JP5835006B2 - Organic substance gasification method and organic substance gasification apparatus - Google Patents

Description

  The present invention relates to a method for reforming and gasifying an organic substance to convert the organic substance such as waste plastic into a gaseous fuel and the like, and a gasification apparatus used therefor.

At present, most of waste plastic, oil-impregnated sludge, waste oil, etc. are incinerated. However, incineration treatment has a high environmental load such as CO ₂ generation, and there is a problem of thermal damage of the incinerator, and establishment of chemical recycling technology is required.
Among chemical recycling technologies, technologies for converting organic substances into gaseous fuels and liquid fuels have been variously studied mainly with respect to waste plastics. For example, the following proposals have been made.

In Patent Document 1, a coke oven gas (COG) having a hydrogen concentration of 60 vol% or more, preferably 80 vol% or more and a temperature of 600 ° C or more is reacted with an organic material such as waste plastic, thereby hydrogenating the organic material with high efficiency. A method for increasing the heat of COG by decomposition and gasification is disclosed.
Further, Patent Document 2 discloses a method in which petroleum fluid contact catalyst (FCC) is used as a heat medium / catalyst and waste plastic is decomposed at a temperature of 350 to 500 ° C. to be converted into liquid fuel.
Further, in Patent Document 3, when pyrolyzing RDF, wood, etc., the gas generated by pyrolysis is steam reformed, and the gas having a high hydrogen concentration by this steam reforming is circulated to the pyrolysis section to generate hydrogen. A method of performing pyrolysis in a gas atmosphere with a high concentration is disclosed.

JP 2007-224206 A JP 2010-013657 A JP 2001-131560 A

However, the above prior art has the following problems.
First, regarding Patent Document 1, since the hydrogen concentration in COG is 60 vol% or more is limited to the end of the dry distillation in the coal dry distillation process, in the method of Patent Document 1, the gas flow path is opened at the end of the dry distillation. It is necessary to switch and supply COG of 600 ° C. or more containing a large amount of dust to a waste plastic hydrocracking reactor. However, it is difficult to stably operate the flow path switching valve for a long time under such a severe condition, and in this sense, it can be said that the technique is poor in feasibility. Furthermore, for efficient gasification of waste plastic, it is necessary to continuously supply COG containing 60 vol% or more of hydrogen to the hydrocracking reactor. In addition, it is necessary to install a hydrogen concentration meter and a flow path switching valve, which increases the equipment cost.

Moreover, although the method of patent document 2 advances catalytic cracking and aromatization by FCC catalyst addition, since it reacts by an inert gas flow, 13 mass% of heavy oil components and coke are produced | generated in total ( Example 1) is not a satisfactory level as a light fuel production technology.
Further, the gas generated by the method of Patent Document 3 is mainly H ₂ , CO, and CO ₂ , and the combustion heat is about 1800 kcal / Nm ³ that is slightly lower than that of the exhaust gas generated from the metallurgical furnace. The value is limited.

  Accordingly, an object of the present invention is to efficiently reform an organic substance using a gas that can be stably supplied when gasifying an organic substance such as waste plastic into gas fuel, etc. It is to provide an organic substance gasification method and a gasification apparatus capable of obtaining a high-calorie gasification product with high efficiency while suppressing generation of heavy components and carbonaceous matter. .

  As a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention added an excessive water vapor to an exhaust gas containing carbon monoxide generated in a metallurgical furnace to cause a shift reaction, and a gas after the shift reaction. In other words, by bringing a mixed gas containing hydrogen and carbon dioxide generated in the shift reaction and the remaining water vapor into contact with the organic substance in the reforming reactor, the organic substance is reformed to produce a low molecular weight product. And distilling the vapor of the product from the reforming reactor into a gas product and a liquid product, collecting the gas product and refluxing the liquid product to the reforming reactor. The present inventors have found that organic substances can be efficiently gasified at a high gasification rate.

The present invention has been made on the basis of such findings and has the following gist.
[1] Addition of excess water vapor to the exhaust gas (g ₀ ) containing carbon monoxide generated in the metallurgical furnace to cause the shift reaction to consume the hydrogen and carbon dioxide generated by the shift reaction and the shift reaction A mixed gas (g) containing water vapor that has not been produced is brought into contact with the organic substance in the reforming reactor, thereby reforming the organic substance to produce a low molecular weight product. The vapor of the product discharged from the reforming reactor is distilled to separate the gas product and the liquid product, the gas product is recovered, and the liquid product is refluxed to the reforming reactor. A method for gasifying an organic substance.

[2] In the method of [1] above, the exhaust gas (g ₀ ) increases the carbon monoxide concentration by separating at least a part of nitrogen from the exhaust gas containing nitrogen and carbon monoxide generated in the metallurgical furnace. A method for gasifying an organic substance, characterized by being exhaust gas.
[3] A method for gasifying an organic substance according to the method [1] or [2], wherein the water vapor concentration of the mixed gas (g) is 5 to 70 vol%.
[4] In the method of [3] above, the mixed gas (g) is an organic material having a water vapor concentration of 20 to 70 vol%, a hydrogen concentration of 10 to 40 vol%, and a carbon dioxide gas concentration of 10 to 40 vol%. Gasification method for substances.
[5] The method according to any one of [1] to [4] above, wherein the organic substance to be modified is at least one selected from waste plastic, oil-containing sludge, waste oil, and biomass. Gasification method for organic substances.

[6] A shift reactor (1) for adding excess water vapor to an exhaust gas (g ₀ ) containing carbon monoxide generated in a metallurgical furnace to cause a shift reaction, and the shift reactor (1) A reforming reactor (2) for reforming a mixed gas (g) containing the generated hydrogen and carbon dioxide gas and water vapor not consumed in the shift reaction by contacting with an organic substance, and the reforming reactor (2 An organic substance characterized in that it comprises a distillation device (3) for separating the vapor of the product from) into a gaseous product and a liquid product and refluxing the liquid product to the reforming reactor (2) Gasifier.
[7] A method for operating a steel mill, wherein the gas product obtained by any one of the methods [1] to [5] is used as a fuel or / and a reducing agent in the steel mill.

