Stripping apparatus

Abstract

The present application relates to a method for removing an unreacted vinyl chloride monomer (VCM) in polyvinyl chloride (PVC). According to an illustrative stripping apparatus and a stripping method using the stripping apparatus of the present application, in a stripping process using steam, a temperature difference between a raw material including a target substance to be removed and steam is minimized to suppress foam generation in the stripping process, thereby increasing efficiency of removing the target substance to be removed, particularly, an unreacted VCM in PVC. In addition, a cleansing cycle to remove foams generated in the stripping apparatus can be reduced, thereby not only securing economic feasibility of the process, but also preventing degradation in quality of a final product that may occur when an antifoamer to remove the foams is used.

Claims

1. A method for removing an unreacted monomer, the method comprising: introducing a raw material comprising an emulsion polymerization product of a monomer into a raw material supply region of a stripping column; bringing the introduced raw material into contact with steam introduced into a steam supply region of the stripping column to separate an unreacted monomer from the raw material; and adjusting temperatures of the raw material and the steam introduced into the stripping column to satisfy Equation 1:
5 C.T.sub.sT.sub.f<30 C.[Equation 1] wherein T.sub.s represents a temperature of the steam introduced into the stripping column, and T.sub.f represents a temperature of the raw material introduced into the stripping column.

2. The method according to claim 1, wherein the monomer is a VCM.

3. The method according to claim 2, wherein the raw material comprises PVC and an unreacted VCM, and the raw material introduced into the raw material supply region is brought into contact with steam introduced into a steam supply region of the stripping column to separate the unreacted VCM from the raw material.

4. The method according to claim 1, further comprising: decompressing low-pressure steam having a pressure in a range of 2.5 to 5.0 bar using a decompression device; and introducing the decompressed low-pressure steam into the steam supply region of the stripping column.

5. The method according to claim 1, wherein the steam supply region comprises a first outlet, and the method further comprises flowing out a stripped raw material through the first outlet.

6. The method according to claim 1, wherein the raw material supply region comprises a second outlet, and the method further comprises flowing out an outflow comprising an unreacted monomer separated from the raw material and the steam through the second outlet.

7. The method according to claim 6, further comprising condensing steam in the flow flowing out through the second outlet to separate the steam from a non-condensed unreacted monomer.

8. The method according to claim 7, further comprising recovering and reusing the unreacted monomer separated from the flow flowing out through the second outlet.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a view schematically illustrating an illustrative stripping apparatus of the present application.

(2) FIG. 2 is a photograph obtained by photographing the inside of the stripping apparatus according to Example 1 of the present application.

(3) FIGS. 3 and 4 are photographs obtained by photographing the insides of stripping apparatus according to comparative examples 1 and 2, respectively, of the present application.

MODES OF THE INVENTION

(4) Hereinafter, the present application is described in further detail using embodiments in accordance with the present application and comparative examples not in accordance with the present application, but the scope of the present application is not limited by the embodiments described below.

EXAMPLE 1

(5) Emulsion polymerization was performed after putting a vinyl chloride monomer (VCM) and water in a ratio of 1:1 and an emulsifier and a reaction initiator in a batch reactor in a raw material supply region of a stripping apparatus manufactured as in FIG. 1, and a raw material at a temperature of 65 C. including a polymerization product of the batch reactor was introduced into the raw material supply region of the stripping column. At the same time, steam at a temperature of 91 C. and pressure of 0.7 bar was introduced into a steam supply region of the stripping column and a stripping process was performed in a stripping region. In this case, whether a foam is generated inside the stripping apparatus was observed with the naked eye and was evaluated in accordance with criteria below, the result of which is shown in Table 1 below. In addition, a photograph of the inside of the stripping apparatus was taken and is shown in FIG. 2.

(6) <Observation of Whether Foam is Generated>

(7) Whether a foam is generated inside the stripping apparatus was checked with the naked eye, and was evaluated with following criteria in accordance with the number of generated foams.

(8) X: number of foams observed with the naked eye is equal to or less than 10

(9) : number of foams observed with the naked eye is in a range of 10 to 50

(10) O: number of foams observed with the naked eye exceeds 50

Example 2

(11) A stripping process was performed in the same way as Example 1 except that steam at a temperature of 86 C. and pressure of 0.3 bar as introduced into the steam supply region. In this case, whether a foam is generated inside the stripping apparatus was observed, and the result of the evaluation is shown in Table 1.

Example 3

(12) A stripping process was performed in the same way as Example 1 except that steam at a temperature of 78 C. and pressure of 0.3 bar was introduced into the steam supply region. In this case, whether a foam is generated inside the stripping apparatus was observed, and the result of the evaluation is shown in Table 1.

Example 4

(13) A stripping process was performed in the same way as Example 1 except that steam at a temperature of 84 C. and pressure of 0.4 bar was introduced into the steam supply region. In this case, whether a foam is generated inside the stripping apparatus was observed, and the result of the evaluation is shown in Table 1.

Comparative Example 1

(14) A stripping process was performed in the same way as Example 1 except that steam at a temperature of 100 C. and pressure of 1.0 bar was introduced into the steam supply region. In this case, whether a foam is generated inside the stripping apparatus was observed, and the result of the evaluation is shown in Table 1. In addition, a photograph of the inside of the stripping apparatus was taken and is shown in FIG. 3.

COMPARATIVE EXAMPLE 2

(15) A stripping process was performed in the same way as Example 1 except that steam at a temperature of 127 C. and pressure of 1.5 bar was introduced into the steam supply region. In this case, whether a foam is generated inside the stripping apparatus was observed, and the result of the evaluation is shown in Table 1. In addition, a photograph of the inside of the stripping apparatus was taken and is shown in FIG. 4.

(16) A temperature difference between an introduced raw material and steam in the examples and comparative examples is shown in Table 1.

(17) TABLE-US-00001 TABLE 1 (T.sub.s T.sub.f) Whether Foam ( C.) is Generated Example 1 26 X Example 2 21 X Example 3 13 X Example 4 19 X Comparative Example 1 35 Comparative Example 2 62 T.sub.s: Temperature of steam introduced into stripping column T.sub.f: Temperature of raw material introduced into stripping column

(18) As shown in examples 1 to 4, foams were hardly generated in the stripping apparatus of the present application in which a temperature difference between a raw material including an emulsion polymerization product of a VCM and fed steam was adjusted to be equal to or greater than 5 C. and less than 30 C. However, as shown in FIGS. 3 and 4, a great number of foams were produced when a temperature difference between the raw material and the steam was equal to or greater than 30 C.