JP2012035214A - Carbon dioxide-collecting method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon dioxide-collecting method and device which detect with time, the concentration of carbon dioxide in an absorbent, exert a stable carbon dioxide collection performance, enable response to conditional fluctuation or the like, and have high applicability.SOLUTION: Carbon dioxide is absorbed in an absorbent by bringing a carbon dioxide-containing gas G into contact with the absorbent in an absorption tower 10, and the absorbent is regenerated by heating at a regeneration tower 20 to make carbon dioxide release. The absorbing agent concentration in the absorbent is decided by detecting the total organic carbon amount of the absorbent using a total organic carbon analyzer 40, and a control part 43 controls the absorbing agent concentration of the absorbent on the basis of the above decision. Besides, the control part controls the carbon dioxide-collection performance of the absorbent as a circulation system by adjusting a circulation velocity and heating degree.

Description

  The present invention relates to a carbon dioxide recovery method and a carbon dioxide recovery device for separating and recovering carbon dioxide from a gas containing carbon dioxide such as combustion gas and reducing clean gas to the atmosphere.

  Facilities such as thermal power plants, steelworks, and boilers use large amounts of fuel such as coal, heavy oil, and super heavy oil. Sulfur oxides, nitrogen oxides, and carbon dioxide emitted by the combustion of fuel are There is a need for quantitative and concentration restrictions on emissions from the perspective of air pollution prevention and global environmental protection. In recent years, carbon dioxide has been seen as a major cause of global warming, and movements to suppress emissions have become active worldwide. For this reason, in order to enable the recovery and storage of carbon dioxide from combustion exhaust gases and process exhaust gases without releasing them into the atmosphere, various researches have been vigorously advanced. As a carbon dioxide recovery method, for example, PSA ( Known are pressure swinging), membrane separation and concentration, and chemical absorption using reaction absorption by basic compounds.

  In the chemical absorption method, mainly alkanolamine-based basic compounds are used as the absorbent. In the treatment process, an aqueous liquid containing the absorbent is generally used as the absorbent, and carbon dioxide contained in the gas is absorbed into the absorbent. The absorbing solution is circulated so as to alternately repeat the absorbing step to be performed and the regenerating step of regenerating the absorbing solution by releasing the absorbed carbon dioxide from the absorbing solution. In the regeneration process, heating for releasing carbon dioxide is necessary, and the regenerated absorbent is cooled for reuse in the absorption process (see, for example, Patent Document 1 below).

  The water and the absorbent constituting the absorbent are easily vaporized by heating in the regeneration process, and may be consumed due to the decomposition of the absorbent. That is, the concentration of the absorbing liquid changes during circulation between the absorption process and the regeneration process, and thereby the absorption performance also changes. For this reason, the method of managing the density | concentration of an absorption liquid is proposed, for example, in the following patent document 2, the liquid level gauge which measures the liquid level of an absorption liquid is provided, and the liquid level in an absorption process becomes fixed. Thus, it is described that the amount of absorption liquid is kept constant by supplying water. In Patent Document 3 below, the concentration of the amine compound is detected by measuring the refractive index of the absorbing solution at a fixed position in the system where the absorbing solution circulates, and the amine compound of the circulating absorbing solution is detected based on this concentration. Controlling the concentration is described.

JP 2009-214089 A Japanese Patent Laid-Open No. 10-202054 Japanese Patent Laid-Open No. 06-154554

  The absorbing liquid always circulates in the system, and the flow state easily affects the measurement of the liquid level and the refractive index. Therefore, in the methods proposed in Patent Documents 2 and 3, the measurement position is used for accurate measurement. There are problems such as the need to consider the setting and the difficulty of responding to continuous measurement or similar measurement.

  Moreover, when the carbon dioxide content in the gas to be treated fluctuates or the treatment conditions need to be changed, it is difficult to appropriately adjust or change the absorbent concentration of the absorbent.

  The object of the present invention is to solve the above-mentioned problems, and can cope with continuous measurement of absorption liquid used for carbon dioxide recovery and detection of changes over time, and can stably recover carbon dioxide in response to fluctuations in processing conditions. It is to provide a method for recovering carbon dioxide.

  Another object of the present invention is to provide a carbon dioxide recovery device that has high applicability to changes in processing conditions and the like, can exhibit stable carbon dioxide recovery performance, and has a control function of recovery performance according to the processing conditions. Is to provide.

  In order to solve the above problems, the present inventors have conducted extensive research, and as a result, the measurement accuracy of the absorption liquid concentration can be improved using total organic carbon (TOC) measurement. The present inventors have found that it is possible to control so as to stably recover carbon dioxide by acquiring a change with the passage of time and appropriately responding to it, and have completed the present invention.

  According to one aspect of the present invention, the carbon dioxide recovery device is configured to bring a gas containing carbon dioxide into contact with an absorption liquid, so that the absorption liquid absorbs carbon dioxide, and the absorption that has absorbed carbon dioxide. A regeneration tower for regenerating the absorbing liquid by heating the liquid to release carbon dioxide from the absorbing liquid, and detecting the total organic carbon content of the absorbing liquid and determining the absorbing liquid determined from the total organic carbon content detected And a control system that adjusts the absorbent concentration of the absorbent based on the absorbent concentration.

