JP6454575B2 - Operation method of melting furnace - Google Patents

Description

  The present invention relates to a method for operating a melting furnace.

  Conventionally, a melting furnace is known in which combustible gas generated in a gasification furnace is combusted and ash contained in the combustible gas is melted. As such a melting furnace, a so-called swirling flow melting furnace, that is, a combustion chamber in which combustible gas flowing in through an inlet is swirled and combusted, and molten slag formed by melting ash contained in the combustible gas are discharged. There is known a melting furnace having a tap outlet for gas discharge and a gas discharge chamber for discharging exhaust gas after combustion in the combustion chamber. In this melting furnace, slag tends to adhere to the inner surface of the combustion chamber and the inner surface of the gas discharge chamber during operation of the melting furnace.

On the other hand, it is also known to promote melting of the slag by adjusting the basicity (CaO / SiO ₂ ) of the slag adhered in the melting furnace. For example, in Patent Document 1, the basicity of the upstream slag adhering to the combustion chamber is different from the basicity of the downstream slag adhering to the gas exhaust chamber, and the basicity of the upstream slag can be adjusted. There is disclosed a melting furnace including a first supply unit that supplies a first adjusting agent and a second supply unit that supplies a second adjusting agent capable of adjusting the basicity of the downstream slag. A 1st supply part supplies a 1st regulator to a combustion chamber through an inflow port. The second supply unit supplies the second regulator into the gas discharge chamber from above the tap outlet.

JP 2006-349218 A

  Although the downstream slag can also be removed by the operation method of the melting furnace as described in Patent Document 1, the second adjusting agent is uniformly supplied to the entire surface of the downstream slag by the second supply unit. Is difficult.

  The objective of this invention is providing the operating method of the melting furnace which can remove both upstream slag and downstream slag effectively.

  As a result of intensive studies to solve the above problems, the present inventors have found that the combustible gas while forming a swirling flow with the combustible gas in the melting furnace as described in Patent Document 1, that is, the combustion chamber. In the combustion chamber, slag formed by melting a large particle ash having a relatively large particle size out of the ash contained in the combustible gas is likely to adhere to the inner surface of the combustion chamber, while the gas discharge chamber It has been found that slag formed by melting a small particle size ash having a relatively small particle size among the ash easily adheres to the inner surface. Specifically, in the combustion chamber, a relatively large centrifugal force acts on the large particle size ash, so that the large particle size ash collides with the inner surface of the combustion chamber, thereby melting the large particle size ash. The formed slag tends to adhere to the inner surface of the combustion chamber. On the other hand, since the small particle size ash only has a relatively small centrifugal force in the combustion chamber, the small particle size ash is scattered to the gas discharge chamber, and the small particle size ash is transferred from the inlet to the gas discharge chamber. The slag formed by the melting of the small particle size ash is likely to adhere over a wide area in the gas discharge chamber because it is diffused throughout the process.

  Therefore, the present inventors supply, through the inlet, those having a relatively large particle size and those having a relatively small particle size as basicity adjusting agents so as to match the behavior of the ash in the melting furnace. As a result, it was conceived that both the upstream slag adhering to the combustion chamber and the downstream slag adhering to the gas discharge chamber can be effectively removed.

  The present invention has been made from such a viewpoint, and has an inflow port that allows inflow of combustible gas generated in a gasification furnace, and forms a swirl flow with combustible gas that has flowed in through the inflow port. A combustion chamber for burning the combustible gas and melting the ash contained in the combustible gas, and a discharge chamber for discharging molten slag formed by melting the ash is provided below the combustion chamber. A melting furnace including a furnace body having a soot opening and a gas discharge chamber that is provided on the downstream side of the combustion chamber and above the pouring outlet and exhausts exhaust gas after burning in the combustion chamber. A melting step of melting the ash contained in the combustible gas by burning the combustible gas while forming a swirl flow with the combustible gas in the combustion chamber; and A regulator supply step for supplying a basicity adjusting agent capable of adjusting the basicity of slag adhering to the inside of the main body into the furnace body, and in the adjustment agent supply step, the combustion is used as the basicity adjustment agent. A first regulator comprising a component having a particle size that can be captured by an upstream slag adhering to a room and having a basicity of the upstream slag within a predetermined range; and the first regulator. And having a particle size that can be captured by the downstream slag adhering to the gas discharge chamber, and the basicity of the downstream slag can be within the predetermined range. A melting furnace operating method is provided in which a second regulator containing various components is supplied through an inlet of the combustion chamber.

