Exhaust gas treatment apparatus and exhaust gas treatment method

Abstract

To achieve stable apparatus operation.SOLUTION: The exhaust gas treatment apparatus includes: a gas treatment part that performs desulfurization treatment on exhaust gas to be treated using activated carbon; an introduction pipe that introduces the exhaust gas to be treated into the gas treatment part; a desorption part that heats and regenerates the activated carbon after use in the gas treatment; a bypass pipe capable of supplying desorbed exhaust gas containing sulfur oxides to the introduction pipe; and a preheating part that introduces a preheating gas into the inside of the bypass pipe so as to heat at least a part of the bypass pipe.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an exhaust gas treatment device and an exhaust gas treatment method. [Background technology]

[0002] There are known techniques for carrying out desulfurization and denitrification of exhaust gas (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 58-159832 [Patent Document 2] Japanese Patent Publication No. 61-287423 [Patent Document 3] Japanese Patent Application Publication No. 3-254817 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides an exhaust gas treatment device and an exhaust gas treatment method that enable stable operation of the device. [Means for solving the problem]

[0005] [1] An exhaust gas treatment device according to one aspect of the present disclosure includes a gas treatment section that performs desulfurization treatment on exhaust gas to be treated using activated carbon, an inlet pipe that introduces the exhaust gas to be treated into the gas treatment section, a desorption section that heats and regenerates activated carbon after use in the gas treatment, a bypass pipe that is generated by heating the activated carbon in the desorption section and is capable of supplying desorbed exhaust gas containing sulfur oxides to the inlet pipe, and a preheating section that introduces a preheating gas into the inside of the bypass piping so as to heat at least a portion of the bypass piping.

[0006] [2] The exhaust gas treatment device described in [1] above may further include a bypass valve that opens and closes a flow path in the bypass piping. The preheating unit may introduce the preheating gas into each of a section located upstream of the bypass valve in the bypass piping and a section located downstream of the bypass valve in the bypass piping.

[0007] [3] The exhaust gas treatment device described in [1] above may further include a bypass valve that opens and closes a flow path in the bypass piping. The preheating unit may introduce the preheating gas into either a section of the bypass piping that is located upstream of the bypass valve or a section of the bypass piping that is located downstream of the bypass valve.

[0008] [4] The exhaust gas treatment device according to any one of the above [1] to [3] may further include a hot air furnace that generates a heating gas for heating the activated carbon in the desorption section. The preheating section may introduce the heating gas, before being used for heating in the desorption section, into the bypass piping as the preheating gas.

[0009] [5] The exhaust gas treatment device according to any one of the above [1] to [3] may further include a hot air furnace that generates a heating gas for heating the activated carbon in the desorption section. The preheating section may introduce the heating gas, which has been used for heating in the desorption section, into the bypass piping as the preheating gas.

[0010] [6] In the exhaust gas treatment device described in [4] or [5] above, the preheating section may continue to introduce the preheating gas into the bypass piping during a period in which the hot stove is operating.

[0011] [7] An exhaust gas treatment method according to one aspect of the present disclosure includes a gas treatment step of subjecting exhaust gas to desulfurization treatment using activated carbon; an introduction step of introducing the exhaust gas to be treated from an introduction pipe to an area where the gas treatment is performed; a desorption step of heating and regenerating the activated carbon after use in the gas treatment; and a preheating step of introducing a preheating gas into the inside of the bypass piping so as to heat at least a portion of the bypass piping that is generated by heating the activated carbon in the desorption step and that is capable of supplying desorbed exhaust gas containing sulfur oxides to the introduction pipe. Effect of the Invention

[0012] According to the present disclosure, an exhaust gas treatment device and an exhaust gas treatment method capable of achieving stable operation of the device are provided. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing an example of an exhaust gas treatment device. [Diagram 2] 2(a) and 2(b) are schematic diagrams showing an example of the preheating section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment will be described with reference to the drawings. In the description, the same elements or elements having the same functions are denoted by the same reference numerals, and duplicated description will be omitted.

[0015] [Exhaust gas treatment equipment] FIG. 1 shows a schematic diagram of an example of a system configuration of an exhaust gas treatment device according to an embodiment. The exhaust gas treatment device 1 shown in FIG. 1 is a device that removes environmental load substances contained in the exhaust gas to be treated by performing at least a desulfurization process on the exhaust gas to be treated using activated carbon. The exhaust gas treatment device 1 may perform a denitration process in addition to the desulfurization process. The following illustrates a case in which the exhaust gas treatment device 1 performs both the desulfurization process and the denitration process. For example, the exhaust gas treatment device 1 performs a desulfurization process on the exhaust gas to be treated, and then performs a denitration process on the exhaust gas to be treated after the desulfurization process. The exhaust gas treatment device 1 regenerates the activated carbon after it has been used in the desulfurization process and the denitration process, thereby circulating and utilizing the activated carbon.

[0016] The flue gas to be treated by the flue gas treatment device 1 is, for example, a gas discharged from a sintering machine, a power generation boiler, a waste incinerator, a coke oven, or a cement kiln. By performing a desulfurization treatment on the flue gas to be treated, at least a part of the SOx (sulfur oxides) contained in the flue gas is removed. By performing a denitration treatment on the flue gas to be treated, at least a part of the NOx (nitrogen oxides) contained in the flue gas is removed. The flue gas treatment device 1 may release the flue gas to be treated after the desulfurization treatment and the denitration treatment into the atmosphere. In this disclosure, for convenience of explanation, the flue gas to be treated before the desulfurization treatment and the denitration treatment by the flue gas treatment device 1 may be referred to as "flue gas G0", and the flue gas after the desulfurization treatment and the denitration treatment may be referred to as "flue gas G1".

[0017] The exhaust gas treatment device 1 includes a gas treatment section 10, a desorption section 20, a heating gas supply section 30, an exhaust pipe 40, a by-product recovery section 50, a bypass pipe 60, a preheating section 70, and a control device 90. Hereinafter, in the description of the present disclosure, the terms "upstream" and "downstream" are used based on the gas flow. That is, the gas flows from upstream to downstream.

[0018] The gas processing unit 10 is a part that performs desulfurization treatment on the exhaust gas G0 using activated carbon. In one example, the gas processing unit 10 performs gas treatment including desulfurization and denitration on the exhaust gas G0. The gas treatment performed by the gas processing unit 10 includes, for example, a desulfurization treatment using activated carbon and a denitration treatment using activated carbon that is performed after the desulfurization treatment. The gas processing unit 10 is, for example, a single adsorption tower in which a desulfurization section (desulfurization region) and a denitration section (denitration region) are formed. Activated carbon may be introduced into the adsorption tower of the gas processing unit 10 from the top of the adsorption tower.

[0019] In the desulfurization section, for example, activated carbon flows from top to bottom and comes into contact with the exhaust gas G0. When the activated carbon comes into contact with the exhaust gas G0, the SOx contained in the exhaust gas G0 is adsorbed by the activated carbon. This removes at least a portion of the SOx from the exhaust gas G0. The adsorption by the activated carbon may include physical adsorption and chemical adsorption. In the desulfurization process in the desulfurization section, in addition to SOx, other environmental load substances contained in the exhaust gas G0 may be adsorbed. The desulfurization section of the gas treatment section 10 may be formed in any manner as long as it is possible to adsorb and remove the SOx in the exhaust gas G0 by the activated carbon.

[0020] In the denitration section, for example, in a state where NH3 (ammonia) is introduced into the exhaust gas G0 (for example, exhaust gas G0 after desulfurization treatment), activated carbon flows from top to bottom and comes into contact with the exhaust gas G0. When the activated carbon comes into contact with the exhaust gas G0 in a state where NH3 is introduced, NOx contained in the exhaust gas G0 is decomposed into H2O (water) and N2 (nitrogen) by the catalytic action of the activated carbon. As a result, at least a portion of the NOx is removed from the exhaust gas G0.

[0021] In the denitration process, unlike the desulfurization process, removal of substances by adsorption is not performed, so the activated carbon used in the denitration process can be used for the desulfurization process. In the denitration process in the denitration section, other environmental load substances contained in the exhaust gas G0 may be adsorbed in addition to NOx. The denitration section of the gas processing section 10 may be formed in any manner as long as it is possible to remove NOx in the exhaust gas G0 by the catalytic action of the activated carbon. The gas processing section 10 may include a desulfurization tower that performs the desulfurization process and a denitration tower that performs the denitration process. The denitration tower may be installed at a location away from the desulfurization tower.

[0022] The exhaust gas treatment device 1 includes an inlet pipe 12 and an exhaust pipe 14. The inlet pipe 12 is a pipe that introduces the exhaust gas G0 into the gas treatment device 10. The exhaust pipe 14 is a pipe that circulates the exhaust gas G1 discharged from the gas treatment device 10. The exhaust gas G1 that has circulated through the exhaust pipe 14 is released into the atmosphere via a chimney, for example.

