JPH01299621A - Removal of alkali metal compound in combustion gas at high temperature and under high pressure - Google Patents

Abstract

PURPOSE:To remove alkali metal compds. in combustion gas at high temp. and under high pressure and to prevent a gas turbine from troubles by allowing dedusted combustion gas at high temp. and under high pressure to contact with a bed contg. a transition metal oxide such as activated alumina as reaction medium. CONSTITUTION:When a turbine is driven with a gas from a compressed fluidized bed furnace, coal gasification furnace, etc., to recover energy, combustion gas at high temp. and under high pressure is dedusted at first by introducing the gas into dust collectors 5, 6. The combustion gas is then fed to an alkali removing apparatus 1, where it is allowed to contact with a packed bed or fluidized bed comprising granular transition metal oxide such as activated alumina, activated silica, as reaction medium. Thus, the vapor and the mist of the alkali metal compds. in the combustion gas are removed. The gas is then fed to an expansion gas turbine 2 to perform a work. Thus, alkali metals which deposit easily to turbine blades are removed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to introducing high-temperature and high-pressure combustion gas generated from a pressurized fluidized bed furnace, a coal gasification furnace, a pressurized coal partial combustion furnace, etc. into an expansion gas turbine. The present invention relates to a method for removing alkali metal compounds from high-temperature, high-pressure combustion gas in a plant that recovers energy.

[Conventional technology]

In recent years, due to a review of thermal power plants that fire solid fuels such as coal, thermal power plants that use pulverized coal-fired boilers are being constructed. Also, nitrogen oxides (NOX), sulfur oxides (SOx)
), atmospheric pressure fluidized bed furnace (hereinafter referred to as A
A thermal power plant equipped with a boiler (called FBC) is being constructed.

In this case, in a thermal power plant using APBC, fuel such as coal is burned in a furnace in the same way as a pulverized coal-fired boiler, the thermal energy is turned into steam in the boiler, and the energy is converted into electricity in a steam turbine.

In this sense, a thermal power plant that uses AFBC is systemically similar to a pulverized coal-fired boiler.

On the other hand, as shown in FIG. 4, a method is known in which combustion is performed in a fluidized bed furnace at a pressure higher than atmospheric pressure, and this method is called a pressurized fluidized bed furnace 1 (hereinafter referred to as PFBC1). The gas conditions at the outlet of this PFBC1 are typically pressures from about 10 bar to 30 bar and temperatures from 800 to 10 bar.
00°C is common. Further, the gas at the outlet of the PFBC 1 contains a large amount of fine dust such as combustion ash and desulfurizing agent. Generally, the pressure and sensible heat energy of combustion gas discharged from PFBC are used to generate an expansion gas turbine 2.
(hereinafter referred to as gas turbine 2) drives a generator 3 and an air compressor 4 for supplying and pressurizing combustion air.

Before the combustion gas is introduced into the gas turbine 2, the fine dust contained in the combustion gas is sufficiently removed by the primary dust collector JA5 and the secondary dust collector 6, and the contact parts such as the blades and vanes of the gas turbine 2 are thoroughly removed. Prevents wear and tear on the gas section. 1st f! dust machine 5
For example, a single-stage cyclone or a multi-stage cyclone is used, and as a secondary dust collector, a ceramic ivy filter, an electric dust collector, a so-called granular filter using bag filter-1 gravel, etc. are used. Note that 7 is a waste heat boiler, 8 is a boiler heat exchanger tube, and the generated steam is guided to a steam turbine generator (not shown) and used for power generation.
As described above, similarly to the case of PFBC, the coal gasification furnace and the pressurized coal partial combustion furnace have basically the same configuration.

