JP2014124590A - Operation method of boiler system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation method of boiler systems.SOLUTION: In a coal-fired boiler system which includes a denitration device 52 which removes nitrogen oxide in exhaust gas 11 from a coal-fired boiler 51, an air preheater 53 which recovers the heat in the exhaust gas 11 after nitrogen oxide removal, an electrical precipitator 54 which removes the soot dust in the exhaust gas, a desulfurization device 55 which removes sulfur oxide in the exhaust gas after dust removal, a finish desulfurization device 60 which further removes the sulfur oxide remained after desulfurization, and a COrecovery device 70 which consists of an absorption tower 71A which makes carbon dioxide in the exhaust gas after the finish desulfurization get into touch with COabsorbing solution 72 for removing, and a regeneration tower 71B which recovers and reproduces CO, by exhausting COfrom the COabsorbing solution 72, using an SOcontent measuring device 10 which measures SOconcentration in the exhaust gas 11 in a flue 12 at the entrance side of the absorption tower 71A of the boiler system 50A, the misty and gaseous SOin the exhaust gas are measured, and the amount of SOin the exhaust gas which is introduced into the absorption tower 71A is adjusted according to the measured SOconcentration.

Description

  The present invention relates to a method for operating a boiler system.

In recent years, the greenhouse effect due to CO ₂ has been pointed out as one of the causes of global warming, and countermeasures have become urgent internationally to protect the global environment. The source of CO ₂ extends to all human activity fields that burn fossil fuels, and there is a tendency for the demand for emission control to become stronger. Along with this, for the power generation facilities such as thermal power plants that use a large amount of fossil fuel, the combustion exhaust gas of industrial equipment such as boilers and gas turbines is brought into contact with the amine-based CO ₂ absorbent, and the CO ₂ in the combustion exhaust gas An exhaust gas treatment system that stores and recovers the recovered CO ₂ without releasing it to the atmosphere has been energetically studied.

Using an amine-based CO ₂ absorbing solution as described above, as the process of removing and recovering CO ₂ from flue gas, CO ₂ absorption tower (hereinafter, simply referred to as "absorption column".) Flue gas in a CO ₂ absorption Play the step of contacting a liquid, the CO ₂ absorbing liquid absorbent regenerator that has absorbed CO ₂ (hereinafter, simply referred to as "regeneration tower".) is heated at a CO ₂ absorbing solution with dissipating CO ₂ Then, a CO ₂ recovery device having a step of recirculating and reusing the CO ₂ absorption tower has been proposed (see, for example, Patent Document 1).

In the CO ₂ absorption tower, for example, an amine-based CO ₂ absorbing solution such as alkanolamine is used for countercurrent contact, and CO ₂ in the exhaust gas is absorbed into the CO ₂ absorbing solution by a chemical reaction (exothermic reaction), and CO ₂ The exhaust gas from which is removed is discharged out of the system. CO ₂ absorbent that has absorbed CO ₂ is referred to as rich solution. The rich solution is pressurized by the pump, the CO ₂ absorbing solution in a high temperature CO ₂ in the regeneration tower has been regenerated dissipation (lean solution), heated in the heat exchanger, is supplied to the regenerator.

Japanese Patent Laid-Open No. 3-193116

However, the exhaust gas treatment system, the exhaust gas introduced into the CO ₂ absorber that absorbs CO ₂ of the CO ₂ recovery apparatus, the mist-generating substance which is a source of mist generated in the absorption tower of the CO ₂ recovery apparatus, In particular, the influence of SO _{3 in} the exhaust gas is large, but when this is included in the system, the CO ₂ absorbing liquid is lost due to the mist generating material, and the amount of the CO ₂ absorbing liquid scattered outside the system increases. There's a problem.
If there is scattering out of the system such CO ₂ absorbing liquid, with leads to a significant loss of the CO ₂ absorbing solution, since the supplementing unnecessarily CO ₂ absorbing solution, CO out of the system ₂ It is necessary to suppress the absorption liquid from scattering.

Further, when SO ₃ in the exhaust gas is taken into the CO ₂ absorption liquid and this amount increases, the frequency of the reclaiming operation for separately regenerating the absorption liquid becomes high and the economy is remarkably deteriorated. It is necessary to set the SO ₃ concentration in the exhaust gas to a predetermined value or less.

In the conventional analysis, since it could not analyze separately the mist SO ₃ and gaseous SO ₃ in the exhaust gas, even at the portion below the acid dew point unit, mist SO ₃ is trapped by the filter means Therefore, even if the measurement results show that the SO ₃ concentration is not detected, mist-like SO ₃ exists in the absorption tower of the CO ₂ recovery device, and the CO ₂ absorption is out of the system. There are problems that the scattering of the liquid increases and the reclaiming frequency increases.

Conventionally, since a continuous analysis technique for SO ₃ gas in exhaust gas has not been established, chemical analysis is intermittently performed by analysis personnel each time.
Therefore, sampling of exhaust gas from the flue flue and various operations may take 1 to 3 hours / case, and analysis may take several days / case (including take-away analysis), and it takes a lot of time to obtain the measurement results. Was. In addition, since it takes time to measure the SO ₃ content in this way, there is also a problem that it is difficult to grasp the fluctuation range of the operating state.

Previously, there was no continuous measurement technology using equipment analyzers as described above, so measurements were performed by chemical analysis as needed during trial operation after plant construction or during commercial operation, and operation management was performed using this data. It was. Thus, in the past, measurement has been carried out with a great deal of effort, but in recent years there have been examples of SO ₃ measurement in thermal power plants using continuous measurement equipment using infrared spectroscopy such as FT-IR and laser methods. It is starting to be reported.

In view of the above problems, an object of the present invention is to provide a method for operating a boiler system that enables operation with reduced reclaiming frequency while reducing loss of absorbent in a CO ₂ recovery device.

A first invention of the present invention for solving the above-described problems includes a denitration device for removing nitrogen oxides in exhaust gas from a boiler, an air preheater for recovering heat in the exhaust gas after removing nitrogen oxides, A dust collector that removes soot and dust in the exhaust gas, a desulfurization device that removes sulfur oxides in the exhaust gas after dust removal, and carbon dioxide (CO ₂ ) in the exhaust gas after desulfurization is brought into contact with the CO ₂ absorbent. an absorption tower a for removing Te, along with by releasing CO ₂ from the CO ₂ absorbing solution for recovering CO _2, the operation of the boiler system comprising a CO ₂ recovery apparatus comprising a regenerator to regenerate the CO ₂ absorbing solution In the method, an SO ₃ content measuring device for measuring mist and gaseous SO ₃ in the exhaust gas is used to measure the SO ₃ concentration in the exhaust gas on the inlet side of the absorption tower, and to the measured SO ₃ concentration. In response, S in the exhaust gas flowing into the CO ₂ absorption tower In boiler system operating method characterized by adjusting the O ₃ amount.

The second aspect, in the first aspect, SO ₃ content measuring device for measuring the mist and gaseous SO ₃ in the exhaust gas, an exhaust gas containing SO _3, the opening and closing valve for introducing the flue A gas introduction line provided, an SO ₃ measuring instrument connected to the gas introduction line for measuring gaseous SO ₃ in the exhaust gas, and a gas introduction line interposed between the gas introduction line and capturing dust in the introduced exhaust gas while a filter means for selectively passing the gaseous sO ₃ and mist sO _3, the region from the flue of the gas inlet line to on-off valve, the flue of the exhaust gas temperature (T ₁₎ A first heating means for maintaining the temperature of the introduced exhaust gas at a temperature (T ₂ ) equivalent to the gas temperature (T ₁ ) in the flue, and an opening / closing valve of the gas introduction line the region up to SO ₃ meter, SO ₃ gas guide Was heated to a temperature to retain gaseous state inside the line, a second heating means for holding, it comprises a, a mist of SO ₃ in the exhaust gas after passing through said filter means, said second Operation of a boiler system characterized in that gaseous SO ₃ is heated by the heating means, and the total concentration of gaseous and mist SO ₃ floating in the exhaust gas is measured by the SO ₃ measuring instrument. Is in the way.

A third invention has a finishing desulfurization device for further removing sulfur oxide remaining after desulfurization of the desulfurization device in the first or second invention, and measures mist-like and gaseous SO ₃ in the exhaust gas. In accordance with the SO ₃ concentration measured by the SO ₃ content measuring device, the SO ₃ concentration is reduced to a predetermined value by adjusting either or both of the circulation amount and the alkali concentration of the alkali absorbing liquid circulating in the finishing desulfurization device. It is in the operation method of the boiler system characterized by this.

According to a fourth invention, in the first or second invention, a heat exchanger is sprayed between the air preheater and the dust collector, and an alkali agent or ash particles are sprayed into the exhaust gas on the upstream side of the heat exchanger. The spraying amount of the alkali agent or ash particles is adjusted according to the SO ₃ concentration measured by the SO ₃ content measuring device that measures the mist and gaseous SO ₃ in the exhaust gas. It is in the operating method of the boiler system characterized by reducing SO3 concentration to a predetermined value.

