JP2024142094A - Carbon Dioxide Capture Equipment - Google Patents

Abstract

[Problem] To provide a carbon dioxide capture device capable of suppressing the amount of heat-stable salt produced. [Solution] A carbon dioxide capture device 20 includes an absorption tower 21 in which an absorbing solution L that absorbs carbon dioxide from an exhaust gas G1 containing carbon dioxide is stored, a regeneration tower 22 in which an absorbing solution L from which carbon dioxide is separated by heating is stored, a heat exchanger 23 that exchanges heat between the absorbing solution L introduced from the absorption tower 21 to the regeneration tower 22 and the absorbing solution L introduced from the regeneration tower 22 to the absorption tower 21, a concentration meter 33 that measures the concentration of a component that produces a heat-stable salt upon contact with the absorbing solution L in the exhaust gas G1, an induced draft fan 35 and a flow control valve 36 that introduce air into the absorption tower 21, and a control unit 41 that controls the induced draft fan 35 and the flow control valve 36 to introduce outside air G4 into the absorption tower 21 when the concentration measured by the concentration meter 33 exceeds a predetermined first concentration so that the concentration of the component in the exhaust gas G1 introduced into the absorption tower 21 is less than the first concentration. [Selected Figure] Figure 1

Description

The present invention relates to a carbon dioxide capture device.

Reducing carbon dioxide ( _CO2 ) gas, one of the greenhouse gases, is an urgent issue for the cement industry. The chemical absorption method (amine method) is a promising technology for capturing carbon dioxide gas. The chemical absorption method is a carbon dioxide separation and capture technology that utilizes the carbon dioxide absorption and desorption properties of amine-based absorbents, and has the advantage of being suitable for large-volume, low-pressure gas compared to other methods and not affecting existing cement manufacturing processes.

In a carbon dioxide recovery system using the chemical absorption method, the introduced gas containing carbon dioxide is absorbed through gas-liquid contact with the absorbing liquid in the absorption tower, the absorbing liquid that has absorbed the carbon dioxide is heated from the absorption tower by a heat exchanger and then supplied to the regeneration tower, and the absorbing liquid stored in the regeneration tower is heated by a heater, causing the carbon dioxide in the absorbing liquid to be released into the regeneration tower as carbon dioxide gas, and the carbon dioxide is recovered as a high-purity carbon dioxide-containing gas.

However, when the absorbing solution comes into contact with exhaust gas discharged from the cement kiln in a cement manufacturing facility, heat stable salts (HSS) are produced, which reduce the performance of the absorbing solution.

Therefore, for example, Patent Document 1 discloses that, in order to appropriately purify the absorbing liquid in response to a decrease in the performance of the absorbing liquid, the amount of the absorbing liquid introduced into a purification section that purifies impurities such as thermally stable salts in the absorbing liquid is adjusted based on the amount of carbon dioxide gas recovered in the regeneration tower.

Patent Document 2 also discloses that the amount of absorbent regenerated in the regeneration tower is controlled based on the measured viscosity of the absorbent flowing through a pipe that supplies the absorbent regenerated in the regeneration tower to the absorption tower, and a portion of the absorbent is introduced to the reclaimer to remove degraded products such as thermally stable salts.

JP 2022-100713 A International Publication No. 2022/044487

However, the techniques disclosed in the above-mentioned Patent Documents 1 and 2 can purify and remove heat-stable salts, but do not suppress their production.

The present invention aims to provide a carbon dioxide capture device that can suppress the amount of heat-stable salt produced.

The carbon dioxide capture device of the present invention is characterized by comprising an absorption tower in which an absorbing liquid that absorbs carbon dioxide from an exhaust gas containing carbon dioxide that is introduced is stored, a regeneration tower in which an absorbing liquid from which carbon dioxide is separated by heating is stored, a heat exchanger that performs heat exchange between the absorbing liquid introduced from the absorption tower to the regeneration tower and the absorbing liquid introduced from the regeneration tower to the absorption tower, a first concentration measuring device that measures the concentration of a component of the exhaust gas that produces a heat-stable salt upon contact with the absorbing liquid, an air introduction means that introduces air into the absorption tower, and a first control unit that controls the air introduction means to introduce air into the absorption tower when the concentration measured by the first concentration measuring device exceeds a predetermined first concentration so that the concentration of the component in the exhaust gas introduced into the absorption tower is less than the first concentration.

According to the carbon dioxide capture device of the present invention, the components that produce heat-stable salts in contact with the exhaust gas absorption liquid are introduced into the suction tower only at a predetermined first concentration or less. Therefore, it is possible to suppress the amount of heat-stable salts produced in approximately proportion to the concentration of the components that come into contact with the absorption liquid.