[Problem that the invention seeks to solve]

Coal used as fuel contains alkali metals such as Na and X. In particular, imported coal that is affected by seawater due to sea transport and coal from areas where groundwater is salty contains a lot of chloride as NaCl and KCI. In addition, there are various alkali metal compounds such as Na and K, but these alkali metal compounds generally have low melting points, often in the range of 400 to 900°C. Furthermore, the compound of − part, for example NaCl5
C1 shows a high steam partial pressure at 800-1000℃, which is the operating temperature of the fluidized bed, and the NaC contained in the coal
1. Most of KCI volatilizes and becomes vapor. The steamed NaC1 and MCI pass through the primary dust collector and secondary dust collector and reach the gas turbine. As the gas temperature drops, the steam condenses or reacts with Sot in the gas to form NagSO.
In addition, it becomes SO, etc., becomes a liquid or semi-molten solid solution, or a solid mist, which adheres to the gas turbine blades.

Alkali metal deposits not only reduce turbine efficiency due to changes in blade shape, but also react with and corrode turbine blade metal due to complex reactions unique to alkali metal compounds, leading to a decrease in efficiency due to blade deformation. beginning, damage, folding)
This may cause damage to employees, etc.

The present invention has been made in order to eliminate the adverse effects caused by alkali metal compounds on gas turbines.

In addition, “Activated Bauxite an
d DiatomaceousEar thυsad
as Granular 5orbents for
the Removalof Alkali Vapo
rs from Simulated Hot Flu
e Gasof PFBCs” 5heldon H
, D., Lee, William M., 5w1ft an
dIrving Johnson ;^rgonne
National Laboratory.

In 1980, a method of adsorbing alkali vapor with activated bauxite, diatomaceous earth, etc. was reported as an experimental result. However, these methods do not address the high temperature, high pressure gas with high dust concentration discharged from PFBC, which actually occurs as described above. In other words, even if high-temperature, high-pressure, and high-dust-concentration combustion gas is directly treated in a fluidized bed or moving bed type alkali vapor adsorption device (dealkalization device), dust (ash) will remain in the fluidized bed or moving bed. The dust accumulates immediately, and no adsorption reaction can be expected. On the other hand, even if these dusts are continuously discharged from the system, it is difficult to separate the dust from the adsorbent (for example, activated bauxite), and a large amount of heat is generated. This results in losses and loss of adsorbent. In addition, in order to perform an ideal adsorption reaction, a large amount of adsorbent (reaction medium) is required relative to the amount of alkali metal compound in the gas, which also causes a large heat loss and also a large loss of adsorbent. Become.

Furthermore, Japanese Patent Application Laid-open No. 58-128422 discloses a method and apparatus for burning solid fuel using a pressurized fluidized bed combustion furnace, removing dust from the combustion gas, and then introducing it into a gas turbine to generate electricity. However, there is no mention of the removal of alkali metal compounds from combustion gas.

The present invention has been developed in view of the above points, and by efficiently removing the vapor of alkali metal compounds in high-temperature, high-pressure combustion gas, it prevents a decrease in efficiency inside the gas turbine and prevents corrosion within the gas turbine. The purpose is to provide a method that can reduce the amount of water used. Coal gasifier (not shown), coal partial combustion furnace (not shown)
The same problems as in the case of the above-mentioned pressurized fluidized bed furnace occur in the case of the pressurized fluidized bed furnace (because energy recovery is performed by the expansion turbine).

[Means and effects for solving the problem] In order to achieve the above object, the method for removing alkali metal compounds from high-temperature, high-pressure combustion gas of the present invention involves dedusting high-temperature, high-pressure dust-containing combustion gas. After treatment, the high-temperature, high-pressure combustion gas after dedusting is introduced into an expansion turbine and the temperature energy and pressure energy of this gas are used to generate power or other power. The alkali metals contained in the gas are brought into contact with a packed bed or moving bed in which granules of one or more transition metal oxides selected from the group consisting of iron, silicic acid, or titanium oxide are used as a reaction medium. It is characterized by the removal of compound vapors and mist.

