Exhaust gas purification method and exhaust gas purification apparatus

Abstract

An exhaust gas purification method comprising: allowing an exhaust gas containing at least one substance selected from the group consisting of ash dust, hydrogen chloride, a nitrogen oxide, a sulfur oxide, mercury, a volatile organic compound and a carbon oxide to pass through a catalyst bag filter having at least one function selected from the group consisting of a denitration function, an NO oxidation function, an Hg0 oxidation function, a desulfurization function and an adsorption function; bringing the exhaust gas that has passed through the catalyst bag filter into direct contact with a cooling solution to decrease the temperature of the exhaust gas; and subsequently bringing the exhaust gas that has been directly contacted with the cooling solution into direct contact with a CO2 absorption solution to reduce carbon dioxide in the exhaust gas.

Description

Exhaust gas purification method and exhaust gas purification device

[0001] The present invention is directed to the prevention of harmful substances contained in exhaust gases, such as nitrogen oxides (NO ｘ ), sulfur oxides (SO ｘ ), carbon oxides (COx), hydrogen chloride (HCl), mercury (Hg ０ The present application claims priority to Japanese Patent Application No. 2023-038171 filed with the Japan Patent Office on March 10, 2023, the contents of which are incorporated herein by reference.

[0002] Gases emitted from thermal power plants, waste incinerators, cement kilns, aluminum melting furnaces, boilers, etc. contain harmful substances such as nitrogen oxides, sulfur oxides, carbon dioxide, hydrogen chloride, heavy metals, dioxins, and volatile organic compounds. It is said that an increase in the concentration of such harmful substances in the atmosphere will have a negative impact on the global environment. Therefore, there are many systems for removing harmful substances from exhaust gases, such as denitration systems, dust collectors, desulfurization systems, demineralization systems, and CO2 removal systems. ２ Various removal devices have been proposed.

[0003] Known denitrification devices include those that use the ammonia catalytic reduction method. Known desulfurization devices include those that use the wet lime gypsum method, those that use the alkaline solution absorption method or lime slurry absorption method, those that use the spray dry method, and those that use the activated carbon adsorption method. ２ The removal device is a device that uses a liquid containing an amine compound such as alkanolamine (hereinafter referred to as CO ２ It is sometimes called an absorption liquid. ２ Absorbers) are known.

[0004] Even after passing through a denitration device or a desulfurization device, exhaust gas contains several ppm to several tens of ppm of nitrogen dioxide and several ppm to several hundred ppm of sulfur dioxide, and also contains trace amounts of nitrogen monoxide, sulfur trioxide, mercury, dust, and volatile organic compounds. ２Send to the absorber and CO ２ When the removal process is performed, CO ２ The amine compounds contained in the absorption liquid are altered by nitrogen dioxide, sulfur trioxide, mercury, soot, etc., and ２ CO in the absorption solution ２ The absorption performance is reduced. ２ NO in front of the absorber ｘ Scrubbers, desalination and desulfurization agent sprayers, wet electrostatic precipitators, etc. ２ Install a pre-absorption treatment device to ２ It has been proposed to remove substances that alter amine compounds from exhaust gas immediately before it is supplied to an absorption device (Patent Documents 1, 2, 3, 4, and 5).

[0005] WO2013 / 78211A1 JP 2005-40683 A WO2012 / 14831A1 JP 2015-85310 A WO2011 / 152550A1 JP 8-332349 A JP 8-196830 A JP 2002-18241 A JP 2006-7055 A

[0006] However, the above-mentioned conventional CO ２ The absorption pretreatment equipment has high equipment and operating costs, and also has the disadvantage of removing substances that alter amine compounds (especially Hg ０ The object of the present invention is to provide a method for the removal of CO ２ To provide an exhaust gas purification method and an exhaust gas purification device which can extend the life of an absorption solution and efficiently remove harmful substances contained in exhaust gas (nitrogen dioxide, nitrogen monoxide, sulfur oxides, carbon dioxide, mercury, dioxins, volatile organic compounds, etc.) at low cost.

[0007] As a result of investigations to achieve the above object, the present inventors have completed the present invention, which includes the following aspects: [1] A catalytic converter for denitrifying exhaust gas containing at least one selected from the group consisting of soot, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides, which has a denitrification function, an NO oxidation function, an Hg oxidation function, and a ０The exhaust gas is passed through a catalytic bag filter having at least one function selected from the group consisting of an oxidation function, a desulfurization function, and an adsorption function, the exhaust gas that has passed through the catalytic bag filter is cooled to lower the temperature of the exhaust gas, and then the cooled exhaust gas is subjected to CO ２ A method for purifying flue gas, comprising reducing carbon dioxide in the flue gas by direct contact with an absorption liquid.

[0008] [2] The method for purifying exhaust gas according to [1], wherein the exhaust gas is cooled by direct contact with a coolant, and the coolant is plain water, seawater, or an alkaline aqueous solution.

[0009] [3] The method for purifying exhaust gas according to [1] or [2], which comprises subjecting the exhaust gas to at least one treatment selected from the group consisting of denitration treatment, dust collection treatment, desulfurization treatment, and demineralization treatment before passing the exhaust gas through the catalytic bag filter.

[0010] [4] CO ２ The method for purifying an exhaust gas according to any one of [1] to [3], wherein the absorption liquid is an aqueous solution containing an amine compound.

[0011] [5] The method for purifying exhaust gas according to any one of [1] to [4], wherein the temperature of the exhaust gas immediately before passing through the catalytic bag filter is 80 to 250°C.

[0012] [6] CO ２ The method for purifying an exhaust gas according to any one of [1] to [5], wherein the temperature of the exhaust gas immediately before being brought into direct contact with the absorption liquid is 20 to 80°C.

[0013] [7] Denitration function, NO oxidation function, Hg ０ A catalytic bag filter having at least one function selected from the group consisting of an oxidation function, a desulfurization function, and an adsorption function; a gas cooling device configured to be able to cool the gas and lower the temperature of the gas; and a gas and CO ２ A CO2 absorber configured to reduce carbon dioxide in gas by direct contact with an absorbing liquid. ２ The present invention relates to a method for treating exhaust gas containing at least one selected from the group consisting of soot, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides, and the method includes the steps of:２ An exhaust gas purification device configured so that it can pass through an absorber in sequence.

[0014] [8] The present invention further includes a demineralizer configured to reduce hydrogen chloride in the gas, and the exhaust gas containing at least one selected from the group consisting of soot, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides is passed through the demineralizer, catalytic bag filter, gas cooler, and CO ２ The exhaust gas purification device according to [7], configured so that the exhaust gas can pass through the absorption device in that order.

[0015] [9] A method for reducing nitrogen oxides in a gas, further comprising: a denitration device configured to reduce nitrogen oxides in the gas; a dust collector configured to reduce soot and dust in the gas; and a desulfurization device configured to reduce sulfur oxides in the gas, wherein exhaust gas containing at least one selected from the group consisting of soot and dust, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides is filtered through the denitration device, the dust collector, the desulfurization device, the catalytic bag filter, the gas cooler, and the CO ２ The exhaust gas purification device according to [7], configured so that the exhaust gas can pass through the absorption device in that order.

[0016]

[10] The present invention further includes a demineralization device configured to reduce hydrogen chloride in the gas, and the exhaust gas containing at least one selected from the group consisting of soot, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides is treated by a denitration device, a dust collector, a desulfurization device, a demineralization device, a catalytic bag filter, a gas cooler, and a CO ２ The exhaust gas purification device according to [9], configured so that the exhaust gas can pass through the absorption device in that order.

[0017] The method for purifying exhaust gas according to the present invention can efficiently remove harmful substances such as nitrogen dioxide, nitrogen monoxide, sulfur oxides, carbon dioxide, mercury, dioxins, and volatile organic compounds from exhaust gas. ２ Before direct contact with the absorption liquid, ２ Substances that alter the absorbent are removed efficiently, so CO ２ The deterioration of the absorption liquid performance is suppressed, and CO２ The life of the absorption liquid can be extended. The exhaust gas purification device according to the present invention is optimal for carrying out the exhaust gas purification method according to the present invention. The equipment cost and operation cost of the device related to the catalytic bag filter are ｘ Scrubbers, desalination and desulfurization agent sprayers, wet electrostatic precipitators, and other conventional CO ２ It is cheaper than absorption pretreatment equipment.

