JP4216152B2 - Desulfurization decarboxylation method and apparatus - Google Patents

Description

  The present invention relates to a desulfurization decarbonation method and apparatus for removing sulfur oxide and carbon dioxide from a gas containing sulfur oxide and carbon dioxide.

  In recent years, thermal power generation facilities and boiler facilities use a large amount of coal, heavy oil or ultra-heavy oil as fuel, and from the viewpoint of air pollution prevention and cleaning of the global environment, sulfur oxides mainly composed of sulfur dioxide, nitrogen There is a problem of quantitative and concentration suppression regarding the release of oxides, carbon dioxide and the like. Of these, sulfur oxides cause acid rain and may cause damage to human bodies, animals and plants. For this reason, conventionally, dry and wet processing methods have been proposed and implemented. For example, in the flue gas desulfurization apparatus which is the above-described processing facility, a wet lime gypsum method in which gypsum is by-produced using limestone as an absorbent has become mainstream. On the other hand, with regard to carbon dioxide, from the standpoint of preventing global warming together with chlorofluorocarbon and methane gas, for example, suppression of emissions by applying the PSA (pressure swing) method, membrane separation method, reaction absorption method using basic compounds, etc. It is being considered.

In addition, a technique for performing desulfurization and decarboxylation in two stages has been developed (see Patent Document 1). In this technique, in the wet lime-gypsum desulfurization process, after desulfurization treatment so that the sulfur oxide concentration in the gas is within the range of 5 to 10 ppm, the desulfurized gas is brought into contact with the alkanolamine aqueous solution by the decarbonation process. In addition to removing carbon dioxide, sulfur oxide can be removed so that the concentration of sulfur oxide in the gas after decarboxylation is 1 ppm or less.
Japanese Patent No. 3305001

  However, the technique described in Patent Document 1 has a problem that sulfur dioxide is accumulated in the decarboxylation absorbent, and therefore the reclaiming frequency of the decarboxylation absorbent is high. Moreover, since a large amount of the amine compound in the absorbent is also released along with the gas discharged in the decarboxylation step, there is a problem that the operation cost is high.

  Therefore, in view of the above-mentioned problems, the present invention can suppress the accumulation of sulfur oxides in the decarboxylation absorbent, and the amine compound in the absorbent accompanying the gas discharged in the decarboxylation process. It is an object of the present invention to provide a desulfurization decarboxylation method and apparatus capable of reducing the amount.

In order to achieve the above object, a desulfurization and decarboxylation method according to the present invention comprises bringing a gas containing sulfur oxide and carbon dioxide into contact with an absorbing solution containing a basic calcium compound, and sulfur oxide from the gas. A desulfurization step for removing the sulfur, and the gas desulfurized in the desulfurization step is brought into contact with a basic absorbent to further remove sulfur oxide so that the concentration of sulfur oxide in the gas is 5 ppm or less. Advanced desulfurization gas cooling step for cooling the temperature to 50 ° C. or lower, and gas subjected to the advanced desulfurization gas cooling treatment in the advanced desulfurization gas cooling step with an absorbing liquid containing a basic amine compound, and carbon dioxide from the gas the a and decarboxylation step comprising at desulfurization decarboxylation process for removing the highly desulfurized gas cooling step, highly desulfurization step of contacting the desulfurization step desulfurization process gas in a basic absorption liquid And characterized in that the high desulfurization and a step in gas cooling the highly desulfurized gas cooling step, the condensed water obtained by the gas cooling step, mixing said basic absorbent liquid of the high desulfurization step To do.

  As the basic absorbent, an absorbent containing a basic sodium compound is preferable. Moreover, it is preferable to remove the basic absorption liquid accompanying the gas from the gas in contact with the basic absorption liquid.

The condensed water obtained in the gas cooling step can also be used as a gas coolant . Furthermore, it is preferable to remove the gas coolant accompanying the gas from the gas in contact with the gas coolant.

