WO2009157434A1 - 二酸化炭素オフガスの浄化方法および浄化用燃焼触媒、並びに天然ガスの製造方法 - Google Patents
二酸化炭素オフガスの浄化方法および浄化用燃焼触媒、並びに天然ガスの製造方法 Download PDFInfo
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Definitions
- the present invention relates to a method for purifying a gas containing carbon dioxide as a main component (hereinafter referred to as “carbon dioxide off-gas”), a combustion catalyst for purification, and a method for producing natural gas. More specifically, sulfur compounds such as hydrogen sulfide (H 2 S) and mercaptans contained in carbon dioxide off-gas discharged from natural gas, oil-associated gas (hereinafter abbreviated as “natural gas”); benzene Sulfur compounds (excluding sulfur oxides) and VOCs in carbon dioxide off-gas by oxidative decomposition of volatile organic compounds (hereinafter referred to as "VOC”) such as toluene, xylene, etc.
- carbon dioxide off-gas a gas containing carbon dioxide as a main component
- natural gas oil-associated gas
- VOC volatile organic compounds
- the present invention relates to a purification method and a purification combustion catalyst for reducing the concentration of the catalyst.
- VOC is a gas in which light components such as organic solvents and petroleum products are released into the atmosphere, and is said to be a causative substance of photochemical smog and suspended particulate matter. For this reason, worldwide emission regulations have been put in place regarding VOCs.
- off-gas is generated in a natural gas refining process for removing carbon dioxide and sulfur compounds contained in natural gas, and this off-gas contains hydrogen sulfide and VOC.
- VOC combustion catalysts are marketed by many manufacturers, but impurities such as hydrogen sulfide are generated in plants such as natural gas, so the off-gas purification method using VOC combustion catalysts has increased technical hurdles. The process was not established.
- the off-gas when the off-gas is released into the atmosphere, the off-gas is burned under a high temperature condition of about 900 ° C. by direct combustion (Thermal Incinerator) and then released into the atmosphere.
- direct combustion Thermal Incinerator
- the current off-gas treatment method by direct combustion is very expensive because the off-gas generated at room temperature is heated to about 900 ° C. and then burned.
- Patent Document 1 As a purification method of exhaust gas containing VOC, a purification method by catalytic combustion of exhaust gas containing organic silicon, VOC, carbon monoxide and the like is disclosed (for example, see Patent Document 1). Conventionally, organic silicon was considered as a poison for the combustion catalyst. However, in the exhaust gas purification method of Patent Document 1, the exhaust gas containing VOC is used for a long time by using a zeolite carrying a noble metal as a combustion catalyst. It became possible to purify. By the way, in plants such as natural gas, sulfur compounds such as hydrogen sulfide can be cited as poisoning substances for combustion catalysts. However, Patent Document 1 has not studied the resistance of combustion catalysts to sulfur compounds.
- Combustion catalysts for VOC decomposition include (1) those containing calcium salt, amorphous silica and copper compound, (2) those containing amorphous silica and copper compound, (3) crystalline silica and amorphous silica Those containing at least one of calcium salt and copper oxide, and (4) those containing at least one of crystalline silica and amorphous silica and copper oxide are disclosed (for example, see Patent Document 2).
- noble metal catalysts such as platinum have been used for VOC combustion treatment, but the combustion catalysts (1) to (4) can be used at low cost and can exhibit the same combustion performance as noble metal catalysts. It became. However, even in Patent Document 2, the resistance of the combustion catalyst to the sulfur compound has not been studied.
- Acid gas separation (AGR) for removing carbon dioxide in natural gas prevents co-absorbed VOC from evaporating in the low-pressure flash drum in front of the stripping tower (regeneration tower).
- a method of selectively evaporating and removing VOC while controlling temperature and pressure is disclosed (for example, see Patent Document 5). Since the VOC removed by this method is a self-combustible fuel, it is released into the atmosphere by a direct combustion process or is effectively used as a fuel. Further, in this method, the amine absorption liquid containing carbon dioxide and sulfur compound from which most of the VOC has been removed is converted into a gas containing a small amount of VOC, carbon dioxide and sulfur compound, and the amine absorption liquid in the diffusion tower. To be separated.
- the obtained gas is either directly burned or processed in a subsequent sulfur recovery device.
- a sulfur recovery device is provided in the latter stage, if carbon dioxide and a small amount of VOC are supplied to the sulfur recovery device as they are, carbonyl sulfide (COS) and carbon disulfide (CS 2 ) are by-produced, and the Claus catalyst Cause deterioration.
- COS carbonyl sulfide
- CS 2 carbon disulfide
- the Claus catalyst Cause deterioration.
- a hydrogen sulfide concentrating device is installed in the front stage of the sulfur recovery device and a gas mainly composed of carbon dioxide containing a small amount of VOC and hydrogen sulfide discharged from the upper part of the absorption tower is released to the atmosphere, about 900 ° C. It is necessary to directly burn the gas mainly composed of carbon dioxide under the high temperature conditions.
- Patent Document 5 involves a direct combustion process in the purification of VOCs and sulfur compounds contained in the above-mentioned gas containing carbon dioxide as a main component, and therefore has a high fuel consumption and a very high process cost. there were.
- the direct combustion method Since the direct combustion method is a high-temperature treatment, it is necessary to use a heat-resistant material for the combustor and the heat exchanger, and the apparatus cost has been a problem.
- the direct combustion method has a problem of thermal NOx generated by a process involving a flame.
- flue gas In the direct combustion method with heat recovery, flue gas is circulated horizontally instead of vertically to recover heat, so the equipment occupies a large area, and there is a problem in plot layout in small plants and on-board plants. there were.
- VOC combustion catalysts are marketed by many manufacturers, they are resistant to sulfur compounds and there is no catalyst that can maintain a high purification rate of VOC and sulfur compounds for a long period of time. There was no established process.
- Objects of the present invention include the following. i) The concentration of the sulfur compound and VOC is lowered at a lower temperature than before by subjecting the carbon dioxide off-gas discharged from natural gas or the like to oxidative decomposition treatment with a combustion catalyst to the carbon dioxide off-gas containing sulfur compound and VOC. ii) A high purification rate is maintained for a long time without generating thermal NOx. iii) Reduce carbon dioxide emissions associated with large fuel consumption and lower processing costs.
- a gas mainly containing carbon dioxide containing at least VOC and a sulfur compound of 50 ppmv or more and 10,000 ppmv or less is introduced into a catalytic combustor, and the catalyst combustor uses a combustion catalyst.
- the VOC and sulfur compound of the gas mainly containing carbon dioxide are oxidatively decomposed.
- the combustion catalyst is one or more metal oxides selected from the group consisting of zirconium oxide, titanium oxide and silicon oxide, and one or more noble metals selected from the group consisting of platinum, palladium and iridium. Including.
- the concentration of sulfur compounds (excluding sulfur oxides) in the gas after oxidative decomposition treatment is 5 ppmv or less.
- the gas containing carbon dioxide as a main component may be exhausted in the purification of natural gas.
- the reaction temperature of the oxidative decomposition treatment with the combustion catalyst is preferably 250 ° C. or higher and 650 ° C. or lower.
- the pressure of the oxidative decomposition treatment with the combustion catalyst is preferably 0.01 MPa or more and 1 MPa or less. It is preferable to decompose the VOC contained in the gas containing carbon dioxide as a main component into carbon dioxide by oxidative decomposition treatment.
- the VOC preferably contains one or more selected from benzene, toluene, and xylene.
- the concentration of benzene in the gas containing carbon dioxide as a main component is 10 ppmv.
- the toluene concentration is preferably 50 ppmv or less or the xylene concentration is 50 ppmv or less.
- the catalyst combustor after preheating the gas and / or air mainly composed of carbon dioxide.
- Part or all of the preheating is selected from a heat exchanger using heat exchange with a combustion furnace, an electric line heater, a heat storage agent, and a gas mainly composed of carbon dioxide after oxidative decomposition treatment by a combustion catalyst. It is preferable to carry out by one or more means.
- the catalytic combustor includes at least two catalytic combustion regions provided with a combustion catalyst when the upper limit of the reaction temperature is exceeded due to heat generation of the oxidative decomposition treatment, and between the catalytic combustion regions, after the oxidative decomposition treatment It is preferable to supply at least one selected from a gas mainly composed of carbon dioxide, air, and water, and to cool a gas mainly composed of carbon dioxide introduced into the catalytic combustor.
- the gas mainly composed of carbon dioxide is preferably a gas discharged from an acid gas separation device that separates and recovers an acid gas in a natural gas produced from a gas field by bringing the gas into contact with a liquid solvent.
- the gas mainly composed of carbon dioxide is reduced in hydrogen sulfide by any one of a hydrogen sulfide concentrating device, a sulfur recovery device, and a tail gas processing device provided in a subsequent stage of the acidic gas separation device. The latter exhaust gas is preferred.
- the combustion catalyst charged in the catalytic combustor preferably includes a base and a catalyst layer formed on the surface of the base and made of the metal oxide and the noble metal.
- the substrate is preferably a honeycomb structure, a pellet body, or a sphere.
- the substrate is preferably made of ceramics, metal oxide, or metal alloy.
- the thickness of the catalyst layer is preferably 10 ⁇ m or more and 500 ⁇ m or less.
- the content of the noble metal is preferably 0.1 g / liter or more and 10 g / liter or less per catalyst filling volume.
- the specific surface area of the metal oxide is preferably 10 m 2 / g or more and 300 m 2 / g or less.
- the combustion catalyst for purifying carbon dioxide offgas according to the present invention is a combustion for subjecting at least a VOC and a sulfur compound contained in a gas mainly composed of carbon dioxide to an oxidative decomposition treatment at a reaction temperature of 250 ° C. or higher and 650 ° C. or lower. It is a catalyst.
- the combustion catalyst is one or more metal oxides selected from the group consisting of zirconium oxide, titanium oxide and silicon oxide, and one or more noble metals selected from the group consisting of platinum, palladium and iridium. Including.
- the combustion catalyst includes a base and a catalyst layer formed on the surface of the base and made of the metal oxide and the noble metal, and the base is a honeycomb structure, a pellet, or a sphere.
- the metal oxide is titanium oxide
- the content of the noble metal is preferably 0.1 g / liter or more and 10 g / liter or less per catalyst filling volume.
- the oxygen concentration in the gas mainly composed of carbon dioxide is preferably 1% by volume or more and 15% by volume or less.
- the combustion catalyst includes a honeycomb structure substrate having a large number of air passages, a metal oxide layer made of the metal oxide formed on the inner surface of the air passages, and at least a surface layer portion of the metal oxide layer. .1mg / cm 2 or more, and a said noble metal is deposited at a density of 10 mg / cm 2 or less, the substrate, the ceramic may be formed of a metal oxide, or a metal alloy.
- the catalytic combustor includes a container having an inlet at one end and an outlet at the other end, and a plurality of combustion catalysts disposed in the container at an interval between the inlet and the outlet.
- Each of the combustion catalyst units has a honeycomb structure base provided with a large number of air passages through which carbon dioxide off gas passes, and a metal oxide formed of the metal oxide formed on the inner surface of the air passages.
- the noble metal deposited at a density of 0.1 mg / cm 2 or more and 10 mg / cm 2 or less to at least the surface layer portion of the metal oxide layer, and the base is ceramic, metal oxide, or
- the inner diameter of the vent hole of the fuel catalyst unit that is made of a metal alloy and is close to the outlet port may be larger than the inner diameter of the fuel catalyst unit that is close to the inlet port.
- the method for producing natural gas according to the present invention includes a step of supplying raw natural gas to a slag catcher and separating the raw natural gas into a liquid phase and a vapor phase by the slag catcher, and carbon dioxide as a main component from the vapor phase. And an acid gas removing step for separating the carbon dioxide offgas containing VOC and sulfur compound, a moisture removing step for removing the condensed moisture by cooling the raw material gas after separating the carbon dioxide offgas, and after removing the moisture A heavy fraction removal step of fractionating a raw material gas by a distillation column to remove heavy hydrocarbons, and an offgas purification step of treating the carbon dioxide offgas by any of the carbon dioxide offgas purification methods described above. .
- sulfur compounds having a strong toxic and irritating odor such as hydrogen sulfide and mercaptan contained in the carbon dioxide off-gas can be purified and discharged as SOx.
- metal oxides selected from the group consisting of zirconium oxide, titanium oxide, and silicon oxide as the combustion catalyst, the combustion catalyst is deteriorated by sulfation of SOx produced by oxidative decomposition treatment. Can be reduced.
- noble metals selected from the group of platinum, palladium, and iridium as combustion catalysts, these noble metals have high oxidation activity in a low temperature range, and therefore carbon dioxide at a lower temperature than before.
- the off-gas oxidation reaction can proceed. Since metal oxides such as zirconium oxide, titanium oxide and silicon oxide have little sulfur adhesion to sulfur compounds and are not easily affected, they are stable with almost no change in form. The structure is maintained, the oxidative decomposition performance is less deteriorated with time, and the oxidative decomposition performance can be maintained over a long period of time. In addition, carbon dioxide off-gas can be oxidized and decomposed at low cost without generating thermal NOx and with low carbon dioxide emissions.
- natural gas can be produced at low cost while efficiently treating off-gas.
- 6 is a graph showing the relationship between the measured value and the calculated value of the reaction rate of the oxidation reaction of benzene by the combustion catalyst produced in Example 2. It is a graph which shows the relationship between the reaction temperature by the combustion catalyst produced in Example 2, and the conversion rate of benzene.
- the schematic shows the test apparatus used for a combustion catalyst performance test. It is a graph which shows the relationship between the elapsed time from the reaction start by the combustion catalyst produced in Example 2 and Comparative Examples 2 and 4, and the conversion rate of benzene.
- FIG. 1 is a schematic view showing an example of a carbon dioxide off-gas purification apparatus used in the first embodiment of the carbon dioxide off-gas purification method of the present invention.
- This carbon dioxide off-gas purification device (hereinafter abbreviated as “purification device”) 10 includes a heater 11 for heating a gas mainly composed of carbon dioxide (carbon dioxide off-gas) to a predetermined reaction temperature, and heating.
- a preheater 12 for preheating carbon dioxide offgas and / or air and a combustion catalyst for subjecting the carbon dioxide offgas heated by the heater 11 to oxidative decomposition treatment were provided.
- the catalyst combustor 13 and the flow paths 14 to 26 for connecting these and flowing various gases are provided.
- the heater 11 means such as a combustion furnace, an electric line heater, a heat storage agent, a heat exchanger using heat exchange with carbon dioxide off-gas after oxidative decomposition treatment by a combustion catalyst in the catalytic combustor 13 is used.
- the preheater 12 means such as a combustion furnace, an electric line heater, a heat storage agent, a heat exchanger using heat exchange with carbon dioxide off-gas after oxidative decomposition treatment by a combustion catalyst in the catalytic combustor 13 is used.
- a combustion catalyst including a base and a catalyst layer made of a metal oxide and a noble metal formed on the surface of the base is used.
- An oximeter (not shown) is provided in the middle of the flow path 25 or 26 connected to the exhaust port of the catalytic combustor 13.
- a honeycomb structure, a sphere, a pellet, or the like is used as the substrate.
- a honeycomb structure, a sphere, a pellet, or the like is used as the material of this substrate.
- substrate is not specifically limited, According to the amount of combustion catalysts required for the processing amount of one carbon dioxide off gas, it sets suitably.
