Acid gas separation recovery system and acid gas separation recovery method

Abstract

To provide an acid gas separation recovery system and a method capable of separating and recovering carbon dioxide, capable of suppressing the diffusion quantity of nitrosoamine on the ground and being suitable for an environmental aspect.SOLUTION: An acid gas separation recovery system includes: a NOx removal facility to remove NOx in an exhaust gas; and a carbon dioxide separation recovery facility which is installed at the back flow side of a gas flow in the NOx removal facility and where carbon dioxide contained in a processing object gas supplied from the NOx removal facility is adsorbed and desorbed using a solid absorber carried with amine on a porous base material. NOx concentration in the processing object gas supplied from the NOx removal facility to the carbon dioxide separation recovery facility is 63.7 ppm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a system and method for separating and recovering acidic gases that uses a solid absorbent material in which an amine is supported on a porous substrate. [Background technology]

[0002] Separation and capture of acid gases, especially carbon dioxide, from exhaust gas from combustion equipment such as thermal power plants, blast furnaces in steelworks, and boilers is an important technology for global warming countermeasures. Therefore, currently, the amine absorption method for absorbing carbon dioxide contained in exhaust gas has been put to practical use. In recent years, as a further next-generation technology, a carbon dioxide separation and capture process using a solid absorbent material in which an amine is supported on a porous substrate (a solid absorbent material in which an amine solution is applied to the pore surface of a porous substrate, hereinafter also referred to simply as a "solid absorbent material") has attracted attention. According to the carbon dioxide separation and capture process using a solid absorbent material, carbon dioxide can be desorbed using low-temperature exhaust heat (low-temperature thermal energy of 100°C or less that cannot generally be effectively used, which is inevitably generated from various manufacturing industries, power plants, etc.). Therefore, carbon dioxide can be efficiently separated and captured at low cost and with energy savings.

[0003] On the other hand, generally, exhaust gas from combustion equipment is released into the atmosphere after removing the concentrations of acid gases such as NOx (nitrogen oxides), SOx (sulfur oxides), and HCl to below the standard values ​​so as to meet the emission standards. For example, according to the Ministry of the Environment, a waste incinerator (with an exhaust gas volume of 40,000 Nm3) 3 The emission standard value for NOx emitted from incinerators (200,000 m3 / h or more) is set at 250 ppm. 3 The standard value for NOx emissions from boilers of 10000 or more is set at 200 ppm to 250 ppm. In this way, the NOx emission concentration is generally permitted to exceed 100 ppm.

[0004] It is known that NOx reacts with amines to produce nitrosamines, which are highly carcinogenic substances (see Non-Patent Document 1). In Japan, no regulations have been established regarding the exposure concentration of nitrosamines, but in Germany, for example, restrictions on the exposure concentration of nitrosamines in the work environment have already been established. In Germany, the upper limit of the exposure concentration of nitrosamines in the work environment is 1 μg / m 3 Therefore, it is natural to assume that in the future, exposure concentrations will be regulated in Japan as well, due to environmental considerations.

[0005] When carbon dioxide in exhaust gas is absorbed by the amine absorption method, NOx in the exhaust gas is absorbed into a large amount of water, which is a solvent, and strong acids (nitric acid and nitrous acid) are generated, which react with amines preferentially over carbon dioxide (weak acid). As a result, the amines in the absorption solution are oxidized, and the generated nitrosamines dissolve in the absorption solution. The generated nitrosamines are then easily discharged outside the system by being carried away by the mist generated during the operation of the facility or by volatilizing from the absorption solution, and may ultimately pollute the surrounding environment.

[0006] Patent Document 1 discloses an exhaust gas treatment device that further includes a denitration device or the like as a pretreatment device for a carbon dioxide recovery device in order to suppress deterioration of a carbon dioxide absorbing solution (amine absorbing solution). It is expected that such an exhaust gas treatment device can suppress not only deterioration of the amine absorbing solution but also emission of nitrosamines to the outside of the system. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2013-121562 A [Non-patent literature]

[0008] [Non-Patent Document 1] Mitsunori Aoyama, "N-Nitrosamines (Regulations under TRGS 552 and Responses)", Journal of the Society of Rubber Industry, Japan, Vol. 83, No. 8, 2010, pp. 25-28 Summary of the Invention [Problem to be solved by the invention]

[0009] In the carbon dioxide separation and capture process using a solid absorbent, the solid absorbent itself has a low water content. Therefore, it is difficult to predict whether strong acids (nitric acid and nitrous acid) will be generated by the same mechanism as the amine absorption liquid method described above, and further whether nitrosamines will be generated by reaction with the strong acids. In addition, there have been no reports to date of the detection of nitrosamines in the exhaust gas in the carbon dioxide separation and capture process using a solid absorbent.

[0010] As will be described in detail in the Examples below, the inventors have investigated the exhaust gas emitted from a carbon dioxide separation and capture facility using a solid absorbent and found that two types of nitrosamines are produced by an unclear mechanism.

[0011] On the other hand, when a carbon dioxide capture system using a solid absorbent is operated in an actual plant, exhaust gas containing not only carbon dioxide and NOx but also oxygen and various other gases is supplied to the system. Therefore, a solid absorbent used for a long time deteriorates due to oxidation, etc., and the solid absorbent needs to be repaired or replaced at regular intervals. In general, the repair and replacement period of a solid absorbent varies depending on the type of combustion equipment in the plant where the carbon dioxide capture system is installed. However, it is preferable to suppress the amount of nitrosamines diffused to the ground to a small amount during the approximate average regular repair period (specifically, about one year, the operating period is about 8,000 hours, and the remaining period is the inspection period) of a carbon dioxide capture system using a solid absorbent.

[0012] Therefore, an object of the present disclosure is to provide an acid gas separation and recovery system and method that can suppress the amount of nitrosamines diffusing onto the ground and separate and recover carbon dioxide, which is environmentally friendly. [Means for solving the problem]

[0013] The acid gas separation and recovery system according to a first aspect of the present disclosure includes a NOx removal equipment for removing NOx from exhaust gas, A carbon dioxide separation and capture facility is provided downstream of the gas flow of the NOx removal facility, and adsorbs and desorbs carbon dioxide contained in the gas to be treated supplied from the NOx removal facility using a solid absorbent material having an amine supported on a porous substrate; The NOx concentration in the gas to be treated, which is supplied from the NOx removal facility to the carbon dioxide separation and capture facility, is 63.7 ppm or less.

[0014] Alternatively, the acid gas separation and recovery system according to a first aspect of the present disclosure includes a NOx removal equipment that removes NOx in exhaust gas; A carbon dioxide separation and capture facility is provided downstream of the gas flow of the NOx removal facility, and adsorbs and desorbs carbon dioxide contained in the gas to be treated supplied from the NOx removal facility using a solid absorbent material having an amine supported on a porous substrate; The NOx concentration in the gas to be treated supplied from the NOx removal equipment to the carbon dioxide separation and capture equipment is set to a concentration that maintains the maximum landing concentration of nitrosamines after diffusion of the exhaust gas discharged from the carbon dioxide separation and capture equipment at a value that is below a predetermined regulatory value.

[0015] A method for separating and recovering acidic gas according to a second aspect of the present disclosure includes removing NOx from an exhaust gas; and using a solid absorbent material having an amine supported on a porous substrate to adsorb and desorb carbon dioxide contained in the gas to be treated after NOx removal, and to separate and recover the carbon dioxide. The NOx concentration in the gas to be treated after the NOx removal is 63.7 ppm or less.

