Process for preventing color change in preparation of industrial naphthalene from coal tar

Abstract

The invention discloses an anti-discoloration process for preparing industrial naphthalene from coal tar, which is characterized in that carbolic oil vapor is utilized to heat and heat a raw material in a preheater I so as to concentrate the raw material, the carbolic oil vapor is utilized to realize primary heating of the raw material, and the process energy consumption is saved. During rectification, a novel dephenolization tower is adopted, gas and liquid in the dephenolization tower are mixed, nitrogen is used as an isolation hood, air is prevented from entering a mixing area, impurities caused by phenol oxidation in liquefied naphthalene oil are avoided, the temperature of alkali liquor in the tower body is 65-80 DEG C and is lower than the temperature of 70-90 DEG C in a reaction area in a high-pressure isolation gas hood, and the temperature of the alkali liquor in the tower body is higher than that in the reaction area in the high-pressure isolation gas hood. The phenol in the industrial naphthalene steam can be efficiently removed by utilizing the temperature of the area, so that the phenol can be more easily removed by alkali liquor.

Description

Technical Field

[0001] The invention relates to the technical field of preventing discoloration of industrial naphthalene, in particular to a process for preventing discoloration of industrial naphthalene prepared from coal tar. Background Art

[0002] Industrial naphthalene is a colorless and shiny flaky crystal that is insoluble in water, easy to sublimate, and has a special smell. It is the most important polycyclic aromatic hydrocarbon in industry. Industrial naphthalene is mainly used to produce phthalic anhydride, dye intermediates, rubber additives and pesticides. According to the purity, naphthalene can be divided into industrial naphthalene and refined naphthalene. The purity of industrial naphthalene is generally about 96%. After further purification of industrial naphthalene to remove impurities and desulfurize, high-purity refined naphthalene can be obtained. Among them, industrial naphthalene is prone to discoloration during storage, resulting in reduced quality. The main reasons for the deepening of color are two aspects: one is the oxidation of phenolic substances, and the other is the complex reaction of phenol and iron. Phenolic substances are easily oxidized by oxygen in the air to generate colored impurities, resulting in phenolic substances with different degrees of yellow or red. For example, phenol can generate p-benzoquinone or o-benzoquinone after oxidation. These substances have colors themselves, which makes the color of industrial naphthalene darker. On the other hand, the complex reaction of phenol and iron is also an important factor leading to the dark color of industrial naphthalene.

[0003] In the existing means, the phenol in the mixed fraction (steam state) is basically reacted thoroughly with the alkali, that is, the mixed fraction is directly introduced into the alkali molten liquid, and the alkali solution is utilized to absorb the phenol in the mixed fraction. After the alkali solution is introduced, bubbles will be formed, so that the mixed fraction cannot fully react with the alkali solution, which will cause the phenol content in the mixed fraction to remain high; if the mixed fraction is directly introduced into the reactor without directly entering the alkali solution, the liquefied naphthalene oil will float on the top of the alkali solution to block the reaction of the mixed fraction and the alkali solution, which will also cause the phenol content to remain high. The high phenol content makes the existing means mostly adopt continuous multiple washing methods to solve this type of problem. At the same time, it is easy to be mixed with air during the alkali washing process, so that the phenol in the liquefied naphthalene oil is oxidized and discoloration occurs. Summary of the invention

[0004] The technical problem to be solved by the invention is how to solve the problem that the phenol content in industrial naphthalene is high in a single washing and the liquefied naphthalene oil is easily discolored.

[0005] In order to solve the above technical problems, the inventors have obtained the technical solution of the present invention through practice and summary. The present invention adopts the following technical solution:

[0006] A process for preparing industrial naphthalene from coal tar to prevent discoloration, the process steps are as follows:

[0007] Step 1: Preheat

[0008] The raw material is pumped into the preheater 1 through the raw material inlet pipe, and the raw material is heated once in the preheater 1, and then heated twice in the preheater 2;

[0009] Step 2: Initial distillation

[0010] The preheated raw materials enter the primary distillation tower through the pipeline, and the distilled phenol oil vapor escapes from the top of the tower at 190-200℃;

