JP2004051855A - Porous inorganic particle for gasification of organic matter and gasification method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of gasification of organic matters in which troubles in the gasification system of organic matters are easily removed; a long stable operation is possible without troubles in repeatedly usable porous inorganic particles and in a reaction furnace for subjecting organic matters to pyrolysis gasification or steam gasification at a low temperature using the particles; and heat energy from the operation can be efficiently used. <P>SOLUTION: The porous inorganic particles for gasification are porous inorganic particles used in a gasification reaction system of organic matters, which support fine particles of transition metal oxides on the surface or in the pores thereof. The method of gasification of organic matters comprises gasifying the organic matters in a low-temperature reaction furnace for performing pyrolysis gasification or steam gasification in the presence of porous inorganic particles supporting the fine particles, transporting the porous inorganic particles which have adsorbed produced tar and char and support reduced metal oxides to a combustion furnace, introducing a combustion exhaust into the combustion furnace to fire therein the tar and char adsorbed in the porous inorganic particles, transporting metal oxide-supporting porous inorganic particles obtained to the reaction furnace and reusing them for adsorbing the produced tar and char. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gasification reaction for producing a fuel gas by gasifying organic wastes such as coal, heavy hydrocarbons, household waste, plastics, biomass (wood, vegetation, sludge, etc.) and industrial waste. The present invention relates to a porous inorganic particle used and a method for gasifying an organic substance using the same.
[0002]
[Prior art]
In general, in a pyrolysis gasification reaction using organic matter as a raw material such as gasification of organic waste such as biomass and plastics, combustible solid organic matter such as tar components and char generated in the reaction process are generated in various parts of the reaction process. It is known that they are gradually accumulated in the vehicle and become a factor that hinders smooth driving. Above all, when organic matter is gasified at a low temperature, tar and the like are usually significantly generated, and operation troubles accompanying the generation of the tar are further increased.
[0003]
Conventionally, in the case of low-temperature gasification of organic substances, a large amount of a catalyst containing a metal such as calcium is introduced due to the slow reaction rate of decomposition gasification.However, a large amount of tar is generated in this method, and this causes a reaction in the reaction process. Troubles such as clogging and inactivation of the catalyst, which made operation difficult, often occurred. To cope with this problem, it is conceivable to adsorb the tar component generated using an inorganic porous material such as zeolite.However, even if the trouble caused by tar can be avoided, the porous material alone cannot Can only be adsorbed, and the gasification reaction at a low temperature cannot be sufficiently advanced. Further, although the combustion exhaust gas has a high temperature but a low oxygen concentration, it is not sufficiently used for combustion or the like, and the thermal energy of the exhaust gas is not effectively used.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above situation in the related art. That is, an object of the present invention is to provide porous inorganic particles that can easily remove troubles in an organic gasification system and that can be repeatedly used.
Another object of the present invention is to avoid the trouble of a gasification reactor for gasifying organic matter at a low temperature, to operate stably for a long period of time, and to efficiently use the heat energy of the operating operation. It is to provide an optimization method.
[0005]
[Means for Solving the Problems]
The porous inorganic particles for gasification of an organic substance of the present invention are used for a thermal decomposition gasification reaction system or a steam gasification reaction system of an organic substance, and a transition metal oxide on the surface and inner pores of the porous body. It is characterized by carrying fine particles.
In addition, the method for pyrolysis gasification or steam gasification of organic matter according to the present invention is characterized in that the organic matter is cooled to a low temperature in a gasification reaction furnace in the presence of porous inorganic particles carrying fine particles of transition metal oxide on the surface and inner hole. In the presence of water vapor, a hydrogen gas is produced by causing a shift reaction with the generated carbon monoxide, and hydrogen is obtained by a decomposition reaction of water with a reduced metal or metal carbide. And further adsorb the tar and char generated in the reaction process, transfer the porous inorganic particles carrying the reduced metal fine particles to a combustion furnace, and then introduce the combustion exhaust gas to form the porous inorganic particles. The tar and char adsorbed on the surface are burned in a combustion furnace, and the obtained porous inorganic particles supporting the metal oxide are transferred to the reaction furnace, and the generated tar and char are regenerated. And it is characterized in that used for adsorption.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention relates to a gasification process for reusing gaseous substances obtained by thermally decomposing or reacting organic substances such as organic wastes and waste plastics discharged from waste treatment facilities and factories with steam as fuel gas. The operation of a gasification furnace by generating tar and the like generated during the operation of a pyrolysis gas furnace or a steam gasification furnace, utilizing the oxidation-reduction of the metal supported on the inorganic porous body and the adsorption capacity of the porous body In addition to efficiently avoiding troubles, it is intended to save energy by effectively using waste heat energy.
