Denitration system and method based on ammonia carbamate pyrolysis ammonia preparation

Abstract

The invention provides an ammonia preparation and denitration system based on ammonia carbamate pyrolysis, which comprises an ammonia preparation system and a denitration device, and the ammonia preparation system comprises an ammonia carbamate storage tank, a variable frequency metering feeding device, a flue gas and air system and a control device; wherein the ammonia carbamate storage tank comprises an ammonia carbamate discharge port; the variable-frequency metering feeding device comprises a device feed port and a device discharge port, and the device feed port is communicated with the ammonia carbamate discharge port; the flue gas and air system comprises a flue gas and air duct, an ammonia and air mixer and a high-temperature fan, and the discharge port of the device is communicated with the flue gas and air duct. The ammonia preparation system can directly pyrolyze the ammonia carbamate raw material to prepare ammonia, compared with the prior art that a denitration system adopts urea pyrolysis or hydrolysis to prepare ammonia, the links of dehydration, drying and the like in the raw material production process are omitted, a solution does not need to be prepared when the raw material is used for preparing the ammonia, the energy consumption is reduced while water is saved, and the ammonia preparation system has the advantages of less equipment, simple process, low cost and the like. The energy consumption cost is low; the use and the maintenance are easy, and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia denitration, and in particular to a denitration system and a denitration method based on the pyrolysis of carbamate and ammonia to produce ammonia. Background Art

[0002] Ammonia denitrification is a common denitrification technology, which uses liquid ammonia, ammonia water or urea as a reducing agent to achieve denitrification by reacting with nitrogen oxides. Ammonia denitrification technology is widely used in flue gas denitrification in the power, chemical, steel and other industries, and has the advantages of high denitrification efficiency and stable process. The so-called denitrification refers to the process of removing nitrogen oxides from combustion flue gas, mainly for the purpose of preventing environmental pollution.

[0003] Nitrogen oxides (NOx) are an important atmospheric pollutant. At present, my country's atmospheric complex pollution is becoming increasingly serious. NOx is an important precursor to acid rain, secondary fine particulate matter and other problems. NOx emitted from anthropogenic sources mainly comes from the combustion process of fossil fuels such as coal. Coal-fired power plants are the industry with the largest NOx emissions. Among the technical routes for removing NOx from coal-fired power plants, SCR selective catalytic reduction denitrification technology is the most widely used technical route, and the most commonly used reducing agent in this technical route is urea.

[0004] When urea is used as a reducing agent for flue gas denitrification, it has the disadvantages of high price, high energy consumption for urea thermal decomposition or hydrolysis to produce ammonia, complex equipment process, high initial investment, high cost of flue gas denitrification, and poor economic benefits. In addition, urea cannot be directly decomposed to produce ammonia, and water must be involved in the chemical reaction. When used in engineering, a solution with a concentration of 40% to 60% must be prepared. Whether the solution is thermally decomposed or hydrolyzed to produce ammonia, not only water is wasted, but also the energy consumption is greatly increased due to the vaporization or evaporation of water.

[0005] Therefore, it is urgent for researchers in this field to develop a denitrification system and a denitrification method with simple equipment and process and low energy consumption cost. Summary of the invention

[0006] In view of this, in order to solve the above-mentioned problems, the embodiments of the present invention provide a denitration system and a denitration method based on the pyrolysis of ammonia carbamate. The ammonia carbamate raw material in the ammonia carbamate storage tank enters the device feed port of the variable frequency metering feeding device through the ammonia carbamate discharge port, and is mixed with the high-temperature hot flue gas of the smoke duct through the device discharge port. The ammonia carbamate is quickly decomposed into ammonia and carbon dioxide. After passing through the ammonia-air mixer, it is sent to the ammonia injection grid of the denitration reactor of the denitration device for denitration. The denitration system directly pyrolyzes the ammonia carbamate solid. Compared with the prior art, urea does not need to be prepared into a solution, which saves water and reduces energy consumption. It has the advantages of less equipment, simple process, and low energy consumption cost. It solves the technical problems in the prior art that the use of urea pyrolysis or hydrolysis to produce ammonia has high energy consumption, complex equipment process, high denitration cost, and poor economic benefits.