According to a fifth invention, in the first or second invention, a heat exchanger is provided between the air preheater and the dust collector, and spraying means for spraying an alkaline agent into the exhaust gas on the upstream side of the air preheater. And adjusting the spray amount of the alkaline agent according to the SO ₃ concentration measured by the SO ₃ content measuring device for measuring the mist and gaseous SO ₃ in the exhaust gas, thereby adjusting the SO ₃ concentration to a predetermined value. It is in the operating method of the boiler system characterized by reducing even to.

A sixth invention includes a dissolved salt spraying device for spraying a dissolved salt between the dust collector and the desulfurization device in the first or second invention, and the mist-like and gaseous SO ₃ in the exhaust gas is obtained. The SO ₃ concentration is reduced to a predetermined value by adjusting either or both of the spray amount of the dissolved salt and the salt concentration according to the SO ₃ concentration measured by the SO ₃ content measuring device to be measured. It is in the operation method of the boiler system.

According to the present invention, using a SO ₃ content measuring device that measures the SO ₃ concentration in the exhaust gas at the flue on the inlet side of the absorption tower of the boiler system, mist and gaseous SO ₃ in the exhaust gas are continuously added. The amount of SO ₃ in the exhaust gas to be introduced into the absorption tower is adjusted by changing the amount and concentration of the various chemicals according to the measured and detected SO ₃ concentration.
As a result, the amount of SO ₃ mist flowing into the absorption tower of the CO ₂ recovery unit is reduced, and the generation of white smoke of the purified gas discharged from the CO ₂ absorption tower due to the mist is suppressed and absorbed. It is also possible to provide an exhaust gas treatment system that suppresses liquid entrainment loss, reduces reclaiming frequency, and can be economically operated.

FIG. 1 is a schematic diagram of a coal fired boiler system according to a first embodiment. FIG. 2 is a schematic diagram of an apparatus for measuring the content of SO _{3 in} exhaust gas according to the second embodiment. FIG. 3 is a conceptual view of the filter means passing through the filter. FIG. 4 is a schematic diagram of a coal fired boiler system according to the second embodiment. FIG. 5 is a schematic diagram of a coal fired boiler system according to the third embodiment. FIG. 6 is a schematic diagram of a coal fired boiler system according to the fourth embodiment. FIG. 7 is a graph showing the relationship between the SO ₃ concentration at the inlet of the absorption tower and the reclaiming frequency.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example, Moreover, when there exists multiple Example, what comprises combining each Example is also included.

FIG. 1 is a schematic diagram of a coal fired boiler system according to a first embodiment.
As shown in FIG. 1, a coal fired boiler system 50A according to this embodiment includes, for example, a denitration device 52 that removes nitrogen oxides in the exhaust gas 11 from the coal fired boiler 51, and the exhaust gas 11 after the removal of nitrogen oxides. An air preheater 53 that collects the heat of the exhaust gas, an (electric) dust collector 54 that removes soot and dust in the exhaust gas 11, a desulfurization device 55 that removes sulfur oxide in the exhaust gas after dust removal (gas-liquid contact type), A finishing desulfurization device 60 that further removes sulfur oxide remaining after desulfurization, an absorption tower 71A that removes carbon dioxide (CO ₂ ) in the exhaust gas 11 after finish desulfurization by contacting the CO ₂ absorbent 72, and CO _2. A CO ₂ recovery device 70 including a regeneration tower 71B for regenerating the CO ₂ absorption liquid 72 is provided while CO ₂ is recovered by releasing CO ₂ from the absorption liquid 72.
In FIG. 1, reference numeral 55a denotes a dehydrating means for treating the desulfurization waste water from the desulfurization device 55, 55b is gypsum, 55c is a dehydrated filtrate, 73 is a purified gas discharged from the absorption tower 71A, 75a is a reboiler, 75b is steam, 75c is condensed water, 75d is a gas-liquid separator, 75e is recovered CO ₂ , and 75f is a heat exchanger.
In the present embodiment, using the SO ₃ content measuring device 10 that measures the SO ₃ concentration in the exhaust gas 11 at the flue 12 on the inlet side of the absorption tower 71A of the boiler system 50, the mist and gaseous states in the exhaust gas are used. SO ₃ is measured.
Then, according to the SO ₃ concentration measured by the SO ₃ content measuring device 10, the amount of SO ₃ in the exhaust gas introduced into the absorption tower 71A is adjusted.

