MIXING
Mixing dalam operasi TL Equalisasi Netralisasi Koagulasi flokulasi Aerasi Disinfeksi
Alat dalam operasi mixing Mekanikal (Rotating impellerpropeler, turbin, paddle) Pneumatik (Air agitator, mixing jet/pump) Baffle basin
Tipe Impeller Propeller
Turbine
Paddle/dayung
oblique paddle agitator Straight padle agitator
Paraboladisc turbin Arc disc turbin
Agitator spread around Helical ribbon impelller
Special blade agitator
Posisi mixer Top entering mixer Bottom enter Side enter
Vortex The motion of the fluid swirling rapidly around a center is called a vortex. The speed and rate of rotation of the fluid are greatest at the center, and decrease progressively with distance from the center. The fluid pressure in a vortex is lowest in the center (where the speed is greatest) and rises progressively with distance from the center. Vorteks menghalangi operasi mixing dengan cara mengurangi kecepatan impeller relatif terhadap cairan
Vortex dapat dikurangi dengan baffling yang tepat (1/10 – 1/12 dari diameter tangki)
Contoh operasi mixing Koagulasi flokulasi Rapid mixing koagulasi Slow mixing flokulasi
G value (velocity gradient) The degree of mixing is based on the power imparted to the water GT (rapid mixing) (Slow mixing) G (/detik) T (detik) 1000 900 700 20 30 50/> G (/detik) T (menit) 70 35 20 60 Sumber: Reynolds, 1982
Praktek/demo jar test Rapid mixing 100 rpm selama 60 det Slow mixing 60 rpm selama 5 min 40 rpm selama 10 min Latihan: hitung G value