Waste gas after-treatment device and method

Abstract

The invention provides a waste gas after-treatment device and method, and particularly provides a methanol fuel engine waste gas after-treatment device and method, the waste gas after-treatment device comprises a first gas inlet pipeline, a catalytic oxidation module, a second gas inlet pipeline, a mixing area, a denitration module and a gas outlet pipeline which are connected in sequence in the waste gas flowing direction; an ammonia spraying component is arranged on the second gas inlet pipeline; a first flow guide cover and a cylindrical barrel with holes in the peripheral side are arranged in the mixing area; the side, close to the ammonia spraying component, of the cylindrical barrel is open, and the side, away from the ammonia spraying component, of the cylindrical barrel is closed; all the modules have a synergistic effect, unburnt methanol, formaldehyde, formic acid, CO and NOx in waste gas are fully converted into harmless CO2, H2O and N2, so that the emission standard of methanol fuel motor vehicles is met, and pollution to the environment is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of exhaust gas post-treatment, and specifically relates to an exhaust gas post-treatment device and method, and in particular to an exhaust gas post-treatment device and method for a methanol fuel engine. Background Art

[0002] Under the general trend of energy conservation and environmental protection, traditional internal combustion engine technology is in urgent need of green and low-carbon transformation. Methanol is a liquid at room temperature and pressure. It is safe to store, easy to transport and convenient to use. It only requires simple modifications to traditional fuel facilities to achieve methanol filling and utilization. It is regarded as an important synthetic renewable new clean fuel. In order to reduce dependence on non-renewable fossil fuels, new energy methanol reforming fuel cell vehicles are very popular. However, the exhaust gas of methanol fuel engines contains a large amount of incompletely burned methanol fuel pollutants. When methanol is burned inside the engine, by-products such as formaldehyde, acetaldehyde and formic acid are also produced. At the same time, the combustion temperature of methanol fuel is relatively high, and the NO generated in the engine cylinder x The content is higher than that of diesel engines. Therefore, directly using the urea SCR device commonly used in diesel engines for methanol fuel engines will cause major problems, such as: (1) The exhaust gas of methanol fuel engines contains a large amount of methanol and formaldehyde. After urea is injected, methanol and formaldehyde will cause the SCR catalyst to become poisoned and fail; (2) Inside the SCR catalyst, the methanol and formaldehyde in the exhaust gas of the methanol fuel engine react with the NH generated by the hydrolysis of urea 3 The reaction will generate highly toxic hydrogen cyanide, which will cause greater harm to the human body. Based on this, it is necessary to develop a matching post-processing device for the exhaust components of methanol fuel engines.

[0003] For example, CN204200316U discloses a urea SCR post-treatment device for a methanol fuel engine, including an exhaust pipe, an upstream catalyst and an SCR catalyst, wherein the upstream catalyst includes a precious metal catalyst and a metal oxide catalyst. The treatment efficiency of the device is low, and NO in the SCR catalyst is x With NH 3 The contact time is short and the mixing is uneven, resulting in NO x The conversion rate is low and still fails to meet the emission standards.

[0004] CN107989719A discloses an exhaust post-treatment system for a methanol engine, comprising an exhaust gas recirculation unit, a three-way catalytic converter and a calibration unit. The three-way catalytic converter in the device directly treats HC and NO in the exhaust gas. x , CO, methanol and formaldehyde are catalyzed simultaneously. However, this process has strict requirements on the air-fuel ratio. x It is difficult to achieve the maximum conversion rate of NO xThe residence time in the three-way catalytic converter is limited, deep conversion cannot be guaranteed, and the treatment efficiency is low, resulting in the exhaust gas still not meeting the standards after treatment.

[0005] In view of this, how to design an efficient and stable exhaust gas after-treatment device and method for a methanol fuel engine that meets emission regulatory limits has become a difficult problem that urgently needs to be solved. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide an exhaust gas aftertreatment device and method, in particular to provide an exhaust gas aftertreatment device and method for a methanol fuel engine, which can remove incompletely burned methanol, byproducts formaldehyde and formic acid, as well as CO and NO in the exhaust gas of a methanol fuel engine. x The pollutants are fully converted into harmless CO 2 、N 2 and H 2 O, thereby achieving efficient and harmless treatment of methanol fuel engine exhaust gas, making the exhaust gas meet emission standards, and the treatment cost is low, providing a guarantee for the commercialization of methanol fuel engines.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides an exhaust gas post-treatment device, which includes a first air intake pipe, a catalytic oxidation module, a second air intake pipe, a mixing area, a denitration module and an exhaust pipe connected in sequence along the exhaust gas flow direction; an ammonia spraying component is provided on the second air intake pipe;

[0009] The mixing area is provided with a first air guide cover and a cylindrical body with holes on the circumferential side; and the cylindrical body is open at a side close to the ammonia injection component and closed at a side away from the ammonia injection component.

[0010] The catalytic oxidation module, ammonia injection component, mixing area and denitration module in the exhaust gas post-treatment device of the present invention work together to firstly oxidize the incompletely burned methanol, byproducts formaldehyde and formic acid, and CO and other pollutants in the exhaust gas of the methanol fuel engine into CO by using the catalytic oxidation module. 2 and H 2 O, and oxidize part of the NO to NO 2 ; Reuse ammonia injection components to generate NH 3 , and the exhaust gas after catalytic oxidation is mixed with NH 3 After secondary mixing, the NO in the exhaust gas is removed by the denitrification module. x Catalytic reduction to harmless N 2 (SCR reaction), ultimately making the exhaust gas of the methanol fuel engine meet the emission standards and achieving low-cost harmless treatment.

