JP5848983B2 - Co-firing method of pulverized coal and biomass fuel and pulverized coal fired boiler furnace - Google Patents

Description

  The present invention relates to a method of co-firing biomass fuel containing a large amount of water together with pulverized coal in a pulverized coal-fired boiler furnace, and a pulverized coal-fired boiler furnace for biomass fuel co-firing used in the method.

  As one of the methods for suppressing global warming caused by carbon dioxide, it has been noticed that a part of fossil fuel is replaced with biomass fuel. In a pulverized coal fired boiler furnace, a technique for replacing part of the pulverized coal with biomass fuel has been proposed.

  For example, Patent Document 1 discloses that when pulverized wood is mixed with pulverized coal and burned in a boiler furnace, biomass fuel is supplied to a burner other than the lowermost burner. A mixed firing method has been proposed.

  According to the method of Patent Document 1, since the so-called slagging phenomenon in which the unburned residue and ash of pulverized wood powder adhere to the heat transfer surface in the boiler furnace can be mitigated, the operation of the boiler becomes unstable. It is described that the unburned ratio of the powder can be reduced to about 1.5% by mass.

  By the way, the biomass fuel used in the Example described in Patent Document 1 is wood flour having a moisture content of 2.1 mass% and an average particle size of 0.7 mm. This is equivalent to 2% by mass of the moisture of the pulverized coal that has been co-fired, and is in a state of being dried in the atmosphere or equivalent to that. Although the particle size is larger than that of pulverized coal, the biomass fuel is premised on pretreatment such as pulverization.

  However, among the biomass fuels that are currently required to be used, there are those that contain a lot of water, such as coffee (such as coffee coffee and tea chaff). These contain water of several tens of mass%, and at the same time have a particle size of millimeter order.

  Therefore, in order to complete the combustion of the biomass fuel containing several tens of mass% of water and having a particle size of millimeter order by the method proposed in Patent Document 1, the biomass fuel is added before being put into the boiler furnace. Ancillary equipment such as drying equipment and grinding equipment for drying and grinding was necessary.

JP 2007-101135 A

  The problem to be solved by the present invention is to dry and pulverize the biomass fuel in order to complete the combustion of the biomass fuel containing a large amount of water and having a particle size of millimeter order by the method proposed in Patent Document 1. An additional facility such as a drying facility or a grinding facility is necessary.

The method of co-firing pulverized coal and biomass fuel of the present invention,
In order to combust in a pulverized coal fired boiler furnace without requiring additional equipment such as drying equipment and pulverization equipment when co-firing biomass fuel with a lot of moisture and having a particle size of millimeter order with pulverized coal,
When supplying pulverized coal and biomass fuel together with air from the multistage burner to the pulverized coal fired boiler furnace provided with multistage burners in the height direction,
For large-sized biomass fuel with a particle size of 3 mm or less, containing water of more than 40% by mass and within 80% by mass, and an integrated particle size distribution of 80% or more, the vertical direction from the bottom burner The main feature is that it is supplied from a burner placed at a position higher than 5 m.

The method for co-firing pulverized coal and biomass fuel of the present invention is as follows.
In a pulverized coal fired boiler furnace that supplies pulverized coal and biomass fuel together with air from a multistage burner provided in the height direction,
For large-sized biomass fuel with a particle size of 3 mm or less, containing water of more than 40% by mass and within 80% by mass, and an integrated particle size distribution of 80% or more, the vertical direction from the bottom burner This can be carried out using the pulverized coal fired boiler furnace for biomass fuel co-firing of the present invention provided with a system for supplying to a burner arranged at a position 5 m or higher.

  In the present invention, a large-sized biomass fuel having a particle size of 3 mm or less, containing water of more than 40% by mass and not more than 80% by mass, and an accumulated particle size distribution of 80% or more is perpendicular to the bottom burner. Therefore, it can be burned in the boiler furnace without requiring additional equipment such as drying equipment or grinding equipment.

  According to the present invention, even a biomass fuel containing a large amount of water and having a particle size on the order of millimeters does not require ancillary equipment such as drying equipment or grinding equipment, and is mixed with pulverized coal and burned in a boiler furnace Can be made. Therefore, in order to suppress the generation of carbon dioxide, it is possible to greatly expand the options of biomass fuel that substitutes for fossil fuel.

