Method for preparing isopropyl alcohol

1 . A method of preparing isopropyl alcohol, the method comprising:

reacting a propylene monomer and water in a reactor to produce a reaction product stream;

supplying the reaction product stream to an absorption column;

supplying a lower discharge stream including isopropyl alcohol from the absorption column to a gas purification column;

supplying a part of an upper discharge stream including an unreacted propylene monomer from the absorption column to an inert gas removal column;

supplying an upper discharge stream including the unreacted propylene monomer from the gas purification column to the inert gas removal column;

supplying a lower discharge stream including isopropyl alcohol from the gas purification column to an isopropyl alcohol purification section;

refluxing an upper discharge stream including the unreacted propylene monomer from the inert gas removal column to the reactor;

supplying a lower discharge stream including isopropyl alcohol from the inert gas removal column to the isopropyl alcohol purification section,

supplying the lower discharge stream from the absorption column to a first flash drum;

supplying an upper discharge stream from the first flash drum to the inert gas removal column;

supplying a lower discharge stream from the first flash drum to a second flash drum;

supplying an upper discharge stream from the second flash drum to the gas purification column; and

supplying a lower discharge stream from the second flash drum to the isopropyl alcohol purification section.

2 . The method of preparing isopropyl alcohol of claim 1 , further comprising:

passing the lower discharge stream of the absorption column through a first valve to produce a depressurized lower discharge stream from the absorption column;

supplying the depressurized lower discharge stream from the absorption column to the first flash drum;

passing the lower discharge stream of the first flash drum through a second valve to produce a depressurized lower discharge stream from the first flash drum; and

supplying the depressurized lower discharge stream from the first flash drum to the second flash drum.

3 . The method of preparing isopropyl alcohol of claim 1 , wherein a flow rate ratio of a flow rate of the upper discharge stream from the first flash drum to a flow rate of the upper discharge stream from the second flash drum is 1:0.4 to 1:0.8.

4 . The method of preparing isopropyl alcohol of claim 1 , further comprising:

separating inert gas from the upper discharge stream and the lower discharge stream of the inert gas removal column.

5 . The method of preparing isopropyl alcohol of claim 4 , further comprising:

passing the lower discharge stream of the inert gas removal column through a third valve to produce a depressurized lower discharge stream from the inert gas removal column;

supplying the depressurized lower discharge stream from the inert gas removal column to a gas-liquid separation device;

supplying a lower discharge stream including isopropyl alcohol from the gas-liquid separation device to the isopropyl alcohol purification section; and

separating an upper discharge stream including the inert gas from the gas-liquid separation device.

6 . The method of preparing isopropyl alcohol of claim 1 , wherein a ratio of a total number of stages of the gas purification column to a total number of stages of the inert gas removal column is 1:15 to 1:20.

7 . The method of preparing isopropyl alcohol of claim 1 ,

wherein a total number of stages of the gas purification column is 3 to 15, and

wherein a total number of stages of the inert gas removal column is 50 to 90.

8 . The method of preparing isopropyl alcohol of claim 1 , further comprising:

forming a mixed stream of the upper discharge stream of the first flash drum, the upper discharge stream of the absorption column and the upper discharge stream of the gas purification column; and

supplying the mixed stream to the inert gas removal column.

9 . The method of preparing isopropyl alcohol of claim 8 , wherein the mixed stream is supplied to a stage at 5% to 25% of the total number of stages of the inert gas removal column.

10 . The method of preparing isopropyl alcohol of claim 8 , wherein the mixed stream is supplied to a stage at 10% to 20% of the total number of stages of the inert gas removal column.

11 . The method of preparing isopropyl alcohol of claim 1 , wherein an operating pressure of the gas purification column is 0 kg/cm 2 ·g to 2 kg/cm 2 ·g.

12 . The method of preparing isopropyl alcohol of claim 1 , wherein an operating pressure of the inert gas removal column is 15 kg/cm 2 ·g to 25 kg/cm 2 ·g.

13 . The method of preparing isopropyl alcohol of claim 1 , wherein an operating temperature of the gas purification column is 40° C. to 80° C.

14 . The method of preparing isopropyl alcohol of claim 1 , wherein an operating temperature of the inert gas removal column is 40° C. to 170° C.