JP2002028670A - Method for treating hardly decomposable waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating hardly decomposable waste, by which the hardly decomposable waste is completely decomposed in a comparatively shorter time to recover a flammable useful component or to prevent a device for treating the hardly decomposable waste from being corroded by reducing the ratio of oxygen to be supplied when the waste is completely combusted. SOLUTION: An active substance is produced by supplying an oxidizing agent such as hydrogen peroxide together with fuel such as methanol to a first reactor where water is in a subcritical or supercritical state so that the amount of the oxidizing agent to be supplied is 25-100% of the theoretically necessary amount of the oxidizing agent to the combustion of the fuel and partially burning the fuel. The hardly decomposable waste such as noncombustible organic waste is then supplied to the first reactor and thermally decomposed by reacting the waste with the produced active substance to produce a decomposition product. The decomposition product may be recovered or completely decomposed by supplying it together with the oxidizing agent to a second reactor and burning it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a flame-retardant organic waste, a nitrogen-containing oxide waste in subcritical water or supercritical water,
The present invention relates to a method for treating hard-to-decompose waste such as sulfur-containing waste or chlorine-containing waste.

[0002]

2. Description of the Related Art In recent years, techniques for treating waste in subcritical water or supercritical water have been actively developed, but the processing technique in subcritical or supercritical water uses the atmosphere as a medium. Similar to oxidative combustion, it basically burns waste and oxidant in a medium called subcritical water or supercritical water. As a feature, when the medium is supercritical water,
When the waste and the oxidizing agent are supplied into the supercritical water, the waste is uniformly dispersed in the supercritical water. At the same time, the oxidizing agent is also uniformly dispersed in the supercritical water, so that it can be efficiently burned at a relatively low temperature. Further, mild combustion in which harmful oxides such as nitrogen oxide (NOx) and dioxin are hardly generated can be performed.

[0003]

However, most of the organic matter contained in the waste has a flame-retardant aromatic ring unlike a straight-chain organic matter which is easily oxidized and burned. Simply supplying the waste together with the oxidizing agent in supercritical water and burning it does not result in decomposition or takes a long time for the decomposition treatment. For example, in the conventional treatment of waste containing polychlorinated biphenyl (PCB), P
Although chlorine contained in CB is treated in a relatively short time, the remaining aromatic ring portion is sufficiently combusted for a long time by a long tubular secondary reaction tube. In order to burn such a flame-retardant substance,
Since it is necessary to supply a large amount of the oxidizing agent, there is a problem that corrosion in the apparatus due to oxidation is increased. In addition, it is difficult to change the form of waste containing oxide forms such as nitrate ions into more stable chemical substances by simply oxidizing and burning, and further processing is difficult. There was also.

An object of the present invention is to provide a method for treating hard-to-decompose waste, which completely decomposes hard-to-decompose waste in a relatively short time. Another object of the present invention is to provide a method for treating hard-to-decompose waste that recovers combustible useful components. Still another object of the present invention is to provide a method for treating hard-to-decompose waste, which reduces the supply rate of oxygen and reduces the corrosion of the apparatus when completely combusted.

[0005]

The invention according to claim 1 is
The first reactor in the subcritical or supercritical state of water is supplied with the fuel and an oxidant sufficient to partially burn the fuel and the first reactor is supplied with the fuel.
A step of generating an active species from a fuel by setting the inside of the reactor to a high-temperature atmosphere of 700 to 1200 ° C., and a group consisting of flame-retardant organic waste, nitrogen-containing oxide waste, sulfur-containing waste, and chlorine-containing waste Supplying one or more selected hardly decomposable wastes to a reactor and reacting them with active species in a high-temperature atmosphere to thermally decompose the hardly decomposable wastes. This is a method for treating hard-to-decompose waste. In the invention according to claim 1, active species are generated by partially burning the fuel, and the generated active species are reacted with the hard-to-decompose waste in a high-temperature atmosphere created by the partial combustion, whereby the hard-to-decompose waste is generated. Pyrolytic waste can be quickly pyrolyzed.

