WO2018173676A1

WO2018173676A1 - Propylene purification method and purification device

Info

Publication number: WO2018173676A1
Application number: PCT/JP2018/007680
Authority: WO
Inventors: 晃裕桑名; 啓之畑; 孝爾横野
Original assignee: 住友精化株式会社
Priority date: 2017-03-22
Filing date: 2018-03-01
Publication date: 2018-09-27
Also published as: TWI750340B; CN110461804A; KR20190127822A; JP7039560B2; TW201837011A; JPWO2018173676A1; KR102574793B1

Abstract

Provided is a method for purifying propylene from a raw material comprising propylene and impurities. In an absorption column 1 having a temperature adjustment function, a first step is carried out in which the raw material is placed in contact with a silver ion-containing solution (an absorbent) under a first temperature and a first pressure so that the absorbent preferentially absorbs the propylene in the raw material while the unabsorbed gas that was not absorbed by the absorbent is discharged under a second temperature condition which is at or lower than the first temperature through a mist eliminator 4 that has a temperature adjustment function independent of the absorption column 1. In a stripping column 2, a second step is carried out in which the propylene in the absorbent which has been subjected to the first step is desorbed therefrom and recovered under a third temperature and a second pressure. The first step and the second step are carried out continuously in parallel while the absorbent is circulated between the absorption column 1 and the stripping column 2. In the first step, the percentage of raw material that escapes without being absorbed by the absorbent and is disposed as unabsorbed gas is adjusted to be within a range of 1 to 20 mol%.

Description

Propylene purification method and purification apparatus

The present invention relates to a method and an apparatus for concentrating and purifying propylene from a raw material mainly composed of propylene.

Propylene, which is an example of a lower olefin, is known as a raw material for synthetic resin products such as polypropylene and acrylonitrile and synthetic rubber products, but may also be used in the field of electronic materials such as semiconductors. For such applications, propylene is required to be very high purity.

For example, propane is contained as an impurity in the raw material gas mainly composed of propylene used as a highly purified raw material. As a method for purifying propylene gas from this raw material gas, for example, distillation, membrane separation, adsorption separation, or absorption separation is known.

In the absorption separation, for example, propylene is purified by utilizing an interaction between olefin and silver using an absorbing solution using an aqueous silver nitrate solution (see, for example, Patent Document 1).

In the absorption separation using an absorbing solution using a silver nitrate aqueous solution, it is possible to further increase the purity of a high-purity raw material. For example, in Patent Document 1, the concentration of propylene in the raw material is 98 to 99.5 mol%. However, it has been difficult to purify the raw material (crude propylene gas) having a purity lower than this to such a high purity that it can be used in the field of electronic materials such as semiconductors. In recent years, low-priced raw materials containing a relatively large amount of impurities are increasing, and the demand for purifying high-purity propylene from the low-priced raw materials is increasing from the viewpoint of cost reduction.

Japanese Patent No. 5546447

The present invention has been conceived under such circumstances, and is obtained from a relatively low-purity crude propylene raw material having a high purity of a predetermined concentration or higher (e.g., usable in the field of electronic materials such as semiconductors). The main objective is to provide a process for purifying to propylene. In recent years, in addition to propane, low-price raw materials containing a relatively large amount of impurities other than propane (for example, oxygen, nitrogen, carbon dioxide, carbon monoxide, methane, ethane, butane, etc.) are increasing. It is more desirable if impurities can be removed at the same time.

According to the first aspect of the present invention, a method for purifying propylene from a raw material containing propylene and impurities is provided. In the absorption tower having a temperature adjusting function, the above method is such that the raw material is brought into contact with an absorption liquid containing silver ions at a first temperature and a first pressure, and propylene in the raw material is added to the absorption liquid. Non-absorbed by the absorbing liquid at a second temperature that is equal to or lower than the first temperature through a mist remover having a temperature adjustment function independent of the absorption tower while preferentially absorbing. A first step of discharging the absorbed gas; and a second step of releasing and recovering propylene from the absorbing liquid that has passed through the first step at a third temperature and a second pressure in a diffusion tower. While the absorption liquid is circulated between the absorption tower and the stripping tower, the first step and the second step are continuously performed in parallel, and in the first step, Blowing without being absorbed by the absorbent By the ratio of non-absorbing gas is discarded missing is adjusted in the range of 1 to 20 mol%, thereby obtaining a high purity of propylene.

Conventionally, it is known that propylene having a double bond forms a complex with silver ions, but propane does not form a complex with silver ions. Due to this chemical property, under certain conditions, the solubility of propylene in an absorbing solution containing silver ions (for example, an aqueous silver nitrate solution) is considerably greater than the solubility of propane in the absorbing solution. The present inventor has intensively studied a method for obtaining high-purity propylene from a raw material gas containing propylene and propane at a high recovery rate by utilizing the difference in solubility between propylene and propane in the absorbing solution containing silver ions. As a result, an operation of causing the absorbing liquid to absorb the raw material gas and an operation of discharging the non-absorbing gas that has not been absorbed by the absorbing liquid (first step), and an operation of discharging and recovering the dissolved gas from the absorbing liquid It was found that propylene can be obtained with high purity in the recovered gas by continuously performing the (second step) in parallel. Furthermore, it has been found that by operating the two operating temperature conditions in the first step, high purity can be achieved using a crude propylene raw material of lower purity, and the present invention has been completed. That is, in the present invention, by setting the second temperature to be equal to or lower than the first temperature, high purity can be achieved using a low-purity crude propylene raw material. In the absorption tower, propylene is preferentially absorbed, and in the stripping tower, propylene has a boiling point lower than that of water, so that propylene having a higher purity than the crude propylene raw material boils preferentially into a gas state. .

