Five-tower reverse triple-effect heat pump assisted methanol rectification energy-saving device

Abstract

The utility model relates to a five-tower reverse triple-effect heat pump assisted methanol rectification energy-saving device, which is characterized in that a tower top steam recompression type heat pump is adopted by a normal-pressure rectification tower, and a tower bottom liquid phase flash evaporation type heat pump is adopted by a high-pressure rectification tower; part of the gas phase at the top of the normal-pressure rectifying tower is compressed and heated by a compressor at the top of the normal-pressure rectifying tower and then supplies heat to a reboiler I of the high-pressure rectifying tower to heat reduced-pressure wastewater at the bottom of the high-pressure rectifying tower to increase the gasification amount. The process is coupled with the heat pump assisted rectification and multi-effect rectification technology, the comprehensive COP value of a heat pump reaches 3.348, the unit production consumption of refined methanol is 0.25 steam unit consumption and 95kW power consumption, remarkable energy conservation of methanol rectification is realized, and the method is suitable for energy-saving transformation of the existing five-tower reverse double-hot-trap process.

Description

Technical Field

[0001] This utility model relates to the field of distillation technology, specifically to a five-tower reverse triple-effect heat pump assisted methanol distillation energy-saving device. Background Technology

[0002] Global warming has already occurred, and the increase in global temperature will lead to multiple concurrent hazards. Deep, rapid, and sustained emissions reductions can significantly reduce global warming over a period of about 20 years and can significantly alter the composition of the atmosphere within a few years.

[0003] Methanol plays multiple roles in modern chemical systems, serving as an important clean energy carrier and a key precursor for the synthesis of bulk chemicals such as formaldehyde and acetic acid. Industry statistics show that its global consumption ranks fourth among basic organic raw materials, after ethylene, propylene, and benzene. my country has a significant advantage in this field, possessing not only the world's largest cluster of production facilities but also being the largest consumer market. It is worth noting that the annual carbon emission equivalent of the entire industrial chain has reached 200 million tons, with the separation and purification stage being a high-energy-consuming node, accounting for approximately 25% of the total energy consumption. While the currently widely used co-current three-tower distillation process can ensure product purity standards, it has inherent deficiencies in thermodynamic efficiency, making it difficult to meet the requirements of green manufacturing in the new era. This necessitates the development of new separation technologies with greater energy efficiency advantages. Utility Model Content

[0004] To address the technical problems in the background art, this utility model proposes a five-tower reverse triple-effect heat pump-assisted methanol distillation energy-saving device, comprising a pre-distillation tower, an atmospheric distillation tower, a medium-pressure distillation tower, a high-pressure distillation tower, and a methanol recovery tower connected in sequence. The lower part of the pre-distillation tower is connected to two reboilers: a first pre-distillation tower reboiler, a second pre-distillation tower reboiler, a third atmospheric distillation tower reboiler, a fourth high-pressure distillation tower reboiler, and a fifth methanol recovery tower reboiler. The first vapor-phase branch at the top of the medium-pressure distillation tower heats the second pre-distillation tower reboiler, and the second vapor-phase branch at the top of the medium-pressure distillation tower heats the reboiler of the atmospheric distillation tower. The overhead vapor from the high-pressure distillation column heats the reboiler of the medium-pressure distillation column, while the high-temperature wastewater collected from the bottom of the high-pressure distillation column heats the reboiler of the methanol recovery column. The atmospheric distillation column uses a top vapor recompression heat pump, while the high-pressure distillation column uses a bottom liquid flash heat pump. A portion of the vapor from the top of the atmospheric distillation column is compressed and heated by the overhead compressor before being used to heat the reboiler of the high-pressure distillation column.

[0005] As a preferred embodiment, the high-pressure distillation column (T4) extracts high-temperature wastewater.

[0006] As a preferred embodiment, fuel alcohol is collected from the bottom of the methanol recovery tower (T5).

[0007] As a preferred embodiment, the high-temperature wastewater collected from the bottom of the high-pressure distillation tower (T4) is at a temperature of around 140°C, and the fuel alcohol collected from the bottom of the methanol recovery tower (T5) is at a temperature of 75-80°C.

[0008] As a preferred embodiment, refined methanol is collected from the top of the vacuum distillation column (T2), the medium-pressure distillation column (T3), the high-pressure distillation column (T4), and the methanol recovery column (T6).

