WO2025044564A1 - Product gas treatment device and method for production of ammonia from urea - Google Patents

Abstract

A product gas treatment device and method for production of ammonia from urea. The device comprises: a urea hydrolyzer (2), a urea solution reacting in the urea hydrolyzer (2) to generate a product gas; a drying device (3) for drying the product gas from the urea hydrolyzer (2); a heating device (8) for evaporating water absorbed by a drying agent from the drying device (3) and returning the drying agent to the drying device (3); a decarbonization device (5) for decarbonizing the product gas from the drying device (3); and a reaction device (9) for providing quicklime powder to the decarbonization device (5).

Description

A device and method for treating product gas from urea to ammonia

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of the Chinese patent application filed with the China Patent Office on August 29, 2023, with application number 202311094230.4 and invention name “A device and method for treating urea-to-ammonia product gas”, the entire contents of which are incorporated by reference in this application.

Technical Field

The present application belongs to the technical field of urea-ammonia production, and specifically relates to a urea-ammonia production product gas processing device and method.

Background Art

The SCR denitration reaction uses ammonia as a reducing agent. Ammonia can be directly heated and gasified from liquid ammonia, or indirectly prepared by evaporation of ammonia water or decomposition of urea. According to national policy requirements, the denitration reducing agent must be changed from liquid ammonia to urea. Urea is not a dangerous good, and is easy to transport and store. It can be decomposed by heat to produce ammonia. There are two mature technologies for urea production: urea thermal decomposition and hydrolysis. The main equipment of the urea hydrolysis ammonia production system includes urea dissolution tank, urea dissolution pump, urea solution storage tank, urea solution delivery pump and urea hydrolysis reactor. Urea granules are added to the urea dissolution tank, dissolved with water into a urea solution with a mass fraction of about 40% to 60%, and transported to the urea solution storage tank through the urea dissolution pump. After that, the urea solution enters the urea hydrolysis reactor through the urea solution delivery pump, and decomposes in the urea hydrolysis reactor to generate NH ₃ , H ₂ O and CO _2. The urea solution hydrolysis product gas is sent to the furnace side by its own pressure and mixed with the dilution air, and then sprayed into the SCR inlet flue through the ammonia injection device. Unlike liquid ammonia, the hydrolysis product gas needs to be kept at a temperature above 140°C to prevent ammonia and carbon dioxide from reacting inversely at low temperatures to form carbamate, which can cause blockage of downstream ammonia branch pipes and other equipment. Therefore, the hydrolysis product gas transmission pipeline needs to be heated by steam to ensure that the temperature is not lower than 140°C throughout the entire process. Steam heating consumes a lot of energy, especially when the transmission pipeline is long, which requires a lot of steam. On the other hand, local heating is prone to low temperatures, causing the product gas to react inversely, affecting the safe operation of the system.

The Chinese patent application, publication number CN113788484B, discloses a purification device and method for hydrolysis product gas, which uses two parallel processes for dehydration and decarbonization, one of which uses an absorbent for dehydration and decarbonization, and the other for absorbent desorption and recovery. However, this patent has obvious shortcomings:

The hydrolysis product gas needs to maintain a stable pressure. The two-way switching method is prone to cause fluctuations in the product gas pressure in the pipeline, which seriously affects the stability of ammonia supply. The switching time point judgment standard is the appearance of H ₂ O and CO ₂ in the treated product gas, which will cause band-like H ₂ O and CO ₂ peaks in the product, affecting the treatment effect. In addition, this patent requires additional energy consumption to desorb the absorbent to restore the absorption capacity. The waste gas generated during the desorption process contains a small amount of ammonia, which pollutes the environment and is not suitable for direct discharge.

Summary of the invention

In order to solve the technical problems existing in the prior art, the purpose of the present application is to provide a urea-to-ammonia product gas processing device and method.

In order to achieve the above objectives and the above technical effects, the technical solution adopted in this application is:

A urea-ammonia product gas processing device, comprising:

boiler;

Urea hydrolyzer, in which urea solution reacts to generate product gas, the product gas includes NH ₃ , H ₂ O and CO ₂ ;

A drying device, connected to the urea hydrolyzer, for drying the product gas from the urea hydrolyzer;

A heating device, connected to the drying device, for evaporating the water absorbed by the desiccant from the drying device and returning it to the drying device;

A decarbonization device, connected to the drying device, for decarbonizing the product gas from the drying device;

A reaction device, connected to the decarbonization device, for providing quicklime powder to the decarbonization device;

The urea solution reacts in the urea hydrolyzer to generate product gas, which enters the drying device for drying. The dried product gas contains NH ₃ and CO ₂ , and then enters the decarbonization device for CO ₂ removal to obtain product gas containing only NH ₃ .