[0018] 1 is a diagram showing an example of an apparatus configuration suitable for carrying out the exhaust gas purification method of the present invention.

[0019] Hereinafter, examples of embodiments of the method and apparatus of the present invention will be described, but the present invention is not limited to these embodiments.

[0020] The exhaust gas purification method of the present invention includes passing an exhaust gas through a catalytic bag filter, cooling the exhaust gas that has passed through the catalytic bag filter, and then purifying the exhaust gas by CO ２ The method for purifying exhaust gases of the present invention may further include, as necessary, subjecting the exhaust gas to at least one treatment selected from the group consisting of denitration treatment, dust collection treatment, desulfurization treatment, and demineralization treatment before passing the exhaust gas through the catalytic bag filter.

[0021] The exhaust gas purification device of the present invention comprises a catalytic bag filter 1, a gas cooler 2, and a CO ２ The exhaust gas purification apparatus of the present invention may further include a denitration device 6, a dust collection device 7, a desulfurization device 8, or a demineralization device 9, as required. ２ A recovery device 4 may further be included.

[0022] Exhaust gases to which the method or apparatus of the present invention can be applied contain at least one selected from the group consisting of soot, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides. They may also contain other harmful substances such as dioxins, phosphorus oxides, and arsenic. They may also contain urea, ammonia, and the like, which can be added in denitration treatment using ammonia catalytic reduction.

[0023] Exhaust gases applicable to the present invention may be gases emitted from exhaust gas generating sources 5 such as thermal power plants, refuse incinerators, cement kilns, aluminum melting furnaces, and boilers.

[0024] The temperature of the exhaust gas immediately before passing through the catalytic bag filter is preferably 80 to 250°C, more preferably 100 to 200°C. ２ The temperature of the exhaust gas immediately before it is brought into direct contact with the absorbing liquid is preferably 20 to 80°C, more preferably 30 to 65°C, and even more preferably 40 to 50°C.

[0025] The catalytic bag filter used in the present invention has a denitration function, a NO oxidation function, and a Hg ０ The catalytic bag filter has at least one function selected from the group consisting of an oxidation function, a desulfurization function, and an adsorption function. The catalytic bag filter is a bag filter configured to capture particulate matter (soot, dust, etc.) (dust removal process), and is loaded with catalysts or functional substances that can add various functions. Examples of catalytic bag filters that can be used in the present invention include those described in Patent Documents 6, 7, and 9.

[0026] Although not limited to this example, the bag filter may be made of a filter cloth including one or more base fabrics made of woven or nonwoven fabric and one or more felt layers laminated on one or both sides of the base fabric. The base fabric or felt layer can be made of a fiber material made of a heat-resistant organic resin such as polyphenylene sulfide resin or polytetrafluoroethylene resin, or a heat-resistant inorganic fiber material such as glass fiber, carbon fiber, or titania fiber (see JP 2002-113311 A).

[0027] It may be preferable to provide a felt layer on the exhaust gas inflow side. The felt layer may be useful for capturing, for example, submicron-sized particulate matter. The base fabric and / or felt layer may also serve as a carrier for supporting catalysts, functional materials, etc.

[0028] The bag filter is not particularly limited in its external shape. Examples include cylindrical, bottomed cylindrical, and bag-shaped. Examples of cylindrical, bottomed cylindrical, and bag-shaped bag filters include those having a cylindrical, bottomed cylindrical, or bag-shaped filter cloth and a gauge (retainer) incorporated into the filter cloth. The bag filter itself has the function of capturing soot, particulate matter (PM), and the like.

[0029] The catalytic bag filter used in the present invention has various other functions in addition to the collection function. These functions include denitration, NO oxidation, Hg ０ The denitrification function includes at least one selected from the group consisting of an oxidation function, a desulfurization function, and an adsorption function. ２ These include NOx reduction functions such as NO reduction function and NO reduction function.

[0030] The catalytic bag filter used in the present invention can have a precoat layer containing slaked lime. The precoat layer is preferably provided on the exhaust gas inflow side. The slaked lime contained in the precoat layer neutralizes acid gases such as hydrogen chloride and SOx contained in the exhaust gas. The precoat layer also serves to capture unreacted acid gases or soot. The precoat layer can be formed on the base fabric and / or felt layer by adding slaked lime to the exhaust gas inflow side of the base fabric and / or felt layer.

[0031] The catalytic bag filter used in the present invention is made of activated alumina (Al ２ O ３ ), diatomaceous earth, activated clay, silica (SiO ２The filter may have an adsorption layer containing powder with a fine pore structure such as activated carbon. The adsorption layer is preferably provided near the side where the exhaust gas flows in. The powder with a fine pore structure is useful for adsorbing and removing chlorides, sulfur oxides, acidic ammonium sulfate, VOCs, dioxins, etc., which may be contained in the exhaust gas. Adding an element such as zinc or sulfur, or a metal halide such as zinc iodide or copper chloride to the powder with a fine pore structure may improve the adsorption capacity. The adsorption layer can be formed by supporting the powder with a fine pore structure on a gauge (retainer), a base fabric and / or a felt layer, or by sandwiching it between base fabric and / or felt layers. In addition, activated alumina (Al ２ O ３ ), diatomaceous earth, activated clay, silica (SiO ２ The adsorption layer may be formed by accommodating granular materials having a fine pore structure, such as activated carbon. Furthermore, a base fabric or felt layer may be formed by using fibers having a fine pore structure, and this layer itself may serve as the adsorption layer.

[0032] The catalytic bag filter used in the present invention may have a catalyst layer. The catalyst layer is preferably provided at a position farther from the exhaust gas inflow side than the adsorption layer or precoat layer, from the viewpoint of suppressing catalyst degradation. The denitration catalyst that can be used in the catalyst layer is useful for reducing and reducing nitrogen oxides (NOx) that may be contained in exhaust gas. The denitration catalyst and the NOx oxidation catalyst may also be used together. The NOx oxidation catalyst oxidizes NO to NO ２ Convert to NO ２ Depending on the composition, denitration catalysts can help oxidize particulate matter (PM). ０ Although it may have oxidizing properties, Hg ０ The oxidation catalyst removes Hg, which is difficult to remove from exhaust gas. ０ It is oxidized to remove easily removable mercury compounds (HgO, HgCl ２ Denitrification catalyst, Hg ０ The oxidation catalyst and / or the NOx oxidation catalyst may be used in any combination as at least one catalyst layer. ０The oxidation catalyst layer and / or the NOx oxidation catalyst layer may be provided as separate catalyst layers in any combination. ０ This can accelerate the oxidation reaction of hydrogen chloride (boiling point -38.83°C), and hydrogen chloride (boiling point -85.09°C) can be converted to mercury(II) chloride (melting point 277°C), which can be easily removed using a filter. As a result, most of the NOx, NO, and mercury contained in the exhaust gas before passing through the catalytic bag filter are removed simply by passing through the filter.

[0033] The catalytic bag filter used in the present invention may have a dioxin decomposition catalyst layer. The dioxin decomposition catalyst helps to decompose and reduce dioxins that may be contained in exhaust gas. The dioxin decomposition catalyst layer may be provided separately from the above-mentioned catalyst layer, or the above-mentioned catalyst and a dioxin decomposition catalyst may be used in any combination to provide at least one catalyst layer.

[0034] Denitrification, NO oxidation, Hg ０ The composition and manufacturing method of catalysts suitable for oxidation or dioxin decomposition are known, and will not be described in detail here. ０ Examples of catalyst compositions suitable for oxidation or dioxin decomposition include those containing at least one base metal element selected from the group consisting of W, Mo, and V, those containing noble metals such as Pt, Ru, Pd, and Rh, those containing titanium oxide, silicon oxide, gypsum, alumina, etc., those containing aluminosilicates, zeolites, etc., and any combinations of these. The catalyst layer can be formed by supporting such catalysts on a base fabric and / or felt layer, or by sandwiching them between base fabric and / or felt layers.