[0011] The equation for the reaction carried out in the catalytic oxidation module of the present invention is as follows:

[0012] 2CH 4 O+3O 2 →2CO 2 +4H 2 O;

[0013] CH 2 O+O 2 →CO 2 +H 2 O;

[0014] HC+O 2 →CO 2 +H 2 O;

[0015] 2NO+O 2 →2NO 2 ;

[0016] 2CO+O 2 →2CO 2 .

[0017] The equation for the SCR reaction performed in the denitration module of the present invention is as follows:

[0018] NO+NO 2 +2NH 3 →2N 2 +3H 2 O;

[0019] 4NO+O 2 +4NH 3 →4N 2 +6H 2 O;

[0020] 2NO 2 +O 2 +4NH 3 →3N 2 +6H 2 O.

[0021] The mixing area is provided with a first air guide cover and a cylindrical body with holes on the circumference; the cylindrical body is open on one side close to the ammonia injection component and closed on the other side away from the ammonia injection component; the exhaust gas after catalytic oxidation and NH 3 Secondary mixing is performed to extend the time between exhaust gas and NH 3 The residence time in the mixing area makes the two mixed more evenly, which is conducive to the full denitration reaction in the subsequent denitration module. Compared with the traditional device without a mixing area and only mixing once in the second air intake pipe, the exhaust gas and NH 3The uniformity of mixing, NO in exhaust gas x Convert to N 2 The conversion rate is higher; compared with a cylindrical body with no holes on the circumference and open on both sides, the design of the cylindrical body of the present invention increases the conversion of exhaust gas and NH 3 The residence time of the mixed gas in the mixing area further makes the two mixed more evenly and further improves the NO in the exhaust gas x conversion rate.

[0022] Preferably, the openings on the circumference of the cylindrical body are evenly distributed.

[0023] Preferably, the shape of the peripheral openings includes any one of rectangle, circle or rhombus, or a combination of at least two of them, wherein typical but non-limiting combinations include a combination of rectangle and circle, a combination of rectangle and rhombus, or a combination of circle and rhombus, etc.

[0024] Preferably, the number of the peripheral openings is 4 to 8, for example, 4, 5, 6, 7 or 8.

[0025] Preferably, the total opening area of ​​the circumferential openings accounts for ≥80% of the total circumferential area of ​​the cylindrical body, for example, it may be 80%, 82%, 85%, 93%, 95% or 99%, etc., preferably 80% to 85%.

[0026] The present invention further preferably has 4 to 8 peripheral openings, and the total opening area of ​​the peripheral openings accounts for 80 to 85% of the total peripheral area of ​​the cylindrical body, further improving the separation of exhaust gas and NH 3 The residence time in the mixing area allows the two to mix more fully, which is beneficial to the subsequent removal of NO x The same total opening area but a smaller number of peripheral openings, or the same number of peripheral openings but a larger total opening area, will result in the conversion of exhaust gas and NH 3 The residence time in the mixing area is short, resulting in insufficient mixing, which is not conducive to subsequent denitrification. If the total opening area is the same but the number of peripheral openings is large, or the number of peripheral openings is the same but the total opening area is small, the mixing speed of the two will be too slow, slowing down the entire post-treatment process.

[0027] Preferably, a catalytic oxidation catalyst is arranged in the catalytic oxidation module, and the catalytic oxidation catalyst comprises a first honeycomb carrier and a first catalyst coating.

[0028] Preferably, the diameter of the first honeycomb carrier is 150-300 mm, for example, it may be 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm or 300 mm.

[0029] Preferably, the length of the catalytic oxidation module accounts for 7% to 12% of the total length of the exhaust gas after-treatment device, for example, it may be 7%, 9%, 11% or 12%.

[0030] Preferably, a spoiler is further provided between the first air intake duct and the catalytic oxidation module.

[0031] Preferably, the spoiler comprises a circular plate with circular holes evenly distributed thereon.

[0032] Preferably, the spoiler has a thickness of 20-50 mm, for example, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm or 50 mm.

[0033] Preferably, the spoiler is made of stainless steel.

[0034] The present invention further arranges a spoiler between the first air intake duct and the catalytic oxidation treatment module. The exhaust gas is rectified by the spoiler, and the airflow distribution is more uniform, which is conducive to subsequent sufficient catalytic oxidation. If the spoiler is not arranged, the exhaust gas entering the catalytic oxidation module is unevenly distributed, resulting in insufficient catalytic oxidation of methanol, formaldehyde, formic acid, CO and NO in the exhaust gas, thereby causing the exhaust gas emissions to still not meet the standards.

[0035] Preferably, ammonia injection components are symmetrically arranged on the second air intake pipe.

[0036] Preferably, the number of spray holes of the ammonia spray component is ≥4, for example, it can be 4, 5, 6, 7 or 8, and is preferably 4-6.

[0037] Preferably, the spray holes of the ammonia spray component are evenly distributed in radial direction.

[0038] Preferably, the diameter of the spray hole of the ammonia spray component is 0.4-0.8 mm, for example, it can be 0.4 mm, 0.5 mm, 0.7 mm or 0.8 mm.

[0039] Preferably, the ammonia spraying component is also provided with a heat insulation component.

[0040] It is worth noting that the function of the ammonia injection component of the present invention is to provide vaporized NH 3 , providing NH for subsequent denitrification reactions 3 The ammonia source is selected from any one of urea, aqueous ammonia or liquid ammonia, or a combination of at least two of them, wherein typical but non-limiting combinations include a combination of urea and aqueous ammonia, a combination of urea and liquid ammonia, or a combination of aqueous ammonia and liquid ammonia, etc., preferably urea.

[0041] Urea decomposes to form NH 3 The equation is as follows:

[0042] CO(NH2 ) 2 +H 2 O→2NH 3 +CO 2

[0043] The present invention further optimizes the number and diameter of the spray holes of the ammonia spray component, so that NH 3 More uniform distribution is beneficial to the exhaust gas and NH 3 The uniform mixing is conducive to the subsequent selective catalytic reduction reaction (SCR), so that the exhaust gas can be fully denitrated.

