Air pollution control system and air pollution control method

Patent metadata

Field	Value
Publication number	US-9802151-B2
Application number	US-201515119545-A
Country	US
Kind code	B2
Filing date	Jan 26, 2015
Priority date	Feb 24, 2014
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

The air pollution control system including: a flue gas duct through which flue gas flows; a heat exchanger provided to the flue gas duct; a limestone supply device for reducing SO 3 in the flue gas supplies CaCO 3 to the flue gas flowing in an upstream of the heat exchanger; an upstream SO 3 measurement device measures the SO 3 in the flue gas flowing in a stream upper than a position where the limestone supply device supplies the CaCO 3 ; and a control device determines a quantity supplied of the CaCO 3 based on a relationship between a quantity of the SO 3 measured by the upstream SO 3 measurement device and a molar ratio of SO 3 to CaCO 3 and which supplies the determined quantity supplied of the CaCO 3 from the limestone supply device to the flue gas duct.

First claim

The invention claimed is:

1. An air pollution control system, comprising:
a flue gas duct through which flue gas flows;
a heat exchanger disposed in part of the flue gas duct;
a limestone supply device for reducing SO 3 in the flue gas provided to an upstream of the heat exchanger which supplies CaCO 3 to the flue gas;
an upstream SO 3 measurement device provided to a stream upper than a position where the limestone supply device for reducing the SO 3 in the flue gas supplies the CaCO 3 , the upstream SO 3 measurement device measures the SO 3 in the flue gas,
a downstream SO 3 measurement device provided to a stream downer than the heat exchanger, the downstream SO 3 measurement device measures the SO 3 in the flue gas; and
a control device which determines a quantity supplied of the CaCO 3 based on a relationship between a quantity of the SO 3 measured by the upstream SO 3 measurement device and a molar ratio of SO 3 to CaCO 3 , which corrects the determined quantity supplied of the CaCO 3 based on a quantity of the SO 3 measured by the downstream SO 3 measurement device and which supplies to the flue gas duct the corrected quantity supplied of the CaCO 3 from the limestone supply device for reducing the SO 3 in the flue gas,
wherein, among the upstream SO 3 measurement device and the downstream SO 3 measurement device, at least the downstream SO 3 measurement device is configured to measure the gaseous SO 3 and the mist-like SO 3 in the flue gas independently each other.

2. The air pollution control system according to claim 1 , wherein the control device sets the molar ratio of CaCO 3 /SO 3 to be 2.0 or more.

3. The air pollution control system according to claim 2 , wherein the control device sets a reference value of the molar ratio of CaCO 3 /SO 3 and a SO 3 reducing characteristics curve so as to determine, as the quantity supplied of the CaCO 3 , a quantity within an allowable range set from the reference value and the SO 3 reducing characteristics curve.

4. The air pollution control system according to claim 1 , further comprising a precipitator which is disposed in the stream lower than the heat exchanger and reducing dust in the flue gas after heat recovery.

5. The air pollution control system according to claim 4 , further comprising a circulation system which separates CaCO 3 contained in the dust reduced by the precipitator and supplies the separated CaCO 3 to the upstream of the heat exchanger,
wherein the control device determines the quantity supplied of the CaCO 3 as taking into account the CaCO 3 circulated in the circulation system.

6. The air pollution control system according to claim 1 , further comprising:
a precipitator disposed in the stream upper than the heat exchanger and reducing dust in the flue gas;
a desulfurization device disposed in the stream downer than the heat exchanger and reducing, with an absorbent, sulfur oxides contained in the flue gas from which the dust has been removed and which has passed through the heat exchanger; and
a limestone supply device for the desulfurization device supplying CaCO 3 to the desulfurization device,
wherein the control device determines the quantity of the CaCO 3 to be supplied from the limestone supply device for the desulfurization device to the desulfurization device in accordance with a quantity of the CaCO 3 to be supplied from the limestone supply device for removing the SO 3 in the flue gas, and supplies the determined quantity of the CaCO 3 from the limestone supply device for the desulfurization device to the desulfurization device.

7. The air pollution control system according to claim 6 , wherein the combustion engine is a boiler, and the heat exchanger is a heat-recovery unit for recovering heat of the flue gas after the dust removal and for raising a temperature of the flue gas emitted from a stack,
the air pollution control system further comprising:
a denitrification device which is disposed in the flue gas duct and which reduces nitrogen oxides from the flue gas emitted from the boiler; and
an air heater which is disposed in a downstream of the denitrification device of the flue gas duct as well as in an upstream of the precipitator and which recovers the heat of the flue gas which has passed through the denitrification device.

8. The air pollution control system according to claim 6 , further comprising a SO 2 measurement device which is disposed in at least either an upstream, or a downstream of the desulfurization device and which measures SO 2 in the flue gas,
wherein the control device determines the quantity of the CaCO 3 to be supplied from the limestone supply device for the desulfurization device to the desulfurization device as taking into account a quantity of the SO 2 measured by the SO 2 measurement device.

9. The air pollution control system according to claim 6 , further comprising a CaCO 3 measurement device which measures CaCO 3 in the absorbent,
wherein the control device determines the quantity of the CaCO 3 to be supplied from the limestone supply device for the desulfurization device to the desulfurization device as taking into account the quantity of the CaCO 3 measured by the CaCO 3 measurement device.

10. An air pollution control method by supplying CaCO 3 to an upstream of a heat exchanger in an air pollution control system including a flue gas duct through which the flue gas emitted from a combustion engine that combusts fuel flows and including the heat exchanger which is disposed in the flue gas duct,
the method comprising:
an upstream measurement step of measuring SO 3 in the flue gas flowing in a stream upper than a position where the CaCO 3 is supplied;
a downstream measurement step of measuth SO 3 of the flue gas flowing in a stream downer than the heat exchanger;
a determination step of determining a quantity supplied of the CaCO 3 based on a relationship between the measured quantity of the SO 3 in the upstream measurement step and a molar ratio of SO 3 to CaCO 3 ;
a correction step of correcting the determined quantity supplied of the CaCO 3 based on a quantity of the SO 3 measured in the downstream measurement step; and
a supply step of suppling the corrected quantity supplied of the CaCO 3 to the flue gas duct,
wherein, among the upstream measurement step and the downstream measurement step, at least the downstream measurement step measures the gaseous SO 3 and the mist-like SO 3 in the flue gas independently each other.

Assignees

• Mitsubishi Hitachi Power Sys

Inventors

• Kamiyama Naoyuki
• Kagawa Seiji
• Fukuda Toshihiro
• Ushiku Tetsu

Classifications

• F23J2219/40

  Sorption with wet devices, e.g. scrubbers · CPC title

• F23J2215/20

  Sulfur; Compounds thereof · CPC title

• B01D2251/404

  of calcium · CPC title

• F23J2219/50

  Sorption with semi-dry devices, e.g. with slurries · CPC title

• F23J15/06

  of coolers · CPC title