.In the given tank, there are two feeds and one output. Consider a 2 hour operation; the feed rates are 4000 kg/hr and 6000 kg/hr. The accumulated material inside the tank is 2000 kg. What is the output rate kg/hr of the material? *
a) 9000
b) 8000
c) 7000
d) 6000
Answers
Explanation:
Material balances are important first step when designing a new process or analyzing an
existing one. They are almost always prerequisite to all other calculations in the solution of
process engineering problems.
Material balances are nothing more than the application of the law of conservation of mass,
which states that mass can neither be created nor destroyed. Thus, you cannot, for example,
specify an input to a reactor of one ton of naphtha and an output of two tons of gasoline or
gases or anything else. One ton of total material input will only give one ton of total output,
i.e. total mass of input = total mass of output.
A material balance is an accounting for material. Thus, material balances are often compared
to the balancing of current accounts. They are used in industry to calculate mass flow rates of
different streams entering or leaving chemical or physical processes.
4.2. The General Balance Equation
Suppose propane is a component of both the input and output streams of a continuous process
unit shown below, these flow rates of the input and output are measured and found to be
different.
qin (kg propane/h) qout (kg propane/h)
If there are no leaks and the measurements are correct, then the other possibilities that can
account for this difference are that propane is either being generated, consumed, or
accumulated within the unit.
A balance (or inventory) on a material in a system (a single process unit, a collection of units,
b is correct