JP2009047390A - Mixed combustion boiler of pulverized coal and natural gas and combustion method thereof - Google Patents

Abstract

A mixed combustion boiler of pulverized coal and natural gas capable of reducing the generation amount of environmental pollutant gases such as smoke, NOx, SOx, etc. generated when using low quality pulverized coal and supplying a predetermined calorific value, and The combustion method is provided.
In a boiler in which coal is made into pulverized coal and burned with a burner 20 and steam is produced with a water pipe disposed in a furnace, a natural gas supply pipe 8 is inserted into the pulverized coal supply pipe 3, and the pulverized coal 1 And a mixture of natural gas 7 is burned at the outlet of the burner 20.
[Selection] Figure 1

Description

  A burner 17 used in a boiler of a conventional thermal power generation facility will be described with reference to FIG. The burner 17 shown in FIG. 6 is provided on the furnace wall (not shown) of the boiler, and is composed of a pulverized coal supply pipe 2, a primary air supply pipe 4, and a secondary air supply pipe 6 arranged concentrically. . The pulverized coal 1 supplied to the pulverized coal supply pipe 2, the primary air 3 supplied to the primary air supply pipe 4, and the secondary air 5 supplied to the secondary air supply pipe 6 are jetted and mixed at the outlet of the burner 17. While burning in the combustion space in the furnace.

  In many cases, boilers of thermal power generation facilities use coals having different characteristics from those at the start of operation. This is because if the cost of coal is high and it is necessary to use low-quality coal that has a lower calorific value than the originally used coal, or if the coal mining site is dug, Is when something different comes out and you have to use it.

  In many cases, high quality coal is less used than originally used, and low quality coal, that is, ash / water content and volatile matter is often used. When using low quality coal, the calorific value generally tends to decrease, and the unburned rate tends to increase.

In order to cope with this decrease in heat generation, an auxiliary burner using heavy oil or natural gas is additionally installed on the furnace wall to compensate for the decreased heat generation.
On the other hand, in order to reduce the amount of NOx generated, it is also known that a pulverized coal burner is provided with a natural gas injection port and combusted by combining pulverized coal and natural gas (Patent Document 1).
Special Table 2000-504406

In existing boilers for thermal power generation, when using low quality coal, that is, coal with high ash / moisture content and low volatile content, soot and harmful gases are generated in large quantities. The current situation is that power is generated at a partial load by reducing the amount of steam generated. At that time, if natural gas with a small amount of generated CO ₂ is additionally installed at a position different from that of the pulverized coal boiler, both combustion by natural gas and combustion by pulverized coal have large combustion forms and flame formation forms. Due to the difference, a local temperature rise occurred in the water pipe on the outer surface of the upper superheater and the boiler, which caused deterioration of the upper superheater and the water pipe. In addition, since natural gas combustion itself is a non-luminous flame, the thermal emissivity is low, and it is difficult to maintain the heat absorption amount in the water pipe that depends on the absorption of radiant heat.

  In addition, the pulverized coal burner provided with the natural gas injection port described in Patent Document 1 is provided with a natural gas supply path around the pulverized coal supply path and burns both in a flame furnace. Then, when pulverized coal is low quality, pulverized coal and natural gas cannot be burned uniformly and efficiently in a flame furnace, and cannot be applied to low quality pulverized coal.

  The present invention has been made to solve the above problems, and uses natural gas as an auxiliary fuel when using low-grade pulverized coal, and reduces the generation of environmental pollutant gases such as soot, NOx, and SOx. In addition, an object is to provide a mixed combustion boiler of pulverized coal and natural gas capable of supplying a predetermined calorific value, and a combustion method thereof.

  In order to achieve the above-mentioned object, the present invention is to insert a natural gas supply pipe into a pulverized coal supply pipe in a boiler that produces coal with pulverized coal, burns it with a burner, and produces steam with a water pipe arranged in the furnace section. The mixture of pulverized coal and natural gas is burned at the outlet of a burner.

  Further, the present invention provides a boiler for producing coal with pulverized coal, burning it with a burner, and producing steam with a water pipe disposed in a furnace section, inserting a natural gas supply pipe into the pulverized coal supply pipe, It mixes with pulverized coal inside a charcoal supply pipe, and burns the mixture of the pulverized coal and the natural gas at the exit of a burner.

  The present invention also relates to a boiler combustion method in which coal is made into pulverized coal, burned with a burner, and steam is produced with a water pipe arranged in a furnace section, a natural gas supply pipe is inserted into the pulverized coal supply pipe, Is mixed with pulverized coal inside the pulverized coal supply pipe, and the mixture of the pulverized coal and the natural gas is burned at the outlet of a burner.