According to the present invention, when an organic substance such as waste plastic is gasified to be converted into gaseous fuel, the organic substance can be efficiently reformed using a gas that can be stably supplied, and a high gasification rate is obtained. As a result, a high-calorie gasification product can be obtained with high efficiency while suppressing the generation of heavy components and carbonaceous matter.
Also, with regard to implementation facilities, there is no need for special measuring instruments or flow path switching valves, and organic substances can be gasified even at relatively low reaction temperatures. it can. In addition, since CO ₂ produced by the shift reaction changes to CO during the reforming of the organic material, it is possible to carry out chemical recycling of the organic material without increasing the amount of CO ₂ generated. It becomes.

In the shift reaction performed by adding water vapor to the converter gas, a graph showing the relationship between the amount of water vapor added and the composition of the gas after the shift reaction (calculated equilibrium composition at a temperature of 430 ° C.) Explanatory drawing which shows typically one Embodiment of the gasification apparatus of the organic substance which concerns on this invention Explanatory drawing which shows typically other embodiment of the gasification apparatus of the organic substance which concerns on this invention Explanatory drawing which shows typically other embodiment of the gasification apparatus of the organic substance which concerns on this invention In the polyethylene reforming test conducted under the same conditions as in Invention Examples 2 to 10 except that the liquid product was not refluxed to the reforming reactor, the water vapor concentration of the shift reaction product gas and the reforming of polyethylene (lower molecular weight) Showing the relationship between gasification rate and liquefaction rate In the polyethylene reforming test conducted under the same conditions as in Invention Examples 2 to 10 except that the liquid product was not refluxed to the reforming reactor, the water vapor concentration of the shift reaction product gas and the reforming of polyethylene (lower molecular weight) Showing the relationship between the gas product and the liquid product obtained in Example 1 and LHV In the polyethylene reforming test conducted under the same conditions as in Invention Examples 2 to 10 except that the liquid product was not refluxed to the reforming reactor, the water vapor concentration of the shift reaction product gas and the reforming of polyethylene (lower molecular weight) Showing the relationship with polyethylene degradation rate In the polyethylene reforming test conducted under the same conditions as in Invention Examples 2 to 10 except that the liquid product was not refluxed to the reforming reactor, the carbon dioxide concentration of the shift reaction product gas and the reforming of polyethylene (lower molecular weight) ) Graph showing the relationship with the hydrogen concentration of the gas product obtained in In the polyethylene reforming test conducted under the same conditions as in Invention Examples 2 to 10 except that the liquid product was not refluxed to the reforming reactor, the hydrogen concentration of the shift reaction product gas and the reforming of polyethylene (lower molecular weight) Graph showing the relationship between carbon dioxide concentration and gaseous product obtained in

In the method of the present invention, an excess water vapor is added to an exhaust gas (g ₀ ) containing carbon monoxide generated in a metallurgical furnace (hereinafter sometimes referred to as “metallurgical furnace generated exhaust gas”) to cause a shift reaction. A mixed gas (g) containing hydrogen and carbon dioxide gas generated in the shift reaction and water vapor not consumed in the shift reaction, and this mixed gas (g) (hereinafter sometimes referred to as “shift reaction product gas”). Is brought into contact with the organic substance in the reforming reactor, thereby reforming the organic substance to produce a low molecular weight product. Then, the product vapor from the reforming reactor is distilled to separate the gas product and the liquid product, and the gas product is recovered, and the liquid product is refluxed to the reforming reactor. Convert to product.
Note that adding excess steam to the exhaust gas (g ₀ ) means adding steam so that excess steam that is not consumed in the shift reaction remains in the mixed gas (g).

In such a method of the present invention, the reduction of the molecular weight of the organic substance is efficiently promoted even at a relatively low reaction temperature, the hydrogen consumption is small, and the generation of heavy components and carbonaceous matter is hardly observed.
Generally, high molecular weight organic substances such as waste plastic are known to start thermal decomposition when heated at a temperature of 300 to 400 ° C. or higher, but at this time, they become lighter and heavier. Coexistence of hydrogen during thermal decomposition is effective in suppressing heavy formation and reducing the molecular weight because hydrogen addition reaction and hydrocracking reaction to hydrocarbon species proceed. However, the high temperature is required for hydrocracking, and the hydrogen consumption is a problem.

On the other hand, steam reforming and carbon dioxide reforming can be regarded as oxidation of hydrocarbons by oxygen in H ₂ O and CO ₂ molecules, achieving low molecular weight and suppressing carbonaceous production with a small amount of hydrogen addition. it can. Furthermore, steam reforming and carbon dioxide reforming are characterized in that the reaction temperature decreases as the carbon chain of the organic molecule to be modified becomes longer. In the method of the present invention, the low molecular weight of an organic substance is efficiently promoted even at a relatively low reaction temperature, the amount of hydrogen consumption is small, and the generation of heavy components and carbonaceous matter is hardly recognized. It is considered that the four reactions of hydrogenation, hydrocracking, steam reforming, and carbon dioxide reforming proceed simultaneously by reforming (reducing molecular weight) the organic substance using (g).
Furthermore, in the present invention, a gas product can be obtained with high efficiency by refluxing the liquid product produced by the reforming to the reforming reactor.
Incidentally, as the hydrogenation reaction, not only hydrogenation reaction to hydrocarbon species, that is gaseous products that also proceed hydrogenation reaction to CO and CO ₂ to produce a light hydrocarbon such as methane It is suggested from the analysis results. In the description of the present invention, for the sake of simplicity, the hydrogenation reaction to CO or CO ₂ is simply described as hydrogenation (or hydrogenation reaction) without being distinguished from the hydrogenation reaction to hydrocarbon species.

For example, the exhaust gas generated from a metallurgical furnace such as a converter usually contains about 25 to 80 vol% of CO. Therefore, when water vapor is added thereto, H ₂ and CO ₂ are generated by the following shift reaction (1).
CO + H ₂ O → H ₂ + CO ₂ (1)
In the method of the present invention, since excess water vapor is added to the exhaust gas (g ₀ ), the mixed gas (g) after the shift reaction includes H ₂ , CO ₂ generated by the shift reaction, and H ₂ O of excess addition. Will be included. In the reforming of organic substances (lower molecular weight) by this shift reaction product gas (g), four reactions of hydrogenation, hydrocracking, steam reforming, and carbon dioxide reforming by each gas component proceed simultaneously. it is conceivable that.

