JPH0474581A - Method for incinerating waste with reduced carbon dioxide generation - Google Patents

Abstract

PURPOSE:To contrive a treatment of waste wherein generation of carbon dioxide is reduced by incompletly burning waste to leave unburnt matter and fixing the non-combustion matter in a molten body. CONSTITUTION:Waste dried if necessary, is burnt in a primary combustion furnace, that is, a partial combustion melting furnace by air whose amount is equal to or less than a theoretical air ratio but generates quantity of heat sufficient to reach temp. melting formed ash, for example, 1300 - 1450 deg.C. Subsequently, the combustion gas from the partial combustion melting furnace is burnt in a secondary combustion furnace. The secondary combustion furnace may be integrated with or separated from the primary combustion furnace. To give the instance of the incineration and melting of sewage sludge, the solid unburnt matter falling from a primary combustion chamber 1 comes into contact with a molten body (8b) of ash before it comes into contact with secondary air to be fixed therein. Gaseous unburnt (incomplete combustion matter is burnt by secondary air blown in thereafter and exhaust gas is raised in temp. to issued from an exhaust gas outlet (3).

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an incineration method that reduces the amount of carbon dioxide gas generated when incinerating waste, particularly sewage sludge and municipal garbage.

[Conventional technology]

Solid wastes such as sewage sludge and municipal waste are generated in large quantities, and if dried, they will weigh 4,000 to 5,000 kg.
Since it has a calorific value of cal/Ky, it is generally incinerated to reduce its volume. On the other hand, carbon dioxide gas is considered to promote global warming.
Efforts are being made to reduce emissions in both industry and daily life. Therefore, it is desirable to reduce the amount of carbon dioxide generated during waste incineration.

[Problem to be solved by the invention] An object of the present invention is to enable a process that reduces the generation of carbon dioxide when incinerating waste, which is an inevitable process. [Means to solve the problem]

In the waste incineration method of the present invention, in incineration of waste in which the ash produced by incineration forms a molten body, the waste is incompletely combusted to leave unburned matter, and this unburned matter is recycled.
This is a method of incinerating waste that reduces the generation of carbon dioxide gas by fixing it in the molten material described above. Wastes that can be incinerated in this way include the sewage sludge and municipal waste mentioned above, as well as floor sludge and industrial wastewater sludge. The calorific value of the dry waste is 4000 Kca, I!
It is preferable to use waste that contains a certain amount of ash that melts at a temperature of 9 or higher and 1,300°C or lower. If it has enough heat to reach the melting temperature of ash just by using it, it can be covered by the present invention. Raw sludge generally meets this requirement, but requires drying. For example, sewage sludge should have a moisture content of 10% or less. Digested sludge cannot be used due to lack of heat. The primary air for partial combustion of waste is determined from the viewpoint of ensuring sufficient heat generation to reach a temperature at which the ash produced melts. A suitable amount of air is usually about 0.7 to 0.9, where the amount of air required for complete combustion is 1. When the ash produced by combustion is insufficient for fixing unburned materials, or when it is desired to lower the melting temperature or melt viscosity of the slag, it is preferable to add a melting aid. The melting aid is selected depending on the composition of the ash to be produced, especially its basicity. Generally, (basic component in ash) /
Selecting the type and amount of the melting aid so that the ratio of (S i 02 ) is in the range of 0.5 to .1.5 helps lower the melting temperature. Lime and shirasu are easy-to-handle and inexpensive melting aids.

