JP2948344B2 - Thermal decomposition method of organic matter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for thermally decomposing organic substances, and more particularly to an organic substance containing chlorine (for example, a trans-oil containing polychlorinated biphenyl (PCB)).
The present invention relates to a pyrolysis method that is effective for:

[0002]

2. Description of the Related Art Organic chlorides such as PCBs are not only harmful and toxic but also are chemically stable, and the detoxification processing technology has been closed as social news since around 1971 when the pollution problem of PCBs surfaced. Due to the problems of dioxins such as polychlorinated dibenzodioxin (PCDD) and polychlorinated dibenzofuran (PCDF), it has become an urgent issue to establish technology for completely detoxifying organic substances containing chlorine. I have. As a method for detoxifying organic substances containing chlorine, Japanese Patent Application Laid-Open No.
No. 1143, a dechlorination method using a catalyst, a method disclosed in Japanese Patent Publication No. 52-47459, a decomposition method using ionizing radiation, ultraviolet light, and the like.
Various treatment methods have been proposed, such as a chemical reaction treatment method under microwave irradiation and a microbial decomposition method described in 1-51956, but these methods can be applied only to a small amount of treatment. Organic substances containing a small amount of chlorine (for example, trans oil containing a small amount of PCB) often require large-scale treatment, but the above-mentioned method cannot economically treat the organic matter.

[0003] As a method of mass processing, reference 1. Although there is a high-temperature incineration method as introduced in [Pollution and Countermeasures, Vol.22, NO.7, p.33 (1986)], this kind of incineration method has the following disadvantages.

[0004] The first disadvantage is the loss of valuable resources. If the organic chloride alone or its content is high, incineration may be unavoidable from the viewpoint of detoxification of harmful substances, but if the chlorine content is low,
With the incineration process, the organic matter itself must be incinerated,
It will be easy to understand that it will lead to resource loss.

[0005] The second drawback is that it is extremely difficult to completely detoxify substances that are difficult to decompose thermally, such as PCBs, by this method. As introduced in Document 1, when a liquid processing object is sprayed into a pyrolysis furnace with a burner, the particle size of the sprayed droplets is reduced so that the droplets evaporate simultaneously with the spraying into the furnace. It is important that such a burner does not exist, and even if sprayed with fine particles, droplets coalesce after spraying, and large droplets are necessarily generated. Large droplets ride on the air flow in the cracking furnace and the relative speed with the air flow decreases, as a result, the heat transfer speed between the air flow and the droplets decreases, only ensuring the thermal decomposition temperature of the substance in the droplets In addition, it is difficult to secure the residence time required for thermal decomposition. For this reason, in this kind of decomposition furnace, it is necessary to increase the furnace volume more than necessary in order to secure the residence time, and it is also necessary to increase the temperature in the furnace, which causes damage to the furnace and durability. In addition, in the case of air combustion, the generation of nitrogen oxides becomes a problem.

[0006] A third disadvantage is that the generation of secondary pollution sources, which requires the most caution, cannot be suppressed in the thermal decomposition operation of organic substances containing chlorine. Everyone has experienced the generation of black smoke (including soot) when burning organic matter, especially high molecular weight organic matter and aromatic organic matter. It is also well known to those skilled in the art that it is extremely difficult to eliminate this black smoke even with existing excellent combustion equipment, and that once generated black smoke cannot be easily removed even by means such as afterburning. is there.

It is said that black smoke, especially soot, is the primary cause of secondary pollution in combustion facilities for substances containing even trace amounts of chlorine. In fact, not only are dioxins, which are considered to be very poisonous, detected in soot from various types of combustion equipment,
It is well known that when ash containing unburned carbon such as soot collected from dust collection equipment for combustion equipment exhaust gas is heated in air, the amount of dioxins abnormally increases at around 300 ° C. This means that once smoke is generated, even if dioxins are not detected at that time, there is a danger of generating dioxins by heating such as post-incineration, etc. Decomposition should never generate black smoke such as soot.

[0008]

DISCLOSURE OF THE INVENTION In view of the above-mentioned state of the art, the present invention is intended to completely detoxify harmful substances such as PCBs and other organic substances containing chlorine and prevent the generation of secondary pollution sources. It is intended to provide a method of thermally decomposing an organic substance capable of producing a gas containing hydrogen (H ₂ ) and carbon monoxide (CO) as main components, a so-called reducing gas, from the organic substance.

[0009]

According to the method of the present invention, a gaseous substance of an organic substance is premixed with water vapor and / or carbon dioxide (CO ₂ ), and the mixture is placed in a pyrolysis furnace in an atmosphere at a temperature for thermal decomposition of the organic substance. This is a method of supplying and a method of premixing an oxygen-containing gas such as oxygen or air into the premixed gas body below an explosion limit (combustion range) lower limit.

