Device and method for recovering phenol from tar by multi-effect rectification

Abstract

The present invention relates to a device and method for recovering phenol from tar by multi-effect distillation, comprising a No. 1 recovery tower, a No. 2 recovery tower, a condenser, a flow regulating valve, a liquid level regulating valve, a gas-liquid separation subcooler, a No. 1 recovery tower reboiler, a low-temperature condenser, a No. 2 recovery tower reboiler, a No. 2 recovery tower condenser, a No. 1 recovery tower vacuum system, and a No. 2 recovery tower vacuum system. In the phenol recovery method, the No. 1 recovery tower and the No. 2 recovery tower are operated at negative pressure, a portion of the overhead steam from the No. 1 recovery tower passes through the flow regulating valve to the No. 2 recovery tower reboiler, a portion is condensed through the condenser, and the two streams of condensate flow to the gas-liquid separation subcooler, wherein the liquid phase portion is refluxed to the No. 1 recovery tower, and a portion is used as feed to the No. 2 recovery tower. Compared with the traditional phenol distillation recovery method, the double-effect distillation of the present invention significantly reduces the total energy consumption of the entire distillation tower system during the phenol recovery process, saves operating costs, and achieves the purpose of energy saving and efficiency improvement.

Description

Technical Field

[0001] The present invention belongs to green, environmentally friendly and energy-saving technology, and particularly relates to a device and method for recovering phenol from tar by multi-effect distillation. Background Art

[0002] Distillation is the most widely used industrial separation method, widely used in chemical, petroleum, food, and light industries. Although technological advancements have led to the industrialization of new separation technologies, its dominant position remains unshaken for a while. While distillation separation technology is mature and easily industrialized, its drawback is high energy consumption. Traditional distillation separation consumes over 40% of total industrial energy consumption, a significant burden in the 21st century, where energy is increasingly scarce.

[0003] Phenol tar is a byproduct of phenol-acetone production using cumene as the raw material. It is the distillation residue after separating phenol and acetone from the reaction products. Separating phenol from phenol tar often involves distillation, which consumes a lot of energy and utilities.

[0004] Patent CN101835732 discloses a method for recovering acetophenone during the production of phenol. The method comprises treating one or more alkylbenzenes including sec-butylbenzene to produce a feed containing phenol and acetophenone, separating a crude fraction from the feed under crude phenol separation conditions that effectively produce a crude phenol heavies, and separating the acetophenone directly from the crude heavies under azeotropic distillation conditions. A comparative analysis of the patents reveals that the process is for a system in which phenol and acetophenone are produced from sec-butylbenzene or multiple alkylbenzenes, and phenol and acetophenone are obtained by distillation purification. The system involved is not a system using cumene as a raw material, and therefore, the purification raw material composition is different, and the purification process and requirements are different. In addition, the purification adopts a conventional distillation scheme and does not involve distillation energy integration.

[0005] Patent CN102153092B discloses a trichlorosilane purification device and process that integrates heat pump distillation and multi-effect distillation. The device utilizes the overhead steam of the high-pressure tower, i.e., the de-weighting tower, to heat the bottom liquid of the low-pressure tower, i.e., the de-lighting tower. The overhead steam of the de-lighting tower is condensed, and this process is a multi-effect distillation process. At the same time, the overhead steam of the de-lighting tower is heated and pressurized by a compressor to heat the bottom liquid of the de-weighting tower. The overhead steam of the de-lighting tower is condensed, and this process is a heat pump distillation process. A comparative analysis of the patents shows that the process integrates heat pump distillation and multi-effect distillation by adding a compressor. The compressor cannot adjust the negative pressure operating conditions of the tower. Therefore, the distillation device and process can only operate under normal pressure or pressurized conditions, and is not suitable for multi-effect distillation operations under reduced pressure. Summary of the Invention