Optionally, the device further comprises a quicklime powder storage tank, in which quicklime powder is stored, the quicklime powder storage tank is connected to the decarbonization device via a delivery pump c, and the quicklime powder storage tank and the delivery pump e are connected to the reaction device.

Optionally, the drying device is a sealed three-compartment shell structure, including a desiccant bin, a dehumidifying drying bin and a desiccant bin to be processed, which are arranged in sequence from top to bottom. The desiccant bin is connected to the dehumidifying drying bin via a regulating valve b, and the dehumidifying drying bin is connected to the desiccant bin to be processed via a regulating valve c. The desiccant bin and the desiccant bin to be processed are respectively connected to the bottom and top of the heating device, and the desiccant can flow between the desiccant bin, the dehumidifying drying bin, the desiccant bin to be processed and the heating device.

Optionally, a regulating valve a is provided on the top of the desiccant bin, and a level meter a and a regulating valve b are provided on the bottom. The level meter a is used to monitor the amount of desiccant in the desiccant bin, and the opening of the regulating valve b is adjustable to control the flow rate of the desiccant into the dehumidifying and drying bin; a regulating valve c is provided at the bottom of the dehumidifying and drying bin, and the openings of the regulating valve b and the regulating valve c are always consistent to ensure that a certain amount of desiccant is always maintained in the dehumidifying and drying bin, and a humidity sensor is provided at the exhaust port of the dehumidifying and drying bin; a level meter b is provided on the top of the desiccant bin to be treated, and the desiccant to be treated is provided at the top of the desiccant bin to be treated. A regulating valve d is provided at the bottom of the bin.

Optionally, the decarbonization device includes a decarbonization reaction tower, a quicklime powder injection device is provided at the top of the decarbonization reaction tower, which is used to evenly spray quicklime powder into the decarbonization reaction tower, a regulating valve e is provided at the bottom, and a _CO2 sensor is provided at the exhaust port. The bottom of the decarbonization reaction tower is connected with the reaction device through the regulating valve e, the delivery pump d and the regulating valve h in sequence, and the top of the decarbonization reaction tower is connected with the quicklime powder storage tank through the quicklime powder injection device and the delivery pump c, and the quicklime powder storage tank stores quicklime powder.

Optionally, the bottom of the heating device is connected to the desiccant bin via regulating valve g, delivery pump b and regulating valve a in sequence, and the top of the heating device is connected to the desiccant bin to be treated via regulating valve f, delivery pump a and regulating valve d in sequence.

Optionally, the heating device includes a heating evaporation tower, which is provided with a regulating valve f at the top, a regulating valve g at the bottom, and a heating coil inside. The gas in the heating coil is isolated from the gas in the heating device. The air inlet of the heating coil is connected to the air preheater inlet flue, and the exhaust is connected to the air preheater outlet flue. The air preheater inlet flue gas pressure is 1 to 2 kPa higher than the air preheater outlet flue gas pressure, and the flue gas temperature is 300 to 400°C. The temperature in the heating evaporation tower is always higher than 100°C.

Optionally, the heating evaporation tower is connected to a compressed air storage tank, and compressed air is introduced into the heating evaporation tower through the compressed air storage tank, and the evaporated water is taken away by the compressed air, and the exhaust gas is connected to the air preheater outlet flue.

Optionally, the reaction device includes a high-temperature pyrolysis tower, which is connected to the boiler. The high-temperature flue gas in the boiler enters the high-temperature pyrolysis tower. The limestone powder in the high-temperature pyrolysis tower is decomposed into CaO and _CO2 under the action of high temperature. The gaseous _CO2 circulates with the boiler flue gas and is not discharged to the outside. The CaO returns to the quicklime powder storage tank.

