Project Description

VDU Vacuum column overheads vapour phase 2010 Project Review

The Client asked ProDecon® to decontaminate the vacuum Column, Overhead Condensers, Ejector condensate drum, Sour Gas Receiver & Off Gas Clean up Column using our proven Vapour phase method. There was to be no ‘Boil out’ or liquid circulation of the bottom of the column on this occasion. The scope of decontamination included removal of hydrocarbons and finely divided pyrophoric Iron Sulphide prior to man entry and possible hot work being performed.

ProDecon®®> engineers worked closely with the refinery operations to integrate vapour phase decontamination with the refinery shutdown procedure to offer the greatest time saving. Suitable injection points were strategically identified to introduce our Decon-88VP chemistry into the steam flow for the most efficient decontamination.  With just six injection points, required unit preparations were minimal.

Whilst neutralisation of any remaining finely divided Iron Sulphide can be applied in the vapour phase, the client opted for a in a liquid cascade method. Taking advantage of ProDecon®’s skid mounted, diesel driven 300m3/hr, high head pumps, this allowed oxidation, removal of insoluble materials and rapid cool down to suitable conditions for man-entry to be achieved in a single step.

Throughout the decontamination process, samples were taken of vapour (from high point vents) and condensate (from low point drains) and analysed for:

  • LEL,
  • Benzene,
  • H2

Analysis showed gas free conditions in less than 12 hours from the start of chemical injection. The refinery continued the reduced steam out for a further 3-4 hours.

When the temperature at the top of column was indicated to be < 60o>C ProDecon® commenced the demineralised water / Pro-Ox™ solution cascade down through the column.

Samples of the Pro-Ox™ solution were collected from the column drain. When tests proved an excess of Pro-Ox™ is present at the sample point the Circulation/ cascade of Pro-Ox™ was stopped. The refinery confirmed that the average temperature of the column was less than 35o>C. The column was now gas free, pyrophoric free and cool enough for man-entry on opening all in less than the 24 hour target window.

Once the equipment was opened for inspection the client was satisfied by the high standards of cleaning that were achieved in such a short period of time. Following are some photos of the equipment that was decontaminated.

Customer Verified results

ProDecon® completed this Project, successfully, within the allowable time frame of 24 hours. Testing proved the effectiveness of both the decontamination and the pyrophoric neutralisation stages.

It was noted that there was less residual chemical odour and no complaints regarding irritation, from those working inside the vessel, as compared to when other decontamination chemistry was used. There were no issues with interference to sampling / monitoring equipment, which has caused vessel entry delays in the past, when other decontamination chemistry was used. The cleanliness of the vessel internals was noted to be very good. The boot of the tower was clean and coke free’.