JP2006105448A - Sludge and incinerated ash gasified melting method and gasifying melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sludge and incinerated ash gasifying melting method for giving high-efficiency and low-cost treatment to incinerated ash and sewage sludge by making maximally effective use of energy possessed by sludge itself. <P>SOLUTION: Dried sludge and incinerated ash produced by incinerating the sludge are blown into an air flow bed gasifying melting furnace while blowing and carrying an air flow with oxygen whose amount is 0.2-0.9 time a theoretical oxygen amount required for complete combustion and partially burnt at 1100-1700°C to convert ash components in the dried sludge and the incinerated ash into slug and convert organic materials in the dried sludge and the incinerated ash into combustible gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention gasifies and melts incinerated ash generated by incinerating surplus activated sludge generated from a biological treatment facility of sewage together with dry sludge after drying the activated sludge, and combustible gas. And technology for converting to slag.

  Surplus activated sludge (hereinafter abbreviated as sludge) generated when purifying sewage by biological treatment is accompanied by the spread of sewage and the introduction of advanced treatment processes (such as removal of nitrogen and phosphorus) at sewage treatment plants. It tends to increase more and more. Currently, most of these sludges are simply disposed of in landfills after volume reduction treatment. As the sludge form at that time, there is still a case where the so-called dehydrated cake after dehydration (water content of about 80% by mass) is still being reclaimed. In most cases, incinerators are landfilled in the form of so-called incineration ash after incineration volume reduction.

  At present, the majority of sludge incinerators are so-called fluidized bed incinerators. Sludge generally has a calorific value of about 6300 to 21000 kJ / kg-dry in a dry state, but still a large amount of about 80% by mass in the state of a dehydrated cake which is the final form in a normal sewage treatment plant. Therefore, if heat loss (heat dissipated from the furnace body, latent heat of water evaporation, sensible heat brought out by entrained nitrogen and water vapor in the combustion air) is taken into account, only the calorific value of the sludge itself can be obtained. It is difficult to burn (i.e., self-combustion). Therefore, in the current fluidized bed sludge incinerator, it is indispensable to use auxiliary fuel by some method (added directly into the furnace, used as air preheating fuel, etc.).

  In recent years, ash melting treatment has been partially implemented with the aim of further reducing the volume of incinerated ash or using it effectively for reasons such as tightness in landfills. In other words, it is a technology for converting incineration ash generated from an incinerator into slag by putting it into an ash melting furnace and setting it to a high temperature above the melting point of the incineration ash. Ash melting treatment is an extremely effective technology from the viewpoints of reducing the bulk density of incinerated ash (volume reduction), promoting effective use as construction materials, etc., and preventing elution of heavy metals contained in incinerated ash. Some systems such as an electric (arc) melting furnace or a swirl melting furnace have already been put into practical use.

For example, in Patent Document 1, there is an ash melting method in which waste incineration ash including sewage sludge is melted in a swirl melting furnace using pure oxygen as a fuel combustion gas and converted into molten slag. Proposed.
In Patent Document 2, dry sludge is converted into combustible gas and slag by gasifying it with oxygen or oxygen-enriched air in a swirl type melting furnace of an airflow bed, and its high temperature combustible A sludge incineration method has been proposed in which sensible heat of volatile gas is recovered as steam in a boiler and used as a heat source for a dryer.
JP-A-9-38620 JP-A-11-159722

FIG. 1 shows a basic flow of a conventional combined sludge incineration and ash melting process. The conventional process is a two-stage process in which the ash melting furnace 2 is installed downstream of the sludge incinerator 1 that reduces the volume by burning the sludge 4 with the air 5. As described above, in the sludge incinerator 1, it is indispensable to input the auxiliary fuel 6. Furthermore, the incinerated ash 7 after almost burning the combustible component in the sludge incinerator 1 is used in the next ash melting furnace 2. In order to make the temperature higher than the melting point in this case, of course, it is necessary to add some necessary heat source (electric power, fuel) 9 from the outside, so when combined with the energy consumed in the sludge incinerator 1, enormous energy is consumed in the entire process. The fact is that it is consuming. In particular, when energy derived from fossil fuel is used as an energy source, it is very undesirable from the viewpoint of global warming due to depletion of natural resources and CO ₂ emission.

