Temperature control method for coal direct liquefaction reaction and coal direct liquefaction system

Abstract

The present application provides a coal direct liquefaction reaction temperature control method and coal direct liquefaction system, comprising: 1) coal pyrolysis hydrogenation reaction is carried out in the first reactor by using oil coal slurry heated by oil coal slurry heating furnace and hydrogen heated by hydrogen heating furnace; 2) after the reaction product obtained from the first reactor is quenched, hydrocracking reaction is carried out in the second reactor, and the coal liquefaction reaction product of the hydrocracking reaction is subjected to gas-liquid-solid separation; when the temperature T in the first reactor is 460℃≤T≤465℃ and the pressure P in the first reactor and the second reactor is all ≤20MPa, dilution oil is added into the oil coal slurry heating furnace; when the pressure P in the first reactor or the second reactor is >20MPa, or the temperature T in the first reactor or the second reactor is >465℃, the reactor pressure is released. The present application maintains the temperature in the reactor stable by adjusting the reactor temperature, so that the liquefaction reaction is carried out at the optimum temperature.

Description

Technical Field

[0001] This invention belongs to the field of direct coal liquefaction in the coal chemical industry, and specifically relates to a method for controlling the reaction temperature of a direct coal liquefaction reactor and a direct coal liquefaction system. Background Technology

[0002] Direct coal liquefaction (DCL) is a technology that converts coal into liquid fuel through hydrogenation under high temperature and pressure and the action of a catalyst. The DCL process is an extremely complex process involving multiple reactions that occur synergistically. These reactions include the breaking down of the coal macromolecule structure, the breaking of chemical bonds, the transfer of free radicals, and free radical hydrogenation. Furthermore, the stringent hydrogenation conditions and complex coal structure make the mechanism of DCL difficult to fully understand. Temperature has a significant impact on coal conversion rate and oil yield during DCL. If the reaction temperature is too low, incomplete coal powder conversion and a high bituminous yield result, failing to achieve a high oil yield. Conversely, if the reaction temperature is too high, a high gas yield also results in a low oil yield and increases the risk of reactor overheating.

[0003] To address the aforementioned issues, a number of representative direct coal liquefaction processes have been developed, but all have only completed small-scale and pilot-scale tests and have not yet been put into industrial-scale production. Furthermore, there is still no mature industrial application experience regarding the reaction temperature control methods for direct coal liquefaction reactors.

[0004] Given the current situation, it is necessary to design an industrially feasible method for controlling the reaction temperature in direct coal liquefaction reactors. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a temperature control method and control system for direct coal liquefaction reaction. By adjusting the reactor temperature, the system rapidly maintains a stable temperature within each reactor, enabling the direct coal liquefaction reaction to proceed at the optimal temperature.

[0006] To achieve the objectives of this invention, the following technical solution is adopted:

[0007] The present invention provides a temperature control method for direct coal liquefaction reaction in a first aspect, characterized by comprising the following steps:

[0008] 1) The oil-coal slurry heated by the oil-coal slurry heater and the hydrogen heated by the hydrogen heater are sent to the first reactor to carry out the coal pyrolysis hydrogenation reaction;

[0009] 2) The reaction products obtained from the first reactor are rapidly cooled and then sent to the second reactor for further hydrocracking. The coal liquefaction reaction products obtained from the hydrocracking reaction are subjected to gas-liquid-solid separation to obtain heavy oil slurry, light oil, tail gas and acidic water.

[0010] When the temperature T in the first reactor is 460℃≤T≤465℃ and the pressure P in both the first reactor and the second reactor is ≤20MPa, diluent oil is added to the oil-coal slurry heater, wherein the diluent oil is selected from coal liquefaction product oil and / or solvent oil;

[0011] When the pressure P in the first reactor or the second reactor is greater than 20 MPa, or when the temperature T in the first reactor or the second reactor is greater than 465°C, the pressure in the first reactor or the second reactor shall be released.

[0012] In step 1) of the control method of the present invention, the oil-coal slurry heated by the oil-coal slurry heater and the hydrogen gas heated by the hydrogen gas heater are mixed in a pipeline and transported to the first reactor for reaction, releasing a large amount of heat of reaction. In some specific embodiments, the mass concentration of the oil-coal slurry in the oil-coal slurry heater is 40-50%, for example, 45%.

[0013] In some specific embodiments, step 2) of the control method of the present invention involves adding a quenching medium to the reaction products of the first reactor. By injecting the quenching medium, the temperature of the reactants in the second reactor is controlled, indirectly ensuring that the reaction temperature of the second reactor is consistent with that of the first reactor, allowing both reactors to operate simultaneously at their optimal temperatures. In some preferred embodiments, depending on the reactor structure and the required hydrogen partial pressure, either quenched hydrogen or quenched oil can be used, or other quenching media can be selected. In some specific embodiments, the quenching oil can be coal liquefaction product oil and / or solvent oil.

[0014] In some specific embodiments of the control method of the present invention, the temperature of the coal pyrolysis hydrogenation reaction carried out in the first reactor is 440-460°C (excluding 460°C), preferably 450-459°C, for example, 455°C, 458°C; the pressure is 16-19 MPa, preferably 17-19 MPa, for example, 18 MPa, 18.5 MPa.

[0015] In some specific embodiments of the control method of the present invention, the temperature of the hydrocracking reaction carried out in the second reactor is 440-460°C (excluding 460°C), preferably 450-459°C, for example, 455°C, 458°C; the pressure is 16-19 MPa, preferably 17-19 MPa, for example, 18 MPa, 18.5 MPa.

[0016] In some specific embodiments, in step 2) of the method of the present invention, the gas-liquid-solid separation process includes sequential hot high-pressure separation and cold high-pressure separation; specifically, after hot high-pressure separation, the coal liquefaction reaction products are obtained as heavy oil slurry and other products, and the other products are then separated by cold high-pressure separation to obtain tail gas, light oil and acidic water.

[0017] In some preferred embodiments, the hot-high pressure separation can be carried out in a hot-high pressure separator, under the following conditions: temperature of 390-420°C, preferably 400-410°C, for example, 405°C or 409°C; and pressure of 16-19 MPa, preferably 17-18 MPa, for example, 17.5 MPa.

[0018] In the process of direct coal liquefaction, when the temperature in the first reactor exceeds 460°C (i.e., a runaway temperature occurs), the control method of the present invention reduces the concentration of coal powder in the entire raw material medium by injecting diluent oil into the coal-oil slurry heater, thereby delaying the coal pyrolysis hydrogenation reaction and lowering the temperature in the first reactor until it is below 460°C, thus achieving the purpose of controlling the temperature of the direct coal liquefaction reaction.

[0019] In a second aspect, the present invention provides a direct coal liquefaction system utilizing the above-described method, the system comprising:

[0020] Oil-coal slurry heater: used for heating oil-coal slurry;

[0021] Hydrogen heater: Used for heating hydrogen gas;

[0022] Diluent oil feed line: used to supply diluent oil into the oil-coal slurry heating furnace;

[0023] First reactor: used to carry out coal pyrolysis hydrogenation reaction between oil-coal slurry heated by the oil-coal slurry heater and hydrogen heated by the hydrogen heater.

[0024] Quenching line: used to deliver quenching medium to the reaction products of the first reactor;

[0025] Second reactor: used to perform hydrocracking reaction on the reaction products of the first reactor after rapid cooling;

[0026] Hot high pressure separator: used to separate the products of coal liquefaction after hydrocracking reaction under hot high pressure to obtain heavy oil slurry and other products;

[0027] Cold high-pressure separator: used to perform cold high-pressure separation of other products after separation by hot high-pressure separator to obtain tail gas, light oil and acidic water.

[0028] In some specific embodiments, the oil-coal slurry heating furnace in the system of the present invention is provided with a feed inlet for injecting diluent oil and oil-coal slurry into the heating furnace.

[0029] The coal direct liquefaction system provided by this invention also includes a pressure relief valve for releasing pressure within the system. In some specific embodiments, the relief valve is located at the tail gas outlet of the cold high-pressure separator, thereby reducing the pressure within the system by releasing the tail gas.

[0030] In some specific implementations, a high-pressure heat exchanger is also provided between the hot high-pressure separator and the cold high-pressure separator in the system, for heat exchange treatment of the other products after separation by the hot high-pressure separator, excluding heavy oil slurry.

[0031] In some specific embodiments, the liquefaction system provided by this invention further includes a reaction temperature monitoring system, specifically comprising internal temperature monitoring thermocouples and external temperature monitoring thermocouples. Internal temperature monitoring uses thermocouples arranged at different heights and positions within each reactor to indicate the internal temperature of the direct coal liquefaction reactor. The reaction temperature of the reactor is obtained through weighted average calculation, which guides the adjustment direction of the aforementioned methods. External temperature monitoring uses thermocouples arranged at different heights and positions on the external walls of each reactor to assist in determining the reactor's reaction temperature.

[0032] The above technical solution achieves the following technical effects:

[0033] The temperature control method provided by this invention injects diluent oil into the first reactor when a temperature runaway phenomenon occurs (temperature exceeds 460°C), thereby reducing the concentration of coal powder reactant in the entire raw material medium and slowing down the release of exothermic reaction. At the same time, the control method of this invention also reduces the temperature of the reaction raw materials, indirectly reducing the reaction temperature of the direct coal liquefaction reactor.

[0034] The control method of this invention can rapidly adjust the reactor temperature, maintaining a stable temperature within each reactor and enabling the direct coal liquefaction reaction to proceed at the optimal temperature. Compared to traditional methods of adjusting gas levels using oil-coal slurry heaters or hydrogen heaters, the method of this invention is more effective and faster. Attached Figure Description

[0035] Figure 1 This invention provides one embodiment of the direct coal liquefaction system.

[0036] Among them, 1. Oil-coal slurry heater, 2. Hydrogen heater, 3. First reactor, 4. Second reactor, 5. Hot high-pressure separator, 6. Cold high-pressure separator, 7. Diluent oil feed line, 8. Quenching line, 9. Pressure relief valve, 10. High-pressure heat exchanger. Detailed Implementation

[0037] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0038] The direct coal liquefaction system provided by this invention, such as Figure 1 As shown, the system includes: an oil-coal slurry heater 1, a hydrogen heater 2, a first reactor 3, a second reactor 4, a hot high-pressure separator 5, and a cold high-pressure separator 6;

[0039] Among them, oil-coal slurry heating furnace 1: used to heat the oil-coal slurry in the furnace;

[0040] Hydrogen heater 2: Used to heat the hydrogen inside the furnace;

[0041] Diluent oil feed line 7: Used to supply diluent oil to the oil-coal slurry heater 1;

[0042] First reactor 3: used to carry out coal pyrolysis hydrogenation reaction between the oil-coal slurry heated by oil-coal slurry heater 1 and the hydrogen heated by hydrogen heater 2;

[0043] Quenching line 8: Used to deliver quenching medium to the reaction products of the first reactor 3;

[0044] Second reactor 4: used to perform hydrocracking reaction on the reaction products after rapid cooling;

[0045] Hot high pressure separator 5: Used to hot high pressure separate the coal liquefaction reaction products after hydrocracking reaction to obtain heavy oil slurry and other products;

[0046] Cold high-pressure separator 6: Used to perform cold high-pressure separation on other products except heavy oil slurry after separation by hot high-pressure separator 5, to obtain tail gas, light oil and acidic water.

[0047] The system provided by the present invention also includes a pressure relief valve 9 for releasing pressure within the system.

[0048] In the system of this invention, a high-pressure heat exchanger 10 is also provided between the hot high-pressure separator 5 and the cold high-pressure separator 6 for heat exchange treatment of the products other than heavy oil slurry separated by the hot high-pressure separator 5. Both the first reactor 3 and the second reactor 4 are equipped with reaction temperature monitoring systems and pressure monitoring systems to monitor the temperature and pressure within the reactors.

[0049] Example 1

[0050] 1) Coal-oil slurry is fed into the coal-oil slurry heater 1 at a feed rate of 565 t / h, and the coal-oil slurry is heated from 166°C to 366°C. The fuel gas consumption of the coal-oil slurry heater 1 is approximately 12000 Nm³. 3 / h; Hydrogen is supplied to hydrogen heater 2 at an inlet flow rate of 22t / h, heating the hydrogen from 391℃ to 538℃, with a fuel gas consumption of approximately 1000Nm³. 3 / h;

[0051] The oil-coal slurry heated by the oil-coal slurry heater 1 and the hydrogen heated by the hydrogen heater 2 are mixed to form a reaction raw material (temperature 382℃), which is then sent to the first reactor 3 for coal pyrolysis hydrogenation reaction.

[0052] 2) When the reaction temperature of the first reactor 3 reaches 455℃, quench hydrogen (temperature 131℃, flow rate 10t / h) and quench oil (temperature 54℃, flow rate 22t / h) are transported to the reaction products of the first reactor 3 through the quench pipeline 8 and then sent to the second reactor 4 to continue the hydrocracking reaction. The coal liquefaction reaction products obtained from the hydrocracking reaction are subjected to gas-liquid-solid separation to obtain heavy oil slurry, light oil, tail gas and acidic water.

[0053] After running under the above conditions for 1 hour, the reaction temperature of the first reactor 3 rapidly rose to 465℃ (i.e., a runaway temperature occurred) and the pressure of the first reactor 3 was 19MPa. The pressure inside the second reactor was also 19MPa. Diluent oil was injected into the oil-coal slurry heater 1 through the diluent oil feed pipeline 7 (injection rate of 80t / h, temperature of 90℃). Within 10 minutes, the reaction temperature of the first reactor 3 returned from 465℃ to 455℃. After stopping the injection of diluent oil, the reaction continued.

[0054] Example 2

[0055] 1) Coal-oil slurry is fed into the coal-oil slurry heater 1 at a feed rate of 500 t / h, and the coal-oil slurry is heated from 170°C to 370°C. The fuel gas consumption of the coal-oil slurry heater 1 is approximately 11500 Nm³. 3 / h; Hydrogen is supplied to hydrogen heater 2 at an inlet flow rate of 16t / h, heating the hydrogen from 400℃ to 540℃, with a fuel gas consumption of approximately 900Nm³. 3 / h;

[0056] The oil-coal slurry heated by the oil-coal slurry heater 1 and the hydrogen heated by the hydrogen heater 2 are mixed to form a reaction feedstock, which is then sent to the first reactor 3 for coal pyrolysis hydrogenation reaction.

[0057] During the stable operation under the above conditions, the feed rate suddenly dropped sharply from 500t / h to below 300t / h. The material flow state in the first reactor 3 changed, and the temperature suddenly rose sharply to 470℃ (i.e., a runaway temperature phenomenon occurred). The pressure in the first reactor 3 rapidly rose to 20.5MPa, and the pressure in the second reactor 4 was also 20.5MPa. The pressure in the first reactor 3 and the second reactor 4 was released to below 16MPa through the pressure relief valve. The temperature and pressure in the reactors stopped rising. Within 10 minutes, the reaction temperature in the first reactor 3 returned to 455℃. After the pressure relief was stopped, the reaction continued.

[0058] Comparative Example

[0059] 1) Coal-oil slurry is fed into the coal-oil slurry heater 1 at a feed rate of 565 t / h, and the slurry is heated from 166°C to 366°C. The fuel gas consumption of the coal-oil slurry heater 1 is approximately 12000 Nm³. 3 / h; Hydrogen is supplied to hydrogen heater 2 at an inlet flow rate of 22t / h, heating the hydrogen from 391℃ to 538℃, with a fuel gas consumption of approximately 1000Nm³. 3 / h;

[0060] The oil-coal slurry heated by the oil-coal slurry heater 1 and the hydrogen heated by the hydrogen heater 2 are mixed to form a reaction raw material (temperature 382℃), which is then sent to the first reactor 3 for coal pyrolysis hydrogenation reaction.

[0061] 2) The reaction temperature of the first reactor 3 reaches 455℃; quench hydrogen (temperature 131℃, flow rate 10t / h) and quench oil (temperature 54℃, flow rate 22t / h) are transported to the reaction products of the first reactor 3 through the quench pipeline 8 and then transported to the second reactor 4 to continue the hydrocracking reaction. The coal liquefaction reaction products obtained from the hydrocracking reaction are subjected to gas-liquid-solid separation to obtain heavy oil slurry, light oil, tail gas and acidic water.

[0062] When operating under the above conditions, the reaction temperature of the first reactor 3 rapidly rises to 464℃ (i.e., a runaway temperature occurs) or the pressure of the first reactor 3 rapidly rises to 19.5MPa, while the pressure inside the second reactor is 19.4MPa. The inlet temperature of the reactor is reduced to below 360℃ by reducing the amount of fuel gas used in the heating furnace, but the cooling rate is not as fast as the temperature rise rate inside the first reactor 3. The temperature inside the first reactor 3 exceeds the design temperature of the equipment materials, resulting in equipment damage, leakage, and other accidents.

Claims

1. A method for temperature control in direct coal liquefaction reaction, characterized in that, Includes the following steps: 1) The oil-coal slurry heated by the oil-coal slurry heater and the hydrogen heated by the hydrogen heater are sent to the first reactor to carry out the coal pyrolysis hydrogenation reaction; 2) The reaction products obtained from the first reactor are rapidly cooled and then sent to the second reactor for further hydrocracking. The coal liquefaction reaction products obtained from the hydrocracking reaction are subjected to gas-liquid-solid separation to obtain heavy oil slurry, light oil, tail gas and acidic water. When the temperature T in the first reactor is 460℃≤T≤465℃ and the pressure P in both the first reactor and the second reactor is ≤20 MPa, diluent oil is added to the oil-coal slurry heater, wherein the diluent oil is selected from coal liquefaction product oil and / or solvent oil; When the pressure P in the first reactor or the second reactor is greater than 20 MPa, or when the temperature T in the first reactor or the second reactor is greater than 465°C, the pressure in the first reactor or the second reactor shall be released. The temperature of the coal pyrolysis hydrogenation reaction is 440~460℃, and the pressure is 16~19 MPa; The hydrocracking reaction is carried out at a temperature of 440-460°C and a pressure of 16-19 MPa.

2. The temperature control method according to claim 1, characterized in that, The mass concentration of the oil-coal slurry mentioned in step 1) is 40-50%.

3. The temperature control method according to claim 1, characterized in that, In step 2), the quenching process involves adding a quenching medium to the reaction products of the first reactor.

4. The temperature control method according to claim 3, characterized in that, The quenching medium is quenching hydrogen and / or quenching oil.

5. The temperature control method according to any one of claims 1 to 4, characterized in that, The gas-liquid-solid separation described in step 2) includes hot high-pressure separation and cold high-pressure separation; The coal liquefaction reaction products are separated by hot high pressure to obtain heavy oil slurry and other products. The other products are then separated by cold high pressure to obtain tail gas, light oil and acidic water.

6. The temperature control method according to claim 5, characterized in that, The conditions for the thermo-high pressure separation are: temperature 390~420℃, pressure 16~19 MPa; The conditions for the cold-high pressure separation are: temperature of 40~60℃ and pressure of 16~19 MPa.

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