Optimized butane isomerization device

Abstract

The utility model relates to the technical field of butane isomerization treatment equipment, in particular to an optimized butane isomerization device, which comprises an upper deisobutane tower and a lower deisobutane tower, a tower bottom liquid phase of the upper deisobutane tower is pumped to the top of the lower deisobutane tower through a middle pump to be used as reflux of the lower deisobutane tower, a top gas phase of the lower deisobutane tower automatically flows into the bottom of the upper deisobutane tower, and an n-butane product is extracted from a lower side liquid phase of the upper deisobutane tower. The DIB tower is divided into the upper deisobutane tower and the lower deisobutane tower, the heights of the two towers are greatly reduced compared with that of one tower, the construction difficulty is reduced, meanwhile, the heat exchanger of the upper deisobutane tower is arranged, the steam consumption is greatly reduced, the gas phase load of the lower deisobutane tower is greatly reduced, the tower diameter of the lower tower is reduced, and the production cost is reduced. And the n-butane product is extracted from the liquid phase of the side line of the deisobutane upper tower, so that the load of a subsequent cooling system is reduced.

Description

Technical Field

[0001] This utility model relates to the technical field of butane isomerization equipment, specifically an optimized butane isomerization device. Background Technology

[0002] The isobutane dehydrogenation unit converts isobutane into isobutene, which is then used as a feedstock for MTBE, a high-octane gasoline blending component with high demand. The feedstock for the isobutane dehydrogenation unit is refined isobutane, which is relatively expensive. To expand feedstock sources and improve the unit's economic efficiency, a mixed butane system (typically containing 40%–98% n-butane, with the remainder being mainly isobutane and less than 1% of C3 and C5 components) with large market supply and lower prices is generally purchased. This isobutane is then isomerized into isobutane using a matching butane isomerization unit, which serves as the feedstock for isobutane dehydrogenation.

[0003] The main energy-consuming equipment in the butane isomerization unit is the deisobutane tower (DIB tower), such as... Figure 1 As shown, the column produces isobutane (>98.5%) at the top, n-butane (>96%) from the side stream, which is sent to the isomerization reactor. Heavy components (C5 and above) are collected at the bottom. The top vapor phase is refluxed, and the bottom reboiler is heated by 0.4 MPaG steam. This column typically employs conventional single-tower distillation. Due to the small boiling point difference between isobutane and n-butane (approximately 11.2°C) and the high purity requirements for product separation, the reflux ratio is large, resulting in high steam consumption (approximately 80% of the isomerization unit's steam consumption). Furthermore, it presents challenges such as a large number of trays, large column diameter, high column height, and significant construction difficulties. Utility Model Content

[0004] To address the problems of high energy consumption, large tower diameter, high tower height, and difficult construction of DIB towers, this utility model provides an optimized butane isomerization device.

[0005] To solve the above-mentioned technical problems, this utility model provides the following technical solution:

[0006] An optimized butane isomerization unit includes an upper deisobutane column and a lower deisobutane column. The upper deisobutane column is connected to a mixed butane inlet in the middle. The bottom liquid phase of the upper deisobutane column is pumped to the top of the lower deisobutane column via an intermediate pump as reflux for the lower deisobutane column. The top gas phase of the lower deisobutane column flows by gravity into the bottom of the upper deisobutane column. The lower side stream liquid phase of the upper deisobutane column is used to collect n-butane product.

[0007] The isobutane at the top of the deisobutane column is connected to a compressor. The compressor outlet is connected to a heat exchanger via a pipeline. After passing through the heat exchanger, part of the compressor outlet gas is collected as isobutane product, and part is returned to the top of the deisobutane column. The heat exchanger is also connected to the bottom material of the deisobutane column. The bottom material is heated and then returned to the bottom of the deisobutane column.

[0008] This invention splits a DIB tower into two towers: an upper tower for isobutane removal and a lower tower for isobutane removal. The height of the two towers is greatly reduced compared to a single tower, and the number of trays and the height of each tower can be adjusted adaptively, which greatly reduces the difficulty of construction.

[0009] In addition, the mixed butane enters the middle of the deisobutane upper column from the mixed butane inlet line. The gaseous isobutane at the top of the deisobutane upper column is pressurized by the compressor and then enters the heat exchanger. Its heat serves as the heat source for the reboiler inside the deisobutane upper column. The deisobutane upper column does not require steam to heat the reboiler, which greatly saves steam consumption.

[0010] Furthermore, the isobutane at the top of the deisobutane column is connected to the compressor inlet buffer tank, which is connected to the compressor via a pipeline.

[0011] The upper column for isobutane removal is equipped with a liquid collection tank. The bottom of the liquid collection tank is connected to a liquid phase n-butane outlet pipe, which extends to the outside of the upper column for isobutane removal.

[0012] The above-mentioned structure allows the side-stream n-butane to be extracted from the liquid phase instead of the existing gas phase, reducing the gas phase load in the tower and reducing energy consumption. Liquid phase extraction can also reduce the subsequent cooling load.

