A device for preparing ammonia

Abstract

The present invention discloses a device for preparing ammonia, which is characterized by comprising an ammonia generator and a spoiler surface arranged on the inner wall of the ammonia generator, a support frame is arranged on the inner wall of the ammonia generator, and the support frame is provided with a spoiler surface; the number of the ammonia generator and the spoiler surface is at least one; the spoiler surface is arranged at the outlet of the ammonia generator. The spray gun is inserted into the ammonia generator, and the flue gas enters from the bottom inlet of the spoiler surface. The present invention has the advantages of high efficiency, simple structure, safety and reliability, energy saving and environmental protection, and low manufacturing and operating costs. The present invention improves the ammonia conversion rate of urea by optimizing the design of the ammonia generator structure. The arrangement of the spoiler surface can enhance the intensity of the turbulence and eddy current formed.

Description

Technical Field

[0001] The invention relates to a device for preparing ammonia, in particular to a device for improving the ammonia conversion rate of urea, and belongs to the field of flue gas denitration. Background Art

[0002] With the development of industrial economy, air pollution is becoming more and more serious. One of the main air pollutants is nitrogen oxides, which not only harm animals and plants, destroy the ozone layer, and irritate the human respiratory system, but are also one of the main substances causing greenhouse effect, acid rain and photochemical reactions. The emission restrictions on nitrogen oxides are becoming more stringent around the world.

[0003] At present, the main technical solutions for reducing nitrogen oxide emissions are: (1) low-nitrogen combustion technology, that is, controlling the generation of nitrogen oxides during the combustion process, which is mainly applicable to large coal-fired boilers, etc.; (2) Selective catalytic reduction technology (SCR, Selective Catalytic Reduction), which is the mainstream application technology in flue gas denitrification technology in my country; (3) Selective non-catalytic reduction technology (SNCR, Selective Non-Catalytic Reduction), which is mainly used for medium and small boilers such as waste incineration plants. The technology is mature, but its efficiency is lower than SCR process technology; (4) Selective catalytic reduction technology (SCR) + selective non-catalytic reduction technology (SNCR), which is mainly used for low nitrogen oxide emissions of large coal-fired boilers and site constraints, and is also more suitable for old boiler renovation projects.

[0004] The basic principle of mainstream selective catalytic reduction technology (SCR process technology) is to use a reducing agent (such as NH3, etc.) on the catalyst surface to convert nitrogen oxides into harmless nitrogen through catalytic action, thereby achieving the purpose of reducing nitrogen oxide emissions. The preparation technology of reducing agent ammonia plays a key role in the flue gas denitrification system.

[0005] Among the existing technical solutions involving the preparation of ammonia as a reducing agent for flue gas denitrification, Patent No. CN106966409A discloses an ammonia production system. Although this technology involves the preparation of ammonia as a reducing agent for flue gas denitrification, this technology uses a method of evaporating liquid ammonia to prepare ammonia; Patent No. CN108796537A discloses a thermal power plant electrolytic hydrogen production and ammonia synthesis system. Although this technology involves the preparation of ammonia as a reducing agent for flue gas denitrification, this technology uses a method of electrolyzing water to produce hydrogen and then synthesize ammonia.

[0006] CN106966409A and CN108796537A are respectively used for the preparation of ammonia gas, a reducing agent required for flue gas denitration systems. The liquid ammonia used in CN106966409A is highly harmful to the human body and is restricted for use as a dangerous article. CN108796537A uses a technology of electrolyzing water to produce hydrogen and then synthesizing ammonia gas with nitrogen. The technology involves complex processes and equipment, high costs, and low efficiency in generating ammonia gas, and is not suitable for the preparation of ammonia gas required for flue gas denitration systems.

[0007] In order to solve the problem of preparing ammonia as a reducing agent required for a flue gas denitrification system, the present invention proposes a device for preparing ammonia, which has the advantages of high efficiency, simple structure, safety and reliability, energy saving and environmental protection, and low manufacturing and operating costs. The present invention improves the ammonia conversion rate of urea by optimizing the design of the ammonia generator structure. Summary of the invention

[0008] The main purpose of the present invention is to solve the problem of preparing ammonia gas, a reducing agent required for a flue gas denitration system.

[0009] To achieve the above object, the technical solution adopted by the present invention is a device for preparing ammonia, characterized in that it includes an ammonia generator and a spoiler surface (6-2) arranged on the inner wall (6-1) of the ammonia generator, a support frame is arranged on the inner wall (6-1) of the ammonia generator, and the spoiler surface (6-2) is arranged on the support frame; the number of the ammonia generator and the spoiler surface is at least one; the spoiler surface (6-2) is arranged at the outlet of the ammonia generator. The spray gun (11) is inserted into the ammonia generator, and the smoke enters from the bottom inlet of the spoiler surface (6-2).

[0010] The device for preparing ammonia gas has a cross-sectional shape of a plurality of continuously connected curved or broken lines along the axial direction of the inner wall (6-1) of the ammonia gas generator, each of which is curved or broken line-shaped; the cross-sectional shape of the inner wall (6-1) of the ammonia gas generator is a structure that is wide in the middle and narrow at both ends; the axial length at the smoke inlet of the ammonia gas generator, i.e., the axial distance from the smoke inlet to the widest part of the cross-sectional shape of the ammonia gas generator, is smaller than the axial length at the smoke outlet of the ammonia gas generator, i.e., the axial distance from the smoke outlet to the widest part of the cross-sectional shape of the ammonia gas generator.

[0011] The cross-sectional shape of the spoiler surface (6-2) along the axial direction is a curve or a broken line.

[0012] In the device for preparing ammonia, each ammonia generator is connected in series or in parallel.

[0013] The device for preparing ammonia is characterized in that: each ammonia generator is arranged in series; Figure 2-1 and Figure 2-2Two specific modes of series arrangement are shown: the first mode is that a spoiler surface is provided on the inner wall of each ammonia generator, with a total of M spoiler surfaces; the second mode is that the Mth series ammonia generator spoiler surface (6-2-M) is only provided at the Mth series ammonia generator, with a total of one spoiler surface; the number and position of the spoiler surface arrangement are determined according to the results of numerical simulation calculations, and M is a positive integer.

[0014] The device for preparing ammonia is characterized in that: each ammonia generator is arranged in parallel; Figure 3 The figure shows a specific mode of parallel arrangement; the outlets of the various ammonia generators are connected in parallel via pipelines.

[0015] The device for preparing ammonia is characterized in that when the flue gas velocity in the flue is lower than 0.5 m / s, the spoiler surface (6-2) may not be added.

[0016] The device for preparing ammonia is characterized in that the optimal working condition of the device for preparing ammonia is that the flue gas temperature entering the ammonia generator is 300-650°C.

[0017] The urea solution is atomized in the ammonia generator (6) under the action of compressed air and the nozzle of the spray gun (11), such as Figure 1 The atomized urea micro-droplets diffuse along with the flow of flue gas and mix with the flue gas. The mixed flue gas forms turbulence and eddy current under the joint action of at least one arc-shaped inner wall (6-1) of the ammonia generator and the curved spoiler surface (6-2). The turbulence of the flue gas can enhance the intensity of diffusion of the urea micro-droplets in the flue gas, so that the urea micro-droplets and the flue gas are more fully mixed. The eddy current of the flue gas can prolong the time for the urea micro-droplets to generate ammonia in the ammonia generator (6). The atomized urea micro-droplets decompose to generate ammonia under the condition of flue gas temperature of 400-550° C. in the ammonia generator (6). The spoiler surface (6-2) plays a role in enhancing the intensity of the turbulence and eddy current formed.

[0018] Compared with the prior art, the present invention has the following beneficial effects.

