Flue gas treatment apparatus and flue gas treatment method

1. A flue gas treatment apparatus for removing sulfur contents contained in combustion flue gas, comprising:

treatment agent feeding means for feeding a treatment agent into a flue through which the combustion flue gas flows;

temperature decreasing means for cooling the combustion flue gas to which the treatment agent has been fed to condense SO 3 components in the combustion flue gas;

an electric dust collection apparatus provided in a flue arranged on a downstream side of the temperature decreasing means in a direction of flow of flue gas;

a desulfurization apparatus based on a lime-gypsum process, provided downstream of the electric dust collection apparatus in a direction of flow of the flue gas; and

circulation means for feeding a portion of dust particles recovered by the electric dust collection apparatus into a flue arranged upstream of the temperature decreasing means in the direction of flow of the flue gas for circulated use of the portion of the dust particles as the treatment agent; and

control means for controlling an amount of the dust particles to be disposed of, an amount of the dust particles to be circulated for reuse, and an amount of the treatment agent to be additionally fed so as to satisfy, at a timing (t), the following expressions (I):

D ( t )= Z ( t )× Y /( X 0 +Y )× K 1 ( t )

R (SO 3 )( t )= Z ( t )− D ( t )

X (SO 3 )( t )= X 0 −R (SO 3 )( t )  (I)

wherein D(t) denotes an amount of the dust particles to be disposed of, of the dust particles recovered by the electric dust collection apparatus, Z(t) denotes the total amount of the dust particles recovered by the electric dust collection apparatus, X 0 denotes an amount of the treatment agent to be fed before circulation is started, Y denotes an amount of SO 3 to be removed from the combustion flue gas, R(SO 3 )(t) denotes an amount of the dust particles to be circulated by the circulation means for reuse, X(SO 3 )(t) denotes an amount of the treatment agent to be additionally fed, and K 1 (t) denotes a correction amount of the dust particles to be disposed of.

2. The flue gas treatment apparatus according to claim 1 , wherein the treatment agent is selected from the group consisting of calcium carbonate, activated carbon, ash, and gypsum.

3. The flue gas treatment apparatus according to claim 1 , reusing means for feeding another portion of the dust particles recovered by the electric dust collection apparatus to the desulfurization apparatus.

4. The flue gas treatment apparatus according to claim 3 , wherein the treatment agent is calcium carbonate or activated carbon.

5. A flue gas treatment apparatus for removing sulfur contents contained in combustion flue gas, comprising:

treatment agent feeding means for feeding a treatment agent into a flue through which the combustion flue gas flows;

temperature decreasing means for cooling the combustion flue gas to which the treatment agent has been fed to condense SO 3 components in the combustion flue gas;

an electric dust collection apparatus provided in a flue arranged on a downstream side of the temperature decreasing means in a direction of flow of flue gas;

a desulfurization apparatus based on a lime-gypsum process, provided downstream of the electric dust collection apparatus in a direction of flow of the flue gas;

circulation means for feeding a portion of dust particles recovered by the electric dust collection apparatus into a flue arranged upstream of the temperature decreasing means in the direction of flow of the flue gas for circulated use of the portion of the dust particles as the treatment agent;

reusing means for feeding another portion of the dust particles recovered by the electric dust collection apparatus to the desulfurization apparatus; and

control means for controlling the amount of the dust particles to be disposed of, the amount of the dust particles to be circulated for reuse, the amount of the treatment agent to be additionally fed, the amount of the dust particles to be reused in the desulfurization apparatus, and the amount of a desulfurization agent to be additionally fed to the desulfurization apparatus so as to satisfy, at a timing (t), the following expressions (II):

D ( t )= Z ( t )× Y /( X 0 +Y )× K 2 ( t )

R (SO 2 )( t )= F

R (SO 3 )( t )= Z ( t )− D ( t )− R (SO 2 )( t )

X (SO 2 )( t )= R (SO 2 )( t )× Y /( X 0 +Y )× K 2 ( t )

X (SO 3 )( t )= X 0 −R (SO 3 )( t )  (II)

wherein D(t) denotes an amount of the dust particles to be disposed of after the dust particles have been recovered by the electric dust collection apparatus, Z(t) denotes the total amount of the dust particles that have been recovered by the electric dust collection apparatus, X 0 denotes an amount of the treatment agent to be fed before circulation is started, Y denotes an amount of SO 3 to be removed from the combustion flue gas, R(SO 3 )(t) denotes an amount of the dust particles to be circulated by the circulation means for reuse, X(SO 3 )(t) denotes an amount of the treatment agent to be additionally fed, K(t) denotes a correction amount of the dust particles to be disposed of, R(SO 2 )(t) denotes an amount of the dust particles to be reused in the desulfurization apparatus, F denotes an amount required in the desulfurization apparatus, and X(SO 2 )(t) denotes an amount of a desulfurization agent to be additionally fed to the desulfurization apparatus.