[0006] The purpose of the present invention is to solve the above problems and provide a device and method for recovering phenol from tar by multi-effect distillation, so as to reduce the energy consumption of recovering phenol from tar.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A device for recovering phenol from tar by multi-effect distillation, comprising a No. 1 recovery tower and a No. 2 recovery tower, further comprising a No. 1 recovery tower condenser, a gas-liquid separation subcooler, a low-temperature condenser, a No. 1 recovery tower vacuum system, a No. 2 recovery tower reboiler, a No. 2 recovery tower condenser, and a No. 2 recovery tower vacuum system;

[0009] The 2# recovery tower reboiler is arranged at the bottom of the 2# recovery tower, and the gaseous material at the top of the 1# recovery tower directly enters the 2# recovery tower reboiler for heat exchange through a part of the pipeline, and the other part enters the 1# recovery tower condenser;

[0010] The steam condensate of the 2# recovery tower reboiler and the 1# recovery tower condenser enters the gas-liquid separation subcooler through a pipeline;

[0011] The gas phase material at the top of the gas-liquid separation subcooler is connected to the low-temperature condenser and the vacuum system of the 1# recovery tower in sequence through pipelines. A portion of the liquid phase material at the bottom of the gas-liquid separation subcooler is refluxed to the top of the 1# recovery tower, and a portion enters the 2# recovery tower;

[0012] The gaseous material at the top of the 2# recovery tower is connected to the 2# recovery tower condenser and the 2# recovery tower vacuum system in sequence through pipelines. After the gaseous material at the top of the tower is condensed by the 2# recovery tower condenser, a part of it flows back to the 2# recovery tower, and a part of it is extracted and collected.

[0013] Furthermore, a 1# recovery tower reboiler is provided at the bottom of the 1# recovery tower.

[0014] Furthermore, a flow regulating valve is provided in the pipeline connecting the gas phase material at the top of the 1# recovery tower and the reboiler of the 2# recovery tower.

[0015] Furthermore, a portion of the liquid phase material at the lower portion of the gas-liquid separation subcooler is pumped into the top of the No. 1 recovery tower through a reflux pump, and a portion is pumped into the No. 2 recovery tower as feed.

[0016] Furthermore, a liquid level regulating valve is provided in the pipeline for the liquid phase material from the gas-liquid separation subcooler to enter the No. 2 recovery tower.

[0017] Furthermore, the 1# recovery tower and the 2# recovery tower are both at negative pressure, which are adjusted by the 1# recovery tower vacuum system and the 2# recovery tower vacuum system respectively.

[0018] A method for recovering phenol from tar by multiple-effect distillation is carried out using the above-mentioned device, and specifically includes the following steps:

[0019] The tar raw material containing phenol enters the 1# recovery tower. The operating pressure of the 1# recovery tower is controlled by the vacuum system of the 1# recovery tower to be negative pressure operation. The material is heated and vaporized in the 1# recovery tower. Part of the gas phase material at the top of the 1# recovery tower enters the reboiler of the 2# recovery tower for heat exchange and serves as the energy source for the reboiler of the 2# recovery tower kettle. The rest enters the condenser of the 1# recovery tower.

[0020] The steam condensate from the reboiler of the 2# recovery tower and the condenser of the 1# recovery tower enter the gas-liquid separation subcooler together. The gaseous material in the gas-liquid separation subcooler passes through the low-temperature condenser and enters the vacuum system of the 1# recovery tower. Part of the liquid material in the gas-liquid separation subcooler flows back to the top of the 1# recovery tower, and part of it enters the 2# recovery tower as feed. The material in the kettle of the 1# recovery tower is collected outside the boundary.

[0021] The operating pressure of the 2# recovery tower is controlled to be negative pressure operation through the vacuum system of the 2# recovery tower. The liquid phase material entering the 2# recovery tower is heated and vaporized, and the gas phase material on the top of the tower is condensed by the 2# recovery tower condenser. Part of the condensate is refluxed to the 2# recovery tower, and part is collected to obtain high-purity phenol recovery liquid. The heavy components in the bottom of the 2# recovery tower are collected outside the boundary.

[0022] Furthermore, the operating pressure of the 1# recovery tower is 5-90 kPa absolute pressure, and the preferred operating pressure is 40-60 kPa absolute pressure.

[0023] Furthermore, the operating pressure of the 2# recovery tower is 1-70 kPa absolute pressure, and the preferred operating pressure is 20-40 kPa.

[0024] Furthermore, the phenol mass content in the phenol recovery liquid is greater than 99%.

[0025] The double-effect distillation system of the present invention utilizes the latent heat of the high-pressure tower overhead steam to provide heat to the reboiler of the low-pressure tower. Compared with conventional distillation, it greatly improves energy utilization, significantly reduces the energy consumption of the distillation unit, and produces high-quality and high-yield distilled products.

[0026] The key to the present invention lies in the connection between the 1# recovery tower and the 2# recovery tower. Through the device and process of the present invention, the gaseous material at the top of the 1# recovery tower directly enters the 2# recovery tower reboiler for heat exchange through a portion of the pipeline, and the other portion enters the 1# recovery tower condenser. The steam condensate from the 2# recovery tower reboiler and the 1# recovery tower condenser enters the gas-liquid separation subcooler through a pipeline. Part of the liquid phase material at the bottom of the gas-liquid separation subcooler is refluxed to the top of the 1# recovery tower, and part enters the 2# recovery tower. The top steam of the 1# recovery tower is used as the energy source for the reboiler of the 2# recovery tower kettle, significantly reducing the amount of refrigerant at the top of the 1# recovery tower and eliminating the amount of heat medium in the reboiler of the 2# recovery tower kettle, thereby reducing the operating cost of the distillation system. The gas-liquid separation subcooler serves as a collection tank for the steam condensate at the top of the 1# recovery tower to maintain the stable pressure of the 1# recovery tower under negative pressure operating conditions, and can regulate the amount of steam from the top steam of the 1# recovery tower to the 2# recovery tower reboiler 10.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) Compared with the solution of purifying phenol by cracking phenol tar, the present invention adopts a negative pressure distillation method to avoid recombination and cracking, and can separate phenol in two towers, with a simple process flow;

[0029] (2) Compared with the solution of distillation purification of phenol, the present invention adopts a multi-effect distillation method, which effectively reduces the total energy consumption of the distillation system and reduces operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the process of the device for recovering phenol from tar by multiple-effect distillation of the present invention;

[0031] In the figure: 1# recovery tower 1; 2# recovery tower 2; 1# recovery tower condenser 3; flow control valve 4; liquid level control valve 5; gas-liquid separation subcooler 6; reflux pump 7; 1# recovery tower reboiler 8; low-temperature condenser 9; 2# recovery tower reboiler 10; 2# recovery tower condenser 11; 1# recovery tower vacuum system 12; 2# recovery tower vacuum system 13. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. However, this should not be construed as limiting the scope of the present invention to the embodiments. Various substitutions and modifications may be made based on common technical knowledge and customary means in the art without departing from the technical principles of the present invention, and all such substitutions and modifications are intended to be within the scope of the present invention.

[0033] like Figure 1A device for recovering phenol from tar by multi-effect distillation includes a 1# recovery tower 1 and a 2# recovery tower 2, as well as a 1# recovery tower condenser 3, a gas-liquid separation subcooler 6, a low-temperature condenser 9, a 1# recovery tower vacuum system 12, a 2# recovery tower reboiler 10, a 2# recovery tower condenser 11 and a 2# recovery tower vacuum system 13; a 1# recovery tower reboiler 8 is provided at the bottom of the 1# recovery tower.