[0044] Preferably, at least two (eg, two, three or four, etc.) parallel-arranged denitration catalysts are provided in the denitration module; the denitration catalyst comprises a second honeycomb carrier and a second catalyst coating.

[0045] Preferably, the diameter of the second honeycomb carrier is 150-300 mm, for example, it may be 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 280 mm or 300 mm.

[0046] Preferably, the length of the denitration module accounts for 7% to 12% of the total length of the exhaust gas post-treatment device, for example, it may be 7%, 9%, 10% or 12%.

[0047] Preferably, a second air guide cover is provided between the first air intake duct and the spoiler.

[0048] Preferably, a third air guide cover is provided between the catalytic oxidation device and the second air intake duct.

[0049] Preferably, a fourth air guide cover is provided between the denitration module and the gas outlet pipe.

[0050] Preferably, a control valve is provided between the ammonia injection component and the mixing area.

[0051] In a second aspect, the present invention provides an exhaust gas post-treatment method, which is performed using the exhaust gas post-treatment device described in the first aspect.

[0052] The exhaust gas post-treatment method of the present invention adopts the exhaust gas post-treatment device described in the first aspect to carry out, through the control strategy of high selectivity MOC+dual SCR (reaction in the catalytic oxidation module+two catalytic reduction reactions in the denitration module), so that the incomplete combustion of methanol, by-products formaldehyde and formic acid, and CO, NO in the exhaust gas of the methanol fuel engine are reduced to 100% by weight. x Fully converted into harmless CO 2 、N 2 and H 2O, so that the exhaust gas emission meets the standard and the treatment efficiency of the exhaust gas of the methanol fuel engine is improved; and the exhaust gas post-treatment method has a simple operation process and low treatment cost.

[0053] Preferably, the exhaust gas post-treatment method comprises the following steps:

[0054] The exhaust gas is first catalytically oxidized by the first catalyst coating and then reacts with NH 3 The mixture is mixed and then denitrated under the action of a second catalyst coating to obtain purified gas.

[0055] Preferably, in terms of volume percentage, the exhaust gas includes 1-13% methanol, 0.03-1% formaldehyde, 0.03-1% formic acid, 0.01-2% carbon monoxide and 0.1-4% nitrogen oxides, with the remainder being air.

[0056] For the aftertreatment of exhaust gas from a methanol fuel engine, according to different working conditions of the methanol fuel engine, the exhaust gas includes 1-13% methanol, for example, 1%, 1.5%, 5%, 7.5%, 8.9%, 10.1%, 12%, 12.5% ​​or 13%, etc.; 0.03-1% formaldehyde, for example, 0.03%, 0.09%, 0.25%, 0.33%, 0.54%, 0.67%, 0.71%, 0.88%, 0.91% or 1%, etc.; 0.03-1% formic acid, for example, 0.03%, 0.11%, 0.3%, 0.37%, 0.46%, 0.73%, 0.78%, 0.84%, 0.90% or 1% etc.; 0.01-2% carbon monoxide, for example, it can be 0.01%, 0.18%, 0.23%, 0.57%, 1.55%, 1.59%, 1.68%, 1.82%, 1.98% or 2% etc.; 0.1-4% nitrogen oxides, for example, it can be 0.1%, 0.28%, 1.43%, 1.87%, 2.31%, 2.66%, 3.26%, 3.52%, 3.99% or 4% etc.

[0057] Preferably, the exhaust gas is subjected to turbulence before the catalytic oxidation treatment.

[0058] Preferably, the first catalyst coating layer comprises a first carrier and a first active component.

[0059] Preferably, the first carrier comprises β-molecular sieve and / or ZSM-5 molecular sieve.

[0060] Preferably, the first active component comprises a noble metal element or a combination of a noble metal element and a metal oxide, preferably a combination of a noble metal element and a metal oxide.

[0061] Preferably, the mass ratio of the noble metal element to the metal oxide is 1:(1-100), for example, it can be 1:1, 1:10, 1:20, 1:40, 1:50, 1:60, 1:70, 1:90 or 1:100, etc., preferably 1:(50-70).

[0062] The first active component of the present invention is preferably a combination of a noble metal element and a metal oxide, and further preferably the mass ratio thereof is 1:(50-70). The noble metal element is dispersed by the metal oxide to improve the utilization rate of the noble metal, thereby increasing the conversion rate of impurity gases in the exhaust gas and improving the exhaust gas treatment effect.

[0063] Preferably, the noble metal element includes Pt and / or Pd.

[0064] Preferably, the metal oxide comprises La 2 O 3 , BaO or CeO 2 Any one or a combination of at least two of the following, wherein a typical but non-limiting combination includes La 2 O 3 Combination of BaO and CeO 2 Combination or La 2 O 3 and CeO 2 combinations of etc.

[0065] The present invention further prefers the type of active component of the first catalyst coating to have high selectivity, thereby avoiding the secondary pollution problem caused by a large amount of formaldehyde produced due to the difficulty in complete catalytic oxidation of methanol.

[0066] Preferably, the NH 3 The volume ratio of nitrogen oxides is (1.0-1.4):1, for example, it can be 1:1, 1.1:1, 1.2:1, 1.3:1 or 1.4:1.

[0067] Preferably, the second catalyst coating comprises a second carrier and a second active component.

[0068] Preferably, the second carrier comprises ZSM-5 molecular sieve and / or SAPO-34 molecular sieve.

[0069] Preferably, the second active component comprises Cu.

[0070] Preferably, the mass content of the second active component in the second catalyst coating is 1.5wt% to 5.0wt%, for example, it can be 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt% or 5.0wt%, etc.

