Ship dual-fuel engine flue gas oxidation demethanization system and method

Abstract

The invention discloses a ship dual-fuel engine flue gas oxidation demethanization system and method. The system comprises an oxidation tower, an oxidizing solution recovery device and a liquid supplementing device. The oxidation tower comprises a tower body; the first reactor is arranged in the tower body and is communicated with the flue gas input pipe; the second reactor is arranged in the tower body and arranged on the periphery of the first reactor in a sleeving manner, the top of the second reactor is communicated with the flue gas output pipe, and a flue gas inlet pipe is further arranged on the side wall of the second reactor; the first spraying assembly is used for conveying an oxidizing solution into the first reactor; the second spraying assembly is used for conveying an oxidizing solution to the outside of the second reactor; the oxidizing solution recovery device comprises a liquid inlet end and a liquid outlet end, the liquid inlet end is communicated with an outlet in the bottom of the tower body, and the liquid outlet end is communicated with the first spraying assembly and the second spraying assembly; and the liquid supplementing device is used for supplementing the oxidizing solution. According to the ship dual-fuel engine flue gas oxidation demethanization system and method, escape methane in flue gas can be efficiently decomposed.

Description

Technical Field

[0001] The present application relates to the technical field of flue gas treatment, and in particular to a system and method for oxidative demethanization of flue gas from a ship dual-fuel engine. Background Art

[0002] With increasingly stringent environmental protection requirements and adjustments to the energy structure, the shipping industry has gradually adopted dual-fuel engines, such as the mixed use of liquefied natural gas (LNG) and traditional fuels, to reduce greenhouse gas emissions. Although dual-fuel engines can significantly reduce carbon dioxide and nitrogen oxide emissions during operation, there is still a certain amount of escaped methane (CH 4 ), which is a potent greenhouse gas with a global warming potential (GWP) much higher than that of carbon dioxide.

[0003] Therefore, how to efficiently decompose the escaped methane in the flue gas has become a technical problem that needs to be solved urgently in the shipping industry. Summary of the invention

[0004] The technical problem actually solved by the technical solution of this application is how to efficiently decompose the escaped methane in the flue gas.

[0005] In order to solve the above technical problems, the technical solution of the present application provides a ship dual-fuel engine flue gas oxidation demethanization system, including: an oxidation tower, an oxidizing solution recovery device and a liquid replenishing device; wherein: the oxidation tower is used to input flue gas and oxidizing solution, and output treated flue gas and unreacted oxidizing solution, and the oxidation tower includes: a tower body with an outlet at the bottom, a flue gas input pipe, and a flue gas output pipe; a first reactor is arranged in the tower body and is connected to the flue gas input pipe, and has a first output end at the bottom; a second reactor is arranged in the tower body and is sleeved on the outer periphery of the first reactor, and has a second output end at the bottom , wherein the first output end extends out of the second output end, the top of the second reactor is connected to the smoke output pipe, and the side wall of the second reactor is also provided with a smoke inlet pipe; a first spray assembly is used to transport an oxidizing solution to the inside of the first reactor; a second spray assembly is used to transport an oxidizing solution to the outside of the second reactor; the oxidizing solution recovery device includes a liquid inlet end and a liquid outlet end, and the liquid inlet end is connected to the outlet at the bottom of the tower body, and the liquid outlet end is connected to the first spray assembly and the second spray assembly; the liquid replenishing device is connected to the tower body, and is used to replenish the oxidizing solution.

[0006] In some embodiments, the first output end includes at least two air ducts, and the air outlets at the ends of each of the air ducts are bent in a clockwise or counterclockwise direction.

[0007] In some embodiments, the number of the flue gas input pipe and the number of the flue gas inlet pipe are both two, wherein the two flue gas input pipes are symmetrically arranged relative to the axis center of the first reactor, and the two flue gas inlet pipes are symmetrically arranged relative to the axis center of the second reactor.

[0008] In some embodiments, the oxidation tower further includes: a heat exchange coil, which is disposed in the tower body, sleeved on the outer periphery of the second reactor, and located below the flue gas inlet pipe.

[0009] In some embodiments, the oxidation tower further includes: a first catalyst packing layer, which is disposed in the tower body, located at the outer periphery of the second reactor, and located below the flue gas inlet pipe.

[0010] In some embodiments, the ship dual-fuel engine flue gas oxidation demethanization system also includes an oxidation dehydration device, and the oxidation dehydration device includes: an oxidation dehydration chamber, whose side wall is provided with a smoke inlet, the top is provided with a smoke outlet, and the bottom is provided with a liquid outlet, wherein the smoke inlet is connected to the smoke output pipe, the smoke outlet is used to output clean flue gas, and the liquid outlet is connected to the liquid outlet end of the oxidizing solution recovery device; a second catalyst packing layer is arranged inside the oxidation dehydration chamber and is located above the smoke inlet; a fourth spray assembly is used to spray the oxidizing solution above the second catalyst packing layer; a defog assembly is arranged inside the oxidation dehydration chamber and is close to the smoke outlet.

[0011] In some embodiments, the ship dual-fuel engine flue gas oxidation demethanization system also includes: a first heat exchange device, one end of which is connected to the flue gas output pipe and the other end is connected to the smoke inlet, and is used to cool the flue gas supplied to the interior of the oxidation dehydration chamber to a first target temperature; a second heat exchange device, one end of which is connected to the liquid outlet of the oxidizing solution recovery device and the other end is connected to the fourth spray assembly, and is used to cool the oxidizing solution supplied to the fourth spray assembly to a second target temperature.

