Exhaust-gas treatment equipment and gas-capture-material deterioration-state estimating method

The present invention relates to exhaust-gas treatment equipment that processes exhaust gas emitted from various plants and power-driven machinery, and a gas-capture-material deterioration-state estimating method implemented in the exhaust-gas treatment equipment.

The exhaust-gas processing technique that uses a solid material such as a capture material or a catalyst to capture specific gas from exhaust gas, desorbs and separates the captured gas, and neutralize the separated gas has been applied to a lot of fields including power plants, synthetic plants, and automobiles, and systemized. However, in most cases, since the exhaust gas emitted from the plants and so on contains components that deteriorate the capture material or catalyst, the capture material or catalyst deteriorates with time. Therefore, to detect the deterioration level of the capture material or catalyst and efficiently manage the system is important in improving the operation and reducing running costs in exhaust-gas processing equipment.

For example, in the exhaust-gas treatment equipment that uses a carbon dioxide (hereinafter referred to as CO 2 ) capture material to recover CO 2 from a boiler exhaust gas of a thermal power plant, the boiler exhaust gas contains components that deteriorate the CO 2 capture material, such as SO x , NO x , and smoke and dusts. Accordingly, if the CO 2 capture receives such components incoming, the CO 2 capture material deteriorates in CO 2 capture performance with time. After capturing CO 2 , the CO 2 capture material is caused to desorb the captured CO 2 by heating or depressurization, and is continuously reused for capture of CO 2 . The CO 2 capture performance of the CO 2 capture material can be also lowered due to thermal and pressure hysteresis caused by repeated cycles of capture and desorption.

Generally, the CO 2 capture material generates heat at capture of the CO 2 . Thus, when the CO 2 capture performance lowers, the amount of captured CO 2 decreases, in turn, the amount of generated heat decreases. Accordingly, by measuring the temperature of the CO 2 capture material in the flow of the exhaust gas containing CO 2 , the deterioration state of the CO 2 capture material can be indirectly recognized. For example, Patent literature 1 discloses the technique of estimating the deterioration state of a catalyst according to position in a reaction container by installing a plurality of temperature measuring elements along the flow of gas in the reaction container filled with the catalyst, and monitoring temperatures of the catalyst using the installed temperature measuring elements.

Patent Literature

Patent Literature 1: JP 2002-260700 A

Technical Problem

According to the technique disclosed in Patent literature 1, the deterioration state of the catalyst can be reliably estimated according to the position in the reaction container. However, to accurately estimate the deterioration state of the catalyst according to the position in the reaction container, as illustrated in FIG. 1 , it is required to install a lot of temperature measuring elements in the reaction container. That is, the conventional technique has a problem that to accurately estimate the deterioration state of the capture material and the catalyst in the reaction container, a lot of temperature measuring elements are needed.

Thus, an object of the present invention is to provide a gas treatment equipment and a gas-capture-material deterioration-state estimating method that can estimate a deterioration state of a gas capture material based on temperatures measured by a few temperature measuring elements.

Solution to Problem

Exhaust-gas treatment equipment according to the present invention includes: a reaction container filled with a gas capture material that captures a particular gas component, the reactor container emitting gas obtained by removing the particular gas component from supplied gas by reaction of the supplied gas with the gas capture material; a temperature measuring element disposed in the reaction container, the temperature measuring element measuring a temperature of the gas capture material in the reaction container; a moving unit that freely moves the temperature measuring element in a direction that is parallel to a flow of the supplied gas flowing in the reaction container; and a control unit that estimates a deterioration state of the gas capture material using temperatures of the gas capture material at a plurality of different positions in the reaction container, the temperatures being measured by the temperature measuring element when the temperature measuring element is moved by means of the moving unit.

Advantageous Effects of Invention

The present invention provides gas treatment equipment and a gas-capture-material deterioration-state estimating method that can estimate a deterioration state of a gas capture material based on temperatures measured by a few temperature measuring elements.

FIG. 1 is a view illustrating an example of the configuration of exhaust-gas treatment equipment in in accordance with an embodiment of the present invention;

FIGS. 2A to 2F are views illustrating the deterioration state of a CO 2 capture material in a CO 2 capture container in a time series basis;

FIGS. 3A and 3B are views schematically illustrating a deterioration model of the CO 2 capture material in the CO 2 capture container, FIG. 3A is a graph illustrating relationships between material positions and a maximum possible CO 2 capture amount of the CO 2 capture material, and FIG. 3B is a graph illustrating relationships between the material positions and a maximum possible heat amount of the CO 2 capture material;

FIGS. 4A to 4C are views illustrating a deterioration state of the CO 2 capture material based on temperatures in the CO 2 capture container in a capturing step;

FIGS. 5A and 5B are views illustrating an example of a method of determining suitable positions of temperature measuring elements;

FIG. 6 is a flow chart illustrating a flow of CO 2 -capture-material deterioration-state estimating processing by use of a computer; and

FIGS. 7A and 7B schematically illustrate an example of specific arrangement of the CO 2 capture material and the temperature measuring elements in the CO 2 capture container, FIG. 7A is a schematic perspective view, and FIG. 7B is a schematic bottom view.

An embodiment of the present invention will be described below in detail with reference to accompanying figures. Common constituents are given the same reference numerals and description thereof is omitted.

<Configuration of Exhaust-Gas Treatment Equipment and Recovery Step of CO 2 >

FIG. 1 illustrates an example of the configuration of exhaust-gas treatment equipment 100 according to an embodiment of the present invention. As illustrated in FIG. 1 , the exhaust-gas treatment equipment 100 includes a CO 2 capture container (reaction container) 201 , a heat exchanger 510 , ventilators 501 , 502 , and 503 , condensers 601 , 602 , and 603 , and compressors 701 , and 702 , and the like. In FIG. 1 , thick lines with arrows represent flow paths for gas and so on, which are formed of pipes connecting the above-mentioned constituents to each other, and valves 101 , 102 , 103 , 104 , and 105 are appropriately provided in the middle of the flow paths.

For example, the exhaust-gas treatment equipment 100 illustrated in FIG. 1 recovers CO 2 from exhaust gas from a boiler of a power plant, and refines liquefied carbonic acid. Accordingly, a main constituent of the exhaust-gas treatment equipment 100 is a CO 2 capture container 201 filled with the CO 2 capture material containing cerium oxide (CeO 2 ). The CO 2 recovery step includes three steps of capture, heating, and cooling.

That is, in the capturing step, the exhaust gas from the boiler is circulated in the CO 2 capture container 201 , and CO 2 contained in the exhaust gas is captured by the CO 2 capture material filled in the CO 2 capture container 201 . Next, in the heating step, heating gas is circulated in the CO 2 capture material that captures CO 2 , thereby desorbing CO 2 from the CO 2 capture material to increase the CO 2 concentration of the gas emitted from the CO 2 capture container 201 . Then, gas having a high CO 2 concentration is extracted to further condense CO 2 by the condensers 601 , 602 , and 603 , refining liquefied carbonic acid. In the cooling step, air of room temperatures is circulated in the CO 2 capture container 201 to cool the CO 2 capture material in the CO 2 capture container 201 .

In this embodiment, temperature measuring elements 301 , 302 , and 303 formed of thermocouples or the like are disposed in the CO 2 capture container 201 , and a moving unit 401 for vertically moving the temperature measuring elements 301 , 302 , and 303 is disposed outside the temperature measuring elements. The moving unit 401 is connected to a control unit 450 constituted of a generally-used computer or the like. The control unit 450 moves the temperature measuring elements 301 , 302 , and 303 to respective predetermined positions through the moving unit 401 , and acquires temperatures of the CO 2 capture material, which are measured by the temperature measuring elements 301 , 302 , and 303 . Further, the control unit 450 estimates the deterioration state of the CO 2 capture material in the CO 2 capture container 201 based on the acquired temperatures. Details thereof will be described with reference to other figures.

First, each constituent of the exhaust-gas treatment equipment 100 will be described in detail, and each of the capture, heating, and then, cooling steps for CO 2 recovery using the CO 2 capture container 201 will be described.

As illustrated in FIG. 1 , the exhaust-gas treatment equipment 100 includes three flow paths through which exhaust gas from the boiler, atmospheric air, and heating gas are allowed to flow, respectively, as inlet flow paths into the CO 2 capture container 201 that is the reaction container. These three flow paths are provided with the valves 101 , 103 , and 104 , respectively. One of the valves is opened and the other valves are closed in each of the capture, heating, and cooling steps. The exhaust-gas treatment equipment 100 also includes a flow path leading from the CO 2 capture container 201 to the atmospheric air or the heat exchanger 510 via the valves 102 and 105 . One of the valves 102 and 105 is opened and the other is closed in each of the capture, heating, and cooling steps.

First, in the capturing step, the valves 101 and 102 are opened, and the valves 103 , 104 , and 105 are closed, thereby causing the exhaust gas to flow from the boiler in the CO 2 capture container 201 , and capturing CO 2 in the exhaust gas by use of the CO 2 capture material filled in the CO 2 capture container 201 . At this time, the CO 2 capture material captures H 2 O as well.

Here, it is given that the temperature of the exhaust gas from the boiler is 50° C., and the composition is N 2 : 70 vol %, CO 2 : 13 vol %, H 2 O: 12 vol %, O 2 : 5 vol %, SO x : 1 ppm, and NO x : 10 ppm.

Next, in the heating step, the valves 104 and 105 are opened, the valves 101 , 102 , and 103 are closed, and the ventilator 502 is operated. At this time, gas emitted from the CO 2 capture container 201 is sent from the heated heat exchanger 510 , and is heated by the heat exchanger 510 . The gas heated by the heat exchanger 510 as the heating gas is circulated in the CO 2 capture container 201 . It is assumed that vapor of about 200° C. extracted from a vapor turbine is supplied to the heat exchanger 510 , and the temperature of the heating gas heated by the heat exchanger 510 is 160° C.

Here, the CO 2 capture material in the CO 2 capture container 201 contacts the heating gas to be heated to about 150° C. Then, the captured CO 2 and H 2 O are gradually desorbed. Accordingly, in the heating step, the ventilator 502 is operated, allowing the gas containing CO 2 and H 2 O desorbed from the CO 2 capture material to be heated through the heat exchanger 510 and circulate in the CO 2 capture container 201 , and further desorbing CO 2 and H 2 O, to form a cyclic process.

When the CO 2 concentrations of CO 2 and H 2 O in the gas flowing out of the CO 2 capture container 201 increase as a result of repetition of the above-mentioned cyclic process, the ventilator 503 is operated to extract a portion of the heated gas and sent the extracted portion to the condenser 601 . At this time, since the condenser 601 is cooled with cooling water of, for example, 25° C. (room temperatures), H 2 O in the gas condenses. As a result, the gas with reduced H 2 O concentration and condensed water are separated and emitted from the condenser 601 .

The gas emitted from the condenser 601 (gas emitted from the condenser 601 into the flow path as represented by a broken arrow in FIG. 1 ) contains H 2 O of about saturated vapor pressure. To remove the H 2 O, the compressors 701 compresses the gas and then, the condenser 602 condenses H 2 O again. At this time, like the condenser 601 , the condenser 602 is cooled with cooling water of room temperatures. Accordingly, the gas with further reduced H 2 O concentration and condensed water are separated and emitted from the condenser 602 .

The reason why the gas to be taken into the condenser 602 is compressed by the compressors 701 is that the ratio total pressure: saturated vapor pressure is high in high-pressure gas such that the purity of CO can be readily increased. However, when the partial pressure of CO exceeds 7.4 MPa, CO 2 becomes liquefied carbonic acid or supercritical CO 2 , which is not suitable for separation from H 2 O. Accordingly, in the compressors 701 , the partial pressure of CO 2 is preferably controlled to be equal to or smaller than 7.4 MPa.

The gas emitted from the condenser 602 (gas emitted from the condenser 601 into the flow path as represented by a broken arrow in FIG. 1 ) is compressed by the compressors 702 and then, is sent to the condenser 603 and is cooled with cooling water. At this time, CO 2 in the gas condenses and becomes liquefied carbonic acid. Remaining gas is discharged into atmospheric air.

In compression in the compressors 702 , when the partial pressure of N 2 is equal or greater than 3.4 MPa, N 2 contained in the gas becomes liquid N 2 or supercritical N 2 , which is not suitable for separation from CO 2 . To extract CO 2 as liquefied carbonic acid using cooling water of 25° C., N 2 is preferably compressed by the compressors 702 such that the partial pressure of N 2 becomes equal or greater than 7.4 MPa or more. Accordingly, to set the partial pressure of CO 2 to 7.4 MPa or more and the partial pressure of N 2 to 3.4 MPa or less, the ratio of CO 2 :N 2 in the recovered gas (gas emitted from the condenser 602 ) is preferably, 7.4 MPa/3.4 MPa=68/32 or more. That is, the CO 2 concentration in the recovered gas without consideration of the O 2 concentration is preferably, 68% or more, more preferably, 80% or more. When the temperature of the recovered gas is lower than 25° C., the pressure may be lower than the above-mentioned pressure. However, in this case, a cooler is required, increasing power consumption of the equipment.

In the cooling step, the valve 102 and the valve 103 are opened, the valves 101 , 104 , and 105 are closed, and the ventilator 501 is operated. That is, in the cooling step, by circulating atmospheric air in the CO 2 capture container 201 , the temperature of the CO 2 capture material is lowered to about 50° C. In that case, to prevent moisture in the gas from condensing in the capturing step, cooling is stopped at a temperature that is higher than the dew point of the exhaust gas flowing in the CO 2 capture container 201 .

To smoothly execute each of the above-mentioned capturing, heating, and cooling steps, opening/closing of the valves 101 to 105 , and operation of the ventilators 501 to 503 , the heat exchanger 510 , the condensers 601 to 603 , and the compressors 701 , 702 are controlled by a computer. Here, a computer constituting the control unit 450 is used. In FIG. 1 , small arrows from the block of the control unit 450 represent signals for controlling the above-mentioned processes. The computer that controls the processes may be a computer other than the control unit 450 .

<CO 2 Capture Material Deterioration Model>

In the exhaust-gas treatment equipment 100 , a cycle including the three processes of capture, heating, and cooling for CO 2 recovery is repeated, such that poisoning gas such as SO x and NO x as well as smoke and dusts adsorb on or combine with the CO 2 capture material in the exhaust-gas treatment equipment 100 . For this reason, the CO 2 capture performance of the CO 2 capture material gradually deteriorates. In other words, the maximum possible amount of CO 2 that can be captured by the CO 2 capture material, that is, the maximum possible CO 2 capture amount gradually decreases.

FIGS. 2A to 2F are views illustrating the deterioration state of the CO 2 capture material in the CO 2 capture container 201 on a time-series basis. In each of graphs of FIGS. 2A to 2F , a vertical axis represents the material position at which the CO 2 capture material is disposed, and the horizontal axis represents the maximum possible CO 2 capture amount of the CO 2 capture material disposed at the material position. In FIGS. 2A to 2F , the deterioration of the CO 2 capture material progresses in the order of (a), (b), (c), (d), (e), and (f).

Here, the exhaust gas containing CO 2 enters from the top of the CO 2 capture container 201 , and CO 2 contained in the gas is captured by the CO 2 capture material. Then, the gas without CO 2 is emitted from the bottom of the CO 2 capture container 201 (see FIG. 1 ). Accordingly, the material positions in the graphs of FIGS. 2A to 2F represent the positions of the CO 2 capture material in the direction that is parallel to the flow of the exhaust gas containing CO 2 flowing in the CO 2 capture container 201 , which means the height of the filled CO 2 capture material from the bottom of the container. That is, the material position=0 represents the lowest position of the CO 2 capture material, and the material position=h represents the highest position of the CO 2 capture material.

First, in the state where a new CO 2 capture material is just filled in the CO 2 capture container 201 (initial state), as expressed by a thick solid line 210 in FIG. 2A , the maximum possible CO 2 capture amount of the CO 2 capture material is uniform at any material position. The maximum possible CO 2 capture amount in this state is referred to as an initial maximum possible CO 2 capture amount, and in figures subsequent to FIG. 2B , is expressed by thick broken line 211 .

When the three processes of capture, heating, and cooling are repeated plural times, the exhaust gas flows from the top. Thus, the CO 2 capture material disposed at the highest position starts to deteriorate (see FIG. 2B ). In this case, the CO 2 capture material located closer to the top directly receives exhaust gas containing more smoke and dusts, and deteriorates more rapidly. Accordingly, as expressed by an inclined segment of the thick solid line 210 , the maximum possible CO 2 capture amount becomes smaller as the material position is higher, and becomes larger as the material position is lower. That is, the position of the CO 2 capture container 201 is lower, the deterioration level of the CO 2 capture material decreases.

However, typically, the maximum possible CO 2 capture amount does not recover to the initial maximum possible CO 2 capture amount (thick broken line 211 ) (vertical linear segment of the thick solid line 210 ). This may be due that each time the processes are repeated, the CO 2 capture material in the CO 2 capture container 201 deteriorates gradually but wholly. In the figures subsequent to FIG. 2B , a deterioration amount of the maximum possible CO 2 capture amount is represented as a difference 212 between the thick broken line 211 indicating the initial maximum possible CO 2 capture amount and the thick solid line 210 indicating the maximum possible CO 2 capture amount.

Next, when the processes are further repeated, the deterioration of the CO 2 capture material gradually progresses from the top toward the bottom (see FIG. 2C ) and first, the CO 2 capture material located at the upper position has approximately 0 maximum possible CO 2 capture amount, losing its CO 2 capture performance (see FIG. 2D ). When the processes are further repeated, the CO 2 capture material located at the lower position starts to deteriorate (see FIG. 2E ), and finally, CO 2 capture material disposed near the bottom of the CO 2 capture container 201 has almost 0 maximum possible CO 2 capture amount (see FIG. 2F ).

FIGS. 3A and 3B are schematically illustrating a deterioration model of the CO 2 capture material in the CO 2 capture container 201 , FIG. 3A is a graph illustrating relationships between the material positions and the maximum possible CO 2 capture amount of the CO 2 capture material, and FIG. 3B is a graph illustrating relationships between the material positions and a maximum possible heat amount of the CO 2 capture material. The maximum possible heat amount refers to the amount of heat generated when the CO 2 capture material captures all CO 2 of the maximum possible CO 2 capture amount at the material position.