[For use]

In the process of researching waste incineration, the inventor found that the amount of sewage sludge supplied to the incinerator was excessive, the particle size of the sludge was large, and the amount of air blown into the incinerator was insufficient. The present invention was conceived based on the experience that unburnt components are fixed in molten ash in some cases. A typical flow of the method of the present invention is shown in Fig. 1, in which the dried waste is transferred to a secondary combustion furnace, that is, a partial combustion melting furnace, where the ash content is lower than the stoichiometric air ratio. For example, the temperature at which it melts is 1300 to 14
Generates enough heat to reach 50℃

[Burn with the amount of air. Subsequently, the combustion gas from the partial combustion melting furnace is combusted in a secondary combustion furnace. This gas contains a small amount of CO, so it is burned to make it harmless before being discharged. In the combustion of waste such as sewage sludge and municipal garbage, even if the air ratio is low enough to completely stop combustion, the generated C (including polymeric carbon compounds) is quickly fixed in the molten ash. By being
It has been found that relatively little CO is produced by the reaction between C and CO2. The secondary combustion furnace may be integrated with the primary combustion furnace as in the example described later, or may be separate. Since the combustion exhaust gas has a high temperature, it can be used to preheat the air supplied to the upper two types of furnaces, as well as to dry the waste to be fed into the dryer. For example, a furnace with a structure as shown in Figure 2 is used. Vertical primary combustion furnace (
In 1), most of the waste input from the supply port (4) is combusted by the air from the second air supply (5), and the generated ash (8A) becomes a melt and burns on the furnace wall. It flows down and accumulates at the bottom of the secondary combustion chamber (2), and is discharged from the outlet (7A). - Even if unburned materials that were not completely burned in the secondary combustion chamber fall into the secondary combustion chamber, they will be combusted by the air supplied from the secondary air inlet (6A) located at the inlet (left end in the figure). . To carry out the method of the present invention using this type of furnace, some modifications are made as shown in FIG. That is, the ash melt discharge port (7B) is located at the bottom of the secondary combustion chamber, but directly below the primary combustion chamber, and the secondary air supply port (6B) is located from it to the exhaust gas outlet (3). ) side. - It goes without saying that the air ratio in the secondary combustion chamber is lower than in the case of FIG. This results in
- The solid unburnt material that has fallen from the secondary combustion chamber comes into contact with the ash melt (8B) and is fixed therein before it comes into contact with the secondary air. The gaseous unburned (incompletely burned) substances are then combusted by the blown secondary air, raising the exhaust gas temperature and exiting from the exhaust gas outlet (3). Although the illustrated example is a swirl melting furnace, surface melting furnaces can also be used. [Example] Dried sewage sludge (calorific value 4230 k on dry weight basis)
ca! J/Ky) was incinerated at 1400° C. using an apparatus having the structure shown in FIG. The sludge supply rate is 1
550Kg/hr, air ratio 0.8. The results are shown below in comparison with the case of incineration for complete combustion using the apparatus shown in FIG. 2 according to the prior art. In this way, a portion of the carbon content in waste is converted into carbon instead of turning into CO2.
By fixing carbon dioxide (including in the form of high-molecular carbon compounds), it is possible to reduce CO2 emissions by approximately 24%.

【Effect of the invention】

When waste is incinerated by the incineration method of the present invention, the amount of CO2 generated by combustion can be effectively reduced, contributing to the reduction of CO2 emissions.

[Brief explanation of drawings]

FIG. 1 is Chart 1 to show a typical flow of the waste incineration method of the present invention. 2 and 3 are cross-sectional views of an apparatus for incinerating sewage sludge using a rotating melting furnace, with FIG. 2 showing the prior art and FIG. 3 showing the present invention. 1... - Secondary combustion furnace 2... Secondary combustion furnace 3.
...Exhaust gas outlet 4...Sludge population 5...-
Secondary air inlets 6A, 6B...Secondary air population

Claims (3)

[Claims] (1) When incinerating waste in which the ash produced by combustion forms a molten body, the waste is incompletely combusted to leave unburned matter, and this unburned matter is fixed in the molten body. A waste incineration method that reduces carbon dioxide emissions. (2) The incineration method according to claim 1, wherein the incineration is performed with the addition of a melting aid to increase the amount of molten ash and/or adjust the viscosity. (3) Claim 1 where the waste is sewage sludge or municipal garbage
Or incineration method 2.