CN108854532B

CN108854532B - Ship tail gas denitration SCR reactor

Info

Publication number: CN108854532B
Application number: CN201811049095.0A
Authority: CN
Inventors: 付忆华; 钟文琪; 展锦程
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2018-09-10
Filing date: 2018-09-10
Publication date: 2021-02-26
Anticipated expiration: 2038-09-10
Also published as: CN108854532A

Abstract

The invention discloses an SCR reactor for denitration of ship tail gas, comprising a reactor main body, on which a tail gas inlet pipe and a tail gas outlet pipe are arranged; After the outlet is bent, it is connected to the exhaust gas outlet pipe, a deflector is arranged in the bending section, the first catalyst is arranged in the extension section, and the second catalyst is arranged in the exhaust gas outlet pipe. The reactor of the invention has a compact structure, is suitable for ship space, and has high denitrification efficiency; the arrangement of the bending section, the confluence section and the guide plate can increase the uniformity of the flow field and each gas component; the arrangement of the catalyst layer is the most efficient. The first catalyst that first contacts the exhaust gas can use a sulfur-resistant or medium-high temperature catalyst, and the second catalyst can use a low-temperature or poor sulfur-resistant catalyst, which reduces the effect of deposition on the catalyst on the denitration efficiency to a certain extent. Improve the utilization rate of the catalyst layer and improve the denitration efficiency.

Description

Ship tail gas denitration SCR reactor

Technical Field

The invention relates to an SCR (selective catalytic reduction) reactor, in particular to a ship tail gas denitration SCR reactor, and belongs to the field of ship energy conservation and emission reduction.

Background

With the development of the economic globalization, the world trade situation is changed dramatically, and the total international trade quantity is increased by nearly 22 times in 2002 to 2011. The rapid increase of international trade leads to the rapid increase of ship transportation in the world, and the environmental pollution caused by ship tail gas is increasingly severe. Nitrogen oxides are one of the main components of marine exhaust pollutants, and the hazards include: photochemical smog, acid rain, tropospheric ozone, ozone layer depletion, and the like. Since 2016, the international maritime organization has established stricter emission regulations, and after the ship enters an emission control area specified by the international maritime organization, the emission must reach the specified limit, which requires that the ship must adopt a technology with higher denitration efficiency.

Selective Catalytic Reduction (SCR) is one of the denitration technologies that have high denitration efficiency and are relatively mature in technology at present. The SCR system is complex, and as shown in fig. 1, the conventional SCR shuttle reactor occupies a large space, which is not suitable for a ship with a relatively small space. Because boats and ships tail gas velocity of flow is higher (can reach 15m/s the highest), and the reason of the setting of traditional SCR reactor entrance expansion pipe in addition, can have among the denitration process that gas residence time reduces, the mixed degree reduces, urea evaporation decomposition rate reduces the scheduling problem, and then can lead to the appearance of following several kinds of condition: scouring the catalyst inlet and forming a deposit; a negative backflow area is easily generated at the periphery of the traditional shuttle-shaped expansion pipe; poor catalyst utilization except for the center; an increase in ammonia slip rate, etc., all of which lead to a decrease in denitration efficiency.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide an SCR denitration reactor which is suitable for a compact space of a ship and can achieve higher denitration efficiency.

The technical scheme is as follows: the ship tail gas denitration SCR reactor comprises a reactor main body, wherein a tail gas inlet pipeline and a tail gas outlet pipeline are arranged on the reactor main body; the tail gas inlet pipeline is provided with an inlet section, a bending section and an extending section which are sequentially connected, the outlet of the extending section is communicated with the tail gas outlet pipeline after being bent, a guide plate is arranged in the bending section, a first catalyst is arranged in the extending section, and a second catalyst is arranged in the tail gas outlet pipeline.

Preferably, the number of the tail gas inlet pipelines is two, the tail gas inlet pipelines are symmetrically arranged relative to the tail gas outlet pipeline, and the extending sections of the two tail gas inlet pipelines are converged and communicated with the tail gas outlet pipeline.