In the present invention, the concentration of water vapor, hydrogen, and carbon dioxide in the gas is controlled by appropriately controlling the excess ratio of water vapor added excessively to the exhaust gas (g ₀ ) and the reaction rate of the shift reaction. A mixed gas (g) for material modification can be obtained. However, the general composition of the metallurgical furnace generated exhaust gas stored in the gas holder (for example, a general gas holder used in a steelworks) is CO: 50 to 70 vol%, CO2: 10 to ₂₀ vol%, N _{2: 10~20vol%,} H _2: because of the order 0~5vol% (including other saturated steam) generally is not necessary to carry out until the reaction rate control of the shift reaction, only by adjusting the excess percentage of water vapor Thus, each concentration of water vapor, hydrogen and carbon dioxide in the mixed gas (g) can be controlled to a desired level.
The reaction rate of the shift reaction can be controlled by adjusting the residence time in the shift reactor. For example, in order to shorten the residence time, a method in which the shift reactor length is reduced or the catalyst charge amount is reduced is generally used. In this case, the shift reactor length and the catalyst charge amount are almost until equilibrium. What is necessary is just to set it as about 1 / 2-1 / 4 in the case of advancing reaction. In addition, it is well known that the shift reaction usually proceeds to almost equilibrium.

As an example, converter gas of 100 kmol / h (= 2240 Nm ³ / h) having a composition of CO: 65 vol%, CO ₂ : 15 vol%, N ₂ : 18 vol%, H ₂ : 1 vol%, H ₂ O: 1 vol% In the case of performing the shift reaction by changing the amount of water vapor added from 60 kmol / h (= 1340 Nm ³ / h) to 540 kmol / h (= 1100 Nm ³ / h), the amount of water vapor added and the composition of the gas after the shift reaction ( The calculated equilibrium composition at a temperature of 430 ° C. is shown in FIG. According to this, it can be seen that the concentration of water vapor, hydrogen, and carbon dioxide in the mixed gas (g) can be controlled only by adjusting the amount of water vapor added, and a preferable gas composition as described later can be obtained. In addition, it is well known that the shift reaction usually proceeds to almost equilibrium.

Hereinafter, details and preferred conditions of the method of the present invention will be described.
In the present invention, the reason why the metallurgical furnace generated exhaust gas is used as the exhaust gas (g ₀ ) for the shift reaction is that the metallurgical furnace generated exhaust gas contains carbon monoxide at a relatively high concentration and the concentration of unnecessary nitrogen is low. . As the metallurgical furnace-generated exhaust gas (g ₀ ) containing carbon monoxide, any one can be used. The most representative is the converter gas generated from the converter where the decarburization process of the steel manufacturing process is performed, but other than that, for example, it is generated from a hot metal pretreatment furnace, a smelting reduction furnace, a shaft furnace, etc. Exhaust gas to be used can be exemplified, and one kind or a mixture of two or more kinds thereof can be used.
The secondary combustion rate (CO ₂ / (CO + CO ₂ ) × 100), which is the rate at which carbon monoxide produced in the metallurgical process is further oxidized to produce carbon dioxide, is generally only about 10 to 50%. Also, in the exhaust gas (g ₀₎ are also included hydrogen and nitrogen, H ₂ concentration varies depending on the metallurgical process, it is about 0~20vol%. Nitrogen is supplied for in-furnace agitation and flue safety, and the concentration in the exhaust gas (g ₀ ) is usually about 10 to 30 vol%.

From the above points, the composition of general metallurgical furnace-generated exhaust gas (g ₀ ) is generally in the following range.
CO: 80-25 vol% (equivalent to 10-50% secondary combustion rate)
CO _2: 10~25vol% (corresponding to the secondary combustion rate 10-50%)
N _2: 10~30vol%
H2: 0 to ₂₀ vol%
Although carbon monoxide is required for the shift reaction, there is no particular problem with the composition of the exhaust gas (g ₀ ) as long as the gas composition is in the above range. Here, nitrogen does not contribute at all to the chemical reactions (shift reaction, hydrogenation, hydrocracking, steam reforming, carbon dioxide reforming) that occur in the present invention, while diluting the gas product produced. , Lower combustion heat (hereinafter referred to as “LHV”). In particular, when the nitrogen concentration exceeds 50 vol%, the LHV of the gas product is significantly reduced and the shift reaction rate tends to be reduced. Therefore, the nitrogen concentration is preferably within the above composition range.

As mentioned earlier, gas holder (e.g., typical gas holder used in steelworks) General composition of metallurgical furnace generation exhaust gas to be stored in the, CO: 50~70vol%, CO 2 : 10 ˜20 vol%, N ₂ : 10 to ₂₀ vol%, H ₂ : 0 to 5 vol% (including saturated steam in addition), and this composition is high in the composition of the above general metallurgical furnace generated exhaust gas. It corresponds to the CO concentration composition. Since the gas stored in the gas holder is used as fuel gas at each factory in the steelworks, it is necessary to prevent a decrease in combustion efficiency at the use destination. Therefore, setting the lower limit value of the CO concentration in the gas as a storage condition in the gas holder is the reason why the composition has a high CO concentration.
In the present invention, the composition of the exhaust gas generated in the general metallurgical furnace as described above is used even if the exhaust gas has a relatively high CO concentration as stored in a general gas holder used in a steelworks. However, it can be used as exhaust gas (g ₀ ).

By the way, some of the metallurgical furnace-generated exhaust gas (g ₀ ) contains carbon monoxide but has a relatively high nitrogen concentration. Such a metallurgical furnace-generated exhaust gas (g ₀ ) contains at least nitrogen contained therein. A part may be separated (removed) to increase the carbon monoxide concentration, and then an excess of water vapor may be added to cause the shift reaction.
As typical exhaust gas that is preferably subjected to nitrogen separation, blast furnace gas can be mentioned, but in addition to this, exhaust gas generated from an electric furnace or a shaft furnace operating under a condition where the nitrogen concentration becomes high can be mentioned. it can. In addition, the nitrogen gas is separated from an exhaust gas containing a relatively high concentration of carbon monoxide such as a converter gas, and the shift reaction can be performed after further increasing the carbon monoxide concentration.

