Batch unit operation
Batch unit operation means a unit operation involving intermittent or discontinuous feed into equipment, and, in general, involves the emptying of equipment after the batch cycle ceases and prior to beginning a new batch cycle. Mass, temperature, concentration and other properties of the process may vary with time. Addition of raw material and withdrawal of product do not simultaneously occur in a batch unit operation.
40 CFR § 63.1423
The following terms used in this subpart shall have the meaning given them in subparts A ( 63.2), F ( 63.101), G ( 63.111), and H ( 63.161) as specified after each term: