Dry denitration method and device for low-flue-gas-flow high-concentration NOx flue gas

Abstract

The invention discloses a dry denitration method and device for low-flue-gas-flow high-concentration NOx flue gas, and the method comprises the following steps: introducing flue gas into a pipeline, arranging a reserved catalyst layer at the initial end of the pipeline, arranging multiple stages of catalyst layers in the pipeline at the rear end of the reserved catalyst layer, arranging ammonia spraying grids on the reserved catalyst layer and the multiple stages of catalyst layers, and spraying ammonia on the ammonia spraying grids. Heat exchangers are arranged at the rear ends of other catalyst layers except the last stage; when the flue gas enters the pipeline, the flue gas is heated to a reaction temperature at the inlet of the pipeline, ammonia gas is sprayed out through the ammonia spraying grid, so that the flue gas and the ammonia gas are subjected to a multi-stage reaction under the action of a catalyst when passing through the reserved catalyst layer and the multi-stage catalyst layer, and during the period, the heat exchanger is used for heat exchange and temperature control to maintain each stage of reaction temperature at the reaction temperature, so that denitration is realized. The method has the characteristics of high denitration efficiency, low ammonia consumption, simple equipment, controllable system temperature, no wastewater generation and the like.

Description

Technical Field

[0001] The present invention relates to the field of flue gas treatment technology, and in particular to a low flue gas flow rate high concentration NO x Dry denitrification method and device for flue gas. Background Art

[0002] NO in nuclear industry flue gas x (Nitrogen oxides) mainly come from the fuel combustion process. Especially when nuclear facilities require auxiliary energy (such as electricity and heat), the flue gas produced by combustion may contain high concentrations of NO x In addition, although the nuclear industry itself does not directly produce NO x However, other industrial activities or transportation around nuclear facilities may also affect air quality, indirectly increasing NO x Emissions, NO x It is a major air pollutant that causes great harm to human health and the ecological environment. It can not only lead to the formation of photochemical smog and affect atmospheric visibility, but also generate nitric acid and nitrate aerosols through chemical reactions in the atmosphere, thus forming acid rain and causing acidification pollution to water bodies and soil. At the same time, NO x It is also one of the greenhouse gases and has a certain impact on global climate change.

[0003] In the existing technology, low nitrogen combustion technology, SNCR (selective non-catalytic reduction) technology, ozone oxidation technology, etc. are generally used. Among them, the principle of low ammonia combustion technology is to establish a reducing combustion zone in the combustion space to make it burn in the absence of oxygen to produce reducing agents such as CO, CH4, H2, HCN and fixed carbon. These reducing agents react with NO in the flue gas. x React to convert NO x Reduced to non-polluting inert gases such as N2. In addition, the combustion of fuels such as pulverized coal under oxygen-deficient conditions also inhibits the generation of fuel-type NO x Produced, thus achieving NO x Emission reduction; SNCR technology refers to the selective reduction of NO in flue gas by an amino reducing agent in the effective temperature range (such as 800-1050°C) without the action of a catalyst. x , generating N2 and H2O. Different reducing agents have different reaction temperature ranges, which are called temperature windows. When the reaction temperature is too high, such as over 1100°C, the decomposition of ammonia will also cause NO x The reduction rate is reduced; ozone oxidation technology mainly utilizes the strong oxidizing property of ozone to oxidize insoluble low-valent nitrogen oxides into soluble high-valent nitrogen oxides, and then absorbs the nitrogen oxides in the scrubbing tower to achieve the purpose of removal.

[0004] However, the above-mentioned existing technologies have at least the following shortcomings: although the investment and operation costs of low-nitrogen combustion technology are relatively low, the denitrification efficiency is also relatively low and cannot meet the requirements of deep emission reduction environmental protection emission standards; SNCR technology has been used in most industries, but with increasingly stringent environmental protection requirements and subsequent reductions in emission standards, the simple SNCR denitrification technology can no longer meet the more stringent environmental protection emission standards; ozone oxidation technology requires the configuration of an absorption system, and the overall investment is relatively high. Although the denitrification efficiency can meet the needs of deep emission reduction, it will bring about problems such as increased wastewater discharge and dust emission concentrations. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a low flue gas flow rate high concentration NO x The dry denitrification method and device for flue gas have the characteristics of high denitrification efficiency, low ammonia consumption, simple equipment, controllable system temperature, and no wastewater generation.

