JP2005195283A - CO2 absorption method in by-product gas using waste heat of circulating refrigerant of stave cooler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CO<SB>2</SB>absorbing method of absorbing CO<SB>2</SB>from by-product gas generated in iron works using waste heat of circulating refrigerant in a stave cooler in an absorbing liquid without discharging CO<SB>2</SB>. <P>SOLUTION: In this CO<SB>2</SB>absorbing method, by-product gas generated in iron works is introduced into an absorbing tower 2, and brought into contact with absorbing liquid supplied to the absorbing tower 2 and regenerated in a regeneration tower 3 to absorb CO<SB>2</SB>in the by-product gas in the absorbing liquid, and the CO<SB>2</SB>absorbing liquid absorbing CO<SB>2</SB>in the absorbing tower 2 is heated in the regenerating tower 3 to be separated into the CO<SB>2</SB>and the absorbing liquid. The waste heat possessed by the circulating refrigerant taken from the stave cooler 5 of a blast furnace 1 is taken as a heat source to heat the absorbed liquid taken from the regenerating tower 3 by heat exchange. The heated absorbed liquid is returned to the regenerating tower 3 and circulated and simultaneously the CO<SB>2</SB>absorbed liquid is separated into CO<SB>2</SB>and the absorbing liquid to regenerate the absorbing liquid. Some of the regenerated absorbing liquid is supplied to the absorbing tower 2, and the cooled circulated refrigerant cooled by heat exchange is again used as a refrigerant of the stave cooler 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention, in the CO ₂ absorption method for absorbing carbon dioxide gas (CO ₂₎ using absorption liquid such as an amine, a circulating refrigerant of stave cooler for cooling the furnace wall as the energy required for regeneration of the CO ₂ absorbing solution The present invention relates to a CO ₂ absorption method using waste heat.

To prevent global warming due to the release of the CO ₂ in the atmosphere, as a method for the CO ₂ in the exhaust gas recovery to reduce CO ₂ emissions to the atmosphere, by utilizing the absorbing liquid such as amine CO method for recovering is proposed CO ₂ by ₂ chemical absorption to be absorbed into the recovery liquid (see Patent Document 1).

In the CO ₂ recovery method proposed in Patent Document 1, combustion exhaust gas containing CO ₂ generated in a boiler such as a power plant is cooled by a cooling tower, and the cooled combustion exhaust gas is introduced into an absorption tower. The absorption liquid regenerated in the regeneration tower is supplied, and CO ₂ in the combustion exhaust gas comes into contact with the absorption liquid and is absorbed, and the combustion exhaust gas from which CO ₂ is removed passes through the exhaust pipe of the absorption tower to the gas use destination. Supplied.

The CO ₂ absorption liquid that has absorbed CO ₂ in the combustion exhaust gas in the absorption tower is supplied to the regeneration tower in order to separate the CO ₂ and the absorption liquid and regenerate the absorption liquid. Before being heated, the CO ₂ absorbent is heat-exchanged with the regenerative absorbent having a relatively high temperature from the regeneration tower and heated. The heated CO ₂ absorption liquid is supplied to a high-temperature regeneration tower and separated into CO ₂ and the regeneration absorption liquid while flowing down the gas-liquid contact member. The regeneration absorption liquid is taken out from the regeneration tower, heated by heat exchange with low-pressure steam in a heat exchanger (reboiler) outside the regeneration tower, returned to the regeneration tower, and used as energy for heating the CO ₂ absorbent in the regeneration tower. Used. Some of the regenerated absorption liquid is returned to the absorption tower in order to absorb CO _2.

  On the other hand, stave coolers are used in blast furnaces at steelworks to cool the furnace walls. FIG. 2 is a schematic cross-sectional view showing an example of a blast furnace stave cooler.

In FIG. 2, a stave cooler 5 disposed in the height direction around the blast furnace 1 forms a coolant passage 9 inside a cast iron or copper casting, and coolant water is passed through the coolant passage 9 as coolant to pass through the furnace wall 10. It is what cools. Cooling water or steam of the stave cooler 5 heated by the transfer of heat in the blast furnace is taken out, cooled by heat exchange in the heat exchanger 11, and returned to the stave cooler 5 by the circulation pump 12 for circulation (Patent Document). 2).
JP 2003-225537 A JP-A-6-322418

In general, CO ₂ absorption method using absorption liquid CO _2, by heating the CO ₂ absorbent having absorbed CO ₂ is separated into a CO ₂ and absorbing liquid, while playing the absorbing liquid, reproduction Therefore, in Patent Document 1, a heat exchanger is provided on the outlet side of the absorption tower and the regeneration tower, and the heat of the CO ₂ absorption liquid from the absorption tower and the heated absorption liquid from the regeneration tower is disclosed in Patent Document 1. The amount of heat is collected through replacement. However, since the heat source for regeneration of the absorption liquid that requires the highest temperature cannot be applied only by heat recovery by heat exchange using the mutual heat of the CO ₂ absorption liquid and the regeneration absorption liquid, the regeneration absorption liquid of the regeneration tower The low temperature steam is supplied to the heat exchanger to compensate for the temperature rise. In order to generate the low-pressure steam, another energy such as electricity and fuel is required, and CO ₂ is released to generate the low-pressure steam.

