Experimental device and method for detecting NH4Cl crystallization characteristics in U-shaped heat exchange tube bundle

Abstract

The present invention discloses an experimental device and method for detecting the crystallization characteristics of NH4Cl in a U-shaped heat exchange tube bundle. The main material of the heat exchange tube bundle part is organic glass, and the outside is covered with an organic glass sleeve. A deposition probe is inserted into the bend of the main material. The bundle inlet of the heat exchange tube bundle part is connected to the material inlet part, and the bundle outlet of the heat exchange tube bundle part is connected to the material outlet part. The organic glass sleeve is provided with an inlet and an outlet. The inlet and outlet of the organic glass sleeve are connected to the cooling system to form a circulation loop; the heat flux density is calculated by the temperature difference between the inner and outer surfaces of the deposition probe to characterize the crystallization solution of NH4Cl salt, and the crystallization conditions of NH4Cl salt at different places of the bend of the heat exchange tube bundle are obtained. The present invention is simple to operate, and the phenomenon is obvious and visible, and can be used to solve the problem of ammonium salt crystallization deposition corrosion in U-shaped heat exchangers in the current petrochemical industry.

Description

Technical Field

[0001] The invention relates to a device and method for detecting characteristics of a heat exchange tube bundle, belonging to the technical field of petrochemical corrosion testing, and in particular to an experimental device and method for detecting NH4Cl crystallization characteristics of a U-shaped heat exchange tube bundle. Background Art

[0002] Petrochemical industry is an important support for my country's energy industry. Heat exchanger is one of the important equipment in the process flow. It is in high temperature and high pressure conditions for a long time. It is very easy to have unplanned shutdown accidents caused by flow corrosion such as deposition-erosion, which has become a major obstacle that seriously affects the healthy and benign development of the petrochemical industry. Therefore, the study of flow corrosion failure of heat exchangers has always been a focus of academic and engineering circles.

[0003] As my country's crude oil processing becomes inferior, the flow corrosion environment of the equipment system is complex, and the NH4Cl salt crystallization in the heat exchanger is serious. The accompanying flow corrosion phenomena such as tube bundle blockage and leakage are increasing. The frequent failure of the tube bundle restricts the safe, stable and long-term operation of the device. Many research teams have also carried out relevant research in a targeted manner, and proposed corresponding measures to prevent corrosion from the aspects of process, fluid, control, etc., and have achieved certain results. However, the crystallization position and process morphology of NH4Cl salt in the heat exchanger tube bundle are not visible in the actual heat exchanger, the crystallization rate of NH4Cl salt cannot be specifically quantified and evaluated, and the critical characteristics of NH4Cl salt crystallization deposition cannot be predicted. Since the heat exchanger is in high temperature and high pressure conditions for a long time, there are almost no experimental platforms specifically for the crystallization deposition of NH4Cl salt in the heat exchanger. Similar experiments mainly focus on the deposition of easy-to-crystallize components in multiphase flow. At present, some scientific research institutes at home and abroad have designed a variety of multiphase flow deposition experimental devices, aiming to study the deposition mechanism of easy-to-crystallize components using experimental research methods. However, the shortcomings of the current multiphase flow deposition experimental device are mainly that the experimental device lacks specificity for the deposition of specific reactants, the deposition process cannot be monitored online in real time, it is difficult to carry out critical characteristics testing of multiphase flow deposition, and it is impossible to study the mechanism of water injection and salt washing.

