Coal tar dehydration and desalination method and system

Abstract

According to the coal tar dehydration and desalination method and system provided by the invention, high-concentration brine is added into impurity-removed coal tar subjected to centrifugal impurity removal, heating and stirring are carried out, demulsification operation of emulsified water is realized through heating and stirring, and the high-concentration brine and the impurity-removed coal tar are fully mixed, so that salt in the high-concentration brine enters the emulsified water; the density of the emulsified water is rapidly increased, the coal tar with the small density is located on the upper layer in the subsequent constant-temperature standing process, the emulsified water and the high-concentration brine with the large density sink to be located on the middle layer and the bottom layer, the layered upper layer is extracted, and the dehydrated and desalted coal tar can be obtained. According to the method, the high-concentration brine is utilized to enable the emulsified water to obtain the effect of increasing the salinity density, so that the emulsified water and the high-concentration brine sink and are layered in the constant-temperature standing process, and the dehydrated and desalted coal tar is obtained from the upper layer; the operation is complicated, the energy consumption is high and the cost is high due to the fact that a large number of electro-desalting and dewatering devices are used.

Description

Technical Field

[0001] The invention belongs to the technical field of coal tar processing, and in particular relates to a coal tar dehydration and desalination method and system. Background Art

[0002] Coal tar, also known as coal paste, coal distillate oil and coal tar solution, is a chemical product obtained from the dry distillation and gasification process of coal. It has wide applications and important value in many fields such as chemical industry, energy, transportation, and construction.

[0003] During the production process of coal tar, it often contains a certain amount of water, and this water also contains salt. During the use of coal tar, this water containing salt will produce steam, which will lead to pressure fluctuations in the coal tar heating furnace, accelerate equipment aging, and affect the life of the catalyst. This brings risks to the use of coal tar. Therefore, it is of great significance to dehydrate coal tar. However, the water in coal tar often exists in the form of emulsified water, and conventional means are difficult to achieve more thorough dehydration and desalination. Therefore, how to dehydrate and desalinate coal tar is a problem of concern to those skilled in the art, and related technical solutions are also disclosed in some patent documents.

[0004] For example, the patent application document with application number CN201710705421.8 discloses a coal tar electric desalting and dehydrating system and method, in which the coal tar is dehydrated and desalted by a first electric desalting and dehydrating device and a second electric desalting and dehydrating device, which solves the dehydration problem of coal tar to a certain extent. However, due to the large-scale use of electric desalting and dehydrating devices and demulsifiers, the operation is complicated, the energy consumption is high, and the cost is high. Summary of the invention

[0005] In order to solve the technical problems of complex operation, high energy consumption and high cost caused by the extensive use of electric desalination and dehydration devices in the process of dehydrating coal tar in the background technology, the present invention provides a coal tar dehydration and desalination method and system.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for dehydrating and desalting coal tar, characterized in that the method for dehydrating and desalting coal tar comprises:

[0008] S1: centrifugally remove impurities from the raw coal tar to obtain impurity-free coal tar;

[0009] S2: adding highly concentrated brine to the de-mixed coal tar, and performing steam heating and stirring to demulsify the emulsified water in the de-mixed coal tar;

[0010] S3: the mixture of the steam-heated and stirred decontaminated coal tar and highly concentrated brine is allowed to stand at a constant temperature until obvious upper, middle and lower stratifications appear;

[0011] S4: extracting the upper layer from the stratified layers to obtain dehydrated and desalted coal tar.

[0012] Optionally, in step S2, the concentration of the highly concentrated brine added to the decontaminated coal tar is 20% to 30%, its mass should be 4 to 6 times the water content in the raw coal tar, and its density is greater than the density of coal tar.

[0013] Optionally, in step S2, the highly concentrated brine includes any one or more inorganic salts of sodium chloride, magnesium chloride or potassium chloride.

[0014] Optionally, in step S2, the steam heating and stirring is performed by steam stirring with 0.5 MPa, 151° C. steam.

[0015] Optionally, in step S3, the mixture of the decontaminated coal tar and highly concentrated brine after steam heating and stirring is allowed to stand at a constant temperature of 65 to 75 degrees Celsius for 25 to 35 minutes.

[0016] Optionally, the coal tar dehydration and desalination method further comprises step S5: extracting or refluxing the middle layer according to the water content of the coal tar in the middle layer of the stratification; and refluxing the highly concentrated brine in the bottom layer.

[0017] Optionally, in step S5, when the water content of the coal tar in the middle layer is less than 0.5%, the coal tar in the middle layer is extracted as dehydrated and desalted coal tar; when the water content of the coal tar in the middle layer is greater than or equal to 0.5%, the coal tar in the middle layer is refluxed.

