Method and apparatus for treating acidic tail gas by using ammonia process flue gas

Abstract

A flue gas-treating method for treating acid tail gas by using an ammonia process, comprising the following steps of: 1) controlling the concentration of sulfur dioxide in an acid tail gas entering an absorber to be ≦30,000 mg/Nm 3 ; 2) spraying and cooling with a process water or/and an ammonium sulfate solution in the inlet duct of the absorber or inside the absorber; 3) providing an oxidation section in the absorber, wherein the oxidation section is provided with oxidation distributors for oxidizing the desulfurization absorption solution; 4) providing an absorption section in the absorber wherein the absorption section achieves desulfurization spray absorption by using absorption solution distributors via an absorption solution containing ammonia; the absorption solution containing ammonia is supplied by an ammonia storage tank; 5) providing a water washing layer above the absorption section in the absorber, wherein the water washing layer washes the absorption solution in the tail gas to reduce the slip of the absorption solution; 6) providing a demister above the water washing layer inside the absorber to control the concentration of mist droplets contained in the cleaned tail gas. In the coal chemical industry, the integration of the Claus sulfur recovery process and the ammonia desulfurization technology can reduce the investment of the post-treatment and simplify the operation process, and provide intensive advantages to the environmental control of plants.

1 . A flue gas-treating method for treating acid tail gas by using an ammonia process, characterized in that, comprising the following steps of:
 1) according to the concentration of sulfur dioxide in the tail gas, adding air into the raw tail gas to make the concentration of sulfur dioxide reach a suitable absorbing condition; the concentration of sulfur dioxide to be introduced into the absorber is ≦30,000 mg/Nm3;   2) setting process water spray cooling and/or ammonium sulfate solution spray cooling in the inlet duct of the absorber or inside the absorber, in order to cool and wash the tail gas; when using the ammonium sulfate solution spray cooling, the concentration of ammonium sulfate solution is increased;   3) providing an oxidation section in the absorber, wherein the oxidation section is provided with oxidation distributors for oxidizing the desulfurization absorption solution;   4) providing an absorption section in the absorber wherein the absorption section achieves sulfurization spray absorption by using absorption solution distributors via an absorption solution containing ammonia; the absorption solution containing ammonia is supplied by an ammonia storage tank;   5) providing a water washing layer above the absorption section in the absorber, wherein the water washing layer washes the absorption solution within the tail gas to reduce the slip of the absorption solution;   6) providing a demister above the water washing layer inside the absorber to control the content concentration of mist droplets contained in the cleaned tail gas;   the process of the flue gas-treating method for treating acid tail gas by using an ammonia process is described as follows: the concentration of sulfur dioxide in the acid tail gas is adjusted through adding air from an air blower inside the inlet duct of the absorber; the process gas flows into the absorber after being cooled by the cooling spray layer at the inlet of the absorber or/and by the cooling spray layer of the ammonium sulfate solution in the absorber; sulfur dioxide is removed after being cleaned by the absorption spray layer inside the absorber; after washing and absorption in the water washing layer, the mist droplets are removal via the demister, and the cleaned tail gas is discharged from a stack through a cleaned gas duct.   
     
     
         2 . The flue gas-treating method for treating acid tail gas by using an ammonia process according to  claim 1 , characterized in that, the absorption solution circulation is an one-stage absorption solution circulation or a two-stage absorption solution circulation; the two-stage circulation system is the concentration and crystallization circulation of the cooling spray solution, wherein the ammonium sulfate solution is pumped by a cooling washing pump from an ammonium sulfate storage tank into the cooling washing spray layer inside the absorber and/or into the cooling washing layer at inlet of the absorber to cool the flue gas, while the ammonium sulfate solution evaporates, concentrates, or even partially crystallized. 
     
     
         3 . The flue gas-treating method for treating acid tail gas by using an ammonia process according to  claim 1 , characterized in that, the temperature of the acid tail gas flowing into the absorption spray layer in the absorber is ≦80° C.; the operation temperature of the absorption spray layer in the absorber is ≦65° C.; the temperature of absorption solution is ≦65° C. 
     