[0006] The technical solution of the present invention to solve the above technical problems is:

[0007] According to a first aspect of the present invention, there is provided a low flue gas flow rate high concentration NO x The dry denitrification method of flue gas includes:

[0008] The flue gas is passed into the pipeline, and a reserved catalyst layer is arranged at the initial end of the pipeline, a multi-stage catalyst layer is arranged in the pipeline at the rear end of the reserved catalyst layer, an ammonia spraying grid is arranged at both the reserved catalyst layer and the multi-stage catalyst layer, and a heat exchanger is arranged at the rear end of all catalyst layers except the last stage; when the flue gas enters the pipeline, the flue gas is heated to the reaction temperature at the pipeline inlet, and ammonia is sprayed out through the ammonia spraying grid, so that the flue gas undergoes a multi-stage reaction with ammonia under the action of the catalyst when passing through the reserved catalyst layer and the multi-stage catalyst layer, during which the reaction temperature of each stage is maintained at the reaction temperature by using the heat exchanger for heat exchange and temperature control to achieve denitrification.

[0009] Optionally, the pipeline is divided into multiple sections, and the reserved catalyst layer and each stage of the catalyst layer in the multi-stage catalyst layer are arranged in each section of the pipeline respectively.

[0010] Optionally, each catalyst layer in the multi-stage catalyst layer is arranged at equal intervals, and the multi-stage catalyst layer includes at least four catalyst layers.

[0011] Optionally, the reaction temperature is 220-400°C.

[0012] Optionally, the ammonia injection grid adopts a microporous grid, and the coverage of the grid ammonia injection is made to completely cover the reserved catalyst layer and the multi-stage catalyst layer.

[0013] Optionally, a gas sensor is arranged on the ammonia injection grid and linked with the ammonia injection switch of the ammonia injection grid through a control system. When the gas sensor detects that the flue gas contains NO x Then ammonia spraying is automatically carried out.

[0014] Optionally, a gas sensor is arranged on each ammonia injection grid and electrically connected to the control system, and three-dimensional modeling is performed by means of three-dimensional modeling. The pipeline and the reserved catalyst layer, multi-stage catalyst layer, ammonia injection grid, and heat exchanger at the corresponding internal positions are displayed in the form of a system model on the control system. At the same time, the flue gas parameters collected by each gas sensor are displayed at the corresponding positions of the system model.

[0015] Optionally, a temperature sensor is arranged on each heat exchanger and electrically connected to the control system, and the current flue gas temperature parameters collected by each temperature sensor are displayed at the corresponding position of the system model. Based on the flue gas parameters and the current flue gas temperature parameters, the working conditions of the current process unit are synthesized in the form of a line graph, and stored with a corresponding timestamp, and an alarm is issued when the parameters exceed the set normal threshold.

[0016] Optionally, an exhaust gas heat exchanger is arranged at the outlet of the pipeline to recover heat from the gas after the reaction of the last-stage catalyst layer.

[0017] According to a second aspect of the present invention, there is provided a low flue gas flow rate high concentration NO x A dry denitration device for flue gas comprises a pipeline, a reserved catalyst layer and a multi-stage catalyst layer, wherein the pipeline is used to introduce flue gas, and a heater is provided at the pipeline inlet; the reserved catalyst layer and the multi-stage catalyst layer are both arranged in the pipeline, wherein the pre-catalyst layer is located at the initial end of the pipeline, and the multi-stage catalyst layer is located in the pipeline at the rear end of the reserved catalyst layer, and an ammonia spraying grid is provided in the reserved catalyst layer and the multi-stage catalyst layer, and a heat exchanger is provided in the pipeline at the rear end of each catalyst layer except the last stage, when the flue gas enters the pipeline, the heater is used to heat the flue gas to a reaction temperature, the ammonia spraying grid is used to spray out ammonia, so that the flue gas undergoes a multi-stage reaction with ammonia under the action of the catalyst when passing through the reserved catalyst layer and the multi-stage catalyst layer, and the heat exchanger is used to maintain the reaction temperature of each stage at the reaction temperature through heat exchange.

[0018] Optionally, the pipeline includes multiple sections, the reserved catalyst layer and each stage of the catalyst layer in the multi-stage catalyst layer are separately arranged in each section of the pipeline, and each section of the pipeline is sealed and connected.