[0018] In a second aspect, the present invention further provides a coal tar dehydration and desalination system, which is used in any of the above-mentioned coal tar dehydration and desalination methods, and the coal tar dehydration and desalination system comprises: a centrifugal impurity removal unit, a heating and stirring unit, a constant temperature static unit and an extraction unit;

[0019] The centrifugal impurity removal unit is used to centrifugally remove impurities from the raw coal tar to obtain impurity-removed coal tar;

[0020] The heating and stirring unit is connected to the centrifugal impurity removal unit, and is used to obtain impurity-removed coal tar, add highly concentrated brine to the impurity-removed coal tar, and perform steam heating and stirring;

[0021] The constant temperature static unit is connected to the heating and stirring unit, and is used to statically stabilize the mixed solution of the decontaminated coal tar and the highly concentrated brine after heating and stirring;

[0022] The extraction unit is used to extract the upper layer in the stratification to obtain dehydrated and desalted coal tar.

[0023] Optionally, the heating and stirring unit is a steam stirrer.

[0024] Optionally, the constant temperature standing unit includes a constant temperature storage tank, which is provided with a layered observation window and multiple sampling ports; the constant temperature storage tank is used to keep the mixed liquid of demixed coal tar and high-concentration brine at a constant temperature after steam heating and stirring; the extraction unit is connected to the constant temperature storage tank.

[0025] The beneficial effects of the present invention are:

[0026] (1) The present invention provides a method for dehydrating and desalting coal tar, wherein highly concentrated brine is added to the de-mixed coal tar after centrifugal de-mixing, and steam heating and stirring are performed, and the emulsified water is demulsified by steam heating and stirring, so that the highly concentrated brine and the de-mixed coal tar are fully mixed, so that the salt in the highly concentrated brine enters the emulsified water, and the density of the emulsified water is rapidly increased, and in the subsequent constant temperature standing process, the coal tar with a smaller density is in the upper layer, while the emulsified water and highly concentrated brine with a larger density sink to the middle layer and the bottom layer, and the upper layer after stratification is extracted to obtain dehydrated and desalinated coal tar. The method for dehydrating and desalting coal tar provided in the present invention uses highly concentrated brine to increase the salt density of the emulsified water, so that the emulsified water and the highly concentrated brine sink and stratify during the constant temperature standing process, so that the dehydrated and desalinated coal tar is obtained in the upper layer, which solves the technical problems of complex operation, high energy consumption and high cost caused by the large-scale use of electric desalination and dehydration devices in the prior art.

[0027] (2) The coal tar dehydration and desalination method of the present invention can also reflux the highly concentrated brine at the bottom layer, and after adjusting the concentration to the required concentration, use it again for coal tar desalination and dehydration treatment, thereby improving the utilization rate, reducing the discharge of highly concentrated brine, and reducing damage to the environment; at the same time, the present invention utilizes highly concentrated brine and steam heating and stirring to demulsify and separate the emulsified water, without the need to use a demulsifier, thereby avoiding the risk of secondary pollution to the coal tar.

[0028] (3) The coal tar dehydration and desalination method provided by the present invention can be used to dehydrate and desalinate coal tar, and a desalination rate of more than 80% can be achieved, and the coal tar yield can reach 98%. The chloride ion in the coal tar can be reduced from 18ppm before treatment to 1.5ppm, and the water content can be reduced from the original 3.68wt% to 0.36wt%. In summary, the coal tar dehydration and desalination method provided by the present invention can be simple to operate, low in energy consumption, and can also effectively ensure the dehydration and desalination effect of coal tar.

[0029] (4) The present invention also provides a coal tar dehydration and desalination system, which utilizes highly concentrated brine to increase the salt density of emulsified water, causing the emulsified water and highly concentrated brine to sink and stratify during a constant temperature static state, thereby obtaining dehydrated and desalted coal tar in the upper layer, thereby solving the technical problems of complex operation, high energy consumption and high cost caused by the extensive use of electric desalination and dehydration devices in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the steps of the coal tar dehydration and desalination method of the present invention;

[0031] Figure 2 It is a schematic flow diagram of the coal tar dehydration and desalination method of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described 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, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0035] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0036] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0037] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] Coal tar is a chemical product obtained from coal distillation and gasification. Due to production raw materials and processes, coal tar often contains water. The water in coal tar includes free water and emulsified water. Free water is easier to remove and can be basically removed during the coal tar production process. When removing free water, most of the salt in the coal tar will be removed. However, emulsified water still contains a certain amount of salt, and because emulsified water is an oil-in-water emulsion, it is difficult to completely remove. During the use of coal tar, emulsified water containing salt will produce steam, which will lead to pressure fluctuations in the coal tar heating furnace, accelerate equipment aging, and affect the life of the catalyst.

