JPS61213408A - Burning method for solid material containing impurities at circular flow melting equipment - Google Patents

Abstract

PURPOSE:To reduce the amount of generated NOX and dust by burning particles which are shifted within a certain limited size and supplied to a furnace after solid materials containing impurities are crushed by a crusher. CONSTITUTION:Dried sludge in a sewage disposal plant is sent to a crusher 30 through a dried sludge conveyor 3. The crusher 30 is so selected from among various kinds of machines that the machine is capable of crushing the sludge into particles having size under 3,000mum and the ratio of fine particles under 200mum size is made as small as possible. Then, crushed sludge is sent to a sifter 31. Sludge (200-300mum) which is adjusted in grain size to a circular fow melting furnace 9 is injected tangentially into the furnace with preheated air for burning at high velocity. Sludge particles being injected at high velocity are separated from air by centrifugal force and reach a inner wall of the furnace and are captured by melted sludge existing in the place and burnt. At that time, incombustibles contained in sludge particles are melted and flowed down together along the inner wall of the furnace and sent to a smelt desolver 15 with burnt waste gas via a outlet of smelt burning waste gas 14.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention is directed to the combustion of solid substances containing non-combustible materials such as sewage sludge and coal in a swirling flow melting furnace, and to melting of non-combustible materials. The present invention relates to a method for burning solid materials containing non-combustible materials in swirling flow melting equipment, which significantly reduces NOx (nitrogen oxides) and at the same time reduces the amount of scattered dust.

``Prior art'' A swirling flow melting furnace applies the principle of centrifugal separation of a cyclone, and supplies the air necessary for combustion and pulverized solid fuel to the furnace at the same high speed in the tangential direction. This makes it possible to perform a strong turning motion. Due to the action of the centrifugal force generated at this time, fuel particles reach the inner wall of the furnace, are separated and adhere to it, while thin particles that cannot reach the wall are mixed with air in the center of the combustion chamber. High-temperature combustion occurs, but due to the short residence time, complete combustion is not achieved and the fuel is scattered outside the combustion chamber.

゛In addition, coarse particles that do not reach the wall surface are captured on the slag film covering the wall surface and burn while flowing slowly with the slag, and non-combustible substances in the coarse particles are melted by the heat of combustion and turn into slag. , covering the entire surface inside the combustion chamber. Therefore, the residence time of the coarse particles trapped on the slag film is as long as about 60 seconds, and complete combustion takes place under an extremely high load.

On the other hand, although the air inside the combustion chamber is uniformly distributed, the solid fuel supplied one after another burns on the wall surface, so that the excess air ratio locally becomes less than /θ. Therefore, the reaction proceeds in two stages: one in which the fuel particles trapped on the wall are decomposed to generate flammable gas, and the other in the center of the combustion chamber, in which the pyrolysis gas combines with oxygen and burns. Low NO
It is said that x-combustion can be achieved.

However, in reality, since there are many particles supplied to the center of the combustion chamber, rapid space combustion occurs at high temperatures, and a large amount of NOx is generated. For this reason, various studies have been conducted to suppress the generation of NOx.
For example, in a swirling flow melting furnace, the combustion air ratio is set to 0. g~
A two-stage combustion system is known in which the combustion engine is operated at θ de, partially converted into combustible gas, and then completely combusted in a secondary combustion furnace provided at the subsequent stage to reduce NOx production.

