Material balance and Energy balance steady state reaction systems.

Law of conservation of mass

Where, Mi = input mass of materialsMo = output mass of materials

If Mi and Mo are different then there are four possible explanation:-

(i) measurement of Mi and Mo may be different

(ii) System has may be some leakage

(iii) Particular material may be consumed or generated by reaction in the system

(iii) Particular material may be accumulated in the system

Continuous systemMi Mo

• If we assume that measurements are correct and there is no leakage in the system.

• Therefore difference between Mi and Mo must be due to consumption or generation by the reaction or may be due to accumulation in the system

• On the basis of above assumption, a general mass balance equation can be written as:

Mass in through the system boundaries +

Mass out through the system boundaries

Mass generated within the system

Mass consumed within the system

Mass accumulated within the system

-

- =

In the above equation right side can be +ve and –ve

Negative accumulation means depletion of pre-exiting reserve material

Mass in the above equation can be –Total massOr mass of particular molecule or atomic speciesOr biomass

----(i)

• Type of material balance – (i) Differential balance method or approach • Each term of equation based on rate • Applicable for continuous process

– (ii) Integral balance method or approach• Based on quantity of mass not on rate• Applicable for batch or semi-batch process

• If continuous process is at steady state then the accumulation is zero

• Mass in + mass generated = mass out + mass consumed

---------------------(ii)

• This equation is known as general steady state mass balance equation.• This is also applicable over entire duration for batch and semi-batch

processes

If reaction does not occur in the system, then both generation =0 and

consumption =0 Therefore, Mass in = mass out ----(iii)