There is no particular restriction on the method for separating nitrogen from exhaust gas, and any method such as adsorption separation method or distillation separation method can be applied. However, since the boiling point difference between nitrogen and carbon monoxide is small, the adsorption separation method is Particularly preferred. For example, since activated carbon supporting Cu ⁺ , which is known as a CO adsorbent, also adsorbs CO ₂ , blast furnace gas (general composition: N ₂ : 50 vol%, CO ₂ ) is obtained by PSA method using Cu ⁺ supported activated carbon as an adsorbent. : _25vol%, CO 2: approximate composition as desorbed gas from 25 vol%) is _{N 2: 15vol%, CO:} 45vol%, CO 2: it is possible to obtain a 40 vol% of the gas, which separates the nitrogen in the blast furnace gas Thus, the carbon monoxide is concentrated.

The shift reaction in the method of the present invention may be carried out by a known method and is not particularly limited. Generally, water vapor is added to the metallurgical furnace-generated exhaust gas (g ₀ ) in advance, and this is introduced into a fixed bed reactor filled with a catalyst to perform a shift reaction. Alternatively, the water vapor to be added in advance may be partially used, the catalyst may be packed in multiple stages in the reactor, and the remaining water vapor may be added between the catalyst layer and the catalyst layer.
If water vapor, hydrogen, and carbon dioxide are added to the metallurgical furnace-generated exhaust gas (g ₀ ) without performing the shift reaction as in the present invention, the mixture for organic substance modification obtained by the shift reaction in the present invention is used. Although a gas having a composition equivalent to that of the gas (g) can be obtained, in such a method, in addition to water vapor, expensive hydrogen gas and carbon dioxide gas must be added, resulting in an increase in cost.

In the present invention, the mixed gas (g) for reforming the organic substance obtained by the shift reaction contains water vapor, hydrogen and carbon dioxide gas, and there is no particular limitation on the concentration thereof. Therefore, the water vapor concentration is preferably 5 to 70 vol%. In other words, when the water vapor concentration is low, the decomposition rate of organic substances such as waste plastics is low. However, by setting the water vapor concentration to 5 vol% or more, a certain level of organic material decomposition rate can be secured, and the rate of production of gas products. (Gasification rate) can be maintained at a constant level, and the amount of heavy components produced can be reduced. On the other hand, if the water vapor concentration is high, CO ₂ tends to remain in the reforming reaction product gas of the organic substance (gas generated by low molecular weight reforming of the organic substance; hereinafter the same), and the LHV of the gas product is low. However, if the water vapor concentration is 70 vol% or less, it is possible to suppress the residual CO _{2 in} the reforming reaction product gas, and to suppress the decrease in LHV of the gas product.
Further, from the viewpoint of ensuring the decomposition rate of the organic substance, both the hydrogen concentration and the carbon dioxide concentration of the mixed gas (g) are preferably 5 vol% or more.

Moreover, for the following reasons, the more preferable composition of the mixed gas (g) for organic substance reforming is: water vapor concentration: 20 to 70 vol%, hydrogen concentration: 10 to 40 vol%, carbon dioxide concentration: 10 to 40 vol%. It is. In addition, it does not prevent that other gas components (for example, nitrogen etc.) are contained in this mixed gas (g). By setting the water vapor concentration to 20 vol% or more, the decomposition rate of the organic substance can be sufficiently increased, and the LHV of the gas product can be increased. The reason for setting the water vapor concentration to 70 vol% or less is as described above. By setting the hydrogen concentration to 10 vol% or more (more preferably 12 vol% or more), it is possible to suppress CO ₂ from remaining in the gas product even when a reforming reaction of an organic substance is performed at a relatively low temperature. be able to. By setting the carbon dioxide gas concentration to 10 vol% or more (more preferably 13 vol% or more), H ₂ that is a low-calorie gas component is less likely to remain in the gas product as compared to hydrocarbons and CO. Moreover, the decomposition rate of organic substances, such as a waste plastic, can be made into a preferable level by making hydrogen concentration and carbon dioxide gas concentration into 40 vol% or less. Moreover, from the above viewpoints, a more preferable gas composition of the mixed gas (g) is a water vapor concentration: 25 to 65 vol%, a hydrogen concentration: 15 to 35 vol%, and a carbon dioxide concentration: 15 to 35 vol%. In addition, it does not prevent that other gas components (for example, nitrogen etc.) are contained in this mixed gas (g).

Next, conditions for modifying (lowering the molecular weight) of an organic substance with the mixed gas (g) obtained by the shift reaction will be described.
In the present invention, there is no particular limitation on the organic material to be reduced in molecular weight by modification, but high molecular weight organic material is suitable, for example, waste plastic, oil-containing sludge, waste oil, biomass, etc. One or more of these can be targeted.

Although there is no special restriction | limiting in the kind of waste plastics made into object, For example, the object plastics etc. which are an industrial waste type | system | group and a container packaging recycling law can be mentioned. More specifically, polyolefins such as PE and PP, thermoplastic polyesters such as PA and PET, elastomers such as PS, thermosetting resins, synthetic rubbers, foamed polystyrene and the like can be mentioned. In addition, inorganic substances such as fillers are added to many plastics. However, in the present invention, such inorganic substances are not involved in the reaction, so that they are reformed (low molecular weight) reactors (organic substances) as solid residues. Is discharged from a reactor for reducing the molecular weight by modifying the same. In addition, the waste plastic is preliminarily cut to an appropriate size as required, and then charged into the reforming reactor.
Further, if the waste plastic contains a chlorine-containing resin such as polyvinyl chloride, chlorine is generated in the reforming reactor, and this chlorine may be contained in a gas product or a liquid product. Therefore, when there is a possibility that the waste plastic contains a chlorine-containing resin, a chlorine absorbent such as CaO is introduced into the reforming reactor so that chlorine is not contained in the generated gas product. It is preferable.

  Oil-containing sludge is a sludge-like mixture generated in an oil-containing waste liquid treatment step, and generally contains about 30 to 70% by mass of water. Examples of the oil in the sludge include, but are not limited to, various mineral oils, natural and / or synthetic oils and fats, and various fatty acid esters. In addition, in order to improve handling property, such as when supplying oil-impregnated sludge to the reforming reactor, moisture in the sludge may be reduced to about 30 to 50% by mass by a method such as centrifugation.

Examples of the waste oil include, but are not limited to, various used mineral oils, natural and / or synthetic fats and oils, and various fatty acid esters. Moreover, the mixture of these 2 or more types of waste oil may be sufficient. In addition, in the case of waste oil generated in the steel mill rolling process, it generally contains a large amount of water (usually more than about 80% by mass), but this water is also reduced in advance by a method such as specific gravity separation. It is advantageous in terms of handleability.
When the organic substance contains water, water vapor is generated in the reforming reactor. Therefore, the excess ratio of water vapor added in the shift reaction is determined in consideration of the amount.