[0035] The catalytic bag filter is housed in a bag filter house having a gas inlet and a gas outlet, and exhaust gas is supplied through the gas inlet of the bag filter house, making it easy to pass the exhaust gas through the catalytic bag filter. The exhaust gas that has passed through the catalytic bag filter exits through the gas outlet of the bag filter house. By optimizing the functions imparted to the catalytic bag filter in a balanced manner, multiple harmful substances contained in the exhaust gas immediately before passing through the catalytic bag filter can be simultaneously and significantly reduced by the exhaust gas passing through the catalytic bag filter. When soot, dust, particulate matter, etc. accumulate on the catalytic bag filter and the pressure loss exceeds a predetermined value, the accumulated substances can be removed by vibration or backwashing using a pulse jet (see, for example, Patent Document 8).

[0036] Next, the exhaust gas that has passed through the catalytic bag filter is cooled to lower the temperature of the exhaust gas. The exhaust gas can be cooled by indirect contact with a refrigerant via a heat exchanger, or by direct contact with a coolant. The coolant can be ordinary water, seawater, or an alkaline aqueous solution (NaOH, KOH, Ca(OH) ２ Preferably, a basic aqueous solution of a reducing substance (such as dithionite, thiosulfate, sulfite, bisulfite, iodide, etc.) or a basic aqueous solution of a reducing substance (such as dithionite, thiosulfate, sulfite, bisulfite, iodide, etc.) can be used. The direct contact of the exhaust gas with the cooling liquid can be carried out by a gas-liquid contact operation known in the art. Examples of apparatuses for the gas-liquid contact operation include plate (plate, tray) towers, packed towers, wetted-wall towers, spray towers, scrubbers, etc. Among these, spray towers are preferred. By this cooling, the exhaust gas is cooled to a temperature suitable for the next step of CO ２ The temperature is adjusted to a suitable temperature for absorption. The cooling liquid after the gas-liquid contact operation can be cooled by a chiller or the like if necessary, and consumed base and reducing substances can be replenished as necessary, and it can be reused for direct contact with exhaust gas.

[0037] When an alkaline aqueous solution is used as the coolant, a base such as sodium hydroxide reacts with sulfur dioxide in the exhaust gas to produce sulfite (for example, SO ２ + 2NaOH → Na ２ SO ３ +H ２Sulfite reacts with sulfur dioxide in the exhaust gas to produce hydrogen sulfite (e.g., SO ２ +Na ２ SO ３ +H ２ O → 2NaHSO ３ These reactions remove sulfur dioxide from exhaust gas. During this process, the sulfite concentration of the alkaline solution increases due to the reaction with sulfur dioxide in the exhaust gas. However, the pH of the alkaline solution decreases due to the reaction with nitrogen dioxide and sulfur dioxide in the exhaust gas. A decrease in the pH of the alkaline solution, i.e., a decrease in base, reduces the reaction with sulfur dioxide and the production of sulfite or bisulfite salts. Therefore, direct contact between the alkaline solution and the exhaust gas reduces the sulfite concentration overall. When an aqueous solution of sulfite or bisulfite salts is used, sulfite ions react with nitrogen dioxide in the exhaust gas and are reduced to nitrogen or nitrogen oxide. This reaction removes nitrogen dioxide from the exhaust gas.

[0038] The cooled exhaust gas is then ２ Reduces carbon dioxide in exhaust gas by directly contacting it with the absorption liquid. ２ As the absorption liquid, an aqueous solution containing an amine compound is preferably used. Examples of the amine compound include alcoholic hydroxyl group-containing primary amines such as monoethanolamine and 2-amino-2-methyl-1-propanol, alcoholic hydroxyl group-containing secondary amines such as diethanolamine and 2-methylaminoethanol, alcoholic hydroxyl group-containing tertiary amines such as triethanolamine and N-methyldiethanolamine, polyethylene polyamines such as ethylene diamine, triethylene diamine and diethylene triamine, cyclic amines such as piperazines, piperidines and pyrrolidines, polyamines such as xylylene diamine, amino acids such as methylaminocarboxylic acid, and mixtures thereof. ２ The absorption liquid may contain a carbon dioxide absorption promoter or a corrosion inhibitor, and further may contain other media such as methanol, polyethylene glycol, and sulfolane.