The carbon dioxide capture device of the present invention preferably includes a second concentration measuring device that measures the carbon dioxide concentration of the exhaust gas, a high-concentration carbon dioxide gas introduction means that introduces carbon dioxide gas with a higher concentration than the exhaust gas into the absorption tower, and a second control unit that, when the carbon dioxide concentration measured by the second concentration measuring device is less than a predetermined second concentration, controls the high-concentration carbon dioxide gas introduction means to introduce the high-concentration carbon dioxide gas into the absorption tower so that the carbon dioxide concentration of the exhaust gas introduced into the absorption tower is equal to or greater than the second concentration.

In this case, exhaust gas containing carbon dioxide at a predetermined second concentration or higher is introduced into the suction tower. This makes it possible to suppress the decrease and fluctuation of the carbon dioxide capture rate in the carbon dioxide capture device.

In the carbon dioxide capture device of the present invention, for example, the concentration of the component that produces a thermally stable salt upon contact with the absorbing liquid in the exhaust gas is either the concentration of sulfur oxides, the concentration of nitrogen oxides, or the combined concentration of sulfur oxides and nitrogen oxides in the exhaust gas.

In addition, the carbon dioxide capture device of the present invention preferably includes a carbon dioxide storage means for compressing and storing the carbon dioxide separated in the regeneration tower, and the high-concentration carbon dioxide gas introduction means preferably introduces carbon dioxide gas having a higher concentration than the exhaust gas from the carbon dioxide storage means.

In this case, there is no need to install an additional external gas source as a source of high-concentration carbon dioxide gas to be introduced into the absorption tower.

FIG. 1 is a schematic diagram showing a cement calcination apparatus and a carbon dioxide capture apparatus according to an embodiment of the present invention attached thereto.

A carbon dioxide capture device 20 according to an embodiment of the present invention, which is attached to a cement burning facility 10, will be described with reference to the drawings.

The cement firing equipment 10 fires the cement raw material powder P and is composed of a preheater 11, a calciner 12, and a cement kiln 13.

The preheater 11 is a preheater consisting of a multi-stage, here four-stage, arrangement of cyclones 11a-11d. Cement raw material powder P is supplied to the top-stage cyclone 11a from a cement raw material powder production facility (not shown), preheated as it moves downward through the cyclones 11a-11c, supplied from cyclone 11c to the calciner 12, and finally supplied to cyclone 11d. The preheater 11 preheats the cement raw material powder P by heat exchange with high-temperature exhaust gas G that is sucked up and rises by the induction fan 14.

The calciner 12 is provided below the preheater 11 and is equipped with a burner and the like. The type of the calciner 12 is not limited, but may be, for example, a fluidized bed type, a fluidized bed type, a spouted bed type, or the like. The calciner 12 may be omitted, and the cement raw material powder P may be directly supplied from the preheater 11 to the cement kiln 13.

The cement kiln 13 is equipped with a burner 13a and burns the cement raw material powder P calcined in the calciner 12 at 1350°C to 1450°C to produce cement clinker C. The type of the cement kiln 13 is not limited, but may be, for example, a rotary type.

The cement clinker C obtained in the cement kiln 13 falls from the discharge port and is fed into the clinker cooler 15, where it is cooled to about 100°C. The cooled cement clinker C is taken out from the outlet of the clinker cooler 15. A portion of the exhaust gas G, which has become hot after cooling the cement clinker C in the clinker cooler 15, flows into the calciner 12.

The carbon dioxide capture device 20 is composed of an absorption tower 21, a regeneration tower 22, a heat exchanger 23, etc. The absorption liquid L that absorbs carbon dioxide by chemical absorption in the carbon dioxide capture device 20 is an amine-based absorption liquid such as MEA, MDEA, AMP, or PZ/PIPA.

Exhaust gas G1 containing carbon dioxide (CO ₂ ) is sucked in by the induced draft fan 31 and introduced into the absorption tower 21. Although not shown, this exhaust gas G1 is discharged from a cement raw material powder production facility that produces cement raw material powder P from cement raw materials and supplies the cement burning facility 10, and is extracted via a dust collection means such as an electric dust collector just before being released into the atmosphere from a chimney. The exhaust gas G1 introduced by the induced draft fan 31 comes into gas-liquid contact with the absorbing liquid L in the absorption tower 21, and the carbon dioxide is absorbed by the absorbing liquid L. The temperature of the absorbing liquid L is, for example, about 40°C.