[0004] In summary, in view of the unclear characteristics of NH4Cl salt crystallization deposition in the tube bundle of the U-tube heat exchanger and the mechanism of water injection and salt washing, the existing technology lacks an experimental device and method for evaluating the crystallization degree of NH4Cl salt in the tube bundle of the U-tube heat exchanger to evaluate the degree of NH4Cl salt crystallization, quantify the crystallization rate of NH4Cl salt, and reveal the mechanism of water injection and salt washing. Summary of the invention

[0005] In view of the shortcomings of the current multiphase flow deposition experimental device in the prior art, the present invention proposes an experimental device and method for detecting the crystallization characteristics of NH4Cl in a U-shaped heat exchange tube bundle, which is suitable for testing the crystallization deposition characteristics of NH4Cl in a U-shaped heat exchange tube bundle and water injection and salt washing.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0007] 1. An experimental device for detecting the crystallization characteristics of NH4Cl in a U-shaped heat exchange tube bundle:

[0008] The device includes a heat exchange tube bundle part, a material inlet part, a material outlet part and a cooling system. The main material of the heat exchange tube bundle part is organic glass, and an organic glass sleeve is provided on the outside. A deposition probe is inserted into the bend of the main material. The tube bundle inlet of the heat exchange tube bundle part is connected with the material inlet part, and the tube bundle outlet of the heat exchange tube bundle part is connected with the material outlet part. The organic glass sleeve is provided with an inlet and an outlet. The inlet and outlet of the organic glass sleeve are connected with the cooling system to form a circulation loop.

[0009] The heat exchange tube bundle part includes a U-shaped organic glass heat exchange tube, an organic glass sleeve, a thermometer, a first deposition probe, a second deposition probe and a third deposition probe; the organic glass sleeve is sleeved outside the U-shaped organic glass heat exchange tube and is consistent with the shape of the U-shaped organic glass heat exchange tube; the first deposition probe is located in the middle of the half section of the semicircular arc bending section of the U-shaped organic glass heat exchange tube close to the inlet side, and is inserted into the U-shaped organic glass heat exchange tube at a radial angle; the second deposition probe is located in the middle of the entire section of the semicircular arc bending section of the U-shaped organic glass heat exchange tube, and is inserted into the U-shaped organic glass heat exchange tube at a radial angle The thermometer is installed at the beginning of the semicircular bending section of the U-shaped plexiglass heat exchange tube; in this way, the first deposition probe is inserted into the bend of the heat exchange tube bundle at 45° to the horizontal direction, the second deposition probe is inserted into the bend of the heat exchange tube bundle in the horizontal direction, and the third deposition probe is inserted into the bend of the heat exchange tube bundle at -45° to the horizontal direction.

[0010] The material inlet part includes a feeding system and a water injection system;

[0011] The feeding system includes a blower, a heater, a peristaltic pump, a temperature measuring element, and a rotor flowmeter; the blower outlet is connected to the inlet of a U-shaped organic glass heat exchange tube via a peristaltic pump, a temperature measuring element and a rotor flowmeter are installed on the pipeline between the peristaltic pump and the inlet of the U-shaped organic glass heat exchange tube, an ammonia tank and a hydrogen chloride tank are also arranged between the temperature measuring element and the rotor flowmeter, the ammonia tank is connected to the pipeline between the temperature measuring element and the rotor flowmeter via a first digital display flow control valve, the hydrogen chloride tank is connected to the pipeline between the temperature measuring element and the rotor flowmeter via a second digital display flow control valve, and the ammonia tank access point is before the hydrogen chloride tank access point;

[0012] The water injection system comprises a water injection tank, a water injection pump and a third digital flow control valve connected in series in sequence; the water injection tank is connected to the inlet of the U-shaped organic glass heat exchange tube via the water injection pump, and the third digital flow control valve is connected and installed on the pipeline between the water injection pump and the inlet of the U-shaped organic glass heat exchange tube, and the outlet of the third digital flow control valve is connected to the outlet end of the rotor flow meter of the feeding part;

[0013] The material outlet part includes a check valve and a solution tank connected in series; the check valve inlet is connected to the outlet of the U-shaped organic glass heat exchange tube, and the check valve outlet is connected to the solution tank;

[0014] The cooling system includes a cooler, a cooling water tank, a cooling water pump and a regulating valve connected in series in sequence; the outlet of the organic glass sleeve is connected to the cooling water tank via the cooler, and the cooling water tank is then connected back to the inlet of the organic glass sleeve via the cooling water pump, and the pipeline connection between the cooling water pump and the inlet of the organic glass sleeve is installed with a regulating valve.

