JPH0578727B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is used to incinerate materials with high moisture content such as so-called dehydrated cakes obtained by preliminary dehydration of various sludges such as human waste and sewage water. Therefore, there is no need for any preliminary drying outside the incinerator.
This invention relates to a step-type incinerator that can efficiently incinerate materials with high moisture content to be incinerated as they are.

(Prior Art) As shown in FIG. 6, a conventional stepped incinerator usually has fixed and movable grates 30 and movable grates 31 of approximately the same shape arranged in a stair-like manner alternately.
0 is supported and fixed to the furnace body, each movable grate 31 is attached to a connecting rod 33 via a mounting hardware 32, and the connecting rod 33, which is slidably supported on a slide 34, is driven by a drive device 35. While sliding at a constant pitch in the front-back direction, the air duct 37 from the forced draft fan 36, each hopper 38, both grates 30,
The structure is such that combustion air is supplied to the upper surface of the fire bed through the gap provided between the holes.
No. 183212).

When the material to be incinerated, such as dehydrated cake, is fed into the incinerator, the material to be incinerated is sequentially stirred and moved forward due to the movement of the movable grate 31 and the head difference between the grate, and during that time, It will be burned at a high temperature.

However, in the case where materials to be incinerated with a high moisture content such as dehydrated cake with a moisture content exceeding 60 to 65% are directly put into the incinerator, each grate 30, 31 has approximately the same shape and the head There is no change in the amount of material to be incinerated, and since the stirring effect on the material to be incinerated depends only on the movement of the movable grate 31 and the height of the grate, the material to be incinerated completely covers the top surface of the grate, and the air supply is interrupted. Coupled with the fact that this is done from below the grate, ventilation is significantly impaired. As a result, the combustion state inevitably becomes unstable, and there is a problem that substances with a high water content such as dehydrated cake cannot be incinerated efficiently.

On the other hand, a stepped incinerator is capable of high-temperature combustion of around 1200°C on the grate, and as a result, the incinerated ash can be discharged as semi-molten clinker that can be used effectively. In order to take advantage of the good properties of this incinerated ash and to efficiently incinerate dehydrated cakes, etc., incineration is done in advance outside the incinerator using steam generated by recovering the exhaust heat of the incinerator. A system has been developed and implemented in which materials are dried and the pre-dried materials to be incinerated are burned at high temperatures in a stepped incinerator.

However, even in the above system, the system configuration of the incinerator plant becomes too complicated, and
Since the operator must have qualifications such as boiler engineer,
In the case of small and medium-sized incinerator plants, various problems arise in terms of management systems.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems in the incineration of high moisture content materials such as dehydrated cakes using conventional step incinerators, that is, the materials to be incinerated are sent directly to the incinerator. When charging, the top surface of the grate will be completely covered with the material to be incinerated, which will obstruct ventilation and make combustion unstable.If the material to be incinerated is pre-dried in advance, This project aims to solve problems such as complicated plant configurations that require time-consuming operation management, and by making improvements to the structure of the drying grate of stepped incinerators, it is possible to reduce the amount of dehydrated cake, etc. To provide a step-type incinerator that can supply a high moisture content substance directly into the incinerator and incinerate it stably with high efficiency while taking advantage of the good properties of incinerated ash.

(Means for Solving the Problems) The present invention provides a step-type incinerator equipped with a drying grate and a combustion grate for incinerating materials with a high moisture content such as dehydrated cake. The fire bed section is formed of a drying fire bed consisting of a movable grate and a fixed grate, and a gas blowing pipe disposed above the drying fire bed in a direction perpendicular to the direction of movement of the drying fire bed. The basic structure of the invention is to blow drying exhaust gas into the material to be incinerated from the vent hole of the gas blowing pipe.

(Function) The materials to be incinerated with a high moisture content sent to the drying grate 3 by the pusher are stacked on the drying grate 22, and the movable grate 22a and the relatively large grate are stacked on the drying grate 22. It gradually moves downward depending on the head.

