A marine diesel engine exhaust gas denitration system and an evaporation mixing device thereof

Abstract

The application provides a kind of marine diesel engine exhaust gas denitration system evaporation mixing device, wherein, evaporation mixing device includes the first layer evaporation mixing component and the second layer evaporation mixing component arranged in sequence;The first layer evaporation mixing component includes two first flow guide plates and two second flow guide plates, the first flow guide plate and the second flow guide plate are alternately arranged between and connected by support plate;The second layer evaporation mixing component includes two first flow guide plates, and the two first flow guide plates are connected by support plate between.The evaporation mixing device is installed in the exhaust pipe before the reactor inlet front end by connecting rib plate.The application realizes low pressure loss, can change the direction of gas flow, increase the turbulence of flow field, promote the evaporation, decomposition and mixing of urea solution with high temperature gas, improve the uniformity of reducing agent distribution at the reactor inlet.

Description

Technical Field

[0001] This invention relates to the field of marine diesel engine exhaust gas purification technology, specifically to a marine diesel engine exhaust gas denitrification system and its low-pressure-loss evaporative mixing device. Background Technology

[0002] Selective catalytic reduction (SCR), as a flue gas denitrification technology, has become the mainstream technology for denitrification treatment of marine diesel engine exhaust. Increasingly stringent regulations, coupled with space constraints on board ships, have placed higher demands on the denitrification efficiency of SCR reactors. On the one hand, higher catalyst efficiency is required, and on the other hand, the SCR system must occupy less space, allowing the reducing agent mixed with the exhaust gas to be more evenly distributed across the catalyst cross-section within a compact SCR reactor.

[0003] In marine SCR systems, urea is injected into the exhaust gas duct and evaporates and mixes within the duct. The high-speed airflow within the duct carries urea droplets into the reactor, resulting in incomplete mixing of the urea solution before it is forced into the reactor. Due to space constraints, the duct system cannot be extended indefinitely. Therefore, there is a pressing need in the field to incorporate a mixing device into the SCR system to increase airflow turbulence within the duct and the residence time of urea droplets within the duct, thereby ensuring complete evaporation and decomposition of the urea droplets and thorough mixing with the exhaust gas. However, the design of this device requires careful consideration of the resulting pressure loss to avoid excessively increasing the system's back pressure.

[0004] Currently, no descriptions or reports of technologies similar to this invention have been found, and no similar information has been collected domestically or internationally. Summary of the Invention

[0005] To address the aforementioned shortcomings in the prior art, this invention provides a marine diesel engine exhaust gas denitrification system and its low-pressure-loss evaporative mixing device.

[0006] According to one aspect of the present invention, an evaporative mixing device for a marine diesel engine exhaust gas denitrification system is provided, comprising a first layer of evaporative mixing components and a second layer of evaporative mixing components arranged sequentially; wherein:

[0007] The first layer evaporation mixing assembly includes two first guide plates and two second guide plates, which are alternately arranged and connected by a support plate;

[0008] The second-layer evaporation mixing assembly includes two first guide plates, which are connected by a support plate.

[0009] Optionally, the opening directions of the first layer evaporation mixing component and the second layer evaporation mixing component are set at a certain angle.

[0010] Optionally, the included angle is 90°.

[0011] Optionally, the first guide vane is an isosceles triangle with the apex removed.

[0012] Optionally, the second guide vane is an isosceles trapezoidal structure.

[0013] Optionally, the two first guide plates are arranged at an angle to each other and connected by the support plate, and the two second guide plates are arranged opposite to each other between the two first guide plates. The two sides of the second guide plates are in close contact with the plate surface of the first guide plates to form the first layer of evaporation mixing assembly.

[0014] The two first guide plates are arranged at an angle to each other and connected by the support plate to form the second layer of evaporation mixing assembly.

[0015] Optionally, the trapezoidal bottom of the second guide vane forms an angle of 60° with the two sides.

[0016] Optionally, the first guide plate and the second guide plate are alternately arranged to form a first layer of evaporation mixing assembly in the shape of a square pyramid.

[0017] Optionally, the two first guide vanes are arranged at a 60° angle to each other.

[0018] Optionally, the support plate adopts a thin trapezoidal structure, and the two waist sides of the trapezoidal structure are respectively connected to the plate surface of the first guide plate.

[0019] Optionally, the bottom edges of the first guide plate and the second guide plate are respectively provided with trapezoidal grooves arranged at equal intervals.

[0020] Optionally, the trapezoidal grooves on the oppositely positioned guide plates are staggered.

[0021] Optionally, the device further includes: a first support rib and a second support rib; wherein:

[0022] The first support ribs are respectively connected to the outer surface of the first guide plate, and the second support ribs are respectively installed through the two second guide plates.

[0023] Optionally, the length of the second support rib is greater than the length of the first support rib.

[0024] Optionally, the first support rib and the second support rib are arranged perpendicularly to each other and staggered.

[0025] Optionally, the first support rib and / or the second support rib adopt a thin, elongated rectangular structure.

[0026] According to another aspect of the present invention, a marine diesel engine exhaust gas denitrification system is provided, which employs one or more of the evaporative mixing devices described in any one of the above claims, wherein the evaporative mixing devices are sequentially installed in the exhaust gas pipe at the front end of the reactor inlet of the marine diesel engine exhaust gas denitrification system.

[0027] Optionally, the evaporation mixing device is connected between the exhaust gas pipes via the end faces of the supporting ribs disposed on the first guide plate and the second guide plate.

[0028] By adopting the above technical solution, the present invention has at least one of the following beneficial effects compared with the prior art:

[0029] The marine diesel engine exhaust gas denitrification system and its evaporative mixing device provided by the present invention redistribute the high-speed airflow input in the pipeline radially in the cross section of the mixing device through the guide plate structure. Through the multi-layer mixing components, the airflow is disturbed, further increasing the turbulence of the gas velocity and promoting further mixing of the reducing agent and exhaust gas.

[0030] The marine diesel engine exhaust gas denitrification system and its evaporative mixing device provided by the present invention have a trapezoidal groove structure at the tail end that effectively reduces the friction loss caused by the vortex caused by the airflow rushing directly to the inner wall of the pipe, resulting in less pressure loss, which can be reduced by more than 15% compared with the device without grooves.

[0031] The marine diesel engine exhaust gas denitrification system and its evaporation mixing device provided by the present invention have two sets of evaporation mixing components with their opening directions at a certain angle, which are used to change the flow direction, increase the turbulence of the flow field, promote the evaporation and decomposition of urea solution and its mixing with high-temperature gas, and improve the uniformity of the reducing agent distribution at the inlet of the SCR reactor. Attached Figure Description

[0032] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0033] Figure 1 This is a schematic diagram of the overall structure of the evaporation mixing device in a preferred embodiment of the present invention; wherein, (a) is the first layer of evaporation mixing component, and (b) is the second layer of evaporation mixing component.

[0034] Figure 2 This is a front view of an evaporation mixing device in a preferred embodiment of the present invention; wherein, (a) is a first layer evaporation mixing component, and (b) is a second layer evaporation mixing component.

[0035] Figure 3 This is a schematic diagram of the connection structure between the first guide plate and the second guide plate of the first layer evaporation mixing component in a preferred embodiment of the present invention.

[0036] Figure 4The vector diagram shows the velocity of the airflow through the low-pressure-loss evaporative mixing device of the marine denitrification system in a preferred embodiment of the present invention; wherein, (a) is without slots and (b) is with slots.

[0037] Wherein, 1 is the first guide plate, 2 is the support plate, 3 is the second guide plate, 4 is the second support rib, and 5 is the first support rib. Detailed Implementation

[0038] The embodiments of the present invention are described in detail below: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0039] One embodiment of the present invention provides an evaporative mixing device for a marine diesel engine exhaust gas denitrification system. This device helps the diesel engine exhaust gas in the exhaust pipe to mix evenly with the reducing agent over a shorter distance, improves the uniformity of the reducing agent before reaching the catalyst, and minimizes the pressure loss.

[0040] like Figures 1-3 As shown, the evaporative mixing device of the marine diesel engine exhaust gas denitrification system provided in this embodiment may include a first layer of evaporative mixing components and a second layer of evaporative mixing components arranged sequentially; wherein:

[0041] The first layer of evaporation mixing assembly includes two first guide plates 1 and two second guide plates 3, which are alternately arranged and connected by a support plate 2;

[0042] The second-layer evaporation mixing assembly includes two first guide plates 1, which are connected by a support plate 2.

[0043] In a preferred embodiment, the opening directions of the first evaporation mixing assembly and the second evaporation mixing assembly form a certain angle. Further, this angle is 90°.

[0044] In a preferred embodiment, the first guide plate 1 is an isosceles triangle with the apex removed.

[0045] In a preferred embodiment, the second guide plate 3 is an isosceles trapezoidal structure.

[0046] In a preferred embodiment, two first guide plates 1 are arranged at an angle to each other and connected by a support plate 2. Two second guide plates 3 are arranged opposite to each other between the two first guide plates 1. The two sides of the second guide plates 3 are closely attached to the plate surface of the first guide plates 1 to form a first layer of evaporation mixing assembly.

[0047] The two first guide plates 1 are arranged at an angle to each other and are connected by a support plate 2 to form the second layer of evaporation mixing assembly.

[0048] In a preferred embodiment, the trapezoidal bottom of the second guide plate 3 forms an angle of 60° with the two sides.