  In the ash melting furnace 2, a method for melting ash using electricity (for example, an arc-type melting furnace) and a fuel (for example, heavy oil, kerosene, light oil, LPG, LNG, city gas, digestion gas, etc.) are burned by an air burner. There exists a method (for example, a swirl melting furnace, a surface melting furnace) which melts ash by doing. The ash melting furnace 2 that uses electricity has a merit that the amount of exhaust gas discharged from the furnace can be reduced, but is disadvantageous in terms of cost because it uses electricity as an energy source. In addition, when the efficiency related to power production (power generation efficiency) is taken into account, there is also a problem that the amount of energy consumption becomes extremely large. On the other hand, the ash melting furnace 2 using the fuel can reduce the energy consumption and the energy cost itself as compared with the system using electricity, but the amount of the exhaust gas generated from the furnace is extremely small due to the air combustion of the fuel. There is a problem that the scale of the exhaust gas treatment equipment 3 (dedusting, desulfurization, etc.) that is essential in the later stage increases.

  In Patent Document 1, pure oxygen is used as a combustion gas for the purpose of reducing the generation amount of nitrogen oxides accompanying combustion of fuel in the melting furnace, but it prevents the furnace from excessively rising in temperature. In order to achieve this, exhaust gas circulation must be performed, and as a result, the amount of exhaust gas from the melting furnace increases in the same manner as when air is used as the combustion gas. Further, since the reaction in the melting furnace is not a partial oxidation reaction but a combustion reaction, it is impossible to recover the combustible gas.

  In patent document 2, it is possible to gasify dry sludge with oxygen or oxygen enriched air, and to collect combustible gas and slag. However, the in-furnace conditions (temperature, oxygen amount) when only dry sludge is gasified cannot simultaneously melt incinerated ash after incineration of sludge in the same furnace. That is, in order to raise the temperature of the incinerated ash to the melting temperature (above the melting point of ash), it is necessary to excessively supply oxygen exceeding the appropriate amount of oxygen to gasify the dry sludge. There is. In particular, when a desulfurizing agent such as lime is added in a sludge incinerator, the melting temperature of the incineration ash becomes extremely high, so it is important to appropriately manage the in-furnace conditions.

  An object of the present invention is to provide a gasification and melting method and gas of sludge and incineration ash capable of melting incineration ash and sewage sludge at high efficiency and low cost by making maximum use of the energy of sludge itself. It is to provide a chemical melting furnace.

In order to achieve the above object, the gist of the present invention is as follows.
(1) Dry sludge generated by biological treatment of sewage, containing organic matter, and incinerated ash generated by incineration of sludge, 0.2 to 0.9 times the theoretical oxygen amount required for complete combustion Blowing into oxygen gas or oxygen-enriched air into an air-flow bed type gasification and melting furnace by air conveyance and partial combustion at 1100 to 1700 ° C to convert dry sludge and ash in incinerated ash into slag, and dry sludge and incineration A method for gasifying and melting sludge and incinerated ash, characterized by converting organic matter in the ash into combustible gas.
(2) The particle size of the incinerated ash is 0.1 μm to 2 mm, the particle size of the dried sludge is 0.1 μm to 3 mm, and the moisture content of the dried sludge is 20% by mass or less ( 1) Gasification and melting method of sludge and incineration ash as described.
(3) The method for gasifying and melting sludge and incinerated ash according to (1) or (2), wherein the incinerated ash is blown into the gasification and melting furnace from the same height as or above the dried sludge. .
(4) Incineration ash and dry sludge are blown so as to draw a swirl circle in the circumferential direction in the gasification melting furnace, and the sludge according to any one of (1) to (3), Gasification and melting method for incineration ash.
(5) The combustible gas generated by the organic substance conversion described in any one of (1) to (4) is used as an auxiliary fuel for sludge incineration that generates the incinerated ash. Gasification and melting method of sludge and incineration ash.
(6) An incinerated ash and sludge air-bed type gasification and melting furnace having a raw material supply nozzle by air flow conveyance, wherein the raw material supply nozzle is 1/2 to 1/1 with respect to the furnace diameter of the gasification melting furnace. A gasification and melting furnace for sludge and incinerated ash, wherein a plurality of them are installed in a tangential direction of a turning circle coaxial with a furnace having a diameter of 5.
The slag in the present invention is a state in which the ash content in the dried sludge or incinerated ash is melted by raising the temperature to the melting point or higher, or a state in which the ash in the molten state is solidified again by cooling. Refers to things.

