JP3442907B2 - Apparatus and method for oxidizing CaS-containing limestone - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an apparatus and method for oxidizing CaS-containing limestone at high temperature to produce CaSO ₄ from CaS.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. In FIG. 7, 1 is a reactor that constitutes the CaS oxidation device,
A dispersion plate 9 is provided inside. Nozzle 2 is reactor 1
It penetrates the dispersion plate 9 from outside and communicates with the inside of the reactor 1. A fluidized bed 1A is formed on the bottom dispersion plate 9 in the reactor 1. Limestone particles containing char and CaS 100
Is supplied from the nozzle 2 to the fluidized bed 1A.

A mixed gas 101 of oxygen, water vapor and nitrogen is supplied from the nozzle 3 into the wind box 1D. The mixed gas 101 is supplied to the fluidized bed 1A via the dispersion plate 9 and vigorously mixes the particles 100 in the fluidized bed 1A. The oxygen concentration of the combustion gas 103 exiting the fluidized bed 1A is set to 3 to 4% or more. Unless the oxygen concentration is set to 3 to 4% or more, it is difficult to set the SO ₂ concentration in the gas to 100 ppm or less.

In the fluidized bed 1A, (1) CaS + 3 / 2O ₂ → CaO + SO ₂ , between CaS and oxygen in the gas,
(2) CaS + 2O ₂ → CaSO ₄ , (3) CaO + S
A reaction of O ₂ + 1 / 2O ₂ → CaSO ₄ occurs.

SO ₂ generated in the reaction (1) is the fluidized bed 1A.
By reacting with CaO in the reaction (3) CaSO ₄
Fixed as. CaS as a whole in the fluidized bed 1A
The ratio of conversion from CaSO ₄ to CaSO ₄ is large, the ratio of CaO is small, and CaS exists inside the particles.

A heat exchanger 6 is installed in the fluidized bed 1A to recover the heat of the particles in the fluidized bed 1A and heat the heat transfer medium fluid 107 flowing inside. Combustion gas 1 leaving reactor 1
08 enters cyclone 7 and is dedusted combustion gas 109
And it becomes the collected particles 110c. Recovered particles 11
0c is a particle 111c that is distributed by the particle distributor 8 and is extracted to the outside of the system, and fine particles 112 that are returned to the fluidized bed 1A.
c. The fine particles 112c are supplied to the fluidized bed 1A via the nozzle 5.

Among the ash contained in the char, coarse particles which are not particularly pulverized in the fluidized bed and remain in the fluidized bed 1A and are not accompanied by the gas 103 are
It is taken out of the system through the nozzle 4 attached to the dispersion plate 9.

[0008]

In the conventional apparatus, CaO or CaSO ₄ is contained in the particles 111c extracted from the system.
A high concentration of CaS that was not converted to was contained. CaS contained in the particles 111c at a high concentration has a drawback that it slowly decomposes to generate H ₂ S, which adversely affects the environment.

The present invention relates to CaS contained in limestone.
It is an object of the present invention to provide an oxidizer capable of highly efficiently oxidizing carbon dioxide to CaSO ₄ , and a CaS oxidation method using the oxidizer.

[0010]

In order to solve the above-mentioned problems, the present invention is arranged at the bottom of the reactor and formed at the top thereof.
A gas dispersion plate for supplying a gas containing oxygen to the fluidized bed, a nozzle for supplying limestone containing CaS into the fluidized bed formed on the gas dispersion plate, and a nozzle disposed above the gas dispersion plate. On the upper dispersion plate and the upper dispersion plate
Provided is a CaS-oxidizing device for limestone containing CaS, which comprises a nozzle for supplying a gas containing oxygen and a heat exchanger arranged above the upper dispersion plate.

With this CaS oxidation device of the present invention, Ca
In order to oxidize S, the temperature in the reactor is 870-10.
The temperature was set to 50 ° C., a gas containing oxygen was supplied to the upper part of the upper dispersion plate, and the oxygen partial pressure in the gas discharged from the fluidized bed formed on the upper part of the gas dispersion plate to the upper part of the upper dispersion plate was set to 0.
03ata [ata = atm absolute (absolute pressure)] and make the oxygen partial pressure in the gas in the upper part of the upper dispersion plate after mixing the same gas and the gas containing oxygen larger than 0.05ata. It is preferable to control it.