[0034] The connection relationship between the components is as follows: the 2# recovery tower reboiler 10 is arranged at the bottom of the 2# recovery tower 2, the gas phase material at the top of the 1# recovery tower 1 directly enters the 2# recovery tower reboiler 10 for heat exchange through a part of the pipeline, and the other part enters the 1# recovery tower condenser 3; a flow regulating valve 4 is provided in the pipeline connecting the gas phase material at the top of the 1# recovery tower 1 and the 2# recovery tower reboiler 10, and the steam condensate of the 2# recovery tower reboiler 10 and the 1# recovery tower condenser 3 enters the gas-liquid separation subcooler 6 together through the pipeline; the gas phase material on the upper part of the gas-liquid separation subcooler 6 is connected in sequence through the pipeline. Connect the low-temperature condenser 9 and the 1# recovery tower vacuum system 12. Part of the liquid phase material at the bottom of the gas-liquid separation subcooler 6 is pumped into the top of the 1# recovery tower 1 through the reflux pump 7, and part is pumped into the 2# recovery tower 2 as feed. A liquid level regulating valve 5 is provided in the pipeline where the liquid phase material from the gas-liquid separation subcooler 6 enters the 2# recovery tower 2. The gas phase material at the top of the 2# recovery tower 2 is connected to the 2# recovery tower condenser 11 and the 2# recovery tower vacuum system 13 in sequence through a pipeline. After the gas phase material at the top of the tower is condensed by the 2# recovery tower condenser 11, part of it is refluxed to the 2# recovery tower 2, and part of it is extracted and collected.

[0035] The above-mentioned device is used to recover phenol from tar, which specifically includes the following methods:

[0036] The tar feedstock containing phenol enters the 1# recovery tower 1, and the operating pressure of the 1# recovery tower 1 is controlled to be a negative pressure operation by the 1# recovery tower vacuum system 12. The operating pressure of the 1# recovery tower 1 is 5-90 kPa absolute pressure, and the preferred operating pressure is 40-60 kPa absolute pressure. The material is heated and vaporized in the 1# recovery tower 1. A portion of the gaseous material at the top of the 1# recovery tower 1 enters the 2# recovery tower reboiler 10 for heat exchange and serves as an energy source for the 2# recovery tower kettle reboiler 10, and a portion enters the 1# recovery tower condenser 3;

[0037] The steam condensate from the condenser 3 of the 2# recovery tower and the steam condensate from the 1# recovery tower enter the gas-liquid separation subcooler 6 together. The gaseous material in the gas-liquid separation subcooler 6 passes through the low-temperature condenser 9 and enters the vacuum system 12 of the 1# recovery tower. Part of the liquid material in the gas-liquid separation subcooler 6 is refluxed to the top of the 1# recovery tower 1, and part of it is used as feed to enter the 2# recovery tower 2. The material in the bottom of the 1# recovery tower 1 is collected outside the boundary.

[0038] The operating pressure of the 2# recovery tower 2 is controlled to be negative pressure operation by the 2# recovery tower vacuum system 13. The operating pressure of the 2# recovery tower 2 is 1-70 kPa absolute pressure, preferably 20-40 kPa. The liquid phase material entering the 2# recovery tower 2 is heated and vaporized, and the top gas phase material is condensed by the 2# recovery tower condenser 11. A portion of the condensate is refluxed to the 2# recovery tower 2, and a portion is extracted and collected to obtain a high-purity phenol recovery liquid with a phenol mass content of greater than 99%. The heavy components in the bottom of the 2# recovery tower 2 are extracted and collected outside the boundary.