Furthermore, the entry section of the tail gas entry pipeline is horizontally arranged and is vertical to the extension section, the tail gas exit pipeline is horizontally arranged, and at the moment, the main body of the reactor is E-shaped; or the inlet section of the tail gas inlet pipeline is vertically arranged and is perpendicular to the extension section, the tail gas outlet pipeline is vertically arranged, and the main body of the reactor is in a Chinese character 'shan' shape, so that better mixing efficiency can be achieved.

When the reactor main body is E-shaped or E-shaped, the distance between the inlet of the first catalyst in the extension section and the outlet of the bending section is A, the distance between the outlet of the first catalyst and the inlet of the tail gas outlet pipeline is B, the distance between the inlet of the second catalyst and the extension section is C, wherein the length of A, B, C is 100mm-300mm, and the distance takes the adjustment and replacement of the catalyst and the guide plate in the later period into consideration.

The guide plate comprises an outward-bent guide plate and an inward-bent guide plate, wherein the outward-bent guide plate is located in the bending section and close to the outer side, the inward-bent guide plate is close to the inner side, the outward-bent guide plate is composed of a straight line portion and an arc portion, and the inward-bent guide plate is arc-shaped. The arrangement of the guide plates can enable the uniform flow field distribution, prevent fluid from scouring the wall surface at the bent pipe, finally improve the urea decomposition rate and achieve better denitration efficiency.

Preferably, the linear portion of the outwardly curved baffle does not exceed the length of the edge of the inwardly curved baffle.

Preferably, the guide plates are at least two plates which are arranged in parallel, the distance between every two adjacent guide plates is more than 300mm, and if the distance is too small, liquid drops are hung on the wall, the resistance is too large, and the like.

The first catalyst is a medium-high temperature catalyst or a catalyst with better sulfur resistance; wherein, the first catalyst can be a vanadium-titanium catalyst or a molecular sieve catalyst; further, the vanadium-titanium based catalyst may be V₂O₅/TiO₂、V₂O₅-WO₃/TiO₂Or V₂O₅/TiO₂-Al₂O₃(ii) a The molecular sieve catalyst may be Cu-ZSM-5 or Fe-ZSM-5.

The second catalyst is a catalyst with poor sulfur resistance or a low-temperature catalyst; wherein the second catalyst can be a manganese-cerium catalyst or a manganese-cerium catalyst.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: firstly, the reactor has compact structure and is suitable for ship space, and particularly, one or two dents can be inserted and installed in a pipeline, so that the utilization rate of the ship space can be improved; secondly, the arrangement of the bending section and the guide plate therein can prolong the retention time of the tail gas, increase the uniformity of a flow field, prevent the tail gas from scouring the bending part, avoid a backflow area, improve the utilization rate of a catalyst layer, improve the denitration efficiency and avoid ammonia escape; in addition, the catalyst layer is arranged in a smart design mode, the first catalyst which is firstly contacted with the tail gas can use a sulfur-resistant or medium-high temperature catalyst, the second catalyst can use a low-temperature or poor sulfur-resistant catalyst, and the method reduces the influence of catalyst deposition on the denitration efficiency to a certain extent.

Drawings

FIG. 1 is a schematic view of a conventional shuttle-type reactor;

FIG. 2 is a schematic structural diagram of a ship tail gas denitration SCR reactor;

FIG. 3 is a schematic structural view of a baffle in a bend section;

FIG. 4 is a smooth distribution of baffles within a bend;

fig. 5 is an enlarged view of the vector distribution of the flow field at the box position in fig. 4.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings.