[0019] Optionally, each catalyst layer in the multi-stage catalyst layer is arranged at equal intervals, and the number of stages of the multi-stage catalyst layer is at least four.

[0020] Optionally, the ammonia injection grid is a microporous grid, and the coverage of its ammonia injection completely covers the reserved catalyst layer and the multi-stage catalyst layer.

[0021] Optionally, the system further comprises a control system, wherein each ammonia injection grid is provided with a gas sensor, wherein the gas sensor is electrically connected to the control system and is used to collect the flue gas parameters at each catalyst layer and transmit them to the control system; wherein the control system is electrically connected to each ammonia injection grid, and is used to receive and display the flue gas parameters transmitted by each gas sensor. x Each ammonia injection grid is controlled to automatically spray ammonia.

[0022] Optionally, a three-dimensional modeling module is provided in the control system for three-dimensionally modeling the pipeline and the reserved catalyst layer, multi-stage catalyst layer, ammonia injection grid and heat exchanger at corresponding internal positions and displaying them in model form.

[0023] Optionally, each heat exchanger is provided with a temperature sensor, and each is electrically connected to the control system for collecting the flue gas temperature parameters at each heat exchanger and transmitting them to the control system; the control system is also used to receive and display the flue gas temperature parameters transmitted by each temperature sensor.

[0024] Optionally, the system further comprises an exhaust gas heat exchanger, which is disposed at the outlet of the pipeline and is used for recovering heat from the gas after the reaction of the last-stage catalyst layer.

[0025] The low flue gas flow rate and high concentration NO x Compared with the prior art, the dry denitrification method and device for flue gas have the following beneficial effects:

[0026] (1) The present invention adopts a hot blast furnace, an ammonia spraying grid, a reserved catalyst layer, a multi-stage catalyst layer, and a heat exchanger to treat flue gas. The hot blast furnace is used to ensure that the flue gas inlet temperature meets the process requirements. The ammonia spraying grid is used to position each catalyst layer for ammonia spraying. The multi-stage ammonia spraying is coordinated with the catalyst layer arrangement to treat the denitration reaction in a staged manner, which can solve the problem of large amounts of heat energy generated by the reducing agent reaction and the problem of ammonia escape, thereby improving the reaction efficiency and denitration efficiency and reducing ammonia consumption. By arranging a heat exchanger after each catalyst layer, the flue gas temperature can be ensured to be suitable, and the excess heat generated during the reaction can be taken away to avoid affecting the catalyst life.

[0027] (2) The present invention is a dry treatment, which can avoid corrosion, crystallization, etc., and multi-stage treatment, which can adapt to high concentration NO X Flue gas has no additional by-products generated, avoiding the problem of re-treatment, and dry treatment requires a small device volume.

[0028] (3) The present invention can display the flue gas parameters and the current flue gas temperature parameters at the corresponding positions by establishing a system model, and synthesize the working conditions of the current process device in the form of a line graph, and alarm when the parameters exceed the set normal threshold value, which is more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The low flue gas flow rate and high concentration NO in the embodiment of the present invention x Schematic diagram of a dry denitrification method and system for flue gas;

[0030] Figure 2 The low flue gas flow rate and high concentration NO in the embodiment of the present invention x Schematic diagram of the basic principle of the dry denitrification method for flue gas.

[0031] In the figure: 1. pipeline; 2. reserved catalyst layer; 31. primary catalyst layer; 32. secondary catalyst layer; 33. tertiary catalyst layer; 34. quaternary catalyst layer; 4. heater; 5. ammonia injection grid; 6. heat exchanger; 7. fan; 8. exhaust gas heat exchanger. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0033] The existing technology has low denitrification efficiency, is difficult to meet the requirements of deep emission reduction environmental protection emission standards, or has high equipment investment. x The dry denitrification method of flue gas comprises: passing the flue gas into a pipeline, arranging a reserved catalyst layer at the initial end of the pipeline, arranging a multi-stage catalyst layer in the pipeline at the rear end of the reserved catalyst layer, arranging an ammonia spraying grid at both the reserved catalyst layer and the multi-stage catalyst layer, and arranging a heat exchanger in the pipeline at the rear end of each catalyst layer except the last stage; when the flue gas enters the pipeline, the flue gas is brought to a reaction temperature at the pipeline inlet, and ammonia is sprayed out through the ammonia spraying grid, so that the flue gas undergoes a multi-stage reaction with ammonia under the action of the catalyst when passing through the reserved catalyst layer and the multi-stage catalyst layer, during which the reaction temperature of each stage is maintained at the reaction temperature by using the heat exchanger for heat exchange and temperature control, thereby achieving denitrification.

