JPH04347307A - Method for separating carbon dioxide from exhaust gas and device thereof - Google Patents

Abstract

PURPOSE:To efficiently separate CO2 n exhaust gas generated from the exhaust gas generating source of a boiler, a furnace, an internal combustion engine, and the like. CONSTITUTION:After exhaust gas is cooled, it is led into an expander 10 to be cooled down to the liquefied temperature of CO2 or less or a freezing temperature or less, and the condensed or frozer CO2 is separated by a CO2 separator 16. In this case, a CO2 absorption separator 86 is used in stead of the CO2 separator 16, or both of them are used jointly.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention deals with carbon dioxide (CO2)
A method and apparatus for efficiently separating CO2 from a gas containing CO2, specifically, after cooling the gas containing CO2, it is introduced into an expander and expanded to a low temperature, thereby separating CO2, water, sulfur oxides (SOx), etc. ), nitrogen oxides (NOx)
The present invention relates to a method and apparatus for separating one or more types of dinitrogen monoxide (N2O) by liquefying and/or solidifying them, or for adsorbing and separating CO2.

0002

2. Description of the Related Art When carbon-based fuel is combusted, CO2 is contained in the combustion gas. The technology to separate CO2 from combustion gas, which is considered the biggest cause of global warming, is still in the exploratory stage, and various methods are being tried, but none of them are close to being put to practical use. Carbon-based fuels, such as coal, contain large amounts of sulfur and nitrogen, and they generate SOx and N during combustion.
Removal of Ox is also a major issue in terms of installation space and cost. Therefore, as a method currently being considered, the combustion system such as a boiler is housed in a pressure vessel, and the
A pressurized boiler method that burns fuel under high pressure of g/cm2 A and injects a desulfurizing agent into the boiler for in-furnace desulfurization;
For example, a pressurized fluidized bed system is known. Another feature is that the boiler section can be made significantly more compact by pressurizing it in this way. For in-furnace desulfurization, it is effective to set the temperature of the fluidized bed, which is the combustion part, to around 850°C, and in most conventional normal pressure fluidized bed boilers, a temperature of around 850°C is selected. On the other hand, a lot of NOx is generated when the temperature is high, and 850℃ is compared to 1600℃ of other combustion
The temperature is significantly lower than ~1700℃, and the NOx concentration is generally 100ppm compared to the lower limit of NOx concentration of 200ppm for normal pulverized coal-fired boilers.
It is not difficult to make it below pm. To configure this pressurized boiler system, it is necessary to make the air for combustion high pressure, and a gas turbine is used.

[0003] Furthermore, Japanese Patent Laid-Open No. 60-40733 discloses that carbon generated in a closed cycle gas turbine system is
Apparatus have been described in which O2 is removed by absorption into an absorbent liquid medium, such as a potassium carbonate solution.

0004

[Problem to be solved by the invention] As mentioned above, CO2
In the method of removing C by absorbing it in an absorption liquid, the absorbed C
A device for separating O2 and the absorption liquid, that is, an absorption liquid regeneration device is required. Table 1 shows the physical properties of various gas compounds contained in the combustion gas. Note that each numerical value is a value under normal pressure.

[0005]

[Table 1]

Table 2 shows the physical properties of the solidified substances contained in the combustion gas.

[0007]

[Table 2]

[0008] CO2 liquefies at around -60°C (under pressure, it liquefies at a higher temperature, for example around -50°C).
, it solidifies at -78.9°C and becomes dry ice. Other pollutants (N2O, NO2, NO, SO2) also liquefy at around -100°C, except for NO. In view of the above points, the present inventor has devised a method to lower the temperature of combustion gas discharged from a pressurized combustion device through heat exchange, etc., and then introduce it into a gas turbine and expand it to lower it to a temperature lower than around -60°C. Accordingly, C
In 1991, we developed a method and device that can liquefy and/or solidify O2, etc. and separate it efficiently and easily.
A patent application has already been filed on April 2nd.

[0009] However, in the method of this previously applied application, the heat of the air that becomes high temperature by pressurization can be effectively used in the boiler or furnace, and the combustion gas contains a large amount of moisture, so it is better to use the pressurized state. Although it has the advantage of being easy to remove (moisture can be removed to a negligible level even at about 40°C depending on the pressure), it has the limitation that it can only be applied to pressurized systems.