[0009] As a preferred option, the process is suitable for energy-saving retrofitting of existing five-tower reverse (dual heat sink) processes.

[0010] As a preferred embodiment, the atmospheric distillation column (T2) employs a top vapor recompression heat pump, and the high-pressure distillation column (T4) employs a bottom liquid flash heat pump. A portion of the vapor phase at the top of the atmospheric distillation column (T2) is compressed and its temperature and grade are increased by the heat pump to heat the wastewater at the bottom of the high-pressure distillation column (T4), which has been depressurized and cooled. The heated and vaporized wastewater at the bottom of the high-pressure distillation column (T4) is then compressed by the compressor and returned to the bottom of the high-pressure distillation column (T4). The overall COP value of the heat pump reaches 3.348.

[0011] As a preferred embodiment, the residual load at the bottom of the high-pressure distillation column (T4) is heated by 0.5 MPa (G) steam.

[0012] As a preferred embodiment, the compression ratios of both the atmospheric distillation column top compressor (C1) and the high-pressure distillation column bottom compressor (C2) are less than 6, thus avoiding excessively high compression ratios.

[0013] As a preferred option, the process coupling relationship is relatively complex, requiring a carefully designed control scheme.

[0014] To reduce energy consumption, this invention proposes for the first time an innovative five-tower reverse triple-effect heat pump-assisted methanol distillation energy-saving device. The process couples heat pump-assisted distillation technology with multi-effect distillation technology, including a pre-distillation tower, an atmospheric distillation tower, a medium-pressure distillation tower, a high-pressure distillation tower, and a methanol recovery tower. The atmospheric distillation tower employs a top vapor recompression heat pump, while the high-pressure distillation tower uses a bottom liquid-phase flash heat pump, achieving bidirectional integration of the two heat pump technologies and introducing a new structure and operating method to the methanol distillation process. In this invention, the overall COP of the heat pump reaches 3.348, with a unit methanol production consumption of only 0.25 kW of steam and 95 kW of electricity, achieving significant energy savings in methanol distillation. It is suitable for energy-saving retrofitting of existing five-tower reverse (dual heat trap) processes.

[0015] This application has the following advantages:

[0016] 1. In this process, the atmospheric distillation column, medium-pressure distillation column, and high-pressure distillation column form a counter-current triple-effect system. Simultaneously, the pre-distillation column and methanol recovery column act as heat sinks. The first vapor phase branch at the bottom of the medium-pressure distillation column heats the second reboiler of the pre-distillation column, and the high-temperature wastewater collected from the bottom of the high-pressure distillation column heats the reboiler of the methanol recovery column. Furthermore, the process employs heat pump-assisted distillation technology. The atmospheric distillation column uses a top vapor recompression heat pump, and the high-pressure distillation column uses a bottom liquid flash heat pump. A portion of the vapor phase at the top of the atmospheric distillation column is compressed and its temperature and grade are increased by the heat pump to heat the wastewater from the bottom of the high-pressure distillation column, which has been depressurized and cooled, thereby increasing the vaporization rate.

[0017] 2. The production capacity of refined methanol is dispersed. Among them, the top of the atmospheric distillation tower, medium-pressure distillation tower, high-pressure distillation tower and methanol recovery tower produce refined methanol products with high yield. The tower equipment is small in size, which is convenient for manufacturing, transportation and installation.

[0018] 3. The compression ratios of both the overhead compressor of the atmospheric distillation column and the bottom compressor of the high-pressure distillation column are less than 6, thus avoiding excessively high compression ratios.

[0019] 4. The process couples heat pump-assisted distillation technology with multi-effect distillation technology, making full use of waste heat. The overall COP value of the heat pump reaches 3.348, and the unit methanol production has a steam consumption of only 0.25 kW and an electricity consumption of 95 kW, achieving the goal of energy saving. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the process of this application;

[0021] T1 Pre-distillation column, T2 Atmospheric distillation column, T3 Medium-pressure distillation column, T4 High-pressure distillation column, T5 Methanol recovery column, R1A Pre-distillation column reboiler 1, R1B Pre-distillation column reboiler 2, R2 Atmospheric distillation column reboiler, R3 Medium-pressure distillation column reboiler, R4A High-pressure distillation column reboiler 1, R4B High-pressure distillation column reboiler 2, R5 Methanol recovery column reboiler, CX1 Atmospheric distillation column condenser, CX2 Medium-pressure distillation column condenser, CX3 High-pressure distillation column condenser, CX4 Methanol recovery column condenser, D1 Pre-distillation column reflux tank, C1 Atmospheric distillation column top compressor, C2 High-pressure distillation column bottom compressor, V1 Pressure reducing valve. Detailed Implementation

[0022] The following is in conjunction with the appendix Figure 1 The specific embodiments of this utility model will be described in detail below. It should be noted that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of this utility model.