  According to the mixed combustion boiler of pulverized coal and natural gas and the combustion method thereof according to the present invention, natural gas is used as an auxiliary fuel when using low-quality pulverized coal, and environmental pollutant gases such as soot, NOx, SOx, etc. It is possible to reduce the generation amount and supply a predetermined heat generation amount.

Hereinafter, an embodiment of a mixed combustion boiler of pulverized coal and natural gas according to the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a configuration diagram of a mixed combustion burner 20 used in a mixed combustion boiler of pulverized coal and natural gas according to a first embodiment of the present invention. In addition, the boiler which concerns on this invention is a boiler for normal pulverized coals of the type which carries out steam manufacture with the water pipe arrange | positioned at the furnace part, and a figure is abbreviate | omitted.

  In FIG. 1, a burner 20 is located upstream of a pulverized coal supply pipe 2, a primary air supply pipe 4, a secondary air supply pipe 6, a natural gas supply pipe 8, and a natural gas supply pipe 8 into which pulverized coal 1 is introduced together with air. The check valve 12 is provided. One of the natural gas supply pipes 8 is inserted and fixed to the center of the pulverized coal supply pipe 2 for a predetermined length, and the upstream part of the natural gas supply pipe 8 is reversed to prevent the pulverized coal 1 from entering the natural gas supply system. A stop valve 12 is provided.

  In the first embodiment of the present invention, the natural gas 7 discharged from the outlet end of the natural gas supply pipe 8 is sufficiently mixed with the pulverized coal 1 and the solid-gas mixed phase flow of air inside the pulverized coal supply pipe 2. The mixture 9 is ejected from the outlet of the burner and burned homogeneously in the boiler.

  According to the first embodiment, the combustion is performed in a state where the pulverized coal 1, the solid-gas mixed phase flow of air and the natural gas are sufficiently mixed, so that homogeneous combustion is possible, and a local temperature rise occurs. The upper superheater and the water pipe are not deteriorated, and generation of soot and harmful gas can be suppressed.

(Second Embodiment)
A mixed combustion burner 20 of pulverized coal and natural gas according to a second embodiment of the present invention will be described with reference to FIG.

  In the second embodiment, in order to further improve the stirring and mixing of the pulverized coal 1, the solid-gas mixed phase flow of air, and the natural gas 7, the rotary blade 10 and / or, for example, the torsion is provided inside the natural gas supply pipe 8. A swiveling member 11 made of a tape is provided. In addition, although these members may be provided independently, in order to raise stirring efficiency further, as shown in FIG. 2, of course, both the rotary blade 10 and the turning member 11 may be provided in the natural gas supply pipe 8. It is.

  According to the second embodiment, the pulverized coal 1, the solid-gas mixed phase flow of air and the natural gas 7 are further satisfactorily mixed by mixing, so that the mixture 9 can be more homogeneously combusted and the local temperature There is no rise or deterioration of the upper superheater or water pipe, and it is possible to further suppress the generation of smoke and harmful gases.

(Third embodiment)
A mixed combustion burner 20 of pulverized coal and natural gas according to a third embodiment of the present invention will be described with reference to FIG.

  In the third embodiment, a plurality of natural gas supply pipes 8a are connected to the outer peripheral portion of the pulverized coal supply pipe 2 while being eccentrically set by a predetermined angle α with respect to the center of the pulverized coal supply pipe (FIG. 3 (a )). The eccentric angle α is preferably 30 ° to 90 ° for promoting mixing and stirring (FIG. 3B).

  According to the third embodiment, the natural gas 7 is discharged from the natural gas supply pipe 8a while turning into the pulverized coal supply pipe 2, so that the mixing and stirring of the pulverized coal 1 and the natural gas 7 is promoted. Further, this configuration can prevent the backflow of the pulverized coal 1 to the natural gas supply pipe 8a, and can further improve the amount of heat generated by the radiation due to combustion at the outlet of the burner 20.

(Fourth embodiment)
A mixed combustion burner 20, 21 of pulverized coal and natural gas according to a fourth embodiment of the present invention will be described with reference to FIG.

  In the fourth embodiment, when the region where the mixed natural gas 7 and pulverized coal 1 burn is defined as the primary combustion region 14, the primary combustion region 14 has unburned pulverized coal. Alternatively, when the unburned portion is intentionally generated, the unburned portion is burned in the reburning region 15 above the first combustion region 14 in the furnace portion. For this purpose, an auxiliary burner 21 for ejecting the secondary natural gas 16 and the tertiary air toward the reburning region 15 is provided at the upper part of the burner 20.

