System for preventing hydrogenation reaction effluent ammonium salt from crystallizing

Abstract

The utility model relates to the technical field of petroleum processing, and discloses a system for preventing hydrogenation reaction effluent ammonium salt from crystallizing, which comprises a heating unit, a hydrogenation reaction unit and a separation unit, the hydrogenation reaction unit is used for carrying out hydrogenation reaction on raw oil to generate hydrogenation product flow; the separation unit is used for separating a gas phase and a liquid phase in the hydrogenation product flow, and a material circulation pipeline of the separation unit is provided with a liquid injection port; and the heating unit is used for enabling the temperature of the hydrogenation product flow between the hydrogenation reaction unit and the liquid injection port of the separation unit to be higher than the crystallization point of the ammonium salt. The device has the advantage of avoiding ammonium salt deposition.

Description

Technical Field

[0001] The utility model relates to the technical field of petroleum processing, and particularly relates to a system for preventing ammonium salt crystallization of hydrogenation reaction effluent. Background Technique

[0002] With the increasingly strict environmental protection requirements in the petroleum and petrochemical industries, the quality standards of vehicle gasoline and diesel products are constantly improving. In the secondary processing technology of raw oil, the fraction oil hydrogenation technology is an important means for producing clean gasoline and diesel and high-quality chemical raw materials, and hydrogenation units have rapidly developed into indispensable production units in the refinery process. The main equipment of the hydrogenation unit includes a hydrogenation reactor, a high-pressure heat exchanger, a high-pressure air cooler, a high-pressure separator, etc. During the production operation of the hydrogenation unit, the high-pressure heat exchanger exchanges heat between the reaction product and the raw material, and provides the main heat source for the hydrogenation reaction of the raw material. Its heat exchange effect directly affects the normal production of the entire unit.

[0003] Since the raw oil of each hydrogenation unit usually contains impurities such as S, N, and CL, corrosive media such as H2S, NH3, and HCL are generated after the hydrogenation reaction. When the reaction effluent enters the cooling and separation system and the temperature gradually drops to the crystallization point, NH3 in the gas phase will react with HCL and H2S to form NH4CL and NH4HS crystals. The ammonium salt deposits on the inner surface of the pipeline or equipment, resulting in a decrease in the heat exchange efficiency of the high-pressure heat exchanger, a continuous increase in the pressure drop of the reaction system, and under-deposit corrosion, causing cracks in the tube bundle. Accidents of corrosion and leakage of the tube bundle of the air cooler and heat exchanger in the hydrogenation unit have occurred in many refineries, seriously affecting the safe operation of the hydrogenation unit.

[0004] Currently, the commonly adopted solution is to set water injection points in the equipment where ammonium salt precipitation may occur to dissolve the ammonium salt. Generally, intermittent water injection is set before the high-pressure heat exchanger of the hot high-pressure separator gas at a relatively high temperature. When the pressure drop of the high-pressure heat exchanger exceeds the normal range, the water injection is started. When the pressure drop of the high-pressure heat exchanger significantly decreases and stabilizes, the water injection is stopped. A continuous water injection point is set before the high-pressure air cooler of the hot high-pressure separator gas, which can effectively remove H2S in the hydrogenation reaction effluent and avoid blockage of the heat exchange tube bundle, under-deposit corrosion, dew point corrosion, and erosion caused by the deposition of NH4CL salt and NH4HS salt.

[0005] CN101655336A discloses a method for optimizing water injection of a hydrogenation reaction effluent air cooler system. The method includes optimizing water injection points, water injection methods and water injection amount. The operating parameters of the hydrogenation reaction effluent air cooler system are read through a DCS control system database, combined with the test analysis data of the hydrogenation reaction effluent air cooler system, and the deposition temperature of NH4CL and NH4HS during the variable operating condition operation of the hydrogenation reaction effluent air cooler system, combined with the inlet and outlet temperatures of the air cooler and the relative humidity before and after water injection of the hydrogenation reaction effluent, the water injection point, water injection method and water injection amount are optimized to avoid under-scale corrosion and local erosion of REAC system pipelines and tube bundles caused by the deposition of NH4CL and NH4HS, and to provide operators with optimization of the water injection of the REAC system, effectively avoiding unplanned shutdown accidents caused by failure of the REAC system, and ensuring the safe, stable and long-term operation of the REAC system.

[0006] CN 204583158U discloses a device for preventing arsenic salt crystallization in hydrogenation reaction. The device for preventing arsenic salt crystallization in hydrogenation reaction specifically includes a reactor, a refining reactor, a heat exchanger, a new hydrogen inlet, a feedstock oil inlet, a water injection point, and a water injection line. It is characterized in that four heat exchangers are connected in series, the reactor and the refining reactor are connected in series, and a three-level water injection point is set in front of the heat exchanger so that they are connected in series and used intermittently according to demand. The water injection point is changed to the E210A / B outlet for water injection, and the circulation volume of the device can be restored to normal, and the system pressure drop is significantly reduced. The temperature of the water injection point should be adjusted between the arsenic salt crystallization point and the water dew point temperature, and the water injection point and water injection flow rate are adjusted according to the flow rate to achieve the best heat exchange effect to eliminate the crystallization of solid arsenic salt.

[0007] In the study of ammonium salt crystallization, two formulas of Gibbs function are usually used together to obtain two relationship equations about temperature and NH3, HCL and H2S according to the thermodynamic data of each component, and the crystallization equilibrium constants of ammonium salt crystallization reaction are defined as K p1 =P NH3 ×P HCL and K p2 =P H2S ×P NH3, the crystallization curves of ammonium chloride and ammonium hydrogen sulfide are obtained by formula combination and data processing. According to the crystallization curve of ammonium salt, the crystallization temperature of NH4HS and NH4CL is determined. NH4HS crystallization is generally between 30℃ and 60℃, and this temperature range is just the inlet and outlet pipelines of the high-pressure air cooler. A continuous water injection point is generally set in front of the high-pressure air cooler, which can effectively remove H2S in the hydrogenation reaction effluent and effectively prevent the blockage and under-scale corrosion of the heat exchange tube bundle caused by NH4HS salt deposition. NH4CL crystallization is generally between 170℃ and 220℃, and this temperature range is just the inlet and outlet pipelines of the hot high-pressure heat exchanger. Chlorine content is the most important factor affecting the crystallization temperature of NH4CL. Desalting and dechlorination should be strengthened in the process of crude oil processing to avoid the appearance of NH4CL crystal particles upstream of the water injection point. The best water injection location should be the crystallization and deposition location of NH4CL. When designing the reaction effluent system, the water injection point should be reasonably set according to the chlorine and nitrogen content of the raw oil, and 25vol% of liquid water should be kept from being vaporized after water injection to achieve the best effect of water injection. A large number of actual engineering cases have shown that water injection can alleviate the blockage of NH4CL crystallization and deposition to a certain extent, but when the water injection point is not set reasonably, its effect is very limited. Summary of the invention

[0008] The purpose of the utility model is to overcome the problem that water injection in the crude oil hydrogenation process in the prior art can slow down the NH4CL crystallization deposition blockage to a certain extent, but when the water injection point is set unreasonably, its effect is very limited. A system for preventing the crystallization of ammonium salt of hydrogenation reaction effluent is provided, which has the advantage of avoiding ammonium salt deposition.

[0009] In order to achieve the above object, the utility model provides a system for preventing the crystallization of ammonium salt in hydrogenation reaction effluent, the system for preventing the crystallization of ammonium salt in hydrogenation reaction effluent comprises a heating unit, a connected hydrogenation reaction unit and a separation unit, wherein:

[0010] The hydrogenation reaction unit is used to cause the feedstock oil to undergo a hydrogenation reaction to generate a hydrogenation product stream;

[0011] The separation unit is used to separate the gas phase and the liquid phase in the hydrogenation product logistics, and a liquid injection port is provided on the material flow pipeline of the separation unit;

[0012] The second high-pressure heat exchanger is arranged on the material pipeline between the hydrogenation reaction unit and the liquid injection port of the separation unit, and is used to make the hydrogenation reaction effluent preheat the feed of the hydrogenation reaction unit;

[0013] The heating unit is used to make the temperature of the hydrogenation product flow between the hydrogenation reaction unit and the liquid injection port of the separation unit higher than the crystallization point of the ammonium salt.

[0014] In some embodiments, the system for preventing ammonium salt crystallization of the hydrogenation reaction effluent includes a fractionation unit, which is connected to the liquid-phase discharge pipeline of the separation unit and is used for fractionating the liquid phase to obtain product oil.

[0015] In some embodiments, the heating unit includes a feed heat exchanger, which is used for preheating the feed material of the hydrogenation reaction unit with the discharge material of the fractionation unit.

[0016] In some embodiments, the separation unit includes a hot high-pressure separator, and the feed end of the hot high-pressure separator is connected to the discharge end of the hydrogenation reaction unit; the liquid injection ports include:

[0017] An intermittent liquid injection port A opened on the liquid-phase discharge pipeline of the hot high-pressure separator, and an intermittent liquid injection port B and a continuous liquid injection port C successively opened on the gas-phase discharge pipeline of the hot high-pressure separator.

[0018] In some embodiments, the gas-phase discharge pipeline of the hot high-pressure separator is connected to a cold high-pressure separator, and a first high-pressure heat exchanger and a hot high-pressure gas air cooler are successively arranged between the hot high-pressure separator and the cold high-pressure separator along the material flow direction. Among them, the intermittent liquid injection port B is arranged between the hot high-pressure separator and the first high-pressure heat exchanger, and the continuous liquid injection port C is arranged between the first high-pressure heat exchanger and the hot high-pressure gas air cooler.

[0019] In some embodiments, the liquid-phase discharge pipeline of the hot high-pressure separator is connected to a hot low-pressure separator. A hot low-pressure gas air cooler is installed on the top discharge pipeline of the hot low-pressure separator and is connected to a cold low-pressure separator. Among them, the intermittent liquid injection port A is opened between the hot low-pressure separator and the hot low-pressure gas air cooler.