In the method of the present invention, activated alumina (Altoz,
Actually bauxite), activated silica (Sing), ferric oxide (Fe*Os, actually iron ore), silicic acid (xsiO
Granules and recycled granules (hereinafter simply referred to as granules) of transition metal oxides such as titanium oxide (TiO, actually diatomaceous earth) and titanium oxide (TiO, actually titanium ore) are used as adsorbents.

Below, a chemical reaction formula for adsorbing NaCI onto activated alumina and activated silica at 950 to 800°C will be illustrated.

2NaC1+HzO+ ^IzOt→NazO・Al2
O3+2HC1 (gas) (gas) (solid) (solid) (gas) Similar reactions are performed for other adsorbents.

On the other hand, the same applies to MCI. Furthermore, the carbonates NatCO3 and 2CO1 may exit the furnace as heem or mist, but this is adsorbed by the following reaction.

In the above reaction formula, a similar reaction occurs even if alumina (^h(h)) is used instead of iron oxide (Fe□0.).

Each of these reactions is the principle utilized in the present invention. For example, sodium aluminate (NatO・＾1□0゜ or NazA1104) and sodium ferrate (Nano・Fe
Both zO and NagFegOJ have melting points exceeding 1300°C.

In order to promote these adsorption reactions, the reaction medium is made into granules, formed into a packed bed or a moving bed, and the particle size of the granules placed in the high temperature and high pressure combustion gas is in the range of 0.5 to foam. However, an average particle size of 1.0 to 3.0 am is preferred in order to increase the contact area with the gas and to make the behavior of the particulates suitable in the packed bed or the moving bed.

If the particle size is less than 0.5 mm, the reaction contact surface of each particle increases, but unless the speed of passing gas is extremely reduced, the particle, which is the reaction medium, will jump out of the reaction layer. Therefore, there is a disadvantage that there is a risk of failure such as blow-through in a part of the moving bed or packed bed, especially when the gas flow rate or pressure changes suddenly such as when starting or stopping.
On the other hand, when the particle size exceeds low, the reaction efficiency decreases due to an extreme reduction in the contact surface with the gas. Furthermore, if the lumps are too large, it becomes difficult to form a moving bed or a packed bed and to handle them.

It is better to keep the particle size distribution as uniform as possible to improve the reaction effect and to facilitate handling and equipment design.

The reaction medium initially supplied is diatomaceous earth, bauxite, naturally occurring activated silica such as iron ore, activated alumina,
Active ferric oxide and active titanium oxide with an average particle size of 1.0~
It should be around 3.0 dragons and used with undercut of less than 0.51.

In order to keep the active reaction medium effective for a long time, the dust concentration in the combustion gas is kept below 100 7 N-3.

Preferably, it is below the local environmental standards and below the technical constraints for the expansion turbine. For example, 50■/
Nm' or less or 101 mg/Nm' or less. That is, although the packed bed or the moving bed has the ability to collect dust, this function is not exerted as much as possible, and only the adsorption reaction is performed.

In addition, in the method of the present invention, the reaction medium is continuously or intermittently extracted from the system, washed with water or hot water to remove the alkali metal component by dissolving it in water, and the regenerated reaction medium with a large particle size after washing is removed. Dehydrate, dry and reuse.

That is, during use, the reaction medium is continuously or intermittently removed from the system and washed with water, preferably hot water.

As a result of this washing, in the case of aluminum oxide and iron oxide, the reaction occurs as follows, and the alkali metal component is dissolved in water.

For example, soda-based sodium silicate (NazSiOs)
Since it is soluble in water, the reacted sodium component is directly discharged from the system along with the water. Also, sodium ferrate (Na
JL”zOn), sodium aluminate (Na□Alto4
), a hydrolysis reaction occurs in the following reaction, and caustic soda (
NaOH) and water-soluble soda compounds, such as some sodium aluminate and alumina (8hos) and iron oxide (FeJs).

