JP2948345B2 - 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 thermal decomposition (including incineration) of organic matter by partial oxidation, and more particularly to thermal decomposition and low-pollution incineration of organic matter which becomes liquid by heating such as treatment of liquid organic matter and thermoplastics. The present invention relates to a pyrolysis method applicable to the method.

[0002]

2. Description of the Related Art Conventionally, a method of thermal decomposition or incineration by partial oxidation (partial combustion) of an organic substance has been known in which an organic substance and a gasifying agent (oxygen and water vapor) or air are individually supplied to a high-temperature pyrolysis furnace. A method is employed in which they are contact-reacted in a pyrolysis furnace.

[0003]

A disadvantage of the conventional method is that a large amount of soot and other dust is generated even in the incineration of organic matter. Even if measures to increase the excess combustion air rate and increase the incineration temperature, which are usually adopted to suppress the generation, it is difficult to completely suppress the generation of dust, and it is necessary to take such measures. It is well-known that the emission of nitrogen oxides (NOx), which is a pollutant, is increased.

The amount of soot and dust generated even in the incineration process increases in a thermal decomposition operation by a partial oxidation method, which is a kind of incomplete combustion, and measures to generate soot and dust are a major technical problem. It is well known that a great deal of effort is being paid not only in the upsizing of equipment but also in the treatment and disposal of collected soot and dust.

[0005] Dioxins such as polychlorinated dibenzodioxin and polychlorinated dibenzofuran, which are known as highly toxic, have been detected from soot and soot generated from various combustion facilities. It was requested to know that the amount of dioxins increased abnormally, and unburned carbon such as soot was feared as a source of pollution, and establishment of technology to prevent its generation is an urgent issue. In particular, when chlorine is present in the thermal decomposition system, it is necessary to take care to never generate unburned carbon such as soot.

The mechanism of the generation of unburned carbon during the combustion or pyrolysis of organic matter is as follows from the results of experimental studies by the present inventors. That is, in an atmosphere having a temperature equal to or higher than the ignition temperature of the organic substance, combustion occurs at a place having an oxygen concentration equal to or higher than the lower limit of the combustion range of the organic substance, and the temperature of the combustion portion rapidly rises. In this high-temperature combustion stagnation region, it is expected that thermal decomposition of organic matter proceeds rapidly, and that thermal decomposition products containing hydrogen and carbon monoxide are generated. In addition, the lower limit of the oxygen concentration in the combustion range of the pyrolysis products is low,
In addition, components that are easily combustible (such as hydrogen) are expected to consume oxygen first, and there is a shortage of reactive substances such as oxygen that consumes active free radicals (free radicals) of carbon generated by thermal decomposition, and free radicals of carbon are consumed. It is expected that comrades will combine to produce unburned carbon such as soot. That is, combustion
It is considered that unburned carbon such as soot is generated due to an imbalance between the rate of the thermal decomposition reaction and the rate of diffusion of the reactants.

As in the conventional method, when an organic substance to be thermally decomposed and an oxygen-containing gas are separately introduced into a high-temperature pyrolysis furnace, the two undergo a combustion reaction before they are uniformly mixed, resulting in an extreme reaction. It is expected that the situation will partially occur.

Further, when chlorine coexists in the reaction stagnation area, it is considered that chlorine is taken into soot and a precursor substance of dioxins is generated.

The present invention has been made in view of the above technical level, and aims to provide a method for thermally decomposing organic substances, which can prevent the generation of unburned carbon such as soot, which is the root of various evils, during the thermal decomposition (or incineration) of organic substances. is there.

[0010]

According to the present invention, from the results of the above inferences, in order to prevent the generation of unburned carbon, a rapid reaction such as combustion should not be caused to concentrate in one area of a pyrolysis furnace. Further, the present inventors have found that it is important that the reaction participants are uniformly mixed before the start of the reaction, and have completed the present invention based on this finding.

According to the present invention, a liquid phase portion of an organic substance is provided at the bottom of a pyrolysis furnace, and a mixed gas of water vapor and oxygen or an oxygen-containing gas is blown into the liquid phase portion so that the vapor of the organic substance is contained in the mixed gas. This is a method for thermally decomposing organic substances, which is introduced into a thermal decomposition zone.

[0012]

When a mixed gas of water vapor and oxygen or an oxygen-containing gas (hereinafter referred to as a gasifying agent) is blown into the liquid phase of an organic substance, the vapor of the organic substance is contained in the liquid phase in the gasifying agent stream. The content volume ratio is substantially a value obtained by dividing the saturated vapor pressure of the organic matter by the internal pressure of the pyrolysis furnace.

[0013] Since the gasifying agent and the vapor of the organic substance are mixed, they flow out of the liquid phase of the organic substance and are introduced into the pyrolysis or combustion stagnant zone. In addition, no extreme combustion reaction occurs unlike the conventional method.
In addition, steam not only has the effect of suppressing rapid combustion reactions, but also has the effect of suppressing the production of free carbon in the pyrolysis process. According to the method of the present invention, soot and the like in the thermal decomposition or incineration operation of organic substances are used. Of unburned carbon can be prevented.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a system diagram of the equipment used in the experiment. In FIG. 1, 1 is a pyrolysis furnace, 2 is a liquid phase portion of an organic substance provided at the bottom of the pyrolysis furnace, and 3 is an outlet gas cooling of the pyrolysis furnace 1. Indicates a container.
In addition, 4 is a conduit for injecting a gasifying agent into the liquid phase portion 2 of organic matter, 5 is a conduit for supplying organic matter to the pyrolysis furnace 1, and 6 is oxygen or an oxygen-containing gas (hereinafter, oxidized gas) of the pyrolysis furnace 1. 7) a conduit for extracting pyrolysis gas;
Is a conduit for extracting sludge and the like.

The supply of the organic matter to the pyrolysis furnace 1 is carried out from the conduit 5 so that the liquid level of the organic matter in the decomposition furnace 1 becomes substantially constant.

The amount of water vapor in the gasifying agent blown from the conduit 4 is based on the total amount of carbon in the organic matter supplied from the conduit 5.
The organic substance and the steam are introduced so that the molar ratio of the total amount of hydrogen (H ₂ / C ratio) becomes 1 or more, and the temperature is adjusted according to a desired pyrolysis gas composition and a temperature in the pyrolysis furnace 1. The flow rate of the oxidizing gas in the gasifying agent is supplied in an amount sufficient to evaporate the organic matter supplied to the cracking furnace 1.

The flow rate of the oxidizing gas supplied from the conduit 6 is adjusted according to the desired composition of the pyrolysis gas and the temperature inside the pyrolysis furnace 1.

In the experiment, the temperature of the organic liquid phase 2 at the bottom of the pyrolysis furnace 1 was controlled by the temperature of the gasifying agent supplied from the conduit 4, but in industrial practice, known methods such as indirect heating and cooling were used. It is also possible to use the means in combination.

The pyrolysis gas is cooled to 100 to 200 ° C. in the cooler 3.
After being cooled, it is cleaned by a gas purification device (not shown). Note that a waste heat recovery boiler may be provided instead of the cooler 3 to recover heat. The conduit 8 is used for extracting sludge or the like.

The organic material used in the experiment was a transformer oil (hereinafter referred to as a test oil) having high thermal stability so that the effect of the present invention could be confirmed, and containing about 2% by weight of PCB which was liable to generate dioxins during the thermal decomposition operation. Material). The composition analysis result of the test material was 84.94% by weight of carbon and 14.
The composition is 03% by weight and 1.03% by weight of chlorine, and is a composition that easily generates unburned carbon such as soot during combustion.

Sampling of the pyrolysis gas is carried out from the conduit 7 at the outlet of the cooler 3 through the literature 1 [Journal of the Waste Society of Japan, Vol. 1, No. 1,
P20 (1990)], and the analysis of dioxins was performed according to this document. In addition, the analysis of PCB is described in Reference 2 [Osaka Municipal Environmental Science Research Institute Annual Report, No. 50 (1987) P11
(1988)], and other analyzes were performed based on JIS. The total internal volume of the thermal cracking furnace 1 used in the experiment was 64.5 liters, of which 20 liters were provided as a reservoir for organic substances at the bottom of the thermal cracking furnace 1.

