JPH0195212A - Ash melting furnace - Google Patents

Abstract

PURPOSE:To promote combustion and melting by setting a narrowed part of a passage formed by a weir to a combustion zone for increasing the combustion gas speed, and forming a burnt ash filling zone on this side of the narrowed part and a free port which is larger than the narrowed part on the rear side of the narrowed part. CONSTITUTION:Solid wastes 7 are supplied to an incinerator, and ignited by an assist burner and burns by itself and burnt ashes 20 are introduced into an ash melting furnace but unburnt carbon remains. The burnt ashes 20 are laminated on a fire bed plate 8 through a hopper part 2a and are preheated to approximately 900 deg.C in the filling zone 5 and then shift to a combustion zone 6. Since the temperature of a fire bed plate 8 in the combustion zone 6 is controlled to 1,100 deg.C, unburnt carbons at the lower surface of the inner part is ignited and naturally burn by combustion air of high temperatures discharged through an air nozzle 10 positioned on the lower surface of the inner part of the burnt ashes 20. The flame or combustion gas generated escape from the combustion zone 6 to the free port 7. The speed of the combustion gas becomes high by the weir 4, and natural combustion of high density is concentrated on the burnt ashes 20, and the burnt ashes 20 are heated and molten with good thermal efficiency into a molten metal 21. Therefore, combustion and melting are promoted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for discharging incineration residual liquid (incineration ash) of solid waste such as municipal waste and industrial waste onto a grate formed in a passageway of a furnace body. This relates to an ash melting furnace that burns and melts unburned carbon in the incinerated ash while transporting the ash.

[Prior art] Conventionally, incinerated ash discharged from an incinerator is transferred onto a fire bed formed in a passageway of a furnace body, and air is supplied to the incinerated ash to burn unburned carbon in the incinerated ash. An ash melting furnace is known that melts incinerated ash using the heat generated by combustion as a melting heat source.

[Problems to be Solved by the Invention] However, in the conventional ash melting furnace, although combustion air is supplied, the passage of the furnace body is configured as a monotonous downward slope, so that the combustion gas is The high-temperature part of the flame could not be concentrated in the incineration ash layer, and the sensible heat of the flame could not be fully utilized.

The purpose of the present invention is to fully utilize the sensible heat of flame to
An object of the present invention is to provide an ash melting furnace that promotes melting.

[Means for Solving the Problems] The present invention provides an ash melting furnace that burns and melts unburned carbon in the incinerated ash while transferring the incinerated ash onto the grate formed in the passage of the furnace body. In this method, a weir hanging down from above is provided in the middle of the passage of the furnace body, and the narrow part of the passage formed by this weir is used as a combustion zone that increases the combustion gas velocity. It is characterized by forming a filling zone for incinerated ash on the front side and a free port larger than the narrowed part on the rear side of the narrowed part.

[Function] The narrow part of the passage in the furnace body is the combustion zone, the front side is the incineration ash filling zone, and the rear side is the free port, so the flow of combustion gas through the combustion zone becomes faster and its Heat density increases. That is, in the combustion zone, high-temperature parts of the flame and combustion gas concentrate on the incinerated ash layer, increasing thermal efficiency and promoting combustion and melting.

[Example] Embodiments of the present invention will be described below with reference to the accompanying drawings.

In Figure 1, 1 is an ash melting furnace, which is connected to the end of a mechanical incinerator (stoker type furnace, rotating gill type, etc.) that incinerates solid waste such as municipal waste. Incineration residue (incineration ash) incineration ash 20 containing unburned carbon discharged from the furnace is transferred to a fire bed and burned, and the incineration ash 20 is converted into molten slag (molten metal) 21 by the heat.

The ash melting furnace 1 includes a furnace body 2 covered with a refractory insulation material,
A downwardly sloping passage 3 is formed inside the furnace body. A hopper 2a serving as an inlet for receiving incinerated ash 20 from the incinerator is formed in the upper part of the furnace body 2, and the hopper communicates with the upper upstream side 3a of the passage 3. Further, the lower end of the furnace body 2 is connected to a slab discharge passage 16 and continues to a slag cooling water tank. The combustion exhaust gas is sent from the flue 17 to a blower (not shown) in the same direction as the melt/1i21 flowing.
is sucked in and discharged.