[0010] The present inventor has conducted various studies as described below in order to further advance his research and develop a method and apparatus that can be applied to any gas containing CO2, regardless of whether it is a pressurized system or a normal pressure system. Ta. First, we examined the power and amount of heat required to separate CO2. (1) Calorific value of condensation and solidification It varies slightly depending on temperature and pressure, but when 1 kg of CO2 condenses, it releases 88.12 kcal, and when it changes from liquid to solid, it releases 45.56 kcal. do. Conversely, when CO2 changes from solid to gas, it takes away 136.89 kcal of heat from others (88.1
2+45.56=133.68). (2) The amount of CO2 in the combustion gas varies considerably depending on the type of combustion and the type of combustion device, but
It can be estimated that the molar concentration is about 4 to 15% (6 to 20% by weight). In general, boilers have a small excess air ratio, so CO
The concentration of 2 is high. (3) Conventional methods for separating CO2 Conventionally, gas containing a high concentration of CO2 of 20% or more or extremely low concentration of CO2 from the atmosphere has been removed. At high concentrations, chemical absorption, physical adsorption,
Membrane separation methods have been used, but in any case, the gas is compressed to 5 to 20 kg/cm 2 and separation is performed under high pressure. In the case of low concentrations, methods are used such as condensing and depositing on a regenerator kept at an extremely low temperature, or adsorbing it on an adsorbent under high pressure. With a high concentration of CO2-containing gas, the ratio of power to the amount of separated CO2 is small, but with a low concentration of gas this is disadvantageous. On the other hand, the method of solidifying and depositing a small amount of CO2 at an extremely low temperature and separating it also requires a large amount of power due to the extremely low temperature, and the amount of power used is large in comparison to the amount of separated CO2. Therefore, this is also not advantageous for separating CO2 from low CO2 concentration gas, but since cryogenic equipment has a low temperature heat source and low CO2 concentration, it is possible to
Since the amount of heat for condensing and solidifying O2 is small, this method can be said to be acceptable only in such cases. In other words, low concentration CO
Applying this method to gas No. 2 to separate CO2 cannot be said to be an advantageous method economically, from the point of view of energy use or CO2 reduction. The present invention was made in view of the above points, and aims to provide a method and apparatus for efficiently and easily separating CO2 from gas containing CO2 discharged from boilers, furnaces, internal combustion engines, etc. be.

[0011]

[Means and Actions for Solving the Problems] In order to achieve the above object, the method of separating carbon dioxide from exhaust gas according to claim 1 includes cooling exhaust gas as shown in FIGS. 1, 3 and 4. After that, the carbon dioxide is introduced into an expander 10 and expanded to a temperature below the solidification temperature of carbon dioxide, and then the condensed or solidified carbon dioxide is separated. Furthermore, the method according to claim 2 is characterized in that in the method according to claim 1, the remaining gas from which CO2 has been separated is compressed and pressurized by the compressor 18, and then released into the atmosphere. The gas pressure after compression is, for example, a pressure slightly higher than atmospheric pressure (for example, atmospheric pressure + 100 m
mAq). Note that 100 mmAq is the resistance for releasing into the atmosphere. In the expander 10, the expansion ratio ε is selected so that the temperature of the exhaust gas after expansion is equal to or lower than the solidification temperature of CO2 (-78.9° C.). FIG. 5 shows, as an example, the relationship between the expander inlet gas temperature and the expander outlet gas temperature when the expansion ratio ε is 10 to 30. Note that this value is when the efficiency ηT is 0.87.

In the method of claim 3, as shown in FIG. 6, after the exhaust gas is cooled, it is introduced into a compressor 18 and compressed, and then the compressed exhaust gas is introduced into an expander 10 and expanded to produce carbon dioxide. It is characterized by separating the condensed or solidified carbon dioxide by reducing the temperature to below the liquefaction temperature or solidification temperature of carbon. In the method of claim 3, the compression step is performed in multiple stages,
In some cases, intermediate cooling is performed.

In the method of claim 5, as shown in FIG. 9, the exhaust gas from the internal combustion engine 70 is guided to the exhaust heat recovery boiler 72 without reducing the pressure, and after heating the feed water and steam, it is cooled, and then the exhaust gas is passed to the expander. It is characterized in that the carbon dioxide is introduced into a carbon dioxide tube 10 and expanded to a temperature below the solidification temperature of carbon dioxide, and the condensed or solidified carbon dioxide is separated. And exhaust heat recovery boiler 72
The steam generated in the steam turbine 78 can be introduced into the steam turbine 78 to generate power, or the heat discarded to the condenser 80 of the steam turbine 78 can be used as a high-temperature heat source for the second power generation device, and the low-temperature gas at the outlet of the expander can be used as the second power generation device. It is used as a low-temperature heat source for the device.

In the method of claim 8, as shown in FIGS. 10 and 11, after the exhaust gas is cooled, it is introduced into the compressor 18 and compressed, and then, after the compressed exhaust gas is further cooled, the temperature is lowered. The reduced exhaust gas is introduced into the expander 10 and expanded to further lower the temperature, and this low-temperature gas is brought into contact with the carbon dioxide adsorbent 84. In the method of claim 8, the carbon dioxide adsorbent 84 is heated with a heating fluid to separate the adsorbed carbon dioxide, and the separated carbon dioxide is transferred to the carbon dioxide storage container 102. Furthermore, the exhaust gas at the inlet of the expander 10 is precooled with the residual gas from which carbon dioxide has been separated. Further, the residual gas after pre-cooling is used to heat the carbon dioxide adsorbent 84. Further, the residual gas that has become low temperature after heating the carbon dioxide adsorbent 84 may be used as a cold source for other cooling equipment 104 .

In the method of claim 13, as shown in FIG. 12, after the exhaust gas is cooled, it is introduced into an expander 10 and expanded to below the freezing temperature of carbon dioxide, and then part of the condensed or solidified carbon dioxide is After the gas is separated, the residual gas is brought into contact with a carbon dioxide adsorbent 84 to adsorb and remove the remaining carbon dioxide in the residual gas. Further, after pre-cooling the exhaust gas at the inlet of the expander 10 with the residual gas from which a part of the carbon dioxide has been separated, this residual gas is transferred to the carbon dioxide adsorbent 84.
may be brought into contact with.