[0023] The desorption section 20 is a section that heats and regenerates the activated carbon after it has been used in gas processing in the gas processing section 10. The exhaust gas processing device 1 is equipped with a transport line 16, which transports the activated carbon after it has been used in gas processing from the gas processing section 10 to the desorption section 20. The transport line 16 is a transport device such as a conveyor. When the activated carbon approaches an adsorption saturation state due to adsorption of SOx in the desulfurization process in the gas processing section 10, the SOx removal performance of the activated carbon decreases. The desorption section 20 desorbs the adsorbed SOx by heating the activated carbon whose SOx removal performance has decreased. This allows the activated carbon to be reused in the desulfurization process, and the activated carbon is regenerated.

[0024] The desorption section 20 desorbs SOx from the activated carbon by, for example, heating the activated carbon in an inert atmosphere (oxygen-free atmosphere). The desorption section 20 may include a heating section 22 and a cooling section 24 arranged vertically in one desorption tower. The heating section 22 is disposed above the cooling section 24. The activated carbon transported by the transport line 16 may be introduced into the desorption tower of the desorption section 20 from its upper end. The activated carbon passes through the heating section 22 and the cooling section 24 in this order, and flows from top to bottom in each of the heating section 22 and the cooling section 24.

[0025] The heating section 22 is supplied with gas for heating the activated carbon (hereinafter referred to as "heating gas") from the heating gas supply section 30. The heating section 22 may function as an indirect heat exchanger, for example, by flowing activated carbon inside a tube and flowing heating gas Gh outside the tube. The activated carbon is heated by heat exchange between the activated carbon inside the tube and the heating gas Gh. As the activated carbon is heated, SOx is desorbed from the activated carbon. As a result, exhaust gas containing SOx is generated in the heating section 22. The exhaust gas containing SOx generated by heating the activated carbon in the desorption section 20 is referred to as "desorbed exhaust gas Gs" to distinguish it from exhaust gas G0 and the like. The desorbed exhaust gas Gs is extracted to the outside of the desorption section 20 (heating section 22).

[0026] A cooling medium cm is supplied to the cooling section 24 to cool the activated carbon after it has been heated by the heating section 22. The cooling section 24 may function as an indirect heat exchanger, for example, by flowing activated carbon inside a tube and flowing cooling medium cm outside the tube. The cooling medium cm may be cooling water or air. The activated carbon is cooled by heat exchange between the activated carbon in the tube and the cooling medium cm. The cooled activated carbon is discharged outside the desorption section 20 (cooling section 24).

[0027] The exhaust gas treatment device 1 is equipped with a transfer line 18, which receives the regenerated activated carbon and transfers the activated carbon to the gas treatment device 10. The transfer line 18 is a transfer device such as a conveyor. As described above, in the exhaust gas treatment device 1, the activated carbon circulates between the gas treatment device 10 and the desorption device 20.

[0028] The heating gas supplying unit 30 supplies the heating gas to the heating unit 22 of the desorption unit 20. The heating gas supplying unit 30 recovers the heating gas after it has been used to heat the activated carbon in the heating unit 22. For ease of explanation, the heating gas before it is used to heat the activated carbon in the heating unit 22 is referred to as "heating gas Gh0", and the heating gas after it has been used to heat the activated carbon in the heating unit 22 is referred to as "heating gas Gh1". The temperature of the heating gas Gh0 is higher than the temperature of the heating gas Gh1. The temperature of the heating gas Gh0 may be 400°C to 550°C, 420°C to 530°C, or 440°C to 500°C. The temperature of the heating gas Gh1 may be 250°C to 450°C, 270°C to 430°C, or 290°C to 400°C.

[0029] The heated gas supplying section 30 includes, for example, a hot stove 32, a fuel supplying section 34, a supply pipe 36, a suction device 37, and a recovery pipe 38. The hot stove 32 is a furnace that generates a heated gas Gh0 for heating the activated carbon in the desorption section 20. The fuel supplying section 34 supplies fuel for generating the heated gas Gh0 to the hot stove 32. The fuel supplied from the fuel supplying section 34 is, for example, coke oven gas (COG), blast furnace gas (BFG), or light oil. The supply pipe 36 is a pipe that distributes the heated gas Gh0 from the hot stove 32 to the heating section 22 of the desorption section 20.

[0030] The suction device 37 sucks the heating gas Gh1 (the heating gas after being used to heat the activated carbon) from the heating section 22. As the suction device 37 sucks the heating gas Gh1, the heating gas Gh1 is discharged from the heating section 22. The recovery pipe 38 is a pipe for circulating the heating gas Gh1, and returns a portion of the heating gas Gh1 discharged from the heating section 22 to the hot air stove 32. In the hot air stove 32, the fuel from the fuel supply section 34 and the heating gas Gh1 recovered by the recovery pipe 38 are used to generate the heating gas Gh0.