[0071] The present invention further prefers the type of the second carrier and the second active component of the second catalyst coating, which has a certain effect on NO x The window temperature of full conversion is greater than 380°C, which can meet the complex working conditions of methanol fuel engines; and it is further preferred that the mass content of the second active component is 1.5wt% to 5.0wt%, further making NO x Fully converted into N 2 , so that the exhaust gas meets the emission standards.

[0072] As a further preferred technical solution of the present invention, the denitration method comprises:

[0073] After the turbulence, the exhaust gas is first subjected to catalytic oxidation treatment under the action of the first catalyst coating, then mixed with NH3, and then subjected to denitration treatment under the action of the second catalyst coating to obtain purified gas;

[0074] The NH 3 The volume ratio of nitrogen oxides is (1.0-1.4):1;

[0075] The first catalyst coating includes a first carrier and a first active component; the first carrier includes β-molecular sieve and / or ZSM-5 molecular sieve; the first active component includes a combination of a noble metal element and a metal oxide in a mass ratio of 1:(1-100); the noble metal element includes Pt and / or Pd; the metal oxide includes La 2 O 3 , BaO or CeO 2 Any one or a combination of at least two of the following:

[0076] The second catalyst coating layer includes a second carrier and a second active component; the second carrier includes a ZSM-5 molecular sieve and / or a SAPO-34 molecular sieve; the second active component includes Cu; the mass content of the second active component in the second catalyst coating layer is 1.5wt% to 5.0wt%.

[0077] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0078] Compared with the prior art, the present invention has the following beneficial effects:

[0079] (1) The exhaust gas aftertreatment device provided by the present invention utilizes the synergistic effect of the catalytic oxidation module, the ammonia injection component, the mixing area and the denitration module, and is matched with the first catalyst coating and the second catalyst coating to fully oxidize the incompletely burned methanol, formaldehyde, formic acid, CO and NO in the exhaust gas of the methanol fuel engine into CO 2 , H 2 O and NO 2 , and NO 2 Fully reduced to N 2 ; and further add spoilers and mixing areas, etc., to further enable the catalytic oxidation reaction and denitrification reaction (catalytic reduction) to proceed fully, so that the exhaust gas meets the emission standards and avoids pollution to the environment.

[0080] (2) The exhaust gas post-treatment method provided by the present invention is carried out by using the above-mentioned exhaust gas post-treatment device, and further improving the selectivity of each catalyst by selecting the first catalyst coating and the second catalyst coating, thereby improving the oxidation rate of unburned methanol, formaldehyde, formic acid and CO, preferably up to 98% or more; and improving NO x The conversion rate is preferably as high as 97% or more, meeting the needs of various working conditions of methanol fuel engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 is a schematic structural diagram of an exhaust gas post-treatment device provided in Example 1 of the present invention;

[0082] Figure 2 is a schematic side structural diagram of the spoiler in the exhaust gas after-treatment device provided in Example 1 of the present invention;

[0083] Figure 3 45° top view of the structure of the cylindrical body in the exhaust gas after-treatment device provided in Example 1 of the present invention when placed longitudinally; wherein the shaded portion indicates a closed state;

[0084] In the figure, 1. first air intake duct; 2. second air guide cover; 3. spoiler; 4. catalytic oxidation module; 5. third air guide cover; 6. second air intake duct; 7. ammonia injection component; 8. control valve; 9. mixing area; 901. cylindrical body; 902. first air guide cover; 10. denitrification module; 11. fourth air guide cover; 12. outlet duct. DETAILED DESCRIPTION

[0085] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0086] It should be understood that, in the description of the present invention, the orientation or positional relationship indicated by the terms "outer wall", "one side", "close to", "far away" or "radial" is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and the terms "first", "second" and the like do not indicate the degree of importance, and therefore cannot be understood as a limitation on the present invention.

[0087] 1. Implementation

[0088] Example 1

[0089] This embodiment provides an exhaust gas post-treatment device, such as Figure 1 As shown, the exhaust gas post-treatment device comprises a first air intake pipe 1, a catalytic oxidation module 4, a second air intake pipe 6, a mixing area 9, a denitration module 10 and an air outlet pipe 12 connected in sequence; the second air intake pipe 6 is provided with an ammonia injection component 7;

[0090] The mixing area 9 is provided with a first air guide 902 and a cylindrical body 901 with peripheral openings; the cylindrical body is open on one side close to the ammonia spraying component 7 and closed on the other side away from the ammonia spraying component 7; the peripheral openings of the cylindrical body 901 are evenly distributed; the peripheral openings are rectangular in shape; the number of the peripheral openings is 6; the total opening area of ​​the peripheral openings accounts for 85% of the total peripheral area of ​​the cylindrical body 901 (e.g., Figure 3 shown);

[0091] The catalytic oxidation module 4 is provided with a catalytic oxidation catalyst, and the catalytic oxidation catalyst includes a first honeycomb carrier and a first catalyst coating; the diameter of the first honeycomb carrier is 200 mm; the length of the catalytic oxidation module 4 accounts for 8% of the total length of the exhaust gas post-treatment device; a spoiler 3 is further provided between the first intake pipe 1 and the catalytic oxidation module 4; the spoiler 3 is a circular plate with evenly distributed circular holes (such as Figure 2 As shown); the thickness of the spoiler 3 is 35 mm;

[0092] The second air intake pipe 6 is symmetrically provided with an ammonia spraying component 7; the number of spray holes of the ammonia spraying component 7 is 4; the spray holes of the ammonia spraying component 7 are evenly distributed in radial direction; the diameter of the spray holes of the ammonia spraying component 7 is 0.5 mm;

[0093] The denitration module 10 is provided with a denitration catalyst; the denitration catalyst comprises two denitration catalysts arranged in parallel; the denitration catalyst comprises a second honeycomb carrier and a second catalyst coating; the diameter of the second honeycomb carrier is 200 mm; the length of the denitration module 10 accounts for 13% of the total length of the exhaust gas post-treatment device;

[0094] A second air guide cover 2 is arranged between the first air intake pipe 1 and the spoiler 3; a third air guide cover 5 is arranged between the catalytic oxidation module 4 and the second air intake pipe 6; a fourth air guide cover 11 is arranged between the denitration module 10 and the air outlet pipe 12; and a control valve 8 is arranged between the ammonia injection component 7 and the mixing area 9.