It is a schematic block diagram of the one-dimensional laminar flow furnace (test apparatus) used for the investigation of a combustion characteristic. The figure which showed the comparison of the combustion rate of the biomass fuel obtained from the dry fuel test and the wet fuel test, (a) is the figure which showed the influence of the particle diameter with respect to a combustion rate, (b) is the furnace temperature with respect to a combustion rate FIG. It is the figure which showed the relationship between the particle diameter of a coffee grinder in case a furnace temperature is 1200 degreeC, and required residence time. It is the figure which showed the distance between the superficial velocity in a boiler furnace in the case of a standard operating state, and each burner. It is the figure which showed the fall behavior of the coffee bowl with a particle diameter of 2 mm. The figure shows the floating and falling behavior of particles, (a) when the gas flow rate is 2 m / sec, (b) when the gas flow rate is 5 m / sec, (c) when the gas flow rate is 8 m / sec. It is.

  The present invention aims to burn biomass fuel in a boiler furnace without requiring additional equipment such as drying equipment and crushing equipment when co-firing biomass fuel with a large amount of water and having a particle size on the order of millimeters with pulverized coal. The biomass fuel was supplied from the burner at a position 5 m or higher in the vertical direction from the lowest burner.

  The inventors investigated the combustion characteristics of biomass fuel containing a large amount of moisture, and obtained guidelines for co-firing biomass fuel containing a lot of moisture with pulverized coal in a pulverized coal-fired boiler furnace.

FIG. 1 shows a test apparatus used for investigating the combustion characteristics.
An alumina tube 1 is a reaction tube. A fuel nozzle 3 connected to the fuel feeder 2 is inserted concentrically with the alumina tube 1 from the upper end of the alumina tube 1 in the height direction. A mesh material 4 is installed on the outer periphery of the upper end opening of the fuel nozzle 3, and a pipe 5 is introduced above the mesh material 4, and O ₂ gas and N _{2 in the} gas cylinders 6 a to 6 c are passed through the pipe 5. Gas and air are mixed as appropriate, preheated by the heater 7, and then supplied to the outer peripheral portion of the fuel nozzle 3.

  Further, an electric furnace 8 is provided on the outer peripheral portion of the alumina tube 1, and a temperature at a required height position in the alumina tube 1 heated by the electric furnace 8 is detected by a thermocouple 9, and based on the detected temperature, The heating temperature in the alumina tube 1 is controlled by the temperature controller 10.

  On the other hand, a water-cooled probe 11 is inserted concentrically from the lower end in the height direction of the alumina tube 1, and its tip position can be arbitrarily changed by raising and lowering the water-cooled probe 11. At the base end of the water-cooled probe 11, a suction pipe 14 having a filter 12 for collecting solid particles at the front end and a suction fan 13 at the base end is installed, and gas analysis installed in the middle of the suction pipe 14. The apparatus 15 analyzes the components of the suction gas.

  And the test detected with the thermocouple 9, and based on the temperature data taken in to PC16, the temperature controller 10 was used and the inside of the alumina tube 1 was raised to the temperature of test conditions with the electric furnace 8. FIG.

  Thereafter, biomass fuel is introduced from above through the fuel nozzle 3, and combustion particles of biomass fuel falling from the top are sampled by the water-cooled probe 11. At that time, the burning rate of the biomass fuel for each residence time in the furnace is grasped by changing the sampling position of the particles.

  For the test, coffee mash was used as biomass fuel. The water content of the coffee grounds used in the dry fuel test was 6% by mass, and the water content of the coffee grounds used in the wet fuel test was 60% by weight.

  FIG. 2 is a diagram comparing the combustion rates of biomass fuels obtained from the dry fuel test and the wet fuel test conducted using the test apparatus shown in FIG.

  As shown in FIG. 2, in the case of the wet fuel test, the evaporation time of water contained in the biomass fuel becomes longer. Therefore, in order to obtain a combustion rate comparable to that of the dry fuel test, a longer residence time is required than in the dry fuel test. I found out that The time required for the evaporation of moisture is considered to depend on the particle size and the furnace temperature.