NaJ8zOa + 2HxO→2NaOH+ Fez
es ↓NazAlzOn +2HzO-2NaOH
+AIgOs ↓A similar reaction occurs in the case of potassium. This hot water washing removes Na components and at the same time
Separates and removes the reaction medium and dust that have become pulverized during the adsorption reaction or handling. The washed and separated regenerated reaction medium having a large particle size is dehydrated and dried, and returned to the dealkalization apparatus consisting of a packed bed or a moving bed in order to be used again as a regenerated reaction medium in the adsorption reaction. The particles of the recycled granules become porous through the reaction, increasing the reaction area and exerting a great effect on the reaction when reused. According to the results of actual measurement of the specific surface area, assuming that the specific surface area of the new reaction medium is 1, it is 7 to 15 at the first regeneration, and 10 at the second and subsequent regenerations.
~25.

Furthermore, in the method of the present invention, wastewater containing a finely divided reaction medium generated when washing with water or hot water to remove alkali metal components is precipitated to separate water and a finely divided precipitate. After dehydrating and drying the waste W, this fine powder is
A water-soluble binder such as honey, pulp waste liquid, starch aqueous solution, or water glass aqueous solution is added and granulated, and the granulated product is reused as a reaction medium.

That is, the above-mentioned pulverized reaction medium is transferred to waste water by washing with water, and the waste water is subjected to precipitation treatment to separate fine powder.The separated precipitate is dehydrated and dried.

The degree of dryness is set to a moisture content of 15% or less, preferably 5% or less.

The regenerated reaction medium in fine powder is granulated using a water-soluble binder such as blackstrap molasses, valve waste liquid, starch aqueous solution, or water glass aqueous solution. The granulation method is either kneading well with a small amount of binder and compression granulation, or granulation using a rotating plate type granulator.
Either method of granulation using a drum may be used. The granulation method can be arbitrarily changed depending on the type and amount of the binder, the particle size of the recycled fine powder, residual moisture, etc.

Advantageously, the binder contains small amounts of combustible organic matter. That is, waste water honey, starch aqueous solution, valve waste liquid, etc. are suitable as binders. The organic matter in the binder reacts with excess oxygen in the hot combustion gas and burns. This contributes to the sintering of the granules during combustion and increases their strength. Further, after the organic matter is combusted (gasified), the granulated material becomes porous, the reaction active area increases, and the reactivity becomes better than that of the granular regenerated reaction medium, resulting in a good effect.

〔Example〕

Examples of the present invention will be described below. FIG. 1 shows a pressurized fluidized bed power plant with a dealkalization device for carrying out the method of the present invention, FIG. 2 shows details of the dealkalization device in FIG. 1, and FIG. 3 shows a regeneration plant in FIG. Showing details of the device.

FIG. 1 shows a conventional pressurized fluidized bed power generation plant shown in FIG. 4, in which a dealkalization device 10 is installed downstream of the secondary dust collector, and a regenerator 11 is connected to the bottom of this dealkalization device 10. It is something.

The pressurized fluidized bed furnace 1 is operated at about 950° C. and about 16 bar, and the high temperature and high pressure combustion gas contains about 2 kg/Nm' of dust. This combustion gas is introduced into the primary dust collector 5 to remove large particle size dust, and then the combustion gas (approximately 100 g/Nm2 of dust) is introduced into the secondary dust collector 6 to remove small particle size dust. Next, combustion gas (dust about 50■/
Nm'') is introduced into the dealkalization device 10 to remove the vapor and mist of the alkali metal compound in the combustion gas,
After being supplied to the expansion gas turbine 2 to do work, the heat is recovered by the waste heat boiler 7 and released to the atmosphere. The gas temperature at the outlet of the dealkalizer 10 is about 900°C, the gas temperature at the outlet of the gas turbine 2 is about 350°C, and the pressure is about 1.03 bar.