By the way, in the past, sludge generated at sewage treatment plants was treated by reducing the volume of sludge through dehydration, composting, or incineration, and then dumping it, but as the amount increased, it became necessary to secure a disposal site for the incinerated ash. This is becoming increasingly difficult due to secondary pollution problems such as the scattering of ash and the elution of heavy metals. Against this background, in recent years, a new treatment method has been developed in which dry sludge is subjected to self-combustion high-load combustion in a swirling flow melting furnace, and the resulting ash is converted into water-cooled slag, which reduces the volume of sludge, makes it harmless, and It has been attracting attention as a method of stabilization and recycling, and is being actively researched. When this dried sewage sludge is incinerated and melted in a swirling flow melting furnace, it is necessary to melt the incombustibles in the sludge, so the temperature inside the furnace is
Must be maintained at 1I00°C ~/mO°C. Therefore, in the conventional method, the sewage sludge to be supplied is pulverized into fine particles of 202 m or less in size and supplied in order to disperse the sewage sludge well in the combustion air in the furnace and accelerate combustion. For this reason, the supplied sewage sludge undergoes rapid combustion at high temperatures, and the generation of a large amount of NOx is unavoidable. θ0
NOx of 0 to 200P (02/2 CH conversion value) has been detected. Furthermore, since fine sludge is injected into the furnace at high speed and under pressure, there is a large amount of scattered dust, and under the above combustion conditions, 20 g/Nryl (02/2% equivalent value) of dust was detected in the combustion waste gas. For this reason, the above NOx
In order to reduce the generation of is the actual situation. This two-stage combustion system is, for example, as shown in Figure 1. To briefly explain this, first, dehydrated sludge sent to the sludge dryer 2 by the dehydrated sludge feeder 1 is - After being dried by this sludge dryer 2, this dried sludge is transferred to a crusher 4 via a dry sludge conveyor 3, and in the crusher 4, coarse particles are returned by a coarse sludge returning conveyor 5. The sludge is crushed together with the sludge, further passed through one crushed sludge conveyor 6, and the sieved portion is transferred to a device 7.
It is sent to the sieve and sieved. Then, fine sludge (27θμ
m or less) is sent into the swirling flow melting F9 via the sludge feeder 8, and is fed into the -next nitrogen gas purifier 10, the -next nitrogen gas duct 11,
Together with the preheated air transferred via the rush preheater 12 and the preheated air duct 13, it is blown in at high speed in the tangential direction so that a strong swirling flow occurs in the furnace, while the air ratio is suppressed to θj ~ 0.9. . Next, the smelt generated in the furnace and combustion waste gas partially containing combustible gas are sent from the smelt combustion waste gas outlet 14 to the smelt desolpa 15, where the smelt is turned into water-cooled slag and taken out of the system. The combustion waste gas is supplied into the secondary combustion furnace 17 via the combustion waste gas duct 16.
It reacts with the secondary air sent through the secondary air blower 18 and the secondary air duct 19 at the internal pressure, resulting in complete combustion.
Further, it is configured to pass through a combustion waste gas duct 20, an air preheater 12, and a combustion waste gas duct 21.

"Problems to be solved by the invention" However, in the above conventional method, sludge is
In order to make a fine powder of 0 μm or less, 1 the sludge crusher 4 requires a high-power device such as a high-speed rotation crusher or a ball mill. There is a problem in that the cost of processing the gas increases. Furthermore, since the secondary combustion furnace 17 is required to reduce the generation of NOx, there are problems in that the equipment cost is high, the system becomes complicated, and the operation method becomes difficult.

In view of the above circumstances, the inventors of the present invention have conducted extensive research to eliminate the drawbacks of the conventional methods described above, and as a result, it has been discovered that the particle size of the supplied substance has a large effect on the generation of NOx. This was done based on this knowledge, and its purpose is to significantly reduce the amount of NOx generated in the swirling flow melting furnace, as well as reduce the amount of dust scattered in the combustion waste gas. It is an object of the present invention to provide a method for combustion of solid materials including non-combustible materials in a swirl flow melting facility, which can reduce the amount of combustion of solid materials containing non-combustible materials.

"Means for Solving the Problems" In order to achieve the above object, the present invention provides a method for crushing solid materials containing non-combustible materials, and then sieving them to a size of 200 μm or more and within the range where a cyclone effect can be obtained. The particles are fed into a swirling flow melting furnace and burned. Here, the particle size at which the cyclone effect can be obtained varies depending on the size of the swirling flow melting furnace and the physical properties of the particles being handled, such as the specific gravity of the particles.
000 μm or less.

"Operation" In the combustion method of the present invention, by limiting the particle size of the solid material sent and held in the swirling flow melting furnace to coopm or more and within a range where a cyclone effect can be obtained.
Since the solid material sent into the swirling flow melting furnace is trapped and burned on the inner wall of the furnace nine times, there is a partial lack of air, and partial combustion occurs. A part of the substance is gasified and the gas is further combusted, resulting in two-stage combustion in the swirling flow melting furnace, and NOx
The generation of dust and the amount of scattered dust can be suppressed.

