JP5916470B2 - Fluidized bed processing system and N2O removal method of fluidized bed combustion exhaust gas - Google Patents

Description

The present invention relates to a fluidized bed treatment system and a method for removing N ₂ O from fluidized bed combustion exhaust gas, which can significantly reduce the content of nitrous oxide (N ₂ O) in exhaust gas discharged from combustion equipment.

In the second evaluation report (1995) of the Intergovernmental Panel on Climate Change (IPCC), as greenhouse gases (Greenhouse Gas: GHG), carbon dioxide (CO ₂ ), methane (CH ₄ ) Nitrous oxide (N ₂ O), hydrofluorocarbon, perfluorocarbon, and sulfur hexafluoride have been designated, and the reduction of greenhouse gases has become an urgent task due to recent stricter regulations.

In this greenhouse gas (GHG), the global warming coefficient of nitrous oxide (N ₂ O) is 310 times that of carbon dioxide (CO ₂ ), and there is an urgent need to reduce its generation amount.

Therefore, conventionally, it has been proposed to reduce the N ₂ O, which is a greenhouse gas, by maintaining the temperature in the free board section of the circulating fluidized bed boiler at a high temperature of 850 to 950 ° C. (Patent Document 1). ).

JP 2002-130641 A

By the way, when the fluidized bed equipment is operated at a high temperature (850 ° C. or higher), the amount of nitrous oxide (N ₂ O) generated is reduced, but the high-temperature combustion causes the melting of fly ash in the exhaust gas and the ash Adhesion problems occur in the convection heat transfer section on the wake side. Therefore, in a circulating fluidized bed boiler, there is a problem that performing high temperature combustion exceeding 900 ° C. has many restrictions in terms of equipment and operation.

Therefore, the appearance of a fluidized bed processing system that reduces nitrous oxide (N ₂ O) in exhaust gas while operating at a stable operating temperature of 800 to 900 ° C. in a fluidized bed processing facility is desired.

In view of the above problems, the present invention provides a fluidized bed treatment system and a method for removing N ₂ O from fluidized bed combustion exhaust gas, which can greatly reduce the content of nitrous oxide (N ₂ O) in the exhaust gas discharged from the combustion facility. It is an issue to provide.

A first invention of the present invention for solving the above-described problems includes a fluidized bed boiler that performs a fluidized bed combustion process on supplied fuel, and a heat transfer unit that recovers heat of combustion exhaust gas discharged from the fluidized bed boiler. And an air preheater that is provided on the downstream side of the heat transfer section and preheats the air supplied to the fluidized bed boiler, and is provided on the downstream side of the air preheater and removes dust in the combustion exhaust gas. A hydrocarbon-based reducing agent mainly composed of propylene as a reducing agent that removes N ₂ O contained in the combustion exhaust gas is disposed in a combustion exhaust gas exhaust line between the dust removal device and the fluidized bed boiler and the heat transfer section. A reducing agent supply unit that supplies the heat transfer unit, the heat transfer unit includes at least one superheater, and at least one economizer, and at least one or more in the heat transfer unit. Providing the first stationary catalyst unit and performing the combustion In fluidized bed processing system and removing the N ₂ O in the gas.

The second aspect, in the first shot bright, the each of the combustion exhaust gas discharge line downstream of the fluidized bed boiler and the heat transfer section, by including a N ₂ O measurement meter for measuring the N ₂ O concentration The fluidized bed processing system is characterized.

A third invention is the fluidized bed processing system according to the first or second invention, further comprising an in-furnace catalyst supply unit for supplying the in-furnace supply catalyst into the fluidized bed boiler.

A fourth aspect based on the third aspect, as furnace catalyst feed supplied to the fluidized bed boiler, when supplying aluminum oxide, when the supply of the aluminum oxide is more than 30 wt%, prior Symbol hydrocarbon The fluidized bed processing system is characterized by switching from a reducing agent to ammonia.
According to a fifth invention, in the second or third invention, when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold, the supply amount of the hydrocarbon-based reducing agent is increased. In the processing system.

According to a sixth invention, in any one of the second to fifth inventions, when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold, the combustion temperature of the fluidized bed boiler is controlled to a high temperature side. The fluidized bed processing system is characterized.

A seventh invention is characterized in that, in any one of the third to sixth inventions, when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold, the supply amount of the in-furnace supply catalyst is increased. In fluidized bed processing system.

According to an eighth invention, in any one of the first to seventh inventions, a metal recovery means for recovering valuable metals from the dust removed by the dust removing device, and a catalyst supply for supplying the recovered metal to the combustion exhaust gas as a catalyst lying in the fluidized bed processing system according to claim comprising a part.

