Accurate urea solution preparation system

Abstract

The utility model relates to an accurate urea solution preparation system which is characterized in that a discharge port of a urea granule bin is communicated with a feed port of a first-stage spiral feeder, the feed port of the first-stage spiral feeder is communicated with a feed port of a second-stage weighing quantitative feeder, and a discharge port of the second-stage weighing quantitative feeder is communicated with a feed port of a jet mixer; a liquid inlet of the jet mixer is used for introducing liquid mixed with urea particles, a liquid outlet of the jet mixer is communicated with a liquid inlet of the buffer mixing tank, a liquid outlet of the buffer mixing tank is communicated with a liquid inlet of the filter, a liquid outlet of the filter is communicated with a liquid inlet of the mass flow meter, and a liquid outlet of the mass flow meter outputs a urea solution. Wherein the feeder comprises a first-stage spiral feeder and a second-stage weighing quantitative feeder, feeding and weighing can be accurately controlled through two-stage feeding, the jet mixer is an annular jet mixer, rapid dissolution of urea particles is facilitated, and the whole system is beneficial to accurate, rapid and automatic control and configuration of the required urea solution concentration.

Description

Technical Field

[0001] This utility model relates to the field of flue gas denitrification, and more specifically, to a system for the precise preparation of urea solution. Background Technology

[0002] Common reducing agents for flue gas denitrification include liquid ammonia, ammonia water, and urea. Liquid ammonia and ammonia water with a concentration >10% are classified as hazardous chemicals, and their transportation, storage, and use are prone to danger. The control of hazardous chemicals is becoming increasingly stringent. Liquid ammonia, in particular, is a major hazard source due to the presence of flammable, explosive, and toxic ammonia gas. Its storage requires careful consideration of safety requirements during the design phase, and its large fire-fighting distance can lead to limited on-site space. Therefore, urea will increasingly be used as the preferred reducing agent for flue gas denitrification in the future.

[0003] However, purchased urea is generally in granular solid form, while flue gas denitrification ultimately requires a 50% concentration urea solution. Therefore, it is necessary to dissolve the urea granules to prepare a 50% solution. Traditional urea dissolution and preparation systems typically use manual feeding, mechanical stirring, and steam heating to prepare the urea solution. This method is not only costly, requires a large area, and has high energy consumption, but also makes it difficult to precisely control the solution concentration. Compared to traditional precise urea solution preparation systems, the jet injector method requires less space, consumes less energy, and has a higher degree of automation.

[0004] In related technologies, the precise urea solution preparation system relies solely on a single-stage screw feeder or feed valve for quantitative feeding of urea granules. However, the density of urea granules varies significantly in a fluidized state, making it difficult to ensure precise feeding using only a screw feeder. This hinders the rapid and accurate automatic control of urea solution concentration. Furthermore, to monitor urea solution concentration, a mass flow meter is installed on the pipeline where the urea solution is pumped from the buffer mixing tank. However, some incompletely dissolved urea granules settle at the bottom of the mixing tank and enter the mass flow meter with the pump, leading to discrepancies between the measured and actual concentrations. This results in some incompletely dissolved urea solution being pumped out. Utility Model Content

[0005] The purpose of this invention is to provide a precise urea solution preparation system to improve the accuracy of urea solution concentration measurement.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0007] This utility model provides a precise urea solution preparation system, which includes: a urea granule silo, a feeder, a jet mixer, a buffer mixing tank, a filter, and a mass flow meter;

[0008] The outlet of the urea granule silo is connected to the inlet of the feeder, the outlet of the feeder is connected to the inlet of the jet mixer, the inlet of the jet mixer is used to introduce liquid mixed with urea granules, the outlet of the jet mixer is connected to the inlet of the buffer mixing tank, the outlet of the buffer mixing tank is connected to the inlet of the filter, the outlet of the filter is connected to the inlet of the mass flow meter, and the outlet of the mass flow meter outputs urea solution.

[0009] The filter's return outlet is connected to the buffer mixing tank's return inlet, and the filter is equipped with a filter screen. The filter screen is used to block incompletely dissolved urea particles flowing from the filter to the mass flow meter, and to allow incompletely dissolved urea particles to flow to the buffer mixing tank.

[0010] In some embodiments of this application, the urea solution precision preparation system further includes a urea solution storage tank;

[0011] The outlet of the mass flow meter is connected to the inlet of the urea solution storage tank, and an outlet valve is provided on the connecting pipe between the mass flow meter and the urea solution storage tank.