[0013] The liquid collection tank is located between the two trays of the isobutane removal column.

[0014] The lower column of the isobutane removal tower is equipped with a steam reboiler. Since the upper column of the isobutane removal tower is equipped with a reboiler, most of the rising gas phase in the upper column of the isobutane removal tower can be supplied by the reboiler. Therefore, the gas phase load of the lower column of the isobutane removal tower can be greatly reduced, requiring only a small amount of steam heating.

[0015] The bottom of the deisobutane lower column is connected to the output line for C5 and above heavy components.

[0016] The beneficial effects achieved by this utility model are:

[0017] (1) This utility model adopts two series-connected upper and lower isobutane removal columns. The top gas phase of the upper isobutane removal column is pressurized by a compressor and used as the heat source for the reboiler in the upper isobutane removal column. The upper isobutane removal column does not require steam to heat the reboiler. The lower column is equipped with a steam reboiler, which only requires a small amount of steam for heating. This greatly reduces the steam consumption of the butane isomerization device, reduces the overall energy consumption, and has a significant energy-saving effect.

[0018] (2) In this utility model, since a reboiler is installed in the upper column of the deisobutane removal column, most of the rising gas phase in the upper column of the deisobutane removal column can be provided by the reboiler. Therefore, the gas phase load of the lower column of the deisobutane removal column can be greatly reduced. Since the gas phase load determines the column diameter, the lower column of the deisobutane removal column can use a column with a very small diameter, which greatly reduces the construction difficulty and equipment investment.

[0019] (3) In this utility model, the side-stream n-butane is changed from gas phase extraction to liquid phase extraction, which reduces the gas phase load in the tower and reduces energy consumption. At the same time, the side-stream n-butane cooling system is changed from gas phase condensation cooling to liquid phase cooling, which greatly reduces the cooling load. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 This is a schematic diagram of the structure of an isobutane removal tower in the prior art;

[0022] Figure 2 This is a schematic diagram of the structure of this utility model;

[0023] Figure 3 This is a partial structural diagram of the interior of the deisobutane upper column (the arrows in the diagram indicate the direction of liquid flow).

[0024] In the diagram: 1. Isobutane removal upper column; 2. Top gaseous isobutane; 3. Compressor inlet buffer tank; 4. Compressor; 5. Output line for C5 and above heavy components; 6. Heat exchanger; 7. Mixed butane inlet line; 8. Liquid n-butane outlet pipe; 9. Isobutane removal lower column; 10. Intermediate pump; 11. Bottom liquid phase; 12. 99th tray; 13. Liquid collection tank; 14. 97th tray; 15. Steam reboiler. Detailed Implementation

[0025] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0026] Example:

[0027] like Figure 2 , Figure 3 As shown, an optimized butane isomerization unit includes an upper isobutane removal column 1 and a lower isobutane removal column 9. The upper isobutane removal column 1 is connected to a mixed butane inlet line 7 in the middle. The bottom liquid phase 11 of the upper isobutane removal column 1 is pumped to the top of the lower isobutane removal column 9 via an intermediate pump 10 as reflux. The top gas phase of the lower isobutane removal column 9 flows by gravity into the bottom of the upper isobutane removal column 1. The lower side stream liquid phase of the upper isobutane removal column 1 yields n-butane product. The bottom of the lower isobutane removal column 9 is connected to an output line 5 for C5 and above heavy components.

[0028] This invention splits a DIB tower into two towers: an upper deisobutane tower 1 and a lower deisobutane tower 9. The height of the two towers is greatly reduced compared to a single tower, and the number of trays and the height of each tower can be adjusted adaptively, greatly reducing the difficulty of construction.

[0029] The isobutane 2 at the top of the isobutane removal column 1 is connected to the compressor inlet buffer tank 3. The compressor inlet buffer tank 3 is connected to the compressor 4 through a pipeline. The outlet of the compressor 4 is connected to the heat exchanger 6 through a pipeline. After passing through the heat exchanger 6, part of the gas phase at the outlet of the compressor 4 is collected as isobutane product, and part is returned to the top of the isobutane removal column 1 as reflux. The heat exchanger 6 is also connected to the bottom material of the isobutane removal column 1. The bottom material is heated and then returned to the bottom of the isobutane removal column 1.

[0030] The mixed butane enters the middle of the isobutane removal column 1 through the mixed butane inlet 7. The isobutane 2 at the top of the column 1 is pressurized by the compressor 4 and enters the heat exchanger 6. Its heat serves as the heat source for the reboiler inside the column 1. The column 1 does not require steam to heat the reboiler, which greatly saves steam consumption.

[0031] The lower column 9 for isobutane removal is equipped with a steam reboiler 15. Since the upper column 1 for isobutane removal is equipped with a reboiler, most of the rising gas phase in the upper column 1 for isobutane removal can be supplied by the reboiler. Therefore, the gas phase load of the lower column 9 for isobutane removal can be greatly reduced, requiring only a small amount of steam for heating. The steam consumption is 8.6% of the original, and the overall energy consumption is reduced by 67.5%, resulting in significant energy saving.