- a catalyst layer made of a metal oxide and a noble metal is formed on the inner wall surface of the cell of the honeycomb structure.
- a catalyst layer made of a metal oxide and a noble metal is formed on the outer surface of the substrate.
- the number of cells is preferably 10 cpi 2 (number of cells per inch square) or more and 1000 cpi 2 or less, more preferably 100 cpi 2 or more and 500 cpi 2 or less.
- the number of cells of the honeycomb structure is less than 10 cpi 2 , the total surface area of the catalyst layers provided on the inner wall surface of the cells becomes small, and the carbon dioxide off-gas cannot be efficiently oxidized and decomposed by the combustion catalyst.
- honeycomb structure may be damaged.
- the catalytic combustor 13 has a cylindrical or rectangular tube-shaped container 212 having an inlet 214 at one end (upper end in this example) and an outlet 216 at the other end (lower end).
- the inlet 214 is connected to the flow path 24 and the outlet 216 is connected to the flow path 25.
- the upper part and the lower part of the container 212 are tapered in a tapered shape toward the inlet port 214 and the outlet port 216.
- An annular flange 218 is formed at the upper and lower ends of the container 212 so that piping connection can be made.
- a plurality of combustion catalyst units 220A to 220I are arranged in the straight body portion of the container 212 at intervals in the longitudinal direction of the container, and the off-gas introduced from the inlet 214 is the combustion catalyst units 220A to 220I. , In order, and exit from the outlet 216.
- a gap is formed between adjacent combustion catalyst units.
- the catalyst substrate is a honeycomb structure, the air gap between these units serves to rectify the gas channeling. This is because when gas is fed to the honeycomb structure, the gas cannot diffuse in the direction perpendicular to the flow, but rectification can be improved by providing a gap between the units. Moreover, you may connect the coolant supply path which is not shown in figure to each of these space
- At least one selected from gas, air, and water mainly composed of carbon dioxide after oxidative decomposition treatment is supplied, and the temperature of the downstream combustion catalyst unit is lowered, Reaction conditions may be controlled.
- This control may be feedback control by automatically opening and closing the valves of the respective coolant supply paths in accordance with the output of the temperature sensor provided downstream of the catalyst combustor 13 and controlling the supply amount of the cooling fluid. .
- Each of the combustion catalyst units 220A to 220I has a plate shape having a certain thickness, and is configured by arranging rectangular parallelepiped catalyst blocks 222 as shown in FIG. 13 in the horizontal direction without gaps. All of the catalyst blocks 222 are fixed to the inner wall of the container 212 by a support structure (not shown).
- the catalyst block 222 has a substrate composed of a square frame portion 224 and a honeycomb structure portion 226 arranged in a fine lattice pattern inside the frame portion 224.
- the honeycomb structure portion 226 in this example is a square lattice, but may be a hexagonal lattice, a triangular lattice, or a round hole.
- each lattice is a cell (air passage) that reaches a constant inner diameter from the upper end to the lower end, and off-gas flows evenly through these cells.
- the cell density is preferably in the above-mentioned range, but is not limited thereto.
- the base material may be as described above.
- the inner diameter of the air passage (cell) of the fuel catalyst unit close to the outlet 216 is made larger than the inner diameter of the fuel catalyst unit close to the inlet 214. More specifically, the cell inner diameter (flow channel cross-sectional area) increases in three stages in the order of the combustion catalyst units 220A to 220C, 220D to 220F, and 220G to 220I. As the cell inner diameter increases in this way, the flow resistance is reduced even when the offgas is heated by heat generation and the gas flow rate is accelerated in the process of the offgas flowing from the inlet 214 to the outlet 216. There is an advantage that can be suppressed.
- the off gas rises in temperature and the flow velocity increases. For this reason, when the combustion catalyst units 220A to 220I have the same cell inner diameter, the flow resistance is increased in the downstream combustion catalyst unit, and the flow resistance of the catalyst combustor 13 as a whole is increased. .
- the rate of change of the inner diameter of the cell is S2 when the cross-sectional area of the individual cells of the most upstream combustion catalyst unit 220A is S1, and the cross-sectional area of the most downstream combustion catalyst unit 220I is S2. It is preferably about 1 to 1/5 times S1. More preferably, it is 1 to 1/3 times.
- the inner diameter of the cell (flow passage cross-sectional area) is increased in three stages in the order of the combustion catalyst units 220A to 220C, 220D to 220F, and 220G to 220I.
- the total number of combustion catalyst units may be changed. In this embodiment, the number of combustion catalyst units 220 is nine, but the present invention is not limited to this. In general, the number is preferably about 1 to 30 from the viewpoint of cost.
- a metal oxide layer made of a metal oxide is formed on the surface of each combustion catalyst unit 220A to 220I including the inner surface of each cell (air passage).
- the metal oxide is zirconium oxide (ZrO 2), titanium oxide (TiO 2), one kind or two or more materials selected from the group consisting of silicon oxide (SiO 2) can be used. Particularly preferred is titanium oxide or zirconium oxide.
- a noble metal is attached to at least the surface layer portion of the metal oxide layer at a density of 0.1 mg / cm 2 or more and 10 mg / cm 2 or less.
- the noble metal is preferably one or more selected from the group consisting of platinum (Pt), palladium (Pd), and iridium (Ir). Particularly preferred is platinum (Pt).
- Pt platinum
- Pd palladium
- Ir iridium
- platinum (Pt) platinum
- a more preferable noble metal adhesion density is 0.001 mg / cm 2 or more and 0.1 mg / cm 2 or less. Within this range, the performance is further enhanced.
- Examples of combinations of noble metals and metal oxides include Pt / ZrO 2 , Pt / CeO 2 .ZrO 2 , Pt / TiO 2 , Pt / SiO 2 , Pd / ZrO 2 , Pd / CeO 2 .ZrO 2 , Pd / Examples include TiO 2 , Pd / SiO 2 , Ir / ZrO 2 , Ir / CeO 2 .ZrO 2 , Ir / TiO 2 , and Ir / SiO 2 . Particularly preferred from the viewpoint of performance and cost are (Pt / ZrO 2 , Pt / TiO 2 ).
- the thickness of the catalyst layer made of such metal oxide and noble metal is preferably 10 ⁇ m or more and 500 ⁇ m or less, more preferably 20 ⁇ m or more and 100 ⁇ m or less.
- the thickness of the catalyst layer is less than 10 ⁇ m, it is difficult to efficiently disperse the noble metal on the support. If the distribution is non-uniform, it is difficult to improve the processing efficiency of the oxidative decomposition process using the combustion catalyst.
- the thickness of the catalyst layer exceeds 500 ⁇ m, cost is increased, and the pressure loss increases because the inner diameter of the cell is reduced.
- the precious metal content (supported amount) is preferably 0.1 g / liter or more and 10 g / liter or less, more preferably 1 g / liter or more and 5 g / liter or less.
- the content of the noble metal is less than 0.1 g / liter, the catalytic activity is lowered, and it is necessary to increase the reaction temperature of the oxidative decomposition treatment of carbon dioxide off gas, resulting in an increase in the treatment cost.
- the content of the noble metal exceeds 10 g / liter, although the catalytic activity increases, the material cost increases and it is not practical.
- the noble metal does not form a dense film, but is preferably distributed on the surface and inside of the metal oxide as fine particles having a particle size of about 0.1 to 10 ⁇ m.
- the distribution of the noble metal may be attached only to the surface of the metal oxide layer, or may be distributed at a substantially uniform concentration throughout the thickness direction of the metal oxide layer, or in the thickness direction of the metal oxide layer.
- the concentration distribution may be such that the concentration is higher on the surface side, but the concentration is preferably higher on the surface side in terms of cost and reaction efficiency.
- the metal oxide preferably has an average particle size of 0.01 ⁇ m or more and 50 ⁇ m or less, more preferably 0.5 ⁇ m or more and 10 ⁇ m or less.
- the average particle diameter of the metal oxide is less than 0.01 ⁇ m, the viscosity becomes high when it is made into a slurry when coating, which is not practical.
- the average particle diameter of the metal oxide exceeds 50 ⁇ m, it is difficult to form a uniform slurry because the particles settle, and the coating layer is likely to be uneven when the slurry is supported, and the support is made of a noble metal made of a metal oxide. It becomes difficult to disperse uniformly with respect to the surface of the substrate, and the total surface area of the noble metals exposed on the surface of the support becomes small, resulting in a low catalytic activity.
- the metal oxide preferably has a BET specific surface area (hereinafter referred to as “specific surface area”) of 10 m 2 or more and 300 m 2 or less, more preferably 10 m 2 or more and 100 m 2 or less. That is, the metal oxide layer is not a dense film but is microscopically porous.
- specific surface area of the metal oxide is less than 10 m 2 , no improvement in the treatment efficiency of the oxidative decomposition treatment by the combustion catalyst is observed. Even if the specific surface area of the metal oxide exceeds 300 m 2 , the noble metal can be supported, but the specific surface area decreases due to heat resistance, water resistance, change of form due to sulfur, etc. Therefore, the catalytic activity becomes low and is not practical.
- the combustion catalyst is not limited to the honeycomb structure as described above, and pellets, spheres, or irregularly shaped particles may be packed in a column with a gap between them.
- the type, concentration, thickness, and the like of the substrate, metal oxide, and noble metal may be the same as those of the honeycomb type catalyst described above.
- the size of the catalyst particles is preferably 0.1 mm or more and 50 mm or less as an average particle diameter, and more preferably 2 mm or more and 20 mm or less.
- the average particle size is less than 0.1 mm, the contact efficiency between the carbon dioxide off-gas and the catalyst is high, but the pressure loss increases.
- the average particle diameter exceeds 50 mm the pressure loss can be kept low, but the contact efficiency between the carbon dioxide off-gas and the catalyst deteriorates and is not practical.
- a method for producing the combustion catalyst will be described.
- a metal oxide, a sol (binder) of this metal oxide, and a polar solvent are mixed with a mortar, a lye machine, a kneader or the like to prepare a metal oxide-containing slurry.
- the blending mass ratio between the metal oxide and the sol (binder) of this metal oxide is preferably in the range of 95/5 to 30/70.
- Water (pure water) is the best polar solvent, but polar organic solvents such as alcohols such as methanol, ethanol and propanol, ethers such as diethyl ether and tetrahydrofuran, esters, nitriles, amides and sulfoxides. Can also be used.
- Metal oxide-containing slurry is applied to the surface of the substrate (inner wall surface for honeycomb structure, outer surface for sphere or pellet), and excess slurry is removed by air blowing.
- the substrate coated with the metal oxide-containing slurry is dried at 100 ° C. or higher and 200 ° C. or lower for 1 hour or longer with a dryer.
- the substrate is baked in a baking furnace at 400 ° C. or more and 600 ° C. or less for 1 hour or more and 8 hours or less to form a layer made of a metal oxide on the surface of the substrate.
- an organic salt or an inorganic salt can be used as the metal oxide.
- the organic salt include acetate, acetylacetonate, and cyanate.
- the inorganic salt include nitrate and chloride. Examples thereof include salts.
- aqueous solution of a noble metal compound (noble metal compound) and a polar solvent are mixed to prepare a noble metal compound solution having a predetermined concentration.
- a noble metal compound either an organic salt or an inorganic salt can be used.
- the organic salt include acetate, acetyl acetonate, and cyan salt
- examples of the inorganic salt include nitrate and chloride. Etc. are exemplified.
- a noble metal compound solution is applied to the surface of the metal oxide layer, the layer made of the metal oxide absorbs this solution, and excess solution is removed by air blowing.
- the substrate coated with the noble metal compound solution is dried at 100 ° C. or higher and 200 ° C. or lower for 1 hour or longer with a dryer.
- This substrate is baked in a baking furnace at 400 ° C. or higher and 600 ° C. or lower for 1 hour or longer and, if necessary, reduced in a hydrogen stream at 400 ° C. or higher and 600 ° C. or lower, and the surface of the substrate is metalized.
- a combustion catalyst having a catalyst layer made of an oxide and a noble metal is obtained.
- carbon dioxide off-gas purification method using the purification apparatus 10 will be described.
- carbon dioxide off-gas is introduced into the purification device 10 through the flow path 14 and air for auxiliary combustion (hereinafter referred to as “support combustion” from the flow path 18 into the purification device 10.
- support combustion auxiliary combustion
- air Abbreviated as “air”.
- Carbon dioxide off-gas is mainly composed of carbon dioxide, hydrogen sulfide (H 2 S), mercaptan (R—SH, R is an organic group) of 50 ppmV or more and 10,000 ppmV or less, carbonyl sulfide (COS), carbon disulfide (CS 2 ). ), A gas containing at least a sulfur compound such as sulfur dioxide (SO 2 ).
- the carbon dioxide off-gas include a gas discharged by a natural gas refining process in a natural gas or petroleum-related gas plant.
- carbon dioxide off-gas includes VOCs such as benzene, toluene, and xylene, and may include carbon monoxide, methane, water, and the like.
- the VOC contained in the carbon dioxide off gas contains at least one of 50 ppmv or more and 2000 ppmv or less of benzene, 100 ppmv or more and 2000 ppmv or less of toluene, and 100 ppmv or more and 2000 ppmv or less of xylene.
- the auxiliary combustion air is used as an oxidant for the burner fuel of the heater 11 and then used as an oxidant for carbon dioxide off-gas in the catalytic combustor 13.
- the catalytic combustor 13 can be combusted with a low concentration of oxygen compared to the burner combustion conditions.
- the heater 11 since the combustion exhaust gas and the carbon dioxide off gas are mixed, the heater 11 can be used for raising the temperature of the carbon dioxide off gas without losing the amount of heat held by the combustion exhaust gas, so that the thermal efficiency is high. Therefore, the auxiliary combustion air is effectively used not only as an oxidant for carbon dioxide off-gas but also as an oxidant for the heater 11.
- the preheating of the carbon dioxide off gas in the preheater 12 reduces the energy consumption (fuel consumption) when the temperature of the carbon dioxide off gas in the heater 11 is raised to a temperature higher than the oxidation decomposition treatment temperature by the combustion catalyst in the catalytic combustor 13. To be done.
- This preheating of the auxiliary combustion air in the preheater 12 reduces the energy consumption (fuel consumption) in the heater 11 when the auxiliary combustion air is heated to a temperature higher than the oxidation decomposition treatment temperature by the combustion catalyst in the catalytic combustor 13. Done for.
- either the carbon dioxide off gas or the auxiliary combustion air is preheated to a predetermined temperature, or both the carbon dioxide off gas and the auxiliary combustion air are preheated to a predetermined temperature. May be.
- the preheater 12 may be omitted.
- the preheating temperature of carbon dioxide off gas and auxiliary combustion air in the preheater 12 is preferably 100 ° C. or higher and 400 ° C. or lower.
- the energy consumption (fuel consumption) when the temperature of the carbon dioxide off gas is raised above the oxidation decomposition treatment temperature by the combustion catalyst in the heater 11 increases. .
- part or all of the carbon dioxide off-gas and the auxiliary combustion air in the preheater 12 is performed by one or more means selected from the above means.
- a heat exchanger using heat exchange with the carbon dioxide off-gas after oxidative decomposition treatment by the combustion catalyst in the catalytic combustor 13 is used, it is not necessary to separately supply energy (heat) required for preheating. Therefore, it is excellent in thermal efficiency and processing costs can be reduced.