[0040] See also Figure 1 and Figure 2 , showing a schematic diagram of a coal tar dehydration and desalination method described in the present application, the coal tar dehydration and desalination method comprising:

[0041] S1: centrifugally remove impurities from the raw coal tar to obtain impurity-free coal tar;

[0042] S2: adding highly concentrated brine to the de-mixed coal tar, and performing steam heating and stirring to demulsify the emulsified water in the de-mixed coal tar;

[0043] S3: the mixture of the steam-heated and stirred decontaminated coal tar and highly concentrated brine is allowed to stand at a constant temperature until obvious upper, middle and lower stratifications appear;

[0044] S4: extracting the upper layer from the stratified layers to obtain dehydrated and desalted coal tar.

[0045] In this embodiment, the raw coal tar produced is centrifugally decontaminated to remove mechanical impurities contained in the raw coal tar to obtain decontaminated coal tar, and the decontaminated coal tar still contains emulsified water; highly concentrated brine is added to the decontaminated coal tar, and steam heating and stirring are performed to achieve demulsification of the emulsified water by steam heating and stirring, so that the highly concentrated brine, the decontaminated coal tar and the emulsified water are fully mixed, and the solubility of salt in coal tar is much lower than that in water, so that the salt in the highly concentrated brine enters the emulsified water while avoiding the salt from mixing into the coal tar, thereby rapidly increasing the density of the emulsified water; the highly concentrated brine and the decontaminated coal tar after heating and stirring are kept at a constant temperature, and during the constant temperature standing process, the coal tar with a smaller density rises to the upper layer, while the highly concentrated brine and the emulsified water with a larger density due to the absorption of salt gradually sink to the middle and bottom layers, and the upper layer after stratification is extracted to obtain dehydrated and desalted coal tar.

[0046] The coal tar dehydration and desalination method provided in the present invention utilizes highly concentrated brine to increase the salt density of emulsified water, so that the emulsified water and highly concentrated brine sink and stratify during constant temperature standing, thereby obtaining coal tar with low water content and salt content in the upper layer, solving the technical problems of complex operation, high energy consumption and high cost caused by the large-scale use of electric desalination and dehydration devices and demulsifiers in the desalination and dehydration of coal tar in the prior art. At the same time, the present invention utilizes highly concentrated brine and steam heating and stirring to demulsify and separate emulsified water, without the need to use demulsifiers, thereby avoiding the risk of secondary pollution to coal tar.

[0047] Specifically, by using the coal tar dehydration and desalination method provided by the present invention, the coal tar is dehydrated and desalted to achieve a salt removal rate of more than 80%, and the salt content can be reduced from 13.2 mg / L in the raw coal tar to 2.52 mg / L, the coal tar yield can reach 98%, the chloride ions in the coal tar can be reduced from 18 ppm before treatment to 1.5 ppm, and the water content can be reduced from the original 3.68 wt% to 0.36 wt%. In summary, the coal tar dehydration and desalination method provided by the present invention can be simple to operate, low in energy consumption, and can effectively ensure the dehydration and desalination effect of coal tar.

[0048] Optionally, in step S2 of the present invention, the concentration of the highly concentrated brine added to the decontaminated coal tar is 20% to 30%, its mass should be 4 to 6 times the water content in the raw coal tar, and its density is greater than the density of coal tar.

[0049] In this embodiment, the concentration of the highly concentrated brine added to the decontaminated coal tar is 20% to 30%, specifically 20%, 25% or 30%; its mass is 4 to 6 times the water content in the raw coal tar, specifically 4 times, 5 times or 6 times; and its density is greater than the density of coal tar, so that the highly concentrated brine can naturally sink to the bottom layer during the constant temperature standing process.

[0050] Optionally, in step S2 of the present invention, the highly concentrated brine includes any one or more inorganic salts of sodium chloride, magnesium chloride or potassium chloride.

[0051] In this embodiment, the highly concentrated brine includes any one or more inorganic salts of sodium chloride, magnesium chloride or potassium chloride, that is, the highly concentrated brine may be the associated wastewater generated during the desalination operation in the coal tar production process. In the present invention, the wastewater generated during the desalination operation in the coal tar production process can be treated and used as highly concentrated brine in the coal tar dehydration and desalination method of the present invention, thereby realizing the reuse of wastewater and reducing the discharge of salt-containing wastewater.

