阅读说明：本技术 一种煤焦油预处理净化的方法及系统 (Method and system for pretreatment and purification of coal tar ) 是由 王庆元 周晓晓 程建龙 岳广祥 赵正权 常伟先 任鹏 黄云 于 2020-06-12 设计创作，主要内容包括：本发明提供一种煤焦油预处理净化的方法及系统,所述方法包括：向煤焦油中加入净化剂并对所述煤焦油进行脱水脱固处理,对脱水脱固后的所述煤焦油进行固液分离后再进行分馏切割,得到塔顶油、侧线油以及塔底煤沥青；对得到的塔底煤沥青进行溶剂萃取,萃取相进行溶剂回收处理得到溶剂和脱沥青油,所述溶剂循环进行所述溶剂萃取,所述脱沥青油与所述塔顶油以及侧线油混合进行加氢处理；所述溶剂萃取得到的萃余相进行沥青汽提,得到的溶剂和油品进行所述溶剂回收,所述沥青汽提得到的脱油沥青作为产品采出。所述方法能最大限度提高煤焦油的利用率,净化后煤焦油直接进入固定床加氢反应系统,成熟稳定,流程及投资远低于沸腾床、浆态床等加氢反应系统。(The invention provides a method and a system for pretreating and purifying coal tar, wherein the method comprises the following steps: adding a purifying agent into coal tar, dehydrating and removing solids of the coal tar, performing solid-liquid separation on the coal tar after dehydration and removal of solids, and then performing fractional cutting to obtain tower top oil, side line oil and tower bottom coal pitch; performing solvent extraction on the obtained tower bottom coal pitch, performing solvent recovery treatment on an extract phase to obtain a solvent and deasphalted oil, performing solvent extraction circularly by using the solvent, and mixing the deasphalted oil with the tower top oil and the side line oil for hydrotreating; and (3) carrying out asphalt stripping on a raffinate phase obtained by the solvent extraction, recovering the solvent and an oil product, and taking the deoiled asphalt obtained by the asphalt stripping as a product for extraction. The method can improve the utilization rate of the coal tar to the maximum extent, the purified coal tar directly enters a fixed bed hydrogenation reaction system, the coal tar is mature and stable, and the flow and the investment are far lower than those of hydrogenation reaction systems such as a boiling bed, a slurry bed and the like.)

1. A method for pretreating and purifying coal tar, which is characterized by comprising the following steps:

(1) adding a purifying agent into coal tar, dehydrating and removing solids of the coal tar, performing solid-liquid separation on the coal tar after dehydration and removal of solids, and then performing fractional cutting to obtain tower top oil, side line oil and tower bottom coal pitch;

(2) performing solvent extraction on the tower bottom coal tar pitch obtained in the step (1), performing solvent recovery treatment on an extract phase to obtain a solvent and deasphalted oil, circularly performing the solvent extraction by using the solvent, and mixing the deasphalted oil with the tower top oil and the side line oil obtained in the step (1) for hydrotreating;

(3) and (3) carrying out asphalt stripping on a raffinate phase obtained by the solvent extraction in the step (2), recovering the solvent and the oil product obtained in the step (2), and taking the deoiled asphalt obtained by the asphalt stripping as a product for extraction.

2. The method according to claim 1, wherein the coal tar of step (1) comprises any one or a combination of at least two of low-temperature coal tar, medium-low temperature coal tar, medium-temperature coal tar, high-temperature coal tar, coal-based gasified oil or heavy oil;

preferably, the addition amount of the purifying agent in the step (1) is 0.2-1 wt% of the amount of the coal tar;

preferably, the scavenger of step (1) comprises any one of ammonium sulfate, phosphate, polyphosphate or organic phosphoric acid or a combination of at least two thereof.

3. The method according to claim 1 or 2, wherein the dehydration and solidification treatment in step (1) comprises: carrying out flash evaporation on the coal tar to remove water, and filtering the dehydrated coal tar to remove solid impurities;

preferably, the temperature of the flash evaporation is 120-180 ℃.

4. The process of any one of claims 1-3, wherein the bottom coal pitch of step (1) comprises 10-25 wt% of the total product of the fractional cutting.

