Introduction to Ammonia Desulfurization and Denitration Process for Kiln Boiler Desulfurization

（1） Principle of ammonia desulfurization:

Flue gas desulfurization is a very typical chemical process, and any FGD process includes two basic chemical reaction processes: ① absorption: SO2 absorption generates sulfite; ② Catalysis: Oxidation of sulfite to sulfate. Ammonia desulfurization is based on the reaction of SO2 and NH3 in aqueous solution:

Absorption: SO2+H2O+xNH3=(NH4) xH2 xSO3 (ammonium sulfite)

Catalysis: (NH4) xH2 xSO3+1/2O2+(2-x) NH3=(NH4) 2SO4 (ammonium sulfate)

This is a recycling method, which has the obvious characteristics of no secondary waste residue, wastewater, and exhaust gas pollution; Recycling SO2, producing ammonium sulfate, and realizing the value of SO2 recovery.

2、 Description of ammonia desulfurization process:

After dust removal, the flue gas is pressurized by an induced draft fan and enters the Class A venturi pre desulfurization section of the desulfurization absorption system. The sulfur dioxide in the flue gas neutralizes with a certain concentration of injected insufficient ammonia water to generate ammonium sulfite, with a desulfurization efficiency of over 80%; The generated ammonium sulfite solution enters the collection tank at the bottom of the desulfurization tower along with the flue gas.

Under the action of the external circulation pump of the desulfurization tower, the ammonium sulfite solution is sprayed onto the two spray layers in the upper part of the tower. After being atomized by the * nozzle, a highly superimposed spray zone is formed, which undergoes absorption reaction with residual acidic gases such as SO2 in the flue gas, generating ammonium bisulfite and falling into the collection tank at the bottom of the desulfurization tower. At the same time, a large amount of water in the ammonium sulfite solution washes and absorbs trace amounts of ammonia that may be brought in by the flue gas,

It also enters the collection tank at the bottom of the desulfurization tower, where the ammonia water added to the collection tank neutralizes with ammonium bisulfite in the collection tank to generate ammonium bisulfite. The SO2 absorption efficiency of this level is over 90%, and the comprehensive desulfurization efficiency of the two levels reaches over 98%; In this way, SO2 gas is absorbed in a large amount in a cyclic manner, purifying the flue gas. At the same time, most of the solid dust particles contained in the flue gas are also washed and separated, and the desulfurization process is completed at this time. During the contact and washing process between flue gas and desulfurization slurry, SO2 is absorbed by the slurry and the following total reactions occur:

SO2+2NH3+H2O=(NH4)2SO3

SO2+(NH4)2SO3+H2O=2NH4HSO3

NH3+ NH4HSO3=(NH4)2SO3

After purification, the flue gas passes through the top demister of the desulfurization tower to remove the large particle droplets contained in the flue gas. Then, a layer of demister blocks a small amount of liquid droplets in the flue gas that are in the form of foam to prevent them from being carried out of the tower body. At this time, the water mist and liquid droplets in the flue gas are blocked from flowing into the tower bottom along the tower wall. The flue gas passes through the top liquid baffle plate (which again prevents the possibility of the flue gas taking away the water mist) and is directly discharged into the atmosphere through the chimney at the top of the tower, At this point, the defogging process is complete.

The ammonium sulfite solution with a certain concentration generated at the bottom of the desulfurization tower, when being exported from the desulfurization tower, first enters the dust filtration device to remove the submicron dust that may exist in the ammonium sulfite solution but is not removed by the dust collector. After being filtered by a filter, the filtrate is pumped into a specially designed catalytic converter, and the air brought in by the injector itself is used to catalyze ammonium sulfite and sulfite

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