Evaporation line revamping in edible oils refinery

In today’s fast-paced industrial landscape, staying competitive requires much more than just keeping processes running: it demands continuous optimization, energy efficiency, and compliance with ever-evolving standards. Many industrial plants, especially in the food, oil, and chemical sectors, face the challenge of operating aging equipment that no longer meets modern production demands or efficiency targets.

This article demonstrates how thoughtful engineering can optimize complex processes, reduce costs, and minimize downtime, delivering tangible results for our clients.

By applying an integrated engineering approach and advanced simulation and design tools, we developed a set of technical solutions to adapt the existing process line to new operating conditions, maximize process efficiency, and retain as much of the existing infrastructure as possible.

Our mission is to help clients unlock the full potential of their existing assets, ensuring their plants are ready to face current and future challenges in a sustainable and profitable way.

1. Problem Description

Our client, who is a manufacturer of vegetable edible oils and fats, contacted us to carry out a study of the solvent evaporation line at their refinery to detect potential failures or deficiencies in their current design.

The main goal of this study was: on one hand, to identify design shortcomings that prevented the process from meeting the required specifications, while on the other hand, to seek solutions to optimize the line and adapt it to the new operating conditions, using as much as existing equipment as possible, in other words, to do a process revamping.

An exhaustive study of the existing evaporation line revealed several operational problems and limitations:

• Feed did not enter near its bubble point temperature, causing that the evaporator would be wasting energy by heating the oil-solvent mixture.
• The evaporator design was deficient (insufficient tubes and large diameter), requiring excessive steam to achieve the necessary separation, leading to dry tube walls (film boiling). For solving this issue, it was required significant recirculation of clean oil back into the dirty feed, causing a major exergy loss.
• The lower body evaporator became ineffective as feed entered too hot to vaporize solvent.
• Fouling and clogging were identified in the upper and intermediate evaporator liquid distributors.
• The final stripping column operates at a very low flooding. Moreover, in a column with such a small diameter and without liquid redistribution, the liquid will most likely run down the inner wall bypassing the packing, making most of the installed packing height ineffective.
• The current Pall ring random packing is outdated compared to modern structured packings, which provide lower pressure drop and better flow distribution.

2. Solutions

Modifications to the Evaporation Line:

• Replace the upstream preheating exchanger with a new one in order to preheat the feed closer to the bubble point temperature, improving separation at the evaporator.
• The evaporator section was completely redesigned by changing to a suitable geometry for optimal operation. The flash head was modified, the evaporator and intermediate chamber were replaced with new elements, while the lower shell and torispherical bottom remained unchanged. (new tube bundle, remove intermediate liquid redistribution, nozzles updated, installation of vents, expansion joint for safety start-ups, handhole and sights for maintenance/cleaning, progressive reducer assembly to connect feed and recycle lines, substitution of the siphon tube to simplify the feeding system)
• As there were not modifications on the dimensions of evaporation section, as well as the existing flash head was reused, and the bottom of the evaporator remains plug and play, this is an advantage as the current piping will not have to be modified.
• Every valve was verified to check the pressure drop and their suitability under the new conditions.
• Exhaust column can handle the new conditions and requires no modifications.
• Current Stripping column was reused but modifying internal components and upgrading air feeding pipelines in order to increase the air flowrate and work at suitable flooding, checking if necessary the vacuum system.
• Randomly packed Pall rings were replaced with a modern structured packing divided in two sections adding in the middle a wall wiper clamped between body flanges for liquid redistribution.
• Installation of spray nozzle to atomize the feedstream uniformly on the structured packing upper surface.

3. Results

After implementing all proposed modifications, the theoretical model predicts an outlet oil stream with 1 ppm of solvent at the design maximum feed flowrate.

4. Conclusion

In conclusion, the evaporation line for an oil and fat processing industry was studied, detecting design areas that could be improved, which were preventing to meet the required degree of solvent separation.

The process was analysed from a global point of view detecting bottlenecks. Then, the necessary actions were planned to improve the efficiency of the whole process.

This project was carried out by integrating company’s expertise in multidisciplinary fields like conceptual and detailed engineering, use of advanced software tools for simulations of mass & energy rigorous balances, thermal hydraulic and equipment’s mechanical design, manufacturing process management with reliable workshops, and logistics of assembly and dismantling operations.

In cases such as this one, revamping may be the best option to upgrade and modernize process plants without building new infrastructure, it is a time and cost-effective alternative to complete equipment renewal.

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