[0012] In some embodiments, the oxidizing solution is acidic hydrogen peroxide, and the mass concentration of the acidic hydrogen peroxide is 20% to 30%, and the pH is 5 to 6; The first catalyst packing layer and / or the second catalyst packing layer include a graphene composite material, and the graphene composite material includes: a graphene matrix and a rare earth oxide attached to the graphene matrix, wherein the mass of the rare earth oxide accounts for 50% to 70% of the total mass of the graphene composite material, and the rare earth oxide includes rhenium oxide, neodymium oxide and cerium dioxide in a mass ratio of 1:1:1.

[0013] In some embodiments, the ship dual-fuel engine flue gas oxidation demethanization system further includes a pH detection device for monitoring the pH value of the oxidizing solution at the liquid outlet of the oxidizing solution recovery device.

[0014] The present application also provides a method for oxidative demethanization of flue gas from a ship dual-fuel engine, which adopts the ship dual-fuel engine flue gas oxidative demethanization system described in any of the above items, and the method includes: inputting flue gas and an oxidizing solution into an oxidation tower, and the oxidation tower outputs treated flue gas and unreacted oxidizing solution, wherein the heat of the flue gas vaporizes the oxidizing solution into oxidizing steam, and the flue gas and the oxidizing steam undergo an oxidation reaction; recovering the unreacted oxidizing solution through an oxidizing solution recovery device and conveying it to the oxidation tower; when it is detected that the pH value of the oxidizing solution at the liquid outlet of the oxidizing solution recovery device increases, discharging the oxidizing solution in the oxidation tower and the oxidizing solution recovery device, and replenishing the oxidizing solution to the oxidation tower through a liquid replenishing device.

[0015] Compared with the prior art, the ship dual-fuel engine flue gas oxidation demethanization system and method of the technical solution of the present application has the following beneficial effects: The ship dual-fuel engine flue gas oxidation demethanization system and method of the present application can achieve gas-vapor contact between flue gas and oxides. Compared with the gas-liquid contact method of the traditional scrubber, it can greatly increase the contact probability between flue gas and oxides, thereby significantly improving the oxidation decomposition efficiency of flue gas, and can also reduce the amount of oxidizing solution, thereby achieving efficient decomposition of escaped methane in flue gas. At the same time, the waste heat of flue gas can directly vaporize the oxidizing solution without the need for an external heat source, which can not only avoid the energy consumption of external heating, but also reduce the manufacturing cost and maintenance difficulty of the equipment.

[0016] Furthermore, the first output end of the first reactor includes at least two air ducts, and the air outlets at the end of each air duct are bent together in a clockwise or counterclockwise direction, so that a vortex wind field can be formed at the bottom of the tower body. This can not only increase the mixing and contact probability of the flue gas and the oxidizing solution, but also increase the residence time of the flue gas in the tower body, thereby further improving the oxidation efficiency.

[0017] Furthermore, the flue gas input pipe is arranged symmetrically with respect to the axis center of the first reactor, so that the input flue gas can form a cyclonic wind field in the first reactor, which is conducive to the flue gas and oxidizing steam swirl downward in the first reactor. The flue gas inlet pipe is arranged symmetrically with respect to the axis center of the second reactor, so that the flue gas entering the second reactor forms a cyclonic wind field, which improves the gas-liquid separation effect.

[0018] Furthermore, the first catalyst packing layer and / or the second catalyst packing layer includes a specific graphene composite material, which can significantly improve the methane removal rate. When the flue gas temperature is above 245°C, the methane removal rate can reach more than 92.1%. In particular, when the flue gas temperature is 411°C, the methane removal rate reaches 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following drawings describe in detail the exemplary embodiments disclosed in this application. The same reference numerals represent similar structures in several views of the drawings. Those skilled in the art will understand that these embodiments are non-limiting, exemplary embodiments, and the drawings are only used for the purpose of illustration and description, and are not intended to limit the scope of this application. Other embodiments may also accomplish the inventive intent in this application. It should be understood that the drawings are not drawn to scale. Among them: Figure 1 This is a schematic structural diagram of a flue gas oxidation demethanization system for a ship dual-fuel engine according to an embodiment of the present application; Figure 2 This is a schematic diagram of the structure of an oxidation tower according to an embodiment of the present application; Figure 3 This is a schematic diagram of the structure of the first reactor and the second reactor of the oxidation tower of the embodiment of the present application; Figure 4 This is a schematic diagram of the top view of the oxidation tower of an embodiment of the present application; Figure 5 This is a schematic diagram of the structure of the air guide duct according to an embodiment of the present application; Figure 6 This is a cross-sectional schematic diagram of the first catalyst packing layer of an embodiment of the present application; Figure 7 This is a schematic structural diagram of another ship dual-fuel engine flue gas oxidation demethanization system according to an embodiment of the present application; The meanings of the reference numerals are as follows: 1- oxidation tower; 2- oxidizing solution recovery device; 3- liquid replenishment device; 4- oxidation dehydration device; 5- first heat exchange device; 6- second heat exchange device; 7- pH detection device; 8- circulation pump; 9- supplementary pump; 10- tower body; 11- smoke inlet pipe; 12- smoke outlet pipe; 13- smoke inlet pipe; 41-oxidation and dehydration chamber; 42-second catalyst packing layer; 43-fourth spray assembly; 44-demist assembly; 100-first reactor; 101-first cylindrical section; 102-first conical section; 103-second cylindrical section; 104-air duct; 200 - second reactor; 201 - third cylindrical section, 202 - second conical section; 203 - fourth cylindrical section; 300-first spray assembly; 301-first spray head; 302-first spray head pipeline; 400-second spray assembly; 401-second spray head pipeline; 402-second spray head; 500-first catalyst packing layer; 600-heat exchange coil; 700 - the third spray assembly; 701 - the third spray head; 702 - the third spray head pipeline. DETAILED DESCRIPTION

[0020] The following description provides specific application scenarios and requirements of the present application, with the purpose of enabling those skilled in the art to make and use the contents of the present application. Various local modifications to the disclosed embodiments are apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the embodiments shown, but to the widest scope consistent with the claims. The oxidation tower of the present application embodiment is described in detail below in conjunction with the accompanying drawings.