[0007] To achieve the above-mentioned objectives, an embodiment of the present invention provides, on the one hand, a system for producing ammonia and denitrifying based on pyrolysis of ammonia carbamate, comprising an ammonia production system and a denitrifying device, wherein the ammonia production system comprises a carbamate ammonia storage tank, a variable frequency metering feeding device and a smoke and air system; wherein the carbamate ammonia storage tank comprises a carbamate ammonia discharge port; the variable frequency metering feeding device comprises a device feed port and a device discharge port, and the device feed port is connected to the carbamate ammonia discharge port; the denitrifying device comprises a smoke and air duct, an ammonia-air ammonia-air mixer and a high-temperature fan arranged on the smoke and air duct, and the device discharge port is connected to the smoke and air duct.

[0008] Furthermore, the ammonia production system also includes a control device, which is connected to the variable frequency metering feeding device and is used to control and adjust the output amount of carbamate ammonia.

[0009] Furthermore, the high temperature fan is connected to the control device.

[0010] Furthermore, along the gas flow direction of the smoke and air duct, the connection between the device discharge port and the smoke and air duct is located upstream of the ammonia-air mixer; the high-temperature fan is located upstream of the connection to ensure sufficient mixing of the produced ammonia gas and the hot smoke and air.

[0011] Furthermore, the denitration device comprises a denitration reactor, which is an SCR reactor, the reactor smoke inlet of the SCR reactor is connected to the outflow port of the smoke duct, and the reactor smoke outlet of the SCR reactor is connected to the inflow port of the smoke duct.

[0012] Furthermore, the denitration device comprises a denitration reactor, which is an SCR reactor, a reactor smoke inlet of the SCR reactor is connected to an outlet of the smoke and air duct, and an inlet of the smoke and air duct is connected to the hot primary air of the boiler.

[0013] Another embodiment of the present invention provides a denitration method, including the denitration system based on pyrolysis of carbamate and ammonia to produce ammonia as described in any of the above embodiments, the method comprising the following steps:

[0014] S1. transporting the ammonium carbamate raw material to the site and transferring it to the ammonium carbamate storage tank for standby use;

[0015] S2, start the high temperature fan to make the smoke and air duct reach the preset temperature;

[0016] S3, start the variable frequency metering feeding device, the carbamate ammonia raw material enters the device feed port of the variable frequency metering feeding device through the carbamate ammonia discharge port, and is mixed with the hot flue gas of the flue gas duct through the device discharge port to complete the ammonia production;

[0017] S4. After the ammonia production is completed, the ammonia gas and the hot flue gas enter the ammonia-air mixer arranged on the flue gas duct, and then enter the denitrification reactor for denitrification.

[0018] Furthermore, after the high-temperature fan is started, when the temperature in the smoke and air duct reaches a preset temperature, it is fed back to the control device, and the control device controls the variable frequency metering feeding device to start feeding; otherwise, feeding is prohibited.

[0019] Furthermore, according to the amount of nitrogen oxides contained in the flue gas from the boiler outlet, the frequency conversion metering feeding device is controlled by the control device to adjust the output of the carbamate ammonia.

[0020] Furthermore, the inlet of the smoke and air duct is communicated with the reactor smoke outlet of the SCR reactor and / or the hot primary air of the boiler.

[0021] Beneficial effects of the present invention:

[0022] The present invention provides a denitration system and a denitration method based on the pyrolysis of carbamate ammonia to produce ammonia. The denitration system includes an ammonia production system. The ammonia production system can directly pyrolyze carbamate ammonia raw materials to produce ammonia. Compared with the denitration system in the prior art that uses urea pyrolysis or hydrolysis to produce ammonia, it omits the steps of dehydration and drying, does not need to be prepared into a solution, saves water and reduces energy consumption;

[0023] Moreover, the energy required for the direct decomposition of carbamate to produce ammonia is much less than the energy required for the two-step decomposition of urea to produce ammonia. While saving energy, it can also reflect the characteristics of fast and efficient ammonia production of the denitrification system, and further avoid the risk of incomplete decomposition of urea and easy crystallization to clog the pipeline.