[0023] Example 1:

[0024] like Figure 1As shown, this embodiment provides a five-tower reverse triple-effect heat pump assisted methanol distillation energy-saving device, including a pre-distillation tower T1, an atmospheric distillation tower T2, a medium-pressure distillation tower T3, a high-pressure distillation tower T4, and a methanol recovery tower T5 connected in sequence. This invention, through careful process design, achieves bidirectional coupling between the top vapor recompression heat pump and the bottom liquid-phase flash heat pump, further improving energy efficiency by combining multi-effect distillation technology. Its process flow includes the following steps:

[0025] 1) The raw material, crude methanol, flows into the pre-distillation column T1. The vapor at the top of the column is partially condensed to separate light non-condensable components. Part of the bottom stream of the pre-distillation column T1 flows into the reboiler R1A of the pre-distillation column and is heated by steam. The other part of the stream flows into the reboiler R1B of the pre-distillation column and is heated by the first gas phase branch at the top of the medium-pressure distillation column T3. After being heated and vaporized, it flows into the pre-distillation column T1. The remaining stream flows into the lower part of the atmospheric distillation column T2 for separation.

[0026] 2) The vapor phase at the top of the atmospheric distillation column T2 is compressed and heated by the compressor C1 at the top of the atmospheric distillation column to heat the reboiler of the high-pressure distillation column. The remaining vapor phase at the top of the atmospheric distillation column T2 is completely condensed in the condenser CX1 of the atmospheric distillation column, and part of it is refluxed and part of it flows out of the boundary area as refined methanol product. The bottom stream of the atmospheric distillation column T2 flows into the reboiler R2 of the atmospheric distillation column and is heated by the second vapor phase branch at the top of the medium-pressure distillation column T3. After being heated and vaporized, it flows into the atmospheric distillation column T2. ​​The remaining stream flows into the lower part of the medium-pressure distillation column T3 for separation.

[0027] 3) The first vapor branch at the top of the medium-pressure distillation column T3 supplies heat to the reboiler of the pre-distillation column, and the second vapor branch supplies heat to the reboiler of the atmospheric distillation column. After being heated, the vapor flows back to the condenser CX2 of the medium-pressure distillation column. After total condensation, part of the vapor is refluxed, and part of it flows out of the boundary area as refined methanol product. The bottom stream of the medium-pressure distillation column T3 flows into the reboiler R3 of the medium-pressure distillation column. It is heated by part of the steam at the top of the high-pressure distillation column. After being heated and vaporized, it flows into the medium-pressure distillation column T3. The remaining stream flows into the lower part of the high-pressure distillation column T4 for separation.

[0028] 4) The top steam of the high-pressure distillation column T4 is used to heat the reboiler R3 of the medium-pressure distillation column; the bottom stream of the high-pressure distillation column T4 flows into the high-pressure distillation column reboiler R4A after being depressurized and flashed by the pressure reducing valve V1, and is heated by the compressed gas phase at the top of the medium-pressure distillation column T2. ​​After being heated, it is compressed by the compressor C2 at the bottom of the high-pressure distillation column and enters the bottom of the high-pressure distillation column T4. The other stream flows into the high-pressure distillation column reboiler R4B and is heated by steam. After being heated and vaporized, it flows into the high-pressure distillation column T4. The high-temperature wastewater collected at the bottom of the column is used to heat the methanol recovery column reboiler R5 before flowing out of the boundary area.

[0029] 5) The top steam of the T5 methanol recovery tower is partially refluxed after complete condensation, and part of it flows out of the boundary as refined methanol product. The bottom stream flows out of the boundary as fuel alcohol product.

[0030] The operating pressure of the pre-distillation column T1 is 150 kPa; the operating pressure of the atmospheric distillation column T2 is 100 kPa and the reflux ratio is 1.5; the operating pressure of the medium-pressure distillation column T3 is 320 kPa and the reflux ratio is 2; the operating pressure of the high-pressure distillation column T4 is 600 kPa and the reflux ratio is 2; and the operating pressure of the methanol recovery column T5 is 100 kPa and the reflux ratio is 3.5.