[0034] Accordingly, the present invention also provides a low flue gas flow rate high concentration NO xA dry denitration device for flue gas comprises a pipeline, a reserved catalyst layer and a multi-stage catalyst layer, wherein the pipeline is used to introduce flue gas, and a heater is provided at the pipeline inlet; the reserved catalyst layer and the multi-stage catalyst layer are both arranged in the pipeline, wherein the pre-catalyst layer is located at the initial end of the pipeline, and the multi-stage catalyst layer is located at the rear end pipeline of the reserved catalyst layer, and an ammonia spraying grid is provided in the reserved catalyst layer and the multi-stage catalyst layer, and a heat exchanger is provided in the rear end pipeline of each catalyst layer except the last stage, when the flue gas enters the pipeline, the heater is used to heat the flue gas to a reaction temperature, the ammonia spraying grid is used to spray out ammonia, so that the flue gas undergoes a multi-stage reaction with ammonia under the action of the catalyst when passing through the reserved catalyst layer and the multi-stage catalyst layer, and the heat exchanger is used to maintain the reaction temperature of each stage at the reaction temperature through heat exchange.

[0035] Example 1

[0036] like Figure 1 As shown, this embodiment discloses a low flue gas flow rate and high concentration NO x The dry denitrification method of flue gas includes:

[0037] The flue gas is introduced into the pipeline 1, a reserved catalyst layer 2 is arranged at the initial end of the pipeline, a multi-stage catalyst layer is arranged in the pipeline at the rear end of the reserved catalyst layer, and an ammonia injection grid 5 is arranged at the reserved catalyst layer and the multi-stage catalyst layer, and a heat exchanger 6 is arranged in the pipeline at the rear end of each catalyst layer except the last stage;

[0038] When the flue gas enters the pipeline 1, the flue gas is heated to the optimal reaction temperature at the inlet of the pipeline 1, and ammonia is sprayed out through the ammonia spraying grid 5, so that the flue gas passes through the reserved catalyst layer 2 and reacts with the flue gas under the action of the catalyst by cooperating with the ammonia spraying grid 5 to spray ammonia. Subsequently, the flue gas enters the multi-stage catalyst layer, and ammonia sprayed by the ammonia spraying grid 5 of each catalyst layer is used to carry out a multi-stage reaction with the ammonia under the action of the catalyst. During this period, the heat exchanger 6 is used for heat exchange and temperature control to maintain the reaction temperature of each stage at the optimal reaction temperature, thereby realizing denitrification. The exhaust gas after denitrification is discharged through the fan 7 at the pipeline outlet.

[0039] Specifically, if Figure 2 As shown, the method is to use the ammonia spraying grid 5 to spray ammonia as a reducing agent in stages under a certain temperature and the action of a catalyst, and selectively react with NO in the flue gas. x Reaction, NO in flue gas x Reduction into nitrogen and water to achieve denitrification, the basic principle is as follows:

[0040] 4NO+4NH3+O2→4N2+6H2O

[0041] 4NH3+2NO2+O2→3N2+6H2O

[0042] NO2+NO+2NH3→2N2+3H2O

[0043] Since the catalytic reaction between the flue gas and ammonia is an exothermic reaction, if the reaction is concentrated at a certain level of catalyst, the heat of the reaction will cause the temperature of the catalyst at that level to rise too high, resulting in catalyst deactivation. In this method, a reserved catalyst layer 2, a multi-stage catalyst layer and an ammonia injection grid 5 are arranged to allow the flue gas and ammonia to undergo a catalytic reaction in stages. The reaction heat can be distributed to the multi-stage catalyst layers, thereby avoiding catalyst deactivation and improving the reaction efficiency and denitrification efficiency. For example, the inlet temperature of the first-stage catalyst layer is 220°C, and the temperature rises to 400°C after the reaction. A heat exchanger is used at the rear end of the first-stage catalyst layer to reduce the flue gas temperature to 220°C, and then the flue gas enters the second-stage catalyst layer. After the reaction in the second-stage catalyst layer, the temperature rises to 400°C, and the heat exchanger is used to cool it down, and then the flue gas enters the third-stage catalyst layer, and this process is repeated. For high-concentration NO x At least 3-4 levels of catalyst are required to ensure that the catalyst will not sinter and deactivate while ensuring that the outlet NO x Meet the standard.

[0044] In some embodiments, the pipeline 1 is divided into multiple sections, and the reserved catalyst layer 2 and each stage of the multi-stage catalyst layer are arranged in each section of the pipeline respectively. This is particularly convenient for use under very small flux conditions or in scenarios where the installation and construction space is very limited.

[0045] In some embodiments, the reserved catalyst layer 2 is separately arranged at the front end of the pipeline 1, the catalyst layers of each stage in the multi-stage catalyst layer are arranged at equal intervals, and each section of the pipeline is sealed and connected through a flange.

[0046] In some embodiments, the multi-stage catalyst layer includes at least four catalyst layers, for example, Figure 1 As shown, the multi-stage catalyst layer includes a primary catalyst layer 21 , a secondary catalyst layer 32 , a tertiary catalyst layer 33 and a quaternary catalyst layer 34 .

[0047] In some embodiments, the reaction temperature is controlled at 220-400°C. Specifically, the inlet of pipeline 1 is heated by a hot air furnace (i.e., heater 4) to reach the reaction temperature, and the catalyst layer 2 and each catalyst layer in the multi-stage catalyst layer are reserved at their rear ends to directly exchange heat with the flue gas by arranging a water-cooled heat exchanger (i.e., heat exchanger 6) to maintain the reaction temperature, and the water-cooled liquid after heat exchange by the water-cooled heat exchanger is discharged for recycling.

[0048] In some embodiments, the ammonia injection grid 5 is a microporous grid, and the coverage of the grid ammonia injection is made to completely cover the reserved catalyst layer 2 and the multi-stage catalyst layer.

[0049] It should be noted that when the NO in the flue gas is treated xWhen the concentration is low, since the heat release of the catalytic reaction is not large, the method can also perform single-stage precise ammonia injection at the front end without the need for graded ammonia injection.

[0050] In some embodiments, a gas sensor (not shown in the figure) is arranged on each ammonia injection grid 5, and the gas sensor is interlocked with the ammonia injection switch of the ammonia injection grid 5 through a control system (not shown in the figure). x Ammonia spraying will be automatically carried out after that, otherwise no ammonia spraying is required.

[0051] In some embodiments, the method further arranges a gas sensor on each ammonia injection grid 5 and electrically connects it to a control system, and performs three-dimensional modeling on the process device of the method through three-dimensional modeling means, and displays the reserved catalyst layer 2, multi-stage catalyst layer, ammonia injection grid 5, and heat exchanger 6 at the corresponding positions of the pipeline and the internal parts in the form of a system model at the control system, and at the same time, the flue gas parameters collected by each gas sensor are respectively displayed at the corresponding positions of the system model.

[0052] In some embodiments, the method further arranges a temperature sensor (not shown in the figure) on each heat exchanger 6 and electrically connects it to the control system, displays the current flue gas temperature parameters collected by each temperature sensor at the corresponding position of the system model, and synthesizes the working conditions of the current process device in the form of a line graph based on the flue gas parameters and the current flue gas temperature parameters, and stores them with a corresponding timestamp, and issues an alarm when the parameters exceed the set normal threshold.

[0053] In some embodiments, a tail gas heat exchanger 8 is arranged at the outlet of the pipeline 1 to recover heat from the gas after the reaction of the last-stage catalyst layer.

[0054] The low flue gas flow rate and high concentration of NO in this embodiment x Compared with the existing technology, the dry denitrification method of flue gas has the following beneficial effects:

[0055] (1) This method uses a hot blast furnace, an ammonia spraying grid, a reserved catalyst layer, a multi-stage catalyst layer, and a heat exchanger to treat flue gas. The hot blast furnace is used to ensure that the flue gas inlet temperature meets the process requirements. The ammonia spraying grid is used to position each catalyst layer for ammonia spraying. The multi-stage ammonia spraying is combined with the catalyst layer arrangement to treat the denitration reaction in stages, which can solve the problem of large amounts of heat energy generated by the reducing agent reaction and the problem of ammonia escape, thereby improving the reaction efficiency and denitration efficiency and reducing ammonia consumption. A heat exchanger is arranged after each catalyst layer to ensure that the flue gas temperature is suitable, take away the excess heat generated during the reaction, and avoid affecting the catalyst life.