[0010]

That is, since the method of the present invention supplies the organic matter to the pyrolysis furnace in gaseous form, the problem caused by the size of the spray droplets, which has been a problem in the conventional liquid spray supply method, is solved. You. In addition, when reducing gas is produced by premixing with steam and / or carbon dioxide gas or by further mixing oxygen with the premixed gas below the explosion limit value, not only during incineration but also by partial oxidation of organic matter. The generation of unburned carbon such as soot can be completely prevented.

In the process of conducting experimental research on the combustion and thermal decomposition methods of organic matter, the present inventors completely changed the supply of liquid spray to the decomposition furnace to the gas supply method, and thus completely generated unburned carbon such as soot. The present invention has been accomplished by conducting research from the viewpoint that it cannot be suppressed to a low level and there is a problem other than liquid spraying.

Reference 1. However, as introduced, even in the case of incineration, conventional methods focus only on the combustion reaction. It is considered that it is necessary to considerably increase the oxygen concentration in order to suppress the generation of unburned carbon in the combustion reaction, and it is expected that even if the oxygen concentration is excessive, it is impossible to completely prevent the generation of unburned carbon. Furthermore, it is impossible with conventional methods to produce a reducing gas without generating soot by a method of partial oxidation of organic matter, which is a kind of incomplete combustion.

The reason for this is inferred from the research results of the present inventors. In the high temperature combustion zone, the thermal decomposition of organic matter proceeds rapidly, and the combustion of hydrogen and carbon monoxide, which are the thermal decomposition products, is easy. As a result of the components consuming oxygen first, there is also a microscopically low oxygen concentration portion, which results in the generation of active free radicals (free radicals) of carbon, which are bound together to form soot. Etc. are expected to be generated.
Further, when chlorine is present, it is considered that chlorine is taken into soot to generate a precursor substance of dioxins.

In the conventional method, since the organic matter to be thermally decomposed and the oxygen-containing gas are separately introduced into the high-temperature decomposition furnace, before the two are uniformly mixed, a combustion reaction takes place before the mixture is mixed. Is thought to occur.

From the results of this inference, the present inventors have thought that it is important to suppress the rapid combustion reaction of organic substances and to uniformly mix the reaction-participants before the start of thermal decomposition, which has not been taken into account so far. It is.

That is, according to the method of the present invention, steam or carbon dioxide having the effect of suppressing a rapid combustion reaction and suppressing the generation of free carbon in the pyrolysis process is mixed in advance with the vapor of an organic substance to produce heat. It is supplied to the cracking furnace, and it is clear that the conventional disadvantages are eliminated. Further, premixing the mixed gas with oxygen is an improvement measure for making the oxygen concentration uniform in the thermal decomposition stagnation region, and the effect can be easily understood.

[0017]

Next, one embodiment of the present invention will be described with reference to FIG. 1, and the effects of the present invention will be described. FIG. 1 shows a system diagram of the equipment used in the experiment. In FIG. 1, 1 is a pyrolysis furnace, 2 is a gas burner for the pyrolysis furnace, 3 is a soot inhibitor (steam and / or carbon dioxide) and an oxidizer. (Oxygen or oxygen-containing gas) gasifier regulator, 4 is a premixer of the vapor of the organic substance to be thermally decomposed and the gasifier adjusted by gasifier regulator 3, 5 is a pyrolysis furnace 1 outlet gas cooler, 6 is pyrolysis furnace 1
3 shows an outlet gas sampling port. 7 is a conduit for supplying a soot suppressant to the gasifying agent regulator 7, 8 is a conduit for supplying an oxidizing agent, 8 'is a conduit for directly supplying an oxidizing agent to the gas burner 2, and 9 is a premix. A conduit for supplying a gasifying agent to the vessel 4, a conduit 10 for supplying organic vapor to the premixer 4,
Reference numeral 11 denotes a conduit for supplying a gas mixture of a premixed gasifying agent and organic vapor to the gas burner 2, and reference numeral 12 denotes a conduit for discharging a pyrolysis gas.

The gasifying agent regulator 3 is provided as a means for uniformly mixing the soot suppressant and the oxidizing agent, and is unnecessary when the purpose is achieved by in-line mixing or the like.
Similarly, the premixer 4 is also provided for the purpose of uniformly mixing the gasifying agent and the vapor of the organic matter before being put into the pyrolysis furnace 1, and the purpose is achieved by another means. It is unnecessary in the case. When an indirect heater is used as a means for generating vapor of a liquid organic substance or the like, the gasifying agent can be supplied by a heater in order to prevent coking in the heater.

The upper limit of the oxygen supply amount in the oxidant supplied from the conduit 9 is the lower limit of the oxygen concentration at the explosion limit (combustion range) of the organic matter to be thermally decomposed at the inlet of the pyrolysis furnace 1. The supply amount of the oxidizing agent supplied from 8 'to the pyrolysis furnace 1 is adjusted according to the desired pyrolysis gas composition and the temperature in the pyrolysis furnace.

The supply amount of the soot suppressant (steam and / or carbon dioxide gas) is determined by the molar ratio of the hydrogen component to the carbon component (H ₂ / C ratio) in the total composition supplied to the pyrolysis furnace 1.
Is supplied so as to be 1 or more, and is adjusted according to a desired pyrolysis gas composition and a temperature in the pyrolysis furnace.

Evaporation (vaporization) of a liquid or solid organic substance at ordinary temperature can be performed by a conventionally known means such as indirect heating or direct heating.

The pyrolysis gas is cooled to 100 to 200 ° C. in the cooler 5.
After being cooled, it is cleaned by a gas purification device (not shown). In the industrial practice, a waste heat recovery boiler may be provided instead of the cooler 5 to recover heat.

The organic substance used in the experiment has a high thermal stability (hardly thermally decomposable) so that the effect of the present invention can be confirmed, and a transformer containing about 2% by weight of a PCB which easily generates dioxins during the thermal decomposition operation. Oil (hereinafter referred to as test material) was used. The composition analysis result of the test material was 84.94% by weight of carbon, 14.03% by weight of hydrogen, and 1.03% by weight of chlorine.

The sampling of the pyrolysis gas is performed at the sampling port 6 in FIG.誌 Journal of Waste Management Society, Vo
l.1, No.1, p20 (1990)｝
Analysis of dioxins was also performed according to this document.

The analysis of PCB is described in Reference 3.報告 Report from Osaka City Institute of Environmental Science Research and research annual report No. 50 (1987) p
11 (1988)｝, and other analyzes were based on JIS.

The internal volume of the pyrolysis furnace used in the experiment was 64.5 liters.

(Example 1) Incineration experiment An experiment was performed for comparison with a conventional incineration method. Using a propane gas as a fuel, a test material and a gasifying agent were supplied into a pyrolysis furnace preheated to about 1000 ° C., and set to predetermined operating conditions. In addition, the air supplied to the gasifying agent and the decomposition furnace was clean air that had been removed by a filter in order to evaluate the amount of generated dust. Sampling for analysis was performed when the operation of the pyrolysis furnace became steady. Table 1 shows the experimental results.

[Table 1]

As is evident from the experimental results, PCB and dioxins in the gas at the outlet of the pyrolysis furnace were below the detection limit, the soot and dust concentrations were within the measurement error range by the JIS method, and the NOx concentration was extremely small. It is.

(Example 2) Production experiment of reducing gas Production experiment of reducing gas by using steam and oxygen (purity: 99% by volume or more) as gasifying agents, using the same supply amount of the test material as in Example 1. Was done.

As in Example 1, the pyrolysis furnace was preheated using propane gas and air.
When the temperature reached 000 ° C., the test material and the gasifying agent were switched to and set to predetermined conditions. Table 2 shows the experimental results at the time of steady operation of the pyrolysis furnace.

[Table 2]

In this experimental result, as in Example 1, almost no PCB, dioxins, dust, etc. were detected.
In addition, a reducing gas that can be used as a fuel gas or a synthesis gas for a chemical raw material is obtained, and the effect of the present invention is simply demonstrated.

[0032]

According to the present invention, a PC which is the most difficult to thermally decompose and which is most liable to produce harmful dioxins and soots which are said to be precursors thereof as a thermal decomposition product.
B can also be completely decomposed in a reducing atmosphere, and is an epoch-making technology for detoxifying and recycling chlorine-containing organic substances.

It can be easily understood that the method of the present invention is effective not only for organic matter containing chlorine but also for thermal decomposition of gaseous organic matter.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an experimental facility according to one embodiment of the present invention.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshiyuki Takeuchi 4-2-2, Kannonshinmachi, Nishi-ku, Hiroshima-shi Hiroshima Research Institute, Sanishi Heavy Industries Co., Ltd. (72) Hirotoshi Horizoe 4-6-1 Kannonshinmachi, Nishi-ku, Hiroshima 22 Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd. (56) References JP-A-56-100213 (JP, A) JP-A-50-114068 (JP, A) JP-A-4-365702 (JP, A) 58-223602 (JP, A) Fully open 58-119021 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F23G 5/027 A62D 3/00 C10J 3/00 F23G 7 / 00

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein the gaseous organic substance is premixed with steam and / or carbon dioxide gas and supplied to a pyrolysis furnace in an atmosphere for pyrolyzing the organic substance. Pyrolysis method. 2. The method according to claim 1, wherein oxygen or an oxygen-containing gas is further premixed into the mixed gas of the organic substance and water vapor and / or carbon dioxide gas within a range not exceeding the lower limit of the oxygen concentration at the explosion limit of the organic substance. The method for thermally decomposing an organic substance according to claim 1.