Four-tower reverse double-hot-trap double-effect methanol rectification energy-saving device and process method

Abstract

The invention provides a four-tower reverse double-hot-trap double-effect methanol rectification energy-saving device and a process method.The four-tower reverse double-hot-trap double-effect methanol rectification energy-saving device comprises a pre-rectification tower, a vacuum rectification tower, a high-pressure rectification tower and a recovery tower which are sequentially connected, and the lower portion of the pre-rectification tower is connected with two reboilers; the lower parts of the vacuum rectifying tower and the high-pressure rectifying tower are respectively connected with a vacuum rectifying tower reboiler and a high-pressure rectifying tower reboiler; and the lower part of the recovery tower is connected with two reboilers. Wherein part of gas at the top of the high-pressure rectifying tower supplies heat to a vacuum rectifying tower reboiler, part of gas supplies heat to a pre-rectifying tower reboiler II, and a small part of top gas enters the pre-rectifying tower through a vacuum rectifying tower top vacuum injection pump and a recovery tower top vacuum injection pump to generate low pressure, so that negative pressure of the vacuum rectifying tower and the recovery tower is realized; and high-temperature wastewater produced at the bottom of the high-pressure rectifying tower supplies heat to the reboiler I of the recovery tower. Compared with the Haldor Topsoe flow process, the unit consumption of the steam for producing the refined methanol is reduced by 10-20%, and the obvious energy-saving effect of the methanol rectification flow process can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of distillation, and in particular to a four-tower reverse double-heat-trap double-effect methanol distillation energy-saving device and a process method. Background Art

[0002] Methanol is an important basic organic chemical raw material and fuel resource with excellent performance. It is widely used in organic synthesis, dyes, medicines, pesticides, coatings, transportation, national defense and other industries, and ranks fourth in the world's chemical raw material consumption. With the continuous development of modern science and technology and the world's energy structure, new methods for producing high-purity methanol are emerging in an endless stream, but distillation is still considered to be the first choice for improving the purity of methanol. However, the comprehensive energy consumption of distillation is high, accounting for about 20% of the total energy consumption of methanol production. Therefore, the technology to reduce the energy consumption of methanol distillation plays an important role in reducing the cost of methanol production and the economic benefits of enterprises. At present, the three-tower double-effect methanol distillation scheme has been widely used in my country's industrial methanol production. This scheme uses pressurized tower top steam to drive the atmospheric tower reboiler. The atmospheric tower does not require saturated steam, but the pre-distillation tower reboiler still requires saturated steam as a heat source. Therefore, the energy consumption of the methanol distillation unit is still at a high level. Summary of the invention

[0003] Under this technical background, in order to reduce energy consumption, the present invention proposes for the first time an innovative four-tower double heat sink double-effect methanol distillation energy-saving device and process. The process uses the pre-distillation tower and the vacuum distillation tower as double heat sinks, and the top steam of the high-pressure distillation tower as the heat source to realize distributed double-effect distillation, including a pre-distillation tower, a vacuum distillation tower, a high-pressure distillation tower and a recovery tower, which introduces a new structure and operation mode for the methanol distillation process. In the present invention, the unit steam consumption of refined methanol production is reduced by 10-20% compared with the TOPSOE four-tower forward double effect.

[0004] A technical solution proposed by the present invention is a four-tower reverse double heat sink double-effect methanol distillation energy-saving device, comprising a pre-distillation tower, a vacuum distillation tower, a high-pressure distillation tower, and a recovery tower connected in sequence, the lower part of the pre-distillation tower is connected with a pre-distillation tower reboiler 1 and a pre-distillation tower reboiler 2, the lower parts of the vacuum distillation tower and the high-pressure distillation tower are respectively connected with a vacuum distillation tower reboiler and a high-pressure distillation tower reboiler, and the lower part of the recovery tower is connected with a recovery tower reboiler 1 and a recovery tower reboiler 2. Part of the gas at the top of the high-pressure distillation tower heats the vacuum distillation tower reboiler, and part of the gas heats the pre-distillation tower reboiler 2. A small part of the top gas passes through the vacuum distillation tower top vacuum jet pump and the recovery tower top vacuum jet pump to the pre-distillation tower to generate low pressure, thereby realizing negative pressure of the vacuum distillation tower and the recovery tower, and the high-temperature wastewater produced at the bottom of the high-pressure distillation tower heats the recovery tower reboiler 1.

[0005] As a preferred solution, the bottom of the vacuum distillation tower (T2) serves as a low-temperature heat sink with a temperature of 70-75°C.

[0006] As a preferred solution, high-temperature wastewater is extracted from the bottom of the high-pressure distillation tower (T3).

[0007] As a preferred solution, fuel alcohol is extracted from the bottom of the recovery tower (T4).

[0008] As a preferred solution, the temperature of the high-temperature wastewater produced from the bottom of the high-pressure distillation tower (T3) is 140±10°C, and the temperature of the fuel alcohol produced from the bottom of the recovery tower (T4) is 80-85°C.

[0009] As a preferred solution, refined methanol is extracted from the top of the vacuum distillation tower (T2) and the high-pressure distillation tower (T3).

[0010] As a preferred solution, the unit steam consumption of the process is slightly lower than that of the four-tower forward distributed double-effect process.

[0011] As a preferred solution, the unit steam consumption of the process is reduced by 10-20% compared with the TOPSOE four-tower forward double-effect process.

[0012] As a preferred embodiment, the process comprises a vacuum tower vacuum jet pump (P1) and a recovery tower vacuum jet pump (P2), and 2% of the steam at the top of the high-pressure distillation tower (T3) is sent to the pre-distillation tower (T1) via the vacuum tower vacuum jet pump (P1) and the recovery tower vacuum jet pump (P2).

[0013] Another technical solution provided by the present invention is a process method based on the above-mentioned four-tower reverse double heat trap double-effect methanol distillation energy-saving device, comprising a pre-distillation tower (T1), a vacuum distillation tower (T2), a high-pressure distillation tower (T3), and a recovery tower (T4) connected in sequence, using a distributed double-effect distillation technology, including the following steps:

[0014] 1) The raw material crude methanol flows into a pre-distillation tower (T1), and the steam at the top of the tower is partially condensed to separate the light component non-condensable steam; part of the stream at the bottom of the pre-distillation tower (T1) flows into the reboiler 1 (R1A) of the pre-distillation tower to be heated by steam, and another part of the stream flows into the reboiler 2 (R1B) of the pre-distillation tower to be heated by part of the top gas of the high-pressure distillation tower (T3), and flows into the pre-distillation tower (T1) after being heated and vaporized, and the remaining stream flows into the middle and lower part of the vacuum distillation tower (T2) for separation;

[0015] 2) After full condensation, part of the vapor at the top of the vacuum distillation tower (T2) is refluxed, and part of it flows out of the boundary area as a refined methanol product; the bottom stream of the vacuum distillation tower (T2) flows into the reboiler (R2) of the vacuum distillation tower, is heated by the gas phase at the top of the high-pressure distillation tower (T3), and flows into the vacuum distillation tower (T2) after being heated and vaporized; the remaining stream of the bottom stream of the vacuum distillation tower (T2) flows into the middle and lower part of the high-pressure distillation tower (T3) for separation;

[0016] 3) A portion of the steam from the top of the high-pressure distillation tower (T3) is used to heat the reboiler 2 (R1B) of the pre-distillation tower and then condensed and refluxed, and the other portion of the steam is used to heat the reboiler (R2) of the vacuum distillation tower and then condensed and refluxed, and the refluxed stream flows out of the boundary area as the refined methanol product; the side line produced stream of the stripping section of the high-pressure distillation tower (T3) enters the recovery tower (T4) for separation; the high-temperature waste water produced from the bottom of the high-pressure distillation tower (T3) is used to heat the reboiler 1 (R4A) of the recovery tower and then flows out of the boundary area.

[0017] 4) After full condensation, part of the steam from the top of the recovery tower (T4) is refluxed, part of it is used as refined methanol to produce a boundary area, and fuel alcohol is produced from the bottom of the tower and flows out of the boundary area.

[0018] As a preferred embodiment, the operating pressure of the pre-distillation tower (T1) is 150 kPa; the operating pressure of the vacuum distillation tower (T2) is 55 kPa, and the reflux ratio is 1.5; the operating pressure of the high-pressure distillation tower (T3) is 350 kPa, and the reflux ratio is 2; the temperature of the wastewater extracted from the bottom of the high-pressure distillation tower (T3) is 140°C, and the methanol content is less than 50 ppm; the operating pressure of the recovery tower (T4) is 65 kPa, and the reflux ratio is 5; the temperature of the fuel alcohol extracted from the bottom of the recovery tower (T4) is 80°C.

