JP5274312B2 - Gas separation method - Google Patents

Description

  The present invention relates to a gas separation method capable of separating carbon dioxide and hydrogen from a mixed gas containing carbon dioxide and hydrogen.

  Conventionally, it is known that gas components can be separated by a polymer membrane. Such a polymer film is used, for example, in a gas sensor for detecting hydrogen gas in the air (see, for example, Patent Document 1). This gas component separation technique using a polymer membrane has advantages such as requiring less energy and miniaturizing the apparatus, and is used in various fields.

  In recent years, a technique for selectively separating carbon dioxide with a polymer membrane (carbon dioxide separation membrane) has been provided from the viewpoint of global environmental conservation. For example, in order to separate and recover carbon dioxide from exhaust gas from a boiler of a thermal power plant, a garbage incinerator or the like, application of this separation technique is being studied.

JP 2008-180529 A

  However, even though conventional carbon dioxide separation membranes can separate and separate oxygen and nitrogen from carbon dioxide, the permeability coefficient of carbon dioxide and the permeability coefficient of hydrogen are not so large, so hydrogen and carbon dioxide are separated. It was difficult to do.

  For this reason, for example, in the field where carbon dioxide is recovered from coal gasification gas produced in a gasification furnace, hydrogen is separated, and this hydrogen is supplied as combustion fuel for a combined power generation system, the amount of gas handled Therefore, the conventional carbon dioxide separation membrane has a problem that it cannot be put to practical use.

  Therefore, it has been desired to provide a gas separation means capable of separating the carbon dioxide and the hydrogen from a mixed gas containing carbon dioxide and hydrogen.

  This invention is made | formed in view of the above, Comprising: It aims at providing the gas separation method which can isolate | separate the said carbon dioxide and the said hydrogen from the mixed gas containing a carbon dioxide and hydrogen.

  In order to achieve the above object, the present invention provides the following gas separation method.

(1) A gas separation method for separating carbon dioxide and hydrogen from a mixed gas containing carbon dioxide and hydrogen, wherein the carbon dioxide is liquefied by pressurizing and cooling the mixed gas. , seen containing a carbon dioxide removal step of removing the liquefied said carbon dioxide, wherein the mixed gas, sulfur is removed coal gasification furnace from the coal gasification gas produced by gasification, further shift It is generated by converting carbon monoxide contained in the coal gasification gas into carbon dioxide by a reaction, and for cooling the carbon dioxide in the carbon dioxide liquefaction step, gas from the gas in the gasification furnace is used. It is characterized by using cold heat generated by a cryogenic separator that generates gaseous oxygen and gaseous nitrogen used in the oxidization reaction and produces liquid oxygen and liquid nitrogen .

  According to the invention of (1), hydrogen remains in the mixed gas by liquefying carbon dioxide by the carbon dioxide liquefaction step and removing the liquefied carbon dioxide by the carbon dioxide removal step. Therefore, the carbon dioxide and the hydrogen can be separated from the mixed gas containing carbon dioxide and hydrogen.

According to the invention of (1 ), hydrogen supplied to the combined power generation system can be separated from the mixed gas, and carbon dioxide emissions can be reduced during operation of the combined power generation system.

In addition, according to the invention of (1 ), the energy required for removing carbon dioxide from the coal gasification gas can be reduced by using the cold heat from the cryogenic separator, and the carbon dioxide can be separated efficiently. Can do.

  According to the present invention, the carbon dioxide and the hydrogen can be separated from the mixed gas containing carbon dioxide and hydrogen.

It is explanatory drawing which shows the carbon dioxide collection system which concerns on 1st Embodiment of this invention. It is a figure which shows the thermal material balance calculation result in each point of FIG. It is a graph which shows the relationship between the saturation pressure of carbon dioxide, and temperature. It is explanatory drawing which shows the carbon dioxide collection system which concerns on 2nd Embodiment of this invention. It is a figure which shows the thermal material balance calculation result in each point of FIG.

  Embodiments of the present invention will be described below in detail with reference to the drawings. Moreover, the example which applies the gas separation method which concerns on embodiment of this invention to a carbon dioxide recovery system below is demonstrated. In addition, this invention is not limited by this embodiment.

[First Embodiment]
FIG. 1 is an explanatory diagram showing a carbon dioxide recovery system 10 according to the first embodiment of the present invention. In FIG. 1, carbon monoxide is indicated as CO, and carbon dioxide is indicated as CO2.