[0031] The discharge pipe 40 is a pipe for passing the desorbed exhaust gas Gs generated in association with the regeneration of the activated carbon from the desorption section 20 to the by-product recovery section 50. The desorbed exhaust gas Gs is a gas containing high concentration SOx, and can also be called SOx-rich gas. The temperature of the desorbed exhaust gas Gs discharged from the desorption section 20 to the discharge pipe 40 may be about 350°C to 450°C. The desorbed exhaust gas Gs contains high concentrations of SO3 and H2O. In the desorbed exhaust gas Gs, the concentration of SO3 may be 0.01% to 1%, and the moisture concentration may be 8% to 50%. The acid dew point of the desorbed exhaust gas Gs is, for example, 100°C to 250°C, 110°C to 240°C, or 120°C to 230°C. The acid dew point is the temperature at which SO3 combines with H2O to become sulfuric acid mist and begin to condense. The discharge pipe 40 allows the desorbed exhaust gas Gs to flow to the by-product recovery section 50 so that the temperature of the desorbed exhaust gas Gs does not become equal to or lower than the acid dew point.

[0032] The by-product recovery section 50 is a section that recovers SOx from the desorbed exhaust gas Gs. The by-product recovery section 50 converts the SOx components in the desorbed exhaust gas Gs into sulfuric acid (H2SO4) and / or gypsum (CaSO4H2O) and solidifies them, for example. This reduces the amount of SOx in the desorbed exhaust gas Gs. The by-product recovery section 50, for example, releases the remaining gas after solidifying the SOx components and recovering them as a by-product into the atmosphere.

[0033] The bypass pipe 60 is a pipe capable of supplying the desorbed exhaust gas Gs to the introduction pipe 12. One end of the bypass pipe 60 is connected to the middle of the discharge pipe 40, and the other end of the bypass pipe 60 is connected to the middle of the introduction pipe 12. The bypass pipe 60 is installed in preparation for the case where the by-product recovery section 50 abnormally stops due to some cause. Due to legal regulations, etc., there are cases where the desorbed exhaust gas Gs discharged from the desorption section 20 cannot be released directly to the atmosphere, and when the by-product recovery section 50 abnormally stops, there is no discharge destination for the desorbed exhaust gas Gs. Therefore, when the by-product recovery section 50 abnormally stops or is abnormally stopped, the desorbed exhaust gas Gs is returned to the introduction pipe 12 via the bypass pipe 60 and introduced into the gas treatment section 10.

[0034] The exhaust gas treatment device 1 includes a discharge valve 42. The discharge valve 42 is a valve that switches between an open and closed state of a flow path in the discharge pipe 40. When the discharge valve 42 is in an open state, the desorbed exhaust gas Gs is introduced into the by-product recovery section 50, and when the discharge valve 42 is in a closed state, the introduction of the desorbed exhaust gas Gs into the by-product recovery section 50 is stopped. The discharge valve 42 is provided in the flow path in the discharge pipe 40, and may be disposed between a connection point of the discharge pipe 40 with the bypass pipe 60 and the by-product recovery section 50.

[0035] The exhaust gas treatment device 1 includes a bypass valve 62. The bypass valve 62 is a valve that switches between an open and closed state of a flow path in a bypass pipe 60. When the bypass valve 62 is in an open state, the desorbed exhaust gas Gs is introduced from the middle of the exhaust pipe 40 through the bypass pipe 60 into the introduction pipe 12. When the bypass valve 62 is in a closed state, the desorbed exhaust gas Gs does not flow through the bypass pipe 60.

[0036] The bypass valve 62 may be disposed in a position of the bypass pipe 60 closer to the connection point between the discharge pipe 40 and the bypass pipe 60. In this case, the section 60a located upstream of the bypass valve 62 in the bypass pipe 60 is shorter than the section 60b located downstream of the bypass valve 62 in the bypass pipe 60. In other words, the pipe length of the section 60a may be shorter than the pipe length of the section 60b.

[0037] The preheating section 70 is a section that introduces gas for preheating the inside of the bypass piping 60 (hereinafter referred to as "preheating gas") so as to heat at least a part of the bypass piping 60. When the temperature of the desorbed exhaust gas Gs falls below the acid dew point, condensation of sulfuric acid occurs. Therefore, if there is a portion in the bypass piping 60 where the temperature is at room temperature, corrosion (acid dew point corrosion) may occur in the bypass piping 60 due to condensation of sulfuric acid when the by-product recovery section 50 abnormally stops and the desorbed exhaust gas Gs is introduced into the introduction piping 12 via the bypass piping 60. If acid dew point corrosion occurs in the bypass piping 60, a hole may occur in the piping.

