Six-tower reverse triple-effect methanol rectification device and method

Abstract

The six-tower reverse triple-effect methanol rectification device comprises a pre-rectification tower, a high-pressure rectification tower, a medium-pressure rectification tower, a normal-pressure rectification tower, a recovery tower and a methanol-ethanol separation tower which are connected in sequence, and a gas phase at the top of the high-pressure rectification tower supplies heat to a reboiler of the medium-pressure rectification tower. One branch gas phase at the top of the medium-pressure rectifying tower supplies heat to the pre-rectifying tower reboiler II, and the other branch gas phase supplies heat to the normal-pressure rectifying tower reboiler. According to the process, backmixing and repeated heating are reduced by designing a side line of a pre-rectifying tower and controlling the ratio of methanol to ethanol at the bottom of the tower, waste heat is fully recovered by adopting a multi-effect rectifying technology, the unit production consumption of refined methanol in the process is 0.5-0.6 steam unit consumption, remarkable energy conservation of methanol rectification is realized, and the process is suitable for a large methanol device of more than 1 million tons.

Description

Technical Field

[0001] The present invention relates to the technical field of distillation, and in particular to a six-tower reverse triple-effect methanol distillation device and method. Background Art

[0002] Methanol is an important basic organic chemical raw material and fuel resource with excellent properties. It is widely used in industries such as organic synthesis, dyes, pharmaceuticals, pesticides, coatings, transportation, and national defense, ranking fourth in global chemical raw material consumption. With the continuous advancement of modern science and technology and the global energy structure, new methods for producing high-purity methanol are emerging, but distillation remains the preferred method for improving methanol purity. However, distillation consumes a high amount of energy, accounting for approximately 20% of the total energy consumption in methanol production. Therefore, technologies that reduce the energy consumption of methanol distillation are crucial for lowering methanol production costs and improving the economic benefits of enterprises. Currently, a three-tower, dual-effect methanol distillation solution has been widely adopted in industrial methanol production in my country. This solution uses pressurized overhead steam to drive the atmospheric column reboiler. While the atmospheric column does not require saturated steam, the pre-distillation column reboiler still requires saturated steam as a heat source. Furthermore, to ensure the quality of the overhead and bottom products, a fusel oil stream is produced in the middle section of the atmospheric column. Currently, the byproduct fusel oil has been listed as a national hazardous waste. Therefore, the coal-based methanol distillation process needs to be improved accordingly, converting it to anhydrous mixed alcohol fuel with a water content of less than 1000ppm to avoid the production of fusel oil. Furthermore, the energy efficiency of this distillation process can be further improved. Summary of the Invention

[0003] In order to solve the technical problems in the background technology, the present invention proposes a six-tower reverse three-effect methanol distillation device and method.

[0004] The six-tower reverse triple-effect methanol distillation energy-saving device of the present invention comprises a pre-rectifying tower (T1), a high-pressure rectifying tower (T2), a medium-pressure rectifying tower (T3), an atmospheric distillation tower (T4), a recovery tower (T5), and a methyl ethanol separation tower (T6) connected in sequence, wherein the lower portion of the pre-rectifying tower (T1) is connected to a pre-rectifying tower reboiler 1 (R1A) and a pre-rectifying tower reboiler 2 (R1B), the lower portion of the high-pressure rectifying tower (T2) is connected to a high-pressure rectifying tower reboiler (R2), the lower portion of the medium-pressure rectifying tower (T3) is connected to a medium-pressure rectifying tower reboiler (R3), the lower portion of the atmospheric distillation tower (T4) is connected to an atmospheric distillation tower reboiler (R4), the lower portion of the recovery tower (T5) is connected to a recovery tower reboiler (R5), and the lower portion of the methyl ethanol separation tower (T6) is connected to a methyl ethanol separation tower reboiler (R6);