[0016] Alternatively, a method for separating and recovering acidic gas according to a second aspect of the present disclosure includes removing NOx from an exhaust gas; Using a solid absorbent material having an amine supported on a porous substrate, carbon dioxide contained in the gas to be treated after NOx removal is adsorbed and desorbed, and the carbon dioxide is separated and recovered; The NOx concentration in the gas to be treated after the NOx removal is set to a concentration that maintains the maximum landing concentration of nitrosamines after diffusion of the exhaust gas discharged after the separation and capture of the carbon dioxide at or below a predetermined regulatory value. Effect of the Invention

[0017] According to the present disclosure, it is possible to provide an acid gas separation and recovery system and method capable of suppressing the amount of nitrosamines diffusing onto the ground and separating and recovering carbon dioxide, which is environmentally friendly. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of an acidic gas separation and recovery system according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram of an example of the configuration of the carbon dioxide separation and capture facility in the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram of another example of the configuration of the carbon dioxide separation and capture facility in the first embodiment. [Figure 4] FIG. 4 is a schematic diagram of an acidic gas separation and recovery system according to the second embodiment. [Diagram 5] FIG. 5 is a schematic diagram for explaining a mechanism for collecting trace components in a gas by solid-phase extraction in the embodiment. [Figure 6] FIG. 6 is a schematic diagram for explaining the mechanism of collecting trace components in a gas by the liquid phase extraction method in the embodiment. [Figure 7] FIG. 7 is a graph showing the vapor pressure curves of diethanolamine and NDEA in the examples. [Figure 8]FIG. 8 is a graph of nitrosamine emission concentrations when the NOx concentration is set to 10 ppm, 40 ppm, 63.7 ppm, or 150 ppm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] As described in detail in the Examples below, the inventors have verified whether compounds that may affect the surrounding environment are emitted into the gas discharged from a carbon dioxide capture facility using a solid absorbent material. As a result, they have detected and identified two types of nitrosamines that are produced by an unclear mechanism and are contained in the exhaust gas.

[0020] In this specification, the term "exhaust gas" is not particularly limited as long as it contains carbon dioxide and NOx. Examples of such gas include gas discharged from combustion facilities such as thermal power plants using coal, heavy oil, natural gas, etc. as fuel, blast furnaces in steelworks that reduce iron oxide with coke, converters in steelworks that burn carbon in pig iron to make steel, and boilers in various manufacturing plants, and gas discharged from transportation equipment such as automobiles, ships, and aircraft that use gasoline, heavy oil, light oil, etc. as fuel.

[0021] In this specification, "NOx" refers to oxides of nitrogen that are produced when substances burn at high temperatures, and examples of such oxides include NO, NO2, N2O, and N2O3.

[0022] In this specification, the term "gas to be treated" refers to a gas from which at least NOx has been partially or completely removed from exhaust gas, the NOx concentration in the gas to be treated is 63.7 ppm or less, and which is to be treated in a carbon dioxide separation and capture process using a solid absorbent. The carbon dioxide content and temperature in the gas to be treated are not particularly limited as long as the gas to be treated can absorb carbon dioxide when it comes into contact with the solid absorbent. For example, the carbon dioxide partial pressure may be 1 kPa or more, and the temperature may be 20°C to 60°C.

[0023] In this specification, "exhaust gas" refers to gas that may contain trace amounts of nitrosamines and is discharged from the exhaust line (chimney, flue, etc.) of the carbon dioxide separation and capture facility after adsorption and desorption of carbon dioxide contained in the gas to be treated. The exhaust gas then diffuses into the atmosphere and reaches the ground.

[0024] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the scope of the present disclosure is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present disclosure.

[0025] 1. Acid gas separation and recovery system An embodiment of an acidic gas separation and recovery system according to a first aspect of the present disclosure will be described below.

[0026] (Embodiment 1) Fig. 1 shows a schematic diagram of an acidic gas separation and recovery system in embodiment 1. As shown in Fig. 1, an acidic gas separation and recovery system 10 includes a NOx removal facility 1 and a carbon dioxide separation and recovery facility 2 that adsorbs and desorbs carbon dioxide using a solid absorbent material.

[0027] 1, the NOx removal equipment 1 removes NOx from exhaust gas discharged from a combustion equipment 10A such as a power plant, a blast furnace, a boiler, etc. The exhaust gas is supplied from the combustion equipment 10A to the NOx removal equipment 1 through an exhaust gas supply line L0.

[0028] The NOx removal equipment 1 reduces the NOx concentration in the gas to be treated, which is supplied to the carbon dioxide separation and capture equipment 2 installed downstream of the NOx removal equipment 1, to 63.7 ppm or less. If the NOx concentration in the gas to be treated is 63.7 ppm or less, the amount of nitrosamines that diffuse to the ground from the carbon dioxide separation and capture equipment 2 described below can be suppressed to an extremely small amount during an approximate average regular repair period of the carbon dioxide separation and capture equipment (specifically, about one year, or about 8,000 hours of operation) (specifically, the maximum landing concentration of nitrosamines on the ground after diffusion (hereinafter also simply referred to as "maximum landing concentration of nitrosamines") can be suppressed to 1 μg / m 3 (0.167 ppb or less in terms of the molar composition of N-nitrosodiethanolamine). The method of calculating the upper limit of 63.7 ppm for the NOx concentration in the gas to be treated will be described in detail in the Examples below.

[0029] In order to more strictly consider the risk of nitrosamines diffusing to the ground, the NOx concentration in the gas to be treated that is supplied to the carbon dioxide separation and capture facility 2 is preferably 60 ppm or less, more preferably 55 ppm or less, even more preferably 50 ppm or less, particularly preferably 47 ppm or less, and even more preferably 45 ppm or less. As will be described in detail in the following examples, this NOx concentration is a concentration assuming that the nitrosamines diffusing to the ground are N-nitrosodiethanolamines (hereinafter also referred to as "NDEA"). The volatility of nitrosamines varies depending on their types. Therefore, the maximum allowable NOx concentration in such gas to be treated may be appropriately adjusted depending on the volatility of the nitrosamines generated. Furthermore, the replacement period of the solid absorbent varies depending on the type of combustion equipment to which the carbon dioxide separation and capture facility is attached. Therefore, the maximum allowable NOx concentration in such gas to be treated may also be appropriately adjusted depending on the type of combustion equipment.

[0030] In this specification, "NOx concentration (in gas)" refers to the concentration of nitrogen oxides in the atmosphere measured by an automatic measuring instrument using the chemiluminescence method, as specified in JIS B 7953:2004 "Automatic measuring instrument for nitrogen oxides in the atmosphere."

[0031] Such NOx removal equipment 1 is not particularly limited as long as it is any denitrification equipment known to those skilled in the art. For example, the NOx removal equipment 1 may be an equipment for removing NOx in exhaust gas using a solid absorbent material in which an amine is supported on a porous substrate, similar to the carbon dioxide separation and capture equipment 2 described later. When the NOx removal equipment 1 is an equipment using such a solid absorbent material, the NOx concentration in the gas to be treated can be easily reduced to the extremely low concentration described above.

[0032] Furthermore, in such a case, it is preferable that the type of amine used in the solid absorbent of the carbon dioxide separation and capture equipment 2 described below is the same as the type of amine used in the solid absorbent of the NOx removal equipment 1. By using the same type of amine, it is possible to prevent a type of amine different from the amine used in the carbon dioxide separation and capture equipment 2 from entering from the NOx removal equipment 1 and affecting the adsorption and desorption of carbon dioxide in some way.

[0033] Moreover, it is more preferable that the solid absorbent used in the NOx removal equipment 1 includes a solid absorbent used for adsorbing and desorbing carbon dioxide in the carbon dioxide separation and capture equipment 2 described later. That is, it is preferable to reuse a part or all of the solid absorbent that has already been used for a certain period of time in the carbon dioxide separation and capture equipment 2 described later as the solid absorbent for the NOx removal equipment 1. NOx has a stronger bond with amines than carbon dioxide. Therefore, even if a solid absorbent that has already been used for a certain period of time (for example, about one to three years, which is a general replacement period) for carbon dioxide separation and capture is used, a sufficient amount of NOx can be removed. In this way, by reusing the solid absorbent in the NOx removal equipment 1, an acid gas separation and capture system 10 that is environmentally favorable can be realized at low cost.

[0034] Alternatively, the NOx removal equipment 1 may be a general denitration equipment to which any method known to those skilled in the art is applied. Examples of such NOx removal equipment 1 include denitration equipment to which an ammonia selective catalytic reduction method, a flue gas denitration method, a non-catalytic selective reduction method, or the like is applied.