[0032] The upper column 1 for isobutane removal is equipped with a liquid collection tank 13. The bottom of the liquid collection tank 13 is connected to a liquid phase n-butane outlet pipe 8, which extends to the outside of the upper column 1. This structure changes the side-stream n-butane extraction from the gas phase to the liquid phase, reducing the gas phase load within the column and lowering energy consumption. Liquid phase extraction also reduces the subsequent cooling load by 87.5%. The cooling system is simplified from the original air-cooling and water-cooling combination to a single small water cooler, reducing circulating water consumption by 87.5%. The investment and footprint of the cooling system are also significantly reduced.

[0033] like Figure 3 As shown, the liquid collection tank 13 is located between the two trays of the isobutane removal tower 1. Specifically, the 98th tray is removed, and the liquid collection tank 13 is set between the 97th tray 14 and the 99th tray 12. The liquid collection tank 13 has a U-shaped structure, and the bottom of its concave structure is connected to the liquid phase n-butane outlet pipe 8.

[0034] In practical applications, taking a 240,000-ton / year butane isomerization unit as an example:

[0035] use Figure 1 The prior art device shown has a steam consumption of 35 t / h at 0.4 MPaG, 140 trays, isobutane is extracted from the top of the tower, n-butane is extracted from the gas phase at the 100th tray on the side, and C5 and above heavy components are extracted from the bottom of the tower. The tower diameter is 4.2 m and the total tower height is 78.5 m.

[0036] By adopting the technical solution of this utility model, the following technical effects can be achieved:

[0037] 1. The steam reboiler 15 of the isobutane removal tower 9 reduced the steam flow rate from 35t / h to 3t / h, a reduction of 91.4%. The shaft power of the newly added compressor 4 is 2455kw, and the overall energy consumption is reduced by 67.5%.

[0038] 2. The upper tower 1 for isobutane removal has 100 trays, a diameter of 4.2m, and a total height of 52.6m. The lower tower 9 for isobutane removal has 50 trays, and the diameter is reduced from the conventional 4.2m to 1.6m. The diameter of the lower tower 9 for isobutane removal is greatly reduced, and the total height is 39.4m. The total height of both towers is less than 55m, which greatly reduces the difficulty of construction.

[0039] 3. The side-sourced n-butane is now produced from the liquid phase instead of the gas phase. The C5 content in n-butane increases from 1.2% to 1.5%, but remains within the quality control target of 2%, meeting the quality requirements. The load on the side-sourced n-butane cooling system is reduced by 87.5%. The cooling system is simplified from the original combination of air and water cooling to a single small water cooler, reducing the circulating water consumption by 87.5%. The investment and footprint of the cooling system are also greatly reduced.

Claims

1. An optimized butane isomerization apparatus, characterized in that, The system includes an upper deisobutane tower (1) and a lower deisobutane tower (9). The upper deisobutane tower (1) is connected to a mixed butane inlet line (7) in the middle. The bottom liquid phase (11) of the upper deisobutane tower (1) is sent to the top of the lower deisobutane tower (9) via an intermediate pump (10) as reflux for the lower deisobutane tower (9). The top gas phase of the lower deisobutane tower (9) flows by gravity into the bottom of the upper deisobutane tower (1). The lower side stream liquid phase of the upper deisobutane tower (1) is used to collect n-butane product. The isobutane (2) at the top of the deisobutane upper column (1) is connected to the compressor (4). The outlet of the compressor (4) is connected to the heat exchanger (6) through a pipeline. After passing through the heat exchanger (6), part of the gas phase at the outlet of the compressor (4) is used as isobutane product for external purchase, and part of it is used as reflux to enter the upper end of the deisobutane upper column (1). The heat exchanger (6) is also connected to the bottom material of the deisobutane upper column (1).

2. The optimized butane isomerization apparatus according to claim 1, characterized in that, The isobutane (2) at the top of the deisobutane upper column (1) is connected to the compressor inlet buffer tank (3), and the compressor inlet buffer tank (3) is connected to the compressor (4) through a pipeline.

3. The optimized butane isomerization apparatus according to claim 1, characterized in that, The upper column (1) for removing isobutane is provided with a liquid collection tank (13), and the bottom of the liquid collection tank (13) is connected to a liquid phase n-butane outlet pipe (8), which extends to the outside of the upper column (1) for removing isobutane.

4. The optimized butane isomerization apparatus according to claim 3, characterized in that, The liquid collection tank (13) is located between the two trays of the isobutane removal column (1).

5. The optimized butane isomerization apparatus according to claim 1, characterized in that, The deisobutane lower column (9) is equipped with a steam reboiler (15).

6. The optimized butane isomerization apparatus according to claim 1, characterized in that, The bottom of the deisobutane lower column (9) is connected to the output line (5) for heavy components of C5 and above.

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