[0005] As a preferred solution, the overhead gas from the high-pressure distillation tower (T2) provides heat to the reboiler (R3) of the medium-pressure distillation tower, and part of the heat is refluxed after condensation, and part of the heat is used as a refined methanol product to flow out of the boundary area;

[0006] As a preferred solution, a branch gas phase at the top of the medium-pressure distillation tower (T3) supplies heat to the second reboiler (R1B) of the pre-distillation tower, and after the heat is supplied, it flows out of the boundary area as the refined methanol product; another branch gas phase supplies heat to the reboiler (R4) of the atmospheric distillation tower, and after the heat is condensed, part of it refluxes, and part of it flows out of the boundary area as the refined methanol product;

[0007] As a preferred solution, the overhead stream of the atmospheric distillation tower (T4) is cooled and completely condensed, and part of it is refluxed, and part of it flows out of the boundary area as a refined methanol product;

[0008] As a preferred solution, the bottom stream of the atmospheric distillation tower (T4) is heated and vaporized and then flows into the vacuum distillation tower (T4), and the remaining stream flows out of the boundary area as wastewater;

[0009] As a preferred solution, the atmospheric distillation tower (T4) utilizes back-mixing in the tower to advance the side-line extraction flow into the recovery tower (T5) for separation.

[0010] As a preferred solution, refined methanol is extracted from the tops of the high-pressure distillation tower (T2), the medium-pressure distillation tower (T3), the atmospheric-pressure distillation tower (T4) and the methyl-ethanol separation tower (T6).

[0011] As a preferred solution, the top stream of the recovery tower (T5) is cooled with cooling water and completely condensed, and then part of it is refluxed and part of it flows into the methyl ethanol separation tower (T6). The bottom stream is heated by steam, heated and vaporized, and then flows into the recovery tower (T5). The remaining stream flows out of the boundary area as wastewater.

[0012] As a preferred solution, the top vapor of the methyl ethanol separation tower (T6) is partially refluxed after full condensation, and part of it flows out of the boundary area as the refined methanol product, and the bottom flow flows out of the boundary area as the fuel alcohol product.

[0013] The second technical solution of the present invention is a process method using the above-mentioned device, comprising the following steps:

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

[0015] Secondly, the overhead steam from the high-pressure distillation tower (T2) is used to heat the reboiler R3 of the medium-pressure distillation tower. After condensation, part of the heat is refluxed, and part flows out of the boundary area as the refined methanol product. The bottom stream of the high-pressure distillation tower (T2) is heated and vaporized by steam and flows into the high-pressure distillation tower (T2). The remaining stream flows into the middle and lower part of the medium-pressure distillation tower (T3) for separation.

[0016] A portion of the overhead steam from the medium-pressure distillation tower (T3) is used to heat the reboiler 2 of the pre-distillation tower, and after the heat is supplied, it flows out of the boundary area as the refined methanol product. Another portion of the overhead steam is used to heat the reboiler R4 of the atmospheric distillation tower, and after the heat is condensed, part of it is refluxed, and part of it flows out of the boundary area as the refined methanol product. The bottom stream of the medium-pressure distillation tower (T3) is heated and vaporized, and then flows into the medium-pressure distillation tower (T3). The remaining stream flows into the middle and lower part of the atmospheric distillation tower (T4) for separation.

[0017] The overhead stream of the atmospheric distillation tower (T4) is cooled and completely condensed, and part of it is refluxed, and part of it flows out of the boundary area as the refined methanol product; the side-line produced stream of the stripping section of the atmospheric distillation tower (T4) enters the recovery tower (T5) for separation; the bottom stream of the atmospheric distillation tower (T4) is heated and vaporized, and then flows into the vacuum distillation tower (T4), and the remaining stream flows out of the boundary area as wastewater;

[0018] The top stream of the recovery tower (T5) is cooled and condensed, and part of it is refluxed, and part of it flows into the methyl ethanol separation tower (T6). The bottom stream is heated by steam, heated and vaporized, and then flows into the recovery tower (T5). The remaining stream flows out of the boundary area as wastewater.

