Understand Pilot-Plant Design Specifications | AIChE

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Understand Pilot-Plant Design Specifications

Plant Design

Although pilot- and commercial-scale plants may appear similar, they must be designed with different objectives in mind. Find out how the design criteria for pilot and commercial plants differ, and why commercial specifications should not be applied to pilot plants.

Pilot and demonstration plants can behave like, and even look like, large-scale commercial plants, just at a smaller scale. This misconception of sameness can lead engineers to design their pilot facilities with the same equipment and specifications as commercial-scale plants. However, while this choice may seem rational, considering that both types of plants need to be designed and fabricated in accordance with federal and local codes and standards, use the same engineering principles, and have similar electrical and control systems, this line of thinking is actually a trap that can deliver subpar research results and incur unnecessary expenses.

Contrary to the intuition of many engineers, commercial plant specifications should not be applied to pilot plants.

Pilot plants vs. commercial plants

The differences between the specifications for pilot plants and those for commercial plants can be attributed to their different objectives. Pilot plants are designed and built so that engineers can learn more about a process to make decisions regarding new technologies or other process configurations. Data collection is central to achieving this goal, as it provides process engineers with boundary conditions for scale-up. Pilot plants expose potential problems, and allow alternative solutions to be engineered and tested before continuing to scale up or transferring technology to full-scale operation.

To achieve its purpose, a pilot plant needs to be flexible and adaptable so that operators can quickly make modifications to test configurations and operating conditions to establish optimal operation. Owners of pilot plants are less concerned with efficiency of operation and more so with proof of concept. For example, recovering heat from hot streams is not required, nor is it practical; instead, controlling the reactor temperature is the critical issue. Though commercial-scale operations run continuously with a few weeks of shutdown per year, pilot plants operate intermittently for one to ten days a campaign.

Commercial plants are built to produce a set volume of a well-defined product of consistent quality to maximize profits. To achieve economies of scale, the plants are large and typically require a high capital investment, which incurs high fixed operating costs in the form of depreciation. Operating at a high utilization maximizes the value of the assets, which controls costs and protects profit margins. Because quality is an important component of maintaining strong sales, standard procedures that break tasks into discrete steps — that are reproducible and uniform — are implemented.

Assuming sales and the order backlogs are stable, it is the responsibility of plant management to ensure that the plant is well maintained to maximize uptime. Unlike pilot-scale operations, preventive and predictive maintenance is paramount. In commercial plants, plant layouts can be sprawling, necessitating the need for smart devices to alert personnel when equipment replacement is required. Controlling costs is equally as important as maintaining the plant. Some methods of cost control include: recycling solvents and gases that can be reused, recovering heat from effluent streams, and capitalizing on the energy value of waste gases.

Design criteria

Design specifications for pilot plants are primarily driven by the need for flexibility and representative data collection. Flexibility allows the order of unit operations to be reconfigured, new unit operations to be added, and a range of operating conditions to be tested. Other criteria that help define design specifications for pilot plants include:

  • complete design and fabrication quickly to minimize time to market
  • maintain the accuracy of small-scale metering and measurements
  • minimize the layout space of the plant
  • represent process conditions accurately
  • ensure the system is safe
  • minimize the cost of the system.

These criteria are often...

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