Flue gas treatment system and flue gas treatment method

Patent metadata

Field	Value
Publication number	US-2016129395-A1
Application number	US-201514888113-A
Country	US
Kind code	A1
Filing date	Jun 17, 2015
Priority date	Nov 7, 2014
Publication date	May 12, 2016
Grant date	—

Abstract

The present invention provides a flue gas treatment system and a flue gas treatment method that enable the stable long-term operation of a plant by reducing NO x in a combustion flue gas and reducing the concentration of SO 3 more compared with that available conventionally. The flue gas treatment method of removing NO x and SO 3 in the gas that includes NO x and SO 3 includes a denitration and SO 3 reduction step of denitrating the gas and reducing SO 3 into SO 2 , in which NH 3 as a first additive and a second additive including one or more selected from the group consisting of an olefinic hydrocarbon expressed by a general formula: C n H 2 , (n is an integer of 2 to 4) and a paraffinic hydrocarbon expressed by a general formula: C m H 2m+2 (m is an integer of 2 to 4) are added to the gas before bringing the gas into contact with a catalyst.

First claim

1 . A flue gas treatment system which removes NO x and SO 3 in a flue gas including NO x and SO 3 , the system comprising a denitration and SO 3 reduction apparatus configured to simultaneously perform denitration of NO x and reduction of SO 3 in the combustion flue gas by adding a first additive and a second additive to the combustion flue gas before bringing the combustion flue gas into contact with a catalyst, and
wherein the first additive is NH 3 , the second additive is a 3C-5C olefinic hydrocarbon (unsaturated hydrocarbon), and the catalyst does not include a noble metal.

2 . The flue gas treatment system according to claim 1 , wherein the second additive is an olefinic hydrocarbon having an allyl structure.

3 . The flue gas treatment system according to claim 1 , wherein the olefinic hydrocarbon is C 3 H 6 .

4 . The flue gas treatment system according to claim 3 , wherein a load of the C 3 H 6 is 0.1 to 2.0 by molar ratio of C 3 H 6 /SO 3 .

5 . The flue gas treatment system according to claim 1 , wherein the catalyst includes an oxide, a mixed oxide, or a complex oxide selected from the group consisting of TiO 2 , TiO 2 —SiO 2 , TiO 2 —ZrO 2 , and TiO 2 —CeO 2 as a carrier.

6 . The flue gas treatment system according to claim 5 , wherein SiO 2 in the TiO 2 —SiO 2 complex oxide is contained within a range of 5% to 60% by a percentage ratio of SiO 2 /(TiO 2 +SiO 2 ).

7 . The flue gas treatment system according to claim 1 , further comprising:
an air preheater arranged on a back stream side of the denitration and SO 3 reduction apparatus and configured to recover heat from the combustion flue gas; an electric precipitator arranged on a back stream side of the air preheater and configured to collect dust from the combustion flue gas; and a denitration apparatus arranged on a back stream side of the electric precipitator and configured to absorb and remove SO 2 remaining in the combustion flue gas or obtained by reducing SO 3 by bringing the SO 2 into contact with slurry formed from calcium carbonate.

8 . The flue gas treatment system according to claim 7 ,
wherein the combustion flue gas is a flue gas from a low-grade fuel-fired power generation plant, the system further comprising: a third addition device arranged on a front stream side of the electric precipitator and configured to further add NH 3 and/or CaCO 3 to the combustion flue gas including SO 3 remaining therein as a third additive.

9 . A flue gas treatment method of removing NO x and SO 3 in a combustion flue gas including NO x and SO 3 , the method comprising:
a denitration and SO 3 reduction step of simultaneously performing denitration of NO x and reduction of SO 3 in the combustion flue gas by adding NH 3 that is a first additive and a second additive that is a 3C-5C olefinic hydrocarbon (unsaturated hydrocarbon) to the combustion flue gas before bringing the combustion flue gas into contact with a catalyst that does not include a noble metal.

10 . The flue gas treatment method according to claim 9 , wherein the second additive is an olefinic hydrocarbon having an allyl structure.

11 . The flue gas treatment method according to claim 9 , wherein the olefinic hydrocarbon is C 3 H 6 .

12 . The flue gas treatment method according to claim 11 , wherein a load of the C 3 H 6 is 0.1 to 2.0 by molar ratio of C 3 H 6/ SO 3 .

13 . The flue gas treatment method according to claim 9 , wherein the catalyst includes an oxide, a mixed oxide, or a complex oxide selected from the group consisting of TiO 2 , TiO 2 —SiO 2 , TiO 2 —ZrO 2 , and TiO 2 —CeO 2 as a carrier.

14 . The flue gas treatment method according to claim 13 , wherein SiO 2 in the TiO 2 —SiO 2 complex oxide is contained within a range of 5% to 60% by a percentage ratio of SiO 2/ (TiO 2 +SiO 2 ).

15 . The flue gas treatment method according to claim 9 , the method further comprising:
an air preheating step of recovering heat from the combustion flue gas that has undergone the denitration and SO 3 reduction step; a precipitation step of collecting dust from the combustion flue gas that has undergone the air preheating step; and a denitration step of absorbing and removing SO 2 remaining in the combustion flue gas that has undergone the precipitation step or obtained by reducing SO 3 by bringing the SO 2 into contact with slurry formed from calcium carbonate.

16 . The flue gas treatment method according to claim 15 ,
wherein the combustion flue gas is a flue gas from a low-grade fuel-fired power generation plant, the method further comprising: a third addition step of further adding NH 3 to the combustion flue gas before being subjected to the precipitation step including SO 3 remaining therein, as a third additive.

Assignees

• Mitsubishi Hitachi Power Sys

Inventors

• Masuda Tomotsugu
• Miyoshi Takahito
• Higashino Koji

Classifications

• B01D53/343

  Heat recovery · CPC title

• B01D2255/40

  Mixed oxides · CPC title

• B01D53/869

  Multiple step processes · CPC title

• B01D2255/65

  Catalysts not containing noble metals · CPC title

• B03C3/017

  Combinations of electrostatic separation with other processes, not otherwise provided for · CPC title