Gas blowing pipe 2 installed horizontally above the drying fire bed 22
3 is in a state that it has sunk into the stack of materials to be incinerated, and due to the presence of the gas blowing pipe 23, the layer of materials to be incinerated moving downward is divided into upper and lower layers,
This results in a so-called stirring action.

Further, from the gas blowing pipe 23, a high temperature and low oxygen concentration drying exhaust gas is blown into the layer of the material to be incinerated, thereby heating the material to be incinerated and discharging the generated steam. will be further promoted.

In addition, in the drying grate part 3, the drying grate 22
A part of the combustion exhaust gas S is also fed into the material to be incinerated from below, and is dried together with the high temperature drying exhaust gas from the gas blowing pipe 23.

The materials to be incinerated with a moisture content of 60 to 65% or more are dried while passing through the drying grate section 3 until the moisture content reaches about 40 to 55%, and then sent to the combustion grate section 4. Here, it is sequentially burned at high temperatures.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 5.

FIG. 1 is a schematic system diagram of an incineration plant using a stepped incinerator according to the present invention.
2 is a pusher, 3 is a drying grate, 4 is a combustion grate, 5 and 6 are hoppers, 7 and 8 are retard conveyors, 9
10 is a refining mixer; 10 is a slag outlet; 11 is a flue for discharging circulating gas provided above the drying grate 3;
Reference numeral 12 denotes a flue for discharging combustion gas provided above the combustion grate 4.

Further, 13 is a primary gas air heater, 14 is a secondary gas air heater, 15 is a circulation fan for high-temperature drying exhaust gas, 16 is a combustion air fan, 17 is a circulation fan for drying combustion exhaust gas, 18 is an induction fan, 1
9 is a circulating gas blowing duct, 20 is a combustion air blowing duct, and 21 is a combustion exhaust gas blowing duct.

The stoker device disposed within the furnace main body is composed of a drying grate 3 and a combustion grate 4, and the drying grate 3 has two main parts, as shown in FIGS. 2 to 4. It is formed from a drying fire bed 22 and a gas blowing pipe 23 arranged above it.

The drying grate 22 is formed of a movable grate 22a having a substantially square cross section and a fixed grate 22b having the same shape, and each grate 22a, 22b has a ventilation hole 24 in its floor surface. There are also 25 ventilation holes on the front.
are formed respectively. From both the vent holes 24 and 25, a combustion exhaust gas blowing duct 21 is connected as described later.
A combustion exhaust gas S having an O ₂ concentration of about 6 to 8% is ejected.

The movable grate 22a and the fixed grate 22b
The front surface is formed at a height L of approximately 95 to 150 mm, and the grate of the combustion grate 22, which will be described later, is
Their height dimensions differ significantly.

The gas blowing pipe 23 has both fire grates 22a, 22
Located about 80 to 120 mm above the floor of b,
It is disposed perpendicular to the moving direction of the movable grate 22a, and a plurality of ventilation holes 26 are bored therein. As shown in FIG. 3, the gas blowing pipe 23 is supported and fixed to a gas duct 19a provided on the furnace wall, and the O ₂ concentration pumped into the gas duct 19a is at a high temperature of about 8 to 10%. The drying exhaust gas (circulating exhaust gas) G is discharged through the vent hole 26 into the incinerated material K having a high moisture content such as a dehydrated cake.

In this embodiment, the exhaust gas G taken out from the circulating gas exhaust flue provided above the drying grate 3 is
The combustion exhaust gas S taken out from the flue 12 for discharging combustion gas disposed above the combustion grate section 4 is supplied to the gas blowing pipe 23 after heating and raising the temperature. You may also do so.

On the other hand, the combustion grate 27 constituting the combustion grate section 4 is formed of a movable grate 27a and a fixed grate 27b, each having a square cross section as shown in FIG. A plurality of ventilation holes 28 are provided in the front surfaces of both the fire grates 27a and 27b, through which the combustion air A is blown out.