5. The method according to any one of claims 1 to 4, wherein the solvent used in the solvent extraction in step (2) comprises any one or a combination of at least two of cyclohexane, pentane, benzene, toluene, light oil fraction or mixed aromatic hydrocarbon;

preferably, the volume ratio of the solvent to the bottom coal pitch in the solvent extraction in the step (2) is (1-10): 1, preferably (2-4): 1;

preferably, the temperature of the solvent extraction in the step (2) is 100-200 ℃, and the pressure is 0.1-2.0 MPaG;

preferably, the temperature of the solvent extraction in the step (2) is 150 ℃ and the pressure is 1.0 MpaG.

6. The method according to any one of claims 1 to 5, wherein the solvent extraction rate in the step (2) is 50 to 90%.

7. The process of any one of claims 1 to 6, wherein the temperature of asphalt stripping in step (3) is 250 to 280 ℃ and the pressure is 0.1 to 0.3 MpaG.

8. The method according to any one of claims 1-7, characterized in that the method comprises the steps of:

(1) adding a purifying agent into coal tar and carrying out dehydration and solid removal treatment on the coal tar, wherein the adding amount of the purifying agent is 0.2-1 wt% of the coal pitch, carrying out solid-liquid separation on the coal tar after dehydration and solid removal, and then carrying out fractional cutting to obtain top oil, side oil and bottom coal pitch, wherein the bottom coal pitch accounts for 10-25 wt% of the total products of the fractional cutting;

the dehydration and solidification removal treatment method in the step (1) comprises the following steps: carrying out flash evaporation on the coal tar to remove water, and filtering the dehydrated coal tar to remove solid impurities, wherein the temperature of the flash evaporation is 120-180 ℃;

(2) performing solvent extraction on the tower bottom coal tar pitch obtained in the step (1), wherein the volume ratio of a solvent to the tower bottom coal tar pitch is (1-10): 1, the temperature is 100-200 ℃, the pressure is 0.1-2.0 MpaG, an extraction phase is subjected to solvent recovery treatment to obtain a solvent and deasphalted oil, the solvent is circularly subjected to the solvent extraction, and the deasphalted oil is mixed with the tower top oil and the side line oil obtained in the step (1) for hydrogenation treatment;

(3) and (3) carrying out asphalt stripping on a raffinate phase obtained by the solvent extraction in the step (2), wherein the temperature of the asphalt stripping is 250-280 ℃, the pressure is 0.1-0.3 MpaG, the solvent and the oil product obtained are subjected to the solvent recovery in the step (2), and the deoiled asphalt obtained by the asphalt stripping is taken as a product to be extracted.

9. The coal tar pretreatment purification system used in the method according to any one of claims 1 to 8, characterized in that the system comprises a dehydration and solidification device, a fractionation device, an extraction device and a stripping device which are connected in sequence, wherein an extraction phase outlet of the extraction device and a light component outlet of the stripping device are respectively and independently connected with a raw material inlet of a solvent recovery device, and a solvent outlet of the solvent recovery device is connected with an extractant inlet of the extraction device;

preferably, the dewatering and dewatering device comprises a flash evaporation device and a filtering device which are connected in sequence.

10. The system of claim 9, wherein the fractionation unit is a fractionation column comprising an overhead oil outlet, a side oil outlet, and a pitch outlet, the pitch outlet coupled to the pitch inlet of the extraction unit;

preferably, a raffinate phase outlet of the extraction device is connected with a raw material inlet of the stripping device;

preferably, the injection line of the depurative is connected to a line between the fractionation unit and the extraction unit.

Technical Field

The invention belongs to the field of coal tar treatment, and relates to a method and a system for coal tar pretreatment and purification.

Background

Coal tar is a liquid product of coal in the process of pyrolysis or dry distillation and gasification, is dark brown viscous liquid at normal temperature, has estimated component composition of about 10000, is separated from the liquid product and is determined to be only about 500, and is mainly aromatic compounds, and most of the coal tar is condensed ring aromatic compounds with more than two rings. According to the different production methods and pyrolysis temperatures, the following coal tar can be obtained: low temperature coal tar (450-600 ℃), medium temperature coal tar (600-800 ℃), medium temperature coal tar (700-900 ℃), and high temperature coal tar (900-1000 ℃).