As shown in FIG. 2, the dealkalization device 10 is formed by filling a particulate reaction medium 13 between air permeable supports 12, 12 such as louvers, punched metal, wire mesh, etc. 1
4 is a gas inlet, 15 is a gas outlet, 16 is a reaction medium inlet,
17 is a reaction medium outlet, and 18 is a rock feeder.

Note that a current plate 20 is provided as necessary.

The gas introduced from the gas outlet 14 contains vapor and mist of an alkali metal compound of about 20 ppm as Na, and the gas discharged from the gas outlet 15 contains about 0.5 ppm as NatO. ~0.2p of alkali metal compound vapors and mist are included. De-A/L
/The gas velocity inside the potash device 10 is approximately 0.1w/in linear velocity.
s~0.2m8, and the moving speed of the reaction medium is about 1oc
a110r or less. Further, the pressure loss (ΔP) of the dealkalizer 10 is about 10 to 1100 a water column. Note that the above numerical values are shown as an example, and are not limited thereto.

The reaction medium adsorbing the vapor and mist of the alkali metal compound is discharged from the reaction medium outlet 17 and introduced into the regenerator 11 shown in FIG. 3. That is, the used reaction medium is first introduced into a hydrolysis tank 21 and hydrolyzed, then washed with water or warm water in a water washer 22, and then washed with water or hot water in an underwater classifier 23 to remove recycled granules and fine powder. It is separated into water. Water from the underwater classifier 23 is sent to the water washer 22,
A portion of the waste water from the water washer 22 is returned to the hydrolysis tank 21, and the remainder of the waste water from the water washer 22 is sent to a waste water treatment device (not shown).

The recycled granules from the underwater classifier 23 are sent to a dehydrator 24 to be dehydrated, then sent to a dryer 25 to be dried, and then stored in a reaction medium storage tank 26. Water from the dehydrator 24 is returned to the underwater classifier 23.

On the other hand, water containing fine powder from the underwater classifier 23 is transferred to the settling tank 2.
7 to separate fine powder precipitate and water, the water is returned to the underwater classifier 23, and the precipitate is dehydrated in a dehydrator 28. The dehydrated water is returned to the settling tank 27. The dehydrated fine powder is dried in a dryer 30 and then sent to a granulator 31. Water-soluble baingu is added to this granulation 9131 from the binder storage tank 32, and after granulating the fine powder, it is cured in the curing section 33 and stored in the reaction medium storage tank 26.

The granules and granules in the reaction medium storage tank 26 are reused as reaction medium in the dealkalization device.

〔Effect of the invention〕

Since the present invention is configured as described above, it has the following effects.

fll By reducing the vapor and mist of the alkali metal compound, it is possible to prevent a decrease in efficiency due to dust adhesion inside the gas turbine, and maintenance time can be reduced.

(2) Reduced vapor and mist of alkali metal compounds reduces corrosion in the metal within the turbine, prevents loss of turbine efficiency, and requires less maintenance.

+31 (11) The result of (2) enables long-term continuous operation.

(4) Since the dealkalization device introduces the combustion gas after dedusting and is not intended to remove dust, the effect of the reaction medium (adsorbent) can be maintained for a long period of time. That is, the residence time of the reaction medium can be increased, less high-temperature reaction medium is taken out of the system, and heat loss and reaction medium loss are reduced.

(5) If the reaction medium is regenerated and used, the cost of the reaction medium can be significantly reduced.

(6) When the reaction medium is regenerated and used, the particles become porous, making it easier for the reaction to proceed, and the adsorption effect is further exhibited.

(7) When regenerating the reaction medium, since the dust in the reaction medium is separated and classified using water, no special dust-proofing measures are required, and the classification can be easily performed.

(8) Since the fine powder reaction medium can be granulated and reused as necessary, the reaction effect is good and it is economical.

(9) The particle size of the reaction medium can be sufficiently controlled;
Eliminates re-scattering of dust attached in the gas.