[0038] The preheating gas introduced by the preheating section 70 has a temperature higher than room temperature and at a temperature at which condensation of the sulfuric acid does not occur when the desorbed exhaust gas Gs is introduced into the bypass piping 60. The temperature of the preheating gas is, for example, 250°C or more, 270°C or more, 290°C or more, or 300°C or more. The temperature of the preheating gas may be 550°C or less. The preheating gas is a gas generated in the exhaust gas treatment device 1, and may be a gas (a part of a gas) generated for use in the bypass piping 60 for a purpose other than preheating.

[0039] In one example, the preheating unit 70 introduces the heating gas Gh0 into the bypass piping 60 as a preheating gas, and introduces the heating gas Gh1 into the bypass piping 60 as a preheating gas. The preheating unit 70 includes, for example, an introduction piping 72 and an introduction piping 74. When the desorbed exhaust gas Gs is not returned to the introduction piping 12 by the bypass piping 60, the bypass valve 62 is maintained in a closed state. The preheating unit 70 may continue to introduce the preheating gas into the bypass piping 60 during the period in which the hot stove 32 is continuously operated.

[0040] The introduction pipe 72 is a pipe that introduces the heating gas Gh1 into the bypass pipe 60 as a preheating gas. One end of the introduction pipe 72 is connected to the middle of the recovery pipe 38, and the other end of the introduction pipe 72 is connected to the middle of the bypass pipe 60. The other end of the introduction pipe 72 may be connected to the section 60b of the bypass pipe 60. That is, the introduction pipe 72 may introduce the heating gas Gh1 into the section 60b located downstream, without introducing it into the section 60a located upstream. A part of the heating gas Gh1 discharged from the heating section 22 of the desorption section 20 that is not returned to the hot stove 32 may be introduced (extracted) into the introduction pipe 72 from the recovery pipe 38. Approximately 80% to 90% of the heating gas Gh1 discharged from the heating section 22 may be returned to the hot stove 32, and the remaining heating gas Gh1 may be introduced into the bypass pipe 60.

[0041] The introduction pipe 74 is a pipe that introduces the heating gas Gh0 into the bypass pipe 60 as a preheating gas. One end of the introduction pipe 74 is connected to the middle of the supply pipe 36, and the other end of the introduction pipe 74 is connected to the middle of the bypass pipe 60. The other end of the introduction pipe 74 may be connected to the section 60a of the bypass pipe 60. That is, the introduction pipe 74 may introduce the heating gas Gh0 into the section 60a located upstream, without introducing it into the section 60b located downstream. A part of the heating gas Gh0 generated in the hot stove 32 may be extracted before being introduced into the heating section 22, and introduced into the introduction pipe 74.

[0042] The control device 90 is a computer that controls at least the discharge valve 42 and the bypass valve 62. The control device 90 includes, for example, a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface. The control device 90 outputs an operation signal to the discharge valve 42, and switches the open / closed state of the discharge valve 42. The control device 90 outputs an operation signal to the bypass valve 62, and switches the open / closed state of the bypass valve 62.

[0043] The control device 90 may switch the open / closed states of the discharge valve 42 and the bypass valve 62 based on instructions from an operator. In a normal state in which there are no problems such as abnormalities and the by-product recovery section 50 is operating, the discharge valve 42 is maintained in an open state, and the bypass valve 62 is maintained in a closed state. In this normal state, the desorption flue gas Gs discharged from the desorption section 20 is introduced into the by-product recovery section 50, and is not introduced into the bypass piping 60. Note that, instead of using the control device 90, the open / closed states of the discharge valve 42 and the bypass valve 62 may be manually switched by an operator.

[0044] [Exhaust gas treatment method] Next, as an example of an exhaust gas treatment method, various processes executed in the exhaust gas treatment device 1 will be described. The exhaust gas treatment method includes a gas treatment process, an introduction process, a desorption process, a circulation process, a recovery process, and a preheating process. While the exhaust gas treatment device 1 continues to operate and the by-product recovery section 50 is in a normal state, the gas treatment process, the introduction process, the desorption process, the circulation process, the recovery process, and the preheating process are continued.

[0045] The gas treatment process is a process of performing gas treatment including at least desulfurization treatment on the exhaust gas G0, which is the exhaust gas to be treated, using activated carbon. In the gas treatment process, gas treatment including desulfurization treatment and denitrification treatment may be performed in the gas treatment unit 10. The introduction process is a process of introducing the exhaust gas G0 from the introduction pipe 72 into the region where the gas treatment is performed.