[0019] As a preferred solution, the process includes a vacuum tower vacuum jet pump (P1) and a recovery tower vacuum jet pump (P2), and 2% of the steam at the top of the high-pressure distillation tower (T3) is sent to the pre-distillation tower (T1) via the vacuum tower vacuum jet pump (P1) and the recovery tower vacuum jet pump (P2).

[0020] As a preferred solution, the temperature of the high-temperature wastewater extracted from the bottom of the high-pressure distillation tower (T3) is 140±10°C.

[0021] As a preferred solution, the temperature of the fuel alcohol extracted from the bottom of the recovery tower (T4) is 80-85°C.

[0022] The present invention has the following advantages:

[0023] 1. The pre-distillation tower and vacuum distillation tower are used as double heat sinks. Part of the gas phase at the top of the high-pressure distillation tower heats the reboiler of the vacuum distillation tower, and part of the gas phase heats the second reboiler of the pre-distillation tower. A small part of the top gas goes to the pre-distillation tower through the vacuum jet pump at the top of the vacuum distillation tower and the vacuum jet pump at the top of the recovery tower to generate low pressure, thereby achieving negative pressure in the vacuum distillation tower and the recovery tower. The high-temperature wastewater produced at the bottom of the high-pressure distillation tower heats the first reboiler of the recovery tower to improve the distillation efficiency. The production capacity of refined methanol is dispersed, among which the refined methanol product is produced from the top of the vacuum distillation tower, the high-pressure distillation tower and the fuel alcohol recovery tower, with a high yield.

[0024] 2. The production capacity of refined methanol is dispersed, and refined methanol products are produced from the top of the vacuum distillation tower, high-pressure distillation tower and recovery tower with high yield.

[0025] 3. Both the pre-distillation tower and the recovery tower are under negative pressure, which reduces the heat sink temperature and reduces the temperature difference between the top and bottom of the tower.

[0026] 4. The process adopts distributed double-effect distillation technology, which makes full use of the waste heat at the top of the high-pressure distillation tower, reduces effective energy loss, and saves energy consumption.

[0027] 5. The unit steam consumption of producing refined methanol by the process of the present invention is reduced by 10-20% compared with the Haldor Topsoe process, thus achieving the goal of energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the process of the present invention;

[0029] T1 pre-distillation tower, T2 vacuum distillation tower, T3 high-pressure distillation tower, T4 recovery tower, R1A pre-distillation tower reboiler 1, R1B pre-distillation tower reboiler 2, R2 vacuum distillation tower reboiler, R3 high-pressure distillation tower reboiler, R4A recovery tower reboiler 1, R4B recovery tower reboiler 2, C1 vacuum distillation tower condenser, C2 recovery tower condenser, D1 pre-distillation tower reflux tank, P1 vacuum distillation tower top jet vacuum pump, P2 recovery tower top jet vacuum pump. DETAILED DESCRIPTION

[0030] The following is combined with Figure 1 The specific implementation of the present invention is described in detail. It should be noted that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0031] Embodiment 1:

[0032] like Figure 1As shown, this embodiment provides a four-tower reverse double heat trap double-effect methanol distillation energy-saving device and process, including a pre-distillation tower T1, a vacuum distillation tower T2, a high-pressure distillation tower T3, and a recovery tower T4 connected in sequence. The present invention adopts a distributed double-effect distillation technology, and its process flow includes the following steps:

[0033] The raw material crude methanol flows into the pre-distillation tower T1, and the top steam is partially condensed to separate the light component non-condensable steam; part of the bottom stream of the pre-distillation tower T1 flows into the reboiler 1 R1A of the pre-distillation tower for heating by steam, and another part of the stream flows into the reboiler 2 R1B of the pre-distillation tower for heating by part of the top gas of the high-pressure distillation tower T3, and flows into the pre-distillation tower T1 after being heated and vaporized, and the remaining stream flows into the middle and lower part of the vacuum distillation tower T2 for separation.

