignition tube to the furnace;
• and
• reducing a velocity of air coming out of the laser tube to a velocity that is slower than a velocity of the flow of the mixture of fuel and air in the fuel transport tube, creating a recirculation zone in a region between an outlet of the laser tube and an inlet to the ignition tube, wherein the mixture of fuel and air carried in the fuel transport tube recirculates for more exposure in the recirculation zone to the beam of laser light prior to entering the ignition tube.