The traditional coal tar hydrogenation adopts fixed bed hydrogenation, because the coal tar contains water, metal, asphaltene and other impurities which influence the long-period operation of a fixed bed hydrogenation catalyst, about 15-20% of coal pitch rich in metal and other impurities is usually removed by reduced pressure distillation, and the rest components enter a hydrogenation system, so that the yield of oil products is low. Therefore, the core of coal tar hydrogenation is pretreatment, and after impurities influencing fixed bed hydrogenation are removed, the whole fraction enters a fixed bed reactor as far as possible to carry out hydrogenation reaction.

CN 110093176A discloses a method for purifying coal tar. The method comprises the following steps: extracting a powder removing agent, wherein the mass of the powder removing agent is 0.05-0.1% of that of the coal tar to be purified; mixing the powder removing agent with coal tar to be purified to form a coal tar mixture; conveying the coal tar mixture to a settling tank; the powder removing agent is a compound capable of accelerating coalescence and sedimentation separation of solid impurities in the coal tar. The method can settle and separate solid impurities in the coal tar, the mechanical impurities in the coal tar can be reduced to 0.05 percent after 48-120 hours of settlement, the removal rate of the solid impurities can reach 90 percent, and a large amount of oil washing and coal tar dilution are not needed in the settling and separating process.

CN 206646066U discloses a clean system of coal tar, including first heater, electric desalting apparatus, the second heater, the fractionating tower, cooler and knockout drum, first heater, be used for output after the coal tar heating, electric desalting apparatus links to each other with first heater, be used for carrying out the electric desalting processing to the coal tar, obtain the desalination coal tar and export, the second heater links to each other with electric desalting apparatus, be used for export after the desalination coal tar heating, the fractionating tower links to each other with the second heater, be used for carrying out flash evaporation dehydration to the desalination coal tar, obtain desalination dehydration coal tar and oily sewage and export, the cooler links to each other with the fractionating tower, be used for export after the oily sewage cooling treatment, the knockout drum links to each other with the cooler, be used for carrying out the separation processing to oily sewage, obtain light oil and export.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention provides a method and a system for pretreating and purifying coal tar, wherein the method can improve the utilization rate of the coal tar to the maximum extent, the purified coal tar directly enters a fixed bed hydrogenation reaction system, the coal tar is mature and stable, and the flow and the investment are far lower than those of hydrogenation reaction systems such as a boiling bed, a slurry bed and the like.

In order to achieve the purpose, the invention adopts the following technical scheme:

one of the purposes of the invention is to provide a method for pretreating and purifying coal tar, which comprises the following steps:

(1) adding a purifying agent into coal tar, dehydrating and removing solids of the coal tar, performing solid-liquid separation on the coal tar after dehydration and removal of solids, and then performing fractional cutting to obtain tower top oil, side line oil and tower bottom coal pitch;

(2) performing solvent extraction on the tower bottom coal tar pitch obtained in the step (1), performing solvent recovery treatment on an extract phase to obtain a solvent and deasphalted oil, circularly performing the solvent extraction by using the solvent, and mixing the deasphalted oil with the tower top oil and the side line oil obtained in the step (1) for hydrotreating;

(3) and (3) carrying out asphalt stripping on a raffinate phase obtained by the solvent extraction in the step (2), recovering the solvent and the oil product obtained in the step (2), and taking the deoiled asphalt obtained by the asphalt stripping as a product for extraction.

According to the method, the coal tar is subjected to solid removal and dehydration and then is cut into the top oil, the side oil and the bottom coal pitch through distillation, the coal pitch is subjected to solvent extraction to remove impurities such as metals in the coal pitch and the like which affect the fixed bed hydrogenation, the coal pitch and the top oil and the side oil enter a fixed bed hydrogenation system together, the metal content of the coal tar after pretreatment and purification is less than 20ppm, the yield reaches 95-97%, the feeding requirement of the fixed bed hydrogenation system is met, and the oil yield is greatly improved.

