A method for separating n-hexane and methylcyclopentane by extractive distillation dividing wall column

Abstract

This invention relates to the field of chemical separation and extractive distillation technology, and discloses a method for separating n-hexane and methylcyclopentane using an extractive distillation partitioned-wall column. The apparatus comprises two parts: a cyclohexane separation column and an extractive distillation partitioned-wall column. The technological innovation lies in installing a vertical intermediate partition in a conventional distillation column, coupling a conventional two-tower extractive distillation process into a single column, enabling the separation of three or more mixtures. This apparatus effectively avoids component backmixing, thereby improving thermodynamic efficiency; it also saves on a reboiler and some piping, reducing equipment investment and energy consumption. This method can meet the purity requirements of industrial products and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a method for separating n-hexane and methylcyclopentane using an extractive distillation divider column. Background Technology

[0002] Solvents produced in petroleum processing are typical mixtures of aliphatic hydrocarbons in the petrochemical field, mainly including n-alkanes and cycloalkanes. n-Hexane and methylcyclopentane are very important organic solvents and chemical raw materials, widely used in industry. n-Hexane is used as a solvent for extracting edible oils from vegetables, which is its main application. It is also widely used in pharmaceuticals, rubber, and other fields. Methylcyclopentane can be used as a solvent and a standard substance for chromatographic analysis. However, n-Hexane has a boiling point of 341.88 K, and methylcyclopentane has a boiling point of 344.96 K; their boiling points are close, making them prone to forming azeotropes. Industrial methods for separating these azeotropes mainly include ordinary distillation, molecular sieve adsorption, and extractive distillation. Ordinary distillation consumes a lot of energy and produces products with low purity; molecular sieve adsorption has strong selectivity, high adsorption capacity, and high temperature resistance, but it is prone to saturation and difficult to regenerate, resulting in high industrial costs; extractive distillation has advantages over ordinary distillation in terms of energy saving, reduced consumption, and improved product purity, but conventional extractive distillation suffers from reduced thermodynamic efficiency due to backmixing. Therefore, it is essential to develop a separation process with high thermodynamic efficiency and energy saving. Divided-wall columns are an important means of achieving multi-component separation by adding partitions to a column. This invention combines a divided-wall column with extractive distillation, integrating them into a single extractive distillation divided-wall column. This achieves the desired component separation while improving thermodynamic efficiency and reducing energy consumption and equipment costs. Summary of the Invention

[0003] The purpose of this invention is to provide a method for separating n-hexane and methylcyclopentane using an extractive distillation divider column, thereby addressing the problems existing in the prior art for n-hexane and methylcyclopentane azeotropic systems. The application of this technology and apparatus can meet the purity requirements of industrial products while reducing energy consumption and equipment costs.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] This invention provides a method for separating n-hexane and methylcyclopentane using an extractive distillation partition wall column. The apparatus comprises a cyclohexane separation column (T1), an extractive distillation partition wall column main column (T2), an extractive distillation partition wall column side column (T3), a first reflux tank (D1), a second reflux tank (D2), a third reflux tank (D3), a first condenser (C1), a second condenser (C2), a third condenser (C3), a first reboiler (R1), a second reboiler (R2), and a mixer (M1).

[0006] The process flow is as follows:

[0007] (1) The industrial raw material is fed into the cyclohexane separation tower (T1). The light component n-hexane and methylcyclopentane azeotrope is distilled off from the top of the cyclohexane separation tower and condensed in the first condenser (C1) at the top of the tower. It then enters the first reflux tank (D1) and is divided into two parts: one part is returned to the cyclohexane separation tower (T1) as reflux liquid, and the other part is entered into the main column (T2) of the extractive distillation partition wall tower as the azeotrope of n-hexane and methylcyclopentane.

[0008] (2) The light component n-hexane and methylcyclopentane azeotrope from the top of the cyclohexane separator (T1) enters the main column (T2) of the extractive distillation partition wall column. After contacting with the extractant NMP entering from the top of the main column (T2), the extractive distillation partition wall column (T1) is condensed by the second condenser (C2) at the top of the column and enters the second reflux tank (D2). It is divided into two parts: one part is returned to the main column (T2) of the extractive distillation partition wall column as reflux liquid, and the other part is discharged from the column as n-hexane product.