In this embodiment, the SO ₃ concentration is reduced in the finishing desulfurization device 60 installed on the downstream side of the desulfurization device 55.

The finish desulfurization device 60 is a finish flue gas desulfurization device that further removes sulfur oxide remaining in the exhaust gas 11 desulfurized by the desulfurization device 55 to an extremely low concentration, and sulfur oxidation in a small amount of introduced sulfur oxide. A final desulfurization section 60A for desulfurization by bringing the absorbent 60a into contact with the product, a wet electric dust collection section 60B provided on the downstream side of the final desulfurization section 60A, for removing soot and dust in the exhaust gas after the final desulfurization, A cooling unit 60 </ b> C that cools the combustion exhaust gas is provided on either one of the front and rear sides of the dust collection unit 60 </ b> B (the wake side in this embodiment).
In the present embodiment, the finishing desulfurization section 60A is supplied with, for example, lime (CaCO ₃ ) absorption liquid through the circulation line L ₁₁ by the pump P _{1 as} the absorption liquid 60a for removing sulfur oxide of the lime gypsum method.

  In addition, dust can be removed by the wet electrostatic precipitator 60B provided on the upper side of the finish desulfurizer 60A.

Here, examples of the absorbing solution 60a used in the finish desulfurization section 60A include alkali absorbing solutions such as NaOH, Na ₂ CO ₃ , NaHCO ₃ , Ca (OH) ₂ , and Mg (OH) _{2 in} addition to CaCO _3. Can do.
Examples of the cleaning liquid 60b used in the wet electrostatic precipitator 60B include alkali absorbing liquids such as Na ₂ CO ₃ and NaHCO _{3 in} addition to NaOH.

As an example of adjusting the amount of SO ₃ in the exhaust gas according to the SO ₃ concentration measured by the SO ₃ content measuring device 10 in the final desulfurization device 60, the absorption liquid 60a of the final desulfurization unit 60A or the wet electrostatic precipitator 60B. The removal amount of SO _{3 in} the exhaust gas is increased by adjusting either or both of the circulation amount and the alkali concentration of the alkali absorbing solution used for the cleaning liquid 60b. Here, the cleaning solution 60b is supplied through the circulation line L ₁₂ by a pump P _2.
The cooling water 60c of the cooling unit 60C is supplied through the circulation line L ₁₃ by the pump P _3.

For example, when a boiler load is applied and the sulfur oxide concentration in the exhaust gas temporarily increases, the SO ₃ concentration in the exhaust gas introduced into the absorption tower 71A becomes high in a normal setting. ₃ in accordance with the sO ₃ concentration measured by the content of the measuring device 10 is to adjust the sO ₃ content in the exhaust gas.

Here, in the conventional analysis, when measuring SO ₃ in the exhaust gas, gaseous SO ₃ is measured. Since mist-like SO ₃ could not be analyzed, the downstream of the desulfurization apparatus When it falls below the acid dew point on the side, mist-like SO ₃ is trapped by the filter means, so even if the analysis results show that the SO ₃ concentration is not detected in terms of measurement, the CO ₂ recovery device There was a possibility that mist-like SO ₃ was present in the absorption tower, the scattering of the CO ₂ absorption liquid was increased outside the system, and the reclaiming frequency was increased.

FIG. 7 is a graph showing the relationship between the SO ₃ concentration at the inlet of the absorption tower and the reclaiming frequency.
As shown in FIG. 7, when the concentration is higher than a predetermined concentration, the number of reclaiming times (days) tends to increase. Therefore, it is necessary to reduce the inlet concentration (several ppm or less).

In this embodiment, the SO ₃ content measuring device 10 installed on the upstream side of the absorption tower 71A uses a device that measures the gaseous and mist-like SO ₃ present in the exhaust gas.