[0007]
In the present invention, as the porous inorganic material, porous particles having a high porosity and an average particle diameter of 50 to 400 μm, which are made of silica, silica-alumina, titania, zirconia, alumina or the like, are used. Further, the transition metal oxide supported on the porous inorganic particles is an oxide of a metal that is oxidized and reduced, and is reduced to a metal atom in the presence of an organic substance heated to 600 ° C. or lower, and Any metal element that can be oxidized into a metal oxide in the presence of an oxidizing agent can be used, and examples thereof include nickel, iron, copper, and calcium. The metal or metal oxide is preferably used as ultrafine particles having an average particle size of 0.05 to 0.5 μm.
[0008]
In the pyrolysis gasification method of the present invention, in the gasification furnace, in the presence of the porous inorganic particles supporting the metal oxide described above, municipal waste, organic raw materials such as industrial waste, oxidizing agents such as air, steam, A diluent or the like is introduced as necessary, and organic substances are thermally decomposed and gasified under a relatively low temperature condition of 600 ° C. or lower, preferably 400 to 600 ° C., more preferably 450 to 550 ° C. In this gasification reaction, gaseous substances such as hydrogen, carbon monoxide, and carbon dioxide, tar and char are generated, and the generated tar is adsorbed on the surfaces and pores of the porous inorganic particles. At that time, the metal oxide supported on the porous inorganic particles can be reduced by the carbon fraction in the gasification reaction furnace to become metal atoms, thereby promoting decomposition gasification.
Moreover, in the steam gasification method, the obtained carbon monoxide further reacts with steam to generate carbon dioxide and hydrogen, so that the carbon conversion rate as a whole is more than three times that of pyrolysis. Become.
[0009]
Next, the porous inorganic particles that sufficiently adsorb the tar component and carry the metal are sent to the combustion furnace. In this combustion furnace, exhaust gas, air and the like discharged from a turbine exhaust gas and the like are introduced, and the tar component is burned by burning at a temperature of 700 ° C. or more, and at the same time, the metal supported on the porous inorganic particles is oxidized. To form a metal oxide. In this combustion, since the gas is completely burned with a low-concentration oxygen gas having an oxygen concentration of about 5 to 12%, the exhaust gas after the combustion can be reused. This means that the flue gas has a low oxygen concentration but a high temperature and can be reused directly for combustion, reducing the amount of air used as an oxidizing agent for combustion, preventing heat loss due to preheating and conserving energy. It is shown that it is.
[0010]
Next, by feeding the metal oxide-supported porous inorganic particles obtained in the combustion furnace to the gasification reaction furnace, it can be used again to promote the thermal decomposition gasification by adsorbing the tar component and reducing the metal oxide. . This operation can be performed repeatedly.
At that time, by introducing the metal oxide-supporting porous inorganic particles into the reaction furnace in an overheated state, the oxygen atoms concentrated by the metal oxide and the sensible heat transport by the porous inorganic particles are possible, so that energy can be effectively used. Can be used.
[0011]
Further, the present invention will be further described with reference to the drawings.
FIG. 1 is a conceptual diagram for explaining a main part of the pyrolysis gasification system of the present invention. In FIG. 1, 1 is a combustion furnace, 2 is a solid-gas separator, 3 is a gasification furnace, 4 is a high temperature combustion exhaust gas or air, etc., 5 is an exhaust gas from the combustion furnace, 6 is an organic material, 7 is steam or an inert gas. A gas, 8 is a gas generated by the gasification reaction (CO, CO ₂ , H ₂ , CH _4, etc.), 9 is metal oxide particles (MO), and 10 is metal particles (M). Reference numeral 11 denotes a metal carbide (MC), which is obtained by reducing a metal oxide to a metal and then bonding to carbon. Reference numeral 12 denotes a carbide adsorbed (precipitated) on a metal or a carrier. In this system, MO becomes M or MC in the gasification furnace 3, while metal becomes metal oxide in the combustion furnace.
[0012]
2 and 3 show a cross-sectional structure of an example of the porous inorganic particles for gasification of the present invention. FIG. 2 shows that the metal oxide is present on the surface and in the pores of the porous inorganic particles (carrier). FIG. 3 is a schematic structural view of the supported porous inorganic particles for gasification, and FIG. 3 is a schematic structural view showing a state of the particles in a gasification furnace. 2 and 3, A is porous particles, B is metal fine particles, C is metal oxide fine particles, D is metal carbide, and E is precipitated carbon.
FIG. 4 is a graph showing the relationship between the production amounts of various gas components and the gasification time observed during pyrolysis of polyethylene (PE) at a gasification reactor temperature of 500 ° C. It can be seen that despite the reactor temperature of 470 ° C., hydrogen and carbon dioxide are being produced.