[0046] The desorption process is a process for heating and regenerating the activated carbon after it has been used in gas processing. The desorption process includes generating a heated gas Gh0 in the hot air stove 32, introducing the heated gas Gh0 into the heating section 22 of the desorption section 20, and recovering a heated gas Gh1 from the heating section 22. In the desorption process, the activated carbon is heated by heat exchange between the heated gas Gh0 introduced into the heating section 22 and the activated carbon in a non-contact state. The desorption process includes introducing a desorbed exhaust gas Gs generated by heating the activated carbon into the by-product recovery section 50.

[0047] The circulation step is a step of circulating the activated carbon between the gas treatment section 10 and the desorption section 20. The circulation step includes transporting the activated carbon after use in gas treatment to the desorption section 20 via the transport line 16. The circulation step includes transporting the activated carbon after regeneration in the desorption section 20 to the gas treatment section 10 via the transport line 18.

[0048] The recovery process is a process of removing at least a part of the SOx components from the desorbed exhaust gas Gs introduced into the by-product recovery section 50. The recovery process includes, for example, converting the SOx components in the desorbed exhaust gas Gs into sulfuric acid (H2SO4) and / or gypsum (CaSO4H2O) and solidifying them.

[0049] The preheating step is a step of introducing a preheating gas into the bypass piping 60 so as to heat at least a part of the bypass piping 60 capable of supplying the desorbed exhaust gas Gs generated by heating the activated carbon in the desorption step to the introduction piping 72. In the preheating step, a preheating gas may be introduced into each of a section 60a located upstream of a bypass valve 62 provided in the bypass piping 60 and a section 60b located downstream of the bypass valve 62.

[0050] In the preheating step, the heated gas Gh0 generated in the hot stove 32 and the heated gas Gh1, which is the heated gas (heated exhaust gas) after heat exchange with activated carbon in the heating section 22, may each be introduced into the bypass piping 60. In one example, the heated gas Gh1 is introduced into the section 60b by the introduction piping 72, and the heated gas Gh0 is introduced into the section 60a by the introduction piping 74. The preheating step may be continued while the operation of the hot stove 32 is continued.

[0051] When some abnormality occurs in the by-product recovery section 50, the exhaust gas treatment device 1 switches from normal mode operation to abnormal mode operation. For example, the control device 90 switches the discharge valve 42 from an open state to a closed state and switches the bypass valve 62 from a closed state to an open state based on an instruction from an operator, thereby switching to the abnormal mode operation. Alternatively, the open / close states of the discharge valve 42 and the bypass valve 62 are manually switched. In the abnormal mode operation, a gas circulation process is performed in which the desorbed exhaust gas Gs generated in the heating section 22 is returned to the introduction pipe 12 via the bypass pipe 60.

[0052] The desorbed exhaust gas Gs returned to the introduction pipe 12 via the bypass pipe 60 is introduced into the gas treatment unit 10 together with the exhaust gas G0, and is subjected to the above-mentioned gas treatment. A member for preventing the desorbed exhaust gas Gs from being introduced into the preheating unit 70 from the bypass pipe 60 while the gas circulation step is being performed may be provided in the preheating unit 70. When the abnormality in the by-product recovery unit 50 is resolved, the exhaust gas treatment device 1 switches from operation in the abnormal mode to operation in the normal mode.

[0053] [Variations] The exhaust gas treatment device 1 and the exhaust gas treatment method described above are merely examples and may be modified as appropriate. The introduction pipe 72 may introduce the heating gas Gh1 to the section 60a instead of the section 60b. The introduction pipe 74 may introduce the heating gas Gh0 to the section 60b instead of the section 60a.

[0054] As shown in FIG. 2(a), the exhaust gas treatment device 1 may include a preheating section 70A instead of the preheating section 70. The preheating section 70A differs from the preheating section 70 in that the preheating section 70A has an inlet pipe 72A instead of the inlet pipes 72 and 74. The inlet pipe 72A is a pipe that introduces the heating gas Gh1 to each of the sections 60a and 60b. One end of the inlet pipe 72A is connected to the middle of the recovery pipe 38, and the inlet pipe 72A branches from the one end and is connected to each of the sections 60a and 60b. As described above, the inlet pipe 72A (preheating section 70A) introduces the heating gas Gh1 into the inside of the bypass pipe 60 without introducing the heating gas Gh0.