[0015] Each of the deposition probes is made of stainless steel and is a hollow cylindrical piece with one end closed and the other end open. The deposition probe has two axial holes close to the inner wall and the outer wall. A K-type thermocouple is installed in the axial holes. The end of the thermocouple extends into the U-shaped plexiglass heat exchange tube along with the deposition probe.

[0016] 2. A method for detecting the crystallization characteristics of NH4Cl in a U-shaped heat exchange tube bundle, the method comprising the following steps:

[0017] Step 1: Assemble the experimental device, open the check valve, blower, peristaltic pump, regulating valve and cooling water pump in sequence, so that the outside wind is blown into the U-shaped organic glass heat exchange tube, and the water flows between the organic glass sleeves of the cooling water tank of the cooling system;

[0018] Step 2: Turn on the heater and use the temperature measuring element to detect the temperature T of the air blown in. air Always above the crystallization temperature of NH4Cl;

[0019] Turn on the cooler and adjust the power of the heater and cooler to ensure that the thermometer temperature reaches the crystallization temperature T0 of NH4Cl at normal pressure;

[0020] Step 3: Open the first digital flow control valve and the second digital flow control valve to release NH3 and HCl from the ammonia tank and hydrogen chloride tank respectively, and adjust the flow rates of NH3 and HCl to the preset values ​​Q NH3 , Q HCl , record the flow rate Q0 detected by the rotor flowmeter;

[0021] Step 4: At fixed time intervals t, record the inner wall temperature T collected by the first deposition probe, the second deposition probe, and the third deposition probe in,i and the outer wall temperature Tout,i Observe and record the crystal deposition of the first deposition probe, the second deposition probe, and the third deposition probe extending into the test part of the U-shaped organic glass heat exchange tube, and take pictures at a fixed time interval t;

[0022] Step 5: Close the first digital flow control valve, the second digital flow control valve, the heater, the cooler, the cooling water pump and the regulating valve in sequence, and close the check valve, the blower and the peristaltic pump after blowing for a period of time; take out the first deposition probe, the second deposition probe and the third deposition probe, observe and take photos to record the crystal deposition of the test part where the first deposition probe, the second deposition probe and the third deposition probe are inserted into the U-shaped organic glass heat exchange tube; clean the U-shaped organic glass heat exchange tube;

[0023] Step 6: According to the experimental process of steps 1 to 5, adjust the ratio of NH3 and HCl entering the heat exchange tube bundle to test the crystallization of ammonium salt at the elbow of the U-shaped organic glass heat exchange tube; repeat the experimental process of steps 1 to 5, and test the crystallization of ammonium salt at the elbow of the U-shaped organic glass heat exchange tube by adjusting the water injection amount.

[0024] During the test in step 6, by changing the flow rate Q of NH3 NH3 , HCl flow rate Q HCl , total flow rate Q0, and then calculate the heat flux density of the deposition probe at different positions of the U-shaped organic glass heat exchange tube elbow under different proportions of NH3 and HCl;

[0025] During the test in step 6, the water volume Q injected from the water injection tank is adjusted by controlling the third digital flow control valve. w , and then calculate the heat flux density of the deposition probe at different positions of the U-shaped organic glass heat exchange tube elbow under different water injection amounts;

[0026] The degree of crystallization of NH4Cl salt was characterized by the heat flux density of the deposition probe.

[0027] The heat flux density of the deposition probe is obtained by using the following formula:

[0028]

[0029] In the formula, q i is the heat flux density of the i-th deposition probe, i represents the sequence number of the deposition probe, which is 1, 2, or 3; λ is the thermal conductivity of the deposition probe material; T out,i and T in,i are the outer surface temperature and inner surface temperature of the i-th deposition probe, respectively; R is the radius of the deposition probe; r out is the distance from the center of the deposition probe to the small hole on the outer wall; r in is the distance from the center of the deposition probe to the small hole on the inner wall.