In this embodiment, as illustrated in FIG. 3A , the model of the deterioration state of the maximum. possible CO 2 capture amount of the CO 2 capture material in the CO 2 capture container 201 is constituted of:

(1) a thick solid line 210 a in which the maximum possible CO 2 capture amount is approximately 0 at the upper material position;

(2) a thick solid line 210 b in which the maximum possible CO 2 capture amount linearly decreases with respect to a change in the material position at the middle material position; and

(3) a thick solid line 210 c in which the maximum possible CO 2 capture amount becomes almost constant and does not change at the lower material position.

The deterioration model illustrated in FIG. 3A can be associated with FIGS. 2D to 2E . In FIG. 3A , the case where the thick solid line 210 a having almost 0 maximum possible CO 2 capture amount is not present can be associated with FIGS. 2B and 2C , and the case where the thick solid line 210 c is not present can be associated with FIG. 2F .

A deterioration amount 213 of the maximum possible CO 2 capture amount, which is acquired by subtracting the thick solid line 210 c from the thick broken line 211 (the initial maximum possible CO 2 capture amount) in FIG. 3A is referred to as an overall deterioration amount. That is, the overall deterioration amount is a deterioration amount by which the CO 2 capture material in the CO 2 capture container 201 deteriorates almost uniformly when the capture, heating, and cooling steps are repeated. A deterioration amount 214 of the maximum possible CO 2 capture amount, which is acquired by subtracting the thick solid line 210 a or the thick solid line 210 b from the thick solid line 210 c , is referred to as a local deterioration amount. That is, the local deterioration amount is a deterioration amount by which the CO 2 capture material deteriorates depending on the material position when the heating and cooling steps are repeated.

The maximum possible heat amount of the CO 2 capture material is substantially proportional to the maximum possible CO 2 capture amount of the CO 2 capture material. In this case, the relationships between the material positions and the maximum possible CO 2 capture amount as represented by the thick solid lines 210 a , 210 b , and 210 c in FIG. 3A can be replaced with relationships between the material positions and the maximum possible heat amount as represented by thick solid lines 220 a , 220 b , and 220 c in FIG. 3B .

Here, a thick broken line 221 in FIG. 3B represents an initial maximum possible heat amount (maximum possible heat amount before deterioration) of the CO 2 capture material. Accordingly, a decrease 222 of the maximum possible heat amount due to the deterioration of the CO 2 capture material corresponds to a difference between the thick broken line 221 and the thick solid lines 220 a , 220 b , and 220 c . That is, the relationships between the material positions and the maximum possible heat amount as represented by the thick solid lines 220 a , 220 b , and 220 c in FIG. 3B can be also said to represent the deterioration model of the CO 2 capture material.

<CO 2 Capture Material Deterioration-State Estimating Method>

FIGS. 4A to 4C are views illustrating a basic concept of estimating the deterioration state of the CO 2 capture material based on temperatures in the CO 2 capture container 201 in the capturing step. Here, the deterioration state of the CO 2 capture material is estimated based on the temperatures measured by the temperature measuring elements 301 , 302 , and 303 disposed at three different material positions in the CO 2 capture container 201 (see FIG. 1 ). At this time, deterioration state of the CO 2 capture material follows the deterioration model illustrated in FIG. 3A .

Here, heat generation of the CO 2 capture material in the capturing step is considered. First, since CO 2 is not captured in the material position segment in which the maximum possible CO 2 capture amount is 0 (the material position segment represented by the thick solid line 210 a in FIG. 3A ), the heat amount of the CO 2 capture material becomes 0. Since CO 2 to be captured from the flowing exhaust gas is not left in the material position segment in which the maximum possible CO 2 capture amount is constant (the material position segment represented by the thick solid line 210 c in FIG. 3A ), the heat amount of the CO 2 capture material can be considered to be approximately 0. On the contrary, the maximum possible CO 2 capture amount increases in the flowing direction of the exhaust gas (downward) in the material position segment represented by the thick solid line 210 b in FIG. 3A . This means that CO 2 is captured to generate heat in this region.

In the capturing step, when exhaust gas of temperature T 0 (for example, 50° C.) is supplied to the CO 2 capture container 201 , the CO 2 capture material does not generate heat in the material position segment represented by the thick solid line 210 a in FIG. 3A and thus, the temperature of the flowing exhaust gas does not rise. Thus, at any position of the material position segment, as illustrated in FIG. 4A , the temperature of the flowing exhaust gas does not change from the temperature T 0 (for example, 50° C.).

Next, when the exhaust gas passes through the material position segment in which the CO 2 capture material generates heat (the material position segment represented by the thick solid line 210 b in FIG. 3A ), the temperature of the exhaust gas rises due to heat generation of the CO 2 capture material. Moreover, since the exhaust gas moves downward, the temperature of the exhaust gas rises toward the bottom. Accordingly, in the material position segment, as represented by a thick solid line 230 b in FIG. 4A , the temperature of the exhaust gas gradually rises from the temperature T 0 to a temperature T 3 (wherein, T 1 >T 0 ). Although not required, for simplicity, it is assumed that there is a linear relationship between the material position and the temperature rise.

Next, when the exhaust gas passes through the material position segment in which the CO 2 capture material does not generate heat (the material position segment represented by the thick solid line 210 c in FIG. 3A ), the temperature of the exhaust gas does not rise and thus, remains to be the temperature T 3 as represented by a thick solid line 230 c in FIG. 4A .

Thus obtained graph represented by the thick solid lines 230 a , 230 b , and 230 c in FIG. 4A indicates temperature distribution of the CO 2 capture material along the flowing direction of the exhaust gas in the CO 2 capture container 201 .

Subsequently, the temperature measuring elements 301 and 302 are disposed at material positions z 1 and z 2 included in the thick solid line 230 b in FIG. 4A , and temperatures measured at the material positions z 1 and z 2 are defined as T 1 and T 2 , respectively. Similarly, the temperature measuring element 303 is disposed at a material position z 3 included in the thick solid line 230 c in FIG. 4A , and the temperature measured at the material position z 3 is defined as T 3 .

Next, the above-mentioned measurement data is plotted in a graph having temperature (T) as a horizontal axis and material position (z) as a vertical axis, and plotted points are defined as P 1 , P 2 , and P 3 . Then, a straight line L 1 passing the points P 1 and P 2 is found, and a straight line L 2 that passes the point P 3 and is constant in temperature is found. Further, points at which the straight line L 1 crosses a straight line having T=T 0 and a straight line (straight line L 2 ) having T=T 3 are defined as Q 1 , Q 2 , respectively, and their material positions are defined as h 1 , h 2 , respectively.