Moreover, the desulfurization decarboxylation method according to the present invention , as another aspect , removes sulfur oxide from the gas by bringing a gas containing sulfur oxide and carbon dioxide into contact with an absorbent containing a basic calcium compound. Desulfurization step, contacting the gas desulfurized in the desulfurization step with the basic absorbent to further remove sulfur oxide so that the concentration of sulfur oxide in the gas is 5 ppm or less, and adjust the gas temperature. The advanced desulfurization gas cooling step for cooling to 50 ° C. or lower, and the gas subjected to the advanced desulfurization gas cooling treatment in the advanced desulfurization gas cooling step are brought into contact with an absorbent containing a basic amine compound to remove carbon dioxide from the gas. to a comprising at desulfurization decarboxylation method and decarboxylation step, the altitude desulfurization gas cooling step, by contacting the gas from cooling the basic absorbent liquid, removing sulfur oxides And performing the cooling of the gas at the same time.

In another aspect, the present invention provides a desulfurization and decarbonation apparatus, a desulfurization means for contacting an absorption liquid containing a basic calcium compound with a gas, contacting the basic absorption liquid with the gas, and cooling the gas. Advanced desulfurization gas cooling means, decarbonation means for contacting the gas with an absorbent containing a basic amine compound, piping for introducing the desulfurized gas of the desulfurization means into the advanced desulfurization gas cooling means, and the advanced desulfurization gas In the desulfurization decarbonation apparatus comprising a pipe for introducing the gas cooled by the gas cooling means to the decarbonation means, the advanced desulfurization gas cooling means includes an advanced desulfurization section for bringing a basic absorbent into contact with the gas, A gas cooling section for cooling the gas brought into contact with the basic absorbent, and the advanced desulfurization gas cooling means includes a pipe for mixing the condensed water obtained in the gas cooling section with the basic absorbent. It is characterized in.

  As the basic absorbent, an absorbent containing a basic sodium compound is preferable. The advanced desulfurization gas cooling means preferably includes a demister that removes the basic absorbent accompanying the gas from the gas.

The advanced desulfurization gas cooling means may also include a pipe for supplying condensed water obtained in the gas cooling unit to the gas cooling unit as a gas coolant . Furthermore, the advanced desulfurization gas cooling means preferably includes a demister that removes the gas coolant accompanying the gas from the gas.

Further, the desulfurization decarboxylation apparatus according to the present invention includes, as another aspect, a desulfurization means for bringing an absorption liquid containing a basic calcium compound into contact with a gas, an advanced degree of bringing the basic absorption liquid into contact with the gas, and cooling the gas. A desulfurization gas cooling means, a decarbonation means for contacting an absorption liquid containing a basic amine compound with the gas, a pipe for introducing the desulfurized gas of the desulfurization means into the advanced desulfurization gas cooling means, and the advanced desulfurization gas cooling in the desulfurization decarboxylation apparatus comprising a pipe for introducing a gas cooled by means to the decarboxylation means, the highly desulfurized gas cooling means, comprising the absorption liquid cooling means for cooling the basic absorption liquid And A heat exchanger or the like can be used as the absorbing liquid cooling means.

  As described above, according to the present invention, sulfur oxides contained in the gas after the desulfurization treatment are removed to suppress the accumulation of sulfur oxides in the decarboxylation absorbent, and to the exhaust gas in the decarbonation process. It is possible to provide a desulfurization and decarboxylation method and apparatus for reducing the amount of the amine compound in the accompanying absorption liquid.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic view showing an outline of a desulfurization decarboxylation apparatus according to the present invention. As shown in FIG. 1, this apparatus is mainly composed of a desulfurization means 10, an advanced desulfurization gas cooling means 20 provided on the downstream side, and a decarbonation means 50 provided on the downstream side. The desulfurization means 10 can employ a known flue gas desulfurization apparatus that brings an absorbing liquid containing a basic calcium compound into contact with a gas to be treated to remove sulfur oxides in the gas. Further, the advanced desulfurization gas cooling means 20 and the decarbonation means 50 are wet-type absorption devices that bring the absorbent into contact with the gas to be treated, and in particular, the devices shown in FIG. 2 or FIG. 3 and FIG. It is preferable to adopt.