The passage 3 of the furnace body 2 is divided into three areas by a weir 4 which is provided midway down from the upper wall. That is, the incinerated ash filling zone 5 is located on this side of the weir 4 when viewed in the direction of transfer of the incinerated ash 20, the combustion zone 6 is the passage portion narrowed by the weir 4, and the area expanded from immediately after the weir 4. and a free port 7 which is a passage section. Passage 3 like this
The reason for providing the weir 4 in the middle of the filling zone 5 is that when the incinerated ash in the filling zone 5 is burned, the passage of the combustion gas (flame) is narrowed to increase the combustion gas velocity. This is to increase the load) and promote melting of the incinerated ash 20 only by self-combustion heat. The presence of the filling zone 5 and the free port 7 region is an effective means for concentrating the high temperature portion of the flame or combustion gas in the incineration ash layer and promoting combustion melting.

In this embodiment, the length of the grate formed by the grate plate 5 is 1800 mm.
mm, the weir 4 has an internal diameter of 400 mm from the top of the fire bed in the constriction of the passage 3 (combustion zone 6) formed thereby.
The height of the narrowed part from the grate plate 5 to the lower end of the weir 4 is 100 to 400 mm.
It is formed to have a diameter of 0.00 mm. It is preferable that the size of the free port 7 is relatively large, at least twice the height of the stenosis, and that the upper wall is flat. This is because if there are no obstructions or protrusions on the earthen wall of the free port 7, the speed of flame flow will decrease and the amount of unmelted ash will increase.

In the passage 3 of the furnace body 2, a plurality of grate plates 8 made of ceramic such as silicon carbide are arranged in a stepped manner to form an inclined grate. A high-temperature electric heater 9 made of a rod-shaped silicon carbide heating element is integrated into each grate plate 8 . 1
0 is an air nozzle (diffuser pipe) that blows out high-temperature combustion air sent from both sides of the passage 3;
0 means that the grate plates 8 are disposed within the interval that occurs at the overlapping portion of the adjacent grate plates 8.

2 and 3'', each grate plate 8 has a flange 81 for preventing molten metal from getting around, and a heater insertion hole 84 is bored in the lower part of the grate plate main body 80. A heater protector 83 made of an insulating material is integrally provided. 85 indicates a hole for an electrothermal couple.

The upper surface 82 of each grate plate 8 is formed in a figure 7 shape to collect and flow down the molten metal. Specifically, the 7-shaped upper surface 82 of the grate board has an inclined guide surface 82a that collects the molten metal generated from the incinerated ash 20 that is being melted while being transported along this surface in one central location, and an inclined guide surface 82a that collects the molten metal that is collected at one location in the center. It consists of a trough 82a that allows the incinerated ash 20 to flow down in the transport direction.

Returning to FIG. 1, each grate plate 8 having the above configuration has a flange portion
is located on the downstream side in the direction of transfer of the incinerated ash 20, and the flange portion 81 of the L-side grate plate 8 is sequentially overlapped with the adjacent lower grate plate 8, thereby forming a stepped grate. Arrange as follows. Further, when forming a one-step firebed, these firebed plates 8 are arranged so that an envelope connecting the upper corners of each of the flanges 81, that is, the upper surface of the hearth, has a constant angle of inclination. On the other hand, the electric heater 9 is housed in the insertion hole 84 of the heater protector 83 and integrated with the grate plate 8, thereby protecting the electric heater 9 from the inflow of molten metal and efficiently heating the grate plate β from inside. do it like this.

The first role of the electric heater 9 is to heat the grate plate 8 from inside and apply ignition heat from the bottom surface of the incinerated ash 20 stacked in the combustion zone 6 using radiant heat from the surface of the grate plate 8. It is in. This means that, together with the high-temperature air supplied to the inner lower surface of the incinerated ash by the air nozzle IO, combustion and melting are performed from the inner lower surface of the incinerated ash layer in the combustion zone 6. Therefore, the highest temperature is required. This reduces heat loss by covering the area with a layer of incinerated ash to keep it warm. Another role of the electric heater 9 is to preheat the incinerated ash 20 in the filling zone, that is, the incinerated ash 20 that will be burned next, to a high temperature to promote combustion and melting, and also to promote molten slag, that is, molten metal, in the molten zone of the free port 7. 21 from sticking inside the furnace body 2.