A ninth invention is the second stationary catalyst according to any one of the first to eighth inventions, which is provided in a combustion exhaust gas line on the downstream side of the heat transfer section and removes N ₂ O in the process gas. And a fluidized bed processing system.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, a branch / circulation line that returns after branching the combustion exhaust gas on the downstream side of the dust removing device is provided, and a heat exchanger and In the fluidized bed processing system, a third stationary catalyst unit is interposed to remove N ₂ O in the combustion exhaust gas.

  An eleventh invention is characterized in that, in any one of the first to tenth inventions, a ceramic filter is provided on the upstream side of the heat transfer section and carries a catalyst for removing dust in the processing gas. In a fluidized bed processing system.

In a twelfth aspect of the invention, a fluidized bed boiler for treating a supplied fuel with a fluidized bed combustion, a heat transfer unit for recovering heat of combustion exhaust gas discharged from the fluidized bed boiler, and a downstream side of the heat transfer unit An air preheater that preheats the air supplied to the fluidized bed boiler, a dust removing device that is provided on the downstream side of the air preheater to remove the dust in the combustion exhaust gas, and the fluidized bed boiler and the heat transfer And a reducing agent supply unit that supplies a hydrocarbon-based reducing agent mainly composed of propylene as a reducing agent that removes N ₂ O contained in the combustion exhaust gas. In addition, a branch / circulation line for branching the combustion exhaust gas on the downstream side of the dust removing device and then returning to the fluidized bed boiler side is provided, and a heat exchanger and a third stationary catalyst unit are interposed in the branch / circulation line. Otherwise, the N ₂ O of the combustion exhaust gas In fluidized bed processing system, characterized by removed by.

  A thirteenth invention is the fluidized bed treatment system according to any one of the first to twelfth inventions, wherein the fuel is at least one of biomass fuel, coal fuel, and petroleum coke fuel.

A fourteenth aspect of the invention relates to a heat transfer comprising at least one or more superheaters and at least one or more economizers for recovering the heat of combustion exhaust gas discharged from a fluidized bed boiler that performs a fluidized bed combustion process on supplied fuel. In the heat transfer section, at least one first stationary catalyst section is installed to remove N ₂ O in the combustion exhaust gas, and the combustion exhaust gas between the fluidized bed boiler and the heat transfer section N in the fluidized bed combustion exhaust gas, wherein a reduction treatment is performed by supplying a hydrocarbon hydrocarbon-based reducing agent mainly composed of propylene as a reducing agent for removing N ₂ O contained in the combustion exhaust gas to an exhaust line. ₂ O removal method.

A fifteenth invention, in the fourteenth invention, wherein the supplying a fluidized bed boiler furnace feed catalyst, N ₂ O of the fluidized bed combustion exhaust gas, characterized in that to suppress the generation of N ₂ O in the furnace In the removal method.
A sixteenth aspect of the present invention is first in the 15 invention, as furnace catalyst feed supplied to the fluidized bed boiler, when supplying aluminum oxide, when the supply of the aluminum oxide is more than 30 wt%, the charcoal hydrocarbon-based The present invention resides in a method for removing N ₂ O from a fluidized bed combustion exhaust gas, characterized by switching from a reducing agent to ammonia.

According to a seventeenth aspect of the present invention, in the fourteenth aspect of the invention, the fluidized bed boiler and the combustion exhaust gas discharge line on the downstream side of the heat transfer section each include an N ₂ O measuring meter for measuring the N ₂ O concentration. In the method of removing N ₂ O from fluidized bed combustion exhaust gas, control is performed to increase the supply amount of the hydrocarbon-based reducing agent when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold value. .

An eighteenth invention is the invention of the first 4 or the first 5, wherein each of the combustion exhaust gas discharge line downstream of the fluidized bed boiler and the heat transfer portion, N ₂ O measurement meter for measuring the N ₂ O concentration And a control device that controls the combustion temperature of the fluidized bed boiler to a high temperature side when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold value. ₂ O removal method.

A nineteenth invention is the in fifteenth invention, the each of the combustion exhaust gas discharge line downstream of the fluidized bed boiler and the heat transfer section, to measure the N ₂ O concentration meter, N ₂ O of the combustion exhaust gas A fluidized bed combustion exhaust gas N ₂ O removal method comprising: a control device that executes control to increase the supply amount of the in-furnace supply catalyst when the concentration exceeds a predetermined threshold value.

A twentieth aspect of the present invention uses any one of the fluidized bed processing systems according to any one of the first to thirteenth aspects, and first uses biomass fuel as the fuel, and then burns using coal fuel and / or petroleum coke fuel. This is a method for removing N ₂ O from fluidized bed combustion exhaust gas.

