JP2010077219A - Method for reforming tar-containing gas - Google Patents

Abstract

The present invention relates to a crude gas which is generated when a carbonaceous raw material such as coal or biomass is pyrolyzed and contains tar and at a high concentration of hydrogen sulfide in the presence of a catalyst. An object of the present invention is to provide a method for reforming a tar-containing gas which is converted into a hydrocarbon.
By using a metal oxide having nickel, magnesium, cerium, or aluminum as a constituent element as a catalyst, the catalyst contains a high concentration of hydrogen sulfide and a large amount of tar mainly composed of condensed polycyclic aromatic hydrocarbons. Even if the gas is reformed, it is difficult for the catalyst to undergo a decrease in activity or carbon deposition due to sulfur poisoning, so that tar in the crude gas can be stably reformed with little deterioration over time.
In addition, the catalyst is regenerated by contacting at least one of water vapor or air even if the catalyst performance deteriorates due to carbon deposition or sulfur poisoning after reforming the tar-containing gas (crude gas) for a long time. By doing so, stable operation is possible for a long time.
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Description

  The present invention is a method for reforming a high-temperature tar-containing gas generated when a carbonaceous raw material is pyrolyzed, and a reforming catalyst that converts it into a gas centered on hydrogen, carbon monoxide, and methane, The present invention relates to a method for reforming a tar-containing gas using the catalyst, and a regeneration method when a reforming catalyst for the tar-containing gas is deteriorated.

  The steel industry is an energy-intensive industry that accounts for about 10% of Japan's total energy consumption, but about 40% of the blast furnace integrated steelmaking process is unused waste heat. Among them, there is sensible heat of high-temperature unrefined COG (coke oven gas, hereinafter referred to as crude COG) generated from a coke oven as a heat source that is easily recovered but has not been used conventionally. As a technique for recovering sensible heat of the crude COG, methods mainly using indirect heat recovery have been proposed in Patent Documents 1 and 2, and are transmitted inside the coke oven ascending pipe or between the ascending pipe part and the collecting pipe part. A method of recovering sensible heat by providing a heat tube and circulating a heat medium inside the heat transfer tube is disclosed. However, in these methods, tar, light oil, etc. accompanying the generated COG on the outer surface of the heat transfer tube, and densification due to carbonization / aggregation progress, and the problems of deterioration in heat transfer efficiency and heat exchange efficiency over time are inevitable. . As a technology to solve these problems, a catalyst such as crystalline aluminosilicate or crystalline silica is applied to the outer surface of the heat transfer tube, and deposits such as tar are decomposed into low molecular weight hydrocarbons via the catalyst, thereby improving heat transfer efficiency. Patent Document 3 discloses a method for stably maintaining the above. However, this method also does not leave the area of indirect heat recovery technology for crude COG sensible heat, and whether or not the decomposition products of heavy hydrocarbons such as tar become light hydrocarbons that are easy to use as gas fuel etc. Not considered. Furthermore, the influence of deterioration over time of the decomposition activity due to catalyst-toxic sulfur compounds such as high-concentration hydrogen sulfide contained in the crude COG has not been studied.

  There is almost no technology that uses sensible heat for reactive gas generated at high temperature to introduce chemical reaction directly into chemical energy in the presence of a catalyst to convert it to chemical energy. Conventionally, sensible heat of high temperature gas is indirectly recovered. In most cases, the cooled gas is used after being subjected to various treatments. However, even though crude COG has sensible heat, the content of sulfur compounds exceeds 2000 ppm, and it is considered extremely difficult to realize from the viewpoint of catalytic reaction design for the decomposition of heavy hydrocarbons such as tar. In the past, studies were made as described in Patent Document 6, but the reforming activity was not always sufficient. In addition, since energy conversion catalysts are susceptible to sulfur poisoning and carbon deposition, they produce catalysts suitable for the decomposition reaction of tars mainly composed of condensed polycyclic aromatic compounds that tend to cause carbon deposition in an atmosphere containing the above high-concentration sulfur compounds. It was difficult to do. In addition, once the reaction has progressed and the performance has deteriorated, air combustion for regeneration can easily cause sintering of the supported metal particles, which makes it difficult to reproduce the activity by regeneration.

  On the other hand, as a reforming catalyst for methane generally used as a raw material for reforming hydrocarbons, many studies have been made for a long time. For example, as a partial oxidation catalyst for methane, as described in Non-Patent Document 1, nickel, As a catalyst produced from a magnesium / aluminum solution via a precipitate, and a reforming catalyst using water vapor of methane or carbon dioxide, an oxide composed of nickel, magnesium and calcium is used as disclosed in Patent Document 7. A catalyst in which at least one of a group 3B element, a group 4A element, a group 6B element, a group 7B element, a group 1A element, and a lanthanoid element is mixed has been studied. In addition, as a steam reforming catalyst with lower hydrocarbons mainly composed of methane, as disclosed in Patent Document 8, magnesium, aluminum, nickel are used as constituent elements, and alkali metals, alkaline earth metals, Zn, Co, Ce are used. Catalysts containing one or more elements selected from Cr, Fe, and La are being studied. Also, as in Non-Patent Document 2, magnesia and Ni supported catalysts for ceria zirconia compounds as well as Ni supported catalysts for ceria, zirconia, and ceria zirconia compounds are studied for tri reforming reaction of methane with carbon dioxide, steam and oxygen. Has been. On the other hand, as a catalyst that contains sulfur in raw materials such as city gas, isooctane, kerosene, and propane and generates hydrogen for fuel cells from relatively lower hydrocarbons, a porous carrier composed of aluminum and magnesium as in Patent Document 9 In addition, oxides of at least one element selected from silicon, zirconium, cerium, titanium, aluminum, yttrium, scandium, Group 1A elements, Group 2A elements have been studied, and propane, butane, city gas, etc. As a catalyst for producing hydrogen from lower hydrocarbons, a catalyst containing magnesium, aluminum and nickel as constituent elements and containing silicon as disclosed in Patent Document 10 has been proposed and disclosed. However, the hydrocarbons that are the targets of these catalysts are all low-chain hydrocarbons that are easily decomposed, and the sulfur content that can be a catalyst poison contained in the raw material is at most 50 ppm as shown in Patent Document 9. These known catalysts have not been studied at all for reforming heavy hydrocarbons such as tar in a gas atmosphere containing a high concentration of sulfur in the tar-containing gas in these known catalysts. It was.