In the case where h 1 is equal to or larger than h (h: the highest position), the deterioration state of the CO 2 capture material is still an initial state, and corresponds to the deterioration state illustrated in FIG. 2B or 2 ( c ). Accordingly, in this case, there is no segment of the thick solid line 230 a , in which the temperature does not change from the temperature of the supplied exhaust gas. In the case of h>h 1 and h 2 >0, the deterioration of the CO 2 capture material progresses, but the available CO 2 capture material is left. This deterioration state corresponds to the deterioration state illustrated in FIG. 2D to 2E . In the case where h 2 is equal to or smaller than 0, the CO 2 capture material almost deteriorates, and the deterioration state corresponds to the deterioration state illustrated in FIG. 2F .

In this manner, the thick solid lines 230 a , 230 b , and 230 c representing the relationships between the material positions and the temperatures in the CO 2 capture container 201 as illustrated in FIG. 4C can be acquired. These thick solid lines 230 a , 230 b , and 230 c can be associated with the thick solid lines 210 a , 210 b , and 210 c representing the relationships between the material positions and the maximum possible CO 2 capture amount in FIG. 3A , respectively. Accordingly, the deterioration state of the CO 2 capture material in the CO 2 capture container 201 can be estimated based on the shape of the thick solid lines 230 a , 230 b , and 230 c in FIG. 4C , or the values h 1 and h 2 of the material positions of points Q 1 and Q 2 in FIG. 4C .

In this embodiment, the material positions at the temperature measuring elements 301 , 302 , and 303 are disposed can be vertically moved by a moving unit 402 . Accordingly, the temperature measuring element 303 for determining the straight line L 2 may be at the material position close to the bottom of the CO 2 capture container 201 , that is, the material position that is slightly higher than 0. At least initially, the temperature measuring element 301 for determining the straight line L 1 may be disposed at the material position close to the top of the CO 2 capture container 201 , that is, the material position that is slightly lower than h. Then, the temperature measuring element may be moved appropriately depending on the progress of the deterioration of the CO 2 capture material. In cooperation with the temperature measuring element 301 , the temperature measuring element 302 may be disposed at the material position that is lower than the material position of the temperature measuring element 301 by a predetermined distance.

FIGS. 5A and 5B are views illustrating an example of a method of determining suitable positions of the temperature measuring elements 301 and 302 . Here, first, in the capturing step, the temperature measuring elements 301 , 302 , and 303 are disposed at the material positions z 1 , z 2 , and z 3 , respectively, and measure the temperatures T 1 , T 2 , and T 3 . Next, as illustrated in FIGS. 4A to 4C , measurement data is plotted in a graph having material position as a vertical axis and temperature as a horizontal axis to acquire points P 1 , P 2 , and P 3 . Subsequently, a straight line passing the points P 1 and P 2 is defined as L 1 , and a straight line that passes the point P 3 and is constant in temperature (T=T 3 ) is defined as L 2 . Further, points at which the straight line L 1 crosses the straight line having T=T 0 and the straight line having T=T 3 (straight line L 2 ) are defined as Q 1 , Q 2 , respectively, and their material positions are defined as h 1 , h 2 .

At this time, the points P 1 and P 2 may be disposed at any position on the straight line L 1 . That is, the points P 1 and P 2 may be biased toward the point Q 1 , or toward the point Q 2 . However, when the points P 1 and P 2 are biased, suitable inclination of the straight line L 1 may not be achieved. Here, the points P 1 and P 2 , that is, the temperature measuring elements 301 and 302 are moved such that a center Pg between the points P 1 and P 2 is located at a center Pc of a line segment P 1 -P 2 .

For this reason, first, a difference ΔT (=T 3 −T 0 ) between the temperature T 3 measured by the temperature measuring element 301 and the temperature T 0 of the exhaust gas supplied to the CO 2 capture container 201 is found. Next, a temperature Tc (=T 0 +ΔT/2) at a center Pc between a line segment Q 1 -Q 2 , and a material position hc (=(h 1 +h 2 )/2) are found based on the straight line L 1 , and a point expressed by the temperature Tc and the material position hc is defined as Pc. Then, material positions z 1 ′ and z 2 ′, to which the temperature measuring elements 301 and 302 are to be moved, are calculated according to following equations (see FIG. 5B ).

z 1′= hc +( z 1− z 2)/2   (1)

z 2′= hc −( z 1− z 2)/2   (2)

Subsequently, the temperature measuring elements 301 and 302 are moved to the material positions z 1 ′ and z 2 ′, and temperatures T 1 ′ and T 2 ′ measured at the material positions are acquired. The, as illustrated in FIG. 5B , data on the temperatures T 1 ′ and T 2 ′ at the material positions z 1 ′ and z 2 ′ is plotted in a graph having material position as a vertical axis and temperature as a horizontal axis, and the points are defined as P 1 ′ and P 2 ′. Next, a new straight line L 1 ′ passing the points P 1 ′ and P 2 ′ is found, and material positions h 1 ′ and h 2 ′ of points Q 1 ′ and Q 2 ′ at which the straight line L 1 ′ crosses a straight line having T=T 0 and a straight line having T=T 3 (straight line L 2 ) are found.

In this case, the temperature measuring element 303 is not moved and however, may be appropriately moved at the material position of z<h 2 . Even when moved, the temperature measuring element 303 basically measures the same temperature T 3 .

Thus acquired inclination of the straight line L 1 ′ and the material positions h 1 ′ and h 2 ′ of the points Q 1 ′ and Q 2 ′ can be regarded as more suitable values than the inclination of the straight line L 1 and the material positions h 1 and h 2 of the points Q 1 and Q 2 , which are acquired before movement of the temperature measuring elements 301 and 302 . That is, since the temperature measuring elements 301 and 302 are disposed substantially at the center of the material position segment of the CO 2 capture material generating heat due to capture of CO 2 (the segment represented by the thick solid line 230 b in FIG. 4C ), the temperatures measured by the temperature measuring elements and its inclination (change rate of temperature with respect to the material position) are more stabilized.