The invention relates to a ship tail gas denitration SCR (selective catalytic reduction) reactor, which comprises a reactor main body 1, wherein a tail gas inlet pipeline 2 and a tail gas outlet pipeline 3 are arranged on the reactor main body 1; the tail gas inlet pipeline 2 is provided with an inlet section 201, a bending section 202 and an extension section 203 which are connected in sequence, the outlet of the extension section 203 is bent and then communicated with a tail gas outlet pipeline 3, wherein a guide plate 204 is arranged in the bending section 202, a first catalyst 205 is arranged in the extension section 203, and a second catalyst 206 is arranged in the tail gas outlet pipeline 3. In a specific implementation, the entry section 203 of the exhaust gas entry duct may be parallel to the exhaust gas outlet duct 3, for example both in horizontal form, or both in vertical form, or both at an angle, preferably both horizontal or vertical. The preferred reactor is a U-shaped structure, or the U-shaped structure is rotated by 90 degrees; of course, the technical scheme of the invention can be realized to a certain extent by corresponding structures obtained by rotating the reactor at other various angles. In practice, one reactor can be arranged independently according to the gas flow, or a plurality of reactors can be operated simultaneously. Each reactor is provided with a recess, so that pipelines on the ship can be conveniently inserted and installed, and the utilization rate of the space of the ship can be improved.

Referring to fig. 2, the second ship tail gas denitration SCR reactor of the present invention is an E-shaped reactor, and if the reactor is rotated 90 degrees to the left, a chevron-shaped reactor can be obtained. Be equipped with two tail gas admission pipes 2 and tail gas outlet pipe way 3 on the reactor main part 1, two tail gas admission pipes 2 set up about 3 symmetries of tail gas outlet pipe way, wherein, tail gas admission pipe 2 has the entering section 201 that connects gradually, bend section 202 and extension 203, the extension 203 that two tail gas admission pipes said collects intercommunication tail gas outlet pipe way 3, be equipped with guide plate 204 in the bend section 202, arrange first catalyst 205 in the extension 203, arrange second catalyst 206 in the tail gas outlet pipe way 3.

In specific implementation, the structures of the baffles 204 in the two reactors are shown in fig. 3, and the baffles include an outward-curved baffle 208 located inside the bending section and close to the outer side, and an inward-curved baffle 209 located inside the bending section, wherein the outward-curved baffle is composed of a straight portion 210 and an arc portion 211, and the inward-curved baffle 209 is arc-shaped. The radius of the outer bend guide plate is large, the straight line part plays a role in drainage, and the inner bend guide plate can prevent negative pressure from causing the generation of a backflow area.

The bending section and the guide plate arranged in the bending section can prolong the retention time of the tail gas, increase the uniformity of a flow field, prevent the tail gas from scouring the bending part, avoid a backflow area, improve the utilization rate of a catalyst layer, improve the denitration efficiency and avoid ammonia escape. Fig. 4 is a flow field distribution diagram after the guide plate is arranged, the flow velocity of fluid with high inlet flow velocity is reduced after passing through the guide plate, the flow field distribution is more uniform, the condition of overlarge flow velocity does not occur on the outer curved wall surface of the reactor, and an obvious reflux region does not appear on the inner curved surface. Fig. 5 is a velocity vector diagram of the inner bend, and it can be seen from the vector diagram that the fluid is uniformly distributed, and the directions of the vector arrows are consistent, so that no obvious backflow area exists.

In the concrete implementation, the guide plate 204 guide plate in above-mentioned two kinds of reactors is two at least, and the interval between the adjacent guide plate is more than 300mm, and the interval undersize can lead to aggravating gaseous and guide plate area of contact, and vapor condenses in the guide plate in the tail gas and generates the sulfate, and long-term operation easily causes the guide plate to corrode, and the interval undersize still can cause certain resistance loss, thereby easily cause certain exhaust backpressure to influence the diesel engine performance.

In practice, the length of the straight portion 210 of the outwardly curved baffle 208 does not exceed the edge of the inwardly curved baffle 209 because the straight portion is too long and is exposed to the flow stream alone at the inlet section due to the small amount of SO in the exhaust₂Vapor in gas and tail gas is condensed on the guide plate to generate sulfate, so that the corrosion is easily caused after long-term operation.

The catalyst support 207 is arranged in the extension section 203 of the tail gas inlet pipeline 2, and the first catalyst 205 is arranged on the catalyst support 207; furthermore, a manual operation hole 4 can be formed in the reactor shell corresponding to the catalyst and used for installation, replacement and the like of the catalyst.