[0012] In some embodiments of this application, the urea solution precision preparation system further includes a hydrophobic tank and a circulating water pump;

[0013] The outlet of the condensate tank is connected to the inlet of the jet mixer and the inlet of the circulating water pump, and an inlet valve is provided on the connecting pipe between the condensate tank and the circulating water pump.

[0014] The circulation outlet of the buffer mixing tank is connected to the inlet of the circulating water pump, and a circulation valve is provided on the connecting pipe between the buffer mixing tank and the circulating water pump.

[0015] The outlet of the circulating water pump is connected to the inlet of the jet mixer, and the connecting pipe between the circulating water pump and the jet mixer is equipped with a jet mixer inlet flow meter.

[0016] In some embodiments of this application, a buffer mixing tank level gauge is provided inside the buffer mixing tank;

[0017] The urea solution storage tank is equipped with a urea solution storage tank level gauge.

[0018] The precise urea solution preparation system also includes a delivery pump;

[0019] The outlet of the buffer mixing tank is connected to the inlet of the delivery pump;

[0020] The outlet of the delivery pump is connected to the inlet of the filter;

[0021] The precise urea solution preparation system also includes a controller;

[0022] The controller signal is connected to the level gauge of the buffer mixing tank and the level gauge of the urea solution storage tank, and is used to control the feeder, the circulation valve, the delivery pump, the inlet valve and the outlet valve.

[0023] In some embodiments of this application, the urea solution precision preparation system further includes an inlet water flow meter;

[0024] The outlet of the condensate tank is connected to the inlet flow meter;

[0025] The outlet of the inlet flow meter is connected to the inlet of the circulating water pump and the makeup water inlet of the buffer mixing tank.

[0026] The inlet valve is located on the connecting pipe between the inlet flow meter and the circulating water supply pump;

[0027] A water supply valve is provided on the connecting pipe between the inlet flow meter and the buffer mixing tank;

[0028] The controller is also used to control the water supply valve.

[0029] In some embodiments of this application, the hydrophobic tank is equipped with a hydrophobic tank heater and a hydrophobic tank level gauge.

[0030] In some embodiments of this application, a thermometer is provided inside the urea solution storage tank;

[0031] The precise urea solution preparation system also includes a steam heating system, which is used to heat the urea solution in the urea solution storage tank and to allow the heated steam to enter the hydrophobic tank.

[0032] In some embodiments of this application, the buffer mixing tank has two reflux inlets, namely a first reflux inlet and a second reflux inlet;

[0033] The filter’s reflux outlet is connected to the first reflux inlet of the buffer mixing tank, and a first reflux valve is provided on the connecting pipe between the filter and the buffer mixing tank.

[0034] The outlet of the mass flow meter is also connected to the second reflux inlet of the buffer mixing tank, and a second reflux valve is provided on the connecting pipe between the mass flow meter and the buffer mixing tank.

[0035] In some embodiments of this application, the feed inlet and water inlet of the jet mixer are both located at the first end of the jet mixer;

[0036] The water inlet of the jet mixer is annular and surrounds the feed inlet of the jet mixer.

[0037] The outlet of the jet mixer is located at the second end of the jet mixer.

[0038] In some embodiments of this application, the feeder includes a primary screw feeder and a secondary weighing and metering feeder;

[0039] The outlet of the urea granule silo is connected to the inlet of the primary screw feeder;

[0040] The discharge port of the primary screw feeder is connected to the discharge port of the secondary weighing and metering feeder;

[0041] The urea solution precision preparation system also includes a buffer hopper;

[0042] The outlet of the secondary weighing quantitative feeder is connected to the inlet of the buffer hopper;

[0043] The outlet of the buffer hopper is connected to the inlet of the jet mixer.

[0044] As can be seen from the above technical solution, the embodiments of this utility model have at least the following advantages and positive effects:

[0045] In the urea solution precision preparation system of this embodiment, urea particles in the urea particle hopper are fed into a jet mixer via a feeder and mixed with the liquid entering the jet mixer. The urea feeder includes a primary screw feeder and a secondary weighing and metering feeder. The two-stage feeding allows for precise control of feeding and weighing. The jet mixer can be a ring-shaped jet mixer, which facilitates precise, rapid, and automatic control of the required urea solution concentration. This system solves the problem of large density changes in urea particles during fluidization, which makes precise feeding and solution preparation difficult.