In this case, the upper dispersion plate and the heat exchanger form the fluidized bed so as to be located in the fluidized bed in the reactor or above the fluidized bed.

CaS to CaSO_FourIn forming
SO as shown by point A in FIG.₂High concentration and oxygen concentration
When the reaction proceeds in a high frequency range, CaS to CaSO_Four
Is easy to form. However, under the conditions like point A, CaS oxidation
As shown in FIG. 4, when CaS is performed, CaS to CaSO_Four
Quickly converts to CaSO, but only on the outer surface of the particles CaSO _Four
Form.

Since the volume of CaSO ₄ is larger than the volume of CaS, the CaSO ₄ formed on the outer surface is (b) in FIG.
As shown in (3), the inside of the particles is not oxidized to stop diffusion of oxygen and remains as CaS. Therefore, when the inside of the fluidized bed is set to a condition such as point A, CaS tends to remain inside the particles.

If the condition in the fluidized bed is a reducing atmosphere with a low oxygen concentration and a low SO ₂ concentration, such as point B, C
aO is easily formed. CaS is stabilized when the entire fluidized bed is made into a reducing atmosphere, so that a part of the fluidized bed is in a reducing atmosphere,
The conditions are set so that a part of the fluidized bed becomes an oxidizing atmosphere. Under the same temperature, the rate of formation of CaO from CaS in an oxidizing atmosphere is faster than the rate of formation of CaS from CaO, so that the entire fluidized bed is under the condition of increasing CaO.

By reducing the oxygen partial pressure of the combustion gas in the fluidized bed,
By setting the temperature to 870 to 1050 ° C., a zone such as point B where the oxygen concentration is very small is generated near the lower part of the fluidized bed, and the oxygen concentration is increased at the upper part of the fluidized bed such as point A. A condition arises.

Therefore, at the point B, CaO is produced from CaS, and at the point A, CaSO ₄ is produced from CaO. As a result, oxygen diffuses into the particles as shown in FIG.
Can be converted to SO ₄ . Further, by supplying a gas containing oxygen from the upper dispersion plate and further increasing the oxygen partial pressure above it, CaO can be converted to CaSO ₄ .

Further, the outer surface is covered with C in a zone where the oxygen partial pressure is high.
Even if the aSO ₄ is covered, if these particles go to the zone where the oxygen partial pressure is low at the bottom of the fluidized bed, CaSO ₄ will become CaO _4.
Alternatively, oxygen can be diffused into the inside of the particles again in order to convert to CaS.

At the same temperature, the rate of formation of CaO from CaS in an oxidizing atmosphere is faster than the rate of formation of CaS from CaO, so that the content of CaO in the inside of these particles is higher than that of CaS. As described above, by creating zones with different oxygen partial pressures in the fluidized bed, CaS
It becomes possible to convert into CaSO ₄ via aO.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an apparatus according to the present invention and embodiments of an oxidation method according to the present invention will be specifically described below with reference to the drawings. In the following embodiments, the same components as those of the conventional device shown in FIG. 7 are designated by the same reference numerals for simplification of description.

(First Embodiment) First, an explanation will be given based on the apparatus of the first embodiment shown in FIG. In the apparatus shown in FIG. 1, the nozzle 2 penetrates the dispersion plate 9 and communicates with the inside of the reactor 1. A fluidized bed 1A is formed on the bottom dispersion plate 9 in the reactor 1. Limestone particles 100 containing char and CaS are supplied from the nozzle 2 to the fluidized bed 1A.
A mixed gas 101 of oxygen, water vapor, and nitrogen is supplied from the nozzle 3 into the wind box 1D. The mixed gas 101 is supplied to the fluidized bed 1A via the dispersion plate 9 and vigorously mixes the particles 100 in the fluidized bed 1A. The oxygen partial pressure of the combustion gas 103 exiting the fluidized bed 1A is set to be 0.03ata or less.

In the fluidized bed 1A, between CaS and oxygen in the gas, (1) CaS + 3 / 2O ₂ → CaO + SO ₂ ,
(2) The reaction of CaS + 2O ₂ → CaSO ₄ occurs.
Since the oxygen concentration is low in the fluidized bed 1A, the reaction (1) is more likely to occur than the reaction (2).

Further, in a portion where the oxygen partial pressure is locally high,
CaO generated in reaction (1) is SO ₂When you meet
(3) CaO + SO₂+ 1 / 2O₂→ CaSO_FourReaction of
By CaSO_FourIs generated.

Further, since the oxygen concentration in the fluidized bed 1A is low, a part of the fluidized bed 1A becomes a reducing atmosphere, and there is a portion where H ₂ or CO is generated. Further there (4)
CaSO ₄ + 4H ₂ → CaO + H ₂ S + 3H ₂ O,
(5) CaSO ₄ + 4CO → CaO + COS + 3CO ₂
The reaction of occurs.

In the fluidized bed 1A, CaS to C as a whole
The rate of conversion to aO is high, and the rate of CaSO ₄ is low. The upper part of the fluidized bed 1A is partitioned by the upper dispersion plate 11. The structure of the upper dispersion plate 11 is shown in FIG. Gas 104 containing oxygen is electrically via the nozzle 11c
A large number of small holes 11b that are inserted and installed in the upper dispersion plate 11
Is ejected as a mixed gas 105 of oxygen, water vapor, and nitrogen.

The combustion gas 103 rises and passes through the hole 11a formed through the upper dispersion plate 11 and flows into the fluidized bed 1F formed on the upper dispersion plate 11, and the small holes of the upper dispersion plate 11 are generated. Gas 105 containing oxygen blown out from 11b
To form combustion gas 106. The oxygen gas partial pressure of the combustion gas 106 is set to 0.05 ata or higher.

The combustion gas 106 exiting the fluidized bed 1F rises in the particle selection space 1B. In the particle selection space 1B, the coarse particles that accompany the combustion gas 106 gradually decrease in velocity to zero due to gravity, and start falling. In this way, the coarse particles are separated from the gas and returned to the fluidized bed 1A again.

Of the SO ₂ generated in the fluidized bed 1A in the fluidized bed 1F, S which did not react with CaO in the fluidized bed 1A.
O ₂ reacts with CaO of limestone as in the reaction formula (3), and the SO ₂ concentration in the gas decreases. The heat exchanger 6 is installed in the fluidized bed 1F, and the gas 106 and the fluidized bed 1F are
The heat of the particles is recovered and the heat medium fluid 107 in the heat exchanger 6 is heated. The overflow pipe 10 is installed in the fluidized bed 1F, and the coarse particles 113 in the fluidized bed 1F are extracted to the outside of the system.

By adjusting the aperture ratio of the through holes 11a of the upper dispersion plate, the amount of particles flowing into the fluidized bed 1F from the fluidized bed 1A can be adjusted. When CaS is contained in the coarse particles 113 extracted from the overflow pipe 10, by reducing the aperture ratio of the through holes 11a,
The CaS content in the coarse particles 113 can be reduced.

The combustion gas 108 leaving the reactor 1 enters the cyclone 7 and becomes the combustion gas 109 dedusted and the fine particles 110 recovered. The collected fine particles 110 are distributed by the particle distributor 8 and extracted to the outside of the system.
11 and fine particles 112 returned to the fluidized bed 1A.
The fine particles 112 are supplied to the fluidized bed 1A via the nozzle 5. The residence time of the fine particles 112 in the fluidized bed 1A is very short, and they become particles that circulate in the fluidized bed 1A accompanied by gas.

The amount of particles circulated in the fluidized bed 1A accompanied by the gas is such that the fine particles 1 extracted from the particle distributor 8 to the outside of the system.
It can be adjusted by increasing or decreasing 11. The amount of particles circulated along with the gas in the fluidized bed 1A is controlled in order to secure an amount such that the limestone particle concentration is sufficient to sufficiently advance the SO ₂ desulfurization reaction in the fluidized bed 1F. adjust.

Among the ash contained in the char, coarse particles 1 which are not entrained by the gas 103 and which remain in the fluidized bed 1A without being pulverized in the fluidized bed and remain particularly large.
02 is taken out of the system through the nozzle 4 attached to the dispersion plate 9.

(Second Embodiment) Next, an explanation will be given based on the apparatus of the second embodiment shown in FIG. In the apparatus of FIG. 6, the nozzle 2 penetrates the dispersion plate 9 and communicates with the inside of the reactor 1. A fluidized bed 1A is formed on the bottom dispersion plate 9 in the reactor 1. Limestone particles 100 containing char and CaS are supplied from the nozzle 2 to the fluidized bed 1A.