(Example 1) Incineration experiment The state of generation of unburned carbon such as soot in a combustion incineration operation,
PCB decomposition status, dioxin generation status, NOx
The survey was conducted mainly on the situation of occurrence. After preliminarily charging 20 liters of the test material to the bottom of the pyrolysis furnace 1, the inside of the pyrolysis furnace 1 is preheated to about 1000 ° C. with a propane gas burner (not shown) attached to the conduit 6 mounting portion of the pyrolysis furnace 1. The gasifying agent from the conduit 4 is gradually blown. During this time, the organic matter is replenished so that the liquid level of the organic matter at the bottom of the cracking furnace 1 becomes constant, and the supply amount of the gasifying agent is adjusted so that the replenished organic matter amount becomes a predetermined value.

Further, the amount of oxidizing gas blown from the conduit 6 is adjusted so that the temperature inside the cracking furnace 1 becomes a predetermined value. In addition,
As the gasifying agent and the oxidizing gas supplied from the conduit 6, those which had been removed in advance by a filter were used in order to accurately evaluate the amount of generated dust.

The sampling of the gas at the outlet of the cracking furnace 1 for analysis was carried out when the operation of the cracking furnace 1 became steady. Table 1 shows the experimental results.

[Table 1]

As is clear from the experimental results, the pyrolysis furnace 1
PCB and dioxins in the outlet gas are below the detection limit, and the soot concentration is within the measurement error range. Also NO
The x concentration is also a very small value.

(Example 2) Production experiment of reducing gas The production amount of the test material was made the same as in Example 1, and the production experiment of the reducing gas was carried out using steam and oxygen (purity: 99% by volume or more) as the gasifying agent. The procedure was performed in the same manner as in Example 1.

Table 2 shows the experimental results during steady operation of the pyrolysis furnace 1.
Shown in

[Table 2]

In the results of this experiment, PCB,
Dioxins, dust and the like are hardly detected, and a reducing gas that can be used as a fuel gas or a synthesis gas for chemical raw materials is obtained.

Although PCB is known to be the most difficult to thermally decompose and is liable to produce soot and the like during the pyrolysis operation, experimental results show that such a substance can be completely decomposed in a reducing atmosphere. You can understand the effect.

Although examples of thermal decomposition of liquid organic substances are shown in the examples, those skilled in the art can easily understand that the method of the present invention can be applied to organic substances which become liquid by heating, such as thermoplastics. .

[0031]

According to the present invention, not only can organic substances, especially liquid organic substances be thermally decomposed without generating harmful substances, but also a reducing gas useful as a chemical raw material can be produced at the same time.

[Brief description of the drawings]

FIG. 1 is an explanatory view of one embodiment of a method for thermally decomposing an organic substance of the present invention.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshiyuki Takeuchi 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City Inside Hiroshima Research Laboratory, Sanishi Heavy Industries Co., Ltd. 22 Hiroshima Laboratory, Mitsubishi Heavy Industries, Ltd. (56) References JP-A-4-292689 (JP, A) JP-A-6-135855 (JP, A) JP-A-51-28882 (JP, A) JP JP-A-4-284206 (JP, A) JP-A-2-218484 (JP, A) JP-A-53-39669 (JP, A) JP-A-62-46117 (JP, A) JP-A-60-38331 (JP , U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F23G 5/027 A62D 3/00 B09B 3/00 C10J 3/00 F23G 7/00

Claims (1)

(57) [Claims] An organic liquid phase is provided at the bottom of a pyrolysis furnace, and a mixed gas of water vapor and oxygen or an oxygen-containing gas is blown into the liquid phase to contain the organic vapor in the mixed gas. A method for thermally decomposing organic substances, which is introduced into a decomposed region.