[0030] The beneficial effects of the present invention are:

[0031] The present invention can meet the requirements of visualization test of ammonium salt deposition characteristics of U-shaped heat exchange tube bundle and water injection and salt washing mechanism experiment; the experimental device and test method of the present invention can test the heat flux density of ammonium salt deposition probe of U-shaped heat exchange tube bundle under different ratios of NH3, HCl and water injection, characterize the degree of ammonium salt crystallization deposition by the heat flux density of the deposition probe, establish a quantitative relationship between the degree of ammonium salt crystallization deposition and influencing factors such as the ratio of NH3, HCl and water injection amount, and obtain the mechanism and situation of ammonium salt crystallization deposition of U-shaped heat exchange tube bundle, thereby providing a basis for ammonium salt crystallization process prevention and control measures of heat exchangers in actual engineering, and providing a scientific reference for determining critical characteristic indicators of safe operation status parameters of equipment systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural diagram of the experimental device of the present invention;

[0033] Figure 1 In: 1. Blower, 2. Heater, 3. Peristaltic pump, 4. Temperature measuring element, 5. Ammonia tank, 6. Hydrogen chloride tank, 7. First digital flow control valve, 8. Second digital flow control valve, 9. Rotor flowmeter, 10. U-shaped organic glass heat exchange tube, 11. Organic glass sleeve, 12. Thermometer, 13. First deposition probe, 14. Second deposition probe, 15. Third deposition probe, 16. Solution tank, 17. Regulating valve, 18. Cooling water pump, 19. Cooling water tank, 20. Cooler, 21. Water injection tank, 22. Water injection pump, 23. Third digital flow control valve, 24. Check valve;

[0034] Figure 2 is a diagram of the deposition probe mechanism;

[0035] Figure 2 Middle: 25, deposition probe test section, 26, outer wall thermocouple, 27, inner wall thermocouple.

[0036] Figure 3 is a cross-sectional view of the deposition probe. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0038] like Figure 1As shown, the device includes a heat exchange tube bundle part, a material inlet part, a material outlet part and a cooling system. The main material of the heat exchange tube bundle part is organic glass, and an organic glass sleeve is sheathed on the outside. A deposition probe is inserted into the bend of the main material. The tube bundle inlet of the heat exchange tube bundle part is connected to the material inlet part, and the tube bundle outlet of the heat exchange tube bundle part is connected to the material outlet part. The organic glass sleeve is provided with an inlet and an outlet. The inlet and outlet of the organic glass sleeve are connected to the cooling system to form a circulation loop.

[0039] like Figure 1 As shown, the heat exchange tube bundle includes a U-shaped organic glass heat exchange tube 10, an organic glass sleeve 11, a thermometer 12, a first deposition probe 13, a second deposition probe 14 and a third deposition probe 15; the organic glass sleeve 11 is sleeved outside the U-shaped organic glass heat exchange tube 10 and is consistent with the shape of the U-shaped organic glass heat exchange tube 10. The first deposition probe 13 is located in the middle of the half section of the semicircular curved section of the U-shaped organic glass heat exchange tube 10 close to the inlet side, and is inserted into the U-shaped organic glass heat exchange tube 10 at a radial angle; the second deposition probe 14 is located in the entire section of the semicircular curved section of the U-shaped organic glass heat exchange tube 10. The third deposition probe 15 is located in the middle of the half section of the semicircular curved section of the U-shaped organic glass heat exchange tube 10 close to the outlet side, and is inserted into the U-shaped organic glass heat exchange tube 10 at a radial angle. The thermometer 12 is installed and inserted into the starting point of the semicircular curved section of the U-shaped organic glass heat exchange tube 10. In this way, the first deposition probe 13 is inserted into the bend of the heat exchange tube bundle at 45° with the horizontal direction, the second deposition probe 14 is inserted into the bend of the heat exchange tube bundle in the horizontal direction, and the third deposition probe 15 is inserted into the bend of the heat exchange tube bundle at -45° with the horizontal direction.