[0046] After mixing, the resulting urea solution enters a buffer mixing tank. The urea solution flowing out of the buffer mixing tank is filtered through a filter to remove any incompletely dissolved urea particles before flowing into a mass flow meter.

[0047] This invention addresses the problem of undissolved urea particles entering the mass flow meter, causing inaccurate solution density measurements and the issue of partially undissolved urea solution being transferred to the finished product storage tank. It enables the mass flow meter to accurately measure the concentration of the urea solution. Simultaneously, undissolved urea can be recycled back to the buffer mixing tank for further dissolution. Attached Figure Description

[0048] The various objectives, features, and advantages of this invention will become more apparent from the following detailed description of preferred embodiments in conjunction with the accompanying drawings. The drawings are merely illustrative illustrations of the invention and are not necessarily drawn to scale. In the drawings, the same reference numerals always denote the same or similar parts. Wherein:

[0049] Figure 1 A connection diagram of the urea solution precision preparation system according to the first embodiment of this utility model is shown.

[0050] Figure 2 A connection diagram of the urea solution precision preparation system according to the second embodiment of this utility model is shown.

[0051] The following are explanations of the reference numerals in the attached diagram: 11. Urea granule silo; 12. Primary screw feeder; 13. Secondary weighing and quantitative feeder; 14. Buffer hopper; 15. Conveying hose; 21. Jet mixer; 22. Buffer mixing tank; 23. Circulating water pump; 24. Circulation valve; 25. Inlet valve; 26. Drainage tank; 27. Drainage tank inlet valve; 28. Drainage tank heater; 29. ​​Make-up valve; 31. Conveying pump; 32. Filter; 33. First reflux valve; 34. Mass flow meter; 35. Second reflux valve; 36. Outlet valve; 37. Urea solution storage tank; 38. Steam heating inlet valve; 39. Steam heating coil; 41. Controller; 42. Inlet flow meter; 43. Jet inlet flow meter; 44. Buffer mixing tank level gauge; 45. Urea solution storage tank level gauge; 46. Drainage tank level gauge. Detailed Implementation

[0052] Although the present invention can be readily embodied in various forms, only some specific embodiments are shown in the accompanying drawings and will be described in detail in this specification. It is understood that this specification should be regarded as an exemplary illustration of the principles of the present invention and is not intended to limit the present invention to what is described herein.

[0053] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the present invention, and does not imply that every embodiment of the present invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0054] In the embodiments shown in the accompanying drawings, the directional indications (such as up, down, left, right, front, and back) used to explain the structure and movement of the various elements of this invention are relative rather than absolute. These descriptions are appropriate when these elements are in the positions shown in the drawings. If the descriptions of the positions of these elements change, these directional indications also change accordingly.

[0055] Please see Figure 1 , Figure 1 A connection diagram of the urea solution precision preparation system according to a first embodiment of the present invention is shown. The urea solution precision preparation system provided in one embodiment of the present invention mainly includes a urea granule silo 11, a feeder, a jet mixer 21, a buffer mixing tank 22, a filter 32, and a mass flow meter 34.

[0056] The outlet of the urea granule silo 11 is connected to the inlet of the feeder, the outlet of the feeder is connected to the inlet of the jet mixer 21, the inlet of the jet mixer 21 is used to introduce liquid mixed with urea granules, the outlet of the jet mixer 21 is connected to the inlet of the buffer mixing tank 22, the outlet of the buffer mixing tank 22 is connected to the inlet of the filter 32, the outlet of the filter 32 is connected to the inlet of the mass flow meter 34, and the outlet of the mass flow meter 34 outputs urea solution.

[0057] The return outlet of filter 32 is connected to the return inlet of buffer mixing tank 22, and filter 32 is equipped with a filter screen. The filter screen is used to block the incompletely dissolved urea particles flowing from filter 32 to mass flow meter 34, and to make the incompletely dissolved urea particles flow to buffer mixing tank 22.

[0058] Through the above structural design, urea granules in the urea granule silo 11 are fed into the jet mixer 21 via a feeder and mixed with the liquid entering the jet mixer 21. The urea feeder includes a primary screw feeder 12 and a secondary weighing and metering feeder 13. The two-stage feeding allows for precise control of feeding and weighing. The jet mixer 21 can be a ring-shaped jet mixer, which facilitates precise, rapid, and automatic control of the required urea solution concentration. This design solves the problem of large density changes in urea granules during fluidization when feeding into the jet mixer 21, making precise feeding and solution preparation difficult.

