Chemical Manufacturing Methods: Batch vs. Continuous Processing
Chemicals are manufactured using one of two distinct methods:
batch or continuous. A continuous operation requires a constant raw
material feed to the process vessel and continual product withdrawal. A
batch process, which is used by specialty chemical manufacturers,
requires intermittent introduction of frequently changing raw materials,
varying process conditions within the vessel, and different removal
methods. In batch processing, vessels are often idle while waiting for
raw materials or undergoing quality control checks and cleaning. Thus,
emissions from batch processing are substantially different from those
of continuously operating processes.
Because of this specialized nature of the business, specialty
chemical manufacturers are typically small, averaging fewer than 100
employees. Batch processing is efficient and is often the only method of
producing small quantities of chemicals to meet customer demands for
specific products. Continuous operations are larger and often use
batch-produced chemicals or polymers as raw materials to manufacture
large volumes of chemicals and plastics.
Legislation and regulations that are based on performance
characteristics of large continuous operations often have significant
adverse impact on small batch processing operations.
Batch processors must retain operational flexibility because they:
- Develop products to perform the specific applications.
Often a specialty manufacturer produces a prototype product for the
customer to evaluate. The customer provides feedback that enables the
manufacturer to modify the product. The cycle is repeated in rapid
succession until the customer has a satisfactory product. In such a
development project, the raw materials used might change for each
iteration of improvement.
- Supply low-volume demand. While some chemicals, including
basic petrochemicals, are made in high-volume continuous process plants,
for economic and technical reasons, most chemicals cannot be made using
a continuous process. Small batches are not typically made using
dedicated equipment, as the same equipment might be used for 10 or 20
- Supply seasonal demand. Because many end products have
seasonal uses, batch processed chemicals are often manufactured in a
brief production campaign at a particular time of the year, which is
often set by the customer.