The present application also discloses a method for treating product gas from urea to ammonia, using the above-mentioned device for treating product gas from urea to ammonia, the method comprising the following steps:

1) Product gas drying:

The regulating valve a and regulating valve d are closed, and the regulating valve b and regulating valve c are opened, and the openings of regulating valve b and regulating valve c are consistent, and the opening size can be adjusted dynamically. According to the monitoring of the humidity sensor, if _H2O is detected, the openings of regulating valve b 34 and regulating valve c continue to be opened until the treated product gas is completely dry and a certain margin is left. At this time, the desiccant in the desiccant bin flows into the dehumidification drying bin, and the desiccant after absorbing water flows into the desiccant bin to be treated. The product gas in the urea hydrolyzer enters from the lower air inlet of the dehumidification drying bin and is discharged from the upper exhaust port, so that the desiccant that first contacts the product gas flows into the desiccant bin to be treated first. When the material level meter a detects that the desiccant bin is insufficient, the regulating valve b and regulating valve c are closed, the regulating valve a is opened, and the delivery pump b quickly delivers the desiccant that has been heated to restore the drying capacity to the desiccant bin. This process takes a short time and the desiccant bin can be quickly filled in a short time; then, the regulating valve b is closed, and the regulating valve c is opened, and the conveying ... is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened, and the conveying pump b is opened Valve a and delivery pump b are closed, and regulating valve b and regulating valve c are reopened. When level meter b detects that the desiccant bin to be treated has reached the upper limit, regulating valve b and regulating valve c are closed, regulating valve d and regulating valve f are opened, and delivery pump a quickly delivers the desiccant after absorbing water to the heating evaporation tower. This process takes a short time, and all the desiccant in the desiccant bin to be treated can be quickly delivered to the heating evaporation tower in a short time. Subsequently, regulating valve f, regulating valve d and delivery pump a are closed, and regulating valve b and regulating valve c are reopened.

2) Product gas decarbonization:

The product gas no longer contains H ₂ O after being dried by the drying device, and is discharged from the exhaust port on the top of the dehumidification drying chamber and flows into the decarbonization device to remove CO ₂ :

The product gas flows in from the lower part of the decarbonization reaction tower and is discharged from the upper part. The delivery pump c continuously delivers the quicklime powder in the quicklime powder storage tank to the quicklime powder injection device. The output power of the delivery pump c is adjusted according to the _CO2 content in the product gas monitored by the _CO2 sensor. If _CO2 is detected, the output power of the delivery pump c is quickly increased to ensure the decarbonization effect and leave enough margin. The quicklime powder injection device on the top of the decarbonization reaction tower sprays the quicklime powder into the decarbonization reaction tower. The quicklime powder settles downward under the action of gravity and can fully react with the countercurrent product gas to absorb the _CO2 therein to generate limestone powder. The decarbonization effect can be improved through countercurrent contact reaction. The limestone powder accumulates at the bottom of the decarbonization reaction tower. The regulating valve e is set to open at a timed interval. When it is opened, the delivery pump d and the regulating valve h are opened, and the limestone powder can be quickly transported to the high-temperature pyrolysis tower for pyrolysis reaction to generate CaO and _CO2 . The reaction time is short and the gaseous CO ₂ It circulates with the boiler flue gas. After the set time, the regulating valve i opens and the delivery pump e starts to deliver the quicklime powder to the quicklime powder storage tank. In this way, it can be recycled and reused, but there will still be a small amount of loss. The quicklime powder can be regularly added to the quicklime powder storage tank;

The product gas after treatment by the decarbonization device is _NH3 gas, which flows into the denitrification inlet flue through pipelines and ammonia injection devices without the need for heating to achieve the denitrification function.

Compared with the prior art, the beneficial effects of this application are:

The present application discloses a device and method for treating ammonia product gas produced by urea. The device and method realize continuous and stable removal of _H2O and _CO2 in the ammonia product gas produced by urea through a drying device and a decarbonization device. The product gas can be transported without heating, which can reduce the consumption of heating energy on the one hand, and improve the reliability of the system on the other hand, avoiding the problem of crystallization blockage caused by low temperature of the product gas. The drying and decarbonization processes do not need to adopt two-way parallel switching, and the removal process is continuous, which ensures the stability of the product gas pressure and avoids the band-like peaks of _H2O and _CO2 in the product caused by the switching process. The high-temperature flue gas of the boiler is used to form a high-temperature atmosphere, and the desiccant is heated to evaporate water to realize the reuse of the desiccant. With the help of the differential pressure of the boiler flue gas itself, spontaneous flow is realized without adding a driving device. There is no external discharge of pollutants in the entire drying process, and the evaporated water vapor is also returned to the desiccant. Boiler circulation; utilize the heat of the boiler to pyrolyze the decarbonization product limestone powder to achieve the reuse of the decarbonizer quicklime powder. The entire decarbonization process does not have any external pollutants. The _CO2 produced by the treatment is returned to the boiler circulation, and the decarbonizer is returned to the storage bin for reuse. After drying and decarbonization, only _NH3 remains in the hydrolysis product gas, _which can be transported at room temperature without the need for heating. This application not only realizes the dehydration and decarbonization treatment of urea hydrolysis product gas and eliminates the heating of product gas, but also has the characteristics of energy saving and consumption reduction, low carbon and environmental protection, and recycling. It can improve the stability of the system and has important significance and value for the new construction and renovation of urea hydrolysis and safe operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of the present application;

FIG2 is a schematic diagram of the structure of the boiler of the present application;

Among them: 1. Boiler; 2. Urea hydrolyzer; 3. Drying device; 4. Humidity sensor; 5. Decarbonization device; 6. CO ₂ sensors; 7. quicklime powder storage tank; 8. heating device; 9. reaction device; 10. compressed air storage tank; 11. delivery pump a; 12. delivery pump b; 13. delivery pump c; 14. delivery pump d; 15. delivery pump e; 31. regulating valve a; 32. desiccant bin; 33. material level meter a; 34. regulating valve b; 35. dehumidification and drying bin; 36. regulating valve c; 37. material level meter b; 38. desiccant bin to be treated; 39. regulating valve d; 51. quicklime powder injection device; 52. decarbonization reaction tower; 53. regulating valve e; 81. regulating valve f; 82. heating evaporation tower; 83. heating coil; 84. regulating valve g; 91. regulating valve h; 92. high-temperature pyrolysis tower; 93. regulating valve i; 16. air preheater inlet flue; 17. air preheater outlet flue.

DETAILED DESCRIPTION

The present application is described in detail below so that the advantages and features of the present application can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present application.

A brief summary of one or more aspects is given below to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceived aspects, and is neither intended to identify the key or critical elements of all aspects nor to define the scope of any or all aspects. Its only purpose is to give some concepts of one or more aspects in a simplified form as a prelude to a more detailed description that will be given later.

As shown in FIG1-2, a urea-to-ammonia product gas processing device comprises:

Boiler 1;

Urea hydrolyzer 2, urea solution reacts in urea hydrolyzer 2 to generate product gas, the product gas includes NH ₃ , H ₂ O and CO ₂ ;

The drying device 3 is connected to the urea hydrolyzer 2 and is a sealed three-compartment housing structure, including a desiccant compartment 32, a dehumidification and drying compartment 35 and a desiccant compartment 38 arranged in order from top to bottom; wherein the desiccant compartment 32 stores Desiccant: the desiccant is fine-grained silica gel with good fluidity. A regulating valve a 31 is provided on the top of the desiccant bin 32, and a material level meter a 33 and a regulating valve b 34 are provided on the bottom. The regulating valve a 31 is opened when the desiccant is replenished and is closed under normal circumstances. The material level meter a 33 can monitor the amount of desiccant in the desiccant bin 32. When the desiccant drops to the lower limit, the regulating valve a 31 needs to be opened to replenish the desiccant. The opening size of the regulating valve b 34 can be adjusted to control the flow rate of the desiccant flowing into the dehumidifying and drying bin 35. A certain amount of desiccant is always maintained in the dehumidifying and drying bin 35 for dehydration and drying. The product gas enters from the air inlet at the bottom of the dehumidifying and drying bin 35 and is discharged from the air outlet at the top. The top of the dehumidifying and drying bin 35 is connected to the desiccant bin 32 through the regulating valve b 34. The bottom of the dehumidifying and drying bin 35 is provided with a regulating valve c 36 for communicating with the desiccant bin 38 to be processed. The regulating valve b 34 is connected to the regulating valve c 36. The opening of valve 36 is always consistent, ensuring that the amount of desiccant entering and exiting the dehumidification and drying bin 35 is the same, so as to ensure that a fixed amount of desiccant is always maintained inside; the desiccant after absorbing water is stored in the desiccant bin 38 to be processed, the top of the desiccant bin 38 to be processed is connected to the dehumidification and drying bin 35 through a regulating valve c 36, the bottom of the desiccant bin 38 to be processed is provided with a regulating valve d 39, and the upper part of the desiccant bin 38 to be processed is provided with a material level meter b 37, when the material level meter b 37 monitors that the desiccant after absorbing water accumulates to the upper limit value, the desiccant after absorbing water is output to the heating device 8 in time;

The decarbonization device 5 has a decarbonization reaction tower 52 as its main body. The decarbonization reaction tower 52 is a sealed shell structure. A quicklime powder injection device 51 is provided on the top to spray the quicklime powder evenly. A regulating valve e 53 is provided on the bottom.

Quicklime powder storage tank 7;

The heating device 8 has a main body which is a heating evaporation tower 82. The heating evaporation tower 82 is a sealed shell structure, with a regulating valve f 81 on the top, a regulating valve g 84 on the bottom, and a heating coil 83 inside. The gas in the heating coil 83 is isolated from the gas in the heating device 8. The air intake of the heating coil 83 is connected to the air preheater inlet flue 16, and the exhaust is connected to the air preheater outlet flue 17. The boiler 1, the denitrification device, and the air preheater are arranged in sequence. The flue gas pressure at the air preheater inlet is 1 to 2 kPa higher than the flue gas pressure at the air preheater outlet. The flue gas temperature is 300-400°C. The above flue gas can flow spontaneously without the need for an extraction device, and without the need to increase a power device and energy consumption. In this way, the temperature in the heating evaporation tower 82 can be kept always higher than 100°C, and the moisture absorbed by the desiccant can be evaporated. Compressed air is introduced into the heating evaporation tower 82 through the compressed air storage tank 10, and the evaporated water is taken away by the compressed air. The exhaust gas is connected to the air preheater outlet flue 17. Since the compressed air is at positive pressure and the air preheater outlet is at negative pressure, the above gas can flow spontaneously, and the evaporated waste gas returns to the boiler 1 for circulation and is treated by the boiler environmental protection equipment;

The reaction device 9 has a main body of a high-temperature pyrolysis tower 92, which is connected to the furnace of the boiler 1. The product gas flows in from the lower part of the decarbonization device 5 and is discharged from the upper part. A filter screen is set at the exhaust port to prevent the powder from being carried out in large quantities by the air flow, causing loss. The _CO2 sensor 6 is located at the exhaust port and is used to monitor the _CO2 in the treated product gas. The quicklime powder storage tank 7 stores quicklime powder (CaO). The quicklime powder can be transported to the quicklime powder injection device 51 through the delivery pump c13. The limestone powder (CaCO ₃ ) after absorbing CO ₂ is sent to the reaction device 9, and the high-temperature flue gas (＞1000℃) in the boiler 1 is used to form a high-temperature reaction atmosphere. The limestone powder (CaCO ₃ ) is decomposed into CaO and CO ₂ under the action of high temperature. The gaseous CO ₂ circulates with the boiler flue gas and is not discharged to the outside. The quicklime powder (CaO) returns to the quicklime powder storage tank 7.

The chemical equation for the urea hydrolysis reaction to produce ammonia is:

The concentration of the urea solution in the urea hydrolysis reactor is about 40-60%, the pressure of the gas-liquid two-phase equilibrium system is about 0.4-0.6 MPa, and the temperature is about 140-170°C.

A method for treating product gas from urea to ammonia comprises the following steps:

1) Product gas drying:

The regulating valve a 31 and regulating valve d 39 are closed, and the regulating valve b 34 and regulating valve c 36 are opened, and the openings of the regulating valve b 34 and regulating valve c 36 are consistent, and the openings can be adjusted dynamically. According to the monitoring of the humidity sensor 4, if H ₂ O is detected, the openings of the regulating valve b 34 and regulating valve c 36 continue to be opened until the treated product gas is completely dry, and a certain margin is left. At this time, the desiccant in the desiccant bin 32 flows into the dehumidification drying bin 35, and the desiccant after absorbing water flows into the desiccant bin to be treated 38. The product gas enters from the lower air inlet of the dehumidification drying bin 35 and is discharged from the upper exhaust port. This design allows the desiccant that first contacts the product gas to flow into the desiccant bin to be treated 38 first, because the desiccant that first contacts the product gas absorbs the most water and is also the first part to lose its drying ability. When the material level meter a 33 detects that the desiccant bin 32 is insufficient, the regulating valve b 34 and the regulating valve c 36 are closed, the regulating valve a 31 is opened, and the delivery pump b 12 quickly delivers the desiccant that has been heated and restored to its drying capacity to the desiccant bin 32. This process takes a short time, and the desiccant bin 32 can be quickly filled in a short time. Subsequently, the regulating valve a 31 and the delivery pump b 12 are closed, and the regulating valve b 34 and the regulating valve c 36 are reopened. Because the replenishment time is very short, it will basically not affect the treatment effect of the desiccant in the dehumidification and drying bin 35. When the material level meter b 37 detects that the desiccant bin 38 to be processed has reached the upper limit, the regulating valve b 34 and the regulating valve c 36 are closed, the regulating valve d 39 and the regulating valve f 81 are opened, and the delivery pump a 11 quickly delivers the desiccant after absorbing water to the heating evaporation tower 82. This process takes a short time, and all the desiccant in the desiccant bin 38 to be processed can be quickly delivered to the heating evaporation tower 82 in a short time. Subsequently, the regulating valve f 81, the regulating valve d 39 and the delivery pump a 11 are closed, and the regulating valve b 34 and the regulating valve c 36 are reopened. Because the discharge time is very short, it will basically not affect the treatment effect of the desiccant in the dehumidification and drying bin 35.

2) Product gas decarbonization:

The product gas does not contain H ₂ O after being dried by the drying device 3, and is discharged from the exhaust port at the top of the dehumidification drying chamber 35, and flows into the decarbonization device 5 to remove CO ₂ : the product gas flows into the lower part of the decarbonization reaction tower 52, and is discharged from the upper part, and the delivery pump c 13 continuously delivers the quicklime powder (CaO) in the quicklime powder storage tank 7 to the quicklime powder injection device 51. The output power of the delivery pump c 13 is adjusted according to the CO ₂ content in the product gas monitored by the CO ₂ sensor 6. If CO ₂ is detected, the output power of the delivery pump c 13 is quickly increased to ensure the decarbonization effect and leave enough margin. The quicklime powder injection device 51 on the top of the decarbonization reaction tower 52 sprays the quicklime powder into the decarbonization reaction tower 52. The quicklime powder settles downward under the action of gravity and can fully react with the countercurrent product gas to absorb the CO ₂ therein to generate limestone powder (CaCO ₃ ). The countercurrent contact reaction can improve the decarbonization effect. The limestone powder accumulates at the bottom of the decarbonization reaction tower 52. The regulating valve e53 is set to open at a timed interval. When it is opened, the delivery pump d 14 and the regulating valve h 91 are opened, so that the limestone powder can be quickly delivered to the high-temperature pyrolysis tower 92 for pyrolysis reaction to generate CaO and CO _2. The reaction time is short and the gaseous CO ₂ circulates with the boiler flue gas. After a set time, the regulating valve i 93 is opened, and the delivery pump e 15 is turned on to deliver the quicklime powder (CaO) to the quicklime powder storage tank 7. In this way, it can be recycled and reused, but there will still be a small amount of loss. The quicklime powder can be regularly replenished to the quicklime powder storage tank 7;

The product gas treated by the decarbonization device 5 is NH ₃ gas, which flows into the denitrification inlet flue through the pipeline and the ammonia injection device without heating to realize the denitrification function.

Compared with the prior art, this application has at least the following technical effects:

1. This application achieves the purpose of transporting product gas without heating by drying and decarbonizing the product gas, greatly saving energy consumption and improving the reliability of system operation;

2. This application utilizes the heat of boiler flue gas to realize repeated recycling of desiccant and decarbonizer, reducing resource and energy consumption and the generation of by-products, greatly saving costs and without environmental pollution;

3. This application sets up the absorption treatment and recovery treatment process of the desiccant and decarbonizer separately, ensuring the continuous and stable drying and decarbonization process and the stable product gas pressure.

Parts or structures not specifically described in this application may adopt existing technologies or existing products and will not be described in detail here.

The above description is only an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims (10)

A urea-ammonia product gas processing device, characterized by comprising: boiler; Urea hydrolyzer, in which urea solution reacts to generate product gas, the product gas includes NH ₃ , H ₂ O and CO ₂ ; A drying device, connected to the urea hydrolyzer, for drying the product gas from the urea hydrolyzer; A heating device, connected to the drying device, for evaporating the water absorbed by the desiccant from the drying device and returning it to the drying device; A decarbonization device, connected to the drying device, for decarbonizing the product gas from the drying device; A reaction device, connected to the decarbonization device, for providing quicklime powder to the decarbonization device; The urea solution reacts in the urea hydrolyzer to generate product gas, which enters the drying device for drying. The dried product gas contains NH ₃ and CO ₂ , and then enters the decarbonization device for CO ₂ removal to obtain product gas containing only NH ₃ . The urea-to-ammonia product gas processing device according to claim 1 is characterized in that it also includes a quicklime powder storage tank, in which quicklime powder is stored, and the quicklime powder storage tank is connected to the decarbonization device through a delivery pump c, and the quicklime powder storage tank and the delivery pump e are connected to the reaction device. The urea-to-ammonia product gas processing device according to claim 1 is characterized in that the drying device is a sealed three-compartment shell structure, including a desiccant bin, a dehumidification drying bin and a desiccant bin to be treated, which are arranged in sequence from top to bottom, and the desiccant bin is connected to the dehumidification drying bin through a regulating valve b, and the desiccant bin is connected to the desiccant bin to be treated through a regulating valve c, and the desiccant bin and the desiccant bin to be treated are respectively connected to the bottom and top of the heating device, and the desiccant can flow between the desiccant bin, the dehumidification drying bin, the desiccant bin to be treated and the heating device. The urea-to-ammonia product gas processing device according to claim 3 is characterized in that a regulating valve a is provided on the top of the desiccant bin, and a level meter a and a regulating valve b are provided on the bottom, the level meter a is used to monitor the amount of desiccant in the desiccant bin, and the opening size of the regulating valve b is adjustable to control the flow rate of the desiccant flowing into the dehumidification and drying bin; a regulating valve c is provided at the bottom of the dehumidification and drying bin, and the openings of the regulating valve b and the regulating valve c are always consistent to ensure that a certain amount of desiccant is always maintained in the dehumidification and drying bin, and a humidity sensor is provided at the exhaust port of the dehumidification and drying bin; a level meter b is provided on the top of the desiccant bin to be treated, and a regulating valve d is provided at the bottom of the desiccant bin to be treated. The urea-to-ammonia product gas processing device according to claim 1 is characterized in that the decarbonization device comprises a decarbonization reaction tower, a quicklime powder injection device is provided at the top of the decarbonization reaction tower, which is used to evenly spray the quicklime powder into the decarbonization reaction tower, a regulating valve e is provided at the bottom, a _CO2 sensor is provided at the exhaust port, and the bottom of the decarbonization reaction tower is provided according to the The first step is connected to the reaction device through the regulating valve e, the delivery pump d and the regulating valve h. The top of the decarbonization reaction tower is connected to the quicklime powder storage tank through the quicklime powder injection device and the delivery pump c. The quicklime powder storage tank stores quicklime powder. The urea-to-ammonia product gas processing device according to claim 1 or 3 is characterized in that the bottom of the heating device is connected to the desiccant bin through the regulating valve g, the delivery pump b and the regulating valve a in sequence, and the top of the heating device is connected to the desiccant bin to be treated through the regulating valve f, the delivery pump a and the regulating valve d in sequence. The urea-to-ammonia product gas processing device according to claim 1 is characterized in that the heating device comprises a heating evaporation tower, a regulating valve f is provided at the top of the heating evaporation tower, a regulating valve g is provided at the bottom, a heating coil is provided inside, the gas in the heating coil is isolated from the gas in the heating device, the air intake of the heating coil is connected to the air preheater inlet flue, and the exhaust is connected to the air preheater outlet flue, the air preheater inlet flue gas pressure is 1 to 2 kPa higher than the air preheater outlet flue gas pressure, the flue gas temperature is 300 to 400°C, and the temperature in the heating evaporation tower is always higher than 100°C. The urea to ammonia product gas processing device according to claim 7 is characterized in that the heating