[0055] As shown in FIG. 2(b), the exhaust gas treatment device 1 may include a preheating section 70B instead of the preheating section 70. The preheating section 70B differs from the preheating section 70 in that the preheating section 70B has an inlet pipe 74B instead of the inlet pipe 72 and the inlet pipe 74. The inlet pipe 74B is a pipe that introduces the heating gas Gh0 to each of the sections 60a and 60b. One end of the inlet pipe 74B is connected to the middle of the supply pipe 36, and the inlet pipe 74B branches from the one end and is connected to each of the sections 60a and 60b. As described above, the inlet pipe 74B (preheating section 70B) introduces the heating gas Gh0 into the inside of the bypass pipe 60 without introducing the heating gas Gh1.

[0056] The preheating units 70, 70A, and 70B may introduce a preheating gas (for example, either the heating gas Gh0 or the heating gas Gh1) into either the section 60a or the section 60b, instead of into both the section 60a and the section 60b. For example, when the piping length of the section 60a is sufficiently short, heat is transferred from the bypass piping 60 to the section 60a, so that the preheating gas is not introduced into the section 60a, but is introduced into the section 60b. Alternatively, when the section 60b is maintained at a high temperature by some means, the preheating gas is not introduced into the section 60b, but is introduced into the section 60a. In one example of the various examples described above, at least a part of the matters described in the other examples may be combined.

[0057] [Summary of this disclosure] The exhaust gas treatment device 1 described above comprises a gas treatment unit 10 that performs desulfurization treatment on the exhaust gas G0 using activated carbon, an inlet pipe 12 that introduces the exhaust gas G0 into the gas treatment unit 10, a desorption unit 20 that heats and regenerates the activated carbon after use in the gas treatment, a bypass pipe 60 that is generated by heating the activated carbon in the desorption unit 20 and is capable of supplying the desorbed exhaust gas Gs containing sulfur oxides (SOx) to the inlet pipe 12, and preheating units 70, 70A, 70B that introduce a preheating gas into the inside of the bypass pipe 60 so as to heat at least a portion of the bypass pipe 60.

[0058] The SOx contained in the desorbed exhaust gas Gs generated in the desorption section 20 is recovered by a recovery device (by-product recovery section 50), and the gas after SOx is removed from the desorbed exhaust gas Gs is released to the atmosphere. In addition, a bypass pipe 60 is provided in preparation for an abnormality occurring in the recovery device. If the bypass pipe 60 is at room temperature, when an abnormality occurs in the recovery device and the desorbed exhaust gas Gs is circulated through the bypass pipe 60, the temperature of the desorbed exhaust gas Gs drops to or below the acid dew point, and corrosion (acid dew point corrosion) may occur in the bypass pipe 60 due to condensation of sulfuric acid. In contrast, in the exhaust gas treatment device 1, since a preheating gas is introduced into the bypass pipe 60, when an abnormality occurs in the recovery device and the desorbed exhaust gas Gs is circulated through the bypass pipe 60, the acid dew point corrosion is unlikely to occur. Therefore, the exhaust gas treatment device 1 can achieve stable operation of the device. In addition, since the preheating gas is introduced into the inside of the bypass pipe 60 for preheating, it is possible to achieve both simplification of the device and stable operation.

[0059] The exhaust gas treatment device 1 described above may further include a bypass valve 62 that opens and closes the flow path in the bypass piping 60. The preheating units 70, 70A, and 70B may introduce preheating gas into each of the section 60a located upstream of the bypass valve 62 in the bypass piping 60 and the section 60b located downstream of the bypass valve 62 in the bypass piping 60. In this case, the bypass piping 60 is preheated in both the sections upstream and downstream of the bypass valve 62, making it more difficult for the acid dew-point corrosion to occur. Therefore, it is possible to further stabilize the operation of the device.

[0060] The exhaust gas treatment device 1 described above may further include a bypass valve 62 that opens and closes the flow path in the bypass piping 60. The preheating units 70, 70A, and 70B may introduce preheating gas into either the section 60a located upstream of the bypass valve 62 in the bypass piping 60 or the section 60b located downstream of the bypass valve 62 in the bypass piping 60. Depending on the configuration of the exhaust gas treatment device 1, acid dew-point corrosion may occur in either the section 60a or the section 60b. In the above configuration, since the preheating gas is introduced into one of the sections, it is possible to simplify the device configuration of the preheating unit.

[0061] The exhaust gas treatment device 1 described above may further include a hot air furnace 32 that generates a heating gas for heating the activated carbon in the desorption section 20. The preheating sections 70, 70B may introduce the heating gas (heating gas Gh0) before it is used for heating in the desorption section 20 into the bypass piping 60 as a preheating gas. The heating gas before it is used for heating in the desorption section 20 has a high temperature, and the bypass piping 60 can be preheated by introducing a small amount of gas into the bypass piping 60. This makes it possible to achieve both stable operation of the device and a simplified device configuration of the preheating section.

