Sodium bicarbonate injection FGD

Sodium based powder is put into the flue before the dust remover. The sodium based powder is activated by thermal decomposition under the action of high temperature flue gas. The flue gas in the flue gas is fully in contact with the activated sodium based powder for chemical reaction, and the SO2 and other acidic media in the flue gas are absorbed and purified.

Main chemical reactions:

2NaHCO₃→Na₂CO₃+ H₂O+CO₂

SO₂+Na₂CO₃→Na₂SO₃+CO₂

2Na₂SO₃+O₂→2Na₂SO₄

The desulfurization and drying powder particles are attached to the cloth bag with air flow and further desulfurization and purification treatment. The efficiency of sodium dry flue gas desulfurization is more than 95%, and the operation resistance of flue gas system is hardly increased.

The principle of denitrification by SCR technology is as follows: under the action of catalyst, ammonia is put into flue gas at a temperature of 280 ℃~420 ℃, and NOX is reduced to N2 and H2O.

The main reactions are as follows:

4NO+4NH3+O2→4N2+6H2O

6NO+4NH3→5N2+6H2O

When there is oxygen in the flue gas, the first formula of the reaction takes precedence, so there is a one-to-one relationship between ammonia consumption and NO reduction. In boiler flue gas, NO2 generally accounts for about 5% of the total NOX concentration. The reactions in which NO2 is involved are as follows:

2NO2+4NH3+O2→3N2+6H2O

6NO2+8NH3→7N2+12H2O

1) The desulphurizer is stored temporarily in the silo, the material enters the grinding machine evenly through the feeding valve, the grinding disk and the grading wheel of the grinding machine rotate at high speed under the drive of the motor, the NaHCO3 material is crushed after being hit by the high speed rotating grinding disk, the material feeding grading wheel meets the requirements and enters the injection system, and the large particles re-enter the grinding area through the action of the special air flow guide ring to crush again until the particle size meets the design requirements.

2) In the desulphurization reaction system, sodium-based powder is put into the flue before the dust remover through the conveying fan. The sodium-based powder is activated under the action of high temperature flue gas. The flue gas in the flue gas is fully in contact with the activated sodium-based powder for chemical reaction, and the SO2 and other acidic media in the flue gas are absorbed and purified.

3) Adopts imported desulphurizer, and the desulphurizer is used once and does not need to be recycled. According to a certain molar ratio of desulphurizer NaHCO3 to SO2, the injection amount can be adjusted according to the output SO2 concentration from time to time.

4) The desulphurization reaction system has the function of on-line automatic adjustment, and the amount of NaHCO3 powder can be adjusted according to the concentration of SO2 in input and output.

5) The desulphurization ash produced by desulphurization reaction is collected by bag filtration in the integrated device of dust removal and denitrification. The collected desulphurization ash is transported by pneumatic transportation and pumped to the desulphurization ash bin through the lower part of the ash hopper of the integrated device. Pneumatic conveying device is used in ash transportation system.

Conclusion: for gas boilers, Sodium Bicarbonate Duct Injection method is the most stable, reliable and up to standard method.

1) Simple process, less one-time investment, low operation cost, small area, simple operation and maintenance, all-dry treatment;

2) The catalyst of denitrification system is modular, which is convenient for catalyst replacement. The denitrification reactor is composed of several independent units. It can repair equipment or replace catalyst on-line, and single unit maintenance does not affect the normal operation of other units;

3) The SO3 content in flue gas is very low. The oxidation rate of SO2 by denitrification catalyst is less than 0.5%. Before denitrification, the SO3 content in flue gas after denitrification catalyst is also very low. The temperature of flue gas in the whole process is always much higher than that of water dew point and acid dew point. Therefore, the temperature of flue gas after purification will not be lower than that of acid dew point, which will cause corrosion and acid rain around the chimney;

4) The temperature drop of the desulfurization and denitrification system is about 20 C, which does not affect the process flow of the subsequent waste heat boiler.