The pipe diameter of the reactor inlet 101 of the invention is the same as that of the pipeline of the external system, the pipe diameter is increased after passing through the bending section, and the pipe diameter is related to the space velocity of the required catalyst along with the tail gas flow. As the two gases mix, the tube diameter of the reactor outlet 102 is larger than the tube diameter of the external system piping.

In the present invention, the first catalyst may be a medium-high temperature catalyst or a catalyst having a high sulfur resistance, for example, a vanadium-titanium catalyst (V)₂O₅/TiO₂、V₂O₅-WO₃/TiO₂Or V₂O₅/TiO₂-Al₂O₃) Molecular sieve catalysts (Cu-ZSM-5 or Fe-ZSM-5), etc.; the second catalyst may be a less sulfur resistant catalyst or a low temperature catalyst, such as a manganese cerium based catalyst (MnO)_X-Fe-CeO₂Or MnO_X-Pr-CeO₂) Modified activated carbon-based catalysts, and the like. The purpose of the first catalyst and the second catalyst arrangement can reduce the influence of catalyst deposition on denitration efficiency to some extent.

In particular implementations, the first catalyst and the second catalyst may be arranged in a double layer. Further, when the reactor main body is E-shaped or E-shaped, the distance between the inlet of the first catalyst in the extension section and the outlet of the bending section is A, the distance between the outlet of the first catalyst and the inlet of the tail gas outlet pipeline is B, and the distance between the inlet of the second catalyst and the extension section is C, wherein the length of A, B, C is 100mm-300 mm.

The reaction process is as follows: the tail gas enters the tail gas inlet pipeline 2 from an external system pipeline through the reactor inlet 101, enters the tail gas outlet pipeline 3 after passing through the first catalyst 205 in the inlet section 201, the bending section 202 and the extending section 203, and is discharged to an external system pipe from the reactor outlet 102 after passing through the second catalyst 206.

Example 1

When the ship uses the diesel engine, the exhaust flow reaches 50000m under the rated load³/h-60000m³At the hour of/h, the airspeed is 8000h^-1Catalyst, total volume of catalyst required 6.25m³-7.5m³. Wherein the first catalyst has a cross-sectional area of 1.39m²-1.67m²Length of 1.5m and cross-sectional area of 2.77m²-3.33m²And the length is 0.75 m. The final E-type SCR has a length of 5.27m to 5.43m and a width of 2.23m to 2.34m in consideration of installation size and the like. 4-5 guide plates are arranged, wherein 1 guide plate is bent outwards, and 3-4 guide plates are bent inwards. Under this example, a type E SCR denitration efficiency of 90.2% is designed herein. The total length of the traditional shuttle-type SCR reaches 6.08-6.40 m and the width of the traditional shuttle-type SCR reaches 3.33-3.65 m under the same denitration efficiency. Due to the fact that the flow rate is large, the denitration efficiency of the shuttle-type reactor with the same length and width of the E-type reactor is only 79.0% at most.

Example 2

When the ship uses the diesel engine, the exhaust flow reaches 40000m under the rated load³/h-50000m³At the hour of/h, the airspeed is 8000h^-1Catalyst, the total volume of catalyst required is 5.00m³-6.25m³. Wherein the first catalyst has a cross-sectional area of 1.11m²-1.39m²Length of 1.5m and cross-sectional area of 2.22m²-2.77m²And the length is 0.75 m. The final E-type SCR has a length of 5.09m to 5.27m and a width of 2.10m to 2.23m, considering the mounting size and the like. 4 guide plates are arranged, wherein 1 guide plate is bent outwards, and 3 guide plates are bent inwards. Under this example, a model E SCR denitration efficiency of 91.0% is designed herein. The total length of the traditional shuttle-type SCR reaches 5.73-6.08 m and the width of the traditional shuttle-type SCR reaches 2.98-3.33 m under the same denitration efficiency. Due to the fact that the flow is large, the denitration efficiency of the shuttle-type reactor with the same length and width of the E-type reactor is only 81.1% at most.