  According to the present invention, incineration ash and sewage sludge generated by incinerating surplus activated sludge generated from a biological treatment facility of sewage can be melted at high efficiency and at low cost.

Hereinafter, the present invention will be described in detail. FIG. 2 shows an example of a flow sheet relating to the present invention.
The dewatered cake 4 discharged from the treatment facility of the sewage plant by the biological treatment of the sewage is burned by the air 5 at a temperature of about 800 to 900 ° C. in the sludge incinerator 1 such as a fluidized bed type. The composition of the dewatered cake varies depending on the treatment method in the sewage treatment plant and the season, but generally, the moisture content is 70 to 90% by mass (based on the total weight of the dehydrated cake), and the ash content is 5 to 40% by mass (dried sludge). Weight basis) and organic matter 60 to 95 mass% (dry sludge weight basis). The exhaust gas (combustion exhaust gas) and the incineration ash released from the sludge incinerator 1 are recovered from the gas sensible heat by the waste heat recovery unit 11, and then the majority of the incineration ash 7 in the cyclone 12 and the exhaust gas desulfurization equipment 13 in the exhaust gas. The polluted materials are removed, and the fine incineration ash 7 remaining in the electrostatic precipitator 14 is removed, and then, it is released from the chimney. Note that other dust collection equipment (for example, a metal filter, a ceramic filter, and a bag filter) may be used instead of the cyclone 12 and the electric dust collector 14.

On the other hand, a part of the dewatered cake 4 discharged from the sewage treatment plant is introduced into a sludge drying facility 16 such as an air dryer and the drying process is performed.
The dried sludge 17 discharged from the sludge drying facility 16 is put together with the incinerated ash 7 generated in the previous sludge incinerator 1 into the gas bed type gasification and melting furnace 20 by air flow of nitrogen or air. In the gasification melting furnace 20, the organic matter in the dried sludge 17 (containing about 60 to 95% by mass based on the weight of the dried sludge) and the organic matter slightly mixed in the incineration ash 7 (unburned matter, incineration ash Is contained at a high temperature of 1100 to 1700 ° C. by a partial oxidation reaction (incomplete combustion) using oxygen 19 or oxygen-enriched air as a gasifying agent. (The main components are H ₂ , CO, CH ₄ , CO ₂ , H ₂ O). At the same time, the ash content in the dried sludge 17 and the ash content in the incineration ash 7 (incineration ash occupies most of the ash content of about 90% by mass) are melted and converted into slag. Most of the slag is extracted from the bottom of the gasification melting furnace, but a part of the slag is scattered in the high-temperature combustible gas discharged from the gasification melting furnace 20, so that the gas cooling at the top of the gasification melting furnace 20 is performed. Spraying water or quenching gas 22 is blown in the vessel 21 to cool to 1000 ° C. or less, and the scattered molten slag is solidified to prevent ash adhesion trouble (slagging).

  The high-temperature combustible gas 23 discharged from the gasification melting furnace 20 is input to the sludge incinerator 1 and used as auxiliary fuel. At this time, the combustible gas 23 discharged from the gas cooler 21 is immediately put into the sludge incinerator 1 so that the sensible heat of the combustible gas 23 can be efficiently maintained to maintain the temperature in the sludge incinerator 1 (direct). To be available). Note that the properties (heat generation amount, generated amount) of the combustible gas 23 generated in the gasification melting furnace 20 vary depending on various gasification conditions (temperature, sludge properties, heat release amount, etc.). Further, in the sludge incinerator 1, the amount of heat that needs to be supplemented with auxiliary fuel also varies depending on various incineration conditions (temperature, sludge properties, heat release amount, etc.). Therefore, if the generated combustible gas 23 alone cannot cover all the heat required by the sludge incinerator 1, the auxiliary fuel 6 may be added to the sludge incinerator 1 and conversely combustible. If the gas becomes surplus, the surplus combustible gas 24 may be used for other purposes.