  Further, according to another aspect of the present invention, the carbon dioxide recovery device is configured to bring a gas containing carbon dioxide into contact with an absorption liquid, so that the absorption liquid absorbs carbon dioxide, and absorbs the carbon dioxide. The absorption liquid is heated so that carbon dioxide is released from the absorption liquid to regenerate the absorption liquid, and the absorption liquid is alternately and repeatedly supplied to the absorption tower and the regeneration tower. Circulatory system that circulates, and detecting at least one of the total organic carbon amount and inorganic carbon amount of the absorption liquid, and using at least one of the detected total organic carbon amount and inorganic carbon amount, absorption as the circulating system The gist of the invention is to have a control system for controlling the carbon dioxide recovery performance of the liquid.

  Furthermore, according to one aspect of the present invention, the method for recovering carbon dioxide comprises contacting an absorption liquid with a gas containing carbon dioxide to absorb the carbon dioxide in the absorption liquid, and absorbing the carbon dioxide. The regeneration step of heating the absorption liquid to release carbon dioxide from the absorption liquid to regenerate the absorption liquid, and detecting the total organic carbon amount of the absorption liquid, and the absorption determined from the detected total organic carbon amount And a control step of adjusting the absorbent concentration of the absorbent based on the absorbent concentration of the liquid.

  According to another aspect of the present invention, a method for recovering carbon dioxide includes: an absorption step in which a gas containing carbon dioxide is brought into contact with an absorption liquid, and the absorption liquid absorbs carbon dioxide; The absorption liquid is heated so as to release carbon dioxide from the absorption liquid to regenerate the absorption liquid, and the absorption liquid is alternately supplied to the absorption process and the regeneration process. Circulating the circulation process, detecting the total amount of organic carbon and inorganic carbon in the absorption liquid, and using at least one of the total organic carbon and inorganic carbon detected, as a circulation system of the absorption liquid And a control process for controlling the carbon recovery performance.

  According to the present invention, in the process of recovering carbon dioxide contained in a gas, data including concentration fluctuations of the absorbing solution is acquired to accurately cope with concentration adjustment and exhibit stable carbon dioxide recovery performance. Therefore, it is possible to provide a carbon dioxide recovery device that can efficiently process in response to a change in the state of the gas to be processed and can contribute to energy saving and environmental protection. It is economically advantageous because it can be carried out easily using general equipment without requiring special equipment or expensive equipment.

1 is a schematic configuration diagram showing a carbon dioxide recovery apparatus according to a first embodiment of the present invention. The schematic block diagram which shows the collection | recovery apparatus of the carbon dioxide which concerns on the 2nd Embodiment of this invention.

  In the absorption process of carbon dioxide by the chemical absorption method, an absorption process in which carbon dioxide contained in the gas is absorbed by a low-temperature absorption liquid, and a high-temperature regeneration in which the absorbed carbon dioxide is released from the absorption liquid and the absorption liquid is regenerated. The absorption liquid is circulated between the processes, and the absorption process and the regeneration process are alternately repeated. In the absorption process, the absorption liquid generates heat due to the absorption of carbon dioxide, and in the regeneration process, it is heated at a high temperature. Therefore, in any process, the discharged gas contains water vapor and an absorbent that are vaporized from the absorption liquid. obtain. Therefore, the concentration of the absorbing solution varies during circulation, and if left unattended, the amount of carbon dioxide that can be absorbed / released by the absorbing solution changes and affects the carbon dioxide recovery efficiency. Therefore, in order to maintain the carbon dioxide recovery performance of the absorption liquid, it is necessary to detect the concentration change of the absorption liquid and perform some correction accordingly, in order to grasp the concentration change as accurately as possible. It is desirable that continuous measurement is possible.

  In the present invention, in consideration of the above points, the concentration measurement of total organic carbon (TOC), which has become possible to track changes with time by providing an on-line type measurement device, is adopted. ), A total organic carbon meter (TOC meter) capable of detecting the concentrations of inorganic carbon (IC) and organic carbon (total organic carbon, TOC). As a measurement method of the TOC meter, there are a UV oxidation conductivity method, a fuel catalyst oxidation method, and the like, but any method may be used. In the TOC meter, the objects to be actually detected are TC and IC, and the TOC concentration is detected as a value obtained by subtracting the IC concentration from the TC concentration (TC-IC).

  The carbon-containing component contained in the absorption liquid is basically carbon dioxide and an absorbent. Carbon dioxide is detected as IC, and the absorbent in the absorption liquid is measured as TOC (= TC-IC) and prepared in advance. The absorbent concentration can be determined from the TOC concentration based on the calibration curve. Measurement of the TOC concentration of the absorption liquid may be performed in any of the circulation paths of the absorption liquid, but the data obtained by measurement after the absorption process or after the regeneration process is advantageous in terms of control accuracy. In this measurement, not only the concentration of the absorbent but also the amount of carbon dioxide recovered can be determined as the amount of absorption / release subtraction in both steps based on the amount of carbon dioxide obtained as the IC value. Therefore, it is preferable in that it can be confirmed whether or not the effect of the adjustment of the absorbent concentration actually occurs, and feedback that corrects the concentration adjustment by using this is possible. Furthermore, it is possible to control the carbon dioxide recovery performance of the absorbing liquid by adjusting factors other than the concentration, and feedback for correcting the control is also possible.

  That is, using the measurement data including the TOC concentration of the absorbent, control can be performed so that the absorbent exhibits the desired carbon dioxide recovery performance based on the absorbent concentration and the carbon dioxide concentration determined from them.