According to the fluidized bed processing system of the present invention, the content of nitrous oxide (N ₂ O) in the combustion exhaust gas discharged from the fluidized bed boiler can be greatly reduced.

FIG. 1 is a schematic diagram of a fluidized bed processing system according to the first embodiment. FIG. 2 is a schematic diagram of a fluidized bed processing system according to the second embodiment. FIG. 3 is a schematic diagram of a fluidized bed processing system according to the third embodiment. FIG. 4 is a relationship diagram of N ₂ O and NOx removal rates using ammonia and propylene. FIG. 5 is a relationship diagram between the supply amount of the in-furnace supply catalyst and the concentrations of N ₂ O and NOx.

  Exemplary embodiments of a fluidized bed processing system according to the present invention will be described below 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 fluidized bed processing system according to the first embodiment. FIG. 4 is a relationship diagram of N ₂ O and NOx removal rates using ammonia and propylene. FIG. 5 is a relationship diagram between the supply amount of the in-furnace supply catalyst and the concentrations of N ₂ O and NOx.
As shown in FIG. 1, a fluidized bed processing system 10A according to the present embodiment is a circulating fluidized bed that performs fluidized bed combustion processing of supplied fuel (biomass fuel F ₁ , coal fuel F ₂ , petroleum coke fuel F ₃ ) F. Boiler 11, heat transfer section 13 that recovers the heat of combustion exhaust gas 12 discharged from circulating fluidized bed boiler 11, and air that is provided on the downstream side of heat transfer section 13 and that is supplied to circulating fluidized bed boiler 11 14, an air preheater 15 that preheats 14, and a bag filter 16 that is provided on the downstream side of the air preheater 15 and removes the dust in the combustion exhaust gas 12. Has at least one superheater (two superheaters 13a ₁ and 13a _{2 in} this embodiment) and at least one economizer (two economizers 13b ₁ and 13b _{2 in} this embodiment). In the heat transfer section 13 Providing at least one or more first electrostatic standing catalyst unit 17, it is to remove the N ₂ O in the combustion exhaust gas 12.
In FIG. 1, reference numeral 18 is a chimney, L _{1 to} L ₄ are combustion exhaust gas discharge lines, L _{11 to} L ₁₃ are fuel supply lines, L ₁₄ is an air supply line for supplying air 14 to the circulating fluidized bed boiler 11, and L ₁₅ shows an activation fuel supply line for supplying the activation fuel 22 to the circulating fluidized bed boiler 11.

In the present embodiment, the second superheater 13a ₂ and the primary economizer 13b ₁ of the heat transfer section 13 are respectively located at two locations between the primary economizer 13b ₁ and the secondary economizer 13b ₂ . Although one stationary catalyst unit 17 is provided, the present invention is not limited to this.

The ash 23 from the circulating fluidized bed boiler 11 is cooled by a bed ash cooler 35 and separately collected and processed.
Further, the ash 26 recovered by the bag filter 16 is sent to a metal recovery means 24 for recovering the metal in the ash 26 via the ash recovery line L ₅ , where the recovered metal 25 is separated and then separately recovered and recovered. It is processed.
Metal recovery means recovering metal 25 recovered in 24 by flue catalyst supply unit 27, and supplied to the combustion exhaust gas line L _3, thereby exerting a metal catalysis with flue.

Further, a catalyst (Fe powder, activated carbon, etc.) is sprayed and added to a combustion exhaust gas line L ₃ on the upstream side of the bag filter 16 from a catalyst supply means (not shown) so that N ₂ O in the exhaust gas is further decomposed. Also good.

In the present embodiment, the second stationary catalyst unit 28 is further interposed in the combustion exhaust gas line L ₂ on the downstream side of the heat transfer unit 13, and the combustion exhaust gas 12 is normally disposed in the bypass exhaust gas line L _6. I try to flow.
Then, if necessary, the switching valve 29 is switched to allow the second stationary catalyst unit 28 to pass through to remove N ₂ O in the combustion exhaust gas 12.

Furthermore, in the present embodiment, an in-furnace catalyst supply unit 32 that supplies the in-furnace supply catalyst 31 via the catalyst line L ₇ is provided in the circulating fluidized bed boiler 11 and is discharged from the circulating fluidized bed boiler 11. N ₂ O in the combustion exhaust gas 12 is removed.

As a catalyst for reducing and removing N ₂ O used in each of the first stationary catalyst unit 17 and the second stationary catalyst unit 28 provided in the heat transfer unit 13 in this embodiment, for example, iron (Fe), Copper (Cu), zeolite catalyst supporting cobalt (Co), metallosilicate catalyst (iron (Fe), rhodium (Rh) exchange), noble metal catalyst (for example, rhodium (Rh), ruthenium (Ru), palladium (Pd), Iridium (Ir) and the like) and titanium oxide (TiO ₂ ).
Examples of the zeolite catalyst include a beta type catalyst, a ZSM-5 type catalyst, and a mordenite type catalyst.
The stationary catalyst is preferably a honeycomb catalyst.

Even in the heat transfer section 13, the temperature of the combustion exhaust gas 12 is 500 ° C. or less on the downstream side of the secondary superheater 13 a ₂ , and is about 350 ° C. on the downstream side of the primary economizer 13 b ₁ . A copper-based catalyst or the like exhibits a catalytic function.
Further, in order to exhibit the catalytic function of the honeycomb type catalyst, the catalytic activity is enhanced by heating means (indirect heating or direct heating) (not shown) as necessary.

  Moreover, as the catalyst shapes of the first stationary catalyst unit 17 and the second stationary catalyst unit 28, a honeycomb type catalyst is suitable.

In the present embodiment, a ceramic filter 19 for removing the dust in the combustion exhaust gas 12 discharged from the circulating fluidized bed boiler 11 is provided on the upstream side of the heat transfer section 13, and the first stationary catalyst section. The catalyst poisoning used in the 17 and the second stationary catalyst unit 28 is prevented.
Since this ceramic filter 19 is installed at a high temperature environment of about 900 ° C., it can carry a catalyst mainly composed of alumina having high temperature durability.
Thereby, N ₂ O can be efficiently removed.

In the present embodiment, a reducing agent supply unit 21 that supplies the reducing agent 20 into the combustion exhaust gas 12 is provided on the upstream side of the ceramic filter 19.
Here, the reducing agent 20 is supplied to promote the reduction process in the first stationary catalyst unit 17 provided in the heat transfer unit 13.

  Examples of the reducing agent 20 include nitrogen-based reducing agents such as ammonia and urea, hydrocarbon-based reducing agents such as methane, ethane, propane, propylene, methanol, and dimethyl ether, hydrogen, CO, and the like.

In particular, as the reducing agent 20, propylene is preferable in terms of N ₂ O removal since the removal rate of N ₂ O is higher than that of ammonia as shown in FIG.
This test uses an iron catalyst as the catalyst, the combustion temperature is 500 ° C., N ₂ O is included in the simulated combustion exhaust gas, and the N ₂ O removal rate due to the difference in the reducing agent (ammonia: 114 ppm, propylene: 140 ppm). Asked.

As shown in the results of FIG. 4, ammonia was effective as a reducing agent for denitration, but the removal rate of N ₂ O was slightly low (70%).
In contrast, propylene was ineffective as a denitration function, but the N ₂ O removal rate was as high as 97%.

When the N ₂ O concentration in the combustion exhaust gas 12 exceeds a predetermined threshold, the supply amount of the reducing agent 20 is gradually increased to efficiently remove N ₂ O.

Even when the reducing agent 20 is not supplied, if the N ₂ O can be removed by the catalytic activity of the stationary catalyst part, the reducing agent 20 may be supplied as appropriate. , Not necessarily supply.

Here, the content of N ₂ O contained in the combustion exhaust gas 12 is obtained by an N ₂ O measuring meter (N ₂ O sensor) 30, for example, combustion exhaust gas on the downstream side of the circulating fluidized bed boiler 11. line L _1, the combustion exhaust gas line L ₂ of the downstream side after the heat transfer section 13, each provided in necessary places, such as the combustion exhaust gas line L ₂ of the downstream side after the second static standing catalyst unit 28, the N ₂ O concentration I am trying to measure.

Examples of the N ₂ O sensor 30 include a detector using a non-dispersive infrared absorption method (NDIR method) and a gas chromatograph / electron capture detector (ECD). It is not limited to.

When the N ₂ O concentration in the combustion exhaust gas 12 is high, the combustion of the circulating fluidized bed boiler 11 is controlled, the fuel type is changed, the type of the reducing agent 20 is changed as appropriate, and the amount of N ₂ O discharged Maintains a predetermined emission standard.

Here, means for reducing the N ₂ O emission amount by controlling the fuel will be described.
As the fuel F, for example, in addition to the biomass fuel F ₁ , which generates less N ₂ O than the coal fuel F ₂ or the like, for example, waste tires, industrial waste solidified materials (for example, Refuse Derived Fuel: RDF, Refuse Paper & Plastic Fuel (RPF)), sludge ash fuel, etc. can be used.