According to a second aspect of the present invention, there is provided the first aspect of the present invention, wherein the oxidizing agent is supplied so that the theoretical amount of the oxidizing agent for the combustion of the fuel is 25 to 100%. This is a processing method for generating. In the invention according to claim 2, the oxidizing agent is supplied such that the temperature of the reactor becomes 700 to 1200 ° C. If the supply amount of the oxidizing agent is less than 25% and the temperature is less than 700 ° C., the unburned portion of the fuel increases, and active species cannot be sufficiently generated. On the other hand, if it exceeds 100%, the fuel is almost burned and active species cannot be sufficiently generated. In addition, the first reactor becomes an oxidizing atmosphere, and the heat of the hardly decomposable waste is very low even in a high temperature atmosphere. Decomposition does not proceed. The temperature in the first reactor is 80
0-1000 ° C is preferred.

[0007] The invention according to claim 3 is the invention according to claim 1 or 2, wherein when the hardly decomposable waste partially contains an easily decomposable substance, the hardly decomposable waste together with the fuel and the oxidizing agent is used. This is a treatment method in which a part of water is supplied to a first reactor in a subcritical or supercritical state of water to generate active species by burning a part of the hardly decomposable waste. In the invention according to claim 3, the fuel supply amount is reduced by burning a part of the hardly decomposable waste,
The inside of the first reactor can be easily made to have a high temperature atmosphere.
Examples of easily decomposable substances include linear hydrocarbons.

The invention according to claim 4 is the invention according to claims 1 to 3
In the invention according to any of the above, when the hard-to-decompose waste contains a halogen compound or a sulfur compound, sodium, potassium, calcium hydroxide or carbonate together with the hard-to-decompose waste is subcritical or supercritical water. This is a treatment method in which the decomposition product is supplied to the first reactor in a neutral state to neutralize decomposition products. Claim 4
In the invention according to the above, ions of sodium, potassium and calcium neutralize halogens or sulfur contained in the decomposition product of the hardly decomposable waste to make them harmless.

The invention according to claim 5 is the invention according to claims 1 to 4.
The invention according to any one of the above, wherein a decomposition product of the hardly decomposable waste discharged from the first reactor is converted into a second supercritical water.
This is a treatment method in which the decomposition product is completely burned by supplying it to the reactor together with the oxidizing agent. In the invention according to claim 5, the decomposition product is supplied to the second reactor in a supercritical state of water together with the oxidizing agent, and is completely burned. When the hardly decomposable waste is a sulfur-containing waste, hydrogen sulfide contained in the decomposition product is oxidized to a sulfur oxide. When the hard-to-decompose waste is nitrogen-containing oxide waste, it becomes ammonium by the action of the active species, which is oxidized and converted to harmless nitrogen gas.

The invention according to claim 6 is the invention according to claims 1 to 5
The invention according to any one of the above, wherein the fuel is one or more hydrocarbon compounds selected from the group consisting of ethanol, methanol, propanol, butanol, pentanol, and a hydrocarbon having 1 to 5 carbon atoms. Processing method.
In the invention according to claim 6, the fuel is one or a mixture of two or more selected from the group consisting of ethanol, methanol, propanol, butanol, pentanol, and a hydrocarbon having 1 to 5 carbon atoms. Particularly, methanol and ethanol are preferable because they easily burn. The invention according to claim 7 is the processing method according to any one of claims 1 to 6, wherein the oxidizing agent is hydrogen peroxide, oxygen, or air.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The hard-to-decompose waste to be treated according to the present invention contains at least one kind of flame-retardant organic waste, nitrogen-containing oxide waste, sulfur-containing waste or chlorine-containing waste. Flame-retardant organic waste, which is abundant in substances containing an aromatic ring, includes phthalic acids, styrenes, and other phenyl compounds contained in PVC. Examples of the nitrogen-containing oxide waste include ammonium nitrate, nitrates and nitrates. In addition, sulfur-containing waste includes
Thiophene-based compounds such as DBT are exemplified. Furthermore,
Examples of the chlorine-containing waste include PCB and dioxins. Examples of the active species that act on the decomposition of the hardly decomposable substance at a high temperature include H ₂ , CH, CH ₂ , CH ₃ , and OH. The subcritical state of water of the present invention is 700 to 1200 ° C,
The state of 10-22MPa, the supercritical state of water is 4
It refers to a state of 50 to 1200 ° C. and 22 to 35 MPa.

The first embodiment will be described with reference to FIG. 1 in which dibenzothiophene ((C ₆ H ₄ ) ₂ S: hereinafter, referred to as DBT) is used as the sulfur-containing waste. (a) Heat generation and generation of active species by partial combustion and water gasification reaction of fuel First, an oxidant sufficient to partially burn this fuel is supplied together with fuel to a first reactor in a subcritical or supercritical state of water. In this embodiment, ethanol is used as fuel and oxygen is used as oxidant. The supply amount of the oxidant is supplied so as to be 25 to 100% of the theoretical required amount of the oxidant for fuel combustion.
The ratio of the oxygen in the oxidant to the carbon in the fuel (O / C) is 1-3. The temperature in the first reactor before partial combustion is 7
If the temperature is lower than 00 ° C. and the pressure is lower than 10 MPa, it is difficult to decompose. In the case of further processing by combustion in the second reactor described below, the pressure condition of the first reactor is set to 22 to
Preferably, the pressure is 35 MPa.

C ₂ H ₅ OH + aO ₂ → bCO ₂ + cH ₂ O + dH ₂ +... + Q (1) C ₂ H ₅ OH + eH ₂ O + Q ′ → fCO ₂ + gH ₂ + _{hCH + iCH 2 + jCH 3 +} kOH ... (2) It should be noted, shows the Q and Q 'heat in the chemical formula.

As shown in the above equations (1) and (2),
The fuel, which is a fuel supplied during the subcritical or supercritical state of water, is partially burned to generate a gas containing active hydrogen and heat. Hydrogen, which is an active species generated by this reaction, is extremely reactive in a temperature range of 700 to 1200 ° C., and even if it is a hardly decomposable organic substance, it is accompanied by generation of a residue due to a hydrogenolysis reaction or the like. It can be quickly decomposed without any need. Further, the reactor is heated by the heat generated by the reaction represented by the above formula (1), and becomes a high temperature of 700 to 1200 ° C. The temperature in the first reactor does not rise,
At a relatively low temperature of about 00 ° C., since the reaction of the formula (2) is an endothermic reaction, the generation rate of active hydrogen according to the formula (2) decreases. In this case, by adding formic acid additionally, as shown in equation (3), the temperature rise due to the combustion of the fuel shown in equation (1) and the generation of active hydrogen by the decomposition of formic acid in the atmosphere are performed. , Can also promote decomposition.

HCOOH + Q → CO ₂ + H ₂ (3) (b) Decomposition reaction of sulfur-containing waste by reaction with active species Next, DBT, which is sulfur-containing waste, is supplied into the first reactor. Then, DBT is brought into contact with active hydrogen, which is an active species generated by the reaction of the formulas (1) and (2), to decompose the DBT by a hydrogenation reaction or the like as shown in the above formula (4). Further, a neutralizing agent such as NaOH is added together with the waste and supplied to the first reactor for complete combustion of the decomposition product described below.

(C ₆ H ₄ ) ₂ S + hH ₂ → iCH ₄ + jC ₂ H ₂ + kC ₂ H ₄ +... + H ₂ S (4) The substance produced by this decomposition is useful. Since it is a highly fuel substance, it can be recovered and used effectively as a chemical raw material. It can also be used as a fuel substitute.

(C) Complete Combustion of Decomposition Products The substances decomposed and generated by the hydrogenation reaction and the like can be further processed by combustion in the second reactor. That is, the decomposition product decomposed by the reaction of the formula (4) in the first reactor is supplied to the second reactor together with the oxidizing agent to be decomposed by combustion as shown in the formula (5). The combustion decomposition reaction in the second reactor is performed at a temperature of 450 to 650 ° C and a pressure of 22 to
This is performed in a supercritical state of 25 MPa water. The alkali metal or alkaline earth metal of the neutralizing agent added in the first reactor is supplied to the second reactor together with the decomposition products.

CH ₄ + C ₂ H ₂ + C ₂ H ₄ +... + H ₂ S + O ₂ → mCO ₂ + nH ₂ O + SOx (5) This decomposition product is lightened. Therefore, oxidative combustion at low temperature is also possible, and combustion decomposition occurs quickly,
Since the supply ratio of the oxidizing agent is small, oxidative corrosion in the reactor is reduced. In the formula (5), H ₂ S generated by the reaction of the formula (4) is oxidized to an oxide SOx. This SO
x reacts with the alkali metal or alkaline earth metal supplied from the first reactor to the second reactor, and is easily neutralized, rendered harmless and removed out of the system, for example, as shown in Formula (6). Is done.

2Na ⁺ + SO ₄ ^2- → Na ₂ SO ₄ (6) Next, a case where ammonium nitrate is used as nitrogen-containing oxide waste in the second embodiment will be described. (a) Heat generation and generation of active species by partial combustion and water gasification reaction of fuel First, an oxidant sufficient to partially burn this fuel is supplied together with fuel to a first reactor in a subcritical or supercritical state of water. Here, similarly to the reaction in the first embodiment, the oxidizing agent is supplied so that the oxidizing agent ratio (O / C) becomes 1 to 3, and as shown in the equations (1) and (2), the subcriticality of water is obtained. Alternatively, ethanol supplied in the supercritical state is partially burned to generate a gas containing active hydrogen and heat.

(B) Decomposition reaction of nitrogen-containing oxide waste by reaction with active species
Active hydrogen, which is an active species generated by the reaction of Formulas (1) and (2) supplied into the reactor, is brought into contact with ammonium nitrate, and as shown in Formula (7), ammonium nitrate is hydrogenated. To convert nitrogen oxides contained in ammonium nitrate into ammonia.

NH ₄ NO ₃ + 4H ₂ → 2NH ₃ + 3H ₂ O (7) (c) Complete Combustion of Decomposition Products Ammonia, which is a decomposition product generated by the reaction of the formula (7), is subjected to the second reaction. An oxidizer may be blown into the vessel to further oxidize and burn as shown in equation (8). In the oxidation in air, ammonia becomes NOx which is an oxide, but in combustion in supercritical water, ammonia does not become NOx,
It becomes harmless because it becomes water and nitrogen gas. 4NH ₃ + 3O ₂ → 6H ₂ O + 2N ₂ …… (8)

[0022]

Next, embodiments of the present invention will be described. <Example 1> 1% by weight of D as a simulated sulfur-containing waste
BT was prepared. Further, ethanol was prepared as a fuel, and hydrogen peroxide was prepared as an oxidizing agent. First, this ethanol was added together with hydrogen peroxide to an oxidizer ratio (O / C) of 1.0, which is a ratio of oxygen in the oxidizer to carbon in the fuel, at a combustion section temperature of 1000 ° C. and 700 near the reaction section outlet.
C. and supplied to a first reactor maintained at a pressure of 25 MPa. The concentration of the active hydrogen species generated in the first reactor was measured from the gas generation amount, and was found to be 25% by volume. Next, the simulated material was supplied to the first reactor. The simulated material was retained in the first reactor for about 5 seconds and thermally decomposed to generate a decomposition product.