[0039] Exhaust gas and CO ２The direct contact with the absorbing liquid can be carried out by a gas-liquid contacting operation known in the art. Examples of apparatuses for the gas-liquid contacting operation include a plate (plate, plate plate, tray) tower, a packed tower, a wetted-wall tower, a spray tower, and a scrubber. Of these, a plate tower and a packed tower are preferred. The exhaust gas flows, for example, from the bottom of the absorption tower, rises in the absorption section, passes through the water washing section, and is discharged from the top of the absorption tower as purified gas 12. A CO 2 solution is added to the top of the absorption section. ２ The absorbing liquid is poured down and comes into countercurrent contact with the exhaust gas in the absorption section, absorbing the carbon dioxide in the exhaust gas and accumulating at the bottom of the absorption tower.

[0040] CO accumulated at the bottom of the absorption tower ２ The absorption liquid has a high concentration of carbon dioxide. ２ The absorption liquid is sent to a desorption tower, for example, and heated with steam or the like to remove CO ２ Carbon dioxide is desorbed from the absorption liquid, and carbon dioxide 13 is discharged from the top of the desorption column. ２ The absorbent accumulates at the bottom of the desorption tower and is returned to the absorption tower for recycling to absorb carbon dioxide. Meanwhile, the carbon dioxide 13 emitted from the top of the desorption tower is subjected to various treatments in the next process. For example, the carbon dioxide can be stored underground or in the ocean, or it can be used in enhanced oil recovery technology, welding, dry ice, synthesis of chemicals (oxygenated compounds (polycarbonate, urethane, etc.), general-purpose materials, etc.), synthesis of fuels (methanol, ethanol, methane, etc.), synthesis of carbonates, absorption into concrete products, absorption into seaweed, seaweed, and microalgae (biofuel synthesis), etc.

[0041] In the present invention, harmful substances such as nitrogen dioxide, sulfur dioxide, and mercury are efficiently removed by the catalytic bag filter and the gas cooling device that directly contacts the coolant. ２ The exhaust gas that comes into direct contact with the absorption solution contains CO ２ It contains almost no nitrogen dioxide or sulfur dioxide, which can cause a decrease in the carbon dioxide absorption capacity of the absorption liquid. ２ The decrease in the carbon dioxide absorption capacity of the absorption liquid is suppressed, and CO ２ The life of the absorbent is significantly extended. ２ Stop the operation of the absorber and CO ２This is economical because it reduces the frequency of the operation (reclaimer) to remove nitrates and other salts from the absorption liquid.

[0042] In the present invention, examples of treatments that can be applied to the exhaust gas, if necessary, before the exhaust gas is passed through the catalytic bag filter include at least one of the group consisting of denitration treatment, dust collection treatment, desulfurization treatment, and demineralization treatment.

[0043] Denitration devices (denitration treatment) reduce nitrogen oxides in exhaust gas. Denitration treatment can be carried out by passing exhaust gas through the denitration device. The denitration device is not particularly limited, but an ammonia catalytic reduction denitration device using a catalyst composition containing titanium oxide is preferred. The catalyst may contain, in addition to titanium oxide, at least one element selected from the group consisting of W, Mo, and V, gypsum, silica, etc. Examples of catalysts to be installed in denitration devices include catalyst compositions formed into honeycomb, columnar, or cylindrical shapes, and catalyst compositions formed into corrugated sheets by adhering them to metal substrates such as metal lath or ceramic or glass mesh woven fabrics. In the present invention, corrugated sheets are preferably used.

[0044] Dust collection devices (dust collection treatment) reduce soot (combustion ash, particulate matter (PM), etc.) in exhaust gas. Dust collection treatment can be performed by passing the exhaust gas through a dust removal device. The dust removal device used in the present invention is not particularly limited. For example, an electric dust collector, a bag filter device, etc. can be used.

[0045] A desulfurization device (desulfurization treatment) reduces sulfur oxides in exhaust gas. Desulfurization treatment can be performed by passing the exhaust gas through the desulfurization device. Although there are no particular limitations on the desulfurization device used in the present invention, devices using the wet limestone gypsum method or the magnesium hydroxide method are preferred.