[0059] After mixing, the resulting urea solution enters the buffer mixing tank 22. The urea solution flowing out of the buffer mixing tank 22 is filtered by the filter 32 to remove any incompletely dissolved urea particles before flowing into the mass flow meter 34.

[0060] This invention addresses the problem of undissolved urea particles entering the mass flow meter, causing inaccurate solution density measurements and the issue of partially undissolved urea solution being transferred to the finished product storage tank. It enables the mass flow meter 34 to accurately measure the concentration of the urea solution. Simultaneously, undissolved urea can be recycled back to the buffer mixing tank 22 for further dissolution.

[0061] The urea solution precision preparation system also includes a urea solution storage tank 37. The outlet of the mass flow meter 34 is connected to the inlet of the urea solution storage tank 37, and an outlet valve 36 is provided on the connecting pipe between the mass flow meter 34 and the urea solution storage tank 37.

[0062] To save space and to ensure that the concentration of most solutions in the buffer mixing tank 22 is relatively uniform, the volume of the buffer mixing tank 22 should be as small as possible. It is essential to ensure that the urea solution is basically completely dissolved in the jet mixer, and the buffer tank is only used for temporary small-scale buffering. The urea solution storage tank 37 can store the urea solution.

[0063] The outlet valve 36 can be a regulating valve, which can open or close the connecting pipe between the mass flow meter 34 and the urea solution storage tank 37, and can adjust the flow rate of the connecting pipe between the mass flow meter 34 and the urea solution storage tank 37.

[0064] The urea solution precision preparation system also includes a condensate tank 26 and a circulating water pump 23. The outlet of the condensate tank 26 is connected to the inlet of the jet mixer 21 and the inlet of the circulating water pump 23, and an inlet valve 25 is provided on the connecting pipe between the condensate tank 26 and the circulating water pump 23. The circulation outlet of the buffer mixing tank 22 is connected to the inlet of the circulating water pump 23, and a circulation valve 24 is provided on the connecting pipe between the buffer mixing tank 22 and the circulating water pump 23. The outlet of the circulating water pump 23 is connected to the inlet of the jet mixer 21, and an jet mixer inlet flow meter 43 is provided on the connecting pipe between the circulating water pump 23 and the jet mixer 21.

[0065] The condensate tank 26 supplies water to the jet mixer 21 for mixing with urea particles, and enables the jet mixer 21 to form a high vacuum negative pressure through a high-speed liquid phase flow, thereby drawing in and rapidly mixing the urea particles. Using a jet mixer to prepare urea solution instead of traditional manual feeding and mechanical stirring dissolving devices can significantly reduce the footprint, investment cost, and operating energy consumption of the precise urea solution preparation system. It boasts a high degree of automation and can accurately prepare urea solutions of the required concentration.

[0066] The inlet valve 25 can be a regulating valve, which can open or close the connecting pipe between the condensate tank 26 and the circulating water pump 23, and can adjust the flow rate of the connecting pipe between the condensate tank 26 and the circulating water pump 23.

[0067] The circulating water pump 23 is used to provide power for pumping water flow. The circulating valve 24 can be a regulating valve, which can open or close the connecting pipe between the buffer mixing tank 22 and the circulating water pump 23, and can adjust the flow rate of the connecting pipe between the buffer mixing tank 22 and the circulating water pump 23.

[0068] The buffer mixing tank 22 is equipped with a buffer mixing tank level gauge 44. The urea solution storage tank 37 is equipped with a urea solution storage tank level gauge 45. The urea solution precision preparation system also includes a transfer pump 31. The outlet of the buffer mixing tank 22 is connected to the inlet of the transfer pump 31, and the outlet of the transfer pump 31 is connected to the inlet of the filter 32. The urea solution precision preparation system also includes a controller 41. The controller 41 is signal-connected to the buffer mixing tank level gauge 44 and the urea solution storage tank level gauge 45, and is used to control the feeder, circulation valve 24, transfer pump 31, inlet valve 25, and outlet valve 36.

[0069] The mixing tank level gauge is used to measure the liquid level in the buffer mixing tank 22, and the urea solution storage tank level gauge 45 is used to measure the liquid level in the urea solution storage tank 37. The transfer pump 31 is used to provide power for pumping water flow.

