Dual fuel grid burner

Claim 2

In a grid burner having a plurality of spaced burner elements and adapted for flow of a combustion-supporting gas across said burner elements to be heated thereby, the improvement comprising: a burner element having a plurality of fuel nozzles spaced along said element, each nozzle being adapted for introduction of gas or liquid fuels to said nozzle at separate gas and liquid inlets, and arranged for combustion of either of said fuels, a gas manifold conduit supporting said nozzles and communicating with said gas inlets, a liquid manifold conduit disposed within and extending along the length of said gas manifold conduit so as to be shielded thereby, a plurality of tubular expansion coils arranged to support the liquid manifold, each with one end connected to said liquid manifold and the other end connected to said liquid inlet of one of said nozzles, whereby said expansion tubes supply liquid to the nozzles and support the shielded liquid manifold for thermal expansion and contraction relative to the gas manifold.

Claim 3

The combination according to claim 1 further including: a source of liquid fuel connected to one end of said liquid manifold conduit, means closing off the other end of the liquid manifold conduit, and a liquid recirculation pipe disposed inside the liquid manifold and being adapted to return unused liquid fuel from the closed-off end and alonG the length of said liquid manifold in heat transfer relationship therewith, whereby tendency toward nozzle ''''starving'''' and boiling of the liquid fuel at said closed-off end is reduced.

Claim 4

The combination according to claim 1 and further including: an open grid burner frame, means arranged to support said gas manifold along its length in said grid burner frame, a gutter-type flameholder with divergent walls extending above said gas manifold and having first openings to admit the ends of said nozzles and second openings adjacent said first openings arranged to admit said combustion-supporting gas and to stabilize the flame, and bracket means connected between the flameholder and said supporting means and arranged to support the flameholder therefrom.

Claim 5

The combination according to claim 3, wherein said second openings are opposed slots defined by said flamenholder walls adjacent each of said nozzles.

Claim 6

The combination according to claim 3, wherein said second openings are defined in a perforated screen supported by said nozzles and forming an extension of said flameholder walls.

Claim 7

The combination according to claim 1, wherein each of said fuel nozzles comprises: a nozzle retainer fixedly mounted in said gas manifold and defining first ports admitting gas to the retainer, flow-metering swirler means mounted coaxially within said retainer and defining second ports sized and arranged to meter the gas and to impart a swirl to the gas, liquid orifice means mounted coaxially within said flow-metering swirler means and connected to one end of a said tubular expansion coil to supply liquid to the orifice.

Claim 8

The combination according to claim 1, wherein each of said tubular expansion coils is in the shape of a helix surrounding said liquid manifold and secured at one end in the top thereof, the number of turns in said coils increasing along the burner element toward the center of the grid.

Claim 9

A dual fuel grid burner for supplementary firing of a combustion-supporting exhaust gas comprising: a supporting frame having sidewalls forming portions of a duct carrying said exhaust gas, a plurality of spaced burner elements extending into the frame and supported on one end by the frame sidewalls, a grid mesh covering the bottom of the frame below said burner elements to straighten the flow to the burner elements, each of said burner elements comprising: a gas manifold pipe extending into the frame and closed off at its inner end, a plurality of fuel nozzles spaced along said gas manifold pipe, each of said nozzles being adapted for burning of gaseous of liquid fuel and having separate gas inlet ports and liquid inlet ports, a liquid manifold pipe disposed within and extending along said gas manifold pipe and being closed off at its inner end, a plurality of helical tubular expansion coils disposed around said liquid manifold pipe and each having one end connected to a fuel nozzle inlet and the other end connected to said liquid pipe so as to communicate therewith and supply liquid fuel while supporting said pipe, a liquid recirculation pipe disposed inside the liquid manifold pipe and being adapted to return unused fuel from the closed-off end, and a gutter-type flameholder extending above said gas manifold and having first openings to admit said nozzles and second openings to admit said combustion-supporting exhaust gas.

Claim 10

A dual fuel grid burner for supplementary firing of a combustion-supporting exhaust gas comprising: a supporting frame having sidewalls forming portions of a duct carrying said exhaust gas, a plurality of spaced burner elements extending into the frame and supported on one end by the frame sidewalls, a grid mesh covering the bottom of the frame below said burner elements to straighten the flow to the burner elements, each of said burner elements comprising: a gas manifold pipe extending into the frame and closed off at its inner end, a plurality of fuel nozzles spaced along said gas manifold pipe, each of said nozzles being adapted for burning of gaseous of liquid fuel and having separate gas inlet ports and liquid inlet ports, a liquid manifold pipe disposed within and extending along said gas manifold pipe and being closed off at its inner end, a plurality of helical tubular expansion coils disposed around said liquid manifold pipe and each having one end connected to a fuel nozzle inlet and the other end connected to said liquid pipe so as to communicate therewith and supply liquid fuel while supporting said pipe, a liquid recirculation pipe disposed inside the liquid manifold pipe and being adapted to return unused fuel from the closed-off end, and a gutter-type flameholder extending above said gas manifold and having first openings to admit said nozzles and second openings to admit said combustion-supporting exhaust gas.