JPH0195280A - Chilling separating method and device for carbon monoxide - Google Patents

Abstract

PURPOSE: To separate and refine CO at a high yield in a simple apparatus by cooling a raw material gas, guiding liquefied CO and unliquefied gas in a rectifier, mixing the liquefied CO with hydrogen gas, performing evaporation and cooling the unliquefied gas. CONSTITUTION: A cooled raw material gas via a duct 42 is fed to a high pressure part 61 of a rectifier 6, and cooled by a condenser 63 and most of CO in the gas is liquefied. A gas remaining unliquefied becomes rich in H2 and introduced into a CO evaporator 9 via a duct 43. The liquefied CO is fed to this Co evaporator 9 to evaporate at the tube side and the high pressure H2 rich gas fed to the shell side is cooled and CO in the gas is further liquefied. The liq. CO is brought into contact with a CO gas contg. methane in a low pressure part 62 of the rectifier 6 to refine the gas to a high purity, and the refined gas and liq. CO contg. methane and discharged via the ducts 53, 54 respectively and both are heated in a main heat exchanger 3 and the former is discharged as a product CO gas.

Description

Detailed Description of the Invention (Industrial Application Field) This invention relates to a cryogenic separation method for CO for separating CO from a mixed gas containing carbon monoxide (CO) and hydrogen (H2) as main components, and a method for the cryogenic separation of CO. It is related to the device.

(Prior art) Conventionally, carbon was extracted from a mixed gas containing CO and 1-12 as main components.
As a cryogenic separator for separating O, for example, one shown in FIG. 6 is known. This system includes a gas compressor (not shown) that provides energy for the process to the raw material gas, a pair of adsorption purifiers 2 with adsorbents for surface treatment, a main heat exchanger 3, and a main heat exchanger 3 that separates and purifies CO. It basically consists of a rectification column 60.

One method of conventional cryogenic cooling section using the above device will be described. The raw crude gas usually contains 30 to 70% CO, a few percent or less of hydrocarbons such as methane, and a small amount of carbon dioxide (CO2) and water, and is supplied to the fractionation process at a pressure of 20 to 50 kg/dG. Ru. The supplied raw material gas is cooled as it is or cooled to about 5° C. and then guided to the adsorption purifier 2, where moisture and CO2 in the gas are adsorbed and removed.

The purified raw material gas is sent through the conduit 21 to a deep cooling section provided in the cold box 18 . The gas from conduit 21 is led to main heat exchanger 3 where it is cooled to near its liquefied humidity (which varies depending on pressure and composition).

Note that a refrigerator 4 may be attached to assist cooling.

The raw material gas cooled to the liquefaction temperature is led through the conduit 22 to the condenser 61 provided at the bottom of the rectification column 60, where a portion of the co2 in the raw material gas is liquefied. Then, after the liquefied fraction is removed in the gas-liquid separator 71, the gas is
It is led to nitrogen cooling 390 through pipe 23 and cooled to -190 to -200°C by liquid nitrogen ('a suspension 2) under reduced pressure, and most of the CO present in the gas is liquefied. After being sent to the gas-liquid separator 73 to remove the liquefied fraction, the gas fraction, most of which is N2, is sent from the liquid CO supercooler 5 to the main heat exchanger 3 through the conduit 24. It is heated in this main heat exchanger 3 and discharged to the outside of the system.

This t12 gas contains 7 to 10% CO, and this CO will be wasted. Also, 1 above
” 2 In order to increase the concentration of the gas as much as possible, a nitrogen cooler 9
Sufficient cooling at 0 is necessary, and here the ceiling-mounted liquid N2
Is required.

The liquefied fraction separated by the gas-liquid separator 71 is transferred to the conduit 25
The liquid CO is sent to the subcooler M unit 5 through the cooling tube, where it is cooled by 7 J], depressurized to 2-3 N9/cri G, and enters the gas-liquid portion 151t372, where it is added to the liquid at a rate of 1-3%. After releasing the dissolved N2, it enters the rectification column 60. The operating pressure of the rectification column 60 is typically 0.1 to 0.3 Kg/CdG, which is slightly higher than atmospheric pressure.

The liquefied fraction in the gas-liquid separator 73 is similarly reduced in pressure, and after being discharged from the gas-liquid separator 74, it enters the distillation column 60. The flash gas discharged from the gas-liquid separators 72 and 74 is reduced in pressure to approximately 0.2 Kg/cMG, and then sent to the conduit 26.
Combined at, liquid CO subcooled 7.11 vessel, main heat exchange ',!
After passing through A3 and being heated, it flows out of the system as waste gas.

The liquefied fraction led to the rectification column 60 is purified here, and pure CO is taken out from the top through the conduit 27, and liquid CO containing methane is discharged from the bottom through the conduit 28. The gas and liquid are each heated in the main heat exchanger 3, and the former is used outside the system as product CO gas and the latter as methane-rich gas.

Cooling of the entire device is provided by an attached nitrogen circulation cycle. That is, the circulating N2 gas first passes through the compressor 1.
After being compressed to 4F/cmG from 5 to 25 in the first nitrogen heat exchanger 15, it is cooled to -100 to -150°C and sent out through the conduit 31, and a part of it is compressed to i[f1
Adiabatic engraving through 16a, -180~-195℃
The temperature of the nitrogen gas is reduced to a certain degree, and the nitrogen gas is sent to the second nitrogen heat exchanger 16. The remaining high-pressure N2 gas sent from the conduit 31 to the second nitrogen heat exchanger 16 is cooled and liquefied. The remaining liquefied N2 is supplied to the nitrogen cooler 90 through the expansion valve 50.

Nitrogen cooling" S90 is normally operated under reduced pressure, and liquid N2 evaporates at -195 to -200°C. This evaporated N2 is sent through conduit 33 to each liquid co'a cooling 5 and then to the first nitrogen heat Heated through exchanger 15 and vacuum blower 17
After being back-pressured by and merging with low-pressure N2, the compressor 14
To 6, it circulates.

The total amount of refrigeration required to cool these devices as a whole is determined by the heat retention equation of all the gases entering the system at the high temperature ends of the main heat exchanger 3 and the first nitrogen heat exchanger 15 and the output heat. It is equal to the sum of the difference in heat (the amount of heat held by all the gases emitted by the helicopter 1 outside the system) and the amount of heat that enters the system through the cold box 18,
This heat is taken out of the system by the refrigerator 4 and the engraving 1116a.

The difference in heat input and output at the high-temperature end of a heat exchanger is a joule difference that varies depending on the humidity, temperature difference, pressure difference, and composition at the high-temperature end.
Changed by the Thomson effect, and cold box 18
The heat input from the cold box 18 changes depending on the insulation method of the cold box 18.

The conventional method described above is equipped with a III machine 16a for liquid N2 in order to sufficiently cool the cryogenic part.
Therefore, there is a problem that the device becomes complicated and expensive.

Note that in a relatively small-sized device, instead of supplying the circulating N2 gas of the nitrogen circulation cycle to the nitrogen cooler 90,
A method has been proposed in which liquid N2 is supplied from the outside to the nitrogen cooler 90, and the liquid N2 cools the device and liquefies CO. Moreover, only at startup”−
The liquid N2 is supplied, and during steady operation, the supply is stopped and a part of the liquid CO is supplied to the nitrogen cooler 90, and this liquid CO
The h method has also been proposed, in which the above-mentioned CO is liquefied.

However, in these methods, in order to increase the CO recovery rate, it is necessary to supply the raw material gas at a relatively high pressure of 15 to 30 to 9/1yiG, and in order to lower the evaporation temperature in the nitrogen cooler 90. A vacuum evacuation device is required to forcibly exhaust the evaporated gas and reduce the pressure to below atmospheric pressure.