[0070] The urea solution precision preparation system also includes an inlet flow meter 42. The outlet of the condensate tank 26 is connected to the inlet flow meter 42. The outlet of the inlet flow meter 42 is connected to the inlet of the circulating water pump 23 and the makeup water inlet of the buffer mixing tank 22. An inlet valve 25 is located on the connecting pipe between the inlet flow meter 42 and the circulating water pump 23. A makeup water valve 29 is located on the connecting pipe between the inlet flow meter 42 and the buffer mixing tank 22. The controller 41 is also used to control the makeup water valve 29.

[0071] The inlet flow meter 42 is used to measure the flow rate of water flowing out of the drain tank 26. The water supply valve 29 can be a regulating valve, which can open or close the connecting pipe between the inlet flow meter 42 and the buffer mixing tank 22, and can adjust the flow rate of the connecting pipe between the inlet flow meter 42 and the buffer mixing tank 22.

[0072] The condensate tank 26 is equipped with a condensate tank heater 28 and a condensate tank level gauge 46. The condensate tank heater 28 is used to heat the water in the condensate tank 26 to improve the solubility of urea particles in the water. The condensate tank level gauge 46 is used to measure the liquid level in the condensate tank 26.

[0073] The inlet of the steam trap 26 can be connected to the steam drain or hot water supply in the plant area, and the connecting pipe is equipped with a steam trap inlet valve 27.

[0074] The urea solution storage tank 37 is equipped with a thermometer. The urea solution precision preparation system also includes a steam heating system, which is used to heat the urea solution in the urea solution storage tank 37 and to allow the heated steam to enter the condensate tank 26.

[0075] In this embodiment, a steam heating coil 39 is provided inside the urea solution storage tank 37, which is used to heat the urea solution inside the urea solution storage tank 37. A steam heating inlet valve 38 is provided on the connection channel between the steam from the plant area and the steam heating coil 39.

[0076] A thermometer is used to measure the temperature of the urea solution in the urea solution storage tank 37. Since 50% urea solution begins to crystallize at 18°C, crystallization may occur in the storage tank at low temperatures. Therefore, the urea solution storage tank 37 is equipped with steam heating and a thermometer. The solution temperature is controlled between 25 and 40°C by controlling the steam heating inlet valve 38. The heated steam drains into the condensate tank 26 for collection and recycling.

[0077] The buffer mixing tank 22 has two reflux inlets, namely a first reflux inlet and a second reflux inlet. The reflux outlet of the filter 32 is connected to the first reflux inlet of the buffer mixing tank 22, and a first reflux valve 33 is provided on the connecting pipe between the filter 32 and the buffer mixing tank 22. The outlet of the mass flow meter 34 is also connected to the second reflux inlet of the buffer mixing tank 22, and a second reflux valve 35 is provided on the connecting pipe between the mass flow meter 34 and the buffer mixing tank 22.

[0078] The first reflux valve 33 can be a regulating valve, which can open or close the connecting pipe between the filter 32 and the buffer mixing tank 22, and can adjust the flow rate of the connecting pipe between the filter 32 and the buffer mixing tank 22. The second reflux valve 35 can be a regulating valve, which can open or close the connecting pipe between the mass flow meter 34 and the buffer mixing tank 22, and can adjust the flow rate of the connecting pipe between the mass flow meter 34 and the buffer mixing tank 22.

[0079] In this embodiment, the first reflux inlet is located at the bottom of the buffer mixing tank 22. A small portion of the urea solution, mixed with incompletely dissolved urea particles, flows back to the bottom of the buffer mixing tank 22, increasing bottom disturbance and facilitating mixing and redissolving. The second reflux inlet is located at the top of the buffer mixing tank 22.

[0080] The feed inlet and water inlet of the jet mixer 21 are both located at the first end of the jet mixer 21. The water inlet of the jet mixer 21 is annular and surrounds the periphery of the feed inlet of the jet mixer 21. The liquid outlet of the jet mixer 21 is located at the second end of the jet mixer 21.

[0081] The water flows around the feed inlet, generating suction and circumferential shear force. The annular jet wraps around the fluid being absorbed (urea particles), resulting in a large surface area and rapid mixing, which is more conducive to the rapid dissolution and mixing of urea particles and hot water.

[0082] In a traditional jet mixer 21, water flows from the center while the material being drawn in flows in from the side in a ring. This results in poor mixing. During adjustment, it is easy for the solution density to not meet the required output density while the buffer mixing tank 22 is already full. In order to meet the solution concentration control requirements, the inlet water flow rate needs to be reduced, which may result in the water volume entering the jet mixer being too low, affecting the stability of urea feeding.