[0035] As shown in Fig. 1, the carbon dioxide separation and capture equipment 2 is installed downstream of the gas flow of the NOx removal equipment 1, and the gas to be treated is supplied from the NOx removal equipment 1 through a gas to be treated supply line L1. The carbon dioxide in the gas to be treated is then separated and captured by the carbon dioxide separation and capture equipment 2. The exhaust gas after separation and capture is discharged as carbon dioxide-free exhaust gas through a carbon dioxide-free exhaust gas discharge line L2. At the same time, the carbon dioxide in the gas to be treated is captured (not shown).

[0036] The carbon dioxide separation and capture equipment 2 may have any configuration as long as it is equipment capable of adsorbing and desorbing carbon dioxide contained in the gas to be treated using a solid absorbent material in which an amine is supported on a porous substrate.

[0037] The configuration of such carbon dioxide separation and capture equipment 2 is not particularly limited, but examples thereof include the following configuration.

[0038] Fig. 2 shows a schematic diagram of an example of the configuration of a carbon dioxide separation and capture system in the first embodiment. The carbon dioxide separation and capture system 2 in Fig. 2 is a moving bed type carbon dioxide separation and capture system 2 in which a solid adsorbent is transferred in the order of an adsorption tower, a regeneration tower, and a drying tower. The solid adsorbent is returned from the drying tower to the adsorption tower by a conveyor or the like. Note that the configurations of the adsorption tower, the regeneration tower, and the drying tower may be appropriately changed from the configuration shown in Fig. 2.

[0039] In the adsorption tower, the gas to be treated supplied through the gas to be treated supply line L1 comes into contact with the solid absorbent packed in the adsorption tower. As a result, the carbon dioxide in the gas to be treated is adsorbed and removed by the solid absorbent. Therefore, the carbon dioxide-free exhaust gas from which the carbon dioxide has been removed is discharged from the adsorption tower through the carbon dioxide-free exhaust gas discharge line L2. The solid absorbent after carbon dioxide adsorption is transferred to the regeneration tower.

[0040] In the regeneration tower, the transferred solid absorbent after carbon dioxide adsorption comes into contact with steam supplied through the steam supply line L3. The temperature of the steam is not particularly limited, but is, for example, 60°C or higher. As a result, carbon dioxide is desorbed from the solid absorbent, and carbon dioxide gas is discharged from the regeneration tower through the carbon dioxide discharge line L4. The solid absorbent to which the steam has been attached is transferred to the drying tower.

[0041] In the drying tower, the solid absorbent with the transferred steam attached thereto comes into contact with dry air supplied through the dry air supply line L5. As a result, the moisture and other substances attached to the solid absorbent evaporate, and the water vapor and dry gas resulting from the evaporation are discharged through the moisture-containing air discharge line L6. The solid absorbent after drying is returned to the adsorption tower.

[0042] Furthermore, Fig. 3 shows a schematic diagram of another example of the configuration of the carbon dioxide separation and capture equipment in the first embodiment. In the carbon dioxide separation and capture equipment 2 shown in Fig. 3, one tank filled with a solid absorbent material functions as the adsorption tower, regeneration tower, and drying tower described above for the absorption process, regeneration process, and drying process, respectively. These three processes, the absorption process, regeneration process, and drying process, are then repeated periodically. That is, the carbon dioxide separation and capture equipment 2 in Fig. 3 is a fixed-bed type carbon dioxide separation and capture equipment.

[0043] In the carbon dioxide separation and capture equipment 2 shown in Fig. 3, the number of tanks filled with the solid absorbent material is one, but the number of tanks may be two or more. When the number of tanks is two or more, continuous processing is possible.

[0044] As shown in Fig. 3, supply lines are configured so that the gas to be treated, steam, and dry air can each be supplied from the gas to be treated supply line L1, the steam supply line L3, and the dry air supply line L5 to the tank of the carbon dioxide separation and capture equipment 2. Furthermore, exhaust lines are configured so that the carbon dioxide-free flue gas, carbon dioxide, and moisture-containing air can each be discharged from the carbon dioxide-free flue gas exhaust line L2, the carbon dioxide exhaust line L4, and the moisture-containing air exhaust line L6. However, these supply lines and exhaust lines are each provided with an on-off valve.

[0045] In detail, in the absorption step, the gas to be treated is supplied to the tank through the gas to be treated supply line L1 and comes into contact with the solid absorbent filled in the tank. As a result, the carbon dioxide in the gas to be treated is adsorbed by the solid absorbent. Therefore, the carbon dioxide-free exhaust gas from which the carbon dioxide has been removed is discharged through the carbon dioxide-free exhaust gas discharge line L2. In the absorption step, the on-off valves other than those of the gas to be treated supply line L1 and the carbon dioxide-free exhaust gas discharge line L2 are closed.

[0046] Next, in the regeneration step, steam is supplied through the steam supply line L3 and contacts the solid absorbent after carbon dioxide adsorption. As a result, carbon dioxide is desorbed from the solid absorbent by the heat of the steam, and the carbon dioxide gas is discharged through the carbon dioxide discharge line L4 and then collected. In the regeneration step, the on-off valves other than the steam supply line L3 and the carbon dioxide discharge line L4 are closed.

[0047] Finally, in the drying process, low-temperature dry air is supplied through the dry air supply line L5 and comes into contact with the solid absorbent material to which steam has been attached. As a result, moisture and other substances attached to the solid absorbent material evaporate, and dry air containing water vapor resulting from the evaporation is discharged through the moisture-containing air discharge line L6. In the drying process, the on-off valves other than those of the dry air supply line L5 and the moisture-containing air discharge line L6 are closed.

[0048] Next, the configuration of the solid absorbent material, which is used in the carbon dioxide separation and capture equipment 2 and has an amine supported on a porous substrate, will be briefly described below.

[0049] The type of the porous substrate is not particularly limited. The porous substrate can be made of any material known to those skilled in the art that can support the amine described below and has a large number of pores that can adsorb and desorb carbon dioxide.

[0050] Specifically, examples of the porous substrate include silica such as silica gel or mesoporous silica, alumina such as activated alumina, zeolite, titania, zirconia, magnesia, activated carbon, metal organic framework (MOF), etc. When these materials are in powder form, they may be granulated using an appropriate binder and used as the porous substrate.

[0051] The type of amine is not particularly limited, and any amine or polyamine that can be supported on any porous substrate known to those skilled in the art and can adsorb and desorb carbon dioxide can be used. Examples of the amine include monoethanolamine, diethanolamine, triethanolamine, polyethyleneimine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. One type of amine may be used, or two or more types of amines may be used in combination.

[0052] The method for producing the solid absorbent material is not particularly limited, but it can be produced, for example, by the following method.

[0053] First, the above-mentioned amine is dissolved in a solvent to prepare an amine absorbent solution. The concentration of the amine in the amine absorbent solution is not particularly limited, but may be adjusted to an appropriate value in the range of 5% by mass to 70% by mass depending on the type of amine used.

[0054] Next, the porous substrate (for example, the above-mentioned porous particles) is placed in an immersion container filled with the amine absorbent solution, and the porous substrate is impregnated with the amine absorbent solution. The immersion time is not particularly limited as long as the inside of the pores is sufficiently degassed. For example, the immersion time can be 24 hours.

[0055] The porous substrate is then removed from the amine absorbent solution, and excess liquid is removed by suction filtration, etc. The porous substrate is then dried by air drying or vacuum drying at a temperature close to room temperature, to obtain a solid absorbent.

[0056] As described above, in the acidic gas separation and capture system 10 in the present embodiment 1, the NOx concentration in the gas to be treated is 63.7 ppm or less. Therefore, the amount of nitrosamines generated by the reaction between NOx and amines in the carbon dioxide separation and capture equipment 2 can be suppressed to a very small amount during the approximate average regular repair period of the carbon dioxide separation and capture equipment (specifically, about one year, or about 8,000 hours of operation). Therefore, the acidic gas separation and capture system 10 can suppress the amount of nitrosamines diffused to the ground to an extremely small amount (specifically, the maximum landing concentration of nitrosamines is suppressed to 1 μg / m 3 This is environmentally friendly and enables carbon dioxide to be separated and captured efficiently.