  The carbon dioxide recovery performance of the absorption liquid includes an inherent recovery performance of the absorption liquid itself and a systematic recovery performance as the absorption liquid circulation system. The recovery performance of the absorbent itself varies depending on the absorbent concentration. Specifically, the increase or decrease of the carbon dioxide absorption capacity (maximum amount of carbon dioxide that can be absorbed per unit) due to the increase or decrease of the absorbent concentration It becomes an element that raises and lowers performance. On the other hand, the recovery performance as a circulatory system not only fluctuates depending on the upper and lower of the inherent recovery performance described above, but also decreases in the amount of carbon dioxide absorbed due to an increase in the liquid temperature in the absorption process, the liquid temperature in the regeneration process (the amount of energy supplied) ) It also decreases due to a decrease in carbon dioxide emission due to a decrease and a decrease in contact area in contact with gas. Since the surface area on the packing material in the absorption tower is constant, the contact area varies depending on the ratio of the amount of absorption liquid to the amount of gas to be treated supplied to the absorption tower per unit time. That is, systematic recovery performance can be increased or decreased depending on the increase or decrease in the circulation rate of the absorbing liquid. Such operational recovery performance determined by the liquid temperature and circulation speed of the absorption liquid and the specific recovery performance due to the absorbent concentration of the absorption liquid are comprehensively demonstrated, and systematic carbon dioxide recovery performance and Become. In the present invention, based on the data of the absorption liquid obtained by the TOC meter, not only the recovery performance unique to the absorption liquid but also the operational recovery performance can be controlled, whereby carbon dioxide as a circulation system of the absorption liquid can be controlled. Collective performance can be controlled overall.

  As described above, specific methods for controlling the carbon dioxide recovery performance of the absorption liquid are: A) a technique for controlling the recovery performance of the absorption liquid itself, and B) a technique for controlling the recovery performance by controlling the operation of the circulation system. The control of A) is controlled by adjusting the absorbent concentration (≈carbon dioxide absorption capacity) of the absorption liquid, and the control of B) is the liquid temperature of the absorption liquid in the absorption process and / or the regeneration process ( For example, by adjusting the supply energy amount) and adjusting the circulation rate of the absorption liquid (the supply ratio of the absorption liquid to the gas to be treated).

  Regarding the control of A), the absorbent concentration of the absorbent is adjusted by the addition of water and / or absorbent, and the absorbent concentration decreases by adding water, and the absorbent (or practically high concentration of absorption) As the concentration of the absorbent increases due to the addition of the aqueous solution of the absorbent, the increase / decrease of the concentration is determined based on the detected concentration of the absorbent, and according to this, liquid supply means such as a pump for supplying water and / or the absorbent and the supply It can be adjusted by controlling the switching valve.

  If the concentration of the absorbent in the absorbent is excessively high, there is a high risk in the event of a liquid leak, etc., and it is likely to cause operational problems due to an increase in the viscosity of the absorbent. When it is necessary to temporarily increase the carbon dioxide recovery capacity of the absorbent due to fluctuations in the carbon dioxide concentration, it is practical to respond not by the control of A) but by the control of B) regarding the operating conditions. is there. Specifically, increasing the circulation rate of the absorption liquid to increase the proportion of the absorption liquid that comes into contact with the gas to be treated, or strengthening the heating in the regeneration tower to promote the release of carbon dioxide, thereby circulating the absorption liquid. The carbon dioxide recovery ability as a system increases.

  Regarding the control of B), the adjustment of the liquid temperature of the absorption liquid in the absorption process is directly controlled by adjusting the cooler that cools the absorption liquid supplied to the absorption process and the temperature adjustment of the cooling tower. The cooling temperature of the gas to be treated introduced into the absorption tower is an element that affects the liquid temperature of the absorption liquid, and can be indirectly controlled by this adjustment.

  The adjustment of the liquid temperature (supply energy amount) of the absorption liquid in the regeneration step is a direct means of adjusting the heating means of the absorption liquid in the regeneration tower. Since the heating temperature in the regeneration tower is generally set in the vicinity of the boiling point of the absorption liquid, in practice, there is a limit to the feedback adjustment based on the detection liquid temperature in the absorption process. For this reason, it is practically carried out as adjustment of the amount of energy (heat amount) supplied from the heating means to the absorption liquid, rather than adjustment based on the liquid temperature of the absorption liquid. Since carbon dioxide contained in the absorption liquid absorbs heat when released from the liquid, the release of the absorption liquid is continued without lowering by strengthening the supply of heat by the heating means.

  The circulation speed of the absorbing liquid is adjusted by controlling the driving of fluid conveying means such as a pump. If the amount of carbon dioxide contained in the gas to be treated is excessive compared to the carbon dioxide absorption capacity (absorbent concentration) of the absorbing liquid itself, the absorbing liquid reaches saturation during the contact between the gas to be treated and the absorbing liquid, It is difficult to increase the recovery rate beyond that, but if the absorption liquid is supplied to the regeneration process by increasing the circulation speed of the absorption liquid and reaching the saturation state, the absorption / regeneration is increased by increasing the number of circulations per unit time. The repetition rate increases and the recovery rate can be increased. If the recovery rate is still insufficient even when the circulation rate is increased to the maximum, reduce the supply rate of the gas to be treated (treatment amount per unit time) supplied to the absorption tower, and reduce the absorption liquid to the gas to be treated. This can be dealt with by relatively increasing the ratio.