The height L' of the front surface of each grate 27a, 27b forming the combustion grate 4, that is, the combustion grate 27, is approximately
The height is selected to be about 95 to 100 mm, and the height dimension is significantly smaller than that of the grate 22a, 22b of the drying grate 22.

Next, the operation of the stepped incinerator will be explained.

Materials to be incinerated, such as human waste sludge and sewage sludge,
Dehydrated cake K (hereinafter referred to as high moisture cake) with a moisture content of 60 to 65% or more after pre-dehydration treatment of various sludges such as clean water sludge and low-quality sludge is transferred from input hopper 1 to pusher 2 on a drying bed. 3, and a cake layer of a constant thickness is formed on the drying grate 22.

A gas blowing pipe 23 is disposed above the drying fire bed 22 so as to be hidden inside the cake layer K, and from the gas blowing pipe 23, the primary gas heater 1 is connected.
In step 3, the high temperature drying exhaust gas (circulated exhaust gas G) preheated to 500°C to 600°C is ejected into the cake layer K to dry it. That is, the cake layer K on the drying grate 22 is sequentially sent to the lower front stage due to the movement of the movable grate 22a and the relatively large grate drop, but the step difference between the grate 22a and 22b is large. In addition, due to the existence of the gas blowing pipe 23 that blows out the high temperature circulating exhaust gas G, the cake layer K is divided into upper and lower parts, receives a so-called stirring action, and the high temperature circulating gas G is introduced into the cake layer K. By supplying it, the drying will be further accelerated.

The high temperature drying exhaust gas (circulated exhaust gas G) is
The primary gas air heater 1 is heated at a temperature of about 200 to 300°C from the circulating gas discharge path 11 by the circulation fan 15.
3, where it is heated to 500° C. to 600° C., and then supplied to the gas blowing pipe 23 of the drying grate 3 through the circulating gas blowing duct 19.

In addition, a secondary gas air heater 1 is used to assist in blowing the high temperature circulating exhaust gas G into the drying grate 3.
Exhaust gas S branched out from the outlet of No. 4 is sent from below the drying fire bed 22 through an exhaust gas blowing duct 21 by an exhaust gas circulation fan 17.
By blowing in the exhaust gas S, the air permeability of the cake layer K is further improved, and the steam generated within the cake layer K is efficiently purged to the outside of the layer.

On the other hand, the falling objects from the drying grate 22 are collected on the ridgling conveyor 7 via the hopper 5,
It is sent to the refining mixer 9. Then, it is mixed with the high moisture cake K to adjust its moisture content. At this time, it is also possible to appropriately mix so-called heat exchanger dust, cyclone dust, etc.

The high moisture cake K pre-dried in the drying grate section 3 is finally dried to a moisture content of 40 to 55%, and then sent to the combustion grate section 4. Although the drying grate section 3 and the combustion grate section 4 have a somewhat large head difference, they are a series of stepped stokers, and the cake layer K is continuously transferred downward. .

In the combustion grate section 4, combustion air A is supplied from below the combustion grate 27 through a combustion air blowing duct 20, whereby the cake K starts to burn. Note that the air A is sent to the secondary gas air heater 14 by the combustion air fan 16, where it is preheated to 150° to 250°C.

The combustion exhaust gas S generated in the combustion grate section 4 is
It is a high temperature gas of 800° to 1000°C, and as a result, most of the odor components have been oxidized and decomposed. Combustion exhaust gas S discharged from the flue 12 for exhausting combustion gas
is sent to the primary gas air heater 13, where the heat is recovered to the drying exhaust gas (circulated exhaust gas) G side.
The temperature reaches 250° to 350°C, and is further sent to the secondary gas air heater 14, where the heat is recovered to the combustion air A side, and the temperature reaches about 200° to 250°C, where it is discharged into the atmosphere.

In the incinerator, the amount of evaporated moisture generated in the drying grate 3 increases the amount of gas, but if the amount of circulating exhaust gas is constant, the increase increases the amount of gas generated in the upper part of the combustion grate 4. through which a flue 12 for exhausting combustion gases
It is discharged from.