αDen: If dust leaks due to some kind of accident in the dust collector installed upstream of the dealkalization equipment, the dealkalization equipment has the ability to collect dust (99.5% in experiments).
By temporarily operating the dealkalization equipment, operation can be continued without shutting down the entire plant, and the reliability of the plant can be improved.

In this example, a pressurized fluidized bed (PFBC) was exemplified as a source of high-temperature, high-pressure dust-containing combustion gas, but this example also applies to coal gasifiers and pressurized coal partial combustion furnaces. The invention can be applied in the same way.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an apparatus for carrying out the method of removing alkali metal compounds from high-temperature, high-pressure combustion gas according to the present invention;
Figure 2 is an enlarged explanatory diagram showing details of the dealkalization equipment that adsorbs vapor and mist of alkali metal compounds in Figure 1, Figure 3 is an explanatory diagram showing details of the regeneration equipment in Figure 1, and Figure 4 is FIG. 1 is an explanatory diagram showing a conventional pressurized fluidized bed power generation plant. 1... Pressurized fluidized bed furnace (PFBC), 2... Expansion gas turbine, 3... Generator, 4... Air compressor, 5... Primary dust collector, 6... Secondary dust collector ,7...
・Exhaust heat boiler, 8... Boiler heat exchanger tube, 10... Dealalkalizer, 11... Regenerator, 12... Breathable support, 13... Reaction medium, 14... Gas inlet , 15
...Gas outlet, 16...Reaction medium population, 17...
Reaction medium outlet, 18... Roch feeder, 20...
- Current plate, 21... Hydrolysis tank, 22... Water washer,
23... Underwater classifier, 24... Dehydrator, 25...
Dryer, 26... Reaction medium storage tank, 27... Sedimentation tank, 28... Dehydrator, 30... Dryer, 3... Granulator, 32... Binder storage tank, 33...・For curing section
Request Person Kawasaki Heavy Industries, Ltd.

Claims (1)

[Scope of Claims] 1. A method of dedusting high-temperature, high-pressure dust-containing combustion gas, introducing it into an expansion turbine, and utilizing the temperature energy and pressure energy of this gas to generate power or other motive power. The high-temperature, high-pressure combustion gas after dust treatment is treated with granules of one or more transition metal oxides selected from the group consisting of activated alumina, activated silica, iron oxide, silicic acid, or titanium oxide as a reaction medium. A method for removing an alkali metal compound from a high-temperature, high-pressure combustion gas, the method comprising removing vapor and mist of the alkali metal compound contained in the gas by bringing the gas into contact with a packed bed or a moving bed. 2. The method for removing alkali metal compounds from high-temperature, high-pressure combustion gas according to claim 1, wherein the particle size of the granules as the reaction medium is 0.5 to 10 mm. 3 The average particle size of the granules that are the reaction medium is 1.0 to 3.0.
2. The method for removing alkali metal compounds from high-temperature, high-pressure combustion gas according to claim 1. 4. The method for removing alkali metal compounds from high-temperature, high-pressure combustion gas according to claim 1, 2 or 3, wherein naturally occurring diatomaceous earth, bauxite, iron ore, or titanium ore is used as the granular material serving as the reaction medium. 5. Continuously or intermittently extracting the reaction medium from the system;
The high temperature according to claim 1, 2, 3 or 4, wherein the alkali metal component is removed by dissolving it in water by washing with water or hot water, and the regenerated reaction medium having a large particle size after washing is dehydrated and dried for reuse.・Method for removing alkali metal compounds from high-pressure combustion gas. 6. Precipitate the waste water containing the pulverized reaction medium generated when washing with water or hot water to remove alkali metal components, separate the water and the fine precipitate, and dehydrate the fine precipitate.
After drying, the fine powder is granulated by adding a water-soluble binder such as blackstrap molasses, pulp waste liquid, starch aqueous solution, or water glass aqueous solution, and the granulated product is reused as a reaction medium. Method for removing alkali metal compounds from high pressure combustion gas.