[0019] The top vapor of the methyl ethanol separation tower (T6) is partially refluxed after full condensation, and part of it flows out of the boundary area as the refined methanol product, and the bottom flow flows out of the boundary area as the fuel alcohol product.

[0020] Furthermore, the operating pressure of the pre-distillation tower (T1) is 150±5kPa; the operating pressure of the high-pressure distillation tower (T2) is 600±5kPa, and the reflux ratio is 1.5-2; the operating pressure of the medium-pressure distillation tower (T3) is 320±5kPa, and the reflux ratio is 2-3; the operating pressure of the atmospheric distillation tower (T4) is 101±5kPa, and the reflux ratio is 2-3; the operating pressure of the recovery tower (T5) is 50±5kPa, and the reflux ratio is 4-5; the operating pressure of the methyl ethanol separation tower (T6) is 50±5kPa, and the reflux ratio is 3-4.

[0021] Furthermore, the temperature of the wastewater extracted from the bottom of the recovery tower (T5) is 80±5°C.

[0022] Furthermore, the temperature of the fuel alcohol extracted from the bottom of the methyl ethanol separation tower (T6) is 60-65°C.

[0023] Furthermore, it is applicable to large-scale methanol plants with a capacity of more than 1 million tons.

[0024] As a preferred solution, the process has lower requirements on steam quality, and the bottom load of the high-pressure distillation tower (T2) is heated by 0.5 MPa (G) steam.

[0025] As a preferred solution, the process has a high methanol yield and reduces the organic matter content in the wastewater.

[0026] The present invention offers the following advantages: To reduce energy consumption, it proposes an innovative six-tower reverse triple-effect methanol distillation apparatus and method, introducing a new structure and operating method for the methanol distillation process. The process produces no fusel oil by-products, and the unit steam consumption per unit of refined methanol production is only 0.6-0.7, achieving significant energy savings in methanol distillation. The process is suitable for large-scale methanol plants with a capacity of over 1 million tons.

[0027] 1. The overhead gas from the medium-pressure distillation tower provides heat to the reboiler of the pre-distillation tower and the reboiler of the atmospheric distillation tower, making full use of waste heat to achieve the goal of energy saving.

[0028] 2. The atmospheric distillation tower uses back mixing in the tower to advance the side-line extraction logistics into the recovery tower for separation, removing part of the water, avoiding repeated heating of the water, and removing part of the ethanol to reduce the difficulty of subsequent separation.

[0029] 3. The production capacity of refined methanol is dispersed, with refined methanol products extracted from the top of the high-pressure distillation tower, medium-pressure distillation tower, atmospheric distillation tower and methyl ethanol separation tower. The yield is high and the tower equipment is small in size, which is easy to manufacture, transport and install.

[0030] 4. The atmospheric distillation tower, recovery tower and methyl ethanol separation tower are all operated at atmospheric pressure, which reduces the steam quality requirements and reduces the temperature difference between the top and bottom of the tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic flow diagram of the present invention;

[0032] T1 pre-distillation tower, T2 high-pressure distillation tower, T3 medium-pressure distillation tower, T4 atmospheric distillation tower, T5 recovery tower, T6 methyl ethanol separation tower, R1A pre-distillation tower reboiler 1, R1B pre-distillation tower reboiler 2, R2 high-pressure distillation tower reboiler, R3 medium-pressure distillation tower reboiler, R4 atmospheric distillation tower reboiler, R5 recovery tower reboiler, R6 methyl ethanol separation tower reboiler, CX1 high-pressure distillation tower condenser, CX2 medium-pressure tower condenser, CX3 atmospheric pressure tower condenser, CX4 recovery tower condenser, CX5 methyl ethanol separation tower condenser, D1 pre-distillation tower reflux tank. DETAILED DESCRIPTION

[0033] The following is combined with Figure 1The specific embodiments of the present invention are described in detail. It should be noted that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0034] Example:

[0035] like Figure 1 As shown, this embodiment provides a six-tower reverse triple-effect methanol distillation device, including a pre-distillation tower T1, a high-pressure distillation tower T2, a medium-pressure distillation tower T3, an atmospheric distillation tower T4, a recovery tower T5, and a methyl ethanol separation tower T6 connected in sequence. The process method of the present invention adopts reverse triple-effect distillation technology, and its process flow includes the following steps:

[0036] First, the raw material crude methanol flows into the pre-distillation tower T1, the top steam is partially condensed to separate the light component non-condensable steam, and the condensate is returned to the pre-distillation tower T1; part of the flow at the bottom of the pre-distillation tower T1 flows into the pre-distillation tower reboiler R1A for steam heating, and another part of the flow flows into the pre-distillation tower reboiler R1B and is heated by the top gas from the top of the medium-pressure distillation tower T3. After heating and vaporization, it flows into the pre-distillation tower T1, and the remaining flow flows into the middle and lower part of the high-pressure distillation tower T2 for separation.

[0037] The steam from the top of the high-pressure distillation tower T2 is used to heat the reboiler R3 of the medium-pressure distillation tower. After the heat is condensed, part of it refluxes, and part of it flows out of the boundary area as the refined methanol product; the bottom flow of the high-pressure distillation tower T2 flows into the reboiler R2 of the high-pressure distillation tower and is heated by steam. After heating and vaporization, it flows into the high-pressure distillation tower T2, and the remaining flow flows into the middle and lower part of the medium-pressure distillation tower T3 for separation.

[0038] Part of the overhead steam of the medium-pressure distillation tower T3 is used to provide heat for the second reboiler R1B of the pre-distillation tower, and after the heat is provided, it flows out of the boundary area as the refined methanol product. The other part of the overhead steam is used to provide heat for the reboiler R4 of the atmospheric distillation tower, and after the heat is condensed, part of it is refluxed, and part of it flows out of the boundary area as the refined methanol product; the bottom stream of the medium-pressure distillation tower T3 flows into the medium-pressure distillation tower reboiler R3, and is heated by the overhead steam of the high-pressure distillation tower T2. After being heated and vaporized, it flows into the medium-pressure distillation tower T3, and the remaining stream flows into the middle and lower part of the atmospheric distillation tower T4 for separation.

[0039] The overhead stream of the atmospheric distillation tower T4 is completely condensed by process cooling water, and part of it is refluxed, and part of it flows out of the boundary area as the refined methanol product; the side line produced stream of the stripping section of the atmospheric distillation tower T4 enters the recovery tower T5 for separation; the bottom stream of the atmospheric distillation tower T4 flows into the reboiler R4 of the vacuum distillation tower, is heated by the steam from the overhead of the medium-pressure distillation tower T3, and flows into the vacuum distillation tower T4 after being heated and vaporized, and the remaining stream flows out of the boundary area as wastewater.

[0040] The top stream of the recovery tower T5 is completely condensed by process cooling water and partially refluxed, and partially flows into the methyl ethanol separation tower T6. The bottom stream flows into the recovery tower reboiler R5 and is heated by steam. After heating and vaporization, it flows into the recovery tower T5, and the remaining stream flows out of the boundary area as wastewater.

[0041] After full condensation, part of the vapor from the top of the methyl ethanol separation tower T6 is refluxed, part of it flows out of the boundary area as the refined methanol product, and the bottom flow flows out of the boundary area as the fuel alcohol product.

[0042] The operating pressure of the pre-distillation tower T1 is 150±5kPa; the operating pressure of the high-pressure distillation tower T2 is 600±5kPa, and the reflux ratio is 1.5-2; the operating pressure of the medium-pressure distillation tower T3 is 320±5kPa, and the reflux ratio is 2-3; the operating pressure of the atmospheric distillation tower T4 is 101±5kPa, and the reflux ratio is 2-3; the operating pressure of the recovery tower T5 is 50±5kPa, and the reflux ratio is 4-5; the operating pressure of the methyl ethanol separation tower T6 is 50±5kPa, and the reflux ratio is 3-4.