"Embodiment" Hereinafter, an embodiment of the present invention will be described based on FIGS. 1 to 3. In this embodiment, the same reference numerals are given to the parts having the same configuration as those of the conventional example shown in FIG.
Simplify the explanation.

At the first low pressure, first, the sludge dehydrated by the sewage treatment hot water dehydrator is supplied to the sludge dryer 2 by the dehydrated sludge feeder IK. Here, the supplied sludge is dried to a moisture content of 70% or less, preferably to an absolutely dry state, and then the dried sludge is sent to the crusher 30 through the dry sludge conveyor 3. This crusher 30 needs to be selected as a model that crushes the dried sludge to 300 μm or less, while reducing the proportion of fine powder of 200 μm or less as much as possible.

Next, the sludge crushed by the crusher 30 is sieved and sent to the device 31 by the crushed sludge conveyor 6. For this sieve, the device 31 has a sieve mesh of 2o o pm and 3oooμ
A two-stage wire mesh of 3,000 μm or more is attached, and coarse particles of 3000 μm or more are returned to the crusher 30 by a coarse sludge reconstitution conveyor 32 and crushed again. Fine particles of 200 μm or less that cause KNOx generation during combustion are returned by the fine sludge return conveyor 33, mixed with dewatered sludge, and supplied to the sludge dryer 2 where they are re-granulated.

Next, the sludge C; 100 pW1 to 3000 pn@) was sieved by the device 31 and the particle size was adjusted.
The sludge is sent to the swirling flow melting furnace 9 by the sludge feeder 8, the secondary air blower 10, the secondary air duct 11, and the air preheater 12.
, together with preheated combustion air sent through the preheated air duct 13, is blown into the swirling flow melting furnace 9 at high speed in a tangential direction so as to generate a strong swirling flow in the swirling flow melting furnace 9. 7QO inside due to the combustion pressure of the supplied sludge.
O℃～t! ;Kept at 00℃. In this state, the sludge particles blown into the swirling flow melting furnace 9 at high speed are separated from the air by the centrifugal force that removes insects, reach the furnace wall, and become part of the molten slag present there. Captured and burned. At this time, the incombustibles contained in the sludge particles flow down along the wall surface while melting on the furnace inner wall surface, pass through the smelt combustion waste gas outlet 14 together with the combustion waste gas, and enter the smelt resolver 15. The smelt falls into the cooling water, becomes water-cooled slag, and is taken out of the system, while the combustion waste gas passes through the combustion waste gas duct 34 and is sent to the air preheater 12 for combustion from the secondary air blower 10. After exchanging heat with air, the combustion waste gas is sent to the gas purification device through the duct 35.

In this way, I was busy adjusting the particle size of the sludge fed into the swirling flow melting furnace 9, and trying not to feed fine particles of 200 μm or less, which would cause NOx generation, into the swirling melting furnace 9.
The sludge particles that have been forced into the swirling flow melting furnace 9 are trapped one after another by the inner wall of the furnace, resulting in a partially air-deficient state, and when partial combustion occurs, some of the sludge particles are By converting the gas into combustible gas and further burning the gas, a two-stage combustion is performed in the swirling flow melting furnace 9, and NO.
The generation of x and the amount of scattered dust are significantly suppressed.

Next, a case in which the method of the present invention described above is specifically implemented will be described.◇ Here, the physical properties of the dried sewage sludge used are as follows.

Moisture 16% Ash 5-7% Combustible content 7% Total calorific value lza30 kcdlk& Dried sewage sludge with physical properties as described above is sieved using device 31, and KPL is adjusted so that the particle size is shown in Table 1. Then, it was supplied into the swirling flow melting furnace 9.

Dried sewage sludge with adjusted particle size as shown in Table 1,
The material was fed into a swirling flow melting furnace 9 operated at 0.degree. C. under the operating conditions shown in Table 2, and incinerated and melted.