First, as the fuel F, for example, biomass fuel F ₁ is used, and combustion is started in the circulating fluidized bed boiler 11. The combustion start temperature is assumed to be from 850 ° C., which is an upper limit temperature of 800 ° C. to 850 ° C., which is a preferable combustion temperature in the circulating fluidized bed boiler 11.

In general, the combustion of biomass fuel F ₁ is considered to generate little N ₂ O, but due to differences in the composition and type of biomass fuel F ₁ , if combustion is continued for a predetermined time at 850 ° C., the concentration of N ₂ O May reach a predetermined reference value (for example, 10 ppm).
When this predetermined standard is reached, the combustion temperature is set slightly higher (for example, 860 ° C.), and the amount of N ₂ O generated is reduced by high-temperature combustion.

Thus, by using the biomass fuel F _1, it is possible to maintain the combustion of the low N ₂ O.
When the removal of N ₂ O in the heat transfer section 13 is appropriate, the catalyst in the second stationary catalyst section 28 and the flue catalyst supply section 27 on the downstream side is not necessary.

Therefore, in this case, the combustion exhaust gas 12 is allowed to pass through the bypass exhaust gas line L ₆ that bypasses the second stationary catalyst unit 28, and the supply of the recovered metal 25 is stopped.
In contrast, in N ₂ O sensor 30 installed in the combustion exhaust gas line L ₂ of the downstream side of the downstream side of the combustion exhaust gas line L ₂ and the second electrostatic standing catalyst portion 28 of the heat transfer section 13, N ₂ O When the concentration exceeds a predetermined value (10 ppm), the switching valve 29 is switched so as to pass through the second stationary catalyst unit 28 or the supply of the recovered metal 25 is started to remove N ₂ O. I am doing so.

In addition, even if it is below a normal predetermined value (N ₂ O: 10 ppm), N ₂ O is removed by passing and supplying these catalysts. Therefore, N ₂ O discharged from the chimney 18 to the outside is removed. It can contribute to lowering the emission concentration.

Then, when measures are taken to reduce N ₂ O by increasing the combustion temperature, for example, when the temperature reaches 900 ° C., the fuel F is switched from, for example, biomass fuel F ₁ to coal fuel F ₂ and petroleum coke fuel F ₃ to flow Continue layer combustion.

When combustion is performed using coal fuel F ₂ or petroleum coke fuel F ₃ having a large amount of fixed carbon, in addition to removal of N ₂ O by a stationary catalyst, an in-furnace supply catalyst 31 is further supplied from the in-furnace catalyst supply unit 32. Is gradually introduced into the circulating fluidized bed boiler 11 to decompose and remove N ₂ O in the circulating fluidized state, and the N ₂ O concentration of the combustion exhaust gas 12 discharged from the circulating fluidized bed boiler 11 is discharged from the biomass fuel F ₁ . The N ₂ O sensor 30 is used to monitor and reduce the amount to the same level as the amount.

Accordingly, in the stationary catalyst, the first stationary catalyst unit 17 and / or the second stationary catalyst unit 28 similar to the N ₂ O concentration in the combustion exhaust gas 12 when using the biomass fuel F ₁ is used. This process can reduce N ₂ O.

Here, as the furnace supply catalyst 31, for example, aluminum oxide (alumina: Al ₂ O ₃ ), calcium oxide (CaO), or the like can be used.

  Here, the supply amount of the in-furnace supply catalyst 31 supplied to the circulating fluidized bed boiler 11 may be 100% that completely replaces the fluidized material. In this case, since the supply amount of the in-furnace supply catalyst 31 is increased, the running cost is increased.

Further, as described above with reference to FIG. 4, ammonia is effective as a reducing agent for denitration, but the removal rate of N ₂ O is slightly low (70%).
On the other hand, propylene is ineffective as a denitration function, but the removal rate of N ₂ O is as high as 97%. Therefore, in the case where the in-furnace supply catalyst 31 is supplied and the reducing agent 20 is used, first propylene is used. After that, when the supply of alumina serving as the in-furnace supply catalyst 31 exceeds 30 wt%, it is possible to efficiently remove N ₂ O by switching to ammonia.

In this case, when alumina is supplied as the in-furnace supply catalyst 31, since NOx is not generated at the beginning of supply, N ₂ O removal is performed using propylene. Then, when the supply of alumina is increased and the amount of NOx generated due to the action as an oxidation catalyst increases, when the alumina supply exceeds 30 wt%, the reducing agent 20 is switched from propylene to ammonia so that denitration is efficiently performed. Yes.
Be switched reducing agent 20 to ammonia, as shown in FIG. 5, the concentration of N ₂ O is reduced, even those slightly lower N ₂ O removal efficiency compared to propylene, N ₂ O removal is surely performed.

