Upside-down type low NOx boiler

Patent metadata

Field	Value
Publication number	US-9958153-B2
Application number	US-200913124989-A
Country	US
Kind code	B2
Filing date	Dec 8, 2009
Priority date	Dec 12, 2008
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

In a low NOx boiler of the present invention, a high-temperature reductive combustion zone is provided to an upper portion of a rectangular combustion chamber, and a second-step combustion zone is provided to a middle stage of the combustion chamber. A wall provided below the second-step combustion zone is tapered to narrow the combustion chamber, with a taper angle of approximately 35° or so, relative to a vertical line. An ash discharge port is provided to a furnace bottom portion, and a gas outlet port communicated with a rear pass is provided to a lower side face of the second-step combustion zone. This rear pass is connected with a further post-treatment step, via a super-heater tube and an economizer.

First claim

The invention claimed is:

1. An upside-down type low NOx boiler comprising:
a vertical combustion chamber;
the vertical combustion chamber including:
a high-temperature reductive combustion zone provided to an upper portion of the combustion chamber and surrounded by a refractory material and having a burner;
a low-temperature oxidative combustion zone provided below the high-temperature reductive combustion zone and surrounded by a water wall and having a second-step combustion air nozzle;
a combustion gas outlet port provided below the low-temperature oxidative combustion zone; and
an ash discharge mechanism provided to a bottom portion of the combustion chamber and connected with a steam drum and a non-heated downcomer pipe for cooling the low-temperature oxidative combustion zone,
wherein the burner combusts a low-quality fuel under a high-temperature reductive atmosphere in the high-temperature reductive combustion zone, so as to produce a combustion gas, and
wherein the second-step combustion air nozzle supplies a second-step combustion air having a temperature lower than a temperature of the combustion gas, so as to further combust a partly combusted gas flowed downward from the high-temperature reductive combustion zone, under a low-temperature oxidative atmosphere,
wherein the combustion gas is flowed out from the combustion gas outlet port, and an ash that is accumulated on a furnace bottom portion of the combustion chamber is discharged, during the operation of the furnace, by using the ash discharge mechanism, and
wherein a narrowed portion for reducing the horizontal cross section of the combustion chamber by 20%-50% is provided between the high-temperature reductive combustion zone and the low-temperature oxidative combustion zone.

2. The upside-down type low NOx boiler according to claim 1 , wherein the furnace bottom portion of the combustion chamber is tapered, and the ash discharge mechanism is provided to a lower end of the furnace bottom portion.

3. The upside-down type low NOx boiler according to claim 2 , wherein the angle of the furnace bottom portion is less than or equal to 45° relative to a vertical line.

4. The upside-down type low NOx boiler according to claim 1 , wherein the burners are arranged along two opposite side faces of the high-temperature reductive combustion zone, respectively, horizontally in parallel with one another, with the flame axes of the burners respectively oriented not to cross one another, and the combustion gas creates a vortex flow.

5. An upside-down type low NOx boiler comprising:
a vertical combustion chamber;
the vertical combustion chamber including:
a high-temperature reductive combustion zone provided to an upper portion of the combustion chamber and surrounded by a refractory material and having a burner;
a low-temperature oxidative combustion zone provided below the high-temperature reductive combustion zone and surrounded by a water wall and having a second-step combustion air nozzle;
a combustion gas outlet port provided below the low-temperature oxidative combustion zone and communicated with a rear pass; and
an ash discharge mechanism provided to a bottom portion of the combustion chamber and connected with a steam drum and a non-heated downcomer pipe for cooling the low-temperature oxidative combustion zone,
wherein the burner combusts a low-quality fuel under a high-temperature reductive atmosphere in the high-temperature reductive combustion zone, so as to produce a combustion gas, and
wherein the second-step combustion air nozzle supplies a second-step combustion air having a temperature lower than a temperature of the combustion gas, so as to further combust a partly combusted gas flowed downward from the high-temperature reductive combustion zone, under a low-temperature oxidative atmosphere,
wherein the combustion gas flowed downward from the low-temperature oxidative combustion zone is flowed out from the combustion gas outlet port, and the combustion gas flowed out from the combustion gas outlet port is flowed upward in the rear pass and then passes through a super-heater tube, and
wherein an ash that is accumulated on a furnace bottom portion of the combustion chamber is discharged, during the operation of the furnace, by using the ash discharge mechanism.

6. The upside-down type low NOx boiler according to claim 5 , wherein a narrowed portion for reducing the horizontal cross section of the combustion chamber by 20%-50% is provided between the high-temperature reductive combustion zone and the low-temperature oxidative combustion zone.

7. The upside-down type low NOx boiler according to claim 5 , wherein the furnace bottom portion of the combustion chamber is tapered, and the ash discharge mechanism is provided to a lower end of the furnace bottom portion.

8. The upside-down type low NOx boiler according to claim 7 , wherein the angle of the furnace bottom portion is less than or equal to 45° relative to a vertical line.

9. The upside-down type low NOx boiler according to claim 5 , wherein the burners are arranged along two opposite side faces of the high-temperature reductive combustion zone, respectively, horizontally in parallel with one another, with the flame axes of the burners respectively oriented not to cross one another, and the combustion gas creates a vortex flow.

10. The upside-down type low NOx boiler according to claim 6 , wherein the furnace bottom portion of the combustion chamber is tapered, and the ash discharge mechanism is provided to a lower end of the furnace bottom portion.

11. The upside-down type low NOx boiler according to claim 10 , wherein the angle of the furnace bottom portion is less than or equal to 45° relative to a vertical line.

Assignees

• Suemitsu Nobuo
• Muto Sadayuki
• Toda Shinichi
• Igarashi Minoru
• Kawasaki Heavy Ind Ltd

Inventors

• Suemitsu Nobuo
• Muto Sadayuki
• Toda Shinichi
• Igarashi Minoru

Classifications

• F23C6/04 Primary

  in series connection (consuming smoke or fumes in separate combustion apparatus F23G7/06) · CPC title

• F23G5/165

  arranged at a different level · CPC title

• F23C2201/101

  in vertical direction, e.g. alternating lean and rich zones · CPC title

• F23C6/045

  with staged combustion in a single enclosure · CPC title

• F23C5/08

  Disposition of burners · CPC title