[0039] The following are specific application examples

[0040] Example 1

[0041] like Figure 1 , using this device and process. The tar raw material containing phenol is composed of: 19.9% phenol, 10.3% acetophenone, 0.1% xylenol, 21.7% cumylphenol and 48.0% other heavy components (all by mass). The raw materials enter the 1# recovery tower for separation and recovery. The 1# recovery tower reboiler uses high-pressure steam. The material is heated and vaporized through the 1# recovery tower reboiler 8. Part of the overhead steam passes through the flow regulating valve 4 to the 2# recovery tower reboiler 10. Its steam condensate enters the gas-liquid separation subcooler 6. The remaining steam passes through the 1# recovery tower condenser 3 and the liquid level regulating valve 5 to enter the gas-liquid separation subcooler 6. The gas phase material in the gas-liquid separation subcooler 6 passes through the low-temperature condenser 9 and enters the 1# recovery tower vacuum system 12; the liquid phase material in the gas-liquid separation subcooler 6 is pumped into the top of the 1# recovery tower through the reflux pump 7, and part is pumped into the 2# recovery tower as feed. The material in the 1# recovery tower kettle is collected outside the boundary.

[0042] The liquid phase from the gas-liquid separator subcooler 6 enters the No. 2 recovery tower. The tower's operating pressure is controlled by the No. 2 recovery tower vacuum system 13. The material is heated and vaporized in the No. 2 recovery tower reboiler 10. The overhead vapor is condensed in the No. 2 recovery tower condenser 11. A portion of the condensate is refluxed, while a portion is collected and extracted to produce a high-purity phenol recovery liquid with a purity of up to 99.1%. Heavy components in the No. 2 recovery tower's bottom chamber are collected outside the tower.

[0043] The energy consumption of the method of the present invention is compared with that of conventional double-tower distillation. The specific energy consumption is shown in Table 1.

[0044] Table 1 Comparison of energy consumption of Example 1 and conventional distillation

[0045] project unit Conventional double-tower distillation Example 1 Double-effect distillation steam t / h 3.5 2.3 circulating water t / h 109 40 Total energy saving rate ％ / 36％

[0046] As shown in Table 1, the double-effect distillation adopted in this embodiment uses the top steam of the 1# recovery tower as the heat source for the reboiler of the 2# recovery tower kettle. Compared with the conventional double-tower distillation, the comprehensive energy consumption is reduced by 36%.

[0047] Example 2

[0048] According to the conditions and steps of Example 1, only the raw material composition was changed to 23.0% phenol, 11.3% acetophenone, 0.1% xylenol, 22.3% cumylphenol, and 43.3% other heavy components, to obtain a high-purity phenol recovery liquid with a phenol purity of up to 99%.

[0049] The energy consumption of double-effect distillation is compared with that of conventional distillation as shown in the following table.

[0050] The energy consumption of this embodiment is compared with that of conventional double-tower distillation. The specific energy consumption is shown in Table 2.

[0051] Table 2 Comparison of energy consumption of Example 2 and conventional distillation

[0052] project unit Conventional double-tower distillation Example 2 Double-effect distillation steam t / h 4.2 2.7 circulating water t / h 120 46 Total energy saving rate ％ / 37％

[0053] As can be seen from the above table, the double-effect distillation adopted in this embodiment uses the recovery tower overhead steam as the heat source for the recovery tower kettle reboiler, which reduces the comprehensive energy consumption by 37% compared with the conventional double-tower distillation.

[0054] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A device for recovering phenol from tar by multi-effect distillation, characterized in that: It includes a 1# recovery tower (1) and a 2# recovery tower (2), and also includes a 1# recovery tower condenser (3), a gas-liquid separation subcooler (6), a low-temperature condenser (9), a 1# recovery tower vacuum system (12), a 2# recovery tower reboiler (10), a 2# recovery tower condenser (11) and a 2# recovery tower vacuum system (13); The 2# recovery tower reboiler (10) is arranged at the bottom of the 2# recovery tower (2); the gaseous material at the top of the 1# recovery tower (1) directly enters the 2# recovery tower reboiler (10) for heat exchange through a portion of the pipeline, and the other portion enters the 1# recovery tower condenser (3); The steam condensate from the 2# recovery tower reboiler (10) and the 1# recovery tower condenser (3) enters the gas-liquid separation subcooler (6) through a pipeline; The gas phase material at the upper portion of the gas-liquid separation subcooler (6) is sequentially connected to the low-temperature condenser (9) and the first recovery tower vacuum system (12) through pipelines. A portion of the liquid phase material at the lower portion of the gas-liquid separation subcooler (6) is refluxed to the top of the first recovery tower (1), and a portion enters the second recovery tower (2). The gaseous material at the top of the 2# recovery tower (2) is connected to the 2# recovery tower condenser (11) and the 2# recovery tower vacuum system (13) in sequence through pipelines. After the gaseous material at the top of the tower is condensed by the 2# recovery tower condenser (11), a portion of the gaseous material is refluxed to the 2# recovery tower (2), and a portion of the gaseous material is collected and extracted; The bottom of the 1# recovery tower is provided with a 1# recovery tower reboiler (8); A flow regulating valve (4) is provided in the pipeline connecting the gas phase material at the top of the 1# recovery tower (1) and the reboiler (10) of the 2# recovery tower; The liquid phase material at the bottom of the gas-liquid separation subcooler (6) is partially pumped into the top of the No. 1 recovery tower (1) through a reflux pump (7), and the remaining portion is pumped into the No. 2 recovery tower (2) as feed; A liquid level regulating valve (5) is provided in the pipeline for the liquid phase material from the gas-liquid separation subcooler (6) to enter the No. 2 recovery tower (2).

2. The device for recovering phenol from tar by multiple-effect distillation according to claim 1, wherein: The 1# recovery tower (1) and the 2# recovery tower (2) are both negative pressure, which are adjusted by the 1# recovery tower vacuum system (12) and the 2# recovery tower vacuum system (13) respectively.

3. A method for recovering phenol from tar by multiple-effect distillation, characterized in that: The method is carried out using the device according to any one of claims 1 to 2, specifically comprising the following method: The tar raw material containing phenol enters the No. 1 recovery tower (1), and the operating pressure of the No. 1 recovery tower (1) is controlled to be a negative pressure operation by the No. 1 recovery tower vacuum system (12). The material is heated and vaporized in the No. 1 recovery tower (1). A portion of the gas phase material at the top of the No. 1 recovery tower (1) enters the No. 2 recovery tower reboiler (10) for heat exchange and serves as an energy source for the No. 2 recovery tower reboiler (10), and a portion enters the No. 1 recovery tower condenser (3); The steam condensate from the reboiler (10) of the 2# recovery tower and the condenser (3) of the 1# recovery tower enters the gas-liquid separation subcooler (6) together. The gaseous material in the gas-liquid separation subcooler (6) passes through the low-temperature condenser (9) and enters the vacuum system (12) of the 1# recovery tower. A portion of the liquid material in the gas-liquid separation subcooler (6) flows back to the top of the 1# recovery tower (1), and a portion of the liquid material enters the 2# recovery tower (2) as feed. The material in the bottom of the 1# recovery tower (1) is collected outside the boundary. The operating pressure of the No. 2 recovery tower (2) is controlled to be a negative pressure operation by the No. 2 recovery tower vacuum system (13). The liquid phase material entering the No. 2 recovery tower (2) is heated and vaporized. The gas phase material at the top of the tower is condensed by the No. 2 recovery tower condenser (11). A part of the condensate is refluxed to the No. 2 recovery tower (2), and a part is collected to obtain a phenol recovery liquid. The heavy components in the bottom of the No. 2 recovery tower (2) are collected outside the boundary.

4. A method for recovering phenol from tar by multiple-effect distillation according to claim 3, characterized in that: The operating pressure of the 1# recovery tower (1) is 5-90 kPa absolute pressure.

5. A method for recovering phenol from tar by multiple-effect distillation according to claim 3, characterized in that: The operating pressure of the 2# recovery tower (2) is 1-70 kPa absolute pressure.

6. The method for recovering phenol from tar by multiple-effect distillation according to claim 3, wherein: The phenol mass content in the phenol recovery liquid is greater than 99%.

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