Furthermore, due to the recent global warming problem, the use of biomass, which is one of the carbonaceous raw materials, has attracted attention as an effective means of reducing carbon dioxide emissions, and research on high-efficiency energy conversion of biomass is being conducted in various places. . In addition, from the viewpoint of securing energy resources in recent years, research on effective utilization of coal, which has been vigorously performed in the past, has been reviewed for practical use. Among them, the method of gasifying tar produced by biomass distillation to produce crude gas (unrefined gas) and utilizing its sensible heat is mainly about catalytic reforming of tar using a catalyst. Various studies have been made including Patent Document 11, Patent Document 12, and the like. However, noble metals are used, which is expensive and has a short catalyst life.
Japanese Patent Publication No.59-44346 JP 58-76487 Japanese Patent Laid-Open No. 8-134456 USP-5516359 Publication JP 2000-54852 JP JP 2003-55671 A Japanese Unexamined Patent Publication No. 2000-469 JP 2006-61760 A Japanese Unexamined Patent Publication No. 2007-313496 JP 2008-18414 A JP 2005-53972 A JP 2007-229548 F. Basile et al., Stud. Surf. Sci. Catal., Vol. 119 (1998) C. Song et al., Catalysis Today, Vol. 98 (2004)

  The present invention is a crude gas that is generated when carbonaceous raw materials such as coal and biomass are pyrolyzed, contains tars composed of heavy chain hydrocarbons, condensed polycyclic aromatic hydrocarbons and the like and contains hydrogen sulfide at a high concentration. It is an object of the present invention to provide a method for reforming a tar-containing gas that can be converted into a light chemical substance such as methane, carbon monoxide, and hydrogen with high performance and stability in the presence of a catalyst.

  The present inventors made contact with a catalyst in a crude gas containing hydrogen sulfide at a high concentration with respect to a tar-containing gas (crude gas) containing hydrogen sulfide at a high concentration generated when pyrolyzing coal or biomass. In addition, the inventors studied diligently how to convert tar in crude gas into light chemicals such as methane, carbon monoxide, and hydrogen. As a result, by using a metal oxide whose constituent elements are nickel, magnesium, cerium, and aluminum as a catalyst, the catalyst contains a high concentration of hydrogen sulfide and a large amount of tar containing a condensed polycyclic aromatic hydrocarbon. Even if the gas is reformed, the catalyst is unlikely to have a decrease in activity or carbon deposition due to sulfur poisoning. Therefore, tar in the crude gas can be stably reformed with little deterioration over time, and methane and carbon monoxide. The inventors have found that they can be converted into light chemical substances such as hydrogen, and have made the invention.

  Further, as a result of further intensive studies by the inventors, the catalyst has been subjected to reforming of the tar-containing gas for a long time, and even if the catalyst performance deteriorates due to carbon deposition or sulfur poisoning, at least either water vapor or air is required. It can be regenerated by contacting the catalyst, and the regenerated catalyst has been found to retain the performance before deterioration, and reforming the tar-containing gas that enables stable operation over a longer period of time. It came to do the method.

  The characteristics are shown below.

(1) A method for reforming a tar-containing gas using a metal oxide as a tar reforming catalyst, wherein the metal constituting the metal oxide catalyst contains nickel, magnesium, cerium, and aluminum, and the metal In the presence of an oxide or in the presence of the metal oxide after reduction, the tar-containing gas generated when pyrolyzing the carbonaceous raw material is contacted with hydrogen, carbon dioxide, and water vapor to contact the tar. A method for reforming a tar-containing gas, wherein the tar in the gas is reformed and gasified. Also,

(2) The tar-containing gas generated when pyrolyzed is brought into contact with at least one of hydrogen, carbon dioxide, and water vapor from outside to reform and gasify the tar-containing gas. (1) The method for reforming a tar-containing gas according to (1). Also,

(3) The method for reforming a tar-containing gas according to (1) or (2), wherein the tar-containing gas is a tar-containing gas containing hydrogen sulfide. Also,

(4) The method for reforming a tar-containing gas according to (3), wherein the tar-containing gas is a coke oven gas discharged from a coke oven. Also,

(5) After carrying out the method for reforming a tar-containing gas according to any one of (1) to (4), the catalyst whose performance has deteriorated due to at least one of carbon deposition and sulfur poisoning, steam, or air A method for reforming a tar-containing gas, wherein the catalyst is regenerated by contacting at least one of the above and used again as the catalyst for tar reforming.

  According to the present invention, tar-containing gas (crude gas) generated when coal or biomass is pyrolyzed can be stably converted into light chemical substances such as methane, carbon monoxide, and hydrogen. In particular, even if the tar-containing gas contains a high concentration of hydrogen sulfide in the tar-containing gas, it is brought into contact with the catalyst as it is without desulfurization to reform the tar in the crude gas, thereby producing methane and monoxide. It can be stably converted into light chemicals such as carbon and hydrogen.