  That is, from FIG. 2 (a) showing the test results when the furnace temperature is 1000 ° C., when the particle size of the coffee grounds, which is biomass fuel, is 74 μm, both the dry fuel test and the wet fuel test have residence time and combustion. The relationship between the rates was almost the same, and it was found that there was almost no need to consider the evaporation time (circles and circles). On the other hand, it was found that when the particle size of the coffee koji is 428 μm, it is necessary to consider the residence time of about 0.5 seconds (□ mark and ■ mark).

  Also, from FIG. 2 (b) showing the test results when the furnace temperature is 1000 ° C. and 1200 ° C., when the furnace temperature is 1200 ° C., the wet fuel test is similar to the dry type in a shorter evaporation time. It was found that the combustion rate can be obtained (□ and ■).

  From the above, as the particle size of the biomass fuel decreases and as the furnace temperature increases, the time required for the water in the particles to evaporate tends to decrease, and the boiler furnace having a furnace temperature of at least 1200 ° C. It was found that a combustion rate comparable to that of the dry type can be obtained with a shorter evaporation time.

  Next, when the in-furnace temperature is 1200 ° C., the residence time required for the coffee mash, which is biomass fuel, to complete combustion is shown in FIG.

  In the case of dry coffee grounds, the residence time required for completion of combustion increases as the particle size increases along the curve indicated by the thin line in FIG. 3, and about 0.6 seconds when the particle size is about 2 mm. It was found that the residence time of

  On the other hand, in the case of an undried (wet) coffee mash, there is an ignition delay of about 0.5 seconds as described above, so as the particle diameter increases along the curve shown by the solid line in FIG. It has been found that the residence time required for completion of combustion is long, and when the particle size is about 2 mm, a residence time of about 1.2 seconds is required.

  Based on the above results, the inventors have determined what conditions are necessary to obtain a residence time of about 1.2 seconds on the premise of coffee mash, which is a biomass fuel with a particle size of 2 mm. investigated. Fig. 4 shows the pulverized coal fired boiler furnace to be studied.

  The brewing position of the coffee slag into the pulverized coal fired boiler furnace 21 shown in FIG. The lower burner 25 has four different locations in the height direction. In addition, 23a, 24a, 25a in FIG. 4 shows the blowing path | routes of the pulverized coal and air to the upper stage burner 23, the middle stage burner 24, and the lower stage burner 25.

  FIG. 4 shows the superficial velocity in the boiler furnace in a standard operating state. As shown in FIG. 4, it can be seen that the superficial velocity increases as the passing gas amount increases and the gas temperature rises from the bottom side to the top side of the boiler furnace.

  From the results of FIG. 4, the coffee mash blown into the pulverized coal-fired boiler furnace burns while dropping in the boiler furnace, so that the combustion can be completed if the blowing position of the coffee mash is at the upper part of the boiler furnace. I understand.

  Fig. 5 shows the dropping behavior when a coffee mash having a moisture content of 60% by mass and a particle diameter of 2mm is blown from each of the above blowing positions, and the evaluation when the coffee mash having a particle diameter of 2mm is blown from the four positions. Shown in Table 1 below.

  Next, the gas flow velocity in each region above the lower burner to middle burner, middle burner to OAP, and OAP is 2 m / sec, 5 m / sec, and 8 m / sec, which are the same as the superficial velocity shown in FIG. The floating and falling behavior of the particles was investigated when the water content was 60% by mass and the particle diameters were 1 mm, 2 mm, and 3 mm. The result is shown in FIG.

  Since the gas flow rate in the region from the lower burner to the bottom of the boiler furnace is considered to be 2 m / sec or less from FIG. 4, the moisture content is 60% by mass and the particle diameter is 2 mm, which is known from the previous survey results. In the case of biomass fuel, it is clear from FIG. 6 that a falling distance of 5 m or more is obtained with a residence time of about 1.2 seconds when combustion is completed. Furthermore, when the particle diameter is 3 mm, the drop distance is further increased.

  Therefore, when a biomass fuel having a water content of 60% by mass and a particle size of 3 mm is blown from a lower burner installed at a position 4 m (see FIG. 4) from the bottom of the boiler furnace, or even when the particle size is smaller than 2 mm, When the water content is more than 60% by mass, combustion is not completed in the boiler furnace.

  On the other hand, although the gas flow velocity in the region from the lower burner to the bottom of the boiler furnace is considered to be 2 m / sec or less from FIG. 4, the value cannot be measured.