FIG. 2 is a schematic diagram of the SO ₃ content measuring device in exhaust gas according to the first embodiment.
As shown in FIG. 2, the SO ₃ content measuring device 10 in the exhaust gas according to the present embodiment introduces an exhaust gas 11 containing SO ₃ burned in, for example, an oil fired boiler from a flue 12. A first gas introduction line 14 having an on-off valve 13, an SO ₃ measuring instrument 20 connected to the first gas introduction line 14 for measuring gaseous SO ₃ in the exhaust gas 11, and the first A filter means 15 that is interposed in one gas introduction line 14 and captures dust in the introduced exhaust gas 11a and selectively passes gaseous SO ₃ and mist SO ₃ ; The first heating region L ₁ from the flange 12 a of the flue 12 to the on-off valve 13 is heated to a temperature equivalent to the gas temperature (T ₁ ) of the exhaust gas 11 in the flue 12, and the gas temperature of the introduced exhaust gas 11 a the gas temperature in the flue in 12 (T ₁ 151 ° C.) and an equivalent temperature (T _2: the first heating means 16A for holding the 151 ° C.), a second heating region from the opening and closing valve 13 of the gas inlet line 14 to the inlet 15a of the SO ₃ instrument 20 And a _second heating means 16B for heating and holding L ₂ at a temperature (200 ° C. or higher, T ₃ : 220 ° C.) at which SO ₃ maintains a gaseous state inside the gas introduction line. The mist-like SO ₃ in the exhaust gas 11b after passing through the filter means 15 is converted into gaseous SO ₃ by the heating of the second heating means 16B, and converted from the gaseous SO ₃ and the mist-like SO ₃ . The total concentration of gaseous SO ₃ is measured by the SO ₃ measuring instrument 20.
In FIG. 2, reference numeral 21A denotes a first temperature control device, 21B denotes a second temperature control device, 22 denotes a gas suction pump, 23 denotes a gas return line, 31 denotes a control device, and 32 denotes display means. To do.

The gas introduction line 14 has a gas introduction part 14a inserted from the flange 12a into the flue 12, and an opening part 14b is formed so as to face the gas flow of the exhaust gas 11 so that the exhaust gas 11 is introduced. Yes.
In addition, the introduction pipe 14 c has a first heating region L ₁ from the flange 12 a of the flue 12 to the filter means 15 and the on-off valve 13, for example, a heater that is the first heating means 16 A. The inside is heated to a temperature equivalent to the gas temperature (T ₁ ) of the exhaust gas 11 inside, and the gas temperature of the introduced exhaust gas 11a is set to a temperature (T ₁ ) equivalent to the gas temperature in the flue 12 (T ₁ : illustrated example 151). ₂ : It is made to hold | maintain at 151 degreeC of illustration examples.

As a result, the gas introduction line 14 in the heating region L ₁ has the same conditions as in the flue.
By adopting the same conditions, _{three components of} gaseous SO ₃ , mist SO ₃ and dust are present in the introduced exhaust gas 11 a at the same ratio as in the flue 12.

FIG. 3 is a conceptual view of the filter means passing through the filter.
As shown in FIG. 3, the first filter means 15 interposed in the first gas introduction line 14A captures only the dust 31 in the introduced exhaust gas 11a, as well as gaseous SO ₃ 32 and mist. Of SO ₃ 33 is selectively passed.
As a result, gaseous SO ₃ 32 and mist SO ₃ 33 from which dust has been removed are present in the exhaust gas 11b that has passed through the filter means 15.

Here, in FIG. 2, the second heating region L ₂ from the on-off valve 13 to the inlet 15a of the SO ₃ measuring instrument 20 is in a state where SO ₃ is in a gaseous state inside the gas introduction line by the second heating means 16B. The temperature is maintained at a temperature (for example, 200 ° C. or higher, T ₃ : 220 ° C. in the illustrated example).
Thus, the exhaust gas 11b dust 31 which has passed through the on-off valve 13A has been removed, when passing through the heating region L _2, the mist of the SO ₃ 33 in the exhaust gas 11b is converted to gaseous SO ₃ 32 Thus, all the exhaust gas 11b becomes gaseous SO ₃ .

By measuring this gaseous SO ₃ with the SO ₃ measuring instrument 20, the total amount of gaseous and mist-like SO ₃ in the exhaust gas 11 in the flue 12 can be measured.

That is, in the flue 12, gaseous SO ₃ and mist SO ₃ are mixed, but when they are introduced through the gas introduction line 14, they are guided by heater trace control at the same temperature as the exhaust gas 11. The filter means 15 captures only the dust 31 and selectively allows only the mist-like SO ₃ 33 and the gaseous SO ₃ 32 to pass therethrough.
After a further pass of the filter unit 15A, the second heating zone L _2, and heated above the temperature at which SO ₃ is to hold the gaseous state inside the gas inlet line "acid dew point + dozens ℃" The SO ₃ mist is gasified into all gaseous SO ₃ , which is led to the SO ₃ measuring device 20, and as a result, it is gasified from the originally existing gaseous SO ₃ 32 and mist-like SO ₃ 33. The sum total with gaseous SO ₃ is detected as the SO ₃ concentration.