[0049] In a preferred embodiment, the first guide plate 1 and the second guide plate 3 are alternately arranged to form a first layer of evaporation mixing assembly in the shape of a square pyramid.

[0050] In a preferred embodiment, the two first guide vanes 1 are arranged opposite each other at a 60° angle.

[0051] In a preferred embodiment, the support plate 2 adopts a thin trapezoidal structure, and the two waist sides of the trapezoidal structure are respectively welded to the plate surface of the first guide plate.

[0052] In a preferred embodiment, the bottom edges of the first guide plate 1 and the second guide plate 3 are respectively provided with trapezoidal grooves arranged at equal intervals.

[0053] In a preferred embodiment, the trapezoidal grooves on the oppositely arranged guide plates are staggered.

[0054] In a preferred embodiment, the device further includes: a first supporting stiffener 5 and a second supporting stiffener 4; wherein:

[0055] The first support ribs 5 are respectively connected to the outer surface of the first guide plate 1, and the second support ribs 4 are respectively installed through the two second guide plates 3.

[0056] In a preferred embodiment, the length of the second support rib 4 is greater than the length of the first support rib 5.

[0057] In a preferred embodiment, the first support rib 5 and the second support rib 4 are arranged perpendicularly to each other and staggered.

[0058] In a preferred embodiment, the first support rib 5 and / or the second support rib 4 adopt a thin, elongated rectangular structure.

[0059] In some embodiments of the present invention:

[0060] The first-layer evaporation mixing assembly mainly consists of two identical first guide plates and two identical second guide plates. The first guide plate is an isosceles triangle with its top corner removed; the second guide plate is an isosceles trapezoid, with the base of the trapezoid forming a 60° angle with its two sides. The first and second guide plates of the first-layer evaporation mixing assembly are connected alternately to form a square pyramid. The first guide plates are connected by a support plate with an included angle of 60°.

[0061] The second-layer evaporation mixing assembly mainly consists of two identical first guide plates. The structure and connection method of the first guide plates are the same as those in the first-layer evaporation mixing assembly, and will not be described again here.

[0062] The supporting ribs are thin trapezoidal structures, with the two sides of the trapezoidal structure welded to the first guide plate.

[0063] The tails (bottom plates) of the first and second guide vanes have staggered trapezoidal grooves.

[0064] The first and second guide plates are also equipped with supporting ribs. The first supporting rib is installed on the outer surface of the first guide plate, and the second supporting rib is installed through the second guide plate. Viewed from the pipeline axis, the first and second supporting ribs are arranged at a 90° angle to each other.

[0065] According to an embodiment of the present invention, a marine diesel engine exhaust gas denitrification system is provided, which employs one or more evaporative mixing devices as described in any of the above embodiments of the present invention, and the evaporative mixing devices are sequentially installed in the exhaust gas pipe at the front end of the reactor inlet of the marine diesel engine exhaust gas denitrification system.

[0066] In a preferred embodiment, the evaporation mixing device is connected to the exhaust gas pipe via the end faces of the supporting ribs disposed on the first and second guide plates.

[0067] In some embodiments of the present invention:

[0068] The first guide plate is connected to the exhaust gas pipe via the first supporting rib plate.

[0069] The second guide plate is connected to the exhaust gas pipe through a second supporting rib plate that penetrates the plate body.

[0070] The supporting stiffeners adopt a thin, long, rectangular structure, with their ends welded between the guide plates and the exhaust gas pipe, connecting all the guide plates to the inner wall of the exhaust gas pipe. Furthermore, the thickness of the guide plates, supporting plates, and supporting stiffeners only needs to ensure strength under operating conditions and should not be too thick.

[0071] like Figure 2 As shown, in each group of evaporation mixing components of the evaporation mixing device, the included angle between the two opposing first guide plates is 60°, and the included angle between the two opposing second guide plates 3 is 60°.

[0072] like Figure 3 As shown, the angle A between the two sides of the first guide vane and the bottom edge ranges from 60° to 70°.

[0073] like Figure 4The figure shows a vector diagram of the axial velocity of gas flowing through an evaporative mixing device. (a) represents an evaporative mixing device without trapezoidal grooves, and (b) represents an evaporative mixing device with trapezoidal grooves. As can be seen from the figure, the evaporative mixing device with trapezoidal grooves can significantly reduce local vortices in the airflow and decrease pressure loss as the airflow passes through the mixing device.

[0074] The marine diesel engine exhaust gas denitrification system and its evaporative mixing device provided in the above embodiments of the present invention, wherein the side length of the guide plate, the side length of the support plate, the length of the support ribs, and the spacing between the evaporative mixing components are all determined according to the diameter of the exhaust gas pipeline to ensure that the evaporative mixing device is suitable for reactors of different specifications. The evaporative mixing device is installed in a straight pipe a certain distance from the inlet end of the reactor (SCR reactor) of the marine diesel engine exhaust gas denitrification system body to improve the uneven mixing of the reducing agent and exhaust gas entering the reactor.

