Exhaust Gas Treatment System and Exhaust Gas Treatment Method Using the Same

Abstract

The exhaust gas treatment system according to the present invention includes a membrane capture device comprising a separation membrane that directly introduces exhaust gas generated in a lime calcination process and containing carbon dioxide (CO2) and sulfur oxides (SOX) without a pretreatment process for sulfur oxides, passes a mixed gas of carbon dioxide and sulfur oxides among the components of the introduced exhaust gas, and filters out residual components, and a scrubber that removes concentrated sulfur oxides from the mixed gas that has passed through the membrane of the membrane capture device and passes carbon dioxide.

Description

Technology Field

[0001] The present invention relates to an exhaust gas treatment system and an exhaust gas treatment method using the same. Background Technology

[0002] Calcination kilns are process facilities used to produce quicklime (CaO) in steel mills or cement in cement companies, and they come in various forms, such as rotary and shaft types.

[0003] The kiln of the lime calcination plant performs the process of producing quicklime required in the steelmaking and sintering processes by calcining limestone (CaCO3) at high temperatures, and the reaction equation for the said process is as follows.

[0005] CaCO3 → CaO + CO2

[0007] As shown in the reaction equation, a large amount of carbon dioxide (CO2) is generated in this process, which consists of carbon dioxide and sulfur oxides (SO₂) produced by the combustion of fuel. x It combines with ) and is emitted as exhaust gas.

[0008] In particular, exhaust gases from lime calcination plants contain a large amount of dust, so they are generally removed using bag filters or similar methods before being discharged into the atmosphere through a stack.

[0009] In addition, sulfur oxides contained in exhaust gas are treated through a separate desulfurization device to satisfy environmental regulation conditions (130 ppm or less based on roasting furnaces installed after February 1, 2007) before being discharged.

[0010] However, in the case of carbon dioxide contained in exhaust gases, the current trend is to emit it as is without separate treatment.

[0011] When the exhaust gas from a lime calcination plant passes through a desulfurization device, it is typically emitted containing 5 to 10 ppm of sulfur oxides and 20% of carbon dioxide.

[0012] Permissible emission standards for air pollutants are becoming stricter every year, and in particular, due to the strengthening of carbon dioxide emission regulations following the implementation of the Framework Act on Carbon Neutrality and Green Growth in 2022, it is expected that processes for removing sulfur oxides from exhaust gases and capturing carbon dioxide will become essential in the future.

[0013] In general, dry or wet desulfurization methods are widely used to remove sulfur oxides from exhaust gases, and membrane capture methods or wet capture methods using liquid absorbents are being considered as methods to capture carbon dioxide.

[0014] Among these, membrane capture technology is more suitable for carbon dioxide capture in lime calcination plants because it is less affected by sulfur oxides compared to wet capture.

[0015] Membrane capture technology is a technology that captures carbon dioxide from multi-component exhaust gases containing carbon dioxide and nitrogen (N2) using a membrane that selectively permeates carbon dioxide.

[0016] However, sulfur oxides contained in the exhaust gas are also discharged into the membrane permeate along with carbon dioxide, and since the concentration of carbon dioxide in the exhaust gas is about 20%, there is a problem that sulfur oxides are concentrated together.

[0017] Therefore, if this method is maintained, permissible emission standards for sulfur oxides may be exceeded in the future due to reasons such as stricter environmental regulations. Furthermore, during the process of producing high-value-added products using Carbon Capture and Utilization (CCU) technology, additional reactions caused by sulfur oxides may occur, potentially resulting in a failure to obtain high-purity final products. In addition, there is a high likelihood of corrosion occurring in pipes and tank trucks during the transportation of carbon dioxide containing sulfur oxides.

[0018] For the reasons mentioned above, it is essential to remove sulfur oxides contained in carbon dioxide captured through membrane capture technology.

[0019] However, since desulfurization devices are currently applied in the calcination plant as well, if an additional desulfurization device is installed to remove concentrated sulfur oxides downstream of the membrane, two desulfurization devices will be operated—one for the calcination plant and one for the downstream of the membrane process—resulting in a problem of high energy consumption. This causes a decrease in the process economics of carbon dioxide capture and the calcination plant.

[0020] Therefore, a method to resolve these problems is required. Prior art literature

[0021] Korean Published Patent No. 10-2021-0046627 Korean Published Patent No. 10-2021-0075195 Korean Registered Patent No. 10-1459457 The problem to be solved

[0022] The present invention is an invention devised to solve the problems of the aforementioned prior art, and aims to provide an exhaust gas treatment system capable of effectively removing sulfur oxides that are concentrated together during the process of capturing carbon dioxide contained in exhaust gas, while preventing energy waste by eliminating the operation of multiple desulfurization devices.

[0023] The problems of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0024] The exhaust gas treatment system of the present invention for achieving the above-mentioned purpose is a carbon dioxide (CO2) and sulfur oxides (SO₂) generated in the lime calcination process. XIt includes a membrane capture device that directly introduces exhaust gas containing ) without a pretreatment process for sulfur oxides, passes a mixture of carbon dioxide and sulfur oxides among the components of the introduced exhaust gas, and filters out residual components, and a scrubber that removes concentrated sulfur oxides from the mixture gas that has passed through the membrane of the membrane capture device and passes carbon dioxide.

[0025] At this time, the present invention may further include a bag filter for removing dust contained in the exhaust gas generated in the lime calcination process and flowing to the membrane collection device.

[0026] In addition, the present invention may further include a residual component recovery unit that separately recovers residual components filtered by the membrane collection device.

[0027] In addition, the present invention may further include a lime water recovery unit that recovers lime water (Ca(OH)2) generated during the washing process of limestone (CaCO3) in the lime calcination process and supplies it to the scrubber.

[0028] Furthermore, the exhaust gas treatment method using the exhaust gas treatment system of the present invention for achieving the above-mentioned purpose involves carbon dioxide (CO2) and sulfur oxides (SO2) generated in the lime calcination process. X (a) a step of directly flowing exhaust gas containing ) toward a membrane capture device including a membrane, wherein carbon dioxide (CO2) and sulfur oxides (SO₂) among the components of the exhaust gas through the membrane of the membrane capture device X The method includes (b) a step of passing a mixed gas through the membrane and filtering out residual components, (c) a step of flowing the mixed gas that has passed through the membrane in step (b) toward a scrubber, (d) a step of removing concentrated sulfur oxides from the mixed gas that has passed through the membrane of the membrane capture device through the scrubber, and (e) a step of recovering carbon dioxide that has passed through the scrubber in step (d).

[0029] At this time, between the above steps (a) and (b), a step (ex1) of removing dust contained in the exhaust gas through a bag filter installed in the flow path of the exhaust gas generated in the lime calcination process and flowing to the membrane collection device may be further performed.

[0030] And after the above step (b), a step (ex2) may be further performed in which a residual component recovery unit separately recovers the residual component filtered by the membrane collection device in the above step (b).

[0031] In addition, the present invention may further include a step (ex3-1) in which a lime water recovery unit recovers lime water (Ca(OH)2) generated during the washing process of limestone (CaCO3) in the lime calcination process, and a step (ex3-2) in which the lime water recovery unit supplies the lime water recovered in step (ex3-1) to the scrubber to utilize it in the process of removing sulfur oxides in step (d). Effects of the invention

[0032] The exhaust gas treatment system and exhaust gas treatment method using the same according to the present invention for solving the above-mentioned problem have the advantage of enabling efficient process operation by effectively reducing process operating costs and minimizing energy consumption in the entire process, by applying a carbon dioxide capture process in which carbon dioxide contained in the exhaust gas discharged from a lime calcination process is captured by a membrane capture device, thereby excluding the provision of a separate desulfurization device in the calcination plant performing the lime calcination process, and by installing a scrubber downstream of the membrane of the membrane capture device to remove concentrated sulfur oxides from the mixed gas that has passed through the membrane.

[0033] Furthermore, by effectively removing sulfur oxides, the present invention can fundamentally prevent unwanted side reactions when converting carbon dioxide into high-value-added products through carbon dioxide utilization technology (CCU), thereby significantly improving the quality of the final product and preventing corrosion in pipes and tank trucks during the transportation of carbon dioxide.

[0034] Therefore, the present invention ultimately makes it possible to achieve carbon neutrality through carbon dioxide free of impurities.

[0035] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0036] FIG. 1 is a diagram schematically showing a process through an exhaust gas treatment system according to a first embodiment of the present invention; FIG. 2 is a diagram showing each process of an exhaust gas treatment method through an exhaust gas treatment system according to a first embodiment of the present invention; FIG. 3 is a diagram showing an additional process of an exhaust gas treatment method through an exhaust gas treatment system according to the first embodiment of the present invention; FIG. 4 is a diagram schematically showing a process through an exhaust gas treatment system according to a second embodiment of the present invention; FIG. 5 is a diagram showing an additional process of an exhaust gas treatment method through an exhaust gas treatment system according to a second embodiment of the present invention; FIG. 6 is a schematic diagram showing a process through an exhaust gas treatment system according to a third embodiment of the present invention; and FIG. 7 is a schematic diagram showing a process through an exhaust gas treatment system according to the fourth embodiment of the present invention. Specific details for implementing the invention

[0037] In this specification, where a component (or region, layer, part, etc.) is described as being "on," "connected," or "combined" with another component, it means that it may be directly placed / connected / combined with the other component, or that a third component may be placed between them.

[0038] Identical reference numerals denote identical components. Additionally, in the drawings, the thicknesses, proportions, and dimensions of the components are exaggerated for the effective illustration of the technical content.

[0039] "And / or" includes all one or more combinations that the associated configurations can define.

[0040] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0041] Additionally, terms such as "below," "lower side," "above," and "upper side" are used to describe the relationships between the components depicted in the drawings. These terms are relative concepts and are described based on the directions indicated in the drawings.

[0042] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Additionally, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and are explicitly defined herein unless interpreted in an ideal or overly formal sense.

[0043] Terms such as "include" or "have" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0045] FIG. 1 is a schematic diagram showing a process through an exhaust gas treatment system according to a first embodiment of the present invention.

[0046] As illustrated in FIG. 1, the exhaust gas treatment system according to the first embodiment of the present invention includes a membrane capture device (100), a scrubber (200), a bag filter (10), and a residual component recovery unit (20).

[0047] It is generated during the lime calcination process carried out in the calcination plant (5) of the membrane capture device (100), and carbon dioxide (CO2) and sulfur oxides (SO₂) X Exhaust gas containing ) is introduced directly without a pretreatment process for sulfur oxides.

[0048] That is, in the conventional case, a desulfurization device was applied to the calcination plant (5), but the present invention excludes the desulfurization device applied to the calcination space (5) and carbon dioxide (CO2) and sulfur oxides (SO2) generated in the lime calcination process X Exhaust gas containing ) is allowed to flow directly into the membrane collection device (100) without pretreatment.

[0049] And the membrane capture device (100) includes a membrane that passes a mixture of carbon dioxide and sulfur oxides among the components of the incoming exhaust gas and filters out residual components.

[0050] Any membrane capable of separating carbon dioxide from exhaust gas can be used as such. For example, materials such as polysulfone, polyethersulfone, polyimide, polycarbonate, cellulose acetate, and polymethyl methacrylate may be used as membrane materials, and these can be used individually or in combination.

[0051] Such a separation membrane can separate carbon dioxide from exhaust gas through diffusion. Specifically, under high pressure conditions, the exhaust gas dissolves on the surface of the separation membrane and diffuses into the interior of the membrane; at this time, carbon dioxide can be separated due to the difference in diffusion rates with other gaseous components.

[0052] However, in the case of sulfur oxides, they can pass through the membrane applied to the membrane collection device (100), and thus high-purity carbon dioxide and sulfur oxides are concentrated at the downstream end of the membrane.

[0053] The scrubber (200) performs the function of removing concentrated sulfur oxides from the mixed gas that has passed through the membrane of the membrane collection device (100) in this way, thereby allowing carbon dioxide to pass through.

[0054] Accordingly, after the mixed gas passes through the scrubber (200), only high-purity carbon dioxide remains, and the captured carbon dioxide can be converted into high-value-added products through carbon dioxide utilization technology (CCU) or used for other purposes.

[0055] And the scrubber (200) can use lime water as an absorbent to separate sulfur oxides from the mixed gas.

[0056] A bag filter (10) is provided to remove dust contained in the exhaust gas generated in the lime calcination process and flowing to the membrane collection device (100), and any type of filter that filters particles of a predetermined size can be applied to the bag filter (10).

[0057] The residual component recovery unit (20) is provided to separately recover the residual component filtered by the membrane collection device (100), and, for example, the residual component may be nitrogen (N2), etc., separated from the exhaust gas by the membrane collection device (100).

[0058] Below, the process of treating exhaust gas through the exhaust gas treatment system of the present embodiment will be described sequentially.

[0059] FIG. 2 is a diagram showing each process of an exhaust gas treatment method through an exhaust gas treatment system according to the first embodiment of the present invention, and FIG. 3 is a diagram showing additional processes of an exhaust gas treatment method through an exhaust gas treatment system according to the first embodiment of the present invention.

[0060] As illustrated in FIGS. 2 and 3, the exhaust gas treatment method using an exhaust gas treatment system according to the first embodiment of the present invention includes steps (a) through (e), step (ex1) is performed between step (a) and step (b), and step (ex2) is performed after step (b).

[0061] First, step (a) is a process of directly flowing exhaust gas containing carbon dioxide and sulfur oxides generated in the lime calcination process to a membrane capture device (100) containing a membrane.

[0062] As described above, since the desulfurization device is excluded from the calcination plant (5) in the present invention, the exhaust gas containing carbon dioxide and sulfur oxides generated in the lime calcination process flows directly to the membrane capture device (100) without pretreatment.

[0063] Next, in step (ex1), a process is performed to remove dust contained in the exhaust gas through a bag filter (10) installed in the flow path of the exhaust gas that is generated in the lime calcination process and flows to the membrane collection device (100).

[0064] Next, step (b) is a process of passing a mixture of carbon dioxide and sulfur oxides among the components of the exhaust gas through the membrane of the membrane collection device (100) and filtering out the residual components.

[0065] Through this process, carbon dioxide and sulfur oxides pass to the downstream side of the separation membrane, while residual components such as nitrogen are filtered by the separation membrane.

[0066] In the subsequent (ex2) step, the residual component recovery unit (20) separately recovers the residual component filtered by the membrane collection device in step (b).

[0067] In addition, after step (b), step (c) of flowing the mixed gas that has passed through the separation membrane toward the scrubber (200) and step (d) of removing the concentrated sulfur oxides from the mixed gas that has passed through the separation membrane of the separation membrane collection device (100) through the scrubber (200) are performed.

[0068] As described above, the scrubber (200) uses lime water as an absorbent to separate sulfur oxides from the mixed gas, and accordingly, in step (e), high-purity carbon dioxide that passed through the scrubber (200) in step (d) is recovered.

[0069] The present invention, as described above, applies a carbon dioxide capture process in which carbon dioxide contained in the exhaust gas discharged from the lime calcination process is captured by a membrane capture device (100). In this process, the requirement to provide a separate desulfurization device in the calcination plant (5) performing the lime calcination process is excluded, and a scrubber (200) is installed at the rear end of the membrane of the membrane capture device (100) to remove concentrated sulfur oxides from the mixed gas that has passed through the membrane. This allows for the minimization of energy consumption required in the entire process and enables efficient process operation by effectively reducing process operating costs.

[0070] Hereinafter, other embodiments of the present invention will be described. In each embodiment described below, redundant descriptions of components identical to those in the first embodiment described above will be omitted.

[0071] FIG. 4 is a schematic diagram showing a process through an exhaust gas treatment system according to a second embodiment of the present invention.

[0072] The exhaust gas treatment system according to the second embodiment of the present invention illustrated in FIG. 4 is characterized by having all the same components as the first embodiment described above, and additionally including a lime water recovery unit (30).

[0073] The lime water recovery unit (30) is a component that recovers lime water (Ca(OH)2) generated during the washing process of limestone (CaCO3) during the lime calcination process and supplies it to the scrubber (200).

[0074] The limestone used as a raw material in the calcination plant (5) must undergo a raw material washing process using water, and since a certain amount of limestone dissolves in the water used in this process, lime water is generated. Generally, the lime water collected in the calcination process (5) is sent to a separate concentration tank for treatment, but the present invention recycles the lime water generated during the washing process of the calcination plant (5) as an absorbent for a scrubber (200) for removing concentrated sulfur oxides at the rear end of the separation membrane.

[0075] And Fig. 5 is a diagram showing an additional process of an exhaust gas treatment method through an exhaust gas treatment system according to a second embodiment of the present invention.

[0076] As illustrated in FIG. 5, the exhaust gas treatment method through the exhaust gas treatment system according to the second embodiment of the present invention includes, in addition to each step of the entire exhaust gas treatment method of the first embodiment described above, steps (ex3-1) and (ex3-2).

[0077] Step (ex3-1) is a process in which the lime water recovery unit (30) recovers lime water generated during the washing process of limestone in the lime calcination process, and Step (ex3-2) is a process in which the lime water recovery unit (30) supplies the lime water recovered in Step (ex3-1) to the scrubber (200) to be used in the process of removing sulfur oxides in Step (d).

[0078] As such, this embodiment additionally provides a lime water recovery unit (30), thereby eliminating the need for a separate process of preparing an absorbent or adsorbent for removing sulfur oxides, allowing for an efficient sulfur oxide removal process to be operated.

[0079] FIG. 6 is a schematic diagram showing a process through an exhaust gas treatment system according to the third embodiment of the present invention.

[0080] The exhaust gas treatment system according to the third embodiment of the present invention illustrated in FIG. 6 is characterized by having all the same components as the second embodiment described above, and additionally includes a lime water monitoring unit (31), a sulfur oxide monitoring unit (110), and a lime water supply unit (210).

[0081] The lime water monitoring unit (31) is provided to measure and monitor the amount of lime water recovered by the lime water recovery unit (30) and supplied to the scrubber (200).

[0082] And the sulfur oxide monitoring unit (110) is provided to measure and monitor the amount of sulfur oxide contained in the mixed gas that passes through the membrane collection device (100) and flows into the scrubber (200).

[0083] Accordingly, this embodiment monitors the amount of sulfur oxide measured by the sulfur oxide monitoring unit (110) and the amount of sulfur oxide measured by the lime water monitoring unit (31) in real time, and based on the reaction equation between sulfur oxide and lime water, if the amount of lime water required for the reaction is insufficient in relation to the amount of sulfur oxide, additional lime water can be supplied from the lime water supply unit (210) to the scrubber (200) to ensure a smooth reaction.

[0084] FIG. 7 is a schematic diagram showing a process through an exhaust gas treatment system according to the fourth embodiment of the present invention.

[0085] The exhaust gas treatment system according to the fourth embodiment of the present invention illustrated in FIG. 7 is characterized by having all the same components as the third embodiment described above, and additionally including a lime water buffer tank (32).

[0086] The lime water buffer tank (32) is provided to store and preserve the lime water recovered by the lime water recovery unit (30) and supplied to the scrubber (200).

[0087] Accordingly, this embodiment monitors the amount of sulfur oxide measured by the sulfur oxide monitoring unit (110) and the amount of sulfur oxide measured by the lime water monitoring unit (31) in real time, and based on the reaction equation between sulfur oxide and lime water, if the amount of lime water is greater than the amount of sulfur oxide, the excess amount of lime water can be stored in the lime water buffer tank (32).

[0088] And the lime water stored in the lime water buffer tank (32) in this way can be controlled to additionally supply lime water to the scrubber (200) if the amount of lime water required for the reaction is insufficient in relation to the amount of sulfur oxides later.

[0089] As described above, preferred embodiments according to the present invention have been examined. It is obvious to those skilled in the art that, in addition to the embodiments described above, the present invention may be embodied in other specific forms without departing from its spirit or scope. Therefore, the embodiments described above should be regarded as illustrative rather than restrictive, and accordingly, the present invention is not limited to the description above but may be modified within the scope of the appended claims and their equivalents. Explanation of the symbols

[0090] 5: Firing Plant 10: Bag filter 20: Residual component recovery unit 30: Limewater recovery unit 31: Limewater Monitoring Department 32: Limewater buffer tank 100: Membrane capture device 110: Sulfur Oxide Monitoring Unit 200: Scrubber 210: Lime water supply unit

Claims

Claim 1 It is generated during the lime calcination process and consists of carbon dioxide (CO2) and sulfur oxides (SO₂). X An exhaust gas treatment system comprising: a bag filter for removing dust contained in exhaust gas including ); a membrane capture device including a separation membrane that directly introduces the exhaust gas that has passed through the bag filter without a pretreatment process for sulfur oxides, passes a mixed gas of carbon dioxide and sulfur oxides among the components of the introduced exhaust gas, and filters out residual components; a scrubber that removes concentrated sulfur oxides from the mixed gas that has passed through the separation membrane of the membrane capture device and passes carbon dioxide; and a lime water recovery unit that recovers lime water (Ca(OH)2) generated during the washing process of limestone (CaCO3) in the lime calcination process and supplies it to the scrubber. Claim 2 delete Claim 3 An exhaust gas treatment system according to claim 1, further comprising a residual component recovery unit that separately recovers residual components filtered by the membrane collection device. Claim 4 delete Claim 5 A step (ex1) of removing dust contained in exhaust gas through a bag filter installed in the flow path of exhaust gas generated in a lime calcination process and flowing to a membrane capture device; a step (a) of directly flowing the exhaust gas that has passed through the bag filter in step (ex1) toward a membrane capture device including a membrane; and removing carbon dioxide (CO2) and sulfur oxides (SO2) among the components of the exhaust gas through the membrane of the membrane capture device. X A method for treating exhaust gas, comprising: (b) a step of passing a mixed gas of ) through and filtering residual components; (c) a step of flowing the mixed gas that has passed through the membrane in step (b) toward a scrubber; (d) a step of removing concentrated sulfur oxides from the mixed gas that has passed through the membrane of the membrane capture device through the scrubber; and (e) a step of recovering carbon dioxide that has passed through the scrubber in step (d); wherein a lime water recovery unit further performs a step (ex3-1) of recovering lime water (Ca(OH)2) generated during the washing process of limestone (CaCO3) in the lime calcination process. Claim 6 delete Claim 7 In claim 5, after step (b) above, a step (ex2) is further performed in which a residual component recovery unit separately recovers the residual component filtered by the membrane collection device in step (b), in an exhaust gas treatment method. Claim 8 A method for treating exhaust gas, further comprising, in claim 5, a step (ex3-2) in which the lime water recovery unit supplies the lime water recovered in step (ex3-1) to the scrubber to be utilized in the sulfur oxide removal process of step (d).

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