Therefore, the inventors considered as follows from the results of FIGS.
When a biomass fuel having a moisture content of 60% by mass and a particle size of 3 mm is blown, if the height in the vertical direction, which is the moving distance from the blowing position to the lower burner, is 5 m or more, the lower burner reaches the bottom of the boiler furnace. Whatever the gas flow rate between them, the residence time of the biomass particles can be secured for about 1.2 seconds.

  Even if the water content increases to 80% by mass, the residence time (about 1.2 seconds) to be secured when the water content is 60% by mass is 80/60, which is about 1.6 seconds.

  Therefore, when the superficial velocity is blown from a position 5 m higher in the vertical direction from the lower burner of 4.1 m / sec, about 1.2 seconds have elapsed when the lower burner is reached (FIG. 6 (b ))), Combustion is completed if the time from the lower burner to the bottom of the boiler furnace is 0.4 sec or more.

  When the gas flow rate is 2 m / sec, the moving distance in 0.4 sec is less than 1 m as seen in FIG. 6A. Therefore, the distance from the lower burner to the bottom of the boiler furnace is 4 m. In this case, even if it is a biomass fuel having a water content of 80% by mass and a particle size of 3 mm, it is considered that the combustion is completed before it falls from the lower burner to the bottom of the boiler furnace.

  Since the present invention is intended for co-firing of biomass fuel having a particle size of millimeter order with a large water content, the water content exceeds 40 mass% and the cumulative particle size distribution of particles of 3 mm or less is 80% or more. It was decided to target.

The present invention has been made based on the above findings of the inventors,
When supplying pulverized coal and biomass fuel together with air from the multistage burner to the pulverized coal fired boiler furnace provided with multistage burners in the height direction,
For large-sized biomass fuel with a particle size of 3 mm or less, containing water of more than 40% by mass and within 80% by mass, and an integrated particle size distribution of 80% or more, the vertical direction from the bottom burner It is a co-firing method of pulverized coal and biomass fuel, characterized in that it is supplied from a burner arranged at a position 5 m or higher.

And the above-mentioned method of the present invention comprises:
As shown in FIG. 4, in a pulverized coal fired boiler furnace 21 that is provided in the height direction, for example, pulverized coal and biomass fuel are supplied together with air from three stages of burners 23 to 25 and co-fired,
For large-sized biomass fuel having a particle size of 3 mm or less, containing water of more than 40% by mass and not more than 80% by mass, and an accumulated particle size distribution of 80% or more, 5 m in the vertical direction from the lower burner 25 It can implement using the pulverized-coal-fired boiler furnace for biomass fuel co-firing of this invention provided with the system | strain 26 supplied to the upper stage burner 23 arrange | positioned above at the high position.

DESCRIPTION OF SYMBOLS 1 Aluminum tube 2 Fuel feeder 3 Fuel nozzle 4 Mesh material 5 Piping 6a-6c Gas cylinder 7 Heater 8 Electric furnace 9 Thermocouple 10 Temperature controller 11 Water cooling probe 12 Filter 13 Suction fan 14 Suction pipe 15 Gas analyzer 16 PC
21 Pulverized coal fired boiler furnace 23 Upper burner 24 Middle burner 25 Lower burner 26 Biomass fuel and air supply system

Claims (2)

When supplying pulverized coal and biomass fuel together with air from the multistage burner to the pulverized coal fired boiler furnace provided with multistage burners in the height direction,
For large-sized biomass fuel with a particle size of 3 mm or less, containing water of more than 40% by mass and within 80% by mass, and an integrated particle size distribution of 80% or more, the vertical direction from the bottom burner A co-firing method of pulverized coal and biomass fuel, characterized in that it is supplied from a burner arranged at a position 5 m or higher. In a pulverized coal fired boiler furnace that supplies pulverized coal and biomass fuel together with air from a multistage burner provided in the height direction,
For large-sized biomass fuel with a particle size of 3 mm or less, containing water of more than 40% by mass and within 80% by mass, and an integrated particle size distribution of 80% or more, the vertical direction from the bottom burner A pulverized coal fired boiler furnace for biomass fuel co-firing, which is provided with a system for supplying to a burner placed at a position 5 m or higher.

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