A mixed gas 101 of oxygen, water vapor and nitrogen is supplied from the nozzle 3 into the air box 1D. The mixed gas 101 is supplied to the fluidized bed 1A via the dispersion plate 9 and vigorously mixes the particles 100 in the fluidized bed 1A. The oxygen partial pressure of the combustion gas 103 exiting the fluidized bed 1A is set to 0.03ata or less.

In the fluidized bed 1A, (1) CaS + 3 / 2O ₂ → CaO + SO ₂ , between CaS and oxygen in the gas,
(2) The reaction of CaS + 2O ₂ → CaSO ₄ occurs.
Since the oxygen concentration in the fluidized bed 1A is low, the reaction (1) is more likely to occur than the reaction (2).

Further, since the oxygen concentration is low, a part of the fluidized bed 1A becomes a reducing atmosphere, and there is a part where H ₂ or CO is generated. There, further, (4) CaSO ₄ +4
H ₂ → CaO + H ₂ S + 3H ₂ O, (5) CaSO ₄ +
A reaction of 4CO → CaO + COS + 3CO ₂ occurs.
In the fluidized bed 1A, the ratio of conversion from CaS to CaO is large and the ratio of CaSO ₄ is small as a whole.

The upper freeboard section of the reactor 1 is divided by the upper dispersion plate 11 into a particle selection space 1B which is a space below the upper dispersion plate 11 and a desulfurization space 1C which is a space above the upper dispersion plate 11. Has been done. Regarding the particle sorting space 1B, it is enlarged as it goes upward so that the cross-sectional area of the space above the fluidized bed 1A is larger than the cross-sectional area of the fluidized bed 1A.

Regarding the expansion of the area, if the gas flow velocity of the fluidized bed 1A is set to 0.7 to 1.2 m / s, the gas flow velocity immediately below the upper dispersion plate 11 is 0.2 to 0.4 m. The area should be reduced to / s. Also, fluidized bed 1
The distance from the upper surface of A to the upper dispersion plate 11 is 3 m or more.

The combustion gas 103 exiting the fluidized bed 1A rises in the particle selection space 1B. In the particle selection space 1B, the coarse particles that accompany the combustion gas 103 gradually decrease in speed due to gravity and become zero, and then start falling. In this way, the coarse particles are separated from the gas and returned to the fluidized bed 1A again.

Combustion gas 10 that has passed through the particle selection space 1B
3 passes through the through hole 11a of the upper dispersion plate 11 and flows into the desulfurization space 1C. A mixed gas of oxygen, water vapor, and nitrogen, which is a mixed gas 104 of oxygen and nitrogen introduced into the upper dispersion plate 11 through the nozzle 11c and ejected from the small holes 11b installed in the upper dispersion plate 11 to the desulfurization space 1C. It becomes 105.

The oxygen partial pressure in the gas 106 in the desulfurization space 1C increases to 0.05 ata or more. In addition, the presence of the upper dispersion plate 11 increases the particle concentration in the gas. Fluidized bed 1
SO ₂ reaction formula of fine limestone particles and gas has been entrained in the gas from the _{A (3) CaS + SO 2} + 1 / 2O 2 →
By reacting like CaSO ₄ , the SO ₂ concentration in the gas decreases.

A heat exchanger 6 is installed in the desulfurization space 1C, recovers the heat of the gas 106 and the particles accompanying the gas 106, and heats the heat medium fluid 107 flowing inside. Combustion gas 108 exiting desulfurization space 1C is cyclone 7
Then, it becomes the combustion gas 109 that has been dedusted and the fine particles 110 that have been recovered. The collected fine particles 110 are distributed by the particle distributor 8 and extracted to the outside of the system.
Then, the fine particles 112 are returned to the fluidized bed 1A.

The fine particles 112 are supplied to the fluidized bed 1A through the nozzle 5. The residence time of the fine particles 112 in the fluidized bed 1A is very short, and they become particles that circulate in the fluidized bed 1A accompanied by gas. The amount of particles circulated in the fluidized bed 1A accompanied by gas can be adjusted by increasing or decreasing the fine particles 111 extracted from the particle distributor 8 to the outside of the system. The amount of particles circulated along with the gas in the fluidized bed 1A is adjusted so as to secure an amount such that the limestone particle concentration is sufficient to sufficiently advance the desulfurization reaction of SO ₂ in the desulfurization space 1C. adjust.

Among the ash contained in the char, coarse particles which are not pulverized in the fluidized bed and are present in the fluidized bed 1A in a particularly large size and which are not accompanied by the gas 103 are:
It is taken out of the system through the nozzle 4 attached to the dispersion plate 9.

[0045]

As described above, according to the present invention,
Oxygen is placed in the fluidized bed formed at the bottom and above it.
The gas dispersion plate that supplies the gas containing the gas and the upper part of the gas dispersion plate
A nozzle for supplying limestone containing CaS into a fluidized bed formed, an upper dispersion plate arranged above the gas dispersion plate, and a gas containing oxygen are supplied to the upper part of the upper dispersion plate.
A nozzle and a heat exchanger arranged above the upper dispersion plate are used, and the temperature in the reactor is set to 87
It is set to 0 to 1050 ° C., a gas containing oxygen is supplied to the upper part of the upper dispersion plate, and the partial pressure of oxygen in the gas discharged from the fluidized bed formed on the upper part of the gas dispersion plate to the upper part of the upper dispersion plate. Of less than 0.03ata, and the upper dispersion after mixing the same gas with the gas containing oxygen.
By operating so that the oxygen partial pressure in the gas in the upper part of the plate becomes greater than 0.05ata, CaS in limestone is
Can be oxidized to CaSO ₄ with high efficiency.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the configuration of a CaS oxidation device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of an upper dispersion plate in the apparatus shown in FIG.

FIG. 3 is a thermodynamic phase equilibrium diagram for explaining CaS oxidation conditions in the present invention.

FIG. 4 is an explanatory diagram for explaining a CaS oxidation reaction process in the present invention.

FIG. 5 is an explanatory diagram for explaining a CaS oxidation reaction process in the present invention.

FIG. 6 is a vertical cross-sectional view showing the configuration of a CaS oxidation device according to a second embodiment of the present invention.

FIG. 7 is a vertical cross-sectional view showing the configuration of a conventional CaS oxidation device.

[Explanation of symbols]

1 Reactor 1A Fluidized Bed 1B Particle Sorting Space 1C Desulfurization Space 1D Air Box 1F Fluidized Bed 2 Nozzle 3 Nozzle 4 Nozzle 5 Nozzle 6 Heat Exchanger 7 Cyclone 8 Particle Distributor 9 Dispersion Plate 10 Overflow Pipe 11 Upper Dispersion Plate 11a Through Hole 11b Small hole 11c Nozzle 100 Char and limestone particles containing CaS 101 Mixed gas of oxygen, steam and nitrogen 102 Coarse particles 103 Combustion gas 104 Mixed gas of oxygen and nitrogen 105 Mixed gas of oxygen, steam and nitrogen 106 Combustion gas 107 Heat medium Fluid 108 Combustion gas 109 Combustion gas 110, 111, 112 Fine particles 113 Coarse particles

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiko Shinoda 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. (56) References JP-A-56-160323 (JP, A) (58) Survey Areas (Int.Cl. ⁷ , DB name) C01F 11/46

Claims (4)

(57) [Claims] 1. A disposed on the bottom of the reactor, on top
A gas dispersion plate that supplies a gas containing oxygen to the fluidized bed that is formed, and CaS into the fluidized bed that is formed above the gas dispersion plate.
A nozzle for supplying limestone containing, an upper dispersion plate arranged above the gas dispersion plate, and an upper part of the upper dispersion plate
A CaS oxidizing device for limestone containing CaS, which comprises a nozzle for supplying a gas containing oxygen to the above and a heat exchanger arranged above the upper dispersion plate. 2. Using the oxidizing device according to claim 1, Ca
When oxidizing S, the temperature in the reactor is set to 870 to 870.
The temperature is set to 1050 ° C., a gas containing oxygen is supplied to the upper part of the upper dispersion plate, and the oxygen partial pressure in the gas discharged from the fluidized bed formed on the upper part of the gas dispersion plate to the upper part of the upper dispersion plate is 0. On the upper dispersion plate after mixing the same gas with the gas containing oxygen,
A method for oxidizing CaS-containing limestone, characterized in that the oxygen partial pressure in the gas in the gas section is made larger than 0.05ata. 3. The C of limestone containing CaS according to claim 2, wherein the fluidized bed is formed such that the upper dispersion plate and the heat exchanger are interposed in the fluidized bed.
aS oxidation method. 4. The CaS oxidation of limestone containing CaS according to claim 2, wherein the fluidized bed is formed so that the upper dispersion plate and the heat exchanger are located above the fluidized bed. Method.