JP4859851B2 - Combustion device for simultaneous combustion of coal and biomass - Google Patents

Description

  The present invention relates to renewable fossil fuels other than fossil fuels containing solid fossil fuels such as coal and fuels derived from living organisms such as plants, waste materials, wastes, sludge or their carbides (hereinafter these fuels are referred to as biomass fuels). The present invention relates to a combustion apparatus that mixes and burns coal and biomass suitable for co-firing.

Due to the problem of global warming caused by CO _{2 in} recent years, biomass is being used more widely as a fuel that does not increase the CO ₂ generated when burned from its biological recycling mechanism. In particular, in order to suppress the increase in the generation of CO ₂ from the conventional solid fossil fuel and the energy consumption thereof, it is desired to use a biomass fuel such as a wood system.

  In addition, it is known that coal and biomass fuels are difficult to achieve high efficiency and low NOx combustion by combustion alone, whereas it is known that both fuel combustion efficiency and low NOx combustion can be achieved simultaneously. Research and development of combustion equipment that combusts fuel and biomass fuel at the same time is underway.

  For these reasons, for the time being, a technology that uses a pulverized coal burner with a mainstream coal as the main fuel as a solid fuel and a biomass burner with a woody biomass as an auxiliary fuel, or woody biomass as an auxiliary fuel is added to the pulverized coal. Therefore, it is desired to establish a burner technology for co-firing.

  In Patent Documents 1 and 2, as shown in FIG. 6 (a), there are individually supplied combustion apparatuses that individually pulverize coal and biomass with a mill and individually supply them to the burners 10 and 11 of the furnace 5, respectively. It is disclosed. Coal, which is the main fuel, is supplied into the coal mill 1 together with hot air for conveyance, is pulverized simultaneously with drying inside, passes through the pulverized coal piping 2 as pulverized coal, and is supplied to the pulverized coal burner 10 of the furnace 5. Burned.

  On the other hand, the biomass fuel, which is another fuel, is, for example, a woody biomass fuel as a secondary fuel, and a heat input rate within a range of several to 10% is different from the coal supply system. It is supplied from the pipe 7 to the furnace 5. Like coal, the biomass is dried and pulverized in the biomill 6 together with the hot gas, becomes fine-grained bio, passes through the biomass piping 7, is supplied from the biomass burner 11 into the furnace 5, and is subjected to combustion.

  In Patent Document 3, as shown in FIG. 6 (b), coal and biomass are individually pulverized by mills 1 and 6, and at least two kinds of fuels composed of pulverized coal and biomass fuel are separately provided in a furnace 5. The burner 3 is configured to jet biomass into the furnace from the biomass jet nozzle 3a on the center side and to jet coal into the furnace 5 from the outer peripheral side of the jet nozzle 3a (coaxial supply system). It is disclosed. Patent Document 3 describes that a co-firing burner 3 having excellent ignitability and stable combustibility can be obtained by using this coaxial supply type burner 3.

  Further, in FIG. 7 (a), coal and biomass are individually pulverized by mills 1 and 6, and then the biomass pipe 7 is connected to the pulverized coal pipe 2 which is the main pipe, and the mixed fuel is mixed with the burner 3 A combustion apparatus having a configuration (line blend method) for supplying to a fuel is disclosed. The only currently available line blending system is a combustion system manufactured by Gelderland in the Netherlands (see FIG. 8).

  Further, FIG. 7 (b) shows a combustion in which coal and biomass are pulverized by the same mill 12 to be mixed fuel, and the mixed fuel is supplied from the mixed fuel pipe 13 to the mixed combustion burner 3 (same burner method). Indicates the device.

In addition, in FIG. 6 (a)-FIG.7 (b), although only one coal mill 1 and the mixed-burner burner 3, the pulverized-coal burner 10, and the biomass burner 11 are each illustrated for simplification, it is large-sized. The number of mills 1, 6, or 12 increases as the number of furnaces becomes 5, and a large number of burners 3, 10, or 11 distributed from each mill 1, 6, or 12 is provided to respond to changes in start-up / load, etc. Make it possible.
JP 2005-291534 A JP 2005-291539 A JP 2003-222310 A

  As shown in a perspective view in FIG. 8, the fuel delivery pipe manufactured by Gelderland has a configuration in which a biomass fuel biomass pipe 7 made of about 5% construction waste is attached to the side surface of the pulverized coal pipe 2 from a direction orthogonal thereto. The pulverized coal and biomass particles after merging are not sufficiently uniformly mixed in the pulverized coal pipe 2.

  In addition, the same burner-type combustion device that supplies mixed fuel obtained by pulverizing coal and biomass fuel in the same mill to the burner has few parts to be modified and high cost performance. And the biomass are pulverized by the same mill, the pulverization is limited, and biomass fuel can be mixed only about 2% on the maximum heat input basis. There is a risk of fire during transportation of the fuel flow path.

  In the inventions described in Patent Documents 1 and 2, coal and biomass are individually supplied and burned from separate burners 10 and 11 provided in the furnace 5, and the coal and biomass are pulverized in the mills 1 and 6, respectively. In addition, there is an advantage that the supply to the burners 10 and 11 is not affected by each other, but it is necessary to provide a biomass pipe 7, the burner 11 and an air port (not shown), or to divert a part of the pulverized coal burner 10. is there.

In addition, the invention described in Patent Document 3 which is a coaxial supply system has the advantage that the supply of coal and biomass to the burner 3 is not interfered with each other and can be mixed with a single burner 3, but the replacement cost of the burner 3 Is bulky.
Moreover, it is described in the method of the said patent document 3 that a combustion effect with favorable combustibility is acquired by mixing coal fuel and biomass fuel uniformly in the single mixed combustion burner 3. FIG. In particular, the fuel flow path upstream of the mixed combustion burner disclosed in FIG. 6 of Patent Document 3 is provided with a venturi portion on the inner wall surface, and further provided with a concentrator on the downstream side (burner side), so that pulverized coal and biomass particles The fuel is concentrated at the flame holding plate portion at the outlet of the burner, and stable ignition and the formation of a high-temperature reducing flame are possible while promoting the mixing of the two particles to achieve uniform mixing of both particles.

However, in the conventional biomass charging method manufactured by Gelderland, the biomass particle group is biased to one side of the pulverized coal pipe at the junction, so this bias is also maintained at the outlet of the combustion burner, and the biomass and the entire cross section of the burner are separated. The pulverized coal does not flow evenly dispersed (see FIG. 5B).

  Then, the subject of this invention is providing the combustion apparatus for coal and biomass which can aim at the uniform mixing property of pulverized coal and biomass particulates in the fuel flow path of the upstream side of a mixed combustion burner.

The problems of the present invention are solved by the following means.
That is, the invention described in claim 1 is for simultaneous combustion of coal and biomass fuel including a furnace that co-fires at least two kinds of fuels composed of solid fossil fuel and biomass fuel, and a fuel supply device that supplies fuel to the furnace. In this combustion apparatus, a solid fossil fuel supply flow path for supplying pulverized solid fossil fuel to a furnace, a burner provided at the tip of the solid fossil fuel supply flow path, and a solid fossil fuel supply flow immediately before the burner A biomass fuel supply flow path for supplying pulverized biomass fuel connected to the passage to the combustion furnace, and a wall surface of the solid fossil fuel supply flow path at a connection portion of the biomass fuel supply flow path to the solid fossil fuel supply flow path can be disposed of at a position 4 equally divided in the radial direction, characterized in that a venturi portion on the inner wall surface of the biomass fuel supply passage in the vicinity of the connecting portion to the solid fossil fuel supply channel It is a coal and combustion equipment for biomass fuel simultaneous combustion to be.

  The mixed state of both fuels in the fuel supply pipe of the present invention and in the fuel supply pipe shown in FIG. 8 is schematically shown in the pipe cross-sectional views in FIGS. 5 (a) and 5 (b), respectively. Is smaller in specific gravity than pulverized coal particles and is transported immediately in a laminar flow of pulverized coal flow at the junction of both fuels in the fuel supply pipe shown in FIG. The biomass fuel flow is biased to the side surface on one side of the pipe 2 ′. On the other hand, the flow rate of the biomass fuel increases at the venturi portion 7b on the inner wall surface of the biomass fuel pipe 7 immediately before the junction of both fuels in the fuel supply pipe of the present invention shown in FIG. Is obtained. Since the biomass fuel flow penetrates the pulverized coal flow even after merging with the pulverized coal flow due to the penetration force of the biomass fuel flow, as a result, the biomass fuel particles and the pulverized coal particles are uniformly mixed.

According to the present invention, since the venturi portion is provided on the inner wall surface of the biomass fuel supply flow channel in the vicinity of the connection portion to the solid fossil fuel supply flow channel, the biomass fuel is solidified to rapidly expand after being squeezed by the venturi portion. Easily disperse in the solid fossil fuel flow in the fossil fuel supply flow path to facilitate uniform mixing of both fuels, and achieve uniform mixing of pulverized coal and biomass particulates in the fuel flow path upstream of the co-fired burner. since it is possible to achieve, than the individual combustion of the solid fuel alone can be further renewable energy by utilizing NOx reduction and biomass, dust, wastes, etc. effective use solid fossil fuel savings and CO ₂ generation amount suppression It is.
Furthermore, since the attachment portion of the biomass fuel channel to the solid fossil fuel supply channel can be changed by 90 degrees around the axis of the solid fossil fuel supply channel, the biomass fuel supply channel can be attached to the solid fossil fuel supply channel. You can change the location.

