1.Desulfurization

Theories:

?The dual alkali desulphurization is a wetscrubbing technology, carried out in the tower. After reaction between NaOH andSO₂, it forms a solution instead of slurry, which may lead toblocking. The spent caustic solution circulates into reaction champers, whereNaOH is regenerated by Ca(OH)₂. The reproductive caustic solutioncirculates back into the scrubbing tower. The dual alkali desulphurizationneeds lower capital and operating cost. Meantime, it has good flexibility withflue gas fluctuation. Therefore, this system will be widely applied inpurifying smoke from coal-fire boiler, combustion in FCC and smoke from steelsintering. ?

     Reactions:

     Desulfurization

     SO₂+2Na( OH)₂=Na₂SO₃+H₂O

     Na₂SO₃+SO₂+H₂O=2NaHSO₃

     Recycle:

     2NaHSO₃+Ca(OH)₂=CaSO₃+Na₂SO₃+2H₂O

Features:

     Dual alkali desulfurization has “3 high, 2low, 1 small”features.

     1.Highdesulfurization efficiency.  

     2.Highutilization of alkali. 

     3.Highreliability.  

     4.Lowinvestment cost.  

     5.Lowrunning cost. 

     6.Smalloccupied area.  

Process flow：

2.Limestone (CaCO₃)-Lime (CaO)desulfurization

Application areas:

     This technology is usedin boilers from coal fire power plant, cogeneration energy plant, centralheating system, sintering machines, coking furnaces, glass furnaces, etc.

Theories:

     This method uses a slurryof alkali sorbent, limestone or lime. In case of limestone, the slurry is amixture of water and grinded limestone powder. In case of lime, the slurry isthe result of hydration of lime. In the flue gas desulfurization (FGD) tower,the flue gas fully contacts with the slurry, produces CaSO₃. Then,CaSO₃ is further oxidized to produce marketable CaSO₄?2H₂O(gypsum).

Components:

     The system is consist offlue gas collecting system, absorption and oxidization system, limestone/limeslurry preparation system, by-product treatment system, waste water treatmentsystem, utility system( including water, compressed air, accident tank, etc.),electrical control system.

Reaction formulas:

Desulfurization:

      CaCO₃+SO₂+1/2 H₂O=CaSO₃?1/2H₂O+CO₂

     Ca(OH)₂+SO₂=CaSO₃?(1/2)H₂O+1/2H₂O     

     CaSO₃·1/2H₂O+SO₂+1/2H₂O=Ca(HSO₃)₂

     Oxidization:

     2CaSO₃?(1/2)H₂O+O₂+3H₂O=2CaSO₄?2H₂O

     Ca(HSO₃)₂+O₂+2H₂O=CaSO₄?2H₂O+H₂SO₄

Features:

     This technology has “5 high, 3 large, 2 low” features, which are listedbelow.

         High desulfurizationefficiency

         High operating efficiency

         High reliability

         High investment cost

         High operating cost

         Large capacity of fluegas disposal

         Large capacity of SO2treatment

         Large space occupied

         Low Ca to S ratio

         Low price of absorbent

Process flow：