[0034] The steam from the top of the vacuum distillation tower T2 is partially refluxed after full condensation, and part of it flows out of the boundary area as refined methanol product; the bottom stream of the vacuum distillation tower T2 flows into the reboiler R2 of the vacuum distillation tower, is heated by the partial gas phase from the top of the high-pressure distillation tower T3, and flows into the vacuum distillation tower T2 after being heated and vaporized; the remaining stream of the bottom stream of the vacuum distillation tower T2 flows into the middle and lower part of the high-pressure distillation tower T3 for separation.

[0035] Part of the steam from the top of the high-pressure distillation tower T3 is used to heat the reboiler R1B of the pre-distillation tower and then condensed and refluxed. The other part of the steam is used to heat the reboiler R2 of the vacuum distillation tower and then condensed and refluxed. The reflux logistics part flows out of the boundary area as the refined methanol product; the side line logistics of the stripping section of the high-pressure distillation tower T3 enters the recovery tower T4 for separation; the high-temperature waste water produced from the bottom of the high-pressure distillation tower T3 is used to heat the reboiler R4A of the recovery tower and then flows out of the boundary area.

[0036] After full condensation, part of the steam from the top of recovery tower T4 is refluxed, part of it is used as refined methanol to produce the boundary area, and fuel alcohol is produced from the bottom of the tower and flows out of the boundary area.

[0037] The operating pressure of the pre-distillation tower T1 is 150kPa; the operating pressure of the vacuum distillation tower T2 is 55kPa, and the reflux ratio is 1.5; the operating pressure of the high-pressure distillation tower T3 is 350kPa, and the reflux ratio is 2; the operating pressure of the recovery tower T4 is 65kPa, and the reflux ratio is 5. The temperature of the wastewater extracted from the bottom of the high-pressure distillation tower T3 is 140°C, and the methanol content is less than 50ppm; the temperature of the fuel alcohol extracted from the bottom of the recovery tower T4 is 80°C. The water content of the crude methanol raw material is about 4%.

[0038] Compared with the existing industrial process, the unit consumption of refined methanol production in this solution is reduced by 10-20%, the yield is 99.99%, and the purity of refined methanol is as high as 99.99%.

[0039] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings; however, the present invention is not limited to the specific details in the above embodiments; within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0040] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the various possible combinations of the present invention will not be described separately.

[0041] In addition, the various embodiments of the present invention may be arbitrarily combined, as long as they do not violate the concept of the present invention, and the invention should also be regarded as the content disclosed by the present invention.

Claims

1. A four-tower reverse double heat sink double-effect methanol distillation energy-saving device, characterized in that: The invention comprises a pre-distillation tower (T1), a vacuum distillation tower (T2), a high-pressure distillation tower (T3), and a recovery tower (T4) which are connected in sequence, wherein the lower part of the pre-distillation tower (T1) is connected with a pre-distillation tower reboiler 1 (R1A) and a pre-distillation tower reboiler 2 (R1B), the lower part of the vacuum distillation tower (T2) is connected with a vacuum distillation tower reboiler (R2), the lower part of the high-pressure distillation tower (T3) is connected with a high-pressure distillation tower reboiler (R3), the lower part of the recovery tower (T4) is connected with a recovery tower reboiler 1 (R4A) and a recovery tower Reboiler 2 (R4B); wherein, part of the gas at the top of the high-pressure distillation tower (T3) supplies heat to the reboiler (R2) of the vacuum distillation tower, and part of the gas supplies heat to the reboiler 2 (R1B) of the pre-distillation tower, and a small part of the top gas goes to the pre-distillation tower (T1) through the vacuum jet pump (P1) at the top of the vacuum distillation tower and the vacuum jet pump (P2) at the top of the recovery tower to generate low pressure, thereby achieving negative pressure in the vacuum distillation tower (T1) and the recovery tower (T4), and the high-temperature wastewater produced at the bottom of the high-pressure distillation tower (T4) supplies heat to the reboiler 1 (R4A) of the recovery tower.

2. A four-tower reverse double heat trap double-effect methanol distillation energy-saving device according to claim 1, characterized in that: The bottom of the vacuum distillation tower (T2) serves as a low-temperature heat sink with a temperature of 70-75°C.

3. A four-tower reverse double heat sink double-effect methanol distillation energy-saving device according to claim 1, characterized in that: High-temperature wastewater is produced at the bottom of the high-pressure distillation tower (T3).