[0021] The embodiment of the present application provides a ship dual-fuel engine flue gas oxidation demethanization system, which can oxidize the input gas and can be applied to the demethanization treatment of the flue gas of the ship LNG dual-fuel engine.

[0022] refer to Figure 1 The flue gas oxidation demethanization system of the dual-fuel engine of the present application embodiment comprises: an oxidation tower 1, an oxidizing solution recovery device 2 and a liquid replenishing device 3. The oxidation tower 1 is used to input flue gas and oxidizing solution, and output treated flue gas and unreacted oxidizing solution. The oxidizing solution recovery device 2 is used to recover unreacted oxidizing solution and transport the unreacted oxidizing solution to the oxidation tower 1 to complete the recovery and reuse of the oxidizing solution. The liquid replenishing device 3 is used to replenish the oxidizing solution to the oxidation tower 1.

[0023] Combination Figure 2 and Figure 3 The oxidation tower includes a tower body 10 with an outlet at the bottom, a flue gas input pipe 11, a flue gas output pipe 12, a first reactor 100, a second reactor 200, a first spray assembly 300 and a second spray assembly 400.

[0024] The first reactor 100 is disposed in the tower body 10 and is connected to the smoke inlet pipe 11, and has a first output end at the bottom. The smoke inlet pipe 11 is used to transport smoke into the first reactor 100. In some embodiments, the smoke inlet pipe 11 can be disposed on the side wall of the first reactor 100, and the first end of the smoke inlet pipe 11 is connected to the first reactor 100, and the second end of the smoke inlet pipe 11 extends out of the tower body 10.

[0025] The number of the flue gas input pipe 11 is at least one. In some preferred embodiments, the number of the flue gas input pipe 11 is at least two, and the two flue gas input pipes 11 are configured so that the input flue gas can form a cyclonic wind field in the first reactor 100, and the cyclonic wind field can make the flue gas, oxidizing steam and unvaporized oxidizing solution continuously swirl toward the bottom of the first reactor 100 and flow out from the first output end. In some specific embodiments, such as Figure 4 As shown, the number of the flue gas input pipes 11 is two, and the two flue gas input pipes 11 are symmetrically arranged relative to the axis center of the first reactor 100 .

[0026] The first spray assembly 300 is used to transport the oxidizing solution into the first reactor 100. Since the temperature of the flue gas is usually high and higher than the vaporization temperature of the oxidizing solution, the oxidizing solution is vaporized into oxidizing steam, thereby realizing the gas-steam contact oxidation method. Compared with the traditional gas-liquid contact oxidation method, the contact probability between the flue gas and the oxidizing steam is greatly improved, thereby significantly improving the oxidation decomposition efficiency of methane.

[0027] In some specific embodiments, the first spray assembly 300 includes: a first spray head 301 and a first spray head pipe 302, wherein the first spray head 301 is disposed at the top of the first reactor 100, a first end of the first spray head pipe 302 is connected to the first spray head 301, and a second end of the first spray head pipe 302 extends out of the tower body 10. The flue gas input pipe 11 is disposed close to the first spray head 301 to increase the contact probability between the flue gas and the oxidizing solution, thereby improving the vaporization efficiency of the oxidizing solution and the oxidative decomposition efficiency of the flue gas.

[0028] In some embodiments, the first output end of the first reactor 100 includes at least two air ducts 104, and is configured to form a cyclone wind field at the bottom of the tower body 10 for the output flue gas and oxidizing steam. On the one hand, the cyclone wind field can increase the probability of mixing and contacting the flue gas with the oxidizing solution, thereby improving the oxidation decomposition efficiency; on the other hand, the cyclone wind field can increase the flow of the flue gas in the horizontal direction, thereby increasing the residence time of the flue gas in the tower body 10, thereby improving the oxidation decomposition efficiency.

[0029] In some embodiments, the air outlets at the ends of each of the air guide pipes 104 are bent together in a clockwise or counterclockwise direction to form a swirl wind field. Figure 5 As shown, there are four air ducts 104, and the air outlets at the ends of each air duct 104 are bent clockwise or counterclockwise. More specifically, two adjacent air ducts 104 are perpendicular to each other, and the air outlets at the ends of each air duct 104 are bent 90 degrees counterclockwise.

[0030] In some specific embodiments, the first reactor 100 includes a first cylindrical section 101, a first conical section 102, and a second cylindrical section 103, which are smoothly connected in sequence from the top to the bottom of the first reactor 100, wherein the inner diameter of the first cylindrical section 101 is greater than the inner diameter of the second cylindrical section 103.