[0046] A demineralizer (desalination process) reduces acidic substances such as hydrogen chloride and sulfur oxides in flue gas. Demineralization can be performed by passing the flue gas through the demineralizer. The demineralizer used in the present invention is not particularly limited, but is a device that can directly contact the flue gas with a demineralizing and desulfurizing agent. Examples of demineralizing and desulfurizing agents that can be used include alkaline aqueous solutions such as sodium bicarbonate (baking soda) solution and slaked lime solution. The temperature of the flue gas immediately before passing through the demineralizer can be adjusted using a gas temperature regulator. Examples of gas temperature regulators that can be used include a heat exchanger and a heater. The medium discharged from heat exchanger 10, which adjusts the temperature of the flue gas immediately before passing through the desulfurizer (recovers heat from the flue gas), can be used as the medium for heat exchanger 11, which adjusts the temperature of the flue gas immediately before passing through the demineralizer (supplies heat to the flue gas). The medium that transferred heat to the flue gas in heat exchanger 11 can be returned to heat exchanger 10 and used to recover heat from the flue gas.

[0047] The temperature of the exhaust gas immediately before passing through the catalytic bag filter can be adjusted by a desulfurization device or demineralization device, which may be installed upstream of the catalytic bag filter, or a gas temperature regulator. Examples of gas temperature regulators that can be used include a heat exchanger and a heater. The medium discharged from heat exchanger 10, which adjusts the temperature of the exhaust gas immediately before passing through the desulfurization device (recovers heat from the exhaust gas), can be used as the medium for heat exchanger 15, which adjusts the temperature of the exhaust gas immediately before passing through the catalytic bag filter (supplies heat to the exhaust gas). The medium that transferred heat to the exhaust gas in heat exchanger 15 can be returned to heat exchanger 10 and used to recover heat from the exhaust gas.

[0048] 1: Catalytic bag filter 2: Gas cooler 3: CO ２ Absorber 4: CO ２ Recovery device 5: Exhaust gas source 6: Denitrification device 7: Dust collector 8: Desulfurization device 9: Demineralization device 10: Gas temperature regulator (heat exchanger for heat recovery) 11: Gas temperature regulator (heat exchanger for heat supply) 12: Purified exhaust gas (to chimney) 13: Carbon dioxide 14: Denitrification agent (ammonia, urea, etc.) 15: Gas temperature regulator (heat exchanger for heat supply)

Claims

2024234197   15 Sep 202615THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS1. An exhaust gas purification method, comprising:allowing exhaust gas containing at least one selected from the group consisting of soot dust, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides to pass through a catalyst bag filter which has at least one function selected from the group consisting of a denitration function, an NO oxidization function, an Hg0 oxidization function and a desulfurization function;cooling the exhaust gas after passing through the catalyst bag filter to decrease a temperature of the exhaust gas; andbringing the exhaust gas after cooling into direct contact with a CO2 absorbent liquid to reduce carbon dioxide in the exhaust gas.

2. The exhaust gas purification method according to claim 1, further comprising:before allowing the exhaust gas to pass through the catalyst bag filter, performing at least one process selected from the group consisting of a denitration process, a dust collection process, a desulfurization process and a dehydrochlorination process on the exhaust gas.

3. The exhaust gas purification method according to claim 1 or 2,20 wherein the temperature of the exhaust gas immediately before passing through the catalyst bag filter is 80 to 250°C.

4. The exhaust gas purification method according to any one of claims 1 to 3,wherein the temperature of the exhaust gas immediately before directly contacting the 25 CO2 absorbent liquid is 20 to 80°C.

5. An exhaust gas purification apparatus, comprising:a catalyst bag filter which has at least one function selected from the group consisting of2024234197   15 Sep 202615a denitration function, an NO oxidization function, an Hg0 oxidization function, and a desulfurization function;a gas cooling device configured to be capable of cooling a gas to decrease a temperature of the gas; anda CO2 absorption device configured to be capable of reducing carbon dioxide in the gas through direct contact between the gas and a CO2 absorbent liquid,wherein the exhaust gas purification apparatus is configured such that the exhaust gas containing at least one selected from the group consisting of soot dust, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides is capable of passing through the catalyst bag filter, the gas cooling device, and the CO2 absorption device in this order.