[0062] The exhaust gas treatment device 1 described above may further include a hot air furnace 32 that generates a heating gas for heating the activated carbon in the desorption section 20. The preheating sections 70, 70A may introduce the heating gas after being used for heating in the desorption section 20 into the bypass piping 60 as a preheating gas. Even when the heated exhaust gas, which is the heating gas after being used for heating in the desorption section 20, is used in a circulated manner, a part of it needs to be discharged outside the system. Therefore, in the above configuration, the bypass piping 60 is preheated by using a part of the heated exhaust gas discharged outside the system, so that it is possible to achieve both stable operation of the device and reduction in energy usage.

[0063] In the exhaust gas treatment device 1 described above, the preheating units 70, 70A, 70B may continue to introduce the preheating gas into the bypass piping 60 while the hot stove 32 is in operation. In this case, the possibility that the temperature of the bypass piping 60 will drop during a certain period of time is reduced, making the acid dew-point corrosion less likely to occur. This makes it possible to further stabilize the operation of the device.

[0064] The above-described exhaust gas treatment method includes a gas treatment step of subjecting the exhaust gas G0 to a desulfurization treatment using activated carbon, an introduction step of introducing the exhaust gas G0 from the introduction pipe 12 into an area where the desulfurization treatment is performed, a desorption step of heating and regenerating the activated carbon after use in the gas treatment, and a preheating step of introducing a preheating gas into the bypass pipe 60 so as to heat at least a part of the bypass pipe 60 that can supply the desorbed exhaust gas Gs containing sulfur oxides, which is generated by heating the activated carbon in the desorption step, to the introduction pipe 12. This exhaust gas treatment method is capable of ensuring stable operation of the device, similar to the above-described exhaust gas treatment device 1. [Explanation of symbols]

[0065] 1...exhaust gas treatment device, 10...gas treatment device, 12...introduction piping, G0, G1...exhaust gas, 20...desorption section, 32...hot air furnace, Gh0, Gh1...heating gas, Gs...desorbed exhaust gas, 60...bypass piping, 60a, 60b...compartment, 62...bypass valve, 70, 70A, 70B...preheating section.

Claims

1. a gas treatment unit that performs desulfurization treatment on the exhaust gas to be treated using activated carbon; an introduction pipe for introducing the exhaust gas to be treated into the gas treatment unit; a desorption section for heating and regenerating the activated carbon after the gas treatment; a bypass pipe capable of supplying a desorbed exhaust gas containing sulfur oxides, which is generated by heating the activated carbon in the desorbing section, to the introduction pipe; a preheating unit that introduces a preheating gas into the inside of the bypass piping so as to heat at least a portion of the bypass piping.

2. Further comprising a bypass valve for opening and closing a flow path in the bypass pipe, 2. The exhaust gas treatment device according to claim 1, wherein the preheating unit introduces the preheating gas into each of a section of the bypass piping that is located upstream of the bypass valve and a section of the bypass piping that is located downstream of the bypass valve.

3. Further comprising a bypass valve for opening and closing a flow path in the bypass pipe, 2. The exhaust gas treatment device according to claim 1, wherein the preheating unit introduces the preheating gas into either a section of the bypass piping that is located upstream of the bypass valve or a section of the bypass piping that is located downstream of the bypass valve.

4. A hot air furnace is further provided for generating a heating gas for heating the activated carbon in the desorption section. The exhaust gas treatment device according to claim 1 , wherein the preheating section introduces the heating gas, which has not yet been used for heating in the desorption section, into the bypass piping as the preheating gas.

5. A hot air furnace is further provided for generating a heating gas for heating the activated carbon in the desorption section. The exhaust gas treatment device according to claim 1 , wherein the preheating section introduces the heating gas after being used for heating in the desorption section into the bypass piping as the preheating gas.

6. The exhaust gas treatment device according to claim 4 or 5, wherein the preheating unit continues to introduce the preheating gas into the bypass piping during a period in which the hot stove is continuously operated.

7. a gas treatment process in which the exhaust gas to be treated is subjected to desulfurization treatment using activated carbon; an introduction step of introducing the exhaust gas to be treated from an introduction pipe into a region where the desulfurization treatment is performed; a desorption step of heating the activated carbon after use in the gas treatment to regenerate it; a preheating step of introducing a preheating gas into the bypass piping so as to heat at least a part of the bypass piping capable of supplying the desorbed exhaust gas containing sulfur oxides, the desorption being generated by heating the activated carbon in the desorption step, to the inlet piping.

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