[0095] This embodiment also provides an exhaust gas post-treatment method using the exhaust gas post-treatment device, the exhaust gas post-treatment method comprising the following steps:

[0096] After the exhaust gas is turbulent, it is first catalytically oxidized by the first catalyst coating and then reacts with NH 3 The mixture is mixed and then denitrated under the action of a second catalyst coating to obtain purified gas;

[0097] The nitrogen oxides and NH 3 The volume ratio is 1.05:1;

[0098] The first carrier in the first catalyst coating is a β-molecular sieve, and the first active component is Pt and La in a mass ratio of 1:60. 2 O 3 The second carrier in the second catalyst coating is ZSM-5 molecular sieve, the second active component is Cu, and the mass content of Cu is 3.5wt%.

[0099] The exhaust gas described in this embodiment is the exhaust gas of a methanol fuel engine, and its original exhaust components, corresponding contents and corresponding oxidation rates / conversion rates are shown in Table 1;

[0100] Table 1

[0101] Components <![CDATA[CH 4 The]]> <![CDATA[CH 2 The]]> <![CDATA[CH 2 THE 2 ]]> CO <![CDATA[NO x ]]> Volume content / v% 2.33 0.19 0.05 0.13 2.2 Oxidation rate / conversion rate / % 99.33 98.61 98.59 99.98 97.31

[0102] Example 2

[0103] This embodiment provides an exhaust gas post-treatment device, which includes a first air intake pipe, a catalytic oxidation module, a second air intake pipe, a mixing area, a denitration module and an exhaust pipe connected in sequence; an ammonia spraying component is provided on the second air intake pipe;

[0104] The mixing area is provided with a first air guide cover and a cylindrical body with peripheral openings; the cylindrical body is open on one side close to the ammonia spraying component and closed on the other side away from the ammonia spraying component; the peripheral openings of the cylindrical body are evenly distributed; the peripheral openings are rectangular in shape; the number of the peripheral openings is 8; the total opening area of ​​the peripheral openings accounts for 83% of the total peripheral area of ​​the cylindrical body;

[0105] The catalytic oxidation module is provided with a catalytic oxidation catalyst, and the catalytic oxidation catalyst includes a first honeycomb carrier and a first catalyst coating; the diameter of the first honeycomb carrier is 300 mm; the length of the catalytic oxidation module accounts for 10% of the total length of the exhaust gas after-treatment device; a spoiler is also provided between the first intake pipe and the catalytic oxidation module; the spoiler is a circular plate with evenly distributed circular holes; the thickness of the spoiler is 20 mm;

[0106] The second air intake pipe is symmetrically provided with an ammonia spray component; the number of spray holes of the ammonia spray component is 6; the spray holes of the ammonia spray component are evenly distributed in radial direction; the diameter of the spray holes of the ammonia spray component is 0.4 mm;

[0107] A denitration catalyst is arranged in the denitration module; the denitration catalyst comprises two second honeycomb carriers and a second catalyst coating arranged in parallel; the diameter of the second honeycomb carrier is 300 mm; the length of the denitration module accounts for 18% of the total length of the exhaust gas post-treatment device;

[0108] A second air guide cover is arranged between the first air intake pipe and the spoiler; a third air guide cover is arranged between the catalytic oxidation module and the second air intake pipe; a fourth air guide cover is arranged between the denitration module and the air outlet pipe; and a control valve is arranged between the ammonia injection component and the mixing area.

[0109] This embodiment also provides an exhaust gas post-treatment method using the exhaust gas post-treatment device, the exhaust gas post-treatment method comprising the following steps:

[0110] After the exhaust gas is turbulent, it is first catalytically oxidized by the first catalyst coating and then reacts with NH 3 The mixture is mixed and then denitrated under the action of a second catalyst coating to obtain purified gas;

[0111] The nitrogen oxides and NH 3 The volume ratio is 1.1:1;

[0112] The first carrier in the first catalyst coating is ZSM-5 molecular sieve, and the first active component is Pd and BaO in a mass ratio of 1:50; the second carrier in the second catalyst coating is SAPO-34 molecular sieve, and the second active component is Cu, and the mass content of Cu is 1.5wt%.

[0113] The exhaust gas described in this embodiment is the exhaust gas of a methanol fuel engine, and its original exhaust components, corresponding contents and corresponding oxidation rates / conversion rates are shown in Table 2;

[0114] Table 2

[0115] Components <![CDATA[CH 4 The]]> <![CDATA[CH 2 The]]> <![CDATA[CH 2 THE 2 ]]> CO <![CDATA[NO x ]]> Volume content / v% 5.33 0.79 0.85 1.13 1.2 Oxidation rate / conversion rate / % 99.56 99.11 99.93 99.99 99.31

[0116] Example 3

[0117] This embodiment provides an exhaust gas post-treatment device, which includes a first air intake pipe, a catalytic oxidation module, a second air intake pipe, a mixing area, a denitration module and an exhaust pipe connected in sequence; an ammonia spraying component is provided on the second air intake pipe;

[0118] The mixing area is provided with a first air guide cover and a cylindrical body with peripheral openings; the cylindrical body is open on one side close to the ammonia spraying component and closed on the other side away from the ammonia spraying component; the peripheral openings of the cylindrical body are evenly distributed; the peripheral openings are rectangular in shape; the number of the peripheral openings is 4; the total opening area of ​​the peripheral openings accounts for 80% of the total peripheral area of ​​the cylindrical body;