6. The flue gas treatment apparatus according to claim 5 , wherein the treatment agent is calcium carbonate or activated carbon.

7. A flue gas treatment method for removing sulfur contents contained in combustion flue gas, the method comprising:

feeding a treatment agent into a flue through which the combustion flue gas flows;

cooling the combustion flue gas to which the treatment agent has been fed by using temperature decreasing means;

removing dust from the cooled combustion flue gas by using an electric dust collection apparatus; and

treating the combustion flue gas from which the dust has been removed, by using a desulfurization apparatus based on a lime-gypsum process,

wherein a portion of the dust particles recovered by the electric dust collection apparatus is fed into a flue arranged on an upstream side of the temperature decreasing means for circulated use of the portion of the dust particles as the treatment agent; and

wherein an amount of the dust particles to be disposed of, an amount of the dust particles to be circulated for reuse, and an amount of the treatment agent to be additionally fed are controlled so as to satisfy, at a timing (t), the following expressions (I):

D ( t )= Z ( t )× Y /( X 0 +Y )× K 1 ( t )

R (SO 3 )( t )= Z ( t )− D ( t )

X (SO 3 )( t )= X 0 −R (SO 3 )( t )  (I)

wherein D(t) denotes an amount of the dust particles to be disposed of, of the recovered dust particles, Z(t) denotes the total amount of the dust particles that have been recovered by the electric dust collection apparatus, X 0 denotes an amount of the treatment agent to be fed before circulation is started, Y denotes an amount of SO 3 to be removed from the combustion flue gas, R(SO 3 )(t) denotes an amount of the dust particles to be circulated for reuse, X(SO 3 )(t) denotes an amount of the treatment agent to be additionally fed, and K 1 (t) denotes a correction amount of the dust particles to be disposed of.

8. The flue gas treatment method according to claim 7 , wherein the treatment agent is selected from the group consisting of calcium carbonate, activated carbon, ash, and gypsum.

9. The combustion flue gas treatment method according to claim 7 , further comprising reusing another portion of the recovered dust particles by feeding the same into the desulfurization apparatus.

10. The combustion flue gas treatment method according to claim 9 , wherein the treatment agent is calcium carbonate or activated carbon.

11. A flue gas treatment method for removing sulfur contents contained in combustion flue gas, the method comprising:

feeding a treatment agent into a flue through which the combustion flue gas flows;

cooling the combustion flue gas to which the treatment agent has been fed by using temperature decreasing means;

removing dust from the cooled combustion flue gas by using an electric dust collection apparatus; and

treating the combustion flue gas from which the dust has been removed, by using a desulfurization apparatus based on a lime-gypsum process,

wherein a portion of the dust particles recovered by the electric dust collection apparatus is fed into a flue arranged on an upstream side of the temperature decreasing means for circulated use of the portion of the dust particles as the treatment agent and another portion of the recovered dust particles by the electric dust collection apparatus is reused by feeding the same into the desulfurization apparatus; and

wherein an amount of the dust particles to be disposed of, an amount of the dust particles to be circulated for reuse, an amount of the treatment agent to be additionally fed, an amount of the dust particles to be reused in the desulfurization apparatus, and an amount of a desulfurization agent to be additionally fed to the desulfurization apparatus are controlled so as to satisfy, at a timing (t), the following expressions (II):

D ( t )= Z ( t )× Y /( X 0 +Y )× K 2 ( t )

R (SO 2 )( t )= F

R (SO 3 )( t )= Z ( t )− D ( t )− R (SO 2 )( t )

X (SO 2 )( t )= R (SO 2 )( t )× Y /( X 0 +Y )× K 2 ( t )

X (SO 3 )( t )= X 0 −R (SO 3 )( t )  (II)

wherein D(t) denotes an amount of the dust particles to be disposed of after the dust removal step, Z(t) denotes the total amount of the recovered dust particles, X 0 denotes an amount of the treatment agent to be fed before circulation is started, Y denotes an amount of SO 3 to be removed from the combustion flue gas, R(SO 3 )(t) denotes an amount of the dust particles to be circulated for reuse, X(SO 3 )(t) denotes an amount of the treatment agent to be additionally fed, K(t) denotes a correction amount of the dust particles to be disposed of, R(SO 2 )(t) denotes an amount of the dust particles to be reused, F denotes an amount required in the desulfurization apparatus, and X(SO 2 )(t) denotes an amount of a desulfurization agent to be additionally fed to the desulfurization apparatus.

12. The combustion flue gas treatment method according to claim 11 , wherein the treatment agent is calcium carbonate or activated carbon.