[0013]
FIG. 5 shows that carbon deposited when a gas having an oxygen concentration of 5% and a nitrogen concentration of 95% was flowed while heating the deposited carbon deposited on the carrier by the thermal decomposition of PE from around 470 ° C. to 700 ° C. 2 shows a production curve of carbon monoxide and a change in temperature. Since the supply of oxygen is started at the moment when the temperature is increased, carbon dioxide starts to be generated even at 470 to 480 ° C., and it can be seen that the combustion reaction is occurring. During the temperature rise, the carbon dioxide generation rate once decreases at around 500 ° C., but once it exceeds 500 ° C., the generation rate starts to increase again. Thereafter, the rate of carbon dioxide generation decreases rapidly, which is considered to be because all carbon near the surface has disappeared and carbon in the pores has begun to burn. In any case, even if the temperature is not 700 ° C, most of the carbides burn smoothly even at a low oxygen concentration due to the heat generated by the oxidation reaction of Ni, and the combustion exhaust gas discharged from other equipment is directly used in this process. It was found that it could be used for combustion of coal.
FIG. 6 shows the change over time of the composition of the product gas when 7.5 g of polyethylene (PE) was charged into the metal oxide-supported carrier of the present invention at a temperature of 570 ° C. in 15 divided portions and used for the thermal decomposition reaction. It can be seen that almost 100% of the hydrogen atoms of PE are generated.
[0014]
FIG. 7 shows the time course of the product gas composition when 2.5 g of polyethylene (PE) was charged into the metal oxide-carrying support of the present invention at 570 ° C. at 2.5 g in five batches and further used for steam gasification. It is a graph showing a change, and it can be seen that almost 100% of hydrogen is generated when it is assumed that the water gasification reaction and the shift reaction have progressed in addition to the hydrogen of PE. However, in general, the water gasification reaction does not occur under this temperature condition, so that CO is generated from the metal oxide and hydrogen is generated by the shift reaction, and the case of metal carbide or reduced metal generated simultaneously with CO generation. It is presumed that hydrogen was generated by water splitting.
[0015]
FIG. 8 shows changes in the accumulated product gas amount and the composition with time. Of the three bar graphs, the measured values are on the left, and all hydrogen in polyethylene is converted to hydrogen in the center, and 1 mole of hydrogen is generated when 1 mole of CO is generated by the reforming reaction and ₂ moles of hydrogen is generated when 1 mole of CO ₂ is generated. This shows the configuration of the hydrogen source when it is assumed. The rightmost bar graph assumes that CO is generated by partial oxidation with NiO, and the relationship is such that if one mole of CO ₂ is generated, one mole of hydrogen is generated. From FIG. 8, it can be seen that hydrogen is generated in an amount equal to or greater than the amount of hydrogen generated only on the basis of CO and CO _2. It is guessed that sometimes the central part is hydrogen generated by the reaction of the part remaining as metal with water vapor.
[0016]
FIG. 9 shows the composition of the gas generated between 16 minutes and 32 minutes, 32 minutes and 45 minutes, and 45 and 60 minutes after the first sample was charged. It is considered that the amount of hydrogen generated from CO and CO ₂ decreases with time, and the amount of hydrogen from an oxide having a large number of carbon atoms increases. In particular, in the period of 45 to 60 minutes, this hydrogen is very large, and it can be said that there is a high possibility that hydrogen is generated by the reaction between the metal portion remaining unoxidized near the particle center and water vapor.
[0017]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
Example 1
100 g of porous silica gel (trade name: MS-GEL) having an average particle size of about 300 μm is immersed in an aqueous solution of nickel nitrate, and the dried product is baked in the air to produce nickel oxide ultrafine particles having an average particle size of 300 nm on the surface. And porous silica gel (Ni / SiO ₂ ratio = 31% by weight) attached to the inner hole.
Next, 12 g of the obtained porous silica gel was introduced into a small glass reactor, and the inside of the reactor was replaced with nitrogen gas to form a nitrogen atmosphere. Then, nitrogen was charged at 0.5 l / min.
At about 570 ° C., 0.5 g of plastics containing polyethylene and polypropylene (PP) as main components were added and reacted for 0.1 hour. As a result, a fuel containing carbon monoxide, hydrogen and carbon dioxide as main components was obtained. A gas for synthesis was generated, and 0.3 g of the tar-like substance generated in the reactor was adsorbed on the porous silica gel.
If steam is introduced instead of nitrogen, a fuel / synthesis gas with a higher hydrogen concentration will be generated, and in addition to the hydrogen brought in by the plastics, hydrogen generated by the water gasification reaction and the shift reaction will be generated. Occurrence was confirmed.