[0119] The catalytic oxidation module is provided with a catalytic oxidation catalyst, and the catalytic oxidation catalyst includes a first honeycomb carrier and a first catalyst coating; the diameter of the first honeycomb carrier is 150 mm; the length of the catalytic oxidation module accounts for 12% of the total length of the exhaust gas after-treatment device; a spoiler is also provided between the first intake pipe and the catalytic oxidation module; the spoiler is a circular plate with evenly distributed circular holes; the thickness of the spoiler is 50 mm;

[0120] The second air intake pipe is symmetrically provided with an ammonia spray component; the number of spray holes of the ammonia spray component is 5; the spray holes of the ammonia spray component are evenly distributed in radial direction; the diameter of the spray holes of the ammonia spray component is 0.8 mm;

[0121] A denitration catalyst is arranged in the denitration module; the denitration catalyst comprises two second honeycomb carriers and a second catalyst coating arranged in parallel; the diameter of the second honeycomb carrier is 150 mm; the length of the denitration module accounts for 20% of the total length of the exhaust gas post-treatment device;

[0122] A second air guide cover is arranged between the first air intake pipe and the spoiler; a third air guide cover is arranged between the catalytic oxidation module and the second air intake pipe; a fourth air guide cover is arranged between the denitration module and the air outlet pipe; and a control valve is arranged between the ammonia injection component and the mixing area.

[0123] This embodiment also provides an exhaust gas post-treatment method using the exhaust gas post-treatment device, the exhaust gas post-treatment method comprising the following steps:

[0124] After the exhaust gas is turbulent, it is first catalytically oxidized by the first catalyst coating and then reacts with NH 3 The mixture is mixed and then denitrated under the action of a second catalyst coating to obtain purified gas;

[0125] The nitrogen oxides and NH 3 The volume ratio is 1.2:1;

[0126] The first carrier in the first catalyst coating is β-molecular sieve, and the first active component is Pt and BaO with a mass ratio of 1:100; the second carrier in the second catalyst coating is ZSM-5 molecular sieve, and the second active component is Cu, and the mass content of Cu is 5.0wt%.

[0127] The exhaust gas described in this embodiment is the exhaust gas of a methanol fuel engine, and its original exhaust components, corresponding contents and corresponding oxidation rates / conversion rates are shown in Table 3;

[0128] Table 3

[0129] Components <![CDATA[CH 4 The]]> <![CDATA[CH 2 The]]> <![CDATA[CH 2 THE 2 ]]> CO <![CDATA[NO x ]]> Volume content / v% 8.58 0.88 0.94 1.73 2.91 Conversion rate / % 98.16 98.78 98.94 99.99 98.55

[0130] Example 4

[0131] This embodiment provides an exhaust gas after-treatment device, which is the same as the first embodiment except that the spoiler is not provided.

[0132] This embodiment further provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the exhaust gas post-treatment device provided in this embodiment is used for the exhaust gas post-treatment method.

[0133] Example 5

[0134] This embodiment provides an exhaust gas after-treatment device, which is the same as that of Embodiment 1 except that the diameters of the first honeycomb carrier and the second honeycomb carrier are both 140 mm.

[0135] This embodiment further provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the exhaust gas post-treatment device provided in this embodiment is used for the exhaust gas post-treatment method.

[0136] Example 6

[0137] This embodiment provides an exhaust gas after-treatment device, which is the same as that of Embodiment 1 except that the diameters of the first honeycomb carrier and the second honeycomb carrier are both 320 mm.

[0138] This embodiment further provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the exhaust gas post-treatment device provided in this embodiment is used for the exhaust gas post-treatment method.

[0139] Example 7

[0140] This embodiment provides an exhaust gas after-treatment device, which is the same as the first embodiment except that the number of the peripheral openings of the cylindrical body is 3.

[0141] This embodiment further provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the exhaust gas post-treatment device provided in this embodiment is used for the exhaust gas post-treatment method.

[0142] Example 8

[0143] This embodiment provides an exhaust gas after-treatment device, which is the same as Embodiment 1 except that the total opening area of ​​the peripheral openings accounts for 75% of the total peripheral area of ​​the cylindrical body.

[0144] This embodiment further provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the exhaust gas post-treatment device provided in this embodiment is used for the exhaust gas post-treatment method.

[0145] Example 9

[0146] This embodiment provides an exhaust gas after-treatment device, which is the same as Embodiment 1 except that the total opening area of ​​the peripheral openings accounts for 90% of the total peripheral area of ​​the cylindrical body.

[0147] This embodiment further provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the exhaust gas post-treatment device provided in this embodiment is used for the exhaust gas post-treatment method.

[0148] Example 10

[0149] This embodiment provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the first active component in the first catalytic coating is only Pt.

[0150] Embodiment 11

[0151] This embodiment provides an exhaust gas post-treatment method, wherein the exhaust gas post-treatment method removes the first active components Pt and La in the first catalytic coating. 2 O 3 Except that the mass ratio of is 1:45, the rest is the same as that in Example 1.

[0152] Example 12

[0153] This embodiment provides an exhaust gas post-treatment method, wherein the exhaust gas post-treatment method removes the first active components Pt and La in the first catalytic coating. 2 O 3 Except that the mass ratio of is 1:75, the rest is the same as in Example 1.

[0154] Example 13

[0155] This embodiment provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the mass content of Cu in the second catalytic coating is 1.2 wt %.

[0156] Embodiment 14

[0157] This embodiment provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the mass content of Cu in the second catalyst coating is 5.2 wt %.

[0158] Embodiment 15

[0159] This embodiment provides an exhaust gas post-treatment method, which is the same as that of Embodiment 1 except that the active component in the second catalyst coating is Pt.