As apparent from FIGS. 2A to 2F , each time the capture, heating, and cooling steps are repeated, the straight line L 1 gradually moves downward, and the straight line L 2 gradually moves to left. In other words, the line segment Q 1 -Q 2 (the segment represented by the thick solid line 230 b in FIG. 4C ) becomes shorter as it moves downward. Accordingly, each time capturing step is performed, the material positions of the temperature measuring elements 301 and 302 are determined to move the temperature measuring elements 301 and 302 according to the above-mentioned method, thereby determining material positions suitable for the temperature measurement, and enabling more accurate estimation of the deterioration state of the CO 2 capture material.

<CO 2 Capture Material Deterioration-State Estimation Processing>

The control unit 450 illustrated in FIG. 1 includes a computer. The computer executes acquisition and storage of data on temperatures at positions, and predetermined calculations, and further controls execution of the capture, heating, and cooling steps for CO 2 recovery. In the capturing step, the processing of acquiring temperatures measured by the temperature measuring elements 301 , 302 , and 303 is combined with the processing of driving the moving unit 401 to vertically move the temperature measuring elements 301 , 302 , and 303 to achieve CO 2 -capture-material deterioration-state estimating processing.

FIG. 6 is a flow chart illustrating a flow of the CO 2 -capture-material deterioration-state estimating processing by use of the computer. Desirably, each time the capturing step for CO 2 recovery is performed, the CO 2 -capture-material deterioration-state estimating processing is executed at the time close to the end of the capturing step, at which the temperature in the CO 2 capture container 201 is stable. Details of the CO 2 -capture-material deterioration-state estimating processing will be described below with reference to FIGS. 2A to 2F and FIGS. 5A and 5B .

First, before executing the CO 2 -capture-material deterioration-state estimating processing in FIG. 6 , the computer initializes the material positions of the temperature measuring elements 301 , 302 , and 303 to z 1 , z 2 , and z 3 , respectively. Here, when the initial capturing step is executed, for example, z 1 =h×0.9, z 2 =h×0.8, z 3 =h×0.1 are set as initial values of the material positions z 1 , z 2 , and z 3 . h indicates the highest material position, given that the material position of the CO 2 capture material at the bottom of the CO 2 capture container 201 is set to 0 (zero) (height: see FIGS. 4A to 4C ). When the second or subsequent capturing step is executed, the material positions z 1 ′ and z 2 ′, and z 3 ′ of the temperature measuring elements 301 , 302 , and 303 after execution of the last capturing step may be used as the initial values of the material positions z 1 , z 2 , and z 3 .

Subsequently, when the capturing step is started and the temperature at each material position in the CO 2 capture container 201 becomes stabilized, the computer starts the CO 2 -capture-material deterioration-state estimating processing illustrated in FIG. 6 . The time when the temperature at each material position becomes stabilized may be the time when a predetermined time elapse from the start time of the capturing step. Alternatively, the temperature stabilization may be determined by monitoring the temperatures of the temperature measuring elements 301 , 302 , and 303 .

As illustrated in FIG. 6 , the computer acquires temperatures T 1 , T 2 , and T 3 (measurement data) from the temperature measuring elements 301 , 302 , and 303 (Step S 11 ), to determine whether T 2 =T 3 or not (Step S 12 ). However, T 2 =T 3 herein means that T 2 is equal to T 3 with a predetermined error of about 0.5, for example. That is, it is determined whether or not |T 2 −T 3 | is equal to or smaller than the predetermined error.

In the case where T 2 is equal to T 3 as a result of the determination in Step S 12 (Yes in Step S 12 ), the deterioration state of the CO 2 capture material is as illustrated in FIG. 2B , and in FIG. 5A , the point P 1 is located on the straight line L 1 and the points P 2 and P 3 are located on the straight line L 2 . Thus, for example, the computer displays a message indicating that the CO 2 capture material is just used on a display device (Step S 21 ).

On the contrary, in the case where T 2 is not equal to T 3 as a result of the determination in Step S 12 (No in Step S 12 ), in FIGS. 5A and 5B , the points P 1 and P 2 are located on the straight line L 1 . Thus, the computer calculates the equation of the straight line L 1 passing the points P 1 and P 2 , and the equation of the straight line L 2 that passes the point P 3 and is constant in temperature (Step S 13 ). Next, the computer calculates material positions h 1 and h 2 of the points Q 1 and Q 2 at which the straight line L 1 crosses the straight line having T=T 0 and the straight line having T=T 3 (straight line L 2 ), respectively (Step S 14 ).

Subsequently, the computer calculates the material positions z 1 ′ and z 2 ′ to which the temperature measuring elements 301 and 302 are to be moved according to the method of moving the temperature measuring elements 301 and 302 , which is described with reference to FIGS. 5A and 5B , that is, using the equations (1) and (2) (Step S 15 ). Next, the computer moves the temperature measuring elements 301 and 302 to the calculated material positions via the moving unit 401 (Step S 16 ). Here, the temperature measuring element 303 is assumed to be located close to the bottom of the CO 2 capture container 201 (for example, the location of z 3 =h×0.1), and is not moved.

Subsequently, the computer acquires the temperatures T 1 ′, T 2 ′, and T 3 ′ measured at the moved material positions from the temperature measuring elements 301 , 302 , and 303 (Step S 17 ). Next, the computer calculates the equation of the straight line L 1 ′ passing the points P 1 ′ and P 2 ′, and the equation of the straight line L 2 ′ that passes the point P 3 ′ and is constant in temperature (Step S 18 ). Since the temperature measuring element 303 does not change the material position, T 3 ′ is equal to T 3 , and the point P 3 ′ and the straight line L 2 ′ are the same as the point P 3 and the straight line L 2 , respectively.

Subsequently, the computer calculates the material positions h 1 ′ and h 2 ′ of the points Q 1 ′ and Q 2 ′ at which the straight line L 1 ′ crosses the straight line having T=T 0 and the straight line having T=T 3 (straight line L 2 ) (Step S 19 ). Next, the computer determines whether or not the material position h 1 ′ of the point Q 1 ′ is larger than the highest material position h of the CO 2 capture material, that is, h 1 ′ is larger than h (Step S 20 ). When h 1 ′ is larger than h as a result of the determination (Yes in Step S 20 ), the deterioration state of the CO 2 capture material is as illustrated in FIG. 2B or 2 ( c ). Thus, for example, the computer displays a message indicating that the CO 2 capture material is just used on a display device (Step S 21 ).