Example 2 The same simulated material as in Example 1 was prepared except that the ratio of the oxidizing agent was 1.5, and the simulated material was reacted under the same conditions as in Example 1. Excess water was added to make the combustion temperature the same. The concentration of the active hydrogen species generated in the first reactor was measured by the gas generation amount, and was found to be 20% by volume. <Comparative Example 1> The same simulated material as in Example 1 was prepared except that the oxidizing agent ratio was changed to 3.0, and the simulated material was reacted under the same conditions as in Example 1. Excess water was added to make the combustion temperature the same. The concentration of the active hydrogen species generated in the first reactor was 3% by volume when measured from the gas generation amount. <Comparative Evaluation 1> Table 1 shows the decomposition rate of DBT, which is a simulated product of Examples 1 and 2 and Comparative Example 1, in the first reactor.

[0024]

[Table 1] As is clear from Table 1, the decomposition rates are higher in Examples 1 and 2 than in Comparative Example 1 where the oxidizing agent ratio is large. Example 2
It was confirmed that the concentration of the active species and the decomposition rate were higher in Example 1 where the oxidizing agent ratio was smaller than that of Example 1, and that the active species was generated at a higher ratio when the oxidizing agent ratio was lower. That is, it was found that decomposition by active species is more effective for hardly decomposable substances than oxidative decomposition by oxidizing agents.

Example 3 As a simulated nitrogen-containing oxide waste, 1000 ppm of ammonium nitrate was prepared.
Further, ethanol was prepared as a fuel, and hydrogen peroxide was prepared as an oxidizing agent. First, this ethanol was supplied together with hydrogen peroxide at a ratio of an oxidant of 1.0 to a first reactor maintained at a temperature of 1000 ° C. and a pressure of 25 MPa. First
The concentration of the active hydrogen species generated in the reactor was measured from the gas generation amount, and was found to be 25% by volume. Next, the simulated material was supplied to the first reactor. The simulated material was allowed to stay in the first reactor for about 5 seconds to react.

Example 4 The same simulated material as in Example 3 was prepared except that the oxidizing agent ratio was changed to 1.5, and the simulated material was reacted under the same conditions as in Example 3. The concentration of the active hydrogen species generated in the first reactor was measured by the gas generation amount, and was found to be 20% by volume. <Comparative Example 1> The same simulated material as in Example 3 was prepared except that the oxidizing agent ratio was changed to 3.0, and the simulated material was reacted under the same conditions as in Example 3. The concentration of the active hydrogen species generated in the first reactor was measured based on the amount of gas generated.
% By volume. <Comparative Evaluation 2> Table 2 shows the conversion ratio of ammonium nitrate in the first reactor in Examples 3, 4 and Comparative Example 2.

[0027]

[Table 2] As is clear from Table 2, Comparative Example 2 in which the concentration of the active species was low
In comparison, in Examples 3 and 4, it was confirmed that the conversion ratio increased as the concentration of the active species increased.

Example 5 The decomposition product obtained in Example 3 was prepared as a measurement sample. In addition, hydrogen peroxide was prepared as an oxidizing agent. The hydrogen peroxide was added together with the measurement sample at an oxidizing agent ratio of 1.1 to the theoretical amount for burning hydrogen in ammonia at a temperature of 500 ° C. and a pressure of 25 MPa.
To the second reactor maintained at The feed was maintained in the second reactor for about 1 minute to complete combustion. Combustion material is collected and measured with an ion electrode type ammonia meter,
The amount of remaining ammonia was measured.

Example 6 The same measurement sample as in Example 5 was prepared except that the oxidizing agent ratio was changed to 1.2.
The reaction was carried out in the second reactor under the same conditions as described above. <Comparative Example 1> The same measurement sample as in Example 5 was prepared except that the ratio of the oxidizing agent was set to 1.0, and reacted in the second reactor under the same conditions as in Example 5. <Comparative Evaluation 3> Table 3 shows the amount of ammonia remaining in the second reactor of the combustion products of Examples 5, 6 and Comparative Example 3. In addition, ND in Table 3 shows below the detection limit.

[0030]

[Table 3] As is clear from Table 3, the residual ammonia in Examples 5 and 6 is lower than the detection limit of the measuring device as compared with Comparative Example 3 in which the ratio of the oxidizing agent is small, indicating that the ammonia is detoxified.

[0031]

As described above, according to the present invention, it has conventionally been a long time to treat hard-to-decompose waste such as waste having a high molecular weight and waste in oxide form. ,
Partial combustion by supplying a fuel such as ethanol to a first reactor in a subcritical or supercritical state of water together with an oxidizing agent such as hydrogen peroxide so that the oxidizing agent ratio becomes 25 to 100% of the theoretically required amount. By reacting the active species generated by the above with the hardly decomposable waste supplied to the first reactor, the hardly decomposable waste can be quickly thermally decomposed and changed into a stable substance. When the decomposition products generated by the decomposition of waste are useful combustible components, they can be recovered and used. An oxidizing agent may be supplied to the decomposition product to perform a complete decomposition treatment by combustion. In this case, since the decomposition products are lightened, the supply ratio of oxygen can be reduced and the corrosion of the device can be reduced as compared with the conventional combustion treatment.

[Brief description of the drawings]

FIG. 1 is a diagram showing a processing method according to a first embodiment of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07C 25/18 C07C 25/18 (72) Inventor Akira Tanaka 1-3-25 Koishikawa, Bunkyo-ku, Tokyo Mitsubishi Material Co., Ltd. System Business Center F term (reference) 4D050 AA13 AB12 AB15 AB17 AB18 AB19 AB37 BB01 BB09 BC01 BC02 BC10 BD06 BD08 CA13 4H006 AA05 AC13 AC26 BA02 BA28 BB31 BC10 BC34 BE30 BE32 EA22

Claims (7)

[Claims] 1. A fuel is supplied to a first reactor in a subcritical or supercritical state of water together with a fuel and an oxidizing agent for partially burning the fuel to make a high temperature atmosphere of 700 to 1200 ° C. in the first reactor. Producing an active species from the fuel by the method described above; and one or more types of difficulties selected from the group consisting of flame-retardant organic waste, nitrogen-containing oxide waste, sulfur-containing waste, and chlorine-containing waste. Thermally decomposing the hard-to-decompose waste by supplying the decomposable waste to the reactor and reacting with the active species under the high-temperature atmosphere. Processing method. 2. The processing method according to claim 1, wherein the oxidizing agent is supplied so that the oxidizing agent is supplied in an amount of 25 to 100% of the theoretical required amount of the oxidizing agent for fuel combustion. 3. The first reactor in a subcritical or supercritical state in which a part of the hard-to-decompose waste together with a fuel and an oxidizing agent is water when the hard-to-decompose waste partially contains an easily decomposable substance. The method according to claim 1, wherein the activated species is generated by burning a part of the hardly decomposable waste by supplying the waste to the wastewater. 4. When the hard-to-decompose waste contains a halogen compound or a sulfur compound, a hydroxide or carbonate of sodium, potassium or calcium is added together with the hard-to-decompose waste in the subcritical or supercritical state of water. The treatment method according to any one of claims 1 to 3, wherein the decomposition product is neutralized by supplying the decomposition product to one reactor. 5. The decomposition product of the hardly decomposable waste discharged from the first reactor is supplied together with an oxidizing agent to a second reactor in a supercritical state of water to completely burn the decomposition product. 5. The processing method according to any one of 1 to 4. 6. A fuel comprising ethanol, methanol, propanol, butanol, pentanol and a hydrocarbon having 1 to 5 carbon atoms.
The treatment method according to any one of claims 1 to 5, which is one or more hydrocarbon compounds selected from the group consisting of hydrocarbons. 7. The processing method according to claim 1, wherein the oxidizing agent is hydrogen peroxide, oxygen, or air.