  For example, a biomass chemical distillation gas containing about several tens of ppm to 2,000 ppm of hydrogen sulfide and a tar-containing gas such as crude COG can be converted into a light chemical by a reforming reaction with high efficiency and stability by the catalyst of the present invention. Can be converted.

  Further, according to one aspect of the present invention, after reforming the tar-containing gas, the catalyst is regenerated by bringing at least one of water vapor and air into contact with the catalyst after the reaction, and the regenerated catalyst is tar again. It can be used for reforming the contained gas, and stable operation is possible for a long time while suppressing deterioration of catalyst performance.

Hereinafter, the present invention will be described in more detail with reference to specific examples.
The tar reforming catalyst used in the tar-containing gas reforming method of the present invention is a metal oxide catalyst containing nickel, magnesium, cerium, and aluminum as constituent metals.

  Among these, nickel functions as a main active component that causes a reforming reaction to proceed with water vapor, hydrogen, and carbon dioxide, which are heavy hydrocarbons present in the gas or introduced from the outside. Even when high-concentration hydrogen sulfide coexists in the tar-containing gas, the nickel metal is finely dispersed in clusters on the catalyst surface to increase the surface area, and the active metal particles are poisoned during the reaction in a reducing atmosphere. However, since new active metal particles are finely precipitated from the matrix (solid solution phase with magnesia), it is considered that the active metal particles are hardly affected by the decrease in activity due to sulfur poisoning. From this matrix compound, active metal particles can be precipitated in a fine cluster under a reducing atmosphere. In addition, the condensed polycyclic aromatic-based tar is also highly reactive at high temperatures immediately after dry distillation, and is highly efficient by contacting finely dispersed highly active nickel metal having a high specific surface area. It is thought to be converted to light hydrocarbons and decomposed. In addition, since the precipitated nickel is firmly bonded to the matrix compound, it is considered that the aggregation (sintering) between the nickel particles is suppressed, and the catalytic activity is hardly lowered even during a long-time reaction. .

  Of the components compounded with nickel element, magnesia is a basic oxide and reacts with hydrocarbon-derived precipitated carbon on the main active component element by possessing the function of adsorbing carbon dioxide. In order to exert the role of oxidizing and removing as carbon monoxide, it seems that the catalyst surface can be kept clean and the catalyst performance can be stably maintained for a long time.

  Cerium is not dissolved in the nickel-magnesium solid solution oxide, but exists as cerium oxide in the vicinity of the nickel-magnesium surface, and exhibits an oxygen absorption / release function even in a tar-containing gas atmosphere, thereby oxidizing the nickel-magnesium solid solution. It is presumed to play a role of reducing nickel from the product and precipitating more nickel metal particles.

  Alumina not only acts as a support as a reaction field, but also partially precipitates on the surface from each crystal phase by reacting with a nickel magnesium compound and finely dividing the oxide crystal phase containing nickel and magnesium. Therefore, it is presumed that the active species nickel is in a highly dispersed state, in particular, the unevenly distributed portion of nickel that is likely to be the starting point of carbon deposition is not easily formed, and the function of exhibiting high carbon deposition properties is also achieved.

  The carbonaceous raw material referred to in the present invention is a raw material containing carbon that is thermally decomposed to generate tar, and refers to a wide range of materials including carbon in constituent elements such as coal and biomass and plastic containers and packaging. Biomass can be reused as woody biomass such as forest land residues, thinned wood, unused trees, lumber residue, construction waste, or secondary products such as wood chips and pellets, and recycled paper. Paper biomass such as waste paper that has been lost, herbaceous biomass such as weeds harvested in parks, rivers, and roads including Sasa and Susuki, food waste biomass such as straw, agriculture such as rice straw, wheat straw, rice husk It refers to residues, sugar resources such as sugar cane, starch resources such as corn, resource crops such as oil and fats such as rapeseed, sludge, livestock excrement, etc.

  Tar generated when pyrolyzing a carbonaceous raw material differs in properties depending on the raw material to be pyrolyzed, but it is an organic compound that is liquid at room temperature and contains 5 or more carbons. This refers to a mixture composed of aromatic hydrocarbons, etc., if coal pyrolysis, for example, condensed polycyclic aromatics such as naphthalene, phenanthrene, pyrene, anthracene, etc. are the main components, and if pyrolysis of wood waste For example, benzene, toluene, naphthalene, indene, anthracene, phenol, etc., if it is a thermal decomposition of food waste, for example, in addition to the above, hetero compounds containing different elements such as nitrogen in 6-membered or 5-membered rings such as indole and pyrrole Is also included, but is not particularly limited thereto. Pyrolysis tar exists in a gaseous state at a high temperature immediately after pyrolysis.

  As a pyrolysis method for carbonaceous raw materials, a coke oven is generally used when coal is used as a raw material, and an externally heated rotary kiln, moving bed furnace, fluidized bed furnace, etc. are used when biomass is used as a raw material. However, the present invention is not limited to these.

  The tar reforming reaction, which gasifies by catalytic cracking of tar, is a reaction that converts heavy hydrocarbon-based tar into light chemicals such as methane, carbon monoxide, and hydrogen, but the reaction route is complex. Although not necessarily clear, a hydrogenation reaction, a steam reforming reaction, a dry reforming reaction, or the like that can occur in a tar-containing gas or with hydrogen, water vapor, carbon dioxide, oxygen, or the like introduced from the outside can be considered. These series of reactions are endothermic, so when applied to an actual machine, the gas with high sensible heat entering the reactor is reformed in the catalyst layer and the temperature drops at the outlet, but tar and the like are more efficient. When reforming heavy hydrocarbon components, air or oxygen is introduced into the catalyst layer as necessary, so that the temperature of the catalyst layer is controlled to some extent by the heat of combustion that partially burns hydrogen and hydrocarbon components. It is also possible to proceed with the reforming reaction while maintaining it.

