JPH06134261A - Distillation apparatus and method for separating two substances approximate in saturated steam pressure - Google Patents

Abstract

PURPOSE:To constitute a distillation apparatus separating two substances approximate in saturated steam pressure without requiring a high distillation tower by dividing a distillation tower into a plurality of stages over the range from a raw material supply part to a product taking-out part to arrange the respective distillation towers in parallel in a horizontal direction and connecting the bottom parts of the distillation towers on a raw material supply side to the top parts of the distillation towers on a product taking-out side by liquid phase sully pipes and gaseous phase supply pipes. CONSTITUTION:Distillation towers 1a-1c are constituted in a divided form over the range from a raw material supply part 2 to a product taking-out part 3 and arranged in parallel in a horizontal direction. The bottom parts of the distillation towers 1a, 1b on the side of the raw material supply part 2 and the top parts of the distillation towers 1b, 1c on the side of the product taking-out part 3 are allowed to communicate with each other by the liquid phase supply pipes 4ab, 4bc directed from the bottom parts to the top parts and the gaseous phase supply pipes 5ba, 5cb directed from the top parts to the bottom parts. Further, heating means are provided to the bottom parts of the distillation towers and cooling means are provided to the top parts of the distillation towers and pressure raising means are provided to the gaseous phase supply parts and flow rate control means are provided to the liquid phase supply pipes. As a result, an apparatus for separating two substances approximate in saturated steam pressure is constituted without requiring an extremely high distillation tower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distillation apparatus and method for separating two substances having a saturated vapor pressure close to each other.

[0002]

2. Description of the Related Art Isotopes having exactly the same chemical properties are separated and
As a method for concentrating, a continuous distillation method is used in which a difference in saturated vapor pressure caused by a slight difference in weight between these isotopes is utilized in a distillation column.

However, unlike the distillation of heavy oil and the like, the saturated vapor pressure difference between isotopes is extremely small, so that it is relatively difficult to secure a target concentration capacity, for example, carbon present in the natural world at about 1.1%. Concentration of the stable isotope ¹³ C of C to 99% requires a large number of theoretical plates.

Therefore, conventionally, a substance having a relatively large saturated vapor pressure difference is used as the distillation substance so that the concentration can be carried out with as few theoretical plates as possible, and the height of the distillation column is made extremely high. We are trying to secure the target concentration capacity. For example, the stable isotope ¹³ C of the above carbon
In the case of the above-mentioned concentration, carbon monoxide is used as a distillation substance.

[0005]

The above conventional methods have the following problems. The height of the distillation column is limited due to construction technology or cost constraints. In a very high distillation column, the distillation must be performed in a pressure zone that is disadvantageous in terms of separation coefficient, and the efficiency of distillation deteriorates. Carbon monoxide, which is used to enrich the stable carbon isotope ¹³ C, is toxic and difficult to handle, so it may be difficult to select a distillation material. The present invention aims to solve such problems.

[0006]

In order to solve the above-mentioned problems, in the present invention, the distillation column is divided into a plurality of stages from the raw material supply side to the product take-out side, and these distillation columns are arranged side by side. The bottom part of the distillation column on the raw material supply side and the top part of the distillation column on the product extraction side are connected by a liquid phase supply pipe from the bottom part to the top part and a gas phase supply pipe from the top part to the bottom part. A heating means is provided at the bottom of the distillation column and a cooling means is provided at the top of the distillation column, and a pressure increasing means is provided in the gas phase supply pipe.
We propose a distillation device with a flow rate control means in the liquid phase supply pipe.

In the above structure, the boosting means may be a pump or a cooling means for cooling the middle of the gas phase supply pipe. Further, the flow rate suppressing means can be configured by providing a throttle portion in the liquid phase supply pipe.

Further, in the distillation apparatus of the present invention, in the above configuration, a configuration is proposed in which the number of distillation columns for each stage is set to be larger on the raw material supply side.

Further, in the present invention, in the distillation apparatus having the above-mentioned constitution, the distillation method in which the flow rate in the liquid phase supply pipe and the gas phase supply pipe is suppressed to a minimum of about 1/100 of the circulation amount in the distillation column To propose.

Then, the present invention proposes a method of separating ¹³ CH ₄ and ¹² CH ₄ by using the above-mentioned apparatus and method.

[0011]

[Function] The liquid-phase substance concentrated at the bottom of the distillation column on the raw material supply side is vaporized while flowing through the liquid-phase supply pipe due to the pressure difference from the bottom to the top, and reaches the top of the distillation column on the product extraction side. It flows in, is condensed again by the cooling means, and is further concentrated in this distillation column. On the other hand, the gas phase substance at the top of the distillation column on the product take-out side flows through the gas phase supply pipe against the pressure difference from the bottom to the top by the pressurizing means, and reaches the bottom of the distillation column at the raw material supply side, It is again provided for concentration in this distillation column.

The liquid phase supply pipe is opened at the same concentration position at the top of the distillation column on the product take-out side, and the gas phase supply pipe is opened at the same concentration position at the bottom of the distillation column at the raw material supply side. The substances supplied from these supply pipes do not adversely affect the distillation action in each distillation column.

In the above operation, the flow rate in the liquid-phase supply pipe and the gas-phase supply pipe is suppressed to a minimum amount of about 1/100 of the circulation amount in the distillation column, thereby affecting each distillation column. Can be kept low. That is, the supply of such a small amount of substance hardly impairs the stable operation of the distillation column even when the temperature level matching with the substance in the distillation column and the uniform mixing are hardly considered.

Further, in the case of supplying such a small amount of substance, it is possible to easily insulate the supply pipes as needed, and it is also possible to reduce the required energy of the boosting means such as a pump.

In the case of separating substances such as ¹³ CH ₄ and ¹² CH ₄ having a very small difference in saturated vapor pressure, the extraction ratio (=
The product output / raw material supply (eg, 0.001 to 0.0001) is extremely small, and the flow rate in the liquid phase supply pipe and the gas phase supply pipe is
As described above, even if it is suppressed to about 1/100 of the circulation amount in the distillation column, the deterioration of the separation capacity is very small, and the number of theoretical plates can be maintained almost the same as that arranged vertically.

Rather, by arranging the distillation columns of each stage in the horizontal direction instead of in the vertical direction, it becomes possible to carry out distillation in an advantageous pressure zone in each of the distillation columns, and the above-mentioned supply is performed. It is possible to overcome the deterioration of the separation ability due to the suppression of the flow rate in the pipe.

Therefore, in the enrichment of stable carbon isotope ¹³ C, the conventional toxic carbon monoxide was not used,
It is possible to use non-toxic methane or the like, which has a small saturated vapor pressure difference.

[0018]

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 conceptually shows the distillation apparatus of the present invention, in which a distillation column 1 is divided into three stages A, B and C from the raw material supply side to the product takeout side. The A-stage distillation column 1a provided with the raw material supply part 2 at the upper part is constituted by 5 columns in parallel, the B-stage distillation column 1b is then provided with 3 columns in parallel, and the product extraction part 3 is provided at the bottom part. The C-stage distillation column 1c has only one stage. These distillation columns 1a, 1b, 1c are arranged side by side in the lateral direction.

The bottoms of the distillation towers 1a, 1b on the raw material supply side and the tops of the distillation towers 1b, 1c on the product take-out side are liquid phase supply pipes 4ab, 4bc extending from the bottom to the top, and air flowing from the top to the bottom. It communicates with the phase supply pipes 5ba and 5cb. Further, pumps 6ba and 6cb as pressure increasing means are installed in the respective gas phase supply pipes 5ba and 5cb.

FIG. 2 shows an example of the installation structure of the liquid phase supply pipe 4ab and the vapor phase supply pipe 5ba at the bottom of the distillation column 1a. The vapor phase supply pipe 5ba has an opening 7 at a position lower than that of the bottom of the distillation column 1a. It is positioned above and the concentration of the substance in the distillation column 1a at this position is made equal to the concentration of the substance supplied from the distillation column 1b via the gas phase supply pipe 5ba. The position of the opening 7 can be designed in consideration of the required safety level based on the concentration distribution obtained theoretically or experimentally. Therefore, as described above, it is not necessary for the opening 7 to correspond to the position where the concentrations are exactly the same, even though it is "to make the concentrations of the substances equal". That is, the opening 7 is appropriately located above the position where the density is assumed to be exactly the same.
By designing so that the theoretical stage of distillation is sacrificed, the degree of safety can be increased. A heating means 8 constituting a reboiler is provided at the bottom of the distillation column 1a, and this heating means 8 is used for the other distillation columns 1b, 1b.
It is also installed in c. Reference numeral 11 is a heat insulating material, and this heat insulating material 11 is also provided in the other distillation columns 1b and 1c.

FIG. 3 shows an example of the installation structure of the liquid phase supply pipe 4ab and the gas phase supply pipe 5ba at the top of the distillation column 1b. The liquid phase supply pipe 4ab has an opening 9 at a position higher than that of the top of the distillation column 1b. It is located below, and the concentration of the substance in the distillation column 1b at this position is made equal to the concentration of the substance supplied from the distillation column 1a via the liquid phase supply pipe 4ab. The position of the opening 9 does not always have to correspond to the position where the density is exactly the same, and the opening 9 should be designed to be appropriately lower than the position where the density is assumed to be exactly the same. Causes the theoretical stage of distillation to be sacrificed,
The degree of safety can be increased. A cooling means 10 which constitutes a condenser is provided at the top of the distillation column 1b, and this cooling means 10 is also installed in the other distillation columns 1a and 1c. Further, in this embodiment, the liquid phase supply pipe 4ab is provided with the cooling means 10 'only on the side of the opening 9 thereof.

In the above structure, the liquid phase substance concentrated at the bottom of the distillation column 1a on the raw material supply side flows through the liquid phase supply pipe 4ab toward the distillation column 1b due to the pressure difference. The flow rate of the substance flowing through the liquid-phase supply pipe 4ab can be adjusted by appropriately setting the inner diameter of the liquid-phase supply pipe 4ab, providing a throttle part, or providing a flow control valve or the like. It is suppressed to a low value compared to the flow rate. Liquid phase supply pipe 4
The substance flowing through ab flows into the top of the distillation column 1b on the product take-out side while gradually vaporizing due to heat input from the outside, is condensed again by the cooling means 10 and flows into the distillation column 1b through the opening 9. , Is mixed with the substance in the distillation column 1b. At this time, the opening 9 is located below the top of the distillation column 1b, and the concentration of the substance in the distillation column 1b at this position is set to the concentration of the substance supplied from the distillation column 1a via the liquid phase supply pipe 4ab. Since they are equal to each other or higher in consideration of safety, mixing of these substances does not adversely affect the separation action. The trace amount of substance thus concentrated in the distillation column 1a is further separated and concentrated in the distillation column 1b, further concentrated in the distillation column 1c at the final stage, and then taken out from the product extraction section 3.

On the other hand, the gas phase substance at the top of the distillation column 1b on the product take-out side flows through the gas phase supply pipe 5ba against the above-mentioned pressure difference by the pump 6ba as a pressure increasing means. The flow rate of the substance flowing through the gas phase supply pipe 5ba is suppressed to a low value as compared with the flow rate of the substance in the distillation column 1b by operating the pump 6ba. The pressure raising means is not a pump, but a distillation column 1
It can also be constituted by a cooling means for cooling and condensing the substance in the gas phase supply pipe 5ba on the b side. That is, an operation equivalent to pressurization can be performed by the weight of the liquid phase substance condensed in the gas phase supply pipe 5ba.

The substance flowing in the gas phase supply pipe 5ba flows into the bottom of the distillation column 1a on the raw material side and is mixed with the substance in the distillation column 1a. At this time, the opening 7 of the vapor phase supply pipe 5ba is located above the bottom of the distillation column 1a, and the concentration of the substance in the distillation column 1a at this position is supplied from the distillation column 1b via the vapor phase supply pipe 5ba. Since the concentration is equal to or lower than the concentration of the substance to be treated, even if these substances are mixed, the separation action is not adversely affected. The substance refluxed from the distillation column 1b in this manner is the distillation column 1
It is used for separation and concentration of the substance in a.

The present invention as described above can be applied to the natural world by about 1.1%.
When utilizing stable carbon isotope ¹³ C that is present as a means of concentrating to a concentration of, for example, 99%, when using substances with extremely small differences in saturated vapor pressure, such as ¹³ CH ₄ and ¹² CH ₄ , The flow rate in the liquid phase supply pipe 4 and the gas phase supply pipe 5 can be suppressed to a minimum amount of about 1/100 of the circulation amount in the distillation column 1.

That is, in the case of separating a substance having a very small difference in saturated vapor pressure as described above, the extraction ratio (= product extraction amount / raw material supply amount) is extremely small, and thus the distillation column 1 is Even if it is suppressed to about 1/100 of the circulation amount, it has little effect on the separation capacity.

Since the flow rates of the substances flowing through the liquid-phase supply pipe 4 and the vapor-phase supply pipe 5 between the distillation columns 1 of the respective stages can be suppressed to a low level, the temperature level of the substances in the distillation column can be controlled. Even if little consideration is given to matching and uniform mixing, the stable operation of the distillation column is hardly impeded, and the influence on each distillation column 1 can be suppressed to a low level. Further, it becomes easy to control the latent heat of the substances flowing through these supply pipes 4 and 5 and the heat input to the substances, and the heat insulating structure of these parts as required becomes easy, and
It is also possible to reduce the required energy of the boosting means such as the pump 6.

Further, from the above, the distillation column 1 which is arranged side by side in the lateral direction and is connected by the liquid phase supply pipe 4 and the gas phase supply pipe 5 has the liquid phase supply pipe 4 and the gas phase supply pipe 5 interposed therebetween. Of the circulation amount in the distillation column 1 as described above.
Even if it is suppressed to about 1/100, the deterioration of the separation capacity is very small, and the number of theoretical plates can be maintained almost the same as the one arranged vertically.

Rather, by arranging the distillation columns at the respective stages in the horizontal direction instead of in the vertical direction, it becomes possible to carry out distillation in an advantageous pressure zone in each of the distillation columns, and the above-mentioned supply is performed. It is possible to overcome the deterioration of the separation ability due to the suppression of the flow rate in the pipe.

The control of each component in the above operation is as follows.
It can be done as follows. First, the liquid phase supply pipe 4
The flow rate of the substance in the gas phase supply pipe 5 can be controlled by operating the pump or adjusting the diameter of the pipe.

Further, the distillation column 1 may be controlled by constant pressure control at the top and bottom of each column. That is, at the top, the pressure can be controlled to a predetermined pressure by controlling the cooling means 10, and at the bottom, the pressure can be controlled to a predetermined pressure by controlling the heating means 8.

FIG. 4 shows the stable isotope ¹³ C of carbon, for example, 99%.
In use as a means of concentrating up to a concentration, the operation of the present invention using a methane, ¹² CH ₄ in the liquid phase concentration x
It is expressed by using an xy diagram showing the relationship between and the gas phase concentration y.

In the figure, a curve C is a saturated vapor pressure curve, and straight lines A and B show the states inside the supply pipe and inside the distillation column 1, respectively. The slope of the straight line A is 1 + product amount / circulation amount in supply pipe, and the slope of the straight line B is 1 + product amount / circulation amount in distillation column.

Points P ₁ and P ₂ indicate a supply pipe portion, point P ₁ is a raw material supply side, that is, a supply pipe portion between distillation columns 1a and 1b, and point P ₂ is a product take-out side, that is, distillation columns 1b and 1c. It corresponds to the portion of the supply pipe between. Then, with respect to a point in the supply pipe, for example, the point P ₁ , the value a of x indicates the liquid phase concentration and the value of y indicates the gas phase concentration. On the other hand, the point P ₃ corresponds to the product take-out section 3, and when ¹³ CH ₄ is concentrated to a concentration of, for example, 99% as described above, the liquid phase concentration of ¹² CH ₄ is x = 0.01, that is, 1 Corresponds to%.

In the above figures, in order not to affect the system as a whole even if the flow rate in the liquid phase supply pipe and the gas phase supply pipe is suppressed to a very small amount, As shown, the point P ₁ must fall within the saturated vapor pressure curve C.
That is, the line segment uv> the line segment P ₁ v is a necessary condition. Line segment uv
Can be obtained using Raoul's law as follows. First, the Raoult's law, the following equation (1) holds, y = x / {x + δ (1-x)} ......... (1) where, [delta] = (of ¹³ CH ₄ vapor pressure / ¹² CH ₄ Vapor pressure) As a result of approximation, the line segment uv = (1-δ) / 4,
Substituting the value of, the line segment uv≈0.001. Therefore,
When the slope of the straight line A is about 1 + 0.002, that is, when the product amount / circulation amount in the supply pipe becomes larger than 0.2%, the above requirement is not satisfied and the distillation capacity starts to decrease.

Since the present invention is as described above, it has the following effects. Since there is no need to build a very high distillation column, there are no problems in construction technology and the cost is low. It is not necessary to repeatedly perform distillation in a pressure zone that is disadvantageous in terms of separation coefficient, unlike a conventional distillation apparatus in which a plurality of distillation columns are vertically arranged, and distillation is performed in an advantageous pressure zone in each distillation column. It is possible to improve the efficiency of distillation in this respect. Since it is not always necessary to use only a substance having a relatively large difference in saturated vapor pressure as a distillation substance, the range of selection of the distillation substance is widened, and for example, the concentration of stable carbon isotope ¹³ C is concentrated in the conventional toxic one. Non-toxic methane can be used in place of carbon oxide.

[Brief description of drawings]

FIG. 1 is a system diagram conceptually showing a distillation apparatus of the present invention.

FIG. 2 is an explanatory diagram showing an example of an installation structure of a liquid phase supply pipe and a gas phase supply pipe at the bottom of a distillation column.

FIG. 3 is an explanatory view showing an example of an installation structure of a liquid phase supply pipe and a gas phase supply pipe at the top of a distillation column.

FIG. 4 is an xy diagram showing an operation example of the present invention.

[Explanation of symbols]

 1 Distillation Tower 2 Raw Material Supply Section 3 Product Extraction Section 4 Liquid Phase Supply Pipe 5 Gas Phase Supply Pipe 6 Pumps 7, 9 Openings 8 Heating Means 10, 10 'Cooling Means 11 Insulation Materials

Claims (9)

[Claims] 1. A distillation tower is divided into a plurality of stages from a raw material supply side to a product take-out side, and these distillation towers are horizontally arranged side by side to distill the bottom of the distillation tower on the raw material supply side and the product take-out side. The top of the tower, the liquid phase supply pipe from the bottom to the top,
In addition to communicating with the gas phase supply pipe from the top to the bottom, heating means and cooling means are provided at the bottom of each distillation column, and the gas phase supply pipe is provided with pressure increasing means and at the same time as the liquid phase supply pipe. Is a distillation apparatus for separating two substances having a saturated vapor pressure close to each other, which comprises a flow rate suppressing means. 2. The liquid phase supply pipe according to claim 1 is opened at the same concentration position at the top of the distillation column on the product take-out side, and the gas phase supply pipe has the same concentration at the bottom of the distillation column on the raw material supply side. A distillation apparatus for separating two substances having a close saturated vapor pressure, which is opened at a position 3. The distillation apparatus for separating two substances having a close saturated vapor pressure, wherein the pressurizing means according to claim 1 is a pump. 4. The distillation apparatus according to claim 1, wherein the pressurizing means is constituted by a cooling means for cooling the middle of the gas phase supply pipe. 5. The distillation apparatus according to claim 1, wherein the flow rate suppressing means comprises a gas phase supply pipe provided with a throttle portion. 6. The distillation apparatus according to any one of claims 1 to 5, wherein the number of distillation columns for each stage is increased on the raw material supply side to separate two substances having a saturated vapor pressure close to each other. 7. The distillation apparatus for separating two substances having a close saturated vapor pressure, wherein the two substances separated by the distillation apparatus according to claims 1 to 6 are ¹³ CH ₄ and ¹² CH _4. 8. The distillation apparatus according to any one of claims 1 to 6, wherein the flow rate in the liquid phase supply pipe and the gas phase supply pipe is suppressed to a minimum amount of about 1/100 of the circulation amount in the distillation column. Distillation method for separating two substances having similar saturated vapor pressures 9. The distillation method for separating two substances having a close saturated vapor pressure, wherein the two substances separated by the distillation method according to claim 8 are ¹³ CH ₄ and ¹² CH _4.