4. A four-tower reverse double heat sink double-effect methanol distillation energy-saving device according to claim 1, characterized in that: The fuel alcohol is extracted from the bottom of the recovery tower (T4).

5. A four-tower reverse double heat sink double-effect methanol distillation energy-saving device according to claim 1, characterized in that: Refined methanol is extracted from the tops of the vacuum distillation tower (T2), the high-pressure distillation tower (T3) and the recovery tower (T4).

6. A process method for a four-tower reverse double-heat-trap double-effect methanol distillation energy-saving device according to any one of claims 1 to 5, comprising a pre-distillation tower (T1), a vacuum distillation tower (T2), a high-pressure distillation tower (T3), and a recovery tower (T4) connected in sequence, characterized in that: The distributed double-effect distillation technology is adopted, including the following steps: 1) The raw material crude methanol flows into a pre-distillation tower (T1), and the steam at the top of the tower is partially condensed to separate the light component non-condensable steam; part of the stream at the bottom of the pre-distillation tower (T1) flows into the reboiler 1 (R1A) of the pre-distillation tower to be heated by steam, and another part of the stream flows into the reboiler 2 (R1B) of the pre-distillation tower to be heated by part of the top gas of the high-pressure distillation tower (T3), and flows into the pre-distillation tower (T1) after being heated and vaporized, and the remaining stream flows into the middle and lower part of the vacuum distillation tower (T2) for separation; 2) After full condensation, part of the vapor at the top of the vacuum distillation tower (T2) is refluxed, and part of it flows out of the boundary area as a refined methanol product; the bottom stream of the vacuum distillation tower (T2) flows into the reboiler (R2) of the vacuum distillation tower, is heated by the gas phase at the top of the high-pressure distillation tower (T3), and flows into the vacuum distillation tower (T2) after being heated and vaporized; the remaining stream of the bottom stream of the vacuum distillation tower (T2) flows into the middle and lower part of the high-pressure distillation tower (T3) for separation; 3) A portion of the steam from the top of the high-pressure distillation tower (T3) is used to heat the reboiler 2 (R1B) of the pre-distillation tower and then condensed and refluxed, and another portion of the steam is used to heat the reboiler (R2) of the vacuum distillation tower and then condensed and refluxed, and the refluxed stream flows out of the boundary area as the refined methanol product; the side line production stream of the stripping section of the high-pressure distillation tower (T3) enters the recovery tower (T4) for separation; the high-temperature wastewater produced from the bottom of the high-pressure distillation tower (T3) is used to heat the reboiler 1 (R4A) of the recovery tower and then flows out of the boundary area; 4) After full condensation, part of the steam from the top of the recovery tower (T4) is refluxed, part of it is used as refined methanol to produce a boundary area, and fuel alcohol is produced from the bottom of the tower and flows out of the boundary area.

7. The process according to claim 6, characterized in that: The operating pressure of the pre-distillation tower (T1) is 150 kPa; the operating pressure of the vacuum distillation tower (T2) is 55 kPa, and the reflux ratio is 1.5; the operating pressure of the high-pressure distillation tower (T3) is 350 kPa, and the reflux ratio is 2; the temperature of the wastewater produced from the bottom of the high-pressure distillation tower (T3) is 140°C, and the methanol content is less than 50 ppm; the operating pressure of the recovery tower (T4) is 65 kPa, and the reflux ratio is 5; the temperature of the fuel alcohol produced from the bottom of the recovery tower (T4) is 80°C.

8. The process according to claim 6, characterized in that: The process includes a vacuum tower vacuum jet pump (P1) and a recovery tower vacuum jet pump (P2). 2% of the steam at the top of the high-pressure distillation tower (T3) goes to the pre-distillation tower (T1) through the vacuum tower vacuum jet pump (P1) and the recovery tower vacuum jet pump (P2).

9. The process according to claim 6, characterized in that: The temperature of the high-temperature wastewater extracted from the bottom of the high-pressure distillation tower (T3) is 140±10°C.

10. A four-tower reverse double-heat-sink double-effect methanol distillation energy-saving device according to claim 6, characterized in that: The temperature of the fuel alcohol extracted from the bottom of the recovery tower (T4) is 80-85°C.

Images