[0031] The second reactor 200 is arranged in the tower body 10 and is sleeved on the outer periphery of the first reactor 100, and has a second output end at the bottom, wherein the first output end at the bottom of the first reactor 100 extends out of the second output end at the bottom of the second reactor 200 to prevent the flue gas and oxidizing steam outputted from the first reactor 100 from rising and entering the second reactor 200. The top of the second reactor 200 is connected to the flue gas output pipe 12, and the side wall of the second reactor 200 is also provided with a flue gas inlet pipe 13.

[0032] In some specific embodiments, the first end of the flue gas output pipe 12 is in communication with the top of the second reactor 200, and the second end of the flue gas output pipe 12 extends out of the tower body 10, and is used to output the flue gas to the outside of the tower body 10. The first end of the flue gas inlet pipe 13 is in communication with the side wall of the second reactor 200, and the second end of the flue gas inlet pipe 13 is in communication with the interior of the tower body 10, and is used to transport the flue gas after oxidation decomposition in the tower body 10 to the second reactor 200. Since the oxidation decomposition products of methane in the flue gas are carbon dioxide and water, the flue gas after oxidation decomposition is a gas-liquid mixture, which enters the second reactor 200 through the flue gas inlet pipe 13 for gas-liquid separation, and the separated gas phase will be output from the tower body 10 through the flue gas output pipe 12, and the separated liquid phase will flow out from the second output end at the bottom of the second reactor 200.

[0033] The number of the flue gas inlet pipe 13 is at least one. In some preferred embodiments, the number of the flue gas inlet pipe 13 is at least two, and is configured so that the input flue gas after oxidation and decomposition forms a cyclonic wind field in the second reactor 200 to improve the gas-liquid separation effect. Figure 4 As shown, the number of the flue gas inlet pipes 13 is two, and they are symmetrically arranged relative to the axis center of the second reactor 200.

[0034] In some specific embodiments, the second reactor 200 includes a third cylindrical section 201, a second conical section 202 and a fourth cylindrical section 203, which are smoothly connected in sequence from the top to the bottom of the second reactor 200, wherein the inner diameter of the third cylindrical section 201 is greater than the inner diameter of the fourth cylindrical section 203.

[0035] The second spray assembly 400 is used to transport the oxidizing solution to the outside of the second reactor 200. The waste heat of the flue gas output from the first output end of the first reactor 100 can vaporize the oxidizing solution, thereby increasing the concentration of the oxidizing steam and further improving the oxidative decomposition efficiency of methane.

[0036] In some specific embodiments, the second spray assembly 400 includes: at least one second nozzle pipe 401, and the second nozzle pipe 401 includes: an annular pipe section surrounding the outer circumference of the second reactor 200, and the annular pipe section is evenly provided with a plurality of second nozzles 402, wherein the input end of the second nozzle pipe 401 extends out of the tower body 10.

[0037] In order to accelerate the oxidative decomposition process of the flue gas and make the escaped methane decompose more thoroughly, a first catalyst packing layer 500 can be provided inside the tower body 10, and the first catalyst packing layer 500 is located at the periphery of the second reactor 200 and below the flue gas inlet pipe 13. In some embodiments, the first catalyst packing layer 500 is located between the flue gas inlet pipe 13 and the second spray assembly 400. Figure 6 The cross-sectional view of a first catalyst filler layer 500 is shown. The first catalyst filler layer 500 may include conventional catalyst fillers as long as they can play a catalytic role. As an example, the catalyst filler is an oxide filler of metals such as manganese, copper, and titanium.

[0038] In some embodiments, reference Figure 2 The oxidation tower further includes a heat exchange coil 600, which is disposed in the tower body 10, and is sleeved on the outer periphery of the second reactor 200, and is located below the flue gas inlet pipe 13. In some embodiments, the heat exchange coil 600 is also located below the first catalyst packing layer 500. The heat exchange coil 600 is used to absorb the waste heat of the flue gas and the oxidizing steam, wherein the oxidizing steam will produce a temperature drop after absorbing heat, and then precipitate small droplets, which will fall to the bottom of the tower body 10. When the heat exchange coil 600 is working, a waste heat recovery medium such as cold water is input at the input end of the heat exchange coil 600, and the waste heat recovery medium flows in the heat exchange coil 600, absorbs the waste heat to form hot water or steam, and is discharged from the tower body 10 at the output end of the heat exchange coil 600.

[0039] In some embodiments, reference Figure 2 and Figure 3 The oxidation tower also includes: a third spray assembly 700, which is used to transport an oxidizing solution into the second reactor 200, and can oxidize the flue gas input into the second reactor 200, thereby improving the oxidation treatment effect of the oxidation tower.

[0040] In some specific embodiments, the third spray assembly 700 includes: a third spray head 701 and a third spray head pipe 702, wherein the third spray head 701 is disposed on the inner side wall of the second reactor 200 and is located above the flue gas inlet pipe 13. A first end of the third spray head pipe 702 is connected to the third spray head 701, and a second end of the third spray head pipe 702 extends out of the tower body 10.

[0041] In some specific embodiments, the input ends of the first nozzle pipe 302 of the first spray assembly 300 , the second nozzle pipe 401 of the second spray assembly 400 , and the third nozzle pipe 702 of the third spray assembly 700 are connected to a delivery pipe for the oxidizing liquid outside the tower body 10 .

[0042] Combination Figure 1 , Figure 2 and Figure 7 The oxidizing solution recovery device 2 includes a liquid inlet and a liquid outlet, and the liquid inlet is connected to the outlet at the bottom of the tower body 10, and the liquid outlet is connected to the first spray assembly 300 and the second spray assembly 400. Specifically, the liquid outlet is connected to the first spray head pipeline 302 of the first spray assembly 300 and the second spray head pipeline 401 of the second spray assembly 400.