[0019] The present invention provides a device for preparing ammonia, which has the advantages of high efficiency, simple structure, safety and reliability, energy saving and environmental protection, and low manufacturing and operating costs. The present invention improves the ammonia conversion rate of urea by optimizing the design of the ammonia generator structure. The arrangement of the spoiler surface can enhance the intensity of the turbulent and eddy currents formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a device for preparing ammonia.

[0021] In the figure: 6-1, inner wall of ammonia generator, 6-2, spoiler surface, 11, spray gun.

[0022] Figure 2-1 A schematic diagram of a series arrangement of a device structure for preparing ammonia.

[0023] In the figure: 6-1-M, the inner wall of the Mth ammonia generator, 6-2-M, the Mth spoiler surface; M is a positive integer.

[0024] Figure 2-2 A schematic diagram of a series arrangement of a device structure for preparing ammonia 2.

[0025] Figure 3 A schematic diagram of a parallel arrangement of a device structure for preparing ammonia.

[0026] In the figure: 6-1-N, inner wall of the Nth ammonia generator, 6-2-N, spoiler surface of the Nth ammonia generator, 11, spray gun; N is a positive integer.

[0027] Figure 4 A schematic diagram of a flue gas tail denitrification system for a gas internal combustion engine.

[0028] In the figure: 1. gas boiler, 2. lithium bromide equipment, 3. low-temperature SCR reactor, 4. low-temperature catalyst, 5. chimney, 6. ammonia generator, 7. urea solution tank, 8. compressed air tank, 9. urea solution pipe, 10. compressed air pipe, 11. spray gun, 12. regulating valve, 13. fan, 14. bypass flue, 15. flue, 16. heat exchanger. DETAILED DESCRIPTION

[0029] The present invention is further described below by taking a flue gas denitration system of a 4.4MW gas internal combustion engine unit in a distributed energy station as an example in conjunction with the figures.

[0030] Flue gas denitrification system of a 4.4MW gas internal combustion engine unit in a distributed energy station, such as Figure 1 and Figure 4 The flue gas temperature at the gas internal combustion engine (1) is 430-550°C, and can reach up to 600°C. The power generation output is 4.4MW. When the gas internal combustion engine load rate is 100%, the flue gas volume is 19888Nm in dry state. 3 / h, under standard state, dry basis 5% O2 conditions, NO x Both 500mg / Nm 3 The flue gas outlet temperature of the lithium bromide device (2) is 145°C; the suitable temperature range of the low-temperature catalyst (4) is 170-400°C; a heat exchanger (16) is added between the low-temperature SCR reactor (3) and the chimney (5).

[0031] The amount of flue gas in the bypass flue (14) is adjusted by means of a high-temperature variable frequency fan (13) and a regulating valve (12) so that the flue gas temperature at the inlet of the low-temperature SCR reactor (3) is 175° C.; the flue gas temperature at the outlet of the low-temperature SCR reactor (3) and at the inlet of the heat exchanger (16) is substantially 175° C., and the temperature of the flue gas after passing through the heat exchanger (16) is 72° C. and is discharged through a chimney (5).

[0032] After a heat exchanger (16) is added between the low-temperature SCR reactor (3) and the chimney (5), the energy efficiency is higher.

[0033] The urea solution with a concentration of 30-50% in the urea solution tank (7) enters the spray gun (11) through the urea solution pipe (9), and the compressed air with a pressure of 0.3-0.8 kg in the compressed air tank (8) enters the spray gun (11) through the compressed air pipe (10). The spray gun (11) is vertically inserted into the ammonia generator (6). The urea solution is atomized in the ammonia generator (6) under the action of the compressed air and the nozzle of the spray gun (11). Figure 1 The atomized urea micro-droplets diffuse along with the flow of flue gas and mix with the flue gas. The mixed flue gas forms turbulence and eddy current under the joint action of at least one arc-shaped inner wall (6-1) of the ammonia generator and the curved spoiler surface (6-2). The turbulence of the flue gas can enhance the intensity of diffusion of the urea micro-droplets in the flue gas, so that the urea micro-droplets and the flue gas are more fully mixed. The eddy current of the flue gas can prolong the time for the urea micro-droplets to generate ammonia in the ammonia generator (6). The atomized urea micro-droplets decompose to generate ammonia under the condition of flue gas temperature of 400 to 550° C. in the ammonia generator (6). By treating the ammonia generator (6) as Figure 1 The structural optimization design improves the ammonia conversion rate of urea.