  According to such a configuration, first, the combustion exhaust gas 1 containing sulfur oxide and carbon dioxide is introduced into the desulfurization means 10. The gas to be treated is not limited to the combustion exhaust gas 1 but may be a fuel gas, and various other gases can be applied. The target gas may contain moisture, oxygen, and other components. The pressure of the gas may be pressurized or normal pressure, and the temperature may be low or high, and is not particularly limited. Preferably, it is an atmospheric pressure combustion exhaust gas.

  In the desulfurization means 10, the introduced combustion exhaust gas 1 and the desulfurization absorption liquid 2 containing a basic calcium compound are brought into contact with each other to remove most of the sulfur oxides. As the basic calcium compound, for example, calcium carbonate, calcium hydroxide, and calcium oxide can be used. The desulfurization absorption liquid 2 can contain one of these compounds or a mixture of two or more, and is usually used as a suspension. The absorbent 2 after contact with the combustion exhaust gas 1 is sent to a solid-liquid separator (not shown), and the sulfur oxide absorbed in the absorbent 2 is separated and recovered as gypsum.

  The desulfurized gas 3 from which most of the sulfur oxide has been removed by the desulfurization means 10 is introduced into the advanced desulfurization gas cooling means 20 installed on the downstream side. In the advanced desulfurization gas cooling means 20, the advanced desulfurization gas 3 and the basic absorbent 4 are brought into contact with each other so that the sulfur oxide concentration in the post-desulfurization gas 3 is 5 ppm or less, preferably 1 ppm or less. To process. When the sulfur oxide concentration exceeds 5 ppm, sulfur oxide accumulates in the decarboxylation absorbent described later, and the frequency of reclaiming the decarboxylation absorbent increases.

  As the basic absorbent 4, for example, an absorbent containing one basic compound or a mixture of two or more of calcium carbonate, calcium hydroxide, magnesium hydroxide, sodium hydroxide, sodium carbonate and the like can be used. it can. Among these, from the viewpoint of desulfurization performance, it is preferable to use an absorbing solution containing a basic sodium compound such as sodium hydroxide or sodium carbonate. The basic compound is usually used as an aqueous solution of 0.1 to 30% by weight.

  Further, the advanced desulfurization gas cooling means 20 cools the gas 3 after the desulfurization treatment or the gas subjected to the advanced desulfurization treatment to 50 ° C. or less, preferably 45 ° C. or less, more preferably 30 to 45 ° C. When the temperature of the gas exceeds 50 ° C., the amount of the amine compound in the absorbing liquid accompanying the exhaust gas in the decarbonation step described later increases, and the amine compound is consumed wastefully, resulting in an increase in operating costs. On the other hand, if the temperature is less than 30 ° C., it is not preferable because of an increase in cost. The highly desulfurized and cooled advanced desulfurized gas 5 is introduced into decarbonation means 50 installed on the downstream side.

  In the decarbonation means 50, the introduced desulfurized gas 5 after the cooling treatment is brought into contact with the decarboxylated absorbent 6 containing a basic amine compound, and the carbon dioxide in the gas 5 and the remaining sulfur oxide are removed from the decarboxylated absorbent. 6 is absorbed and removed from the gas. Examples of basic amine compounds include monoethanolamine, alcoholic hydroxyl group-containing primary amines such as 2-amino-2-methyl-1-propanol, diethanolamine, 2-methylaminoethanol, 2-ethylaminoethanol, and the like. Alcoholic hydroxyl group-containing secondary amines, triethanolamine, N-methyldiethanolamine, 2-dimethylaminoethanol, 2-diethylaminoethanol and other alcoholic hydroxyl group-containing tertiary amines, polyethylenediamines such as ethylenediamine, triethylenediamine and diethylenetriamine Further, cyclic amines such as piperazines, piperidines and pyrrolidines, polyamines such as xylylenediamine, and amino acids such as methylaminocarboxylic acid can be used.

  The decarboxylation absorbent 6 can contain one of these compounds or a mixture of two or more. The basic amine compound is usually used as a 10 to 70% by weight aqueous solution. In addition, a carbon dioxide absorption accelerator and a corrosion inhibitor can be added to the absorbing liquid 6, and methanol, polyethylene glycol, sulfolane, and the like can be added as other media. The decarbonation-treated gas 7 from which carbon dioxide and remaining sulfur oxides have been removed by the decarbonation means 50 is discharged from the decarbonation means 50 and released or sent to the next necessary step (not shown).

  As described above, since the decarboxylation absorbing liquid 6 absorbs sulfur oxide in addition to carbon dioxide, the basic desorption gas cooling means 20 performs basic absorption in advance before introducing the desulfurized gas 3 into the decarbonation means 50. By making it contact with the liquid 4 and performing a high desulfurization treatment so that the sulfur oxide concentration is 5 ppm or less, accumulation of sulfur oxide in the decarbonized absorbent 6 can be suppressed. Thereby, the reclaiming frequency of the decarboxylation absorbent 6 can be reduced. In the present embodiment, the temperature of the decarbonation-treated gas 7 is set according to the gas temperature at the inlet of the decarbonation means 50. That is, before introducing the desulfurized gas 3 into the decarbonation means 50, the temperature of the gas 3 is cooled to 50 ° C. or less in advance in the advanced desulfurization gas cooling means 20, thereby decarbonation discharged from the decarbonation means 50. The amount of the amine compound in the absorbent 6 accompanying the gas 7 after the treatment can be remarkably suppressed. Therefore, the operation cost can be reduced.

  FIG. 2 is a schematic diagram showing an outline of an embodiment of the advanced desulfurization gas cooling means in the present invention. As shown in FIG. 2, the advanced desulfurization gas cooling tower 21 includes an advanced desulfurization section 22, an advanced desulfurization section demister 23, a gas cooling section 24, and a gas cooling section demister 25 in order from the bottom of the tower. In the advanced desulfurization gas cooling tower 21, a gas introduction line 31 for introducing the desulfurized gas 3 to the bottom of the advanced desulfurization gas cooling tower 21, and the advanced desulfurization gas cooling treatment gas 5 from the top of the advanced desulfurization gas cooling tower 21. A gas discharge line 32 for sending to a decarbonation means (not shown), an absorption liquid circulation line 33 for sending the basic absorbent 4 from the bottom to the top of the advanced desulfurization section 22, and a gas coolant 8 from the bottom to the top of the gas cooling section 24. Coolant extraction line 35 for extracting a part of the gas coolant 8 from the coolant circulation line 34 to be sent and the coolant circulation line 34 and supplying it to the absorption liquid circulation line 33, and supply containing a basic compound to the absorption liquid circulation line 33 A supply liquid addition line 36 for supplying the liquid 9 is provided. The coolant circulation line 34 is provided with a heat exchanger 26 that cools the gas coolant 8.

  According to such a configuration, first, the desulfurized gas 3 is introduced from the gas introduction line 31 into the advanced desulfurization gas cooling tower 21. When the gas 3 comes into contact with the basic absorbent 4 circulating in the advanced desulfurization section 22, sulfur oxide in the gas is highly removed, and the concentration of sulfur oxide in the gas becomes 5 ppm or less. The mist of the basic absorbent 4 accompanying the gas is removed and recovered by the advanced desulfurization section demister 23. The recovered basic absorbent 8 is supplied again to the advanced desulfurization section 23 through the absorbent circulation line 33. In addition, the density | concentration of the basic compound in the basic absorption liquid 4 falls gradually by a high desulfurization process. Therefore, in order to add a basic compound that matches the amount of sulfur oxide removed, the supply liquid 9 containing the basic compound at a high concentration is added from the supply liquid addition line 36.

  Further, the gas after the advanced desulfurization treatment is cooled by coming into contact with the gas coolant 8 circulating in the gas cooling unit 24, and the temperature of the gas becomes 50 ° C. or less. The mist of the gas coolant 8 accompanying the gas is removed and collected by the gas cooling unit demister 25. The amount of the gas coolant to be recovered increases the amount of moisture condensed from the gas as compared with the amount of the gas coolant to be contacted. Therefore, an amount corresponding to this increased amount is extracted and added to the basic absorbent 8 in the absorbent circulation line 33 via the coolant withdrawal line 36. The remaining gas coolant 8 is cooled by the heat exchanger 26 and then supplied again to the gas cooler 24 via the coolant circulation line 34. The gas 5 after the advanced desulfurization gas cooling treatment is sent to the downstream decarbonation means (not shown) via the gas discharge line 32.