  Examples of biomass include, but are not limited to, sewage sludge, paper, construction waste, thinned wood, and other processed biomass such as waste solid fuel (RDF). Since biomass usually contains a large amount of water, it is preferable to dry it beforehand in view of energy efficiency. In addition, in the case of biomass containing relatively high concentrations of alkali metals such as sodium and potassium, alkali metals may be deposited in the reforming reactor. It is preferable to keep it. In addition, large biomass such as construction waste is cut in advance and charged into the reforming reactor.

The reaction temperature during organic substance modification is preferably as follows according to the type of organic substance. In the case of waste plastic or biomass, a reaction temperature of about 400 to 900 ° C. is appropriate. When the reaction temperature is less than 400 ° C, the decomposition rate of waste plastics and biomass is low. On the other hand, when the reaction temperature exceeds 900 ° C, the production of carbonaceous matter increases. In the case of oil-containing sludge or waste oil, the reaction temperature is suitably about 300 to 800 ° C. When the reaction temperature is less than 300 ° C., the decomposition rate of oil-containing sludge and waste oil becomes low. On the other hand, even if the reaction temperature exceeds 800 ° C., there is no effect on the reforming (lower molecular weight) characteristics of the oil-containing sludge or waste oil, but it is not economical because the temperature is higher than necessary.
Moreover, when the mixture which consists of waste plastics and / or biomass and oil-containing sludge and / or waste oil is made into object, about 400-800 degreeC is suitable for reaction temperature from the point mentioned above. Since almost no influence of pressure is observed, it is economical to operate the reforming reactor at normal pressure or slightly pressurized of about several kg / cm ² .

The type of reforming reactor to be used is not particularly limited, but organic substances such as waste plastic move smoothly in the reactor and can be efficiently contacted with the mixed gas (g) for organic substance reforming. Therefore, a horizontal moving bed type reactor such as a rotary kiln is preferable.
In the present invention, a catalyst is not particularly required for reforming the organic substance, but the reaction may be carried out by filling the catalyst. As the catalyst, one or more kinds of catalysts each having steam reforming activity, carbon dioxide reforming activity, hydrogenation activity, and hydrocracking activity can be used. Specific examples include Ni-based reforming catalysts, Ni-based hydrogenation catalysts, Pt / zeolite-based petroleum refining catalysts, and the like. Also, converter-generated dust, which is known to be composed of fine Fe particles, can be used as a reforming catalyst or a hydrocracking catalyst.

  When the catalyst is packed, the contact between the organic material such as waste plastic and the catalyst is good, so a vertical reforming reactor is used instead of a horizontal moving bed reforming reactor such as a rotary kiln. May be adopted. In this case, the mixed gas (g) obtained by the shift reaction is supplied from the lower part and / or the side part rather than the upper part of the reforming reactor. Is preferable.

  As a vertical reforming reactor, a general fixed bed reactor used in the chemical industry can be used, but in particular, when a method of supplying a mixed gas (g) from the lower part of the reforming reactor is employed. In addition, a blast furnace, a shaft furnace, or a converter, which is an iron manufacturing facility, can be used as a reforming reactor. When a blast furnace or shaft furnace is used as a reforming reactor, organic substances and catalyst are continuously fed from the top of the furnace and mixed gas (g) is continuously fed from the bottom of the furnace to make countercurrent contact, and products are produced from the top of the furnace. It is preferable that the (product vapor) is a moving bed type in which the catalyst is continuously extracted from the lower part of the furnace because the reaction efficiency is increased. When a converter is used as a reforming reactor, an organic substance and a catalyst are introduced into the furnace, then a mixed gas (g) is continuously supplied from the lower part of the furnace, and the product (product vapor) is A batch reaction system similar to blowing can be used in which the catalyst is continuously extracted from the upper part of the furnace, and the catalyst is extracted by tilting the furnace after a certain time of reaction.

  In the method of the present invention, as described above, the organic substance is reformed in the reforming reactor to produce a low molecular weight product, and the product vapor discharged from the reforming reactor is distilled to obtain a gas product. And the liquid product are recovered, the gaseous product is recovered, and the liquid product is refluxed to the reforming reactor. For this reason, as will be described later, a distillation apparatus is attached to the reforming reactor. The liquid product refluxed to the reforming reactor is further reformed and converted into a gaseous product. Thus, a very high gasification rate can be achieved by separating the liquid product from the vapor of the product exiting the reforming reactor and refluxing it to the reforming reactor.

Next, the gasifier of the present invention will be described.
FIG. 2 schematically shows an embodiment of the gasifier of the present invention.
The gasification apparatus of the present invention includes a shift reactor 1 (shift reaction apparatus) for adding excess steam to an exhaust gas (g ₀ ) containing carbon monoxide generated in a metallurgical furnace to cause a shift reaction, A reforming reactor 2 (reforming reaction apparatus) for reforming a mixed gas (g) containing hydrogen and carbon dioxide gas produced in the shift reactor 1 and water vapor not consumed in the shift reaction by contacting with an organic substance And a distillation apparatus 3 that separates the vapor of the product from the reforming reactor 2 into a gas product and a liquid product, and refluxes the liquid product to the reforming reactor 2.
The distillation apparatus 3 of the present embodiment includes a distillation column 30 provided independently from the reforming reactor 2, a water-cooled condenser 31 provided on the downstream side of the distillation tower 30 (upper part of the distillation tower), and the water-cooled condenser 31. And a pipe 32 for refluxing the liquid product separated from the gaseous product to the reforming reactor 2. The pipe 32 has a branch pipe 320 for refluxing a part of the liquid product to the distillation column 30.