[0056] (2) This method is a dry treatment method, which can avoid corrosion, crystallization, etc., and multi-stage treatment, which can adapt to high concentration NO xFlue gas has no additional by-products generated, avoiding the problem of re-treatment, and dry treatment requires a small device volume.

[0057] (3) This method can display the flue gas parameters and the current flue gas temperature parameters at the corresponding positions by establishing a system model, and synthesize the working conditions of the current process equipment in the form of a line graph, and issue an alarm when the parameters exceed the set normal threshold, which is more reliable.

[0058] Example 2

[0059] like Figure 1 As shown, this embodiment discloses a low flue gas flow rate and high concentration NO x A dry denitration device for flue gas, which can be used for the dry denitration method described above, comprises a pipeline 1, a reserved catalyst layer 2 and a multi-stage catalyst layer; the inlet end of the pipeline 1 is connected to a flue gas inlet pipe for introducing flue gas, and a heater 4 is provided at the inlet of the pipeline 1; the reserved catalyst layer 2 and the multi-stage catalyst layer are both arranged in the pipeline, wherein the pre-catalyst layer 2 is located at the initial end of the pipeline 1, and the multi-stage catalyst layer is located in the rear end pipeline of the reserved catalyst layer 1, and an ammonia spraying grid 5 is provided in the reserved catalyst layer 2 and the multi-stage catalyst layer, and a heat exchanger 6 is provided in the rear end pipeline of each catalyst layer except the last stage, and a fan 7 is provided at the outlet of the pipeline, when the flue gas enters the pipeline 1, the heater 4 is used to heat the flue gas to the reaction temperature, and the ammonia spraying grid 5 is used to spray ammonia, so that the flue gas undergoes a multi-stage reaction with ammonia under the action of the catalyst when passing through the reserved catalyst layer 2 and the multi-stage catalyst layer, the heat exchanger 6 is used to maintain the reaction temperature of each stage at the reaction temperature through heat exchange, and the fan 7 is used to guide the exhaust gas after denitration for discharge.

[0060] In this embodiment, the heater 4 is specifically a hot air furnace; the heat exchanger 6 is specifically a water-cooled heat exchanger, which directly exchanges heat with the flue gas after each stage of reaction to maintain the reaction temperature, and the water-cooled liquid after heat exchange in the water-cooled heat exchanger is discharged for recycling.

[0061] In some embodiments, the pipeline 1 includes multiple sections, and the reserved catalyst layer 2 and each stage of the catalyst layer in the multi-stage catalyst layer are separately arranged in each section of the pipeline, and each section of the pipeline is sealed and connected.

[0062] In some embodiments, each catalyst layer in the multi-stage catalyst layer is arranged at equal intervals, and the number of stages of the multi-stage catalyst layer is at least four. Figure 1 As shown, the multi-stage catalyst layer includes a primary catalyst layer 21 , a secondary catalyst layer 32 , a tertiary catalyst layer 33 and a quaternary catalyst layer 34 .

[0063] In some embodiments, the ammonia injection grid 5 is a microporous grid, and the coverage of its ammonia injection covers the reserved catalyst and the multi-stage catalyst.

[0064] In some embodiments, the system further includes a control system (not shown in the figure), each ammonia injection grid 5 is provided with a gas sensor (not shown in the figure), the gas sensor is electrically connected to the control system, and is used to collect the flue gas parameters at each catalyst layer and transmit them to the control system; the control system is electrically connected to the ammonia injection switch of each ammonia injection grid 5, and the control system is used to receive the flue gas parameters transmitted by each gas sensor and display them. When the flue gas contains NO x Each ammonia injection grid 5 is controlled to automatically spray ammonia.

[0065] In some embodiments, a three-dimensional modeling module (not shown in the figure) is provided in the control system for three-dimensionally modeling the pipeline 1 and the reserved catalyst layer 2, the multi-stage catalyst layer, the ammonia injection grid 5 and the heat exchanger 6 at the corresponding positions inside and displaying them in the form of a model.

[0066] In some embodiments, each heat exchanger 6 is provided with a temperature sensor (not shown in the figure), and is electrically connected to the control system for collecting the flue gas temperature parameters at each heat exchanger and transmitting them to the control system. The control system is also used to receive and display the flue gas temperature parameters transmitted by each temperature sensor.