In the present invention, the fractionation and cutting are common processes in the art, and the specific fractionation conditions can be adjusted according to the ratio of cutting each component, and therefore, the details are not repeated in the specification.

As a preferred technical solution of the present invention, the coal tar in step (1) includes any one or a combination of at least two of low temperature coal tar, medium temperature coal tar, high temperature coal tar, coal-based gasified oil, and heavy oil, and the combination is typically but not limited to: the combination of low-temperature coal tar and medium-low temperature coal tar, the combination of medium-low temperature coal tar and medium-low temperature coal tar, the combination of medium-temperature coal tar and high-temperature coal tar, the combination of high-temperature coal tar and coal-based gasified oil, the combination of coal-based gasified oil and heavy oil or the combination of low-temperature coal tar, medium-low temperature coal tar, medium-temperature coal tar and high-temperature coal tar, and the like.

Preferably, the scavenger added in step (1) is 0.2 to 1 wt% of the amount of the coal tar, such as 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, or 0.9 wt%, but not limited to the enumerated values, and other non-enumerated values within the numerical range are also applicable.

Preferably, the scavenger in step (1) comprises any one or a combination of at least two of ammonium sulfate, phosphate, polyphosphate or organic phosphoric acid, such as a combination of ammonium sulfate and phosphate, a combination of phosphate and polyphosphate, a combination of polyphosphate and organic phosphoric acid, a combination of organic phosphoric acid and ammonium sulfate, a combination of ammonium sulfate and polyphosphate, a combination of ammonium sulfate, phosphate and polyphosphate, and the like.

As a preferable embodiment of the present invention, the method of dehydration and solidification removal treatment in step (1) includes: and (3) carrying out flash evaporation on the coal tar to remove water by adopting flash evaporation, and filtering the dehydrated coal tar to remove solid impurities.

Preferably, the temperature of the flash evaporation is 120 to 180 ℃, such as 130 ℃, 140 ℃, 150 ℃, 160 ℃ or 170 ℃, but not limited to the recited values, and other values not recited in the range of values are also applicable.

As a preferred embodiment of the present invention, the bottom coal pitch of step (1) accounts for 10-25 wt%, such as 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt% or 24 wt% of the total product of the fractional cutting, but not limited to the recited values, and other values not recited in the range of the recited values are also applicable.

As a preferred technical scheme of the present invention, the solvent used in the solvent extraction in the step (2) comprises any one or a combination of at least two of cyclohexane, pentane, benzene, toluene, light oil fraction or mixed aromatic hydrocarbon, and the combination is typically but not limited to: a combination of cyclohexane and pentane, a combination of benzene and toluene, and a combination of toluene and light oil fractions.

Preferably, the volume ratio of the solvent to the bottom coal pitch in the solvent extraction in the step (2) is (1-10): 1, such as 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1, but not limited to the enumerated values, and other non-enumerated values within the range are equally applicable, preferably (2-4): 1.

Preferably, the temperature of the solvent extraction in the step (2) is 100-200 ℃, and the pressure is 0.1-2.0 MpaG.

The temperature may be 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃ or 190 ℃ and the pressure may be 0.2MpaG, 0.5MpaG, 0.8MpaG, 1.0MpaG, 1.2MpaG, 1.5MpaG or 1.8MpaG, but the pressure is not limited to the recited values, and other values not recited in the above numerical ranges are also applicable.

Preferably, the temperature of the solvent extraction in the step (2) is 150 ℃ and the pressure is 1.0 MpaG.

In a preferred embodiment of the present invention, the solvent extraction rate in step (2) is 50 to 90%, such as 55%, 60%, 65%, 70%, 75%, 80%, or 85%, but is not limited to the values listed above, and other values not listed above within the range of values are also applicable.

In a preferred embodiment of the present invention, the asphalt in step (3) is stripped under conditions of 250 to 280 ℃, such as 255 ℃, 260 ℃, 265 ℃, 270 ℃ or 275 ℃, and under a pressure of 0.1 to 0.3MpaG, such as 0.12MpaG, 0.15MpaG, 0.18MpaG, 0.20MpaG, 0.22MpaG, 0.25MpaG or 0.28MpaG, but not limited to the recited values, and other values not recited in the above range are also applicable.