[0043] In some embodiments, the ship dual-fuel engine flue gas oxidation demethanization system further includes an oxidation dehydration device 4 for oxidizing and dehydrating the treated flue gas output from the oxidation tower 1. The oxidation dehydration device 4 may include: an oxidation dehydration chamber 41, a second catalyst packing layer 42, a fourth spray assembly 43, and a demisting assembly 44.

[0044] The side wall of the oxidation dehydration chamber 41 is provided with a smoke inlet, the top is provided with a smoke outlet, and the bottom is provided with a liquid outlet, wherein the smoke inlet is connected to the smoke output pipe 12, and is used to input treated smoke into the interior of the oxidation dehydration chamber 41, and the smoke outlet is used to output clean smoke, that is, demethanized smoke, and the liquid outlet is connected to the liquid outlet end of the oxidizing solution recovery device 2, and is used to output the liquid output by the oxidation dehydration device 4 to the liquid outlet end of the oxidizing solution recovery device 2.

[0045] The second catalyst packing layer 42 is arranged inside the oxidation dehydration cavity 41 and above the smoke inlet. The second catalyst packing layer 42 may include a conventional catalyst packing, which may be the same or different from the material of the first catalyst packing layer 500 as long as it can play a catalytic role. As an example, the catalyst packing is an oxide packing of metals such as manganese, copper, and titanium. The structure of the second catalyst packing layer 42 may refer to the first catalyst packing layer 500.

[0046] The fourth spray assembly 43 is used to spray the oxidizing solution above the second catalyst packing layer 42. The fourth spray assembly 43 may include a fourth nozzle pipeline and a fourth nozzle, wherein the first end of the fourth nozzle pipeline is connected to the liquid outlet of the oxidizing solution recovery device 2, and the second end of the fourth nozzle pipeline is connected to the fourth nozzle.

[0047] The demisting assembly 44 is arranged inside the oxidation dehydration chamber 41 and close to the smoke outlet for dehydrating the smoke. The specific structure of the demisting assembly 44 is not required, as long as it can play a dehydrating role.

[0048] After the treated flue gas is transported to the interior of the oxidative dehydration chamber 41, it enters the second catalyst packing layer 42. At the same time, the oxidizing solution is sprayed into the second catalyst packing layer 42 through the fourth spray assembly 43. The flue gas and the oxidizing solution are in countercurrent contact in the second catalyst packing layer 42. The oxidizing solution can catalytically oxidize the remaining methane, thereby improving the methane removal rate of the flue gas.

[0049] The unreacted oxidizing solution in the oxidation and dehydration chamber 41 will be output to the liquid outlet of the oxidizing solution recovery device 2 through the liquid outlet of the oxidation and dehydration chamber 41, and after merging with the unreacted oxidizing solution output from the liquid outlet of the oxidizing solution recovery device 2, it will be output to the first spray component 300, the second spray component 400, the third spray component 700 and the fourth spray component 43 to achieve the recovery and reuse of the oxidizing solution.

[0050] In some embodiments, the ship dual-fuel engine flue gas oxidation demethanization system also includes a first heat exchange device 5 and a second heat exchange device 6. The first end of the first heat exchange device 5 is connected to the flue gas output pipe 12, and the second end is connected to the smoke inlet of the oxidation dehydration chamber 41, and is used to cool the flue gas supplied to the inside of the oxidation dehydration chamber 41 to a first target temperature. The first end of the second heat exchange device 6 is connected to the liquid outlet of the oxidizing solution recovery device 2, and the second end is connected to the fourth spray assembly 43, and is used to cool the oxidizing solution supplied to the fourth spray assembly 43 to a second target temperature. As an example, the first target temperature and the second target temperature are 25~35°C.

[0051] In some specific embodiments, the first heat exchange device 5 and the second heat exchange device 6 are both seawater heat exchangers, and low-temperature seawater is transported to the first heat exchange device 5 and the second heat exchange device 6 by a seawater pump to absorb heat, and the formed high-temperature seawater will be discharged.

[0052] The refilling device 3 is connected to the tower body 10 and is used to replenish the oxidizing solution into the tower body 10. In some embodiments, when the pH value of the oxidizing solution at the liquid outlet of the oxidizing solution recovery device 2 is detected to be increased, it means that the oxidizing property of the oxidizing solution in the system is reduced, and it is necessary to replenish new oxidizing solution into the tower body 10 through the refilling device 3. In some embodiments, the ship dual-fuel engine flue gas oxidation demethanization system further includes a pH detection device 7 for monitoring the pH value of the oxidizing solution at the liquid outlet of the oxidizing solution recovery device 2.

[0053] In some specific embodiments, a circulation pump 8 is further provided at the liquid outlet of the oxidizing solution recovery device 2, and the circulation pump 8 is used to transport the unreacted oxidizing solution. The liquid replenishing device 3 is connected to the tower body 10 through a supplementary pump 9, and the supplementary pump 9 is used to input the oxidizing solution in the liquid replenishing device 3 into the tower body 10.

[0054] The following combination Figure 2 and Figure 7 The overall operation process of the ship dual-fuel engine flue gas oxidation demethanization system according to the embodiment of the present application is further described.