- the fuel gas introduced into the purification device 10 through the flow path 22 becomes combustion exhaust gas after combustion in auxiliary combustion air, and then mixed with carbon dioxide off-gas, and the mixed gas is heated. Then, the temperature is raised to the reaction temperature (250 ° C. or higher, 650 ° C. or lower) of the oxidative decomposition treatment with the combustion catalyst in the catalytic combustor 13. Specifically, the temperature of the mixed gas is preferably 350 ° C. or more and 500 ° C. or less by the heater 11.
- Fuel gas is a gas containing methane, ethane, propane, n-butane, i-butane, and the like.
- the mixed gas heated to a predetermined temperature by the heater 11 is supplied to the catalytic combustor 13 filled with the combustion catalyst, and the carbon dioxide off gas is brought into contact with the carbon dioxide off gas.
- sulfur compounds such as hydrogen sulfide, mercaptan, carbonyl sulfide, carbon disulfide, and sulfur dioxide contained in the carbon dioxide off-gas into sulfur oxide (SOx).
- SOx sulfur oxide
- VOCs such as benzene, toluene and xylene contained in carbon dioxide off-gas are converted into carbon dioxide by oxidative decomposition treatment.
- carbon monoxide is contained in the carbon dioxide off gas, the carbon monoxide is converted into carbon dioxide.
- the reaction temperature is preferably 250 ° C. or higher and 650 ° C. or lower, more preferably 350 ° C. or higher and 550 ° C. or lower.
- the reaction temperature of the oxidative decomposition treatment with the combustion catalyst is less than 250 ° C., the oxidative decomposition reaction of the sulfur compound and VOC contained in the carbon dioxide off-gas does not proceed sufficiently.
- the reaction temperature of the oxidative decomposition treatment with the combustion catalyst exceeds 650 ° C., the combustion catalyst is deteriorated by heat, and the purification rate of carbon dioxide off-gas cannot be kept high for a long time.
- the material of the catalytic combustor needs to be a heat-resistant material, which increases the material cost.
- the amount of fuel consumed for the oxidative decomposition treatment increases, the processing cost increases, and the amount of carbon dioxide emission increases. Furthermore, there is a possibility that thermal NOx is generated.
- the difference between the temperature when entering the first combustion catalyst and the temperature when leaving the last combustion catalyst is about 30 to 300 ° C., more preferably about 50 to 200 ° C. preferable. If it is too large, the passage resistance will increase, resulting in adverse effects such as changing the pressure conditions of the upstream process and having to install a vacuum pump or a high chimney in the downstream.
- the pressure of the carbon dioxide off gas (the pressure of the carbon dioxide off gas supplied to the catalytic combustor 13) is preferably 0.01 MPa or more and 1 MPa or less, and more preferably. Is 0.05 MPa or more and 0.15 MPa or less. If the pressure of the carbon dioxide off gas is 0.2 MPa or more and 1 MPa or less, the volume of the carbon dioxide off gas is reduced, the residence time in the catalytic combustor 13 is shortened, the treatment efficiency is improved, and the treated carbon dioxide off gas is reduced. Since the power can be recovered by the gas expander before being released into the atmosphere, the processing cost can be reduced.
- the pressure of the carbon dioxide off gas is appropriately adjusted according to the carbon dioxide off gas recovery device to be described later and the release (discharge) destination of the treated carbon dioxide off gas.
- the carbon dioxide off-gas recovery device is operated at a pressure as close to atmospheric pressure as possible.
- the amine solution is flashed at a high pressure of 0.5 to 1 MPa without using an amine regeneration tower, or about 180 ° C. using an amine solution with high heat resistance.
- the amine regeneration tower is operated at a high temperature of 0.5 to 1 MPa. In this case, high-pressure carbon dioxide off-gas of 0.5 to 1 MPa is generated.
- the concentration of sulfur compounds (excluding sulfur oxides) contained in the carbon dioxide off-gas becomes 5 ppmV or less by performing oxidative decomposition treatment with a combustion catalyst in the catalytic combustor 13.
- VOCs such as benzene, toluene, and xylene contained in the carbon dioxide off gas have a benzene concentration of 10 ppmV or less, a toluene concentration of 50 ppmV or less, and a xylene concentration of 50 ppmV or less by oxidative decomposition treatment.
- the amount of fuel gas input for raising the temperature to the reaction temperature of the oxidative decomposition treatment increases and the thermal efficiency deteriorates.
- Catalytic combustion so that the concentration of oxygen contained in the treated carbon dioxide off-gas measured by an oxygen concentration meter provided in the subsequent stage is 0.5 to 15% by volume, more preferably 0.5 to 5% by volume. It is preferable to control the amount of auxiliary combustion air supplied to the vessel 13.
- the treated carbon dioxide off-gas discharged from the catalyst combustor 13 is introduced into the preheater 12 through the flow path 25.
- the preheater 12 is a heat exchanger, in this heat exchanger, either carbon dioxide off-gas after processing and carbon dioxide off-gas or auxiliary combustion air before processing, or carbon dioxide off-gas and auxiliary combustion before processing. Heat exchange with both of the air is performed, and the carbon dioxide off-gas or auxiliary combustion air before treatment is preheated to a predetermined temperature.
- the treated carbon dioxide off-gas (including sulfur oxide (SOx)) that has passed through the preheater 12 is discharged from the purification device 10 through the flow path 26.
- the carbon dioxide off-gas purification method of this embodiment after removing mercury such as organic mercury, ionic mercury and elemental mercury contained in the carbon dioxide off-gas, catalytic combustion of the carbon dioxide off-gas after removing the mercury is performed. It is preferable to introduce into the vessel 13.
- the process of removing mercury contained in the carbon dioxide off gas is performed before introducing the carbon dioxide off gas into the purification device 10 or before introducing the carbon dioxide off gas into the heater 11 in the purification device 10. .
- the removal process of mercury contained in the carbon dioxide off gas is performed by an adsorption process such as activated carbon.
- mercury contained in carbon dioxide offgas is released into the atmosphere.
- this mercury can be prevented from adversely affecting the human body and ecosystem.
- the carbon dioxide off-gas treated by the carbon dioxide off-gas purification method of the present invention includes, for example, (1) acid gas separation in which acid gas in natural gas produced from a gas field is separated and recovered by contacting with a liquid solvent. Gas discharged from the apparatus, and (2) most of the hydrogen sulfide in any one of the hydrogen sulfide concentrating device, the sulfur recovery device, and the tail gas processing device provided in the subsequent stage of the acid gas separation device. Exhaust gas etc. after removing is mentioned.
- FIG. 2 is a schematic view showing a first example of a carbon dioxide off-gas recovery apparatus processed by the carbon dioxide off-gas purification method of the present invention.
- This carbon dioxide off-gas recovery device (hereinafter abbreviated as “recovery device”) 30 forms an acid gas separation device (Acid Gas Removal, AGR).
- acid Gas Removal Acid Gas Removal
- the absorption tower 31 carbon dioxide contained in natural gas is a main component, and hydrogen sulfide, trace amounts of sulfur compounds (mercaptan, carbonyl sulfide, carbon disulfide, sulfur dioxide), and VOC (benzene, toluene, xylene), etc.
- the impurity gas composed of hydrocarbons is selectively absorbed by the chemical absorption liquid or the physical absorption liquid (hereinafter collectively referred to as “absorption liquid”) in the absorption tower 31.
- the natural gas absorbed in the absorption liquid is discharged as a purified gas from the top of the absorption tower 31 via the flow path 36 and is collected in a product or another processing step.
- the absorbing solution that has absorbed the impurity gas may be extracted from the bottom of the absorption tower 31 and then supplied to the flash drum 32 via the flow path 37 after the pressure is lowered. It may be lowered.
- the flash drum 32 In the flash drum 32, light hydrocarbons are recovered through the flow path 38 as flash gas.
- the absorption liquid from which the light hydrocarbons have been removed is extracted from the bottom of the flash drum 32 and supplied to the regeneration tower 33 via the flow path 39.
- the regeneration tower 33 By heating the regeneration tower 33 to a predetermined temperature, the impurity gas is released from the absorbing liquid as carbon dioxide off gas, and the carbon dioxide off gas is supplied to the flash drum 34 via the flow path 40.
- the absorption liquid from which the carbon dioxide off-gas has been released is extracted from the bottom of the regeneration tower 33, supplied to the absorption tower 31 via the flow path 41, and reused.
- a part of the absorption liquid extracted from the bottom of the regeneration tower 33 is supplied to the regeneration tower 33 through the flow path 42 and again subjected to a treatment (heating) for releasing carbon dioxide off-gas.
- carbon dioxide off-gas is recovered as flash gas.
- the recovered carbon dioxide off-gas is discharged from the flash drum 34 via the flow path 43 and supplied to the purification device as shown in FIG.
- a very small amount of absorption liquid mixed in the carbon dioxide off gas is extracted from the bottom of the flash drum 34 and supplied to the regeneration tower 33 via the flow path 44.
- FIG. 3 is a schematic view showing a second example of the carbon dioxide off-gas recovery apparatus processed by the carbon dioxide off-gas purification method of the present invention. 3, the same components as those of the recovery apparatus shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.
- the carbon dioxide off-gas A discharged from the recovery device 30 is sulfided through the flow path 43 together with the gas from which moisture has been removed after the tail gas treatment. It supplies to the absorption tower 51 of a hydrogen concentrator (Acid Gas, Enrichment, AGE).
- an impurity gas comprising a large amount of hydrogen sulfide, a small amount of carbon dioxide, a sulfur compound (mercaptan, carbonyl sulfide, carbon disulfide), and VOC (benzene, toluene, xylene) contained in the carbon dioxide off-gas A.
- absorption liquid a chemical absorption liquid or the physical absorption liquid
- a carbon dioxide off-gas B containing a trace amount of a sulfur compound (hydrogen sulfide, mercaptan, carbonyl sulfide, carbon disulfide, sulfur dioxide), VOC, carbon monoxide and the like is discharged from the top of the absorption tower 51 through the flow path 56.
- a sulfur compound hydrogen sulfide, mercaptan, carbonyl sulfide, carbon disulfide, sulfur dioxide
- VOC carbon monoxide and the like
- the impurity gas is released from the absorption liquid as a hydrogen sulfide enriched gas, and this hydrogen sulfide enriched gas is supplied to the flash drum 53 via the flow path 58.
- the absorption liquid from which the hydrogen sulfide-concentrated gas has been released is extracted from the bottom of the regeneration tower 52, supplied to the absorption tower 51 through the flow path 59, and reused.
- a part of the absorption liquid extracted from the bottom of the regeneration tower 52 is supplied to the regeneration tower 52 via the flow path 60 and again subjected to a treatment (heating) for releasing the hydrogen sulfide-enriched gas. .
- the hydrogen sulfide concentrated gas is recovered as flash gas.
- the recovered hydrogen sulfide concentrated gas is discharged from the flash drum 53 via the flow path 61 and supplied to a sulfur recovery unit (Sulfur Recovery Unit, SRU) 54 including a combustor and a multistage Claus reactor. .
- SRU sulfur Recovery Unit
- a very small amount of absorbing liquid mixed in the hydrogen sulfide concentrated gas is extracted from the tower bottom of the flash drum 53 and supplied to the regeneration tower 52 via the flow path 62.
- a tail gas mainly composed of nitrogen containing a small amount of sulfur compound (hydrogen sulfide, carbonyl sulfide, carbon disulfide, sulfur dioxide) and carbon dioxide is discharged from the sulfur recovery device 54, and the fuel gas supplied from the flow path 64 and Auxiliary combustion air and hydrogen supplied from the flow path 65 are supplied to a tail gas treatment device (TGT) 55 including a hydrotreatment reactor via the flow path 66.
- TGT tail gas treatment device
- the tail gas processing device 55 sulfur compounds other than hydrogen sulfide (carbonyl sulfide, carbon disulfide, sulfur dioxide) are reduced to hydrogen sulfide.
- the obtained hydrogen sulfide is discharged from the tail gas processing device 55, supplied to the absorption tower 51 via the flow path 67, and recirculated. Water contained in the hydrogen sulfide discharged from the tail gas processing device 55 is discharged from a drainage channel 68 provided in the middle of the channel 67.
- FIG. 4 is a schematic view showing a third example of the carbon dioxide off-gas recovery apparatus processed by the carbon dioxide off-gas purification method of the present invention.
- the same components as those of the recovery device shown in FIGS. 2 and 3 are denoted by the same reference numerals, and the description thereof is omitted.
- the carbon dioxide off-gas A discharged from the recovery device 30 is sulfided through the flow path 43 together with the gas from which moisture has been removed after the tail gas treatment. It supplies to the absorption tower 51 of a hydrogen concentrator.
- an impurity gas comprising a large amount of hydrogen sulfide, a small amount of carbon dioxide, a sulfur compound (mercaptan, carbonyl sulfide, carbon disulfide), and VOC (benzene, toluene, xylene) contained in the carbon dioxide off-gas A.
- absorption liquid a chemical absorption liquid or the physical absorption liquid
- a carbon dioxide off-gas B containing a trace amount of a sulfur compound (hydrogen sulfide, mercaptan, carbonyl sulfide, carbon disulfide, sulfur dioxide), VOC, carbon monoxide and the like is discharged from the top of the absorption tower 51 and passed through the flow path 56. And supplied to the channel 66.
- the absorbing solution that has absorbed the impurity gas is extracted from the bottom of the absorption tower 51 and supplied to the regeneration tower 52 of the hydrogen sulfide concentrating device via the flow path 57.
- the impurity gas is released from the absorption liquid as a hydrogen sulfide enriched gas, and this hydrogen sulfide enriched gas is supplied to the flash drum 53 via the flow path 58.
- the absorption liquid from which the hydrogen sulfide-concentrated gas has been released is extracted from the bottom of the regeneration tower 52, supplied to the absorption tower 51 through the flow path 59, and reused.
- a part of the absorption liquid extracted from the bottom of the regeneration tower 52 is supplied to the regeneration tower 52 via the flow path 60 and again subjected to a treatment (heating) for releasing the hydrogen sulfide-enriched gas. .
- a part of the absorption liquid extracted from the bottom of the regeneration tower 52 is supplied to the absorption tower 71 of the tail gas processing apparatus via the flow path 74.
- the hydrogen sulfide concentrated gas is recovered as flash gas.
- the recovered hydrogen sulfide concentrated gas is discharged from the flash drum 53 via the flow path 61 and supplied to the sulfur recovery device 54.
- a very small amount of absorbing liquid mixed in the hydrogen sulfide concentrated gas is extracted from the tower bottom of the flash drum 53 and supplied to the regeneration tower 52 via the flow path 62.
- the sulfur recovery device 54 most of the sulfur content is recovered as single sulfur by the oxidative decomposition treatment of the hydrogen sulfide concentrated gas using the fuel gas and auxiliary combustion air supplied from the flow path 63 into the sulfur recovery device 54.
- a small amount of sulfur compounds (hydrogen sulfide, carbonyl sulfide, carbon disulfide, sulfur dioxide) and tail gas mainly composed of nitrogen containing carbon dioxide were discharged from the sulfur recovery device 54 and discharged from the top of the absorption tower 51.
- the carbon dioxide off gas B, the fuel gas and auxiliary combustion air supplied from the flow path 64, and the hydrogen supplied from the flow path 65 are supplied to the tail gas processing device 55 via the flow path 66.
- the tail gas processing device 55 sulfur compounds other than hydrogen sulfide (carbonyl sulfide, carbon disulfide, sulfur dioxide) contained in the tail gas and the carbon dioxide off gas B are reduced to hydrogen sulfide.