Preferably, the impurity includes at least one selected from the group consisting of propane, oxygen, nitrogen, carbon dioxide, carbon monoxide, methane, ethane, and butane.

Preferably, the concentration of propylene in the raw material is 96.84 mol% or more and less than 99.99 mol%.

Preferably, the absorbing solution is a silver nitrate aqueous solution.

Preferably, the contact between the raw material and the absorbing liquid in the first step is performed by countercurrent contact.

According to the second aspect of the present invention, an apparatus for purifying propylene from a raw material containing propylene and impurities is provided. The apparatus brings the raw material into contact with an absorbing liquid containing silver ions at a first temperature and a first pressure, and preferentially absorbs propylene in the raw material into the absorbing liquid. In order to extract the non-absorbed gas that has not been absorbed into the tower, the absorption tower having a temperature adjustment function and the non-absorbed gas derived from the absorption tower at a second temperature lower than the first temperature are used. A mist remover having a temperature adjustment function independent of the absorption tower, a third temperature and a second pressure to separate contained mist, return liquid components to the absorption tower and discharge gas. A absorption tower for diffusing and recovering propylene from the absorption liquid that has absorbed propylene, and a circulation means for circulating the absorption liquid between the absorption tower and the diffusion tower. In the tower, A propylene purification apparatus configured to obtain high-purity propylene by adjusting the ratio of the non-absorbed gas blown through and discarded without being absorbed by the absorbent to be 1 to 20 mol%. Provided.

According to a preferred embodiment of the second aspect of the present invention, the absorption tower is a bubble tower provided with a gas introduction pipe for introducing the raw material, and the bubble tower is circulated from the upper part thereof. The liquid is introduced, and the gas introduction pipe is opened at the lower part of the bubble column.

According to another preferred embodiment of the second aspect of the present invention, the absorption tower is a packed tower provided with a gas introduction pipe for introducing the raw material, and the packed tower has a packing in the upper part thereof. The absorption liquid which is packed and circulated in the upper part is introduced, and the gas introduction pipe is opened below the filling.

If the apparatus for purifying propylene according to the second aspect of the present invention is used, the purification method according to the first aspect of the present invention can be effectively carried out.

Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a schematic block diagram of the propylene gas purification apparatus which concerns on this invention. It is a schematic block diagram of the absorption tower which concerns on this invention. It is a table | surface which shows the example of refinement | purification of propylene.

Hereinafter, as a preferred embodiment of the present invention, a method for concentrating and purifying propylene from a raw material gas containing propylene and propane will be specifically described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a propylene purification apparatus X according to the present invention. The propylene purification apparatus X is configured to purify crude propylene supplied from the cylinder Y. The propylene purification apparatus X includes an absorption tower 1, a stripping tower 2, a flow rate regulator 3, mist removers 4 and 5, a flow rate control valve 6, a pump 7, a gas discharge port 8, and a gas recovery port 9. And piping connecting these elements.

The cylinder Y is for supplying crude propylene as a raw material gas to the propylene purification apparatus X, and crude propylene is sealed under high pressure conditions. Crude propylene contains, for example, propylene as a main component and propane as an impurity. Further, the impurities may include not only propane but also at least one selected from the group consisting of oxygen, nitrogen, carbon dioxide, carbon monoxide, methane, ethane, and butane. The concentration of propylene contained in the crude propylene raw material is preferably 96.84 mol% or more and less than 99.99 mol%. Although FIG. 1 shows the case where the source gas is supplied from the cylinder Y, the supply mode of the source gas is not limited to the vapor phase supply from the cylinder Y. For example, a liquefied gas may be supplied from a container equipped with a liquid phase supply line, and a gas vaporized using a vaporizer may be used as a raw material gas.

The absorption tower 1 has a tower main body 1A, a gas introduction pipe 1b, an absorption liquid outlet pipe 1c, and a gas outlet pipe 1d, and brings the raw material gas into contact with the absorption liquid. The tower body 1A is a sealed container, and an absorption liquid made of a silver ion-containing solution is received therein. This absorbing liquid is, for example, an aqueous silver nitrate solution prepared to a predetermined concentration. The end of the gas introduction pipe 1b is opened in the absorbing liquid at the lower part of the tower body 1A, for example, and introduces the source gas supplied from the cylinder Y into the tower body 1A. The open end of the gas introduction pipe 1b may have a single opening, for example, or may have a plurality of openings to diffuse. The absorption liquid outlet pipe 1c has an end opened in the absorption liquid at the lower portion of the tower main body 1A, and guides the absorption liquid in the absorption tower 1 to the outside of the tower. The gas outlet pipe 1d is connected to the upper part of the tower body 1A, and guides the gas (non-absorbed gas) that has not been absorbed by the absorbing liquid to the outside of the tower.

As the absorption tower 1 having the above configuration, for example, a known bubble tower, packed tower, wet wall tower, spray tower, scrubber, plate tower, etc. can be employed. FIG. 1 shows a case where the absorption tower 1 (tower body 1A) is a bubble tower. Further, the absorption tower 1 is provided with a temperature adjusting device (not shown) for maintaining the absorbing liquid in the tower main body 1A at a desired temperature. The temperature adjusting device causes a temperature control medium made of, for example, gas or liquid to flow through a jacket provided around the tower body 1A.

The diffusion tower 2 has a tower body 2A, an absorption liquid introduction pipe 2b, an absorption liquid outlet pipe 2c, and a gas outlet pipe 2d, and dissipates gas components absorbed in the absorption liquid in the absorption tower 1. The tower main body 2A is a hermetically sealed container, and a predetermined amount of the absorbing liquid can be received therein. The end of the absorption liquid introduction pipe 2b is open in the upper space in the tower main body 2A, and the absorption liquid led out from the absorption tower 1 is introduced into the tower main body 2A. Further, the absorption liquid introduction pipe 2 b is connected to the absorption liquid outlet pipe 1 c of the absorption tower 1 through the pipe L 1 and the flow rate control valve 6.