The absorption liquid L that has absorbed carbon dioxide in the absorption tower 21 is sent to the heat exchanger 23 by the pump 24, where it is heated and then supplied to the regeneration tower 22.

This absorption liquid L is stored in the lower part of the regeneration tower 22 and heated by a heater 25 using a boiler or steam, etc., to approximately 70°C to approximately 120°C. As a result, the carbon dioxide in the absorption liquid L is released into the regeneration tower 22 as carbon dioxide gas. This gas G2 containing high-purity carbon dioxide rises inside the regeneration tower 22 and is discharged from the top, compressed by a compressor 26 such as a centrifugal compressor, dried by a dryer 27 to remove moisture, and then stored in the carbon dioxide storage tank 28 as gas G5 containing high-purity carbon dioxide.

Meanwhile, the absorbent L from which carbon dioxide has been removed and regenerated is sent by pump 29 to heat exchanger 23 where it is cooled, and then supplied from the top of absorption tower 21 to again absorb carbon dioxide from exhaust gas G1. Exhaust gas G3 from which carbon dioxide has been removed rises inside absorption tower 21 and is introduced into a cement raw material powder production facility (not shown).

A concentration meter 33 is installed in the pipe 32 containing the exhaust gas G1 introduced into the absorption tower 21 from the outlet of the preheater 11 via the induction fan 31 to measure the concentration of various components contained in the exhaust gas G1. The concentration detector 33 measures the concentration of components that cause the generation of thermally stable salts, specifically, sulfur compounds and nitrogen compounds. The concentration detector 33 also measures the concentration of carbon dioxide. Data indicating the measurement results measured by the concentration meter 33 is transmitted to the control unit 41. The concentration meter 33 corresponds to the first and second concentration meters of the present invention, and the control unit 41 corresponds to the first and second control units of the present invention.

Then, the pipe 32 is connected to a pipe 34 through which air (outside air) G4 is introduced from the outside, and an induced draft fan 35 and a flow control valve 36 are installed in this pipe 34. The induced draft fan 35 and the flow control valve 36 are controlled by the control unit 41 based on the measurement results measured by the concentration measuring device 33. The induced draft fan 35 and the flow control valve 36 correspond to the air introduction means of the present invention.

Furthermore, the pipe 32 is connected to a pipe 37 through which gas G5 containing high-purity carbon dioxide is introduced from the carbon dioxide storage tank 28, and this pipe 37 is equipped with an induced draft fan 38 and a flow control valve 39. The induced draft fan 38 and the flow control valve 39 are controlled by the control unit 41 based on the measurement results measured by the concentration measuring device 33. The induced draft fan 38 and the flow control valve 39 correspond to the high-concentration carbon dioxide gas introduction means of the present invention.

Next, we will explain how the control unit 41 controls the induced draft fans 35, 38 and the flow control valves 36, 39.

When the control unit 41 determines that at least one of the sulfur compound concentration, the nitrogen compound concentration, or the total concentration of sulfur compounds and nitrogen compounds measured by the concentration measuring device 33 exceeds a predetermined first concentration set in advance for each, the control unit 41 controls the induction fan 35 and the flow control valve 36 to introduce outside air G4 into the piping 32. The amount of the outside air introduced is determined by the control unit 41 so that the sulfur compound concentration, the nitrogen compound concentration, and the total concentration of sulfur compounds and nitrogen compounds are all equal to or less than the predetermined first concentration.

As a result, sulfur compounds and nitrogen compounds are introduced into the suction tower 21 at a predetermined first concentration or less. This makes it possible to suppress the amount of thermally stable salts produced. Note that the amount of thermally stable salts produced increases approximately in proportion to the concentration of nitrogen compounds and sulfur compounds that come into contact with the absorption liquid L, so the first concentration can be determined according to the performance and operating frequency of the device that removes the thermally stable salts.

When the control unit 41 determines that the carbon dioxide concentration measured by the concentration measuring device 33 is less than a preset second concentration, it controls the induction fan 38 and the flow control valve 39 to introduce gas G5 containing high-purity carbon dioxide from the carbon dioxide storage tank 28 into the piping 32. The amount of gas introduced is determined by the control unit 41 so that the carbon dioxide concentration is equal to or greater than the preset second concentration.

As a result, exhaust gas G1 containing carbon dioxide at or above a predetermined second concentration is introduced into the suction tower 21. This makes it possible to suppress the decrease and fluctuation of the carbon dioxide capture rate in the carbon dioxide capture device 20. The predetermined second concentration is, for example, 15 vol.%, 20 vol.%, etc., and may be determined according to the rating of the carbon dioxide capture device 20.