Therefore, the electric heaters 9 are divided into groups to control the temperature of the grate plate 8 in several sections. In this example, the preheating zone of the filling zone 5 is 900°C, the combustion zone of the combustion zone 6 which is the narrow part of the passage is 1100°C, the melting zone of the free port 7 is 1300°C, and the discharge q (gate part) 8d is 1350°C. Temperature control as in °C. By controlling the preheating zone, combustion zone, melting zone, and sprue section separately in this way, it is possible to appropriately control the temperature of combustion and melting and to save heating power. In addition, the amount of combustion air blown from the air nozzle 10 is controlled to 20% in the preheating zone and 60% in the combustion zone by changing the supply pressure from the air supply pipe 11. efficiently.

On the other hand, on the upstream end wall of the furnace body 2, there is a large pusher 12 that mainly stirs and transfers the incinerated ash 20 in the filling zone 5 and the combustion zone 6, and a large pusher 12 that mainly stirs and transfers the incinerated ash 20 in the melting zone of the free port 7. A small elongated pusher 13 is provided for making a hole that will become a runner. The small pusher 13 is connected to the large pusher 12 together with its hydraulic cylinder.
The tapered tip 13a of the grate plate 8
It is arranged so that it can be inserted and removed directly above the center of the

The reason why the small pusher 13 is inserted and removed while floating from the grate plate 8 and is not slid onto the grate plate 8 is to leave a permanent layer of molten metal on the grate plate 8 to form a protective film for the grate plate 8.

However, if the small pusher 13 is placed too far away from the grate plate 8, the hole made between the grate plate 8 and the incinerated ash will no longer function as a runner, so an appropriate gap must be provided. In the case of the example shown in Figure 1, 30~
A gap of 50 mm was good. The diameter of the small pusher 13 at this time was about 50 to 100 mm,
In order to secure a runner, a thinner one is preferable.

An encoder 14 is attached to the large pusher 12 and the small pusher 13 for the purpose of detecting their ejection speed and current position. The output pulses from the encoder 14 are input to a pre-7 shear controller 15 that has a built-in computer (CPU), and this controller 15
The two pushers 12 and 13, large and small, are controlled in conjunction.

Next, the operation of the ash melting furnace having the above configuration will be explained.

Solid waste 7 such as municipal waste is supplied to an incinerator (not shown), where it is ignited by an auxiliary burner and then self-combusted by combustion air, and the incinerated ash 20 is transferred from a hopper part 2a to an ash melting furnace 2. be introduced. At this time, although unburned carbon remains in the incineration ash 20, combustion in the incinerator is controlled so that the amount remains in the range of 7 to 25% by weight, preferably 10 to 20% by weight. Ru. Specifically, it is made to remain by adjusting the input amount of waste, the amount of combustion air, the stoker feed rate in a stoker type furnace, the rotation speed in a rotary kiln type furnace, etc.

The incineration ash 20 containing unburned carbon passes through the hopper part 2a, is stacked on the grate plate 8 in the melting furnace 2, is preheated to about 900° C. in the filling zone 5, and then moves to the combustion zone 6. Since the temperature of the grate plate 8 in the combustion zone 6 is normally controlled at 1100°C, the high temperature combustion air blown out from the air nozzle 10 located at the bottom of the inside of the incinerated ash 20 first causes the bottom of the inside of the incinerated ash 20 to heat up. The unburned carbon ignites, and the incinerated ash 20 self-combusts from within. The flame or combustion gas generated during this combustion escapes from the combustion zone 6 to the free port 7, but since the combustion zone 6 is narrowed by the weir 4, the combustion gas velocity in the combustion zone 6 becomes high, and its heat density increases. It gets expensive. That is, this high-density natural combustion heat is concentrated on the incinerated ash 20, and the incinerated ash 20 is heated and melted with good thermal efficiency, becoming molten slag, that is, molten metal 21.

The minimum temperature for this molten metal 21 to flow on the grate plate 8 is 1250
As mentioned above, the temperature of the grate plate 8 is 1300 C in the melting zone of the free port 7, and a slightly higher temperature of 1350 C at the sprue part (the leading edge of the grate plate 8) 8d.
℃ to prevent the molten metal from sticking inside the furnace.