[0011] The escaped phenol oil vapor enters the preheater 1 to complete the primary concentration, the concentrated phenol oil vapor enters the concentrator to complete the secondary concentration, and the concentrated phenol oil enters the phenol oil reflux tank;

[0012] Step 3: Distillation

[0013] The bottom oil after the initial distillation is pumped into the distillation tower through a pipeline, and the evaporated industrial naphthalene vapor escapes from the top of the tower at 218-220°C, and enters the dephenolization tower after the raw material is heated by heat exchange in the second preheater. A nitrogen high-pressure cyclone flow is arranged in the dephenolization tower, and the industrial naphthalene vapor is introduced into the middle of the nitrogen high-pressure cyclone flow. The lower part of the nitrogen high-pressure cyclone flow is the alkali mist generation area. When the alkali mist flows toward the industrial naphthalene vapor, ripples will be generated in the alkali mist generation area. The industrial naphthalene vapor reacts with the alkali mist in the nitrogen high-pressure cyclone flow to dephenolize and floats on the surface of the alkali solution, and is smoothly transported to the outside by the nitrogen high-pressure cyclone flow, flows out from the overflow pipe on the side wall of the dephenolization tower, enters the industrial naphthalene reflux tank after oil-water separation, and is then pumped into the industrial naphthalene tank through a pipeline and nitrogen-sealed, and the washed oil part enters the washed oil processing pipeline system.

[0014] Preferably, the dephenolization tower comprises a tower body, and an overflow pipe is provided on the side of the tower body for overflow introduction into the oil-water separator;

[0015] An industrial naphthalene inlet pipe is arranged on the top of the tower body, and several nitrogen pipes are evenly distributed on the outside of the inlet pipe. The nitrogen pipes are used to output high-pressure nitrogen gas flow, and the output high-pressure nitrogen gas flow is distributed in a vortex shape from top to bottom to form a high-pressure isolation gas hood. An ultrasonic atomizer is arranged at the bottom center of the high-pressure isolation gas hood. The ultrasonic atomizer is used to atomize the alkali solution in the tower body, and the atomized alkali solution particles are evenly distributed inside the high-pressure isolation gas hood and are fully mixed with the industrial naphthalene vapor.

[0016] Preferably, the ratio of the amount of alkali solution atomized per unit time to the amount of industrial naphthalene vapor introduced is 2-10:1;

[0017] A thermometer and a jacket on the outside are installed in the tower body. The alkali liquid temperature of the tower body is between 65℃ and 90℃. Steam is introduced into the jacket to adjust the alkali liquid temperature inside the tower body.

[0018] Preferably, a flow equalizer is installed on the tower body below the ultrasonic atomizer, and an alkali solution filling pipe is provided at the bottom of the flow guide plate;

[0019] A flow-homogenizing cylinder is installed in the tower body. The flow-homogenizing cylinder is sleeved on the outside of the ultrasonic atomizer and is located outside the high-pressure isolation gas hood, and is used for lateral flow-homogenizing transportation of dephenolized naphthalene oil.

[0020] Preferably, the bottom oil in the primary distillation tower is pumped to the distillation tower through a pipeline for distillation, and the remaining part is led to the reboiler through a pipeline to heat up to 270-275°C and reflux into the primary distillation tower to provide heat for distillation in the primary distillation tower to maintain the top temperature of the tower.

[0021] Preferably, the wash oil inside the distillation tower is pumped to a tubular heating furnace to be heated to 290±5° C. and then pumped back into the distillation tower to provide heat for distillation in the distillation tower to maintain the tower top temperature.

[0022] Preferably, the dephenolized naphthalene oil in the industrial naphthalene reflux tank is partially refluxed into the distillation tower through a pipeline to maintain the tower top temperature and the naphthalene content within the tower top temperature gradient range.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention utilizes phenol oil vapor to heat up the raw material in a preheater so that the raw material can be concentrated and processed, and utilizes phenol oil vapor to achieve a one-time heating of the raw material, thereby saving process energy consumption.