Furthermore, when the control unit 41 predicts that the carbon dioxide concentration of the exhaust gas G1 flowing through the pipe 32 will be less than a predetermined second concentration as a result of controlling the induced draft fan 35 and the flow control valve 36 to introduce outside air G4 into the pipe 32, it controls the induced draft fan 38 and the flow control valve 39 to introduce gas G5 containing high-purity carbon dioxide from the carbon dioxide storage tank 28 into the pipe 32. The amount of gas introduced is determined by the control unit 41 so that the carbon dioxide concentration is equal to or greater than the predetermined second concentration.

As a result, even if the concentration of carbon dioxide in the exhaust gas G1 decreases due to the introduction of outside air G4, the exhaust gas G1 containing carbon dioxide at or above a predetermined second concentration is introduced into the suction tower 21. Therefore, it is possible to suppress the decrease and fluctuation of the carbon dioxide capture rate in the carbon dioxide capture device 20.

The present invention is not limited to the carbon dioxide capture device 20 specifically described in the above embodiment, and may be modified as appropriate within the scope of the claims.

For example, the gas G5 containing high-purity carbon dioxide introduced through the pipe 37 is not limited to that introduced from the carbon dioxide storage tank 28. For example, the gas G5 containing high-purity carbon dioxide may be introduced through the pipe 37 from a commercially available carbon dioxide gas cylinder or the like.

10...Cement burning equipment, 11...Preheater, 11a-11d...Cyclone, 12...Calciner, 13...Cement kiln, 13a...Burner, 14...Induced draft fan, 15...Clinker cooler, 20...Carbon dioxide recovery device, 21...Absorption tower, 22...Regeneration tower, 23...Heat exchanger, 24...Pump, 25...Heater, 26...Compressor, 27...Dryer, 28...Carbon dioxide storage tank, 29...Pump, 31...Induced draft fan, 32, 34, 37...Pipe, 33...Concentration meter (first concentration meter, second concentration meter), 35...Induced draft fan (air introduction means), 36...Flow control valve (air introduction means), 38...Induced draft fan (high concentration carbon dioxide gas introduction means), 39...Flow control valve (high concentration carbon dioxide gas introduction means), 41: control unit (first control unit, second control unit), C: cement clinker, G: exhaust gas, G1: exhaust gas, G2: exhaust gas containing high-purity carbon dioxide, G3: exhaust gas from which carbon dioxide has been removed, G4: outside air, G5: gas containing high-purity carbon dioxide, L: absorption liquid, P: cement raw material powder.

Claims (4)

an absorption tower in which an absorption liquid that absorbs carbon dioxide from an introduced exhaust gas containing carbon dioxide is stored;
a regeneration tower storing an absorption liquid from which carbon dioxide is separated by heating;
a heat exchanger that performs heat exchange between an absorption liquid introduced from the absorption tower to the regeneration tower and an absorption liquid introduced from the regeneration tower to the absorption tower;
A first concentration measuring device that measures a concentration of a component that produces a heat stable salt upon contact with the absorption liquid of the exhaust gas;
An air introduction means for introducing air into the absorption tower;
and a first control unit that controls the air introduction means to introduce air into the absorption tower when the concentration measured by the first concentration measuring device exceeds a predetermined first concentration so that the concentration of the component in the exhaust gas introduced into the absorption tower is less than the first concentration. A second concentration measuring device that measures the concentration of carbon dioxide in the exhaust gas;
a high-concentration carbon dioxide gas introducing means for introducing carbon dioxide gas having a higher concentration than the exhaust gas into the absorption tower;
and a second control unit that controls the high-concentration carbon dioxide gas introduction means to introduce the high-concentration carbon dioxide gas into the absorption tower when the carbon dioxide concentration measured by the second concentration measuring device is less than a predetermined second concentration so that the carbon dioxide concentration of the exhaust gas introduced into the absorption tower is equal to or greater than the second concentration. The carbon dioxide recovery device according to claim 1 or 2, characterized in that the concentration of the components of the exhaust gas that come into contact with the absorption liquid to produce a thermally stable salt is either the concentration of sulfur oxides, the concentration of nitrogen oxides, or the combined concentration of sulfur oxides and nitrogen oxides in the exhaust gas. A carbon dioxide storage means is provided for compressing and storing the carbon dioxide separated in the regeneration tower,
3. The carbon dioxide recovery apparatus according to claim 2, wherein the high-concentration carbon dioxide gas introduction means introduces carbon dioxide gas having a higher concentration than the exhaust gas from the carbon dioxide storage means.

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