[0057] In addition, the carbon dioxide separation and capture method using a solid absorbent is more environmentally friendly than the method using an amine absorbing solution because it can desorb carbon dioxide from the solid absorbent using exhaust heat that cannot generally be used effectively.

[0058] In addition, by installing the NOx removal equipment 1 on the upstream side of the gas flow of the carbon dioxide separation and capture equipment 2 in the first embodiment, it is fully expected that SOx, HCl, HF, etc. other than NOx can also be removed at the same time. Like NOx, it cannot be said that there is no possibility that SOx, HCl, HF, etc. will react with the amine supported on the solid absorbent to generate other harmful substances. Therefore, the acid gas separation and capture system 10 in the first embodiment is highly likely to contribute to suppressing the generation of such harmful substances.

[0059] (Embodiment 2) Fig. 4 shows a schematic diagram of an acidic gas separation and recovery system in embodiment 2. As shown in Fig. 4, an acidic gas separation and recovery system 20 includes a NOx removal facility 1 installed in a combustion facility 20A, and a carbon dioxide separation and recovery facility 2 that adsorbs and desorbs carbon dioxide using a solid absorbent material.

[0060] In the above-described first embodiment, the acidic gas separation and recovery system 10 in which the NOx removal equipment 1 is installed on the downstream side of the gas flow of the combustion equipment 10A and on the upstream side of the gas flow of the carbon dioxide separation and recovery equipment 2 has been described.

[0061] 4, the acidic gas separation and recovery system 20 in the second embodiment differs from the acidic gas separation and recovery system 10 in the first embodiment in that a denitration device already installed in a general combustion facility 20A such as a power plant, a blast furnace, or a boiler has the same function as the above-mentioned NOx removal facility 1. In other words, the acidic gas separation and recovery system 20 is configured to enhance the denitration effect of a denitration device already installed in the general combustion facility 20A so that the NOx concentration in the gas to be treated supplied to the carbon dioxide separation and recovery facility 2 is 63.7 ppm or less.

[0062] The detailed configurations and functions of the NOx removal equipment 1, the carbon dioxide separation and capture equipment 2, and their respective supply lines are the same as those in the first embodiment described above.

[0063] Similarly to the above-described first embodiment, the acidic gas separation and capture system 20 in the second embodiment can suppress the amount of nitrosamines generated by the reaction between NOx and amines in the carbon dioxide separation and capture equipment 2 to a very small amount during an approximate average scheduled repair period for the carbon dioxide separation and capture equipment (specifically, about one year, or about 8,000 hours of operation). Therefore, the acidic gas separation and capture system 20 can also suppress the amount of nitrosamines diffused to the ground to an extremely small amount (specifically, the maximum ground concentration of nitrosamines is suppressed to 1 μg / m 3 This is environmentally friendly because it allows for the efficient separation and capture of carbon dioxide.

[0064] (Modification of acid gas separation and recovery system) The modified acid gas separation and recovery system according to the first aspect of the present disclosure includes a NOx removal facility and a carbon dioxide separation and recovery facility that adsorbs and desorbs carbon dioxide using a solid absorbent, similar to the acid gas separation and recovery system in the above-described first or second embodiment. The details of the configurations of the NOx removal facility and the carbon dioxide separation and recovery facility are similar to those of the above-described first or second embodiment.

[0065] In the above-mentioned first or second embodiment, the NOx concentration in the gas to be treated is 63.7 ppm or less, but in this modified example, the NOx concentration in the gas to be treated is set to a specific concentration or less. The specific concentration is a concentration that can maintain a value that keeps the maximum landing concentration of nitrosamines after diffusion of the exhaust gas discharged from the carbon dioxide capture and separation equipment at a preset regulation value or less. The period for maintaining such a value is preferably the scheduled repair period of the carbon dioxide capture and separation equipment.

[0066] In this specification, the "maximum landing concentration of nitrosamines (on the ground) after diffusion" refers to the concentration of nitrosamines at a ground point estimated to have the smallest dilution ratio, calculated from the values ​​of the exhaust gas volume, gas temperature, stack height, atmospheric stability, effective stack height, and diffusion parameters consisting of the evaluation time, PG diagram evaluation time, and power exponent of the horizontal diffusion width, when a plant such as an arbitrary coal-fired power plant is used as a model case, as will be described in detail in the Examples below. Furthermore, in this specification, the maximum landing concentration of nitrosamines is the largest concentration among the concentrations estimated by the weak wind puff method, the puff method, and the plume method.

[0067] In this specification, the "predetermined regulation value" may be set arbitrarily according to the surrounding work environment on the ground. For example, in a place with a valuable natural environment or a place with many people living nearby, the regulation value should be set as low as possible. Also, in a place with almost no nature or few people living nearby, the regulation value may be set to a normal value.

[0068] According to this modified acid gas separation and recovery system, the amount of nitrosamines diffusing onto the ground can be reduced to an amount suitable for the surrounding environment, which is environmentally friendly, and carbon dioxide can be efficiently separated and recovered.

[0069] In addition, in this modified example, the NOx concentration in the gas to be treated is set to 1 μg / m until the maximum landing concentration of nitrosamines reaches 8,000 hours of operation of the carbon dioxide capture and separation equipment. 3 The concentration may be set to a level that can maintain the concentration of nitrosamines at or below 0.167 ppb (or below 0.167 ppb in terms of the molar composition of NDEA). With this configuration, the amount of nitrosamines diffusing onto the ground can be suppressed to a very small amount, which is environmentally friendly and allows carbon dioxide to be efficiently separated and recovered.

[0070] 2. Acid gas separation and recovery method An embodiment of the method for separating and recovering acidic gas according to the second aspect of the present disclosure will be described below. The method for separating and recovering acidic gas in this embodiment includes removing NOx and separating and recovering carbon dioxide.

[0071] In removing NOx, the NOx in the exhaust gas is removed, and the NOx concentration in the gas to be treated after the NOx removal is set to 63.7 ppm or less. The preferred upper limit of the NOx concentration in the gas to be treated is the same as that described in the acidic gas separation and recovery system according to the first aspect. Note that the maximum value of the NOx concentration in the gas to be treated can be appropriately adjusted according to the type of combustion equipment that emits the exhaust gas to which the acidic gas separation and recovery method of this embodiment is applied.

[0072] In removing NOx, it is preferable to remove NOx in the exhaust gas using a solid absorbent, as in the acid gas separation and recovery system according to the first aspect described above.Moreover, it is more preferable that the solid absorbent contains a solid absorbent used for adsorbing and desorbing carbon dioxide when separating and recovering carbon dioxide, as in the acid gas separation and recovery system according to the first aspect described above.Alternatively, as in the acid gas separation and recovery system according to the first aspect described above, in removing NOx, any denitrification equipment, device, denitrification method, etc. known to those skilled in the art may be applied.

[0073] In the separation and recovery of carbon dioxide, a solid absorbent material in which an amine is supported on a porous substrate is used to adsorb and desorb carbon dioxide contained in the gas to be treated. In the separation and recovery of carbon dioxide, as in the acid gas separation and recovery system according to the first aspect described above, any equipment (e.g., moving bed or fixed bed carbon dioxide separation and recovery equipment), device, method, etc. known to those skilled in the art that can adsorb and desorb carbon dioxide contained in the gas to be treated using a solid absorbent may be used.

[0074] In this way, in the acid gas separation and recovery method of this embodiment, as in the acid gas separation and recovery system according to the first aspect described above, the amount of nitrosamines generated by the reaction between NOx and amines when carbon dioxide is separated and captured can be suppressed to a very small amount during the approximate average scheduled repair period of the carbon dioxide separation and recovery equipment (specifically, about one year, or about 8,000 hours of operation). Therefore, the acid gas separation and recovery method of this embodiment can suppress the amount of nitrosamines diffused to the ground to an extremely small amount (specifically, the maximum landing concentration of nitrosamines can be suppressed to 1 μg / m 3 This is environmentally friendly because it allows for the efficient separation and capture of carbon dioxide.