Of course, when the combustible gas 23 generated in the gasification melting furnace 20 is not used as an auxiliary fuel for the sludge incinerator 1 due to reasons such as the sludge incineration furnace 1 is not close to the gasification melting furnace 20, After being treated with gas (waste heat recovery, dedusting, desulfurization, etc.), various effective uses (sludge dryer fuel, power generation fuel, chemical synthesis raw materials such as methanol, hydrogen production raw materials, etc.) It doesn't matter.
The system of the sludge incinerator 1 may be either a fluidized bed incinerator (including a circulating fluidized bed incinerator) or a multistage incinerator that occupies most of the current sewage sludge incinerator. The combustion air 5 to be introduced into the sludge incinerator 1 may be preheated by passing through the waste heat recovery device 11 in advance or using another heat source.

The heat recovered in the waste heat recovery unit 11 is used as the heat source of the sludge drying facility 16. As a method of the sludge drying equipment 16 at this time, a direct heating type sludge dryer (specifically, an air dryer, a hot air pulverizer dryer, a fluidized bed dryer, a rotation with a stirrer) that directly contacts high temperature hot air and sludge. When using a drum dryer or the like, the waste heat recovery unit 11 is a gas / gas heat exchanger type. In addition, when using a so-called indirect heating type sludge dryer that uses a heat medium such as steam as a heat source and dries the sludge by conduction heat transfer through the heating wall, the waste heat recovery unit 11 is of the boiler type. Is adopted. When the heat quantity supplied from the waste heat recovery unit 11 alone cannot cover the necessary heat amount in the sludge drying facility 16, it may be used in combination with some other heat source.
The sludge dryer generates odor gas 26 peculiar to sludge, and it is desirable to introduce the odor gas 26 into the sludge incinerator 1 and perform deodorization treatment. Of course, you may install another deodorizing apparatus (activated carbon deodorization, biological deodorization, etc.).

  The dried sludge 17 discharged from the sludge drying facility 16 in this way has a calorific value of about 6300 to 21000 kJ / kg-dry. When the dried sludge 17 is blown into the gasification melting furnace 20, the particle size is preferably about 0.1 μm to 3 mm. Even if the particle size is larger than 3 mm, it is possible to perform gasification, but the specific surface area of the particles decreases (decrease in the contact area with oxygen) or the gasification rate decreases due to the decrease in the heating rate. Along with this, unburned materials increase, and the conversion rate of sludge into gas decreases. On the other hand, in order to make the particle size of the dried sludge 17 smaller than 0.1 μm, a pulverizer that consumes much power is separately required. Therefore, the particle size is preferably in the above range.

Since sludge is mainly a collection of fine microorganisms or bacteria, it can be easily dried by a hot air drier, etc., or after crushing by a simple crusher after drying, it can be easily about 0.1 μm to 3 mm. The particle size.
In addition, in order to prevent the efficiency reduction due to the latent heat of vaporization of the gasification melting furnace 20 and to make the particle diameter of the sludge 3 mm or less, it is desirable that the water content in the sludge be 20 mass% or less as much as possible. .

On the other hand, as for the incineration ash 7 generated from the sludge incinerator 1, it is preferable to blow into the gasification melting furnace 20 having a particle diameter of 0.1 μm to 2 mm. That is, large particles (so-called clinker ash) having an apparent particle diameter of 2 mm or more due to reasons such as sintering or agglomeration of ash particles in the incinerated ash 7 put into the gasification melting furnace 20 together with the dried sludge 17. If included, it is desirable to make the particle size 2 mm or less by using a pulverizer such as a ball mill or a roll mill in advance. Since the incinerated ash 7 has a particle density larger than that of the dried sludge 17, when the particle size is larger than 2 mm, the incinerated ash 7 cannot fall on the airflow in the furnace after being put into the gasification melting furnace 20 and falls directly to the furnace bottom. Therefore, the residence time in the furnace for the incineration ash 7 to melt sufficiently cannot be obtained. Further, the lower limit of the particle size is not particularly defined, but a particle size smaller than 0.1 μm is not preferable because it causes shelves in the hopper of the transport system. In particular, fine incineration ash (so-called fly ash) that cannot be collected by the cyclone 5 and collected by the subsequent electrostatic precipitator 14 may contain harmful heavy metal components at a high concentration. You may process separately outside the system of this process.
The temperature in the gasification melting furnace 20 is set to a temperature corresponding to the melting point of the ash contained in the incinerated ash 7 and the dried sludge 17 and is set to a temperature higher than the melting point of the ash. The above high temperature is not preferable because it extremely shortens the life of the furnace wall in the gasification melting furnace 20 and increases heat loss due to heat dissipation, so the temperature is set to 1700 ° C. or lower.

  As the oxygen 19 added as a gasifying agent at the time of gasification, it is preferable to use oxygen as high as possible from the viewpoint of reducing the sensible heat brought out by the accompanying nitrogen. However, producing oxygen 19 having a concentration higher than necessary not only increases demerits such as an increase in input energy in the oxygen production facility 18, but has little influence on gasification itself, so that the oxygen 19 used here is generally used. A concentration (80% or more) that can be produced by a simple oxygen production method (pressure swing adsorption method <PSA>, cryogenic separation method).

The amount of oxygen to be added here is less than the amount of oxygen necessary for completely burning the organic matter in the dried sludge 17 and the incinerated ash 7 (so-called theoretical oxygen amount). The ratio varies depending on how many times the sludge heat generation amount and the temperature in the gasification melting furnace 20 are set, but it should be adjusted within the range of 0.2 to 0.9 when the theoretical oxygen amount is 1. Is preferred. When the oxygen ratio is less than 0.2, the amount of organic matter that is converted into unburned material without being gasified becomes extremely large. When the oxygen ratio exceeds 0.9, combustible gases (CO, H ₂ , CH ₄ ) and the like, and most of them are converted to combustion gases (CO ₂ , H ₂ O), which is not preferable for the purpose of the present invention.
Further, for the purpose of controlling the temperature in the gasification melting furnace 20, steam may be used in combination with the oxygen 19 as a gasifying agent.

  In addition, although the pressure in the gasification melting furnace 20 is not particularly defined, a pressure lower than the atmospheric pressure is not preferable because there is a risk of explosion due to leakage of air from the outside. Moreover, when it is set as the pressurization condition higher than atmospheric pressure, the merit which can make the gasification melting furnace 20 compact, and the produced | generated combustible gas 23 is sludge incineration which is drive | operated by the pressure of a normal pressure. There is also an advantage that it can be fed into the furnace 1 without a blower.

  The temperature in the gasification melting furnace 20 is substantially maintained by the reaction heat (exothermic reaction) associated with the partial oxidation reaction of the dried sludge 17, and the incineration ash 7 is charged into the furnace as the ash is heated and dissolved. It is accompanied only by endotherm (ie, temperature drop). The vertical temperature distribution in the gasification melting furnace 20 has a distribution in which the temperature at the blowing position height of the dried sludge 17 is maximum, but the generated slag is discharged from the outlet (slag tap) at the bottom of the furnace. Therefore, it is necessary to maintain at a particularly high temperature in order to be stably extracted outside the furnace. Accordingly, when the incinerated ash 7 and the dried sludge 17 are separately blown into the gasification melting furnace 20 using dedicated transport equipment, the blowing position of the incinerated ash 7 should be lower than the blowing position of the dried sludge 17. Is not preferable because it causes a temperature drop at the bottom of the furnace, that is, a clogging of the slag tap.

  Further, when a large amount of incinerated ash 7 is blown too much with respect to the amount of dry sludge 17 blown, it is no longer possible to raise the incinerated ash 7 to a melting temperature or higher only with the reaction heat associated with the partial oxidation reaction of the dry sludge 17. Since it becomes impossible, it is not preferable for the purpose of the present invention. The amount of incinerated ash 7 that can be blown into the amount of dry sludge 17 blown differs depending on various conditions (melting furnace temperature, dry sludge heat generation, incinerated ash heat capacity, furnace body heat release, etc.) Although not stipulated, the combustible gas 23 is of good quality while maintaining a state (partial oxidation reaction, melting of ash) in the gasification melting furnace 20 that is not more than 3 times the dry sludge 17 weight (dry basis), particularly stable. In order to obtain the slag 10, it is desirable to make it equal to or less than the same size.

Desirably, the dried sludge 17 and the incinerated ash 7 are sufficiently blown into the gasification and melting furnace 20 so as to make a swirl in the circumferential direction of the furnace to ensure a sufficient residence time in the furnace.
In FIG. 3, an example of the blowing part of the incinerated ash 7 and the dry sludge 17 in the gasification melting furnace 20 is shown.
The blowing portion has a raw material supply nozzle 27 by airflow conveyance, and the raw material supply nozzle 27 is coaxial with a furnace having a diameter of 1/2 to 1/5 with respect to the furnace inner diameter 28 of the gasification melting furnace. A plurality of pieces are installed in the tangential direction of the turning circle 29.

The blowing direction of the incinerated ash 7 and the dried sludge 17 is a swirl flow so that the particle residence time in the gasification melting furnace 20 is as long as possible, and the partial oxidation reaction of the organic matter and the ash melting (slagging) sufficiently occur. Is preferable. For that purpose, it is necessary to blow incineration ash 7 and dry sludge 17 from the respective raw material supply nozzles 27 (burners) in the tangential direction of the swirl circle 29.
If the diameter of the swirl circle 29 at that time is larger than 1/2 with respect to the in-furnace diameter 28 of the gasification melting furnace 20, erosion by particles on the wall of the gasification melting furnace 20 may occur, which is not desirable. Conversely, when the diameter of the swirl circle 29 is smaller than 1/5 with respect to the furnace diameter 28 of the gasification melting furnace 20, a swirl flow for ensuring a sufficient particle residence time does not occur. Therefore, the diameter of the turning circle 29 is preferably in the range of 1/2 to 1/5 with respect to the in-furnace diameter 28 of the gasification melting furnace 20.

  In addition, the dry sludge 17 and the incineration ash 7 are prepared by preparing two series of transport facilities (hopper, feeder, transport pipe) and separately blowing them into the gasification melting furnace 20 from the dedicated raw material supply nozzle 27. Either method may be employed in which both are mixed in advance and then blown into the gasification melting furnace 20 from the same raw material supply nozzle 27. It is desirable from the viewpoint that the temperature of the incinerated ash 7 can be increased rapidly in association with the partial oxidation reaction (exothermic reaction) of the dried sludge 17 to supply both in advance. However, when there is a large difference in particle size density between both the dried sludge 17 and the incinerated ash 7, there is a possibility that troubles such as blockage may occur in a series of conveyance supply system facilities. It is preferable.

The required gas residence time in the gasification melting furnace 20 varies depending on the properties (heat generation amount, particle size, moisture content, etc.) of the dried sludge 17 and the temperature, but is preferably 0.2 to 10 seconds. . When the gas residence time is shorter than 0.2 sec, the dried sludge 17 cannot be sufficiently gasified, and conversely when it is longer than 10 sec, the volume of the gasification melting furnace 20 becomes unnecessarily large. This is not preferable because it leads to an increase in equipment costs. This gas residence time is defined as in the following equation.
(Gas residence time [sec]) = (Internal volume of gasification melting furnace 20 [m ³ ])
/ (Gasification melting furnace 20 outlet gas flow rate [m ³ / sec])

