Consider the following sedimentation tank which is used as one of the components of any continuous water treatment system. Suspended particles and solids larger than 0.5 mm are settled/separated by gravity in the sedimentation tanks. The sedimentation tank was working at steady state with the following information until a rain starts. Inlet: Flowrate: Fv₁=10 m³/hr concertation CAL=50 kg/m³ Outlet 1 (sludge) Flowrate: Fv2=0.816 m³/hr concertation CA2=500 kg/m³ Outlet 2 (decanting outflow) Flowrate: Fv3=? Concertation: CA=? An assumption has been made that the sedimentation tank is fully mixed similar to a CSTR (this assumption is really far from the reality). This means that CA in decanting outflow is the same as CA in the sedimentation tank. Due to rain, the solid concentration in the inlet increased from 50 kg/m³ to 150 kg/m³ while all of the flowrates and the concentration of solid in the sludge remained unchanged as follow: Inlet: Flowrate: Fv₁-10 m³/hr concertation CA-150 kg/m³ Outlet 1 (sludge) Flowrate: Fv2=0.816 m³/hr concertation CA-500 kg/m³ Outlet 2 (decanting outflow) Flowrate: Fv3=? Concertation: CA=? sludge collecting trough sludge inlet Volume of the sedimentation tank: V=1000 m³ decanting trough (outflow) 山 sludge scraper arm

Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
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Consider the following sedimentation tank which is used as one of the components of any continuous
water treatment system. Suspended particles and solids larger than 0.5 mm are settled/separated by
gravity in the sedimentation tanks. The sedimentation tank was working at steady state with the following
information until a rain starts.
Inlet:
Flowrate: Fv₁=10 m³/hr
concertation CA1=50 kg/m³
An assumption has been made that the sedimentation tank is fully mixed similar to a CSTR (this
assumption is really far from the reality). This means that CA in decanting outflow is the same as CA in the
sedimentation tank.
Flowrate: Fv₁=10 m³/hr
concertation CA1=150 kg/m³
Outlet 1 (sludge)
Flowrate: Fv₂=0.816 m³/hr
concertation CA2-500 kg/m³
Due to rain, the solid concentration in the inlet increased from 50 kg/m³ to 150 kg/m³ while all of the
flowrates and the concentration of solid in the sludge remained unchanged as follow:
Inlet:
Outlet 1 (sludge)
Outlet 2 (decanting outflow)
sludge collecting trough
sludge<
inlet
Flowrate: Fv₂=0.816 m³/hr
concertation CA2=500 kg/m³
Volume of the sedimentation tank: V=1000 m³
Outlet 2 (decanting outflow)
Flowrate: Fv3=?
Concertation: CA=?
decanting trough
(outflow)
sludge scraper arm
Flowrate: Fv3=?
Concertation: CA=?
Transcribed Image Text:Consider the following sedimentation tank which is used as one of the components of any continuous water treatment system. Suspended particles and solids larger than 0.5 mm are settled/separated by gravity in the sedimentation tanks. The sedimentation tank was working at steady state with the following information until a rain starts. Inlet: Flowrate: Fv₁=10 m³/hr concertation CA1=50 kg/m³ An assumption has been made that the sedimentation tank is fully mixed similar to a CSTR (this assumption is really far from the reality). This means that CA in decanting outflow is the same as CA in the sedimentation tank. Flowrate: Fv₁=10 m³/hr concertation CA1=150 kg/m³ Outlet 1 (sludge) Flowrate: Fv₂=0.816 m³/hr concertation CA2-500 kg/m³ Due to rain, the solid concentration in the inlet increased from 50 kg/m³ to 150 kg/m³ while all of the flowrates and the concentration of solid in the sludge remained unchanged as follow: Inlet: Outlet 1 (sludge) Outlet 2 (decanting outflow) sludge collecting trough sludge< inlet Flowrate: Fv₂=0.816 m³/hr concertation CA2=500 kg/m³ Volume of the sedimentation tank: V=1000 m³ Outlet 2 (decanting outflow) Flowrate: Fv3=? Concertation: CA=? decanting trough (outflow) sludge scraper arm Flowrate: Fv3=? Concertation: CA=?
Part 1: Write the steady state mass balance equation and complete the following table:
Before rain
Fv3
CA
Part 2: Consider your time =0 When the rain starts (this is when the change in the inlet concentration
happens). Complete the following table
What is the inlet
concentration at
t=0?
After rain (at steady state if rain continues)
Fv3
CA
What is the concentration
of suspended particles in
the tank at t=0?
What is the concentration
of suspended particles in
outlet 1 at t=0?
What is the
concentration of
suspended particles
in outlet 2 at t=0?
Part 3: Write the unsteady state mass balance equation for the process and find an equation for the
change of CA with time (how does CA in tank change with time due to the inlet change).
Part 4: How could you check if your derived equation for CA with respect to time is correct, double
check here.
Transcribed Image Text:Part 1: Write the steady state mass balance equation and complete the following table: Before rain Fv3 CA Part 2: Consider your time =0 When the rain starts (this is when the change in the inlet concentration happens). Complete the following table What is the inlet concentration at t=0? After rain (at steady state if rain continues) Fv3 CA What is the concentration of suspended particles in the tank at t=0? What is the concentration of suspended particles in outlet 1 at t=0? What is the concentration of suspended particles in outlet 2 at t=0? Part 3: Write the unsteady state mass balance equation for the process and find an equation for the change of CA with time (how does CA in tank change with time due to the inlet change). Part 4: How could you check if your derived equation for CA with respect to time is correct, double check here.
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