Example 3

When the ship uses the diesel engine, the exhaust flow reaches 30000m under rated load³/h-40000m³At the hour of/h, the airspeed is 8000h^-1A catalyst,the total volume of the catalyst required was 3.75m³-5.00m³. Wherein the first catalyst has a cross-sectional area of 0.83m²-1.11m²Length of 1.5m and cross-sectional area of the second catalyst of 1.67m²-2.22m²And the length is 0.75 m. The final E-type SCR has a length of 4.89m to 5.09m and a width of 1.96m to 2.10m, considering the mounting size and the like. 4 guide plates are arranged, wherein 1 guide plate is bent outwards, and 3 guide plates are bent inwards. Under this example, a type E SCR denitration efficiency of 90.7% is designed herein. The total length of the traditional shuttle-type SCR reaches 5.33m-5.75m and the width of the traditional shuttle-type SCR reaches 2.58m-2.98m under the same denitration efficiency. Under the flow range, the denitration efficiency of the shuttle-type reactor with the same length and width of the E-type reactor is only 82.9 percent at most.

Example 4

When the ship uses the diesel engine, the exhaust flow reaches 20000m under the rated load³/h-30000m³At the hour of/h, the airspeed is 8000h^-1Catalyst, total volume of catalyst required 2.50m³-3.75m³. Wherein the first catalyst has a cross-sectional area of 0.56m²-0.83m²Length of 1.5m and cross-sectional area of the second catalyst of 1.11m²-1.67m²And the length is 0.75 m. The final E-type SCR has a length of 4.65m to 4.89m and a width of 1.79m to 1.96m, considering the installation size and the like. 3-4 guide plates are arranged, wherein 1 guide plate is bent outwards, and 2-3 guide plates are bent inwards. Under this example, a type E SCR denitration efficiency of 90.0% is designed herein. The total length of the traditional shuttle-type SCR reaches 4.86-5.33 m and the width thereof reaches 2.11-2.58 m under the same denitration efficiency. Under the flow range, the denitration efficiency of the shuttle-type reactor with the same length and width of the E-type reactor is only 83.1 percent at most.

Example 5

When the ship uses the diesel engine, the exhaust flow reaches 10000m under rated load³/h-20000m³At the hour of/h, the airspeed is 8000h^-1Catalyst, total volume of catalyst required 1.25m³-2.50m³. Wherein the first catalyst has a cross-sectional area of 0.28m²-0.56m²Length of 1.5m and cross-sectional area of the second catalyst of 0.56m²-1.11m²And the length is 0.75 m. The final E-type SCR has a length of 4.35m to 4.65m and a width in consideration of the installation size and the likeIs 1.58m-1.79 m. The guide plates are provided with 2-3 pieces, wherein the guide plates are bent outwards 1 piece, and the guide plates are bent inwards 1-2 pieces. Under this example, a type E SCR denitration efficiency of 90.2% is designed herein. The total length of the traditional shuttle-type SCR reaches 4.24-4.86 m and the width thereof reaches 1.49-2.11 m under the same denitration efficiency. Under the flow range, the denitration efficiency of the shuttle-type reactor with the same length and width of the E-type reactor is only 84.5 percent at most.

Example 6

When the diesel engine is used by the ship, the exhaust flow rate is less than or equal to 10000m under rated load³At the hour of/h, the airspeed is 8000h^-1Catalyst, total volume of catalyst required 1.25m³. Wherein the first catalyst has a cross-sectional area of 0.28m²Length of 1.5m and cross-sectional area of the second catalyst of 0.56m²And the length is 0.75 m. The final E-type SCR has a length of 4.35m and a width of 1.58m in consideration of the mounting size and the like. The guide plate is provided with 2 guide plates, wherein the guide plate is bent outwards by 1 guide plate, and the guide plate is bent inwards by 1 guide plate. Under this example, a type E SCR denitration efficiency of 89.1% is designed herein. The total length of the traditional shuttle-type SCR reaches 4.24m and the width of the traditional shuttle-type SCR reaches 1.49m under the same denitration efficiency. Under the flow range, the denitration efficiency of the shuttle-type reactor with the same length and width of the E-type reactor is only 84.9 percent at most.