[0043] The temperature of the wastewater extracted from the bottom of the atmospheric distillation tower T4 and the recovery tower T5 is 80±5°C, and the methanol content is less than 50ppm; the temperature of the fuel alcohol extracted from the bottom of the methyl ethanol separation tower T6 is 63.6±5°C.

[0044] The water content of the crude methanol raw material is about 4%.

[0045] Compared with the existing industrial process, the unit consumption of refined methanol production in this solution is 0.6-0.7 steam unit consumption, the yield is 99.99%, and the purity of refined methanol is as high as 99.99%.

[0046] 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, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0047] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the various possible combinations of the present invention will not be described separately.

[0048] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, the invention should also be regarded as the content disclosed by the present invention.

Claims

1. Six-tower reverse triple-effect methanol distillation device, characterized in that: The invention comprises a pre-rectification tower (T1), a high-pressure rectification tower (T2), a medium-pressure rectification tower (T3), an atmospheric distillation tower (T4), a recovery tower (T5), and a methyl ethanol separation tower (T6) connected in sequence, wherein the lower portion of the pre-rectification tower (T1) is connected to a pre-rectification tower reboiler 1 (R1A) and a pre-rectification tower reboiler 2 (R1B), the lower portion of the high-pressure rectification tower (T2) is connected to a high-pressure rectification tower reboiler (R2), the lower portion of the medium-pressure rectification tower (T3) is connected to a medium-pressure rectification tower reboiler (R3), the lower portion of the atmospheric distillation tower (T4) is connected to an atmospheric distillation tower reboiler (R4), the lower portion of the recovery tower (T5) is connected to a recovery tower reboiler (R5), and the lower portion of the methyl ethanol separation tower (T6) is connected to a methyl ethanol separation tower reboiler (R6); The overhead gas from the high-pressure distillation tower (T2) provides heat to the reboiler (R3) of the medium-pressure distillation tower, and part of the heat is refluxed after condensation, and part of the heat is used as a refined methanol product to flow out of the boundary area; A branch gas phase at the top of the medium-pressure distillation tower (T3) provides heat to the second reboiler (R1B) of the pre-distillation tower, and after the heat is provided, it flows out of the boundary area as the refined methanol product; another branch gas phase provides heat to the reboiler (R4) of the atmospheric distillation tower, and after the heat is condensed, part of it refluxes and part of it flows out of the boundary area as the refined methanol product; The overhead stream of the atmospheric distillation tower (T4) is cooled and completely condensed, and part of it is refluxed, and part of it flows out of the boundary area as the refined methanol product; The bottom stream of the atmospheric distillation tower (T4) is heated and vaporized and then flows into the vacuum distillation tower (T4), and the remaining stream flows out of the boundary area as wastewater; The atmospheric distillation tower (T4) uses back-mixing in the tower to advance the side-line extraction flow into the recovery tower (T5) for separation.

2. The device according to claim 1, characterized in that Refined methanol is extracted from the tops of the high-pressure distillation tower (T2), the medium-pressure distillation tower (T3), the atmospheric-pressure distillation tower (T4) and the methyl-ethanol separation tower (T6).

3. The device according to claim 1, characterized in that The top stream of the recovery tower (T5) is completely condensed by cooling water and partially refluxed, and partially flows into the methyl ethanol separation tower (T6). The bottom stream is heated by steam, heated and vaporized, and then flows into the recovery tower (T5). The remaining stream flows out of the boundary area as wastewater.

4. The device according to claim 1, characterized in that The top steam of the methyl ethanol separation tower (T6) is partially refluxed after full condensation, and part of it flows out of the boundary area as the refined methanol product, and the bottom stream flows out of the boundary area as the fuel alcohol product.