[0031] The wastewater collected from the bottom of the high-pressure distillation column T4 has a temperature of 140°C and a methanol content of less than 50 ppm; the fuel alcohol collected from the bottom of the methanol recovery column T5 has a temperature of 78.6°C.

[0032] The crude methanol feedstock has a water content of about 4%.

[0033] Compared with existing industrial processes, this solution consumes only 0.25 kW of steam and 95 kW of electricity per unit of refined methanol, with a yield of 99.99% and a purity of 99.99% for the refined methanol.

[0034] The preferred embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0035] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the various possible combinations in this application will not be described separately.

[0036] Furthermore, various different implementations of this application can be combined in any way, as long as they do not violate the spirit of this application, and such combinations should also be regarded as the content disclosed in this application.

Claims

1. A five-column reverse triple-effect heat pump assisted methanol rectification energy-saving device, characterized in that, The process comprises pre-distillation column (T1), atmospheric distillation column (T2), medium pressure distillation column (T3), high pressure distillation column (T4), methanol recovery column (T5) connected in sequence; the first gas phase branch of the medium pressure distillation column (T3) top provides heat for pre-distillation column reboiler two (R1B), the second gas phase branch of the medium pressure distillation column (T3) top provides heat for atmospheric distillation column reboiler (R2); The gas phase of the high pressure distillation column (T4) top provides heat for medium pressure distillation column reboiler (R3), the high temperature waste water of the high pressure distillation column (T4) bottom provides heat for methanol recovery column reboiler (R5); The atmospheric distillation column (T2) adopts top vapor recompression heat pump, the partial gas phase of the atmospheric distillation column (T2) top is compressed and heated by atmospheric distillation column top compressor (C1) to provide heat for high pressure distillation column reboiler one (R4A); The high pressure distillation column (T4) adopts bottom liquid flash heat pump, the high pressure distillation column (T4) bottom material is heated and gasified, then returned to the bottom through high pressure distillation column bottom compressor (C2).

2. The five-column reverse triple-effect heat pump assisted methanol rectification energy-saving device according to claim 1, characterized in that, The lower part of the pre-distillation column (T1) is connected with pre-distillation column reboiler one (R1A) and pre-distillation column reboiler two (R1B), the lower part of the atmospheric distillation column (T2) is connected with atmospheric distillation column reboiler (R2), the lower part of the medium pressure distillation column (T3) is connected with medium pressure distillation column reboiler (R3), the lower part of the high pressure distillation column (T4) is connected with high pressure distillation column reboiler one (R4A) and high pressure distillation column reboiler two (R4B), the lower part of the methanol recovery column (T5) is connected with methanol recovery column reboiler (R5).

3. The five-column reverse triple-effect heat pump assisted methanol rectification energy-saving device according to claim 1, characterized in that, The high temperature waste water of the high pressure distillation column (T4) bottom is discharged.

4. The five-column reverse triple-effect heat pump assisted methanol rectification energy-saving device according to claim 1, characterized in that, The fuel alcohol of the methanol recovery column (T5) bottom is discharged.

5. The five-tower reverse triple-effect heat pump assisted methanol distillation energy-saving device according to claim 1, characterized in that, The refined methanol of the atmospheric distillation column (T2), medium pressure distillation column (T3), high pressure distillation column (T4) and methanol recovery column (T5) top is discharged.

6. The energy-saving device of claim 1, wherein the device further comprises a fifth tower. It is suitable for energy saving reconstruction of existing five-column reverse double heat sink process.

7. The five-tower reverse triple-effect heat pump assisted methanol distillation energy-saving device according to claim 1, characterized in that, The atmospheric distillation column (T2) adopts top vapor recompression heat pump, the high pressure distillation column (T4) adopts bottom liquid flash heat pump, the partial gas phase of the atmospheric distillation column (T2) top is compressed and heated by heat pump to provide heat for the high pressure distillation column (T4) bottom material waste water which is reduced in pressure and temperature, the high pressure distillation column (T4) bottom material which is gasified after heating is returned to the high pressure distillation column (T4) bottom through compressor.

8. The five-column inverse triple-effect heat pump assisted methanol rectifying energy-saving device according to claim 1, characterized in that, The remaining load of the high pressure distillation column (T4) bottom is provided by 0.5Mpa (G) steam.

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