The flow dividing points of examples 1-6 were calculated and the relevant design parameters are shown in the table below for reference with different flow rates.

TABLE 1 values of the parameters in examples 1-6

From the above, when the same volume of catalyst is used, under the condition of larger flow rate, the length and width of the reactor are smaller, the width can be reduced by 1.2m at most, the length can be reduced by 0.7m at most, and the reactor is provided with one or two recesses, so that the reduction of the total occupied volume is more remarkable; when the flow is small, although the length and the width of the reactor are similar to those of the traditional SCR reactor, the reactor provided by the invention can be arranged between pipelines at the concave part, so that the total occupied space of the reactor is far smaller than that of the traditional shuttle-type reactor; meanwhile, the denitration efficiency of the reactor is higher than that of the traditional reactor.

Claims

1. A ship tail gas denitration SCR reactor is characterized in that: comprising a reactor main body (1), and the reactor main body (1) is provided with a tail gas inlet pipe (2) and a tail gas outlet pipe (3); the tail gas The inlet pipe (2) comprises an inlet section (201), a bending section (202) and an extension section (203) connected in sequence, and the outlet of the extension section (203) is connected to the exhaust gas outlet pipe (3) after being bent, wherein all the A deflector (204) is arranged in the bending section (202), a first catalyst (205) is arranged in the extension section (203), and a second catalyst (206) is arranged in the exhaust gas outlet pipe (3); the exhaust gas enters There are two pipelines (2), which are arranged symmetrically with respect to the exhaust gas outlet pipeline (3), and the extension sections (203) of the two exhaust gas inlet pipelines (2) are collected and communicated with the exhaust gas outlet pipeline (3).

2. The SCR reactor for ship exhaust gas denitration according to claim 1, characterized in that: the inlet section (201) of the exhaust gas inlet pipe (2) is arranged horizontally and is perpendicular to the extension section (203), and the exhaust gas outlet pipe (3) ) horizontally arranged, the reactor main body (1) is E-type; or the inlet section (201) of the exhaust gas inlet pipe (2) is arranged vertically and is perpendicular to the extension section (203), and the exhaust gas outlet pipe (3) is arranged vertically , the main body (1) of the reactor is a mountain shape.

3. The SCR reactor for denitration of marine exhaust gas according to claim 1, characterized in that: the deflector (204) comprises an outwardly curved deflector (208) located in the bending section (202) and close to the outside, and a deflector (208) close to the An inner curved deflector (209) on the inner side, wherein the outer curved deflector (208) is composed of a straight portion (210) and an arc portion (211), and the inward curved deflector (209) is an arc shape.

4. The SCR reactor for denitration of marine exhaust gas according to claim 3, wherein the length of the straight portion (210) of the outwardly curved deflector (208) does not exceed the edge of the inwardly curved deflector (209). .

5. The SCR reactor for denitration of ship exhaust gas according to claim 1, characterized in that: the deflectors (204) are at least two plates arranged in parallel, and the spacing between adjacent deflectors (204) is 300mm or more.

6 . The SCR reactor for denitration of ship exhaust gas according to claim 1 , wherein the first catalyst ( 205 ) is a medium-high temperature catalyst or a sulfur-resistant catalyst. 7 .

7 . The SCR reactor for denitration of ship exhaust gas according to claim 6 , wherein the first catalyst ( 205 ) is a vanadium-titanium-based catalyst or a molecular sieve catalyst. 8 .

8. The SCR reactor for denitration of marine exhaust gas according to claim 1, wherein the second catalyst (206) is a low temperature catalyst.

9 . The SCR reactor for denitration of ship exhaust gas according to claim 8 , wherein the second catalyst ( 206 ) is a manganese-cerium-based catalyst or a manganese-cerium-based catalyst. 10 .