5. The process of the device according to claims 1 to 4, characterized in that: The steps include: First, the raw material crude methanol flows into the pre-distillation tower (T1), the overhead vapor is partially condensed to separate the light component non-condensable vapor, and the condensate is refluxed; part of the stream at the bottom of the pre-distillation tower (T1) flows into the pre-distillation tower reboiler 1 to be heated by steam, another part of the stream flows into the pre-distillation tower reboiler 2 to be heated by the overhead gas from the medium-pressure distillation tower (T3), and then flows into the pre-distillation tower (T1) after being heated and vaporized. The remaining stream flows into the middle and lower part of the high-pressure distillation tower (T2) for separation; Secondly, the overhead steam from the high-pressure distillation tower (T2) is used to heat the reboiler R3 of the medium-pressure distillation tower. After condensation, part of the heat is refluxed, and part flows out of the boundary area as the refined methanol product. The bottom stream of the high-pressure distillation tower (T2) is heated and vaporized by steam and flows into the high-pressure distillation tower (T2). The remaining stream flows into the middle and lower part of the medium-pressure distillation tower (T3) for separation. A portion of the overhead steam from the medium-pressure distillation tower (T3) is used to heat the reboiler 2 of the pre-distillation tower, and after the heat is supplied, it flows out of the boundary area as the refined methanol product. Another portion of the overhead steam is used to heat the reboiler R4 of the atmospheric distillation tower, and after the heat is condensed, part of it is refluxed, and part of it flows out of the boundary area as the refined methanol product. The bottom stream of the medium-pressure distillation tower (T3) is heated and vaporized, and then flows into the medium-pressure distillation tower (T3). The remaining stream flows into the middle and lower part of the atmospheric distillation tower (T4) for separation. The overhead stream of the atmospheric distillation tower (T4) is cooled and completely condensed, and part of it is refluxed, and part of it flows out of the boundary area as the refined methanol product; the side-line produced stream of the stripping section of the atmospheric distillation tower (T4) enters the recovery tower (T5) for separation; the bottom stream of the atmospheric distillation tower (T4) is heated and vaporized, and then flows into the vacuum distillation tower (T4), and the remaining stream flows out of the boundary area as wastewater; The top stream of the recovery tower (T5) is cooled and condensed, and part of it is refluxed, and part of it flows into the methyl ethanol separation tower (T6). The bottom stream is heated by steam, heated and vaporized, and then flows into the recovery tower (T5). The remaining stream flows out of the boundary area as wastewater; The top vapor of the methyl ethanol separation tower (T6) is partially refluxed after full condensation, and part of it flows out of the boundary area as the refined methanol product, and the bottom flow flows out of the boundary area as the fuel alcohol product.

6. The method according to claim 5, characterized in that The operating pressure of the pre-distillation tower (T1) is 150±5kPa; the operating pressure of the high-pressure distillation tower (T2) is 600±5kPa, and the reflux ratio is 1.5-2; the operating pressure of the medium-pressure distillation tower (T3) is 320±5kPa, and the reflux ratio is 2-3; the operating pressure of the atmospheric distillation tower (T4) is 101±5kPa, and the reflux ratio is 2-3; the operating pressure of the recovery tower (T5) is 50±5kPa, and the reflux ratio is 4-5; the operating pressure of the methyl ethanol separation tower (T6) is 50±5kPa, and the reflux ratio is 3-4.

7. The method according to claim 5, characterized in that The temperature of the wastewater taken out from the bottom of the recovery tower (T5) is 80±5°C.

8. The method according to claim 5, characterized in that The temperature of the fuel alcohol extracted from the bottom of the methyl ethanol separation tower (T6) is 60-65°C.

9. The method according to claim 5, characterized in that Applicable to large-scale methanol plants with a capacity of more than 1 million tons.

10. The method according to claim 5, characterized in that The bottom load of the high-pressure distillation tower (T2) is heated by 0.5 MPa (G) steam.

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