[0052] Optionally, in step S2 of the present invention, the steam heating and stirring is performed by steam stirring with 0.5 MPa, 151° C. steam.

[0053] In this embodiment, 0.5Mpa, 151°C steam stirring is used to heat and stir the highly concentrated brine and de-mixed coal tar, and steam is used to accelerate the demulsification effect of the emulsified water. At the same time, the de-mixed coal tar is heated to 65°C to 75°C to facilitate subsequent constant temperature static operation.

[0054] Furthermore, in this embodiment, the stirring rate when steam-heating and stirring the highly concentrated brine and de-mixed coal tar is 1100 r / min to 1300 r / min, specifically, it can be 1100 r / min, 1200 r / min or 1300 r / min, so that the highly concentrated brine and the de-mixed coal tar are fully mixed, the salt in the highly concentrated brine enters the emulsified water, and the density of the emulsified water is increased.

[0055] Optionally, in step S3 of the present invention, the mixture of the decontaminated coal tar and highly concentrated brine after steam heating and stirring is allowed to stand at a constant temperature of 65 to 75 degrees Celsius for 25 to 35 minutes.

[0056] In this embodiment, the mixture of decontaminated coal tar and highly concentrated brine after steam heating and stirring is allowed to stand at a constant temperature of 65 to 75 degrees Celsius for 25 to 35 minutes to allow the coal tar, highly concentrated brine and emulsified water to be fully stratified, wherein the coal tar with a lower density rises to the upper layer, while the highly concentrated brine and the emulsified water with a higher density due to the absorption of salt gradually sink to the middle and bottom layers. The desalted and dehydrated coal tar can be obtained by extracting the coal tar in the upper layer.

[0057] Optionally, the coal tar dehydration and desalination method of the present invention further comprises step S5: extracting or refluxing the middle layer according to the water content of the coal tar in the middle layer of the stratification; and refluxing the highly concentrated brine in the bottom layer.

[0058] Optionally, in step S5 of the present invention, when the water content of the coal tar in the middle layer is less than 0.5%, the coal tar in the middle layer is extracted as dehydrated and desalted coal tar; when the water content of the coal tar in the middle layer is greater than or equal to 0.5%, the coal tar in the middle layer is refluxed.

[0059] In this embodiment, when the water content of the coal tar in the middle layer is less than 0.5%, the coal tar in the middle layer is extracted as dehydrated and desalted coal tar, that is, the water content of the coal tar in the middle layer also reaches a relatively low standard and can be used as subsequent dehydrated and desalted coal tar; if the water content of the coal tar in the layer is greater than or equal to 0.5%, it means that it still contains a lot of water. At this time, the coal tar in the middle layer is refluxed and dehydrated and desalted again by the coal tar dehydration and desalination method of the present invention. In addition, in the present invention, the highly concentrated brine in the bottom layer is refluxed and recycled after the concentration is adjusted for another dehydration and desalination of coal tar.

[0060] Furthermore, part of the high-concentration brine in the bottom layer can be discharged as replacement wastewater to prevent salt enrichment, which will lead to saturation of the circulating high-concentration brine and adversely affect the dehydration and desalination of coal tar.

[0061] In a second aspect, the present invention further provides a coal tar dehydration and desalination system, which is used in any of the above coal tar dehydration and desalination methods, and the coal tar dehydration and desalination system comprises: a centrifugal impurity removal unit, a heating and stirring unit, a constant temperature static unit and an extraction unit;

[0062] The centrifugal impurity removal unit is used to centrifugally remove impurities from the raw coal tar to obtain impurity-free coal tar;

[0063] The heating and stirring unit is connected to the centrifugal impurity removal unit, and is used to obtain impurity-removed coal tar, add highly concentrated brine to the impurity-removed coal tar, and perform steam heating and stirring;

[0064] The constant temperature static unit is connected to the heating and stirring unit and is used to statically stabilize the mixed liquid of the decontaminated coal tar and the highly concentrated brine after steam heating and stirring;

[0065] The extraction unit is used to extract the upper layer in the stratification to obtain dehydrated and desalted coal tar.

[0066] It should be noted that the implementation process and effect of the coal tar dehydration and desalination system in the present invention correspond to the coal tar dehydration and desalination method in the above embodiment, which will not be described in detail here. In this embodiment, a coal tar dehydration and desalination system is provided, which uses highly concentrated brine to increase the salt density of emulsified water, so that the emulsified water and highly concentrated brine sink and stratify during the constant temperature static process, thereby obtaining dehydrated and desalted coal tar in the upper layer, solving the technical problems of complex operation, high energy consumption and high cost caused by the large-scale use of electric desalination and dehydration devices in the prior art.