Embodiments of the present invention will be described with reference to the drawings.
This embodiment is applied to a line blend type combustion apparatus shown in FIG.
The main fuel coal (China 80 wt%, Indonesia 20 wt%) is supplied into the coal mill 1 shown in FIG. 7A together with a carrier gas such as air, and is pulverized simultaneously with drying inside the mill 1. The pulverized coal having a 200 mesh pass (about 37 microns) 80 wt% and a specific gravity of 0.2 passes through the pulverized coal pipe 2, is supplied to the mixed combustion burner 3, and then is put into the furnace 5 and burned.

  On the other hand, the biomass as auxiliary fuel is obtained in the present embodiment by using a biomill 6 to obtain a pulverized mixture of bark and thinned wood having a specific gravity of 0.1 to 3 milliunder and a specific gravity of 0.1 as woody biomass fuel. Is supplied to the mixed combustion burner 3 from the bio-conveying pipe 7 of a different system by the carrier air by a blower or the like. The mixing ratio of biomass particles to pulverized coal is generally about several to 10% in terms of heat input ratio, but in this example, it was set to 5%.

Next, the structure of the burner part and the fuel piping on the upstream side thereof is shown in FIGS.
FIG. 1 shows a partial cross-sectional view of a front end of a fuel supply pipe to a furnace that co-fires two kinds of fuels composed of coal and biomass and a mixed combustion burner 3 connected to the tip. Although the side wall surface 2a of the pulverized coal pipe 2 is illustrated on the base side of the burner 3 shown in FIG. 1, the side wall surface 2a is provided with a connection portion 2a1 to the biomass pipe 7. The connecting portion 2a1 divides the side wall surface 2a of the pulverized coal pipe 2 into four equal parts in the radial direction so that the attachment portion of the biomass pipe 7 to the pulverized coal pipe 2 can be changed by 90 degrees around the axis of the pulverized coal pipe 2. It can be installed at the place to do.

  FIG. 2 is a view seen from the direction of arrow A in FIG. Is provided. FIG. 3 shows a cross-sectional view of the connecting portion 7a made of the bent pipe of the biomass pipe 7. As shown in FIG. The connecting portion 7a is constituted by the bent pipe shown in FIG. 3 in order to obtain a space saving effect. A venturi portion 7b is provided on the inner wall surface of the biomass pipe 7 in the vicinity of the connection portion to the side wall surface 2a of the pulverized coal pipe 2, and the biomass fuel supplied from the upstream side of the connection portion 7a formed of a curved pipe is pulverized coal. It is throttled just before merging with the fuel and expanded immediately after that. Therefore, after the biomass fuel flowing through the biomass pipe 7 is squeezed by the venturi portion 7b, the biomass fuel rapidly expands so that it can be easily dispersed in the pulverized coal flow in the pulverized coal pipe 2 to facilitate uniform mixing of both fuels. . In particular, since the connecting portion 7a to the side wall surface 2a of the pulverized coal pipe 2 is provided in the vicinity of the burner 3, the air flow energy of the pulverized coal fuel is a region where the energy is rapidly weakened, and the biomass fuel is the venturi portion 7b of the biomass pipe 7. After being squeezed, the effect of rapidly expanding and dispersing the flow of biomass fuel particles within the pulverized coal flow in the pulverized coal pipe 2 is high.

  Further, as shown in FIG. 4, even when the biomass pipe 7 is attached to the fuel in the pulverized coal pipe 2 at a tilt angle of 90 ° or less from the upstream side in the flow direction (arrow A), the biomass fuel is After being squeezed by the venturi portion 7b, it rapidly expands, so that it is easily dispersed in the pulverized coal flow in the pulverized coal pipe 2, so that both fuels can be more uniformly mixed.

  FIG. 8 is a perspective view of the fuel supply pipe of the combustion apparatus manufactured by Gelderland, and a biomass fuel cylindrical auxiliary supply pipe 7 ′ is attached to the side surface of the pulverized coal fuel main supply pipe 2 ′ from a direction orthogonal thereto. FIG. 8 shows an external view of the fuel line structure of the line blend system. Since the fuel pipe shown in FIG. 8 does not have the venturi part (throttle part) 7b of the biomass pipe 7 of this embodiment, it is introduced into the pulverized coal pipe 2 ′. Since the specific gravity of the biomass is smaller than that of pulverized coal, it flows along the inner wall surface side of the pulverized coal pipe 2 ', and the degree of mixing with pulverized coal is inferior to that of the present embodiment.