In this manner, the biomass fuel F ₁ is sequentially switched from the coal fuel F _{2 to} the petroleum coke fuel F ₃ and burned in the circulating fluidized bed boiler 11. As a result, the N ₂ O sensor 30 exceeds the predetermined reference value. In this case, if the operation is continued any longer, N ₂ O exceeding the reference value is released to the outside together with the combustion exhaust gas 12, so that the N ₂ O emission from the current fuel state (for example, petroleum coke fuel F ₃ ). The biomass fuel F ₁ is reduced and the combustion is restarted at 850 ° C.
Thus, by using the biomass fuel F ₁ low emissions of N ₂ O, it is possible to continue the operation.

As described above with reference to the embodiments, according to the present invention, N ₂ O in combustion exhaust gas can be efficiently removed when combustion is performed in a fluidized bed boiler using different types of fuel. As a result, the fluidized bed boiler combustion can be performed with a low warming coefficient of 310 times that of carbon dioxide (CO ₂ ) and low N ₂ O emission.

Note that, in the decomposition treatment of N ₂ O by the in-furnace mixed catalyst method in the circulating fluidized bed boiler 11 using the in-furnace supplied catalyst, the consumption amount of the input catalyst becomes the running cost as it is, so that it is steady. It can be difficult to operate.
However, when the fuel type is various and it is necessary to follow load fluctuations such as factory operation, the combined use with the decomposition treatment of N ₂ O by the stationary catalyst parts 17 and 28 with low running cost is possible. , Fluidized bed boiler combustion with less N ₂ O emission can be performed.

  Further, in this embodiment, the circulating type circulating fluidized bed boiler is used as the fluidized bed boiler. However, the present invention is not limited to this, and may be applied to, for example, a bubble type fluidized bed boiler. it can.

FIG. 2 is a schematic diagram of a fluidized bed processing system according to the second embodiment. The same members as those in the fluidized bed processing system according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
As shown in FIG. 2, the fluidized bed processing system 10B according to the present embodiment branches and circulates the exhaust gas from the combustion exhaust gas line L ₄ on the downstream side of the bag filter 16 and then returns to the circulating fluidized bed boiler 11 side. A line L ₈ is provided, and a heat exchanger 36 and a third stationary catalyst unit 37 are interposed in the branch / circulation line L ₈ .

Some fuel F in the circulating fluidized bed boiler 11 has a large amount of dust in the fuel exhaust gas 12. In the case of treating such combustion exhaust gas 12, dust is removed by the bag filter 16, the exhaust gas is reheated by the heat exchanger 36, and then the N ₂ O is decomposed and passed through the third stationary catalyst 37. Can be removed.

As a catalyst for reducing and removing N ₂ O used in the third stationary catalyst unit 37, for example, a zeolite catalyst supporting iron (Fe), copper (Cu), cobalt (Co), a metallosilicate catalyst (iron ( Fe), rhodium (Rh) exchange), noble metal catalysts (for example, rhodium (Rh), ruthenium (Ru), palladium (Pd), iridium (Ir), etc.) and titanium oxide (TiO ₂ ). Examples of the zeolite catalyst include a beta type catalyst, a ZSM-5 type catalyst, and a mordenite type catalyst. The stationary catalyst is preferably a honeycomb catalyst.

The reheating of the combustion exhaust gas 12 may be either indirect heating or direct heating. For example, in the case of indirect heating, as shown in FIG. 2, the heat exchanger 36 of the fluidized bed inner tube of the circulating fluidized bed boiler 11 is used. Heat exchange is performed, for example, the temperature is raised to about 300 to 400 ° C., and then the heated exhaust gas is passed through the third stationary catalyst unit 37 to decompose and remove N ₂ O in the exhaust gas.

In the case where bypass lines L ₂₀ , L ₂₁ , and L ₂₂ that bypass the ceramic filter 19 and the first stationary catalyst parts 17 and 17 in the heat transfer part 13 are provided, and the dust concentration in the combustion exhaust gas 12 is high. The switching valve 29 is switched to pass through the first stationary catalyst unit 17 and the second stationary catalyst unit 28 and dust is removed by the bag filter 16, and then the switching valve 33 is switched to change the combustion exhaust gas 12. After being introduced into the branch / circulation line L ₈ and heated by the heat exchanger 36, the exhaust gas is heated by passing through the third stationary catalyst unit 37 to decompose and remove N ₂ O in the exhaust gas. ing.