[0067] In some embodiments, the system further includes an exhaust gas heat exchanger 8, which is disposed at the outlet of the pipeline and is used to recover heat from the gas after the reaction of the last-stage catalyst layer.

[0068] The low flue gas flow rate and high concentration of NO in this embodiment x Compared with the existing technology, the dry denitrification device for flue gas has the following beneficial effects:

[0069] (1) This device uses a hot blast furnace to ensure that the flue gas inlet temperature meets the process requirements. Through the ammonia spraying grid, each catalyst layer is positioned to spray ammonia. The multi-stage ammonia spraying is coordinated with the catalyst layer arrangement to grade the denitration reaction. This can not only solve the problem of large amounts of heat energy generated by the reducing agent reaction, but also solve the problem of ammonia escape, improve the reaction efficiency and denitration efficiency, and reduce ammonia consumption. By arranging a heat exchanger after each catalyst layer, the flue gas temperature can be guaranteed to be suitable, and the excess heat generated during the reaction can be taken away to avoid affecting the catalyst life.

[0070] (2) This device is a dry treatment device, which can avoid corrosion, crystallization, etc., and has multi-stage treatment, which can adapt to high concentration NO x Flue gas has no additional by-products generated, avoiding the problem of re-treatment, and dry treatment requires a small device volume.

[0071] (3) By establishing a system model, the device can display the flue gas parameters and the current flue gas temperature parameters at the corresponding positions, and synthesize the working conditions of the current process device in the form of a line graph, and alarm when the parameters exceed the set normal threshold, which is more reliable.

[0072] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A low flue gas flow and high concentration NO x The dry denitrification method of flue gas is characterized by: include: The flue gas is introduced into the pipeline, and a reserved catalyst layer is arranged at the initial end of the pipeline, a multi-stage catalyst layer is arranged in the pipeline at the rear end of the reserved catalyst layer, an ammonia injection grid is arranged at the reserved catalyst layer and the multi-stage catalyst layer, and a heat exchanger is arranged at the rear end of all catalyst layers except the last stage; When the flue gas enters the pipeline, the flue gas is heated to the reaction temperature at the pipeline inlet, and ammonia is sprayed out through the ammonia spray grid, so that the flue gas undergoes multi-stage reactions with ammonia under the action of the catalyst when passing through the reserved catalyst layer and the multi-stage catalyst layer. During this period, the heat exchanger is used to control the temperature to maintain the reaction temperature of each stage at the reaction temperature to achieve denitrification.

2. The low flue gas flow rate and high concentration NO according to claim 1 x The dry denitrification method of flue gas is characterized by: The pipeline is divided into multiple sections, and the reserved catalyst layer and each level of the catalyst layer in the multi-stage catalyst layer are arranged in each section of the pipeline respectively.

3. Low flue gas flow and high concentration NO according to claim 1 x The dry denitrification method of flue gas is characterized by: The catalyst layers of each stage in the multi-stage catalyst layer are arranged at equal intervals, and the multi-stage catalyst layer includes at least four stages of catalyst layers.

4. The low flue gas flow and high concentration NO according to claim 1 x The dry denitrification method of flue gas is characterized by: The reaction temperature is 220-400°C.

5. The low flue gas flow rate and high concentration NO according to claim 1 x The dry denitrification method of flue gas is characterized by: The ammonia injection grid adopts a microporous grid, and the coverage range of the grid ammonia injection is made to completely cover the reserved catalyst layer and the multi-stage catalyst layer.

6. The low flue gas flow rate and high concentration NO according to claim 1 x The dry denitrification method of flue gas is characterized by: A gas sensor is arranged on the ammonia injection grid and linked with the ammonia injection switch of the ammonia injection grid through a control system. When the gas sensor detects that the flue gas contains NO x Then ammonia spraying is automatically carried out.

7. The low flue gas flow rate and high concentration NO according to claim 6 x The dry denitrification method of flue gas is characterized by: Gas sensors are arranged on each ammonia injection grid and electrically connected to the control system. Three-dimensional modeling is performed by means of three-dimensional modeling. The pipeline and the reserved catalyst layer, multi-stage catalyst layer, ammonia injection grid and heat exchanger at the corresponding internal positions are displayed in the control system in the form of a system model. At the same time, the flue gas parameters collected by each gas sensor are displayed at the corresponding positions of the system model.