The apparatus for separating carbon dioxide from exhaust gas according to claim 15, as shown in FIGS. 1, 3, and 4, includes a precooler 14 that cools the exhaust gas, and an expander 10 that expands the cooled exhaust gas. and a CO2 separator 16 that separates condensed or solidified carbon dioxide from the exhaust gas whose temperature has decreased after expansion. Also,
It is practical to provide a compressor 18 for compressing the residual gas from which carbon dioxide has been separated. In the above device, as shown in FIG.
, 28 is connected to the CO2 separation tank 30, and this CO2
A vacuum pump 32 is connected to the separation tank 30 so that carbon dioxide in the CO2 separator can be introduced. Furthermore, CO
A sequence control instruction device 38 is connected to the 2 separator 16 via a CO2 level detection device 36, and the operation of the vacuum pump 32 and the opening and closing of the gate valves 26 and 28 are controlled by signals from the sequence control instruction device. . Then, the CO2 separation tank 30 is configured to be airtight, or the CO2 storage container 34 is connected to the CO2 separation tank,
It is desirable that the outer surface of the CO2 separation tank or CO2 storage container after being filled with CO2 is provided with a protective coating layer against seawater. Furthermore, as shown in FIG.
In some cases, the compressor 18 and the compressor 18 are coaxially driven by a prime mover 46, and the exhaust conduit 48 of the prime mover 46 is connected to the exhaust gas conduit at the inlet of the expander 10.

[0017] The apparatus according to claim 21, as shown in FIG.
A precooler 14 that cools exhaust gas, a compressor 18 that pressurizes the precooled exhaust gas, at least one cooler 50, 52 that cools the compressed exhaust gas, and an expander that expands the cooled exhaust gas. 10, and C for separating condensed or solidified carbon dioxide from the exhaust gas whose temperature has decreased after expansion.
It is characterized by including an O2 separator 16. 22. The apparatus of claim 21, as shown in FIG.
The O2 separator 16 includes a cyclone body 57 having a tangential cooling exhaust gas inlet 54 on the side and an exhaust gas outlet 56 on the top, and a cyclone body 57 provided horizontally at the bottom of the cyclone body 57 for condensed and solidified CO2 discharge. piston 60
, a CO2 outlet 61 provided in the direction of movement of the piston 60, and a sealable container 62 connected to the CO2 outlet 61. As shown in FIG. 8, it is desirable that a sealable container 62 filled with condensed and solidified CO2 is sealed and a concrete covering layer 68 is provided around the container 62.

[0018] The apparatus according to claim 24, as shown in FIG.
An exhaust heat recovery boiler 72 that uses exhaust gas from the internal combustion engine 70 as a heat source, at least one cooler 74 and 76 that cools the exhaust gas from the exhaust heat recovery boiler 72, and an expander 10 that expands the cooled exhaust gas. , CO that separates condensed or solidified carbon dioxide from the exhaust gas whose temperature has decreased after expansion.
2 separator 16.

As shown in FIG. 10, the apparatus of claim 25 includes a compressor 18 for compressing exhaust gas, a precooler 52 for cooling the compressed exhaust gas, and an expander 10 for expanding the precooled exhaust gas. and a CO2 adsorption separator 8 which introduces the exhaust gas whose temperature has decreased after expansion and adsorbs and separates carbon dioxide.
It is characterized by including 6 and 6. In the apparatus according to claim 25, as shown in FIG. It consists of a group of heat transfer tubes 94 that hold a carbon dioxide adsorbent 84, and is configured so that the carbon dioxide adsorbent and the cooled exhaust gas are in contact with each other. In addition, a plurality of CO2 adsorption separators 86 are provided in parallel, and gate valves 9 are provided before and after the CO2 adsorption separators 86.
8,100 is installed, and when the adsorption capacity of carbon dioxide is saturated and the adsorption capacity is reduced, it is shut off with a gate valve and the exhaust gas is diverted to other carbon dioxide.
Direct it to the O2 adsorption separator. Furthermore, the gate valve 98
, 100 of the heat exchanger tube 9 of the CO2 adsorption separator 86
A heated fluid inlet 97 is provided on one side of the main body 92, a heated fluid outlet 99 is provided on the other side of the main body 92, and a CO2 At the same time as connecting the storage container 102, a vacuum pump or a compressor is connected to the main body 92, and the carbon dioxide desorbed by the vacuum pump or compressor is transferred to the CO2 storage container 10.
It is desirable to configure it so that it moves to 2.

[0020] The apparatus according to claim 29, as shown in FIG. 12, includes at least one cooler 50, 52 for cooling the exhaust gas.
, an expander 10 that expands the cooled exhaust gas, a CO2 separator 16 that separates condensed or solidified carbon dioxide from the exhaust gas whose temperature has dropped after expansion, and an exhaust gas from the CO2 separator that is introduced into the exhaust gas. It is characterized by including a CO2 adsorption separator 86 that adsorbs and separates remaining carbon dioxide. CO2 is different from water,
Shows special behavior due to phase change. In other words, -56.6℃
Below, the liquid state does not exist except in the supercooled state. In a pressurized state at a low temperature, when the pressure becomes 5.11 ata or less, liquid CO2 changes to gas and solid and does not exist in liquid form. In other words, even if it is expanded from atmospheric pressure to a low temperature, it does not become a liquid state but directly becomes a solid. On the other hand, when expanded from a high pressure state, depending on the conditions at the expander inlet (temperature, pressure), it temporarily liquefies, and then either exists as a liquid in a supercooled state or separates into gas and solid. . For example, when expanding from an inlet pressure of 20 ata, it will not liquefy if the inlet temperature is around 25 degrees Celsius, but if it is expanded from around 0 degrees Celsius or lower, it will always liquefy at a time of 5.11 ata or higher and below -56.6 degrees Celsius. .