According to the fourth embodiment, the unburned portion generated in the primary combustion zone 14 is efficiently burned in the reburning zone 15 to reduce the unburned portion, and further generation of smoke and harmful gases. Can be suppressed.
Of course, the auxiliary burner 21 can be used in combination with the burner 20 according to the first to third embodiments.

(Fifth embodiment)
A mixed combustion barber 20 of pulverized coal and natural gas according to a fifth embodiment of the present invention will be described with reference to FIG.

  In the fifth embodiment, the outlet of the natural gas supply pipe 8 extends to the outlet of the burner 20 without releasing the natural gas 7 into the pulverized coal supply pipe 2 as in the first to third embodiments. And burn with mixing with pulverized coal at the outlet of the burner. Rotating blades 10 and / or swirling members 11 are inserted into the natural gas supply pipe 8 to generate a swirl flow in the natural gas 7, and finally the pulverized coal 1 and the natural gas 7 are discharged at the outlet of the natural gas supply pipe 8. Mix and burn.

  According to the fifth embodiment, the natural gas 7 and the pulverized coal 1 that have turned into a swirl flow are efficiently mixed with the outlet of the burner 20 and burned, and the amount of heat generated by the radiation at the burner outlet is improved. Can be made.

The block diagram of the mixed combustion burner of pulverized coal and natural gas which concerns on the 1st Embodiment of this invention. The block diagram of the mixed combustion burner of pulverized coal and natural gas which concerns on the 2nd Embodiment of this invention. FIG. 3A is a configuration diagram of a mixed combustion burner of pulverized coal and natural gas according to a third embodiment of the present invention, and FIG. 3B is a cross-sectional view of a portion b of FIG. The block diagram of the mixed combustion burner of pulverized coal and natural gas which concerns on the 4th Embodiment of this invention. The block diagram of the mixed combustion burner of pulverized coal and natural gas which concerns on the 5th Embodiment of this invention. The block diagram of the conventional pulverized coal burner.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pulverized coal, 2 ... Pulverized coal supply pipe, 3 ... Primary air, 4 ... Primary air supply pipe, 5 ... Secondary air, 6 ... Secondary air supply pipe, 7 ... Natural gas, 8, 8a ... Natural gas supply Pipes, 9 ... mixture of pulverized coal and natural gas, 10 ... rotating blades, 11 ... swirl member, 12 ... check valve, 13 ... tertiary air, 14 ... primary combustion zone, 15 ... reburning zone, 16 ... Secondary natural gas, 17 ... burner, 20 ... mixed combustion barber, 21 ... auxiliary burner.

Claims (8)

  In a boiler in which coal is pulverized and burned with a burner and steam is produced with a water pipe arranged in the furnace, a natural gas supply pipe is inserted into the pulverized coal supply pipe, and the mixture of the pulverized coal and natural gas is burnered. Combustion boiler of pulverized coal and natural gas, characterized by burning at the outlet of   In a boiler where coal is pulverized and burned with a burner and steam is produced with a water pipe arranged in the furnace, a natural gas supply pipe is inserted into the pulverized coal supply pipe, and the natural gas is placed inside the pulverized coal supply pipe. A mixed combustion boiler for pulverized coal and natural gas, wherein the mixture is mixed with pulverized coal and the mixture of the pulverized coal and the natural gas is burned at an outlet of a burner.   The mixed combustion boiler for pulverized coal and natural gas according to claim 1 or 2, wherein the natural gas supply pipe is provided with rotating blades and / or swirling members.   In a boiler that uses coal to make pulverized coal, burns it with a burner, and produces steam with a water pipe arranged in the furnace, a plurality of natural gas supply pipes are eccentric to the center of the pulverized coal supply pipe. A mixed combustion boiler of pulverized coal and natural gas, characterized by being connected to each other.   5. The pulverized coal and natural gas according to claim 4, wherein an eccentric angle when connecting the plurality of natural gas supply pipes eccentrically with respect to a center of the pulverized coal supply pipe is 30 ° to 90 °. Mixed combustion boiler.   The mixed combustion boiler for pulverized coal and natural gas according to any one of claims 1 to 5, wherein an auxiliary burner for ejecting air and natural gas is provided at an upper portion of the burner.   The mixed combustion boiler for pulverized coal and natural gas according to any one of claims 1 to 6, wherein a check valve is provided upstream of the natural gas supply pipe.   In a combustion method of a boiler in which coal is made into pulverized coal and burned with a burner and steam is produced with a water pipe arranged in a furnace, a natural gas supply pipe is inserted into the pulverized coal supply pipe, and the natural gas is supplied to the pulverized coal supply pipe. A combustion method of a mixed combustion boiler of pulverized coal and natural gas, wherein the mixture of pulverized coal and natural gas is burned at the outlet of a burner.

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