[0009] (3) The light component n-hexane and methylcyclopentane azeotrope from the top of the cyclohexane separator (T1) enters the main column (T2) of the extractive distillation partition wall column. After contacting with the extractant NMP entering from the top of the main column (T2), the extractive distillation partition wall column (T1) is condensed by the second condenser (C2) at the top of the column and enters the second reflux tank (D2), which is divided into two parts: one part is returned to the main column (T2) of the extractive distillation partition wall column as reflux liquid, and the other part is discharged from the column as n-hexane product;

[0010] (4) The vapor stream coming out of the top of the extractive distillation partition wall column (T3) is condensed by the third condenser (C3) at the top of the column and enters the first reflux tank (D3), where it is divided into two parts: one part is returned to the extractive distillation partition wall column (T3) as reflux liquid, and the other part is discharged from the column as methylcyclopentane product;

[0011] (5) A portion of the bottom stream of the extractive distillation partition wall column (T2) is heated by the second reboiler (R2) and returned to the extractive distillation partition wall column (T2). Another portion of the high-purity extractant NMP is collected, cooled by the heat exchanger (E1), mixed with the supplementary NMP, and then enters the extractive distillation partition wall column (T2).

[0012] The cyclohexane separation tower (T1) has a theoretical number of 55 to 62 plates, a feed position of 22 to 28 plates, a reflux ratio of 5 to 6, and an extractant feed position of 3 to 6 plates.

[0013] The main column (T2) of the extractive distillation partition wall column has a theoretical number of 95 to 100 plates, a feed position of 36 to 40 plates, and a reflux ratio of 7 to 8. The side column (T3) of the extractive distillation partition wall column has a theoretical number of 10 to 15 plates.

[0014] The ratio of the mass of the extractant to the mass of the raw material, i.e., the solvent ratio, is 4 to 5.

[0015] The present invention discloses the following technical effects:

[0016] This invention utilizes an extractive distillation method with a partitioned wall column to separate n-hexane and methylcyclopentane, yielding 98.69% (wt) n-hexane and 94.35% (wt) methylcyclopentane for industrial production. This invention achieves the separation of n-hexane and methylcyclopentane, recovering two high-purity products. Applying partitioned wall column technology to extractive distillation reduces energy consumption and carbon dioxide emissions, demonstrating significant environmental benefits. Coupled with conventional dual-tower extractive distillation, it reduces equipment costs, and the extractant NMP can be recycled, saving economic costs. Attached Figure Description

[0017] To better illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used will be briefly described below. It should be noted that the drawings provided in the following description are only some embodiments of the present invention, and those skilled in the art can obtain other related drawing information based on these drawings without making creative modifications.

[0018] Figure 1 This is a schematic diagram of the process for separating n-hexane and methylcyclopentane using an extractive distillation partition wall column in Example 1 of the present invention. Detailed Implementation

[0019] Example 1:

[0020] The feed flow rate is 2199.95 kg / h, with a mass fraction of 0.61 for n-hexane, 0.22 for methylcyclopentane, and 0.16 for cyclopentane. The cyclopentane separator (T1) has 58 theoretical plates, a reflux ratio of 5.8, and feed location at plate 26. The extractive distillation partition wall column (T2) has 95 theoretical plates, a reflux ratio of 7.2, feed location for the cyclohexane-free component at plate 40, extractant feed location at plate 4, extractant flow rate of 8800 kg / h, solvent ratio of 4.00, and vapor phase extraction location at plate 65. The extractive distillation partition wall column (T3) has 10 side columns, with liquid phase returned to the extractive distillation partition wall column (T2) at plate 65. 98.69% (wt) of n-hexane was obtained at the top of the main column (T2) of the extractive distillation partition wall column, and 94.35% (wt) of methylcyclopentane was obtained in the side column (T3) of the extractive distillation partition wall column.