<Description of overall configuration of carbon dioxide recovery system>
The carbon dioxide recovery system 10 includes a gasification furnace 11 that generates coal gasification gas, a desulfurization device 12, a CO shift device 13, a dehumidification device 14, a gas cooling device 16, and a carbon dioxide recovery device 18. Prepare.

  The carbon dioxide recovery system 10 includes a cryogenic separation device 20, oxygen supply lines L 1, L 2, and L 3 that supply gaseous oxygen to the gasification furnace 11, and liquid oxygen that supplies cold heat of liquid oxygen to the gas cooling device 16. A supply line L11 and a liquid nitrogen supply line L12 that supplies the cold heat of liquid nitrogen to the carbon dioxide recovery device 18 are provided.

<Description of gasifier>
The gasification furnace 11 generates coal gasification gas mainly containing hydrogen, carbon monoxide and the like by partially burning coal (gasification reaction) under high temperature and high pressure. The gasification furnace 11 is connected to oxygen supply lines L1, L2, and L3 for blowing gaseous oxygen.

  From the oxygen supply lines L1 and L2, gaseous oxygen generated by the cryogenic separator 20 described later is supplied. From the oxygen supply line L3, liquid oxygen generated in the cryogenic separator 20 is supplied with oxygen vaporized by heat exchange with the gas flowing through the gas cooler 16.

  The gasification furnace 11 is connected to a nitrogen supply line L4 for supplying gaseous nitrogen from a carbon dioxide recovery device 18 described later. This gaseous nitrogen is effectively used as a carry gas when supplying gaseous oxygen to the gasification furnace 11.

  As described above, since only the gaseous oxygen separated from the air is supplied to the gasifier 11, the gas discharged from the gasifier 11 and passing through the line L5 is carbon monoxide (CO), hydrogen (H2). , Water (H 2 O) and carbon dioxide (CO 2). The gasification furnace 11 is connected to the desulfurization device 12 by a line L5.

<Description of desulfurization equipment>
The desulfurization device 12 removes the sulfur content in the coal gasification gas that has flowed from the gasification furnace 11 through the line L5. By removing the sulfur content in the coal gasification gas, it contributes to corrosion prevention of each device constituting the system. The desulfurization apparatus 12 is connected to the CO shifter 13 by a line L6.

<Description of CO shifter>
The CO shifter 13 shifts carbon monoxide (CO) in the coal gasification gas flowing through the line L6 from the desulfurizer 12 to carbon dioxide (CO2) and hydrogen (H2) due to the presence of steam (CO + H2O → CO2 + H2).

  Note that the steam necessary for this shift reaction may be, for example, extracted steam from a middle / low pressure turbine or the like (not shown) of the combined power generation system, and the supply source is arbitrary. The CO shifter 13 is connected to the dehumidifier 14 by a line L7.

<Description of dehumidifier>
The dehumidifier 14 is configured to be able to remove moisture from the coal gasification gas that has passed through the CO shifter 13. This is to prevent ice from adhering to the heat transfer tubes of the gas cooling device 16 when the coal gasification gas is introduced into the gas cooling device 16 described later and cooled (heat exchange).

  The dehumidifier 14 supplies, for example, a coal gasification gas into a dehumidifying refrigerant (eg, silicon oil) to cool and solidify the moisture of the coal gasification gas, and the solidified moisture (ice) It can comprise so that it may collect in the refrigerant | coolant for dehumidification.

  The dehumidifier 14 may be configured to include a moisture adsorbent such as activated alumina that adsorbs moisture of the coal gasification gas and releases the moisture adsorbed by heating. The dehumidifying device 14 is connected to the gas cooling device 16 by a line L8.

<Description of gas cooling device>
The gas cooling device 16 is a heat exchanger that exchanges heat between the coal gasification gas that has passed through the dehumidifying device 14 and the liquid oxygen generated by the cryogenic separation device 20. The gas cooling device 16 is connected to the cryogenic separator 20 by the liquid oxygen supply line L11, connected to the gasifier 11 by the oxygen supply line L3, and further connected to the carbon dioxide recovery device 18 by the line L9. Yes.