  In this method, the first regulator having a relatively large particle size adheres to the surface of the upstream slag that adheres to the combustion chamber while swirling by receiving a large centrifugal force in the combustion chamber, while having a relatively small particle size. Since the second adjusting agent has substantially uniformly adhered to the surface of the downstream slag that scatters to the gas discharge chamber and adheres to the gas discharge chamber, it effectively removes both the upstream slag and the downstream slag. be able to. Specifically, since the first adjusting agent has a particle size that can be captured by the upstream slag, in other words, a large mass, a large centrifugal force is exerted on the first adjusting agent in the combustion chamber. Thus, the first adjusting agent tends to adhere to the surface of the upstream slag that adheres to the inner surface of the combustion chamber. On the other hand, since the centrifugal force acting on the second adjusting agent in the combustion chamber is smaller than the centrifugal force acting on the first adjusting agent, the second adjusting agent scatters to the gas discharge chamber, and Since the 2 adjusting agent is sufficiently diffused in the process from the inlet to the gas discharge chamber, it tends to adhere substantially uniformly to the surface of the downstream slag. Therefore, in this method, since the basicity of the upstream slag adhering to the combustion chamber is effectively adjusted by the first regulator having a relatively large particle size, melting of the upstream slag is promoted, and the comparison is made. Since the basicity of the downstream slag adhering to the gas discharge chamber is effectively adjusted by the second adjusting agent having a small particle size, melting of the downstream slag is promoted.

In this case, in the adjusting agent supplying step, the first adjusting agent has a particle diameter of 150 μm or more and the second adjusting agent has a particle diameter of 15 μm or more and 40 μm or less. It supplied to the furnace body through the inlet.

  In this way, the first adjusting agent is more reliably captured by the upstream slag, and the second adjusting agent is more reliably captured by the downstream slag. Specifically, by setting the particle diameter of the first adjusting agent to 150 μm or more, a sufficiently large centrifugal force acts on the first adjusting agent in the combustion chamber, so that the first adjusting agent is located upstream in the combustion chamber. Effectively captured by slag. Then, by setting the particle size of the second adjusting agent to 15 μm or more and 40 μm or less, the second adjusting agent is effectively captured by the downstream slag in the gas discharge chamber. Specifically, by setting the particle size of the second adjusting agent to 15 μm or more, the second adjusting agent is not trapped by the downstream slag, and the equipment (such as a bag filter) provided on the downstream side of the melting furnace. Scattering is suppressed. And by making the particle diameter of a 2nd adjustment agent 40 micrometers or less, the centrifugal force which acts with respect to a 2nd adjustment agent in a combustion chamber becomes small, and, thereby, a 2nd adjustment agent is capture | acquired by upstream slag. Is suppressed.

  As described above, according to the present invention, it is possible to provide a melting furnace operating method capable of effectively removing both the upstream slag and the downstream slag.

It is a figure which shows the outline of the gas melting furnace of one Embodiment of this invention. It is a figure which shows the relationship between the particle size of a basicity adjusting agent, and the capture | acquisition rate in the melting furnace of a basicity adjusting agent. It is a figure which shows the frequency distribution of the basicity adjustment agent capture | acquired with the bag filter.

  A gasification melting furnace according to an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the gasification melting furnace of this embodiment includes a gasification furnace 10 and a melting furnace 15.

  The gasification furnace 10 is a furnace that takes out combustible gas from the waste by heating the waste. In the present embodiment, a fluidized bed gasifier is used as the gasifier 10. Specifically, the fluidized bed gasification furnace is a furnace that takes out combustible gas from the waste by heating the waste in a fluidized bed formed by fluidizing the fluidized medium with the fluidized gas. . The combustible gas generated in the gasification furnace 10 flows into the melting furnace 15 through a duct 40 connecting the gasification furnace 10 and the melting furnace 15.