  Pulverized coal (83 wt% Chinese coal, 17 wt% Indonesian coal), 100 wt% biomass fuel, and a mixture of the pulverized coal and biomass fuel (79 wt% Chinese coal, 16 wt% Indonesian coal, 5 wt% biomass) Table 1 shows the characteristic evaluation data at the time of co-firing regarding).

The ash softening temperature of the biomass fuel alone is about 1250 ° C., and there is potential for slagging, but the ash content is low at around 1%, so the slagging property was not adversely affected by the mixture of pulverized coal and biomass fuel. Regarding fouling, the biomass fuel alone has a high content of NaO and K ₂ O in the ash and needs attention, but in this example, it was at a level with no problem.

  Regarding the amount of NOx generated, the amount of volatile components (56%) of biomass alone is large and the amount of nitrogen (0.5%) is small, so the amount of NOx generated is low, and about 15% of the base NOx value during pulverized coal combustion Diminished.

  In the above-described embodiments, two types of fuel supply systems are shown with coal as the main fuel and woody biomass as the secondary fuel. However, other types of fuels such as waste, waste materials, and waste may be simultaneously supplied. Even when the different type of fuel is used, the use form is not particularly limited as long as the volatile matter is basically higher than that of the main fuel (coal), and the configuration of the burner portion is the same. As a result, the combustion effect of high efficiency and low NOx can be obtained.

  The present invention has high industrial applicability through establishment of a technique for co-firing biomass fuel with coal in order to suppress carbon dioxide emission due to fossil fuel combustion.

The partial cross section figure of the fuel-combustion burner connected to the front-end | tip part of the fuel supply piping to the furnace which carries out the co-combustion of the 2 types of fuel which consists of coal and biomass of one Example of this invention is shown. The figure seen from the arrow A direction of FIG. Sectional drawing of the connection part of the piping which supplies the biomass fuel connected to the pulverized coal slag of the base side of the mixed combustion burner of FIG. 1 is shown. The modification of FIG. 2 is shown. FIG. 5A is a cross-sectional view of a pipe schematically showing a mixed state of pulverized coal and biomass in the fuel supply pipe of the present invention (FIG. 5A) and FIG. 5B is a cross-sectional view of a conventional fuel supply pipe. is there. A schematic diagram of the combustion system of the individual supply system (Fig. 6 (a)) that separately pulverizes coal and biomass separately in a mill and supplies them separately to the furnace burner, and separate coal and biomass into a combined combustion burner of the furnace A schematic diagram of the combustion apparatus (FIG. 6B) is shown in which the biomass is supplied to the burner in the burner and coal is injected into the furnace from the outer peripheral side of the biomass injection nozzle. Combustion device schematic diagram (Fig. 7 (a)) with a configuration (line blend system) that connects each supply pipe of coal and biomass separately pulverized by a mill and supplies both mixed fuels to a mixed combustion burner; FIG. 7B shows a schematic diagram of the combustion device (FIG. 7B) in which coal and biomass are pulverized by the same mill and mixed fuel is supplied to the burner from the fuel supply pipe (same burner method). The external view of the fuel blend structure of the line blend system which attached the cylindrical auxiliary supply piping of the biomass fuel from the direction orthogonal to the side surface of the main supply piping of the pulverized coal fuel in the combustion apparatus made from Gelderland is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coal mill 2 Pulverized coal piping 2a Side wall surface 2a1 Pipe connection part 3 Mixed combustion burner 3a Biomass injection nozzle 5 Furnace 6 Biomill 7 Biomass piping 7a Biomass pipe connection part 7b Venturi part 10 of biomass pipe connection part inner wall 10 Pulverized coal burner 11 Biomass burner 12 Mill 13 Mixed fuel piping

Claims (1)

In a combustion apparatus for simultaneous combustion of coal and biomass fuel, comprising a furnace for co-firing at least two kinds of fuel consisting of solid fossil fuel and biomass fuel, and a fuel supply apparatus for supplying fuel to the furnace,
A solid fossil fuel supply passage for supplying the ground solid fossil fuel to the furnace;
A burner provided at the tip of the solid fossil fuel supply flow path;
A biomass fuel supply flow path for supplying pulverized biomass fuel to the combustion furnace, the tip connecting to the solid fossil fuel supply flow path immediately before the burner,
The connecting portion of the biomass fuel supply channel to the solid fossil fuel supply channel can be installed at a location that divides the side wall surface of the solid fossil fuel supply channel into four equal parts in the radial direction,
A combustion apparatus for simultaneous combustion of coal and biomass fuel, characterized in that a venturi portion is provided on the inner wall surface of the biomass fuel supply flow path in the vicinity of the connection portion to the solid fossil fuel supply flow path.

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