[0040] The material inlet part includes a feeding system and a water injection system.

[0041] The feeding system includes a blower 1, a heater 2, a peristaltic pump 3, a temperature measuring element 4, and a rotor flowmeter 9; the outlet of the blower 1 is connected to the inlet of the U-shaped organic glass heat exchange tube 10 through the peristaltic pump 3, the temperature measuring element 4 and the rotor flowmeter 9 are installed on the pipeline between the peristaltic pump 3 and the inlet of the U-shaped organic glass heat exchange tube 10, and an ammonia tank 5 and a hydrogen chloride tank 6 are also arranged between the temperature measuring element 4 and the rotor flowmeter 9. The ammonia tank 5 is connected to the pipeline between the temperature measuring element 4 and the rotor flowmeter 9 through a first digital display flow control valve 7, and the hydrogen chloride tank 6 is connected to the pipeline between the temperature measuring element 4 and the rotor flowmeter 9 through a second digital display flow control valve 8. The access point of the ammonia tank 5 is before the access point of the hydrogen chloride tank 6.

[0042] The water injection system includes a water injection tank 21, a water injection pump 22 and a third digital flow control valve 23 connected in series in sequence; the water injection tank 21 is connected to the inlet of the U-shaped organic glass heat exchange tube 10 through the water injection pump 22, and the third digital flow control valve 23 is connected and installed on the pipeline between the water injection pump 22 and the inlet of the U-shaped organic glass heat exchange tube 10, and the outlet of the third digital flow control valve 23 is connected to the outlet end of the rotor flowmeter 9 of the feed part.

[0043] The material outlet part includes a check valve 24 and a solution tank 16 which are connected in series in sequence; the inlet of the check valve 24 is connected to the outlet of the U-shaped organic glass heat exchange tube 10 , and the outlet of the check valve 24 is connected to the solution tank 16 .

[0044] The cooling system includes a cooler 20, a cooling water tank 19, a cooling water pump 18 and a regulating valve 17 which are connected in series in sequence; the outlet of the organic glass sleeve 11 is connected to the cooling water tank 19 via the cooler 20, and the cooling water tank 19 is then connected back to the inlet of the organic glass sleeve 11 via the cooling water pump 18, and the pipeline connection between the cooling water pump 18 and the inlet of the organic glass sleeve 11 is installed with a regulating valve 17.

[0045] like Figure 2 and Figure 3 As shown, each deposition probe is made of stainless steel and is a hollow cylindrical piece with one end closed and the other end open. The deposition probe test section 25 has two axial holes close to the inner wall and the outer wall. A K-type outer wall thermocouple 17 is installed in the axial hole of the outer wall, and a K-type inner wall thermocouple 17 is installed in the axial hole of the inner wall. The end of the thermocouple is inserted into the U-shaped organic glass heat exchange tube 10 along with the deposition probe.

[0046] The crystallization characteristics testing process of the present invention is as follows:

[0047] Step 1: Assemble the experimental device, open the check valve 24, the blower 1, the peristaltic pump 3, the regulating valve 17 and the cooling water pump 18 in sequence, so that the outside wind is blown into the U-shaped organic glass heat exchange tube 10, and the water flows between the cooling water tank 19 and the organic glass sleeve 11 of the cooling system;

[0048] Step 2: Turn on the heater 2 and use the temperature measuring element 4 to detect the temperature T of the air blown in. air Always above the crystallization temperature of NH4Cl;

[0049] Turn on the cooler 20, adjust the power of the heater 2 and the cooler 20, and ensure that the temperature of the thermometer 12 reaches the crystallization temperature T0 of NH4Cl under normal pressure;