[0075] (Modification of acid gas separation and recovery method) The modified acidic gas separation and recovery method according to the second aspect of the present disclosure includes removing NOx, and using a solid absorbent to adsorb and desorb carbon dioxide contained in the gas to be treated after the NOx removal, and separating and recovering the carbon dioxide, as in the acidic gas separation and recovery method in the above-described embodiment. The details of the removal of NOx and the separation and recovery of carbon dioxide are the same as those in the above-described embodiment.

[0076] In the above-mentioned embodiment, the NOx concentration in the gas to be treated is 63.7 ppm or less, but in this modified example, the NOx concentration in the gas to be treated is set to a specific concentration or less. The specific concentration is a concentration that can maintain a value that keeps the maximum landing concentration of nitrosamines after diffusion in the exhaust gas discharged after separation and capture of carbon dioxide at or below a preset regulatory value. The period for maintaining such a value is preferably the period of regular repairs of the equipment used for separation and capture of carbon dioxide. The meanings of "maximum landing concentration of nitrosamines after diffusion" and "preset regulatory value" are as described above.

[0077] According to this modified acid gas separation and recovery method, the amount of nitrosamines diffusing onto the ground can be reduced to an amount suitable for the surrounding environment, which is environmentally friendly, and carbon dioxide can be efficiently separated and recovered.

[0078] In this modification, the NOx concentration in the gas to be treated is controlled so that the maximum landing concentration of nitrosamines is 1 μg / m until the total time for separating and capturing carbon dioxide (i.e., the operation time of the carbon dioxide separation and capture equipment, etc.) reaches 8,000 hours. 3 The concentration may be set to a level that can maintain the concentration of nitrosamines at or below 0.167 ppb (or below 0.167 ppb in terms of the molar composition of NDEA). With this configuration, the amount of nitrosamines diffusing onto the ground can be suppressed to a very small amount, which is environmentally friendly and allows carbon dioxide to be efficiently separated and recovered.

[0079] [Summary of this disclosure] The specific embodiments described above include disclosures having the following configurations.

[0080] The acid gas separation and recovery system according to a first aspect of the present disclosure includes a NOx removal equipment for removing NOx from exhaust gas, A carbon dioxide separation and capture facility is provided downstream of the gas flow of the NOx removal facility, and adsorbs and desorbs carbon dioxide contained in the gas to be treated supplied from the NOx removal facility using a solid absorbent material having an amine supported on a porous substrate; The NOx concentration in the gas to be treated, which is supplied from the NOx removal facility to the carbon dioxide separation and capture facility, is 63.7 ppm or less.

[0081] According to the above-mentioned configuration, it is possible to provide an acid gas separation and recovery system capable of suppressing the amount of nitrosamines diffusing onto the ground and separating and recovering carbon dioxide, which is environmentally friendly.

[0082] In the above-mentioned acidic gas separation and recovery system, the NOx removal equipment may remove NOx in the exhaust gas using a solid absorbent material in which an amine is supported on a porous substrate.

[0083] According to the above-mentioned configuration, the NOx concentration in the gas to be treated can be easily reduced to an extremely low concentration.

[0084] In the above-mentioned acid gas separation and recovery system, the solid absorbent material used in the NOx removal facility may include a solid absorbent material used to adsorb and desorb carbon dioxide in the carbon dioxide separation and recovery facility.

[0085] According to the above configuration, since the solid absorbent material can be reused, an environmentally friendly acid gas separation and recovery system can be realized at low cost.

[0086] Alternatively, the acid gas separation and recovery system according to a first aspect of the present disclosure includes a NOx removal equipment that removes NOx in exhaust gas; A carbon dioxide separation and capture facility is provided downstream of the gas flow of the NOx removal facility, and adsorbs and desorbs carbon dioxide contained in the gas to be treated supplied from the NOx removal facility using a solid absorbent material having an amine supported on a porous substrate; The NOx concentration in the gas to be treated supplied from the NOx removal equipment to the carbon dioxide separation and capture equipment is set to a concentration that maintains the maximum landing concentration of nitrosamines after diffusion of the exhaust gas discharged from the carbon dioxide separation and capture equipment at a value that is below a predetermined regulatory value.

[0087] According to the above-mentioned configuration, the amount of nitrosamines diffusing onto the ground can be suppressed to an amount suitable for the surrounding environment, and an acid gas separation and recovery system capable of separating and recovering carbon dioxide, which is environmentally preferable, can be provided.

[0088] In the acid gas separation and recovery system, the NOx concentration in the gas to be treated is such that the maximum landing concentration of nitrosamines after diffusion of the exhaust gas is 1 μg / m until the operation time of the carbon dioxide separation and recovery equipment reaches 8000 hours. 3 The concentration may be set to a level that maintains the following:

[0089] According to the above-mentioned configuration, it is possible to provide an acid gas separation and recovery system capable of suppressing the amount of nitrosamines diffusing onto the ground and separating and recovering carbon dioxide, which is environmentally friendly.

[0090] A method for separating and recovering acidic gas according to a second aspect of the present disclosure includes removing NOx from an exhaust gas; and using a solid absorbent material having an amine supported on a porous substrate to adsorb and desorb carbon dioxide contained in the gas to be treated after NOx removal, and to separate and recover the carbon dioxide. The NOx concentration in the gas to be treated after the NOx removal is 63.7 ppm or less.

[0091] According to the above-mentioned method, the amount of nitrosamines diffused onto the ground can be suppressed, and a method for separating and recovering acidic gases capable of separating and recovering carbon dioxide, which is environmentally friendly, can be provided.

[0092] In the above-mentioned method for separating and recovering acidic gases, in removing NOx, NOx in the exhaust gas may be removed using a solid absorbent material in which an amine is supported on a porous substrate.

[0093] According to the above method, the NOx concentration in the gas to be treated can be easily reduced to an extremely low concentration.

[0094] In the above-mentioned acidic gas separation and recovery method, the solid absorbent material used in removing NOx may include a solid absorbent material used for adsorbing and desorbing carbon dioxide when separating and recovering the carbon dioxide.

[0095] According to the above method, since the solid absorbent material can be reused, an environmentally friendly method for separating and recovering acid gases can be realized at low cost.

[0096] Alternatively, a method for separating and recovering acidic gas according to a second aspect of the present disclosure includes removing NOx from an exhaust gas; and using a solid absorbent material having an amine supported on a porous substrate to adsorb and desorb carbon dioxide contained in the gas to be treated after NOx removal, and to separate and recover the carbon dioxide. The NOx concentration in the gas to be treated after the NOx removal is set to a concentration that maintains the maximum landing concentration of nitrosamines after diffusion of the exhaust gas discharged after the separation and capture of the carbon dioxide at or below a predetermined regulatory value.

[0097] According to the above-mentioned method, the amount of nitrosamines diffused onto the ground can be suppressed to an amount suitable for the surrounding environment, and a method for separating and recovering acidic gases capable of separating and recovering carbon dioxide, which is environmentally preferable, can be provided.

[0098] In the above-mentioned acid gas separation and recovery method, the NOx concentration in the gas to be treated is such that the maximum landing concentration of nitrosamines after diffusion of the exhaust gas is 1 μg / m until the total time for separating and recovering carbon dioxide reaches 8000 hours. 3 The concentration may be set to a level that maintains the following:

[0099] According to the above-mentioned method, the amount of nitrosamines diffused onto the ground can be suppressed, and a method for separating and recovering acidic gases capable of separating and recovering carbon dioxide, which is environmentally friendly, can be provided. EXAMPLES

[0100] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples in any way.