  That is, the gas cooling device 16 cools the coal gasification gas by using the cold heat of the liquid oxygen generated when the gaseous oxygen supplied to the gasification furnace 11 is produced by the cryogenic separation device 20. It is a thing.

  In the gas cooling device 16, the oxygen vaporized by cooling the coal gasification gas is supplied to the gasification furnace 11 through the oxygen supply line L3.

<Description of the cryogenic separator>
The cryogenic separation device 20 is configured to generate liquid oxygen and liquid nitrogen by pressurizing and cooling air as a raw material and generating gaseous oxygen and gaseous nitrogen. That is, the cryogenic separator 20 is connected to the gasification furnace 11 through oxygen supply lines L1 and L2, and is configured to be able to supply gaseous oxygen and gaseous nitrogen to the gasification furnace 11 through the oxygen supply lines L1 and L2. ing.

  Further, the cryogenic separation device 20 is connected to the gas cooling device 16 by a liquid oxygen supply line L <b> 11 and is configured to be able to supply the generated liquid oxygen to the gas cooling device 16. Further, the cryogenic separator 20 is connected to the carbon dioxide recovery device 18 by a liquid nitrogen supply line L12, and is configured to be able to supply the generated liquid nitrogen to the carbon dioxide recovery device 18.

  In order to generate liquid oxygen to be supplied to the gas cooling device 16 and liquid nitrogen to be supplied to the carbon dioxide recovery device 18, cooling energy is required. Therefore, in order to reduce the load on the cryogenic separation device 20, It is preferable that the generated liquid oxygen and liquid nitrogen are the minimum necessary.

<Description of carbon dioxide recovery device>
The carbon dioxide recovery device 18 cools the coal gasification gas that has passed through the gas cooling device 16 with the cold heat of the liquid nitrogen generated by the cryogenic separation device 20, and liquefies and separates the carbon dioxide contained in the coal gasification gas. Heat exchanger to be recovered.

  The carbon dioxide recovery device 18 is connected to the cryogenic separator 20 by the liquid nitrogen supply line L12, is connected to the gasifier 11 by the nitrogen supply line L4, and is further connected to the combined power generation system (not shown) by the line L10. Connected with.

  That is, the coal gasification gas from which carbon dioxide has been removed by the carbon dioxide recovery device 18 becomes hydrogen-rich gas mainly composed of hydrogen, and is supplied to the turbine combustor (not shown) of the combined power generation system by the line L10. It has become so.

  In the carbon dioxide recovery device 18, the nitrogen vaporized by cooling the coal gasification gas is supplied to the gasification furnace 11 through the nitrogen supply line L4. This gaseous nitrogen is effectively used as a carry gas when supplying gaseous oxygen to the gasification furnace 11.

  The liquid carbon dioxide (liquefied CO2) separated and removed from the coal gasification gas is configured to be sent out of the system from the line L13.

<Description of action and effect of carbon dioxide recovery system>
Next, the operation (action and effect) of the carbon dioxide recovery system 10 will be described with reference to FIGS. Here, FIG. 2 is a figure which shows the thermal material balance calculation result in each point (point P1-point P10) of FIG. That is, FIG. 2 shows the phase, temperature, pressure, average molecular weight, molar flow rate, and composition of the coal gasification gas at each point (point P1 to point P10) in FIG. FIG. 3 is a graph showing the relationship between the saturation pressure of carbon dioxide and the temperature.

  The gasification furnace 11 is generated by the cryogenic separator 20 described later from the oxygen supply lines L1 and L2 by gaseous nitrogen (temperature is about 5 degrees at the point P8) supplied as a carry gas from the nitrogen supply line L4. Gas oxygen (at a temperature of about 25 degrees at point P9 and point P10) is supplied.

  The gasification furnace 11 is also supplied with gaseous oxygen (at a temperature of about 5 degrees at the point P6) from the oxygen supply line L3. Thereby, the gasification furnace 11 produces | generates coal gasification gas mainly containing hydrogen (H2), carbon monoxide (CO), etc. by carrying out partial combustion (gasification reaction) of coal under high temperature and high pressure.

  Since only gas oxygen separated from air is supplied to the gasification furnace 11, the coal gasification gas generated in the gasification furnace 11 is carbon monoxide (CO), hydrogen (H2), water (H2O). ) And carbon dioxide (CO2). This coal gasification gas is sent to the desulfurization apparatus 12 through the line L5.