As sludge 4 used in the present invention, in addition to sewage sludge, surplus activated sludge generated from biological wastewater treatment facilities (for example, coke oven wastewater (safe water) treatment equipment, stainless pickling wastewater treatment equipment, Excess sludge discharged from wastewater treatment facilities of various food factories) may be used.
In addition, the incineration ash 7 to be introduced into the gasification melting furnace 20 is not limited to the incineration ash 7 derived from sewage sludge, but incineration derived from general waste (eg, garbage) discharged from each household. Any incineration ash 7 such as ash 7, incineration ash 7 derived from industrial waste such as building waste, shredder dust, or coal-derived incineration ash 7 generated from a coal-fired boiler may be used. However, when the incinerated ash 7 having a melting temperature exceeding 1600 ° C. is used, the temperature in the gasification melting furnace 20 needs to be further increased, which is not preferable because it causes a decrease in the thermal efficiency of the furnace. In this case, it is desirable to add some melting point depressant (for example, iron-based flocculant such as lime, iron sulfate or iron chloride) to the incineration ash 7 in advance. Of course, even if the melting point of the incinerated ash 7 is 1600 ° C. or lower, the temperature inside the gasification melting furnace 20 may be lowered, that is, the thermal efficiency may be improved by adding a melting point depressant.

  The present invention is preferably applied when a new ash melting function needs to be added to the already operating sludge incinerator 1. That is, if the sludge drying equipment 16 and the gasification melting furnace 20 are newly installed, it is natural that a simple ash melting function is added to the conventional sludge incineration process, and the heat source supply function necessary for the sludge incinerator 1 is also provided. At the same time, the amount of auxiliary fuel 6 used can be reduced. In other words, by effectively utilizing the energy (calorific value) of the sludge itself as biomass, the input energy derived from fossil fuels from outside is reduced, and the life expectancy of fossil resources, which are limited and valuable energy sources, is extended. Will contribute.

According to the flow shown in FIG.
The analysis values of the sewage sludge used are shown in Table 1, and the analysis values of ash contained in the sludge 4 are shown in Table 2. This sludge 4 is what was discharged | emitted from the dehydrator of the sewage treatment plant (dehydrated cake). Moreover, incinerated ash 7 after incineration in the sludge incinerator 1 contained 3% by mass of unburned carbon, but the composition of ash was the composition of ash in the original sewage sludge (Table 2). And almost the same.

100 t / day of sewage sludge (dehydrated cake) is dried in the sludge drying facility 8 and then generated dry sludge 17 (21 t / day) (water content 5 mass%, particle size 7 μm to 1.2 mm (average particle size 220 μm)) Together with the incinerated ash 7 (4 t / day) (particle size 0.5 μm to 350 μm (average particle size 30 μm)) generated from the fluidized bed sludge incinerator 1 into the gasification and melting furnace 20 by air current conveyance using nitrogen. (Incineration ash / dry sludge = 1.9). The dried sludge 17 and the incinerated ash 7 were fed from two raw material supply nozzles 27 installed at opposing positions so as to draw a swirl circle diameter of 1/3 with respect to the diameter of the gasification melting furnace 20. All the raw material supply nozzles 27 (four in total) are installed at the same height level of the gasification melting furnace 200, and the two raw material supply nozzles 27 for blowing the dry sludge 17 have a burner structure. Then, oxygen 19 was introduced into the furnace together with the dried sludge 17.
In addition, the steam 32 collect | recovered with the waste-heat boiler 31 of the back | latter stage of the sludge incinerator 1 was used for the required heat source in the sludge drying equipment 16. In order to adjust the melting point of ash (melting point drop), lime 30 was added in advance to the dried sludge and incinerated ash so that the basicity (CaO / SiO ₂ ) of the ash composition was 1.0.

In the gasification melting furnace 20, the dried sludge 17 and the incineration ash 7 are gasified and melted at a temperature of 1300 ° C. together with oxygen 19 (oxygen concentration 93%) produced in the oxygen production facility 18, and high-temperature combustible gas and slag are produced. Switched to. The generated high-temperature combustible gas is cooled to 900 ° C. by the water spray 22 in the gas cooler 21 at the upper part of the gasification melting furnace 20 and then introduced into the sludge incinerator 1 to incinerate the sludge (dehydrated cake) 4. Was used as a heat source. The exhaust gas after combustion discharged from the sludge incinerator 1 was released into the atmosphere from the chimney after gas treatment (waste heat recovery, dust removal, desulfurization). The exhaust gas (odor gas) generated from the sludge drying facility 16 was put into the sludge incinerator 1 for deodorization treatment.
Regarding this example, it was not necessary to add any auxiliary fuel from the outside except during startup.

  Table 3 shows examples of the present invention (Examples) and conventional sludge incineration ash melting process ((1) fluidized bed sludge incinerator + slewing ash melting furnace, (2) fluidized bed sludge incinerator + electric ash melting A comparison of the amount of auxiliary fuel used in the furnace is shown. In the example of the present invention, the amount of auxiliary fuel used can be significantly reduced compared to the conventional method, and the running cost can be reduced to 70% of the conventional method. In addition, the equipment configuration is much simpler and more compact than the conventional method, so that the equipment cost and equipment installation space can be greatly reduced.

It is the flow sheet regarding a prior art. It is a flow sheet concerning the present invention. It is a figure showing the blowing method in the gasification melting furnace of the dry sludge and incineration ash of this invention. It is the mass balance (test result) of the process in the Example of this invention.

Explanation of symbols

1 Sludge incinerator 2 Ash melting furnace 3 Exhaust gas treatment equipment 4 Sludge (dehydrated cake)
5 Air 6 Auxiliary fuel 7 Incinerated ash 8 Exhaust gas 9 Necessary heat source (electric power, fuel) 10 Slag 11 Waste heat recovery device 12 Cyclone 13 Flue gas desulfurization equipment 14 Electric dust collector 15 Exhaust gas (to chimney) 16 Sludge drying equipment 17 Dry sludge 18 Oxygen Production equipment 19 Oxygen 20 Gasification melting furnace 21 Gas cooler 22 Spray water or quench gas 23 Combustible gas 24 Combustible gas (excess)
25 Hot Air or Steam 26 Odor Gas 27 Raw Material Supply Nozzle 28 Furnace Diameter 29 Swirling Circle 30 Lime 31 Waste Heat Boiler 32 Steam

Claims (6)

Oxygen or oxygen 0.2 to 0.9 times the theoretical oxygen amount necessary for complete combustion of dry sludge generated by biological treatment of sewage and containing organic matter, and incinerated ash generated by incineration of sludge It is blown into the gas bed type gasification melting furnace with enriched air by air flow conveyance and partially combusted at 1100-1700 ° C to convert the ash in the dried sludge and incinerated ash into slag, and in the dried sludge and incinerated ash A method for gasifying and melting sludge and incinerated ash, characterized by converting organic matter into combustible gas. The particle size of the incinerated ash is 0.1 μm to 2 mm, the particle size of the dried sludge is 0.1 μm to 3 mm, and the moisture content of the dried sludge is 20% by mass or less. Gasification and melting method of sludge and incinerated ash. The method for gasifying and melting sludge and incinerated ash according to claim 1 or 2, wherein the incinerated ash is blown into the gasification and melting furnace from the same height as or above the dried sludge. Incineration ash and dry sludge are blown so as to draw a swirl circle in the circumferential direction in the gasification melting furnace, gasification and melting of sludge and incineration ash according to any one of claims 1 to 3 Method. The combustible gas produced | generated by conversion of the organic substance of any one of Claims 1-4 is used as an auxiliary fuel for the sludge incineration which generate | occur | produces the incineration ash of sludge and incineration ash characterized by the above-mentioned Gasification melting method. An incinerated ash and sludge gas bed type gasification and melting furnace having a raw material supply nozzle by air flow conveyance, wherein the raw material supply nozzle has a diameter of 1/2 to 1/5 of the diameter of the gasification melting furnace in the furnace. A gasification and melting furnace for sludge and incinerated ash, wherein a plurality of them are installed toward the tangential direction of a swirling circle coaxial with the furnace made of

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