In addition, the recovery and removal of CO ₂ contained in by-product gas generated from various furnaces such as blast furnaces, converters, coke ovens, etc., installed in steelworks is per unit volume of the recovered gas. Increasing the amount of heat can not only improve the thermal efficiency in the process using the blast furnace exhaust gas, but also reduce the CO ₂ diffused into the atmosphere.

  On the other hand, the circulating refrigerant flowing in the stave cooler used for cooling the furnace wall of the blast furnace is heated by the transfer of the heat of the furnace wall, but the heat possessed by the circulating refrigerant is not utilized. Instead, the circulating refrigerant is merely used for cooling the stave cooler.

Accordingly, the present invention does not discharge the CO _2, which provides a CO ₂ absorption method be absorbed by the absorption liquid CO ₂ from byproduct gas generated in ironworks by using waste heat with the circulating refrigerant stave cooler It is.

The present invention comprises an absorption tower and a regeneration tower, introduces a by-product gas generated in an ironworks into the absorption tower, and is supplied to the absorption tower and brought into contact with an absorption liquid regenerated in the regeneration tower. the CO ₂ is absorbed into the absorbing solution, CO ₂ absorbent having absorbed CO ₂ in the absorption tower in the CO ₂ absorption method for separating the absorption liquid with CO ₂ by heating in the regenerator, the stave cooler of the blast furnace The absorbed liquid taken out from the regeneration tower is heated by heat exchange using the waste heat held by the extracted circulating refrigerant as a heat source, and is returned to the regeneration tower and circulated to separate the CO ₂ absorbent into CO ₂ and the absorbent. Then, the absorption liquid is regenerated, a part of the regenerated absorption liquid is supplied to the absorption tower, and the circulating refrigerant cooled by heat exchange is used again as a refrigerant for the stave cooler.

In the above-described configuration, the circulating refrigerant is pre-pressurized, and the absorbing liquid taken out from the regeneration tower is heated by heat exchange by using the waste heat held by the circulating refrigerant taken out from the stave cooler in the form of high-pressure hot water or steam as heat source. _The temperature is raised to a temperature at which the ₂ absorbent can be separated into CO ₂ and the absorbent.

Since the present invention effectively uses the waste heat, which is unused energy that does not discharge CO ₂ , from the blast furnace stave cooler, the energy required for CO ₂ recovery in the by-product gas generated at the steelworks is effectively reduced. ₂ can be carried out without using energy generated by discharging CO ₂ such as electricity, so that the CO ₂ suppression effect is high, and when it is carried out using energy accompanying CO ₂ emission such as electricity. In comparison, the CO ₂ absorption process can be constructed at low cost.

Because the blast furnace stave cooler captures CO ₂ in the blast furnace exhaust gas using the huge waste heat of the blast furnace, it is blessed with geographical conditions, the heat quantity of the blast furnace gas is increased, and the thermal efficiency in the process using the blast furnace gas is improved. improves.

FIG. 1 is a flow chart of the CO ₂ absorption method of the present invention, and is a flow showing an example in which CO ₂ is recovered by an absorbing liquid (amine liquid) from a blast furnace gas (BFG) containing CO ₂ generated from a blast furnace.

Schematic flow for removing CO ₂ from the BFG is the CO ₂ in the BFG generated from the blast furnace 1 is absorbed and removed by the absorbing solution in the absorption tower 2, the CO ₂ absorbent having absorbed CO ₂ is heated in the regeneration tower 3 Then, the separated absorption liquid is separated into CO ₂ and the absorption liquid, and the regenerated absorption liquid is sent to the absorption tower 2 and used for absorption of CO ₂ . In the present invention, the heating for playing by separating the CO ₂ and absorbing liquid from the CO ₂ absorbing solution, utilizes waste heat of the stave cooler 5 for cooling a furnace wall of the blast furnace 1 as a heat source for heat exchanger 4.

This will be described in detail below with reference to FIG. BFG generated from the blast furnace 1 is sent to an absorption tower 2 that absorbs CO ₂ . Amine solution for absorbing CO ₂ absorption tower 2, in BFG is sprayed from the top of the absorber 2. BFG from which CO ₂ has been removed by the absorption tower 2 is stored in a gas tank. BFG from which CO ₂ has been removed is improved in thermal efficiency in a process using BFG by increasing the amount of heat per unit volume.