[0083] The feeder includes a primary screw feeder 12 and a secondary weighing and metering feeder 13. The outlet of the urea granule silo 11 is connected to the inlet of the primary screw feeder 12. The outlet of the primary screw feeder 12 is connected to the outlet of the secondary weighing and metering feeder 13. The urea solution precision preparation system also includes a buffer hopper 14. The outlet of the secondary weighing and metering feeder 13 is connected to the inlet of the buffer hopper 14, and the outlet of the buffer hopper 14 is connected to the inlet of the jet mixer 21.

[0084] The primary screw feeder 12 is used for coarse feeding, while the secondary weighing and quantitative feeder 13 is used for precise control of feeding and weighing. Urea granules exhibit significant density variations in the fluidized state, making it difficult to ensure accurate feeding using only the primary screw feeder 12, which is detrimental to achieving automatic and precise control. The combination of the primary screw feeder 12 and the secondary weighing and quantitative feeder 13 facilitates precise and automatic control of the required urea solution concentration.

[0085] In this embodiment, the controller 41 is also connected to the condensate tank level gauge 46 and is used to control the condensate tank inlet valve 27, the condensate tank heater 28, the first return valve 33, the second return valve 35, the steam heating inlet, etc.

[0086] The working principle of the urea solution precision preparation system of the first embodiment of this utility model is explained in detail below.

[0087] Hot water (70-90℃) from the condensate tank 26 enters the buffer mixing tank 22 through the water supply valve 29. Once the level gauge 44 indicates the tank is approximately 1 / 2 to 2 / 3 full, the water supply valve 29 is closed. The circulation valve 24 and circulation pump 23 are then opened, and water circulates through the jet mixer 21 into the buffer mixing tank 22. The circulation valve 24 is opened and adjusted so that the inlet flow meter reaches the set value required for stable suction of the jet mixer. After approximately one minute of normal and stable operation, and after verifying that the urea solution precision preparation system is functioning correctly, the feeder is activated for internal circulation feeding.

[0088] The primary screw feeder 12 and the secondary weighing and metering feeder 13 are activated to precisely control the feeding rate of urea granules. Urea from the urea granule silo 11 enters the buffer hopper 14 through the primary screw feeder 12 and the secondary weighing and metering feeder 13, and then connects to the jet mixer 21 through the conveying hose 15. The jet mixer 21 forms a high negative pressure under high-speed water flow, and the urea granules in the buffer hopper 14 are drawn into the jet mixer 21 through the connected conveying hose 15. In the jet mixer, the urea granules and hot water are vigorously mixed and dissolved to form a urea solution, which enters the buffer mixing tank 22.

[0089] The urea solution in the buffer mixing tank 22 exits from the bottom of the tank and is pumped by the transfer pump 31 to the filter 32. The filter 32 can intercept some of the incompletely dissolved urea particles. A circulation pipe is located before the filter 32, and a small amount of solution is circulated back to the bottom of the buffer mixing tank 22 via the first reflux valve 33. The circulating turbulent water flow further dissolves the remaining undissolved urea particles at the bottom, ensuring that the urea solution output after filtration by the filter 32 is completely dissolved. Most of the urea solution after passing through the filter 32 then passes through a mass density flow meter.

[0090] It should be noted that during the initial configuration of the internal circulation system, the urea solution concentration is low, and the second reflux valve 35 needs to be opened first to return the solution to the buffer mixing tank 22. When the mass flow meter 34 shows that the urea solution concentration has risen to 48% (2% difference from the set concentration of 50%), the regulating inlet valve 25 should be opened quickly. The inlet flow rate should be adjusted to the required set value according to the inlet flow meter 42. For example, if 24 tons of 50% urea solution need to be prepared per hour, the inlet flow rate should be adjusted to 12 tons / hour. During this period, the opening of the circulation valve 24 should be adjusted and reduced simultaneously to keep the total flow rate of the inlet flow meter constant, meet the set value required for the stable suction of the ejector, and ensure stable feeding. At this time, the urea solution precision preparation system switches to the normal continuous preparation mode.

[0091] When the mass flow meter 34 displays that the urea solution has reached the set concentration, such as 50%, the outlet valve 36 is opened and the second reflux valve 35 is closed, and the urea solution enters the urea solution storage tank 37 for storage.