Figure 1 shows the results of measuring the NOx concentration contained in the combustion exhaust gas discharged by operating sludge with each particle size shown in Table 1 under the operating conditions shown in Table 2. show. In this figure, the horizontal axis represents the average particle diameter of the supplied sludge, and the vertical axis represents the KNOx concentration (Ox
/2'A conversion value), and the symbols S-1 and S in the figure
-2, 8-3, 'S-4 correspond to the sample NOK shown in Table 1.

As is clear from FIG. 2, the NOx concentration is significantly reduced by the operating method of the present invention. Next, FIG. 3 shows the results of measuring the dust concentration in the combustion exhaust gas in the same experiment.

In this figure, the horizontal axis shows the average particle diameter of the supplied sludge, and the vertical axis shows the dust concentration (Ot/2% conversion value).
1, S-2, S-3, and S-4 correspond to the sample floors shown in Table 1. As is clear from FIG. 3, it can be seen that the dust concentration is significantly reduced by the operating method of the present invention.

゛ "Effects of the Invention" As explained above, the present invention is capable of crushing solid materials containing non-combustible materials, and then rotating the sieved particles with a size of 200 μm or more and within the range where a cyclone effect can be obtained. Since it is supplied to a flow melting furnace and combusted, the particle size of the solid material fed into the swirl flow melting furnace is 2o.
OPM or more and within the range where a cyclone effect can be obtained, the solid materials introduced into the swirling flow melting furnace are captured one after another by the furnace inner wall and burnt. If there is no air shortage, partial combustion will occur, so that part of the solid substance will be gasified, and as this gas will be combusted, a two-stage combustion will occur in the swirling flow melting furnace. NO generated in flow melting furnace
x big #! In addition, it is possible to significantly reduce the amount of dust scattered in the combustion waste gas. Therefore, there is no need to install a secondary combustion furnace as in the conventional method, which reduces equipment costs, simplifies one combustion system, and facilitates operation management. Costs can be kept low.

In addition, when the combustion method of the present invention is applied to sewage treatment, sludge fine particles of 200pW1 or less are mixed with dewatered sewage sludge and re-granulated in a sludge dryer, and
Coarse particles exceeding the range where a cyclone effect of m or more can be obtained are returned to the crusher for re-shredding, which reduces the consumption of the crusher compared to the conventional method in which the crusher crushes them into fine particles of less than ``Coopm.'' It has excellent effects such as being able to reduce power.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an example of equipment that is used to carry out the combustion method of the present invention, and Fig. 2 is a characteristic showing the measurement results of NOx concentration (O1!/2ts conversion value) in combustion waste gas. 3 are characteristic diagrams showing measurement results of dust concentration in combustion waste gas, and FIG. 4 is a schematic configuration diagram showing an example of equipment used to carry out a conventional combustion method. 2...Sludge dryer, 9...Swirling flow melting furnace, 30...Crushing machine, 31...The curved part is the device,
32・Song・Coarse sludge return conveyor, 33...
Fine sludge return conveyor. Figure 1 Figure 2 Figure F3

Claims (1)

[Scope of Claims] 1) A method for burning a solid substance containing noncombustibles in a swirling flow melting facility in which a solid substance containing noncombustibles is incinerated in a swirling flow melting furnace, and the noncombustibles are melted. After passing the solid material containing it through a crusher, it was sieved to 200μm
A method for combustion of solid substances containing non-combustible materials in a swirling flow melting equipment, characterized in that the particles having the above size and within a range in which a cyclone effect can be obtained are fed to the swirling flow melting furnace and burned. 2) When sewage sludge is subjected to combustion treatment as a solid substance containing the above-mentioned incombustibles, when the dried sewage sludge crushed by the above-mentioned crusher is sieved, fine particles of 200 μm or less are mixed with the dehydrated sewage sludge and converted into sludge. Particles that are coarser than the range that can be re-granulated using a dryer and obtain the above-mentioned cyclone effect are
2. A method for burning solid materials containing incombustibles in a swirling flow melting facility according to claim 1, characterized in that the solid materials are returned to the crusher and crushed again.