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. However, unless there is a specific description, the shapes of the components described in this example, their relative positions, the temperatures described in the drawings, etc. are intended to limit the scope of the present invention to only those described. not of
This is just an illustrative example. FIG. 1 is an embodiment of the apparatus for separating carbon dioxide from exhaust gas according to the present invention, and shows an apparatus that expands the carbon dioxide using an expander 10 and lowers the temperature to remove CO2. In FIG. 1, the CO2-containing gas is made as low as possible using cooling water, air, etc. to remove moisture, and then expanded in an expander 10. As shown in FIG. 5, if the expander inlet gas temperature and expansion ratio ε are appropriately selected, the expander outlet gas temperature reaches the temperature at which CO2 solidifies. However, the partial pressure of CO2 has decreased due to the lower pressure, and when the expansion ratio is 15, the total pressure after expansion is 760/15 = 50.7 mmH
g. Therefore, if the CO2 molar concentration was 15% at the inlet, 760 x 0.15/15 = 7.6 after expansion.
mmHg. The saturation temperature of CO2 at this pressure is -12
This is 0.2°C, and it is necessary to lower the expander outlet temperature below this value. To satisfy this requirement, it is necessary to lower the temperature at the inlet of the expander to 10°C. However, since the vapor pressure of solid CO2 at -120.2°C is 10 mmHg, it does not actually solidify.

Calculating backwards from this, when the expansion ratio ε=15 and the expander inlet temperature is 10°C, the concentration of CO2 at the expander inlet must be 10.0/7.6×15=20% molar concentration or higher. Does not coagulate. In this case, it is necessary to make ε larger or to lower the expander inlet temperature to lower the expander outlet temperature. When ε=30 and the expander inlet is set to -75°C, the expander outlet temperature is lowered to about -180.4°C. Since the vapor pressure of CO2 at -140°C is 0.5 mmHg, it is 760 x 0.15/30 = 3.8 mmHg. In other words, 3.8-0.5=3.3mmHg of CO
2 can be solidified. However, for 1 kg of total gas flow rate, about 0.25 kg of CO2 is included (
15% molar concentration gas), and considering that the temperature rise of the gas from -180.4℃ to -140℃ is due to the solidification heat of CO2, the gas specific heat is 0.24kcal/kg, (
-140+180.4)×0.24×1=9.7kca
l of heat is required. On the other hand, the solidification heat of CO2 is 136.
89 x 0.25 x 3.3/3.8 = 29.7 kcal, the solidification heat of CO2 is much larger, and the gas temperature is -1
It becomes higher than 40℃. In other words, CO2 is 3.3mmHg
It cannot be solidified and balances at a temperature higher than -140°C. When calculating this, it is balanced at around -129℃, and it is 1.4
mmHg minute, or 1.4/3.8 = 0.37 (37%
) of CO2 solidifies, and 63% is released as residual gas along with N2 and O2. It can be seen that the method in FIG. 1 is advantageous when the CO2 content is high. Further C
The fact that the percentage of O2 is high and there is a lot of CO2 to be removed means that
The amount of residual gas decreases, and the power to compress it to atmospheric pressure decreases.
In this respect as well, it is advantageous when the CO2 concentration is high. However, in reality, if there is a lot of water contained in the gas at the inlet of the expander (even if it is cooled to 40 degrees Celsius, the partial pressure of water vapor is still high at atmospheric pressure even after removal), this will condense or form snow. This results in heat generation, which is less favorable than the above estimate. Therefore, it can be applied to gases with low moisture content.

Specifically, as shown in FIG. 1, an exhaust gas generation source (such as a boiler,
The exhaust gas from the furnace (furnace, other combustion equipment) 12 is cooled (e.g. to around 0°C) with a cooling source such as air or cooling water in the precooler 14 to remove moisture from the exhaust gas, and The expansion ratio at 10 was selected to lower the combustion gas temperature below the freezing point of CO2 (-78.9°C), and after expansion, CO
2 is solidified and separated by a CO2 separator 16, CO2
The residual gas separated is pressurized to a predetermined pressure by the compressor 18 and released to the atmosphere. 20 is a generator, 22 is a drive machine, 2
4 is an exhaust stack.

In the separation of CO2 at the outlet of the expander 10, as shown in FIG. Connect the pump 32,
The inside of the CO2 separation tank 30 is brought to a low pressure by the vacuum pump 32, and the separated CO2 at the outlet of the expander 10 is introduced into the low pressure CO2 separation tank 30 and separated from the combustion gas system. Also, CO
2 The amount of CO2 stored in the separator 16 (e.g. level)
is detected, and the operation of the vacuum pump 32 of the CO2 separation tank 30 and the opening/closing of the gate valves 26 and 28 are controlled based on the signal. Furthermore, the CO2 separation tank 30 may have a structure that can be sealed, or the CO2 separation tank 30 may contain CO2.
After the storage container 34 is connected and filled with CO2, a protective coating layer against seawater (for example, hardened with concrete) is provided on the outer surface of the CO2 separation tank 30 or the CO2 storage container 34. 36 is a CO2 level detection device (for example, a level meter);
38 is a sequence control instruction device, 40 is a compressed air supply pipe, and 42 and 44 are control valves.

Further, as shown in FIG. 3, the axis of the expander 10 and the axis of the compressor 18 are made coaxial and driven by a prime mover 46, and the exhaust gas of the prime mover 46 is expanded through an exhaust gas conduit 48. It may also be introduced at the entrance of the machine 10. Furthermore, as shown in FIG. 4, heat exchange may be performed between the low temperature gas from the CO2 separator 16 and the exhaust gas at the inlet of the expander 10 in a precooler 49.

FIG. 6 shows another embodiment of the present invention, in which the compressor 18
This shows a method of compressing and then expanding. Since a gas with a high water content releases a large amount of heat when condensed, it is advantageous to perform the expansion step after separating the gas in advance to lower the temperature of the gas. In particular, gaseous fuels such as natural gas,
This is the case when burning coal, etc. that contains a large amount of moisture. By performing intercooling, the power of the compressor 18 is reduced, and the power of the drive machine 22 can be reduced. Specifically, as shown in FIG.
After cooling through 4, for example, 20 to 30
kg/cm2 A, then cooled in a cooler 50, and further cooled in a cooler 52 with cooling gas from the CO2 separator 16 so that the exhaust gas temperature at the inlet of the expander 10 is as close to 0°C as possible. The condensed or solidified CO2 is converted into CO2 by selecting the expansion ratio so as to lower the gas temperature below the condensation point or freezing point (-78.9°C) of CO2. They are separated by a separator 16. When compressing with the compressor 18, the compression process may be performed in multiple stages and intermediate cooling may be performed. FIG. 7 shows an example of the CO2 separator 16. The low-temperature combustion gas introduced tangentially from the low-temperature exhaust gas inlet 54 turns into solid CO2 (dry ice) while swirling.
Or the liquefied CO2 is separated and the clean gas is passed through the exhaust gas outlet 56.
is discharged from. The separated CO258 accumulated at the bottom is pushed out by the piston 60 and falls into a sealable container 62. 64 is a heat insulating material. 57 is the cyclone body, 6
1 is a CO2 exhaust port. As shown in FIG. 8, the separated dry ice or liquefied CO2 is placed in a sealable container 62, and the container 62 is sealed with a flange 66 or with a stopper as shown by the broken line and welded around the container 62. The surrounding area is hardened with a concrete covering layer 68 and left alone. In some cases,
Dump into the deep sea. Even if the container 62 were to break, CO2 would not leak out due to the pressure of the deep sea. Even if it leaks out in small quantities, it will be absorbed into the seawater or remain as a liquid in the deep sea.

FIG. 9 shows another embodiment of the present invention, in which high-pressure and high-temperature gas is discharged from the expansion process of an internal combustion engine 70 such as a diesel engine, the heat is recovered by a boiler, etc., and the low-temperature gas is expanded. The method is shown. In an internal combustion engine, gas is normally released from the cylinder at a pressure significantly higher than atmospheric pressure. In the present invention, the exhaust pressure is slightly increased compared to the conventional exhaust pressure, and the exhaust gas temperature increases by the increased pressure. Therefore, an exhaust heat recovery boiler 72 is installed in the exhaust system as shown in FIG. After lowering the temperature of the gas, the temperature is further lowered using other coolers 74 and 76 as necessary, and then the expander 10 expands the gas to a low temperature to reduce the temperature of the gas to C.
This is a method of condensing and solidifying O2. In this embodiment, the exhaust gas is passed through the turbocharging turbine, or when there is no turbocharging turbine, the exhaust gas is passed through the exhaust heat recovery boiler 72 without reducing the pressure.
lead to. 16 is a CO2 separator, 78 is a steam turbine, 80 is a condenser, and 82 is a generator. Note that in the case of an internal combustion engine, the concentration of CO2 in the exhaust gas may be low, and this embodiment is not suitable for cases where the concentration is very low.

FIG. 10 shows another embodiment of the present invention, in which CO2 is adsorbed on a CO2 adsorbent at low temperatures. C.O.
Activated carbon, zeolite, molecular sieve, etc. are known as substances that adsorb 2. Furthermore, it is generally well known that the properties of these adsorbents are that the higher the pressure and the lower the temperature, the easier they are to adsorb. Separating all the CO2 contained in exhaust gas by liquefaction or solidification has disadvantages such as a decrease in power generation efficiency, an increase in the size and cost of the equipment, and an increase in the required compression power. It's coming. The invention of this example is
These can be resolved. To explain with Figure 10,
In FIG. 10, as in the case of FIG. 6, the gas containing CO2 is cooled with cooling water as much as possible in the precooler 14, the compression power is reduced including the removal of water, and then the gas is compressed in the compressor 18. After the high-pressure gas is further cooled with cooling water or the like to remove moisture, it is precooled with a cooler 52 if necessary, and then expanded with an expander 10 to lower the gas temperature. The gas temperature after expansion when the expansion ratio and expander inlet gas temperature are given is as shown in FIG. This low-temperature gas is guided to a CO2 adsorption separator 86 containing a carbon dioxide adsorbent 84, as shown in FIG.

This CO2 adsorption separator 86 has a cooled exhaust gas inlet 88 on one side and an exhaust gas outlet 90 on the other side.
The main body 92 has a main body 92, and a group of heat transfer tubes 94 that holds the carbon dioxide adsorbent 84 housed in the main body 92 on the surface or inside surface (in the drawing, it is held on the surface as an example). 96 is a blind plate, 97 is a heating fluid inlet, and 99 is a heating fluid outlet. A carbon dioxide adsorbent 84 such as activated carbon, zeolite, or molecular sieve is provided on the outer surface (not necessarily the outer surface; in FIGS. 10 and 11, the outer surface is an example) of the heat transfer tube 94. , as it is cooled by the low-temperature gas, the temperature becomes low and CO2
adsorbs large amounts of. Because of the low temperature, most of the CO2 in the gas can be adsorbed. However, since heat of condensation is released when CO2 is adsorbed, both the gas temperature and the temperature of the adsorbent rise. As in the previous example, 0.25 kg of C is contained in 1 kg of combustion gas.
In cases containing O2 gas, 0.25 kg of CO
2 is all adsorbed and condensed, 88.12kcal/
kg x 0.25 = 20.03 kcal of heat is generated. If we balance this heat with the sensible heat of 1 kg of gas, we get
Δt=83.5℃ from 20.03=0.24×Δt×1
becomes. In other words, even if the temperature of the adsorbent rises to 0℃,
If the adsorbent has enough weight to have adsorption capacity, it is sufficient to lower the gas temperature to -83.5°C. On the other hand, if a molecular sieve is used as the adsorbent, the equilibrium pressure can be selected to be 1 mmHg. In other words, at a 15% molar concentration of CO2, it is 114 mmHg, so almost 99% can be removed by adsorption (if the weight of the molecular sieve is small, the equilibrium pressure increases). If gas containing CO2 continuously flows into the CO2 adsorption separator 86, it will eventually become saturated and no longer absorbed, so at this time the gas is switched and separated by another CO2 adsorption separator. on the other hand,
The saturated CO2 adsorption separator is shut off by gate valves 98 and 100, and while the inside is evacuated using the attached vacuum pump, the heated fluid is flowed onto the inner surface of the heat transfer tube, and the adsorbed carbon is removed.
O2 evaporates. At this time, the characteristics are determined by the temperature of the heated heat transfer tube and the ultimate vacuum of the vacuum pump, but since the ultimate vacuum of the vacuum pump can be set to 10-2 mmHg, almost all of the CO2 is It can be recovered. In this case, if the CO2 storage container 102 to which the gas is to be transferred using a vacuum pump is evacuated in advance, CO2 gas with approximately 100% purity can be obtained. This gas can be compressed using a compressor and filled into cylinders.

[0030] When the adsorbed CO2 evaporates, it takes away heat, so the temperature of the adsorbent decreases. Therefore, there is a possibility of freezing in gases containing moisture. For this reason, the gas exiting the cooler 52 from which CO2 has been removed (moisture has been removed)
This eliminates the problem of water freezing, and this dry, low-temperature gas can be used for other purposes. For example, it can be used as a cold source for another cooling facility (cold energy utilizing facility) 104. Note that when adsorption is performed at 0°C, CO
The gas exiting the second adsorption separator 86 has a temperature of 0°C, and if the gas at the inlet of the expander 10 is precooled with this, the temperature can be lowered only to about 10°C. However, at 10°C, the temperature of the expander outlet gas can be easily lowered to -83.5°C.

FIG. 12 shows still another embodiment of the present invention, showing a system in which the embodiment shown in FIGS. 10 and 11 and other embodiments are combined. For example, CO2-containing gas is brought to a low temperature using the compression-then-expansion method shown in FIG. 6, and CO2 is separated from some of the gases using the method shown in FIG. gas from)
CO2 can be adsorbed and separated in the downstream of the cooler 52 by the method shown in FIGS. 10 and 11. Further, as shown in FIG. 12, after the exhaust gas is cooled by the cooler 52,
The CO2 is introduced into the expander 10 and condensed or solidified at a low temperature, and the CO2 separator 16 removes a portion of the CO2. The gas is then led to the CO2 adsorption separator 86 to remove the remaining CO2. In this case, it is desirable to pre-cool the exhaust gas at the inlet of the expander 10 with the residual gas from which part of the CO2 has been removed in the cooler 52, and then introduce this residual gas to the CO2 adsorption separator 86. 106 is a cooling facility that cools other substances, such as air for air conditioning.

[0032]

[Effects of the Invention] Since the present invention is constructed as described above, it has the following effects. (1) Since CO2 is separated while the exhaust gas is cooled, CO2 in the exhaust gas can be efficiently separated.
Moreover, since CO2 can be separated in liquid or solid form,
It is easy to handle (also in the case of FIG. 10, CO2 is ultimately liquefied by a compressor and stored in a container). (2) Since low-temperature exhaust gas is generated during CO2 separation, this low-temperature exhaust gas can be effectively used as a cold heat source for power generators and the like.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an embodiment of an apparatus for implementing the method of separating carbon dioxide from exhaust gas of the present invention.

FIG. 2 is an explanatory diagram showing details around the CO2 separator in FIG. 1;

FIG. 3 is a flow sheet showing another embodiment of the apparatus of the present invention.

FIG. 4 is a flow sheet showing another embodiment of the apparatus of the present invention.

FIG. 5 is a graph showing the relationship between expander inlet gas temperature and expander outlet gas temperature when the expansion ratio is changed.

FIG. 6 is a flow sheet showing another embodiment of the apparatus of the present invention.

FIG. 7 is a sectional view showing an example of a CO2 separator used in the device of the present invention.

FIG. 8 is a sectional view showing an example of a method for treating separated CO2 in the present invention.

FIG. 9 is a flow sheet showing another embodiment of the apparatus of the present invention.