Here, the second heating region L ₂ may be set to a temperature at which SO ₃ maintains a gaseous state inside the gas introduction line, for example, an acid dew point + several tens of degrees Celsius or more. because varies with the sO ₃ concentration and the water content of 11, in the present invention, it is preferable to 200 ° C. or higher (as an example in the present embodiment, T _3: is a 220 ° C..).

As a result, all of the mist-like SO ₃ present in the exhaust gas 11b after passing through the filter means 15 is gasified into gaseous SO ₃ .

As a result, a mist-like concentration of SO ₃ that could not be measured conventionally can also be measured as the SO ₃ concentration.

Here, the first filter means 15A that captures dust in the introduced exhaust gas 11a and selectively passes through gaseous SO ₃ and mist SO ₃ will be described.
Any first filter means 15A may be used as long as it captures only the dust 31 and can selectively pass only mist-like SO ₃ and gaseous SO ₃ .

For example, ceramic filter paper with an opening equivalent to the particle size of the dust 31 or an inertia filter, a metal mesh filter that does not react with SO ₂ and SO ₃ , a filter made of a metal porous body, and the same opening can be backwashed A filter using a simple ceramic filter can be exemplified.

  In addition, an electrostatic filter (having a fixed electrical polarity), an electric field filter (capable of removing dust and removing the solvent by arbitrarily changing the electrical polarity), or the like may be used.

However, these filter means are sometimes replaced with new ones, or if the clogging is significant, the dust stored in the filter means is removed as a maintenance operation or heated at a high temperature to mainly store SO ₃ or unburned carbon. It is recommended to perform an operation that gasifies and blows off the dust.

In this way, by using the SO ₃ content measuring device 10 in the exhaust gas shown in FIG. 2 according to the present embodiment, the total SO ₃ in the exhaust gas introduced into the absorption tower 71A of the CO 2 recovery device 70 (gaseous state) The total amount of SO ₃ and mist-like SO ₃ ) can be grasped, and based on this measurement result, for example, the circulation amount or alkali of the alkali absorbing liquid of the cleaning liquid 60b of the wet electrostatic precipitator 60B of the finishing desulfurization apparatus 60 is controlled by the control device 31 By adjusting either one or both of the concentrations, the removal amount of SO _{3 in} the exhaust gas is increased.

FIG. 4 is a schematic diagram of a coal-fired boiler system according to the second embodiment. In addition, about the same member as the system of Example 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
As shown in FIG. 4, the coal fired boiler system 50 </ b> B according to this embodiment includes a heat exchanger (gas gas heater) 80 between the air preheater 53 and the electric dust collector 54, and the upstream side of the heat exchanger 80. The spraying means (not shown) for spraying the alkali agent (or ash) 82 into the exhaust gas and the alkali agent (or ash) supply means 81 having the control valve 83 are provided.
At the upstream side of the absorption tower 71A, the SO ₃ content measuring device 10 for measuring the mist and gaseous SO ₃ in the exhaust gas is provided, the SO ₃ concentration measured by the SO ₃ content measuring device 10 Accordingly, the control valve 83 is adjusted to adjust the spray amount of the alkali agent or ash particles so as to increase the removal amount of SO ₃ in the exhaust gas.

Examples of the alkali agent include calcium carbonate (CaCO ₃ ), slaked lime (Ca (OH) ₂ ), sodium sulfite (NaHSO ₃ : SBS), and the like, and besides the alkali agent, ash particles (fly ash), etc. Can be used.

For example, the case where calcium carbonate (CaCO ₃ ) is sprayed as an alkaline agent will be described.
Since a heat exchanger (GGH) 80 for lowering the exhaust gas temperature is provided on the upstream side of the desulfurization device 55 on the downstream side for spraying calcium carbonate (CaCO ₃ ), the temperature of the exhaust gas 11 is reduced by the heat exchanger 80. the with less sulfuric acid dew point, by condensing the gaseous SO ₃ and mist SO _3, the SO ₃ condensed at the surface or in the pores of the sprayed calcium carbonate in an exhaust gas 11 (CaCO ₃₎ It adheres and neutralizes to remove mist-like SO ₃ from the exhaust gas 11. Further, when the spray medium is ash, SO ₃ is reduced by utilizing the same adsorption mechanism.

In this way, SO ₃ in the exhaust gas 11 is condensed from the gas state and removed as a mist state, and the amount of SO ₃ mist introduced into the absorption tower 71A of the CO ₂ recovery device 70 is reduced.
Therefore, the generation of white smoke in the purified gas 73 discharged from the CO ₂ absorption tower 71A due to mist is suppressed, and the accompanying loss of the absorbing liquid 72 is suppressed.
In addition, it is possible to provide an exhaust gas treatment system that can reduce the frequency of reclaiming and can be economically operated.