[0024] Specifically, the ammonia carbamate raw material in the ammonia carbamate storage tank of the present invention enters the device feed port of the variable frequency metering feeding device through the ammonia carbamate discharge port, is mixed with the high-temperature hot flue gas of the flue gas duct through the device discharge port, and the ammonia carbamate is quickly decomposed into ammonia and carbon dioxide. After passing through the ammonia-air mixer, it is sent to the ammonia injection grid of the denitration reactor in the denitration device for denitration, which has the beneficial effects of less equipment, simple process, low energy consumption cost, and easy use and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following drawings are used to provide a further understanding of the present application, constitute a part of the present application, and are only intended to provide an illustrative explanation and description of the present invention, and are not intended to limit the scope of the present invention. In the drawings:

[0026] Figure 1 This is a schematic diagram of the structure of a denitration system in which the inlet of the smoke and air duct is connected to the smoke outlet of the SCR reactor in the embodiment of the present application;

[0027] Figure 2 This is a schematic diagram of the structure of a denitration system in which the inlet of the smoke and air duct is connected to the hot primary air of the boiler in another embodiment of the present application;

[0028] Figure 3 This is a flow chart of a method for producing ammonia and denitrification based on pyrolysis of carbamate ammonia in another embodiment of the present application.

[0029] Reference numerals:

[0030] 1. Ammonium carbamate storage tank; 10. Ammonium carbamate discharge port;

[0031] 2. Frequency conversion metering feeding device; 21. Device feed port; 22. Device discharge port;

[0032] 3. Ammonia-air mixer;

[0033] 4. High temperature fan;

[0034] 5. Smoke and air duct; 51. Inlet of the smoke and air duct; 52. Outlet of the smoke and air duct;

[0035] 6. Control device;

[0036] 7. Denitrification reactor; 71. Reactor smoke inlet; 72. Reactor smoke outlet. DETAILED DESCRIPTION

[0037] Several embodiments of the present application will be disclosed below with diagrams to clearly and completely describe the technical solution of the present application, which constitute a part of the specification of the present application and are used to provide a further understanding of the present invention. The schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0038] It should be noted that unless a direction is defined separately, the directions such as up, down, left, and right mentioned in this document are based on the embodiments of this application. Figure 1 The directions of up, down, left, right, etc. shown in the figure shall prevail. If the specific posture changes, the directional indication will also change accordingly. The words "first", "second" and similar words used in this application do not indicate any order, quantity or importance, but are only used to distinguish different components. In addition, in various embodiments of the present disclosure, the same or similar reference numerals represent the same or similar components.

[0039] In the present invention, unless otherwise clearly defined and specified, the terms "connection", "fixation" and the like should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral body, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0041] Embodiment 1

[0042] Please refer to Figure 1As shown, in this embodiment, a denitration system for producing ammonia based on pyrolysis of ammonia carbamate is provided, and the denitration system comprises an ammonia production system and a denitration device, wherein the ammonia production system comprises an ammonia carbamate storage tank 1, a frequency conversion metering feeding device 2 and a smoke and air system; wherein the ammonia carbamate storage tank 1 comprises an ammonia carbamate discharge port 10; the frequency conversion metering feeding device 2 comprises a device feed port 21 and a device discharge port 22, and the device feed port 21 is connected with the ammonia carbamate discharge port 10; the smoke and air system comprises a smoke and air duct 5, an ammonia-air mixer 3 and a high-temperature fan 4 arranged on the smoke and air duct 5, and the device discharge port 22 is connected with the smoke and air duct 5, so that the ammonia carbamate raw material in the ammonia carbamate storage tank 1 is driven by the frequency conversion metering feeding device, the ammonia carbamate raw material is mixed with the high-temperature hot smoke and air of the smoke and air duct, and the ammonia carbamate is quickly decomposed into ammonia and carbon dioxide, and is sent to the ammonia injection grid of the denitration reactor after passing through the ammonia-air mixer for denitration.

[0043] It should be noted that the ammonium carbamate in this embodiment is an organic compound with a chemical formula of NH2COONH4, which is an intermediate product in the urea production process in the chemical industry. It is a white solid powder at room temperature and pressure, and further a white tetragonal, columnar, plate-like or flaky crystalline powder. Ammonium carbamate is unstable and easily decomposed into ammonia and carbon dioxide. The reaction formula for its decomposition by heat is:

[0044] Furthermore, the connection mode between the device discharge port 22 and the smoke and air duct 5 in this embodiment is specifically a pipeline connection, and the direction of the pipeline can preferably be diagonally downward as shown by the arrow in the figure, which is conducive to the flow of ammonia carbamate powder and facilitates the implementation of ammonia production.

