Process engineering: which statement best describes a continuous process in industry?

Introduction / Context:
Industrial processes are often classified as batch, semi-batch, or continuous. Understanding the nature of a continuous process is critical for selecting instrumentation, control strategies, and maintenance regimes.

Given Data / Assumptions:

• Continuous processes run steadily for extended periods when in normal operation.
• Typical examples: oil refining, chemical reaction trains, paper mills.
• Startups/shutdowns can occur for maintenance; “continuous” does not mean “never stops.”

Concept / Approach:
In a continuous process, inputs (raw materials, energy) flow into the plant while outputs (products, by-products) flow out at roughly steady rates. Control focuses on maintaining setpoints (temperature, flow, pressure) and responding to disturbances. The definition does not limit controller type to analog; modern plants use digital/PLC-based control extensively.

Step-by-Step Solution:
Reject “never shuts down”—maintenance and turnarounds exist.Reject limitations to “simple tasks” or “only analog controllers.”Choose the self-contained, continuous in/out description.

Verification / Alternative check:
P&IDs of refineries or polymer plants show continuous feed and product streams, aligning with the chosen definition.

Why Other Options Are Wrong:
(a) Complexity varies; many continuous plants are highly sophisticated. (b) Absolute “never” is false. (d) Digital control is common. (e) Not applicable since (c) is correct.

Common Pitfalls:
Equating continuous with uninterrupted uptime; confusing process mode with controller technology.

Final Answer:
Self-contained: raw materials enter and an identifiable product exits continuously