CASE STUDY: RECOVERY AND DISCHARGE OF PROBLEMATIC BY PRODUCTS

Designing a plant for recovering and disposing of by-products usually takes a secondary role compared to designing the main product processing plant. Since they are by-products, there might be a temptation to make quick design decisions aimed primarily at reducing initial investment costs. Often, standard solutions and lower-performing components are sufficient for handling by-products without affecting the quality of the main product. While this approach can sometimes be adopted without particular consequences, in other cases, it is necessary to carefully evaluate certain factors before implementing conventional solutions. Savings in the design and construction phase might result in increased operating costs due to more frequent maintenance and downtime. To avoid operational problems, it’s always advisable to thoroughly study the by-product, its chemical-physical characteristics, and its behavior during conveyance (and possibly storage), both under normal and extraordinary conditions.

How to Handle the Liquid Mixture for Pharmaceutical Coating

A representative example of the difficulties in designing a by-product recovery plantwas addressed by Granzotto for a company in the pharmaceutical industry. This case involves handling and disposing of a liquid mixture used for coating a drug. The mixture is prepared in slightly excess quantities to meet daily production needs. The excess amount produced daily must then be recovered and disposed of. However, due to substances that tend to polymerize and others that tend to sediment, the mixture cannot be sent to the industrial waste line, as it would eventually clog pipes and damage the treatment plant. Studies showed that the liquid tends to thicken with even small temperature increases due to unwanted polymerization reactions. Additionally, in certain segments of the system, the talc present in the mixture tends to settle and accumulate, creating various problems for channeling equipment (pumps and valves).

To address the issues related to the nature of the by-product, Granzotto designed a separate conveyance and disposal plant from the industrial waste line, directing the mixture to a large tank located at the plant’s central unit.

Periodically, the by-product stored in the tank is collected by a tanker truck and appropriately disposed of. The plant was designed to initially convey the by-product through a properly sloped manifold into a small basin, from which it is then pumped to a larger storage tank (about 20 cubic meters).

Storing the Mixture

Storing the mixture is a delicate operation due to the issues of polymerization and talc sedimentation. The tank’s contents must be kept in motion and at a constant temperature. This was achieved by installing a pneumatic pump for recirculation and an external heat exchanger to maintain temperature.

Granzotto’s Custom Design Based on By-Product Behavior

In this context, an unconventional design choice was made that merits a brief discussion. The thermal exchange function and the plant context suggested installing a plate heat exchanger, given its advantages like reduced size and higher thermal exchange coefficients. However, tests showed progressive talc deposition in some fluid channels between the plates. This phenomenon, caused by excessive reduction in fluid speed, was undesirable and would lead to more frequent and costly maintenance. The design choice therefore fell on a single-tube exchanger with an external cooling jacket, which has a much simpler geometry and more uniform fluid flow speeds. This solution minimizes talc deposition in the exchanger while still maintaining the desired temperature.

Knowing the criticalities of the by-product to be recovered, several other specific choices were made, such as avoiding electric pumps throughout the recovery plantto prevent local temperature rises that could trigger polymerization.

Additionally, the disposal network was built from stainless steel with proper slopes, and near-sanitary welding was used to prevent talc or other substances from accumulating at the weld seams. Finally, the plant was equipped with a multitude of sensors, including redundant ones, to monitor process parameters, particularly the by-product’s temperature.

Conclusion

This case study highlights the importance of careful plant design, even for by-product recovery and disposal. Neglecting certain aspects during the initial design phase can lead to serious operational problems and extraordinary maintenance costs. It also demonstrates Granzotto’s attention to plant design for its pharmaceutical industry clients. By understanding client needs and leveraging extensive industry experience, Granzotto aims to provide the most effective solutions for reliable long-term plant operation.

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Industrial plants and systems for the complete management of liquid products in the food, chemical, and oenological sectors.