On the contrary, when h 1 ′ is not larger than h as a result of the determination in Step S 20 (No in Step S 20 ), the computer determines whether or not the material position h 2 ′ of the point Q 2 ′ is smaller than the material position 0 at the bottom of the CO 2 capture material, that is, h 2 ′ is smaller than 0 (Step S 22 ). When h 2 ′ is smaller than 0 as a result of the determination (Yes in Step S 22 ), the deterioration state of the CO 2 capture material is as illustrated in FIG. 2F . Thus, for example, the computer displays an alarm message to prompt an exchange of the CO 2 capture material on a display device (Step S 24 ).

When h 2 ′ is not smaller than 0 as a result of the determination in Step S 22 (No in Step S 22 ), the deterioration state of the CO 2 capture material is as illustrated in FIG. 2D or 2E . Thus, for example, the computer displays a message indicating that the CO 2 capture material is still available on a display device (Step S 23 ). In Steps S 21 to S 24 , graphs indicating the deterioration state of the CO 2 capture material, such as FIGS. 2A to 2F , may be displayed along with the messages.

The above-mentioned CO 2 -capture-material deterioration-state estimating processing can estimate the deterioration state of the CO 2 capture material in the CO 2 capture container 201 accurately and appropriately. The administrator of the exhaust-gas treatment equipment 100 can recognize the exchange timing of the CO 2 capture material according to the message displayed on the display device, enabling appropriate exchange of the CO 2 capture material. Thus, the exhaust-gas treatment equipment 100 can be operated efficiently and economically.

FIGS. 7A and 7B schematically illustrate an example of specific arrangement of the CO 2 capture material and the temperature measuring elements in the CO 2 capture container 201 , FIG. 7A is a schematic perspective view, and FIG. 7B is a schematic bottom view. As illustrated in FIGS. 7A and 7B , a gas flowing portion 202 and a gas non-flowing portion 203 are provided in the CO 2 capture container 201 . In this embodiment, the exhaust gas containing CO 2 flows in a direction represented by a block arrow in FIG. 7A , that is, from the top toward the bottom.

The gas flowing portion 202 is filled with the vertically-long columnar CO 2 capture material having a honeycomb cross section. The gas non-flowing portion 203 is provided with a sleeve pipe 511 vertically extending in the flowing direction of the exhaust gas, and is filled with a heat insulating material in the portion other than the sleeve pipe 511 . The temperature measuring elements 301 , 302 , and 303 that can be vertically moved by the moving unit 401 are disposed in the sleeve pipe 511 .

Preferably, the sleeve pipe 511 is constituted of a material having a high thermal conductivity, for example, a metal pipe. In this case, more preferably, openings for allowing the temperature measuring elements 301 , 302 , and 303 to directly contact or approach the CO 2 capture material are formed on contact places of the sleeve pipe 511 with the gas flowing portion 202 filled with the CO 2 capture material.

Further, in this example, a second sleeve pipe 512 is disposed below the bottom of the gas flowing portion 202 , and extends from the center toward the outer circumference of the gas flowing portion 202 . The temperature measuring element 304 that can be horizontally moved by the second moving unit 402 is disposed in the second sleeve pipe 512 . Here, preferably, a lot of holes or openings are formed on the second sleeve pipe 512 except for the structure supporting the temperature measuring element 304 . In this case, the gas emitted from the gas flowing portion 202 readily flows into the second sleeve pipe 512 , the temperature of the gas can be accurately measured.

The second sleeve pipe 512 , the temperature measuring element 304 , and the second moving unit 402 are not essential. However, following effects can be expected by providing these constituents. That is, the computer that controls the exhaust-gas treatment equipment 100 can measure the temperature of the gas emitted from the gas flowing portion 202 while radially moving the temperature measuring element 304 by the moving unit 402 to acquire information on the radial change of the temperature of the exhaust gas. In the CO 2 -capture-material deterioration-state estimating processing (see FIG. 6 ), the computer can appropriately correct the temperatures measured by the temperature measuring elements 301 , 302 , and 303 according to the information on the radial change of the temperature of the exhaust gas, thereby further improving the accuracy of estimating the deterioration state of the CO 2 capture material.

Examples of the temperature measuring elements 301 to 304 include thermocouples, thermistors, and radiation thermometers. However, considering that the temperature measuring elements are moved in the sleeve pipes 511 , 512 in the CO 2 capture container 201 , easily-miniaturized thermocouples or thermistors are preferable. Further, the temperature measuring elements 301 to 303 may directly contact the CO 2 capture material and however, does not preferably contact the CO 2 capture material to suppress wear of the capture material due to the movement.

In the embodiment described with reference to FIG. 1 to FIGS. 7A and 7B , the temperature of the CO 2 capture material in the CO 2 capture container 201 is measured by the three temperature measuring elements 301 , 302 , and 303 . However, only one temperature measuring element 301 can perform the above-mentioned method of estimating the deterioration state of the CO 2 capture material. In this case, the temperatures of the CO 2 capture material at the three different material positions may be measured while vertically moving the temperature measuring element 301 along the flow of the exhaust gas by the moving unit 401 . However, in this case, since the temperatures are measured at the positions with a slight time shift, as compared with the case of using the three temperature measuring elements 301 , 302 , and 303 , the accuracy of the relationships between the material positions and temperatures becomes lower. However, a thermal capacity of the temperature measuring element 301 is sufficiently smaller than a thermal capacity of the CO 2 capture material, and time for movement of the temperature measuring element 301 via the moving unit 401 is sufficiently smaller than time for deterioration of the CO 2 capture material. Accordingly, even when only one temperature measuring element 301 is used, the deterioration state of the CO 2 capture material can be estimated with a practically enough accuracy.

As has been described, the exhaust-gas treatment equipment 100 in accordance with this embodiment can accurately estimate the deterioration state of the CO 2 capture material (gas capture material) using three temperature measuring elements or only one temperature measuring element.

