Limestone Injection System
In order to meet the State Environmental requirement of desulphurization, limestone is doped
for the FGD of CFB boilers. Normally, the limestone is fed separately from the Coal Feeding
system, and the feeding quantity of limestone can be changed according to the different emission
of SO2, which could ensure the emission per requirement economically. The property of
limestone is as follow:
1. The abrasive powder of limestone is multi-angular and hard.
2. The permeability of limestone powder is great.
3. The range of particle size is large (30um～10mm).
4. The density is great (1.1~1.4 t/m3).
5. The content of CaO is high, the water absorption and viscosity is high.
The limestone powder is hard to be conveyed pneumatically, the wear is great on pipeline, the
fluidized property is poor, and the material is easy to be depositional and hygroscopic. If the
selection and design is improper, blockage would be a big problem.
3.1 Limestone Conveying System From the IntermediateSilo in Milling Shop to Storage Bunker
The compressed air as conveying air and
blow-tank as conveyor are used, the
limestone is transported from milling shop to
two nos. storage Bunkers near boiler through
pipeline
o The system is designed based
on the material property, with
right conveying velocity and
little wear.
o The limestone powder with
diameter of (30um～10mm)
can be well conveyed.
o Proper air compensation
device is arranged, to avoid
the deposition of materials,
and reduce the sweeping time.
o The long conveying distance
of 1500m is possible.
Limestone Conveying System at Heshuyuan Power Plant, Mei
County, Guangdong Baolihua New Energy Stock Co .,Ltd
3.2 Limestone Injection System From Limestone Bunker to Boiler
Two stages conveying is normally used for the limestone injection system from bunker to
boiler. The first stage is pneumatic conveying from bunker to furnace bin; and the secondary
stage is from furnace bin to boiler by pressured conveying with frequency-feeder and Roots
blower.
After a lot of research for many years, based on the advanced international technology,
Longking developed the Screw-feeding Blow-tank Pneumatic Conveying System, to inject
limestone powder from bunker to boiler directly, which simplified the two-stages conveying
system, save investment and improve the stability and reliability of system.
Realized the single-stage conveying with distance of 500m,
continuous conveying, and equal injection.
With the screw feeder inside blow-tank, the fluidized blow-tank
is well combined with screw feeder.
The distributing diverter makes the Deviation of capacity of
branches in no more than 5%.
Frequency is used for screw feeder, which makes the
adjustment of capacity is available according to the FGD
requirement The range of adjustment can be 10:1.
Between inlet and outlet of screw feeder there is no pressure
drop, which reduces the wear of screw dramatically.
The system is suitable for the limestone injection requirement
of 600MW unit.