8. The low flue gas flow rate and high concentration NO according to claim 7 x The dry denitrification method of flue gas is characterized by: Temperature sensors are arranged on each heat exchanger and electrically connected to the control system. The current flue gas temperature parameters collected by each temperature sensor are displayed at the corresponding position of the system model. Based on the flue gas parameters and the current flue gas temperature parameters, the working conditions of the current process unit are synthesized in the form of a line graph and stored with a corresponding timestamp. An alarm is issued when the parameters exceed the set normal threshold.

9. The low flue gas flow rate and high concentration NO according to any one of claims 1 to 8. x The dry denitrification method of flue gas is characterized by: An exhaust gas heat exchanger is arranged at the outlet of the pipeline to recover heat from the gas after the reaction of the last-stage catalyst layer.

10. A low flue gas flow and high concentration NO x The dry denitration device for flue gas is characterized by: Including pipelines, reserved catalyst layers and multi-stage catalyst layers, The pipeline is used to let in flue gas, and a heater is provided at the inlet of the pipeline; The reserved catalyst layer and the multi-stage catalyst layer are both arranged in the pipeline, wherein the pre-catalyst layer is located at the initial end of the pipeline, and the multi-stage catalyst layer is located in the pipeline at the rear end of the reserved catalyst layer. In addition, the reserved catalyst layer and the multi-stage catalyst layer are equipped with an ammonia injection grid, and the rear end pipelines of each catalyst layer except the last stage are equipped with a heat exchanger. When the flue gas enters the pipeline, the heater is used to heat the flue gas to the reaction temperature, the ammonia spray grid is used to spray out ammonia, so that the flue gas undergoes a multi-stage reaction with ammonia under the action of the catalyst when passing through the reserved catalyst layer and the multi-stage catalyst layer, and the heat exchanger is used to maintain the reaction temperature of each stage at the reaction temperature through heat exchange.

11. The low flue gas flow rate and high concentration NO according to claim 10 x The dry denitration device for flue gas is characterized by: The pipeline comprises multiple sections, the reserved catalyst layer and each stage of the catalyst layer in the multi-stage catalyst layer are separately arranged in each section of the pipeline, and each section of the pipeline is sealed and connected.

12. The low flue gas flow rate and high concentration NO according to claim 10 x The dry denitration device for flue gas is characterized by: The catalyst layers in the multi-stage catalyst layer are arranged at equal intervals, and the number of the multi-stage catalyst layers is at least four.

13. The low flue gas flow rate and high concentration NO according to claim 10 x The dry denitration device for flue gas is characterized by: The ammonia injection grid is a microporous grid, and the coverage of its ammonia injection completely covers the reserved catalyst layer and the multi-stage catalyst layer.

14. The low flue gas flow rate and high concentration NO according to any one of claims 10 to 13. x The dry denitration device for flue gas is characterized by: The system also includes a control system, and each ammonia injection grid is provided with a gas sensor. The gas sensor is electrically connected to the control system and is used to collect flue gas parameters at each level of the catalyst layer and transmit them to the control system; The control system is electrically connected to each ammonia injection grid, and is used to receive and display the flue gas parameters transmitted by each gas sensor. x Each ammonia injection grid is controlled to automatically spray ammonia.

15. The low flue gas flow rate and high concentration NO according to claim 14 x The dry denitration device for flue gas is characterized by: The control system is provided with a three-dimensional modeling module for three-dimensionally modeling the pipeline and the reserved catalyst layer, multi-stage catalyst layer, ammonia injection grid and heat exchanger at corresponding positions inside and displaying them in the form of a model.

16. The low flue gas flow rate and high concentration NO according to claim 15 x The dry denitration device for flue gas is characterized by: Each heat exchanger is provided with a temperature sensor, and is electrically connected to the control system, for collecting the flue gas temperature parameters at each heat exchanger and transmitting them to the control system; The control system is also used to receive and display the flue gas temperature parameters transmitted by each temperature sensor.

17. The low flue gas flow rate and high concentration NO according to claim 16 x The dry denitration device for flue gas is characterized by: The system also includes an exhaust gas heat exchanger, The tail gas heat exchanger is arranged at the outlet of the pipeline and is used for recovering heat from the gas after the reaction of the last stage catalyst layer.

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