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Chemical plant revamp – Making it easier with Vahterus

Project

In 2006 one of the biggest manufacturers of methyl methacrylate decided to revamp their plant where the main component of methyl methacrylate, cyanohydrin is produced. The cyanohydrin production process always acquires thermal treatment: heating, cooling, condensation, and evaporization. The project had the following targets:

  • Achieving the same production level with a clean cut to energy consumption
  • Reducing the number of the potential danger points, and the relevant safety distances
  • Completing the revamp without updating existing foundations and steel structures


Challenges

The process plant was inside a complex of many different companies, all working in symbiosis. The cooling, using liquid ammonia as cooling media, was a centralized service. The solution had some critical points:

  • Potential danger points (valves, flanges, etc.) were too many
  • Safety valves pressure set point was very low, due to the centralized plant
  • Power absorption was high since the centralized plant had very big machines and Arkema’s consumption was low
  • Plant safety system had to take into account that ammonia is a toxic fluid

Heating, cooling, condensation and evaporization of the cyanohydrin production process are normally done by using large and heavy shell&tube exchangers which also have maintenance issues, specially due to polymerization, obliging to stop the production to restore efficiency through a thorough cleaning.


Solutions and benefits with Vahterus PSHE

After investigating all options, Arkema technicians decided that the solution was to replace the cooling system of the cyanohydrin by using ethylene glycol cooled with a chiller sized according to the requirements of the production.  It meant adding two new exchangers that should be of dimensions suitable to be positioned inside the existing plant easily and to guarantee the required thermal cycle, not forgetting that they had to have the characteristic to run in “lethal service” area. Furthermore, the new units should have the aim to make the maintenance simpler.

Together with plant technicians, Vahterus’ distributor studied the solution concluding that Vahterus PSHE were fulfilling all requirements.

Since the start-up, the process parameters have been according to the design. There have never been maintenance problems due to polymerization of the media because the thermal level has constantly been under the safety limits, the crossing time of the exchangers was really small and the turbulent flow helps to avoid polymerization. Other benefits reached with the reliable Vahterus PSHE:

  • Easy positioning of two heat exchangers which also enables placing additional tank for chemicals
  • The process became more efficient and the decreasing of power consumption meant an important saving of money
  • Many safety valves etc. could be dismantled as ammonia was replaced with ethylene glycol
  • Maintenance stops and cost were reduced significantly