The molten metal 21 on each grate plate 8 is guided by a figure 7-shaped inclined guide surface 82a.
After proceeding upward toward the valley 82a and being collected in the valley 82a, it becomes a single stream along the valley 82a and flows to the sprue 8d. Since the molten metal is concentrated in one place on the grate plate 8 and does not spread out on the grate plate 8, the flow of the molten metal is good and it does not show signs of sticking as it would with a flat grate plate. The molten metal 21 flowing over the sprue 8 and coming out from the sprue 8d is
Slag cooling water tank (not shown) via slag discharge passage 16
where it is cooled and solidified.

The large pusher 12 and the small pusher 13 agitate and transfer the incinerated ash 20 through a linked operation, thereby contributing to the combustion e-melting control of the incinerated ash 20, as well as preventing bridging of the incinerated ash 20 and forcibly discharging molten unsuitable materials. At this time, if the large pusher 12 that has been sent out stops before reaching the specified stroke length, it is considered that tarinka (fixed slag) has occurred in the passage 3. In addition, large pusher 12
If the delivery speed of the passage 3 is slower than the specified speed,
It is thought that signs of slag adhesion, that is, tarlinka, are occurring within the steel.

Therefore, when feeding the large pusher 12, the controller 15 monitors whether the number of output pulses per unit time (feeding speed) generated from the encoder 13 falls below a predetermined value. , it is determined that there are signs of slag fixation. Furthermore, when the number of output pulses per unit time generated from the encoder 13 is zero, that is, when the large pusher 12 has stopped, the large pusher 1
Compare the integrated value of the number of output pulses generated from the encoder 13 until the encoder 2 stops from the home position with a predetermined set value, and if the integrated value has not yet reached the set value, it is determined that the cause is the occurrence of tarlinker. It is determined that the stop has stopped. When the controller 15 detects such slag, it strengthens the energization of the electric heater 9 in the area where the slag occurs, and uses the combination operation of the large pusher 12 and the small pressurer 13 to peel off and discharge the stuck slag. conduct.

On the other hand, the molten metal 21 is often difficult to flow out due to the obstruction of unmelted ash. If the molten metal 21 remains, it may stick to the grate plate 8J1m, cause wake flow with unmelted ash, or cause unmelted ash to flow out. The mixture with the incinerated ash increases the ventilation resistance to the incinerated ash layer and inhibits the combustion of the incinerated ash. Therefore, especially in the melting zone of the free port 7, the controller 15 operates the small pusher 13 to insert and remove the small pusher 13 directly above the center of the grate board 8. This creates a hole between the grate plate 8 and the incinerated ash 20, which will serve as a runner, and the runner will improve the flow of the molten metal.

In the above embodiment, an ash melting furnace in which the hearth was formed by a plurality of grate plates 8 was described, but an ash melting furnace using a flat grate plate, or even an ash melting furnace using heat from an oil burner, etc. Even in an ash melting furnace, by providing the weir 4 and increasing the combustion gas velocity in the combustion zone 6, the heat density there can be increased and the thermal efficiency can be increased.

[Effects of the Invention] As described above, the present invention forms a narrow part in the middle of the passage of the furnace body, and makes this the combustion zone, the front side thereof the incineration ash filling zone, and the rear side the free port. Therefore, the flame flow through the combustion zone is faster and its heat density is higher. That is, in the combustion zone, the flame and high-temperature parts of the combustion gas are concentrated in the incineration ash layer, and the sensible heat of the flame is fully utilized, increasing thermal efficiency and promoting combustion and melting.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the ash melting furnace of the present invention;
The figure is a front view of the grate board, and Figure 3 is a side view thereof. In the figure, l is an ash melting furnace, 2 is a furnace body, 3 is a passage, 4 is a weir, and 5
is the filling zone, 6 is the combustion zone, 7 is the free port, 8
is a fire bed board, 9 is an electric heater, 10 is an air nozzle, 12 is a large pusher, 13 is a small pusher, 14 is an encoder, 15 is a pusher controller, 20 is incinerated ash, 21
indicates molten metal.

Claims (1)

[Claims] In an ash melting furnace where the incinerated ash is transferred onto the grate formed in the passageway of the furnace body and unburned carbon in the incinerated ash is burned and melted, the ash is suspended from above midway inside the passageway of the furnace body. A weir is provided, the narrow part of the passage formed by this weir is used as a combustion zone that increases the combustion gas velocity, and a filling zone of incinerated ash is provided on the near side of the narrow part when viewed in the direction of transport of incinerated ash.
An ash melting furnace characterized in that a free port larger than the narrowed part is formed on the rear side of the narrowed part.