As a result, in the case of the combustion exhaust gas 12 with a large amount of dust, the ceramic filter 19, the first stationary catalyst parts 17, 17 and the second stationary catalyst part 28 are bypassed to poison these catalysts. After the dust is removed by the bag filter 16, the switching valve 33 is switched, the combustion exhaust gas 12 is introduced into the branching / circulation line L ₈ , heated by the heat exchanger 36, and then supplied to the third stationary catalyst 37. By aeration, N ₂ O in the combustion exhaust gas 12 can be decomposed and removed.

FIG. 3 is a schematic diagram of a fluidized bed processing system according to the third embodiment. The same members as those in the fluidized bed processing systems of Examples 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted.
As shown in FIG. 3, the fluidized bed processing system 10 </ b> C according to the present embodiment is provided with a branch / circulation line L ₈ that branches from the combustion exhaust gas line L ₄ on the downstream side of the bag filter 16. A heat exchanger 36 and a third stationary catalyst unit 37 are interposed in L ₈ .
In this embodiment, a heat exchanger 36 is installed in a bed ash cooler 35 that cools the ash 23 discharged from the circulating fluidized bed boiler 11, and the exhaust gas is heat-exchanged and raised to, for example, about 300 to 400 ° C. The gas is passed through the third stationary catalyst unit 37 to decompose and remove N ₂ O in the exhaust gas.

Here, in Examples 2 and 3, the third stationary catalyst unit 37 is added to the fluidized bed processing system in which the ceramic filter 19, the first stationary catalyst units 17 and 17, and the second stationary catalyst unit 28 are installed. The added type is illustrated as a combined type, but the present invention is not limited to this, and the ceramic filter 19, the first stationary catalyst parts 17 and 17, and the second stationary catalyst part 28 are installed. In a non-treatment system, the branch / circulation line L _{8 is provided} with a heat exchanger 36 and a third stationary catalyst unit 37, dust is removed by the bag filter 16, and the exhaust gas is reheated by the heat exchanger 36. Thereafter, N ₂ O in the combustion exhaust gas 12 having a high dust concentration may be decomposed and removed through the third stationary catalyst unit 37.

10A to 10C Fluidized bed treatment system 11 Circulating fluidized bed boiler 12 Combustion exhaust gas 13 Heat transfer unit 14 Air 15 Air preheater 16 Bag filter 17 First stationary catalyst unit 20 Reducing agent 21 Reducing agent supply unit 28 Second stationary type Catalyst part 31 Furnace supplied catalyst 36 Heat exchanger 37 Third stationary catalyst part F ₁ biomass fuel F ₂ coal fuel F ₃ petroleum coke fuel

Claims (20)