- the obtained tail gas containing hydrogen sulfide and carbon dioxide off-gas B are discharged from the tail gas processing device 55 and supplied to the absorption tower 71 of the tail gas processing device via the channel 67.
- the water contained in the tail gas and the carbon dioxide off gas B discharged from the tail gas processing device 55 is discharged from a drainage channel 68 provided in the middle of the flow path 67.
- the absorption tower 71 hydrogen sulfide contained in the tail gas and the carbon dioxide off-gas B is selectively absorbed by a chemical absorption liquid or a physical absorption liquid (hereinafter collectively referred to as “absorption liquid”) in the absorption tower 71.
- the A carbon dioxide off-gas C containing a trace amount of a sulfur compound (hydrogen sulfide, mercaptan, carbonyl sulfide, carbon disulfide, sulfur dioxide), VOC, carbon monoxide and the like is discharged from the top of the absorption tower 71 through the flow path 72. , And supplied to the purification device as shown in FIG.
- the absorption liquid that has absorbed hydrogen sulfide is extracted from the bottom of the absorption tower 71, supplied to the regeneration tower 52 via the flow path 73, and recirculated.
- sulfur compounds that are highly toxic and irritating odors such as hydrogen sulfide and mercaptan contained in carbon dioxide off-gas are purified, and sulfur oxides ( SOx) and the concentration of sulfur compounds (excluding sulfur oxides) contained in the treated carbon dioxide off-gas can be reduced to 5 ppmV or less.
- SOx sulfur oxides
- concentration of sulfur compounds (excluding sulfur oxides) contained in the treated carbon dioxide off-gas can be reduced to 5 ppmV or less.
- these noble metals By using one or more kinds of noble metals selected from the group of platinum, palladium, and iridium as combustion catalysts, these noble metals have high oxidation activity in a low temperature range, and therefore carbon dioxide at a lower temperature than before. The off-gas oxidation reaction can proceed.
- VOCs such as benzene or toluene or xylene having carcinogenicity contained in carbon dioxide off gas can be reduced to a benzene concentration of 10 ppmV or less, a toluene concentration of 50 ppmV or less, or a xylene concentration of 50 ppmV or less by oxidative decomposition treatment with a combustion catalyst.
- the influence of the VOC on the human body can be reduced.
- Photochemical smog and VOC which are the cause of suspended particulate matter, can be purified and the environmental load can be reduced.
- carbon dioxide off-gas can be oxidized and decomposed at low cost without generating thermal NOx and with low carbon dioxide emissions.
- a conventional Mn / CuO-based catalyst does not contain a noble metal and is inexpensive in price, so that the supported amount can be increased.
- this Mn / CuO-based catalyst exhibits high oxidative decomposition performance when used in the absence of a sulfur compound, but when a sulfur compound or halogen-based material is present, these materials, Mn salt, and Cu salt are produced. In addition, the oxidative decomposition performance is significantly reduced.
- the Pt / TiO 2 catalyst used in the carbon dioxide off-gas purification method of the present invention has a form of TiO 2 as a carrier that is less affected by sulfur adhesion to sulfur compounds and is not easily affected. Stable with little change. Therefore, the Pt / TiO 2 catalyst is a catalyst that maintains the initial catalyst structure and has little deterioration with time in oxidative decomposition performance. Similarly, SiO 2 and ZrO 2 are also excellent in durability against sulfur, and combustion catalysts using these metal oxides can maintain oxidative decomposition performance over a long period of time.
- the configuration of the carbon dioxide off-gas purification device (hereinafter abbreviated as “purification device”) is adjusted to the concentration of combustible gas (such as methane) contained in the carbon dioxide off-gas. It is determined accordingly.
- concentration of the combustible gas contained in the carbon dioxide off gas is within a range in which the reaction temperature can be controlled to 250 ° C. or more and 650 ° C. or less even after heat generation due to the oxidative decomposition treatment of the carbon dioxide off gas, as shown in FIG.
- a purification device having a catalytic combustor provided with one catalytic combustion region provided with a combustion catalyst is used.
- the combustible gas concentration contained in the carbon dioxide off-gas is in a range where the reaction temperature exceeds 650 ° C. due to heat generated by the oxidative decomposition treatment of the carbon dioxide off-gas
- at least two catalytic combustion regions provided with combustion catalysts are provided.
- a catalytic combustor is provided, and at least one selected from carbon dioxide off-gas after oxidative decomposition treatment, air, and water is supplied between catalytic combustion regions, and carbon dioxide off-gas introduced into the catalytic combustor is supplied.
- a purification device configured to cool is used.
- FIG. 5 is a schematic view showing an example of a purification apparatus used in the second embodiment of the carbon dioxide off-gas purification method of the present invention.
- the carbon dioxide off-gas purification device 80 includes a heater 81 for heating the carbon dioxide off-gas to a predetermined reaction temperature, and a preheater 82 for preheating the carbon dioxide off-gas or air before being introduced into the heater 81.
- a catalyst combustor 83 including two catalytic combustion regions 83a and 83b provided with a combustion catalyst for subjecting the carbon dioxide off-gas heated by the heater 81 to oxidative decomposition treatment, and these, It is generally composed of flow paths 84 to 97 for flowing various gases.
- the heater 81 the same one as the heater 11 is used.
- the preheater 82 the same one as the above preheater 12 is used.
- the reaction temperature of the carbon dioxide off-gas oxidative decomposition treatment is set within a predetermined temperature range.
- a quench fluid supply region 83c for supplying air for cooling the carbon dioxide off gas, and the catalyst combustion regions 83a and 83b are filled with the combustion catalyst.
- An oxygen concentration meter (not shown) is provided in the middle of the flow path 95 connected to the exhaust port of the catalytic combustor 83.
- carbon dioxide off-gas is introduced into the purification device 80 via the flow path 84 and auxiliary combustion air is introduced into the purification device 80 from the flow path 88.
- concentration of flammable gases such as benzene, toluene, xylene and other VOCs and methane contained in the carbon dioxide off-gas is high.
- the preheating of the carbon dioxide off-gas in the preheater 82 is based on the energy consumption (fuel consumption) when the carbon dioxide offgas is heated to a temperature higher than the oxidation decomposition treatment temperature by the combustion catalyst in the catalytic combustor 83 in the heater 81. Done to reduce.
- the auxiliary combustion air is supplied to the heater 81 through the flow path 90.
- the auxiliary combustion air is supplied to the preheater 82 via the flow path 89, and after preheating the auxiliary combustion air to a predetermined temperature in the preheater 82, the flow path 91, Carbon dioxide off-gas is supplied to the heater 81 through the flow path 90.
- the preheating of the auxiliary combustion air in the preheater 82 reduces the energy consumption (fuel consumption) when the auxiliary heater air is heated to a temperature higher than the oxidation decomposition treatment temperature by the combustion catalyst in the catalytic combustor 83 in the heater 81. Done for.
- either the carbon dioxide off gas or the auxiliary combustion air is preheated to a predetermined temperature, or both the carbon dioxide off gas and the auxiliary combustion air are increased to a predetermined temperature. You may preheat. In order to reduce the apparatus cost, the preheater 82 may be omitted.
- the preheating temperature of the carbon dioxide off gas and the auxiliary combustion air in the preheater 82 is preferably 100 ° C. or higher and 400 ° C. or lower.
- the energy consumption (fuel consumption) when the temperature of the carbon dioxide off gas is raised to the oxidative decomposition treatment temperature or higher by the combustion catalyst in the heater 81 increases. .
- the fuel gas introduced into the purification device 80 via the flow path 92 becomes combustion exhaust gas after combustion by auxiliary combustion air, and subsequently mixed with carbon dioxide off-gas, and the mixed gas is heated. Then, the temperature is raised to the reaction temperature (250 ° C. or higher and 650 ° C. or lower) of the oxidative decomposition treatment with the combustion catalyst in the catalytic combustor 83.
- the temperature of the mixed gas is preferably 350 ° C. or more and 500 ° C. or less by the heater 81.
- the mixed gas heated to a predetermined temperature by the heater 81 is supplied to the catalyst combustor 83 filled with the combustion catalyst, and the carbon dioxide off gas is brought into contact with the carbon dioxide off gas.
- sulfur compounds such as hydrogen sulfide, mercaptan, carbonyl sulfide, carbon disulfide, and sulfur dioxide contained in the carbon dioxide off-gas into sulfur oxide (SOx).
- SOx sulfur oxide
- VOCs such as benzene, toluene and xylene contained in carbon dioxide off-gas are converted into carbon dioxide by oxidative decomposition treatment.
- carbon monoxide is contained in the carbon dioxide off gas, the carbon monoxide is converted into carbon dioxide.
- the reaction temperature is preferably 250 ° C. or higher and 650 ° C. or lower, more preferably 350 ° C. or higher and 500 ° C. or lower.
- the reaction temperature of the oxidative decomposition treatment with the combustion catalyst is less than 250 ° C., the oxidative decomposition reaction of the sulfur compound and VOC contained in the carbon dioxide off-gas does not proceed sufficiently.
- the reaction temperature of the oxidative decomposition treatment with the combustion catalyst exceeds 650 ° C., the combustion catalyst is deteriorated by heat, and the purification rate of carbon dioxide off-gas cannot be kept high for a long time.
- the material of the catalytic combustor needs to be a heat-resistant material, which increases the material cost.
- the amount of fuel consumed for the oxidative decomposition treatment increases, the processing cost increases, and the amount of carbon dioxide emission increases. Furthermore, there is a possibility that thermal NOx is generated.
- the pressure of the carbon dioxide off gas (the pressure of the carbon dioxide off gas supplied to the catalytic combustor 83) is preferably 0.01 MPa or more and 1 MPa or less, and more preferably. Is 0.05 MPa or more and 0.15 MPa or less.
- the pressure of the carbon dioxide off gas is 0.01 MPa or more and 1 MPa or less, the volume of the carbon dioxide off gas is reduced, the residence time in the catalytic combustor 83 is shortened, the treatment efficiency is improved, and the treated carbon dioxide off gas is reduced. Since the power can be recovered by the gas expander before being released into the atmosphere, the processing cost can be reduced.
- the quench fluid supply region 83 c of the catalytic combustor 83 includes Auxiliary combustion air is supplied as a quench fluid through a flow path 97 branched from the middle of the flow path 90.
- This auxiliary combustion air cools the carbon dioxide off-gas at the outlet of the catalytic combustion region 83a, suppresses the temperature in the catalytic combustion region 83b from excessively rising, and the reaction temperature in the oxidative decomposition treatment falls within the above temperature range. Control.
- the concentration of sulfur compounds (excluding sulfur oxides) contained in the carbon dioxide off-gas becomes 5 ppmV or less.
- VOCs such as benzene, toluene, and xylene contained in the carbon dioxide off gas have a benzene concentration of 10 ppmV or less, a toluene concentration of 50 ppmV or less, and a xylene concentration of 50 ppmV or less by oxidative decomposition treatment.
- the amount of fuel gas input for raising the temperature to the reaction temperature of the oxidative decomposition treatment increases and the thermal efficiency deteriorates.
- Catalytic combustion so that the concentration of oxygen contained in the treated carbon dioxide off-gas measured by an oxygen concentration meter provided in the subsequent stage is 0.5 to 15% by volume, more preferably 0.5 to 5% by volume. It is preferable to control the amount of auxiliary combustion air supplied to the vessel 83.
- the treated carbon dioxide off gas discharged from the catalyst combustor 83 is introduced into the preheater 82 through the flow path 95.
- the preheater 82 is a heat exchanger
- this heat exchanger either carbon dioxide off-gas after treatment, carbon dioxide off-gas before treatment or auxiliary combustion air, or carbon dioxide off-gas before treatment.
- heat exchange with both the auxiliary combustion air and the auxiliary combustion air is performed, and the carbon dioxide off-gas or auxiliary combustion air before treatment is preheated to a predetermined temperature.
- the treated carbon dioxide off-gas (including sulfur oxide (SOx)) that has passed through the preheater 82 is discharged from the purification device 80 through the flow path 96.
- the carbon dioxide off-gas after removing the mercury Is preferably introduced into the catalytic combustor 83.
- the treatment for removing mercury contained in the carbon dioxide off-gas is performed before introducing the carbon dioxide off-gas into the purification device 80, or before introducing the carbon dioxide off-gas into the heater 81 in the purification device 80.
- the removal process of mercury contained in the carbon dioxide off gas is performed by an adsorption process such as activated carbon.
- FIG. 11 is a flowchart showing an embodiment of a natural gas production method according to the present invention.
- This method includes a liquid phase removal step 200 in which a raw material natural gas collected from a well is first weighed and then supplied to a slag catcher to separate the raw natural gas into a liquid phase and a gas phase by the slag catcher or the like.
- the gas phase from which the liquid phase has been removed is sent to an acid gas removal step 202, where carbon dioxide off gas containing carbon dioxide as a main component and containing VOC and sulfur compounds is separated.
- the separation method may be a conventionally known chemical absorption method, physical absorption method, or a combination thereof.
- the raw material gas after separating the carbon dioxide off-gas is sent to the moisture removal step 204, where it is cooled to near the temperature at which the gas hydrate is formed, and the condensed moisture is removed.
- the source gas from which moisture has been removed is sent to a mercury removal step 206, and the mercury concentration in the source gas is reduced to near 0.1 to 0.01 ⁇ m by an impregnated activated carbon adsorption method or the like.
- the raw material gas from which mercury has been removed is sent to the heavy component removal step 208 and fractionated by a plurality of distillation towers to remove heavy hydrocarbons and the like that are pentane or higher to obtain natural gas. Further, the raw material gas from which the heavy hydrocarbons have been removed is sent to the liquefaction step 210, where it is cooled and compressed to fill the tank.
- the carbon dioxide off gas is sent to the off gas purification step 201, and the off gas is purified by the carbon dioxide off gas purification method of any one of the embodiments described above.
- the carbon dioxide off gas is supplied to the combustor 101 via the flow path 106.
- the carbon dioxide off gas is supplied to the carbon dioxide off gas preheater 103 via the flow path 105, and the carbon dioxide off gas is heated to a predetermined temperature in the carbon dioxide off gas preheater 103.
- the carbon dioxide off gas is supplied to the combustor 101 through the flow path 107 and the flow path 106.
- the carbon dioxide off-gas and auxiliary combustion air supplied to the combustor 101 are directly combusted together with the fuel gas introduced into the purification device 100 via the flow path 112 in the combustor 101.
- the reaction temperature is set to 900 ° C.
- the treated carbon dioxide off-gas discharged from the combustor 101 is introduced into the air preheater 102 via the flow path 113 and further introduced into the carbon dioxide off-gas preheater 103 via the flow path 114.
- the air preheater 102 and the carbon dioxide offgas preheater 103 are heat exchangers, heat exchange between the treated carbon dioxide offgas and the auxiliary combustion air or carbon dioxide offgas before the treatment is performed in this heat exchanger.
- the auxiliary combustion air or carbon dioxide off gas before treatment is preheated to a predetermined temperature.
- the treated carbon dioxide off gas (including sulfur oxide (SOx)) that has passed through the carbon dioxide off gas preheater 103 is discharged from the purification device 100 via the flow path 115.
- SOx sulfur oxide
- Example 4 From the results of Table 4, the fuel consumption of the direct combustion method of Comparative Example 1 is 8,300 Nm 3 / h, whereas the fuel consumption of the catalytic combustion method of Example 1 is 2,200 Nm 3 / h. It was suggested that fuel consumption can be reduced by more than 70%.