[0055] The flue gas is input into the first reactor 100 through the flue gas input pipe 11, and the oxidizing solution is transported into the first reactor 100 through the first spray assembly 300. The high temperature of the flue gas causes the oxidizing solution to vaporize and undergo an oxidation reaction. The formed gas-liquid vapor is output through the first output end of the first reactor 100, and the liquid phase drips to the bottom of the tower body 10 and is output to the oxidizing solution recovery device 2. The gas phase contacts the oxidizing solution sprayed by the second spray assembly 400 to vaporize and undergo an oxidation reaction. The liquid phase generated in this process drips to the bottom of the tower body 10 and is output to the oxidizing solution recovery device 2. The concentration of the oxidizing vapor in the flue gas is further increased, and enters the first catalyst packing layer 500 to undergo catalysis. Oxidation reaction, oxidatively decomposes the methane in the flue gas, and the output gas-liquid mixture enters the second reactor 200 through the flue gas inlet pipe 13 for gas-liquid separation, and the oxidizing solution is transported to the second reactor 200 through the third spray assembly 700 to oxidize the flue gas again. The separated liquid phase is output through the second output end of the second reactor 200, drips to the bottom of the tower body 10, and is output to the oxidizing solution recovery device 2. The separated gas phase is discharged from the tower body 10 through the flue gas output pipe 12, and after being cooled to the first target temperature by the first heat exchange device 5, enters the oxidation and dehydration chamber 41 for oxidation and dehydration treatment, and outputs demethanized flue gas, thereby realizing the demethanization treatment of the flue gas of the ship LNG dual-fuel engine. The liquid generated by oxidation and dehydration is output to the liquid outlet of the oxidizing solution recovery device 2, and after merging with the unreacted oxidizing solution output from the liquid outlet of the oxidizing solution recovery device 2, it is output to the first spray assembly 300, the second spray assembly 400, the third spray assembly 700 and the fourth spray assembly 43. Before being transported to the fourth spray assembly 43, it is cooled to the second target temperature by the second heat exchange device 6 to achieve the recovery and reuse of the oxidizing solution. During the above oxidation treatment process, the pH value of the oxidizing solution at the liquid outlet of the oxidizing solution recovery device 2 is monitored by the pH detection device 7. When the pH value is detected to be increased, new oxidizing solution is added to the tower body 10 by the liquid replenishing device 3.

[0056] At present, when traditional ship dual-fuel engines use catalytic oxidation to decompose methane escaping from flue gas, the catalyst used is easily contaminated by impurities in the flue gas, which causes the catalyst to fail and the catalytic oxidation equipment to be unable to operate stably. Traditional purification absorption towers usually use agents to absorb pollutants in flue gas, such as SO 2 Use alkali or weak alkaline seawater to absorb CO 2 Absorb with amine solution, etc., but CH 4 Insoluble in acid, alkali and organic solvents. Therefore, this application uses a water-soluble strong oxidant to react with CH 4 Reaction to eliminate CH 4 Greenhouse effect on the Earth.

[0057] In some preferred embodiments, the oxidizing solution is acidic hydrogen peroxide, and the mass concentration of the acidic hydrogen peroxide is 20%-30%, and the pH is 5-6.

[0058] In some preferred embodiments, the catalyst filler of the first catalyst filler layer 500 and / or the second catalyst filler layer 42 includes a graphene composite material, and the graphene composite material includes: a graphene matrix and a rare earth oxide attached to the graphene matrix, wherein the mass of the rare earth oxide accounts for 50% to 70% of the total mass of the graphene composite material, and the rare earth oxide includes rhenium oxide, neodymium oxide and cerium dioxide in a mass ratio of 1:1:1. Graphene is composed of layers of neatly arranged carbon atoms, each carbon atom forms a covalent bond with three surrounding carbon atoms to form a hexagonal structure. The structure of graphene is similar to a honeycomb grid, which makes graphene have extremely high strength and stability. At the same time, the grid structure can accommodate more metal oxides, increase the attachment amount of effective catalytic materials, and thus improve the catalytic efficiency.

[0059] In some preferred embodiments, the method for preparing the graphene composite material comprises: (1) Provide 25nm~50nm graphene particles and rare earth oxides.

[0060] The method for preparing the graphene particles may include: spray-drying the graphene material in a nitrogen atmosphere at 100° C. to form dry graphene particles, and screening graphene particles with a size of 25 nm to 50 nm.

[0061] The rare earth oxide includes a mixture of rhenium oxide, neodymium oxide and cerium dioxide in a mass ratio of 1:1:1.

[0062] (2) Mixing and depositing the graphene particles and the rare earth oxide by a vapor deposition method to obtain a graphene composite material, wherein the mass fraction of the rare earth oxide is 50% to 70%.

[0063] The vapor deposition method is to generate an instantaneous extremely high temperature by an electric arc to evaporate the rare earth oxide, and then quickly introduce graphene particles at -35°C, and the rare earth oxide crystallizes in the graphene particles. Through vapor deposition, a larger amount of effective catalytic material can be attached, thereby increasing the contact area between the catalyzed substance and the catalyst, and further improving the catalytic efficiency.

[0064] In some specific embodiments, the graphene composite material is made into particles with a diameter of 10 mm by a granulator for filling the catalyst bed of the actual device (1 Nm 3 Smoke needs 0.011m 3 catalyst).

[0065] use Figure 7 The shown ship dual-fuel engine flue gas oxidation demethanization system demethans the flue gas, wherein the oxidizing solution is an acidic hydrogen peroxide with a pH of 6 and a mass concentration of 25%, and compares the flue gas methane removal rate of different catalyst fillers. Methane removal rate = (C 初始甲烷 -C 处理后甲烷 ) / C 初始甲烷 ×100%,C 初始甲烷 represents the concentration of methane in the initial flue gas, C 处理后甲烷 Represents the concentration of methane in the flue gas after oxidation treatment. These two concentration values ​​can be measured at the corresponding positions using a concentration meter. In the catalyst packing layer, the total mass of the oxides loaded on the graphene particles accounts for 60%. The only difference between different catalyst packings is the type of oxide loaded on the graphene matrix. The results are shown in Table 1.