[0045] In addition, if Figure 1 As shown, the denitrification device in this embodiment is an existing commonly used denitrification equipment, and the denitrification device includes a denitrification reactor. The denitrification reactor 7 is an SCR reactor. The reactor smoke inlet 71 of the SCR reactor is connected to the outflow port 52 of the smoke duct, and the reactor smoke outlet 72 of the SCR reactor is connected to the inflow port 51 of the smoke duct. In this way, the heat required for the decomposition of carbamate ammonia can make full use of the heat of the flue gas at the outlet of the SCR reactor. Compared with the existing urea ammonia production denitrification system, there is no need to set up an additional heat source separately, which has the beneficial effect of saving the overall energy consumption of the denitrification system.

[0046] Furthermore, if Figure 1As shown, the denitrification device in this embodiment includes a control device 6, which is connected to the variable frequency metering feeding device 2 and is used to control and adjust the discharge amount of carbamate ammonia. That is to say, the discharge amount is adjusted in real time according to the NOx concentration value measured by cems at the smoke inlet of the reactor. When the measured NOx concentration value exceeds the preset threshold, the feed amount is increased through the program control of the control device. When the measured NOx concentration value is lower than the preset threshold, the feed amount is reduced through the program control of the control device.

[0047] As a preferred embodiment, Figure 1 As shown, a high-temperature fan 4 is provided on the smoke and air duct 5 in this embodiment, and the high-temperature fan 4 is connected to the control device 6 .

[0048] Specifically, after the high-temperature fan 4 is started, when the temperature in the smoke and air duct reaches the preset temperature, it is fed back to the control device, and the control device controls the variable frequency metering feeding device to start feeding; otherwise, feeding is prohibited; this greatly ensures the effective utilization of the chemical energy of the carbamate ammonia raw material by the denitrification system of the present application, and is beneficial to the reduction of the overall energy consumption of the denitrification system.

[0049] Furthermore, along the gas flow direction of the smoke and air duct, the connection point where the device discharge port 22 is connected to the smoke and air duct 5 is located upstream of the ammonia-air mixer 3, which is beneficial for the ammonia gas to be fully mixed with the hot smoke air blown by the high-temperature blower after ammonia production, and to undergo a denitrification reaction with the flue gas containing nitrogen oxides entering from the reactor smoke inlet 71 of the SCR reactor at the ammonia injection grid of the denitrification reactor, and the flue gas after denitrification flows out through the reactor smoke outlet 72.

[0050] It should be noted that the flue gas temperature at the outlet of the SCR reactor is generally greater than 300°C. The ammonia production system of this embodiment just uses this temperature of the flue gas. While ensuring that no reverse reaction occurs after the thermal decomposition of carbamate ammonia, it avoids the risk of instability caused by too low temperature in the ammonia production system of this application, making the ammonia production system of this application more stable and reliable.

[0051] Embodiment 2

[0052] The difference between this embodiment and the first embodiment is that: Figure 2 As shown, the reactor smoke inlet 71 of the SCR reactor in this embodiment is connected to the outflow port 52 of the smoke and air duct, and the inflow port 51 of the smoke and air duct is connected to the hot primary air 8 of the boiler.

[0053] It should be noted that the temperature of the hot primary air of the boiler is generally greater than 300°C. The ammonia production system of this embodiment just uses this temperature of the flue gas to ensure that no reverse reaction occurs after the thermal decomposition of carbamate ammonia, thereby avoiding the risk of instability caused by too low temperature in the ammonia production system of this application, making the ammonia production system of this application more stable and reliable.

[0054] Embodiment 3

[0055] like Figure 3 As shown, an embodiment of the present invention provides a denitration method, including the denitration system based on the pyrolysis of carbamate and ammonia to produce ammonia as described in the above-mentioned embodiment 1 and embodiment 2, and the method includes the following steps:

[0056] S1. transporting the ammonium carbamate raw material to the site and transferring it to the ammonium carbamate storage tank for standby use;

[0057] S2, start the variable frequency metering feeding device, the carbamate ammonia raw material enters the device feed port of the variable frequency metering feeding device through the carbamate ammonia discharge port, and is mixed with the hot flue gas of the flue gas duct through the device discharge port, the carbamate ammonia decomposes to generate ammonia and carbon dioxide, and the ammonia production is completed;

[0058] S3. After the ammonia production is completed, the ammonia gas and the hot flue gas enter the ammonia-air mixer arranged on the smoke and air duct, and then enter the denitrification device for denitrification.

