JP2001179001A - Packed column distillation tower having different diameters - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the point problem of flooding and to enhance distillation capacity of a packed column distillation tower. SOLUTION: In a distillation tower using a packed column as a tower body, the diameter of an upper packed column is made larger than that of a lower packed column. Preferably, the diameter (a) of the upper packed column, the length (k) thereof and the diameter (b) of the lower packed column and the length (n) thereof are set to 2>a/b>1 and 1/3>k/n>1/12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a packed column type distillation column used for rectification operations such as separation and purification.

[0002]

2. Description of the Related Art A packed column is a cylindrical column packed with irregular packing such as Berl saddle, McMahon packing, terraret, and pole ring or regular packing such as Raschig ring. It is used as a conventional means for precision distillation because of its small size and simple manufacture. For convenience of filling work, convenience of construction of distillation tower, etc.
Usually, a circular pipe of the same diameter according to the processing capacity is 3m-6m.
In many cases, a module having a length of about one unit is formed, and a plurality of modules are joined with a flange or the like to form a tower having a length corresponding to the separation performance.

[0003] In general, a packed column packed with an irregular packing as described above has excellent separation performance. However, the packed column is packed in a column as compared with a column packed with a structured packing such as a Raschig ring or a lessing ring. The pressure loss of the rising gas is large.

[0004]

In a distillation column using a column packed with random packing, flooding generally tends to occur at the top of the column due to a large gas pressure loss. Flooding refers to a phenomenon in which the liquid flowing down the column cannot flow down due to the increase in the flow rate of the gas rising in the packed column, but it is particularly likely to occur at the top of the column where the linear velocity of the gas is large, and the reflux from the top The liquid cannot flow down.

In order to stably perform the distillation operation while avoiding flooding, it is necessary to operate the gas at a reduced linear velocity, which reduces the heat load of the reboiler of the distillation column, and consequently the lower portion of the column is filled. The processing capacity of the column cannot be fully utilized. An object of the present invention is to improve such a problem that flooding is likely to occur in a packed column type distillation column and improve the processing capacity.

[0006]

According to the present invention, the above-mentioned problem is solved by changing the shape of the column in the tower portion where flooding easily occurs. That is, the present invention
In a distillation column using a packed column as a tower body, an invention of a different-diameter packed column type distillation column is characterized in that the diameter of an upper packed column is larger than the diameter of a lower packed column.

[0007] The tower body may be one in which unit columns are joined in series, but depending on the purpose used for fractionation, the tower body is constituted by a plurality of packed columns in parallel. A set of different diameter packed column type distillation columns may be used.

The effect of making the diameter of the upper packed column larger than the diameter of the lower packed column is considered as follows. The mass velocity of the material to be distilled flowing in the distillation column is determined by the amount of boil-up from the reboiler, and the mass velocity of the rising gas and the flowing liquid is constant under all reflux conditions. The mass velocity of the ascending gas is represented by the product of the linear velocity of the gas, the density of the gas, and the cross-sectional area of the flowing packed column.Since the density of the gas is small near the top of the distillation column where the pressure is low, the linear velocity is It will increase near. Therefore, when the throughput of the distillation column is increased and the mass velocity of the distillation target is increased, first, flooding occurs at the top of the column. However, if the diameter of the upper packed column is doubled, for example, the cross-sectional area is quadrupled, so that the linear velocity can be reduced to 1/4 and flooding can be avoided. That is, even if the column diameter is slightly increased, the linear velocity of the gas can be reduced by a factor of two. As described above, since the linear velocity gradually increases toward the top of the column, it is theoretically sufficient to increase the diameter of the column upward. However, in practice, if the diameter of the upper column, which is likely to cause flooding, is increased once from the diameter of the lower column, the linear velocity of the rising gas can be effectively reduced, and as a result, the throughput of the distillation column can be improved. I can do it.

[0009]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing a schematic cross section of a column portion of a distillation column according to the present invention. Length of filling part 2
1, 31 and the full length (1 span) are the same specification, for example, 3 full length
A tower body is formed by connecting a plurality of −6 m unit columns in series. The connection part 4 is airtightly joined by the flange. The unit columns 3 forming the upper column 30 having a total length k, for example, 5 m, have the same diameter a, for example, 100 m.
m, and the unit columns forming the lower column 20 having a total length n, for example, 25 m, have the same diameter b, for example, 80 mm. The upper end of the upper column 30 is connected to the tower top 5. The entire tower is covered with a heat insulating material 60. The lower part of the tower is connected to a reboiler (not shown).

The vapor or non-condensable gas component of the distillate is
It rises from the lower column 20 toward the top 5 while gradually increasing the linear velocity. However, since a> b, the gas linear velocity is effectively reduced in the upper column 30 and flooding is avoided. The distillation column according to the present invention is effective in avoiding flooding, regardless of whether the form of the packing is regular or irregular. However, in the case of irregular packing, the effect of avoiding flooding is particularly remarkable, and the effect of improving the processing capacity of the distillation column is clearly shown.

For example, a = 80 mm, b filled with a helipak (commercially available, Tokyo Special Wire Mesh Co., Ltd.)
= 50 mm, k = 6 m, n = 30 m using a tower body,
As a result of the purification of liquefied methane by low-temperature distillation, the distillation throughput was improved by about 15% as compared with the case of the conventional technique.

As another embodiment, a plurality of unit columns formed by connecting a plurality of unit packed columns in series may be arranged in parallel to form a set of collective columns. By adopting such a configuration, it is possible to centrally manage a plurality of unit towers while maintaining the effects of the present invention for each unit tower, thereby improving rectification productivity.

[0013]

The use of the distillation column according to the present invention makes it possible to reduce the linear velocity of gas in the column where the flooding is likely to occur, so that the amount of reflux liquid can be increased,
High-purity precision distillation products can be obtained. For example, high purification of liquefied methane or separation of stable isotopes can be achieved.

When the distillation column according to the present invention is used, the flooding limit of the column portion, which is liable to cause flooding particularly under reduced pressure distillation, is remarkably improved, and has a high practical value for low temperature distillation of liquefied gas.

If the distillation column according to the present invention is used, the linear velocity of the gas in the tower portion where flooding is likely to occur can be reduced, so that the distillation capacity of the lower column can be fully utilized, and as a result, the distillation column can be used. Processing capacity is improved.

[0016]

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a column portion of a distillation column according to the present invention.

[Explanation of symbols]

 2 Lower unit packing column 20 Lower packing column 21 Filling unit 3 Upper unit packing column 30 Upper packing column 31 Filling unit 4 Junction 5 Tower top 60 Heat insulation

Continued on the front page F-term (reference) 4D076 AA15 AA22 AA24 BB04 BB13 CA01 CA02 CC12 CC13 CC14 DA02 EA08X EA08Y EA12X EA12Y EA13X EA13Y EA16Y EA17X EA17Y EA50 FA31 HA20 JA02

Claims (3)

[Claims] 1. A distillation column using a packed column as a column, wherein the diameter of an upper packed column is larger than the diameter of a lower packed column. 2. The different diameter packed column type distillation column according to claim 1, wherein the ratio of the diameter a of the upper packed column to the diameter b of the lower packed column is 2> a / b> 1. 3. The ratio of the length k of the upper packed column to the length n of the lower packed column is 1/3> k / n> 1/1.
3. The column of different diameter packed column type according to claim 1 or 2, wherein