[0066] Table 1 Flue gas methane removal rate results of different catalyst fillers Flue gas temperature Oxide composition Quality Ratio Methane removal rate 411℃ Rhenium oxide + neodymium oxide + cerium dioxide 1:1:1 100% Manganese dioxide + titanium dioxide 1:1 71.3% 245℃ Rhenium oxide + neodymium oxide + cerium dioxide 1:1:1 92.1% Manganese dioxide + titanium dioxide 1:1 38.9% 51℃ Rhenium oxide + neodymium oxide + cerium dioxide 1:1:1 42.2% Manganese dioxide + titanium dioxide 1:1 11.3%

[0067] As can be seen from Table 1, when the catalyst filler is the same, the methane removal rate tends to increase with the increase of the input flue gas temperature. This is because, as the flue gas temperature increases, more acidic hydrogen peroxide vaporizes and the oxidation efficiency is improved. When the input flue gas temperature is the same, when the composition of the loaded oxide is a mixture of rhenium oxide, neodymium oxide and cerium dioxide in a mass ratio of 1:1:1, the methane removal rate is significantly improved. In particular, when the input flue gas temperature is 411°C, the methane removal rate is as high as 100% when the loaded oxide of this specific composition is used, achieving complete removal of escaping methane in the flue gas.

[0068] The present application also provides a method for oxidative demethanization of flue gas from a ship dual-fuel engine, using the above-mentioned system for oxidative demethanization of flue gas from a ship dual-fuel engine, and the method comprises the following steps: S1: Flue gas and an oxidizing solution are input into an oxidation tower, and the oxidation tower outputs treated flue gas and unreacted oxidizing solution, wherein the heat of the flue gas vaporizes the oxidizing solution into oxidizing steam, and the flue gas and the oxidizing steam undergo an oxidation reaction; S2: recovering the unreacted oxidizing solution through an oxidizing solution recovery device and transporting it to the oxidation tower; S3: When it is detected that the pH value of the oxidizing solution at the liquid outlet of the oxidizing solution recovery device increases, the oxidizing solution in the oxidation tower and the oxidizing solution recovery device is discharged, and the oxidizing solution is replenished into the oxidation tower through the liquid replenishment device.

[0069] In some embodiments, the ship dual-fuel engine flue gas oxidation demethanization method also includes step S1-2: using an oxidation dehydration device to oxidize and dehydrate the treated flue gas output from the oxidation tower, and outputting demethanized flue gas and liquid, wherein the liquid is output to the liquid outlet end of the oxidizing solution recovery device, and after merging with the unreacted oxidizing solution output from the oxidizing solution recovery device, it is output to the first spray assembly, the second spray assembly, the third spray assembly and the fourth spray assembly to achieve the recovery and reuse of the oxidizing solution.

[0070] It should be noted that different embodiments may produce different beneficial effects. In different embodiments, the beneficial effects that may be produced may be any one or a combination of the above, or any other beneficial effects that may be obtained.

[0071] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of this specification. Although not explicitly stated here, those skilled in the art may make various modifications, improvements and corrections to this application. Such modifications, improvements and corrections are suggested in this specification, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of this application.

[0072] It should be noted that in the description of this application, unless otherwise clearly specified and limited, the terms "installation", "connection", "connected", "connection", and "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a rotational connection or a sliding connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood in combination with specific circumstances.

[0073] In addition, when terms such as "first", "second", and "third" are used in the specification of this application to describe various features, these terms are only used to distinguish these features and cannot be understood as indicating or implying the relationship between the features, the relative importance, or implicitly indicating the number of features indicated.

[0074] In addition, the present specification describes exemplary embodiments by reference to idealized exemplary cross-sectional views and / or plan views and / or stereograms. Therefore, differences from the illustrated shapes due to, for example, manufacturing techniques and / or tolerances are foreseeable. Therefore, the exemplary embodiments should not be interpreted as being limited to the shapes of the regions shown herein, but should include deviations in shapes caused by, for example, manufacturing. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shapes of the regions of the device nor to limit the scope of the exemplary embodiments.

[0075] At the same time, the present application uses specific words to describe the embodiments of this specification. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in the present application does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0076] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this application, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0077] Finally, it should be understood that the embodiments described in this application are only used to illustrate the principles of the embodiments of the present application. Other variations may also fall within the scope of the present application. Therefore, as an example and not a limitation, the alternative configurations of the embodiments of the present application may be considered to be consistent with the teachings of the present application. Accordingly, the embodiments of the present application are not limited to the embodiments explicitly introduced and described in the present application.