  From the above, the control of the inherent recovery performance of A) is suitable when the absorption fluid circulation system is essentially adjusted to exhibit stable carbon dioxide recovery performance, and the control of the operational recovery performance of B). It is understood that it is useful when the collection performance is temporarily changed in order to cope with a change in the processing target, etc., but it is not necessary to limit in this way. It is possible to appropriately select whether or not to execute, and what degree of adjustment is to be executed may be determined depending on the situation and application target.

  By continuously measuring the concentration of the absorbent in the absorbent with a TOC meter and examining the changes over time, it is possible to confirm the presence and extent of the effect when adjusting the concentration of the absorbent, and feed back the concentration adjustment based on this. Control can be compensated.

  In the TOC meter, since the carbon dioxide concentration of the absorbing solution can be determined by IC measurement, the amount of carbon dioxide released, that is, the recovered amount is calculated as the difference between the IC values of the absorbing solution after the absorption step and after the regeneration step. That is, the carbon dioxide recovery performance of the absorbing liquid is obtained, and the effectiveness of the control A) or B) described above can be confirmed with reference to this. In particular, in order to confirm the effect of B) control by operative adjustment, the amount of carbon dioxide released / recovered is calculated by measuring the IC value of the absorbing solution, except for examining the amount of carbon dioxide gas actually recovered. Will do.

  Hereinafter, the carbon dioxide recovery method and recovery apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is an embodiment for explaining the control A) described above, and includes a system for controlling carbon dioxide recovery performance by adjusting the absorbent concentration of the absorbent, and FIG. 2 explains the control B). And a system for controlling the carbon dioxide recovery performance by adjusting the circulation rate of the absorbing liquid or the amount of heating energy. These embodiments can be appropriately modified and combined as necessary, and practically, it is preferable to combine both embodiments. In the figure, connections indicated by broken lines are electrical connections for transmitting and receiving electrical signals such as data signals and control signals.

  FIG. 1 shows a first embodiment of a carbon dioxide recovery method and a recovery apparatus for carrying out the same according to the present invention. The recovery device 1 brings the gas G containing carbon dioxide into contact with the absorption liquid, heats the absorption tower 10 that absorbs the carbon dioxide in the absorption liquid, and the absorption liquid that has absorbed the carbon dioxide, and removes the carbon dioxide from the absorption liquid. It has a regeneration tower 20 that regenerates the absorbing liquid by discharging and a cooling tower 30 for precooling before supplying the gas G containing carbon dioxide to the absorption tower 10. There is no particular limitation on the gas G supplied to the absorption tower 10, various gases such as combustion exhaust gas and process exhaust gas can be handled, and the cooling tower 30 can be easily maintained at a low temperature suitable for carbon dioxide absorption. Is provided. The absorption tower 10, the regeneration tower 20, and the cooling tower 30 are each configured as a countercurrent gas-liquid contact device, and hold fillers 11, 21, 31 for increasing the contact area. The fillers 11, 12, and 31 are generally made of a ferrous metal material such as stainless steel or carbon steel, but are not particularly limited, and are materials having durability at a processing temperature and corrosion resistance. It is preferable to select a shape that can provide the contact area. As the absorbing liquid, an aqueous liquid containing a compound having an affinity for carbon dioxide such as alkanolamines as an absorbent is used.

  The gas G supplied from the bottom of the cooling tower 30 passes through the filler 31 held in the tower, is cooled by the cooling water supplied from the upper part of the cooling tower 30, and is then supplied to the absorption tower 10. This prevents the temperature of the absorption tower 10 from rising due to the gas G. The cooling water whose temperature has been increased by cooling the gas G is sent to the water-cooled cooler 33 by the pump 32, cooled, and then returned to the cooling tower 30.

  The gas G containing carbon dioxide that has passed through the cooling tower 30 is supplied from the lower part of the absorption tower 10, and the absorption liquid is supplied from the upper part of the absorption tower 10, while the gas G and the absorption liquid pass through the filler 11. The carbon dioxide in the gas G is absorbed by the absorption liquid through gas-liquid contact.

  The absorption liquid A1 having absorbed carbon dioxide in the absorption tower 10 is stored at the bottom, and is supplied by the pump 12 from the flow path 16 connecting the bottom of the absorption tower 10 and the top of the regeneration tower 20 to the regeneration tower 20. The gas G ′ from which carbon dioxide has been removed is discharged from the top of the absorption tower 10. Since the absorption liquid absorbs carbon dioxide and generates heat and the liquid temperature rises, the gas G ′ may contain water vapor and the like. However, the cooling condenser 13 is provided at the top of the absorption tower 10 to condense the water vapor and the like. By separating and removing from the gas G ′, leakage to the outside of the tower can be suppressed. In order to further ensure this, a pump 15 that circulates between the cooler 14 provided outside the absorption tower and a part of the condensed water (which may include gas G ′ in the tower) is circulated between the cooler 14. The condensed water or the like cooled by the cooler 14 and supplied to the top of the tower maintains the cooling condensing unit 13 at a low temperature and reliably cools the gas G ′ passing through the cooling condensing unit 13. Moreover, the composition fluctuation | variation of the absorption liquid in a tower is compensated by the condensed water which recirculate | refluxs to the filler 11. The temperature of the gas G ′ discharged to the outside of the tower is preferably about 60 ° C. or lower, more preferably 45 ° C. or lower. Although the cooler 14 of this embodiment is a water-cooling type, other cooling methods may be used, and more reliable cooling may be possible using a refrigeration cycle using a refrigerant.

  The absorption liquid A1 containing carbon dioxide in the absorption tower 10 is supplied to the upper part of the regeneration tower 20, passes through the filler 21, and is stored at the bottom. A reboiler is attached to the bottom of the regeneration tower 20. That is, a circulation path for circulating the absorption liquid outside the tower and a steam heater 22 for heating the absorption liquid are attached, and a part of the absorption liquid A2 at the bottom of the tower is supplied to the steam heater 22 through the circulation path, so And then refluxed into the column. By this heating, carbon dioxide is released from the absorption liquid at the bottom, and carbon dioxide is also released from the absorption liquid during gas-liquid contact on the filler 21 that is indirectly heated.

  The absorption liquid A2 regenerated by releasing carbon dioxide in the regeneration tower 20 is refluxed to the absorption tower 10 by the pump 23 through the flow path 17 connecting the bottom of the regeneration tower 20 and the upper portion of the absorption tower 10, and heat exchange is performed between them. In the vessel 24, heat is exchanged with the absorption liquid A1 supplied from the absorption tower 10 to the regeneration tower 20, and then cooled, and the water-cooled cooler 25 sufficiently cools to a temperature suitable for carbon dioxide absorption. Is done.

  The recovered gas containing carbon dioxide released by heating in the regeneration tower 20 is discharged from the top through the condensing part 26 at the upper part of the regeneration tower 20, and water vapor and absorbent contained in the recovered gas are condensed by the condensing part 26. Release to the outside of the tower is suppressed.

  The recovered gas discharged from the regeneration tower 20 is further sufficiently cooled by a cooler 27 using cooling water, condensed water vapor as much as possible, and then removed condensed water by a gas-liquid separator 28. , Recovered as a gas containing recovered carbon dioxide C. The recovered carbon dioxide can be fixed and reorganized in the ground by, for example, injecting it into the ground or oil fields. The condensed water separated in the gas-liquid separator 28 is refluxed to the upper part of the regeneration tower 20 by the pump 29 to cool the condensing part 26. This is useful for suppressing the release of the absorbent and the like, and can compensate for the composition fluctuation of the absorbing solution in the tower.

  The collection device 1 has a TOC meter 40 for measuring the TC, IC and TOC of the absorption liquid, collects the absorption liquid from the collection part 41 on the flow path 16 and the collection part 42 on the flow path 17, Measurement is performed for each of the absorption liquid after the absorption process and the absorption liquid after the regeneration process. The absorption liquid may be collected and measured continuously or intermittently at regular intervals. In this embodiment, a sampling line for connecting the sampling units 41 and 42 and the TOC meter 40 is provided so that the sampling and measurement can be automatically performed. It may be collected directly and measured manually.

  The TOC meter 40 is electrically connected to the control unit 43, and absorption liquid data such as the absorbent concentration measured by the TOC meter 40 is transmitted to the control unit 43, and carbon dioxide recovery of the absorption liquid is performed based on the data. It is determined whether there is a need to control performance. When it is necessary to execute the control, it is further determined which of the items A) and B) is to be adjusted. In this embodiment, a description will be given specifically for the concentration adjustment of A).

  In order to adjust the concentration of A), the pure water tank 44, the absorption liquid tank 45 that contains an absorption liquid having a higher concentration than the absorption liquid circulating in the recovery device, and the pure water and the high concentration absorption liquid that are contained in these absorption liquids Are provided to the absorption liquid in the flow path 17. The pumps 46 and 47 are electrically connected to the control unit 43, and when the control unit 43 determines that the concentration of the absorbing solution needs to be lowered, pure water is added to the absorbing solution in the flow path 17 by driving the pump 46. If it is determined that the concentration of the absorbing solution is increased, the high concentration absorbing solution is added by driving the pump 47. The amount of change in the concentration of the absorbent can be adjusted by controlling the pump supply pressure and drive time. The supply path for the pure water and the high-concentration absorbing liquid is connected to the flow path 17 on the upstream side and the downstream side of the cooler 25, and is configured to be supplied to either by the switching valve 48. The necessity of cooling is determined based on the liquid temperature in the tanks 44 and 45, and when the temperature is inappropriate for supply to the absorption tower 10, the temperature is changed to supply to the upstream side of the cooler 25 and the temperature of the absorption liquid is changed. Prevent the rise.

  A collection method implemented in the collection apparatus 1 of FIG. 1 will be described.

  In the absorption tower 10, when gas G containing carbon dioxide such as combustion exhaust gas or process exhaust gas is supplied from the bottom, and absorption liquid is supplied from the top, the gas G and the absorption liquid come into gas-liquid contact on the filler 11. Then, carbon dioxide is absorbed by the absorbing solution. Since carbon dioxide is well absorbed at low temperatures, the temperature of the absorbing liquid or the temperature of the absorption tower 10 (particularly the packing material 11) is set to the cooler 14 so that it is generally about 50 ° C. or lower, preferably 40 ° C. or lower. Use and adjust. Since the absorbing liquid generates heat due to absorption of carbon dioxide, it is desirable to consider that the liquid temperature and the temperature of the gas G ′ do not exceed 60 ° C. in consideration of the rise in liquid temperature caused by this. The gas G supplied to the absorption tower 10 is also adjusted to an appropriate temperature by the gas cooling tower 30. An aqueous liquid containing a compound having affinity for carbon dioxide as an absorbent is used as the absorbent. Examples of the absorbent include alkanolamines and hindered amines having an alcoholic hydroxyl group. Specific examples of the alkanolamine include monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, diisopropanolamine, diisopropanol. Examples of the hindered amine having an alcoholic hydroxyl group include 2-amino-2-methyl-1-propanol (AMP), 2- (ethylamino) ethanol (EAE), and 2- (methylamino). ) Ethanol (MAE) and the like can be exemplified. Usually, the use of monoethanolamine (MEA) is preferred. The absorbent concentration of the absorption liquid can be appropriately set according to the amount of carbon dioxide contained in the gas to be processed, the processing speed, etc. A concentration of about 10 to 50% by mass is applied. For example, an absorbent having a concentration of about 30% by mass is suitably used for the treatment of the gas G having a carbon dioxide content of about 20%. The supply rates of the gas G and the absorbing liquid are appropriately set so that the absorption proceeds suitably according to the amount of carbon dioxide contained in the gas, the gas-liquid contact efficiency, and the like.

  When the absorption liquid A1 that has absorbed carbon dioxide is supplied to the regeneration tower 20, it is heated to a high temperature near the boiling point, but before being supplied to the regeneration tower 20, the heat exchanger 24 recirculates from the regeneration tower 20. Since the heat exchange with the absorbing liquid A2 is performed, the absorbing liquid A1 is charged into the regeneration tower 20 in a state in which the temperature is raised to a temperature close to the temperature of the regeneration tower 20 and carbon dioxide is easily released. Further, the release of carbon dioxide is promoted in the gas-liquid contact state on the filler 21, and the release of carbon dioxide further proceeds by heating the bottom of the regeneration tower 20. The absorbing liquid A2 stored at the bottom of the regeneration tower 20 is regenerated by sufficiently releasing carbon dioxide by heating by partial circulation to the steam heater 22 and the heat exchanger 24. The boiling point of the absorbing liquid A2 depends on the composition (absorbent concentration), and the upper limit of the liquid temperature varies depending on the absorbing liquid used.

  The absorption liquid circulates between the absorption tower 10 and the regeneration tower 20, and the absorption process and the regeneration process are alternately repeated. The absorption liquid A2 refluxed from the regeneration tower 20 is absorbed in the heat exchanger 24 with the absorption liquid A1. Since the heat exchange is performed, the temperature is lowered to near the temperature of the absorption tower 10 and is input to the absorption tower 10 in a state where carbon dioxide is easily absorbed.

  During the above-described processing, samples for measuring the absorption liquid A1 after the absorption process and the absorption liquid A2 after the regeneration process are collected and sent to the TOC meter 40 in the collection units 41 and 42, and the IC value and the TC value are measured. The calculation of the TOC value and the determination of the absorbent concentration are executed, and these data are transmitted to the control unit 43. In the control unit 43, the specified value X of the absorbent concentration of the absorbent and the allowable fluctuation range ± ΔX of the absorbent concentration are set in advance, and the absorbent concentrations X1, X2 of the sample measured with the TOC meter 40 are set. Is compared with a defined value X. When the difference between the absorbent concentrations X1 and X2 and the specified value X exceeds the fluctuation range ± ΔX, execution of concentration adjustment is determined, and the pump 46 or 47 is driven according to the difference and pure water or high concentration absorbent is It is added to the absorption liquid in the flow path 17 and the concentration of the absorbent decreases or increases. The effect of the addition of pure water or high-concentration absorption liquid can be detected by the variation in the measured concentration X1 of the sample in the collection unit 41, and when the same variation appears in the measurement concentration X2 in the collection unit 42, the absorption liquid has almost gone through. It will be. The concentration adjustment is continued until the difference between the absorption liquid concentrations X1, X2 and the specified value X falls within the fluctuation range ± ΔX.

  As described above, the absorbent concentration of the circulating absorbent is adjusted to the range of the specified value X ± ΔX. Therefore, the concentration and adjustment can be adjusted by setting the specified value X and the fluctuation range ± ΔX as necessary. The accuracy can be changed as appropriate.

  In the measurement of the TOC meter 40, the carbon dioxide content of the absorbing liquid can be determined from the measured IC value, and the difference between the carbon dioxide contents Y1, Y2 of the samples of the sampling parts 41, 42 (Y1-Y2) The actual carbon dioxide recovery amount ΔY (that is, carbon dioxide recovery ability) of the absorbing liquid can be calculated. Therefore, it is possible to confirm whether the above-described adjustment of the absorbent concentration is effective with reference to the carbon dioxide content Y1, Y2 or the carbon dioxide recovery amount ΔY. For example, if a corresponding change is not observed in the carbon dioxide contents Y1 and Y2 and the carbon dioxide recovery amount ΔY despite the increase in concentration due to the addition of the high-concentration absorbing solution, an abnormality warning or processing Safety can be ensured by deciding to stop. Moreover, since the relationship between the absorbent concentration of the absorbent and the carbon dioxide absorption amount can be examined in advance, the carbon dioxide content and the carbon dioxide recovery amount of the absorbent are determined from the absorbent concentrations X1 and X2 based on the TOC measurement values. Can be assumed. Therefore, these assumed values are calculated, and compared with these, when the carbon dioxide content and the carbon dioxide recovery amount based on the actual measurement values of IC are small, chemical alteration / decomposition of the absorbent in the absorbent, Since organic substance contamination caused by the gas to be treated can be considered, it can be a target for warning or processing stoppage.

  It is not preferable in terms of work efficiency to frequently change the absorbent concentration of the absorbent, but when the concentration of carbon dioxide contained in the gas G fluctuates or when it is necessary to temporarily change the gas processing amount, etc. As described above, when a temporary change or a relatively small change in the carbon dioxide absorption performance of the absorption liquid is necessary, the control of B) described above, i.e., the liquid of the absorption liquid, is not performed without adjusting the absorbent concentration. This can be dealt with by adjusting the temperature (the amount of energy supplied) or the circulation speed. FIG. 2 is an embodiment specifically described for the control of B), and the other points are the same as those of the apparatus of FIG. 1, and thus the description thereof will be omitted.

  The recovery device 2 of FIG. 2 does not include equipment for adding water and / or an absorbent, but has a TOC meter 40 for measuring the TC, IC, and TOC of the absorbent and an operation control unit 43 ′. Then, similarly to the collection device 1 of FIG. 1, the absorption liquid is collected from the collection unit 41 and the collection unit 42, and each of the absorption liquid after the absorption process and the absorption liquid after the regeneration process is measured. The absorption liquid may be collected and measured continuously or intermittently at regular intervals. In this embodiment, it is configured such that collection and measurement can be automatically performed using a sample collection line that connects the collection units 41 and 42 and the TOC meter 40. The TOC meter 40 is electrically connected to the operation control unit 43 ′, and the absorption liquid data measured by the TOC meter 40 is transmitted to the operation control unit 43 ′. Based on the data, the carbon dioxide recovery capability of the absorption liquid It is determined whether or not it is necessary to execute the control. If control is required, execute control B) by adjusting the operation. In order to adjust the operation, the operation control unit 43 ′ is electrically connected to the pumps 12 and 23 and the steam heater 22, and the circulation rate of the absorption liquid can be adjusted by driving control of the pumps 12 and 23. By controlling the supply of heat, the heat energy supplied to the absorption liquid in the regeneration tower can be adjusted. In this embodiment, the temperature of the absorption tower is not adjusted, but the cooling tower 30 may be cooled or the temperature of the cooler 25 that cools the absorption liquid supplied to the cooling tower may be adjusted.

  In order to increase the carbon dioxide recovery performance of the absorbing liquid, the circulation speed is increased by the pumps 12 and 13, or the heat amount supply of the steam heater 22 is increased. Both may be performed. When the recovery performance is lowered, the control opposite to the above is performed.

  In the TOC meter 40, based on the measurement of the IC value, as the difference (Y1−Y2) between the carbon dioxide contents Y1 and Y2 of the samples of the collection parts 41 and 42, the actual carbon dioxide recovery amount ΔY (that is, the dioxide dioxide) of the absorbing liquid. Carbon recovery ability) can be calculated. Therefore, this value is compared with the required carbon dioxide recovery amount ΔY ′ to determine the control amount (ΔY′−ΔY) of the carbon dioxide recovery performance, and the amount of change in the circulation speed that can be achieved, Calculate the amount of change in thermal energy supply. The concentration of the absorbent necessary for calculating the amount of change in the circulation rate and the heat supply can be determined from the total organic carbon with reference to the absorption liquid data. Moreover, since the carbon dioxide absorption amount in the saturated state of the absorbing liquid having a predetermined absorbent concentration can be examined in advance, the carbon dioxide content Y1, Y2 is compared with any of the circulation speed and the heat amount supply. Can determine if adjustment is appropriate. That is, if neither the increase in absorption in the absorption process nor the increase in release in the regeneration process can be expected from the carbon dioxide contents Y1 and Y2, the increase in circulation rate is determined. Control of the pumps 12 and 23 and / or control of the steam heater 22 corresponding to the amount of change described above is executed. Referring to the carbon dioxide content Y1, Y2 or the carbon dioxide recovery amount ΔY measured after starting the adjustment of the circulation speed and / or the heat supply, it is confirmed whether the adjustment of the heat supply or the circulation speed described above is effective. The above adjustment is continued until the required carbon dioxide recovery ΔY ′ is reached. In spite of having performed the above-mentioned adjustment, when a corresponding change is not seen in the carbon dioxide contents Y1 and Y2 and the carbon dioxide recovery amount ΔY, a warning of abnormality occurrence or a process stop is determined and safety is improved. It can be secured.

  INDUSTRIAL APPLICABILITY The present invention is useful for reducing the amount of carbon dioxide released and its influence on the environment, for example, in the treatment of carbon dioxide-containing gas discharged from facilities such as thermal power plants, ironworks, and boilers. Since the stability of the processing performance is improved and the processing corresponding to the content fluctuation of the target gas is possible, it is possible to provide a carbon dioxide recovery device that is highly applicable and can contribute to environmental protection.

1, 2: Recovery device 10: Absorption tower, 20: Regeneration tower, 30: Gas cooling tower, 40: TOC meter 11, 21, 31: Filler,
12, 15, 23, 29, 32, 46, 47: pump,
13: Cooling condensing part, 14, 25, 27, 33: Cooler,
22: Steam heater, 24: Heat exchanger, 26: Condensing part,
28: Gas-liquid separator, 41, 42: Collection unit,
43: control unit, 43 ': operation control unit,
44: Pure water tank, 45: High concentration absorbent tank G, G ': Gas, A1, A2: Absorbent, C: Recovered carbon dioxide

Claims (12)

An absorption tower in which a gas containing carbon dioxide is brought into contact with an absorption liquid, and the absorption liquid absorbs carbon dioxide;
A regeneration tower that regenerates the absorbing liquid by heating the absorbing liquid that has absorbed carbon dioxide and releasing carbon dioxide from the absorbing liquid;
And a control system that detects the total organic carbon content of the absorbent and adjusts the absorbent concentration of the absorbent based on the absorbent concentration determined from the detected total organic carbon. Recovery equipment. An absorption tower in which a gas containing carbon dioxide is brought into contact with an absorption liquid, and the absorption liquid absorbs carbon dioxide;
A regeneration tower that regenerates the absorbing liquid by heating the absorbing liquid that has absorbed carbon dioxide and releasing carbon dioxide from the absorbing liquid;
A circulation system for circulating the absorption liquid so that the absorption liquid is alternately and repeatedly supplied to the absorption tower and the regeneration tower;
Detecting at least one of the total organic carbon content and inorganic carbon content of the absorption liquid, and using at least one of the detected total organic carbon content and inorganic carbon content, the carbon dioxide recovery performance of the absorption liquid as the circulation system A carbon dioxide recovery device having a control system for controlling.   The control system includes a total organic carbon meter that measures at least one of a total organic carbon amount and an inorganic carbon amount of the absorption liquid, and an operation control unit, and the operation control unit includes an absorbent concentration of the absorption liquid. The carbon dioxide gas according to claim 2, wherein at least one of a circulation rate of the absorption liquid in the circulation system, a liquid temperature of the absorption liquid in the absorption tower, and heating of the absorption liquid in the regeneration tower is adjusted. Recovery device.   The operation control unit includes at least an absorbent concentration of the absorbing liquid determined from the total organic carbon amount measured by the total organic carbon meter, and a carbon dioxide content of the absorbing liquid determined from the inorganic carbon amount. The carbon dioxide recovery device according to claim 3 which controls the carbon dioxide recovery performance of said absorption liquid based on one side.   The control system includes a first collection unit for collecting an absorption liquid that has absorbed carbon dioxide in the absorption tower for measurement, and a second collection for collecting the absorption liquid regenerated in the regeneration tower for measurement. The carbon dioxide recovery device according to any one of claims 1 to 4, further comprising:   The said control system has a supply means which supplies at least one of water and an absorbent to the said absorption liquid, and controls the said supply means and adjusts the absorbent concentration of the said absorption liquid. The carbon dioxide recovery device described in 1. An absorption step in which a gas containing carbon dioxide is brought into contact with the absorption liquid, and the absorption liquid absorbs carbon dioxide;
A regeneration step of regenerating the absorbing liquid by heating the absorbing liquid that has absorbed carbon dioxide and releasing carbon dioxide from the absorbing liquid;
A control step of detecting the total organic carbon content of the absorbent and adjusting the absorbent concentration of the absorbent based on the absorbent concentration of the absorbent determined from the detected total organic carbon content. Collection method. An absorption step in which a gas containing carbon dioxide is brought into contact with the absorption liquid, and the absorption liquid absorbs carbon dioxide;
A regeneration step of regenerating the absorbing liquid by heating the absorbing liquid that has absorbed carbon dioxide and releasing carbon dioxide from the absorbing liquid;
A circulation step of circulating the absorption liquid so that the absorption liquid is alternately and repeatedly supplied to the absorption step and the regeneration step;
Detect at least one of the total organic carbon content and inorganic carbon content of the absorption liquid, and control the carbon dioxide recovery performance as a circulation system of the absorption liquid using at least one of the total organic carbon content and inorganic carbon content detected And a carbon dioxide recovery method.   The control process includes a measurement process for measuring at least one of the total organic carbon content and the inorganic carbon content of the absorption liquid, and an operation control process, and the operation control process includes the absorbent concentration of the absorption liquid and the absorption. The carbon dioxide recovery method according to claim 8, wherein at least one of a circulation rate of the liquid, a liquid temperature of the absorption liquid in the absorption step, and an amount of heat supplied to the absorption liquid in the regeneration step is adjusted.   The operation control step includes the step of determining the absorbent concentration of the absorbent from the total amount of organic carbon measured in the measurement step, and the carbon dioxide content of the absorbent from the amount of inorganic carbon measured in the measurement step. The carbon dioxide recovery method according to claim 9, comprising at least one of steps of determining an amount, and controlling carbon dioxide recovery performance of the absorbent based on the absorbent concentration or the carbon dioxide content.   The control step includes a first collection step for collecting the absorption liquid that has absorbed carbon dioxide in the absorption step for measurement, and a second collection for collecting the absorption liquid regenerated in the regeneration step for measurement. The method for recovering carbon dioxide according to claim 7, further comprising a step.   The said control process has a supply process which supplies at least one of water and an absorbent to the said absorption liquid, and controls the supply in the said supply process, and adjusts the absorbent concentration of the said absorption liquid. The carbon dioxide recovery method according to any one of the above.

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