Next, a method for producing the tar reforming catalyst of the present invention will be described.
For example, there is a method in which a solution containing a nickel compound, a magnesium compound, and a cerium compound is supported on a powder or molded alumina carrier, and each compound is applied to the carrier surface by an incipient wetness method, an evaporation to dryness method, or the like. It can be prepared by a conventional impregnation method. The method for supporting each element may be a simultaneous impregnation method in which a solution containing all the elements is supported at once, or after impregnating a solution containing a part of each compound, A sequential impregnation method in which the solution containing the compound is impregnated once or plural times may be used.

  The catalyst precursor thus prepared is dried at 50 to 150 ° C. to remove water or the organic solvent. At that time, when an organic solvent is used, it is desirable to recover and reuse the organic solvent from the economical aspect. Subsequently, it can prepare by baking the obtained catalyst precursor dried product. The final calcination temperature is preferably appropriately determined in consideration of the thermal decomposition temperature and speed of each compound, the strength of the molded body, and the like. However, the tar reforming catalyst of the present invention is not limited to this production method.

  By using the tar reforming catalyst produced by the above method, it contains a large amount of hydrogen sulfide generated when the carbonaceous raw material is pyrolyzed, and is a condensed polycyclic aromatic-based tar-containing gas that easily causes carbon deposition. Even so, it exhibits high carbon precipitation resistance, and reforms the accompanying heavy hydrocarbons such as tar with high efficiency, and is stable to light chemicals mainly composed of hydrogen, carbon monoxide, and methane with little deterioration over time. Can be converted to

  In the tar reforming method of the present invention, the reforming reaction proceeds stably even in an atmosphere containing hydrogen sulfide. However, the lower the hydrogen sulfide concentration in the gas, the less poisonous it is, and a concentration of 4000 ppm or less is preferable. preferable. Further, a concentration of 3000 ppm or less is more preferable.

  Furthermore, the tar reforming catalyst used in the tar reforming method of the present invention preferably has a nickel content of 1 to 50% by mass as the main active component. If it is less than 1% by mass, the nickel reforming performance is not sufficiently exhibited, which is not preferable. When the content exceeds 50% by mass, the content of magnesium and aluminum forming the matrix is small, so the concentration of nickel metal deposited on the catalyst is high and it is easy to coarsen. There is a fear.

  The magnesium content is preferably 1 to 45% by mass. If the amount is less than 1% by mass, the property of the basic oxide of magnesia is utilized to suppress carbon deposition of hydrocarbons, and the catalyst performance tends to be difficult to maintain stably for a long period of time. If it exceeds 45% by mass, the content of other nickel and aluminum decreases, so that there is a possibility that the catalyst's reforming activity cannot be fully exhibited. Furthermore, the magnesium content is more preferably 4 to 45% by mass. If it is less than 4% by mass, the nickel concentration in the solid solution of magnesium and nickel becomes high, so the nickel particles precipitated from the solid solution phase are likely to become coarse, and the amount of carbon deposited on the catalyst after the reforming reaction of the tar-containing gas is large. 4% by mass or more is more preferable because it tends to be likely to occur.

  Moreover, it is preferable that content of cerium is 1-40 mass%. If it is less than 1% by mass, nickel precipitation from nickel magnesia due to the oxygen storage ability of cerium oxide tends to hardly occur. If it exceeds 40% by mass, the ratio of nickel, which is the main active component, and magnesia that suppresses carbon deposition will be low, and there is a possibility that the catalyst's reforming activity cannot be fully exhibited.

  Furthermore, the alumina content is preferably 20 to 80% by mass. If it is less than 20% by mass, it becomes a ceramic mainly composed of nickel magnesia, and the strength tends to be remarkably lowered when it is molded, so 20% by mass or more is preferable. If it exceeds 80% by mass, the ratio of nickel, which is the main active component, and magnesia that suppresses carbon deposition will be low, and there is a possibility that the reforming activity of the catalyst cannot be fully exhibited. The reforming catalyst of the present invention has a nickel content of 1 to 35 mass%, a magnesium content of 6 to 35 mass%, a cerium content of 3 to 30 mass%, and an alumina content of 20 to 80 mass%. It is more preferable to manufacture so that it becomes.

  In addition, it is preferable to appropriately adjust the pore volume and the pore diameter of the alumina carrier in consideration of the surface area and the strength, and particularly the shape and the like in the case of a molded body. In order to adjust the content of each metal species to be in the above range, each starting material is preferably prepared in advance by calculation. In addition, once the catalyst has the target component composition, it may be prepared by blending at that time thereafter.

  Further, in addition to the above elements, inevitable impurities mixed in the catalyst manufacturing process and the like and other components that do not change the catalyst performance may be included, but it is desirable that impurities are not mixed as much as possible.

  Note that a method called a scanning high frequency inductively coupled plasma method (ICP) was used as a method for measuring the content of each metal species constituting the reforming catalyst. Specifically, after pulverizing the sample, an alkali melting agent (for example, sodium carbonate, sodium borate, etc.) is added and heated and melted in a platinum crucible. After cooling, the whole amount is dissolved in a hydrochloric acid solution under heating. When the solution is injected into the ICP analyzer, the sample solution is atomized and thermally excited in the high-temperature plasma state in the device, and when this returns to the ground state, an emission spectrum with a wavelength unique to the element is generated. In addition, the element type and amount can be qualitatively and quantitatively determined from the strength.

  Here, the reforming catalyst of the present invention may be in the form of a powder or a molded body. In the case of a molded body, a spherical shape, a cylindrical shape, a ring shape, a wheel shape, a granular shape, and a metal or ceramic honeycomb. Any of those obtained by coating a catalyst substrate with a catalyst component may be used.

  Next, the tar reforming method using the catalyst of the present invention is a method for producing hydrogen in a tar-containing gas generated when a carbonaceous raw material is pyrolyzed in the presence of the above-described tar reforming catalyst or in the presence of a catalyst after reduction. , Carbon dioxide and water vapor are brought into contact with each other to reform and gasify the tar in the tar-containing gas.

  Further, by adding at least one of the hydrogen, carbon dioxide, and water vapor to the tar-containing gas generated when the carbonaceous raw material is thermally decomposed in the presence of the tar reforming catalyst or in the presence of the catalyst after the reduction, The tar in the gas is reformed and gasified.

  Here, the tar reforming reaction in which tar is gasified by catalytic reforming has a complicated reaction path and is not always clear. However, the tar reforming reaction is represented by, for example, Formula 1 between the tar-containing gas and hydrogen introduced from the outside. It is considered that the conversion reaction to light hydrocarbons such as methane proceeds by hydrogenolysis of the condensed polycyclic aromatic, which is the main component in tar, as shown in Formula 1 Write down). Further, between the tar-containing gas and carbon dioxide introduced from the outside, hydrogen and monoxide by dry reforming with the condensed polycyclic aromatic carbon dioxide, which is the main component in the tar, as represented by Formula 2. Conversion to carbon proceeds. Furthermore, steam reforming and water gas shift reaction as represented by Formula 3 proceed in the tar-containing gas or with water vapor introduced from the outside.

C _n H _m + (2n-m / 2) H ₂ → nCH ₄ (Formula 1)
C _n H _m + nCO ₂ → 2nCO + m / 2H ₂ (Formula 2)
C _n H _m + 2nH ₂ O → nCO ₂ + (m / 2 + 2n) H ₂ (Formula 3)

  Therefore, when producing high calorie gas such as methane, it is desirable to add hydrogen from the outside. Further, when producing hydrogen or carbon monoxide, it is desirable to add carbon dioxide from the outside. Furthermore, when producing more hydrogen, it is desirable to add water vapor from the outside.

  Here, the tar reforming catalyst is preferably reduced. However, the reduction does not have to be performed because the reduction proceeds during the reaction. However, particularly when the tar reforming catalyst requires a reduction treatment before the reaction, the reduction condition is that the active metal nickel particles are precipitated in the form of fine clusters from the catalyst of the present invention. In addition, there is no particular limitation as long as it is a reducing atmosphere, but for example, in a gas atmosphere containing at least one of hydrogen, carbon monoxide, and methane, or in a gas atmosphere in which water vapor is mixed with these reducing gases. Alternatively, an atmosphere in which an inert gas such as nitrogen is mixed with these gases may be used. The reduction temperature is preferably 500 ° C. to 1000 ° C., for example, and the reduction time depends on the amount of catalyst to be charged. For example, 30 minutes to 4 hours is suitable, but it is necessary to reduce the entire packed catalyst. As long as the time is long, it is not particularly limited to this condition.

  As the catalyst reactor, a fixed bed type, a fluidized bed type, a moving bed type or the like is suitably used, and the inlet temperature of the catalyst layer is preferably 500 to 1000 ° C. When the inlet temperature of the catalyst layer is less than 500 ° C., the catalytic activity for reforming tar into light hydrocarbons mainly composed of hydrogen, carbon monoxide, and methane is hardly exhibited, which is not preferable. On the other hand, when the inlet temperature of the catalyst layer exceeds 1000 ° C., the reformer becomes expensive because it requires a heat-resistant structure, which is economically disadvantageous. The inlet temperature of the catalyst layer is more preferably 550 to 1000 ° C. It is possible to proceed the reaction at a relatively high temperature when the carbonaceous raw material is coal, and at a relatively low temperature when it is a biomass such as woody waste, papermaking waste or food waste.

  Here, even if the tar-containing gas generated by pyrolyzing or partially oxidizing the carbonaceous raw material is a tar-containing gas having a very high hydrogen sulfide concentration such as a high-temperature coke oven gas discharged from the coke oven, The tar in the gas can be reformed and gasified. Here, the thermal decomposition or partial oxidation specifically refers to dry distillation or production of a tar-containing gas by oxidizing only a part of a carbonaceous raw material for gasification. In the current coke oven, coke is produced by heating and dry distillation after filling the raw material coal into the furnace. As shown in FIG. 1, the coke oven gas generated is connected to the riser 1 at the top of the furnace. Aqueous water 2 (ammonia water) is sprayed from the part called and cooled, and then collected in a dry main 4 which is an air collecting tube. However, although the gas component has a sensible heat of about 800 ° C in the riser 1 of the coke oven 3, it is rapidly cooled to 100 ° C or less after spraying with aqueous water 2 to effectively use the sensible heat. If this gas sensible heat can be used effectively and heavy hydrocarbon components such as tar can be converted into fuel components such as hydrogen and light hydrocarbons such as methane, it will not only lead to energy amplification but also be generated there. If the process of producing reduced iron by applying it to iron ore becomes possible, for example, if the volume of reducing gas produced is greatly amplified, carbon dioxide emissions generated in the blast furnace process that currently reduces iron ore with coke Can be significantly reduced.

  On the other hand, the tar reforming catalyst incorporated in the catalytic reactor is obtained by carbon deposited on the catalyst surface during conversion from tar to light chemicals mainly composed of hydrogen, carbon monoxide, and methane, or obtained in the thermal decomposition step. The sulfur component contained in the generated pyrolysis gas is adsorbed on the catalyst, so that the performance of the catalyst deteriorates. Therefore, as a method of regenerating a deteriorated catalyst, water vapor is introduced into the catalytic reactor, and carbon on the catalyst surface is removed by the reaction of water vapor and carbon, or sulfur adsorbed on the catalyst is removed by the reaction of water vapor and sulfur. Thus, the catalyst can be regenerated. Also, by introducing some or all of the water vapor into air, carbon on the catalyst surface is removed by the combustion reaction of oxygen and carbon in the air, or sulfur adsorbed on the catalyst is removed by the reaction of oxygen and sulfur. Thus, it is possible to regenerate the catalyst. The entire amount of the regenerated catalyst can be reused, or a part of the regenerated catalyst can be replaced with a new catalyst.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
Ce (NH ₄ ) ₂ .6H ₂ O, Mg (NO ₃ ), which is a precursor of cerium oxide, magnesium oxide, and nickel, to alumina (surface area: 143 m ² / g) pre-fired at 1200 ° C. for 3 hours _{2 · 6H 2 O, Ni (} NO 3) after the impregnation of 2 · 6H ₂ O aqueous solution containing, dried over 12 hours at 110 ° C., calcined at a catalyst preparation method of performing over the next 3 hours at 500 ° C., nickel A modification in which the mass ratio is 12 mass%, the cerium mass ratio is 12 mass% (cerium oxide mass ratio is 15 mass%), the magnesium mass ratio is 1 mass% (magnesium oxide mass ratio is 2 mass%), and the balance is alumina. A catalyst was obtained.

  Using 1 g of this reforming catalyst, cedar flour (about 0.2 mm, C: 51.1%, H: 5.9%, O: 42.5%, N) as biomass in a fixed bed reactor : 0.1%, ash content: 0.3%).

Cedar flour was continuously supplied from the top of the fixed bed reactor using N ₂ as a carrier gas. The reaction temperature was controlled by a thermocouple attached to the reactor outer wall. The flow rate of the produced gas was measured with a soap film flow meter, and the gas composition was analyzed using a gas chromatograph. Of _{H 2} at Shimadzu CG-14B gas chromatograph using TCD (molecular sieve 13X), the other products analyzed using FID (gas chromatography pack 54), the recording integrator (Shimadzu Chromatopack CR-5A) I went there.

The reactor used was a dual bed system in which the reforming catalyst and char (deposited solid carbon component) were stored separately. As an advantage of the dual bed system, char and ash generated during biomass gasification are not brought into direct contact with the catalyst, so that the catalyst life can be extended. In addition, the composition of the product gas can be made more useful by not gasifying the char, which is almost only CO ₂ even when burned. A dewar with ice was installed downstream of the reactor to trap steam and tar.

The test conditions are as follows. Reforming catalyst amount: 1 g, Cedar powder supply rate: 60 mg / min (C: 2191 μmol / min, H: 3543 μmol / min, O: 1475 μmol / min), carrier gas N ₂ : 60 cc / min, H ₂ O /C=0.5 (H ₂ O: 1110 μmol / min), reaction time: 15 minutes, hydrogen reduction: 500 ° C., 30 minutes.

The performance of the reforming catalyst was judged by the tar decomposition rate (Tar-conv.%), The H ₂ production rate of the outlet gas, and the hydrogen composition in the outlet gas, and these were calculated by the following formula. The production rate, gas composition, and inlet Tar amount of the biomass gasification gas generated under the test conditions are as shown in Table 1, and the concentration of hydrogen sulfide contained in the gas was about 20 ppm.

C-conv. % = (CO + CO ₂ + CH ₄ production rate) / (total C atomic weight of supplied biomass) × 100
coke% = (C atomic weight in coke) / (total C atomic weight of supplied biomass) × 100
char% = (C atomic weight in char) / (total C atomic weight of supplied biomass) × 100
tar% = (100− (C−conv.%) − (char%) − (coke%))
Inlet Tar amount ( μmol · min ⁻¹ ) = Inlet tar% × (Total C supply rate of supplied biomass)
Outlet Tar amount ( μmol · min ⁻¹ ) = Outlet tar% × (Total C supply rate of supplied biomass)
Tar-conv. % = (1− (Outlet Tar amount) / (Inlet Tar amount)) × 100
The coke is carbon deposited on the surface of the reforming catalyst, and char is a fixed carbon content generated by pyrolysis of biomass and remaining without being gasified.

Moreover, the measuring method of C atomic weight in coke and C atomic weight in char is as follows.
(C atomic weight in coke)
1. After a 15-minute reform test, the biomass supply is stopped and N ₂ is added to the reactor to drive off the gas in the reactor.
2. O ₂ is added from the upper part of the reactor, and the amount of CO and CO ₂ generated during combustion of char generated in the reforming catalyst is measured by a gas chromatograph.
3. The amount of C atoms in the char is calculated from the CO and CO ₂ generation amounts.

(C atomic weight in char)
1. After completion of the measurement of the amount of C in the coke, the addition of O ₂ from the top of the reactor is stopped and O ₂ from the bottom of the reactor is added.
2. Similarly to the measurement of C content in coke, the amount of CO and CO ₂ generated during char combustion is measured with a gas chromatograph.
3. The amount of C atoms in the char is calculated from the CO and CO ₂ generation amounts.

In the fluidized bed reactor as described above, a reforming test was conducted for 15 minutes at 550, 600, and 650 ° C., as shown in Table 1. Results of production rate, gas composition and outlet Tar amount / cracking rate are obtained. Compared with Table 1, the tar cracking rate (Tar-conv.) Is high at any reaction temperature. Alternatively, it was confirmed that hydrogen was amplified more than the hydrogen gas composition (hydrogen gas generation rate or hydrogen gas composition) and exhibited highly active performance.