- Example 1 since the combustion treatment was performed at a temperature lower than that of the conventional one, it was expected that the flammability of methane (CH 4 ) contained in the carbon dioxide off-gas deteriorated. Therefore, in Example 1, the conversion rate of methane was assumed to be 0%, and the influence on the emission amount of carbon dioxide due to slippage of methane having a warming coefficient 21 times that of carbon dioxide was examined.
- the slip amount of methane is converted into carbon dioxide, and the amount of carbon dioxide emission ((a) + (b) in Table 4) associated with each combustion process is 10% in the direct combustion method of Comparative Example 1. While it was 900 Nm 3 / h, the carbon dioxide emission of the catalytic combustion system of Example 1 was 5,300 Nm 3 / h, suggesting that the carbon dioxide emission can be reduced by 50% or more.
- the total amount of carbon dioxide emission ((a) + (b) + (c) in Table 4) associated with each combustion process is The carbon dioxide emission amount of the direct combustion method is 103,300 Nm 3 / h, whereas the carbon dioxide emission amount of the catalytic combustion method of Example 1 is 97,700 Nm 3 / h, and the carbon dioxide emission amount is 5 % Reduction was suggested.
- Example 2 58.6 g of titanium oxide powder (anatase type, trade name: PC-500, manufactured by Millennium), 138.0 g of titania sol (trade name: TA-15, manufactured by Nissan Chemical Industries), and 103.5 g of pure water Mixing was performed to prepare a slurry containing titanium oxide powder.
- This titanium oxide powder-containing slurry was applied to the inner wall surface of a cordierite honeycomb (400 cpi 2 , manufactured by NGK Corporation), and excess slurry was removed by air blowing.
- the cordierite honeycomb coated with the titanium oxide powder-containing slurry was dried at 150 ° C. for 6 hours with a dryer. This cordierite honeycomb was fired in a firing furnace at 500 ° C. for 2 hours to form a layer having a titanium oxide powder content of 50 g / liter.
- a dinitrodiamine platinum aqueous solution platinum content: 4.5 mass%
- 211.11 g of pure water platinum aqueous solution having a platinum content of 1.33 mass%.
- This platinum aqueous solution is applied to the inner wall surface of the cordierite honeycomb on which the layer made of titanium oxide powder is formed, and this solution is absorbed by the layer made of titanium oxide powder, and the excess solution is removed by air blowing to oxidize.
- the aqueous platinum solution was absorbed in the layer made of titanium oxide powder so that the content of the aqueous platinum solution in the layer made of titanium powder was 150 g / liter.
- the cordierite honeycomb coated with the platinum aqueous solution was dried at 150 ° C. for 6 hours by a dryer.
- This cordierite honeycomb was fired at 500 ° C. for 2 hours in a firing furnace, and further subjected to reduction treatment at 500 ° C. for 2 hours in a hydrogen atmosphere, and a Pt / TiO 2 catalyst layer having a platinum content of 2 g / liter.
- the combustion catalyst of Example 2 was obtained.
- Example 3 In the same manner as in Example 2, a layer having a titanium oxide powder content of 52 g / liter was formed. 30 g of palladium nitrate aqueous solution (palladium content 10.0 mass%) and 270 g of pure water were mixed to prepare a palladium aqueous solution having a palladium content of 1.33 mass%. This palladium aqueous solution is applied to the inner wall surface of the cordierite honeycomb on which the layer made of titanium oxide powder is formed, and this solution is absorbed by the layer made of titanium oxide powder, and the excess solution is removed by air blowing to oxidize.
- the aqueous palladium solution was absorbed in the layer made of titanium oxide powder so that the content of the aqueous palladium solution in the layer made of titanium powder was 150 g / liter.
- the cordierite honeycomb coated with the aqueous palladium solution was dried at 150 ° C. for 6 hours with a dryer. This cordierite honeycomb was fired in a firing furnace at 500 ° C. for 2 hours to form a Pd / TiO 2 catalyst layer having a palladium content of 2 g / liter, and the combustion catalyst of Example 3 was obtained.
- Example 4 Zirconium oxide powder (trade name: RC-100, manufactured by Daiichi Rare Chemicals Co., Ltd.) 50.8 g, zirconia sol (trade name: NZS-30A, manufactured by Nissan Chemical Industries Ltd.) 69.0 g, and pure water 180.2 g And a slurry containing zirconium oxide powder was prepared.
- This zirconium oxide powder-containing slurry was applied to the inner wall surface of a cordierite honeycomb (400 cpi 2 , manufactured by NGK Corporation), and excess slurry was removed by air blowing.
- the cordierite honeycomb coated with the zirconium oxide powder-containing slurry was dried with a dryer at 150 ° C. for 6 hours.
- This cordierite honeycomb was fired in a firing furnace at 500 ° C. for 2 hours to form a layer having a zirconium oxide powder content of 50 g / liter.
- a dinitrodiamine platinum aqueous solution platinum content: 4.5 mass%
- 211.11 g of pure water platinum aqueous solution having a platinum content of 1.33 mass%.
- This platinum aqueous solution is applied to the inner wall surface of the cordierite honeycomb on which the layer made of zirconium oxide powder is formed, and this solution is absorbed by the layer made of zirconium oxide powder, and the excess solution is removed by air blowing to oxidize.
- the platinum aqueous solution was absorbed in the layer made of zirconium oxide powder so that the content of the platinum aqueous solution in the layer made of zirconium powder was 150 g / liter.
- the cordierite honeycomb coated with the platinum aqueous solution was dried at 150 ° C. for 6 hours by a dryer.
- This cordierite honeycomb was fired at 500 ° C. for 2 hours in a firing furnace, and further subjected to reduction treatment at 500 ° C. for 2 hours in a hydrogen atmosphere to form a Pt / ZrO 2 catalyst layer having a platinum content of 2 g / liter.
- the combustion catalyst of Example 4 was obtained.
- Comparative Example 2 43.3 g of aluminum oxide powder (trade name: NST-5, manufactured by JGC Universal), 138.0 g of alumina sol (trade name: A-10, manufactured by Kawaken Fine Chemical Co., Ltd.) and 76.7 g of pure water were mixed. A slurry containing aluminum oxide powder was prepared. This aluminum oxide powder-containing slurry was applied to the inner wall surface of a cordierite honeycomb (400 cpi 2 , manufactured by NGK Corporation), and excess slurry was removed by air blowing. The cordierite honeycomb coated with the aluminum oxide powder-containing slurry was dried with a dryer at 150 ° C. for 6 hours. This cordierite honeycomb was fired in a firing furnace at 500 ° C. for 2 hours to form a layer having an aluminum oxide powder content of 50 g / liter.
- cordierite honeycomb 400 cpi 2 , manufactured by NGK Corporation
- a dinitrodiamine platinum aqueous solution platinum content: 4.5 mass%
- 211.11 g of pure water platinum aqueous solution having a platinum content of 1.33 mass%.
- This platinum aqueous solution is applied to the inner wall surface of the cordierite honeycomb on which the layer made of aluminum oxide powder is formed, and this solution is absorbed by the layer made of aluminum oxide powder, and the excess solution is removed by air blowing to oxidize.
- the aqueous platinum solution was absorbed in the layer made of aluminum oxide powder so that the content of the aqueous platinum solution in the layer made of aluminum powder was 150 g / liter.
- the cordierite honeycomb coated with the platinum aqueous solution was dried at 150 ° C. for 6 hours by a dryer.
- This cordierite honeycomb was fired in a firing furnace at 500 ° C. for 2 hours, and further subjected to reduction treatment at 500 ° C. for 2 hours in a hydrogen atmosphere, so that a Pt / Al 2 O 3 catalyst having a platinum content of 2 g / liter.
- a layer was formed to obtain a combustion catalyst of Comparative Example 2.
- “Comparative Example 3” 43.3 g of aluminum oxide powder (trade name: NST-5, manufactured by JGC Universal), 138.0 g of alumina sol (trade name: A-10, manufactured by Kawaken Fine Chemical Co., Ltd.) and 76.7 g of pure water were mixed. A slurry containing aluminum oxide powder was prepared. This aluminum oxide powder-containing slurry was applied to the inner wall surface of a cordierite honeycomb (400 cpi 2 , manufactured by NGK Corporation), and excess slurry was removed by air blowing. The cordierite honeycomb coated with the aluminum oxide powder-containing slurry was dried with a dryer at 150 ° C. for 6 hours. This cordierite honeycomb was fired in a firing furnace at 500 ° C. for 2 hours to form a layer having an aluminum oxide powder content of 50 g / liter.
- a cordierite honeycomb 400 cpi 2 , manufactured by NGK Corporation
- palladium nitrate aqueous solution (palladium content 10.0 mass%) and 270 g of pure water were mixed to prepare a palladium aqueous solution having a palladium content of 1.33 mass%.
- This palladium aqueous solution is applied to the inner wall surface of the cordierite honeycomb on which the layer made of aluminum oxide powder is formed, and this solution is absorbed by the layer made of aluminum oxide powder, and the excess solution is removed by air blowing to oxidize.
- the palladium aqueous solution was absorbed in the layer made of aluminum oxide powder so that the content of the aqueous palladium solution in the layer made of aluminum powder was 150 g / liter.
- the cordierite honeycomb coated with the aqueous palladium solution was dried at 150 ° C. for 6 hours with a dryer.
- This cordierite honeycomb was fired in a firing furnace at 500 ° C. for 2 hours to form a Pd / Al 2 O 3 catalyst layer having a palladium content of 2 g / liter, and a combustion catalyst of Comparative Example 3 was obtained.
- “Comparative Example 4” As Cu / Mn powder, 84.0 g of hopcalite powder (trade name: N-840, manufactured by Zude Chemie), 148.5 g of silica sol (trade name: Snowtex C, manufactured by Nissan Chemical Industries), and 67.5 g of pure water. Were mixed to prepare a slurry containing Cu / Mn powder. This Cu / Mn powder-containing slurry was applied to the inner wall surface of a cordierite honeycomb (400 cpi 2 , manufactured by NGK Corporation), and excess slurry was removed by air blowing. The cordierite honeycomb coated with the Cu / Mn powder-containing slurry was dried at 150 ° C. for 6 hours with a dryer.
- a cordierite honeycomb 400 cpi 2 , manufactured by NGK Corporation
- This cordierite honeycomb was fired in a firing furnace at 400 ° C. for 2 hours to form a Cu / Mn layer having a Cu / Mn powder content of 100 g / liter, and a combustion catalyst of Comparative Example 4 was obtained.
- Reatment rate of benzene with combustion catalyst When the oxidative decomposition treatment of hydrogen sulfide and benzene (C 6 H 6 ) was performed using a catalytic combustor having a combustion catalyst made of a cordierite honeycomb having a Pt / TiO 2 catalyst layer produced in Example 2, Regarding the oxidation reaction of benzene (C 6 H 6 + 15 / 2O 2 ⁇ 6CO 2 + 3H 2 O), the reaction rate was expressed by the following Langmuir-Hinshelwood equation (formula (1)).
- R is the reaction rate (mol / h / g-cat)
- k is the reaction rate constant (mol / h / g-cat / Pa base) depending on the temperature T (K)
- P i the partial pressure of i component
- K i is the adsorption equilibrium constant of i component dependent on the temperature T (K) (1 / Pa )
- the a and b shows the reaction order.
- a combustion catalyst comprising a cordierite honeycomb having a Pt / TiO 2 catalyst layer produced in Example 2 with a GHSV (space velocity) of 30,000 h ⁇ 1 , a benzene concentration of 500 ppm, and a catalytic combustor pressure of 1 atm.
- Fig. 5 shows the relationship between the reaction temperature and the conversion rate (decomposition rate) of benzene at the hydrogen sulfide concentration and oxygen concentration shown in Table 5 when hydrogen sulfide and benzene (C 6 H 6 ) are subjected to oxidative decomposition treatment. It is shown in FIG.
- the oxidation reaction of benzene using the combustion catalyst comprising a cordierite honeycomb provided with the Pt / TiO 2 catalyst layer produced in Example 2 is affected by the concentration of coexisting hydrogen sulfide and oxygen. It was suggested. It was suggested that the reaction temperature should be 250 ° C. or higher in order to proceed the benzene oxidation reaction.
- FIG. 9 is a schematic view showing a test apparatus used for the combustion catalyst performance test. Using this test apparatus 120, the performance test of the combustion catalyst was performed by the following method. First, a new combustion catalyst 122 was placed in the catalyst combustor 121 for each test condition, and a quartz crushed product 123 was placed in the previous stage (upstream side in the flow direction of the gas to be treated).
- Carbon dioxide was supplied from the gas cylinder 124 to the catalytic combustor 121 while controlling the flow rate with the floating precision flow meter 125.
- air was supplied from the gas cylinder 126 to the catalytic combustor 121 while controlling the flow rate with the floating ball type precision flow meter 127.
- Carbon dioxide and air supplied to the catalytic combustor 121 were heated to a predetermined temperature by an electric furnace 128 disposed around the catalytic combustor 121.
- the rotary pump 130 started supplying water from the container 129 containing water to the catalytic combustor 121.
- VOC benzene, toluene, p-xylene
- this VOC is volatilized, and a predetermined amount of VOC is supplied to the catalytic combustor 121.
- nitrogen containing a predetermined amount of hydrogen sulfide or mercaptan was supplied from the gas cylinder 134 to the catalytic combustor 121 while controlling the flow rate by the mass flow controller 135.
- a Tedlar bag was installed at a sample collection port 136 provided on the outlet side of the catalytic combustor 121, and an outlet side gas sample was collected. After the collection of the gas sample on the outlet side was completed, a Tedlar bag was installed at the sample collection port 137 provided on the inlet side of the catalytic combustor 121 to collect the inlet side gas sample.
- the benzene concentration or toluene concentration or p-xylene concentration is measured, the hydrogen sulfide concentration or mercaptan concentration, and the carbon monoxide concentration are measured, and the oxidation reaction of these gases is measured.
- the reaction rate and product were analyzed. After collecting the gas sample, the supply of gases other than air and carbon dioxide was stopped, and the measurement was terminated.
- the concentration of benzene, toluene or p-xylene contained in the gas to be treated was measured by gas chromatography.
- gas chromatography GC-14B (manufactured by Shimadzu Corporation) was used.
- FID flame flame ionization detector
- the concentration of hydrogen sulfide, mercaptan or carbon monoxide contained in the gas to be treated was measured with a gas detector manufactured by Gastec.
- Conversion rate (%) (1 ⁇ (benzene concentration, toluene concentration, p-xylene concentration on the outlet side of the catalytic combustor / benzene concentration, toluene concentration, p-xylene concentration on the inlet side of the catalytic combustor) ⁇ 100
- sulfur compounds that are highly toxic and irritating odors such as hydrogen sulfide and mercaptans contained in carbon dioxide off-gas can be purified and discharged as SOx, which is industrially applicable. Have sex.