The increased amount of exhaust gas is extracted by the induction fan 18.
This is done by automatically controlling a damper device 29 provided on the inlet side of the incinerator so that the inside of the incinerator has a slightly negative pressure (-5 to -10 mmAq). Moreover, the bleed gas contains odor components such as NH ₃ and H ₂ S, but the high temperature region in the upper part of the combustion grate section 4 is heated before being discharged from the flue 12 for exhausting combustion gas. Most of it will be oxidized and decomposed here. It goes without saying that an exhaust gas treatment device (not shown) may be installed if necessary.

Combustion progresses in the combustion grate section 4, and the combustion grate 27
The incineration ash produced above is sequentially discharged out of the furnace from the slag outlet 10 and is processed by the same means as in the conventional step-type incinerator. Also, combustion grate 27
A small amount of ash that has fallen into the hopper 6 is returned to the refining mixer 9 by the riddling conveyor 8.
It is used to adjust the moisture content of high moisture cake K.

(Effects of the Invention) In the present invention, the height difference between the movable grate and the fixed grate constituting the drying grate is made larger than that of the grate of the combustion grate, and A gas blowing pipe is disposed at a position intersecting with the moving direction of the movable grate, and is configured to blow out drying exhaust gas having a high temperature and low oxygen concentration into the interior of the material to be incinerated which has a high moisture content. As a result, the material to be incinerated descending in a layered manner through the drying firebed is divided into upper and lower parts as it moves downward by the gas blowing pipe, making it difficult to stir the material to be incinerated. It is done.

In addition, the high-temperature drying exhaust gas that is blown directly into the material to be incinerated from the gas blowing pipe efficiently imparts its retained heat to the material to be incinerated, and purges the generated steam outside of the material to be incinerated. This allows extremely efficient drying of incinerated materials.

As described above, according to the present invention, by directly feeding a dehydrated cake etc. with a high moisture content into the furnace,
This can be stably and efficiently incinerated, and the incinerated ash can be used as aggregate, etc., and has excellent practical utility.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram of a step-type incinerator according to the present invention. FIG. 2 is a schematic partial cross-sectional view of the drying grate, and FIG. 3 is a perspective view showing how the gas blowing pipe is attached. FIG. 4 is a perspective view showing a part of the grate forming the drying grate, and FIG. 5 is a perspective view showing a part of the grate forming the combustion grate. FIG. 6 is a schematic diagram of a conventional stepped incinerator. 3...Drying grate part, 4...Combustion grate part, 11...
... Flue for exhausting circulating gas, 12... Flue for discharging combustion gas, 22... Drying bed, 22a... Movable grate, 22b... Fixed grate, 23... Gas blowing pipe, 26... Ventilation hole, 27... Combustion grate, 27
a...Movable grate, 27b...Fixed grate, G...
...Recirculating exhaust gas, S...Combustion exhaust gas, K...Incineration material with high moisture content.

Claims (1)

[Scope of Claims] 1. In a stepped incinerator equipped with a drying grate section 3 and an incineration grate section 4 for incinerating materials to be incinerated with high moisture content such as dehydrated cake, the drying grate section 3 is , a drying grate 22 consisting of a movable grate 22a and a fixed grate 22b, and a gas blowing pipe 23 disposed above the drying grate 22 in a direction perpendicular to the direction of movement of the drying grate 22. A step-type incinerator configured to blow out drying exhaust gas from the vent hole 26 of the gas blowing pipe 23 into the material to be incinerated. 2. The drying exhaust gas is discharged from the circulating gas exhaust flue 11 provided above the drying grate 3, and the combustion exhaust gas S is discharged from the combustion gas exhaust flue 12 provided above the combustion grate 4. The step-type incinerator according to claim 1, wherein the circulating exhaust gas G is heated and heated by. 3. The step-type incinerator according to claim 1, in which the drying exhaust gas is the combustion exhaust gas S from the combustion gas discharge flue 12 provided above the combustion grate 4.