  Sulfur content is removed from the coal gasification gas sent to the desulfurization apparatus 12. Then, the coal gasification gas is sent to the CO shifter 13 through the line L6.

  The coal gasification gas sent to the CO shifter 13 shifts carbon monoxide (CO) in the coal gasification gas by supplying steam (not shown) (CO + H 2 O → CO 2 + H 2). That is, in the CO shifter 13, carbon dioxide (CO2) and hydrogen (H2) are generated by this shift reaction. Then, the coal gasification gas is sent to the dehumidifier 14 through the line L7.

  The coal gasification gas sent to the dehumidifying device 14 is dehydrated and sent to the gas cooling device 16 through the line L8. Since the coal gasification gas introduced into the gas cooling device 16 has already been dehydrated, when it is cooled (heat exchanged) in the gas cooling device 16, ice adheres to the heat transfer tubes of the gas cooling device 16. I won't let you.

  At this time, at the point P1 of the line L8, as shown in FIG. 2, for example, the temperature of the coal gasification gas is 5 ° C. and the pressure is 7.6 MPa. The composition of the coal gasification gas is, for example, 53% for hydrogen and 37.4% for carbon dioxide, which account for about 90%.

  Then, the coal gasification gas sent to the gas cooling device 16 is cooled by the cold heat of liquid oxygen supplied from the liquid oxygen supply line L11 of the cryogenic separation device 20.

  For example, at the point P5 of the liquid oxygen supply line L11, as shown in FIG. 2, the temperature of the liquid oxygen is about −196 ° C. The coal gasification gas is cooled to −23 ° C. (refer to the value of point P2 of the line L9 shown in FIG. 2) by this liquid oxygen, and is sent to the carbon dioxide recovery device 18 through the line L9.

  As described above, the gas cooling device 16 can sufficiently cool the coal gasification gas by effectively using the cold heat of the liquid oxygen supplied from the cryogenic separation device 20. Moreover, the liquid oxygen which cooled coal gasification gas vaporizes, and is supplied to the gasification furnace 11 through the oxygen supply line L3.

  The coal gasification gas sent to the carbon dioxide recovery device 18 is cooled by the cold heat of the liquid nitrogen supplied from the liquid nitrogen supply line L12 of the cryogenic separator 20.

  Then, carbon dioxide (including gaseous carbon dioxide) contained in the coal gasification gas is completely liquefied and separated from the mainstream coal gasification gas. The separated liquid carbon dioxide is recovered from the line L13.

  For example, at the point P7 of the liquid nitrogen supply line L12, the temperature of liquid nitrogen is −196 ° C. as shown in FIG. The coal gasification gas is cooled by this liquid nitrogen to about −56.5 ° C. under a pressure of about 7.58 MPa (see the value of point P3 in FIG. 2). Under these conditions, gaseous carbon dioxide in the coal gasification gas is liquefied (see FIG. 3). In addition, the temperature of the liquid carbon dioxide collect | recovered from the line L13 at this time is about -56.5 degreeC (refer the value of the point P4 of FIG. 2).

  When the liquid carbon dioxide is separated in this way, the coal gasification gas becomes a hydrogen rich gas in which hydrogen is about 74.8% (refer to the value of point P3 in FIG. 2), and the combined power generation system passes through the line L10. To a turbine combustor (not shown).

  As described above, according to the gas separation method applied to the carbon dioxide recovery system 10 according to the first embodiment, the cold heat of the cryogenic separation device 20 that generates the fuel (gaseous oxygen) of the gasifier 11 is converted into coal. It can be utilized when carbon dioxide is liquefied and removed from the gasification gas.

  Therefore, energy required for removing carbon dioxide from the coal gasification gas can be reduced, and carbon dioxide can be efficiently separated and recovered.

  In addition, if this carbon dioxide recovery system 10 is applied to a coal gasification power plant, carbon dioxide can be efficiently separated and recovered from the coal gasification gas, so that the coal gasification power generation further reduces the carbon dioxide emission. A plant can be provided.

  Moreover, although the exhaust gas in a normal power plant or the like is normal pressure, the coal gasification gas in the carbon dioxide recovery system 10 is high pressure (about 7.6 MPa), so the cooled carbon dioxide is solidified. Since it can be removed as liquid carbon dioxide, subsequent handling is easy.