In this gasification facility, a metallurgical furnace-generated exhaust gas (g ₀ ) to which excess water vapor has been added is introduced into the shift reactor 1 to perform a shift reaction, and the mixed gas (g) after this shift reaction (shift reaction product gas) ) Is introduced into the reforming reactor 2. The reforming reactor 2 is charged with an organic substance such as waste plastic, and the organic substance is reformed (lower molecular weight) by the mixed gas (g). The product vapor generated in the reforming reactor 2 rises and enters the distillation column 30. In the distillation column 30, at least a part of the liquid product condensed in the water-cooled condenser 31 is refluxed to the distillation column 30 through the branch pipe 320, so that distillation is performed by exchanging heat with the rising product vapor. Among the products, products having a relatively high boiling point such as kerosene and light oil components are returned to the reforming reactor 2 in a liquid state from the lower part of the distillation column, and as a result, products having a relatively low boiling point such as LPG components are produced. The substance is concentrated and rises to the water-cooled condenser 31 while remaining in a vapor state. In the water-cooled condenser 31, the product condensed near room temperature changes to a liquid, and this liquid product is refluxed to the reforming reactor 2 and the distillation column 30 through the pipe 32 and the branch pipe 320. On the other hand, components that are not condensed in the water-cooled condenser 31 are recovered as gas products. The liquid product refluxed directly from the pipe 32 to the reforming reactor 2 without being refluxed to the distillation tower 30 by the branch pipe 320 and the liquid refluxed from the lower part of the distillation tower to the reforming reactor 2 in the liquid state as described above. The product is further reformed in the reforming reactor 2 and converted into a gaseous product. Thereby, a very high gasification rate can be achieved.

In the present invention, relatively low-precision distillation separation is usually sufficient. This is because the gas product obtained in the present invention becomes a gas mixture at normal temperature in which hydrogen or carbon monoxide is mixed with hydrocarbon having 1 to 4 to 5 carbon atoms. Therefore, the number of theoretical stages of the distillation apparatus 3 is about 1 to 5 and there is no problem, and the ratio of the reflux amount from the branch pipe 320 to the distillation column 30 and the reflux quantity from the pipe 32 to the reforming reactor 2 (normally) (Corresponding to the reflux ratio in the distillation operation) is a low value of about 1 to 5 and is not a problem. However, in the case where the gas product obtained in the present invention is used in a cold region, the accuracy of distillation separation is increased, the content of pentane or butane having a boiling point near room temperature is decreased, and the gas product is It is preferable to prevent the condensation of the water. In such a case, the number of theoretical plates is preferably about 5 to 20, and the reflux ratio is preferably about 5 to 20. In particular, pentane having a boiling point of 36 ° C. is not limited, but the content is preferably 0.1% or less from the viewpoint of preventing condensation.
In order to control the reflux ratio, a reflux ratio control mechanism, such as a flow rate adjusting valve, not shown in FIG. The multi-stage distillation column is not particularly limited, and may be a packed column or a plate column.

When the reflux is not performed, the liquid product is mainly a mixture of naphtha (C5 to C8 hydrocarbon), kerosene (C9 to C12 hydrocarbon), and light oil (C13 to C24 hydrocarbon). The distillation column 30 is operated at the same atmospheric pressure as the reforming reactor ² or a slight pressure of about several kg / cm ² , and the liquid product and the gas product are separated by the water-cooled condenser 31 installed at the top of the column. Although the distillation apparatus 3 may be operated under reduced pressure, a pressure reducing valve or the like that can be operated at about 600 ° C. must be installed between the reforming reactor 2 and the distillation apparatus 3, which complicates the apparatus. It is not preferable.

The reforming reactor 2 and the distillation column are independent facilities as in the embodiment of FIG. 2, and these may be installed in series, or the reforming reactor 2 and the distillation column may be integrated. Good. Moreover, you may make it isolate | separate a liquid product and a gaseous product by making a distillation tower into an air cooling or a water cooling type instead of providing a water cooling condenser.
FIG. 3 schematically shows another embodiment of the gasification apparatus of the present invention. A distillation unit 30a is connected to the upper part of the reforming reactor 2, and the reforming reactor 2 and the distillation tower are connected. These are integrated and correspond to a so-called reactive distillation apparatus. This embodiment is the same as the embodiment of FIG. 2 until the product vapor rising from the reforming reactor 2 enters the distillation section 30a, but the water vapor condenser 31 is different from FIG. All the components are in a so-called total reflux state in which all components are refluxed to the distillation section 30a. The liquid product condensed in the water-cooled condenser 31 is refluxed to the distillation unit 30a through the pipe 33. Further, the liquid product in the distillation section 30a flows down to the reforming reactor 2, and further reforming is performed. The advantage of this embodiment is that a flow rate adjusting valve for controlling the reflux ratio is unnecessary, and piping and a control method are simple. The gas product separated by the water-cooled condenser 31 is recovered as product gas.

  FIG. 4 schematically shows another embodiment of the gasification facility of the present invention. A distillation section 30a is connected to the upper part of the reforming reactor 2, and the reforming reactor 2 and the distillation tower are connected. Instead of providing a water-cooled condenser, the distillation tower 30a is air-cooled or water-cooled, and corresponds to a so-called internal reflux system. In this embodiment, the product vapor rising from the reforming reactor 2 enters the distillation section 30 a where it is separated into a gas product and a liquid product, and the liquid product flows down to the reforming reactor 2. Thus, further modification is performed. Only the gaseous product is discharged from the distillation tower 30a and recovered as product gas. The advantage of this embodiment is that the flow control valve for reflux ratio control is unnecessary and the apparatus is simple. However, since the distillation section 30a is directly cooled by air cooling or water cooling, the controllability of distillation separation accuracy is low. Is a drawback. In this embodiment, the distillation unit 30a is not limited to an apparatus designed and manufactured as a distillation column, and a simple pipe may be connected to the upper part of the reforming reactor 2 to form the distillation unit 30a. The length of the distillation section 30a, which is a pipe, can be calculated from the heat transfer area required for cooling by air cooling or water cooling.

The organic substance reformed product (gas product) obtained by the method of the present invention is usually a mixed gas of carbon monoxide and light hydrocarbons of about C1 to C4, and is suitable as a gaseous fuel.
The LHV in the gaseous product is about 6-10 Mcal / Nm ^3, which is comparable to natural gas. Nevertheless, since the carbon monoxide concentration is high, it is characterized by higher combustibility than natural gas. Because of its high carbon monoxide concentration and high combustibility, it is safer to use it as a city gas alternative fuel in factories with metallurgical furnaces such as steelworks than to supply it as household city gas. preferable. Further, the gas product can be used as a reducing agent for a blast furnace, not as a fuel.
That is, as a method for operating a steel mill, the gas product obtained by the method of the present invention can be used as a fuel or / and a reducing agent in the steel mill.