[0034] The generated ammonia enters the low-temperature SCR reactor (3) along with the flue gas, and the nitrogen oxides in the flue gas react with the generated ammonia on the surface of the low-temperature catalyst (4) to generate nitrogen. NO at the outlet of the low-temperature SCR reactor (3) x 30mg / Nm at standard state, dry basis 5% O2 concentration 3 .

[0035] Special case: When the flue gas velocity in the flue is lower than 0.5m / s, no spoiler surface is required.

[0036] Finally, it should be noted that the above implementation modes are only used to illustrate the present invention, rather than to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above implementation modes, it should be understood by those skilled in the art that the present invention can still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A device for preparing ammonia, characterized in that: The invention comprises an ammonia generator and a curved spoiler surface (6-2) arranged on the inner wall (6-1) of the ammonia generator, a support frame is arranged on the inner wall (6-1) of the ammonia generator, and a curved spoiler surface (6-2) is arranged on the support frame; the number of the ammonia generator and the spoiler surface is at least one; the spoiler surface (6-2) is arranged at the outlet of the ammonia generator; the spray gun (11) is inserted into the ammonia generator, and the smoke enters from the bottom inlet of the spoiler surface (6-2); The cross-sectional shape of the inner wall (6-1) of the ammonia generator along the axial direction is a curve shape with multiple sections connected continuously; the cross-sectional shape of the inner wall (6-1) of the ammonia generator is a structure that is wide in the middle and narrow at both ends; the axial length at the smoke inlet of the ammonia generator, i.e., the axial distance from the smoke inlet to the widest part of the cross-sectional shape of the ammonia generator, is shorter than the axial length at the smoke outlet of the ammonia generator, i.e., the axial distance from the smoke outlet to the widest part of the cross-sectional shape of the ammonia generator; The urea solution is atomized in the ammonia generator (6) under the action of compressed air and the nozzle of the spray gun (11); the atomized urea micro-droplets diffuse along with the flow of flue gas and mix with the flue gas; the mixed flue gas forms turbulence and eddy flow under the joint action of at least one arc-shaped inner wall (6-1) of the ammonia generator and the curved spoiler surface (6-2); the turbulence of the flue gas can enhance the intensity of diffusion of the urea micro-droplets in the flue gas, so that the urea micro-droplets are more fully mixed with the flue gas; The flue gas vortex prolongs the time for the urea micro-droplets to generate ammonia in the ammonia generator (6); the atomized urea micro-droplets decompose to generate ammonia under the flue gas temperature of 400-550° C. in the ammonia generator (6); and the spoiler surface (6-2) plays a role in enhancing the intensity of the turbulence and vortex formed.

2. The device for preparing ammonia according to claim 1, characterized in that: The ammonia generators are connected in series or in parallel.

3. The device for preparing ammonia according to claim 2, characterized in that: The ammonia generators are arranged in series; there are two specific ways of series arrangement: the first way is that a spoiler surface is provided on the inner wall of each ammonia generator, with a total of M spoiler surfaces; the second way is that the Mth series ammonia generator spoiler surface (6-2) is only provided at the Mth series ammonia generator, with a total of one spoiler surface; the number and position of the spoiler surfaces are determined according to the results of numerical simulation calculations, and M is a positive integer.

4. The device for preparing ammonia according to claim 2, characterized in that: The ammonia generators are arranged in parallel; and the outlets of the ammonia generators are connected in parallel through pipelines.

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