[0020] In some embodiments, the hydrogenation reaction unit includes a hydrogenation reactor, the discharge end of the hydrogenation reactor is connected to the hot high-pressure separator, and the feed end of the hydrogenation reactor is connected to the feed part equipped with a feed heat exchanger.

[0021] In some embodiments, the feed part includes a feedstock oil feed pipeline, a hydrogen feed pipeline, and a mixed material pipeline. Among them, the feed end of the mixed material pipeline is connected to the feedstock oil feed pipeline and the hydrogen feed pipeline, the discharge end of the mixed material pipeline is connected to the feed end of the hydrogenation reactor, and a feed heat exchanger is installed on the feedstock oil feed pipeline.

[0022] In some embodiments, a second high-pressure heat exchanger and a heating furnace are successively installed on the mixed material pipeline along the material flow direction. Among them, the cold material pipeline of the second high-pressure heat exchanger is used for flowing the mixed stream of feedstock oil and hydrogen, and the hot material pipeline of the second high-pressure heat exchanger is used for flowing the discharge material of the hydrogenation reactor.

[0023] In some embodiments, the fractionation unit includes a fractionating column, and the fractionating column is provided with a bottom reflux pipeline. Along the material flow direction, a circulation pump and a bottom reboiler are installed on the bottom reflux pipeline.

[0024] Through the above technical solution, the system for preventing ammonium salt crystallization of the hydrogenation reaction effluent of the present utility model adds a heating unit to make the temperature of the hydrogenation product logistics between the injection port of the hydrogenation reaction unit and the separation unit higher than the crystallization point of the ammonium salt, so as to avoid problems such as the blockage of the tube bundle of the heat exchanger, under-deposit corrosion, dew point corrosion, and erosion caused by ammonium salt deposition. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the system for preventing ammonium salt crystallization of the hydrogenation reaction effluent in an embodiment of the present utility model.

[0026] Description of the Reference Numerals

[0027] 1 Feed heat exchanger; 2 Crude oil buffer tank; 3 Feed pump; 4 Second high-pressure heat exchanger; 6 Heating furnace; 7 Discharge heat exchanger; 8 Hydrogenation reactor; 9 Hot high-pressure separator; 10 First high-pressure heat exchanger; 12 Hot high-pressure gas air cooler; 13 Cold high-pressure separator; 14 Drip tank; 15 Recycle hydrogen compressor; 16 Hot low-pressure separator; 17 Hot low-pressure gas air cooler; 18 Cold low-pressure separator; 19 Circulation pump; 20 Bottom reboiler; 21 Withdrawal pump; 22 Heat exchanger; 28 Fractionating column; 27 Air cooler. Detailed Embodiments

[0028] The following will describe in detail the specific embodiments of the present utility model with reference to the drawings. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present utility model, and are not used to limit the present utility model.

[0029] In the present utility model, unless otherwise stated, the orientation words such as "upper, lower, top, bottom" are generally in the direction shown in the drawings or in the vertical, perpendicular or gravitational direction for describing the relative positional relationship of each component.

[0030] The utility model discloses a system for preventing ammonium salt crystallization of hydrogenation reaction effluent. The system for preventing ammonium salt crystallization of hydrogenation reaction effluent includes a heating unit, a hydrogenation reaction unit and a separation unit which are connected. Among them, the hydrogenation reaction unit is used to carry out hydrogenation reaction on the feedstock oil to generate a hydrogenation product stream; the separation unit is used to separate the gas phase and the liquid phase in the hydrogenation product stream. A liquid injection port is arranged on the material flow pipeline of the separation unit, and the liquid injection port is used to add an ammonium salt dissolving agent; a second high-pressure heat exchanger 4 is arranged on the material pipeline between the hydrogenation reaction unit and the liquid injection port of the separation unit to preheat the feed of the hydrogenation reaction unit with the hydrogenation reaction effluent; the heating unit is used to make the temperature of the hydrogenation product stream between the hydrogenation reaction unit and the liquid injection port of the separation unit higher than the crystallization point of the ammonium salt.

[0031] It should be noted that the feedstock oil usually contains impurities such as S, N, and CL. After the hydrogenation reaction, corrosive media such as H2S, NH3, and HCL are generated. As the temperature of the reaction effluent gradually decreases to the crystallization point, NH3 in the gas phase will react with HCL and H2S to form NH4CL and NH4HS crystals, which will deposit on the inner surface of the pipeline or equipment, resulting in a decrease in the heat transfer efficiency of the high-pressure heat exchanger, a continuous increase in the pressure drop of the reaction system, and corrosion of the pipeline, affecting the safe operation of the hydrogenation unit. In the prior art, generally, water injection is used to dissolve the ammonium salt. The inventor of the present utility model found that when the heat exchange process between the hydrogenation reaction unit and the liquid injection port of the separation unit is relatively long, when the temperature of the hydrogenation product stream is lower than the crystallization point of the ammonium salt, ammonium salt deposition will occur in the pipeline between the hydrogenation reaction unit and the liquid injection port. And because water is generally used as the ammonium salt dissolving agent in the prior art, the inventor further found that even if water is injected, it will quickly vaporize and cannot dissolve the ammonium salt. Therefore, there is no water injection point at the inlet of such high-pressure heat exchangers. For this reason, the present utility model adds a heating unit that can increase the temperature of the hydrogenation product stream between the hydrogenation reaction unit and the liquid injection port of the separation unit, and moves the ammonium salt crystallization point behind the liquid injection port to avoid ammonium salt deposition in the pipeline between the hydrogenation reaction unit and the liquid injection port.