In addition, from the point mentioned above, if the mixed gas of the composition equivalent to the mixed gas (g) obtained by this invention is used, an organic substance can be decomposed | disassembled efficiently and a molecular weight can be reduced. In particular, water vapor concentration: 20-70 vol%, hydrogen concentration: 10-40 vol%, carbon dioxide concentration: 10-40 vol%, more preferably water vapor concentration: 25-65 vol%, hydrogen concentration: 15-35 vol%, carbon dioxide concentration: By using a mixed gas of 15 to 35 vol%, the decomposition rate of the organic substance can be sufficiently increased, and the LHV of the gas product can be increased. In addition, it does not prevent that other gas components (for example, nitrogen etc.) are contained in this mixed gas.
The reason for limiting the gas composition is the same as the reason for limitation in the method of the present invention described above. In order to obtain a mixed gas having such a composition other than the method of the present invention, for example, one or more of water vapor, hydrogen, and carbon dioxide gas is added to the base gas.
The conditions for modifying (decreasing the molecular weight) of the organic substance by the mixed gas are the same as the conditions for modifying (decreasing the molecular weight) in the method of the present invention described above.

Therefore, the gist of the method is as follows [i] to [iii], and examples of the present invention described later are also examples of the following methods [i] to [iii].
[I] The organic material is modified by bringing a mixed gas having a water vapor concentration of 20 to 70 vol%, a hydrogen concentration of 10 to 40 vol%, and a carbon dioxide gas concentration of 10 to 40 vol% into contact with the organic material in the reforming reactor. To produce a low molecular weight product, and the product vapor from the reforming reactor is distilled to separate the gas product and the liquid product. A method for gasifying an organic substance, wherein the product is refluxed to the reforming reactor.
[Ii] In the method of [i] above, the mixed gas is an organic substance gas having a water vapor concentration of 25 to 65 vol%, a hydrogen concentration of 15 to 35 vol%, and a carbon dioxide concentration of 15 to 35 vol%. Method.
[Iii] In the method of [i] or [ii] above, the organic substance to be modified is at least one selected from waste plastic, oil-containing sludge, waste oil, and biomass. Gasification method.

・ Invention Example 1
A branch pipe is provided in the gas discharge pipe of the gas holder for temporarily storing the converter gas, and a part of the converter gas can be extracted through the branch pipe. Downstream of this branch pipe is a flow control valve, steam mixer, preheater (for converter gas and steam mixed gas), shift reactor (cylindrical vertical type), reforming reactor (externally heated rotary kiln), A simple distillation column with a water-cooled condenser at the top was placed in this order. In addition, a liquid reflux pipe from the water-cooled condenser to the reforming reactor was provided, and a branch pipe from the liquid reflux pipe to the single distillation column was provided. On the inlet side of the reforming reactor, a screw conveyor type waste plastic quantitative charging device was installed. A sampling port and a flow meter were installed in the outlet piping of the shift reactor and the outlet piping of the gas after cooling of the gas cooler. The entire single distillation column was air-cooled.

The average composition of the converter gas in the gas _{holder, H 2: 12vol%, CO} : 54vol%, CO 2: 17vol%, H 2 O: 1vol%, N 2: was 16 vol%. The converter gas 74 nm ³ / h, a steam pressure 10 kg / cm ² G and 100 Nm ³ / h supplied as steam against a steam mixer, after raising the temperature to 320 ° C. in the preheater, the shift reactor (Fe- (Cr-based high temperature shift catalyst filling). Due to the shift reaction in the shift reactor, gas having a gas composition of H ₂ : 26 vol%, CO: ₂ vol%, CO ₂ : 28 vol%, H ₂ O: 37 vol%, N ₂ : 7 vol% (shift reaction product gas) Obtained. This shift reaction product gas had a flow rate of 172 Nm ³ / h (170 kg / h in mass flow rate) and a reactor outlet gas temperature of 430 ° C.

The externally heated rotary kiln, which is a reforming reactor, is preheated to 500 ° C. in advance, and 880 kg of polyethylene that has been crushed into granules as a model material of waste plastic is introduced into this reforming reactor while introducing a shift reaction product gas. / H, and the temperature was raised to 800 ° C., which is the planned reaction temperature. After reaching 800 ° C., the entire amount of liquid product separated from the gaseous product with a water-cooled condenser is refluxed to a single distillation column through a branch pipe, and the waste plastic is reformed for another hour. After the continuation, the gas product separated by the water-cooled condenser was analyzed to determine the production amount, composition, LHV, and the gasification rate of polyethylene. The results are shown in Table 1. According to this, it is clear that a high gasification rate can be achieved without reducing the LHV of the gaseous product.
The gasification rate is the ratio of the production amount (kg / h) of the gas product to the total amount (kg / h) of the supplied shift reaction product gas and polyethylene, and the definition of the gas product is from H _2. Up to C4.

Comparative example 1
Except for bypassing the water-cooled condenser and the simple distillation tower and modifying the polyethylene without refluxing the liquid product to the reforming reactor, the experiment was carried out in the same manner as in Invention Example 1, and the gas product was analyzed and produced. While calculating | requiring the quantity, a composition, and LHV, the gasification rate of polyethylene was calculated | required. The results are shown in Table 1.
As shown in Table 1, in the example of the present invention, the gasification rate of the organic substance can be greatly improved by refluxing the liquid product to the reforming reactor as compared with the comparative example.

Inventive examples 2 to 10
In the same equipment as Example 1, except that the steam flow supplied to the shift reactor was changed variously, and the reforming reaction temperature of polyethylene was set at two levels of 800 ° C and 500 ° C, the same as in Example 1 Then, experiments were conducted on the shift reaction of the converter gas and the reforming reaction of polyethylene using the shift reaction product gas. The results are shown in Table 2.

