Method for demetalizing coal tar

Abstract

The invention belongs to the field of coal tar processing, and particularly relates to a coal tar demetalization method which comprises the following steps: a) mixing a coal tar raw material with a demetalization agent A solution, reacting, and filtering and separating to obtain a primary filtered sample; in the step a), a demetallization agent A in the demetallization agent A solution is selected from one or more of tartaric acid, citric acid, oxalic acid, malic acid and benzoic acid; b) mixing the primarily filtered sample with a demetalization agent B solution, reacting, and filtering and separating to obtain demetalized coal tar; in the step b), a demetallization agent B in the demetallization agent B solution is selected from one or more of diethylenetriamine pentaacetic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diglycolic acid and iminodiacetic acid. The demetallization method provided by the invention is simple in process, low in cost, good in demetallization effect and suitable for treatment of coal tar with high metal element content.

Description

Technical Field

[0001] The present invention belongs to the field of coal tar processing, and particularly relates to a method for removing metals from coal tar. Background Art

[0002] Coal occupies a dominant position in China's energy structure. During its processing and utilization, the annual output of coal tar exceeds 20 million tons. Therefore, the deep processing and utilization of coal tar have attracted much attention. Hydrotreating to produce vehicle fuel oils and chemicals is one of the important directions for the deep processing of coal tar. However, if a large amount of metal elements are contained in coal tar, it will cause the hydrotreating catalyst to deactivate more rapidly, severely limiting the operation cycle of the hydrotreating unit. Therefore, it is necessary to remove the high-content metal elements in coal tar before hydrotreating. And performing demetallization pretreatment on coal tar is one of the effective methods. It can not only solve the problem of rapid catalyst deactivation but also improve the quality of coal tar, providing a more high-quality raw material for the subsequent hydrotreating process, thereby improving the efficiency and product quality of the entire coal tar processing process. Through the analysis and identification of coal tar, it is known that the total metal element content in it is relatively high and most of them exist in the form of oil-soluble organic salts. In addition, there is also a certain amount of metal elements in the form of water-soluble inorganic salts and toluene-insoluble substances. Different metal elements will bring various harms to the coal tar processing process, such as deteriorating the structure and performance of the catalyst, affecting the product distribution and product quality, shortening the service life of the catalyst; aggravating the fouling of heating and heat exchange pipelines, reducing the heat transfer efficiency, and increasing the energy consumption of the unit. Therefore, it is necessary to significantly reduce the metal element content in coal tar to prevent its harm to the subsequent processing and utilization process of coal tar.

[0003] The existing demetallization technologies in the industry mainly include electro - desalting and demetallization, centrifugal demetallization, hydro - demetallization, filtration demetallization, and adsorption demetallization. Among them, the electro - desalting and demetallization technology is relatively mature in the refineries in our country. However, the density of coal tar is close to that of water and it has strong hydrophilicity, making the oil - water separation very difficult. Moreover, coal tars produced in different regions usually require different types of demulsifiers. The hydro - demetallization technology has a high demetallization efficiency. For coal tars with different metal element contents, the screening of hydro - demetallization catalysts and the determination of parameters are also different. When the metal element content in coal tar is high, a large amount of hydro - demetallization catalyst needs to be significantly increased during grading, which significantly increases the reactor pressure drop and also increases the risk of bed plugging during operation. Therefore, it is uneconomical to use only the hydro - method for coal tar with a high metal element content. The key link in the adsorption demetallization technology is the screening of adsorbents. However, the adsorbents themselves usually contain metal elements. If the adsorbent impurities remain in the oil sample, it will cause secondary pollution of the oil sample. Moreover, coal tar usually has a high viscosity and is extremely easy to block the pores of the adsorbent, seriously affecting the mass transfer process. Therefore, this demetallization method is not easy to control and has a large operation difficulty. The centrifugal demetallization technology is similar to the filtration demetallization technology and can only remove metal elements existing in the form of solid impurities. However, the filtration demetallization technology has simple operation and low energy consumption and can be used as a pretreatment technology for removing solid impurities and is suitable for combined use with other demetallization methods. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a demetallization method for coal tar. The demetallization method provided by the present invention has simple process, low cost, and good demetallization effect, and is suitable for the treatment of coal tar with a high metal element content.

[0005] The present invention provides a demetallization method for coal tar, including the following steps:

[0006] a) Mix the coal tar raw material with the solution of demetallizing agent A and react, and obtain a primary filtered sample after filtration and separation;

[0007] In step a), the demetallizing agent A in the solution of demetallizing agent A is selected from one or more of tartaric acid, citric acid, oxalic acid, malic acid, and benzoic acid;

[0008] b) Mix the primary filtered sample with the solution of demetallizing agent B and react, and obtain the demetallized coal tar after filtration and separation;

[0009] In step b), the demetallizing agent B in the solution of demetallizing agent B is selected from one or more of diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diglycolic acid, and iminodiacetic acid.

[0010] Preferably, in step a), the total metal element content of the coal tar raw material is above 300 μg / g.

[0011] Preferably, in step a), the temperature of the reaction is 60 - 100 °C, the stirring speed is 250 - 350 r / min, and the time is 30 - 100 min.

[0012] Preferably, in step a), the pore size of the filtration medium is 10 - 15 μm, the temperature is 70 - 90 °C, and the time is 30 - 90 min.

[0013] Preferably, in step a), the preparation step of the demetallizing agent A solution includes: mixing the demetallizing agent A with a solvent to obtain the demetallizing agent A solution.

[0014] Preferably, the temperature for mixing the demetallizing agent A and the solvent is 20 - 80 °C, the stirring speed is 250 - 350 r / min, and the time is 20 - 40 min.

[0015] Preferably, in step b), the temperature of the reaction is 60 - 100 °C, the stirring speed is 250 - 350 r / min, and the time is 30 - 100 min.

[0016] Preferably, in step b), the pore size of the filtration medium is 10 - 15 μm, the temperature is 70 - 90 °C, and the time is 30 - 90 min.

[0017] Preferably, in step b), the preparation step of the demetallizing agent B solution includes: mixing the demetallizing agent B with a solvent to obtain the demetallizing agent B solution.

[0018] Preferably, the temperature for mixing the demetallizing agent B and the solvent is 20 - 80 °C, the stirring speed is 250 - 350 r / min, and the time is 20 - 40 min.

[0019] Compared with the prior art, the present invention provides a method for demetallizing coal tar, comprising the following steps: a) mixing a coal tar raw material with a demetallizing agent A solution and reacting, and obtaining a primary filtration sample after filtration and separation; in step a), the demetallizing agent A in the demetallizing agent A solution is selected from one or more of tartaric acid, citric acid, oxalic acid, malic acid, and benzoic acid; b) mixing the primary filtration sample with a demetallizing agent B solution and reacting, and obtaining the demetallized coal tar after filtration and separation; in step b), the demetallizing agent B in the demetallizing agent B solution is selected from one or more of diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diglycolic acid, and iminodiacetic acid. The demetallizing method provided by the present invention combines a chemical precipitation reaction with filtration and separation. First, metal elements present in the form of water-soluble inorganic salts and oil-soluble organic salts in the coal tar are converted into insoluble forms by adding a demetallizing agent, and then the insoluble substances rich in metal elements are further removed by filtration operation to obtain coal tar with qualified properties and low metal content. The demetallizing method provided by the present invention has a simple process, low cost, and good demetallizing effect, is suitable for the treatment of oils with high metal content, and can effectively solve problems such as catalyst deactivation and bed plugging caused by high content of metal elements in coal tar during subsequent processing and utilization. Experimental results show that after the coal tar is demetallized by the demetallizing method provided by the present invention, the total metal element content in the oil can be reduced to below 45 μg / g. Detailed Embodiments

[0020] The technical solutions in the embodiments of the present invention are clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] The present invention provides a method for demetallizing coal tar, comprising the following steps:

[0022] a) Mixing a coal tar raw material with a demetallizing agent A solution and reacting, and obtaining a primary filtration sample after filtration and separation;

[0023] b) Mixing the primary filtration sample with a demetallizing agent B solution and reacting, and obtaining the demetallized coal tar after filtration and separation.

[0024] The present invention converts metal elements present in the form of water-soluble inorganic salts and oil-soluble organic salts in the coal tar into insoluble forms by adding a demetallizing agent, and then further removes the insoluble substances rich in metal elements by filtration operation to obtain coal tar with qualified properties and low metal content.

[0025] In the present invention, in step a), the total metal element content of the coal tar is preferably 300 μg / g or more, more preferably 400 μg / g or more; among them, the representative metal elements contained through analysis and determination include one or more of calcium, iron, aluminum, sodium, and magnesium; the content of calcium is preferably 100-400 μg / g, more preferably 200-300 μg / g; the content of iron is preferably 50-300 μg / g, more preferably 100-200 μg / g; the content of aluminum is preferably 10-50 μg / g, more preferably 20-30 μg / g; the content of sodium is preferably 5-30 μg / g, more preferably 10-20 μg / g; the content of magnesium is preferably 1-15 μg / g, more preferably 5-10 μg / g. The present invention has no special limitation on the determination method. The occurrence state of metal elements in the coal tar is separated by a Soxhlet extractor, a distillation instrument, a filter, etc. The types and contents of metal elements in the coal tar and other oil samples are determined by an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0026] In the present invention, in step a), the composition of the demetallizing agent A solution includes demetallizing agent A and a solvent; among them, the demetallizing agent A is selected from one or more of tartaric acid, citric acid, oxalic acid, malic acid, and benzoic acid; the solvent includes but is not limited to one or more of water, methanol, ethanol, and N,N-dimethylformamide, and is preferably water.

[0027] In the present invention, in step a), the preparation steps of the demetallizing agent A solution preferably include: mixing the demetallizing agent A and the solvent to obtain the demetallizing agent A solution. Among them, the temperature of the mixing is preferably 20-80 °C, more preferably 25 °C; the stirring speed of the mixing is preferably 250-350 r / min, more preferably 300 r / min; the mixing time is preferably 20-40 min, more preferably 30 min.

[0028] In the present invention, in step a), the dosage of the demetallizing agent A corresponding to each g of the coal tar raw material is preferably 500-1500 μg, and specifically may be 500 μg, 600 μg, 700 μg, 800 μg, 900 μg, 1000 μg, 1100 μg, 1200 μg, 1300 μg, 1334 μg, 1400 μg, or 1500 μg.

[0029] In the present invention, in step a), the reaction device is preferably a constant temperature stirring device.

[0030] In the present invention, in step a), the specific process of carrying out the reaction and filtration separation preferably includes: adding a coal tar raw material into a constant-temperature stirring device reactor; adding a demetallizing agent A solution under a certain mass ratio condition to carry out a chemical reaction with the original coal tar sample, and then performing a filtration operation on the oil sample after the reaction ends. After filtration separation, a primary filtration sample is obtained.

[0031] In the present invention, in step a), the temperature of the reaction is preferably 60 - 100 °C, more preferably 80 °C; the stirring speed of the reaction is preferably 250 - 350 r / min, more preferably 300 r / min; the time of the reaction is preferably 30 - 100 min, more preferably 60 min.

[0032] In the present invention, in step a), the pore diameter of the filtration medium is preferably 10 - 15 μm; the temperature of the filtration is preferably 70 - 90 °C, more preferably 80 °C; the pressure of the filtration is preferably 101.325 kPa; the time of the filtration is preferably 30 - 90 min, more preferably 60 min.

[0033] In the present invention, in step b), the composition of the demetallizing agent B solution includes a demetallizing agent B and a solvent; wherein, the demetallizing agent B is selected from one or more of diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diglycolic acid, and iminodiacetic acid; the solvent includes but is not limited to one or more of water, methanol, ethanol, and N,N-dimethylformamide, and is preferably water.

[0034] In the present invention, in step b), the preparation steps of the demetallizing agent B solution preferably include: mixing the demetallizing agent B with the solvent to obtain a demetallizing agent B solution. Among them, the temperature of the mixing is preferably 20 - 80 °C, more preferably 50 °C; the stirring speed of the mixing is preferably 250 - 350 r / min, more preferably 300 r / min; the time of the mixing is preferably 20 - 40 min, more preferably 30 min.

[0035] In the present invention, in step b), the dosage of the demetallizing agent B corresponding to each g of the coal tar raw material is preferably 200 - 800 μg, and specifically can be 200 μg, 250 μg, 300 μg, 350 μg, 400 μg, 450 μg, 500 μg, 550 μg, 600 μg, 650 μg, 666 μg, 700 μg, 750 μg, or 800 μg.

[0036] In the present invention, in step b), the reaction device is preferably a constant-temperature stirring device.

[0037] In the present invention, in step b), the specific process of the reaction and filtration separation preferably includes: under a certain mass ratio condition, mixing the solution of demetallizing agent B with the primary filtration sample obtained after filtration separation, carrying out a chemical reaction, and then performing a filtration operation on the oil sample after the reaction to obtain the coal tar after demetallization.

[0038] In the present invention, in step b), the temperature of the reaction is preferably 60 - 100 °C, more preferably 80 °C; the stirring speed of the reaction is preferably 250 - 350 r / min, more preferably 300 r / min; the time of the reaction is preferably 30 - 100 min, more preferably 60 min.

[0039] In the present invention, in step b), the pore diameter of the filtration medium is preferably 10 - 15 μm; the temperature of the filtration is preferably 70 - 90 °C, more preferably 80 °C; the pressure of the filtration is preferably 101.325 kPa; the time of the filtration is preferably 30 - 90 min, more preferably 60 min.

[0040] The demetallization method provided by the present invention uses a technical route combining chemical precipitation reaction and filtration separation for demetallization, which can achieve deep removal of metal elements in coal tar. Finally, coal tar with qualified properties and low metal content can be obtained, providing a more high-quality raw material for the subsequent hydro-upgrading process. The demetallization method provided by the present invention has a simple process and low cost, and has a significant demetallization effect on coal tar with a high metal element content. After demetallization pretreatment, the total metal element content in the oil product is lower than 45 μg / g, which can effectively alleviate problems such as rapid deactivation of catalysts and significant decline in the efficiency of heat exchange equipment caused by high metal element content in the subsequent processing and utilization process of coal tar.

[0041] For the sake of clarity, the following will be described in detail through the following examples. The basic physical properties of the coal tar used in the following examples of the present invention are shown in Table 1.

[0042] Table 1 Basic physical property data of the coal tar in the examples of the present invention

[0043] Test Items Data <![CDATA[Density (20 °C), g / cm 3 > 1.010 Kinematic viscosity (50 °C), mPa·s 112.0 Acid value, mgKOH / g 3.85 Water content, wt.% 4.50 Ash content, wt.% 0.11 Content of main metal elements, μg / g Calcium 266.02 Iron 155.57 Aluminum 25.16 Sodium 14.30 Magnesium 8.56 Total 469.61

[0044] Example 1

[0045] (1) Add the coal tar raw material and the solution of demetallizing agent A into the reactor, place the reactor on a constant temperature stirring device, and the reaction operating conditions are: the reaction temperature is 80 °C, the stirring speed is 300 r / min, and the dosage of the active ingredient A of the demetallizing agent solution is 800 μg / g; after reacting for 1 h, a primary filtration sample is obtained after filtration separation, and the filtration operating conditions are: the filtration temperature is 80 °C, the filtration pressure is 101.325 kPa, the pore diameter of the filtration medium is 10 - 15 μm, and the filtration time is 1 h.

[0046] (2) Take the initially filtered sample obtained in step (1), add the demetallizing agent B solution, place the reactor on a constant-temperature stirring device, and the reaction operating conditions are: the reaction temperature is 80 °C, the stirring speed is 300 r / min, and the dosage of the active ingredient B in the demetallizing agent solution is 400 μg / g; after reacting for 1 h, the final sample is obtained after filtration and separation, and the filtration operating conditions are: the filtration temperature is 80 °C, the filtration pressure is 101.325 kPa, the pore size of the filtration medium is 10 - 15 μm, and the filtration time is 1 h.

[0047] Determine the metal element content of the pretreated oil product obtained in step (2) of Example 1. The results are shown in Table 2, and the corresponding metal element removal rates are shown in Table 3.

[0048] Example 2

[0049] (1) Add the coal tar raw material and the demetallizing agent A solution to the reactor, place the reactor on a constant-temperature stirring device, and the reaction operating conditions are: the reaction temperature is 80 °C, the stirring speed is 300 r / min, and the dosage of the active ingredient A in the demetallizing agent solution is 1000 μg / g; after reacting for 1 h, the initially filtered sample is obtained after filtration and separation, and the filtration operating conditions are: the filtration temperature is 80 °C, the filtration pressure is 101.325 kPa, the pore size of the filtration medium is 10 - 15 μm, and the filtration time is 1 h.

[0050] (2) Take the initially filtered sample obtained in step (1), add the demetallizing agent B solution, place the reactor on a constant-temperature stirring device, and the reaction operating conditions are: the reaction temperature is 80 °C, the stirring speed is 300 r / min, and the dosage of the active ingredient B in the demetallizing agent solution is 500 μg / g; after reacting for 1 h, the final sample is obtained after filtration and separation, and the filtration operating conditions are: the filtration temperature is 80 °C, the filtration pressure is 101.325 kPa, the pore size of the filtration medium is 10 - 15 μm, and the filtration time is 1 h.

[0051] Determine the metal element content of the pretreated oil product obtained in step (2) of Example 2. The results are shown in Table 2, and the corresponding metal element removal rates are shown in Table 3.

[0052] Example 3

[0053] (1) Add the coal tar raw material and the demetallizing agent A solution to the reactor, place the reactor on a constant-temperature stirring device, and the reaction operating conditions are: the reaction temperature is 80 °C, the stirring speed is 300 r / min, and the dosage of the active ingredient A in the demetallizing agent solution is 1200 μg / g; after reacting for 1 h, the initially filtered sample is obtained after filtration and separation, and the filtration operating conditions are: the filtration temperature is 80 °C, the filtration pressure is 101.325 kPa, the pore size of the filtration medium is 10 - 15 μm, and the filtration time is 1 h.

[0054] (2) Take the initially filtered sample obtained in step (1), add the demetallizing agent B solution, place the reactor on a constant-temperature stirring device, and the reaction operating conditions are: the reaction temperature is 80 °C, the stirring speed is 300 r / min, and the dosage of the active ingredient B in the demetallizing agent solution is 600 μg / g; after reacting for 1 h, the final sample is obtained after filtration and separation, and the filtration operating conditions are: the filtration temperature is 80 °C, the filtration pressure is 101.325 kPa, the pore size of the filtration medium is 10 - 15 μm, and the filtration time is 1 h.

[0055] Determine the metal element content of the pretreated oil product obtained in step (2) of Example 3. The results are shown in Table 2, and the corresponding metal element removal rates are shown in Table 3.

[0056] Example 4

[0057] (1) Add the coal tar raw material and the demetallizing agent A solution to the reactor, place the reactor on a constant-temperature stirring device, and the reaction operating conditions are: the reaction temperature is 80 °C, the stirring speed is 300 r / min, and the dosage of the active ingredient A in the demetallizing agent solution is 1334 μg / g; after reacting for 1 h, the initially filtered sample is obtained after filtration and separation, and the filtration operating conditions are: the filtration temperature is 80 °C, the filtration pressure is 101.325 kPa, the pore size of the filtration medium is 10 - 15 μm, and the filtration time is 1 h.

[0058] (2) Take the initially filtered sample obtained in step (1), add the demetallizing agent B solution, place the reactor on a constant-temperature stirring device, and the reaction operating conditions are: the reaction temperature is 80 °C, the stirring speed is 300 r / min, and the dosage of the active ingredient B in the demetallizing agent solution is 666 μg / g; after reacting for 1 h, the final sample is obtained after filtration and separation, and the filtration operating conditions are: the filtration temperature is 80 °C, the filtration pressure is 101.325 kPa, the pore size of the filtration medium is 10 - 15 μm, and the filtration time is 1 h.

[0059] Determine the metal element content of the pretreated oil product obtained in step (2) of Example 4. The results are shown in Table 2, and the corresponding metal element removal rates are shown in Table 3.

[0060] Table 2 Metal element content data of the demetallized coal tar obtained in Examples 1 - 4 of the present invention

[0061]

[0062] Table 3 Metal element removal rates of the demetallized coal tar obtained in Examples 1 - 4 of the present invention

[0063]

[0064] As can be seen from the results in Table 2, after the coal tar is subjected to demetallization pretreatment by the demetallization method provided by the present invention, the contents of the five main metal elements in the oil product all decrease significantly, and the total amount of the main metal elements drops below 45 μg / g, and can be as low as 27.59%. As can be seen from Table 3, the demetallization rate of calcium element in coal tar by the demetallization method provided by the present invention is higher than 98%, the demetallization rate of aluminum element is higher than 91%, the demetallization rate of sodium element is higher than 88%, the demetallization rates of iron and magnesium elements are higher than 76%, and the total demetallization rate of the main metal elements is higher than 90%.

[0065] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for demetallizing coal tar, characterized in that: The following steps are involved: a) mixing the coal tar raw material with the demetallizing agent A solution and reacting them, and obtaining a primary filtered sample after filtering and separation; In step a), the demetallizing agent A in the demetallizing agent A solution is selected from one or more of tartaric acid, citric acid, oxalic acid, malic acid and benzoic acid; b) mixing the initially filtered sample with a demetallizing agent B solution and reacting the mixture to obtain demetallized coal tar after filtering and separation; In step b), the demetallizing agent B in the demetallizing agent B solution is selected from one or more of diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, diglycolic acid and iminodiacetic acid.

2. The demetallization method according to claim 1, characterized in that: In step a), the total metal element content of the coal tar raw material is above 300 μg / g.

3. The demetallization method according to claim 1, characterized in that: In step a), the reaction temperature is 60-100° C., the stirring speed is 250-350 r / min, and the reaction time is 30-100 min.

4. The demetallization method according to claim 1, characterized in that: In step a), the pore size of the filtering medium is 10-15 μm, the temperature is 70-90° C., and the time is 30-90 min.

5. The demetallization method according to claim 1, characterized in that: In step a), the preparation steps of the demetallizing agent A solution include: The demetallizing agent A is mixed with a solvent to obtain a demetallizing agent A solution.

6. The demetallization method according to claim 5, characterized in that: The demetallizing agent A and the solvent are mixed at a temperature of 20 to 80° C., a stirring speed of 250 to 350 r / min, and a time of 20 to 40 min.

7. The demetallization method according to claim 1, characterized in that: In step b), the reaction temperature is 60-100° C., the stirring speed is 250-350 r / min, and the reaction time is 30-100 min.

8. The demetallization method according to claim 1, characterized in that: In step b), the pore size of the filtering medium is 10-15 μm, the temperature is 70-90° C., and the time is 30-90 min.

9. The demetallization method according to claim 1, characterized in that: In step b), the preparation steps of the demetallizing agent B solution include: The demetallizing agent B is mixed with a solvent to obtain a demetallizing agent B solution.

10. The demetallization method according to claim 9, characterized in that: The demetallizing agent B and the solvent are mixed at a temperature of 20 to 80° C., a stirring speed of 250 to 350 r / min, and a mixing time of 20 to 40 min.

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