Experiments have proved that when the dust concentration in flue gas is treated to 15mg/Nm3, the residual dust is ultrafine particle, which is smaller than PM2.5 and very difficult to be captured through common methods, like electrical precipitator, bag-type filter and so on. Based on our project experience, we have explored our own integrated solution to make dust emission lower than 5mg/Nm3.
On the condition that dust concentration from precipitator outlet is treated lower than 15mg/Nm3, flue gas cooling and residual heat recovery unit at absorber inlet (optional), improved tray structure and high efficient demister will work as the main components in our integrated solution.
Special improvements:
◆Flue gas cooler before absorber tower(recover the waste heat at the same time): fluoroplastic tubes filling with cooling water installed in the flue,
a) cool down flue gas lower than dew-point temperature in the partial space around heat exchange tube, make part of vapor condense into water, so that liquid particles can wrap solid particles and then adhere on the vertically installed heat exchange tubes.When the liquid with particles aggregates into water film, it will flow down slowly and be cleaned by regularly rinsing.
b) tube diaphragm has mechanical interception effect for liquid drops with particles.
c)even if the condensed droplets with solid particles is not captured by the cooler, it still can be more easily captured by the subsequent absorber system.
◆Improved tray structure: improve removal efficiency for SO2 and dust through the optimization of air flow distribution, and also ensure the performance of high efficient demister; on another hand, when slurry goes through the sieve pore of tray structure, the tiny particles would be more easily captured by the liquid film on the tray.
◆High efficient demister: limit drop size (D99.5)~15μm means most of slurry droplets could be captured and it would collaboratively ensure the emission concentration of dust is equal to or lower than 5 mg/Nm3.
Main technical specification:
Absorber tower outlet soot concentration ≤5 mg/Nm3 (demand the outlet concentration of precipitator ≤15mg/Nm3) Demister outlet droplet concentration ≤30 mg/Nm3
Tray pressure drop ≤200Pa, high efficient demister pressure drop ≤200Pa
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