In order to investigate the influence of the shift reaction product gas composition on the reforming reaction of polyethylene, a polyethylene reforming test was conducted under the same conditions as in Invention Examples 2 to 10 except that the liquid product was not refluxed to the reforming reactor. . The results are shown in FIGS.
FIG. 5 shows the relationship between the water vapor concentration of the shift reaction product gas and the gasification rate and liquefaction rate in the reforming of polyethylene (reaction temperature: 800 ° C.). As described above, the gasification rate is the ratio of the production amount (kg / h) of the gas product to the total amount (kg / h) of the supplied shift reaction product gas and polyethylene, and the definition of the gas product Is from H ₂ to C 4 as shown in Table 1. Similarly, the liquefaction rate is a ratio of the production amount (kg / h) of the liquid product to the total amount (kg / h) of the supplied shift reaction product gas and polyethylene, and the definition of the liquid product is shown in Table 1. As shown, it was from C5 to C24. FIG. 6 shows the relationship between the water vapor concentration of the shift reaction product gas and the LHV of the gas product and liquid product obtained by the modification of polyethylene (reaction temperature: 800 ° C.). Here, the LHV of the liquid product was expressed as LHV per volume in the standard state in terms of gas of the liquid product. FIG. 7 shows the relationship between the water vapor concentration of the shift reaction product gas and the polyethylene decomposition rate due to the modification of polyethylene. In particular, it shows that the polyethylene decomposition rates are equivalent at reaction temperatures of 500 ° C. and 800 ° C. It is a thing. FIG. 8 shows the relationship between the carbon dioxide concentration of the shift reaction product gas and the hydrogen concentration of the gas product obtained by the reforming of polyethylene (reaction temperature: 800 ° C.). FIG. 9 shows the relationship between the hydrogen concentration of the shift reaction product gas and the carbon dioxide concentration of the gas product obtained by the reforming of polyethylene (reaction temperature: 500 ° C.).

-Invention Example 11
Blast furnace gas was used as an exhaust gas generated from a metallurgical furnace containing carbon monoxide. The composition of the blast furnace gas after desulfurization / drying treatment was H ₂ : 3 vol%, CO: 23 vol%, CO ₂ : 21 vol%, N ₂ : 53 vol%, so that nitrogen separation was performed by the PSA method described below, Increased concentration of carbon monoxide.
In nitrogen separation by the PSA method, the above blast furnace gas was supplied at 136 Nm ³ / h at normal pressure to an adsorption tower packed with 400 kg of Cu ⁺ supported activated carbon as an adsorbent. Desorption is performed at 7 kPa (absolute pressure), and the composition of the desorption gas (= blast furnace gas enriched with carbon monoxide) is H ₂ : <1 vol%, CO: 47 vol%, CO ₂ : 37 vol%, N ₂ : 16 vol%, The flow rate was 58 Nm ³ / h. The carbon monoxide and steam 73 nm ³ / h a pressure 10 kg / cm ² G was supplied to the steam mixer as blast furnace gas 58 nm ³ / h and steam were concentrated and subjected to a shift reaction in the same manner as in Invention Example 1. As a result, a gas (shift reaction product gas) having a gas composition of H ₂ : 19 vol%, CO: ₂ vol%, CO ₂ : 35 vol%, H ₂ O: 37 vol%, and N ₂ : 7 vol% was obtained.

This shift reaction product gas had a flow rate of 130 Nm ³ / h (146 kg / h in mass flow rate) and a reactor outlet gas temperature of 430 ° C. A polyethylene reforming reaction was performed in the total reflux state in the same manner as in Invention Example 1 except that this shift reaction product gas was used and the reforming reaction temperature was 600 ° C. The reaction results are 550 kg / h of gas product, 54% gasification rate, LHV 7.5 Mcal / Nm ³ of gas product, and the reaction proceeds with high efficiency even from blast furnace gas enriched with carbon monoxide. Was confirmed. Moreover, since the LHV of the blast furnace gas is 770 kcal / Nm ³ , it was possible to obtain a gas with 9 times or more combustion heat.

Comparative example 2
In order to examine the reforming reaction efficiency of polyethylene with a gas having a low water vapor and hydrogen concentration, H ₂ : 1 vol%, CO: 61 vol%, CO ₂ : 19 vol%, H ₂ O: 1 vol%, N ₂ : 18 vol% A standard gas of composition was made, and a polyethylene reforming reaction experiment was conducted with this gas. As a result, even at a temperature of 800 ° C., the polyethylene degradation rate was only 16%, the gasification rate was 10%, and the liquefaction rate was only 5%.

DESCRIPTION OF SYMBOLS 1 Shift reactor 2 Reforming reactor 3 Distillation equipment 30 Distillation tower 30a Distillation part 31 Water-cooled condenser 32 Piping 320 Branching piping 33 Piping

Claims (7)

By adding excess water vapor to the exhaust gas (g ₀ ) containing carbon monoxide generated in the metallurgical furnace to cause the shift reaction, hydrogen and carbon dioxide generated by the shift reaction were not consumed in the shift reaction. A mixed gas (g) containing water vapor is brought into contact with the organic substance in the reforming reactor to produce a product having a reduced molecular weight by modifying the organic substance. The product vapor from the reforming reactor is distilled to separate the gas product and the liquid product, the gas product is recovered, and the liquid product is refluxed to the reforming reactor. Gasification method for organic substances. The exhaust gas (g ₀ ) is an exhaust gas whose carbon monoxide concentration is increased by separating at least a part of nitrogen from exhaust gas containing carbon monoxide and nitrogen generated in a metallurgical furnace. The gasification method of the organic substance as described in 2.   The method for gasifying an organic substance according to claim 1 or 2, wherein the mixed gas (g) has a water vapor concentration of 5 to 70 vol%.   The method for gasifying an organic substance according to claim 3, wherein the mixed gas (g) has a water vapor concentration of 20 to 70 vol%, a hydrogen concentration of 10 to 40 vol%, and a carbon dioxide concentration of 10 to 40 vol%. .   The method for gasifying an organic substance according to any one of claims 1 to 4, wherein the organic substance to be reformed is at least one selected from waste plastic, oil-containing sludge, waste oil, and biomass. A shift reactor (1) for adding an excess water vapor to an exhaust gas (g ₀ ) containing carbon monoxide generated in a metallurgical furnace to cause a shift reaction, and hydrogen produced in the shift reactor (1) A reforming reactor (2) for reforming by contacting a mixed gas (g) containing carbon dioxide gas and water vapor not consumed in the shift reaction with an organic substance, and leaving the reforming reactor (2) A gasification device for an organic substance, comprising a distillation device (3) for separating the vapor of the product into a gas product and a liquid product and refluxing the liquid product to the reforming reactor (2) .   A method for operating a steel mill, wherein the gas product obtained by the gasification method according to any one of claims 1 to 5 is used as a fuel or / and a reducing agent in the steel mill.

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