JPH10141626A - Gasifying and melting method for waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gasifying and melting method for waste, gasifying and melting the waste to recover fuel gas, molten slag and molten metal. SOLUTION: Waste is gasified and molten employing a gasifying and melting furnace for the waste, in which the waste, charged into the furnace, is burnt to gasify organic substances in the waste and recover the same as energy gas while ash and metals in the waste are recovered as molten substances. In such a method, the waste is changed into solid fuel previously by applying the treatment of crushing-drying-classifying (classifying as well as recovering of valuable metals and classifying and removing of incombustibles)-volume reduction and molding, then, charged into the gasifying and melting furnace to gasify and melt the waste. On the other hand, when dust, discharged out of the gasifying and melting furnace, is recycled (added and mixed into the waste after classification), condensation of heavy metals, contained in the dust, can be effected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a gas (hereinafter referred to as "waste") which can be used as a fuel by converting general waste and industrial waste (hereinafter, also simply referred to as waste).
The present invention relates to a method of gasifying and melting waste, which collects ash and metals contained in these wastes as molten slag and molten metal, respectively.

[0002]

2. Description of the Related Art As a method of treating general waste mainly composed of municipal waste and industrial waste mainly composed of shredder dust of discarded automobiles and home electric appliances, a method of landfill disposal or landfill disposal after incineration is known. Has been adopted. However, under the recent tight situation that it is extremely difficult to secure landfill sites, the incineration method generally used so far has been reviewed.

[0003] Further, instead of using a method of directly disposing of waste or landfilling after incineration, waste once reduced in volume and solidified, that is, RDF (Refu) is generally used.
se Derived Fuel (meaning fuel derived from waste)
There is also a system in which the fuel is incinerated after it has been converted into a solid fuel. Examples of this system include a TC-system (technique for converting flammable waste into solid fuel) by Japan Recycling Management Co., Ltd. and a J-Catrel system (also from flammable waste) by EBARA CORPORATION. Solid fuel technology),
Another example is the conversion of combustibles to solid fuel, which is planned in the Mie Prefecture's Recycling Energy Center concept (The 6th Seminar Abstract on Solid Waste Fuel Conversion Technology, June 28, 1996 (Environmental Planning Center) ).

On the other hand, from the standpoint of protecting limited resources, these wastes or RDF are not simply incinerated,
It is desirable to recover recyclable materials as resources (useful substances) or energy (heat energy).
The following are examples that are currently in practical use.

[0005] 1. Material recovery Separation and recovery of metals (aluminum cans, steel cans, etc.) Separation and recovery of plastics (PET bottles, etc.) Separation and recovery of waste paper (newspaper, etc.) 2. Material conversion and recovery Recovery of plastics as fuel oil by pyrolysis oil recovery Recovery of plastics as fuel gas by pyrolysis gasification Thermal energy recovery Steam recovery at the time of waste incineration Since the above item 1 is a pre-treatment method before waste, the recovery of useful substances from waste after separation must rely on the above two or three means. I can't. In particular, recently, general waste and industrial waste contain various substances due to changes in lifestyle (diversification). Chemical systems are in the spotlight.

[0006] As the gasification system, the following one can be mentioned.

A. Coke bed direct melting system ("Steel Industry Bulletin" No.1674, 1996.3.21
(Japan Iron and Steel Federation), “Fuel and Combustion,” Vol. 61, No. 8, (1994), pp. 572-578, and Tokuhei 7-35
The melting furnace main body is a single-stage tuyere vertical shaft furnace, into which coke and limestone are charged together with waste from the center of the furnace.
Inside the furnace, from the top, a preheating / drying zone (about 300 ° C), a thermal decomposition zone (300 to 1000 ° C), and a combustion / melting zone (1700)
８００1800 ° C.). In the preheating / drying zone, waste is heated and moisture evaporates. The dried waste gradually descends and moves to the pyrolysis zone where the organic matter is gasified. The generated gas is exhausted from the upper part of the furnace, is completely burned in a combustion chamber at a later stage, and heat energy is recovered by a heat recovery system such as a waste heat boiler.

[0008] On the other hand, the remaining gasified ash and inorganic substances fall into the combustion / melting zone together with coke. The coke is burned by the air supplied from the tuyere, and the heat causes the ash and inorganic substances to completely melt. The melt is adjusted to an appropriate viscosity and basicity by the charged limestone, and discharged from the taphole to the outside of the furnace.

In order to save coke, a method is disclosed in which a separate charging system for coke and waste is used to utilize the sensible heat of exhaust gas for drying and preheating of waste to increase the thermal efficiency of the furnace. (Japanese Patent Publication No. 7-35889).

B. High temperature gasification direct melting system ("Steel Industry Bulletin" No.1674, 1996.3.21
(The Japan Iron and Steel Federation)) The melting furnace body is a vertical furnace having tuyeres divided into three stages in the height direction, and the flow formed by the dry distillate of waste maintained at a high temperature of about 1000 ° C. Waste is directly injected into the formation along with auxiliary fuel such as coke. By blowing air from the middle tuyere (two-stage tuyere) into the fluidized bed, part of the generated gas is burned and the temperature is maintained.

[0011] The dry distillate containing incombustibles descends to the moving bed at the lower part of the furnace together with the auxiliary fuel, and is burned and gasified at a high temperature by oxygen-enriched air from the lower tuyere (main tuyere). It is melted, dropped and separated from metal by the difference in specific gravity. On the other hand, the free board temperature is always 1000 by the air from the tuyere (three-stage tuyere)
The temperature is maintained at not less than ° C., thereby preventing the generation of tar components and the production of dioxins and their precursors.

C. Thermoselect method (Thermoselect (1995.5.26),
PART1 "Foundation for the continuos conversio
ns of solid waste ”) The furnace used in this method is a pressurized tubular pyrolyzer that evaporates water in waste and pyrolyzes organic matter, and the combustion of pyrolysis residue (char) by oxygen, ash This is a pyrolysis melting furnace that is integrally connected with a combustion melting furnace that melts and reforms gas.In the combustion melting furnace, first, the decomposition gas of organic substances from the pyrolyzer is sent to the middle part of the furnace. Guided,
The char descends to the bottom of the furnace, and is burned at a high temperature by oxygen to melt the ash. At the same time, conversion of organic decomposition gas to CO and H ₂ (gas reforming) proceeds in a high-temperature atmosphere at the top of the furnace.

However, the above conventional method has the following problems.

That is, the vertical shaft furnace of the above system A requires expensive coke and completely burns the generated gas, so that only the sensible heat can be recovered. Further, in this method, since the temperature of the preheating / drying zone in the upper part of the furnace is about 300 ° C., a large amount of hydrocarbons such as tar and dioxins which cannot be sufficiently decomposed are discharged outside the furnace.

The vertical furnace of the system B also requires expensive coke as in the case of the system A. Further, in order to keep the free board always at 1000 ° C. or higher, a large free board is required, and an increase in the size of the furnace is inevitable.

Although the furnace used in the method C is said to integrally connect two reactors (furnace), it is actually clearly separated into two furnaces, a pyrolysis furnace and a combustion melting furnace. .
Therefore, it is structurally complicated and the equipment cost increases. Further, since the pyrolysis furnace is an indirect heating type furnace separated from the combustion melting furnace, the sensible heat of the exhaust gas of the combustion melting furnace is not sufficiently utilized.

[0017]

SUMMARY OF THE INVENTION In connection with the problem of landfill sites, the present invention is to effectively use combustibles, ash, iron, etc. in wastes, and to reduce the costs associated with landfills. It is intended to utilize the by-product gas generated as fuel for power generation and the like.

That is, an object of the present invention is not to simply incinerate general wastes and industrial wastes, but to gasify organic substances contained in the wastes and collect them as energy gas, and to include the wastes in the wastes. An object of the present invention is to provide a method for recovering ash and metals as a molten slag and a molten metal, respectively. Specifically, a series of processes of gasification melting of waste, dehydration / pyrolysis, and gas reforming are performed in one furnace without using expensive coke, solving the problems in the above-described conventional technology, It is another object of the present invention to provide a gasification and melting method capable of producing a clean exhaust gas containing substantially no tar or dioxin.

[0019]

The gist of the present invention resides in the following gasification melting method.

The organic matter in the waste is gasified and recovered as an energy gas, and the waste is gasified and melted by using a waste gasification and melting furnace for recovering ash and metals in the waste as a melt. In the method, the waste is
A method for gasification and melting of waste, wherein the method is subjected to the following processes (1) to (4) in advance and then charged into the gasification and melting furnace and gasified and melted.

(1) Step of crushing waste (2) Step of drying crushed waste (3) Separation and collection of valuable metals such as copper and aluminum from the dried waste, and incombustibility such as rubble and earth and sand (4) Step of adding and mixing lime to the waste after the separation and collection and the separation and removal of the above (3) to reduce the volume of the waste. A gasification and melting method for waste, characterized in that dust discharged from the gasification and melting furnace is added to and mixed with the waste to be treated in the step (4).

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method for gasifying and melting waste (the method of the present invention) of the present invention will be described in detail.

First, in the method of the present invention, the reason why the waste charged into the gasification and melting furnace is subjected to the treatment in the above-mentioned steps (1) to (4), that is, the RDF conversion is described.

FIG. 1 is a diagram showing a schematic manufacturing process of an RDF. As shown, this step consists of four steps: grinding, drying, fractionation and volume reduction molding.

(1) Pulverization Step Although the collected wastes vary in quality, they also range in size from small to oversized garbage. If such a wide range of wastes are directly charged into a gasification and melting furnace, it is difficult to maintain stable air permeability, and this may cause operation troubles such as hanging on a shelf or blowing through.

That is, the minute-sized waste causes clogging of the packed bed and increases the amount of scattered waste. On the other hand, when the garbage becomes oversized, a portion in which the combustion is not uniform occurs inside the gasification and melting furnace, so that not only the gas permeability is disturbed but also the dispersion of the components of the energy gas recovered as the exhaust gas increases. Also,
Since the charging equipment has to be manufactured according to the largest waste, the equipment is over-specified, wasteful and economical.

Therefore, it is necessary to subject the waste to pulverization before charging the waste into a gasification and melting furnace. The size of the crushed waste is not generally determined, but is generally 1 size.
It is preferable to set it to about 50 mm or less. The mechanical equipment used for pulverization is not limited to a specific one, but a conventionally used uniaxial shearing type is preferred.

(2) Drying process General waste such as municipal solid waste contains a large amount of water. Taking garbage as an example, the average water content is 3
0 to 60%, and may exceed 70% in some cases. If such waste is directly charged into a gasification and melting furnace, a large amount of energy is required to evaporate water. Essentially, in a gasification and melting furnace, valuable energy must be consumed to thermally decompose and gasify organic matter in waste and to melt ash, which is a residue after pyrolysis. It is desirable that the contained water be removed before being charged into the gasification and melting furnace.

In order to remove the moisture contained in the waste outside the gasification and melting furnace, a conventionally used method such as a method of effectively utilizing the waste heat of the gasification and melting furnace or a method of mechanically compressing the waste is used. I just need.

(3) Separation Step As described above, it is desirable to separate and collect valuable resources such as metals and plastics contained in the waste in advance.

In this step, if metals such as copper, aluminum and iron in the waste can be removed, the amount of metals brought into the gasification and melting furnace is reduced, so that energy for melting the metals becomes unnecessary. In addition, the content of metals, especially iron oxide and lead oxide, brought into the molten slag is reduced. As a result, effective use of molten slag, for example, cement raw materials,
It can be used in a wider range such as tiles, blocks, and roadbed materials. Further, if the iron oxide and the lead oxide contained in the molten slag are reduced, the coke conventionally required for the reduction of the molten slag and the recovery of metals in the gasification melting furnace can be eliminated.

Further, if slags such as debris and earth and sand in the waste can be removed in this step, the amount of slag brought into the gasification and melting furnace is reduced, so that energy for melting the slag becomes unnecessary. In addition, there is an advantage that the amount of slag-forming agent such as limestone added to stably discharge the molten slag without causing clogging or the like can be reduced.

If the metals and slags in the waste have been removed in advance, the waste to be charged into the gasification and melting furnace contains a large amount of combustible materials, and the waste itself has The calorific value is increased, and it is not necessary to use expensive coke, coal, and auxiliary fuels such as kerosene and heavy oil in the gasification and melting furnace.

It is difficult to separate and collect the above-mentioned metals or slags such as debris and earth and sand from the waste in which various kinds of substances are mixed. However, in the method of the present invention, it is already pulverized and dried. Since the treatment is performed, it is relatively easy to select heavy and light materials by a difference in specific gravity, and to sort irons by magnetic force.

(4) Volume Reduction Molding Step In this step, the waste that has been pulverized and dried in the pretreatment is volume reduced and molded to obtain a uniform-sized waste, that is, RDF. There is no particular limitation on the mechanical equipment used for volume reduction molding, but a single-screw extruder of a conventionally used type is suitable. The size after molding is the diameter of the gasification and melting furnace,
It may be appropriately determined according to the charging inlet diameter and the like, but usually 10 to
It is preferable to set it to about 100 mm.

When the RDF obtained as described above is charged into a gasification and melting furnace, the size is uniformized.
In the furnace, a packed layer (a layer in which RDF is relatively densely packed) is naturally formed. As a result, the gas permeability in the furnace is improved, and a stable gasification and melting operation can be performed. Further, it is not necessary to make the raw material charging equipment of the gasification melting furnace excessively large, and it is possible to design the raw material charging equipment to have an appropriate size.

Since the RDF has improved compactness unlike the waste before volume reduction, it gradually undergoes thermal decomposition and decomposition in a gasification and melting furnace.
Gasifies and burns. A fire like coke plays a role of good fuel. The packed layer of RDF is
Due to the tightly formed and solid structure, the scattering loss of waste is significantly reduced.

Furthermore, if limes such as quicklime, slaked lime or limestone are added in the stage of volume reduction molding treatment within a range that does not hinder the molding, lime particles will be contained in the RDF, and In the chemical melting furnace, the following effects are also provided.

(A) S (sulfur) removal and Cl (chlorine) removal are promoted.

(B) Since the production of chlorophenols and chlorobenzenes, which are considered to be precursors of dioxin production, is suppressed, the amount of dioxin produced is reduced.

(C) Melting of ash, which is a residue after thermal decomposition, is promoted.

In addition, if dust discharged from the gasification and melting furnace is added at the stage of volume reduction molding processing (see FIG. 1),
Heavy metals contained in dust, especially Cr, Pb, Hg,
It becomes possible to concentrate Cd, Zn, As and the like. That is, the dust discharged from the gasification and melting furnace is circulated and reused many times, and heavy metals in the dust finally discharged from the gasification and melting furnace are concentrated to a high concentration. by this,
Extraction of these heavy metals from dust is facilitated, opening the way for reuse. The extraction of heavy metals can be performed by a common wet method using an alkali or an acid.

Next, a furnace used for gasifying and melting the RDF obtained by the above steps (1) to (4) will be described.

This furnace is configured to burn waste, gasify organic matter in the waste and collect it as an energy gas, and collect ash and metals in the waste as a melt. Any gasification and melting furnace may be used.

The method of the present invention uses an RDF
It is characterized by the fact that waste gas is charged and gasified and melted. As a result, the various effects of the above-described RDF conversion are maximized.

As an example, a case where a gasification and melting furnace (Japanese Patent Application No. 8-249797) filed by the present inventors has been described.

FIG. 2 is a schematic vertical sectional view showing the structure of an example of the gasification and melting furnace. In addition, this gasification melting furnace,
Since RDF waste is treated, here, RDF
It is called a gasification melting furnace.

As shown, the RDF gasification and melting furnace 1
Is an RDF loading inlet 11- for loading RDF in the upper part.
1 and a gas outlet 3-1 for discharging generated gas. The hopper 11 is connected to the RDF loading port 11-1.
-2 and a pusher 10 are attached, and a gas exhaust port 3-1 has a duct 3 for collecting exhaust gas 4.
-2 is attached. A discharge port 9 for discharging the molten slag and the molten metal 13 is provided in the lower part of the furnace.

Between the RDF loading inlet 11-1 on the furnace side wall and the discharge port 9 for molten slag and molten metal, three steps in the height direction in which the supporting gas and the auxiliary fuel can be blown independently. There are separate tuyeres. That is, in order from the bottom of the furnace, the tuyere (lower stage) for injecting the combustion supporting gas 7-1 and the auxiliary fuel 6-1 into the packed bed 14 mainly composed of carbide generated by dehydrating, heating, and thermally decomposing the RDF. (Hereinafter referred to as “primary tuyere 5-1”)
And a tuyere (a middle tuyere, hereinafter referred to as a “secondary tuyere”) for injecting the combustible gas 7-2 and the auxiliary fuel 6-2 into the packed bed 15 composed mainly of RDF in a charged state. 5-2 ") and a tuyere (upper tuyere, hereinafter referred to as a" tertiary tuyere 5-3 ") for blowing the combustible gas 7-3 and the auxiliary fuel 6-3 into the free board 16. ). Note that the supporting gas is pure oxygen or a gas containing oxygen.
The auxiliary fuel is a solid fuel such as pulverized coal, a liquid fuel such as heavy oil, or a gaseous fuel such as natural gas.

Further, at the upper part of the furnace, the R
A sounding device 17 as a means for measuring the level of the DF (height level, hereinafter referred to as a raw material layer top level) is provided, and a sounding weight 18 attached to the tip of the device 17 is placed in the furnace. It is hanging.

A thermocouple 2 for measuring the temperature near the level of the tuyere (secondary tuyere 5-2) at the middle stage is provided on the furnace side wall.
0 and a thermocouple 2 for measuring the temperature of the atmospheric gas in the upper part of the furnace (that is, the temperature of the exhaust gas in the freeboard space).
1 and a temperature converter 19 for converting the signals of the thermocouples into temperatures. The temperature near the middle tuyere (secondary tuyere 5-2) level means the temperature of the second zone corresponding to the secondary tuyere 5-2.

As described above, the RDF gasification and melting furnace is a vertical, one-furnace type gasification and melting furnace. Since it is a one-furnace system, equipment is simplified, equipment costs are low, and heat loss from the furnace body is small.

In order to gasify and melt RDF using this RDF gasification and melting furnace, the RDF is put into a hopper 11-2, pushed in by a pusher 10 and pushed into an RDF inlet 11-1.
And into the furnace, and by the reactions in the first to third zones described in detail below, an energy gas containing CO and H ₂ as main components, molten slag and molten metal, and the former is placed in the upper part of the furnace. The gas is recovered from the gas outlet 3-1 provided, and the latter is recovered from the molten slag and molten metal outlet 9 provided in the lower part of the furnace.

The interior of the furnace has three zones depending on the reaction that takes place:
That is, in order from the lower part of the furnace, a region where gasification and melting of carbides occur (first zone), a region where dehydration / pyrolysis of RDF occurs (second zone), and a region where gas reforming proceeds (third zone). (See FIG. 2), each of which is divided into a first zone, a second zone and a third zone.
The above-mentioned primary tuyere 5-1, secondary tuyere 5-2 and tertiary tuyere 5-3, which can independently inject the supporting gas and auxiliary fuel necessary for the reaction into the zone, respectively. It is attached. By adopting such a configuration,
It is possible to avoid the hanging and the blow-through (specifically, which is likely to occur when coke is not used as in the method of the present invention) peculiar to the vertical furnace.

In the first zone, a reaction represented by the following equation occurs. This reaction is a reaction in which the carbide (filled bed) formed in the second zone and descending is burned by the oxidizing gas 7-1 blown from the primary tuyere 5-1. It becomes a reducing gas mainly composed of CO at a temperature of 2000 ° C. or higher. In addition, the ash (inorganic oxide) and metals contained in the carbide are melted by the sensible heat to form molten slag and molten metal. The primary tuyere 5-1 may be used if necessary.
Supplies the auxiliary fuel 6-1.

The reducing gas moves to the second zone,
The molten slag and the molten metal are recovered from an outlet 9 at the bottom of the furnace.

C + 1 / 2O ₂ = CO where C: carbide supplied from the second zone O ₂ : oxygen in the supporting gas blown from the primary tuyere RDF in the second zone The reason why this carbide is gasified and melted in the first zone by dehydrating and pyrolyzing the carbonized material is to promote the heating of the carbide, the molten slag and the molten metal This is because heat radiation loss can be effectively suppressed.

In the first zone, it is necessary to completely melt the ash and metals contained in the carbide by the sensible heat of the reducing gas to be generated.
It is preferable to keep the temperature at or above C. For this purpose, the oxygen concentration in the supporting gas is set to 50% by volume or more (hereinafter,% of the gas means volume%), and auxiliary fuel is blown if necessary. In order to extract molten slag and molten metal smoothly from the outlet at the bottom of the furnace without clogging, etc., RD
It is preferable to lower the viscosity of the slag by simultaneously charging lime from above the furnace when the F is charged into the furnace, or by blowing powdery lime as a slag-making material from the primary tuyere. In addition,
The charging or blowing of the lime is preferably performed not only when the lime is not added at the stage of the volume reduction molding treatment but also when the lime is added, because the amount is not sufficient.

In the second zone, the reactions represented by the following formulas (1) to (3) occur. The reaction of the formula is the dehydration heating of RDF,
This is performed by the sensible heat of the high-temperature reducing gas supplied from the first zone. The reduction gas is also generated by sensible heat generated when the secondary combustion is performed in accordance with the reaction formula of the combustible gas 7-2 blown from the secondary tuyere 5-2. As a result, the organic matter in the RDF is thermally decomposed into a carbide (however, represented as C in the formula and the formula) and hydrocarbon gas according to the formula and the formula. The auxiliary fuel 6-2 is supplied from the secondary tuyere if necessary.

The carbide obtained in this step moves to the first zone, and the hydrocarbon gas moves to the third zone.

[0061] _{H 2 O (liq) = H} 2 O (gas) ··· C p H q O r = r / 2CO 2 + q / nC m H n + (p-r / 2-qm / n) C · _{·· C m H n = n /} 4CH 4 + {m- (n / 4)} C ··· CO + 1 / 2O 2 = CO 2 ··· here, H ₂ O (liq): moisture in RDF C _p H _q O _r: organic matter in the RDF C _m H _n: hydrocarbon gas produced by the decomposition of organic matter in RDF C: carbides are supplied to the first zone CO: carbides produced by burning in the first zone CO ₂ : oxygen in the combustible gas blown from the secondary tuyere As described above, if lime is added at the stage of waste volume reduction molding processing, limestone, quick lime, etc. are also sized. A dense packed layer is formed by the agglomerate formed, and the packed layer of the RDF becomes more solid. Contact time between the longer, said (a) ~
In addition to the effect of (c), an effect that thermal efficiency is improved can be obtained.

The reason why the high-temperature reducing gas is subjected to the secondary combustion is to promote the heating by using the secondary combustion heat of the formula and to control the thermal decomposition temperature to 800 to 1000 ° C.
This secondary combustion heat is much larger than the combustion heat (primary combustion heat) in the above equation, and is effective in replenishing the heat required for dehydration and thermal decomposition of RDF. At this time, in order to suppress the sensible heat loss by reducing the amount of generated gas to prevent scattering of waste and to suppress the calorie reduction of the generated gas, the oxygen concentration in the supporting gas should be 50% or more. It is preferred that

In the third zone, the following equation and the reaction represented by the equation occur. These reactions are thermal decomposition reactions (gas reforming reactions) of hydrocarbon gas supplied from the second zone.
Gas with CO and H ₂ as main components (energy gas)
Is obtained. These reactions proceed by the reaction with the combustible gas 7-3 blown from the tertiary tuyere 5-3. The auxiliary fuel 6-3 is supplied from the tertiary tuyere if necessary.

C _m H _n + m / 2O ₂ = mCO + n / 2H ₂ ··· CH ₄ + 1 / 2O ₂ = CO + 2H ₂ ··· Here, C _m H _n : RDF is generated by thermal decomposition in the second zone. hydrocarbon gas CH _4: methane O ₂ in which the second zone C _m H _n is generated by thermal decomposition: reaction with oxygen the third zone of the combustion assisting gas blown from 3 tuyeres free The reason why the reaction is performed in such a cavity, which is performed in the board section 16, is to smoothly advance a gas reforming reaction, which is a reaction between gases. Controlling the atmosphere temperature in the cavity to 800 to 1000 ° C. is preferable because the reforming reaction sufficiently proceeds.

It is preferable that the oxygen concentration in the supporting gas is 50% or more. This is because the calorie of the recovered gas is increased so that the gas can be easily used in applications such as power generation in the next process. Further, in order to suppress the generation of dioxins and their precursors, the temperature of the gas is preferably 500 ° C. or higher.

As described above, in the method of the present invention, the first
By the reaction in the zone to the third zone, the energy gas containing CO and H ₂ as main components, the molten slag and the molten metal are recovered. Therefore, the R for implementing the method of the present invention is
In the DF gasification and melting furnace, three-stage tuyeres of primary to tertiary are provided.

Further, the tuyere of each stage is configured to be capable of independently injecting the supporting gas and the auxiliary fuel. The reason is as follows.

First, in the case of the primary tuyere, the amount of C (carbide) involved in the reaction of the formula varies depending on the formula and the degree of progress of the reaction represented by the formula. Also, if the composition of the RDF changes, the formula and the amount of the reaction product represented by the formula naturally change. Therefore, the amount of the supporting gas blown from the primary tuyere can be determined independently of other steps. The same applies to auxiliary fuel supplied as needed.

Next, the amount of the supporting gas blown from the secondary tuyere is determined by the reaction formula, and the amount of CO in the formula is determined by the reaction formula. Is considered to be linked to However, in fact, it is not necessary to perform secondary combustion on all of the CO gas generated by the reaction formula. In the second zone, at least heat required for dehydration heating of moisture in the RDF and thermal decomposition of organic substances in the RDF are added.
Further, it is only necessary to apply heat necessary to maintain the atmosphere temperature in the second zone at 800 to 1000 ° C. Therefore,
The amount of combustible gas from the secondary tuyere varies greatly depending on the components contained in the RDF. That is, the amount of the supporting gas blown from the secondary tuyere can also be determined independently. The same applies to auxiliary fuel.

The amount of the supporting gas blown from the tertiary tuyere is determined by the reaction formula. Since the amount of C _m H _n and CH ₄ is changed by containing components even in RDF this case, 3
The amount of combustible gas blown from the next tuyere can also be determined independently. The same applies to the auxiliary fuel.

In the above-mentioned RDF gasification and melting furnace, the tuyeres are provided in three stages, and are configured so that the supporting gas and the auxiliary fuel can be blown independently of each other. It is for a reason.

The blowing amount of the supporting gas and the amount of the auxiliary fuel to be supplied if necessary are determined as follows.

When the target of the treatment is, for example, general waste in which different kinds of wastes are mixed into RDF, the component analysis is not usually performed before charging the waste into the furnace. Is burned or thermally decomposed, and it is practically impossible to predict the amount of produced gas and its contained components.

Under these conditions, the level of the loaded RDF (the top level of the raw material layer) is sequentially measured. This makes it possible to indirectly grasp the change in the thickness of the packed bed (the packed bed of RDF and the packed bed of carbide) in the furnace. That is, as the amount of combustion increases, the loading of the carbide packed layer formed in the first zone decreases, and the top level of the raw material layer decreases. Therefore, a predetermined raw material layer top level is determined empirically in advance, and then the supporting gas from the primary tuyere and the auxiliary fuel supplied as necessary are blown based on the vertical fluctuation of the raw material layer top level. The amount may be determined. In addition, as a raw material layer top level meter to be used, a sounding device known as a raw material layer top level meter inside a blast furnace in the field of steelmaking is suitable.

By the way, since the RDF-filled layer formed in the second zone exists on the carbide-filled layer formed in the first zone, the measured raw material layer top level is different from that of the first zone. It appears as the sum of the respective amounts of change in the second zone. Therefore, it is necessary to distinguish the amount of change between the first zone and the second zone, but the change in the reaction in the second zone can be indirectly grasped by sequentially measuring the temperature change in the second zone. That is, in the second zone, at least dehydration heating of water in RDF and RDF
The heat required to thermally decompose the organic matter in the medium and the heat required to maintain the ambient temperature of the second zone at 800 to 1000 ° C. are sufficient. Therefore, the temperature of the RDF in the region of the second zone is sufficient. The change is measured successively, and if it decreases, it is judged that the heat is insufficient, and the amount of the supporting gas from the secondary tuyere is increased to increase the amount of CO to be subjected to secondary combustion (secondary combustion of CO generated by the reaction formula). The amount to be made). Conversely, if the temperature rises, it can be determined that there is a thermal margin, so the amount of the supporting gas from the secondary tuyere may be reduced to reduce the amount of CO to be subjected to secondary combustion. The temperature change of the RDF is the second
This can be regarded as a change in the temperature of the zone. The change in the temperature of the second zone can be determined, for example, by installing a thermocouple on the surface of the lining brick in the second zone and measuring the surface temperature.

As described above, by successively measuring the level value by the raw material layer top level meter and the surface temperature of the lining brick in the second zone, the auxiliary gas to be supplied as necessary and the supporting gas in the first and second zones are measured. Each fuel injection amount can be independently determined.

In the third zone, if the ambient temperature at the outlet of the second zone (on the free board side) is maintained at 800 to 1000 ° C., hydrocarbons in the exhaust gas, especially tar and the like, which cause troubles such as pipe clogging. All hydrocarbons having 5 or more carbon atoms (C _m H _n : m ≧ 5) can be decomposed. Therefore, a thermometer is installed in the freeboard space of the third zone, and the temperature is sequentially measured. When the temperature drops below 800 ° C., the tertiary tuyere provides the supporting gas and, if necessary, the auxiliary fuel. Just blow it. In particular, immediately after charging the RDF into the furnace, the temperatures at the top of the raw material layer in the second zone and the freeboard in the third zone drop sharply. In order to decompose hydrocarbons (C _m H _n : m ≧ 5), it is effective to blow a supporting gas and, if necessary, an auxiliary fuel.

The case where the method of the present invention is carried out using an RDF gasification melting furnace has been described above as an example. According to the method of the present invention, a series of steps of gasification, melting, dehydration / pyrolysis, and gas reforming are performed in one furnace without using expensive coke for the RDF waste, Etc. can be obtained as clean exhaust gas. that time,
As mentioned above, improvement of gas permeability inside the furnace and stable gasification and melting operation based on it, reduction of energy (auxiliary fuel, etc.) for melting by collecting and removing metals and slags from waste Various effects can be obtained, such as expansion of the range of use of molten slag and reduction of slag-forming agents such as limestone.

[0079]

EXAMPLE An RDF gasification / melting test was conducted using an RDF gasification / melting furnace having the structure shown in FIG. In addition, the dimension of each part of a vertical furnace, the number of tuyere and other attachment parts, and their arrangement are as follows.

Dimensions Furnace diameter: 0.5 m (furnace inner diameter after brick lining) Furnace height: 1.8 m (however, height from furnace bottom to furnace top after brick lining) Furnace from primary tuyere Height from furnace bottom to secondary tuyere: 0.6 m Height from furnace bottom to tertiary tuyere: 1.2 m Position of thermocouple in second zone: 0.8 m (The position of the thermocouple in the second zone refers to the height of the thermocouple attached to the surface of the lining brick in the second zone from the furnace bottom.) The position of the thermocouple in the third zone: 1.0 m (No. The position of the thermocouple in the three zones is the height of the thermocouple installed in the freeboard space from the furnace bottom.) Quantity Primary tuyere: 3 Secondary tuyere: 3 Tertiary tuyere : 3 Molten slag and molten metal outlet: 1 Sounding device (raw material layer top level meter): 1 Sounding weight: 1 2nd zone thermocouple: 3 pieces 3rd zone thermocouple: 3 pieces Arrangement Primary tuyere: Evenly spaced every 120 degrees in the circumferential direction Secondary tuyere: Evenly spaced every 120 degrees in the circumferential direction Tertiary feather Mouth: Equally spaced every 120 degrees in the circumferential direction Molten slag and molten metal outlet: Furnace bottom end Sounding device: Center of the furnace Thermocouple in the second zone: Equally spaced in the circumferential direction every 120 degrees Thermoelectric in the third zone Pair: Equal intervals every 120 degrees in the circumferential direction The waste used in the above test was waste mixed with general municipal solid waste and some waste plastic (referred to as sample 1), and this waste was converted to RDF. When the waste (hereinafter referred to as sample 2) and this waste are converted to RDF, 2% by weight of the dust discharged from the gasification and melting furnace is added to RDF, mixed, and then subjected to volume reduction molding to form RDF. (Sample 3).

Table 1 shows these wastes and two types of RDF.
Is shown. At the time of RDF production, 2% by weight of slaked lime shown in Table 2 was added to the waste. Table 3 shows the composition of the limestone used as the auxiliary raw material, and Table 4 shows the composition of the pulverized coal used as the auxiliary fuel. The size of waste is 5-2
00 mm. The size of the two RDFs is 20 to
It was 50 mm.

[0082]

[Table 1]

[0083]

[Table 2]

[0084]

[Table 3]

[0085]

[Table 4]

Limestone used as an auxiliary material is 10 to 5
It was a lump of 0 mm. The pulverized coal used as the auxiliary fuel was a powdery material of 3 mm or less that had been dried in advance.

The combustible gas blown from the primary tuyere, the secondary tuyere and the tertiary tuyere is a gas based on oxygen and slightly mixed with nitrogen. Table 5 shows the flow rates (the flow rates of oxygen and nitrogen, respectively). In the table,
Primary means primary tuyere. The same applies to the second and third orders.

Table 5 also shows the test conditions and results. In the table, the conditions are the conditions under which this test was performed (steady state), and were determined for each of Samples 1, 2 and 3 according to the following procedures 1 to 8. In the test, first, the sample 1 was charged into the furnace, and the sample 1 in Table 4 was obtained.
, And then changed to Sample 2 and processed under the same conditions as shown in the column of Sample 2, and then changed to Sample 3 and processed under the conditions shown in the column of Sample 3. Was done. The processing time of each sample is 24 hours, and the amount of waste during that time is 1 ton (3 tons in total) for each sample.
And

(Procedure for Setting Processing Conditions) Waste to be charged first (here, refers to sample 1)
Was determined in advance by analyzing the composition. This is necessary to determine the approximate value of the amount of oxygen to be blown, and also to determine the amount of limestone to be charged as a slag-making material. In this test, the amount of limestone was adjusted so that the molten slag had the best slag basicity (ie, slag basicity = 0.9).

2. The gasification and melting furnace was heated in advance by a burner or the like, and the waste was ignited even at room temperature without heating the supporting gas blown from the tuyere.

3. The waste was charged into the furnace and piled up to a sounding height of 0.8-1.0 m. The sounding height means the height from the furnace bottom to the top of the raw material layer.

4. After oxygen gas was gradually flowed from the primary tuyere, the outlets for the molten slag and the molten metal were opened.

[0093] 5. During the test, the top level of the raw material layer decreased due to the burning of the waste, and the level was reduced to 0.8 to 1.0 m.
The raw materials (waste and limestone) were sequentially charged so as to maintain the range. In the steady state, the input speed of waste was always set at 40 kg / h.

6. The primary tuyere so that the temperature measured by the thermocouple attached to the surface of the lining brick of the second zone and the thermocouple attached to the freeboard space of the third zone always maintains 800 to 1000 ° C. The amount of oxygen gas blown from the secondary tuyere and the tertiary tuyere was adjusted. That is, when the unloading speed was high and the temperatures in the regions of the second zone and the third zone exceeded 1000 ° C., the oxygen gas from the primary tuyere was reduced. Conversely, the second
When the temperature of the zone was lower than 800 ° C., oxygen gas was blown from the secondary tuyere. When the temperature of the third zone was lower than 800 ° C., oxygen gas was blown from the third tuyere.

7. The temperatures of the molten slag and the molten metal are measured (this measurement is conventionally performed), and a predetermined temperature (at least a temperature at which the molten slag and the molten metal do not solidify, but a preferable temperature range (14)
50 to 1550 ° C.)
Pulverized coal was blown from the next tuyere. In the case where the sample 1 is the case, when the water content in the waste is large and the calorific value is small, it is necessary to supply the auxiliary fuel from the primary tuyere.

8. By repeating the above steps 5 to 7, the optimum amount of the supporting gas and auxiliary fuel to be blown (that is, the amount shown in the condition column of Table 5) could be derived. Also, change the sample (from sample 1 to sample 2,
And from sample 2 to sample 3),
I was able to respond appropriately.

The results obtained in the above tests are shown in the column of results in Table 5. The unit is indicated by the amount per waste ton or RDF ton. In Samples 1 to 3 in Table 5, only oxygen gas was blown in the second zone, and the temperature of the second zone was set to 800 to 1 using the reaction heat generated by the secondary combustion of the reducing gas.
The temperature was controlled at 000 ° C.

Although not described in Table 5, pulverized coal is blown together with oxygen gas from the secondary tuyere and the combustion heat is used to raise the temperature of the second zone to 800.
It was possible to control to ~ 1000 ° C.

Hereinafter, a comparative example using sample 1 and sample 2
A description will be made in comparison with an example in which gasification and melting were performed by the method of the present invention using the method of the present invention.

1) Although the waste of sample 1 contains small-sized waste, the RDF of sample 2 is formed to a substantially uniform size, so that the dust content in the exhaust gas is very small. Was. This is because the scattering loss was significantly reduced.

2) When the RDF of sample 2 was used, the permeability in the gasification melting furnace was improved, so that the dispersion of the hydrocarbon-based gas in the exhaust gas was eliminated and the absolute amount was reduced. Further, at a concentration hydrocarbon entirely negligible, such as hydrocarbons in the exhaust gas, C _m H _n is a cause of particular cause pipe blockages (m ≧ 5).

3) While the waste of Sample 1 contains about 50% moisture, the RDF of Sample 2 has undergone a drying step, so the moisture content is only 7% or less. Therefore, the energy input into the gasification melting furnace, that is, the total oxygen consumption was reduced to about 3/4. In addition, sample 1 required pulverized coal injection of auxiliary fuel (or charging of coke) into zone 1 whereas sample 2 required
Then there was no need. This is the second for sample 2
This is because the residue (carbide) after the organic matter was thermally decomposed in the zone and sufficiently carbonized was supplied to the lower first zone.

4) Since the carbide sufficiently carbonized as described above exists at the lower portion (that is, because of a reducing atmosphere), FeO and Pb in the molten slag of Sample 2 were
The O content was also halved. This is also because some metals have been recovered and removed during RDF production. As a result, the molten slag recovered by the method of the present invention could be effectively used as a raw material such as cement after cooling.

5) In sample 2, since a part of slag such as debris and earth and sand was removed at the time of RDF conversion, the amount of limestone charged into the gasification and melting furnace could be reduced. The reason why the amount of generated molten slag was increased in Sample 2 is that the amount of slag contained in the sample was larger than that in Sample 1 (see Table 1).

6) In sample 2, since slaked lime was contained during RDF conversion, removal of S and Cl in the gasification and melting furnace were promoted. Therefore, S-containing gas (SO ₂ , COS, H ₂ S, etc.) and Cl-based gas (H
(Represented by Cl) significantly decreased.

7) In Sample 2 in which slaked lime was installed during the production of RDF, the melting of the slag was promoted, so that the variation in the temperature of the molten slag and the molten metal discharged from the gasification melting furnace was reduced. That is, stable discharge of molten slag and metal was possible.

Next, an example using sample 2 and sample 3
This will be described in comparison with an example using (RDF to which dust is added).

1) CaO, SiO ₂
When sample 3 is used, the amount of molten slag slightly increases, and the consumption of oxygen for CO combustion required for supplying energy for melting the sample slightly increases. Increased. However, there was no great difference as compared with Sample 2.

2) Since the added dust contains about 10% of chlorine as CaCl ₂ , HC in the exhaust gas
1 concentration increased significantly. However, since this chlorine can be sufficiently removed by treating the exhaust gas with water, there is no problem in the process.

[0110]

[Table 5]

[0111]

According to the method of the present invention for converting waste into RDF and gasifying and melting, the organic matter contained in the waste is gasified and recovered as energy gas, and the ash and metals contained in the waste are recovered. Can be recovered as a molten slag and a molten metal, respectively. As a result, it is possible to reduce the cost of landfilling general wastes and industrial wastes, which are currently a problem, and to use the generated by-product gas as fuel for power generation.

Since the RDF is used, it is possible to improve gas permeability in the furnace and perform a stable gasification and melting operation based on the permeability, reduce the amount of energy (auxiliary fuel, etc.) used for melting, and use the range of molten slag. Various effects can be obtained, such as expansion of limestone and reduction of slag-forming agents such as limestone.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic manufacturing process of an RDF used in the method of the present invention.

FIG. 2 is a schematic vertical sectional view showing a configuration of an example of a waste gasification and melting furnace used for carrying out the method of the present invention.

[Explanation of symbols]

1: Gasification and melting furnace main body 2: Refractory brick 3-1: Gas discharge port 3-2: Gas discharge duct 4: Exhaust gas flow 5-1: Primary tuyere 5-2: Secondary tuyere 5-3: Tertiary tuyere 6-1: Auxiliary fuel to be blown into primary tuyere 6-2: Auxiliary fuel to be blown into secondary tuyere 6-3: Auxiliary fuel to be blown into tertiary tuyere 7-1: To blow into primary tuyere Supporting gas 7-2: Supporting gas blown into secondary tuyere 7-3: Supporting gas blowing into tertiary tuyere 8: Flow of molten slag and molten metal 9: Discharge of molten slag and molten metal Outlet 10: Pusher 11-1: RDF loading inlet 11-2: Hopper 12: RDF 13: Molten slag and molten metal 14: Packing layer mainly composed of carbide 15: Packing layer mainly composed of RDF 16: Free board 17: Sounding device (raw material layer top level meter) 18: Sau Switching weight 19: Temperature converter (device for converting the signal of the thermocouple into temperature) 20: Thermocouple provided on the surface of the lining brick in the second zone 21: Thermocouple provided in the free board space of the third zone

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuya Isaka 4-33, Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd. (72) Hideaki Anfuku 4-chome, Kitahama, Chuo-ku, Osaka, Osaka 5-33 No. Sumitomo Metal Industries, Ltd.

Claims (2)

[Claims] An organic waste gas is gasified and recovered as an energy gas, and the ash and metals in the waste are recovered as a molten material. In the method for melting, the waste is
A method for gasification and melting of waste, wherein the method is subjected to the following processes (1) to (4) in advance and then charged into the gasification and melting furnace and gasified and melted. (1) Step of crushing waste (2) Step of drying crushed waste (3) Separation and collection of valuable metals such as copper and aluminum from the dried waste, and separation of incombustibles such as rubble, earth and sand Step of removing (4) Step of adding and mixing lime to the waste after the separation and collection and the separation and removal of the above (3) to reduce the volume 2. The method for gasifying and melting waste according to claim 1, wherein the dust discharged from the gasification and melting furnace is added to and mixed with the waste to be treated in the step (4) according to claim 1. A method for gasifying and melting waste.