This indicates that the selective partial oxidation by the metal oxide accelerates the shift reaction, and at the same time, the decomposition of water by the metallic nickel or nickel carbide is progressing. At this time, the nickel oxide supported on the porous silica gel is reduced to metallic nickel.
Next, after sending the obtained porous silica gel to a combustion furnace, exhaust gas having a low oxygen concentration (about 5 to 12%) in a high temperature state (about 600 ° C.) exhausted from a turbine is introduced into the combustion furnace, When a combustion reaction was performed at about 600 ° C. for 0.1 hour, the tar-like substance adsorbed on the porous silica gel was completely burned, and mainly carbon monoxide and carbon dioxide were generated. The nickel metal adhered to the porous silica gel in the combustion furnace has been oxidized to nickel oxide.
Next, the porous silica gel to which the nickel oxide was attached was again introduced into a small-sized reactor, and was repeatedly used for a gasification reaction of plastics.
[0018]
【The invention's effect】
Since the porous inorganic particles of the present invention carry the metal or metal oxide fine particles on the surface and in the pores of the porous carrier, even if they are repeatedly used for pyrolysis gasification of organic substances, the metal due to repeated oxidation and reduction can be obtained. It can be used for a long period of time because loss of the compound is prevented and activity is maintained.
ADVANTAGE OF THE INVENTION According to this invention, since the tar component in the gasification furnace generate | occur | produced by low-temperature gasification of organic waste can be efficiently removed, the tar trouble of a pyrolysis gasification system can be reduced. This means that the gasification of organic waste can be performed at a low temperature of 500 ° C. or less using medium-temperature waste heat, thereby converting medium-temperature waste heat to useful fuel. By doing so, it can be used for power generation or the like according to demand, and can easily respond to fluctuations in demand. In addition, since intermediate-temperature waste heat, which has hardly been used in the past, can be used for gasification and combustion, it contributes to energy saving.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for explaining a main part in a pyrolysis gasification system of the present invention.
FIG. 2 is a schematic structural diagram of a carrier supporting metal or metal oxide fine particles used in the present invention.
FIG. 3 is a schematic structural diagram showing a state in a gasification furnace of a carrier supporting fine particles of metal or metal oxide used in the present invention.
FIG. 4 is a graph showing a temporal change of hydrogen and carbon dioxide concentrations when a gas is generated using the pyrolysis gasification furnace of the present invention.
FIG. 5 is a graph showing the relationship between products and combustion time when polyethylene is burned at a low temperature with a low-concentration oxygen-containing gas.
FIG. 6 is a graph showing a change over time of hydrogen generated by a pyrolysis gasification reaction of polyethylene using the metal oxide-supported carrier of the present invention.
FIG. 7 is a graph showing a change over time of hydrogen generated by a steam gasification reaction of polyethylene using the metal oxide-supported carrier of the present invention.
FIG. 8 is a graph for estimating the cause of the generation of hydrogen generated by the steam gasification reaction of polyethylene using the metal oxide-supported support of the present invention.
FIG. 9 is a graph summarized with time for estimating the cause of the generation of hydrogen generated by the steam gasification reaction of polyethylene using the metal oxide-supported carrier of the present invention.

Claims (3)

Porous inorganic particles for use in a gasification reaction system for organic substances, characterized in that fine particles of a transition metal oxide are supported on the surface and inner pores of the porous inorganic particles. particle. Organic substances were gasified in a low-temperature pyrolysis gasification reactor in the presence of porous inorganic particles carrying fine particles of transition metal oxide on the surface and inner pores, and the generated tar and char were adsorbed and reduced. The porous inorganic particles carrying the metal fine particles are transferred to a combustion furnace, and then, the combustion exhaust gas is introduced, and tar and char adsorbed on the porous inorganic particles are burned in the combustion furnace, and the obtained metal oxide is removed. A method for thermally decomposing and gasifying an organic substance, wherein the supported porous inorganic substance particles are transferred to the reaction furnace, and are used again for adsorbing the generated tar and char. Organic substances are gasified in a low-temperature steam gasification reactor in the presence of porous inorganic particles carrying fine particles of transition metal oxides on the surface and inner pores, adsorb the generated tar and char, and reduce the reduced metal. The porous inorganic particles carrying the fine particles are transferred to a combustion furnace, and then, the combustion exhaust gas is introduced, and tar and char adsorbed on the porous inorganic particles are burned in the combustion furnace, and the obtained metal oxide is carried. A method for gasifying an organic matter by steam, wherein the porous inorganic matter particles are transferred to the reaction furnace and used for adsorbing tar and char generated again.

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