[0101] In this example, first, verification was carried out as to whether or not substances that affect the surrounding environment, particularly nitrosamines, were detected in the gas discharged from a carbon dioxide capture and separation facility using a solid absorbent. Next, based on the results, it was determined that the amount of nitrosamines diffused to the ground was small (specifically, the maximum ground concentration of nitrosamines was 1 μg / m3 or less) during an approximately average regular repair period (specifically, about one year, or about 8,000 hours of operation) of the carbon dioxide capture and separation facility. 3 The upper limit of the NOx concentration (ppm) in the gas to be treated and supplied to the carbon dioxide capture facility was calculated in order to suppress the NOx concentration (ppm) to the maximum value (amount below 10 ppm). This will be explained in detail below.

[0102] 1. Detection and Identification of Nitrosamines To detect nitrosamines in gas, the carbon dioxide capture equipment and experimental exhaust gas described below were used. Furthermore, using these, nitrosamines were detected and identified by a method for collecting trace components in gas discharged from the carbon dioxide capture equipment and a method for detecting and identifying the molecular species of the collected components, described below. In addition, the detected and identified nitrosamines were discussed.

[0103] (Carbon dioxide capture equipment) First, a fixed-bed carbon dioxide separation and capture equipment using a solid absorbent was used, which applied the SA-VSA (Steam-aided Vacuum Swing Adsorption) process. In the SA-VSA process, low-temperature steam is supplied in the desorption process of the solid absorbent after carbon dioxide adsorption. This carbon dioxide separation and capture equipment has almost the same configuration as the carbon dioxide separation and capture equipment 2 shown in Figure 3 described above. However, since the purpose of this experiment is to investigate the effect of NOx in the exhaust gas, no NOx removal equipment is installed on the upstream side of the gas flow of the carbon dioxide separation and capture equipment. Therefore, in the carbon dioxide separation and capture equipment used in this experiment, the treatment target gas supply line L1 shown in Figure 3 is the exhaust gas supply line (L0). Specifically, in the absorption process, the exhaust gas is supplied to a tank through the exhaust gas supply line (L0), comes into contact with the solid absorbent filled in the tank, and the carbon dioxide in the exhaust gas is adsorbed by the solid absorbent.

[0104] The solid absorbent filled in the tank was manufactured by the following method. Specifically, first, silica gel with a particle diameter of 1 mm to 5 mm, which is a porous substrate, was immersed in an aqueous diethanolamine solution. The immersed silica gel was left at room temperature for 8 hours or more. After leaving it, the silica gel was taken out, the excess aqueous diethanolamine solution attached to the silica gel was separated, and dry gas (nitrogen gas at 40°C and 15 L / min) was passed through to dry it (see the manufacturing method of the solid absorbent described in Japanese Patent No. 6055134). The drying end condition for the silica gel supported with diethanolamine (i.e., the solid absorbent) was set to 2 hours after the gas temperature at the outlet of the drying tank for drying the silica gel supported with diethanolamine became stable.

[0105] (Experimental exhaust gas) The experimental exhaust gas supplied through the exhaust gas supply line was a mixture of air and high-purity carbon dioxide, to which 30 ppm of NOx was further added.

[0106] (Method for capturing trace components in gas discharged from carbon dioxide capture equipment) Two collection mechanisms, a trace component collection mechanism using a solid-phase extraction method and a trace component collection mechanism using a liquid-phase extraction method, were installed downstream of the gas flow from the three gas exhaust ports of the carbon dioxide-free exhaust gas exhaust line L2, the carbon dioxide exhaust line L4, and the moisture-containing air exhaust line L6 in the carbon dioxide separation and capture equipment described above.

[0107] FIG. 5 shows a schematic diagram for explaining the mechanism for collecting trace components in gas by solid-phase extraction. As shown in FIG. 5, in the collection mechanism by this solid-phase extraction method, a first cartridge 3 filled with a copolymer, a second cartridge 4 filled with a strong cation exchange resin, and a third cartridge 5 filled with activated carbon are arranged in series, and gas from the three gas outlets is aerated in the direction shown by the arrow in FIG. 5. By aerating gas from the three gas outlets to these three types of cartridges, it is possible to sorb and collect trace components of all acidic, basic, and neutral molecules in the gas. After the aeration of gas from the three gas outlets to the three types of cartridges is completed, methanol and dichloromethane are sequentially fed to the first cartridge 3 filled with the copolymer to obtain an extract in each fraction in which the sorbed trace components are dissolved. Similarly, an extract is obtained by feeding a 1% ammonia ethanol solution to the second cartridge 4 filled with a strong cation exchange resin. Similarly, methanol and dichloromethane were successively pumped into the third cartridge 5 filled with activated carbon to obtain extracts for each fraction. Although not shown in Fig. 5, an empty impinger was placed downstream of the gas flow of the three cartridges, and condensed water was also obtained by cooling it.

[0108] FIG. 6 is a schematic diagram for explaining a mechanism for collecting trace components in gas by liquid-phase extraction. As shown in FIG. 6, in the collecting mechanism by liquid-phase extraction, a first impinger 6 holding a 0.1% sulfamic acid solution is placed in the front stage close to the gas flow from the gas outlet. Furthermore, a second impinger 7 holding ultrapure water is placed in the rear stage far from the gas flow from the gas outlet so as to be in series with the first impinger 6. Then, gas from the three gas outlets is passed through the first impinger 6 and the second impinger 7 placed in series in this way in the direction shown by the arrows in FIG. 6 to collect trace components in the gas.

[0109] (Method for detecting and identifying molecular species of collected components) The extract and condensate from each fraction obtained by the solid-phase extraction method, and each absorption liquid and each impinger washing liquid obtained by the liquid-phase extraction method were analyzed using LC-OrbitrapMS and GC-OrbitrapMS as appropriate. The molecular species of the collected components were detected and identified from the analyzed mass spectrum. As an example of the detection and identification results of molecular species, the analysis results of the gas from the gas outlet in the regeneration process in the carbon dioxide separation and capture equipment are shown in the following Tables 1-2 (No. 1-No. 10), Tables 3-4 (No. 11-No. 20), and Tables 5-6 (No. 21-No. 30). In Tables 1-6, "HLB" refers to the first cartridge 3 filled with copolymer, "MC-1" refers to the second cartridge 4 filled with strong cation exchange resin, and "AC2" refers to the third cartridge 5 filled with activated carbon.

[0110] [Table 1]

[0111] [Table 2]

[0112] [Table 3]

[0113] [Table 4]

[0114] [Table 5]

[0115] [Table 6]

[0116] (Discussion of nitrosamines detected and identified) As shown in Tables 1 to 6 above, in addition to diethanolamine actually supported on the solid absorbent, various components were detected in the gas from the three gas exhaust ports of the carbon dioxide separation and capture equipment. As shown in Tables 5 and 6, the detected components also included nitrosamines N-nitrosodibutylamine (No. 29) and NDEA (No. 30). From these detection results, it was found that when exhaust gas containing NOx is supplied to a carbon dioxide separation and capture equipment using a solid absorbent, the amine supported on the solid absorbent reacts with NOx, and nitrosamines are contained in the gas discharged from the gas exhaust port. Therefore, when general exhaust gas with a NOx concentration exceeding 100 ppm is treated by a carbon dioxide separation and capture process using a solid absorbent, these generated nitrosamines may diffuse to the ground and pollute the surrounding environment.

[0117] In addition, it has been reported that the nitroso compound in the diethanolamine aqueous solution is mainly NDEA (No. 30) for diethanolamine actually supported on the solid absorbent (P. Prado, Master Thesis, University of Regina, 2021). Furthermore, the mechanism of nitrosation has also been clarified. However, as shown in Table 6, the main component of the nitrosated product in this detection result is N-nitrosodibutylamine (No. 29). Specifically, the detected concentration of N-nitrosodibutylamine (No. 29) was about 30 times that of NDEA (No. 30), the main nitrosated product of diethanolamine. Specifically, as shown in Table 6, in the results of cartridge collection, the detected concentration of N-nitrosodibutylamine (No. 29) was 781,499,956, and the detected concentration of NDEA was 28,733,260. In addition, in the results of impinger collection, the detected concentration of NDEA was 0. Therefore, the nitrosation mechanism in this detection result is an unclear mechanism that cannot be predicted at all from the conventional technology. From this observation result, it is clear that the generation of nitrosamines in the carbon dioxide separation and capture process using a solid absorbent is not self-evident from the simple nitrosamine generation mechanism in the carbon dioxide separation and capture process using the amine absorption liquid method.

[0118] 2. Calculation of the upper limit of NOx concentration in the gas to be treated and supplied to the carbon dioxide capture facility in order to limit the amount of nitrosamines dispersed onto the ground to a small amount. During an average scheduled maintenance period for a carbon dioxide capture facility (specifically, about one year, or about 8,000 hours of operation), the amount of nitrosamines diffused to the ground is small (specifically, the maximum ground concentration of nitrosamines is 1 μg / m 3 The upper limit of the NOx concentration in the gas to be treated that can be suppressed to an amount equal to or less than the above was calculated using the following method.

[0119] (Summary of calculation method for upper limit of NOx concentration) Nitrosamines are not contained in the solid absorbent in the carbon dioxide capture equipment immediately after it starts to be used. When exhaust gas containing NOx is supplied to the carbon dioxide capture equipment, NOx reacts with diethanolamine, and nitrosamines gradually accumulate in the equipment. As the accumulated concentration of nitrosamines increases, the volatile concentration of nitrosamines also increases. This calculation method determines the NOx concentration in the exhaust gas supplied to the carbon dioxide capture equipment so that the exhaust gas from the exhaust line (chimney, flue, etc.) of the carbon dioxide capture equipment diffuses into the atmosphere and the maximum landing concentration of nitrosamines (more specifically, NDEA) does not exceed the regulatory value for 8,000 hours from the start of operation. This method for calculating the upper limit of NOx concentration has the following three calculation steps. 1) Calculation step of the correlation between the NOx concentration supplied to the solid absorbent of the carbon dioxide capture equipment and the nitrosamine emission concentration in the exhaust gas 2) Calculation step of the dilution rate of exhaust gas diffused into the atmosphere 3) A step for calculating the NOx concentration in the exhaust gas so that the maximum ground concentration of nitrosamines (specifically NDEA) does not exceed the regulatory value for up to 8,000 hours.

[0120] 1) Calculation step of the correlation between the NOx concentration supplied to the solid absorbent of the carbon dioxide capture equipment and the nitrosamine emission concentration in the exhaust gas The relationship between the supply rate (flow rate) of NOx supplied to the solid absorbent of the carbon dioxide capture system and the concentration of NOx supplied can be expressed by the following formula. Formula: (NOx supply rate) = (exhaust gas flow rate) x (NOx concentration)

[0121] When the NOx concentration in the above formula (the NOx concentration supplied to the solid absorbent of the carbon dioxide capture equipment) is changed, we calculated how the nitrosamine emission concentration from the exhaust line (chimney, flue, etc.) of the carbon dioxide capture equipment changes over time, including at least 8,000 hours after the start of operation.

[0122] The flue gas flow rate in the above formula can be determined by the carbon dioxide concentration in the flue gas supplied to the carbon dioxide capture facility, the target carbon dioxide capture rate, and the performance of the solid absorbent. In calculating the correlation between NOx concentration and nitrosamine emission concentration, the following values ​​were set as conditions for a typical coal combustion flue gas carbon dioxide capture facility. Carbon dioxide concentration in exhaust gas: 15% Carbon dioxide recovery rate: 90%

[0123] Furthermore, the performance of the solid absorbent used in the carbon dioxide separation and capture facility was set as follows, based on representative literature on solid absorbents such as diethanolamine. Type of amine supported on solid absorbent: Diethanolamine Amine loading in solid absorbent: 36wt% (see Micropor.Mesopor.Mater.226, p444-453 (2016)) Carbon dioxide absorption: 2.85wt% (see Micropor.Mesopor.Mater.226, p444-453 (2016)) Carbon dioxide absorption time: 30 minutes (set based on the 22 minutes in Micropor.Mesopor.Mater.226, p444-453 (2016)) - Regeneration time of solid absorbent: 2.5 hours (based on the ratio of absorption and desorption times (6 times) calculated from Micropor.Mesopor.Mater.62, p29-45 (2003)) Base material bulk density: 400kg / m 3 (See the catalog value for spherical silica gel manufactured by Kanto Chemical Co., Ltd.) Absorbent bulk density: 625kg / m 3 (Calculated from the bulk density of the substrate and the amount of amine supported)

[0124] An example of a carbon dioxide separation and capture equipment having a carbon dioxide absorption time of 30 minutes and a solid absorbent regeneration time of 2.5 hours as described above is a carbon dioxide separation and capture equipment having five tanks (or towers) as shown in Figure 3, in which exhaust gas is supplied to one of the tanks (or towers) of the carbon dioxide separation and capture equipment while the solid absorbent regeneration process and drying process are carried out in the remaining four tanks (or towers).

[0125] From the above values, the amount of carbon dioxide absorbed per volume of the solid absorbent material of the carbon dioxide separation and capture equipment can be calculated as follows. (Bulk density of absorbent) × (amount of carbon dioxide absorbed) = 0.405 kmol / m 3

[0126] Furthermore, since the amount of carbon dioxide per unit volume is absorbed in 30 minutes, the absorption rate of carbon dioxide is 0.81 kmol / (m 3 Therefore, the exhaust gas flow rate can be calculated as follows: 0.81 kmol / (m 3 h) / ((carbon dioxide recovery rate) × (carbon dioxide concentration in exhaust gas)) = 134 Nm 3 / (h m 3 )

[0127] Next, in order to investigate in more detail the state of nitrosamine emissions from the exhaust lines (chimneys, flues, etc.) of the carbon dioxide capture and recovery equipment, the progress of nitrosation and the state of volatilization in the solid absorbent of the carbon dioxide capture and recovery equipment were estimated.

[0128] First, the following conditions were assumed for the calculation. i) All of the NOx in the exhaust gas supplied to the solid absorbent of the carbon dioxide separation and capture equipment is absorbed by the solid absorbent. ii) NOx is absorbed uniformly by all solid absorbents contained in the carbon dioxide capture system. iii) NOx reacts with diethanolamine to form NDEA, i.e., other absorption reactions, such as NOx reacting with water to produce nitric acid or nitrous acid, which then neutralizes with diethanolamine to form salts, do not occur. iv) Other degradation mechanisms of diethanolamine, such as oxidation and urea formation, are not taken into account.

[0129] According to the above conditions, the solid absorbent of the carbon dioxide capture system supports a specific amount of diethanolamine at 100% purity immediately after it is put into use. However, over time, the amount of diethanolamine decreases due to volatilization, and the amount of diethanolamine supported also decreases due to nitrosation (i.e., production of nitrosamines) caused by reaction with NOx in the exhaust gas.

[0130] The volatilization and nitrosation behavior was simulated as follows. i) Based on Raoult's law, the vapor pressure of each compound in the mixture of diethanolamine and nitrosamine supported on the solid absorbent was calculated. Note that the calculation results of this vapor pressure were used for the calculations from ii) onwards, since the amount of volatilization depends on the vapor pressure. ii) The amount of diethanolamine and nitrosamine that volatilized during a short time period Δt, and the amount of diethanolamine that was converted to nitrosamine were calculated. iii) The amount of diethanolamine supported at time t + Δt (kmol / m) is calculated by subtracting the amount of diethanolamine volatilized and converted to nitrosamine from the amount of diethanolamine supported at time t. 3 ) was calculated. In addition, the amount of diethanolamine converted to nitrosamine was added to the amount of nitrosamine supported at time t, and the amount of nitrosamine volatilized was subtracted to calculate the amount of nitrosamine supported at time t + Δt (kmol / m 3 ) was calculated. iv) By repeating ii) to iv) from time t = 0, the volatilization and nitrosation behavior of diethanolamine and nitrosamine over time was predicted.

[0131] In the calculation, the outlet gas temperature of the absorption step was set to 45°C. The vapor pressure of diethanolamine was calculated using the Antoine parameters described in Klepacova et al., J.Chem.Eng.Data 2011, 56, p2242-248. The vapor pressure of nitrosamine (specifically, NDEA) was calculated by determining the Antoine parameters that reproduce the estimated values ​​at 0°C, 20°C and 40°C described in RG Klein, Toxiclogy, 23, p135-147 (1982) by fitting using the least squares method. Figure 7 shows the vapor pressure curves of diethanolamine and NDEA in the examples.

[0132] In this way, using the vapor pressure of NDEA shown in Figure 7 and based on the predicted behavior of volatilization and nitrosation over time, we calculated the nitrosamine emission concentration over time when the NOx concentration was varied. Figure 8 shows a graph of the nitrosamine emission concentration when the NOx concentration was set to 10 ppm, 40 ppm, 63.7 ppm, or 150 ppm.

[0133] 2) Calculation step of the dilution rate of exhaust gas diffused into the atmosphere The exhaust gas discharged from the exhaust line (chimney, flue, etc.) of the carbon dioxide capture facility is diffused into the atmosphere before reaching the ground. The dilution rate of the exhaust gas at that time can be estimated using a model equation for atmospheric diffusion.

[0134] In this example, calculations were performed using a typical coal-fired power plant as a model case. First, the amount of exhaust gas was 2,210,000 Nm3 on a wet basis. 3 / h, and 1,980,000 m on a dry basis 3 / h, and the gas temperature was 90°C. The stack height was 230m. The atmospheric stability was set to B, i.e., daytime, clear skies, and average wind speed. The effective stack height was calculated using the CONCAWE formula to be 463.9m. The dilution ratio was then estimated using the plume formula. As a result, the location showing the maximum ground concentration was 2876m from the stack, and the dilution ratio at that location was 7.29×10-5 In this case, the diffusion parameters were set as follows: evaluation time was 60 minutes, PG diagram evaluation time was 3 minutes, and the power exponent of the horizontal diffusion width was 0.2.

[0135] As mentioned above, maximum ground concentration was also estimated using the weak wind puff method under weak wind conditions, the puff method under no wind conditions, etc. However, since the maximum ground concentration estimated using the plume method was the largest, the evaluation results using the plume method were used in order to more strictly consider the risk of nitrosamines being dispersed to the ground.

[0136] 3) A step for calculating the NOx concentration in the exhaust gas so that the maximum ground concentration of nitrosamines (specifically NDEA) does not exceed the regulatory value for up to 8,000 hours. According to German regulations (TRGS552), the upper limit of exposure to nitrosamines in the workplace is 1 μg / m 3 Therefore, in this embodiment, the same value was set as the regulation value. 3 Calculated from the molecular weight of NDEA, 134.1 (g / mol), the molar composition of NDEA is 0.167 ppb. This value is calculated by multiplying the dilution rate of 7.29 × 10 calculated in 2) above by -5 Dividing this by 2 gives 2.29 ppm. In other words, the upper limit of nitrosamine emission concentration in exhaust gas discharged from the exhaust line (chimney, flue, etc.) of the carbon dioxide capture and separation facility, which corresponds to the regulatory value of ground concentration, can be set at 2.29 ppm. Furthermore, based on the graph of nitrosamine emission concentration when the NOx concentration obtained in 1) above is varied, it can be confirmed that the NOx concentration in the exhaust gas that does not exceed the upper limit of 2.29 ppm of nitrosamine emission concentration in exhaust gas up to 8,000 hours is 63.7 ppm or less.

[0137] From the above, it can be seen that when a diethanolamine-based material is used as the amine supported on the solid absorbent, in order to keep the amount of nitrosamines diffusing to the ground to a small amount during the average regular maintenance period of 8,000 hours for carbon dioxide separation and capture equipment, the NOx concentration in the exhaust gas must be reduced to approximately 63.7 ppm. [Explanation of symbols]

[0138] 10, 20 Acid gas separation and recovery system 10A, 20A Combustion Equipment 1 NOx removal equipment 2 Carbon dioxide capture and storage facility 3 First Cartridge 4. Second Cartridge 5. 3rd Cartridge 6. First Impinger 7. 2nd Impinger L0 Exhaust gas supply line L1 Treatment gas supply line L2 Carbon dioxide free exhaust gas discharge line L3 Steam supply line L4 Carbon Dioxide Emission Line L5 Dry air supply line L6 Moisture-laden air exhaust line

Claims

1. A NOx removal facility for removing NOx from the exhaust gas; and a carbon dioxide separation and capture facility that is installed downstream of the gas flow of the NOx removal facility and that adsorbs and desorbs carbon dioxide contained in the gas to be treated that is supplied from the NOx removal facility using a solid absorbent material having an amine supported on a porous substrate, An acidic gas separation and recovery system, wherein the NOx concentration in the gas to be treated supplied from the NOx removal equipment to the carbon dioxide separation and recovery equipment is 63.7 ppm or less.

2. 2. The acidic gas separation and recovery system according to claim 1, wherein the NOx removal facility removes NOx in the exhaust gas using a solid absorbent material having an amine supported on a porous substrate.

3. 3. The acid gas separation and recovery system according to claim 2, wherein the solid absorbent material used in the NOx removal facility comprises a solid absorbent material used to adsorb and desorb carbon dioxide in the carbon dioxide separation and recovery facility.

4. Removing NOx from exhaust gas; and using a solid absorbent material having an amine supported on a porous substrate, adsorbing and desorbing carbon dioxide contained in the gas to be treated after the NOx removal, and separating and recovering the carbon dioxide. The method for separating and recovering acidic gases, wherein the NOx concentration in the gas to be treated after the NOx removal is 63.7 ppm or less.

5. 5. The method for separating and recovering acidic gases according to claim 4, wherein the removal of NOx comprises removing NOx from the exhaust gas using a solid absorbent material having an amine supported on a porous substrate.

6. The method for separating and recovering acidic gases according to claim 5 , wherein the solid absorbent material used in removing NOx includes a solid absorbent material used for adsorbing and desorbing carbon dioxide when separating and recovering the carbon dioxide.

7. A NOx removal facility for removing NOx from the exhaust gas; and a carbon dioxide separation and capture facility that is installed downstream of the gas flow of the NOx removal facility and that adsorbs and desorbs carbon dioxide contained in the gas to be treated that is supplied from the NOx removal facility using a solid absorbent material having an amine supported on a porous substrate, An acid gas separation and recovery system, wherein the NOx concentration in the gas to be treated supplied from the NOx removal equipment to the carbon dioxide separation and capture equipment is set to a concentration that maintains a maximum landing concentration of nitrosamines after diffusion of the exhaust gas discharged from the carbon dioxide separation and capture equipment at a value that is below a predetermined regulatory value.

8. The NOx concentration in the gas to be treated is such that the maximum landing concentration of nitrosamines after diffusion of the exhaust gas is 1 μg / m until the operation time of the carbon dioxide separation and capture equipment reaches 8000 hours. ３ The acid gas separation and recovery system according to claim 7, wherein the concentration is set to a level that maintains the following:

9. Removing NOx from exhaust gas; and using a solid absorbent material having an amine supported on a porous substrate, adsorbing and desorbing carbon dioxide contained in the gas to be treated after the NOx removal, and separating and recovering the carbon dioxide. A method for separating and recovering acidic gases, in which the NOx concentration in the gas to be treated after the NOx removal is set to a concentration that maintains a maximum landing concentration of nitrosamines after diffusion of the exhaust gas discharged after the separation and recovery of carbon dioxide at a value that is below a predetermined regulatory value.

10. The NOx concentration in the gas to be treated is such that the maximum landing concentration of nitrosamines after diffusion of the exhaust gas is 1 μg / m until the total time for separating and recovering carbon dioxide reaches 8000 hours. ３ The method for separating and recovering acidic gases according to claim 9, wherein the concentration is set to a level that allows the following to be maintained:

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