[0021] Example 2:

[0022] The feed flow rate is 2199.95 kg / h, with a mass fraction of 0.61 for n-hexane, 0.22 for methylcyclopentane, and 0.16 for cyclopentane. The cyclopentane separator (T1) has 60 theoretical plates, a reflux ratio of 5.7, and feed points at plate 28. The extractive distillation partition wall column (T2) has 99 theoretical plates, a reflux ratio of 7, feed points for the cyclohexane-free components at plate 39, extractant feed points at plate 4, an extractant flow rate of 8500 kg / h, a solvent ratio of 3.86, and vapor phase extraction points at plate 66. The extractive distillation partition wall column (T3) has 10 side columns, with liquid phase returned to the extractive distillation partition wall column (T2) at plate 66. 98.56% (wt) of n-hexane was obtained at the top of the main column (T2) of the extractive distillation partition wall column, and 94.14% (wt) of methylcyclopentane was obtained in the side column (T3) of the extractive distillation partition wall column.

Claims

1. A method for separating n-hexane and methylcyclopentane using an extractive distillation partitioned-wall column, characterized in that: The method includes a cyclohexane separation column (T1), an extractive distillation partition wall main column (T2), an extractive distillation partition wall side column (T3), a first reflux tank (D1), a second reflux tank (D2), a third reflux tank (D3), a first condenser (C1), a second condenser (C2), a third condenser (C3), a first reboiler (R1), a second reboiler (R2), and a mixer (M1); Industrial raw materials are fed into the cyclohexane separation tower (T1). The light component, n-hexane, and the azeotrope of methylcyclopentane are distilled off from the top of the cyclohexane separation tower, condensed in the first condenser (C1) at the top of the tower, and then enter the first reflux tank (D1), where they are divided into two parts: one part is returned to the cyclohexane separation tower (T1) as reflux liquid, and the other part is entered into the main column (T2) of the extractive distillation partition wall tower as the azeotrope of n-hexane and methylcyclopentane. The light component n-hexane and methylcyclopentane azeotrope from the top of the cyclohexane separator (T1) enters the main column (T2) of the extractive distillation partition wall column. After contacting with the extractant NMP entering from the top of the main column (T2), the product is condensed by the second condenser (C2) at the top of the main column (T2) and then enters the second reflux tank (D2). It is divided into two parts: one part is returned to the main column (T2) as reflux liquid, and the other part is discharged from the column as n-hexane product. A stream of gaseous material is drawn from the lower part of the main column (T2) of the extractive distillation partition wall column and enters the bottom of the side column (T3) of the extractive distillation partition wall column. The liquid material at the bottom of the side column (T3) of the extractive distillation partition wall column is returned to the lower part of the main column (T2). The vapor stream exiting from the top of the extractive distillation partition wall column (T3) is condensed by the third condenser (C3) at the top of the column and then enters the third reflux tank (D3), where it is divided into two parts: one part is returned to the extractive distillation partition wall column (T3) as reflux liquid, and the other part is exited as methylcyclopentane product. A portion of the bottom stream of the extractive distillation partition wall column (T2) is heated by the second reboiler (R2) and returned to the extractive distillation partition wall column (T2). Another portion of the high-purity extractant NMP is collected, cooled by the heat exchanger (E1), mixed with the supplementary NMP, and then fed into the extractive distillation partition wall column (T2) through the mixer (M1).

2. The process of claim 1 for separating n-hexane and methylcyclopentane in an extractive distillation dividing wall column, characterized in that: The theoretical number of plates in the cyclohexane separation tower (T1) is 55 to 62, and the reflux ratio is 5 to 6.

3. The method for separating n-hexane and methylcyclopentane using an extractive distillation partition wall column according to claim 1, characterized in that: The main column (T2) of the extractive distillation partition wall column has a theoretical number of 95 to 100 plates, a reflux ratio of 7 to 8, and the feed position of the extractant is the 3rd to 6th plate. The side column (T3) of the extractive distillation partition wall column has a theoretical number of 10 to 15 plates.

4. The process of claim 1 for separating n-hexane and methylcyclopentane in an extractive distillation dividing wall column, characterized in that: The ratio of the mass of the extractant to the mass of the raw material, i.e., the solvent ratio, is 4 to 5.

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