Urea hydrolysis device, denitration system and hydrolysis rate regulation method

Abstract

Provided are a urea hydrolysis device, a denitration system and a hydrolysis rate regulation method. The urea hydrolysis device comprises a heat exchanger (1), a hydrolysis reactor (2) and an ammonia-air mixer (3), wherein the heat exchanger (1) comprises a primary side pipeline and a secondary side pipeline, an inlet of the primary side pipeline being configured to introduce a high-temperature flue gas, and an inlet of the secondary side pipeline being configured to introduce cold air; the hydrolysis reactor (2) comprises a hot air inlet (221), a cold air outlet (222) and a product-gas outlet (23), the hot air inlet (221) being in communication with an outlet of the secondary side pipeline, hot air being used to heat reactants in the hydrolysis reactor (2), and the cold air outlet (222) being in communication with the inlet of the secondary side pipeline; and the ammonia-air mixer (3) comprises a product-gas inlet (31), a dilution-air inlet (32) and a mixed-gas outlet (33), the dilution-air inlet (32) being in communication with the outlet of the secondary side pipeline, and the hot air being used as dilution air such that same and a product gas form a mixed gas. In the above arrangement, the flue gas is used as a heat source, such that the operation cost is reduced; and the flue gas and the cold air are mixed and then sent back to the heat exchanger (1), such that the temperature of cold air at the inlet of the secondary side pipeline is raised, the heat exchange area of the heat exchanger (1) is reduced, and the cost is saved on.

Description

Urea hydrolysis device, denitrification system and hydrolysis rate regulation method Technical Field

[0001] The present invention relates to the technical field of flue gas denitration, and in particular to a urea hydrolysis device, a denitration system and a hydrolysis rate regulating method. Background Art

[0002] The urea hydrolysis reaction usually involves injecting a urea solution with a mass concentration of about 50% into a hydrolysis reactor. After heating to a certain temperature and pressure, a hydrolysis reaction occurs to generate NH3, CO2, and water vapor. The product gas generated by the hydrolysis is mixed with hot dilution air and can be sent to the denitrification reactor for flue gas denitrification. In related technologies, a heat source is required to heat the urea solution to achieve the continuous hydrolysis reaction. The heat source of traditional urea hydrolysis reactors uses high-temperature and high-pressure steam from power plants, which is prepared into 180°C and 1MPa heating steam through a cooling and pressure reduction device. However, the above method consumes a large amount of steam and has high energy consumption indicators.

[0003] Summary of the Invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, an embodiment of the present invention provides a urea hydrolysis device, which can utilize the heat in the high-temperature flue gas to heat the urea solution without consuming high-quality steam, thereby improving the economic efficiency of operation.

[0006] The urea hydrolysis device of the embodiment of the present invention includes a heat exchanger, a hydrolysis reactor and an ammonia-air mixer, the heat exchanger includes a primary side pipeline and a secondary side pipeline, the inlet of the primary side pipeline is used to introduce high-temperature flue gas, the inlet of the secondary side pipeline is used to introduce cold air, and the outlet of the secondary side pipeline can produce hot air; the hydrolysis reactor includes a hot air inlet, a cold air outlet and a product gas outlet, the hot air inlet is connected to the outlet of the secondary side pipeline, the hot air is used to heat the reactants in the hydrolysis reactor, and the cold air outlet is connected to the inlet of the secondary side pipeline; the ammonia-air mixer includes a product gas inlet, a dilution air inlet and a mixed gas outlet, the product gas inlet is connected to the product gas outlet, the dilution air inlet is connected to the outlet of the secondary side pipeline, and the hot air is used as dilution air to form a mixed gas with the product gas.

[0007] In the urea hydrolysis device of the embodiment of the present invention, the heat exchanger can recover the heat in the high-temperature flue gas and use it to produce hot air. A portion of the hot air is used to mix with the product gas to form a mixed gas for denitrification, and the other portion of the hot air is used to supply heat to the hydrolysis reaction process. The above arrangement does not require the consumption of high-quality steam or other heat sources, thereby reducing operating costs. At the same time, the steam cooling and pressure reduction device is eliminated, thereby reducing the structural cost of the device. The hot air after supplying heat to the hydrolysis reaction still has a certain temperature. It can be mixed with cold air and sent back to the heat exchanger, thereby increasing the inlet cold air temperature of the secondary side pipeline, reducing the heat exchange area of ​​the heat exchanger, and saving the purchase cost of the heat exchanger.

[0008] In some embodiments, the urea hydrolysis device includes a hot air pipeline, which includes a main pipeline, a first branch and a second branch. The main pipeline is connected to the outlet of the secondary side pipeline, the first branch is connected to the hot air inlet, and the second branch is connected to the dilution air inlet.

[0009] In some embodiments, the urea hydrolysis device includes an instrument assembly, and the instrument assembly is provided in two groups, one group is provided at the main path, and the other group is provided at the cold air outlet.

[0010] In some embodiments, the instrument assembly includes a temperature gauge and a pressure gauge.

[0011] In some embodiments, a first regulating valve and a first flow meter are provided on the first branch, and a second regulating valve and a second flow meter are provided on the second branch.

[0012] In some embodiments, a third regulating valve and a third flow meter are provided on the pipeline between the product gas outlet and the product gas inlet.

[0013] In some embodiments, the urea hydrolysis device includes an air supply pipeline, which is connected to the inlet of the secondary side pipeline. The secondary air supply pipeline is used to supply air volume.

[0014] In some embodiments, the hydrolysis reactor includes a shell and a coil, the coil is arranged inside the shell, and one end of the coil forms the hot air inlet, and the other end forms the hot air outlet. The shell can hold the reactants, and the coil is used to heat the reactants.

[0015] The embodiment of the present invention further provides a denitration system.

[0016] The denitration system of the embodiment of the present invention includes a denitration reactor and the urea hydrolysis device described in the above embodiment, and the mixed gas outlet of the urea hydrolysis device is connected to the denitration reactor.

[0017] The embodiment of the present invention also provides a method for regulating the hydrolysis rate.

[0018] The hydrolysis rate adjustment method of the embodiment of the present invention is based on the denitration system in the above embodiment:

[0019] Adjust the flow rate of the product gas outlet in real time according to the ammonia demand of the denitrification reactor;

[0020] The hot air flow rate value G required by the hydrolysis reactor is calculated in real time according to the required ammonia amount, the temperature and pressure data of the hot air, and the temperature and pressure data of the cold air, and then the hot air flow rate entering the hydrolysis reactor is adjusted to G in real time to adjust the rate of the hydrolysis reaction in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic diagram of a urea hydrolysis device according to an embodiment of the present invention.

[0022] Figure numerals: 1. Heat exchanger; 2. Hydrolysis reactor; 21. Shell; 22. Coil; 221. Hot air inlet; 222. Cold air outlet; 23. Product gas outlet; 3. Ammonia-air mixer; 31. Product gas inlet; 32. Dilution air inlet; 33. Mixed gas outlet; 4. Hot air pipeline; 41. Main line; 42. First branch; 421. First regulating valve; 422. First flowmeter; 43. Second branch; 431. Second regulating valve; 432. Second flowmeter; 5. Instrument assembly; 51. Thermometer; 52. Pressure gauge; 6. Make-up air pipeline; 7. Third regulating valve; 8. Third flowmeter. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0024] As shown in Figure 1, the urea hydrolysis device of an embodiment of the present invention includes a heat exchanger 1, a hydrolysis reactor 2, and an ammonia-air mixer 3. The heat exchanger 1 includes a primary pipeline and a secondary pipeline. The inlet of the primary pipeline is used to introduce high-temperature flue gas, the inlet of the secondary pipeline is used to introduce cold air, and the outlet of the secondary pipeline can produce hot air. The hydrolysis reactor 2 includes a hot air inlet 221, a cold air outlet 222, and a product gas outlet 23. The hot air inlet 221 is connected to the outlet of the secondary pipeline. The hot air is used to heat the reactants in the hydrolysis reactor 2. The cold air outlet 222 is connected to the inlet of the secondary pipeline. The ammonia-air mixer 3 includes a product gas inlet 31, a dilution air inlet 32, and a mixed gas outlet 33. The product gas inlet 31 is connected to the product gas outlet 23, and the dilution air inlet 32 ​​is connected to the outlet of the secondary pipeline. The hot air is used as dilution air to form a mixed gas with the product gas.

[0025] The outlet of the secondary pipe produces hot air. This can be understood as follows: heat exchanger 1 transfers heat from the high-temperature primary flue gas to the cold secondary air, raising the temperature of the cold air to become hot air. During this process, the high-temperature flue gas cools to low-temperature flue gas, which is then discharged from the primary outlet. Specifically, the hot air temperature at the secondary outlet of flue gas heat exchanger 1 typically exceeds 200°C, while the dilution air required for the product gas generally reaches above 140°C to prevent crystallization.

[0026] Cold air outlet 222 is connected to the inlet of the secondary pipeline. This means that hot air enters hydrolysis reactor 2 through hot air inlet 221 to heat the reactants. The hot air then cools down to cold air and flows out through cold air outlet 222. The cold air then flows through the inlet of the secondary pipeline and enters heat exchanger 1, where it is reheated to hot air. Product gas produced during the hydrolysis reaction is discharged through product gas outlet 23.

[0027] The dilution air inlet 32 ​​is connected to the outlet of the secondary side pipeline, and the hot air is used as dilution air to form a mixed gas with the product gas. It can be understood that the hot air from the secondary side outlet is divided into two paths, one path flows to the hydrolysis reactor 2 for heating the reactants, and the other path flows to the ammonia-air mixer 3 to mix with the product gas.

[0028] In the urea hydrolysis device of the present embodiment, heat exchanger 1 recovers heat from the high-temperature flue gas and uses it to produce hot air. A portion of this hot air is mixed with the product gas to form a mixed gas for denitrification, while the remaining portion is used to provide heat for the hydrolysis reaction. This arrangement eliminates the need for high-quality steam or other heat sources, reducing operating costs. It also eliminates the need for a steam desuperheating and pressure reduction device, lowering the device's structural cost.

[0029] The hot air after supplying heat to the hydrolysis reactor 2 still has a certain temperature, which can be mixed with the cold air and sent back to the secondary side pipeline of the heat exchanger 1, thereby increasing the inlet cold air temperature of the secondary side pipeline, reducing the heat exchange area of ​​the heat exchanger 1, and saving the purchase cost of the heat exchanger 1.

[0030] Optionally, as shown in Figure 1, the urea hydrolysis device includes a hot air pipeline 4, the hot air pipeline 4 includes a main line 41, a first branch 42 and a second branch 43, the main line 41 is connected to the outlet of the secondary side pipeline, the first branch 42 is connected to the hot air inlet 221, and the second branch 43 is connected to the dilution air inlet 32.

[0031] Optionally, as shown in FIG1 , a first regulating valve 421 and a first flow meter 422 are provided on the first branch 42 , and a second regulating valve 431 and a second flow meter 432 are provided on the second branch 43 .

[0032] By providing a first branch 42 and a second branch 43, the hot air can be divided into two paths and delivered to the hydrolysis reactor 2 and the ammonia-air mixer 3, respectively. A first regulating valve 421 and a first flowmeter 422 are provided on the first branch 42 to facilitate regulation of the hot air flow to the hydrolysis reactor 2, thereby controlling the hydrolysis reaction rate. A second regulating valve 431 and a second flowmeter 432 are provided on the second branch 43 to facilitate regulation of the hot air flow to the ammonia-air mixer 3, thereby adjusting the mixing ratio of the dilution air and the product gas.

[0033] In some embodiments, as shown in FIG. 1 , the urea hydrolysis device includes an instrument assembly 5 . The instrument assembly 5 is provided in two groups, one group is provided at the main path 41 , and the other group is provided at the cold air outlet 222 .

[0034] Optionally, as shown in FIG1 , the instrument assembly 5 includes a temperature gauge 51 and a pressure gauge 52 .

[0035] Optionally, as shown in FIG1 , a third regulating valve 7 and a third flow meter 8 are provided on the pipeline between the product gas outlet 23 and the product gas inlet 31 .

[0036] Since the urea hydrolysis reaction consumes a large amount of heat and the product gas flow must always meet the ammonia supply demand of the unit, the hot air flow, pressure and temperature entering the hydrolysis reactor 2 must be monitored in real time. Therefore, the third regulating valve 7 of the product gas outlet 23 can be linked to the first regulating valve 421 to automatically adjust the urea hydrolysis reaction rate.

[0037] In some embodiments, as shown in FIG1 , the urea hydrolysis device includes an air supply pipeline 6 , which is connected to the inlet of the secondary side pipeline. The secondary air supply pipeline 6 is used to supply air volume.

[0038] Since only a part of the hot air flows back to the heat exchanger 1, and the other part enters the ammonia-air reactor and mixes with the product gas, it is necessary to set up an air supply pipeline 6 to supply the air volume.

[0039] In some embodiments, as shown in Figure 1, the hydrolysis reactor 2 includes a shell 21 and a coil 22. The coil 22 is arranged inside the shell 21, and one end of the coil 22 forms a hot air inlet 221, and the other end forms a hot air outlet. The shell 21 can hold reactants, and the coil 22 is used to heat the reactants.

[0040] The following describes a denitration system according to an embodiment of the present invention.

[0041] The denitration system of the embodiment of the present invention includes a denitration reactor and the urea hydrolysis device of the above embodiment, and the mixed gas outlet 33 of the urea hydrolysis device is connected to the denitration reactor.

[0042] The following describes a method for adjusting the hydrolysis rate according to an embodiment of the present invention.

[0043] The hydrolysis rate adjustment method of the embodiment of the present invention is based on the denitration system in the above embodiment:

[0044] The flow rate of the product gas outlet 23 is adjusted in real time according to the ammonia demand of the denitrification reactor;

[0045] The hot air flow rate value G required by the hydrolysis reactor 2 is calculated in real time based on the required ammonia amount, the temperature and pressure data of the hot air, and the temperature and pressure data of the cold air. Then, the hot air flow rate entering the hydrolysis reactor 2 is adjusted to G in real time to adjust the rate of the hydrolysis reaction in real time.

[0046] Specifically, urea hydrolysis is an endothermic reaction, and the reactor operating pressure is generally 0.5-0.6 MPa. The product gas flow rate must always meet the ammonia demand of the denitrification reactor. Therefore, the opening of the third regulating valve 7 must be adjusted to match the product gas flow rate with the unit's ammonia demand. The required hot air flow rate for the hydrolysis reactor 2 is then calculated based on parameters such as the unit's ammonia demand, hot air temperature and pressure, and cold air temperature and pressure. The opening of the first regulating valve 421 is then adjusted to adjust the hydrolysis reaction rate in real time.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are 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 therefore should not be understood as limiting the present invention.

[0048] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0049] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0050] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0051] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0052] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A urea hydrolysis device, characterized in that: include: A heat exchanger, the heat exchanger comprising a primary side pipeline and a secondary side pipeline, the inlet of the primary side pipeline is used to introduce high-temperature flue gas, the inlet of the secondary side pipeline is used to introduce cold air, and the outlet of the secondary side pipeline can produce hot air; A hydrolysis reactor, the hydrolysis reactor comprising a hot air inlet, a cold air outlet and a product gas outlet, the hot air inlet is communicated with the outlet of the secondary side pipeline, the hot air is used to heat the reactants in the hydrolysis reactor, and the cold air outlet is communicated with the inlet of the secondary side pipeline; An ammonia-air mixer comprises a product gas inlet, a dilution air inlet and a mixed gas outlet, wherein the product gas inlet is connected to the product gas outlet, the dilution air inlet is connected to the outlet of the secondary side pipeline, and the hot air is used as dilution air to form a mixed gas with the product gas.

2. The urea hydrolysis device according to claim 1, characterized in that: It comprises a hot air pipeline, which comprises a main pipeline, a first branch pipeline and a second branch pipeline. The main pipeline is connected to the outlet of the secondary pipeline, the first branch pipeline is connected to the hot air inlet pipeline, and the second branch pipeline is connected to the dilution air inlet pipeline.

3. The urea hydrolysis device according to claim 2, characterized in that: It comprises an instrument component, wherein the instrument component is provided with two groups, one group is provided at the main path, and the other group is provided at the cold air outlet.

4. The urea hydrolysis device according to claim 3, characterized in that: The instrument assembly includes a temperature gauge and a pressure gauge.

5. The urea hydrolysis device according to claim 2, characterized in that: The first branch is provided with a first regulating valve and a first flow meter, and the second branch is provided with a second regulating valve and a second flow meter.

6. The urea hydrolysis device according to claim 1, characterized in that: A third regulating valve and a third flow meter are arranged on the pipeline between the product gas outlet and the product gas inlet.

7. The urea hydrolysis device according to claim 1, characterized in that: It includes an air supply pipeline, which is connected to the inlet of the secondary side pipeline, and the secondary air supply pipeline is used to supply the air volume.

8. The urea hydrolysis device according to claim 1, characterized in that: The hydrolysis reactor includes a shell and a coil, wherein the coil is arranged inside the shell, and one end of the coil forms the hot air inlet, and the other end forms the hot air outlet. The shell can contain the reactants, and the coil is used to heat the reactants.

9. A denitration system, characterized in that: include: Denitrification reactor; The urea hydrolysis device according to any one of claims 1 to 8, wherein the mixed gas outlet of the urea hydrolysis device is connected to the denitration reactor.

10. A method for regulating the hydrolysis rate of the denitration system according to claim 9, characterized in that: The flow rate of the product gas outlet is adjusted in real time according to the ammonia demand of the denitrification reactor; The hot air flow rate value G required by the hydrolysis reactor is calculated in real time according to the required ammonia amount, the temperature and pressure data of the hot air, and the temperature and pressure data of the cold air, and then the hot air flow rate entering the hydrolysis reactor is adjusted to G in real time to adjust the rate of the hydrolysis reaction in real time.

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