As described below, the absorption liquid sprayed in the absorption tower 2 is obtained by heating the CO ₂ absorption liquid that has absorbed CO _{2 in the} absorption tower 2 by the waste heat of the circulating refrigerant in the stave cooler 6 in the regeneration tower 3 and CO ₂ and the absorption liquid. The absorption solution that has been separated and regenerated is circulated for use.

The CO ₂ absorbent extracted from the lower part of the absorption tower 2 is heated by the heat exchanger 6 and sprayed from the upper part of the regeneration tower 3 to be separated into CO ₂ and the absorbent. In order to separate the CO ₂ and the absorbing solution, it is necessary to heat the CO ₂ absorbing solution to about 120 ° C. or higher. In order to maintain the regeneration tower 3 at about 120 ° C. or higher, the regeneration extracted from the lower part of the regeneration tower 3 A part of the absorbed liquid is heated by the heat exchanger 4 using the waste heat of the stave cooler 6 of the blast furnace 1 and circulated to the regeneration tower 3. The rest of the regenerated absorption liquid is cooled by heat exchange with the CO ₂ absorption liquid in the absorption tower 2 in the heat exchanger 6 and supplied to the absorption tower 2.

  The cooling water heated by the stave cooler 5 is pressurized to at least 0.2 MPa so that the boiling point becomes equal to or higher than the regeneration temperature, and is supplied to the stave cooler 5 as a high-pressure hot water state or steam. Then, the heat is absorbed by the stave cooler 5 up to a temperature at which regeneration is possible, and is supplied to the heat exchanger (reboiler) 4. The refrigerant regenerated by the heat exchanger 4 and the refrigerant cooled by heat exchange are pressurized again by the pump 7 and circulated to the stave cooler 5 to recover the heat of the blast furnace. As the refrigerant, it is preferable to use pure water produced by a pure water device in order to increase the temperature. Alternatively, there is a method in which the cooling water is evaporated by a stave cooler and heat and steam are used as a medium. In this case, the refrigerant is condensed into steam by the heat exchanger (reboiler) 4 and the latent heat of evaporation can be used, so that the circulation amount of the refrigerant can be reduced.

  At this time, in order to effectively use the latent heat of vaporization of the vapor, pressurization is performed so that the boiling point becomes equal to or higher than the regeneration temperature of the absorbent. The temperature and pressure at this time are as described above.

The CO ₂ separated by the regeneration tower 3 is discharged from the regeneration tower 3, cooled by the heat exchanger 8 to remove water vapor, stored in a tank, and used as a CO ₂ source or the like.

A flow diagram of a CO ₂ absorption method of the present invention, is a flow showing an example of recovering CO ₂ from BFG containing CO ₂ generated from the blast furnace. It is a schematic sectional drawing which shows an example of the stave cooler of a blast furnace.

Explanation of symbols

1: Blast furnace 2: Absorption tower 3: Regeneration tower 4: Heat exchanger 5: Stave cooler 6: Heat exchanger 7: Pump 8: Heat exchanger 9: Refrigerant passage 10: Furnace wall 11: Heat exchanger 12: Circulation pump

Claims (4)

An absorption tower and a regeneration tower are provided, and by-product gas generated at the steel works is introduced into the absorption tower, and the CO _{2 in the} by-product gas is brought into contact with the absorption liquid regenerated in the regeneration tower, which is supplied to the absorption tower. is absorbed into the absorbing solution, CO ₂ absorbent having absorbed CO ₂ in the absorption tower in the CO ₂ absorption method for separating the absorption liquid with CO ₂ by heating in the regenerator,
Using the waste heat held by the circulating refrigerant taken out from the stadium cooler of the blast furnace as a heat source, the absorption liquid taken out from the regeneration tower is heated by heat exchange and returned to the regeneration tower to circulate and absorb the CO ₂ absorbent with CO _2. To separate the liquid and regenerate the absorbent,
A part of the regenerated absorption liquid is supplied to the absorption tower, and the circulating refrigerant cooled by heat exchange is used again as a refrigerant for the stave cooler. CO ₂ absorption method in the gas. The circulating refrigerant is pre-pressurized, and the absorbing liquid taken out from the regeneration tower is heated by heat exchange using the waste heat held by the circulating refrigerant taken out from the stave cooler as a heat source to convert the CO ₂ absorbing liquid into CO ₂ and the absorbing liquid. The method of absorbing CO _{2 in by-} product gas using waste heat of the circulating refrigerant of the stave cooler according to claim 1, wherein the temperature is raised to a temperature at which the refrigerant can be separated into _two . CO ₂ absorption method of byproduct gas with waste heat of the circulating refrigerant stave cooler according to claim 1 or 2, wherein the product gas is blast furnace gas. The method for absorbing CO _{2 in by-} product gas using waste heat of the circulating refrigerant in the stave cooler according to claim 1, 2 or 3, wherein the circulating refrigerant is pure water.

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