[0050] Step 3: Open the first digital flow control valve 7 and the second digital flow control valve 8 to release NH3 and HCl from the ammonia tank 5 and the hydrogen chloride tank 6 respectively, and adjust the flow rates of NH3 and HCl to the preset values ​​Q NH3 , QHCl , record the flow rate Q0 detected by rotor flowmeter 9;

[0051] Step 4: At fixed time intervals t, record the inner wall temperature T collected by the first deposition probe 13, the second deposition probe 14, and the third deposition probe 15 in,i and the outer wall temperature T out,i Observe and record the crystal deposition of the first deposition probe 13, the second deposition probe 14, and the third deposition probe 15 extending into the test portion of the U-shaped organic glass heat exchange tube 10, and take pictures at a fixed time interval t;

[0052] Step 5: close the first digital flow control valve 7, the second digital flow control valve 8, the heater 2, the cooler 20, the cooling water pump 18 and the regulating valve 17 in sequence, and close the check valve 24, the blower 1 and the peristaltic pump 3 after blowing for a period of time; take out the first deposition probe 13, the second deposition probe 14, and the third deposition probe 15, observe and take photos to record the crystal deposition of the test part of the first deposition probe 13, the second deposition probe 14, and the third deposition probe 15 extending into the U-shaped organic glass heat exchange tube 10; clean the U-shaped organic glass heat exchange tube 10;

[0053] Step 6: According to the experimental process of steps 1 to 5, the ratio of NH3 and HCl entering the heat exchange tube bundle is adjusted to test the crystallization of ammonium salt at the U-shaped organic glass heat exchange tube 10;

[0054] Specifically, by changing the NH3 flow rate Q NH3 , HCl flow rate Q HCl , total flow rate Q0, and then calculate the heat flux density of the deposition probe at different positions of the U-shaped organic glass heat exchange tube 10 under different ratios of NH3 and HCl.

[0055] Repeat the experiment of step 1 to step 5, and test the crystallization of ammonium salt at the U-shaped organic glass heat exchange tube 10 by adjusting the water injection amount. Specifically, the water injection amount Q injected from the water injection tank 21 is adjusted by controlling the third digital display flow control valve 23. w , and then calculate the heat flux density of the deposition probe at different positions of the U-shaped organic glass heat exchange tube 10 under different water injection amounts.

[0056] Finally, the heat flux density of the deposition probe obtained from the above two experimental conditions was used to characterize the degree of crystallization of the NH4Cl salt, and the crystallization of the NH4Cl salt at different locations of the bends in the heat exchange tube bundle was evaluated to complete the test.

[0057] The heat flux density of the deposition probe is obtained by the following formula:

[0058]

[0059] In the formula, q i is the heat flux density of the i-th deposition probe, i represents the sequence number of the deposition probe, which is 1, 2, or 3; λ is the thermal conductivity of the deposition probe material; T out,i and T in,i are the outer surface temperature and inner surface temperature of the i-th deposition probe, respectively; R is the radius of the deposition probe; r out is the distance from the center of the deposition probe to the small hole on the outer wall; r in is the distance from the center of the deposition probe to the small hole on the inner wall.

[0060] It can be seen that the present invention is simple to operate, has obvious and visible phenomena, and can be used to solve the problem of ammonium salt crystal deposition corrosion in U-type heat exchangers in the current petrochemical industry.

[0061] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall be covered by the claims of the present invention.

Claims

1. An experimental device for detecting the crystallization characteristics of NH4Cl in a U-shaped heat exchange tube bundle, characterized in that: It includes a heat exchange tube bundle part, a material inlet part, a material outlet part and a cooling system. The main material of the heat exchange tube bundle part is organic glass, and the outside is covered with an organic glass sleeve. A deposition probe is inserted into the bend of the main material. The tube bundle inlet of the heat exchange tube bundle part is connected with the material inlet part, and the tube bundle outlet of the heat exchange tube bundle part is connected with the material outlet part. The organic glass sleeve is provided with an inlet and an outlet. The inlet and outlet of the organic glass sleeve are connected with the cooling system to form a circulation loop. The heat exchange tube bundle portion comprises a U-shaped organic glass heat exchange tube (10), an organic glass sleeve (11), a thermometer (12), a first deposition probe (13), a second deposition probe (14) and a third deposition probe (15); the organic glass sleeve (11) is sleeved outside the U-shaped organic glass heat exchange tube (10) and has the same shape as the U-shaped organic glass heat exchange tube (10); the first deposition probe (13) is located in the middle of the half section of the semicircular curved section of the U-shaped organic glass heat exchange tube (10) close to the inlet side and is inserted into the U-shaped organic glass heat exchange tube (10) at a radial angle. The U-shaped organic glass heat exchange tube (10) is provided with a thermometer (12) which is inserted into the U-shaped organic glass heat exchange tube (10); the second deposition probe (14) is located in the middle of the entire semicircular curved section of the U-shaped organic glass heat exchange tube (10) and is inserted into the U-shaped organic glass heat exchange tube (10) at a radial angle; the third deposition probe (15) is located in the middle of the half section of the semicircular curved section of the U-shaped organic glass heat exchange tube (10) close to the outlet side and is inserted into the U-shaped organic glass heat exchange tube (10) at a radial angle; and the thermometer (12) is installed and inserted into the starting point of the semicircular curved section of the U-shaped organic glass heat exchange tube (10); The material inlet part includes a feeding system and a water injection system; The feeding system comprises a blower (1), a heater (2), a peristaltic pump (3), a temperature measuring element (4), and a rotor flowmeter (9); the outlet of the blower (1) is connected to the inlet of a U-shaped organic glass heat exchange tube (10) via the peristaltic pump (3); the temperature measuring element (4) and the rotor flowmeter (9) are installed on the pipeline between the peristaltic pump (3) and the inlet of the U-shaped organic glass heat exchange tube (10); the ammonia tank (5) is connected to the pipeline between the temperature measuring element (4) and the rotor flowmeter (9) via a first digital display flow control valve (7); the hydrogen chloride tank (6) is connected to the pipeline between the temperature measuring element (4) and the rotor flowmeter (9) via a second digital display flow control valve (8); and the access point of the ammonia tank (5) is before the access point of the hydrogen chloride tank (6); The water injection system comprises a water injection tank (21), a water injection pump (22) and a third digital flow control valve (23) which are connected in series in sequence; the water injection tank (21) is connected to the inlet of the U-shaped organic glass heat exchange tube (10) via the water injection pump (22); the third digital flow control valve (23) is connected and installed on the pipeline between the water injection pump (22) and the inlet of the U-shaped organic glass heat exchange tube (10); and the outlet of the third digital flow control valve (23) is connected to the outlet end of the rotor flow meter (9) of the feeding system; The material outlet portion comprises a check valve (24) and a solution tank (16) which are connected in series in sequence; the inlet of the check valve (24) is connected to the outlet of the U-shaped organic glass heat exchange tube (10), and the outlet of the check valve (24) is connected to the solution tank (16); The cooling system comprises a cooler (20), a cooling water tank (19), a cooling water pump (18) and a regulating valve (17) which are connected in series in sequence; the outlet of the organic glass sleeve (11) is connected to the cooling water tank (19) via the cooler (20), and the cooling water tank (19) is then connected back to the inlet of the organic glass sleeve (11) via the cooling water pump (18); the pipe between the cooling water pump (18) and the inlet of the organic glass sleeve (11) is connected and installed with a regulating valve (17); Each of the deposition probes is made of stainless steel and is a hollow cylindrical piece with one end closed and the other end open. The deposition probe has two axial holes in close contact with the inner wall and the outer wall, and a thermocouple is installed in the axial holes.

2. A method for detecting the crystallization characteristics of NH4Cl in a U-shaped heat exchange tube bundle of the experimental device of claim 1, characterized in that The method comprises the following steps: Step 1: Assemble the experimental device, open the check valve (24), the blower (1), the peristaltic pump (3), the regulating valve (17) and the cooling water pump (18) in sequence, so that the outside wind is blown into the U-shaped organic glass heat exchange tube (10), and the water flows between the cooling water tank (19) and the organic glass sleeve (11) of the cooling system; Step 2: Turn on the heater (2) and use the temperature measuring element (4) to detect the temperature T of the air being blown in. air Always above the crystallization temperature of NH4Cl; Turn on the cooler (20), adjust the power of the heater (2) and the cooler (20), and ensure that the temperature of the thermometer (12) reaches the crystallization temperature T0 of NH4Cl at normal pressure; Step 3: Open the first digital flow control valve (7) and the second digital flow control valve (8), release NH3 and HCl from the ammonia tank (5) and the hydrogen chloride tank (6), respectively, and adjust the flow rates of NH3 and HCl to the preset values ​​Q NH3、 Q HCl , record the flow rate Q0 detected by the rotor flowmeter (9); Step 4: At fixed time intervals t, record the inner wall temperature T collected by the first deposition probe (13), the second deposition probe (14), and the third deposition probe (15). in,i and the outer wall temperature T out,i Observe and record the crystal deposition of the test part of the first deposition probe (13), the second deposition probe (14), and the third deposition probe (15) extending into the U-shaped organic glass heat exchange tube (10), and take photos at a fixed time interval t; Step 5: close the first digital flow control valve (7), the second digital flow control valve (8), the heater (2), the cooler (20), the cooling water pump (18) and the regulating valve (17) in sequence, and close the check valve (24), the blower (1) and the peristaltic pump (3) after blowing for a period of time; take out the first deposition probe (13), the second deposition probe (14), and the third deposition probe (15), observe and take photos to record the crystal deposition of the test part of the first deposition probe (13), the second deposition probe (14), and the third deposition probe (15) extending into the U-shaped organic glass heat exchange tube (10); clean the U-shaped organic glass heat exchange tube (10); Step 6: According to the experimental process of steps 1 to 5, the ratio of NH3 and HCl entering the heat exchange tube bundle is adjusted to test the ammonium salt crystallization at the bend of the U-shaped organic glass heat exchange tube (10); the experimental process of steps 1 to 5 is repeated to test the ammonium salt crystallization at the bend of the U-shaped organic glass heat exchange tube (10) by adjusting the water injection amount.

3. The method for detecting the crystallization characteristics of NH4Cl in a U-shaped heat exchange tube bundle according to claim 2, characterized in that: During the test in step 6, by changing the flow rate Q of NH3 NH3 , HCl flow rate Q HCl , the total flow rate Q0, and then calculate the heat flux density of the deposition probe at different positions of the U-shaped organic glass heat exchange tube (10) under different ratios of NH3 and HCl; during the test process of step 6, the injection amount Q injected from the water injection tank (21) is adjusted by controlling the third digital display flow control valve (23) w , and then calculate the heat flux density of the deposition probe at different positions of the U-shaped organic glass heat exchange tube (10) at different water injection amounts; The degree of crystallization of NH4Cl salt was characterized by the heat flux density of the deposition probe.

4. A method for detecting NH4Cl crystallization characteristics of a U-shaped heat exchange tube bundle according to claim 2 or 3, characterized in that: The heat flux density of the deposition probe is obtained by using the following formula: In the formula, q i is the heat flux density of the i-th deposition probe, i represents the ordinal number of the deposition probe, which is 1, 2, or 3; λ is the thermal conductivity of the deposited probe material; T out,i and T in,i are the outer surface temperature and inner surface temperature of the i-th deposition probe, respectively; R is the radius of the deposition probe; r out is the distance from the center of the deposition probe to the small hole on the outer wall; r in is the distance from the center of the deposition probe to the small hole on the inner wall.

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