[0067] Optionally, the heating and stirring unit in the present invention is a steam stirrer.

[0068] Furthermore, the source of heating steam can be selected as the heating steam network in the chemical plant, and the dehydrated and desalted coal tar can be output to the fluidized bed reaction raw material tank for further processing.

[0069] Optionally, the constant temperature standing unit includes a constant temperature storage tank, which is provided with a layered observation window and multiple sampling ports; the constant temperature storage tank is used to keep the mixed liquid of demixed coal tar and high-concentration brine at a constant temperature after steam heating and stirring; the extraction unit is connected to the constant temperature storage tank.

[0070] In this embodiment, a stratification observation window and a plurality of sampling ports are provided on the constant temperature storage tank for observing the stratification status and sampling each layer for component analysis.

[0071] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0072] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for dehydrating and desalting coal tar, characterized in that: The coal tar dehydration and desalination method comprises: S1: centrifugally remove impurities from the raw coal tar to obtain impurity-free coal tar; S2: adding highly concentrated brine to the de-mixed coal tar, and performing steam heating and stirring to demulsify the emulsified water in the de-mixed coal tar; S3: the mixture of the steam-heated and stirred decontaminated coal tar and highly concentrated brine is allowed to stand at a constant temperature until obvious upper, middle and lower stratifications appear; S4: extracting the upper layer from the stratified layers to obtain dehydrated and desalted coal tar.

2. The method for dehydrating and desalting coal tar according to claim 1, characterized in that: In step S2, the concentration of the highly concentrated brine added to the decontaminated coal tar is 20% to 30%, the mass of which is 4 to 6 times the water content in the raw coal tar, and the density of which is greater than that of the coal tar.

3. The method for dehydrating and desalting coal tar according to claim 2, characterized in that: In step S2, the highly concentrated brine includes any one or more inorganic salts of sodium chloride, magnesium chloride or potassium chloride.

4. The method for dehydrating and desalting coal tar according to claim 1, characterized in that: In step S2, the steam heating and stirring is performed by steam stirring using 0.5 MPa, 151° C. steam.

5. The method for dehydrating and desalting coal tar according to claim 1, characterized in that: In the step S3, the mixture of the decontaminated coal tar and the highly concentrated brine after steam heating and stirring is allowed to stand at a constant temperature, wherein the standing temperature is between 65 degrees Celsius and 75 degrees Celsius and the standing time is between 25 minutes and 35 minutes.

6. The method for dehydrating and desalting coal tar according to claim 1, characterized in that: The coal tar dehydration and desalination method further comprises step S5: extracting or refluxing the middle layer according to the water content of the coal tar in the middle layer of the stratification; and refluxing the highly concentrated brine in the bottom layer.

7. The method for dehydrating and desalting coal tar according to claim 6, characterized in that: In step S5, when the water content of the coal tar in the middle layer is less than 0.5%, the coal tar in the middle layer is extracted as dehydrated and desalted coal tar; when the water content of the coal tar in the middle layer is greater than or equal to 0.5%, the coal tar in the middle layer is refluxed.

8. A coal tar dehydration and desalination system, used in the coal tar dehydration and desalination method according to any one of claims 1 to 7, characterized in that: The coal tar dehydration and desalination system comprises: a centrifugal impurity removal unit, a heating and stirring unit, a constant temperature static unit and an extraction unit; The centrifugal impurity removal unit is used to centrifugally remove impurities from the raw coal tar to obtain impurity-removed coal tar; The heating and stirring unit is connected to the centrifugal impurity removal unit, and is used to obtain impurity-removed coal tar, add highly concentrated brine to the impurity-removed coal tar, and perform steam heating and stirring; The constant temperature static unit is connected to the heating and stirring unit, and is used to statically stabilize the mixed solution of the decontaminated coal tar and the highly concentrated brine after heating and stirring; The extraction unit is used to extract the upper layer in the stratification to obtain dehydrated and desalted coal tar.

9. The coal tar dehydration and desalination system according to claim 8, characterized in that: The heating and stirring unit is a steam stirrer.

10. The coal tar dehydration and desalination system according to claim 8, characterized in that: The constant temperature static unit includes a constant temperature storage tank, and the constant temperature storage tank is provided with a layered observation window and a plurality of sampling ports; The constant temperature storage tank is used to keep the mixed liquid of the decontaminated coal tar and the highly concentrated brine at a constant temperature after being heated and stirred by steam; The extraction unit is connected to the constant temperature storage tank.

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