[0032] In the present utility model, the system for preventing ammonium salt crystallization of hydrogenation reaction effluent includes a fractionation unit. The fractionation unit is connected to the liquid phase discharge pipeline of the separation unit and is used to fractionate the liquid phase to obtain product oil. On this basis, for energy conservation and consumption reduction, the heating unit is provided with a raw material heat exchanger 1 to utilize the waste heat of the fractionation product to increase the temperature of the hydrogenation product stream between the hydrogenation reaction unit and the liquid injection port of the separation unit. Considering that the temperature of the fractionation product is lower than that of the hydrogenation product stream, the raw material heat exchanger 1 of the present utility model is used to preheat the feed material of the hydrogenation reaction unit with the discharge material of the fractionation unit. In this way, the energy consumption required for the hydrogenation reaction can be reduced.

[0033] In the present utility model, the separation unit includes a hot high-pressure separator 9. The feed end of the hot high-pressure separator 9 is connected to the discharge end of the hydrogenation reaction unit; the liquid injection port includes:

[0034] An intermittent liquid injection port A opened on the liquid-phase discharge pipeline of the hot high-pressure separator 9, and

[0035] An intermittent liquid injection port B and a continuous liquid injection port C successively opened on the gas-phase discharge pipeline of the hot high-pressure separator.

[0036] Specifically, the gas-phase discharge pipeline of the hot high-pressure separator 9 is connected to the cold high-pressure separator 13, and a first high-pressure heat exchanger 10 and a hot high-pressure gas air cooler 12 are successively arranged between the hot high-pressure separator 9 and the cold high-pressure separator 13 along the material flow direction. Among them, multiple first high-pressure heat exchangers 10 can be arranged in series. For example, Figure 1 2 in series as described in [], named the first high-pressure heat exchanger I 10a and the first high-pressure heat exchanger II 10b. The intermittent liquid injection port B is arranged between the hot high-pressure separator 9 and the first high-pressure heat exchanger I 10a, and the continuous liquid injection port C is arranged between the first high-pressure heat exchanger II 10b and the hot high-pressure gas air cooler 12. The liquid-phase discharge pipeline of the hot high-pressure separator 9 is connected to the hot low-pressure separator 16. A hot low-pressure gas air cooler 17 is installed on the top discharge pipeline of the hot low-pressure separator 16 and is connected to the cold low-pressure separator 18. Among them, the intermittent liquid injection port A is opened between the hot low-pressure separator 16 and the hot low-pressure gas air cooler 17. In this way, water injection points can be respectively provided at the tube-side inlet of the first high-pressure heat exchanger 10, the inlet of the hot high-pressure gas air cooler 12, and the inlet of the hot low-pressure gas air cooler 17 to prevent ammonium salts from precipitating at a lower temperature and depositing on the tube walls of the high-pressure heat exchanger and the air cooler, resulting in problems such as tube bundle blockage, under-deposit corrosion, dew point corrosion, and erosion corrosion.

[0037] Among them, according to the respective differential pressure increase situations of the first high-pressure heat exchanger 10 and the hot low-pressure gas air cooler 17, the intermittent liquid injection port B and the intermittent liquid injection port A are intermittently injected with water to dissolve ammonium salts by using the existing technology. The water injection volume of the continuous liquid injection port C is 1% of the raw material oil volume according to every 200 μg / g of nitrogen content in the raw material oil for water injection to ensure sufficient water volume to dissolve ammonium salts and prevent ammonium hydrosulfide from precipitating at a lower temperature and depositing on the air cooler tube wall, corroding and blocking the air cooler tube bundle; among them, the water injection of the intermittent liquid injection port B, the intermittent liquid injection port A, and the liquid injection port C can use deoxygenated water, demineralized water, or purified water recycled from the hydrogenation unit. It is preferably to use the purified water recycled from the hydrogenation unit to save energy consumption, and the recycling ratio of the purified water should not exceed 50% of the total water injection volume.

[0038] The bottom discharge pipeline of the hot low-pressure separator 16 is connected to the feed end of the fractionation unit, so that the liquid-phase material separated from the gas phase enters the fractionation unit for further fractionation treatment.

[0039] The gas phase separated by the hot high-pressure separator 9 enters the cold high-pressure separator 13 for further separation after being cooled by the first high-pressure heat exchanger 10 and the hot high-pressure gas air cooler 12. The liquid-phase discharge pipeline of the cold high-pressure separator 13 is communicated with the cold low-pressure separator 18, and the discharge end of the cold low-pressure separator 18 is communicated with the feed end of the fractionation unit. Specifically, an outlet heat exchanger 7 is provided on the bottom discharge pipeline of the hot low-pressure separator 16. Along the material flow direction, the discharge end of the cold low-pressure separator 18 is connected to the shell side of the aforementioned first high-pressure heat exchanger 10, so that the produced oil from the cold low-pressure separator 18 and the gas-phase components from the hot high-pressure separator 9 are heat-exchanged through the aforementioned at least one first high-pressure heat exchanger 10 and then sent to the separation unit through the outlet heat exchanger 7.

[0040] The gas-phase discharge pipeline of the cold high-pressure separator 13 is communicated with the feed end of the hydrogenation reaction unit (for example, communicated with the feed end of the following hydrogen feed pipeline or mixed material pipeline) to return the separated hydrogen. A liquid separation tank 14 and a hydrogen circulation compressor 15 are sequentially arranged between the cold high-pressure separator 13 and the hydrogenation reaction unit along the material flow direction.

[0041] In the present utility model, the hydrogenation reaction unit includes two hydrogenation reactors 8 connected in series, so that the feedstock oil and hydrogen react under the action of a catalyst in the reactor. Along the material flow direction, the discharge end of the second hydrogenation reactor 8 is communicated with the hot high-pressure separator 9, and the feed end of the first hydrogenation reactor 8 is communicated with the feed part of the installed raw material heat exchanger 1.

[0042] The hydrogenation reactor 8 of the present utility model can be a fixed-bed reactor. The inlet temperature of the reactor is 280 - 320 °C, the inlet hydrogen-oil volume ratio is 400 - 600:1, the hydrogen partial pressure is 5 - 15 MPa, the catalyst volume space velocity is 0.5 - 2.0 h-1, and the average reaction temperature is 320 - 390 °C. The refined oil after hydrogenation enters the separation unit.

[0043] Among them, the feed part includes a feedstock oil feed pipeline, a hydrogen feed pipeline, and a mixed material pipeline. Among them, the feed end of the mixed material pipeline is communicated with the feedstock oil feed pipeline and the hydrogen feed pipeline, the discharge end of the mixed material pipeline is communicated with the feed end of the hydrogenation reactor, and a raw material heat exchanger 1, a crude oil buffer tank 2, and a feed pump 3 are sequentially installed on the feedstock oil feed pipeline along the material flow direction. Among them, the cold material pipeline of the raw material heat exchanger 1 is used for circulating the feedstock oil, and the hot material pipeline of the raw material heat exchanger 1 is used for circulating the discharge material of the fractionation unit.

[0044] Among them, a second high-pressure heat exchanger 4 and a heating furnace 6 are successively installed on the mixing material pipeline along the material flow direction (heating the mixed flow of raw material oil and hydrogen to 280-310°C and then entering the reactor). Among them, the cold material pipeline of the second high-pressure heat exchanger 4 is used to circulate the mixed flow of raw material oil and hydrogen, and the hot material pipeline of the second high-pressure heat exchanger 4 is used to circulate the discharge material of the hydrogenation reactor 8 (hydrogenation product logistics). It can be understood that the number of the second high-pressure heat exchangers 4 can be set to multiple, and multiple are connected in series on the mixing material pipeline to realize multi-stage heat exchange of the materials in the mixing material pipeline, and cool the hydrogenation product logistics to 180-250°C and then send it into the hot high-pressure separator 9. For example Figure 1 As shown, two second high-pressure heat exchangers 4 are provided, named the second high-pressure heat exchanger I 4a and the second high-pressure heat exchanger II 4b. If the hydrogenation product logistics directly exchanges heat with the mixed flow of raw material oil and hydrogen through two series-connected second high-pressure heat exchangers 4 in sequence, the inlet temperature of the hydrogenation product logistics entering the hot material pipeline of the second high-pressure heat exchanger I 4a is above 250°C, and the outlet temperature of the hydrogenation product logistics from the hot material pipeline of the second high-pressure heat exchanger II 4b is below 200°C. Since the inlet temperature of the second high-pressure heat exchanger 4 is relatively high, even if water is injected, it will quickly vaporize and cannot dissolve ammonium salts (such as NH4CL). Therefore, no water injection point is set at the inlet of such high-pressure heat exchangers. With the foregoing setting, after using the raw material heat exchanger 1 to preheat the feed material of the hydrogenation reaction unit with the discharge material of the fractionation unit, and then exchanging heat with the hydrogenation product logistics through the second high-pressure heat exchanger 4, the heat loss of the hydrogenation product logistics can be reduced, so as to increase the temperature of the hydrogenation product logistics between the hydrogenation reaction unit and the injection port of the separation unit. Such a setting can achieve energy conservation and consumption reduction while avoiding ammonium salt deposition in the pipeline between the hydrogenation reaction unit and the injection port, so as to avoid a decrease in the heat exchange efficiency of the high-pressure heat exchanger and a continuous increase in the pressure drop of the reaction system, resulting in an increase in the heating furnace load of the reaction system, forcing the unit to reduce the production rate or requiring shutdown for dismantling and cleaning of the high-pressure heat exchanger and other problems.