     
         4 . The flue gas-treating method for treating acid tail gas by using an ammonia process according to  claim 3 , characterized in that, the superficial gas velocity is 1.5 m/s to 4 m/s; the liquid gas ratio of the cooling absorption solution is ≦6 L/m3; the liquid gas ratio of absorption spraying is 1 L/m3 to 15 L/m3; the concentration of the ammonium sulfate solution is ≧15%. 
     
     
         5 . The flue gas-treating method for treating acid tail gas by using an ammonia process according to any one of  claims 1 - 4 , characterized in that, the acid tail gas ammonia desulfurization treatment is an ammonia desulfurization treating process for treating the acid tail gas from the Claus sulfur recovery process or the improved Claus sulfur recovery process, and the cooling process is achieved by air supplement, water cooling and/or ammonium sulfate solution cooling. 
     
     
         6 . A flue gas-treating apparatus for treating acid tail gas by using an ammonia process, characterized in that, comprising an absorber ( 16 ), an air blower ( 2 ), an ammonia solution tank ( 3 ), an absorber oxidation section ( 4 ), an absorption circulation pump ( 5 ), an ammonium sulfate storage tank ( 6 ), an ammonium sulfate discharge pump ( 7 ), an inlet duct of the absorber ( 8 ), a cleaned gas duct ( 9 ), a stack ( 10 ), a demister ( 11 ), a water washing layer ( 12 ), an absorber absorption spray layer ( 13 ), a cooling washing pump ( 14 ), an inlet cooling washing spray layer ( 15 ), and a spraying pump ( 17 ), wherein the inlet duct is connected to the air blower ( 2 ); a process water or/and ammonium sulfate solution cooling and spraying device is set in the inlet duct of the absorber or inside the absorber; an oxidation section ( 4 ) is provided in the absorber ( 16 ), wherein the oxidation section ( 4 ) is provided with oxidation distributors for oxidizing the desulfurization absorption solution; an absorption section is provided in the absorber ( 16 ) wherein the absorption section achieves desulfurization spray absorption by using absorption solution distributors via an absorption solution containing ammonia; an oxidation blower ( 1 ) is provided in the oxidation section ( 4 ); a solution generated by the oxidation section ( 4 ) is transported into the ammonium sulfate storage tank ( 6 ) and transported out of the apparatus by an ammonium sulfate discharge pump ( 7 ); the cooling spray layer is the cooling spray with a coverage rate over 200%, while the absorption spray layer ( 13 ) consists of two to four layers of spray with the spray tower type or the packed tower type, and the spray coverage rate for each layer is more than 250%. 
     
     
         7 . The flue gas-treating apparatus for treating acid tail gas by using an ammonia process according to  claim 6 , characterized in that, the water washing layer ( 12 ) with a packed tower type is provided above the absorption spray layer ( 13 ), the demister is set at the top of the absorber, and the cleaned gas duct and stack are provided above the absorber. 
     
     
         8 . The flue gas-treating apparatus for treating acid tail gas by using an ammonia process according to  claim 6 , characterized in that, a centrifugal air blower is used to adjust the concentration of acid tail gas by supplying air, and the pressure and flow amount thereof are set according to the parameters of the acid tail gas to ensure the concentration of sulfur dioxide in the tail gas to be no more than 30,000 mg/Nm3. 
     
     
         9 . The flue gas-treating apparatus for treating acid tail gas by using an ammonia process according to  claim 6 , characterized in that, an oxidation air blower is used to oxidize ammonium sulfite to ammonium sulfate and supply the oxidation air, wherein the pressure of the air blower is set according to the liquid level of the oxidation section and is no less than 0.05 MPa, and the flow rate of the oxidation air is more than 150% of a theoretical value. 
     
     
         10 . The flue gas-treating apparatus for treating acid tail gas by using an ammonia process according to  claim 6  or  7 , characterized in that, the height of the absorber is 20 m to 40 m; the oxidation residence time in the oxidation section ( 4 ) is over 30 minutes, and gas-liquid distributors with a plate type or a grid type are provided, and the superficial gas velocity at the absorption spray layer ( 13 ), the water washing layer ( 12 ), and the demister is 1 m/s to 5 m/s, and the demister ( 11 ) has 2 to 3 baffle plates.