Claims

1. A ship dual-fuel engine flue gas oxidation demethanization system, characterized in that: include: An oxidation tower (1), an oxidizing solution recovery device (2) and a liquid replenishing device (3); wherein: The oxidation tower (1) is used to input flue gas and oxidizing solution, and output treated flue gas and unreacted oxidizing solution, and the oxidation tower (1) comprises: A tower body (10) having an outlet at the bottom, a smoke inlet pipe (11), and a smoke outlet pipe (12); A first reactor (100) is disposed in the tower body (10) and is connected to the flue gas input pipe (11), and has a first output end at the bottom; A second reactor (200) is arranged in the tower body (10) and is sleeved on the outer circumference of the first reactor (100), and has a second output end at the bottom, wherein the first output end extends out of the second output end, the top of the second reactor (200) is connected to the smoke output pipe (12), and a smoke inlet pipe (13) is also provided on the side wall of the second reactor; A first spray assembly (300) is used to transport an oxidizing solution into the interior of the first reactor (100); A second spray assembly (400) is used to transport an oxidizing solution to the outside of the second reactor (200); The oxidizing solution recovery device (2) comprises a liquid inlet and a liquid outlet, wherein the liquid inlet is connected to the outlet at the bottom of the tower body (10), and the liquid outlet is connected to the first spray assembly (300) and the second spray assembly (400); The liquid replenishing device (3) is in communication with the tower body (10) and is used to replenish the oxidizing solution.

2. The marine dual-fuel engine flue gas oxidation demethanization system according to claim 1, characterized in that: The first output end comprises at least two air guide pipes (104), and the air outlets at the ends of each of the air guide pipes (104) are bent together in a clockwise or counterclockwise direction.

3. The marine dual-fuel engine flue gas oxidation demethanization system according to claim 1, characterized in that: The number of the flue gas input pipe (11) and the number of the flue gas inlet pipe (13) are both two, wherein the two flue gas input pipes (11) are symmetrically arranged relative to the center axis of the first reactor (100), and the two flue gas inlet pipes (13) are symmetrically arranged relative to the center axis of the second reactor (200).

4. The marine dual-fuel engine flue gas oxidation demethanization system according to claim 1, characterized in that: The oxidation tower further comprises: a heat exchange coil (600), which is arranged in the tower body (10), sleeved on the outer periphery of the second reactor (200), and located below the flue gas inlet pipe (13).

5. The marine dual-fuel engine flue gas oxidation demethanization system according to claim 1, characterized in that: The oxidation tower further comprises: a first catalyst packing layer (500) disposed in the tower body (10), located on the outer periphery of the second reactor (200), and located below the flue gas inlet pipe (13).

6. The ship dual-fuel engine flue gas oxidation demethanization system according to claim 5, characterized in that: The ship dual-fuel engine flue gas oxidation demethanization system further comprises an oxidation dehydration device (4), and the oxidation dehydration device (4) comprises: An oxidation dehydration chamber (41) has a smoke inlet on its side wall, a smoke outlet on its top, and a liquid outlet on its bottom, wherein the smoke inlet is connected to the smoke outlet pipe (12), the smoke outlet is used to output clean smoke, and the liquid outlet is connected to the liquid outlet end of the oxidizing solution recovery device (2); A second catalyst packing layer (42) is arranged inside the oxidation and dehydration cavity (41) and is located above the smoke inlet; a fourth spraying assembly (43), used for spraying an oxidizing solution above the second catalyst packing layer (42); The demisting component (44) is arranged inside the oxidation and dehydration cavity (41) and close to the smoke outlet.

7. The ship dual-fuel engine flue gas oxidation demethanization system according to claim 6, characterized in that: The ship dual-fuel engine flue gas oxidation demethanization system also includes: A first heat exchange device (5), one end of which is in communication with the smoke output pipe (12) and the other end of which is in communication with the smoke inlet, and is used to cool the smoke output to the inside of the oxidation and dehydration chamber (41) to a first target temperature; The second heat exchange device (6) has one end connected to the liquid outlet of the oxidizing solution recovery device (2) and the other end connected to the fourth spray assembly (43), and is used to cool the oxidizing solution supplied to the fourth spray assembly (43) to a second target temperature.

8. The ship dual-fuel engine flue gas oxidation demethanization system according to claim 6, characterized in that: The oxidizing solution is acidic hydrogen peroxide, and the mass concentration of the acidic hydrogen peroxide is 20% to 30%, and the pH is 5 to 6; The first catalyst packing layer (500) and / or the second catalyst packing layer (42) comprises a graphene composite material, and the graphene composite material comprises: a graphene matrix and a rare earth oxide attached to the graphene matrix, wherein the mass of the rare earth oxide accounts for 50% to 70% of the total mass of the graphene composite material, and the rare earth oxide comprises rhenium oxide, neodymium oxide and cerium dioxide in a mass ratio of 1:1:

1.

9. The marine dual-fuel engine flue gas oxidation demethanization system according to claim 1, characterized in that: The ship dual-fuel engine flue gas oxidation demethanization system further comprises a pH detection device (7) for monitoring the pH value of the oxidizing solution at the liquid outlet of the oxidizing solution recovery device (2).

10. A method for oxidative demethanization of flue gas from a ship dual-fuel engine, characterized in that: The marine dual-fuel engine flue gas oxidation demethanization system according to any one of claims 1 to 9 is used, and the method comprises: Flue gas and an oxidizing solution are input into an oxidation tower (1), and the oxidation tower (1) outputs treated flue gas and unreacted oxidizing solution, wherein the heat of the flue gas vaporizes the oxidizing solution into oxidizing steam, and an oxidation reaction occurs between the flue gas and the oxidizing steam; Recovering the unreacted oxidizing solution through an oxidizing solution recovery device (2) and conveying the unreacted oxidizing solution to the oxidation tower (1); When it is detected that the pH value of the oxidizing solution at the liquid outlet of the oxidizing solution recovery device (2) increases, the oxidizing solution in the oxidation tower (1) and the oxidizing solution recovery device (2) is discharged, and the oxidizing solution is replenished into the oxidation tower (1) through the liquid replenishment device (3).

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