The exhaust gas 11 from which the dust is removed by the electrostatic precipitator 54 removes the sulfur oxide in the exhaust gas 11 by the desulfurization device 55, and the removed sulfur oxide supplies limestone (CaCO ₃ ) and oxidizing air, Gypsum is made by the lime / gypsum method, and desulfurization waste water is dehydrated by dehydrating means 55a to form gypsum 55b, and the dehydrated filtrate 55c is separately processed.

FIG. 5 is a schematic view of a coal-fired boiler system according to the third embodiment. In addition, about the same member as the system of Example 1 and 2, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
As shown in FIG. 5, the coal fired boiler system 50 </ b> C according to the present embodiment includes a heat exchanger (gas gas heater) 80 between the air preheater 53 and the electric dust collector 54, and the upstream side of the air preheater 53. Spray means (not shown) for spraying the alkali agent 82 into the exhaust gas, and an alkali agent supply means 81 having a control valve 83.
At the upstream side of the absorption tower 71A, the SO ₃ content measuring device 10 for measuring the mist and gaseous SO ₃ in the exhaust gas is provided, the SO ₃ concentration measured by the SO ₃ content measuring device 10 Accordingly, the control valve 83 is adjusted to adjust the spray amount of the alkaline agent so as to increase the removal amount of SO ₃ in the exhaust gas.

As a result, SO ₃ in the exhaust gas 11 is removed from the gas state as a mist state, and as a result, the amount of SO ₃ mist introduced into the absorption tower 71A of the CO ₂ recovery device 70 is reduced.
Therefore, the generation of white smoke in the purified gas 73 discharged from the CO ₂ absorption tower 71A due to mist is suppressed, and the accompanying loss of the CO ₂ absorption liquid 72 is suppressed.
In addition, it is possible to provide an exhaust gas treatment system that can reduce the frequency of reclaiming and can be economically operated.

FIG. 6 is a schematic diagram of a coal-fired boiler system according to the fourth embodiment. In addition, about the same member as the system of Example 1 and 2, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
As shown in FIG. 6, the coal fired boiler system 50D according to the present embodiment sprays a dissolved salt solution 92 of dissolved salt (Na ₂ SO ₄ , MgSO ₄ ) between the electric dust collector 54 and the desulfurization device 55. A dissolved salt spray device 91 is installed.
Then, an aqueous solution of a soluble salt solution 92 such as Na ₂ SO ₄ or MgSO ₄ is sprayed into the exhaust gas 11 on the upstream side of the desulfurizer 55. A wet type electrostatic precipitator 57 is provided on the downstream side of the desulfurization device 55 to further remove soot and dust in the exhaust gas by a wet method.

By spraying the dissolved salt solution 92 into the exhaust gas 11 having a gas temperature of about 130 ° C. to 150 ° C. on the downstream side of the dry-type electrostatic precipitator 54, finely-divided dried dissolved salt particles are obtained. The SO _{3 in the} gas state is removed from the exhaust gas 11 by adsorbing and fixing the SO ₃ in the gas state.
As a result, SO ₃ in the exhaust gas 11 is removed from the gas state as a mist state, and as a result, the amount of SO ₃ mist introduced into the absorption tower 71A of the CO ₂ recovery device 70 is reduced.
Therefore, the generation of white smoke in the purified gas 73 discharged from the CO ₂ absorption tower 71A due to mist is suppressed, and the accompanying loss of the CO ₂ absorption liquid 72 is suppressed.
In addition, it is possible to provide an exhaust gas treatment system that can reduce the frequency of reclaiming and can be economically operated.

Examples of the dissolved salt include NaCl, NaOH, Na ₂ SO ₄ , Na ₂ CO ₃ , KCl, KOH, K ₂ SO ₄ , K ₂ CO ₃ , KHCO ₃ , MgCl ₂ , MgSO ₄ , and CaCl ₂ .

Here, when Na ₂ SO ₄ is used as the dissolved salt, the reaction of the following formula (1) proceeds by the dissolved salt particles (Na ₂ SO ₄ ) and SO ₃ . As a result, NaHSO ₄ .H ₂ O (solid) is generated.
Na ₂ SO ₄ + SO ₃ + 3H ₂ O → 2NaHSO ₄ .H ₂ O (1)

Since Na ₂ SO ₄ and NaHSO ₄ .H ₂ O are both soluble, they are dissolved in the desulfurization device 555 on the downstream side. For this reason, compared with the case where ammonia is injected, for example, the treatment of the solid substance containing ammonia in the dry electrostatic precipitator 54 becomes unnecessary.