[0025] 2. The present invention adopts a novel dephenolization tower during rectification, utilizes gas-liquid mixing in the dephenolization tower and uses nitrogen as an isolation cover to prevent air from entering the mixing region, avoids phenol oxidation in the liquefied naphthalene oil and brings impurities, the alkali liquid temperature in the tower body is between 65° C. and 80° C., which is lower than the temperature in the reaction region in the high-pressure isolation gas cover between 70° C. and 90° C., utilizes this regional temperature to efficiently remove phenol in the industrial naphthalene steam, and makes it easier to be dephenolized by alkali liquid.

[0026] 3. The present invention adopts nitrogen as the high-pressure isolation gas cover in the dephenolization tower, so that the inside is used as a relatively closed space to prevent phenol oxidation in the naphthalene oil. Secondly, the naphthalene oil floating on the alkali solution surface after the dephenolization can be transported outwards, and the uniform flow tube is coordinated to make the stable outward transport, so as to avoid the occurrence of mixed flow causing the naphthalene oil to have obvious emulsification phenomenon. Since the bottom of the uniform flow tube is a structure with a large upper part and a small lower part, it is beneficial to the outward transport process of the naphthalene oil to further weaken the emulsification phenomenon of the surface naphthalene oil.

[0027] 4. The present invention can ensure the quality of alkali mist by arranging a floating plate at the bottom of the ultrasonic atomizer and introducing the alkali solution at the bottom of the flow-uniform plate through a drainage pipe. A conveying guide is arranged above the ultrasonic atomizer for conveying and draining upward, so that the gas-liquid convection mixing moves outward and downward to fully remove phenol. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0029] Figure 2 It is the internal structure distribution diagram of the dephenolization tower of the present invention.

[0030] Figure 3 This is the nitrogen pipe distribution diagram in the dephenolization tower. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0032] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] Example 1

[0034] like Figure 1 A process for preventing discoloration of industrial naphthalene prepared from coal tar is shown, and the steps are as follows:

[0035] Step 1: Preheat

[0036] The raw material is pumped from the raw material inlet pipe 10 into the preheater 20, and is heated once in the preheater 20, and then heated twice in the preheater 2 30;

[0037] Step 2: Initial distillation

[0038] The preheated raw materials enter the primary distillation tower 40 through the pipeline, and the distilled phenol oil vapor escapes from the top of the tower at 190-200°C;

[0039] The escaped phenol oil vapor enters the preheater 20 to complete the primary concentration, the concentrated phenol oil vapor enters the concentrator 50 to complete the secondary concentration, and the concentrated phenol oil enters the phenol oil reflux tank 60;

[0040] Step 3: Distillation

[0041] The bottom oil after the initial distillation is pumped into the distillation tower 70 through a pipeline, and the evaporated industrial naphthalene vapor escapes from the top of the tower at 218-220° C. and enters the dephenolization tower 80. A nitrogen high-pressure cyclone flow is arranged in the dephenolization tower 80. The industrial naphthalene vapor is introduced into the middle of the nitrogen high-pressure cyclone flow. The lower part of the nitrogen high-pressure cyclone flow is the alkali mist generation area. When the alkali mist flows toward the industrial naphthalene vapor, ripples will be generated in the alkali mist generation area. The industrial naphthalene vapor reacts with the alkali mist in the nitrogen high-pressure cyclone flow to dephenolize and floats on the surface of the alkali solution. It is smoothly transported to the outside by the nitrogen high-pressure cyclone flow and flows out from the overflow pipe 82 on the side wall of the dephenolization tower 80. After oil-water separation, it enters the industrial naphthalene reflux tank 100, and then is pumped into the industrial naphthalene tank 110 through a pipeline and nitrogen-sealed. The washed oil part enters the washed oil processing pipeline system. Through the convection of alkali liquid mist and naphthalene vapor to achieve efficient mixing, the dephenolization operation can be completed in just one time, which simplifies the energy consumption problem and low production efficiency caused by continuous multiple dephenolization treatments in the prior art, and also easily causes the problem of easy discoloration in the subsequent preparation of industrial naphthalene.

[0042] Example 2

[0043] The following improvements are made in the above embodiment: Figure 2 As shown, the dephenolization tower 80 includes a tower body 81 , and an overflow pipe 82 is provided on the side of the tower body 81 for overflow to be introduced into the oil-water separator 90 .

[0044] The top of the tower body 81 is provided with an industrial naphthalene introduction pipe 83, a nitrogen introduction pipe and an explosion-proof membrane, and a plurality of nitrogen pipes 84 are evenly distributed on the outside of the introduction pipe, such as Figure 3 As shown, the nitrogen inlet pipe is introduced into the tower body 81 and then enters the nitrogen pipe 84 after being homogenized by the ring pipe. The nitrogen pipe 84 is set obliquely downward and gradually deviates from the ultrasonic atomizer 85. The nitrogen pipe 84 is used to output a high-pressure nitrogen gas flow, and the output high-pressure nitrogen gas flow is distributed in a vortex shape from top to bottom. The vortex has a small top and a large bottom structure, thereby forming a high-pressure isolation gas hood. An ultrasonic atomizer 85 is set at the bottom center of the high-pressure isolation gas hood. The ultrasonic atomizer 85 is used to atomize the alkali solution in the tower body 81, and the atomized alkali solution particles are evenly distributed inside the high-pressure isolation gas hood and are fully mixed with the industrial naphthalene vapor.

[0045] The air in the tower is isolated by a high-pressure nitrogen gas flow to prevent the oxidation of phenolic substances in the steam. At the same time, the high-pressure nitrogen gas flow will transport the liquefied liquid naphthalene (floating on the liquid surface) to the outside, and enter the oil-water separator 90 through the overflow pipe 82 to remove moisture to obtain liquid naphthalene. After the liquid naphthalene is nitrogen-sealed, it is passed through a crystallizer to obtain industrial naphthalene. The crystallization step is an existing conventional operation.

[0046] Example 3

[0047] The following improvements are made in the above embodiment: Figure 2As shown, in order to ensure that all naphthalene vapor is absorbed to complete the dephenolization operation, the ratio of the amount of alkali solution atomized to the amount of industrial naphthalene vapor introduced within the unit time is 2-10:1.

[0048] When the atomization amount of the alkali solution is relatively low, the temperature can be strictly set to absorb the phenol that has not been removed from the liquid naphthalene, so that it can be dissolved in the alkali solution when it falls on the liquid surface to complete the dephenolization operation. A thermometer and a jacket 86 located on the outside are installed in the tower body 81. The alkali solution temperature of the tower body 81 is between 65°C and 80°C, and the temperature in the reaction area in the high-pressure isolation gas hood is between 70°C and 90°C. Steam is introduced into the jacket 86 to adjust the alkali solution temperature inside the tower body 81.

[0049] The ripples generated by ultrasonic atomization can evenly spread the surface oil film, so that the alkali solution contained inside and the phenol that has not been removed are dissolved into the alkali solution, and are transported outward under nitrogen protection and flow out from the overflow pipe 82.

[0050] Example 4

[0051] The following improvements are made in the above embodiment. In order to avoid turbulence in the liquid surface when adding alkali solution online, a flow equalizer 87 is installed on the tower body 81 below the ultrasonic atomizer 85 to reduce the emulsification of the surface liquid naphthalene, and an alkali solution filling pipe 88 is provided at the bottom of the flow equalizer 87.

[0052] Example 5

[0053] The following improvements are made in the above embodiment. Since the nitrogen high-pressure isolation gas hood has the function of conveying liquid naphthalene floating on the surface, it will also evenly spread the liquid naphthalene near the ultrasonic atomizer 85 outward, so that a small amount of phenol in the liquid naphthalene is dissolved in the alkali solution. At the same time, in order to solve the emulsification problem that is prone to occur near the overflow pipe 82, a flow-leveling cylinder 89 is installed in the tower body 81. The flow-leveling cylinder 89 is mounted on the outside of the ultrasonic atomizer 85 and is located outside the high-pressure isolation gas hood. It is used for horizontal uniform flow conveying of dephenolized naphthalene oil. The bottom of the flow-leveling cylinder 89 is a structure with a larger top and a smaller bottom, and a flow-leveling hole is provided on the surface.