evaporation tower is connected to a compressed air storage tank, compressed air is introduced into the heating evaporation tower through the compressed air storage tank, the evaporated water is taken away by the compressed air, and the exhaust gas is connected to the air preheater outlet flue. The urea-to-ammonia product gas processing device according to claim 1 is characterized in that the reaction device includes a high-temperature pyrolysis tower, which is connected to the boiler, and the high-temperature flue gas in the boiler enters the high-temperature pyrolysis tower. The limestone powder in the high-temperature pyrolysis tower is decomposed into CaO and _CO2 under the action of high temperature, and the gaseous _CO2 circulates with the boiler flue gas and is not discharged to the outside, and the CaO returns to the quicklime powder storage tank. A method for treating ammonia product gas from urea, characterized in that the device for treating ammonia product gas from urea according to any one of claims 1 to 9 is used, and the method comprises the following steps: 1) Product gas drying: The regulating valves a and d are closed, the regulating valves b and c are opened, and the openings of the regulating valves b and c are consistent. The openings can be adjusted dynamically. According to the monitoring of the humidity sensor, if H ₂ O is detected, the regulating valve b 34 and the opening of the regulating valve c continue to be opened until the treated product gas is completely dry with a certain margin. At this time, the desiccant in the desiccant bin flows into the dehumidification drying bin, and the desiccant after absorbing water flows into the desiccant bin to be treated. The product gas in the urea hydrolyzer enters from the lower air inlet of the dehumidification drying bin and is discharged from the upper exhaust port, so that the desiccant that first contacts the product gas flows into the desiccant bin to be treated first. When the level meter a detects that the desiccant bin is insufficient, the regulating valve b and the regulating valve c are closed, the regulating valve a is opened, and the delivery pump b quickly delivers the desiccant that has been heated to restore the drying capacity to the desiccant bin. This process takes a short time and can quickly fill the desiccant bin in a short time; then, the regulating valve a and the delivery pump b are closed, and the regulating valve b and the regulating valve c are reopened. When the level meter b detects that the desiccant bin to be treated is insufficient, the desiccant in the desiccant bin to be treated is insufficient. When the upper limit is reached, the regulating valve b and regulating valve c are closed, the regulating valve d and regulating valve f are opened, and the delivery pump a quickly delivers the desiccant after absorbing water to the heating evaporation tower. This process takes a short time, and all the desiccant in the desiccant bin to be processed can be quickly delivered to the heating evaporation tower in a short time. Subsequently, the regulating valve f, regulating valve d and delivery pump a are closed, and the regulating valve b and regulating valve c are reopened; 2) Product gas decarbonization: The product gas no longer contains H ₂ O after being dried by the drying device, and is discharged from the exhaust port on the top of the dehumidification drying chamber and flows into the decarbonization device to remove CO ₂ : The product gas flows in from the lower part of the decarbonization reaction tower and is discharged from the upper part. The delivery pump c continuously delivers the quicklime powder in the quicklime powder storage tank to the quicklime powder injection device. The output power of the delivery pump c is adjusted according to the _CO2 content in the product gas monitored by the _CO2 sensor. If _CO2 is detected, the output power of the delivery pump c is quickly increased to ensure the decarbonization effect and leave enough margin. The quicklime powder injection device on the top of the decarbonization reaction tower sprays the quicklime powder into the decarbonization reaction tower. The quicklime powder settles downward under the action of gravity and can fully react with the countercurrent product gas to absorb the _CO2 therein to generate limestone powder. The decarbonization effect can be improved through countercurrent contact reaction. The limestone powder accumulates at the bottom of the decarbonization reaction tower. The regulating valve e is set to open at a timed interval. When it is opened, the delivery pump d and the regulating valve h are opened, and the limestone powder can be quickly transported to the high-temperature pyrolysis tower for pyrolysis reaction to generate CaO and _CO2 . The reaction time is short and the gaseous CO ₂ It circulates with the boiler flue gas. After the set time, the regulating valve i opens and the delivery pump e starts to deliver the quicklime powder to the quicklime powder storage tank. In this way, it can be recycled and reused, but there will still be a small amount of loss. The quicklime powder can be regularly added to the quicklime powder storage tank; The product gas after treatment by the decarbonization device is _NH3 gas, which flows into the denitrification inlet flue through pipelines and ammonia injection devices without the need for heating to achieve the denitrification function.