Process Sustainability: In-Line Product Recovery System

How Waste Impacts the Environment and Business Economics

A production process is sustainable over time when it generates value for both the company and society while minimizing environmental impact. The sustainability of a process is evaluated by examining the balance among its economic, social, and environmental dimensions. Given the widely acknowledged need to enhance the sustainability of industrial processes, actions aimed at reducing waste and inefficiencies are indispensable.

One of the primary aspects to address in this context is the generation of waste and by-products during a process. Reducing product waste at any stage of the production cycle provides immediate benefits on both economic and environmental levels. The benefits are even more pronounced when the product involved is highly polluting—due to its potential environmental impact and the high costs of disposal—or when the product is of significant value. Interventions that reduce process waste and by-products greatly enhance the sustainability of the process by improving operational margins and reducing environmental impact.

Managing Waste in the Chemical Industry: In-Line Product Recovery System

In the chemical industry, the handling of highly polluting and/or particularly expensive substances is a constant factor. Reducing waste is thus critically important for improving process sustainability in this sector. Liquid substances are transferred within the chemical industry through complex pipeline systems supported by networks of pumps and valves, enabling the product to flow to its intended destination.

At the end of the transfer process, the pipeline undergoes cleaning operations, and the residual product remaining within the pipes is typically directed to waste collection and treatment facilities. In this scenario, the sustainability of the process can be significantly improved by recovering the residual product at the end of the transfer process and before cleaning operations commence.

For the in-line product recovery system to be truly sustainable, it must operate with minimal impact on production and require limited manual intervention—an essential consideration given the hazardous nature of the substances being recovered.

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How a PIG System Works

One of the most effective systems for recovering liquid products at the end of transfer operations is the pigging technique. This technique uses a mobile device commonly referred to as a “PIG,” which, by traveling along the pipeline, allows for the recovery of extremely high percentages of the residual product. Recovering the product in this manner also facilitates subsequent cleaning operations for the pipeline.

The first PIG systems were employed in the oil industry specifically for performing mechanical cleaning of pipelines—an operation that was difficult to carry out manually. In these early applications, rudimentary devices were used, such as bales of hay wrapped with barbed wire. These devices, as they moved along the pipelines, produced a squealing noise similar to that of pigs, which is how the name “PIG” originated.

Over time, the technique evolved and was adopted by other sectors, with the product recovery function becoming just as important as the cleaning function.

Materials and Fluids Used in the In-Pipe Product Recovery System

As previously mentioned, the pigging system relies on the use of a solid device, the PIG, which features a maximum diameter slightly larger than that of the pipeline through which it travels. The PIG is made from different materials depending on the product to be recovered—for example, silicone for beverages and food products, EPDM rubber, or fluorinated elastomers (e.g., FKM Viton™) for highly aggressive chemicals.

The PIG is launched from a dedicated launching station and propelled through the pipelines using a fluid. The choice of propulsion fluid depends on the characteristics of the system and the product to be recovered. Common propulsion fluids for the PIG include compressed air, carbon dioxide, nitrogen, water, detergents, and solvents. At the end of its course, the PIG is collected in a receiving station and, if necessary, sent back to the launching station, while the product recovered via pigging continues in the processing workflow. Following this, the pipeline and the PIG itself undergo dedicated cleaning operations.

How to Choose a Pigging System

Although the principle behind pigging is relatively simple, implementing an effective and efficient pigging system is a particularly delicate process.

First, the system is typically installed in an existing plant, where it must be integrated into the available space without disrupting regular production. Second, the shape and material of the PIG must be carefully chosen based on the nature of the product to be recovered. The selection of the propulsion fluid also depends heavily on the type of product being handled and the characteristics of the primary system.

Finally, one can choose between unidirectional systems, which require manual extraction of the PIG at the end of its course, or bidirectional systems, which can operate in both directions without operator intervention. Bidirectional systems are particularly suited for recovering highly polluting and/or hazardous chemicals, as the PIG, contaminated by the recovered product, does not exit the system.

G-RECO: Granzotto’s Pigging Solution

Granzotto’s pigging systems, known as “G-RECO,” are specifically designed to recover residual liquid product in an industrial plant. G-RECO systems for the chemical industry are custom-designed with particular attention to the characteristics of the primary plant and the product to be recovered.

By using Granzotto’s pigging systems for product recovery, it is possible to reduce process waste and thus improve sustainability, providing immediate economic and environmental benefits.