  As described above, after the gas is highly desulfurized by the advanced desulfurization unit 22, the gas cooling process is performed by the gas cooling unit 24, thereby advantageously preventing scattering of the basic absorbent and the like.

  FIG. 3 is a schematic view showing an outline of another embodiment of the advanced desulfurization gas cooling means in the present invention. As shown in FIG. 3, the advanced desulfurization gas cooling tower 41 includes an advanced desulfurization gas cooling section 42 and an advanced desulfurization gas cooling section demister 43 in order from the bottom of the tower. In the advanced desulfurization gas cooling tower 41, a gas introduction line 46 for introducing the gas 3 after desulfurization treatment to the bottom of the advanced desulfurization gas cooling tower 41, and the gas 5 after the advanced desulfurization gas cooling treatment from the top of the advanced desulfurization gas cooling tower 41. A gas discharge line 47 for sending to a decarbonation means (not shown), an absorption liquid circulation line 48 for sending the basic absorbent 4 from the bottom to the top of the advanced desulfurization gas cooling section 42, and a supply containing a basic compound in the absorption liquid circulation line 48 An absorption liquid addition line 49 for supplying the liquid 9 is provided. The absorption liquid circulation line 48 is provided with a heat exchanger 44 for cooling the basic absorption liquid 8.

  According to such a configuration, first, the desulfurized gas 3 is introduced into the advanced desulfurization gas cooling tower 41 from the gas introduction line 46. On the other hand, the basic absorbent 4 is cooled by the heat exchanger 44 and then supplied to the advanced desulfurization gas cooling section 42 via the absorbent circulation line 48. In the advanced desulfurization gas cooling unit 42, the introduced gas 3 and the cooled basic absorbent 4 come into contact with each other, so that sulfur oxide in the gas 3 is highly removed, and the concentration of sulfur oxide in the gas is reduced. While being 5 ppm or less, the gas is cooled and the temperature of the gas is 50 ° C. or less. The mist of the basic absorbent 4 accompanying the gas is removed and recovered by the advanced desulfurization gas cooling section demister 43. The recovered basic absorbent 8 is cooled by the heat exchanger 44 and then supplied again to the advanced desulfurization gas cooling section 43 via the absorbent circulation line 48. Since the concentration of the basic compound in the basic absorbent 4 gradually decreases due to the advanced desulfurization gas cooling treatment, the supply liquid 9 containing the basic compound is added from the absorbent addition line 36 as in FIG. The advanced desulfurization gas cooling-treated gas 5 is sent to a downstream decarbonation means (not shown) via a gas discharge line 42.

  As described above, the advanced desulfurization gas cooling section 42 performs the advanced desulfurization process and the gas cooling process at the same time, and thus has an advantage that the device configuration can be simplified.

  FIG. 4 is a schematic diagram showing an outline of an embodiment of the decarboxylation means in the present invention. As shown in FIG. 4, the decarboxylation means is mainly composed of an absorption tower 51 and a regeneration tower 56. The absorption tower 51 includes, in order from the bottom of the tower, a carbon dioxide absorption section 52, a carbon dioxide absorption section demister 53, a water washing section 54, and a water washing section demister 55. The absorption tower 51 has a line for supplying a regenerated absorbent 75 containing a basic amine compound between the dioxygen carbon absorbing section 52 and the dioxygen carbon absorbing section demister 53, the dioxygen carbon absorbing section demister 53 and the water washing section 54. The cleaning liquid 76 is taken out from between the lines, and this is supplied between the water washing section 54 and the water washing section demister 55. From the bottom of the absorption tower 51, the desorbed gas 5 after contact with the gas 5 after the advanced desulfurization gas cooling treatment is regenerated. And a line for releasing the decarboxylated gas 7 from the top of the absorption tower 51 or introducing it to the next step (not shown). Heat exchangers 66 and 67 are provided on the line supplying the regenerated absorbent 75 and the line supplying the cleaning water 76, respectively.

  The regeneration tower 56 includes a recovery unit 57 and a concentration unit 58 in order from the bottom of the tower. In the regeneration tower 56, a line for introducing the load absorbing liquid 74 between the recovery section 57 and the concentrating section 58, a line for supplying the heated load absorbing liquid 74 to the reboiler 61 and the reclaimer 62 from the bottom of the regeneration tower 56, regeneration A line for supplying a carbon dioxide-containing gas 72 generated by heating from the top of the column 56 to the carbon dioxide separator 64 is provided. A capacitor 63 is provided in the line for supplying the carbon dioxide-containing gas 72 to the carbon dioxide separator 64.

  The reboiler 61 is provided with a line for supplying the steam 71 to the lower part of the recovery unit 57 of the regeneration tower 56 and a line for supplying the regenerated absorbent 75 to the absorption tower 51. A heat exchanger 65 for exchanging heat with the line supplying the load absorbing liquid 74 from the absorption tower 51 to the regeneration tower 56 is provided in the line supplying the regeneration absorbing liquid 75. The reclaimer 62 is provided with a line for supplying the regenerated absorbent 75 after the reclaiming operation to the lower part of the recovery unit 57 of the regenerator 56. Further, the carbon dioxide separator 64 has a line for releasing the high-purity carbon dioxide 73 or supplying it to the next step (not shown), and the generated water as the regeneration tower reflux water 77 and the upper part of the concentration section 58 of the regeneration tower 56 and the washing. A line for supplying water 76 to the absorption tower 51 is provided.

  According to such a configuration, first, in the decarbonation means, the gas 5 after the advanced desulfurization gas cooling treatment is introduced into the absorption tower 51 and is brought into contact with the regenerated absorbent 75 containing the basic amine compound in the carbon dioxide absorption section 52. The carbon dioxide and the remaining sulfur oxide in the gas 5 are removed. Further, the gas is washed in the water washing section 54 and then discharged from the absorption tower 51 as the decarboxylated gas 7. On the other hand, the load absorbing liquid 74 after contact is sent to the regeneration tower 56 and heated by steam (not shown) supplied to the reboiler 61 to dissipate carbon dioxide. On the other hand, most of the sulfur oxides in the load absorbing solution 44 are not dissipated and remain in the absorbing solution as sulfates or sulfites.

  When removing the sulfate or sulfite from the absorbent, the absorbent is sent to the reclaimer 62. In the reclaimer 62, after adding the basic sodium compound 78, it heats with steam (illustration omitted), distills an amine compound, and sends it to the regeneration tower 56. The sulfate or sulfite separated from the amine compound is discharged from the reclaimer 62 as sludge 79 which is sodium sulfate or a mixture of sodium sulfate and sodium sulfite. Usually, the regenerated absorbent 75 that has diffused carbon dioxide is supplied to the absorption tower 51 in order to absorb carbon dioxide in the gas 5 after the advanced desulfurization gas cooling treatment again.

  On the other hand, the carbon dioxide diffused by the recovery unit 57 is discharged from the regeneration tower 56 after being washed by the concentration unit 58. The carbon dioxide-containing gas 72 discharged from the regeneration tower 56 is cooled by the condenser 63 and then introduced into the carbon dioxide separator 64. The carbon dioxide separator 64 separates the water into high-purity carbon dioxide 73 and water, and the water is supplied as washing water 76 to the absorption tower 51 and is supplied as regeneration tower reflux water 77 to the regeneration tower 56.

  Thus, in the regeneration tower 56, the sulfur oxides absorbed in the absorption liquid remain as sulfates or sulfites, and in order to remove them, it is necessary to send the absorption liquid to the reclaimer 62 and reclaim it. . According to the present invention, since the sulfur oxide concentration in the gas is previously removed to 5 ppm or less by the basic absorbing liquid, the decarbonation absorbing liquid hardly accumulates sulfur oxide in the examples described later. It is verified by. Therefore, the reclaiming frequency of the decarboxylated absorbent by the reclaimer 62 can be reduced, and the operating cost and the like can be reduced.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these.
Example 1
For coal-fired combustion exhaust gas (200m ³ N / h), desulfurization treatment by wet lime gypsum method, advanced desulfurization treatment with 2% by weight sodium carbonate aqueous solution, cooling condensed water from gas and using as gas coolant Gas cooling treatment and decarboxylation treatment with an alkanolamine aqueous solution were sequentially performed. At this time, the advanced desulfurization treatment and the gas cooling treatment were carried out using the same apparatus as that shown in FIG. And the gas temperature and sulfur oxide density | concentration in a decarboxylation means inlet_port | entrance, the amount of sulfur oxide accumulation in a decarboxylation absorption liquid, and the amount of amine compounds accompanying the gas in a decarboxylation means exit were measured. The results are shown in Table 1.

(Comparative Example 1)
Except that the advanced desulfurization treatment and the gas cooling treatment were not performed, the desulfurization treatment and the decarboxylation treatment of the coal-fired combustion exhaust gas were sequentially performed in the same manner as in Experimental Example 1. The results are shown in Table 1 together with the results of Experimental Example 1.

  As shown in Table 1, in Experimental Example 1 in which advanced desulfurization gas cooling treatment was performed, the gas temperature at the decarbonation means inlet was 40 ° C. and the sulfur oxide concentration was 1 ppm, but advanced desulfurization gas cooling treatment was performed. In Comparative Example 1 that did not exist, the gas temperature at the decarbonation means inlet was as high as 52 ° C., and the sulfur oxide concentration was as high as 30 ppm. The amount of sulfur oxide accumulated in the decarboxylation absorbent in Example 1 is 0.03 times that in Comparative Example 1, and the amount of amine accompanying the gas at the decarboxylation means outlet is also compared with that in Comparative Example 1. It was 0.3 times. Therefore, by reducing the sulfur oxide concentration and reducing the gas temperature in advance before decarboxylation, sulfur oxide accumulates in the decarboxylation absorbent and is released from the decarboxylation means along with the gas. The amount of amine produced can be suppressed.

It is a schematic diagram which shows the outline | summary of the desulfurization decarbonation apparatus which concerns on this invention. It is a schematic diagram which shows one Embodiment of the high desulfurization gas cooling means applicable to this invention. It is a schematic diagram which shows other embodiment of the high desulfurization gas cooling means applicable to this invention. It is a schematic diagram which shows one Embodiment of the decarboxylation means applicable to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Combustion exhaust gas 2 Desulfurization absorption liquid 3 Gas after desulfurization treatment 4 Basic absorption liquid 5 Gas after advanced desulfurization gas cooling treatment 6 Decarbonation absorption liquid 7 Gas after decarbonation treatment 10 Desulfurization means 20 Advanced desulfurization gas cooling means 21, 41 Advanced desulfurization gas Gas cooling tower 22 Advanced desulfurization section 23 Advanced desulfurization section demister 24 Gas cooling section 25 Gas cooling section demister 26, 44 Heat exchanger 31, 46 Gas introduction line 32, 47 Gas discharge line 33, 48 Absorbing liquid circulation line 34 Cooling liquid circulation Line 35 Coolant extraction line 36, 49 Supply liquid addition line 37, 45 Absorption liquid extraction line 42 Advanced desulfurization gas cooling part 43 Advanced desulfurization gas cooling part demister 50 Decarbonation means 51 Absorption tower 52 Carbon dioxide absorption part 53 Carbon dioxide Absorption section demister 54 Flushing section 55 Flushing section demister 56 Regeneration tower 57 Recovery section 58 Concentration section 61 Boiler 62 Reclaimer 63 Condenser 64 Carbon dioxide separator 65-67 Heat exchanger 71 Steam 72 Carbon dioxide containing gas 73 High purity carbon dioxide 74 Load absorption liquid 75 Regeneration absorption liquid 76 Washing water 77 Regeneration tower reflux water 78 Basic sodium compound 79 Sludge

Claims (12)

A desulfurization step for removing sulfur oxide from the gas by bringing a gas containing sulfur oxide and carbon dioxide into contact with an absorbing solution containing a basic calcium compound, and the gas desulfurized in the desulfurization step is made basic An advanced desulfurization gas cooling step in which sulfur oxide is further removed so that the sulfur oxide concentration in the gas is 5 ppm or less by contacting with the absorbing liquid, and the temperature of the gas is cooled to 50 ° C. or less; A desulfurization decarbonation method comprising a decarboxylation step of contacting a gas subjected to a high desulfurization gas cooling treatment in a cooling step with an absorbent containing a basic amine compound to remove carbon dioxide from the gas , The advanced desulfurization gas cooling step includes an advanced desulfurization step in which the gas desulfurized in the desulfurization step is brought into contact with a basic absorbent, and a gas that cools the gas highly desulfurized in the advanced desulfurization step. Retirement and a step, the condensed water obtained by the gas cooling step, said basic absorbent liquid desulfurizing decarboxylation method of mixing the said high desulfurization step. The desulfurization and decarboxylation method according to claim 1, wherein the basic absorbent is an absorbent containing a basic sodium compound. The desulfurization decarboxylation method according to claim 1 or 2 , wherein the condensed water obtained in the gas cooling step is also used as a gas coolant. The desulfurization and decarboxylation method according to any one of claims 1 to 3 , wherein the gas coolant accompanying the gas is removed from the gas in contact with the gas coolant. A desulfurization step for removing sulfur oxide from the gas by bringing a gas containing sulfur oxide and carbon dioxide into contact with an absorbing solution containing a basic calcium compound, and the gas desulfurized in the desulfurization step is made basic An advanced desulfurization gas cooling step in which sulfur oxide is further removed so that the sulfur oxide concentration in the gas is 5 ppm or less by contacting with the absorbing liquid, and the temperature of the gas is cooled to 50 ° C. or less; A desulfurization decarbonation method comprising a decarboxylation step of contacting a gas subjected to a high desulfurization gas cooling treatment in a cooling step with an absorbent containing a basic amine compound to remove carbon dioxide from the gas, The desulfurization decarbonation method , wherein the advanced desulfurization gas cooling step simultaneously removes sulfur oxides and cools the gas by contacting the gas after cooling the basic absorbent. The desulfurization and decarboxylation method according to any one of claims 1 to 5 , wherein the basic absorption liquid accompanying the gas is removed from the gas in contact with the basic absorption liquid. A desulfurization means for contacting an absorption liquid containing a basic calcium compound with a gas, an advanced desulfurization gas cooling means for contacting the basic absorption liquid with a gas and cooling the gas, and an absorption liquid containing a basic amine compound in the gas A decarbonation means to be brought into contact; a pipe for introducing the desulfurized gas of the desulfurization means into the advanced desulfurization gas cooling means; and a pipe for introducing the gas cooled by the advanced desulfurization gas cooling means into the decarbonation means. The advanced desulfurization gas cooling means comprises: an advanced desulfurization unit that brings a basic absorbent into contact with gas; and a gas cooling unit that cools the gas brought into contact with the basic absorbent. A desulfurization and decarbonation apparatus comprising a pipe for mixing the condensed water obtained in the gas cooling section with the basic absorbing liquid . The desulfurization decarboxylation apparatus according to claim 7 , wherein the basic absorption liquid is an absorption liquid containing a basic sodium compound. The desulfurization decarbonation apparatus according to claim 7 or 8 , wherein the advanced desulfurization gas cooling means includes a pipe for supplying condensed water obtained in the gas cooling unit to the gas cooling unit as a gas coolant. The desulfurization decarboxylation apparatus according to any one of claims 7 to 9, wherein the advanced desulfurization gas cooling means includes a demister that removes the gas coolant accompanying the gas from the gas. A desulfurization means for contacting an absorption liquid containing a basic calcium compound with a gas, an advanced desulfurization gas cooling means for contacting the basic absorption liquid with a gas and cooling the gas, and an absorption liquid containing a basic amine compound in the gas A decarbonation means to be brought into contact; a pipe for introducing the desulfurized gas of the desulfurization means into the advanced desulfurization gas cooling means; and a pipe for introducing the gas cooled by the advanced desulfurization gas cooling means into the decarbonation means. a desulfurization decarboxylation apparatus consisting of the highly desulfurized gas cooling means comprises an absorbent liquid cooling means for cooling the basic absorption liquid desulfurization decarbonation apparatus. The desulfurization decarboxylation apparatus according to any one of claims 7 to 11 , wherein the advanced desulfurization gas cooling means includes a demister that removes the basic absorbent accompanying the gas from the gas.

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