1. Process classification
Chemical processes can be classified as batch, continuous, or semibatch and as steady-state or transient. It is important to know which of these categories your process falls, before you can write any material balances.
1. Batch Process:
In this process, the feed is fed into a vessel at the beginning of the process and removed at a later stadium out of the vessel, where no mass crosses the system boundaries between the time the feed is fed and the product is removed.
Example: Add reactants to a tank when the system has come to equilibrium remove the product and unconsumed reactants.
2. Continuous Process:
The input and the output of the process flow continuously throughout the duration of the process.
Example: A mixture of liquids is pumped at a constant rate into a distillation column, and streams are withdrawn at the top and the bottom of the column.
3. Semibatch Process:
This process is neither batch nor continuous process.
Example: A balloon is filled with air at a steady rate.
A process is operating at a steady state if the values of all the variables in the process do not change with time, except for small fluctuations about a constant mean values. A transient or unsteady-state exists when the process variables change with time. Furthermore, batch and semibatch processes are transient operations, and continuous process can be steady-state or transient.
A continuous process is used more often where large production rates is present, whereas a batch process is commonly used when small quantities of a product are to be produced on any single occasion. Most continuous processes are run as close to steady-state processes as possible because transient conditions exist at the beginning of the process and further changes will occur.
Chemical processes can be classified as batch, continuous, or semibatch and as steady-state or transient. It is important to know which of these categories your process falls, before you can write any material balances.
1. Batch Process:
In this process, the feed is fed into a vessel at the beginning of the process and removed at a later stadium out of the vessel, where no mass crosses the system boundaries between the time the feed is fed and the product is removed.
Example: Add reactants to a tank when the system has come to equilibrium remove the product and unconsumed reactants.
2. Continuous Process:
The input and the output of the process flow continuously throughout the duration of the process.
Example: A mixture of liquids is pumped at a constant rate into a distillation column, and streams are withdrawn at the top and the bottom of the column.
3. Semibatch Process:
This process is neither batch nor continuous process.
Example: A balloon is filled with air at a steady rate.
A process is operating at a steady state if the values of all the variables in the process do not change with time, except for small fluctuations about a constant mean values. A transient or unsteady-state exists when the process variables change with time. Furthermore, batch and semibatch processes are transient operations, and continuous process can be steady-state or transient.
A continuous process is used more often where large production rates is present, whereas a batch process is commonly used when small quantities of a product are to be produced on any single occasion. Most continuous processes are run as close to steady-state processes as possible because transient conditions exist at the beginning of the process and further changes will occur.
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