As a preferable technical scheme of the invention, the method for pretreating and purifying the coal tar comprises the following steps:

(1) adding a purifying agent into coal tar and carrying out dehydration and solid removal treatment on the coal tar, wherein the adding amount of the purifying agent is 0.2-1 wt% of the coal pitch, carrying out solid-liquid separation on the coal tar after dehydration and solid removal, and then carrying out fractional cutting to obtain top oil, side oil and bottom coal pitch, wherein the bottom coal pitch accounts for 10-25 wt% of the total products of the fractional cutting;

the dehydration and solidification removal treatment method in the step (1) comprises the following steps: carrying out flash evaporation on the coal tar to remove water, and filtering the dehydrated coal tar to remove solid impurities, wherein the temperature of the flash evaporation is 120-180 ℃;

(2) performing solvent extraction on the tower bottom coal tar pitch obtained in the step (1), wherein the volume ratio of a solvent to the tower bottom coal tar pitch is (1-10): 1, the temperature is 100-200 ℃, the pressure is 0.1-2.0 MpaG, an extraction phase is subjected to solvent recovery treatment to obtain a solvent and deasphalted oil, the solvent is circularly subjected to the solvent extraction, and the deasphalted oil is mixed with the tower top oil and the side line oil obtained in the step (1) for hydrogenation treatment;

(3) and (3) carrying out asphalt stripping on a raffinate phase obtained by the solvent extraction in the step (2), wherein the temperature of the asphalt stripping is 250-280 ℃, the pressure is 0.1-0.3 MpaG, the solvent and the oil product obtained are subjected to the solvent recovery in the step (2), and the deoiled asphalt obtained by the asphalt stripping is taken as a product to be extracted.

The second purpose of the invention is to provide a system for pretreating and purifying the used coal tar, which comprises a dehydration and solidification device, a fractionation device, an extraction device and a stripping device which are sequentially connected, wherein an extraction phase outlet of the extraction device and a light component outlet of the stripping device are respectively and independently connected with a raw material inlet of a solvent recovery device, and a solvent outlet of the solvent recovery device is connected with an extractant inlet of the extraction device.

Preferably, the dewatering and dewatering device comprises a flash evaporation device and a filtering device which are connected in sequence.

As a preferable technical scheme of the invention, the fractionating device is a fractionating tower, the fractionating tower comprises a tower top oil outlet, a side oil outlet and a coal tar pitch outlet, and the coal tar pitch outlet is connected with a coal tar pitch inlet of the extraction device;

preferably, a raffinate phase outlet of the extraction device is connected with a raw material inlet of the stripping device;

preferably, the injection line of the depurative is connected to a line between the fractionation unit and the extraction unit.

Compared with the prior art, the invention at least has the following beneficial effects:

(1) the invention provides a method for pretreating and purifying coal tar, wherein the metal content of the coal tar after pretreatment and purification is less than 20ppm, the yield reaches 93-97%, the feeding requirement of a fixed bed hydrogenation system is met, and the yield of oil products is greatly improved;

(2) the invention provides a method for pretreating and purifying coal tar, which can improve the utilization rate of the coal tar to the maximum extent, the purified coal tar directly enters a fixed bed hydrogenation reaction system, the coal tar is mature and stable, and the flow and the investment are far lower than those of hydrogenation reaction systems such as a fluidized bed, a slurry bed and the like.

Drawings

FIG. 1 is a schematic structural diagram of a coal tar pretreatment purification system provided in embodiment 6 of the present invention;

in the figure: 1-a dehydration and dehydration solid-removing device, 11-a flash evaporation device, 12-a filtering device, 2-a tar fractionating tower, 3-an extraction tower, 4-an asphalt stripping tower and 5-a solvent recovery device.

The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

To better illustrate the invention and to facilitate the understanding of the technical solutions thereof, typical but non-limiting examples of the invention are as follows: