JPS61219711A - Separation and concentration of carbon monoxide - Google Patents

Abstract

PURPOSE:To enable sufficient liberation of CO from absorbing liquid contg. CO at relatively low temp. by using liquid absorbent comprising copper chloride, an oxyacid deriv. of P, and a solvent having higher b.p. than water, and separating CO from the org. solvent in a condenser. CONSTITUTION:Second liquid solvent 20 is fed in the liquid state to a reboiler 11 where it is evaporated to be transformed easily to vapor by being heated at a temp. necessary for liberation of CO and above the b.p. of water, and the vapor is fed to the bottom of a stripper 3. The bottom temp. of the stripper is held at a specified temp. by the second liquid solvent, and the second liquid solvent rises through the stripper 3 in the vapor state and CO contained in large amt. in the liquid flowing down the stripper is liberated. The vapor of the second liquid solvent discharged from the stripper 3 is cooled and liquefied in a condenser 9. After separating CO 8, the second liquid solvent is fed to the reboiler 3 again through a line 10'. Since in this case, the second liquid solvent is used circulatorily through a reboiler 11, stripper 3, condenser 9 and the reboiler 11, there is almost no change in the compsn. of the first solvent in the liquid absorbent at the inlet and outlet of the stripper 3. Thus, a stable condition is maintained.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to a method for separating and concentrating carbon monoxide, and in particular to a method for separating and concentrating carbon monoxide (hereinafter referred to as CO) made of copper chloride, an oxyacid derivative of phosphorus, and an organic solvent. This invention relates to an improvement in stripping in a stripping tower when separating and concentrating CO using an absorption liquid.

(Background of the Invention) The CO separation process by the absorption method is based on the copper-aluminum chloride method and the method using an absorption liquid consisting of copper chloride, an oxyacid derivative of phosphorus, and an organic solvent developed by the applicant (Japanese Patent Application Laid-Open No. 1986-1999-1).
No. 19013), etc., but the basic structure of the process is almost the same, as shown in FIG. 4, except that the absorption liquid is different. That is, the raw material gas 2 containing CO comes into contact with the absorption liquid in the absorption tower 1, and after absorbing and separating the Co gas, the off-gas 19
will be discarded as The absorption liquid that has absorbed CO passes through a conduit 4, is heated by a heat exchanger 5, and is introduced through a conduit 6 into a stripping tower (hereinafter sometimes referred to as a stripper) 3, where Co gas is released. This C6 gas contains absorption liquid vapor and mist, so it condenses from the conduit 7.
Co gas 8 and absorption liquid 10 are separated and recovered. A reboiler 11 is attached to the stripping 3. The reboiler 11 heats the liquid 13 flowing down from the top of the stripper 3 with a heating medium such as steam 14, and returns the heated absorption liquid and the vapor of the absorption liquid components to the bottom of the stripper 3 for separation of Co gas. In addition to being used as a heat source, it is also used as a carrier gas for Co gas. On the other hand, the absorption liquid leaving the stripper 3 passes through the strainer 3, is sent to the heat exchanger 5 by the pump 22, is cooled here, is further cooled by the cooler 18, and is returned to the absorption tower 1.

In such absorption operations, the operating costs of the process,
That is, approximately 50 to 70% of the Co gas separation and recovery cost is accounted for by the cost of the steam 14 in the reboiler 11, and in order to reduce costs, it is necessary to reduce the consumption of the steam 14.

In the stripper 3, it is desirable to use steam as a carrier gas for expelling Co gas from the absorption liquid. However, in the absorption liquid used in the present invention, the presence of a large amount of moisture causes precipitation of copper, leading to deterioration of the absorption liquid. For this reason, an evaporated component of the absorption liquid, such as toluene (boiling point 110° C.), is used, but this has the disadvantage that the steam cost in the reboiler 11 increases due to its high boiling point.

In order to improve this, the present inventors used a low boiling point solvent such as methyl ethyl ketone (MEK, boiling point 80 °C) instead of toluene, and injected Co gas at a temperature 5 to 30 °C higher than the boiling point of the solvent. It has been proposed (Japanese Unexamined Patent Publication No. 57-48328) to release it at a relatively low temperature (85 to 105
C), the Co gas cannot be sufficiently diffused, and the moisture contained in the raw material gas accumulates in the absorption liquid, causing precipitation of copper in the absorption liquid and causing deterioration. In addition, MEK in the absorption liquid generates a large amount of steam at a high temperature of around 110°C, and from the stripper 3 to the absorption tower 1.
Oxygen acid derivatives of phosphorus are present in a high concentration in the absorption liquid that circulates to the pump, resulting in a high viscosity of the absorption liquid, which may cause blockage in the strainer 23 in front of the pump 22, leading to the shutdown of the pump. . Furthermore, due to the large amount of evaporation of MEK, the amount of steam consumed was approximately 2.5 times that required when toluene was used, and it became clear that this was not a desirable method. Furthermore, there have been proposals to use hydrogen or chlorine-based gaseous substances as a carrier gas (Japanese Patent Laid-Open No. 57-086210
No.), it is difficult to separate the generated use gas and carrier gas in gaseous form, and it is not practical.

(Object of the invention).

An object of the present invention is to provide a method for concentrating and separating CO, which eliminates the drawbacks of the above-mentioned conventional techniques and can sufficiently dissipate Co gas from an absorption liquid containing CO at a relatively low temperature.

(Summary of the Invention) The present invention absorbs carbon monoxide in a gas to be treated using an absorption liquid consisting of an oxyacid derivative of copper chloride and phosphorus and an organic solvent (referred to as a first organic solvent). In the method of dissipating carbon monoxide in the absorption liquid by stripping in a dispersion tower, and then separating carbon monoxide from the organic solvent in a condenser, a solvent having a boiling point higher than water is used as the first organic solvent. , and a second substance having a boiling point lower than that of water in the stripping tower.
This method is characterized by adding an organic solvent and performing a stripping operation at 105° C. or higher.

In the present invention, the first organic solvent has a boiling point of 110 to 1
50° C., especially toluene, and the second organic solvent has a boiling point of 79 to 90° C., especially at least one solvent selected from benzene, methyl ethyl ketone, and trichlorethylene. It is desirable to supply the solvent to the stripper after passing through the boiler. The amount of the second organic solvent added is preferably 25% by weight or less relative to the first organic solvent. Further, it is desirable that the second organic solvent be repeatedly used by circulating it through the reboiler, stripper, and condenser.

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the drawings.

(Embodiment of the Invention) FIG. 1 is an apparatus system diagram of a COO condensation separation method showing an embodiment of the present invention. This apparatus is similar to the conventional apparatus shown in FIG. 4, except that the reboiler 11 is provided with a supply line for the second solvent liquid 20, and this line is provided with a recirculation line 10° for the second solvent liquid from the condenser 9. It is a composition. The second solvent liquid 20 is supplied in liquid form to the reboiler 11, where the CO
At the temperature necessary for release and above the boiling point of water (105
℃ or above), becomes steam, is supplied to the bottom of the stripper 3, maintains the temperature at the bottom of the stripper at a predetermined temperature, and rises inside the stripper 3 in vapor form, into the liquid flowing down the stripper. Contains a large amount of Co
Release gas. The second solvent vapor leaving the stripper 3 is cooled and liquefied in a condenser 9, and after the Co gas 8 is separated, the second solvent liquid is supplied to the reboiler 3 again through the recirculation line 10°. In this case, the second solvent is the reboiler 1
1. Since the stripper 3, the condenser 9, and the reboiler 11 are used in circulation, the composition of the first solvent in the absorption liquid hardly changes at the inlet and outlet of the stripper 3, and can be maintained in a stable state. .

Figure 2 shows the temperature dependence of the COO yield of the absorption liquid according to the method of the present invention, with the addition of benzene at 15%, trichlene addition at 20%, and ME as the second solvent.
In either case of K addition of 15%, if the operating temperature of the stripper is 105° C. or higher, the COO yield is almost zero, that is, Co gas can be sufficiently released. Note that when only a solvent with a boiling point higher than water, such as toluene, is used as the second solvent, a temperature of 120 to 125 °C, which is higher than the boiling point of toluene (about 110 °C), is required to sufficiently release Co gas. Furthermore, the properties of the absorbed liquid in the strimper 3 change between the inlet and the outlet, which is undesirable.

Next, FIG. 3 shows the appropriate operating temperature of the stripper 3 when toluene is used as the first solvent in the absorption liquid, the toluene concentration is gradually decreased, and benzene is added as the second solvent by the amount of the decrease. In Figure 0, which shows the amount of reboiler steam used, the broken line at 30 indicates the amount of reboiler steam used as the second solvent.
When the toluene solvent as the solvent is used alone, 32 is when benzene or MEK is added as the second solvent,
34 similarly shows the case where trichlene was added.

From the figure, as the amount of benzene added increases, the stable and suitable operating temperature of the stripper gradually decreases, and by adding benzene (second solvent) in an amount of 25% of the amount of the first solvent, The operating temperature of the stripper can be lowered by about 15 to 20 degrees Celsius compared to the case of
kg can be reduced. This represents about 10% of the reboiler supply steam and 7% of the total utility costs. In addition, by adding 15% of benzene as the second solvent, the stripper operating temperature can be increased by about 10 to 15%.
The amount of steam can be reduced to the amount of COO (n?
) can be reduced by about 0.1 pupil. It has been found that if the amount of benzene added exceeds 25% and the operating temperature is further lowered, the 00 recovery rate decreases, precipitation occurs in the absorption liquid, and it becomes difficult to continue the operation.

It was found that this was because, as mentioned above, water in the absorbent was not sufficiently dissipated and accumulated in the absorbent, resulting in a decrease in the performance of the absorbent.

On the other hand, as a result of investigating the influence of benzene mixing on the absorption liquid, it was confirmed that a predetermined absorption capacity can be obtained depending on the absorption temperature, as shown in FIG.

(Effects of the Invention) According to the present invention, a second solvent such as benzene having a temperature below the boiling point of water is added in an amount of 25% or less to an absorption liquid consisting of copper chloride, an oxyacid derivative of phosphorus, and an organic solvent such as toluene. By adding, the suitable operating temperature of the stripper can be lowered, for example by about 15° C., without precipitation of the absorption liquid and without water accumulation in the absorption liquid, and the steam consumption of the repoiler can also be reduced, for example. It can be reduced to about 15%.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the equipment configuration of the CO separation and absorption method of the present invention, FIG. 2 is a diagram showing the temperature dependence of the CO absorption performance of the absorbing liquid according to the present invention, and FIG. FIG. 4, which is a diagram showing the appropriate operating temperature of the stripper in the invention, is a diagram showing the configuration of a conventional CO separation and absorption method device. 1... Absorption tower, 2... Raw material gas, 3... Stone...
Soba 04... Absorption liquid conduit, 5... Heat exchanger, 6...
- Absorption liquid conduit, 7.8... CO gas, 9... Condenser, 10... (Recovered liquid), 10°... Second solvent liquid, 1
3...Absorption liquid, 14...Steam, 15...Drain, 16.17...Absorption liquid, 1st...Cooler, 19
...Off gas, 20.. Second solvent liquid, 21.. Steam, 22.. Pump, 23.. Strainer. Agent Patent Attorney Takenaga Kawakita Figure 1 Figure 2 Absorption 1A degree

Claims (3)

[Claims] (1) After absorbing carbon monoxide in the gas to be treated using an absorption liquid consisting of an oxygen acid derivative of copper chloride and phosphorus and an organic solvent (referred to as the first organic solvent), the monoxide in the absorption liquid is In a method in which carbon is stripped by stripping in a stripping tower and then carbon monoxide is further separated from an organic solvent in a condenser, a solvent having a boiling point higher than water is used as the first organic solvent, and water is stripped in the stripping tower. A method for separating and concentrating carbon monoxide, which comprises adding a second organic solvent having a boiling point lower than that of the organic solvent and performing a stripping operation at 105°C or higher. (2) In claim (1), the first organic solvent is toluene, the second organic solvent is at least one solvent selected from benzene, methyl ethyl ketone, and trichlene, and the second organic solvent is a boiler. A method for separating and concentrating carbon monoxide, which is characterized in that carbon monoxide is supplied to a stripping tower after passing through the carbon monoxide. (3) A method for separating and concentrating carbon monoxide according to claim (2), characterized in that the second organic solvent is circulated through a reboiler, a stripping tower, and a condenser and used repeatedly.