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Abstract
Description
本願は、2008年6月23日に日本に出願された特願2008-162728号に基づき優先権を主張し、その内容をここに援用する。
従来の天然ガスなどのプラントでは、天然ガスに含まれる二酸化炭素や硫黄化合物を除去する天然ガス精製工程でオフガスが発生し、このオフガスは硫化水素とVOCを含んでいる。VOC燃焼触媒は、多くのメーカーから売り出されているが、天然ガスなどのプラントでは硫化水素などの不純物が発生するため、VOC燃焼触媒を用いたオフガスの浄化方法は技術的ハードルが高くなり、商業プロセスが確立されていなかった。
ゆえに、現状では、上記オフガスを大気放出する際には、直接燃焼(Thermal Incinerator)による900℃程度の高温条件下でオフガスを燃焼処理した後、大気中に放出している。しかしながら、この直接燃焼による現行のオフガスの処理方法は、常温程度で発生したオフガスを900℃程度に昇温した後、燃焼処理しているため、処理コストが非常に高かった。
直接燃焼方式は、高温処理であるため、燃焼器および熱交換器には耐熱材料を用いる必要があり、装置コストが問題となっていた。
直接燃焼方式は、火炎を伴う処理によって生成するサーマルNOxが問題となっていた。
熱回収を伴う直接燃焼方式では、煙道ガスを垂直ではなく、水平に流通させて熱回収を行うため、装置の占有面積が大きく、小型プラントや船上のプラントにおいては、プロット配置上の問題があった。
さらに、VOC燃焼触媒は多くの製造業者から売り出されているものの、硫黄化合物に対する耐性を持ち、VOCおよび硫黄化合物の高い浄化率を長期間維持できる触媒がないため、天然ガスなどのプラントでは、商業的に確立されたプロセスがなかった。
i)天然ガスなどから排出され、硫黄化合物およびVOCを含む二酸化炭素オフガスに、燃焼触媒による酸化分解処理を施すことにより、従来よりも低い温度にて、硫黄化合物およびVOCの濃度を低下させる。
ii)サーマルNOxを発生することなく、高い浄化率を長期間維持する。
iii)大量の燃料消費に伴う二酸化炭素の排出量を減らし、処理コストを安くする。
前記二酸化炭素を主成分とするガスは、天然ガスの精製において排出されたものであってもよい。
前記燃焼触媒による酸化分解処理の反応温度は、250℃以上、650℃以下とすることが好ましい。
前記燃焼触媒による酸化分解処理の圧力は、0.01MPa以上、1MPa以下とすることが好ましい。
前記二酸化炭素を主成分とするガスに含まれるVOCを酸化分解処理により二酸化炭素に分解することが好ましい。
前記VOCは、ベンゼン、トルエン、キシレンのうちから選択される1種または2種以上を含むことが好ましい。
前記予熱の一部または全部を、燃焼炉、電気のラインヒーター、蓄熱剤、燃焼触媒による酸化分解処理後の二酸化炭素を主成分とするガスとの熱交換を利用した熱交換器のうちから選択される1種または2種以上の手段により行うことが好ましい。
前記触媒燃焼器は、酸化分解処理の発熱により、前記反応温度の上限を超える場合、燃焼触媒が設けられた少なくとも2つの触媒燃焼領域を備え、当該触媒燃焼領域の間に、酸化分解処理後の二酸化炭素を主成分とするガス、空気、水のうちから選択される少なくとも1種を供給し、前記触媒燃焼器に導入した二酸化炭素を主成分とするガスを冷却することが好ましい。
前記二酸化炭素を主成分とするガスは、ガス田から産出された天然ガス中の酸性ガスを液体溶媒と接触させることにより分離・回収する酸性ガス分離装置から排出されるガスであることが好ましい。
前記二酸化炭素を主成分とするガスは、前記酸性ガス分離装置の後段に設けられた、硫化水素濃縮装置、硫黄回収装置、テールガス処理装置のうちのいずれか1つの装置にて硫化水素を低減した後の排出ガスであることが好ましい。
前記基体は、ハニカム構造体、ペレット体または球体であることが好ましい。
前記基体は、セラミックス、金属酸化物、または金属合金からなることが好ましい。
前記触媒層の厚みは、10μm以上、500μm以下であることが好ましい。
前記貴金属の含有量は、触媒充填容積あたり0.1g/リットル以上、10g/リットル以下であることが好ましい。
前記金属酸化物の比表面積が10m2/g以上、300m2/g以下であることが好ましい。
前記燃焼触媒による酸化分解処理を施す場合の、二酸化炭素を主成分とするガス中の酸素濃度が1体積%以上、15体積%以下であることが好ましい。
前記金属酸化物は酸化チタンであり、前記貴金属の含有量が触媒充填容積あたり0.1g/リットル以上、10g/リットル以下であることが好ましい。
前記燃焼触媒による酸化分解処理を施す場合の、二酸化炭素を主成分とするガス中の酸素濃度が1体積%以上、15体積%以下であることが好ましい。
図1は、本発明の二酸化炭素オフガスの浄化方法の第一実施形態で用いられる二酸化炭素オフガスの浄化装置の一例を示す概略図である。
この二酸化炭素オフガスの浄化装置(以下、「浄化装置」と略す。)10は、二酸化炭素を主成分とするガス(二酸化炭素オフガス)を所定の反応温度まで加熱するための加熱器11と、加熱器11に導入する前に、二酸化炭素オフガスおよび/または空気を予熱するための予熱器12と、加熱器11にて加熱された二酸化炭素オフガスに酸化分解処理を施すための燃焼触媒が設けられた触媒燃焼器13と、これらを接続するとともに、各種のガスを流すための流路14~26とを有する。
予熱器12としては、燃焼炉、電気のラインヒーター、蓄熱剤、触媒燃焼器13における燃焼触媒による酸化分解処理後の二酸化炭素オフガスとの熱交換を利用した熱交換器などの手段が用いられる。
触媒燃焼器13の排出口に接続されている流路25または流路26の途中には、酸素濃度計(図示略)が設けられている。
この基体の材質としては、コージライト(2MgO2・2Al2O3・5SiO2)、ガラス繊維、ジルコニア酸化物、チタン酸化物、フェクロアロイ、ステンレスなどの耐熱性と基体強度に優れたセラミックス、金属酸化物、または、金属合金などが挙げられる。
基体の大きさは、特に限定されず、一回の二酸化炭素オフガスの処理量に必要とされる燃焼触媒量に応じて、適宜設定される。
ハニカム構造体のセルの数が10cpi2未満では、このセルの内壁面に設けられた触媒層の表面積の総和が小さくなり、燃焼触媒によって二酸化炭素オフガスを効率的に酸化分解処理することができない。ハニカム構造体のセルの数が1000cpi2を超えると、セルの大きさが小さくなり、セルの内壁面に触媒層を形成することが難しくなるとともに、ハニカム構造体における圧力損失が大きくなり、結果として、ハニカム構造体が損傷するおそれがある。
触媒の基体がハニカム構造体の場合、これらユニット間の空隙はガスのチャネリングを整流することに役立つ。ハニカム構造体にガスがフィードされると、流れと垂直方向にガスは拡散できないが、ユニット間に空隙を設けることで整流性を向上できるからである。
また、これら空隙のそれぞれには図示しない冷却剤供給路を接続してもよい。さらに、これら冷却剤供給路を通じて、酸化分解処理後の二酸化炭素を主成分とするガス、空気、水のうちから選択される少なくとも1種を供給し、下流側の燃焼触媒ユニットの温度を下げ、反応条件をコントロールしてもよい。このコントロールは、触媒燃焼器13の下流に設けられた温度センサーの出力に応じて、各冷却剤供給路の弁を自動開閉させ、冷却流体の供給量を制御することにより、フィードバック制御としてもよい。
極性溶媒としては水(純水)が最適であるが、メタノール、エタノール、プロパノールなどのアルコール類やジエチルエーテル、テトラヒドロフランなどのエーテル類、エステル類、ニトリル類、アミド類、スルホキシド類などの極性有機溶媒を用いることもできる。
この基体を、焼成炉により400℃以上、600℃以下にて、1時間以上、8時間以下焼成し、基体の表面に金属酸化物からなる層を形成する。
金属酸化物としては、有機塩、無機塩のいずれをも使用することができ、有機塩としては、酢酸塩、アセチルアセナート塩、シアン塩などが例示され、無機塩としては、硝酸塩、塩化物塩などが例示される。
金属酸化物層の表面に、貴金属化合物溶液を塗布し、金属酸化物からなる層にこの溶液を吸収させるとともに、エアーブローにより余分な溶液を除去する。
貴金属化合物溶液を塗布した基体を、乾燥機により100℃以上、200℃以下にて、1時間以上乾燥する。
この基体を、焼成炉により400℃以上、600℃以下にて、1時間以上焼成し、必要に応じて水素気流中にて400℃以上、600℃以下で還元処理を行い、基体の表面に金属酸化物と貴金属からなる触媒層が形成された燃焼触媒を得る。
この実施形態の二酸化炭素オフガスの浄化方法では、二酸化炭素オフガスを、流路14を介して浄化装置10内に導入するとともに、流路18から浄化装置10内に助燃用の空気(以下、「助燃空気」と略す。)を導入する。
この二酸化炭素オフガスとしては、天然ガス、石油随伴ガスのプラントなどにおいて天然ガスの精製工程により排出されたガスが挙げられる。
二酸化炭素オフガスには、硫黄化合物以外にも、ベンゼン、トルエン、キシレンなどのVOCが含まれ、一酸化炭素、メタン、水なども含まれることがある。
二酸化炭素オフガスに含まれるVOCは、50ppmv以上、2000ppmv以下のベンゼン、100ppmv以上、2000ppmv以下のトルエン、100ppmv以上、2000ppmv以下のキシレンのうち少なくとも1種を含んでいる。
さらに、加熱器11では、燃焼排ガスと二酸化炭素オフガスが混合することで、燃焼排ガスの保有する熱量をロスすることなく、二酸化炭素オフガスの昇温に利用できるため、熱効率が高い。
ゆえに、助燃空気は、二酸化炭素オフガスの酸化剤としてだけでなく、加熱器11の酸化剤として有効利用される。
二酸化炭素オフガスを予熱する場合(β=0)には、流路15を介して予熱器12に二酸化炭素オフガスを供給し、予熱器12において、二酸化炭素オフガスを所定の温度まで予熱した後、流路17、流路16を介して加熱器11に二酸化炭素オフガスを供給する。予熱器12における二酸化炭素オフガスの予熱は、加熱器11において、二酸化炭素オフガスを、触媒燃焼器13における燃焼触媒による酸化分解処理温度以上に昇温する際のエネルギー消費量(燃料消費量)を低減するために行われる。
助燃空気を予熱する場合(α=0)には、流路19を介して予熱器12に助燃空気を供給し、予熱器12において、助燃空気を所定の温度まで予熱した後、流路21、流路20を介して加熱器11に助燃空気を供給する。この予熱器12における助燃空気の予熱は、加熱器11において、助燃空気を、触媒燃焼器13における燃焼触媒による酸化分解処理温度以上に昇温する際のエネルギー消費量(燃料消費量)を低減するために行われる。
従来の直接燃焼方式の二酸化炭素オフガスの浄化方法では、処理後の二酸化炭素オフガスを大気中に放出している。そのため、二酸化炭素オフガスの回収装置は、できるかぎり大気圧に近い圧力で運転されている。
しかし、一部の二酸化炭素オフガスの回収装置では、アミン再生塔を使用せずに、アミン溶液を0.5~1MPaで高圧フラッシュするか、あるいは、耐熱性の高いアミン溶液を用いて180℃程度の高温かつ0.5~1MPaの高圧条件でアミン再生塔を運転している。この場合、0.5~1MPaの高圧の二酸化炭素オフガスが発生している。
この二酸化炭素オフガスに含まれる水銀類の除去処理は、活性炭などの吸着処理によって行われる。
本発明の二酸化炭素オフガスの浄化方法で処理された二酸化炭素オフガスは、例えば、(1)ガス田から産出された天然ガス中の酸性ガスを液体溶媒と接触させることにより分離・回収する酸性ガス分離装置から排出されるガス、(2)前記の酸性ガス分離装置の後段に設けられた、硫化水素濃縮装置、硫黄回収装置、テールガス処理装置のうちのいずれか1つの装置にて大部分の硫化水素を除去した後の排出ガスなどが挙げられる。
不純物ガスを吸収した吸収液は吸収塔31の塔底から抜き出された後、圧力を下げてから流路37を介してフラッシュドラム32に供給してもよく、フラッシュドラム32を介して圧力を下げてもよい。
フラッシュドラム32において、軽質な炭化水素がフラッシュガスとして流路38を介して回収される。
軽質な炭化水素が除去された吸収液は、フラッシュドラム32の塔底から抜き出され、流路39を介して再生塔33に供給される。
再生塔33において、所定の温度に加温することにより、吸収液から不純物ガスを二酸化炭素オフガスとして放出させ、この二酸化炭素オフガスが流路40を介してフラッシュドラム34に供給される。
二酸化炭素オフガスを放出した吸収液は、再生塔33の塔底から抜き出され、流路41を介して吸収塔31に供給され、再利用される。
再生塔33の塔底から抜き出された吸収液の一部は、流路42を介して再生塔33に供給され、再び二酸化炭素オフガスを放出するための処理(加温)が施される。
二酸化炭素オフガスに混入していた微量の吸収液が、フラッシュドラム34の塔底から抜き出され、流路44を介して再生塔33に供給される。
図3は、本発明の二酸化炭素オフガスの浄化方法で処理される二酸化炭素オフガスの回収装置の第二の例を示す概略図である。図3において、図2に示した回収装置の構成要素と同じ構成要素には同一符号を付して、その説明を省略する。
不純物ガスを吸収した吸収液は、吸収塔51の塔底から抜き出され、流路57を介して硫化水素濃縮装置の再生塔52に供給される。
硫化水素濃縮ガスを放出した吸収液は、再生塔52の塔底から抜き出され、流路59を介して吸収塔51に供給され、再利用される。
再生塔52の塔底から抜き出された吸収液の一部は、流路60を介して再生塔52に供給され、再び硫化水素濃縮ガスを放出するための処理(加温)が施される。
硫化水素濃縮ガスに混入していた微量の吸収液が、フラッシュドラム53の塔底から抜き出され、流路62を介して再生塔52に供給される。
微量の硫黄化合物(硫化水素、硫化カルボニル、二硫化炭素、二酸化硫黄)、二酸化炭素を含む窒素を主成分とするテールガスは硫黄回収装置54から排出されて、流路64から供給された燃料ガスおよび助燃空気、並びに、流路65から供給された水素とともに、流路66を介して水素化処理反応器からなるテールガス処理装置(Tail Gas Treatment、TGT)55に供給される。
テールガス処理装置55から排出された硫化水素に含まれる水分は、流路67の途中に設けられた排水路68から排出される。
図4において、図2、3に示した回収装置の構成要素と同じ構成要素には同一符号を付して、その説明を省略する。
不純物ガスを吸収した吸収液は、吸収塔51の塔底から抜き出され、流路57を介して硫化水素濃縮装置の再生塔52に供給される。
硫化水素濃縮ガスを放出した吸収液は、再生塔52の塔底から抜き出され、流路59を介して吸収塔51に供給され、再利用される。
再生塔52の塔底から抜き出された吸収液の一部は、流路60を介して再生塔52に供給され、再び硫化水素濃縮ガスを放出するための処理(加温)が施される。さらに、再生塔52の塔底から抜き出された吸収液の一部は、流路74を介してテールガス処理装置の吸収塔71に供給される。