[0059] It should be noted that the inlet of the smoke duct in this embodiment is connected to the reactor smoke outlet of the SCR reactor, or is connected to the boiler hot primary air, or is connected to the reactor smoke outlet of the SCR reactor and the boiler hot primary air at the same time, to meet the heat required for the decomposition of carbamate ammonia in the ammonia production system. Compared with the existing urea ammonia production and denitrification system, there is no need to set up an additional heat source separately, which has the beneficial effect of saving the overall energy consumption of the denitrification system.

[0060] At the same time, the flue gas temperature at the outlet of the SCR reactor and the temperature of the hot primary air of the boiler are conventionally greater than 300°C. The ammonia production system of the present application just utilizes this temperature to ensure that no reverse reaction occurs after the thermal decomposition of carbamate ammonia, while avoiding the risk of instability of the ammonia production system due to too low temperature, making the ammonia production system more stable, economical and reliable.

[0061] The above description shows and describes the preferred implementation of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other implementations, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the object concept of this article through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not depart from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A system for producing ammonia and denitrification based on pyrolysis of carbamate ammonia, comprising an ammonia production system and a denitrification device, characterized in that: The ammonia production system comprises: An ammonia carbamate storage tank, comprising an ammonia carbamate discharge port; A variable frequency metering feeding device, comprising a device feed port and a device discharge port, wherein the device feed port is connected to the carbamate ammonia discharge port; The smoke and air system comprises a smoke and air duct, an ammonia-air mixer and a high-temperature fan arranged on the smoke and air duct, and the discharge port of the device is connected with the smoke and air duct.

2. The system for producing ammonia and denitrification based on carbamate-ammonia pyrolysis according to claim 1, characterized in that: The ammonia production system also includes a control device, which is connected to the variable frequency metering feeding device and is used to control and adjust the output amount of carbamate ammonia.

3. The system for producing ammonia and denitrification based on carbamate-ammonia pyrolysis as claimed in claim 2, characterized in that: The high temperature fan is connected to the control device.

4. The system for producing ammonia and denitrification based on carbamate-ammonia pyrolysis according to claim 1, characterized in that: Along the gas flow direction of the smoke and air duct, the connection point where the device discharge port is connected to the smoke and air duct is located upstream of the ammonia-air mixer.

5. The system for producing ammonia and denitrification based on carbamate-ammonia pyrolysis according to claim 1, characterized in that: The denitration device comprises a denitration reactor, which is an SCR reactor. The reactor smoke inlet of the SCR reactor is connected to the outflow outlet of the smoke duct, and the reactor smoke outlet of the SCR reactor is connected to the inflow inlet of the smoke duct.

6. The system for producing ammonia and denitrification based on carbamate-ammonia pyrolysis according to claim 1, characterized in that: The denitration device comprises a denitration reactor, which is an SCR reactor. The reactor smoke inlet of the SCR reactor is connected with the outflow port of the smoke and air duct, and the inflow port of the smoke and air duct is connected with the hot primary air of the boiler.

7. A denitration method, characterized in that: The method comprises the system for producing ammonia by pyrolysis of carbamate and ammonia according to claims 1 to 6, and the method comprises the following steps: S1. transporting the ammonium carbamate raw material to the site and transferring it to the ammonium carbamate storage tank for standby use; S2, start the variable frequency metering feeding device, the carbamate ammonia raw material enters the device feed port of the variable frequency metering feeding device through the carbamate ammonia discharge port, and is mixed with the hot flue gas of the flue gas duct through the device discharge port, the carbamate ammonia decomposes to generate ammonia and carbon dioxide, and the ammonia production is completed; S3. After the ammonia production is completed, the ammonia gas and the hot flue gas enter the ammonia-air mixer arranged on the flue gas duct, and then enter the denitrification device for denitrification.

8. The denitration method according to claim 7, characterized in that: After the high-temperature fan is started, when the temperature in the smoke and air duct reaches the preset temperature, it is fed back to the control device, and the control device controls the variable frequency metering feeding device to start feeding; otherwise, feeding is prohibited.

9. The denitration method according to claim 7, characterized in that: According to the amount of nitrogen oxides contained in the flue gas from the boiler outlet, the frequency conversion metering feeding device is controlled by the control device to adjust the output of the carbamate ammonia.

10. The denitration method according to claim 7, characterized in that: The inlet of the smoke and air duct is communicated with the reactor smoke outlet of the SCR reactor and / or the hot primary air of the boiler.

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