Transcript Lecture 4 (2014)

Philadelphia University
Faculty of Engineering
Department of Civil Engineering
Lecture no.
Reactor
Environmental Engineering
Dr Jawad Al-rifai
Definition:
• The tanks in which physical, chemical and
biochemical. Ex Water softening &
Wastewater treatment
Reactor Types
1- Batch reactor
• Fill & draw types; materials are added to the tank, mixed for
sufficient time to allow reaction to occur and then drained.
Ex. Laboratory experiment.
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Size < 150m3/d
Inexpensive
Easy to operate & build
No influent or effluent –step increase or pulse;
Mass balance
Ct/Co=e-kt
Co: concentration at time zero
Ct: concentration at time t
K: rate of reaction
T: time
Continuous flow stirred tank reactor
(CSTR)(Completely mixed flow reactor (CMFR))
• Material flows into, through and out of the reactor at all times
• uniform throughout the tank
• Ex rapid mix or flash mix tank for Water treatment, wastewater
treatment
• Ex natural system; lake, mixing of two streams, air in the room
• Water flow > 150m3/d
• The composition of the effluent is the same as the composition in
the tank
• Mass balance express as
Qin = Qout at no reaction
Ct=Co exp (-t/to)
Plug flow reactors (PFR)
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Fluid particles pass through the tank in sequence.
Those that inter first leave first.
Assuming no mixing occur in the lateral direction.
As long as the flow conditions remain steady, the
composition of the effluent remains constant.
• Ex. Pipes, long narrow rivers, biological treatment in
WWTp
• MB eq:
In (Cout/Cin)=-K L/U= -k V/Q
L: length of plug-flow segment
u: Linear velocity, m/s