Hydrocarbon decontamination best practice? 3

[turnaroundeng]

Hi,

I would like to know what are common practices for decontamination of oil refinery plants in preparation for a turnaround.

Currently, our operations department uses regular steaming (175#) for most pipelines and vessels, however at times i've seen heavy oil systems steamed with detergent (simple green) as well as the use of Zyme for pyrophoric servies.

 

[pennpiper]

There is also an orange oil based 'Citra-Clean' product I have seen used.

Might be worth checking into.

Sometimes its possible to do all the right things and still get bad results

 

[EmmanuelTop]

By definition, decontamination/inertization is a preparatory activity for unit turnarounds. Cleaning (incl. chemical cleaning) is a part of turnaround activities. Somehow we have mixed the two.

Steam is by far the cheapest fluid that can be used for decontamination. I doubt there will be any other more effective and cheaper way invented in future.

On the other side, the list of chemicals and fluids used for equipment cleaning is quite exhaustive. Apart from special detergents, light hydrocarbon fractions and hot water are commonly used for rinsing/removing of sludge and salt deposits accumulated inside the equipment. There are special chemicals for descaling of boilers, washing of turbine and compressor rotor blades, degreasing of fin-fan tubes etc.

Dejan IVANOVIC
Process Engineer, MSChE

 

[turnaroundeng]

Thanks,

Equipment steaming (for gas freeing)is a lengthy process for vessels with internal parts (towers with trays) so I was wondering what else can be done to accelerate the process for towers especially

 

[pennpiper]

The existing tried and true methods have been working just fine.
Any shortcut method you or anyone else comes up with you have to get it past all safety tests and agency approvals.
-
Then you have to ask yourself: will you allow your kids, your spouse or your mother to enter that vessel?

Sometimes its possible to do all the right things and still get bad results

 

[EmmanuelTop]

I worked in refinery CDU's and I completely understand the issue you are talking about. On many occasions, I noticed the following:

1) The procedure for steaming of columns was really not developed, neither tested, nor improved based on actual field observations. Operators tend to introduce steam and then open all vents and drains, and keep it going that way forever until somebody says "hey, maybe we should stop and do the gas test". It is a terrible way of doing things but it happens almost everywhere. If this is the way Operations perform steaming in your refinery, maybe you can talk to the plant supervisor and try to put a decent steaming procedure as a start.

2) Draining of liquid inventory is the key for reduced timeline. Column bottoms, pump suction, draw off trays, and any other pocket where liquid can accumulate - you need to remove the inventory as much as possible. Otherwise it will take ages to vaporize all that liquid. The problem is usually with chimney trays where design leak rates are very small.

3) Look at the schematics of the isolated column and associated pipework and locate the vent and drain valves which should be open, and keep the other ones closed. Reduce the section volume as much as possible. If the section is very long, you won't see significant velocities at the pressurized end of the system. This further prolongs duration of steaming.

4) In some instances, it may be worthwhile to consider circulating hot water through the dirtiest section (column bottom/pump/hot preheat train/furnace/column) to get rid of sticky, viscous crude residue.

Dejan IVANOVIC
Process Engineer, MSChE