[0092] The delivery pump 31 can be a variable frequency pump, or the outlet valve 36 can be a regulating valve. During operation, the flow rate of the finished urea solution delivered to the urea solution storage tank 37 can be adjusted by changing the frequency of the delivery pump 31 or the opening of the outlet valve 36. Under normal operation, the liquid level in the buffer mixing tank 22 can be maintained at the middle position by adjustment, which is beneficial for stable and precise control of the urea solution concentration. This reduces the need to change the inlet flow rate of the inlet valve 25 or even stop the batching process due to the liquid level in the buffer mixing tank 22 being too high or too low, thus reducing the need for readjustment of stable operating conditions.

[0093] During normal operation, to ensure that the urea solution concentration is better controlled at the set value of around 50% during normal preparation, the inlet water flow rate is generally kept constant, and the inlet water flow meter 42 is used to fine-tune the inlet water valve 25 for control. The feeding rate of the primary screw feeder 12 and the secondary weighing and metering feeder 13 is adjusted according to the change in urea solution concentration.

[0094] When the concentration is too low, increase the feed rate; when the concentration is too high, decrease the feed rate. If the concentration deviation exceeds 2%, close the outlet valve 36 and open the second reflux valve 35. Once the concentration is adjusted to meet the set value, open the outlet valve 36 again and close the second reflux valve 35 to ensure that the urea solution entering the urea solution storage tank 37 is accurately controlled at 50±2%.

[0095] At the same time, a high liquid level interlock is set for the buffer mixing tank 22. If the urea solution concentration does not meet the external output concentration requirements, resulting in an abnormal situation where the liquid level of the buffer mixing tank 22 is high, and the liquid level cannot be adjusted by adjusting the external output solution, the inlet valve 25 is adjusted to reduce the inlet water flow rate, and the urea feed rate is adjusted according to the solution concentration.

[0096] A 50% urea solution begins to crystallize at 18°C. Therefore, the urea solution in the storage tank 37 may crystallize at low temperatures. The solution temperature is controlled between 25 and 40°C by controlling the steam heating inlet valve 38. The heated steam drains into the drain tank 26 for collection and recycling.

[0097] Meanwhile, the urea solution storage tank 37 is equipped with a urea solution storage tank level gauge 45. When a high level alarm occurs (this alarm level is set at the position where the remaining capacity of the storage tank can only meet the full level of one buffer mixing tank 22), the controller 41 interlocks and stops the primary screw feeder 12, then stops the circulating water pump 23, and closes the inlet valve 25. The delivery pump 31 continues to run until the buffer mixing tank 22 triggers a low level alarm. Then, the delivery pump 31 is interlocked and stopped, the outlet valve 36 is closed, and the preparation process ends.

[0098] The condensate tank 26 is equipped with a condensate tank level gauge 46. If the liquid level is low during the preparation process, the condensate tank inlet valve 27 can be interlocked open; if the liquid level is high, it can be closed. A condensate tank heater 28 and a thermometer are also provided. When the condensate temperature in the plant area is below 70℃, heating is activated to maintain the hot water temperature used for preparing the urea solution, ensuring complete urea dissolution. Heating stops when the temperature exceeds 90℃. The condensate tank heater 28 can be selected for electric heating or steam heating, with steam heating being preferred. When steam heating is used, the heating steam is directly introduced into the condensate tank 26 for heating, making full use of the steam and condensate.

[0099] Please see Figure 2 , Figure 2A connection diagram of the urea solution precision preparation system according to the second embodiment of this utility model is shown. The difference between the second embodiment and the first embodiment is that the condensate tank 26 is omitted in the second embodiment. When the hot water or steam condensate in the plant area is stable, the inlet of the condensate tank 26 is directly connected to the hot water or steam condensate in the plant area for water supply. The rest of the process in the second embodiment is the same as that in the first embodiment, and will not be described again here.

[0100] Although the present invention has been described with reference to several typical embodiments, it should be understood that the terminology used is descriptive and exemplary, and not restrictive. Since the present invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A system for the precise preparation of urea solution, characterized in that, Includes urea granule silo, feeder, jet mixer, buffer mixing tank, filter and mass flow meter; The feeder includes a primary screw feeder and a secondary weighing and metering feeder. The outlet of the urea granule silo is connected to the inlet of the primary screw feeder, the inlet of the primary screw feeder is connected to the inlet of the secondary weighing and metering feeder, the outlet of the secondary weighing and metering feeder is connected to the inlet of the jet mixer, the liquid inlet of the jet mixer is used to introduce liquid mixed with urea granules, the liquid outlet of the jet mixer is connected to the liquid inlet of the buffer mixing tank, the liquid outlet of the buffer mixing tank is connected to the liquid inlet of the filter, the liquid outlet of the filter is connected to the liquid inlet of the mass flow meter, and the liquid outlet of the mass flow meter outputs urea solution. The filter's return outlet is connected to the buffer mixing tank's return inlet, and the filter is equipped with a filter screen. The filter screen is used to block incompletely dissolved urea particles flowing from the filter to the mass flow meter, and to allow incompletely dissolved urea particles to flow to the buffer mixing tank.