(Example 2)
The test was conducted in the same manner as in Example 1 except that 40 mg of the catalyst prepared in Example 1 was used. When the raw material of cedar powder was continuously supplied for 4 hours at a reaction temperature of 650 ° C., the reforming activity was Since it remained almost constant, it was confirmed that the stability of this catalyst was high.

(Example 3)
Using 30 cc of the catalyst prepared in Example 1, it was fixed with quartz wool so as to be located at the center of the SUS reaction tube, a thermocouple was inserted at the center position of the catalyst layer, and these fixed bed reaction tubes were set at predetermined positions. .

Before starting the reforming reaction, the reactor was first heated to 800 ° C. under a nitrogen atmosphere, and then reduced for 30 minutes while flowing hydrogen gas at 100 cc / min. After that, as simulated gas for coke oven gas, hydrogen: nitrogen = 1: 1, H ₂ S was introduced by adjusting each gas to the concentration shown in Table 2 and totaling 125 cc / min. The reaction was evaluated at each temperature shown. In addition, 1-methylnaphthalene, which is a liquid substance that is actually contained in tar and has a low viscosity at room temperature, is used as a representative substance as a simulated substance for tar generated during coal dry distillation, and it reacts at a flow rate of 0.025 g / min with a precision pump. Introduced into the tube. Moreover, pure water was introduced into the reaction tube at a flow rate of 0.1 g / min with a precision pump so that (number of moles of H ₂ O) / (number of moles of carbon of 1-methylnaphthalene) = 3. The product gas discharged from the outlet was passed through a room temperature trap and an ice temperature trap to remove naphthalene and moisture, respectively, and then injected into gas chromatography (HP 6890 manufactured by Hewlett-Packard) to perform TCD and FID analysis. The degree of reaction of the reforming reaction (decomposition rate of methylnaphthalene) was judged by methane selectivity, CO selectivity, CO ₂ selectivity, and carbon deposition rate deposited on the catalyst. They were calculated by the following formula from the concentration of each component in the outlet gas.

Methane selectivity (%) = (volume of CH ₄ ) / (C supply of methylnaphthalene supplied) x 100
CO selectivity (%) = (CO volume) / (C supply of methylnaphthalene supplied) x 100
CO ₂ selectivity (%) = (volume of CO ₂ ) / (C supply of methylnaphthalene supplied) x 100
Carbon deposition rate (%) = (precipitate carbon weight) / (C supply amount of supplied methylnaphthalene) × 100
In addition, the ratio of the outlet hydrogen gas volume to the inlet hydrogen gas volume (hydrogen amplification factor) is also shown.

As a result of No. 1 to 3 in Table 3, the decomposition rate (methane selectivity + CO selectivity + CO ₂ selectivity + carbon deposition rate) increases with increasing reaction temperature even in an atmosphere containing H ₂ S as high as 2000 ppm. ) Is improved. Thus, it can be seen that the decomposition reaction of methylnaphthalene, which is a simulated tar, is proceeding even under severe conditions where it is highly susceptible to sulfur poisoning and has high carbon deposition properties. Further, since the hydrogen amplification rate also increased with the increase in the decomposition rate of the simulated tar, it is considered that hydrogen combined with carbon constituting methylnaphthalene was converted into hydrogen molecules along with the reforming by the catalyst.

Example 4
On the alumina, the nickel mass ratio is 6 mass%, the cerium mass ratio is 13 mass% (cerium oxide mass ratio is 16 mass%), the magnesium mass ratio is 17 mass% (magnesium oxide mass ratio is 28 mass%), and the balance is alumina. A catalyst was prepared by the same preparation method as in Example 1, except that

Using this catalyst, the same evaluation method as in Example 3 was used under the conditions of No. 2 in Table 3. As a result, methane selectivity 3.0%, CO selectivity 24.3%, CO ₂ selectivity 24.8%, carbon deposition rate 8.1 %, The tar decomposition rate was 60.2%, and the hydrogen amplification rate was 1.9. From this result, it was found that the present catalyst exhibits a high tar reforming activity even under the condition that the H ₂ S concentration is 2000 ppm at 800 ° C. Moreover, when compared with the result of No. 2 in Table 3, it was found that the higher the mass ratio of magnesium oxide, the lower the carbon deposition rate.

(Example 5)
On the alumina, the nickel mass ratio is 12 mass%, the cerium mass ratio is 23 mass% (cerium oxide mass ratio is 28 mass%), the magnesium mass ratio is 6 mass% (magnesium oxide mass ratio is 10 mass%), and the balance is alumina. A catalyst was prepared by the same preparation method as in Example 1, except that

Using this catalyst, the same evaluation method as in Example 3 was used under the conditions of No. 2 in Table 3. As a result, methane selectivity 2.9%, CO selectivity 33.3%, CO ₂ selectivity 29.4%, carbon deposition rate 9.5 %, The tar decomposition rate was 75.1%, and the hydrogen amplification rate was 2.1. From this result, it was found that the present catalyst exhibits a high tar reforming activity even under the condition that the H ₂ S concentration is 2000 ppm at 800 ° C. Moreover, when compared with the results of No. 2 in Table 3, it was found that the carbon deposition rate can be kept low because the mass ratio of magnesium oxide is high despite the tar decomposition rate being the same level.

(Example 6)
After continuing the reaction for 8 hours under the conditions of No. 2 in Example 3, the charging of the raw material was stopped, and N ₂ 60cc / min as the carrier gas and H ₂ O in a gas equivalent of 60cc / min. Then, after the carbon and sulfur deposited on the catalyst were removed by keeping the catalyst layer temperature at 800 ° C. for 5 hours, the raw material charging was newly started under the same conditions as in Example 2, and more than 90% before the regeneration. It was confirmed to show activity. In addition, the hydrogen concentration in the reformed gas in this test was high, and it was confirmed that hydrogen, carbon monoxide, and methane were converted to the main gas.