(Objective of the Invention) This invention was made to eliminate such conventional drawbacks, and it is possible to separate and purify CO with a high yield using a simple device without using an expander in the cryogenic section. The purpose of the present invention is to provide a cryogenic separation method that can perform the following steps.

(Structure of the Invention) The first gist of the present invention is a cryogenic separation method for recovering carbon monoxide from a mixed gas containing carbon monoxide and hydrogen as main components, which comprises cooling a raw material gas and rectifying it. The carbon monoxide that has been liquefied in the rectification column and the gas that has not been liquefied are introduced into the evaporator, and after hydrogen gas is mixed into the liquid carbon monoxide, the liquid carbon monoxide is evaporated to achieve the liquefaction. It is characterized by cooling the gas that did not cool down.

In the above configuration, cooling in the cryogenic section is performed not by evaporation of liquid N2, but by evaporation of liquid CO during the evaporation process, and by mixing 1-12 into the liquid CO, the evaporation temperature of the liquid Go can be lowered. Since the temperature is lowered, the mixed gas can be sufficiently cooled. Therefore, the cryogenic equipment can be simplified by omitting the supply of liquid N2 for cooling, its expander, vacuum evacuation device, etc., and the CO recovery rate can be improved.

In addition, since a low temperature of 1 minute can be obtained for cooling, the supply pressure can be lowered.

The second gist of the invention is that the main heat exchanger cools the raw material gas, the distillation column purifies and separates carbon monoxide from the raw material gas, and the evaporator cools the gas by evaporating liquid carbon monoxide. The rectification column and the evaporator are connected so that liquid carbon monoxide liquefied in the rectification column and unliquefied gas can be supplied from the rectification column to the evaporator. A hydrogen gas header is provided in the circulation path of liquid carbon monoxide, and this hydrogen gas header has a large number of fine blow-off holes extending through it, and is connected to a hydrogen gas supply pipe.

(Example) The apparatus shown in FIG. 1 includes a nitrogen cooler 90 in the conventional apparatus shown in FIG. 1 nitrogen heat exchanger 15, 2nd nitrogen heat exchanger 1
6. The expansion &v 116a, vacuum blower 17, etc. are omitted, and instead of these, a CO evaporator 'a9 is provided in association with the rectification column 6, which blows H2 gas into the liquid CO inside.

In FIG. 1, the precision 1vfI6 has a high voltage section 61 at the bottom,
A low voltage section 62 is formed in the upper part, and a capacitor 63 is provided below these sections. The CO evaporator 9 is constructed of a thermo-ifton type evaporator having a shell-and-tube heat exchanger 91, with a gas header 92 provided below the heat exchanger 91.

This H2 gas header 92 is made by bending pipes so that they are concentric, m-wound, or arranged in parallel when viewed from above. A large number of pores 921, which are H2 gas blow-off holes, are formed through the hole. The upper surface of this H2 gas header 92 is the lower part 912 of the heat exchanger tube 911.
A frontage (handling port) 49 of a conduit 49 that extracts liquid CO from the bottom of the CO heat generator 9.
1 (for example, 1 from the opening of the conduit 49)
5-20cm above) and the lower population 9 above.
It is located near 12.

As a result, the H2 gas blown out from the H2 gas header 92 is uniformly dispersed and mixed into the liquid CO circulating on the tube side (inside the heat transfer tube 911), and is refluxed from the conduit 49 to the distillation column 6. H2 in liquid CO
This prevents gas bubbles from getting trapped.

As shown in FIGS. 1 and 2, the CO gas generator 9 and the viscosity column 6 are connected from the evaporation side of the condenser 63 to the shell side of the CO evaporator 9 (outside of the heat transfer tube 911) through a conduit 43. A conduit 45 connects liquid CO from the condensation side of the condenser 63 to the tube side of the CO evaporator 9, respectively, and a conduit 49 connects the bottom of the CO evaporator 9 to the low pressure of the rectification column 6. Liquid C in part 62
It is connected so that O is supplied as a reflux liquid.

A gas-liquid separator 10 is connected to the CO evaporator 9, and the H2 rig gas that has passed through the shell side is guided to the gas-liquid separator 10 through a conduit 46, and the liquid C separated in the gas-liquid separator 10 is
The configuration is such that O is returned to the duplex side of the CO evaporator S9 by the J pipe 47. Also, this gas-liquid separator 10
A portion of the separated 1"2 gas is supplied to the H2 gas header 92 through the conduit 55, and the remainder is discharged through the conduit 48.

Next, a method for cryogenically separating CO from a raw material gas based on the apparatus shown in FIG. 1 will be explained. First, the raw material gas is heated to 5 K, which is relatively lower than in the conventional process, due to gas compression ta1.
g/ci G or more and guided to the adsorption purifier 2, where CO2 and moisture are adsorbed and removed from the raw material gas, and the raw material gas is supplied to the deep cooling section through the conduit 41. This raw material gas has already been separated [''2 gas,
By exchanging heat with CO gas, methane rich gas, etc. in the main heat exchanger 3, it is cooled to around the liquefaction start temperature. In this cooling step, the cooling may be assisted by freezing.

The cooled raw material gas is introduced into the high-pressure section 61 of the rectification column 6 through the conduit 42, passes up the column and is cooled by the condenser 63, whereby most of the CO in the raw material gas is condensed and liquefied. The gas that remains without being liquefied becomes H2-rich,
This 1 (2) rich gas is passed through conduit 43 to CO evaporator 9.
to go into.

A part of the CO liquefied in the condenser 63 absorbs methane from the gas while flowing downward in the high-pressure section 61, is extracted from the bottom through the conduit 44, and is sent to the gas-liquid separator 8. Sent. In this gas-liquid separator 8, the H2 component dissolved in the liquid CO is separated and removed, and the remaining liquid CO
is supplied to the low pressure section 62 of the rectification column 6. By this distillation operation, the methane component is removed from the raw material gas at the top of the high pressure section 61 of the rectification column 6, and the methane fraction with a high boiling point is substantially no longer present in the gas and liquid at the top of the high pressure section 61.

The remainder of the CO liquefied in the condenser 63 is reduced in pressure and supplied to the CO evaporator 9 through the conduit 45. This liquid CO is at approximately atmospheric pressure <0 on the tube side of the CO evaporator 9.
The high-pressure 112-rich gas supplied to the shell side through the conduit 43 (112-rich gas contains approximately 40 to 70%, although it varies depending on the pressure of the ore gas) is evaporated at a rate of about 2 to 9/cdG). The CO in the gas is further liquefied.

In the cooling process by evaporation of the liquid CO, the liquid CO
As shown in FIG. 2, bubbles of H2 gas blown out from the gas header 92 are mixed in when it is sucked into the lower inlet of the heat transfer tube 911, and as a result, the evaporation temperature of liquid CO is 8.
The temperature decreases by the amount that 2111 degrees rises.

That is, the evaporation temperature of liquid Go (t (2 m degrees 0%)) at the working pressure of 1.2 ata of the CO evaporator 9 is approximately -188°C as shown in Fig. 3. When ~50% (T12 concentration) is mixed, the evaporation temperature becomes -192.5 to -195.4°C, and due to this evaporation, the cooling temperature of 112 rich gas increases from -190 to -190.
-193℃ is 1W. Therefore, in the CO evaporator 9, the tri-rich gas is cooled down to 12
CO in the rich gas is sufficiently liquefied. As a result, the COr remaining in the gas: 1 degree can be reduced to 8% (in the case of a concentration of 42 of 50%), compared to 12% when the 112 concentration of the liquid CO is 0%.

This gas is sent to the gas-liquid separator 10 through the conduit 46 and separated into gas and liquid, and the separated H2 gas has a concentration of 92%.
(in the case of 50% concentration of contaminating H2)
The liquid C0 is sent through the JJI subcooler 5, the main heat exchanger 3, and then discharged to the outside of the system. In addition, the gas-liquid separator 10
The liquid CO separated is passed through a conduit 47 to a CO evaporator 9.
The vapor pressure of the CO evaporated inside the CO evaporator 9 is thereby lowered, and the temperature of the liquid CO inside is lowered.

CO gas containing H2 flows from the top of the CO evaporator 9 to the conduit 5.
1, this gas joins with the gas discharged from the gas-liquid separator 8 on the way, passes through the liquid CO subcooler 5, the main heat exchanger 3, is heated, and passes through the conduit 52 to the gas compressor 1. The gas is recycled as raw material gas to the suction side of the gas.

Out of the liquid CO supplied to the CO evaporator 9 by the conduit 45 and the conduit 47, the surplus liquid CO that was not emitted by the fish
is supplied as a reflux liquid to the low pressure section 62 of the rectification column 6 through the conduit 49. At this time, since the return port of the conduit 49 and the H2 gas header 92 are sufficiently separated, and the H2 gas outlet is formed only in the upper half, bubbles of H2 gas are mixed into the refluxing liquid CO. It won't happen.

In the low pressure section 62 of the No. 11 distillation column 6, CO and methane are distilled. That is, the CO gas containing methane flowing up the inside of the column comes into contact with the liquid CO, the methane component is dissolved in the liquid, and the gas is purified to a high degree of purity. High-purity CO gas is discharged from the top through a conduit 53, and liquid CO containing methane is discharged from the bottom through 34 pipes 54, and these gas and liquid are heated in the main heat exchanger 3, respectively. The former is discharged outside the system as product CO gas, and the latter as methane-rich gas.

According to the cryogenic separation method described above, by mixing 142 gas into the liquid co evaporated in the CO evaporator 9, it is possible to sufficiently cool CO when separating and recovering CO from H2-rich gas. Like liquid N
There is no need to use 2. Furthermore, since the amount of CO liquefied increases by the amount of sufficient cooling, the CO recovery rate can also be improved. For example, the CO degree in the raw material gas is 50%.
In the case of , the CO recovery rate was 86.4% when the above H2 gas was not mixed, whereas it was 91.3% when the concentration of the above mixture 1-12 was set to 50%. .

In the above embodiment, the pretreated raw material gas is directly supplied to the main heat exchanger 3, but the adsorption purifier 2
and main heat exchange! For example, a gas membrane separator 13 having a cellulose acetate-based gas is interposed between the H2 ridge gas and the crude CO gas. Good too.

By supplying this crude CO gas to the main heat exchanger 3, the CO recovery rate can be greatly improved.

Further, in the above embodiment, H2 from the capacitor 63
CO evaporates rich gas! For example, in the case of a relatively small device, an N2 cooler 12 is installed in the middle of the conduit 43, and liquid N2 is supplied from the outside only at startup for auxiliary cooling. Good too.

FIGS. 4 and 5 show CO evaporation in FIG. 1: a
An example of a count of nine is shown. This CO evaporator 9a is a thermosiphon-type evaporator that applies a plate-fin type heat exchanger, and H2-rich gas enters from the upper side of the fin part 93 through the conduit 43, and while flowing downward through the fin part 93. The CO in the gas liquefies, and this liquid C
O accumulates in the lower header 931. A portion of the liquid CO containing the 1"2 gas passes through the pressure reducing valve and the conduit 57 to the H2 gas provided in the lower side header 932 of the fin portion 93.
It is sent to gas header 933. This H2 gas header 93
3 is formed with a large number of fine blow-off holes 934, from which the H2 gas blows out in the form of fine bubbles, and the liquid C flows in from the gas-liquid separation section 94 through the conduit 56.
The H2 gas header 933 is configured to be dispersed in O.

On the other hand, liquid CO is supplied from the rectification column 6 to the gas-liquid separation section 94 from the lower side through the conduit 45, and this liquid CO
While flowing upward through the fin portion 93 through the conduit 56, heat is exchanged with the H2-rich gas and a portion of it evaporates. Since the H2 gas blown out from the H2 gas header 933 is absorbed into this evaporating liquid CO, its evaporation temperature is further lowered. From the lower header 931, CO in a gas-liquid state is sent to the gas-liquid separator 10 (see FIG. 1) through the conduit 46, and the separated liquid CO is supplied to the gas-liquid separator 94 through the conduit 47. circulate. Then, the reflux liquid CO to the rectification column 6 is deposited at the bottom of the gas-liquid separation section 94.
Since the H2 gas is extracted through four conduits, the bubbles of H2 gas from the H2 gas header 933 will not be drawn into the reflux liquid CO.

(Effects of the Invention) According to the cryogenic separation method for CO, which is the first gist of the present invention, cooling in the cryogenic section is performed by evaporation of liquid CO during the process, and furthermore, Since the evaporation temperature of the liquid CO is lowered by introducing the liquid CO, the mixed gas can be sufficiently cooled.

Therefore, it is possible to simplify the cryogenic equipment by omitting the supply of liquid N2, its engraving machine, vacuum evacuation device, etc. for cooling, and it is also possible to improve the CO recovery rate. Furthermore, since a sufficiently low temperature is obtained for cooling, the supply pressure can also be lowered.

Furthermore, according to the cryogenic separator, which is the second feature, it is possible to evenly mix H2 gas into liquid CO in just four simple units, and it is possible to reliably lower the evaporation temperature of the liquid CO.

[Brief explanation of the drawing]

Fig. 1 is an overall layout diagram of an apparatus showing an embodiment of the present invention, Fig. 2 is a cross-sectional explanatory diagram of the CO evaporator shown in Fig. 1, and Fig. 3 is an H2
Figure 4 shows the relationship between the evaporation temperature of liquid CO mixed with gas and the concentration of CO on that day. Fig. 5 is a partially cutaway perspective view of the main parts of the CO evaporator shown in Fig. 4, and Fig. 6 is an overall layout diagram of a conventional deep cooling section m device. . 3... Main heat exchanger, 6... Rectification column, 9... CO evaporator, 55.57... Conduit (hydrogen gas supply pipe), 9
1... Evaporator heat exchanger, 92,933... H2 gas header, 491... Opening (reflux liquid extraction port), 9
12...Lower inlet of heat exchanger, 921,934...
Air outlet. Patent applicant: Representative of Kobe Steel, Ltd. Patent attorney: Etsushi Kotani
Patent Attorney Chief 1) 1 Patent Attorney Yasuo Itaya Figure 2 Hz f) f, /j (%) Figure 4

Claims (1)

[Claims] 1. A cryogenic separation method for recovering carbon monoxide from a mixed gas containing carbon monoxide and hydrogen as main components, in which the raw material gas is cooled and led to a rectification column to perform rectification. The carbon monoxide that has been liquefied in the tower and the gas that has not been liquefied are led to an evaporator, hydrogen gas is mixed into this liquid carbon monoxide, and then the liquid carbon monoxide is evaporated to produce the gas that has not been liquefied. A cryogenic separation method for carbon monoxide, characterized by cooling the carbon monoxide. 2. It has a main heat exchanger that cools the raw material gas, a rectification column that purifies and separates carbon monoxide from the raw material gas, and an evaporator that cools the gas by evaporating liquid carbon monoxide. The evaporator is the lower part of the evaporator where the liquid carbon monoxide liquefied in the rectification column and the unliquefied gas are connected so that they can be supplied from the rectification column to the evaporator. A cryogenic separation device for carbon monoxide, characterized in that the hydrogen gas header is provided with a hydrogen gas header, a large number of fine blow-off holes are formed through the hydrogen gas header, and a hydrogen gas supply pipe is connected to the hydrogen gas header. 3. The hydrogen gas header is located between the outlet of the reflux liquid to the rectification column and the lower inlet of the heat exchanger in the evaporator,
The cryogenic separation device for carbon monoxide according to claim 2, characterized in that it is provided at a position close to a heat exchanger.