[0075] The marine diesel engine exhaust gas denitrification system and its evaporative mixing device provided in the above embodiments can redistribute the high-speed airflow input into the pipeline radially along the cross-section of the mixing device. Through a multi-layer mixing structure, the airflow is disturbed, further increasing the turbulence of the gas velocity and promoting further mixing of the reducing agent and exhaust gas. The trapezoidal groove structure at the tail of the mixing device effectively reduces frictional losses caused by eddies resulting from the airflow directly impacting the inner wall of the pipeline, thereby reducing system pressure loss.

[0076] The marine diesel engine exhaust gas denitrification system and its evaporative mixing device provided in the above embodiments of the present invention achieve low pressure loss. The guide plate has a serrated structure at its tail, and the entire mixing device is fixed in the exhaust gas duct by supporting ribs. The opening directions of the two sets of evaporative mixing components are at a certain angle to change the flow direction, increase the turbulence of the flow field, promote the evaporation and decomposition of urea solution and its mixing with high-temperature gas, improve the uniformity of the reducing agent distribution at the inlet of the SCR reactor, and at the same time, the serrated structure at the tail reduces the pressure drop of the mixing device by about 17%.

[0077] Any matters not covered in the above embodiments of the present invention are well-known in the art.

[0078] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An evaporative mixing device for a marine diesel engine exhaust gas denitrification system, characterized in that, It includes a first layer of evaporation mixing assembly and a second layer of evaporation mixing assembly arranged sequentially; wherein: The first layer evaporation mixing assembly includes two first guide plates and two second guide plates, which are alternately arranged and connected by a support plate; The second-layer evaporation mixing assembly includes two first guide plates, which are connected by a support plate. The two first guide plates are arranged at an angle to each other and connected by the support plate. The two second guide plates are arranged opposite to each other between the two first guide plates. The two sides of the second guide plates are in close contact with the plate surface of the first guide plates, forming the first layer of evaporation mixing assembly. The two first guide plates are arranged at an angle to each other and connected by the support plate to form the second layer of evaporation mixing assembly; The first guide plate and the second guide plate are alternately arranged to form a first layer of evaporation mixing assembly in the shape of a square pyramid; The support plate adopts a thin trapezoidal structure, and the two waist sides of the trapezoidal structure are respectively connected to the plate surface of the first guide plate.

2. The evaporative mixing device for the marine diesel engine exhaust gas denitrification system according to claim 1, characterized in that, The first guide vane is constructed with an isosceles triangle structure minus its apex, and the second guide vane is constructed with an isosceles trapezoid structure; and / or The opening directions of the first layer evaporation mixing component and the second layer evaporation mixing component are set at a certain angle.

3. The evaporative mixing device for the marine diesel engine exhaust gas denitrification system according to claim 1, characterized in that, Also includes: The trapezoidal bottom of the second guide vane forms an angle of 60° with the two sides. And / or, the two first guide vanes are arranged opposite each other at a 60° angle.

4. The evaporative mixing device for the marine diesel engine exhaust gas denitrification system according to claim 1, characterized in that, The bottom edges of the first guide plate and the second guide plate are respectively provided with trapezoidal grooves arranged at equal intervals.

5. The evaporative mixing device for the marine diesel engine exhaust gas denitrification system according to claim 4, characterized in that, The trapezoidal grooves on the relatively arranged guide plates are staggered.

6. The evaporative mixing device for the marine diesel engine exhaust gas denitrification system according to any one of claims 1 to 5, characterized in that, Also includes: First supporting stiffener and second supporting stiffener; wherein: The first support ribs are respectively connected to the outer surface of the first guide plate, and the second support ribs are respectively installed through the two second guide plates.

7. The evaporative mixing device for the marine diesel engine exhaust gas denitrification system according to claim 6, characterized in that, It also includes any one or more of the following: The length of the second support rib is greater than the length of the first support rib; The first support rib and the second support rib are arranged perpendicularly to each other and staggered. The first support rib and / or the second support rib adopt a thin, elongated rectangular structure.

8. A marine diesel engine exhaust gas denitrification system, characterized in that, Using any one of claims 1 to 7, the evaporative mixing device is sequentially installed in the exhaust gas pipe at the front end of the reactor inlet of the marine diesel engine exhaust gas denitrification system.

9. The marine diesel engine exhaust gas denitrification system according to claim 8, characterized in that, The evaporation mixing device is connected between the exhaust gas pipes via the end faces of the supporting ribs disposed on the first guide plate and the second guide plate.

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