[0045] In the present utility model, a fractionation unit is provided with a fractionating tower 28. The fractionating tower 28 is provided with a top reflux pipeline, and the top reflux pipeline is provided with a naphtha product discharge pipeline. The fractionating tower 28 is provided with a bottom reflux pipeline. Along the material flow direction, a circulation pump 19 and a bottom reboiler 20 are installed on the bottom reflux pipeline to heat the material flow recycled to below a tray of the fractionating tower 28, indirectly control the bottom temperature, and ensure that there is sufficient distillation heat energy at the bottom of the fractionating tower. A diesel product discharge pipeline is also provided at the bottom of the fractionating tower 28. The diesel product discharge pipeline is successively provided with a withdrawal pump 21, at least one discharge heat exchanger 22, and a raw material heat exchanger 1 discharge air cooler 27 along the material flow direction. After multiple coolings, the diesel product is cooled to ≤50 °C and then discharged to the product tank area. In this way, by utilizing the waste heat of the fractionation system products, a raw material heat exchanger 1 for heat exchange between the raw material oil and the fractionation products is added. After increasing the raw material oil feed temperature, the heat exchange temperature of the high-pressure heat exchanger is further increased. By controlling the heat exchange temperature, the ammonium salt crystallization point is shifted to after the reaction water injection point. In this way, the ammonium salt crystallization problem upstream of the water injection point can be solved, and the waste heat of the fractionation products can be fully utilized, resulting in obvious energy conservation and consumption reduction.

[0046] It can be understood that the heat exchanger in the present utility model can be a threaded locking ring heat exchanger, and a temperature control bypass regulating valve in the prior art is provided in the shell side of the heat exchanger.

[0047] In the present utility model, the raw material oil components are mainly one or more of coking gasoline, catalytic gasoline, or straight-run naphtha.

[0048] In the present utility model, the diesel components are mainly one or more of coking diesel, catalytic diesel, or straight-run diesel.

[0049] In the present utility model, the distillation range of the raw material oil is 30 - 375 °C, the sulfur content is not higher than 0.5%, the nitrogen content is not higher than 0.2%, the chloride ion content is not higher than 3 μg / g, and the metal content is not higher than 1 μg / g.

[0050] The advantages of the present utility model will be illustrated by the following embodiments, but the present utility model is not limited thereto.

[0051] Embodiment

[0052] This embodiment adopts Figure 1 the system for preventing ammonium salt crystallization of the hydrogenation reaction effluent as shown, and the operation process is as follows:

[0053] 1) Hydrogenation reaction unit process

[0054] The raw material is a mixed feedstock oil composed of coking gasoline and diesel produced by a coking unit and catalytic diesel produced by a fluid catalytic cracking unit. The properties of the mixed feedstock oil are shown in Table 1, and the temperature is 35°C. After the mixed feedstock oil exchanges heat with the feedstock heat exchanger 1, the temperature rises to 81°C and enters the crude oil buffer tank 2. The feedstock heat exchanger 1 is equipped with a temperature control bypass line to adjust the outlet temperature of the feedstock oil on the shell side. The feedstock oil is pressurized to 8.9 MPa by the feed pump 3 and sent to the reverse mixture pipeline, where it converges with hydrogen from the hydrogen feed pipeline or hydrogen-rich gas from the recycle hydrogen compressor 15. It exchanges heat with the hydrogenation reaction product oil in the shell sides of two series-connected second high-pressure heat exchangers II 4b and second high-pressure heat exchanger I 4a. Temperature control bypass valves are provided in the shell sides of the second high-pressure heat exchanger II 4b and the second high-pressure heat exchanger I 4a to control the inlet temperature of the heating furnace 6 and the outlet temperature of the tube side of the second high-pressure heat exchanger II 4b. The hydrogen-rich gas is heated to 297°C by the heating furnace 6 and enters the hydrogenation reactor 8 for refining reactions such as desulfurization, denitrification, and aromatics saturation. Impurities such as S, N, and Cl in the feedstock oil react to form NH3, H2S, and HCl, which flow out with the reaction effluent stream. The temperature of the reaction effluent is 375°C, and after being cooled by heat exchange with the second high-pressure heat exchanger I 4a and the second high-pressure heat exchanger II 4b, it enters the hot high-pressure separator 9.

[0055] Among them, the relevant data before and after the transformation of the new feedstock heat exchanger 1 using low-temperature waste heat technology are shown in Table 2. Based on the relevant data in Table 1 and Table 2, the molar fractions of NH3, H2S, and HCl in the gas phase of the reaction effluent are calculated through simulation, and the partial pressures of H2S, NH3, and HCl are calculated as follows: P [H2S] = 3.0897 psia, P [NH3] = 4.2373 psia, P [HCL] = 0.0005578 psia. Through the ammonium salt deposition temperature equation, the deposition temperature coefficient KP [NH4HS] = P [H2S] ×P [NH3] = 13.092 psia 2 , KP [NH4CL] = P [H2S] ×P [NH3] = 0.00236 psia 2 . Through the ammonium salt deposition temperature equation, the crystallization temperature T NH4CL of NH4Cl is calculated to be 190°C, and the crystallization temperature T NH4HSIt is 5.5°C. As can be seen from Table 2, the outlet temperature of the tube side of the second high-pressure heat exchanger II4b before the optimization of the heat exchange system was 187°C, which was within the ammonium salt crystallization range, resulting in obvious NH4CL crystallization in the second high-pressure heat exchanger 4 and causing the problem of low heat exchange efficiency of the high-pressure heat exchanger. After adding the raw material heat exchanger 1 and raising the temperature of the raw material oil, the outlet temperature of the tube side of the second high-pressure heat exchanger II4b was controlled at 203°C, which well avoided a series of problems such as the reduction of the heat exchange efficiency of the high-pressure heat exchanger caused by NH4CL crystallization.

[0056] 2) Separation system process

[0057] After the hydrogenation reaction product is cooled, it enters the hot high-pressure separator 9 for the primary separation of gas and liquid phases. The liquid component is discharged to the hot low-pressure separator 16 under the control of the liquid level. The gas component exchanges heat and is cooled through the tube sides of two series-connected first high-pressure heat exchangers I10a and first high-pressure heat exchangers II10b with the product oil from the cold low-pressure separator 18, and then is cooled to 50°C by the hot high-pressure gas air cooler 12 and enters the cold high-pressure separator 13. To prevent ammonium salt crystallization from clogging the high-pressure heat exchanger and the air cooler, an intermittent injection port B is set in front of the first high-pressure heat exchanger I10a, and intermittent water injection is carried out to dissolve the ammonium salt according to the rising differential pressure of the first high-pressure heat exchanger 10. A continuous injection port C is set in front of the hot high-pressure gas air cooler 12, and the water injection volume is 1% of the raw material oil volume according to the nitrogen content of every 200 μg / g in the raw material oil for water injection to ensure sufficient water volume to dissolve the ammonium salt. The cooled hot high-pressure gas enters the cold high-pressure separator 13 for the three-phase separation of gas, oil, and water. The gas is discharged from the top and enters the liquid separation tank 14 set at the inlet of the recycle hydrogen compressor 15, and the gas enters the recycle hydrogen compressor 15 and is sent to the hydrogenation reactor 8 for recycling. The oil in the cold high-pressure separator 13 enters the cold low-pressure separator 18 for further oil-water separation;

[0058] The hot high-pressure oil undergoes secondary separation in the hot low-pressure separator 16. The flashed oil vapor is cooled to 50°C by the hot low-pressure gas air cooler 17. An intermittent injection port A is set in front of the hot low-pressure gas air cooler 17, and intermittent water injection is carried out to dissolve the ammonium salt according to the rising differential pressure of the hot low-pressure gas air cooler 17. The gas condensate from the hot low-pressure separator 16 and the oil from the cold high-pressure separator 13 are further separated into gas, oil, and water in the cold low-pressure separator 18, and the water therein is discharged to the sewage treatment device; the oil therein exchanges heat with the hot high-pressure gas through the shell sides of the first high-pressure heat exchanger I10a and the first high-pressure heat exchanger II10b, and then converges with the oil discharged from the hot low-pressure separator 16 and is sent to the fractionation system.

[0059] 3) Fractionation system process

[0060] The oil product from the separation system exchanges heat with the diesel product in the shell side of the outlet heat exchanger 7 and then enters the fractionating tower 28. The naphtha component is drawn out from the top of the fractionating tower. After heat exchange, cooling and separation, it is sent to the naphtha product storage area. The bottom draw of the fractionating tower is divided into two paths. One path is drawn out by the circulating pump 19 and then divided into four paths, which evenly enter the bottom reboiler furnace 20, and are heated and circulated back to below the first tray of the fractionating tower to indirectly control the bottom temperature of the tower and ensure that there is sufficient distillation heat energy at the bottom of the fractionating tower. The other path is drawn out by the draw pump 21, cooled by the heat exchanger i017, heat exchanger ii22, heat exchanger iii23, heat exchanger iv24, heat exchanger v25, the fractionated product heat exchanger 26 and the feedstock heat exchanger 1, and then cooled by the air cooler 27 to ≤50°C and sent to the diesel product storage area. Before optimization, the temperature after cooling by the last heat exchanger 22 was 122°C, and the waste heat of the product was not fully utilized. After adding the feedstock heat exchanger 1, the waste heat of the product was fully utilized, and the waste heat of the diesel product dropped to 66°C.

[0061] In summary, as can be seen from the embodiments, the method provided by the present utility model not only effectively solves the problem of ammonium salt crystallization in the high-pressure heat exchanger, but also fully utilizes the waste heat of the fractionated product and saves a large amount of fuel gas. After calculation, the fuel gas consumption can be saved by about 7,000 tons / year, and the economic benefits are remarkable.

[0062] Table 1: Properties of the mixed feedstock oil

[0063] Item Value <![CDATA[w(Sulfur) / (μg·g -1 )]]> 2500 <![CDATA[w(nitrogen) / (μg·g -1 )]]> 1500 <![CDATA[Density (20 °C) / (kg·m -3 )]]> 823 <![CDATA[Chlorine / (μg·g -1 )]]> 0.5 Distillation Range (ASTM D86) / ℃ IBP / 10% 39.3 / 93.5 50％ / 90％ 243.5 / 343.4 95％ 356.4 EBP 367.1

[0064] Table 2: Operating data before and after low-temperature waste heat utilization in the embodiment

[0065]

[0066]

[0067] The preferred embodiments of the present utility model have been described in detail above in conjunction with the accompanying drawings. However, the present utility model is not limited thereto. Within the scope of the technical concept of the present utility model, various simple modifications can be made to the technical solutions of the present utility model, including the combination of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present utility model will not separately describe various possible combination methods. But these simple modifications and combinations should also be regarded as the content disclosed by the present utility model and all fall within the protection scope of the present utility model.

Claims

1. A system for preventing ammonium salt crystallization in the hydrogenation reaction effluent, characterized in that, The system for preventing ammonium salt crystallization of hydrogenation reaction effluent includes a heating unit, a hydrogenation reaction unit and a separation unit which are connected. Among them, the hydrogenation reaction unit is used to make the feedstock oil undergo a hydrogenation reaction to generate a hydrogenation product stream; the separation unit is used to separate the gas phase and the liquid phase in the hydrogenation product stream, and a liquid injection port is arranged on the material flow pipeline of the separation unit; A second high-pressure heat exchanger (4) is arranged on the material pipeline between the hydrogenation reaction unit and the liquid injection port of the separation unit, and is used to preheat the feed of the hydrogenation reaction unit with the hydrogenation reaction effluent; the heating unit is used to make the temperature of the hydrogenation product stream between the hydrogenation reaction unit and the liquid injection port of the separation unit higher than the crystallization point of the ammonium salt.

2. The system for preventing ammonium salt crystallization of the hydrogenation reaction effluent according to claim 1, wherein The system for preventing ammonium salt crystallization of hydrogenation reaction effluent includes a fractionation unit, and the fractionation unit is connected to the liquid phase discharge pipeline of the separation unit and is used to fractionate the liquid phase to obtain product oil.

3. The system for preventing ammonium salt crystallization of the hydrogenation reaction effluent according to claim 2, characterized in that, The heating unit includes a raw material heat exchanger (1), and the raw material heat exchanger (1) is used to preheat the feed material of the hydrogenation reaction unit with the discharge material of the fractionation unit.

4. The system for preventing ammonium salt crystallization of the hydrogenation reaction effluent according to claim 1, wherein The separation unit includes a hot high-pressure separator (9), and the feed end of the hot high-pressure separator (9) is connected to the discharge end of the hydrogenation reaction unit; The liquid injection port includes: An intermittent liquid injection port A opened on the liquid phase discharge pipeline of the hot high-pressure separator (9), and An intermittent liquid injection port B and a continuous liquid injection port C which are successively opened on the gas phase discharge pipeline of the hot high-pressure separator.

5. The system for preventing ammonium salt crystallization of the hydrogenation reaction effluent according to claim 4, wherein, The gas phase discharge pipeline of the hot high-pressure separator (9) is connected to a cold high-pressure separator (13), and a first high-pressure heat exchanger (10) and a hot high-pressure gas air cooler (12) are successively arranged between the hot high-pressure separator (9) and the cold high-pressure separator (13) along the material flow direction. Among them, the intermittent liquid injection port B is arranged between the hot high-pressure separator (9) and the first high-pressure heat exchanger (10), and the continuous liquid injection port C is arranged between the first high-pressure heat exchanger (10) and the hot high-pressure gas air cooler (12).

6. The system for preventing ammonium salt crystallization of hydrogenation reaction effluent according to claim 4 or 5, characterized in that, The liquid phase discharge pipeline of the hot high-pressure separator (9) is connected to a hot low-pressure separator (16), a hot low-pressure gas air cooler (17) is installed on the top discharge pipeline of the hot low-pressure separator (16) and is connected to a cold low-pressure separator (18). Among them, the intermittent liquid injection port A is opened between the hot low-pressure separator (16) and the hot low-pressure gas air cooler (17).

7. The system for preventing ammonium salt crystallization of the hydrogenation reaction effluent according to claim 1, characterized in that, The hydrogenation reaction unit includes a hydrogenation reactor (8), the discharge end of the hydrogenation reactor (8) is connected to the hot high-pressure separator (9), and the feed end of the hydrogenation reactor (8) is connected to the feed part equipped with the raw material heat exchanger (1).

8. The system for preventing ammonium salt crystallization of the hydrogenation reaction effluent according to claim 7, wherein The feed part includes a feedstock oil feed pipeline, a hydrogen feed pipeline and a mixture pipeline. Among them, the feed end of the mixture pipeline is connected to the feedstock oil feed pipeline and the hydrogen feed pipeline, the discharge end of the mixture pipeline is connected to the feed end of the hydrogenation reactor, and the raw material heat exchanger (1) is installed on the feedstock oil feed pipeline.

9. The system for preventing ammonium salt crystallization of the hydrogenation reaction effluent according to claim 8, wherein A second high-pressure heat exchanger (4) and a heating furnace (6) are successively installed on the mixture pipeline along the material flow direction.

10. The system for preventing ammonium salt crystallization of the hydrogenation reaction effluent according to claim 2 or 8, characterized in that, The fractionation unit includes a fractionating tower (28), and the fractionating tower (28) is provided with a bottom reflux pipeline. Along the material flow direction, a circulation pump (19) and a bottom reboiler furnace (20) are installed on the bottom reflux pipeline.

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