硫化水素濃縮ガスに混入していた微量の吸収液が、フラッシュドラム53の塔底から抜き出され、流路62を介して再生塔52に供給される。
微量の硫黄化合物(硫化水素、硫化カルボニル、二硫化炭素、二酸化硫黄)、二酸化炭素を含む窒素を主成分とするテールガスは硫黄回収装置54から排出されて、吸収塔51の塔頂から排出された二酸化炭素オフガスB、流路64から供給された燃料ガスおよび助燃空気、並びに、流路65から供給された水素とともに、流路66を介してテールガス処理装置55に供給される。
テールガス処理装置55から排出されたテールガスおよび二酸化炭素オフガスBに含まれる水分は、流路67の途中に設けられた排水路68から排出される。
硫化水素を吸収した吸収液は、吸収塔71の塔底から抜き出され、流路73を介して再生塔52に供給されて、再循環される。
燃焼触媒として、酸化ジルコニウム、酸化チタン、酸化ケイ素の群から選択される1種または2種以上の金属酸化物を用いることにより、酸化分解処理により生成したSOxの硫酸塩化によって、燃焼触媒が劣化するのを低減できる。
燃焼触媒として、白金、パラジウム、イリジウムの群から選択される1種または2種以上の貴金属を用いることにより、これらの貴金属は低温域における酸化活性が高いので、従来よりも低い温度にて二酸化炭素オフガスの酸化反応を進行させることができる。
さらに、サーマルNOxを発生することなく、二酸化炭素の排出量も少なく、低コストで二酸化炭素オフガスを酸化分解処理できる。
同様に、SiO2、ZrO2も硫黄に対する耐久性に優れ、これらの金属酸化物を用いた燃焼触媒は長期間にわたって酸化分解性能を維持できる。
以下、図面を参照して、本発明の二酸化炭素オフガスの浄化方法の第二の実施形態を説明する。
ところで、本発明の二酸化炭素オフガスの浄化方法では、二酸化炭素オフガスの浄化装置(以下、「浄化装置」と略す。)の構成は、二酸化炭素オフガスに含まれる可燃性ガス(メタンなど)の濃度に応じて適宜決定される。
二酸化炭素オフガスに含まれる可燃性ガス濃度が、二酸化炭素オフガスの酸化分解処理に伴う発熱後も反応温度を250℃以上、650℃以下に制御できる範囲内である場合、図1に示したような、燃焼触媒が設けられた触媒燃焼領域を1つ備えた触媒燃焼器を有する浄化装置が用いられる。二酸化炭素オフガスに含まれる可燃性ガス濃度が、二酸化炭素オフガスの酸化分解処理に伴う発熱で反応温度が650℃を超える範囲である場合、燃焼触媒が設けられた触媒燃焼領域を少なくとも2つ備えた触媒燃焼器を有し、触媒燃焼領域の間に、酸化分解処理後の二酸化炭素オフガス、空気、水のうちから選択される少なくとも1種を供給して、触媒燃焼器に導入した二酸化炭素オフガスを冷却する構成の浄化装置が用いられる。
図5は、本発明の二酸化炭素オフガスの浄化方法の第二の実施形態で用いられる浄化装置の一例を示す概略図である。
この二酸化炭素オフガスの浄化装置80は、二酸化炭素オフガスを所定の反応温度まで加熱するための加熱器81と、加熱器81に導入する前に、二酸化炭素オフガスまたは空気を予熱するための予熱器82と、加熱器81にて加熱された二酸化炭素オフガスに酸化分解処理を施すための燃焼触媒が設けられた2つの触媒燃焼領域83a、83bを備えた触媒燃焼器83と、これらを接続するとともに、各種のガスを流すための流路84~97とから概略構成されている。
この実施形態の二酸化炭素オフガスの浄化方法では、二酸化炭素オフガスを、流路84を介して浄化装置80内に導入するとともに、流路88から浄化装置80内に助燃空気を導入する。
この実施形態では、二酸化炭素オフガスに含まれるベンゼン、トルエン、キシレンなどのVOC、メタンなどの可燃性ガスの濃度が高くなっている。
二酸化炭素オフガスを予熱する場合(β=0)には、流路85を介して予熱器82に二酸化炭素オフガスを供給し、予熱器82において、二酸化炭素オフガスを所定の温度まで予熱した後、流路87、流路86を介して加熱器81に二酸化炭素オフガスを供給する。この予熱器82における二酸化炭素オフガスの予熱は、加熱器81において、二酸化炭素オフガスを、触媒燃焼器83における燃焼触媒による酸化分解処理温度以上に昇温する際のエネルギー消費量(燃料消費量)を低減するために行われる。
助燃空気を予熱する場合(α=0)には、流路89を介して予熱器82に助燃空気を供給し、予熱器82において、助燃空気を所定の温度まで予熱した後、流路91、流路90を介して加熱器81に二酸化炭素オフガスを供給する。この予熱器82における助燃空気の予熱は、加熱器81において、助燃空気を、触媒燃焼器83における燃焼触媒による酸化分解処理温度以上に昇温する際のエネルギー消費量(燃料消費量)を低減するために行われる。
二酸化炭素オフガスと助燃空気の予熱温度が低温である場合、加熱器81において、二酸化炭素オフガスを、燃焼触媒による酸化分解処理温度以上に昇温する際のエネルギー消費量(燃料消費量)が増加する。
燃焼触媒による酸化分解処理の反応温度が250℃未満では、二酸化炭素オフガスに含まれる硫黄化合物やVOCの酸化分解反応が十分に進行しない。燃焼触媒による酸化分解処理の反応温度が650℃を超えると、燃焼触媒が熱により劣化し、二酸化炭素オフガスの浄化率を長期間、高い状態に維持することできなくなる。触媒燃焼器の材質を耐熱材料にする必要が生じ、材料コストが高くなる。酸化分解処理に要する燃料消費量が多くなり、処理コストが高くなるとともに、二酸化炭素の排出量が増加する。さらに、サーマルNOxが生成するおそれがある。
二酸化炭素オフガスの圧力を0.01MPa以上、1MPa以下とすれば、二酸化炭素オフガスの体積が小さくなり、触媒燃焼器83における滞留時間が短くなり、処理効率がよくなるとともに、処理後の二酸化炭素オフガスを大気中に放出する前にガス膨張機によって動力を回収できるので、処理コストを低くできる。
二酸化炭素オフガスの圧力が0.01MPa未満では、二酸化炭素オフガスの体積が大きく、触媒燃焼器83における滞留時間が長くなり、処理効率が悪くなる。二酸化炭素オフガスの圧力が1MPaを超えると、触媒燃焼器83およびその上流機器が耐圧容器となり、装置コストが高くなり、助燃空気などの圧縮動力が必要となり、運転コストが高くなるなどの弊害が大きくなる。
この助燃空気により、触媒燃焼領域83a出口の二酸化炭素オフガスを冷却し、触媒燃焼領域83b内の温度が上昇し過ぎるのを抑制し、酸化分解処理における反応温度が上記の温度範囲内となるように制御する。
この二酸化炭素オフガスに含まれる水銀類を除去する処理は、二酸化炭素オフガスを浄化装置80内に導入する前段、あるいは、浄化装置80内において、二酸化炭素オフガスを加熱器81に導入する前段にて行う。
この二酸化炭素オフガスに含まれる水銀類の除去処理は、活性炭などの吸着処理によって行われる。
(3)天然ガスの製造方法および製造装置の実施形態
図11は、本発明に係る天然ガスの製造方法の一実施形態を示すフロー図である。この方法は、まず、井戸から採取された原料天然ガスを計量した後、スラグキャッチャーに供給し前記スラグキャッチャー等により原料天然ガスを液相と気相とに分離させる液相除去工程200を備える。
二酸化炭素オフガスを分離した後の原料ガスは、水分除去工程204に送られ、ガスハイドレートを形成する温度近くまで冷却され、凝縮した水分が除去される。
水銀を除去した後の原料ガスは、重質分除去工程208に送られ、複数の蒸留塔により分留されて、ペンタン以上の重質炭化水素等を除去して天然ガスを得られる。さらに、重質炭化水素を除去された原料ガスは、液化工程210に送られ、冷却および圧縮してタンクに充填される。二酸化炭素オフガスは、オフガス浄化工程201に送られ、前述したいずれかの実施形態の二酸化炭素オフガスの浄化方法によりオフガスが浄化される。
図1に示す触媒燃焼方式の二酸化炭素オフガスの浄化装置において、α=1およびβ=1とし、表1に示す二酸化炭素オフガス、表2に示す助燃空気、および、表3に示す燃料ガスを用いて、二酸化炭素オフガスの酸化分解処理を行った。触媒としては、後述する実施例2で作成した触媒を用いた。
処理条件と結果を表4に示す。
図6に示す直接燃焼方式の二酸化炭素オフガスの浄化装置において、α=1およびβ=1とし、表1に示す二酸化炭素オフガス、表2に示す助燃空気、および、表3に示す燃料ガスを用いて、二酸化炭素オフガスの酸化分解処理を行った。
処理条件と結果を表4に示す。
浄化装置100を用いた二酸化炭素オフガスの浄化方法では、二酸化炭素オフガスを、流路104を介して浄化装置100内に導入するとともに、流路108から浄化装置100内に助燃空気を導入する。
空気予熱器102と二酸化炭素オフガス予熱器103が熱交換器である場合、この熱交換器にて、処理後の二酸化炭素オフガスと、処理前の助燃空気または二酸化炭素オフガスとの熱交換が行われ、処理前の助燃空気または二酸化炭素オフガスが所定の温度まで予熱される。
実施例1では、従来よりも低温の燃焼処理であるため、二酸化炭素オフガスに含まれるメタン(CH4)の燃焼性が悪化することが予想された。そこで、実施例1において、メタンの転化率を0%と仮定し、二酸化炭素に比べて温暖化係数が21倍のメタンがスリップすることによる二酸化炭素の排出量への影響を調べた。メタンのスリップ量を二酸化炭素に換算し、各燃焼処理に伴う二酸化炭素の排出量(表4の(a)+(b))は、比較例1の直接燃焼方式の二酸化炭素排出量が10,900Nm3/hであるのに対して、実施例1の触媒燃焼方式の二酸化炭素排出量が5,300Nm3/hであり、二酸化炭素排出量を50%以上削減できることが示唆された。
さらに、二酸化炭素オフガスに含まれる二酸化炭素の排出量を考慮し、各燃焼処理に伴う二酸化炭素の総排出量(表4の(a)+(b)+(c))は、比較例1の直接燃焼方式の二酸化炭素排出量が103,300Nm3/hであるのに対して、実施例1の触媒燃焼方式の二酸化炭素排出量が97,700Nm3/hであり、二酸化炭素排出量を5%削減できることが示唆された。
酸化チタン粉末(アナターゼ型、商品名:PC-500、ミレニアム社製)58.6gと、チタニアゾル(商品名:TA-15、日産化学工業社製)138.0gと、純水103.5gとを混合し、酸化チタン粉末含有スラリーを調製した。
コージライトハニカム(400cpi2、日本ガイシ社製)の内壁面に、この酸化チタン粉末含有スラリーを塗布し、エアーブローにより余分なスラリーを除去した。
酸化チタン粉末含有スラリーを塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により500℃にて、2時間焼成し、酸化チタン粉末の含有量が50g/リットルの層を形成した。
酸化チタン粉末からなる層が形成されたコージライトハニカムの内壁面に、この白金水溶液を塗布し、酸化チタン粉末からなる層にこの溶液を吸収させるとともに、エアーブローにより余分な溶液を除去し、酸化チタン粉末からなる層における白金水溶液の含有量が150g/リットルとなるように、酸化チタン粉末からなる層に白金水溶液を吸収させた。
白金水溶液を塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により500℃にて、2時間焼成し、更に水素雰囲気下で500℃にて2時間還元処理を行い、白金の含有量が2g/リットルのPt/TiO2触媒層を形成し、実施例2の燃焼触媒を得た。
実施例2と同様にして、酸化チタン粉末の含有量が52g/リットルの層を形成した。
硝酸パラジウム水溶液(パラジウム含有量10.0質量%)30gと、純水270gとを混合し、パラジウム含有量1.33質量%のパラジウム水溶液を調製した。
酸化チタン粉末からなる層が形成されたコージライトハニカムの内壁面に、このパラジウム水溶液を塗布し、酸化チタン粉末からなる層にこの溶液を吸収させるとともに、エアーブローにより余分な溶液を除去し、酸化チタン粉末からなる層におけるパラジウム水溶液の含有量が150g/リットルとなるように、酸化チタン粉末からなる層にパラジウム水溶液を吸収させた。
パラジウム水溶液を塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により500℃にて、2時間焼成し、パラジウムの含有量が2g/リットルのPd/TiO2触媒層を形成し、実施例3の燃焼触媒を得た。
酸化ジルコニウム粉末(商品名:RC-100、第一希元素化学工業社製)50.8gと、ジルコニアゾル(商品名:NZS-30A、日産化学工業社製)69.0gと、純水180.2gとを混合し、酸化ジルコニウム粉末含有スラリーを調製した。
コージライトハニカム(400cpi2、日本ガイシ社製)の内壁面に、この酸化ジルコニウム粉末含有スラリーを塗布し、エアーブローにより余分なスラリーを除去した。
酸化ジルコニウム粉末含有スラリーを塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により500℃にて、2時間焼成し、酸化ジルコニウム粉末の含有量が50g/リットルの層を形成した。
酸化ジルコニウム粉末からなる層が形成されたコージライトハニカムの内壁面に、この白金水溶液を塗布し、酸化ジルコニウム粉末からなる層にこの溶液を吸収させるとともに、エアーブローにより余分な溶液を除去し、酸化ジルコニウム粉末からなる層における白金水溶液の含有量が150g/リットルとなるように、酸化ジルコニウム粉末からなる層に白金水溶液を吸収させた。
白金水溶液を塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により500℃にて、2時間焼成し、更に水素雰囲気下で500℃にて2時間還元処理を行い白金の含有量が2g/リットルのPt/ZrO2触媒層を形成し、実施例4の燃焼触媒を得た。
酸化アルミニウム粉末(商品名:NST-5、日揮ユニバーサル社製)43.3gと、アルミナゾル(商品名:A-10、川研ファインケミカル社製)138.0gと、純水76.7gとを混合し、酸化アルミニウム粉末含有スラリーを調製した。
コージライトハニカム(400cpi2、日本ガイシ社製)の内壁面に、この酸化アルミニウム粉末含有スラリーを塗布し、エアーブローにより余分なスラリーを除去した。
酸化アルミニウム粉末含有スラリーを塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により500℃にて、2時間焼成し、酸化アルミニウム粉末の含有量が50g/リットルの層を形成した。
酸化アルミニウム粉末からなる層が形成されたコージライトハニカムの内壁面に、この白金水溶液を塗布し、酸化アルミニウム粉末からなる層にこの溶液を吸収させるとともに、エアーブローにより余分な溶液を除去し、酸化アルミニウム粉末からなる層における白金水溶液の含有量が150g/リットルとなるように、酸化アルミニウム粉末からなる層に白金水溶液を吸収させた。
白金水溶液を塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により500℃にて、2時間焼成し、更に水素雰囲気下で500℃にて2時間還元処理を行い白金の含有量が2g/リットルのPt/Al2O3触媒層を形成し、比較例2の燃焼触媒を得た。