[0054] A conveying guide 810 is provided above the ultrasonic atomizer 85, and a guide portion 811 is provided on the top of the conveying guide 810. The conveying guide 810 is provided above the ultrasonic atomizer 85 for conveying and draining upward, so that the gas-liquid convection mixing moves outward and downward for sufficient dephenolization.

[0055] Example 6

[0056] The following improvements are made in the above embodiment: Figure 2As shown, since the amount of dephenolized naphthalene floating on the surface continues to increase, it is bound to affect the atomization effect of the ultrasonic atomizer 85, so a floating plate 851 is provided at the bottom of the ultrasonic atomizer 85, and a drainage pipe 852 is inserted at the bottom of the floating plate 851. The bottom of the drainage pipe 852 is located at the middle and lower part of the tower body 81 and below the flow-leveling plate 87. The drainage pipe 852 is used to input alkali solution into the ultrasonic atomizer 85. The alkali solution introduced through the drainage pipe 852 is always at the bottom of the flow-leveling plate 87.

[0057] Example 7

[0058] In the above embodiment, the following improvement is made: the bottom oil in the primary distillation tower 40 is pumped to the distillation tower 70 through a pipeline for distillation, and the remaining part is led to the reboiler 120 through a pipeline to heat it to 270-275°C and reflux into the primary distillation tower 40 to provide heat for distillation in the primary distillation tower 40 to maintain the top temperature of the tower.

[0059] The wash oil inside the distillation tower 70 is pumped to the tubular heating furnace 130 to be heated to 290±5° C. and then pumped back into the distillation tower 70 to provide heat for distillation in the distillation tower 70 to maintain the tower top temperature.

[0060] The dephenolized naphthalene oil in the industrial naphthalene reflux tank 100 partially refluxes into the distillation tower 70 through a pipeline to maintain the tower top temperature and the naphthalene content within the tower top temperature gradient range.

[0061] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. The replacement may be a replacement of a part of the structure, device, method step, or a complete technical solution. Any equivalent replacement or change according to the technical solution and the inventive concept of the present invention shall be covered within the protection scope of the present invention.

Claims

1. A process for preventing discoloration of industrial naphthalene from coal tar, characterized in that: The process steps are as follows: Step 1: Preheat The raw material is pumped into the preheater 1 (20) through the raw material inlet pipe (10), and the raw material is heated once in the preheater 1 (20), and then heated twice in the preheater 2 (30); Step 2: Initial distillation The preheated raw materials enter the primary distillation tower (40) through the pipeline, and the distilled phenol oil vapor escapes from the top of the tower at 190-200°C; The escaped phenol oil vapor enters the preheater 1 (20) to complete primary concentration, the concentrated phenol oil vapor enters the concentrator (50) to complete secondary concentration, and the concentrated phenol oil enters the phenol oil reflux tank (60); Step 3: Distillation The bottom oil after the initial distillation is pumped into a distillation tower (70) through a pipeline, and the industrial naphthalene vapor evaporated escapes from the top of the tower at 218-220° C. and enters a dephenolization tower (80). A nitrogen high-pressure cyclone flow is arranged in the dephenolization tower (80). The industrial naphthalene vapor is introduced into the middle of the nitrogen high-pressure cyclone flow. The lower part of the nitrogen high-pressure cyclone flow is an alkali mist generation area. When the alkali mist flows toward the industrial naphthalene vapor, ripples are generated in the alkali mist generation area. The industrial naphthalene vapor reacts with the alkali mist in the nitrogen high-pressure cyclone flow to dephenolize and floats on the surface of the alkali solution. The industrial naphthalene vapor is smoothly transported to the outside by the nitrogen high-pressure cyclone flow and flows out from the overflow pipe (82) on the side wall of the dephenolization tower (80). After oil-water separation, it enters the industrial naphthalene reflux tank (100), and then is pumped into the industrial naphthalene tank (110) through a pipeline and subjected to nitrogen sealing treatment. The washed oil part enters the washed oil processing pipeline system.

2. The process for preventing discoloration of industrial naphthalene from coal tar according to claim 1, characterized in that: The dephenolization tower (80) comprises a tower body (81), and an overflow pipe (82) is arranged on the side of the tower body (81) for overflow to be introduced into the oil-water separator (90); The top of the tower body (81) is provided with an industrial naphthalene introduction pipe (83), and a plurality of nitrogen pipes (84) are evenly distributed on the outside of the introduction pipe. The nitrogen pipes (84) are used to output a high-pressure nitrogen gas flow, and the output high-pressure nitrogen gas flow is distributed in a vortex shape from top to bottom to form a high-pressure isolation gas hood. An ultrasonic atomizer (85) is provided at the bottom center of the high-pressure isolation gas hood. The ultrasonic atomizer (85) is used to atomize the alkali solution in the tower body (81), and the atomized alkali solution particles are evenly distributed inside the high-pressure isolation gas hood and are fully mixed with the industrial naphthalene vapor.

3. The process for preventing discoloration of industrial naphthalene from coal tar according to claim 2, characterized in that: The ratio of the amount of alkali solution atomized per unit time to the amount of industrial naphthalene vapor introduced is 2-10:1; A thermometer and a jacket (86) located outside the tower body (81) are installed in the tower body (81). The temperature of the alkali solution in the tower body (81) is between 65° C. and 80° C., and the temperature in the reaction area in the high-pressure isolation gas hood is between 70° C. and 90° C. Steam is introduced into the jacket (86) to adjust the temperature of the alkali solution in the tower body (81).

4. The process for preventing discoloration of industrial naphthalene from coal tar according to claim 3, characterized in that: A flow equalizer (87) is installed on the tower body (81) below the ultrasonic atomizer (85), and an alkali solution filling pipe (88) is arranged at the bottom of the flow equalizer (87).

5. The process for preventing discoloration of industrial naphthalene from coal tar according to claim 4, characterized in that: A flow homogenizing cylinder (89) is installed in the tower body (81), and the flow homogenizing cylinder (89) is sleeved on the outside of the ultrasonic atomizer (85) and located outside the high-pressure isolation gas cover, and is used for horizontal homogenizing and conveying the dephenolized naphthalene oil; The bottom of the flow-uniform cylinder (89) is a structure that is larger at the top and smaller at the bottom, and flow-uniform holes are arranged on the surface.

6. The process for preventing discoloration of industrial naphthalene from coal tar according to claim 5, characterized in that: A conveying guide member (810) is arranged above the ultrasonic atomizer (85), and a guide portion (811) arranged obliquely downward is arranged on the top of the conveying guide member (810).

7. The process for preventing discoloration of industrial naphthalene from coal tar according to claim 6, characterized in that: A floating plate (851) is provided at the bottom of the ultrasonic atomizer (85), a drainage pipe (852) is inserted into the bottom of the floating plate (851), the bottom of the drainage pipe (852) is located in the middle and lower part of the tower body (81) and below the flow-uniform plate (87), and the drainage pipe (852) is used to input alkali solution into the ultrasonic atomizer (85).

8. The process for preventing discoloration of industrial naphthalene from coal tar according to claim 7, characterized in that: The bottom oil in the primary distillation tower (40) is pumped to the distillation tower (70) through a pipeline for distillation, and the remaining part is introduced into the reboiler (120) through a pipeline to be heated to 270-275° C. and refluxed into the primary distillation tower (40) to provide heat for distillation in the primary distillation tower (40) to maintain the tower top temperature.

9. The process for preventing discoloration of industrial naphthalene from coal tar according to claim 8, characterized in that: The wash oil inside the distillation tower (70) is pumped to the tubular heating furnace (130) to be heated to 290±5°C and then pumped back into the distillation tower (70) to provide heat for distillation in the distillation tower (70) to maintain the tower top temperature.

10. The process for preventing discoloration of industrial naphthalene from coal tar according to claim 9, characterized in that: The dephenolized naphthalene oil in the industrial naphthalene reflux tank (100) is partially refluxed into the distillation tower (70) through a pipeline to maintain the tower top temperature and the naphthalene content within the tower top temperature gradient range.

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