10 SO ₃ content measuring apparatus 11 flue gas 12 flue 13 opening valve 14 the gas inlet line 15 filter unit 16A first heating means 16B second heating means 20 SO ₃ meter 50A~50D coal-fired boiler system

Claims (6)

A denitration device for removing nitrogen oxides in exhaust gas from the boiler;
An air preheater that recovers heat in the exhaust gas after removal of nitrogen oxides;
A dust collector for removing the dust in the exhaust gas;
A desulfurizer that removes sulfur oxides in the exhaust gas after dust removal;
An absorption tower A for removing carbon dioxide in the flue gas after the desulfurization of (CO ₂₎ is brought into contact with the CO ₂ absorbing solution, thereby recovering the CO ₂ to release CO ₂ from the CO ₂ absorbing solution, CO ₂ absorbing solution In the operation method of the boiler system comprising a CO ₂ recovery device comprising a regeneration tower for regenerating
With SO ₃ content measuring device for measuring the mist and gaseous SO ₃ in the exhaust gas, in accordance with the measurement SO ₃ concentration while measuring the SO ₃ concentration in the exhaust gas at the inlet side of the absorption tower, A method for operating a boiler system, comprising adjusting an amount of SO ₃ in exhaust gas flowing into a CO ₂ absorption tower. In claim 1,
An SO ₃ content measuring device that measures mist and gaseous SO ₃ in exhaust gas,
A gas introduction line having an on-off valve for introducing exhaust gas containing SO ₃ from the flue;
An SO ₃ measuring instrument connected to the gas introduction line for measuring gaseous SO ₃ in the exhaust gas;
Interposed in the gas inlet line, as well as capture the dust introduced in the exhaust gas, and filter means for selectively passing the gaseous SO ₃ and mist SO _3, opening and closing the flue of the gas inlet line The area up to the valve is heated to a temperature equivalent to the gas temperature (T ₁ ) of the exhaust gas in the flue, and the gas temperature of the introduced exhaust gas is set to a temperature (T ₂ ) equivalent to the gas temperature (T ₁ ) in the flue A first heating means for holding;
And a second heating means for heating and holding the region from the on-off valve of the gas introduction line to the SO ₃ measuring device to a temperature at which SO ₃ maintains a gaseous state inside the gas introduction line. Become
Mist SO ₃ in the exhaust gas after passing through the filter means is converted to gaseous SO ₃ by the heating of the second heating means, and the total concentration of gaseous and mist SO ₃ floating in the exhaust gas is determined. , boiler system operating method characterized by comprising measured by the SO ₃ meter. In claim 1 or 2,
A finishing desulfurization device for further removing sulfur oxide remaining after desulfurization of the desulfurization device;
Depending on the SO ₃ concentration measured by the SO ₃ content measuring device that measures the mist and gaseous SO ₃ in the exhaust gas, either the circulating amount or alkali concentration of the alkali absorbent circulating in the finishing desulfurization device or A method for operating a boiler system, characterized by adjusting both to reduce the SO ₃ concentration to a predetermined value. In claim 1 or 2,
A heat exchanger between the air preheater and the dust collector, and spray means for spraying alkali agent or ash particles in the exhaust gas on the upstream side of the heat exchanger,
According to the SO ₃ concentration measured by the SO ₃ content measuring device that measures mist and gaseous SO ₃ in the exhaust gas, the spray amount of the alkali agent or ash particles is adjusted to the SO ₃ concentration to a predetermined value. A method for operating a boiler system, characterized in that it is reduced. In claim 1 or 2,
A heat exchanger between the air preheater and the dust collector, and a spray means for spraying an alkaline agent into the exhaust gas on the upstream side of the air preheater, and mist and gaseous SO in the exhaust gas _3. A boiler system operating method, comprising adjusting the spray amount of the alkaline agent to reduce the SO ₃ concentration to a predetermined value according to the SO ₃ concentration measured by the SO ₃ content measuring device for measuring ₃ . In claim 1 or 2,
A dissolved salt spraying device for spraying dissolved salt between the dust collector and the desulfurization device;
Depending on the SO ₃ concentration measured by the SO ₃ content measuring device that measures mist and gaseous SO ₃ in the exhaust gas, either or both of the dissolved salt spray amount and the salt concentration are adjusted to adjust the SO ₃ concentration. _3. A boiler system operation method characterized by reducing the concentration to a predetermined value.

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