酸化アルミニウム粉末(商品名:NST-5、日揮ユニバーサル社製)43.3gと、アルミナゾル(商品名:A-10、川研ファインケミカル社製)138.0gと、純水76.7gとを混合し、酸化アルミニウム粉末含有スラリーを調製した。
コージライトハニカム(400cpi2、日本ガイシ社製)の内壁面に、この酸化アルミニウム粉末含有スラリーを塗布し、エアーブローにより余分なスラリーを除去した。
酸化アルミニウム粉末含有スラリーを塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により500℃にて、2時間焼成し、酸化アルミニウム粉末の含有量が50g/リットルの層を形成した。
酸化アルミニウム粉末からなる層が形成されたコージライトハニカムの内壁面に、このパラジウム水溶液を塗布し、酸化アルミニウム粉末からなる層にこの溶液を吸収させるとともに、エアーブローにより余分な溶液を除去し、酸化アルミニウム粉末からなる層におけるパラジウム水溶液の含有量が150g/リットルとなるように、酸化アルミニウム粉末からなる層にパラジウム水溶液を吸収させた。
パラジウム水溶液を塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により500℃にて、2時間焼成し、パラジウムの含有量が2g/リットルのPd/Al2O3触媒層を形成し、比較例3の燃焼触媒を得た。
Cu/Mn粉末として、ホプカライト粉末(商品名:N-840、ズードケミー社製)84.0gと、シリカゾル(商品名:スノーテックスC、日産化学工業社製)148.5gと、純水67.5gとを混合し、Cu/Mn粉末含有スラリーを調製した。
コージライトハニカム(400cpi2、日本ガイシ社製)の内壁面に、このCu/Mn粉末含有スラリーを塗布し、エアーブローにより余分なスラリーを除去した。
Cu/Mn粉末含有スラリーを塗布したコージライトハニカムを、乾燥機により150℃にて、6時間乾燥した。
このコージライトハニカムを、焼成炉により400℃にて、2時間焼成し、Cu/Mn粉末の含有量が100g/リットルのCu/Mn層を形成し、比較例4の燃焼触媒を得た。
実施例2で作製したPt/TiO2触媒層を備えたコージライトハニカムからなる燃焼触媒を有する触媒燃焼器を用いて、硫化水素とベンゼン(C6H6)の酸化分解処理を行った場合、ベンゼンの酸化反応(C6H6+15/2O2→6CO2+3H2O)に関して、反応速度を下記のLangmuir-Hinshelwood式(式(1))にて表現した。
上記の式(1)によって反応速度を表現した結果、図7に示すように反応速度の実測値と計算値がほぼ一致することが確認された。
GHSV(空間速度)を30,000h-1、ベンゼン濃度を500ppm、触媒燃焼器の圧力を1気圧とし、実施例2で作製したPt/TiO2触媒層を備えたコージライトハニカムからなる燃焼触媒を用いて、硫化水素とベンゼン(C6H6)の酸化分解処理を行った場合、表5に示す硫化水素濃度、酸素濃度における、反応温度とベンゼンの転化率(分解率)との関係を図8に示す。
ベンゼンの転化率を下記の式で定義した。
転化率(%)=(1-(触媒燃焼器の出口側におけるベンゼン濃度/触媒燃焼器の入口側におけるベンゼン濃度)×100
図8に示す解析例2、4の結果から、酸素濃度が5.0体積%から2.0体積%に低下すると、ベンゼンの酸化反応における反応活性が低下することが示唆された。すなわち、酸素濃度が2.0体積%の時、酸素濃度が5.0体積%の時と同様にベンゼンの酸化反応を進行させるためには、反応温度を20℃程度上昇させる必要があることが示唆された。
以上の結果から、実施例2で作製したPt/TiO2触媒層を備えたコージライトハニカムからなる燃焼触媒を用いたベンゼンの酸化反応は、共存する硫化水素および酸素の濃度の影響を受けることが示唆された。ベンゼンの酸化反応を進行させるためには、反応温度を250℃以上とする必要があることが示唆された。
実施例2で作製したPt/TiO2触媒層を備えたコージライトハニカムからなる燃焼触媒を、表6に示す高温雰囲気下に曝した後、表7に示す反応条件にて、ベンゼンの酸化分解処理を行った。
結果を表8に示す。
以上の結果から、実施例2で作製したPt/TiO2触媒層を備えたコージライトハニカムからなる燃焼触媒を用いたベンゼンの酸化反応において、反応温度の上限は、触媒の耐熱性の点から650℃程度であることが示唆された。
実施例2~4および比較例2~4で作製した燃焼触媒を用いて、燃焼触媒の基本性能、燃焼触媒の寿命性能、燃焼触媒の性能と反応条件との関係について試験した。
図9は、燃焼触媒性能試験に用いられる試験装置を示す概略図である。
この試験装置120を用いて、以下に示す方法で燃焼触媒の性能試験を行った。
まず、触媒燃焼器121内に試験条件ごとに新しい燃焼触媒122を配置し、その前段(処理対象のガスの流れ方向の上流側)に石英破砕品123を配置した。
触媒燃焼器121に供給した二酸化炭素および空気を、触媒燃焼器121の周囲に配された電気炉128により所定の温度まで加熱した。
ロータリーポンプ130により、水が入った容器129から触媒燃焼器121に水の供給を開始した。
出口側のガスサンプルの採取が終了した後、触媒燃焼器121の入口側に設けられたサンプル採取口137にテドラーバックを設置し、入口側ガスサンプルを採取した。
ガスサンプルの採取後、空気および二酸化炭素以外のガスの供給を止め、測定を終了した。
ガスクロマトグラフィーとしては、GC-14B(島津製作所社製)を用いた。
検出器としては、FID(水素炎イオン化検出器)を用いた。
被処理ガスに含まれる硫化水素またはメルカプタンまたは一酸化炭素の濃度測定を、ガステック社製のガス検知管により行った。
転化率(%)=(1-(触媒燃焼器の出口側におけるベンゼン濃度、トルエン濃度、p-キシレン濃度/触媒燃焼器の入口側におけるベンゼン濃度、トルエン濃度、p-キシレン濃度)×100
実施例2~4および比較例2~4で作製した燃焼触媒を用いて、表9に示す反応条件により、硫黄化合物およびVOCを含む二酸化炭素の酸化分解処理を行った。
ベンゼンの転化率を、表10に示す。
比較例2、3の酸化アルミニウム(Al2O3)を用いた燃焼触媒は、硫黄化合物の酸化物である硫酸により硫酸塩化し、活性金属種(白金、パラジウム)が同じ場合でも、安定した酸化分解性能を発揮できないことが確認された。
比較例4の燃焼触媒は、活性金属として、貴金属を用いていないので、表9に示した反応条件では、350℃と400℃における反応性が著しく低いことが確認された。
実施例2および比較例2、4で作製した燃焼触媒を用いて、表11に示す反応条件により、硫黄化合物およびVOCを含む二酸化炭素の酸化分解処理を行った。
ベンゼンの転化率を、図10に示す。
比較例2の酸化アルミニウムを用いた燃焼触媒は、硫黄化合物の酸化物であるSOxにより徐々に硫酸塩化し、活性金属種(白金)が同じ場合でも、活性の低下が早く、安定した酸化分解性能を発揮できないことが確認された。
比較例4の燃焼触媒についても、硫黄化合物の酸化物であるSOxの影響により、活性の低下が早く、安定した酸化分解性能を発揮できないことが確認された。
(a)ベンゼン、トルエン、p-キシレンを含む場合の反応性
実施例2で作製した燃焼触媒を用いて、表12に示す反応条件により、硫化水素、並びに、ベンゼン、トルエンおよびp-キシレンを含む二酸化炭素の酸化分解処理を行った。
ベンゼン、トルエン、p-キシレンの転化率を、表13に示す。
実施例2で作製した燃焼触媒を用いて、表14に示す反応条件により、硫化水素およびメルカプタン、並びに、ベンゼンを含む二酸化炭素の酸化分解処理を行った。
ベンゼンの転化率を、表15に示す。
実施例2で作製した燃焼触媒を用いて、表16に示す反応条件により、硫化水素およびベンゼンを含む二酸化炭素の酸化分解処理を行った。
ベンゼンの転化率を、表17に示す。
実施例2で作製した燃焼触媒を用いて、表18に示す反応条件により、硫化水素およびベンゼンを含む二酸化炭素の酸化分解処理を行った。
ベンゼンの転化率を、表19に示す。
実施例2で作製した燃焼触媒を用いて、表20に示す反応条件により、硫化水素およびベンゼンを含む二酸化炭素の酸化分解処理を行った。
ベンゼンの転化率を、表21に示す。
11,81 加熱器
12,82 予熱器
13,83 触媒燃焼器
14~26,84~97 流路
212 容器
214 導入口
216 導出口
220A~220I 燃焼触媒ユニット
Claims (14)
- 二酸化炭素を主成分とするガス中の揮発性有機化合物および硫黄化合物を酸化分解する二酸化炭素オフガスの浄化方法であって、
揮発性有機化合物、および50ppmv以上、10000ppmv以下の硫黄化合物を少なくとも含む二酸化炭素を主成分とする二酸化炭素オフガスを触媒燃焼器に導入する工程と、
前記触媒燃焼器中の燃焼触媒によって、前記揮発性有機化合物および前記硫黄化合物を酸化分解する工程を具備し、
前記燃焼触媒は、酸化ジルコニウム、酸化チタン、酸化ケイ素の群から選択される1種または2種以上の金属酸化物と、白金、パラジウム、イリジウムの群から選択される1種または2種以上の貴金属とを含んでおり、
酸化分解処理後のガス中における、硫黄酸化物を除く硫黄化合物濃度を5ppmv以下とする二酸化炭素オフガスの浄化方法。 - 前記二酸化炭素を主成分とするガスおよび/または空気を予熱した後、前記触媒燃焼器に供給する請求項1記載の二酸化炭素オフガスの浄化方法。
- 前記触媒燃焼器は、燃焼触媒が設けられた少なくとも2つの触媒燃焼領域を備え、当該触媒燃焼領域の間に、酸化分解処理後の二酸化炭素を主成分とするガス、空気、水のうちから選択される少なくとも1種を供給し、前記触媒燃焼器に導入した二酸化炭素を主成分とするガスを冷却する請求項1記載の二酸化炭素オフガスの浄化方法。
- 前記二酸化炭素を主成分とするガスに含まれる水銀類を除去した後、当該水銀類を除去した後の二酸化炭素を主成分とするガスを触媒燃焼器に導入する請求項1記載の二酸化炭素オフガスの浄化方法。
- 前記二酸化炭素を主成分とするガスは、ガス田から産出された天然ガス中の酸性ガスを液体溶媒と接触させることにより分離・回収する酸性ガス分離装置から排出されるガスである請求項1に記載の二酸化炭素オフガスの浄化方法。
- 前記二酸化炭素を主成分とするガスは、前記酸性ガス分離装置の後段に設けられた、硫化水素濃縮装置、硫黄回収装置、テールガス処理装置のうちのいずれか1つの装置にて硫化水素を低減した後の排出ガスである請求項5に記載の二酸化炭素オフガスの浄化方法。
- 前記触媒燃焼器に充填される燃焼触媒は、基体と、この基体の表面に形成された、前記金属酸化物と前記貴金属からなる触媒層とを具備しており、前記金属酸化物の比表面積が10m2/g以上、300m2/g以下である請求項1記載の二酸化炭素オフガスの浄化方法。
- 前記燃焼触媒は、多数の通気路を備えたハニカム構造の基体と、前記通気路の内面に形成された前記金属酸化物からなる金属酸化物層と、前記金属酸化物層の少なくとも表層部に0.1mg/cm2以上、10mg/cm2以下の密度で付着された前記貴金属とを有し、前記基体は、セラミックス、金属酸化物、または金属合金で形成されている請求項1記載の二酸化炭素オフガスの浄化方法。
- 前記触媒燃焼器は、一端に導入口、他端に導出口が形成された容器と、前記容器内に前記導入口と前記導出口との間で互いに間隔を空けて配置された複数の燃焼触媒ユニットとを有し、前記燃焼触媒ユニットはそれぞれ、二酸化炭素オフガスを通過させる多数の通気路を備えたハニカム構造の基体と、前記通気路の内面に形成された前記金属酸化物からなる金属酸化物層と、前記金属酸化物層の少なくとも表層部に0.1mg/cm2以上、10mg/cm2以下の密度で付着された前記貴金属とを有し、前記基体は、セラミックス、金属酸化物、または金属合金で形成されており、
前記導出口に近い前記燃料触媒ユニットの前記通気口の内径は、前記導入口に近い前記燃料触媒ユニットの内径よりも、大きくされている請求項1記載の二酸化炭素オフガスの浄化方法。 - 前記二酸化炭素を主成分とするガス中に少なくとも含まれる揮発性有機化合物および硫黄化合物を、250℃以上、650℃以下の反応温度において酸化分解処理するための燃焼触媒であって、
前記燃焼触媒は、酸化ジルコニウム、酸化チタン、酸化ケイ素の群から選択される1種または2種以上の金属酸化物と、白金、パラジウム、イリジウムの群から選択される1種または2種以上の貴金属とを含む二酸化炭素オフガスの浄化用燃焼触媒。 - 前記燃焼触媒は、基体と、該基体の表面に形成された、前記金属酸化物と前記貴金属からなる触媒層とを具備してなり、前記基体は、ハニカム構造体、ペレット体または球体である請求項10に記載の二酸化炭素オフガスの浄化用燃焼触媒。
- 前記燃焼触媒は、多数の通気路を備えたハニカム構造の基体と、前記通気路の内面に形成された前記金属酸化物からなる金属酸化物層と、前記金属酸化物層の少なくとも表層部に0.1mg/cm2以上、10mg/cm2以下の密度で付着された前記貴金属とを有し、前記基体は、セラミックス、金属酸化物、または金属合金で形成されている請求項11に記載の二酸化炭素オフガスの浄化用燃焼触媒。
- 前記触媒燃焼器は、一端に導入口、他端に導出口が形成された容器と、前記容器内に前記導入口と前記導出口との間で互いに間隔を空けて配置された複数の燃焼触媒ユニットとを有し、前記燃焼触媒ユニットはそれぞれ、二酸化炭素オフガスを通過させる多数の通気路を備えたハニカム構造の基体と、前記通気路の内面に形成された前記金属酸化物からなる金属酸化物層と、前記金属酸化物層の少なくとも表層部に0.1mg/cm2以上、10mg/cm2以下の密度で付着された前記貴金属とを有し、前記基体は、セラミックス、金属酸化物、または金属合金で形成されており、
前記導出口に近い前記燃料触媒ユニットの前記通気口の内径は、前記導入口に近い前記燃料触媒ユニットの内径よりも、大きくされている請求項11に記載の二酸化炭素オフガスの浄化用燃焼触媒。 - 原料天然ガスから天然ガスを製造する天然ガスの製造方法であって、
原料天然ガスをスラグキャッチャーに供給し前記スラグキャッチャーにより原料天然ガスを液相と気相とに分離させる工程と、
前記気相から、二酸化炭素を主成分とし揮発性有機化合物および硫黄化合物を含む二酸化炭素オフガスを分離する酸性ガス除去工程と、
二酸化炭素オフガスを分離した後の原料ガスを冷却して凝縮した水分を除去する水分除去工程と、
水分を除去した後の原料ガスを蒸留塔により分留して重質炭化水素を除去して天然ガスを得る重質分除去工程と、
前記二酸化炭素オフガスを、請求項1記載の二酸化炭素オフガスの浄化方法により浄化するオフガス浄化工程とを具備する天然ガスの製造方法。
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RU2010136325A (ru) | 2012-07-27 |
JPWO2009157434A1 (ja) | 2011-12-15 |
AU2009263401A1 (en) | 2009-12-30 |
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