2. The urea solution precision preparation system according to claim 1, characterized in that, The precise urea solution preparation system also includes a urea solution storage tank; The outlet of the mass flow meter is connected to the inlet of the urea solution storage tank, and an outlet valve is provided on the connecting pipe between the mass flow meter and the urea solution storage tank.

3. The urea solution precision preparation system according to claim 2, characterized in that, The precise urea solution preparation system also includes a hydrophobic tank and a circulating water pump; The outlet of the condensate tank is connected to the inlet of the jet mixer and the inlet of the circulating water pump, and an inlet valve is provided on the connecting pipe between the condensate tank and the circulating water pump. The circulation outlet of the buffer mixing tank is connected to the inlet of the circulating water pump, and a circulation valve is provided on the connecting pipe between the buffer mixing tank and the circulating water pump. The outlet of the circulating water pump is connected to the inlet of the jet mixer, and the connecting pipe between the circulating water pump and the jet mixer is equipped with a jet mixer inlet flow meter.

4. The urea solution precision preparation system according to claim 3, characterized in that, The buffer mixing tank is equipped with a buffer mixing tank level gauge; The urea solution storage tank is equipped with a urea solution storage tank level gauge. The precise urea solution preparation system also includes a delivery pump; The outlet of the buffer mixing tank is connected to the inlet of the delivery pump; The outlet of the delivery pump is connected to the inlet of the filter; The precise urea solution preparation system also includes a controller; The controller signal is connected to the level gauge of the buffer mixing tank and the level gauge of the urea solution storage tank, and is used to control the feeder, the circulation valve, the delivery pump, the inlet valve and the outlet valve.

5. The urea solution precision preparation system according to claim 4, characterized in that, The precise urea solution preparation system also includes an inlet water flow meter; The outlet of the condensate tank is connected to the inlet flow meter; The outlet of the inlet flow meter is connected to the inlet of the circulating water pump and the makeup water inlet of the buffer mixing tank. The inlet valve is located on the connecting pipe between the inlet flow meter and the circulating water supply pump; A water supply valve is provided on the connecting pipe between the inlet flow meter and the buffer mixing tank; The controller is also used to control the water supply valve.

6. The urea solution precision preparation system according to claim 3, characterized in that, The condensate tank is equipped with a condensate tank heater and a condensate tank level gauge.

7. The urea solution precision preparation system according to claim 3, characterized in that, A thermometer is installed inside the urea solution storage tank; The precise urea solution preparation system also includes a steam heating system, which is used to heat the urea solution in the urea solution storage tank and to allow the heated steam to enter the hydrophobic tank.

8. The urea solution precision preparation system according to claim 2, characterized in that, The buffer mixing tank has two reflux inlets, namely a first reflux inlet and a second reflux inlet; The filter’s reflux outlet is connected to the first reflux inlet of the buffer mixing tank, and a first reflux valve is provided on the connecting pipe between the filter and the buffer mixing tank. The outlet of the mass flow meter is also connected to the second reflux inlet of the buffer mixing tank, and a second reflux valve is provided on the connecting pipe between the mass flow meter and the buffer mixing tank.

9. The precise urea solution preparation system according to claim 1, characterized in that, The feed inlet and water inlet of the jet mixer are both located at the first end of the jet mixer; The water inlet of the jet mixer is annular and surrounds the feed inlet of the jet mixer. The outlet of the jet mixer is located at the second end of the jet mixer.

10. The precise urea solution preparation system according to claim 1, characterized in that, The feeder includes a primary screw feeder and a secondary weighing and metering feeder; The outlet of the urea granule silo is connected to the inlet of the primary screw feeder; The discharge port of the primary screw feeder is connected to the discharge port of the secondary weighing and metering feeder; The urea solution precision preparation system also includes a buffer hopper; The outlet of the secondary weighing quantitative feeder is connected to the inlet of the buffer hopper; The outlet of the buffer hopper is connected to the inlet of the jet mixer.

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