6. The exhaust gas purification apparatus according to claim 5, further comprising:a dehydrochlorination device configured to be capable of reducing hydrogen chloride in the gas,wherein the exhaust gas purification apparatus is configured such that the exhaust gas containing at least one selected from the group consisting of soot dust, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides is capable of passing through the dehydrochlorination device, the catalyst bag filter, the gas 20 cooling device, and the CO2 absorption device in this order.

7. The exhaust gas purification apparatus according to claim 5, further comprising:a denitration device configured to be capable of reducing nitrogen oxides in the gas;a dust collection device configured to be capable of reducing soot dust in the gas; and25 a desulfurization device configured to be capable of reducing sulfur oxides in the gas, wherein the exhaust gas purification apparatus is configured such that the exhaust gas containing at least one selected from the group consisting of soot dust, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides is2024234197   15 Sep 202615capable of passing through the denitration device, the dust collection device, the desulfurization device, the catalyst bag filter, the gas cooling device, and the CO2 absorption device in this order.

8. The exhaust gas purification apparatus according to claim 7, further comprising:a dehydrochlorination device configured to be capable of reducing hydrogen chloride in the gas,wherein the exhaust gas purification apparatus is configured such that the exhaust gas containing at least one selected from the group consisting of soot dust, hydrogen chloride, nitrogen oxides, sulfur oxides, mercury, volatile organic compounds, and carbon oxides is capable of passing through the denitration device, the dust collection device, the desulfurization device, the dehydrochlorination device, the catalyst bag filter, the gas cooling device, and the CO2 absorption device in this order.

9. The exhaust gas purification method according to claim 1,wherein the catalyst bag filter has the denitration function and at least one function selected from the group consisting of the NO oxidization function, the Hg0 oxidization function, the desulfurization function, and the adsorption function.20   10. The exhaust gas purification method according to claim 1,wherein the catalyst bag filter includes a catalyst layer supporting the catalyst and an adsorption layer having the adsorption function, andwherein the catalyst layer is disposed at a position farther from an inflow side of the exhaust gas compared to the adsorption layer.2511. The exhaust gas purification method according to claim 10,wherein the catalyst bag filter further includes a precoat layer including slaked lime, and wherein the catalyst layer is disposed at a position farther from the inflow side of the2024234197   15 Sep 202615exhaust gas compared to the adsorption layer and the precoat layer.

12. The exhaust gas purification method according to claim 1, comprising:bringing the exhaust gas after passing through the catalyst bag filter into direct contact with a cooling liquid to decrease the temperature of the exhaust gas.

13. The exhaust gas purification method according to claim 2, comprising:allowing the exhaust gas to pass through the catalyst bag filter after the exhaust gas passes through a dust collection device configured to be capable of reducing soot dust in the gas.

14. The exhaust gas purification apparatus according to claim 5,wherein the catalyst bag filter has the denitration function and at least one function selected from the group consisting of the NO oxidization function, the Hg0 oxidization function, the desulfurization function, and the adsorption function.

15. The exhaust gas purification apparatus according to claim 5, wherein the catalyst bag filter includes a catalyst layer supporting the catalyst and an adsorption layer having the adsorption function, and20 wherein the catalyst layer is disposed at a position farther from an inflow side of the exhaust gas compared to the adsorption layer.

16. The exhaust gas purification apparatus according to claim 15,wherein the catalyst bag filter further includes a precoat layer including slaked lime, and25 wherein the catalyst layer is disposed at a position farther from the inflow side of the exhaust gas compared to the adsorption layer and the precoat layer.

17. The exhaust gas purification apparatus according to claim 5,2024234197   15 Sep 2026wherein the gas cooling device is configured to bring the exhaust gas after passing through the catalyst bag filter into direct contact with a cooling liquid to decrease the temperature of the exhaust gas.5   18. The exhaust gas purification apparatus according to claim 5, further comprising:a dust collection device configured to be capable of reducing soot dust in the gas, wherein the exhaust gas purification apparatus is configured such that the exhaust gas after passing through the dust collection device passes through the catalyst bag filter.

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