(Example 7)
As in Example 4, the reaction was continued for 8 hours under the condition No. 2 of Example 3, and then the charging of the raw material was stopped. Under conditions of N ₂ 60 cc / min and air 60 cc / min as the carrier gas After removing carbon and sulfur deposited on the catalyst by keeping the catalyst layer temperature at 800 ° C. for 2 hours, and starting to supply raw materials under the same conditions as in Example 1, more than 90% of the activity before regeneration It was confirmed that In addition, the hydrogen concentration in the reformed gas in this test was high, and it was confirmed that hydrogen, carbon monoxide, and methane were converted to the main gas.

(Example 8)
A batch furnace that can simulate a coke oven is charged with 80 kg of charging coal used in the actual coke oven, heated to 800 ° C according to the actual coke oven, and the actual coke oven gas and accompanying actual tar are added. Generated. The tar in the tar-containing gas at that time was about 0.04 g / L. The gas was collected with a suction pump and used in the experiment. Molding prepared by placing a reaction tube inside an electric furnace heated to a reaction temperature of 800 ° C., and supporting each component on a ring-shaped alumina carrier so that the composition is the same as in Example 4 at the center. After installing the catalyst and reducing hydrogen at 10 NL / min for 2 hours, the catalytic cracking activity of the actual coke oven gas and associated real tar is continuously evaluated for 5 hours by flowing the gas collected from the batch furnace to the catalyst layer. did. The inlet gas flow rate was about 10 NL / min, and the catalyst charge was about 1 L. It was confirmed by gas chromatography that the inlet gas composition was almost the same as the actual coke oven gas. In addition, it was confirmed that the gas contained 2400-2500 ppm of hydrogen sulfide. The tar concentration in the gas was evaluated by the following method. That is, each gas is collected by attaching a 1 L vacuum collection bottle, which has been evacuated in advance, to an openable / closable cock attached to the inlet and outlet of the catalyst layer and opening the cock. And the inside of a collection bottle was wash | cleaned with the dichloromethane, and the mass of the liquid component after removing dichloromethane completely at normal temperature was quantified. And the tar decomposition rate was calculated | required from the ratio of the mass of the tar component in catalyst layer exit gas with respect to the mass of the tar component in catalyst layer entrance gas collected by the said method. As a result, the tar decomposition rate reached about 90% after 2 hours from the start of the reaction, and the hydrogen amplification rate reached 2.35 on average for 5 hours, compared to the coal dry distillation tar-containing gas almost the same as that discharged from the coke oven. Then, it was verified that the catalytic dry gasification reaction was in progress.

(Comparative Example 1)
In the same experimental procedure as in Example 3, the reforming test of simulated coal dry distillation tar was performed with the naphtha primary reforming catalyst (SC11NK; Ni-20 mass% supported) made by Sud Chemie, which is one of the industrial catalysts as the catalyst under the condition of No.2. As a result, the methane selectivity was 2.5%, the CO selectivity was 4.2%, the CO ₂ selectivity was 5.9%, the carbon deposition rate was 32.8%, the decomposition rate was 45.4%, and the hydrogen amplification rate was 1.3.

  Therefore, although the industrial catalyst has a very high strength, the conversion rate of methylnaphthalene into a gas component is low (12.6%), while the carbon deposition rate is very high. Because the carbon deposition rate is very high, there is a possibility that the catalyst life is short, and even if regeneration treatment is performed after the reaction, it is necessary to perform oxidation treatment at a high temperature or for a long period of time. It is expected that the catalytically active particles cause sintering due to heat, and the performance after regeneration is further lowered.

(Comparative Example 2)
In the same manner as in Example 1, except that 40 mg of a catalyst prepared by supporting nickel and cerium on an alumina support at 12% by mass and 12% by mass (the remainder being alumina) was used, the same evaluation method as in Example 1 was used. A gasification test of biomass tar was carried out at a reaction temperature of 650 ° C. for continuously supplying cedar powder as a raw material for 4 hours. As a result, after 2 hours from the start of the reaction, the reforming activity of the catalyst suddenly decreased and showed almost no activity, so the test was stopped. From this result, it was found that the stability of the catalyst was low.

It is the figure which showed the part from which coke oven gas is discharged | emitted from a coke oven.

Explanation of symbols

1 Climbing Pipe 2 Aqueous Water 3 Coke Oven 4 Dry Main

Claims (5)

A method for reforming a tar-containing gas using a metal oxide as a tar reforming catalyst,
The metal constituting the metal oxide catalyst contains nickel, magnesium, cerium, and aluminum,
In the presence of the metal oxide or in the presence of the metal oxide after reduction, hydrogen, carbon dioxide, and water vapor in the tar-containing gas generated when the carbonaceous raw material is pyrolyzed is contacted, A method for reforming a tar-containing gas, wherein the tar-containing gas is reformed and gasified.   2. The tar-containing gas generated during the thermal decomposition is brought into contact with at least one of hydrogen, carbon dioxide, and water vapor from outside to reform and gasify the tar-containing gas. The method for reforming a tar-containing gas as described.   The method for reforming a tar-containing gas according to claim 1 or 2, wherein the tar-containing gas is a tar-containing gas containing hydrogen sulfide.   The method for reforming a tar-containing gas according to claim 3, wherein the tar-containing gas is a coke oven gas discharged from a coke oven.   After carrying out the method for reforming a tar-containing gas according to any one of claims 1 to 4, the catalyst whose performance has been deteriorated by at least one of carbon deposition and sulfur poisoning, at least one of water vapor and air A method for reforming a tar-containing gas, wherein the catalyst is regenerated by contacting it and used again as the catalyst for tar reforming.

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