A fluidized bed boiler for subjecting the supplied fuel to fluidized bed combustion processing;
A heat transfer section for recovering the heat of the combustion exhaust gas discharged from the fluidized bed boiler;
An air preheater that is provided on the downstream side of the heat transfer section and preheats the air supplied to the fluidized bed boiler;
A dust removing device that is provided on the downstream side of the air preheater and removes the dust in the combustion exhaust gas;
The flue gas discharge line between the fluidized bed boiler and the heat transfer section, reducing supplies coal hydrocarbon-based reducing agent mainly composed of propylene as a reducing agent for removing N _{2 O} contained in the combustion exhaust gas An agent supply unit,
The heat transfer section includes at least one superheater and at least one economizer, and at least one or more first stationary catalyst sections are provided in the heat transfer section, and the combustion exhaust gas A fluidized bed processing system characterized by removing N ₂ O therein. In claim 1,
Each of the fluidized bed boiler and the combustion exhaust gas discharge line on the downstream side of the heat transfer section includes an N ₂ O measuring meter for measuring the N ₂ O concentration. In claim 1 or 2,
An in-furnace catalyst supply unit for supplying an in-furnace supply catalyst into the fluidized bed boiler. In claim 3,
As supplies furnace supply catalyst to the fluidized bed boiler, when supplying aluminum oxide, flow the supply of oxidation Aruminimu is when more than 30 wt%, and switches from the previous SL hydrocarbon reductant to ammonia Layer processing system. In claim 2 or 3,
A fluidized bed treatment system, wherein when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold, the supply amount of the hydrocarbon-based reducing agent is increased. In any one of Claims 2 thru | or 5,
A fluidized bed treatment system that controls the combustion temperature of the fluidized bed boiler to a high temperature side when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold value. In any one of Claims 3 thru | or 6,
A fluidized bed treatment system, wherein when the concentration of N ₂ O in the combustion exhaust gas exceeds a predetermined threshold, the supply amount of the catalyst supplied in the furnace is increased. In any one of Claims 1 thru | or 7,
Metal recovery means for recovering valuable metals from the dust removed by the dust remover;
A fluidized bed processing system comprising a catalyst supply unit that supplies recovered metal as a catalyst to combustion exhaust gas. In any one of Claims 1 to 8,
A fluidized bed processing system comprising a second stationary catalyst unit that is provided in a combustion exhaust gas line on the downstream side of the heat transfer unit and removes N ₂ O in the processing gas. In any one of Claims 1 thru | or 9,
A branch / circulation line for branching and returning the flue gas on the downstream side of the dust remover is provided, and a heat exchanger and a third stationary catalyst unit are interposed in the branch / circulate line, so that N in the flue gas A fluidized bed treatment system characterized by removing ₂ O. In any one of Claims 1 thru | or 10,
A fluidized bed processing system comprising a ceramic filter provided on the upstream side of the heat transfer section and carrying a catalyst for removing dust in the processing gas. A fluidized bed boiler for subjecting the supplied fuel to fluidized bed combustion processing;
A heat transfer section for recovering the heat of the combustion exhaust gas discharged from the fluidized bed boiler;
An air preheater that is provided on the downstream side of the heat transfer section and preheats the air supplied to the fluidized bed boiler;
A dust removing device that is provided on the downstream side of the air preheater and removes the dust in the combustion exhaust gas;
A reducing agent that supplies a hydrocarbon-based reducing agent mainly composed of propylene as a reducing agent that removes N ₂ O contained in the combustion exhaust gas to a combustion exhaust gas discharge line between the fluidized bed boiler and the heat transfer section. A supply unit;
After branching the flue gas on the downstream side of the dust remover, a branch / circulation line is provided to return to the fluidized bed boiler, and a heat exchanger and a third stationary catalyst unit are interposed in the branch / circulation line. A fluidized bed processing system, wherein N ₂ O in the combustion exhaust gas is removed. In any one of claims 1 to 12,
The fluidized bed processing system, wherein the fuel is at least one of biomass fuel, coal fuel, and petroleum coke fuel. In a heat transfer section comprising at least one superheater and at least one economizer that recovers the heat of combustion exhaust gas discharged from a fluidized bed boiler that processes the supplied fuel in a fluidized bed combustion process,
In the heat transfer part, at least one or more first stationary catalyst parts are installed to remove N ₂ O in the combustion exhaust gas,
Reduction is performed by supplying a hydrocarbon-based reducing agent mainly composed of propylene as a reducing agent for removing N ₂ O contained in the combustion exhaust gas to the combustion exhaust gas discharge line between the fluidized bed boiler and the heat transfer section. A method for removing N ₂ O from fluidized bed combustion exhaust gas, characterized by comprising: In claim 14,
A method for removing N ₂ O from a fluidized bed combustion exhaust gas, characterized in that an in-furnace supply catalyst is supplied to the fluidized bed boiler to suppress generation of N ₂ O in the furnace. In claim 15,
As supplies furnace supply catalyst to the fluidized bed boiler, when supplying aluminum oxide, flow the supply of the aluminum oxide is in the case of more than 30 wt%, and switches the ammonia from the coal hydrocarbon-based reducing agent A method for removing N ₂ O from bed combustion exhaust gas. In claim 14,
Each of the fluidized bed boiler and the combustion exhaust gas discharge line on the downstream side of the heat transfer section is provided with an N ₂ O meter for measuring the N ₂ O concentration,
A method for removing N ₂ O from fluidized bed combustion exhaust gas, wherein control is performed to increase the supply amount of the hydrocarbon-based reducing agent when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold value. In claim 14 or 15,
Each of the fluidized bed boiler and the combustion exhaust gas discharge line on the downstream side of the heat transfer section is provided with an N ₂ O meter for measuring the N ₂ O concentration,
A method for removing N ₂ O from fluidized bed combustion exhaust gas, comprising a control device for controlling the combustion temperature of the fluidized bed boiler to a high temperature side when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold value. . In claim 15,
Measure the N ₂ O concentration in each of the fluidized bed boiler and the combustion exhaust gas discharge line on the downstream side of the heat transfer section,
A method for removing N ₂ O from fluidized bed combustion exhaust gas, wherein control is performed to increase the supply amount of the catalyst supplied in the furnace when the N ₂ O concentration in the combustion exhaust gas exceeds a predetermined threshold value. Using the fluidized bed processing system according to any one of claims 1 to 13,
A method for removing N ₂ O from fluidized bed combustion exhaust gas, characterized in that the fuel is first burned using biomass fuel and then burned using coal fuel and / or petroleum coke fuel.

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