[0160] 2. Comparison

[0161] Comparative Example 1

[0162] This comparative example provides an exhaust gas after-treatment device, which is the same as Example 1 except that the circumference of the cylindrical body in the mixing area is not opened with holes, but both sides are open.

[0163] This comparative example also provides an exhaust gas post-treatment method, which is the same as Example 1 except that the exhaust gas post-treatment device provided in this comparative example is used.

[0164] Comparative Example 2

[0165] This comparative example provides an exhaust gas post-treatment device, which is the same as the first embodiment except that the mixing area is not provided.

[0166] This comparative example also provides an exhaust gas post-treatment method, which is the same as Example 1 except that the exhaust gas post-treatment device provided in this comparative example is used.

[0167] Comparative Example 3

[0168] This comparative example provides an exhaust gas after-treatment device, which is the same as Example 1 except that a mixing area is directly provided after the catalytic oxidation module instead of a second air intake pipe, and an ammonia injection component is provided on a first air guide cover in the mixing area.

[0169] This comparative example also provides an exhaust gas post-treatment method, which is the same as Example 1 except that the exhaust gas post-treatment device provided in this comparative example is used.

[0170] 3. Test Results

[0171] The oxidation rates of unburned methanol, formaldehyde, formic acid and CO and NO in the exhaust gas post-treatment methods provided in the above embodiments and comparative examples were tested and calculated respectively. x The conversion rate is shown in Table 4.

[0172] Table 4

[0173]

[0174]

[0175] From Table 4, we can see the following points:

[0176] (1) It can be seen from Examples 1 to 3 that the exhaust gas aftertreatment device and method provided by the present invention can fully oxidize the incompletely burned methanol, byproduct formaldehyde, formic acid and CO in the exhaust gas of a methanol fuel engine, with an oxidation rate of more than 98%; NO x The conversion rate is as high as over 97%, which makes the exhaust gas meet the emission standards and avoids environmental pollution.

[0177] (2) Combining Example 1 with Examples 4 to 6, it can be seen that compared with Example 1, Example 4 does not have a spoiler, which leads to uneven airflow entering the catalytic oxidation module, thereby causing a decrease in the oxidation rate of formaldehyde, formaldehyde, CO and NO. The exhaust gas entering the denitration module subsequently still contains methanol and formaldehyde, which will react with NH 3 reaction, generating hydrogen cyanide and NO x The conversion rate decreases, and the exhaust gas emissions still do not meet the standards; in Example 5, since the diameters of the first honeycomb carrier and the second honeycomb carrier are too small, the entire exhaust gas treatment process is slowed down; in Example 6, the diameters of the first honeycomb carrier and the second honeycomb carrier are too large, resulting in the exhaust gas passing through the catalytic oxidation device quickly, the catalytic oxidation reaction is insufficient, and the oxidation rates of various pollutants decrease; this shows that the present invention further improves the catalytic oxidation effect of pollutants in the exhaust gas by further arranging a spoiler or further preferably the diameter of the first honeycomb carrier is 150 to 300 mm.

[0178] (3) Combining Example 1 with Examples 7 to 9, it can be seen that the number of openings on the circumferential side of the cylindrical body in Example 7 is small, resulting in a larger average area of ​​each opening, which reduces the waste gas and NH 3 The residence time in the mixing device leads to NO x The conversion rate of NO decreased to 71.05%. The total opening area of ​​the peripheral openings in Example 8 was small, which slowed down the entire exhaust gas treatment process and increased the reaction kinetic resistance. x The conversion rate of NO decreased to 72.88%. The total area of ​​the peripheral openings in Example 9 is relatively large, and its effect is equivalent to that of the cylindrical body with both sides open.x The conversion rate of NO is reduced to 75.05%. This shows that the present invention further preferably has 4 to 8 peripheral openings, and the total opening area of ​​the peripheral openings accounts for 80% to 85% of the total peripheral area of ​​the cylindrical body, which further improves the NO x conversion rate of conversion rate.

[0179] (4) Combining Example 1 with Examples 10 to 12, it can be seen that in Example 10, the first active component in the first catalytic coating is only Pt, and no metal oxide is added; and in Example 11, the first active component in the first catalytic coating is Pt and La. 2 O 3 The larger the value, the less the oxidation rate will be. 2 O 3 It is too small and does not significantly improve the oxidation effect of incompletely burned methanol, by-products formaldehyde, formic acid, CO and NO, but increases the cost of exhaust gas treatment. This shows that the present invention further prefers that the first active component in the first catalytic coating adopts a combination of a noble metal element and a metal oxide, and further prefers that the mass ratio of the two is 1: (50-70), which further improves the oxidation effect of incompletely burned methanol, by-product formaldehyde, formic acid, CO and NO in the exhaust gas of a methanol fuel engine.

[0180] (5) Combining Example 1 with Examples 13 to 15, it can be seen that the mass content of Cu in the second catalytic coating in Example 13 is too small, resulting in incomplete denitration treatment, NO x The conversion rate of NO decreased to 43.12%; the mass content of Cu in the second catalytic coating in Example 14 was too high, and NO x The conversion effect was not significantly improved, and the post-processing cost increased; in Example 15, the second active component was replaced by Pt, and Pt has a high x The selective catalytic reduction reaction is ineffective, causing the catalyst to lose its SCR function.

[0181] (6) Based on Example 1 and Comparative Examples 1 to 3, it can be seen that: since the cylindrical body in the mixing area in Comparative Example 1 has no holes on the circumference, but is open on both sides, the exhaust gas and NH 3 The residence time in the mixing area is short and the mixing is insufficient, resulting in NO x The conversion rate of the exhaust gas and NH 3 The air can only be mixed once in the second intake pipe, which results in uneven mixing and NO xThe conversion rate of NO was reduced to 43.26%. In Comparative Example 3, since the second air intake pipe was not provided, a mixing area was provided directly after the catalytic oxidation module, and the ammonia injection component was provided on the first guide cover of the mixing area, it could only be mixed once in the mixing device and could not be mixed evenly, resulting in NO x The conversion rate dropped to 65.74%.

[0182] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. An exhaust gas post-treatment device, characterized in that: Along the exhaust gas flow direction, the exhaust gas post-treatment device includes a first air intake pipe, a catalytic oxidation module, a second air intake pipe, a mixing area, a denitration module and an exhaust pipe connected in sequence; the second air intake pipe is provided with an ammonia spraying component; The mixing area is provided with a first air guide cover and a cylindrical body with holes on the circumferential side; and the cylindrical body is open at a side close to the ammonia injection component and closed at a side away from the ammonia injection component.

2. The exhaust gas aftertreatment device according to claim 1, characterized in that: The openings on the circumference of the cylindrical body are evenly distributed; Preferably, the shape of the peripheral openings includes any one of a rectangle, a circle or a diamond, or a combination of at least two of them; Preferably, the number of the peripheral openings is 4 to 8; Preferably, the total opening area of ​​the peripheral openings accounts for ≥80% of the total peripheral area of ​​the cylindrical body, preferably 80-85%.

3. The exhaust gas aftertreatment device according to claim 1 or 2, characterized in that: The catalytic oxidation module is provided with a catalytic oxidation catalyst, and the catalytic oxidation catalyst comprises a first honeycomb carrier and a first catalyst coating; Preferably, the diameter of the first honeycomb carrier is 150-300 mm; Preferably, the length of the catalytic oxidation module accounts for 7% to 12% of the total length of the exhaust gas after-treatment device; Preferably, a spoiler is further provided between the first air intake duct and the catalytic oxidation module; Preferably, the spoiler comprises a circular plate with evenly distributed circular holes; preferably, the thickness of the spoiler is 20 to 50 mm.

4. The exhaust gas post-treatment device according to any one of claims 1 to 3, characterized in that: Ammonia spraying components are symmetrically arranged on the second air intake pipe; Preferably, the number of spray holes of the ammonia spray component is ≥ 4, preferably 4 to 6; Preferably, the spray holes of the ammonia spray component are evenly distributed in radial direction; Preferably, the diameter of the spray hole of the ammonia spray component is 0.4-0.8 mm.

5. The exhaust gas post-treatment device according to any one of claims 1 to 4, characterized in that: At least two parallel denitration catalysts are arranged in the denitration module; the denitration catalyst comprises a second honeycomb carrier and a second catalyst coating; Preferably, the diameter of the second honeycomb carrier is 150-300 mm; Preferably, the length of the denitration module accounts for 12-20% of the total length of the exhaust gas post-treatment device.

6. A method for post-treatment of exhaust gas, characterized in that: The exhaust gas post-treatment method is carried out using the exhaust gas post-treatment device according to any one of claims 1 to 5.

7. The exhaust gas post-treatment method according to claim 6, characterized in that: The exhaust gas post-treatment method comprises the following steps: The exhaust gas is first subjected to catalytic oxidation treatment under the action of the first catalyst coating, then mixed with NH3, and then subjected to denitration treatment under the action of the second catalyst coating to obtain purified gas.

8. The exhaust gas post-treatment method according to claim 6 or 7, characterized in that: The exhaust gas includes 1-13% methanol, 0.03-1% formaldehyde, 0.03-1% formic acid, 0.01-2% carbon monoxide and 0.1-4% nitrogen oxides in terms of volume percentage; Preferably, the exhaust gas is subjected to turbulence before the catalytic oxidation treatment; Preferably, the first catalyst coating comprises a first carrier and a first active component; Preferably, the first carrier comprises β-molecular sieve and / or ZSM-5 molecular sieve; Preferably, the first active component comprises a noble metal element or a combination of a noble metal element and a metal oxide, preferably a combination of a noble metal element and a metal oxide; Preferably, the mass ratio of the noble metal element to the metal oxide is 1:(1-100), preferably 1:(50-70); Preferably, the noble metal element comprises Pt and / or Pd; Preferably, the metal oxide includes any one of La2O3, BaO or CeO2, or a combination of at least two of them.

9. The exhaust gas post-treatment method according to any one of claims 6 to 8, characterized in that: The volume ratio of NH3 to nitrogen oxides in the exhaust gas is (1.0-1.4):1; Preferably, the second catalyst coating comprises a second carrier and a second active component; Preferably, the second carrier comprises ZSM-5 molecular sieve and / or SAPO-34 molecular sieve; Preferably, the second active component comprises Cu; Preferably, the mass content of the second active component in the second catalyst coating is 1.5 wt% to 5.0 wt%.

10. The exhaust gas post-treatment method according to any one of claims 7 to 9, characterized in that: The method comprises the following steps: After the turbulence, the exhaust gas is first subjected to catalytic oxidation treatment under the action of the first catalyst coating, then mixed with NH3, and then subjected to denitration treatment under the action of the second catalyst coating to obtain purified gas; The volume ratio of NH3 to nitrogen oxides in the exhaust gas is (1.0-1.4):1; The first catalyst coating includes a first carrier and a first active component; the first carrier includes a β-molecular sieve and / or a ZSM-5 molecular sieve; the first active component includes a combination of a noble metal element and a metal oxide in a mass ratio of 1:(1-100); The noble metal element includes Pt and / or Pd; the metal oxide includes any one of La2O3, BaO or CeO2 or a combination of at least two thereof; The second catalyst coating layer includes a second carrier and a second active component; the second carrier includes a ZSM-5 molecular sieve and / or a SAPO-34 molecular sieve; the second active component includes Cu; the mass content of the second active component in the second catalyst coating layer is 1.5wt% to 5.0wt%.

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