How to remove ethylene oxide from the autoclave at the end of the sterilization cycle?


Technologies: Scrubber and the catalytic sistem

Industries are increasingly aware of the importance of protecting the environment. In the field of ethylene oxide sterilization autoclaves, the environment aspect is also on today's agenda. Ethylene oxide also known as ETO is a gas with multiple properties that allows the sterilization of several objects, especially the so-called thermo-sensitive ones, which cannot be sterilized by traditional processes such as steam, dry heat, super-heated water, etc.

This sterilization process is well known and has been implemented in many countries and companies in the pharmaceutical and medical sectors. It has increased its struggle to protect the environment, since ethylene oxide is an explosive gas, but also flammable, mutagenic and Carcinogenic (C2H4O).

In order to remove the ethylene oxide from the autoclave at the end of the sterilization cycle, 2 technologies can be used:

  • Scrubber
  • Catalytic System

What is the Scrubber technique?

It is a device that allows the conversion of ethylene oxide, dangerous gas, into a product called ethylene glycol, being not dangerous for people. This chemical transformation occurs when ethylene oxide, water and sulphuric acid come into contact, in certain proportions.

How does Scrubber work?

Its operation is relatively simple; the equipment receives the ETO from the vacuum pumps coming from the autoclave, and passes through several columns with showers of water + sulphuric acid (The efficiency of the neutralization depends directly on the number of columns). The ethylene oxide is then polymerized to ethylene glycol before being dropped into a tank. Once this ethylene glycol is saturated into the deposit, caustic soda is added in order to reach a neutral PH, before being generally collected by an external company.


What is Catalytic System technique?

It is a more complex installation than Scrubber, as it tries to eliminate almost all of the ethylene oxide instead of transforming it. This time ethylene oxide is converted to CO2 + H2O before being released into the atmosphere.

How does Catalytic System work?

This process is separated into two phases:

  • The gas comes from the autoclave vacuum pumps, and is sent to the tank A. This device is responsible for diluting the gas with water, without sulphuric acid (we do not want any chemical transformation). The water is then temporally saturated with ethylene oxide to reduce the ETO concentration in the inner atmosphere of the tank (less than 3%).
  • Then a reservoir B receives ethylene oxide which is gradually released from tank A with a low concentration (less than 3%, which is the lower limit of ETO explosion), and acts as a burner before releasing the residues to the atmosphere via its ventilated fireplace.
    The most known catalytic systems for ETO autoclaves are from the Lesni and Donalson brands.

Protection environment

The protection of the environment is an important and key point in an ETO sterilization process, that's why the manufacturers of ETO sterilization autoclaves propose those 2 processes, and with an increasing tendency to choose the catalytic system due to its advantages over the Scrubber that are:

  • Cleaner process, ensuring an ETO waste to the atmosphere of less than 1ppm, during an 8h process.
  • Totally autonomous system, unlike the Scrubber for which the ethylene glycol tank needs to be emptied frequently.

Both ETO sterilizer manufacturers and ETO sterilization companies are working to achieve "clean" installations in order to make the process respecting the environment as much as possible. The ecosystem is a matter of concern to everyone, and industries in this sector have it in mind.

If you look for design engineering, manufacturing, commissioning, installation of pharmaceutical equipment (steam sterilizers, superheated water sterilizers, ethylene oxide sterilizers, vacuum chambers…) or even for any improvements/modifications of existing installation, do not hesitate to contact us.