11-08-2012, 02:09 PM
MASS BALANCE ANALYSIS
ppt of mass balance.pptx (Size: 279.37 KB / Downloads: 28)
Principle of mass balance analysis
Mass balance concept is based on the fundamental physical principle that mass neither be created nor be destroyed but can altered from one form to another form.
This is also known as law of conservation of mass.
So mass balance equation can be written as
(INPUT RATE)=(OUTPUT RATE)+(DECAY
RATE)+(ACCUMULATION
RATE)
PREPARATION OF MASS BALANCE
1.Prepare a simplified schematic or flow diagram of the system or process
2.Define the limits over which the mass balance is applied .
3.List of the pertinent data and assumptions that will be used in the preparation of mass balance.
4.List of the rate expressions for the biological or chemical reaction that occur with in the system.
5.Select a convenient basis on which the numerical calculation will be based.
APPLICATION OF MASS BALANCE ANALYSIS
1.In steady state system with conservative substance
2. In steady state system with non conservative substance
3.In Ideal (stirred) Batch reactor
4.In Ideal tank reactor, also named Continuous Stirred Tank Reactor (CSTR)
5.In Ideal Plug Flow Reactor (PFR)
Steady state system with conservative substances
When a substance is conserved meaning no radioactive decay ,bacterial decomposition or chemical reaction occuring . For such conservative substances ,the decay rate is zero.
Thus mass balance equation for conservative system is –
INPUT RATE = OUTPUT RATE
Steady state system with nonconservative substances
Many substances undergo chemical ,biological or nuclear reactions with the time considered as nonconservative substances.
For such system mass balance equation is –
INPUT RATE = OUTPUT RATE +DECAY RATE
But decay of nonconservative substances is frequently modeled as a first order reaction that is ,
dC/dT = -KC
Where, K is a reaction rate coefficient
C is the concentration of substance
T is the decay time for substances