<Extension of Embodiment>

The above-mentioned embodiment may be partially replaced with various embodiments. For example, the exhaust-gas treatment equipment 100 illustrated in FIG. 1 is equipment that recovers CO 2 from exhaust gas emitted from the boiler of the power plant and however, is not limited to such equipment. Accordingly, the exhaust gas is not limited to the exhaust gas from power plants, and may be exhaust gas from chemical plants, automobile exhaust gas, and synthesis gas. In this case, examples of components of the exhaust gas include N 2 , O 2 , Co 2 , CO, hydrocarbon, smoke and dusts, SO x , No x , H 2 , CH 4 , and H 2 S. That is, the exhaust-gas treatment equipment 100 only needs to remove or recover one of these components.

The CO 2 capture container 201 illustrated in FIG. 1 is filled with the CO 2 capture material. However, the CO 2 capture container 201 should be generally referred to as a reaction container, and the CO 2 capture material should be referred to as a gas capture material that captures a certain gas component.

The gas capture material used to capture gas, in particular, CO 2 and H 2 O may be any material, and may be metallic oxides, activated carbon, alkali metal carbonates, alkali metal hydroxides, layered composite hydroxides, and solid organic compounds. The CO 2 capture material may be a single-type CO 2 capture material or a combination of a plurality of types of CO 2 capture materials. One may be used as a carrier, while the other may be carried by impregnation or so on.

The metal oxide is preferably, a porous metal oxide, and more preferably, an oxide or a composite oxide containing at least one metal selected from Ce (selenium), a rare earth metal other than Ce, and Zr (zirconium). By using the composite oxide, the capture material can absorb CO 2 even after contact with H 2 O, and CO 2 desorption temperature can be lowered. This is due to that, in the above-mentioned oxide, the surface of the oxide reacts with H 2 O to form a hydroxyl group (—OH), and by reaction of the functional group with CO 2 , CO 2 can be absorbed on the surface in the form of hydrogencarbonate (—CO 3 H).

Examples of the method of synthesizing the above-mentioned gas capture materials include impregnation method, mixing method, coprecipitation method, and sol-gel method. For example, a basic compound such as ammonia water, sodium hydroxide, or calcium hydroxide may be added to a solution containing a Ce nitrate to adjust pH to 7 to 10, precipitating the material. When an oxide is formed by precipitation, the oxide may be used as it is, or may be further oxidized by firing.

The gas capture material has any shape, and for example, may be shaped into powder, particle, pellet, honeycomb, and plate (monolith). When it is attempted to increase the reaction rate for gas capture, the powder, particle, or pellet-shaped gas capture material is preferable. When the amount of gas flowing in the reaction container is large and a pressure loss is easy to increase, honeycomb or plate-shaped gas capture material is preferable.

In the case of honeycomb-shaped gas capture material, a temperature measuring element may be installed in a honeycomb cell. However, in this case, the area of the openings of the honeycomb cell becomes smaller by the area of the installed temperature measuring element. As a result, the gas flow rate decreases at the site of the installed temperature measuring element, lowering the deterioration level of the gas capture material at the site due to flowing of poisoning gas lowers. That is, the accuracy of estimating the deterioration state of the gas capture material is considered to be degraded.

To reduce the effect of lowering of the gas flow rate, the diameter of the honeycomb cell including the temperature measuring element may be increased in advance, or the temperature measuring element may be installed on the outer circumferential face or non-gas flowing site of the honeycomb cell (for example, see FIGS. 7A and 7B ). Alternatively, a temperature measuring element having a small diameter and a small cross-sectional area may be used. However, in this case, the strength of the measuring element decreases, which is unsuitable. Alternatively, the honeycomb cell may be hollowed to install the temperature measuring element therein. However, in this case, the strength of the honeycomb cell decreases.

Captured CO 2 may be desorbed from the gas capture material by heating, depressurization, or both of the gas capture material. In the embodiment described with reference to FIG. 1 , the heating gas is circulated in the CO 2 capture container 201 (reaction container) to heat the CO 2 capture material, thereby desorbing CO 2 . Alternatively, a heat transfer pipe that circulates a heated heat medium therein may indirectly heat the CO 2 capture material (gas capture material). In the case of depressurization, the reaction container may be depressurized by use of a pump or the like. In the case where both of heating and depressurization are performed, since depressurization decreases the gas-induced thermal conductivity to slow down the heating rate, heating is preferably performed prior to depressurization.

When the gas capture material is heated in the heating step and then, the gas capture material is reused, the gas capture material is cooled. As a cooling method, as described in the embodiment illustrated in FIG. 1 , cooling gas (atmospheric air of room temperatures) may be circulated in the reaction container to cool the gas capture material, or a heat transfer pipe that circulates a coolant therein may indirectly cool the gas capture material.

When CO 2 is desorbed using the heated gas capture material, the capture, heating, and cooling steps may be switched in any suitable manner. For example, the position of the gas capture material in the reaction container is fixed, and gas supplied to the reaction container or an output of heating/cooling means is changed to switch the processes (fixed floor method). Alternatively, a space for each of the capture, heating, and cooling steps is decided, and the capture material is moved into the space to switch each process (fluid bed method or rotator method). When the capture material rotates as in the rotator method, preferably, the temperature measuring element is installed so as to hardly change with respect to rotation, for example, is located in the vicinity of a central axis of the rotator. In the case of using a thermocouple or thermistor as the temperature measuring element, the temperature measuring element may be coated with lubricating oil to prevent the breaking of a wire due to twisting.

The present invention is not limited to the above-mentioned embodiment and modification examples, and include other various modification examples. For example, the above-mentioned embodiment and modification examples describe the present invention in detail to facilitate understanding of the present invention, and do not necessarily include all of the described constituents. In addition, a portion of the configuration of any embodiment or modification example may be replaced with the configuration of another embodiment or modification example. Alternatively, the configuration of any embodiment or modification example may be combined with the configuration of another embodiment or modification example. Further, with respect to a portion of the configuration of each of the embodiment and modification examples, addition, deletion, and replacement of the configuration of another embodiment and modification example may be made.

100 : Exhaust-gas treatment equipment

101 to 105 : Valve

201 : CO 2 Capture container (Reaction container)

202 : Gas flowing portion

203 : Gas non-flowing portion

301 to 304 : Temperature measuring element

401 : Moving unit

402 : Second moving unit

450 : Control unit

501 to 503 : Ventilator

511 : Sleeve pipe

512 : Second sleeve pipe

601 to 603 : Condenser

701 , 702 : Compressor