FIG. 10 is a flow sheet showing another embodiment of the apparatus of the present invention.

11 is an enlarged sectional view showing an example of the CO2 adsorption separator in FIG. 10. FIG.

FIG. 12 is a flow sheet showing still another embodiment of the apparatus of the present invention.

[Explanation of symbols]

10 Expander 12　　　Exhaust gas generation source 14 Pre-cooler 16 CO2 separator 18 Compressor 26 Gate valve 28 Gate valve 30 CO2 separation tank 32 Vacuum pump 34 CO2 storage container 36 CO2 level detection device 38 Sequence control instruction device 46 Prime mover 48 Exhaust pipe 50 Cooler 52 Cooler 54 Cooling exhaust gas inlet 56 Exhaust gas outlet 57 Cyclone body 60 Piston 61 CO2 exhaust port 62 Sealable container 68 Concrete covering layer 70 Internal combustion engine 72 Exhaust heat recovery boiler 74 Cooler 76 Cooler 78 Steam turbine 80 Condenser 84 Carbon dioxide adsorbent 86 CO2 adsorption separator 88 Cooling exhaust gas inlet 90 Exhaust gas outlet 92 Main body 94 Heat exchanger tube 97 Heating fluid inlet 98 Gate valve 99 Heating fluid outlet 100 Gate valve 102 CO2 storage container 104 Cooling equipment

Claims (29)

[Claims] [Claim 1] After cooling the exhaust gas, an expander (10)
A method for separating carbon dioxide from exhaust gas, characterized by introducing the carbon dioxide into a gas, expanding it to a temperature below the solidification temperature of carbon dioxide, and then separating the condensed or solidified carbon dioxide. [Claim 2] The residual gas after separating carbon dioxide is compressed and
The method for separating carbon dioxide from exhaust gas according to claim 1, characterized in that the pressure is increased and the carbon dioxide is discharged into the atmosphere. [Claim 3] After cooling the exhaust gas, the compressor (18)
The compressed exhaust gas is then introduced into an expander (10) and expanded to a temperature below the liquefaction temperature or below the solidification temperature of carbon dioxide, and the condensed or solidified carbon dioxide is separated. A method of separating carbon dioxide from exhaust gas. 4. The method for separating carbon dioxide from exhaust gas according to claim 3, wherein the compression step is performed in multiple stages and intermediate cooling is performed. 5. Exhaust gas from the internal combustion engine (70) is guided to the exhaust heat recovery boiler (72) without reducing pressure to heat feed water and steam, cooled, and then introduced to the expander (10) for expansion. A method for separating carbon dioxide from exhaust gas, which comprises: reducing the temperature to below the solidification temperature of carbon dioxide and separating condensed or solidified carbon dioxide. 6. The method for separating carbon dioxide from exhaust gas according to claim 5, characterized in that steam generated in the exhaust heat recovery boiler (72) is introduced into a steam turbine (78) to generate electricity. [Claim 7] A condenser (80) of a steam turbine (78).
) The method for separating carbon dioxide from exhaust gas according to claim 6, characterized in that the heat disposed of in the second power generation device is used as a high temperature heat source of the second power generation device, and the low temperature gas at the outlet of the expander is used as a low temperature heat source of the second power generation device. . [Claim 8] After cooling the exhaust gas, the compressor (18)
Then, after further cooling the compressed exhaust gas, the exhaust gas whose temperature has decreased is introduced into an expander (10) and expanded to further lower the temperature, and this low-temperature gas is passed through a carbon dioxide adsorbent ( 84) A method for separating carbon dioxide from exhaust gas. 9. A claim characterized in that the carbon dioxide adsorbent (84) is heated with a heating fluid to separate the adsorbed carbon dioxide, and the separated carbon dioxide is transferred to the carbon dioxide storage container (102). Item 8. The method for separating carbon dioxide from exhaust gas. [Claim 10] Residual gas from which carbon dioxide has been separated,
The method for separating carbon dioxide from exhaust gas according to claim 8 or 9, characterized in that the exhaust gas at the inlet of the expander (10) is precooled. 11. The method for separating carbon dioxide from exhaust gas according to claim 10, characterized in that residual gas after pre-cooling is used to heat the carbon dioxide adsorbent (84). 12. The remaining gas, which has become low temperature after heating the carbon dioxide adsorbent (84), is transferred to another cooling equipment (104).
12. The method for separating carbon dioxide from exhaust gas according to claim 11, characterized in that the method is characterized in that the method uses a cold source as a cold heat source. Claim 13: After cooling the exhaust gas, an expander (10
) and expand it to below the freezing temperature of carbon dioxide,
Then, after separating a part of the condensed or solidified carbon dioxide, the remaining gas is brought into contact with a carbon dioxide adsorbent (84),
A method for separating carbon dioxide from exhaust gas, which is characterized by adsorbing and removing the remaining carbon dioxide in the residual gas. 14. A claim characterized in that after precooling the exhaust gas at the inlet of the expander (10) with the residual gas from which a portion of the carbon dioxide has been separated, this residual gas is brought into contact with the carbon dioxide adsorbent (84). Item 14. The method for separating carbon dioxide from exhaust gas. [Claim 15] Precooler (14) for cooling exhaust gas
and an expander (10) that expands the cooled exhaust gas.
An apparatus for separating carbon dioxide from exhaust gas, comprising a CO2 separator (16) for separating condensed or solidified carbon dioxide from exhaust gas whose temperature has decreased after expansion. 16. Claim 1, further comprising a compressor (18) for compressing residual gas from which carbon dioxide has been separated.
5. A device for separating carbon dioxide from exhaust gas according to 5. 17. A CO2 separation tank (3) equipped with a CO2 separator (16) and gate valves (26) and (28) at the front and rear.
0), and a vacuum pump (32) is connected to the CO2 separation tank (30) so as to introduce carbon dioxide in the CO2 separator.
6. A device for separating carbon dioxide from exhaust gas according to 6. [Claim 18] CO2 in the CO2 separator (16)
A sequence control instruction device (38) is connected via the level detection device (36), and a signal from this sequence control instruction device causes the vacuum pump (32) to operate and the gate valve (26) to operate.
, (28) are controlled to open and close. 19. The CO2 separation tank (30) has a structure that can be sealed, or the CO2 storage container (30) is installed in the CO2 separation tank (30).
19. The device for separating carbon dioxide from exhaust gas according to claim 17 or 18, wherein a protective coating layer against seawater is provided on the outer surface of the CO2 separation tank or CO2 storage container after connecting 4) and filling with CO2. . 20. The expander (10) and compressor (18) are coaxial and driven by a prime mover (46), and the exhaust conduit (48) of the prime mover (46) is connected to the inlet of the expander (10). Claim 15, characterized in that it is connected to an exhaust gas conduit.
20. A device for separating carbon dioxide from exhaust gas according to 16, 17, 18 or 19. [Claim 21] Precooler (14) for cooling exhaust gas
and a compressor (18) that pressurizes the pre-cooled exhaust gas.
at least one cooler for cooling the compressed exhaust gas (
50), (52), an expander (10) that expands the cooled exhaust gas, and from the exhaust gas whose temperature has decreased after expansion,
A device for separating carbon dioxide from exhaust gas, characterized in that it includes a CO2 separator (16) for separating condensed or solidified carbon dioxide. 22. A cyclone body (57) in which the CO2 separator (16) has a tangential cooling exhaust gas inlet (54) on the side and an exhaust gas outlet (56) on the top;
A piston (60) for discharging condensed/solidified CO2 provided horizontally at the bottom of the cyclone body (57), a CO2 discharging port (61) provided in the direction of movement of this piston (60), and a CO2 discharging port (61) provided in the direction of movement of this piston (60). 22. Device for separating carbon dioxide from exhaust gas according to claim 21, characterized in that it comprises a sealable container (62) connected to the outlet (61). 23. The method according to claim 22, characterized in that a sealable container (62) filled with condensed and solidified CO2 is sealed, and a concrete covering layer (68) is provided around the container (62). A device that separates carbon dioxide from exhaust gas. 24. An exhaust heat recovery boiler (72) using exhaust gas from the internal combustion engine (70) as a heat source, and an exhaust heat recovery boiler (
at least one cooler (74), (76) for cooling the exhaust gas from 72), an expander (10) for expanding the cooled exhaust gas, and condensation or solidification from the exhaust gas whose temperature has decreased after expansion. 1. A device for separating carbon dioxide from exhaust gas, comprising: a CO2 separator (16) for separating carbon dioxide. 25. A compressor (18) that compresses exhaust gas, a precooler (52) that cools the compressed exhaust gas, an expander (10) that expands the precooled exhaust gas, and a temperature control device after expansion. 1. A device for separating carbon dioxide from exhaust gas, comprising: a CO2 adsorption separator (86) which introduces exhaust gas with reduced carbon dioxide and adsorbs and separates carbon dioxide. 26. The CO2 adsorption separator (86) has a cooled exhaust gas inlet (88) on one side and an exhaust gas outlet (88) on the other side.
90), and a group of heat transfer tubes (94) holding a carbon dioxide adsorbent (84) housed in the main body (92), so that the carbon dioxide adsorbent and the cooled exhaust gas come into contact with each other. 26. An apparatus for separating carbon dioxide from exhaust gas according to claim 25. 27. A plurality of CO2 adsorption separators (86) are provided in parallel, and gate valves (98) and (100) are provided before and after the CO2 adsorption separators (86), so that carbon dioxide adsorption is saturated. 27. The apparatus for separating carbon dioxide from exhaust gas according to claim 25 or 26, characterized in that when the adsorption capacity decreases, the exhaust gas is shut off with a gate valve and the exhaust gas is guided to another CO2 adsorption separator. 28. The heated fluid can be passed through the side of the heat transfer tube (94) group of the CO2 adsorption separator (86) that is shut off by the gate valves (98) and (100), which is different from the adsorbent holding surface. , a heated fluid inlet (97) is provided on one side of the main body (92), a heated fluid outlet (99) is provided on the other side of the main body (92), and a CO2 storage container (102) is connected to the exhaust gas outlet (90), 28. Dioxide from exhaust gas according to claim 27, characterized in that a vacuum pump or a compressor is connected to the main body (92), and carbon dioxide desorbed by the vacuum pump or compressor is transferred to the CO2 storage container (102). A device that separates carbon. 29. At least one cooler (50), (52) that cools the exhaust gas, an expander (10) that expands the cooled exhaust gas, and condensation or CO2 separating solidified carbon dioxide
Separating carbon dioxide from exhaust gas, characterized by including a separator (16) and a CO2 adsorption separator (86) that introduces exhaust gas from the CO2 separator and adsorbs and separates carbon dioxide remaining in the exhaust gas. Device.