[Second Embodiment]
FIG. 4 is an explanatory diagram showing a carbon dioxide recovery system 30 according to the second embodiment of the present invention. FIG. 5 is a diagram showing a thermal mass balance calculation result at each point (point P1 to point P10) in FIG.

  That is, FIG. 5 shows the type, temperature, pressure, average molecular weight, molar flow rate, and composition of the coal gasification gas phase at each point (point P1 to point P10) in FIG. In the following description, members that are the same as or correspond to those already described are assigned the same reference numerals, and redundant description is omitted or simplified.

<Description of overall configuration of carbon dioxide recovery system>
As shown in FIG. 4, the carbon dioxide recovery system 30 according to the second embodiment is configured between the dehumidifying device 14 and the gas cooling device 16 in the configuration of the carbon dioxide recovery system 10 according to the first embodiment (see FIG. 1). The main difference is that the compressor 15 is provided in the line L8, and the compressor 17 is provided in the line L9 between the gas cooling device 16 and the carbon dioxide recovery device 18.

<Description of compressor configuration>
That is, as shown in FIG. 4, the compressor 15 is connected to the dehumidifying device 14 by a line L8a, and is connected to the gas cooling device 16 by a line L8b. The compressor 17 is connected to the gas cooling device 16 through a line L9a, and is connected to the carbon dioxide recovery device 18 through a line L9b.

<Description of action by compressor>
The coal gasification gas (pressure is 3.2 MPa at point P1 in FIG. 5) that has passed through the dehumidifier 14 is compressed by the compressor 15 (pressure is 5.4 MPa at point P2 in FIG. 5). Although the coal gasification gas is heated by this compression (temperature is 5 ° C. (point P 1 in FIG. 5) to about 49 ° C. (point P 2 in FIG. 5)), it is supplied from the cryogenic separator 20 in the gas cooling device 16. Cooled by liquid oxygen.

  Further, the coal gasification gas that has passed through the gas cooling device 16 (the pressure is approximately 5.4 MPa at the point P3 in FIG. 5) is compressed by the compressor 17 (the pressure is approximately 7.4 MPa at the point P4 in FIG. 5). This compression increases the temperature of the coal gasification gas (the temperature ranges from −15 ° C. (point P3 in FIG. 5) to about 9.9 ° C. (point P2 in FIG. 5)). Cooled by liquid oxygen supplied from

  Thus, since the saturation pressure of the carbon dioxide contained in coal gasification gas can be raised by compression by the compressors 15 and 17, liquefaction of a carbon dioxide can be accelerated | stimulated (refer FIG. 3), and liquid dioxide The carbon recovery rate can be improved. Other configurations and effects are substantially the same as in the case of the first embodiment, and a duplicate description is omitted.

  As described above, according to the gas separation method applied to the carbon dioxide recovery system 30 according to the second embodiment, the same effect as in the case of the first embodiment is obtained, and the carbon dioxide recovery rate is improved. be able to.

DESCRIPTION OF SYMBOLS 10 Carbon dioxide recovery system 11 Gasification furnace 12 Desulfurization device 13 CO shift device 14 Dehumidification device 15, 17 Compressor 16 Gas cooling device 18 Carbon dioxide recovery device 20 Cryogenic separation device 30 Carbon dioxide recovery system L1, L2, L3 Oxygen supply Line L4 Nitrogen supply line L5, L6, L7, L8, L8a, L8b, L9, L9a, L9b, L10 line L11 Liquid oxygen supply line L12 Liquid nitrogen supply line L13 line

Claims (1)

A gas separation method for separating carbon dioxide and hydrogen from a mixed gas containing carbon dioxide and hydrogen,
A carbon dioxide liquefaction step of liquefying the carbon dioxide by pressurizing and cooling the mixed gas;
A carbon dioxide removal step of removing the liquefied said carbon dioxide only contains,
The mixed gas is obtained by removing sulfur from coal gasification gas generated by gasifying coal in a gasification furnace, and further converting carbon monoxide contained in the coal gasification gas into carbon dioxide by a shift reaction. Generated
The carbon dioxide in the carbon dioxide liquefaction step is cooled by a cryogenic separator that generates gaseous oxygen and gaseous nitrogen used in the gasification reaction in the gasification furnace from the air and produces liquid oxygen and liquid nitrogen. A gas separation method, wherein cold heat is used .

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