The absorption liquid outlet pipe 2c has an end opened to the absorption liquid at the lower part of the tower body 2A, and guides the absorption liquid in the stripping tower 2 to the outside of the tower. Further, the absorption liquid outlet pipe 2 c is connected to the middle of the gas outlet pipe 1 d of the absorption tower 1 through the pipe L <b> 2 and the pump 7. The pump 7 sends the absorption liquid in the stripping tower 2 to the gas outlet pipe 1d. The absorbing liquid outlet pipe 1c, the pipe L1, the flow rate control valve 6, the absorbing liquid inlet pipe 2b, the absorbing liquid outlet pipe 2c, the pipe L2, the pump 7, and the gas outlet pipe 1d constitute an absorbing liquid circulation means. The gas outlet pipe 2d is connected to the upper part of the stripping tower 2, and guides the stripped gas diffused from the absorbing liquid to the outside of the stripping tower 2. As the stripping tower 2 having such a structure, a structure in which the absorbing liquid is dispersed is suitable, and examples thereof include a known packed tower and spray tower. Further, the stripping tower 2 is provided with a temperature adjusting device (not shown) for maintaining the absorbing liquid in the tower main body 2A at a desired temperature.

The flow rate regulator 3 controls the raw material gas supplied from the cylinder Y to a predetermined flow rate.

The mist remover 4 is connected to the gas outlet pipe 1d of the absorption tower 1, and separates the mist contained in the non-absorbing gas led out through the gas outlet pipe 1d. The mist remover 4 is connected to a pipe L3 for guiding the gas that has passed through the mist remover 4 to the gas outlet 8. A back pressure valve 10 and a pressure gauge 11 are provided in the pipe L3. The back pressure valve 10 is controlled in opening degree so that the inside of the absorption tower 1 has a predetermined pressure. The mist remover 4 is attached with a temperature adjusting device (not shown) for maintaining the inside at a desired temperature.

The mist remover 5 is connected to the gas outlet pipe 2d of the diffusion tower 2, and separates the mist contained in the released gas led out through the gas outlet pipe 2d. The mist remover 5 is connected to a pipe L4 for guiding the gas that has passed through the mist remover 5 to the gas recovery port 9. A back pressure valve 12 and a pressure gauge 13 are provided in the pipe L4. The back pressure valve 12 is controlled in opening degree so that the inside of the diffusion tower 2 has a predetermined pressure. The mist remover 5 is attached with a temperature adjusting device (not shown) for maintaining the interior at a desired temperature.

When the propylene purification method of the present invention is executed using the propylene purification apparatus X having the above configuration, the cylinder Y enters the tower main body 1A of the absorption tower 1 through the flow rate regulator 3 and the gas introduction pipe 1b. Supply raw material gas continuously.

As described above, the raw material gas contains propylene as a main component and propane as an impurity, for example. The propylene concentration of the raw material gas supplied from the cylinder Y is, for example, 96.84 mol% or more and less than 99.99 mol%. The supply amount of the raw material gas to the absorption tower 1 is, for example, 1 to 100 dm ³ / s per 1 m ^{2 of the} cross-sectional area of the tower, and for example, 40 to 4000 cm ³ / min in the laboratory scale.

In the tower body 1A of the absorption tower 1, when the raw material gas is released from the end of the gas introduction pipe 1b, the raw material gas is sequentially absorbed by the absorbing liquid by coming into contact with the absorbing liquid. Here, since the solubility of propylene in the absorption liquid (for example, silver nitrate aqueous solution) is considerably larger than the solubility of impurities such as propane, propylene in the raw material gas is preferentially absorbed by the absorption liquid. For this reason, as the source gas rises while being absorbed, the propylene concentration in the gas decreases while the impurity concentration (for example, propane concentration) increases.

On the other hand, for the absorption liquid in the tower body 1A, the absorption liquid that has absorbed the raw material gas in the absorption tower 1 flows out of the absorption tower 1 from the lower part of the tower body 1A through the absorption liquid outlet pipe 1c at a predetermined flow rate. On the other hand, the absorption liquid from which the gas component has been diffused in the diffusion tower 2 flows into the tower from the upper part of the tower body 1A through the pump 7 and the gas outlet pipe 1d. Thereby, in the absorption liquid (liquid bath) in the tower body 1A, a downward flow is generated. Therefore, the raw material gas released from the gas introduction pipe 1b is brought into countercurrent contact with the absorbing liquid, and the non-absorbing gas that has not been absorbed by the contact blows out into the upper space of the tower body 1A. The non-absorbed gas is sent to the mist remover 4 through the gas outlet pipe 1d, and after the liquid component is separated and removed, it is discharged out of the tower through the pipe L3 and the gas outlet 8. On the other hand, the liquid component separated by the mist remover 4 falls as a droplet through the gas outlet pipe 1 d and returns to the absorption tower 1.

The temperature control devices installed in the mist remover 4 and the absorption tower 1 (the tower main body 1A) can be set to different temperatures, and the temperature difference between the mist remover 4 and the tower main body 1A is given. be able to.

About the absorption liquid (for example, silver nitrate aqueous solution) in the absorption tower 1, since the one where the density | concentration is high increases the amount of propylene absorbed per unit volume and unit time, it is preferable. From a practical viewpoint, the concentration of the aqueous silver nitrate solution is, for example, in the range of 1 to 6 mol / dm ³ , and more preferably 3 to 5 mol / dm ³ . Regarding the temperature of the silver nitrate aqueous solution, it is advantageous that the temperature is low because the amount of propylene absorbed increases, and it is, for example, in the range of 0 to 60 ° C., more preferably 0 to 50 ° C. As for the internal pressure of the tower body 1A, a higher pressure is preferable within a certain range because the amount of propylene absorbed increases. From a practical point of view, the internal pressure of the tower body 1A is, for example, 0.1 to 0.8 MPa (G) (G indicates a gauge pressure). Moreover, it is desirable that the internal temperature of the mist remover 4 is equal to or lower than the internal temperature of the tower body 1A.

In this way, in the absorption tower 1, when the continuously supplied raw material gas comes into contact with the absorbing liquid, propylene in the raw material gas is preferentially absorbed by the absorbing liquid, while the non-absorbing gas is outside the tower. Is discharged.

The absorption liquid that has absorbed the raw material gas in the absorption tower 1 is caused by the pressure difference between the internal pressure of the absorption tower 1 and the internal pressure of the diffusion tower 2, and the absorption liquid outlet pipe 1c, the pipe L1, the flow rate control valve 6, and the absorption liquid introduction. It flows into the tower body 2A of the stripping tower 2 through the pipe 2b. In addition, when the said pressure difference is small, you may transfer absorption liquid using a pump. At this time, the inflow of the absorbing liquid into the tower main body 2A is adjusted by the flow control valve 6 and is, for example, 0.1 to 10 dm ³ / s per 1 m ^{2 of the} sectional area of the tower. 500 cm ³ / min.

In the tower body 2A of the diffusion tower 2, the gas component in the absorbing liquid is diffused. From the viewpoint of efficiently diffusing the gas component, the internal temperature of the tower body 2A is preferably higher than that of the absorption tower 1, and the internal pressure is preferably lower than that of the absorption tower 1. The temperature of the absorbing liquid in the tower body 2A is preferably 10 to 70 ° C., for example, and more preferably 20 to 70 ° C. The internal pressure of the tower body 2A is preferably, for example, −0.09 to 0.3 MPa (G), and more preferably 0 to 0.3 MPa (G). Here, the diffused gas diffused from the absorption liquid is sent to the mist remover 5 through the gas outlet pipe 2d, and after the liquid component is removed, it is recovered as purified gas through the pipe L4 and the gas recovery port 9. The The liquid component separated by the mist remover 5 falls as a droplet through the gas outlet tube 2d and returns to the diffusion tower 2.

The absorbing liquid from which the gas component has been diffused is sent to the gas outlet pipe 1d by the pump 7 through the absorbing liquid outlet pipe 2c, and then falls into the tower main body 1A of the absorber tower 1. At this time, the flow rate of the absorption liquid sent out by the pump 7 is set to be approximately the same as the flow rate of the absorption liquid flowing from the absorption tower 1 through the flow rate control valve 6 into the diffusion tower 2. Thereby, the absorption liquid in the absorption tower 1 and the absorption liquid in the stripping tower 2 circulate in balance with each other (circulation step).

In this way, in the stripping tower 2, the gas component of the absorption liquid that continues to flow at a predetermined flow rate is diffused and the stripped gas is recovered outside the tower. Since the emission gas is an emission liquid from which the propylene in the source gas is preferentially absorbed, the propylene concentration is higher than that of the source gas.

As described above, for example, crude propylene gas (raw material gas) containing, for example, propane as an impurity can be purified to obtain high-purity propylene.

Propylene solubility in silver nitrate aqueous solution is reported in literature (Solubility of Propylene in Aqueous Silver Nitrate, IH Cho, DL Cho, HK Yasuda, and T. R. Marrero, J.Chem. Eng. Data 1995, 40, 102-106) It is shown in detail in This document also shows that the solubility of propane in the aqueous silver nitrate solution is low. According to the data shown in this document, in order to obtain high-purity propylene (purity 99.99% or higher), the recovery rate of propylene is theoretically lowered as shown below.

Based on the data shown in the above document, in a sealed system, when the pressure range is 0 to 0.6 MPa (G) and the temperature range is 10 to 40 ° C., the gas-liquid of propylene and propane with respect to the aqueous silver nitrate solution The equilibrium constant is about 150. That is, (gas phase propane concentration / gas phase propylene concentration) / (liquid phase propane concentration / liquid phase propylene concentration) = 150. Simulation of propylene gas purification using this vapor-liquid equilibrium constant is as follows.

It is considered that crude propylene gas containing 1 mol% of propane as an impurity is absorbed in an aqueous silver nitrate solution, and the absorbed gas component is diffused to obtain high purity propylene. First, assuming that 95% of propylene contained in the raw material gas is absorbed by the silver nitrate aqueous solution, propane / (propylene + propane) in the liquid phase is 0.11 mol%, and the initial propane concentration is 1 mol. % Is about 1/10. At this time, the propane concentration in the gas phase is 15.21 mol%, and propane which is an impurity is concentrated. However, the propylene concentration in the liquid phase is 99.89 mol%, and it is difficult to obtain high-purity propylene having a target purity of 99.99 mol% or higher under these conditions.

Therefore, assuming that 30 mol% of propylene contained in the raw material gas is absorbed by the aqueous silver nitrate solution, the same calculation is performed using the above gas-liquid equilibrium constant, and the propylene concentration in the liquid phase is 99.99 mol%. The propylene concentration in the gas phase becomes 98.58 mol%, and the propylene purity in the liquid phase reaches the target value at this stage. That is, only 30 mol% of high-purity propylene can be recovered from the crude propylene gas.

As an application of this method, purification was actually attempted in a batch system. A crude propylene gas having a purity of 99 mol% containing 1 mol% of propane in a 5 mol / dm ³ aqueous silver nitrate solution was dissolved at a temperature of 25 ° C. and a pressure of 0.6 MPa (G) until an equilibrium state was reached. At this time, the volume ratio of the gas phase portion / liquid phase portion was 0.56. Next, first, the pressure is lowered from 0.6 MPa (G) to 0.2 MPa (G) to gradually dissipate the gas component from the silver nitrate aqueous solution, and then the temperature of the absorption tower is increased by 25 ° C./min. The remaining gas components were regenerated by heating from 40 ° C to 40 ° C. The emitted gas in the early stage of emission contains propane at a high concentration, but the propane concentration becomes lower as the emission progresses. When about 35 mol% of the absorbed crude propylene gas was diffused, the propylene purity of the emitted gas was 99.99 mol%. As can be seen from this, in the batch system, in order to obtain high-purity propylene gas, the recovery rate of propylene gas has to be lowered, and there is a trade-off relationship between purity and recovery rate. ing.

For this problem, in Patent Document 1, as in the present embodiment, in the case of a continuous type in which the absorption and emission of the raw material gas (crude propylene gas) with respect to the absorption liquid (eg, aqueous silver nitrate solution) are continuously performed in parallel, It is disclosed that high-purity propylene can be obtained at a high recovery rate by adjusting conditions such as the temperature, pressure, raw material gas supply mode, absorption liquid mode (concentration, amount used, circulation flow rate).

According to Patent Document 1, the ratio of the amount of non-absorbed gas that is blown away without being absorbed by the absorption liquid in the absorption tower 1 depends on the propylene gas purity of the raw material gas and the desired propylene gas purity after purification, By adjusting the raw material gas in the range of, for example, 1 to 20 mol%, high purity propylene having a purity of 99.99 mol% can be obtained. The adjustment of the amount of non-absorbed gas can be realized by adjusting the supply amount of the raw material gas, the concentration of the absorbing liquid, the residence time of the absorbing liquid in the tower body 1A, the temperature and pressure in the tower body 1A, and the like. is there. When the concentration of impurity propane in the raw material gas is high, it is necessary to increase the amount of non-absorbed gas, but for example, when purifying crude propylene gas (propane concentration: 1.0 mol%) with a purity of 99.0 mol% High purity propylene having a non-absorbed gas amount of 5 mol% and a purity of 99.99 mol% can be obtained. On the other hand, when the concentration of impurity propane in the raw material gas is low, for example, when purifying crude propylene gas having a purity of 99.9 mol% (propane concentration 0.1 mol%), the ratio of the amount of non-absorbed gas is 1 mol. High purity propylene having a purity of 99.99 mol% can be obtained even when the content is suppressed to about%. Thus, in the case of the continuous type, even if the amount of non-absorbed gas to be discarded is reduced to increase the recovery rate, high-purity propylene (purity 99.99 mol%) can be obtained. This result cannot be assumed from the theoretical calculation based on the gas-liquid equilibrium constant described above. The reason why the above effect is obtained is not clear, but for example, focusing on the state in which the raw material gas is absorbed in the absorption liquid, the batch type is in a static equilibrium state for both gas and liquid, whereas the continuous type is This is considered to be related to a dynamic equilibrium state due to liquid contact. In addition, since propylene gas and silver ions form a complex, the speed at which propylene gas dissolves in the absorbing liquid is faster than the speed at which propane gas dissolves in the absorbing liquid. Patent Document 1 discloses that the propylene gas is absorbed in the gas and the high-purity propylene gas is diffused in the diffusion tower, which may be one factor for obtaining the above effect. ing.

In Patent Document 1, the propylene concentration in the raw material gas is set to 98 to 99.5 mol%. However, the raw material propylene gas having a purity lower than this has been difficult to purify to a propylene purity that can be used in the field of electronic materials such as semiconductors. That is, it is difficult to purify only a crude propylene raw material containing 0.5 to 2.0 mol% of impurities with high purity.

In Patent Document 1, since only the temperature of the absorption tower is adjusted to a predetermined value, the mist remover that follows the absorption tower dissipates heat when the evaporated absorption liquid condenses, so the temperature inside the mist remover is There was a tendency to be higher than the internal temperature. In contrast, in the present invention, the temperature control devices installed in the mist remover 4 and the tower body 1A are improved so that they can be set to different temperatures, and the internal temperature of the mist remover 4 is changed to the tower body 1A. When the propylene concentration in the crude propylene raw material is outside the range disclosed in Patent Document 1 (98 to 99.5 mol%), the propylene concentration is 96.84 mol% or more and 99.99. It was also found that high purity propylene having a purity of 99.98 mol% or higher can be obtained as a purified gas with a high recovery rate. Further, the present inventors have found that even when impurities include not only propane but also at least one of oxygen, nitrogen, carbon dioxide, carbon monoxide, methane, ethane, and butane, it is possible to purify to the required propylene purity. In particular, even if the propylene concentration in the crude propylene raw material is low purity (in the range of 96.84 mol% or more and less than 98 mol%), it can be highly purified to a predetermined concentration or more, thereby containing a relatively large amount of impurities. Low-priced raw materials can be used in the field of electronic materials such as semiconductors that require high purity, and are expected to be used in a wide range of fields.

The embodiment of the present invention has been described above, but the scope of the present invention is not limited to the above-described embodiment. The specific structures of the propylene purification apparatus according to the present invention and the propylene purification method according to the present invention can be variously modified without departing from the spirit of the invention.

The contact method between the raw material gas and the absorption liquid in the absorption tower 1 is not necessarily a countercurrent contact. For example, the absorption liquid outlet pipe 1c may be opened above the liquid bath of the absorption liquid. In this case, the portion where the absorption liquid and the raw material gas contact in countercurrent is a slight range above the end of the absorption liquid outlet pipe 1c. Even in this case, high-purity propylene can be obtained with a high recovery rate. it can.

In the above-described embodiment, the case where the absorption tower 1 (tower body 1A) is a bubble tower has been described as an example, but other configurations may be adopted as the absorption tower (tower body). FIG. 2 shows a schematic configuration when the absorption tower (column body) is a packed tower. In the tower main body 1B shown in the figure, the packing F is packed near the upper part in the tower, and the pipe L2 for introducing the absorbing liquid sent from the stripping tower 2 into the tower is the packing F. Is open at the top. The end of the gas introduction pipe 1b is open in the central space in the tower. When the raw material gas is released from the end of the gas introduction pipe 1b in the tower main body 1B, the raw material gas efficiently makes countercurrent contact with the absorbing liquid introduced via the pipe L2 on the surface of the packing F, It is sequentially absorbed by the absorbent.

Next, the usefulness of the present invention will be described with reference to examples.

[Example 1]
In this example, the propylene purification apparatus X shown in FIG. 1 was used, and propylene was purified from the raw material gas using the raw material gas as a crude propylene gas.

In this example, stainless steel cylindrical tubes (inner diameter 56.5 mm × height 150 mm: volume 375 cm ³ ) were used as the tower main body 1A of the absorption tower 1 (bubble tower) and the tower main body 2A of the stripping tower 2, respectively. As the absorbing solution, an aqueous silver nitrate 3 mol / dm ³ in the column body 1A 225 cm ³ (depth 90 mm) was received, 225 cm silver nitrate solution having the same concentration in the column body 2A ³ (depth 90 mm) it was received. The conditions in the absorption tower 1 were adjusted such that the internal pressure of the tower body 1A was 0.3 MPa (G), the internal temperature of the tower body 1A was 50 ° C., and the internal temperature of the mist remover 4 was 5 ° C. The conditions in the stripping tower 2 were adjusted so that the internal pressure of the tower main body 2A was 0.1 MPa (G) and the internal temperature was 40 ° C. The silver nitrate aqueous solution received in the tower

main bodies

1A and 2A was circulated between the tower

main bodies

1A and 2A at a flow rate of 20 cm ³ / min. The raw material gas supplied to the absorption tower 1 includes a propylene concentration of 96.84 mol%, a propane concentration of 3.07 mol%, a methane concentration of 660 molppm, an ethane concentration of 220 molppm, and a butane concentration of 20 molppm. The thing of was used. The supply amount of the source gas was a flow rate of 196 cm ³ / min.

The result of analyzing the purified gas from the stripping tower 2 and the non-absorbing gas from the absorption tower 1 during steady operation is shown in the table of FIG. In the present embodiment, a high-purity propylene gas having a purity of 99.99 mol% (propane concentration: 72 mol ppm, methane concentration: 1.0 mol ppm, ethane concentration not detected, butane concentration not detected) is purified from the stripping tower 2 as a purified gas. It was obtained at 166.6 cm ³ / min and a recovery rate of 85 mol%. Further, non-absorbed gas was discharged from the absorption tower 1 at 29.4 cm ³ / min, and the discharge rate was 15 mol%. The measurement concentration “not detected” means less than the measurement lower limit (less than 0.1 mol ppm), and the same applies to the following.

From the results of Example 1, the purification capacity of impurity propane = (propane concentration in raw material propylene) / (propane concentration in purified propylene) = 3.07 mol% / 72 mol ppm = 426.4. If the impurity in the propylene is a raw material containing only propane, for example, a crude propylene raw material containing a propane concentration of 4.26 mol% as an impurity, it is calculated from the purifying ability of the impurity propane under the conditions of Example 1 in the purified gas. The concentration of propane is 99.9 mol ppm, and it is estimated that high-purity propylene having a purity of 99.99% can be obtained. That is, in the present invention, it can be said that separation of propane in the crude propylene raw material is possible up to a raw material concentration of about 4.26 mol%. That is, since the allowable range of impurities in the purified gas having a purity of 99.99 mol% is less than 100 mol ppm, in order to obtain propylene having a purity of 99.99% in the present invention, separation of propane from the crude propylene raw material is performed. The propane concentration in the crude propylene raw material that can be applied to is from 100 mol ppm to 4.26 mol%.

[Example 2]
In this example, the same propylene purification apparatus X as in Example 1 was used, and propylene was purified from the raw material gas under conditions different from those in Example 1.

In this embodiment, as an absorbing solution, an aqueous silver nitrate 3 mol / dm ³ in the column body 1A 225 cm ³ (depth 90 mm) was received, 225 cm silver nitrate solution having the same concentration in the column body 2A ³ (depth 90 mm) to receive It was. The conditions in the absorption tower 1 were adjusted so that the internal pressure of the tower body 1A was 0.3 MPa (G), the internal temperature of the tower body 1A was 25 ° C., and the internal temperature of the mist remover 4 was 25 ° C. The conditions in the stripping tower 2 were adjusted so that the internal pressure of the tower main body 2A was 0.1 MPa (G) and the internal temperature was 40 ° C. The silver nitrate aqueous solution received in the tower

main bodies

1A and 2A was circulated between the tower

main bodies

1A and 2A at a flow rate of 20 cm ³ / min. The raw material gas supplied to the absorption tower 1 includes a propylene concentration of 99.55 mol%, a propane concentration of 0.15 mol%, a methane concentration of 75 molppm, an ethane concentration of 40 molppm, and a nitrogen concentration of 2800 molppm. The oxygen concentration was 30 mol ppm, the carbon dioxide concentration was 0.2 mol ppm, and the carbon monoxide concentration was 0.1 mol ppm. The supply amount of the source gas was a flow rate of 500 cm ³ / min.

The result of analyzing the purified gas from the stripping tower 2 and the non-absorbing gas from the absorption tower 1 during steady operation is shown in the table of FIG. In the present embodiment, high-purity propylene gas having a purity of 99.99 mol% (propane concentration 10 mol ppm, methane concentration not detected, ethane concentration not detected, nitrogen concentration 1.0 mol ppmm, oxygen from the stripping tower 2 as purified gas) A concentration of 0.2 mol ppm, a carbon dioxide concentration of 0.1 mol ppm, and a carbon monoxide concentration not detected) were obtained at 425 cm ³ / min and a recovery rate of 85 mol%. Further, non-absorbed gas was discharged from the absorption tower 1 at 75 cm ³ / min, and the discharge rate was 15 mol%.

Example 3
In this example, the same propylene purification apparatus X as in Example 1 was used, and propylene was purified from the raw material gas under conditions different from those in Example 1.

main bodies

1A and 2A was circulated between the tower

main bodies

1A and 2A at a flow rate of 20 cm ³ / min. The raw material gas supplied to the absorption tower 1 includes a propylene concentration of 99.65 mol%, a propane concentration of 0.1 mol%, a methane concentration of 1 molppm, an ethane concentration of 1 molppm, and a butane concentration of 20 molppm. A nitrogen concentration of 2400 mol ppm, an oxygen concentration of 50 mol ppm, a carbon dioxide concentration of 0.2 mol ppm, and a carbon monoxide concentration of 0.1 mol ppm were used. The supply amount of the source gas was a flow rate of 450 cm ³ / min.

The result of analyzing the purified gas from the stripping tower 2 and the non-absorbing gas from the absorption tower 1 during steady operation is shown in the table of FIG. In the present embodiment, high-purity propylene gas having a purity of 99.98 mol% (propane concentration 6 mol ppm, methane concentration not detected, ethane concentration not detected, butane concentration not detected, nitrogen concentration 1. 8 mol ppmm, oxygen concentration 0.7 mol ppm, carbon dioxide concentration 0.1 mol ppm, carbon monoxide concentration not detected) were obtained at 382.4 cm ³ / min and a recovery rate of 85 mol%. Further, non-absorbed gas was discharged from the absorption tower 1 at 67.6 cm ³ / min, and the discharge rate was 15 mol%.

Example 4
In this example, the same propylene purification apparatus X as in Example 1 was used, and propylene was purified from the raw material gas under conditions different from those in Example 1.

In this embodiment, as an absorbing solution, an aqueous silver nitrate 3 mol / dm ³ in the column body 1A 225 cm ³ (depth 90 mm) was received, 225 cm silver nitrate solution having the same concentration in the column body 2A ³ (depth 90 mm) to receive It was. The conditions in the absorption tower 1 were adjusted so that the internal pressure of the tower body 1A was 0.3 MPa (G), the internal temperature of the tower body 1A was 50 ° C., and the internal temperature of the mist remover 4 was 20 ° C. The conditions in the stripping tower 2 were adjusted so that the internal pressure of the tower main body 2A was 0.1 MPa (G) and the internal temperature was 40 ° C. The silver nitrate aqueous solution received in the tower

main bodies

1A and 2A was circulated between the tower

main bodies

The result of analyzing the purified gas from the stripping tower 2 and the non-absorbing gas from the absorption tower 1 during steady operation is shown in the table of FIG. In the present embodiment, high-purity propylene gas having a purity of 99.98 mol% (propane concentration: 148 mol ppm, methane concentration: 1.4 mol ppm, ethane concentration not detected, butane concentration not detected) is supplied from the stripping tower 2 as a purified gas. It was obtained at 166.6 cm ³ / min and a recovery rate of 85 mol%. Further, non-absorbed gas was discharged from the absorption tower 1 at 29.4 cm ³ / min, and the discharge rate was 15 mol%.

Example 5
In this example, the same propylene purification apparatus X as in Example 1 was used, and propylene was purified from the raw material gas under conditions different from those in Example 1.

In this embodiment, as an absorbing solution, an aqueous silver nitrate 3 mol / dm ³ in the column body 1A 225 cm ³ (depth 90 mm) was received, 225 cm silver nitrate solution having the same concentration in the column body 2A ³ (depth 90 mm) to receive It was. The conditions in the absorption tower 1 were adjusted such that the internal pressure of the tower body 1A was 0.3 MPa (G), the internal temperature of the tower body 1A was 50 ° C., and the internal temperature of the mist remover 4 was 5 ° C. The conditions in the stripping tower 2 were adjusted so that the internal pressure of the tower main body 2A was 0.1 MPa (G) and the internal temperature was 40 ° C. The silver nitrate aqueous solution received in the tower

main bodies

1A and 2A was circulated between the tower

main bodies

1A and 2A at a flow rate of 20 cm ³ / min. As the raw material gas supplied to the absorption tower 1, one having a propylene concentration of 96.91 mol% and a propane concentration of 3.09 mol% was used. The supply amount of the source gas was a flow rate of 200 cm ³ / min.

The result of analyzing the purified gas from the stripping tower 2 and the non-absorbing gas from the absorption tower 1 during steady operation is shown in the table of FIG. In this example, a high-purity propylene gas (propane concentration 75 mol ppm) having a purity of 99.99 mol% was obtained from the stripping tower 2 at 170 cm ³ / min and a recovery rate of 85 mol% as a purified gas. Further, non-absorbed gas was discharged from the absorption tower 1 at 30 cm ³ / min, and the discharge rate was 15 mol%.

Example 6
In this example, the same propylene purification apparatus X as in Example 1 was used, and propylene was purified from the raw material gas under conditions different from those in Example 1.

In this embodiment, as an absorbing solution, an aqueous silver nitrate 3 mol / dm ³ in the column body 1A 225 cm ³ (depth 90 mm) was received, 225 cm silver nitrate solution having the same concentration in the column body 2A ³ (depth 90 mm) to receive It was. The conditions in the absorption tower 1 were adjusted such that the internal pressure of the tower body 1A was 0.3 MPa (G), the internal temperature of the tower body 1A was 50 ° C., and the internal temperature of the mist remover 4 was 50 ° C. The conditions in the stripping tower 2 were adjusted so that the internal pressure of the tower main body 2A was 0.1 MPa (G) and the internal temperature was 40 ° C. The silver nitrate aqueous solution received in the tower

main bodies

1A and 2A was circulated between the tower

main bodies

1A and 2A at a flow rate of 20 cm ³ / min. The raw material gas supplied to the absorption tower 1 includes a propylene concentration of 96.85 mol%, a propane concentration of 3.09 mol%, a methane concentration of 380 molppm, an ethane concentration of 200 molppm, and a butane concentration of 20 molppm. The thing of was used. The supply amount of the source gas was a flow rate of 517 cm ³ / min.

The result of analyzing the purified gas from the stripping tower 2 and the non-absorbing gas from the absorption tower 1 during steady operation is shown in the table of FIG. In the present embodiment, high-purity propylene gas having a purity of 99.98 mol% (propane concentration 220 mol ppm, methane concentration 2.0 mol ppm, ethane concentration not detected, butane concentration not detected) is supplied from the stripping tower 2 as a purified gas. It was obtained at 439.4 cm ³ / min and a recovery rate of 85 mol%. Further, non-absorbed gas was discharged from the absorption tower 1 at 77.6 cm ³ / min, and the discharge rate was 15 mol%.

X Propylene purification unit Y Cylinder 1 Absorption tower 1A Tower body (bubble tower)
1B Tower body (packed tower)
1b Gas inlet pipe 1c Absorbing liquid outlet pipe 1d Gas outlet pipe 2 Stripping tower 2A Tower body 2b Absorbing liquid inlet pipe 2c Absorbing liquid outlet pipe 2d Gas outlet pipe 3 Flow regulator 4 Mist remover 5 Mist remover 6 Flow control valve 7 Pump 8 Gas exhaust port 9

Gas recovery port

10, 12

Back pressure valve

11, 13 Pressure gauge F Filling L1, L2, L3, L4 Piping

Claims

A method for purifying propylene from a raw material containing propylene and impurities,
In an absorption tower having a temperature adjusting function, the raw material is brought into contact with an absorbing liquid containing silver ions at a first temperature and a first pressure, and propylene in the raw material is preferentially absorbed by the absorbing liquid. The non-absorbed gas that has not been absorbed by the absorbing liquid is discharged at a second temperature that is equal to or lower than the first temperature through a mist remover having a temperature adjustment function independent of the absorption tower. The first step;
A second step of dissipating and recovering propylene from the absorbing solution that has undergone the first step at a third temperature and a second pressure in a stripping tower;
While the absorption liquid is circulated between the absorption tower and the diffusion tower, the first step and the second step are continuously performed in parallel. A method for purifying propylene, wherein a high-purity propylene is obtained by adjusting the ratio of the non-absorbed gas blown through and discarded without being absorbed by the absorbing solution in a range of 1 to 20 mol%.
The method for purifying propylene according to claim 1, wherein the impurities include at least one selected from the group consisting of propane, oxygen, nitrogen, carbon dioxide, carbon monoxide, methane, ethane, and butane.
The method for purifying propylene according to claim 1 or 2, wherein the concentration of propylene in the raw material is 96.84 mol% or more and less than 99.99 mol%.
The method for purifying propylene according to any one of claims 1 to 3, wherein the absorbing solution is an aqueous silver nitrate solution.
The method for purifying propylene according to any one of claims 1 to 4, wherein the contact between the raw material and the absorbing liquid in the first step is performed by countercurrent contact.
An apparatus for purifying propylene from a raw material containing propylene and impurities,
At the first temperature and the first pressure, the raw material is brought into contact with an absorbing liquid containing silver ions, and the absorbing liquid preferentially absorbs propylene in the raw material and is not absorbed by the absorbing liquid. An absorption tower having a temperature adjustment function to lead out the non-absorbed gas to the outside of the tower;
In order to separate the mist contained in the non-absorbing gas derived from the absorption tower at a second temperature lower than the first temperature, return the liquid component to the absorption tower and discharge the gas, the absorption tower A mist remover having a temperature adjustment function independent of
A stripping tower for stripping and recovering propylene from the absorbent that has absorbed propylene at a third temperature and a second pressure;
A circulation means for circulating the absorption liquid between the absorption tower and the diffusion tower,
In the absorption tower, high purity propylene can be obtained by adjusting the ratio of the non-absorbed gas that is blown away without being absorbed by the absorbent in the raw material within a range of 1 to 20 mol%. Propylene purification equipment configured as above.
The apparatus for purifying propylene according to claim 6, wherein the impurity includes at least one selected from the group consisting of propane, oxygen, nitrogen, carbon dioxide, carbon monoxide, methane, ethane and butane.
The propylene purification apparatus according to claim 6 or 7, wherein the concentration of propylene in the raw material is 96.84 mol% or more and less than 99.99 mol%.
The absorption tower is a bubble tower provided with a gas introduction pipe for introducing the raw material, and the bubble tower is configured to introduce the absorption liquid circulated from the upper part thereof, and the gas introduction pipe The apparatus for purifying propylene according to any one of claims 6 to 8, which is open at a lower portion of the bubble column.
The absorption tower is a packed tower provided with a gas introduction pipe for introducing the raw material, and the packed tower is packed with a packing in the upper part thereof, and the absorbing liquid circulated in the upper part is introduced. The apparatus for purifying propylene according to any one of claims 6 to 8, wherein the gas introduction pipe is open below the packing.