  The melting furnace 15 is a furnace for melting the ash contained in the combustible gas by burning the combustible gas generated in the gasification furnace 10. In the present embodiment, a swirling flow melting furnace is used as the melting furnace 15. The melting furnace 15 includes a furnace body 20 and a basicity adjusting agent supply unit 30. The furnace body 20 includes a combustion chamber 21, a tap outlet 20 b, and a gas discharge chamber 26.

  The combustion chamber 21 has an inflow port 21a that allows inflow of combustible gas, and combusts the swirling combustible gas that has flowed in through the inflow port 21a. Combustion air for burning the combustible gas is supplied to the combustion chamber 21. The combustion chamber 21 has a shape extending in the vertical direction. In the present embodiment, the combustion chamber 21 includes an upstream combustion chamber 22 having an inlet 21a, a downstream combustion chamber 23 disposed below the upstream combustion chamber 22, an upstream combustion chamber 22 and a downstream combustion chamber. 23, and a diaphragm 24 provided at the boundary with the head 23.

  The upstream combustion chamber 22 is formed in a cylindrical shape, and is arranged in a posture in which the central axis is parallel to the vertical. The inlet 21 a is formed in the upper part of the upstream combustion chamber 22. The duct 40 is connected to a portion of the upstream combustion chamber 22 surrounding the inflow port 21a. The duct 40 is connected to the upstream combustion chamber 22 in such a posture that a combustible gas flowing into the upstream combustion chamber 22 through the inflow port 21 a forms a swirling flow that swirls along the inner peripheral surface of the upstream combustion chamber 22. Has been. Specifically, the duct 40 is connected to the upstream combustion chamber 22 in such a posture that the combustible gas flows into the upstream combustion chamber 22 from the inlet 21a in a direction different from the center of the upstream combustion chamber 22. Yes. In the present embodiment, the flow rate of the combustible gas flowing from the duct 40 into the combustion chamber 21 is set in the range of 15 m / s to 25 m / s.

  The downstream combustion chamber 23 has a bottom wall 23a having a shape extending obliquely downward from the lower portion of the throttle portion 24 toward the tap outlet 20b. Molten slag formed by melting the ash contained in the combustible gas during combustion of the combustible gas in the combustion chamber 21 flows down on the bottom wall 23a and is discharged from the outlet 20b. The throttle portion 24 has an inner diameter that is smaller than the inner diameter of the lower end portion of the upstream combustion chamber 22.

  The gas discharge chamber 26 is provided on the downstream side of the combustion chamber 21 and above the outlet 20b, and has a shape for discharging the exhaust gas after burning in the combustion chamber 21. The gas discharge chamber 26 is disposed on the opposite side (the right side in FIG. 1) of the combustion chamber 21 with respect to the tap outlet 20b. The gas discharge chamber 26 has a shape surrounding a space extending obliquely upward from the tap outlet 20b. The gas discharge chamber 26 has a bottom wall 27 having a shape that inclines upward as it is separated from the tap hole 20b.

  The basicity adjusting agent supply unit 30 supplies a basicity adjusting agent capable of adjusting the basicity of the slags S1 and S2 attached in the furnace body 20. Specifically, the basicity adjusting agent supply unit 30 has, as the basicity adjusting agent, a first adjusting agent having a particle size that can be captured in the combustion chamber 21, and a particle size of the first adjusting agent. A second regulator having a particle size that is small and can be captured in the gas discharge chamber 26 is supplied into the combustion chamber 21 through the inlet 21a. In the present embodiment, the basicity adjusting agent supply unit 30 is connected in the duct 40.

Here, “basicity” refers to a numerical value represented by CaO / SiO ₂ . That is, the basicity increases with the addition of calcium carbonate or the like, and decreases with the addition of silica or glass. For this reason, when the basicity is low, calcium carbonate or the like is added. Conversely, when the basicity is high, silica or glass is added.

  In the present embodiment, the “particle diameter” refers to a so-called 50% particle diameter (median diameter). The 50% particle size is a particle size when the cumulative rate of particles in the cumulative distribution (volume distribution) table is 50%. This particle size is measured by a laser diffraction / scattering method.

  The first adjusting agent includes a component capable of keeping the basicity of the upstream slag S1 attached in the combustion chamber 21 within a predetermined range (for example, 0.6 to 0.9). The upstream slag S1 is formed by melting of ash contained in the combustible gas that has flowed into the combustion chamber 21 through the inlet 21a and having a relatively large particle size. The second adjusting agent includes a component capable of keeping the basicity of the downstream slag S2 attached in the gas discharge chamber 26 (on the bottom wall 27 in the present embodiment) within a predetermined range. The downstream slag S2 is formed by melting of the ash contained in the combustible gas that has flowed into the combustion chamber 21 through the inlet 21a and having a relatively small particle size.

  In the present embodiment, the basicity adjusting agent supply unit 30 is a furnace having a particle size of 150 μm to 350 μm as the first adjusting agent and a particle size of 15 μm to 40 μm as the second adjusting agent. It is supplied into the main body 20. The reason for this will be described with reference to FIGS.

  FIG. 2 shows the relationship between the 50% particle size of the basicity adjusting agent and the capture rate of the basicity adjusting agent in the melting furnace 15. This relationship is obtained based on the supply amount of the basicity adjusting agent from the basicity adjusting agent supply unit 30 and the trapped amount captured in the slag obtained through the outlet 20b of the melting furnace 15. . Specifically, when the basicity adjusting agent is added to the ash flowing into the melting furnace 15, the amount of basicity component in the slag obtained through the tap outlet 21 b changes, so that the molten component of the ash flowing into the melting furnace 15 Is obtained in advance, and the amount of the basicity adjusting agent taken into the slag out of the basicity adjusting agent supplied through the inflow port 21a is obtained by obtaining the component of the slag obtained through the tap outlet 21b. it can. Using this, the capture rate of the basicity adjusting agent in the melting furnace 15 was determined. In FIG. 2, an area including an upper limit value and a lower limit value of a plurality of test results is displayed. In addition, although the capture rate in the melting furnace 15 is not 100% depending on the situation, a cause of this is a shift in the timing of measurement. Here, when the movement of the particles for each particle diameter was confirmed by simulation, most of the basicity adjusting agent having a relatively large particle diameter was discharged as slag through the outlet 21b, and FIG. Since consistency with the data is obtained, it is considered that most of the basicity adjusting agent supplied from the basicity adjusting agent supply unit 30 adheres to the upstream slag S1 in the combustion chamber 21. For the basicity adjuster having a relatively small particle size, the smaller the particle size, the larger the amount that passes through the combustion chamber 21 and moves to the bag filter. It was found that some of the particles moving to the bag filter contact the downstream slag S2 attached to the bottom wall 27 of the gas discharge chamber 26. Therefore, most of the basicity adjusting agent trapped in the combustion chamber 21 is discharged as slag through the outlet 21b, but the basicity adjusting agent having a relatively small particle size passes through the combustion chamber 21. Only a part of the movement to the bug filter contributes to the basicity adjustment of the slag. That is, FIG. 2 can be regarded as indicating the trapping amount of the basicity adjusting agent in the combustion chamber 21.

  As shown in FIG. 2, in the range where the 50% particle size of the basicity adjusting agent is 150 μm or more, 50% or more of the basicity adjusting agent supplied from the basicity adjusting agent supply unit 30 is in the combustion chamber 21. Captured (attaches to the upstream slag S1). For this reason, as the first adjusting agent, one having a 50% particle diameter of 150 μm or more is preferably selected, and further, one having a 50% particle diameter of 200 μm or more is preferably selected. Further, among the ash generated in the gasification furnace 10, although the particle size of 350 μm or more is very small, the upper limit value of the particle diameter of the first adjusting agent is set to 350 μm because the scattering amount to the melting furnace 15 is very small. Good.

  On the other hand, as shown in FIG. 2, in the range where the 50% particle size of the basicity adjusting agent is 40 μm or less, the capture rate of the basicity adjusting agent supplied from the basicity adjusting agent supply unit 30 in the combustion chamber 21 is high. Less than 40%. The low capture rate in the melting furnace 15 means that the particles pass through the melting furnace 15 and reach the bag filter disposed at a later stage than the melting furnace 15. It has been found that some of the particles passing through 21 and reaching the bag filter adhere to the furnace wall (bottom wall 27 of the gas discharge chamber 26) after the outlet 21b. Here, when ash is attached to the bottom wall 27 as slag, it is considered that the slag grows little by little starting from this. For this reason, it is preferable to select what has a 50% particle diameter of 40 micrometers or less as said 2nd regulator. From the viewpoint of moving the particles to the subsequent stage from the melting furnace 15, the 50% particle diameter of the second adjusting agent may be 30 μm or less.

  And it is preferable that the lower limit of the 50% particle diameter of a 2nd regulator is set to 15 micrometers. The reason for this will be described with reference to FIG. FIG. 3 shows the frequency distribution of the basicity adjusting agent captured by the bag filter at two sites (waste treatment facilities). As shown in FIG. 3, in the range where the 50% particle size of the basicity adjusting agent is smaller than 15 μm, most of the basicity adjusting agent supplied from the basicity adjusting agent supply unit 30 is a bag filter. In order to be captured, that is, to pass through the gas discharge chamber 26, the 50% particle diameter of the second adjusting agent is preferably set to 15 μm or more.

  Next, the operation method of the gasification melting furnace of this embodiment is demonstrated.

  First, waste is thrown into the gasifier 10. Then, combustible gas generated in the gasification furnace flows into the melting furnace 15 through the duct 40. The inflow speed of the combustible gas into the melting furnace 15 is about 15 m / s to 25 m / s.

  The combustible gas that has flowed into the combustion chamber 21 through the inflow port 21a burns while swirling in the combustion chamber 21, whereby the ash contained in the combustible gas is melted. The molten slag formed by melting the ash flows down on the bottom wall 23a of the downstream combustion chamber 23 and is discharged from the tap outlet 20b. On the other hand, the exhaust gas after burning in the combustion chamber 21 goes to the equipment on the downstream side of the melting furnace 15 through the gas discharge chamber 26.

Here, during operation of the gasification melting furnace, as shown in FIG. 1, the upstream slag S <b> 1 adheres to the inner surface of the combustion chamber 21 and the downstream slag S <b> 2 adheres to the inner surface of the gas discharge chamber 26. Therefore, the basicity adjusting agent (first adjusting agent and second adjusting agent) is supplied from the basicity adjusting agent supply unit 30. For example, when the basicity of the upstream slag S1 is low and the basicity of the downstream slag S2 is high, the upstream slag S1 can be captured as the first adjusting agent from the basicity adjusting agent supply unit 30. A particle having a particle size and containing a component (CaCO ₃ or the like) capable of increasing the basicity of the upstream slag S1 is supplied, and a particle size smaller than the particle size of the first adjusting agent is supplied as the second adjusting agent. In addition, a material having a particle size that can be captured by the downstream slag S2 and containing a component (such as SiO ₂ ) that can lower the basicity of the downstream slag S2 is supplied.

  Then, the first adjusting agent having a relatively large particle size adheres to the surface of the upstream slag S1 that adheres in the combustion chamber 21 while turning by receiving a large centrifugal force in the combustion chamber 21, while relatively small particles The second adjusting agent having a diameter scatters to the gas discharge chamber 26 and adheres substantially uniformly to the surface of the downstream slag S2 that adheres in the gas discharge chamber 26, so that the upstream slag S1 and the downstream slag S2 Both can be effectively removed. Specifically, since the first adjusting agent has a particle size that can be captured by the upstream slag S1, in other words, a large mass, the first adjusting agent has a large centrifugal force relative to the first adjusting agent in the combustion chamber 21. A force acts, whereby the first adjusting agent tends to adhere to the surface of the upstream slag S1. On the other hand, since the centrifugal force acting on the second adjusting agent in the combustion chamber 21 is smaller than the centrifugal force acting on the first adjusting agent, the second adjusting agent scatters to the gas discharge chamber 26, and Since the second adjusting agent is sufficiently diffused in the process from the inlet 21a to the gas discharge chamber 26, it tends to adhere substantially uniformly to the surface of the downstream slag S2 that adheres over a wide area in the gas discharge chamber 26. Therefore, in this embodiment, the basicity of the upstream slag S1 adhering in the combustion chamber 21 is effectively adjusted by the first regulator having a relatively large particle size, so that the melting of the upstream slag S1 is promoted. In addition, the basicity of the downstream slag S2 adhering to the inside of the gas discharge chamber 26 is effectively adjusted by the second adjusting agent having a relatively small particle size, so that the melting of the downstream slag S2 is promoted. .

  In the present embodiment, the basicity adjusting agent supply unit 30 has a particle size of 150 μm or more as the first adjusting agent, and a particle size of 15 μm or more and 40 μm or less as the second adjusting agent. Are supplied into the furnace body 20 through the inflow port 21a, so that the first adjusting agent is more reliably captured by the upstream slag S1, and the second adjusting agent is more reliably captured by the downstream slag S2. .

  Conventionally, when the basicity adjusting agent is supplied from one place, it is supplied for the purpose of being captured in the melting furnace, but it is also considered in which part of the melting furnace it is captured and the base It has not been studied until the particle size of the degree-adjusting agent is changed and mixed and used, and the type of the basicity adjusting agent to be mixed is changed as necessary. In this embodiment, since the particle size of the basicity adjusting agent is adjusted according to the location where the melting furnace is to be captured, the basicity is adjusted according to the location where the slag is deposited, and the upstream slag S1 and Each of the downstream slag S2 can be effectively removed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  The particle size of the basicity adjusting agent is not limited to 50% particle size. A so-called mode diameter may be employed as the particle diameter. Even in this case, the same effect as described above can be obtained.

  Further, the connection destination of the basicity adjusting agent supply unit 30 is not limited to the duct 40. The connection destination of the basicity adjusting agent supply unit 30 can be set in a range in which the basicity adjusting agent is supplied into the furnace body 20 through the inflow port 21a. For example, the basicity adjusting agent supply unit 30 may be connected to a portion of the combustion chamber 21 that surrounds the inflow port 21a. The basicity adjusting agent supply unit 30 may supply the basicity adjusting agent to the gasification furnace 10 together with the waste.

  Further, the shape of the furnace body 20 of the melting furnace 15 is not limited to the example of the above embodiment. For example, the combustion chamber 21 and the tap hole 20b may have a shape that overlaps in the vertical direction, or the gas discharge chamber 26 and the tap hole 20b may overlap in the vertical direction. Further, the bottom wall 27 of the gas discharge chamber 26 is not limited to a shape that is inclined so as to go upward as it goes downstream.

DESCRIPTION OF SYMBOLS 10 Gasification furnace 15 Melting furnace 20 Furnace main body 20b Outlet 21 Combustion chamber 21a Inlet 26 Gas discharge chamber 30 Basicity adjusting agent supply part 40 Duct

Claims (1)

It has an inlet that allows inflow of combustible gas generated in the gasification furnace, and combusts the combustible gas while forming a swirl flow with the combustible gas that flows in through the inlet, and is included in the combustible gas. A combustion chamber for melting the ash content, an outlet for discharging molten slag formed by melting the ash content, a downstream side of the combustion chamber and the outlet. A method for operating a melting furnace including a furnace body having a gas discharge chamber for discharging exhaust gas after being burned in the combustion chamber;
In the combustion chamber, a melting step of melting ash contained in the combustible gas by combusting the combustible gas while forming a swirl flow with the combustible gas;
A regulator supply step of supplying a basicity adjusting agent capable of adjusting the basicity of the slag adhering in the furnace body into the furnace body, and
In the adjusting agent supplying step, the basicity adjusting agent has a particle size that can be captured by the upstream slag adhering to the combustion chamber, and the basicity of the upstream slag falls within a predetermined range. And having a particle size that is smaller than the particle size of the first regulator and that can be captured by the downstream slag adhering to the gas discharge chamber. Supplying a second regulator containing a component capable of keeping the basicity of the downstream slag within the predetermined range, through the inlet of the combustion chamber ;
In the adjusting agent supplying step, the first adjusting agent having a particle size of 150 μm or more and the second adjusting agent having a particle size of 15 μm or more and 40 μm or less through the inlet are provided in the furnace. supplied into the body, the method of operating a melting furnace.

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